sedimentary

Polymictic conglomerate

Conglomerate; clast-supported polymictic conglomerate in a dark matrix

AI-generated identification · may be incorrect

Rounded to subrounded pebbles and granules of varied colors and lithologies cemented in a dark, likely sandy or muddy matrix; clasts commonly include quartz, feldspar, and lithic fragments. Hardness varies roughly 3–7 Mohs, with generally dull to locally vitreous luster and no consistent cleavage.

Identified September 6, 2026More sedimentary →

Explore Polymictic conglomerate in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed when stream, beach, or debris-flow deposits of rounded gravel were buried, compacted, and cemented by silica, carbonate, or iron oxides. Its precise age cannot be determined from the image; conglomerates range from ancient Precambrian to modern lithified deposits.

Uses & applications

Used locally as building or decorative stone, aggregate, and landscape material; attractive polished pieces may be sold as lapidary specimens.

Geological facts

The mixed clast population indicates erosion from multiple source rocks and transport before deposition. Orange-brown colors likely reflect iron-oxide staining.

Field identification & locations

Identify it by clearly rounded, pebble-sized clasts enclosed in a continuous cemented matrix; a hand lens and fresh surface help distinguish it from breccia, whose fragments are angular. Common in river channels, alluvial fans, and coarse shoreline deposits.