Pearls, natural or cultured, are formed when a mollusk produces layers of nacre (pronounced NAY-kur) around some type of irritant inside its shell. In natural pearls, the irritant may be another organism from the water. In cultured pearls, a mother-of-pearl bead or a piece of tissue is inserted (by man) into the mollusk to start the process.
Freshwater Pearls are grown in freshwater lakes, rivers, and ponds, predominately in China. Although many are white and resemble the akoya cultured pearls in shape and size, they can also be produced in various shapes and in an array of pastel colors.
Many freshwater pearls don’t have a bead nucleus — only a piece of tissue — resulting in a pearl with thicker nacre than the akoya.