gemstone

Polished carnelian agate

Cryptocrystalline silica, SiO₂; chalcedony variety colored by iron oxides

AI-generated identification · may be incorrect

Translucent orange-brown with curved reddish-brown banding, waxy-to-glassy luster, and polished surfaces. Mohs hardness 6.5–7; no visible cleavage; trigonal microcrystalline quartz structure; specific gravity about 2.60–2.65.

Identified September 5, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rocks, with iron impurities producing orange-red colors; successive silica layers create the banding. Most specimens formed in Cenozoic to older volcanic environments, though exact age depends on locality.

Uses & applications

Used for cabochons, beads, carvings, seals, and ornamental objects; durable and affordable jewelry material. Common polished pieces generally have modest collector value.

Geological facts

The specimen appears to be a small polished cabochon or tumbled stone, possibly sold as carnelian, banded agate, or sardonyx depending on its locality and band definition.

Field identification & locations

Identify by its translucency, curved internal bands, glass scratch resistance, and lack of cleavage; quartz should scratch ordinary glass, though testing can damage the polish. Common sources include Brazil, Uruguay, India, Madagascar, and Botswana.