sedimentary

Rounded polymictic conglomerate (pebble)

Clast-supported conglomerate; mainly quartz- and feldspar-bearing lithic clasts in a sandy matrix

AI-generated identification · may be incorrect

Hardness approximately 6–7 overall; brown-gray, speckled, and strongly rounded from abrasion, with a dull to slightly granular luster. It consists of visible pebble-sized fragments cemented in a finer matrix; cleavage is absent and specific gravity is roughly 2.5–2.7.

Identified September 4, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when gravel and sand accumulated in a high-energy stream, beach, or alluvial-fan environment and lithified by compaction and silica, iron-oxide, or carbonate cement. Its exact geological age cannot be determined from the photograph.

Uses & applications

Used as decorative stone, landscaping material, aggregate, and teaching or collector specimens; this small rounded piece has little commercial value.

Geological facts

Conglomerate is distinguished from breccia by rounded rather than angular clasts, recording prolonged transport before burial and cementation.

Field identification & locations

Look for clearly rounded pebbles of differing colors and compositions embedded in a finer matrix; a hand lens and acid test can help identify carbonate cement. Common in ancient river channels, alluvial fans, and coastal deposits worldwide.