Monday, August 29, 2011

Precious Pearls: How They Are Formed, Colors and Shapes

At one time, many believed pearls to be the “tears of the gods.” Others thought them to be “dewdrops filled with moonlight that fell into the ocean and were swallowed by oysters.”  As mystical as pearls are, the truth is, a pearl is a natural gem created by a living organism.

There are essentially two types of pearls: natural, (freshwater and saltwater) and cultured. A natural pearl (often called an Oriental pearl) forms when an irritant works its way into a particular species of oyster, mussel, or clam. As a defense mechanism, the mollusk secretes a fluid (nacre) to coat the irritant. Layer upon layer of this coating is deposited on the irritant until a lustrous pearl is formed. Regardless of the method used to acquire a pearl, the process usually takes several years. Mussels must reach a mature age, which can take up to 3 years, and then be implanted or naturally receive an irritant. Once the irritant is in place, it can take up to another 3 years for the pearl to reach its full size. Often, the irritant may be rejected, or the oyster may simply die from disease or countless other complications. By the end of a 5 to 10 year cycle, only 50% of the oysters will have survived.

Natural pearls  are formed when something becomes lodged - like a piece of shell, bone, coral or parasite and the oyster starts nacre production. This is true for both Freshwater and Seawater natural pearls. Most natural wild pearls are off-round or baroque (a general term for irregular shape).

 Cultured pearls undergo the same process. The only difference is that the irritant is a surgically implanted bead or piece of shell called Mother of Pearl. Often, these shells are ground oyster shells that are worth significant amounts of money in their own right as irritant-catalysts for quality pearls. The resulting core is, therefore, much larger than in a natural pearl. Yet, as long as there are enough layers of nacre (the secreted fluid covering the irritant) to result in a beautiful, gem-quality pearl, the size of the nucleus is of no consequence to beauty or durability.
Although formed with the aid of human intervention, cultured pearls are still a product of nature. Typically, saltwater pearls tend to be higher quality, although there are several types of freshwater pearls that are considered high in quality as well. Freshwater pearls tend to be very irregular in shape, with a puffed rice appearance. Nevertheless, it is each individual pearls merits that determines value more than the source of the pearl.
Saltwater oysters have a round shell bead (usually from an American freshwater mussel) grafted in as the irritant. This is called 'nucleating'. Oysters are suspended in water from rafts and risk typhoons, parasites, predators and algae. Saltwater pearls are found or cultivated in salt water oysters in a bay, ocean, gulf, or sea. These also can be irregular in shape, especially when natural, although the best cultured ones are known for their fine round shape. The most valuable baroque pearls are South Sea and Tahitian. Due to the length of time under cultivation a high percentage of the pearl harvest is baroque.

Freshwater mussels have a small piece of mantle tissue (nacre producing tissue from another mussel) introduced as the irritant.
Freshwater pearls—are found or cultivated in freshwater mussels in lakes, rivers, creeks, or ponds. They are often irregular in shape, but also can be perfectly round and come in a variety of gorgeous colors. Natural colors vary by breed of mollusk. Other influences include diet, water temperature and pollutants. No-one can predict or control what color pearls will be produced in any hatchery.

pearl colours

Naturally colored black pearls come from the pearl farms of French Polynesia (Tahitian pearls) as well as Indonesia and the Philippines. Except for freaks, there are no natural black freshwater or Akoya pearls though these may be dyed or irradiated to simulate black pearls.
Black pearls are rarely jet black but blue, green, grey, peacock and more. Green is the predominant color.

Pearl Shapes Typically Found in Pearl Jewelry

Biwa Pearls come from Lake Biwa - a large freshwater lake near Kyoto in Japan.
Pink Biwa Stick Natural Freshwater Pearl Necklace in Sterling Silver
Pink Biwa Pearl Necklace by epicetera
Keshi Pearls are accidents which happen when the mollusk rejects the nucleus and grows a 'free form' pearl.
Natural Keshi Pearl and Swarovski Crystal Necklace, Sterling Silver
Keshi Pearl Necklace by epicetera

Bead nucleated pearls (pearls seeded with a round shell bead) may develop a tail on one side. These unusual Keshi Pearls have a tail, but are flat and diamond shaped.
Natural Keshi Freshwater Pearl Baroque Bracelet in Sterling Silver
Keshi Freshwater Pearl Bracelet by epicetera
Baroque Pearl--asymmetrical free-form freshwater pearl. 

Morning Sky - Turquoise and Keshi Pearl Necklace
Button Pearl--freshwater pearl which is flat on one side.

Yellow Pearls Swarovski Crystals Sterling Earrings Handmade OOAK
Yellow Button Pearl Earrings by ShadowdogDesigns
Coin Pearl--round freshwater pearl, flat on both sides.

Genuine Coin Pearl and Pink Spinel Cluster Earrings
Coin Pearl Earrings by WindysDesigns

Circle or Ring Pearl--saltwater pearl with concave concentric lines.

Freshwater Pearl and Green Glass Earrings with Leaf Charms
Freshwater Ring Pearl Earrings by PrettyGonzo

Off-Round Pearl--nearly round fresh water or salt water pearl.

Garnet, Sea Pearl Earrings
Sea Pearl and Garnet Earrings by ShanghaiTai

Below are 2 examples of the latest trend in pearls: faceting. Faceted pearls require a pearl to age 3 years longer than normal to build up more layers of nacre.

  Oval Pearl--egg-shaped freshwater or salt water pearl.
Rutilated Quartz Necklace, Lampworked Pendant, Faceted Pearls
Oval Faceted Freshwater Pearl Necklace by LindaLandig
Faceted Pearl

Potato Pearl--oblong irregularly shaped cultured pearl.

Necklace Potato Pearl and Turquoise Lime Crystal and Pearl Pendant
Potato Pearl Necklace by PinkSunsetJewelryDesigns

 Rice Pearl--Irregular-shaped pearl with crinkled surface.

Mabe Pearl or Half-Pearl--dome-shaped pearl, flat on one side.
Blue Mabe Pearl Bracelet with Austrian Crystals in Sterling Silver
Blue Mabe Pearl Bracelet by epicetera

Mostly Round/Round Pearl--nearly perfectly round cultured pearl.

Triple Strand Pearl Necklace Retro Vintage Style Crystal Cabachon
Retro Vintage Triple Strand Pearl Necklace by epicetera

All designs featured in this article were handmade by members of the JCUiN Guild on ArtFire.