sedimentary
Sandstone (River Cobble)
Sandstone (composed predominantly of SiO2 - Quartz)
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
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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.
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