Tokyoite

 Tokyoite is a rare barium manganese vanadate mineral with the chemical formula: Ba2(Mn3+,Fe3+)OH(VO4)2. It is the manganese analogue of the iron rich gamagarite[2] and the barium analogue of the lead vanadate, brackebuschite.[3]

Tokyoite
General
CategoryVanadate mineral
Formula
(repeating unit)		Ba2(Mn3+,Fe3+)OH(VO4)2
Strunz classification8.BG.05
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Unit cella = 9.104 Å, b = 6.132 Å
c = 7.895 Å; β = 112.2°; Z = 2
Identification
ColorReddish black
Crystal habitOccurs as splotchy, anhedral crystals forming inclusions
CleavageNone observed
Mohs scale hardness4.5 - 5
LusterVitreous
StreakDeep brownish red
DiaphaneityTranslucent
Specific gravity4.62 calculated
Optical propertiesBiaxial (?)
Refractive indexa=1.99, g=2.03
Birefringence0.0400
PleochroismDistinct, reddish orange to dark brownish red
References[1][2][3]

It occurs in low-grade metamorphosed sedimentary manganese ore deposits[1] associated with hyalophane, braunite and tamaite.[3]

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.[2] It has been found in two mines in Italy and one in Japan, for which it was named.


This article uses material from the Wikipedia article
 Metasyntactic variable, which is released under the 
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Attribution-ShareAlike 3.0 Unported License.