mineral

Carnelian (Red Agate)

Silicon dioxide (SiO2) with iron oxide impurities

Hardness: 6.5-7 (Mohs); Color: Red-orange to reddish-brown; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None; Specific Gravity: 2.58-2.64

Hardness: 6
Color: Red-orange to reddish-brown
Luster: Waxy to vitreous

Identified May 31, 2026More mineral →

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Physical properties

Hardness: 6.5-7 (Mohs); Color: Red-orange to reddish-brown; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None; Specific Gravity: 2.58-2.64

Formation & geological history

Formed in low-temperature hydrothermal environments where silica-rich fluids deposit in volcanic rock cavities or sedimentary layers. Its color comes from hematite impurities.

Uses & applications

Predominantly used as a gemstone for jewelry, beads, seals, and carvings. Historically used for signet rings and amulets.

Geological facts

Ancient Romans and Egyptians used carnelian for signet rings because hot wax does not stick to it. It has been used for jewelry since the Neolithic period over 4,000 years ago.

Field identification & locations

Identify by its translucent reddish-orange color, waxy luster, and lack of visible crystalline structure. Commonly found in India, Brazil, Madagascar, and Uruguay.

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