Diamond Mimicry - Identification of Synthetic Silicon Carbide

Diamond, the king of precious stones, is also one of the most expensive gems. Therefore, there are always people who attempt to make real profits and profits. Prior to the synthesis of zirconium carbide, diamond mimics include cubic zirconia and YAG (yttrium aluminum garnet). Because AYC is susceptible to wear and fading, the scratch test on the YAC with a boron oxide pen will make it appear as it is. So it is rare to see its sight now.

Cubic zirconia has a high hardness and a wide spread, and is suitable as a clothing. Some outlaws sell cubic zirconia as a natural diamond. In fact, the easiest way to distinguish between cubic zirconia and diamonds is to clean the test article with a clean cloth or suede and press it with your finger on the test article. If there is a fingerprint on the test article, it is a diamond. Since diamonds are oleophilic, cubic zirconia is the opposite because cubic zirconia is hydrophilic. Synthetic silicon carbide, molybdenite, is the latest diamond imitation. Its common color is slightly yellow, the chemical composition is silicon carbide, Mohs hardness of 9.25, specific gravity 3. ?twenty two. With birefringence, refractive index 2.648-2.691, birefringence is 0.043. The thermal conductivity of synthetic silicon carbide is close to that of diamonds. Diamond reaction occurs when synthetic silicon carbide is tested with a diamond thermal conductivity meter. Therefore, it cannot be determined by a thermal conductivity meter. Because of the high hardness and high refractive index characteristics of synthetic silicon carbide, it has been cut. Synthetic silicon carbide surface reflection and gloss are very close to the diamond. Even with a hardness pen, it is not easy to distinguish diamond from synthetic silicon carbide.

Then the following identification instruments can be used for detection:

First, observe with a 10x magnifying glass.

1. Although the hardness of synthetic silicon carbide with faceted ridges is as high as 9.25, it is still far inferior to diamonds, so the facet ridges are still less sharp than diamonds.

2. The double vision observes the diamond single refraction, while the synthetic silicon carbide is birefringent, and the two values ​​are very different, so it will produce a double shadow, that is, the facet ridge will become two images. However, when cutting synthetic silicon carbide, it is often the direction without the ghosting (ie, the optical axis direction) perpendicular to the desktop, so it must be tilted at an angle or side observation to see the phenomenon of multiplicity.

3. Internal features Diamonds often contain horny minerals or cracks. Synthetic silicon carbide often contains needle-like features.

Second, the use of synthetic silicon carbide / diamond tester detection. Synthetic silicon carbide is almost a semiconductor material like diamonds, and its impurity content is extremely low. With the tester, the relative transparency in the near-ultraviolet region was measured. Near-ultraviolet light, near-colorless diamonds are transparent, while synthetic silicon carbide absorbs. The polished facet of the gemstone to be tested is brought into contact with the probe of the apparatus while a small, high-intensity halogen lamp is irradiated obliquely toward 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 number of inclusions, the instrument cannot be correctly identified.