polydymite

{{Infobox mineral | name = Polydymite | image = Polydymite-614287.jpg | alt = | caption = | category = Sulfide mineral Thiospinel group Spinel structural group | formula = Ni3S4 | IMAsymbol = Pld | strunz = 2.DA.05 | dana = | system = Cubic | class = Hexoctahedral (mm) H-M symbol: (4/m 2/m) | symmetry = Fdm | unit cell = a = 9.48 Å; Z = 8 | color = Pale to steel-gray | habit = As octahedral crystals, massive, granular to compact | twinning = Twinning on {111} | cleavage = Indistinct on {001} | fracture = Conchoidal to uneven | tenacity = | mohs = 4.5 – 5.5 | luster = Metallic | streak = Black gray | diaphaneity = Opaque | gravity = 4.5 – 4.8 | density = | polish = | opticalprop = | refractive = | birefringence = | pleochroism = | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = Tarnishes to copper-red | other = | prop1 = | prop1text = | references = }} Polydymite, Ni2+Ni23+S4, is a supergene thiospinel sulfide mineral associated with the weathering of primary pentlandite nickel sulfide.

Polydymite crystallises in the isometric system, with a hardness of 4.5 to 5.5 and a specific gravity of about 4, is dark violet gray to copper-red, often with verdigris and patina from associated copper and arsenic sulfides, and is typically in amorphous to massive infill of lower saprolite ultramafic lithologies.