Mother of pearl, also called nacre, is an iridescent layer of material which forms the shell lining of many mollusks. Pearl oysters and abalone are both sources of mother of pearl, which is widely used as an inlay in jewelry, furniture, and musical instruments. Mother of pearl comes in several natural colors, and is often bleached and dyed for decorative use. The dye retains the shimmering layers which make mother of pearl so sought after.

Two substances actually combine to create mother of pearl. The first is plates of aragonite, a material which is secreted by the mollusk. Aragonite contains calcium carbonate and conchiolin, a natural protein. Alone, the plates are very hard, but also very brittle. As a result, the organism also secretes organic material similar to silk to layer between the plates. The result is a strong, flexible material which can withstand hard use.

Mollusks create mother of pearl to protect themselves. In addition to forming part of the shell, mother of pearl also insulates mollusks from bacterial infection, and reduces irritation from organic material which drifts into the shell. Irregularities often form in the mother of pearl as a result of irritation. If the irritation is extensive enough, the mollusk will form a large bump, prized in the human world as a pearl. Only the outer layer of the pearl is covered in mother of pearl, which is why it is important to care well for pearls so that they do not crack, revealing the source of irritation beneath.

The pearly lining of mollusk shells has long been noted by people living near the ocean. Many early cultures used mother of pearl extensively in jewelry, and it came to be highly prized. Although the popularity of mother of pearl has waned, many modern cultures can still appreciate the beauty of mother of pearl jewelry, and elaborate furniture inlays. Some homes integrate mother of pearl into tiles and other fixtures, although it is no longer used as extensively as it once was.

Like other substances found in nature, mother of pearl develops irregularities as it forms. As a result, every piece of mother of pearl jewelry or inlay is slightly different. Sometimes these differences are appreciated, and the artisan works with the unusual features of a specific piece to highlight them. These irregularities may also appear in cheaper jewelry which is not as meticulously constructed. Use mild soaps and water on mother of pearl to clean it, and avoid storing it with jewelry which may scratch it, wearing away the luminous layers of nacre.