Diabase is a hard, brittle rock used as a base component for construction of roads and for building foundations.
There are defined belts of this rock, also known as trap rock, south of Leesburg and near Washington Dulles International Airport.
The crushed-stone quarries that extract diabase are a substantial economic resource. Loudoun County diabase is some of the best rock for concrete and road base material found on the East Coast. Continuing construction activities in the greater Washington area will ensure that diabase continues to be an important local economic resource.