tetrahedrite series

{{Infobox mineral | name = Tetrahedrite | category = Sulfosalt mineral | boxwidth = | boxbgcolor = | image = Tetrahedrite - Black Pine mine, Granite Co., Montana, USA.jpg | imagesize = 260px | caption = Tetrahedrite crystal with traces of quartz (in middle) and micro mimetite, specimen size 3.5 × 2.5 × 2.5 cm | formula = | molweight = | strunz = 2.GB.05 | system = Cubic | class = Hextetrahedral (3m) H-M symbol: ( 3m) | symmetry = I3m | unit cell = a = 10.39(16) Å; Z = 2 | color = Steel gray to iron-gray | habit = Groups of tetrahedral crystals; massive, coarse to fine compact granular | twinning = Contact and penetration twins on {111} | cleavage = None | fracture = Uneven to subconchoidal | tenacity = Somewhat brittle | mohs = 4 | luster = Metallic, commonly splendent | streak = Black, brown to dark red | polish = | refractive = n greater than 2.72 | opticalprop = Isotropic | birefringence = | dispersion = | pleochroism = | fluorescence= | absorption = | gravity = 4.97 | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Opaque, except in very thin fragments | other = | references = }} Tetrahedrite is a copper antimony sulfosalt mineral with the formula: . It is the antimony endmember of the continuous solid solution series with arsenic-bearing tennantite. Pure endmembers of the series are rarely 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.

==Mineralogy== Tetrahedrite gets its name from the distinctive tetrahedron shaped cubic crystals. The mineral usually occurs in massive form, it is a steel gray to black metallic mineral with Mohs hardness of 3.5 to 4 and specific gravity of 4.6 to 5.2.