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Skutterudite
Current inventory:  0 gems
 

Chemistry:  (Co,Ni)As_2-3  [Cobalt Nickel Arsenide]

Discovered in 1845;   IMA status: Valid (pre-IMA; Grandfathered).
Skutterudite is named after its discovery locality of Skutterud Mines (Modum Cobalt Mines), Snarum, Modum, Buskerud, Norway.

Classification

Mineral Classification:

Sulfides

Strunz 8th Ed. ID:

2/D.29-10

Nickel-Strunz 10th Ed. ID:

2.EC.05

2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
E : Metal Sulfides, M: S <= 1:2
C : M:S = 1:>2

Related to:

Skutterudite Group. Nickel - Skutterudite Series. The cobalt analogue of Feroskutterudite and Nickel-Skutterudite. The Arsenic rich form of Smaltite.

Crystal Data

Crystallography:

Isometric - Diploidal

Crystal Habit:

Crystals are cubes, octahedra, dodecahedra, to 9 cm; rarely prismatic; in skeletal growth forms, distorted aggregates; also massive, granular and dense.

Twinning:

On {112} as sixlings and complex shapes; also reported on {011}.

Physical Properties

Cleavage:

[001] Distinct, [111] Distinct; in traces on [011]

Fracture:

Irregular/Uneven, Conchoidal

Tenacity:

Brittle

Hardness (Mohs):

5.5 - 6.0

Density:

6.50 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Tin-White to Silver-Gray, tarnishes Gray or iridescent; in polished section, Gray, Creamy or Golden White.

Transparency:

Opaque

Luster:

Metallic

Refractive Index:

R: (400) 55.3, (420) 56.0, (440) 56.4, (460) 56.6, (480) 56.4, (500) 56.1, (520) 55.7, (540) 55.3, (560) 55.0, (580) 54.7, (600) 54.4, (620) 54.1, (640) 53.8, (660) 53.5, (680) 53.1, (700) 52.7

Birefringence:

0.00 (Opaque)

Dispersion:

Strong

Pleochroism:

None

Occurances

Geological Setting:

Typically in medium- to high-temperature hydrothermal veins with other Ni–Co sulfide minerals.

Common Associations:

Arsenopyrite, Barite, Bismuth, Calcite, Cobaltite, Nickeline, Quartz, Siderite, Silver, Silver Sulfosalts

Common Impurities:

S, Bi, Cu, Pb, Zn, Ag, Fe, Ni

Type Locality:

Skuterud (Skutterud) Mines (Modum Cobalt Mines), Snarum, Modum, Buskerud, Norway

Year Discovered:

1845

View mineral photos:

Skutterudite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Skutterudite is a fairly common sulfide mineral. Cabochons are rarely available since it resembles other metallic sulfides and arsenides and would be considered a unusual collector's gem. It is opaque with a metallic luster and tin-white to silver-gray color. It is sought by mineral specimen collectors for its Pyrite-like crystal forms and bright silver colors.

Skutterudite is found at many localities worldwide as an accessory mineral, only rarely as an important ore or in fine specimens. In Norway, at the Type Locality of Skutterud, Modum. At Schneeberg, Annaberg, and Freiberg, Saxony, Germany. From Austria, at Lölling, Carinthia. In Spain, in the valley of Gistain, Huesca Province. From France, at Riomanou, Hautes-Pyrénées, and on Mount Chalanches, Isére. At Talnotry, Kirkcudbrightshire, Scotland. From a number of mines in Cornwall, England. At Khovu-Akay, Tuva, Russia. Well-crystallized from the Aghbar (Arhbar) and Irhtem (Ightem) mines, Bou Azzer district, Morocco. In the USA, in Connecticut, at Chatham, Middlesex County; and from Mine la Motte, Madison County, Missouri. In Canada, in large amounts at Cobalt; in South Lorrain Township; at Sudbury; and Gowganda, Ontario.
 

  
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