Conichalcite
Conichalcite, CaCu(AsO4)(OH), is a relatively common arsenate mineral related to duftite (PbCu(AsO4)(OH)). It is green, often botryoidal, and occurs in the oxidation zone of some metal deposits. It occurs with limonite, malachite, beudantite, adamite, cuproadamite, olivenite and smithsonite.
| Conichalcite | |
|---|---|
A thin crust of conichalcite on a rock. | |
| General | |
| Category | Arsenate minerals |
| Formula (repeating unit) | CaCu(AsO4)(OH) |
| IMA symbol | Con |
| Strunz classification | 8.BH.35 |
| Dana classification | 41.5.1.2 |
| Crystal system | Orthorhombic |
| Crystal class | Disphenoidal (222) (same H-M symbol) |
| Space group | P212121 |
| Unit cell | a = 7.39(1) Å, b = 9.23(1) Å, c = 5.83(1) Å; V = 397.66 ų; Z = 4 |
| Identification | |
| Color | Grass-green to yellowish green, pistachio-green, emerald-green; may be zoned; light green to yellowish green in transmitted light. |
| Crystal habit | Crusts of acicular to almost fibrous crystals. Also as botryoidal masses and compact crusts. |
| Twinning | Rare on {001} |
| Cleavage | Absent |
| Fracture | Uneven |
| Tenacity | Brittle |
| Mohs scale hardness | 4.5 |
| Luster | Vitreous, greasy |
| Streak | Green |
| Diaphaneity | Translucent |
| Specific gravity | 4.3 |
| Optical properties | Biaxial (+/−) |
| Refractive index | nα = 1.778 – 1.800 nβ = 1.795 – 1.831 nγ = 1.801 – 1.846 |
| Birefringence | δ = 0.023 – 0.046 |
| Pleochroism | Visible |
| Dispersion | Strong r < v to r < v moderate |
| References | |
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