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Conglomerate

Pictures of Sedimentary Rock Types

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Conglomerate could be thought of as a giant sandstone, containing grains of pebble size (greater than 4 mm) and cobble size (>64 mm). (more below)
A rock of stones
Photo (c) 2009 Andrew Alden licensed to About.com
Conglomerate forms in a very energetic environment, where rocks are eroded and carried downhill so swiftly that they aren't fully broken down into sand. Another name for conglomerate is puddingstone, especially if the large clasts are well rounded and the matrix around them is very fine sand or clay. These specimens could be called puddingstone. A conglomerate with jagged, broken clasts is usually called a breccia, and one that is poorly sorted and without rounded clasts is called a diamictite.

Conglomerate is often much harder and resistant than the sandstones and shales that surround it. Conglomerate is scientifically valuable because the individual stones are samples of the older rocks that were exposed as it was forming—important clues about the ancient environment.

See more examples of conglomerate in the Conglomerate Gallery and other sedimentary rocks in the Sedimentary Rocks Gallery.

Other galleries:
Fossils
Geologic Features and Processes
Glaciers and Ice
Landforms
Minerals
Rocks
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