Natural Tourmaline Research Articles

Chemical Composition and Spectral Variation in Gem-Quality Blue Iron-Bearing Tourmaline from Brazil

This study, conducted a spectroscopic analysis of 10 gem-quality blue tourmaline samples from Minas Gerais, Brazil, focused on detailed variations in their infrared, Raman, and UV-VIS spectra. Conventional gemological tests, electron-probe microanalysis, infrared spectroscopy (mid- and near-infrared), Raman spectroscopy, and UV-visible spectroscopy were used to systematically analyze the chemical composition and spectral characteristics of the samples. The infrared spectra revealed vibrations of [YO6], [TO4], [BO3], [OH], and H2O groups, indicating different bonding profiles, with the [OH] vibrational frequency showing a direct correlation with FeO and MnO content. The Raman spectra primarily reflected the stretching vibrations of metal–oxygen bonds and hydroxyl groups, indicating the complexity of the local environment in the crystal structure. The UV-VIS spectra showed that the broad absorption band around 725 nm was due to intermetallic charge transfer between Fe2+ and Fe3+. This work provides new insights into the local bonding environment within the crystal structure by providing precise spectral data of natural blue tourmaline, and a more accurate classification and evaluation of blue tourmaline through fine spectral change characteristics related to crystal chemistry has important implications for both academic research and the gemstone industry.

Tourmaline/pyrite dual mineral photocatalysis with a powerful surface electric field for efficient antibiotic removal

Pyrite (FeS2) has garnered attention due to its narrow bandgap, high light absorption, and low cost. However, the rapid recombination of charge carriers hinders its practical application. Surface electric field is a unique characteristic of tourmaline, which can induce effective separation of photo generated electrons and holes. This study successfully combined two directly mined natural minerals, tourmaline and pyrite, to form TFS. Characterization and experiments show that the surface electric field of tourmaline can significantly enhance the photocatalytic activity of TFS. Tetracycline (TC, 50 ppm) was degraded by 95% with 60 min, and the TFS reaction rate constant reached 0.0439 min−1, which is 6.1 times and 17.3 times higher than that of tourmaline and FeS2. Additionally, it significantly improved light absorption and charge carrier separation capabilities. After simulating various natural environmental factors, TFS demonstrated practicality. Considered analysis of active substances and detection revealed that h+ and 1O2 radicals are significant contributors, and the photocatalytic mechanism was proposed. Furthermore, the transformation pathways and toxicity of metabolites were studied. This research offers further inspiration and insights for improving photocatalytic material performance and the green governance environment of natural resources.

Electric field driven tourmaline/hematite dual mineral photocatalysis for efficient antibiotic removal

Hematite (Fe2O3) has garnered attention due to its stability, economic viability, and non-toxic nature. However, the rapid recombination of charge carriers hampers its practical application. On the other hand, tourmaline's inherent surface electric field facilitates the rapid separation of photogenerated electrons and holes. In this study, two directly mined natural minerals, tourmaline and hematite (TFO), were successfully combined. Characterization and experiments indicate that the pronounced enhancement of photocatalytic activity in Fe2O3 is attributed to the electric field effect on the surface of tourmaline. TFO successfully removes 93% of tetracycline (TC, 50 ppm) within 60 min. The reaction rate constant for TFO composite material (0.0410 min−1) is 8.5 times that of tourmaline (0.0048 min−1) and 14.1 times that of hematite (0.0029 min−1). Simultaneously, it markedly improves light absorption and charge carrier separation capabilities. Through simulations of various natural environmental factors, TFO demonstrates excellent practicality. Analyzing and detecting active species revealed the involvement of four types of active species, with ·OH radicals making the most significant contribution. The photocatalytic mechanism was proposed. Furthermore, the degradation pathway of tetracycline and the toxicity of its metabolites were investigated. This work provides additional inspirations and insights for photocatalytic materials performance enhancement and natural resources green governance environment.

Natural iron-rich tourmalines as effective catalysts for the heterogeneous and homogeneous activation of HCO3−/H2O2 to achieve the degradation of typical dyes

Natural iron-rich tourmalines as effective catalysts for the heterogeneous and homogeneous activation of HCO3−/H2O2 to achieve the degradation of typical anionic (MO) and cationic (MB and RhB) dyes.

3D-printed flexible energy harvesting devices designed using non-layered two-dimensional natural tourmaline silicates

This paper shows how non-layered naturally occurring tourmaline silicates can be exfoliated into 2D structures for use in fabrics and 3D printed biomedical health monitoring devices.

Integrating natural tourmaline with energy conversion ability to magnetically assembled electrode: Boosted electrochemical oxidation wastewater treatment performance

Novel anodes are desirable in the development of electrochemical oxidation wastewater treatment (EOWT). Magnetically assembled electrode (MAE) is a novel modular electrode format that physically adsorbs magnetic particles (auxiliary electrodes, AEs) onto the main electrode (ME) by magnetic force which realizes an effective and sustainable EWOT process but puts a new requirement on AEs polarization. Therefore, tourmaline (Tml), a natural mineral with ferroelectricity, pyroelectricity, and piezoelectricity, was introduced into the MAE in this study. Tml particles were expected to utilize waste heat or mechanical energies in electrolysis (e.g., Joule heat, bubble strike) and give extra electricity to the stacked AEs (Fe3O4/Sb-SnO2 granules herein) to fully active MAE. Tml’s effects were investigated via different MEs (Ti/IrO2-Ta2O5, graphite, Ti/Sb-SnO2), different wastewater, different Tml sizes, loading amounts, and different conditions (e.g., current density). Results show that all these conditions could affect the buffering of Acid red G degradation, Tml could offer a 10∼40% buff. Medium Tml size and loading as well as low or medium current density (e.g., 2 mA·cm−2 or 20 mA·cm−2) are appropriate. For real wastewater degradation, Tml facilitates macromolecule destruction. This study may start a new application route of abundant natural energy-converting materials in the EOWT area.

Tourmaline-mediated electrochemical system for sulfamethoxazole degradation: performance, mechanism, and toxicity evaluation

Antibiotics are emerging contaminants that have become a global concern because of their refractory and toxic characteristics. The treatment of antibiotic contaminants using advanced electrochemical oxidation processes is currently gaining interest. In this study, we constructed a natural iron-mediated electrochemical system for the removal of antibiotics using natural tourmaline (TM) as the heterogeneous iron catalyst, platinum (Pt) as the anode, and nickel foam (NiF) as the cathode. Sulfamethoxazole (SMX) was selected as the target antibiotic. The surface properties and components of TM were characterized using energy-dispersive X-ray spectroscopy, N2 adsorption–desorption isotherms, X-ray diffraction, and X-ray photoelectron spectroscopy. Compared with the Pt-NiF electrochemical system, the Pt-NiF-TM electrochemical system showed a 23 times enhanced reaction rate constant of SMX degradation under the optimal conditions of current density 4.17 mA/cm2, 200–400 mesh, TM dosage 3 g/L, and initial pH 3, in which SMX was almost completely degraded (removal rate = 99.92 %) after 60 min. The ·OH and ·O2– radicals generated in the Pt-NiF-TM electrochemical system were the active species for SMX degradation. Thirteen SMX degradation intermediates were identified and possible SMX degradation pathways were proposed. Density functional theory calculations demonstrated that C3 and N11 are the sites with higher electrophilic reactivity in SMX. Furthermore, toxicity calculations and analysis of SMX and its degradation products showed that after treatment with the Pt-NiF-TM electrochemical system, the toxicity of SMX to the microalgae Oocystis was reduced. Overall, this study provides a novel and environmentally friendly electrochemical system mediated by TM for the highly efficient degradation of antibiotic contaminants.

Natural tourmaline for pyroelectric dye decomposition under 25–60 °C room-temperature cold-hot fluctuation

Tourmaline is a typical natural pyroelectric material. In this work, the pyroelectric property of tourmaline micro-powder is used to chemically deal with dyes wastewater under room-temperature cold-hot alternation. Under 25–60 °C heating-cooling cycles excitation, the decomposition ratio of Rhodamine B wastewater can achieve 84.7%. In the dye decomposition process, dissolved oxygen and hydroxide in the solution react with pyroelectrically induced positive and negative charges, respectively. This reaction triggers the production of superoxide radicals (O2–) and hydroxyl radicals (OH), which possess highly potent oxidation capabilities towards dye molecules. This work highlights the potential application of tourmaline mineral for dye decomposition in harvesting the environmental cold-hot alternation heat energy in future.

Multiple interface coupling on natural tourmaline enables high-efficiency removal of antibiotic: Superior property and mechanism

Reasonably designing highly active, environmentally friendly, and cost-effective catalysts for efficient elimination of pollutants from water is desirable but challenging. Herein, an efficient heterogeneous photo-Fenton catalyst tourmaline (TM)/tungsten oxide (WO3-x) (named TW10) containing tungsten/boron/iron (W/B/Fe) synergistic active centers and 90% of cheap natural tourmaline (TM) mineral rich in Fe and B elements. The TW10 catalyst can quickly activate peroxymonosulfate (PMS) to generate massive active free radicals, which may induce the rapid and efficient degradation of tetracycline (TC). The TW10/PMS/Visible light system can effectively degrade up to 98.7% of tetracycline (TC) in actual waters (i.e. seawater, Yellow River, and Yangtze River water), and the catalytic degradation rates reach 1.65, 5.569, and 2.38 times higher than those of TM, WO3-x, and commercial P25 (Degussa, Germany), respectively. In addition, the catalyst can be recycled and reused multiple times. Electron spin resonance spectroscopy (EPR), X-ray photoelectron spectroscopy (XPS), and liquid chromatograph-mass spectrometer (LC-MS) analyses confirm that the synergistic catalytic effect of W/B/Fe sites on the TW10 catalyst accelerates the electron transfer between Fe(II) and Fe(III), as well as between W(V) and W(VI), and thus promotes the rapid degradation of TC. The catalytic reaction mechanism and degradation pathway of TC were explored. This work provides a feasible route for the design and development of new eco-friendly and efficient catalyst.

Natural tourmaline activated peracetic acid for efficient degradation of sulfadiazine: Reaction mechanisms and catalyst reusability

Peracetic acid (PAA) has received extensive attention in the water treatment due to its high oxidation potential and low toxicity of by-products. In this study, natural non-toxic mineral tourmaline (TM) was used to activate PAA to remove sulfadiazine (SDZ). The TM/PAA system could remove 92 ​% SDZ in 120 ​min. The radical analysis confirmed the co-existence of both free radical and non-free radical degradation pathways in the TM/PAA system, indicating that singlet oxygen (1O2) and acetyl(per)oxy radicals (CH3C(O)O· and CH3C(O)OO·) were the main reactive oxygen species. The Fe2+/Fe3+ ratio on the TM surface decreased during the degradation of SDZ due to Fe2+ consumption. The effect of water matrix on SDZ removal indicated that Cl−, SO42− and NO3− posed little effect on SDZ removal, while CO32− inhibited SDZ removal by affecting pH. Particularly, humic acid (HA) slightly promoted SDZ removal. Ten by-products of SDZ were identified by HPLC-MS/MS, and four possible transformation pathways (SO2 detachment, S–N breakage, amino acid oxidation, and hydroxylation) were proposed. TM was recycled five times and the removal of SDZ remained above 85 ​%, confirming its excellent reusability. This work indicates the TM/PAA system is of great potential for the application on the organic contaminant removal.

Natural piezoelectric tourmaline mineral for piezocatalytic decomposition of organic dyes under vibration

AbstractPiezoelectric materials can convert mechanical energy into electrical energy, and further piezocatalysis can be designed based on the product between piezoelectric effect and electrochemical redox effect, which is hopeful for the actual dye decomposition. Tourmaline is a natural mineral with spontaneous polarization, which is an ideal piezocatalytic material and is rarely reported in dye decomposition. In this work, after 100 mg tourmaline powder is vibrated for 120 min, the piezocatalytic dye decomposition ratios of rhodamine B (RhB), methylene blue, and methyl orange are ∼95%, ∼46%, and ∼23%, respectively. The corresponding first‐order reaction kinetic values for these three dyes are 0.02681, 0.00639, and 0.00246 min−1, respectively. By adjusting the pH value of the initial RhB solution to 5, the decomposition ratio can reach ∼99% after only 60 min of vibration. In the process of dye decomposition, it is determined that the main active substances are hydroxyl radicals and superoxide radicals via electron spin–resonance spectra test. The spontaneous polarization performance of tourmaline can effectively adsorb dye molecules to promote the catalytic reaction. Natural tourmaline minerals are abundant, low cost, and environmentally friendly making them suitable for large‐scale piezocatalysis of mineral materials.

Harvesting Friction Energy for Tribo‐catalytic Degradation of Organic Pollutions via Natural Tourmaline

AbstractFriction, a very common phenomenon in daily life, can be easily converted into electric energy via triboelectricity and can further drive oxidation and reduction reactions to degrade dye wastewater, which is named tribo‐catalysis. In this work, the friction energy between the stirring rod and the natural tourmaline powder was applied to realize the efficient tribo‐catalytic dye degradation. As the catalyst mass increases from 0 g to 0.15 g, the degradation ratio quickly increases at first and then slightly decreases during the tribo‐catalytic process. 0.10 g tourmaline powder shows excellent dye degradation ratio, which is up to ∼96 % at 400 r.p.m. stirring for 5 h. In addition, the dye degradation ratio can be improved through adjusting pH value of the dye solution to 7 or increasing the contact area between the natural tourmaline powder and the stirring rod. The electron spin‐resonance spectra experiment confirms that the primary active substances are hydroxyl radicals (⋅OH) and superoxide radicals (⋅O2−). The natural tourmaline with excellent tribo‐catalytic performance is prospective to treat the organic pollutions through harvesting the friction energy in the environment.

Infrared spectra study of the Moslavacka Gora (Croatia) tourmalines O-H stretching region: Inference of fluid involvement in the Late Cretaceous igneous evolution of a complex Adria-Europe convergence zone

Infrared spectra (IR) in the O-H stretching region were recorded for natural tourmalines from the magmatic and magmatic-hydrothermal systems of Moslavacka Gora (Croatia). Samples of disseminated tourmaline (schorl) representing magmatic products were collected from leucogranite. Nodular tourmaline (intermediate members of the schorl-dravite series) from twomica granite represents a magmatic-hydrothermal mineral related to the final stage of granite crystallization. IR spectra of the typically disseminated tourmaline show four sharp O-H stretching bands: 3643, 3633, 3550, and 3484 cm?1, while typical nodular tourmaline shows spectra with asymmetric and relatively broad O-H stretching bands on 3635 and 3554 cm?1 with shoulders at the higher and lower wavenumber side. The broadening in the lower wavenumber region of nodular tourmaline compared to disseminated tourmaline indicates a higher water content in the nodular type. At the same time, the observed shifts between the corresponding bands can be explained by the shortening of the O-H1 and O-H3 distances, which can be attributed to different genetic and/or evolutionary processes. According to the models applicable to the Moslavacka Gora, disseminated tourmaline from the leucogranite can be considered a typical magmatic (pegmatitic) product and a standard accessory phase of the leucogranite. The origin of nodular tourmaline, which was the last mineral to crystallize in the evolved Late Cretaceous granitic system of Moslavacka Gora, is attributed to the interaction of a fluid phase from the residual granitic melt with the fluid originating from the wall-rock in the low-pressure crustal setting, which was accompanied by relatively rapid cooling. This interaction resulted in an increased dravite content of the nodular tourmaline and is reflected in the observed IR spectral features.

Thermal expansion of minerals in the tourmaline supergroup

Abstract The thermal behavior of 15 natural tourmaline samples has been measured by X-ray powder diffraction from room temperature to ~930 °C. Axial thermal expansion is generally greater along the c crystallographic axis (αc 0.90–1.05 × 10–5/K) than along the a crystallographic axis and the symmetrically equivalent b axis (αa 0.47–0.60 × 10–5/K). Ferro-bearing samples show lower expansion along a than in other tourmalines. In povondraite the thermal expansion along the c axis is higher than in other tourmalines, whereas along a it is lower [αa = 0.31(2) and αc = 1.49(3) × 10–5/K]. Volume expansion in the tourmaline-supergroup minerals is relatively low compared with other silicates such as pyroxenes and amphiboles. Volume also exhibits a relatively narrow range of thermal expansion coefficients (1.90–2.05 × 10–5/K) among the supergroup members. An interpretation for the small changes in thermal expansion in a compositionally heterogeneous group like tourmaline is that all members, except povondraite, share a framework of dominantly ZAlO6 polyhedra that limit thermal expansion. Povondraite, with a framework dominated by ZFe3+O6 polyhedra, displays thermal expansion that is different from other members of the group. Unit-cell dimensions of tourmalines having significant Fe2+ deviate from linearity above 400 °C on plots against temperature (T); along with the resulting substantial reduction in unit-cell volume, these effects are likely the result of deprotonation/oxidation processes. Lithium-rich and Fe2+-free tourmalines deviate similarly at T > 600 °C. In Li- and Fe2+-free tourmalines, no such deviation is observed up to the highest temperatures of our experiments. It is not clear whether this is due to cation order-disorder over Y and Z sites that occurs during the highest temperature measurements, a phenomenon that is apparently inhibited (at least in the short term) in Li-free/Mg-rich samples. If so, this must occur at a relatively rapid rate, as no difference in unit-cell values was detected at 800 °C after heating in both one- and 12-h experiments on Na-rich rossmanite.

Tourmalines pyroelectric effect depending on the chemical composition and cation oxidation state

Tourmaline (the first natural pyroelectric material discovered) is the most common borosilicate on Earth characterized by a great variety of ionic substitutions at all structural sites. In this work the mosaicity and chemical inhomogeneity of single crystal samples of natural Fe-Mg and synthetic Ni- and Cu-rich tourmalines were characterized by X-ray diffraction (rocking curves, ω – 2θ scanning) and energy-dispersive X-ray spectroscopy. The iron oxidation state (Fe3+/ΣFe) in natural tourmalines was determined by Mӧssbauer spectroscopy. The pyroelectric properties of tourmalines were examined at room temperature by the dynamic pyroelectric measurement method. This approach allowed estimating the primary pyroelectric coefficient with the error smaller than ±0.15 μCm-2K-1. Based on the original and published data, it was shown that one of the main factors determining the pyroelectric properties of tourmaline is the ion oxidation state. It was found that the values of the Na-tourmaline pyroelectric coefficient were inversely proportional to the amount of divalent cations (Mg, Fe) and/or directly proportional to the amount of Al3+. This can be used for the directed synthesis of tourmalines with the required pyroelectric properties.

Insights into the nonradical degradation mechanisms of antibiotics in persulfate activation by tourmaline

A natural mineral tourmaline (TM) was used to activate persulfate (PS) for sulfamethazine (SMT) removal. No adsorption of SMT by TM was observed and the SMT removal by PS alone was only 10%. The TM/PS system presented a 97.8% SMT removal in 150 min with a reaction rate constant (k) of 0.026 min−1 at [SMT]0 = 5 mg/L, [PS]0 = 4 mM, [TM]0 = 5 g/L, T = 25 °C, and pH = 5. High removal efficiency was achieved in a wide pH range (2–10) with the highest k (0.0423 min−1) obtained at initial pH 2 and similar ks (0.0252 min−1, 0.0261 min−1 and 0.0225 min−1) obtained at pH 5, 7 and 10. SMT removal could still reach over 80% at the fifth reuse of TM. The radical quenching experiments verified that 1O2 and holes rather than OH and SO4− were the main reactive species for SMT degradation. Electron paramagnetic resonance spectroscopy was used to confirm the generation of 1O2. Electrochemical measurements indicated that the charge transfer rate and the electron-hole separation efficiency on the surface of TM were effectively improved in the presence of PS. The activation of PS by TM as a cheap and effective catalyst presented a promising method for contaminant removal, which could avoid the water matrix interference.

Raman spectroscopy and high pressure study of synthetic Ga,Ge-rich tourmaline

We present Raman spectroscopic analysis of the synthetic Ga,Ge-rich tourmalines at pressures up to 30 GPa for the first time. Based on the experimental data, we obtained correlation between the Raman band positions and the cation substitutions in the tetrahedral and octahedral sites at ambient conditions. A new band of Ge–O stretching vibrations, which is not common in natural tourmalines, occurs at ~ 870 cm−1. The main Raman bands shift to the higher frequencies with increasing pressure due to decrease in the bond lengths, associated with structural deformations. The lattice dynamic calculated spectra of tourmalines with various compositions resemble those measured experimentally. Analysis of experimental and theoretical data reveals a possible phase transition at ~ 18.4 GPa in the tourmalines with up to 10 wt% Ga2O3 and 9 wt% GeO2.

Development and Re‐Evaluation of Tourmaline Reference Materials for In Situ Measurement of Boron δ Values by Secondary Ion Mass Spectrometry

Six tourmaline samples were investigated as potential reference materials (RMs) for boron isotope measurement by secondary ion mass spectrometry (SIMS). The tourmaline samples are chemically homogeneous and cover a compositional range of tourmaline supergroup minerals (primarily Fe, Mg and Li end‐members). Additionally, they have homogeneous boron delta values with intermediate precision values during SIMS analyses of less than 0.6‰ (2s). These samples were compared with four established tourmaline RMs, that is, schorl IAEA‐B‐4 and three Harvard tourmalines (schorl HS#112566, dravite HS#108796 and elbaite HS#98144). They were re‐evaluated for their major element and boron delta values using the same measurement procedure as the new tourmaline samples investigated. A discrepancy of about 1.5‰ in δ11B was found between the previously published reference values for established RMs and the values determined in this study. Significant instrumental mass fractionation (IMF) of up to 8‰ in δ11B was observed for schorl–dravite–elbaite solid solutions during SIMS analysis. Using the new reference values determined in this study, the IMF of the ten tourmaline samples can be modelled by a linear combination of the chemical parameters FeO + MnO, SiO2 and F. The new tourmaline RMs, together with the four established RMs, extend the boron isotope analysis of tourmaline towards the Mg‐ and Al‐rich compositional range. Consequently, the in situ boron isotope ratio of many natural tourmalines can now be determined with an uncertainty of less than 0.8‰ (2s).

The Nature of the Mn(III) Color Centers in Elbaite Tourmalines.

The characteristic red color of many natural tourmalines is due to the presence of Mn(III) cations substituting for aluminum and lithium. These sites originate as Mn(II) and are oxidized by natural γ-irradiation over geologic time as they sit in the Earth's crust. Presented here is a thorough analysis of the spin-allowed and spin-forbidden transitions which give rise to the color of these gemstones. Ligand field analysis, supplemented by time-dependent density functional theory, was used to correct the historical assignments of the symmetry-allowed transitions in the polarized UV-visible absorption spectrum. Heat-induced reduction of the oxidized manganese sites provided a probe of the relationship between the spin-allowed and spin-forbidden bands. Notably, the intensity of the spin-forbidden transition was highly dependent on the neighboring ions in the Y-site. Simulations and modeling showed that increased intensity was observed only when two Mn(III) ions occupied adjacent substitutions in the Y-site via a proposed exchange-coupling mechanism.

The nature and sources of ore-forming fluids in the Bhukia gold deposit, Western India: constraints from chemical and boron isotopic composition of tourmaline

Gold mineralization in the newly discovered Bhukia deposit in northwestern India is hosted in Proterozoic metamorphosed volcano-sedimentary rocks of the Aravalli-Delhi Belt. Three generations of tourmaline occurring in different textural settings are recognized in the host rocks of the deposit. Fine-grained texturally early tourmalines (Tur-I) precipitated during the gold-sulfide mineralization stage. They are dravitic in composition and occur parallel to the S1 tectonic foliation as fine-grained crystals in tourmaline-albite layers within quartz-albite rock and as scattered grains in calc-silicate rocks. Coarse-grained texturally later schorls (Tur-II) are also restricted to calc-silicate and quartz-albite rocks and characterized by sector zoning. Late-stage type III tourmaline (Tur-III), also of schorl composition, replaces Tur-II along fractures and margins. They are interpreted to have formed during a phase of ore remobilization. All tourmalines, especially the schorls, are strongly enriched in Li, Ga, Mn and Zn with Ga concentrations being the highest ever reported in natural tourmalines (up to 1380 ppm). The boron isotope composition is similar in all three tourmaline types with the consistently light δ11B (−10.4‰ to −7.2‰) indicative of a continental source for B. The chemical and B-isotopic composition of tourmaline is suggestive of the involvement of two fluids, a granitic-derived hydrothermal fluid and metapelite-derived metamorphic fluid. The δ11B variations in the tourmalines can be explained by mixing between 11B-poor granitic-derived hydrothermal fluid and 11B-rich metamorphic-hydrothermal fluid. While high V (2110–4247, avg. 3339 ppm) in the early dravitic tourmalines indicate mixing of granitic-derived hydrothermal fluid with pelite-derived metamorphic hydrothermal fluids during gold-sulfide mineralization, the enrichment of Li, Mn, Zn and Ta, and depletion of V in the later schorlitic tourmalines suggest increasing influence of granitic-derived hydrothermal fluids during ore remobilization.