Conglomerate

Physical Properties

Hardness: Variable (clasts often 7, matrix 3-6); Color: Brown, tan, orange, with white/clear quartz pebbles; Luster: Dull to earthy matrix with vitreous clasts; Crystal structure: Clastic (rounded grains); Specific gravity: 2.6-2.8

Formation & Geological History

Formed in high-energy environments such as riverbeds, alluvial fans, or beaches where rounded pebbles are deposited and later cemented together by minerals like silica, calcite, or iron oxide.

Uses & Applications

Used primarily in the construction industry as coarse aggregate for concrete and road fill. Occasionally used as a decorative building stone.

Geological Facts

Conglomerates are often referred to as 'puddingstone' because the rounded clasts resemble raisins or nuts in a pudding. They are essential indicators of ancient high-energy water environments.

Field Identification & Locations

Identify in the field by looking for rounded, water-worn pebbles larger than 2mm embedded in a finer-grained matrix. It is commonly found in sedimentary basins and ancient river channels.

Identified on: 4/25/2026

Mode: Standard