{{Short description|Rare zeolite mineral}} {{Infobox mineral | name = | boxwidth = | boxbgcolor = | image = | imagesize = | alt = | caption = | category = Tectosilicate minerals | group = Zeolite group | formula = {{Format molecular formula|Na2BeSi4O10·4H2O}} | molweight = 391.84 | strunz = 8/J.0- | dana = 77.1.5.11 | system = Orthorhombic | class = Disphenoidal | symmetry = ''P2<sub>1</sub>2<sub>1</sub>2<sub>1</sub>'' (No. 19) | unit cell = a=9.748Å, b=10.133Å, c=12.954Å | colour = Colourless, white | habit = Platy, thin/flat | twinning = | cleavage = Good | fracture = Brittle, uneven | tenacity = | toughness = | mohs = 5-6 | luster = Vitreous | streak = White | diaphaneity = Transparent | gravity = 2.16 | density = 2.16 | polish = | opticalprop = | refractive = | birefringence = 0.012 | pleochroism = | 2V = | dispersion = | extinction = | length fast/slow = }} '''Nabesite''' is a rare silicate mineral of the zeolite group with the chemical formula Na<sub>2</sub>BeSi<sub>4</sub>O<sub>10</sub>·4(H<sub>2</sub>O). 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<sub>α</sub>=1.499, n<sub>β</sub>=1.507, and n<sub>γ</sub>=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.
== References == *[http://webmineral.com/data/Nabesite.shtml Webmineral.com data] *[http://mindat.org/min-11439.html Mindat.org]
==External links== *[http://helios.princeton.edu/zeomics/cgi-bin/view_structure.pl?src=iza&id=NAB Structure type NAB]
Category:Sodium minerals Category:Beryllium minerals Category:Zeolite group Category:Orthorhombic minerals Category:Minerals in space group 19
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