It was first described in 1964 for an occurrence in San Bernardino County, California, and named after the mineralogist and physical chemist Joseph W. Greig (1895–1977).

[6] The mineral typically appears as microscopic (< 0.03 mm) isometric hexoctahedral crystals and as minute sooty masses.

Association minerals include montmorillonite, chlorite, calcite, colemanite, veatchite, sphalerite, pyrite, marcasite, galena and dolomite.

[3] Ni impurities are of particular interest because the structural similarity between Ni-doped greigite and the (Fe,Ni)S clusters present in biological enzymes has led to suggestions that greigite or similar minerals could have acted as catalysts for the origin of life.

The S anions form a cubic close-packed lattice, and the Fe cations occupy both tetrahedral and octahedral sites.