sedimentary

Rounded river cobble, likely weathered sandstone or quartzite

Indeterminate clastic silicate rock; possibly quartz-rich sandstone (SiO₂-dominant)

AI-generated identification · may be incorrect

Pale tan-gray, massive, fine-grained, dull to slightly earthy luster, with rounded abrasion surfaces and minor fractures. Estimated hardness is ~6–7 if quartz-rich; cleavage is absent and specific gravity roughly 2.5–2.7.

Identified August 24, 2026More sedimentary →

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At a glance

Common name: Rounded river cobble, likely weathered sandstone or quartzite
Scientific name: Indeterminate clastic silicate rock; possibly quartz-rich sandstone (SiO₂-dominant)
Category: sedimentary
Identified: August 24, 2026
Method: Standard

AI Estimated Value

$0–$10 as an ordinary cobble; typically under $20 unless laboratory testing shows a collectible mineral or unusual provenance.

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 as a sedimentary clastic rock and later rounded by transport in a river or beach environment; exact geological age and origin cannot be determined from the photograph.

Uses & applications

Common cobbles are used for landscaping, drainage, decorative stone, and educational collections; this specimen has little commercial or jewelry value unless testing reveals an unusual composition.

Geological facts

Its smooth, subdued shape indicates prolonged mechanical weathering and abrasion rather than crystal growth. The small dark inclusions may be iron oxides, lithic grains, or surface debris.

Field identification & locations

Field identification requires a fresh surface, hand lens, streak, and acid test: quartz-rich material is hard, does not scratch with a steel knife, and shows no fizz with dilute hydrochloric acid. Similar cobbles occur in river gravels worldwide.