Atacamite
| Atacamite | |
|---|---|
 Atacamite from Mt. Gunson mines, South Australia | |
| General | |
| Category | Halide mineral |
| Formula | 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.
Occurrence
[edit]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]
Synthetic Occurrence
[edit]Atacamite has been discovered in the patina of the Statue of Liberty, and as alteration of ancient bronze and copper artifacts. The bronze of the Antikythera mechanism had turned to atacamite under the sea.[7]
The mineral has been found as a pigment in sculpture, manuscripts, maps, and frescoes discovered in Eurasia, Russia, and Persia.[6]
Biomineral
[edit]Atacamite occurs as a biomineral in the jaws of bloodworms.[8][9]
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Atacamite prisms from Chile -
Atacamite from Chile displayed in the Harvard Museum of Natural History -
Atacamite from Mt. Gunson, South Australia
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References
[edit]
- ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- ^ a b c Atacamite on Mindat.org
- ^ a b c Handbook of Mineralogy
- ^ Atacamite on Webmineral
- ^ Mineralienatlas
- ^ a b "Atacamite – CAMEO". cameo.mfa.org. Retrieved 2017-10-15.
- ^ Alex Wilkins (Apr 17, 2025). "Ancient computer's gears may not have been able to turn". New Scientist.
- ^ Lichtenegger HC, Schöberl T, Bartl MH, Waite H, Stucky GD (October 2002). "High abrasion resistance with sparse mineralization: copper biomineral in worm jaws". Science. 298 (5592): 389–92. Bibcode:2002Sci...298..389L. doi:10.1126/science.1075433. PMID 12376695. S2CID 14001250.
- ^ Lichtenegger HC, Schöberl T, Ruokolainen JT, et al. (August 2003). "Zinc and mechanical prowess in the jaws of Nereis, a marine worm". Proc. Natl. Acad. Sci. U.S.A. 100 (16): 9144–9. Bibcode:2003PNAS..100.9144L. doi:10.1073/pnas.1632658100. PMC 170886. PMID 12886017.
External links
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