tsilaisite
{{Expand German}}{{Infobox mineral|category=Tourmaline|formula=NaMn2+3Al6Si6O18(BO3)3(OH)3OH| IMAsymbol = Tsl{{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}}|system=Trigonal|mohs=7 to 7.5|luster=Vitreous|streak=White}}
Tsilaisite is a manganese rich variety of elbaite tourmaline.{{Cite book|last=Manutchehr-Danai|first=Mohsen|url=https://books.google.com/books?id=2UX1CAAAQBAJ|title=Dictionary of Gems and Gemology|date=2013-03-09|publisher=Springer Science & Business Media|isbn=978-3-662-04288-5|pages=485|language=en}} It is also known as Tsilaizite.{{Cite web|date=2017-03-27|title=Tsilaisite |url=https://nationalgemlab.in/tsilaisite/|access-date=2021-09-27|website=National Gem Lab|language=en-US}} Tsilaisite is related Fluor-tsilaisite.{{Cite journal|last1=Bosi |first1=Ferdinando|last2=Andreozzi |first2=Giovanni B.|last3=Agrosi|first3=Giovanna|last4=Scandale |first4=Eugenio|date=February 2015|title=Fluor-tsilaisite, NaMn3Al6(Si6O18)(BO3)3(OH)3F, a new tourmaline from San Piero in Campo (Elba, Italy) and new data on tsilaisitic tourmaline from the holotype specimen locality |url=https://www.cambridge.org/core/journals/mineralogical-magazine/article/abs/fluortsilaisite-namn3al6si6o18bo33oh3f-a-new-tourmaline-from-san-piero-in-campo-elba-italy-and-new-data-on-tsilaisitic-tourmaline-from-the-holotype-specimen-locality/01BE7B7D01B2B491E4A512C9E83D4CC0|journal=Mineralogical Magazine|volume=79 |issue=1|pages=89–101|doi=10.1180/minmag.2015.079.1.08|s2cid=129149776|issn=0026-461X}} The gem is named after the location it was first found.
History
It was first reported in the Tsilaisina (also called Tsilaizina) Mine in Vakinankaratra, Madagascar.
The gem was originally described as tsilaisite. But then it was discredited in 2006. In 2011 it was reapproved as tsilaisite.{{Cite web|title=Tsilaisite|url=https://www.mindat.org/min-8016.html|access-date=2021-09-27|website=www.mindat.org}}
Characteristics
= Color =
In plane polarized light, the gem is pleochroic.{{Cite book|url=https://books.google.com/books?id=u6s6aRTPoU4C&dq=Tsilaisite&pg=PA677|title=Issues in Geology and Mineralogy: 2013 Edition|date=2013-05-01|publisher=ScholarlyEditions|isbn=978-1-4901-0698-4|pages=677|language=en}} Tsilaisite can be deep pink, red, orangish-yellow, brownish-gold, or greenish-yellow.