sedimentary

Conglomerate

Hardness: 2-3 (clastic matrix) to 7 (if quartz clasts); Color: Reddish-brown, gray, or tan; Luster: Dull or earthy; Structure: Clastic, containing rounded pebbles over 2mm in diameter embedded in a finer-grained matrix; Cleavage: None.

Hardness: 2-3 (clastic matrix) to 7 (if quartz clasts)
Color: Reddish-brown, gray, or tan
Luster: Dull or earthy

Identified July 17, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the lithification of rounded rock fragments (clasts) that have been transported by high-energy water environments like fast-moving rivers or coastal wave actions, usually deposited in alluvial fans or glacial environments.

Uses & applications

Primarily used as a coarse aggregate in the construction industry for roads and building foundations; occasionally used as decorative stone in architecture if well-cemented and colorful.

Geological facts

Conglomerate is often called 'puddingstone' because it resembles fruit in a pudding. Identifying the type of clasts within the rock can help geologists reconstruct the history of ancient river systems and mountains.

Field identification & locations

Identify by looking for rounded pebbles (not angular) cemented together. Found globally in ancient riverbeds, sedimentary basins, and near mountain ranges. Collectors look for unique 'puddingstone' varieties with contrasting colors.