Mother of pearl is the iridescent coating on the inside of some mollusc species which is composed of aragonite and calcite, a calcium carbonate polymorph.. Mother-of-pearl is also the primary material used in pearl nucleus manufacturing. Mother of pearl is used extensively as the nucleus in pearl cultivation. The shell of a mussel is cut into squares and then run through a process that rounds the pieces into beads. These beads are implanted into the oysters, which then secrete nacre upon the mother-of-pearl beads to form the cultured pearl. See nacre for a more complete description. Mother of pearl has two functions: it provides protection from predators, and provides shelter from the elements. The shielding of the mollusc from predators and parasites is a process called encystation. Nacre secreted by the mollusc traps and entombs invading parasites and foreign detritus, smoothing over the irritant and thus creating a pearl. | 
