An example of a calcareous rock is limestone. Limestone is a sedimentary rock that is formed from the accumulation of calcium carbonate, which is typically derived from the shells and skeletons of marine organisms such as corals and mollusks. It is primarily composed of calcite mineral, and its texture ranges from fine-grained to coarse-grained. Due to its high calcium content, limestone is often used as a building material and in the production of cement.