Cobaltpentlandite
Pentlandite is an iron–nickel sulfide with the chemical formula (Fe,Ni)9S8. Pentlandite has a narrow variation range in nickel to iron ratios (Ni:Fe), but it is usually described as 1:1. In some cases, this ratio is skewed by the presence of pyrrhotite inclusions. It also contains minor cobalt, usually at low levels as a fraction of weight. Pentlandite forms isometric crystals, but it is normally found in massive granular aggregates. It is brittle with a hardness of 3.5–4 and specific gravity of 4.6–5.0 and is non-magnetic. It has a yellowish bronze color and a metallic luster.
Intro adapted from Wikipedia (CC BY-SA).
Cobaltpentlandite is an IMA-recognized mineral species in the sulfide class, with the chemical formula Co₉S₈.
It crystallizes in the cubic crystal system (space group Fm3m). It is a member of the Pentlandite structural group.
Key properties: specific gravity 5.22; Metallic. R: (400) 36.9, (420) 41.9, (440) 45.9, (460) 49.2, (480) 51.7, (500) 53.8, (520) 55.6, (540) 57.0 luster.
IMA symbol Copn, IMA status: approved, named in 1959.
With other sulfides and arsenides in hydrothermal deposits.
It is found associated with Pyrite, marcasite, pyrrhotite, troilite, chalcopyrite, cubanite, bornite, chalcocite, digenite, linnaeite, siegenite, parkerite, bravoite, langisite, magnetite.
The name refers to the cobalt content and the relation with pentlandite.