Limestone is composed of carbonate minerals, notably calcite,but also aragonite, siderite and other carbonates species, such as ankerite. It may containe inorganic carbonate that precipitates directly from saline water or organic carbonate from fragments of the shells of marine organisms or coral. Chalk is a type of limestone that contains the remains of carbonate micro – organisms.
Caves form naturally in dolomite or limestone because carbonate minerals dissolve easily in slightly acidic groreaundwater leaving vast underground chambers lined with stalactites, stalagmites and other cave deposits. When such underground caves manifest themselves on the surface, they can form sinkholes with disastrous consequences, as in the 1960s in Carletonville in Gauteng, South Africa.
May stalactites and stalagmites are composed of travertine, a finest crystalline limestone that has concentric rings or radiating growth patterns. Another chemical sedimentary rock, tufa, is composed of calcium carbonate. It originates around groundwater or springs where calcium – rich water is present , and forms characteristic concretionary or bulbous s deposits. Calcrete is a rock composed or calcium carbonate and usually forms from precipitation of calcium carbonate in upper soil layers as a result of evaporation.
Dolomite is a calcium – magnesium carbonate mineral species, but the term also refers to a rock composed of dolomite – crystals. Although dolomite can be formed by evaporation of saline water, many limestones become dolomitized by magnesium – rich saline solutions that percolate through the limestone and chemically replace the limestone with secondary dolomite.
The main commercial use of limestone is in the cause manufacture of cement, made by burning (sintering) limestone with silica, aluminium and iron oxides. Limestone used as flux in the production of non – ferrous metals. It has several other uses, notably water and sewerage purification, stone dusting in coal mines and as a filler in paint, rubber, wood, putty, vinyl tiles and asphalt. Dolomite is used for refractory bricks and limestone. Both dolomite and limestone are used as fertilizers to neutralize acidic soils and are important aquifers that store vast amounts of underground water.
|Colour||Pale - Pink to Rose Red|
SOURCES FOR THIS GEMSTONE
In the United States, lime is produced in a number of states. Companies in Texas, Alabama, Kentucky, Missouri, Ohio and Pennsylvania account for more than one-half of U.S. production annually. In addition, lime is imported from Canada and Mexico. Other nations producing lime include Belgium, Brazil, China, France, Germany, Italy, Japan, Poland, Romania,Tanzania and the United Kingdom.