mineral
Botryoidal chalcedony (agate/geode fragment)
Chalcedony, microcrystalline SiO₂; likely quartz with minor iron-oxide and carbonate inclusions
AI-generated identification · may be incorrectHardness 6.5–7 Mohs; translucent gray-brown to honey color, waxy to vitreous luster, cryptocrystalline quartz, no cleavage, specific gravity about 2.6. Rounded botryoidal growths and druzy crystalline patches are visible.
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Physical properties
Hardness 6.5–7 Mohs; translucent gray-brown to honey color, waxy to vitreous luster, cryptocrystalline quartz, no cleavage, specific gravity about 2.6. Rounded botryoidal growths and druzy crystalline patches are visible.
Formation & geological history
Forms when silica-rich groundwater fills cavities, fractures, or vesicles in volcanic rock and precipitates in successive layers; iron impurities create the brown coloration. The specimen’s precise geological age and locality cannot be determined from the image.
Uses & applications
Used as a lapidary and ornamental stone, in carvings, cabochons, polished specimens, and occasionally industrial silica products.
Geological facts
Botryoidal texture means grape-like rounded surfaces produced by radiating microscopic quartz fibers; later cavities may develop sparkling druzy quartz.
Field identification & locations
Identify it by its waxy translucence, conchoidal fracture, rounded layered texture, and hardness sufficient to scratch ordinary glass; common sources include Brazil, Uruguay, Mexico, India, and the western United States.
