Sea salt, obtained by evaporation of sea water, is a salt used as an ingredient in cooking and in products such as cosmetics. Its mineral content gives it a different taste from table salt, which is mostly sodium chloride that is either purified from sea salt or made from rock salt (halite), a mineral that is dug from mines. Table salt also sometimes contains additives, such as iodides (as a dietary supplement) and various anticaking agents. Sea salt is thought by some to be a healthier alternative to table salt. Various areas of the world produce specialized sea salt, including France, Ireland, and Cape Cod. Sea salt produced in Hawaii may have a distictive red-brown color (see red dirt) derived from iron-rich volcanic soil present as an impurity. One common use of sea salt is in premium potato chips. Sea salt is generally more expensive than table salt.
In several countries, including China and India, sea salt was the sole source of salt. Regulating the sales of sea salt was highly profitable for the governments. About 110 BC, Emperor Han Wu Di of China started the monopoly of the salt trade, making salt piracy a crime worthy of capital punishment. In 1930, the British government of India imposed a salt tax, which led to the famous salt march from March 12 to April 5 when Mohandas Gandhi led thousands of people to the sea to collect their own salt rather than pay the salt tax.