gemstone

Tumbled banded agate

Agate, microcrystalline quartz (SiO₂), commonly chalcedony with iron-oxide inclusions

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent brown, gray, cream, and reddish bands; waxy to vitreous luster; cryptocrystalline structure with no visible cleavage. The rounded shape indicates tumbling and polishing.

Identified September 17, 2026More gemstone →

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Physical properties

Formation & geological history

Forms as concentric or layered chalcedony deposits lining cavities in volcanic rocks, often during the Cenozoic or older volcanic episodes. Silica-rich groundwater deposits successive bands, while iron produces red-brown colors.

Uses & applications

Used for cabochons, beads, carvings, paperweights, and decorative objects; durable and popular in inexpensive jewelry and lapidary collections.

Geological facts

Agate banding may be straight, curved, or fortification-like, and each specimen is distinctive. Its colors commonly result from iron and manganese impurities.

Field identification & locations

Identify it by curved microcrystalline banding, translucency, and quartz-like hardness; it should scratch glass but not be scratched by a steel knife. Common sources include Brazil, Uruguay, India, Mexico, and the United States.