sedimentary

Rounded gray river pebble, likely fine-grained sandstone or siltstone

Indeterminate clastic sedimentary rock; possibly quartz-rich sandstone or siltstone

AI-generated identification · may be incorrect

Gray-green, fine-grained, dull to subtly satin luster, with thin planar laminations and rounded water-worn surfaces. Estimated Mohs hardness 4–7 depending on cement and quartz content; no visible crystals or cleavage.

Identified August 11, 2026More sedimentary →

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At a glance

Common name: Rounded gray river pebble, likely fine-grained sandstone or siltstone
Scientific name: Indeterminate clastic sedimentary rock; possibly quartz-rich sandstone or siltstone
Category: sedimentary
Identified: August 11, 2026
Method: Standard

AI Estimated Value

$1–$10 as an ordinary pebble; up to about $10–$30 if unusually patterned, provenance-labeled, or sold as a teaching 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 formed from compacted and cemented sand or silt, then rounded by stream or beach transport; its exact geological age and formation basin cannot be determined from the image.

Uses & applications

Primarily a teaching, landscaping, or collectible pebble; sandstone and siltstone may be used as building stone or aggregate, though this small specimen has no industrial value.

Geological facts

The visible parallel bands suggest sedimentary bedding or weak foliation; the smooth triangular shape is characteristic of abrasion during transport.

Field identification & locations

Common in riverbeds, beaches, glacial deposits, and gravel bars. Confirm identification with a hand lens, streak test, and acid test: quartz-rich sandstone is usually nonreactive, while carbonate-cemented material may fizz weakly in dilute acid.