Luster is a phenomenon used to describe the diffraction of light from the Nacre'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 Nacre crystals are uniform and the layers thin and numerous, letting the light diffract uninterrupted. Nacre that has a bright mirror-like finish commands higher prices, whereas cheaper quality Nacre has a low luster appearing dull with a flat finish. The quality of the Nacre's 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.

If the waters reach a high temperature of 30 degrees Celsius, as in the Pacific, the mollusks metabolism is increased and they grow faster secreting more nacre than a mollusk who lives in colder waters. However the layers of nacre are thick and not as translucent and the crystal structure is not perfect resulting in a duller, less lustrous Mother-of-Pearl. Therefore Mother of Pearl is rarely harvested in the hotter summer months.

However, when temperatures go down to 16 degrees Celsius the mollusks metabolism is low, and produces nacre at a slower rate. These nacre layers are thinner and the crystal structure more even resulting in an increased translucency and better luster.