mineral
Tumbled yellow chalcedony (likely yellow jasper or silicified material)
Microcrystalline quartz, SiO₂; precise identification requires testing
AI-generated identification · may be incorrectCream-to-yellow, opaque, smoothly water-worn or tumbled, with a dull-to-waxy luster and no visible cleavage; quartz hardness is about 7 Mohs and specific gravity about 2.6. The surface shows cloudy granular mottling rather than distinct crystals.
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Physical properties
Cream-to-yellow, opaque, smoothly water-worn or tumbled, with a dull-to-waxy luster and no visible cleavage; quartz hardness is about 7 Mohs and specific gravity about 2.6. The surface shows cloudy granular mottling rather than distinct crystals.
Formation & geological history
Forms when silica-rich groundwater fills cavities or replaces volcanic or sedimentary material; the specimen is likely naturally rounded or human-tumbled. Its exact geological age and source cannot be determined from the image.
Uses & applications
Used as a lapidary stone, carving material, decorative pebble, and inexpensive jewelry component; typically valued mainly for appearance.
Geological facts
Yellow coloration commonly comes from iron oxides or hydroxides. A steel file should not easily scratch quartz-rich material, while glass can usually be scratched by it.
Field identification & locations
Common in silica-rich volcanic terrains, sedimentary deposits, and gravel beds worldwide; localities include Oregon, California, Brazil, India, and Madagascar. Confirm with a hardness test, streak (white), and absence of fizz in dilute acid.
