sedimentary

Rounded sandstone cobble

Quartz-rich sandstone (likely), with grains cemented by silica, calcite, or iron oxides

AI-generated identification · may be incorrect

Brown, dull to slightly granular surface; apparently fine- to medium-grained and well rounded. Typical sandstone hardness is about 6–7 where quartz-rich; individual grains are crystalline, but the rock has no visible cleavage. Composition and specific gravity cannot be confirmed from the image.

Identified October 8, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when sand accumulated, compacted, and cemented in a sedimentary basin, then rounded by transport in water or abrasion. Its age and precise depositional setting cannot be determined visually.

Uses & applications

Sandstone is widely used as building and paving stone, landscaping material, and aggregate; this rounded piece is mainly a decorative or collection specimen.

Geological facts

The smooth shape likely reflects prolonged abrasion, such as movement in a river or along a shore.

Field identification & locations

Look for visible sand-sized grains and a gritty texture; a fresh broken surface would help confirm sandstone and distinguish it from siltstone or a fine-grained igneous rock. Sandstone occurs worldwide in sedimentary formations and river deposits.