Diamond, the king of gems, is also one of the most expensive gems. Therefore, there are always some people who are trying to make profits by falsifying the truth. Before the synthesis of zirconium carbide, diamond imitation products include cubic zirconia, YAG (yttrium aluminum garnet) and the like. Since AYC is prone to wear and fading, the boring test on the YAC with a boron oxide pen will make it look as it is. So it is rare to see it now. Cubic zirconia has a high hardness and is popular for a wide range of clothing. Some criminals sell cubic zirconia as a natural diamond. In fact, the easiest way to distinguish cubic zirconia from diamonds is to wipe the test article with a clean cloth or suede and press it with your finger on the test object. If there is a clear fingerprint on the test article, it is a diamond. Because the diamond is oleophilic, and vice versa is cubic zirconia, because cubic zirconia is hydrophilic.
Synthetic silicon carbide, moissanite, is the latest diamond imitation. Its common color is yellowish, the chemical composition is silicon carbide, Mohs hardness of 9.25, specific gravity 3. & 127; It has a birefringence, a refractive index of 2.648-2.691, and a birefringence of 0.043.
The thermal conductivity of synthetic silicon carbide is close to that of diamond. The diamond reaction is tested by diamond thermal conductivity tester, so it can not be identified by thermal conductivity meter. Due to the high hardness and high refractive index of synthetic silicon carbide, it has been cut. The surface of the synthetic silicon carbide is very reflective and the gloss is very close to that of the diamond. It is not easy to distinguish between diamond and synthetic silicon carbide with a hardness pen. Then use the following identification instruments for testing:
First, observe with a 10x magnifying glass.
1. The hardness of the faceted ridgeline synthetic silicon carbide is as high as 9.25, but it is still far less than diamond, so the faceted ridgeline is still not as sharp as diamond.
2, the shadow observation of diamond single refraction, and synthetic silicon carbide is birefringence, and the two values ​​are very different, so it will produce a complex image, that is, the facet ridge line will become two images. However, when cutting synthetic silicon carbide, the direction without the complex image (ie, the optical axis direction) is often perpendicular to the table top, so it is necessary to tilt an angle or side to observe the phenomenon of ghosting.
3. Internal characteristics Diamonds often contain horn-like minerals or cracks. Synthetic silicon carbide often contains needle-like features.
Second, using a synthetic silicon carbide / diamond tester.
Synthetic silicon carbide is almost a semiconductor material like diamond, and its impurity content is extremely low. The relative transparency of the near ultraviolet region was measured with a tester. For near-ultraviolet light, near-colorless diamonds are transparent, while synthetic silicon carbide is absorbed. The polished facet of the gemstone to be tested is brought into contact with the probe of the instrument while a small high-intensity halogen lamp is illuminated obliquely to it. If the indicator light is on and there is a beep, it indicates that the diamond is being measured, and if it is not, it is synthetic silicon carbide. However, if the diamond contains a large amount of inclusions, the instrument will not be able to distinguish correctly.
How to distinguish synthetic carbon silica from diamonds
1. Visual observation of synthetic carbon silica fire is stronger than diamonds, but often less than diamonds.
2. Synthetic carbon silica has the highest color equivalent to diamond H, I color, and has a clear green and gray hue from the pavilion.
3. The synthetic carbon-silica bare stone floats in the 3.33g/cm heavy liquid, and the diamond sinks.
4. The synthetic carbon silica is rotated 360 under the orthogonal polarizer to form a four-four-dark non-homogeneous extinction phenomenon. The diamond is completely dark and homogeneous.
5. Enlarged inspection, synthetic carbon-silica common slender white needle-like inclusion, from the kite surface, the upper side of the upper waist can be seen near the sharp bottom of the ridge line has a ghost image, like a lotus; from the table top oblique waist reflection also Ghosting. Diamonds contain natural crystalline bodies, clouds, cracks and other inclusions, and there is no ghost phenomenon, the original crystal face is common at the waist.
6. Synthetic carbon silica is less polished than diamonds, and the ridge lines are more rounded or the polished textures of adjacent facets are parallel to each other.
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