Pearl: Queen of Gems! Part I

Published: October 2011
by Antoinette Matlins, PG; Gem Expert & Author of The Pearl Book: The Definitive Buying Guide and Jewelry & Gems At Auction (GemStone Press)

Part 1 of a 3-part series on pearls. See Part II and Part III.

The richest merchandise of all, and the most soveraigne commoditie throughout the whole world, are these pearles.
C. Plinius Secundus (Pliny the Elder), Roman Historian and Writer, from Natural History, 77 A.D.

old illustration of woman in pearls

The pearl. A wonderful, natural gift from the sea. A lustrous gem created by a living creature. There is no other gem that can compare. It has captivated man's imagination since the beginning of time. Throughout history, it is the pearl that women have cherished most--for its radiance and soft sensuality, for its depth and mystery. From among their most magnificent and precious gems, it is with pearls that Societys great ladies have wished to adorn themselves for the portraits that will immortalize them; it is in pearls they wish to be seen for all time. A stroll through the portrait collections of museums such as the Louvre in Paris, the Hermitage in St. Petersburg, London's National Portrait Gallery, or New York's Metropolitan Museum of Art vividly illustrates the singular and unrivaled reverence reserved for the pearl in every age.

The pearls of yesterday were natural pearls, that is, an accident of nature, formed without human intervention, and among the rarest of all gems. It is estimated that from among 25,000 oysters, one would find only one fine, beautiful natural pearl, so it is easy to see how entire oyster beds were wiped out by fishermen hoping to find a natural pearl. And pearls were reserved for the world's richest and most one else could ever hope to own natural pearls. Today a fine natural pearl necklace may appear on the auction block, but prices are setting new records, and some command millions of dollars!

old photo of man catching oysters

By the dawn of the 20th century, natural pearls were almost extinct, and were it not for the introduction by Kokichi Mikimoto of cultured pearls, only the worlds richest would be enjoying the luxury of wearing pearls at all in our modern society. For three-quarters of a century, the vast majority of pearls sold by jewelers have been cultured, and there is no question that today's pearl market is a cultured pearl market! And today women still seek beautiful, exotic cultured pearls for the same qualities that women in every era have sought them -- that soft radiance and sensual character. Today, however, advances in pearl culturing techniques, and the introduction of pearl culturing in many more places around the world, have resulted in far more choices than ever before, and in more colors, sizes, shapes. Once reserved for only the wealthiest, today there is a beautiful pearl within the reach of every woman, whatever your budget or personal style.

To help you know what type of pearl best meets your needs, and pocketbook, this three-part series will discuss how pearls are created, how to judge quality differences, the types of pearls now available and how they compare to one another, and how to care for your pearls. We'll begin with a discussion of how pearls are produced and how their quality is judged, since quality is evaluated in the same way no matter what type of pearl you choose.

Keep in mind that the information provided here is intended to give you interesting and useful information, but cannot cover everything in depth. For those who would like to know more, please refer to my book, The Pearl Book: The Definitive Buying Guide Buying Guide, available in libraries and also from JTV.

What Is A pearl And How Do Natural Pearls Differ From Cultured Pearls?

Both natural and cultured pearls are produced by mollusks. There are many types of mollusks, including oysters, clams, scallops, and mussels, but only a few can produce beautiful pearls. Certain species of oysters produce the rare and prized sea pearls (saltwater pearls) and mussels produce freshwater pearls. Most pearls are produced in bi-valve mollusks (having a top & bottom shell, held together by a hinge). Saltwater pearls are usually found in certain types of oysters, although rare purple natural quahog pearls can be found in clams, and lovely pink-to-purple-pink or salmon color natural conch pearls from the sea conch (a large saltwater uni-valve mollusk, similar to a snail) are also highly prized. Freshwater pearls are found in certain species of mussels.

The pearls within these mollusks are formed as a result of defensive action taken when the mollusk is invaded by an intruder of some type. In the case of natural pearls, this is usually a small, often microscopic, sea parasite; in cultured pearls, it is a nucleus or piece of mantle tissue inserted by highly skilled technicians. The mollusk isolates the intruder by coating it in conchiolin (kon-kye'-oh-lin), a darkish, porous substance, over which calcium carbonate, the pearl substance we call nacre (nay' ker)--the same substance that forms the lustrous lining on the inside of the shell--is deposited. The nacre gradually envelopes the intruder, and crystallizes around it. Over time, layer upon layer gradually build up, thus forming the pearl.

Where natural pearls are concerned, it takes many years for a pearl to form, even a small pearl, and the entire pearl consists of nacre. In saltwater oysters, cultured pearls remain in the mollusk a relatively short time, typically from 6 months to 2 years, during which time the nucleus is covered by a pearl coating. The size of a cultured pearl is primarily a result of the size of the shell bead that was used as the nucleus rather than the length of time it has remained within the mollusk; the round shell nucleii used for cultured pearl production range from about 2 millimeters in diameter to over 16 millimeters. In freshwater natural pearls, the process is the same; in cultured Chinese freshwater pearls, the process may be started by inserting numerous pieces of tissue from a mollusk of the same type; where each piece of tissue is inserted into the pearl-producing mussel, a pearl will be produced, and in this type of production, the pearls are essentially all nacre (since there is not really a nucleus). The shape of the pearls resulting from this process is usually baroque, often an elongated shape similar to a rice krispie; these "rice krispies" can then be polished into round shapes and reinserted and used as a round, "all-nacre" nucleus, resulting in more or less round, "all-nacre" pearls. The Chinese are also using shell nucleii today, and experimenting with other substances for use as nucleii, such as "mud"! There are also American freshwater pearls, but these are produced by an entirely different technique and are much more expensive than most Chinese freshwater pearls (for more information on American freshwater pearls, see my book, The Pearl Book: The Definitive Buying Guide)

When buying any nucleated cultured pearl, the thickness of the pearl coating over the nucleus is critically important; the longer the nucleus remains inside the mollusk the thicker the build-up of nacre, and thick nacre is needed in order to have a a pearl that is beautiful and will retain its beauty and endure over the years. A thin nacre layer can chip and peel off.

In saltwater cultured pearl production, typically the oyster produces one or 2 pearls; in the early days of culturing, the oyster was sacrificed during the harvest period, but today the same oyster may be used several times; the second harvest often produces the finest pearl. In Chinese freshwater pearl production (China is now the primary producer of freshwater pearls) the mussel used for culturing is much larger than the oyster used to produce the classic round, white, "Akoya" pearl (named after the oyster in Japan that was initially used for pearl culturing) and the freshwater mussel used in China produces many more pearls at a time. The quantity of pearls produced by each mussel, and the number of times that the same mussel can be used to produce pearls, results in many more pearls than can be produced by any other mollusk. Because so many are produced, Chineses freshwater pearls lack the rarity of saltwater pearls and this is the primary reason they cost so much less that saltwater cultured pearls.

Before the age of cultured pearls, when divers risked their lives in the hope of finding a single pearl, with only one in 25,000 oysters yielding a beautiful pearl of any worth, entire oyster populations were completely wiped out by pearl-divers; this, combined with pollution following the discovery of oil in the middle east (where most natural pearls were found), resulted in natural pearls becoming virtually extinct by the beginning of the 20th century. Where cultured pearls are concerned, there is a steady supply of mollusks that are raised to produce pearls, and the same mollusk can often be used repeatedly to produce cultured pearls.

Cultured pearl production is arduous and expensive

Freshwater cultured pearl production is responsible for some of the most exciting developments in today's pearl world, and freshwater pearls are now among the most exotic, beautiful, and affordable. We've touched upon freshwater pearl production above, but techniques are closely guarded and ever-changing. The costliest pearls are saltwater pearls, and production techniques are well understood, so we will focus on saltwater pearls in the discussion below, but keep in mind that there are many overlaps in terms of labor and natural factors...

old photo of cultured pearl inventor Mikimoto

At the end of the 19th century, an Australian named William Saville-Kent and three Japanese inventors a biologist named Tokichi Nishikawa, a carpenter named Tatsuhei Mise, and the son of a noodle maker, Kokichi Mikimotodiscovered techniques for culturing pearls. By 1920, Mikimoto was selling them around the world. Known as the father of the cultured pearl industry, Mikimoto quickly established Japan as the primary source of cultured pearls for almost a century. While techniques have changed and improved in most respects in the years since Mikimoto brought cultured pearls to the world, the basic techniques have changed little.

In saltwater cultured pearl production, the oysters that will be used for pearl cultivation are raised in protected farms. After about 2 years, the farmers bring them out of the water and hand-select the healthiest and most robust for pearl cultivation. These are then transported in vats to a specially equipped room in which highly skilled technicians perform a very delicate surgical operationusing a scalpel and specially designed toolswhereby a small piece of freshly cut mantle tissue is inserted in the area of the gonad, alongside of which the shell nucleus is subsequently inserted. The shell nucleus is also an organic substance, usually a round, shell bead, shaped from the shell of certain types of molluscs (many of the nucleii are made from shells from the rivers and lakes of Tennessee because theyre less brittle, much whiter, and more uniform in color than shells of other molluscs or from other localities). Immediately after the implantation procedure, they are placed in sacs and lowered back into the sea, in bays protected from waves, strong tides, and sea prowlers. After about 3 months, they are raised out of the water once again. Approximately 1/3 of the oysters will have died during this time, but the survivors will be checked and carefully cleaned by hand, then transferred back to the sea. This process if repeated periodically throughout the cultivation period. As time passes, successive layers of nacre build up to form the cultured pearl.

A fine pearl requires a cultivation period of 18 months to three years inside the oyster. Though the nucleus is round and smooth at the start, as the coating of nacre thickens, it can become misshapen or spotted. As a result, a short cultivation period results in a larger crop of rounder pearls with smoother surfaces, but the pearl coating will be thinner. If harvested too early, the pearly coating will be too thin to have any lustrous glow, and will require some type of artificial coating to create a lustrous surface, but this can eventually wear off leaving a chalky pearl in its place (Pearls should feel very cool to the touch or when held in the palm of your hand, whereas coated pearls often dont). More importantly, if it is very, very thin, it can chip and peel, revealing the shell nucleus, and eventually wear off entirely, leaving worthless shell beads! These pearls have a different look than fine pearls with thick nacrethey lack the intense glow that seems to come from the very core of the pearl, and with proper lighting you can sometimes see banding from the shell nucleus. If you examine the pearls at each drill hole, with the help of a jewelers loupe (a hand-held 10x magnifying lens), you can usually see chipping of the nacre, where the nacre was too thin to withstand the drilling; in some cases, so much nacre has already chipped off that you can see a large area of the shell bead, now exposed because the very thin nacre covering has chipped off.

photo of fresh pearl photo of long cultivation pearl

Pearls left within the oyster for a longer cultivation period will have thicker nacre, but when harvested there will be a yield of far fewer pearls with perfectly round shapes and spotless surfaces. This is why the finest round cultured pearls are so rare and costly.

Pearl producers have little control over the results of implantation; they cant control whether the oysters will accept or reject the nucleus; they cant control the quality of what each oyster produceseach individual oyster determines the lustrousness, shape, color, surface smoothness, and so on; and they cant control or prevent natural disasters such as a deadly red tide that can kill an entire oyster population, weather that can alter water purity and temperature (which affect the nacre production), or earthquakes, monsoons, and other acts of nature.

Despite research, advanced science and technology and relentless hard work, 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. When a pearl crop is harvested and the pearls cleaned, sorted and graded, producers find only a very small percentage that will be classified as fine. Following each pearl harvest, producers offer their pearls at auction, with major buyers having been invited from around the world. Competition can be keen for the best lots. From here they find their way to the worlds major jewelers. As with diamonds and other gemstones, pearl prices do not vary much from country to country because they are largely based on what the major players have paid for each harvest.

In cultured saltwater pearls, size is determined primarily by the size of the nucleus and the size and age of the mollusk. A smaller variety of oyster, or one that is too young, will not tolerate a large nucleus and will either eject it or die! This is why the classic round, white pearl know as the "Akoya" (from Japan and now from China) are rarely over 9 millimeterseven in mature oysters, most akoyas are too small to accept a nucleus large enough to produce a 10-11 mm pearl. By comparison, the South Sea cultured pearl is grown in the Pinctada maxima variety of oyster, which grows to more than a foot across, so it can accommodate a very large nucleus. Larger pearls are produced by larger oysters and/or by inserting a larger nucleus; smaller pearls by implanting a smaller nucleus. So for every type of pearl, there are a variety of sizes produced at harvest time. There is little difference in the time required to produce a large cultured pearl and a smaller cultured pearl.

At first glance, this might suggest its easy to get any size pearl the grower wishes, including large sizes, but this is not the case. As the size of the implanted nucleus increases, the greater the rejection rate by the oyster, so there are fewer pearls in larger sizes at harvest, and far fewer fine pearls because oysters can't tolerate larger nucleii as well as nucliee that are smaller. So fine quality cultured pearls in large sizes are rarer and costlier than small pearls. In cultured pearls, the larger the pearl, the thicker the nacre, and more perfectly formed and aligned the crystals in each layer, the more beautiful, rare, and costly the cultured pearl.

It is important to understand that there are no universally accepted standards for pearl grading. When experts use the term fine, it is understood that the nacre is at least 0.5 millimeters thick, the shape very symmetrical, the luster very nice, the surface free of unsightly blemishes, and that the color is beautiful color. In white pearls, a very white color is rarer than the creamier tones, and will cost more, but a creamier color may look better on the wearer. Those with a faint pink overtone are especially desirable in white pearls, while a greenish overtone will reduce value. In fancy colors, the deeper the color, the rarer and costlier; in naturally black cultured pearls, a green or blue overtone adds value. But whatever color you seek, the larger the pearl, the more difficult it is to have all these characteristics.

Pearls are often graded by retailers using an A,B,C scale, with AAA, AA or A being the top quality. But keep in mind that the AAA-quality at one store might be equivalent to the B or C quality at another store. To see quality differences in pearls, they must be compared side-by-side, against a neutral background color (flat white, light beige or light gray) under a diffused light source. This is rarely the way pearls are shown in most jewelry stores. Evenso, if you carry a piece of white tissue paper, on which you can lay the pearls, and you move away from the spot lights, you will be surprised at the differences you will be able to see.

Let's clarify the terms natural, cultured with imitation!

All too often sales people assume that when customers use the term pearl they are referring to cultured pearls, so when asked if a pearl is natural, they will usually answer yes thinking the customer wants to make sure the pearls are not imitation. It is important to clarify what you mean when asking about pearls. If you are asking whether a pearl is a natural pearl and not a cultured pearl, you must ask that explicitly, is this a natural pearl one made without human intervention -- or is it a cultured pearl? If you are trying to determine whether or not a pearl has been treated, dont ask whether or not it is natural; ask explicitly whether or not the pearl has been treated. Or, state clearly that youre not asking whether the pearls are imitation or cultured, but rather, whether or not they have been treated. If the sales person doesnt understand what youre asking, I suggest you buy from someone more knowledgeable about pearls! If the seller insists that what you are buying is natural in every wayno nucleus, no human intervention, no treatments be sure this is stated in writing and then take them to a gemologist-appraiser for confirmation. Where bracelets and necklaces are concerned, gemologists can usually confirm whether the pearls are cultured or natural by examining the drill holes; in some cases, where the nacre is extremely thick, or if the pearl has very thick nacre and is undrilled, it may be necessary to send them to a gem testing laboratory where special tests combined with X-ray examination can provided for confirmation.

Imitation pearlsalso called faux, simulated or semi-culturedare not created by a living creature and have never been inside a mollusk. They should not be referred to as genuine or cultured because they are entirely artificial. Imitation pearls are made from round glass, shell, or plastic beads that are coated in a substance called pearlessencea mixture of ground fish scales and lacqueror a type of epoxy.

The difference can usually be seen right away when compared side by side. One of the most obvious differences is in the luster; imitations usually have 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. An easy, reliable test for spotting the fake in most cases is the tooth test. Run the pearl gently along the edge of your teeth (the upper teeth are more sensitive; the test wont work with false teeth, and be thoughtful and remove any lipstick prior to doing this). A pearl (natural or cultured) will have a mildly abrasive or gritty feel (think of the gritty feeling of sand at the seasideand 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. Youll never forget it! Most jewelers also sell imitation pearls and its easy to do the comparison in any jewelry store. This test will not harm any pearl. I do it frequently at international gem shows because it not only aids in separating cultured from imitation, but it can be an indicator of surface treatment. Sometimes when I examine a pearl with my loupe and see indicators that it is, indeed, a pearl, but then do the tooth test, the feeling is too smooth, suggesting the pearl has either been polished, surface-coated, or both. Another simple test is temperature. If you take a real pearl (natural or cultured) from a showcase that is properly lighted with cool lights (warm lights are not good for pearls and will cause the nacre to dry and crack) and place them immediately in the palm of your hand, they should feel quite cool. By comparison, imitation pearlsand some surface-coated pearlswill feel warmer. This may take some practiceand it wont work if someone has warmed them up by holding them or wearing them for several minutes immediately before you do this test, but here again, once you learn to feel the difference, it can be a valuable indicator that something may be wrong.

Whether natural or cultured, not everything created within the mollusk is considered a gem. Differences in quality determine desirability and value. The more perfect the pearl, the rarer and costlier; in pearl strands used for necklaces or bracelets, the better matched the pearls are, the rarer and costlier. Among fine quality pearls, as size goes up, value increases; among the largest pearls, if quality is exceptional, value increases exponentially. You must take time to understand what to look for and what factors are judged to determine the quality and value. And you must keep in mind that many treatments are used today to improve appearance.

Judging pearl quality

In general, pearl quality is judged in five areas that affect the value of pearlscultured and natural alikeand each factor influences their beauty, desirability, rarity and cost.

Luster & Orient. This is what gives the pearl its luminescence, a character that sets pearl apart from all other gems. This is the first and most immediate visual indicator of the quality and thickness of the nacre, the "pearl" layers covering the shell nucleus. The richer or more intense the lustre, the finer the pearl. Luster is the luminous glow seen in fine pearls. It is associated with the formation and alignment of the crystalline layers of the pearl coating. The more intense the luster, the rarer and costlier the pearl; low-luster pearls are much less desirable, and less costly, because they have a chalky appearance. Orient refers to an iridescent play-of-color across a pearls surface, resulting from a prismatic effect created by light passing through the crystal layers of nacre. It is seen only in the finest pearls. Pearls with a combination of lustrousness and orient possess a unique beauty and character that is extremely rare. Such pearls are costlier than others and can cost much more than larger pearls that lack this combination, even if comparable in other ways.

Size/weight. The larger the pearl, the rarer and the more difficult to find perfection. Most natural pearls are sold by weight, in grains or carats (1 carat = 4 grains) but millimeter dimensions are also provided to indicate size. In cultured pearls, size is always indicated in millimeter dimensions.

Shape. Round pearls are the rarest, but it is extremely rare to find a perfectly round natural pearl. Symmetrical shapessuch as oval, drop- or pear-shape, acorn, and buttonare less rare than round, but can still be very rare and costly, especially in matched pairs. Asymmetrical shapes are often referred to as baroque. They can be quite whimsical and desireable, but these are less rare and costly than round or symmetrical shapes.

Color. The whiter the body color, the rarer, although creamy colors and natural color black or gray pearls are desirable but less costly than white pearls. Today we also have a wide range of pastel colored cultured pearls from which to choose. Pearls also have overtones of other colors such as pink or green. In white pearls, pink overtones add value while green overtones reduce value. In black pearls, green or blue overtones add value; in gray pearls, pink or lavendar overtones are sought. Evenness and uniformity of color is important. When buying a fancy-color pearl, be sure to ask whether or not the color is natural since this will dramatically affect cost. Pearls can be dyed or treated in other ways to enhance color; there is nothing wrong with buying treated-color pearls as long as you know the color is treated and pay an appropriate price.

Surface Perfection. The presence of surface blemishes such as tiny pits, blisters, or cracks, their location in terms of visibility, and whether or not they affect durability is important in valuing any pearl. While a flawless surface is extremely rare, pearls with blemishes that are small and barely noticeable or located where visibility is reduced or can be concealed by a setting, are more desirable than those with visible or unsightly surface blemishes, and they will cost more than those with more visible blemishes.In addition to the five factors above, in jewelry such as necklaces and bracelets--in any piece of jewelry using multiple pearls--the matching of the pearls in terms of each of these factors is an important factor affecting cost.

Keep in mind, however, that each of these quality factors can be artificially altered to appear better than they are and "bargains" may not be what they appear to be. Let me stress that there is nothing wrong with buying pearls that have been treated as long as you know, and as long as you are paying an appropriate price. However, where treated pearls are concerned, especially those with treatments to enhance the surface lustrousness or color, their appearance may change in the future. For these reasons, it is especially important when buying "fine" pearls to make sure you are buying from a reliable source that has knowledgeable buyers and will stand behind its product.

Shop all pearls and pearl jewelry.

Related Articles

pearls in oyster

Pearl, Nature's Living Gemstone

Modified April 2011

blue and purple gemstones

Natural or Artifical Gems?

Modified April 2011

purple and silver gemstone necklace

Jewelry Education

Published May 2011