Nacre
Nacre
Nacre (/ˈneɪkər/ NAY-kər), also known as mother of pearl, is an organic-inorganic composite material produced by some molluscs as an inner shell layer. It is also the material that makes up the outer coating of pearls. It is strong, resilient, and iridescent.
Etymology
The word nacre comes from the French nacre, which in turn originates from the Arabic naqqarah. In English, the term nacre is mostly used in the context of shellfish and pearls.
Production
Nacre is secreted by the epithelial cells of the mantle tissue of certain species of mollusk. In the case of pearls, a foreign substance becomes trapped inside the mollusk. In response, the mollusk's defense mechanism triggers the secretion of nacre to coat the irritant. This process is repeated many times, creating a pearl.
Structure
Nacre is composed of hexagonal platelets of aragonite (a form of calcium carbonate) 10–20 µm wide and 0.5 µm thick arranged in a continuous parallel lamina. These layers are separated by sheets of organic matrix composed of elastic biopolymers (such as chitin, lustrin and silk-like proteins). This mixture of brittle platelets and the thin layers of elastic biopolymers makes the material strong and resilient.
Uses
Nacre is used in a variety of applications, from jewelry to musical instruments to buttons. It is also studied in the fields of materials science and biotechnology for its unique properties.
Related Terms
- Pearl: A hard, roundish object produced within the soft tissue of a living, shelled mollusk.
- Mollusk: A large phylum of invertebrate animals, many of which produce shells lined with nacre.
- Aragonite: A carbonate mineral, one of the two common, naturally occurring crystal forms of calcium carbonate.
- Mantle (mollusk): A significant part of the anatomy of mollusks; it is the dorsal body wall which covers the visceral mass and usually protrudes in the form of flaps well beyond the visceral mass itself.
External links
- Medical encyclopedia article on Nacre
- Wikipedia's article - Nacre
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