All waterborne organisms living within shells, called mollusks, have the ability to produce Mother of Pearl. However, very few mollusks with single shells, called gastropods, do so. High quality Mother of Pearl is produced by the mollusk family called bivalves, which have two-part shells. The popular belief that Mother of Pearl and Pearl are formed as a result of a grain of sand entering a mollusks shell is false. Both Mother of Pearl (Nacre) and Pearl form when an organic irritant such as a parasite or food-particle become trapped within the mollusk, or if the mollusk is injured in some way.

Luster is a phenomenon used to describe the diffraction of light from the Mother of Pearl’s surface brilliance, together with its inner, deeper radiance. The radiance is the light that is reflected, not just off the surface, but also off the internal layers. A better luster is achieved if the Mother of Pearl crystals are uniform and the layers thin and numerous, letting the light diffract uninterrupted. Mother of Pearl that has a bright mirror like finish commands higher prices, whereas cheaper quality has a low luster appearing dull with a flat finish. The quality of the Mother of Pearl luster is also dependant on external factors. Mother of Pearl is the creation of a living organism and environmental factors play a crucial role in its formation. Mother of Pearl producing mollusks cannot regulate their body temperature, and so are susceptible to changes in external conditions.