mineral
Tumbled pale chalcedony (likely quartz)
Microcrystalline quartz, SiO₂; possibly pale agate or quartz
AI-generated identification · may be incorrectHardness about 7 Mohs; cream-yellow, translucent, waxy to vitreous luster, with no obvious cleavage and conchoidal fracture. Rounded and polished, with faint internal clouding or banding visible.
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Physical properties
Hardness about 7 Mohs; cream-yellow, translucent, waxy to vitreous luster, with no obvious cleavage and conchoidal fracture. Rounded and polished, with faint internal clouding or banding visible.
Formation & geological history
Formed when silica-rich groundwater fills cavities or fractures in volcanic rock and precipitates microcrystalline quartz, commonly during Cenozoic or older geologic episodes. Tumbled shaping is human-processed.
Uses & applications
Used as a lapidary stone, cabochon, ornament, and inexpensive jewelry or collectible specimen. Usually modest commercial value.
Geological facts
Chalcedony is quartz whose crystals are too small to see unaided; agate is a banded variety. The pale color may result from iron staining or other trace impurities.
Field identification & locations
Identify by its glassy/waxy appearance, translucency, lack of cleavage, and ability to scratch ordinary glass; a steel knife should not scratch it. Common sources include Brazil, Uruguay, India, Madagascar, and the western United States.
