| Tokyoite | |
|---|---|
 Tokyoite ore displayed at the Mining Museum of Akita University, Japan | |
| General | |
| Category | Vanadate mineral |
| Formula | Ba2(Mn3+,Fe3+)OH(VO4)2 |
| IMA symbol | Tky1 |
| Strunz classification | 8.BG.05 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Unit cell | a = 9.104 Å, b = 6.132 Å c = 7.895 Å; β = 112.2°; Z = 2 |
| Identification | |
| Color | Reddish black |
| Crystal habit | Occurs as splotchy, anhedral crystals forming inclusions |
| Cleavage | None observed |
| Mohs scale hardness | 4.5 - 5 |
| Luster | Vitreous |
| Streak | Deep brownish red |
| Diaphaneity | Translucent |
| Specific gravity | 4.62 calculated |
| Optical properties | Biaxial (?) |
| Refractive index | a=1.99, g=2.03 |
| Birefringence | 0.0400 |
| Pleochroism | Distinct, reddish orange to dark brownish red |
| References | 234 |
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 gamagarite3 and the barium analogue of the lead vanadate, brackebuschite.4
It occurs in low-grade metamorphosed sedimentary manganese ore deposits2 associated with hyalophane, braunite and tamaite.4
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 2003.3 It has been found in two mines in Italy and one in Japan, for which it was named.2
References
References
- Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- Mindat
- Webmineral data
- 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