How to distinguish natural black pearls from artificial black pearls?

Abstract: Black pearl is a very precious kind of jewelry, and it is the most colorful pearl jewelry, which is deeply favored by people. It is precisely because black pearls are expensive and precious that some unscrupulous merchants have moved their minds and used fake black pearls or dyed black pearls. As an ordinary consumer, how to identify the authenticity of black pearls? How to distinguish natural black pearls from artificial black pearls? Let's have a look. First of all, the species of black pearls

Black pearls on the market can generally be divided into the following three types:

1, natural black pearl

Black pearls cultured by nuclear implantation (cultured in Pinctadamargaritiferacumingi, maybe in some kind of mother-of-pearl). This mother-shell lives in the coral reef waters of French Polynesia.

2. Rare brown to black seedless cultured pearls.

There are more and more colored pearls, including dyed black pearls, radiated pearls and the latest so-called "laser-treated" pearls.

3. Imitation pearls made of black shells

Some rare imitations are coated with a black essencedeorient film on the surface of the ball core, or made into beads with black shells to polish the pearl luster.

Distinguish natural black pearls from cultured black pearls, colored black pearls and imitations. Careful observation of the luster of the coated pearls shows that the pearlescence of the coated pearls comes from the bottom of the polymer thin layer, while that of the untreated pearls comes from the top layer of the pearls. The abnormal reflection of the color on the top surface of the pearl can also be observed, which is also helpful for the detection of this kind of pearl. The color of this pearl is pink from the top and blue from the side; The black pearls treated in this way have purplish tops and green sides.

Second, the characteristics of high-quality pure black pearls

1, the pearl surface is particularly smooth.

2. pearls feel sticky.

3. It's hard to see the edge of the laminated nacre, but you can see sharp instruments and concave colorless covering.

Third, the common means of pearl dyeing

1. silver salt treatment: the pearl is soaked in nitrate and dilute ammonia solution, and then reduced in strong light or hydrogen sulfide gas to make the pearl black.

2. Irradiation: The pearl turns black when exposed to gamma rays from cobalt sources.

3. Dyeing pearl nucleus: implant the pearl nucleus into pearl shell after blackening. When the pearl is formed, the black pearl core makes the translucent pearl look black.

4. Coating: Coating a thin layer of black glue on the pearl surface.

4. How to distinguish natural black pearls from artificial black pearls?

1, color

Black pearls have different shades of light gray to black, and its beauty lies in the accompanying color in the look tone. Turn the black pearl slowly, and you can see the slight rainbow-like flash changing constantly. No two pearls are exactly the same. If you see a string (or even a few strings) of black pearls with the same depth and bright colors, you can almost be sure that they are dyed pearls. After dyeing, the color of the beads is dim, and the black color gathered in the holes and defects is deep, which is easy to observe under a magnifying glass of ten times.

Step 2 shape

Are the black pearls you see particularly round? Exquisite round black pearls are extremely rare and of high value. Typical black pearls are oblate, pear-shaped, oval and irregular, and many of them have flaws or rings, so the "super-value black pearls" you see are smooth and round, and they are probably dyed.

Step 3 size

The diameter of seawater pearls in China or Japan is usually less than 9 mm, while the diameter of black pearls is at least 8 to 9 mm, so round black pearls smaller than 8 mm are mostly dyed pearls.

4. Price

Are the black pearls you see surprisingly cheap? An 8mm round black pearl costs more than 1000 yuan, while a dyed pearl of the same size only costs 1200 yuan. If you are lucky enough to buy cheap black pearls, Jinji requires the merchant to indicate on the receipt that the color of the pearls is natural.

Verb (abbreviation of verb) Identification method of natural black pearl

If you want to buy expensive black pearls, the above appraisal method is still not at ease, so consider taking them to the jewelry appraisal unit for an exact appraisal with instruments:

1, ultraviolet fluorescence test

Under the irradiation of ultraviolet rays, black pearls often emit fluorescence, ranging in color from bright red to coffee red, but most dyed pearls do not respond to ultraviolet rays or show dark green fluorescence.

2.x-ray testing

The film sent by X-ray can see the dyed pearls treated with silver salt, and there is a circle of pale white between the nacre and the nucleus of the dyed pearls, which proves its dyeing composition.

3.x-ray fluorescence test

Pearl will emit radiation with a specific wavelength under X-ray irradiation, and the chemical composition and the existence of silver salt can be detected by measuring the degree of wavelength with a spectral measuring instrument.

4, infrared photography test

The black pearl image taken by infrared film is light blue, while the dyed pearl image treated by silver salt is yellow, or blue-green to yellow-green.