Pyrrhotite: Gemstone Information
Pyrrhotite is Fe1-xS (x0–0.2) and provides bronze-yellow to pinchbeck brown masses whose surface quickly tarnishes, sometimes to give an attractive iridescence. Pyrrhotite is monoclinic, pseudohexagonal with hardness 3.5–4.5 and SG 4.58–4.65. RI details not published. Specimens may be attracted by a magnet. Pyrrhotite occurs mainly in mafic igneous rocks and in pegmatites and high-temperature hydrothermal and replacement veins. Material is widespread around the world, localities including Sudbury, Ontario, Canada, and Herja (Kisbanya), Romania, where crystals have been found.