Nichromite | |
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General | |
Category | Spinel group |
Formula | (Ni,Co,Fe)(Cr,Fe,Al)2O4 |
Strunz classification | 4.BB.05 |
Crystal system | Isometric |
Crystal class | Hexoctahedral (m3m) H-M symbol: (4/m 3 2/m) |
Space group | Fd3m |
Unit cell | a = 8.32 Å; V = 573.86 Å3; Z = 8 |
Identification | |
Color | Dark green, black |
Crystal habit | Granular, anhedral to subhedral |
Fracture | Conchoidal |
Mohs scale hardness | 6-6+1⁄2 |
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]