Where Found (Encyclopedia of Global Resources)
Marbles, geologically defined as metamorphically altered calcareous rocks, are found in the core areas of younger mountain chains formed by the collision of tectonic plates and the consequent uplift and distortion of carbonate sedimentary strata. They are also found in the exposed roots of ancient, very eroded mountain chains of continental shield areas. Important marble-producing areas include the Carrara area in the Italian Apennines and Vermont, Georgia, and Alabama in the United States.
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Primary Uses (Encyclopedia of Global Resources)
Technical Definition (Encyclopedia of Global Resources)
Geologists define marble as a type of rock produced by metamorphic processes acting on either limestone or dolomite (dolostone), causing recrystallization through heat and pressure to produce a coarser-grained, harder rock. Stonemasons and quarriers have a more generic definition, which calls almost any hard rock that accepts a fine polish marble.
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Description, Distribution, and Forms (Encyclopedia of Global Resources)
As defined geologically, marble is a type of rock composed primarily of calcite. It can be, like limestone, monomineralic in nature—that is, a rock composed of only one, or nearly one, mineral. Thus it can be up to 99 percent calcite (calcium carbonate). True marble can be derived from either limestone or dolomite (sometimes called dolostone). Dolomite (calcium magnesium carbonate) is a carbonate rock in which much, if not most, of the original calcium carbonate has been replaced by magnesium. True marbles are formed by two types of metamorphism: regional and contact. Regional metamorphism is usually tectonic in nature and involves the slow compression and heating of rocks by large-scale crustal movements of the Earth over long periods of time. Contact metamorphism is caused by rocks coming into contact, or near contact, with sources of great geologic heat, such as intruding bodies of magma; in these cases change can be effected within a short period of time.
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History (Encyclopedia of Global Resources)
Marble in its various forms has been known and admired since remote antiquity as a stone of choice for many applications. Some of the earliest known works of true architecture that have survived from ancient Mesopotamia, Egypt, and Greece featured marble as either decorative or structural elements. Sculptures, bas-reliefs, dedicatory columns, and triumphal arches have frequently featured various marbles. Thus marble has been in use at least five thousand years, dating back to the first civilizations, and its use continues up to the present. Many sculptors through the ages—among them such giants as Michelangelo, working in the fifteenth and sixteenth centuries in Italy—have preferred marble, especially the pure white varieties.
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Obtaining Marble (Encyclopedia of Global Resources)
Marbledeposits are quarried in large operations that may involve hundreds of workers. In Europe marble is often obtained from quarries that have been worked continuously since antiquity. Until the last century or so, work was laboriously performed with age-old traditional tools and methods, but with the advent of power equipment the methodology and speed of extraction have greatly improved. Some constants have remained, such as the general strategy regarding extraction of large blocks of marble: removing the overburden (overlying sediments and rubble, if any), defining a quarry floor and front by quarrying monolithic blocks of marble parallel to their natural jointing planes, cutting away large blocks on all sides and removing the marble to the quarry floor, trimming, removing the marble from the quarry, and transporting it to the purchaser (often by use of specially built railroad systems).
Marble extraction has never had significant environmental effects, as the true marbles are chemically inert for all practical purposes. The metamorphism they underwent in their natural development stabilized their constituent minerals, including the trace minerals such as iron and magnesium from which colored marbles derive their patterns and hues.
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Uses of Marble (Encyclopedia of Global Resources)
The primary importance of marble is its use in architectural columns, floorings, wall coverings, sculpture, vases and other receptacles, and monuments of all sorts. Beginning in the twentieth century, new minor uses were found for marble, including electrical outlet baseplates and other electrical insulators, as it is a good natural insulator.
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Further Reading (Encyclopedia of Global Resources)
Dietrich, R. V., and Brian J. Skinner. Gems, Granites, and Gravels: Knowing and Using Rocks and Minerals. New York: Cambridge University Press, 1990.
Kogel, Jessica Elzea, et al., eds. “Decorative Stone” and “Dimension Stone.” In Industrial Minerals and Rocks: Commodities, Markets, and Uses. 7th ed. Littleton, Colo.: Society for Mining, Metallurgy, and Exploration, 2006.
Mannoni, Luciana, and Tiziano Mannoni. Marble: The History of a Culture. New York: Facts On File, 1985.
Pellant, Chris. Rocks and Minerals. 2d American ed. New York: Dorling Kindersley, 2002.
Price, Monica T. The Sourcebook of Decorative Stone: An Illustrated Identification Guide. Buffalo, N.Y.: Firefly Books, 2007.
Robinson, George W. Minerals: An Illustrated Exploration of the Dynamic World of Minerals and Their Properties. Photography by Jeffrey A. Scovil. New York: Simon & Schuster, 1994.
Schumann, Walter. Handbook of Rocks, Minerals, and Gemstones. Translated by R. Bradshaw and K. A. G. Mills. Boston: Houghton Mifflin, 1993.
U.S. Geological Survey. Crushed Stone: Statistics and Information. http://minerals.usgs.gov/minerals/pubs/commodity/stone_crushed
U.S. Geological Survey. Dimension Stone: Statistics and Information. http://minerals.usgs.gov/minerals/pubs/commodity/stone_dimension
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Marble (World of Earth Science)
Marble is metamorphosed limestone, that is, limestone that has been melted and allowed to resolidify. If the original limestone is a calcite limestone, then the marble is a calcite marble (i.e., mostly CaCO3); if the original limestone is a dolomitic limestone, then the marble is a dolomitic or magnesian marble (i.e., mostly CaMg (CO3)2). In nongeological contexts the term marble is often used to refer to any hard, calcite rock that can be cut or polished, including some unmetamorphosed limestones. In geology, however, it is reserved strictly for metamorphosed limestones.
Certain marbles have been valued since antiquity for sculpture and for architectural uses. The marbles prized for statuary are usually quite pure (i.e., white in color and free from inclusions or marks) and reflect light softly or semitranslucently due to their property of allowing some incident light to penetrate to a depth of about an inch (1.5 cm) before reflecting it.
Some marbles that show colorful patterning are used for decorative architecture. Patterning in marble arises from various trace minerals, most often silicates (e.g., quartz, olivine, garnet), graphite, pyrite, and organic substances. The magma responsible for metamorphosing the original limestone may also contribute impurities.
Wrinkled thin layers that show in cross-section as sinuous lines are common in marbles. These layers are termed stylolites. Stylolites consist of silicates or other accessory minerals and are usually darker than the surrounding marble. They do not form as sedimentary layers in the original limestone, but result from the selective removal of limestone by water. Calcite is a highly soluble mineral; when part of the original limestone is dissolved by infiltrating water, the fine particles that are left are compacted into an irregular layer or stylolite. Comparison of accessory mineral concentrations in adjacent marble and in stylolites shows that 40% or more of a limestone bed may be dissolved in the process of forming stylolites.
Calcite marble, like any other calcite rock, effervesces vigorously (yielding carbon dioxide [CO2]) when tested with hydrochloric acid. Dolomitic marble effervesces more weakly. Otherwise, they are difficult to distinguish.
See also Field methods in geology; Industrial minerals