“Pass the salt” should be the simplest request in the world, one requiring no further elucidation. But in recent years, salt has become an accessory in the fickle world of fashionable food. What was a simple question has become complicated. Now the questions might be: “Which salt? What color? What size crystals? Sea salt or the mined kind? From where?”In addition to the standard iodized variety, there is clay red salt from Hawaii; Celtic gray from the coast of Brittany; stone-ground, greenish salt from Bali in fine round crystals; bronze salt that has been smoked; and others types of salt in grains that are coarse and pyramid-shaped. There is, currently, controversy between those who swear by England’s slightly bitter, snowy Maldon flakes and the cohort (which include me) that prefers the silkier, more subtle fleur de sel from France’s Camargue region. In fact, salt connoisseurship is now such a popular gourmet game that at the justly celebrated Per Se restaurant in New York City, a salt tasting is a separate course on the Degustation menu.For Jews, there is nothing new about the specialness of this condiment. It is declared sacred in many books of the Hebrew Bible. Here’s Levitius 2:13: “And every offerings of your grain offering you shall season with salt; you shall not allow the salt of the covenant of your God to be lacking from your grain offering.” To this day, some people salt pieces of challah before they eat them on the Sabbath, and, at Passover, salt water, recalling the tears shed by slaves in Egypt, is the dip for parsley, lettuce, radishes, and hard-boiled eggs.The attributes that make salt a symbol of steadfastness are not only its role as a preserver and purifier, and as an essential mineral, but its virtual indestructibility. Even if the crystals dissolve in liquid, they reform when that liquid evaporates. You might have witnessed this phenomenon after boiling pasta in well-salted water; afterward, chalky white spots remain on the stove top when the steam and water splashes have dried.Then there is what’s known as kosher salt—but which should more accurately be called koshering salt. A mineral, salt is considered pareve as long as it has not been adulterated. Some brands of salt have a kosher symbol on the package only to indicate that nothing has defiled its contents. What makes this salt right for koshering meat and poultry is the size of the crystals. The object of koshering meat is to draw out blood, which Jews are forbidden to eat. If fine crystals were used, they would be absorbed into the meat quickly and draw in fluids. By contrast, coarse salt stays on the surface longer, leeching out the blood.Much the same is true of pickling and dry curing. Salt preserves by drawing moisture out of living things, bacteria included, thereby killing them. That is why nothing lives in the Dead Sea. Also, coarse kosher salt is generally preferred by chefs because it is unadulterated. (Even iodized salt can add an unwanted chemical flavor to food.)Given the spiritual importance salt has to Jews, and its usefulness in preserving many foods, such as salmon, herring, whitefish, corned beef, pastrami, pickled tomatoes, cabbage, and cucumbers, perhaps it’s no wonder we have developed a special taste for this flavor enhancer. That is fortunate up to a point. Salt—sodium chloride—has properties that enhance physical well-being, but if overeaten, it can cause physical harm.Whether salt comes from the sea or a mine, it is essentially the same, though there are regional differences. “Nearly all solid salt deposits in the earth originally came from the sea,” explained Harold McGee, the Curious Cook columnist for The New York Times, a food scientist, and the author of On Food and Cooking. “Both mine and sea salts from different places will have different impurities that become insignificant when the salt is refined. Sea salt, derived from water that is allowed to evaporate in the sun, is not changed as to mineral composition. But it is in its biological composition, as living things such as fish, algae, and insects could be altered by heat and light.”Sea and mined salt provided me with two of the most unforgettable food-related sights I have seen in my travels. The first took place many years ago on Avery Island in Louisiana. Home of the McIlhenny family and the site of their Tabasco production, Avery Island sits on deep salt mines, through the years leased to various salt companies. The first step that gave me pause was having to sign a waiver saying, in effect, that if I was injured in any way—say buried in a mine collapse—I would not hold anyone responsible. Then, fitted with a hard hat and stiff protectors that clamped over the tips of my shoes, I rode down in a elevator to the mine where we boarded a Jeep and drove through winding passages under the soaring gray-white caves that reminded me of medieval Carcassone late on a snowy evening.Far less claustrophobic were the huge, flat, shallow pans of salt water evaporating in the sun along roads around Trapani on the Sicilian coast. Driving by and unaware of the sea salt processing, my husband and I first thought we were looking at huge wading pools filled with milk. A closer look made it plain what we were seeing and, since then, I have never opened a container of sea salt without a mental flashback to that glorious, first sight of salt-sea air.If an ingredient as commonplace as salt has so many diverse and complex aspects, it’s daunting to imagine what we might discover by delving into the whys and wherefores of pepper.Mimi Sheraton is a former restaurant critic for The New York Times and the author of several books including The Bialy Eaters.