Sea salt is usually obtained by allowing salt water to evaporate in specially designed salt evaporation ponds. It has been harvested this way since ancient times. Sea salt is different from other table salts in a number of ways, but it contains very little bromine and only the smallest traces of iodine and iodide. For this reason, even though people think that sea salt is healthier, there is no nutritional evidence to back up this belief.
From Wikipedia: “Sea salt is salt produced from the evaporation of seawater, rather than by being extracted from sedimentary deposits. It is used in cooking and cosmetics. It is also called bay salt or solar salt. Like mineral salt, production of sea salt has been dated to prehistoric times. Some cooks believe it tastes better than salt from mines. However, there is little or no health benefit to using sea salt over other forms of sodium chloride salts.”
Historical and modern production:
“The principle of production is evaporation of the water from the sea brine. In warm and dry climates this may be accomplished entirely by using solar energy, but in other climates fuel sources have been used. Modern sea salt production is almost entirely found in Mediterranean and other warm, dry climates. Such places are today called salt works, instead of the older English word saltern. ...
The dilute brine of the sea was largely evaporated by the sun. In Roman areas, this was done using ceramic containers known as briquetage. Workers scraped up the concentrated salt and mud slurry and washed it with clean sea water to settle impurities out of the now concentrated brine. They poured the brine into shallow pans (lightly baked from local marine clay) and set them on fist-sized clay pillars over a peat fire for final evaporation. Then they scraped out the dried salt and sold it.
Today, salt labelled "sea salt" in the US might not have actually come from the sea, as long as it meets the FDA's purity requirements.”
“Some gourmets believe sea salt tastes better and has a better texture than ordinary table salt. In applications that retain sea salt's coarser texture, it can provide a different mouth feel, and may change flavor due to its different rate of dissolution. The mineral content also affects the taste. The colors and variety of flavors are due to local clays and algae found in the waters the salt is harvested from. For example, some boutique salts from Korea and France are pinkish gray, some from India are black. Black and red salts from Hawaii may even have powdered black lava and baked red clay added in. Some sea salt contains sulfates. It may be difficult to distinguish sea salt from other salts, such as pink "Himalayan salt", Maras salt from the ancient Inca hot springs, or rock salt (halite).”
“According to The Mayo Clinic and Australian Professor Bruce Neal, the health consequences of ingesting sea salt or regular table salt are the same, as the content of sea salt is still mainly sodium chloride. In comparison, table salt is more heavily processed to eliminate minerals and usually contains an additive to prevent clumping.
Iodine, an element essential for human health, is present only in small amounts in sea salt. Iodised salt is table salt mixed with a minute amount of various salts of the element iodine.”
Fleur de Sel and gray salt (sel gris):
“Fleur de sel is the most expensive type of sea salt. It forms as a paper-thin layer on the surface of the water and is collected manually using a wooden rake on days when it is hot, sunny, and there is very little wind. ...
Fleur de sel contains over 97% sodium chloride, 0.5% calcium sulfate, 0.3% magnesium chloride, 0.2% magnesium sulfate (Epsom salt), and about 0.1% potassium chloride. The remainder is residual moisture.
Gray salt (sel gris) is harvested from the water at lower depths under the fleur de sel. ... It contains a high level of residual moisture and has to be crushed in a rustproof salt mill or with a mortar and pestle.*”
Note (italics): * = Translation from a German Wikipedia entry