Use
The natural pyrite consists of yellow cubic crystals; density 5.02g/cm3; hardness 6.3 Mohs; melts at 1,171C; soluble in dilute acids.
The mineral marcasite constitutes yellow rhombic crystals; density 4.87g/cm3; transforms to more stable pyrite form when heated at 480C; insoluble in dilute acids. Both forms dissolve in concentrated nitric acid and are insoluble in water (4.9 mg/L at 20C).