Marble is a nonfoliated metamorphic rock resulting from the metamorphism of limestone, composed mostly of calcite (a crystalline form of calcium carbonate, CaCO3). It is extensively used for sculpture, as a building material, and in many other applications. The word "marble" is colloquially used to refer to many other stones that are capable of taking a high polish.
Pure white marble is the result of metamorphism of very pure limestones. The characteristic swirls and veins of many colored marble varieties are usually due to various mineral impurities such as clay, silt, sand, iron oxides, or chert which were originally present as grains or layers in the limestone. Green coloration is often due to serpentine resulting from originally high magnesium limestone or dolostone with silica impurities. These various impurities have been mobilized and recrystallized by the intense pressure and heat of the metamorphism.
Some historically important kinds of marble, named after the locations of their quarries, include
|Boticena and Onyx(Green)||Pakistan|
|Brač||Island of Brač||Croatia|
|Carrara marble||white or blue-gray||Carrara||Italy|
|Durango Marble||Coyote Quarry||Mexico|
|Llano Pink||Central Texas|
|Katni Marble||Green Marble||India|
|Parian marble||Fine-grained semitranslucent pure-white||Island of Paros||Greece|
|Penteli Marble||Flawless white with a uniform, faint yellow tint||Penteli||Greece|
|Proconnesus Marble||Island of Marmara||Turkey|
|Rouge de Rance||Red||Rance||Wallonia|
|Thassos||Snow white, White, Grayish white, White with pink veining||Island of Thassos||Greece|
|Vietnam White||Grayish White||Vietnam|
|Yule||Uniform pure white||Marble, Colorado||Colorado|
White marbles, like Carrara in Italy, Royal White and Beijing White in China and Malagori of Pakistan, have been prized for sculpture since classical times. This preference has to do with the softness and relative isotropy and homogeneity, and a relative resistance to shattering. Also, the low index of refraction of calcite allows light to penetrate several millimeters into the stone before being scattered out, resulting in the characteristic "waxy" look which gives "life" to marble sculptures of the human body.
According to the United States Geological Survey, U.S. dimension marble production in 2006 was 46,400 tons valued at $18.1 million, compared to 72,300 tons valued at $18.9 million in 2005. Crushed marble production (for aggregate and industrial uses) in 2006 was 11.8 million tons valued at $116 million, of which 6.5 million tons was finely ground calcium carbonate and the rest was construction aggregate. For comparison, 2005 crushed marble production was 7.76 million tons valued at $58.7 million, of which 4.8 million tons was finely ground calcium carbonate and the rest was construction aggregate. U.S. dimension marble demand is about 1.3 million tons. The DSAN World Demand for (finished) Marble Index has shown a growth of 12% annually for the 2000-2006 period, compared to 10.5% annually for the 2000–2005 period. The largest dimension marble application is tile.
Places named after the stone include Marblehead, Ohio; Marble Arch, London; the Sea of Marmara; India's Marble Rocks; and the towns of Marble, Minnesota; Marble, Colorado; and Marble Hill, Manhattan, New York. The Elgin Marbles are marble sculptures from the Parthenon that are on display in the British Museum. They were brought to Britain by the Earl of Elgin.