sedimentary

Polymict conglomerate

Clastic conglomerate, likely polymictic and matrix-supported

AI-generated identification · may be incorrect

Rounded to subrounded pale quartz/feldspar-rich pebbles occur in a dark gray-brown, iron-stained matrix; overall texture is coarse and noncrystalline. Hardness is approximately 6–7 where quartz-rich, with dull to earthy luster and no consistent cleavage; variable specific gravity is about 2.4–2.7.

Identified September 10, 2026More sedimentary →

Explore Polymict 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 gravel and cobbles were transported, rounded, deposited in a high-energy river, alluvial fan, or beach, then compacted and cemented. Its exact geologic age cannot be determined from the photograph; conglomerates range from ancient to modern.

Uses & applications

Used locally as building stone, decorative aggregate, landscaping material, and occasionally as a polished ornamental specimen. It has little gemstone value.

Geological facts

The mixed clast population makes it polymictic; the dark matrix may contain volcanic fragments, mafic minerals, iron oxides, or cement. Conglomerate differs from breccia because its clasts are rounded rather than sharply angular.

Field identification & locations

Identify it by visible rounded pebble-sized fragments embedded in a finer matrix; a hand lens and fresh broken surface help confirm texture. Common in river basins, mountain-front deposits, and sedimentary outcrops worldwide.