mineral
Amethyst cluster (quartz geode fragment)
Amethyst, purple variety of quartz; silicon dioxide (SiO₂) colored mainly by iron-related defects
AI-generated identification · may be incorrectTypically Mohs hardness 7, vitreous luster, hexagonal quartz crystals, and no true cleavage; purple crystal tips contrast with a gray-white quartz and darker matrix, likely basalt or another host rock. Specific gravity is about 2.65.
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Physical properties
Typically Mohs hardness 7, vitreous luster, hexagonal quartz crystals, and no true cleavage; purple crystal tips contrast with a gray-white quartz and darker matrix, likely basalt or another host rock. Specific gravity is about 2.65.
Formation & geological history
Forms when silica-rich groundwater deposits quartz crystals in cavities of volcanic rock, commonly during late-stage hydrothermal activity. Individual deposits range from relatively young volcanic settings to Paleozoic and older rocks, depending on locality.
Uses & applications
Used as a specimen, ornament, and gemstone; fine transparent material is faceted, while clusters are sold for décor and mineral collections. It has little construction or industrial value compared with ordinary quartz.
Geological facts
Amethyst’s purple color can fade with prolonged heat or intense sunlight; heating may produce yellow or orange citrine-like colors. Large commercial deposits occur in Brazil, Uruguay, Zambia, and Morocco.
Field identification & locations
Identify it by purple, glassy quartz crystals with six-sided points and hardness sufficient to scratch ordinary glass; unlike fluorite, it lacks prominent cleavage. The image appears to show a small natural cluster on matrix, though locality cannot be determined visually.
