This type of salt comes in about as many different varieties as coffee and from about as many different places around the world. The "gourmet" versions can be rather expensive. In general, the types sold in grocery stores, natural food markets and gourmet shops have been purified enough to use in food. It's not very suitable for food preservation, though, because the mineral content it contains (other than the Sodium chloride) may cause discoloration of the food, use canning salt instead.