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The Jewelry Hut
The Cultured Pearl
The Buying Guide
Getting to know Gems
How to select, buy, and care for, and enjoy Pearl Jewelry
What is a Pearl?
Pearls in the making
A pearl is an organic “gem,” that is, a pearl that comes from a living thing. Coral (formed from a colony of marine invertebrates) and amber (fossilized tree sap) are also organic gems. In the case of the pearl, it is produced by several species of saltwater and freshwater molluscs, soft bodied animals protected by a hard exterior shell. But don’t expect to get lucky at the dinner table; most pearl producing varieties are not edible types!
Molluscs includes oyster, clams, mussels, snails, squid, octopus, and many other shellfish. There are over 100,000 different types, but only a few varieties of mollusc produce the lovely pearls for which we long.
Pearls are produced in particular varieties of bivalve molluscs (having two shells, such as mussels and oysters), but only in those with a “pearly” lining on the interior of the shell. Not all bivalves that produce “mother-of-pearl,” as this shell lining is called, actually produced pearls, but only such types can produces a true pearl.
In the case of natural parasite finds its way into a mollusc’s shell, and lodges itself inside. If the mollusc can’t get rid of it, it begins to produce something to soothe the irritation the intruder causes; this soothing is a brownish substance called conchiolin (Kon-KY-oh-lin, “ky” as in “sky”), over which another substance is secreted, usually a whitish substance, called nacre (NAY-ker). The conchiolin binds the nacre together to form the pearl.
What we know as a “pearl” is the result of the buildup of layer after layer of nacre, enveloping the intruder. Nacre is the same substance that forms the lining within the shell. It is composed of microscopic crystals of calcium carbonate, primarily calcite and aragonite. When there are a sufficient number of layers, and when the crystals are properly aligned with each other, a prismatic effect is created as light travels through each layer. This prismatic effect creates a rainbow like glow across the pearl’s surface; a soft iridescence, which is referred to as the pearl’s “orient.” This lustrous glow and soft iridescent quality produced by the nacre is what gives a fine pearl its unique beauty and character. The thicker the nacre, and more perfectly aligned each crystal layer, the more beautiful, rare, and costly the pearl.
A pearl is not very hard compared to other gems; 2.5 - 3.5 on Mohs’ hardness scale, but its compact nature makes it surprisingly durable and very resistant to knocks and blows; many pearls have retained their beauty for hundreds of years, as the legendary pearls we’ve mentioned can attest.
Natural pearls are produced by wild mollusc in their native habitat, but most wild molluscs don’t contain pearls. Depending upon a variety of conditions, it can take 10 years or longer for an oyster to produce a 6 millimeter pearl, and far longer for pearls of 7 or 8 millimeters. The longer the pearl remains in the mollusc, however, the more likely that its beauty will marred, especially its surface, so large natural pearls of fine quality are especially rare. a pearl diver might dive an entire lifetime and amass only a handful of natural pearls, and of those, most of the larger pearls will not be very beautiful.
The Fine pearls so much in demand; the “naceous” variety consisting of many layers of nacre, are only produced by certain types of molluscs, or shellfish, as we mentioned earlier. Other types of shellfish can produce a pearl like product, but few have lasting beauty or commercial value.
The largest, most beautiful pearls sought throughout history are produced by saltwater molluscs. While we refer to them as pearl producing oysters, this may really be a misnomer; oyster are an edible mollusc from the family ostreidae and most saltwater pearls are produced by non-edible molluscs more akin to the scallop family.
Today, most of the world’s wild, natural pearl producing molluscs have vanished because of overfishing and pollution, so beautiful natural pearls are rarer than ever before. Some jewelers still obtain them occasionally for special clients who can appreciate and afford them (primarily from auctions, estate jewelry, and agents for private estates), but they continue to be reserved for the privileged few.
The pearl market is a cultured pearl market today
As natural pearls were becoming extinct, the Japanese were developing techniques for producing cultured pearls, also called cultivated pearls. A cultured pearl is also a natural product, produced by a mollusc in essentially the same way it produces a natural pearl, but with the help of science. In the cultured pearl, technicians start the process by implanting the object that stimulates the oyster to produce the conchiolin and nacre that results, ultimately, in the creation of the pearl.
Differences between cultured pearls and natural pearls
One way to understand the difference between a natural pearl and a cultured pearl is to think of the natural pearl as a product of the mollusc working alone, and the cultured pearl as a product of science helping nature. In the natural pearl, the irritating intruder; often microscopic, such as a parasitic worm that bores its way through the shell into the oyster tissue; in the cultured pearl, technicians surgically implant the intruder. In round saltwater and freshwater cultured pearls, the implant is normally a round bead, accompanied by a piece of mantle tissue; this round bead/mantle tissue implant is called the nucleus and these are referred to as “nucleated” cultured pearls. The mantle tissue carries the cells that start the production of conchiolin and nacre; placing it next to the round bead assures that the bead will be nacre-coated, hopefully becoming a nice, round pearl.
In most freshwater cultured pearls, the lovely irregularly shaped pearls that resembles rice-krispies, the implants may be mantle tissue alone; these are referred to as “tissue graft” or “non-nucleated” cultured pearls. Freshwater pearls produced from mantle tissue alone are usually not round, but elongated and asymmetrical in shape.
The implant, whether bead and mantle tissue or mantle tissue alone, is referred to as the “nucleus” and it is the implanting of a nucleus that cause the irritation that the mollusc must soothe, thus creating the pearl. The prized round pearls so coveted today are bead-nucleated pearls, produced by saltwater oysters.
Inserting the nucleus requires a very delicate operation performed by highly skilled technicians. The nucleus is made from a natural, organic substance. For round, saltwater pearls, the nucleus is normally a smooth, round sphere made from the shell of a particular type of mollusc that lives only in the United States, in rivers and lakes fed by the Mississippi River. A different variety of shell was recently used (as an experiment) by some pearl producers in Japan and china, with disastrous results; the pearls containing the se experimental nuclei began to change color in just months, and the nucleus itself; the very core of the pearl, began to deteriorate within, weakening the pearl and resulting in a life expectancy under two years. If you buy pearls that begin to discolor after so short a time, return them to your jeweler immediately.
A fine pearl requires a cultivation period of two to three years in the oyster to acquire a thick nacre coating that will give it lasting beauty. But there is a delicate interplay of numerous factors occurring within the mollusc during the cultivation period that affects the final appearance of the pearl, and the longer it remains in the mollusc, the higher the probability that certain desirable characteristics will be adversely affected, especially shape and surface perfection. Remember that the nucleus is round and smooth at the very start, before any nacre has begun to cover it. As the nacre coating accumulates and thickens around the sphere at its core, it can become increasingly out of round or misshapen, and increasingly spotted. So, a short cultivation period result in a much larger crop of rounder pearls with smoother surfaces, but with thin nacre and less longevity; a longer cultivation period results in thicker nacre and longer life, but fewer pearls with perfectly round shapes and spotless surfaces. This is why the finest round pearls are so rare, and costly.
During the cultivation period, the oysters receive constant attention and care to help assure that they will thrive and produce the best possible pearl crop. But there are no guarantees. The culturing process is very delicate and fragile, and after all of the effort that requires, one will still has little control over the final results. Pearls farmers can’t control whether or not the oysters will accept or reject the nucleus after the implant procedure; they can’t control the quality of the pearl the oyster produces, for each individual oyster determines the lustrousness, shape, color, surface smoothness, and so on; and they can’t control or prevent the natural disasters that can destroy the oysters, their habitat, or their lustrous creations; typhoons, earthquakes, disease, or other acts of God. The Japanese have suffered great loss as result of the deadly “red tide,” and Kobe, the pearl capital of Japan, was nearly destroyed in 1995 by one of the most serious earthquakes in modern history. Indonesian South Sea pearl production has been plagued by repeated earthquakes as well, and the American freshwater cultured pearl harvest was severely damaged as result of chemicals leaching into the water from a nearby state road project in which lime was being used.
Despite the best efforts of pearl producers, and the advances of science and technology, in the end it is the oyster and nature that determine whether or not there will be a pearl at all, and if so, whether or not it will be beautiful and valuable.
How long does it take to make a beautiful pearl?
In the case of natural pearls, as mentioned earlier, it can take many years to create a beautiful pearl. With cultured pearls, the cultivation period; the amount of time the nucleus remains in the mollusc after the implant procedure, normally ranges from about two years to six months, or less. The shorter the cultivation period, the thinner the nacre; the longer the cultivation period, the thicker the nacre. If the cultivation period is too short, the pearl will not last. Buyers must be careful not to buy pearls with nacre that is too thin.
The length of the cultivation period is a matter of serious debate today. At one time pearls remained in the oyster fro much longer periods, up to five years; in the 1920s to 1940s, the cultivation period was much longer it is today so most cultured pearls had very thick nacre. However, surfaces were more spotted. For cultured pearl growers today, escalating production costs and ever present natural risks to the oyster crop are reduced by shortening the cultivation period, as are deviations in shape and imperfections across the surface of the pearl. Each pearl producer must decide how to best balance all the factors involved so that a lovely pearl is produced, at an affordable price. without unnecessary risk.
How much of the pearl is really “pearl”?
The primary physical differences between natural and cultural pearls are related to the thickness of the actual “pearl” substance, the nacre. The thickness of the nacre affects size, shape, beauty, and how long the pearl will last.
In cultured pearls, the size of the nucleus dictates the size of the pearl; in cultured pearl production, larger pearls are produced by inserting a larger nucleus, smaller pearls by implanting a smaller nucleus. The time required to produce a large pearl is essentially the same as that required to produce a smaller cultured pearl.
Implanting normally begins in January/February with harvesting in November. The largest nuclei are implant first, to give them the advantage of a slightly longer cultivation period; the smaller are planted last, sometimes several months later, and usually have a shorter cultivation period, but since the nucleus is smaller the ratio of nacre is normally still comparable to larger pearls.
While it takes several years to raise the mollusc and produce a fine cultured pearl, natural pearls take many years, even for very small pearls. With natural pearls, the pearl is essentially all nacre, with no nucleus at its core. The process that creates the natural pearl is usually started by a very small intruder, so the size of the pearl is an indication of the number of years the pearl has been in the mollusc rather than the size of an implant. Small natural pearls have normally been in the mollusc for a shorter time; larger pearls a much longer time.
Large natural pearls of fine quality are among the rarest of earth’s treasures. Keep in mind that among all the pearl producing molluscs, only a very small percentage ever experience that unique set of natural circumstances that results in the creation of the pearl. Furthermore, in nature there are more variables affecting the quality and beauty of the pearl; not all natural pearls are fine quality; not all are beautiful and desirable. The larger the pearl, the less likely it will be fine and beautiful; as in cultured pearls, the longer the pearl remains in the mollusc, the greater the likelihood that there will be defects in its shape, surface perfection, nacre crystallization, and so on. And, last but not least, natural pearl producing molluscs have never been conveniently located for easy access, and diving for natural pearls has always been very perilous, often ending in death. Divers have spent entire lifetimes diving for pearls, to end up with little more than a handful of small pearls for their work. Among all the known natural pearls, including famous historical pearls, fine large pearls are few and far between.
Diving for natural pearls continues today in various parts of the world, but for the most part, the oyster beds known for fine natural pearls have been killed by pollution. Discovering so rare a treasure as a large, fine, natural pearl holds a powerful allure to some, but for most the discovery will never be more than a dream.
Some very fine jewelry form still seek and acquire fine natural pearls, but they are even rarer today than ever before. A very fine 15 millimeters round cultured pearl is as rare as the natural, but it is still a costly treasure. Whether cultured or natural, the larger the pearl, the rarer and costlier.
In cultured pearls, cultivators insert several different size nuclei into molluscs, producing a variety of pearl sizes at harvest. At first glance this might suggest that it is easy to get any size pearl the grower wishes, including large sizes, but this is not the case. Only a very small percentage ever experience the unique set of circumstances that results in the creation of a beautiful, fine quality pearl, and, as the size of the nucleus increase, the quantity of fine quality pearls actually harvested decreases. As the size of nucleus increases, fewer molluscs survive the implant operation, and more molluscs reject the nucleus, so fewer pearls are actually harvested. Furthermore, the larger the nucleus, the more difficult it becomes for the mollusc to produce a pearl with fine color, luster, surface perfection and shape. This means there are fewer pearls actually harvested, and far fewer fine pearls. This is why larger cultured pearls of fne quality are rarer, and whu they cost so much more than comparable smaller cultured pearls.
Differences you can see and differences you can not see
The thickness of the nacre affects size, shape, beauty, and how long the pearl will last. The natural pearl is all pearl, or all nacre, while most cultured pearls consists of a nucleus coated with nacre. The thicker the nacre coating on the cultured pearls, the more beautiful it will be.
Very few people can see any difference between a very fine cultured pearl with thick nacre and a very fine natural pearl. Both will exhibit a rich, deep, intense lustrousness accentuated by a beautiful, soft iridescent “play of color”; sometimes referred to as “orient”, that can be seen moving across the surface of the pearl as it moves in the light.
Generally speaking, however, there are some visual clues that might suggest natural or cultured:
Matching. Because of their scarcity and limited supply, matching of natural pearls was often ignored, especially as the size increased, so necklaces often contain pearls with marked differences in size, color, and shape.
Pearl Color. In term of color, natural pearls are usually creamier than today’s finest cultured pearls.
Pearl Shape. In term of shape, natural pearls are rarely truly “round,” and necklaces often seem to contain pearls that seem out-of-round to today’s pearl buyer.
Cultured Taste may not recognize natural treasures!
Finding an appreciative buyer for such a rare beauty as a strand of natural pearls may be rare than pearls themselves. The reason for this isn’t difficult to understand if you think about it for a moment. There is really nothing in nature that is truly “perfect,” a fact that, where gems are concerned, was more fully appreciated and accepted in days gone by. Natural pearls are just that, natural. As such, differences abound, and given their rarity to begin with, there was often no choice about what available to use. With cultured pearls there are much larger quantities of pearls from which to choose, so it is easier to find and carefully match them.
Since cultured pearls now dominate the market, we have come to expect a certain look in pearls, a look rarely found in natural pearls; uniformity, whiteness, roundness, and much larger sizes than are normally seen in natural pearls. Ironically, this has had a negative impact on natural pearls. While much rarer than cultured pearls, a strand of small natural pearls will have a perceived value of much less than a larger strand of cultured pearls.
Absence of uniformity may hint at natural treasure
In a market so totally dominated by cultured pearls, we’ve come to expect precise matching in pearl strands, and perfection of shape and surface smoothness in individual pearls; pearl that aren’t perfect or well matched are assumed to be poor quality cultured pearls. As a result, natural, natural pearls are sometimes ignored because they aren’t recognized for what they are.
Small natural pearl necklaces and other pieces of jewelry with small natural pearls are often ignored today at auctions or estate sales, and the absence of uniformity is often the first visible. clue. So, while, the finest natural pearls can command stellar prices, many smaller natural pearls can now be acquired at auction and from private estate at very attractive prices. If the idea of owning a rare natural pearl necklace appeals to you, remember that uniformity in a strand is rarely the case, and one indicator of what you might have may well be the absence of uniformity!
How to tell the natural pearl from the cultured pearl
Appreciation for natural pearls is increasing as people learn more about them and how they compare to cultured pearls, and as interest in heirloom jewelry, antiques and estate pieces increases. Strengthening prices for natural pearls at auction and among fine estate dealers seems to indicate that they are a collectible with a lustrous future. Here is how one can determine whether a pearl is cultured or natural:
Examine the drill hole. If a pearl has been drilled, a jeweler or gemologist can usually identify a cultured pearl very easily. By examining several pearls, looking into the drill hole carefully with a loupe (a jeweler’s special magnifying lens), the line of demarcation between the mother-of-pearl nucleus and the layer of conchiolin may be visible, sometimes appearing as a darker line. It may not be visible in all pearls, and you may only see a portion of the line in a given pearl. If the strand is tightly knotted (as in a newly strung necklace), you may have tot ry several pearls before finding enough space between the pearl and knot to be able to use the loupe. When this darker area is visible, you can be sure you have a cultured pearl. Note: Many cultured pearls have been bleached to remove the brownish conchiolin line. Also, it won’t be seen in cultured pearls with extremely thick nacre. When you can’t see this brownish layer, you must test further.
The size of the drill hole is sometimes an important indicator. Very small drill hole may indicate “natural.” Since natural pearls are valued in part by weight, great care was taken to keep the hole as small as possible to minimize loss weight, and maintain maximum value.
Examine with an ultraviolet lamp, using long-wave ultraviolet radiation (an inexpensive “black light” is all you need). Examination with ultraviolet light is often helpful when examining pearls that don’t show any line of demarcation, when it’s difficult to view the drill hole, or in cases where the pearl is not drilled. It can be especially useful with necklaces or bracelets. When examined under ultraviolet light, cultured pearls normally have a strong milky , bluish-white appearance. In the case of cultured pearl strands, this response will be uniform throughout; in a natural strand, there will be variations from pearl to pearl in the intensity of color when viewed under ultraviolet light.
Examine with a strong penlight or fiber optic light. View the pearl from several different directions while holding a strong light in direct contact with it, slowly moving it around the pearl’s surface without losing contact. If viewed in this manner, it is sometimes possible to see dark, parallel lines from the mother-of-pearl nucleus showing through the nacre (especially in cultured pearls with very thin nacre). These dark, parallel line always indicate cultured pearl.
With a strong light, viewed in this way, you might also notice some orangey colored, irregularly shaped spots, some large and some small. This is an indication of cultured pearl.
Cultured Pearls X-ray examination. Cultured pearls can often be identified as cultured by the above tests. However, such tests are inconclusive on undrilled pearls with extremely thick nacre such as South sea cultured pearls or American fresh water pearls. In these pearls must be x-rayed.
If you think you might have a strand of natural pearls but are not sure, submit them to a reliable testing laboratory for documentation. natural pearls must be x-rayed to confirm authenticity. If you are buying pearls represented to be natural, make sure there is an accompanying identification report from a reliable lab, or make the sale contingent upon getting one. Always be sure to have proper documentation, no matter how old the piece, who the owner is, or how wealthy. Note: Be sure to have an experienced gem testing laboratory perform the tests and make the determination. People have made costly mistakes based on the erroneous reading of an x-ray by a dentist of friend.
Cultured pearls versus imitation pearls
Today, when jewelers speak of “genuine” or “real” pearls, they mean cultured pearls. This is what you see in jewelry stores, and this is what we will be talking about, unless otherwise indicated in these articles. According to the United States’ Federal Trade Commission Guidelines, however, the terms “real” and “genuine” can be used only for natural pearls unless followed immediately by the term “cultured,” and the term “cultured” immediately preceding the word “pear,” and with equal conspicuity.
How do imitation pearls differ from cultured pearls?
Natural pearls and cultured pearls are produced in rivers, lakes, and bays by living molluscs and can be very similar in appearance. Imitation pearls; also called “faux,” “simulated,” and most recently, “semi-cultured,” are not created by any living creature. They should not be referred to in any way as genuine or cultured. Imitation pearls have never seen inside of a mollusc. They are entirely artificial, made from round glass, plastic, or mother-of-pearl beads dipped in a bath of ground fish scales and lacquer (called pearlessence), or one of the new plastic substances. The difference can usually be seen right away when compared side by side. One of the most obvious differences is in the luster. Give it the luster test; the cultured pearl will have a depth of luster that the fake can not duplicate. The fake usually has a surface “shine” but no inner “glow.” Look at a fine cultured pearl and an imitation pearl side by side (away from direct light) and notice the difference.
Use the pearl “tooth test” to spot the fake
There are some fine imitation pearls today that can be very convincing. Some have actually been mistaken for fine cultured pearls. An easy, reliable test in most cases is the tooth test. Run the pearl gently along the edge of your teeth ( the upper teeth are more sensitive, and also be aware that the test won’t work with false teeth). The genuine pearl will have a mildly abrasive or gritty feel (think of the gritty feeling of sand at the seaside; real pearls come from the sea), while the imitation will be slippery smooth (like the con artist, slippery smooth signifies a fake!). Try this test on pearls you know are genuine, and then on known imitations to get a feel for the difference. You will never forget it!
The tooth test may be unreliable for amateurs when applied to the imitation “Majorica” pearl, however. Although to th trained eye they have a very different look from cultured pearls, this is an imitation pearl which might be mistaken for genuine. Close examination of the surface under the magnification will reveal a fine “pinpoint” surface that is very different from the smooth surface of a cultured pearl or natural pearl. An experienced jeweler or gemologist can quickly and easily identify the Majorica pearl for you.
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