Carnelian (Agate/Chalcedony)

Physical Properties

Hardness: 6.5-7 on Mohs scale; Color: Orangish-red to brownish-red; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.64

Formation & Geological History

Formed as a result of low-temperature silica-rich fluids percolating through cavities in volcanic or sedimentary rocks. The red color comes from iron oxide (hematite) impurities.

Uses & Applications

Used primarily in jewelry (beads, cabochons, cameos), decorative carvings, and as a popular collector's specimen.

Geological Facts

Carnelian has been used as a gemstone since the Neolithic period and was highly prized by ancient Egyptians, who believed it had protective properties. It was also commonly used for signet rings in the Roman Empire because hot wax does not stick to it.

Field Identification & Locations

Look for a translucent, waxy appearance with a distinct orange to reddish hue and curved, shell-like (conchoidal) fractures. Common locations include Brazil, India, Madagascar, and the Pacific Northwest of the USA.

Identified on: 4/16/2026

Mode: Standard