sedimentary

Conglomerate

Conglomerate rock

Hardness: variable depending on clasts (6.5-7 for quartz); Color: Brown, red, or tan matrix with multi-colored clasts; Luster: Dull/Earthy; Structure: Clastic, containing rounded pebbles over 2mm; Cleavage: None.

Hardness: variable depending on clasts (6
Color: Brown, red, or tan matrix with multi-colored clasts
Luster: Dull/Earthy

Identified April 8, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the lithification of rounded gravel and pebbles. They typically originate in high-energy environments like fast-flowing riverbeds, alluvial fans, or beaches where water rounds the stones before they are buried and cemented by minerals like silica or calcite.

Uses & applications

Used primarily as heavy-duty construction aggregate, fill material for roads, and occasionally as decorative dimension stone for walls or floors.

Geological facts

Conglomerate is often called "puddingstone" because the rounded stones resemble raisins or fruit in a pudding. It is the sedimentary opposite of breccia, which contains sharp, angular fragments.

Field identification & locations

Look for rounded, water-worn pebbles cemented together in a solid matrix. It is commonly found in ancient riverbeds or mountain basins. For collectors, look for unique color combinations or high-contrast matrices.