sedimentary

Conglomerate

Conglomerate (lithified rudite)

Hardness: variable (depends on clast composition); Color: multi-colored with a gray or tan matrix; Luster: dull to earthy; Texture: clastic (coarse-grained); Composition: rounded gravel-sized clasts (>2mm) of quartz, chert, or other rock fragments cemented by silica, calcite, or iron oxide.

Hardness: variable (depends on clast composition)
Color: multi-colored with a gray or tan matrix
Luster: dull to earthy

Identified April 5, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation and subsequent lithification of rounded water-worn pebbles and gravel, typically in high-energy environments like riverbeds, alluvial fans, or beaches. These deposits vary in age from the Precambrian to recent epochs.

Uses & applications

Primarily used as a low-grade construction aggregate for roads and concrete. Some attractive specimens are used for ornamental stones or 'puddingstone' interior decor. Historically used as building stone.

Geological facts

Conglomerate is often called 'puddingstone' because of its resemblance to a fruit pudding. It is one of the easiest rocks to identify because the rounded pebbles are clearly visible to the naked eye, representing ancient high-velocity water flows.

Field identification & locations

Identify in the field by looking for 'cemented gravel' appearance with smooth, rounded stones. Common in ancient mountain belts and river basins globally. For collectors, look for versions with high color contrast between pebbles and matrix.