gemstone

Tumbled carnelian

Cryptocrystalline quartz (chalcedony), SiO₂, colored mainly by iron oxides

AI-generated identification · may be incorrect

Typically orange-red to reddish brown, translucent to opaque, with a waxy/glassy luster and no visible crystals; Mohs hardness 6.5–7, specific gravity about 2.6. The rounded shape indicates mechanical tumbling and polishing.

Identified September 4, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures, depositing chalcedony that later acquires red coloration from oxidized iron. Deposits occur in volcanic rocks and gravels, generally ranging from Paleozoic to Cenozoic in age.

Uses & applications

Used for beads, cabochons, carvings, ornaments, and inexpensive jewelry; historically used for seals and signet rings. It has little industrial value compared with ordinary quartz.

Geological facts

Carnelian is a reddish variety of chalcedony; deeper, more even color generally increases desirability. Heating pale chalcedony can intensify its orange-red color.

Field identification & locations

Identify it by its fine-grained, non-crystalline appearance, hardness, translucency, and resistance to scratching by steel; it should not fizz in dilute acid. Common sources include India, Brazil, Uruguay, Madagascar, and the United States.