Carnelian (Chalcedony)

Physical Properties

Hardness: 6.5-7 on Mohs scale; Color: Reddish-orange to brownish-red; Luster: Waxy to vitreous; Crystal Structure: Hexagonal (cryptocrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58–2.64

Formation & Geological History

Formed through the deposition of silica from groundwater into cavities of volcanic rocks (lavas) or sedimentary rocks. The red coloring is caused by iron oxide (hematite) impurities.

Uses & Applications

Predominantly used as a gemstone in jewelry, lapidary carvings, seals, and as decorative tumbled stones for collectors.

Geological Facts

In ancient times, carnelian was believed to have protective qualities and was used in Roman signet rings to seal correspondence because hot wax does not stick to it.

Field Identification & Locations

Identify by its translucent, waxy appearance and orange-red hue. It is often found as pebbles in riverbeds or within basaltic rock formations in India, Brazil, and Uruguay.

Identified on: 4/17/2026

Mode: Standard