atacamite
{{Short description|Halide evaporite mineral}}
{{Infobox mineral
| name = Atacamite
| boxwidth =
| boxbgcolor =
| image = Atacamite on malachite - Mt Gunson mines, South Australia.jpg
| imagesize = 260px
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| caption = Atacamite from Mt. Gunson mines, South Australia
| category = Halide mineral
| formula = Cu2Cl(OH)3
| molweight =
| strunz = 3.DA.10a
| dana =
| system = Orthorhombic
| class = Dipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
| symmetry = Pnma
| unit cell = a = 6.03, b = 9.12
c = 6.865 [Å]; Z = 4
| color = Bright green, dark emerald-green to blackish green
| colour =
| 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 = 3–3.5
| luster = Adamantine to vitreous
| streak = Apple green
| diaphaneity = Transparent to translucent
| gravity = 3.745–3.776
| density =
| polish =
| opticalprop = Biaxial (−)
| refractive = nα = 1.831 nβ = 1.861 nγ = 1.880
| birefringence = δ = 0.049
| pleochroism = X = pale green; Y = yellow-green; Z = grass-green
| 2V = Calculated: 74°
| dispersion = r < v, strong
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| references = [http://www.mindat.org/min-406.html Atacamite on Mindat.org][http://rruff.geo.arizona.edu/doclib/hom/atacamite.pdf Handbook of Mineralogy][http://www.webmineral.com/data/Atacamite.shtml Atacamite on Webmineral][https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Atacamite Mineralienatlas]
}}
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. The Atacama Desert is also the namesake of the mineral.
Occurrence
Atacamite is polymorphous with botallackite, clinoatacamite, and paratacamite. 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. The mineral has also been found naturally on oxidized copper deposits in Chile, China, Russia, Czech Republic, Arizona, and Australia. It occurs in association with cuprite, brochantite, linarite, caledonite, malachite, chrysocolla and its polymorphs.
= Synthetic Occurrence =
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.{{Cite web|url=http://cameo.mfa.org/wiki/Atacamite|title=Atacamite – CAMEO|website=cameo.mfa.org|language=en|access-date=2017-10-15}}
=== Biomineral ===
Atacamite occurs as a biomineral in the jaws of bloodworms.{{cite journal|date=October 2002|title=High abrasion resistance with sparse mineralization: copper biomineral in worm jaws|journal=Science|volume=298|issue=5592|pages=389–92|bibcode=2002Sci...298..389L|doi=10.1126/science.1075433|pmid=12376695|vauthors=Lichtenegger HC, Schöberl T, Bartl MH, Waite H, Stucky GD|s2cid=14001250}}{{cite journal |vauthors=Lichtenegger HC, Schöberl T, Ruokolainen JT, etal |title=Zinc and mechanical prowess in the jaws of Nereis, a marine worm |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=100 |issue=16 |pages=9144–9 |date=August 2003 |pmid=12886017 |pmc=170886 |doi=10.1073/pnas.1632658100 |bibcode=2003PNAS..100.9144L |doi-access=free }}
Atacamite-235102.jpg|Atacamite prisms from Chile
Harvard Museum of Natural History. Atacamite. Miraflores Mine, Tierra Amarilla, Atacama, Chile (DerHexer) 2012-07-20.jpg|Atacamite from Chile displayed in the Harvard Museum of Natural History
Atacamite-168148.jpg|Atacamite from Mt. Gunson, South Australia
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References
{{commons category|Atacamite}}
{{reflist}}
External links
- [https://web.archive.org/web/20050911055400/http://mineral.galleries.com/minerals/halides/atacamit/atacamit.htm Mineral galleries]
Category:Orthorhombic minerals
Category:Minerals in space group 62
Category:Minerals described in 1802
{{Halide-mineral-stub}}