Composition: Be3Al2(SiO3)6
crystal System:  Hexagonal
Habit: Prismatic
Refractive Index: 1.56-1.59
Double Refraction and Optic Sign: 0.005-0.008 negative
Dispersion: Low (0.014)
Specific Gravity: 2.7-2.8
Hardness:  7.5-8.0
Cleavage: Poor (basal)
Fracture: Concohoidal to Uneven
Lustre:  Vitreous
Pleochroism: Medium toWeak.
Absorption Spectrum: Ordinary ray  680nm, 683nm 637nm broad weak band centred at 600nm, chrome rich stones 477nm. extraordianry ray 680/683nm is stronger 637nm is missing, but two diffuse lines at 646nm aaand 662nm, broad absorbtion is much weaker
Inclusions: Two phase inclusions, rain and mica, most stones are free from inclusions
Occurrence:  Afgahanistan, Brazil,Colombia, India, Pakistan, South Africa, USSR, Zambia & Zimbabwe.


John Cadby Jewellers
 Goldsmith, Silversmith,
Diamond Merchants, Appraiser & Engraver.
3, White Hart Yard, Trowbridge, Wiltshire.  BA14 8BY
Tel: 01225 776322  E-Mail: