sedimentary

Conglomerate

Clastic Sedimentary Rock (Conglomerate)

AI-generated identification · may be incorrect

Hardness: variable (depends on clasts, often 6-7 if quartz-heavy); Color: multi-colored with a gray or tan matrix; Luster: dull/earthy matrix with glassy clasts; Structure: clastic/coarse-grained; Cleavage: none.

Hardness: variable (depends on clasts, often 6-7 if quartz-heavy)
Color: multi-colored with a gray or tan matrix
Luster: dull/earthy matrix with glassy clasts

Identified March 24, 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 (clasts) larger than 2mm, typically in high-energy environments like riverbeds, alluvial fans, or beaches. Geological age can range from Precambrian to Holocene.

Uses & applications

Used primarily in the construction industry as coarse aggregate for concrete and road stone. Rarely used in jewelry unless it contains semi-precious clasts (e.g., Puddingstone).

Geological facts

Conglomerates are often called 'puddingstone' because the rounded pebbles look like raisins in a pudding. They are key indicators for geologists of ancient high-speed water currents.

Field identification & locations

Identify in the field by looking for rounded, water-worn pebbles cemented into a finer matrix. Commonly found in sedimentary basins and ancient river courses. Collectors look for unique color contrasts between pebbles and matrix.