Siegenite , Dolomite Locality: Buick Mine (Amax Buick Mine; Moloc Mine), Bixby , Viburnum Trend District, Iron County, Missouri , USA ( Locality at mindat.org ) Size: 5.1cm x 3.3cm x 2.9cm Numerous, silvery gray, metallic, 3 to 6mm siegenite crystals are attractively set amongst numerous, saddle-shaped, pinkish white crystals of dolomite. Siegenite is a rare cobalt-nickel sulfide and this piece comes from the better finds at the Buick Mine in the 1980's. Well composed pieces like this with both siegenite and dolomite are rarely available today. Ex Tim Campbell collection. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Siegenite
A nickel-cobalt sulfide of the linnaeite group — studied today as a battery-electrode material.
Intro adapted from Wikipedia (CC BY-SA).
Siegenite is an IMA-recognized mineral species in the sulfide class, with the chemical formula CoNi₂S₄.
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) 42.8, (420) 43.2, (440) 43.7, (460) 44.3, (480) 44.8, (500) 45.4 luster.
IMA symbol Seg, grandfathered status — known before the IMA’s founding, named in 1850.
Found in hydrothermal veins with other Cu–Ni–Fe sulfides.
It is found associated with Chalcopyrite, pyrrhotite, galena, sphalerite, pyrite, millerite, gersdorffite, ullmannite.
The name refers to the occurrence in the Siegen district, Germany.