sedimentary

Conglomerate

Clastic sedimentary rock (Puddingstone)

Hardness: 6.5-7 (variable based on clasts); Color: Mottled grey, tan, and brown; Luster: Dull/Earthy matrix with waxy clasts; Structure: Clastic, coarse-grained with rounded pebbles; Specific Gravity: 2.6-2.8.

Hardness: 6
Color: Mottled grey, tan, and brown
Luster: Dull/Earthy matrix with waxy clasts

Identified March 27, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in high-energy environments like riverbeds or alluvial fans where water rounds rock fragments before they are lithified by a mineral matrix (calcite, silica, or iron oxide). Ages range from Precambrian to Holocene.

Uses & applications

Used primarily in the construction industry as coarse aggregate for concrete, road fill, or as decorative dimension stone in architecture. Occasionally used in rustic jewelry if clasts are semi-precious.

Geological facts

Commonly nicknamed 'Puddingstone' in the UK and North America because the rounded pebbles look like raisins or plums in a pudding. It is an essential indicator for geologists to locate ancient river channels.

Field identification & locations

Identify by the presence of rounded (not angular) pebbles larger than 2mm embedded in a finer sandy or silty matrix. Look in areas with ancient fluvial activity. Collectors value specimens with colorful or rare clasts like jasper or agate.

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