PENTLANDITE

    Class : Sulfides and sulfosalts
    Subclass : Sulfides
    Crystal system : Cubic
    Chemistry : (Fe,Ni)9S8
    Rarity : Quite common

Pentlandite is a fairly common sulfide of iron and nickel, which may contain several percent cobalt. It is mainly a sulfide of magmatic origin linked to basic rocks and in particular to norites in mafic stratified complexes. More rarely, pentlandite appears in thin areas in serpentinites, associated with other nickel minerals (heazlewoodite). It was named in honor of the Irish naturalist Joseph Barclay Pentland who was the first to study the mineral. Pentlandite occurs in small, disseminated grains or in centimeter-sized masses, gathered in levels rich in more or less massive sulfides where pyrrhotite dominates. The distinct crystals are exceptional but can reach large dimensions : they are generally octahedra which can reach up to 10 cm. Pentlandite has a metallic luster and a light bronze-yellow color, as well as good cleavage according to {111}. It is the main nickel ore, ahead of garnierite.

Main photo : Pentlandite from the serpentinites of Piasco, Piedmont, Italy © Peter Lof

Pentlandite in the World

Pentlandite is the essential mineral in all nickel deposits on the planet. Good samples were discovered in the largest of them: Thompson (Manitoba, Canada) and Sudbury (Ontario, Canada), Norilsk district (Russia), Coolgardie and Kambalda (Australia), but also in large blades at Outokumpu and Makkola (Finland).

Pentlandite in France

In France we find pentlandite in peridotites, serpentinites and certain lavas, but no collection specimens are to be reported.

Twinning

No twins known for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 3 to 4
Density : 4.6 to 5
Fracture : Conchoidal
Streak : Brown-bronze

TP : Opaque
RI : -
Birefringence : 0
Optical character : None
Pleochroism : None
Fluorescence : None

Solubility : -

Magnetism : ParamagneticRadioactivity : None