Pentlandite is a iron-nickel sulfide, (Fe,Ni)9S8. Pentlandite usually has a Ni:Fe ratio of close to 1:1. It also contains minor cobalt.

Pentlandite forms isometric crystals, but is normally found in massive granular aggregates. It is brittle with a hardness of 3.5 – 4 and specific gravity of 4.6 – 5.0 and is non-magnetic. It has a yellowish bronze color.

Pentlandite is the chief ore of nickel. Typically associated with pyrrhotite, niccolite, biotite, millerite, pyrite, and chalcopyrite Major occurrence is the Sudbury deposit in Ontario, Canada.