MORE PEARL ISSUES:

     There's a lot of information to know about Tahitian Black Cultured pearls.
    
     This section helps you with ideas for taking care of your pearls as well as sections on spotting imitation pearls.

TAKING CARE OF YOUR BLACK PEARLS:
Preservation
     Pearls are meant to be worn. Wearing them only enhances their beauty. But they can't be worn indefinitely, so they must be regularly put away for safe-keeping as well as for preservation. Owners of Tahitian cultured pearls must bear in mind that pearls are produced by a living organism. They contain calcareous crystals that are sensitive to chemicals and acids. They also contain water and protein and may dry out and crack if not properly taken care of. That's why it is recommended that pearls be dampened from time to time in lightly salted water. It is also why they should never be wrapped in cotton or wool because the heat generated would add to the risk of drying out, threatening to turn the pearls brown. Since pearls are not as hard as precious stones, they should not be stored in direct contact with other pieces of jewellry, which may scratch them. Also to be avoided is contact between the pearls and dishwashing liquid and acidic products, such as hair spray, perfume, vinegar and lemon juice.

Pearl Sensitivity to Women's Skin
     Some people's skin is more acid than others. If a Tahitian pearl necklace is regularly worn, as it should be, some of the pearls will constantly be in close contact with the woman's skin on her neck at the shoulder line. Pearl pendants do not always have such constant contact with a woman's skin. Unless carefully and regularly checked, the pearls in the necklace will gradually absorb acid from the skin. The acid will slowly eat into the spherical pearl. Over time the pearl will not only lose its luster, but will become barrel-shaped.

Cleaning Your Pearls
     When the moment comes to put pearls away for the night, owners should make it a habit of rinsing and drying them off. You may even polish them with a soft cloth containing a drop of olive oil so that they maintain their luster and do not dry out.

Cleaning "Don'ts"
      What must be kept in mind is that the softness of pearls and their low resistance to heat and chemicals mean that special precautions must be taken when cleaning them.

Here are some important guidelines:

* Do not use commercial jewellry cleaners on pearls unless the product label states they are safe for pearls. Many such products contain ammonia, which will cause deterioration.
* Never clean pearls in an ultrasonic cleaner. That can damage the pearls.
* Never steam-clean pearls. Heat can harm them.
* Never use detergents, bleaches, powdered cleansers, baking soda or ammonia-based cleaners on pearls.
* Do not wear pearls when their string is wet. Wet strings stretch and attract dirt, which is hard to remove. Likewise, do not hang pearls to dry.
* Do not use toothbrushes, scouring pads or abrasive materials to clean pearls. They can scratch the pearls' surface. If there is a lump of dirt that can't be rubbed off with a soft cloth, trying using a fingernail, which has a hardness of only 2.5 or less.

Cleaning "Do's"
     Cleaning pearls is not complicated. After you wear them just wipe them off with a soft cloth or chamois, which may be dry or damp. This will prevent dirt from accumulating and keep perspiration, which is slightly acidic, from eating away at the pearl nacre.

* When taking off a pearl ring, grasp the shank, or metal part, rather than the pearl. This will prevent the pearl from loosening and coming into contact with skin oil on your hand.
* If pearls have not been kept clean and are very dirty, they can be cleaned by your jeweler or they can be washed in water and a mild soap, such as Ivory or Lux Liquid and cleaned with a soft cloth. Some liquid soaps, such as Dawn, can damage pearls. Pay attention to the areas around the drill holes where dirt may tend to collect.
* After washing your pearls, lay them flat in a moist kitchen towel to dry. When the towel is dry, your pearls should be dry.
* About every six months have a jewelry professional verify that the pearls on your jewelry are securely mounted or that the string is still good. Many jewelers will do this free of charge, and they'll be happy to answer your questions about the care of your jewelry.

IMITATION BLACK PEARLS:
      At one time, if a cultured pearl was black it was certainly stained artificially, usually by immersion in a solution of silver nitrate.

     Natural black pearls do occur, although more rarely than ever, while naturally-colored black cultured pearls from Tahiti and other places are increasingly common due to the use of the black-lipped pearl oyster known as the Pinctada Margaritifera.

     But imitation black pearls are not so common as other color imitations since the true black pearl has a color that is far from being a matte black. In fact, the natural and cultured black pearl both have a beautiful sheen. Sometimes this sheen is a greenish hue against a black background. At other times the sheen is a bluish-black color that is very difficult to adequately describe.

Faint Reddish Glow Characterizes Natural Black Pearl
     Natural black pearls have a faint reddish glow when viewed through crossed filters, such as when bathed in blue light from a copper sulphate solution and examined through a red filter. Artificially-stained black pearls do not have this red glow reaction. It has been found that overlong exposure to X rays will blacken some freshwater pearls without a nucleus. But this is not so serious as possible blackening of natural pearls.

Some Imitations Have Immediate Giveaway Signs
     Imitation pearls are found in graduated and chocker necklaces of such sizes and matching symmetry and color as to be obviously anything but natural or cultured pearls. The immediate giveaway reason is that so many large, perfectly matched pearls would cost a small fortune. But less pretentious imitations still have a giveaway sign. That is the drill hole. It is never so precise in imitation pearls as it is in natural or cultured pearls, which are individually drilled. The mass-produced imitation pearls literally have their hallmark at the drill hole, which shows signs of unevenness and rough formations due to the lack of finish applied to the manufactured pearl. Thick "tears" of the coating may appear at the drill hole as coagulations.

10x Lens Easily Reveals Imitations
     Such telltale signs are quickly and easily revealed when an examination of the suspected imitation pearl is made with a 10x lens. Equally, an examination of the surface of glass beads will reveal bubbles just below the surface, or a mat pattern totally unlike the wandering serrated cloissons seen in natural pearls. Likely candidates for treated, imitation black pearls are the hard-to-sell, less popular colors. The typical treatment uses a solution containing a silver salt, such as silver nitrate. The pearl oyster picks up a silver precipitate, which is blackened by exposure to light or hydrogen sulfide gas. The treated color is non-fading.

Ways of Detecting Treated Color Pearls
     The treated color can be detected by a number of tests, such as certain types of X-ray analysis and infrared photography. Such tests detect the treated color's comparative lack of ultraviolet fluorescence and its response to dilute acids.

Radiation Used to Alter Cultured Pearls' Colors
      In recent years, gamma rays (and other forms of radiation) have been fired at cultured pearls to alter their colors. The radiation is thought to have a "charring" effect on the conchiolin layer, which is the organic matter layed out in thin sheets on the external side of the oyster shell. The new color is dark, generally a shade of gray or bluish gray, but not really like the black achieved by the silver salt treatment. The color is stable and the treatment does not make the pearl radioactive.

      Naturally colored black or dark pearls usually show reddish fluorescence under long wave ultraviolet. Gamma treated colors usually show only the yellowish fluorescence typical of bead-nucleated and freshwater pearls.

     Some cultured pearls derive their color from bead nuclei that were dyed before the grafting process. On rare occasions, pearls have also been found with thin plastic coatings to add superficial color. The coating makes them feel strange and, with wear, tends to develop "bald spots".


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