Editing Atacamite (section)

{{Short description|Halide evaporite mineral}}
{{Infobox mineral
| name        = Atacamite
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| image       = Atacamite on malachite - Mt Gunson mines, South Australia.jpg
| imagesize   = 260px
| alt         = 
| caption     = Atacamite from Mt. Gunson mines, South Australia
| category    = [[Halide mineral]]
| formula     = Cu<sub>2</sub>Cl(OH)<sub>3</sub>
|IMAsymbol=Ata<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}</ref>
| molweight   = 
| strunz      = 3.DA.10a
| dana        = 
| system      = [[Orthorhombic]]
| class       = Dipyramidal (mmm) <br/>[[H-M symbol]]: (2/m 2/m 2/m)
| symmetry    = ''Pnma''
| unit cell   = a = 6.03, b = 9.12 <br/>c = 6.865&nbsp;[Å]; Z&nbsp;=&nbsp;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  = n<sub>α</sub> = 1.831 n<sub>β</sub> = 1.861 n<sub>γ</sub> = 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  = <ref name=Mindat>[http://www.mindat.org/min-406.html Atacamite on Mindat.org]</ref><ref name=HBM>[http://rruff.geo.arizona.edu/doclib/hom/atacamite.pdf Handbook of Mineralogy]</ref><ref name=Webmin>[http://www.webmineral.com/data/Atacamite.shtml Atacamite on Webmineral]</ref><ref>[https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Atacamite Mineralienatlas]</ref>
}}

'''Atacamite''' is a [[copper]] [[halide mineral]]: a [[Dicopper chloride trihydroxide|copper(II) chloride hydroxide]] with formula Cu<sub>2</sub>Cl(OH)<sub>3</sub>. It was first described for deposits in the [[Atacama Desert]] of [[Chile]] in 1802 by [[Dmitri Alekseyevich Gallitzin|Dmitri de Gallitzin]].<ref name="Mindat" /> The Atacama Desert is also the namesake of the mineral.