salt salt salt!!!Sea salt contains many varieties of "salts", the main one being, of course, Sodium Chloride (NaCl). These "salts" are ionic compounds, which means they are soluble in water. Examples might be Magnesium Chloride, Sodium Iodide, Aluminum Sulphate, etc. I tend not to think of them as "impurities" but rather they mimic, to some degree, the variety of salts in the human body.
Sea salt made by dehydrating sea water in the sun will contain many other impurities, such as insoluble things like dirt, dead fish parts, bug debris, etc. Sea salt made by using pure water and filtration methods will contain less impurities, but will roughly be the same in terms of the constituent "salts" if the seawater comes from the same source.
===== as posted by someone else, yes, salt in its purest form, is composed of NaCl molecules in a cubic crystalline structure. a close look at common table salt will make this obvious. HOWEVER!! a close look at other forms of salt will reveal some interesting observations!!
i happen to have some eight or nine different salts in my kitchen. the finest is pickling salt but i find no need to buy this specifically. simply put regular salt in a coffee grinder and go at it. for cooking, i use regular table salt (with iodine) or kosher salt (i have diamond as well as morton kosher)as the recipe calls for ... the regular table salt does have iodine in it (prevents goiters) and an anti-caking ingredient so i use it less than the kosher salt ( in the 1:2 ratio previously mentioned). in heavier flavored stews and such it really doesn't matter which you use. i also have a "himalayan" salt allegedly from tibet that is pink and about the texture of coarse kosher salt; a hawai'ian salt that is dark orange from the clay pits it is picked from; a hand picked french sea salt (medium grey colored) that is rough grained and actually moist to the touch (sticks to food very easily!); a flavored italian sea salt caled "sale alle erbe" (seasalt where various herbs are put into the salt fresh and the salt draws out the moisture, and therefore flavor, into the salt. omigod ... what a nice salt to sprinkle on top of fresh pasta!!); and finally the coarsest salt i own is baleine brand "sel de mer gros", a very gritty lumpy salt from france.
do they make a difference? i think they do. the different salts do have very distinct size and "crunch" differences that when used as a finishing salt can subtlely alter the texture of the food. also, with the coarser salts, there is the distinctive "pop" of saltiness when you chew the food that is different that when a finer grain salt is used. nitpicky?? maybe, but there are lots of foodies out there that are looking for these little special touches in the finished product. :lips: