Atacamite | |
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![]() Atacamite from Mt. Gunson mines, South Australia | |
General | |
Category | Halide mineral |
Formula (repeating unit) | Cu2Cl(OH)3 |
IMA symbol | Ata[1] |
Strunz classification | 3.DA.10a |
Crystal system | Orthorhombic |
Crystal class | Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) |
Space group | Pnma |
Unit cell | a = 6.03, b = 9.12 c = 6.865 [Å]; Z = 4 |
Identification | |
Color | Bright green, dark emerald-green to blackish green |
Crystal habit | Slender prismatic crystals, fibrous, granular to compact, massive |
Twinning | Contact and penetration with complex twinned groupings |
Cleavage | Perfect on {010}, fair on {101} |
Fracture | Conchoidal |
Tenacity | Brittle |
Mohs scale hardness | 3–3.5 |
Luster | Adamantine to vitreous |
Streak | Apple green |
Diaphaneity | Transparent to translucent |
Specific gravity | 3.745–3.776 |
Optical properties | Biaxial (−) |
Refractive index | nα = 1.831 nβ = 1.861 nγ = 1.880 |
Birefringence | δ = 0.049 |
Pleochroism | X = pale green; Y = yellow-green; Z = grass-green |
2V angle | Calculated: 74° |
Dispersion | r < v, strong |
References | [2][3][4][5] |
Atacamite is a copper halide mineral: a copper(II) chloride hydroxide with formula Cu2Cl(OH)3. It was first described for deposits in the Atacama Desert of Chile in 1802 by Dmitri de Gallitzin.[2] The Atacama Desert is also the namesake of the mineral.
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