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Cobaltite
Cobaltite, or Cobaltine (CoS2+CoAs), the arseno-sulphide of cobalt, is a silver-white mineral with a pinkish tarnish, resembling pyrite in crystallising in the cubic system. Heated in the closed tube it is unaltered: in the open tube it gives off sulphurous fumes and a sublimate of arsenious acid. It has a greyish-black streak, and also resembles smaltite (q.v.) in hardness (5.5 to 6) and specific gravity (6.4 to 7.2). It is a valuable ore of cobalt, and occurs at Botallack and St. Austell, in Cornwall; in Sweden, Norway, Westphalia, etc.