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Definition: breccia from The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide

Coarse-grained sedimentary rock, made up of broken fragments (clasts) of pre-existing rocks held together in a fine-grained matrix. It is similar to conglomerate but the fragments in breccia are jagged in shape.

Summary Article: Breccia
from Rock and Gem

BRECCIAS ARE LITHIFIED SEDIMENTS with the same size clasts as conglomerates, but in breccias the clasts are angular or only slightly rounded. The lack of rounding indicates little or no transportation has taken place. Breccias can form in several ways: firstly, a rock body can break and then become cemented in its original position; secondly, rock fragments accumulating at the base of a cliff can become cemented where they fell; thirdly, in areas of active faulting, newly broken material along the line of the fault can be cemented in place; and fourthly, where faulting takes place underwater, newly shattered material can move in underwater landslides and become cemented.

  • Properties
  • Rock type Marine, freshwater, and glacial detrital sedimentary
  • Fossils Very rare
  • Major minerals Any hard mineral can be present
  • Minor minerals Any mineral can be present
  • Color Varies
  • Texture Very coarse, angular clasts
© 2008 Dorling Kindersley Limited

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