Crushed stone can be composed of limestone, granite, traprock or any other hard rock that is produced by blasting and then by crushing to a specified size at the site in stationary or portable plants. 

The word aggregate refers to any combination of sand, gravel and crushed stone in its natural or processed state.  Aggregates are divided into two categories:  fine aggregate and coarse aggregate. 

Most hard rocks are potentially useful for coarse aggregate.  Coarse grained, igneous rock (granite) and sedimentary, carbonate rock (limestone) are two commonly used rocks in the construction industry. The choice of aggregate for use in various end products can be based on the results of many quality control tests such as sieve analysis, grading, and specific gravity. Quality control is an ongoing process that takes continuous monitoring and sampling.

The geographic diversity of the aggregate industry is unique among businesses mining and producing natural materials. Aggregate producers operate in most counties in North America because the materials are vital ingredients in all Portland cement, concrete and asphaltic products.  The source of these products - quarries, sand pits and asphalt plants – must be located within reasonable distances for the most efficient transportation of crushed stone products. 

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