Pyrrhotite (Fe₁₋ₓS) is non-stoichiometric iron sulfide — chemically variable Fe(1-x)S — and is unique among common sulfides for its magnetism (the only common sulfide that is magnetic). Bronze color and slow tarnish are diagnostic. Pyrrhotite forms in mafic-ultramafic igneous rocks (Sudbury Ni-Cu-PGE), contact-metamorphic skarns, and high-T hydrothermal veins.
Key Facts
- Mohs hardness 3.5–4.5.
- Hexagonal/Monoclinic polytypes; the only common magnetic sulfide.
- Bronze-yellow color; tarnishes brown.
- Common gangue in Ni-Cu-PGE deposits (Sudbury, Norilsk, Jinchuan).
- Often paired with pentlandite, chalcopyrite, magnetite.
Notable Localities
Sudbury (Ontario, Canada) and Norilsk (Russia) host massive ore. Jinchuan (Gansu) is China’s major Ni-Cu-PGE deposit.
Found at these Localities
- Tunaberg (图纳贝里钴矿(瑞典))
- Dachang Tin-Polymetallic Field (大厂锡多金属矿田)
