gemstone

Tumbled carnelian (red-orange chalcedony)

Carnelian, a microcrystalline variety of quartz; SiO₂

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent reddish-orange to brown, vitreous-to-waxy luster, cryptocrystalline structure, and no visible cleavage. The rounded, glossy form indicates tumbling and polishing; internal fractures or color zoning are common.

Identified August 26, 2026More gemstone →

Explore Tumbled carnelian (red-orange chalcedony) in the encyclopedia →

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Physical properties

Formation & geological history

Forms when iron-bearing silica or chalcedony is deposited in cavities and later oxidized, producing red-orange coloration. It occurs mainly in volcanic rocks and sedimentary silica deposits, generally formed from Paleozoic to Cenozoic geological processes.

Uses & applications

Used for beads, cabochons, carvings, seals, and ornamental objects; durable enough for jewelry but less valuable than fine agate or high-grade jasper.

Geological facts

Carnelian’s color comes chiefly from dispersed iron oxides; heating can intensify or redden the color. It is closely related to sard, which is typically darker brown-red.

Field identification & locations

Identify it by its orange-red translucent body, waxy/vitreous polish, lack of cleavage, and quartz hardness; it can scratch glass, though this is not recommended. Common sources include India, Brazil, Uruguay, Madagascar, and Indonesia.