NACRE
(NAY-kuhr)
A
pearly substance which lines the interior of many shells Common
clue: Mother-of-pearl;
Button stuff; Mollusk’s secretion; Bead material; Inlay
material; Abalone product; Iridescent shell layer; Shell's pearly
layer Crossword
puzzle frequency:
3 times a year
Nacre,
also known as mother of pearl, is an organic mixture of calcium
carbonate (CaCO3) in the form of platy crystals of aragonite and
conchiolin (a scleroprotein).
A
piece of nacre.
Nacre
is secreted by the ectodermic cells of the mantle tissue of
certain species of mollusk. In these mollusks, nacre is
continually deposited onto the inner surface of the animal's
shell (the iridescent nacreous layer, commonly known as mother of
pearl), both as a means to smooth the shell itself and as a
defense against parasitic organisms and damaging detritus.
The
iridescent inner layer is considered highly attractive by many
cultures and is often used in making jewelry or as inlays in wood
furniture and guitars.
When
a mollusk is invaded by a parasite or is irritated by a foreign
object that the animal cannot eject, a process known as
encystation entombs the offending entity in successive,
concentric layers of nacre. This process eventually forms what we
call pearls and continues for as long as the mollusk lives.
This
article is licensed under the GNU
Free Documentation License.
It uses material from the Wikipedia
article "Nacre".
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