sedimentary

Rounded quartz-rich river pebbles

Alluvial gravel; commonly quartzite, chert, and quartz-bearing sandstone fragments

AI-generated identification · may be incorrect

Mostly cream, tan, gray, and brown rounded clasts with dull to glassy luster; quartz-rich pieces are Mohs 7, while mixed fragments vary from 5–7. Textures range from fine-grained quartzite/chert to granular sandstone, with no consistent crystal structure or cleavage.

Identified September 13, 2026More sedimentary →

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Physical properties

Formation & geological history

These are weathered and water-rounded fragments transported in a river, beach, or alluvial deposit; individual clasts may derive from much older igneous, sedimentary, or metamorphic rocks, commonly Paleozoic to Precambrian in source terrain.

Uses & applications

Used as landscaping stone, drainage aggregate, concrete aggregate, decorative gravel, and occasional lapidary material; attractive pieces may be polished or used in crafts.

Geological facts

The specimen is a mixed gravel assemblage rather than one identifiable rock. Strong rounding and surface polish indicate prolonged abrasion by moving water or waves.

Field identification & locations

Identify quartz-rich pieces by their hardness, pale color, and inability to scratch them with steel; chert is waxy and opaque, while sandstone feels granular. Common in riverbeds, beaches, and glacial or alluvial deposits.