Which mineral is the main component of most limestone?

Calcite is the principal mineral in limestone and has the chemical formula CaCO3. Limestone forms in many environments, including shallow tropical seas, reefs, and lake basins, where calcium carbonate precipitates or accumulates from shells and skeletons. When limestone is subjected to heat and pressure, it can metamorphose into marble. Calcite is also one of the most common minerals on Earth and is a key building block of many sedimentary rocks. Its widespread presence makes it important in geology, industry, and paleontology.