sedimentary

Agate

Silicon dioxide (chalcedony), SiO2

AI-generated identification · may be incorrect

Hardness of 6.5-7 on the Mohs scale, waxy to vitreous luster, microcrystalline crystal structure, conchoidal fracture, specific gravity of 2.58-2.64, and displays distinct concentric banding in various colors.

Identified October 20, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the deposition of silica from groundwater in cavities of igneous and sedimentary rocks, often over millions of years.

Uses & applications

Widely used in jewelry, ornamental carvings, polished specimens for collectors, and precision instruments like mortars and pestles.

Geological facts

Agate was highly prized in ancient civilizations as a talisman and for making intaglio seals and ornate vessels.

Field identification & locations

Easily identified in the field by its characteristic waxy luster and translucent concentric bands; commonly found in volcanic rock cavities worldwide.