Calaverite
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.
| Calaverite | |
|---|---|
Platy calaverite crystals on matrix from the Cripple Creek District (size: 6 x 5 x 3.5 cm) | |
| General | |
| Category | Telluride mineral |
| Formula (repeating unit) | AuTe2 |
| IMA symbol | Clv |
| 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 | |
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.