Nickeline
Nickeline or niccolite is a mineral consisting primarily of nickel arsenide (NiAs). The naturally-occurring mineral contains roughly 43.9% nickel and 56.1% arsenic by mass, but composition of the mineral may vary slightly.
| Nickeline | |
|---|---|
| General | |
| Category | Arsenide mineral |
| Formula (repeating unit) | nickel arsenide (NiAs) |
| IMA symbol | Nc |
| Strunz classification | 2.CC.05 |
| Crystal system | Hexagonal |
| Crystal class | Dihexagonal dipyramidal (6/mmm) H-M symbol: (6/m 2/m 2/m) |
| Space group | P63/mmc |
| Unit cell | a = 3.602 Å, c = 5.009 Å; Z = 2 |
| Identification | |
| Color | Pale copper red with blackish tarnish. white with strong yellowish pink hue on polished section strongly anisotropic |
| Crystal habit | Massive columnar to reniform, rarely as distorted, horizontally striated, {1011} terminated crystals |
| Twinning | On {1011} producing fourlings |
| Cleavage | {1010} Imperfect, {0001} Imperfect |
| Fracture | Conchoidal |
| Tenacity | Brittle |
| Mohs scale hardness | 5 – 5.5 |
| Luster | metallic |
| Streak | brownish black |
| Diaphaneity | Opaque |
| Specific gravity | 7.8 |
| Pleochroism | Strong (reflected light) |
| Fusibility | 2 |
| Other characteristics | garlic odor on heating |
| References | |
Small quantities of sulfur, iron and cobalt are usually present, and sometimes the arsenic is largely replaced by antimony. This last forms an isomorphous series with breithauptite (nickel antimonide).
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