sedimentary

Rounded gray-brown cobble, likely weathered sandstone or quartzite

Tentatively quartz-rich sandstone (SiO₂-dominated); exact identification requires hardness and acid tests

AI-generated identification · may be incorrect

Fine-grained, dull to weakly earthy luster, tan-brown weathering rind, gray interior, and rounded water-worn form; likely hardness ~6–7 if quartz-rich, with no obvious cleavage. The photograph does not resolve grain size or cement confidently.

Identified August 11, 2026More sedimentary →

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At a glance

Common name: Rounded gray-brown cobble, likely weathered sandstone or quartzite
Scientific name: Tentatively quartz-rich sandstone (SiO₂-dominated); exact identification requires hardness and acid tests
Category: sedimentary
Identified: August 11, 2026
Method: Standard

AI Estimated Value

Typically $0–$10 as an ordinary cobble; perhaps $10–$30 if unusually attractive, provenance-labeled, or used educationally.

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 transported and rounded by stream, river, or beach abrasion; the original rock may have formed from lithified sand, potentially hundreds of millions of years old. A metamorphosed equivalent would be quartzite, so classification remains provisional.

Uses & applications

Common sandstone is used as building stone, paving, aggregate, and landscaping material; attractive pieces may be collected as natural specimens. This ordinary cobble has little commercial value.

Geological facts

Quartz-rich sandstone and quartzite can look similar in photographs. A steel nail or knife should not readily scratch quartzite, while dilute hydrochloric acid should not visibly fizz unless carbonate cement is present.

Field identification & locations

Look for visible sand grains, bedding, and a gritty texture for sandstone; quartzite is typically harder, more crystalline, and fractures across grains. Common worldwide in river gravels, beaches, and eroded sedimentary terrains.