sedimentary

Conglomerate

Conglomerate (clastic sedimentary rock)

AI-generated identification · may be incorrect

Hardness: Variable (approx. 6-7 for quartz clasts); Color: Brown, tan, and rusty orange due to iron oxide staining; Luster: Dull/Earthly matrix with vitreous clasts; Structure: Clastic, containing rounded pebbles (clasts) greater than 2mm in diameter embedded in a finer-grained matrix.

Hardness: Variable (approx
Color: Brown, tan, and rusty orange due to iron oxide staining
Luster: Dull/Earthly matrix with vitreous clasts

Identified March 17, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in high-energy environments like riverbeds, beaches, or alluvial fans where water current is strong enough to transport large pebbles. Over time, these sediments are buried and cemented together by minerals like calcite or silica. This specimen likely dates from the Phanerozoic eon depending on the local strata.

Uses & applications

Primarily used as a coarse aggregate in the construction industry for concrete and roads. Some attractive specimens are sliced and polished for use as ornamental stone or 'puddingstone' decor.

Geological facts

Conglomerate is often called 'puddingstone' because the rounded pebbles look like raisins or nuts 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 'concrete-like' appearance with distinct, rounded smoothed stones stuck in a natural cement. It is commonly found in ancient river channels and mountain basements globally. For collectors, look for high contrast between the pebbles and the matrix.