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Admontite

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Admontite
General
CategoryNesoborates
Formula
(repeating unit)
MgB6O10·7H2O[1] or
MgB6O7(OH)6·4H2O[2]
Strunz classification6.FA.15
Dana classification26.6.3.1
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
H-M symbol: (2/m)
Space groupP21/c
Identification
Colorcolorless
CleavageAbsent
FractureConchoidal - Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz)
Mohs scale hardness2 - 3 - Gypsum-Calcite
StreakWhite
Density1.82 - 1.87, Average = 1.84
Optical propertiesBiaxial (-)
Refractive indexnα = 1.442 nγ = 1.504
Birefringenceδ = 0.062
DispersionNone
References[2][1][3]

Admontite is a hydrated magnesium borate mineral with formula MgB6O10·7H2O.

Occurrence - In a gypsum deposit. Associations: gypsum, anhydrite, hexahydrite, löweite, eugsterite, pyrite, quartz.

It is named after Admont, Austria. Its Mohs scale rating is 2 to 3.

References