Tourmaline Structure Research Articles

Oscillatory Zoned Liddicoatite from Anjanabonoina, Central Madagascar. III. Trace Elements

Abstract Large crystals of liddicoatite (tourmaline) from the Anjanabonoina Pegmatite of Central Madagascar are well-known for their distinct patterns of oscillatory zoning. This study follows two previous investigations, in which the crystal chemistry (Lussier et al. 2011a) and variations of major chemical constituents (Lussier & Hawthorne 2011) were characterized in detail. Here, the variations of elements present only at the trace level are investigated. The measurement by laser ablation inductively coupled plasma mass spectrometry of 26 trace elements, with abundances spanning four orders of magnitude (∼10−1 to 103 ppm) is reported. Trace elements were analyzed along continuous analytical traverses from the core to the rim of the crystal. Abundance profiles for most of the trace elements quantified (21 of 26) show clear oscillations that coincide with optical oscillatory zoning features. Throughout the crystal, the occurrence of compositional oscillation is independent of trace-element abundance; even where mean abundance is low, ∼1 ppm (e.g., V3+, Y3+, Th4+), oscillatory behavior is clear. Conversely, the magnitude of the oscillatory amplitude shows a strong near-linear dependence on element abundance. Within individual oscillatory zones, four unique line-shapes are observed, each differentiated by (1) the direction of a compositional discontinuity at the zone limits and (2) the orientation of the nonlinear curvature across the zone. For any individual zone, the variation in element concentration, C, can be fitted to the equation C = ±Aeλ(x−Φ)+ Δ where A is the zone amplitude; Φ is a reference position, and λi and Δi are fitted parameters. Comparison of the fitted equations shows that linear correlation between element pairs is common, occurring between pairs consisting of trace–trace, trace–major, and major–major elements. The oscillatory behavior of constituent elements is related to the location of the trace element in the tourmaline structure, with elements at the X- and Y-sites typically showing increases and decreases in abundance over single oscillatory zones. Throughout each zone, Mg has high abundance (∼104 ppm) at the start of each zone, followed by an extremely abrupt decrease in abundance, typically over a distance of <1 mm, making its behavior different to that of other elements (both trace and major). Finally, there are systematic differences in trace-element abundances between pyramid {201} and prism {100} sectors of the crystal, echoing the differences observed for major elements between these two sectors and consistent with face-dependent differences in element uptake.

Lowering R3m Symmetry in Mg-Fe-Tourmalines: The Crystal Structures of Triclinic Schorl and Oxy-Dravite, and the Mineral luinaite-(OH) Discredited

Discreditation of the monoclinic tourmaline mineral species luinaite-(OH), ideally (Na,▯)(Fe2+,Mg)3Al6(BO3)3Si6O18(OH)4 was approved by the IMA-CNMNC (proposal 21-L) and is described. We analyzed two luinaite-(OH) samples: one from the type locality Cleveland tin mine, Luina, Waratah, Tasmania, Australia, and the other from Blue Mountain Saddle (Bald Hornet Claim), North Bend, King County, Washington, DC, USA. Biaxial (−) crystals representative of the studied samples were spectroscopically (Mössbauer, polarized Fourier transform infrared, optical absorption spectroscopy), chemically (nuclear microprobe analysis and electron microprobe analysis), and structurally characterized (single-crystal X-ray diffraction). Results show the occurrence of a triclinic structure for the studied luinaite-(OH) samples, which differs only in terms of a slight structural distortion from typical trigonal tourmaline structure (the topology of the structure is retained). As a result, following the IMA-CNMNC and tourmaline nomenclature rules, the triclinic luinaite-(OH) from the type locality (Australia) can be considered as the triclinic dimorph of schorl, as its chemical composition corresponds to schorl, and thus it should be referred as schorl-1A. Similarly, the triclinic sample from the USA can be considered as the triclinic dimorph of oxy-dravite, as its chemical composition corresponds to oxy-dravite, and then is referred to as oxy-dravite-1A.

Preparation and adsorption properties of nano-graphene oxide/tourmaline composites

Abstract This research addresses the asphalt smoke emission in the process of asphalt pavement construction. The nano-graphene oxide (GO)/tourmaline composites were prepared to alleviate the asphalt smoke emission and improve the construction environment. The macrocharacteristics and micromorphology of the composites were analyzed, and their optimal preparation process was determined. Using material microanalysis methods, such as X-ray diffractometer, Raman spectroscopy, and Fourier transform infrared spectrometer, the structural characteristics and material composition of the composites were studied. The adsorption properties of the composites on asphalt smoke were clarified. It will provide technical support for the improvement of infrastructure construction environment. The results show that 3-aminopropyl triethoxysilane is superior than hexadecyl trimethyl ammonium bromide in surface modification of tourmaline. During the composite process, surface modifiers and GO had no significant effect on the structure of tourmaline. GO could enhance the adsorption properties of tourmaline on asphalt smoke. When the GO content was 1.5 wt%, the improvement was the largest, which is 17.42%. At that time, the emission-reduction rate of asphalt smoke reached 41.11%.

Ln3+ (Ln3+ = La, Nd, Eu, Yb) incorporation in synthetic tourmaline analogues: Towards tourmaline REE pattern explanation

Tourmaline rare-earth element (lanthanides + Y) patterns could provide valuable geological information as tourmalines are the most abundant borosilicates on Earth and are stable at extreme PT conditions. The lanthanide-bearing tourmalines were synthesized for the first time in a series of high- (4 GPa) and low-pressure (0.2 GPa) hydrothermal experiments. We have found that Ln-content (Ln = La3+, Nd3+, Eu3+ and Yb3+) in synthetic tourmalines varies significantly (1.13–8.35 wt% Ln2O3) with Yb < La ≤ Nd < Eu independent of pressure conditions. Ln-content in synthetic tourmalines, obtained at low pressure is 2–3 times higher, than those from high-pressure experiments. The Nd- and Eu-rich synthetic tourmalines exhibit cathodo- photoluminescence properties (blue and violet luminescence colors for Nd and Eu, respectively), which confirms trivalent state of Ln in tourmaline structure. Single-crystal X-ray diffraction data for synthetic tourmalines (Nd-rich a 15.893(1), c 7.130(1) Å; Eu-rich a 15.903(5), c 7.168(3) Å) show that Eu3+ and Nd3+ occupy the 9-coordinated X-site in the tourmaline structure. The general formula of obtained synthetic tourmalines can be expressed as Ln3+1-x (Mg,Al)3 (Al,Mg)6 (Si6O18) (BO3)3 (OH,O)3 (OH,O) (0.05 ≤ x ≤ 0.97). The crystal-chemical features and lanthanide speciation in synthesized tourmalines are herein discussed and compared to natural and synthetic compounds.

(Ga,Ge)-Analogue of Tourmaline: Crystal Structure and Composition

Crystals of a (Ga,Ge)-analogue of tourmaline have been synthesized by hydrothermal method in the temperature range of 600–650°C under a pressure of 100 MPa. The composition is analyzed, and the structure of single crystals is determined by X-ray diffraction (XRD) analysis. The rhombohedral-cell parameters are found to be a = 16.0102(4) A, c = 7.18423(19) A, sp. gr. R3m, and Z = 3. The distribution of cations over nonequivalent sites in the structure under study is determined to be as follows: Na0.57(Al1.20Ga1.20 $${\text{Fe}}_{{0.60}}^{{2 + }}$$ )(Al4.728 $${\text{Fe}}_{{1.20}}^{{2 + }}$$ Ti0.072)((Si4.80Ge0.78Al0.42)O18)(BO3)3(OH)3(O0.42ОН0.58). The results obtained confirm possibility for obtaining Ge-substituted crystals with tourmaline structure, which (by analogy with the Ge-analogue of quartz) exhibit high piezo- and pyroelectric properties.

Considerations About Bi and Pb in the Crystal Structure of Cu-Bearing Tourmaline

Copper- and Mn-bearing elbaitic tourmaline (“Paraíba tourmaline”) sometimes contains significant amounts of Pb and Bi. Their position in the tourmaline crystal structure was studied with correlation analysis and bond valence calculations. Correlations between the F content and the X-site charge allow predicting the X-site occupancy. Three sets of tourmaline analyses were studied: (1) Pb-rich tourmalines from the Minh Tien pegmatite, Vietnam; (2) Cu-, Pb- and Bi-bearing tourmalines from the Mulungu mine, Brazil; (3) Cu- and Bi-bearing tourmalines from the Alto dos Quintos mine, Brazil. Two correlations were plotted: (1) the charge by considering only Na1+, Ca2+ and K1+; (2) the charge by adding Pb2+ and Bi3+ to the X-site charge. When plotting correlations for the Minh Tien tourmalines, the correlation significantly improves by adding Pb2+ to the X site. For the Alto dos Quintos tourmalines, only a slight increase of the correlation coefficient is observed, while such a correlation for tourmalines from Mulungu interestingly shows a slight decrease of the correlation coefficient. Bond valence calculations revealed that Bi3+ and Pb2+ can indeed occupy the X site via BiLi(NaAl)−1, PbLi(NaCu)−1 and possibly PbCu(NaAl)−1 substitutions as seen in the investigated tourmaline samples. At the Y site, Pb4+ can be substituted via PbLi(AlCu)−1, and PbVO(AlVOH)−1, while Bi5+ does not have any stable arrangement in Cu-bearing fluor-elbaite. The occurrence of Pb4+ at the Y site could be one explanation for the results of the correlations of the Mulungu tourmalines. Another explanation could be that during the tourmaline crystallization some additional Bi and Pb came into the pegmatitic system and hence disturbed the correlation between the average X-site charge and the F content. Further plots of such correlations in “Paraíba tourmaline” samples might also help to distinguish between the worldwide localities of these rare and sought-after tourmalines.

Synthesis and crystal structure of Pb-dominant tourmaline

Pb-dominant tourmaline was synthesized at 700 °C and 200 MPa in two hydrothermal experiments in the system MgO-Al 2 O 3 -B 2 O 3 -SiO 2 -PbO-H 2 O (run OV-4-2) and MgO-Al 2 O 3 -B 2 O 3 -SiO 2 -PbO-CaO-Na 2 O-H 2 O (run OV-5-3), respectively. Run OV-4-2 forms needle-like (lengths up to 7 μm), lead-rich (up to 13.3 wt% PbO) crystals that are chemically homogeneous. Run OV-5-3 forms columnar (lengths up to 400 μm) crystals that are chemically zoned (Pb-rich cores, up to 14.7 wt% PbO, and Pb-poor rims, ~2 wt% PbO). Additional phases that form in trace amounts are Pb-feldspar, quartz, diaspore (in OV-4-2) and talc, mullite, spinel, quartz (in OV-5-3). Single-crystal structure refinement (SREF) of the central zone of Pb-rich tourmaline from the run OV-5-3 proves that Pb 2+ cations occupy the X -site in the tourmaline structure. The unit-cell parameters of the studied tourmaline are: a = 15.9508(10) Å, c = 7.2024(6) Å. The formula derived from SREF results of this Pb-rich tourmaline is X (Pb 0.63 ◻ 0.37 ) Y (Al 1.71 Mg 1.29 ) Z (Al 5.04 Mg 0.96 ) T (Si 6.00 O 18 ) (BO 3 ) 3 V (OH) 3.00 W (O 1.00 ). Accordingly, the studied crystal is a Pb-analog of hypothetical “oxy-uvite,” and thus referred to here as “Pb-oxy-uvite.” Similarities between (1) the paragenesis of Minh Tien tourmaline, and (2) the final experimental phase assemblages observed here, indicate comparable P-T conditions of formation.

Compressibility and structure behaviour of maruyamaite (K-tourmaline) from the Kokchetav massif at high pressure up to 20 GPa

The structural behaviour of maruyamaite (K-dominant tourmaline) X(K0.54Na0.28Ca0.19)Y(Mg1.3Al1.17Fe0.39Ti0.14)Z(Al5Mg)[Si5.95Al0.05O18](BO3)3V,W[O1.69(OH)2.31] from the ultrahigh-pressure metamorphic rocks of Kokchetav massif was studied using synchrotron based single-crystal diffraction up to 20 GPa. Within the whole pressure range the compression is regular and anisotropic, with the c direction being more compressible than the a direction. Fitting the V/P data with the 2nd and 3rd order Birch-Murnaghan equations of state gives: V0 = 1587.2(7) A3, K0 = 115.6(9) GPa at fixed K′ = 4, and V0 = 1588(1) A3, K0 = 112(3) GPa, K′ = 4.5(4). The bulk modulus values are slightly higher as compared to those found for dravite and cation-deficient synthetic K-dravite. The pressure evolution of the main structural parameters of K-tourmaline is similar to those of dravite. However, a minor change in the rigidity of local contacts of the X site with 6-membered ring, due to the presence of K, is apparently critical for stabilization of tourmaline structure within 15–20 GPa, which is evinced by the absence of the phase transition observed in dravite near 15.4 GPa. The stabilizing function of K becomes apparent at P > 15 GPa. The comparison of the HP structural behaviour of maruyamaite and dravite supports the recent suggestion that the large X site plays a secondary role in the elastic behaviour of tourmaline, compared to the octahedral framework. In addition, the present study reveals several new features of polyhedra distortions, which demonstrate their complex interaction on compression.

Insight into the Thermal Behavior of Tourmaline Mineral

The thermal behavior of tourmaline mineral during the whole process from solid state at room temperature to molten salt at high temperature and back to solid state at room temperature has been systematically investigated. Surface characterization based on observation of the sintering point, thermogravimetry-differential scanning calorimetry, high-temperature x-ray diffraction analysis, field-emission transmission electron microscopy, and high-temperature Raman spectrometry did not reveal any significant changes in the crystal structure of tourmaline except for a slight decrease in grain size during the heating process from room temperature to 890°C. Further increase in the temperature to 1050°C resulted in a phase transformation into cordierite along with a sharp decrease in grain size; the phase transformation was complete at 1200°C. When the temperature was decreased to 890°C, the tourmaline phase was observed to precipitate in the molten salt, and the grain size was found to grow gradually. A continuous decrease in temperature resulted in more tourmaline with slightly smaller grain size due to the pinning effect at second-phase grain boundaries.

Study on a new type of pyroelectric materials with structure of tourmaline

Pyroelectricity is mainly affected by the structure of materials. To explore the influence of the structure on pyroelectricity, a new type of pyroelectric materials with structure of tourmaline consisting of Li9Mg3[PO4]4F3, Ba3Sr4(BO3)3F5 and tourmaline have been systematically studied in this work. Based on the comparison results of the pyroelectric coefficient of Li9Mg3[PO4]4F3 and Ba3Sr4(BO3)3F5 after heating and the variations of electric dipole moment, it suggests the tetrahedron is less stable than trigon, and is easily to cause the distortion and deformation of structure, which leads to the great enhancement of pyroelectricity. Additionally, it can find that the tetrahedron has the most contribution to the pyroelectricity by comparing the pyroelectric coefficient and total electric dipole moment of Li9Mg3[PO4]4F3, Ba3Sr4(BO3)3F5 and tourmaline which have different polyhedrons.

High-pressure study of dravite tourmaline: Insights into the accommodating nature of the tourmaline structure

Author(s): O'Bannon, E; Beavers, CM; Kunz, M; Williams, Q | Abstract: The high-pressure behavior of dravite tourmaline [Na(Mg3)Al6(Si6O18)(BO3)3(OH)3(OH)] has been studied using luminescence spectroscopy and synchrotron-based single-crystal diffraction up to ~65 and ~24 GPa, respectively. Two emission bands associated with Cr3+/V2+ substitution are constant in energy up to ~9.0 GPa, and they shift to longer wavelength at higher pressures, suggesting that a change in compressional mechanism could occur at this pressure. Single-crystal diffraction data show subtle changes in ring ditrigonality occur near 9.0 GPa, which could cause the observed change in luminescence. Near 15 GPa, a splitting of one of the emission bands is observed, suggesting that a phase transition occurs at this pressure and that two unique octahedral sites are present in the high-pressure phase. Hysteresis is not observed on decompression, which indicates that this is a second-order transition, and the high-pressure structure appears to be metastable up to ~65 GPa. Single-crystal diffraction measurements show that a phase transition from rhombohedral R3m to rhombohedral R3 occurs at pressures near 15.4 GPa. The high-pressure phase is characterized by a distorted Si6O18 ring (e.g., the Si-Si-Si angles deviate from 120°), and the Si, Al, O6, O7, and O8 sites of the low-pressure phase split, implying that the high-pressure phase of tourmaline is a higher entropy phase. The large X-site exerts the primary control on compressibility, and the substitution of larger cations into this site will likely lower the pressure at which this transition occurs. Dravite tourmaline shows anisotropic compression with the c-axis being more compressible than the a-axis. The pressure and volume data up to ~15.4 GPa were fit with second- and third-order Birch-Murnaghan equations of state. We obtain a bulk modulus, K0 = 109.6(3.2) GPa, and a pressure derivative, K0′ c K'0 = 4.6(8) GPa, and with the pressure derivative set to 4, a bulk modulus of 112.0(1.0) GPa is derived. Moreover, our high-pressure results show that massive overbonding of the X and Y sites can be accommodated by the tourmaline structure. This unexpected result may explain the extraordinary structural tolerance with respect to chemical substitution on the X, Y, and Z sites.

Tourmaline crystal chemistry

Tourmalines form the most important boron rock-forming minerals on Earth. They belong to the cyclosilicates with a structure that may be regarded as a three-dimensional framework of octahedra ZO6 that encompass columns of structural “islands” made of XO9, YO6, BO3, and TO4 polyhedra. The overall structure of tourmaline is a result of short-range and long-range constraints resulting, respectively on the charge and size of ions. In this study, published data are reviewed and analyzed to achieve a synthesis of relevant experimental results and to construct a crystal-chemical model for describing tourmalines and their compositional miscibility over different length scales. Order-disorder substitution reactions involving cations and anions are controlled by short-range structural constraints, whereas order-disorder intracrystalline reaction involving only cations are controlled by long-range structural constraints. The chemical affinity of a certain cation to a specific structural site of the tourmaline structure has been established on the basis of structural data and crystal-chemical considerations. This has direct implications for the tourmaline nomenclature, as well as on petrogenetic and provenance information. Some assumptions behind the classification scheme of tourmaline have been reformulated, revealing major agreement and significant improvements compared to earlier proposed scheme.

Crystallographic Basis for the Stability of Abundant (Popular) Structure Types

In compliance with the hypothesis that the crystal structure stability increases with a decrease in the degrees of freedom of the constituent atoms, we propose quantitative criteria for structures: the ratio between the amount of the degrees of freedom of atoms to their number in a primitive cell (S) and the fundamental volume (V*)–the quotient of the cell volume (asymmetric unit) and the order of the symmetry group (M) that is the general position multiplicity. The crystallographic analysis of diamond and spinel structure types and their comparative analysis with stability and packing criteria are performed. The study uses the findings from the analysis of abundant less symmetrical tourmaline and apatite structure types which confirm the existence of standard frameworks–symmetrical spatial configurations of atomic sites that can be taken by atoms of various types.

Terahertz frequency characterization of anisotropic structure of tourmaline

The absorption coefficient and refractive index of tourmaline in different directions were characterized for the first time using terahertz time-domain spectroscopy. Results show that the absorption and refractive index of terahertz frequency are related to the structure of tourmaline. Absorption along the optical axis direction is more sensitive than that along the vertical direction. This result indicates that the identification and characterization of crystals as well as minerals can be realized by the terahertz method.

Crystallographic analysis of apatite and tourmaline structure types: Rules of maximum symmetrization and coherent assembly

Following the maximum symmetrization principle (maximum decrease in the degrees of freedom of atoms in the structure), the results of the crystallographic analysis of structures of the very abundant apatite type (P63/m), rare krasheninnikovite mineral (P63/mcm), and also abundant tourmaline (R3m) are discussed. The configuration of cations defining the structure in the first two minerals is created by a set of “skeletal” planes of the cubic and hexagonal sublattices, whereas tourmaline contains only a cubic sublattice, with a great similarity to the former in the cation framework geometry.

The characterization of tourmaline and its effects on plant growth

The purpose of this study was to investigate the characteristics of ACERALIVEN™, a commercial tourmaline, and to test its effect on plant growth. According to our analysis, ACERALIVEN™ belongs to the Si-Al-Mg tourmaline structure. It contains some trace metals such as zirconium, potassium, and iron and able to emit far-infrared energy in the emissivity of 0.829. Introducing the tourmaline into water changes the water to be more alkaline. Tourmaline also releases negative hydroxyl ions and dissolved oxygen creating what is called as hydrogen water. Mung beans submerged with ACERALIVEN™ shows a longer lifetime than without submerging the tourmaline. Additionally, the tourmaline can promote plant growth by removing chlorine and releasing far-infrared which is beneficial for plant’s metabolism.

Cubic cation framework in trigonal structures of tourmalins: The core of structural type stability

The crystallographic analysis of the tourmaline structure type with the general formula XY3Z6(T6O18)(BO3)3V3W (R3m, Z = 3, a ≈ 16 A, c ≈ 7.2 A) shows that tetrahedrally coordinated T (Si, Al, …) cations, octahedrally coordinated Z (Al, Fe, Mg), and Y (Fe, Mg, Mn, …) form a joint cation framework with a sublattice whose geometry is close to F cub (a к ≈ 4.40 A, αк ≈ 93°) with 40% vacant positions in it. The anion ordering is less regular.

Effect of heat treatment on structure, surface composition, infrared emission and surface electrical properties of tourmaline

Crystal structure, surface composition, infrared emission properties and surface electrical properties of tourmaline from Guangxi of China, when subjected to heat treatment in air atmosphere had been studied by some methods, including X-ray fluorescence spectrum (XRF), X-ray diffraction (XRD) meter, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), energy dispersion spectroscopy (EDS), scanning electron microscope (SEM) and Zeta potential analyzer, etc. Experimental results show that the unit cell of tourmaline would shrink during heat treatment because Fe[Formula: see text] were oxidized. Moreover, the Fe[Formula: see text]/Fe[Formula: see text] inside tourmaline can be raised after treatment. Infrared normal total emissivity of tourmaline reaches 0.87, and infrared radiation energy density is [Formula: see text]. It can maintain excellent infrared emission properties at high temperature. Simultaneously, tourmaline presents negative Zeta potential in the aqueous solution, and its Zeta potential reaches −18.04 mV. Zeta potential of tourmaline was increased to −24.83 mV after heat treatment at 400[Formula: see text]C, and decrease to −11.78 mV after heat treatment at 600[Formula: see text]C. These findings may provide reference data for tourmaline’s application in the field of functional materials.

Кристаллографический анализ структурных типов апатита и турмалина: правила максимальной симметризации и когерентной сборки

Кристаллографический анализ структурных типов апатита и турмалина: правила максимальной симметризации и когерентной сборки

First high-pressure synthesis of rossmanitic tourmaline and evidence for the incorporation of Li at the X site

Lithium is an important component of some tourmalines, especially in chemically evolved granites and pegmatites. All attempts at synthesizing Li-rich tourmaline have so far been unsuccessful. Here we describe the first synthesis of rossmanitic tourmaline at 4 GPa and 700 °C in the system Li2O–Al2O3–SiO2–B2O3–H2O (LASBH) from seed-free solid starting materials consisting of a homogenous mixture of Li2O, γ-Al2O3, quartz and H3BO3. The solid run products after 12-day run duration comprise rossmanitic tourmaline (68 wt%), dumortierite (28 wt%) and traces of spodumene (3 wt%) and coesite (1 wt%). Tourmaline forms idiomorphic, large prismatic crystals (30 × 100 μm), which are inclusion free and chemically unzoned. The refined cell dimensions of the tourmaline are: a = 15.7396(9) A, c = 7.0575(5) A, V = 1514.1(2) A3. Conventionally, the Li+ ion is assumed to exclusively occupy the octahedral Y site in the tourmaline structure to a maximum of 2 Li per formula unit (pfu). However, the chemical composition of our synthetic tourmaline determined by electron microprobe and secondary ion mass spectroscopy results in the formula: X(☐0.67(11)Li0.33(11))Y(Al2.53(10)Li0.47(10))Z(Al6)T(Si5.42(15)B0.58(15))O 18 B (BO3) 3 V+W [(OH)2.40(3)O1.60(3)], wherein a significant amount of Li occupies the X site for charge balance requirements. Reliable assignment of the OH-stretching vibrations in a polarized single-crystal Raman spectrum such as a single-crystal XRD structure refinement, confirms the incorporation of Li at the X site [0.24(9) and 0.15(5) XLi pfu, respectively]. The SREF data show that the Li–O1 distances are shortened significantly in order to compensate for the smaller ionic radius of Li+ compared to Na+, K+ or Ca2+ at the X site, i.e., Li is closer to the Si6O18 ring and to a sevenfold coordination with oxygen.