The Spectral Characterization of Blue Spinel and Other Blue Gemstones with the Alexandrite Effect

Zhou Jiling, Wang Chengsi, Zhao Xishan, Yang Yunqi, Shen Andy Hsitien

Zhou Jiling, Wang Chengsi, Zhao Xishan, Yang Yunqi, Shen Andy Hsitien. The Spectral Characterization of Blue Spinel and Other Blue Gemstones with the Alexandrite Effect[J]. Journal of Gems & Gemmology, 2024, 26(4): 69-76. DOI: 10.15964/j.cnki.027jgg.2024.04.008
Citation: Zhou Jiling, Wang Chengsi, Zhao Xishan, Yang Yunqi, Shen Andy Hsitien. The Spectral Characterization of Blue Spinel and Other Blue Gemstones with the Alexandrite Effect[J]. Journal of Gems & Gemmology, 2024, 26(4): 69-76. DOI: 10.15964/j.cnki.027jgg.2024.04.008

详细信息
  • 中图分类号: TS93

The Spectral Characterization of Blue Spinel and Other Blue Gemstones with the Alexandrite Effect

Funds: 

the Youth Foundation Project, Basic and Applied Research Foundation of Guangdong Province of China 2022A1515110780

China Postdoctoral Science Foundation 2023M743293

China Univerisity of Geosciences (Wuhan) Gemmological Institute research project GICTXM-04-S202103

More Information
    Author Bio:

    Zhou Jiling: Jiling Zhou(1998—), female, master of gemmology, mainly engages in researches about the photoluminescence spectra of spinel and its application in provenance tracing. E-mail: chowkeiling@cug.edu.cn

    Corresponding author:

    Wang Chengsi: Chengsi Wang(1992—), female, post-doctor, main research interests focus on gemmology and nano-mineralogy. E-mail: wangcs@cug.edu.cn

    Shen Andy Hsitien: Andy Hsitien Shen(1962—), male, professor, main research interests focus on gemstone deposits and physical and chemical properties of gemstones. E-mail: shenxt@cug.edu.cn

  • Abstract:

    In gemmology, the term "Alexandrite effect" is used to describe colour change phenomenon when a gemstone is observed under different light sources, usually between daylight and incandescent light. The definition of the Alexandrite effect is constantly being broadened with new discovery of gem resource. The traditional definition of the Alexandrite effect attributing the colour change phenomenon to the presence of two maximum transmission regions and a maximum absorption region in the absorption spectra. In this study, 7 blue spinels and 5 blue gemstones (including tanzanite, kyanite, fluorite, and 2 sapphires) showing the Alexandrite effect were investigated. The goal is to explain the cause of blue-to-violet alexandrite effect and the spectral features causing such colour change. In the UV-Vis spectra, all samples showed a maximum absorption peak in the range of 534-610 nm, within the green region to orange region. The traditional explanation of green to red Alexandrite effect required a transmission window in the red region; however, some of our samples did not show this transmission window and the blue-to-violet alexandrite effect was still visible. Therefore, it is incomplete to explain the mechanism of the Alexandrite effect according to their characteristic absorption spectra, a systematic study based on modern colour science and colour perception in human vision is required to elucidate the blue-to-violet alexandrite effect.

  • In gemmology, the colour change of minerals under different illumination conditions is known as the Alexandrite effect, which was initially observed in chromium-rich chrysoberyl from the Ural Mountains, Russia, showing an apparent change in colour from green or bluish green in daylight to purplish red in incandescent light. This gemstone was named "Alexandrite" to commemorate Tsar Alexander Ⅱ because it was discovered on the Tsar's birthday, and its green and red colour represented Holy Russia (Güberlin et al., 1982; Liu et al., 1994). With the discovery of other mineral resources, an increasing number of gemstones have demonstrated colour changes from green to red or from one colour to another under different light sources. Schmetzer and Gübelin (1982) proposed a traditional explanation of this phenomenon based on a common spectral feature of all minerals that display the Alexandrite effect, which included two maximum transmissions in the visible blue-green and red regions of the absorption spectrum and a minimum transmission in the yellow region, but did not consider the colour perception by the naked eye. This explanation is widely applied to explain the Alexandrite effect in other gems such as apatite (Chen et al., 2021), diaspore (Chen et al., 2023), and garnet (Qiu et al., 2021).

    Although several other works disputed this explanation, Liu et al. (1994) demonstrated that the Alexandrite effect was a non-colour-constant phenomenon, thereby confirming that the traditional explanation was incomplete. They quantitatively characterized this effect and defined four categories of gemstones based on the calculated hue angle of gemstones. The absorption spectra of gemstones with the Alexandrite effect contained not only two transmittance bands but also other, more complex bands. Liu and Fry (2006) reported that tourmaline from Mozambique exhibited the Alexandrite effect but its spectrum did not exhibit the traditional transmission bands (Liu et al., 2006). Moreover, blue spinel with the Alexandrite effect did not exhibit the expected transmission bands in this study.

    Blue spinel with a vivid cobalt blue colour is one of the most valuable spinels on the gem market, and can be categorized into Co-rich and Fe-rich spinels, based on their dominant chromophores. The chemical composition and appearance of blue spinel are important characteristics for distinguishing between these two spinel types. Previous studies have suggested that spinels can be classified into bright blue, dark blue, and violet blue spinels based on the ratio of their Co, Fe, and Cr contents (Chauviré et al., 2015; Schollenbruch et al., 2021). Furthermore, spinel with a vivid cobalt blue colour is also a definitive factor of Co-spinel on the gem market. This resembled the definitions of ruby and pink sapphires in the gem trade, which required corundum containing Cr with a vivid red colour to be named ruby. However, in gemmology, the definition of Co-rich spinel (Co spinel) lacks strict criteria and therefore remains unclear.

    Blue-to-violet alexandrite effect spinels are sought-after on the gem market. An increasing number of these spinels have emerged on the gem market, attracting customer attention because of their unique colour-change properties. However, few studies have investigated the mechanism of the Alexandrite effect in blue spinels. Previous studies in this area primarily examined their chemical compositions and absorption spectra. Schmetzer and Gübelin (1982) reported that a colour-change spinel from Sri Lanka was richer in iron than typical blue spinels. A comprehensive study of blue spinels conducted by Chauvié et al. (2015) demonstrated that the absorption spectra of a blue spinel with slight changes in colour contained two transmission windows in the blue and red regions owing to the substitution of Co2+ with Mg2+ ions. Similarly, a blue spinel with the Alexandrite effect has been reported after the discovery of new blue spinel mines. Senoble (2010) found that some blue spinels from Luc Yen in Vietnam exhibited a colour change from blue in the morning under a cloudy sky to "lavender" at approximately noon in sunny conditions (Senoble, 2010). Later, similar absorption spectra in purple spinels from Vietnam with slight colour changes were observed by Belley and Palke (2021). From these considerations, previous studies deduced the mechanism of the Alexandrite effect in blue spinel by analyzing trace elements and absorption spectra.

    In the present study, we analyzed the chemical compositions and absorption spectra of blue spinels with the Alexandrite effect and compared the obtained results with the absorption spectra of other blue gemstones demonstrating the same effect. The aims of this work were (1) to establish the relationship between trace elements and the absorption spectrum of blue spinel and (2) to investigate the correlation between the absorption spectra of gemstones exhibiting the blue-to-violet colour-change and the Alexandrite effect. Additionally, the factors influencing the blue-to-violet alexandrite effect in gemstones are discussed.

    Seven natural blue spinels with the Alexandrite effect were investigated, 5 of which possessed a vibrant cobalt blue colour. One of the remaining stones was light blue, and the other was dark blue. To further examine the blue-to-violet colour change due to the Alexandrite effect, 5 natural blue gemstones with the same effect were analyzed for comparison, including fluorite, tanzanite, kyanite, and 2 sapphires. All samples were obtained from jewelry markets in Guangzhou, China.

    The chemical compositions of the 7 spinels, 2 sapphires, and tanzanite were determined using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The procedure was performed at Wuhan Sample Solution Analytical Technology Co., Ltd., using a 193 nm ArF excimer laser ablation system coupled with an Agilent 7500a ICP-MS instrument. The testing conditions included a laser ablation aperture size of 44 μm, frequency of 5 Hz, and laser energy density of 5.5 mJ/cm2. Reference materials consisted of USGS (BHVO-2G, BCR-2G, BIR-1G, and GSE-1G) and NIST (SRM 610) glasses used as external calibration standards. Mg, Al, and Si were used as the normalizing elements in spinel, sapphire, and tanzanite, respectively, to calculate the contents of 54 trace elements with the ICPMS DataCal 12.2 software (State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan, China) (Liu et al., 2008). The trace element contents were reported in parts per million atomic (ppma) units computed using Equation (1):

    $$ { ppma }=\frac{\left({ molecular \;weight\;of\;} {MgAl}_2 {O}_4\right) / 7}{({ \;atomic \; weight })} \;\times p p m w $$ (1)

    The ppma units are more suitable for investigating elemental substitution patterns in crystals than parts per million weight (ppmw) because crystal substitutions depend on the number of atoms rather than mass.

    The chemical compositions fluorite was quantitatively determined at the Gemmological Institute, China University of Geosciences, Wuhan, China using a Thermo ARL Quant'x X-ray fluorescence spectrometer. The testing conditions were low Za, low Zb, low Zc, mid Za, mid Zb, mid Zc, high Za, and high Zb, and each parameter had a lifetime of 60 s. The analysis was conducted in a vacuum, within a 6-28 kV voltage range.

    The absorption spectra of all specimens were recorded at the Gemmological Institute, China University of Geosciences (Wuhan), using a JASCO MSC5200 micro-ultraviolet-visible-near-infrared spectrometer equipped with a 30 W deuterium lamp and 20 W halogen lamp as light sources. The spectral range was 380-800 nm with an aperture diameter of 200 μm, data collection interval of 0.5 nm, and scanning speed of 400 nm/min.

    Based on the definition of the Alexandrite effect, we selected a D65 light source to simulate daylight illumination and a light source for incandescent illumination to observe the specimens. The saturations of the 7 blue spinel specimens varied as illustrated in Fig. 1a. Samples Abspi-1 to Abspi-5 appear cobalt blue, Abspi-6 shows a light blue hue, and Abspi-7 exhibits a dark blue hue. All samples presented in Fig. 1b exhibit colour change from blue to violet after exposure to both incandescent illumination. Regardless of the hue colour of the samples, all spinels showed the significant blue to violet alexandrite effect.

    Figure  1.  (a) and (c): Photographs of the 7 blue spinel samples and other blue gemstone samples obtained under the D65 light source simulating daylight illumination. (b) and (d): Blue spinel samples and the other blue gemstone samples observed under incandescent illumination.

    According to Fig. 1c and Fig. 1d, the other blue gemstones also demonstrate the Alexandrite effect. All gemstones appear blue under the D65 light source but exhibit a purple colour under the incandescent light source.

    LA-ICP-MS demonstrated that Abspi-1 to Abspi-7 primarily consist of Al2O3 (68.3-69.2 wt.%) and MgO (25.5-28.8 wt.%). According to a previous study, Abspi-1 to Abspi-7 can be classified as spinels (Bosi et al., 2019). All spinel samples contained significant concentrations of multiple chromophores, including Ti, V, Cr, Mn, Fe, Co, Ni, and Cu (Table 1). The Cr, Mn, Fe, and Co contents in the studied samples ranged from 0.74-918, 53.0-272, 1 050-8 810 ppma, and 4.93-124 ppma, respectively. The specimens with a strong Alexandrite effect (Abspi-1 to Abspi-6) possess lower Fe and higher Cr concentrations than those with a slight colour-change effect (Abspi-7).

    Table  1.  Average concentrations of trace elements in the blue spinel samples  /ppma
    Element Abspi-1 Abspi-2 Abspi-3 Abspi-4 Abspi-5 Abspi-6 Abspi-7 Detection Limit
    Ti 33.5 8.07 7.37 6.85 6.27 2.18 0.48 0.509-2.59
    V 45.4 19.2 82.9 38.2 64.5 9.35 0.87 0.057 7-0.284
    Cr 598 306 918 343 386 10.4 0.74 0.850-4.90
    Mn 53.0 56.5 66.1 68.6 57.9 272 116 0.410-2.02
    Fe 3 350 4 980 3 740 3 010 3 920 1 050 8 810 12.8-63.2
    Co 55.2 54.5 69.8 69.4 124 4.93 5.52 0.055 1-0.252
    Ni 164 123 51.8 151 187 0.31 6.42 0.661-2.87
    Cu 0.089 4 Bdl1 0.253 0.260 0.868 0.046 1 0.14 0.118-0.592
    1 Below the detection limit.
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    Based on the chemical compositions of the investigated blue spinels, the Cr/Fe and Fe/Co ratios could influence the hue of the samples but did not have a significant relationship between the Alexandrite effect phenomenon. Fig. 2 shows that the Cr/Fe ratios in the bright cobalt blue spinels exceed 0.05, while the Fe/Co ratios are less than 200, which distinguishes the light blue spinel (Abspi-6) from the dark blue spinel (Abspi-7). However, no significant correlation is observed between the Cr/Fe and Fe/Co ratios in the samples and the phenomenon of the colour change in the blue spinel. All the samples with various Cr/Fe and Fe/Co ratios could produce blue to violet alexandrite effect. Therefore, the trace elements producing colour in the blue spinel demonstrated no direct correlation with the Alexandrite effect, and the Cr/Fe and Fe/Co ratios solely impacted its hue.

    Figure  2.  The chemical ratio of Cr/Fe and Fe/Co in blue spinels with Alexandrite effect.

    The compositions of the other blue gemstones were determined via LA-ICP-MS and X-ray fluorescence (XRF) spectroscopy. Table 2 lists the chemical concentrations of samples Sapphire-1, Sapphire-2, Tanzanite and Kyanite which were measured using LA-ICP-MS. The sapphires are mainly composed of Al2O3 (98.6 wt.%) and contain different concentrations of Ti, V, Mn, Fe, and Cu. The main chemical components of tanzanite are Al2O3 (33.6 wt.%), SiO2 (40.8 wt.%), and CaO (24.9 wt.%) with various concentrations of Ti, V, Cr, Mn, Fe, Co, Ni, and Cu atoms. The kyanite is mainly composed of Al2O3 (61.3 wt.%) and SiO2(38.4 wt.%). Among the trace elements, the sapphires have the highest Fe content (980 ppma), and Tanzanite has the highest V content (1 030 ppma). In addition, fluorite was examined via a qualitative XRF analysis, which revealed that contained Cu and Y species.

    Table  2.  Concentrations of various trace elements in the other blue gemstones  /ppma
    Element Sapphire-1 Sapphire-2 Tanzanite Kyanite Detection Limit
    Ti 24.5 46.6 38.2 15.7 0.815-3.05
    V 2.10 9.41 1 030 68.8 0.120-8.49
    Cr 1.11 0.977 91.9 42.1 1.03-6.64
    Mn Bdl1 0.323 8.73 0.0368 0.242-1.140
    Fe 896 980 25.2 393 3.88-30.0
    Co 0.002 08 0.020 8 0.021 2 Bdl1 0.014 5-0.125
    Ni Bdl1 Bdl1 0.320 Bdl1 0.231-2.02
    Cu 0.0875 0.165 0.092 2 3.049 0.040-0.413
    1 Below the detection limit.
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    As shown in Fig. 3a, the main absorption peaks at 550, 583 nm and 623 nm in the spectra of Abspi-1 to Abspi-6 were the predominant origins of the colours of the samples. Similarly, the peaks at 555, 590 nm and 630 nm were responsible for the coloration of Abspi-7. The peaks at 550, 583 nm and 623 nm in the green to orange region with a characteristic Co peak were assigned to the splitting of the 4T1(4P) states in a low-symmetry crystal field. They were typically observed in the spectra of crystals with tetrahedral Co2+ ions (Yumashev et al., 2000). Additionally, the Fe peak at 387 nm was observed in the spectra of Abspi-1 through Abspi-5. The peaks at 550 nm and 590 nm were due to the Fe2+ spin forbidden transitions 5E3T2 and 5E3T1 at the tetrahedral site, respectively (D'Ippolito et al., 2015). However, the peak shape in the spectrum of Abspi-6 at 550 nm differed from those in the spectra of Abspi-1 to Abspi-5, suggesting that this peak was produced by a combination of Co2+ and Fe2+ ions. In addition, the peak at 630 nm in the spectrum of Abspi-7 was unclear. In a previous study, the peak at 630 nm was attributed to Co2+ species (Belley et al., 2021); however, the chemical composition of Abspi-7 did not support this conclusion, suggesting that this peak corresponded to a combination of the Co2+ peak at 623 nm, and another peak at 665 nm owing to the intervalence change transfer between Fe2+ and Fe3+ ions (D'Ippolito et al., 2015). The remaining peak (460 nm) in the spectrum of Abspi-7 was attributed to Fe (D'Ippolito et al., 2015), while the peaks at 421 nm and 450 nm were assigned to Mn species (Bosi et al., 2007; Toru et al., 2017).

    Figure  3.  Absorption spectra of (a) Abspi-1 to Abspi-7 and (b) sapphire, kyanite, tanzanite, and fluorite

    The absorption spectra of all blue gemstones (Fig. 3b) display a wide absorption peak in the green or yellow visible region caused by the presence of trace elements. The absorption peaks at 387, 450 nm and 586 nm were observed in the spectra of both blue sapphire samples. The peak at 387 nm originated from Fe3+ ions and was assigned to the 4T2(D) transition, whereas the peak at 450 nm was attributed to Fe3+/Fe3+ pairs (Lehmann et al., 1970; Mungchamnankit et al., 2012). A broad absorption peak was observed at 586 nm, which was assigned to Fe-Ti pairs (Wongrawang et al., 2016). Furthermore, blue kyanite produced a peak at 610 nm, which was caused by Cr3+ ions and assigned to the spin-allowed 4A2(F)→4T2(F) transition (Wildner et al., 2012). The tanzanite absorption peaks at 534, 592 nm and 755 nm were attributed to V3+ species (Faye et al., 1971). The fluorite peaks at 398 nm and 578 nm were caused by the yttrium-associated F centers (Bill et al., 1978). The assignments of all absorption peaks to chromophore elements are presented in Table 3.

    Table  3.  Absorption peak positions of various chromophore elements in all samples
    Sample Peak positions/nm Assignment
    Abspi-1 to Abspi-5 387 Fe
    555, 583, 623 Co
    Abspi-6 421, 450 Mn
    555 Fe + Co
    583, 623 Co
    685 Cr
    Abspi-7 460, 550, 590 Fe
    Sapphire-1 to Sapphire-2 387, 450 Fe
    586 Fe-Ti
    Kyanite 610 Cr
    Tanzanite 534, 592, 755 V
    Fluorite 398, 578 Y-associated F center
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    According to the obtained absorption spectra, Abspi-7 was different from the other blue spinels. A previous study reported that the absorption spectra of gemstones with the Alexandrite effect exhibited one absorption maximum and two transmission peaks in the visible region (Güberlin, Schmetzer, 1982). The absorption spectra of Abspi-1 to Abspi-6 (Fig. 3a) show the maximum absorption peaks in the green-to-yellow visible region. The absorption maximum in the yellow region in the previous study was caused by vanadium (571 nm), which was present in the blue spinel with the Alexandrite effect. In this work, V was substituted with Co to produce absorption peaks in the yellow region (580 nm) for Abspi-l to Abspi-6. Furthermore, the two maximum transmission zones in the violet to green (420-500 nm) and red (above 670 nm) regions were observed in the spectra of Abspi-1 to Abspi-5, whereas that of Abspi-6 exhibited maximum transmission zones in the blue-green (480-515 nm) and red (above 730 nm) regions.

    In contrast, in the spectrum of Abspi-7, Fe demonstrated the maximum absorption at 555 nm. The maximum transmission in the red region was not observed, and the maximum transmission in the blue-to-green region (485-500 nm) was not consistent with the absorption characteristics expected of materials that exhibit the Alexandrite effect. Hence, it can be inferred that the maximum transmission in the red region was not required for the Alexandrite effect of blue spinel. To verify this conclusion, the spectra were compared with those of the other 5 blue gemstones with the blue-to-violet alexandrite effects. As shown in Fig. 3b, all samples produced absorption peaks in the yellow-to-green region, although the factors contributing to their formation were different. Sapphire, kyanite, and tanzanite exhibited maximum transmissions in the blue-violet region at 415-470, 400-450 nm and 430 nm, respectively, and did not produce transmission peaks in the red region. However, fluorite exhibited two transmission zones in the blue-violet (centered at 480 nm) and red (above 695 nm) regions. The absorption spectra of the blue gemstones, such as Abspi-7, Sapphire-1, Sapphire-2, and Kyanite, showed only one transmission band in the violet-blue region, which could also show the blue-to-violet alexandrite effect. From these results, it can be concluded that the existence of a transmission peak in the red visible region did not significantly influence the blue-to-violet alexandrite effect.

    Seven blue spinels and 5 blue gemstones with the Alexandrite effect were investigated. The obtained results revealed that the main chromophore elements of the blue spinels with the Alexandrite effect were Co and Fe. All the blue gemstones showed maximum absorption peaks within the visible green to orange region owing to the presence of different chromophore elements. Trace elements such as Co, Fe, Cr, V, and Y give rise to absorption peaks in that visible region. However, in the present study, the absorption spectral features of blue gemstones were inconsistent with the traditional understanding of the spectral features. The presence or absence of the maximum transmission in the red visible region does not affect the blue-to-violet alexandrite effect in blue gemstones. The presence of specific chromophore elements in all studied samples produced different absorption spectral features; however, the relationship between these spectral features and the cause of the blue-to-violet alexandrite effect remains unclear. Hence, the traditional explanation is insufficient to elucidate the mechanism of the blue-to-violet alexandrite effect, and additional in-depth studies combined with colour research are required to achieve a more comprehensive understanding of this phenomenon.

  • Figure  1.   (a) and (c): Photographs of the 7 blue spinel samples and other blue gemstone samples obtained under the D65 light source simulating daylight illumination. (b) and (d): Blue spinel samples and the other blue gemstone samples observed under incandescent illumination.

    Figure  2.   The chemical ratio of Cr/Fe and Fe/Co in blue spinels with Alexandrite effect.

    Figure  3.   Absorption spectra of (a) Abspi-1 to Abspi-7 and (b) sapphire, kyanite, tanzanite, and fluorite

    Table  1   Average concentrations of trace elements in the blue spinel samples  /ppma

    Element Abspi-1 Abspi-2 Abspi-3 Abspi-4 Abspi-5 Abspi-6 Abspi-7 Detection Limit
    Ti 33.5 8.07 7.37 6.85 6.27 2.18 0.48 0.509-2.59
    V 45.4 19.2 82.9 38.2 64.5 9.35 0.87 0.057 7-0.284
    Cr 598 306 918 343 386 10.4 0.74 0.850-4.90
    Mn 53.0 56.5 66.1 68.6 57.9 272 116 0.410-2.02
    Fe 3 350 4 980 3 740 3 010 3 920 1 050 8 810 12.8-63.2
    Co 55.2 54.5 69.8 69.4 124 4.93 5.52 0.055 1-0.252
    Ni 164 123 51.8 151 187 0.31 6.42 0.661-2.87
    Cu 0.089 4 Bdl1 0.253 0.260 0.868 0.046 1 0.14 0.118-0.592
    1 Below the detection limit.
    下载: 导出CSV

    Table  2   Concentrations of various trace elements in the other blue gemstones  /ppma

    Element Sapphire-1 Sapphire-2 Tanzanite Kyanite Detection Limit
    Ti 24.5 46.6 38.2 15.7 0.815-3.05
    V 2.10 9.41 1 030 68.8 0.120-8.49
    Cr 1.11 0.977 91.9 42.1 1.03-6.64
    Mn Bdl1 0.323 8.73 0.0368 0.242-1.140
    Fe 896 980 25.2 393 3.88-30.0
    Co 0.002 08 0.020 8 0.021 2 Bdl1 0.014 5-0.125
    Ni Bdl1 Bdl1 0.320 Bdl1 0.231-2.02
    Cu 0.0875 0.165 0.092 2 3.049 0.040-0.413
    1 Below the detection limit.
    下载: 导出CSV

    Table  3   Absorption peak positions of various chromophore elements in all samples

    Sample Peak positions/nm Assignment
    Abspi-1 to Abspi-5 387 Fe
    555, 583, 623 Co
    Abspi-6 421, 450 Mn
    555 Fe + Co
    583, 623 Co
    685 Cr
    Abspi-7 460, 550, 590 Fe
    Sapphire-1 to Sapphire-2 387, 450 Fe
    586 Fe-Ti
    Kyanite 610 Cr
    Tanzanite 534, 592, 755 V
    Fluorite 398, 578 Y-associated F center
    下载: 导出CSV
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  • 收稿日期:  2024-03-05
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