mineral
Tumbled amethyst
Quartz, purple variety; silicon dioxide (SiO₂), colored mainly by iron impurities and irradiation
AI-generated identification · may be incorrectMohs hardness 7; translucent purple to reddish-violet, vitreous luster, hexagonal crystal structure, and no prominent cleavage. The rounded surface indicates mechanical tumbling and polishing.
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Physical properties
Mohs hardness 7; translucent purple to reddish-violet, vitreous luster, hexagonal crystal structure, and no prominent cleavage. The rounded surface indicates mechanical tumbling and polishing.
Formation & geological history
Forms in silica-rich hydrothermal fluids filling volcanic cavities, especially basaltic geodes; many commercial specimens formed in Mesozoic to Cenozoic volcanic rocks. Its purple color develops through trace iron and natural radiation.
Uses & applications
Used as an ornamental stone, jewelry, carvings, beads, and mineral specimens; lower-grade material is widely sold as tumbled stones.
Geological facts
Amethyst is the February birthstone and the most valued quartz variety. Heating can turn it yellow-orange, producing citrine or ametrine-like material.
Field identification & locations
Identify it by its purple color, glassy luster, hardness, and lack of obvious cleavage; it can scratch glass but should not be confused with dyed glass or purple fluorite. Major sources include Brazil, Uruguay, Zambia, and Bolivia.
