Carnelian (Red Agate/Chalcedony)

Physical Properties

Hardness: 6.5-7 on Mohs scale; Color: Reddish-orange to brownish-red; Luster: Vitreous to waxy; Crystal structure: Trigonal/Microcrystalline; Cleavage: None; Specific Gravity: 2.58–2.64

Formation & Geological History

Formed in volcanic environments and sedimentary rocks at low temperatures. It occurs as a result of silica-rich groundwater filling cavities in volcanic lavas. The red color comes from iron oxide (hematite) impurities.

Uses & Applications

Commonly used as a gemstone for jewelry (cabochons, beads), decorative carvings, and in alternative healing or metaphysical practices. Historically used for signet rings and seals.

Geological Facts

Ancient Romans and Greeks used carnelian for signet rings because hot wax does not stick to it. It has been used for jewelry for over 4,000 years, dating back to the Indus Valley Civilization.

Field Identification & Locations

Identify by its translucent nature and brownish-orange to deep red hue. It lacks the distinctive sharp banding of many other agates but may show some mottling or cloudiness. Commonly found in Brazil, India, Uruguay, and Madagascar.

Identified on: 4/18/2026

Mode: Standard