Sedimentary
Conglomerate
Conglomerate
Variable hardness depending on clast and matrix composition, typically earth tones (red, brown, gray, yellow), dull or earthy luster, clastic texture with rounded gravel-sized clasts (>2mm) in a finer-grained matrix.
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Physical properties
Variable hardness depending on clast and matrix composition, typically earth tones (red, brown, gray, yellow), dull or earthy luster, clastic texture with rounded gravel-sized clasts (>2mm) in a finer-grained matrix.
Formation & geological history
Formed in high-energy environments such as fast-flowing rivers or beaches where strong water currents can transport and round large particles, before they are deposited and eventually cemented together.
Uses & applications
Often used in construction as aggregate, decorative stone, and sometimes as a minor aquifer if porosity is sufficient. Occasionally used for display by collectors.
Geological facts
Conglomerates are known as 'puddingstones' in some regions, notably the Roxbury Conglomerate in Massachusetts.
Field identification & locations
Easily identified by the presence of large, rounded clasts suspended in a finer matrix (like sand or silt). Commonly found in ancient riverbeds and alluvial fan deposits.
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