Amethyst
Varietyof Quartz
Amethyst is the violet-to-purple variety of quartz. As a variety of Quartz, it shares that species' composition (SiO2), crystal structure, and hardness; the distinction is the appearance defined above.
Photos
About Quartz
Full reference data — crystallography, X-ray diffraction, and cited physical properties — is on the Quartz species page.
| Formula | SiO2 |
|---|---|
| Hardness (Mohs) | 7 |
| Specific gravity | 2.6-2.64 |
| Density (calculated) | 2.65 |
| Crystal system | trigonal |
| Color range | black, blue, brown, colorless, green, red, yellow |
| Luster | dull, greasy, vitreous |
| Streak | white |