- Nichromite
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Nichromite General Category Spinel Group Chemical formula (Ni,Co,Fe)(Cr,Fe,Al)2O4 Strunz classification 04.BB.05 Crystal symmetry Isometric, m3m(4/m32/m) hexoctahedral Unit cell a=8.32 Å V=573.86 ų; Z = 8 Identification Color Dark green, black Crystal habit Granular, anhedral to subhedral Crystal system Isometric Fracture Conchoidal Mohs scale hardness 6-6½ Luster Metallic Streak Greyish green Diaphaneity Opaque Specific gravity 5.10 Optical properties Isotropic References [1][2][3][4] Nichromite (Ni,Co,Fe)(Cr,Fe,Al)2O4[1] is a black cubic metallic mineral and member of the spinel group.[5] Nichromite was originally reported from the Bon Accord nickel deposit in Barberton District, South Africa.[1] Occurring naturally in a nickel deposit, nichromite is named for chromite with dominant nickel.[2]
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.[6]
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.[4]
References
- ^ a b c Nichromite on Mindat.org
- ^ a b 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.
- ^ a b Cabri, L. J., Chao G.Y., Pabst, Adolf, Fleischer, Michael. (1980) New Mineral Names. American Mineralogist, 65, 811.
- ^ Glossary of Geology
- ^ Wyckoff, R.W.G. (1965) Crystal Structures (Second Edition). 75-86 p. University of Arizona, Tucson, Arizona.
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