Limestone is a carbonate sedimentary rock that is often composed of the skeletal fragments of marine organisms such as coral, foraminifera, and molluscs. These are sedimentary carbonate materials that accumulate in water as layers or beds through various chemical and biological processes. Predominantly of calcium and magnesium the chemistry of these carbonates often include other elements such as iron that will play a part in the structure, colour and patterning found in these materials. A limestone will frequently exhibit structures and other relic features that give clues to the age and environment that existed when the deposit was laid down. Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate.
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