Carnelian (Chalcedony)

Physical Properties

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

Formation & Geological History

Formed through the deposition of silica from groundwater into cavities of igneous rocks, particularly volcanic lavas. The red color is caused by iron oxide impurities. It can be found in sedimentary environments through erosion.

Uses & Applications

Primarily used in jewelry (cabochons and beads), decorative carvings, and seal stones. Historically used for signet rings due to its ability to not stick to wax.

Geological Facts

Carnelian has been used for over 4,500 years; the Ancient Egyptians called it 'The Setting Sun' and used it in protective amulets for the dead. It is one of the oldest gemstones known to mankind.

Field Identification & Locations

Identify by its translucent to semi-opaque orange-red hue and lack of visible crystals. Commonly found in Brazil, India, Uruguay, and Madagascar. In the field, look for waxy-lustered nodules in riverbeds or volcanic outcrops.

Identified on: 5/13/2026

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