Skutterudite - Encyclopedia

    Class : Sulphides and sulphosalts
    Subclass : Arsenides
    Crystal system : Cubic
    Chemistry : CoAs2-3
    Rarity : Uncommon


Skutterudite is the most common of the metallic cobalt minerals. It is a primary mineral of high temperature hydrothermal nickel and cobalt deposits, polymetallic Ni-Co-Bi-Ag-U veins and some silver deposits. It forms a series with nickel-skutterudite (ex chloanthite), but some authors consider this mineral to be a nickel-bearing variety of skutterudite ; smaltine is a arsenic deficient skutterudite variety. It is a mineral which owes its name to its locality of discovery : Skutterud, near Modum in Norway. Skutterudite has a metallic luster and a pewter white to silver gray color. It occurs in compact to granular masses or in crystals derived from the cube with sometimes curved edges. On the outcrop, it alters quite easily, its most characteristic alteration product being the hydrated arsenate of purple hue : erythrite. It is locally an important ore of cobalt and nickel. Cobalt is mainly used in alloys for the manufacture of electromagnets and high speed cutting tools. Cobalt oxide, "cobalt blue", is used in the making of stained glass and pottery.

Skutterudite in the World

The most spectacular specimens come from the Bou Azzer district in Morocco : these are shiny rhombododecahedral crystals (up to 10 cm) included in calcite. Magnificent centimetric crystals also came out of the Saxon mines of Germany as well as the Harz.

Skutterudite in France

In France, several veins from Ste-Marie-aux-Mines (Vosges) have provided cubo-octahedral crystals of up to 3 cm.

Twinning

Twins are reported on {112} and {011}.

Fakes and treatments

No fake recorded for this mineral species.



Hardness : 5.5 to 6
Density : 6.5
Fracture : Urregular to conchoidal
Trace : Black




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


Solubility : Nitric acid

Magnetism : None
Radioactivity : None