Mother of pearl is the nacreous, iridescent inner shell coating of pearl-producing mollusks. It is found all over the world, and is much more common than pearl, due to the fact that the mollusks that produce pearls will always have a shell, but will only rarely produce a pearl. Therefore it's possible to have much bigger sizes and a range of shapes. It comes most commonly in shades of ivory, pink, yellow and black. The abalone shell is the most prized with its peacock shades of purples, greens, blues and silvers.