Stones by zodiac signs

What is the difference between cultured pearls and natural pearls?

The word “pearl” is of Chinese-Mongolian origin (the Chinese “gonchu” was transformed in Mongolian pronunciation into “zhenzhu”, and then in Russian – “into “pearls”). The word “pearl” passed into the Russian language from Old French, where it came from Latin as a modified form of the word “perna” – the name of a variety of large shells. Pearls are formed mainly by bivalve mollusks, less often by single-vave mollusks. Pearls consist of nacre, which is an organo-mineral aggregate of calcium carbonate (usually in the form of aragonite) and horny substance (conchiolin). Conchiolin, as an organic substance, is subject to change, primarily to drying. This can lead to “aging” and even “death” of the pearl. First, the pearls become dull (“get sick”), then cracks appear in them, and eventually the balls begin to peel off, their shells peel off. It is impossible to guarantee a specific lifespan for pearls; According to available estimates, it averages 100-150 years. There are, however, excellent-looking pearls of very considerable age – up to several hundred years. Careful care of pearls undoubtedly contributes to its long-term preservation. Extreme dryness and high humidity are contraindicated for pearls. It is also very sensitive to the effects of acids, skin sweat, cosmetics, hairspray (especially in the form of aerosols.). Pearls come in a variety of sizes: from a pinhead to a pigeon’s egg. The largest pearl ever found weighs 450 carats (1800 grains); it is kept in London, at the South Kensington Geological Museum. Pearls are formed in the shells of sea oysters and mussels, freshwater mollusks of the unionid family, in some cases also in the shells of snails (gastropods) and even cephalopods – nautiluses. They arise as a result of the mollusk’s reaction to irritation caused by the entry of a foreign body into the gap between the shell valve and the mantle (see figure) or its introduction into the mantle. The outer shell of the mantle – the epithelium – produces nacre and normally builds shell valves from it, but if necessary, it also covers any foreign body with concentric layers of nacre, isolating it and thereby giving rise to the future pearl. Seashells that produce pearls live near the shore at a depth of about 15 m, grouped in extended oyster banks. Their average size is 8 cm in diameter, life expectancy is up to 11-13 years. The most important fishing area is the Persian Gulf, where the best varieties of pearls are mined (“oriental”: white with a snowy pink or cream tint). Pearl fishing has existed here since time immemorial. In this area, all natural saltwater pearls, regardless of where they were actually obtained, began to be called “oriental pearls.” Ancient pearl fishing is also carried out on the banks of the Gulf of Manara (between India and the island of Sri Lanka); These Indian pearls are pale pink or soft yellow in color and are usually small (the so-called “seed pearls”, “seed”: at least 4 pearls per grain). Other commercial pearl fishing areas are the coastal waters of Central America and Northern Australia. On average, a pearl is found in only one out of 30-40 shells.

Cultured pearls

The growing demand for pearls has led to them being grown (cultivated) in large quantities. Such cultured pearls are not an imitation, but a natural formation, but one that arose with human participation. Today, cultured pearls account for 90% of the total pearl trade. The principle of pearl cultivation is very simple: having understood how pearls arise in nature, a person encourages mollusks to produce pearls by introducing foreign bodies into their shells. Already in the 1761th century. in China, small lead figurines of Buddha were attached to the inner walls of the valves of pearl shells so that the mollusks would cover them with mother-of-pearl. Round pearls were first grown in 1893 by the famous Swedish naturalist Carl Linnaeus. In XNUMX, the Japanese K. Mikimoto managed to obtain hemispherical pearls – blisters. Modern cultivation of round pearls is based on the research of the German scientist F. Alverdes and Japanese biologists T. Nishikawa.T. Mize and K. Mikimoto, executed at the beginning of the last century. To force oysters to produce pearls, pearl balls are ground from the shells of North American freshwater pearl barley, wrapped in a piece of epithelium cut from the mantle of the oyster Pinctada martensii, and then, through a complex operation, implanted into the connective tissue of the mantle of another oyster of the same species. The transplanted epithelium retains its functional abilities; it plays the role of a pearl bag, into which the release of mother-of-pearl will now begin. The most important element in the formation of pearls is the epithelium, and not a foreign body, which theoretically could be completely neglected. However, in practice, the entire enterprise would then become unprofitable, since the formation of a sufficiently large pearl would take too long. The introduction of a ready-made core significantly reduces the “working time” of the oyster: it only has to deposit a shell around the core, which gives the pearl the necessary shine. Inserting the nucleus into the mantle of a mollusk requires very skilled hands. Women do this best. They handle between 300 and 1000 oysters per day. With a normal pearl ball diameter of 6-7 mm, three-year-old oysters are needed, but if the nuclei are smaller, then the oysters can be younger. Too large balls (more than 9 mm) cause the death of up to 80% of oysters into whose tissues they are introduced. Prepared mollusks are kept in sea bays, suspended in wire baskets or, preferably, in plastic cages on bamboo rafts or on cables attached between buoys, which keep them floating in the water. Mollusks stay in water for 3-4 years. During this period, they manage to deposit a shell of nacre approximately 0,8–1,2 mm thick around the core. A longer stay of oysters in the sea is fraught with the danger of their disease, death, or distortion of the shape of the pearls. Oysters older than 7 years generally stop producing nacre. At the same time, too small a shell thickness reduces the value of cultured pearls. After harvesting, the pearls are removed from their shells, washed, dried and sorted by color, size and quality. Only about 10% of all pearl production is suitable for fine jewelry; waste amounts to 15-20%. Cultivation of freshwater mollusks, as well as marine ones, is carried out in cells hanging in water at a depth of 1-2 m on bamboo frames. The yield of quality pearls is about 60%. It is clearly higher than on plantations in salt water, apparently also for the reason that in Lake Biwa there are fewer dangers for shellfish.

Application and evaluation of pearls

Pearls are among the most expensive jewelry stones. It has served people as decoration for 6000 years. In China, another 2500 BC. e. There was a trade in pearls. Pearls are loved and appreciated because pearls are very beautiful and do not need processing. In their natural form, they are fully characterized by the desired bright shine – chandeliers. About 70% of mined pearls are used in the form of beads. The most common length of strings of pearls is about 40 cm; necklaces that are twice as long are called “sautoir” (French: sautoir). If all the pearls in a necklace are the same, it is called a “choker”; and if the size of the pearls decreases in both directions from the middle of the necklace, where the largest bead is located, it is called a “chute” or they say that the necklace “rolls down” towards the ends. The selection of pearls for necklaces and chokers is done only by eye. Pearls are drilled in places where they have defects or look less beautiful, thereby eliminating these flaws. According to international agreement, the diameter of the hole should be 0,3 mm. To attach pearls in the form of pendants to earrings, pins and rings, it is enough to drill a hole with a depth of 2/3 to 3/4 of the diameter of the pearl. Blue pearls should never be drilled as they are prone to discoloration due to air entering through the drilled hole. Spotted or damaged pearls can be improved by removing the outermost layer of the shell. The most defective places are cut out; the rest of the ball is sold as half or 3/4 pearls (not to be confused with blister pearls!). This material is readily used for earrings or brooches. A specialist is usually able to “revive” pearls that have lost their attractiveness when worn or due to improper storage. The evaluation of pearls depends on the shape and color, size and shine of the pearls. The round shape is most valued. Semicircular pearls (flat on one side) are called “buttons” (French bouton), pearls of irregular shape are called “baroque” or “baroque”. If, when worn, the pearls become worn, abraded, and take on the shape of a small barrel, they are called “barrel-shaped.” Pinkish pearls (French rose) in Europe and the USA are especially in demand among blondes with white skin and delicate complexions. Brunettes and dark-haired southerners prefer cream-colored pearls. Pearls of dull colors are often bleached or artificially dyed. The mass of pearls is usually expressed in grains (1 grain = 0.05 g = 0,25 ct), but recently the carat is increasingly used for this: the Japanese unit “momma” (3,75 g = 18,75 ct) is practically not used on the European market . The cost of pearls is determined according to the following scheme: the mass of a large pearl in grains is squared: the resulting number should be multiplied by a coefficient that can only be determined by a specialist, because it takes into account the quality of the pearl and all other pricing factors. This coefficient can be equal to 1, or maybe 40. It acquires especially high values ​​for necklaces and chokers consisting of a large number of equal pearls. The word “pearl” without any definitions is allowed to be used only for natural pearls. To avoid misunderstandings, cultured pearls should always be called that.

How to distinguish natural pearls from cultured and imitation pearls

Natural and cultured pearls look the same, making it difficult to distinguish one from the other. This can be done by determining their density, which for most (but not all!) cultured pearls is above 2,73, and for natural pearls it is often (but not always!) below this value. The luminescence of cultured pearls is yellowish in ultraviolet rays, and greenish in x-rays. A reliable difference between natural and cultured pearls is the control of the internal structure. In real pearls it is concentrically shell-like, but in cultured pearls it is different, and different, depending on the nature of the core. Specialists use special instruments (endoscopes) to monitor the internal structure of the pearls along the drilled hole. The X-ray method is very convenient and reliable, applicable to both drilled and solid pearls and at the same time determining the thickness of the natural nacre shell of cultured pearls. Like other most valuable jewelry stones, pearls also have numerous imitations. These include, strictly speaking, cultured blister pearls (“Japanese pearls”) from Australia: after all, these are not real cultured pearls. Such a blister consists only of a thin-walled mother-of-pearl shell, and all its other parts are manufactured technically. It is obtained in the following way: first, a core made of clay or synthetic resin is attached to the inner wall of the mollusk shell, and after it is covered with a thin mother-of-pearl shell, the blister is removed from the shell (by drilling the valve from the outside, as a result of which the mollusk dies), the core is cut out from the shell and replaced its mother-of-pearl hemisphere. Such blisters are obtained in Australia and processed in Japan. A blatant imitation is represented by hollow glass balls coated on the inside with a film made from the silvery scales of certain types of fish (bleak). Sometimes the balls are made solid (for example, from mother-of-pearl or plastic) and covered with a film on the outside, like enamel. Other imitations use parts of snail shells (“Antillean pearls”), bivalves (“Takara pearls” from Japan) or sea cow teeth (“Dugong pearls”). There are also imitations on the market, made entirely from artificial materials. The operculum (“Chinese cat’s eye”) is the flat-convex operculum of the shell of sea snails (gastropods) from Oceania; with its porcelain appearance and shape it resembles a blister. The inhabitants of the islands of the Australasian region use operculum as a material for jewelry: it is less known in Europe. There are three types of pearls: natural pearls, or wild pearls; cultured natural pearls and artificial pearls, imitation pearls. Natural cultured pearls are pearls grown in natural conditions with human intervention.

Natural pearls

It is almost impossible to find natural pearls on sale today. And the price of natural pearls will be incredibly high. To find one good quality pearl you need to kill hundreds of oysters. In pursuit of saturating the market, the harvest of many species of shellfish has brought them to the brink of extinction. And this, in turn, dealt a blow to the marine ecosystem as a whole. Since the days of pearl cultivation on farms, the harvesting of wild pearls has practically ceased. Natural forms of pearls are varied, and the least common among them are round stones.

Natural cultured pearls

Natural cultured pearls are born as a result of the joint efforts of man and shellfish. If natural pearls are formed completely by chance, it is impossible to predict the shape and size of the pearl in advance. And as a result of cultivation, pearls of a pre-planned shape, size and color are obtained. The process of formation of natural and cultured pearls is almost the same. The difference in the case of the formation of natural pearls is that the foreign body is small parasites, but for the formation of cultured pearls the person himself begins the process of maturation of the pearl by inserting the foreign body into the shell of the mollusk. The quality of a cultured pearl depends on the size of the foreign object (usually a ball), the length of time the oyster is “ripened” and the thickness of the nacre that covers the ball layer by layer. In a short period of time, a few months, the ball will be covered with a thin layer, while a pearl that grows from one to two years will have a stronger and more durable nacre. X-rays are used to determine the thickness of the pearl layer.

Imitation pearls

Artificial pearls or so-called imitation pearls are truly artificial pearls created by man. The mollusk is not involved in its appearance. Only humans take part in the production of artificial pearls from start to finish. Balls made of plastic or glass are coated many times with various pearlescent paints. Imitation pearls cannot contain such a variety of color shades as natural pearls; such pearls are much cheaper. If used carelessly, the coating can wear off quickly. Natural pearls are not perfectly smooth. And all artificial pearls are equally smooth. Due to this, it looks even more neat in jewelry, although the price is significantly lower than natural. You need to know that expensive high-quality glass-based artificial pearls feel cold to the touch, while cheap ones (plastic-based) feel warm. If artificial pearls are of very high quality, then it is practically impossible for a non-specialist to distinguish them from natural ones with the naked eye.

12 ways to distinguish natural pearls from artificial ones

Today, professionals have developed several methods to help distinguish a natural mineral. After familiarizing yourself with them, the question of how to distinguish real pearls from artificial ones will no longer frighten beginners. So, here are the main ways to distinguish natural goods:

  • Price. First of all, you should pay attention to the price of the product. The low cost for natural pearls is unacceptable, although some scammers can sell fakes at a higher price than natural pearls.
  • The weight. A natural pearl has more weight because it consists exclusively of mother-of-pearl, but an artificial one contains lighter materials.
  • Try. Since ancient times, a well-known way to distinguish a fake is to “test it.” If you run your teeth over a pearl, a natural stone will creak, but a fake one will not make a sound. If you already have experience in distinguishing pearls, then you can tap it on your teeth – real and artificial ones will give different sensations.
  • The fall. When dropped from a height of about half a meter, a real stone will bounce off the surface, while artificial pearls will simply fall without moving, which is explained by different densities.
  • Friction. Owners of a pearl necklace can easily check the stones present in it using friction. If you rub a pair of pearls against each other with minimal pressure until pearl powder is formed, small scratches will remain on the natural one, which disappear quite quickly, while the layer of mother-of-pearl will simply be erased from the fake one.
  • Comparison. In addition to the previous method, necklace owners can check the pearls using comparison. Natural stones are individual and not similar to all others, so there should not be identical pearls in the jewelry.
  • Inspection. A rather interesting way for novice scientists is to look at a pearl through a microscope. A natural one will have a clearly visible scaly surface, while a fake one will be uniform.
  • Shine. A real pearl differs from a fake one by its uniform and deep shine, which for professionals is visible to the naked eye. If the pearls are dull, then this indicates their artificiality or low quality, so you should not purchase such a product.
  • Hole. You need to carefully consider the place where the hole is drilled. Cracks will not form in a natural pearl, since it has a high density, but a fake pearl will have a lot of chips visible around the edges.
  • Field. Place a pearl in an electromagnetic field, a natural one will remain motionless, and a cultured one will begin to roll. This is explained by the fact that inside the fake there is a special ball made of a material that reacts to an electromagnetic field.
  • Specialist. The most reliable way at any time was to contact a specialist – a gemologist. Using a special X-ray machine, he will quickly determine the originality and quality of the jewelry.

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