Cornubite
Cornubite is a rare secondary copper arsenate mineral with formula: Cu5(AsO4)2(OH)4. It was first described for its discovery in 1958 in Wheal Carpenter, Gwinear, Cornwall, England, UK. The name is from Cornubia, the medieval Latin name for Cornwall. It is a dimorph of cornwallite, and the arsenic analogue of pseudomalachite.
| Cornubite | |
|---|---|
Cornubite from Majuba Hill, Nevada, US. Specimen size 5 cm | |
| General | |
| Category | Arsenate minerals |
| Formula (repeating unit) | Cu5(AsO4)2(OH)4 |
| Strunz classification | 8.BD.30 |
| Dana classification | 41.04.02.01 |
| Crystal system | Triclinic |
| Crystal class | Pinacoidal (1) (same H-M symbol) |
| Space group | P1 |
| Identification | |
| Color | Light or dark green |
| Crystal habit | Fibrous, botryoidal, globular or massive, also rare tabular crystals |
| Cleavage | Distinct in two directions |
| Mohs scale hardness | 4 |
| Luster | Vitreous |
| Streak | Light green |
| Diaphaneity | Translucent to transparent |
| Specific gravity | 4.64 |
| Optical properties | Biaxial (−) |
| Refractive index | Nα = 1.87, Nβ not determined, Nγ = 1.90 |
| Birefringence | r>v |
| Other characteristics | Not radioactive |
| References | |
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