Black metallic crystals of tsumoite, a bismuth telluride, from one of the best known localities for the mineral: Bjorkdal Mine, Västerbotten, Sweden. — Photo: David Hospital · CC BY-SA 4.0
Tsumoite
Tsumoite is an IMA-recognized mineral species in the sulfide class, with the chemical formula BiTe.
It crystallizes in the hexagonal crystal system (space group P-3m1). It is a member of the Tetradymite structural group.
Key properties: specific gravity 8.16; Steel-gray streak; Metallic luster.
IMA symbol Tsm, IMA status: approved, named in 1974.
Found in massive Ni–Cu–PGE deposits; in Cu–Zn–Pb deposits, with sulfosalts, formed at lower temperatures.
It is found associated with Pentlandite, chalcopyrite, pyrrhotite, sperrylite, parkerite, maucherite, michenerite, tetradymite, pilsenite, cosalite, altaite, bismuthinite, galena.
The name refers to the Tsumo mine, Japan, where it was first found.