Tennantite is a copper sulfosalt mineral 4S and zinc It is gray-black, steel-gray, iron-gray or black in color. A closely related mineral, tetrahedrite (Cu12Sb 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 substitute up to about 15% for the copper site.
The mineral was first described for an occurrence in Cornwall , England in 1819, where it occurs as small crystals of cubic or dodecahedral form, and was named after the English chemist Smithson Tennant
It is found in hydrothermal and contact deposits in association with other Cu–Pb–Zn–Ag sulfides and sulfosalts, pyrite , calcite , barite
The arsenic component of tennantite causes the metal smelted from the ore to be harder than that of pure copper, because it is a copper-arsenic alloy. In the later 20th century it was found that arsenical coppers had been more widely used in antiquity than had been previously realised, and it has been proposed that discoveries made by smelting ores like tennantite were significant steps in the progress towards the Bronze Age