gemstone

Amethyst

Quartz (SiO₂), purple variety colored mainly by iron impurities and irradiation

AI-generated identification · may be incorrect

Mohs hardness 7; purple to violet, vitreous luster, trigonal crystal structure, no cleavage, conchoidal fracture, specific gravity about 2.65. The specimen appears to be a rough, partially translucent crystal cluster or fragment.

Identified August 29, 2026More gemstone →

Explore Amethyst 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 hydrothermal fluids or groundwater fill cavities in volcanic rocks, commonly alongside quartz, calcite, and zeolites. Individual deposits range from Precambrian to Cenozoic age, depending on locality.

Uses & applications

Used for faceted gemstones, cabochons, beads, carvings, geodes, and mineral collections; less commonly used as an ornamental stone.

Geological facts

Amethyst is February’s birthstone and is the most valued purple variety of quartz. Heating can transform its color to yellow, orange, or brown citrine-like tones.

Field identification & locations

Identify it by its purple color, glassy luster, hardness sufficient to scratch ordinary glass, and lack of cleavage; beware dyed quartz or glass. Important sources include Brazil, Uruguay, Zambia, Namibia, and Russia.