sedimentary

Conglomerate

Conglomerate (clastic sedimentary rock)

AI-generated identification · may be incorrect

Hardness: variable (3-7 Mohs depending on clasts/cement); Color: multicolored with a gray, brown, or tan matrix; Luster: dull/earthy; Structure: clastic texture with rounded gravel-sized grains (clasts) larger than 2mm; Specific Gravity: 2.1-2.9.

Hardness: variable (3-7 Mohs depending on clasts/cement)
Color: multicolored with a gray, brown, or tan matrix
Luster: dull/earthy

Identified March 18, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the lithification of rounded gravel and pebbles, typically in high-energy environments such as riverbeds, alluvial fans, or beaches where water action rounds the stones. These formations can date from any geological era where water transport occurred.

Uses & applications

Used primarily as heavy aggregate in the construction industry for road beds, concrete, and fill. Occasionally used as dimension stone or decorative masonry if the clasts are colorful (e.g., 'puddingstone').

Geological facts

Conglomarate is often called 'puddingstone' because the rounded pebbles look like raisins in a pudding. It is the sedimentary 'cousin' of Breccia, which contains angular rather than rounded fragments.

Field identification & locations

Identify in the field by looking for a 'natural concrete' appearance with rounded stones firmly embedded in a finer-grained matrix. Commonly found in ancient river systems; popular with beginners due to the visible variety of embedded minerals.