sedimentary

Polymict conglomerate with a projecting pebble

Conglomerate; clast-supported polymict conglomerate, dominated by quartz/feldspar and lithic fragments in a cemented matrix

AI-generated identification · may be incorrect

Rounded to subrounded multicolored clasts in a dark, probably siliceous or carbonate matrix; typically Mohs 6–7 for quartz-rich pieces, dull to weakly vitreous luster, no consistent cleavage, and specific gravity about 2.3–2.7.

Identified August 12, 2026More sedimentary →

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At a glance

Common name: Polymict conglomerate with a projecting pebble
Scientific name: Conglomerate; clast-supported polymict conglomerate, dominated by quartz/feldspar and lithic fragments in a cemented matrix
Category: sedimentary
Identified: August 12, 2026
Method: Standard

AI Estimated Value

About $5–$30 for a common hand specimen; $30–$100+ for unusually colorful, polished, or locality-documented specimens.

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 when water-worn gravel accumulated in a river, alluvial fan, or shoreline and was lithified by burial and cementation. Its exact age cannot be determined from the photograph and may range from ancient to geologically recent.

Uses & applications

Used locally as building stone, aggregate, paving material, and decorative rock; attractive polished pieces are collected, though it is generally not a jewelry gemstone.

Geological facts

The defining feature is rounded clasts larger than 2 mm; angular fragments would indicate breccia instead. The protruding gray clast may be quartzite, chert, or another resistant rock fragment.

Field identification & locations

Identify it by visible rounded pebbles cemented together and contrasting clast colors; freshly broken surfaces reveal the matrix and clast boundaries. Conglomerates occur worldwide in former river channels and basin margins.