Polydymite Dimensions: 20 mm x 18 mm x 14 mm; Field of view: 2,4 mm; largest crystal: 1,7 mm Locality: Grüneau Mine, Schutzbach, Betzdorf, Siegerland, Rhineland-Palatinate, Germany Description: Collection and photograph Christian Rewitzer 5.2014 — Photo: Christian Rewitzer · CC BY-SA 3.0 de
Polydymite
A nickel thiospinel of the supergene zone — the weathering product of pentlandite in nickel deposits.
Intro adapted from Wikipedia (CC BY-SA).
Polydymite is an IMA-recognized mineral species in the sulfide class, with the chemical formula Ni²⁺Ni³⁺₂S₄.
It crystallizes in the cubic crystal system (space group Fd3m). It is a member of the Spinel structural group.
Key properties: Mohs hardness 4.5–5.5; specific gravity 4.5–4.8; Metallic, brilliant on fresh surface. R: (400) 44.3, (420) 44.8, (440) 45.3, (460) 45.7, (480) 46.0, (500) 46.2 luster.
IMA symbol Pld, grandfathered status — known before the IMA’s founding, named in 1876.
Found in hydrothermal veins.
It is found associated with Chalcopyrite, pyrrhotite, pyrite, millerite, gersdorffite, ullmannite, sphalerite, galena, bismuthinite, quartz, siderite.
Its name comes from the Greek for many and twin, as the mineral is observed in twinned forms.