Stannite
STANNITE, a rare mineral consisting of tin, copper and iron sulphide (a sulpho-stannate, Cu2FeSnS4), containing, when pure, tin 27-5, copper 29-5%. It has a metallic lustre, and, when pure, is iron-black in colour: more often, however, it is bronzeyellow, owing to tarnish or to the presence of intimately admixed chalcopyrite: for this reason it is known to miners as " bell-metal-ore " or as " tin pyrites." The hardness is 3^ and the specific gravity 4-45. It usually occurs as granular to compact masses, rarely as crystals. Minute crystals from Bolivia have been shown to be tetragonal and hemihedral, like chalcopyrite; and to be invariably twinned, giving rise to pseudocubic forms. The mineral has been found in a number of Cornish tin mines, and was formerly worked to a limited extent as an ore. At Zinnwald in Bohemia it occurs with blende and galena, and in Bolivia with silver ores. (L. J. S.)
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)
