Hauerite is a sulfide mineral in the pyrite group. It is the mineral form of Manganese(IV) disulfide . It forms reddish brown or black octahedral crystals with the pyrite structure and it is usually found associated with the sulfides of other transition metals such as rambergite. It occurs in low temperature, sulfur rich environments associated with solfataras and salt deposits in association with native sulfur, realgar, gypsum and calcite.
Under high pressure conditions (P>11 GPa), Hauerite undergoes a large collapse in unit cell volume (22%) driven by a spin-state transition.