Variety · Quartz group
Amethyst
SiO2
Amethyst is purple quartz coloured by iron and natural irradiation, the most popular decorative mineral in the world. Uruguayan geodes from Artigas (Arapey basalt) give deep saturated purple with small crystals; Brazilian cathedrals from Ametista do Sul run larger and paler; Veracruz and Thunder Bay produce prized crystal specimens. Colour, crystal size and lack of damage set the price.
| Formula | SiO2 |
|---|---|
| IMA status | variety |
| Crystal system | Trigonal |
| Mohs hardness | 7 |
| Group | Quartz group |
| Type locality | None (variety) |
Fakes and treatments
Heated pale amethyst becomes 'citrine' or 'prasiolite' (green); synthetic hydrothermal amethyst is common in gem rough. Geodes are cut, base-flattened and sometimes given cement backs and painted rims; some are dyed. State whether colour is natural, as the Stratum sample record does.
Elsewhere
- Wikidata: Q79058
- Wikipedia: amethyst
- Mindat: Amethyst
Cite this article
Stratum Study. "Amethyst" (Mineral). Stratum Study pack 2026.09, as of 2026-09-19. https://stratum.black/study/minerals/amethyst. Accessed 2026-09-20.
@misc{stratum-amethyst,
title = {Amethyst},
author = {{Stratum Study}},
howpublished = {\url{https://stratum.black/study/minerals/amethyst}},
year = {2026},
note = {Mineral article, Stratum Study pack 2026.09, as of 2026-09-19; sources: stratum, wikidata, commons. Accessed 2026-09-20.}
} Citations carry the pack version and the article's as-of date so they resolve to the same text later. The facts themselves belong to the sources listed below; cite those for the science.