mineral
Amethyst geode fragment
Quartz, SiO₂; purple color from irradiation-related iron impurities
AI-generated identification · may be incorrectAmethyst is quartz with Mohs hardness 7, vitreous luster, white-to-purple color, and hexagonal crystal structure; it has indistinct cleavage and specific gravity around 2.65. The specimen appears to be a cut or broken geode section with purple drusy crystals and a gray-green outer rind, possibly including chalcedony or…
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Physical properties
Amethyst is quartz with Mohs hardness 7, vitreous luster, white-to-purple color, and hexagonal crystal structure; it has indistinct cleavage and specific gravity around 2.65. The specimen appears to be a cut or broken geode section with purple drusy crystals and a gray-green outer rind, possibly including chalcedony or matrix minerals.
Formation & geological history
Forms when silica-rich groundwater deposits quartz crystals in cavities of volcanic basalt, commonly during the Mesozoic or Cenozoic eras. Major sources include Brazil, Uruguay, Zambia, and Mexico.
Uses & applications
Used for jewelry, carvings, mineral displays, metaphysical objects, and polished geode décor; ordinary pieces have modest commercial value.
Geological facts
Amethyst is the purple variety of quartz and is February’s birthstone. Strong heating can turn it yellow-orange, producing citrine-like material.
Field identification & locations
Identify it by its purple, glassy quartz crystals, lack of metallic appearance, and hardness sufficient to scratch glass. Value is typically $10–$40 for a small common fragment, or $50–$200+ for vivid, well-crystallized specimens.
