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Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (CaCO3). Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera. Limestone makes up about 10% of the total volume of all sedimentary rocks. The solubility of limestone in water and weak acid solutions leads to karst landscapes, in which water erodes the limestone over thousands to millions of years. Most cave systems are through limestone bedrock. Limestone has numerous uses, including as a building material, as aggregate to form the base of roads, as white pigment or filler in products such as toothpaste or paints, and as a chemical feedstock. (source: Wikipedia) A yellowish, ooltic limestone called Cotswold stone, extremely common in the Cotwolds region of England from which iyt gets its name and a white piece of limestone from south central Oklahoma. Photos by Michael Marcotte Return to List Back to Michael's Hobbies page Back to Michael Marcotte's HomePage