Pyrite, FeS2, is the most common member of the sulfide group. It is a common mineral in strong reducing conditions, forming in saturated soils and in peats. It has a cubic crystal system. It will oxidize into a variety of iron sulfate compounds when subjected to an oxidizing environment.
Pyrite is a common sulphide mineral and occurs in igneous, sedimentary and metamorphic rock. It often replaces fossils and will spark when struck with steel.
Bayliss, P. 1977. Crystal structure refinement of a weakly anisotropic pyrite. American Mineralogist. 62:1168-1172.