Sodium chloride salt crystals can be grown from table salt dissolved in water by allowing the solution to evaporate undisturbed. It is believed that dissolved sea salt or pickling salt, which is pure salt, produces larger crystals while iodized salt appears to promote the growth of smaller crystals. Allowing the evaporation process to go undisturbed is important because any ripples that occur in the solution while it is in the growing container will cause the forming crystals to be smaller.
The salt crystal evaporation process is used with seawater to produce gourmet varieties of salt known as "fleur de sel," which is French for "flower of salt." Certain varieties of this delicate and crunchy cooking salt are known as "flake salt." The harvesting of fleur de sel is done by hand by scraping only the top layer of salt crystals from the evaporating pans before they can sink to the bottom.
In certain regions of the world the combination of local climate and seawater have enabled towns like Guerande and Noirmoutier in Brittany to become known for the specialized fleur de sel they produce. Spain and Portugal are also known for exporting specialized regional seawater salts and the North American Pacific Northwest has recently begun harvesting gourmet salt in the coastal areas of Vancouver and Oregon.
These specialized cooking salts have a greater degree of mineral complexity than table salt. A sample of seawater-produced fleur de sel can contain small quantities of magnesium, calcium, iron and potassium.