mineral
Polished amethyst-bearing quartz
Quartz, SiO₂; purple coloration from trace iron and irradiation, likely in an amethyst/quartz matrix
AI-generated identification · may be incorrectHardness 7 Mohs; translucent gray, lavender, and purple; vitreous luster; trigonal crystal structure, though crystals are obscured by polishing; no prominent cleavage and conchoidal fracture. The green-gray areas may be chlorite or other matrix minerals.
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Physical properties
Hardness 7 Mohs; translucent gray, lavender, and purple; vitreous luster; trigonal crystal structure, though crystals are obscured by polishing; no prominent cleavage and conchoidal fracture. The green-gray areas may be chlorite or other matrix minerals.
Formation & geological history
Amethyst forms when iron-bearing quartz grows in volcanic cavities, commonly in basaltic geodes, with coloration developing through irradiation and heating over geological time. The polished cabochon is human-processed; exact age and locality cannot be determined from the image.
Uses & applications
Used for cabochons, beads, carvings, ornamental objects, and mineral collections; gem-quality amethyst is used in jewelry. Common material has modest commercial value.
Geological facts
Purple intensity varies with iron content and treatment; heating can turn some amethyst yellow-orange, producing citrine. Color zoning and contrasting matrix are useful identifying features.
Field identification & locations
Common sources include Brazil, Uruguay, Zambia, and Mexico. Identify by glassy luster, purple zoning, hardness near 7, and lack of bubbles; a scratch test should be avoided on the polished surface.
