{{Short description|Rare silicate mineral}} {{Infobox mineral | name = Charoite | category = Silicate mineral | boxwidth = | boxbgcolor = #e181de | image = Czaroit1.jpg | imagesize = | caption = | formula = {{chem|K|(Ca,Na)|2|Si|4|O|10|(O|H,F)|•H|2|O}} | IMAsymbol = Cha<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 = | system = Monoclinic | class = Prismatic (2/m) <br/><small>(same H-M symbol)</small> | symmetry = ''P2''<sub>1</sub>/m | color = Violet, lilac, light brown | habit = Fibrous, massive | twinning = | cleavage = Good in three directions | fracture = Conchoidal | mohs = 5 - 6 | luster = Vitreous to pearly | refractive = n<sub>α</sub> = 1.550 <br/>n<sub>β</sub> = 1.553 <br/>n<sub>γ</sub> = 1.559 | opticalprop = Biaxial (+) | birefringence = 0.009 | pleochroism = |fluorescence=Weakly fluorescent| streak = White | gravity = 2.54 - 2.58 | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Translucent |impurities=Al, Fe, Mn, Sr, Ba| other = 25px Radioactive 10.69% (K) | references = <ref>[https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Charoite Mineralienatlas]</ref><ref name="barthelmy-david"/><ref name=Mindat>{{mindat|id=972|title=Charoite|access-date=4 July 2022}}</ref><ref name=Handbook>{{cite web |last1=Anthony |first1=John W. |last2=Bideaux |first2=Richard A. |last3=Bladh |first3=Kenneth W. |last4=Nichols |first4=Monte C. |title=Charoite |url=http://www.handbookofmineralogy.org/pdfs/charoite.pdf |website=Handbook of Mineralogy |publisher=Mineral Data Publishing |access-date=4 July 2022 |date=2005 |archive-date=7 November 2022 |archive-url=https://web.archive.org/web/20221107090457/http://www.handbookofmineralogy.org/pdfs/Charoite.pdf |url-status=dead }}</ref> }}

'''Charoite''' ({{IPAc-en|tʃ|æ|r|oʊ|.|aɪ|t}} {{respell|CHAR|ow|ait}}) is a rare silicate mineral with the chemical composition {{chem|K|(Ca,Na)|2|Si|4|O|10|(O|H,F)|•H|2|O}}, first described in 1978. It is named after the Chara River, despite its being {{convert|70|km}} away from the discovery place.<ref>Ian Frazier, ''Travels in Siberia'', Farrar, Straus and Giroux, New York (NY), 2010, ISBN 978-0-374-27872-4, [https://books.google.com/books?id=Qc8UsH-rAL0C&pg=PA394 page 394]</ref><ref name="barthelmy-david">{{Cite web |last1=Barthelmy |first1=David |year=2014 |website=Webmineral.com |title=Charoite Mineral Data |url=http://www.webmineral.com/data/Charoite.shtml |access-date=2022-04-12 }}</ref> When it was discovered, it was thought to be a fake, dyed purple to give it its striking appearance.<ref name="capecod-crystals">{{Cite web |title=Charoite Meaning, History and Detailed Information with Photos |url=https://capecodcrystals.com/pages/charoite |website=Cape Cod Crystals |language=en |access-date=2022-04-12}}</ref>

== Properties == Charoite is translucent lavender to purple in color with a pearly luster. Charoite is strictly massive in nature, and fractures are conchoidal. It has an unusual swirling, fibrous appearance, sometimes chatoyant, and that, along with its intense color, can lead many to believe at first that it is synthetic or enhanced artificially. Though reportedly discovered in the 1940s, it was not known to most of the world until its description in 1978. It is said to be opaque and unattractive when found in the field; a fact that may have contributed to its late recognition.<ref name=Handbook/> Charoite consists of oxygen (43.75%), silicon (27.65%) and calcium (17.53%) mainly, but its composition includes potassium (10.69%) - which gives it its radioactive properties - and hydrogen (0.39%) as well. It has a barely detectable, 0.65% radioactivity concentration per Gamma Ray American Petroleum Institute Units.<ref name="barthelmy-david" />

Inclusions mainly come in the swirly patterns of the mineral.<ref name=":3">{{Cite web |title=What is Charoite? – A Complete Buying Guide {{!}} Jewelry Guide |url=https://www.jewelryshoppingguide.com/what-is-charoite-gemstone/ |access-date=2022-04-12 |language=en-US}}</ref> The black spots on some specimens are either augite or aegirine, the latter occurring in almost all charoites since they commonly grow together. Larger round greenish spots are feldspar. Lighter colored stones or ones with translucent areas are likely due to canasite. The yellowish brown spots are tinaksite, which was discovered at the same time as charoite was. Charoite's silky, fibrous structure results in a shimmery looking polished stone. Sometimes, the very white flashes are tiny white feldspar.<ref name="capecod-crystals" /> Sugilites and charoites can be confused, as both are purple, and sugilite can have black and white inclusions, however sugilite lacks the swirling pattern that are present in charoite stones, and it also lacks the chatoyant effect.<ref name=":3" />

== Occurrences == It has been reported only from the Aldan Shield, Sakha Republic, Siberia, Russia. It is found where a syenite of the Murun Massif has intruded into and altered limestone deposits producing a potassium feldspar metasomatite,<ref name=Handbook /> and forms between 200 - 250&nbsp;°C.<ref name="barthelmy-david" /> Tinaksite, canasite and charoite are associated and black aegirine is also common where these three minerals grow. Common impurities include aluminium, iron, manganese, strontium and barium.<ref name="capecod-crystals" /> Charoitite is a rock like lapis lazuli, but unlike the latter one, charoitite mostly consists of the mineral charoite.<ref name=":4">{{Cite web |title=Charoite Value, Price, and Jewelry Information |url=https://www.gemsociety.org/article/charoite-jewelry-and-gemstone-information/ |access-date=2022-04-12 |website=International Gem Society |language=en}}</ref>

==Gallery== <gallery widths="250px" heights="220px" > Charoitite, sw Yakutia Siberia.jpg|Charoitite, a charoite-dominated potassic metasomatite rock from the type area. Photo is 5.7&nbsp;cm wide. 2000 Charoite 613.jpg|Charoite postage stamp, 2000, from a series commemorating "300 Years of Mining and Geological Service in Russia." </gallery>

==References== {{reflist}}

{{Commons category|Charoite}} {{Wiktionary|charoite}} {{Gemstones}}

Category:Calcium minerals Category:Sodium minerals Category:Potassium minerals Category:Inosilicates Category:Monoclinic minerals Category:Minerals in space group 11