Demantoid

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Demantoid Garnet
Chemical composition Ca3Fe2(SiO4)3

Calcium iron silicate

Crystal system Cubic
Habit Dodecahedra
Cleavage None
Hardness 6.5
Optic nature Isotropic
Refractive index 1.85-1.89
Birefringence None
Specific gravity 3.85
Lustre Vitreous to adamantine