Carnelian Agate

Physical Properties

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

Formation & Geological History

Formed through the deposition of silica from groundwater into the cavities (vugs) of igneous rocks, particularly volcanic lavas. The red-orange color is caused by iron oxide impurities. It can be found in sedimentary environments after being eroded from primary volcanic sources.

Uses & Applications

Primarily used in jewelry (beads, cabochons), lapidary arts, and ornamental carvings. Historically significant for making cylinder seals and signet rings.

Geological Facts

Carnelian was highly prized in Ancient Egypt, where it was thought to assist high-status individuals in their journey to the afterlife. It was also one of the twelve stones in the Breastplate of Aaron.

Field Identification & Locations

Identify in the field by its translucent quality when held to light, waxy luster, and smooth conchoidal fracture. Commonly found in riverbeds, beaches, and areas with volcanic history such as Brazil, India, and the Pacific Northwest of the USA.

Identified on: 4/13/2026

Mode: Standard