sedimentary

Sandstone (River Cobble)

Sandstone (composed predominantly of SiO2 - Quartz)

AI-generated identification · may be incorrect

Hardness: 6-7 on Mohs scale. Color: Tan, beige, brownish-grey. Luster: Dull, earthy. Texture: Granular, fine-to-medium-grained feel. Structure: Massive, well-rounded due to water erosion.

Hardness: 6-7 on Mohs scale
Color: Tan, beige, brownish-grey
Luster: Dull, earthy

Identified July 25, 2026More sedimentary →

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Physical properties

Hardness: 6-7 on Mohs scale. Color: Tan, beige, brownish-grey. Luster: Dull, earthy. Texture: Granular, fine-to-medium-grained feel. Structure: Massive, well-rounded due to water erosion.

Formation & geological history

Formed by the accumulation and cementation of sand-sized mineral grains or rock fragments over millions of years, typically in riverbeds, lakes, or deserts. This specific sample has been rounded and smoothed by transport in stream or river water.

Uses & applications

Commonly used as construction material, landscaping stone, flagstone, paving, and decorative garden pebbles.

Geological facts

River-worn pebbles like this one show natural erosion known as fluvial abrasion, where water currents tumble rocks against each other over thousands of years to create smooth, oval shapes.

Field identification & locations

Look for a fine, gritty sand-paper-like texture and uniform light brown or tan color. Commonly found in riverbeds, stream channels, beaches, and glacial deposits. Very common field specimen.