Supriya Ghosh (Editor)

Polybasite

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Category
  
Sulfosalt minerals

Space group
  
C2/c

Strunz classification
  
2.GB.15

Polybasite

Formula (repeating unit)
  
[(Ag,Cu)6(Sb,As)2S7][Ag9CuS4]

Crystal system
  
Monoclinic and trigonal polytypes

Crystal class
  
Prismatic (2/m) (same H-M symbol)

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.

References

Polybasite Wikipedia