Atacamite
Halide evaporite mineral From Wikipedia, the free encyclopedia
Halide evaporite mineral From Wikipedia, the free encyclopedia
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.
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 polymorphous with botallackite, clinoatacamite, and paratacamite.[2] Atacamite is a comparatively rare mineral, formed from primary copper minerals in the oxidation or weathering zone of arid climates. It has also been reported as a volcanic sublimate from fumarole deposits, as sulfide alteration products in black smokers.[3] The mineral has also been found naturally on oxidized copper deposits in Chile, China, Russia, Czech Republic, Arizona, and Australia.[6] It occurs in association with cuprite, brochantite, linarite, caledonite, malachite, chrysocolla and its polymorphs.[3]
Atacamite has been discovered in the patina of the Statue of Liberty, and as alteration of ancient bronze and copper artifacts. The mineral has been found as a pigment in sculpture, manuscripts, maps, and frescoes discovered in Eurasia, Russia, and Persia.[6]
Atacamite occurs as a biomineral in the jaws of bloodworms.[7][8]