Pearceite
| Pearceite | |
|---|---|
Pearceite from Butte, Montana, US | |
| General | |
| Category | Minerals |
| Formula | Cu(Ag,Cu)6Ag9As2S11 |
| IMA symbol | Pea |
| Strunz classification | 2.GB.15 (10 ed) 2/E.05-20 (8 ed) |
| Dana classification | 3.1.8.1 |
| Crystal system | Monoclinic or trigonal |
| Space group | P3m1 (no. 164) |
| Identification | |
| Formula mass | 2,096.80 g/mol |
| Color | Black |
| Crystal habit | Pseudohexagonal prisms |
| Cleavage | {001} Poor |
| Fracture | Conchoidal to irregular |
| Tenacity | Brittle |
| Mohs scale hardness | 3 |
| Luster | Metallic |
| Streak | Black |
| Diaphaneity | Opaque |
| Specific gravity | 6.15 |
| Optical properties | Biaxial |
| Refractive index | 2.7 |
| Birefringence | 2.7 |
| Pleochroism | RL Pleochroism (in reflected plane polarised light): Very weak in air, fair in oil |
| Other characteristics | Non-fluorescent, nonmagnetic, not radioactive |
| References | |
Pearceite is one of the four so-called "ruby silvers", pearceite Cu(Ag,Cu)6Ag9As2S11, pyrargyrite Ag3SbS3, proustite Ag3AsS3 and miargyrite AgSbS2. It was discovered in 1896 and named after Dr Richard Pearce (1837–1927), a Cornish–American chemist and metallurgist from Denver, Colorado.