Formula: NiAsS
Sulphide, cobaltite group, forms a series with cobaltite, and a complete solid solution with krutovite. (AM83.403)
Specific gravity: 5.9
Hardness: 5½
Streak: Grey-black
Colour: Gray, grayish black, silver white, or tin white

Hydrothermal environments

Gersdorffite occurs in hydrothermal vein deposits formed at moderate tempertures. (Webmin) Associated minerals include nickeline, nickelskutterudite, cobaltite, ullmannite, maucherite, löllingite, platinum-group minerals, millerite, pyrite, marcasite, chalcopyrite and siderite. (HOM, Mindat)

At Ait Ahmane, Bou Azzer, Morocco, gersdorffite is embedded in calcite, sometime associated with nickelskutterudite and quartz. Crystals are often zoned, with the outer zone richer in cobalt. (MinRec 38.5.375)

Common impurities: Co,As,Bi,Fe,Co,Sb,Cu

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