mineral

Tumbled agate and chalcedony specimens

Microcrystalline quartz (SiO₂), chiefly chalcedony/agate

AI-generated identification · may be incorrect

Small polished or naturally rounded pieces with translucent white, cream, honey, and pale brown colors; waxy to glassy luster and no obvious cleavage. Quartz hardness is 7 Mohs, with specific gravity about 2.60–2.65; banding or crystalline druse may be present.

Identified August 15, 2026More mineral →

Explore Tumbled agate and chalcedony specimens 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

Agate forms when silica-rich groundwater fills cavities in volcanic rock, depositing chalcedony and quartz in layers over long periods, commonly during the Cenozoic or older volcanic episodes. The pieces shown appear tumbled and may include quartz druse or iron staining.

Uses & applications

Used for cabochons, beads, carvings, decorative objects, and lapidary practice; attractive banded pieces are used in jewelry and collecting.

Geological facts

Agate is a variety of chalcedony distinguished by patterned layering, while chalcedony itself may be nearly uniform. Iron oxides commonly produce the yellow-brown coloration.

Field identification & locations

Identify by translucency, waxy surface, conchoidal fracture, and hardness sufficient to scratch glass; acid does not react. Common sources include Brazil, Uruguay, Mexico, India, Madagascar, and the western United States.