Marble - Group of rocks used for ornamental purposes. True marble is formed from calcium carbonate that recrystallized through metamorphism. This marble is white or lightly colored and usually contains dark veins and inclusions. Some marble is also formed from Dolomite and Serpentine. Marble may be light to dark in color, and there are dozens of different types. (See also Calcite , Verde Antique, Travertine)