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Chemical composition Beryllium sillicate


Crystal system Trigonal
Habit Tabular to prismatic
Fracture Conchoidal (brittle)
Cleavage Indistinct (one direction)
Hardness 7.5 - 8
Optic nature uniaxial +
Refractive index 1.651 - 1.670
Birefringence 0.016
Dispersion Low, 0.015
Luster Vitreous
Specific gravity 2.92 - 2.97
Pleochroism Seen in strongly coloured stones
Fluorescence Sometimes pale greenish / blue or pale rose