The word marble comes from the Greek word marmaros which means shining stone. To the geologist, marble is a non-foliated, granular metamorphic rock that is formed by the metamorphism of limestone and dolostone. It is usually formed by regional metamorphism but sometimes is formed by contact metamorphism. Both limestone and marble are calcium carbonate (CaCO3) which is also the composition of the mineral calcite. The metamorphism of limestone causes the calcite grains to grow in size and to interlock with one another. The result is that marble is noticeably more dense and harder than limestone. Limestone frequently contains invertebrate fossils. However, these fossils are almost always destroyed by metamorphism.
In industry, the term “marble” is also applied to serpentine rocks that can be polished to a high shine. Technically, “marble” and “serpentine” are two different metamorphic rocks. Serpentine is formed by the metamorphism of rocks called peridotites and another called pyroxenes. True marble is a carbonate rock (which means it has CO3 in its chemistry). Serpentine is a silicate rock meaning it has silicon and oxygen in its chemistry. It is important to be aware that the technical scientific terms (in this case “marble”) can have a different meaning in industry. Dark green serpentine “marble” is frequently referred to as verde antique.
Pure, bright white marble is highly desired because of its even color. Since the days of ancient Rome, it has been used for statues and architectural decorations because of its pure, bright color and its hardness. Marble’s hardness allows it to be polished to a smooth, bright, shining surface. However, marble typically has lines and veins running throughout it. This look is what is typically referred to as “marbling.” The lines and veins are from silt, sand, clay and other impurities that were in the original limestone from which the marble was formed.
A number of minerals and gems can form in marble. Spinel from Vietnam, ruby and sapphire from Myanmar (formerly Burma) and lazulite from Afghanistan are just a few examples.
Marble is found, literally, all over the world. It is most notably located in regions of dramatic metamorphism, especially regional metamorphism. Carrara, Italy produced some of the most famous and desired marble in history. From the quarries of Carrara have come enormous blocks of pure white, extremely hard marble. The Pantheon was constructed from Carrara marble. Michelangelo’s famous sculpture David was carved from Carrara marble. Spain, Greece, Turkey, China, Poland, Ireland and Mexico have all produced marble of various colors and patterns. In the United States, Danby, Vermont and Marble, Colorado have produced significant quantities of high-quality marble for use as dimension stone both for construction as well as for carving purposes.
Quarries in the United States produce 11.8 million metric tons of crushed marble. Five companies operate a total of six mines in five different states. In order of production, from greatest to least, the states are Georgia, Vermont, Tennessee, Colorado and Alabama. A total of 1.3 billion tons of crushed rock is produced in the United States annually. Of this, less than 6% is marble. (In fact, sandstone, quartzite, scoria, volcanic cinder, marble and miscellaneous stone, all together, account for less than 6% of the total crushed stone production in the U.S.)
United States marble quarries produced approximately 210,000 tons for dimension stone annually (“dimension stone” is any rock that is quarried to be cut into specific sizes and shapes). Significant amounts of marble are imported from Italy, Turkey, China and Mexico.
Some marble is crushed and used in many applications, with many other types of crushed stone, most notably for road and highway construction and repair. A relatively small amount of marble is used in cement and lime production.
Marble as dimension stone is used for construction of buildings: 40% of the marble is cut as rough blocks which is used for building construction; another 34% is used as finishing stone where the marble is cut into thin sheets, slabs and veneers that are given a very high polish and used to finish or cover walls, floors and the exteriors of buildings.
Substitutes and Alternative Sources
Sources of marble are widespread and plentiful. There is no danger of running out of marble in the near, or distant, future. However, specific types of marble that have very specific colors or veining patterns, may become depleted. When a particular look is desired and the actual marble is no longer available, other materials are typically used, including ceramic tiles, brick, concrete, and resin-agglomerated stone. Additionally, a builder may choose to use aluminum, plastics, glass or steel in place of marble.
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