gemstone

Polished carnelian (reddish-brown chalcedony)

Carnelian, a microcrystalline variety of quartz (SiO₂)

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent reddish-brown to orange, vitreous/waxy luster, cryptocrystalline structure, and no visible cleavage. The smooth oval surface indicates tumbling and polishing; color commonly comes from iron oxides.

Identified August 8, 2026More gemstone →

Explore Polished carnelian (reddish-brown chalcedony) in the encyclopedia →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures, with iron staining during or after deposition; it occurs in volcanic rocks and sedimentary gravels, generally from many geological ages rather than one specific period.

Uses & applications

Used for cabochons, beads, carvings, seals, and ornamental objects; common polished pieces have modest collector value.

Geological facts

Carnelian is part of the agate/chalcedony family and may become more orange or red when heat-treated. Ancient Egyptians and Romans used it extensively for jewelry and engraved signet rings.

Field identification & locations

Common sources include India, Brazil, Uruguay, Madagascar, Germany, and the United States. Identify it by its uniform reddish translucent body, waxy polish, and lack of cleavage; glass may show bubbles or a more glassy appearance.