Sardonyx
From The Gemology Project
| Sardonyx | |
|---|---|
| Chemical composition | SiO2 Silicon dioxide |
| 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 |
