gemstone
Tumbled amethyst
Amethyst, purple quartz (SiO₂)
AI-generated identification · may be incorrectMohs hardness 7; translucent purple with vitreous luster and possible white quartz inclusions. It has a trigonal crystal structure, typically lacks visible cleavage, and has specific gravity about 2.65.
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Physical properties
Mohs hardness 7; translucent purple with vitreous luster and possible white quartz inclusions. It has a trigonal crystal structure, typically lacks visible cleavage, and has specific gravity about 2.65.
Formation & geological history
Forms when iron-bearing quartz crystallizes in gas cavities of volcanic rocks, especially basalt; irradiation and trace iron produce the purple color. Most amethyst deposits formed in hydrothermal or volcanic environments over millions of years.
Uses & applications
Used for cabochons, beads, carvings, mineral specimens, and ornamental objects; high-quality transparent stones are faceted for jewelry.
Geological facts
Amethyst is the purple variety of quartz and is February’s birthstone. Heat can turn some amethyst yellow or orange, producing citrine-like material.
Field identification & locations
Identify it by its purple color, glassy luster, hardness, and resistance to scratching by steel; a scratch test should be avoided on finished specimens. Common sources include Brazil, Uruguay, Zambia, and Mexico.
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