Carrollite
Carrollite is a sulphide that is rare of and cobalt has rarely seen faceted. It is opaque, metallic black and extremely dense. It is a gem for “black gem” collectors.
Distribution of Carrollite is into the USA, from Carroll County, Maryland, in the Patapsco mine, Finksburg [TL], and the Mineral Hill mine, Sykesville. At Boleo, Baja Ca, Mexico. Within the Carrizal Alto copper district, Atacama, Chile. From near Chernomorets, Burgas, Bulgaria. At Vysna Boca, Nizke Tatry Mountains, Slovakia. Into the Kohlenbach mine, near Eiserfeld, and throughout the Siegerland district, North Rhine-Westphalia, Germany. From Gladhammar, Kalmar, Sweden. At Tsumeb, Namibia. Large crystals from Kambove, and in the Kamoto and Musonoi mines, near Kolwezi, Katanga Province, Congo (Shaba Province, Zaire). Through the Rokana mine, Kitwe, Zambia. At the Madziwa (Dry Nickel) mine, Bindura, and Shamva, Zimbabwe. In the Sazare mine, Ehime Prefecture, therefore the Shirataki mine, Kochi Prefecture, Japan. At the Hol Kol Au–Cu mine, about 75 km southeast of Pyongyang, Suan Co., North Korea. From Kambalda, 56 km south of Kalgoorlie, Western Australia. A number that is significant of minor occurrences are known.
| Category: | Sulfide mineral Thiospinel group (Spinel structural group) |
| Chemical Formula: | Cu(Co, Ni)2S4 |
| Copper Cobalt Nickel Sulfide | |
| Molecular Weight: | 309.55 gm |
| Composition: | Cobalt | 28.56 % | Co | ||
| Copper | 20.53 % | Cu | |||
| Nickel | 9.48 % | Ni | |||
| Sulfur | 41.43 % | O | |||
| 100.00 % |
| Crystallography: | Isometric – Hexoctahedral |
| Crystal Habit: | Octahedral crystals, to 10 cm; commonly massive, disseminated granular to compact. |
| Twinning: | On {111}; may show polysynthetic twin lamellae |
| Cleavage: | Imperfect on {001} |
| Fracture: | Irregular/Uneven to Sub-Conchoidal |
| Tenacity: | Brittle |
| Moh’s Hardness: | 4.5 – 5.5; VHN = 507–586 (100 g load) |
| Density: | 4.50 – 4.80 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Color: | Pale gray to steel-gray, tarnishing easily to copper-red or violet-gray |
| Transparency: | Opaque |
| Luster: | Metallic |
| Refractive Index: | Isotropic; R: (400) 41.4, (420) 41.5, (440) 41.6, (460) 41.8, (480) 42.0, (500) 42.3, (520) 42.6, (540) 42.9, (560) 43.1, (580) 43.3, (600) 43.5, (620) 43.9, (640) 44.3, (660) 44.7, (680) 45.0, (700) 45.3 |
| Birefringence: | 0.00; Isotropic |
| Dispersion: | None |
| Pleochroism: | None |
