Chrysocolla
Chrysocolla is a hydrated copper
phyllosilicate mineral with formula:
Cu2−xAlx(H2−xSi2O5)(OH)4·nH2O (x<1)[1] or
(Cu,Al)2H2Si2O5(OH)4·nH2O.[3] The
structure of the mineral has been
questioned, as spectrographic studies
suggest material identified as chrysocolla
may be a mixture of the copper hydroxide
spertiniite and chalcedony.
Chrysocolla
Chrysocolla, Ray Mine, Scott Mountain area,
Mineral Creek District, Pinal County, Arizona, USA
General
Category Phyllosilicate mineral
Formula Cu2−xAlx(H2−xSi2O5)
(repeating unit) (OH)4·nH2O (x<1)[1]
Strunz classification 9.ED.20
Crystal system Orthorhombic
Unknown space group
Unit cell a = 5.7 Å, b = 8.9 Å,
c = 6.7 Å; Z = 1
Identification
Color Blue, cyan or blue-
green, green
Crystal habit Massive, nodular,
botryoidal
Cleavage none
Fracture Irregular/uneven, sub-
conchoidal
Tenacity Brittle to sectile
Mohs scale hardness 2.5 - 3.5 ( or 7 -
chrysocolla chalcedony,
high silica content )
Luster Vitreous to dull
Streak white to a blue-green
color
Diaphaneity Translucent to opaque
Specific gravity 1.9 - 2.4
Optical properties Biaxial (-)
Refractive index nα = 1.575 - 1.585 nβ =
1.597 nγ = 1.598 - 1.635
Birefringence δ = 0.023 - 0.050
References [2][3][1][4]
Properties
Powder-blue chrysocolla as stalactitic growths and as
a thin carpet in vugs inside a boulder of nearly solid
tyrolite from the San Simon Mine, Iquique Province,
Chile (size: 14.1 x 8.0 x 7.8 cm)
Chrysocolla has a cyan (blue-green) color
and is a minor ore of copper, having a
hardness of 2.5 to 3.5.
Name and discovery
The name comes from the Ancient Greek:
χρυσός κολλα (chrysos kolla), "gold
glue",[5] in allusion to the name of the
material used to solder gold, and was first
used by Theophrastus in 315 BCE.
Formation and occurrence
Banded white to blue green chrysocolla from Bisbee,
Arizona (size: 12.2 x 5.5 x 5.2 cm)
It is of secondary origin and forms in the
oxidation zones of copper ore bodies.
Associated minerals are quartz, limonite,
azurite, malachite, cuprite, and other
secondary copper minerals.
It is typically found as botryoidal or
rounded masses and crusts, or vein
fillings. Because of its light color, it is
sometimes confused with turquoise.
Notable occurrences include Bacan Island
Indonesia, Israel, Democratic Republic of
Congo, Chile, Cornwall in England, and
Arizona, Utah, Idaho, Colorado, New
Mexico, Michigan, and Pennsylvania in the
United States.
Questions regarding mineral
status
A 2006 study has produced evidence that
chrysocolla may be a microscopic mixture
of the copper hydroxide mineral spertiniite,
amorphous silica and water.[6][1]
See also
Chrysocolla (gold-solder)
References
Wikimedia Commons has media related
to Chrysocolla.
1. Mindat
2. Mineralienatlas
3. Handbook of Mineralogy
4. Webmineral data
5. Spencer, Leonard James (1911).
"Chrysocolla". In Chisholm, Hugh.
Encyclopædia Britannica. 6 (11th ed.).
Cambridge University Press. p. 320.
6. François Farges, Karim Benzerara,
Gordon E. Brown, Jr.; Chrysocolla Redefined
as Spertiniite; SLAC-PUB-12232; 13th
International Conference On X-Ray
Absorption Fine Structure (XAFS13); July 9-
14, 2006; Stanford, California
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