[EYEWITNESS @®HANDBOOKS|

‘The visual guide to more

than 130 gemstone varieties

Precious Opal

Pyrope Cally Hall rene

EYEWITNESS
@® HANDBOOKS

GEMSTONES
EYEWITNESS@ HANDBOOKS

GEMSTONES
CALLY HALL

Photography by
HARRY TAYLOR
(Natural History Museum)

Editorial Consultant
JOSEPH J. PETERS

DK
 A DK PUBLISHING BOOK

Project Editor Alison Edmonds

Project Art Editor Alison Shackleton
Series Editor Jonathan Metcalf
Series Art Editor Spencer Holbrook
Production Controller Caroline Webber
U.S. Consultant Joseph J. Peters
U.S. Editor Charles A. Wills

First American Edition, 1994

6810975

Published in the United States by DK Publishing, Inc.

95 Madison Avenue, New York, NY 10016
Copyright © 1994 Dorling Kindersley Limited, London
Text copyright © 1994 Cally Hall

All rights reserved under International and Pan-American Copyright

Conventions. No part of this publication may be reproduced, stored in a
retrieval system, or transmitted in any form or by any means, electronic,
photocopying, recording or otherwise, without the written permission of the
copyright owners. Published in Great Britain by Dorling Kindersley Ltd.
Distribution by Houghton Mifflin Company, Boston.

Library of Congress Cataloging-in-Publication Data

Hall, Caroline.
Gemstones / Caroline Hall.--1st American ed.
p. cm.-- (Eyewitness handbooks)
Includes index.
ISBN 1-56458-499-2 (hardcover): $29.95 -- ISBN 1-56458-498-4 (flexibinding) $17.95
1. Precious stones. 2. Gems. I. Tide. Tl Senies
TS752.1218 1993
553.8--dc20 93-28348 CIP

Computer page makeup by Adam Moore

‘Text film output by ‘The Right Type, Great Britain
Reproduced by Colourscan, Singapore
Printed and bound by Kyodo Printing Co., Singapore
 CONTENTS
INTRODUCTION ® 6
Author’s Introduction 6
How this Book Works 9
What are Gemstones? /0
How Gemstones are Formed /2
Where Gemstones are Found /4
Physical Properties /6
Crystal Shapes /8
Optical Properties 20
Natural Inclusions 24
Faceting 26
Polishing, Carving, and Engraving 28
Gems Through the Ages 30
History and Folklore 32
Synthetic Gemstones 34
Imitation and Enhancement 36
Color Key 38

a ie
PRECIOUS METALS e 48

CUT STONES e 54

ORGANICS @ 138

‘Table of Properties /50

Glossary /56
Index /58
Useful Addresses /60
Acknowledgments /60
6° INTRODUCTION

AUTHOR’S INTRODUCTION
The mysterious appeal ofgemstones, their exquisite colors and the play of
light within them, would alone have made them precious to many, but their
rarity, hardness, and durability have made them doubly valuable. The
natural beauty, strength, and resthence of gems have inspired beliefs in their
supernatural origins and magical powers, and stones that have survived the
centuries have gathered a wealth of history and romance around them.

fe ARE OVER 3,000 different

minerals, but only about 50 are
commonly used as gemstones. Others
are cut for collectors of the unusual but
are not suitable for wear because they
are too soft and easily scratched. ‘The
number of minerals commonly used as
gemstones constantly changes as new
sources and varieties are found and
fashions change. Over 130 gem species,
including some exceptionally rare
stones, are described in this book,
illustrating the very. wide range of
; ‘ rm an Ay ) ~

naturally occurring gemstones. SOR! ING SAPPHIRES

Workers in Myanmar (Burma) sort through
Wuat Is A GEMSTONE? sapphires collected from river sediment. When
: cut, they epitomize the allure of gemstones.
lo be regarded as a gemstone, ;
a mineral (or occasionally
an organic material) must
be beautiful, most
importantly 1n its color.
RIVER PEARL
(UNCUT)

DIAMOND (BRILLIANT CUT)

FIVE MAJOR GEMSTONES

These five stones are the most
highly prized. All except pearl
have a particular cut that brings .
out their best qualities. RuBY (STEP CUT) EMERALD
(OCTAGONAL CABOCHON)
 INTRODUCTION e 7

A gemstone must also be durable — hard

enough to survive constant use or
handling without becoming scratched
or damaged. Finally, it must be rare,
because its very scarcity endows it
with a greater market value.
THE SCIENCE OF GEMOLOGY
Gems are scientifically fascinating, too.
Gemologists make a complete study of
each stone they acquire, both as it is
found in rocks and after it has been cut
and polished. ‘That is why the species EMBLEMS OF POWER
entries in this book show the gem in The Cullinan I diamond (above),
its rough, natural state, perhaps still adorns the Royal Scepter of the
embedded in the host rock (or matrix), British crown jewels (right).

as well as after it has been

cut, polished, or carved.
Many entries also feature a
microphotograph that reveals the
internal structure of the stone by
magnifying it. In this world within
a world the gemologist may turn
detective, being able to distinguish
between two similar species, or
between a natural stone and a fake.
| f.eOOC IWiQeicrerol KINGS AND COMMONERS
SESE OO 20.0} ‘Throughout the ages, gemstones

C6 See have been seen as representations

of wealth and power. Symbols of
supremacy, from crowns to richly
decorated robes, have traditionally
been adorned with jewels. But

PRIVATE COLLECTION
The Mathews collection in
London comprises 4 boxes of
unmounted gems from all
around the world (above),
and a group of Colombian
emeralds (right). The scope of
this collection is unique, but
many fine examples of cut
and uncut gemstones are on
public display in museums.
8 e INTRODUCTION

gemstones are not just for the wealthy |

or the scientifically minded: they can be
appreciated by anyone, from the
amateur gem-spotter to the enthusiast
who enjoys their beauty and history.
For this reason, the Hyewstness Handbook
of Gemstones is not intended as a
textbook but as a general introduction
and an initial guide to identification.

COLLECTING GEMS
For many, the real satisfaction comes
from actually owning gems. Most
people cannot afford the more

A Box OF JEWELS
In the 18th century, jeweled trinkets like this
decorative box were very fashionable. A large
citrine is in the center, surrounded by amethyst,
agates, amazonite, garnet, and pearls.

MINING IN CAMBODIA
In many parts ofthe world, traditional methods
and equipment are still employed for the
collection ofgemstones.
expensive stones, but anybody can
collect a few minerals that, even if not
gem quality, are still very attractive.
You may even chance on a piece of
amber on a beach, or come across a FOSSICKING IN AUSTRALIA
beautiful P iece of jewelry in a local Fossicking (foraging) for sapphires and opals ts
auction. No matter how modest your still possible in parts of Australia, as long as you
collection, it will give you hours of first obtain a permit from the authorities. River
fascination and enjoyment. beds and streams are the best locations.
 INTRODUCTION #9

How ‘THIS BOOK WORKS

HIS BOOK is divided into three monoclinic, and triclinic), but with
parts: precious metals, cut a final section on amorphous gems.
stones, and organics. Cut stones are Within these sections, gem species
arranged by crystal structure into are grouped with other species ofa
seven groups (cubic, tetragonal, similar mineralogical type. ‘The page
hexagonal, trigonal, orthorhombic, below explains a typical entry.

crystal group to basic chemical mean hardness of gem,

which gem belongs ¢ composition of gem measured on Mohs scale
|

Crystal structure Trigonal Composition Silicon dioxide |Haraness 7

gem’s common ~ AMETHYST (QUARTZ)

name, with i Crystalline quartz in shades of purple, lilac, or
mineral group nm mauve Is called amethyst, a stone traditionally
brackets (when worn to guard against drunkenness and to instill . closeup
appropriate) a sober and serious mind. Amethyst is dichroic, h Cai
showing a bluish or reddish purple tinge when : P Lolograp G
viewed from different angles. Usually faceted = : = of inclusions
; - as a mixed or step cut, amethyst has distinctive ; in gem (if
gem s chief inclusions that look like tigerstripes, thumbprints, Characteristic tigerstripe appropriate)
physical or feathers. Some amethyst Is heat treated to inclusions are caused by
characteristics change the color to yellow, producing citrine parallel, liquid-filled canals.
(see opposite). Crystals that are part citrine and Tie PIN
part amethyst are called ametrine. Amethyst jewelry was popular in the
@ OCCURRENCE Amethyst is found in alluvial late 19th century. This handsome ‘
deposits or in geodes. Some ofthe largest geodes gold tie pin is adorned with an ae example of
where and e——— containing amethyst are in Brazil. Amethyst from octagonal step-cut amethyst. Jewelry or
how gem the Urals (Russia) has a reddish tinge; Canadian = ornament
amethyst is violet. Other localities include Sri : 2 I :
isan Lanka, India, Uruguay, Madagascar, the USA, . Na, iM
Germany, Australia, Namibia, and Zambia. : - Sie Some entries 0
found ¢ REMARK Poor quality material is often t : iMustrate use
tumbled to make beads. If a stone is pale it
may be set in a closed setting or have foil placed
rae al behind it to enhance the color. Amethyst has
additional been imitated by glass and synthetic corundum. typical/ bof
5 i ps—e oe
example 0 of
information - purplish ‘Oe
, = purple stone ty a faceted gem,
relevant to from Russia hy : labeled with
;
. color Aa : := iEe
gem species
or type : ==, polished. <<, name of cut
5 iz CONVEX ,
front
alternate colors
due to twinning e
other color ; OvaL MIXED CUT
varieties and
cuts shown to ———e — : ; color darkens
Pio ee : 2a ; — toward tp of ‘
oie lj F : @ amethyst crystal +——e annotation
identification highlights key
HEXAGONAL = > FF ‘ais
MIXED CuT ZS = = Gas - physical
characteristics
slice cut
perpendicular E ° ‘ 4 : ‘ :
to length of Se Be: e a © specimen of
arystal e SR ae eK Se gem as it occurs
faceting styles ae ee eee SY = naturally, often
and shapes Ve ea shown in host
popular for TZN eee ea ee rock (matrix)
this gem 4 =a Y “/ AMETHYST CRYSTALS
— Ree j ASSOCIATED WITH
Baguette RoOcK CRYSTAL

Lustel Vitreous

mean figure mean range of refrac- » mean value of © surface shine

for specific tive values (singly birefraction or “look” of gem
gravity of gem refractive gems have (doubly refractive
one mean value only) gems only)
10 INTRODUCTION

WHAT ARE GEMSTONES?

Ce are generally minerals A few gems, like amber and pearl, come
that have been, or may be, fashioned from plants or animals and are known as
to use for personal adornment. As a rule, organics. Others, called synthetics, do
they are beautiful, rare, and durable. not have a natural origin but are made in
Most are minerals: natural, inorganic laboratories. heir physical properties
materials with a fixed chemical com- are similar to those of natural gems, and
position and regular internal structure. they may be cut to imitate the real thing.

POLISHED STONE
PRECIOUS METALS Crystals may be rounded
‘The precious metals are gold, silver, and and polished naturally
platinum. ‘They are not true gemstones, (like this emerald pebble,
but they are attractive and easily worked rolled in a stream) or
and have their own intrinsic value, often ground mechanically.
as settings for gems. Platinum 1s the rarest
and the most valuable.

GOLD RING

GOLD NUGGET
(UNWORKED)

ORGANICS
Gem materials produced by living organ-
isms are called organics. ‘Their sources
are as diverse as shellfish (which produce
pearls), polyps (whose skeletal remains
form coral), and the fossilized resin from
trees (which makes amber). Ivory, jet, and NATURAL CRYSTAL
shell are also organics. hese materials In its natural state, the
are not stones and are not as durable as mineral may be a prism,
mineral gems. Instead of being faceted with clearly defined faces.
like mineral gems, they are usually
polished or carved, or drilled and
threaded as beads. CuT STONES
Like the emerald shown here, almost all cut
gems begin life in a crystalline form (see
pp.18-19), embedded in a host rock known
as the matrix. In this state, the stone is
referred to as a rough. Many natural crystals
are attractive enough to be displayed as they
AMBER BEAD
are. Others are faceted and polished to en-
AMBER ROUGH hance their beauty (see pp.26—29), then set
in a piece of jewelry or an ornament.
 IN'TRODUCTION « 11

CABOCHON IMITATION EMERALD

| A simple fashion for stones (GARNET ON GLASS)
is to cut them en cabochon,
producing a domed, highly FACETED STONE
polished surface. Most gemstones are cut to
give them a number offlat
surfaces, called facets. The
facets absorb and reflect
light, to magical effect. IMITATIONS
Gemstones have been imitated
throughout the ages. Many
lesser stones have been used,
as well as glass paste and other
manmade materials. Compos-
ite stones, like the red garnet
on green glass (above), are
made of more than one piece.

JEWELRY
A piece ofjewelry,
usually one or several
polished or faceted
eet Ges == stones set in a mount of
, precious metal, is often
the finished product.

SYNTHETICS
Manmade synthetic stones (see
| pp.34-35) are similar in chemical
| composition and optical proper-
ties to their natural equivalents.
In the flux method, crystals are -
grown, then faceted (right). SYNTHETIC SYNTHETIC
CRYSTALS FACETED EMERALD
12 ¢eINTRODUCTION

How GEMSTONES ARE FORMED

( eee HAVE a mineral origin IGNrEous Rocks
,
are foun
=
d in rock s or in gem grav els JOTI as 1Qli oe
TOG ARE ae
below ground. This erodes and is deposited ?
ee.
derived from these rocks. Rocks them- as sediments.
selves are made up of one or more
minerals and may be
divided into three main
types. The formation
“a

of these three types — —C——S—

igneous, sedimentary, i
or metamorphic — is a
continuous process,
described in terms of the
rock cycle (shown right).
Gem-quality minerals with-
in these rocks may be easily
accessible at the Earth’s surface
or lie buried deep beneath : it. ¢ SEDIMENTARY ROCKS ¢ METAMORPHIC ROCKS
Others, se parate d from their are formed from the accumulation may be either sedimentary or
: ; ARES and compression of eroded rock igneous rocks whose character
hos t rock by erosion, are carried fragments. They may eventually be is fundamentally changed by
by rivers to lakes or the sea. buried back below the surface. heat and pressure.

peridot
crystals form IGNEOUS ROCKS
as lava cools e—
Igneous rocks have solidified from molten
rock, which comes from deep beneath the
Earth’s surface. Some, called extrusive
igneous rocks, are thrown out from volcanoes
as lava, volcanic bombs (see left), or ash.
Intrusive igneous rocks are those that solidify
beneath the surface. Essentially, the slower a
rock cools and solidifies, the larger the
crystals — and therefore the gemstones —
formed within it. Many large gemstone
VOLCANIC crystals form in a kind of intrusive igneous
BOMB FORMED rock known as pegmatite.
FROM BASALTIC LAVA

METAMORPHIC ROCKS kyanite and staurolite

Metamorphic rocks are either igneous Es eee ae
or sedimentary rocks that have been
changed by heat and pressure within
the Earth to form new rocks with new
minerals. As this happens, gemstones can
grow within them. Garnets, for example,
form in rocks called mica schists, which
were once mudstones and clays. Marble,
formed from limestone that has been
subjected to intense pressure and high
temperatures, may contain rubies. KYANITE-STAUROLITE SCHIST
 INTRODUCTION e« 13

SEDIMENTARY ROCKS
© blue-green
Sedimentary rocks are formed by the opal in veins
accumulation of rock fragments produced and fissures
by weathering. In time, these fragments
settle down and harden into rock once
more. Sedimentary rocks are usually laid
down in layers, and these may be shown
as a feature in decorative stones. Most
Australian opal occurs in sedimentary
rocks; turquoise occurs mainly as veins
in sedimentary rocks such as shale; halite
AUSTRALIAN OPAL IN SEDIMENTARY ROCK
and gypsum ave sedimentary rocks.

ORGANIC GEMS
Organic gems come from plants and animals.
Natural pearls form around foreign bodies
that have made their way inside the shells of
marine or freshwater shellfish. Cultured
pearls are produced artificially in large
fisheries, many in the shallow waters off the
shores of Japan and China. Shells treated as
gems may come from animals as diverse as
snails and turtles, living in the ocean, in fresh
water, or on land. Coral is made up of the
skeletons of tiny marine animals called coral
polyps. Bone, or ivory from the teeth or tusks
of mammals, may come from recently living
animals or from fossils thousands of years old. “TREASURE FROM ‘THE SEA
Amber is fossilized tree resin, collected from The action ofseawater has given this piece of
soft sediments or the sea. Jet is fossilized amber (fossilized tree resin), washed up on a beach
wood, found in some sedimentary rocks. in Norfolk, England, a pitted and worn surface.

MODERN DIAMOND MINE IN BOTSWANA ALLUVIAL MINING FOR SAPPHIRES

Some gemstones are so valuable that large-scale Small-scale mining with traditional methods and
mining, in which tons of rock may be extracted to equipment, such as this in Sterra Leone, 1s still
collect tiny amounts of gemstone, are still viable. common in many CouNTTIEs.
14° INTRODUCTION

WHERE GEMSTONES ARE FOUND

Sor GEM MINERALS, such as quartz quality. Ihe main gem localities of the
and garnet, are found worldwide. world are therefore those where gem-
Others, like diamonds and emeralds, are quality material occurs in sufficient

SF
rarer, due to the more unusual geological quantity to make production economical.
conditions necessary for their formation.
Even when a mineral is found ~~
worldwide, only a minute oat, Se
proportion may be of gem i sit,
~
&

Germany

Italy
DIAMONDS OF AFRICA
The kimberlite rocks of southern
Africa are mined in a modern,
large-scale way, producing vast
quantities of diamonds for both
industrial and gem use.

Zambia

Botswana -

South Africa

KEY TO SYMBOLS
Ay

oR,
mm) DF
As)

DIAMOND RUBY SAPPHIRE EMERALD

AQUAMARINE
@
CHRYSOBERYL
6
TOPAZ
ec
TOURMALINE
‘TWELVE KEY GEMS
The 12 varieties of gemstone shown on this map

@
PERIDOT
@
GARNET
0
PEARL
AaOPAL
represent some of the world’s best-known gems.
All are popular and highly prized, but some
are far rarer than others.
 INTRODUCTION ©.15

PEARLS IN JAPAN
The shallow coastal waters of the
Japanese islands offer ideal conditions
for farming pear! oysters. Pearls are
organic gems and therefore independent
of geological conditions.

former ~
(.\ Czechoslovakia

WORLD
© DISTRIBUTION
Afghanistan Chine Japan ‘This map shows the main
localities for 12 key gems.
Each gem may of course
Pakistan :
sen Myanmar occur in other places, but
© (Burma) probably not in sufficient
India @ ae quantities to make its ex-
——* Thailand ; :
traction economical.
re) Some sites, although
Zaire Sri Lanka ) historically important,
ge may now be worked out.
| East Africa
@

©
— 8 =
Madagascar Australia 8 )
_8 a.

RUBIES IN MYANMAR
The rich mineral deposits of Mogok
in Myanmar (Burma) have yielded
some of the world’s finest rubies,
extracted by traditional methods.
Sapphires are also mined here.
16 e INTRODUCTION

PHYSICAL PROPERTIES
Pe PHYSICAL PROPERTIES of gem- the hardest natural material known, and
stones, their hardness, their specific graphite is one of the softest, yet both
gravity or density, and the way they are made of the same element, carbon.
break or “cleave,” depend on chemical It is the way in which the carbon atoms
bonding and the atomic structure with- are bonded together in diamond that
in the stone. For example, diamond is gives it a greater hardness and resilience.

HARDNESS KNOOP SCALE | nn 67)

One of the key qualities of a This scale shows the | )
gemstone, hardness may be indentation caused
measured by how well a stone by a diamond point
resists scratching. Every stone when it meets the | |
can be tested and classified surface ofa mineral. 9 | |
using the Mohs scale of The 10 stages corres- owe
hardness (below), which pond to Mohs? points. — —
gives every mineral a figure
from one to ten. Intervals MOHS SCALE OF HARDNESS
between numbers on the scale The Mohs scale was devised by the German
are not equal, most obviously mineralogist Friedrich Mohs as a means of
‘TESTERS between nine and ten (see the classifying the relative hardness of minerals.
Each of these Knoop scale, right). Hardness He took 10 common minerals and put them
testing pencils testing 1s destructive, however, in order of “scratchability”: each one will
is tipped witha and should be used on a gem- scratch those below it on the scale but will
Mohs mineral. _ stone only if other tests fail. be scratched by those above tt.

y- MOouHs’ MINERALS

1 2 3 4 5 6 7 8 9 10
TALC GYPSUM CALCITE FLUORITE APATITE ORTHOCLASE QUARTZ TOPAZ CORUNDUM DIAMOND

SPECIFIC GRAVITY PYRITE

The specific gravity (SG) of agem
is an indication of its density. It is
calculated by comparing the stone’s
weight with the weight of an equal
volume of water. The greater a stone’s
specific gravity, the heavier it will feel.
For example, a small cube of pyrite
(SG 5.2) will feel heavier than a larger
RELATIVE WEIGHTS
piece of fluorite with an SG of 3.18; and a The smaller piece of pyrite (SG
ruby (SG 4.00) will feel heavier than an 5.2) feels heavier than the fluorite
emerald (SG 2.71) of similar size. FLUORITE (SG 3.18), because it is more dense.
 INTRODUCTION « 17

CLEAVAGE AND FRACTURE <] PERFECT CLEAVAGE

Gemstones may break in two ways: Fragile barite has three
they either cleave or they fracture. directions of easy cleavage,
Which way they break depends on giving smooth surfaces.
the internal atomic structure of the
stone. Gems that cleave tend to
break along planes of weak atomic
bonding (cleavage planes). ‘hese
planes are usually parallel, perpen-
dicular, or diagonal to the crystal
faces (as both planes and faces are
directly related to the stone’s atomic
structure). A gemstone may have one
or more directions of cleavage, which
may be defined as perfect (almost
perfectly smooth), distinct, or
indistinct (examples are A DISTINCT CLEAVAGE
shown right). Gems with BARITE
Although not perfectly
perfect cleavage include smooth, albite’s cleavage
diamond, fluorite, <J INDISTINCT surfaces can be clearly seen.
spodumene, topaz, CLEAVAGE
and calcite. Cleavage direction
When a gemstone 1s indistinct in
breaks along a surface aquamarine.
that is zof related to
its internal atomic
structure, it 1s said
to fracture. Fracture
surfaces are generally
uneven, and each type
has its own descriptive DUMORTIERITE %
A UNEVEN FRACTURE
name, shown in the ex-
An uneven fracture surface 1s
amples below and right. typical of fine-grained or
AQUAMARINE massive gems like dumortierite.
A
OBSIDIAN
NEPHRITE

A CONCHOIDAL
FRACTURE HACKLY FRACTURE A
The type most commonly Rough, uneven fracture
found in gemstones, the surface 1s seen on the right SPLINTERY >
name refers to the shell- of this gold specimen. FRACTURE
like fracture surface. Interlocking texture
causes splintery fracture.
18 e INTRODUCTION

CRYSTAL SHAPES some crystals form

with a characteristic
this natural pyramidal end «
IM MINERAL GEMSTONES are glass cooled too
fast for crystals
crystalline, with their atoms —e to form
arranged in regular and symmetrical
patterns, like a lattice; a few are
amorphous, with no or only a weak
crystal structure. Crystalline minerals
may consist of a single crystal or of
many in a group. Polycrystalline
minerals are made up of many, usually
small, crystals; in cryptocrystalline
minerals, the crystals are too small to AMORPHOUS PYRAMIDAL
see without the aid of a microscope.
Crystalline minerals are made up of
rutile needles in , |
a number of flat surfaces called faces; this rock crystal ! ei
the orientation of these faces defines have an acicular
habit
the overall shape, which is known as
the habit. Some minerals have a
single, characteristic habit, such as
this crystal
pyramidal or prismatic; others may with six faces
have several. A lump of crystalline and flat ends
is ust one
mineral without a definite habit is of many
called massive. Amorphous gem- prismatic
types
stones, like obsidian and tektites,
have an irregular shape. Examples ACICULAR
(NEEDLE-LIKE)
of common habits are shown right.

PRISMATIC
TWINNING
Natural crystals are seldom perfect.
‘Their growth is influenced by external irregularly
shaped mass with
| factors such as temperature, pressure, no apparent
space, and the medium in which they crystal habit
grow. One irregularity that may occur is
known as twinning — when the internal
structure of the crystal is repeated. MASSIVE
‘Twins grow
together ina
number of
different
ways.
twinned crystal
crystals may habit 1s
show alternate branchlike
colors

TWINNED AMETHYST
 INTRODUCTION e« 19

CRYSTAL SYSTEMS
Crystals are classified into seven .~ CUBIC
different systems, according to the Crystals in the
minimum symmetry of their faces. cubic system
This depends on a crystal’s axes of / (also known
symmetry — imaginary lines (shown in as the isometric system) have
black in the artworks on this page) the highest symmetry, ¢.£.,
around which a crystal may rotate and cubes, octahedra, and penta-
still show identical aspects. ‘The gonal dodecahedra. The
number of times the same aspect may minimum symmetry 1s
be seen — in one 360-degree rotation four threefold axes.
around an axis — defines that axis as PYRITE
twofold, threefold, etc., up to six.

ee
‘TETRAGONAL
This system 1s
HEXAGONAL/ defined by one
‘TRIGONAL fourfold axis.
These systems moe | Typical crystal
(thought by shapes include four-sided
some to be one ‘ prisms and pyramids,
system) share the trapezohedra, and eight-
same axis of sym- sided pyramids.
metry. Hexagonal
crystals have six-
fold symmetry; trigonal
crystals threefold.

MILKY QUARTZ ZIRCON

— MONOCLINIC C
----—
| —~
'
The minimum
symmetry of this
.

The monoclinic system has system 1s three two-

| a minimum symmetry of fold axes. Typical
| one twofold axis. Prisms crystal shapes are rhombic
with basal pinacoids are common prisms and pyramids with
crystal shapes found in this system. basal pinacoids, and
rhombic double
pyramids.

TOPAZ

‘TRICLINIC
Triclinic crystals
~ have no axis of
symmetry, sO
gemstones within this system
are the least symmetrical.
BRAZILIANITE AXINITE
20 e INTRODUCTION

OPTICAL PROPERTIES
OLOR IS THE MOST OBVIOUS visual light in a unique way and determines
feature of a gem, but in fact it is just the optical properties of each gem
one of many optical properties, all of species. Effects produced by light
which are dependent upon light. ‘The passing “Arough a gem are described
individual crystalline structure of a here; those produced by the reflection
gemstone (see pp.18—-19) interacts with of light are described on pages 22-23.

WHAT MAKES COLOR?

‘The color of a gem depends largely on the
way it absorbs light. White light 1s made
up of the colors of the rainbow (spectral
colors), and when it strikes a gem some
spectral colors are “preferentially absorbed.”
‘Those that are not absorbed pass through or
are reflected back, giving the gem its color.
Each gem in fact has a unique color “finger-
print” (known as its absorption spectrum),
SPLITTING LIGHT THROUGH A PRISM
but this is visible only when viewed with
The splitting ofwhite light into tts spectral colors ts
a spectroscope (see p.38). ‘To the naked
called dispersion. It gives gems their internal fire.
eye, many gems look the same color.

ALLOCHROMATIC GEMS
Allochromatic (“other-colored”) gems RUBY (RED
are colored by trace elements or (CORUNDUM)
other impurities that are not an
essential part of their chemical
composition. Corundum, for
example, is colorless when
pure, but impurities in it
(usually a metal oxide) create
the red stones we Know as
rubies, blue, green, and yellow
sapphires, and orange-pink
padparadscha. Allochromatic
gems are often susceptible to
PURE CORUNDUM SAPPHIRE
color enhancement or change.
(BLUE
CORUNDUM)

IDIOCHROMATIC GEMS
The color of idiochromatic (“self-
colored”) gems comes from
elements that are an essential part
of their chemical composition. ‘Thus
idiochromatic gems generally have
only one color or show only a narrow
range of colors. Peridot, for example,
is always green, because the color is
derived from one of its essential
constituents, iron. PERIDOT PERIDOT
 IN'TRODUCTION e 21

MULTICOLORED GEMS
A crystal that consists of different-colored
parts is called multicolored. It may be bicolored crystals
can make attractive
made up of two colors (bicolored), three gemstones; JUNCTIONS
(tricolored), or more. The color may be ofcolor zones
distributed unevenly within the crystal or may be distinct (as
« here) or gradual
in zones associated with growth. ‘The many
different varieties of tourmaline probably
show the best examples of multicoloring,
showing as many as 15 different colors or
WATERMELON
shades within a single crystal. TOURMAI INE 1olite 1S strongly
pleochroic: colorless from
one direction, blue when
PLEOCHROIC GEMS e rotated 90 degrees
Gems that appear one color from
one direction but that exhibit one
or more other shades or colors if
viewed from different directions
are known as pleochroic. Amor-
phous or cubic stones show one
color only; tetragonal, hexagonal,
or trigonal stones show two colors
(dichroic); orthorhombic, mono-
clinic, or triclinic stones may show
IOLITE
three colors (trichroic).
(BLUE ASPECT)
IOLITE
calcite is highly
REFRACTIVE INDEX (RI) birefractive, (COLORLESS ASPECT)
When a ray of light meets the surface producing double
of a polished gemstone, some 9 Images
light is reflected but
ees
most passes in. Because
the gem has a different
optical density from that
of air, the light slows
down and 1s bent from its _ Z
original path (refracted). ‘The ‘= tn
amount of refraction within a SEEING DOUBLE
gem 1s called its refractive index
Zircon’s back facets look
(RI) and, with the DR (below), can CALCITE
doubled, due to strong
be used to help identify the stone.
double refraction (DR).
Ba 22,
BIREFRACTION (DR)
When viewed through a
refractometer (far right),
cubic minerals like spinel
are singly refractive,
showing a single shadow
edge; doubly refractive
minerals like tourmaline
split light rays in two,
producing two shadow
edges. The difference TOUR-
SPINEL
between the two gives the MALINE
“birefraction” (DR).
22 e INTRODUCTION

iLLUSTER
‘The overall appearance of agemstone, its luster,
is determined by the way light is reflected from hematite crystals, like pyrite
its surface. ‘This is related to the degree of surface and the precious metals,
display metallic luster
polish, which increases with the stone’s hardness.
Gemologists use a variety of terms to describe
luster and its degree ofintensity. “Splendent”
means that the stone reflects light like a
mirror; but iflittle light is reflected, the luster
may be described as “earthy” or “dull.”
Stones with a luster comparable to diamond
are described as “adamantine” and are the
most desirable. Most transparent, faceted
gems have a glasslike, “vitreous” luster; METALLIC LUSTER
the precious metals have a metallic
luster; and organic gems show a the glasslike luster of this
: goth ve 9 hard and highly ruby is the most common
range, ? from “resinous” to lished, the look of
polished, for cut stones .
“pearly” and “waxy.” Some a diamond defines
gemstone species vary in —e adamantine luster

their luster: garnets, for

example, range from the
resinous hessonite garnet
to the adamantine luster
of demantoid garnet.
Rough lazulite and
howlite have a dull,
earthy luster, which
is vitreous after
polishing. _ _ VITREOUS LUSTER

waxy luster ts
most commonly
associated with
turquoise
% the greasy luster
of this polished
imperial jadette ts
comparatively rare

WAXY LUSTER
GREASY LUSTER

satin spar
é psum Is
gy :
OTZGNIC.} e———_=
commonly
gems, like this
ambe r bead, citedmeto
am
describe
may occur in
silky luster e
a range of
lusters,
depending on
the nature of
the material

RESINOUS LUSTER SILKY LUSTER

 INTRODUCTION #23

INTERFERENCE
Interference is an optical property caused moonstone feldspar
exhibits a bluish
by the reflection of light off structures white shimmer or
within a gemstone. ‘This internal reflec- e sheen
tion gives a play of color. In some stones
it will produce the full range of the
spectral colors; in others just one color
may predominate. In opal, interference
occurs because of the structure of the stone
itself —spheres arranged in regular three- ADULARESCENCE
dimensional patterns. ‘This produces the
rainbow effect called iridescence, shown by ‘ .
light reflected from
a number of other gems such as ee ee
hematite, labradorite, and iris quartz. rainbow effect ¢
In moonstone feldspar, Net
interference at the junctions
of its internal layers (thin,
alternating layers of
different types of
feldspar) produces a LIGHT LAYERS
shimmering effect just Iridescence appears at
below the surface of the layers within labradorite.
stone, known as adular-
escence, opalescence, or
a schiller (sheen). IRIDESCENCE

hematite
shows a play
=e of color

blue and green &

: may predominate
IRIDESCENCE within opal
IRIDESCENCE

reflection from parallel fibers

CAT’S-EYES AND STARS acicular (needle- within the stone
When a gemstone is cut e7 ‘ like) rutile produce the cat’s-
cabochon (with a domed, polished crystals gives a e eye “flash”
—e six-rayed star
surface), light reflecting from
the stone’s internal features,
such as cavities or fibrous or
needlelike inclusions (see
pp.24—25), may create a cat’s-eye
effect (chatoyancy) or star stones
(asterism). One set of parallel fibers
gives rise to the cat’s-eye effect; SAPPHIRE STAR
two sets of fibers produce a four- STONE
rayed star, three sets of fibers a
six-rayed star, and so on. JHRYSOBERYL
CAT’S-EYE
24 e INTRODUCTION

NATURAL INCLUSIONS
i ARE INTERNAL features of usually regarded as flaws, inclusions
gems. They may be solids, liquids, today are often seen as adding interest
or gases that the crystal enclosed as it to a stone. They can also be invaluable
grew, or cleavages, cracks, and fractures in identifying a gem, because some are
that filled (or partly filled) after the host peculiar to a particular species, while
material finished growing. Although others occur only in a particular locality.

FORMATION OF INCLUSIONS
Solid inclusions have usually formed before the
MICROSCOPE
host stone — the crystals of the host have grown
A microscope that
around them and enclosed them. ‘They may
magnifies between 10 and
be distinct crystals or amorphous masses.
40 times 1s one of the
Solids and liquid inclusions formed at
most useful instruments
the same time as the host are aligned |
for examing inclusions
to its atomic structure. For instance,
in gemstones.
the stars in star rubies and sapphires
are caused by needlelike crystals of
. ae : stone holder to
rutile, which formed parallel to the 7 ES ailow cian
crystal faces at the same time as the : —_ a from any angle
host corundum crystals. Cavities filled
or fractures healed after the formation
of the host give inclusions that resemble
feathers, insect wings, or fingerprints.

DIAMOND WITH GARNET

Solid inclusions may be the same
gem type as the host or different —
like the garnet in this diamond.

PERIDOT “WATER LILY” (MAGNIFIED 30 TIMES)

Inclusions that look like water lily leaves are a typical
feature of peridot from Arizona. Each inclusion consists of
a central chromite crystal surrounded by liquid droplets.
 INTRODUCTION e 25

INSECT IN AMBER
Insects are sometimes found trapped in
MOONSTONE “CENTIPEDES” amber, caught by the sticky resin as it was
These insectlike inclusions (magnified 35 times) exuded. To create a natural effect, insects
are a common feature of moonstone. Infact they are sometimes added to imitation amber.
are parallel cracks caused by strain.

ALMANDINE
GARNET (ABOVE)
Magnified 45 times,
the gray patch on the
left is a rounded
apatite inclusion. The
bright interference
colors to the right are
due to a zircon crystal.
RUTILE NEEDLES
This carved rock crystal EMERALD (LEFT)
perfume bottle contains Rectangular cavities
inclusions of needlelike rutile with tails (magnified
crystals. Tourmaline and gold 40 times) are some-
are also found tn rock crystal. times found in natural
. Indian emeralds.
26 e INTRODUCTION

FACETING
@ las MOST USUAL METHOD of fashion- into account its color, clarity, and weight.
ing a gem Is to cut the surface into a ‘The lapidary may have to compromise
number of flat faces, known as facets. to retain its weight and therefore value.
‘This gives the stone its final shape, or ‘The blue diagrams on the opposite page,
cut. The gem cutter, or lapidary, tries to which show the most popular cuts, are
show the stone’s best features, taking used throughout the book.

How A STONE IS FACETED

‘There are several stages in the cutting of a stone is a different shape, or has imperfec-
gemstone, each of which may be carried out tions within it, or because retaining the
by a different expert. In our example, a rough weight is of paramount importance, the cut
diamond crystal is fashioned into a brilliant in its ideal form (the “make” ) may not be
cut. This is the most popular possible. Nevertheless, the essential aim is
cut for this stone because to make the diamond bright and sparkling,
it maximizes the showing flashes of color called fire. ‘To this
gem’s naturally end, the size, number, and angles of the
strong light facets are mathematically calculated. ‘The
dispersion. How- rough crystal is sawn or cleaved to obtain a
ever, because each basic workable piece, then turned on a lathe
against another diamond to give it a round
shape. The facets are then cut and
CTOWN =e
polished in stages, and the stone is
given a final polish before mounting.
bezel e
table
» facet
1. ROUGH 4
EA

A rough diamond ZAM

crystal ts selected e girdle
The top 1s cut
Sor faceting. off, and the stone 3. GRIND
rounded on a lathe The central
by another diamond. facet — the
upper girdle flat table — 1s
e bezel facet ¢ ground first, then
facet
the bexel facets.

4. ‘TOP AND BOTTOM

More facets are put on in
groups and in sequence: Star

the star facets and upper facet

girdle facets on the crown; 5. FINISHING

then the lower girdle A “brilhanteer” then adds 6. MOUNTING
facets and the culet on the a further 24 facets above After a final polish, the stone ts
pavilion (the underside). the girdle and 16 below. mounted in precious metal.
 IN'TRODUCTION e 27

BRILLIANT CUTS
The brilliant cut is the most popular for
diamonds and for many other stones, partic-
ularly colorless ones. It ensures that maxi-
mum light is reflected out through the front,
giving brightness and fire.
Variations in the outline
give the oval, the pear-
shaped pendeloque,
and the boat-shaped
marquise or navette.

eau)
% s RINGS OF FIRE
o These gold rings from the house of Cartier are set
BRILLIANT-CUT \ with diamonds, sapphires, rubies, and emeralds,
SAPPHIRE OvaAL = in avariety of cuts from brillant to fancy.

STEP CUTS
‘The step cut (or
trap cut) shows
colored stones to
advantage, having a ENE,

rectangular or square TABLE

table facet and
girdle, with parallel
rectangular facets.
‘The corners of fragile
gems may be removed,
making octagonal stones
—as, for example, in OCTAGONAL STEP-
most emeralds. CUT SPESSARTINE

MIXED CUTS FANCY CUTS

Mixed-cut stones are usually rounded ‘These have
in outline, with the crowns (above the several possible
girdle) cut as brilliants and the pavilions outlines, such as
(below the girdle) step cut. Sapphires, triangular, kite-
rubies, and most transparent colored shaped, lozenge-
stones are cut in this style. shaped, pentagonal,
or hexagonal. ‘The
cut may be used for
rare gems, or to make
FANCY-cuUT the most of a flawed or
HELIODORE — irregularly shaped gem.

MIXED-CUT
PERIDOT PENDELOQUE MARQUISE SCISSORS
2o°¢ INTRODUCTION
ee

POLISHING, CARVING, AND ENGRAVING

t t i n g t h e m f r o m a l a r g e r m a s s o f
L S A N D G
n E
e M S — u s u a l l y — b y c u
|B maesseivee, MmiEcTrAocrystalli stones and —_ material. Engraved images are made
organics — can be worked by polishing, by scratching out lines or holes or by
carving, or engraving. Polishing is the cutting away to leave a raised image.
oldest form of fashioning. Carving Carving and engraving require tools
produces three-dimensional objects harder than the material being worked.

POLISHING drum contains

abrasive grits and
‘The shine given to the surface of a stone — polishing powders ¢
by rubbing it either with grit or powder or
against another stone — is its polish. Dark-
colored gemstones and those that are
translucent or opaque, for instance opal
and turquoise, are often polished rather
than faceted, as are organic gems. ‘They
may be polished as beads or as flat pieces
to be used in inlay work, or cut e7 cabochon
with a smooth, rounded surface and usually
a highly polished, domed top and flat base.

PEBBLE
POLISHER
Gem fragments of
similar hardness may
be turned into attrac-
tive pebbles (left) by
tumbling in a drum con-
taining abrasive grits and MOTOR-DRIVEN TUMBLING
polishing powders (right). DRUM FOR POLISHING

CARVING
Carving usually refers to the cutting of
decorative objects from a larger mass. Stones |
as hard as 7 on the Mohs scale were carved
in ancient Egypt, Babylonia, and China.
Impure corundum (emery) was used for
carving and engraving in India; nowadays
a hand-held chisel or turning machine is
used. Popular stones for carving include
serpentine, Blue John, malachite, azurite,
rhodonite, and rhodochrosite.

CHINESE CARVING
Carving of gemstones in China dates back to the
Neolithic period. The most prized material was
imported nephrite jade, and decorative objects
like this model pagoda are still made.
 INTRODUCTION e 29

ENGRAVING
Engraving usually refers to the decoration of
the surface of a gemstone by the excavation
(scratching out) of lines, holes, or trenches
with a sharp instrument, known as a graver or
‘turin. Cameos and intaglios are perhaps the
‘most popular of all engraved objects. A
cameo is a design (often a human profile) in
flat relief, around which the background has
been cut away. In an intaglio it is the subject,
not the background, that is cut away, creating
i
y fi

a negative image that may be used as a seal Z

Mf
f] Wy
/ Pz
in clay or wax. Intaglios were particularly
popular with the ancient Greeks and Romans GOLD ENGRAVING
and are still prized by collectors. The surface of gold and other precious metals used
in sewelry may be decorated with intricate
———e pearl bead patterns, using a hand-held chisel called a graver.

Engraved gemstones gained prominence in

Europe in the Renaissance period. During
the Elizabethan period in Britain cameo
portraits were often given as gifts, particularly
among the nobility. All through the ages,
chrysobery/ «
cabochon layered stones have been used for cameos or
intaglios, with onyx and sardonyx particularly
popular. Other gems suitable for engraving
include rock crystal, amethyst, citrine, beryl,
peridot, garnet, lapis lazuli, and hematite, as
well as organic materials such as ivory and jet.
BEAD CABOCHON
| Spherical gems such as This simple cut 1s used
pearls may be pierced to display colors and
and threaded as beads optical effects in opaque MODERN DESIGNS
on necklaces. and translucent stones. This citrine prism, with its
clean, architectural lines
moonstone
and exquisite engraving,
@ CaMeCO0
demonstrates the flair and
craftmanship of modern
designers. Its maker, Bernd
Munsteiner, uses conven-
tional cuts to create classic
lapis « modern jewels akin to
lazulh
polished pieces of sculpture. Bernd
slab Munsteiner is one of
many artists working
in Idar-Oberstein in
Germany. logether with
Hong Kong, Idar-
CARVING POLISHED STONE Oberstein is considered
The cameo symbol used Decorative stones given to be one of the most
in this book denotes a flat, polished surface important centers for
both carvings and may be used in orna- carving and engraving
engravings. ments and jewelry. gemstones today. ENGRAVED CITRINE
30 e INTRODUCTION

(GEMS THROUGH THE AGES

i) ees FASCINATION with gem- to adorn themselves. ‘loday, there are
stones is as old as history itself. more gem-producing areas than ever
People everywhere, throughout the before, new stones are increasingly
ages, have followed a natural instinct to available, and jewelry designs continue
collect things of beauty and value, and to evolve. But the inherent attraction
have used whatever gemstones they of gems — their beauty, durability, and
found locally — from shells to sapphires — rarity — remains the same.

FIRST USES
Gem materials were probably first used as
much for their durability as their beauty.
But beauty was not ignored, even then. For
example, the Stone Age obsidian ax below
has been wrought to be attractive as well as
practical, and ancient civilizations did fashion
gems purely for adornment. Although most
were primitive in design, some were highly
intricate, with painted surfaces. Down
the ages, gems have also been offered
as prestigious gifts, and their portability
and intrinsic value gave them
a natural use as currency.

QUARTZ BEADS
The pebbles in this neck-
lace from Ghana were once
used as a form of currency.

EARLY COLLECTORS
The earliest collectors found gems with no
more equipment than a stick or shovel, a
basket, and a sharp eye. Similar Stone Age
tools found in the Mogok area of Myanmar
show that rubies have been mined there for
thousands of years — and the same methods
of panning the stream with wicker OBSIDIAN AX
baskets are used today. Evidence A natural volcanic glass, obsidian
of more organized early could be fashioned into a raxor-
mining — for example, sharp tool or weapon.
abandoned mines and
waste dumps — 1s
found in the Urals
of Russia, on the
shores of the @ EMERALD IN LIMESTONE
Mediterranean, in a ee: Emerald has been sought after
Cornwall, England, for many thousands ofyears. The
and in many other earliest known mines date
places worldwide. back to Egypt, 2000 Be.
 INTRODUCTION ® 31

ANCIENT JEWELRY
Little jewelry made before the 18th century
survives. The best examples are probably
those of ancient Egypt. Many of these pieces
are gold set with gems such as turquoise, lapis
lazuli, and carnelian. It shows the great skill of
the Egyptian goldsmiths: the gold refined,
annealed, and soldered; the gems fashioned —
probably using silica sand, a technique also
known to the ancient Chinese. ‘The Romans
went on to develop the polished stone rather
than the setting. The art of the goldsmith and
lapidary survived in the Dark Ages, though in
medieval times gothic
style was functional —
mainly buckles,
clasps, and
rings.

CLOTHED IN JEWELS
Civilizations through the ages have used sewelry
for adornment. This late 18th-century miniature
shows an Indian woman clothed in richly jeweled
necklaces, earrings, bracelets, and amulets.

MERMAN
In this typical 16th-
century pendant, a
pearl forms the torso,
a with diamonds and
| 4 \ rubies set in gold
around tt.

UP TO THE PRESENT
With the discovery of the Americas in the
15th century, European trade in gemstones
expanded, and 16th- and 17th-century
jewelers could use gems from all over the
world. With the rise of an affluent merchant
class, jewelry became more widely owned
and diamonds first became fashionable. In
the 20th century, an increase in demand for GEM-ENCRUSTED MODERN BROOCH
affordable gems and the scarcity of the most Jewelry has passed through many styles, from
valuable will doubtless continue the trend to baroque in the 16th century and floral themes
use more varied gem species in jewelry. in the 17th, to Art Deco and beyond tn the 20th.
32 e INTRODUCTION

) | \HERE ARE NUMEROUS

myths and legends
associated with gems. Some
tell of cursed stones;
others of stones with
special powers of
healing, or that protect
or give good luck to
the wearer. Some of
the largest known
diamonds have
legends associated
Bienes* = DEATH MASK |
with them that have
BS) hagas” This Aztec funeral
been told and retold over etre OSE mask adorned with
centuries, and many now lost ‘ turquoise may have
are surrounded by tales of speeded entry to the
intrigue and murder. Some next world.
mines are thought to be cursed —
probably rumors spread by the PERUVIAN GOD
mine owners to keep unwanted This 12th-century ceremonial knife from
prospectors away. In Myanmar Peru 1s made from gold adorned with
(Burma), for instance, where ail turquoise. The handle has been formed
gemstones belonged to the into the image of a deity. |
monarch, the belief that
anyone who took a stone
from a mine would be cursed
may have been deliberately
cultivated to curb losses of
a valuable national asset.

CRYSTAL GAZING rock crystal

Since Greek and Roman times , Lah SHOE
by Japanese
balls of polished rock crystal ° dragons
have been used to see into ‘THUMB GUARD
the future. ‘The difficulty of This 17th-century ring,
finding a flawless piece large mounted with rubies and
enough to be polished adds emeralds, was designed to
to the mystique. ‘The protect an archer’s thumb
mystic gazes at the when releasing arrows.
ball, lets the eyes
go out of focus,
and then
interprets
the misty
“image.”

CRYSTAL BALL
 IN'TRODUCTION e 33

BIRTHSTONES
Certain gems have traditionally been
associated with different months of the
year and are thought lucky or important
for people born under their influence.
This probably stems from the ancient
belief that gems came from the heavens.
Many cultures associate gems with the
signs of the zodiac, and others associate JANUARY FEBRUARY MARCH
them with the months of the year. The (GARNET) (AMETHYST) (AQUAMARINE)
selection varies from country to country,
perhaps influenced by availability of
gems, local traditions, or fashions. ‘The
custom of wearing birthstone jewelry
started in 18th-century Poland and has
since spread throughout the world. ‘The
most popular selection is shown at right.
APRIL May JUNE
(DIAMOND) (EMERALD) (PEARL)

JULY AUGUST SEPTEMBER

(RUBY) (PERIDOT) (SAPPHIRE)

SIGNS OF THE ZODIAC

This rock crystal is shaped with 12
OCTOBER NOVEMBER DECEMBER
pentagonal faces, each engraved
(OPAL) (TOPAZ) (TURQUOISE)
with one of the signs of the zodiac.

CRYSTAL HEALING
Belief in the healing properties of gems has
a very long history, as the rituals of medic ine
men in ancient tribes attest. Crystal healers
today believe that each gem has the power 3
to influence the health and well-being of
a specific part of the body. The light
reflected off stones placed on vital nerve
points is thought to be absorbed by the
body, supplying it with healing energy.

ROCK CRYSTAL CRYSTAL PENDANT

Prized for their beauty Gems worn close to the
and clarity, rock crystals are skin are believed to
often chosen for use in crystal healing. heal or protect.
34 © INTRODUCTION
a

SYNTHETIC GEMSTONES
YNTHETIC GEMSTONES are made in However, they can usually be identified
laboratories or factories, not in rocks. by their distinctive inclusions. Many
‘They have virtually the same chemical gems have been synthesized in the
composition and crystal structure as laboratory but only a few are produced
natural gemstones, so their optical and commercially. ‘These are generally used
physical properties are very similar. for industrial and scientific purposes.

MAKING A SYNTHETIC FLUX-MELT |

Man has tried to replicate gemstones for
‘TECHNIQUE |
thousands of years, but it was not until the
Pioneered by the French —
late 1800s that any substantial success was
chemist Edmond
achieved. In 1877, French chemist Edmond
Frémy, the flux-melt {
Frémy grew the first gem-quality crystals of
technique 1s still used
reasonable size (see bottom right), and then
to make emeralds. The
around 1900 August Verneuil devised his
powdered ingredients
technique to manufacture ruby. With a few
are melted and fused
modifications, the Verneuil flame-fusion
in a solvent (flux) in a
method is still in use today. The powdered
crucible. The material
ingredients are dropped into a furnace and
must be kept at a very
melt as they fall through a flame hotter
high temperature for
than 3,630°F (2,000°C), fusing into liquid
months, before being
drops. ‘These drip on to a pedestal and
left to cool very slowly.
crystallize. As the pedestal is withdrawn,
a long, cylindrical crystal, which is known
FLUX-MELT
as a boule, forms. SYNTHETIC EMERALD |

synthetic ruby
crystals grown
FLAME-FUSION CORUNDUM in a crucible
Synthetic corundum manufactured
by flame-fusion grows as a single
mass called a boule. It has the same
inner structure as a natural crystal
and can be cut to shape.

corundum
boules tend to
split down their
length

EDMOND FREMY
French chemist Edmond Frémy, the
first to grow emerald crystals of a
reasonable size, went on to grow
ruby crystals by melting aluminum
oxide and chromium in a crucible.

+ pedestal on
which boule (CORUNDUM
forms BOULES
 INTRODUCTION e 35

SHAPES AND COLORS

Because of the way they are made, synthetic gems may
show subtle differences in shape and color that help
distinguish them from their natural counterparts. For
instance, corundum produced by flame fusion has
curved growth lines rather than straight ones, because
the ingredients have not mixed
together fully. Some synthetic
gems may also suffer from
uneven color distribution.
Flame-fusion spinel is
manufactured to imitate
SYNTHETIC SPINEL
gems such as ruby, sapphire,
Synthetic spinel (above), colored
aquamarine, blue zircon,
red, may make a better imitation
tourmaline, peridot, and
gem than flame-fusion ruby (left).
chrysoberyl.

DISTINCTIVE INCLUSIONS
Synthetic gems have different
|
inclusions from those of natural
| gems, so often the best way to
} tell them apart 1s to examine
|
them with a loupe (below) or
a microscope. Synthetic
inclusions may be typical of a
process, or of a synthetic gem
species. For instance, in
Verneuil rubies, gas bubbles
have well-defined outlines; in
flux-melt emeralds (right), GILSON EMERALD INCLUSIONS
characteristic veil and GILSON FLUX- Synthetic emeralds from the French manu-
feather patterns form. MELT EMERALD facturer Gilson have characteristic veil-hke
inclusions. The gems are made from poor-
quality material by a flux-melt method.
LOUPE
This hand-held
lens 1s powerful
enough to assist in gem
identification. With tts ten-
fold magnification it may
be possible to distinguish
between natural and
synthetic inclusions.
GILSON LAPIS
LAZULI
GILSON GEMS
Lapis lazuli, turquoise, and coral produced GILSON
by the French manufacturer Gilson are sues
similar to their natural counterparts but are
not true synthetics because their optical and
physical properties differ from the natural
gems. Gilson lapis lazuli, for example, is
; GILSON
more porous and has a lower specific gravity.
CORAL
36 e INTRODUCTION

IMITATION AND ENHANCEMENT

(eur GEMS have the appearance different gems, but natural stones can
of their natural counterparts, but their — also be modified to resemble more
physical properties are different. ‘They valuable gems. It 1s possible to enhance
are intended to deceive. Manmade authentic gemstones by hiding cracks
materials, such as glass and synthetic and flaws, or by using heat treatment or
spinel, have been used to imitate many irradiation to improve their color.

GLASS IMITATIONS ‘ 7S creer

GLAssS “RUBY tlass imitations
ise tah 4
often contain
Glass has been used for centuries to
pronounced
imitate gemstones. It can be made inclusions
either transparent or opaque in
almost any color, and, like many
gems, it has a vitreous luster. At first
sight, therefore, it may easily be
mistaken for the reai thing. However,
it can usually be detected by its warmer
feel and by the evidence of wear and tear
that results from its greater softness. Chipped « glass can be
facets and internal swirls and bubbles are as to imitate
; Sse : almost any
common. In addition, unlike most of the transparent
gem
gems it imitates, glass is singly refractive.
SNOWFLAKE INCLUSION
IN GLASS
OPAL IMITATIONS
Gemologists call the flashes of color
in opal its “play of color,” or
iridescence. It is caused by the
interference of light from the
minute spheres ofsilica gel
that make up the gem. This
structure is imitated to great
effect in opals made by the
French manufacturer Gilson,
although the difference can be
seen in the mosaiclike margins of POLYSTYRENE
the patches of color (see p.135). LATEX OPAL
There are various other opal imita- = GILSON OPAL
tions, including stones made of polystyrene
latex, or of different pieces assembled as
one. In an opal doublet (two pieces) the top
is natural precious opal, but the base is
common (potch) opal, glass, or chalcedony.
A triplet (three pieces) has an additional
protective dome of rock crystal.

SLOCUM STONES
American manufacturer John Slocum developed
imitation opals with a good play of color, but they
lack the silky, flat color patches of genuine opal
and the structure looks crumpled when magnifted.
 INTRODUCTION ¢ 37

GARNET-TOPPED DOUBLET red garnet

One of the most common composite Crown ¢
stones (stones made of more than
one piece) is the garnet-topped
doublet, or GTD. A thin section
of natural garnet is cemented to a
colored glass base, which gives
the GTD its apparent color.
The deception is most easily Fe green
~
GTD JUNCTION
seen at the junction of the two oa ee LE ae
GARNET-TOPPED “" luster are visible where
= a , TS “a 7 - .

layers, which may be obvious.

DOUBLET garnet and glass meet.
DIAMOND IMITATIONS softer,
Many natural materials have more
been used to imitate diamond, y 3 ff17e ey

but zircon is the most convinc- 2"

ing. Synthetic imitations are
popular, but each has its faults ‘eS pe
(right). Imitations can usually YTTRIUM diamond
be detected by testing the heat ALUMINUM CUBIC STRONTIUM
conductivity of the stone. GARNET (YAG) ZIRCONIA TITANATE

HEAT TREATMENT IRRADIATION

Heating may enhance or Gems may change color if
change the color or exposed to radiation. ‘This
clarity of some gems. may come from radioactive
‘Techniques range elements within the Earth’s
from throwing crust or from artificial
gems in a fire to sources. Natural radia-
“cook,” to the use tion may take millions
of sophisticated of years to have an
equipment. ‘The effect, while artificial
outcome is certain irradiation may take
for some gems (like only a few hours to
aquamarine, which BROWN ZIRCON change a gem’s color.
changes from green to HEATED TO In some cases a gem will =
blue), but less so for others. BLUE later revert to its original i)
color or may fade with
| av f: a er =
STAINING time. Many changes can IRRADIATED,
Stains, dyes, or chemicals be reversed or modified HEAT-TREATED
can alter the appearance by heat treatment. TOPAZ
of a gem, coating just the
surface or changing the OILING
whole specimen. For Oils may enhance
Staining to be effective, a gem’s color
a stone must be porous and disguise
Or contain cracks and fissures and
flaws through which the blemishes. It is
color can enter. Porous common to oil
white howlite, for ex- emeralds in order
ample, can be stained STAINED to fill their natural
to imitate turquoise. HOWLITE cracks and flaws. OILED EMERALD
38 e COLOR KEY

COLOR KEY
Wis IDENTIFYING a gemstone, a an indication of hardness, while a search
gemologist will hold it, feel it, and inside the stone may reveal character-
examine it from all angles. ‘This is done istic inclusions. ‘These features may be
to assess the appearance of the stone by __ unique to one gem, but further tests
noting the color, the luster, and any may be necessary to identify synthetic
other features. A hand-held loupe (see or imitation stones. From this initial
p.35) may be used to search for scratches examination, however, the gemologist
and flaws on the surface that may give should know which tests to perform.

How THE COLOR KEY WORKS

‘This key puts all gems into one of seven
color categories, though color varieties
within some species may appear (or be
listed, if not pictured in the book itself)
in more than one. Each color category is
divided into three sections: gems that are
always that color, gems usually that color,
and gems sometimes that color.

category — A pr aera oy
heading esi pes i To a '

SPECTROSCOPE
Many gems appear the
J 8 PP representative
RUBY same color, but can be eee |
distinguished when |
viewed with a spectro-
scope (above). This gem |
ALMANDINE GARNET reveals an absorption name eo _ a

spectrum (left) that ts

. Rusy 94 ———* page
unique to each L£em- ey . . eins red number
! of
identification Distinctive
stone (see p.21). features e— pe ae main entr) |

RED GLASS

(COLORLESS GEMSTONES

ALWAYS COLORLESS

HAMBERGITE //5 PHENAKITE 9S ALBITE /30 GOSHENITE 77 BERYLLONITE //8

Perfect cleavage, Silvery look Vitreous to Spiky inclusions Lacks fire,
large birefraction if well cut pearly luster common soft, brittle
 COLOR KEY « 39

ROCK CRYSTAL &/ PETALITE /29 DATOLITE /29 ACHROITE /02

Vitreous luster, Vitreous luster, Tinge of yellow, Extremely
transparent transparent green, or white rare

SCHEELITE 70 CELESTINE /05 DIAMOND 54 DANBURITE //0 CERUSSITE /05

Very soft, good Soft, cut for Adamantine Yellow/pink tinge, Adamantine luster,
fire, uncommon collectors only luster, good fire bright, lacks fire high density, soft

| DOLOMITE 99 EUCLASE /29 MOONSTONE /23 COLORLESS SCAPOLITE 7/

Soft, vitreous Rare, black Opalescence, blue ORTHOCLASE /22 Rare, vitreous
to pearly luster mineral inclusions or white sheen Three good cleavages luster

OTHER GEMS
ENSTATITE ///
GROSSULAR 6/
Toraz 106

FLUORITE 66 ZIRCON 72 SAPPHIRE 96 APATITE 79

Soft, lacks fire, Adamantine Rare, high density, Fairly soft
hematite inclusions luster, good fire extremely hard
40 e COLOR KEY

RED OR PINK

ALWAYS RED OR PINK

ROSE QUARTZ 83 KUNZITE /20 MORGANITE 78 THULITE //6 PINK GROSSULAR 60

Cloudy, distinctive Strongly pleochroic, Distinctive Distinctive color Distinctive color,
pinkish color good cleavage color, hard mix, massive _ fine-grained, opaque

TUGTUPITE 74 RHODOCHROSITE /00 — RHODONITE /32 RED BERYL 78 Rusy 94

Opaque, may be Fine-grained, banded; Black veins in Extremely rare, Distinctive red
mottled, massive . also clear faceted stones — massive material seldom cut color, hard

USUALLY RED OR PINK

ALMANDINE 59 PYROPE 58 RUBELLITE /0/ TAAFFEITE 80 SPESSARTINE 58

Distinctive color, — Distinctive color, — Pleochroic, cat’s- Extremely rare, Lacelike inclusions,
high luster inclusions rare eye cabochons fairly hard rare at gem quality

SOMETIMES RED OR PINK

JADEITE /24 Topaz 106 WATERMELON SAPPHIRE 97

Dimpled surface Distinctive color, TOURMALINE /03 High density,
when polished hard, high density Distinctive colors hard, pleochroic
 COLOR KEY e« 41

OTHER GEMS
ZIRCON 73
RUTILE 7/
SMITHSONITE 99
SCAPOLITE 7/
GARNET-TOPPED
Cora /42 SPINEL 64 : 2
JASPER 92 DOUBLET 6/
Grain on surface, Hard, singly Distinctive
soft, may fade refractive color, opaque

WHITE OR SILVER

ALWAYS WHITE OR SILVER

MILKY QUARTZ 85 PLATINUM 52 SILVER 50 How ite /28

Distinctive milky Metallic luster, high Metallic luster, Very soft,
white color density, opaque soft, opaque chalky, opaque

, a a
Ivory /46 MEERSCHAUM //9 Gypsum /28 PEARL /38 SHELL /44
Soft, growth Chalky, opaque, Silky to vitreous Pearly luster, Iridescent,
lines on surface _fine-grained, soft luster, soft very soft very soft

SOMETIMES WHITE OR SILVER

OTHER GEMS
AGATE S88
Cora /42
OPAL /34
MOONSTONE /23

CALCITE 98 SERPENTINE /27 NEPHRITE /25

Soft, large Vitreous to greasy Tough interlocking
birefraction luster, translucent structure
42 eCOLOR KEY

YELLOW TO BROWN GEMSTONES

ANGLESITE //4 CITRINE 8&3 BRAZILIANITE //8 SINHALITE //4 HELIODOR 77

High density, Distinctive Fragile, brittle, Pleochroic, large Pleochroic, hard,
fragile, good fire fairly soft, rare birefraction pastel shades

GOLD 48 PADPARADSCHA 95 CARNELIAN 93 FIRE OPAL /34 SARDONYX 90

Distinctive Distinctive orange- Translucent, Low density, Distinctive white
color, soft pink color, hard reddish brown transparent bands

HESSONITE 60 SUNSTONE /30 HYPERSTHENE //2 DRAVITE /02 CASSITERITE 70

Granular Bright metallic Reddish iridescence, Pleochroic, showing two High density,
inclusions inclusions fairly soft shades of body color good fire

OTHER GEMS
TOPAZOLITE /07
PYRITE 63

TORTOISESHELL /44 SMOKY QUARTZ 84 EpIDOTE /2/

Distinctive mottling Distinctive grayish Strongly pleochrotc,
on surface brown color fragile, rarely cut
 COLOR KEY e 43

USUALLY YELLOW-BROWN

AMBLYGONITE /32 YELLOW VESUVIANITE 74 SPHALERITE 63 TITANITE /2/

Vitreous to pearly ORTHOCLASE /22 Pleochrotc, vitreous Good fire, metallic Very good fire,
luster Fragile, cat’s-eyes to adamantine luster to vitreous luster pleochroic

AMBER /48 AVENTURINE AXINITE /33 ENSTATITE /// STAUROLITE //7

Very soft, QUARTZ 8&5 Pleochrotc, Fragile, distinctive Opaque, twinned
resinous luster Platy inclusions easily chipped absorption spectrum crystals cross-shaped

SOMETIMES YELLOW-BROWN

PREHNITE //5 SCHEELITE 70 CHATOYANT Moss AGATE 89

Good fire, needle- Usually cloudy Fairly soft, QUARTZ S6 Translucent,
like inclusions and translucent good fire Fibrous structure mosslike pattern

OTHER GEMS
DIAMOND 54
DEMANTOID 62
FLUORITE 66
ZIRCON /2
APATITE 79
SAPPHIRE 96
TOURMALINE /0/
ARAGONITE /04 SPESSARTINE 58 BARITE /04 SHRYSOBERYL /08 Topaz 106
Very soft, micro- Hard, lacelike Highdensity, Hard, strongly KORNERUPINE //3
crystalline inclusions very soft pleochroic
44 e COLOR KEY

GREEN GEMSTONES

ALWAYS GREEN

CHRYSOCOLLA /26 EMERALD 75 Peripor //3 HIDDENITE /20

Distinctive color, Distinctive color, Distinctive oily Distinctive color,
opaque, very soft seldom flawless green color pleochroic

DIOPTASE 99 BLOODSTONE 93 UVAROVITE 59 PRASE 92

Distinctive color, Opaque, red Distinctive color, Translucent, dark
large birefraction Spots crystals fragile green color

MALACHITE /26 MOLDAVITE /37 ALEXANDRITE /08 ANDALUSITE //0

Characteristic bands Glassy, inclusions of Color changes, Very strong
ofcolor, soft bubbles and swirls pleochroic, high density pleochroism

USUALLY GREEN

SERPENTINE /27 JADEITE /24 DiopsipE //9 DEMANTOID 62

Vitreous to greasy Fine-grained, Large birefraction Asbestos inclusions,
luster, fairly soft may be dimpled adamantine luster
 COLOR KEY « 45

OTHER GEMS
PREHNITE //5

AVENTURINE QUARTZ 85 NEPHRITE /25

Platy inclusions, Tough interlocking structure,
vitreous luster greasy to pearly luster

MICROCLINE /23 AGATE 38 WATERMELON DIAMOND 56 SAPPHIRE 96

Distinctive blue- Translucent, TOURMALINE /03 Hardest natural High density,
green color distinct banding Bicolored substance, good fire hard, pleochroic

APATITE 79 ZIRCON 7/2 GROSSULAR GARNET-TOPPED ENSTATITE ///

Distinctive Good fire, adaman- GARNET 6/ DoOuBLET 6/ Distinctive
absorption spectrum tine to resinous luster Vitreous luster Two parts joined absorption spectrum

OTHER GEMS
FLUORITE 66
KYANITE /33
TOURMALINE /03
SMITHSONITE 99
KORNERUPINE //3 SPHALERITE 63 EUCLASE /29
Strongly pleochroic, Very soft, good
rare as gem quality fire, high density
46 e COLOR KEY

BLUE OR VIOLET GEMSTONES

AQUAMARINE 76 LAZULITE /28 HAUYNE 68 TURQUOISE /3/ INDICOLITE /0/

Tubular inclusions, Often Small stones, Distinctive color, Strongly |
pleochroic mottled rarely cut fragile pleochroic |

AZURITE 126 Lapis LAZULI 69 SODALITE 68 ZOISITE 1/16 AMETHYST 82

Distinctive color, Distinctive blue, Distinctive Strongly Tigerstripe
fragile, soft pyrite inclusions blue color pleochroic inclusions

USUALLY BLUE OR VIOLET

SILLIMANITE 7/7. DUMORTIERITE //7 BENITOITE 80 IOLITE //2 KYANITE /33

Distinctly pleochroic, — Usually massive, Good fire, Strongly Pleochrotc,
good cleavage distinctive color birefraction pleochroic brittle, flaky

SOMETIMES BLUE OR VIOLET

FLUORITE 66 Topaz 106 ZIRCON 72 SMITHSONITE 99 SAPPHIRE 95

Lacks fire, soft, Pleochrotc, hard, Good fire, adaman- Distinctive High density,
good cleavages tearlike inclusions tine to resinous luster blue color hard, pleochroic
 COLOR KEY e 47

OTHER GEMS
APATITE 79
AGATE (STAINED) 56
HOWLITE (STAINED) /25
DIAMOND 54
EUCLASE /29
SCAPOLITE 7/ SPINEL 64 AXINITE /33 CHRYSOBERYL /08
Cat’s-eyes, fibrous Hard, singly Pleochroic, GARNET-TOPPED
inclusions refractive brittle DOUBLET 6/

USUALLY BLACK

HEMATITE /00 SCHORL /03 Jet 140 OBSIDIAN /36

Metallic luster, Opaque, Very soft, coal-lke Glassy, fairly hard,
opaque, iridescent vitreous luster smell when warm bubblelike inclusions

MELANITE 62 DIAMOND 54 TEKTITE /37 Cora /42

Adamantine to Adamantine Glassy, cracks Sensitive to
vitreous luster luster, hard on surface heat, soft

OPAL 134 FIRE AGATE 8&7 LABRADORITE /30 MOTHER-OF-PEARL /45

Iridescent colors, Inidescence resembles Iridescence on dark Blue and purple
may dry and crack atly rings of color body color iridescence on surface
48 e PRECIOUS METALS

rystal | structure
Cc r t Giihie
~ ® Compositi
ition Gold
‘ Hardness 2,

GOLD smooth, waterworn

‘The color of gold depends upon the amount and @ surface
type of impurities it contains. Native gold is
typically golden yellow, but in order to vary its
color and increase its hardness for use in jewelry,
gold may be alloyed with other metals. Silver,
platinum, nickel, or zinc may be added to give a
pale or white gold. Copper is added for rose or
pink gold; iron for a tinge of blue. Gold purity is
defined by the proportion of pure gold metal
present, expressed as its carat (ct) value. ‘The
purity of gold used in jewelry varies from
9 carat (37% percent or more pure gold), through
14, 18, and 22 carat, to 24 carat, which is pure
gold. In many countries, gold jewelry is
GOLD NUGGET “™ e metallic |
“hallmarked” to indicate its degree of purity.
luster
¢ OCCURRENCE Gold is found in igneous
rocks and in associated quartz veins, often in
small quantities invisible to the naked eye. It is
also concentrated in secondary “placer” deposits octahedral |
er 3
= as nuggets or grains in river
- d P crystals of gold |i
7 sands and gravels. ina
: ee |
Gold may still be extracted from placer deposits framework
by the traditional panning method, but modern
commercial mining involves large earth-moving
machinery and concentrated acids for processing
the ore. The main gold-bearing rocks occur in
Africa, California and Alaska, Canada, the former
USSR, South America, and Australia.
¢ REMARK Gold has been used for coins,
decoration, and jewelry for thousands of years. It
is attractive and easily worked and wears well.

typically rounded
and flattened CRYSTALLIZED GOLD NUGGET
grains ty grains collected
‘is from placer a
deposits by (aie
panning

gold usually e
occurs as fine i «
grains, not groups
of crystals like these

GOLD IN
GOLD GRAINS QUARTZ MATRIX
 PRECIOUS METALS e 49

crystalline
nugget

TIE PIN
This unusual GOLD, DIAMONDS, AND PEARLS
piece of This gold neckpiece is set with pink —
jewelry pearls and clusters of diamonds. Gold is
features a a popular setting for precious stones as It
gold nugget is easy to fashion and is hard-wearing
set into a and resistant to acids and tarnishing.
gold tie pin.
groups of
diamonds
LE
LLL
mM
natural
pearl

LLL
Ny

GOLD BANGLE
This flexible bracelet is
made from 18-carat rose
and yellow gold.

GOLD MOLD
This ivy leaf motif set
was made by casting
18-carat gold ina
wax mold.

softness of gold
accommodates
GOLD BANGLE intricate working
The hallmark that shows
the purity of worked gold
is just visible on this
delicate bangle. In this
case, it indicates the GOLD RING
gold is 18 carat. Gold is a popular
and resilient material
for rings. Here it is the
square-cut setting for a green
demantoid garnet demantoid garnet.
50 ¢«PRECIOUS METALS

Crystal
ystal structure ture (1,‘ Composition
ition Giver
q. Hardness 2V,

SILVER
surface tarnished
Silver usually occurs in massive form as natural,
e by silver oxide
nuggets or grains, although it may also branchlike
be found in wiry, dendritic (treelike) ° habit
aggregates. When newly mined or
recently polished, it has a characteristic
bright, silver-white color and metallic
luster. However, on exposure to oxygen in
the air, a black layer of silver oxide readily
forms, tarnishing the surface. Because of this,
and the fact that it is too soft to be used in
most jewelry in its pure or native form, silver is
often alloyed with other metals or given a cover-
ing layer of gold. Electrum, an alloy of gold and
silver in use since the time of the ancient Greeks,
contains 20-25 percent silver. Sterling silver -
contains 92% percent or more pure silver (and DENDRITIC
usually some copper), and Britannia silver has a SILVER CRYSTALS
silver content of 95 percent or more. Both alloys
are used as standards to define silver content. e polished silver
¢ OCCURRENCE Most silver is a by-
product of lead mining and is often
associated with copper. The main silver
mining areas of the world are South
America, the USA, Australia, and the
former USSR. The greatest single
producer of silver is probably Mexico,
where silver has been mined for almost
500 years. The finest native silver, which
occurs naturally in the shape of twisted
wire, is from Kongsberg, Norway.

POLISHED SLICE OF
SILVER AND COPPER ORE
maker's
mark Pi 5:
dendritic silver
from Kongsberg
crystals have is renowned for
wirelike habit Ws its quality

SILVER WINE CUP

This part-gilt silver cup
was fashioned in 1493,
when silver was valued
as highly as gold.

NATIVE SILVER FROM

KONGSBERG, NORWAY

°F 10.50
 PRECIOUS METALS « 51

‘TOWER BROOCHES highly

‘These modern silver
polished silver
brooches, made by
British silversmith
V. Ambery-Smith,
have additional SILVER BRACELET
decoration in rose This sterling silver
and yellow gold. bracelet also features
. 18-carat gold thread.

silver

18-carat :
gold thread #

SILVER DISH
Fashioned in 1973, this
dish features a leaf et it
motif border made oxidation
from oxidized x aD alters color
silver. FP Bel ey eh © of silver

ornate
carving WATCH CASE
Because of its softness,
silver is extremely
popular for fine
metalwork, as _~
seen in this .
18th-centur : \
y silver lends a
watch. os J
/ simple elegance
| to modern |
\ designs e
\
\ \

MODERN USEs
Silver is prized for
ornamental items,
such as these key
rings. ‘Today it is also
used in electronics
and photography.
52 e PRECIOUS METALS

Crystal structure ;
Pest”
Composition
Placinum
-

PLATINUM nuggets are

; ound in placer
Platinum has been used for thousands of years, I wy
‘ deposits such as rounded, uneven
but it was not recognized as a chemical element
river gravels
until 1735. Of the three precious metals — gold,
silver, and platinum — it is the rarest and the
most valuable. Chemically inert and resistant
to corrosion, platinum does not tarnish when
exposed to the atmosphere, unlike silver. It is
silvery gray, gray white, or white in color,
opaque, and has a metallic luster. It is slightly ;
more dense than pure gold and about twice as of.
dense as silver. Early jewelers had difficulty
achieving the 3,223°F (1,773°C) needed to
melt platinum: it was not until the 1920s that
the technology was developed sufficiently
to work this precious metal. PLATINUM NUGGET |
¢ OCCURRENCE Platinum forms in igneous
rocks, usually as ores in which the grains of
platinum are often too minute to be seen with
the naked eye. It may also occur in secondary isolated crystals
“placer” deposits in river sands and gravels, and are rare in
glacial deposits — usually as grains, more rarely nature
as nuggets. The main occurrences of platinum
have been in South Africa, Canada (Sudbury),
the USA (Alaska), Russia (the River Perm and
other rivers running down from the Urals),
Australia, Colombia, and Peru.
e REMARK Although nuggets had been set
in rings before 1920, most platinum jewelry
dates from after this time. Soft and easy to
distinct cubic
carve, platinum is often fashioned into
structure
quite intricate designs.

silvery
grains are found
color e
cele PG : in secondary
‘ deposits, rarely
in the host rock

opaque,
with metallic
luster

_.; cavities denote

OSItION O
PLATINUM GRAINS poriginal matrix
f

CRYSTALLIZED PLATINUM
 PRECIOUS METALS « 53

RING AND EARRING SUITE Ss.ay ae)

This modern suite is set with mee eS
square-cut precious stones in all
the colors of the rainbow.

FILIGREE NECKLACE
Like gold and silver, platinum is
quite a soft material, making it ideal
for the sort of intricate working
seen in this necklace. Unlike silver,
platinum does not tarnish when
exposed to the atmosphere.

© platinum
setting

platinum
filigree
MODERN BROOCH
Platinum is a popular
and stylish material
diamond-set e for modern jewelry.
detail at back
of necklace
two hoops ex
provide
framework
for design

NECKLACE WITH DIAMONDS

Platinum is a perfect, if very
expensive, setting for cut
diamonds, as the colors
complement each other well.

pendeloque- ¢
cut aquamarine

AQUAMARINE
RING
Platinum provides
inlaid a cool setting for this
diamonds pendeloque-cut ice-blue pendeloque-
aquamarine e——— cut aquamarine and its
twenty diamonds.
54¢«CUT STONES

Crystal structure :
Peston
Composition
Carbon
,,
a0
DIAMOND
Diamond is the hardest mineral on Earth, and e colored
this, combined with its exceptional luster and diamonds, such
brilliant fire, has made it the most highly as this yellowish
prized of all gems. Pure, colorless diamond is green variety, are
the most popular, but other varieties — from known as “fancy”
yellow and brown to green, blue, pink, red,
gray, and black — are also found, depending on
the impurities present. Because of the uniform
arrangement of their constituent carbon atoms,
diamond crystals are well formed — usually BRILLIANT CUT
octahedral with rounded edges and slightly
convex faces. Their perfect cleavage facilitates most diamonds
the early stages of fashioning (see p.26), but are faceted as a
they can be polished only by other diamonds. brilliant cut.
¢ OCCURRENCE Diamond forms at high which brings out
temperatures and pressures 50 miles (80 km) or their natural fire
more underground. When India and later Brazil
were the main producers, most diamond came
from secondary sources, such as river gravels.
pale pink
STONE @
However, since the discovery of diamond in
kimberlite rock in South Africa (around 1870),
its extraction has involved processing vast
quantities of rock. Australia is the main pro-
ducer today; other localities include Ghana, brilliant cut reflects
Sierra Leone, Zaire, Botswana, Namibia, as much light as
the former USSR, the USA, and Brazil. possible out through
¢ REMARK Diamonds are graded by the front of stone
four C’s: color, cut, clarity, and carat (weight).

BRILLIANT CUT diamonds

subtle gray- may be
green color transparent
to opaque
pink-red
variety
minimum
light leakage
through back
facets

BRILLIANT CUT
typical convex
green and black surfaces ote
inclusions

rounded
edges FIVE UNPOLISHED
DIAMOND CRYSTALS
 CUT SPONES*@ 55

LEAF DESIGN BRACELET

The extraordinary fire and luster
of diamond produce an almost
shimmering effect in this bracelet.

colorless,
| brilhant-cut
round, brilhant- platinum
t diamonds
cut diamonds @. ring
marquise-cut
’ diamonds

CRESCENT BROOCH
Colorless diamonds
are the most highly
prized. In this brooch, CLUSTER RING
many fine, brilliant- AND EARRINGS
cut examples have Diamonds are
been mounted in gold. popular for all
¥ jewelry, from
> ay the simplest to
e e
ee LE eel
thean iese
sophisticated,
NBR UP See sa because of
SOUS
SS BS IF their hardness,
superb luster, and by —@ diamond-
spectacular fire. studded
earring

sugarlike surface
texture
=e cubic habit
NC .
Me ETEO” rough diamond
with convex
crystal faces e

DIAMOND
oe crics conglomerate of
pebbles and
mineral grains e

Brilliant Cushion

DIAMOND IN
Old Mine Pendeloque Marquise CONGLOMERATE
(early MATRIX
Brilliant)
56¢ CUT STONES

Crystal structure , ,- Composition re Hardness 10

y Cubic Jarbon
'

e different color
varieltes are
caused by minute
traces of other
minerals
’

3-0 unusual, opaque, black

semitranslucent, “bort” variety Inclusions in this diamond
milky white derives color cause asterism in the form
stone from graphite of a double six-rayed star.
e inclusions

colorless stone
BRILLIANT CUT |
marred by black,
carbon-filled
inclusions |
pinkish
brown
color

BRILLIANT-CUT
BorRT DIAMOND

dodecahedral |
(12-sided) |
‘ . i — e habit |

BRILLIANT CUT

dark green volcanic, diamond- |

color due to colorless bearing kimberhite
exposure to diamond rock, first identified
radioactive ¢ crystal in Kimberley, ‘
radium e South Africa

characteristic
three-sided
face, known
as a trigon

FANCY DIAMOND DIAMOND IN

CRYSTAL KIMBERLITE
 CUY STONES*®* 57

DIAMOND BROOCH © pearl

Diamonds and emeralds
set in gold make up this
—e colorless
bird-shaped brooch, with
diamonds
pearls top and bottom.

e emeralds black diamond

variety, often used
industrially
damaged
facet e

BUTTERFLY BROOCH
This glittering brooch, set with more than
150 diamonds, shows examples of round,
| square, drop, pendeloque, and fancy cuts.
.

lacks © soft
e fire Bort
black bort occurs as FACETED
rounded masses with DIAMOND
radiating structure e

GLASS e over three-

too much quarters of
e fire all mined
diamonds are
of industrial
quality

CRYSTALLIZED
CUBIC ZIRCONIA STRONTIUM TITANATE Base DiAMOND

_ DIAMOND IMITATIONS
Diamonds may be imitated by any colorless stone,
by glass, and by manmade gems like YAG (yttrium in eel
_ aluminum garnet). None is an exact copy (see above). habit e

black micro-
crystalline
Cushion variety, often
used in
5 0) tA industry e

ft ‘ iy CARBONADO
= DIAMOND
Old Mine Pendeloque Marquise ROUGH
(early
Brilliant)
58° CUTSTONES

Crystal str r . mpositi . . “1s

YSESt SUMS? Cubic Composition Magnesium aluminum silicate Hardness 717,

PYROPE (GARN ET) brilliant-cut

‘The blood red color of pyrope is due to its iron and a oe
chromium content. It rarely has inclusions, but
when present they are rounded crystals or have
irregular outlines. As with all garnets, pyrope has no
cleavage, and fracture is subconchoidal to uneven. vitreous
¢ OCCURRENCE Pyrope is found in volcanic rock luster e
and alluvial deposits and may, along with certain
other minerals, indicate the presence of diamond-
bearing rocks. Localities include the USA OVAL BRILLIANT CUT
(Arizona), South Africa, Argentina,
BOHEMIAN EARRINGS
Australia, Brazil, Myanmar, Scotland,
Switzerland, and ‘Tanzania. Perfectly transparent, hornblende
clear, uniformly colored ¢ schist matrix
¢ REMARK Pyrope comes from the
crystals like these were
Greek pyropos, meaning fiery. Swiss
popular for jewelry in ~ PYOE
and South African pyropes are lighter the 18th and 19th crystals »
red than stones from Bohemia, centuries.
where pyrope jewelry has been .
made for over 500 years. , SZ fiery red
=i ‘Bohemian
—e pyrope

PYROPE CRYSTALS
IN MATRIX

SPESSARTINE (GARNET)
Gem-quality spessartine is uncommon. It is
bright orange when pure, but an increase in
the iron content makes the stone darker orange liquid
inclusions
to red. Inclusions are lace- or featherlike.
¢ OCCURRENCE Spessartine occurs in granitic
pegmatites and alluvial deposits. It is found in -e vitreous
Sri Lanka, Madagascar, Brazil, Sweden, Australia, luster
Myanmar, and the USA; also Germany and Italy,
but crystals there are too small to facet. OCTAGONAL STEP CUT
¢ REMARK Spessartine is named after
the Spessart district of Bavaria,
Germany. It can be confused with
hessonite garnet or yellow topaz,
fe oe f e lacy
but on close examination o aoliaat
inclusions it is distinguishable.

flat crystal
jc.

la C SPESSARTINE
———— ABOCHON “fe
Brilliant Step Cabochon CRYSTAL |
 CUE STONES © 59

Eryetal structure O bic Composition Tron aluminum silicate Hardness 71,

ALMANDINE (GARNET) © brilliant cut

enhances
Almandine is generally darker red than
frery red
pyrope and may appear black, although color
pinkish red specimens are found. It is
usually opaque or subtranslucent, but
the rare transparent stones have high
luster. Although dense, almandine is
brittle, and facet edges chip. Many
stones show characteristic inclusions, Needlelike crystals of rutile
or hornblende are typical
and four-rayed stars may be seen when
inclusions in almandine.
the stones are cut en cabochon. The
darker almandines are frequently) cut *e : ‘ hollow b a r .
hollow back allowsae
as cabochons or used as abrasives in ROUND BRILLIANT CUT © in more light
garnet paper. The underside of dark
almandine is often hollowed out to let black mineral
more light filter through the stone. inclusions
¢ OCCURRENCE Almandine is
found in metamorphic rocks, such
as garnet mica schist, and less
frequently in granitic pegmatites.
It has a worldwide occurrence.
CABOCHON
¢ REMARK Slices of garnet have
been used in windows in churches
rounded
and temples, and legend has it almandine
that Noah suspended garnet in crystals e
the ark in order to disperse light.
Garnet was once said to
cure melancholy and to granulite se
warm the heart. Drop EARRINGS matrix
The pale pinkish red
almandine garnets of
these 18th-century © cut shows
earrings have been triangular faces
f \ faceted in the rose
ss see cut and set in gold. ALMANDINE

striations —yvarovite
UVAROVITE (GARNET) on crystal crystals skarn
face e matrix
The attractive bright green color of
uvarovite is due to the presence of
chromium. The crystals are very fragile,
with subconchoidal to uneven fracture.
¢ OCCURRENCE Uvarovite
occurs in serpentine rocks.
The best clear crystals
are found in the Urals in
UVAROVITE CRYSTAL
Russia, lining cavities or
rock fissures. Other sources UVAROVITE CRYSTALS
are Finland, Turkey, and Italy. Brilliant IN MATRIX
60 e CUT STONES

Crystal structure Oy bic Composition Cajicium aluminum silicate Hardness 71,

HE S S O N I T E ( G R O S S U L A R dee
G ARN ET) e colored stone

Grossular garnets occur in a very

wide range of colors, from colorless
to black. Their name is derived
from the first specimen ever
found, a distinctive gooseberry
green color (see opposite). ‘The Hessonite garnet has
orange-brown color of hessonite swirls of inclusions, giving
grossular garnet is due to manganese ita honeylike appearance.
and iron inclusions.
¢ OCCURRENCE The best = =» color due to
hessonite garnets are found in Sri ; manganese
Lanka in metamorphic rocks or gem granular and tron
gravels and sands. In Madagascar, inclusions
hessonite is often referred to as
cinnamon stone. Other local- \ ye) bright
ities include Brazil, Canada, hessonite has ‘ee by orange-
and Siberia (Russia), as well as no cleavage @ 2 brown
the USA (Maine, California, ieee | hessonite
and New Hampshire). 4 crystals
OvAL MIXED CuT
¢ REMARK Both the ancient
Greeks and Romans made ; roinned
cameos, intaglios, and cabochons | crystals
from hessonite, and faceted
stones for jewelry.

HESSONITE
ROUND CRYSTALS
MIXED CUT ON MATRIX

PINK GROSSULAR (GARNET) limestone

matrix
Pure grossular garnet is colorless, but
impurities incorporated during its formation
pink grossular
cause a wide range of colors. This pink crystals
variety results from the presence of iron.
¢ OCCURRENCE Pink grossular
is found in Mexico, usually as a
massive form in metamorphic x _
rocks. Crystals are rare. It also 2 |, CRYSTALS IN MATRIX
occurs in South Africa. -
e REMARK . - pink and green
Pinkish grossular a s banded material
from Mexico may = ee ae — Bi be called
be known as . Transvaal jade
rosolite. Polished GROSSULAR GARNET POLISHED SLAB
 CUT STONES « 61

Erystal structure Cy hic Composition Calcium aluminum silicate

GREEN GROSSULAR rated:

CATOM IMM AN

(GARNET) vanadium Create

‘There are two varieties of green e rich green color

grossular: one is found as transparent
crystals, the other is massive. Massive
green grossular from South Africa is
called ‘Transvaal jade, after its main
source and because it resembles
jade. It may contain black specks of
the mineral magnetite. Since the
1960s, a transparent green grossular
garnet, tsavorite, has been mined in
Kenya. Massive green grossular is
used as a decorative stone; tsavorite a oa BEAD NECKLACE
agi BRILLIANT CUT — gooseberry Rete ee
is faceted as a em. ye Sie. Polished massive green
¢ OCCURRENCE Found in Canada, age grossular beads have a
Sri Lanka, Pakistan, the former USSR, speckly appearance due
‘Tanzania, South Africa, and the USA. to magnetite inclusions.
Kenya is the main source for tsavorite.
¢ REMARK The name “grossular” is groups of green
derived from the botanical name of the grossular
gooseberry, R. grossularia. Massive crystals e
grossular garnet of a gooseberry green
color was first discovered in the former
USSR. Since then it has also been
found in Hungary and Italy.
MASSIVE POLISHED
SLAB

Se
GREEN GROSSULAR
Bead Polished CRYSTALS IN MATRIX

Crystal structure Wasiable Composition Variable Hardness \7, able

DOUB Ler red almandine

GARN ET-TOPPED
garnet cemented to
A doublet is a stone made of two _e green glass base
separate pieces cemented together to
create the appearance of a precious luster and color
stone. Glass topped by red almandine change at junction
garnet is the most common form, of stones @
with green glass used to imitate
emerald, blue to imitate sapphire.
Once joined, the stone is
faceted and polished.
¢ REMARK These CUSHION-CUT
stones were very pop- DOUBLET
ular in Britain and
the rest of Europe ALMANDINE GARNET
in the Victorian era. Brilliant Brilliant ON GLASS BASE
62 e CUT STONES

Crystal structure Cubic Composition Calcium iron silicate Hardness 6%

- PT,
ANDRADITE GARNET bi gh fi re
Slashé Ss of
gr ve s
Garnets containing titanium and manganese e color
are grouped as andradite garnet. The
most valuable is demantoid, whose
emerald green color is due to the
presence of chromium. It has a higher
dispersion than diamond and can be
recognized by the characteristic
Demantoid garnet has
“horsetails,” which are fine, hairlike
inclusions of fine, hair-
inclusions of asbestos. ‘Topazolite, the like asbestos fibers,
yellow variety of andradite garnet, varies known as “horsetails.”
from pale to dark yellow. Only small
crystals are found. Melanite is generally a BRILLIANT-CUT “horsetail”
black form, but can also be dark red. DEMANTOID : e inclusions
¢ OCCURRENCE The best demantoid ~
is found in the Urals in Russia and is typically worn
associated with gold-bearing sands and _facet edges due
metamorphic rocks. Other localities to softness of
include northern Italy, Zaire, and demantoid e
Kenya. Topazolite crystals are
found in the Swiss and
Italian Alps in
metamorphic rocks.
Melanite is found in
metamorphic rocks and
volcanic lavas; fine MIXED-CUT DEMANTOID
crystals are found on the
island of Elba (Italy) and serpentine a

@ matrix
in France and Germany.

crystal face has BRILLIANT-CUT

vitreous to DEMANTOID
e metallic luster

demantoid e
crystals

typically black, DEMANTOID GARNET

opaque stone CRYSTALS IN MATRIX

serpentine
rock e
yellowish green gs
crust of aan
topaxolite
crystals e

BRILLIANT-CUT
MELANITE

TOPAZOLITE
Mixed CRYSTALS IN MATRIX

on
 CUT STONES ©« 63

. PYRITE
With its brassy yellow color, pyrite is often
mistaken for gold (hence its other name, striations may
fool’s gold). It occurs as cubes or as occur on crystal faces
“pyritohedra,” which have twelve faces,
each with five edges. Pyrite has been
used in jewelry for thousands of years,
and examples from the ancient “pyritohedral” crystal
civilizations of the Greeks, Romans, has twelve faces
and Incas have been found. Today it is
used mainly in costume jewelry, but
is brittle and requires careful cutting. P?
© OCCURRENCE Pyrite is found
worldwide in igneous, metamorphic, and PYRITE CRYSTAL
sedimentary rocks. Fine specimens come
from Spain, Mexico, Peru, Italy, and France. nS
¢ REMARK The name comes cubic form has six
from the Greek word pyr, wes A a ale aie
meaning fire, since
sparks are caused L.
if pyrite isstruck (ees)
with a hammer. Cabochon Polished PYRITE CRYSTAL

SPHALERITE back facets

— are doubled
Sphalerite, also known as blende, is an important
ore of zinc. It is usually very dark brown to black
in color, but occasionally transparent, yellowish
brown, or green stones are found that can be
faceted. Since sphalerite is soft and has perfect
cleavage, it is not suitable for jewelry, and is
faceted for museums and collectors only.
© OCCURRENCE Sphalerite crystals are rich
usually pseudo-octahedral in shape, a s OCTAGONAL STEP CUT reddish
forming in hydrothermal veins with arena brown
other minerals, such as galena, quartz, al high fire shows e crystals
pyrite, and calcite. Transparent, rainbow ———
cuttable stones are found in 9 colors
Santander (Spain) and Mexico.
¢ REMARK In the past, sphalerite
has often been confused with
galena (lead sulfide), to
which it is very similar. sitreous
luster e

BRILLIANT CUT
SPHALERITE
Brilliant Brilliant CRYSTALS IN MATRIX
64° CUT STONES |

Crystal StUctUre Cubic Composition Magnesium aluminum oxide

SPINEL —© vitreous
luster
Spinel is found in a wide range of colors due
to the presence of various impurities and is
transparent to almost opaque. Red spinel
colored by chromium and iron is the most
popular, although for many years it was
thought to be a variety of ruby. The orange-
yellow or orange-red variety is called rubicelle
(a diminutive of the French word for ruby). red stones |
Blue spinel is colored by iron and less originally |
commonly by cobalt. Occasionally, inclusions ~ known as
of crystals such as magnetite or apatite may Balas rubies |
occur, and some Sri Lankan spinels may OCTAGONAL MIXED CUT |
include zircon crystals surrounded by brown
haloes. Star stones are rare, but when cut e”
cabochon may show 4-rayed or 6-rayed stars. blood red |
¢ OCCURRENCE Spinel occurs in granites pener
and metamorphic rocks and is often found in sometimes
association with corundum. Octahedral known as '
crystals and waterworn pebbles in a wide ruby spinel
range of colors are found in the gem gravels
of Myanmar, Sri Lanka, and Madagascar.
Other localities include Afghanistan,
Pakistan, Brazil, Australia, Sweden, Italy,
Turkey,
Ue the former USSR,
sre va and the USA. Ee
visible ' ;
e REMARK Synthetic spinel has been |
manufactured since 1910. It has been a OVAL BRILLIANT CUT /
used to imitate diamond or colored
to imitate stones such as aqua-
marine and zircon. Blue synthetic
spinel, colored by cobalt, has pink stone from
been used to imitate sapphire. Myanmar
‘The name may derive from the
Latin word spina, meaning “little
thorn,” referring to the sharp
points on some crystals.
red color due to
chromium and
OCTAGONAL STEP CUT iron impurities
bright red
color e—

watlerworn
fragments
found in gem
gravels of Sri
Lanka

& CRYSTALS AND FRAGMENTS

oY AGGREGATE OF
SPINEL CRYSTALS
 CUT STONES 65

6-rayed star
brought out by ae
e cabochon cut brilliant-cut
e crown facets

——e asterism 18
rare in spinel

e@ Slép-cul
pavilion
: fac eLs
STAR-STONE CABOCHON

CUSHION MIXED CUT

|} . ——«
ik
liquid-filled
pinkish mauve %~
| color «fi Be | Ree inclusions

pale pinkish
purple stone from
S7i Lanka e
CUSHION MIXED CUT
blue
gahnospinel
CONLAINS ZINC @ OCTAGONAL STEP CUT
gahnospinel 1s
named after
Swedish chemist
e J.G. Gahn pale pinkish
e mauve color

e synthetics have
been manufactured
since 1910

dark, xinc-rich
e spinel crystals

BRILLIANT-CUT
SYNTHETIC SPINEL

Brilliant quarts matrix e

—_——

si SPINEL CRYSTALS
Cabochon Mixed IN MATRIX
66 e CUT STONES

Crystal structure Oy pic Composition Calcium fluoride

FLUORITE bright golden

Formerly called fluorspar, fluorite has limited yellow color
use as a gemstone because it is relatively soft
and therefore easily scratched. However, the
wide range of colors (including yellow, blue,
pink, purple, and green), the frequent
incidence of more than one color in a single
specimen, and zoning or patchy distribution of stones are
color make it an interesting stone. Despite its faceted for
fragility and perfect octahedral cleavage, stones collectors only
are faceted (usually for collectors) and can be
polished very brightly. Cabochons of fluorite OCTAGONAL STEP CUT
have been capped with rock crystal (see p.81)
to protect them from scratches. iron ore
® OCCURRENCE Localities include Canada, matrix
golden yellow
the USA (where some of the largest crystals are culic fluorite
found), South Africa, Thailand, Peru, Mexico,
crystals
China, Poland, Hungary, Czechoslovakia,
Norway, England, and Germany. Pink octa-
hedral crystals are found in Switzerland. A
purple- and yellow-banded variety called
Blue John occurs in England.
e REMARK The ancient Egyptians used
fluorite in statues and to carve scarabs, and
the Chinese have used it in carvings for more
than 300 years. In the 18th century, fluorite
was powdered in water to relieve the FLUORITE CRYSTALS
symptoms of kidney disease.
twinned
crystals IN MATRIX

fluorite ts
soft and
difficult green cubic
to facet crystals

pale bluish black hematite

green color inclusions |

FLUORITE CRYSTALS SE |
IN MATRIX ee ON

fluorite may be
mistaken for
glass, feldspar, colorless
beryl, or quarts cubic
crystals

FLUORITE se |
CRYSTALS IN MATRIX

Luster Vitreous
 CUT STONES © 67

tiny white
quartz crystals
cubic fluorite
| pale pink crystals e
;
| color

| specks of black
hematite e

cut stones may be CUSHION STEP CUT

. highly polished
and bright mauve cubic
| fluorite FLUORITE CRYSTALS
crystals e & IN MATRIX

white quartz
ee _—____—@ CYYSIGIS

FLUORITE CRYSTALS
OCTAGONAL STEP CUT
INTERGROWN WITH QUARTZ

masstve
) yellow and r smooth cleavage
| purple Z- ? ——e surface
banding e——

green and
purple
banding e—

(CCLEAVED FLUORITE
CRYSTAL
BLUE JOHN VASE
‘This attractive banded
variety of fluorite has been
carved since Roman times.
‘The ancient Romans
believed that drinking
alcohol from a cup made
of Blue John would allow
the drinker to imbibe
without becoming drunk.
68 © CUT STONES

Crystal structure Cubic Composition codium aluminum Hardness 5%

silicate

SODALITE © white
Sodal; ake ; ee iy Le calcite
Sodalite, whose name reflects its sodium content, patches
is found in all shades of blue and is a major
constituent of the rock lapis lazuli (opposite), so
the two are easily confused. However, unlike
lapis lazuli, sodalite very rarely contains brassy
pyrite specks, and it has a lower specific gravity. —@ VILTCOUus
Sodalite may contain white streaks of the mineral luster
calcite, and can be carved for use in jewelry.
¢ OCCURRENCE Sodalite is usually found as CABOCHON
masses in igneous rocks. Crystals are very rare,
but twelve-sided crystals have been found in
the lavas of the volcano Vesuvius in Italy, ——e semitranslucent
although they are too small to be used in stone
jewelry. Other localities include Brazil,
Canada, India, Namibia, and the USA.
¢ REMARK The most important
commercial source of sodalite is white patches
of calcite
Bancroft in Ontario, Canada. It veins of
was discovered during a royal calcite e OVAL BRILLIANT CUT
visit by Princess Margaret
of England. For this
reason, sodalite
from Bancroft is
sometimes called
Princess Blue.
uneven e
fracture

ae POLISHED —
Cabochon Cameo SODALITE SODALITE ROUGH

HAUYNE stones are

Hauyne forms part of lapis lazuli (opposite). It typically
is usually intergrown with other minerals and small
is seldom found as individual crystals. Hauyne
has perfect cleavage, making cutting BRILLIANT CUT
difficult, so it is faceted
primarily for collectors. patches of
¢ OCCURRENCE crystals form e lilac
Hauyne is found as small, in Malrix @ hauyne
rounded grains in vol- crystals
canic rocks. Ancient
volcanoes of Germany —e matrix
and Morocco are the HAUYNE
best known sources. CRYSTALS
Brilliant IN MATRIX
 CUT STONES ¢ 69

Crystal structure VWrious Composition Rock containing lazurite and other minerals Hardness sy,

a
BEAD NECKLACE
LAPIS LAZULI (LAZURITE) Specks of pyrite and
Lapis lazuli is a blue rock made up of several _ streaks of calcite are
different minerals, including lazurite, sodalite, _visible in these lapis
hauyne, calcite, and pyrite. The composition lazuli beads.
and color of lapis lazuli varies, but it is the
intense dark blue, with minor patches of
: @ pale
white calcite and brassy yellow pyrite, that eon
is considered to be the best quality. of calcite
@ OCCURRENCE Lapis lazuli is usually
found as boulders or within limestones.
The best quality lapis lazuli is from
brassy
Afghanistan and has been used in many
pyrite e
famous pieces, including the mask of
Tutankhamen. Argentinian lapis lazuli
is also of a high quality. A pale blue
variety occurs in the former USSR
and in Chile. Lapis lazuli from the
USA 1s a darker shade of blue;
Canadian specimens are lighter blue.
¢ REMARK Lapis lazuli has been BUDDHA CARVING
This carving is made
worn in the belief that it will protect onc hiahest
the wearer from evil. It has been quality Epis Coali
imitated by stained jasper and by from Afghanistan.
paste with inclusions of copper.
Imitation lapis lazuli produced by
Pierre Gilson in France has a main ingredient brassy pyrite
composition very similar to of imitation: stone
e specks
; —e 1s lazurite
natural lapis lazuli.

imitation stone e———

softer than natural
lapis lazuli

GILSON IMITATION CABOCHON GILSON IMITATION SLAB

nans of Uneven blue color due to

oad fracture presence of lazurite e
pyrite e ;

streaks of
rock ts sawn aja 6——
open and
ground with Fg
grits to give 7
flat surface
POLISHED LAPIS LAZULI SLAB

uneven
x fracture e
£
[ | a
Cabochon Cameo Polished Lapis LAZULI ROUGH

SG . c - =
70 © CUT STONES

Crystal structure "Te tragonal Composition Calcium tungstate

SCHEELITE good fire

Scheelite is quite soft and is therefore faceted scratches show
stone 1s soft
only for collectors of the unusual. It has high
and easily
dispersion and good fire, and varies in color © damaged
from a pale yellowish white to brown. Colorless
synthetic scheelite is used to imitate diamond
but can be distinguished by its birefraction. It
may also be colored by trace metals corners cut
in order to imitate other gemstones. offtoavoid
® OCCURRENCE Scheelite is found © chipping BRILLIANT CUT creamy yellow
in pegmatites and metamorphic rocks. 4 scheelite
Very large crystals over 1 Ib (0.5 kg) crystals e
Lray
have been collected in Brazil, but
magnetite
generally, larger crystals are not matrix
sufficiently transparent to be faceted.
Other localities include Australia,
Italy, Switzerland, Sri Lanka,
Finland, France, and England.

SQUARE STEP CUT

SCHEELITE
CRYSTALS IN MATRIX

double images
C.ASSITERITE of rear
Cassiterite is the principal ore of tin. It is facets
usually recovered from mines as black opaque visible
grains, which are of little use in jewelry. Crystals
are generally short, stubby prisms, though
—e 7aTe
transparent, reddish brown crystals with —¢g/orless
transparent,
adamantine luster are sometimes found, stone with
reddish
and faceted for collectors. They could be —_ye//owish brown stone
confused with diamond, brown zircon, linge @ OVAL BRILLIANT CUT
and titanite, but casserite has higher
specific gravity and distinct dichroism. black mineral
opaque, short,
* OCCURRENCE Cassiterite occurs —e inclusions
prismatic
in pegmatites and can be washed into e crystals
alluvial deposits. Localities include the
Malay Peninsula, England, Germany,
Australia, Bolivia, Mexico, and Namibia.
¢ REMARK The
name “cassiterite”
comes from the
Greek word, BRILLIANT CUT
kassiteros,
meaning tin. CASSITERITE
Brilliant Mixed CRYSTALS IN MATRIX

SG 6 95 Rl > 00-2.10 OR 9 100 Luster 4 damantine

 CUT STONES ¢ 71

Crystal structure Te trasonal Composition Complex silicate

SCAP OLITE Se. transparent

stone
Also called wernerite after the German geologist
A.G. Werner, scapolite ranges in color from pink,
purple, blue, yellow, and gray to colorless.
These colors reflect variations in composition, step-cut
from sodium-rich to calcium-rich. Crystals are crop
found as prisms that resemble sticks, giving facets brilliant-cut
pavilion facets
rise to the name “scapolite,” derived from
the Greek words scapos, meaning rod, .
and /ithos, meaning stone. ‘ MIXED CUT B27 Oe os
¢ OCCURRENCE Scapolite is found — sss sanliagl
as crystals in pegmatites and in meta- ie taeiaae
morphic rocks like mica schist and © cause gray tinges
gneiss. It also occurs in massive form. i
Localities include Brazil, Myanmar,
Canada, Kenya, and Madagascar. eos
° REMARK A cat’s-eye effect ee ] Cacao
can be seen in some pink and ie nee ;
purple stones. Scapolite may massive
easily be confused with <. w yellowish
amblygonite, chrysobery], = tj rough
and golden beryl. . i,

=~ pale yellow
- |\fF elie %. Xs variety

RUTILE. . wii ee
needlelike stone 1s known
Natural rutile has many times the fire rutile as sagenite when
shown by diamond, but it is masked by inclustons inclusions
the red, brown, or black body color. The intersect at 60°
black material has been used in mourning
jewelry, but rutile is most usually seen as ea
rich, reddish brown, needlelike inclusions - sycductons matrix
within quartz or within other stones, covered by
where the rutile crystals create a crystalline
star effect by reflecting light. QUARTZ © rutile
¢ OCCURRENCE Igneous and adcssois
metamorphic rocks and alluvial
deposits in Australia, Brazil, the
USA, Italy, Mexico, and Norway.

+ dh
POLISHED RUTILE “3
Baguette Mixed QUARTZ ROUGH 7)”
~

Rh2 62-2.90 DR ¢ 287 Luster Vitreous to metallic

12° CUT STONES

Crystal structure Tetragonal Composition 7 -conium silicate Hardness TY,

ZIRCON |

Zircon is most famous for its colorless stones, ae @& w® 2 —— e colorless |

which closely resemble diamonds and have ZITCON
been used both intentionally and mistakenly produced
in their place. Although colorless when pure, by heating :

impurities will produce yellow, orange, blue, reddish

red, brown, and green varieties. Brown stones brown
from ‘Vhailand, Vietnam, and Kampuchea are material
usually heat treated to change them into the
colorless or blue stones popular in jewelry.
Blue stones that revert to brown will regain RECTANGULAR STEP CUT
the blue if reheated. Blue zircon reheated in
the presence of oxygen will change to golden
yellow. Zircon may be distinguished from
diamond by its double refraction and by wear
and tear on its facet edges. It has been imitated green stones are
by both colorless glass and synthetic spinel. often decayed
Some zircon contains radioactive thorium -e “low” zircon
and uranium, which eventually break down
the crystal structure. Decayed stones are
waterworn pebble |
known as “low” zircon, with a “metamict”
with polished
structure; undamaged material is “high” zircon. @ surface
¢ OCCURRENCE Gem-quality crystals are
usually found as pebbles in alluvial deposits.
OVAL BRILLIANT CUT
Sri Lanka has been a source of gem material
for over 2,000 years; other localities include
Myanmar, Thailand, Cambodia, Vietnam,
Kampuchea, Australia, Brazil, Nigeria, natural golden
‘Tanzania, and France. e yellow color
® REMARK Zircon was believed to
provide the wearer with wisdom,
honor, and riches, and loss of
luster was said to warn of
danger. The name is from me GREEN
the Arabic zargun, which “METAMICT”’
derives from the Persian PEBBLE
for “gold color.”

ZITCON
OvAL MIXED CUT crystal e—

golden brown
is most popular pegmatite
color for zircon matrix
Jewelry
CUSHION | = ~e dark
BRILLIANT CUT CRYSTALS IN MATRIX Diotite mica

Rl 1.93-1.98 DR 9.059 L :
uster Resinous to adamantine
‘
 GUT STONES. 73

doubling of
_e back facets uneven color
e distribution

yellowish
—_@ reflections
smooth
surface

—e stone heat
treated to
achieve blue
color

ROUND BRILLIANT CUT

doubling of WATERWORN
back facets untreated reddish PEBBLES
| | e brown color
| © green =ITCOn May
have “metamict”
structure
dark golden
brown stone e

(CUSHION
BRILLIANT CUT

f : double
RECTANGULAR STEP CUT CTOW N e@
re: pyramidal
Jace ends @

ZIRCON RINGS
Its adamantine luster, strong SQUATEC CTOSS
birefraction, hardness, and SCCLION @
vast color range make zircon
an attractive stone when set
in a ring. Unfortunately, its
use is restricted by its brittle
nature; cutting is difficult
leaf green and the cut stone is
mixed-cut easily damaged.
ZITCON

TETRAGONAL
ZIRCON CRYSTAL

yellow zircon in & ~

center, flanked by eran
pale blue-violet stones
74¢CUT STONES

Crystal structure Tetragonal Composition Calcium aluminum silicate Hardness 6%

VESUVIANITE
PLA ?
yellowish
green
I his mineral was first discovered on the polished variety
Italian volcano Vesuvius as small, perfect massive
crystals. Also called idocrase, it may be red, mareria/ e
yellow, green, brown, or purple. It is seldom
used in jewelry, but it may be cut for
collectors. Crystals are usually thick
prisms with a square cross section.
@¢ OCCURRENCE There are CUSHION CUT
several varieties: californite from
California is green; rare blue
cyprine is found in Norway; striations
on tg
yellowish green xanthite is from parallel to
New York; green wiluite crystals length of
are from the former USSR. Other ; — .. oases.
localities include Austria, Canada, CALIFORNITE CABOCHON
Italy, and Switzerland. adamantine
¢ REMARK Vesuvianite may be luster
confused with demantoid garnet,
diopside, epidote, smoky quartz,
tourmaline, zircon, and peridot.
tetragonal
prism with
smooth faces

TUGTUPITE white albite feldspar Ces

associated with A Pee
‘Tu gtu pit e was first discovered in 1960 in tugtupite a by polishing
: aa urface
Greenland, where it is carved for jewelry. Surf
Colors include dark red to bright pink
and shades of orange. It may look mottled.
When it is placed in the dark, the paler
parts of the rock fade to white, but
exposure to light restores the color. pink
¢ OCCURRENCE Tugtupite is found tugtupite
as Massive opaque material in pegmatite
veins. It also occurs in northern Russia.
¢ REMARK The name derives from its
occurrence in ‘Tugtup, Greenland, and Nats

means “reindeer stone.”

POLISHED STONE

intergrown albite
Jeldspar

Polished TUGTUPITE ROUGH

Cabochon Cameo

RI 1 49-1.50 DR 9.006 Luster Vitreous

 CUT STONES ¢ 75

Crystal structure Fexagonal Composition Beryllium aluminum silicate nae 7,

EMERALD (BERYL) inclusions

make stone
Emerald derives its beautiful green color look cloudy
from the presence of chromium and
vanadium. Emeralds are rarely flawless,
so stones are often oiled to fill and disguise
cracks, hide flaws, and enhance color. ‘To
minimize the loss of material, the step cut
(also called the emerald cut) is commonly
‘Tremolite inclusions may
used, but ancient engravings are known,
be found in emeralds as
and cameos, intaglios, and beads can short rods or long fibers.
make the best of a flawed stone.
¢ OCCURRENCE Found in granites,
pegmatites, and schists, as well as alluvial
deposits, the finest emeralds are from PENDELOQUE
Colombia. Other sources are Austria, India, unusual
Australia, Brazil, South Africa, Egypt, the domed front
' USA, Norway, Pakistan, and Zimbabwe. eine eae:
e REMARK Most emeralds used in SS eee
historical jewelry were from
group of
Cleopatra’s mines in Egypt,
inclusions
which now yield only poor-
quality emeralds.
OCTAGONAL CABOCHON

cracks and inclusions

e common in emerald
brilhant-cut
POLISHED PEBBLE crown facets @ _

Synthetic emeralds have

characteristic veil or wisp-
like, liquid-filled inclusions.

good emerald- is ek ce
green color 25 MIXED CUT

: crystals
A often found white
4: worn or calcite
ei has .dl etched crystals
int

flat ends i

:r .
Res.
-

a *
HEXAGONAL LS
CRYSTAL ;
<4

ee Se)

Pendeloque Step Step Cabochon CRYSTAL IN MATRIX

76° CUT STONES

Crystal structure Fiexagonal Composition Bery|lium aluminum silicate

AQUAMARINE (BERYL)
untreated, sky
In the 19th century the preferred color for blue stone e
aquamarine was sea green, and indeed the
name itself means seawater. Today the most cat’s-eye effect
valued colors are sky blue and dark blue. visible on
Aquamarine 1s dichroic, appearing blue cabochon e
or colorless as the stone is viewed AES

from different angles. Gem-quality

aquamarine is found as hexagonal
crystals, which may be up to 39 in
(1 m) long and flawless, with
;
striations along the length of the :

crystal. Aquamarine is often cut ———e fibrous habit

with the table facet parallel to the
length of the crystal in order to
emphasize the deepest coloration. step cut heat treatment
¢ OCCURRENCE The best of the ‘ypical for has lightened
gem-quality aquamarine is found in
CABOCHON aquamarine @ A
| |
Brazil, where it occurs in pegmatites
and alluvial deposits of gravel, locally untreated stone has
called cascal/ho. Other localities include © greenish tinge
the Urals (Russia), Afghanistan,
Pakistan, India, and, more recently
exploited, Nigeria. A dark blue
variety occurs in Madagascar.
¢ REMARK Almost all aqua-
marine on the market has been
heat treated to enhance its color.
Care must be taken not to
overheat the stones, as they OCTAGONAL STEP CUT
may become colorless.

many small crystal ts too green

facets e and will require
heat treatment

poor-quality
flawed stone

popular
aquamarine
vf =

AQUAMARINE CRYSTALS

Brilliant Step Cabochon

 GUE SEONES.* 77

| Crystal structure Fiexasonal Composition Beryllium aluminum silicate maraness77,

HELIODOR (BERYL) idealin

lowing,

Heliodor, a yellow or golden yellow form of — color e——

beryl, has always been linked with the sun.
Gem-quality specimens are occasionally
found, but more often inclusions of
fine, slender tubes are present that heart-shaped cut
are visible to the naked eye. keeps maximum
¢ OCCURRENCE Heliodor is found possible weight « ScssGne COL
associated with aquamarine in granitic ee bevel-edeed
pegmatites. The finest quality crystal with
stones are found in the Urals _—*® flat ends
(Russia). Brazilian heliodor is often
a pale yellow and is step cut to
give depth of color. Heliodor from
Madagascar is a finer color. Other
localities include the Ukraine,
Namibia, and the USA.

FANCY CUT

Marquise Table Baguette HELIODOR CRYSTALS IN MATRIX

GOSHENITE (BERYL)
—@ SfOnNeS ATC
Goshenite is the pure, colorless variety of transparent
beryl. It has been used to imitate ‘ey
diamond or emerald, by placing silver
or green-colored metal foil behind a VILTEOUS @ MK.
luster y
cut goshenite gemstone, then placing
the stone in a closed setting so that
the foil cannot be detected.
® OCCURRENCE Goshenite is
named after Goshen, Massachusetts,
where it was first found. Present FANcy CUT crystals have
localities include Canada, Brazil, spiky inclusions hexagonal
and the former USSR. are common « y outline
¢ REMARK Pale and colorless
beryl was once used for the lenses in =
spectacles, thus the German word for TS
spectacles, dri//e, may have been
derived from the word “beryl.”
78 e CUT STONES

Crystal structure Hexagonal

Composition Bery|lium aluminum silicate Hardness 71,

MORGANITE (BERYL) ——e typical

.
pale pink
. ya .
Colored by manganese impurities, the pink,
%|

rose, peach, and violet varieties of beryl are color

called morganite, after banker and gem
enthusiast, J. Pierpoint Morgan.
Morganite tends to occur as short many
and stubby (tabular) prisms and small
ee a ee :
is dichroic, showing either two e te
facets OVAL Mie Ge
shades of the body color or
one shade and colorless.
® OCCURRENCE The first
morganite to be described
was a pale rose-colored
specimen from California,
where it occurred with
tourmaline. Some of the
finest morganite is from
Madagascar; Brazil produces
pure pink crystals, as well as
some containing aquamarine
and morganite in the same
crystal. Other localities include
Elba (Italy), Mozambique, DROP-SHAPED CUT
Namibia, Zimbabwe, and pink color from
(recently discovered) Pakistan. manganese
e REMARK Stones with a
yellow or orange tinge may be
heat treated for a purer pink.

liquid-filled =
inclusions oe
ROUND BRILLIANT CUT

MORGANITE ROUGH

Crystal structure H exagonal Composition Beryllium aluminum silicate

prismatic red
RED BERYL berylcrystal «
Very rare, and seldom seen as a cut stone, red
beryl nonetheless has an unusually intense
color, due to the presence of manganese.
¢ OCCURRENCE Found in rhyolites or.
in the Thomas Mountains and Wah
Wah Mountains in Utah. nA dee ae
e REMARK Red bery] is Ay Marea
also called bixbite (not to be ae
confused with bixbyite, a
manganese iron oxide). CRYSTAL
Brilliant IN MATRIX

E
e
 CUT STONES ¢ 79
Crystal structure Hexagonal

APATITE blue-gray
With a value of only 5 on the Mohs scale fibrous
of hardness, apatite is seldom faceted as a apatite
gemstone, except for collectors. However,
when cut correctly, stones are bright with
strong colors. ‘Transparent to opaque, apatite
occurs as colorless, yellow, blue, violet, or
chipped
ete t, facet
green hexagonal prisms or tabular crystals.
¢ OCCURRENCE Apatite is an abundant 86
brittleness
mineral found in many types of rock,
but most gem-quality material is CAT’S-EYE CABOCHON p of stone
associated with pegmatites. Blue
apatite from Myanmar is strongly
dichroic, showing colorless or blue
when viewed from different
directions. Fibrous blue apatite
from Myanmar and Sri Lanka
may be cut en cabochon to show
a cat’s-eye. Chatoyant stones are
also found in Brazil, along with
yellow, blue, and green varieties.
Other localities include the Kola
Peninsula (Russia), Canada, East OCTAGONAL STEP CUT
Africa, Sweden, Spain, and Mexico.
¢ REMARK Spanish apatite is —————-__ a ee Stones are opaque
often called “asparagus stone,” aa Ja=
A to tr a n s p a r e n t
because of its yellowish green color. color

cut stones are

bright and
strongly colored

pyramidal
end
CUSHION MIXED CUT
yellow
hexagonal colorless apatite
prism crystal e
RECTANGULAR
STEP CUT

APATITE
CRYSTAL

quartz e—— |
and gibertite
matrix APATITE CRYSTALS
IN MATRIX
Cabochon

Rly 63-1.64 DR 0.003 Luster Vitreous

80 e CUT STONES |

Crystal structure Hexagonal Composition Beryllium magnesium aluminum oxide |

|

TAAFFEITE @ first specimen

‘Taaffeite is very rare, and is unique in that it is to be identified
the only gemstone not recognized as a new
mineral species until it had been faceted. ‘The
first specimen (see right) was found by Count |

‘Taaffe in Ireland, in a jeweler’s box of stones. It

looked like spinel, had a pale mauve tinge, and © grayish
was cushion cut, but was eventually found to be mauve color
a new, doubly refractive (rather than singly
refractive like spinel) mineral. Since then,
more specimens have been found; :
: 5
these range in hue from red to semi-
blue to almost colorless. Lransparent translucent
¢ OCCURRENCE Taaffeite © stone pebble @
occurs in Sri Lanka, China,
and the former USSR.
¢ REMARK No imitation vitreous
taaffeites appear to exist. luster e

ROUND BRILLIANT CUT

Brilliant Brilliant Cushion TAAFFEITE ROUGH

Crystal structure Hexagonal

Composition Barium titanium silicate

BENITOITE appears colorless

at certain angles
‘The blue crystals of benitoite were pyramidal
discovered in 1906 by a mineral prospector @ end
who mistook them for sapphires. Crystals BRILLIANT CUT
are shaped like flattened triangles and unevenly
have a strong dispersion similar to distributed color
diamond, but this is masked by the
color. Dichroism is strong: the BRILLIANT CUT
stone appears blue or colorless
when viewed from different blue benitoite
angles. Colorless crystals occur ; e crystals
conchotdal
but are rarely faceted. © fracture
¢ OCCURRENCE Crystals
occur in veins in blue schists.
The sole source is in San Benito
County, California, after which
the stone is named.
BENITOITE CRYSTAL .4 2/7 ' = “Ste
FRAGMENT ale % ee
B = ee oy

BENITOITE CRYSTALS
Brilliant Brilliant Cushion IN MATRIX

|
 CUT STONES « 81

Crystal structure T,; gonal Composition Gijicon dioxide

RoOcK CRYSTAL (QUARTZ)

transparent
Colorless and transparent, rock crystal is the stone e
most widely distributed variety of quartz, one
of the most common minerals of the Earth’s
crust. The crystals are usually found as
colorless hexagonal prisms, with pyramidal
ends and striations perpendicular to their
length; they are often twinned. Cleavage facet edges may
is poor and fracture conchoidal. wear on older
¢ OCCURRENCE Although found STONES @
worldwide, the most important
sources of rock crystal are in Brazil.
z- \ ROUND BRILLIANT CUT
Other localities include the Swiss
and French Alps, where fine
crystals occur, and Madagascar, VItTeOUus
the former USSR, and the USA. luster
¢ REMARK The name “quartz”
comes from the Greek word carved
krustallos, meaning ice, because it drilled e grooves
was thought that quartz was ice hole e
formed by the gods. Since the
Middle Ages, crystal balls made
of rock crystal have been used to
predict the future. Today, rock
crystal is used in lamps, lenses,
and the manufacture of glass
and precision instruments.
Synthetic rock crystal has
been produced since 1950 |
for use in watches.

POLISHED ROCK CRYSTAL POLISHED BEAD

This flat disk of polished rock
crystal has been engraved and
set with an enameled mono- pyramidal
gram of blue, black, and gold. e ends
hexagonal
crysta Ise

striations on
colorless through e prism faces
yellowish shading

SINGLE CRYSTAL eg

Brilliant Step CRYSTALS

82 e CUT STONES

Crystal structure Trigonal Composition oi}; on dioxide

AMETHYST (QUARTZ)
Crystalline quartz in shades of purple, lilac, or
mauve is called amethyst, a stone traditionally
worn to guard against drunkenness and to instill
a sober and serious mind. Amethyst is dichroic,
showing a bluish or reddish purple tinge when
viewed from different angles. Usually faceted
as a mixed or step cut, amethyst has distinctive
inclusions that look like tigerstripes, thumbprints, Characteristic tigerstripe
or feathers. Some amethyst is heat treated to inclusions are caused by
change the color to yellow, producing citrine parallel, liquid-filled canals.
(see opposite). Crystals that are part citrine and TIE PIN
part amethyst are called ametrine. Amethyst jewelry was popular in the
¢ OCCURRENCE Amethyst is found in alluvial late 19th century. ‘This handsome
deposits or in geodes. Some of the largest geodes gold tie pin is adorned with an
containing amethyst are in Brazil. Amethyst from octagonal step-cut amethyst.
the Urals (Russia) has a reddish tinge; Canadian
amethyst is violet. Other localities include Sri
Lanka, India, Uruguay, Madagascar, the USA,
Germany, Australia, Namibia, and Zambia.
e REMARK Poor quality material is often
tumbled to make beads. Ifa stone is pale it
may be set in a closed setting or have foil placed
behind it to enhance the color. Amethyst has
been imitated by glass and synthetic corundum. typical
purple stone el Hg
from Russta rolbr

polished,
convex
front alternate colors
due to twinning
OvAL MIXED CUT

color darkens |
toward tip of
>
amethyst crystal
HEXAGONAL
MIXED CUT

slice cut
perpendicular
to length of |
crystal

Zs
[/// AMETHYST CRYSTALS
; —y/
Gz ASSOCIATED WITH
Baguette Bead ROCK CRYSTAL
 CUT STONES ¢ 83

Composition Silicon dioxide

5 =
CITRINE (QUARTZ) One
eee
tinge oft

Citrine is the yellow or golden yellow variety

of quartz. The yellow coloration, due to the
presence of iron, is also responsible for the
name, derived from the word atrus.
Natural citrine is usually a pale yellow,
but rare; most citrine on the market is
heat-treated amethyst (see opposite). MIXED CUT
¢ OCCURRENCE Gem-quality yellow
citrine is extremely rare. The best color due to pyramidal
material is found in Brazil, Spain, presence of ende
Madagascar, and the former USSR. _ iron SS
e REMARK Citrine has been used to
imitate topaz (see pp.106—107) and
was once called Brazilian topaz.

MIXED CUT
PENDELOQUE

ROSE QUARTZ ROSE QUARTZ SEAL

Intaglio seals such as
Pink or peach-colored quartz is called rose this, made with an
quartz and is mainly used in decorative incised rather than
carvings. Its color is thought to be due to a raised design,
the presence of small amounts of titanium. were very popular
Crystals of rose quartz are very rare; more in ancient Rome.
usually, massive lumps are found, which
can be carved or cut en cabochon or
as beads. Transparent material is
uncommon; it is usually cloudy or
cracked, partly because it is so
brittle. Rutile inclusions in rose
quartz may produce a star effect rose Quartz
when the stone is cut en cabochon. crystals e
* OCCURRENCE Rose quartz
is found in pegmatites. The best
material is from Madagascar, but
Brazil produces a greater quantity. BRILLIANT CUT
Other sites are the USA (Colorado),
the former USSR, Scotland, and Spain. crystals are
typically
cloudy

Rose Qu ARTZ
Mixed CRYSTALS

Se
84e CUT STONES

Crystal structure Trigonal Composition ey ee Hardness 7

BROWN QUARTZ
Brown quartz includes crystalline quartz of
a light brown or dark brown color, grayish
brown “smoky” quartz, and the black variety e color may be

called morion. Brown or smoky quartz from due to natural

the Cairngorm Mountains of Scotland is irradiation
called cairngorm. When irradiated, colorless
quartz may change color to grayish brown,
suggesting that brown quartz may have been
formed by natural radiation within the ground.
Brown quartz crystals are hexagonal prisms : aa _~ —=
e = FANCY-CUT SMOKY QUARTZ
with pyramidal ends, in which inclusions of
the mineral rutile may be present.
¢ OCCURRENCE Crystals weighing as much characteristic
as 650 lb (300 kg) have been found in Brazil. vitreous @ grayish
Other localities include Madagascar, the Swiss luster brown
Alps, the USA (Colorado), Australia, and Spain. e color
¢ REMARK Much of the smoky quartz on the
market is in fact irradiated rock crystal. Brown
quartz has been confused with andalusite,
axinite, idocrase, and brown tourmaline.
pyramidal
e end
BRILLIANT-CUT
SMOKY QUARTZ
SNUFF BOTTLE
Like most varieties of
quartz, smoky quartz
may be polished and opaque e
fashioned in many ways. hexagonal
This snuff bottle, with prism
red stopper and spoon,
is of Chinese origin.

horizontal e
striations on
prism face
in t WAY. ad

image e

MORION
INTAGLIO SEAL CRYSTAL
[his incised intaglio was
carved in smoky quartz and
has been set in a polished polishing of one facet
octagon of obsidian, which makes interior visible e
is a natural volcanic glass.
Intaglio seals were popular
with the ancient Romans.
"his piece depicts a
Roman wearing a helmet.

smoky 6
— quarts WATERWORN
Cameo intaglto (CAIRNGORM PEBBLE
 CUT STONES © 85

Crystal structure Trigonal Composition ¢:1;.on dioxide

AVENTURINE QUARTZ brassy yellow

‘This form of quartz contains inclusions of mica inclusions
small crystals that reflect light and give a
range of colors — depending on the nature of
the inclusion. Green aventurine quartz has
platy inclusions of green fuchsite mica; pyrite -——e oval
inclusions give a brown color; a greenish brown orange-brown
color may be due to the mineral goethite. Other cabochon
inclusions result in bluish white, bluish green,
CABOCHON
or orange varieties.
¢ OCCURRENCE Aventurine
quartz is found in Brazil, India, and
Russia. Other localities include the
USA, Japan, and ‘Tanzania. Suchsite
¢ REMARK Aventurine quartz has mica
been confused with aventurine inclusions
feldspar, amazonite, and jade. A Bae
simulant known as goldstone has color
been made to imitate both
The copper inclusions in
aventurine quartz and aventurine
goldstone are visible with
feldspar. It contains small triangles a 10x hand lens.
and hexagons of copper held in
glass. With a 10x hand lens it
should be possible to see the
POLISHED SLAB
outlines of the copper spangles.

cryptocrystalline
quartz with light-
reflecting inclusions
i, AVENTURINE ge ¥
Cabochon Cameo Polished QUARTZ ROUGH ™

MILKY Qu ARTZ 5 BaP

milkiness double
praniaal
due to gas
This form of quartz derives its distinctive and liquid e ends
milky white or cream color from inclusions of | inclusions
gas and liquid bubbles. The degree of
milkiness depends on the number and
SAR.
size of inclusions present. Crystals are _—

hexagonal prisms with pyramidal ends. ——

¢ OCCURRENCE Very large crystals ae

are found in Siberia. Other localities | ¥:
include Brazil, the European e. a)
Alps, Madagascar, the Nahe ae iad
USA, and Namibia. ~_ : ae’ ee.
¢ REMARK When ase
polished or cut en OVAL CUSHION CUT
cabochon, it may be ad d
confused with opal. Brilliant Baia HEXAGONAL CRYSTAL
86 e CUT STONES

Crystal structure Trigonal Composition ¢:1; on dioxide

CHATOYANT QUARTZ
‘The three varieties of quartz described here all
wavy, fibrous e—
have a fibrous structure, with inclusions of structure
crocidolite (blue asbestos) that cause a cat’s-eye
effect known as chatoyancy. ‘This effect is best
seen when the stones are cut en cabochon. Each
stone displays different colors according to the
exact nature of the inclusions. ‘The grayish markings resemble
yellow, semitranslucent appearance of e figerstripes
quartz cat’s-eye is due to inclusions of
crocidolite “asbestos” and, less
commonly, hornblende. It has a
silky luster. “Tiger’s-eye” is black, TIGER’S-EYE
with iron oxide staining that gives POLISHED SLAB
yellow and golden brown stripes.
“Hawk’s-eye” forms when —e yellow-brown
crocidolite changes to quartz, but stripes due to iron
the blue-gray or blue-green color oxide staining
of the original material remains.
¢ OCCURRENCE Quartz cat’s-eye
comes from Sri Lanka, India, and Zs original blue color
Brazil. The most important source of and fibrous
tiger’s-eye is in South Africa, where it is POLISHED structure retained
found in thick slabs, together with the less TIGER’S-EYE
common hawk’s-eye. Chatoyant quartz
is also found in Australia and the USA.
¢ REMARK Chatoyant quartz is always called
quartz cat’s-eye to avoid confusion with other
chatoyant gems, particularly chrysoberyl.

pale, almost
colorless HAWK’S-EYE ROUGH
quartz e
cabochon cut
brings out cat’s-
eye effect

waterworn fragment
HAWK’S-EYE CIGARETTE Box exhilits fibrous
In this attractive ornament, made structure
of polished slices of blue hawk’s-
eye, the wavy, fibrous nature of
the original asbestos can be
clearly seen. Partial oxidation QUARTZ CAT’S-EYE CABOCHON
has created a few yellow waves.
rough displays no
chatoyancy e—

Bead Cabochon Polished CAT’S-EYE ROUGH

 CUT STONES « 87

Composition ilicon dioxide

QUARTZ WITH INCLUSIONS ram‘ PERFUME BOTTLE

Quartz specimens with mineral inclusions are . £ This piece of quartz
very common and make attractive gemstones. Ss contains distinctive
“Rutilated quartz” or “sagenite,” popularly C= ae inclusions of black,
— needlelike tourmaline
known as Venus-hair stone, is quartz with
crystals. It has been
needlelike rutile crystals. These may be shaped, hollowed
red, black, or brassy yellow and have a out, and polished
eee
<ul metallic luster. “Tourmalinated quartz” to make a bottle.
has inclusions of black tourmaline, which
form prismatic or needlelike crystals.
e needlelike
Opaque, metallic yellow inclusions of tourmaline inclusions
gold are found in specimens of “gold
quartz.” Inclusions of silver may also be
found within quartz, often in branchlike
dendrites, and are silvery gray or black,
opaque, and metallic. The iron minerals,
goethite and pyrite, are also found as
inclusions. If cut en cabochon, quartz containing reddish brown
rutile inclusions
goethite may show the cat’s-eye effect.
® OCCURRENCE Quartz with inclusions
is found in Madagascar, Brazil, South Africa, hexagonal
India, Sri Lanka, Germany, and Switzerland.

RUTILATED
QUARTZ CRYSTALS
Cabochon Cameo IN MATRIX

FIRE AGATE (CHALCEDONY)

Fire agate belongs to the chalcedony iridescence
family of microcrystalline quartzes. These brought out by
cabochon cut
stones are either solid colored or have
bands or mosslike or dendritic inclusions
iron oxide
(agates). The distinctive iridescent colors of
inclusions
fire agate are caused by layers of iron oxide
give “oily”
within the quartz. This rainbow effect may
effect
be brought out by cutting en cabochon.
¢ OCCURRENCE Fire agate is found
in the USA (Arizona) and Mexico. FIRE AGATE
¢ REMARK Iris quartz has a similar irides- CABOCHON
cence, but this is caused by internal cracks.
rainbow
colors e—

POLISHED FIRE
AGATE PEBBLE
ss «CUT STONES

Crystal structure -,. . Composition «-,: a Hardness

Trigonal P Silicon dioxide

AGATE (CHALCEDONY) angular and white quartz

Agates occur in nodular masses in rocks such as wavy agale e crystals
volcanic lavas. When split open, they reveal an banding e
amazing variety of colors and patterns and a
distinct banding that distinguishes agate from
other kinds of chalcedony (the compact, micro-
crystalline variety of quartz). Band colors are
determined by the differing impurities present,
although, since it is porous, agate is often dyed
or stained to enhance the natural color. Agate
also occurs in several distinct forms. Fortification
agate has angularly arranged bands resembling
an aerial view of a fortress. Moss agate (or mocha
stone) is translucent and colorless, white or gray,
with dark, moss- or treelike (dendritic) inclusions.
It is usually cut as a thin slab or polished as
ornaments, brooches, or pendants. Petrified
wood is fossilized wood that has had its organic
STAINED AND POLISHED OVAL
matter replaced by agate.
¢ OCCURRENCE Probably the most famous distinctive concentric
area for agates 1s Idar-Oberstein in Germany, more stain banding «
where agate has been collected since 1548. Most taken up in
agate now comes from the huge deposits in some areas e
Uruguay and Brazil. Moss agate occurs in the
Hindustan area of India; also China and the USA.
The most famous petrified wood is found in the
Petrified Forest in Arizona. Agates are also found
in Mexico, Madagascar, Italy, Egypt,
India, China, and
Scotland. parallel bands
© and patterns

STAINED AND POLISHED SLICE

—e agate 1s often
collected and
polished by
enthusiasts agate forms in
cavities in
volcanic rocks

silica-rich e
fluids give
color to
POLISHED SLICE bands

AGATE ROUGH

|
 ) CUT STONES « 89

iron oxides and

hydroxides form tree- LANDSCAPE
like inclusions AGATE
black dendritic
inclusions e

inclusions
appear to
pale cream
create @ Scenic
background
landscape

green, mosslike
inclusions

white quartz
crystals e

Moss AGATE
i Moss AGATE
| BROOCH STONE i
ROUGH

when e———
magnified,
bands in
fortification
agate
resemble
hill forts
colorless quartz
crystals e

CARVED BowL
Agate is a very popular stone for
carving and polishing, although a
piece as delicate as this bowl could
be worked only by an expert
lapidary. The parallel banding is
typical of agate.
parallel e—
but angular
banding

Cabochon Cameo Polished

FORTIFICATION AGATE ROUGH
90 e CUT STONES

Crystal structure ; Composition ,-,- <a Hardn

, ‘Trigonal . Silicon dioxide

ONYX, SARD, AND

SARDONYX (CHALCEDONY )
Onyx, sard, and sardonyx are all varieties of
the microcrystalline quartz, chalcedony. Onyx
is similar to agate (see pp.88-89), but it has
straight rather than curved bands. ‘These may
be brown and white or black and white. Sard
is a brownish red variety, also similar to agate.
Sardonyx, a blend of sard and onyx, has the
straight white bands of onyx and the brownish
red of sard. All three varieties are carved as small
sculptures and intaglios, or they may be polished,
tumbled, or cut as beads. ‘They are renowned as
excellent materials for inlay work. Since ancient
Egyptian times, onyx has been stained to improve FLOWER CAMEO i
or change its color. Much onyx has been produced This cameo was
by soaking agate in a sugar solution, then heating worked from a
it in sulfuric acid to carbonize the sugar particles. single piece of onyx.
Sard may be imitated by saturating chalcedony The Garis eager
with an iron solution. _ ; layer has pees
¢ OCCURRENCE
aS spin Found worldwide,
eutigs aulae they) are aor toe
shape of a flower
formed by the deposition of silica in gas cavities to reveal the pale
in lavas, which results in the distinctive bands. layer beneath.
e REMARK Onyx seals were very popular with
the Romans, who carved the pattern of the seal in
negative relief to give a raised print. They often
used stones with several layers, each of a different
color, which were then individually carved to STRAIGHT SEAL
produce a different pattern in each layer. The straight layers |
of onyx have been
exposed to dramatic /
straight
brown
effect in this seal, an
ornament popular |
and white with the Romans. )
banding,
characteristic
s of onyx vitreous luster on
some surfaces

parallel bands
of different
colors e
4 _ ars

TITS OR SHAT a a
. Tee S

SS SS Seite ae

£ 7
\ ) how \
%& . POLISHED
ONYX SLAB
Bead Cabochon Polished
 CUT STONES «91

_e stone 1s translucent.
wth patchy color

characteristic
brownish red
color

fos FF A + rth
Pitted, pa Thy

e walerworn surface

dark, semti-
translucent stone with
waterworn surface e

polished ©
Su rHace

SARD PEBBLE SARD ROUGH

—_—§e
white and brownish 4 unbanded

red bands are 4 QT€a tS SQTa

characteristic of
sardonyx e Nae.
UNOANGAEAa
Caiceagony e |

SATG ONYX
; bands e

POLISHED SARDONYX

SARDONYX CAMEO
In this intricately carved
cameo, the pattern of a
woman’s head and
winged dragon has been
cut from three different
layers — dark brown, a
white, and red-brown.
A laurel garland is carved
just inside the raised rim.

SARDONYX ROUGH
 \
92° CUT STONE |
S
Crystal structure ‘Trigonal Composition Gijicon dioxide

(CC H R Y S O P R A S E / P R A S E Preast: Camo

E D O N Y ) Set inn gold
gold asas <an
(CH
: A L C fe
ornamental pin,
Used by both the Greeks and Romans as this piece of fine
a decorative stone, chrysoprase,
bed a trans- oe ais nae
deen carved and
lucent, apple green stone, is the most polished into a
valued variety of chalcedony. ‘The color, classically styled
derived from the presence of nickel, may cameo.
fade in sunlight, and stones may then be
confused with fine jade (see pp.124—125).
@¢ OCCURRENCE Mines in Poland and
Czechoslovakia once produced very fine fragments of
chrysoprase. However, since 1965, the ’ host rock
best quality material has come from Queens-
land (Australia). Other localities are Brazil,
California, the Urals (Russia), and Austria.
e REMARK Another green chalcedony, prase,
has a more somber hue and Is very rare.
apple green e
cArysoprase

Crystal structure ‘Trigonal Composition Cilicon dioxide

> , stone may break

JASPER (CHALCEDONY ) easily at junction
Jasper is a massive, fine-grained, opaque variety of stripes e
of chalcedony, believed to protect against sight
defects and drought. It occurs in shades of
brown, grayish blue, red, yellow, and green,
and mixtures of these. “Orbicular” jasper
has white or gray, eye-shaped patterns
polished e
surrounded by red jasper. “Ribbon” jasper surface
is striped and used in carvings, cameos,
and intaglios, which show off its layered
structure. Hornstone is a gray variety. RIBAND JASPER FRAGMENT
¢ OCCURRENCE Red jasper
occurs in India and Venezuela; mammillated
various colors occur in the USA, © habit white
quarts
especially orbicular jasper in
iron oxide gives vem
California; red and green ribbon
red coloring
jasper occurs in Russia. It also
occurs in France and Germany.

RED JASPER ROUGH

Polished RED JASPER ROUGH

 CUT STONES :* 93

Crysta l st ru ct ur e a er i g o n a l

CARNELIAN (CHALCEDONY) = —e typical reddish

Also called cornelian, this translucent, reddish orange stone
orange variety of chalcedony was once from India
thought to still the blood and calm the
temper. Its various shades of red are due color bands
to the presence of iron oxide. Stones may formed by tron
be uniformly colored or faintly banded. oxide impurities @
@¢ OCCURRENCE The best carnelian
is from India, where it is placed in the
sun to change brown tints to red.
¢ REMARK Most carnelian on the
market is stained chalcedony from
Brazil or Uruguay.
POLISHED STONE

POLISHED CARNELIAN
FRAGMENT

BLOODSTONE AND PLASMA

(CHALCEDONY) ROMAN CAMEO
Bloodstone (also called heliotrope) and The typical red
plasma are both opaque, green, spotted spotting in dark
varieties of chalcedony, used for decorative green bloodstone
appears as an
carvings and cameos. ‘The dark green of
almost solid mass
bloodstone is spotted with red because in the high relief
of the presence of iron oxides. ‘These of this cameo.
distinctive spots seem to resemble blood,
giving the stone its name. Plasma is also
green and may have yellowish spots. e raised relief
¢ OCCURRENCE India is the primary carved from
source of bloodstone, but it also occurs red spotting
scattered
in Brazil, China, Australia, and the red spots
USA. Plasma is mined in Zimbabwe. and Veins e
¢ REMARK In the Middle Ages, polished material
bloodstone was attributed with
e often used as inlay
very deep
special powers, as the spots were @ green
thought to be the blood of Jesus
Christ. In Germany, hematite is
also called bloodstone, so this
variety is known as bluestone.

POLISHED
BLOODSTONE SLAB
94 e CUT STONES

Crystal structure Tyi sonal Composition Atminum oxide

RUBY (CORUNDUM)
Ruby — the name given to red, gem-quality corundum — is
one of the best gemstones for jewelry settings. Rubies may be
any shade of red, from pinkish to purplish or brownish
red, depending on the chromium and iron content
of the stone. Frequent twinning of the crystals rubies Were
ee thought to ward
makes the material liable to fracture, yet ruby off misfortune
is a tough mineral, second only to diamond in e and il! health
hardness. Crystal prisms are hexagonal with Rutile inclusions cause a
silky appearance, which
tapering or flat ends. As the crystals grow,
heat treatment will remove.
they form new layers, and, depending on the
geological conditions and minerals present,
color variations called zoning occur.
mixed cut 1s
@ OCCURRENCE Worldwide in igneous and
typical for rubies
metamorphic rocks, or as waterworn pebbles in
alluvial deposits. The finest stones come from
Myanmar; those from Thailand, the primary
source, are brownish red; Afghanistan, Pakistan, star effect seen in
cabochons when rutile
and Vietnam yield bright red stones; those from
inclusions present
India, the USA (North Carolina), Russia, a
Australia, and Norway are dark to opaque. CUSHION MIXED CUT
¢ REMARK In 1902, a Frenchman, Auguste
Verneuil, produced a synthetic ruby crystal by
manufactured by
exposing powdered aluminum
Verneuil method
oxide and coloring material
to the flame of a blowtorch.

stone
weighs over % a y
138 carats = -
ROSSER REEVES RUBY
SS SS

STEP-CUT SYNTHETIC pinkish red

crystal
Color zoning indicates
the layers of growth in
a crystal. They can be
seen here as a series of
concentric hexagons,
which appear parallel to
the prismatic crystal faces.

purplish
red coloration
largest gem- Sim
quality crystals @
are from
Myanmar
 CUTSTONES'* 95

Crystal structure “Trigonal Composition Aji minum oxide

SAPPHIRE (CORUNDUM) e rutile inclusions

All gem-quality corundum that is not red is _ create 6-rayed star
called sapphire, yet this name is popularly effect in cabochons
associated with the color blue. Variation in
color, due to iron and titanium impurities,
spans many shades, but the most valuable is
a clear, deep blue. Some stones, called “color-
change sapphire,” exhibit different shades of
blue in artificial and natural light.
@ OCCURRENCE Good-quality sapphire
is found in Myanmar, Sri Lanka, and STAR CABOCHON
India. The best Indian sapphire is De ae
cornflower blue and is found in Since the Middle Apes,
| Kashmir, either in pegmatites sapphire has symbolized
| or as waterworn pebbles in the tranquility of the
alluvial deposits. Sapphire heavens, bestowing
from Thailand, Australia, peace and amiability
and Nigeria is dark blue, upon the wearer and
and may appear nearly suppressing wicked and
| black. Montana produces impure thougnts.
sapphire of an attractive
| metallic blue. Other localities % “Kashmir
| include Cambodia, Brazil, == blue”
, Kenya, Malawi, and Colombia. BRILLIANT CUT © = —_e crystals
¢ REMARK Synthetic sapphire
production began in the late 19th
century. Commercial quantities became
available in the early 20th century.

sapphire crystal
has intergrown q
with tourmaline 4? . ~~ an
; BLUE SAPPHIRE ‘aie a i black
Brilliant Cabochon Cameo CRYSTAL — tourmaline

| )
eee Ga
PADPARADSCHA (CORUNDUM) ; | characteristic
ey! Po ae pinkish orange
Padparadscha is a very rare, pinkish orange sapphire.
It is the only variety of corundum other than ruby
that is given its own name, rather than being
referred to as a sapphire of a particular color.
The name derives from a Sinhalese word
meaning “lotus blossom.” vitreous hd, : i
® OCCURRENCE Sri Lanka. luster e _ a. DD» eee truncated
¢ REMARK Like all : ig heart shape
varieties of corundum,
padparadscha is an excellent
jewelry stone, second only to MIXED CUT
diamond in hardness. Mixed
96 © CUT STONES

COLORLESS SAPPHIRE cabochon shows

6-rayed star e
(CORUNDUM)
‘The different colors found within members of
the corundum group are due to small amounts
near-colorless
of metal oxide impurities. Corundum without
stone with
impurities (and therefore without color) is rare, grayish tinge e—
but when found is classified as colorless
sapphire. Stones made up of different colors,
including colorless areas, are more common.
Stones like these are generally oriented by the
cutter so that the color is at the base. ‘Then,
when viewed from above, color fills the stone.
¢ OCCURRENCE Truly colorless sapphire is
found in Sri Lanka. Cloudy or milky- colorless {
colored sapphire 1s also found in Sri sapphire \
Lanka and referred to locally as geuda. is free |
Heat treatment of geuda produces
from
bubblelike impurities
blue sapphire, much of which is
inclusions
faceted and used in jewelry. Some
pyramidal
Sri Lankan corundum shows red,
blue, and colorless areas, which
may be faceted or polished to
give an interesting stone. . pure,
¢ REMARK Synthetic colorless
colorless corundum has been stones are,
produced by the Verneuil rare
method since about the
1920s and has been
called diamondite. twinned,
prismatic
crystal
MIXED CUT

Brilliant Brilliant Cabochon COLORLESS CRYSTAL

SG 400 eg? DR 9.008 Luster Vitreous }

Crystal structure Trigonal Composition Atami oxide Hardness 9

GREEN SAPPHIRE (CORUNDUM) very dark

From medieval times until the end of the 19th green color
century, green sapphire was known as “oriental
peridot.” Many sapphires that appear green
actually consist of very fine alternating bands
of blue and yellow sapphire, which may be
visible under a microscope.
¢ OCCURRENCE Green ~e Vitreous
sapphires are found in luster
Thailand, Sri Lanka, and
Australia (Queensland
and New South Wales). Brilliant SUSHION CU

Rl 4 76-1.77 DR 0.008 Luster Vitreous

 GUT STONES ¢.97
Crystal structure Trigonal Composition iens caiosade

PINK SAPPHIRE
e pink color
(CORUNDUM) derives from
Pure pink sapphire is colored by very-small chromium
quantities of chromium, and with increasing
amounts of chromium it forms a continuous
color range with ruby. Tiny amounts of iron
may produce pink-orange stones called e S71 Lankan
padparadscha (see p.95), or iron and titanium stones range
impurities together may make a purplish stone. from pale
Pink sapphires are often cut with a deep profile. pink to red
¢ OCCURRENCE Pink sapphires, from a very
pale and delicate pink to a near-red, occur in CUSHION MIXED CUT
Sri Lanka, Myanmar, and East Africa. striations on
¢ REMARK Like rubies (see p.94), stones may be worn next to the skin 9% (TYSta /face
pink sapphires are believed to ward e for maximum reputed benefit
off ill health and misfortune. For
the wearer to gain the benefit
of the stone, however, it has
been thought necessary for
it to be worn directly on the
skin. Therefore stones are
cut so that, when set ina
piece of jewelry, the back
makes contact with the skin.

Cushion — Pendeloque PINK SAPPHIRE CRYSTAL

YELLOW SAPPHIRE e yellow sapphire,

(CORUNDUM) formerly known as
oriental topax
Until the end of the 19th century, yellow
sapphire was known as “oriental topaz”
(only blue corundum was called sapphire).
Nevertheless, yellow and greenish yellow
sapphires make unusual and attractive
barrel-shaped
gemstones in their own right.
crystal with
® OCCURRENCE In Queensland and @ tapering ends
New South Wales (Australia), a
greenish yellow sapphire is CUSHION
found that may be faceted. z MIXED CUT
Similar stones occur in
Thailand and pure yellow
stones in Sri Lanka, the USA WATERWORN
(Montana), and East Africa.
Brilliant CRYSTAL

Rly 76-1.77 DR 1).008 Luster Vitreous

98 eCUT STONES

Crystal structure Trigonal Composition Calcium carbonate Hardness 3

CALCITE caloite crystals

are highly
°

Common worldwide, calcite is the

oy, . . .

principal component of limestones hirefractive

and marbles and of most stalactites
and stalagmites. It can also be found as vitreous luster
large, transparent, colorless, complex on, front, pearly
crystals, or as prismatic crystals inter- luster at sides
grown with other minerals. Because
of its softness it is faceted only for red tinge due to
the collector, but marbles and brown, iron oxides
banded calcite from limestone caves are
used for both decoration and carving. “ICELAND SPAR” ,
¢ OCCURRENCE Italy is famous for fine- RHOMB
quality marbles, particularly the creamy
Carrara marble. Transparent, colorless transparent,
rhombs are known as “Iceland spar”; a colorless €%
white fibrous variety, cut e” cabochon,
crystals e———+
§
shows the cat’s-eye
effect. Pink and
green crystals
occur in the
USA, Germany, LOE PRISMATIC
and England. Step Polished CALCITE CRYSTALS |

RI 148-1.66 Pie Luster Vitreous to pearly

SS ae
PHENAKITE phenakite has
Phenakite is a rare mineral found as white or silvery look
when cut well
colorless tabular crystals or stubby prisms.
‘Twinning is common and distinguishes it from
rock crystal (see p.81), with which it is often
confused (hence its name, derived from the VILTeCOUus
Greek word for “cheat”).Transparent crystals are luster
faceted for the collector and are hard and bright.
¢ OCCURRENCE Phenakite occurs in
pegmatites, granites, and mica schists. The BRILLIANT CUT
best crystals are found in Brazil, the Urals
(Russia), and the USA (Colorado). < . ae only transparent EERE
Other localities include Italy, Sri gil ea stones are faceted Dan
Lanka, Zimbabwe, and Namibia. ends
¢ REMARK A pebble weighing
1,470 carats was found in Sri
Lanka and faceted to a 569-carat
oval and several smaller stones.

BRILLIANT CUT

PHENAKITE CRYSTAL

Luster Vitreous
 CUT STONES e 99

Crys ta l s t r u c t u r e T r i g o n a l
Composition Hydrated copper silicate

emerald to
DIOP TASE crystals bluish green
Dioptase is a beautiful, vivid emerald green with have perfect e coloration
a hint of blue. It has very high fire, but this is cleavage e
masked by its strong color, which may make stones
translucent rather than transparent. Prized by the
collector for its color, it is nonetheless rarely
faceted, as stones are brittle and fragile, and too soft
to be worn. It is sometimes confused with emerald.
¢ OCCURRENCE The
best quality crystals
are found in copper
deposits in Russia,
Namibia, Zaire, Chile,
and the USA (Arizona).

curved colorless
DOLOMITE faces quarts ¢
Dolomite is found as colorless, white, pink, are
or yellow crystals, often with distinctive = ee opaque
curved faces. Rarely faceted, because of its Se : dolomite
softness and perfect cleavage, its mainuse § crystals @
is in massive form, as a decorative stone. ~~
¢ OCCURRENCE Found in limestones
and marbles, the
best crystals are
from Italy,
Switzerland, % >
Germany, and SS TWINNED DOLOMITE
the USA. CRYSTALS IN MATRIX

ee blue
SMITHSONITE EEE yy srithsonite
Toys 2 oe: , @ (7UST
Smithsonite is usually found as bluish green or
green botryoidal masses or soft layers, which
are polished and used as an ornamental stone opaque white
(sometimes called bonamite). It may also smithsonite @
be colored pink by cobalt or yellow by
cadmium. Crystals may also be found,
but are faceted for the collector only. ; = ag :
© OCCURRENCE Colorless crystals “97 “Ag™ e’ «oF SUITES ONILE
in Namibia and Zambia; Pend e ON' MADREX
blue-green masses in
the USA, Spain, and \ Ps
Greece; yellow in the i . 4 % SMITHSONITE
USA and Sardinia. 4 ON MATRIX
100 e CUT STONES

Crystal structure Tri sonal Composition \{4nganese carbonate Hardness 4

RHODOCHROSITE alternate pink

e and red bands
Rhodochrosite derives its pink color
from manganese. Gem-quality crystals
do occur and are cut for collectors, © polished cross
but the fine-grained, banded rock is Section
more commonly used for decoration. pinkish red
® OCCURRENCE Rhodochrosite crystals @
occurs in veins associated with
manganese, copper, silver, and lead
deposits. Argentina has the oldest
mines; its banded rhodochrosite
is sometimes called “Inca rose.”
‘Today, the prime commercial
sources are in the USA.
BANDED
RHODOCHROSITE

RHODOCHROSITE
Bead Cabochon Cameo CRYSTALS IN MATRIX

RI 1 60-1.80 OR 0 276 Luster Vitreous to pearly

HEMATITE
CARVED FROG
Hematite usually occurs as massive, Ae 7* | Wich a hardaces or
opaque material with a metallic luster, wm SE q 6%, hematite is
showing a blood red color when cut into Pe OL ae easily carved, but
thin slices. However, it can also occur as RQ OF Pe i 22S must be taken
short, black, rhombohedral crystals and may aoe to prevent scratch-
have iridescent surfaces. When arranged like ing. ‘This oriental-
the petals of a flower, hematite is called an ee at ae mae: frog has a gray
“iron rose.” Shiny crystals may be called lis ee elec Tusk.
“specular” hematite, a name derived
from their traditional use in mirrors. shiny crystals
¢ OCCURRENCE Main deposits are -” “% were once used
in igneous rocks around Lake « ‘S * as mirrors
Superior, Canada (Quebec), Brazil, : \
Venezuela, and England. Iron roses
are found in Switzerland and a a Ne play of light
Brazil; cuttable material in rc, "wh Wee on surface
England, Germany, and Elba. Sw |
¢ REMARK Powdered, it may be
used as an artist’s pigment or for
polishing. In the past it was worn
as protection against bleeding.

arrangement
of crystals

= IRIDESCENT
Cabochon Cameo HEMATITE CRYSTALS
 CUT STONES «101

Crystal structure Trigonal Composition

Complex borosilicate
Hardness 7
2

RUBELLITE (TOURMALINE) dark pink

Members of the tourmaline family of minerals e color
have the same basic crystal structure, but
occur in many colors. Rubellite (from the —e fibrous
Latin for red) is the name given to the habit visible
pink or red variety, with ruby red stones in cat s-eye
the most highly prized. Rubellite translucent “flash”
crystals are striated, with a triangular Stone @
cross section and a rounded
CABOCHON
outline. They may also occur with
a fibrous habit, and show a cat’s- rubellite
eye when cut en cabochon. crystals 9
¢ OCCURRENCE Russian pink rock
and red tourmaline occurs in crystal e
weathered granites. Other sites
include Madagascar, the USA,
Brazil, Myanmar, and East Africa.
e REMARK The specific gravity
of tourmaline varies with color —
dark red has a higher SG than pink.

RECTANGULAR STEP CUT

\ RUBELLITE CRYSTALS
Pendeloque Step Cabochon IN MATRIX

Crystal structure : Composition , ae Hardness ~,

. Trigonal e Complex borosilicate (EZ

INDICOLITE (TOURMALINE)
Dark blue tourmaline is called indicolite or, inky blue semt-
occasionally, indigolite. Indicolite is often translucent
heat treated to lighten its color and stone: ©
produce a more attractive stone.
¢ OCCURRENCE An important source
for indicolite is Siberia (Russia), where greenish blue
it occurs in yellow clays formed from transparent stone
weathered granites. Fine, bright blue trom Brazl @ OvAL MIXED CUT
tourmaline has recently been found
in Paraiba, Brazil. Other localities fractured
include Madagascar and the USA. vertical e surface
¢ REMARK A lilac to violet blue striations e

or reddish blue variety (first found

in Russia) is known as siberite.

RECTANGULAR STEP CUT

102 eCUT STONES

Crystal structure Ty sonal Composition Complex borosilicate

DRAVITE (TOURMALINE) ne Say

‘i. os iy golden brown
Dravite is a very dark-colored (usually: brown) va e
e color
form of tourmaline, rich in magnesium. It is
possible to lighten the color by heat treatment.
Dravite shows strong dichroism and should
therefore be cut with the table facet parallel
to the length of the crystal, in order to show © stones may
a lighter and more attractive color. be lightened
by heat
¢ OCCURRENCE Dravite can occur
treatment
as single crystals or as parallel or orange-
radiating groups. Brown tourmaline brown ROUND BRILLIANT CUT
and yellow tourmaline occur together color » la
in the gem gravels of Sri Lanka. It prismanc
is also found in the USA, Canada, habit ¢
Mexico, Brazil, and Australia.
¢ REMARK The name
“dravite” is derived from the
district of Drave, in Austria. opaque,
dark
brown
crystal

CUSHION MIXED CUT CRYSTAL

Brilliant Cushion FRAGMENT

ACHROITE (TOURMALINE) he e se
colorless stone e
‘This particularly rare, colorless stone is a
variety of elbaite, a member of the tourmaline
group. It does not show the strong dichroism girdle around
characteristic of most tourmaline varieties “watst” ofstone
and therefore can be cut with the table facet
either parallel or perpendicular to the length
of the crystal. Colorless tourmaline may
also be produced by applying heat to
light pink tourmalines.
¢ OCCURRENCE Achroite occurs
with colored tourmalines in the
pegmatites of Madagascar and in fracture 1s
the USA (Pala, California). conchoidal °
¢ REMARK Achroite is named after
the Greek word achroos, meaning
“without color.”

Brilliant Brilliant
 CUT SHONES © 103

Crystal structure Trigonal Composition Complex borosilicate Hardness 7,

WATERMELON TOURMALINE
green and pink
‘Tourmaline crystals with a pink center and a
parts occur in
green rim, or vice versa, are called watermelon
single crystal
tourmaline, because their coloring is similar to
the pink flesh and green rind of awatermelon.
Many other tourmalines are made up of two or characteristic
more colors, individual crystals containing up color zoning @
to 15 different colors or shades.
¢ OCCURRENCE Watermelon tourmaline
is found in South Africa, Brazil, East Africa,
and in many other localities.
¢ REMARK Parti- and multicolored
tourmaline is carved
orcutand polished = ane TABLE CUT
to show off the a aye
different colors to CRYSTAL
best effect. Baguette Cabochon SECTION

~| ScHORL (TOURMALINE) - =< aw

Schorl is the black, iron-rich form of tourmaline “oS
and is very common. ‘The opaque, prismatic
crystals may be several yards in length.
¢ OCCURRENCE Found in pegmatites.
) ¢ REMARK During the Victorian era in Britain, é vertical
) black tourmaline was ii —— striations
widely used for )
| mourning jewelry,
| but today it has
little, if any, value
as a gemstone.

7 semt-
GREEN AND YELLOW
transparent

TOURMALINE , i be gine
Yellow-green is the most common of all
greenish
tourmaline color varieties, but emerald green is yellow 1s
much rarer and more valuable. Indeed, until the most
18th century it was often confused with emerald. common
¢ OCCURRENCE Emerald color
green stones are found in © variety
Brazil, ‘Tanzania, and
Namibia; fibrous yellow
material occurs in Sri Lanka.
Brilliant
104¢CUT STONES

rystal structure ; Composition _, ; Hardness a, .

Crystal st Orthorhombic P Calcium carbonate

ARAGONITE layering revealed

in cut and polished
Aragonite is usually transparent or —e section
translucent and colorless or white
when pure. Impurities may cause
shades of yellow, blue, pink, or green
to occur. It is found in many different crystals growing
habits: small, elongate, prismatic e out of matrix
crystals form in radiating groups, and
concretions and stalactites are also
common. It has poor cleavage. STALACTITIC r)
¢ OCCURRENCE Found mainly in 7 ee
sedimentary environments, aragonite ¢ \
may form as tufa (porous rock) in
= ; : crystals
Czechoslovakia and ‘Turkey. Other -
eae ts : colorless
localities include = ‘
Spain F . when
Spain, France, the pure e .
USA (Colorado),
and Cumbria aa CRYSTAL SPRAYS
(England). Bead Polished ON MATRIX

$8 7.94 153-168 | R 0.155

Cela Suyoue Orthorhombic SomineS Hon Barium sulfate

BARITE stones are

Barite occurs in a variety of colors, faceted for
including colorless, white, yellow, and collectors
only
blue, but its softness, perfect cleavage,
brittleness, and high density make it of
little use as a gemstone, and it is cut for
collectors only. Crystals vary a great deal
and may be transparent to opaque, with a tabular,
variety of habits from tabular to massive. double-ended
¢ OCCURRENCE Barite is OCTAGONAL MIXED CUT
; 9 crystal
)

commonly found in lead and

silver mines. It also occurs crystal layers build
in limestones, and may be in concentric bands
deposited by hot springs. as stalagmite
Crystals up to 40 in (1 m) in e forms
length have been found in
Cumbria, Cornwall, and
Derbyshire, in England.
Other good localities
include Czechoslovakia,
SONS aTe
Romania, Germany, the easily
USA, and Italy. damaged
STALAGMITE SECTION

Polished
 CUT STONES « 105

Crystal structure (+h orhombic

CELESTINE colorless
celestine 1s the
Celestine is usually found as colorless, milky most common
white, yellow, orange, or pale blue prismatic © variety
crystals, or in fine-grained masses. With a hard-
ness of only 3% on the Mohs scale and perfect
cleavage, celestine is extremely fragile. It has
been cut for the collector, however, and some cut stones
fine specimens can be seen in museums. are rare and
© OCCURRENCE Celestine may © /ack fire
occur with sandstones or limestones, wEN
in evaporite deposits, in pegmatites,
sulfur
in cavities in volcanic rocks, or with MIXED CUT matrix e
galena and sphalerite in mineral
veins. Most of the material that is transparent to
capable of being faceted is found semitranslucent
in either Namibia or Madagascar. colorless
It is also found in Italy (including e crystal
Sicily), England, Czechoslovakia,
the USA, and Canada.
colorless
celestine
CTYS tals e

(CCELESTINE
Brilliant
CRYSTAL CRYSTALS IN MATRIX <=

Nie2163 | oot

CERUSSITE @ very pale

gray color
Cerussite is usually colorless, but white,
gray, and black specimens have been worn facet edges
found. Its two most distinctive features © due to softness
are its high density and its adamantine
luster. Crystals have a stubby tabular or
elongate habit. Cerussite is attractive,
but it is too soft to have much value as a
gemstone and is cut for collectors only.
® OCCURRENCE Cerussite is usually
found around lead ores. Large, clear, trans-
parent, colorless, cuttable crystals have been
found in Isumeb (Namibia). Other localities RouND BRILLIANT CUT ‘, i
include Austria, Australia, Czechoslovakia,
the USA, Germany, Scotland, and Italy, colorless,
including Sardinia. crystal “twin” e
¢ REMARK Sometimes
confused with diamond
and other colorless gems,
it may be distinguishable
by its higher density.
Brilliant Brilliant PRISMATIC CRYSTAL
EL
I
aLE
A
A
106 ¢ CUT STONES

Crystal structure Orthorhombic |COMPOSitON Aluminum fl uorohydroxysilicate

TOPAZ
pale
‘Vopaz occurs in a range of different colors:
yellow
deep golden yellow topaz (sometimes called
© 10paz
sherry topaz) and pink topaz are the most
valuable; blue and green stones are also
popular. Natural pink stones are rare — most
pink topaz is heat treated yellow material.
Much colorless topaz is irradiated and heat
treated to a range of blues, some almost
indistinguishable from aquamarine when
seen with the naked eye. Some topaz has
tear-shaped cavities, containing a gas bubble —@ stones up to
or several immiscible (nonmixing) liquids. os 35,000 carats
Other inclusions such as cracks, streaks, and | have been
veils also occur. Prismatic topaz crystals have OvAL MIXED CUT faceted |
a characteristic lozenge-shaped cross section 1

and striations parallel to their length. Topaz pink color

has one perfect cleavage. eee
¢ OCCURRENCE Topaz occurs in
igneous rocks such as pegmatites, granites,
and volcanic lavas. It may also be found in set in gold
and worn
alluvial deposits as waterworn pebbles. around the neck, topax
Localities include Brazil, the USA, Sri is reputedto dispel bad
Lanka, Myanmar, the former USSR, omens, heal poor vision,
Australia, Tasmania, Pakistan, Mexico, and calm anger
Japan, and Africa. Brazil, Pakistan, and
Russia are sources of pink topaz. characteristic
¢ REMARK In the 17th century the wedge-shaped
Braganza diamond (1,640 carats) in the ends
Portuguese crown was thought to be the
largest diamond ever found. This was never
confirmed, and it is now believed to have
been a colorless topaz. The name “topaz” is
thought to be derived from the Sanskrit
word /apas, meaning fire. OVAL STEP CUT

TOPAZ RING
A salmon
pink, step-
cut, eight-
sided topaz,
setina
gold ring.

FLOWER BROOCH
The heart of this flower-
shaped brooch is a round,
brilliant-cut topaz, surrounded
by 36 sherry-colored topaz
TRANSPARENT
gems — some triangular, some
diamond-shaped. SHERRY-COLORED CRYSTAL
aD GUT STONES ¢ 107

very pale stones are

4 grayish green typically
color transparent

——e 21,005-
carat
stone, once
the largest
gem ever
faceted

<a SQUARE CUSHION CUT

— ; (“THE BRAZILIAN PRINCESS’’)

ELONGATED OVAL MIXED CUT

pale green
blue topaz 1s
P topaz crystal e-
also popular

-____@ blue topaz

may be
produced by
heat treating
colorless
SEONES Topaz CRYSTAL
IN MATRIX
|
© pegmatite
rock

stone 1s partially
cut before being
heat treated to
OCTAGONAL STEP CUT e turn it blue
characteristic
tear-shaped
inclusions e-
|

Cushion Pendeloque

PENDELOQUE CUT

COLORLESS, PARTIALLY
FACETED PEBBLE
108 e CUT STONES

Crystal structure Orrhorhombic |S°™PSINON Beryilium aluminum oxide Hardness g1/,

(CCHRYSOBERYL lransparent
Chrysoberyl occurs in a range of colors, from @ stone

green, greenish yellow, and yellow to brown. It

is a hard, durable stone, particularly suitable for
use in jewelry. When cut well, gems are brilliant
but lack fire. ‘Two varieties, alexandrite and
cat’s-eye, have unique qualities of their own. —e dark
The very rare and valuable alexandrite changes greenish
brown color S
from green in daylight to red, mauve, or brown
under incandescent light. Synthetic chrysobery],
synthetic corundum, and synthetic spinel have (CUSHION MIXED CUT
all been produced to imitate alexandrite’s color
change. Cat’s-eye, when cut en cabochon, has a
near-white line across a yellowish gray stone,
due to canal- or featherlike fluid inclusions, or golden brown e—
needlelike inclusions of rutile. The most highly color is highly
prized cat’s-eye color is a light golden brown, prized
often with a shadow that gives a light and dark,
“milk and honey” effect. Yellow chrysobery]l,
popular in Portuguese jewelry of the 18th and
19th centuries, was also known as chrysolite.
cut stones are
© OCCURRENCE Although most has been brilliant but
mined out, the best chrysoberyl, including may lack fire e
alexandrite, has been found in mica schists in
the Urals (Russia). The largest faceted
chrysoberyl from Russia weighs 66 carats. Large greenish yellow
waterworn pebbles of various colors are found in cabochon shows CUSHION MIXED CUT
the gem gravels of Sri Lanka. Chrysobery] also faint cat’s-eye e
occurs in Myanmar, Brazil, Zimbabwe,
Tanzania, and Madagascar. Cat’s-eye is cat’s-eye chrysoberyl
found in Sri Lanka, Brazil, and China. has also been known
e REMARK The name chrysobery] is as cymophane
from the Greek chrysos, meaning
golden, and dery//os, which refers to
the beryllium content. Known for
thousands of years in Asia, it was typical wedge-
highly valued for the protection it e shaped ends
afforded from the “evil eye.”
POLISHED CABOCHON

FINGER RING
This very large ring,
made of many cushion-
cut chrysoberyl stones greenish
in a gold setting, is yellow
most probably of 18th- twinned
century Spanish origin. crystals e—
The chrysoberyl was
collected from a vein
running through chalk.
SPRAY OF
CCHRYSOBERYL
CRYSTALS
 CUT STONES € 109
————eeEeEeEeEeEeEeEeEeEeEeEeEeEeEeEeeeeee_eess
eaeeeeee eee

alexandrite
stones show a alexandrite was found on the
color change in birthday of Tsar Alexander II
—e incandescent light and named after him e

e golden
brown
changes
to red

ALEXANDRITE MIXED CUT

only chrysobery! cat’s- J

eve may be termed ALEXANDRITE CRYSTALS
simply “cat’s-eye” ¢ © intergrown
crystals
o ee blue
é: dark brown
jiash in stone with
catat’s-eye
s-e) e orange and WyY
e red tinges

cat’s-
eye

effect

CAT’S-EYE DOUBLE
CABOCHON
CAT’S-EYE CABOCHON
CHRYSOBERYL CROSS
A cross made up of 11
minute, tubelike specimens of yellow-green
inclusions produce chrysoberyl, each cut as a
chatoyancy e double cabochon to show O Re
the cat’s-eye effect. ‘The
stones are arranged so that
flashes across the centers
CAT’S-EYE DOUBLE of the cabochons are in
CABOCHON a variety of positions.

VICTORIAN BROOCH
‘This exquisite brooch
from the Victorian era in
Britain is made up of
/ Brilliant
greenish yellow, faceted
chrysoberyls set in gold
filigree. Its hardness and
[sa \ durability make chryso-
— beryl a particularly good
Cabochon stone for use in jewelry.
110e CUT STONES

Crystal structure (rthorhombic Composition Ajuminum silicate Hardness 71,

ANDALUSITE
Andalusite varies in color from a pale yellowish —e pleochroism
brown to a dark bottle green, dark brown, or creates flashes
the most popular greenish red. It has strong of yellow,
and distinctive pleochroism, so that, when green, and red
turned, the same stone may appear yellow,
green, and red. Large crystals may be vertically
striated prisms with a square cross section and
pyramidal ends, but these are rare. More usual
are opaque, rodlike aggregates of crystals
OCTAGONAL STEP CUT
or waterworn pebbles. It is the pebbles
that are usually cut as gemstones. “cross”
¢ OCCURRENCE Andalusite - once used opaque crystals
is usually found in pegmatites. ; as religious with rhombic
Pebbles occur in the gem gravels © symbol CrOSS SCCliOn
of Sri Lanka and Brazil. Other
localities include Spain,
Canada, Russia, Australia,
and the USA.
e REMARK An opaque,
yellowish gray variety,
chiastolite, occurs as long
prisms, which make a cross
when cut and polished.
pol: ished
surface
CHIASTOLITE
Cross SECTION
ANDALUSITE
Brilliant Baguette CRYSTALS IN MATRIX

Crystal structure Orrhorhombic |C°MP°S'tON Calcium borosilicate Hardness 7

stone from ube
; characteristic
DANBURITE Myanmar has
slight yellowish
stones
re
are wedge-shaped
: , ie bright b
Generally colorless, danburite crystals tinge @ ee but end
e lack fire
may also be yellow or pink. They form
wedge-shaped prisms, similar to those
of colorless topaz but may be distin-
guished by their cleavage (poor in
danburite, perfect in topaz) and
specific gravity (lower in danburite).
¢ OCCURRENCE First found in the
town of Danbury, Connecticut. Gem-
quality crystals occur in Myanmar,
Mexico, Switzerland, Italy, and Japan. “ F |
“ ;
# hae re ( ]

BRILLIANT CUT 2 iv |

WHITE DANBURITE
CRYSTALS
 CUT STONES « 111

Crystal structure Or thorhombic |©C°™P°S'#O" Magnesium iron silicate Hardness 51

3 ie famil double
nstatite is one of the pyroxene family —a ee
series of magnesium- to iron-rich silicates. shows cat’s-
Crystals occur as short prisms, but are rare: eye effect e—
most gem-quality material is faceted from
rolled pebbles. Cuttable enstatite varies in
color from a gray- to yellowish green or olive
green, to an iron-rich brownish green. A
brilliant emerald green variety, colored
by chromium, also occurs.
CAT’S-EYE CABOCHON
¢ OCCURRENCE Enstatite is
often found with kimberlites in
~e clear, yellowish
South Africa. Brownish green
green stone from
: enstatite is found in Myanmar, South Africa
|| Norway, and the USA (California).
| Some Sri Lankan and Indian enstatite
OvAL MIXED CUT uneven
is chatoyant. It also occurs in the USA, fracture e
Switzerland, Greenland, Scotland,
Japan, and the former USSR. Massive,
fibrous
material ee

[ i \ ENSTATITE
Cabochon ROUGH

| 3.27 Mic6-1.67 [PRo.10

Crystal structure Orthorhombic |COMPSON Aluminum silicate Relea (7

| SILLIMANITE e pale violet

stone from
Sillimanite (named after Professor Silliman of Myanmar
Yale University) is blue to green with distinct
pleochroism showing pale yellowish green,
dark green, and blue from different angles. @ Sl 4SSOTS-
When crystals occur in long slender prisms in cut Crown
parallel groups, resembling fibers, the facets
material is often called fibrolite.
| ® OCCURRENCE Sillimanite is long, slender
_| found in metamorphic rocks and perpendicular |CUSHION MIXED Cut e crystals
occasionally in pegmatites. Blue fibers ¢
and violet stones are found in
Myanmar; greenish gray stones
in Sri Lanka; fibrolite in the
USA (Idaho). Other sites are
Czechoslovakia, India, Italy,
Germany, and Brazil.

FIBROLITE
LABOCHON
SILLIMANITE
CRYSTALS IN MATRIX
112 CUT STONES
Crystal structure Qrthorhombic | COMPOSttON Tron magnesium silicate Marchese 517

HYPERSTHENE
colors range
Hypersthene is an iron-rich pyroxene in from green to
the same series of minerals as enstatite (see grayish black
p.111) and bronzite. It is distinguished by its —e and brown
reddish iridescence, which is due to platy
inclusions of goethite and hematite. Often
too dark to facet, it may be cut en cabochon
instead to show the sparkling inclusions.
Bronzite, a greenish brown variety with a opaque crystal
bronzelike luster, is also a collector’s RECTANGULAR STEP CUT
fragment e
stone — dark, slightly brittle, and brassy |
not generally used in jewelry. effect platy inclusions
© OCCURRENCE Most gem e visible '

hypersthene is found in India,

Norway, Greenland, Germany,
and the USA. Bronzite is
found in Austria.

POLISHED BRONZITE

Cushion Baguette HYPERSTHENE ROUGH

Crystal structure Orrhorhombic | COMPOSitION \facnesium aluminum silicate

——
e

IOLITE rich ee. more

r. ie ee wiolet- intense
Violet-blue iolite (also known as cordierite) blue dolor
has been called water sapphire because of its tinge @ aicibie
similarity to blue sapphire when cut. It can from
be recognized by its strong pleochroism, front
visible without equipment, which gives
the gem its other name of dichroite. The — pa/er color
best blue color is seen down the length visible from
of prismatic crystals; they may appear this angle @
colorless when viewed across. lOLITE CUBE ~ VIEW 1
¢ OCCURRENCE Gem-quality ste” ti TS purplish
iolite is found in alluvial deposits PS re blue crystal
as small, transparent, waterworn |
pebbles in Sri Lanka, Myanmar,
Madagascar, and India. Other
localities include Namibia and
‘Tanzania. Crystals are found in
Germany, Norway, and Finland.

—;

AAS
\\
F

\
I
~~
 CUT STONES 113

Crystal structure thorhombic |COMPSON Magnesium aluminum borosilicate pales Gy,

KORNERUPINE Histinctive
Although kornerupine was named in 1884, grayish green
it was not until 1912 that gem-quality color e
material was found. Even now tt 1s
uncommon and cut only for collectors.
Strongly pleochroic, it appears green
or reddish brown when viewed from
different directions. ‘lo show the best
color, it is cut with the table facet
parallel to the length of the crystal. RECTANGULAR STEP CUT
e OCCURRENCE Localities ‘
include Madagascar, Sri Lanka, , ee kornerupine
and East Africa, which also pro- - =.gems are rare dark
duces an emerald green variety. and prized by kornerupine
Cat’s-eye gems are cut from Sri ‘eS 3 collectors 9 crystals
Lankan and East African stones. fans 4
e REMARK It has been confused
with tourmaline and enstatite.
MIXED CUT

CRYSTALS
IN MATRIX

Crystal structure Qrehorhombic |COMPSON \Maenesium iron silicate reraness Gy,

PERIDOT
@ 2reen
Gem-quality specimens of the mineral olivine color due
are called peridot by gemologists. Peridot has fo 1ron
an olive- or bottle green color that is due to the
presence of iron, and a distinctive oily or greasy
luster. It has a high birefraction, so doubling
of the back facets can easily be seen in larger
distinctive bottle
specimens when viewed from the front.
green color e
Good-quality crystals are very rare.
® OCCURRENCE Sources of peridot include
OVAL MIXED CUT
St. John’s Island (Egypt), China, Myanmar,
Brazil, Norway, the USA (Arizona and : peridot was
Hawaii), Australia, and South Africa. y often used
¢ REMARK The Crusaders brought Bis in religious
peridot to Europe in the Middle —0 jewelry
Ages from St. John’s Island in the
Red Sea, where it had been mined
for over 3,500 years.

OCTAGONAL MIXED CUT

©)
Pendeloque CRYSTAL FRAGMENT
114-CUT STONES

Crystal structure Orthorhombic |COMPOSitiON |ead sulfate

ANGLESITE © stones often

have a slight
Anglesite is usually colorless or with a yellowish tinge
slight yellowish tinge but may also be
found as gray, green, purple, brown, or wansparent
black crystals (the black coloring is anglesite ;
due to inclusions of galena). Crystals crystal with
are heavy but as they are fragile and pointed end
soft, with perfect cleavage, they
are faceted for collectors only.
¢ OCCURRENCE Anglesite is
formed by oxidation of galena (lead
sulfide) and may be found in Anglesey
in Wales (hence the name) and in the
Leadhills district of Scotland. The
best crystals are found in
‘Tsumeb (Namibia) and
Morocco. Other localities
include Germany, the
USA, and Sardinia.

SINHALITE P a pale yellowish

Until 1952, sinhalite was thought to be a brown stone
brown variety of peridot, but on closer
investigation it was found to be a completely
new mineral. It varies from a pale yellowish
brown to a dark greenish brown. Crystals have 9G é ;
distinct pleochroism, showing pale brown, ) i Pe a slightly
greenish brown, and dark brown when 4“ - bs irregular
viewed from different directions. : , 7 £0 conserve
Occasionally, sinhalite has been faceted for — ee weight
the collector. Cut stones may be confused
with peridot, chrysoberyl, and zircon. CUSHION MIXED CUT double-ended,
¢ OCCURRENCE Most gem-quality waterworn
sinhalite is found as rolled pebbles Bane ¢ prism
in the gem gravels of Sri Lanka. oa 22 yellow- |
Crystals occur in Myanmar but — brown
are rare. Sinhalite is also found in |
the former USSR, and non-gem-
quality material in the USA.
¢ REMARK Sinhalite is named
after sinhala, which is the
Sanskrit name for Sri Lanka.

CUSHION MIXED CUT

SINHALITE CRYSTAL
 CUT STONES e« 115

Crystal structure Orthorhombic Composition Beryllium hydroxyborate Hardness ‘DA

HAMBERGITE ee e
stones for
Hambergite, named after Axel Hamberg, faceting
the Swedish mineralogist, occurs as color- are rare
less to yellowish white crystals, but it is
rare at gem quality. Brittle, with perfect
cleavage, it is very fragile and suitable
only for collectors. When cut, it looks
like glass, but double images of
the back facets may be seen
through the table facet due _
to its high birefraction. OVAL MIXED CUT deep striations
¢ OCCURRENCE Gem- surface coloring along length
quality hambergite is found from host rock
in Kashmir (India), and also
in Madagascar.
brown
mineral
inclusions

OVAL MixED Cur HAMBERGITE

CRYSTAL

PREHNITE stones are generally

translucent
Often an oily green, prehnite may BRILLIANT-CUT
also range from pale yellowish to STONES
brown. Columnar or tabular crystals
are rare: it occurs more usually as
aggregates of barrel-shaped crystals faceted
or as botryoidal masses. Some pale BOUES CTE:
yellowish brown prehnite is fibrous usually
enough to be cut en cabochon and may small
show the cat’s-eye effect.
¢ OCCURRENCE Prehnite is found STEP CUT
in basaltic volcanic rocks, in intrusive isienx2 Franslirsineriale
igneous rocks, and in some meta- cin veddish
bs in onaaal
morphic rocks. Pale green masses masses
inclusions
are found in Scotland; dark green or Cee
greenish brown masses in Australia;
aggregates of crystals in France.
¢ REMARK Prehnite is named after
Colonel von Prehn, who first
introduced prehnite to Europe.

ho» POLISHED FRAGMENT

Cabochon CRYSTALS ON MATRIX
116 e CUT STONES
Crystal structure Orthorhombic Composition ( Hardness 6Y,
Jalcium aluminum hydroxysilicate
| |

ZOISITE stone has been

heat treated
Zoisite occurs in a number of varieties, the
to enhance
most sought after being tanzanite, a variety
e color
colored sapphire blue by the presence of
vanadium. Tanzanite crystals have distinct
pleochroism, showing either purple, blue, or
slate gray, depending on the angle they are —e color varies
viewed from. There may also be a slight color from purple to
change in incandescent light, when stones may blue due to
appear more violet. A massive green variety of pleochroism
zoisite, containing rubies and occasionally dark
hornblende inclusions, may be polished, carved,
ale '
or tumbled to make ornaments or an attractive Nhe
decorative stone. Thulite, a massive, pinkish 2 '
;
red variety colored by manganese, is also stones
Stone: are o—*— Gap & violet
oe \|
lished arved al all :
polished or carved to make small ornaments. soft
Aritthand colo
brittle
‘Tanzanite has been confused with sapphire, and
thulite with rhodonite. Some heating of zoisite
varieties may enhance their color.
© OCCURRENCE Tanzanite was first found
in Tanzania (hence the name). Yellow and TANZANITE STEP CUT
green zoisite occurs in ‘Tanzania and
Kenya. Thulite is found in Norway, —+___ fanzanite
Austria, western Australia, Italy, and in has perfect violet-blue
the USA (North Carolina). cleavage ee |
¢ REMARK Discovered by Baron von 9 crysta
Zois in the Sau-Alp mountains of
Austria, zoisite
Austria, Zoisite called saualpite.
wa firstt calle
was p Any ai 7
Can ee

ieMe RE#
et © polished pinkish red color
ae: zolsite 1s often e due to manganese
used for
decorative :
work

TANZANITE CRYSTAL
IN MATRIX

MASSIVE
habit e

THULITE CABOCHON

intergrown
grayish white
quarts e

Step Cabochon Cameo THULITE ROUGH

: 7
, :
/

i
 CUT STONES « 117

Crystal structure rthorhombic |COMP°S'tOn Aluminum iron hydroxysilicate

STAUROLITE cross shape formed by

Wore beck
Opaque, cross-shaped staurolite “twins” staurolite
twinned crystals
e crystals
are used in jewelry more often than
the transparent stones, which are
rare and cut only for collectors.
opaque aed
“Cross stones,” as twins are called,
—e stone
have been used as amulets and in
religious jewelry. Crystals are
reddish brown to black, with
distinct pleochroism.
¢ OCCURRENCE Staurolite
occurs in Switzerland, Germany,
the former USSR, the USA, Brazil,
France, and Scotland.
Cross STONE

cy CRYSTALS
Baguette Step Cameo IN MATRIX

Crystal structure Qrthorhombic | C°MP°S'ON Aluminum iron borosilicate

DUMORTIERITE
Dumorttierite is best known in its massive surface may
form, which makes an attractive violet become pitted
and blue decorative stone when polished. e when polished
Reddish brown and red varieties also
occur. Prismatic crystals larger than %s 1n
(1 mm) are very rare. Dumortierite distinctive deep
is also found intergrown with rock blue color e
crystal (colorless quartz) and is DUMORTIERITE
then called dumortierite quartz. QUARTZ CABOCHON
This material is usually cut ev
cabochon or polished to make CARVED BOTTLE
decorative stones. Hard but attractive,
¢ OCCURRENCE Most gem- dumortierite is often
quality material is found in polished and carved
Nevada. Other localities to make decorative
include France, Madagascar, objects, like this
Norway, Sri Lanka, Canada, bottle adorned with
Poland, Namibia, and Italy. the image of a bird.
* REMARK Dumortierite
was named after the French
splintery
scientist M.E. Dumortier.
surface e

S MASSIVE
Cabochon Cameo Polished DUMORTIERITE
118 e CUT STONES
fay bie
Crystal structure Monoclinic iti Sodium
Composition : :
beryllium phosphate Hardness 5%

BERYLLONITE crystals
Beryllonite crystals are colorless, white, are usually |
or pale yellow, but its weak fire and low colorless
dispersion make it a dull gemstone. In
addition, its softness, perfect cleavage, and weak fire and
brittle fracture make it fragile, although with | low dispersion
care it may be faceted for collectors. mean gems
¢ OCCURRENCE Beryllonite is a pegmatite -© appear dull
mineral found associated with the minerals
phenakite and berylin in Maine. It is also
age cleavage
found in Finland and Zimbabwe but CUSHION MIXED CUT pes
remains a rare gem. visible
¢ REMARK Beryllonite is named stones are soft
after the beryllium content in its and easily
chemical composition. It has been damaged
confused with other colorless
gemstones of low dispersion.

CUSHION MIXED CUT \

Brilliant Cushion Pendeloque BERYLLONITE CRYSTAL ap ==

Se ——_

BRAZILIANITE distinctive
Brazilianite is a rare and unusual gemstone. Cut greenish
yellow color
for collectors only, its yellow or yellowish green
color is nonetheless striking. Crystals are
fragile and brittle, with conchoidal fracture and
perfect cleavage perpendicular to their length.
¢ OCCURRENCE The main localities are
in Brazil, where crystals up to 6 in (15 cm)
have been found. Smaller crystals have
been mined in New Hampshire. stones apatite
@ REMARK Found in Minas Gerais chip and crystals
in Brazil in 1944, brazilianite was first flaw easily
thought to be chrysoberyl, but closer
examination revealed it to be a iy
completely new mineral. It was named __
mn bra xih ani te
after the country in which it was found crystals
a“
_
but has since been confused with in
=

chrysoberyl, beryl, and topaz.

Ll
STEP CUT

Cushion Pendeloque Baguette GROUP OF CRYSTALS

 CUT STONES «© 1:19

Crystal structure 4 onoclinic Composition Caicium magnesium silicate paenes> 57

DIOPSIDE
flaws are
Crystals of diopside may be colorless but
due to chrome diopside
are more usually bottle green, brownish
diopside’s variety is bright
green, or light green. The more iron-rich and fragility
magnesium-poor they are, the darker the color emerald green
— almost to black. Very bright green diopside,
colored by chromium, is known as chrome
diopside. Violet-blue crystals, colored by
manganese, have been found in Italy and the
USA, and may be called violane. It is polished
as beads when massive, cut for collectors when
transparent, and cut e” cabochon when fibrous.
¢ OCCURRENCE Gem-quality chrome
diopside is found in Myanmar, Siberia
(Russia), Pakistan, and South Africa. Other
diopside localities include Austria, Brazil,
Italy, the USA, Madagascar, Canada, and Sri
Lanka. Dark green to black diopside, which
shows a 4-rayed star when cut en cabochon, has
been found in southern India since 1964.
RECTANGULAR
STEP CUT

dark green
Ss) a ;
diopside crystals e
aa a hou
Sees | |
DIOPSIDE IN
Baguette Step Cabochon MATRIX

MEERSCHAUM BEAD NECKLACE

=: Se Ls Soft and light,
Meerschaum, also known as sepiolite, is a 9 <> »- meerschaum is easy
very fine-grained, soft, light rock. Found ) ( to carve into intricate
as Compact, opaque masses with an earthy a objects, such as the
or chalky appearance, it may be white or : individually worked
gray with a yellowish or reddish tinge. | "2 beads on this delicate
‘Turkish necklace.
Easily fashioned and often intricately
carved, meerschaum is still used in
Turkey for pipe bowls. With use, the dull, earthy
smoke changes the white stone to an ” luster
attractive yellow color. ,a :
® OCCURRENCE Today the most ~s ¥ .
important source is Eskischehir in Turkey. ie » ———
Other localities include Czechoslovakia, QI
Spain, Greece, and the USA.
© REMARK Light and light, porous,é’
porous enough to float \ creamy white

on water, meerschaum } meerscthaum e

derives its name from the 7
German for “sea foam. Bead MASSIVE ROUGH
“ + ”
120° CUT STONES

Crystal structure Monoclinic

Composition | ithium aluminum silicate Hardness 7

lilac-pink
SPODUMENE color due to
Spodumene occurs in a range of colors, e manganese
although the most common variety is
yellowish gray. ‘Iwo gem varieties — lilac-
Characteristic
pink kunzite (colored by manganese) and
bright emerald green hiddenite (colored
striations
parallel to
|
by chromium) — are very popular with length |
collectors, although perfect cleavage
makes them fragile gemstones. Strong
pleochroism is easily seen in gem
material, showing colorless and two
shades of the body color when viewed
from different directions. Stones should
always be cut to show the best color
through the table facet. ‘The pink
color may fade with time, but some CUSHION-CUT
material is irradiated to intensify it. KUNZITE
¢ OCCURRENCE Spodumene was
discovered in 1877 in Brazil, although it was
not until 1879 that kunzite and hiddenite
were recognized as different varieties
of the same mineral. Spodumene is
also found in Madagascar, Myanmar,
the USA, Canada, the former USSR,
Mexico, and Sweden.
¢ REMARK Lilac-pink kunzite is
named after the gemologist G.F.
Kunz, who first described it in
1902; hiddenite is named
after W.E. Hidden, who 4,4 pale e
discovered it in North green color
OCTAGONAL STEP CUT
Carolina in 1879.
KUNZITE CRYSTAL
emerald green
closeup of
color e hiddenite
crystals e
© fragments
display different
colors because of
pleochroism

STEP-CUT
HIDDENITE

HIDDENITE CRYSTAL
FRAGMENTS
gneiss
matrix

HIDDENITE
CRYSTALS IN
Brilliant Pendeloque Step MATRIX
 CWT STONES’ 124

Crystal structure Monoclinic Composition C Hardness 6Y%

alcium aluminum iron hydroxysilicate

EPIDOTE
This fairly dense, fragile mineral has
distinct cleavage and is rarely cut as a 2 aw) @ sfoneS ATC
gemstone. Crystals are yellow, green, or ve" fragile and
dark brown columnar prisms, with faces easily flawed
finely striated parallel to the crystal’s
length. Pleochroism ts strong, dark brown
showing either yellow, green, or colo r e M I X E D C u 1 columnar
brown. Rock made up mainly of epidote
epidote may be polished or e crystals
tumbled and sold as “unakite.”
¢ OCCURRENCE Dark green
crystals occur in the Austrian parallel e
and French Alps. Epidote is also striations
found in the former USSR,
Italy, the island of Elba (Italy),
Mozambique, and Mexico.

EPIDOTE
RECTANGULAR CRYSTALS
Be TABLE CUT
Cushion Step
IN MATRIX

Crystal structure \agnoclinic Composition Oajcium titanium silicate

TITANITE
doubling of e
Titanite, also known as sphene, is known back facets
for its very strong fire (its dispersion 1s due to high a
higher than that of diamond) and rich colors, hirefraction
. p .
© High7;

but it is seldom used in jewelry because it dispersion

is too brittle and soft. Nevertheless, gives facets
transparent yellow, green, or brown gem- of varying
quality material is cut for collectors. colors
Titanite is strongly pleochroic (showing
three different colors) and has high CUSHION MIXED CUT
birefraction (seen as doubling of the twinned titanite
characteristic
back facets) and adamantine luster. 9 crystals
wedge-shaped
¢ OCCURRENCE Gem-quality ends @
titanite occurs in cavities in metamor-
phic rocks such as gneiss and schist
and also in granite. Locations include TITANITE RING
Austria, Canada, Switzerland, Faceted stones, like
this bright yellow
Madagascar, Mexico, and Brazil.
brilliant cut set in
gold, have high fire
and rich colors.

TITANITE CRYSTALS
Brilliant Baguette IN MATRIX

RI 1.84—2.03 DR 0.120 Luster 4 damantine

122 e CUT STONES

Crystal structure \4gnoclinic Composition porassium aluminum silicate Hardness ¢,

COLORLESS ORTHOCLASE colorless,

Orthoclase, an alkali feldspar, occurs in a range transparent
of colors, the most common being colorless. stone @
Adularia, a colorless, transparent variety from
Adular-Bergstock in Switzerland, has a bluish
white “schiller,” or sheen, called adularescence.
¢ OCCURRENCE Orthoclase feldspar occurs
in intrusive igneous rocks and is one of the main
constituents of granitic pegmatites. It is also internal cracks
found in metamorphic rocks such as schist and e orflaws
gneiss. Clear, colorless orthoclase occurs
in Madagascar. Yellow and colorless
cuttable material, cat’s-eyes, and some
star stones occur in the gem gravels of
Sri Lanka and Myanmar.
¢ REMARK Feldspars are the most white orthoclase
common rock-forming minerals at the crystals
Earth’s surface. They are divided into
two groups, the alkali feldspars and
the plagioclase feldspars (see p.130).
Orthoclase derives its name from the
Greek for “break
straight,” a
reference to
its perfect
cleavage at > ad
near 90 degrees. Brilliant Mixed ORTHOCLASE WITH QUARTZ

YELLOW ORTHOCLASE
‘The yellow variety of orthoclase feld- step cut 1s most
common, because
spar (see colorless orthoclase above) is
offragility of stone
usually faceted as a step cut because the
stones are often fragile. The yellow
color is due to the presence of iron. crystals may be
translucent to
Orthoclase crystals are columnar or
semitranslucent
tabular prisms, and are often twinned.
® OCCURRENCE The best yellow
orthoclase is found in Madagascar in
pegmatites, and may be faceted for
the collector. Yellow orthoclase from
Madagascar and Germany may be cut
en cabochon to show the cat’s--eye effect.
¢ REMARK Feldspars form in igneous
and metamorphic rocks.
Which type is formed
depends on the
temperature it forms
at and how it cools. CRYSTAL FRAGMENT
 CUT STONES « 123

MOONSTONE ( O R T H O C L A S E ) milky opalescence

on table facet
Moonstone is the opalescent variety of
orthoclase, with a blue or white sheen (or
“schiller”), rather like the shine of the
moon. This is caused by the reflection
of light from the internal structure,
made up of alternating layers of
albite and orthoclase feldspar. Thin
albite layers give an attractive blue;
while thicker layers produce a white CUSHION
“schiller.” Stones of large size and BRILLIANT CUT
fine quality are rare.
pitted surface
® OCCURRENCE The best material
has frosted glass
is from Myanmar and Sri Lanka. Other
appearance e
localities include India, Madagascar, BLUE MOon
Brazil, the USA, Mexico, Tanzania, The moonstone in this
and the European Alps. finely detailed cameo has
a distinct blue “schiller.”
Moon worshippers
through the ages have
used it in their jewelry.

WATERWORN PEBBLE

Crystal structure Triclinic Composition Potassium aluminum silicate

amazonite may be
MICROCLINE characteristic blue- confused with jade
A form of alkali feldspar, microcline may be green color e © or turquolse
colorless, white, yellow, pink, red, gray,
green, or blue-green. However, the semi- =
opaque, blue-green variety called amazonite 4

(named after the Amazon River) is most

commonly used in jewelry, and may be some surfaces
cut, usually en cabochon, up to almost have silky
any size. Its striking color is due to e /uster
the presence of lead.
@ OCCURRENCE The most
important source of amazonite is
India. Other localities include the AMAZONITE CABOCHON
USA, Canada, the former USSR,
Madagascar, Tanzania, and Namibia. polished surface —_blue, masstve
¢ REMARK Although microcline shows cleavage e material
has the same composition as ortho-
clase, its crystal structure is triclinic.
124° CUT STONES )

tal pigs iti Ser : sae

A li ci Monoclinic Pompasion Sodium aluminum silicate

J ADEITE (J ADE )
characteristic
For centuries, jade was thought to be a single black inclusions e emerald green
gemstone, but in 1863 two types were recog- e color —
nized: jadeite and nephrite. Nephrite (opposite)
is more common, but both are tough, fine-grained
rocks, suitable for carving. Jadeite, made up of
interlocking, granular pyroxene crystals, occurs
in a wide range of colors including green, lilac,
white, pink, brown, red, blue, black, orange, and
yellow. The most prized variety, imperial jade, is
a rich emerald green, due to chromium. Jadeite
commonly has a dimpled surface when polished.
¢ OCCURRENCE Jadeite is found in meta-
morphic rocks and as alluvial pebbles or boulders.
Some boulders develop a brown skin from
weathering, and this is often incorporated into
POLISHED IMPERIAL JADE
carvings and worked pieces. The most important
source of jade is Myanmar, which has supplied
China with translucent imperial jade for over
200 years. Historically, Guatemala was an
important source ofjade, providing the —/ MEXICAN MASK
material for the carvings of the Central a. This opaque, mottled
American Indians. Jadeite also occurs in = green mask was
Japan and the USA (California). carved in Mexico,
¢ REMARK The Spanish conquista- Oe ars. eee ee :
sea : er jadeite
dores adopted the use of jadeite when f= carvings have a
they invaded Central America, and k x. characteristic pitted
often wore amulets made from it. ; surface: modern
They called it predra de hijada (\oin it abrasives give a
stone) or piedra de los rinones (kidney ,. ~<a. smoother finish.
stone), believing it prevented or f
cured hip and kidney complaints.

massive habit e

mottled jadeite,
fashioned and
polished

violet color caused

by traces of iron e———
JADEITE SPHERE

Cameo Polished
 CUT STONES © 125

| structure = Composition : 5 : soe Hardness 6;

Elystal © ~ Monoclinic Calcium magnesium iron silicate

NEPHRITE (JADE) CHINESE

CARVING
Nephrite, recognized as a separate type of Nephrite jade has
jade since 1863 (see opposite), is found as been carved in
aggregates of fibrous amphibole crystals. China for centuries
These form an interlocking structure tougher and is tough enough
than steel, hence nephrite’s popularity as a to be worked into
intricate designs.
material for carving — first for weapons and
China ts still one of
later for ornaments. Colors vary from a dark the world’s main
green, iron-rich nephrite to a cream-colored, jade-cutting centers.
magnesium-rich variety. Nephrite jade may
be homogeneous 1n color, blotchy, or banded.
¢ OCCURRENCE Nephrite jade has been
carved by the Chinese for over 2,000 years,
though the raw material was probably first
imported from ‘[urkestan, Central Asia,
and later from Myanmar. Other localities
include Siberia (dark green rocks, often with
black spots), Russia (spinach-colored stones),
and China. Nephrite jade is also found in
various rocks in the North and South Islands
of New Zealand (pieces carved in the 17th
DAGGER HANDLE
century include Maori clubs called meres).
Because of its great
Other localities include Australia (black strength, nephrite has
nephrite), the USA, Canada, Mexico, Brazil, been used since prehistoric
‘Taiwan, Zimbabwe (dark green), Italy, times to make weapons.
Poland, Germany, and Switzerland. In fact, at one time it was
¢ REMARK Nephrite may be con- | known as “ax stone.”
fused with bowenite serpentine; it ~
may be imitated by composite
stones or dyed to improve color.

color may
_* be blotchy

ss FABERGE SNAIL
5 The greasy luster of nephrite jade
a A enhances this witty carving by the
: - famous Russian jeweler, Fabergé.
a tough,
interlocking
SITUCTUTE @
CHINESE CAMEL
The shape of the original boulder
has been integrated into the design
of this carving. Only one side of the
boulder has been fashioned.

NEPHRITE
Bead Cameo Polished BOULDER

cS)
Myor163 [P0027
126° CUT STONES

Crystal structure nf onoclinic Compesiten Copper hydroxycarbonate

MALACHITE common
Malachite is usually found in opaque @ concentric botryoidal
green to near- habit
green masses, its color derived from
black banding
copper. Crystals are too small for
faceting, but the massive material is
carved or polished in many ways to
reveal the alternating bands of light and
dark green. In the past, malachite was
worn to ward off danger and illness.
¢ OCCURRENCE Malachite occurs
in small quantities worldwide
and in larger quantities in y
eee,
copper-mining areas. Zaire is POLISHED
the most important producer. Cabochon MALACHITE

crystals are very

CHRYSOCOLLA small (micro-
brown
Chrysocolla usually occurs as a bright patches of ° crystalline)
green or bluish crust, or as compact, copper ore
grapelike groups. Crystals intergrown
with quartz or with opal are more
commonly used in jewelry.
¢ OCCURRENCE Copper-mining
areas, particularly Chile, the former
USSR, and Zaire. “Eilat PN
Stone” (intergrown with ¢
malachite and turquoise)
reputedly came from POLISHED
King Solomon’s mines. CHRYSOCOLLA

Crystal structure Monoclinic Composition Copper hydroxycarbonate Hardness 3Y,

dark blue |
AZURITE eS bands of azurite
? green malachite crystals
Azurite is an azure blue copper
mineral, occasionally found as —e polished
prismatic crystals (rarely faceted), stone
but more usually in massive form
intergrown with malachite.
¢ OCCURRENCE Found
particularly in copper-mining
areas such as Australia,
Chile, the former USSR,
Africa, and China. Stones
from Chessy, near Lyons in AZURITE _
France, are called chessylite. BANDED CRYSTALS green
Cameo CHESSYLITE ON MATRIX malachite

SG 377
 CUTSTONES © 127

Crystal structure 4 onoclinic Composition \faenesium hydroxysilicate

SERPENTINE i characteristic
y atches formed
‘The name serpentine refers to a group of r : p yan bie
predominantly green minerals that occur 1n :
masses of tiny intergrown crystals. ‘The two 2 : az partly
main types used in jewelry are bowenite . : 2: 7 83=s prans/ucent
(translucent green or blue-green) and the rarer ;
williamsite (translucent, oily green, veined or rock composed
spotted with inclusions). ‘They may be carved, of various
engraved, or polished. Various marbles serpentine
minerals
also contain serpentine veins.
¢ OCCURRENCE Bowenite |
is found in New Zealand, ye 8 So WILLIAMSITE
China, Afghanistan, South ME TO) 7 \. ‘ CABOCHON
Africa, and the USA; cae |
Williamsite occurs in Italy,
color due
England, and China. to thinness
of slice

SERPENTINITE
Cameo Polished ROCK

pale blue-green
PHOSPHOPHYLLITE color 1s most
‘This is one of the rarest of gem- e sought after
stones, and is highly prized by
collectors. The crystals, which are cuttable material
prismatic or with a thick, tabular mainly from
habit, range from colorless to Bohvia
deep bluish green, but the best
specimens are a very delicate
bluish green. Nevertheless,
phosphophyllite is rarely cut, RECTANGULAR STEP CUT
as the material is brittle and small
fragile, and large crystals are fragments can crystals
too valuable to be broken up. be faceted crack STEP CUT
® OCCURRENCE The easily
finest crystals, and the only phosphophyliite
ones to be faceted, are from e crystals
Bolivia. Other localities
include Germany and the
USA (New Hampshire).

PHOSPHOPHYLLITE CRYSTALS

PHOSPHOPHYLLITE
Brilliant CRYSTALS ON PYRITE
i238 *CUT STONES

Crystal structure \{onoclinic Composition \{aenesium aluminum hydroxyphosphate Hardness 51,

LAZULITE a blue and white

mottling
Crystals of lazulite are rare. Colors vary bipyramidal
from a mottled pale blue to dark blue. lazulite
‘Transparent stones are pleochroic, crystal @
showing blue and colorless, but often
lazulite is not transparent. Semi-
translucent or opaque stones, found
as small crystal fragments, may be
polished, carved, or tumbled to
make beads or decorative stones. POLISHED CABOCHON
¢ OCCURRENCE Localities
include the USA, Brazil, India, £
Sweden, Austria, Switzerland, [ LAZULITE
Madagascar, and Angola. Cabochon IN MATRIX

HOWLITE tained blue Uitte bowdery,

Howlite is a soft, light mineral with a chalky Pi LORE Vane Cees
white color, commonly with black or brown ; TORIES
veins. Crystals are occasionally found in
groups. It is very porous and may be dyed to
imitate other minerals, especially turquoise.
® OCCURRENCE Howlite has been
found in large quantities in the
USA (California). pe —
¢ REMARK Though it is f \ vilreous
soft, howlite will withstanda | luster
polish and is occasionally used
as a decorative stone.

G YPSUM parallel
cat’s-eye fibrous
Several varieties of gypsum are used as effect structure @
decorative stones. The most important,
alabaster, is found as fine-grained masses
in pastel shades but is commonly stained
in stronger colors. Selenite is colorless,
occasionally cut for collectors, but is
very soft. Satin spar is a fibrous variety,
polished or cut en cabochon. Rose shapes satin
(called “desert rose”) also occur. luster
¢ OCCURRENCE Localities a
include Italy and England 7 POLISHED
(alabaster); Italy, Mexico, the Kosa | SATIN SPAR
USA, and Chile (selenite). Cabochon SATIN SPAR ROUGH

Rly 52-1.53 PR 9.010 Luster Silky to vitreous

 GUT STONES 129

Crystal structure Monoclinic

Composition Calcium hydroxyborosilicate

D ATOLITE crystals are cut for colorless.

collectors only e with tinge
‘Transparent, colorless crystals of of yellow e—
datolite are cut for the collector only.
A tinge of yellow, green, or white may
also be present. More often, however,
datolite occurs as a massive material,
which may contain copper inclusions.
¢ OCCURRENCE Localites include
Austria, Italy, Norway, the USA,
Germany, and England. The
main source of massive
datolite with inclusions
OCTAGONAL
is the Lake Superior area
STEP CUT
of North America.

fine stones are

PETALITE e rare and fragile — fibrous, massive
ale ; material ¢
Fine petalite is rare and fragile. For |
this reason it is only occasionally
cut for the collector. Crystals are
transparent, colorless, or white,
occurring as tabular or columnar
prisms with a glassy appearance.
Massive petalite is more
common, cut en cabochon.
¢ OCCURRENCE Elba
(Italy), Brazil, Australia,
CUSHION MIXED CUT
Sweden, Finland, USA, Z
Zimbabwe, and Namibia. Cushion PETALITE ROUGH

EUCLAS
:
E a
black striat ed
mineral = Aci
Euclase is a rare gem. The most e inclusions ' pve
attractive color is a pale aquamarine
blue, but it also occurs in white, green,
and colorless forms. Crystals are
prismatic with a perfect cleavage,
which means they are fragile and must
be cut and handled with care.
© OCCURRENCE Euclase
occurs mainly in pegmatites.
Localities include Brazil, SQUARE STEP CUT
Tanzania, Zaire, Kenya,
conchoidal fracture e
the former USSR, India,
Zimbabwe, and the USA. PRISMATIC CRYSTAL

RI 4 65-1.67 DR 9 019 Luster Vitreous

130° CUT STONES
Crystal structure AeA ine Composition ,_ ,. ‘ : sae Hardness
y Triclinic P Sodium calcium aluminosilicate 6

ALBITE albite 1s
usually cream-colored,
Albite is one of six species in the plagio- © colorless e opaque crystals
clase feldspar series. Each species is
defined by its albite and anorthite content:
albite itself has the highest albite content.
It is usually white, though gems are often
colorless. Peristerite, an albite-oligoclase
mix, has a blue sheen, like moon-
stone (see p.123).
¢ OCCURRENCE
The best specimens MIXED CUT
of peristerite are
found in Canada. Brilliant Brilliant ALBITE CRYSTALS

AN 54-155 PR 0.009 Luster Vitreous to pearly

OLIGOCLASE -
SUNSTONE PIN
The bight
Oligoclase is a species of plagioclase spangles in this
feldspar (see above). The variety used cabochon, set
in jewelry is called sunstone or, less as a tie pin,
commonly, aventurine feldspar. It has ' are caused by
tiny inclusions
reflective inclusions of red, orange, or
of hematite.
green platy crystals, which give it a
metallic glitter. Sunstone may be facet-
ed or carved, often as cabochons. hematite flakes
¢ OCCURRENCE Sunstone produce sparkling
occurs in metamorphic and es parallel bands
igneous rocks in Norway, é »
the USA, India, the former
USSR, and Canada. Cabochon SUNSTONE ROUGH

LABRADORITE play of color Kee

ne

Labradorite is the plagioclase feld- , Pas “a Junctions of

spar (see albite, above) that is most ’ on pots internal
surface structures
commonly faceted as a gemstone. It
may be orange, yellow, colorless, or
red, but the material that shows a play
of color, or “schiller,” is the most
popular for use in jewelry. CABOCHON
© OCCURRENCE Occurs ir.
metamorphic and1os
rocks in Labrador
(Canada), Finland,
Norway, and the LABRADORITE
former USSR. fw) Polished ROUGH

"156-157 | Rooro
 CUT STONES « 131

pee uuctle Triclinic Compasiien Hydrated copper aluminum phosphate

TURQUOISE GREEN FACE

This greenish blue
One of the first gemstones to be mined, turquoise stone has
turquoise has long been prized for its intense been carved in the
color, which varies from sky blue to green, image of a child’s
depending on the quantities of iron and copper face, set in reliefin
within it. Turquoise is commonly found in a swivel ring.
microcrystalline, massive form, usually as
encrustations, in veins, or as nodules. It is
opaque to semitranslucent, light and very PERSIAN BLUE
fragile, with conchoidal fracture. Some ‘These two ornaments,
engraved and inlaid with gold,
material is very porous, leading to fading and
are made from the finest
cracking, so it may be impregnated with
sky blue turquoise, mined
Wax or resin to maintain its appearance. in Persia (now Iran) for
¢ OCCURRENCE Sky blue turquoise over 3,000 years. The
from Iran is generally regarded as the distinctive color is
most desirable, but in Tibet a due to the presence
greener variety is preferred. of copper and traces
Localities in Mexico and the USA of iron. Persian
produce a greener, more porous turquoise was intro-
duced to Europe via
material that tends to fade more
‘Turkey — hence its
quickly. Other localities include the name, derived from
former USSR, Chile, Australia, the word “Turkish.”
‘Turkestan, and Cornwall (England).
¢ REMARK Turquoise has been thought
to warn the wearer of danger or illness by
changing color. It has been imitated by pattern e——+—
stained howlite, fossil bone or tooth, engraved
limestone, chalcedony, glass, and and inlaid ©
enamel. In 1972, an imitation turquoise with gold
was produced in France by Gilson.

laboratory-made
cut and polished stone has uniform
as cabochon “spiderweb”
turquoise has
—e black veins

intense
blue-green
color e.

GILSON “SPIDERWEB”
IMITATION

GILSON IMITATION
thin crust of 8
turquoise e—-¢

et
TURQUOISE
Bead Cabochon Cameo IN MATRIX Galatia
132 sCUT STONES

Crystal structure , ES Composition “rE Hardness

lriclinic P Manganese silicate 6

RHODONITE | me —-lack-veined stones

are the most
Rhodonite has a distinct pink or rose
© popular
red color, although material contain-
ing black veins is more popular than
a uniform pink. Massive rhodonite is
usually opaque to translucent and is
carved or cut as cabochons or beads.
‘Transparent crystals are rare and fragile,
but some have been cut for collectors. characteristic
pink-red color
¢ OCCURRENCE Both crystals and
massive material have been found in the Urals
MASSIVE
(Russia), Sweden, and Australia. Other localities OvAL CABOCHON
habit e
for fine-grained rhodonite include Brazil, Mexico,
the USA, Canada, Italy, India, Madagascar, South
Africa, Japan, New Zealand, and England.
¢ REMARK The name comes from rhodos, the
Greek for “rose,” referring to the distinct color.

black areas rich e

in manganese

RHODONITE
ROUGH

Crystal structure eee oe Composition

Lithium aluminum hydroxyphosphate

AMBLYGONITE
Amblygonite is found in a wide range of
color
colors from white, pink, green, and blue
to golden yellow and, more rarely, color-
less. Large transparent to translucent
crystals may occur, but as amblygonite —e stones are too
is relatively soft, they are cut solely for soft to be popular
collectors. Amblygonite is also found for sewelry
as cleavable or compact masses.
¢ OCCURRENCE Amblygonite is straw yellow
found in pegmatites. Brazil is the color is most
source of most gem-quality (OU
material, but it is also found
in the USA. A pale mauve pale yellow
variety occurs in Namibia. eee olor
e REMARK Amblygonite
has been confused with
brazilianite and scapolite.
perfect
cleavage e—#
OVAL BRILLIANT CUT

Brilliant Brilliant Mixed INCOMPLETE CRYSTAL

 CWTS TONES: © 133

Triclinic Eompesien Complex borosilicate

AXINITE ITON gIVes

Axinite gets its name from its sharp-edged, stone its rich
axhead-shaped crystals. Although attractive —e brown color
and hard, they are brittle and rarely flaw-
less and are faceted for collectors only.
Brown is the most usual color, although it
also occurs 1n honey yellow and plum purple
varieties. A rare Tanzanian axinite is blue.
Axinite is strongly pleochroic. fragile,
® OCCURRENCE Axinite is found in cavities sharp-edged
; ; OVAL STEP CUT ees
in granite and in metamorphic rocks. crystals e
Localities include New Jersey, pale blue color
| where the attractive honey yellow due to low tron
| crystals are found, Mexico, @ content

| Cornwall (England), France, and

in the gem gravels of Sri Lanka.
¢ REMARK Darker axinite has
been confused with smoky quartz.

BRILLIANT CUT

Brilliant Brilliant Mixed AXINITE CRYSTALS

SG RI R es
1.6/7—1.70 a 0.011 oe Vitreous

Crystal struct Ais iti : Be is

y rucmre Triclinic eompcsion Aluminum silicate HalaDeSs 5-or7/

KYAN ITE cracks due to

formation at
rich blue
© color
*
Gem-quality kyanite crystals are pale to deep high pressure e
blue or white, gray, or green. Color dis-
tribution in crystals may be uneven, with
darker blue patches towards the interior.
¢ OCCURRENCE Kyanite is found in
metamorphic gneiss and schist and in uneven color
pegmatite veins through metamorphic ¢ distribution
rocks. It may be weathered out into
alluvial deposits. Gem-quality crystals
are found in Myanmar, Brazil, Kenya, RECTANGULAR STEP CUT
and the European Alps. Alluvial staurolite crystals kyanite crystals e
deposits are found in India, Australia, commonly occur
and Kenya, and in parts of the USA. with kyanite e
¢ REMARK Kyanite crystals have two
hardness values: they are softer parallel
to the direction of cleavage and harder
perpendicular to it.

/ CRYSTAL

| Baguette Step Cabochon CRYSTALS IN MATRIX

| e173 EF O:017 ruster Vitreous to pearly

134¢eCUT STONES }

Crystal structure Composition ae H i

Amorphous : Hydrated silica gel |

OPAL © precious opal

Opal is a hardened silica gel, usually with dark
containing 5—10 percent water. It is background
therefore noncrystalline, unlike most is called
other gemstones, and may eventually black
dry out and crack. ‘here are two opal
varieties: precious opal, which shows
flashes of color (iridescence), depending
on the angle of viewing; and common or —e cracks due
to loss of
—

“potch” opal, which 1s often opaque and

displays no iridescence. ‘The iridescence of original water
We 2 = ; content |
precious opal is caused by the way the
structure, a regular arrangement of tiny silica
spheres, diffracts light — the larger the BLACK PRECIOUS OPAL
spheres, the greater the range of colors. high-quality
Precious opal occurs in a number of color black opal from
varieties, some of which are shown here. e Australia
¢ OCCURRENCE Opal fills cavities in matrix e
sedimentary rocks or veins in igneous
rocks. It forms stalagmites or stalactites
and replaces organic material in fossil
wood, shell, and bone. Australia has
been the main producer of opals since
the 19th century. Other localities
include Czechoslovakia, the USA,
Brazil, Mexico, and southern Africa.
¢ REMARK Opals have been imitated
by Slocum stone, a tough, manmade glass, |
and, in 1973, Gilson made an imitation opal |
in the laboratory (see p.36). |
BLACK PRECIOUS OPAL IN MATRIX |
transparent |
good-quality e—— volcanic fire opal
stones are rhyolite
transparent, matrix @
not milky

beautiful, rich e
orange body color
givesfire opal its
name

FIRE OPAL BRILLIANT

FIRE OPAL RING opaque

Although many opals white opal
are cut en cabochon, this
transparent fire opal
has been faceted as
an octagonal step cut OPAL IN
and set in a gold ring. MATRIX
 CUT STONES « 135

opal has
filled cavity
in host rock
iridescent
Slashes of green
and blue

convex front
surface

iron nodule,
split open to
reveal opal
Pigilic MATRIX OPAL
replaced
| by precious
| opal play of
color caused by
diffraction of
light off closely
packed silica
spheres

Magnification reveals the

OPALIZED FOSSIL mosaiclike structure of
this Gilson imitation opal.

WHITE OPAL mosaic pattern,

. Although soft visible under
§ 2 and easily magnification
ee damaged, (above),
b precious opal identifies
» | femains a popular Stone as
Z \. eg Stone for rings. imitation e—

OPALS
: AND
VD PEARL S stunning,
This exquisite gold bright
cross, designed to be colors
worn on a chain, is set
with five precious white
opals, cut en cabochon,
and two pearls. The
opals show flashes of
red, blue, and green. 3ILSON
IMITATION OPAL
aN

x —e manmade glass
/ > imitates play ofcolor
: S of natural opal
Step Cabochon Cameo
SLOCUM STONE
136 e CUT STONES

Crystal structure Composition 4: me Hardness

- Amorphous i Mainly silicon dioxide

OBSIDIAN é speckled effect |

neat characteristic caused by tiny
Obsidian is a natural glass. It is formed from dark color e » gas bubbles |
volcanic lava that cooled too quickly for
|
significant crystallization to occur. Hence it
is amorphous, with no cleavage; fracture is
conchoidal. Obsidian is usually black, but
brown, gray, and, more rarely, red, blue, and
green material is found. The color may be
uniform, striped, or spotted. Some inclusions
give obsidian a metallic sheen, while internal
bubbles or crystals (called crystallites) produce
a “snowflake” effect (called snowflake obsidian)
or an iridescence seen as flashes of color.
¢ OCCURRENCE Obsidian is found in areas
where there is or has been volcanic activity, such
as Hawaii, Japan, and Java. Other localities
include Iceland, Hungary, the Lipari Islands
off Italy, the former USSR, Mexico, Ecuador, OBSIDIAN CABOCHON
and Guatemala. Dark nodules
found in Arizona and New Mexico
are called “Apache tears.”
¢ REMARK Obsidian has been rare red
obsidian
used since prehistoric times for
making tools, weapons, masks,
mirrors, and jewelry. The very
sharp shards of the natural
glass have been fashioned as
blades, arrowheads, and
T 4: banding
daggers. loday most obsidian
Shes: as caused by
jewelry comes from North } - Saeeeg ye
eee 1A solidification
and Central America. eee
6/400
polished specimen
has smooth, glassy
e sur ace

mineral-lined
cavities, called
spherules

rough
specimen has
uneven surface

APACHE TEARS
amorphous
black obsidian e

Cabochon Polished OBSIDIAN ROUGH = . i nical

 CUT STONES « 137

Crystal structure Compositio |Hardness -

Amorphous " Mainly silicon dioxide »

TEKTITES dark brown, semi- dark stones are faceted

The first tektites were found in 1787 in the ;
Moldau River in Czechoslovakia, hence their
original name of “moldavites.” Other color
varieties of this natural glass have since been
found in many different localities. Tektites
are usually translucent and occur in a range
of colors from green to brown. Their surfaces
are usually uneven or rough, with a distinctive
lumpy, jagged, or scarred texture. Tektites do
not contain the crystallites found in obsidian
(opposite). They may, however, have
characteristic inclusions of round or torpedo-
shaped bubbles or honeylike swirls.
¢ OCCURRENCE The Moldau River in
Czechoslovakia is now the only known locality
for green, transparent tektite. Tektites from
| Thailand have been carved as small, way MHOMEN

| decorative objects worn in the belief

that they give protection from evil.
| @ REMARK Several ideas have been
| put forward to explain the mysterious
origin of tektites. One theory is that
they came to Earth from outer space,
melting as they passed through the
atmosphere and thus forming their
characteristic shape and surface texture.
A second theory is that the impact of a
large meteorite caused the surrounding TEKTITE ROUGH
rocks to melt and scatter, with cracks and
scars then appearing as they cooled. lektilevarienes aTé e
ae ee
named ajter their

pla € Of OTIZ~IN

stone may be AUSTRALITE ROUGH

confused with | —e green, transparent
diopside material ts most distinctive crage
because 0}
- ~ Fs y7 - - -
suitable for faceting e uneven surfa
green color e

MOLDAVITE translucent e
BRILLIANT CUT and transparent
in parts

Luster , --
Vitreous
138 e ORGANICS
Crystal structure . Composition 5 ee Hardn |
y Orthorhombic P Calcium carbonate, conchiolin, and water

PEARL pearl color is

Pearls are formed in shellfish — especially oysters 3 : Ashe
and mussels — as a natural defense against an -© and luster
ap: , pearl of
irritant such as a piece of grit. Layers of Giants
aragonite, known as nacre, are secreted around gigas
the irritant and gradually build up to form the ~~ NATURAL PINK PEAR
L
solid pearl. Light reflecting from these
overlapping layers produces a characteristic
iridescent luster, also Known as the “orient
of pearl.” An irritant is introduced to
initiate the formation of a cultured pearl. pearl of Tridacna
In a “nucleated” cultured pearl a small gigas
bead is used as the nucleus upon which
the layers of nacre are secreted. Pearls
vary in color from white, or white with NATURAL WHITE PEARL |
a hint of color (often pink), to brown or brick colored where |
black, depending on the type of mollusk attached to shell
and the water. They are sensitive to |
acids, dryness, and humidity, and so are pearls form = |
less durable than many other gems. as spheres |
¢ OCCURRENCE Natural pearls have when irritant |
been harvested from the Persian Gulf, is not attached
the Gulf of Manaar (Indian Ocean), and to shell pinkish
:
the Red Sea for thousands of years. tinge
The coasts of Polynesia and Australia
produce mainly cultured pearls. Both
freshwater and saltwater pearls are NATURAL FRESHWATER
cultivated in Japan and China. PEARLS :
Freshwater pearls occur in the rivers
of Scotland, Ireland, France, Austria, shell of the
Germany, and the USA (Mississippi). pearl oyster
¢ REMARK Pearls were once (Pinctada
thought to be the tears of the gods. maxima)

irregular
shapes may
develop if
irritant 1s
attached to
shell

natural
white pearl

mother-
of-pearl
lining
iridescent, @
“pearly” luster

NATURAL FRESHWATER NATURAL PEARL

PEARLS IN OYSTER SHELL

RI 1 53-1.68 OR Not applicable

 f ORGANICS « 139
een eee ee eee —————————————eee—ee——————————————S—EeEE

pearl buddhas
formed on
A “BOMBAY BUNCH” casts placed
For hundreds of years, Bombay
e inside shell
| has been an important center
for the buying and selling of
pearls. To present them for
selling, pearls are sorted by
size, then strung into
bunches on silk thread.

| different sizes
are included so
that a complete
| necklace can be
| made from a i
a. ,

| “bunch”
ca? é
ond aed
2 & f Pi

Pe

BUDDHA PEARLS
‘To produce miniature
images of the Buddha, tiny
casts were placed into the shell
of this pearl mussel (C7staria
plicata). The mussel laid down
nacreous layers over the casts, forming
“blister” pearls. The pearls are later
removed and the backs hidden in the
mount or covered with mother-of-pearl.
JAPANESE CULTURE
‘This necklace, made by
the Mikimoto company
of Japan, uses saltwater
cultured pearls. Japan
leads the world in the
production of cultur-
——e cultured pearls ed pearls, although
have the same they have been used
by the Chinese for
pearly luster as
hundreds of years.
natural specimens

silver-wire @
tassels
140 e ORGANICS

Crystal structure Composition V. area Hardness

Amorphous ariety of lignite 2 y,

Jet is organic in origin. Like coal, it was formed

from the remains of wood immersed in stagnant
water millions of years ago, then compacted and
fossilized by the pressures of burial. Jet is black
or dark brown but may contain pyrite inclusions,
which have a brassy color and metallic luster.
Jet takes a good polish and is often faceted.
’ gems made Because jet 1s organic, it
When burned or touched with a hot needle, =) J Be
: ely Hof l from set take may dry out, causing
it exudes the characteristic smell of coal. :
a good polish e geste: yt ere
the surface to crack.
© OCCURRENCE Evidence suggests that jet
has been mined since about 1400 Bc, and work-
ed pieces of jet have been found in prehistoric
burial mounds. During the Roman opaque,
occupation of the British Isles, worked with velvety
pieces of jet were shipped to Rome. © /uster |
Perhaps.the most famous historical
source is Whitby in Yorkshire, England,
where much of the jet that was so
popular for the mourning jewelry of the
19th century originated. During this time
the mining and fashioning of jet provided the
town with much of its income. Other localities
include Spain, France, Germany, Poland, India, OvAL CABOCHON |
‘Turkey, the former USSR, China, and the USA. |
e REMARK Jet was popular for mourning |
jewelry in the 19th century because of its somber uppermost |
color and modest appearance, and it has been surface 18 CONVEX;
traditionally fashioned into rosaries for monks. back 1s flat e
Jet has also been known as black amber, as it
may induce an electric charge like that of amber faceting can
when rubbed. Powdered jet added to water or add life to an
wine was believed to have medicinal powers. otherwise
dull gem e
triangular
facets ©
surface cracks
resulting from
—e dehydration ROSE CUT

fine-grained,
fragile specimen
with rough,
cracked surfaces e—

dull, earthy luster

before polishing e
DRILLED AND
FACETED BEAD

DR x7 :
Mae eae Not applicable ai Velvety to waxy
 ORGANICS « 141

VICTORIAN EARRINGS
Jet is light to wear, and so it is par-
ticularly suitable for earrings. It was
very popular for mourning jewelry
in Victorian England.

BLACK ROSE
This piece of carved
Whitby jet, with a finely
wrought rose at the center,
dates from the latter part
of the 19th century.

FOSSIL- JET PENDANT

BEARING JET This exquisite
‘The ammonite pendant of a dove
and bivalve fossils with a heart in its
trapped in this jet beak shows how
specimen are evidence well jet can be
ammonite of its organic origin. carved and
fossil @ polished.

e bivalve
iossil

highly
polished
beads e

TURKISH BEADS
This necklace from eastern
‘Turkey is made from beads
of polished and drilled jet.
The high polish has given
the beads an attractive luster.

Dee

Bead Cameo Polished

142 e ORGANICS

Crystal structure -,, . Composition , | - 5 hia Hardness

¥ ‘Trigonal P Calcium carbonate or conchiolin .

CORAL vivid red

Coral is made up of the skeletal remains of —e color
marine animals called coral polyps. These tiny
creatures live in colonies that form branching
structures as they grow, eventually forming coral |
reefs and atolls. ‘The surface of these coral |
“branches” has a distinctive pattern made
by the original animals — either striped or like
© high polish
shows vitreous |
|
wood grain. Most corals — red, pink, white, and luster
blue varieties — are made of calcium carbonate;
black and golden corals are made of a hornlike |
substance called conchiolin. Red coral is the |
most valuable and has been used in jewelry RED CORAL CABOCHON |
for thousands of years. Dull at first, all coral has
a vitreous luster when polished but is sensitive to
heat and acids and may fade with wear. Coral polished
surface
may be imitated by porcelain, stained bone,
glass, plastic, or rubber and gypsum mixtures.
¢ OCCURRENCE Most precious coral is found
in warm waters. Japanese coral is red, pink, or cross section
white. Red and pink coral is also found on the reveals
Mediterranean and African coasts, the Red Sea, intricate
and the waters off Malaysia and Japan. Black and banded
StTUCTUTEe
golden coral is found off the coasts of the West
Indies, Australia, and the Pacific islands.
¢ REMARK Coral has been said
to protect children, and parents
may still give a gift of coral
to their young
RED CORAL SLICE
children. ?

branches
form from
coral polyp
skeletons

red coral
from the
Mediterranean

distinctive “wood
bs ”
grain pattern on
surface of branches
RED CORAL CARVING
This piece of red coral (Cora/lium
rubrum) from the Mediterranean
has been carved to show a monkey
RED CORAL climbing a blossoming tree.
 ORGANICS « 143

distinctive coral colonies

pitted surface naturally form
| Heliopora caerules branched, tree-
coral found in seas like structures
2 around Philippines

black coral ts
nade from
hornlike
conchiolin e
highly
polished
surface e

= blue coral is
often used to
make beads

oval
cabochon «

BLACK CORAL

BLACK CORAL CABOCHON

imitation slabs may be

BLUE CORAL carved, polished, or
polished bead fashioned as beads e
manufactured by
Gilson of France
to imitate dark
pink coral e—

IMITATION
IMITATION CoRAL BEAD
CORAL
These beads are IMITATION CORAL
made of vegetable
ivory (see p.147),
stained to imitate
pink coral. Imitations
are generally even in / \ -
color and fail to show the X
) /
V Ss \
& { |
distinctive “wood grain”
structure of natural coral. Bead Cabochon Cameo
144 * ORGANICS
Crystal structure :
Pest
Composition
Calcium carbonate
,, , - Hardness
24
SHELL
Shells come in a wide variety of sizes, shapes, and
colors and may be fashioned into beads, buttons,
jewelry, inlay, knife handles, snuff boxes, and
other decorative items. Conch shells with
pink and white layers may be carved into
intricate and attractive cameos, as may
helmet shells, which have white outer
layers and golden brown or orange inner
layers. ‘he large pearl oysters (Pinctada
maxima and P. margaritifera), abalones
(paua), and topshells (Trochidae) are all
prized for their iridescent (mother-of-pearl)
shell linings. ‘Tortoiseshell comes not from the
tortoise but from the hard shell (carapace) of the TIGER CowRIE CAMEO
Hawksbill Turtle. It has rich brown mottling or This Asian woman has been carved in a Tiger
flamelike patterns on a warm, translucent, golden Cowrie shell (Cypraea ngris). The different |
yellow background and is fashioned by warming colored layers have been cut away to create
the shell to flatten it and to scrape off the ridges. the effect of foreground and background.
It is then polished and cut to shape. |
¢ OCCURRENCE Pinctada oysters are found
off northern Australia. Abalones are found off
the coasts of the USA and paua shells off New
Zealand. The Hawksbill ‘Turtle is found in the S A i

warm waters of Indonesia and the West Indies. lick oe d

e REMARK Tortoiseshell has now been Hass J
be used for
largely replaced by plastic imitations. inlay work

shell found on
inshore sands of
Indo-Pacific e

surface
layers cut away
to leave image
in high relief

ROMAN CAMEO
‘This cameo has been
carved into the shell of
Cassidae madagascarensi1.
The detail is picked out in SPIDER CONCH
the upper layers of the shell.
(LAMBIS LAMBIS)
 ORGANICS « 145

HINGED Box
The lid and base of
this box show the
distinctive coloring
and patterning of
tortoiseshell. Some
light areas are
transparent to semi-
translucent; darker When magnified, spots can
areas are opaque. be seen in natural but not
in imitation tortoiseshell.

distinctive rich
brown mottling e

HAIR COMB
This tortoise-
shell comb shows
attractive, almost
fiery, patterns of
yellow and
brown, with
darker patches.

ridges are
ba scraped away
iridescent colors are during
prized in many fashioning e
forms ofjewelry i
and decorative
items e

nacreous TORTOISESHELL (CARAPACE

lining 1s used OF HAWKSBILL TURTLE)
for sewelry
—e and inlays
SHELL PILLBOX
The inlay in the lid
of this pillbox has
been fashioned
from the layered,
iridescent lining of
a shell from the
Haliotis family of
shellfish.

Cabochon Cameo Polished

MOTHER-OF-PEARL
SHELL
146 e ORGANICS

Crystal steers Amorphous Composition Catcium hydroxyphosphate and organic er

—

IVORY =
Ivory has been prized for thousands of years for its A *
rich, creamy color, its fine texture, and its ease of ee “4
carving. Until quite recently it was a popular
material for both jewelry and ornaments, but
international restrictions on trading now help to
protect the animals from which ivory is taken.
‘The teeth or tusks of mammals all have ivory as
a constituent. Although usually associated with
elephants, ivory from the Hippopotamus, Wild
Boar, and Warthog is also used. Marine mammals
such as the Sperm Whale, Walrus, Sea Lion, and
Narwhal have ivory as well. Fossil ivory — from
prehistoric animals such as mammoths, masto-
dons, or dinosaurs — can also be carved.
¢ OCCURRENCE African Elephants’ ivory is
the most highly valued, with a warm tint and
little grain or mottling. Indian Elephants’ ivory
is a denser white, softer, and easier to work, but
it yellows more easily. Ivory markets include
Europe, Myanmar, and Indonesia.
e REMARK One piece of carved INDIAN ELEPHANT Ivory
mammoth ivory found in France 1s This intricately fashioned
estimated to be over 30,000 years scene was probably carved from
old. In China and Japan ivory the tusk of an Indian Elephant,
carving remains popular, even whose ivory is softer and whiter
than the African Elephant’s.
today. However, elsewhere,
the use of ivory simulants —
bone, horn, jasper, vegetable
ivory, plastic, and resin — has distinctive
been strongly encouraged curved growth
in order to protect ivory- lines
bearing animals.

thin canals containing

nerve fibers

AFRICAN ELEPHANT IVORY

Made from warm, mellow African
Elephant ivory, this Roman head
is worked in the style popular in
the 4th to 5th century BC.

cut and polished

molar tooth e—
ELEPHANT Ivory Cup
Looking down into this cup, the POLISHED SECTION
crisscrossing, curving pattern
OF ELEPHANT TOOTH
unique to elephant ivory is visible.

Rl 953254 R Not applicable Luster Dull to greasy

 ORGANICS °¢ 147

outer surface
has yellowed
with time e—__—_

radial
lines e

DRILLED BONE
Bone may be used as an ivory simulant. These
two pieces have been worked as buttons or
beads, with a plain back and carved front.

SECTION OF
HIPPOPOTAMUS TUSK
surface of
Sperm Whale \
wory yellows
with age <
8 | WALRUS IVORY green-stained
) 4 This necklace is beads are
| . made from stained intended to
= walrus ivory. Ivory imitate jade
| . is porous and takes
\ a dye readily.
C

tough outer
rim surrounds =
concentric inner A
structure

PART OF WHALE TOOTH

seed of the
e Doom Palm

VEGETABLE IvoRY
This necklace is made
of polished and drilled
vegetable ivory beads, beads stained
:
given a pale, artificial pink 10
stain to imitate coral. imitate coral
Imitation ivory is now
greatly encouraged, as
more and more ivory-
bearing animals face
extinction.

hard, creamy white nut e

used to imitate elephant
and other twortes
Cameo Polished
VEGETABLE Ivory IN SHELL
148 e ORGANICS

Crystal structure Composition , ,- ; .

; Amorphous pose" Mixture of organic plant resins sleiee 4)

AMBER characteristic
Amber is the fossilized resin of trees. Most golden orange
amber is golden yellow to golden orange, but color: ¢«=——_—=
green, red, violet, and black amber has been
found. ‘Iransparent to translucent, it usually
occurs as nodules or small, irregularly shaped
masses, often with a cracked and weathered
surface. Amber may contain insects (and more
rarely frogs, toads, and lizards), moss, lichen, or resinous
pine needles that were trapped millions of luster e
years ago while the resin was still sticky. Air \
\ transparent
bubbles may give amber a cloudy appearance, bead
but heating in oil will clear this. When rubbed,
amber produces a negative electrical charge
that attracts dust. “Ambroid” is formed by
heating and pressing together scraps of amber.
¢ OCCURRENCE The most famous deposits
are in the Baltic region, particularly along the
coasts of Poland and the former USSR. Baltic
amber (known as succinite) washed from
the seabed may reach as far as the coasts of
England, Norway, and Denmark. Amber from POLISHED BEADS
Myanmar ts called burmite; Sicilian amber is
known as simetite. Other localities include cracks produce cracks may be
the Dominican Republic, Mexico, France,
spangling effect ’ caused by heat
Spain, Italy, Germany, Romania, Canada, treatment
Czechoslovakia, and the USA.
¢ REMARK Amber has had a number of
medicinal uses attributed to it, but today it
is used almost exclusively for jewelry. It has
been imitated by plastic, glass, synthetic
resin, and other natural resins, like copal.

cloudy,
opaque area

POLISHED “SUN-SPANGLED” BEAD weathered

surface e
transparent
area

PARTLY POLISHED
AMBER
pebble found
washed up
on beach e— ~~

BALTIC AMBER ROUGH

Luster ;
RN 5 4-1.55 OR Not applicable Resinous
 ORGANICS e 149

probably ofRomano- amber may contain

British origin, around Sly trapped in plants and insects,
Ist century AD e sticky resin, before and occasionally
fossilization e e frogs or hzards

.-
=e golden
_ yellow color

———e river water has

protected bead
from drying out

ROMAN BEAD FOUND

IN RIVER SILT FLY IN AMBER
ambroid is made
| a. by warming and “a
| artificially compressing small
| colored pieces of amber
| brown,
| although
| a range
of colors BEAD NECKLACE
| may be Some of the 31 drilled,
| produced cut, and polished amber
| beads that make up this
| necklace show signs of
| dehydration. This is a
| common problem with
amber jewelry, which
| SQUARE AMBROID will dry out if left in
| the sun or worn in the
heat of the day.

EER cracked
ORNAMENT surface
This Chinese ear ¢
ornament has 6
been worked in
the shape of a
panda bear. The
cracks are due to
dehydration of
the stone.

transparent
beads have

Cabochon Cameo Polished numerous @

four-sided
facets
150 e TABLE OF PROPERTIES

‘TABLE OF PROPERTIES
ci TABLE INCLUDES all of the ‘They are related to crystal structure: a
technical information for each gem gem with cubic structure has a single
species, arranged alphabetically by gem value as its refractive index (RI); doubly /

name. By so doing, it is intended to give refracting gems have two refractive

the reader an at-a-glance reference to indices (see p.21). Doubly refracting
the more important physical and optical gems also have a value of birefraction
properties of each gem species. (DR), found by using a refractometer.
‘The chemical composition of each This figure is the difference between
gem 1s shown here by a formula, which the highest and the lowest refractive
includes all essential elements of that indices. Physical and optical properties
gem. Composition may vary slightly, are continually reviewed as new miner-
depending on locality and conditions of als are discovered and new deposits
formation. The physical properties of exploited, so all figures given here are
the gems — their hardness and specific mean values, to be used as a guide only.
gravity — are given as mean (average)
values. Hardness is denoted by a figure
KEY TO CHEMICAL ELEMENTS
from the Mohs scale of hardness, a scale
IN THIS BOOK
used to classify the hardness of minerals
ALUMINUM Mg MAGNESIUM
relative to one another. ‘The intervals SILVER Mn MANGANESE
between successive values are unequal, GOLD SODIUM
and an intermediate value such as 3% BORON OXYGEN
denotes that the hardness is between 3 BARIUM PHOSPHORUS
and 4, but it is not necessarily exactly BERYLLIUM LEAD
CARBON PLATINUM
halfway between. Hardness may vary
CALCIUM SULFUR
slightly depending upon exact chemical CHLORINE SILICON
content, so a mean figure 1s given here. CHROMIUM TIN
The values for specific gravity (SG), COPPER STRONTIUM
which give an indication of the density FLUORINE ‘TITANIUM
of a gem, are also given as mean figures. IRON ‘TUNGSTEN
HYDROGEN ZINC
‘The optical properties of the gems
POTASSIUM ZIRCONIUM
are represented here by the refractive LITHIUM
indices (RI) and the birefraction (DR).

NAME & CHEMICAL COMPOSITION STRUCTURE HARDNESS SG RI

ACHROITE (TOURMALINE)
Na(Li,Al),Al,(BO,),Si,O,,(OH), ‘Trigonal Th 3.06 1.62-1.64
AGATE (CHALCEDONY)
SiO, ‘Trigonal 2.61 1.53-1.54
ALBITE
(Na,Ca)AISi,O, Triclinic 2.64 1.54-1.55
ALMANDINE (GARNET) :
Fe,AL(SiO,), Cubic 1.76-1.83
AMBER
mainly C,,H,,O Amorphous 1.54-1.55
 TABLE OF PROPERTIES ¢ 151

~ NaME & CHEMICAL COMPOSITION STRUCTURE HARDNESS SG RI DR

AMBLYGONITE Triclinic 3.02 1.57-1.60 0.026

LiAl(RKOH)PO,
AMETHYST (QUARTZ)
‘Trigonal 2.65 1.54-1.55 0.009
SiO,
ANDALUSITE
Orthorhombic 1.63—1.64 0.010
AL,S10,
ANDRADITE GARNET
Cubic 1.85-1.89 None
Ca,Fe,(SiO,),
ANGLESITE
Orthorhombic 1.87-1.89 0.017
PbSO,
APATITE
Hexagonal 1.63—1.64 0.003
Ca(F,Cl)Ca,(PO,),
AQUAMARINE (BERYL)
Hexagonal 1.57-1.58 0.006
Be,AlL(SiO;),
ARAGONITE
Orthorhombic 1.53-1.68 0.155
CaCO,
AVENTURINE QUARTZ
‘Trigonal 1.54-1.55 0.009
SiO,
AXINITE
Triclinic 1.67-1.70 0.011
CaFeMgBALSi,0,.(OH)
AZURITE
Monoclinic 1.73-1.84 0.110
Cu,(OH),(CO,),
BARITE
Orthorhombic 1.63-1.65 0.012
BaSO,
BENITOITE
Hexagonal 1.76—1.80 0.047
BaTiSi 305
BERYLLONITE
Monoclinic 1.55-1.56 0.009
NaBePO,
BLOODSTONE (CHALCEDONY)
‘Trigonal 1.53-1.54 0.004
SiO,
BRAZILIANITE
Monoclinic 1.60-—1.62 0.021
Al,Na(PO,),(OH),
BROWN QUARTZ (SMOKY QUARTZ)
‘Trigonal 1.54-1.55 0.009
SiO,
CALCITE
‘Trigonal 1.48-1.66 0.172
CaCO,
CARNELIAN (CHALCEDONY)
1.53-1.54 0.004
SiO, ‘Trigonal

CASSITERITE
‘Tetragonal 2.00-2.10 0.100
SnO,
CELESTINE
Orthorhombic 1.62—1.63 0.010
SrSO 4
CERUSSITE
Orthorhombic 1.80-2.08 0.274
PbCO,
CHALCEDONY
‘Trigonal 1.53-1.54 0.004
SiO,
CHATOYANT QUARTZ
‘Trigonal 1.54-1.55 0.009
SiO,
CHRYSOBERYL
Orthorhombic 1.74-1.75 0.009
BeAl,O ik
152° TABLE OF PROPERTIES

NAME & CHEMICAL COMPOSITION STRUCTURE HARDNESS RI

CHRYSOCOLLA
Monoclinic 1.57-1.63
(Cu,Al),H,Si,0(OH),.nH,O
CHRYSOPRASE (CHALCEDONY)
‘Trigonal 1.53-1.54
SiO,
CITRINE (QUARTZ)
‘Trigonal 1.54-1.55
SiO,
CORAL
‘Trigonal 1.49-1.66
CaCO, (or C,H,.N,O,,)
DANBURITE
Orthorhombic 1.63—1.64
CaB,(SiO,),
DATOLITE
Monoclinic 1.62-1.65
Ca(B,OH)SiO,
DIAMOND
Cubic 2.42
€
DIOPSIDE
Monoclinic 1.66-1.72
CaMg(SiO,),
DIOPTASE
‘Trigonal 1.67-1.72
CuOSiO,H,O
DOLOMITE
‘Trigonal 1.50-1.68
CaMg(CO,),
DRAVITE (TOURMALINE)
‘Trigonal 1.61-1.63
NaMg, Al, (BO,),Si,O,,(OH),
DUMORTIERITE
Orthorhombic 1.69-1.72
AL(BO,)(SiO,),0,
EMERALD (BERYL)
Hexagonal 1.57-1.58
Be,Al(SiO,),
ENSTATITE
Orthorhombic 1.66-1.67
Mg,S1,0,
EPIDOTE
Monoclinic 1.74-1.78
Ca,(Al,Fe),(OH)(Si0,),
EUCLASE
Monoclinic 1.65-1.67
Be(Al,OH)Si0,
FIRE AGATE (CHALCEDONY)
‘Trigonal 1.53-1.54
SiO,
FLUORITE
Cubic 1.43
CaF,
GOLD
Cubic None
Au
GOSHENITE (BERYL)
Hexagonal 1.58-1.59
Be,AlL(SiO,),
GROSSULAR (GARNET)
Cubic 1.69-1.73
Ca,Al,(SiO,);
GYPSUM
Monoclinic 1.52-1.53
CaSO,.2H,O0
HAMBERGITE
Orthorhombic 1.55-1.63
Be,(OH)BO,
HAUYNE 1.50
(Na,Ca), ,Al,Si,(O,S),,(SO,C)),_, Cubic
(mean)
HELIODOR (BERYL)
Hexagonal 1.57-1.58
Be,AL(SiO,),
 TABLE OF PROPERTIES © 153

NAME & CHEMICAL COMPOSITION STRUCTURE — HARDNESS SG RI DR

a Trigonal 6%, 520 |208322 0.280

ceLS = Cae) Cubic Th 365 122% None
C.B.SiO,OH), Monoclinic 3% 2.58 1.58-1.59 0.022

FeMpsio. Orthorhombic 5% 355 1.65-1.67 0.010

NatLi A,B60.) $0, (0K), Trigonal Ths 3.06 «162-164 0.018

Mg ALSiO; Orthorhombic 7 2.63 1.53-1.55 0.010

Ca.(PO,) (OH) and organic material DY Ee ate 1.90 1.53-1.54 N/A

Soa ;25.0, Monoclinic 7 333 toetee. 0.012

co. —a. ‘Trigonal 7 2.61 1.53-1.54 0.004

a Amorphous 2%, 1.33 1.64-1.68 N/A

Mg.(ALFe),(6i,B),0,,(OH) Orthorhombic 6% 3:52 1.66-1.68 0.013

ALSIO, ‘Triclinic 5 or 7 3.68 L7i-t7s 0.017

eae ALSi),0, ‘Triclinic 6 2.70 1.56-1.57 0.010

rrr cr cc
MeAL FO, (OF), Monoclinic 5% 3.10 1.61-1.64 0.031

Gx (OH),CO, Monoclinic 4 3.80 oe 0.025

Me.6i,0,.(0H), 6H,0 Monoclinic 2h 1.50 1.51-1.53 None

KAIS.O, ‘Triclinic 6 2.56 1.52-1.53 0.008

30, cori Trigonal 7 2.65 1.54-1.55 0.009

Ago. er Monoclinic 6 257 1521.53 0.005

BeAL(SIO), 2 Hexagonal Th 2.80 1.58-1.59 0.008

Petes. 0,(00, Monoclinic 6% 2.96 1.61-1.63 0.027

Mainly SiO, os . Amorphous 5 2.35 (esi) None

eal $,0, | agate 6 2.64 1.54-1.55 0.007

SiO, | ‘Trigonal 7 2.61 153-154 | 0.004

154 ¢e‘TABLE OF PROPERTIES

NaME & CHEMICAL COMPOSITION | STRUCTURE RI

sa

OPAL
SiO,.nH,O Amorphous 1.37-1.47

KAISLO, Manoelinic | 1.51-1.54

PADPARADSCHA (CORUNDUM ' ;
ALO, ) ‘Trigonal 1.76-1.77

PEARL
Orthorhombic 2.71 1.53-1.68
CaCO,,C,H,,N,O,,.nH,O
PERIDOT Z
(Mg,Fe),SiO, Orthorhombic 1.64-1.69

PETALITE —
Li,OAI,O,8Si0, Monoclinic 2.42 1:50-1:51

PHENAKITE
‘Trigonal 1.65-1.67
Be,SiO,
PHOSPHOPHYLLITE
Monoclinic 1.59-1.62
Zn,(Fe,Mn)(PO,),.4H,O0
PLASMA (CHALCEDONY)
‘Trigonal 1.53-1.54
SiO,
PLATINUM
Cubic None
Pr
PRASE (CHALCEDONY)
‘Trigonal 1.53-1.54
SiO,
PREHNITE
1.61—1.64
Ca,AI,Si,O (OH), Orthorhombic

PYRITE
Cubic None
FeS,
PYROPE (GARNET)
Cubic 1.72-1.76
Mg,Al,(Si0,),
RHODOCHROSITE
‘Trigonal 1.60—1.80
MnCO,
RHODONITE
‘Triclinic 1.71-1.73
(Mn,Fe,Mg,Ca)SiO,
ROCK CRYSTAL (QUARTZ)
‘Trigonal 1.54-1.55
SiO,
ROSE QUARTZ
Trigonal 1.54-1.55
SiO,
RUBELLITE (TOURMALINE)
‘Trigonal 1.62—1.64
Na(Li,Al),Al,(BO,),Si,0(OH),
Rusy (CORUNDUM)
1.76-1.77
ALO; ‘Trigonal

RUTILE
TiO,
‘Tetragonal 2.62-2.90

SAPPHIRE (CORUNDUM)
‘Trigonal 1.76-1.77
ALO,
SARD
‘Trigonal 1.53-1.54
SiO,
SARDONYX (CHALCEDONY)
‘Trigonal 1.53-1.54
SiO,
SCAPOLITE
‘Tetragonal 1.54-1.58
Na,Al,Si,O,,Cl-Ca,Al,Si,O,,(CO,,SO,)
 TABLE OF PROPERTIES ¢ 155

NAME & CHEMICAL COMPOSITION STRUCTURE RI

SCHEELITE
‘Tetragonal 5 1.92-1.93
CaWO,
SCHORL (‘TOURMALINE)
‘Trigonal : 1.62-1.67
NaFe,Al,(BO,),Si,0,.(OH),
SERPENTINE
Monoclinic 4 1.55—1.56
Mg,(OH),Si,0,,,
SHELL
Various F 153-159 N/A
CaCO, and C,,H,.N,0,,
SILLIMANITE
Orthorhombic : 1.66—1.68 0.019
AL,SiO,
SILVER
Cubic None None
Ag
SINHALITE
Orthorhombic : 1:67-1:71 0.038
Mg(Al,Fe)BO,
SMITHSONITE ;
ZnCO, ‘Trigonal ; 162-155 0.230

; 1.48
SODALITE
3NaAlSiO,NaCl Cubic Gacy |None
SPESSARTINE (GARNET)
Cubic , 1.79-1.81 None
Mn,AL,(Si0,),
SPHALERITE
Cubic ‘ 2.30-2.37 None
(Zn,Fe)S
SPINEL
Cubic : P71 -1.73 None
MgAl,O,
ae eoees
SPODUMENE
Monoclinic ‘ 1.66-1.67 0.015
LiAl(SiO;),
STAUROLITE
Orthorhombic : 74-175 0.013
(Fe,Mg,Zn),Al,(Si,Al),O,,(OH),
‘TAAFFEITE
BeMg, Al,O, Hexagonal ‘ 1.72-1.77 0.004

TEKTITES
Amorphous : 1.48-1.51 None
Mainly SiO,
nso. (SPHENE) Moanoclinic : 1.84-2.03 0.120

TOPAZ :
Orthorhombic : 1:62-1:63 0.010
Al,(F,OH),SiO,
‘TUGTUPITE
Na,AIBeSi,O,,Cl ‘Tetragonal ; 1.49-1.50 0.006
‘TURQUOISE SENS
CuAl,(PO,),(OH),.5H,O ‘Triclinic : 1.61-1.65 0.040

UVAROVITE (GARNET)
Cubic ; 1.86-1.87 None
Ca,Cr,(SiO,);
VESUVIANITE (IDOCRASE) ‘ se
Ca,Al(AlOH)(SiO,)< ‘Tetragonal 1.70-1.75 0.005

WATERMELON ‘TOURMALINE ;
Na(Li,Al),Al,(BO,),Si,0,.(OH), ‘Trigonal E 1.62—1.64 0.018
3 :
ZIRCO
71Si0, ‘Tetragonal , 1.93-1.98 0.059
F
ZOISITE
Ca,(AlOH)AL(SiO,), Orthorhombic ; 1.69-1.70 0.010
156 e GLOSSARY

(GLOSSARY
WORDS PRINTED in bold type © COMPOSITE STONE ¢ FACES
have their own definition Stone assembled from several Flat surfaces that make up the
elsewhere in the glossary. pieces, often to imitate a gem. external shape of a crystal.
@ CONCHOIDAL FRACTURE ¢ FACET
¢ ABSORPTION SPECTRUM Shell-like fracture. See Fracture. Surface of acut and polished gem.
Pattern of dark lines or bands seen ¢ CROWN ¢ FACETING
when a gem is viewed through a ‘Top part of a cut stone, above Cutting and polishing of the
spectroscope. the girdle. surfaces of a gemstone into facets.
¢ ALLOCHROMATIC © CRYPTOCRYSTALLINE The number and shape of the
Refers to gems colored by Mineral structure in which facets give the stone its style of cut.
impurities, without which the crystals are so small they are not e FANCY CUT
gem would be colorless. distinguishable with a microscope. Name applied to a stone given an
¢ ALLUVIAL DEPOSITS ¢ CRYSTAL unconventional shape when cut.
Concentrations of material that Solid that has a definite internal ¢ FIRE
have been separated by weathering atomic structure, producing a See Dispersion.
from the host rock, then deposited characteristic external shape and ¢ FRACTURE
by rivers or streams. physical and optical properties. Chipping or breaking of a stone in
¢ AMORPHOUS ¢ CRYSTAL STRUCTURE a way unconnected to the internal
Without a regular internal atomic Internal atomic structure ofa atomic structure. Because of this,
structure or external shape. crystal. All crystalline gems may be fracture surfaces are usually
¢ ASSOCIATED MINERALS classified in one of seven groups, uneven. See a/so Cleavage.
Minerals found growing together, according to the symmetry of their ¢ GEMSTONE
though not necessarily intergrown. structure: cubic, tetragonal, Decorative material, usually a
¢ ASTERISM hexagonal, trigonal, orthorhombic, mineral, prized for some or all of
Star effect seen on some stones monoclinic, and triclinic. the qualities of beauty, durability,
when cut en cabochon. e CUT and rarity. It is used synonymously
¢ BASAL PINACOID ‘Term used to describe the way in with “gem” and “stone” through-
Feature relating to crystal sym- which a stone is faceted. See a/so out this book.
metry. A columnar or prismatic Faceting. ¢ GEODE
crystal with flat ends may be refer- ¢ DICHROIC Cavity within a rock, in which
red to as having a basal pinacoid. Refers to a gem that appears two crystals line the inner surface
¢ BIREFRACTION (DR) different colors or shades when and grow toward the center.
The difference between the viewed from different directions. ¢ GIRDLE
highest and the lowest refractive ¢ DIFFRACTION Band around the widest part of a
indices in doubly refractive gems. The splitting of white light into its cut stone, where the crown meets
¢ BOTRYOIDAL constituent spectral colors — the the pavilion.
Shape similar to a bunch of grapes. colors of the rainbow — when it ¢ GRANITE
¢ CABOCHON passes through a hole or grating. Coarse-grained igneous rock
Gem cut and polished to have a ¢ DISPERSION comprising mainly quartz,
domed upper surface. Such stones The splitting of white light into its feldspar, and mica.
are said to be cut en cabochon. constituent spectral colors — the ¢ Habit
¢ CAMEO rainbow colors — when it passes Shape in which a crystal
Design in low relief, around which through inclined surfaces, such as naturally occurs.
the background has been cut away. those on a prism or faceted gem. ¢ HARDNESS
¢ CARAT (CT) Dispersion in gems is called fire. See Mohs Scale of Hardness.
Unit of weight used for gems — a ¢ DOUBLE REFRACTION (DR) ¢ HEAT TREATMENT
carat is one-fifth of a gram. It is also Phenomenon in which each ray of Application of heat to a gem with
used to describe the purity of gold light is split in two as it enters a the purpose of enhancing the
— pure gold is 24 carat. noncubic mineral. Each ray travels color or clarity.
¢ CHATOYANCY at a different speed and has its own ¢ HYDROTHERMAL
The cat’s-eye effect shown by some refractive index. See a/so Refers to processes that involve the
stones when cut en cabochon. Birefraction. alteration or deposition of minerals
¢ CLEAVAGE ¢ DouBLET by water heated by igneous activity.
Breaking of a stone along lines of Composite stone made of two © [DIOCHROMATIC
weakness related to the internal pieces cemented or glued together. Describes gems whose color is due
atomic structure. See a/so Fracture. @ EVAPORITE DEPOSIT to elements that are an essential
¢ COLUMNAR Sedimentary rock or mineral part of their chemical composition.
‘Type of habit in which crystals resulting from the evaporation of ¢ IGNEOUS ROCKS
form in the shape of columns water from mineral-bearing fluids, Rocks formed from erupted
(elongated prisms). usually seawater. volcanic lava or solidified magma.
 GLOSSARY #157

¢ IMITATION GEMSTONE e¢ MIXED CUT ¢ RHOMB

Material that has the outward Cut in which the facets above and Shape much like a skewed cube.
appearance of the gem it is below the girdle are styled in e Rock
intended to imitate, but which has different ways — usually brilliant Material made up of one or more
different physical properties. See cut above and step cut below. minerals.
also Synthetic gemstone. ¢ MOHS SCALE OF HARDNESS ¢ ROUGH
¢ INCLUSIONS Measure of amineral’s hardness in ‘Term used to describe a rock or
Markings or foreign bodies found relation to other minerals, based on crystal still in its natural state,
within a stone. Some can be used its ability to resist scratching. before faceting or polishing.
to identify a particular species. ¢ MULTICOLORED ¢ SCHILLER/SHEEN
¢ INTAGLIO Used to describe single crystals Form of iridescence.
Design in which the subject is cut made of different colored parts. ¢ SCHIST
lower than the background. ¢ OPALESCENCE Metamorphic rock in which
¢ INTERGROWN Milky blue form of iridescence. the crystals are in parallel
When two or more minerals grow ¢ ORE arrangement.
together and become interlocked. Rock that contains metals capable ¢ SECONDARY DEPOSIT
¢ INTRUSIVE of being extracted commercially. Gems or minerals that have been
Igneous rock that has solidified ¢ ORGANIC GEM separated from their original rock
within other rocks, below the Gem made by or derived from and redeposited elsewhere. See a/so
Earth’s surface. living organisms. Primary deposit.
¢ [RIDESCENCE ¢ PASTE ¢ SEDIMENTARY ROCKS
Reflection of light off internal Glass made to imitate gems. Rocks formed by the consolidation
features In a gem, giving rise toa ¢ PAVILION and hardening of rock fragments,
rainbowlike play of colors. Lower part of a cut stone, below organic remains, or other material.
¢ LAPIDARY the girdle. ¢ SPECIES
Craftsman who cuts and polishes ¢ PEGMATITE Used in this book to refer to
gemstones. An igneous rock formed as individual gems that have distinct
e Lava residual liquids from magma cool, characteristics which may be
Molten rock erupted from often forming large crystals. defined and verified.
volcanoes. See a/so Magma. ¢ PLACER DEPOSIT ¢ SPECIFIC GRAVITY (SG)
¢ LUSTER Concentrated (secondary) deposit Density, measured as the weight of
Shine or “look” of agemstone due of minerals, usually in rivers or seas. the material compared with that of
to reflection of light off the surface. e PLATY an equal volume of water.
© MAGMA Habit characterized by flat, thin, ¢ SPECTROSCOPE
Rock in a molten state below the platelike crystals. Instrument used to view the
Earth’s surface. See a/so Lava. ¢ PLEOCHROIC absorption spectra of gemstones.
¢ MAMMILLATED Term used to describe a gem that ¢ STEP CUT (OR TRAP CUT)
Smooth, rounded shape. appears two or more different colors Cut characterized by a rectangular
¢ MASSIVE or shades when viewed from table facet and girdle, with rect-
Used to describe minerals that different directions. angular facets parallel to these.
have an indefinite shape, or that ¢ POLYCRYSTALLINE e STONE
consist of small crystals in masses. Refers to a mineral made of many ‘Term used for any gemstone.
© MATRIX small crystals. e STRIATION
The rock in which a gem is found. ¢ PRIMARY DEPOSIT Parallel scratch, groove, or line.
Also known as host or parent rock. Material still in its original rock. e SYMMETRY, AXIS OF
¢ METAMICT See also Secondary deposit. Imaginary line through a crystal. If
Refers to material that is breaking ¢ PRISMATIC the crystal were rotated about its
down from a crystalline to an Habit in which parallel pairs of axis 1t would present an identical
amorphous state, due to the rectangular faces form prisms. aspect two or more times in a
presence of radioactive elements. ¢ PSEUDOMORPH rotation of 360 degrees.
¢ METAMORPHIC ROCKS One mineral occurring in the e SYNTHETIC GEMSTONE
Rocks that have been changed by crystal shape of another. Laboratory-made stone whose
heat and/or pressure to form new © REFRACTION chemical composition and optical
rocks consisting of new minerals. Bending of light as it passes from properties are similar to those of its
© MICROCRYSTALLINE air into a different medium. natural equivalent.
Mineral structure in which @ REFRACTIVE INDEX (RI) ¢ TABLE FACET
crystals are too small to be Measure of the slowing down and Central facet on a gem’s crown.
detected by the naked eye. bending of light rays as they enter a ¢ TRICHROIC
¢ MINERALS gemstone. May be used to identify Refers to a gem that appears three
Inorganic, naturally occurring individual gem species. different colors or shades when
materials with a constant chemical @ REFRACTOMETER viewed from different directions.
composition and regular internal Apparatus used to measure the ¢ VITREOUS
atomic structure. refractive indices of gems. Glasslike (used to describe luster).
158 e INDEX

INDEX
A boule 34
bowenite 127
citrine 83
cleavage 17 IF
achroite 102 brazilianite 118 color key 38 faceting 26
adularia 122 brown quartz 84 colorless orthoclase 122 fibrolite 111
agate 88 bronzite 112 colorless sapphire 96 fire agate 87
alabaster 128 burmite 148 coral 142 fluorite 66
albite 130 cordierite 112 fool’s gold 63
alexandrite 108 cornelian 93
C
formation 12
allochromatic gems 20 corundum fortification agate 88
almandine 59 cairngorm 84 colorless sapphire 96 fracture 17
amazonite 123 calcite 98 green sapphire 96
amber 148
amblygonite 132
californite 74
carnelian 93
padparadscha 95
pink sapphire 97 G
ambroid 148 carving 28 ruby 94 gahnospinel 65
amethyst 82 cassiterite 70 sapphire 95 garmet
ametrine 82 cat’s-eye 108 yellow sapphire 97 almandine 59
andalusite 110 celestine 105 crystal shapes 18 andradite 62
andradite garnet 62 cerussite 105 crystal systems 19 cinnamon stone 60
anglesite 114 chalcedony cutting 10 demantoid 62
apatite 79 agate 88 cymophane 108 green grossular 61
aquamarine 76 bloodstone 93 cyprine 74 hessonite 60
aragonite 104 carnelian 93 pink grossular 60

D
asparagus stone 79 chrysoprase 92 pyrope 58
australite 137 cornelian 93 rosolite 60
aventurine quartz 85 fire agate 87 danburite 110 spessartine 58
aventurine feldspar 130 fortification agate 88 datolite 129 Transvaal jade 61
axinite 133 heliotrope 93 demantoid garnet 62 tsavorite 61
azurite 126 jasper 92 diamond 54 uvarovite 59
landscape agate 89 dichroite 112 garnet-topped doublet 61

B
moss agate 88 diopside 119 gemology 7 /
onyx 90 dioptase 99 gems, collecting 8
barite 104 plasma 93 dolomite 99 gemstones
benitoite 80 prase 92 dravite 102 defined 10 |
beryl sard 90 dumortierite 117 distribution 14 ,
aquamarine 76 sardonyx 90 dumortierite quartz 117 folklore 32
bixbite 78 chatoyant quartz 86 history 30
chessylite 126 Gilson gems 35
E
emerald 75
goshenite 77 chiastolite 110 gold 48
heliodor 77 chrome diopside 119 emerald 75 goshenite 77
morganite 78 chrysoberyl 108 engraving 29 green and yellow
red 78 chrysocolla 126 enstatite 111 tourmaline 103
beryllonite 118 chrysoprase 92 epidote 121 green grossular 61
birefraction 21 cinnamon stone 60 euclase 129 green sapphire 96
birthstones 33 grossular garnet 60
bixbite 78 gypsum 128
blende 63
bloodstone 93
Blue John 67 H
hambergite 115
hardness 16
hauyne 68
hawk’s-eye 86
heat treatment 37
heliodor 77
heliotrope 93
hematite 100
hessonite 60
hiddenite 120
howlite 128
hypersthene 112
 INDEX e 159

I
idiochromatic gems 20
idocrase 74
igneous rocks 12
imitation 36
Inca rose 100
inclusions 24
indicolite 101
indigolite 101
interference 23
iolite 112
iron rose 100
irradiation 37
ivory 146
optical properties 20
organic gems 13 R staurolite 117
succinite 148
orthoclase rainbow quartz 87 sunstone 130

J colorless 122
moonstone 123
red beryl 78
refractive index 21
synthetic gems 34

i
jade yellow 122 rhodochrosite 100
jadeite 124 rhodonite 132

P
nephrite 125 rock crystal 81 taaffeite 80
jasper 92 rose quartz 83 tanzanite 116
jet 140 padparadscha 95 rosolite 60 tektites 137
pearl 138 rubellite 101 thulite 116
peridot 113 rubicelle 64 tiger’s-eye 86
K peristerite 130
petalite 129
ruby 94
rutilated quartz 87
titanite 121
topaz 106
Knoop scale 16
kornerupine 113 petrified wood 88 rutile 71 tortoiseshell 144
kunzite 120 phenakite 98 tourmalinated quartz 87
kyanite 133 phosphophyllite 127
physical properties 16 5 tourmaline
achroite 102
pink grossular 60 dravite 102
L
sagenite 87
pink sapphire 97 sapphire 95 green and yellow 103
labradorite 130 plasma 93 colorless 96 indicolite 101
landscape agate 89 platinum 52 green 96 indigolite 101
lapis lazuli 69 pleochroic gems 21 pink 97 rubellite 101
lazulite 128 polishing 28 yellow 97 schorl 103
loupe 35 prase 92 sard 90 siberite 101
luster 22 prehnite 115 sardonyx 90 watermelon 103
pyrite 63 satin spar 128 ‘Transvaal jade 61
pyrope 58 scapolite 71 tsavorite 61
MN scheelite 70 tugtupite 74

QO
malachite 126 schorl 103 turquoise 131
meerschaum 119 sedimentary rocks 13

UVW
metamorphic rocks 12 quartz selenite 128
microcline 123 amethyst 82 sepiolite 119
milky quartz 85 aventurine 85 serpentine 127 unakite 121
mocha stone 88 brown 84 shell 144 uvarovite 59
Mohs scale 16 cairngorm 84 siberite 101 vesuvianite 74
moldavite 137 cat’s-eye 86 sillimanite 111 violane 119
moonstone 123 chatoyant 86 silver 50 watermelon tourmaline
morganite 78 hawk’s-eye 86 simetite 148 103
moss agate 88 milky 85 sinhalite 114 wernerite 71
multicolored 21 rainbow 87 Slocum stones 36 williamsite 127
nephrite 125 rock crystal 81 smithsonite 99 wiluite 74
rose 83 smoky quartz 84

O XYZ
rutilated 87 sodalite 68
sagenite 87 specific gravity 16
obsidian 136 smoky 84 spessartine 58 xanthite 74
oiling 37 tiger’s-eye 86 sphalerite 63 yellow orthoclase 122
oligoclase 130 tourmalinated 87 sphene 121 yellow sapphire 97
onyx 90) with inclusions 87 spinel 64 zircon 72
opal 134 quartz cat’s-eye 86 spodumene 120 zoisite 116
160 e ACKNOWLEDGMENTS

USEFUL ADDRESSES
Gemological Institute of America Canadian Gemmologist Appraisers Association
1660 Stewart Street, Santa Monica, CA 9040 PO Box 69024, Vancouver, BC, V3K 4W3

American Gem Trade Association Canadian Gemmological Association

181 World ‘Trade Center, 2050 Stemmons 21 Dundas Square, Suite 1209, Toronto, Ontario,
Expressway, Dallas, ‘TX 75207 M5B 1B7

The Smithsonian Institution Gemmological Association of Great Britain

Washington DC, 20560 27 Greville Street, London, EC1N 8SU

International Colored Gemstones Association The Gemmological Association of Australia

609 Fifth Avenue, New York, PO Box 1155, North Richmond, Victoria, 3121,
NY 10017 Australia

ACKNOWLEDGMENTS
The author would like to thank the Mineralogy 49 (cl); Bridgeman Art Library 57 (tc); Cartier 27 (tr),
Department curatorial team at the Natural History 29 (tr); Crown Copyright (reproduced by permission of
Museum (Alan Hart, David Smith, Peter Tandy, Henry the Controller of Her Majesty’s Stationery Office) 7 (tr);
Buckley, Andrew Clark) and the team leader Dr. Robert De Beers 13 (bl & br), 14 (cl); Garrard, the Crown
Symes for their help in getting gem specimens to Harry Jewellers 49 (br), 55 (t); Andrew Farmer 28 (bl); Michael
‘Taylor in the Photographic Department; my husband, Holford 11 (r), 31 (tr), 32 (c & tr), 59 (tc), 106 (br); The
Robert, and daughters, Alice and Emily, for giving me Hutchison Library 8 (br); Alan Jobbins 6 (tr), 8 (c), 15 (tr
time to work quietly in my study, with only a few inter- & bl), 20 (er), 24 (br), 25 (tl, er, & br), 32 (er), 35 (cr), 36
ruptions; Dr. Roger Harding, Alan Jobbins, Dr. Joseph (tr & br), 37 (tr), 56 (tr), 59 (tr), 60 (tr), 62 (tr), 75 (tr & cl),
Peters, and Christine Woodward for their expert help; 82 (tr), 86 (bl), 94 (tr & cl), 135 (er & br), 140 (tr), 145 (tr);
and the team at Dorling Kindersley, especially Alison Bernd Munsteiner 2, 29 (br); The Natural History
Edmonds, Alison Shackleton, Jonathan Metcalf, Mary- Museum 11 (bl), 13 (er), 21 (br), 23 (tr), 24 (bl), 38 (tl);
Clare Jerram, Lesley Malkin, and Lucinda Hawksley. The Platinum Advisory Centre 26 (br), 53 (tl &
br)/Nicolas Sapieha 53 (tr); The Smithsonian Institution
Dorling Kindersley would like to thank: Michael Allaby 76 (tr), 94 (cr), 107 (tr); Tiffany & Co 51 (tr & br), 55 (cr);
for compiling the index; Caroline Church for the The Victoria & Albert Museum 31 (cl), 32 (br), 125 (cr);
endpapers; Neal Cobourne for the jacket design; Peter Werner Forman Archive 30 (cr); The Worshipful
Bull for the rock cycle diagram 12 (tr); Janos Marffy for Company of Gold-
all additional artwork; Julia Pashley for picture research;
smiths 49 (tr),
Harry ‘Taylor for his patience and co-operation during 50 (bl), 51 (bl
photography; Alastair Wardle for gem diagrams and the
& cr), 53 (bl).
map on pp.14—-15; Alison Edmonds for the loan of
diamond jewelry for photography, 55 (cl); R. Keith
Mitchell for the loan of taaffeite for photography 80 (t);
Lesley Malkin and Constance Novis for additional
editorial assistance; Peter Cross, Ann Thompson, and
Kevin Ryan for additional design assistance.
All specially commissioned photography by Harry
Taylor, except 11 (tr), 12 (cl), 13 (tr), 17 (bl & br), 18 (br),
19 (cl), 21 (cl), 26 (cutting a brilliant), 27 (br), 28 (tl & tr),
33 (tl, tr, bl, & br), 34 (tr, bl, & br), 35 (br), 36 (tl, cl & cr),
48 (c & bl), 50 (t & br), 55 (br), 57 (tl), 60 (br), 63 (tr &
br), 67 (bl), 68 (cr), 69 (tr & br), 70 (er & br), 71 (cl, cr, &
br), 72 (cr), 74 (cl), 76 (bce), 77 (cl & cr), 78 (br), 81 (br),
82 (br), 83 (br), 85 (br), 87 (tc), 88 (bl & br), 92 (tr, cl, &
bl), 93 (tr & c), 94 (br), 95 (cr & c), 98 (tr), 100 (br), 101
(ter), 104 (tr), 106 (br), 107 (cr), 109 (tr), 110 (br), 112 (br),
113 (br), 117 (bl), 120 (tl, tr, & cl), 124 (bl), 125 (tr, cl, bl,
& br), 130 (cl, er, & br), 134 (c), 135 (be), 138 (br), 139 (1),
141 (cl), 142 (bl & br), 143 (tl), 145 (cl, cr, bl, & br), 148
(br) by Colin Keates; 30 (tr) by Dave King; and 144 (t, bl,
& br) by Matthew Ward.
The publishers would also like to thank the
following for permission to reproduce their w
photographs and illustrations:
Vicky Ambery-Smith 50 (tl); Asprey Ltd 31 (br),
 STON ES
A new generation of field guides, the Eyewstness
Handbooks make identification of individual
specimens sure, simple, and
straightforward. Each volume
includes hundreds of superb
photographs combined with
concise, informative descriptions
of over 100 specimens. ‘The
Kyewitness Handbook of Gemstones 1s packed
with more than 800 vivid
full-color photographs.
It is an invaluable
resource for every
enthusiast.

ISBN 1-56458-498-4
~ae a : 90000>

WY K
ee : = 7

6-70040 12, TN
Printed in Singapore a 781564"584984