Polybasite

Polybasite
General
Category Sulfosalt minerals
Formula
(repeating unit)
[(Ag,Cu)6(Sb,As)2S7][Ag9CuS4]
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 [1][2][3][4]

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.

Images

References

  1. Polybasite: mindat.org
  2. Webmineral.com
  3. Handbook of Mineralogy
  4. 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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