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Chemical composition Complex borosilicate
Crystal system Orthorhombic
Habit Prismatic
Cleavage Prismatic
Fracture Conchoidal
Hardness 6.5
Optic nature Biaxial -
Refractive index 1.67 -1.68
Birefringence 0.013
Dispersion Low, 0.019
Specific gravity 3.28 - 3.35
Lustre Vitreous
Pleochroism Distinct (green, yellow, brown)
Faceted Kornerupine
Photo courtesty of The Gem Trader