sedimentary

Weathered sandstone cobble

Quartz-rich sandstone, likely ferruginous sandstone

AI-generated identification · may be incorrect

Composed mainly of quartz grains with feldspar, clay minerals, and iron-oxide cement. Typically Mohs 6–7 for quartz grains, tan to reddish-brown, dull to slightly gritty, opaque, and lacking visible cleavage; the rounded shape reflects abrasion and weathering.

Identified August 18, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when sand was compacted and cemented in an ancient river, shoreline, dune, or basin environment; iron oxidation produced the warm color. Its precise geological age cannot be determined from the photograph.

Uses & applications

Used as aggregate, building stone, paving, landscaping material, and occasionally as a decorative cobble. Ordinary field specimens generally have little commercial or collector value.

Geological facts

The smooth, bulbous surface is consistent with prolonged weathering or transport, while the uneven texture suggests exposed sand grains or partial surface alteration. Color can intensify where iron-bearing minerals oxidize.

Field identification & locations

Identify it by its gritty texture, sand-sized grains, earthy tan-orange color, and lack of strong crystal faces or cleavage; a steel nail may scratch weakly cemented varieties. Common in sedimentary terrains and river gravels worldwide.