Nickeline: Gemstone Information
Nickeline is NiAs and the occasional opaque cabochon is fashioned from granular aggregates of the hexagonal system. The colour ranges from a pale copper-red, tarnishing grey to near-black. The hardness is 5–5.5 and the SG 7.78–7.83. Nickeline occurs in vein deposits in igneous rocks, with silver minerals, bismuth and bismuthinite. Large masses occur in the Cobalt district, Ontario, Canada, and elsewhere.