Crushed LimestoneSold In 1 Cubic Yard Bag Limestone has numerous uses, primarly as building material and as aggregate to form the base of roads and in many landscaping projects. Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (CaCO3). Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera.