SUMMER 2022

VOLUME LVIII

THE QUARTERLY JOURNAL OF THE GEMOLOGICAL INSTITUTE OF AMERICA

Diamonds from Guyana

Surface Features of Ekanite from Sri Lanka
A Study of Gems from Napoleon III’s Crown
A New Source of Amber in Vietnam
 Summer 2022
VOLUME 58, No. 2
EDITORIAL
137 Diamonds from Guyana, Ekanite from Sri Lanka, a New Amber Source in
Vietnam, and More...
Duncan Pay

FEATURE ARTICLES
138 A Look at Diamonds and Diamond Mining in Guyana
Roy Bassoo and Kenneth Befus
Reports on diamonds from Guyana’s alluvial deposits, including mining history and practices.
p. 146
156 The Shape of Ekanite
Lutz Nasdala, K.A. Geeth Sameera, G.W.A. Rohan Fernando, Manfred Wildner,
Chutimun Chanmuang N., Gerlinde Habler, Annalena Erlacher, and Radek Škoda
Discusses the unusual surface characteristics of ekanite from secondary deposits in Sri Lanka.
168 A Gemological and Spectroscopic Study with Mobile Instruments of
“Emeralds” from the Coronation Crown of Napoleon III
Stefanos Karampelas, Eloïse Gaillou, Annabelle Herreweghe, Farida Maouche,
Ugo Hennebois, Sophie Leblan, Bérengère Meslin Sainte Beuve, Michel Lechartier,
Didier Nectoux, and Aurélien Delaunay
An examination of 45 gems from the coronation crown of Napoleon III, using nondestruc-
p. 170 tive mobile spectroscopic and gemological testing methods.
184 Characteristics of Newly Discovered Amber from Phu Quoc, Vietnam
Le Ngoc Nang, Pham Trung Hieu, Lam Vinh Phat, Pham Minh Tien, Ho Nguyen Tri Man, and
Ha Thuy Hang
Offers the first detailed summary of amber from the Vietnamese island of Phu Quoc and a
comparison with Baltic, Dominican, and Burmese material.
196 Natural Radioactivity in Select Serpentinite-Related Nephrite Samples:
A Comparison with Dolomite-Related Nephrite
Dariusz Malczewski, Michał Sachanbiński, and Maria Dziurowicz
Uses gamma-ray spectrometry to directly measure internal radioactivity in green nephrite
p. 184 from deposits in Poland, Russia, Canada, and New Zealand.

REGULAR FEATURES
214 Lab Notes
Orange benitoite • Set of blue “rough” stones • Type IIb De Beers Cullinan Blue diamond
p. 219 • Green diamond with unusual radiation stains • 10 ct HPHT-treated CVD-grown diamond
• Reported Cassis pearl from Florida • RFID device in South Sea bead cultured pearl
necklaces • A star and cat’s-eye color-change sapphire • Bicolor cuprian tourmaline

226 G&G Micro-World

Apatite cluster in emerald • Blue apatite in garnet • Large diamond in diamond • Network of
etch channels in diamond • Eye pattern in rock • Filler patterns in fracture-filled emerald
• Flux synthetic beryl overgrowth • “Boomerang” in topaz • Quarterly Crystal: Cinnabar in
p. 226 fluorite

234 Colored Stones Unearthed

A look at inclusions in gemstones and what they mean for gemologists and geoscientists.

244 Gem News International

Aquamarine with unusual etch features • Topaz in red beryl • Cat’s-eye omphacite fei cui
jade • Three-rayed asterism in quartz • Zircon with strong photochromic effect
• Myne London • Glass-and-quartz triplet imitating emerald • Heated ruby: A costly mistake
• Yellow sapphires with unstable color • Spring 2022 auction highlights • The Big Find: Fifty
years of Maine tourmaline • Brilliance at the Natural History Museum of Los Angeles
p. 266 County • American diamonds at the Smithsonian • The GIA Alumni Collective
Editorial Staff
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About the Cover

This 95.5 × 64.0 mm figure of a grizzly bear with a freshly caught salmon is carved from Canadian nephrite jade from
the Polar Jade mine in northwest British Columbia. The measurement of natural radioactivity concentrations in
nephrite from Canada and other major sources is the subject of a feature article from this issue. Photo by Robert
Weldon/GIA; courtesy of Jade West Group (Blaine, Washington).
Printing is by L+L Printers, Carlsbad, CA.
GIA World Headquarters The Robert Mouawad Campus 5345 Armada Drive Carlsbad, CA 92008 USA
© 2022 Gemological Institute of America All rights reserved. ISSN 0016-626X
 Diamonds from Guyana, Ekanite
from Sri Lanka, a New Amber Source in
Vietnam, and More...
Welcome to the Summer issue of Gems & Gemology! This installment is packed with interesting
new content, including five feature articles ranging from reports on new and lesser-known gem
sources to a study of the emeralds once embedded in the crown of Napoleon III.

In our lead article, Roy Bassoo and Kenneth Befus explore diamonds and diamond mining in
Guyana. Drawing on their own observations of diamonds from various alluvial deposits, coupled
with government reports, datasets,
and historical accounts, the authors “…an overview
of diamond production and
provide an overview of diamond mining practices in Guyana, along with
production and mining practices in findings on color...”
Guyana, along with findings on
color, morphology, nitrogen content, and luminescence.

Our second article investigates the uneven shapes and surface features of ekanite from Sri Lanka. Lutz Nasdala and his team
analyze ekanite fragments and ekanite-containing specimens of rock discovered near Ampegama, comparing the samples to
those from other Sri Lankan sources to identify the processes that led to the distinctive shape and surface features.

As part of an ongoing effort to research gemstones of historical significance, Stefanos Karampelas and coauthors present
their analysis of 45 “emeralds” formerly set in the coronation crown of Napoleon III. Using nondestructive mobile
spectroscopic and gemological means at Mines Paris - PSL, they verified that 41 of these 45 gems were emeralds, likely of
Colombian provenance, while the remaining four were glass containing iron and/or copper.

Next, a team led by Le Ngoc Nang examines the gemological properties and commercial potential of a newly discovered
amber source on Phu Quoc island in Vietnam. They conclude that based on the high quality of the amber and the wide
distribution of the host rock on the island, Vietnam’s only known amber locality may have a promising future in the market.

In our final article, Dariusz Malczewski and colleagues present their study on natural radioactivity in nephrite. After
examining 11 serpentinite-related nephrite samples from Poland, Russia, Canada, and New Zealand, the authors deter-
mined that there is no radiological risk to handling nephrite and that the levels of the radioactive isotopes studied are
very low.

Our regular columns deliver interesting finds from around the world. Highlights from the Lab Notes section include a
very rare large bright orange benitoite, the famed De Beers Cullinan Blue diamond, and pearls embedded with RFID
devices. In Micro-World, the inner beauty of gems comes alive with an impressive blue apatite inclusion in garnet, eye-
visible etch channels in a natural diamond, and a rock fragment exhibiting a very realistic eye pattern. Gem News
International keeps you up to date with the latest developments, including unusual chatoyancy in omphacite fei cui jade, a
company with a mission to support women in the gem trade, testing of color instability in yellow sapphire, and a
museum exhibit celebrating a major tourmaline discovery in Maine. Colored Stones Unearthed returns to cover inclusions
in gems, explaining how they form, how they are studied, and what they mean for gemologists and geoscientists.

Finally, we invite you to join our Facebook group at www.facebook.com/groups/giagemsgemology. Since its launch in
February 2020, our growing community has surpassed 25,000 members. Thank you for your continued support and
interest in G&G!

Duncan Pay | Editor-in-Chief | dpay@gia.edu

EDITORIAL GEMS & GEMOLOGY SUMMER 2022 137

FEATURE ARTICLES

A LOOK AT DIAMONDS AND

DIAMOND MINING IN GUYANA
Roy Bassoo and Kenneth Befus

Diamonds have been mined in Guyana for more than 130 years and are traded in major diamond centers in Belgium,
Israel, and the United Arab Emirates. Notwithstanding this long history, the primary source rocks of Guyana’s dia-
monds remain a mystery. The diamonds are likely detrital material derived from sedimentary rocks of the Roraima
Supergroup, but a primary igneous, kimberlitic source has not been eliminated. Diamond exploration and mining
in Guyana remain a mostly artisanal endeavor. In a similar fashion, scientific studies have rarely addressed these di-
amonds’ provenance and formation, and very few were aimed at a gemological audience. Here we present a detailed
gemological description of Guyana’s diamonds to serve as a comparison with other diamond populations in the
Guiana Shield and globally. We use our direct observations of diamonds from various alluvial deposits in Guyana.
We combine government reports and datasets as well as historical accounts to provide an overview of diamond
production and mining practices in Guyana. Details concerning color, morphology, nitrogen content, and lumines-
cence are also included.

S
ituated on the northern edge of South America, birthed a culture that is distinctly Guyanese (Rodney,
Guyana (figure 1) is the continent’s only Eng- 1981; Ishmael, 2013; https://guyanatourism.com).
lish-speaking nation. Originally, Guyana was Guyana’s population is concentrated near the
populated by the first nations of Akawaio, Carib, coastal deltas. Most of the population is engaged in
Patamona, Lokono, Macushi, Pemon, Waiwai, agriculture, as the tropical climate, flat terrains, and
Wapishana, and Warao. Dutch, French, and finally fertile soils support sugarcane and rice cultivation.
English colonialism brought advances in agriculture The scenery becomes increasingly pristine as one
and technology. Sadly, these advances were also in- moves inland. Cultivated plains and infrastructure
tertwined with the violent history of transatlantic give way to tropical rainforests and rolling hills car-
slavery and indentured servitude. Laborers from
Ghana, Togo, India, China, and Portugal were
brought to Guyana, either by force or voluntarily.
The colonial economy was based on the cultivation In Brief
of sugarcane throughout the nineteenth and twenti- • Guyana has contributed to the global supply of dia-
eth centuries. Guyana’s legacy of colonialism has monds for more than 130 years.
been one of violence, racism, and poverty, which • Guyanese diamonds are prized for their clarity and
peaked during the social upheavals of the 1960s green colors.
(Spencer, 2007). It has been difficult for Guyana to • Morphology and luminescence suggest that recycled
fully divorce itself from its colonial past. However, paleoplacer diamonds and more recent primary dia-
Guyana today is a peaceful and diverse mix of cul- monds coexist in the same deposit.
tures and ethnic groups from around the world. This • Guyana’s alluvial deposits host not only diamonds and
little melting pot of different languages, clothing gold but also underexploited ruby, sapphire, and topaz.
styles, cuisines, traditional dance, and music has

peted by the Amazon jungle. The country’s western

boundary is dominated by the towering, flat-topped
See end of article for About the Authors and Acknowledgments.
GEMS & GEMOLOGY, Vol. 58, No. 2, pp. 138–155,
tepuis of the Roraima Mountains (figure 2). It is
http://dx.doi.org/10.5741/GEMS.58.2.138 within the mountainous northwest where most of
© 2022 Gemological Institute of America the diamond deposits are located. The lead author,

138 DIAMONDS FROM GUYANA GEMS & GEMOLOGY SUMMER 2022

 Ciudad Bolivar
Placer diamond
CO occurrences
EK
KU Georgetown Major placer
diamond deposits
Paramaribo
GU Primary diamond
KM deposits
JW KW
RO Cayenne
NA 5˚N
MK FRENCH
MM GUIANA
SURINAME DC
TE
BV
VENEZUELA
N
GUYANA

SOUTH AMERICA 0˚N

BRAZIL
60˚W 50˚W 250 km

Figure 1. Google Earth satellite image of northern South America showing various diamond occurrences in Brazil
(BV—Boa Vista, TE—Tepequém), Venezuela (CO—Los Coquitos, GU—Guaniamo), Guyana (EK—Ekereku, JW—
Jawalla, KM—Kamarang, KU—Kurupung, KW—Konawaruk, MK—Maikwak, MM—Monkey Mountain), Suriname
(NA—Nassau, RO—Rosebel), and French Guiana (DC—Dachine).

a Guyanese native, grew up hearing about jungle the northern margin of the Amazonian Craton (figure
diamonds found deep in the mountainous interior, 3). The evolution of the Guiana Shield was domi-
a topic that sparked his imagination and scientific nated by episodes of accretionary mountain-building
curiosity. events during Archean to Proterozoic times, evi-
Geologically, the diamond-bearing rocks that denced by outcrops of quartzite, schists, gneisses,
occur in the country’s interior are part of the Guiana greenstone belts, and amphibolites (Tassinari, 1997;
Shield, which is exposed over ~3,000,000 km2 along Reis et al., 2000; Fraga et al., 2009; Kroonenberg et

Figure 2. Left: Roraima Mountain tepuis (elevation ~2000 m) near the source of the Kurupung River in Guyana.
Right: Outcrop of Roraima Supergroup rocks. Photos by Kenneth Befus.

DIAMONDS FROM GUYANA GEMS & GEMOLOGY SUMMER 2022 139

 West Ciudad Bolivar
Guiana African CO Proto Atlantic Ocean N
Shield Craton
Georgetown
EK KU
KM JW AM Paramaribo
Amazonian Guaporé GU
Craton KW
Shield
RO Cayenne
5˚N MK NA

MM

TE DC
BV

0˚N

250 km

70˚W 60˚W

Phanerozoic sedimentary rocks (<0.5 Ga) Roraima Supergroup sandstones, conglomerates, and ash-fall tuffs
(2.12–1.78 Ga)
Mesoproterozoic sedimentary rocks (1.3–1.2 Ga)
Paleoproterozoic granitoids and felsic volcanics (1.99–1.95 Ga)
Mesoproterozoic felsic intrusives (1.59–1.51 Ga)
Paleoproterozoic granulites and charnockites (2.08–1.98 Ga)
Paleoproterozoic migmatite gneisses (1.86–1.72 Ga)
Paleoproterozoic greenstone belts (2.26–2.09 Ga)
Paleoproterozoic granitoids and felsic volcanics (1.89–1.81 Ga)
Archean metamorphic rocks (>2.5 Ga)
Paleoproterozoic mafic intrusives (<1.79 Ga)
Platform cover
Placer diamond deposits
Shield/craton
Primary diamond deposits

Figure 3. Modern simplified geologic map of the Guiana Shield. The Amazonian Craton consists of the Guiana and
Guaporé Shield, separated by fluvial cover of the Amazon drainage basin (Gibbs and Barron, 1993; Kroonenberg et
al., 2016). Note the current extent of the Roraima Supergroup (red dashed border), from which most diamonds of
the Guiana Shield are derived (AM—Amatuk, BV—Boa Vista, CO—Los Coquitos, DC—Dachine, EK—Ekereku,
GU—Guaniamo, JW—Jawalla, KM—Kamarang, KU—Kurupung, KW—Konawaruk, MK—Maikwak, MM—Mon-
key Mountain, NA—Nassau, RO—Rosebel, TE—Tepequém). Modified from Kroonenberg et al. (2016) and refer-
ences therein.

al., 2016). In western Guyana, the basement rocks of deposition of sedimentary sequences. The Upper Pro-
the Guiana Shield are unconformably overlain by terozoic was marked by a period of uplift with no ev-
the Roraima Supergroup, which is an interbedded, idence of sedimentation (Gibbs and Barron, 1993).
2300 m thick sequence of sandstones, conglomer- Since the late Triassic, drainage patterns and deposi-
ates, and ash-fall tuffs with an age of 2.12–1.78 Ga tional systems have evolved in response to faulting
(billions of years), deposited from rocks eroding from and rifting associated with the opening of the Atlantic
earlier greenstone terranes (Priem et al., 1973; Santos Ocean. Where cratonic igneous and metamorphic
et al., 2003). Paleoproterozoic mafic dikes of the rocks are buried, Guyana’s jungle interior is underlain
Avanavero Suite crosscut the entire Roraima Super- by a complex network of high alluvial, terrace, alluvial
group sequence. flat, riverbed, buried channel, and plateau deposits (fig-
Throughout much of the Phanerozoic (the time ure 4). These repeated cycles of erosion and deposition
since the Cambrian ~541 million years ago), the region have led to complex diamond placer deposits with
has been a stable craton, only modified by erosion and variable provenances and timing.

140 DIAMONDS FROM GUYANA GEMS & GEMOLOGY SUMMER 2022

 Aeolian sand deposit

Alluvial diamond deposit

Figure 4. Top: Buried

alluvial diamond de-
posit underlying a fine-
grained aeolian sand
deposit, with Guyanese
geotechnician Nigel
Blackman standing for
scale. Photo by Roy
Alluvial diamond deposit Bassoo. Bottom: Close-
up view of an alluvial
deposit. Photo by Uwe
Van Dijk.

DIAMONDS FROM GUYANA GEMS & GEMOLOGY SUMMER 2022 141

 DIAMOND PRODUCTION IN GUYANA
500,000 2000
Diamond production
Price of gold

400,000 1600 Figure 5. Diamond pro-

PRICE PER TROY OUNCE (USD)

duction (green bars) in
Guyana (Kimberley
Process Rough Dia-
300,000 1200 mond Statistics, n.d.)
CARATS

and price of gold

(dashed red line) per
troy ounce (National
200,000 800
Mining Association,
n.d.). Also plotted is the
historical average pro-
duction per year (gray
100,000 400
68,068 carats dashed line).

0
1911 1931 1951 1971 1991 2009
YEAR

GUYANA’S DIAMOND PRODUCTION to 2019. Gold is by far the most important mineral
According to the Guyana Bureau of Statistics, mining resource, accounting for ~82% of all exported ore re-
accounted for ~12% of the country’s GDP from 2000 sources by monetary value. Diamonds are third most

Figure 6. Global price per carat value of diamond-producing countries for 2020 (left). Guyana’s historical diamond
price per carat and average price per carat indicated by the gray dashed line (top right) and exports versus produc-
tion (bottom right) (Kimberley Process Rough Diamond Statistics, n.d.).

260
PRICE PER CARAT (USD)

Lesotho
Namibia
China
220
Brazil
Liberia $175.11
Sierra Leone per carat
180
Tanzania
Guyana $164.49
Botswana
140
Central African Republic
COUNTRY

India
Angola
100
South Africa
Cameroon
Russia 200,000 Production
Canada Export
CARATS

Republic of Congo 150,000

Venezuela
Zimbabwe
Guinea 100,000
Ivory Coast
Ghana 50,000
Australia
Dem. Republic of Congo
0
0 100 200 300 400 500 2008 2010 2012 2014 2016 2018 2020
2020 PRICE PER CARAT (USD) YEAR

142 DIAMONDS FROM GUYANA GEMS & GEMOLOGY SUMMER 2022

important and currently account for 2% of all ex-
ported ore materials (second is bauxite at 16%). His-
torically, diamond production is intimately tied to
gold mining because both tend to be found in the
same alluvial deposits. When gold prices are low,
miners tend to extract more diamonds, which is one
explanation for the cyclical nature of diamond pro-
duction in Guyana (figure 5).
Although it is not well publicized, Guyana has
contributed to the global supply of diamonds for
more than 130 years. Their trade name has been
“British diamonds,” hinting at the country’s colonial
past (Persaud, 2010). In the twenty-first century,
Guyana’s declared diamond production has averaged
~68,000 carats per year (figure 5). In 2004, Guyana
recorded its highest production to date of 445,540
carats. From 2008 to 2012, there was a steady decline
in production, likely exacerbated by financial chal-
lenges associated with the 2008 global financial cri-
sis. After 2012, there was a steady increase in
diamond production. Production today, however, re-
mains relatively low, which can be attributed to ris-
ing gold prices (figure 5). With a historical average
price per carat of US$175 (figure 6), Guyana’s dia-
monds remain fairly profitable when compared to
the global average price per carat of US$151 in 2020
(figure 6, left). They fall within the per-carat price
range of diamonds from Sierra Leone (US$186) and
Botswana (US$148) (figure 6). Declared diamonds are
taxed at a 3% royalty and 2% withholding tax
(Guyana Geology and Mines Commission,
Figure 7. This brownish yellow diamond from
https://ggmc.gov.gy/law/all). Guyana, a 1.01 ct pear brilliant measuring 7.39 ×
There remains room for expansion and increased 5.19 × 3.62 mm, is set beneath a colorless round bril-
production. Marketing is one such possible avenue liant diamond. Photo by Nathan Renfro; courtesy of
to growth. From the 1920s to the 1980s, Guyana’s Michelle Bassoo.
production was limited mostly to rough diamond
sales in the UK, Trinidad, and Barbados (Lee, 1981).
menite, gold, tourmaline, minor garnet, and
Since the 1990s, a growing number of Guyanese-
chromite (figure 8). The Guyana Geology and Mines
owned and operated manufacturing houses have
Commission (GGMC) is the regulatory body that
started to polish and set diamonds into beautiful
oversees mining, safety, environmental protection,
pieces (figure 7).
and education in diamond mining and geology. Al-
though this resource is available, most miners are
DIAMOND MINING IN GUYANA not well educated in prospecting or alluvial
Diamond exploration has been driven mostly by processes. Instead, they frequently rely on anecdotal
Guyanese artisanal miners who prospect along river- evidence and superstition, only prospecting in areas
banks for unconventional, and locally specific, detri- that have produced diamonds in the past. The result
tal indicator minerals to which they ascribe fanciful is that the discovery and exploitation of new dia-
names. “Sweetman,” “cantankerer,” “blue jacket,” mond deposits is very rare. Regardless, production
and “tin” refer to waterworn quartz, ruby, sapphire, has continued to provide income for artisanal miners
and rutile, respectively (figure 8). Other diamond in- for more than 100 years since the first discovery of
dicator minerals include topaz, jasper, zircon, il- diamonds in 1887 on the Potaro River (Lee, 1981).

DIAMONDS FROM GUYANA GEMS & GEMOLOGY SUMMER 2022 143

 Jasper

Diamond Quartz

Rutile

Figure 8. Top left: Washed alluvial gravel sample in a batel (a gold panning tool made of iron with a riffled inte-
rior). Top right: Accessory minerals found with Guyana diamonds, including rounded quartz, jasper, and rutile
(field of view 17 cm). Photos by Uwe Van Dijk. Recovered corundum (bottom left) and topaz (bottom right) of var-
ious colors. Photos by Roy Bassoo.

Artisanal mining in Guyana was born in the Prospecting and hand mining for gold and diamonds
decades after the abolition of slavery in 1838. Many in the relatively unexplored and undeveloped inte-
freed slaves of predominantly West African heritage rior offered both literal and metaphorical independ-
sought a livelihood away from the sugar plantations ence. Toward the end of the nineteenth century,
and their former slave owners (Josiah, 2011). these artisanal miners were called “pork knockers”

144 DIAMONDS FROM GUYANA GEMS & GEMOLOGY SUMMER 2022

Figure 9. Wood carving (left) and historical photograph (right) of an unknown early twentieth-century Afro-
Guyanese “pork knocker” at the Guyana National Museum, which shows how little capital investment was re-
quired to pursue economic independence. To his left is a small sluice box for filtering gold and diamonds from
sediment called a “tom and box” (Lee, 1981). Notice he carries on his head an iron batel of conical shape and rif-
fled interior used not only for panning but also to protect the wearer from the sun. He also carries cooking utensils,
a cutlass, and a handcrafted wooden pipe for smoking. Worn just below his left knee is a red cotton cloth, believed
to protect against rheumatoid arthritis and ensure good fortune. The wariishi secured to his head is handwoven
from palm fronds and serves as a supply basket. Photos by Roy Bassoo.

(figure 9). This nickname is likely a creolization of miners divert water channels using mud and wood
“pork noshers,” a label applied to artisanal miners dams. Pickaxes and shovels are used to move
because of their consumption of salted and cured prospective diamond gravels into manmade ponds
pork. It is theorized that a predominantly Jewish di- screened with 0.2–1.0 cm sieves. Sediment <0.2 cm
amond merchant class coined this term (J. is discarded into the holding ponds. The artisanal
Krakowsky, pers. comm., 2019). Legendary pork miners also excavate small pits of 6–7 m depth that
knockers, spinning tales of fist-sized diamonds and are shored up using cut timber (Lee, 1981). Larger
hills topped with gold, have stirred the public’s groups of miners may form collectives and syndi-
imagination. The stories of Makantali, who wore all cates. Alternatively, claim owners contract small
white and flung money into the air when arriving at teams to prospect alluvial deposits. Individual min-
the port of Bartica, and Gold Dawg, who became the ers are sometimes paid a salary, but diamonds are
first person in his village to own a car (Bascom, often used as currency in the jungle for purchasing
1996), add enchantment to the mining industry in fuel, services, and food (Persaud, 2010). Complemen-
Guyana even today. tary activities that support the mining industry in-
Artisanal “pork knocking” today is typically a clude food service, bookkeeping, and cleaning.
small-scale, independent or cooperative effort. Oper- Larger-scale ventures rely upon heavy equipment and
ations are conducted on a tribute basis, where an ar- techniques borrowed from the gold industry. Placer
tisanal miner receives a share of the proceeds. These deposits are removed by an excavator and formed

DIAMONDS FROM GUYANA GEMS & GEMOLOGY SUMMER 2022 145

 Figure 10. Top: Hy-
draulic mining of allu-
vial deposits. Photo by
Roy Bassoo. Bottom: Ex-
amining a sieve “wash”
for diamonds. Photo by
James Herbison.

146 DIAMONDS FROM GUYANA GEMS & GEMOLOGY SUMMER 2022

Figure 11. A campsite of artisanal miners. Photos by Roy Bassoo.

into a slurry using hydraulic techniques, and this economics of the diamond trade in Guyana are influ-
slurry is then pumped to a sluice box and jig to ex- enced heavily by market fluctuations, fuel supply, and
tract both gold and diamonds (figures 10–12). Heavy the rainy season. Heavy rains in May–June and Sep-
minerals, including diamond, are then handpicked tember–October significantly limit mining activity. In
from the rest of the washed and sieved minerals and the offseason, miners seek alternative forms of em-
stored for sale (see video at www.gia.edu/gems- ployment in the construction, security, or food service
gemology/summer-2022-diamonds-from-guyana). industries. However, off-season unemployment is
In the early years, a “bush trader” ventured into widespread (J. Krakowsky, pers. comm., 2019). Miners
the field to sell food, liquor, and equipment in ex- are often poorly educated on the relative value of in-
change for diamonds. This practice has evolved to be- dividual diamonds in their parcels, tending to rely
come more stationary, where a bush trader owns a solely on carat weight as the metric of value. There is
property near a port town specifically for transactions. a need for educational outreach in this regard, where
Today, miners often carry their own diamond parcels an improved understanding of how rough diamonds
to the capital city of Georgetown, visiting different are manufactured into cut diamonds would improve
brokers to gather quotes before confirming a sale. The the negotiating position of local miners.

Figure 12. A typical small- to medium-scale diamond mining operation in Guyana using a diamond jig attached
to a sluice box. Photo by Roy Bassoo.

Diamond jig
Sluice box Excavated alluvial placer

DIAMONDS FROM GUYANA GEMS & GEMOLOGY SUMMER 2022 147

 8 mm 5 mm

2 mm

Figure 13. Top left: Guyanese diamonds recovered by artisanal mining. Top right: Gem-quality Guyanese dia-
monds. Photos by Kenneth Befus. Bottom: Selected specimens highlighting color and morphology. Photo by
Nathan Renfro.

148 DIAMONDS FROM GUYANA GEMS & GEMOLOGY SUMMER 2022

Figure 14. Left and center: Two greenish blue Guyanese diamonds (~0.27 and ~0.10 ct) from the GIA collection,
donated by Roger Krakowsky. Photos by Roy Bassoo. Right: A larger diamond with a green skin (~6 ct). Photo by
James Krakowsky.

GUYANA’S DIAMONDS defects, reflect/transmit green wavelengths. Further-

Color and Size. Economically viable diamonds in more, the type of radiation influences the intensity
Guyana are small, mostly ranging from 0.1 to 0.4 ct. and depth of green color penetration in the diamond,
Diamonds with sizes up to 10 ct have been found but with gamma radiation creating the deepest penetra-
are uncommon. The largest gem-quality stones ever tion of green color and alpha radiation the least
recovered were 56.75 and 42 ct, found in the Ewang (Breeding et al., 2018; Eaton-Magaña et al., 2018).
region in 1926 and in the Perenong region in 2001,
respectively (Persaud, 2010). Polished Guyanese dia- Morphology and Surface Textures. Guyana’s dia-
monds are predominantly near-colorless, with ap- monds range in crystal shape from octahedral to do-
proximately 93% of them G–J and 7% K–M, and very decahedral and occasionally display flattened cuboid
rarely in white or near-opaque bodycolors (J. forms. Twinned diamonds and aggregates are rare.
Krakowsky, pers. comm., 2019). Fine stepped, lamellar trigonal faces are common,
Of special note, many of Guyana’s rough dia- whereas flat faces and sharp edges are not. Resorption
monds (~42%) display green to green-blue skins or textures such as terraces, teardrop hillocks, and dis-
green spotting that covers up to ~100% of the surface solution pits are found in 95% of the diamonds (figure
area (figure 13). While diamonds with a green body- 15). Flat-bottom dissolution pits including trigons ac-
color are rare (figure 14) (Bassoo et al., 2021), they are count for ~69% of all dissolution pits and frequently
relatively abundant in Guyana compared to other penetrate into the {111} crystal faces (Bassoo et al.,
sources such as Brazil, Ghana, and Zimbabwe (Breed- 2021). Most of the octahedral diamonds have resorbed
ing et al., 2018). Guyana has a relatively higher abun- edges and can be fully resorbed to dodecahedrons.
dance of green diamonds because the placer diamonds Late-stage etching features such as corrosion sculp-
may have resided within the sedimentary environ- tures, shallow depressions, ruts, and glossy surfaces
ment for up to two billion years (Bassoo et al., 2021). are observed in two-thirds of the diamonds.
Diamonds thus may accumulate radioactive damage Edge abrasion, found in 44% of the abraded dia-
over hundreds of millions of years. Alpha, beta, and monds, is the most commonly observed surface tex-
gamma radiation from nearby radioactive minerals ture (figure 15). Most Guyanese diamonds have
such as zircon, monazite, and potassium feldspar cre- some degree of surface abrasion from minor
ated vacancy and interstitial defects in the diamonds. scratches and edge abrasion. Some have no apparent
Photoluminescence spectroscopy reveals these va- surface abrasion, however. This distinction subdi-
cancy defects to have a zero phonon line (ZPL) at 741 vides Guyana’s diamonds into 85% abraded and
nm and are classed as the GR1 or neutral vacancy (V0) 15% non-abraded (Bassoo et al., 2021). Abraded dia-
defect. Vacancy defects absorb in the red portion of monds may reflect an older population with a long
the visible spectrum and, in the presence of nitrogen history of repeated transport within streams and

DIAMONDS FROM GUYANA GEMS & GEMOLOGY SUMMER 2022 149

Trigons Hexagons Tetragons Trapezoids Hillocks Rut

100 μm 200 μm 200 μm 200 μm 200 μm 200 μm

Non-abraded Abraded Edge abrasion Percussive marks

200 μm 500 μm 200 μm 200 μm

Figure 15. Examples of Guyanese diamond surface morphology. Photos by Roy Bassoo.

rivers. Non-abraded diamonds may reflect a shorter Luminescence. Guyana’s diamonds display lumines-
distance and/or time of transport. Alternatively, the cence colors of blue, green, orange, yellow, red, and
15% non-abraded population may be derived from turquoise (figure 16) (Bassoo et al., 2021). Of 472 dia-
undiscovered kimberlites or lamproites (Bassoo et monds, the abraded diamonds dominantly show
al., 2021). Abraded and non-abraded diamonds also green to turquoise (~60%) and some blue (~20%)
display differences in luminescence. cathodoluminescence responses. Non-abraded dia-

Figure 16. Luminescence responses of Guyana’s diamonds. UV luminescence (280–315 nm) response colors (top)
and cathodoluminescence response colors (bottom). Photos by Roy Bassoo.

UV luminescence colors

Yellow Green Orange Red

Cathodoluminescence colors

Blue Yellow Green Orange Red Turquoise

150 DIAMONDS FROM GUYANA GEMS & GEMOLOGY SUMMER 2022

monds cathodoluminesce predominantly blue minescence to green or other colors corresponding
(~60%) and moderate green to turquoise (~25%). Ul- with a shift in ZPL from ~503 nm to higher
traviolet (UV) luminescence (280–315 nm) also yields wavenumbers has been observed in diamonds from
a distinction between abraded and non-abraded sam- unmetamorphosed and metamorphosed rocks, re-
ples. Abraded diamonds luminesce green (~85%) pre- spectively (Iakoubovskii and Adriaenssens, 1999;
dominantly with very minor orange, red, and yellow Collins et al., 2005; Bruce et al., 2011). The Roraima
(~8%). In contrast, ~50% of the non-abraded dia- Supergroup, from which Guyana’s abraded dia-
monds show green UV luminescence, and a larger monds are likely derived, has been metamorphosed
proportion (~45%) exhibit none at all. to zeolite and greenschist facies (Beyer et al., 2015).
Cathodoluminescence spectroscopy reveals de- This observation may explain the relative propor-
fect changes preserved within diamonds that have tion of blue to green luminescence response colors
resided within metasedimentary rocks for billions of Guyanese diamonds.
of years. Cathodoluminescence spectroscopy is a
technique that can be used to infer primary or sec- Composition and Inclusions. The carbon isotope
ondary diamond sources. Most kimberlite-derived composition (δ13C) of Guyanese diamonds ranges
diamonds have a blue luminescence response (Bu- from –2.8 to –16.1‰, similar to that of Brazilian dia-
lanova, 1995; Lindblom et al., 2005). Blue lumines- monds (Tappert et al., 2006). The carbon isotopic
cence is often related to the N3 defect (ZPL ~503 composition of Guyana’s diamonds indicates they
nm), which consists of three nitrogen atoms sur- formed from upper mantle rocks (Bassoo et al.,
rounding a vacancy (Clark et al., 1992; Shigley and 2021). Nitrogen contents can be as high as ~2000
Breeding, 2013). Metamorphosed paleoplacers, such ppm, with >50% being type IaAB (figure 17). A
as those in Guyana, tend to preserve a smaller pop- small percentage (~9%) are type IaB, having more
ulation of blue luminescent diamonds compared to nitrogen platelets. Type IIa and IaA diamonds are of
green and other luminescence response colors (Bruce similar abundances, within 6% of each other. No
et al., 2011; Kopylova et al., 2011). Green lumines- type IIb or Ib diamonds have been reported. The ni-
cence could be related to the H3 to H4 defect, con- trogen type and concentration were used to derive
sisting of more complex arrangements of four a residence temperature of ~1120°C, indicating that
nitrogen atoms surrounding two vacancies (H3) or Guyanese diamonds are lithospheric (Bassoo et al.,
two nitrogen atoms separated by a vacancy (H4) 2021). Inclusion composition also indicates an
(Shigley and Breeding, 2013). A change from blue lu- upper mantle origin.

NITROGEN AGGREGATION TYPE

16.8% Type IaA

Type IaAB
Type IaB
8.7%
Type IIa

21.9% Figure 17. Distribution

of nitrogen type in
Guyanese diamonds
(Bassoo et al., 2021).

52.7%

DIAMONDS FROM GUYANA GEMS & GEMOLOGY SUMMER 2022 151

 Inclusions occur in ~15% of the diamonds and region. These diamonds are very small (~1 mm), gray-
have been identified by comparing their Raman spec- ish yellow to brown, irregular to cuboid (figure 18,
tra with those in the RRUFF spectra database (La- middle), and mostly contain sulfide inclusions (Car-
fuente et al., 2016; Bassoo et al., 2021). Most of the tigny, 2010; Smith et al., 2016).
inclusions in Guyanese diamonds consist of Alluvial diamond data from Venezuela is difficult
forsterite, enstatite, and chromite, indicating the di- to assess because illegal mining and smuggling are
amonds formed from peridotitic upper mantle rocks. prevalent (e.g., Blore, 2006). Also, most alluvial de-
There are some diamonds that contain rutile, coesite, posits are located in inaccessible parts of the Amazon
and clinopyroxene, and these are interpreted to have jungle near the Brazil and Guyana borders, where iso-
formed from eclogitic upper mantle rocks (Bassoo et lated Amerindian tribes such as the Yanomami are
al., 2021). Raman thermobarometry of entrapped leery of outsiders (Heylmun, 2001). Further west in
olivine and Cr-pyrope inclusions indicates internal Venezuela is the Guaniamo area, where there exists
pressures of ∼6.2 GPa, again lending evidence to their a unique deposit of primary diamond-bearing kim-
formation in the upper mantle (Bassoo and Befus, berlite dikes (Capdevila et al., 1999; Channer et al.,
2021). Guyana’s diamonds are typical of peridotitic 2001; Kaminsky et al., 2000, 2004; Smith et al.,
to eclogitic cratonic diamonds. 2016). Guaniamo diamonds are small, ranging from
1 to 2 mm, and colorless to gray with common green
COMPARISONS TO OTHER DIAMONDS FROM skins, frequently occurring in resorbed dodecahe-
NORTHERN SOUTH AMERICA drons and octahedrons (figure 18, bottom). Diamonds
from Guaniamo contain inclusions of the predomi-
Guyana’s diamonds are part of a larger story about the
nantly eclogitic variety, including almandine garnet,
evolution of cratons and residence within sedimentary
clinopyroxene, rutile, ilmenite, pyrrhotite, and co-
systems. Their morphological and geochemical fea-
esite (Taylor, 1999; Kaminsky et al., 2000).
tures compare and distinguish them from other dia-
monds of the Guiana Shield in northern South
America (figure 18). Important deposits occur in CONCLUSIONS
Brazil, Venezuela, Suriname, and French Guiana. Guyana’s diamonds are found in gravels along the
Alluvial diamonds are mined in Brazil and Suri- eastern edge of the Roraima Supergroup. Most origi-
name. In the Guiana Shield portion of northern nate as paleoplacers from as yet unknown rocks of
Brazil, diamonds are recovered from alluvial terraces the Roraima Supergroup. Similar alluvial diamonds
shed from conglomerates of the Tepequém Forma- are found in nearby Venezuela, Brazil, and Suriname,
tion (Santos et al., 2003; Reis et al., 2017). The dia- suggesting the Roraima is a common source. Indeed,
monds are generally 2–3 mm in size and occur in a these paleoplacers represent a regional diamond ter-
flattened octahedral to dodecahedral form. They are rane with a lateral extent of at least 450,000 km2. Di-
colorless to gray, oftentimes resorbed, and contain amonds from Guyana are of scientific interest
peridotitic-type inclusions such as forsterite (Araújo because they are survivors of >2 Ga of weathering
et al., 2011). The Tepequém Formation represents a and erosion. As such, they are >2 billion-year-old
regional high-energy, depositional basin that was a xenocrysts from the mantle, brought to the surface
diamond sink, synchronous with emplacement by by some of the earth’s oldest kimberlite or lamproite
several episodes of kimberlite volcanism within the eruptions. They are an important source of informa-
Guiana Shield during the middle Paleoproterozoic tion on the cratonic root of northern South America
(>2.0 Ga) (Santos et al., 2003; Schulze et al., 2006). In during the Paleoproterozoic (Schulze et al., 2006; Bas-
Suriname, alluvial diamonds are thought to be de- soo and Befus, 2021).
rived from rocks of the Rosebel Formation (Naipal et There is opportunity for expanded economic use
al., 2020). These are colorless to brown to slightly of Guyana’s diamonds. Although small, they are val-
green, and green skins are common (figure 18, top). ued for their lack of color and their clarity, especially
Resorption textures including trigons and frosting are as melee stones. Artisanal mining practices result in
common, and inclusions such as forsterite and ensta- a relatively low price point, and they are not subject
tite are peridotitic. French Guiana is also home to to prohibitive taxation. With continued exploration
primary diamond-bearing igneous sources, but these efforts, new paleoplacer deposits are sure to be dis-
are metamorphosed ultramafic and pyroclastic covered. The discovery of a primary kimberlite de-
shoshonites or lamprophyres found in the Dachine posit should not be expected, but abrasion and

152 DIAMONDS FROM GUYANA GEMS & GEMOLOGY SUMMER 2022

 2 mm

1 mm

4 mm

Figure 18. Top: Diamonds (0.10–2.12 ct) from Suriname; from Naipal et al. (2020). Middle: French Guiana dia-
monds; from Cartigny (2010). Bottom: Alluvial diamonds from Guaniamo, Venezuela. Photo by Maha Tannous;
courtesy of Ric Taylor.

DIAMONDS FROM GUYANA GEMS & GEMOLOGY SUMMER 2022 153

luminescence information could indicate that some common knowledge regarding their quality or
stones have experienced little transport and thermal sources. Tourmaline is also present but has only been
alteration. We also recognize an opportunity for the documented as schorl. Such diverse gem and mineral
exploration and improved recovery of other gem- wealth bodes well for future discoveries in this Eng-
stones. Ruby, sapphire, and topaz are considered in- lish-speaking nation with an established gemstone
dicator minerals for gold and diamonds. There is no mining and trade network.

ABOUT THE AUTHORS ACKNOWLEDGMENTS

Dr. Bassoo is a Guyanese geoscientist and consulting geologist The authors sincerely thank James Krakowsky (general manager
who is currently a postdoctoral researcher at GIA in Carlsbad, of Kays Diamond Enterprise Ltd.) for his gemological input and
California. Dr. Befus is a petrologist and volcanologist who serves samples donated for study. Gordon Nestor (manager at the
as a professor of geology at Baylor University in Waco, Texas. Guyana Geology and Mines Commission) provided valuable lo-
gistical support. We are grateful to Jim Shigley of GIA for his en-
couragement to prepare this article for the gemological
community. We also thank Rachelle Turnier and Aaron Palke of
GIA for their assistance in identifying corundum specimens.

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to present, http://www.nma.org/pdf/g_prices.pdf tion of the Earth’s mantle and the distance to their kimberlitic
Persaud K. (2010) The diamond industry and exploration for dia- sources. Economic Geology, Vol. 101, No. 2, pp. 453–470,
monds in Guyana. Guyana Geology and Mines Commission. http://dx.doi.org/10.2113/gsecongeo.101.2.453
Priem H.N.A., Boelrijk N.A.I.M., Hebeda E.H., Verdurmen Tassinari C.C.G. (1997) The Amazonian Craton. In M.J. De Wit
E.A.Th., Verschure R.H. (1973) Age of the Precambrian Ro- and M.J. Ashwal, Eds., Greenstone Belts. Clarendon Press, Ox-
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For online access to all issues of GEMS & GEMOLOGY from 1934 to the present, visit:

gia.edu/gems-gemology

DIAMONDS FROM GUYANA GEMS & GEMOLOGY SUMMER 2022 155

FEATURE ARTICLES

THE SHAPE OF EKANITE

Lutz Nasdala, K.A. Geeth Sameera, G.W.A. Rohan Fernando, Manfred Wildner, Chutimun Chanmuang N.,
Gerlinde Habler, Annalena Erlacher, and Radek Škoda

Despite its high thorium content, and consequent radioactivity, ekanite is still commonly traded in the Sri Lankan
gem market. Gem-quality ekanite is derived from several gravel deposits in the country. However, rough speci-
mens do not show rounded shapes that would be expected for stones transported by water; rather, they have
remarkably uneven surfaces with multitudes of hollows, bumps, and cavities. Only after the recent discovery of
ekanite in its host calc-silicate rock near Ampegama, Southern Province, can the striking shapes be understood.
Fluid-driven alteration of ekanite, still inside the host rock, results in the formation of banded nodules with het-
erogeneous disintegration rims of an earthy consistency. These rims are readily removed by weathering, whereas
the interior remnant consisting of chemically and physically resistant, unaltered ekanite persists.

I
n secondary gem deposits in Sri Lanka, ekanite is
a rare mineral, but when found, it frequently oc-
curs with gem characteristics. Rough pebbles have
remarkable outer shapes that show concave dents
and hollows (figure 1). Apart from its shape, the
gemological properties of ekanite resemble those of
the borosilicate kornerupine. The most highly valued
stones from Sri Lankan deposits are clear, transpar-
ent, and show a vivid yellowish green that is remi-
niscent of the tender leaves of banana plants (figure
2). Most ekanite specimens are rich in inclusions and
show a turbid aspect and in some cases four-rayed as-
terism (Gübelin, 1961). Ekanite (ideally Ca2ThSi8O20)
is a phyllosilicate whose thorium content of about
24 wt.%, along with minor uranium, causes harmful
radioactivity (Tennakone, 2011) that makes stones
unsuitable for setting in daily-worn jewelry, though
different assessments seem to exist. Ashbaugh (1988)
found that gem ekanite is tens of times more radioac-
tive than “low zircon” stones of comparable weight.
Gübelin (1961) came to the conclusion that ekanites
could be worn in jewelry without any greater harm, Figure 1. This specimen (2.95 g, 22 mm in longest
whereas De Silva (2008) mentioned “three reported dimension) from Ellawala, Sabaragamuwa
deaths due to keeping ekanites at close proximity to Province, shows the typical surface texture of rough
three gem dealers.” High-quality faceted ekanites are ekanite found in Sri Lankan placers. Photo by Man-
nevertheless highly sought-after collector items, fred Wildner.
even though prospective buyers should exercise safe
handling.
Ekanite is named after its discoverer, Francis Leo
Danvil Ekanayake (1898–1971), a Colombo-based
customs officer and Fellow of the Gemmological As-
See end of article for About the Authors and Acknowledgments.
GEMS & GEMOLOGY, Vol. 58, No. 2, pp. 156–167,
sociation of Great Britain. Ekanayake’s contempo-
http://dx.doi.org/10.5741/GEMS.58.2.156 raries considered him a capable and painstaking
© 2022 Gemological Institute of America gemologist with a flair for the unusual (Mitchell,

156 THE SHAPE OF EKANITE GEMS & GEMOLOGY SUMMER 2022

 Figure 2. In transmitted
light, many ekanite
specimens show an at-
tractive yellowish green
color. The rough stone
(2.90 g) measures 20
mm in longest dimen-
sion and the cut stones
are 0.65 ct and 2.73 ct.
All the specimens origi-
nate from placers near
Okkampitiya, Uva
Province. Photo by
Manfred Wildner.

1961), in addition to being well-versed in rare gem Over the intervening years, ekanite has been dis-
minerals (Gübelin, 1961). In 1953, Ekanayake came covered in several other localities in Sri Lanka (Dis-
across two unusual glassy cabochons in the local sanayake and Rupasinghe, 1993; Mathavan et al.,
Colombo gem market that originated from a river- 2000; Nasdala et al., 2017; Sameera et al., 2020a,b; see
bed gem pit near Ellawala. Immediately he was con- figure 3) and other countries (e.g., Demartin et al.,
vinced he had found a new gem species, whereas 1982; Walstrom and Dunning, 2003; Russo et al.,
others considered the material to be devitrified nat-
ural or antique glass (Mitchell, 1954). Ekanayake’s
conviction was supported by the observation that the
material, despite being a glass, contained numerous In Brief
acicular inclusions having crystallographic orienta- • Despite being found in gravel deposits, Sri Lankan gem
tion (Mitchell, 1961). Investigations continued for ekanites do not show rounded but remarkably uneven
more than seven years, until a note describing the shapes.
new mineral was published (Anderson et al., 1961). • Only recently, ekanite was found in its calc-silicate
The original ekanite was characterized as meta- host rock.
mict by Anderson et al. (1961). The notion of metam- • Here, ekanites show features of fluid-driven alteration
ict goes back to Brøgger (1893), who used metamikte progressing inward, and botryoidal growth of alteration
to describe a class of minerals that show well-shaped products leads to convex surface shapes of the prod-
uct-phase aggregates.
crystal forms despite being amorphous. Today, the
term is applied irrespective of the outer form to de- • After weathering of the alteration products, chemically
durable ekanite remnants having concave surface fea-
lineate minerals that were initially crystalline but
tures are left.
transformed to a glassy state due to internally or ex-
ternally sourced irradiation over time (Hamberg,
1914; Ewing et al., 1987; Ewing, 1994). It took more
than two decades after the initial description until a 2013). One remarkable feature of Sri Lankan ekanite
non-metamict ekanite (tetragonal space group I422) is that most specimens, unlike other gems in placer
was found in the Tombstone Mountains of Canada’s deposits, are not water-worn crystals or rounded peb-
Yukon Territory (Szymański et al., 1982). bles. Rather, the rough material typically shows

THE SHAPE OF EKANITE GEMS & GEMOLOGY SUMMER 2022 157

 Kurunegala N
Ampara
Kandy
Figure 3. Simplified geo-
logical map of southern
Nuwara Eliya
Badulla
Sri Lanka (modified
7°N COLOMBO Passara from Mathavan and
? Fernando, 2001; Kröner
Ellawala
Buttala et al., 2013). Locations
Okkampitiya
? Ratnapura of ekanite occurrences
B
are highlighted in red
(major cities are in
Rakwana KO
black). Question marks
K between Highland
Complex and Wanni
Ampegama
Makumbura
Complex were adopted
from the original refer-
Galle
6°N Matara ences; they indicate
that the boundary is
Wanni Complex Highland Complex Kadugannawa Complex
uncertain and merely
B = Buttala Klippe
inferred based on field
Vijayan Complex K = Kataragama Klippe Miocene to Quaternary evidence.
KO = Kuda Oya Klippe
Ranna Complex
80°E 81°E 0 50 km

shapes that—along with the green color—bear a strong plane-parallel sections (250 and 1020 μm thickness)
resemblance to moldavite-type tektite (see again fig- were prepared from a separated ekanite fragment.
ure 1; compare to Bouška, 1994; Hyršl, 2015). The un- After measuring the refractive index and obtaining
derlying causes of the rough surface textures in optical absorption spectra, the slabs were heat-
ekanite are discussed in the present paper, along with treated in air (the 250 mm slab at 1400°C and the
an explanation of why attempts by local gem dealers 1020 μm slab at 750°C) for 48 h. After gentle repol-
to enhance ekanite by heat treatment invariably fail. ishing, even the (now dull) 250 μm slab was found to
be still too thick for optical absorption spectroscopy
SAMPLES AND EXPERIMENTAL METHODS and therefore thinned to 110 μm thickness. After we
The authors have studied ekanite fragments and obtained another optical absorption spectrum, this
ekanite-containing specimens of calc-silicate rock slab was embedded in epoxy and subjected to chemo-
we collected in a quarry near Ampegama (for a brief mechanical repolishing with an alkaline colloidal sil-
petrological description, see Sameera et al., 2020a), ica suspension on a polyurethane plate, for the
located about 20 km north-northwest of the city of removal of potential near-surface strain. After being
Galle in Southern Province (see again figure 3). Ekan- coated with carbon, it was subjected to forward-scat-
ite specimens from Ellawala in Sabaragamuwa tered electron (FSE) imaging, as described below.
Province and Okkampitiya in Uva Province were Specific gravity was determined by weighing three
photographed to illustrate the typical shapes of this ekanite chips in distilled water and in air. A drop of
mineral in Sri Lankan gem placers. These are the lead liquid detergent was added to the distilled water to de-
author’s samples, purchased from local miners. crease surface tension. Refraction of the polished slab
Four Ampegama rock samples containing ekanite was measured using a Krüss ER601-LED refractome-
were impregnated with Araldite epoxy and cut using ter equipped with a diode lamp emitting 589 nm light.
a diamond saw blade. A polished section and an ex- Both measurements were repeated five times.
posed 25 mm thin section attached to a glass slide Macroscopic luminescence images were taken
were produced from each rock sample. Thin sections using a long-wave UV lamp or 385 nm LED illumina-
were carbon-coated for back-scattered electron (BSE) tion. Photomicrographs of thin sections (including op-
imaging and electron probe micro-analysis (EPMA), tical images in plane-polarized transmitted-light mode
as described below. In addition, double-side polished and luminescence images in reflected-light mode)

158 THE SHAPE OF EKANITE GEMS & GEMOLOGY SUMMER 2022

were obtained by means of a modified Olympus BX- Analyses were done using a Horiba LabRAM HR
series microscope equipped with a USH-103OL mer- Evolution spectrometer. This dispersive system was
cury burner and DP 70 digital camera, using a equipped with an Olympus BX-series optical micro-
UV-transmissive XL Fluor 4×/340 objective (numeri- scope and a Peltier-cooled, Si-based charge-coupled
cal aperture 0.28). Here, luminescence images were device detector. Raman spectra of the inclusions in
obtained with a beam splitter and filters in the optical ekanite were excited using a 473 nm diode laser (11
pathway that allowed us to illuminate the sample mW at the sample), Raman measurements of the al-
with UV light (<370 nm wavelength) and to photo- teration rims were conducted with a 633 nm He-Ne
graph only the sample’s visible emissions (>400 nm (10 mW) and a 785 nm diode laser (24 mW), and PL
wavelength). BSE and FSE images were obtained in an was excited using an external, air-cooled 407 nm
FEI Quanta 3D FEG dual-beam field-emission gun diode laser (500 mW; unfocused laser beam). The
scanning electron microscope (FEG-SEM) operated at emitted PL and Raman scattered light, respectively,
15 kV and 4 nA. The sample tilt was 70°, and the FSE were collected using a 50× objective (numerical aper-
detector position was adjusted to yield predominant ture 0.50; free working distance 10.6 mm) and dis-
orientation contrast. For the basic principles of FSE persed using a diffraction grating with 1800 grooves
orientation-contrast imaging, see Prior et al. (1996). per millimeter. The spectral resolution was about 1
Major-element analyses were done using wave- cm–1. More experimental details are described else-
length-dispersive X-ray spectrometry on a Cameca where (Zeug et al., 2018).
SX 100 EPMA system operated at 15 kV. The beam
current was set to 20 nA for analyzing unaltered (or RESULTS AND DISCUSSION
“fresh”) ekanite and 10 nA for alteration products.
The focal-spot diameter of the electron beam was 8– General Characterization. Near Ampegama, ekanite
10 μm. The following minerals and synthetic mate- is found as a rare constituent of a calc-silicate meta-
rials were used for calibration (lines analyzed and morphic rock composed primarily of diopside, wollas-
peak counting times are quoted in parentheses): an- tonite, K-feldspar, and scapolite, occasionally together
dalusite (Al-Kα, 20 s), wollastonite (Si-Kα, 20 s; Ca- with minor fluorite and graphite (Sameera et al.,
Kα, 20 s), almandine (Fe-Kα, 20 s), vanadinite 2020a). Ekanite mostly occurs as xenomorphic nod-
(Pb-Mα, 120 s), CaTh(PO4)2 (Th-Mα, 20 s) and UO2 ules up to 3 cm in size. Many but not all of them are
(U-Mβ, 80 s). Background counting times were half surrounded by orange to pale brownish alteration rims
of the respective peak counting times. Cameca’s with an earthy consistency. In fresh conditions, the
Peaksight software, which is based on the method of mineral is vivid olive green to yellowish green. Close
Ziebold (1967), was used to calculate detection lim- to the alteration rims, it may in some cases show dis-
its. Matrix correction and data reduction were done coloration and appear greenish blue (figure 4A). The
using the modified ϕ(ρz) routine of Merlet (1994). Ad- material is transparent and exhibits conchoidal to un-
ditional EPMA experimental details are described even fracture. Unaltered ekanite has a vitreous luster
elsewhere (Breiter et al., 2009; Škoda et al., 2015). and is isotropic. As ekanite is in fact tetragonal, the
Room-temperature optical absorption spectra were observed isotropy indicates that the material is pres-
obtained using a Bruker IFS66v/S spectrometer ent in a metamict (i.e., glassy) state. Its RI was 1.59 ±
equipped with a mirror-optics IR-scope II microscope 0.01, and the SG was determined as 3.27 ± 0.01. Ekan-
and quartz beam splitter. The following combinations ite is apparently non-luminescent under both long-
of light sources and detectors were used: W lamp and wave and short-wave UV light.
Ge detector (for the spectral range 7500–10000 cm–1), The results of EPMA chemical analyses are sum-
W lamp and Si detector (10000–20000 cm–1), and Xe marized in table 1. Ekanite from Ampegama, if unal-
lamp and GaP detector (20000–26000 cm–1). All optical tered, has a relatively uniform chemical composition
absorption spectra therefore consist of a combination that corresponds to the formula Ca2Th0.9U0.1Si8O20
of three sub-spectra, which were aligned to match in (calculated on the basis of 20 oxygen atoms per for-
absorbance if necessary. Circular areas 200 μm in di- mula unit). The composition is fairly similar to that
ameter were analyzed in transmission geometry. of ekanite from Ellawala (Anderson et al., 1961) and
Room-temperature Raman spectra of inclusions Okkampitiya (Nasdala et al., 2017). To the best of our
in ekanite were obtained from chips and polished knowledge, no analysis of ekanite from Rakwana in
sections, and photoluminescence (PL) spectra of the Sabaragamuwa Province, Passara in Uva Province
alteration rims were obtained from thin sections. (both were quoted by Dissanayake and Rupasinghe,

THE SHAPE OF EKANITE GEMS & GEMOLOGY SUMMER 2022 159

A B

C D

Figure 4. A: Transmitted-light photo of a rough ekanite (field of view 6 mm) from Ampegama with alteration-induced dis-
coloration and characteristic conchoidal fracture. It contains a large K-feldspar and numerous acicular inclusions. B: Needles
in the glassy host have a crystallographically controlled orientation conforming to the host’s previously tetragonal symme-
try (field of view 1.6 mm). C: Partially filled hollow needle (field of view 120 μm). D: Xenomorphic thorite inclusion associ-
ated with silica glass, wollastonite, and apatite (field of view 630 μm). Photomicrographs by Chutimun Chanmuang N.

1993), or Makumbura in Southern Province (Sameera Concordant 206Pb/238U and 207Pb/235U ratios of ekan-
et al., 2020b) has been undertaken thus far. ite from Okkampitiya (Nasdala et al., 2017) indicate

TABLE 1. Mean chemical composition (in wt.%) of Ampegama ekanite and its alteration products, obtained by
EPMA analysis.
Major oxidesa Unaltered ekanite Alteration rim (colorless) Alteration rim (brownish) Detection limit
(n = 13) (n = 6) (n = 7)

Al2O3 0.13 ± 0.01a,b 0.30 ± 0.33 0.14 ± 0.04 0.03

SiO2 56.2 ± 0.3 43.3 ± 1.4 51.8 ± 7.6 0.03

CaO 13.26 ± 0.11 9.82 ± 0.33 8.13 ± 4.26 0.05

FeO 0.23 ± 0.03 0.33 ± 0.03 0.18 ± 0.11 0.07

PbO 0.81 ± 0.05 0.83 ± 0.23 0.52 ± 0.17 0.10

ThO2 27.5 ± 0.5 35.0 ± 0.4 27.5 ± 2.8 0.13

UO2 2.61 ± 0.63 3.61 ± 0.32 2.76 ± 1.93 0.19

Total 100.7 ± 0.6 93.3 ± 1.3 91.1 ± 3.4

a
The elements F, Na, Mg, P, Sc, Ti (all 0.05), Mn (0.07), Sr (0.15), Y (0.08), Zr (0.11), La (0.15), Ce (0.16), Pr (0.24), Nd (0.23), and Sm (0.12) were
also sought for, but mean concentrations were below the EPMA detection limits (values in brackets, in wt.%).
b
All errors are quoted at the 2σ level.

160 THE SHAPE OF EKANITE GEMS & GEMOLOGY SUMMER 2022

that lead is mainly radiogenic and hence was widely phase inclusions that show a crystallographically
excluded during the primary growth of this mineral. controlled orientation of needles with the long axes
Assuming the same is true for the Ampegama ekanite, at 90° angles to each other (figure 4, A and B). This is
the measured mean concentrations of thorium (24.2 explained by the primary formation of tetragonal
wt.%), uranium (2.30 wt.%), and lead (0.75 wt.%; con- ekanite with crystallographically oriented inclusions
verted from the respective oxide concentrations quoted within the host crystal, followed by irradiation-in-
in table 1) are converted to a “chemical age” (Montel duced vitrification of ekanite that did not affect the
et al., 1996; Suzuki and Kato, 2008) of roughly 525 Ma. orientations of the inclusions. Some of the needles
From this age and present thorium and uranium con- are filled incompletely (figure 4C). Solid inclusions
centrations, and using the equation of Murakami et al. of irregular shape (figure 4D), determined by Raman
(1991), a time-integrated self-irradiation dose of 14.0 × spectroscopy, include thorite, quartz and silica glass,
1019 alpha events per gram of material is calculated. K-feldspar, apatite, wollastonite, and calcite.
This value exceeds the threshold of Sri Lankan zircon
to alpha-event amorphization (Zhang et al., 2000; Nas- Optical Absorption and Heat Treatment. Optical ab-
dala et al., 2002) by about one order of magnitude. It sorption spectra obtained from a natural ekanite slab
explains the present glassy state of ekanite as resulting and its heat-treated analogues are presented in figure
from extensive radioactive self-irradiation of initially 5. The green color of natural (metamict) ekanite is due
tetragonal ekanite over long time periods. to two main spectral features. First, there is an absorp-
This assignment is also supported by microscopic tion continuum, tentatively assigned to defect-related
observations. Similar to ekanite from Ellawala “color centers” (see, for instance, Greenidge, 2018),
(Mitchell, 1961; Gübelin, 1961), the Ampegama that gradually increases toward the blue–violet–UV
ekanite contains numerous acicular fluid and two- range of the electromagnetic spectrum. Second, there

Figure 5. Optical absorption spectra of green metamict ekanite, its analogue annealed at 750°C (left; sample thick-
nesses 1.02 mm), and a brownish green chip that was annealed at 1400°C (right; sample thickness 110 μm). The
reference spectrum of a green “low zircon” was obtained from sample N-17 (described in detail by Nasdala et al.,
2002). The reference spectrum of irradiation-spotted diamond is from Nasdala et al. (2013) and that of U4+-doped
ZrSiO4 from Zeug et al. (2018). Reference spectra are presented on an arbitrary absorbance scale. Spectral ranges
that are invisible to the human eye have gray background shade. Note the vast increase of the linear absorption
coefficient after high-temperature treatment of ekanite.

OPTICAL A BSORPTION SPECTRA

WAVELENGTH (nm) WAVELENGTH (nm)
1000 800 600 500 400 1000 800 600 500 400
8
LINEAR ABSORPTION COEFFICIENT (cm–1)

LINEAR ABSORPTION COEFFICIENT (cm–1)

Ekanite (annealed at 750˚C) Metamict zircon 150 Ekanite (annealed at 1400˚C)

Ekanite (natural) Green-spotted U4+-doped ZrSiO4
diamond
6

4
100

0 50

10000 15000 20000 25000 10000 15000 20000 25000

WAVENUMBER (cm–1) WAVENUMBER (cm–1)

THE SHAPE OF EKANITE GEMS & GEMOLOGY SUMMER 2022 161

is a pronounced absorption band in the red to orange
range whose maximum lies near 15700 cm–1 (637 nm
wavelength). This band could be assigned to Fe2+ or
Fe2+–Fe3+ charge transfer (Smith, 1978; compare to Ten-
nakone, 2011), which appears rather unlikely, how-
ever, because of the low iron concentration of 0.18
wt.% (converted from the FeO content of 0.23 wt.%
quoted in table 1). Note that Okkampitiya ekanite (see
again figure 2) is vivid yellowish green in spite of its
even lower iron content of only 0.11 wt.% (Nasdala et
al., 2017). Alternative assignments of the red-orange
band include the—strongly broadened—analogue of
the main U4+ absorption band in zircon (Kempe et al.,
2016), or an analogue of defect absorption in diamond
(GR1 = neutral carbon vacancy; Clark and Walker,
1973; Nasdala et al., 2013) or zircon (electron-hole de-
fect; Kempe et al., 2016). In the case of the latter, it ap- 20 μm

pears likely that the red-orange absorption band of Figure 6. Forward-scattered electron (FSE) image of
metamict ekanite is assigned to an oxygen-site va- ekanite annealed at 1400°C showing predominantly
cancy. Clarification of the issue might require syn- crystal-orientation contrast. The majority of the
thetic ekanite to be subjected to ion-irradiation flawed material (>98 vol.%) consists of polycrys-
experiments. talline ekanite whose individual polygonal crystals
The green color is explained by the joint effect of have diverse orientations, indicated by different lev-
a short-wavelength absorption continuum and a red- els of gray. Image by Gerlinde Habler.
orange band that bracket a “reduced absorption win-
dow” in the green to yellow range, at around 17850
cm–1 (560 nm). The fact that ekanite also transmits ray powder diffraction and Raman spectroscopy (Nas-
well in the long-wavelength range below 15000 cm–1 dala et al., 2017). In agreement with this latter result,
(above 665 nm) does not significantly affect the col- heating of Ampegama ekanite to 750°C in the present
oration, because of the relatively poor sensitivity of study did not affect the metamict state, and heating
the human eye in this spectral range. to 1400°C yielded polycrystalline, tetragonal ekanite.
Although Sri Lankan ekanite typically has green Recrystallized ekanite has an unattractive appear-
hues that are quite attractive for gem purposes, local ance, as it is brownish green to pale brownish and non-
dealers have undertaken several—always ineffec- transparent. Mitchell (1961) described it as
tive—attempts to enhance its color by heating. Pub- “putty-colored.” Compared to the transparent metam-
lished results on how metamict ekanite responds to ict starting material, the increase of the absorption
heating are decidedly contradictory. According to An- continuum toward low wavelengths is depleted, and
derson et al. (1961), recrystallization of the metamict the total absorbance is about 30–40 times higher (figure
material to a tetragonal phase with a body-centered 5, right). There are a number of narrow lines we assign
unit cell occurs in the range 650–1000°C. This unit to tetravalent uranium, based on their similarity to the
cell was later assigned to “true crystalline ekanite” absorption of U4+ in zircon (compare to Richman et al.,
by Szymański et al. (1982). At temperatures above 1967; Mackey et al., 1975). The huge increase in total
1000°C, Anderson et al. (1961) observed remelting absorbance, visually recognizable from the loss of
and formation of huttonite (ThSiO4). In contrast, transparency, is assigned to the transformation of a
Zeug et al. (2015) found that ekanite remains glassy glass to a polycrystalline compound. The texture of the
and transparent up to 900°C, while the yellowish annealing product is visualized through FSE imaging
green color becomes slightly more bluish (see also fig- (figure 6): The material consists mainly of numerous
ure 5, left). Zeug et al. (2015) detected initial nucle- polygonal, variably oriented ekanite crystals up to 50
ation of several poorly ordered phases only at around mm in size. Minor phases (USiO4, silica, Ca3Si3O9, and
1000°C. Between 1100 and 1450°C, crystalline ekan- others) occur as inclusions inside the ekanite crystals
ite formed, without any sign of melting. The 1450°C or along grain boundaries. Note that in initial recrys-
annealing product was identified as ekanite using X- tallization stages in a glassy phase, nucleation of other

162 THE SHAPE OF EKANITE GEMS & GEMOLOGY SUMMER 2022

phases may be energetically favored (Capitani et al., which is supported by their strongly deficient EPMA
2000). Also, high-temperature heating typically causes totals (table 1). Deficient analytical totals of alteration
loss of the radiogenic lead, which in turn disturbs the products may be caused by the presence of light ele-
initial equilibrium of Th+U+Pb with Ca and Si. Slight ments that are not analyzed in the EPMA, and they
deviation of the total composition from that of ekanite may also be due to their common sub-micrometer
necessarily leads to minor formation of other phases porosity (Pointer et al., 1988; Nasdala et al., 2009).
(for analogous effects in the annealing of zircon, see In plane-polarized transmitted light (figure 8), the
Nasdala et al., 2002). Both the presence of nanocrystals alteration rims appear heterogeneous, often with a
of these additional phases and the high number of grain banded texture, and consist of colorless and brownish
boundaries of fine-grained ekanite aggregates cause domains and zones. Compared to unaltered ekanite,
loss of transparency and increased absorption. In sum- the colorless alteration phase is strongly depleted in
mary, heating of metamict ekanite below the temper- silicon and calcium, whereas thorium is notably en-
ature of spontaneous nucleation (about 1000°C) has riched (table 1). The brownish domains show pro-
minor effects, whereas high-temperature annealing of nounced heterogeneity. Some yield lower and others
the material leads to the formation of a dull, polycrys- higher BSE intensity, compared to the neighboring un-
talline compound. The latter is therefore ill-advised in altered ekanite (figure 8, far left images). Correspond-
attempting enhancement. ingly the chemical composition of the brownish
domains is decidedly heterogeneous, indicated by
Study of Alteration Products. In the host rock, green large standard deviations from the mean values (table
ekanite is typically surrounded (or even completely 1). In cross-polarized transmitted light (figure 8), the
replaced) by yellowish gray to ochre assemblages of colorless alteration material does not show any inter-
secondary phases (figure 7A). These phases are inter- ference color, indicating that it has a glassy structure.
preted as products of fluid-driven alteration processes, The majority of brown regions, in contrast, show low

Figure 7. A: Hand-specimen (width 10.5 cm) of calc-silicate rock from Ampegama, containing several clear, dark
bottle-green ekanite nodules surrounded by yellow-to-ochre alteration products. Some smaller nodules are altered
completely (three are marked by arrows). B: Only the alteration products show intense greenish luminescence
under the long-wave UV lamp. C: PL image of a polished rock specimen (field of view 14 mm) obtained under 385
nm LED illumination. Alteration of the central metamict ekanite has started from the outer rim and internal frac-
tures. Photos by Manfred Wildner.

A C

THE SHAPE OF EKANITE GEMS & GEMOLOGY SUMMER 2022 163

Figure 8. Two series of BSE, plane-polarized transmitted-light, cross-polarized transmitted light, and PL images
(from left to right) showing heterogeneous alteration rims surrounding fresh metamict ekanite in the center. The
alteration rims emit intense green, uranyl-related photoluminescence. 30 μm thin section; field of view 1.72 mm.
BSE images by Chutimun Chanmuang N., all others by Lutz Nasdala.

birefringence. In some of the dark brown regions (fig- (figure 8, far bottom right image); here the green
ure 8, bottom row), aragonite was detected, whereas uranyl-related band is overlain by a broad band in the
the identification of all other alteration material using orange-red range whose cause remains unknown.
Raman spectroscopy failed, as no evaluable band pat- The PL spectra of many, but not all, uranyl-con-
terns were obtained. Interestingly, there is no signifi- taining crystalline minerals show a pattern consist-
cant lead loss in the alteration products, compared to ing of energetically equidistant bands (Gorobets and
fresh ekanite. The virtually unvaried presence of lead Sidorenko, 1974; deNeufville et al., 1981; Wang et al.,
in the alteration products may indicate either that 2008). Such patterns are also observed from natural
these phases did not exclude lead upon formation or opal (Fritsch et al., 2015; Othmane et al., 2016), syn-
that alteration occurred soon after ekanite formation, thetic glasses (Mahurin et al., 2003), and even uranyl
with subsequent transformation of thorium and ura- ions and complexes in solutions (McGlynn and
nium to lead in the alteration products themselves. Smith, 1961; Moulin et al., 1995). For comparison,
Further investigations will be needed to address this we collected the PL spectra of the uranyl-containing
issue. species metatobernite, hyalite, and a uranyl glass
Most of the alteration products show distinct under the same conditions (figure 9). Thus, the pres-
greenish luminescence under UV or violet-blue ex- ence or absence of a pattern of equidistant bands does
citation, while the fresh ekanite appears inert (figures not depend on the host’s crystallinity. Such patterns
7 and 8). A representative PL spectrum is presented are assigned to the coupling of electronic transitions
in figure 9. We assign the broad-band green emission with oscillations of the linear O=U=O groups. Ener-
to hexavalent uranium ions that are present in the getic differences among neighboring bands depend on
form of (UO2)2+ (i.e., uranyl) groups. The observation the frequencies of uranyl stretching vibrations and
of green, uranyl-related emission is consistent with hence allow the calculation of U=O bond distances
significant concentrations of uranium and relatively (Jones, 1959). The observation that the studied alter-
low concentrations of iron in the alteration products ation rims yield non-structured emission is ascribed
(table 1; compare to Gaillou et al., 2008). Only arag- to an overlay of many vibrational modes, due to ex-
onite-containing zones yield even more intense PL tensive irregularity of U=O bonds caused by exten-

164 THE SHAPE OF EKANITE GEMS & GEMOLOGY SUMMER 2022

 PL SPECTRA
WAVELENGTH (nm) In optical microscopy, the practical benefit of the
700 650 600 550 500 450 intense uranyl luminescence of the alteration prod-
ucts is that the shape of the central remnant of fresh
Alteration rim around ekanite
Uranyl glass
ekanite, which does not luminesce, is easily recog-
Hyalite nized (figure 10). The latter exhibits concave surface
Metatorbernite features analogous to that of rough ekanite speci-
mens (compare to figure 1). The formation of concave
surfaces is therefore explained by the alteration of
ekanite in its host rock, whose identity for all sec-
ondary deposits remains unknown. Fluid-driven al-
teration presumably has progressed inward, resulting
INTENSITY

in concentrically grown reaction rims of secondary

phases, at the expense of primary ekanite.

CONCLUSIONS
The physical properties, chemical composition, and
general appearance of Ampegama ekanite are broadly
similar to ekanite from other Sri Lankan locations, ex-
cept that the material is not found in a secondary de-
posit but in situ. In the calc-silicate host rock,
fluid-driven chemical alteration decomposes primary
ekanite, and the botryoidal growth of alteration prod-
15000 17500 20000 22500
ucts leads to convex surface shapes of the product-
WAVENUMBER (cm–1) phase aggregates, which in turn result in the concave
shapes of the ekanite remnant. It is a simple conclu-
Figure 9. PL spectrum (407 nm excitation) of the green- sion by analogy that the same may have happened in
luminescing alteration rim surrounding ekanite, com-
the (still unknown) host rocks of ekanite found near
pared with the spectra of three other uranyl-bearing
substances.
Ellawala and Okkampitiya. After weathering of the
host rock, the soft and earthy alteration products are
effectively removed, leaving behind rough ekanite
sively irregular arrangements of nearest neighbor with their dimpled surface patterns. As rough ekanite
atoms in the glassy structure. specimens found near Ellawala and Okkampitiya gen-

Figure 10. Pair of plane-

polarized transmitted-light
(left) and photoluminescence
(right) photomicrographs of a
strongly altered ekanite nod-
ule in its host calc-silicate
rock (30 μm thin section).
The central, well-preserved
remnant of metamict ekan-
ite is colorless and non-lumi-
nescent; its irregular shape
corresponds to that of rough
specimens found in placers.
Photomicrographs by Lutz
Nasdala; field of view 5.1
mm.

THE SHAPE OF EKANITE GEMS & GEMOLOGY SUMMER 2022 165

erally show high degrees of preservation of such sur- ing of the host rock to the place of deposition must be
face features, in most cases virtually without abrasion short. Consequently, it appears likely that the ekanite
signs, transport pathways from the point of weather- is rather eluvial or colluvial.

ABOUT THE AUTHORS ACKNOWLEDGMENTS

Professor Dr. Nasdala is chairholder for Mineralogy and Spec- Most of the samples studied herein were obtained during a
troscopy, Prof. Dr. Wildner and Dr. Chanmuang N. are re- February 2020 field trip co-organized by E. Gamini Zoysa. Ex-
searchers, and Ms. Erlacher is a student, at the Institut für port permission for rock samples was kindly granted by the Ge-
Mineralogie und Kristallographie, University of Vienna. Mr. ological Survey and Mines Bureau. Sample preparation was
Sameera is a geologist working at the Geological Survey and done by Andreas Wagner. Gerald Giester, Christoph A.
Mines Bureau in Sri Jayawardenepura Kotte, and student at the Hauzenberger, Friedrich Koller, and Robert F. Martin are
Postgraduate Institute of Science, University of Peradeniya. Prof. thanked for helpful discussions. Constructive comments and
Dr. Fernando is chairholder for Geology at the Department of suggestions of three anonymous peers are gratefully acknowl-
Physics, Faculty of Natural Sciences, The Open University of Sri edged. Authors LN and AE acknowledge travel support from
Lanka in Nugegoda. Dr. Habler is a researcher at the Department the Faculty of Geosciences, Geography and Astronomy, Uni-
für Lithosphärenforschung, Vienna University. Dr. Škoda is a re- versity of Vienna.
searcher at the Department of Geological Sciences, Faculty of
Science, Masaryk University in Brno.

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THE SHAPE OF EKANITE GEMS & GEMOLOGY SUMMER 2022 167

FEATURE ARTICLES

A GEMOLOGICAL AND SPECTROSCOPIC

STUDY WITH MOBILE INSTRUMENTS OF
“EMERALDS” FROM THE CORONATION
CROWN OF NAPOLEON III
Stefanos Karampelas, Eloïse Gaillou, Annabelle Herreweghe, Farida Maouche, Ugo Hennebois, Sophie Leblan,
Bérengère Meslin Sainte Beuve, Michel Lechartier, Didier Nectoux, and Aurélien Delaunay

Forty-five “emeralds,” formerly set in the coronation crown of Napoleon III, were studied using nondestructive
mobile spectroscopic and gemological means. Adorned with emeralds, diamonds, and gold, the crown was cre-
ated in 1855 by royal jeweler Alexandre Gabriel Lemonnier but dismantled in 1887 for the auctioning of the
French crown jewels. Some of the emeralds were donated to the École des Mines (Paris School of Mines, now
known as Mines Paris - PSL) in 1887, prior to the auction. Our examination revealed that 41 out of 45 gems
were indeed natural emeralds, presenting no evidence of clarity enhancement. Their gemological characteristics
and age suggest a Colombian provenance. The other four samples were determined to be artificial glass con-
taining iron and/or copper and possibly other chromophores. These glass imitations could have been set when
the crown was created or shortly thereafter. This study is part of an effort to examine gemstones of historical
meaning and significance worldwide.

T
he collection of the French crown jewels was were heavily guarded and attracted large crowds of
established on June 15, 1530, by Francis I and admirers. However, the popularity of the two events
enriched by later kings and emperors, such as did not prevent the unprecedented sale of this na-
Henry II, Henry IV, Louis XIV, Napoleon I, Louis tional treasure.
XVIII, and Napoleon III. This important collection
of loose gemstones and high-end jewelry included
many significant gems: the Regent, Grand Sancy,
and French Blue (later Hope) diamonds; the Grand In Brief
Sapphire; and the Côte de Bretagne red spinel (see • Forty-five “emeralds” formerly set in the coronation
Bapst, 1889 and Morel, 1988 for details on the col- crown of Napoleon III were studied with nondestruc-
lection and its history). It is worth mentioning that tive mobile gemological and spectroscopic means.
most of the jewels were kept as individual stones • Of these, 41 samples were found to be natural emer-
and used in custom settings designed for each new alds from Colombia without clarity enhancement.
sovereign, and then dismantled again when a succes- • Four samples were found to be artificial glass con-
sor came to power. taining iron and/or copper and possibly other
After the end of the French Empire, the crown chromophores; no evidence of recently fabricated
jewels were exhibited twice in Paris, in 1878 at the glass was found.
Exposition Universelle (World’s Fair) and in 1884 in
the State Room at the Louvre. Both exhibitions
During the French Third Republic, most of the
crown jewels were dismantled and sold at an auction
See end of article for About the Authors and Acknowledgments.
GEMS & GEMOLOGY, Vol. 58, No. 2, pp. 168–183,
at the Louvre, held May 12–23, 1887. The auction
http://dx.doi.org/10.5741/GEMS.58.2.168 was intended to get rid of these symbols of royalty
© 2022 Gemological Institute of America and empire. Some unset gems, however, were put

168 STUDY OF GEMS FROM THE CROWN OF NAPOLEON III GEMS & GEMOLOGY SUMMER 2022
 Figure 1. The original
document detailing the
donation of the unset
gems from the French
crown jewels to the
École des Mines, dated
February 8, 1887. There
are three lines in the list-
ing that mention emer-
ald: 46 beads of emerald
(not part of this study),
16 emeralds weighing
16.79 carats total, and
34 small emeralds
weighing 10.03 carats
total. Catalog no.
M.4849, year 1887,
ENSMP Mineralogy Mu-
seum collection. Photo
by Didier Nectoux; ©
Museum of Mineralogy,
Mines Paris - PSL.

aside and given to various French museums, includ- crown jewels as part of the “Earth’s Treasures” ex-
ing the French Natural History Museum, the Louvre, hibit. Most of the other gems and jewels are still in
and the École des Mines, all in Paris. On February 8, private collections, though a few have found their
1887, the École des Mines received two small dia- way into museums, including the Napoleon dia-
monds, 915 pearls, 96 Colombian emeralds, 177 mond necklace (Gaillou and Post, 2007) and the
Siberian amethysts, and 59 Brazilian pink topazes Hope diamond (Patch, 1976; Balfour, 1987; Post and
(figure 1). For additional historical background on the Farges, 2014) at the Smithsonian Institution in Wash-
French crown jewels, see Morel (1988). ington, DC.
Since the late twentieth century, the Louvre has This article presents the results of research con-
bought back a few pieces of jewelry, which are on ex- ducted on emeralds formerly mounted in Napoleon
hibit at the Apollo Gallery and in the Apartments of III’s coronation crown. It follows previous scientific
Napoleon III. The National Museum of Natural His- articles dedicated to the study of historic gems in mu-
tory in Paris displays its loose gems from the French seums worldwide (e.g., Bosshart, 1989; Kane et al.,

STUDY OF GEMS FROM THE CROWN OF NAPOLEON III GEMS & GEMOLOGY SUMMER 2022 169
Figure 2. Left: A reproduction of the crown of Napoleon III, displayed at the Abeler collection of crowns and re-
galia in Wuppertal, Germany. Modified from Wikimedia Commons. Right: The royal jeweler Lemonnier also pro-
duced a very similar crown for Empress Eugénie in 1855. Photo by Stéphane Maréchalle; courtesy of RMN-Grand
Palais (Louvre Museum).

1990; Fritsch et al., 2007; Gaillou and Post, 2007; Gail- rectangular step-cut stones forming an equator
lou et al., 2010, 2012, 2022; Galopim de Carvalho, around the globe atop the crown (and topped with a
2014; Post and Farges, 2014; Farges et al., 2015). These diamond cross) with a total weight of 10.03 carats,
gems from the crown were kept in the vault of the and 16 round and oval brilliant-cut stones circling
museum of the École des Mines in Paris until 2016, the midsection, with a total weight of 17.26 carats.
when the museum opened an exhibition of gems from Morel (1988, p. 338) notes that shortly after the
the French crown jewels. The present paper is part of crown’s creation, the eight large diamonds were re-
an ongoing project on the study of the gems previously moved and later used in other jewels of Empress Eu-
adorning historic jewels, led by the French Gemmo- génie, replaced by “strass” (artificial glass, possibly
logical Laboratory (LFG) and the Museum of Mineral- containing lead) imitations. Morel also noted that the
ogy, Mines Paris - PSL, which owns the gems. emeralds were left set in the crown.
The crown (figure 2, left) was created in 1855 by Five years after the fall of the empire, the eight
royal jeweler Alexandre-Gabriel Lemonnier and pre- large emeralds were restituted to Empress Eugénie
sented at the “Exposition Universelle” in Paris the on October 5, 1875. In 1887, Napoleon III’s crown
same year. Lemonnier’s very similar crown for Em- was melted down and the stones were separated into
press Eugénie is shown in figure 2 (right). Napoleon different suites. During the auction of the French
III’s crown was adorned at the bottom part with eight crown jewels in May 1887, the eight large diamonds
large emeralds ranging from 14.5 to 23.7 ct (with a were sold to the highest bidder (the diamond cross
total weight of more than 150 carats) as well as eight was sold to the jeweler Boucheron earlier that year).
large diamonds weighing 17.00 to 26.33 ct that were The 50 smaller “emeralds” were part of the donation
previously mounted in another royal crown. These to the École des Mines. Today, 33 of the 34 gems
diamonds included the 19.07 ct Grand Mazarin, the from the upper part of the crown as well as 12 of the
19.22 ct De Guise, and the 25.53 ct Fleur-de-Pêcher. 16 gems from the midsection are cataloged in the
Fifty smaller “emeralds” were also incorporated: 34 Museum’s collection, and these are presented below.

170 STUDY OF GEMS FROM THE CROWN OF NAPOLEON III GEMS & GEMOLOGY SUMMER 2022
MATERIALS AND METHODS As the ENSMP collection has evolved over the
Examined here are the 45 green stones, reportedly 135 years since the gems from the crown jewels ar-
emeralds, that were donated during the Third Repub- rived, the donation that was deposited under a single
lic’s historical deposit of 1887 into the collection of reference number was dispatched into several catalog
the École des Mines (formally the École Normale numbers. The 50 emeralds from Napoleon III’s crown
Supérieure des Mines de Paris, or ENSMP), now were divided into three series. The first series con-
called Mines Paris - PSL. The catalog numbers of the sists of the previously mentioned 34 emeralds from
school’s mineral, gem, meteorite, and rock collection the top part of the crown, under the name ENSMP
still bear the initials “ENSMP,” all entered under a 69880, 33 of which are still in the collection (figure
single catalog number: all entered under a single old 3 and table 1; note that sample ENSMP 69880_5 is
catalog number: M. 4849. missing). The second series of 16 emeralds from the
This study investigates some of the 96 emeralds midsection of the crown was split into at least two
that were part of this original donation; the 46 emer- catalog numbers—four stones under ENSMP 69881
ald beads are excluded. We only focus on the gems and eight under ENSMP 69866 (figure 4 and table
mentioned as “16 emeralds of 16.79 carats” and “34 1)—while the last four remain missing. The reason
emeralds of 10.03 carats” in total weight (see again for splitting this second series is not clear, but as we
figure 1), as these can be traced back to the corona- will see later, series ENSMP 69881 has characteris-
tion crown of Napoleon III. Among the 50 emeralds tics unlike the others.
donated in 1887, 45 of them are still in the museum’s As the set of 45 samples is considered a national
collection, the curators having no record of the re- treasure, the project had to be conducted on-site at
maining five. the Museum of Mineralogy, Mines Paris - PSL. Be-

Figure 3. The 33 emeralds of suite ENSMP 69880, originally set in the crown of Napoleon III, ranging from 0.180 to
0.408 ct. Photo by Eloïse Gaillou; © Museum of Mineralogy, Mines Paris - PSL.

STUDY OF GEMS FROM THE CROWN OF NAPOLEON III GEMS & GEMOLOGY SUMMER 2022 171
TABLE 1. Properties of samples from the crown of Napoleon III.

Reference number Weight (ct) Dimensions (mm) Shape/Cutting Style

ENSMP 69866_1 1.156 7.12–7.19 × 3.48 Round/Brilliant

ENSMP 69866_2 1.071 7.11–7.22 × 3.42 Round/Brilliant

ENSMP 69866_3 0.955 6.90 × 6.23 × 3.67 Oval/Brilliant

ENSMP 69866_4 1.339 7.06–7.18 × 4.11 Round/Brilliant

ENSMP 69866_5 1.036 7.10–7.21 × 3.23 Round/Brilliant

ENSMP 69866_6 0.929 6.92–7.13 × 3.10 Round/Brilliant

ENSMP 69866_7 1.091 6.95–7.19 × 3.40 Round/Brilliant

ENSMP 69866_8 0.854 6.93–7.07 × 3.07 Round/Brilliant

ENSMP 69880_1 0.366 4.67 × 3.73 × 3.05 Rectangular/Step

ENSMP 69880_2 0.299 4.43 × 3.78 × 2.45 Rectangular/Step

ENSMP 69880_3 0.408 4.77 × 3.81 × 3.23 Rectangular/Step

ENSMP 69880_4 0.293 4.44 × 3.59 × 2.65 Rectangular/Step

ENSMP 69880_6 0.305 4.60 × 3.69 × 2.52 Rectangular/Step

ENSMP 69880_7 0.317 4.48 × 3.72 × 2.71 Rectangular/Step

ENSMP 69880_8 0.310 4.14 × 3.85 × 3.03 Rectangular/Step

ENSMP 69880_9 0.342 4.38 × 3.71 × 2.91 Rectangular/Step

ENSMP 69880_10 0.358 4.65 × 3.73 × 2.90 Rectangular/Step

ENSMP 69880_11 0.214 3.86 × 3.42 × 2.47 Rectangular/Step

ENSMP 69880_12 0.364 4.54 × 3.72 × 3.03 Rectangular/Step

ENSMP 69880_13 0.361 4.62 × 3.70 × 3.10 Rectangular/Step

ENSMP 69880_14 0.303 4.67 × 3.67 × 2.66 Rectangular/Step

ENSMP 69880_15 0.343 4.44 × 3.68 × 2.91 Rectangular/Step

ENSMP 69880_16 0.344 4.61 × 3.70 × 2.80 Rectangular/Step

ENSMP 69880_17 0.315 4.60 × 3.64 × 2.48 Rectangular/Step

ENSMP 69880_18 0.371 4.63 × 3.74 × 3.06 Rectangular/Step

ENSMP 69880_19 0.331 4.54 × 3.66 × 2.84 Rectangular/Step

ENSMP 69880_20 0.236 3.88 × 3.45 × 2.44 Rectangular/Step

ENSMP 69880_21 0.317 4.47 × 3.69 × 2.81 Rectangular/Step

ENSMP 69880_22 0.381 4.70 × 3.71 × 3.18 Rectangular/Step

172 STUDY OF GEMS FROM THE CROWN OF NAPOLEON III GEMS & GEMOLOGY SUMMER 2022
TABLE 1 (continued). Properties of samples from the crown of Napoleon III.

Reference number Weight (ct) Dimensions (mm) Shape/Cutting Style

ENSMP 69880_23 0.318 4.54 × 3.61 × 2.64 Rectangular/Step

ENSMP 69880_24 0.297 4.61 × 3.64 × 2.54 Rectangular/Step

ENSMP 69880_25 0.240 3.87 × 3.47 × 2.68 Rectangular/Step

ENSMP 69880_26 0.327 4.55 × 3.69 × 2.75 Rectangular/Step

ENSMP 69880_27 0.245 3.91 × 3.65 × 2.57 Rectangular/Step

ENSMP 69880_28 0.229 3.90 × 3.40 × 2.56 Rectangular/Step

ENSMP 69880_29 0.217 3.93 × 3.81 × 2.09 Rectangular/Step

ENSMP 69880_30 0.287 3.97 × 3.50 × 3.02 Rectangular/Step

ENSMP 69880_31 0.233 4.34 × 3.88 × 2.08 Rectangular/Step

ENSMP 69880_32 0.247 3.91 × 3.62 × 2.42 Rectangular/Step

ENSMP 69880_33 0.221 3.91 × 3.61 × 2.27 Rectangular/Step

ENSMP 69880_34 0.180 3.83 × 3.67 × 1.88 Rectangular/Step

ENSMP 69881_1 0.939 5.86–5.87 × 4.04 Round/Brilliant

ENSMP 69881_2 0.703 5.28–5.39 × 3.83 Round/Brilliant

ENSMP 69881_3 0.929 5.84–5.87 × 3.98 Round/Brilliant

ENSMP 69881_4 0.919 5.80–5.83 × 3.92 Round/Brilliant

cause of this constraint, the samples were studied gemological tools. The samples and their dimensions
using LFG’s mobile spectrometers as well as classical are listed in table 1. All samples were examined with

Figure 4. A: The eight emeralds from suite ENSMP 69866, ranging from 0.854 to 1.339 ct. B: The four stones from
suite ENSMP 69881, weighing from 0.703 to 0.939 ct. Photos by Eloïse Gaillou; © Museum of Mineralogy, Mines
Paris - PSL.

A B

STUDY OF GEMS FROM THE CROWN OF NAPOLEON III GEMS & GEMOLOGY SUMMER 2022 173
classic gemological tools. Observation was performed RESULTS AND DISCUSSION
using a Zeiss Stemi 508 binocular microscope (mag-
Gemological Properties and Appearance. Dimen-
nification up to 80×) equipped with a fiber-optic light
sions, weights, and shapes and cutting styles of the
source and an incorporated camera to acquire photos
45 examined samples are presented in table 1. The
all mounted on an Eickhorst Gemmaster base. Lumi-
first suite of 33 gems (ENSMP 69880) consists of rec-
nescence was examined using a 6-watt ultraviolet
tangular step cuts, weighing from 0.180 to 0.408 ct
lamp (Vilber Lourmat VL-6.LC) with long-wave UV
(figure 3). The total weight of the 33 samples from
(365 nm) and short-wave UV (254 nm) light, equipped
series ENSMP 69880 is 9.919 carats instead of the
with a CN-6 darkroom (10 cm distance between the
10.030 carats mentioned in the archives, registering
sample and the lamp). Refractive indexes were taken
all 34 original samples. The second suite (ENSMP
with a refractometer and mass and density with a
69866) is composed of eight roundish brilliants (one
hydrostatic balance.
with a more oval shape), weighing from 0.854 to
Raman and photoluminescence (PL) spectra were
1.339 ct, for a total weight of 8.431 carats (figure 4A).
obtained using a mobile Raman spectrometer (Magi-
The last suite (ENSMP 69881) is composed of four
labs GemmoRaman-532SG) with a 532 nm laser exci-
round brilliants weighing from 0.703 to 0.939 ct (fig-
tation and spectral resolution of 11 cm–1, ranging for
ure 4B), for a total weight of 3.49 carats.
Raman spectra from 200 to 2000 cm–1 (with 1 second
All 33 rectangular gems of suite ENSMP 69880
exposure time and 4 accumulations) and for PL spectra
(figure 3) and all eight roundish gems of suite ENSMP
from 540 to 760 nm (0.3 to 0.4 second exposure time
69866 (figure 4A) presented a vivid green color. The
and 30 accumulations). All spectra were acquired with
four round-shaped stones from suite ENSMP 69881
the laser pointing at the table, the flattest part of the
displayed instead an intense green with a slightly yel-
stone. Calibration of the Raman spectrometer was
lowish tint (figure 4B). The refractive index of sam-
made with a diamond, using its 1331.8 cm–1 Raman
ples from series ENSMP 69866 and ENSMP 69880
line. Due to this study requiring the use of a mobile
varied from 1.570 to 1.588, and their specific gravity
instrument, the spectral resolution was over 10 cm–1.
values from 2.60 to 2.75, consistent with beryl. The
This precluded us from reaching a conclusion regard-
color observed for those samples was consistent with
ing the alkali content, which would have required the
the emerald variety of beryl. All samples were inert
use of the exact position and full width at half maxi-
under UV lamp excitation, except for one (ENSMP
mum of the band at 1070 cm–1 to differentiate emeralds
69866_3) that exhibited a weak red fluorescence to
containing either low or high concentrations of alkali
long-wave UV only. This difference in fluorescence
elements (Huong et al., 2014; Bersani et al., 2014;
behavior could be explained by a slightly larger ratio
Jehlička et al., 2017; Karampelas et al., 2019). Indeed,
of chromium to iron in this emerald; fluorescence is
in order to obtain the real shape of this band, relatively
present when the ratio is significant and becomes
high spectral resolution (<2 cm–1) must be used in the
less intense with a decrease in chromium to iron
acquisition of the Raman spectra. Moreover, the spec-
ratio (Bosshart, 1991b).
tral resolution of the instrument could also affect the
Samples from series ENSMP 69881 presented
exact position of the PL bands. For example, if the spec-
completely different characteristics: a refractive
tral resolution is not optimal, the real shape of the band
index of about 1.64, a specific gravity between 3.56
is not obtained and it appears broader and in slightly
and 3.78 (depending on the stone), and a chalky yel-
shifted positions. The suggestion that the exact posi-
lowish fluorescence that was weaker to long-wave
tion of the Cr3+ R1 line can give information regarding
UV than to short-wave UV. The RI, SG, and UV re-
an emerald’s country of origin (Moroz et al., 2000;
action are similar to those observed in artificial glass
Thomson et al., 2014) should be considered with cau-
containing lead (Nassau, 1980; Webster and Ander-
tion. Visible/near-infrared (Vis-NIR) spectra were ac-
son, 1983).
quired from 365 to 1000 nm using a mobile instrument
(0.05 to 0.10 seconds acquisition time and 50 accumu-
lations) with an integrating sphere (Magilabs Gemmos- Macroscopic and Microscopic Observations. Stan-
phere). Fourier-transform infrared (FTIR) spectra were dard macroscopic observation revealed surface-reach-
obtained with a mobile instrument (Bruker Alpha II) ing cracks in some samples (figure 5). This could be
in the 400 to 8000 cm–1 range (4 cm–1 spectral resolu- attributed to multiple uses of gems in different jew-
tion and 100 scans) using a DRIFT accessory as a beam elry pieces over time. This practice of reusing gem-
condenser (Hainschwang et al., 2006). stones from the French crown jewels, sometimes

174 STUDY OF GEMS FROM THE CROWN OF NAPOLEON III GEMS & GEMOLOGY SUMMER 2022
 A B

Figure 5. Photos of speci-

mens from this study
presenting visible cracks
and fractures, possibly
due to multiple uses in
jewelry. A: ENSMP
69866_3 (0.955 ct). B:
ENSMP 69880_2 (0.299
ct). C: ENSMP 69880_6
C D (0.305 ct). D: ENSMP
69881_3 (0.929 ct). Pho-
tos by B.M.S. Beuve/LFG
(A) and U. Henne-
bois/LFG (B–D);
© Museum of Mineral-
ogy, Mines Paris - PSL.

even recutting them, is well known (e.g., Bapst, 1889; Under the microscope, samples from suites
Morel, 1988). The purpose was to create contempo- ENSMP 69866 and ENSMP 69880 (41 of the 45 stud-
rary pieces of jewelry in style with the era, which ied samples) presented natural features such as multi-
then could be used by the new ruler. Interestingly, phase inclusions with jagged outlines, color zoning,
sample ENSMP 69881_3 shows a conchoidal fracture transparent crystals (possibly carbonates), and gota de
(figure 5D). aceite (Spanish for “drop of oil”) patterns (figures 6

A B
Figure 6. A: Color zon-
ing observed in ENSMP
69880_9; field of view 2
mm. B and C: Multi-
phase inclusions with
jagged outlines observed
in ENSMP 69880_23 and
in ENSMP 69866_4;
fields of view 1.2 and
0.5 mm, respectively. D:
C D
A transparent crystal
(possibly a carbonate)
observed in ENSMP
69880_22; field of view 1
mm. Photomicrographs
by Ugo Hennebois/LFG;
© Museum of Mineral-
ogy, Mines Paris - PSL.

STUDY OF GEMS FROM THE CROWN OF NAPOLEON III GEMS & GEMOLOGY SUMMER 2022 175
 one displayed “flow patterns” (figure 8), along with
bubbles characteristic of glass (Webster and Anderson,
1983; Gübelin and Koivula, 1986).

Raman Spectroscopy. Raman spectra of three repre-

sentative samples, from suites ENSMP 69866 and
ENSMP 69880, are presented in figure 9A. Spectra
showed bands typical of beryl. The vibration at
around 685 cm–1 is linked to Be-O stretching; at
around 1070 cm–1, the vibration is related to Si-O
and/or Be-O stretching, along with a less intense
band at around 1010 cm–1 due to Si-O stretching. The
weaker bands between 200 and 600 cm–1 are linked
to Si6O18 ring vibrations (Adams and Gardner, 1974;
Hagemann et al., 1990; Kim et al., 1995; Moroz et al.,
2000; Bersani et al., 2014; Jehlička et al., 2017). The
spectra presented some differences in the relative in-
tensities of the Raman bands (see again figure 9A).
These result from the different crystallographic ori-
entations in which the gems are cut and the spectra
acquired. The band at around 685 cm–1 is the most in-
tense, with the bands at around 1010 and 1070 cm–1
Figure 7. Gota de aceite structures observed in having a similar intensity (e.g., sample ENSMP
ENSMP 69866_2; field of view 1.5 mm. Photo- 69880_3, red line in figure 9A) when the spectrum is
micrograph by Ugo Hennebois/LFG; © Museum of acquired with the laser beam parallel to the c-axis of
Mineralogy, Mines Paris - PSL. the crystal. When spectra are acquired with the laser
perpendicular to the c-axis of the crystal (e.g., sample
ENSMP 69866_1, black line in figure 9A), the band
and 7). Inclusions with jagged outlines are observed at 1070 cm–1 is slightly more intense than that at 685
in natural emeralds from Colombia and occasionally cm–1, while the band at around 1010 cm–1 is signifi-
from Afghanistan, China, and a small occurrence in cantly less intense (Moroz et al., 2000; Bersani et al.,
Zambia (specifically from Musakashi and not the 2014; Jehlička et al., 2017; Karampelas et al., 2019).
more productive Kafubu deposits), as well as mines All samples from suites ENSMP 69866 and ENSMP
of more academic interest (Bosshart, 1991b; Saeseaw 69880 (representing 41 of the 45 samples) showed the
et al., 2014, 2019; Schmetzer, 2014; Krzemnicki et al.,
2021). The gota de aceite appearance such as that ob-
served in ENSMP 69866_2 (figure 7) is documented Figure 8. These “flow patterns” were observed in
in emeralds from Colombia but seldom observed in ENSMP 69881_3; field of view 2 mm. Photo-
emeralds from other origins (Ringsrud, 2008; Hain- micrograph by Ugo Hennebois/LFG; © Museum of
schwang, 2010; Fritsch et al., 2017). These structures Mineralogy, Mines Paris - PSL.
display octagonal color zoning due to fibrous growth
at a fast growth rate, followed by a later growth
episode, possibly slower, which filled the space be-
tween the fibers. The gota de aceite appearance is
most likely due to light scattering at the irregular in-
terface between the two growth episodes (Fritsch et
al., 2017). No indications of treatment, such as the
clarity enhancement applied to emerald since well be-
fore the fourteenth century (Johnson et al., 1999;
Kiefert et al., 1999), were observed microscopically in
any of these samples. The four samples from suite
ENSMP 69881 presented no mineral inclusions. Only

176 STUDY OF GEMS FROM THE CROWN OF NAPOLEON III GEMS & GEMOLOGY SUMMER 2022
 RAMAN SPECTRA

A ENSMP 69866_1 B ENSMP 69881_1

ENSMP 69880_17 ENSMP 69881_2
ENSMP 69880_3
685
1070
480
790
960
1030
INTENSITY

INTENSITY
1010

490 975 1040

775

200 400 600 800 1000 1200 200 400 600 800 1000 1200
RAMAN SHIFT (cm –1) RAMAN SHIFT (cm –1)

Figure 9. Raman spectra obtained using a mobile instrument with 532 nm laser excitation, in the range of 200 to
1200 cm–1, of some typical samples (all spectra are shifted for clarity). A: Typical spectra for the ENSMP 69866 and
69880 suites, showing vibrations characteristic of beryl. The differences from spectrum to spectrum are due to dif-
ferent crystallographic orientations of the gems; the spectrum of 69866_1 is obtained nearly perpendicular to the c-
axis, and the spectrum of 69880_3 is obtained nearly parallel to the c-axis. B: Typical spectra for the ENSMP 69881
suite, showing large bands sometimes detected in glass, centered at slightly different positions.

beryl-related Raman bands, which only differ in rel- 2.00, depending on lead content—and dispersion) is
ative intensity. known to have been manufactured for several cen-
Raman spectra of all samples from suites ENSMP turies (Ben Kacem et al., 2017).
69866 and ENSMP 69880 presented strong lumines-
cence phenomena above 2000 cm–1 (i.e., from the yel- Photoluminescence Spectroscopy. PL spectra of all
low to the red part of the electromagnetic spectrum). ENSMP 69866 and ENSMP 69880 samples presented
For that reason, it was impossible using this instru- a sharp band at around 680 nm and another more in-
ment to study the type I water (lacking a nearby al- tense sharp band at around 684 nm. These emission
kali ion) and type II water (with alkali ions nearby) bands are linked to Cr3+ R2 and R1 lines, respectively,
vibrations appearing at around 3609 and 3598 cm–1, in the beryl structure. They are accompanied by a
respectively (Huong et al., 2010; Bersani et al., 2014; broad band in the red part of the visible range, centered
Jehlička et al., 2017; Karampelas et al., 2019). around 710 nm (see two examples in figure 10A), pos-
Raman spectra of two of the four samples from sibly also linked to chromium (Wood, 1965; Moroz et
suite ENSMP 69881 are presented in figure 9B. The al., 2000; Thomson et al., 2014). Positions and relative
spectra showed broad bands at slightly different po- intensities of the R lines presented some orientation
sitions, similar to those observed in glassy silicates, effects (see again figure 10A). In the studied samples,
with Si-O stretching and bending and corresponding the R1 line ranged from 683.7 to 683.9 nm, similar to
Raman bands at around 1000 cm–1 and 500 cm–1, re- some emeralds from Colombia as well as some from
spectively (Colomban et al., 2006). Glasses are rela- Russia and Afghanistan (Thomson et al., 2014; Karam-
tively poor Raman scatterers, and the signal-to-noise pelas et al., 2019).
ratio of the mobile Raman instrument did not allow The four ENSMP 69881 samples presented a
us to draw clear conclusions; however, the spectra broad PL band at 560 nm with a shoulder at around
are similar to those observed in lead glass (Colomban 580 nm, less intense for sample ENSMP 69881_2 (fig-
et al., 2006; Robinet et al., 2006; Ben Kacem et al., ure 10B, black line), along with a broader band cen-
2017). This kind of glass (e.g., “flint glass,” which tered at around 700 to 710 nm, with different relative
may display a relatively high refractive index—up to intensities for the two samples (see again figure 10B).

STUDY OF GEMS FROM THE CROWN OF NAPOLEON III GEMS & GEMOLOGY SUMMER 2022 177
 PL SPECTRA

A ENSMP 69880_3 B ENSMP 69881_1

ENSMP 69866_1 ENSMP 69881_2
Raman
bands
684
680
560
INTENSITY

INTENSITY
710

580

700

710

540 570 600 630 660 690 720 750 540 570 600 630 660 690 720 750
WAVELENGTH (nm) WAVELENGTH (nm)

Figure 10. Typical PL spectra of the samples studied, in the range of 540 to 750 nm (spectra are shifted for clarity).
A: In the ENSMP 69866 and 69880 suites, PL bands related to chromium in the beryl structure in the red part of
the electromagnetic spectrum are observed in all spectra. B: In the ENSMP 69881 suite, large bands possibly due to
oxygen-related centers in glass are observed. Both spectra show the Raman bands below 570 nm.

The bands in the green part are possibly due to oxy- slight differences in position and relative intensity of
gen deficiency–related centers (Skuja, 1998). In the the absorption bands are also due to crystallographic
red part of the spectra, the observed bands might be orientation effects. The small sharp band at around
due to non-bridging oxygen-hole centers in glass 960 nm is due to the presence of water in beryl.
(Sakurai et al., 1999). Green luminescence under UV Figure 11B presents two Vis-NIR spectra of the
light can be found in glass imitations of gems (Web- suite of four ENSMP 69881 specimens, all four spec-
ster and Anderson, 1983). tra being similar in shape. A large absorption band
centered at around 800 nm due to Fe2+ and/or Cu2+ is
Visible/Near-Infrared (Vis-NIR) Spectroscopy. Two observed, along with a total absorption (cut off) from
typical Vis-NIR spectra of samples from suites 380 to 400 nm due to Fe3+ (or Fe3+-S2−) and a transmis-
ENSMP 69866 and ENSMP 69880 are shown in figure sion window in the green part of the visible range at
11A. All 41 stones from these suites presented similar around 510 nm (Schreurs and Brill, 1984; Carl et al.,
spectra. The broad absorptions at around 430 and 610 2007; Meulebroeck et al., 2010, 2011). Using this mo-
nm are both linked to Cr3+ and V3+ in beryl. The two bile Vis-NIR instrument, a clear image of the absorp-
sharp bands of weak intensity at around 680 nm are tion in the NIR (above 1000 nm) and in the UV
due to Cr3+ R1 and R2 lines. No absorptions linked to (below 365 nm) cannot be obtained to better charac-
iron are observed in the near-infrared part of the elec- terize the exact cause of the color. However, we ob-
tromagnetic spectrum (Wood and Nassau, 1968; served no absorption bands due to elements used for
Bosshart, 1991b; Saeseaw et al., 2014, 2019; Schmet- recent glass coloration. For example, the use of
zer, 2014). Most natural emeralds from Colombia, as chromium began after the second half of the nine-
well as some from Afghanistan and a small occur- teenth century, and it was not observed in any of the
rence recently discovered in Zambia, present spectra studied glasses (Meulebroeck et al., 2016).
without any absorption linked to iron, or with low-
to medium-intensity bands linked to iron in the NIR Infrared (IR) Absorption Spectroscopy. Figure 12A
region (Bosshart, 1991b; Saeseaw et al., 2014, 2019; presents a typical FTIR spectrum of a sample from
Giuliani et al., 2019; Giuliani and Groat, 2019; series ENSMP 69866 (black line). At around 3500
Karampelas et al., 2019; Krzemnicki et al., 2021). The cm−1, a total absorption is observed, which is due to

178 STUDY OF GEMS FROM THE CROWN OF NAPOLEON III GEMS & GEMOLOGY SUMMER 2022
 VIS-NIR SPECTRA

A ENSMP 69866_1 B ENSMP 69881_2

ENSMP 69880_3 ENSMP 69881_1
425 615

435
ABSORBANCE

ABSORBANCE
600 680
800

960

400 500 600 700 800 900 1000 400 500 600 700 800 900 1000
WAVELENGTH (nm) WAVELENGTH (nm)

Figure 11. Visible/near-infrared (Vis-NIR) spectra from 365 to 1000 nm of representative samples of the different
suites. All spectra are shifted for clarity. A: Representative spectra of suites ENSMP 69866 and 69880. Bands re-
lated to both chromium and vanadium in the beryl structure are observed at around 430 and 610 nm. Crystallo-
graphic orientation can affect the exact position and relative intensity of these bands. B: Representative spectra of
suite ENSMP 69881. These show a large band centered at around 800 nm, possibly due to ferrous iron (and/or cop-
per), and a cutoff from 380 to 400 nm, possibly due to ferric iron (possibly with the participation of sulfur).

vibrations linked to the stretching of water mole- varied when spectra were acquired under different
cules in the beryl structure. The combination water crystallographic orientations. No bands linked to
bands are situated in the range of 4500 to 8000 cm−1. clarity enhancement of emerald, which are com-
For example, a series of bands at around 5270 cm−1 monly observed at around 3000 cm–1 (Johnson et al.,
due to type I water (without an alkali ion nearby) and 1999; Kiefert et al., 1999), were identified in any of
type II water (with alkali ions nearby) can be ob- these samples.
served (Wood and Nassau, 1967, 1968). In the NIR re- In figure 12A, a typical spectrum of a sample from
gion at about 1400 nm (7142 cm−1), the absorption is the ENSMP 69881 suite is also presented in red. It is
due to type I water; at around 1408 nm (7102 cm−1), similar to the FTIR spectrum produced by other ar-
the band is due to type II water (figure 12, A and B). tificial glasses (Stephan, 2020; Cooper et al., 2020).
Using the mobile FTIR instrument, the signal-to- Below 3200 cm–1, large bands due to combination
noise ratio in the NIR (i.e., above 6500 cm−1) was modes and overtones of silicate glasses are observed.
sometimes low and the bands were not always well The bands at around 3500 cm–1 are possibly due to
resolved (see again figure 12A). However, in all spec- symmetric stretching of water molecules and/or
tra of samples from suites ENSMP 69866 and stretching vibrations of the Si-OH group. The weaker
ENSMP 69880, the bands due to type I water were of bands at around 4500 cm–1 are due to combination
equal or greater intensity than those due to type II Si-OH modes (Efimov and Pogareva, 2006).
water. This characteristic was also observed for
emeralds with low alkali element concentration, Summary of Results. Of the 45 samples, 41 were con-
such as those from Colombia (Saeseaw et al., 2014; firmed to be emerald (suites ENSMP 69866 and
Karampelas et al., 2019). From 2200 to 2850 cm−1, 69880). As these stones are of gem quality and were
some weak bands linked to H2O, D2O, CO2, and set in the crown of Napoleon III in 1855, we can ex-
chlorine were observed (de Donato et al., 2004; clude any “young” emerald provenances, such as
Rondeau et al., 2008). Notably, beryl’s FTIR spectra mines in Zambia and Zimbabwe, or even historic de-
also presented strong crystallographic orientation posits with emeralds of lesser gem quality, such as
phenomena: The relative intensity of these bands those in Egypt and Austria (Giuliani et al., 2000, 2019).

STUDY OF GEMS FROM THE CROWN OF NAPOLEON III GEMS & GEMOLOGY SUMMER 2022 179
 FTIR SPECTRA

A ENSMP 69866_5 B ENSMP 69866_5

ENSMP 69881_3

1400
1408
ABSORBANCE

ABSORBANCE
2000 3000 4000 5000 6000 7000 8000 1300 1325 1350 1375 1400 1425 1450 1475 1500
WAVENUMBER (cm–1) WAVELENGTH (nm)

Figure 12. FTIR spectra of representative samples in this study. All spectra are shifted for clarity. A: FTIR spectra in
the range of 2000 to 8000 cm–1 for samples ENSMP 69866_5 and ENSMP 69881_3. Bands characteristic of vibra-
tions in the beryl structure are observed in the black spectrum, and large bands linked to glass are observed in the
red spectrum. B: FTIR spectrum in the range of 1300 to 1500 nm (about 7692–6666 cm–1) of sample ENSMP
69866_5. The intensity of the band at about 1400 nm (due to type I water) is stronger than the intensity of the
band at about 1408 nm (due to type II water).

From the sixteenth century until the early twentieth taining lead. The spectroscopic characteristics of the
century, the vast majority of gem-quality emeralds artificial glasses from Napoleon III’s crown do not
originated from Colombia (Keller, 1981; Bosshart, present any evidence of a recently fabricated glass. It
1991a, Giuliani et al., 2000; Schmetzer et al., 2020). is therefore possible that these imitations were part of
The existence of the specific inclusion scene (e.g., the 1887 donation and not substituted at a later stage
three-phase inclusions with jagged outlines and gota at the museum. Still, the cut and shape differ signifi-
de aceite), the fact that the NIR band related to type cantly from the identified emeralds, suggesting they
I water in beryl is of equal or greater intensity than were not set at the same time as the original crown’s
the band related to type II water (signifying the pres- creation in 1855. Instead, they could have been re-
ence of relatively low concentrations of alkali met- placements shortly thereafter, when the eight large
als), and the absence of iron-related absorption bands main diamonds were removed for use in other jewels
in the Vis-NIR spectra all suggest that the samples created for Empress Eugénie (Morel, 1988).
came from Colombian mines. None of the samples Additional nondestructive measurements of the
presented microscopic or spectroscopic evidence of trace elements with a well-calibrated energy-disper-
clarity enhancement. Emeralds with similar charac- sive X-ray fluorescence (EDXRF) spectrometer might
teristics are found in other jewels from the same pe- help to further study the fabrication of the green
riod (Keller, 1981; Karampelas and Wörle, 2022). glasses and also support the Colombian origin of the
The microscopic and spectroscopic data of the four emeralds. Moreover, the use of a Raman spectrometer
samples from suite ENSMP 69881 were found to be with more than one laser excitation wavelength and
consistent with artificial glass. This was first ac- better spectral resolution, combined with the use of
counted for in the museum’s internal gem identifica- spectrometers covering the UV region down to 250
tion report by one of the authors (FM), who made the nm and the NIR up to 1500 nm, would provide fur-
determination using classic gemological tools in the ther assistance in identifying the fabrication of the
2010s. Their relatively high refractive index and spe- green glasses and further confirming the emeralds’
cific gravity values point toward artificial glass con- Colombian origin.

180 STUDY OF GEMS FROM THE CROWN OF NAPOLEON III GEMS & GEMOLOGY SUMMER 2022
CONCLUSIONS AND PERSPECTIVES logical tools and mobile spectrometers. In the last
In all, 41 out of 45 samples from ENSMP 69866 and two decades, several instruments useful for charac-
ENSMP 69880 showed natural inclusions along with terizing gems in situ have been developed in mobile
standard gemological observations characteristic of versions, drawing the interest of researchers from
emerald. The Vis-NIR spectra presented absorption various disciplines (Reiche et al., 2004; Petrová et al.,
bands characteristic of Cr3+ and V3+, while iron-related 2012; Barone et al., 2016; Panczer et al., 2021; Karam-
bands were not observed in any of the spectra. In the pelas and Wörle, 2022).
NIR region, as analyzed by FTIR spectroscopy, the Only a few gemstones that once belonged to crown
bands due to type I water were of equal or greater in- jewels or regalia have been scientifically examined—
tensity than those due to type II water. A combination some still belong to royalty (Spain and the United
of spectroscopic and classic gemological methods Kingdom, for example), while others have been stud-
points to Colombia as the most likely source of these ied for their historical or artistic merit but not their
41 natural emeralds, given the crown’s age. gemological value. However, there has been a stronger
The four samples from suite ENSMP 69881 pre- desire over the last few decades to overcome these bi-
sented different characteristics. Classic gemological ases, and some museums are putting national treas-
testing methods identified them as artificial glasses ures under their microscopes and spectrometers,
containing lead. Their Vis-NIR spectra revealed Fe2+ publishing and sharing their results. We can acknowl-
and/or Cu2+ as well as Fe3+ (or Fe3+-S2−) as the main edge George Bosshart for conducting one of the first
causes of their coloration. We uncovered no evi- gemological studies of the Dresden Green, a 41 ct di-
dence of the glass having been recently fabricated. amond from one of the oldest museums in the world,
Consequently, it is possible that these four artificial the Green Vaults (1723) in Dresden, Germany
glass stones were set in the crown prior to their do- (Bosshart, 1989). As the French crown jewels were dis-
nation to the École des Mines. Morel (1988, p. 338) persed in 1887, a few pieces eventually landed in mu-
reports that the eight large diamonds were removed seums equipped with instruments and researchers
from the crown not long after its creation and re- willing to study great and historical gem treasures,
placed by “strass” (glass imitations, possibly con- such as the Hope diamond and the Napoleon diamond
taining lead). The substitution of these green glass necklace at the Smithsonian Institution (Gaillou and
stones for the original emeralds could have occurred Post, 2007; Gaillou et al., 2010, 2012, 2022; Post and
at the same time. Farges, 2014) and the Grand Sapphire of Louis XIV at
As part of an ongoing collaboration between the the National Museum of Natural History in Paris
LFG and the Mineralogy Museum of the École des (Farges et al., 2015). These gemstones are all remark-
Mines, the authors will continue investigating other able not only for their history and consummate lap-
gems that once belonged to the French crown jewels. idary and jewelry skills, but also for the overall quality
It is only logical that in addition to exhibiting these of the stones themselves and our understanding of
gems, the Museum seeks to understand the science their geologic and geographic origin. We can only hope
behind them, as educational and outreach tools. As that more museums will allow in situ nondestructive
this set of gems is considered a priceless national studies of their gemstones, whether set in jewels or
treasure, such studies can only be conducted within not, in order to tell the full story and offer these treas-
the Museum, using classical nondestructive gemo- ures the appreciation they deserve.

ABOUT THE AUTHORS ACKNOWLEDGMENTS

Dr. Karampelas (s.karampelas@lfg.paris) is chief gemologist, Mrs. Sophie Guermann from University of Neuchâtel, Switzerland, is
Herreweghe, Mr. Hennebois, Mrs. Leblan, and Mrs. Meslin Sainte thanked for some of the information on the history of the crown.
Beuve are gemologists, and Mr. Delaunay is director, at the Labora- Constructive comments and suggestions of three anonymous re-
toire Français de Gemmologie (LFG) in Paris. Dr. Gaillou (eloise.gail- viewers are gratefully acknowledged.
lou@minesparis.psl.eu) is curatrix, Mrs. Maouche is exhibit
specialist, Mr. Lechartier is technician, and Dr. Nectoux is curator
and director, of the Museum of Mineralogy, Mines Paris - PSL.

STUDY OF GEMS FROM THE CROWN OF NAPOLEON III GEMS & GEMOLOGY SUMMER 2022 181
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jewel. Rocks & Minerals, Vol. 89, No 1, pp. 16–26, Wood D.L., Nassau K. (1967) Infrared spectra of foreign molecules
http://dx.doi.org/10.1080/00357529.2014.842831 in beryl. The Journal of Chemical Physics, Vol. 47, No. 7, pp.
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STUDY OF GEMS FROM THE CROWN OF NAPOLEON III GEMS & GEMOLOGY SUMMER 2022 183
FEATURE ARTICLES

CHARACTERISTICS OF NEWLY DISCOVERED

AMBER FROM PHU QUOC, VIETNAM
Le Ngoc Nang, Pham Trung Hieu, Lam Vinh Phat, Pham Minh Tien, Ho Nguyen Tri Man, and Ha Thuy Hang

The authors examine the gemological properties and commercial potential of a new source of amber, discovered
in 2020 on the Vietnamese island of Phu Quoc. It is the only known amber locality in Vietnam so far. The Phu
Quoc amber possesses reddish orange to orangy yellow hues and is transparent, with sizes up to 10 cm. The
samples exhibited strong blue fluorescence under ultraviolet light (both long-wave and short-wave). Internally,
they displayed disk-like inclusions and gas bubbles, but few botanical inclusions were found. Their characteristic
FTIR peaks can be distinguished from those of amber found in other sources worldwide. Although amber from
Phu Quoc is a recent discovery and has only been investigated in two small areas, its commercial potential is
promising based on the samples’ quality and the wide distribution of the host rock on the island.

A
mber, an organic gemstone fossilized from tree Research and Application Center (LIULAB) in Ho Chi
resin (Ross, 1999), comes from several sources Minh City, where they were identified as amber. With
globally, most notably the Baltic region, Myan- the miner’s help, the authors visited the site to collect
mar, the Dominican Republic, and Indonesia. Amber amber samples. During our field trip, we found a sec-
from each locality shows distinctive characteristics. In ond deposit, also in a sandstone mine, located about a
2020, a sandstone miner working on the Vietnamese kilometer from the first amber outcrop (figure 2).
island of Phu Quoc came across an orange-yellow ma-
terial buried inside the sandstone layers. He collected
loose and bedrock-hosted samples, the largest up to 10 In Brief
cm (figure 1), and submitted them to Liu Gemological
• Vietnamese amber was first discovered on the island of
Phu Quoc in 2020.
Figure 1. Amber from Phu Quoc: matrix measuring • The amber is characterized by strong blue fluorescence
approximately 6 × 10 cm and a 1.69 ct, 11.93–9.41 × under UV lighting and weak green fluorescence under
4.98 mm cabochon of transparent, orangy red amber daylight-equivalent illumination.
set in a 14K gold ring. Photo by Le Ngoc Nang.
• Amber nodules were found in sandstone, accompa-
nied by veins of black jet. The wide coverage of sand-
stone on the island suggests the possibility of additional
discoveries.
• Phu Quoc amber’s gemological properties are rela-
tively similar to those from other global sources, but it
can be differentiated by FTIR spectroscopy.

In the present study, Phu Quoc amber was char-

acterized with standard gemological methods and
Fourier-transform infrared spectroscopy (FTIR). Our
results, combined with other published data from
Baltic, Burmese, and Dominican amber (Wolfe et al.,

See end of article for About the Authors and Acknowledgments.

GEMS & GEMOLOGY, Vol. 58, No. 2, pp. 184–194,
http://dx.doi.org/10.5741/GEMS.58.2.184
© 2022 Gemological Institute of America

184 AMBER FROM PHU QUOC, VIETNAM GEMS & GEMOLOGY SUMMER 2022
 104˚ 00'

B N

Holocene sediments

Pleistocene sediments

Neogene sedimentary rocks

Fault

Sample location

10˚ 10˚
20' 20'

A 1
CHINA
Ha Noi

LAOS
Vinh Hainan

Hue
THAILAND
Hoang Sa

CAMBODIA VIETNAM Gulf of Thailand

Nha
Study area Trang
Ho Chi Minh

Phu Quoc Truong Sa 10˚

2 km 104˚ 00' 10'

Figure 2. Geological map of northern Phu Quoc, from Duong et al. (1998) and modified by Le Ngoc Nang (2021).
The two study areas (1 and 2) were visited in November 2020.

2009; Leelawatanasuk et al., 2013; Sun et al., 2015; GEOLOGICAL SETTING

Zhang et al., 2020), allowed us to compare the Phu The island of Phu Quoc lies in the Gulf of Thailand,
Quoc samples with amber from commercially im- about 45 km off the southwestern coast of Vietnam.
portant sources. The island has an area of 574 km2. The terrain con-

AMBER FROM PHU QUOC, VIETNAM GEMS & GEMOLOGY SUMMER 2022 185
 A

B C

Amber

10 cm 1 cm

Figure 3. A: Sandstone mine (site 1). B and C: Nodules of amber found in sandstone boulders, recovered from a
depth of 15–20 m at site 1. Photos by Lam Vinh Phat.

sists mainly of low mountains, with the highest peak stone, distributed on the eastern margin of the is-
standing at 607 m (Duong et al., 1998). The amber land; the upper part is jet- and amber-bearing quartz
sites found so far are in an area that is easily accessi- sandstone with cross-bedding structure, distributed
ble by vehicle. throughout most of northern Phu Quoc (My and
The geological formations in Phu Quoc are Linh, 2005). The upper part is unconformably over-
mostly sandstone and siltstone from the Miocene to lain by Holocene sediments.
the Holocene. The Phu Quoc amber source lies in The Phu Quoc amber is hosted in gray to whitish
the northern center of the island (figure 2), mainly gray and fine- to medium-grained sandstone (My and
containing Neogene sedimentary rocks, and is di- Linh, 2005; Fyhn et al., 2010) (figure 3). Found in
vided into two parts. The lower part is interbedded sandstone as nodules, samples are nearly round or
conglomerate, sandstone, and gray and green silt- distorted oval in shape, varying in size from a few

186 AMBER FROM PHU QUOC, VIETNAM GEMS & GEMOLOGY SUMMER 2022
centimeters to 10 centimeters. The boundary be- worker, and ten samples (nos. 3–12: eight loose and
tween amber and sandstone is clear but uneven and two in matrix) from the authors’ set of 38 samples
difficult to detach (figures 1 and 3). Surrounding from both sites (figure 2). The samples were chosen
amber in sandstone is black jet in the form of plates, based on size and quality. Five samples were cut
with veins in matrix ranging in size from a few cen- into cabochons by one of the authors (PMT), and
timeters to several tens of centimeters. Part of the seven were kept rough (figure 5). For refractive index
amber boundary is in contact with the sandstone, and FTIR measurements, the authors selected rough
and the rest is attached to the jet. The sedimentary samples that had at least one flat-polished surface,
rocks containing amber are situated at a depth of were free of pores, and weighed more than 5 ct. The
about 15–20 m and are about 30 m thick, accompa- amber-bearing sandstones consisted mainly of
nied by lamellar-like jet. The amber-bearing sedi- amber and jet.
mentary rock is quartz sandstone with massive We used three additional samples from Myanmar
structure. Rock-forming minerals are >90% quartz (A-3), the Baltic Sea (Poland, A-2), and the Domini-
and <10% cement (sericitized clay minerals), as seen can Republic (A-1) to compare with the Phu Quoc
under a petrographic microscope (figure 4). amber by conducting gemological testing and FTIR
advanced analysis at LIULAB (figure 5). Those three
MATERIALS AND METHODS samples belong to the collection of minerals and
A total of 38 amber samples (31 loose samples and gems of the Faculty of Geology, University of Sci-
7 samples in matrix) were collected from two loca- ence, Ho Chi Minh City.
tions (sites 1 and 2) on November 17 and 18, 2020. Standard gemological methods were used to con-
These consisted of 26 samples (22 loose and 4 in firm the identity of the studied samples as amber. The
matrix) from site 1 and 12 samples (nine loose and amber’s color was observed under a 60 W GLS LED
three in matrix) from site 2. In addition, we received daylight bulb (5000–6000K). Specific gravity values for
three samples (two loose and one in matrix) from samples 1–6 and 9–12 were measured using a hydro-
the sandstone mine worker from site 1. Twelve of static scale, and their refractive indexes were recorded
the Phu Quoc samples were used for research analy- with a standard gemological refractometer. A polar-
sis: two loose samples (nos. 1 and 2) from the mine iscope was used to observe optical features on the

Qtz

Figure 4. An amber-
bearing sandstone thin
section containing
quartz (Qtz) and a
Cm Qtz small amount of cement
(Cm; mainly sericitized
clay minerals) surround-
ing the quartz grains.
Cm Photomicrograph by Ha
Thuy Hang; field of view
Qtz 0.6 mm.
Qtz

AMBER FROM PHU QUOC, VIETNAM GEMS & GEMOLOGY SUMMER 2022 187
 1 6 7

2 9

3 10 8

4 11

5 12 A-3
A-1 A-2

Figure 5. The amber samples used in this study were in bedrock, rough, or cut into cabochons. Samples 1–12 are
from Phu Quoc, A-1 from the Dominican Republic, A-2 from the Baltic region, and A-3 from Myanmar. Photos by
Le Ngoc Nang.

same samples. Fluorescence reaction was tested on all microscope with 7× to 50× magnification. A 3 μm thin
the samples under ultraviolet light, both long-wave section of amber-bearing sandstone was examined
(365 nm) and short-wave (254 nm). Internal features under an Olympus CH-2 petrographic microscope at
were observed under a Carton SPZV50 gemological magnifications of 100×, 200×, and 400×.

188 AMBER FROM PHU QUOC, VIETNAM GEMS & GEMOLOGY SUMMER 2022
 For all samples, a hot needle test was applied to reous to resinous luster, and many samples displayed
check for the characteristic scent of natural resin. We good transparency (figure 5). The samples also exhib-
also checked the reaction to acetone as a means of ited a white streak.
separating amber from copal. Amber does not react
with acetone, while copal reacts with acetone after Gemological Characteristics. The specific gravity val-
20 seconds (Ross, 1999). ues of the 10 tested samples ranged from 1.03 to 1.04,
Twelve amber samples—nine from Phu Quoc corresponding to the SG of amber (Ross, 1999; Sun et
and one each from the Baltic Sea, Myanmar, and the al., 2015). These same 10 samples were singly refrac-
Dominican Republic—were analyzed using an Agi- tive and had refractive index values ranging from
lent Cary 630 FTIR spectrometer. Data were ac- 1.540 to 1.543, also consistent with amber (Ross, 1999;
quired with a spectral range of 4000–650 cm–1, a Sun et al., 2015) (table 1). Under long-wave and short-
resolution of 8 cm–1, and a scan time of 32 s. wave UV light, all Phu Quoc amber samples displayed
strong to very strong light blue fluorescence (figure 6,
RESULTS AND DISCUSSION top). They emitted green fluorescence on the surface
Under daylight-equivalent illumination, the amber under daylight-equivalent illumination (figure 6, bot-
samples from Phu Quoc were predominantly reddish tom right) or against a dark background. The fluores-
orange or orangy yellow. Black patches and spots in cence phenomenon of the Phu Quoc amber is similar
some samples (6 and 10) were preserved flora (tree to that of Dominican and Indonesian amber (Poinar,
bark). The samples exhibited predominantly subvit- 2010; Leelawatanasuk et al., 2013; Liu et al., 2014;

Figure 6. Luminescence of Phu Quoc amber. All of the samples emitted strong to very strong light blue fluores-
cence in both long-wave (top left) and short-wave (top right) UV light. The bodycolor of Phu Quoc amber sample
3 is reddish orange (bottom left) and emitted weak green fluorescence under daylight-equivalent illumination
(bottom right). Photos by Le Ngoc Nang.

1 cm 1 cm

1 cm 1 cm

AMBER FROM PHU QUOC, VIETNAM GEMS & GEMOLOGY SUMMER 2022 189
TABLE 1. Gemological properties of amber from Phu Quoc, Vietnam.

Sample no. Weight (ct) Color Shape SG RI Inclusions

1 17.92 Yellowish orange Irregular 1.04 1.540 Spangle, gas bubble

2 22.11 Intense reddish orange Irregular 1.06 1.541 Spangle, gas bubble, flora

3 7.22 Reddish orange Irregular NA NA Gas bubble, flora

4 10.03 Intense reddish orange Irregular 1.04 1.542 Gas bubble, flora

5 5.18 Orangy red Irregular 1.05 1.540 Gas bubble, flora

6 5.10 Brownish yellowish orange Pear 1.05 1.541 NA

7 122.77a Yellow Roundish nodule NA NA NA

8 76.40a Reddish orange In matrix NA NA Gas bubble, flora

9 1.69 Reddish orange Oval 1.05 1.541 Spangle, gas bubble

10 1.99 Intense bluish reddish orange Drop 1.04 1.543 Gas bubble

11 0.82 Reddish orange Oval 1.04 1.542 Spangle, gas bubble

12 1.05 Orangy yellow Oval 1.03 1.542 Spangle, gas bubble

A-1 4.68 Yellow Near-round 1.04 NA None

A-2 7.16 Orangy yellow Near-round 1.07 1.542 Spangle, gas bubble

A-3 11.94 Yellow-orange Drop 1.03 1.540 Gas bubble, insect

a
Total weight of sample, including host rock, in grams. NA: not available

Kocsis et al., 2020; Zhang et al., 2020). However, the 45°. Although there are no detailed studies to explain
Phu Quoc amber showed weaker fluorescence under the phenomenon, this optical characteristic known
daylight than Dominican or Indonesian amber. as anomalous double refraction (ADR) is commonly
Hot needle testing on all 12 amber samples re- seen under a polariscope. Accordingly, internal stress
leased the natural scent of resin, distinguishing it from helps to explain the degree of anomalous extinction
the burning scent of synthetic polymer (Ross, 1999). in amber (Kratochvíl, 2009).
None of the Phu Quoc samples reacted to acetone,
proving they were amber and not copal (Ross, 1999). Internal Characteristics. The Phu Quoc samples con-
tained four types of internal characteristics: gas bub-
Optical Characteristics. Under the polariscope, the bles, disk-like inclusions (spangle) with a colorless
Phu Quoc amber presented the phenomenon of al- core inside, round-film inclusions, and flora inclusions
ternately blinking light and dark when rotated every (figure 7 and table 1). Gas bubble inclusions indicating

190 AMBER FROM PHU QUOC, VIETNAM GEMS & GEMOLOGY SUMMER 2022
the origin as tree resin (viscous and cool) are found in Dominican amber are shown in figure 8, B–D. The re-
amber from most sources worldwide. In Phu Quoc sults were consistent with previously published FTIR
samples, the gas bubble inclusions were accompanied spectra of Burmese amber (Jiang et al., 2020), Baltic
by a typical flow structure. The disk-like inclusions amber (Guiliano et al., 2007; Wolfe et al., 2009), and
contained air bubbles at the center, suggesting the Dominican amber (Xin et al., 2021).
condition of Phu Quoc amber, which were influenced Phu Quoc amber exhibited an absorption band at
by geothermal heat due to sedimentary depth (depth around 2900 cm–1 with two peaks at 2923 and 2861
of burial) (Ross, 1999). Round-film inclusions are quite cm–1, representing the stretching vibration of the sp3
commonly seen, and they are also the spangles that hybridized C-H bond of the methyl and methylene
reflect light to create interference colors. The flora in- groups (Guiliano et al., 2007). These are the typical ab-
clusions were remnants of reddish brown wood fibers. sorption bands of amber and plastic or materials con-
Significantly, insects were not found in any of the taining the C-H bond.
amber samples inspected, unlike amber from most In the range of 2800–1800 cm–1, Phu Quoc amber
other sources (Penney, 2016). displayed a weak band at 2100 cm–1 caused by alkyne
C≡C stretching, which was similar to that of Domini-
FTIR Analysis. The FTIR spectra of the Phu Quoc can samples. Meanwhile, Burmese and Baltic amber
samples shown in figure 8A include peaks at 2923, did not show any significant bands in this region.
2861, 2100, 1695, 1455, 1379, 1261, 1156, 970, and The spectral range between 1800 and 1200 cm–1 for
815 cm–1. The FTIR results of Baltic, Burmese, and Phu Quoc amber included a peak at 1455 cm–1 for

A B

Figure 7. Inclusions in
Phu Quoc amber. A: A
spangle with an inclu-
sion at the center. B:
Gas bubbles assembled
with botanical rem-
nants. C: A spangle
C D with interference colors.
D: Tree bark remnants.
Photomicrographs by Le
Ngoc Nang; fields of
view 4.5 mm (A and C)
and 5.5 mm (B and D).

AMBER FROM PHU QUOC, VIETNAM GEMS & GEMOLOGY SUMMER 2022 191
methylene (CH2) bending and another at 1379 cm–1 for assigned to C-O stretching of tertiary alcohol (Pavia
methyl (CH3) bending (Pavia et al., 2014). The strong et al., 2014). Additionally, the Baltic amber presented
absorption bands at 1695 and 1261 cm–1 are related to a spectral peak at 888 cm–1. For Phu Quoc amber, no
C=O stretching and C-O carbonyl bonds, respectively peaks were detected at 3048, 1642, and 887 cm–1,
(possibly ester and acid). The simultaneous presence proving it was genuine amber rather than copal (Sun
of the peaks shows that there are many types of car- et al., 2015).
bonates in this amber’s composition (Sun et al., 2015). The FTIR spectra of Phu Quoc samples exhib-
In the 1800–1200 cm–1 range, the spectral absorption ited characteristics similar to those of Baltic,
bands were similar to those of the Dominican samples. Burmese, and Dominican amber. However, the
Meanwhile, the absence of a 1261 cm–1 peak in spectra of Phu Quoc amber displayed some charac-
Burmese and Baltic amber differentiated them from teristics unique to the deposit. The existence of
Phu Quoc amber. 1261 and 1156 cm–1 bands and the absence of 3450
Between 1200 and 800 cm–1, the Phu Quoc amber and 1149 cm–1 peaks revealed distinguishing fea-
displayed weak absorption peaks at 1156, 970, and tures in both composition and polymer structures.
815 cm–1, while Burmese, Baltic, and Dominican These differences play an important role in defining
amber displayed medium absorption peaks at 1149, the geographic origin of amber from global sources
1031, 975, and 813 cm–1. The weak 1156 cm–1 peak is (including Phu Quoc amber).

Figure 8. FTIR spectra of amber from Phu Quoc (A) and other sources (B–D).

FTIR SPECTRA

A Phu Quoc amber B Baltic amber

1.00 1.00
TRANSMITTANCE

TRANSMITTANCE

0.95
2100 0.98 3380
0.90 No. 1
970 No. 2
0.85 0.96
815 1156 1695 No. 4
0.80 No. 5
1261
No. 6 0.94
0.75 1379 No. 9 813 1695
1375 2855
0.70 1455 2861 No. 10 888
0.92
No. 11 1031 1149 1449
0.65 2923 No. 12 2922
0.60 0.90
650 1150 1650 2150 2650 3150 3650 650 1150 1650 2150 2650 3150 3650
WAVENUMBER (cm–1) WAVENUMBER (cm–1)

C Burmese amber D Dominican amber

1.00 1.00
TRANSMITTANCE

0.95 3450 0.98

TRANSMITTANCE

0.90 813
1720 0.96 2100 3388
975
0.85 1031 1448 0.94
2853
0.80 1149
2920 975 1720
1228 0.92
0.75 1375 1149 2866
0.90
813 1257 1377 1457 2924
0.70
650 1150 1650 2150 2650 3150 3650 650 1150 1650 2150 2650 3150 3650
WAVENUMBER (cm–1) WAVENUMBER (cm–1)

192 AMBER FROM PHU QUOC, VIETNAM GEMS & GEMOLOGY SUMMER 2022
Figure 9. Gem-quality amber from Phu Quoc: an 11.16 ct rough and cabochons weighing 1.02–1.40 ct. Photo by Le
Ngoc Nang.

COMMERCIAL POTENTIAL the commercial potential of Phu Quoc amber, fur-

Based on our initial evaluation, Phu Quoc amber is ther assessment is needed.
of high enough quality to be suitable for jewelry
manufacturing (figures 1 and 9). The color ranges CONCLUSIONS
from highly valued yellowish orange to orangy red, Standard gemological properties, FTIR spectroscopy,
similar to that of Baltic and Burmese amber. Most and other tests confirmed that the samples represent
are transparent, especially the samples smaller than the first Vietnamese source of amber. The material’s
1 cm. The Phu Quoc amber is suitable for cabochons attractive color, transparency, and size make it suit-
and carvings. Although we carried out our research able for jewelry. In addition, the wide distribution of
within a small area, the sandstone formation (amber the Neogene sandstone host rock on this island in-
host rock) covers almost the entire island (My and dicates strong commercial potential. With the dis-
Linh, 2005), suggesting the possibility of finding covery of amber on Phu Quoc, Vietnam could
amber over a wide area. While these factors signal become an important supplier of this organic gem.

ABOUT THE AUTHORS nam National University. Ha Thuy Hang is a lecturer in the Faculty
Le Ngoc Nang is a postgraduate in the Faculty of Geology at the of Geology at the University of Science, Vietnam National Univer-
University of Science (https://en.hcmus.edu.vn), Vietnam National sity Ho Chi Minh City.
University Ho Chi Minh City, and CEO of Liu Gemological Re-
search and Application Center. Dr. Pham Trung Hieu is associate ACKNOWLEDGMENTS
professor in the Faculty of Geology at the University of Science, The authors sincerely thank Mr. Nguyen Thanh Nha from the Insti-
Vietnam National University Ho Chi Minh City. Lam Vinh Phat is tute of Chemical Technology for his support in utilizing advanced
manager of gemstone identification, and Pham Minh Tien is a analysis methods. We also express gratitude to our clients for the
technical specialist, at Liu Gemological Research and Application use of their samples to carry out this research. This research was
Center. Ho Nguyen Tri Man is a lecturer in the Faculty of Geology funded by Vietnam National University Ho Chi Minh City (VNU-
and Petroleum Engineering at the University of Technology, Viet- HCM) under grant number C2022-18-31.

AMBER FROM PHU QUOC, VIETNAM GEMS & GEMOLOGY SUMMER 2022 193
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194 AMBER FROM PHU QUOC, VIETNAM GEMS & GEMOLOGY SUMMER 2022
FEATURE ARTICLES

NATURAL RADIOACTIVITY IN SELECT

SERPENTINITE-RELATED NEPHRITE SAMPLES:
A COMPARISON WITH DOLOMITE-RELATED
NEPHRITE
Dariusz Malczewski, Michał Sachanbiński, and Maria Dziurowicz

The published literature offers only a few records of direct measurement of the natural radioactivity in nephrite.
The present study used high-purity germanium (HPGe) low-background gamma-ray spectrometry to measure
activity concentrations of primordial radionuclides in 11 serpentinite-related nephrite (ortho-nephrite) samples
from deposits in Poland, Russia, Canada, and New Zealand, along with three samples of rodingite and serpen-
tinite from a nephrite deposit in Nasławice, Poland. All nephrite samples exhibited very low 40K, 232Th, and 238U
activity concentrations that fell within the range of published values for ultrabasic and basic rocks. The nephrite
samples from Jordanów (Poland) gave the highest uranium and thorium activity concentration values. Two sam-
ples of plagiogranitic rodingite showed significantly higher 238U and 232Th activity concentrations than the values
measured for nephrite. Nephrite thorium and uranium concentrations correlated strongly (r = 0.98), and the
corresponding Th/U ratios appear unique according to geographical location. The mean estimated potassium,
thorium, and uranium concentrations from ortho-nephrite analyzed here were compared with corresponding
mean values previously reported for dolomite-related nephrite (para-nephrite). The comparison indicates that
the ortho-nephrites studied have similar uranium concentrations but lower mean potassium concentrations and
higher mean thorium concentrations than those reported for para-nephrite in the literature.

N
ephrite jade is an almost monomineral rock Nephrite’s internal structure typically appears fi-
made of full-grained (felted), cryptocrystalline brous, with an intricately woven microstructure of
amphiboles (actinolite and tremolite) (Łoboś thin tremolite filaments and microtubules that form
et al., 2008; Adamo and Bocchio, 2013; Gil et al., kidney-like shapes. The name “nephrite” thus de-
2020; Gao et al., 2020). Nephrite usually appears rives from the Greek word for kidney (Łoboś et al.,
green with varying degrees of saturation but may also 2008). It is characterized by a high degree of compact-
exhibit white, gray, black, yellow, brown, and red col- ness and coherence as well as extreme compressive
oration (Luo et al., 2015; Gil et al., 2020). In most strength. One nephrite from British Columbia,
cases, the color of nephrite is influenced by Cr3+, Fe2+, Canada, exhibited a fracture strength of about 200
and Fe3+ ions that produce a wide range of light to dark MN m–2 (Makepeace and Simandl, 2001). By contrast,
green hues (Suturin et al., 1980; Hobbs, 1982). The in- nephrite has a hardness of approximately 6.5 on the
tensity of the green coloration is mainly a function of Mohs scale. The specific gravity of nephrite usually
the total iron content (Wilkins et al., 2003; Grapes and ranges between 2.90 and 3.06 (Żaba, 2006). The main
Yun, 2010). This sometimes creates mottled, striped, global economic deposits of nephrite jade occur in
or veined varieties with marbled patterns. Canada, Russia, China, the United States, South
Korea, New Zealand, Australia, Poland, Italy, and
Switzerland. These are usually classified as:
See end of article for About the Authors and Acknowledgments.
GEMS & GEMOLOGY, Vol. 58, No. 2, pp. 196–213,
1. Endogenic deposits formed as a result of geo-
http://dx.doi.org/10.5741/GEMS.58.2.196 logical processes of internal origin. The origin
© 2022 Gemological Institute of America of these deposits relates to serpentinites

196 RADIOACTIVITY IN SERPENTINITE-RELATED NEPHRITE GEMS & GEMOLOGY SUMMER 2022

 (ortho-nephrite, serpentinite-related nephrite) Consensus holds that ortho-nephrite forms due to
and dolomites (para-nephrite, dolomite-re- initial rodingitization and subsequent serpentinite
lated nephrite). transformation under the influence of gabbroic or acid
magma injection (Gil et al., 2015). Genetic relations
2. Exogenic deposits representing secondary
between these phases and associated rock types thus
placer deposits of nephrite blocks associated
warranted investigation of both serpentinite and
with river and stream sediments, for instance,
rodingite that co-occur at the Nasławice locality.
in East Sayan (Russia), New Zealand, and
British Columbia (Canada).
This study measured the radioactivity concentra-
tion of 40K, 232Th, and 238U in ortho-nephrite samples In Brief
from five known nephrite deposits using gamma-ray • Gamma-ray measurements indicate very low 40K,
spectrometry. A major goal of this research was to as- 232
Th, and 238U activity concentrations in 11 serpenti-
certain whether, as valued decorative stones and nite-related (ortho-nephrite) samples.
gemstones, nephrite may pose a radiological risk to • Two samples of plagiogranitic rodingite from a nephrite
those who handle them, such as artisans or collec- deposit in Nasławice (Poland) showed significantly
tors. The authors also sought to compare Th/U ratios higher 238U and 232Th activity concentrations than those
of ortho- and para-nephrite. As a secondary goal, the measured for nephrite samples.
research sought evidence that Th/U concentration • Thorium and uranium concentrations correlate posi-
ratios vary with the geographic origin of nephrite. tively and linearly in the ortho-nephrites analyzed.
The results were compared with limited data avail- • Nephrite, a valued decorative stone and gemstone, does
able from previous studies on samples from the same not pose a radiological risk to artisans or collectors.
localities. Previously published data consist prima-
rily of potassium concentrations but also include
thorium and uranium concentrations reported for
para-nephrite and obtained by other analytical meth- MATERIALS AND METHODS
ods (Leaming, 1978; Łoboś et al., 2008; Grapes and This study analyzed samples of gem-quality ortho-
Yun, 2010; Burtseva et al., 2015; Gil et al., 2015). nephrite originating from Poland (Nasławice, Jor-
Dolomite-related nephrite forms at the contact danów), Russia (Siberia, East Sayan), Canada (British
between dolomite marble and a granitic intrusion or Columbia), and New Zealand (South Island). Pol-
siliceous metasediments (Nichol, 2000; Yui and ished nephrite samples referred to as NS1, NS2, and
Kwon, 2002; Gil et al., 2015). Different formation NS3 (table 1 and figure 1, A–C) were collected by M.
processes cause ortho-nephrite and para-nephrite to Sachanbiński from an active serpentinite and
vary in terms of their concentrations of transition nephrite quarry in Nasławice (Łoboś et al., 2008).
metals and trace elements. Due primarily to lower Raw jade samples referred to as JR1, JR2, and JR3
iron and chromium concentrations, para-nephrite (table 1 and figure 1, D–F) belong to the collection of
displays lighter colors ranging from white to light M. Sachanbiński and come from the historic jade
green (Luo et al., 2015). Ratios of iron to magnesium quarry in Jordanów (Prichystal, 2013). Nephrite in
and concentrations of chromium, nickel, cobalt, and Nasławice and nearby Jordanów occurs in serpenti-
manganese distinguish para-nephrite from ortho- nite of the Gogołów-Jordanów Massif (GJM), which
nephrite. Along with trace element concentrations, forms part of the Ślęża Ophiolite, itself part of the
hydrogen and oxygen stable isotopic ratios have Mid-Sudetic Ophiolite (Gil, 2013; Gil et al., 2020).
been used to determine the geographic origin of se- These nephrites occur as irregular bodies within the
lect dolomite-related nephrite deposits (Gao et al., so-called black wall, a chlorite body within a contact
2020). As many concentrations of minor elements zone of rodingite dikes and serpentinite. The serpen-
overlap for both types of nephrite, expanding the tinites in Jordanów and Nasławice host completely
range of trace element determinations and overall transformed gabbro and plagiogranites as well as par-
geochemical datasets could refine models and crite- tially rodingitized leucogranites. Nephrite from Jor-
ria for distinguishing dolomite-related and serpenti- danów and Nasławice is considered of high
nite-related nephrite. Expanded geochemical gemological quality and usually appears green but
datasets also offer greater accuracy and precision to without uniform coloration. Varied shades of green
studies of nephrite provenance. create unique patterns on the material’s surface.

RADIOACTIVITY IN SERPENTINITE-RELATED NEPHRITE GEMS & GEMOLOGY SUMMER 2022 197

 A B C

D E F

G H I

J K

Figure 1. Photographs of ortho-nephrite samples analyzed. A: From Nasławice (NS1), 7 cm in length. B: From
Nasławice (NS2), 7 cm in length. C: From Nasławice (NS3), 3 cm in length. D: From Jordanów (JR1), 4 cm in
length. E: From Jordanów (JR2), 4 cm in length. F: From Jordanów (JR3), 4 cm in length. G: From Siberia (SB1), 3
cm in length. H: From Siberia (SB2), 3 cm in length. I: From Siberia (SB3), 3 cm in length. J: Bear carving from
British Columbia (CN1), 7 cm in length. K: From New Zealand (NZ1), ~7 cm across. All photos by D. Malczewski.

198 RADIOACTIVITY IN SERPENTINITE-RELATED NEPHRITE GEMS & GEMOLOGY SUMMER 2022

Actinolite represents the main mineral comprising Samples RN1, RN2, and RN3 represent rodingite
nephrite, and secondary minerals include chlorite, (table 1). Rodingite is a rare type of metasomatic
antigorite, grossular, chromite, and iron oxides. rock consisting of grossular, diallage, and accessory
Russian nephrite samples SB1, SB2, and SB3 (table magnetite, apatite, and serpentinized olivine. It can
1 and figure 1, G–I) belong to the collection of M. be enriched in epidote, prehnite, and vesuvianite
Sachanbiński. These were donated by a Russian ge- (Bell et al., 1911; O’Brien and Rodgers, 1973; Hatzi-
ologist during the International Mineralogical Asso- panagiotou and Tsikouras, 2001; Kobayashi and
ciation conference in Novosibirsk, Russia, in Kaneda, 2010; Heflik et al., 2014). The samples and
September 1978. The samples come from the Ospa rock type are considered to have high ornamental
deposit located in the East Sayan nephrite-bearing value. The analyzed samples belong to the collec-
area (southern folded periphery of the Siberian cra- tion of S. Madej from the University of Wrocław
ton). This deposit represents an apo-ultrabasic and come from an active serpentinite and jade
nephrite (Burtseva et al., 2015). Nephrite from the de- quarry in Nasławice. Dubińska et al. (2004) distin-
posit appears greenish blue in color and exhibits dif- guish two types of rodingite. The first type, boninite
ferent degrees of saturation (Suturin et al., 1980). rodingite, contains relict clinopyroxene and vesu-
Mineral compositions consist primarily of actinolite vianite, garnet, and diopside. The second type, pla-
and tremolite fibers, pyroxene, diopside, serpentine, giogranite rodingite, contains relics of checkerboard
talc, chromite, graphite, and fuchsite. Accessory albite and hydrogrossular, clinozoisite, zoisite, and
mineral content ranges from 0.5 to 1.5%. All of the late diopside. Macroscopically, samples RN1 and
above-mentioned nephrite samples from Nasławice RN2 (plagiogranite rodingites; figure 2, A and B) ex-
and Jordanów (Poland) and Siberia (Russia) will be do- hibit alternating, fine-grained, light and pink-col-
nated to the Mineralogical Museum of the Univer- ored laminae and medium-grained, dark gray
sity of Wrocław (Poland). laminae. In their study of the phase compositions
Canadian sample CN1 is a dark green nephrite of this type of rodingite, Szełęg (2006) reported
carved in the form of a small bear (table 1 and figure quartz (approx. 63%), zoisite (approx. 25%), carbon-
1J). This carving also belongs to the collection of M. ate-hydroxyl apatite, hydrogrossular, albite, and
Sachanbiński and was purchased during the 17th Gen- smaller amounts of apatite, titanite, chromite,
eral Meeting of the IMA in Toronto in August 1998. uraninite, and thorianite. Sample RN3 (boninite
It was made by a First Nations artisan using material rodingite) (figure 2C) exhibits dull to light green
from British Columbia, where more than 50 nephrite color and varied mineral composition.
occurrences have been reported. These consist of in- Sample SRN (table 1, figure 2D) belongs to the
dividual blocks, talus blocks, boulder fields, and in collection of M. Sachanbiński and represents a typi-
situ bodies that occur primarily at contacts between cal serpentinite from the deposit in Nasławice. Ser-
serpentinite and cherts, or other metasedimentary and pentinites occurring there formed as a result of
igneous rocks formed in submarine environments. complex, long-term transformation of harzburgite
Secondary minerals in the nephrite include spinel, and lherzolite (Dubińska and Gunia, 1997). These be-
diopside, uvarovite, titanite, chlorite, and talc (Leam- long to the Gogołów-Jordanów Serpentinite Massif
ing, 1978; Makepeace and Simandl, 2001). of the Ślęża Ophiolite and probably formed at around
Nephrite sample NZ1 from the South Island of 400 Ma (million years ago) (Gil et al., 2015). The ser-
New Zealand exhibits a waxy luster and blackish pentinite from Nasławice appears dark green in color
green color (table 1, figure 1K). This sample was do- and consists primarily of antigorite and sometimes
nated to the Mineralogical Museum at the Institute contains olivine, bronzite, diallage, diopside, and
of Earth Sciences, University of Silesia by L. hornblende. They sometimes resemble nephrite or
Sajkowski, a Polish geologist living and working in are nephritized to varying degrees. Subordinate min-
New Zealand. Grapes and Yun (2010) describe this erals include magnesite, braunite, chromite, apatite,
nephrite from northern Westland as occurring as rare garnet, and others. Macroscopically, these minerals
pebbles and boulders weighing up to several tons, are prized for their decorative value. The use of ser-
found in glacial outwash gravels and till. They also pentinite as tools or decorative objects dates back to
appear in streams and rivers that drain the nephrite the Neolithic (around 3000 BCE) in Lower Silesia.
source area of the pounamu ultramafic rocks located The stone was originally used in tools and weapons
in the northern part of the Southern Alps (Ireland et (e.g., axes, knives, and hoes) and is used today in or-
al., 1984; Cooper, 1995). namental objects (see box A).

RADIOACTIVITY IN SERPENTINITE-RELATED NEPHRITE GEMS & GEMOLOGY SUMMER 2022 199

 A B

C D

Figure 2. Samples of rodingite and serpentinite from Nasławice. A: Plagiogranitic rodingite (RN1), 4 cm in length.
B: Plagiogranitic rodingite (RN2), 6 cm in length. C: Boninitic rodingite (RN3), 6.5 cm in length. D: Serpentinite
(SRN), 6 cm in length. All photos by D. Malczewski.

The activity concentrations (in Bq kg–1) of the nat- and serpentinite samples, shown in table 1, were
urally occurring radionuclides in nephrite, rodingite, measured using a GX4018 gamma-ray spectrometry

BOX A: USE OF NEPHRITE JADE

The practical and ornamental use of nephrite jade by hu- Jade continues to be used for ornamental and decora-
mans dates back to at least the early Neolithic. Because tive objects such as jewelry and art. Some of the highest-
its fracture yields sharp, durable edges, nephrite was ini- quality nephrite, referred to as pounamu in the Maori
tially used to make axes, knives, scrapers, and other sim- language, is mined in New Zealand (Hobbs, 1982; Prichys-
ple cutting tools. A pile deposit discovered along the tal, 2013). The Maori utilized jade for ornaments, art, and
shores of Lake Constance, Switzerland, contained 30,000 tools—in the latter case until the introduction of metal in
jade axes weighing a total of 6000 kg (Hobbs, 1982; the nineteenth century. Chinese culture and artwork have
Prichystal, 2013). A younger Stone Age site near Jor- featured jade since its earliest inception, and jade carving
danów (Jordansmuhl) in Lower Silesia, Poland, is inter- is particularly well developed in East Asia (Douglas, 2005;
preted as a serpentinite and nephrite mining and Wang, 2011). Nephrite jade has been considered a symbol
processing center (Prichystal, 2013). A block of jade of wealth and power, and thus many jade artifacts have
weighing over two tons excavated from the Jordanów survived intact into modern times. From antiquity to the
site in 1889 was on display in the New York Metropoli- present day, nephrite jade has been considered a store of
tan Museum of Art (Gil, 2013). value and items made from it have been prized as gifts.

200 RADIOACTIVITY IN SERPENTINITE-RELATED NEPHRITE GEMS & GEMOLOGY SUMMER 2022

TABLE 1. Measured radionuclide activity concentrations and calculated weight concen-
trations of 40K, 232Th, and 238U from ortho-nephrite, rodingite, and serpentinite samples.a
40 232 238
K Th U

Rock/Sample Bq kg–1 Total K wt.%b Bq kg–1 ppm Bq kg–1 ppm

Nephrite

NS1 1.5 0.005 0.5 0.12 1.6 0.13

NS2 1.2 0.004 0.6 0.15 1.8 0.15

NS3 5.5 0.018 2.0 0.49 4.5 0.36

JR1 17 0.055 4.4 1.08 19 1.34

JR2 13 0.042 4.7 1.16 20 1.62

JR3 14 0.045 4.3 1.06 17 1.38

SB1 5.1 0.016 1.9 0.47 6.2 0.50

SB2 6.8 0.022 2.0 0.49 5.9 0.48

SB3 5.1 0.016 1.9 0.47 6.6 0.53

CN1 27 0.087 0.8 0.20 1.2 0.10

NZ1 4.2 0.014 1.5 0.37 1.3 0.11

Rodingite

RN1 14 0.045 130 32.0 292 23.6

RN2 28 0.091 18 4.43 172 13.9

RN3 2.7 0.009 4.6 1.13 10 0.81

Serpentinite

SRN 1 0.003 0.7 0.17 1.1 0.09

a
Measurement uncertainties are plotted with this data in figures 4–7.
b
The following conversion factors were used: K (wt.%) = 40K (Bq kg –1)/309.11; Th (ppm) = 232Th (Bq kg –1)/4.06;
and U (ppm) = 238U (Bq kg –1)/12.35 (International Atomic Energy Agency, 2003). Uncertainties fell within 5–
10% of measured values for activity concentrations below 2 Bq kg –1.

system at the Laboratory of Natural Radioactivity, tor (45.2% efficiency) in a lead and copper shield (10.2
Institute of Earth Sciences, University of Silesia cm) with a multichannel-buffer Lynx instrument.
(Malczewski et al., 2018a, 2018b; see also box B). The The energy resolutions of the detector were 0.8 keV
system uses a high-purity germanium (HPGe) detec- at 122 keV and 1.7 keV at 1330 keV. Each sample was

RADIOACTIVITY IN SERPENTINITE-RELATED NEPHRITE GEMS & GEMOLOGY SUMMER 2022 201

analyzed for 96 h. The activity concentrations of activity concentration (MDA) for measured radionu-
232
Th and 238U were determined based on the gamma- clides was 0.1 Bq kg–1. Figure 3 shows examples of
ray activity concentrations of 208Tl, 212Pb, and 228Ac gamma-ray spectra for nephrite samples NS1 and JR1
for thorium, and 214Pb and 214Bi for uranium. Ra- and rodingite sample RN1.
dionuclide activity concentrations were calculated
from the following gamma-ray transitions (energy in
RESULTS AND DISCUSSION
keV): 40K (1460.8); 208Tl (583.1, 860.5, 2614.5); 212Pb
(238.6, 300.1); 214Pb (242, 295.2, 351.9); 214Bi (609.3, Table 1 lists measured activity concentrations for 40K,
232
1120.3, 1764.5); and 228Ac (338.32, 911.6, 964.6, Th, and 238U in Bq kg–1 and calculated potassium
969.1). Laboratory Sourceless Calibration Software (wt.%), thorium (ppm), and uranium (ppm) concentra-
(LabSOCS) and Genie 2000 v.3.4 software packages tions for nephrite, rodingite, and serpentinite samples.
were both used to analyze spectra, calibrate effi-
40
ciency, and determine radionuclides. K. As seen in figure 4 and table 1, the 40K activity
Consistency of the activity concentrations calcu- concentrations recorded for nephrite samples analyzed
lated for gamma-ray transitions for a given multiline ranged from 1.2 Bq kg–1 for NS2 to 27 Bq kg–1 for CN1.
radionuclide (e.g., 208Tl, 214Bi, 214Pb, and 228Ac) were Nephrite from Nasławice, Jordanów, and Siberia gave
checked using line activity consistency evaluator average values of 2.7, 15, and 5.7 Bq kg–1, respectively.
(LACE) analysis. For all measurements, the multiline The New Zealand nephrite (NZ1) had an intermediate
radionuclides gave activity concentration ratios ap- value of 4.2 Bq kg–1. The average value for all samples
proaching unity. The average minimum detectable was 9.1 Bq kg–1 (figure 4). These values exceed 40K ac-

BOX B: NATURAL RADIOACTIVITY

Natural radioactivity results from the spontaneous decay ically range from 900–1400, 50–200, and 37–72 Bq kg–1
of naturally occurring radioisotopes. All elements having for 40K, 232Th, and 238U, respectively.
an atomic number greater than 83 consist only of radioac- The activity concentration index assesses radiologi-
tive isotopes. The three natural types of radioactive nuclei cal hazards to human health posed by building materials,
decay include alpha (α, emission of helium nuclei), beta (β, including rock surfaces used in paneling or countertops.
emission of electrons or positrons), and gamma (γ, emis- The European Union standard index I, as defined by the
sion of the shortest electromagnetic waves) decay. The SI European Atomic Energy Community (2013), represents
unit of radioactivity is the becquerel (Bq), equal to one the sum of three isotopic fractions expressed as:
decay per second. The becquerel replaced the curie (Ci),
ARa ATh AK
the unit equal to 3.7 × 1010 disintegrations per second or I= + +
300 Bq kg –1 200 Bq kg –1 3000 Bq kg –1
the radioactivity of 1 g of 226Ra (1 Bq = 0.27 × 10–10 Ci). The
main source of radioactivity in minerals, rocks, and soils where ARa, ATh, and AK represent 226Ra (238U), 232Th, and
derives from the 232Th, 235U, 238U decay series, and 40K (non- 40
K (Bq kg–1) activity concentrations in surroundings or
series). The 232Th, 235U, and 238U series consist of 6 α and 4 material. The value of index I should not exceed unity,
β, 7 α and 4 β, and 8 α and 6 β decays, respectively. Many which corresponds to the indoor dose rate of 1 mSv y–1.
of the α and β decays are accompanied by gamma-ray ra- The sievert (Sv) is the SI unit of equivalent dose and ef-
diation. The major gamma transitions from potassium, fective dose equal to 1 J kg–1. The external hazard index
thorium, and uranium are commonly used in estimating Hex is also commonly used to evaluate the radiological
weight concentrations based on measured activity concen- risk of building materials. It is calculated as follows:
trations. Due to the low natural abundance of 235U (0.72%
ARa ATh AK
of natural uranium), the activity concentration of this iso- Hex = + +
370 Bq kg –1 259 Bq kg –1 4810 Bq kg –1
tope is usually negligible compared to that of 238U. Its ac-
tivity concentration is thus not taken into account. An Hex index equal to unity corresponds to an external
Typical soils and carbonate rocks give average 40K, gamma-ray dose of 1.5 mSv y–1 from a material. With a
232
Th, and 238U activity concentrations of 400, 30, and 35 few exceptions, the overwhelming majority of rock
Bq kg–1 and 80, 7, and 27 Bq kg–1, respectively (Van building materials are characterized by I and Hex values
Schmus, 1995; UNSCEAR, 2000). Among the most com- less than one. All ortho-nephrites measured in this
mon rock types, acidic igneous rocks such as granite and study have extremely low average I and Hex values of
rhyolite give the highest radioactivity values. These typ- 0.04 and 0.03, respectively.

202 RADIOACTIVITY IN SERPENTINITE-RELATED NEPHRITE GEMS & GEMOLOGY SUMMER 2022

 GAMMA RAY SPECTRA
200

A
Nephrite sample NS1

150
TI-208 Pb-212
Ra-226
Pb-212
COUNTS

100
Pb-214
Pb-214

Bi-214

K-40
TI-208

50
TI-208

TI-208
Ac-228
Bi-214

Bi-214

Bi-214
Bi-212

Ac-228

Bi-214
Bi-214
0
0 500 1000 1500 2000 2500 3000
600

B
Pb-214

Nephrite sample JR1

Figure 3. Gamma-ray
Pb-212

spectra from nephrite

Pb-214 Ac-228

450
sample NS1 (A),
nephrite sample JR1 (B),
Bi-214

and rodingite sample

COUNTS

RN1 (C). Characteristic

Ra-226

300
gamma-ray emitters are
Pb-209

marked above the cor-

Pb-212

responding peaks. Note

the different y-axis
150
TI-208

count scales for the

Bi-214
TI-208
Ac-228

Ac-228
Ac-228

Bi-214
Bi-214

K-40

three samples.
Bi-214

TI-208
Bi-214

Bi-214

0
0 500 1000 1500 2000 2500 3000
16000
Pb-212

C
Rodingite sample RN1
Pb-214
Pb-212

12000
Pb-214 Ac-228
COUNTS

8000
Bi-214
Ac-228
Ra-226
Pb-209

TI-208

4000
Ac-228
U-235

TI-208

Bi-214
Ac-228

Bi-214
Ac-228

Bi-214
Bi-212

TI-208
Bi-214
TI-208

Bi-214
Bi-214
Bi-214

Bi-214

Bi-214
Bi-214
K-40

0
0 500 1000 1500 2000 2500 3000
ENERGY (keV)

RADIOACTIVITY IN SERPENTINITE-RELATED NEPHRITE GEMS & GEMOLOGY SUMMER 2022 203

 M EASURED 40K ACTIVITY CONCENTRATION VALUES
30
Average 40K value from all samples
40
K activity concentration from serpentinite sample

25

Figure 4. Measured 40K

activity concentration
20 values. The thick hori-
zontal line represents
K (Bq kg –1)

the average 40K value

measured from all sam-
15
ples in this study. The
thin horizontal line rep-
40

resents the 40K activity

10 9.1 concentration for the
serpentinite sample
(SRN). The thin vertical
5
lines are error bars.

0
S1

S2

S3

Z1
JR

SB

CN
SB

SB
JR
JR
N

N
NEPHRITE SAMPLE NO.

tivity concentration values estimated from ultramafic nite (1 Bq kg–1) but fell below average values measured
rocks (~ 0.3 Bq kg–1; Van Schmus, 1995) and serpenti- in gabbros from Lower Silesia (73 Bq kg–1; Plewa and

M EASURED 232Th ACTIVITY CONCENTRATION VALUES

6
Average 232Th value from all samples
232
Th activity concentration from serpentinite sample

Figure 5. Measured
232
Th activity concen-
4 tration values. The
thick horizontal line
Th (Bq kg –1)

represents the average

232
Th values from all
3
samples. The thin hori-
zontal line represents
232

2.2
the 232Th activity con-
2 centration for the ser-
pentinite sample (SRN).
The thin vertical lines
are error bars.
1
0.7

0
S1

S2

S3

Z1
JR

SB

CN
SB

SB
JR
JR
N

NEPHRITE SAMPLE NO.

204 RADIOACTIVITY IN SERPENTINITE-RELATED NEPHRITE GEMS & GEMOLOGY SUMMER 2022

 M EASURED 238U ACTIVITY CONCENTRATION VALUES
24
Average 238U value from all samples
238
U activity concentration from serpentinite sample

20

Figure 6. Measured 238U

activity concentration
16 values. The thick hori-
zontal line represents
U (Bq kg –1)

the average 238U value

from all samples in this
12
study. The thin hori-
zontal line represents
238

the 238U activity con-

8 7. 7 centration for the ser-
pentinite sample (SRN).
The thin vertical lines
4
are error bars.

1.1

0
S1

S2

S3

Z1
JR

SB

CN
SB

SB
JR
JR
N

N
NEPHRITE SAMPLE NO.

238
Plewa, 1992). Typical granites give values ranging from U. Table 1 and figure 6 show that the nephrite sam-
900–1400 Bq kg–1. ples from Jordanów had the highest average activity
concentration associated with 238U series isotopes (19
232
Th. As seen in table 1 and figure 5, the nephrite Bq kg–1). Samples from Siberia gave the second-high-
from Jordanów had the highest activity concentra- est average value at 6.3 Bq kg–1. Samples CN1 and
tion values associated with 232Th series isotopes. Val- NZ1 showed the lowest 238U activity concentrations
ues of 4.3, 4.4, and 4.7 Bq kg–1 yielded an average of 1.2 and 1.3 Bq kg–1, respectively. As with their 40K
232
Th activity concentration of 4.5 Bq kg–1. The sam- and 232Th values, the NS1 and NS2 nephrites from
ples from Siberia and Nasławice (NS3) showed the Nasławice gave lower 238U activity concentration val-
second-highest values at about 2 Bq kg–1. Sample ues (1.6 and 1.8 Bq kg–1) relative to sample NS3 (4.5
NZ1 had a similar value of 1.5 Bq kg–1. The samples Bq kg–1). All samples had higher 238U activity concen-
from Nasławice (NS1 and NS2) gave the lowest 232Th tration values than those measured from ultrabasic
activity concentrations of 0.5–0.6 Bq kg–1. Sample rocks (~0.1 Bq kg–1; Van Schmus, 1995) and from the
CN1 also had a low value of 0.8 Bq kg–1. All samples serpentinite sample SRN (1.1 Bq kg–1). As shown in
combined gave an average 232Th activity concentra- figure 6, the 238U activity concentration average of 7.7
tion of 2.2 Bq kg–1 (figure 5). All measured activity Bq kg–1 measured for all nephrite samples exceeded
concentrations exceeded values reported for ultraba- the average of 4.1 Bq kg–1 measured from gabbros
sic rocks of an order of 10–2 Bq kg–1 (Van Schmus, (Plewa and Plewa, 1992). This relatively high value
1995). The 232Th activity concentration for all sam- arises from the significantly higher 232Th activity con-
ples except NS1 and NS2 exceeded that measured centration measured in the nephrite samples from
from SRN (0.7 Bq kg–1). Activity concentrations for Jordanów. The calculated mean for the ortho-
nephrite samples analyzed fell below the average es- nephrites analyzed fell below the previously reported
timated for gabbros from Lower Silesia (6.4 Bq kg–1) average values for granite of 40 Bq kg–1 (Eisenbud and
and well below that previously estimated for gran- Gesell, 1997).
ites, which give 232Th activity concentrations ranging This study also compared 40K, 232Th, and 238U ac-
from 50–200 Bq kg–1 with an average of 70 Bq kg–1 tivity concentrations from ortho-nephrite with those
(Eisenbud and Gesell, 1997). previously measured from marbles using the same

RADIOACTIVITY IN SERPENTINITE-RELATED NEPHRITE GEMS & GEMOLOGY SUMMER 2022 205

technique. Calcite marbles from the Sławniowice higher average 238U activity concentration of 57 Bq
quarry (Lower Silesia, Poland) and Alpine marbles kg–1 for commercial marbles from Egypt.
from the vicinity of Aussois (France) gave average
232
Th activity concentration values of 2.4 Bq kg–1 Rodingite. As noted earlier, the rodingite samples as-
(Malczewski and Żaba, 2012; Moska, 2019). This ap- sociated with the Nasławice and Jordanów nephrite
proximated average value for 232Th (2.2 Bq kg–1) was deposits classify as boninite (RN3) and plagiogranite
measured from the ortho-nephrites analyzed. The rodingite (RN1 and RN2). As shown in table 1 and
238
U activity concentrations in calcite marbles ranged figure 7, sample RN1 gave the highest 238U and 232Th
from 16–23 Bq kg–1. Nephrite 238U activity concentra- activity concentrations of 292 and 130 Bq kg–1, re-
tions ranged from 2 to 20 Bq kg–1 with an average spectively. These values significantly exceed the ac-
value of ~8 Bq kg–1. The measured 40K activity con- tivity concentrations of all examined nephrites and
centrations for calcite marbles ranged from 12–80 Bq activity concentrations of typical granites of 40 and
kg–1, while that for nephrite ranged from 1.2–27 Bq 70 Bq kg–1 for 238U and 232Th, respectively (Eisenbud
kg–1 with an average of 9 Bq kg–1. The dolomite mar- and Gesell, 1997). Sample RN2 also exhibited high
bles collected from the Sławniowice mine gave 40K uranium activity concentration but lower thorium-
activity concentrations of 122 Bq kg–1 and 232Th activ- related activity concentration relative to sample
ity concentrations of 5 Bq kg–1. These exceeded values RN1. The high 238U and 232Th activity concentration
measured from calcite marbles, but the two rock values in RN1 and RN2 rodingite samples likely re-
types exhibited similar 238U concentrations of ~13 Bq flect the presence of accessory zircon, thorianite, and
kg–1. The ortho-nephrites analyzed gave comparable uraninite (Szełęg, 2006). As expected, sample RN3,
232
Th and 238U activity concentration values but lower which was collected from a body in direct contact
40
K activity concentration values relative to those of with the nephrite-bearing zone, exhibited signifi-
calcite and dolomite marbles. Based on their analyses cantly lower 238U and 232Th activity concentrations
using an HPGe detector, Fares et al. (2011) reported a than samples RN1 and RN2. Activity concentrations

M EASURED 40K, 232Th, AND 238U ACTIVITY CONCENTRATION VALUES

300
Average 232Th value activity concentrations
Average 238U value activity concentrations
40
K
250 232
Th
238
U

Figure 7. Measured 40K,

232
Th, and 238U activity
200
concentration values
for rodingite. The thin
and thick horizontal
(Bq kg –1)

150 lines respectively show

the average 232Th and
238
U activity concentra-
tions in typical granites
100
(Eisenbud and Gesell,
70
1997). The thin vertical
lines are error bars.
50 40

0
RN1 RN2 RN3

RODINGITE SAMPLE NO.

206 RADIOACTIVITY IN SERPENTINITE-RELATED NEPHRITE GEMS & GEMOLOGY SUMMER 2022

measured from RN3 for 238U (10 Bq kg–1) and 232Th (5 40
K activity concentration value of 27 Bq kg–1 (0.087
Bq kg–1) exceeded those observed in ortho-nephrite wt.%). Grapes and Yun (2010) report average potas-
samples from Nasławice, Siberia, British Columbia, sium concentrations for South Island nephrite of
and South Island but resembled those measured from 0.012 wt.% based on electron microprobe analysis.
the Jordanów samples. The rodingite samples exhib- These correspond to a 40K activity concentration of
ited relatively low 40K activity concentrations with a 3.8 Bq kg–1 and fall within the measurement uncer-
mean value of 15 Bq kg–1, which exceeded the mean tainty of potassium values obtained for sample NZ1
value of 9.1 Bq kg–1 measured from the nephrite sam- (4.2 Bq kg–1 and 0.014 wt.%). The above-mentioned
ples. As with 238U and 232Th activity concentrations, literature sources provide no data on thorium and ura-
sample RN3 gave the lowest 40K activity concentra- nium concentrations.
tion of 3 Bq kg–1. Samples RN1 and RN2 gave higher Ortho-nephrite samples from the East Sayan area
activity concentrations of 14 and 28 Bq kg–1. These exhibit relatively large differences in potassium, tho-
resembled values measured from the Jordanów rium, and uranium concentrations. Inductively cou-
nephrite samples and from CN1. pled plasma–mass spectrometry (ICP-MS) analysis
gave average potassium concentrations of 0.05 wt.%
Comparison of K, Th, and U Concentrations with (16 Bq kg–1 of 40K) for samples from the area (Burtseva
Previous Data. Concentrations estimated for potas- et al., 2015). This value exceeds the average value of
sium (wt.%), thorium (ppm), and uranium (ppm) 0.016 wt.% (6 Bq kg–1 of 40K) obtained for samples
showed similar trends among the samples as those SB1, SB2, and SB3. Burtseva et al. (2015) reported av-
observed for the 40K, 232Th, and 238U activity concen- erage thorium and uranium concentrations for nine
tration values. Nephrite potassium concentrations samples of 0.06 ppm (~0.3 Bq kg–1 for thorium) and
varied from 0.004 wt.% for sample NS2 to 0.087 0.05 ppm (~0.6 Bq kg–1 for uranium). The present
wt.% for sample CN1, and the samples overall gave study obtained mean thorium and uranium activity
a mean value of 0.03%. Concentrations estimated for concentrations of 1.9 and 6.2 Bq kg–1, corresponding
potassium, thorium, and uranium generally resem- to concentrations of 0.48 and 0.51 ppm from East
bled the few previously obtained results for ortho- Sayan nephrite (table 1).
nephrite from the same locations. The nephrite
samples from Nasławice in particular showed similar Comparison of K, Th, and U Concentrations Meas-
potassium concentrations. Łoboś et al. (2008) report ured from Para-Nephrite. Luo et al. (2015) present de-
average potassium concentrations of 0.004, 0.008, and tailed laser ablation–inductively coupled–mass
0.016 wt.% for three types of nephrite based on elec- spectrometry (LA-ICP-MS) trace element data for
tron microscope analysis. These values correspond to 138 samples collected directly from eight major
40
K activity concentrations of approximately 1.2, 2.5, dolomite-related nephrite deposits in East Asia. Fig-
and 5.0 Bq kg–1 and thus agree very well with activity ure 8 compares mean potassium, thorium, and ura-
concentrations measured from samples NS1, NS2, nium concentrations reported in Luo et al. (2015)
and NS3 by gamma-ray spectrometry (table 1). with results from ortho-nephrite samples reported
Prompt gamma neutron activation energy analysis in this study. As seen in figure 8A, the ortho-
(PGAA) indicated a bulk-rock potassium concentra- nephrites exhibit an average potassium concentra-
tion of about 0.016 wt.% for the Jordanów nephrite tion of 0.03 wt.%, whereas the para-nephrites from
sample. This value corresponds to a 40K activity con- East Asia exhibit an average potassium concentra-
centration of less than 5 Bq kg–1 (Gil et al., 2015). The tion of 0.07 wt.% (22 Bq kg–1) with standard devia-
concentration value and associated 40K activity con- tions of 0.02 and 0.04%, respectively. Nichol (2000)
centration fell below values obtained by this study for reports a mean potassium concentration of 0.1 ± 0.02
the three samples from Jordanów, which gave an av- wt.% for para-nephrite samples from southern Aus-
erage potassium concentration of 0.050 wt.% and an tralia. This corresponds to a 40K activity concentra-
average 40K activity concentration of 15 Bq kg–1 (table tion of approximately 30 Bq kg–1, a value that
1). Extensive studies by Leaming (1978) and Nichol resembles that measured for sample CN1, which
(2000) report an average potassium concentration of gave the highest 40K activity concentration among
0.038 wt.% and a corresponding 40K activity concen- the ortho-nephrite samples (table 1). Similarly,
tration of 12 Bq kg–1 for Canadian nephrite from dolomite-related nephrite from Val Malenco (Italy)
British Columbia. Gamma-ray measurements (table had a mean potassium concentration of 0.04 ± 0.004
1) of sample CN1 indicate a higher but comparable wt.%, which slightly exceeded the average values

RADIOACTIVITY IN SERPENTINITE-RELATED NEPHRITE GEMS & GEMOLOGY SUMMER 2022 207

 CALCULATED AVERAGE CONCENTRATIONS
0.12 mean potassium concentration calculated from
Serpentinite-related A ortho-nephrite 40K activity concentration generally
Dolomite-related
falls below that measured for para-nephrite (figure
8A). However, potassium concentrations often over-
0.08
0.07 lap for both types of nephrite. Serpentinite-related
K (wt. %)

nephrites gave an estimated average thorium con-

centration of 0.55 ± 0.30 ppm, which exceeds that
0.04 estimated for para-nephrite (0.26 ± 0.18 ppm or 1.1
0.03
± 0.7 Bq kg–1) by a factor of two (figure 8B). The rela-
tively large dispersion of thorium concentrations for
both types of nephrite means that value ranges par-
0.00 tially overlap. Excluding the Jordanów samples with
0.90 the highest thorium concentrations gives a calcu-
B lated mean of 0.35 for the remaining serpentinite-re-
Serpentinite-related lated nephrites. This value still exceeds the values
Dolomite-related
estimated for dolomite-related nephrite. As shown
0.60 0.55 in figure 8C, serpentinite-related nephrites gave an
Th (ppm)

average U concentration of 0.63 ± 0.57 ppm, while

dolomite-related nephrites had an average uranium
concentration of 0.74 ± 0.44 ppm (9.1 ± 5.4 Bq kg–1).
0.30 0.26
Ortho-nephrite and para-nephrite showed very sim-
ilar average uranium concentrations, but samples
from different nephrite deposit locations give rela-
0.00 tively variegated values. In summary, the relatively
large standard deviations associated with calculated
1.50 mean potassium, thorium, and uranium concentra-
Serpentinite-related C tions suggest that these parameters alone would not
Dolomite-related
be enough to clearly distinguish ortho-nephrite from
para-nephrite but may serve as approximate indica-
1.00
tors of host rock type, especially in terms of their
U (ppm)

0.74 potassium and thorium parameters.

0.63

0.50 Correlations Between Th and U Concentrations. As

seen in figure 9, 232Th and 238U concentrations corre-
late strongly in ortho-nephrites analyzed and give a
correlation coefficient of 0.98. A fitted line shows
0.00
samples NS1 and NZ1 deviate slightly from this
trend. Figure 9 shows that Jordanów samples
Figure 8. Comparison of calculated average concen- (JR1–JR3) form a distinct data cluster with uranium
trations of potassium (wt.%), thorium (ppm), and ura- concentrations ranging from 1.3 to 1.7 ppm and tho-
nium (ppm) in ortho-nephrites (serpentine-related, rium concentrations from 1.0 to 1.2 ppm. All other
darker green bar) analyzed in this study and from ortho-nephrite samples range from about 0.1 to 0.6
para-nephrite (dolomite-related, lighter green bar) ppm in terms of both uranium and thorium concen-
data reported by Luo et al. (2015). The thin vertical trations. A gap of 0.7 to 1.3 ppm for uranium and 0.6
lines are error bars. to 1.0 for thorium thus exists between the Jordanów
samples and others. Excluding the CN1 sample, other
samples also show strong K-Th and K-U correlations
obtained for ortho-nephrites reported here. A con- (table 1).
centration of 0.04 wt.% potassium corresponds to a The dolomite-related nephrites from deposits in
40
K activity concentration of about 12 Bq kg–1. This East Asia studied by Luo et al. (2015) showed weaker
estimate resembles values measured for the Jor- correlations between average thorium and uranium
danów nephrites (table 1). Results also show that the concentrations. These gave average thorium concen-

208 RADIOACTIVITY IN SERPENTINITE-RELATED NEPHRITE GEMS & GEMOLOGY SUMMER 2022

 U vs. Th
1.6
r = 0.98

1.4

JR2
1.2
JR1
JR3 Figure 9. Correlation
between thorium (ppm)
1.0 and uranium (ppm) for
ortho-nephrites ana-
Th (ppm)

0.8 lyzed in this study. The

solid line represents the
linear fit of Th (ppm) =
0.6 NS3 SB2
SB1 0.16 + 0.62 × U (ppm),
SB3
with a correlation coef-
NZ1
0.4 ficient of r = 0.98.
CN1
0.2 NS2
NS1

0.0
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
U (ppm)

trations of 0.07 to 0.70 ppm and uranium concentra- (figure 10). The weaker correlation between thorium
tions from 0.2 to 1.4 ppm. Data from these para- and uranium concentrations for para-nephrite (figure
nephrites show a high degree of visible scatter, and 10) compared to that observed for ortho-nephrite (fig-
linear regression gives a correlation coefficient of 0.42 ure 9) most likely arises from greater differentiation of

U vs. Th
0.8
r = 0.42

0.7

0.6 Figure 10. Correlation

between thorium (ppm)
0.5 and uranium (ppm) for
para-nephrites based on
Th (ppm)

data reported in table 2

0.4
of Luo et al. (2015). The
solid line represents a
0.3 linear fit of Th (ppm) =
0.13 + 0.17 × U (ppm),
with a correlation coef-
0.2
ficient of r = 0.42.

0.1

0.0
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
U (ppm)

RADIOACTIVITY IN SERPENTINITE-RELATED NEPHRITE GEMS & GEMOLOGY SUMMER 2022 209

 Th/U CONCENTRATION R ATIOS
5
Average for ortho-nephrites
Average for para-nephrites

Figure 11. Concentra-

tion ratios of Th/U. The
thick horizontal line
Th (ppm) / U (ppm)

3 shows the average for

ortho-nephrites in the
present study. The thin
horizontal line shows
2 the average for para-
nephrites based on data
reported by Luo et al.
1.3 (2015). The thin vertical
lines are error bars.
1
0.5

0
S1

S2

S3

Z1
JR

SB

CN
SB

SB
JR
JR
N

N
NEPHRITE SAMPLE NO.

thorium and uranium concentrations in dolomites imately 2 (Van Schmus, 1995; Pasquale et al., 2001).
(and carbonates in general), which are the host rocks As listed in table 1, the serpentinite from Nasławice
for para-nephrite. (SN1) gave a ratio of 1.9, which approaches the mean
value estimated for ortho-nephrite. Previous studies
Th/U Concentration Ratios. As shown in figure 11, of dolomite and dolomite marble using gamma-ray
Th/U ratios for the serpentinite-related nephrites spectrometry show that the average Th/U ratio for
vary from 0.70 to 3.51 with an average value of 1.30. these rocks is about 0.5 (Chiozzi et al., 2002; Mal-
The average Th/U concentration ratios were 1.11 ± czewski et al., 2005; Malczewski and Żaba, 2012;
0.12, 0.73 ± 0.02, and 0.95 ± 0.05 for nephrite from Moska, 2019). Generally, carbonate rocks have a
Nasławice, Jordanów, and Siberia, respectively. mean Th/U value of 0.8 (Van Schmus, 1995). Again,
Nephrite from these locations can be differentiated the average value of the Th/U ratio calculated for the
within standard deviations based on their Th/U ratio para-nephrites based on the results obtained by Luo
(figure 11). Despite its higher thorium and uranium et al. (2015) agrees well with those reported for car-
concentrations, sample NS3 gave a Th/U ratio simi- bonate rocks and especially dolomites.
lar to that of samples NS1 and NS2. Samples CN1
and NZ1 gave relatively higher Th/U ratios of 2.03 ± CONCLUSIONS
0.14 and 3.51 ± 0.25, respectively. This study reports gamma-ray spectrometric analy-
The data presented by Luo et al. (2015) indicates sis of serpentinite-related nephrite samples from
a calculated mean Th/U value of 0.5 for dolomite-re- several well-known global localities. Measurements
lated nephrite. This value falls below the value of 1.3 indicate very low 40K, 232Th, and 238U activity con-
estimated for serpentinite-related nephrite by the centrations that pose no radiological risk. Measured
present study (figure 11). The calculated values of 1.3 activity concentrations fell below values reported
and 0.5 for serpentinite- and dolomite-related in the literature for acid igneous rocks. By contrast,
nephrite (respectively) resemble Th/U concentration the mean 40K, 232Th, and 238U activity concentration
ratios in the host rocks. Serpentinites and their peri- values exceeded average values reported in litera-
dotite protoliths both exhibit a Th/U ratio of approx- ture sources for ultrabasic rocks and, to a lesser ex-

210 RADIOACTIVITY IN SERPENTINITE-RELATED NEPHRITE GEMS & GEMOLOGY SUMMER 2022

Figure 12. This 90 × 20 mm nephrite carving is from the Kutcho Jade mine in northwest British Columbia,
Canada. Photo by Robert Weldon; courtesy of Jade West Group.

tent, for serpentinites. Compared to gabbroic rocks hibited lower 40K and 232Th activity concentrations
from Lower Silesia (Poland), the ortho-nephrites ex- and slightly higher 238U activity concentrations. The

RADIOACTIVITY IN SERPENTINITE-RELATED NEPHRITE GEMS & GEMOLOGY SUMMER 2022 211

measured serpentinite-related nephrites were char- Th/U ratios, indicating that this parameter may dis-
acterized by extremely low average values of radio- tinguish material from these respective localities.
logical hazard indices I and Hex of 0.04 and 0.03, Our results suggest that relative to para-nephrite,
with the upper levels of both indices equal to unity. ortho-nephrite (figure 12) exhibits lower potassium
Calculated thorium (ppm) and uranium (ppm) con- concentration values and higher thorium concen-
centrations strongly correlate. Nephrite from trations. Both types of nephrite jade exhibit similar
Nasławice, Jordanów, and Siberia show distinct uranium concentrations.

ABOUT THE AUTHORS ACKNOWLEDGMENTS

Dr. Malczewski is a nuclear physicist and assistant professor at This work was partially supported by the National Science Cen-
the Institute of Earth Sciences of the University of Silesia (Poland), tre of Poland through grant no. 2018/29/B/ST10/01495 and
specializing in the field of natural and anthropogenic radioactivity the research program at the Institute of Earth Sciences, Univer-
in the geosphere and researching metamict minerals as natural sity of Silesia, ZB-14-2020. We thank the Mineralogical Mu-
analogues for understanding the storage of high-level nuclear seum at the Institute of Earth Sciences, University of Silesia,
waste. Professor Sachanbiński, who specializes in the physics of and Stanisław Madej for the New Zealand jade sample and
minerals, gemology, and mineralogy, is an emeritus professor at rodingite samples used in this research. The authors would like
the University of Wrocław and teaches at the College of Arts and to thank Sandra Malczewska for the digital processing of pho-
Management in Wrocław. Dr. Dziurowicz is a geologist, geophysi- tos according to publication requirements.
cist, and assistant professor at the Institute of Earth Sciences of
the University of Silesia, specializing in natural and anthropogenic
environmental radioactivity.

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China. Journal of Mineralogical and Petrological Sciences, Vol. Prichystal A. (2013) Lithic Raw Materials in Prehistoric Times
105, No. 3, pp. 112–122, http://dx.doi.org/10.2465/jmps.081224 of Eastern Central Europe. Masaryk University, Brno, Czech
Leaming S.F. (1978) Jade in Canada. Geological Survey of Republic.
Canada, Paper 78-19. Energy, Mines & Resources, Canada, Suturin A.N., Zamaletdinov R.S., Letnikov F.A., Sekerin A.P. Bur-
59 pp. makina G.V., Suturina T.A., Platonov A.N., Belitchenko V.P.,
Łoboś K., Sachanbiński M., Pawlik T. (2008) Nephrite from Vokhmentser A.Y. (1980) Mineralogy and genesis of nephrites
Nasławice in Lower Silesia (SW Poland). Przegląd Geologiczny, in the USSR. In Sidorenko, Eds., Gem Minerals: Proceeding of
Vol. 56, No. 11, pp. 991–999 (in Polish with English abstract). the XI General Meeting of IMA, Novosibirsk, September 4–10,
Luo Z., Yang M., Shen A.H. (2015) Origin determination of 1978 (in Russian).
dolomite-related white nephrite through iterative-binary linear Szełęg E. (2006) Crystalochemistry of titanite from Lower Silesian.
discriminant analysis. G&G, Vol. 51, No. 3, pp. 300–311, PhD thesis. University of Silesia, Katowice, Poland (in Polish).
http://dx.doi.org/10.5741/GEMS.51.3.300 UNSCEAR (2000) Sources and Effects of Ionizing Radiation: Vol
Makepeace K., Simandl G.J. (2001) Jade (nephrite) in British Co- I. United Nations Scientific Committee on the Effects of
lumbia, Canada. Program and Extended Abstracts for 37th Atomic Radiation. UNSCEAR 2000 Report to the General As-
Forum on the Geology of. Industrial Minerals 37, pp. 209– 210. sembly, with Scientific Annexes. United Nations, New York.
Malczewski D., Żaba J. (2012) Natural radioactivity in rocks of the Van Schmus W.R. (1995) Natural radioactivity of the crust and the
Modane-Aussois region (SE France). Journal of Radioanalytical mantle. In T.J. Ahrens, Ed., Global Earth Physics: A Handbook
and Nuclear Chemistry, Vol. 292, No. 1, pp. 123–130, of Physical Constants. AGU Reference Shelf I, American Geo-
http://dx.doi.org/10.1007/s10967-011-1428-9 physical Union, Washington, DC, pp. 283–291.
Malczewski D., Teper L., Lizurek G., Dorda J. (2005) In situ Wang R. (2011) Progress review of the scientific study of Chinese
gamma-ray spectroscopy in common rock raw materials mined ancient jade. Archaeometry, Vol. 53, No. 4, pp. 674–692,
in Kraków vicinity, Poland. In Naturally Occurring Radioac- http://dx.doi.org/10.1111/j.1475-4754.2010.00564.x
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Conference Held in Szczyrk, Poland, 17–21 May 2004. IAEA- (2003) Spectroscopic and related evidence on the coloring and
TECDOC-1472. International Atomic Energy Agency, Lan- constitution of New Zealand jade. American Mineralogist, Vol.
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Malczewski D., Dziurowicz M., Krzykawski T., Grabias A. (2018a) 8-917
Spectroscopic characterization and thermal recrystallization Yui T.F., Kwon S.T. (2002) Origin of a dolomite-related jade deposit
study of an unknown metamict phrase from Tuften Quarry, at Chumcheon, Korea. Economic Geology, Vol. 97, No. 3, pp.
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For online access to all issues of GEMS & GEMOLOGY from 1934 to the present, visit:

gia.edu/gems-gemology

RADIOACTIVITY IN SERPENTINITE-RELATED NEPHRITE GEMS & GEMOLOGY SUMMER 2022 213

 Lab Notes
Editors
Thomas M. Moses | Shane F. McClure

Rare Orange BENITOITE

A bright orange benitoite (figure 1)
weighing 2.29 ct was recently ex-
amined at the Carlsbad laboratory.
Standard gemological testing re-
vealed a refractive index of 1.756 to
over the limit (OTL) and a specific
gravity of 3.68. The fluorescence re-
action was strong orange in long-
wave ultraviolet light and medium
Figure 3. The orange benitoite
blue in short-wave UV (figure 2).
contained several discoid frac-
The benitoite was slightly color-
tures with healed fringes, consis-
zoned orange and blue; the blue por-
tent with heat-treated benitoite.
tion’s pleochroism was very light
Field of view 2.33 mm.
blue and darker blue, while the or-
ange portion’s pleochroism was
orangy yellow and dark orange. Mi- Figure 1. The size and bright This benitoite was faceted by Bill
croscopic examination showed al- color of this 2.29 ct orange Vance of Vance Gems, who stated
tered crystals with discoid fractures benitoite are exceptionally rare. that the rough was colorless prior to
(figure 3) and strong doubling. The
heat treatment. The bright orange
discoid fractures were consistent
the treated material successfully color and large size make this an ex-
with heated benitoite.
changes color, orange benitoite is con- ceptional example of orange benitoite.
Benitoite is a barium titanium sil-
sidered rare (B.M. Laurs et al., “Beni- Very few of these have been examined
icate (BaTiSi3O9) known as the Cali-
toite from the New Idria District, San at GIA, and this 2.29 ct gemstone is
fornia state gem, and it only occurs in
Benito County, California,” Fall 1997 the largest example we have observed.
gem quality in San Benito County,
California. The New Idria District G&G, pp. 166–187). Amy Cooper and Nathan Renfro
produces medium to medium-dark
blue and lighter blue colors. Accord- Figure 2. The orange benitoite’s response to long-wave (left) and short-
ing to a previous study published in wave UV (right).
G&G, pink and colorless examples
are considered rare. In addition, heat
treatment of lighter-color or colorless
benitoite may result in an orange
color. Since only a small portion of

Editors’ note: All items were written by staff

members of GIA laboratories.
GEMS & GEMOLOGY, Vol. 58, No. 2, pp. 214–225.

© 2022 Gemological Institute of America

214 LAB NOTES GEMS & GEMOLOGY SUMMER 2022

 gravity was 2.48. These observations
suggested a glass imitation, which was
confirmed by comparing the infrared
spectrum with that of manmade glass.
The next two were more convinc-
ing imitations of natural sapphire.
They weighed 9.17 and 6.21 ct and
measured approximately 16.00 × 10.06
× 8.30 mm and 10.31 × 9.38 × 8.71
mm, respectively. Resin that coated
the surface (figure 5) resembled matrix
composed of natural minerals com-
monly seen on natural corundum
rough. The resin started to melt with
Figure 4. This set consists of a 48.63 ct piece of manmade glass (left), 9.17 the touch of a hot pointer. Brownish
and 6.21 ct laboratory-grown sapphires with resin imitation of matrix on materials trapped in cavities resembled
the surface (center), and an 8.46 ct natural blue sapphire rough (right). iron oxide stains one would expect to
see in natural rough. Though difficult
to see inside of the stones due to their
Interesting Set of rough surfaces, a few gas bubbles were
stones (figure 4) submitted as natural
BLUE “ROUGH” GEMSTONES observed through a small transparent
sapphire for identification and origin
area. Raman spectroscopy matched co-
The selling of simulants and syn- reports. The largest weighed 48.63 ct
rundum, and immersion in water (fig-
thetics mixed with parcels of natural and measured approximately 22.88 ×
ure 6) revealed curved blue banding.
stones is an old form of deception. It 19.67 × 15.19 mm. The material was
Laser ablation–inductively coupled
usually happens close to mines, partially fashioned, with evidence of
plasma–mass spectrometry (LA-ICP-
where inexperienced buyers assume polish lines on the surfaces. Careful
MS) detected no gallium and revealed
the gemstones come directly from microscopic examination revealed
trace elements of impurities consistent
the source—and where advanced multiple gas bubbles, distinct flow
with synthetic corundum. Hydrostatic
testing is likely not available prior to marks associated with blue coloration,
specific gravity values were 3.76 and
the purchase. and conchoidal fractures. Weak snake
3.59, respectively. Both values were
The Carlsbad laboratory recently pattern bands were observed under the
below the SG of corundum (3.9–4.05),
received a group of four blue rough polariscope. The hydrostatic specific
a result of the lower SG of the resin on
the surface. Both were reported as la-
boratory-grown sapphire with a com-
Figure 5. A resin imitation of matrix on the surface of a laboratory-grown ment stating, “Imitation matrix and
sapphire. Field of view 7.19 mm. resin is present on the surface.”

Figure 6. Curved blue banding

visible in the 6.21 ct laboratory-
grown sapphire immersed in
water.

LAB NOTES GEMS & GEMOLOGY SUMMER 2022 215

 The last piece of rough was a blue (formerly Premier) mine in South Af-
stone weighing 8.46 ct and measuring rica. Compared to the Hope and Wit-
13.85 × 9.89 × 7.60 mm. The frosted telsbach-Graff, both of which were
natural surface made it difficult to see mined in the Golconda region of India,
inside the stone, but some natural- the De Beers Cullinan Blue has some
looking fingerprints and strong, important similarities in gemological
straight inky blue banding were ob- and spectroscopic features but shows
served. The Raman spectrum clear variations. Natural type IIb blue
matched with corundum, and a hy- diamonds over 10 carats are exceed-
drostatic SG of 3.96 confirmed it. The ingly rare.
stone was immersed in methylene io- The blue color is distributed
dide to confirm the zoning was evenly throughout the stone. Visual
straight and not curved. Medium observation under a gem microscope
chalky blue fluorescence to short- Figure 7. The 15.10 ct De Beers revealed a very clean stone. No in-
wave UV and a strong 3309 cm–1 Cullinan Blue diamond. clusions or graining were observed.
series in its Fourier-transform infrared Accordingly, the diamond received a
(FTIR) spectrum proved that heat clarity grade of Internally Flawless.
treatment had been applied to the shares many special gemological char- Under conventional long-wave and
stone. LA-ICP-MS revealed natural acteristics with other rare type IIb short-wave UV radiation, it showed
chemistry, including about 200 ppma (boron-containing) diamonds such as no observable fluorescence or phos-
iron and other trace elements such as the Wittelsbach-Graff, once assumed phorescence. This feature is dramat-
gallium (~25 ppma), vanadium (~3.5 to be cut from the same rough crystal ically different from that of the Hope
ppma), magnesium (~35 ppma), chro- as the Hope. Here we report another and Wittelsbach-Graff, two large
mium (~1.5 ppma), and titanium (~80 special diamond of this group. type IIb blue diamonds that exhibit
ppma). Based on appearance, color Recently graded by GIA and the re- strong and prolonged red phospho-
zoning, and chemistry, this stone was cipient of a special monograph report rescence to conventional short-wave
reported as natural sapphire, heat was a 15.10 ct (17.47 × 11.53 × 7.94 UV radiation.
treated, with Madagascar as the coun- mm) Fancy Vivid blue cut-cornered The absorption spectrum in the
try of origin. rectangular step cut. Named the De mid-infrared region showed typical
This was an interesting study of Beers Cullinan Blue diamond (figure 7; absorption features related to boron
how synthetics and simulants can be see video at www.gia.edu/gems-gem- in diamond, such as strong absorp-
mixed with their natural counterparts ology/summer-2022-lab-notes-de- tion at ~2800 cm–1 and a weak absorp-
to misrepresent a parcel. However, beers-cullinan-blue), it was cut from a tion peak in the range of 1332–1200
careful examination and standard 39.34 ct rough type IIb diamond crys- cm–1 (figure 8). The intensities of
gemological testing are usually tal mined by Petra from the Cullinan these absorptions indicated a high
enough to identify them correctly.
Najmeh Anjomani
Figure 8. The mid-infrared spectrum of the type IIb De Beers Cullinan
Blue diamond.
DIAMONDS
MID-INFRARED SPECTRUM
The Type IIb De Beers Cullinan
ABSORPTION COEFFICIENT (cm–1)

Blue Diamond
Type IIb blue diamonds are extremely 15
rare in nature. When people think of
blue diamonds, the Hope diamond im-
mediately springs to mind. The famed 10
45.52 ct Fancy Deep grayish blue
cushion-cut treasure, now housed in
5
the Smithsonian National Museum of
Natural History in Washington, DC,
has a long and fascinating history.
0
First examined by GIA in 1960 and
graded by GIA in 1988 (R. Crowning- 6000 5000 4000 3000 2000 1000
shield, “Grading the Hope diamond,” WAVENUMBER (cm–1)
Summer 1989 G&G, pp. 91–94), it

216 LAB NOTES GEMS & GEMOLOGY SUMMER 2022

 microscope equipped with crossed po- styles) (see video), 15.10 ct weight, and
larizers revealed a clear tatami pattern Internally Flawless clarity grade is ex-
with a dark gray color (figure 9). Both ceptionally rare. It will remain one of
the Wittelsbach-Graff and the Hope the world’s most important diamonds.
have different patterns and higher in- Paul Johnson, A’Dhi Lall, Madelyn
terference colors, a good indication Dragone, and Stephanie Persaud
that the De Beers Cullinan Blue has a
much less distorted lattice structure.
Under very strong short-wave UV,
this diamond showed a weak aqua
The Grass Is Always Greener…
Figure 9. Observed with cross-
blue fluorescence with a subtle net- The Carlsbad laboratory recently ex-
polarized light was a strong ta-
work of dislocations in the crystal amined a 0.97 ct Fancy grayish green
tami strain pattern with a dark
structure, a pattern clearly different diamond submitted for colored dia-
gray color.
from the tight mosaic patterns ob- mond grading service. Microscopic
served in the Hope and the Wittels- examination revealed a colorless dia-
concentration of uncompensated bach-Graff (figure 10) (Gaillou et al., mond with green radiation stains
boron of ~0.33 ppm. Natural type IIb 2014). scattered across the pavilion (figure
diamonds typically contain 0.24–0.36 These blue diamonds are among 11).
ppm (E. Gaillou et al., “Study of the the rarest of gems. Recent research (E. These radiation stains were par-
Blue Moon diamond,” Winter 2014 Smith et al., “Blue boron-bearing dia- ticularly unusual due to their linear
G&G, pp. 280–286). The diamond’s monds from Earth’s lower mantle,” appearance and resembled blades of
boron concentration is close to that Nature, Vol. 560, No. 7716, 2018, pp. grass in their morphology and color.
of the Hope (~0.36 ppm) and higher 84–87) has demonstrated that their These stains were prevalent along in-
than that of the Wittelsbach-Graff boron derived from pieces of the tentionally preserved rough natural
(~0.19 ppm). Absorption from boron earth’s crust sinking to the extremely diamond surfaces on the pavilion.
is the main contributor of color in deep depths of diamond formation. Faceted surfaces along the pavilion
natural type IIb diamonds. The gemological characteristics of the were polished with particular effort
Observation with a gemological De Beers Cullinan Blue suggest it is to retain some of the green radiation
one of these superdeep diamonds. Its stains. The resultant internal reflec-
combination of Fancy Vivid blue color tion of green light to the table created
Figure 10. Under very strong grade in a step cut (a cut that does not a uniform green bodycolor in this rare
short-wave UV, a weak aqua blue enhance color, unlike other faceting and beautiful diamond.
fluorescence with a subtle net-
work of dislocations was ob-
served (top). After exposure, a Figure 11. Blade-like green radiation stains. Also indicated is the
weak pinkish red phosphores- boundary of the close-up view of the green stains in figure 12. Field of
cence was observed (bottom). view 2.9 mm.

Figure 12

LAB NOTES GEMS & GEMOLOGY SUMMER 2022 217

 Radiation stain “Optical defects in diamond: A quick
reference chart,” Summer 2013
Flat bottom G&G, pp. 107–111). The GR1 defect
trigon area from photoluminescence spectra
can be measured and mapped to indi-
cate the spatial distribution of this de-

Rou
Rou

fect coincident with the radiation

Pol
Pol

gh
stains (figure 13).
gh

ishe
ishe

It is unusual to see green radiation

d
d

stains of this shape that correspond

150 µm 150 µm with indentations on a diamond sur-
face. These features could be a com-
Figure 12. Radiation stains on the rough diamond’s surface also pen-
monly overlooked characteristic of
etrate to a polished side (left). Viewed with reflected light, the surface
green diamonds.
shows acicular indentations coincident with green stains (right).
Michaela Stephan, Roy Bassoo, and
Lo Combs
Surface photomicrographs re- 2022 G&G Micro-World, pp. 64–65)
vealed long, linear, and acicular in- and may result from acicular to tabu-
dentations concentrated near the lar radioactive minerals precipitating 10 ct HPHT-Treated CVD
center of the radiation stains (figure directly on the diamond surface in a LABORATORY-GROWN DIAMOND
12). Indentations crosscut flat-bot- paleoplacer to recent alluvial environ- Recent years have seen several size
tomed trigons, suggesting they post- ment (e.g., R. Lauf, Mineralogy of milestones for faceted diamonds
dated diamond dissolution in the Uranium and Thorium, Schiffer Pub- grown by chemical vapor deposition
earth’s mantle (e.g., R. Tappert and M. lishing, Ltd., Atglen, Pennsylvania, (CVD). In all the published reports
Tappert, Diamonds in Nature: A 2016). Radiation damage created va- that commented on treatment, these
Guide to Rough Diamonds, Springer, cancies in the diamond lattice, which record-size CVD diamonds were indi-
Heidelberg, 2011). The green stains absorb red light and reflect green light, cated to be as-grown and with no in-
along the polished surface indicate resulting in the green color of the ra- dications of post-growth treatment
that the radiation stains penetrated diation stains. Uncharged or neutral (Winter 2016 Lab Notes, pp. 414–416;
some depth into the diamond. These vacancies produce a photolumines- “IGI Hong Kong certifies largest CVD
features have been observed pre- cence response near the 741 nm zero grown diamond to date,” 2020,
viously at GIA (e.g., Spring 2021 phonon line called the GR1 defect https://www.igi.org/gemblog/igi-
G&G Micro-World, pp. 66–67; Spring (e.g., J.E. Shigley and C.M. Breeding, hong-kong-certifies-largest-cvd-
grown-diamond-to-date/; Spring 2022
Lab Notes, pp. 54–56). For other re-
Figure 13. Left: Map of the integrated area beneath the GR1 defect peak of cent milestone CVD diamonds re-
the radiation stains on the diamond surface, derived from photolumines- ported within the trade, we could not
cence spectroscopy. Right: Reflected light image of the surface showing ra- confirm whether they were as-grown
diation stains (outlined in red) coincident with acicular indentations. The or treated. At the time of publication,
measurements were taken with a 532 nm laser at 1 mW power, 25 μm the current benchmark is a 30.18 ct
confocal spot size, 5 μm step size, and 100 Hz. H-color diamond reportedly grown by
Ethereal Green Diamond (Rapaport
News, June 12, 2022).
Against this backdrop, a notable
10.04 ct CVD-grown diamond (figure
14) was recently submitted to the
Carlsbad laboratory for a laboratory-
grown diamond report. This emerald-
cut stone with G color and VS2
clarity had several growth remnants,
including a cloud of dark non-dia-
mond carbon. As with all laboratory-
100 µm 100 µm grown diamonds, it underwent
extensive testing including spectro-
GR1 AREA (cm2)
scopy to verify its CVD origin. IR ab-
3.0 6.0 9.0 12.0 15.0 18.0
sorption spectroscopy identified it as

218 LAB NOTES GEMS & GEMOLOGY SUMMER 2022

 al., “CVD synthetic diamonds from nal of Gems & Gemmology, Vol. 23,
Gemesis Corp.,” Summer 2012 No. 6, 2021, pp. 25–39), this treatment
G&G, pp. 80–97). is not often applied to larger stones.
Many CVD-grown diamonds are Therefore, evidence of HPHT treat-
subjected to high-pressure, high-tem- ment in a CVD-grown diamond larger
perature (HPHT) treatment after than 10 carats is noteworthy. These
growth to remove a brownish appear- products will likely become more
ance caused by extended defects (such commonplace in the future.
as vacancy-related complexes). The Sally Eaton-Magaña
brown color often correlates with a
faster CVD growth rate, which the
manufacturer uses knowing the color
PEARLS
can be reduced by treatment after-
ward. It appears that when manufac- A Reported Cassis Pearl from
turers create a CVD diamond of Key West, Florida
record-setting size, the growth is per- The Carlsbad laboratory recently ex-
formed so slowly that subsequent amined an oval non-nacreous pearl
HPHT treatment is not required for a weighing 29.78 ct and measuring 17.86
colorless to near-colorless grade. × 15.64 × 14.58 mm (figure 16). The
Figure 14. This 10.04 ct G-color While some 80% of colorless to pearl possessed a uniform pinkish or-
CVD-grown diamond proved to near-colorless CVD-grown diamonds ange bodycolor and a porcelaneous sur-
have been HPHT treated. have been subjected to post-growth face with flame structures. The flames
treatment to reduce their brownish were short and wide and tapered to a
coloration (S. Eaton-Magaña et al., point. This fine, well-formed flame
“Laboratory-grown diamond: A gem- structure looked like a homogeneous
type IIb with an uncompensated
ological laboratory perspective,” Jour- spotted pattern throughout the pearl’s
boron concentration of ~2 ppb. Spec-
tral features such as the lack of a 468
nm peak in photoluminescence
along with the coloration in the Dia- Figure 16. This oval pinkish orange porcelaneous pearl weighing 29.78 ct
mondView fluorescence imaging (fig- and measuring 17.86 × 15.64 × 14.58 mm was reportedly found in a queen
ure 15) confirmed it had undergone helmet conch (Cassis madagascariensis), shown on the left with various
post-growth treatment (W. Wang et Cassis species shells. Shells courtesy of Robin Willis.

Figure 15. The green and blue flu-

orescence colors in this Diamond-
View image confirm post-growth
treatment of the 10.04 ct CVD-
grown diamond.

LAB NOTES GEMS & GEMOLOGY SUMMER 2022 219

Figure 17. Left: This porcelaneous pearl exhibited a fine, well-formed flame structure covering the entire surface,
and a homogeneously spotted pattern was visible with the unaided eye. Right: Under magnification with fiber-
optic illumination, the wide and spiky flame structure was evident. Field of view 2.90 mm.

surface (figure 17, left), yet the flame study,” Journal of Molluscan Studies, pod species such as queen conch (Lo-
forms were evident at high magnifica- Vol. 72, No. 2, 2006, pp. 157–162). batus gigas), Melo species, Cassis
tion under the microscope (figure 17, Real-time microradiography (RTX) re- species, and horse conch (Fasciolarii-
right). Subsequently, Raman spectro- vealed a dark gray oval void-like fea- nae subfamily). The flame characteris-
scopic analysis with a 514 nm argon- ture in the center and a growth ring in tics and pinkish orange bodycolor of
ion laser verified the pearl was the outer area of the pearl (figure 18). this pearl were unlike those of orange
composed of aragonite, with peaks at Such a void can be found in natural porcelaneous pearls previously sub-
154, 181, 192, 207, 704, and 1085 cm–1 pearls from a number of porcelaneous mitted to GIA. The client who sub-
(J. Urmos et al., “Characterization of pearl-producing mollusks. mitted the pearl stated that it was
some biogenic carbonates with Raman Orange porcelaneous pearls are found inside a queen helmet conch in
spectroscopy,” American Mineralo- produced from various marine gastro- the early 1960s by Bert Matcovich (fig-
gist, Vol. 76, 1991, pp. 641–646); two
strong polyene peaks at 1131 and 1523
cm–1 were indicative of natural color Figure 19. This photo shows the pearl and the queen helmet shell in
(C. Hedegaard et al., “Molluscan shell which it was found. Photo courtesy of the Bert Matcovich family.
pigments: An in situ resonance Raman

Figure 18. RTX imaging revealed

the growth structure of the pearl:
an ovalish void-like feature of
less radiopacity in the center and
a growth ring in the outer area.

220 LAB NOTES GEMS & GEMOLOGY SUMMER 2022

ure 19), who owned a shell shop in Key
A B
West, Florida. Born into a family of
shellers with more than 60 years of ex-
perience, Matcovich fished the waters
off Key West for conchs and visited
local shrimp boats daily in the 1960s
to purchase various types of shells.
This pearl was a remarkable discovery.
Queen helmet, also known as em-
peror helmet, is the common name
for a marine gastropod species called
Cassis madagascariensis, which be-
longs to the Cassidae family. The C D
species is generally distributed in the
tropical western Atlantic, including
the Caribbean Sea (J.H. Leal, “Gastro-
pods,” in K.E. Carpenter, The Living
Marine Resources of the Western
Central Atlantic, Vol. 1, Rome: Food
and agriculture organization of the
United Nations, 2002, pp. 99–127).
Queen helmet shells have large, thick
whorls with short spires, and three
rows of knobs often appear on the Figure 20. A: Necklace of South Sea bead cultured pearls, 14.80–15.90
body. They have a flat large parietal mm in diameter. B and C: Real-time microradiography (RTX) revealed
shield next to an aperture, and the one bead cultured pearl in the necklace containing an RFID device
color ranges from pale cream to deep showing an obvious demarcation of typical shell bead nuclei. The em-
salmon, often with a dark orangy bedded electronic component is visible as a white opaque stepped
brown color between the “teeth” (see square feature. D: When aligned at right angles to the previous direc-
again figure 19). Owing to their signif- tion, the electronic component is harder to see but can be observed
icant thickness, these colorful shells within a long, sharp laminated plane separating the two parts of the
are widely used for cameo carving. shell bead nucleus.
Cassis pearls typically have a fine
and slender flame structure, often
with intersecting flames. Their colors
traditionally range from light orange South Sea bead cultured pearl neck- electronic components within a few of
to orangy brown, sometimes with laces, each consisting of 29 pearls the pearls. They were visible as opaque
patchy color. This pearl was unlike ranging from 14.80 to 15.90 mm in white squares with a stepped pattern
typical Cassis pearls examined by diameter (strand A, figure 20A) and in keeping with previously examined
GIA, and its mollusk identity could 14.40 × 14.20 mm to 16.20 mm in di- samples containing radio-frequency
not be confirmed with gemological ameter (strand B, figure 21A). General identification (RFID) devices (H.A.
testing. Nonetheless, this fine large observation under a binocular micro- Hänni and L.E. Cartier, “Tracing cul-
natural non-nacreous pearl and its scope revealed clear aragonite plate- tured pearls from farm to consumer: A
discovery story from six decades ago lets characteristic of nacreous pearls, review of potential methods and solu-
are noteworthy. with no indications of treatment. tions,” Journal of Gemmology, Vol. 33,
Real-time microradiography (RTX) No. 7-8, 2013, pp. 239–246; Spring
Artitaya Homkrajae, Michaela revealed obvious demarcation features 2020 Lab Notes, pp. 134–136). Interest-
Stephan, and Amiroh Steen separating the shell bead nucleus from ingly, only a single pearl in strand A
the overlying nacre layers. The nacre (figure 20, B–D) and five pearls in
thickness range was consistent with strand B (figure 21, B–D) contained an
RFID Device Embedded in South bead cultured pearls produced by the RFID device. The device is usually po-
Sea Bead Cultured Pearl Necklaces Pinctada maxima mollusk (N. Stur- sitioned off the center of the bead to
New technologies are increasingly man et al., “Bead cultured and non- avoid being drilled.
being applied to cultured pearls, and bead cultured pearls from Lombok, GIA’s Hong Kong lab has also
it is exciting to witness developments Indonesia,” Fall 2016 G&G, pp. 288– begun seeing similar features in re-
in pearl traceability. GIA’s Bangkok 297). However, the most striking fea- cent submissions (figure 22, A–B). The
laboratory recently received two ture was the presence of some team compared the RTX data with

LAB NOTES GEMS & GEMOLOGY SUMMER 2022 221

 A B
tioned earlier describing RFID devices
in bead cultured pearls have shown
that these nuclei are produced by a
patented pearl technology invented by
Fukui Shell Nucleus Factory, which
also supplies laminated beads to cer-
tain pearl farms. This explains the
link between the laminating tech-
nique and its application in the pro-
duction of RFID shell beads.
C D The use of RFID shell beads is
known to assist in the storage of cer-
tain data such as a pearl farm’s loca-
tion, mollusk data, and harvest date.
However, a specific RFID reader is re-
quired to retrieve the data, so we
were unable to obtain the infor-
mation stored within these particu-
lar devices. Since the RFID devices
do not influence their external ap-
pearance, the pearls containing a
Figure 21. A: Necklace of South Sea bead cultured pearls, 14.40 × 14.20 shell bead nucleus with such compo-
mm to 16.20 mm in diameter. B–D: RTX analysis revealed five bead nents are still identified as bead cul-
cultured pearls containing an off-center RFID device within the shell tured pearls. Because the RFID
bead nucleus. device could increase the weight and
have a misleading effect if unde-
tected, a special comment is rou-
some known bead cultured pearls C–D) and confirmed that they were
tinely included on GIA pearl
containing an RFID device (figure 22, identical. The previous studies men-
identification reports as a means of
disclosure. While pearl tracing tech-
nology has not been extensively
Figure 22. A: Necklace of South Sea bead cultured pearls, 10.04–12.21 mm
adopted by the cultured pearl indus-
in diameter. B: RTX analysis of one of the pearls in the necklace revealed
try, the increasing number of elec-
an RFID device. C: The internal structure was compared with two known
tronic devices in shell bead nuclei
bead cultured pearls containing RFID devices from GIA Hong Kong’s ref-
submitted to the laboratory is note-
erence collection, and they proved to be identical. D: RTX clearly showed
worthy. GIA will continue to mon-
the outline of the square RFID device, as well as the sawn plane and
itor and provide updates to the pearl
small recess where the RFID device had been placed.
trade and consumers.
A B Nanthaporn Nilpetploy and
Ying Wai Au

Combination of Phenomena in
Star and Cat’s-Eye Color-Change
SAPPHIRE
The Tokyo lab recently examined a
transparent 20.49 ct violet to purple
C D color-change double cabochon sap-
phire, measuring 16.67 × 14.69 × 8.51
mm (figure 23) with a specific gravity
of 3.99 and a spot refractive index of
1.77. Usually a star sapphire is only
polished on one side, and the unpol-
ished side does not show any phenom-
ena. But this stone was polished on
both sides, which resulted in a unique

222 LAB NOTES GEMS & GEMOLOGY SUMMER 2022

Figure 23. This 20.49 ct star sap-
phire with a combination of
phenomena exhibited a color
change from violet (top) to pur-
ple (bottom). Side A is shown in Figure 24. Side A: Intersecting sets of parallel needle inclusions producing
these photos. six-rayed asterism. Field of view 5.8 mm. The photomicrograph is not
aligned with the inset.

combination of phenomena. Side A containing two of the rays was much Chatoyancy is displayed when
displayed a six-rayed star. Side B also stronger, which made the phenome- light reflects off a set of dense parallel
displayed a six-rayed star, but one line non reminiscent of a cat’s-eye. elongated inclusions, such as
needles; asterism occurs when such
a set of inclusions is oriented in mul-
Figure 25. Side B: Set of parallel needle inclusions producing chatoyancy. tiple directions. In the case of this
Field of view 5.8 mm. The photomicrograph is not aligned with the inset. stone, side A with the distinct six-
rayed star had three sets of dense par-
allel needles and platelets close to
the surface, intersecting at 60° angles
(figure 24), which is common with
six-rayed asterism. Side B also had
three sets of these needles close to
the surface, but the needles were
more concentrated in one of the di-
rections, producing a cat’s-eye effect
(figures 24 and 25). Interestingly, the
chatoyancy in Side B and one line of
asterism in Side A are contributed by
the same group of needles.
Although color-change star sap-
phire is not particularly rare, color-
change cat’s-eye sapphire is far less
common. Color-change sapphire with
asterism on one side and chatoyancy
on the other is without question a
“phenomenal” gem.
Masumi Saito and
Yusuke Katsurada

LAB NOTES GEMS & GEMOLOGY SUMMER 2022 223

 TABLE 1. Mn, Fe, and Cu concentrations on each side of the
bicolor tourmaline, measured by LA-ICP-MS (in ppmw, average
of three spots).

Mn Fe Cu

Bluish green 22826 566 7850

Dark yellowish green 17233 11287 4953

Detection limit (ppmw) 7.13 3.10 0.11

Figure 26. The 1.62 ct bicolor
copper-bearing tourmaline.

Bicolor Cuprian TOURMALINE addition to the ametrine variety of name. Most bicolor gem materials are
A bicolor gem has two colors in one quartz, other colored gemstones such cut to show different colors that are
stone. Ametrine is a well-known bi- as corundum and tourmaline can be obvious when viewed in face-up
color gem, a purple and yellow quartz naturally bicolor, although most of orientation.
combining amethyst and citrine. In them do not have a specific variety The Tokyo laboratory recently ex-
amined a bicolor rectangular step cut
weighing 1.62 ct and measuring 9.14
× 5.47 × 3.71 mm (figure 26). The
Figure 27. Vis-NIR absorbance of the whole tourmaline (top), the bluish
color was gradually distributed from
green portion (middle), and the dark yellowish green portion (bottom).
bluish green to dark yellowish green
Copper absorption is in the red (approximately 730 nm) and near-infrared
along the length. This stone was
regions (approximately 980 nm). Iron absorption is only in the red region
doubly refractive with a refractive
(approximately 730 nm). Spectra are stacked for clarity.
index of 1.620–1.640 and a specific
gravity of 3.10. Microscopic observa-
VIS-NIR SPECTRA tion revealed networked fluid inclu-
sions and strong doubling. The stone
was identified as tourmaline by these
gemological features.
Paraíba tourmaline, a certain type
of copper-bearing tourmaline, has
been one of the most sought-after
gemstones in the trade over the last
three decades. In 2012, the Laboratory
Manual Harmonisation Committee
ABSORBANCE

(LMHC) updated the definition of Pa-

raíba tourmaline as “a blue (electric
blue, neon blue, violet blue), bluish
green to greenish blue, green (or yel-
lowish green) tourmaline of medium-
light to high saturation and tone
(relative to this variety of tourmaline),
mainly due to the presence of copper
and manganese.” Visible/near-infrared
(Vis-NIR) absorption was collected
with GIA’s custom-made UV-Vis spec-
400 500 600 700 800 900 1000 trometer to determine the chromo-
WAVELENGTH (nm) phore. To be considered Paraíba
tourmaline, the copper-related absorp-

224 LAB NOTES GEMS & GEMOLOGY SUMMER 2022

tion needs to be dominant and the The trace element composition of ence, as in the case of this bicolor
color appearance should be within the each differently colored region was tourmaline with a non-Paraíba iron-
defined range. analyzed by laser ablation–induc- colored portion, is not typical. The
Non-polarized absorption spectra tively coupled plasma–mass spec- dark yellowish green part could have
of the whole stone showed two bands trometry (LA-ICP-MS). As shown in been polished off to make this a typi-
in the red and near-infrared regions table 1, the bluish green side shows cal Paraíba tourmaline.
(figure 27, black line). To measure the lower iron (566 ppmw) and higher Yusuke Katsurada
spectra of each color separately, one copper (7850 ppmw), and the dark yel-
half of the gem was covered with lowish green side shows higher iron
opaque black cardboard to allow light (11287 ppmw) and lower copper (4953
to pass through only one color at a ppmw). Comparing the different Vis-
time. The results indicated that the NIR absorption patterns of these por-
dominant chromophore was different tions (figure 27), the association of PHOTO CREDITS
(figure 27; bluish green and dark green copper and iron for each color portion Nathan Renfro—1–3; Annie Haynes—4, 14;
lines at the middle and bottom, re- is in agreement with Merkel and Najmeh Anjomani—5, 6; Towfiq Ahmed—7;
spectively)—the bluish green part is Breeding (2009). By virtue of its color Madelyn Dragone—9; Stephanie Persaud—
colored by copper, whereas the dark and its chromophore, only the bluish 10; Michaela Stephan—11, 12; Roy Bassoo—
yellowish green part is colored by green portion is consistent with the 12; Taryn Linzmeyer—15; Robert Weldon—16,
17 (left); Artitaya Homkrajae—17 (right); Ami-
iron (P.B. Merkel and C.M. Breeding, definition of Paraíba tourmaline.
roh Steen—18; Nuttapol Kitdee—20A, 21A;
“Spectral differentiation between Sometimes we encounter cuprian
Tony Leung—22A; Shunsuke Nagai—23; 24
copper and iron colorants in gem tourmaline with chemical zoning, (inset), 25 (inset), 26; Yusuke Katsurada—24,
tourmalines,” Summer 2009 G&G, which has varying trace element con- 25
pp. 112–119). centrations within. A drastic differ-

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members, connecting gem enthusiasts from all over the world!

LAB NOTES GEMS & GEMOLOGY SUMMER 2022 225

 Editor: Nathan Renfro

Contributing Editors: Elise A. Skalwold and John I. Koivula

Apatite Cluster in Zambian Emerald Blue Apatite in Tanzanian Garnet

This author recently studied a 1.68 ct faceted emerald In the micro-world, it can be challenging to identify inclu-
containing several inclusions, including blocky fluid in- sions based on sight alone, as many minerals can have a sim-
clusions, transparent brownish crystals, needles, and ilar appearance. Occasionally, though, some inclusions have
particle clouds. These inclusions as well as the trace ele- characteristic features that can aid in their identification.
ment chemistry supported a Zambian geographic origin. Recently this author had the opportunity to observe a
The emerald also exhibited elongated transparent crys- pyrope-spessartine garnet, reportedly from Lindi Province,
tals that resembled amphibole. In this case, Raman spec- Tanzania, that contained blue crystal inclusions ensconced
troscopy confirmed the mineral as apatite. Interestingly, among intersecting needles (figure 2). Analysis with micro-
this apatite formed a distinct inclusion cluster consist- Raman spectroscopy identified the inclusions as apatite.
ing of a large hexagonal prismatic crystal (a morphology Apatites are known for their bright blue hues, and these
typical of the mineral) associated with a multitude of inclusions offered an attractive example.
rod- and bamboo-shaped crystals in various directions
(figure 1). Other solid crystals observed in Zambian em-
erald include mica, actinolite (amphibole), quartz, zir-
Figure 1. An inclusion cluster consisting of a hexago-
con, and chromite.
nal prismatic apatite crystal and many rod- and bam-
Apatite, a common phosphate mineral, has previously
boo-shaped crystals of apatite in a Zambian emerald.
been reported in various forms and in many other types of
Photomicrograph by Ungkhana Atikarnsakul; field of
gems such as corundum, spinel, feldspar, and garnet, and
view 3.60 mm.
it is not surprising to find it in emerald. However, this is
the first time the author has encountered this fantastic
form of apatite in emerald.
Ungkhana Atikarnsakul
GIA, Bangkok

About the banner: The surface of this synthetic amethyst shows a multitude
of rhombohedral crystal faces. Photomicrograph by Nathan Renfro; field of
view 15.67 mm.

GEMS & GEMOLOGY, VOL. 58, NO. 2, pp. 226–233.

© 2022 Gemological Institute of America

226 MICRO-WORLD GEMS & GEMOLOGY SUMMER 2022

 Figure 2. Blue apatite
crystals are beautifully
framed by prominent
rutile needles in a gar-
net from Tanzania.
Photomicrograph by E.
Billie Hughes; field of
view 3.5 mm.

While this sample hails from Tanzania, blue apatite has Large Diamond Inclusion in Diamond
previously been reported as an inclusion in garnet from Recently, the authors examined a 2.01 ct Faint green round
Madagascar (Winter 2020 G&G Micro-World, p. 526). brilliant diamond with a fascinating diamond crystal in-
These inclusions’ distinctive appearance may help gemol- clusion that displayed a transparent, ghost-like appearance.
ogists recognize the material in other samples, but further Due to the large size of this nearly invisible crystal, the
analysis should be performed to identify them definitively. stone was given a clarity grade of SI2.
E. Billie Hughes Photomicrography was used to document the features
Lotus Gemology, Bangkok of this inclusion. Triangular etch features, also known as

MICRO-WORLD GEMS & GEMOLOGY SUMMER 2022 227

Figure 3. Trigons seen on a diamond crystal inclu- Figure 5. DiamondView image of the diamond inclu-
sion visible through the crown of a round brilliant sion in the diamond host. Image by Luthfia Syarbaini.
diamond. Photomicrograph by A’Dhi Lall; field of
view 2.11 mm.

trigons, were seen on the inclusion (figure 3). These are typi- Natural Diamond with Extensive Network of
cally natural growth markings of diamonds, confirming the Etch Channels
inclusion as diamond. The diamond crystal inclusion ap-
The authors recently examined a 5.19 ct type IIa natural
peared to have sharp and easily recognizable faces. Images
diamond (figure 6) displaying numerous etch channels (fig-
with cross-polarized light show strain between the inclu-
ure 7). Etch channels are open tubes whose formation is re-
sion and the host diamond (figure 4). A DiamondView
lated to dissolution processes within the stone. They form
image also reveals the diamond crystal inclusion (figure 5).
due to the dissolution of dislocations inside the crystal dur-
Generally, the beauty and value of a diamond increase
ing or after growth and can result in various patterns; most
with the absence of inclusions. Yet the presence of a dia-
commonly, they form as trigons or rarely as channels that
mond inclusion gave this diamond a certain distinction,
appear as parallel lines, zigzags, or “worm-like” structures
which in the authors’ opinion added to its beauty and value.
(T. Lu et al., “Observation of etch channels in several nat-
Luthfia Syarbaini, A’Dhi Lall, and Paul Johnson ural diamonds,” Diamond and Related Materials, Vol. 10,
GIA, New York 2001, pp. 68–75, and references therein; Spring 2018 G&G

Figure 4. Strain be-

tween the host dia-
mond and the diamond
inclusion is revealed by
the interference colors
in cross-polarized light.
Photomicrograph by
A’Dhi Lall; field of view
13.55 mm.

228 MICRO-WORLD GEMS & GEMOLOGY SUMMER 2022

 Figure 7. A network of natural etch channels gives
this diamond a distinctive appearance. Most of the
channels have a width of ~100–150 μm, while some
(e.g., lower left) show evidence of brown radiation
stains. Photomicrograph by Nathan Renfro; field of
view 4.69 mm.

Figure 6. This 5.19 ct diamond with I color and I2

clarity displays numerous etch channels visible to the network of etch channels in this diamond resulted in an I2
eye. Photo by Annie Haynes. clarity grade.
Photoluminescence (PL) mapping using 455 and 532
nm laser excitation (figures 8 and 9) revealed an increase
in the GR1, 3H, and TR12 centers along the walls of the
Micro-World, pp. 66–67). Etch channels terminate at typi- etch channels; all of these centers are defects associated
cally rhombic openings visible at the surface of the stone with radiation exposure. The nitrogen vacancy centers NV0
(Spring 2018 G&G Micro-World, pp. 66–67). The extensive (zero-phonon line [ZPL] at 575 nm) and NV– (ZPL at 637

Figure 8. Left: False-color map showing the peak area intensity of the radiation-related TR12 center (ZPL at 469.9
nm); this 455 nm PL map was compiled from 18,768 spectra collected at 45 μm pixel size. Right: The false-color
map overlain with a reflected light image of the table facet. Most of the etch channels seen in the false-color map
correspond with an opening observed on the table.

10K
TR12 Intensity

0
2 mm

MICRO-WORLD GEMS & GEMOLOGY SUMMER 2022 229

 GR1 INTENSITY ACROSS DIAMOND TABLE
NORMALIZED PEAK AREA RATIO (GR1/DIAMOND RAMAN) 140

120

100 Figure 9. GR1/Raman

peak area ratios calcu-
80 lated from the 532 nm
PL map (inset) cutting
across multiple channels
60 along the orange line.
Higher GR1/Raman
40 areas are concentrated
along the etch channels.

20

0
0 1000 2000 3000 4000 5000 6000 7000
LATERAL DIMENSION (μm)

nm) were also concentrated along these channels. The con- weighing 3.45 ct that exhibited a very realistic eye pattern
centration of these defects along the etch channels suggests (figure 10). Various shades of yellow and green material
that radioactive fluids once flowed through the tubes. The formed the pupil and iris, while a distinctive white outline
radioactive fluids had an impact on the areas in direct con- surrounded the iris as a sclera. Microscopic observation
tact, creating elevated concentrations of radiation-related revealed different microcrystalline minerals. Raman spec-
peaks. Other prominent PL peaks along the cavities were troscopy identified pyroxene, feldspar, and quartz as the
centered at 474, 598.75, and 461.5 nm. The radiation in most abundant minerals. Energy-dispersive X-ray fluores-
these fluids would have been low enough to not create cence (EDXRF) analysis revealed silicon as the dominant
much observable staining, as patches of green to brown element, while traces of iron and potassium were also de-
color associated with radiation staining were not observed tected.
in most of the etch channels. However, there were some Naturally formed eye patterns in gems are rare but do
isolated spots of green radiation stains and some channels exist, such as a “dragon’s eye” in a fire agate (Winter 2015
with a brownish appearance (figure 7) and elevated concen- G&G Micro-World, p. 441) and a radial eye structure in a
trations of radiation-related features (figures 8 and 9). Ad- sapphire (Summer 2017 G&G Micro-World, pp. 244–245).
ditionally, the exposure to radioactive fluids must have While the textures in rocks are much more diverse than
occurred after the diamond was brought to the near-surface those in single-mineral gemstones, observing such a
region following kimberlite eruption, as these radiation-re- unique feature is always exciting.
lated features would not withstand the high temperatures Ching Yin Sin
within the mantle. GIA, Hong Kong
Similar radiation features have previously been ob-
served in another stone with cavities (Spring 2020 Lab Piradee Siritheerakul
Notes, pp. 126–127), but to a much lesser degree. The ex- GIA, Bangkok
tensive network of etch channels within this diamond is
one more example of the extraordinary possibilities within
the natural world. Fracture-Filled Emerald with Mysterious
Taryn Linzmeyer and Sally Eaton-Magaña Filler Patterns
GIA, Carlsbad Emeralds are known to have natural cracks or fractures.
The filling of surface-reaching fractures with various oils
and resins is the most common practice to minimize frac-
Eye Pattern in a Rock Fragment tures to improve an emerald’s appearance. The author re-
Recently, the authors encountered a partially polished cently examined a 3.04 ct emerald that revealed a
rock fragment measuring 14.50 × 9.43 × 2.43 mm and mysterious filler pattern along the fractures, resembling a

230 MICRO-WORLD GEMS & GEMOLOGY SUMMER 2022

 Figure 10. An eye pat-
tern complete with
pupil, iris, and sclera is
clearly visible in this
rock fragment. Photo-
micrograph by Polthep
Sukpanish; field of view
12.5 mm.

labyrinth and convolution (figure 11). Fracture filling can Flux-Grown Synthetic Beryl Overgrowth
be identified using various methods. In this case, it dis- Most of the synthetic beryl currently on the market has
played a chalky fluorescence under long-wave ultraviolet been created by a hydrothermal process. Hydrothermally
flashlight and was also detected with simple microscopic grown crystals have obviously different crystal forms com-
observation and fiber-optic lighting. The internal graining, pared to their natural counterparts. Hydrothermal syn-
irregular two-phase inclusions, and long needles within thetics are often easily identified by their typical zigzag- or
this stone indicated a natural origin. This was a unique and chevron-patterned graining and color zoning. Flux-grown
visually interesting pattern in the fracture filling material synthetics, though less common, are able to form more
of an emerald. natural-looking crystals. However, despite having natural
Ungkhana Atikarnsakul forms, flux synthetics contain many unusual inclusions
GIA, Bangkok that clearly distinguish them from their natural counter-

Figure 11. Emerald filler with labyrinth- and convolution-like pattern. Photomicrographs by Ungkhana Atikarnsa-
kul; fields of view 2.0 mm (left) and 2.7 mm (right).

MICRO-WORLD GEMS & GEMOLOGY SUMMER 2022 231

 Figure 13. A suite of columbite rods, copper crystals, and
a large air bubble seen within a film of blue flux liquid.
Photomicrograph by Jamie Price; field of view 7.19 mm.

Figure 12. Doubly terminated flux synthetic beryl

crystal, measuring 32.45 × 30.36 × 25.29 mm. Photo prismatic crystals forming a 120° intersection angle. With
by Annie L. Haynes. its shape and backdrop, the twinned crystal resembled a
boomerang flying across the sky (figure 14). This inclusion
was later confirmed to be tantalite-(Mn), based on Raman
parts. Copper platelets that form within the crystal either spectroscopy and comparison with the RRUFF database.
from contamination or intentionally introducing metal in Polarized light and reflected illumination were adopted to
the growth material are obvious indications of synthetic reduce doubling and obtain clearer photomicrographs, and
origin. Flux fingerprints are another easily observed type the images were processed to extend depth of field.
of inclusion unique to flux synthetic crystals. Shu-Hong Lin
Weighing 211.78 ct, the hexagonal doubly terminated Institute of Earth Sciences,
crystal in figure 12 looks like a natural beryl crystal at first National Taiwan Ocean University
glance. Eye-visible well-formed copper platelets and wispy Taiwan Union Lab of Gem Research, Taipei
flux fingerprints indicate that the stone did not form natu- Tsung-Ying Yang, Kai-Yun Huang, and Yu-Shan Chou
rally. A closer look revealed reddish clouds of well-formed Taiwan Union Lab of Gem Research, Taipei
minute copper platelets and copper crystals. Euhedral red
rod-like crystals of columbite were scattered throughout,
similar to those in a natural sample. Partially healed ten-
sion cracks with white secondary flux particles were also Figure 14. The “boomerang” inclusion in this topaz
present. A few areas throughout the crystal had unique thin was confirmed by Raman spectroscopy to be a
angular and jagged films containing blue flux liquid and gas twinned crystal of tantalite-(Mn). Photomicrograph
bubbles (figure 13). Areas with higher clarity reveal the by Shu-Hong Lin; field of view 0.71 mm.
boundary between the natural aquamarine seed crystal and
the flux overgrowth. This stone is a product of synthetic
flux beryl overgrowth on a natural aquamarine seed crystal
produced in a Russian synthetic gem facility.
Jamie Price
GIA, Carlsbad

“Boomerang” Inclusion in a Rough Topaz

A 21.46 ct colorless rough topaz was recently submitted to
Taiwan Union Lab of Gem Research (TULAB) for identifi-
cation service. Microscopic observation showed a few pris-
matic brown inclusions with submetallic luster. One of the
inclusions was a unique twinned crystal composed of two

232 MICRO-WORLD GEMS & GEMOLOGY SUMMER 2022

 Figure 15. Several bright
red to dark red well-
formed trigonal crystals
of cinnabar highlight
the interior of the flu-
orite crystals in this flu-
orite and calcite cluster
from Spain. Photo by
Diego Sanchez.

Quarterly Crystal: Cinnabar in Fluorite mine in the Caravia mining area in the Asturias region of
This issue’s Quarterly Crystal deals with a 362.09 ct crystal northwestern Spain. The Emilio mine is known to produce
cluster of fluorite and calcite recently examined by the au- fluorite crystals with inclusions of various sulfides, including
thors. The 55.79 × 42.80 × 38.63 mm specimen was color- cinnabar. Therefore, the pure red bodycolor of these inclu-
less and transparent to translucent and played host to sions, together with the trigonal symmetry shown in figure
several small bright red to dark red well-formed trigonal 16, strongly suggested they were cinnabar. Using Raman mi-
crystals, visible in figure 15. These crystals were all situ- crospectrometry, we were able to identify the inclusions as
ated on the same growth plane in the fluorite portion. cinnabar, thereby confirming our initial impression.
The fluorite and calcite specimen was obtained from Jordi John I. Koivula and Nathan Renfro
Fabre of Fabre Minerals in Barcelona. It is from the Emilio GIA, Carlsbad

Figure 16. A combination

of optical microscopy
and Raman analysis
served to identify the tri-
gonal inclusions as the
mercury sulfide cinnabar.
Photomicrograph by Na-
than Renfro; field of view
2.35 mm.

MICRO-WORLD GEMS & GEMOLOGY SUMMER 2022 233

 Editors: Aaron C. Palke | James E. Shigley

Inclusions in Gemstones
James E. Shigley, Aaron C. Palke, John I. Koivula, and Nathan D. Renfro

Gem inclusions are mineral crystals or cavities filled with amber, for instance. By observing insects trapped in amber,
fluid and/or gas that occur in a host gemstone. Many gems Pliny the Elder was able to conclude that amber represents
contain microscopic inclusions (ranging in size from >1 fossilized tree resin (Ball, 1950) (figure 1).
mm down to submicroscopic nanoscale inclusions) that However, it was only much later that inclusions began
can reveal much about the host material. As a result, the to be classified and studied in a more systematic fashion.
use of the microscope (or loupe) to examine these inclu- The pioneering scientist Robert Boyle was perhaps one of
sions offers one of the most important methods available the first to describe inclusions in gems—“a specimen of
for gem identification. quartz with a cavity containing a fluid with a moveable gas
Inclusions are important for determining the natural, bubble, and reddish brown hair-like inclusions in
synthetic, or treated character of a gem, and for establishing amethyst” (Boyle, 1672). With the improvements in design
the likely geographic origin of a valuable colored stone. In and functionality of optical microscopes beginning in the
addition to their usefulness for identification, inclusions late 1700s, scientists started to use them to examine tiny
cause certain distinctive and desirable optical phenomena features in rocks and minerals (Kile, 2003, 2013). Déodat
such as asterism and chatoyancy, as well as some of the fea-
tures used in clarity grading. In this new installment of
“Colored Stones Unearthed,” we will discuss inclusions in Figure 1. Inclusions of insects entombed in amber,
gems—how they form, how they are studied, and what they such as these two wasps captured in an eternal em-
mean not only for gemologists but also for geoscientists. brace, offered ancient naturalists a clue to the geolog-
ical origins of this gemstone. Photomicrograph by
Brief History of Inclusion Studies John I. Koivula.

While the study of inclusions might seem to be a modern

concept requiring the use of advanced microscopes with
sophisticated optical lenses, early naturalists did have
some basic knowledge of how inclusions could be used to
understand the geological history of a gem. Consider

Editors’ note: Questions or topics of interest should be directed to Aaron

Palke (apalke@gia.edu) or James Shigley (jshigley@gia.edu).

GEMS & GEMOLOGY, VOL. 58, NO. 2, pp. 234–242.

© 2022 Gemological Institute of America

234 COLORED STONES UNEARTHED GEMS & GEMOLOGY SUMMER 2022

 Figure 2. Oriented in-
clusions such as the ru-
tile needles in this ruby
were recognized as the
cause of asterism early
on in the study of inclu-
sions. Photomicrograph
by Nathan Renfro; field
of view 1.80 mm.

de Dolomieu discussed the presence of a hydrocarbon fluid 1862 article by Gustav Rose identified the presence of ori-
(petroleum oil) in quartz in 1792. In 1819, Chester Dewey ented, needle-like inclusions, such as those seen in the star
detailed a quartz specimen from Massachusetts that dis- ruby in figure 2, as the cause of asterism in minerals. The
played a cavity containing a liquid with a moveable bubble first descriptions of inclusions specifically in gem minerals
and several black or brown particles (1818, pp. 345–346). were published in several articles by Henry Sorby in 1869
Noted scientists Humphry Davy (1822), David Brewster and by Isaac Lea between 1866 and 1876. Other reports on
(1826, 1827, 1844, 1845a,b, 1863), and William Nicol (1828) solid and fluid inclusions in various minerals followed (e.g.,
each described minerals that contained inclusions consist- Hartley, 1876, 1877).
ing of one or more fluids and moveable gas bubbles. In The use of inclusions to understand a gem’s geological
1854, Johann Reinhard Blum and his coauthors published growth environment can be understood with the examples
a book discussing various mineral inclusions they had ob- shown in figures 3–6. Ruby derived from extremely pure
served. By linking observations on mineral inclusions and calcite (CaCO3) marble, as in the deposits of Mogok, Myan-
host rock formation, Henry Clifton Sorby (1858) became mar, often contains calcite inclusions (figure 3), whereas
one of the founders of the geological science of petrography magnesium-rich spinel from the same geological region in
with an article titled “On the microscopical structure of Mogok will likely contain magnesium-rich dolomite
crystals, indicating the origin of minerals and rocks.” An [CaMg(CO3)2] (figure 4). Similarly, emeralds from mica-rich

Figure 3. The geological growth environment of marble-hosted rubies from Myanmar (left) is reflected in their in-
ternal features, such as calcite inclusions (right). Photos by Robert Weldon (left; courtesy of William F. Larson) and
Nathan Renfro (right; field of view 1.44 mm).

COLORED STONES UNEARTHED GEMS & GEMOLOGY SUMMER 2022 235

Figure 4. Left: Magnesium-rich spinel often forms in impure marbles where the magnesium-rich mineral dolomite
is present. Right: These spinels contain inclusions where carbonate minerals are more likely to be dolomite than
calcite, as seen in this dolomite-filled negative crystal. Photos by Robert Weldon (left) and Nathan Renfro (right;
field of view 1.30 mm).

rocks called schists, such as Russian emeralds, often con- matches the mineralogy seen in many emerald-bearing
tain mica inclusions (figure 5). On the other hand, emeralds hand samples from Colombia.
from the hydrothermal deposits in Colombia, where the Beginning in the 1940s, the well-known European
gems occur in veins rich in carbonate, quartz, and pyrite, gemologist Eduard Gübelin began publishing a series of im-
often contain inclusions of carbonate minerals. Figure 6 portant articles in Gems & Gemology and Journal of Gem-
shows an exceptional example of a carbonate inclusion, mology on inclusions and the evidence they could provide
which itself contains a pyrite inclusion that perfectly on the geologic and geographic origin of the host gemstone

Figure 5. Emeralds from mica-rich schists, such as Russian emeralds (left), display inclusions that give away their
geological origins, such as fields of dark mica platelets (right). Photos by Robert Weldon (left; courtesy of R.T. Boyd
Limited) and Nathan Renfro (right; field of view 2.04 mm).

236 COLORED STONES UNEARTHED GEMS & GEMOLOGY SUMMER 2022

Figure 6. Left: Emerald from Chivor, Colombia, on carbonate and pyrite matrix. Right: Inclusions in Colombian
emeralds provide evidence of their unique geological origins, such as this pyrite within a carbonate inclusion. Pho-
tos by Robert Weldon (left; courtesy of Cornerstone Minerals and Greg Turner) and Jonathan Muyal (right; vertical
field of view 2.34 mm).

(e.g., Gübelin, 1944–1946, 1948, 1950, 1953, 1969, 1974). crystal forms of the host. For this reason, these fluid inclu-
Dr. Gübelin’s publications were followed by several impor- sions are often referred to as “negative crystals.”
tant books on gem inclusions coauthored by John Koivula While either solid or liquid at the time of their original
(1986, 2005, 2008) that have been widely used and appre- entrapment in crystals at high temperatures in the earth,
ciated by the gemological community. Hollister and Craw-
ford (1981), Roedder (1984), Samson et al. (2003), and Chi
et al. (2020) contributed technical summaries on fluid in-
clusion research. Figure 7. Fluid inclusions with exsolved gas bubbles and
daughter crystals in a beryl host. These fluid inclusions
entered the host through a fracture. The fracture healed
Inclusions in Minerals and Gems itself, trapping blebs of this fluid with the negative crys-
tal form seen here. Photomicrograph by Nathan Renfro.
Minerals frequently contain small inclusions of foreign ma-
terials (solids, liquids, and gases) that were trapped during
mineral formation, and these can be seen with magnifica-
tion. Crystals that formed during metamorphism by solid-
state recrystallization, or almost entirely in the solid state
without significant involvement of fluids, can display solid
inclusions. Those that occur in igneous and sedimentary
rocks were formed in the presence of a geological fluid and,
as a result, can contain single or multiphase inclusions of
that fluid (as well as solid or vapor inclusions). These geo-
logical fluids consist of high-density silicate or carbonatite
melts, low-density water-rich fluids or vapors, and, in rare
cases, organic hydrocarbons (oils). Following crystallization,
the mineral crystals in all of these rock types can become
cleaved or fractured one or more times, and these cleavages
and fractures can later become healed in the presence of liq-
uid or gaseous fluids. Tiny amounts of these fluids can re-
main as inclusions along the healed zone (figure 7). The
crystal form of the host mineral typically determines the
morphology of these fluid inclusions. Fluid inclusions usu-
ally have a geometric, angular shape that reflects the typical

COLORED STONES UNEARTHED GEMS & GEMOLOGY SUMMER 2022 237

Figure 8. This glassy melt inclusion within a Montana sapphire (left) was originally trapped as a fluid magma that
quenched to a glass upon cooling. This can be seen when these inclusions are polished down to the surface. The
material inside the inclusion does not flow away, indicating it has quenched to a solid, glassy state (right). Photo-
micrographs by Aaron Palke; fields of view 1.26 mm (left) and 0.72 mm (right).

inclusions can undergo phase changes during cooling of the tion relationship cannot always be clearly established
host crystals as the host rocks are brought toward the based on visual or other evidence. Protogenetic primary
earth’s surface. Near the surface, inclusions of fluids nor- solid inclusions were present before the host mineral
mally remain as fluids, while melt inclusions normally so- formed, and the mineral grew around and entrapped
lidify to some type of glass or other solid (figure 8). In some them—these may display irregular or partly dissolved
cases, a fluid can separate into two fluids that are immis- shapes. Syngenetic primary solid, liquid, or gas inclusions
cible (i.e., do not mix with one another at cooler tempera- formed at the same time as the host mineral by being
tures). Solid inclusions can also undergo changes to trapped on growing crystal faces. Solid inclusions some-
lower-density or secondary alteration phases. times have well-formed crystal shapes that represent either
At elevated temperatures in the earth, minerals can ac- their morphology or a morphology imposed on them by the
commodate greater amounts of foreign impurity elements host. Epigenetic secondary inclusions formed after the host
in their crystal structures. But when the minerals cool in by exsolution along a rehealing cleavage or fracture.
the earth’s crust, these impurity elements can no longer be
contained, and they are usually expelled from the structure
(exsolved) as inclusions of different minerals (such as rutile Scientific Study and Geological Importance of
needles in sapphire). At lower pressures and temperatures Inclusions
near the earth’s surface, gases originally dissolved in inclu-
sion fluids can also be exsolved as distinct gas bubbles The study of solid and fluid inclusions provides a way for
within water or carbon dioxide or some other fluid. Sec- the scientist to reconstruct events and processes in the ge-
ondary or “daughter” crystals can also form by coming out ological past. Fluid inclusions represent actual, and often
of the solution from the fluid in the inclusion (figure 7). quite rare, samples of the geological fluids that existed at
Inclusions occur either individually or in small groups. some time in the history of rocks and minerals. As such,
Sometimes they are abundant enough to affect the trans- they can provide information on the physical and chemical
parency of the host mineral. They often occur randomly in conditions that were present during and after rock forma-
the host crystal. But they may also form along certain crys- tion. In particular, studies of inclusions can reveal infor-
tallographic directions, color zones, or healed fractures, or mation on:
they can occur in geometric patterns related to the crystal Temperature: When a mineral and the fluid inclusions
symmetry of the host. Solid inclusions can exhibit their within it cool over geologic time, they shrink at different
own crystal shape, have a rounded or irregular appearance, rates. The inclusion fluid shrinks faster than the solid crys-
or adopt the negative crystal shape of the host mineral. tal host, and this difference is evident in the exsolution
Gemologists categorize inclusions based on their appear- over time of a gas bubble within the fluid at temperatures
ance (shape, size, transparency, color, luster, contrast with existing near the earth’s surface (see figure 9). Through
the host, and orientation) and their association with other gradual, controlled heating of the crystal sample and ob-
mineral inclusions. serving when the gas bubble disappears back into the fluid
Inclusions and their host gemstones can have various (homogenizes), one can estimate the temperature that ex-
age relationships with one another, although this forma- isted when the inclusion itself first formed.

238 COLORED STONES UNEARTHED GEMS & GEMOLOGY SUMMER 2022

Figure 9. When warmed slightly by the well light of a microscope, the carbon dioxide and gas bubble fluid inclu-
sion in this quartz will homogenize to a single fluid (left). When cooled slightly, this fluid separates into distinct
gas and fluid phases (right). Photomicrographs by Nathan Renfro; field of view 2.56 mm.

Pressure: Once the chemical composition of the fluid in- Chemical Composition: The liquids, the solids, and in
clusions is identified, scientists can use experimental lab- some cases the gases present in inclusions can be analyzed
oratory data on similar fluids to get a sense of the pressures to obtain information on the chemical environment of in-
that existed at the time and the environment in which the clusion formation in the earth’s crust and mantle. Inclu-
inclusions were trapped in the host mineral. sions provide important geological information on the deep
earth that may not be available from any other source.
Density: With data on chemical composition, along with
the density and individual volume of the various phases Geologic Age Dating: When solid inclusions in mineral
present in a fluid inclusion, the total average density of all crystals contain small amounts of radioactive trace ele-
the phases in the inclusion can be calculated. This result ments, it is possible to determine the geologic age of the
is important for understanding the types of fluids and their inclusion (figure 10). Radioactive elements undergo a spe-
circulation in the earth’s crust. cific decay over known periods of geologic time, so careful

Figure 10. A zircon inclusion polished down to the surface of the host sapphire, viewed in backscattered electron
imaging (left) and cathodoluminescence imaging (right) using scanning electron microscopy (SEM). Secondary ion
mass spectrometry (SIMS) analysis pits are seen in the image on the left. These analytical tools are able to deter-
mine the age of the zircon inclusion, giving an upper limit on the age of the sapphire host. Images by Rachelle
Turnier, University of Wisconsin/GIA.

COLORED STONES UNEARTHED GEMS & GEMOLOGY SUMMER 2022 239

determination of these elements can be used to calculate • Using gases trapped in inclusion fluids to study the
mineral formation ages. ancient atmosphere

Application of Inclusion Research: The abundance and

frequent occurrence of inclusions in a variety of geologic Gemological Importance of Inclusions
samples offers numerous opportunities for inclusion stud- For the gemologist, inclusion studies combined with doc-
ies that support a multitude of geological investigations, umentation of standard physical properties provide the
such as: basis for gem identification. In some instances, particular
inclusions uniquely identify a gemstone and its geographic
• Verifying the geologic conditions of formation of ore origin. Observation of inclusions is carried out using a
deposits, providing a tool for the field exploration of gemological microscope and various lighting configura-
new deposits tions. These may include brightfield, darkfield, fiber-optic
• Determining the conditions of formation, mineral- lighting at different orientations to the sample, shadowing,
ogy, and geologic history of rocks found in many use of polarizing or colored filters, and other image-pro-
types of crustal and upper mantle environments cessing techniques. Since the 1950s, inclusion photography
(some results cannot be obtained any other way) has been an essential part of gemological education (see
• Inspecting fluid inclusions that contain hydrocar- Koivula, 1981, 2003; Renfro, 2015a,b).
bons, which can be important for oil exploration Inclusions are often the key to determining the geo-
• Determining the metamorphic or magmatic prove- graphic origin of gemstones. Some gems contain inclusions
nance of certain minerals found today in sediments that are very specific to certain localities. Parisite inclu-
and sedimentary rock formations sions in an emerald are a diagnostic indicator of Colombian
origin (figure 11). In other cases, inclusions are one piece
• Ascertaining the conditions and geological ages of
of the puzzle, such as the long, slender rutile silk seen in a
diamonds and coexisting mineral phases in the
Sri Lankan sapphire (figure 12).
lower crust and mantle
Inclusions are an important clue in identifying treat-
• Hypothesizing the conditions of geotectonic events ments applied to gemstones. The observation of internal
such as crustal formation and subduction, mountain diffusion of blue color around relict rutile silk in a sapphire
building and erosion, volcanism, metamorphism, offers evidence of high-temperature heat treatment meant
and sedimentation to enhance the stone’s blue color (figure 13). Microscopy is
• Studying trapped organisms and vegetation found as arguably the most important way to identify many treat-
fossil inclusions in amber to provide information on ments such as heat treatment, dyes, and clarity enhance-
the ancient biosphere ment through fracture filling.

Figure 11. Parisite in-

clusions in emerald are
a diagnostic indicator
of a Colombian origin.
Photomicrograph by
Jonathan Muyal; field
of view 0.82 mm.

240 COLORED STONES UNEARTHED GEMS & GEMOLOGY SUMMER 2022

Figure 12. Long, slender rutile silk inclusions in sap- Figure 13. The rutile silk in this sapphire has been
phire are an indicator, although not diagnostic, of a Sri dissolved into the corundum lattice by heat treat-
Lankan origin. Photomicrograph by Nathan Renfro. ment at high temperature, creating blue coloration
around the partially dissolved silk. Photomicrograph
by Nathan Renfro.

Inclusions as Natural Art Gems & Gemology since 2016 (Renfro et al., 2016;
Inclusions in gems serve as visual works of natural art 2017a,b; 2018; 2019; 2021).
(figure 14). Fortuitous geological processes in the earth The field of gemological research exists at a fascinating
created these inclusions in natural, untreated gems with- intersection between the cold, dispassionate scientific
out any human intervention. Their shape, appearance, method and the impassioned and provocative world of aes-
color(s), and in some cases the constraints imposed by the thetics and art. So perhaps it is fitting that these inclusions
crystal symmetry of the mineral host all combine to cre- that tell us so much about the history and genesis of gems
ate an inclusion “scene” that is entirely unique and never can also move and touch us as works of art. Future install-
to be repeated. The artistic nature of inclusions is perhaps ments will further explore the ways in which scientific in-
best illustrated by a series of photomicrograph charts cre- quiry of the geology of colored stones can deepen our
ated by Nathan Renfro and others that have appeared in appreciation of these gems.

Figure 14. Rutile needle

inclusions in a quartz
host. Cross-polarized
light shows off the
Brazil-law twinning in
the quartz, creating a
spectacular display of
light. Photomicrograph
by Nathan Renfro; field
of view 20.05 mm.

COLORED STONES UNEARTHED GEMS & GEMOLOGY SUMMER 2022 241

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——— (1948b) Die diagnostische Bedeutung der Einschlüsse in Rose G. (1862) Über den Asterismus der Krystalle, insbesondere
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——— (1950) Diagnostic importance of inclusions in gemstones. Berlin, pp. 614–618.
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——— (1953) Inclusions as a Means of Gemstone Identification. Analysis and Interpretation, Topics in Mineral Sciences. Min-
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242 COLORED STONES UNEARTHED GEMS & GEMOLOGY SUMMER 2022

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 GEM NEWS INTERNATIONAL
Contributing Editors
Gagan Choudhary, Gem Testing Laboratory, Jaipur, India (gagan.choudhary@iigjrlc.org)
Christopher M. Breeding, GIA, Carlsbad (christopher.breeding@gia.edu)
Guanghai Shi, School of Gemmology, China University of Geosciences, Beijing (shigh@cugb.edu.cn)

COLORED STONES AND ORGANIC MATERIALS Figure 1. This 778 g (approximately 11 × 4 cm) aquama-
rine crystal from Xinjiang displays a unique natural
A large aquamarine with unusual etch features from Xin- etch pattern (detail in bottom photo). Photos by Ting
jiang, China. Etch features are commonly seen in beryl Zheng; courtesy of Shino Gold Jewelry (Shanghai) Co.
crystals (e.g., T. Lu, “Interesting etch features and cavities
in beryl and quartz,” Spring 2002 GNI, pp. 102–103). Their
formation is related to various factors during or after crys-
tal growth, both internal and external, including chemical
composition, lattice defect types and their distribution,
pressure-temperature conditions of the forming environ-
ment, solvent composition, and dissolution time (R. Ku-
rumathoor and G. Franz, “Etch pits on beryl as indicators
of dissolution behaviour,” European Journal of Mineralogy,
Vol. 30, No. 1, 2018, pp. 107–124).
Recently, Shino Gold Jewelry (Shanghai) Co. submitted
a large piece of rough aquamarine crystal to the National
Gemstone Testing Center (NGTC) lab in Beijing for iden-
tification service. The crystal, weighing 778 g (figure 1,
top), was claimed to have been mined in the Altay region
of Xinjiang, China. Standard gemological testing revealed
a refractive index of 1.577–1.583 and a specific gravity of Unusual etch channel
2.69. These values were typical for aquamarine and were Other etch pits and cavities
confirmed by the infrared and Raman spectra. The numer-
ous hexagonal etch features on the (0001) crystal face (fig-
ure 1, bottom), combined with the contents in the fissures
(mainly kaolinite and hematite) identified by Raman spec-
troscopy, indicate that the crystal is of natural origin. No-
tably, one of the etch features has not been previously
reported to our knowledge—the crystal had two hexagonal
dissolution cavities with openings about 3 mm in diame-

Editors’ note: Interested contributors should send information and illustra-

tions to Stuart Overlin at soverlin@gia.edu or GIA, The Robert Mouawad
Campus, 5345 Armada Drive, Carlsbad, CA 92008.

GEMS & GEMOLOGY, VOL. 58, NO. 2, pp. 244–268.

© 2022 Gemological Institute of America

244 GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SUMMER 2022

 c-axis

(0001)

Figure 4. A 0.22 ct emerald-cut red beryl (5.08 × 3.12 ×

1.91 mm). Photo by Huixin Zhao.

Figure 2. Schematic diagram of the etch feature par-

allel to the c-axis of the aquamarine crystal. Vol. 10, No. 1, 2001, pp. 68–75). Also, the formation of
these special etch features is affected by different dissolu-
tion rates in different directions of the crystal. The se-
lected dissolution on the (0001) plane was very slow, while
the dissolution rate along the c-axis was significantly
ter, connected by a hexagonal etch channel 4 cm long and
faster, resulting in the special funnel-shaped etch pits con-
parallel to the c-axis (figures 2 and 3). Interestingly, the etch
nected by a very long etch channel.
channel appeared to be empty and penetrated throughout
the crystal. Ting Zheng (zhengt1990@foxmail.com),
The formation of this etch feature cannot be fully ex- Qian Deng, and Taijin Lu
plained at present. One possible explanation is that it is National Gemstone Testing Center, Beijing
related to the defects (dislocations) parallel to the c-axis,
which control the locations of the preferred dissolution Topaz crystals in red beryl. Gem-quality beryl comes in
process (T. Lu et al., “Observation of etch channels in sev- various colors, including green, yellow, pink, and rarely
eral natural diamonds,” Diamond & Related Materials, red, which has only been mined in the state of Utah to

Figure 3. The etch features of the crystal: two hexagonal dissolution cavities connected by a hexagonal etch chan-
nel. The channel (left) is about 4 cm long and empty throughout, and the openings have a hexagonal funnel shape
(right). Photomicrographs by Chao Liu (left; field of view 23 mm) and Ting Zheng (right; field of view 6.25 mm).

GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SUMMER 2022 245

 FTIR SPECTRUM

Red beryl
0.6
REFLECTANCE

0.4

0.2

0.0
4000 3500 3000 2500 2000 1500 1000 500
WAVENUMBER (cm–1)

Figure 5. The infrared reflectance spectrum confirmed Figure 7. Exposed crystal inclusions in the red beryl
the identity of the red beryl. showed a fine columnar shape and distinct cleavage
fissures. Photomicrograph by Huixin Zhao; field of
view 1.6 mm.

date. Recently, a red beryl (figure 4) was submitted to Guild

Gem Laboratories in Shenzhen for identification. This
emerald-cut sample weighed 0.22 ct and exhibited a highly beryl. Multiple analytical methods were applied, including
saturated red color. The refractive index values of 1.562– FTIR and UV-Vis-NIR spectroscopy, and EDXRF for chem-
1.569 and birefringence of 0.007 were consistent with ical analysis. FTIR confirmed the sample as beryl (figure
5), and the UV-Vis-NIR spectrum showed a prominent
manganese-related broad band centered at 540 nm, as well
Figure 6. The UV-Vis-NIR spectrum of the red beryl as a weak iron-inducted band at 370 nm (figure 6).
shows a weak peak at 370 nm (Fe3+) and an intense EDXRF results showed that the beryl was rich in iron
peak at 540 nm (Mn3+). (16920 ppm) and manganese (2586 ppm), along with a trace
amount of zinc (787 ppm). Such results were very close to
previously reported values for red beryl from the Wah Wah
UV-VIS-NIR SPECTRUM Mountains of Utah: 15000 ppm iron, 2000 ppm man-
ganese, and 700 ppm zinc, respectively (J.E. Shigley and E.E.
540 Red beryl Foord, “Gem-quality red beryl from the Wah Wah Moun-
370 tains, Utah,” Winter 1984 G&G, pp. 208–221).
1.0
Microscopic observation revealed several two-phase
fluid inclusions along the healed fissures, and purple-blue
ABSORBANCE

flashes were clearly seen within the open fissures, which

indicated clarity enhancement by organic fillers. This was
0.8 confirmed by FTIR, with peaks at 2854, 2871, 2927, and
2963 cm–1. Two transparent crystal inclusions were present
and exposed to the surface near the girdle, showing a pris-
matic crystal habit (figure 7). Within the included crystals,
a series of cleavage layers were prominent. Further testing
0.6 by micro-confocal Raman spectroscopy in the 100–1200
cm–1 range showed distinct peaks at 240, 267, 285, 332,
430, 456, and 927 cm–1, results that agree with topaz ac-
300 400 500 600 700 800 900 1000 cording to the RRUFF online database (figure 8).
WAVELENGTH (nm) Topaz rhyolites are widely distributed across the west-
ern United States, and red beryl occurs in topaz-bearing

246 GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SUMMER 2022

 R AMAN SPECTRA

267 Topaz inclusion

Topaz R050405

240 927
285

332 Figure 8. The Raman

430 456
spectrum of the crystal
INTENSITY

inclusion agreed with

the topaz spectrum in
the RRUFF database.

200 400 600 800 1000

RAMAN SHIFT (cm –1)

rhyolites (J.E. Shigley et al., “Red beryl from Utah: A re- fairly pure omphacite aggregate, considering that no other
view and update,” Winter 2003 G&G, pp. 302–313). mineral impurity was observed or identified (figure 11).
Hence, it is not surprising to see topaz as a mineral inclu-
sion in red beryl, although such an observation does not
appear to have been reported before. Figure 9. This green omphacite fei cui jade (7.4 × 7.0
Yujie Gao, Dan Ju (judan@guildgemlab.com), and mm) displayed chatoyancy under fiber-optic light.
Huixin Zhao Photo by Bowen Zhao.
Guild Gem Laboratories, Shenzhen, China

Unusual cat’s-eye omphacite fei cui jade. A round cabo-

chon set in a ring with round brilliant and rose-cut dia-
monds (figure 9) was recently submitted to the National
Center of Quality Inspection and Testing on Gold-Silver
Products (NGGC) for examination. The center stone,
measuring approximately 7.4 × 7.0 mm in diameter, pos-
sessed a vivid green bodycolor and exhibited pronounced
chatoyancy with a vibrant green sheen. FTIR analysis (fig-
ure 10) revealed that the stone was natural untreated om-
phacite-type fei cui jade, with a typical fingerprint
spectrum corresponding with omphacite, a broad absorp-
tion band centered at 3500 cm–1 caused by the hydrous in-
terstitial minerals, and the functional group region
showing no absorption of any organic filling material com-
monly used in bleaching and filling treatment, such as
Bisphenol A epoxy resin. Subsequent micro-Raman imag-
ing and spectroscopic analysis confirmed the sample as a

GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SUMMER 2022 247

 FTIR SPECTRA

2.7 1.1

2.4 0.9
1075
2.1 0.8
ABSORBANCE

ABSORBANCE
1.8 0.6
573
530
1.5 0.4

1.2 0.2

0.9 0.0

6000 5500 5000 4500 4000 3500 3000 2500 2000 1500 1000 500
WAVENUMBER (cm–1) WAVENUMBER (cm–1)

Figure 10. Both the functional group region (left) and the fingerprint region (right) of the sample’s IR absorption
spectrum were collected with a diffuse reflectance accessory. A K-K transform was applied to the fingerprint spec-
trum collected.

The strongest Raman peaks at 682 cm–1 and 1023 cm–1 Element analysis with energy-dispersive X-ray fluores-
were attributed to symmetrical Si-Ob-Si stretching/bend- cence (EDXRF) showed that the sample’s major elements
ing and symmetrical Si-Onb stretching, respectively. Ob were silicon, calcium, aluminum, magnesium, and iron,
refers to the bridging oxygens, while Onb represents non- consistent with omphacite, whose IMA formula is
bridging oxygens in silicon tetrahedra. (Ca,Na)(Mg,Fe,Al)Si2O6). It is well known that the Fe2+-in-

RAMAN SPECTRA

Chatoyant omphacite
Omphacite R110038
Jadeite R050220
Figure 11. The sample’s
Raman shift confirmed
682
its mineral species. The
1023 sample matched well
370
411 with the RRUFF spec-
INTENSITY

trum for omphacite but

differed considerably
from the RRUFF spec-
trum for jadeite. The
spectra are shifted ver-
tically for clarity.

1200 1000 800 600 400 200

RAMAN SHIFT (cm –1)

248 GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SUMMER 2022

 UV-VIS-NIR SPECTRUM
1.3

1.2
692
Figure 12. Two broad ab-
sorption bands centered
ABSORBANCE

around ~430 and ~650

1.1
nm were formed with the
contributions of both
1.0
iron and chromium. The
692 nm peak convinc-
ingly indicated the pres-
0.9
ence of Cr 3+.

300 400 500 600 700 800 900 1000

WAVELENGTH (nm)

duced grayish bluish green bodycolor is most common even color distribution has always been considered of high
among the green omphacite varieties. However, this cha- quality and rarity, but the chatoyancy of this sample offered
toyant sample was characterized by a relatively high additional value.
chromium content (Cr2O3 ≈ 0.22 wt.%), producing a more Xiaoyu Lv, Bowen Zhao, and Xiaoying Lu
saturated and purer green bodycolor rather than a dull green National Center of Quality Inspection and Testing on
one. This color feature was confirmed by UV-Vis-NIR spec-
Gold-Silver Products (NGGC), Shanghai
troscopy, with only a single transmittance band centered at
535 nm appearing in the visible range (figure 12).
Microscopic observation with finely tuned fiber-optic Three-rayed asterism in quartz. Asterism is a well-known
light revealed a parallel-arrayed fibrous texture throughout (if not the most familiar) optical phenomenon observed in
the sample (figure 13). Meanwhile, a vague honeycomb- numerous gem species. In transparent or translucent gem-
like pattern was observed at two specific sides near the gir- stones, a series of parallel inclusions consisting of tiny nee-
dle (the 12 and 6 o’clock positions of the cabochon in figure dles or channels produces a distinct light band by a complex
9). Thus, under reflected light the stone presented a cha- process of scattering and reflection of light. If the gemstone
toyant sheen parallel to the ring band. is cut as a cabochon, the light band, which is oriented per-
Based on our current knowledge, this green omphacite pendicular to the needle or channel axis, generally produces
fei cui jade was probably from Guatemala. Translucent fei a sharp light line on the surface of the gemstone, an effect
cui jade with such fine texture, vivid green bodycolor, and known as chatoyancy. If several series of parallel inclusions

Figure 13. The om-

phacite fei cui jade’s
parallel-arrayed fibrous
texture (left) and vague
honeycomb-like pattern
(right), shown in fiber-
optic illumination.
Photomicrographs by
Bowen Zhao; fields of
view 10.45 mm (left)
and 8.81 mm (right).

GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SUMMER 2022 249

TABLE 1. Properties of quartz samples showing a network of three-rayed stars.

Sample Transparency Weight (ct) Shape Size Orientation of c-axis

45 mm diameter About 45° inclined to

A Transparent 287 Round
21 mm height the base

52 mm diameter Approximately parallel

B Transparent 463 Round
24 mm height to the base

32 × 22 mm diameter
C Transparent 69.5 Oval Not determined
15 mm height

34 × 28 mm diameter Approximately parallel

D Transparent 93.5 Irregular
13 mm height to the base

are present, we observe several intersecting light bands pro- were purchased at various gem and mineral fairs and were
ducing asterism. The number of rays in a star depends on said by the vendors to originate from Brazil; further details
the number of intersecting light bands. For example, two in- on locality are unknown. The properties of the cabochons
tersecting light bands produce four-rayed stars, three inter- are summarized in table 1.
secting light bands produce six-rayed stars, and so on. Upon first view, the samples showed broad light bands
A single star is observed if all needles or channels are forming a three-rayed star, with all branches of the star
oriented parallel to a single plane. If the inclusions are originating from a center (figure 14). The single branches
found in different planes, we might observe several stars of the three-rayed stars move along the surface of the cabo-
on the surface of a cabochon or sphere (K. Schmetzer et al., chons after rotation of the stone or a change of the position
“Dual-color double stars in ruby, sapphire, and quartz: of the light source or the observer. So far, this observation
Cause and historical account,” Summer 2015 G&G, pp. is consistent with the features of light bands generally ob-
112–143). This effect can be due to the symmetry of the served in asteriated gemstones. But in “normal” gemstones
host, which causes several series of non-planar needles (e.g., star rubies or star sapphires), we see three intersecting
(e.g., in cubic spinel or garnet). Multi-asterism is also pro- light bands forming a six-rayed star.
duced by several series of needles that are independent of
each other, as in quartz or beryl (K. Schmetzer and M. Glas,
“Multi-star quartzes from Sri Lanka,” Journal of Gemmol-
ogy, Vol. 28, No. 6, 2003, pp. 321–332). A combination of Figure 14. Asterism with a three-rayed star seen on
these two variants is observed in garnet. All different vari- a quartz cabochon (sample B) in reflected light
ants may be designated as a “network of stars.” with fiber-optic illumination. Photo by Martin P.
The present contribution describes three-rayed asterism, Steinbach.
a phenomenon that does not really fit into the generally ac-
cepted knowledge about the formation of asterism and
multi-asterism. This variant of asterism in quartz is a rare
optical phenomenon mentioned briefly by Gübelin and
Koivula (Photoatlas of Inclusions in Gemstones, Volume 2,
2005, Opinio-Verlag, Basel, Switzerland, p. 548) and by Stein-
bach (Asterism: Gems with a Star, 2016, MPS Publishing
and Media, Idar-Oberstein, Germany, pp. 649–651). Hain-
schwang (Fall 2007 GNI, pp. 261–262) observed two three-
rayed stars on quartz cabochons with chlorite inclusions.
The two stars had one ray in common and were observed
upon rotation of the cabochon, with one of the three-rayed
stars observed at another end of the ray that is shared by
both stars. Hainschwang assumed that the optical phenom-
enon was caused by the chlorite inclusions, but the forma-
tion mechanism is not completely understood.
Our observation is based on the examination of four
star quartz samples, which came from the private collec-
tion of one of the authors (MPS). The quartz cabochons

250 GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SUMMER 2022

 A B C

D E F

Figure 15. Upon rotation of sample A, the center of a three-rayed star moves to the girdle and another center of a
three-rayed star comes into sight (D); upon further rotation, this star is also moved. The sequence A to F shows the
optical phenomenon described. Photos by Karl Schmetzer; reflected light, fiber-optic illumination.

Surprisingly, upon rotation of the cabochons it was de-

tected that the samples did not show a single three-rayed
star but a multi-star network. Rotating each quartz cabo- A B
chon in a direction in which it was possible to follow one of
the light bands on the cabochon’s surface, at some point this
branch of the star ended in another center of a three-rayed c
star. Repeating this procedure, another center of a three-
rayed star was occasionally detected, unless the branches of c
the three-rayed star ended at the girdle (figure 15).
Figure 16 shows a schematic representation of the multi-
star networks observed in the four samples. It must be un-
derscored that the different patterns drawn represent lines
on curved domes of the different cabochons. If the branches
of the stars are in a position close to the girdle, some lines
C D

Figure 16. Schematic representation of the multi-star net-

work observed on the four quartz cabochons (samples A–
D in table 1). The red lines represent the light bands c
observed on the surface upon various rotations. The pat-
terns in A and B were observed on the round cabochons;
sample C was an oval cabochon, while sample D was an
irregularly shaped cabochon. The direction of the c-axis
for the three transparent samples is also indicated.

GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SUMMER 2022 251

 Figure 17. Fibrous inclu-
sions in a quartz cabo-
chon from Brazil
showing three-rayed as-
terism. Photomicrograph
by Karl Schmetzer; im-
mersion, field of view
7.6 mm.

that appear almost straight in the middle of the cabochon A zircon with strong photochromic effect. Recently, a 6.54
will appear more or less curved. So far, due to the different ct oval faceted gemstone with greenish blue color (figure 18,
orientations of the cabochons and the different shapes, each left) was sent to Taiwan Union Lab of Gem Research
sample represents only part of a full star network that would (TULAB) for identification. The specific gravity of this stone
be seen on the surface of a complete sphere. was 4.68, and the refractive index was over the limit of the
All the samples revealed a dense pattern of needle-like refractometer. Microscopic observation showed strong bire-
to fibrous inclusions (figure 17) typically described as rutile fringence. In addition to standard gemological testing,
(J. Hyršl and G. Niedermayr, Magic World: Inclusions in Raman spectroscopy and comparison with the zircon refer-
Quartz, 2003, Bode Verlag, Haltern, Germany, pp. 82–139). ence spectrum R050203 from the RRUFF database (figure
However, these inclusions are mostly bent or curved, and 19) confirmed it was a zircon. It was particularly worth not-
no series of parallel needles or channels were seen under ing that this zircon showed a significant color change from
the magnification of a gemological microscope (up to greenish blue to very dark yellowish green (figure 18) when
100×). It is uncertain how these curved rutile inclusions, exposed to a long-wave ultraviolet lamp.
sometimes described as “fibers” or “hairs,” contribute to To determine the extent of the color change and whether
the phenomenal pattern observed. it was permanent or reversible, the zircon was first exposed
The mechanism responsible for the observed multi-star to long-wave UV light for one minute and then under 10W
network is unknown; it could be caused by structural fea- white LED light for another minute (the light sources were
tures or inclusions. However, quartzes with similar rutile placed approximately 3 cm away from the gemstone). After
inclusion patterns from Brazil (as shown in figure 17) and repeating this process several times with each exposure one
elsewhere generally do not show three-rayed asterism or minute longer than the previous time, we confirmed that the
the type of three-rayed asterism network described here. It color changed from medium light greenish blue with strong
is possible to create a single three-dimensional network by saturation to a medium dark greenish yellow with lower sat-
a combination of the variants seen in figure 16, A–D. But uration after two minutes of long-wave UV light exposure.
this would be highly speculative, since we cannot (based However, the greenish yellow color gradually returned to the
on the samples available) prove that all variants seen so far stable greenish blue color after photobleaching with LED
contribute to one single pattern. white light for 30 minutes. Therefore, the stone was a pho-
tochromic zircon with reversible color change (as reported
Karl Schmetzer in N.D. Renfro, “Reversible color modification of blue zircon
Petershausen, Germany by long-wave ultraviolet radiation,” Fall 2016 G&G, pp. 246–
Martin P. Steinbach 251). After the color change reached its full extent under
Idar-Oberstein, Germany long-wave UV light, the zircon was analyzed by visible spec-

252 GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SUMMER 2022

Figure 18. This 6.54 ct zircon showed a significant color change from medium light greenish blue (left) to very dark
yellowish green (right) after exposure to long-wave UV for two minutes, and the color was reversible during the
photobleaching process with LED white light. Photos by Kai-Yun Huang.

troscopy to record its continuous spectral change during the range between 450 nm and 550 nm gradually increased dur-
photobleaching process every six minutes (figure 20). The re- ing the photobleaching process, and the greenish blue color
sulting spectra revealed that the light transmittance in the finally returned to a stable state after 30 minutes.

RAMAN SPECTRA

Zircon R050203
Greenish blue zircon

Figure 19. The stacked

Raman spectra of the
greenish blue zircon
INTENSITY

and a zircon reference

spectrum from the
RRUFF database; spec-
tra are normalized and
baseline-corrected.

150 650 1150 1650 2150 2650 3150 3650 4150

RAMAN SHIFT (cm ) –1

GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SUMMER 2022 253

 VISIBLE SPECTRA
1.0

0.8
TRANSMITTANCE

0.6

0.4

0.2
Photobleaching 0 min Photobleaching 6 min Photobleaching 12 min

Photobleaching 18 min Photobleaching 24 min Photobleaching 30 min

0
400 450 500 550 600 650 700 750 800
WAVELENGTH (nm)

Figure 20. Visible spectra of the zircon (after UV light exposure) during the photobleaching process were recorded
every six minutes. The gradually decreasing spectral change implied that the color tended to stabilize.

Although this type of photochromic zircon has previ- community. Inspired by their childhood memories of Pak-
ously been reported, a zircon over 6 ct with such a signifi- istan, Wellington and Gordos are dedicated to making
cant photochromic effect is still rare and worth noting, Swat Valley’s emeralds globally recognized for their trace-
especially since it exhibited a distinct difference in hue, ability and intense vivid green color (figure 21), all while
tone, and saturation. empowering women.
Shu-Hong Lin Myne London partners with local groups in the Swat
Institute of Earth Sciences, Valley region, including miners and mine owners. In addi-
National Taiwan Ocean University tion to sourcing the emeralds directly from the miners,
Taiwan Union Lab of Gem Research, Taipei Myne London is committed to keeping the lapidary work
in Islamabad and providing opportunities for women. Part-
Yu-Shan Chou and Kai-Yun Huang
nering with a local company, they train and hire Pakistani
Taiwan Union Lab of Gem Research, Taipei
women to cut and polish the emeralds (figure 22), a profes-
sion traditionally dominated in the region by men. Myne
RESPONSIBLE PRACTICES London, which employs a 75% female workforce, collabo-
rates with jewelry designers worldwide—mainly women—
Myne London: Sourcing emeralds with a mission. In 2018, to create exquisite pieces featuring the high-quality
sisters Fiona Wellington and Kate Murray Gordos emerald melee, in addition to designing its own fine jew-
founded Myne London (www.mynelondon.co.uk), a Lon- elry collections.
don-based ethical emerald supplier with a goal of support- But Wellington and Gordos aspire to do even more for
ing women in the gem trade. Their emeralds are sourced their female lapidaries. In 2021, they started the Myne Lon-
from lesser-known mines in Swat Valley, Pakistan, where don Foundation, a charitable organization designed to give
they aim to create a sustainable and responsible emerald their employees better access to education, which is lim-
industry and a lasting positive economic impact in the ited for girls in the country. Illiteracy rates are higher than

254 GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SUMMER 2022

Figure 21. Emerald rough from Swat Valley, Pakistan.
Photo courtesy of Myne London.

50% for adult women in Pakistan. The money raised by

the foundation assists the daughters of female employees
with tuition costs, school uniforms, and transportation.
Without money to pay for these costs, children in the
northern regions of Pakistan often do not attend school. Figure 22. Eighty percent of the Pakistani lapidaries
The foundation receives 10% of Myne London’s profits. working in the Myne London workshop are women.
In March 2022, Myne London hosted an inaugural char- Photo courtesy of Myne London.
ity ball for the foundation, raising nearly $20,000, which
has already been put to good use in Pakistan. “We imme-
diately actioned to pay for the daughter of one of our lap-
powerment. But for now, they remain focused on the
idary workers to attend school from now on in Islamabad.
women and emeralds of Swat Valley.
She is six years old. We plan to provide this for her for as
long as she wishes to stay in education,” said Wellington. Erica Zaidman
“We also are committed to find ways to support girls in GIA, Carlsbad
sport, because that is a great leveler and improves confi-
dence as well as health.” Figure 23. Ring designed by Octavia Elizabeth in 18K
Outside of Pakistan, Myne London continues its ethos gold featuring 1.24 carats of Swat Valley emerald.
of women’s economic empowerment by collaborating with Photo courtesy of Octavia Elizabeth/Myne London.
women around the world in jewelry design. Last year, the
company partnered with Los Angeles–based jewelry de-
signer Octavia Zamagias of Octavia Elizabeth, who shares
the same social goals. Using 18K gold, Zamagias created
several stunning pieces featuring Swat Valley emeralds (fig-
ure 23). Looking ahead, Myne London is planning jewelry
collaborations with three other talented women—two
based in London and the other in Florence.
The firm recently partnered with Opsydia, a gemstone
security specialist, to permanently place its brand logo be-
neath the surface of the Swat Valley emerald melee. En-
couraged by Opsydia’s success placing identifiers in melee
diamonds, Myne London aims to promote traceability
using this innovative technology.
With all their success in Swat Valley, Myne London
hopes to expand to other areas of the world someday, using
the same model for ethics, traceability, and women’s em-

GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SUMMER 2022 255

 When examined via water immersion in a direction par-
allel to the girdle plane, one can observe that this triplet was
made of two pieces of colorless material (crown and pavil-
ion), with a green cement slice in between (figure 25). Using
water for the immersion test to observe the internal charac-
teristics did not corrode the sample and yielded better ex-
perimental results. No inclusions were observed in the
crown. Microscopic examination revealed two-phase (liquid
and gas) inclusions, cracks (figure 26A), and lace-like par-
tially healed fissures in the pavilion (figure 26B). In the mid-
dle cement layer, no gas bubbles were observed along the
separation plane in the assemblage, unlike doublets previ-
ously described (H.A. Hänni and U. Henn, “Modern dou-
blets, manufactured in Germany and India,” Journal of
Gemmology, Vol. 34, No. 6, 2015, pp. 479–482; Spring 2019
Lab Notes, p. 92). However, the very thin layer of solidified
Figure 24. This 11.30 ct sample (18.9 × 14.0 × 8.8 mm) cement (approximately 10 μm thick; figure 26C) showed a
was found to be a triplet composed of colorless glass maze-like pattern under the microscope (figure 26D).
and quartz held together by green cement. Photo by This triplet had refractive indexes of 1.515 (crown) and
Biqian Xing. 1.544–1.553 (pavilion) and a hydrostatic specific gravity of
2.59. Its fluorescence under long-wave UV radiation was
green for the crown and blue-white for the pavilion (affected
by the fluorescence of the cement) and inert for both the
SYNTHETICS AND SIMULANTS crown and pavilion under short-wave UV radiation. No ob-
vious absorption was observed with a handheld portable
Unusual glass-and-quartz triplet imitation of emerald. Re- spectroscope, and no reaction was observed with the
cently, an 11.30 ct emerald-cut sample sold as an emerald Chelsea filter.
(figure 24) was provided by an anonymous jewelry manu- The EDXRF and FTIR results identified the crown as
facturer, who suspected an imitation. It resembled a natu- soda-lime-silica glass (69.97 wt.% SiO2, 15.25 wt.% Na2O,
ral emerald with its vivid bluish green color, inclusion and 8.94 wt.% CaO) with characteristic peaks at 1061 (asym-
abundance, and a vitreous luster. However, examination metric vibration modes of the Si-O-Si network), 770 (sym-
identified it as a glass-and-quartz triplet, an occasionally metric vibration modes of the Si-O-Si network), 968
convincing imitation of emerald. (stretching vibration of the Si-O non-bridging oxygen group),

Figure 25. Illuminated with

diffused transmitted light
with water immersion, the
Soda-lime-silica glass assembled nature of this
11.30 ct triplet was obvious
in profile view (top image
Quartz shows a slight downward
view, and bottom image
shows a slight upward
view). The pavilion is
nearly colorless (both top
and bottom images) due to
the refraction and scatter-
Soda-lime-silica glass ing of the green cement by
a large number of inclu-
sions, while the crown is
Quartz colorless and clean under a
certain observation angle
(bottom image). Photo by
Biqian Xing.

256 GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SUMMER 2022

 A B

Figure 26. Microscopic

observation of the
triplet revealed numer-
ous cracks (A), fluid in-
clusions, and lace-like
partially healed fissures
(B) in the pavilion. C:
The cement slice could
be seen under reflected
C D light (as shown by the
arrow). D: A maze-like
pattern in the cement
slice. Photomicrographs
by Biqian Xing; fields of
view 2.51 mm (A),
10.37 mm (B), 2.71 mm
(C), and 1.15 mm (D).

and 465 cm–1 (Si-O-Si and O-Si-O bending modes) (figure 27) temperature of soda-lime silicate glass,” Journal of the Amer-
(A. Agarwal and M. Tomozawa, “Determination of fictive ican Ceramic Society, Vol. 78, No. 3, 1995, pp. 827–829; S.I.

FTIR SPECTRA

Glass (crown)
1061
Quartz (pavilion)

465
968

Figure 27. FTIR spec-

troscopy identified the
770
crown of the triplet as
glass (peaks at 1061,
REFLECTANCE

968, 770, and 465 cm–1)

1140 and the pavilion as
1084
1174 quartz (peaks at 1174,
488 1140, 1084, 800, 781,
693, 540, 488, and 454
cm–1). Spectra are
540 454 stacked for clarity.
781
800
693

1400 1200 1000 800 600 400

WAVENUMBER (cm–1)

GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SUMMER 2022 257

Amma et al., “Specular reflectance (SR) and attenuated total
reflectance (ATR) infrared (IR) spectroscopy of transparent
flat glass surfaces: A case study for soda lime float glass,”
Journal of Non-Crystalline Solids, Vol. 428, 2015, pp. 189–
196). The pavilion was identified as quartz, with 99.54 wt.%
SiO2 and characteristic FTIR peaks at 1174, 1140, 1084 (an-
tisymmetric stretching vibrations of the SiO4 tetrahedron),
800 (SiO4 symmetric stretching), 781 (SiO4 symmetric
stretching), 693 (Si-O-Si bending transition modes), 540, 488,
and 454 cm–1 (figure 27) (A. Hahn et al., “Using Fourier trans-
form infrared spectroscopy to determine mineral phases in
sediments,” Sedimentary Geology, Vol. 375, 2018, pp. 27–
35). Unfortunately, the green cement was too thin to analyze
with a micro-infrared spectrometer or Raman spectrometer. Figure 28. Silk in corundum often unmixes into two dif-
The triplet was a typical imitation of emerald but sur- ferent solid phases, one highly reflective (rutile) and the
prisingly convincing when viewed table-up with the un- other of lower relief (ilmenite or hematite-ilmenite).
aided eye. With its extremely thin cement slice, maze-like When the Mozambique ruby was heated, the lower-re-
pattern, and lack of bubbles, even a jewelry manufacturer lief crystals began to break down, developing irregular
might mistake it for emerald. This investigation reminds white patches, as shown in the yellow circle. Photomi-
us that the examination of potentially composite stones crograph by Richard W. Hughes; field of view 1 mm.
cannot be ignored.
Biqian Xing, Guanghai Shi, and Wenqing Liu
China University of Geosciences, Beijing a stone has been subjected to artificial heat treatment. We
proceeded to examine the gem in the microscope, where we
found two additional pieces of evidence of heat treatment.
TREATMENTS The first feature was rutile silk of a type that is typical
of rubies from East Africa. In these stones, the silk consists
Ruby: An expensive mistake. Gemologists at Bangkok’s of high-relief needles of rutile with attached unidentified
Lotus Gemology recently received a 6 ct ruby for identifi- “daughter” crystals of another substance of lower relief. In
cation. Declared to be an untreated ruby from Mozam- the case of heat-treated stones, the daughter crystals will
bique, the stone featured a superb vivid red color of a type sometimes show a partial breakdown (“GIA Lab reports on
that is often termed “pigeon’s blood” in the trade. As it was low-temperature heat treatment of Mozambique ruby,”
also of good clarity and well cut, it was obvious we were GIA Research News, April 28, 2015). Small amounts of
dealing with a gem of potentially high value. breakdown in the form of irregular white patches were
The UV-Vis-NIR spectrum was typical for ruby/syn- found in this stone (figure 28).
thetic ruby. The infrared spectrum revealed peaks at 3309 But the most obvious evidence of heat treatment was
and 3232 cm–1. The 3232 cm–1 peak generally indicates that the presence of spall marks (figure 29), which are solidified

Figure 29. Spall marks on the surface of the Mozambique ruby prove it was heat treated after cutting and polish-
ing. Note that some of the spall marks have dark halos around them. Photomicrographs by Richard W. Hughes;
fields of view 2.0 and 2.5 mm.

258 GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SUMMER 2022

Figure 30. Left: Before a fade test, this approximately 10 ct sapphire displayed a strong orange hue. Right: After the
fade test, the orange color became less pronounced and the stone appeared yellow. Photos by Ronnakorn Manorotkul.

droplets of material on the surface that melted or were dis- dum. Some sapphires, particularly those with a strong yel-
solved during heating. These spall marks across the stone low component (including padparadscha sapphire), contain
showed that the ruby had been heated after cutting and not unstable color centers that may fade when the stone is ex-
repolished following the treatment. We can only guess posed to light and/or heat (K. Nassau and G.K. Valente,
about the reasons for heating such a valuable gem, but “The seven types of yellow sapphire and their stability to
there is no doubt that this particular roll of the dice was a light,” Winter 1987 G&G, pp. 222–231). We regularly test
losing gamble because the potential improvement in ap- for this in the laboratory by conducting a fade test. Most of
pearance is slight compared to the large price difference be- the sapphires we encounter that have an unstable color are
tween untreated and heated ruby. We concluded that this unheated stones.
was a heat-treated Mozambique ruby. Recently an orange sapphire of approximately 10 ct was
Richard W. Hughes submitted for testing (figure 30). Microscopic examination
Lotus Gemology, Bangkok revealed signs of heat treatment, with partially dissolved
silk, several glassy discoids (figure 31), and melted crystals
Yellow sapphires with unstable color. In recent years, one (figure 32). A fade test was conducted by placing the stone
concern our laboratory has heard from clients and from approximately 5 cm under a 120-watt incandescent spot-
other gemologists is the issue of color stability in corun- light for at least an hour, and a dramatic difference was ob-

Figure 32. This small crystal with a melted appear-

Figure 31. A cluster of glassy discoids suggests that ance provides evidence that the specimen has under-
this sapphire has been heat treated. Photomicrograph gone heat treatment. Photomicrograph by E. Billie
by E. Billie Hughes; field of view 4.0 mm. Hughes; field of view 3.5 mm.

GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SUMMER 2022 259

Figure 33. Before a fade test, the unheated sapphire of approximately 18 ct displayed a highly saturated yellow hue
(left). After a fade test involving light and mild heat, the color faded to a pale yellow (right). Once the stone was
exposed to sunlight for 30 minutes, the more intense yellow color displayed before the fade test came back. The
sapphire was then subjected to a light-only fade test, and the more saturated yellow color remained stable. Photos
by Ronnakorn Manorotkul.

served. The color had changed from orange to a vivid yellow and that the more intense yellow color displayed after expo-
(again, see figure 30). sure to sunlight could indeed be considered the stable color.
Under normal conditions, high-temperature heat treat- We have since adjusted our fade tests to be light-only
ment (at least 1200–1300°C) will bleach any color centers by switching to this cooler light source to avoid the heat
that might be present. This suggests that the orange color generated with the 120-watt spotlight.
was activated after the heat treatment. It is possible that this Our experience with these sapphires has been a fasci-
occurred either by subjecting the stone to artificial irradiation nating case study in the color stability of yellow sapphire.
or by placing it in sunlight (Nassau and Valente, 1987). How- This example reinforces the importance of considering all
ever, we are unable to state definitively what process was possibilities when testing stones in the laboratory. We do
used to activate the orange color. not fully understand the exact causes of these changes, and
Several weeks later, we tested another yellow sapphire much remains to be learned.
of approximately 18 ct (figure 33). In this instance, the E. Billie Hughes
stone’s features were consistent with those of unheated Lotus Gemology, Bangkok
sapphire. Again, a fade test was performed with the 120-
watt spotlight, which mildly warmed the stone to approx-
imately 100°C. Its color also faded after the fade test, and AUCTION REPORTS
the owner was informed. The owner explained that they
had previously put the sapphire in direct sunlight, which Spring 2022 auction highlights. The De Beers Cullinan
would have brought the color back to what was likely its Blue was the early buzz of the spring 2022 auction season,
stable state, a process described by Nassau. with the 15.10 ct Fancy Vivid blue step-cut diamond far
To test this, we placed the stone in direct sunlight for surpassing Sotheby’s presale estimate of $48 million. Bring-
30 minutes, and the more intense yellow color did return. ing $57.5 million, the diamond was the largest of its color
Unfortunately, placing the gem in direct sunlight behind a to ever appear at auction and also the third most valuable
window in our office did not have the same effect. diamond of any color to sell at auction. (To read more about
Upon seeing the color return after being placed in direct GIA’s examination of the De Beers Cullinan Blue, see Lab
sunlight, we decided to try another fade test, this time using Notes in this issue, pp. 216–217.)
a light source that would not warm up the stone. An XD-300 The season continued in Geneva, with Christie’s auc-
xenon light source was used, and the stone was placed within tioning two diamonds weighing more than 200 ct each at
5 cm of a fiber-optic light guide connected to this source. the Magnificent Jewels sale on May 11, beginning with the
After exposure to this cooler light source for over an hour, largest white diamond ever sold at auction. Named the
the color did not fade. This suggests that the mild heat of the Rock (figure 34), the GIA-graded 228.31 ct, G-color, VS1
120-watt spotlight, not just the light, faded the stone’s color pear-shaped diamond sold for $21.9 million, or $96,000 per

260 GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SUMMER 2022

 Figure 34. At 228.31 ct,
the Rock is the largest
white diamond ever
sold at auction. Photo
courtesy of Christie’s.

carat. The previous record holder for the largest white dia- during World War I. At 205.07 ct, the GIA-graded Fancy In-
mond sold at auction weighed 163.41 ct and was sold by tense yellow cushion cut fetched $14.3 million, or $70,000
Christie’s in 2017. per carat, after 11 minutes of competitive bidding, setting
The second diamond, the Red Cross (figure 35), re- an auction record price for a Fancy Intense yellow dia-
turned to Christie’s for a third time at auction. It was first mond. A portion of the proceeds benefited the Interna-
sold at Christie’s in 1918 to benefit the British Red Cross tional Committee of the Red Cross.

GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SUMMER 2022 261

 Figure 35. The 205.07
ct Red Cross diamond
set an auction record
price for a Fancy In-
tense yellow diamond
at Christie’s Geneva
Magnificent Jewels
sale. Photo courtesy of
Christie’s.

A jadeite necklace (figure 36; opposite page) was the top York. The 103.49 ct Light of Africa (figure 37), the fifth
lot at Christie’s May 25 Hong Kong sale, selling for $8.8 most valuable colorless diamond ever offered at Christie’s,
million after 11 minutes of bidding. The stunning piece fea- surpassed its presale estimate of $18 million, with the win-
tures 33 perfectly round, exceptionally large jadeite beads ning bid coming in at just over $20 million—an incredible
ranging from 12.3 to 15.0 mm in diameter, with an 11 ct $195,000 per carat. The GIA-graded emerald-cut type IIa
Burmese ruby clasp surrounded by oval brilliant diamonds. diamond was cut and polished from a 299 ct rough stone
In June, the focus returned to diamonds at Christie’s unearthed from the Cullinan mine.
final Magnificent Jewels auction of the season in New Erica Zaidman

Figure 37. The 103.49 ct

Light of Africa diamond
sold for an impressive
$195,000 per carat at
Christie’s Magnificent
Jewels sale in New
York. Photo courtesy of
Christie’s.

262 GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SUMMER 2022

Figure 36. This necklace featuring 33 jadeite beads was the top lot at Christie’s Magnificent Jewels sale in Hong
Kong. Photo courtesy of Christie’s.

GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SUMMER 2022 263

 Figure 38. These 12 tour-
malines from The Big
Find will be featured in
one-of-a-kind jewelry
pieces. Photos courtesy
of the Maine Mineral &
Gem Museum.

MUSEUM EXHIBITIONS tourmaline. The astounding 1972 discovery, known as

“The Big Find,” unveiled vast pockets of tourmaline of
The Big Find: Celebrating 50 years of Maine tourmaline. every color at an abandoned mine near the top of
October 2022 will mark 50 years since North America’s Plumbago Mountain in Newry, Maine. Yielding more than
largest and most significant unearthing of gem-quality a ton of tourmaline rough from 1972 to 1974, The Big Find

264 GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SUMMER 2022

 Figure 39. Tourmaline
bears on a frosted quartz
base, carved by Gerhard
Becker using tourmaline
from The Big Find in
Newry, Maine. Gifted to
GIA by John Staver and
currently on loan to the
Maine Mineral & Gem
Museum. (See more
tourmaline carvings
from GIA’s collection at
www.gia.edu/gia-
museum-tourmaline-
carvings.) Photo by
Orasa Weldon.

reawakened gem mining in the state of Maine. To cele- ticket information can be found at https://mainemineral-
brate the 50th anniversary of this historic discovery, the museum.org/the-big-find/.
newly opened Maine Mineral & Gem Museum has big The museum is also commemorating the anniversary
plans underway. with special tourmaline exhibits and guest lectures all
The Big Find: A Legend Continues began last year year, including various Maine tourmaline carvings on loan
when the museum sought jewelry designers from across from the GIA Museum (figure 39). After the event, all 12
the country to create jewelry using 12 stones from the pieces of tourmaline jewelry will be on display at the
1972 find, ranging in weight from 9.78 to 49.30 ct (figure Maine Mineral & Gem Museum and then at the 2023 Tuc-
38). Twelve designers selected by jury are now at work son Gem & Mineral Show before being auctioned off to
crafting one-of-a-kind pieces to be presented on October raise money for the museum.
8, 2022, at a runway extravaganza in Newry. Event and Erica Zaidman

GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SUMMER 2022 265

Figure 40. Inside the vault room of the Brilliance: The Art and Science of Rare Jewels exhibit. Photo courtesy of the
Natural History Museum of Los Angeles County.

Brilliance Exhibit at the Natural History Museum of Los from December 8, 2021, through February 21, 2022, in the
Angeles County. A special exhibit of rare gems and miner- Gem Vault in the museum’s Gem and Mineral Hall (figure
als, entitled Brilliance: The Art and Science of Rare Jewels, 40). Over one hundred spectacular objects—necklaces,
was recently displayed at the Natural History Museum of bracelets, rings, earrings, and unmounted gems (many the
Los Angeles County. The exhibit was available for viewing creations of master jewelry designer Robert Procop)—were

Figure 41. Left: The

46.39 ct Fancy blue Ce-
leste diamond and a
100.92 ct colorless dia-
mond were but two of
the exquisite gems on
display at the Natural
History Museum of Los
Angeles County. Right:
This 108.03 ct blue sap-
phire from Sri Lanka is
exceptional in terms of
its clarity, color, and
size. Photos courtesy of
the Natural History
Museum of Los Angeles
County; courtesy of
Robert Procop.

266 GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SUMMER 2022

 and appreciate these unique treasures, this museum event
provided an understanding of how gems and minerals are
used today in a variety of fields, from jewelry design to sci-
entific research. Crystals of gem minerals represent prod-
ucts of some optimum conditions for natural mineral
formation, and the study of rough and faceted gems is in-
creasingly used by scientists today to better understand
Earth’s history.
James E. Shigley and Brooke Goedert
GIA, Carlsbad

Smithsonian’s Great American Diamonds exhibit. Two

extraordinary American diamonds (figure 43) have found a
home at the Smithsonian’s National Museum of Natural
History, where they were unveiled as part of the new Great
American Diamonds exhibit in June. The 16.87 ct Free-
dom diamond, the largest faceted diamond of U.S. origin,
was fashioned from a 28 ct crystal unearthed at Colorado’s
Kelsey Lake mine in 1997. The cushion-cut diamond is
now set in a ring donated by Robert E. and Kathy G. Mau.
The second diamond on exhibit, the emerald-cut Uncle
Sam, was faceted from the largest uncut American dia-
mond crystal ever discovered at 40.23 ct. Uncovered at
Arkansas’ Crater of Diamonds in 1924, the flawless 12.42
Figure 42. The 79.39 ct Royal Pink sapphire is, accord-
ct pinkish brown stone was recently recovered from a pri-
ing to the designer, the largest vivid natural pink sap-
vate collection (after being missing for decades) and do-
phire in the world. Courtesy of Robert Procop.
nated by Peter Buck. This is the first time the Uncle Sam
has been exhibited in more than 50 years.
While diamonds from the United States are exception-
on display along with mineral specimens from the mu- ally rare, the two mines in Colorado and Arkansas pro-
seum’s collection. Colorless and fancy-color diamonds, ru- duced tens of thousands of carats of rough diamonds, from
bies, sapphires, emeralds, as well as color-change and 1919 to 1926 at the Crater of Diamonds and 1996 to 2001
asteriated gems and other spectacular specimens, were rep- at Kelsey Lake. “Most people are surprised to learn that di-
resented (figures 41 and 42). By allowing the public to view amonds have been mined in the United States, and as the

Figure 43. Left: The 16.87

ct Freedom, from Kelsey
Lake in Colorado, is the
largest faceted diamond
from the U.S. Right: The
12.42 ct Uncle Sam is the
largest faceted diamond
from Arkansas, cut from
a 40.23 ct crystal uncov-
ered at the Crater of Dia-
monds. Photo by James
Tiller and Brittany M.
Hance; courtesy of De-
partment of Mineral Sci-
ences, Smithsonian
Institution.

GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SUMMER 2022 267

 Figure 44. The new GIA
Alumni Collective of-
fers a robust educa-
tional and networking
platform for GIA gradu-
ates worldwide.

national museum, we are delighted to introduce these great After successfully completing a GIA program or course,
American diamonds to our visitors,” said Dr. Jeffrey Post, alumni can register for the Collective and stay informed
the museum’s curator-in-charge of gems and minerals. about all the resources available to them by visiting the new
Joining these two impressive donations in the Great GIA Alumni Collective website. The new online commu-
American Diamonds exhibit are two uncut diamonds from nity, collective.gia.edu, serves as a “central hub” where
the museum’s existing collection. The Canary, a golden members can add their profile to the directory, engage and
yellow crystal weighing 17.85 ct, is one of the largest uncut connect directly with other members and global chapters,
diamonds from Arkansas. The 6.45 ct Colorado, which dis- join “virtual” chapters, register to attend professional
plays the typical octahedral shape of a natural diamond events, access more than 20 Continuing Education semi-
crystal, was recovered from the kimberlite host rock during nars at a 10% discount, and more.
mining operations at Kelsey Lake. As part of the Smith- “The new GIA Alumni Collective website and online
sonian’s National Gem and Mineral Collection, these four community is a reflection of our diverse alumni network.
stones are among more than 10,000 precious stones and The collaboration with chapter leaders and other members
pieces of jewelry, including the iconic Hope diamond. brings new energy and a modern look that connects our
Erica Zaidman global network and provides a space to experience the fu-
ture of gems and jewelry,” says Cathryn Ramirez, execu-
tive director of alumni development and continuing
ANNOUNCEMENTS education at GIA.
GIA has more than 155,000 active alumni in 58 chapters
GIA Alumni Collective. GIA’s alumni association has a new spanning the globe—33 in the Americas, 16 in Asia, and
name, a fresh look, and up-to-date features. With a mission three apiece in Europe, the Middle East, and Africa. While
to connect GIA graduates around the world, provide oppor- chapters host their own meetings and events, chapters often
tunities for continuing education, and foster networking co-host to provide additional networking opportunities. The
throughout the gem and jewelry industry, the GIA Alumni GIA Alumni Collective hosts annual events at the AGTA
Collective (figure 44) builds on the association’s long history Tucson and JCK Las Vegas trade shows where hundreds of
with updates that better reflect the creativity, technical alumni from all over the world meet up with longtime
savvy, entrepreneurship, and vitality of GIA’s alumni. friends and colleagues and foster new relationships.

268 GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SUMMER 2022