Skutterudite
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.
| Category: | Arsenide mineral |
| Formula: | CoAs3 |
| Cobalt arsenide | |
| 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}. |
| 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 |
| 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 |
