Valleriite

valleriite

pentlandite

foshagite

troilite

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Formula: 2[(Fe,Cu)S].1.53[(Mg,Al)(OH)2]
Sulphide, valleriite group
Specific gravity: 3.14
Hardness: 1 to 1½
Streak: Black
Colour: Dark grey-bronze-yellow
Common impurities: Ni,Ca,K,Na,Si
Environments

Carbonatites
Hydrothermal environments

Valleriite occurs as an alteration product of chalcopyrite in chromatite and dunite (Webmin), associated with chalcopyrite, cubanite, pyrrhotite, troilite, millerite, pentlandite, pyrite, marcasite, mackinawite, tochilinite and magnetite (HOM).

Localities

At the type locality, the Aurora mine, Kaveltorp Mines, Kopparberg, Ljusnarsberg, Örebro County, Sweden, valleriite is found in grains or as a felted fine grained aggregate in carbonate rock (AM 18.224).

At Phalaborwa, Limpopo, South Africa, valleriite occurs in copper-bearing carbonatites, replacing magnetite (HOM). In the carbonatite, valleriite is usually associated with magnetite or with ferroan spinel, whereas in the foskorite (olivine/serpentine - magnetite - apatite - calcite rock) it generally occurs as coatings on other sulphides and is not associated with magnetite. A specimen has been found where aggregates of valleriite crystals are associated with calcite, magnetite and iowaite, and in another specimen smears of valleriite are associated with clinochlore, calcite, and magnetite.
The formation temperature of valleriite is in excess of 225°C. At Palabora a late-stage alteration of the orebody is believed to have resulted in the deposition of valleriite along shear planes and other fractures, where it replaces all other sulphides, as well as magnetite, carbonate and silicate gangue (R&M 92-5.448-449).

In the basic rocks of the Bushveld complex valleriite has been found intimately intergrown with chalcopyrite and pentlandite (AM 18.224).

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