Chemistry: Berylium borate
Crystal system: Orthorhombic; prism; flattened.
Color: Transparent to translucent; colorless, gray, yellow.
Hardness: 7.5
Cleavage: Perfect: 2 directions; Fracture: brittle, conchoidal to uneven.
Specific gravity: 2.35
Refractive index: 1.553 – 1.631; Biaxial positive; 0.072
Luster: Vitreous.
Dispersion: Low.
Dichroism: -
Occurrence: In pegmatites; Madagascar, Norway.
Notes
Collector’s stone; high DR and vitreous luster (looks like glass); rare; seldom very clean; lowest known density for gem with such a high birefringence; faceted.
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