Method for identifying heat-treated red jadeite

Abstract

The present application relates to a kind of methods for identifying heat-treated red jadeite, by using infrared spectrum reflection method analysis, determine whether the sample to be measured is jadeite, then by infrared spectrum transmission method and ultraviolet-visible reflection spectrum first derivative analysis determine heat-treated red jadeite and natural red jadeite;Comprehensively use infrared spectrum analysis and ultraviolet-visible reflection spectrum first derivative analysis technology, realize the efficient, accurate identification of heat-treated red jadeite.The present application can improve the efficiency and accuracy of heat-treated red jadeite identification, and the present application can reduce the disturbance phenomenon of heat-treated red jadeite to market.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for identifying heat-treated red jadeite, and belongs to the technical field of gem identification. BACKGROUND

[0002] Red jadeite is a relatively rare variety of jadeite (hereinafter referred to as red jade) with bright colors, and its economic value is relatively high. The cause of the natural red jade is secondary, which is due to the filling and impregnation of natural goethite and hematite secondary minerals in the fissures and cleavage planes of primary jadeite, forming a red-yellow hue. In addition to natural red jade, there are also optimized red jade, which refers to improving the color of jadeite that is not red or not bright enough to red, or improving its appearance and quality, so as to be sold as natural high-quality red jade. Among them, heat-treated red jade, also known as red jade, is one of these optimization methods, which refers to improving the color of jadeite with relatively gray-brown and not bright enough to red through heating. The value of heat-treated red jade is greatly different from that of natural red jade, but because the phase composition of the color-causing mineral is similar, the color distribution characteristics and appearance characteristics are similar, so it is difficult to identify.

[0003] At present, the identification of red jade mainly relies on the experience of naked eye observation, and the subjective judgment is made through the color distribution and crack characteristics. However, the above method has the following limitations: the influence of human subjective factors is large, and there is lack of objective scientific basis; it is difficult to effectively distinguish heat-treated red jade from natural red jade; these problems lead to the fact that heat-treated red jade is often sold as natural red jade in the market, which seriously disrupts the market order and damages the rights and interests of consumers.

[0004] In the prior art, although some individual studies attempt to use spectral analysis technology to identify jadeite, most of them are limited to single detection means (such as infrared spectrum or ultraviolet spectrum), and no systematic solution is proposed for the secondary mineral characteristics (such as the combination of goethite and hematite) of red jade. For example, infrared spectrum can detect whether it is jadeite, but it cannot distinguish heat-treated red jade from natural red jade; and if ultraviolet-visible spectrum is not combined with derivative analysis, it is difficult to accurately identify the overlapping characteristics of mineral absorption peaks. SUMMARY

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

[0006] To achieve the above purpose, the technical scheme provided by the present application is as follows: a method for identifying heat-treated red jadeite, comprising the following steps:

[0007] (1) Infrared spectrum reflection method analysis: using infrared spectrometer to test the infrared absorption spectrum of the sample to be tested, the test range is 1500-400cm -1 , by detecting the characteristic group peaks of emerald at 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 group peaks are not detected, it is determined that the sample to be tested is not emerald, and the identification is ended; if the characteristic group peaks are detected, it is determined that the sample to be tested is emerald, and step (2) is entered;

[0008] (2) Infrared spectrum transmission method analysis and ultraviolet-visible reflection spectrum first derivative analysis: using infrared spectrometer to test the infrared absorption spectrum of the sample to be tested determined to be emerald in step (1), the test range is 4000-2500cm -1 , by the wide absorption characteristic peak of crystal water and adsorbed water at 3450cm -1 , the hydroxyl structure water characteristic peak of impurity clay mineral at 3695cm -1 , and the aromatic hydrocarbon characteristic peak at 3037cm -1 and 3057cm -1 , to identify natural red emerald and heat-treated red emerald; then, using ultraviolet-visible reflection spectrometer to test the ultraviolet-visible reflection spectrum of the sample to be tested, the test range is 300-800nm, the spectrum data is processed by first derivative, by the goethite secondary peak near 438nm and the hematite peak near 560-580nm to identify natural red emerald and heat-treated red emerald; wherein, the wide absorption characteristic peak of crystal water and adsorbed water at 3450cm -1 , the hydroxyl structure water characteristic peak of impurity clay mineral at 3695cm -1 , the aromatic hydrocarbon characteristic peak at 3037cm -1 and 3057cm -1 , the goethite secondary peak near 438nm is single peak 3, and the hematite peak near 560-580nm is single peak 4;

[0009] (3) Comprehensive peak information to identify natural red emerald and heat-treated red emerald: according to the peak information in step (2), the sample to be tested is comprehensively judged, 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 emerald; 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 emerald.

[0010] The further improvement of the above technical solution is:

[0011] The infrared spectrum in step (1) is tested by reflection method, the resolution is 4 cm-1, the scanning number is 64 times, and the scanning frequency is 10 khz.

[0012] The infrared spectrum in step (2) is tested by transmission method, the resolution is 4 cm-1, the scanning number is 64 times, and the scanning frequency is 10 khz.

[0013] The test conditions of the ultraviolet-visible reflection spectrum in step (2) are that the integration time is 100 ms, the integration number is 8 times, and the spectrum data is smoothed by 25 window points and then is processed by first derivative.

[0014] The infrared transmission spectrum test position in step (2) is selected in the region where the red of the Hongfei sample is uniform and the thickness is thin.

[0015] The spectrum data processed by first derivative in step (2) is further smoothed by 25 window points.

[0016] According to the above technical solution, the method for identifying heat-treated red jade provided by the application determines whether the sample to be tested is jade by using infrared spectrum reflection method analysis, and then determines the heat-treated red jade and the natural red jade by using infrared spectrum transmission method and ultraviolet-visible reflection spectrum first derivative analysis; the infrared spectrum analysis and ultraviolet-visible reflection spectrum first derivative analysis technology are comprehensively used, and the efficient and accurate identification of the heat-treated red jade is realized. Compared with the prior art, the application has the following advantages:

[0017] (1) Because the technical solution adopted by the application combines infrared spectrum characteristic peak detection and ultraviolet-visible reflection spectrum first derivative processing, an objective discrimination standard based on spectrum characteristics is established, so the application can efficiently distinguish the heat-treated red jade from the natural red jade, improves the scientificity and reliability of identification, avoids the subjectivity and uncertainty caused by relying on naked eye identification, greatly improves the identification efficiency and accuracy, and reduces the transaction disputes caused by misjudgment in the market.

[0018] (2) Because the technical solution adopted by the application introduces spectrum data smoothing and first derivative processing, the application can effectively eliminate background interference, significantly improve the recognition accuracy of mineral characteristic peaks, overcome the misjudgment problem caused by peak overlap in traditional spectrum analysis, highlight the characteristic peak difference between hematite and goethite, thereby enhancing the analysis ability of the secondary mineral combination characteristics of natural red jade, avoiding the identification blind area caused by insufficient resolution of the existing single spectrum technology, and making the identification of natural red jade and heat-treated red jade more intuitive and accurate. BRIEF DESCRIPTION OF DRAWINGS

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

[0020] Figure 2 Fingerprint area infrared reflectance spectrum of a jadeite sample;

[0021] Figure 3 Infrared transmission spectrum of red jadeite No. 1, No. 2 and No. 4 to be tested;

[0022] Figure 4 UV-visible reflectance first derivative spectrum of red jadeite No. 1, No. 2 and No. 4 to be tested;

[0023] Figure 5 Infrared transmission spectrum of red jadeite No. 3, No. 5 and No. 6 to be tested;

[0024] Figure 6 UV-visible reflectance first derivative spectrum of red jadeite No. 3, No. 5 and No. 6 to be tested. DETAILED DESCRIPTION

[0025] The present application will be described in detail below in combination with the drawings and specific examples, but the scope of protection of the present application is not limited to the following examples. In the technical solution provided by the present application, a method for identifying heat-treated red jadeite is shown in the flow chart Figure 1 , which comprises the following steps:

[0026] (1) Infrared spectrum reflectance method analysis: using an infrared spectrometer to test the infrared absorption spectrum of the sample to be tested, the test range being 1500-400 cm -1 , and determining by detecting the jadeite characteristic group peaks 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 is ended; if the characteristic group peaks are detected, it is determined that the sample to be tested is jadeite, and step (2) is entered.

[0027] In the method, the infrared spectrum test is performed by the reflection method, the infrared spectrometer is Bruker Vertex 80 and Hyperion 3000 type, the resolution is 4 cm-1, the scanning number is 64 times, and the scanning frequency is 10 kHz.

[0028] (2) Infrared spectrum transmission method analysis and UV-visible reflectance spectrum first derivative analysis: using an infrared spectrometer to test the infrared absorption spectrum of the sample to be tested, the test range being 4000-2500 cm -1 , and determining by detecting the jadeite characteristic group peaks at 3450 cm -1The broad absorption characteristic peaks of crystal water and adsorbed water at 3695 cm⁻¹ -1 The characteristic peaks of hydroxyl structural water in impurity clay minerals and at 3037 cm⁻¹ -1 and 3057cm -1 The characteristic peaks of aromatic hydrocarbons at 3450 nm were used to distinguish between natural red jadeite and heat-treated red jadeite. Then, the UV-Vis reflectance spectra of the samples were measured using a UV-Vis spectrometer, with a measurement range of 300–800 nm. The spectral data were processed using the first derivative, and the secondary goethite peak near 438 nm and the hematite peak near 560–580 nm were used to distinguish between natural red jadeite and heat-treated red jadeite. -1 The broad absorption characteristic peaks of crystal water and adsorbed water at 3695 cm⁻¹ -1 The characteristic peak of hydroxyl structural water in the impurity clay minerals is a group peak at 1,3037 cm⁻¹. -1 and 3057cm -1 The characteristic peaks of aromatic hydrocarbons at 2 are grouped peaks; the secondary peak of goethite near 438 nm is a single peak; the peak of hematite near 560-580 nm is a single peak;

[0029] The infrared spectroscopy test employed the transmission method with a resolution of 4 cm⁻¹, 64 scans, and a scan frequency of 10 kHz. All acquired spectra were normalized before display. The test location was selected from a region of uniform red color and relatively thin thickness within the sample. The ultraviolet-visible reflectance spectroscopy test conditions included an integration time of 100 ms and 8 integrations. The spectral data underwent first-order derivative processing after smoothing with 25 window points. The spectral data after first-order derivative processing was further smoothed with 25 window points. In this embodiment, smoothing and derivative processing were performed using Origin plotting software.

[0030] (3) Identify natural red jadeite and heat-treated red jadeite by combining peak position information: Based on the peak position information in step (2), make a comprehensive judgment 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 means that the sample to be tested still contains the hydroxyl water peak of impurity clay minerals, which 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 means that the hydroxyl water peak of impurity clay minerals inside the red jadeite has been removed, and it is only colored by hematite. It has not been acid-washed and filled with resin. It is determined that the sample to be tested has been heat-treated and is heat-treated red jadeite.

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

[0032] The detection analysts identify each red jade one by one in an unknown state to obtain a final conclusion, and the verification personnel verify to obtain the accuracy of the invention in identifying heat-treated red jade. In this embodiment, 6 red jade samples to be detected of 2 different types of red jade are involved, the detection analysts only know the types of the red jade, and the verification personnel know the types of the 6 red jade samples to be detected one by one, for details, see Table 1.

[0033] Table 1 Red jade and quantity of known type

[0034] Category Heat-treated red jadeite Natural red jadeite Number of pieces 3 3

[0035] The method for identifying heat-treated red jade provided by the invention is used to operate on the red jade to be detected respectively, the infrared reflection spectrum of each red jade is obtained through step (1), the fingerprint region infrared reflection spectrum peak position diagram of the 6 red jade samples to be detected appears the characteristic group peak of jade, the infrared reflection spectrum peak position diagram of one of the red jade to be detected is shown in Figure 2 ; then further identification of the 6 red jade to be detected is performed through step (2) infrared spectrum transmission method analysis and ultraviolet-visible reflection spectrum first derivative analysis, relevant data is obtained, and then the type of the red jade to be detected is determined according to the data; the specific identification results of the detection analysts are as follows:

[0036] The infrared transmission spectrum of the red jade to be detected No. 1, No. 2 and No. 4 is shown in Figure 3 , the hard jadeite structure water peaks of 3554 cm -1 and 3622 cm -1 appear, the wide absorption characteristic peak of crystal water and adsorbed water near 3450 cm -1 and the hydroxyl structure water characteristic peak (group peak 1) of impurity clay mineral of 3695 cm -1 appear, and the aromatic hydrocarbon characteristic peak (group peak 2) of organic glue of 3037 cm -1 and 3057 cm -1 does not appear; the ultraviolet-visible reflection first derivative spectrum of the red jade to be detected No. 1, No. 2 and No. 4 is 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 red jade to be detected No. 1, No. 2 and No. 4 is natural red jade;

[0037] The infrared transmission spectrum of the red jade to be detected No. 3, No. 5 and No. 6 is shown in Figure 5 , the hard jadeite structure water peaks of 3550 cm -1 and 3622 cm -1 appear, but the wide absorption characteristic peak of crystal water and adsorbed water near 3450 cm -1 and the hydroxyl structure water characteristic peak (group peak 1) of impurity clay mineral of 3695 cm -1the hydroxyl structure water characteristic peak (group peak 1) of the impurity clay mineral of the sample, and the 3037cm -1 , 3057cm -1 aromatic hydrocarbon characteristic peak (group peak 2) in the organic glue does not appear; the ultraviolet-visible reflection first derivative spectrum of the red No. 3, No. 5 and No. 6 to be detected is shown in Figure 1, and a goethite peak (single peak 3) appears near 438nm, and a hematite peak (single peak 4) appears near 560-580nm, so the red No. 3, No. 5 and No. 6 to be detected are determined to be heat-treated red jadeite; Figure 6

[0038] The specific identification results of the detection and analysis personnel of the red jadeite to be detected and the actual results verified by the verification personnel are shown in Table 2.

[0039] Table 2: Identification results and actual results of the red jadeite to be detected

[0040] Red jadeite serial number to be tested Category identified Actual category 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 the identification in the embodiment is 100%, which indicates that the method for identifying the heat-treated red jadeite can improve the identification efficiency and accuracy of the heat-treated red jadeite, reduce the disturbance of the heat-treated red jadeite to the market, maintain the market order, and protect the rights and interests of consumers.​

Claims

1. A method for identifying heat-treated red jadeite, characterized in that, Includes the following steps: (1) Infrared reflectance analysis: The infrared absorption spectrum of the sample is measured using an infrared spectrometer, with a test range of 1500–400 cm⁻¹. -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 The characteristic peaks of jadeite are used to determine the sample; if the characteristic peaks are not detected, the sample is determined not to be jadeite and the identification ends; if the characteristic peaks are detected, the sample is determined to be jadeite and proceed to step (2). (2) Infrared transmission spectroscopy analysis and first derivative analysis of ultraviolet-visible reflectance spectroscopy: For the sample identified as jade in step (1), the infrared absorption spectrum of the sample was measured using an infrared spectrometer, with a test range of 4000–2500 cm⁻¹. -1 , through 3450cm -1 The broad absorption characteristic peaks of crystal water and adsorbed water at 3695 cm⁻¹ -1 The characteristic peaks of hydroxyl structural water in impurity clay minerals and at 3037 cm⁻¹ -1 and 3057cm -1 The characteristic peaks of aromatic hydrocarbons at 3450 nm were used to distinguish between natural red jadeite and heat-treated red jadeite. Then, the UV-Vis reflectance spectra of the samples were measured using a UV-Vis spectrometer, with a measurement range of 300–800 nm. The spectral data were processed using the first derivative, and the secondary goethite peak near 438 nm and the hematite peak near 560–580 nm were used to distinguish between natural red jadeite and heat-treated red jadeite. -1 The broad absorption characteristic peaks of crystal water and adsorbed water at 3695 cm⁻¹ -1 The characteristic peak of hydroxyl structural water in the impurity clay minerals is a group peak at 1,3037 cm⁻¹. -1 and 3057cm -1 The characteristic peaks of aromatic hydrocarbons at 2 are grouped peaks; the secondary peak of goethite near 438 nm is a single peak; the peak of hematite near 560-580 nm is a single peak; (3) Identify natural red jadeite and heat-treated red jadeite by combining peak position information: Based on the peak position information in step (2), make a comprehensive judgment 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 means 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 means 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 was tested using the reflectance method with a resolution of 4 cm⁻¹, 64 scans, and a scan 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 was tested using the 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: In step (2), the test conditions for the ultraviolet-visible reflectance spectrum are an integration time of 100ms, 8 integration times, and the spectral data are smoothed by 25 window points and then processed by the first derivative.

5. The method for identifying heat-treated red jadeite according to claim 1, characterized in that: In step (2), the infrared transmission spectroscopy test location is selected in a region of 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 processed by the first derivative in step (2) is further smoothed by 25 window points.

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