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Chemical composition ZrSiO4 Zirconium silicate
Crystal system Tetragonal
Habit Prismatic (squared) with pyramidal terminations
Cleavage Poor
Hardness 7.5
Optic nature Uniaxial + to isotropic
Refractive index 1.78 - 1.99
Birefringence Up to 0.059
Dispersion High, 0.039
Specific gravity 3.90-4.69
Lustre Vitreous to sub-adamantine
Pleochroism Weak (stronger in heat-treated)