sedimentary

Polished brown river pebble (likely chert or fine-grained sandstone)

Indeterminate; probable microcrystalline quartz (chert) or quartz-rich sandstone

AI-generated identification · may be incorrect

Rounded and polished, brown-tan with mottling, dull to slightly vitreous luster, and no visible crystals or cleavage. Estimated hardness is about 6–7 Mohs if chert, or 5–7 if sandstone; specific gravity roughly 2.5–2.7.

Identified August 26, 2026More sedimentary →

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At a glance

Common name: Polished brown river pebble (likely chert or fine-grained sandstone)
Scientific name: Indeterminate; probable microcrystalline quartz (chert) or quartz-rich sandstone
Category: sedimentary
Identified: August 26, 2026
Method: Standard

AI Estimated Value

Typically $1–$10 for a common polished pebble; potentially $10–$30 if unusually patterned, locally significant, or sold as lapidary material.

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 a naturally water-worn sedimentary cobble, later polished or tumbled; sedimentary material may be millions to hundreds of millions of years old, depending on source formation.

Uses & applications

Used mainly as a decorative pebble, craft material, or inexpensive lapidary specimen; generally little industrial or jewelry value unless it displays attractive patterns.

Geological facts

The image does not show diagnostic features sufficient for a confident species identification. A glassy fracture and ability to scratch ordinary glass would support chert; visible sand grains and weaker hardness would favor sandstone.

Field identification & locations

Common in river gravels and glacial deposits worldwide. Inspect a fresh edge with a loupe, test streak and hardness, and use dilute hydrochloric acid only if carbonate minerals are suspected.