The two primary sources of natural aggregate are crushed stone and sand and gravel. Although potential aggregate is widely distributed throughout the United States in a variety of geologic environ-ments, it is not available everywhere.
Some areas are devoid of aggregate.
In other areas aggregate does not meet the physical or chemical property requirements for the intended use. Furthermore, zoning, govern-mental regulations, or competing land uses may restrict or preclude aggregate development. In the next decade, the restoration and rehabilitation of an aging infrastructure will require enormous amounts of aggregate. Earth scientists will provide input critical to the identification, pro-tection, and extraction of aggregate and equally important to reclamation efforts to return the land to beneficial secondary uses. This information will be used to provide economical supplies of aggregate while providing protection from the impacts of mining to both citizens and environment alike.