mineral

Chalcedony Pebble

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: translucent yellowish-brown to tan; Luster: waxy to greasy; Crystal Structure: microcrystalline trigonal; Cleavage: none, conchoidal fracture

Hardness: 6
Color: translucent yellowish-brown to tan
Luster: waxy to greasy

Identified July 27, 2026More mineral →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: translucent yellowish-brown to tan; Luster: waxy to greasy; Crystal Structure: microcrystalline trigonal; Cleavage: none, conchoidal fracture

Formation & geological history

Formed by precipitating silica solutions at relatively low temperatures in cavities, veins, or sedimentary environments, often rounded by river or beach water erosion.

Uses & applications

Used in jewelry, tumbling, carvings, decorative gemstones, and lapidary arts.

Geological facts

Chalcedony is a cryptocrystalline form of silica, composed of very fine intergrowths of quartz and moganite. Water-worn pebbles often display a distinct waxy luster on their weathered surfaces.

Field identification & locations

Identified by its translucency, smooth water-worn surface, waxy luster, and lack of visible crystal faces. Commonly found in riverbeds, gravel bars, and coastal beaches worldwide.