Botallackite | |
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![]() Botallackite from the Levant Mine, Cornwall | |
General | |
Category | Halide minerals |
Formula (repeating unit) | Cu2(OH)3Cl |
IMA symbol | Blk[1] |
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 | [2][3][4] |
Botallackite, chemical formula Cu2(OH)3Cl is a secondary copper mineral, named for its type locality at the Botallack Mine, St Just in Penwith, Cornwall. It is polymorphous with atacamite, paratacamite and clinoatacamite .[2]
Botallackite crystallises in the monoclinic crystal system. It is mountain-green to green in colour, with one distinct to good cleavage.[2]