mineral

Agate

Silicon dioxide (SiO2)

Hardness: 6.5 to 7 on Mohs scale; Color: Multi-colored, layered, translucent to opaque; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline (Trigonal); Cleavage: None; Specific gravity: 2.58 to 2.64

Hardness: 6
Color: Multi-colored, layered, translucent to opaque
Luster: Waxy to vitreous

Identified June 21, 2026More mineral →

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Physical properties

Formation & geological history

Formed in volcanic and metamorphic rocks through the deposition of silica from groundwater into cavities (vesicles) or cracks. This process can take millions of years.

Uses & applications

Used primarily in jewelry (cabochons, beads), decorative objects, and historically for precision instruments like pestles and mortars due to its hardness.

Geological facts

Agate is named after the Achates River in Sicily where it was first discovered. It is often characterized by its banded patterns, which represent different layers of silica deposition.

Field identification & locations

Identify by its waxy luster, conchoidal fracture, and characteristic banding or translucency. Common in riverbeds, desert surfaces, and volcanic areas globally.