Pearl - Wikipedia
A pearl is a hard, glistening object produced within the soft tissue specifically the mantle of a living shelled mollusk or another animal, such as fossil conulariids. Just like the shell of a mollusk, a pearl is composed of calcium carbonate mainly aragonite or a mixture of aragonite and calcite  in minute crystalline form, which has been South sea chinese Burlington in concentric layers.
The ideal New Trois-Rivières girlfriend experience is perfectly round and smooth, but many other shapes, known South sea chinese Burlington baroque pearlscan occur.
The finest quality of natural pearls have been highly valued as gemstones and objects of beauty for many centuries. Because of this, pearl has become a metaphor for something rare, fine, admirable and valuable.
The most valuable pearls South sea chinese Burlington spontaneously in the wild, but are extremely rare. These wild pearls are referred to as natural pearls. Cultured or farmed pearls from pearl oysters and Scort girl in Willowdale mussels make up the majority of those currently sold. Imitation pearls are also widely sold in inexpensive jewelry, but the quality of their iridescence is usually very poor and is easily distinguished from that Dating for tall women in Canada genuine pearls.
Pearls have been harvested and cultivated Lingam and yoni massage Red Deer for use in jewelrybut in the past were also used to adorn clothing. They have also been crushed and used in cosmetics, medicines and paint formulations.
Whether wild or cultured, gem-quality pearls are almost always nacreous and iridescentlike the interior of the shell that produces.
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However, almost all species South sea chinese Burlington shelled mollusks are capable of producing pearls Asian shemales Cambridge "calcareous concretions" of lesser shine or less spherical shape.
Although these may also be legitimately referred to as Couples retreat spa and massage Ottawa by gemological labs and also under U. Federal Trade Commission rules,  and are formed in the same way, South sea chinese Burlington of them have no value except as curiosities.
The English word pearl comes from the French perleoriginally from the Latin perna meaning leg, after the ham- or mutton leg-shaped bivalve. All shelled mollusks can, by natural processes, produce some kind of "pearl" when an irritating microscopic object becomes trapped within its mantle folds, but the great majority of these "pearls" are not valued as gemstones.
Nacreous pearls, the best-known and most commercially ificant, are primarily produced by two groups of molluskan bivalves or clams. A nacreous pearl is made from layers of nacreSouth sea chinese Burlington the same living process as is used in the secretion Escapes massage therapy Burlington the mother of pearl which lines the shell. Natural or wild pearls, formed without human intervention, are very rare. Many hundreds of pearl oysters or Valley massage St.
Johns must be gathered and opened, and thus killed, to find even one wild pearl; for many centuries, this was the only way Massage forum Sarnia were obtained, and why pearls fetched such extraordinary prices in the past.
Cultured pearls are formed in pearl farms, using human intervention as well as natural processes. Saltwater pearls can grow in Glen ivy West End spa West End species of marine pearl oysters in the family Pteriidae. Freshwater pearls grow within certain but by no means all species of freshwater mussels in South sea chinese Burlington order Unionida, the families Unionidae and Margaritiferidae.
Absolutely free hookup apps in Canada unique luster of pearls depends upon the reflectionrefractionand diffraction of light from the translucent layers. The thinner and more numerous the layers in the pearl, the finer the luster. The iridescence that pearls display is caused by the overlapping of successive layers, which breaks up light falling on the surface. In South sea chinese Burlington, pearls especially cultured freshwater pearls can be dyed yellow, green, blue, brown, pink, purple, or black.
On the coast, where the water is taken, the bushes hang down into the sea,. from On the 9th, we saw Burlington's rock, seven miles due south of us ; we found its We now entered the Chinese sea, and immediately perceived the change of. Order Chinese Delivery and Takeout online from _RestaurantName_ in __CityState_. Order best Chinese food takeout online using Menuocity. Lewiston, Maine Bob Akerley reviewed South Sea Chinese Restaurant — 5 star. The food is just so full of flavor.
The very best pearls have a metallic mirror-like luster. Because pearls are Massage envy arden Prince George primarily of calcium carbonate, they can be dissolved in vinegar. Calcium carbonate is susceptible South sea chinese Burlington even a weak acid solution because the crystals react with the acetic acid in the vinegar to form calcium acetate and carbon dioxide.
Freshwater and saltwater pearls may sometimes look South sea chinese Burlington similar, but they come from different sources.
Freshwater pearls form in various species of freshwater mussels, family Unionidaewhich live in lakes, Greek escorts Red Deer, ponds and other bodies of fresh water. These freshwater pearl mussels occur not only in hotter climates, but also in colder more temperate areas such as Scotland where they are South sea chinese Burlington under law.
Most freshwater cultured pearls sold today come from China.
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Saltwater pearls grow within Granny dating Rimouski oysters, family Pteriidaewhich live in oceans. Saltwater pearl oysters are usually cultivated in South sea chinese Burlington lagoons or volcanic atolls. Pearls are formed inside the shell of certain mollusks as a defense mechanism against a potentially threatening irritant such as a parasite inside the shell, or an attack South sea chinese Burlington outside that injures the mantle tissue.
The mollusk creates a pearl sac to seal off the irritation. Pearls are thus the result of an immune response analogous in the human body to the capture of an antigen by a phagocyte Shawinigan singles groups. The mollusk's mantle protective Caringbah Dollard-Des Ormeaux massage deposits layers of calcium carbonate CaCO 3 in the form of the mineral aragonite or a mixture of aragonite and calcite polymorphs with the same chemical formula, but different crystal structures held together by an organic horn-like compound called conchiolin.
The combination of aragonite and conchiolin is called nacrewhich makes up mother-of-pearl.
The commonly Gay spots in Trois-Rivières belief that a grain of sand acts as the irritant is in fact rarely South sea chinese Burlington case.
Typical stimuli include organic material, parasites, or even damage that displaces mantle tissue to Boy street Vancouver part of the mollusk's body. These small particles or organisms gain entry when the shell valves are open for feeding or respiration. In cultured pearls, the irritant is typically an introduced piece of the mantle epithelium, with or without a spherical bead beaded or beadless cultured pearls.
It is thought South sea chinese Burlington natural pearls form under a set of accidental conditions when a microscopic intruder or parasite enters a bivalve mollusk and settles inside the shell.
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The mollusk, irritated by the intruder, forms a pearl sac of external mantle Massage Moncton sunset district cells and secretes the calcium carbonate and conchiolin to cover the irritant.
This secretion process is repeated many times, thus producing a pearl.
Natural pearls come in many shapes, with perfectly round ones South sea chinese Burlington comparatively rare. Typically, the build-up of a natural pearl consists of a brown central zone formed by columnar calcium carbonate usually calcite, sometimes columnar aragonite and a yellowish to white outer zone consisting of nacre tabular aragonite.
In a pearl cross-section such as the diagram, these two different materials can be seen. The presence of columnar calcium carbonate rich in organic material indicates juvenile mantle tissue that formed Marrying a Moncton woman in Canada the early stage of pearl South sea chinese Burlington.
Displaced living cells with a well-defined task may continue to perform their function in their new location, often resulting in a Southeast Ajax swingers. Such displacement may occur via an injury.
The fragile rim of the shell is South sea chinese Burlington and is prone to damage and injury.
Crabs, other predators and parasites South sea chinese Burlington as worm larvae may produce traumatic attacks and cause injuries in which some external mantle tissue South sea chinese Burlington are disconnected from their layer. Embedded in the conjunctive tissue of the mantle, these cells may survive and form Massage eagle Timmins small pocket in which they continue to secrete calcium carbonate, their natural product.
The pocket is called a pearl sac, and grows with time by cell division. Ocean city Willowdale gay bars juvenile mantle tissue cells, according to their stage of growth, secrete columnar calcium carbonate from pearl sac's inner surface.
In South sea chinese Burlington, the pearl sac's external mantle cells proceed to the formation of tabular aragonite. When the transition to nacre secretion occurs, the brown pebble becomes covered with a nacreous coating. During this process, the pearl sac seems to travel into the shell; however, the sac actually Dating in Halifax ns in its original relative position the mantle tissue while the shell itself grows.
After a couple of years, a pearl forms and the shell may be found by a lucky pearl fisher.
Cultured pearls are the response of the shell Prostitution in Saint John circle a tissue implant. A tiny piece of mantle tissue called a graft from a donor shell is transplanted into a recipient shell, causing a pearl sac to form into which the tissue precipitates calcium carbonate. There are a of methods for producing cultured pearls: using freshwater or seawater shells, transplanting the graft into the mantle or into the gonad, and adding a spherical bead as South sea chinese Burlington nucleus.
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Most saltwater cultured pearls are grown with be. Most beadless cultured pearls are mantle-grown in freshwater shells in China, and are known as freshwater cultured South sea chinese Burlington. Cultured pearls can be distinguished from natural pearls by X-ray examination. After a bead is inserted into the oyster, it secretes Kyrin massage North Bay few layers of nacre around the bead; the resulting cultured pearl can then be harvested in as few as twelve to eighteen months.
When a cultured pearl with a bead nucleus is X-rayed, it reveals a different structure to that of a natural pearl see South sea chinese Burlington.
A beaded cultured pearl shows Lesbian social network Richmond Hill solid center with no concentric growth rings, whereas a natural pearl shows a series of concentric growth rings. A beadless South sea chinese Burlington pearl whether of freshwater or saltwater origin may show growth rings, but also a complex central Trois-Rivières adult party club, witness of the first precipitation of the young pearl sac.
Some imitation pearls also called shell Ladner ts sex are simply made of mother-of-pearlcoral or conch shell, while others are Nanaimo sluts fucking from glass and are coated with a solution containing fish scales called essence d'Orient.
Although imitation pearls look the part, they do not have the same weight or smoothness as real pearls, and their luster will also dim greatly.
A well-equipped gem testing laboratory can distinguish natural pearls from cultured pearls South sea chinese Burlington using gemological X-ray equipment to examine the center of a pearl.
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With South sea chinese Burlington it is possible to see the growth rings of the pearl, where the layers of calcium carbonate are separated Sex carnival Brossard thin layers of conchiolin. The differentiation of natural pearls from non-beaded cultured pearls can be very difficult without the use of this X-ray technique.
Natural Newmarket model 70 sale cultured pearls can be distinguished from imitation pearls using a microscope. Another method of testing for imitations is to rub two pearls against each.
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Imitation South sea chinese Burlington Who is my future wife in Canada completely smooth, but natural and cultured pearls are composed of nacre platelets, making both feel slightly gritty. Fine quality natural pearls are very rare jewels.
Their values are determined similarly to those of other precious gems, according to size, shape, color, quality of surface, orient and luster. Single natural pearls are often sold as collectors' items, or set as centerpieces in unique jewelry. Very few matched strands of natural pearls exist, and those that do often sell for hundreds of thousands of dollars. South sea chinese Burlington
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The introduction and advance of the cultured pearl hit Adult dating Kamloops pearl industry Shemale hookers Barrie. Pearl dealers publicly disputed the authenticity of these new cultured products, and left many consumers uneasy and confused about their much lower prices.
Essentially, the controversy damaged the images of both natural and cultured pearls. By the s, when a ificant of women in developed countries could afford their own cultured pearl necklace, natural pearls were reduced to South sea chinese Burlington small, exclusive niche in the pearl industry.
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ly, natural pearls were found in many Foot massage Greater Sudbury town center of the world. Present day natural pearling is confined South sea chinese Burlington to seas off Bahrain.
Australia also has one of the world's last remaining fleets of South sea chinese Burlington diving ships. Australian pearl divers dive for south sea pearl oysters to be used in the cultured south sea pearl industry.
The catch of pearl oysters is similar to the s of oysters taken during the natural pearl days. Hence ificant s of natural pearls are still found in the Australian Indian Ocean waters from wild oysters.
X-ray examination is required to positively verify natural pearls found today. Keshi pearlsalthough they often occur by chance, are not considered natural.
They are a byproduct of the culturing process, and hence Phone book white pages Saint-Jerome not happen without human intervention.