June’s birthstone is pearl. Most people do not know much about pearls, and many of them don’t realize that there is much to know!
Pearls are the only gemstones grown inside of a living organism. Natural pearls are formed when a small foreign object, such as a parasite, grain of sand, or piece of food lodges itself in the mantle tissue of a mollusk. When the mollusk is invaded by a foreign object that it cannot eject, it responds by defensively entombing the offending entity in successive, concentric layers of nacre. Nacre is a combination of crystalline and organic substances that form the iridescent mother-of-pearl lining of mollusk shells.
Well formed, symmetrical natural pearls that are large in size are extremely rare. For pearls to form in nature it may take many years of near-perfect conditions for them to make a significant gain in size. Before the beginning of the 20th Century, pearl hunting/pearl diving was the most common way of harvesting pearls.
Divers would manually pull oysters from the ocean floor 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. Because of their scarcity, natural pearls are almost always used in single-pearl jewelry pieces. The most common natural pearls are Penn, Abalone, Conch, and Oyster.
It is commonly assumed that only one out of ten-thousand mollusks naturally produce gem quality pearls. Thankfully, the process to culture pearls was developed – otherwise ownership of pearls would still be relegated to the wealthiest and pearl producing mollusks would be on the brink of extinction due to over-harvest.
The principle difference between Natural and Cultured Pearls is the thickness of the nacre, and human intervention. It can take two to five years for a quality natural pearl to fully develop in the oyster. Quality in the culturing process is key: lower quality cultured pearls are created by inserting a large nucleus to hasten the process – resulting 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.
TAHITIAN PEARLS: 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. Not only are the pearls beautiful, but the black-lipped oyster’s mother-of-pearl inner shell is also extremely attractive. By the early part of the 20th century, before conservation and repopulation efforts began, the Tahitian pearl oyster had almost been hunted to extinction for its shell alone.
SOUTH SEA PEARLS: The waters of the South Seas, that lay between the northern coast of Australia and the southern coast of China, are the native habitat of a large oyster known as Pinctada maxima. There are two varieties of Pinctada maxima, the silver-lipped and the gold-lipped. The two are distinguished by their distinct coloration of the outer edge of the interior. This type of shell is also known as mother-of-pearl, and is responsible for the coloration of the cultured pearls produced, therefore the name. The nacre of a South Sea pearl is unusually thick, ranging from 2 – 6 mm, compared to the 0.35 – 0.7 mm of an akoya pearl resulting in a unique, satiny. South Sea pearls also have a subtle array of colors; typically white, silver, and golden, that are rare in other pearl types.
AKOYA: In the early 1900s, Kokichi Mikimoto of the Mikimoto pearl company was the first to successfully and consistently grow round pearls in the akoya pearl oyster utilizing a technique discovered by William Saville-Kent in Australia. The akoya pearls have been synonymous with classic beauty and elegance. They are the roundest of all pearl varieties, and are known for their sharp luster and pink overtones – they are the classic, elegant pearl that springs to most of our minds when we think of a strand of pearls.
