Mineral

Agate

Chalcedony (SiO2)

Form of chalcedony. Hardness of 6.5-7 on the Mohs scale. Colors can vary widely due to trace elements, often showing banding. Waxy luster. Cryptocrystalline structure. No cleavage. Specific gravity of 2.58-2.64.

Identified June 18, 2026More mineral →

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Physical properties

Formation & geological history

Forms primarily within volcanic and metamorphic rocks. Silica-rich fluids fill cavities or vesicles, depositing microscopic layers of silica. Found worldwide.

Uses & applications

Commonly used in jewelry, decorative items, and lapidary arts. Sometimes used in industry for precision instruments due to its hardness and resistance to chemicals.

Geological facts

Agates have been used as gemstones and ornamental objects for thousands of years. The name comes from the Achates River (now Dirillo) in Sicily.

Field identification & locations

Identified by its distinctive banding, waxy luster, and hardness. Often found in volcanic areas. Collectors value unique patterns, colors, and the origin of the specimen.