mineral

Carnelian Agate

Carnelian (Silicon Dioxide - SiO2 with Fe impurities)

Hardness: 6.5–7 (Mohs scale); Color: Orange to reddish-brown; Luster: Vitreous to waxy; Crystal structure: Hexagonal (trigonal) microcrystalline; Cleavage: None; Specific gravity: 2.58–2.64

Hardness: 6
Color: Orange to reddish-brown
Luster: Vitreous to waxy

Identified April 13, 2026More mineral →

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Physical properties

Hardness: 6.5–7 (Mohs scale); Color: Orange to reddish-brown; Luster: Vitreous to waxy; Crystal structure: Hexagonal (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 cavities (vesicles) within volcanic rocks. The orange color is derived from iron oxide impurities.

Uses & applications

Primarily used in jewelry (beads, cabochons), carvings, intaglios, and as a popular specimen for collectors.

Geological facts

Carnelian was highly valued in ancient civilizations; the Romans used it for signet rings because hot wax does not stick to it. It has been used as a gemstone for over 4,500 years.

Field identification & locations

Identify by its translucent reddish-orange hue and waxy luster. In the field, look for nodules in basalt or as water-worn pebbles in riverbeds. These are common in Brazil, India, and Uruguay.

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