sedimentary

Rounded sandstone pebble

Quartz-rich sandstone, commonly subarkose or arkose

AI-generated identification · may be incorrect

Typically Mohs hardness 6–7 for quartz grains, tan to brown color, dull to slightly gritty luster, and granular clastic texture; individual grains are cemented by silica, calcite, or iron oxides. No prominent cleavage; density commonly 2.2–2.7 g/cm³.

Identified September 5, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when sand accumulated, compacted, and cemented into rock, likely during a sedimentary basin’s burial history; its rounded shape reflects abrasion in a stream, beach, or glacial deposit. Exact geological age cannot be determined from the photograph.

Uses & applications

Used as aggregate, paving and landscaping stone, and occasionally as building or decorative stone; this ordinary rounded specimen has little jewelry value.

Geological facts

The visible speckled surface reflects sand-sized mineral grains, mainly quartz with possible feldspar and mica. Iron-oxide staining commonly produces the tan or rusty coloration.

Field identification & locations

Identify it by its gritty granular surface, visible sand grains, and lack of interlocking crystals; a streak or fresh fracture can help distinguish it from quartzite. Common in riverbeds, beaches, and sedimentary terrains.