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Article

A Study on Beryl in the Cuonadong Be-W-Sn Polymetallic Deposit, Longzi County, Tibet, China

by
Jia-Qi Shen
1,
Zhi-Kang Hu
2,
Shi-Yuan Cui
1,
Yu-Fei Zhang
3,
En-Qi Li
1,
Wei Liang
4 and
Bo Xu
1,*
1
School of Gemmology, China University of Geoscience Beijing, 29 Xueyuan Road, Haidian District, Beijing 100083, China
2
Department of Conservation Science, The Palace Museum, 4 Jingshan Front Street, Dongcheng District, Beijing 100009, China
3
School of Earth Sciences and Resources, China University of Geoscience Beijing, 29 Xueyuan Road, Haidian District, Beijing 100083, China
4
Chengdu Institute of Geology and Mineral Resources, China Geological Survey, No.2, North Section 3, 1st Ring Road, Chengdu 610081, China
*
Author to whom correspondence should be addressed.
Crystals 2021, 11(7), 777; https://doi.org/10.3390/cryst11070777
Submission received: 9 May 2021 / Revised: 23 June 2021 / Accepted: 26 June 2021 / Published: 2 July 2021
(This article belongs to the Special Issue Gem Crystals)
Browse Figures
Versions Notes

Abstract

:
Recently, aquamarine was discovered in the Cuonadong Be-W-Sn Polymetallic Deposit, Longzi County, Tibet. Longzi aquamarine is being extracted and is expected to be available over the next decade. This study provides a full set of data through standard gemmological properties, including scenes, color characteristics and advanced spectroscopic and chemical analyses, including micro ultraviolet–visible–near-infrared (UV–Vis–NIR), Raman and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The main inclusions in Longzi aquamarine are gas–liquid inclusions and a great number of quartz inclusions. The content of type I H2O is greater than that of type II H2O because of the low-alkali metal content, and “tetrahedral” substitutions and “octahedral” substitutions exist at the same time.

1. Introduction

Beryl is a common beryllium-bearing cyclosilicate mineral with high transparency, similar to many gem-quality minerals. The iron-bearing green–blue, blue–green or light blue–blue beryl is known as aquamarine. Most aquamarine is generated in highly evolved leucogranites, such as in the Aracuai orogen in Brazil [1].
Crystals 11 00777 g001 550
Figure 1. Aquamarine-producing areas (grey parts). The red dot locates Longzi County. Other sources are [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22].
Figure 1. Aquamarine-producing areas (grey parts). The red dot locates Longzi County. Other sources are [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22].
Crystals 11 00777 g001
Recently, beryl in pegmatite has been found in the Cuonadong dome in Longzi County, Tibet (Figure 1), and some is gem-quality aquamarine. Wang et al. [23] found that beryllium mineralization is quite common in the Himalayan leucogranite belt in southern Tibet, especially in pegmatites such as Ranba, Xiaru, Gaowu, Cuona and Cuonadong. Beryllite content is high, and the crystal form of beryl is complete, up to 1 cm × 1 cm × 3 cm in size. The color is usually light green to dark green, some of the colors can reach the aquamarine level. Huang [24] also found pegmatite containing beryl in the Lalong dome not far from the Cuonadong dome.
In this study, we selected the crystal of aquamarine and the polished chips of aquamarine and adjacent rock in the Cuonadong dome, and we use gemmological tests, spectroscopy tests, inclusion examinations, and major and trace element analyses to illustrate the characteristics of Cuonadong aquamarine and genesis of the deposits. The study also contributes to further resource development in Tibet.
Owing to the lack of studies on aquamarine deposits in the region, the advantages of this study are: (1) it can fill the gaps in the gemmology and mineralogy of aquamarine, and (2) the Himalayan pale granite has a wide range of rare metal mineralization, and beryl and other rare metal minerals are widely distributed, so beryl mineralization has a great potential. The results of this study will provide theoretical support for beryllium and beryl mineralization research in this area.

2. Geological Setting

The Cuonadong super-large Be-W-Sn polymetallic deposit with great economic value is located in the Cuonadong dome, South Tibet. The Cuonadong dome of southern Tibet is located in the THS belt between the Indus–Yaluzangbu River suture zone and Indian plate [25,26,27] (Figure 2a).
The Himalaya tectonic belt can be divided into the northern Himalaya (the THS), higher Himalaya, lower Himalaya and sub-Himalaya from north to south [28]. The Northern Himalayan Gneiss Dome Belt is located in the THS and consists of a series of dome structures oriented E–W [29]. Moreover, there are near E–W-trending leucogranite belts on the THS and higher Himalaya, and the leucogranite belts located in the northern Himalaya are mostly in the form of intrusive stocks in the Tethys dome [30] (Figure 2a,c).
The Cuonadong dome is near the South Tibet Detachment System. The dome consists of three parts: core, mantle and edge (a ring-banded structure). The dome core is formed by granite gneiss and leucogranite and is interspersed by a large number of pegmatite dikes, which are usually blocky texture cut by granite or veins that cut through the gneiss [32] (Figure 2b). Pegmatite is composed of K-feldspar, plagioclase, quartz, muscovite, biotite, and apatite. The widespread apatite consistent with most porphyries in Tibet [33,34], has relatively high Be and Li contents [35] and has beryl formed in it (Figure 3).

3. Materials and Methods

Three beryl crystals (L1 to L3) and two pegmatite slices (LZ-1 and LZ-2) of beryl in Longzi County were examined using standard gemmological techniques.
The gemological tests for the samples were conducted at the Gemological Research Laboratory of China University of Geosciences (Beijing) to determine their optical properties, hydrostatic specific gravity, UV fluorescence and microscopic and macroscopic features.
The refractive index (RI) and birefringence (DR) of the crystal polishing surface were measured with a refractometer (Xueyuan Jewelry Technologies, Wuhan, China) using diiodimethane as refractive oil. The specific gravity (SG) of the sample was obtained by hydrostatic weighing method. The samples was observed by Chelsea Color Filter (CCF) (Baoguang Technologies, Nanjing, China) and it’s fluorescence was observed by the ultraviolet light with main wavelengths of 365 nm and 254 nm.
The ultraviolet–visible (UV–Vis) spectroscopy test used a UV-3600 UV–Vis spectrophotometer ((Shimadzu Corporation, Kyoto, Japan) to measure the absorption value. Slit width: 2.0 nm. Time constant: 0.1 s. Wavelength range (nm): 200.00 to 900.00. Scanning speed: high speed. Sampling interval: 0.5.
A Horiba HR Evolution-type micro-confocal laser Raman spectrometer (Horiba, Ltd., Kyoto, Japan) was used to perform a Raman spectroscopy test at. Laser source: 532 nm. Slit width: 100 μm. Grating: 600 gr/mm. Scan time: 4 s. Integration times: 3. ICS correction range: 100–4000 cm−1.
In this experiment, a laser sheet of LZ-2 was selected as a sample. Uniform parts with no inclusions in beryl were selected for the test to obtain more representative element contents.
Major-element compositions of minerals were measured using a four-spectrometer Jeol JXA 8100 electron probe microanalyzer (JEOL Ltd., Akishima, Japan) in the Key Laboratory of Submarine Geosciences, State Oceanic Administration, Second Institute of Oceanography, Ministry of Natural Administration, with an accelerating potential of 15 kV, a beam current of 20 nA, a counting time of 20 s and a spot size of 10 μm. Element peaks and background were measured with counting times of 10 s and 5 s. NaAlSi2O3 (Na), KAlSi3O8 (k), Cr2O3 (Cr), Diopside (Si, Mg, Ca), Fe2O3 (Fe), Pyrope (Al), Mn2O3 (Mn), TiO2 (Ti) and Ca5P3F (P) have been used as standards. ZAF correction schemes were used for calibration.
Trace-element compositions of minerals were measured using laser-ablation inductively coupled plasma mass spectrometry (LA-ICPMS) (Agilent Technologies, Santa Clara, CA, America) in the Ore Deposit and Exploration Centre, School of Resources and Environmental Engineering, Hefei University of Technology. The laser ablation system was CetacAnalyte HE, and the ICP-MS model was Agilent 7900. The ablation was carried out in He gas, which was then mixed with Ar gas to introduce the samples into the ICPMS.
In determining the mineral trace element content, we used multiple reference standards such as BCR, SRM610 and SRM612, and multiple external standards without internal standards for quantitative calculation. The results were processed and exported using ICPMSD 12.0 [36].

4. Results

4.1. Visual Appearance and Gemmological Properties

The beryl samples are light blue to green–light blue and transparent to translucent with incomplete cleavage and a glassy luster. The fracture has a conchoidal fracture or uneven shape and has a glassy to resin luster. The crystal is hexagonal columnar and hexagonal thick plate-like. The thick parallel plate shows completely parallel doubly terminated (0001) faces. Aquamarine sizes range from 5 mm to 3 cm (Figure 4a–d).
The transparency of the sample is poor under 40× magnification and dark-field illumination (Figure 4b). A large number of cracks are observed, and there are dark inclusions inside and pits on the surface. The longitudinal striation are visible on the crystal face parallel to the c-axis.
The refractive index of the polished A-1 specimen is measured using a gem refractometer. The sample refractive index is 1.578 to 1.583. All samples are inert to longwave and shortwave UV radiation. The specimens are all blue–green under the Chelsea color filter (CCF). The specific gravity (SG) values varied between 2.59 and 2.65.

4.2. Spectral Characteristics

4.2.1. UV–Vis Spectrum

The absorption spectrum of aquamarine is studied using a UV–Vis spectrophotometer. The spectrum of the slices perpendicular and parallel to the c-axis of the sample crystal A-1 is shown in Figure 5.
One wide peak is observed between 700 and 900 nm in both directions. However, the absorption peaks of the slices parallel to the c-axis are wider than those of the slices perpendicular to the c-axis. According to Wood and Nassau [37] and Goldman [38], the absorption peaks in the No (the index of refraction of the ordinary-ray) direction are related to the six coordinated Fe2+ ions that replace the Al3+ ions in the octahedron. The absorption peaks in the Ne (the index of refraction of the especial-ray) direction are caused by the Fe2+ ions in the tunnel structure.

4.2.2. Raman Spectrum

By comparing the Raman spectrum of the beryl on the slice with that in the literature [8,39], we found the following characteristic peaks in the range of 200–1500 cm−1: a strong absorption peak at 685 cm−1 caused by the Si–O–Si internal vibration of deformation, an absorption peak at 1068 cm−1 caused by the Si–O internal vibration of non-bridging oxygen expansion, an absorption peak at 1011 cm−1 caused by the Be–O outer vibration of non-bridging oxygen expansion, an absorption peak at 398 cm−1 caused by the Al–O outer vibration of deformation and an absorption peak at 323 cm−1 caused by the Al–O outer vibration of bending. There are some impure peaks around the range of 400–700 cm−1 (Figure 6a).
The Raman spectrum of the aquamarine channel water is in the 3590–3620 cm−1 range (Figure 6b). A band at 3610 cm−1 (related to type I H2O) is narrow and strong. However, a band at 3600 cm−1 (related to type II H2O) is weak and wide. According to the area ratio, the proportion of type I H2O and type II H2O contents can be calculated: the type I H2O content of Longzi aquamarine is approximately 70–80%.

4.3. Inclusions

The fluid inclusions of beryl in the polished chips are observed under a 50× objective single polarizing microscope (Figure 7c). There are abundant of gas–liquid two-phase needle-like fluid inclusions parallel to the c-axis in the Longzi beryl. They are approximately 10–40 μm long and densely arranged.
There are also a large number of colorless and transparent solid inclusions, whose relief is the same (but slightly lower) as that of the main crystal of beryl (Figure 7c). Because of the thickness limitation of the sheets, the solid inclusions are mostly sheet-like. However, the crystal edges of the solid inclusions are partly visible. Therefore, they may be crystal inclusions. The sizes of such inclusions are approximately 20–80 μm, appearing individually or in groups.
By comparing the Raman spectrum with the standard spectrum, we determined that the solid inclusions are quartz. The characteristic peaks and corresponding vibrations of the quartz inclusions are listed in Figure 7b. The peak at 1161 cm−1 is considered the characteristic peaks of Si–O asymmetric stretching vibration. Two peaks at 808 and 697 cm−1 are caused by Si–O–Si symmetric stretching vibration. The peaks at 466, 396, 353 cm−1 are considered the characteristic peaks of Si–O bending vibration, and the peak at 265 cm−1 is related to the vibration of SiO4 [40]. In addition to the needle-like fluid inclusions parallel to the c-axis, some separate large fluid inclusions can be found in Longzi aquamarine, varying in shapes: rectangular (Figure 8a), oval (Figure 8b) and jagged (Figure 8c,d).
These non-c-axis parallel inclusions isolated and randomly distributed, they exhibit primary textures. The length of these fluid inclusions is approximately 40–50 μm, and the width is approximately 20 μm (Figure 8).
Four fluid inclusions with different shapes and sizes were selected for Raman spectroscopy. These fluid inclusions are two-phase inclusions in which the gas volume is less than that of the liquid one. The gas and liquid compositions are subjected to Raman spectroscopy. The results are as follows.
These non-c-axis parallel inclusions isolated and randomly distributed, they exhibit primary textures. Under the microscope, some inclusions in the beryl are selected for the Raman spectrum test. The results are shown in Figure 8. A band at 3406 cm−1 is considered the characteristic peak of H2O in the inclusions. The peaks at 3600 and 3609 cm−1 are considered the characteristic peaks of type I and type II H2O in the beryl. The N–N bonding Raman spectrum peak at 2331 cm−1 shows that the inclusions contain N2. Two peaks at 1238 and 1385 cm−1 are caused by the Fermi coupling resonance in the CO2 molecule, and the small peaks on both sides are the hot bands of CO2. The peak at 686cm−1 is caused by Si–O–Si bending vibration. The peaks at 1011 and 1069 cm−1 indicate the existence of HCO3− and CO32−, respectively [41]. By analyzing the gas and liquid parts of the same inclusion, it can be seen that the gas part has strong CO2 and N2 peaks, whereas the liquid part has strong H2O peaks.

4.4. Major and Trace Elements

The major and trace elements of LZ-2 are listed in Table A1 and Table A2a,b in Appendix A. According to the test results and calculation of the major and trace elements, the major element contents constituting the beryl chemical formula are SiO2 = 65.045 wt%–65.025 wt%, Al2O3 = 17.180 wt%–18.106 wt%. Be is a major element in beryl, so the results measured by LA-ICP-MS are inaccurate. We used the data measured by EPMA and calculated the ratio of ideal chemical formula to obtain BeO = 12.928 wt%–13.555 wt%. Through calculation, it was found that the chemical formation of LZ-2 is: ch(Na0.079,K0.002)T2Be2.929(Fe0.047,K0.003,Cr0.002,Mg0.005,Mn0.005,Ti0.001)oAl1.914T1Si6.016O18.
The content of the coloring element Fe is 3071.26–6790.75 ppm, and the alkali metal contents are as follows: Li = 649.18–890.43 ppm, Na = 3010.52–5208.05 ppm, K = 93.20–2048.01 ppm and Cs = 758.42–1165.14 ppm. Alkali ions exist because of the lack of equilibrium positive charge [13]. A thorough analysis is presented in Section 5.4.

5. Discussion

5.1. Gemmological Characteristics

The test results, compared with existing aquamarine data from other places (Table A3), show that the optical and physical properties of almost all aquamarine are approximately the same. The color of Longzi aquamarine varies from light green–blue to blue and is lighter than that of other aquamarines. A better color may be obtained through heat treatment and so forth. Most crystals have hexagonal columns and thick plates. The particle size varies from 5 mm to 3 cm, smaller than the size of aquamarine in other places, but larger ones may be found in future development. Most of the crystals have low transparency and many cracks. Moreover, the values of No and Ne of Longzi aquamarine are the same as those of other producing areas.

5.2. Water Molecules in the Channels

Beryl has an open honeycomb hexagonal ring structure [42]. This hexagonal ring structure is cumulatively stacked into open cavities along the c-axis [43] (Figure 9). In beryl, H2O molecules are ordered and oriented in crystal cavities [44].
With the increased alkali content in beryl, the proportion of type II H2O and intensity of its spectrum rose [37]. Zou’s [46] research on beryl with different colors in different producing areas shows that the components of the standard blue, blue–green, yellow–green and green beryl are the same, and the only difference is between the proportion of type I H2O and type II H2O. Green, yellow–green and blue–green beryl will become pure blue aquamarine when the ratio of type I and type II H2O becomes 1:1 [46]. The type I H2O content of Longzi aquamarine is approximately 70–80%. By controlling the temperature and pressure to transfer some type I H2O molecules to the position of type II H2O molecules to increase the proportion of type II H2O, the color of Longzi aquamarine will be more vivid, which can increase the commercial value of aquamarine significantly [46].

5.3. Inclusions

Generally, aquamarine is rich in fluid inclusions. Multiphase inclusions of different shapes are frequently seen in aquamarine from various origins. As distinguishing features of aquamarine, short needle-like two-phase inclusions are also important in Longzi aquamarine. There are a large number of solid inclusions in Longzi aquamarine, and quartz is one of such characteristic inclusions.
Longzi aquamarine abounds with needle-like fluid inclusions approximately 10–40 μm long. Moreover, there exist some fluid inclusions approximately 40–50 μm long and 20 μm wide. The fluid composition is H2O, CO2 and their solution. An N2 characteristic peak is found in the gas portion, indicating that it may contain N2, H2O and CO2 as volatile components, which can be indicators of fugacity when the host crystals formed [45]. This indicates that Longzi aquamarine is formed in a fluid-rich environment. CO2 is the highest valence state of C, and CO2 and H2O in the inclusions are the final products of oxidation. The presence of strong reducing components such as CH4 is not detected in beryl, so the CO2 and H2O in beryl should be generated by the oxidation of CH4 [47], and the magmatic melt may have evolved from a reducing environment to an oxidizing environment.

5.4. Major and Trace Elements

In the beryl crystal structure, there are “octahedral” cation substitutions: Al3+ can be replaced by divalent cations such as Mg2+, Fe2+ and Mn2+ or trivalent cations such as Fe3+, Cr3+, V3+ and Sc3+ [19]. Fe is the most important substitute for Al in Longzi aquamarine. By comparing the Fe-Al substitution to other areas, it can be seen from Figure 10a that there is a significant negative correlation between Al and Fe. Figure 10b shows Al versus the sum of its substituents at the Y site of aquamarine from Longzi and other areas, The data points are evenly distributed near the straight line with Al = 2 apfu and ∑ substitutions in Y site = 1 apfu [13] as the endpoints. It can be seen that there are “octahedral” substitutions in Longzi aquamarine. The substitutional trend in Longzi aquamarine is consistent with most producing area which has relatively high content of Al. In Canada and Vietnam, the Y site values are very high and significantly different from aquamarine from other producing areas.
Li+ mainly replaces Be2+ in [BeO4] tetrahedron, whereas Na+, CS+ and other ions with large radii are distributed in the channel of the beryl structure [50] to compensate for the charge imbalance caused by Li+ replacing Be2+.
Since divalent cations substitute trivalent Al3+ in octahedron, the monovalent cations in the channel need to balance the electricity price. Therefore, the sum of divalent cations in octahedral site (R2+) and monovalent cations in channel (A+) should be proportional to the ideal state, and the slope is 1 [13,19]. It can be seen from Figure 11 that the sum of R2+ and A+ of Longzi aquamarine are close to 1:1, but some points are above the 1:1 line, which indicates that there is a certain amount of Li substituting Be in the tetrahedral T1 position, and there may be “tetrahedral” substitutions in Longzi aquamarine.
After Li+ replaces Be2+, Na+ enters the channels of the structure to maintain charge balance, but Cs+ becomes the main charge balance cation in the pegmatite samples with a higher evolution degree. Generally, when the Na/Li value is 2 to 4, the charge balance changes from Na-dominant to Cs-dominant compensation [51,52]. Using the Na/Li versus Cs diagram for late primary beryl from granitic pegmatites by [53] as the basic model and taking Cs (wt%) content as the abscissa and Na/Li value as the ordinate based on the analysis of the Na, Li and Cs contents of Longzi aquamarine, we conclude that Longzi aquamarine is located in area A in Figure 12, indicating that the pegmatite producing Longzi aquamarine is a barren and geochemically primitive beryl-type pegmatite (including most pegmatites of the rare-earth type).
In Longzi aquamarine, the experimental results also show that the NaO content is between 0.41 and 0.70 wt%. The K2O content is between 0.01 and 0.45 wt%. The Cs2O content is between 0.161 and 0.247 wt%, and the ratio of Na2O/K2O to Na2O/Cs2O is greater than 1. According to the ratio relationship of Na2O/K2O to Na2O/Cs2O by ČErný P et al. [52], because of the ratio value greater than 1, Longzi aquamarine classified as “sodic lithian beryls”.
Li and Cs contents are positively related. The Li versus Cs content shows two concentrated areas: the “low-alkali beryl” and “high-alkali beryl” areas. As observed in Figure 13, aquamarine in most areas belongs to the “low-alkali beryl” area, including Longzi aquamarine.
For aquamarine, Fe is the chromogenic element. By analyzing the Cr-Fe-V content of aquamarine (Figure 14) based on the Cr–Fe–V ternary diagram of the emerald chromogenic element by [56], we conclude that the Cr and V abundance of aquamarine is very low, indicating that as little as 0.04-wt% Cr2O3 is locally sufficient to generate an emerald green color [54]. By partially enlarging the circled area in Figure 14a, the Figure 14b was acquired. It can be seen from Figure 14b that the aquamarine barely contains Cr or V. Compared to other aquamarine, the Longzi aquamarine hardly contains Cr, but it contains a little V which differentiates it from aquamarine in Namibia, Italy and Argentina.

6. Conclusions

Southern Tibet, China, has always been a significant resource reserve base. The discovery of aquamarine in Longzi County in southern Tibet is not only of great research value but also of great commercial value.
Generally speaking, the particle size of Longzi aquamarine is small, and the color ranges from light green–blue to light blue. The fluid inclusions in aquamarine indicate that it is formed in a fluid-rich environment. There is an obvious negative correlation between Fe and Al, and the existence of Li substitutions for Be, indicating that both tetrahedral substitutions and octahedral substitutions exist in Longzi aquamarine. The pegmatite producing Longzi aquamarine is a barren and geochemically primitive beryl-type pegmatite (including most pegmatites of the rare-earth type).
There exists more type I H2O than type II H2O, which is related to the low-alkali metal content. By changing the ratio of the two kinds of H2O, we can improve the color of Longzi aquamarine.

Author Contributions

Writing—original draft, J.-Q.S.; writing—review and editing, J.-Q.S., B.X. and S.-Y.C.; investigation, Z.-K.H., data curation, J.-Q.S., Z.-K.H., S.-Y.C., Y.-F.Z. and E.-Q.L.; software, J.-Q.S., Z.-K.H. and Y.-F.Z., methodology, B.X.; resources, W.L. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by National Key Technologies R&D Program 2019YFC0605201, 2019YFA0708602, 2020YFA0714802, National Natural Science Foundation of China (42073038, 41803045), Young Talent Support Project of CAST, Fundamental Research Funds for the Central Universities and IGCP-662.

Data Availability Statement

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

Acknowledgments

This is the third contribution of BX for National Mineral Rock and Fossil Specimens Resource Center. Thanks to the two reviewers and the editors for their comprehensive and professional suggestions.

Conflicts of Interest

The authors declare no conflict of interest.

Appendix A

Table
Table A1. Chemical compositions with the structural formulas of aquamarine and tourmalines from Longzi occurrence analyzed by EMPA (in wt.%).
Table A1. Chemical compositions with the structural formulas of aquamarine and tourmalines from Longzi occurrence analyzed by EMPA (in wt.%).
LZ-2-1LZ-2-2LZ-2-3LZ-2-4LZ-2-5LZ-2-6LZ-2-7LZ-2-8LZ-2-9LZ-2-10LZ-2-11LZ-2-12LZ-2-13LZ-2-14LZ-2-15LZ-2-16
SiO265.73265.60165.53165.54365.92465.49665.65865.53765.24665.10966.02565.16665.04565.07765.49965.417
Na2O0.4190.4610.4290.3700.3870.4550.4560.4960.4240.5540.3450.5440.4770.4880.3860.364
K2O0.0350.0240.0120.0320.0170.0170.0260.0200.0260.0160.0290.0320.0420.0270.0200.019
Cr2O3bdl0.0690.032bdlbdl0.064bdl0.0500.0050.0870.041bdlbdlbdlbdl0.059
Al2O317.89117.85018.10617.78917.97817.88317.99617.98617.64117.37617.64117.23117.18017.38217.55017.524
MgO0.0280.0240.0230.0130.0380.0180.0240.0020.0770.1000.0600.0720.0380.0440.0070.024
CaO0.0210.0160.0120.011bdl0.0260.0090.0120.0120.0210.0200.0230.0510.0170.0140.014
MnO0.036bdl0.0200.0200.0600.0150.045bdl0.0690.0490.0130.0310.012bdlbdlbdl
P2O50.001bdlbdlbdl0.0050.0170.005bdlbdl0.029bdl0.0120.004bdlbdl0.001
FeO0.6720.5210.4140.4630.6440.3690.3470.2980.5650.8630.5881.0050.7150.8520.8200.771
TiO20.0320.0290.0150.0220.009bdl0.0270.0300.0140.0070.0010.009bdlbdlbdlbdl
NiObdlbdlbdlbdlbdl0.0140.017bdlbdlbdlbdlbdl0.0700.0030.025bdl
BeO13.48513.49013.47813.55513.25013.40513.43813.50313.17312.92813.36512.95313.11513.01313.16813.178
Total98.35298.08598.07297.81898.31297.77998.04897.93497.25297.13998.12897.07896.74996.90397.48997.371
Cations(apfu)
Si4+5.9885.9875.9805.9946.0255.9985.9955.9836.0216.0316.0396.0396.0356.0366.0386.037
Na+0.0740.0820.0760.0660.0690.0810.0810.0880.0760.0990.0610.0980.0860.0880.0690.065
K+0.0040.0030.0010.0040.0020.0020.0030.0020.0030.0020.0030.0040.0050.0030.0020.002
Cr3+0.0000.0050.0020.0000.0000.0050.0000.0040.0000.0060.0030.0000.0000.0000.0000.004
Al3+1.9211.9201.9471.9171.9361.9301.9361.9351.9181.8971.9011.8821.8791.9001.9071.906
Mg2+0.0040.0030.0030.0020.0050.0020.0030.0000.0110.0140.0080.0100.0050.0060.0010.003
Ca2+0.0020.0020.0010.0010.0000.0030.0010.0010.0010.0020.0020.0020.0050.0020.0010.001
Mn2+0.0030.0000.0020.0020.0050.0010.0030.0000.0050.0040.0010.0020.0010.0000.0000.000
P5+0.0000.0000.0000.0000.0000.0010.0000.0000.0000.0010.0000.0000.0000.0000.0000.000
Fe2+0.0510.0400.0320.0350.0490.0280.0260.0230.0440.0670.0450.0780.0550.0660.0630.059
Ti4+0.0020.0020.0010.0020.0010.0000.0020.0020.0010.0000.0000.0010.0000.0000.0000.000
Ni2+0.0000.0000.0000.0000.0000.0010.0010.0000.0000.0000.0000.0000.0050.0000.0020.000
Be2+2.9512.9582.9552.9782.9092.9492.9472.9612.9202.8772.9362.8842.9232.8992.9162.921
bdl = below detection limit.
Table
Table A2. Chemical compositions with the structural formulas of aquamarine and tourmalines from Longzi occurrence analyzed by LA-ICP-MS.
Table A2. Chemical compositions with the structural formulas of aquamarine and tourmalines from Longzi occurrence analyzed by LA-ICP-MS.
(a)
LZ-2-1LZ-2-2LZ-2-3LZ-2-4LZ-2-5LZ-2-6LZ-2-7LZ-2-8LZ-2-9LZ-2-10LZ-2-11LZ-2-12LZ-2-13LZ-2-14LZ-2-15
Lippm715.203693.806711.192846.450799.964715.342712.446799.921662.675748.158731.079750.571703.263695.294742.782
Beppm60745.1 60078.9 59957.3 58953.9 59492.2 59133.5 59305.9 58618.4 59880.3 59372.1 59086.9 59022.4 58762.2 58783.3 59797.1
Na2Owt%0.5490 0.5151 0.5580 0.7020 0.6656 0.5346 0.5068 0.5746 0.4899 0.5442 0.5920 0.5528 0.5030 0.5140 0.5322
MgOwt%0.0367 0.0378 0.0403 0.0369 0.0358 0.0358 0.0362 0.0343 0.0342 0.0337 0.0358 0.0367 0.0368 0.0342 0.0377
Al2O3wt%16.7233 16.7439 16.7029 17.1209 16.9734 17.0526 17.4652 17.0654 16.7129 16.8425 17.0446 17.0041 17.0721 16.8409 17.1147
SiO2wt%64.6118 64.7944 64.8165 64.5638 64.5889 64.7924 64.3083 64.8776 64.9772 64.8955 64.6771 64.8249 64.8757 65.0847 64.5402
P2O5wt%0.0000 0.0000 0.0188 0.0061 0.0025 0.0000 0.0029 0.0053 0.0118 0.0064 0.0063 0.0066 0.0000 0.0161 0.0000
K2Owt%0.0132 0.0185 0.0204 0.0220 0.0237 0.0142 0.0201 0.0227 0.0242 0.0463 0.0548 0.0243 0.0149 0.0306 0.0223
CaOwt%0.0017 0.0110 0.0185 0.0101 0.0070 0.0085 0.0023 0.0032 0.0100 0.0070 0.0308 0.0105 0.0000 0.0006 0.0085
Scppm1.0931 0.9511 0.4921 1.0620 0.6845 1.3038 0.8233 1.1557 1.1206 0.8261 0.6712 0.8133 1.0760 0.3054 0.9512
TiO2wt%0.0005 0.0004 0.0006 0.0004 0.0000 0.0007 0.0005 0.0002 0.0006 0.0000 0.0000 0.0000 0.0003 0.0003 0.0007
Vppm0.0000 0.0000 0.0000 0.0000 0.0037 0.0036 0.0104 0.0000 0.1592 0.0000 0.1142 0.0000 0.0000 0.1121 0.2341
Crppm3.4465 3.2110 0.3962 9.9571 12.6181 0.0000 0.0000 3.4658 0.4511 3.5641 2.1095 4.7183 0.0000 0.0000 1.7384
MnOwt%0.0045 0.0044 0.0044 0.0041 0.0044 0.0041 0.0045 0.0042 0.0044 0.0039 0.0044 0.0042 0.0044 0.0042 0.0043
Mnppm35.0383 33.7892 34.0551 31.8228 33.9539 31.9669 34.5916 32.4021 33.8490 30.3609 34.0674 32.2132 34.1059 32.1896 33.2322
FeOwt%0.8649 0.8697 0.8426 0.8013 0.8278 0.8111 0.8556 0.7866 0.7842 0.7976 0.8025 0.8074 0.8476 0.8249 0.7958
Coppm0.1039 0.1688 0.1157 0.1567 0.1059 0.0547 0.1031 0.0000 0.1563 0.0000 0.0502 0.0000 0.4215 0.0540 0.1546
Nippm0.0000 0.0000 0.9048 0.0000 0.0000 0.4037 2.7413 0.0000 0.0000 0.0000 2.5327 0.0000 0.0000 0.0000 0.9104
Cuppm0.3806 0.0000 1.0122 0.0000 2.0170 0.0751 0.0000 0.5731 0.0339 0.0000 0.3138 0.2595 0.3685 0.0000 0.5388
Znppm533.769 513.283527.378535.312541.082532.413541.579558.067557.726543.848523.440529.238550.523538.951545.313
Gappm34.6520 34.6502 34.4200 32.9861 33.6929 31.5305 33.7457 32.3477 35.0860 32.2658 33.3996 35.7303 31.1790 35.1842 34.3695
Geppm1.4916 0.1405 2.0563 2.9519 0.2158 0.0000 0.1193 0.0000 0.5012 0.3407 1.3821 0.0000 0.0000 2.5080 0.0000
Rbppm47.1708 50.6360 50.2350 52.6792 46.2836 47.9303 51.9793 48.3559 56.8560 55.8966 63.7939 49.2222 47.9509 50.9670 49.5186
Srppm0.0022 0.0606 0.2922 0.5036 0.2083 0.0228 0.0441 0.0000 0.0943 0.1192 1.1129 0.3854 0.0325 0.0000 0.1647
Yppm0.0000 0.0785 0.1129 0.0485 0.0938 0.0000 0.0000 0.0436 0.0000 0.0711 0.4228 0.0325 0.0000 0.0463 0.0000
Zrppm0.2256 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.2290 0.0000 0.0000 0.0000 0.0000 0.2237
Nbppm0.1113 0.0631 0.0680 0.3211 0.2820 0.0000 0.0536 0.0522 0.0573 0.1419 0.1967 0.0778 0.0000 0.0553 0.0000
Moppm0.0000 0.0000 0.1810 0.0000 0.0000 0.1497 0.0000 0.0000 0.0000 0.0000 0.3028 0.0000 0.0000 0.1491 0.3022
Snppm0.8870 0.4463 0.3246 1.8786 3.0023 0.6503 0.1220 0.0000 0.2097 0.0000 0.0692 1.0365 1.3999 0.9692 1.0704
Csppm758.419781.185789.349822.285801.295772.586784.118788.424818.583785.459900.277820.813787.195798.609823.893
Bappm0.0000 0.0000 0.2884 0.0000 0.3601 0.0000 0.0000 0.0000 0.1224 0.0000 0.4805 0.0000 0.0000 0.0000 0.0000
Lappm0.0000 0.0196 0.1268 0.0000 0.0000 0.0000 0.0000 0.0000 0.0179 0.0000 0.0526 0.0000 0.0000 0.0000 0.0175
Ceppm0.0000 0.0000 0.1836 0.0143 0.0000 0.0275 0.0796 0.0000 0.0000 0.0000 0.1554 0.0388 0.0000 0.0139 0.0141
Prppm0.0000 0.0040 0.0130 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0149 0.0000 0.0000 0.0000
Ndppm0.0000 0.0000 0.1585 0.0000 0.0000 0.0000 0.0000 0.1218 0.0000 0.0662 0.0000 0.0000 0.0000 0.0000 0.0000
Smppm0.0000 0.0000 0.0918 0.0000 0.0000 0.0000 0.0000 0.0000 0.0777 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
Euppm0.0187 0.0000 0.0000 0.0000 0.0189 0.0187 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
Gdppm0.0000 0.0000 0.0000 0.0000 0.0719 0.0000 0.1374 0.1339 0.0000 0.0000 0.0724 0.0000 0.0000 0.0716 0.0000
Tbppm0.0000 0.0000 0.0123 0.0000 0.0102 0.0000 0.0000 0.0000 0.0000 0.0000 0.0205 0.0000 0.0000 0.0000 0.0103
Dyppm0.0400 0.0452 0.0487 0.0418 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0404 0.0000 0.0000 0.0398 0.0000
Hoppm0.0000 0.0000 0.0120 0.0000 0.0000 0.0000 0.0000 0.0185 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
Erppm0.0278 0.0000 0.0339 0.0000 0.0560 0.0000 0.0000 0.0000 0.0000 0.0000 0.0279 0.0000 0.0000 0.0275 0.0000
Tmppm0.0000 0.0100 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0091 0.0000 0.0000 0.0000 0.0000 0.0089 0.0000
Ybppm0.0000 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 0.0000
Luppm0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0090 0.0000 0.0000 0.0000 0.0000
Hfppm0.0290 0.0328 0.0705 0.0000 0.0291 0.0287 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
Tappm0.0291 0.0000 0.0118 0.1422 0.1962 0.0194 0.0000 0.0000 0.0000 0.0000 0.0098 0.0000 0.0000 0.0000 0.0000
Wppm0.0000 0.0000 0.2834 0.0000 0.0781 0.0422 0.0053 0.1447 0.1590 0.1972 0.0782 0.0000 0.0000 0.0772 0.0392
Pbppm0.0195 0.0990 0.0689 0.2408 0.3950 0.0824 0.0958 0.0239 0.0508 0.0512 0.2176 0.0058 0.0000 0.0646 0.0210
Thppm0.0090 0.0203 0.0049 0.0187 0.1356 0.0446 0.0000 0.0335 0.0092 0.0366 0.0725 0.0000 0.0127 0.0090 0.0000
Uppm0.0253 0.0000 0.0615 0.0263 0.0133 0.0063 0.0363 0.0591 0.0198 0.0388 0.1349 0.0089 0.0000 0.0319 0.0194
(b)
LZ-2-16LZ-2-17LZ-2-18LZ-2-19LZ-2-20LZ-2-21LZ-2-22LZ-2-23LZ-2-24LZ-2-25LZ-2-26LZ-2-27LZ-2-28LZ-2-29LZ-2-30
Lippm769.031 780.067 649.181 828.200 865.250713.558743.674786.658731.158672.139744.080786.396890.432734.475711.487
Beppm59402.8 57645.3 58181.2 58478.6 56558.2 59599.5 58751.2 58189.8 59661.9 59355.4 58476.3 56813.9 52868.3 58397.3 58017.9
Na2Owt%0.4780 0.4656 0.4173 0.5019 0.5319 0.4705 0.4778 0.4962 0.4523 0.4058 0.4276 0.5220 0.6180 0.4576 0.4087
MgOwt%0.0214 0.0213 0.0213 0.0260 0.0234 0.0248 0.0279 0.0279 0.0263 0.0199 0.0230 0.0223 0.0626 0.0260 0.0206
Al2O3wt%17.3118 17.2000 16.9365 17.1565 17.0674 17.4029 17.2783 17.1964 17.6764 17.6996 17.8065 17.5766 18.2961 18.1240 18.2600
SiO2wt%64.8630 65.3585 65.6906 65.1226 65.6868 64.6704 65.0643 65.1980 64.4358 64.6245 64.7502 65.1129 64.9813 64.3994 64.4599
P2O5wt%0.0059 0.0000 0.0118 0.0000 0.0060 0.0000 0.0009 0.0000 0.0010 0.0114 0.0000 0.0000 0.0129 0.0063 0.0000
K2Owt%0.0786 0.1787 0.0091 0.1995 0.1772 0.0297 0.0380 0.1181 0.0375 0.0171 0.0332 0.1798 0.4521 0.0151 0.0130
CaOwt%0.0058 0.0104 0.0158 0.0035 0.0092 0.0088 0.0147 0.0136 0.0118 0.0074 0.0125 0.0562 0.0207 0.0166 0.0000
Scppm0.9036 0.7664 0.3667 0.7295 0.0202 1.3505 0.0000 0.6513 0.6503 0.7110 0.9074 0.3117 1.0890 0.1612 0.0000
TiO2wt%0.0002 0.0001 0.0000 0.0009 0.0003 0.0003 0.0003 0.0000 0.0000 0.0005 0.0000 0.0000 0.0011 0.0000 0.0008
Vppm0.3313 0.1482 0.1906 0.1816 0.2435 0.1951 0.1082 0.3410 0.3511 0.2050 0.0000 0.0000 0.4217 0.0891 0.4621
Crppm6.0433 69.6262 4.9633 5.9129 4.1448 615.38696.5599 12.3502 2.6787 5.0638 0.2215 5.9643 27.5504 0.0000 0.0000
MnOwt%0.0026 0.0055 0.0026 0.0040 0.0027 0.0026 0.0034 0.0033 0.0031 0.0020 0.0021 0.0034 0.0095 0.0037 0.0030
Mnppm19.9034 42.4059 20.1491 30.8849 20.9126 19.8687 26.5203 25.7848 23.9646 15.7028 16.3865 26.0470 28.4224 23.2917 33.1759
FeOwt%0.4416 0.4412 0.4675 0.4336 0.4652 0.4529 0.4642 0.4727 0.4985 0.4275 0.3933 0.4102 0.5143 0.4468 0.4260
Coppm0.0808 0.0653 0.0000 0.0362 0.0000 0.0031 0.1363 0.0000 0.0000 0.4659 0.0000 0.1292 0.0838 0.2666 0.2000
Nippm4.0107 0.0000 0.0000 0.3468 0.0000 0.0664 0.1063 0.5056 0.1026 0.0000 1.2187 4.0370 0.3648 0.4400 2.2544
Cuppm1.5770 1.0398 1.1706 0.0000 0.0000 0.0000 0.6425 0.2020 1.5168 0.9434 1.5399 0.5648 14.6585 0.7422 0.3702
Znppm244.165249.436253.643220.019230.828251.469257.131237.668239.059254.756266.283240.827269.125232.933250.094
Gappm29.9596 29.8671 28.3699 28.4338 28.5479 28.5576 32.8321 32.8755 35.4523 28.8948 24.7614 26.4684 34.3241 29.1934 26.0395
Geppm3.1691 3.7244 1.6361 3.2608 0.0000 0.0000 3.5595 0.0000 1.1159 2.6516 0.0000 2.9342 2.0260 6.3697 3.2818
Rbppm50.1839 85.4463 45.4418 78.1722 68.2548 39.4126 41.6924 62.8949 39.6254 34.0252 39.8818 78.7061 143.29638.0168 33.8919
Srppm0.1018 0.0052 0.0000 0.0134 0.3300 0.2990 0.0016 2.0282 0.0942 0.0000 0.1347 3.1984 0.8304 0.0000 0.0944
Yppm0.2400 0.3072 0.0297 0.3395 0.1806 0.0000 0.0000 0.1828 0.0000 0.0000 0.0000 0.4110 0.3196 0.0636 0.0000
Zrppm0.3263 0.0000 0.2809 0.0000 0.5673 0.2831 0.0000 0.0000 0.0143 0.2949 0.4289 0.0000 0.0000 0.0000 0.0000
Nbppm0.2456 0.2567 0.0708 0.4049 0.2870 0.0000 0.0000 0.1452 0.0371 0.0000 0.0000 0.2101 1.9543 0.0380 0.0000
Moppm0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.4154 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
Snppm1.3425 1.6707 0.6298 0.0000 0.7715 0.0000 1.8781 0.6917 0.6619 1.4733 0.3066 1.6825 3.4164 0.9137 2.1237
Csppm798.442796.994810.539847.803877.894948.706905.036927.593832.2891073.131038.941165.14860.249834.671959.919
Bappm0.1751 0.1568 0.0000 0.0000 0.1535 0.3071 0.0000 0.3080 0.1566 0.0000 0.0000 0.0000 1.9759 0.0000 0.0000
Lappm0.1020 0.0000 0.0000 0.2242 0.0000 0.0000 0.0000 0.0225 0.0000 0.0000 0.0000 0.2588 0.0293 0.0000 0.0000
Ceppm0.4735 0.0370 0.0000 0.3867 0.0000 0.0000 0.0000 0.0000 0.0000 0.0187 0.0000 0.0698 0.0473 0.0563 0.0561
Prppm0.0472 0.0141 0.0000 0.0346 0.0138 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0183 0.0145 0.0000
Ndppm0.0000 0.0855 0.0000 0.4194 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.1622 0.0000 0.0000 0.0000
Smppm0.1114 0.0000 0.0000 0.2450 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
Euppm0.0000 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 0.0000
Gdppm0.2127 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0949 0.0967 0.0000 0.1399 0.0000 0.0000 0.0974 0.0000
Tbppm0.0301 0.0000 0.0130 0.0166 0.0000 0.0133 0.0000 0.0000 0.0000 0.0000 0.0000 0.0509 0.0000 0.0000 0.0000
Dyppm0.1181 0.1058 0.0511 0.1300 0.0000 0.0000 0.0000 0.0524 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
Hoppm0.0000 0.0000 0.0000 0.0326 0.0000 0.0131 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0171 0.0000 0.0000
Erppm0.0000 0.0000 0.0000 0.0448 0.0358 0.1074 0.0000 0.0000 0.0370 0.0371 0.0000 0.0698 0.0475 0.0000 0.0000
Tmppm0.0133 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0121 0.0000 0.0000 0.0000 0.0000 0.0122 0.0367
Ybppm0.0000 0.0000 0.0527 0.0000 0.0536 0.0000 0.1151 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
Luppm0.0132 0.0119 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
Hfppm0.0000 0.0000 0.0750 0.0000 0.0382 0.0383 0.0000 0.0000 0.0000 0.0000 0.0572 0.0000 0.0000 0.0000 0.0000
Tappm0.0288 0.0129 0.0250 0.0477 0.0380 0.0127 0.0000 0.0140 0.0000 0.0000 0.0000 0.0734 0.2493 0.0528 0.0000
Wppm0.1719 0.0088 0.0000 0.0632 0.1514 0.0505 0.1083 0.0000 0.0000 0.0514 0.0512 0.1912 0.9558 0.1023 0.0000
Pbppm0.3829 0.4076 0.0000 0.3689 0.1503 0.2345 0.2706 0.5072 0.2149 0.0215 0.0000 0.2420 1.4784 0.2441 0.0641
Thppm0.0797 0.1072 0.0115 0.1465 0.0351 0.0000 0.0000 0.0472 0.0000 0.0000 0.0000 0.1347 0.8071 0.0242 0.0000
Uppm0.1805 0.0939 0.0165 0.1370 0.0506 0.0254 0.0545 0.0350 0.0347 0.0087 0.0251 0.0646 0.5471 0.0260 0.0000
Table
Table A3. Characteristics of aquamarine from different producing areas.
Table A3. Characteristics of aquamarine from different producing areas.
OriginColorLusterTransparencyRi(No)Ri(Ne)DrSgUvPleochroism SizeInclusion
Pakistan
Shigar Valley 		pale greenish blue and pale blue to nearly colorlessglassy lustertranslucent to transparent1.574–1.5801.569–1.5750.005–0.0062.60–2.72weak bluish whiteweak dichroism 1–2 cm in length and 0.5–1 cm in diameterTwo-phase or three-phase with various shapes. Other mineral inclusions such as tourmaline, albite, and muscovite and almandine.
Vietnam
Thuong Xuan district, Thanh Hoa Province		Light to medium blueglassy lustertranslucent to transparent1.572–1.5791.569–1.573 2.66–2.70inertobvious dichroism5 to 20 cm long and 1–6 cm in diameterGrowth tubes and angular or elongated two-phase fluid inclusions in all the samples. Multiphase inclusions are seen less frequently. Calcite, albite, hematite and biotite are also found as mineral inclusions.
Italy
Masino-Bregaglia 		light to medium blue to greenish blueglassy lustertransparent to opaque1.580–1.5901.5720.008–0.009 inert several centimeters long, although some crystals attain 15–20 cm in lengthFractures, partially healed fissures with fluid and two-phase inclusions, and growth lines.
Mexico Guadalcázar municipality, San Luis Potosí Statelighter blue tone. Blue to nearly colorlessglassy lustertransparent1.582–1.5871.575–1.5800.0072.70–2.71inertobvious dichroismthe largest of which measured 12.04 × 5.68 × 4.57 mmLacking visible inclusions.
China Xinjiang Altaigreenish blue to pure glassy lusterSemitransparent to
transparent		1.581–1.5821.575–1.5760.005–0.0062.707inertweak dichroism Three-phase inclusions, multi-phase inclusion are mostly fluid.
Brazil Governador Valadares and Aracuaı’ regions in Minas Gerais Statedark blue to greenish blueglassy lustertransparent1.578–1.5921.570–1.5780.004–0.0112.71–2.86 less than
5 cm-long
Ethiopia Shakiso greenish blue to pure mediumglassy lustertransparent1.570–1.582 0.0122.66inertstrong dichroismranged from 2.3 to 16.3 gComplex network of parallel partially healed fissure planes, two-phase fluid inclusions and growth lines.
Madagascar ambatofotsikelymedium blue to slightly greenish blueglassy lustertransparent1.580–1.5821.573–1.5750.006–0.0072.69–2.73 strong dichroism1–35 ctHematite, ilmenite, hollow tube, plate-like reticulated dendrites.
Nigeria Nasarawadark blueglassy lustertransparent1.582–1.590 0.0082.71–2.73inertstrong dichroism Highly reflective, opaque, elongate needles and platelets that appeared light brown to black. Dark color and reflective nature suggest they might be Fe oxides.
Sri Lanka Akkerellapale blue to a saturated dark blueglassy lustertransparent1.584–1.5871.577–1.5800.0072.71inertstrong dichroism ranged up to
10 cm long		“Finger prints,” doubly refractive crystals with reflective halos, minute crystals, stringers of particles, needles, and near parallel reflective dendrites surrounded by clouds.
Canada YukonDark grayish blueglassy lusterSemitransparent to transparent1.6011.592–1.593 0.008–0.009 2.80–2.87 inertmedium dichroismup to 8.20 ctCrystals, multi-phase inclusions “fingerprints”, growth tubes, growth lines, fractures.

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Figure 2. (a) Map of China; the yellow part is Tibet and the positions of b and c are located in the red box. (b) The structure of the Cuonadong dome [31]; the sampling place is marked as the yellow star. (c) Map of the Tethys Himalayan leucogranite belt. [29] The Cuonadong dome is in the lower right corner of the figure. Figure 2b is in the boxed area of Figure 2c.
Figure 2. (a) Map of China; the yellow part is Tibet and the positions of b and c are located in the red box. (b) The structure of the Cuonadong dome [31]; the sampling place is marked as the yellow star. (c) Map of the Tethys Himalayan leucogranite belt. [29] The Cuonadong dome is in the lower right corner of the figure. Figure 2b is in the boxed area of Figure 2c.
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Figure 3. (a) The sample site is located in the southeast part of the Cuonadong dome, where the pegmatitic veins are widely distributed (b,c) The pegmatite crop; some pegmatites are weathered to form boulders with a size of about 10 cm (b), and some pegmatites are tens of meters in size (c). We can see feldspar, mica, tourmaline and other minerals with coarse particles. The beryl crystals are typically hexagonal, ranging in length from 1 to 10 cm, they are pale blue, translucent to micro-transparent, and acicular and columnar tourmaline can be seen in the surrounding adjacent rock.
Figure 3. (a) The sample site is located in the southeast part of the Cuonadong dome, where the pegmatitic veins are widely distributed (b,c) The pegmatite crop; some pegmatites are weathered to form boulders with a size of about 10 cm (b), and some pegmatites are tens of meters in size (c). We can see feldspar, mica, tourmaline and other minerals with coarse particles. The beryl crystals are typically hexagonal, ranging in length from 1 to 10 cm, they are pale blue, translucent to micro-transparent, and acicular and columnar tourmaline can be seen in the surrounding adjacent rock.
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Crystals 11 00777 g004 550
Figure 4. (a,c,d) The aquamarine crystals L1 to L3 of Longzi County, Tibet. (b) 40× gem microscope, dark-field observation specimen A-1, the size of A-1 is 3 × 3 × 8 mm3.
Figure 4. (a,c,d) The aquamarine crystals L1 to L3 of Longzi County, Tibet. (b) 40× gem microscope, dark-field observation specimen A-1, the size of A-1 is 3 × 3 × 8 mm3.
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Figure 5. UV–Vis spectrum of A-1 slices parallel and vertical to the c-axis.
Figure 5. UV–Vis spectrum of A-1 slices parallel and vertical to the c-axis.
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Crystals 11 00777 g006 550
Figure 6. (a) Raman spectrum of Longzi aquamarine. (b) Tunnel water Raman spectrum of Longzi aquamarine.
Figure 6. (a) Raman spectrum of Longzi aquamarine. (b) Tunnel water Raman spectrum of Longzi aquamarine.
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Figure 7. (a) Quartz inclusions and (b) their Raman spectrum. (c) Gas–liquid two-phase fluid inclusions parallel to the c-axis.
Figure 7. (a) Quartz inclusions and (b) their Raman spectrum. (c) Gas–liquid two-phase fluid inclusions parallel to the c-axis.
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Figure 8. (a–d) Four typical isolated fluid inclusions were tested by Raman spectrum, ranging in size from 10 μm to 40 μm. The results are shown on the right. Raman spectra of gas and liquid are shown in blue and green, respectively.
Figure 8. (a–d) Four typical isolated fluid inclusions were tested by Raman spectrum, ranging in size from 10 μm to 40 μm. The results are shown on the right. Raman spectra of gas and liquid are shown in blue and green, respectively.
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Crystals 11 00777 g009 550
Figure 9. Stacked-ring structure of beryl [45]. According to the experimental results of Wood and Nassau [37], there are two types of H2O molecule occupancy in the open cavities of a beryl. When H2O is not paired with an alkali metal ion, the H–H vector is parallel to the c-axis (type I water). When an extra-framework cation is present near H2O molecules, the H2O molecules above and below the cation orient with their H–H vectors vertical to the c-axis because of the electrical attraction between the oxygen of the water molecules and the cation (type II water) [45].
Figure 9. Stacked-ring structure of beryl [45]. According to the experimental results of Wood and Nassau [37], there are two types of H2O molecule occupancy in the open cavities of a beryl. When H2O is not paired with an alkali metal ion, the H–H vector is parallel to the c-axis (type I water). When an extra-framework cation is present near H2O molecules, the H2O molecules above and below the cation orient with their H–H vectors vertical to the c-axis because of the electrical attraction between the oxygen of the water molecules and the cation (type II water) [45].
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Crystals 11 00777 g010 550
Figure 10. (a) Relationship between the major octahedral site ion (Al), and the principal substituent at the octahedral site (Fe), consistent with major Fe-Al substitution: There is a negative correlation between them, in atoms per formula unit (apfu). (b) Al versus the sum of its substituents in Y site, in atoms per formula unit (apfu). Other sources are [3,18,19,21,22,48,49].
Figure 10. (a) Relationship between the major octahedral site ion (Al), and the principal substituent at the octahedral site (Fe), consistent with major Fe-Al substitution: There is a negative correlation between them, in atoms per formula unit (apfu). (b) Al versus the sum of its substituents in Y site, in atoms per formula unit (apfu). Other sources are [3,18,19,21,22,48,49].
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Figure 11. Plots of R2+ (divalent cations in octahedral site, including Mg, Fe, Mn, Ni) versus A+ (monovalent alkali cations in channel, including Na, K).
Figure 11. Plots of R2+ (divalent cations in octahedral site, including Mg, Fe, Mn, Ni) versus A+ (monovalent alkali cations in channel, including Na, K).
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Figure 12. The Na/Li versus Cs diagram for late primary beryl from granitic pegmatites [53]. Different regions in the figure represent different types of pegmatites. A = barren and geochemically primitive beryl-type pegmatites (including most pegmatites of the rare-earth type); B = geochemically evolved beryl–columbite and beryl–columbite–phosphate pegmatites; C = albite–spodumene and complex pegmatites; D = highly fractionated Li-, Cs- and Ta-rich complex pegmatites [53,54].
Figure 12. The Na/Li versus Cs diagram for late primary beryl from granitic pegmatites [53]. Different regions in the figure represent different types of pegmatites. A = barren and geochemically primitive beryl-type pegmatites (including most pegmatites of the rare-earth type); B = geochemically evolved beryl–columbite and beryl–columbite–phosphate pegmatites; C = albite–spodumene and complex pegmatites; D = highly fractionated Li-, Cs- and Ta-rich complex pegmatites [53,54].
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Figure 13. Chemical fingerprint diagram of the log–log plot of Li versus Cs. On the basis of the Li and Cs contents, beryls from different areas are classified as “high-alkali beryl” and “low-alkali beryl”. Other sources are [18,20,21,22,55].
Figure 13. Chemical fingerprint diagram of the log–log plot of Li versus Cs. On the basis of the Li and Cs contents, beryls from different areas are classified as “high-alkali beryl” and “low-alkali beryl”. Other sources are [18,20,21,22,55].
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Figure 14. (a,b) Compared with emerald, the chromogenic elements of aquamarine are single, and the Cr and V contents of aquamarine are very low. Other sources are [18,19,20,22,56,57,58,59,60,61,62].
Figure 14. (a,b) Compared with emerald, the chromogenic elements of aquamarine are single, and the Cr and V contents of aquamarine are very low. Other sources are [18,19,20,22,56,57,58,59,60,61,62].
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Shen, J.-Q.; Hu, Z.-K.; Cui, S.-Y.; Zhang, Y.-F.; Li, E.-Q.; Liang, W.; Xu, B. A Study on Beryl in the Cuonadong Be-W-Sn Polymetallic Deposit, Longzi County, Tibet, China. Crystals 2021, 11, 777. https://doi.org/10.3390/cryst11070777

AMA Style

Shen J-Q, Hu Z-K, Cui S-Y, Zhang Y-F, Li E-Q, Liang W, Xu B. A Study on Beryl in the Cuonadong Be-W-Sn Polymetallic Deposit, Longzi County, Tibet, China. Crystals. 2021; 11(7):777. https://doi.org/10.3390/cryst11070777

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Shen, Jia-Qi, Zhi-Kang Hu, Shi-Yuan Cui, Yu-Fei Zhang, En-Qi Li, Wei Liang, and Bo Xu. 2021. "A Study on Beryl in the Cuonadong Be-W-Sn Polymetallic Deposit, Longzi County, Tibet, China" Crystals 11, no. 7: 777. https://doi.org/10.3390/cryst11070777

APA Style

Shen, J. -Q., Hu, Z. -K., Cui, S. -Y., Zhang, Y. -F., Li, E. -Q., Liang, W., & Xu, B. (2021). A Study on Beryl in the Cuonadong Be-W-Sn Polymetallic Deposit, Longzi County, Tibet, China. Crystals, 11(7), 777. https://doi.org/10.3390/cryst11070777

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