sedimentary

Conglomerate

Conglomerate (SiO2 dominant in clasts)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (for quartz clasts); Color: Variable browns, tans, and whites; Luster: Dull matrix with vitreous clasts; Crystal structure: Amorphous/microcrystalline; Cleavage: None; SG: 2.6-2.7

Hardness: 6
Color: Variable browns, tans, and whites
Luster: Dull matrix with vitreous clasts

Identified April 25, 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

Hardness: 6.5-7 (for quartz clasts); Color: Variable browns, tans, and whites; Luster: Dull matrix with vitreous clasts; Crystal structure: Amorphous/microcrystalline; Cleavage: None; SG: 2.6-2.7

Formation & geological history

Formed through the lithification of rounded gravel and pebbles, typically in high-energy environments like riverbeds, beaches, or alluvial fans where water current rounds the stones.

Uses & applications

Used primarily as coarse aggregate in the construction industry for concrete and road beds; occasionally used as decorative stone or for geological education.

Geological facts

Conglomerate is often called 'puddingstone' because the rounded pebbles look like raisins or nuts in a pudding. It serves as a historical record of ancient water flow speeds.

Field identification & locations

Identify by looking for rounded, smooth pebbles (clasts) larger than 2mm cemented together by a finer-grained matrix. Commonly found in sedimentary basins and ancient river deposits.