Sedimentary

Conglomerate

Conglomerate (Clastic Sedimentary Rock)

AI-generated identification · may be incorrect

Hardness: 2-7 (variable based on matrix and clasts); Color: Variable brown, grey, rust; Luster: Dull/Earthy; Structure: Clastic with rounded clasts larger than 2mm diamater; Specific Gravity: 2.1-2.9.

Hardness: 2-7 (variable based on matrix and clasts)
Color: Variable brown, grey, rust
Luster: Dull/Earthy

Identified March 7, 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 through the lithification of rounded gravel and boulders. Usually found in high-energy environments like riverbeds, alluvial fans, or glacial washouts where water movement is fast enough to round stone edges.

Uses & applications

Used primarily as coarse aggregate in construction, road fill, and occasionally as a decorative facing stone in architecture. Minor value for lapidary work if the clasts are colorful minerals like jasper.

Geological facts

Conglomerate is often called 'puddingstone' because it resembles fruit in a pudding. It is the sedimentary 'cousin' of Breccia, which contains angular rather than rounded fragments.

Field identification & locations

Identify in the field by looking for rounded, smooth pebbles or cobbles cemented together in a finer-grained matrix. Found globally in ancient river systems and mountain basins.