Marble has both scientific and commercial definitions. Marble is limestone that has achieved metamorphosis from intense pressures and high temperatures within the earth. This pressure alters its crystalline structure and in combination with other minerals, marble acquires its amazing colors and beautiful veining. Commercially, any stone capable of taking a polish (with the exception of granite) is known as marble. This includes travertine, onyx, serpentine, and limestone.  Marble is available in slab form and many varieties are also available as tile.