gemstone

Polished carnelian agate

Chalcedony (microcrystalline quartz), SiO₂, iron-oxide colored

AI-generated identification · may be incorrect

Mohs hardness 6.5–7; translucent reddish-brown to orange with cloudy gray bands, waxy-to-vitreous luster, cryptocrystalline structure, and no visible cleavage. The smooth cabochon is tumbled/polished rather than naturally shaped.

Identified September 15, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rocks; iron oxides create the red-brown coloration. Most agate formed during the Cenozoic to older Phanerozoic eras, depending on locality.

Uses & applications

Used for cabochons, beads, carvings, seals, and ornamental objects; durable, attractive pieces have modest jewelry and collector value.

Geological facts

Carnelian is the red-orange variety of chalcedony, while “agate” generally indicates banding or patterned chalcedony. Color may be naturally enhanced by heating.

Field identification & locations

Identify by its translucent warm color, waxy luster, very fine texture, and hardness sufficient to scratch glass; it should not show obvious cleavage. Common sources include Brazil, Uruguay, India, Madagascar, Botswana, and the United States.