Nichromite
{{Infobox mineral
|name=Nichromite
| category = Spinel group
| formula = {{chem2|(Ni,Co,Fe)(Cr,Fe,Al)2O4}}
| strunz = 4.BB.05
| system = Isometric
| class = Hexoctahedral (m{{overline|3}}m)
H-M symbol: (4/m {{overline|3}} 2/m)
| symmetry = Fd{{overline|3}}m
| unit cell = a = 8.32 Å; V = 573.86 Å3; Z = 8
| color = Dark green, black
| habit = Granular, anhedral to subhedral
| mohs = 6-{{frac|6|1|2}}
| fracture = Conchoidal
| luster = Metallic
| refractive =
| opticalprop = Isotropic
| pleochroism =
| streak = Greyish green
| gravity = 5.10
|diaphaneity = Opaque
|references=[http://www.mindat.org/min-2894.html Nichromite on Mindat.org][http://webmineral.com/data/Nichromite.shtml Nichromite on Webmineral]Sawaokaa,A.,Saitoa,S.,Inoueb,K. and Asadab,T. (1971)Effect of high pressure on the lattice constants of chromites having the spinel structure. Materials Research Bulletin, 6, 97-101.Cabri, L. J., Chao G.Y., Pabst, Adolf, Fleischer, Michael. (1980) New Mineral Names. American Mineralogist, 65, 811.
}}
Nichromite {{chem2|(Ni,Co,Fe)(Cr,Fe,Al)2O4}} is a black cubic metallic mineral and member of the spinel group.[http://glossary.agiweb.org/dbtw-wpd/exec/dbtwpub.dll Glossary of Geology] Nichromite was originally reported from the Bon Accord nickel deposit in Barberton District, South Africa. Occurring naturally in a nickel deposit, nichromite is named for chromite with dominant nickel.
The atomic arrangement of the spinel group is a commonly studied structure and characteristically has four closely packed oxygen atoms. The nickel atoms are organized corresponding to a "normal" spinel arrangement.Wyckoff, R.W.G. (1965) Crystal Structures (Second Edition). 75-86 p. University of Arizona, Tucson, Arizona.
The mineral has only been found in the Bon Accord Nickel Deposit in South Africa where it is formed by replacing chromite and rimmed by trevorite.