sedimentary

Agate

Silicon dioxide (Chalcedony), SiO2

Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture, variable colors often banded in layers, specific gravity around 2.60 to 2.65.

Identified August 6, 2026More sedimentary →

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Physical properties

Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture, variable colors often banded in layers, specific gravity around 2.60 to 2.65.

Formation & geological history

Formed mainly in cavities of volcanic and metamorphic rocks through the deposition of silica from groundwater circulating over long geological periods, often associated with ancient volcanic activity.

Uses & applications

Used primarily in lapidary arts, making ornaments, jewelry, decorative items, mortars and pestles in laboratories, and highly sought after by rockhounds and collectors.

Geological facts

Agates are named after the Achates River in Sicily, where stones were found in antiquity. The pitting and surface texture seen on this particular specimen often results from weathering or being exposed to glacial movement.

Field identification & locations

Can be identified by its hardness (scratches glass), waxy luster, and characteristic translucent banded appearance when held to light. Commonly found in river gravels, glacial drift, and volcanic regions worldwide.