metamorphic

Weathered quartz-rich cobble (likely quartzite or siliceous sandstone)

Quartzite, predominantly SiO₂; exact identification requires testing

AI-generated identification · may be incorrect

Hardness about 7 if quartzite; gray-brown, reddish iron staining, granular texture, and dull to slightly glassy luster. Massive with no obvious cleavage; rounded from stream or beach abrasion. Specific gravity roughly 2.6–2.7.

Identified September 11, 2026More metamorphic →

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At a glance

Common name: Weathered quartz-rich cobble (likely quartzite or siliceous sandstone)
Scientific name: Quartzite, predominantly SiO₂; exact identification requires testing
Category: metamorphic
Identified: September 11, 2026
Method: Standard

AI Estimated Value

About $1–$10 as an ordinary specimen; potentially $10–$30 if it has unusual color, provenance, or an attractive polished surface.

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 quartz-rich sandstone recrystallized during metamorphism, then eroded and rounded in a sedimentary or glacial environment. Its precise geological age and provenance cannot be determined from the photograph.

Uses & applications

Common quartzite is used as crushed aggregate, road stone, building stone, and occasionally decorative material; this nondescript cobble has little commercial or jewelry value.

Geological facts

Quartzite commonly breaks across quartz grains rather than around them, producing a sugary or splintery fracture. A steel file should not scratch it, while quartz-rich sandstone may shed individual grains more readily.

Field identification & locations

Look for interlocking quartz grains, hardness near 7, and lack of reaction to dilute acid; a streak test is white. Common worldwide, especially in former sandstone terrains and river gravels.