MOTHER OF PEARL
Nacre, also known as the mother of pearl, is an organic-inorganic composite material produced by some mollusks as an inner shell layer, especially oysters and abalones. It is also the material of which pearls are composed. It is strong, resilient, and iridescent. Nacre appears iridescent because the thickness of the aragonite platelets is close to the wavelength of visible light. These structures interfere constructively and destructively with different wavelengths of light at different viewing angles, creating structural colors.
Mother of pearl has a very distinct multi-colored effect and a faint glow similar to other optically impressive moon-like gemstones. Non-nacre mollusk shells will look more like smooth and uniform porcelain.
The primary distinction between a shell that has a mother of pearl coating and a shell that does not is the iridescent quality. The mother of pearl set into jewelry is comprised of only a thin layer of sediment similar to a boulder opal. This thin layer can be carved or cut into cabochon-like shapes.
Like pearls, mother of pearl jewelry falls in the group referred to as organic jewelry—jewelry that originates from a living creature, plant, or organism.
Mother of pearl jewelry and pearl jewelry look very different in several ways. Mother of pearl jewelry can have much larger focal pieces than pearls since the substance takes up a whole shell's interior. Most mother of pearl is found in fine jewelry settings. Pearls are usually drilled and strung, rather than set. Pearls are thick, rounded gems that max out at a certain size. The mother of pearl is thin and slightly rounded.
The main commercial sources of mother of pearl have been the pearl oyster, freshwater pearl mussels, and to a lesser extent the abalone, popular for their sturdiness and beauty in the latter half of the 19th century.