Polydymite
Polydymite, NiNi2S4, 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.