gersdorffite

Gersdorffite is a rare nickel arsenosulfide mineral with the chemical formula NiAsS. It belongs to the sulfarsenide group and is typically found in hydrothermal nickel-rich ore environments. The mineral crystallizes in the cubic (isometric) system and usually forms small, well-formed crystals that can appear octahedral or cubic; it can also occur in massive aggregates or granular masses. It has a metallic luster and a gray to steel-gray color, and it is opaque. On the Mohs scale, gersdorffite hardness is about 4.5, and its measured specific gravity is in the range of roughly 5.0–5.5.

Occurrence and associations include hydrothermal nickel-bearing sulfide veins and skarn deposits. Gersdorffite is commonly found in association with other nickel-iron sulfides and arsenides such as pentlandite, pyrrhotite, niccolite, arsenopyrite, galena, and sphalerite. The mineral forms as a product of nickel- and sulfur- and arsenic-rich fluids, and its presence can be a useful indicator in the exploration of nickel deposits.

Economic and scientific relevance: gersdorffite is of interest primarily to mineral collectors and researchers for identification and locality studies. It is not a major ore for nickel extraction, but its occurrence helps characterize the mineralogy of Ni-rich hydrothermal systems.

References for further information include standard mineralogy databases and texts such as Mindat, Webmineral, and the Handbook of Mineralogy.