Polybasite
Polybasite is a sulfosalt mineral of silver, copper, antimony and arsenic. Its chemical formula is [(Ag,Cu)6(Sb,As)2S7][Ag9CuS4].
| Polybasite | |
|---|---|
 | |
| General | |
| Category | Sulfosalt minerals |
| Formula (repeating unit) | [(Ag,Cu)6(Sb,As)2S7][Ag9CuS4] |
| IMA symbol | Plb[1] |
| 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 | [2][3][4][5] |
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.
Images
Unusual polybasite specimen from Mayo Mining District, Yukon Territory, Canada.
References
- Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85: 291–320.
- Polybasite: mindat.org
- Webmineral.com
- Handbook of Mineralogy
- Rudolf Dǔd'a and Luboš Rejl (1990). Minerals of the World. Arch Cape Press. p. 40. ISBN 0-517-68030-0.
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