Tennessee State Stone
Limestone is a hard, fine-grained to very coarse-grained sedimentary rock composed primarily of calcium carbonate. Unlike sandstone or shale, which are clastic in origin (formed from particles of older rocks), limestone usually forms from the shells and skeletons of living creatures. These may be mollusks or other larger invertebrates, corals, or single-celled organisms.
In general, limestone is more soluble than sandstone and thus more subject to weathering; however, much of the limestone found in Tennessee is partially metamorphosed, rendering it more durable. Limestone’s color normally ranges from white through buff. The preferred "Tennessee marble" is pinkish.
A STATE SYMBOL
Tennessee designated limestone as its state stone in 1979. The reasons can be seen all over the state in outcrops and on buildings. Tennessee possesses vast stores of limestone, much of it of high quality. While only fully metamorphosed limestone is really marble, the quality of the Tennessee limestone widely used around the U.S. is such that it is commonly called Tennessee marble. The first Tennessee limestone quarry opened in 1838 and produced stone for local building as well as for shipment around the country. The stone was and continues to be favored as a building material within the state; the state capitol and the state supreme court building are fine examples. Dozens of Tennessee quarries still produce limestone for dimension stone and for aggregate.
Limestone is a sedimentary rock that forms by accretion (accumulation) of coarse to very fine particles of shell and sometimes from chemically dissolved calcium carbonate. The particles typically accrete in layers underwater, particularly in marine environments but also sometimes in freshwater. As layers are buried under layers, pressure accumulates, compacting the particles. However, the temperatures and pressures to which limestone is subjected are much lower than those for igneous and metamorphic rocks. Marble is metamorphosed limestone, the result of increased pressure and heat that fuses the particles into a glossy stone.
Sedimentary rocks cover about 80 percent of the earth’s land and most of the ocean floor, yet they form a thin skin, accounting for only eight percent of the volume of the earth’s crust. Limestone specifically makes up about a quarter of this material. Because it lies at the surface, it is readily available all over the world.
USES AND PRODUCTION
Dimension limestone is used in architecture because of its beauty, versatility, and prevalence. It lends itself well to ornamental carving. In 2005, U.S. quarries sold 581,000 metric tons of dimension (cut) limestone in the domestic market, of which 327,000 metric tons were dressed (precisely cut) and the rest was rough. Limestone aggregate is used for industrial purposes such roadbeds. Because of the high pH of calcium carbonate, crushed limestone is used in agriculture to counter acidity of the soil; finely crushed limestone is also used in papermaking to increase the opacity of paper. Nationwide, quarries sell about a billion tons of crushed limestone a year.
Tennessee limestone (usually referred to as Tennessee marble) can be found in monuments and elegant buildings all over the United States. Ten acres of the material pave the floors of San Francisco City Hall, and the stone also paves Chicago’s Union Station, Toronto’s Union Station, and New York City’s Grand Central Station. The New York Public Library’s entrance lions, which have become symbols of that institution, are also made of Tennessee limestone.
Limestone in general has been used for important buildings since ancient times. The Great Pyramid of Giza is made of limestone quarried near the construction site. The Western Wall of Jerusalem is one of the city’s many ancient structures made of local limestone. The famous medieval cathedral at Chartres, France, is made of limestone, as are the British Houses of Parliament and New York’s Empire State Building.
The famous Three Gorges of the Yangtze River (Qutang, Wu, and Xiling Gorges) are spectacular examples of natural limestone formations.
Chemical Formula: CaCO3
Color: White or lightly colored, usually with dark streaks
|Author: World Trade Press|