What’s the difference between sea salt and rock salt?

The earth as we know it today didn’t look the same millions of years ago. What used to be seas have dried up and are now covered with rock and soil. We know them today as subterranean or underground salt mines which have enough rock salt to supply man’s needs for the next so many centuries. So says a documentary on TV recently (Discovery Channel, if I remember correctly) which showed the locations of the largest underground salt mines in the world.

Did I say these salt mines can supply mankind with rock salt for the next so many centuries? Yes, rock salt; not sea salt. There is a difference. Sea salt is made by drying out sea water. So, the cheap rock salt sold in markets comes from the underground salt mines. The more expensive sea salt that we find in gourmet shops comes from the sea. Chemically, there’s not much difference as they are both more than 99% sodium chloride.

That’s sea salt sprinkled on the fish in the photo. We bought a bag just to try it out as some claim there is a difference in “mouth feel” although I can’t say that I’ve noticed. There are also claims that because salinity and presence of other minerals vary from sea to sea, the flavor of sea salt differs depending on which sea water the salt was dried out from. I’ve only tried one bag of sea salt so I can’t comment on the difference of flavors. If that makes me ungourmet, never mind.

Now then, sea salt… rock salt… where does table salt fit in? And kosher salt, for that matter?

In its most common meaning, table salt is refined rock salt. If iodine is added, it is iodized salt. During the term of President Fidel Ramos, one of his projects was the marketing of cheap iodized salt for the benefit of communities that have little access to food that are naturally high in iodine (i.e., seafood). Iodine, according to studies, helps prevent thyroid problems, and even mental retardation and low I.Q.

If both iodine and iron has been added, it is double-fortified salt.

What about kosher salt? The grains of kosher salt are not as fine as that of refined salt but they are not as large as rock salt either. Kosher salt grains are rather flat. Aside from the shape and size, is there any other significance? Note these two conflicting claims.

First from the Food Network.

Kosher salt takes its name from its use in the koshering process. It contains no preservatives and can be derived from either seawater or underground sources. Aside from being a great salt to keep within arm’s reach when you are cooking, it is particularly useful in preserving, because its large crystals draw moisture out of meats and other foods more effectively than other salts.

The second is a “citation needed” paragraph from Wikipedia.

The term “kosher salt” derives not from its being made in accordance with the guidelines for kosher foods as written in the Torah (nearly all salt is kosher, including ordinary table salt), but rather due to its use in making meats kosher, by helping to extract the blood from the meat. Rather than cubic crystals, kosher salt has a flat platelet shape. This is done in some salts by adding yellow prussiate of soda (sodium ferrocyanate). Because kosher salt grains are larger than regular table salt grains, when meats are coated in kosher salt the salt does not dissolve readily; the salt remains on the surface of the meat longer to draw fluids out of the meat.

Too much salt information? Well, it appears that the usefulness of salt is not limited to food and cooking. See the sixty uses of table salt.