Pentlandite
Pentlandite is an iron–nickel sulfide with the chemical formula (Fe,Ni)9S8. Pentlandite has a narrow variation range in nickel to iron ratios (Ni:Fe), but it is usually described as 1:1. In some cases, this ratio is skewed by the presence of pyrrhotite inclusions. It also contains minor cobalt, usually at low levels as a fraction of weight.
| Pentlandite | |
|---|---|
3.1 × 2.6 cm mass of pentlandite with some pyrrhotite | |
| General | |
| Category | Sulfide mineral |
| Formula (repeating unit) | iron nickel sulfide: (Fe,Ni)9S8 |
| IMA symbol | Pn |
| Strunz classification | 2.BB.15a |
| Dana classification | 2.7.1.1 |
| Crystal system | Isometric |
| Crystal class | Hexoctahedral (m3m) H-M symbol: (4/m 3 2/m) |
| Space group | Fm3m |
| Unit cell | a = 9.928 Å, Z = 4 |
| Identification | |
| Formula mass | 771.94 g/mol |
| Color | Yellowish bronze |
| Crystal habit | Hexoctahedral rare; massive to granular |
| Cleavage | Absent – octahedral parting on {111} |
| Fracture | Conchoidal |
| Tenacity | Brittle |
| Mohs scale hardness | 3.5–4 |
| Luster | Metallic |
| Streak | Light bronze-brown Greenish black |
| Diaphaneity | Opaque |
| Specific gravity | 4.6–5.0 |
| Density | 4.6–5 g/cm3 |
| Fusibility | 1.5–2 |
| Other characteristics | Becomes magnetic upon heating |
| References | |
Pentlandite forms isometric crystals, but it is normally found in massive granular aggregates. It is brittle with a hardness of 3.5–4 and specific gravity of 4.6–5.0 and is non-magnetic. It has a yellowish bronze color and a metallic luster.
Pentlandite is found in abundance within ultramafic rocks, making it one of the most important sources of mined nickel. It also occasionally occurs within mantle xenoliths and "black smoker" hydrothermal vents.