gemstone

Amethyst (rough crystal)

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

AI-generated identification · may be incorrect

Mohs hardness 7; translucent purple with a vitreous luster, conchoidal fracture, and hexagonal crystal structure. The specimen appears unpolished and partly crystalline, with pale lavender-to-violet zoning.

Identified August 18, 2026More gemstone →

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Physical properties

Formation & geological history

Forms chiefly in gas cavities and fractures of volcanic basalt when silica-rich hydrothermal fluids deposit quartz; most amethyst is Cenozoic to older, commonly tens to hundreds of millions of years old. Major sources include Brazil, Uruguay, Zambia, and Bolivia.

Uses & applications

Used for cabochons, faceted gemstones, carvings, geodes, jewelry, and mineral collecting; lower-grade material is used decoratively. It has no major industrial use beyond quartz-related applications.

Geological facts

Purple color intensity depends on iron content and radiation exposure; heating can turn some amethyst yellow or orange, producing citrine-like material.

Field identification & locations

Identify by purple quartz color, glassy luster, hardness, lack of prominent cleavage, and six-sided crystal faces or geode context. Common localities include basalt cavities in Brazil and Uruguay.