Class : Sulfides and sulfosalts
    Subclass : Sulfides
    Crystal system : Cubic
    Chemistry : Ni₃S₄
    Rarity : Rare

Polydymite belongs to the linnaeite group, named after the most common mineral. This group with general formula X₃S₄ (with X = Co, Ni or Fe, or [Co+Cu]), can be compared with that of spinels, sulfur replacing oxygen; the octahedral facies is also the most common in both groups. The linnaeite group is composed of three solid solutions : Co (linneite in the strict sense) - Ni (polydymite), the intermediate term being siegenite - Fe (greigite), the intermediate term being violarite and Co+Cu (carrollite). This last solid solution is the only one which is incomplete and stops at carrollite. Polydymite is a rare nickel sulfide found in hydrothermal cobalt-nickel deposits and deposits in carbonate contexts. Its name comes from the Greek polus (many) and didumos (twin) because this mineral frequently occurs in polysynthetic twins. Polydymite is gray to slightly pink in color, it is very sensitive to alteration and gradually transforms into complex nickel oxides. It is sometimes a very incidental ore of nickel.

Main photo : Polydymite from Grüneau Mine, Germany © Stephan Wolfsried

Polysynthetic twins are known for this mineral species.

No fakes listed for this mineral species.