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Chemical composition KNa2B3Si12O30 Borosilicate
Crystal system Hexagonal
Habit Hexagonal and barrel-shaped etched prisms
Cleavage None
Fracture Conchoidal, splintery
Hardness 5-6
Optic nature Uniaxial +
Refractive index 1.510 - 1.532
Birefringence 0.016 - 0.021
Dispersion Unknown
Specific gravity 2.50 - 2.55
Lustre Vitreous
Pleochroism Colorless to pink, depending on body color