sedimentary

Weathered conglomerate pebble

Polymict conglomerate, likely ferruginous and quartz-rich

AI-generated identification · may be incorrect

Rounded cobble with cemented gravel-sized clasts, including reddish-brown iron-oxide-stained material and gray granular quartz/feldspar-rich matrix. Individual mineral hardness is about Mohs 6–7; luster is mostly earthy to dull, with no consistent cleavage; overall specific gravity is roughly 2.5–2.7.

Identified September 11, 2026More sedimentary →

Explore Weathered conglomerate pebble 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 rounded stream or shoreline gravels were buried and lithified by mineral cement, probably silica, carbonate, or iron oxides; its exact age cannot be determined from the photograph. Subsequent erosion produced the smooth cobble shape.

Uses & applications

Primarily a decorative, teaching, or collecting specimen; conglomerate may be used locally as building stone or aggregate, but this small pebble has no industrial value.

Geological facts

The contrasting rounded clasts and matrix distinguish conglomerate from breccia, whose fragments are angular. Brown-red coloration commonly reflects hematite or limonite weathering.

Field identification & locations

Identify it by rounded pebble clasts firmly embedded in a finer matrix and by its gritty texture; common in river gravels, beaches, alluvial fans, and conglomerate outcrops worldwide. A dilute acid test may reveal carbonate cement, while a steel file tests relative hardness.