sedimentary

Conglomerate

Polymictic Conglomerate

Hardness: 6.5-7 (variable based on matrix and clasts); Color: Grey, black, and greenish-brown with white quartz inclusions; Luster: Dull to waxy when wet; Structure: Clastic, consisting of rounded fragments (clasts) cemented together; Specific Gravity: 2.6-2.9.

Hardness: 6
Color: Grey, black, and greenish-brown with white quartz inclusions
Luster: Dull to waxy when wet

Identified July 15, 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 in high-energy aqueous environments such as river beds, beaches, or alluvial fans where water current is strong enough to transport and round large pebbles before they are buried and lithified by pressure and mineral cement.

Uses & applications

Primarily used as a decorative stone in landscaping, a rough construction aggregate, or as a source of information for geologists to determine past water flow paths. Some varieties are polished for ornamental use.

Geological facts

Conglomerate is often called 'puddingstone' in some regions due to the appearance of plums in a pudding. It can act as a reservoir rock for petroleum and natural gas if it has high porosity.

Field identification & locations

Identified by the Presence of rounded, water-worn pebbles larger than 2mm embedded in a finer matrix of sand or silt. Commonly found along active or ancient riverbeds and coastlines. Collectors should look for unique clast compositions or colors.