13 Photos
Tennantite
Chemical Formula	Cu12As4S13
Species	Sulfides
Crystal System	Isometric
Mohs Scale	3-4
Specific Gravity	4.65
Color	Flint-gray to iron-black, cherry-red in transmitted light
Streak	reddish gray
Luster	Metallic
Refractive Index	n greater than 2.72
Diaphaneity	Opaque
Cleavage	None
Fracture	Sub-Conchoidal
Crystal Habit：massive to well formed crystals
Geological Setting：Hydrothermal veins and contact metamorphic deposits.

Tennantite is a copper arsenic sulfosalt mineral. Its chemical formula is Cu₁₂As₄S₁₃. It is grey-black, steel-gray, iron-gray or black in color. A closely related mineral, tetrahedrite (Cu₁₂Sb₄S₁₃) has antimony substituting for arsenic and the two form a solid solution series. The two have very similar properties and is often difficult to distinguish between tennantite and tetrahedrite. Iron, zinc, and silver substitute up to about 15% for the copper site.

The mineral was first described for an occurrence in Cornwall, England in 1819 and named after the English chemist Smithson Tennant (1761-1815).

It is found in hydrothermal veins and contact metamorphic deposits in association with other Cu–Pb–Zn–Ag sulfides and sulfosalts, pyrite, calcite, dolomite, siderite, barite, fluorite and quartz.