mineral

Carnelian Agate

Silicon Dioxide (SiO2) with iron oxide impurities

Hardness: 6.5-7 (Mohs scale); Color: Brownish-red to orange; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline (Trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.64

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

Identified March 4, 2026More mineral →

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Physical properties

Formation & geological history

Formed as a secondary mineral in volcanic rock cavities (vugs) through the deposition of silica-rich groundwater. Most Lake Superior varieties are roughly 1.1 billion years old, formed during the Midcontinent Rift system.

Uses & applications

Primarily used in jewelry making as cabochons or beads, lapidary art, and as highly sought-after specimens for geological collectors.

Geological facts

Carnelian has been used as a gemstone since antiquity; it was used by Ancient Egyptians in amulets to protect the soul and by Romans to create signet rings because hot wax does not stick to it.

Field identification & locations

Identify in the field by its translucency when held to light, waxy texture, and unique banded or 'peeled' potato exterior. Common in the Great Lakes region (Lake Superior Agates), Madagascar, and Brazil.

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