Template:Sardonyx

From The Gemology Project
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Sardonyx
Chemical composition Silicon Dioxide SiO2
Crystal system Trigonal
Habit edit me
Cleavage poor
Fracture very brittle, conchoidal
Hardness 7
Optic nature edit me
Refractive index 1.544 - 1.553
Birefringence 0.009
Dispersion 0.013
Specific gravity 2.65
Lustre Vitreous
Pleochroism None