sedimentary

Conglomerate

Clast-supported polymictic conglomerate

AI-generated identification · may be incorrect

A coarse, poorly sorted sedimentary rock containing rounded to subrounded pebble-sized clasts in a brown sandy matrix, likely cemented by silica, calcite, or iron oxides. Typical hardness is about 3–7 depending on cement; it has a dull to earthy luster and no cleavage.

Identified August 17, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when gravel and sand accumulate in high-energy rivers, alluvial fans, beaches, or glacial deposits and become lithified by compaction and cementation. Its exact age cannot be determined from the image; conglomerates range from Precambrian to modern geological formations.

Uses & applications

Used locally as building or landscaping stone and crushed aggregate, though variable strength limits structural use. Attractive polished pieces may be sold as decorative or teaching specimens.

Geological facts

The rounded clasts indicate transport and abrasion before burial; clast composition can reveal the rocks exposed in the source region.

Field identification & locations

Identify it by visible rounded pebbles larger than 2 mm embedded in a finer matrix; breccia differs by having angular clasts. Common worldwide in river basins and alluvial deposits.