Limestone is a sedimentary rock composed mainly with skeletal fragments. Like most other sedimentary rocks, most limestone is composed of grains. Most grains in limestone are skeletal fragments of marine organisms such as coral. Most limestone’s have a granular texture. Limestone has long fascinated earth scientists because of its rich fossil content. Limestone’s enriched in phosphate by the chemical action of ocean waters constitute a principal source of raw materials for the fertilizer industry. Certain varieties of limestone also serve as a building stone, they are widely used for flooring, exterior and interior facings, and monuments.
Limestone is also the main way you get lime, and lime is one of the things you make cement out of. To get lime, you have to burn limestone. What is left after you burn limestone, is lime. In the middle Ages, people in Europe and the Islamic Empire burned most of the statues of ancient Greece and Rome to turn them into lime. They used the lime to make mortar and cement, and built new buildings out of that.