Pearls are true miracles of nature, formed with infinite precision at the molecular level to be strong, smooth, and resiliant. Through a process known as "biomineralization", mollusks combine calcareous crystals with water and a protein matrix to lay down layer upon layer of hexagonal bricks in an organic mortar. The result is the wondrous material known as nacre, or mother-of-pearl. In response to an irritant (either accidental or intentionally implanted), the molluscan bricklayer uses a form of calcium carbonate known as aragonite and a binding protein matrix, primarily conchiolin, to coat the intruding body with the same sort of material that is found on the interior of its shell. Nacre is formed and secreted by specialized epithelial cells found in the mantle tissue of the animal. The famed luster, color, and iridescence of pearls comes from this layering of protein and calcium carbonate; however, these qualities are exemplified in the pearl because of its spherical shape. In short, these visual qualities derive from a unique combination of chemical components, molecular structure, surface curvature, and light.
Pearls have for centuries been considered one of the most treasured organic gems in the world. Historically, the primary source of natural pearls was the Indian Ocean, the Red Sea, and the Persian Gulf, where pearl oysters of the species Pinctada radiata and Pinctada margaritifera flourished. When pearls were discovered in the New World by Colombus around 1500, the dominance of the Indian Ocean was broken until the Europeans depleted the molluscan resources of their newly-discovered colonies about 150 years later. New World pearls came from Pinctada imbricata on the Atlantic side and Pinctada mazatlanica in the Pacific. After a variety of experimental implanting methods were explored by the Australians and Japanese in the late 1800s and early 1900s, Kokichi Mikimoto was awarded a patent for the culturing of round pearls in 1916 and established himself and Japan as the focus of pearl production in the world. The Japanese held this position of dominance for most of the 20th century, but today the sources of pearls range from China and Japan to the South Seas, from Australia and New Zealand to the atolls of French Polynesia, and even to the Americas, where pearls are once again being produced in small quantities in Mexico and Venezuela, and limited volumes coming from North American freshwater mussels.
In terms of volume, today's pearl production is essentially all cultured. Chinese freshwater pearls, continually improving in quality, make up the majority of this volume, and culturing there is done using tissue implants rather than spherical shell beads. However, the rest of the world's well-known and sought-after marine pearls have at their centers a round implant known as the nucleus, which is made of polished shell material from American mussels. A skilled implanter places this shell bead, along with a piece of mantle tissue with its nacre-producing epithelial cells, into the gonad of a host oyster. The resulting pearl is actually a relatively thin layer of nacre on the surface of this implant. But it is enough to create the beauty and majesty of the pearl, and is essentially indistinguishable from the natural form unless it is cracked open or x-rayed. Depending on the type of oyster used, the location where the animals are grown, the quality of the water, and several other factors, pearls in their incredible variety are produced at farms around the world each year.
Today's pearls come in an astonishing array of colors, including many shades of yellow, white, silver, pink, cream, green, gray, and black.
The most common marine pearl, typically white, farmed in Japan and also produced in China. Derived from Pinctada fucata, rarely
grows larger than 9mm.
WHITE SOUTH SEA
Grown primarily off the coasts of Australia in Pinctada maxima, this is one of the most expensive pearls
and can grow to 14mm and larger. Often silvery but not as lustrous as the
Akoya, it is now available in various pink and golden shades. More difficult to produce on a large scale.
Most commonly known as the black pearls of Tahiti, they are also grown in Hawaii and other Pacific island locations where Pinctada margaritifera thrives. Ranges from 7mm - 17mm in size. Often very expensive in gem qualities.
Locations other than Australia produce small quantities of large pearls from Pinctada maxima, including Burma, Thailand, Vietnam, the Philippines, etc.
NEW WORLD PEARLS
Pearls (primarily mabes) are once again being produced, though in small quantities, in the Americas (Mexico, Panama, and the Venezeulan islands of Cubagua and Isla Margarita) from Pinctada mazatlanica, Pinctada imbricata, and Pteria sterna.
Pearls produced from abalone (Haliotis species) come from the Pacific Coast of North America and from New Zealand. These are blister or mabe varieties.
Grown attached to the inside surface of the shell of the mollusk. When they are removed from the shell, one side contains the nacre-covered implant and the other is left flat and has no nacre coating.
Assembled blister pearls that are cultured by gluing a half-bead nucleus against the inside of the mollusk shell so they have a hemispherical appearance. Once the mollusk has secreted nacre over the bead, the blister pearl is cut from the shell and the bead is removed. These pearls are delicate and are usually used in earrings, rings, pendants, and brooches.
QUARTER OR HALF PEARL
Can be made from either a bead flattened on one side and placed against a mollusk shell (similar to the mabe or blister pearl) or from a round pearl where one side is ground down to remove a significant blemish.
Freshwater pearls from Lake Biwa in Japan. Unfortunately, pollution has greatly affected the production of these pearls. Some limited production still done in Japanese lakes other than Biwa.
Cultivated via freshwater mollusks (Hyriopsis and Cristaria species) found in rivers and lakes. Donor mantle tissue is inserted into the mantle of live animals. The resulting pearls are essentially all nacre and are generally inexpensive. Initially, they were mostly non-round shapes including potato, rice, corn, stick, semi-round, etc., but improvements in cultivation and pure enormity of volumes have produced a wide range of sizes, styles, and colors.
Formed naturally in saltwater cultured pearl oysters. They are tiny in size and sometimes referred to as "seed pearls".
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