mineral

Chalcedony (Agate) Pebble

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5 - 7 on Mohs scale. Color: Translucent grayish-brown, yellowish-tan. Luster: Waxy to vitreous. Crystal system: Microcrystalline trigonal. Cleavage: None (conchoidal fracture).

Hardness: 6
Color: Translucent grayish-brown, yellowish-tan
Luster: Waxy to vitreous

Identified July 27, 2026More mineral →

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Physical properties

Hardness: 6.5 - 7 on Mohs scale. Color: Translucent grayish-brown, yellowish-tan. Luster: Waxy to vitreous. Crystal system: Microcrystalline trigonal. Cleavage: None (conchoidal fracture).

Formation & geological history

Formed via secondary silica deposition in cavities of volcanic, sedimentary, or metamorphic rocks over millions of years, often rounded by river or beach water erosion.

Uses & applications

Used extensively for lapidary arts, jewelry, tumbled stones, decorative carvings, and mineral collections.

Geological facts

Chalcedony is composed of cryptocrystalline intergrowths of quartz and moganite. Its name is derived from the ancient Greek town of Chalcedon in Asia Minor.

Field identification & locations

Identified by its translucency, smooth water-worn surface, waxy luster, and lack of visible crystalline structures. Commonly found along riverbeds, gravel bars, and ocean beaches.