gemstone

Tumbled carnelian (orange-brown chalcedony)

Chalcedony, microcrystalline quartz (SiO₂), colored mainly by iron oxides

AI-generated identification · may be incorrect

Typically Mohs hardness 6.5–7, translucent to opaque, vitreous-to-waxy luster, and no visible cleavage; this wet, rounded specimen is dark reddish brown with subtle internal translucency. Its crystal structure is cryptocrystalline quartz, so individual crystals are not visible.

Identified August 30, 2026More gemstone →

Explore Tumbled carnelian (orange-brown chalcedony) in the encyclopedia →

Identify your own rocks.

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

App Store Google Play

Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures, with iron producing red, orange, or brown coloration; deposits range from ancient volcanic terrains to younger sedimentary environments. This piece appears tumbled and polished rather than naturally weathered.

Uses & applications

Used for cabochons, beads, carvings, and low-to-moderate-value jewelry; historically used for seals and ornamental objects. It is also a popular inexpensive lapidary and collecting material.

Geological facts

Carnelian is a variety of chalcedony, overlapping in usage with sard; deeper brown material may be called sard or brown carnelian. Heating can intensify its red-orange color.

Field identification & locations

Identify it by its hardness, smooth waxy luster, conchoidal fracture, and translucent red-brown body color; it should resist scratching from a steel blade. Common sources include India, Brazil, Uruguay, Madagascar, and Botswana.