Polybasite
| Polybasite | |
|---|---|
| General | |
| Category | Sulfosalt minerals |
| Formula | [(Ag,Cu)6(Sb,As)2S7][Ag9CuS4] |
| IMA symbol | Plb |
| Strunz classification | 2.GB.15 |
| Crystal system | Monoclinic and trigonal polytypes |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | C2/c |
| Identification | |
| Colour | steel black |
| Cleavage | poor on (001) |
| Fracture | uneven |
| Mohs scale hardness | 1.5–2 |
| Lustre | metallic, adamantine or glimmering |
| Streak | black with reddish tint |
| Specific gravity | 6–6.2 |
| References | |
Polybasite is a sulfosalt mineral of silver, copper, antimony and arsenic. Its chemical formula is [(Ag,Cu)6(Sb,As)2S7][Ag9CuS4].
It forms black monoclinic crystals (thin, tabular, with six corners) which can show dark red internal reflections. It has a Mohs hardness of 2.5 to 3. It is found worldwide and is an ore of silver. The name comes from the number of base metals in the mineral.