There are essentially three types of pearls: natural, cultured and imitation.

Natural pearls (also called Oriental pearls) form when a grain of sand or piece of corral works its way into the flesh of an oyster or mollusk - an underwater animal with shells. To protect its soft body from irritation, the mollusk begins to secrete a mucus-like substance called "nacre" around the foreign object as a defense mechanism. Much like what your body does when it forms a callus to protect irritated skin, layer upon layer of this coating (known as nacre) is deposited on the foreign irritant until a lustrous pearl is grown (in three to five years).

Nacre consists of a combination of calcium carbonate and conchiolin - a complex protein secreted by mollusks. In sea water, nacre will harden and form into a pearl. Because the pearl eventually becomes the irritant itself, it will continue to grow in size as the mollusk secretes more and more nacre.

Since they are created in the wild without human interference, natural pearls are extremely rare and therefore very expensive - due to the depleted and polluted pearl oyster beds. Only in 100,000 natural pearls will form as black or grey, meaning a black pearl necklace may cost in excess of $100,000.

Natural pearls, also called oriental pearls, have been harvested from the Persian Gulf, the Gulf of Manaar in the Indian Ocean, and the Red Sea for thousands of years. Today, however, unless you find pearls at an antique show, almost all those sold in the market are cultured pearls mainly produced off the coasts of Japan, China, Polynesia and Australia.

Cultured pearls undergo the same process as natural ones. The only difference is that the irritant is usually a mother-of-pearl bead or nucleus inserted into a living oyster or mollusk along with a piece of tissue, known as the mantel. After the surgical implantation, the oysters convalesce in a "hospital" for four to six weeks. They are then transferred to cages between seven and ten feet under water where nature is allowed to take over the process of evolving and creating the pearl over a period of three to six years. This method allows for the production of significantly larger more plentiful pearls.

Cultured pearls are still "real"; they've simply had a helping hand from a skilled technician to begin formation. To the untrained naked eye, high quality natural and cultured pearls appear identical. Only special X-ray equipments can help a trained eye distinguish between the two. Though cultured pearls tend to have a much larger core than naturals, so long as they possess sufficiently thick nacre to rend them lustrous, the size of the nucleus is irrelevant to the beauty or durability of the pearl. The longer the pearl remains in its shell before it’s plucked, the more concentric layers of nacre it develops, the greater its luminosity. Water trapped between the layers also adds to the pearl’s natural iridescence.

Both cultured and natural pearls come in a bewildering array of colors from white to those with a hint of color such as yellow, rose and pink, to blue, copper brown and dark gray. Each coloration pattern will depend on the specific type of mollusk and the nature of the waters where the mollusk lived.

The world’s record price paid for a cultured pearl jewelry was $2.3 million at Sotheby’s in 1992. The 17-inch strand necklace bore 23 graduated pearls ranging from 16mm to 20mm in diameter (about the size of a dime), and a bead-shaped platinum clasp with 60 round diamonds.

Pearls can come from either salt or freshwater sources:

Freshwater Pearls are produced by the Hyriopsis cumingi mussles, native to remote lakes and rivers in China. They also occur in the rivers of Scotland, Ireland, France, Austria, Germany, and the USA (Mississippi). A piece of mantle (nacre producing tissue from another mussel), is introduced into a large mollusk, resulting in clusters of pearl made of solid nacre resembling puffed rice. Each mollusk can yield up to 30 pearls per harvest. Freshwater pearls are generally oval and long shaped. Since they are produced in clams as opposed to oysters, freshwater pearls possess a different coloration. Available in a wide range of colors including violet, orange, pink, blue and gray, many are dyed after being plucked. Both freshwater and saltwater pearls are cultivated in Japan and China. In China, farming first took place in the 14^th century. In Japan, it started in 1893 but really took off around 1910.

Saltwater pearls nurtured in pearl oysters enjoy more iridescence or orient than those grown in freshwater mollusks, making them more valuable. Black pearls, Akoyas and South Sea pearls are all bred in saltwater.

Akoya Pearls are produced by surgically implanting a small nucleating, nacre producing round bead in the body of Pinctada fucata, a small Japanese saltwater oyster (as opposed to mollusk), which can produce only one pearl at a time. Among cultured pearls, Akoya Japanese pearls are especially cherished for their true roundness and highly reflective shine. Ranging from 2mm to 10 mm; a quality necklace of 40 Akoya pearls measuring 7mm in diameter is worth anywhere between $1,500 to $4,500 depending on its nacre, luster, color and shape. Those larger than 8 mm are quite scarce and precious.

South Sea Pearls are produced by the silver-lipped oyster, Pictada maxima, and gold-lipped oyster, which live along the coasts of Philippines, Myanmar, Indonesia and Australia. Known for their large size, thicker coating of nacre, and luminous satin luster, these white and golden South Sea pearls are indeed the epitome of exotic island treasure. Typically much larger and more exceptional than Akoyas, from harvesting to assembling a single strand of South Sea pearls, it may take many years since each pearl must be matched for luster, size, color, overtone and quality. Ranging from 10 to 20mm in diameter, they command a higher price though their luster may not be as superb. A 16-inch strand of South Sea white pearl necklace retails between $40,000 to $50,000.

Established in 1920 by Dr. Sukeo Fujita, a veteran of the Japanese Akoya pearl industry, the South Sea saltwater pearl enterprise got its start in waters off Celebes, an island in East Indonesia. The advent of World War II, brought the South Sea pearl farming to a complete halt. It was not until the postwar 1950’s that the Australian coast was explored as a new cultivation site. The water content rich from the nutrients of the ocean floor and the local mussels’ tendency to produce relatively large pearls, made the area ideal for nurturing South Sea pearls and took the industry to new heights.

Tahitian Black Pearls are currently the only natural black pearls in the world. Mysterious, exotic and mystical, black South Sea pearls are broduced by the black-lipped oyster known as Pinctada Margaritifera, native to French Polynesian islands. Though they used to exist in parts of the Persian Gulf, their supply was depleted due to over-exploitation and pollution. Ranging from 8 to 18 mm, they come in a mesmerizing rainbow of colors from light gray and silver to bronze or gun metal and deep black, with green, blue, pink and purple overtones. The most gorgeous hues are known as “peacock.” An even deep black color results from "treating" the pearl with silver nitrate. Care must be taken not to confuse polished hematite with black pearl. Even a shiny hematite lacks the inner glow of a real pearl.

Baroque Pearls have extraordinary irregular shapes such as those found amongst Tahitian pearls. Their unusual contours, especially those appearing like animals or humans, make them amenable to the creation of unique jewelry by a skilled jeweler.

Biwa Pearls are irregular shaped pearls formed of all nacre in the freshwaters of Lake Biwa, a large lake near Kyoto in Japan. Unique to Lake Biwa, they came in colors previously unseen in saltwater pearls. Their luster and translucence rivaled natural pearls. Though their production was halted during WWII, by the post-war 1950’s, Biwa pearls became a major source of supplying the world with a cheaper, more colorful alternative to cultured saltwater pearls. In the 1980’s, the Biwa pearl production ended due to heavy industrial pollution from farms and other industries. The vaccum left was filled by China. Its myriad of lakes and rivers combined with unlimited source of labor in desperate need of hard cash, made this vast terrain an ideal place for picking up the slack left by Biwa pearls.

Button (bouton) or blister Pearls grow attached to the inside of the shell, making them round on the one side and flat on the other. In the early 1200’s, the Chinese were the first to create these by inserting tiny lead Buddha images into mussels and immersing them in fresh waters for long periods of time. It wasn’t until hundreds of years later, in 1893 when the famed Japanese Mikimoto plucked five half-pearls from his farming experiments. Inspired by this glimpse of success, he persisted in his efforts until he was able to harvest 4200 blister pearls in a matter of two years. In 1905, his crop was destroyed by red tide, but upon opening the dead oysters, he was overjoyed by discovering that five of the oysters had yielded whole round pearls. By 1908, he had launched the first pearl factory for sale of blister pearl jewelry. Three years later, he was able to reap $200,000 from his creation, worth millions of dollars today.