sedimentary
Conglomerate
Polymictic clast-supported conglomerate
AI-generated identification · may be incorrectCoarse, poorly sorted rounded pebbles and cobbles set in a gray, sandy matrix; clasts include varied rock types. Hardness varies with cement and clasts, typically about 3–7 Mohs; no single crystal structure or cleavage.
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Physical properties
Coarse, poorly sorted rounded pebbles and cobbles set in a gray, sandy matrix; clasts include varied rock types. Hardness varies with cement and clasts, typically about 3–7 Mohs; no single crystal structure or cleavage.
Formation & geological history
Formed when rounded gravel was deposited by energetic rivers or beaches, then compacted and cemented. Its age cannot be determined from the image alone.
Uses & applications
Used locally as building or decorative stone and valued as a geological teaching or display specimen.
Geological facts
The rounded clasts indicate transport and abrasion before burial; a rock containing mostly angular fragments is instead called breccia.
Field identification & locations
Identify by pebble-sized, rounded, contrasting fragments embedded in a finer matrix; found in ancient river, alluvial-fan, and shoreline deposits worldwide. Value: roughly $5–$30 for a small common specimen; larger or polished pieces may cost more.
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