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.
Quarrying operations and related activities in diabase resource areas present challenges to the environment and local residents due to the nature of heavy industrial activities and transport truck traffic. Soils that swell when wet and shrink when dry (shrink-swell clays) often lie on top of diabase bedrock and can cause cracked foundations and structural damage to buildings.
For questions or more information about Diabase and local quarries, please contact the Department of Building and Development at 703-777-0220.