Dolomite is a mineral composed of calcium, magnesium, carbon, and oxygen. It can occur as sedimentary rock or crystals and is similar to calcite. Dolomite is used in construction and the production of fire bricks, and provides an economical source of magnesium. Its formation is a puzzle for geologists.
Dolomite is a mineral composed of calcium, magnesium, carbon and oxygen, with the chemical formula CaMg(CO3)2. Its chemical name is calcium magnesium carbonate. The mineral is named after the French mineralogist Deodat Dolomieu, who first described it in 1791. It can occur as sedimentary rock, found in large deposits in many parts of the world, and also as crystals. In its pure form it is colorless or white, but the rock and crystals often contain impurities, especially iron, which impart color; it is commonly pinkish in color, but can be yellow, gray, brown, or black.
The mineral is similar in many respects to calcite or calcium carbonate (CaCO3), which also forms rock deposits – limestone and gypsum – or crystals. Like limestone, dolomite has some water solubility, especially if the water is slightly acidic, and can form caves with stalactites, stalagmites, and other limestone-like features. The rock form is sometimes known as a dolostone. Dolomite crystals are curved into a saddle shape, due to the stress placed on the crystal structure by the different sizes of calcium and magnesium atoms. This allows the crystalline forms of the two minerals to be easily distinguished from each other.
The rock shapes of calcite and dolomite can look very similar; however, they can be distinguished by their reactions with acids. Calcite reacts vigorously with strong acids, and sensibly with weak acids, releasing carbon dioxide (CO2) and producing effervescence. Dolomite will only react with strong acids and then only slowly and into powder. The two can then be distinguished by placing the samples in a weak acid, such as vinegar.
The formation of dolomite is a puzzle for geologists. Limestone is mainly formed by the secretion of calcium carbonate by marine organisms. Dolomite also appears to form mainly in marine environments, but despite being found in huge deposits, it appears that, contrary to limestone, it does not form in significant quantities today. It is thought that first limestone can form and then, if conditions are right, dolomite gradually forms through the replacement of some of the calcium in the limestone with magnesium.
One of the main uses of dolomite is in crushed rock for the construction industry. It is also used in the production of fire bricks. The material is heated to expel carbon dioxide, leaving a mixture of calcium and magnesium oxides, which, due to their high melting points, make an excellent raw material for brick. It provides an economical source of magnesium for various applications, including the production of the metal itself.
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