mineral

Amethyst quartz

Quartz, silicon dioxide (SiO₂), purple variety colored mainly by iron-related defects

AI-generated identification · may be incorrect

Hardness 7 Mohs; purple to violet, vitreous luster, translucent to transparent, conchoidal fracture, and trigonal crystal structure. The specimen appears as a rough, massive/tumbled piece with possible quartz crystal faces and minor surface coatings or matrix.

Identified August 16, 2026More mineral →

Explore Amethyst quartz in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rocks, especially basalt, where quartz crystals grow over long periods; deposits range from Paleozoic to recent. Common sources include Brazil, Uruguay, Zambia, Namibia, and Mexico.

Uses & applications

Used as an ornamental and lapidary stone, in jewelry, carvings, polished specimens, and mineral collections; powdered quartz also has industrial uses, though gem-quality amethyst is primarily decorative.

Geological facts

Purple color intensity varies with iron content and irradiation; heating can produce yellow citrine. Amethyst is the traditional February birthstone and a variety of quartz rather than a separate mineral species.

Field identification & locations

Identify by its purple color, glassy luster, hardness sufficient to scratch ordinary glass, and lack of obvious cleavage; avoid confusing it with purple glass or fluorite, which is softer. Commonly found in geodes and volcanic cavity deposits.