The Dynamic Earth @ National Museum of Natural History

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[Photo: Sandstone]

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 water route.

[Photo: Microscopic view of sandstone with clay marked.]
Sandstone
A microscope photo of the sandstone (2 mm across) reveals that it contains too much clay to be very durable.

[MAP: Virginia and Maryland with Washington, D.C. demarked. Shows location of Government Island 65 km (40 mi) southwest of the capital.]

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.