Base rock is similar to gravel - a combination of varying sized pieces of stone mixed with sand and clay. Base rock, however, is ​​​angular as opposed to having eroded in the environment to a rounded form. The angles in base rock allow the rock to settle and compact better than gravel. Base rock is not a product of natural weathering. It is mined from bedrock deposits, the rock just below what we see on the surface of the earth.  The bedrock is broken down by mechanical crushers. 

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