Tusionite

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
General
CategoryBorate minerals
Formula
(repeating unit)
MnSn(BO3)2
Strunz classification6.AA.15
Crystal systemTrigonal
Crystal classRhombohedral (3)
H-M symbol: (3)
Space groupR3 (no. 148)
Identification
ColorColorless, light yellow to yellow brown
Crystal habitThin platy crystals in rosettes
Cleavage[001] Perfect
Mohs scale hardness5-6
LusterVitreous
Streakwhite
DiaphaneityTranslucent
Specific gravity4.73
Optical propertiesUniaxial (-)
Refractive indexnω = 1.854 nε = 1.752
Birefringenceδ = 0.102
References[1][2][3][4]

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.

See also

References


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