gemstone

Polished carnelian/chalcedony agate

Microcrystalline quartz (SiO₂), chiefly chalcedony with iron-oxide coloration

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent honey-brown to reddish-brown, with waxy-to-glassy luster, cryptocrystalline structure, and no cleavage. Rounded cavities and flow-like color zoning are typical of agate/chalcedony.

Identified August 30, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rocks, depositing layered chalcedony and quartz; iron oxides create the red-brown colors. Individual pieces may range from Cenozoic to much older, depending on the host rock.

Uses & applications

Commonly cut and polished for cabochons, beads, carvings, worry stones, and decorative objects; durable but generally modestly priced jewelry material.

Geological facts

Carnelian is the red-orange variety of chalcedony, while brown or multicolored material is often marketed as agate or carnelian agate. Color may be naturally enhanced or heat-treated.

Field identification & locations

Identify by its glassy/waxy translucency, hardness, curved fracture, and internal banding or cavities; it should not scratch easily with a steel blade. Common sources include Brazil, Uruguay, India, Madagascar, and the western United States.