Over the past century the growth of American cities and towns, and the construction and maintenance of the highways and byways between those population centers, created a demand for enormous amounts of natural aggregate. Over that same period of time circumstances and events have taken place that have complicated the ability of producers to meet the increasing need for aggregate. Products derived from rocks provide essential materials for society – materials that we need to maintain our current lifestyle. Rock products are used in one form or another for construction of highways, bridges, houses, and other buildings; in industry for making steel, glass, and other consumer products; for environmental applications such as filtering sewage and scrubbing flue gasses during generation of electricity; and for numerous agricultural, metallurgical, and pharmaceutical purposes (Langer and Glanzman, 1993). For many uses there is no readily available substitute.