Nickel-skutterudite Locality: St Johannes Mine, Wolkenstein, Marienberg District, Ore Mountains, Saxony, Germany Field of view 7 mm. Photo Copyright © Leon Hupperichs

Chemical Formula:  (Ni,Co)As3-x
Locality: Schneeberg, Saxony, Germany.
Name Origin: Named as the nickel-rich version of skutterudite.

Skutterudite is a cobalt arsenide mineral that has variable amounts of nickel and iron substituting for cobalt with a general formula: (Co,Ni,Fe)As3. Some references give the arsenic a variable formula subscript of 2-3. High nickel varieties are referred to as nickel-skutterudite, previously chloanthite. It is a hydrothermal ore mineral found in moderate to high temperature veins with other Ni-Co minerals. Associated minerals are arsenopyrite, native silver, erythrite, annabergite, nickeline, cobaltite, silver sulfosalts, native bismuth, calcite, siderite, barite and quartz. It is mined as an ore of cobalt and nickel with a by-product of arsenic.

The crystal structure of this mineral has been found to have important technological uses for several compounds isostructural with the mineral.

The mineral has a bright metallic luster, and is tin white or light steel gray in color with a black streak. The specific gravity is 6.5 and the hardness is 5.5-6. Its crystal structure is isometric with cube and octahedron forms similar to that of pyrite. The arsenic content gives a garlic odor when heated or crushed.

It was discovered in Skuterud Mines, Modum, Buskerud, Norway, in 1845. Smaltite is a synonym for the mineral. Notable occurrences include Cobalt, Ontario, Skuterud, Norway, and Franklin, New Jersey in the United States. The rare arsenide minerals are classified in Dana’s sulfide mineral group, even though it contains no sulfur.

Physical Properties

Cleavage: {001} Distinct, {111} Distinct, {011} Parting
Color:     Gray, Tin white, Gray.
Density: 6.5
Diaphaneity: Opaque
Fracture: Brittle – Conchoidal – Very brittle fracture producing small, conchoidal fragments.
Hardness: 5.5-6 – Knife Blade-Orthoclase
Luminescence: Non-fluorescent.
Luster: Metallic

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Photos :

Nickelskutterudite Locality: Schlema, Schlema-Hartenstein District, Erzgebirge, Saxony, Germany Size: small cabinet, 6.1 x 5.6 x 2.4 cm © Rob Lavinsky
Nickelskutterudite Locality : Schneeberg, Erzgebirge, Saxony Germany © Didier Descouens