gemstone

Amethyst cluster

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

AI-generated identification · may be incorrect

Mohs hardness 7; vitreous luster; purple to violet crystals on a gray-white matrix, with conchoidal fracture and no cleavage. Quartz is trigonal and has specific gravity near 2.65.

Identified August 12, 2026More gemstone →

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Physical properties

Mohs hardness 7; vitreous luster; purple to violet crystals on a gray-white matrix, with conchoidal fracture and no cleavage. Quartz is trigonal and has specific gravity near 2.65.

Formation & geological history

Forms when silica-rich hydrothermal fluids fill cavities in volcanic rocks, especially basaltic lava flows; crystals commonly developed during the Cenozoic, though deposits range widely in age.

Uses & applications

Used as a gemstone, ornamental specimen, jewelry material, and popular mineral-collection piece; small clusters have modest commercial value.

Geological facts

Amethyst’s purple color can fade with prolonged heating or strong sunlight; citrine-like yellow quartz may result from heat treatment.

Field identification & locations

Identify it by purple, six-sided quartz crystals, glassy luster, hardness, and lack of cleavage; major sources include Brazil, Uruguay, Zambia, Namibia, and Mexico. The pictured piece appears to be a small natural cluster on matrix.