sedimentary

Conglomerate

Clastic sedimentary rock (Conglomerate)

Hardness: variable (matrix 3-5, clasts 6-7); Color: brown, gray, tan; Luster: earthy to dull; Structure: clastic (rounded fragments larger than 2mm embedded in a finer-grained matrix); Cleavage: none.

Hardness: variable (matrix 3-5, clasts 6-7)
Color: brown, gray, tan
Luster: earthy to dull

Identified July 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in high-energy environments like riverbeds, alluvial fans, or beaches where water current is strong enough to transport large pebbles. Over time, these rounded fragments are buried and cemented together by minerals like calcite or silica.

Uses & applications

Used primarily in the construction industry as coarse aggregate for concrete and road fill. Occasionally used as ornamental stone if the clasts are colorful.

Geological facts

Conglomerates are often called 'puddingstone' because the rounded pebbles look like raisins or fruit in a pudding. They are key indicators of past water flow on both Earth and Mars.

Field identification & locations

Identify in the field by looking for rounded, smooth pebbles that are naturally 'glued' into a solid mass. Check riverbanks and glacial tilt deposits. Collectors look for high contrast between pebbles and matrix.

Other sedimentary specimens

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Sandstone or Siltstone

Arenite (if sandstone)

Sedimentary

Fossiliferous Concretion

Septarian Concretion containing Brachiopods/Crinoids

fossil

Shale

Shale (clastic sedimentary rock)

sedimentary

Brown Sandstone (River Rock)

Arenite

sedimentary

Mudstone

Argillite / Siliciclastic sedimentary rock

sedimentary

Cone-in-cone structure (Limestone)

Cone-in-cone structure (Secondary Sedimentary Structure)

sedimentary