Plate Tectonics associated with the formation of the Appalachian Mountains caused incredible compressionary forces along the eastern edge of the North American Plate. Sedimentary and igneous rock layers recrystallized to become the metamorphic rock of the Piedmont. Quarries along Rock Creek, and at Little Falls, Maryland, provided Washington, DC with building stone from the Piedmont’s Sykesville Formation, also known as Potomac Bluestone (Gneiss). Foundations of the White House, Capitol, and Washington Monument, along with buildings like the Lock Keeper’s House and the Old Stone House in Georgetown were built with the Sykesville Formation.
No quarry information available for this stone.