sedimentary

Mixed river gravel (alluvial conglomeratic sediment)

Polymictic alluvium; composition includes quartz, feldspar, chert, granite, basalt, and metamorphic rock fragments

AI-generated identification · may be incorrect

Mostly rounded pebbles and granules in a sandy matrix, with varied cream, brown, gray, orange, and black colors; individual minerals range from Mohs 2–7, generally with dull to glassy luster and no consistent cleavage.

Identified August 8, 2026More sedimentary →

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At a glance

Common name: Mixed river gravel (alluvial conglomeratic sediment)
Scientific name: Polymictic alluvium; composition includes quartz, feldspar, chert, granite, basalt, and metamorphic rock fragments
Category: sedimentary
Identified: August 8, 2026
Method: Standard

AI Estimated Value

Typically $0–$10 per handful or $5–$30 per bag for decorative gravel; unusual individual clasts may be worth more, but this sample has low collector value.

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 by weathering, transport, and abrasion in a river or stream, then deposited as alluvial gravel; the clasts may represent rocks of many different ages, commonly Paleozoic to Cenozoic depending on the source watershed.

Uses & applications

Used as landscaping gravel, drainage aggregate, road base, concrete aggregate, and decorative material; attractive pieces may be collected but are rarely gem-grade.

Geological facts

The rounded shape records abrasion during transport, while the mixed colors indicate multiple geological source rocks. A true consolidated equivalent would be polymictic conglomerate.

Field identification & locations

Identify it by its loose, unsorted mixture of rounded clasts and sand; quartz-rich pieces are hard and glassy, whereas dark basalt and softer weathered fragments are more opaque. Common along rivers, beaches, terraces, and glacial outwash deposits.