mineral

Tumbled agate/chalcedony

Microcrystalline quartz (SiO₂), likely banded chalcedony or agate

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent cream, gray, tan, and brown with subtle curved banding; waxy to glassy luster; cryptocrystalline quartz with no visible cleavage; specific gravity about 2.58–2.64.

Identified August 28, 2026More mineral →

Explore Tumbled agate/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 in volcanic rock, depositing chalcedony and quartz in successive layers. The specimen is likely a naturally weathered or tumbled fragment; its precise geological age cannot be determined visually.

Uses & applications

Used for ornamental stones, cabochons, carvings, beads, and lapidary work; attractive pieces have modest collector value.

Geological facts

Agate is a variety of chalcedony distinguished by banding, while unbanded translucent material is called chalcedony. Iron and other impurities produce the tan, brown, and reddish colors.

Field identification & locations

Identify by its waxy translucence, very fine texture, curved layering, lack of cleavage, and ability to scratch glass. Common sources include Brazil, Uruguay, India, Mexico, Madagascar, and the western United States.