sedimentary

Conglomerate

Conglomerate (clastic sedimentary rock)

AI-generated identification · may be incorrect

Hardness varies by cement (usually 6-7 if siliceous); Color: grey matrix with light-colored rounded clasts; Luster: dull; Structure: clastic texture with rounded gravel-sized grains; Specific gravity: 2.6-2.8.

Color: grey matrix with light-colored rounded clasts
Luster: dull

Identified July 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the lithification of rounded water-worn pebbles and cobbles, typically in high-energy environments like riverbeds, alluvial fans, or beaches. These sediments are deposited and then cemented together over millions of years by minerals like quartz or calcite.

Uses & applications

Used in the construction industry as a decorative stone, aggregate for concrete, and occasionally as a building stone. In the energy industry, it can serve as a reservoir rock for petroleum and natural gas.

Geological facts

Conglomerate is often nicknamed 'puddingstone' because the rounded clasts resemble raisins or nuts in a pudding. It is notably distinct from breccia, which contains angular fragments rather than rounded ones.

Field identification & locations

Identify in the field by looking for rounded pebbles (clasts) larger than 2mm embedded in a finer-grained matrix. It is common in ancient river systems and mountain fronts globally. Collectors look for unique 'puddingstone' varieties with colorful clasts.