Limestone is extracted from quarries or mines. Uncommon sources of lime include coral, sea shells, calcite and ankerite. Further classification is done by composition as high calcium, argillaceous (clayey), silicious, conglomerate, magnesian, dolomite, and other limestones. ![]() In the lime industry, limestone is a general term for rocks that contain 80% or more of calcium or magnesium carbonate, including marble, chalk, oolite, and marl. Main article: Calcium oxide § Preparation Otherwise it most commonly means slaked lime, as the more dangerous form is usually described more specifically as quicklime or burnt lime. When the term is encountered in an agricultural context, it usually refers to agricultural lime, which today is usually crushed limestone, not a product of a lime kiln. Burning ( calcination) of calcium carbonate in a lime kiln above 900 ☌ (1,650 ☏) converts it into the highly caustic material burnt lime, unslaked lime or quicklime ( calcium oxide) and, through subsequent addition of water, into the less caustic (but still strongly alkaline) slaked lime or hydrated lime ( calcium hydroxide, Ca(OH) 2), the process of which is called slaking of lime. They may be cut, crushed, or pulverized and chemically altered. The rocks and minerals from which these materials are derived, typically limestone or chalk, are composed primarily of calcium carbonate. Lime is used extensively for wastewater treatment with ferrous sulfate. Lime industries and the use of many of the resulting products date from prehistoric times in both the Old World and the New World. ![]() ![]() These materials are still used in large quantities as building and engineering materials (including limestone products, cement, concrete, and mortar), as chemical feedstocks, and for sugar refining, among other uses. The word lime originates with its earliest use as building mortar and has the sense of sticking or adhering. The International Mineralogical Association recognizes lime as a mineral with the chemical formula of CaO. It is also the name for calcium oxide which occurs as a product of coal-seam fires and in altered limestone xenoliths in volcanic ejecta. Lime is an inorganic material composed primarily of calcium oxides and hydroxides, usually calcium oxide and/or calcium hydroxide. Calcium mineral Limestone quarry in Brønnøy, Norway
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