mineral

Agate

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Multi-colored with distinctive banding; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline (Trigonal); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.60-2.65

Hardness: 7 on Mohs scale
Color: Multi-colored with distinctive banding
Luster: Waxy to vitreous

Identified February 19, 2026More mineral →

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Physical properties

Formation & geological history

Formed as a secondary mineral in host rock cavities, typically volcanic lavas or metamorphic rocks, through the deposition of silica from groundwater. Often found in nodes or geodes ranging from thousands to millions of years old.

Uses & applications

Extensively used in lapidary arts for jewelry, ornaments, and decorative items. Historically used for making precision tools and burnishing tools due to its hardness and resistance to chemical acids.

Geological facts

Agate is named after the Achates River (now Dirillo River) in Sicily where it was first discovered by the Greek philosopher Theophrastus around the 4th century B.C.

Field identification & locations

Identify in the field by looking for translucent edges, waxy luster, and concentric banding. Commonly found in riverbeds, gravel pits, and volcanic regions. Collectors look for unique patterns or bright colors.