How, from what and why are pearls formed in shells? How are natural pearls formed? Pearl shells
Pearls are the only precious stone that is of animal origin: it is not formed in the bowels of the earth, like diamonds or emeralds, but in the shells of bivalve mollusks.
Where do pearls come from inside shells? In Ancient Greece they believed that these were the hardened tears of mermaids. In the Middle Ages, they believed that angels hid the tears of orphans and innocent people in shells, and there they turned into pearls.
The inner layer of the shell, produced by the mantle of the mollusk, is nacre (German). perl– pearls, mutter– mother; Perlmutter- “mother of pearls”). If you find a bivalve shell on a river or seashore, examine its inside. You will see that it is covered with a layer that has a beautiful shine. This is mother of pearl.
Inner surface of the sink
bivalve mollusk
Thus, in the center of the pearl there is always a “crystallization center”, the germ of the pearl. But it also happens that there is no foreign object in the center of the pearl. In this case, the seed for the formation of a pearl can be a gas bubble, a drop of liquid, or a piece of mollusk tissue - during the process of pearl formation, it gradually decomposes.
The shape of a growing pearl depends mainly on where its embryo ends up. If the pearl sac is located near the surface of the shell, then the nacreous layer of the pearl merges with the nacre of the shell and forms an irregular pearl - a blister. The blister does not have a pearlescent layer at the attachment point. If the bag ends up in the mantle of the mollusk, then a pearl of the correct shape grows. Pearls that form in the muscles or in parts adjacent to them have an irregular, often very bizarre shape.
Formation of a pearl sac in the shell of a bivalve mollusk - pearl mussel
First, the cells of the mantle begin to envelop the foreign body with an outer film, forming around it
a pearl sac that is pressed into the tissue of the animal. The inside of the pearl sac is first released
some organic matter, then calcium carbonate crystals in the form of prismatic aragonite and finally
aragonite in the form of a lamellar layer (nacre).
The group of mollusks that are capable of forming pearls is called pearl mussels.
Pearl mussels come in freshwater and marine varieties.
Freshwater, or river, pearls are the most versatile. It has long been used to decorate both the outfits of peasant women and the dresses of noble ladies. River pearls are thousands of times cheaper than sea pearls, since they are obtained easier and faster; In addition, freshwater pearl mussels are larger than sea pearl mussels and are capable of simultaneously growing up to 20 pearls. Freshwater pearls are smaller than sea pearls, have a less regular shape and are less shiny. But river pearls are stronger than sea pearls and more resistant to abrasion. Freshwater pearls account for the largest share of pearl production in the world.
Freshwater pearl beads
The highest quality pearls are produced by marine mollusks of the genera Pinktada and Pteria. They usually form dense settlements - banks, which are located at a depth of 10-15 m.
At first, people obtained pearls by diving for pearl shells. The pearl diving industry dates back more than 4 thousand years. It is very difficult and dangerous, because the diver must dive to great depths (usually up to 20 m) without any auxiliary devices, armed only with a knife, remain there for a sufficient time (usually one to one and a half minutes) to collect as many shells as possible and make up to 30 -40 dives per day! In addition, sharks await the diver in the sea.
Having figured out how pearls are formed, people learned to grow pearls artificially. This technology was invented by the Japanese researcher Kokichi Mikemoto in the 90s of the 19th century. He also created the first pearl growing company. Pearls are grown like this: by opening the shell flaps, foreign bodies, for example, a tiny bead or bead made of natural mother-of-pearl, are introduced under the mantle of the pearl oyster. Then the shell is placed in a special reservoir, in which ideal conditions are created for the mollusks to live. It takes 3 years to grow one good sea pearl, and up to 2 years for a river pearl.
Pearls grown in this way are called cultured pearls. Almost all pearls used in jewelry (90%) are cultured. In terms of its properties, it is no different from natural pearls, and is several times cheaper, despite the fact that not all cultured pearls meet quality standards - there are a lot of defects in this matter.
The main suppliers of cultured pearls are China and Japan, with Australia and Polynesia to a lesser extent.
Incredibly delicate, magically beautiful pearls are so popular in the world that the shortage of their natural reserves began to be felt at the beginning of the 20th century. To satisfy the growing aesthetic needs of the fair half of humanity, men have learned to grow cultured and synthetic pearls. Today, pearls of divine beauty are grown in industrial conditions.
What is the difference between cultured pearls and natural pearls?
What are artificial pearls?
Natural pearls
Natural pearls are formed in the shells of mollusks. It is also called wild pearls.
A grain of sand, larvae of small insects or other foreign body of the smallest size gets into the shell of a mollusk. Inside, the walls of the shell are covered with a mollusk mantle, which has many small nerve endings. They instantly react to a foreign “object” and, as a reaction of a living organism, a substance is released, which is nothing more than the well-known mother of pearl. This is how a tiny pearl grain is first born, which after a few years turns into a full-fledged pearl.
How long does it take for natural pearls to grow and mature?
The growth rate of a pearl is influenced by many different factors - it depends directly on the type of pearl mussel, its age, place of growth (sea, fresh water), and the state of the environment.
A pearl oyster is a mollusk shell. The largest pearls mature in young pearl oysters. With age, the pearl oyster's mantle becomes depleted, and small pearls mature in the shell.
Pearls grow fastest in the first year – 2.3 mm. In subsequent years, pearls grow more slowly - no more than 0.38 mm per year.
Sea pearls are 2 times larger than river pearls. This is due to the richness of the biochemical composition of sea water. But river mollusks are fertile - several pearls ripen in them at the same time.
Cultured pearls
Cultured pearls are not artificial pearls. These are natural pearls grown in a mollusk shell in natural conditions with the help of humans. So-called “cultured” pearls.
Currently, there are incomparably fewer natural pearls on the jewelry market than cultured ones. For example, the American pearl market is 80% cultured pearls.
This happens because natural pearls grow very slowly, and there are more and more people who want to admire them and decorate themselves. Humanity is growing in number, and people's needs are also growing. Therefore, cultured natural pearls are most often used in jewelry.
The process of growing cultured pearls is multi-stage, extremely complex and delicate. Cultured pearls are grown for 3 to 12 years. In rare cases, faster - which depends on the type of mollusk.
An implant is inserted into the mantle of the pearl oyster Pinctada martensi - an artificially carved, tiny ball of mother-of-pearl. Then the shells are lowered into the sea, securing them on special hanging nets. To the appearance of a new irritant, the living mantle reacts by releasing a pearlescent composition, which gradually and very slowly covers the foreign body inside the shell. On average, cultured pearls take 7 years to grow. Some of the largest plantations are located today on the coast of the Sea of Japan.
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A cultured pearl has a perfectly round shape. Almost its entire thickness is made up of the ball itself - 75–90%. The layer of nacre that the pearl oyster secretes is usually 1 mm.
What determines the quality of cultured pearls?
Mainly, it depends on the time of pearl ripening. The longer it matures inside the shell, the thicker the layer of nacre grows, which preserves the pearl in all its glory for many decades. Six-month-old pearls have a fairly thin nacreous layer that wears off quickly. High-quality cultured pearls are considered to be those that have been growing for at least 2 years.
Once cultured pearls are recovered from the depths of the sea, they are first drilled and then dyed in various colors. But not always. It depends on the properties of certain mollusks. The most popular pearl color after classic white is pink.
Cultured pearls in China and Japan
It’s hard to imagine, but the art of cultivating natural pearls is at least 800 years old! The Chinese were the first to cultivate pearls back in the 13th century. They discovered that pearls are formed from foreign bodies trapped in the shell, and began to try to grow them themselves.
Craftsmen carefully opened the shells with bamboo sticks and placed tiny balls of clay or copper, or pieces of wood inside. The shells were then tightly sealed and immersed back into the sea. The pearl harvest took several years to arrive.
One of the most amazing inventions of Chinese masters is the “pearl Buddha”. Copper or lead Buddha images of the smallest size were placed in the mollusk shell, which was then displayed on the ripened pearl.
At the beginning of the 20th century, Chinese technology was patented by enterprising Japanese and they began mass production of this most valuable natural mineral. Today Japan occupies a leading position in the world in the cultivation of cultured pearls. The country has a powerful industrial sector.
Japanese craftsmen cut out a small piece of living tissue from the mantle of a pearl mussel, wrap a ball of various materials in it, then place it in the mantle of the shell of another mollusk, making a neat cut. The pearl matures naturally over several years. Moreover, this process is quite difficult to influence. Recently, they have learned to grow pearls of a certain shape, size and color.
What kind of pearl you will get can only be determined after the shell has been completely opened. After this procedure, the process of growth and maturation stops. It is simply impossible to know in advance what the size of a ripe pearl will be and what shape it will be. Often the mollusk rejects the foreign ball inserted into it immediately after insertion, and the result of the work turns out to be zero. So pearl production has a very certain percentage of commercial risk. Not a single specialist, even the most experienced, will undertake to predict what the percentage of defects will be in each batch of cultured pearls. In practice, on average, only one out of ten pearls meets the required standards, which cannot be called a high “yield”.
Today, cultured natural pearls cost 10 times less than natural ones. Moreover, the price very much depends on whether the pearls are freshwater or saltwater. Growing freshwater pearls is much easier. Up to 7 pearls mature in one growth cycle! Whereas in marine mollusks, in most cases, only 1 pearl is born per cycle. This is why freshwater pearls are cheaper.
In recent years, the Japanese pearl industry has been in the lead and supplied up to 100 tons of cultured sea and freshwater pearls to the world market.
But the catastrophic tsunami in 2011 in Japan destroyed most of the pearl farms, making the Chinese the leaders in pearl cultivation in the world. It should be noted that Chinese pearl farmers have worked very hard and hard to achieve this success. They began to study Japanese advanced cultivation technologies 50 years ago, diligently mastering the experience of their colleagues. For a very long time, Chinese pearls were not quoted on the jewelry market, since they were largely inferior in quality to Japanese ones. Today, Chinese pearl farmers have caught up with the Japanese and become the leaders in pearl farming in the world. But Japanese pearl culture traditions are too strong to disappear. Industry is gradually recovering. Japan maintains its leadership in terms of pearl size. The fact is that in Chinese waters, due to climatic conditions, it is impossible to grow pearls larger than 7 mm in size. And if the size of the pearl exceeds 8 mm, then its cost increases significantly. This fact allows Japanese pearl farmers to maintain a leading position in this category.
Akoya cultured pearls are one of the most popular varieties of cultured pearls in the world. It is grown in large volumes on Chinese and Japanese pearl farms, as well as in small quantities on Vietnamese ones. Akoya pearls have a distinctive feature - a rather intense metallic luster. To ensure that Akoya pearls reach their maximum possible brilliance, they are harvested in late autumn - early winter. This is the optimal harvest time for this oyster variety. It is noteworthy that these are the smallest pearl oysters. An even more amazing fact is that up to 5 pearls can mature in this tiny shell at the same time! Not every large oyster can ripen such a harvest. In addition, she grows the fastest - only 8 months. Here she is, little Akoya.
Akoya is a well-known and long-loved classic in the pearl market.
Popular shades are white, cream, pink. Metallic silver pearls are very beautiful and popular. But most often oysters give birth to yellow, brown, greenish and blue pearls. Perfectly round Akoya pearls are widely used in the jewelry industry - pearls from 5 to 9 millimeters in diameter are excellently selected for necklaces and bracelets.
Artificial pearls
Imitation pearls are imitation pearls created in a factory.
The mollusk shell plays absolutely no role in the creation of synthetic pearls. The entire process is carried out by humans. At the same time, there are separate technologies for creating artificial pearls, which use exclusively natural ingredients - mollusk shells and its components.
It is curious that artificial pearls began to be produced back in the 15th century. In those days, Roman pearls, which were glass balls with paraffin poured inside, were very popular.
A little later, glass pearls were covered with a special “pearl essence”, which for a long time was made from sparkling fish scales. Today, mother of pearl is extracted directly from mollusk shells.
In the 15th and 16th centuries, the ancient Indians mastered the skill of creating artificial pearls. They used clay balls as the core. A special composition of mica and natural mother-of-pearl, which was extracted from the inside of mollusk shells, were used as a mother-of-pearl coating.
Today, the core of artificial pearls is made from a variety of materials - plastic, alabaster, glass, etc. Pearls are cut from pink coral and some varieties of hematite. Depending on the technology and place of production, there are many varieties of artificial pearls.
In the 20th century in the United States of America, a method of multiple coating of beads with varnish was invented - Shell pearl. Synthetic pearls, popular all over the world, are still produced using this technology to this day. The high quality of this variety is evidenced by the fact that it is used in production by the Chanel jewelry house. It feels much nicer to the touch than glass pearls, and is also much better quality and more durable. And in terms of the number of shades, it has no equal, in principle, among all types of pearls. These are hundreds of truly luxurious shades: from classic glossy to modern “acid” ones. Shell pearl is based on a core cut from a natural mollusk shell. The average diameter of such a ball is 10 millimeters. The coating is made from natural mother-of-pearl, which is initially crushed to a powdery state and then mixed with a special binder. The result is a pearl emulsion made from natural mother of pearl. Multi-layer indelible Shell pearl coating is a guarantee of many years of pearlescent shine. Such artificial pearls are in no way inferior in appearance to the beauty of wild natural and cultured pearls. In addition, its composition is almost completely identical to the composition of real pearls. The only visual difference between Shell pearl is the incredible smoothness of the surface. The structure of wild pearls is noticeably porous.
Another of the most common and famous varieties of artificial pearls is “majorica”. Many layers of natural mother-of-pearl are applied to the alabaster ball. Spanish technology is so advanced that this type of synthetic pearl is almost impossible to distinguish from natural pearls with the naked eye. The technique was developed and honed on the Spanish island of Mallorca over 120 years. The founder and developer of this coating technology, German emigrant Eduard Hugo Hosch, dreamed of achieving complete external similarity between artificial pearls and natural ones - and he succeeded! Currently, synthetic Majorica pearls are sold in huge quantities all over the world and are distinguished by their excellent mother-of-pearl luster, ideal round shape and affordable price. Interestingly, under electric lighting, artificial pearls have an unusually beautiful light refraction effect.
Which pearl is better?
Natural wild pearls are a rarity on the jewelry market today. This does not mean that absolutely all pearls offered to customers are artificial. In the vast majority of cases, jewelry is made from cultured pearls - these are also natural pearls, the quality characteristics of which are no worse than the real (wild) ones. Only its cost is several times lower. Real natural pearls are quite expensive - depending on the size and color, the cost can be tens of times higher. Currently, small-scale mining of natural pearls is carried out in Japan, in the Gulf of California. Moreover, out of 100 mollusks, only 5-10 pearls of decent quality can be found. Today, wild natural pearls are on the verge of extinction. Which, in turn, deals a powerful blow to the ecological system of the sea as a whole. To find 1 pearl you have to kill up to 100 mollusks! This is why hunting for wild pearls has virtually ceased throughout the world. Cultured pearls are no worse, cost less and do not destroy nature. It is so identical to the wild one that it is simply impossible for a non-specialist to distinguish it from the natural one. The natural “wild” origin of pearls is evidenced by a slight, barely noticeable surface roughness and other factors.
Shell pearls are unique because they are the only gemstone that is of animal (organic) origin.
The process of pearl formation in a mollusk shell is associated with the latter’s self-defense function. This is a kind of analogue of the human immune system.
For a pearl to appear in a mollusk shell, any foreign body must penetrate there. Next, the self-defense mechanism is activated.
Unlike the human immune system, the mollusk does not destroy the foreign object, but begins to envelop it layer by layer with a specially secreted substance, which in the body of the mollusk is nacre. This process lasts for several decades, resulting in and in the sink.
However, pearls in a shell will not always have the shape of a ball. An important criterion for the quality of a grown pearl will be the location of the foreign body inside the shell of the mollusk. If a foreign object is located at the edge of the shell inside, then the grown pearl will have an irregular shape. Such a pearl is called a blister. The part of it that came into contact with the shell of the mollusk during growth will lack a layer of nacre. In order for pearls to have a regular spherical shape, evenly covered with a layer of nacre, it is necessary that the growth center initially be located in the mantle of the mollusk.
However, not all mollusks are capable of producing pearls; those that have this ability are classified into a separate group called pearl mussels.
Types of pearl fishing in the world
Naturally formed pearls come in two types: freshwater and saltwater. The first, also called river pearls, is significantly inferior in price to sea pearls. This is due to three factors:
- more widespread;
- much easier to mine;
- much inferior in shine and shape.
Freshwater pearls also have their advantages over sea pearls. It is more durable and wear-resistant, wears less over time. To catch freshwater pearls, an underwater mask or a specially adapted tube is enough. The latter was used in ancient times and now will most likely look like an outlandish device. Basically, shells with pearls are located at the bottom of freshwater rivers and lakes and are found there not alone, but in entire colonies. All this greatly simplifies the collection of freshwater pearls, which is often not difficult to do even for an amateur.
In contrast, sea pearls are harvested by professionals. Firstly, the sea shell with pearls lies deep, you have to dive to a depth of 15-20 meters. Secondly, you have to dive several dozen times a day, each time remaining at a depth of more than a minute.
All this requires special skills and training. Moreover, pearl divers at sea are exposed to another danger, namely a possible encounter with a shark.
Nowadays, special farms are used to collect both sea and freshwater pearls. China is famous for its “pearl farms”. In this country, not only fresh waters of rivers and lakes are used for pearl cultivation. Former rice fields, which are flooded with water and have a microclimate comfortable for shellfish, are very popular. In such conditions, pearl mussels multiply quickly and produce high-quality pearls. A person can only control the living conditions of mollusks, such as the composition of the water, its temperature and the acidity factor. The process of pearl growth requires that the shellfish be turned over at times. This will give the pearl shape greater symmetry.
Cultured pearls
Despite all the difficulties and dangers, the extraction of sea pearls has acquired such a large scale that some deposits began to be depleted until they were completely closed. An unexpected solution to this problem appeared in the 90s. XIX century. There are several legends about how the Japanese oyster farm owner Mikimoto came up with the idea of growing (cultivating) pearls on special plantations. His idea was successful, and currently more than 90% of pearls on the world market are cultured.
It is incorrect to consider cultured pearls in a shell to be artificial. It is as natural as pearls grown in natural conditions. Because the growth process itself also occurs in the shell of a mollusk. The only difference is this: a person places the “seed” inside the shell. The process of growing a cultured pearl is quite complex and painstaking. Its duration takes from 3 to 8 years and is constantly being improved. What the final pearl in the shell will be like and how successful the growth will be is unknown.
Currently, there are two ways to culture pearls in shells: nuclear and non-nuclear methods.
The nuclear method of cultivation implies that a seed or nucleus is artificially placed into the pearl oyster. Typically this is a ball measuring from 6 to 9 mm in diameter. And although in the description everything looks quite simple, the procedure itself is complex.
The first thing you need to do is select a mollusk for priming. It should be a young pearl oyster with a well-developed gonad, the reproductive gland that produces nacre. Additionally, she must have a good robe. After the nucleus is implanted, the mollusk goes to a special lagoon, where it spends the remaining time until the pearl appears, in favorable conditions, and is under human supervision.
Despite all this, the effectiveness of this method is not one hundred percent. The pearl mussel may throw away the seed or die. If everything goes well, a centimeter pearl can grow within a year. The advantages of this method include high growth rate and ideal pearl shape. But there are also significant disadvantages: the actual layer of nacre on such a pearl is usually no more than 1 mm. Hence the ideal spherical shape. And it’s quite difficult to call such pearls natural. You don't need to be a professional, just take the pearl in your hand and it heats up quickly. In contrast, natural pearls remain cool in the hand and feel weighty.
More complex is the nuclear-free method of pearl growth. It has become widespread in China. In this case, the seed has tiny dimensions. Usually this is a grain of mother-of-pearl sand taken from the shell itself. This determines the long growth process from 3 to 8 years. However, the long wait is compensated by the excellent quality that cultured pearls in the shell have. It is not inferior to its natural counterpart, often having advantages in color and size.
Natural and cultured pearls
As you can read above, natural pearls are a rarity on the global jewelry market today. This is due not only to the fact that natural pearl plantations had decreased significantly by the beginning of the 20th century. Continuous improvement of pearl cultivation technology is also important. Currently, it is possible to obtain cultured pearls of the desired size and color. It should not be assumed that almost all pearls offered to customers today are artificial. Because if we discard artificial imitations of pearls, then in most cases the jewelry offered on the jewelry market is made from pearls grown under special conditions. And this is also a natural product, the quality of which is no worse than natural.
The only difference is the price. Real natural pearls are much more expensive. But it should also be taken into account that the extraction of natural pearls has its consequences. Currently natural in Japan and also in the Gulf of California. To get a dozen high-quality pearls, you need to catch about a hundred mollusks. People should not forget about the harm they cause to nature while engaging in fishing. It is actually on the verge of extinction. This, in turn, deals a strong blow to the ecological system of the sea as a whole. Therefore, hunting for wild pearls has practically ceased throughout the world.
The precious stone that will be discussed in this article is of interest not only to the charming half of humanity and professional jewelers, but also to scientists.
Pearls in a shell are a biogenic solid material formed as a result of the protective reaction of some mollusks (usually sea, but sometimes river) to foreign bodies entering their bodies - this description of pearls can be found in many scientific articles.
The valuable stone in question is the only formation of animal origin, the structure of which includes the mineral aragonite and conchiolin (an organic substance that forms the framework of pearls).
Some historical facts.
Our ancestors have been making jewelry from pearls by hand for more than four thousand years. Today, the most ancient jewelry made using pearls has been preserved:
Figurine of Aphrodite, created according to various estimates in the 5th or 2nd centuries. BC. (kept in the Boston Museum).
Necklace from Susa (kept in the Louvre).
A large number of ancient items are in private collections, and the largest pearl (Peregrina, weighing 55.95 carats) belongs to Elizabeth Taylor.
The process of pearl formation in a shell
As mentioned above, pearls are the result of self-defense of mollusks when foreign objects enter the shell. They are unable to push out a foreign object, and to prevent damage to the body, the mollusk gradually envelops it with a special substance - mother of pearl. This happens gradually, first one layer, then the second, third, etc. As a result, the foreign body is walled up inside, it becomes smooth and does not cause any inconvenience to the mollusk. This is how pearls appear, which interest jewelers from all over the world.
In some cases, for pearls to appear in the shell and their subsequent formation, there is no need for foreign bodies to enter. The “embryo” can be ordinary water, a gas bubble (regardless of the nature of its origin) or a piece of tissue from the mollusk itself.
The main factor that affects the shape of the future pearl is the place where the foreign body has entered:
the “embryo” at the surface of the shell forms a so-called blister with a missing layer of nacre at the point of attachment to the hard surface of the mollusk;
in the muscles or next to them, pearls of the most bizarre shapes are formed;
formations of regular shape develop in the mantle of the mollusk.
Despite the fact that theoretically all shellfish and oysters can be a source of pearl formation, in practice, some representatives of this species do not have this ability. It should also be noted that only those pearls that are created by bivalves, gastropods and one species of cephalopods have commercial value. At the same time, representatives of freshwater inhabitants “produce” formations that cost a hundred and sometimes a thousand times less than their marine “relatives”. This is due both to the physical properties of valuable stones and to the conditions of their extraction.
Sea pearls are mined mainly off the coast of Sri Lanka, Japan, as well as in the Red Sea and the Persian Gulf, and river pearls are mined in Russia, North America, Germany and China.
Basic properties and valuation of pearls
The number of pearls in a shell is inversely proportional to their size, and can amount to several dozen (sometimes more than a hundred) formations in one mollusk. An important role in determining the cost of the valuable stones in question is played by the size, shape, color, origin of the pearl, as well as the purity of its surface and other individual criteria.
In jewelry, a special classification system is used to evaluate stones, which, in addition to the above parameters, takes into account the thickness of the mother-of-pearl layer of pearls.
"Domestication" of shellfish
For hundreds of years, people have dived for shells to great depths (10-20 m) to get pearls. They had to do up to thirty dives a day without any additional equipment. They often got sick (the result of pressure changes) and became victims of sharks, receiving for their hard work only a small part of the real value of the valuable stones mined. But at the end of the 19th century, a Japanese explorer created the first pearl farm.Many readers, even if they didn’t know what the enterprising Japanese came up with, most likely already guessed the principle of growing valuable stones. Foreign bodies were introduced under the mantle of the mollusks (by slightly opening the shell valve): beads, grains of sand, beads, etc. The shells were placed in special reservoirs, where ideal conditions were created for them. Then nature itself works.
It takes about three years for a good quality pearl to appear in the shell; for freshwater mollusks, the period is one year less. But, given the fact that on the farm the process goes on continuously, some shells need to be implanted with foreign bodies, others are already producing a “harvest,” then there is almost always work on such farms (except for seasonal breaks).
Almost 90% of jewelry presented on the world market is made from pearls, which are obtained from special farms. Most often it is called cultured; the adjective “artificial” in this case is, at a minimum, incorrect to use (after all, pearls are not made by human hands, but in a natural way). According to the main criteria, cultured pearls are in no way inferior to those obtained by divers at a depth of 20 meters, risking their lives every day, hundreds of years ago. The only drawback of the products of the above farms is a fairly high percentage of defects, but even taking this factor into account, cultured pearls are several times cheaper than those obtained without human help.
Video of pearls appearing in a shell
Pearls are one of the few precious stones of organic origin. A grain of sand falls into the shell, grows for about 12 years, becomes overgrown with mother-of-pearl and turns into a pearl pea.
History of pearls
Pearls have been known to people since ancient times. There are references to pearls and jewelry made from them in the Indian Vedas and clay
tablets found in excavations in Persia. The first news of pearl fishing (in the Gulf of Mannar) dates back to the 2nd century AD. e. The oldest known pearl jewelry is a necklace from Susa, found in 1901 (now kept in the Louvre). Bronze figurine of Aphrodite from the Boston Museum of Fine Arts (according to various estimates, created in 500-430 BC, 400-336 BC, or 330-146 BC) decorated with gold earrings with pearls, which are in excellent condition.
Until the late Middle Ages, pearls were considered the greatest treasure. Plutarch has a story that
The famous queen Cleopatra owned two of the largest pearls then known in the world, which were in her earrings. Pearls are often found in women's jewelry in Fayum portraits (Egypt, 1st-3rd centuries AD). The oldest pearl whose history can be traced is the Peregrina, which belonged to Elizabeth Taylor.
Origin of pearls
Pearl is a biogenic formation of a zonal structure, which contains regularly located biogenic particles of the mineral aragonite and the organic horny substance conchiolin. Pearls are formed in the shells of marine and some freshwater mollusks. They arise as a result of a reaction to a foreign body that has penetrated into the mantle of the mollusk. The outer shell of the mantle - the epithelial layer - usually lines the shell of a mollusk with mother-of-pearl and envelops foreign bodies. This results in the formation of a pearl. If the pearl forms as a warty growth on the inside of the shell, then it must be separated from the shell. Therefore, such a pearl has a hemispherical shape. They call it blister pearls.
If a foreign body gets inside the mantle, into the connective tissue, then as a result of a kind of immune defense of the mollusk, free, i.e., appears. pearl rounded on all sides. The epithelial layer drawn into the connective tissue by a foreign particle forms a so-called pearl sac, which, due to cell division, very quickly envelops the foreign body and secretes nacre, resulting in the formation of a pearl.
The size of pearls ranges from the size of a pinhead to a pigeon's egg. The largest pearl in existence (named after Hope's former owner) is 5 centimeters long and weighs 454 carats (90.8 grams). It is kept in the South Kensington Museum (London)
What mollusks produce pearls
As mentioned above, pearls are produced by all types of mollusks from bivalves to cephalopods. The main source of pearls are bivalves. Among the freshwater representatives of the latter, the family Unionidae should be noted. Of them
Representatives of the genera Margaritifera (primarily the European pearl mussel) are of greatest importance. In addition, among freshwater mollusks, pearls are found in various types of barley, toothless, and also in the folded comb.
pearl barley
European pearl mussel
Among the pearl-producing marine bivalve mollusks, representatives of the genus Pinctada stand out. Also worth mentioning is the giant tridacna, whose shells lack the mother-of-pearl layer and contain milky white and pink pearls. IN
The noble pinna is found with pearls of reddish, dark brown and black-violet colors. Pearls are often formed in mussels (for example, Perna viridis, Mytilus edulis), related modiolas (Modiolus), as well as in Placuna placenta, Venerids of the genus Venus and scallops of the genus Pecten.
Noble Pinna
giant tricade
Pearls are also formed in the shells of a number of gastropods. Pink, oval-shaped pearls are found in the shells of the giant strombus; white or greenish-blue with a strong shine - produced by representatives of the abalone family; round orange-yellow - common chalk, pale colored - common buccinum. Lustrous pearls are formed in gastropods such as Triplofusus giganteus, turbinids, trochus, Turbinella rapa and many others.
melo vulgare
Giant Strombus
Among the representatives of cephalopods, yellowish pearls are occasionally found in the shells of the common nautilus (Nautilus pompilius).
Common nautilus (Nautilus pompilius)
Pearl colors
The actual color of pearls varies depending on the type of mollusk and body of water and depends on the color of the upper layer of conchiolin. In jewelry stores you can find pearls of a wide variety of colors: white, pink, black, blue, red, burgundy, silver or gold. Blue pearls are considered the most expensive; they are mined in the Indonesian depths. Dark is found in the Caribbean, pink in India and Japan, in Australia it will be white, and in Panama it will be golden.
Pearl cultivation
The growing demand for pearls has led to the creation of an entire pearl farming industry. Such cultured pearls are not an imitation, but a natural product, although they arose with human participation. Today, cultured pearls account for 90% of the total pearl trade. Pearl farms exist both in the sea and in fresh lakes.
Saltwater cultured pearls
Already in the 13th century, in China, small objects were attached to the inner wall of the shell so that they were covered with mother-of-pearl. Modern cultivation of round pearls is based on the German zoologist F. Alverdes, as well as the Japanese T. Nikashiwa, O. Kuwabara in the second decade of the last century. To stimulate pearl formation, nacre beads, milled from the shell of a North American freshwater mollusk, are typically wrapped in a piece of epithelium from the mantle of an Akoya pearl oyster and then implanted into the connective tissue of the mantle of another pearl oyster. Inserting the core into the shell requires skill. This works best for women. They prepare from 300 to 1000 pearls per day. The prepared oysters are kept in sea bays, where they are kept in baskets or plastic cages.
In Japan, the growth rate of the nacreous layer is about 0.3 mm per year, and in the southern seas it reaches 1.5 mm. The shells remain in water for 3-4 years. One sink can usually only be used once. Once the pearl is removed, most oysters die. Of the total volume of products, only 10% are suitable for expensive jewelry, 60% are of lower quality, and 15-20% are discarded. There are main types of cultured sea pearls:
Akoya. This type of pearl is grown by oysters of the same name. Akoya is a saltwater pearl and is cultivated in Japan and China. This is by far the most popular variety and is an example of classic shape and color. Its dimensions do not exceed 0.7-0.8 cm and it has an amazing refraction of light, which creates a feeling of glowing from within.
- Golden pearls. Grown in the seas of Australia, Indonesia, the Philippines and Myanmar. It differs significantly from oriental pearls: its diameter reaches 1 cm and has a dense top layer of mother-of-pearl, which makes the shine muted.
- Black Pearl. The center of trade for this variety is Tahiti, but production is found in many places. Black pearls are considered royal, they come in different sizes (from 0.8 to 1.8 cm) and are more expensive than others. The color range is strikingly diverse: from silver to black, with tints of blue, purple or green.
- White pearls. It is grown in marine silver-lipped oysters on the shores of Australia, Indonesia and the Philippine Islands. Such pearls can reach 2 cm in diameter. Oysters of this species are very capricious and it is quite difficult to tame them, so these pearls are exclusive, despite the fact that they are cultured.
Freshwater cultured pearls
Since the 1950s, freshwater pearls have been grown in Lake Biwa in northern Honshu. The formation of “nucleated” pearls occurs in several stages. At the first stage, small (4X4 mm) pieces - the ovaries of the mantle epithelium of another mollusk of the same species - are transplanted into cuts made in the edge of the mantle of one mollusk (Hyriopsis schlegeli). Up to 20 ovaries are inserted into some shells. Then the operated mollusk is transplanted into a bamboo cage, suspended from a raft and kept at a depth of 0.5 m. Six months later, when the ovaries are covered with a film of pearls, they are removed, sorted and replanted, but no more than one ovary per shell. The ovary-nucleus can only be grafted in a certain place, so the operator keeps the technique of secondary transplantation secret.
The shell with the ovary is again placed in the cage, returned to the water, where it is kept for one and a half to two years. At this time, the shell is regularly fed with plankton. After this period, the pearls reach 6-8 mm, after two to two and a half years - 12 mm. They have an oval or elongated shape, gray or yellowish-pink color, a beautiful shine, very similar to natural. Weight no more than 5 grains. The resulting pearls are called "biwa pearls". Product yield is high. If the mollusk is returned to the water, then you can get “second harvest” pearls of higher quality. There are up to 10 pearl cultivation facilities operating on the lake, including
they contain about 300 thousand shells. Grown pearls are partially bleached, and in this form they go to market.
Biwa pearls came in previously unseen colors and could also be mass produced. A farmer could plant many pieces of mantle into one mussel, and collect 15-20 pearls from each at a time. Since the 1930s, Biwa pearls have set the standard for the quality of freshwater cultured pearls, and have made pearls more accessible than ever before.
Pearl processing and evaluation
The selection of pearls for necklaces or chokers occurs only by eye. The pearl is drilled in a place that has a defect or
less beautiful, which simultaneously eliminates defects. The hole width according to international standards is 3 mm. To make earrings, pins and rings, it is enough to drill the pearl 2/3-3/4 of its diameter. Blue pearls are not drilled because due to the flow of air at the drilling site they change color. The grading of pearls depends on the shape and color, size and brilliance. The correct spherical shape is most valued.
The value of pearls is determined according to the following scheme: - weight is squared, which in turn is multiplied by a coefficient. This coefficient, determined only by a specialist, takes into account quality and other factors; it can be from 1 to 40. For necklaces and necklaces that require a large number of pearls of equal value, this coefficient is very high.
