sedimentary

Rounded river cobble, likely weathered sandstone or siltstone

Quartz-rich clastic sedimentary rock; exact identification requires a fresh surface and testing

AI-generated identification · may be incorrect

Dull, fine-grained, gray-brown to reddish surface with rounded edges and possible bedding or lamination. Likely hardness about 5–7 depending on cement, no obvious cleavage, and low to moderate specific gravity (~2.3–2.7).

Identified August 11, 2026More sedimentary →

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At a glance

Common name: Rounded river cobble, likely weathered sandstone or siltstone
Scientific name: Quartz-rich clastic sedimentary rock; exact identification requires a fresh surface and testing
Category: sedimentary
Identified: August 11, 2026
Method: Standard

AI Estimated Value

Typically $0–$10 as an ordinary cobble; perhaps $10–$50 if attractive, fossil-bearing, or locally collectible.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

Lithified sand- or silt-sized sediment through compaction and cementation, then rounded by stream or shoreline abrasion; age cannot be determined from the image.

Uses & applications

Commonly used as landscaping stone, aggregate, fill, and decorative cobble; generally little collector value unless fossiliferous or unusually colored.

Geological facts

The smooth shape reflects prolonged transport or wave action, while the subtle linear textures may represent sedimentary bedding or weathering.

Field identification & locations

Common in river gravels, beaches, floodplains, and sedimentary terrains. A fresh broken surface, hand lens, dilute acid test, and hardness test can distinguish sandstone from limestone, shale, or volcanic rock.