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CategoryBorate mineral
Chemical formulaMnSn(BO3)2
ColorColorless, light yellow to yellow brown
Crystal habitThin platy crystals in rosettes
Crystal systemTrigonal
Cleavage[001] Perfect
Mohs Scale hardness5-6
Refractive indexnω = 1.854 nε = 1.752
Optical PropertiesUniaxial (-)
Birefringenceδ = 0.102
Specific gravity4.73

Tusionite is a rare colorless to transparent to translucent yellow brown trigonal borate mineral with chemical formula: MnSn(BO3)2. The mineral is composed of 18.86% manganese, 40.76% tin, 7.42% boron, and 32.96% oxygen. It is a late stage hydrothermal mineral and occurs rarely in granite pegmatites in miarolitic cavities.

Tusionite was named for the location where the mineral was first discovered and described in 1983 in the Tusion River Valley in the Pamir Mountains of Tajikistan. Tusionite has also been reported from Recice in the Czech Republic and in pegmatites at Thomas Mountain, Riverside County, California.


  1. ^ Webmineral data
  2. ^ Mindat w/ location data
  3. ^ Mineral Handbook

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Tusionite". A list of authors is available in Wikipedia.
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