 Limestone is a sedimentary rock, composed mainly of skeletal fragments of marine organisms such as coral, forms and mollusks. Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate Capo-3. About 10% of sedimentary rocks are limestones. The solubility of limestone in water and weak acid solutions leads to karst landscapes, in which water erodes the limestone over thousands to millions of years. Most Cape systems are through limestone bedrock. Limestone has numerous uses, as a building material, an essential component of concrete Portland cement as aggregate for the base of roads, as white pigment or filler in products such as toothpaste or paints, as a chemical feedstock for the production of lime, as of soil conditioner, or as a popular decorative addition to rock gardens. Like most other sedimentary rocks, most limestone is composed of grains. Most grains in limestone are skeletal fragments of marine organisms such as coral or foramina furrow. These organisms secrete shells made of aragonite or calcite, and leave these shells behind then they die. Other carbonate grains comprising limestones are oids, pelloids, intraclasts, and extraclasts. Limestone often contains variable amounts of silica in the form of chert calcite, succulent, jasper, etc. or silicious skeletal fragment sponge spicules, diatoms, radiolarians and varying amounts of clay, silk and sand terrestrial detritus carried in by rivers.