mineral

Carnelian (Agate)

SiO2 (Silicon Dioxide) with Iron Oxide impurities

Hardness: 6.5-7 on Mohs scale. Color: Translucent orange to reddish-brown. Luster: Vitreous to waxy. Crystal Structure: Hexagonal (trigonal) cryptocrystalline. Cleavage: None. Specific Gravity: 2.58-2.64.

Hardness: 6
Color: Translucent orange to reddish-brown
Luster: Vitreous to waxy

Identified July 21, 2026More mineral →

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Physical properties

Formation & geological history

Formed in cavities of volcanic rocks (basalt) or sedimentary environments through the deposition of silica from groundwater. The red-orange hue is caused by iron impurities.

Uses & applications

Extensively used in jewelry (beads, cabochons, rings), seal stones, carvings, and as a popular collector's gemstone. Historically used for amulets and signet rings.

Geological facts

Ancient Romans used carnelian for signet rings because hot wax does not stick to the stone. It is a variety of chalcedony that has been prized for over 4,500 years.

Field identification & locations

Identify by its translucent, waxy appearance and orange-red glow when backlit (as seen in the photo). Commonly found in Brazil, India, Uruguay, and the United States (Pacific Northwest). Collectors look for uniform color and high translucency.

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