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Chemical composition (Zn,Fe)S
Crystal system Cubic
Habit Tetrahedral or dodecahedral
Cleavage Perfect in 6 directions; easily developed
Fracture Concoidal to uneven
Hardness 3.5-4.0
Optic nature Isotropic
Refractive index 2.368 - 2.50 (increases with Fe content)
Specific gravity 3.95-4.10
Lustre Adamantine to Subadamantine