Natural vs. Cultured
Most of the pearls available in jewelry are cultured. This means that the natural process undertaken by the oyster (mollusk) is manipulated by humans. Natural pearls are those that occur as an accident. Natural pearls are exponentially more valuable than cultured pearls, though they are so rare that even most jewelers never come across one. A popularly relied upon source for natural pearls has been antique jewelry made before the widespread cultivation of pearls. However, these antique pearls are not necessarily more valuable because the centuries of wear, exposure to acids, chemicals and dehydration may have left them with poor luster, scratches and yellowed color.
Distinguishing natural pearls from cultured pearls is quite difficult without a labratory. When shopping, you should assume all the pearls you see are cultured and you will most likely need to rely upon the reputation of the seller to tell you acurate information. But some loose guidelines are:
Shape: Cultured pearls are usually more spherical where as matural pearls are more commonly irregular-sometimes lending toward cylindrical.
Inside of the hole: In loose pearl beads, it is possible using a microscopic lens to see the layers of nacre in the pearl. A natural pearl will have many thin easily distinguishable layers whereas a cultured pearl will have a singular thick layer of nacre (pearly substance) around a perfeclty spherical, waxy nucleus.
Color: There is a tendancy for cultured pearls to have a slightly greenish tinge. This is not usual among natural pearls.
Pearls have been imitated for centuries. The most convincing immitation has been spheres of glass or mother of pearl varnished on the outside by a substance made of ground fish scales. Other imitations can include glass ceramic and plastic.
You can distinguish “real” from “fake” pearls by rubbing the pearl against your teeth. The fake one will feel smooth while the real pearl will produce a slight grating feeling against your teeth.
Most cultured and freshwater pearls undergo some kind of treatment before they reach you. Treatments include:
Bleaching: Most white cultured pearls are bleached to purify their white color. This treatment also makes them easier to match because it makes the colors of the pearls more uniform and similar to each other.
Tumbling: Most pearls are tumbled together as a way of “polishing” each other. This improves luster and surface texture.
Filing: If a pearl has a bump or portrusion on its surface, it is usually filed away and the dull spot that is left is used to drill the hole for the bead. Oddly conically shaped pearls also often have the conical tip filed away and the flat space is used as a “backing” for it to be set in a ring or other jewelry.
Dying: It is increasingly popular and common for pearls (especially freshwater) to be dyed. It is considered fraudulent to not disclose that pearls are dyed. Dyed freshwater pearls are not common in fine jewelry and are not considered to be relatively valuable.
Irradiation: Sometimes pearls can be irradiated to darken the seed (nucleus) that is in the center of the pearl beneath the layers of nacre. This has the effect of making a light colored pearl look like a black pearl.
Here is an Illustration of Natural, Cultured, Treated, and Imitation Pearls:
|Natural: This picture is the closest that most of us will ever come to seeing such a collection of natural pearls. The necklace was auctioned for over 7 million dollars.||Cultured: Almost all of the pearls available on the market are cultured.||Dyed: Pearls in nature rarely come in this color – and two identical ones even rarer. Put these factors in combination with a low price, and you can bet the pearls are dyed.||Imitation: These imitation pearls are made by swarovski. Compare them to the natural pearls on the left and you will see that they are “too alike” in color. No two real pearls are ever exactly alike.|