How to identify the authenticity of black pearls

The annual output of high-quality black pearls is estimated to be no more than 6.5438+0.5 million, of which 40% is sold through international auction every year. How to identify the authenticity of such a rare black pearl? The following is how I can identify the authenticity of black pearls for you, hoping to help you.

How to identify the authenticity of black pearl 1, color distribution

After dyeing, the color of black pearls is even, and the black color gathered in holes and cracks is darker. The surface color is pure black, while the natural black pearl is not pure black, but dark blue black with a slight rainbow flash, or black with bronze hue.

2. Powder method

Dyed black pearls have black powder, and black pearls have white powder. However, taking pearl powder is a destructive experiment, so be very careful in operation, especially don't carve on black pearls without holes at will.

3. Particle size method

Most of the black pearls are Pinctada maxima, and the Pinctada maxima produces large nucleus and big beads. Generally, the particle size is rarely less than 9 mm, so those less than 8 mm are round black pearls, mostly irradiated products.

4. Halo

Black pearls discolored by radioactive radiation are rich in halo spectrum and accompanied by strong metallic luster.

5. Dilute acid method

In some cases, cotton balls can also be dipped in dilute nitric acid (2%) to try to wipe pearls in inconspicuous places. Dyed black pearls will make cotton balls black. This method is destructive and should be used with caution. But experienced appraisers can often find the defects of colored pearls.

Identification between natural pearls and cultured black pearls with nuclei The appearance of black pearl necklace was observed with a double-tube fluorescent desk lamp. If the shape and particle size of black pearls are the same, in other words, if a necklace is composed of spherical pearls with uniform size, it is most likely a cultured pearl necklace with a core inserted. Practice has proved that it is very difficult to find a pair of natural pearls with exactly the same shape and size, and it is even more difficult to find a pearl necklace with exactly the same shape and size, which actually does not exist. Natural pearl strings are mostly classified by particle size, and particles of different sizes usually have different shapes.

From the color observation and analysis, the color uniformity of the inserted cultured pearl necklace is much better than that of natural pearls.

Seen from the surface of the bead layer, if any? Circular pattern? And then what? Crow's feet? And other features, probably cultured pearls. Natural pearls do not have this characteristic. Under good optical fiber illumination, observe with a magnifying glass of 10 times. If there is nacre on the nacre? Women's ring pattern? The tooth-shaped appearance is likely to be natural pearls or cultured pearls, which is very different from the result of imitation pearls. The pearl-like structure is smooth in appearance.

Observation of Pearl Borehole with Small Diameter Optical Fiber with brightness level. If it is found that the concentric structure as thin as onion layer is a natural pearl, if it is found that there is a gray to white central shell bead with a thin brown to black organic layer between the shell and the black pearl, then it is a black pearl cultured by inserting nucleus.

The difference between black pearls and dyed pearls 1. To observe whether there are holes on the pearl surface, it is best to use a magnifying glass with 10 times. If there are no holes, most of them are natural pearls (or cultured pearls). If there are holes, they are probably dyed pearls. Because when dyeing, you have to drill holes before dyeing can enter.

2. Using a magnifying glass of 10 times, carefully observe the blue dye on the pearl surface and the small pinholes left by radiation treatment. If there is a blue dye, it is dyed pearls. If there is no blue dye, it is a natural or cultured black pearl; If there are not too many small needles, they are natural or cultured black pearls; If there are many small needles, it is dyed pearls.

3. Carefully observe the borehole with a magnifying glass of 10 times. If there is a blue dye concentration in the borehole, it is a dyed pearl, otherwise it is a natural or cultured black pearl.

4. Observe pearls with polarizing microscope. If they are natural or cultured pearls, the colors are uneven.

5. Infrared photography, taking pictures with infrared film. If it is a natural black pearl, it will be developed into light blue, while the black pearl treated with silver salt will be yellow to blue-green.

6. The fluorescence test showed that natural or cultured black pearls often showed bright red to brown under ultraviolet irradiation, while most dyed black pearls showed no reaction or weak green fluorescence.

7.X-ray inspection: the photos irradiated by X-rays can develop the pearls treated with silver salts, and the dyed black pearls present a gray-white shadow between the nacre and the nucleus.