Nabesite
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.
| General | |
|---|---|
| Category | Silicates |
| Formula (repeating unit) | Na2BeSi4O10·4H2O |
| Strunz classification | 8/J.0- |
| Dana classification | 77.1.5.11 |
| Crystal system | Orthorhombic |
| Crystal class | Disphenoidal |
| Space group | P212121 (No. 19) |
| Unit cell | a=9.748Å, b=10.133Å, c=12.954Å |
| Identification | |
| Formula mass | 391.84 |
| Colour | Colourless, white |
| Crystal habit | Platy, thin/flat |
| Cleavage | Good |
| Fracture | Brittle, uneven |
| Mohs scale hardness | 5-6 |
| Luster | Vitreous |
| Streak | White |
| Diaphaneity | Transparent |
| Specific gravity | 2.16 |
| Density | 2.16 |
| Birefringence | 0.012 |
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.
References
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