Nabesite

(repeating unit)Na₂BeSi₄O₁₀·4H₂OStrunz classification8/J.0-Dana classification77.1.5.11Crystal systemOrthorhombicCrystal classDisphenoidalSpace groupP2₁2₁2₁ (No. 19)Unit cella=9.748Å, b=10.133Å, c=12.954ÅIdentificationFormula mass391.84ColourColourless, whiteCrystal habitPlaty, thin/flatCleavageGoodFractureBrittle, unevenMohs scale hardness5-6LusterVitreousStreakWhiteDiaphaneityTransparentSpecific gravity2.16Density2.16Birefringence0.012

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 n_α=1.499, n_β=1.507, and n_γ=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.