mineral
Tumbled amethyst
Quartz, silicon dioxide (SiO₂), purple variety colored mainly by iron impurities and irradiation
AI-generated identification · may be incorrectMohs hardness 7; translucent purple with vitreous luster, conchoidal fracture, and no cleavage. Hexagonal quartz crystal structure is obscured by tumbling; apparent color zoning and internal fractures are typical.
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Physical properties
Mohs hardness 7; translucent purple with vitreous luster, conchoidal fracture, and no cleavage. Hexagonal quartz crystal structure is obscured by tumbling; apparent color zoning and internal fractures are typical.
Formation & geological history
Forms in silica-rich hydrothermal veins and volcanic geodes, commonly in basalt cavities; major deposits are geologically young to ancient, including Brazilian and Uruguayan occurrences. This specimen has been mechanically polished and rounded.
Uses & applications
Used for inexpensive jewelry, ornamental objects, crystal collecting, and lapidary items; its hardness makes it durable but less scratch-resistant than sapphire.
Geological facts
Amethyst’s purple color can fade with prolonged heat or strong sunlight. Citrine-like yellow quartz may result from heating amethyst, naturally or commercially.
Field identification & locations
Identify by purple color, glassy luster, hardness, and inability to scratch glass only weakly to moderately; glass or dyed quartz can imitate it, so inspect color distribution and inclusions. Common sources include Brazil, Uruguay, Zambia, and Bolivia.