Salt that is used for a variety of industrial and food-related purposes comes primarily from shallow bodies of sea or mineral water and from mining operations dedicated to salt production. The method of production is determined by the location from which the salt is harvested. Location and method also determine the type of salt sold as a final product as well as its intended use.
The three methods of industrial salt production are solution mining, deep-shaft mining and solar evaporation. Most table and industrial salt is produced by solution mining, whereby water is injected into massive deposits of salt forced to the surface of the Earth by tectonic pressures. The water dissolves the salt into a solution, called brine, which is then pumped out and dehydrated at another location.
In deep-shaft mining, or conventional mining, tunnels are dug underground to reach the salt leftover from ancient sea beds, which is then mined like any other mineral. This primarily results in rock salt. The purest salt, however, is harvested through solar evaporation. In warm regions with low rates of precipitation, salt is harvested once a year from shallow ponds and pools evaporated by the sun during the summer. Salt produced in this fashion, called “sea salt,” is a common ingredient in cooking and cosmetics.