mineral

Carnelian

Carnelian (a variety of Chalcedony), SiO2 (Silicon Dioxide)

Hardness: 6.5-7 on the Mohs scale; Color: Reddish-orange to brownish-red; Luster: Vitreous to waxy; Crystal structure: Trigonal (cryptocrystalline); Cleavage: None; Specific Gravity: 2.58-2.64

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

Identified March 30, 2026More mineral →

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Physical properties

Hardness: 6.5-7 on the Mohs scale; Color: Reddish-orange to brownish-red; Luster: Vitreous to waxy; Crystal structure: Trigonal (cryptocrystalline); Cleavage: None; Specific Gravity: 2.58-2.64

Formation & geological history

Formed in volcanic and sedimentary rocks when silica-rich fluids deposit in cavities or veins at low temperatures. Its red color is caused by iron oxide (hematite) impurities.

Uses & applications

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

Geological facts

Ancient Romans and Egyptians used carnelian for seals because hot wax does not stick to it. It has been used for decorative jewelry for over 4,500 years, found in the Royal Tombs of Ur.

Field identification & locations

Identify by its translucent, waxy appearance and warm reddish hue. Common locations include Brazil, India, Madagascar, and Uruguay. In the field, look for smooth, water-worn pebbles in riverbeds or within basalt cavities.

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