sedimentary

Rounded gray sandstone or siltstone cobble

Lithified quartz–feldspar–clay sediment; exact petrographic identification requires testing

AI-generated identification · may be incorrect

Fine-grained, dull to slightly earthy luster, gray-brown color, and weakly visible bedding or weathering lines; estimated Mohs hardness 3–6 depending on cement, with no obvious cleavage. The smooth elongated shape reflects water abrasion rather than crystal structure.

Identified August 30, 2026More sedimentary →

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At a glance

Common name: Rounded gray sandstone or siltstone cobble
Scientific name: Lithified quartz–feldspar–clay sediment; exact petrographic identification requires testing
Category: sedimentary
Identified: August 30, 2026
Method: Standard

AI Estimated Value

Typically $1–$10 as an ordinary cobble; up to about $20–$50 if unusually shaped, locally significant, or sold as a curated specimen.

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

Likely deposited as sand or silt, compacted and cemented into sedimentary rock, then rounded in a stream, beach, or glacial environment. Its geological age cannot be determined from the photograph.

Uses & applications

Usually collected as a natural cobble, garden stone, or educational specimen; sandstone may also be used as building or paving stone, though this piece is too small for industry.

Geological facts

The surface appears weathered and possibly slightly porous, consistent with sandstone or siltstone rather than a crystalline igneous rock.

Field identification & locations

Look for gritty texture, visible grains, bedding, and sediment staining; a glass-scratch test, acid test, and hand lens would help distinguish sandstone from siltstone or weathered basalt. Common worldwide in riverbeds, beaches, and sedimentary terrains.