Carbonate rocks are rocks made up primarily of carbonate minerals (minerals containing the CO3 anionic structure). The two most common carbonate minerals are Calcite - $ CaCO3 $, and Dolomite - $ CaMg (CO3)2 $. Generally, carbonates are associated only with sedimentary rocks, but there have been extremely rare volcanic carbonate eruptions, namely in Mt. Vulture, southern Italy (Abstract), and in Africa.