Chemical Sedimentary Rock
Chemical sedimentary rocks are also called chemical rocks. These rocks are formed by the lithification of substances that dissolved from weathered parent rocks (in solution or colloid form) and then chemically precipitated. Typical types include aluminous rocks, manganous rocks, ferruginous rocks, phosphorous rocks, some siliceous rocks and carbonaceous rocks, and also rock salts. Chemical rocks usually have simple compositions and a crystalline structure, cryptocrystalline structure, pisolitic structure or oolitic structure. Most chemical sedimentary rocks form in marine or lake basins, and some form due to groundwater. The rocks are often important sedimentary mineral deposits, such as ores of rock salt, gypsum, potash, mirabilite, iron, bauxite, limestone and dolomite.