Polybasite

Polybasite
General
CategorySulfosalt minerals
Formula
(repeating unit)		[(Ag,Cu)6(Sb,As)2S7][Ag9CuS4]
IMA symbolPlb[1]
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
Lustremetallic, adamantine or glimmering
Streakblack with reddish tint
Specific gravity6–6.2
References[2][3][4][5]

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

  • Unusual polybasite specimen from Mayo Mining District, Yukon Territory, Canada.
    Unusual polybasite specimen from Mayo Mining District, Yukon Territory, Canada.

References

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Polybasite: mindat.org
  3. ^ Webmineral.com
  4. ^ "Handbook of Mineralogy" (PDF). Archived from the original (PDF) on 2016-03-03. Retrieved 2011-05-16.
  5. ^ 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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