Natural Pearls | History of Pearl Diving
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Natural Pearls
Before the beginning of the 20th Century, pearl hunting (pearl diving) was the most common way of harvesting pearls. Divers manually pulled oysters from ocean floors and river bottoms and checked them individually for pearls. Unfortunately, not all natural oysters produce pearls. It would take nearly one ton of oysters to produce only three or four perfect round pearls, making them highly scarce, and valuable.
Pearl oysters were gathered by ancient Sumerians along the Persian Gulf, as far back as 4000 years. The Bahrain Pearl Banks of the Persian Gulf, and the Gulf of Manaar in Ceylon were known for their exceptional natural pearls, and free-diving or "breath-hold" diving was used extensively until the early 1900s when pearl cultivation was invented.
Traditionally, Japanese pearl diving was done by women who were called "Ama" (above, left). The word ama literally means "sea woman." This Japanese tradition dates back 2000 years. As recently as the 1960s, Ama divers wore only a loincloth. Even today, Ama dive without scuba gear, using free-diving techniques. Free-divers often descend to depths of over 100 feet on a single breath. Only divers who work at tourist attractions use white, partially transparent suits to dive in.
In 1909 the TOA diving apparatus company was founded in Minamisenji, Japan. They also designed a Pearler style diving helmet, copied from the Heinke Pearler helmet (above, right).
A pearl is a hard, rounded object produced by certain mollusks, such as oysters. The pearl is a valued gemstone and is cultivated or harvested for jewelry. Natural pearls are formed when a small foreign object, such as a parasite, grain of sand, or piece of food lodges itself in the gonad or mantle tissue of a mollusk or oyster.
Pearl Formation
Pearls are produced either within the mantle, in other soft tissues of the oyster, or between the mantle, and the interior surface of the shell. Natural pearls require the formation of the pearl-sac which is derived from the internal or external layer of the apithelium of the mantle tissue or gill plates. Specialized epithelial cells within the pearl-sac secret nacre which is deposited on the foreign object.
When the mollusk is invaded by a foreign object that the animal cannot eject, a process known as encystation entombs the offending entity in successive, concentric layers of 'Nacre' (nay'ker). In a defensive response to the irritant, the mollusk secretes nacre as a smooth, protective coating. Nacre is a combination of crystalline and organic substances that form the iridescent mother-of-pearl lining of mollusk shells. The nacre is secreted by the epithelial cells of the mantle tissue in certain species of mollusk.
As the nacre builds up around the irritant, it forms concentric micro-layers, eventually creating a pearl. Natural pearls that are both large in size (diameter), and have a very symmetrical shape are extremely rare. For pearls to form in nature it can take may years of near-perfect conditions for them to make a significant gain in size.
The principle difference between "Natural" and "Cultured Pearls" is the thickness of the nacre, and human intervention. Since natural pearls take longer to develop, there is generally a thicker layer of nacre surrounding the nucleus. It can take two to five years for a quality pearl to fully develop in the oyster. Many lower quality cultured pearls are created by inserting a large nucleus and hastening the process of nacre development. This results in a pearl with a very thin layer of nacre that will not have a great deal of luster, and will not be very durable over a long period.
Pearls In Art
Pearls have been valued throughout the ages. This love of nature's gift has been reflected in artworks dating back more than a thousand years. In Europe, Asia, India, and the Middle East, the pearl has been worn by royalty and traded as a valuable commodity. Mankind's love of pearls is even reflected in important works of art, such as Dutch painter Jan Vermeer van Delft's "Woman with a pearl necklace" painted in the late 1600s
16th century Dutch pen-and-ink drawing of pearl divers (left). Ama ("sea woman") pearl divers use free diving techniques to harvest pearls. This tradition dates back 2000 years (right). Traditionally, Ama women dived wearing only a loincloth.
Cultured Pearls
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