Rock Identifier
Carnelian (a variety of Chalcedony) (Cryptocrystalline Quartz (SiO2) with iron oxide inclusions) — Mineral
Mineral

Carnelian (a variety of Chalcedony)

Cryptocrystalline Quartz (SiO2) with iron oxide inclusions

Hardness: 6.5–7 on the Mohs scale; Color: Orange-red, brownish-red, amber-yellow; Luster: Waxy to vitreous; Crystal structure: Trigonal/Monoclinic (microscopic); Cleavage: None/Conchoidal fracture; Specific gravity: 2.58–2.64

Hardness
6
Color
Orange-red, brownish-red, amber-yellow
Luster
Waxy to vitreous
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Physical properties

Hardness: 6.5–7 on the Mohs scale; Color: Orange-red, brownish-red, amber-yellow; Luster: Waxy to vitreous; Crystal structure: Trigonal/Monoclinic (microscopic); Cleavage: None/Conchoidal fracture; Specific gravity: 2.58–2.64

Formation & geological history

Formed through the deposition of silica from groundwater in volcanic rock cavities or sedimentary environments. The red/orange tint is caused by iron oxide impurities. It can be found in formations ranging from the Cenozoic era to much older deposits.

Uses & applications

Used primarily in lapidary arts for jewelry, beads, cabochons, and decorative carvings. Historically used for signet rings and wax seals because hot wax does not stick to it.

Geological facts

Carnelian was highly prized in ancient Egypt, where it was believed to represent the blood of Isis. It was also used frequently in Greek and Roman intaglios. It is often heat-treated (naturally or artificially) to enhance its reddish hue.

Field identification & locations

Identify in the field by its waxy luster, translucency, and inability to be scratched by a steel knife. Commonly found in riverbeds, beaches, or volcanic regions in India, Brazil, Madagascar, and the United States (Oregon/Washington).

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