Method for identifying heat-treated red jadeite

Abstract

The invention relates to a method for identifying heat-treated red jadeite, which comprises the following steps of: analyzing and judging whether a sample to be detected is jadeite or not by using an infrared spectrum reflection method, and then analyzing and judging the heat-treated red jadeite and natural red jadeite by using an infrared spectrum transmission method and an ultraviolet-visible reflection spectrum first-order derivative. The infrared spectroscopic analysis technology and the ultraviolet-visible reflection spectrum first-order derivative analysis technology are comprehensively utilized, and efficient and accurate identification of the heat-treated red jadeite is achieved. According to the method, the identification efficiency and accuracy of the heat-treated red jadeite can be improved, and the phenomenon that the heat-treated red jadeite disturbs the market can be reduced.

Description

Technical Field

[0001] The present invention relates to a method for identifying heat-treated red jadeite, belonging to the technical field of gem identification. Background Art

[0002] Red jadeite is a relatively rare variety of jadeite (hereinafter referred to as red jadeite for short), and those with bright colors are even rarer, and it has a relatively high economic value. The coloring cause of natural red jadeite is a secondary cause, which is formed by the filling and impregnation of secondary minerals such as goethite and hematite into the cracks and cleavage planes of primary jadeite due to hydrothermal reactions and other effects, resulting in red-yellow tones. In addition to natural red jadeite, optimized and treated red jadeite is also commonly seen, which refers to improving the color of jadeite that was not originally red or had a poor red effect to bright red through a series of technological means, or improving its appearance and quality, and selling it as natural high-quality red jadeite. Among them, heat-treated red jadeite, also known as burnt red jadeite, is one of these optimization and treatment methods, which refers to improving the color of jadeite with a relatively grayish-brown and dull color to red by heating. The value of heat treatment and natural red jadeite varies greatly, but due to the similar mineral phase components of the coloring minerals, and the similar color distribution characteristics and appearance characteristics, it is difficult to identify.

[0003] Currently, the identification of red jadeite mainly relies on the experience of naked-eye observation, and subjective judgments are made through apparent phenomena such as color distribution and crack characteristics. However, the above methods have the following limitations: the influence of human subjective factors is large, and there is a lack of objective scientific basis; it is impossible to effectively distinguish heat-treated red jadeite from natural red jadeite; these problems have led to the fact that heat-treated red jadeite is often impersonated as natural red jadeite in the market, seriously disrupting the market order and damaging the rights and interests of consumers.

[0004] In the prior art, although there are individual studies attempting to use spectral analysis technology for jadeite identification, most are limited to single detection means (such as infrared spectroscopy or ultraviolet spectroscopy), and no systematic solutions have been proposed for the secondary mineral characteristics of red jadeite (such as the combination of goethite and hematite). For example, although infrared spectroscopy can detect whether it is jadeite, it cannot distinguish heat-treated red jadeite from natural red jadeite; while for ultraviolet-visible spectroscopy, if derivative analysis is not combined, it is difficult to accurately identify the overlapping characteristics of mineral absorption peaks. Summary of the Invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a method for identifying heat-treated red jadeite, which can improve the identification efficiency and accuracy of heat-treated red jadeite, and can reduce the disruption of heat-treated red jadeite to the market.

[0006] To achieve the above object, the technical solution provided by the present invention is: a method for identifying heat-treated red jadeite, comprising the following steps:

[0007] (1) Infrared spectroscopy reflection method analysis: Use an infrared spectrometer to test the infrared absorption spectrum of the sample to be tested, with the test range being 1500 - 400 cm -1 , and judge by detecting the characteristic group peaks of jadeite at 433 cm-1, 472 cm-1, 532 cm-1, 588 cm-1, 665 cm-1, 744 cm-1, 852 cm-1, 954 cm-1, 1049 cm-1, 1085 cm-1, and 1172 cm -1 . If the characteristic group peaks are not detected, it is determined that the sample to be tested is not jadeite, and the identification ends; if the characteristic group peaks are detected, it is determined that the sample to be tested is jadeite, and proceed to step (2);

[0008] (2) Infrared spectroscopy transmission method analysis and UV-Vis reflection spectroscopy first derivative analysis: For the sample to be tested determined to be jadeite in step (1), use an infrared spectrometer to test the infrared absorption spectrum of the sample to be tested, with the test range being 4000 - 2500 cm -1 , and identify natural red jadeite and heat-treated red jadeite through the broad absorption characteristic peaks of crystal water and adsorbed water at 3450 cm -1 , the hydroxyl structural water characteristic peaks of impurity clay minerals at 3695 cm -1 , and the aromatic hydrocarbon characteristic peaks at 3037 cm -1 and 3057 cm -1 . Then, use a UV-Vis reflection spectrometer to test the UV-Vis reflection spectrum of the sample to be tested, with the test range being 300 - 800 nm, perform first derivative processing on the spectral data, and identify natural red jadeite and heat-treated red jadeite through the secondary peak of goethite near 438 nm and the hematite peak near 560 - 580 nm; among them, the broad absorption characteristic peaks of crystal water and adsorbed water at 3450 cm -1 , the hydroxyl structural water characteristic peaks of impurity clay minerals at 3695 cm -1 are group peak 1, the aromatic hydrocarbon characteristic peaks at 3037 cm -1 and 3057 cm -1 are group peak 2, the secondary peak of goethite near 438 nm is single peak 3, and the hematite peak near 560 - 580 nm is single peak 4;

[0009] (3) Comprehensive peak position information to identify natural red jadeite and heat-treated red jadeite: Make a comprehensive judgment on the sample to be tested according to the peak position information in step (2). When group peak 1, single peak 3, and single peak 4 appear and group peak 2 does not appear, it indicates that the sample to be tested has not been heat-treated, and it is determined that the sample to be tested is natural red jadeite; when single peak 4 appears and group peak 1, group peak 2, and single peak 3 do not appear, it indicates that the sample to be tested has been heat-treated, and it is determined that the sample to be tested is heat-treated red jadeite.

[0010] A further improvement to the above technical solution is as follows:

[0011] In step (1), the infrared spectrum is tested by the reflection method, with a resolution of 4 cm-1, 64 scanning times, and a scanning frequency of 10 kHz.

[0012] In step (2), the infrared spectrum is tested by the transmission method, with a resolution of 4 cm-1, 64 scanning times, and a scanning frequency of 10 kHz.

[0013] In step (2), the test conditions for the ultraviolet-visible reflection spectrum are an integration time of 100 ms, 8 integration times, and the spectral data is first-order derivative processed after being smoothed with 25 window points.

[0014] In step (2), the test position for the infrared transmission spectrum is selected in the area of the red jadeite sample where the color is uniform and the thickness is relatively thin.

[0015] In step (2), the spectral data after the first-order derivative processing is further smoothed with 25 window points.

[0016] According to the above technical solution, a method for identifying heat-treated red jadeite provided by the present invention analyzes by using the infrared spectrum reflection method to determine whether the sample to be tested is jadeite, and then determines the heat-treated red jadeite and natural red jadeite by the infrared spectrum transmission method and the first-order derivative analysis of the ultraviolet-visible reflection spectrum; by comprehensively using the infrared spectrum analysis and the first-order derivative analysis technology of the ultraviolet-visible reflection spectrum, the efficient and accurate identification of the heat-treated red jadeite is realized. The present invention has the following advantages compared with the prior art:

[0017] (1) Since the technical solution adopted by the present invention combines the detection of infrared spectrum characteristic peaks and the first-order derivative processing of the ultraviolet-visible reflection spectrum, and establishes an objective discrimination standard based on spectral characteristics, the present invention can efficiently distinguish the heat-treated red jadeite from the natural red jadeite, improve the scientificity and reliability of the identification, avoid the subjectivity and uncertainty brought by relying solely on visual inspection, greatly improve the identification efficiency and accuracy, and reduce the trading disputes caused by misjudgment in the market.

[0018] (2) Since the technical solution adopted by the present invention introduces spectral data smoothing and first-order derivative processing, the present invention can effectively eliminate background interference, significantly improve the recognition accuracy of mineral characteristic peaks, overcome the misjudgment problem caused by peak position overlap in traditional spectral analysis, highlight the characteristic peak differences between hematite and goethite, thereby enhancing the analytical ability of the secondary mineral combination characteristics of natural red jadeite, avoiding the identification blind area caused by insufficient resolution of the existing single spectral technology, and making the identification of natural red jadeite and heat-treated red jadeite more intuitive and accurate. Description of the Drawings

[0019] Figure 1 Flow chart of the identification method for heat-treated red jadeite

[0020] Figure 2 Infrared reflection spectrogram of the fingerprint region of a jadeite sample

[0021] Figure 3 Infrared transmission spectrograms of the red jadeites No. 1, No. 2 and No. 4 to be tested

[0022] Figure 4 First derivative spectrograms of ultraviolet-visible reflection of the red jadeites No. 1, No. 2 and No. 4 to be tested

[0023] Figure 5 Infrared transmission spectrograms of the red jadeites No. 3, No. 5 and No. 6 to be tested

[0024] Figure 6 First derivative spectrograms of ultraviolet-visible reflection of the red jadeites No. 3, No. 5 and No. 6 to be tested Specific implementation mode

[0025] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited to the following embodiments. In the technical solution provided by the present invention, a method for identifying heat-treated red jadeite has a process as Figure 1 shown, including the following steps:

[0026] (1) Infrared spectral reflection method analysis: Use an infrared spectrometer to test the infrared absorption spectrum of the sample to be tested, and the test range is 1500 - 400 cm -1 , and judge by detecting the characteristic group peaks of jadeite at 433 cm-1, 472 cm-1, 532 cm-1, 588 cm-1, 665 cm-1, 744 cm-1, 852 cm-1, 954 cm-1, 1049 cm-1, 1085 cm-1 and 1172 cm -1 ; if the characteristic group peaks are not detected, it is determined that the sample to be tested is not jadeite, and the identification ends; if the characteristic group peaks are detected, it is determined that the sample to be tested is jadeite, and enter step (2);

[0027] Among them, the infrared spectrum is tested by the reflection method, and the infrared spectrometer is of the Bruker Vertex 80 and Hyperion 3000 type, with a resolution of 4 cm-1, a scanning number of 64 times, and a scanning frequency of 10 khz.

[0028] (2) Infrared spectral transmission method analysis and first derivative analysis of ultraviolet-visible reflection spectrum: For the sample to be tested determined to be jadeite in step (1), use an infrared spectrometer to test the infrared absorption spectrum of the sample to be tested, and the test range is 4000 - 2500 cm -1 , and pass through 3450 cm -1The broad absorption characteristic peaks of crystal water and adsorbed water at [specific position], 3695 cm -1 The characteristic peak of hydroxyl structural water of impurity clay minerals at [specific position] and 3037 cm -1 and 3057 cm -1 The characteristic peaks of aromatic hydrocarbons at [specific position] are used to identify natural red jadeite and heat-treated red jadeite; then, a UV-Vis reflection spectrometer is used to test the UV-Vis reflection spectrum of the sample to be tested, with the test range of 300 - 800 nm. The spectral data is subjected to first-order derivative processing, and natural red jadeite and heat-treated red jadeite are identified by the secondary peak of goethite near 438 nm and the hematite peak near 560 - 580 nm; among them, the broad absorption characteristic peaks of crystal water and adsorbed water at 3450 cm -1 The broad absorption characteristic peaks of crystal water and adsorbed water at [specific position], 3695 cm -1 The characteristic peak of hydroxyl structural water of impurity clay minerals at [specific position] is group peak 1, the characteristic peaks of aromatic hydrocarbons at 3037 cm -1 and 3057 cm -1 The characteristic peaks of aromatic hydrocarbons at [specific position] are group peak 2, the secondary peak of goethite near 438 nm is single peak 3, and the hematite peak near 560 - 580 nm is single peak 4;

[0029] Among them, the infrared spectrum is tested by the transmission method, with a resolution of 4 cm-1, 64 scanning times, a scanning frequency of 10 kHz, and the collected spectra are all normalized for display; the test position is selected in the area of the sample to be tested with uniform red color and relatively thin thickness; the test conditions of the UV-Vis reflection spectrum are an integration time of 100 ms, 8 integration times, and the spectral data is smoothed with 25 window points and then subjected to first-order derivative processing; the spectral data after first-order derivative processing is further smoothed with 25 window points. In this embodiment, smoothing and derivative processing are performed using Origin plotting software.

[0030] (3) Comprehensive peak position information to identify natural red jadeite and heat-treated red jadeite: Based on the peak position information in step (2), a comprehensive judgment is made on the sample to be tested. When group peak 1, single peak 3, and single peak 4 appear and group peak 2 does not appear, it indicates that the sample to be tested still contains the hydroxyl water peak of impurity clay minerals and is colored by goethite and hematite. It is determined that the sample to be tested has not been heat-treated and is natural red jadeite; when single peak 4 appears and group peak 1, group peak 2, and single peak 3 do not appear, it indicates that the hydroxyl water peak of impurity clay minerals inside the red jadeite has been removed and is only colored by hematite, and it has not been pickled and filled with glue. It is determined that the sample to be tested has been heat-treated and is heat-treated red jadeite.

[0031] In this embodiment, in order to verify the identification efficiency and accuracy of the method for identifying heat-treated red jadeite of the present invention, the researchers of the present invention selected heat-treated red jadeite and natural red jadeite for research. The specific test process is as follows:

[0032] The detection and analysis personnel identified each red jadeite one by one in an unknown state to obtain the final conclusion. After verification by the verification personnel, the correct rate of the present invention for identifying heat-treated red jadeite was obtained. In this embodiment, 6 red jadeite samples to be tested of 2 different types of red jadeite were involved. The detection and analysis personnel only knew the types of red jadeite, and the verification personnel knew the corresponding types of the 6 red jadeite samples to be tested one by one. The details are shown in Table 1.

[0033] Table 1 Red jadeite of known types and quantities

[0034] Type Heat-treated red jadeite Natural red jadeite Quantity / PCS 3 3

[0035] The red jadeite samples to be tested were respectively operated according to a method for identifying heat-treated red jadeite provided by the present invention. The infrared reflection spectra of each red jadeite were obtained through step (1). The fingerprint region infrared reflection spectral peak diagrams of the 6 red jadeite samples to be tested all showed the characteristic group peaks of jadeite. The infrared reflection spectral peak diagram of one of the red jadeite samples to be tested is as shown in Figure 2 ; Then, the 6 red jadeite samples to be tested were further identified by infrared spectral transmission analysis and first-order derivative analysis of ultraviolet-visible reflection spectrum through step (2) to obtain relevant data, and then the types of the red jadeite samples to be tested were determined according to the data; The specific identification results of the detection and analysis personnel are as follows:

[0036] The infrared transmission spectra of the 1st, 2nd, and 4th red jadeite samples to be tested are as shown in Figure 3 ; The jadeite structure water peaks at 3554 cm -1 and 3622 cm -1 appear, the broad absorption characteristic peaks of crystal water and adsorbed water near 3450 cm -1 and the hydroxyl structure water characteristic peak (group peak 1) of impurity clay minerals at 3695 cm -1 appear, and the aromatic hydrocarbon characteristic peaks (group peak 2) in the organic glue at 3037 cm -1 and 3057 cm -1 do not appear; The ultraviolet-visible reflection first-order derivative spectra of the 1st, 2nd, and 4th red jadeite samples to be tested are as shown in Figure 4 ; The goethite peak (single peak 3) near 438 nm and the hematite peak (single peak 4) near 560 - 580 nm appear, and it is determined that the 1st, 2nd, and 4th red jadeite samples to be tested are natural red jadeite;

[0037] The infrared transmission spectra of the 3rd, 5th, and 6th red jadeite samples to be tested are as shown in Figure 5 ; The jadeite structure water peaks at 3550 cm -1 and 3622 cm -1 appear, but the broad absorption characteristic peaks of crystal water and adsorbed water near 3450 cm -1 and the hydroxyl structure water characteristic peak of impurity clay minerals at 3695 cm -1The hydroxyl structural water characteristic peak (group peak 1) of the impurity clay mineral was not observed at 3037 cm -1 , nor was the aromatic hydrocarbon characteristic peak (group peak 2) in the organic glue at 3057 cm -1 . The ultraviolet-visible reflection first derivative spectra of the red jadeite samples to be tested, namely samples 3, 5, and 6, are as shown in Figure 6 . There is a goethite peak (single peak 3) near 438 nm and a hematite peak (single peak 4) near 560 - 580 nm, indicating that the red jadeite samples 3, 5, and 6 to be tested are heat-treated red jadeite;

[0038] The specific identification results of the testing personnel for the red jadeite samples to be tested and the actual verification results of the verification personnel are shown in Table 2.

[0039] Table 2 Identification results and actual results of the red jadeite samples to be tested

[0040] Serial number of red jadeite to be tested Identified type Actual type 1 Natural red jadeite Natural red jadeite 2 Natural red jadeite Natural red jadeite 3 Heat-treated red jadeite Heat-treated red jadeite 4 Natural red jadeite Natural red jadeite 5 Heat-treated red jadeite Heat-treated red jadeite 6 Heat-treated red jadeite Heat-treated red jadeite

[0041] According to the identification results in Table 2, the correct rate of identification in this embodiment is 100%, indicating that the method for identifying heat-treated red jadeite of the present invention can improve the identification efficiency and accuracy of heat-treated red jadeite, reduce the disruption of the market by heat-treated red jadeite, maintain market order, and protect the rights and interests of consumers.

Claims

1. A method for identifying heat-treated red jadeite, characterized in that: The following steps are involved: (1) Infrared spectral reflection analysis: Use an infrared spectrometer to test the infrared absorption spectrum of the sample to be tested, with a test range of 1500 to 400 cm -1 , by detecting 433cm-1, 472cm-1, 532cm-1, 588cm-1, 665cm-1, 744cm-1, 852cm-1, 954cm-1, 1049cm-1, 1085cm-1 and 1172cm -1 If the characteristic peaks are not detected, the sample to be tested is determined not to be jadeite, and the identification ends; if the characteristic peaks are detected, the sample to be tested is determined to be jadeite, and the process goes to step (2); (2) Infrared spectral transmission analysis and first-order derivative analysis of UV-visible reflectance spectra: For the sample determined to be jadeite in step (1), an infrared spectrometer is used to test the infrared absorption spectrum of the sample in the test range of 4000 to 2500 cm -1 , through 3450cm -1 The broad absorption peaks of crystal water and adsorbed water at 3695 cm -1 The characteristic peaks of hydroxyl structure water of impurity clay minerals and 3037cm -1 and 3057cm -1 The characteristic peaks of aromatic hydrocarbons at 3450cm are used to identify natural red jadeite and heat-treated red jadeite. Then, the UV-visible reflectance spectra of the samples to be tested are tested using a UV-visible reflectance spectrometer in the test range of 300-800nm. The spectral data are processed by first-order derivatives, and the natural red jadeite and heat-treated red jadeite are identified by the secondary peaks of goethite near 438nm and the hematite peaks near 560-580nm. Among them, the peak at 3450cm -1 The broad absorption peaks of crystal water and adsorbed water at 3695 cm -1 The characteristic peak of hydroxyl structural water in impurity clay minerals is group peak 1, 3037 cm -1 and 3057cm -1 The characteristic peak of aromatic hydrocarbons at is group peak 2, the secondary peak of goethite near 438nm is single peak 3, and the peak of hematite near 560-580nm is single peak 4; (3) Comprehensive peak position information to identify natural red jadeite and heat-treated red jadeite: Make a comprehensive judgment on the sample to be tested based on the peak position information in step (2). When group peak 1, single peak 3, and single peak 4 appear, and group peak 2 does not appear, it indicates that the sample to be tested has not been heat-treated, and the sample to be tested is determined to be natural red jadeite. When single peak 4 appears, and group peak 1, group peak 2, and single peak 3 do not appear, it indicates that the sample to be tested has been heat-treated, and the sample to be tested is determined to be heat-treated red jadeite.

2. The method for identifying heat-treated red jadeite according to claim 1, characterized in that: In step (1), the infrared spectrum is tested by reflection method with a resolution of 4 cm-1, 64 scans and a scanning frequency of 10 kHz.

3. The method for identifying heat-treated red jadeite according to claim 1, characterized in that: In step (2), the infrared spectrum is tested by transmission method with a resolution of 4 cm-1, 64 scans and a scanning frequency of 10 kHz.

4. The method for identifying heat-treated red jadeite according to claim 1, characterized in that: The test conditions of the UV-visible reflectance spectrum in step (2) are as follows: an integration time of 100 ms, an integration number of 8 times, and the spectral data is smoothed with 25 window points and then first-order derivative processed.

5. The method for identifying heat-treated red jadeite according to claim 1, characterized in that: In step (2), the infrared transmission spectrum test location is selected from the area of ​​the red jadeite sample where the red color is uniform and the thickness is relatively thin.

6. The method for identifying heat-treated red jadeite according to claim 1, characterized in that: The spectral data after the first-order derivative processing in step (2) is further smoothed by 25 window points.

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