mineral

Agate (Chalcedony)

Silicon Dioxide (SiO2)

Hardness: 6.5 to 7 on the Mohs scale. Color: Translucent to opaque, brownish-grey to honey-tan tones. Luster: Waxy to vitreous. Cleavage: None (conchoidal fracture). Specific Gravity: 2.58-2.64.

Hardness: 6
Color: Translucent to opaque, brownish-grey to honey-tan tones
Luster: Waxy to vitreous

Identified July 27, 2026More mineral →

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Physical properties

Hardness: 6.5 to 7 on the Mohs scale. Color: Translucent to opaque, brownish-grey to honey-tan tones. Luster: Waxy to vitreous. Cleavage: None (conchoidal fracture). Specific Gravity: 2.58-2.64.

Formation & geological history

Formed as a secondary mineral in volcanic cavities (geodes) or sedimentary layers through the deposition of silica-rich fluids over thousands to millions of years. Naturally rounded and smoothed by stream or beach erosion.

Uses & applications

Commonly used in lapidary arts, jewelry making, tumbling, cabochon cutting, decorative objects, and for hobbyist rock collecting.

Geological facts

Agate is a microcrystalline variety of quartz. Weathered river or beach pebbles of chalcedony/agate often develop a thin, pale exterior rind while retaining a waxy, translucent interior visible under sunlight.

Field identification & locations

Look for a waxy or greasy surface luster, soft translucency when held up to a light source, and a smooth, water-worn texture without true cleavage planes. Commonly found in riverbeds, lake shores, and gravel deposits worldwide.