Editing Internet Texts/Gemstones/Amethyst
Amethyst
editAmethyst is a violet colored macrocrystalline variety of quartz. It is also the most valuable of all quartz varieties. Its color can vary from light violet to deep purple. Heating amethyst gives rise to yellow and colorless tones.
At the end of the 18th century, amethyst was ranked among the most valuable gemstones and was as expensive as diamonds and rubies. Unfortunately, after the discovery of large amethyst deposits in Brazil, it was reduced to the status of a semi-precious gem.
Basic properties
edit| Composition | SiO2 |
| Class | Oxydes and hydroxydes |
| Crystal system | Trigonal |
| Mohs' hardness | 7 |
| Fracture | Conchoidal |
| Cleavage | None |
| Lustre | Glassy |
| Streak | White |
| Localities | Brazil, Uruguay, Mexico, Russia, Namibia, France, Morocco |