What Are Cultured Pearls?
When people hear the phrase cultured pearls, classic, round Japanese Akoya ocean pearls
generally come to mind. Developed in Japan during the 1920s, Akoya pearls dominated the market during much of the 20th century, and so molded the perception of pearls among two generations.
Surprisingly, cultured pearls come closer to perfection than natural pearls. This is due in large part to the use of spherical shell nuclei to determine shape. Dependent on the natural growth characteristics of pearl "oysters" (smaller members of the genus Pinctada)
, cultured pearls could not match the degree of perfection easily attained by imitation pearls made with modern industrial equipment. For a time, this led to an obsession with flawlessness and unnatural color that is, in fact, quite unreasonable for a product cultured by living animals.
The Culturing Process
Pearl cultivation is a labor of love. Exact details vary from farm-to-farm and from species- to-species. For example, oysters can be collected or bred, and the period of caring for them before they are implanted varies. Generally speaking, the implantation process is as follows:
- The animals are cleaned and a skilled grafter performs a quick and precise "surgery" of implanting a bead nucleus made of organic material (often mother of pearl).
- The bead nucleus is followed by a bit of mantle tissue from another mollusk. The mantle tissue contains cells that ensure the production of conchiolin and nacre. By giving the host animal a bit of familiar tissue, risk of nuclei rejection is reduced. The grafter's choice of mantle tissue contributes to the pearl's natural color.
- After the animal is implanted with nuclei it must be carefully maintained in clean, healthy waters to avoid unnecessary disturbances.
Once an oyster is implanted, it begins to secrete calcium carbonate (nacre) that coats the bead nucleus. This pearly layer naturally develops irregularities in direct relation to thickness; therefore, it has to be kept extremely thin to appear flawless. Pearls tend to take on the color of their host mollusk. Most ocean pearl oysters have creamy, greenish, golden and yellow shells, so pearls need intense bleaching with hydrogen peroxide to achieve the desired white or white-pink colors.
Both thin nacre and harsh bleaching techniques can cause a rapid loss of luster, and sometimes the entire nacre layer, so take care when purchasing pearls. On the other hand, natural characteristics of oysters make it possible to choose durable Akoya pearls that could become heirlooms. Kojima Company prides itself on hand-inspecting each and every pearl, raising the likelihood of acquiring such treasures. Please browse our jewelry store
Cultured pearls are the "canaries" of their host waters. As animals will not prosper in polluted waters, neither will pearls grow. Tragic examples have occurred in the coastal waters off of Japan, and also in their fresh waters. Lake Biwa and Lake Kasumi Ga Ura both halted pearl production due to unclean waters. The perpetrator in both cases was tainted runoff from nearby industry.
It is the overwhelming responsibility of any pearl farmer to ensure clean water for their animals. Throughout the entire precious gem industry, pearl cultivators are the only group that acts as environmental protectors. As mountains are moved in search of gems and precious metals, and impoverished people are made to work in mines against their will, it is refreshing to know that the existence of pearls is a testament to healthy water throughout the world.
Cultured freshwater pearls vs. cultured saltwater pearls
Cultured saltwater pearls
(i.e. Akoya pearls)
are typically seeded with a bead nucleus and left to incubate for approximately 12 months. This is the point at which they reach peak roundness--- beyond that they tend to take on an out-of-round or baroque shape. In cultured freshwater pearls
, the bead nucleus is often bypassed and only a bit of graft tissue is implanted. The method of grafting with only the soft mantle tissue is a much easier process, and can yield dozens of pearls per one freshwater shell.
Freshwater pearl production mainly occurs in China. In recent years Chinese pearl farmers have gained remarkable skill in implanting freshwater mollusks with shell nuclei, and setting them directly into the body of the animal. This is the same process that has been used in saltwater pearl production for decades. Now, more and more, we see "bead nucleated" Chinese freshwater pearls on the market. In far lesser quantities, we also see examples of using more creative nuclei in unconventional shapes (discs, stars, animals, hearts etc.); wax and plastic; and sometimes even semi-precious stones. Cultured freshwater pearls (especially those with only tissue nuclei) are most often baroque.
A Word About Keshi Pearls:
As China became increasingly aggressive with pearl production, a multitude of new pearl shapes began to appear, including those that resembled Rice Krispies® cereal. The need soon arose to name these new shapes. Terms such as petals, rosebuds, and coins are often used, along with most popular, albeit misused keshi pearls
. Regardless of the name, these unique, asymmetrical creations make for some of the most interesting pieces of jewelry.
Both saltwater and freshwater pearls can take on overtones in every color of the rainbow with many shades in between. Colors largely depend on the type of mollusk in which the pearl is grown; for example, Tahitian pearls
come from black-lipped pearl oysters (Pinctada margaritifera
) which secrete the dark nacre that is responsible for their extraordinary color.
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