✩Cultured Freshwater Pearls✩ Cultured Pearls are real pearls, they have been made by the mollusc. Once the nucleus (usually a mother-of-pearl bead) is inserted into the oyster or mussels, the pearl growing process is the same as that of a natural pearl. Their outer coatings (Nacre) are the same material as a natural pearl, and they take years to form in a mollusc's mantle. Nacre is formed from iridescent layers of crystallised calcium carbonate. It’s pretty much impossible to tell the difference between a natural and cultured pearl by just looking at its outer appearance. The only way to make absolute certain whether a pearl is natural or cultured is to perform an x-ray of the internal structure of the pearl.