mineral
Amethyst druzy geode slice
Quartz, SiO₂, purple variety (amethyst), with likely chalcedony/banded agate
AI-generated identification · may be incorrectViolet crystalline quartz lining a cavity, with gray-white translucent banding and brown iron-oxide staining; glassy luster, trigonal crystal structure, no cleavage, conchoidal fracture, Mohs hardness 7, specific gravity about 2.65.
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Physical properties
Violet crystalline quartz lining a cavity, with gray-white translucent banding and brown iron-oxide staining; glassy luster, trigonal crystal structure, no cleavage, conchoidal fracture, Mohs hardness 7, specific gravity about 2.65.
Formation & geological history
Formed when silica-rich groundwater deposited chalcedony and quartz crystals in volcanic-rock cavities; purple color results from iron impurities and natural irradiation. Typically Cenozoic to Mesozoic in age, depending on locality.
Uses & applications
Used as a decorative specimen, lapidary material, jewelry, and ornamental geode; generally more collectible when crystals are vivid, well formed, and undamaged.
Geological facts
The fine sparkling crystal coating is called druzy. Color intensity can fade with prolonged sunlight or heat.
Field identification & locations
Identify by purple quartz crystals, hardness sufficient to scratch glass, and agate-like concentric banding; common sources include Brazil, Uruguay, Mexico, and the United States.
