Method for identifying emerald green producing area based on 2600-2850 cm <-1 > waveband infrared spectrum

Abstract

According to the method for identifying the emerald producing area based on the 2600-2850 cm <-1 > wave band infrared spectrum, a BRUKER TENSOR II Fourier transform infrared spectrometer is used, a condensation transmission accessory PIKE 6 * Beam Condenser is arranged, absorption peaks related to HDO and D2O molecules in an emerald channel within the range of 2600-2850 cm <-1 > can be sensitively detected, and wave band absorption is often slightly neglected in previous research; similar common important emerald green producing areas, such as Columbia, Sapabia and Afwei, can be quickly distinguished in a lossless and simple manner; the infrared spectrum test has no special requirement on the state of the sample, is a nondestructive test, is suitable for samples (raw stones, gem facets, gem plain surfaces, jades, inlaid jewelry and the like) in various states, and is high in detection speed and visual and accurate in detection result.

Description

Technical Field

[0001] The present invention relates to the field of gem identification technology, and in particular to a method based on 2600~2850cm –1 Method of identifying the origin of emerald by using infrared spectroscopy. Background Art

[0002] Emerald is one of the four precious colored gemstones. Its origin can bring significant added value to it. The price of Colombian emeralds of similar quality may be several times that of Zambian emeralds. Therefore, the origin identification of emeralds is an important core technology of gem laboratories. Traditional emerald origin identification methods mainly rely on the characteristic inclusions, ultraviolet-visible-near infrared (UV-Vis-NIR) spectra and major and trace components of emeralds (Groat et al., 2019; Zheng Yuyu et al., 2024). Emerald infrared spectroscopy (IR) has always been considered to be of limited help in origin identification. Current research believes that the only water molecules (H2O2) in the structural channels of emeralds have a certain significance for origin identification. 2 The hexagonal rings stacked along the crystallographic c-axis of emerald form a large-radius crystal structure channel, in which water molecules and alkali metal cations exist (Wood and Nassau, 1967; Aurisicchio et al., 1994). Water molecules in the channel usually have two orientations, depending on their distance from the cations. When there are no cations around the water molecules, due to the structural oxygen and hydrogen bonds in the channel, the water molecules are oriented as type I water, with the secondary axis of the molecule perpendicular to the crystal c-axis. When there are cations around, due to the electrostatic interaction between the cations and oxygen atoms, the water molecules change their orientation to type II water, with the symmetry axis parallel to the crystal c-axis. The relative intensity of the infrared absorption peaks of type I water and type II water in the channel can be used to identify the origin of emerald. The difference in alkali metal content in emeralds from different origins leads to the difference in the intensity of the type II water absorption peak. For example, in the infrared spectrum of Zambian emeralds with high Na content, the relative intensity of the infrared absorption peaks of type I water and type II water in the channel can be used to identify the origin of emerald. The difference in alkali metal content in emeralds from different origins leads to the difference in the intensity of the type II water absorption peak. For example, in the infrared spectrum of Zambian emeralds with high Na content, the relative intensity of the infrared absorption peaks of type II water in Zambian emeralds with high Na content is 3500~3900cm –1 The band usually shows extremely strong type II water absorption and weak type I water absorption (Zhang and Yu, 2023). Therefore, the infrared spectrum pattern of channel water has a certain significance for identifying the origin, but the challenges are: 1) Due to the limitations of thickness and other conditions, the samples to be tested are usually between 3500 and 3900 cm –1 The band shows the saturated absorption of water; 2) There are strong individual differences in alkali metal content, and different emerald samples from the same origin may show different channel water absorption patterns. Therefore, the infrared spectrum of emerald is usually not taken seriously in the origin identification process.

[0003] However, the heavy water molecules containing hydrogen isotopes (HDO and D 2 O) in the emerald channel have recently been proven to have a close connection with their origin in the infrared absorption pattern within the range of 2600 - 2850 cm –1 band (de Donato et al., 2004; Mashkovtsev et al., 2016; Qiao et al., 2019; Zheng et al., 2024). Through precise infrared spectroscopy measurements, the infrared absorption related to the –OD vibration in emeralds from different origins has significantly different patterns. Through comparison and classification, these patterns can provide reliable conclusion support for judging the origin of emeralds. Summary of the Invention

[0004] In order to make up for the deficiencies of the prior art, the present invention provides a method for identifying the origin of emeralds based on the infrared spectrum in the 2600 - 2850 cm –1 band. As a precious gemstone, the origin of emeralds has significant added value, and the judgment of its origin is the core technology of gemstone laboratories at home and abroad. In the current origin identification process, due to the limitations mentioned in the above background technology, the use of the non-destructive detection method of infrared spectrum is lacking. Based on the infrared spectrum data of emerald samples from 10 origins tested in this patent, the differences between different origins are compared and analyzed, and the infrared spectrum patterns are classified. This classification system can effectively and non-destructively distinguish emeralds from different origins, and the content of this patent can promote the gemological research of emeralds and guide jewelry identification work.

[0005] 1. The present invention is realized through the following technical solutions: A method for identifying the origin of emeralds based on the infrared spectrum in the 2600 - 2850 cm –1 band, characterized in that it specifically includes the following steps: Step S1: Use an infrared spectrometer to measure the infrared spectrum generated from the emerald sample: Step S1-1: Use a Fourier transform infrared spectrometer equipped with a PIKE 6* condenser transmission accessory BeamCondenser; Step S1-2: Clean the emerald sample, place the cleaned sample on the sample stage of the condenser transmission accessory, and make the infrared light source spot pass through the interior of the gemstone; Step S1-3: During the test, the incident infrared light passes through the concave mirror on the Fourier transform infrared spectrometer to form parallel light and then enters the Michelson interferometer. The interferometer includes a beam splitter, a moving mirror, and a fixed mirror. The pulsating light beam leaving the interferometer is projected onto a swinging mirror, causing the light beam to alternately pass through the corundum sample of the metamorphic rock type, and then through the swinging mirror again, so that the light beam is focused on the detector. The detector digitizes the interference signal through Fourier transform by means of a computer terminal, and finally displays it as an infrared spectrogram; Step S2: Select the range of 2600 - 2850 cm –1 in the infrared spectrum obtained in Step S1 for amplified observation, confirm whether there is an absorption peak, determine the peak position and absorption intensity, and more clearly display the infrared absorption pattern of heavy water molecules through baseline processing and Gaussian fitting; Step S3: Analyze the characteristics of the heavy water infrared absorption pattern obtained in Step S2 and compare it with the spectrogram patterns of different groups in the current classification system to obtain the conclusion of the origin of emeralds; Step S3-1: The absorptions in the range of 2600 - 2830 cm –1 in the emerald infrared spectrum related to HDO and D 2 O molecules are as follows: A weak to medium-intensity absorption peak 1, i.e., AP1, near 2640 cm –1 is attributed to the symmetric stretching vibration v 2 of D 1 O; A sharp and strong absorption peak 2, i.e., AP2, near 2672 cm –1 is attributed to the -OD vibration v OD of type II HDO; A weak to medium-intensity and narrow absorption peak 3, i.e., AP3, near 2685 cm –1 is attributed to the -OD vibration v OD of type I HDO; A broad combined absorption peak 4, i.e., AP4, in the range of 2730 - 2750 cm –1 is attributed to the asymmetric stretching vibration v 2 of D 3 O; A weak to medium-intensity absorption peak 5, i.e., AP5, in the range of 2808 - 2815 cm –1 is attributed to the absorption related to chloride ions or the asymmetric stretching vibration + rotation v 2 of D 3+r O; Step S3-2: According to the presence, peak position, and relative intensity relationship of the above five absorption peaks, the heavy water-related infrared absorption patterns of emeralds from different origins can be divided into three types, including IR-pattern I, IR-pattern II, and IR-pattern III, where IR-pattern III has two subtypes, specifically as follows: 1) IR-pattern I, the intensity of the absorption peak AP2 of type II HDO is higher than that of D 2O-related absorption peaks AP1 and AP4, D 2 Ov 1 The AP1 peak generated by vibration is extremely weak or absent, AP5 2815 cm –1 is usually absent; IR-style I is defined as an HDO-type infrared style and is defined as the Zambia group; 2) IR-style II, which is a transitional style between HDO type and D 2 O type. All five absorption peaks within the range are present. AP2 of type II HDO is dominant, but D 2 Ov 1 The AP1 peak generated by vibration is usually very obvious, and AP5 is significantly present; The peak position fitting results show that the broad 2735 absorption peak AP4 is a combined peak of infrared absorption at 2722 cm –1 and 2745 cm –1 and is attributed to the v 2 vibration of type II and type I D 3 O respectively; This style can be defined as the Afghanistan group, and its AP5 usually appears at 2808 cm –1 , and may also shift to 2812 cm –1 ; 3) IR-style III, where AP4 generated by D 2 Ov 3 vibration is dominant, and it is defined as a D 2 O-type infrared style; At the same time, according to the type of HDO molecules in the channel, style III is divided into two subtypes: The Muzo emerald in Colombia shows style IIIa, with type II HDO mainly in its channel, and the infrared absorption intensity of AP2 at 2672 cm –1 is higher, and AP5 is located at 2815 cm –1 ; The Gwantu emerald in Nigeria shows a unique style IIIb, characterized by AP3 of type I HDO being stronger than AP2 of type II HDO. This phenomenon is different from other styles and is only observed in Gwantu emeralds.

[0006] As a preferred solution, the model of the Fourier transform infrared spectrometer in step S1 is BRUKER TENSOR II.

[0007] As a preferred solution, the parameters of the Fourier transform infrared spectrometer during the test in step S1-3 are as follows: The test mode is the transmission mode, the ordinate is set to Absorbance absorbance, the scanning range is 400~7500 cm –1 , the resolution is 4 cm –1 , and the number of scans is 8~32 times.

[0008] Due to the adoption of the above technical solutions, the present invention has the following beneficial effects compared with the prior art: (1) By using a BRUKER TENSOR II Fourier transform infrared spectrometer equipped with a condenser transmission accessory PIKE 6*BeamCondenser, absorption peaks related to HDO and D –1 O molecules in the emerald channel can be sensitively detected in the range of 2600 - 2850 cm 2 . Absorptions in this band are often weak and overlooked in previous studies; (2) It can quickly distinguish important and common emerald origins that are similar in a non-destructive and simple manner, such as Colombia, Zambia, and Afghanistan; (3) Infrared spectroscopy testing has no special requirements for the state of the sample and is non-destructive. It is applicable to samples in various states (raw stones, gemstone facettes, gemstone plain surfaces, jade, inlaid jewelry, etc.). At the same time, the detection speed is fast, and the detection results are intuitive and accurate.

[0009] The additional aspects and advantages of the present invention will become apparent in the following description section or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, wherein: Figure 1 : Three different heavy water infrared absorption patterns of emeralds from 10 origins, in the range of 2600 - 2830 cm –1 ; Figure 2 : Heavy water-related infrared absorption pattern of Zambian Kafubu emerald - IR - Pattern I. The black line is the spectrum after baseline subtraction, the cyan line is the fitted peak, the red dashed line is the spectrum after fitting, and the thumbnail is the peak shape before baseline processing; Figure 3 : Heavy water-related infrared absorption pattern of Afghan Panjshir emerald - IR - Pattern II. The black line is the spectrum after baseline subtraction, the cyan line is the fitted peak, the red dashed line is the spectrum after fitting, and the thumbnail is the peak shape before baseline processing; Figure 4 : Heavy water-related infrared absorption pattern of Colombian Muzo emerald - IR - Pattern IIIa. The black line is the spectrum after baseline subtraction, the cyan line is the fitted peak, the red dashed line is the spectrum after fitting, and the thumbnail is the peak shape before baseline processing; Figure 5 : Heavy water-related infrared absorption pattern of Nigerian Gwantu emerald - IR - Pattern IIIb. The black line is the spectrum after baseline subtraction, the cyan line is the fitted peak, the red dashed line is the spectrum after fitting, and the thumbnail is the peak shape before baseline processing. Detailed implementation manners

[0011] In order to more clearly understand the above objects, features and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation manners. It should be noted that, without conflict, the embodiments of the present application and the features in the embodiments may be combined with each other.

[0012] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0013] The following is combined with Figures 1 to 5 to specifically describe the method for identifying the origin of emeralds based on the infrared spectrum in the range of 2600 - 2850 cm –1 of the embodiments of the present invention.

[0014] The present invention provides a method for identifying the origin of emeralds based on the infrared spectrum in the range of 2600 - 2850 cm –1 band, which specifically includes the following steps: Step S1: Use an infrared spectrometer to measure the infrared spectrum generated from the emerald sample: The model of the Fourier transform infrared spectrometer is BRUKER TENSOR II.

[0015] Step S1-1: The model of the used infrared spectrometer is the BRUKER TENSOR II Fourier transform infrared spectrometer, which is equipped with a PIKE 6* beam condenser for light collection and transmission attachment; Step S1-2: Clean the emerald sample, place the cleaned sample on the sample stage of the light collection and transmission attachment, and make the infrared light source spot pass through the interior of the gemstone; it should be noted that the infrared spectrum related to heavy water molecules has directionality, and its infrared activity is different for different crystal orientations. Therefore, it is necessary to avoid the long axis of the crystal (i.e., the crystal c-axis) being parallel to the incident infrared light direction, and no infrared absorption peak related to heavy water can be obtained in this direction.

[0016] Step S1-3: During the test, the incident infrared light passes through the concave mirror on the BRUKER TENSOR II Fourier transform infrared spectrometer to form parallel light and then enters the Michelson interferometer. The interferometer includes a beam splitter, a moving mirror, and a fixed mirror. The pulsating light beam leaving the interferometer is projected onto a swinging mirror, causing the light beam to alternately pass through the corundum sample of the metamorphic rock type, and then through the swinging mirror again, causing the light beam to be focused on the detector. The detector digitizes the interference signal through Fourier transform by means of a computer terminal and finally displays it as an infrared spectrogram. The parameters of the Fourier transform infrared spectrometer during the test are as follows: the test mode is the transmission mode, the vertical coordinate is set to Absorbance (absorbance), the scanning range is 400~7500 cm –1 , and the resolution is 4 cm –1 . The number of scans is 8~32 times. When the transparency of the sample is poor, the number of scans should be increased to obtain a more high-quality and smooth spectrogram.

[0017] Step S2: Select the range of 2600~2850 cm in the infrared spectrum obtained in Step S1 –1 and magnify it for observation, confirm whether there is an absorption peak, determine the peak position and absorption intensity, and more clearly display the infrared absorption pattern of heavy water molecules through baseline processing and Gaussian fitting; Step S3: Analyze the characteristics of the heavy water infrared absorption pattern obtained in Step S2 and compare it with the spectrogram patterns of different groups in the current classification system ( Figure 1 ), and obtain the conclusion of the origin of emerald; Step S3-1: The absorptions in the emerald infrared spectrum in the range of 2600~2830 cm –1 related to HDO and D 2 O molecules are as follows: A weak to medium-intensity absorption peak 1, i.e., AP1, near 2640 cm –1 , is attributed to the symmetric stretching vibration v 2 of D 1 O; A sharp and strong absorption peak 2, i.e., AP2, near 2672 cm –1 , is attributed to the –OD vibration v OD of type II HDO; A weak to medium-intensity narrow absorption peak 3, i.e., AP3 (AP3 is usually absent), near 2685 cm –1 , is attributed to the –OD vibration v OD of type I HDO; A broad combined absorption peak 4, i.e., AP4, in the range of 2730~2750 cm –1 , is attributed to the asymmetric stretching vibration v 2 of D 3 O; A weak to medium-intensity absorption peak 5, i.e., AP5, in the range of 2808~2815 cm –1 , is attributed to the absorption related to chloride ions or the asymmetric stretching vibration + rotation v of D 2 O3+r ; Step S3-2: According to the presence, peak positions, and relative intensity relationships of the above five absorption peaks, the heavy water-related infrared absorption patterns of emeralds from different origins can be divided into three types, including IR-pattern I, IR-pattern II, and IR-pattern III. Among them, IR-pattern III has two subtypes, which are specifically as follows: 1) IR-pattern I, as Figure 2 shown, the absorption peak AP2 of type II HDO is much stronger than the absorption peaks AP1 and AP4 related to D 2 O. The AP1 peak generated by D 2 Ov 1 vibration is extremely weak or absent, and AP5 at 2815 cm –1 is usually absent; IR-pattern I is defined as an HDO-type infrared pattern, which is the most common heavy water absorption pattern and mainly appears in emeralds from Zambia, Brazil, Ethiopia, and Russia. Therefore, it is defined as the Zambia group; 2) IR-pattern II, as Figure 3 shown, this pattern is a transitional pattern between HDO-type and D 2 O-type. All five absorption peaks within the range exist. The AP2 of type II HDO dominates, but the AP1 peak generated by D 2 Ov 1 vibration is usually very obvious, and AP5 is significantly present; The peak position fitting results show that the broad 2735 absorption peak AP4 is a combined peak of infrared absorptions at 2722 cm –1 and 2745 cm –1 and is attributed to the v 2 vibrations of type II and type I D 3 O respectively; The emeralds from Panjshir, Afghanistan, have a typical IR-pattern II. Therefore, this pattern can be defined as the Afghanistan group, and its AP5 usually appears at 2808 cm –1 , and may also shift to 2812 cm –1 ; 3) IR-pattern III, as Figure 4 and Figure 5 shown, the AP4 generated by D 2 Ov 3 vibration dominates. Therefore, it can be defined as a D 2 O-type infrared pattern; At the same time, according to the type of HDO molecules in the channel, pattern III is divided into two subtypes: The emeralds from Muzo, Colombia, show the IIIa type pattern ( Figure 4 ), which mainly contains type II HDO in the channel. The infrared absorption intensity of AP2 at 2672 cm –1 is higher, and AP5 is located at 2815 cm –1; The Gwantu emeralds in Nigeria show a unique type IIIb pattern ( Figure 5 ), characterized by significantly stronger AP3 of type I HDO than AP2 of type II HDO. This phenomenon is different from other patterns and has only been observed in Gwantu emeralds so far.

[0018] The above classification can help quickly and non-destructively distinguish between Zambian, Afghan, Colombian, and Nigerian emeralds, and can also help identify Ethiopian, Russian, Pakistani, and Brazilian emeralds.

[0019] The infrared spectral patterns of HDO and D 2 O reflect the content of alkali metals in the channels; Figure 5 It shows that for Nigerian emeralds with extremely low alkali metal (mainly Na) content, the absorption of type I HDO and D 2 O in the channels is more obvious, manifested as higher AP3 intensity and a shift of AP4 to higher wavenumbers. For Colombian and Russian emeralds with relatively low alkali metal content, AP3 can occasionally be observed. However, for emeralds in places like Zambia with relatively high alkali metal content, AP3 is usually absent.

[0020] The infrared spectral patterns of HDO and D 2 O are also closely related to the deuterium content in the emerald channels. Pattern I indicates that the deuterium content in Zambian (Kafubu), Brazilian, Ethiopian, and Russian emeralds is relatively low, and the heavy water molecules in the channels tend to exist in the form of HDO molecules. While the Nigerian emeralds with pattern III indicate relatively rich deuterium in the channels, and the heavy water molecules are mainly in the form of D 2 O. In the infrared spectrum of pattern II, AP1–AP5 can all be clearly observed, indicating a medium deuterium content, and both type I and type II HDO and D 2 O molecules exist in the channels.

[0021] Example 1: Zambian emerald (1) Use an infrared spectrometer to measure the infrared spectrum generated from the emerald sample; (2) Select the 2600~2850 cm –1 band in the infrared spectrum for enlarged observation, confirm the existence of absorption peaks, and more clearly display the absorption lines through baseline processing and Gaussian fitting ( Figure 2 ). Determine the positions and intensities of the absorption peaks: weak AP1 is at 2638 cm –1 , strong AP2 is at 2671 cm –1 , and wide AP4 is at 2740 cm –1 .

[0022] (3)Analyze the heavy water infrared absorption pattern features obtained in the above steps and compare with the spectral patterns of different groups in the current classification system ( Figure 1 ): Observe and determine the absence of AP3 and AP5 in the sample spectrum; Observe the peak shape and determine that AP2 is much stronger than AP1 and AP4, indicating that HDO >> D 2 O, belonging to HDO type IR - pattern I, and it is judged that the origin of the emerald may be Zambia.

[0023] Example 2: Afghan emerald (1)Use an infrared spectrometer to measure the infrared spectrum generated from the emerald sample; (2)Select the 2600 - 2850 cm –1 band in the infrared spectrum for enlarged observation, confirm the presence of absorption peaks, and more clearly display the absorption lines through baseline processing and Gaussian fitting ( Figure 3 ). Determine the positions and intensities of the absorption peaks: Medium - intensity AP1 is located at 2640 cm –1 , strong AP2 is located at 2672 cm –1 , weak AP3 is located at 2684 cm –1 , wide AP4 is located at 2740 cm –1 , medium - intensity AP5 is located at 2808 cm –1 .

[0024] (3)Analyze the heavy water infrared absorption pattern features obtained in the above steps and compare with the spectral patterns of different groups in the current classification system ( Figure 1 ): Observe the peak shape and determine that AP2 is slightly stronger than AP1 and AP4, indicating that HDO ≥ D 2 O, belonging to the HDO - D 2 O transitional IR - pattern II, with AP5 present and located at 2808 cm –1 , and it is judged that the origin of the emerald is Afghanistan.

[0025] Example 3: Colombian emerald (1)Use an infrared spectrometer to measure the infrared spectrum generated from the emerald sample; (2)Select the 2600 - 2850 cm –1 band in the infrared spectrum for enlarged observation, confirm the presence of absorption peaks, and more clearly display the absorption lines through baseline processing and Gaussian fitting ( Figure 4 ). Determine the positions and intensities of the absorption peaks: Strong AP1 is located at 2640cm –1 , medium - intensity AP2 is located at 2672 cm –1 , weak AP3 is located at 2685 cm –1 , strong AP4 wide peak is located at 2740 cm –1 , strong AP5 is located at 2814 cm–1 。

[0026] (3) Analyze the characteristics of the heavy water infrared absorption pattern obtained in the above steps and compare with the spectral patterns of different groups in the current classification system ( Figure 1 ): Observe the peak shape to determine that AP1 and AP4 are stronger than AP2, indicating that D 2 O >> HDO, belonging to the D 2 O type IR-pattern III; AP2 is stronger than AP3, indicating it is IR-pattern IIIa, there is an AP5 and it is located at 2814 cm –1 . It is determined that the origin of the emerald is Colombia.

[0027] Example 4: Emerald from Nigeria (1) Use an infrared spectrometer to measure the infrared spectrum of the emerald sample; (2) Select the 2600 - 2850 cm –1 band in the infrared spectrum for enlarged observation, confirm the existence of absorption peaks, and more clearly display the absorption spectral lines through baseline processing and Gaussian fitting ( Figure 5 ). Determine the positions and intensities of the absorption peaks: Weak AP1 is located at 2641 cm –1 , weak AP2 is located at 2673 cm –1 , medium-intensity AP3 is located at 2686 cm –1 , strong AP4 wide peak is located at 2741 cm –1 , strong AP5 is located at 2815 cm –1 .

[0028] (3) Analyze the characteristics of the heavy water infrared absorption pattern obtained in the above steps and compare with the spectral patterns of different groups in the current classification system ( Figure 1 ): Observe the peak shape to determine that AP4 is much stronger than AP2, indicating that D 2 O >> HDO, belonging to the D 2 O type IR-pattern III; AP3 is stronger than AP2, indicating it is IR-pattern IIIb, there is an AP5 and it is located at 2815 cm –1 . It is determined that the origin of the emerald is Nigeria.

[0029] In the description of the present invention, the term "a plurality of" means two or more, unless otherwise clearly defined. The orientation or positional relationship indicated by terms such as "upper", "lower", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention; terms such as "connection", "installation", "fixation", etc. should all be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] In the description of this specification, the descriptions of terms such as "one embodiment", "some embodiments", "specific embodiments", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or instance. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0031] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method based on 2600~2850cm –1 The method for identifying the origin of emerald by using infrared spectrum of wavelength band is characterized by , specifically including the following steps: Step S1, using an infrared spectrometer to measure the infrared spectrum generated from the emerald sample: Step S1-1, using a Fourier transform infrared spectrometer equipped with a PIKE 6* beam transmission accessory BeamCondenser; Step S1-2, cleaning the emerald sample, placing the cleaned sample on the sample stage of the focusing transmission accessory, so that the infrared light source beam spot passes through the inside of the gemstone; Step S1-3, during the test, the incident infrared light is parallelized by the concave reflector on the Fourier transform infrared spectrometer and then enters the Michelson interferometer. The interferometer includes a beam splitter, a moving mirror and a fixed mirror. The pulsating light beam leaving the interferometer is projected onto a swinging reflector, so that the light beam alternately passes through the metamorphic corundum sample, and then through the swinging reflector, the light beam is focused onto the detector. The detector digitizes the interference signal through Fourier transform of the computer terminal, and finally displays it as an infrared spectrum. Step S2: Select the infrared spectrum from 2600 to 2850 cm in step S1. –1 Band magnification observation, confirm whether there is an absorption peak, determine the peak position and absorption intensity, and more clearly display the infrared absorption pattern of heavy water molecules through baseline processing and Gaussian fitting; Step S3, analyzing the infrared spectrum characteristics of heavy water obtained in step S2 and comparing them with the spectrum patterns of different groups in the current classification system to obtain the conclusion of the origin of the emerald; Step S3-1: The infrared spectrum of emerald is between 2600 and 2830 cm –1 The absorptions associated with HDO and D2O molecules in the range are as follows: 2640 cm –1 The weak to moderate absorption peak 1, AP1, is attributed to the symmetric stretching vibration v1 of D2O; 2672 cm –1 The sharp strong absorption peak 2, namely AP2, is attributed to the –OD vibration of type II HDO. OD ; 2685 cm –1 The weak to moderate intensity narrow absorption peak 3, namely AP3, is attributed to the –OD vibration of type I HDO v OD ; 2730~2750 cm –1 The broad combined absorption peak 4, namely AP4, in the range of 2808-2815 cm –1 The weak to moderate absorption peak 5, AP5, is attributed to the chloride ion-related absorption or the antisymmetric stretching vibration + rotation of D2O. 3+r ; Step S3-2: According to the existence, peak positions and relative intensity relationships of the above five absorption peaks, the heavy water-related infrared absorption patterns of emeralds from different origins can be divided into three types, including IR-pattern I, IR-pattern II and IR-pattern III, wherein IR-pattern III has two subtypes, as follows: 1) IR-style I and II HDO absorption peak AP2 has higher intensity than D2O-related absorption peaks AP1 and AP4. The AP1 peak generated by D2Ov1 vibration is very weak or absent. AP5 is 2815 cm –1 Usually absent; IR-pattern I is defined as an HDO-type IR pattern, defined as the Zambian group; 2) IR-style II, which is a transitional style between HDO and D2O. All five absorption peaks in the range exist. AP2 of type II HDO is dominant, but the AP1 peak generated by D2Ov1 vibration is usually very obvious, and AP5 is obviously present. The peak position fitting results show that the broad absorption peak of 2735 cm-1 is AP4 at 2722 cm-1. –1 and 2745 cm –1 The combined peaks of infrared absorption at 2808 cm-1 are attributed to the v3 vibration of type II and type I D2O, respectively; this pattern can be defined as the Afghan group, whose AP5 usually appears at 2808 cm-1. –1 , may also shift to 2812 cm –1 ; 3) IR-style III, AP4 generated by D2Ov3 vibration is dominant, which is defined as D2O-type infrared style; at the same time, style III is divided into two subtypes according to the type of HDO molecules in the channel: Colombian Muzo emerald shows type IIIa style, in which type II HDO is dominant in the channel, 2672 cm –1 The infrared absorption intensity of AP2 is higher at 2815 cm –1 ; Gwantu emeralds from Nigeria show a unique type IIIb style, characterized by AP3 of type I HDO being stronger than AP2 of type II HDO. This phenomenon is different from other styles and is only observed in Gwantu emeralds.

2. A method according to claim 1 based on 2600~2850cm –1 The method for identifying the origin of emerald by using infrared spectrum of wavelength band is characterized by ,The model of the Fourier transform infrared spectrometer in step S1 is BRUKER TENSOR II.

3. A method according to claim 1 based on 2600~2850cm –1 The method for identifying the origin of emerald by using infrared spectrum of wavelength band is characterized by The parameters of the Fourier transform infrared spectrometer during the test in step S1-3 are as follows: the test mode is the transmission mode, the ordinate is set to Absorbance, and the scanning range is 400~7500 cm –1 , with a resolution of 4 cm –1 , scanning times 8~32 times.

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