Formula: CoAs
Arsenide, nickeline group
Crystal System: Hexagonal
Specific gravity: 8.17 calculated
Hardness: 6 to 6½
Colour: Pink

Hydrothermal environments

Langisite occurs in pockets of ore minerals, and in breccia cemented with calcite and quartz. Associated minerals include cobaltpentlandite, siegenite, parkerite, pyrite variety bravoite, safflorite, maucherite, pyrite and marcasite (HOM).


At the type locality, the Langis mine, Casey Township, Cobalt Area, Cobalt-Gowganda region, Timiskaming District, Ontario, Canada, an unusual assemblage of arsenides, sulphides and native bismuth has been found in an ore-bearing fault vein. The arsenides are safflorite, langisite and maucherite. The sulphides consist of two distinct sub-assemblages, one of pyrite and marcasite intimately intergrown, and the other of bismuthinite, parkerite, cobaltpentlandite, siegenite, pyrite variety bravoite and late pyrite. The sequence of deposition was firstly arsenides, then pyrite-marcasite, native bismuth, and finally other sulphides.
The langisite was found only as irregular grains and lamellae in safflorite. It is generally present near the sulphides, but most of it is separated from the sulphides by safflorite (CM 9.597-616).

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