From the economic perspective, Ni9S8, the mineral pentlandite, is the chief source of mined nickel.

In this structure, nickel is octahedral and the sulfide centers are in trigonal prismatic sites.

This conversion involves heating the sulfide ores in air:[1] The mineral millerite is also a nickel sulfide with the molecular formula NiS, although its structure differs from synthetic stoichiometric NiS due to the conditions under which it forms.

It occurs naturally in low temperature hydrothermal systems, in cavities of carbonate rocks, and as a byproduct of other nickel minerals.

The inclusions eventually convert to the beta phase (stable at low temperature), increasing in volume and causing cracks in the glass.