gemstone

Banded amethyst (polished)

Quartz, SiO₂; purple coloration from trace iron and irradiation

AI-generated identification · may be incorrect

Hardness 7 Mohs; pale purple and white banding, vitreous luster, trigonal crystal structure, no cleavage, conchoidal fracture, specific gravity about 2.65. The specimen is a cut and polished cabochon or slab.

Identified September 20, 2026More gemstone →

Explore Banded amethyst (polished) 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, commonly alongside agate and chalcedony; purple quartz develops through iron impurities and natural radiation. Most specimens formed in Mesozoic–Cenozoic volcanic environments, though age varies by locality.

Uses & applications

Used for cabochons, carvings, beads, ornamental objects, and mineral collecting; less commonly used as an industrial quartz source because of its decorative value.

Geological facts

The white zones are likely milky quartz or chalcedony, while the purple areas are amethyst. Color can fade with prolonged strong sunlight or heating.

Field identification & locations

Identify by purple quartz coloration, hardness, glassy luster, and lack of cleavage; it should scratch glass but not be scratched by a steel knife. Common sources include Brazil, Uruguay, Mexico, Zambia, and Namibia.