Since the Fourier infrared spectrometer is used to classify unknown substances, it is more convenient and non-destructive, and the risk of harm to the measured object and the test system is relatively small. Therefore, it is also particularly suitable for processing precious samples of gems.

The main principle of identification using Fourier infrared spectrometer is: infrared radiation will cause the material's molecular vibrational energy level transition to produce infrared spectrum. We can get the molecular structure by analyzing the functional groups in the spectrum. Almost no infrared spectra of two substances are the same, so infrared spectroscopy is also called "fingerprint spectrum". The editor also checked some relevant gem identification standards and some documents. In summary, the identification methods using Fourier infrared spectrometer can be divided into the following methods:

1. Fourier near infrared spectroscopy

Near-infrared spectroscopy mainly refers to the infrared spectrum in the 12500 ~ 4000 cm-1 band. This band is the frequency doubling and combined band of the mid-infrared spectrum. It is characterized by strong penetrating ability, with a penetration depth of more than 1mm, while the penetrating ability of mid-infrared light can only reach about 40μm. When the surface of Jade B is thickly waxed, it is difficult for mid-infrared light to penetrate the wax layer, and it is impossible to obtain information about the resin filled below the paraffin layer, which may cause misjudgments. Near-infrared light can penetrate more than 1mm into the gemstone, and the spectral information of resin and paraffin will not be missed, which ensures the accuracy of identification. Therefore, we can use mid- and near-infrared dual-band Fourier infrared spectrometers to determine the authenticity of gemstones by observing the configuration of water in the near-infrared spectral region around 7000cm-

2. Attenuated reflectance spectroscopy:

For thick jade or finished products inlaid with gold and platinum, infrared light is difficult to penetrate, and the transmission spectrum cannot be collected. In this case, diffuse reflection spectrum accessories are required. Testing the infrared reflectance spectrum of the gemstone surface is a mature method to solve the above problems. This method can not only identify the filling and modification of the gemstone, but also obtain complete structural information of the gemstone, which is often used to identify the authenticity of the gemstone.

3. Transmission spectroscopy:

Infrared light penetrating the gemstone can easily obtain the structure information of the substance in it. Taking jade as an example, we can easily identify the presence of organic resin fillers in the jadeite through the band of 3200 to 2750 cm-1, and can identify whether there is a coloring agent, so as to quickly identify whether the jade is A, B or C goods. This method is simple and effective, and is often used to identify gems such as rubies, sapphires and diamonds.

In addition to the aforementioned gem identification, Fourier infrared spectrometers are often used in quality analysis and product accident investigations. Its function is like a fingerprint identification instrument for substances, and because of its simple sample preparation, it is the most commonly used and most basic method in product failure analysis.