sedimentary

Rounded sandstone pebble

Quartz-rich sandstone, likely arkosic or feldspathic sandstone

AI-generated identification · may be incorrect

Typically 6–7 Mohs hardness, tan to buff color, dull earthy luster, and granular texture; composed mainly of quartz with feldspar and cement. No obvious cleavage; rounded edges indicate abrasion by water or sediment transport.

Identified August 19, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when sand-sized grains were compacted and cemented, commonly by silica, calcite, or iron oxides. The exact geologic age cannot be determined from the image; its smooth shape likely reflects river, beach, or gravel-bed transport.

Uses & applications

Used as decorative landscaping stone, aggregate, paving material, and occasionally as a building stone; generally not jewelry-grade.

Geological facts

The pale crusty patches may be weathered carbonate or silica cement, while the brown color may reflect iron-oxide staining. A vinegar test can indicate calcite cement if it fizzes after scratching a fresh surface.

Field identification & locations

Identify it by visible sand grains, granular fracture, subdued luster, and lack of glassy conchoidal fracture; common in river gravels, beaches, and sedimentary terrains worldwide. A hand lens and acid test improve identification.