Carrollite
Carrollite, CuCo2S4, is a sulfide of copper and cobalt, often with substantial substitution of nickel for the metal ions, and a member of the linnaeite group. It is named after the type locality in Carroll County, Maryland, US, at the Patapsco mine, Sykesville.
| Carrollite | |
|---|---|
| General | |
| Category | Sulfide mineral Thiospinel group (Spinel structural group) |
| Formula (repeating unit) | CuCo2S4 |
| IMA symbol | Cli |
| Strunz classification | 2.DA.05 |
| Dana classification | 2.10.1.2 |
| Crystal system | Isometric |
| Crystal class | Hexoctahedral (m3m) H-M symbol: (4/m 3 2/m) |
| Space group | Fd3m |
| Identification | |
| Color | Light to dark gray, rarely tarnishes to copper red or violet gray |
| Crystal habit | Octahedral and cubic crystals, also massive, granular or compact |
| Twinning | {111} Polysynthetic or spinel twins |
| Cleavage | Imperfect on {001} |
| Fracture | Conchoidal, subconchoidal or uneven |
| Tenacity | Very brittle |
| Mohs scale hardness | 4.5 to 5.5 |
| Luster | Metallic |
| Streak | Grey black |
| Diaphaneity | Opaque. R is 43% to 45% for lambda = 560 nm |
| Specific gravity | 4.5 to 4.8 measured, 4.83 calculated |
| Refractive index | n is not determined for an opaque mineral |
| Solubility | Minerals of the linneite group are partly etched by nitric acid, with slight effervescence. |
| Other characteristics | Not radioactive, not fluorescent |
| References | |
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