https://wiki-pathfindersonline.designerthan.at/api.php?action=feedcontributions&feedformat=atom&user=4.7.181.181 2026-05-04T14:08:36Z User contributions MediaWiki 1.35.5 https://wiki-pathfindersonline.designerthan.at/index.php?title=AY_Honors/Shells_-_Advanced/Answer_Key&diff=17189 2005-01-13T01:51:37Z

<p>4.7.181.181: </p> <hr /> <div>[[image:nacre.jpg|thumb|A piece of nacre]]<br /> <br /> '''Nacre''', also known as '''mother of pearl''', is an organic mixture of [[calcium carbonate]] (CaCO&lt;sub&gt;3&lt;/sub&gt;) in the form of platy crystals of [[aragonite]] and [[conchiolin]] (a [[scleroprotein]]). <br /> <br /> Nacre is secreted by the [[ectoderm|ectodermic]] [[cell (biology)|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 [[parasite|parasitic organisms]] and damaging detritus.<br /> <br /> 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 [[pearl]]s and continues for as long as the mollusk lives.<br /> [http://www.pearlparadise.com/qualitypearls.html Pearl Cross Section Showing Nacre]<br /> <br /> {{Wiktionary}}</div>

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