How to identify dyed black pearls
The pearls of the general color do not need to be changed in color. Only the black (dark) pearls are lightly colored because of the low yield. Therefore, the light-colored pearls are colored to make them dark. The current methods of color change include dyeing and radioactive radiation.
1, dyed pearls
Pour the light-colored pearls into a nitric acid solution and ammonia water, then remove them with sunlight or smoke with hydrogen sulfide, which will turn grayish black.
2, irradiation color pearl
Light-colored pearls can be blackened by r-irradiation. However, pearls that can be blackened are limited to freshwater pearls containing trace amounts of manganese in fresh water and nacres inside the freshwater clam shells. Natural pearls that grow in seawater and nacres that are attached to the outer layer of nucleated cultured mother-of-pearl do not change color. That is to say, the radioactive black nucleated pearl, the black color comes from the mother-of-pearl, is a black colorless layer of pearls attached to it, making the nucleated cultured pearls appear pearl black color. This kind of black pearl that has been changed by the permanent irradiation method is also called Akoya pearl in international business. The following five points are used to identify the basis of color-changing black pearls with the naked eye. The color of the dyed black pearl is uniform in color, but in places where there are lesions and cracks, the black color is deep. If you have doubts about the black pearls you hold, you can use a 20% dilute nitric acid solution on cotton to scrub the surface of the dyed black pearls, leaving black marks on the cotton balls.
Color of the powder : The color of the natural black pearl powder is white, while the color of the dyed black pearl powder is black. If you have a small hole in the black pearl, you can use the needle to pick a little powder from the hole to identify it. This is a destructive practice, so be careful when doing it, especially if you can't sculpt it on the black pearl without the hole.
Peeping the core : The natural black pearl has a uniform structure and no core. The nucleated cultured black pearls modified with radioactive radiation are in a white pearl layer of 0.5-2 mm thick, and have a black core. From the place where the black pearl has a hole, peep into it with a 10x magnifying glass. . But for black pearls that are not drilled, this method does not work.
Fainting : The black pearls that have been modified by radiation irradiation, the spectrum of the halo is rich, accompanied by a strong metallic luster particle size, and the pearl of the pearl is bred, which is much larger than the palm of the hand. The black pearls that are cultured are larger, rarely less than 9 mm. Therefore, a circular nucleated black, grayish green or blue-green pearl of less than 8 mm may generally be a product of radioactive irradiation color change.
Another easy way : black natural pearls are very expensive, so pay attention to the difference between them and dyed pearls when buying. Under certain conditions, be sure to put the pearl under the fluorescent lamp and see that it does not emit red fluorescence. If it is red fluorescent, it is a natural pearl, otherwise it is a color-changing pearl. If there is no fluorescent lamp, you can use a 20% dilute nitric acid solution on the cotton ball to gently wipe the pearl in the inconspicuous place. If the pearl is dyed, it will leave black marks on the cotton. Generally, it is not sure. Don't buy it at will.
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