Chemistry:Nabesite

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General
CategorySilicates
Formula
(repeating unit)
Na2BeSi4O10·4H2O
Strunz classification8/J.0-
Dana classification77.1.5.11
Crystal systemOrthorhombic
Crystal classDisphenoidal
Space groupP212121 (No. 19)
Unit cella=9.748Å, b=10.133Å, c=12.954Å
Identification
Formula mass391.84
ColourColourless, white
Crystal habitPlaty, thin/flat
CleavageGood
FractureBrittle, uneven
Mohs scale hardness5-6
|re|er}}Vitreous
StreakWhite
DiaphaneityTransparent
Specific gravity2.16
Density2.16
Birefringence0.012

Nabesite is a rare silicate mineral of the zeolite group with the chemical formula Na2BeSi4O10·4(H2O). It occurs as colorless to white orthorhombic crystals in thin platy mica like sheets. It has the zeolite structure. Its Mohs hardness is 5 to 6 and its specific gravity is 2.16. The reported refractive index values are nα=1.499, nβ=1.507, and nγ=1.511.

It was discovered in the Ilimaussaq intrusive complex, of southwest Greenland, and first recognized in 2000. It occurs in tugtupite-bearing albitite, a rare highly alkaline igneous rock.

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