{{short description|Halide mineral}} {{Use dmy dates|date=April 2022}} {{Infobox mineral | name = Botallackite | category = Halide minerals | boxwidth = | boxbgcolor = | image = Botallackite-sea82b.jpg | imagesize = | caption = Botallackite from the Levant Mine, Cornwall | formula = Cu<sub>2</sub>(OH)<sub>3</sub>Cl | IMAsymbol=Blk<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> | strunz = 3.DA.10b | system = Monoclinic | class = Prismatic (2/m) <br/>(same H-M symbol) | symmetry = ''P2''<sub>1</sub>/m | unit cell = a = 5.717&nbsp;Å, <br/>b = 6.126&nbsp;Å, <br/>c = 5.636&nbsp;Å; β = 93.07°; Z&nbsp;=&nbsp;2 | colour = Shades of green | habit = Platy interlaced crystal crusts | twinning = | cleavage = {100} Perfect | fracture = | tenacity = | mohs = Soft | luster = | polish = | refractive = n<sub>α</sub>= 1.775, n<sub>β</sub>= 1.800, n<sub>γ</sub>= 1.846 | opticalprop = Biaxial (+) | birefringence = δ = 0.071 | dispersion = r > v, strong | pleochroism = Weak – blue green shades | fluorescence= | absorption = | streak = | gravity = 3.6 | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Transparent to translucent | other = | references = <ref name=mindat /><ref name=HBM>[http://rruff.geo.arizona.edu/doclib/hom/botallackite.pdf Handbook of Mineralogy]</ref><ref name=Webmin>[http://www.webmineral.com/data/Botallackite.shtml Webmineral data]</ref> }} '''Botallackite''', chemical formula Cu<sub>2</sub>(OH)<sub>3</sub>Cl is a secondary copper mineral, named for its type locality at the Botallack Mine in St Just in Penwith, Cornwall. It is polymorphous with atacamite, paratacamite and {{interlanguage link|clinoatacamite|qid=Q3680774}}.<ref name=mindat>[http://www.mindat.org/min-732.html Mindat information page for Botallackite]</ref>

Botallackite crystallises in the monoclinic crystal system. It is mountain-green to green in colour, with one distinct to good cleavage.<ref name=mindat />

==Discovery and occurrence== It was first described in 1865 for an occurrence in the Botallack mine, Cornwall, England, and named for the type locality.<ref name =mindat />

Botallackite forms in copper deposits exposed to weathering and salt water.<ref name =mindat /> It is reported from black smoker deposits due to reaction of primary sulfide minerals with seawater. It also occurs on copper bearing slag exposed to seawater. Minerals associated with botallackite include atacamite, paratacamite, brochantite, connellite and gypsum.<ref name=HBM/>

==References== {{Portal|Minerals|Cornwall}} {{reflist}}

{{Commons category}}

Category:Copper(II) minerals Category:Chloride minerals Category:Monoclinic minerals Category:Minerals in space group 11 Category:Minerals described in 1865

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