mineral

Agate

Silicon dioxide (SiO2) - variety Chalcedony

Hardness: 6.5-7 (Mohs scale), Color: Translucent grey/blue with faint banding, Luster: Vitreous to waxy, Structure: Cryptocrystalline, Fracture: Conchoidal

Hardness: 6

Identified May 10, 2026More mineral →

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Physical properties

Hardness: 6.5-7 (Mohs scale), Color: Translucent grey/blue with faint banding, Luster: Vitreous to waxy, Structure: Cryptocrystalline, Fracture: Conchoidal

Formation & geological history

Formed as a secondary mineral in volcanic rock cavities (vesicles) where silica-rich groundwater deposits layers of microcrystalline quartz over thousands of years.

Uses & applications

Used primarily in semi-precious jewelry, lapidary art, tumbled stones for collecting, and industrial applications like mortar and pestles due to its hardness.

Geological facts

Agate is named after the Achates River in Sicily where it was first discovered by ancient Greek philosophers; it is the birthstone for September and is famous for its distinct rhythmic banding.

Field identification & locations

Identify by its translucency when held to light, waxy feel when polished, and lack of visual grains. Commonly found in riverbeds, volcanic regions, and gravel deposits.