mineral

Carnelian (Red Agate)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 Mohs; Color: Brownish-red to orange; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.58-2.64

Hardness: 6
Color: Brownish-red to orange
Luster: Waxy to vitreous

Identified July 5, 2026More mineral →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Brownish-red to orange; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.58-2.64

Formation & geological history

Formed in volcanic and sedimentary environments through the deposition of silica from groundwater into cavities (vugs) within rocks. The reddish color is caused by impurities of iron oxide (hematite).

Uses & applications

Popular in jewelry as cabochons and beads, used for intaglios and seals historically, and widely collected as a semi-precious gemstone.

Geological facts

Carnelian was used by ancient Romans to make seal rings for imprinting wax because hot wax does not stick to it. It has been used for ornamentation for over 4,500 years, dating back to the Early Dynastic period of Mesopotamia.

Field identification & locations

Identify by its waxy luster, translucency, and warm orange-red color. It is common in riverbeds and beaches where volcanic rocks have eroded. Major sources include India, Brazil, and Uruguay.