gemstone

Tumbled carnelian agate

Microcrystalline quartz (chalcedony), SiO₂, colored by iron oxides

AI-generated identification · may be incorrect

Mohs hardness 6.5–7; orange-red to brown, translucent, with waxy to vitreous luster and faint curved banding. Quartz has a trigonal crystal structure, but chalcedony is cryptocrystalline and has no visible cleavage.

Identified August 20, 2026More gemstone →

Explore Tumbled carnelian agate 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 in volcanic rocks; iron impurities create the red-orange color. Individual agate nodules commonly formed during the Cenozoic, though agates occur from Precambrian to recent rocks.

Uses & applications

Used for beads, cabochons, carvings, seals, and ornamental objects; its durability also suits small polished collectibles. Common material is inexpensive, while strongly banded or vivid natural carnelian is more valuable.

Geological facts

Carnelian is the red-orange variety of chalcedony; “agate” generally refers to chalcedony showing banding. Heat treatment can intensify color, and tumbled surfaces produce the rounded glossy finish seen here.

Field identification & locations

Identify it by translucency, waxy luster, hardness, and curved internal bands; it should resist scratching by a steel knife but not quartz. Common sources include Brazil, Uruguay, India, Madagascar, Germany, and the western United States.