sedimentary

Conglomerate

Conglomerate rock

Hardness varies depending on clasts and cement (typically 3 to 7 on Mohs scale); Color varies, usually brownish-gray or tan with multicolored rounded clasts; Luster dull to earthy matrix with variable clasts; Clastic texture with rounded gravel to pebble-sized clasts embedded in a fine-grained matrix.

Identified July 23, 2026More sedimentary →

Explore 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 by the deposition, compaction, and cementation of rounded gravel, pebbles, or cobbles in high-energy aqueous environments such as fast-flowing rivers, beaches, or glacial runoff deposits.

Uses & applications

Used as low-grade aggregate in construction, road base material, decorative landscaping stone, and as an educational geological specimen showing sedimentary processes.

Geological facts

Conglomerate rocks act as geological records of ancient high-energy river channels and coastal environments. Similar conglomerate structures have even been photographed on Mars by NASA rovers, proving ancient water flow on the Red Planet.

Field identification & locations

Identified by distinct, smooth, rounded pebbles embedded within a cemented matrix of sand, silt, or mud. Commonly found along riverbeds, ancient stream channels, and alluvial fans worldwide.