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 structure, translucent to opaque transparency, conchoidal fracture, and specific gravity around 2.60 to 2.65.

Identified July 29, 2026More sedimentary →

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Physical properties

Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline structure, translucent to opaque transparency, conchoidal fracture, and specific gravity around 2.60 to 2.65.

Formation & geological history

Forms primarily within the cavities of volcanic and metamorphic rocks through the deposition of silica from groundwater circulating in systematic layers over millions of years.

Uses & applications

Commonly used for making jewelry, ornamental carvings, polished specimens, decorative objects, and occasionally in industrial applications due to its hardness.

Geological facts

Agate has been used since ancient times for amulets, seals, and ornate vessels; the name comes from the Achates River in Sicily where agates were found in antiquity.

Field identification & locations

Can be identified in the field by its waxy luster, conchoidal fracture, characteristic concentric banding or translucent appearance, and inability to be scratched by a steel knife. Found worldwide, particularly in regions with past volcanic activity.