French sea salt by John Spottiswood.

French sea salt = sel marin This expensive French salt comes from sea water that's pooled into basins and then evaporated. Unlike most American sea salts, it's unrefined, so it retains more of the minerals that naturally occur in seawater. There are several varieties. Gray salt = grey salt = sel gris gets its color from the clay lining the basins. Lafleur de sel (the flower of the salt) is whiter, but has a similar flavor.That trendy gourmets are willing to shell out $5 for a small packet of French sea salt drives chemists crazy, since almost all of it is just plain salt, sodium chloride, NaCl. Salt aficionados counter that French sea salt has a much softer and fresher flavor than ordinary table salt, and that the difference is worth it.These salts comes either coarsely or finely ground. Since salt is an inorganic mineral, there's no point in grinding large crystals with a salt mill so they'll be "fresh." Salt, unlike pepper and spices, never goes stale. It's best to use these salts after the food is cooked, or their subtleties will be lost.