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.

Polydymite is the nickel equivalent of violarite and in many cases these two minerals are formed together, potentially in solid solution.

Polydymite is reported widely from the oxidised regolith above primary nickel sulfide ore systems worldwide.

It is less common than related violarite, due to the high iron content of most primary sulfides.

Polydymite is an important transitional ore in many nickel sulfide mines, as it has increased nickel tenor (Ni% as a total of sulfide) and occupies a position within the mineralised profile where it must be extracted to pay for development down to the more valuable primary (hypogene) mineralisation.