mineral
Tumbled amethyst
Amethyst, purple quartz (SiO₂)
AI-generated identification · may be incorrectMohs hardness 7; translucent purple coloration from trace iron and irradiation; vitreous luster, trigonal crystal structure, conchoidal fracture, no cleavage, and specific gravity about 2.65. The smooth shape is human-tumbled and polished.
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Physical properties
Mohs hardness 7; translucent purple coloration from trace iron and irradiation; vitreous luster, trigonal crystal structure, conchoidal fracture, no cleavage, and specific gravity about 2.65. The smooth shape is human-tumbled and polished.
Formation & geological history
Forms when iron-bearing quartz crystallizes in volcanic cavities, especially basaltic geodes; coloration develops through irradiation and heating processes over geologic time, commonly in the Cenozoic to older volcanic sequences.
Uses & applications
Used for jewelry, ornaments, carvings, crystal specimens, and decorative tumbled stones; it is also the February birthstone. This specimen is primarily a low-cost lapidary item.
Geological facts
Amethyst is the purple variety of quartz, and its color may fade with prolonged strong sunlight or change when heated. Very dark, evenly colored stones are often enhanced or synthetic, though natural amethyst commonly shows zoning.
Field identification & locations
Identify it by purple color, glassy luster, hardness sufficient to scratch glass, and absence of cleavage; quartz varieties can be distinguished by conchoidal fracture. Major sources include Brazil, Uruguay, Zambia, Bolivia, and Mexico.
