mineral
Amethyst fragment
Quartz, purple variety (SiO₂)
AI-generated identification · may be incorrectMohs hardness 7; translucent pale violet to purple, with a vitreous luster and conchoidal fracture. It has trigonal crystal structure and no true cleavage; the pictured piece appears cut or fractured and may be polished.
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Physical properties
Mohs hardness 7; translucent pale violet to purple, with a vitreous luster and conchoidal fracture. It has trigonal crystal structure and no true cleavage; the pictured piece appears cut or fractured and may be polished.
Formation & geological history
Amethyst forms when iron-bearing silica-rich fluids fill cavities in volcanic rocks, where irradiation and heat produce the purple color. Deposits commonly formed during the Mesozoic and younger, though age varies by locality.
Uses & applications
Used as a gemstone, ornamental stone, crystal specimen, and in polished décor; small fragments generally have modest value.
Geological facts
Purple color results mainly from irradiation-altered iron impurities. Heating can turn amethyst yellow-orange, producing citrine.
Field identification & locations
Identify by purple quartz color, glassy luster, hardness, and lack of cleavage; it should scratch ordinary glass but not be scratched by a steel blade. Common sources include Brazil, Uruguay, Zambia, and Mexico.
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