gemstone

Red Agate (Carnelian)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Red to brownish-red; Luster: Vitreous to waxy; Crystal Structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.58-2.64.

Hardness: 6
Color: Red to brownish-red
Luster: Vitreous to waxy

Identified July 19, 2026More gemstone →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Red to brownish-red; Luster: Vitreous to waxy; Crystal Structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.58-2.64.

Formation & geological history

Formed in volcanic environments where silica-rich groundwater fills cavities (vesicles) in igneous rocks. The red color is caused by iron oxide impurities. These can range from millions to hundreds of millions of years in age.

Uses & applications

Used primarily in jewelry as beads, cabochons, and carvings; historically used for signet rings and seals. Also popular in metaphysical practices.

Geological facts

Carnelian was used as early as the 4th millennium BC in the Indus Valley Civilization. Napoleon Bonaparte reportedly found a carnelian seal in Egypt and wore it on his watch chain.

Field identification & locations

Identify by its translucent to semi-opaque nature and even red color. Found globally with major deposits in Brazil, India, and Uruguay. Collectors should look for depth of color and lack of synthetic dyes.