Chemical Formula: NiAsS
Locality: Zinkwand, Schladming, Styria, Austria.
Name Origin: Named after Herr von Gersdorff, owner of Schladming Mine, Austria.
Gersdorffite is a nickel arsenic sulfide mineral with formula NiAsS. It crystallizes in the isometric system showing diploidal symmetry. It occurs as euhedral to massive opaque, metallic grey-black to silver white forms. Gersdorffite belongs to a solid solution series with cobaltite, CoAsS. Antimony freely substitutes also leading to ullmannite, NiSbS. It has a Mohs hardness of 5.5 and a specific gravity of 5.9 to 6.33.
Gersdorffite has three crystallisation forms: Gersdorffite-P213 (NiAsS), Gersdorffite-Pa3 (Ni(As,S)2) and Gersdorffite-Pca21 (NiAsS). Gersdorffite occurs as a hydrothermal vein mineral along with other nickel sulfides. Associated minerals include nickeline, nickel-skutterudite, cobaltite, ullmannite, maucherite, löllingite, platinum-group minerals, millerite, pyrite, marcasite, and chalcopyrite.
Gersdorffite was first described in 1843 and named for Johann von Gersdorff (1781–1849), owner of the nickel mine at Schladming, Austria the type locality.
Physical Properties
Cleavage: {100} Good, {010} Good, {001} Good
Color: Gray, Grayish black, Silver white, Tin white.
Density: 5.9 – 6.33, Average = 6.11
Diaphaneity: Opaque
Fracture: Brittle – Generally displayed by glasses and most non-metallic minerals.
Hardness: 5.5 – Knife Blade
Luminescence: Non-fluorescent.
Luster: Metallic
Magnetism: Nonmagnetic
Streak: grayish black
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