Tetrahedrite

Tetrahedrite
Tetrahedrite crystal with traces of quartz (in middle) and micro mimetite, specimen size 3.5 × 2.5 × 2.5 cm
General
CategorySulfosalt mineral
Formula
(repeating unit)
(Cu,Fe)
12
Sb
4
S
13
Strunz classification2.GB.05
Crystal systemCubic
Crystal classHextetrahedral (43m)
H-M symbol: (4 3m)
Space groupI43m
Unit cella = 10.39(16) Å; Z = 2
Identification
ColorSteel gray to iron-gray
Crystal habitGroups of tetrahedral crystals; massive, coarse to fine compact granular
TwinningContact and penetration twins on {111}
CleavageNone
FractureUneven to subconchoidal
TenacitySomewhat brittle
Mohs scale hardness3+12 – 4
LusterMetallic, commonly splendent
StreakBlack, brown to dark red
DiaphaneityOpaque, except in very thin fragments
Specific gravity4.97
Optical propertiesIsotropic
Refractive indexn greater than 2.72
References[1][2]

Tetrahedrite is a copper antimony sulfosalt mineral with formula: (Cu,Fe)
12
Sb
4
S
13
. It is the antimony endmember of the continuous solid solution series with arsenic-bearing tennantite. Pure endmembers of the series are seldom if ever seen in nature. Of the two, the antimony rich phase is more common. Other elements also substitute in the structure, most notably iron and zinc, along with less common silver, mercury and lead. Bismuth also substitutes for the antimony site and bismuthian tetrahedrite or annivite is a recognized variety. The related, silver dominant, mineral species freibergite, although rare, is notable in that it can contain up to 18% silver.

  1. ^ Handbook of Mineralogy
  2. ^ "Tetrahedrite: Tetrahedrite mineral information and data". Mindat.org. 2014-07-12. Retrieved 2014-07-17.