The Holston Formation, alternately known as the Holston Limestone, is a stratigraphic unit of Ordovician age within the Chickamauga Group in the Ridge-and-Valley physiographic province of the southeastern United States. A long outcrop belt of the Holston in East Tennessee is the source of the decorative building stone known as Tennessee marble. Near Knoxville the Holston Formation is about thick but it thins toward the southwest; near Cleveland, Tennessee it is only 200 feet thick. The rock that is quarried for marble is a highly pure (97% CaCO3) crystalline limestone, pink to cedar-red in color. Use in building and sculpture Among the notable buildings where Tennessee marble is used as a building stone are two in Washington, D.C.: the National Gallery of Art, which uses stone from Knox and Blount counties, and the United States Capitol, which has stairways constructed from Hawkins County marble. References General Mineral Commodities, in Mineral Resources of the Appalachian Region, U.S. Geological Survey and U.S. Bureau of Mines, Geological Survey Professional Paper 580, 1968. Notes External links Knoxville's marble past, Knoxville News Sentinel, August 26, 2008 (article and videos) Ordovician geology of Tennessee Ordovician southern paleotemperate deposits