mineral

Agate Pebble (Desert Agate / Chalcedony Nodule)

Silicon Dioxide (SiO2)

Hardness: 6.5 - 7 on Mohs scale. Color: Translucent yellowish-brown to tan with a micro-crazed or crackled surface texture. Luster: Waxy to vitreous. Crystal Structure: Trigonal (microcrystalline/cryptocrystalline). Cleavage: None, exhibits conchoidal fracture.

Hardness: 6
Luster: Waxy to vitreous

Identified July 22, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the secondary precipitation of silica-rich solutions inside cavities of volcanic rocks or sedimentary deposits. Water and wind erosion over extensive periods round the specimen, leaving a weathered, pitted outer surface often called 'desert patina' or 'snake-skin' texture.

Uses & applications

Used for lapidary arts, jewelry (cabochons, beads), decorative tumbled stones, and rock collections.

Geological facts

The crackled or pitted surface texture on desert agate nodules often results from thermal stress (extreme hot and cold cycles in desert environments) or chemical etching over thousands to millions of years.

Field identification & locations

Can be identified in the field by its high hardness (scratches glass), strong translucency when backlit, smooth rounded pebble shape, and distinctive waxy luster with surface micro-fractures. Commonly found in riverbeds, desert gravels, and alluvial deposits worldwide.

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