mineral

Agate (Chalcedony)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 Mohs; Color: Cream, tan, white with translucent bands; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.58–2.64.

Hardness: 6
Color: Cream, tan, white with translucent bands
Luster: Waxy to vitreous

Identified June 20, 2026More mineral →

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Physical properties

Formation & geological history

Formed as a secondary mineral in volcanic rock cavities or sedimentary vugs. Siliceous groundwater seeps into voids, depositing layers of microcrystalline quartz over thousands of years.

Uses & applications

Used in ornamental jewelry, lapidary arts, high-precision industrial mortars and pestles, and as a popular collector specimen.

Geological facts

The name 'Agate' comes from the Achates River in Sicily. It is one of the oldest materials used in human history for ornaments and hardstone carving.

Field identification & locations

Identify in the field by its distinct concentric banding, translucent edges, and hardness (it can scratch glass). Commonly found in riverbeds or volcanic areas around the world.