{{Short description|Halide mineral}} {{Infobox mineral |boxtextcolor=|boxbgcolor=#cccccc| name = Antarcticite | image = | alt = | caption = | category = Halide mineral | formula = CaCl<sub>2</sub>·6H<sub>2</sub>O |IMAsymbol=Atc<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.BB.30 | dana = | system = Trigonal | class = Trapezohedral (32) <br/>H-M symbol: (32) | symmetry = ''P321'' | unit cell = a = 7.9, c = 3.95 [Å]; Z = 1 | color = Colorless | colour = | habit = Occurs as groups of acicular crystals | twinning = | cleavage = Perfect on {0001}, very good on {1010} | fracture = | tenacity = Brittle | mohs = 2–3 | luster = Vitreous | streak = | diaphaneity = Transparent | gravity = 1.715 | density = | polish = | opticalprop = Uniaxial (−) | refractive = n<sub>ω</sub> = 1.550 n<sub>ε</sub> = 1.490–1.500 | birefringence = δ = 0.060 | pleochroism = | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = Deliquescent | references = <ref name=HBM>{{cite web |last1=Anthony |first1=John W. |last2=Bideaux |first2=Richard A. |last3=Bladh |first3=Kenneth W. |last4=Nichols |first4=Monte C. |title=Antarcticite |url=http://www.handbookofmineralogy.org/pdfs/antarcticite.pdf |website=Handbook of Mineralogy |publisher=Mineral Data Publishing |access-date=5 August 2022 |date=2005}}</ref><ref name=Mindat>{{mindat|id=251|title=Antarcticite|access-date=5 August 2022}}</ref><ref name=Webmin>{{Cite web|last1=Barthelmy|first1=David|year=2014|url=http://www.webmineral.com/data/Antarcticite.shtml|access-date=5 August 2022|title = Antarcticite Mineral Data|website=Webmineral.com}}</ref> }} '''Antarcticite''' is an uncommon calcium chloride hexahydrate mineral with formula CaCl<sub>2</sub>·6H<sub>2</sub>O. It forms colorless acicular trigonal crystals. It is hygroscopic and has a low relative density of 1.715.
As its name implies, it was first described in 1965 for an occurrence in Antarctica where it occurs as crystalline precipitate from a highly saline brine in Don Juan Pond, in the west end of Wright Valley, Victoria Land. This discovery was made by Japanese geochemists Tetsuya Torii and Joyo Ossaka.<ref name=SCI>[https://www.science.org/doi/abs/10.1126/science.149.3687.975 Antarcticite: A New Mineral, Calcium Chloride Hexahydrate, Discovered in Antarctica, Science 27 August 1965: Vol. 149 no. 3687 pp. 975-977]</ref> It was also reported from brine in Bristol Dry Lake, California, and stratified brine within blue holes on North Andros Island in the Bahamas. It has also been noted within fluid inclusions within quartz in pegmatite bodies in the Bushveld complex of South Africa. It occurs in association with halite, gypsum and celestine in the California dry lake.<ref name=HBM/>
A similar mineral, ''sinjarite'', the dihydrate of calcium chloride, crystallizes in the tetragonal system.<ref>[http://www.mindat.org/min-3673.html Sinjarite on Mindat]</ref> Sinjarite is semitransparent, with pale pink color.<ref>{{cite web |last1=Anthony |first1=John W. |last2=Bideaux |first2=Richard A. |last3=Bladh |first3=Kenneth W. |last4=Nichols |first4=Monte C. |title=Sinjarite |url=http://www.handbookofmineralogy.org/pdfs/sinjarite.pdf |website=Handbook of Mineralogy |publisher=Mineral Data Publishing |access-date=21 October 2022 |date=2005}}</ref> Hydrophilite is a now discredited calcium chloride mineral that is considered to be either antarcticite or sinjarite.<ref>[http://www.mindat.org/min-1984.html Hydrophylite on Mindat]</ref><ref>{{Cite journal|last=Hey|first=M. H.|date=1980|title=What was hydrophilite?|journal=Mineralogical Magazine|volume=43|issue=329|pages=682|doi=10.1180/minmag.1980.043.329.23|bibcode=1980MinM...43..682H }}</ref>
==See also== * Geology of Sinjar Mountains, for sinjarite
==References== {{Reflist}}
Category:Chloride minerals Category:Trigonal minerals Category:Minerals in space group 150
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