This 100- to
125-million-year-old sandstone was quarried to build the White House
and Capitol building beginning about 1790. It is an attractive building
stone, although not a particularly durable one. In fact, some blocks
cracked as they were hoisted into place and had to be replaced on the
spot. But the rock was easy to carve. Most importantly, it could be
readily transported to the new federal city by a short, navigable
A microscope photo of the sandstone (2 mm across) reveals that it
contains too much clay to be very durable.
Government Island, source of the sandstone,
lies about 65 km (40 mi) southwest of Washington, D.C. There, workers
loaded rough-cut blocks on barges, then floated them up the Potomac
River to the capital.