Different Types Of Cultured Pearls

Cultured pearl is any pearl grown with the influence of human intervention. A pearl is formed when a small irritant or parasite penetrates and lodges in the mantle tissue of a mollusk. In response, a substance called nacre is secreted, and the creation of a pearl begins. Nacre is a combination of crystalline and organic substances. The nacre builds up in layers, as it surrounds the irritant to protect the mollusk, and after a few years, this build up of nacre forms a pearl.

A saltwater pearl is a pearl produced by a saltwater mollusk in a saline environment.The three most common types of saltwater pearls are akoya pearls, Tahitian pearls, and South Sea pearls.

Akoya oysters are also used by both the Japanese and the Chinese to produce saltwater cultured pearls. Akoya pearls are the most difficult to grow due to the low survival rates of the host oysters. Less than 5 in 10 will survive the nucleation process. Of the survivors, about 40% will successfully encircle the shell nucleus irritant with nacre. Overall, less than 5% of pearl output can be considered "high quality. The akoya oyster is the smallest pearl-producing oyster used in pearl culture today, so akoya pearls also tend to be small, ranging in size from about 2 to 11 millimeters. They also tend to be the most consistently round and near-round pearls, making them ideal in terms of matching for multi-pearl jewelry such as strands and bracelets.

Tahitian pearls are produced in the black-lipped oyster ‘Pinctada margaritifera’, in and around Tahiti and the French Polynesian islands. This oyster itself is quite large - sometimes over 12 inches across and weighing as much as 10 pounds - which often results in much larger-than-average pearls. The pearls are unique because of their natural dark colors. Most "black" Tahitian pearls are not actually black, but are instead silver, charcoal, or a multitude of colors with the dominant color being green. Truly black pearls are among the most beautiful pearls in the world, and are extremely rare.

South Sea pearls are among the largest commercially harvested cultured pearls in the world. The average size of a South Sea pearl is 13 mm, with most harvests producing a range of sizes from 9 mm to 20 mm. The South Seas lie between the northern coast of Australia and the southern coast of China. These waters are the native habitat of a large oyster known as Pinctada maxima. This oyster grows up to 12 inches in diameter, and can be nucleated with a much larger bead than other saltwater oysters such as the akoya.

Freshwater pearls are pearls which grow in non-saline environment in freshwater mussels.

Although the traditional source of pearls has been saltwater mollusks, freshwater mussels, which live in ponds, lakes and rivers, can also produce pearls. China has harvested freshwater pearls in the form of mabe since the 13th century, and has now become the world's undisputed leader in freshwater pearl production.Generally speaking, freshwater pearls are not as round as saltwater pearls, and they do not have the same sharp luster and shine as akoya pearls. However, they appear in a wide variety of shapes and natural colors, and they tend to be less expensive than saltwater pearls, making them very popular with younger people and designers. Also, because freshwater pearls are solid nacre, they are also quite durable, resisting chipping, wear, and degeneration.

There are another kind of keshi pearl.may form in either saltwater or freshwater pearls.A keshi pearl is a non-beaded pearl formed by accident as a by-product of a pearl culturing operation.Keshi pearls are formed when the oyster rejects and spits out the implanted nucleus before the culturing process is complete, or the implanted mantle tissue fractures and forms separate pearl sacs without nuclei. These pearl sacs eventually produce pearls without a nucleus.