Mineral description : Beryllonite

Mineral class Phosphates
Chemical formula NaBePO4
Crystal system Monoclinic, Class : 2/m, Space group P21/n, Z=12
Lattice constants a=8.13kX b=7.76 c=14.17 ß=90º 00´
Diffraction lines 2.84(100) 3.65(90) 2.28(70)
Optical constants alpha=1.5520 beta=1.5579(Na) gamma=1.561 (-)2V=67º 56´
Habitus Crystals tabular to short prismatic, often highly modified. Crystal faces often etched rough. Twinnings on {101} common. Also polysynthetic.
Cleavage {010} perfect. {100} good, interrupted. {101} indistinct. Fracture brittle conchoidal.
Hardness 5.5-6
Density 2.84
Color Usually colorless, white or pale yellow.
Streak  
Luster Transparent to translucent, vitreous, pearly on perfect cleavage.
Description  
Occurance In granite pegmatites.
Associates Albite, tourmaline, herderite, eosphorite, muscovite, quartz ...
Notes  
Locations A rare mineral in Sweden
  • Norrö, near Utö, Stockholm. (see Wilke 1997)
  • Viitaniemi, Finland.

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Last changed : 1998-03-07