Natural diamonds have single refraction, so you can't see fingerprints on your hands, but fake diamonds can. The single refraction of diamond is determined by its essential characteristics. While other natural gemstones or artificial gem are mostly birefringent. When the fake diamond is observed with a magnifying glass of 10 times, it is easy to see that the edges and corners overlap, and two bottom lights are exposed at the same time from the slightly inclined front. If the difference in birefringence is small, such as zircon, you can also see the image of overlapping background light.

2. Detection method of thermal conductivity test

Breathing on the surface of diamond and imitation diamond at the same time, the water mist condensed on the surface of real diamond will evaporate faster than that on imitation diamond, which is detected according to the "high thermal conductivity" principle of diamond. If you plan to buy diamond ornaments locally, you might as well take a diamond imitation with you as a comparison of the experiment. This is the commonly used breath test, that is, breathing on the diamond, such as the water vapor on the diamond immediately disappears into a real diamond; If the water vapor stays on the diamond for a few seconds and then disappears, it is a fake diamond. For this reason, diamond pens used in general jewelry applications are made according to the principle of heat conduction.

3. Water drop test method

Drop a small drop of water on the diamond table. It is true if the water drops swell for a long time, but it is false if they disperse quickly. Because diamonds are oleophilic and hydrophobic, the water droplets on diamonds remain spherical for a long time, while the water droplets on imitations will disperse in a relatively short time. This is the famous dripping identification method: first, wipe the flat surface at the top of the diamond with a diamond cloth, and then drop a drop of water on it. Water droplets will spread around on fake diamonds, while real diamonds are in the shape of regular round water droplets.

4. Similar chemical composition test

The chemical composition of pencils is carbon, just like diamonds, but the physical structure is different, so many people use pencils to detect the authenticity of diamonds, which is a practical and effective method. When identifying, the diamond should be wetted with water first, and then gently scratched with a pencil. On the crystal face of a real diamond, there is no trace where the pencil crosses, but if it is not a diamond, but a material such as glass and crystal, it will leave a trace on the surface. Under normal circumstances,

5. Adsorption of diamonds

Diamonds have a certain affinity for grease and dirt, that is, oil stains are easily adsorbed by diamonds. So touching the diamond with your fingers will feel sticky, and your fingers seem to feel sticky. This is not found in any gem. This method needs training to master the nuances.

6. Look at the luster of the diamond.

The luster of a diamond is a secret that can reveal its true and false identity. After polishing, the real diamond fire color is strong, and the brilliance emitted by those imitations with high refractive index appears stiff and dull. Put the diamond in a white glass and fill it with water. If the light gets dim, it's a fake diamond. Secondly, it depends on whether the edges and corners of the diamond are very sharp. Only the edges and corners of imitations will be worn because the hardness is not high enough, and their edges and corners are blunt at best. At this time, you must rely on a magnifying glass to observe carefully.

7. Look at the growing point

Observing under a magnifying glass, there are often grooves and triangular growth points on the crystal face of real diamonds, but there are three kinds of fakes: ① Ordinary glass with alumina is easy to get into the wrong place, because the refractive index and dispersion increase, but the hardness is lower. (2) Imitated with chemically synthesized sapphire and colorless spinel, the hardness is similar, but the refractive index is low and has birefringence, and the double image can be seen under a magnifying glass.

8. Look at the refractive index of diamonds.

Draw a straight line on the white paper with a pencil. When two kinds of gems are placed in a straight line with their tips facing down, natural diamonds can't see the straight line drawn through the tips, while zircon can see the curved arc.

This is because the refractive index of diamond is the highest among all gems, and diamonds to be made into jewelry need to be cut better, so almost all the light irradiated on the cut surface of diamond is reflected, and almost nothing can be seen from the vertical view of the tip, while the refractive index of cubic zirconia is not so good, and some light will be missed by reflection, so deformed lines can be seen.

9. But if you want to be reliable, you must use advanced instruments.

The identification of diamond imitations and the optimization of processed products are sometimes identified with the help of advanced instruments, which are usually used in the following two ways:

1). Thermal conductivity meter:

It is an instrument designed according to the high thermal conductivity of diamond. The principle is to use the high thermal conductivity of diamond to quickly transfer the heat emitted by thermal sensitive elements, so that the indicator light of the instrument rises rapidly and chirps. There is a copper probe at the front end of the thermal conductivity meter. When measuring, turn on the instrument power supply, preheat it for about 15 seconds, and the work indicator light will be on. At this time, according to the room temperature and the size of the diamond to be measured, the thermal conductivity meter (diamond selector made in Japan) is lifted to contact the surface of the diamond, and the indicator light of the thermal conductivity meter rises rapidly, and the chirping sounds are diamond, natural gem and synthetic gem (imitation diamond). Suitable for rough diamonds, finished diamonds, uncut diamonds and inlaid diamonds. Even a small diamond. It is also a powerful weapon to distinguish imitation diamonds.

2).Mosanite detector:

This is an instrument specially used to identify Mosan stone (sic). The basis is that diamond and mosanite have different properties in near ultraviolet. It should be used in conjunction with the thermal conductivity meter when testing. Because the thermal conductivity of ground stone is similar to that of diamond, most imitation diamonds can be distinguished by thermal conductivity meter, while ground stone cannot be distinguished. Therefore, when the thermal conductivity meter determines that a gem may be a diamond and there is some doubt that it may be mosan stone, the mosan stone detector is used to detect it. ?

If Mosan stone has no detector, it can also be distinguished from diamond by its birefringence and the change of light and shade under the polarizer.

10. In addition, the reliability of certificates should be distinguished.

Europe is many years ahead of China in understanding diamonds. For this reason, a large number of diamonds in the domestic market have overseas certification certificates, which come from different institutions and laboratories. It seems that only overseas certification is the most reliable. Moreover, diamonds with overseas certificates are usually much more expensive than diamonds without certificates or overseas certificates of the same grade, such as GIA's diamond appraisal certificate.

But in fact, overseas certificates are not as reliable as expected. Although there are international uniform identification standards for diamonds, the inspection methods and standards of overseas institutions and laboratories are not uniform. There may be cases where VVS 1 grade diamonds have IF grade certificates and IF grade prices. There are many certificates and many English words, and quite a few people in China will not read them. In fact, many articles only explain the diamond inspection results, which can be regarded as inspection reports, and do not have the authoritative "proof" status.