BRECCIA

 

Breccia is an uncommon, coarse-grained, siliciclastic sedimentary rock.  Breccias form in many ways (sedimentary breccias, volcanic breccias, tectonic breccias/fault breccias, collapse breccias, boiling breccias, hydrothermal breccias, seismite breccias, injectite breccias, etc.), but they all have the same general appearance.  Sedimentary breccias contain a mix of large & small grains.  The large grains (gravel - pebbles or cobbles or boulders) are angular to subangular in shape, and they are surrounded by a finer-grained matrix, usually sand or mud.

 

Breccia

 


  

Jasper Breccia (cut & polished surface) - this attractive breccia contains abundant reddish- and yellowish-colored chert fragments surrounded by a very dark brown matrix of finer-grained material.  I’m not sure of the provenance of this rock, but I suspect it comes from Arkansas or Oklahoma (corrections or verifications are welcome).

 


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