sedimentary

Rounded gray-brown cobble, likely weathered sandstone or quartz-rich sedimentary rock

Probable lithic sandstone; exact identification requires a fresh surface and hardness/streak tests

AI-generated identification · may be incorrect

Fine-grained, dull to slightly earthy luster, tan-gray color, and rounded water-worn shape; likely hardness about 5–7 Mohs with no visible cleavage. The apparent uniformity and abrasion suggest a durable quartz-bearing rock.

Identified August 18, 2026More sedimentary →

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At a glance

Common name: Rounded gray-brown cobble, likely weathered sandstone or quartz-rich sedimentary rock
Scientific name: Probable lithic sandstone; exact identification requires a fresh surface and hardness/streak tests
Category: sedimentary
Identified: August 18, 2026
Method: Standard

AI Estimated Value

$0–$5 as an ordinary field cobble; approximately $5–$20 if unusually attractive, locally significant, or prepared as a polished 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

Probably formed from compacted and cemented sand, then rounded by stream or glacial transport; its depositional age cannot be determined from the photograph. Iron-bearing weathering may produce the brown coloration.

Uses & applications

Common sandstone is used as aggregate, building stone, paving, and landscaping material; this individual specimen has minimal commercial value but may be suitable for casual collecting.

Geological facts

The image does not show diagnostic grains, bedding, or mineral crystals, so alternatives such as weathered quartzite, chert, or fine-grained volcanic rock remain possible.

Field identification & locations

Test hardness against glass, inspect a broken or scratched surface for visible quartz grains, and apply dilute hydrochloric acid to check for carbonate cement; strong fizzing would indicate limestone rather than sandstone. Rounded cobbles occur widely in streambeds, beaches, and glacial deposits.