mineral

Carnelian Agate

Silicon Dioxide with Iron Oxide impurities (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Reddish-orange to brownish-red; Luster: Vitreous to waxy; Crystal structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.58-2.64

Hardness: 6
Color: Reddish-orange to brownish-red
Luster: Vitreous to waxy

Identified April 16, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the deposition of silica in groundwater within the cavities of volcanic rocks (basalt or rhyolite). The color comes from iron oxide (hematite) impurities. It can be found in formations ranging from the Precambrian to recent alluvial deposits.

Uses & applications

Used primarily in jewelry (cabochons, beads, rings), lapidary arts, decorative carvings, and as a semi-precious collector's stone. Historically used for seals and talismans.

Geological facts

Carnelian was famously used by the Romans and Ancient Egyptians for signet rings and amulets because it does not stick to hot wax. Some carnelian is naturally translucent, while cheaper varieties are often produced by heat-treating common grey chalcedony.

Field identification & locations

Identify in the field by its distinctive waxy luster, conchoidal (shell-like) fracture, and translucent orange-red color. It is commonly found in river beds or areas with volcanic activity, notably in Brazil, India, Uruguay, and the Pacific Northwest of the USA.

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