| Nichromite | |
| Category: | Spinel group |
| Strunz: | 4.BB.05 |
| System: | Isometric |
| Class: | Hexoctahedral (mm) H-M symbol: (4/m 2/m) |
| Symmetry: | Fdm |
| Unit Cell: | a = 8.32 Å; V = 573.86 Å3; Z = 8 |
| Color: | Dark green, black |
| Habit: | Granular, anhedral to subhedral |
| Mohs: | 6- |
| Fracture: | Conchoidal |
| Luster: | Metallic |
| Opticalprop: | Isotropic |
| Streak: | Greyish green |
| Gravity: | 5.10 |
| Diaphaneity: | Opaque |
| References: | [1] [2] [3] [4] |
Nichromite [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]