gemstone

Amethyst crystal (likely quartz)

Quartz, crystalline silica (SiO₂), purple variety amethyst

AI-generated identification · may be incorrect

Mohs hardness 7; typically violet to purple with vitreous luster, hexagonal crystal structure, and indistinct cleavage with conchoidal fracture. The bright gold areas may be surface reflections or iron-oxide inclusions, though the image is insufficient for certainty.

Identified August 26, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when iron-bearing silica-rich fluids crystallize in cavities of volcanic rocks, especially basaltic geodes; most specimens are Cenozoic or younger, though quartz deposits occur across geologic ages.

Uses & applications

Used for beads, cabochons, faceted gems, carvings, and mineral collections; high-quality transparent material is jewelry grade.

Geological facts

Amethyst’s purple color commonly results from iron impurities modified by natural irradiation. Heating can turn it yellow-orange, producing citrine-like material.

Field identification & locations

Identify by purple color, glassy luster, hardness, and six-sided quartz crystals or geode lining; common sources include Brazil, Uruguay, Zambia, and Bolivia. A scratch test, loupe examination, and specific-gravity test help distinguish it from glass or fluorite.