tennantiteCu

Tennantite is a mineral species in the sulfosalt group, with the chemical formula (Cu,Fe)12As4S13. It is closely related to tetrahedrite, which has the formula (Cu,Fe)12Sb4S13, differing only in the presence of arsenic instead of antimony. The two minerals form a solid solution series. Tennantite is named in honor of the English chemist Smithson Tennant.

This mineral typically occurs in hydrothermal veins and in some volcanic environments. It is often found associated with other copper and iron sulfides, as well as with gangue minerals like quartz and calcite. Tennantite can be found in various shades of gray, from steel gray to black, and possesses a metallic luster. Its hardness is generally between 3 and 4 on the Mohs scale, and it has a specific gravity of around 4.7.

While not a primary ore of copper, tennantite can be a minor source of this metal. Its occurrence is significant for understanding mineral paragenesis in certain ore deposits. The presence of arsenic in tennantite is a key diagnostic feature that distinguishes it from its antimony-bearing counterpart, tetrahedrite. Both minerals are important members of the tetrahedrite group, which are characterized by their complex crystal structures.