mineral
Tumbled yellow chalcedony (probable)
Chalcedony, microcrystalline quartz (SiO₂), possibly iron-stained jasper
AI-generated identification · may be incorrectPale yellow-beige, opaque to slightly translucent, with a dull-to-waxy luster and smooth rounded surfaces from tumbling. Hardness is about 6.5–7 Mohs; no obvious cleavage, cryptocrystalline quartz structure, and specific gravity near 2.6.
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Physical properties
Pale yellow-beige, opaque to slightly translucent, with a dull-to-waxy luster and smooth rounded surfaces from tumbling. Hardness is about 6.5–7 Mohs; no obvious cleavage, cryptocrystalline quartz structure, and specific gravity near 2.6.
Formation & geological history
Forms when silica-rich groundwater fills cavities, fractures, or vesicles in volcanic rocks, later acquiring yellow coloration from iron oxides or other impurities. Chalcedony deposits range from Precambrian to Recent, depending on locality.
Uses & applications
Used for cabochons, carvings, beads, polishing stones, and decorative objects; lower-grade material has modest collecting value.
Geological facts
Chalcedony is a quartz variety composed of intergrown microscopic quartz fibers and commonly occurs with agate, jasper, and amethyst.
Field identification & locations
Identify it by its waxy appearance, very high scratch resistance, conchoidal fracture, and lack of visible large crystals; it can scratch ordinary glass. Common sources include Brazil, Uruguay, India, Madagascar, Mexico, and the western United States.
