sedimentary

Weathered gray sandstone or siltstone cobble

Clastic sedimentary rock, likely quartz-rich sandstone/siltstone (diagnosis uncertain from image)

AI-generated identification · may be incorrect

Gray-beige, dull to weakly earthy luster, rounded and heavily weathered; likely composed mainly of quartz and feldspar with clay minerals. Typical hardness is about 5–7 Mohs, with no obvious cleavage and granular texture.

Identified August 18, 2026More sedimentary →

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At a glance

Common name: Weathered gray sandstone or siltstone cobble
Scientific name: Clastic sedimentary rock, likely quartz-rich sandstone/siltstone (diagnosis uncertain from image)
Category: sedimentary
Identified: August 18, 2026
Method: Standard

AI Estimated Value

Typically $0–$5 as an ordinary field cobble; perhaps $5–$20 if unusually attractive or demonstrably local/geologically significant.

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

Formed by deposition, compaction, and cementation of sand- or silt-sized sediment, then rounded by transport and weathering. Its geological age cannot be determined from the photograph; such rocks occur from ancient to modern sedimentary sequences.

Uses & applications

Common sandstone is used for building stone, paving, aggregate, and landscaping; attractive pieces may be collected, but this specimen has little commercial or jewelry value.

Geological facts

The smooth, rounded shape indicates abrasion by water, ice, or sediment movement. A fresh broken surface and hand lens would help distinguish sandstone from finer-grained siltstone or weathered volcanic rock.

Field identification & locations

Look for visible sand grains, gritty texture, bedding, and acid-inert behavior; a steel nail usually scratches it only if cement is weak. Common worldwide in river gravels, sedimentary basins, and glacial deposits.