Salt is a mineral. There are two forms of minerals: dietary minerals and real minerals. Salt is the only dietary mineral that is also deemed a real mineral by geologists.
Salt is formed in the sea from sodium ions that enter from rivers, and chloride ions that are formed in seafloor volcanoes. When these ions are present in sufficient concentrations, they react to form solid salt crystals. Salt is an essential dietary requirement, because sodium enables nerves to work properly and muscles to contract, while chloride is important in the digestion of food. Both ions help to regulate fluid levels in the body.