Conglomerate

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.

Identified on: 4/25/2026

Mode: Standard