what is limestone made of
Pure limestone is made of calcium carbonate. Limestone often contains variable amounts of silica in the form of chert or flint, as well as varying amounts of clay, silt and sand as disseminations, nodules, or layers within the rock.The primary source of the calcite in limestone is most commonly marine organisms.These organisms secrete shells that settle out of the water column and are deposited on ocean floors as pelagic ooze or alternatively is conglomerated in a coral reef (see lysocline for information on calcite dissolution).ere, it decays and becomes a part of the rock known as limestone. So, limestone is made of decayed calcium, or calcite.   +++   Almost-but a chemical element cannot decay! The primary mineral of this sedimentary rock is calcite, calcium carbonate, which is a chemical compund (CaCO3).