mineral

Amethyst geode

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

AI-generated identification · may be incorrect

Violet druzy quartz crystals lining a cavity, with a gray-brown host rind likely volcanic rock. Quartz hardness is 7 Mohs, vitreous luster, hexagonal crystal structure, no cleavage, and specific gravity about 2.65.

Identified August 18, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater deposits quartz crystals inside gas cavities of volcanic basalt, commonly during the Jurassic–Cretaceous in major Brazilian and Uruguayan deposits. The specimen appears cut and polished along one edge.

Uses & applications

Used as a decorative specimen, paperweight, and in jewelry or carvings. Value depends on crystal color, sparkle, size, completeness, and whether it is natural or dyed.

Geological facts

Deep, evenly distributed purple with sharp sparkling points generally increases value; pale or uneven color is common. Heat treatment can turn amethyst yellow or orange (citrine).

Field identification & locations

Identify by purple quartz crystals with glassy faces, hardness near 7, and a contrasting volcanic rind; it should not scratch easily with a steel knife. Common sources include Brazil, Uruguay, Bolivia, Mexico, and Zambia. For selling in Tijuana, photograph dimensions, weight, all sides, and disclose any repairs or dyeing.