Application of Hyperspectral Imaging Technique in Identification of Polymer-Impregnated Gemstone: Taking Jadeite and Turquoise as Example

In the 1980s, hyperspectral imaging technique was developed rapidly, which was formed by the combination of traditional imaging technique and spectroscopy. Using hyperspectral imaging tester, 3D data information can be obtained by integrating image data and spectral data. But this technique has not been widely used in gemmology. At present, it mainly depends on FTIR to achieve non-destructive identification of polymer-impregnated gemstones, and sometimes the results are affected by the surface polishing and the transparency of the sample. FTIR is difficult to find out the distribution and degree of the filling. However, the hyperspectral imaging techique can cover those shortages of FTIR. In the papers, hyperspectral imaging technique was used to compare polymer-impregnated and natural jadeite and turquoise samples, and ENVI software was used to process the results. The results are as follows: The imaging spectral information of jadeite and turquoise samples in 1 000-2 500 nm (in NIR band) was obtained. The imaging spectral information of jadeite and turquoise samples in 1 000-2 500 nm band was obtained. The absorption of polymer-impregnated jadeite at 1 733、2 208、2 313 nm was observed. The diagnostic of absorption in 2 000-2 300 nm of polymer-impregnated turquoise could be distinguished from those of natural turquoise, which is inferred that the absorption of 1 733 nm is caused by polymer. By ENVI processing, the distribution of polymer and the degree diagram were obtained and shown distinct.