gemstone

Tumbled reddish-brown chalcedony, possibly carnelian

Chalcedony (microcrystalline quartz), SiO₂; red variety commonly called carnelian

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent reddish-brown body color with a smooth vitreous-to-waxy luster and no visible cleavage. Its rounded shape indicates tumbling and polishing; exact identification is uncertain from the photograph alone.

Identified August 13, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures, depositing microcrystalline quartz, often with iron oxides producing red color. Deposits commonly range from Cenozoic to older volcanic or sedimentary host rocks.

Uses & applications

Used for beads, cabochons, carvings, ornamental objects, and inexpensive jewelry. Common tumbled pieces typically have modest collector value.

Geological facts

Carnelian is colored mainly by iron impurities and may darken or brighten with heating. Chalcedony consists of intergrown microscopic quartz fibers and may show subtle banding under strong transmitted light.

Field identification & locations

Common sources include Brazil, Uruguay, India, Madagascar, Namibia, and the United States. Check for uniform waxy translucence, hardness sufficient to scratch glass, and absence of bubbles; glass imitations may show bubbles and lower hardness.