Marble is a metamorphic rock derived from limestone, composed mostly of calcite (a crystalline form of calcium carbonate, CaCO3). The original source of the parent limestone is the seabed deposition of calcium carbonate in the form of microscopic animal skeletons or similar materials. Marble is formed when the limestone is transformed by heat and pressure after being overlain by other materials. The finest marbles for sculpture have no or few stains (some natural stain can be seen in the sculpture shown at left, which the sculptor has skillfully incorporated into the sculpture).

A recent study of the Altamura Man, an ancient skeleton embedded in a limestone cave in Italy, has yielded surprising results. The fossilized Homo neanderthalensis, which was discovered in theGrotta di Lamalunga by chance in 1993, have been difficult to study due to the rock and thick calcite layers covering it. Using a sample from the scapula, the study also revealed that the prehistoric remains may contain the oldest Neanderthal DNA ever extracted. (Source)