- Beryllonite
Beryllonite is a rare
sodium beryllium phosphate mineral with formula NaBePO4. The tabular to prismaticmonoclinic crystals vary from colorless to white or pale yellowish, and are transparent with a vitreous lustre. Twinning is common and occurs in several forms. It exhibits perfect cleavage in one direction. The Hardness is 5.5 to 6 and thespecific gravity is 2.8. Refractive indices are nα = 1.552, nβ = 1.558 and nγ = 1.561. A few crystals have been cut andfacet ed, but, as the refractive index is no higher than that of quartz, they do not make very brilliantgemstone s.It occurs as a secondary beryllium mineral in granitic and alkalic
pegmatite s. It was first described from complex crystals and as broken fragments in the disintegrated material of agranitic vein atStoneham, Maine , where it is associated withfeldspar , smokyquartz ,beryl andcolumbite . It was discovered byJames Dwight Dana in 1888, and named beryllonite for its beryllium content.References
*Palache, C., H. Berman, and C. Frondel (1951) Dana’s system of mineralogy, (7th edition), v. II, pp. 677–679
* [http://www.mindat.org/min-644.html Mindat with location data]
* [http://www.webmineral.com/data/Beryllonite.shtml Webmineral data]
*1911
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