sedimentary/metamorphic

Weathered quartz-rich cobble, likely sandstone or quartzite

Indeterminate; probable quartz arenite (sandstone) or quartzite, dominated by SiO₂

AI-generated identification · may be incorrect

Brown, tan, and gray, fine- to medium-grained, dull to slightly glassy; apparent hardness about 6–7 Mohs, with irregular fracture and little visible cleavage. Iron-oxide staining produces the rusty color; exact texture is obscured by weathering.

Identified September 9, 2026More sedimentary/metamorphic →

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At a glance

Common name: Weathered quartz-rich cobble, likely sandstone or quartzite
Scientific name: Indeterminate; probable quartz arenite (sandstone) or quartzite, dominated by SiO₂
Category: sedimentary/metamorphic
Identified: September 9, 2026
Method: Standard

AI Estimated Value

About $1–$15 as an ordinary cobble; roughly $20–$75 if sold as an attractive, documented, or unusually patterned specimen.

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 from compacted quartz-rich sand, possibly metamorphosed into quartzite, then rounded by stream or shoreline transport and chemically weathered. Its geological age cannot be determined from the photograph.

Uses & applications

Suitable mainly as a decorative or teaching specimen; quartzite may be used as aggregate, road stone, or building stone. Commercial value is generally low unless provenance or unusual texture is established.

Geological facts

The rounded shape indicates abrasion during transport, while brown coloration commonly reflects limonite/goethite coatings or pore staining. A fresh broken surface would best distinguish sandstone, whose grains and cement are visible, from quartzite, which breaks through fused quartz grains.

Field identification & locations

Common in stream gravels, glacial deposits, beaches, and weathered outcrops worldwide. Test with a steel file or glass: quartz-rich material scratches glass; dilute acid is usually inactive unless carbonate cement is present.