Calaverite
Telluride of gold / From Wikipedia, the free encyclopedia
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Calaverite, or gold telluride, is an uncommon telluride of gold, a metallic mineral with the chemical formula AuTe2, with approximately 3% of the gold replaced by silver. It was first discovered in Calaveras County, California in 1861, and was named for the county in 1868.
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Calaverite | |
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General | |
Category | Telluride mineral |
Formula (repeating unit) | AuTe2 |
IMA symbol | Clv[1] |
Strunz classification | 2.EA.10 |
Crystal system | Monoclinic |
Crystal class | Prismatic (2/m) (same H-M symbol) |
Space group | C2/m |
Unit cell | a = 7.19 Å, b = 4.4 Å, c = 5.08 Å; β = 90.3°; Z = 2 |
Identification | |
Formula mass | 452.17 g/mol |
Color | Brass yellow to silver white |
Crystal habit | Bladed and slender striated prisms, also massive granular |
Twinning | Common on [110] |
Cleavage | None |
Fracture | Uneven to subconchoidal |
Tenacity | Brittle |
Mohs scale hardness | 2.5–3 |
Luster | Metallic |
Streak | Green to yellow grey |
Diaphaneity | Opaque |
Specific gravity | 9.1–9.3 |
Optical properties | Anisotropic |
Pleochroism | Weak |
Ultraviolet fluorescence | None |
References | [2][3][4][5] |
The mineral often has a metallic luster, and its color may range from a silvery white to a brassy yellow. It is closely related to the gold-silver telluride mineral sylvanite, which, however, contains significantly more silver. Another AuTe2 mineral (but with a quite different crystal structure) is krennerite. Calaverite and sylvanite represent the major telluride ores of gold, although such ores are minor sources of gold in general. As a major gold mineral found in Western Australia, calaverite played a major role in the 1890s gold rushes in that area.