Abstract: Abalone shell, as a kind of organic gemstone material, shows the beautiful and unique iridescence. Abalone can be used to produce blister pearl. The gemmological properties of abalone shell are tested systematically, and the structures of the nacre layers of pearls, abalone shells and nautilus shells are observed with the help of scanning electron microscope. Based on the theory of modern optics, the origin of the unique iridescence of abalone shell is analyzed.