Conglomerate

Physical Properties

Hardness: variable (depends on clast type, usually 6-7 for quartz fragments); Color: tan, brown, or grey matrix with multi-colored rounded pebbles; Luster: dull/earthy; Structure: clastic texture with rounded fragments >2mm in diameter.

Formation & Geological History

Formed through the lithification of rounded gravel and pebbles, typically in high-energy environments like river beds, alluvial fans, or beaches where water movement rounds the stones over time.

Uses & Applications

Primarily used as a coarse aggregate in the construction industry for concrete and roads; occasionally used as decorative stone in landscaping or interior design.

Geological Facts

Conglomerate is often called 'puddingstone' because the rounded stones embedded in the matrix look like raisins in a pudding. It is an indicator of ancient high-energy water systems.

Field Identification & Locations

Identify by looking for large, rounded rock fragments cemented together in a finer matrix. Common in sedimentary basins worldwide. It differs from breccia, which contains angular fragments.

Identified on: 5/14/2026

Mode: Standard