Cultured Pearls | Pearl Farms

Cultured Pearls

Almost all pearls (Perle French or German, Perla Spanish or Italian) used for jewelry today are cultured pearls. Cultured pearls are "created" with the assistance of human intervention. A cultured pearl is formed when a small foreign object or irritant (seed nucleus) is embedded in the tissue of a mollusk or oyster by a "seeding" technician. By surgically implanting this foreign object or nucleus into the tissue of the mollusk, the pearl farmer can induce the creation of a pearl. The pearls are usually harvested three to five years after the implanting of the nucleus, but it can take up to six years before a large high-quality pearl is produced.

The only significant difference between "Natural Pearls" and "Cultured Pearls" is that in the case of a natural pearl, the process begins accidentally; in the case of a cultured pearl, the process begins artificially. The end result is relatively the same.

By x-raying a pearl, jewelers can determine whether it has been cultivated or is natural. If the nucleus in the center of the pearl is a perfectly round sphere, the jeweler will know that it has been "cultivated." When most pearl cultivators insert the nucleus or "grit", it is usually pefectly round, so as to produce a more valuable, round pearl. Seed nuclei is created using mollusk shell that has been rounded into small beads. Much of the shell material used to create the seeds comes from a mollusk variety that is indigenous to the Midwest and Southern United States. If the center nuclei is not perfectly round, a jeweler could conclude that the pearl is a "natural" pearl.

Pearl Mollusk Varieties

Pearl farmers typically use three varieties of mollusks to culture pearls. Australian Gold or Silver Lipped varieties of mollusk known as pinctada maxima are used to produce champagne or cream colored South Sea Pearls. Black-Lipped mollusks (pinctada margaritifera) are used to culture black Tahitian pearls and White-Lipped mollusks (pinctada maxima) are used to culture cream, pink, silver or white South Seas pearls.

Akoya Saltwater Pearl Cultivation

Akoya is the Japanese word for Saltwater. Akoya or Saltwater pearl oysters are nucleated using a bead usually prepared from mother-of-pearl. The bead serves as a mold around which the pearl nacre will develop. The resulting pearl will contain the bead at its center. The pearl tends to develop into the same shape as the original bead. Akoya pearls are typically larger than freshwater pearls. They are also smoother, rounder and have a higher luster than their freshwater counterparts.

Cultivation of high quality pearls occurs in coastal waters deeper than 5m. The optimum ocean temperature for oyster/pearl cultivation is between 20º to 25º C, and nacre thickness can be affected by minute daily changes in water temperature. The optimal depth for cultivating pearl oysters is around 15m, and as the depth increases beyond this point, the rate of nacre deposition slows down [5]. At greater depths, pearls with a pinkish coloration can be cultivated.

Freshwater Pearls

Freshwater cultured pearls are grown in freshwater rivers and lakes. Although the traditional source of pearls has been saltwater oysters, mollusks which live in freshwater lakes and rivers are also capable of producing pearls. These pearls are generally less expensive when compared to their saltwater counter parts. Freshwater mollusks are nucleated using a piece of mantle tissue only. The pearl develops around the mantle tissue, which can deteriorate in time, leaving a pearl that is composed almost entirely of nacre.

Freshwater pearls tend to have less surface luster when compared to saltwater varieties, and are characterized by the reflection of rainbow colors in the luster. Many freshwater pearls are oblong shaped, and known as "rice pearls". They are generally less expensive than saltwater pearls, but are available in a wider variety of colors. Freshwater pearls have the additional benefit of being quite durable.

Keshii Pearls

Keshii pearls, Japanese for "poppyseed," can be formed in both saltwater and freshwater oysters. A Keshii Pearl (aka Seed Pearls or Keshis) is a "non-nucleated" pearl that is an accidental byproduct of the cultivating or culturing process, resulting from the oyster spitting out the implanted nucleus before the formation process has completed.

The partially formed Keshii pearl is all nacre, and tends to have a rough organic shape, looking like it was naturally formed. Although no man-made nucleus is used to facilitate their creation, Keshii pearls are not considered to be a true "natural pearl." Keshii pearls range in color from peacock to black, white, grey, and rose or rosea.

Cultured Pearl History

Although some cultures had long been able to artificially stimulate freshwater mollusks into producing pearls, the pearls produced in this manner were generally "Hemispherical" pears or "Mabes", rather than actual round pearls.

The modern art of Culturing Pearls came about in the late 19th and early 20th centuries. Japanese researchers such as Kokichi Mikimoto developed modern techniques for culturing pearls and was able to convince the consuming public to accept these "artificially created" pearls as a valuable commodity. He continued his research into the art of culturing pearls, which by the early 1900's lead to his acquisition of a patent for culturing "Spherical" or "Round" pearls.

Mikimoto discovered a technique for inducing the creation of a round pearl within the oyster's tissue, which revolutionized the pearl industry. Pearl farmers could now cultivate large numbers of high-quality round pearls. This was in stark contrast to the traditional methods of harvesting natural pearls, which are difficult to find and have a wide variety of shapes, sizes, quality levels.

Cultured pearls could now be designed from the start to be "perfectly round" and near flawless in quality. By "farming" the oysters, they could be monitored during the several years that are required for a pearl to become fully formed. This monitoring process would ensure the oyster's health and survival during the pearl-making process. Culturing the pearls took much of the chance, guesswork and risk out of the pearl industry. This allowed the pearl market to become stable and predictable, thereby fostering its rapid growth over the past 100 years.

Today, the cultured pearl industry has effectively replaced the natural pearl industry, turning natural pearls into rare collectors' pieces. By using x-rays, cultured saltwater pearls can often be distinguished from natural pearls by revealing the inner nucleus of the pearl. However, If mantle tissue is used in the stimulation and creation of freshwater pearls, it could be more difficult to detect the nucleus via an x-ray because the inner tissue can broken down and be replaced by only the nacre.

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Bibliography & Suggestions for Further Study on Japanese Pearls

1. Pearl Guide, Japanese Akoya Pearls . www.pearl-guide.com

2. K Mikimoto & Co, Ltd, Pearls . www.mikimoto.com

3. Seikai National Fisheries, Pinctada margaritifera Cultured in Okinawa . www.lib.noaa.gov

4. American Museum of Natural History, Pearls . www.amnh.org

5. U.N. Food & Agriculture Org., Pearl Oyster Taxonomy & Distribution . www.fao.org