Contrary to popular belief, pearls do not come from a grain of sand! Often, it is depicted that pearl formation is due to a grain of sand that has made its way into the oyster. This is hardly ever true. Formation is due to the intrusion of an outside substance that is organic in nature. The invasion can be the result of an injury or an intruding parasite, kind of like a splinter to the oyster. The oyster’s natural reaction is to cover up that irritant to protect itself. It covers the irritant with layers of the same nacre substance that is used to create the shell. Nacre, a calcium carbonate substance, is very similar to the main ingredient in antacid tablets like TUMS. This material is combined with special proteins to create nacre. As layer upon layer of nacre coats the irritant, a pearl is formed! Light that is reflected from these overlapping layers produces a pearl’s characteristic iridescent luster.
Cultured pearls are created with the same process as natural pearls, but are given a slight nudge by pearl harvesters. To create a cultured pearl, the harvester opens the oyster’s shell and makes a small incision in the mantle tissue. Small irritants can then be inserted under the mantle. In freshwater cultured pearls, cutting the mantle is enough to induce the nacre secretion that produces a pearl, whereas in saltwater cultured pearls, an irritant has to be inserted to induce nacre secretion.