gemstone

Tumbled red chalcedony (likely carnelian)

Carnelian, a reddish variety of microcrystalline quartz (SiO₂)

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent reddish-orange to deep red, with a waxy to vitreous luster. It has a cryptocrystalline quartz structure, no visible cleavage, and specific gravity about 2.6.

Identified August 20, 2026More gemstone →

Explore Tumbled red chalcedony (likely carnelian) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness 6.5–7 Mohs; translucent reddish-orange to deep red, with a waxy to vitreous luster. It has a cryptocrystalline quartz structure, no visible cleavage, and specific gravity about 2.6.

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, with iron oxides producing the red color; deposits range from Paleozoic to Cenozoic in age. The rounded surface indicates tumbling and polishing.

Uses & applications

Used for beads, cabochons, carvings, ornaments, and inexpensive jewelry; attractive specimens commonly sell for modest prices.

Geological facts

Carnelian is closely related to orange chalcedony and sard; color may be naturally intensified or enhanced by heating. It was widely used for ancient seals and amulets.

Field identification & locations

Identify it by its uniform red-orange color, translucency, waxy polish, and quartz hardness; it should scratch glass but not be scratched by a steel knife. Common sources include India, Brazil, Uruguay, Madagascar, and Germany.