sedimentary

Agate

Silicon dioxide (Chalcedony), SiO2

AI-generated identification · may be incorrect

Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline crystal structure, translucent to opaque, specific gravity of 2.60 to 2.65, exhibits fine concentric banding or patterns.

Identified August 3, 2026More sedimentary →

Explore 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

Formed mainly in cavities of volcanic and metamorphic rocks by the deposition of silica from groundwater solutions, typically in low-temperature environments over millions of years.

Uses & applications

Used in jewelry, ornaments, carving, lapidary art, mortars and pestles for laboratory use, and highly prized by rockhounds and mineral collectors.

Geological facts

Agate was named by Theophrastus, a Greek philosopher, after the Achates river in Sicily where the stones were first found.

Field identification & locations

Found worldwide, often in volcanic regions, riverbeds, and gravel deposits. Identify by its waxy luster, hardness that scratches glass, and characteristic banded patterns.