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Topic: Nacre

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Animal shell

Mantle (mollusc)

Pearl

Baroque pearl

Ammolite

Less than

Ectoderm

Pearlite

Crucible technique

Martensite

Aperture (mollusc)

Calcite

Aragonite

Operculum

Phase (matter)

	Nacre - Wikipedia, the free encyclopedia
		The iridescent appearance of the nacre is due to the fact that the thickness of the aragonite platelets are about 0.5 micron, which is comparable to the wavelength of visible light.
		Nacre is secreted by the epithelial 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.
	en.wikipedia.org /wiki/Nacre (651 words)

	Pearls Nacre At Pearl-Guide.com
		Nacre, also known as mother-of-pearl, is the basic substance which is secreted by oysters and mollusks to form the inside of their shells.
		Nacre is composed of layers of calcium carbonate (in a crystalline form) and conchiolin (an organic protein substance which provides bonding).
		The specific luster, iridescence, and coloring of nacre -- and, therefore, of any pearl which it forms -- depends on the number and thickness of the various layers, as well as on whether or not the layers overlap one another.
	www.pearl-guide.com /nacre.shtml (127 words)

	PEARL main
		earls are formed in molluskan bivalves (clams, oysters, mussels) of several species by the secretion of a substance known as nacre around an irritant in the outer tissue (mantle) of the organism, or between the outer tissue and the shell.
		Nacre is also the substance that coats the inner surface of bivalve shells.
		The aragonite within the nacre is present as slender crystals that are preferentially oriented perpendicular to the surface being deposited.
	www.geo.utexas.edu /courses/347k/redesign/gem_notes/pearl/pearl_main.htm (3105 words)

	The Sol-Gel Gateway
		Also called nacre, the gleaming, white material is renowned in scientific circles for its strong, yet flexible, properties.
		In the artificial nacre, platelets of a negatively-charged clay called montmorillonite provide the bricks while fibers of a positively-charged polyelectrolyte called poly(diallydimethylammonium) chloride (PDDA) serve as the mortar.
		Because of the artificial nacre's potential for high-strength, protective coatings such as body armor and biocompatible substrates for growing human tissue or organs, Kotov and his colleagues are working with a company to further develop the material and techniques.
	www.solgel.com /articles/aug03/Seashell.asp (506 words)

	Pearls
		Nearly all pearls on the market are "cultured" pearls, where a relatively large bead is placed in the body of the host oyster (cultured saltwater pearls) or a small piece of tissue from a fresh water mussel is inserted into another mussel to stimulate pearl formation (freshwater pearls).
		Some pearls with thin nacre have high luster and are free of blemishes, because they have been left in the water for only a brief time.
		Nacre Thickness: Nacre is the single most important factor in the beauty and durability of the pearl Some pearls with thin nacre have high luster and are free of blemishes, because they have been left in the water for only a brief time.
	www.jewelry-appraisal.com /330_Perls.htm (1504 words)

	Welcome to Tahiti - The Black Pearl (Site not responding. Last check: 2007-10-08)
		Another very beautiful nacre, with a wing-like shape to its shell, known for the fabrication of "mabe", is the Pteria penguin, common in Asian seas, particularly in the waters around Phuket in Thailand.
		When this happens the nacre, in a defensive reaction, begins secreting a thin coat of aragonite, a material that is the same as that of its shell, around the intruder.
		It is a fact that, throughout their history, the nacres have always interested man. This enthusiasm was not for the pearl they might enclose (one pearl for 15,000 nacres, it was said) but for the beauty of the shells.
	www.pacific-promotion.com.fr /PerleEN.html (8683 words)

	What Are Pearls? \| American Museum of Natural History
		The crystalline structure of nacre reflects light in a unique way, giving so-called nacreous pearls their high luster.
		In contrast, some pearls are not nacreous and instead have a low-luster, porcelainlike surface.
		The needlelike crystals of aragonite in these pearls are arranged perpendicularly or at an angle to the surface of the pearl.
	www.amnh.org /exhibitions/pearls/what/form.html (192 words)

	APS - 2005 APS March Meeting - Event - Fracture Toughness of Nacre (Site not responding. Last check: 2007-10-08)
		Nacre exhibits phenomenal fracture strength and toughness properties despite the brittle nature of its constituents.
		This is surprising because it is a ceramic composite made up of about 95\% brittle inorganic phase (aragonite mineral) and only a few percent of the soft organic material, and polymer-matrix composites with such high levels of ceramic fillers do not possess these exceptional combinations of stiffness, fracture strength and toughness.
		The discrete lattice topology of the proposed model is based on nacre's unique brick and mortar microarchitecture, and the mechanical behavior of each of the bonds in the discrete lattice model is governed by the characteristic modular damage evolution of the organic matrix that includes the mineral bridges between the aragonite platelets.
	meetings.aps.org /Meeting/MAR05/Event/23873 (216 words)

	nacre on Encyclopedia.com (Site not responding. Last check: 2007-10-08)
		Inorganic overgrowth of aragonite on molluscan nacre examined by atomic force microscopy.
		Un pectoral en nacre, argent et perle, originaire des Philippines La collection de 252 ornements et bijoux rituels de l'In.
		Un étudiant en seconde année à l'Institut de Design planche sur son projet Les aimants remplacent les boutons de nacre, le.
	www.encyclopedia.com /html/X/X-nacre.asp (234 words)

	Engineers try to match nature's hard case \| The San Diego Union-Tribune
		Nacre is the iridescent material thickly lining the shells of abalone, shellfish native to the Pacific and resembling flattened snails up to a foot wide and prized for their tasty flesh.
		Forms of nacre also strengthen the shells of many other mollusks, bivalves and cephalopods like the chambered nautilus.
		Pearls are pathological growths of nacre formed by oysters irritated by grit wedged between their living tissue and the shells they are making.
	www.signonsandiego.com /uniontrib/20050330/news_1c30shells.html (808 words)

	Jed's Page (Site not responding. Last check: 2007-10-08)
		This nacre is composed of a mixture of the mineral aragonite and an organic horn substance called conchiolin.
		While nacre thickness plays a large part in the value and beauty of a pearl, nacre quality is of equal importance.
		The nacre used by this mollusk is highly iridescent and displays a vivid array of colors.
	www.emporia.edu /earthsci/amber/go340/students/archuleta/index (2289 words)

	TREASURES FROM THE OCEAN
		Nacre consistes mainly of aragonite, a mineral crystal from the calcium carbonate family.
		The purpose of nacre is to make the inside of the shell smooth so that it doesn't irritate the soft body of the mollusk.
		A pearl is simply an abnormal growth of nacre.
	www.suite101.com /article.cfm/gems_and_minerals/25998 (415 words)

	Current Online \| Tuning Out Education, Part 3 (Site not responding. Last check: 2007-10-08)
		NACRE's coziness with the commercials was advertised by the fact that it shared one of its principal committees with the National Association of Broadcasters.[59]
		It might be argued, in fact, that NACRE belonged to one wing of the progressive movement — the Eastern wing, long at odds with Midwestern protest, that proposed the efficiency and generosity of big business as the answer to the nation's problems.
		NACRE was made in the mold of an earlier vehicle of progressive Cooperation, the National Civic Federation.
	www.current.org /coop/coop3.html (3069 words)

	Identification of Alabama Freshwater Mussels
		Nacre is white, but may contain discolored areas.
		Nacre is white, but may contain colored areas.
		Nacre is white but may be pink in Alabama and Tombigbee Rivers.
	www.dcnr.state.al.us /education/generalinfo/mussels/id.cfm (913 words)

	june-02-8
		A pearl is a “nacreous, organic gem formed in the body of a mollusk”.
		The nacre also coats the inside of the mollusk’s shell and is known as “mother-of-pearl”.
		Luster depends on the thickness of the nacre and the arrangement of the layers of nacre.
	www.discoveret.org /kgms/june-02/june02-8.htm (1618 words)

	[No title] (Site not responding. Last check: 2007-10-08)
		South sea pearls are graded by shape, size, colour, lustre, nacre thickness and surface condition.
		Lustre is the soul of the pearl, and refers to the crystallized nacre's reflection of light.
		The pearl is formed inside the soft body of the oyster and must move freely so nacre can evenly and uniformly coat the nucleus.
	www.pinctada.com /html/htm_wisdom.html (333 words)

	NOVA Online \| The Perfect Pearl \| The Culture of Freshwater Pearls
		Most cultured freshwater pearls are composed entirely of nacre, just like their natural freshwater and natural saltwater counterparts.
		The Chinese are nucleating mussels with their own tissue-cultured freshwater pearls, which result in all-nacre round or almost round pearls.
		After one experimenter used small off-round naturals as nuclei, he sent the resulting freshwater pearls to a gem lab and received a report identifying them as "naturals." If pearl farmers can grow cultured pearls that test as naturals, the market may be in for a wild ride.
	www.pbs.org /wgbh/nova/pearl/freshwater.html (1111 words)

	Pearls - Gems from the Deep
		This nacre builds up in layers around the offending object, and the lustrous result of the oyster's irritation is a pearl.
		Nacre - This refers to the quantity of nacre that has grown on the pearl.
		Thin layers of nacre are subject to poor uniformity in the short term and poor durability in the long term.
	www.gomegapath.net /jewelry/allaboutpearls (1350 words)

	Current Online \| Tuning Out Education, Part 4 (Site not responding. Last check: 2007-10-08)
		The mixed ancestry of NACRE was aptly mirrored in the organization's director, Levering Tyson.
		NACRE made its debut in a style that highlighted both its blue-chip connections and the networks' eagerness to publicize their generosity.
		NACRE's Committee on Psychology dejectedly agreed that future talks needed to be done by an expert with ''radio personality.'' The Economics Committee offered an equally glum appraisal of its broadcasting, despite its efforts to enliven its programs with dialogue formats.
	www.current.org /coop/coop4.html (2744 words)

	LUSTER: PEARL'S PINNACLE
		For the layman and jewelry novice, the luster of a pearl can best be described as a combination of a high, reflective sheen on the surface of a pearl combined with an almost three-dimensional glow that seems to emanate from within the heart of a pearl.
		Though the intensity of a pearl's luster can be an indicator of nacre thickness, and thus determine the durability of a pearl, this correlation is not always true.
		Sometimes when nacre crystals are in a very loose formation they do not have the ability to refract and reflect light in the same manner as a pearl with very tightly packed nacre layers.
	www.professionaljeweler.com /archives/articles/1998/mar98/0398fpr1.html (619 words)

	Any issues Call 612-616-9843 Pearl ... (Site not responding. Last check: 2007-10-08)
		It took approximately 2 years of layer after layer of nacre (pearl material) to form this cross.
		There are formed naturally...by chance, there isnt a wire or other "form" inside for nacre material to form a Cross.
		Only one half of 1% of these are harvested resembling the symbolic focus of our faith...the Cross.
	king-cart.com /cgi-bin/cart.cgi?store=Prospecting&product=Pearl+... (5219 words)

	UK nacre websites UK
		Nacre - généralement des produits suivants : a) Nacre dorée Une coloration crème qui s'étendde 1 mm et 2 mm environ.
		The formationThe mantle covers the irritant with layers of the same nacre substance that is used to create the shell.
		This irritates it and it coats it with nacre, the substance real pearls are made of.
	www.splut.co.uk /sub/n/nacre.html (761 words)

	Jewelry Pearls View topic - pearl nacre (Site not responding. Last check: 2007-10-08)
		One way to tell the thickness of the nacre is to examine the drill hole with a 10X loupe to where you actually see depth of the nacre.
		With a pearl of medium to thick nacre, the bead will not be visible through the nacre.
		The harvest at 45 Latitude will most definitely be thiner nacre but because the nacre is produced slower far less surface blemishes and imprefections thus smoother surface thus greater luster.
	www.jewelry-pearls.com /ntopic60.html (790 words)

	The New York Times > Science > Material as Tough as Steel? The Abalone Fits the Bill
		Kenneth Vecchio holds abalone shells, which are thickly lined with the iridescent material nacre.
		Dr. Vecchio credits his new "metallic-intermetallic laminate" composite to the example provided by abalone nacre, or mother of pearl.
		Kotov said he expected it to interest makers of military aircraft: it is strong and does not reflect radar.
	www.nytimes.com /2005/03/22/science/22abal.html?ex=1269147600&en=c1108fb39b740af5&ei=5090&partner=rssuserland (964 words)

	[Jewelry making - Article 00134] - [Orchid] Pearls - a treasure from the ocean
		Because the nacre is deposited in overlapping layers, it doesn't reflect light evenly.
		The quality of the luster depends on how many layers of nacre have been deposited, which depends on how long the pearl has been in the mollusk.
		The more layers of nacre, the greater the luster of the pearl.
	www.ganoksin.com /orchid/archive/200111/msg00134.htm (1127 words)

	Nanostructured artificial nacre
		The ordered brick-and-mortar arrangement of organic and inorganic layers is believed to be the most essential strength- and toughness-determining structural feature of nacre.
		The macromolecular folding effect reveals itself in the unique saw-tooth pattern of differential stretching curves attributed to the gradual breakage of ionic crosslinks in polyelectrolyte chains.
		The tensile strength of the prepared multilayers approached that of nacre, whereas their ultimate Young modulus was similar to that of lamellar bones.
	www.nature.com /cgi-taf/DynaPage.taf?file=/nmat/journal/v2/n6/abs/nmat906.html&dynoptions=doi1114644021 (197 words)

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