mineral
Tumbled purple quartz, likely amethyst
Quartz (SiO₂), purple variety commonly colored by iron impurities and irradiation
AI-generated identification · may be incorrectHardness 7 Mohs; translucent lavender-purple color, vitreous luster, conchoidal fracture, and no cleavage. The rounded shape and smooth surface indicate tumbling or natural water wear; exact identification is uncertain from the image alone.
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Physical properties
Hardness 7 Mohs; translucent lavender-purple color, vitreous luster, conchoidal fracture, and no cleavage. The rounded shape and smooth surface indicate tumbling or natural water wear; exact identification is uncertain from the image alone.
Formation & geological history
Quartz crystallizes from silica-rich hydrothermal fluids and igneous cavities; amethyst commonly forms in volcanic geodes, chiefly during Phanerozoic geologic time. Purple color develops through iron-related defects and natural radiation.
Uses & applications
Used for inexpensive cabochons, beads, carvings, décor, and mineral collections; quartz is also important in glass, electronics, and abrasives.
Geological facts
Amethyst is the best-known purple quartz and is the birthstone for February. Heating can turn some amethyst yellow-orange, producing citrine-like material.
Field identification & locations
Look for glassy luster, hardness sufficient to scratch ordinary glass, and lack of cleavage; purple fluorite is softer and commonly cleaves. Common sources include Brazil, Uruguay, Zambia, and Madagascar.
