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Article

Gemological Characteristics and Trace Chemical Element Analysis of Emerald in Kafubu, Zambia

by
Yiwei Jiang
1,
Siyi Zhao
1,
Zhiyi Zhang
1 and
Bo Xu
1,2,3,*
1
School of Gemology, China University of Geosciences Beijing, 29 Xueyuan Road, Beijing 100083, China
2
State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China
3
Frontiers Science Center for Deep-Time Digital Earth, China University of Geosciences (Beijing), Beijing 100083, China
*
Author to whom correspondence should be addressed.
Crystals 2025, 15(5), 385; https://doi.org/10.3390/cryst15050385
Submission received: 13 March 2025 / Revised: 8 April 2025 / Accepted: 18 April 2025 / Published: 22 April 2025
(This article belongs to the Special Issue Laser–Material Interaction: Principles, Phenomena, and Applications)
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Abstract

:
This study systematically analyzed the color characteristics, microscopic inclusions (including fluid and mineral inclusions), spectral properties, and chemical composition of emerald samples from Kafubu, Zambia using infrared spectroscopy, UV–visible spectroscopy, Raman spectroscopy, and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The results were then compared with research data on emeralds from Afghanistan, Brazil, China, Colombia, Ethiopia, Madagascar, Russia, and the United States. The result establishes a global classification framework for emerald origins based on chromophores (Cr, V, Fe), categorizing deposits into two distinct groups: low-Fe regions and high-Fe regions. For high-Fe type IA emeralds, particularly those from Zambia and Madagascar exhibiting exceptionally similar Fe and Mg concentrations, a multi-element discrimination approach was developed. Using microscopic infrared testing to magnify and analyze the characteristic peaks related to OD in the range of 2550–2800 cm⁻1, it can be classified as HDO-dominant, and the high alkali metal element content in Zambian emeralds can be reflected by the absence of the HDO vOD absorption peak at 2685 cm⁻1. A further in-depth analysis of the trace elements in Zambian emeralds can provide a basis for inferring the possible rich ore geology for subsequent mining and provide more effective reference data for the identification of the origin of emeralds.

1. Introduction

The geographic origin identification of emeralds represents a pivotal technique in gemological laboratories and stands as a prominent research focus within the field of gemology. Although there has been some research of emeralds in Zambia, further research is still needed on the analysis of the chemical composition of emeralds, their formation environment, and the identification and differentiation of emeralds of other origins [1,2,3].
The methodologies for the geographic origin determination of emeralds primarily involve inclusions, spectroscopic characteristic analysis, and the geochemical tracing of trace elements, fundamentally rooted in the distinct geological settings of emerald formation across deposits (Giuliani et al., 2019; Schwarz et al., 2001; Schwarz et al., 2002; Barton et al., 2002) [4,5,6,7]. Fluid inclusions, as critical microscopic features, have been extensively utilized as primary diagnostic criteria (Saeseaw et al., 2014; Marshall et al., 2016; Zachari’ǎ et al., 2005; Long et al., 2021) [1,8,9,10]. However, the diagnostic utility is constrained by their non-unique distribution, exemplified by the presence of three-phase inclusions in emeralds of Colombia (Saeseawet et al., 2014; Karampelas et al., 2019) [8,11], Zambia (Zhang et al., 2023; Zwwan et al., 2005; Saeseawet et al., 2019) [1,2,12], and Brazil (Zwwan et al., 2012; Santiago et al., 2018) [13,14]. Spectroscopically, infrared and Raman spectra exhibit substantial convergence, with only UV–Vis absorption bands (chromophores like Cr3+, V3+, and Fe2+) offering limited regional discrimination (Zheng et al., 2024) [15]. However, chromophores of emeralds from the same origin may also vary greatly, so this classification is not always effective.
The advancement of in situ microanalytical techniques has generated increasingly systematic geochemical datasets for emeralds, thereby enhancing the feasibility and reliability of chemical fingerprinting for geographic provenance determination (Aurisicchio et al., 2018; Karampelas et al., 2019; Alonso-Perez et al., 2024; Araújo Neto et al., 2019; Guo et al., 2020) [11,16,17,18,19]. While this comprehensive dataset improves traceability assessment, provenance discrimination challenges persist due to heterogeneous research progress across various deposits. For instance, the Zambian emerald deposits examined in this study require further refinement of mine-specific geochemical profiles to establish definitive identification criteria.
Crucially, the newest investigation (Zheng et al., 2024) [15] reveals that characteristic spectral peaks in micro-FTIR analysis show diagnostic potential for emerald provenance discrimination. This non-destructive analytical approach presents distinct advantages over traditional destructive methods. The development of region-specific infrared spectral libraries could complement existing geochemical databases for enhanced provenance authentication accuracy.

2. Geological Setting

The samples of this study are collected from the Kafubu area in Zambia.
The emerald deposits in Zambia are located southwest of the Lufilian copper belt [1,20]. The deposits are located near the Kafubu River and are commonly named the Kafubu Emerald Mines. There are approximately 18 deposits in the Kafubu area, and mechanized mining activities are mainly concentrated in the Kagem, Grizzly, Chantete, and Kamakanga deposits [1]. Over the years, compared with other mechanically mined deposits, there have been too few samples from the Kamakanga deposit.
As shown in Figure 1, the Kamakanga deposit is located on the southern side of the Kafubu River and is formed in the Cr-rich metamorphic rock mass of the Muva Supergroup. The Muva Supergroup is composed of metabasite, quartzite, and quartz–mica schist. The metabasite contains talc chlorite ± actinolite ± magnetite schists and it is overlaid with a large block of Be-bearing pegmatite and a nearly 20-kilometer-long hydrothermal vein. The crystallization of Kamakanga emeralds ultimately occurs at the contact zone between the pegmatite and the metabasite. During the late Pan-African Orogeny (about 530 Ma), Be-bearing pegmatites and hydrothermal veins intruded into different crustal units. Emerald mineralization is formed by the metasomatic alteration of Cr-rich metamorphic rocks by Be-bearing fluids.

3. Materials and Methods

Eight emerald samples (i.e., ZMB-1–ZMB-8) from Zambia shown in Figure 2 were subjected to standard gemological tests. All of the samples were rough; three of the studied samples appeared as slabs developed along {0001}, two were well-formed hexagonal columns, while a few were fragments.
The classic gemological analyses were conducted at the Gemological Research Laboratory of China University of Geosciences, Beijing, including observation, specific gravity testing, IR, Raman spectroscopy, and UV–Vis–NIR.
Ten-fold magnification gem microscope is used to carry out the optical observations. The specific gravity is obtained by averaging the results of the hydrostatic method after each sample is tested three times.
IR analysis is carried out utilizing the reflection method, with a Tensor 27 Fourier infrared spectrometer (Bruker, Karlsruhe, Germany). The test conditions were as follows: 18–25 °C scanning temperature; 85–265 V scanning voltage; <70% humidity; 400–2000 cm−1 test range; 4 cm−1 resolution; 6 mm grating; 32 times of scanning signal accumulation, scanning 7–8 times per second.
Using the reflection method to perform the UV–Vis spectroscopy tests, a UV-3600 UV–Vis spectrophotometer (Shimadzu Corporation, Kyoto, Japan) with the following analytical conditions was used: 200–900 nm wavelength; 20 nm slit width; 1.0 s time constant; medium scanning speed; 0.5 s sampling interval.
Raman spectroscopy was performed with an HR Evolution Raman microspectrometer (HORIBA, Kyoto, Japan), and the analytical conditions were as follows: 532 nm laser wavelength; 50 mW laser power; 200–2000 cm−1 scanning range; 4 cm−1 resolution; 600 gr/mm grating; 100 μm slit width; 3 s integration time; 4 s scanning time, accumulating up to two scans.
The laser ablation inductively coupled plasma mass spectrometer of the Institute of Geomechanics, Chinese Academy of Geological Sciences was used to measure trace elements, with a 193 nm excimer laser ablation system (GeoLas HD; Coherent, Santa Clara, CA, USA), a four-stage rod mass spectrometer (Agilent 7900, Agilent, Palo Alto, Santa Clara, CA, USA), and Ar and He as the carrier gases to perform the inline testing. NIST SRM 610 and 612 were used as the external standards, employing 43Ca as an internal marker for the trace element content.

4. Results

4.1. Visual Appearance and Gemological Properties of Emerald

As shown in Table A1, the emerald samples in this experiment are light green to dark green, with a glassy luster. ZMB-1, ZMB-2, and ZMB-8 are standard hexagonal columnar crystals with slight damage and longitudinal lines parallel to the c-axis on the surface of emerald columns. The remaining samples have irregular shapes and are semi-transparent. There are a multitude of inclusions inside the crystal, including black short columnar, brownish red sheet-like, and transparent quartz inclusions. The length of the ZMB samples is 9–12 mm and the thickness is 5–10 mm. The RI of the samples is 1.57–1.59, showing a high refractive index due to the high degree of Al substitution in the lattice. Some samples are inert under SWUV and LWUV, while others show moderate to strong green fluorescence caused by Cr and V.
Furthermore, in Table A2, we have listed the gemological properties of emeralds from other origins. We found that compared to emeralds from other origins, Zambian emeralds have a higher refractive index, a greater specific gravity, and a bluish color.

4.2. Observation Under Microscope

In Zambian emeralds, inclusions are relatively abundant, including gas–liquid two-phase and gas–liquid–solid three-phase inclusions, healed fractures, cavities, hollow tubes, negative crystals, mineral inclusions, etc. The presence of obvious two-phase and three-phase inclusions and other characteristics in Zambian emeralds clearly indicates that the crystallization environment of Zambian emeralds is a hydrothermal or pegmatite environment [1]. Experiments used gem microscopes and polarizing microscopes to observe the rough stones and thin sections, respectively, and Raman tests were conducted on the inclusions to determine the material composition.

4.2.1. Fractures and Fluid Inclusions

In Figure 3, most fluid inclusions are gas–liquid two-phase inclusions (Figure 3A,B), and gas–liquid–solid three-phase inclusions are rare (Figure 3C). Fluid inclusions are in irregular, short columnar, long columnar (Figure 3D), elliptical, and other shapes and can exist alone or may be arranged parallel to the c-axis direction of the emerald crystal. All observed samples contain two-phase or three-phase inclusions (with a size of 100 μm or more).
For the various fluid inclusions observed in the samples, as mentioned above, we attempted to conduct Raman analysis. However, due to their deeply buried positions in the thin mineral sections, we encountered technical challenges, which limited the laser penetration and prevented the acquisition of interpretable spectra. In subsequent studies, we will adopt possible experimental methods to improve and optimize this part of the data.

4.2.2. Mineral Inclusions

Three types of mineral inclusions are commonly found in the eight emerald samples measured: The first one is brown or dark red, spotty, pseudo-hexagonal, or elliptical flaky minerals. In Figure 4A,B, we can clearly see that there is a large accumulation in ZMB-4, while in other samples it is mostly dispersed. It is speculated that it should be mica or hematite. The second one is a black long columnar mineral, mostly attached to the surface of the sample (Figure 4D), and some are also included in the emerald (Figure 4C). Through Raman analysis (Figure 5A), it is determined to be black tourmaline, which is related to the tourmaline veins occurring in the deposit of the Kafubu emeralds in Zambia. The third one is a colorless short columnar mineral (Figure 4D). Raman analysis shows that it is quartz (Figure 5B), speculating that it comes from the Muva Supergroup, which consists of quartzite and quartz–mica schist.
By conducting Raman spectroscopy tests on the mineral inclusions in Zambian emerald samples, the presence of black tourmaline inclusions was found inside the ZMB-7 sample, while the presence of phenakite was found on the surface and inside the ZMB-8 sample, and colorless quartz crystals were attached to the periphery. The specific Raman spectra and locations are shown in the following Figure 4.

4.3. Spectral Characteristics

4.3.1. FTIR Spectroscopy

Figure 6 shows the infrared absorption spectrum of Zambian emerald in the range of 1500–600 cm−1. In this range, the absorption peaks caused by the vibration of functional groups can be clearly observed. They are mainly distributed at 1181, 1027, 946, 811, 749, 679, and 646 cm−1. Among them, the three strong absorption peaks at 1181, 1027, and 946 cm−1 are caused by vasSi-O-Si, vsO-Si-O, and vasO-Si-O. The three medium-weak absorption peaks at 811, 749, and 679 cm−1 are caused by vsSi-O-Si, while the absorption peak at 646 cm−1 is related to Be-O vibration.
Figure 7 highlights the IR absorption in the 2550–2850 cm−1 region, mainly with four different absorption peaks: a weak absorption peak of type I D2O near 2629 cm−1, a sharp and strong absorption peak of type II HDO near 2672 cm−1, a weak to medium absorption peak of type II D2O near 2725 cm−1, and a broad combined peak of type I D2O in the 2750–2763 cm−1 range. The absorption intensity of type II HDO is significantly higher than that related to D2O. The peaks generated by the D2O v₁ vibration. That is to say, the deuterium content in the emerald channel is relatively low, and most of the heavy water molecules exist in the form of HDO molecules. The FTIR spectra of D2O and HDO can further reflect the content of alkali metals in the channels. The emerald with a higher content of alkali metals has a more obvious absorption of type II HDO in its channels, which indicates that the content of alkali metals in Zambian emeralds is higher.

4.3.2. UV–Vis–NIR Spectroscopy

It can be seen from Figure 8 that the characteristic peaks of Fe2+, Cr3+, and V3+ are all present in ZMB-5, 6, and 7. The peak positions of ZMB-5 and ZMB-7 are similar. In the long-wave ultraviolet region, the sharp peak at 340 nm and nearby is caused by the absorption of Fe3+. There are two broad absorption peaks at 508 nm and 705 nm in the visible light region, which are associated with the absorption of Cr3+ and V3+. In ZMB-6, the sharp peak at 370 nm in the long-wave ultraviolet region and the absorption peaks at 337 nm and <337 nm in the sample are caused by the absorption of Fe3+. The two broad absorption peaks near 520 nm and 710 nm in the visible light region are related to the absorption of Cr3+ and V3+, and there is a slight shift from the broad absorption peak at this point in ZMB-5. Absorption bands near 630 nm and 680 nm appear in the sample, so the color is caused by the combined effect of Cr3+ and V3+. No broad absorption band appears near 800 nm, because it is impossible to infer whether there is an element of Fe2+ to cause the color here. Briefly speaking, the chromophores of Zambia emeralds were selective to the absorption of Fe, Cr, and V in the ultraviolet regions [1,8,21,22,23,24].

4.4. LA-ICP-MS Trace Element Analysis

In Table A3, the main elements and trace elements of the Zambian emerald experimental samples are listed. Experiments were carried out on samples, with data measurements at 10 points for each sample.
The elements in Zambian emerald mainly include Na (1.61–1.91 wt.%), with a relatively high content, and Mg (2.16–2.63 wt.%), and the two show a positive correlation. The coloring elements of emeralds are Cr, V, and Fe. The average content of Cr in the samples is 2047 ppm, the average content of V is 153.4 ppm, and the average content of Fe is 8941.4 ppm. For alkali metals such as Li, K, Rb, Sc, the content of Li (554.7 ppm) is relatively high, followed by K (513.4 ppm), while the contents of Rb (70.8 ppm) and Sc (320.9 ppm) are relatively low.

5. Discussion

5.1. OD Vibration and Emerald Origin Determination

FTIR is a non-destructive testing technique. It can not only distinguish the types of minerals through the characteristic spectra in the fingerprint region, but also the relative intensity of the infrared absorption spectra related to the channel water in the functional group region, that is, the type I and type II water, which can play a certain role in determining the origin. In addition, the absorption peak related to the OD vibration in the range of 2600–2800 cm⁻1 can be used for the traceability and classification of the origin of emeralds.
The predecessors in the research labeled (Zheng et al., 2024) [15] the absorption peaks within the range of 2600–2800 cm−1 as five types: (1) 2640 cm−1: type I D2O v1; (2) 2672 cm−1: type II HDO vOD; (3) 2685 cm−1: type I HDO vOD; (4) 2730–2750 cm−1: combination of type I and II D2O v3; (5) 2808–2815 cm−1 [15]. According to the intensity and different combinations of these characteristic absorption peaks, emeralds from different origins can be divided into three FTIR patterns: Pattern I is the HDO-dominant type, Pattern II is the transitional type, and Pattern III is the D2O-dominant type. As shown in Figure 9, the Zambian emerald samples used in the experiment can be classified as IR Pattern I-type emeralds, in which the absorption intensity of type II HDO is the strongest, much higher than the absorption intensities of type I and type II D2O. The absorption peak of type I D2O generated near 2638 cm−1 is very weak, and there is no absorption peak near 2808–2816 cm−1.

5.2. Compositional Diagrams and Emerald Origin Determination

Due to the different mineralization mechanisms and element enrichments in emerald deposits from different origins, the chemical composition characteristics of emerald samples also vary. In this study, LA-ICP-MS data of emerald samples from a total of eight origins worldwide except Zambia were collected, and the LA-ICP-MS data of the studied samples are shown in Table A4. Considering the extremely high Fe content in Zambian emeralds, the data of the three chromogenic elements Cr, V, and Fe were compared in a ternary diagram, and five type IA emerald origin samples with a higher Fe content were screened out. Then, a variety of trace amounts of a large number of sample data from these five origins were plotted, and a detailed analysis was carried out through their distribution and aggregation degree. Finally, the similarities and differences of chemical elements between different origins were obtained, and the origin identification can be carried out by combining them.
Cr and V are the two most important chromogenic elements in all emeralds, while Fe is also abundantly contained in emeralds as an impurity. The incorporation of Fe may cause the color of emeralds to be bluish green or grayish yellow. Therefore, the contents of the three not only determine the color rating but are also important indicators of the source of the ore-forming materials. As shown in Figure 10, the studied emeralds from Colombia, China, Afghanistan, and the United States are well separated. The emeralds from Colombia have the lowest Fe content, and most of them contain mainly V as the chromogenic element (the plotted points are concentrated in V > 40%). The emeralds from China are significantly distinguished from other origins by the characteristics of high Fe and high V. The emeralds from Afghanistan are distinguished into two characteristics: one is that the three elements are relatively average, and the other is that the Fe content is higher, but the Cr and V contents are similar. The emeralds from the United States are characterized by a higher Cr content, and some samples have more Fe. Except for the research samples from the above four origins, the Fe concentration of the research samples from other origins is greater than 50%, and the proportion of Cr is much greater than that of V.
For the five origins of Zambia, Madagascar, Brazil, Ethiopia, and Russia, where the Fe content is very high and a detailed origin distinction cannot be made using chromogenic elements, we found that they all belong to the tectonic–magmatic-related type and are hosted in type IA deposits in basic–ultrabasic surrounding rocks. In order to determine more similarities and differences between them, we selected the data of eight other representative metal elements (Ga, Sc, Li, Na, K, Rb, Cs, Mg) for further comparison. From Figure 11, we concluded that the Fe and Mg contents of emeralds in Zambia and Madagascar are both very high and very close, which can be distinguished from other origins, but more elemental characteristics are needed to distinguish between the two.
As shown in Figure 12A, we selected Fe, Mg, and Ga as the characteristic elements to distinguish Zambia, Madagascar, and the other three origins. Russian emerald is distinguished from other origins due to its extremely low Mg (15 ppm) and lower Fe and Mg. Lower Ga and Mg are characteristics of Brazil. Although the contents of Fe and Mg highly overlap with those of Zambia, the Ga (<10 ppm) of Madagascar is the lowest among the above five origins.
In order to better distinguish between Zambia and Madagascar, which are two high-Fe production areas, a three-dimensional diagram of alkali metal elements Li, Na, and K is presented in Figure 12B. From the previous text, we infer that the alkali metal content in Zambian emeralds is relatively high, and this can be further verified here. The contents of Li (2000–1000 ppm), Na (>7500 ppm), and K (100–1000 ppm) are all in the medium to high concentration range. Although the content of Na (>7500 ppm, and in some individual samples >20,000 ppm) partially overlaps with that of Ethiopia, it is generally much higher than that of other production areas. The sample data of Madagascar shows that it has a very high K (500–3000 ppm) and a lower Li (100 ppm) content. The content of Li in Russia (>700 ppm) is higher. In contrast, the content characteristics of these three alkali metal elements in emeralds from Ethiopia and Zambia do not differ much.

6. Conclusions

This study systematically analyzed the color characteristics, microscopic inclusions (including fluid and mineral inclusions), spectral properties, and chemical composition of emerald samples from the Kafubu area in Zambia using infrared spectroscopy, UV–visible spectroscopy, Raman spectroscopy, and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The results were then compared with emeralds from Afghanistan, Brazil, China, Colombia, Ethiopia, Madagascar, Russia, and the United States. This study established a global classification framework for emerald origins based on chromophores (Cr, V, Fe), categorizing deposits into two distinct groups: low-Fe regions and high-Fe regions. For high-Fe type IA emeralds, particularly those from Zambia and Madagascar exhibiting exceptionally similar Fe and Mg concentrations, a multi-element discrimination approach was developed. Using microscopic infrared testing to magnify and analyze the characteristic peaks related to OD in the range of 2550–2800 cm⁻1, it can be classified as HDO-dominant, and the high alkali metal element content in Zambian emeralds can be reflected by the absence of the HDO vOD absorption peak at 2685 cm⁻1. A further in-depth analysis of the trace elements in Zambian emeralds can provide a basis for inferring the possible rich ore geology for subsequent mining and provide more effective reference data for the identification of the origin of emeralds.

Author Contributions

Writing—original draft, Y.J.; writing—review and editing, Y.J., S.Z. and Z.Z.; investigation, B.X.; data curation, Y.J.; software, Y.J.; methodology, B.X.; resources, B.X. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Innovation and Entrepreneurship Training Program for College Students of China University of Geosciences (Beijing) (S202411415131).

Data Availability Statement

The data presented in this study are available within the article.

Acknowledgments

We would like to thank the Gemological Institute and the Laboratory of the School of Materials of China University of Geoscience, Beijing, as well as the Jewelry Appraisal Centre, the Experimental Center of Science and Research Institute of China University of Geoscience, Beijing and the Key Laboratory of Paleomagnetism and Paleotectonic Reconstruction of the Ministry of Natural Resources for providing experimental guidance.

Conflicts of Interest

The authors declare no conflict of interest.

Appendix A

Table A1. Basic gemological characteristics of Zambian emerald samples.
Table A1. Basic gemological characteristics of Zambian emerald samples.
ZMB-1ZMB-2ZMB-3ZMB-4ZMB-5ZMB-6ZMB-7ZMB-8
PictureCrystals 15 00385 i001Crystals 15 00385 i002Crystals 15 00385 i003Crystals 15 00385 i004Crystals 15 00385 i005Crystals 15 00385 i006Crystals 15 00385 i007Crystals 15 00385 i008
ColorGreen with a hint of yellowGreenGreenDark greenTurquoiseGreenDark greenGreen with a hint of yellow
TransparencyTransparentTransparentTransparentTransparentTransparentOpaqueOpaqueOpaque
Polarizing filterFour bright and four dark extinctionsFour bright and four dark extinctionsFour bright and four dark extinctionsFour bright and four dark extinctionsFour bright and four dark extinctionsFour bright and four dark extinctionsFour bright and four dark extinctionsFour bright and four dark extinctions
BicoloroscopeDichroism is moderate, blue/greenStrong dichroism, blue-green/yellow-greenStrong dichroism, blue/light greenBicolorism is moderate, blue-green/light yellow-green.UnpredictableUnpredictableUnpredictableWeak dichroism, green/light yellowish green
Refractive index1.579–1.5861.577–1.5851.575–1.5821.587–1.595UnpredictableUnpredictableunpredictable1.578–1.585
Density (g/cm3)2.73462.75822.73442.74862.73662.83242.76522.7842
Ultraviolet fluorescenceSW/LW: inertiaSW/LW: inertiaSW/LW: inertiaSW/LW: inertiaSW: inertia; LW: strong green fluorescenceSW: inertia; LW: strong green fluorescenceSW: inertia; LW: medium green fluorescenceSW/LW: inertia
Table A2. The gemological characteristics of emeralds from different origins.
Table A2. The gemological characteristics of emeralds from different origins.
Type of DepositType IA
DepositsZambiaBrazilSouth AfricaEthiopiaZambia
Under a magnifying glass to observeColorless and transparent particles attached to the surface; a large number of two/three-phase inclusions and healed fractures inside; black inclusions (black tourmaline)Negative crystals, forming CO2-rich two-phase inclusions; partially healed fissures with two-phase inclusions—typically square, rectangular, or comma-like; mineral inclusions: rounded crystals of sodic plagioclase, platelets of phlogopite, thin flakes of hematite, and clusters of minute grains of quartzCommon biotite, apatite and quartz, visible hematite, pyrite, pyrrhotite, zircon, molybdenite and galena, etc.Tiny granular grains and iridescent films; the internal growth characteristics are usually straight, presenting prismatic color bands along the crystal prism faces; mineral inclusions: brown mica flakes, plagioclase, magnetite spinel, calcite, quartz, and talcFluid inclusions are usually massive or irregularly shaped multiphase inclusions; brown mica is a common inclusion, and appears as round or pseudo-hexagonal green flakes; oxide minerals such as magnetite, hematite or ilmenite makeup
Chelsea filterDark greenPink to red (stones with saturated colors) or no reactionGreenGreenDark Green
Refractive index1.577–1.595no = 1.587–1.591; ne = 1.578–1.5831.583–1.594no = 1.580–1.593; ne = 1.569–1.584no = 1.585–1.602; ne = 1.578–1.593
SG2.73–2.832.65–2.742.752.68–2.762.71–2.81
Ultraviolet fluorescenceSW: inertia; LW: inertia/medium-strong green fluorescenceInertiaInertiaInertiaSW: inertia; LW: inertia/medium-strong green fluorescence
Data Sourcethis study[14] [31] [31] [5]
Type of DepositType IIBType IIC
DepositsUSAColombiaAfghanistan
Under a magnifying glass to observe Common serrated polyphase inclusions (containing one bubble, one large colorless cubic crystal); possibly with smaller groups of daughter crystals; mineral inclusions: feldspar, carbonate, quartz, dolomite, pyrite, black shale, etc.Small serrated fluid inclusions; rare mineral inclusions: pyrite, limonite, beryl, carbonate minerals, and feldspar
Chelsea filterGreenPink to red (stones with saturated colors) or no reaction.Pink to red
Refractive index1.581–1.588no = 1.571–1.579; ne = 1.565–1.578no = 1.577–1.590; ne = 1.570–1.582
SG2.732.65–2.732.72–2.89
Ultraviolet fluorescence SW: medium green fluorescence; LW: inertia/medium-strong green fluorescenceInertia
Data Source[31][13,32,33][31]
Table A3. The main elements and trace elements of Zambian emerald samples measured by LA-ICP-MS Trace element analysis.
Table A3. The main elements and trace elements of Zambian emerald samples measured by LA-ICP-MS Trace element analysis.
LiBeNa2OMgOAl2O3SiO2K2OScTiO2VCrMnOFeOCo
79232427293945495152555659
ppmppmwt.%wt.%wt.%wt.%wt.%ppmwt.%ppmppmwt.%wt.%ppm
ZMB-2-1293 45674 1.81 2.28 15.0 67.2 0.039 50.2 0.0036 70.9 370 0.0019 0.79 3.53
ZMB-2-2257 48026 1.89 2.57 15.6 65.2 0.037 65.6 0.0043 99.9 1087 0.0007 0.97 1.71
ZMB-2-3276 47506 1.85 2.43 15.5 65.8 0.025 66.4 0.0045 94.3 1133 0.0020 0.89 1.70
ZMB-2-4235 46271 1.68 2.19 17.1 65.1 0.035 65.2 0.0022 88.3 956 0.0019 0.80 1.70
ZMB-2-5490 46083 1.50 1.79 17.0 65.6 0.028 79.4 0.0052 63.5 44.0 0.0000 0.81 3.23
ZMB-2-6363 48239 1.86 2.35 15.7 65.5 0.018 57.3 0.0056 88.3 1090 0.0027 0.78 2.75
ZMB-2-7269 49378 1.87 2.47 15.5 65.3 0.033 70.7 0.0032 102 1083 0.0021 0.88 1.10
ZMB-2-8320 46786 1.81 2.27 16.9 64.8 0.036 73.7 0.0037 94.1 932 0.0015 0.81 1.94
ZMB-2-9402 47373 1.73 2.24 15.8 65.9 0.039 40.8 0.0036 64.3 43.2 0.0026 0.89 2.20
ZMB-2-10245 46898 1.65 2.13 16.0 66.2 0.042 53.4 0.0043 81.4 443 0.0027 0.72 2.39
ZMB-4-1341 45708 1.63 2.19 16.7 65.3 0.040 65.9 0.0038 52.1 93.1 0.0008 1.15 4.64
ZMB-4-2412 46106 1.64 2.39 16.4 65.0 0.046 23.3 0.0039 86.9 134 0.0015 1.39 3.75
ZMB-4-3240 46297 1.84 2.50 16.2 64.8 0.046 34.8 0.0042 88.5 342 0.0010 1.46 4.93
ZMB-4-4246 46856 1.84 2.48 15.1 65.7 0.042 33.2 0.0040 103 285 0.0016 1.48 3.92
ZMB-4-5256 45760 1.72 2.23 16.7 65.1 0.044 61.3 0.0035 58.4 111 0.0013 1.23 5.52
ZMB-4-6275 45806 1.65 2.09 15.5 66.6 0.039 54.1 0.0015 54.5 80.4 0.0023 1.16 4.72
ZMB-4-7290 45139 1.74 2.35 15.8 65.7 0.051 31.0 0.0047 94.2 202 0.0018 1.48 4.75
ZMB-4-8321 47841 1.97 2.63 15.2 65.5 0.028 20.0 0.0049 80.8 132 0.0000 1.10 3.97
ZMB-4-9289 46412 1.91 2.60 15.6 65.7 0.032 23.6 0.0031 79.2 116 0.0004 1.09 2.08
ZMB-4-10302 44518 1.61 2.16 15.4 66.9 0.038 63.1 0.0033 54.6 93.5 0.0020 1.22 5.05
ZMB-8-1280 45402 1.45 1.62 17.5 65.3 0.019 133 0.0029 70.9 628 0.0032 1.17 3.83
ZMB-8-2312 45919 1.42 1.60 17.5 65.4 0.019 134 0.0049 68.8 622 0.0016 1.10 3.58
ZMB-8-3321 45950 1.32 1.59 17.8 65.2 0.025 111 0.0045 71.4 583 0.0012 1.01 5.00
ZMB-8-4241 45509 1.33 1.48 16.7 66.6 0.032 126 0.0038 64.1 376 0.0011 1.02 3.36
ZMB-8-5410 47834 0.99 1.07 17.0 66.7 0.0077 39.0 0.0043 30.0 352 0.0028 0.74 2.71
ZMB-8-6321 45703 1.34 1.59 17.8 65.2 0.030 135 0.0048 70.6 447 0.0011 1.09 4.44
ZMB-8-7294 44903 1.32 1.48 17.5 65.8 0.026 122 0.0044 66.6 655 0.0026 1.09 3.39
ZMB-8-8217 45825 1.40 1.57 17.4 65.5 0.022 129 0.0048 72.1 610 0.0016 1.14 3.38
ZMB-8-9349 46775 1.26 1.47 18.2 64.8 0.014 117 0.0058 65.3 473 0.0025 1.00 4.46
ZMB-8-10297 46047 1.42 1.59 17.7 65.0 0.026 135 0.0035 71.9 600 0.0036 1.17 3.78
NiCuZnGaRbSrYSnCsBaLaCePrNd
60636671858889118133137139140141146
ppmppmppmppmppmppmppmppmppmppmppmppmppmppm
ZMB-2-117.2 0.0000 16.7 9.95 38.5 0.0000 0.0000 1.40 631 0.0000 0.0000 0.0000 0.050 0.0000
ZMB-2-231.1 1.87 22.6 12.2 45.3 0.25 0.10 0.0000 811 0.62 0.0000 0.0000 0.0000 0.0000
ZMB-2-30.0000 6.19 9.76 11.0 30.7 0.20 0.0000 4.13 443 0.0000 0.0000 0.0000 0.0000 0.0000
ZMB-2-423.9 0.90 9.56 9.33 29.0 0.036 0.0000 0.62 469 0.0000 0.021 0.0000 0.069 0.0000
ZMB-2-531.2 1.41 18.0 14.9 73.0 0.0000 0.0000 1.54 2872 0.22 0.0000 0.053 0.0000 0.0000
ZMB-2-636.3 0.0000 25.0 1.08 29.9 0.0000 0.0000 0.65 432 0.0000 0.26 0.0000 0.0000 0.0000
ZMB-2-70.0000 0.0000 18.4 7.93 28.0 0.0000 0.0000 0.0000 344 1.76 0.0000 0.0000 0.0000 0.0000
ZMB-2-810.1 1.88 6.25 6.75 27.4 0.0000 0.077 0.0000 671 0.16 0.0000 0.0000 0.0000 0.0000
ZMB-2-90.0000 0.0000 34.2 12.0 52.2 0.0000 0.043 0.32 964 0.0000 0.0000 0.0000 0.0000 0.0000
ZMB-2-102.07 1.79 17.8 6.70 20.2 0.051 0.0000 0.0000 383 0.25 0.0000 0.0000 0.0000 0.28
ZMB-4-17.19 1.26 23.0 11.6 42.1 0.0000 0.0000 0.73 1498 0.0000 0.012 0.0000 0.0094 0.054
ZMB-4-20.0000 0.0000 9.83 9.84 40.8 0.0000 0.038 0.28 1455 0.0000 0.0000 0.014 0.0000 0.0000
ZMB-4-37.97 0.0000 20.9 8.99 39.9 0.022 0.0000 0.066 1503 0.0000 0.0000 0.0000 0.0000 0.062
ZMB-4-40.0000 0.0000 23.7 10.3 40.6 0.0000 0.036 0.37 1568 0.0000 0.027 0.052 0.0000 0.25
ZMB-4-50.0000 0.24 12.1 12.2 43.7 0.030 0.024 0.0000 1406 0.0000 0.0000 0.0000 0.0000 0.084
ZMB-4-60.0000 1.90 15.7 12.2 45.3 0.0000 0.0000 0.14 1368 0.0000 0.0000 0.027 0.0000 0.0000
ZMB-4-77.73 0.0000 18.1 8.76 40.3 0.0096 0.023 0.41 1522 0.0000 0.0000 0.017 0.014 0.0000
ZMB-4-813.8 0.0000 14.6 8.92 41.3 0.051 0.0000 2.50 958 0.25 0.0000 0.0000 0.0000 0.0000
ZMB-4-90.0000 0.40 7.62 10.7 39.6 0.0000 0.0000 2.79 1014 0.0000 0.0000 0.0000 0.024 0.0000
ZMB-4-101.51 0.0000 11.7 14.0 44.2 0.0000 0.0000 0.18 1395 0.0000 0.0000 0.0000 0.0000 0.0000
ZMB-8-18.67 0.58 36.3 15.4 30.1 0.043 0.035 0.0000 675 0.0000 0.0000 0.0000 0.0000 0.0000
ZMB-8-22.80 5.22 34.5 18.1 28.9 0.0000 0.0000 0.31 684 0.0000 0.0000 0.024 0.0000 0.23
ZMB-8-30.0000 0.0000 26.9 16.2 25.6 0.0000 0.0000 0.0000 603 0.0000 0.0000 0.017 0.0000 0.0000
ZMB-8-40.0000 0.0000 32.5 13.4 22.5 0.0000 0.0000 0.0000 647 0.0000 0.0000 0.0000 0.0000 0.0000
ZMB-8-518.3 2.25 50.8 10.7 18.2 0.066 0.054 1.93 409 0.0000 0.0000 0.0000 0.0000 0.37
ZMB-8-610.2 0.0000 36.4 15.7 26.8 0.038 0.0000 0.0000 684 0.0000 0.0000 0.022 0.0000 0.0000
ZMB-8-79.71 0.15 30.9 12.4 28.2 0.13 0.081 1.45 628 0.0000 0.0000 0.020 0.0000 0.0000
ZMB-8-82.41 0.0000 29.8 16.0 25.9 0.0000 0.0000 0.0000 678 0.15 0.0000 0.0000 0.015 0.34
ZMB-8-914.4 0.0000 25.2 16.0 24.8 0.0000 0.0000 0.92 652 0.0000 0.0000 0.0000 0.0000 0.0000
ZMB-8-1010.9 0.0000 35.3 15.1 30.5 0.033 0.0000 0.0000 699 0.0000 0.0000 0.038 0.0000 0.091
SmEuGdTbDyHoErTmYbLuHfTaWPb
147153157159163165166169172175178181182204
ppmppmppmppmppmppmppmppmppmppmppmppmppmppm
ZMB-2-10.33 0.088 0.89 0.0000 0.35 0.0000 0.0000 0.0000 0.20 0.0000 0.14 0.0000 0.063 0.0000
ZMB-2-20.40 0.0000 0.36 0.0000 0.0000 0.0000 0.15 0.0000 0.0000 0.10 0.0000 0.053 0.0000 0.0000
ZMB-2-30.32 0.0000 0.28 0.0000 0.0000 0.0000 0.0000 0.0000 0.37 0.082 0.27 0.0000 0.18 0.0000
ZMB-2-40.0000 0.0000 0.10 0.0000 0.0000 0.0000 0.044 0.014 0.20 0.060 0.0000 0.0000 0.0000 4.06
ZMB-2-50.0000 0.0000 0.0000 0.020 0.0000 0.020 0.11 0.018 0.0000 0.019 0.0000 0.0000 0.0000 0.0000
ZMB-2-60.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.21 0.0000 0.15 0.0000 0.20 4.67
ZMB-2-70.0000 0.0000 0.0000 0.051 0.20 0.0000 0.0000 0.048 0.075 0.017 0.0000 0.0000 0.22 4.49
ZMB-2-80.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.026 0.0000 0.013 0.0000 0.16
ZMB-2-90.0000 0.090 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0073 0.15 0.0000 0.0000 2.52
ZMB-2-100.0000 0.0000 0.0000 0.022 0.087 0.0000 0.0000 0.041 0.0000 0.042 0.0000 0.0000 0.093 1.79
ZMB-4-10.062 0.033 0.055 0.0000 0.0000 0.0000 0.0000 0.0000 0.037 0.033 0.054 0.0000 0.0000 0.0000
ZMB-4-20.076 0.0000 0.067 0.0000 0.0000 0.0000 0.0000 0.0000 0.13 0.0099 0.033 0.0000 0.043 1.07
ZMB-4-30.0000 0.0000 0.064 0.0096 0.0000 0.0000 0.055 0.0000 0.17 0.0093 0.0000 0.0000 0.0000 0.0000
ZMB-4-40.0000 0.0000 0.0000 0.0000 0.0000 0.019 0.17 0.0000 0.085 0.019 0.062 0.038 0.0000 0.0000
ZMB-4-50.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.025 0.0000 0.0000 0.056 0.0000
ZMB-4-60.15 0.0000 0.0000 0.0000 0.16 0.0000 0.0000 0.038 0.27 0.0000 0.0000 0.020 0.0000 0.94
ZMB-4-70.0000 0.025 0.083 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.024 0.0000 0.0000 0.0000 0.51
ZMB-4-80.0000 0.0000 0.0000 0.0000 0.088 0.0000 0.0000 0.0000 0.097 0.0000 0.0000 0.022 0.28 0.0000
ZMB-4-90.16 0.0000 0.0000 0.022 0.086 0.0000 0.062 0.0000 0.095 0.042 0.069 0.0000 0.18 4.05
ZMB-4-100.13 0.034 0.0000 0.0000 0.069 0.017 0.0000 0.0000 0.076 0.017 0.055 0.017 0.0000 4.14
ZMB-8-10.0000 0.0000 0.0000 0.0000 0.037 0.0093 0.0000 0.017 0.041 0.0090 0.030 0.0000 0.0000 0.0000
ZMB-8-20.13 0.036 0.12 0.0000 0.0000 0.018 0.052 0.0000 0.080 0.018 0.0000 0.0000 0.23 0.0000
ZMB-8-30.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
ZMB-8-40.0000 0.0000 0.0000 0.023 0.0000 0.0000 0.0000 0.021 0.10 0.022 0.15 0.0000 0.097 5.47
ZMB-8-50.0000 0.0000 0.0000 0.0000 0.0000 0.029 0.0000 0.0000 0.13 0.0000 0.0000 0.0000 0.12 7.28
ZMB-8-60.0000 0.0000 0.11 0.0000 0.0000 0.017 0.0000 0.0000 0.0000 0.032 0.0000 0.0000 0.0000 4.00
ZMB-8-70.0000 0.0000 0.097 0.015 0.0000 0.0000 0.0000 0.014 0.0000 0.0000 0.047 0.0000 0.12 0.0000
ZMB-8-80.099 0.0000 0.18 0.013 0.053 0.0000 0.0000 0.0000 0.0000 0.0000 0.043 0.0000 0.056 2.88
ZMB-8-90.0000 0.0000 0.0000 0.031 0.12 0.0000 0.0000 0.029 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
ZMB-8-100.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.063 0.0000 0.0000 0.014 0.0000 2.27
Table A4. LA–ICP-MS of the samples from different origins in ppmw.
Table A4. LA–ICP-MS of the samples from different origins in ppmw.
SamplesElementMin–MaxAverage (SD)Median
Panjsher, Afghanistan
38 samples
[17]		Li93–254172.6161
Na1072.4–12,6806345.86269.4
Mg1320–14,3006510.75786.0
K33.3–713.6496.1662.3
Sc76–669.1275.5277
V36–26801306.41710
Cr576–47401353.81255
Mn---
Fe1394.7–65103202.22235
Co---
Ni---
Zn---
Ga14.4–38.621.517.4
Rb20.2–10265.147.5
Cs35.3–52.340.838.1
Itabira, Brazil
301 samples
(54 samples, [11];
247 samples, [12])		Li30.3–35957.955.1
Na3598–6305.94912.14989.0
Mg6814.3–12,422.79214.39256.7
K33.2–1150257.7238.5
Sc17.5–15360.351.2
V52.5–177116.5117.5
Cr997–57002508.52360
Mn4.5–24.114.113.4
Fe2460–91205225.55217.2
Co1.9–3.02.472.47
Ni----
Zn28.4–87.455.357.2
Ga6.7–13.811.411.9
Rb7.4–91.833.231.3
Cs16.8–113094.078.7
Dayakou, China
126 samples
(112 samples, [34];
6 samples, [25];
8 samples, [35])		Li159.7–654.2345.6320.5
Na4590.3–15,442.08323.08140.4
Mg2634–10,149.35883.35585.2
K11.9–1761.1247.7168.1
Sc7.1–163.063.257.2
V598–11,788.93635.23150.9
Cr1.6–1053.4117.743.9
Mn24.0–272.568.562.0
Fe1266.6–12,9643302.22962
Co0.26–4.151.851.40
Ni9.0–313.9111.393.2
Zn12.5–1489.3117.758.9
Ga4.0–35.910.911.2
Rb8.0–73.123.321.9
Cs535.2–5034.31731.51607.0
Muzo, Colombia
250 samples
(24 samples, [11];
3 samples, [16];
25 samples, [26];
11 samples, [27];
187 samples, [8])		Li24–1647266.6
Na1483.7–98603062.22262.7
Mg1720–68303986.13769.6
K5.4–35922.217.1
Sc2–1093353.0226.6
V317–13,1904675.43520.0
Cr172–10,7003309.52388.5
Mn38–817267.569.5
Fe16.8–5001285.270.0
Co0.02–1.690.260.12
Ni0.29–468.54.5
Zn1–53866.235.5
Ga9.75–7842.339.4
Rb0.6–133.62.0
Cs2.2–5611.310.5
Halo-Shakiso, Ethiopia
191 samples
(20 samples, [11];
2 samples, [16];
11 samples, [28];
4 samples, [12];
3 samples, [29];
151 samples, [17])		Li177.9–531305.4302.1
Na6342.9–15,0009716.47771.0
Mg8750–15,377.613,684.014,171.5
K7.6–889341.7336.9
Sc30.5–150.086.065.1
V85–129105.8102.7
Cr734.3–50102810.92625.0
Mn7.9–75.123.719.6
Fe1960.7–53904020.94006.2
Co1.3–13.82.01.6
Ni8.3–16.012.312.9
Zn20.8–14647.439.4
Ga16.4–24.220.019.6
Rb14.7–16661.260.1
Cs151–675372.4368
Mananjary, Madagascar
165 samples
(26 samples, [11];
2 samples, [16];
12 samples, [27];
4 samples, [8];
113 samples, [36];
8 samples, [30])		Li35–712.2113.9114.8
Na2003.0–8939.57141.17344.5
Mg5608.3–18,995.815,363.815,618.8
K107–31501473.21200
Sc19–30974.248.0
V52–386177.5145.0
Cr232–37701852.51570
Mn4–28.514.515
Fe3320–15,8699315.09140.0
Co1.7–4.53.03.0
Ni9–57.528.227.0
Zn5–12020.915.8
Ga6.1–13.18.88.3
Rb12.7–407.0140.4139.0
Cs97–1945548326
Malysheva, Russia
199 samples
(15 samples, [11];
3 samples, [16];
4 samples, [12];
177 samples, [36])		Li298.4–1641.9747.9738
Na2596.5–4562.53387.83152.9
Mg2834.3–6271.64237.43859.5
K30.5–88301361.595.5
Sc19.5–14858.954.6
V29.8–189.798.1101.9
Cr318–1700820.5775.5
Mn13.5–22.619.220.6
Fe864–88002497.62215.6
Co1.1–2.11.51.5
Ni13.4–23.217.617.6
Zn38.1–62.648.645.4
Ga6.3–19.513.713.7
Rb7.9–36145.716.3
Cs107–2180504.2308
USA
29 samples
[27]		Li---
Na---
Mg---
K---
Sc---
V7.5–31.619.216.3
Cr23.5–40301082.9933
Mn---
Fe125–24601087.41180
Co---
Ni---
Zn---
Ga---
Rb---
Cs---
Kafubu, Zambia
8 samples, this study		Li84–1140554.7569.7
Na7233–23,70014,614.715,326.1
Mg8030.5–23,90015,38415,256
K30–2728513.4466
Sc2.7–1534320.9292.4
V29.9–778153.4112.7
Cr43.2–10,8002047.91771.6
Mn5.3–10321.916.4
Fe4620–22,0008941.48999.9
Co0.9–7.173.12.74
Ni4.7–5018.518.7
Zn3.2–204.429.020.9
Ga1.1–50.513.813.4
Rb9.3–493.670.856.4
Cs128.4–2872.21285.31186.6

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Figure 1. Geological map of Zambia’s regional mining area. (A) The general map of southern Africa. (B) The geological and emerald mining area distribution map of the Kafubu area in Zambia, including the sample collection mining site Kamakanga of this study. Modified from [1].
Figure 1. Geological map of Zambia’s regional mining area. (A) The general map of southern Africa. (B) The geological and emerald mining area distribution map of the Kafubu area in Zambia, including the sample collection mining site Kamakanga of this study. Modified from [1].
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Crystals 15 00385 g002
Figure 2. Eight emerald samples (i.e., ZMB-1–ZMB-8) from Zambia analyzed in this study.
Figure 2. Eight emerald samples (i.e., ZMB-1–ZMB-8) from Zambia analyzed in this study.
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Crystals 15 00385 g003
Figure 3. Fractures and fluid inclusions in Zambian emerald samples. (A) Shaped negative crystals, filled with liquid inside and a single bubble. (B) Fractures and a large quantity of two-phase inclusions. (C) Regular short columnar three-phase inclusion. (D) A large number of irregular fluid-like inclusions with reddish brown minerals inside.
Figure 3. Fractures and fluid inclusions in Zambian emerald samples. (A) Shaped negative crystals, filled with liquid inside and a single bubble. (B) Fractures and a large quantity of two-phase inclusions. (C) Regular short columnar three-phase inclusion. (D) A large number of irregular fluid-like inclusions with reddish brown minerals inside.
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Crystals 15 00385 g004
Figure 4. Mineral inclusions in Zambian emerald samples. (A) In ZMB-4, reddish brown flaky inclusions that are densely distributed within the emerald. (B) In ZMB-8, reddish brown flaky inclusions of varying shades. (C) In ZMB-5, black long columnar inclusions wrapped inside the mineral. (D) In ZMB-5, black irregularly shaped minerals and colorless short columnar minerals exposed on the mineral surface.
Figure 4. Mineral inclusions in Zambian emerald samples. (A) In ZMB-4, reddish brown flaky inclusions that are densely distributed within the emerald. (B) In ZMB-8, reddish brown flaky inclusions of varying shades. (C) In ZMB-5, black long columnar inclusions wrapped inside the mineral. (D) In ZMB-5, black irregularly shaped minerals and colorless short columnar minerals exposed on the mineral surface.
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Crystals 15 00385 g005
Figure 5. Raman spectra of mineral inclusions in Zambian emeralds. (A) Raman spectra of black tourmaline in ZMB-7. (B) Raman spectra of quartz in ZMB-8. (C) Raman spectra of silica beryllium in ZMB-8.
Figure 5. Raman spectra of mineral inclusions in Zambian emeralds. (A) Raman spectra of black tourmaline in ZMB-7. (B) Raman spectra of quartz in ZMB-8. (C) Raman spectra of silica beryllium in ZMB-8.
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Figure 6. Representative IR spectra of emerald samples in the range of 600–1500 cm−1.
Figure 6. Representative IR spectra of emerald samples in the range of 600–1500 cm−1.
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Figure 7. The FTIR patterns of HDO and D2O molecules in Zambian emerald sample.
Figure 7. The FTIR patterns of HDO and D2O molecules in Zambian emerald sample.
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Figure 8. UV–Vis–NIR spectra of emerald samples from Zambia.
Figure 8. UV–Vis–NIR spectra of emerald samples from Zambia.
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Crystals 15 00385 g009
Figure 9. Three FTIR patterns of HDO and D2O molecules in emeralds. Modified from Zheng et al., 2024 [15]. The black solid lines represent Zambian emerald samples used in the experiment.
Figure 9. Three FTIR patterns of HDO and D2O molecules in emeralds. Modified from Zheng et al., 2024 [15]. The black solid lines represent Zambian emerald samples used in the experiment.
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Crystals 15 00385 g010
Figure 10. Ternary plot of Cr vs. V vs. Fe. The reference data are shown in Table A4 [12,15,16,25,26,27,28,29,30].
Figure 10. Ternary plot of Cr vs. V vs. Fe. The reference data are shown in Table A4 [12,15,16,25,26,27,28,29,30].
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Crystals 15 00385 g011
Figure 11. Box plot of representative metallic elements (Fe, Ga, Sc, Li, Na, K, Rb, Cs, Mg) in Zambia, Madagascar, Brazil, Ethiopia, and Russia. The reference data are shown in Table A4.
Figure 11. Box plot of representative metallic elements (Fe, Ga, Sc, Li, Na, K, Rb, Cs, Mg) in Zambia, Madagascar, Brazil, Ethiopia, and Russia. The reference data are shown in Table A4.
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Crystals 15 00385 g012
Figure 12. (A) Three-dimensional graph of Fe, Mg, and Ga. (B) Three-dimensional graph of Li, Na, and K. The reference data are shown in Table A4.
Figure 12. (A) Three-dimensional graph of Fe, Mg, and Ga. (B) Three-dimensional graph of Li, Na, and K. The reference data are shown in Table A4.
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Jiang, Y.; Zhao, S.; Zhang, Z.; Xu, B. Gemological Characteristics and Trace Chemical Element Analysis of Emerald in Kafubu, Zambia. Crystals 2025, 15, 385. https://doi.org/10.3390/cryst15050385

AMA Style

Jiang Y, Zhao S, Zhang Z, Xu B. Gemological Characteristics and Trace Chemical Element Analysis of Emerald in Kafubu, Zambia. Crystals. 2025; 15(5):385. https://doi.org/10.3390/cryst15050385

Chicago/Turabian Style

Jiang, Yiwei, Siyi Zhao, Zhiyi Zhang, and Bo Xu. 2025. "Gemological Characteristics and Trace Chemical Element Analysis of Emerald in Kafubu, Zambia" Crystals 15, no. 5: 385. https://doi.org/10.3390/cryst15050385

APA Style

Jiang, Y., Zhao, S., Zhang, Z., & Xu, B. (2025). Gemological Characteristics and Trace Chemical Element Analysis of Emerald in Kafubu, Zambia. Crystals, 15(5), 385. https://doi.org/10.3390/cryst15050385

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