sedimentary

Rounded river cobble, likely quartz-rich sandstone or quartzite

Indeterminate quartz-rich clastic rock; probable sandstone (SiO₂-rich)

AI-generated identification · may be incorrect

Pale gray, fine-grained, subrounded cobble with dull earthy luster and minor rusty iron-oxide staining. Likely hardness ~6–7 Mohs; no visible cleavage, weak granular texture, and moderate-to-high density (~2.5–2.7 g/cm³).

Identified August 17, 2026More sedimentary →

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At a glance

Common name: Rounded river cobble, likely quartz-rich sandstone or quartzite
Scientific name: Indeterminate quartz-rich clastic rock; probable sandstone (SiO₂-rich)
Category: sedimentary
Identified: August 17, 2026
Method: Standard

AI Estimated Value

$0–$5 as a common natural cobble; up to roughly $10–$20 if unusually attractive, polished, or tied to a documented locality.

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 from compacted and cemented quartz-rich sediment, possibly later metamorphosed into quartzite, then rounded by stream or beach abrasion. Exact age and formation environment cannot be determined from the photograph.

Uses & applications

As an individual specimen it has little commercial value; similar material is used as aggregate, landscaping stone, road base, and occasionally decorative building stone.

Geological facts

The smooth oval shape reflects prolonged transport in moving water or wave action. Rust-colored patches commonly result from oxidation of trace iron-bearing minerals.

Field identification & locations

Test hardness against glass: scratching glass suggests quartzite or strongly cemented sandstone; a dilute hydrochloric-acid test should show no reaction. Common in river gravels, beaches, and glacial deposits.