sedimentary

Conglomerate

Conglomerate (Sedimentary Clastic Rock)

Hardness: variable (grain 6-7, matrix 3-5); Color: tan, buff, and grey; Luster: dull/earthy; Texture: coarse-grained clastic; Structure: rounded clasts (pebbles) embedded in a fine-grained matrix of silt or sand.

Hardness: variable (grain 6-7, matrix 3-5)
Color: tan, buff, and grey
Luster: dull/earthy

Identified July 7, 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

Formation & geological history

Forms through the lithification of rounded gravel and pebbles. Typically deposited in high-energy environments like fast-flowing rivers, alluvial fans, or beaches where water movement is strong enough to round the fragments.

Uses & applications

Used as a heavy-duty aggregate in the construction industry for roads and concrete. Occasional use as decorative stone or dimension stone if it is well-cemented and takes a polish.

Geological facts

Conglomerates are essentially 'natural concrete.' They are important to geologists because they indicate a high-energy depositional environment and can help map the history of ancient river systems.

Field identification & locations

Identify by looking for rounded, pebble-sized rocks 'glued' together by a finer material. Found globally in ancient riverbeds, coastal cliffs, and sedimentary basins. Collectors look for unique inclusions or colorful clasts.

Other sedimentary specimens

See all

Sandstone or Siltstone

Arenite (if sandstone)

Sedimentary

Cone-in-cone structure (Limestone)

Cone-in-cone structure (Secondary Sedimentary Structure)

sedimentary

Sandstone Grain

Clastic Sedimentary Rock Grain (SiO2 dominated)

sedimentary

Chert Breccia

Brecciated Chert (Microcrystalline Silica)

sedimentary

Shale or Slaty Mudstone

Argillaceous sedimentary rock

sedimentary

Sandstone

Arenite (primarily SiO2)

sedimentary