Pearls. . . the oldest known gemstone, treasured by the ancients as the most precious of gems. Throughout the ages pearls were so rare and coveted that only the wealthiest royals could own them. Today, thanks to the success of the culturing process in the early part of the twentieth century, these most majestic of gems can be enjoyed by everyone.
The Birth of a Pearl
A pearl forms when an irritant is trapped within the body of a mollusk. Just as your eye produces tears to wash away a speck of dust, the mollusk produces a material to isolate the irritant. As time passes, this coating, called nacre, is deposited layer upon layer, enveloping the invading particle, and forms a pearl.
Cultured Pearls – a Twentieth Century Miracle
Historically, natural pearls were extremely rare. Today, sadly, pollution and over-harvesting have made them virtually extinct. However, because pearls have always been coveted, attempts have long been made to increase production. Finally, around the turn of the twentieth century, the process of “culturing” was perfected. Cultured pearls share the same properties as natural pearls. They are also grown within live mollusks; however, in a cultured pearl, the initial irritant is inserted by man, then nature completes the process. During the culturing process, the mollusk may stay in the water for up to three or more years. Over the course of this growing time, it is carefully cleaned, checked and cared for. At harvesting time, less than 30% of the implanted mollusks will produce useable pearls. Very few of these will be truly beautiful and desirable. So, even with the modern culturing process, the production of a gem-quality pearl is a rare and lucky occurrence.
Types of Pearls:
Saltwater Cultured Pearls: Akoya
When most people think of pearls, they imagine the fairly round, creamy to white pearls typically cultivated in saltwater lagoons and bays of Japan. These pearls, sometimes called Akoya pearls, were the first to be commercially cultured. In Akoya pearl cultivation, the irritant introduced into the oyster is a round shell bead, accompanied by a piece of oyster tissue which stimulates nacre production (this is sometimes called “nucleation”). Akoya pearls are most commonly available in sizes ranging from 4 to 9 millimeters in diameter, generally spherical or roundish in shape, and are well suited to all kinds of jewelry as well as strung necklaces and bracelets. In the last few years, cultivation of saltwater “Akoya”- type pearls has been accomplished in China as well.
Saltwater Cultured Pearls: South Sea and Tahitian
In the last twenty to thirty years, the culturing process has been adapted to the waters of the South Seas. Here, larger and more exotic species of saltwater oysters are now being cultivated to produce fabulous pearls of up to 20 millimeters in diameter. Shimmering naturally colored silver, white, golden, cream and grey cultured pearls are fished from the waters off Australia, Indonesia and the Philippines, while the cultivated oysters from the lagoons of Tahiti and French Polynesia produce vivid natural shades of black, grey, copper, silver, pistachio and aubergine. These never-before-seen beauties have become highly prized, but are still far rarer than other types of pearls, and because of their rarity and the expense of harvesting in far-off places, they command higher prices.
Saltwater Cultured Pearls: Mabé
A mabé (or mobé) cultured pearl offers the look of a larger pearl at an affordable price. A half-round implant, with flattened back, is affixed to the inner shell of the oyster. Over time, the oyster coats the exposed surface with nacre. When the oyster is opened, the implant is removed, leaving a thin shell of nacre which is filled with liquid resin and usually backed with a thin slice of mother-of-pearl. The large surface of a mabé cultured pearl makes it especially well suited for use in earrings or a pendant.
Saltwater Cultured Pearls: Keshi
Occasionally, when a mollusk is opened at harvesting, an additional, non-nucleated pearl is found. This accidental “bonus,” which is virtually pure nacre, is called a keshi pearl. Often irregular in shape but generally very lustrous and beautiful, the keshi pearl is very rare, and highly valued.
Freshwater Cultured Pearls
Freshwater pearls are cultured through an implantation process similar to that of the saltwater, except that no shell bead is needed. A tiny piece of tissue stimulates the freshwater mussel to produce nacre, coating the tiny implant and creating the freshwater cultured pearl. Freshwater culturing originated in the waters of Lake Biwa in Japan, and the first freshwater cultured pearls were sometimes called “Biwa” pearls. Today, due to heavy pollution, Lake Biwa is no longer a producer of commercial quantities of pearls. Fortunately, China has taken over this role, and recent harvests have yielded breathtaking sizes and qualities of cultured freshwater pearls, in natural pinks, mauves and peaches, as well as color-enhanced blacks, bronzes and greys. Smaller quantities of freshwater cultured pearls are also grown in the southeastern United States, as well as other locales around the world.
Quality and Value in Cultured Pearls:
There is no universally recognized standard for grading cultured pearls, both because it is impossible to create a master comparison set, and because pearls come in an infinite variety of qualities. The criteria described below are most often used to judge pearls.
The most obvious measure of a pearl is its size. A pearl is measured in millimeters, typically perpendicular to its drill hole. Because no pearl is perfectly round, the measurement generally reflects a range. For example, a pearl measuring 6.6 millimeters in one part and 6.8 millimeters in another would be referred to as 7 x 6.5 millimeters in size. Because it is more difficult for a mollusk to successfully accept larger irritants larger pearls are rarer and more costly.
Necklaces composed of very tiny pearls can also be highly valued because the oyster generally produces only one pearl and each tiny pearl must be hand-drilled and matched meticulously to the next.
Coating and Surface
The quality and thickness of the nacre coating is probably the single most important factor in determining the value and longevity of a pearl. Pearls with thick, healthy coatings of nacre will wear best, resist chipping or peeling, and retain their beauty over time. As with all organic materials, pearls become creamier in color as they age and interact with the air around them; however, a thickly-coated pearl will best maintain the purity of its color.
When choosing pearls, the relative thickness and quality of the coating can be seen by comparing a few strands. A well-coated pearl has even color, no striping or banding, and reflects light evenly in all directions. The surface of the pearl should be free of heavy pits and chips, though small “beauty marks” are subtle reminders of nature’s hand.
Luster is the visual reflection of light from the pearl surface back to the observer’s eye. Although a thick healthy nacre tends to produce a more lustrous pearl, this is not always the case. For example, pearls cultivated in the warmer waters of the South Seas have the thickest coatings of all pearls, and yet often have a silky rather than a shiny luster.
Perfectly round pearls are the rarest and hardest to find, and therefore the most valuable. Off-round and baroque pearls, with their unique, freeform shapes, can be very lustrous and beautiful, yet are much less costly due to their more common occurrence. Here, value need not dictate personal preference. Any shape pearl can be very beautiful.
Cultured pearls come in a variety of colors, from shimmering silvery-white to deep midnight-black. There is no single “best” color, although some are rarer than others. To decide which color is best for you, try on a number of different strands and let your own taste guide you.
The artistry and value of a truly fine cultured pearl piece lies in the painstaking hand-matching of the pearls to each other. Except in the case of a graduated pearl necklace, the pearls used traditionally should be of similar size, color and shape. In some newer designs, the artist intentionally mixes these to create a one-of-a-kind look.