Chemistry:Polybasite

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Polybasite
Polybasite-37890.jpg
General
CategorySulfosalt minerals
Formula
(repeating unit)
[(Ag,Cu)
6
(Sb,As)
2
S
7
][Ag
9
CuS
4
]
Strunz classification2.GB.15
Crystal systemMonoclinic and trigonal polytypes
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupC2/c
Identification
Coloursteel black
Cleavagepoor on (001)
Fractureuneven
Mohs scale hardness1.5-2
metallic, adamantine or glimmering|re|er}}metallic, adamantine or glimmering
Streakblack with reddish tint
Specific gravity6-6.2
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)
2
S
7
][Ag
9
CuS
4
]
.

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.