Pentlandite
| Pentlandite | |
|---|---|
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|
| General | |
| Category | Sulfide mineral |
|
Formula (repeating unit) |
iron nickel sulfide:(Fe,Ni)9S8 |
| Strunz classification | 2.BB.15a |
| Crystal system | Isometric |
| Crystal class | Hexoctahedral (m3m) H-M symbol: (4/m 3 2/m) |
| Space group | Fm3m |
| Identification | |
| Color | Yellowish bronze |
| Crystal habit | Hexoctahedral rare; massive to granular |
| Cleavage | absent - octahedral parting |
| Fracture | Conchoidal |
| Mohs scale hardness | 3.5 - 4 |
| Luster | metallic |
| Streak | light bronze-brown greenish black |
| Specific gravity | 4.6 - 5.0 |
| Refractive index | opaque |
| Fusibility | 1.5 - 2 |
| Other characteristics | becomes magnetic on heating |
| References | |
Pentlandite is an iron-nickel sulfide, (Fe,Ni)9S8. Pentlandite has a narrow variation range in Ni:Fe but it is usually described as having a Ni:Fe of 1:1. It also contains minor cobalt, usually at low levels as a fraction of weight.
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.
Pentlandite is an effective electrolytic catalyst of hydrogen from water.
It is named after the Irish scientist Joseph Barclay Pentland (1797–1873), who first noted the mineral.
Pentlandite is the most common terrestrial nickel sulfide. It typically forms during cooling of a sulfide melt. These sulfide melts, in turn, are typically formed during the evolution of a silicate melt. Because Ni is a chalcophile-like element, it has preference for (i.e. it "partitions into") sulfide phases. In sulfide undersaturated melts, Ni substitutes for other transition metals within ferromagnesian minerals, the most usual being olivine, although nickeliferous varieties of amphibole, biotite, pyroxene and spinel are known. Ni substitutes most readily for Fe2+ and Mg2+ because or their similarity in size and charge.
In sulfide saturated melts, Ni behaves as a chalcophile element and partitions strongly into the sulfide phase. Because most Ni behaves as a compatible element in igneous differentiation processes, the formation of nickel-bearing sulfides is essentially restricted to sulfide saturated mafic and ultramafic melts. Minor amounts of Ni sulfides are found in mantle peridotites.
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Wikipedia