Aquia Creek sandstone

Aquia Creek sandstone is a type of brown to light-gray freestone used extensively in building construction in Washington, D.C. in the late 18th and early 19th centuries. Quarried at Aquia Creek in Stafford County, Virginia, the stone was valuable for its ease of shaping and the quarry's proximity to the tidewater portion of the Potomac River, 45 miles south of Washington.

The sandstone was the principal material used in such significant buildings as the White House and the early stages of the U.S. Capitol. The easy availability of the stone and its ability to be carved were offset in time by its susceptibility to weather-induced deterioration. Its best, most enduring uses were as interior decorative elements.

Of Cretaceous age, Aquia Creek sandstone is composed of rounded, coarse- to fine-grains of quartz, cemented with silica and containing scattered pellets of clay as large as an inch in diameter. This sandstone is typically gray or tan, sometimes with streaks or shades of red, yellow or buff, giving the stone a warm effect.

A quarry was established at Wigginton's Island on Aquia Creek by George Brent after 1694, providing stone for tombstones and to houses and churches in northern Virginia, including Gunston Hall, Christ Church in Alexandria, Virginia, Mount Airy in Richmond County, Virginia, and Aquia Church, as well as steps and walkways at George Washington's Mount Vernon.

Washington selected Aquia sandstone as the primary material for use in Washington's government buildings. Acting on the government's behalf, the Wigginton's Island quarry was purchased by Pierre Charles L'Enfant in 1791, becoming known afterward as Government Island. The stone from the quarry was used by James Hoban for the President's House and the Capitol. The earliest portions of the Treasury Building and the Patent Office (now the National Portrait Gallery) also used the stone.

...
Wikipedia