Monitoring and managing dust (i.e., particulate emissions) remains a ubiquitous challenge to the mining industry resulting in outstanding questions regarding the nature and spatial-temporal distribution of fugitive dust emissions to the near-mine environment. In this study, fugitive dust samples were captured up to 1 km from the mine perimeter over a similar to 2-year study period using passive dry deposition samplers (PAS-DD) deployed around an active open-pit gold mine in Northwestern Qu & eacute;bec, Canada. This study demonstrates the utility of the recently developed PAS-DD for long-term (84-285 days) dust sampling under a wide-range of weather conditions (-37 to 32 degrees C), allowing for measurement of the mine-dust footprint, the flux of dust-transported metal to the near-mine environment, and the micro-characterization of dust including its mineralogy. The results show that net dust deposition is highest near mine operations occurring near the open pit and the mine-access road, and that dust deposition reaches reference-site levels between 200 and 1000 m from the mine perimeter. Captured dust comprised 87-99 vol% silicates (primarily chlorite, quartz, muscovite, plagioclase, and amphibole), 1-9 vol% carbonates (calcite, ankerite, and dolomite), and <2 vol% sulfides (pyrite, pyrrhotite, sphalerite and arsenopyrite). Trace amounts (<0.2 vol%) of arsenopyrite in the dust is primarily responsible for the atmospheric deposition of As to the near-mine environment. The highest flux of As to the near-mine environment (<0.003 mg/dm(2)day) was recorded by samplers north of the open pit and mine access road, where net dust deposition is highest. In contrast, south of the mine dust has much lower net deposition rates (comparable to reference site levels), but delivers a higher concentration of As to the environment, resulting in As deposition rates up to 0.001 mg/dm(2)day (similar to 300x reference site levels). Dust captured south of the mine was enriched in arsenopyrite and is interpreted to reflect increased particulate input from the adjacent tailings storage area. The higher concentration of As in dusts reaching the southern near-mine environment correlates with As-enrichment in the organic layer of soils characterized in an earlier study. Overall, this study demonstrates how the geochemical and mineralogical characterization of dust captured by PAS-DD can be used to understand the role of fugitive mine dust in the transport of environmental contaminants to the near-mine environment.

A potential hazard associated with ferrochrome production is the unintentional generation of Cr(VI) in the off-gas dusts produced during smelting. Cr(VI) is a well-known environmental toxin and genotoxic carcinogen. Although Cr(VI) has been identified in baghouse dusts associated with submerged-arc furnaces, its occurrence in DC-arc-furnace dusts has not been previously investigated. In this study, we report the bulk composition and phase make-up, as well as the surface and bulk speciation of Cr and Fe of dusts generated during smelting of chromite ore under basic slag conditions in a pilot-scale DC arc smelter. Dusts are captured from both within the DC furnace as well as along the off-gas handling stream, after passing through the afterburner. The dusts primarily comprise feed material (chromite, flux, reductant), aerosolized slag, and glassy spherules, interpreted as off-gas condensates. Dusts collected from within the furnace, known as freeboard dusts, are dominated by feed materials, with elevated amounts of flux (lime) and lesser amounts of slag and spherules. In contrast, spherules dominate dusts collected along the off-gas handling stream by dust separators that capture the increasingly fine-grained fraction of dust, with the highest proportion of spherules occurring in baghouse dusts. Chromite is the primary host of Cr in all dust samples, whereas the spherules have low Cr contents. Cr(VI) was identified by X-ray photoelectron spectroscopy in the surfaces of dust collected from all parts of the smelter system considered, including from the furnace freeboard, despite the overall reducing conditions present therein. Cr(VI) concentrations are sufficiently high in dusts collected from the off-gas handling stream (post-afterburner, cyclone, and baghouse) to be detected in the bulk dust samples by X-ray absorption spectroscopy. The higher concentration of Cr(VI) in the finer-grained off-gas dusts, especially the baghouse dusts, is consistent with the increased abundance of spherules, the major Cr(VI)-hosting phase, in these samples. Fe is similarly more oxidized in dusts collected down the off-gas handling stream compared to dusts collected from within the furnace, which are dominated by Fe(II). Fe(III) hosted by FeOOH is predominate in dusts collected from all locations along the off-gas handling stream. These results demonstrate that there is sufficient oxygen ingress and sufficiently high temperatures in the closed DC furnace for Cr(VI) to be generated in the freeboard off-gas dusts. Cr(VI) is associated with the finest grained fraction of dusts, underlining the importance of ensuring the continual improvement of dust-capture systems, especially in terms of their ability to target increasingly finer fractions of dust.

Dusts generated during ferrochrome smelting in a pilot-scale DC arc furnace were sampled from the furnace freeboard and from the off-gas handling stream (cyclone and baghouse). The dusts comprise fine-grained feed material (chromite, flux, and reductant); compositionally heterogeneous, glassy micro-spherules, interpreted as gas condensates and/or aerosolized melt droplets; and trace amounts of ferrochrome. Synchrotron-based micro-X-ray-fluorescence and micro-X-ray absorption near-edge structure around the chromium (Cr) K-edge was used to identify the distribution and speciation of Cr in dust particulates from the freeboard and the cyclone. The dust samples contain Cr in multiple oxidation states, including Cr(0) (hosted by ferrochrome), Cr(III), and Cr(VI). The majority of Cr occurs as Cr(III) in chromite. In both the furnace-freeboard and the cyclone dusts, Cr(VI) was consistently associated with the Si-Ca-Mg-rich micro-spherules. A major finding of this study is that Cr oxidation and Cr(VI) formation can occur in aerosolized dusts within the closed DC-arc furnace during ferrochrome smelting under conditions that are deemed to be essentially reducing. The association of Cr(VI) with the micro-spherules forwards the hypothesis that the high temperature of the furnace off-gasses and the flux composition influence the likelihood of Cr(VI) formation within a closed furnace under open-bath smelting conditions.

The response of forsterite, Mg2SiO4, under dynamic compression is of fundamental importance for understanding its phase transformations and high‐pressure behavior. Here, we have carried out an in situ X‐ray diffraction study of laser‐shocked polycrystalline and single‐crystal forsterite (a‐, b‐, and c‐orientations) from 19 to 122 GPa using the Matter in Extreme Conditions end‐station of the Linac Coherent Light Source. Under laser‐based shock loading, forsterite does not transform to the high‐pressure equilibrium assemblage of MgSiO3 bridgmanite and MgO periclase, as has been suggested previously. Instead, we observe forsterite and forsterite III, a metastable polymorph of Mg2SiO4, coexisting in a mixed‐phase region from 33 to 75 GPa for both polycrystalline and single‐crystal samples. Densities inferred from X‐ray diffraction data are consistent with earlier gas‐gun shock data. At higher stress, the response is sample‐dependent. Polycrystalline samples undergo amorphization above 79 GPa. For [010]‐ and [001]‐oriented crystals, a mixture of crystalline and amorphous material is observed to 108 GPa, whereas the [100]‐oriented forsterite adopts an unknown phase at 122 GPa. The first two sharp diffraction peaks of amorphous Mg2SiO4 show a similar trend with compression as those observed for MgSiO3 in both recent static‐ and laser‐driven shock experiments. Upon release to ambient pressure, all samples retain or revert to forsterite with evidence for amorphous material also present in some cases. This study demonstrates the utility of femtosecond free‐electron laser X‐ray sources for probing the temporal evolution of high‐pressure silicate structures through the nanosecond‐scale events of shock compression and release.

The chemical composition of metasediments is a valuable source of paleogeographic information about the protolith's sedimentary environment. Here, we compile major- and trace-element whole-rock data, including B contents, and 10/11B-isotope ratios from the Permo-Triassic metasedimentary cover of the Pfitsch–Mörchner basin, overlying the Variscan basement in the western Tauern Window, Eastern Alps (Austria and Italy). The basement consists of orthogneiss (“Zentralgneis”, metamorphosed Variscan granitoids with intrusion ages between 305 and 280 Ma), and the roof pendant consists of granites (amphibolites, paragneiss, and minor serpentinites). The Zentralgneis is partly hydrothermally altered into pyrite quartzite with high Al–S contents, low Na–Sr–Ca–Mg contents, and very strong depletion of the light rare earth elements. Comparison with published detailed mapping of this and other time-equivalent basins in the western Tauern Window, with radiometric age data in the literature, and with unmetamorphosed basins in the South Alpine realm yields a late Permian to Early Triassic age of sedimentation. Although during Alpine metamorphism all rocks were strongly deformed, the whole-rock chemical compositions of the metasediments were not pervasively changed during deformation. We show that the sediments were deposited in a small, probably lacustrine–fluviatile, intramontane basin, under arid to semi-arid climatic conditions. The sequence starts with metaconglomerates, which can be interpreted as a mixture of the different basement rocks, based on a combination of major-element ratios Na2O / (Na2O + K2O) and MgO / (MgO + Fe2O3) with concentrations of trace elements Cr, V, and Ni. The sequence is overlain by a fining-upwards sequence of clastic sediments, in which the behavior of K, Rb, and Sr allows the reconstruction of intense diagenetic K–B metasomatism, which raised the K2O contents up to ∼ 10 wt %. The average B content of 218 µg g−1 is well above the B content of common sediments, and the B-isotope composition reaches extremely low values of down to −33 ‰ δ11B. The top of the sequence is a lazulite quartzite, interpreted as a former conglomeratic phosphatic sandstone, which marks the transition from a closed Permian basin to an open Triassic basin. Within the clastic sequence, the presence of hydrothermal tourmalinite veins documents a hydrothermal event after deposition but before the onset of Alpine metamorphism. A metamorphosed mafic dike swarm in the orthogneiss indicates a post-Variscan event of basaltic magmatism, and this event is tentatively correlated with increased heat flow in the Triassic basin and hydrothermal activity. A consistent conceptual model of this basin and its diagenetic modifications, based on a combination of geochemical data with petrographical and field information, provides the geodynamic context of the European margin at the onset of the Alpine orogeny.

12 High-pressure single-crystal X-ray diffraction patterns on five synthetic Mg-Al tourmaline of 13 near end-member composition (dravite NaMg3Al6Si6O18(BO3)3(OH)3OH, K-dravite 14 KMg3Al6Si6O18(BO3)3(OH)3OH, magnesio-foitite • (Mg2Al)Al6Si6O18(BO3)3(OH)3OH, oxy15 uvite CaMg3Al6Si6O18(BO3)3(OH)3O, and olenite NaAl3Al6Si6O18(BO3)3O3OH, where • 16 represents an X-site vacancy) were collected to 60 GPa at 300 K using a diamond-anvil cell and 17 synchrotron radiation. No phase transitions were observed for any of the investigated 18 compositions. The refined unit-cell parameters were used to constrain 3-order Birch19 Murnaghan pressure-volume equation of states with the following isothermal bulk moduli (K0 in 20 GPa) and corresponding pressure derivatives (K0’= ∂K0/∂P)T: dravite K0=97(6), K0’=5.0(5); K21 dravite K0=109(4), K0’= 4.3(2); oxy-uvite K0=110(2), K0’=4.1(1); magnesio-foitite K0=116(2), 22 K0’=3.5(1); olenite K0=116(6), K0’=4.7(4). Each tourmaline has highly anisotropic behavior 23 under compression, with the c axis 2.8 3.6 times more compressible than the a axis at ambient 24 conditions. This anisotropy decreases strongly with increasing pressure and the c axis is only 25 ~14% more compressible than the a axis near 60 GPa. The octahedral Yand Z-sites’ 26 composition exerts a primary control on tourmaline’s compressibility, whereby Al content is 27 correlated with a decrease in the c-axis compressibility and a corresponding increase in K0 and 28 K0’. Contrary to expectations, the identity of the X-site-occupying ion (Na, K, or Ca) does not 29 have a demonstrable effect on tourmaline’s compression curve. The presence of a fully vacant X 30 site in magnesio-foitite results in a decrease of K0’ relative to the alkali and Ca tourmalines. The 31 decrease in K0’ for magnesio-foitite is accounted for by an increase in compressibility along the 32 a axis at high pressure, reflecting increased compression of tourmaline’s ring structure in the 33 presence of a vacant X site. This study highlights the utility of synthetic crystals in untangling the 34 effect of composition on tourmaline’s compression behavior. 35 36

Stishovite (rutile-type SiO2) is the archetype of dense silicates and may occur in postgarnet eclogitic rocks at lower-mantle conditions. Sound velocities in stishovite are fundamental to understanding its mechanical and thermodynamic behavior at high pressure and temperature. Here, we use plate-impact experiments combined with velocity interferometry to determine the stress, density, and longitudinal sound speed in stishovite formed during shock compression of fused silica at 44 GPa and above. The measured sound speeds range from 12.3(8) km/s at 43.8(8) GPa to 9.8(4) km/s at 72.7(11) GPa. The decrease observed at 64 GPa reflects a decrease in the shear modulus of stishovite, likely due to the onset of melting. By 72 GPa, the measured sound speed agrees with the theoretical bulk sound speed indicating loss of all shear stiffness due to complete melting. Our sound velocity results provide direct evidence for shock-induced melting, in agreement with previous pyrometry data.

High-pressure single-crystal X-ray diffraction patterns on five synthetic Mg-Al tourmalines with near end-member compositions [dravite NaMg3Al6Si6O18(BO3)(3)(OH)(3)OH, K-dravite KMg3Al6Si6O18(BO3)(3)(OH)(3)OH, magnesio-foitite o(Mg2Al)Al6Si6O18(BO3)(3)(OH)(3)OH, oxy-uvite CaMg3Al6Si6O18(BO3)(3)(OH) (O), and olenite NaAl3Al6Si6O18(BO3)(3)O3OH, where square represents an X-site vacancy] were collected to 60 GPa at 300 K using a diamond-anvil cell and synchrotron radiation. No phase transitions were observed for any of the investigated compositions. The refined unit-cell parameters were used to constrain third-order Birch-Murnaghan pressure-volume equation of states with the following isothermal bulk moduli (K-0 in GPa) and corresponding pressure derivatives (K-0 ' = partial derivative K0/partial derivative P)(T): dravite K-0 = 97(6), K-0 ' = 5.0(5); K-dravite K-0 = 109(4), K-0 ' = 4.3(2); oxy-uvite K-0 = 110(2), K-0"' = 4.1(1); magnesio-foitite K-0 = 116(2), K-0 ' = 3.5(1); olenite K-0 = 116(6), K-0 ' = 4.7(4). Each tourmaline exhibits highly anisotropic behavior under compression, with the c axis 2.8-3.6 times more compressible than the a axis at ambient conditions. This anisotropy decreases strongly with increasing pressure and the c axis is only similar to 14% more compressible than the a axis near 60 GPa. The octahedral Y- and Z-sites' composition exerts a primary control on tourmaline's compressibility, whereby Al content is correlated with a decrease in the c-axis compressibility and a corresponding increase in K-0 and K-0 '. Contrary to expectations, the identity of the X-site-occupying ion (Na, K, or Ca) does not have a demonstrable effect on tourmaline's compression curve. The presence of a fully vacant X site in magnesio-foitite results in a decrease of K-0 ' relative to the alkali and Ca tourmalines. The decrease in K-0 ' for magnesio-foitite is accounted for by an increase in compressibility along the a axis at high pressure, reflecting increased compression of tourmaline's ring structure in the presence of a vacant X site. This study highlights the utility of synthetic crystals in untangling the effect of composition on tourmaline's compression behavior.

Tourmaline is a common accessory mineral in the metasedimentary Pfitsch Formation located in the Pfitscher Joch (Passo de Vizze) area in the Tauern Window of the Eastern Alps. These post-Variscan metasedimentary units experienced peak metamorphic conditions of ~550°C, 1.0GPa during the Alpine orogeny. Tourmaline is most abundant in a ~25m thick unit of feldspathic gneiss (~20–200μg/g B), where it occurs as idiomorphic crystals typically 10mm in length. The abundance and size of the tourmaline crystals increase near coarse-grained quartzofeldspathic segregations (~1200μg/g B), reflecting the mobilization and concentration of B by metamorphic fluids. Near segregations, individual tourmaline crystals have up to three growth zones, recording pro- (~350–500°C, 0.7–1.0GPa) and retrograde (~400°C, 0.2GPa) growth as determined by combining textural information and sector-zoning thermometry. Retrograde tourmaline occurs as individual crystals as well as overgrowths on prograde tourmaline crystals, especially on the surface of extensional fractures formed by E–W extension during regional decompression.Tourmaline in the Pfitsch Formation is dravitic with a variable Fe content that correlates with the Fe content of its respective host unit. Charge balance calculations suggest that a significant proportion of Fe in tourmaline is ferric, supporting the interpretation of a subaerial continental sedimentary protolith. Tourmaline near segregations has the highest inferred ferric iron content, which decreases across growth zones, potentially reflecting a reduction of the fluid during metamorphism. The Mg/(Mg+Fe) ratio increases with prograde tourmaline growth and decreases in retrograde overgrowths. In contrast, the Ca/(Ca+Na) ratio increases gradually from 0.05 to 0.20 with prograde growth and continues to increase up to 0.25 in the retrograde overgrowths, recording the maximum Ca/(Ca+Na) ratio of the fluid during Alpine metamorphism.The metasediments of the Pfitsch Formation have very low and variable whole-rock δ11B values (−14.1 to −33.6‰), with the highest values (−17.7 to −14.1‰) found in B-rich samples (165–1200μg/g B) containing abundant tourmaline, and the lowest values (−24.2 to −33.6‰) in B-depleted samples (21–40μg/g), which lack tourmaline. This observation supports preferential loss of 11B from the rocks during prograde metamorphism. Zoned tourmaline crystals in the Pfitsch formation show successively decreasing B isotope ratios from −7.8 to −11.2‰ in their cores and −17.3 to −20.3‰ in their rims. As supported by a Rayleigh fractionation model, the B-isotope values of the host rocks and the tourmaline crystals are most easily explained by the internal redistribution of B from a B-rich precursor mineral (e.g. mica) to the tourmaline during Alpine metamorphism.

Ca–Na partitioning between tourmaline and a coexisting fluid is investigated in the system CaO–Na2O–B2O3–Al2O3–MgO–SiO2–H2O–Cl between 0.2–4.0 GPa and 500–700 °C. The synthesis experiments produced a mineral assemblage of tourmaline, coesite/quartz, and in some cases additional phases, typically comprising <1 wt% of the solid product. The synthesized tourmalines are solid solutions of dravite [NaMg3Al6Si6O18(BO3)3(OH)3(OH)], “oxy-uvite” (i.e. “Ca–Mg–O root name”) [CaMg3Al6Si6O18(BO3)3(OH)3O], and magnesio-foitite [☐(Mg2Al)Al6Si6O18(BO3)3(OH)3(OH)]. Starting materials comprised a fluid of constant ionic strength (2.00 m) and an oxide mixture with a constant Mg/Al ratio. As a result, the number of vacancies at the X site and the Mg/Al ratio of tourmaline crystals synthesized at the same temperature vary only slightly. The major solid solution is Ca–Na exchange at the X site via the exchange vector X Ca W O[ X Na W (OH)]−1, with the exchange vector X (Ca☐)[ X Na2]−1 serving as a secondary Ca-incorporation mechanism. Tourmaline’s X-site composition reflects the fluid composition, whereby the Ca (or Na) concentration in the fluid corresponds with the Ca (or Na) content in tourmaline at each pressure and temperature. At 0.2 GPa, 700 °C, Ca preferentially partitions into tourmaline, producing the most Ca-rich tourmaline crystals synthesized here. At pressures >1.0 GPa, Ca partitions preferentially into the fluid, resulting in Na-dominant tourmaline compositions. Temperature has a secondary effect on Ca–Na partitioning, with higher temperatures correlating with increased Ca incorporation in tourmaline. Based on the experimental findings, tourmaline is expected to have Ca-rich compositions when it forms in low pressure, high-temperature Ca-rich rocks, consistent with the current record of tourmaline occurrence. The bulk Mg/Al ratio and the pH of the tourmaline-forming system may also affect Ca incorporation in tourmaline, but remain to be investigated experimentally.

Tourmaline was synthesized in the system MgO–Al2O3–B2O3–SiO2–KCl–NaCl–H2O from an oxide mixture and excess fluid at 500–700 °C and 0.2–4.0 GPa to investigate the effect of pressure, temperature, and fluid composition on the relative incorporation of Na and K in dravitic tourmaline. Incorporation of K at the X-site increases with pressure, temperature, and KCl concentration; a maximum of 0.71 K pfu (leaving 0.29 X-vacant sites pfu) was incorporated into K-dravite synthesized at 4.0 GPa, 700 °C from a 4.78 m KCl, Na-free fluid. In contrast, Na incorporation depends predominately on fluid composition, rather than pressure or temperature; dravite with the highest Na content of 1.00 Na pfu was synthesized at 0.4 GPa and 700 °C from a 3.87 m NaCl and 1.08 m KCl fluid. All synthesized crystals are zoned, and the dominant solid solution in the Na- and K-bearing system is between magnesio-foitite [□(Mg2Al)Al6Si6O18(BO3)3(OH)3OH] and dravite [NaMg3Al6Si6O18(BO3)3(OH)3(OH)], with the dravitic component increasing with the concentration of Na in the fluid. In the K-bearing, Na-free system, the dominant solid solution is between magnesio-foitite and K-dravite [KMg3Al6Si6O18(BO3)3(OH)3(OH)], with the K-dravitic component increasing with pressure, temperature, and the concentration of K in the fluid. The unit-cell volume of tourmaline increases with K incorporation from 1555.1(3) to 1588.1(2) Å3, reflecting the incorporation of the relatively large K+ ion. Comparison of our results to the compositional data for maruyamaite (K-dominant tourmaline) from the ultrahigh-pressure rocks of the Kokchetav Massif in Kazakhstan suggests that the latter was formed in a K-rich, Na-poor environment at ultrahigh-pressure conditions near the diamond-stability field.

Steel production is currently the largest industrial source of atmospheric CO2. As annual steel production continues to grow, the need for effective methods of reducing its carbon footprint increases correspondingly. The carbonation of the calcium-bearing phases in steel slag generated during basic oxygen furnace (BOF) steel production, in particular its major constituent, larnite {Ca2SiO4}, which is a structural analogue of olivine {(MgFe)2SiO4}, the main mineral subjected to natural carbonation in peridotites, offers the potential to offset some of these emissions. However, the controls on the nature and efficiency of steel slag carbonation are yet to be completely understood. Experiments were conducted exposing steel slag grains to a CO2–H2O mixture in both batch and flow-through reactors to investigate the impact of temperature, fluid flux, and reaction gradient on the dissolution and carbonation of steel slag. The results of these experiments show that dissolution and carbonation of BOF steel slag are more efficient in a flow-through reactor than in the batch reactors used in most previous studies. Moreover, they show that fluid flux needs to be optimized in addition to grain size, pressure, and temperature, in order to maximize the efficiency of carbonation. Based on these results, a two-stage reactor consisting of a high and a low fluid-flux chamber is proposed for CO2 sequestration by steel slag carbonation, allowing dissolution of the slag and precipitation of calcium carbonate to occur within a single flow-through system.

The crystal structures of synthetic K-dravite [XKYMg 3 Z Al 6 T Si6O18(BO3) 3 V (OH) 3 W (OH)], dravite [XNaYMg 3 Z Al 6 T Si6O18(BO3) 3 V (OH) 3 W (OH)], oxy-uvite [XCaYMg 3 Z Al 6 T Si6O18(BO3) 3 V (OH) 3 W O], and magnesio-foitite [X☐Y(Mg2Al)ZAl 6 T Si6O18(BO3) 3 V (OH) 3 W (OH)] are investigated by polarized Raman spectroscopy, single-crystal structure refinement (SREF), and powder X-ray diffraction. The use of compositionally simple tourmalines characterized by electron microprobe analysis facilitates the determination of site occupancy in the SREF and band assignment in the Raman spectra. The synthesized K-dravite, oxy-uvite, and magnesio-foitite have significant Mg–Al disorder between their octahedral sites indicated by their respective average 〈Y–O〉 and 〈Z–O〉 bond lengths. The Y- and Z-site compositions of oxy-uvite (YMg1.52Al1.48(10) and ZAl4.90Mg1.10(15)) and magnesio-foitite (YAl1.62Mg1.38(18) and ZAl4.92Mg1.08(24)) are refined from the electron densities at each site. The Mg–Al ratio of the Y and Z sites is also determined from the relative integrated peak intensities of the Raman bands in the O–H stretching vibrational range (3250–3850 cm−1), producing values in good agreement with the SREF data. The unit cell volume of tourmaline increases from magnesio-foitite (1558.4(3) Å3) to dravite (1569.5(4)–1571.7(3) Å3) to oxy-uvite (1572.4(2) Å3) to K-dravite (1588.1(2) Å3), mainly due to lengthening of the crystallographic c-axis. The increase in the size of the X-site coordination polyhedron from dravite (Na) to K-dravite (K) is accommodated locally in the crystal structure, resulting in the shortening of the neighboring O1–H1 bond. In oxy-uvite, Ca2+ is locally associated with a deprotonated W (O1) site, whereas vacant X sites are neighbored by protonated W (O1) sites. Increasing the size of the X-site-occupying ion does not detectably affect bonding between the other sites; however, the higher charge of Ca and the deprotonated W (O1) site in oxy-uvite are correlated to changes in the lattice vibration Raman spectrum (100–1200 cm−1), particularly for bands assigned to the T 6O18 ring. The Raman spectrum of magnesio-foitite shows significant deviations from those of K-dravite, dravite, and oxy-uvite in both the lattice and O–H stretching vibrational ranges (100–1200 and 3250–3850 cm−1, respectively). The vacant X site is correlated with long- and short-range changes in the crystal structure, i.e., deformation of the T 6O18 ring and lengthening of the O1–H1 and O3–H3 bonds. However, X-site vacancies in K-dravite, dravite, and oxy-uvite result only in the lengthening of the neighboring O1–H1 bond and do not result in identifiable changes in the lattice-bonding environment.