Carnelian Agate

Physical Properties

Hardness: 6.5–7 on Mohs scale; Color: Reddish-orange to brownish-red; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.58–2.64.

Formation & Geological History

Formed as a microcrystalline variety of silica, primarily in volcanic cavities or sedimentary environments where groundwater rich in silica deposits layers over long periods. The reddish tint is caused by iron oxide (hematite) impurities.

Uses & Applications

Commonly used in jewelry (beads, cabochons), carvings, decorative seals, and as a popular collector's gemstone due to its vibrant color.

Geological Facts

Carnelian was highly prized in ancient times; ancient Romans used it for signet rings because hot wax does not stick to it. It has been used for talismans and decorative arts since the Neolithic period.

Field Identification & Locations

Identify in the field by its waxy luster, conchoidal fracture (curved, glass-like breaks), and translucent to semi-opaque orange-red hue. It can often be found in riverbeds or near ancient volcanic activity.

Identified on: 4/16/2026

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