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Thanks to its rarity and beauty, the pearl is as prized as a precious gem, but it is not In , a remarkable natural creation named the "Great Southern Cross" was The materials for cultured pearls sound simple; they consist of an oyster or .
Table of contents
- Cultured Pearls
- Taking care of Pearls
- What are the Best Pearls to Buy?
- Your Cookie Preferences
- The Originator Of Cultured Pearls
The most valuable pearls occur 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 freshwater 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 of genuine pearls.
Pearls have been harvested and cultivated primarily for use in jewelry , but in the past were also used to adorn clothing.
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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 iridescent , like the interior of the shell that produces them. However, almost all species of shelled mollusks are capable of producing pearls technically "calcareous concretions" of lesser shine or less spherical shape.
Taking care of Pearls
Although these may also be legitimately referred to as "pearls" by gemological labs and also under U. Federal Trade Commission rules,  and are formed in the same way, most of them have no value except as curiosities. The English word pearl comes from the French perle , originally 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 significant, are primarily produced by two groups of molluskan bivalves or clams. A nacreous pearl is made from layers of nacre , by the same living process as is used in the secretion of 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 mussels must be gathered and opened, and thus killed, to find even one wild pearl; for many centuries, this was the only way pearls 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 several species of marine pearl oysters in the family Pteriidae. Freshwater pearls grow within certain but by no means all species of freshwater mussels in the order Unionida, the families Unionidae and Margaritiferidae. The unique luster of pearls depends upon the reflection , refraction , and 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 addition, pearls especially cultured freshwater pearls can be dyed yellow, green, blue, brown, pink, purple, or black. The very best pearls have a metallic mirror-like luster. Because pearls are made primarily of calcium carbonate, they can be dissolved in vinegar. Calcium carbonate is susceptible to 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 quite similar, but they come from different sources.
Freshwater pearls form in various species of freshwater mussels, family Unionidae , which live in lakes, rivers, 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 protected under law.
Most freshwater cultured pearls sold today come from China. Saltwater pearls grow within pearl oysters, family Pteriidae , which live in oceans. Saltwater pearl oysters are usually cultivated in protected 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 from 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 phagocytosis. The mollusk's mantle protective membrane 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 nacre , which makes up mother-of-pearl. The commonly held belief that a grain of sand acts as the irritant is in fact rarely the case.
Typical stimuli include organic material, parasites, or even damage that displaces mantle tissue to another 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 that natural pearls form under a set of accidental conditions when a microscopic intruder or parasite enters a bivalve mollusk and settles inside the shell. The mollusk, irritated by the intruder, forms a pearl sac of external mantle tissue 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 being 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 during the early stage of pearl development.
Displaced living cells with a well-defined task may continue to perform their function in their new location, often resulting in a cyst. Such displacement may occur via an injury. The fragile rim of the shell is exposed and is prone to damage and injury. Crabs, other predators and parasites such as worm larvae may produce traumatic attacks and cause injuries in which some external mantle tissue cells are disconnected from their layer. Embedded in the conjunctive tissue of the mantle, these cells may survive and form a 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. The juvenile mantle tissue cells, according to their stage of growth, secrete columnar calcium carbonate from pearl sac's inner surface. In time, 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 stays 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 to 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 number 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 a nucleus.
Most saltwater cultured pearls are grown with beads. Trade names of cultured pearls are Akoya, white or golden South sea, and black Tahitian. Most beadless cultured pearls are mantle-grown in freshwater shells in China, and are known as freshwater cultured pearls. Cultured pearls can be distinguished from natural pearls by X-ray examination. After a bead is inserted into the oyster, it secretes a 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 diagram.
A beaded cultured pearl shows a solid center with no concentric growth rings, whereas a natural pearl shows a series of concentric growth rings. A beadless cultured pearl whether of freshwater or saltwater origin may show growth rings, but also a complex central cavity, witness of the first precipitation of the young pearl sac.
Some imitation pearls also called shell pearls are simply made of mother-of-pearl , coral or conch shell, while others are made 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 by using gemological X-ray equipment to examine the center of a pearl.
With X-rays it is possible to see the growth rings of the pearl, where the layers of calcium carbonate are separated by 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 and cultured pearls can be distinguished from imitation pearls using a microscope. Another method of testing for imitations is to rub two pearls against each other.
Imitation pearls are 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. The introduction and advance of the cultured pearl hit the pearl industry hard. 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 significant number of women in developed countries could afford their own cultured pearl necklace, natural pearls were reduced to a small, exclusive niche in the pearl industry. Previously, natural pearls were found in many parts of the world.
Present day natural pearling is confined mostly to seas off Bahrain. Australia also has one of the world's last remaining fleets of pearl 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 numbers of oysters taken during the natural pearl days. Hence significant numbers 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 pearls , although they often occur by chance, are not considered natural. They are a byproduct of the culturing process, and hence do not happen without human intervention. They are quite small, typically only a few millimeters. Keshi pearls are produced by many different types of marine mollusks and freshwater mussels in China.
Keshi pearls are actually a mistake in the cultured pearl seeding process. In seeding the cultured pearl, a piece of mantle muscle from a sacrificed oyster is placed with a bead of mother of pearl within the oyster. If the piece of mantle should slip off the bead, a pearl forms of baroque shape about the mantle piece which is entirely nacre.
Therefore, a Keshi pearl could be considered superior to cultured pearls with a mother of pearl bead center. In the cultured pearl industry, the resources used to create a mistaken all nacre baroque pearl is a drain on the production of round cultured pearls. Therefore, they are trying to improve culturing technique so that keshi pearls do not occur.
All nacre pearls may one day be limited to natural found pearls. Tahitian pearls , frequently referred to as black pearls,  are highly valued because of their rarity; the culturing process for them dictates a smaller volume output and they can never be mass-produced because, in common with most sea pearls, the oyster can only be nucleated with one pearl at a time, while freshwater mussels are capable of multiple pearl implants.
Before the days of cultured pearls, black pearls were rare and highly valued for the simple reason that white pearl oysters rarely produced naturally black pearls, and black pearl oysters rarely produced any natural pearls at all. Since the development of pearl culture technology, the black pearl oysters Pinctada margaritifera found in Tahiti and many other Pacific islands including the Cook Islands and Fiji are being extensively used for producing cultured pearls.
The rarity of the black cultured pearl is now a "comparative" issue. The black cultured pearl is rare when compared to Chinese freshwater cultured pearls, and Japanese and Chinese akoya cultured pearls, and is more valuable than these pearls. However, it is more abundant than the South Sea pearl, which is more valuable than the black cultured pearl. This is simply because the black pearl oyster Pinctada margaritifera is far more abundant than the elusive, rare, and larger south sea pearl oyster Pinctada maxima , which cannot be found in lagoons, but which must be dived for in a rare number of deep ocean habitats or grown in hatcheries.
Black pearls are very rarely black: they are usually shades of green, purple, aubergine, blue, grey, silver or peacock a mix of several shades, like a peacock's feather. In the absence of an official definition for the pearl from the black oyster, these pearls are usually referred to as "black pearls". A farm in the Gulf of California , Mexico, is culturing pearls from the black lipped Pinctada mazatlanica oysters and the rainbow lipped Pteria sterna oysters.
Biologically speaking, under the right set of circumstances, almost any shelled mollusk can produce some kind of pearl. However, most of these molluskan pearls have no luster or iridescence. The great majority of mollusk species produce pearls which are not attractive, and are sometimes not even very durable, such that they usually have no value at all, except perhaps to a scientist or collector, or as a curiosity.
These objects used to be referred to as "calcareous concretions" by some gemologists, even though a malacologist would still consider them to be pearls.lifepo4.by/includes/2020-10-09/660-mujeres-solteras.php
What are the Best Pearls to Buy?
Valueless pearls of this type are sometimes found in edible mussels , edible oysters , escargot snails, and so on. The GIA and CIBJO now simply use the term 'pearl' or, where appropriate, the more descriptive term 'non-nacreous pearl' when referring to such items   and, under Federal Trade Commission rules, various mollusk pearls may be referred to as 'pearls', without qualification.
A few species produce pearls that can be of interest as gemstones. These species include the bailer shell Melo , the giant clam Tridacna , various scallop species, Pen shells Pinna , and the Haliotis iris species of abalone. Pearls of abalone, or paua , are mabe pearls, or blister pearls, unique to New Zealand waters and are commonly referred to as 'blue pearls'.
They are admired for their incredible luster and naturally bright vibrant colors that are often compared to opal. Another example is the conch pearl sometimes referred to simply as the 'pink pearl' , which is found very rarely growing between the mantle and the shell of the queen conch or pink conch, Strombus gigas , a large sea snail or marine gastropod from the Caribbean Sea. These pearls, which are often pink in color, are a by-product of the conch fishing industry, and the best of them display a shimmering optical effect related to chatoyance known as 'flame structure'.
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Somewhat similar gastropod pearls, this time more orange in hue, are again very rarely found in the horse conch Triplofusus papillosus. The second largest pearl known was found in the Philippines in and is known as the Pearl of Lao Tzu. It is a naturally occurring, non-nacreous, calcareous concretion pearl from a giant clam. Because it did not grow in a pearl oyster it is not pearly; instead the surface is glossy like porcelain.
Your Cookie Preferences
The largest known pearl also from a giant clam is the Pearl of Puerto , also found in the Philippines by a fisherman from Puerto Princesa , Palawan Island. The ancient chronicle Mahavamsa mentions the thriving pearl industry in the port of Oruwella in the Gulf of Mannar in Sri Lanka.
It also records that eight varieties of pearls accompanied Prince Vijaya 's embassy to the Pandyan king as well as king Devanampiya Tissa 's embassy to Emperor Ashoka. For thousands of years, seawater pearls were retrieved by divers in the Indian Ocean in areas such as the Persian Gulf , the Red Sea and the Gulf of Mannar. Margarita pearls are extremely difficult to find today and are known for their unique yellowish color.
The most famous Margarita necklace that anyone can see today is the one that then Venezuelan President Romulo Betancourt gave to Jacqueline Kennedy when she and her husband, President John F. Kennedy paid an official visit to Venezuela. Before the beginning of the 20th century, pearl hunting was the most common way of harvesting pearls. Divers manually pulled oysters from ocean floors and river bottoms and checked them individually for pearls. Not all mussels and oysters produce pearls. In a haul of three tons, only three or four oysters will produce perfect pearls.
Pearls were one of the attractions which drew Julius Caesar to Britain. Pearling was banned in the U. Today, the cultured pearls on the market can be divided into two categories. The first category covers the beaded cultured pearls, including akoya, South Sea and Tahiti. These pearls are gonad grown, and usually one pearl is grown at a time.
This limits the number of pearls at a harvest period. The pearls are usually harvested after one year for akoya, 2—4 years for Tahitian and South Sea, and 2—7 years for freshwater. This perliculture process was first developed by the British biologist William Saville-Kent who passed the information along to Tatsuhei Mise and Tokichi Nishikawa from Japan. The second category includes the non-beaded freshwater cultured pearls, like the Biwa or Chinese pearls. As they grow in the mantle, where on each wing up to 25 grafts can be implanted, these pearls are much more frequent and saturate the market completely.
An impressive improvement in quality has taken place in the last ten years when the former rice-grain-shaped pebbles are compared with the near round pearls of today. In the last two years large near perfect round bead nucleated pearls up to 15mm in diameter have been produced with metallic luster. The nucleus bead in a beaded cultured pearl is generally a polished sphere made from freshwater mussel shell. Along with a small piece of mantle tissue from another mollusk donor shell to serve as a catalyst for the pearl sac, it is surgically implanted into the gonad reproductive organ of a saltwater mollusk.
In freshwater perliculture, only the piece of tissue is used in most cases, and is inserted into the fleshy mantle of the host mussel. South Sea and Tahitian pearl oysters, also known as Pinctada maxima and Pinctada margaritifera , which survive the subsequent surgery to remove the finished pearl, are often implanted with a new, larger beads as part of the same procedure and then returned to the water for another 2—3 years of growth.
Despite the common misperception, Mikimoto did not discover the process of pearl culture. Nishikawa was granted the patent in , and married the daughter of Mikimoto.
The Originator Of Cultured Pearls
Mikimoto was able to use Nishikawa's technology. After the patent was granted in , the technology was immediately commercially applied to akoya pearl oysters in Japan in Mise's brother was the first to produce a commercial crop of pearls in the akoya oyster. Mitsubishi's Baron Iwasaki immediately applied the technology to the south sea pearl oyster in in the Philippines, and later in Buton, and Palau.
Today, a hybrid mollusk is used in both Japan and China in the production of akoya pearls. Cultured Pearls were sold in cans for the export market. These were packed in Japan by the I. Mitsubishi commenced pearl culture with the South Sea pearl oyster in , as soon as the technology patent was commercialized. By this project was showing signs of success, but was upset by the death of Tatsuhei Mise.
Although the project was recommenced after Tatsuhei's death, the project was discontinued at the beginning of WWII before significant productions of pearls were achieved. Culturing these gems is a tedious, yet a safe process that takes place on pearl farms. Their oysters are nucleated using small pieces of mantle tissue and mother of pearl. Cultured Akoya Pearls come in a wide variety of sizes. Thanks to the art of cultivating pearls, these gems can be found in sizes up to 11 millimeters large.
Although most are round, they can also be found in Keshi and baroque shapes too. They are most commonly used in the creation of pearl earrings and strands of pearls.
These high-quality pearls also look amazing when used with other gems in jewelry. Set them with white gold clasps or yellow gold posts and you have a masterpiece that will last you a lifetime. There are very few blemishes on the pearls. The details these gemstones reflect will absolutely amaze you!
Because they come in perfectly round shapes, near-matching is rarely an issue with cultured Akoya pearls. That means buying a strand of pearls will leave you with a virtually flawless piece of jewelry. They are classic pieces for the church, dinner parties, holidays, family gatherings and weddings.