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Gemstone Crystal System Density Hardness Refractive index Treatments
organic 2.70 2.4-4.0 1.530-1.685 dying,bleaching

Cultured fresh and salt water pearls

All colors; some natural, some dyed.

Moderate. Wear with care.

World wide. Japan is famous for Akoya pearls

Kokichi Mikimoto, along with biologist Tokichi Nishikawa and carpenter Tatsuhei Mise had each independently discovered the secret of pearl culturing -- inserting a piece of oyster epithelial membrane (the lip of mantle tissue) with a nucleus of shell or metal into an oyster's body or mantle causes the tissue to form a pearl sack. That sack then secretes nacre to coat the nucleus, thus creating a pearl.

In 1907 a patent was granted for Mise-Nishikawa method, which remains the heart of pearl culturing. Mikimoto had received an 1896 patent for producing hemispherical pearls, or mabes, and a 1908 patent for culturing in mantle tissue. But he could not use the Mise-Nishikawa method without invalidating his own patents. So he altered the patent application to cover a technique to make round pearls in mantle tissue, which was granted in 1916.

With this technicality, Mikimoto began an unprecedented expansion, buying rights to the Mise-Niskikawa method and eclipsing those originators of cultured pearls, leaving their names only for history books. By mastering many new techniques and years of experimentation, Mikimoto, and hundreds of other Japanese firms, made pearls available to virtually everyone in the world.


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Natural pearls are formed when an irritant becomes lodged in a pearl oyster, and gets coated with a natural secretion of calcium carbonate called nacre. In the beginning of the 1900's, it was discovered that a spherical bead could be placed in an oyster, and pearls could be "cultured". There are varieties of fresh water mollusks that also produce pearls. These pearls can be cultured by artificially embedding bits of muscle tissue into the bivalves. Over ninety per cent of the pearls sold today are cultured, not natural. The great majority are also treated in some way to improve their appearance and color. The most enduring legend concerning pearls, is the story of Cleopatra dissolving pearls in the wine she drank in Mark Antony's presence. Truth be told, wine, nor anything else safely drinkable by humans, would be able to dissolve a pearl!

Oyster Varieties:
Black-Lip Oyster: An oyster of unusual size and diameter found in the South Pacific, from which is derived the famous black pearls known in the industry as Tahitian Pearls. Other colors produced by this mollusk, besides black, are silver to light gray, dark gray, orange, gold, green, blue, and purple.

Gold-Lip Oyster: The large oyster, found in the waters off Australia, Indonesia, Philippines and Japan, which produces gold-colored South Sea Pearls.

Pinctada Fucata: The industry term for the saltwater mollusk that produces Akoya cultured pearls.

Pinctada Maxima: The industry term for the White-lip oyster that produces South Sea Pearls.

Pinctada Margaritifera: The industry term for the saltwater mollusks that produces Tahitian cultured pearls.

Uniondae Hyriopsis Schlegeli: The freshwater mussel, prevalent in China, which produces a strong pearl with thick nacre and a bright luster. Its pearls come in a palette of colors ranging through plum, lavender, peach, apricot, curry, red pepper, cinnamon, celery and sage.

White-Lip Oyster: Large oysters found in the waters around Australia, Indonesia, the Philippines and Japan, and producing good-sized South Sea cultured pearls whose tints include silver-white, pink and cream.