Raman spectrometer is a method for comparative study of molecular structure based on Raman effect. The principle of Raman spectrometer for gemstones is that when a beam of light shines on the surface of gemstones, part of the incident light passes through the substance and part is reflected on the interface of gemstones. In addition, there will be weak scattered light in different directions of the gem. Most of the scattered light is elastic scattered light (Rayleigh scattering) which is the same as the excitation light wave, and the one shorter than the excitation light wave is called "Stokes line" and "anti-Stokes line". This phenomenon is called Raman scattering effect. Raman spectrometer can provide a fast, accurate, non-destructive and non-contact method for gems.
2, infrared spectrum analyzer
Infrared spectrum can solve three problems in jewelry detection. First, it can identify the variety of gemstones, such as whether the tested object is jade or blue jade. Secondly, natural gemstones and synthetic gemstones can be distinguished. For example, there are many crystal balls on the market, and they are very pure in rock crystal. How to accurately distinguish between rock crystals and synthetic crystals is a problem that often puzzles inspectors, and natural products and synthetic products can be easily distinguished by infrared spectrometer. Thirdly, the infrared spectrometer can effectively identify the treated gems, such as some high-grade jadeite B goods on the market, which are almost invisible by conventional methods, while the infrared spectrometer has a good judgment effect on those jadeites that have been bleached and glued.
3, spectrophotometer
Spectrophotometer can directly see the obvious absorption lines (bands) and fluorescence spectra of various gems by using visible light spectrometer. Spectrophotometers include ultraviolet-visible spectrophotometer and infrared spectrophotometer. Ultraviolet-visible spectrophotometer is one of the most widely used in gemstone identification. Based on Lambert-Beer law, it can qualitatively and quantitatively analyze and characterize some components in gemstones by measuring their absorbance at a certain wavelength or within a certain wavelength range. Spectrophotometer is one of the most useful instruments for gem appraisers. In addition, the wavelength range of visible spectrophotometer is190-850 nm; The wavelength range of infrared spectrophotometer is 400 ~ 4500 minus one centimeter. The detection accuracy of spectrophotometer is high, so it is difficult for human eyes to detect those spectral regions that are only partially absorbed, as well as infrared regions and ultraviolet regions other than visible light. The actual information can be detected by spectrophotometer.
4. Electron probe
The full name of electron probe is "electron probe X-ray microanalyzer", which is a very precise chemical composition analysis method in micro-area. The principle is to bombard the sample with high-energy electrons to excite the sample and generate characteristic X-ray signals. The wavelength of the signal is related to the type of elements contained in the sample, and the intensity of the signal is related to the concentration of elements. So as to qualitatively and quantitatively analyze the elements contained in the sample. For example, the table shows the analysis results of chemical components in white jadeite and high-grade green jadeite by electron probe. The application of electron probe in gem detection and identification is mainly to determine the exposed color body composition of gem surface quickly and non-destructively. Test the change of element content in different parts and directions of the gem. The advantages of this method are non-destructive, fast, small beam area, low energy for analyzing the chemical composition of the measured part of the gem, and no damage to the gem.
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