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Chrysocolla



Chrysocolla

Chrysocolla from Nevada, USA
General
CategorySilicate mineral
Chemical formula(Cu,Al)2H2Si2O5(OH)4·nH2O
Identification
ColorBlue, blue-green, green
Crystal habitMassive, nodular, botryoidal
Crystal systemOrthorhombic
Cleavagenone
FractureBrittle to sectile
Mohs Scale hardness2.5 - 3.5
LusterVitreous to dull
Refractive indexnω = 1.460 nε = 1.570
Optical PropertiesUniaxial (+)
Birefringence+0.110
StreakLight green
Specific gravity1.9 - 2.4
DiaphaneityTranslucent to opaque

Chrysocolla (hydrated copper silicate) is a mineral, (Cu,Al)2H2Si2O5(OH)4·nH2O. 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.

Additional recommended knowledge

Chrysocolla has an attractive blue-green colour and is a minor ore of copper, having a hardness of 2.5 to 3.5. It is also used as an ornamental stone. It is typically found as glassy botryoidal or rounded masses and crusts, or vein fillings. Because of its light color, it is sometimes confused with turquoise. Commonly it occurs only as pourous crusts unsuitable for gem use, but high quality, gem grade chrysocolla can be translucent and is highly prized.    

The name comes from the Greek chrysos, "gold", and kolla, "glue", in allusion to the name of the material used to solder gold, and was first used by Theophrastus in 315 BCE.

Notable occurrences include Israel, Democratic Republic of Congo, Chile, Cornwall in England, and Arizona, Utah, New Mexico and Pennsylvania in the United States.

References

  • Handbook of Mineralogy, 2001, Mineral Data Pub.
  • Mindat
  • Webmineral data
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Chrysocolla". A list of authors is available in Wikipedia.
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