One-third of the worldwide sodium chloride (salt) production (about 200 million tons per year) is manufactured in solar saltworks. A solar saltworks is a series of one or more interconnected, shallow concentrating ponds (40 to 70 cm deep) through which seawater flows, evaporates by wind and sun, and deposits sodium chloride on the floors of crystallizer ponds (30 cm to 50 cm deep). In the downstream flow, salts of low solubility (in respect to sodium chloride) precipitate, with calcium carbonate first dropping out near three times, and calcium sulfate (gypsum) first appearing near four times seawater salinity. Shortly before reaching saturation with sodium chloride (about S.G. 1.214), the brine flows into crystallizer ponds (crystallizers), where evaporation continues until 5 to 20 cm of sodium chloride is deposited on the floors. The supernatant liquid, rich in compounds of calcium, magnesium, chloride, and sulfate, is removed, and the salt is harvested, washed, stockpiled for a time to decrease contaminants, and marketed.