metamorphic

Rounded river cobble, likely quartzite

Quartzite (chiefly recrystallized quartz, SiO₂); exact identification is uncertain from the image

AI-generated identification · may be incorrect

Smooth, rounded, tan-brown surface with a fine-grained appearance; quartzite is typically Mohs 7, vitreous to dull, and has no cleavage. The wet surface and lack of a visible fresh fracture obscure diagnostic texture.

Identified September 27, 2026More metamorphic →

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At a glance

Common name: Rounded river cobble, likely quartzite
Scientific name: Quartzite (chiefly recrystallized quartz, SiO₂); exact identification is uncertain from the image
Category: metamorphic
Identified: September 27, 2026
Method: Standard

AI Estimated Value

About $1–$10 for an ordinary small cobble; typically little collector value without a distinctive feature or confirmed identification.

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

If quartzite, it formed when quartz-rich sandstone was metamorphosed under heat and pressure; its age depends on the source formation. The rounded shape indicates prolonged transport and abrasion in water.

Uses & applications

Quartzite is used as aggregate, paving and building stone, and sometimes as a decorative stone; this cobble is primarily a natural specimen.

Geological facts

The image shows a single cobble on a gravel bed, but color and shape alone cannot reliably distinguish quartzite from other hard rocks such as sandstone or fine-grained igneous rock.

Field identification & locations

Look for fused, interlocking quartz grains on a fresh break and test hardness: quartzite generally scratches glass. River gravels worldwide commonly contain rounded cobbles of many rock types.