{{Short description|Barium manganese vanadate mineral}} {{About|mineral|resident of Tokyo|Tokyojin|and|Edokko}} {{infobox mineral | name = Tokyoite | category = Vanadate mineral | image = Tokyoite displayed at Mining Museum of Akita University.jpg | imagesize = 250 | caption = Tokyoite ore displayed at the Mining Museum of Akita University, Japan | formula = Ba<sub>2</sub>(Mn<sup>3+</sup>,Fe<sup>3+</sup>)OH(VO<sub>4</sub>)<sub>2</sub> | IMAsymbol = Tky<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 = 8.BG.05 | dana = | system = Monoclinic | class = Prismatic (2/m) <br/><small>(same H-M symbol)</small> | unit cell = a = 9.104&nbsp;Å, b = 6.132&nbsp;Å <br/>c = 7.895&nbsp;Å; β = 112.2°; Z&nbsp;=&nbsp;2 | color = Reddish black | colour = | habit = Occurs as splotchy, anhedral crystals forming inclusions | twinning = | cleavage = None observed | fracture = | tenacity = | mohs = 4.5 - 5 | luster = Vitreous | streak = Deep brownish red | diaphaneity = Translucent | gravity = 4.62 calculated | density = | polish = | opticalprop = Biaxial (?) | refractive = a=1.99, g=2.03 | birefringence = 0.0400 | pleochroism = Distinct, reddish orange to dark brownish red | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence= | absorption = | melt = | fusibility = | diagnostic = | solubility = | other = | alteration = | references = <ref name=Mindat>[http://www.mindat.org/min-25633.html Mindat]</ref><ref name=Webmin>[http://www.webmineral.com/data/Tokyoite.shtml Webmineral data]</ref><ref name=Matsubara>[http://rruff.geo.arizona.edu/doclib/jmps/vol99/JMPS99_363.pdf Matsubara, Satoshi, et al., ''Tokyoite, Ba2Mn3+(VO4)2(OH), a new mineral from the Shiromaru mine,'' Journal of Mineralogical and Petrological Sciences, V. 99, pp. 363-7, 2004]</ref> }} '''Tokyoite''' is a rare barium manganese vanadate mineral with the chemical formula: Ba<sub>2</sub>(Mn<sup>3+</sup>,Fe<sup>3+</sup>)OH(VO<sub>4</sub>)<sub>2</sub>. It is the manganese analogue of the iron rich gamagarite<ref name=Webmin/> and the barium analogue of the lead vanadate, brackebuschite.<ref name=Matsubara/>

It occurs in low-grade metamorphosed sedimentary manganese ore deposits<ref name=Mindat/> associated with hyalophane, braunite and tamaite.<ref name=Matsubara/>

It was first reported for an occurrence in the Shiromaru Mine, Okutama, Tama district, Tokyo Prefecture, Kantō region, Honshu Island, Japan and approved by the IMA in 2003.<ref name=Webmin/> It has been found in two mines in Italy and one in Japan, for which it was named.<ref name=Mindat/>

==References== {{Reflist}}

Category:Barium minerals Category:Manganese minerals Category:Hydroxide minerals Category:Vanadate minerals Category:Monoclinic minerals Category:Minerals described in 2003

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