Marble is a metamorphic rock that forms when limestone is subjected to the heat and pressure of metamorphism. It is composed primarily of the mineral calcite (CaCO3) and usually contains other minerals, such as clay minerals, micas, quartz, pyrite, iron oxides, and graphite In the United States, the major marble-producing areas are found in Alabama, Colorado, Montana, Tennessee, Texas, and Vermont. Most of the Alabama marble is found in the middle-eastern parts of the state, in Talladega, Bibb, Calhoun, Clay, Coosa, Etowah, Lee, Macon, St. Clair, and Shelby counties.