Botallackite
| Botallackite | |
|---|---|
Botallackite from the Levant Mine, Cornwall | |
| General | |
| Category | Halide minerals |
| Formula | Cu2(OH)3Cl |
| IMA symbol | Blk |
| Strunz classification | 3.DA.10b |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | P21/m |
| Unit cell | a = 5.717 Å, b = 6.126 Å, c = 5.636 Å; β = 93.07°; Z = 2 |
| Identification | |
| Colour | Shades of green |
| Crystal habit | Platy interlaced crystal crusts |
| Cleavage | {100} Perfect |
| Mohs scale hardness | Soft |
| Diaphaneity | Transparent to translucent |
| Specific gravity | 3.6 |
| Optical properties | Biaxial (+) |
| Refractive index | nα= 1.775, nβ= 1.800, nγ= 1.846 |
| Birefringence | δ = 0.071 |
| Pleochroism | Weak – blue green shades |
| Dispersion | r > v, strong |
| References | |
Botallackite, chemical formula Cu2(OH)3Cl is a secondary copper mineral, named for its type locality at the Botallack Mine in St Just in Penwith, Cornwall. It is polymorphous with atacamite, paratacamite and clinoatacamite.
Botallackite crystallises in the monoclinic crystal system. It is mountain-green to green in colour, with one distinct to good cleavage.