Calcite, with the chemical formula Ca[CO 3] or CaO•CO 2, as the main mineral component of limestone, is a calcium carbonate with an island structure. Calcite was first used for calcining lime, so it is also called limestone. In the mineral crystal chemical classification, calcite belongs to the oxysalt category, the carbonate class, and the calcite group. In the structural-functional classification of mineral raw materials in mineral material science, limestone, whose main mineral component is calcite, is classified as a three-dimensional structural rock under the non-functional rock (chemical rock) subcategory. This classification is based on its primary use and largest application as a raw material for cement production.