SKUTTERUDITE
Class : Sulfides 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
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