Iron(III) sulfide

Iron sulfide, also known as ferric sulfide or sesquisulfide, is one of the several binary iron sulfides. It is a solid, black powder that degrades at ambient temperature.

Reactions

precipitates from solutions containing its respective ions:
The resulting solid decays at a temperature over 20 °C into iron(II) sulfide and elemental sulfur:
With hydrochloric acid it decays according to the following reaction equation:

Greigite

Greigite, with the chemical formula, is a mixed valence compound containing both Fe and Fe. It is the sulfur equivalent of the iron oxide magnetite. As established by X-ray crystallography, the S anions form a cubic close-packed lattice, and the Fe cations occupy both tetrahedral and octahedral sites.