Physics and Chemistry of Minerals最新文献

{"title":"Ultimate mechanical properties of enstatite","authors":"Karine Gouriet,&nbsp;Pascal Roussel,&nbsp;Philippe Carrez,&nbsp;Patrick Cordier","doi":"10.1007/s00269-022-01206-5","DOIUrl":"10.1007/s00269-022-01206-5","url":null,"abstract":"<div><p>The ultimate mechanical properties of MgSiO₃ orthoenstatite (OEN), as characterized here by the ideal strengths, have been calculated under tensile and shear loadings using first-principles calculations. Both ideal tensile strength (ITS) and shear strength (ISS) are computed by applying homogeneous strain increments along high-symmetry directions ([100], [010], and [001]) and low index shear planes ((100), (010), and (001)) of the orthorhombic lattice. We show that the ultimate mechanical properties of OEN are highly anisotropic during tensile loading, with ITS ranging from 4.5 GPa along [001] to 8.7 GPa along [100], and quite isotropic during the shear loading with ISS ranging from 7.4 to 8.9 GPa. During tensile test along [100] and [001], a modified structure close to OEN has been found. This modified structure is more stable than OEN under stress (or strain). We have characterized its elastic and ultimate properties under tensile loading. With ITS ranging from 7.6 GPa along [010] to 25.6 GPa along [001], this modified structure appears to be very anisotropic with exceptional strength along [001].</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2022-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00269-022-01206-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4460711","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Application of the double-difference relocation method to acoustic emission events in high-pressure deformation experiments","authors":"Timothy Officer,&nbsp;Lupei Zhu,&nbsp;Ziyu Li,&nbsp;Tony Yu,&nbsp;David R. Edey,&nbsp;Yanbin Wang","doi":"10.1007/s00269-022-01203-8","DOIUrl":"10.1007/s00269-022-01203-8","url":null,"abstract":"<div><p>A methodology has been developed, detailing the theory and workflow, for applying the double-difference relocation method to acoustic emission (AE) event location in high-pressure/high-temperature deformation experiments in the multi-anvil apparatus. The process is predicated on the fact that events originating from a common source region will traverse similar ray paths from the source to the receiver and display similar waveforms in seismograms. This implies their travel-time difference results only from their spatial offset and any velocity heterogeneity along the ray path is negated. To demonstrate the efficacy of this approach we applied it to a transformational faulting experiment on the isostructural olivine analogue Mg₂GeO₄ under controlled deformation at 2.5 GPa and 700 °C while simultaneously monitoring stress, strain, and acoustic activity. Waveforms from all 1456 AE events were cross-correlated to measure differential arrival times and construct multiplet groups of similar events. In total, 110 multiplets were identified whose size is dominated by two large groups containing 272 and 202 events. Relocation of these two multiplets using the double-difference method significantly reduces event separation and improves location uncertainty by more than an order of magnitude when compared to absolute location techniques whose uncertainty rivals that of the sample size. In particular, event locations of the two largest multiplets reveal two dense clusters whose spatial geometry closely mirrors that of macroscopic faulting displayed in computerized tomography images of the recovered sample. In this way, we are able to link specific faults with their associated AE events, which would otherwise not be possible using traditional absolute location methods.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2022-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00269-022-01203-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4254258","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Grain growth inhibited during grain size-sensitive creep in polycrystalline ice: an energy dissipation-rate perspective","authors":"Tess E. Caswell,&nbsp;Reid F. Cooper","doi":"10.1007/s00269-022-01202-9","DOIUrl":"10.1007/s00269-022-01202-9","url":null,"abstract":"<div><p>Experiments in which two identical polycrystalline ice Ih specimens are simultaneously subjected to the same time–temperature history while one of the specimens is actively deformed via grain size-sensitive (GSS) creep demonstrate distinctly different microstructural evolution: for particular ranges of starting grain size and differential stress, grains do not grow in the deforming specimen. Ice Ih specimens having initial, uniform grain sizes in the range <i>d</i> = 6–63 μm were tested in pairs that were subjected to identical time–temperature conditions (durations <i>t</i> = 4–12 days; <i>T</i> = 240 K) but of which only one was subjected to differential stress (<i>σ</i>₁ = 0.25–1.85 MPa; <i>σ</i>₃ = 0). Comparing specimens within a pair, for those with coarser initial grain size, the deformed specimens exhibit suppressed or no grain growth. Our results are interpreted from the perspective of nonequilibrium thermodynamics, specifically comparing the energy dissipation rates associated with both grain growth and plastic flow: if the rate of energy dissipation associated with flow exceeds that of grain growth, the grains will not grow. An examination of the limited database on GSS flow and grain growth in silicates conforms to our analysis. The results are applied to the question of the mechanical evolution of terrestrial glaciers and to the ice-rich shells of the outer satellites.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2022-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4085825","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Equation of state of elbaite at high pressure up to 21.1 GPa and room temperature","authors":"Wei Chen,&nbsp;Shijie Huang,&nbsp;Zhilin Ye,&nbsp;Jiamei Song,&nbsp;Shanrong Zhang,&nbsp;Mengzeng Wu,&nbsp;Dawei Fan,&nbsp;Wenge Zhou","doi":"10.1007/s00269-022-01201-w","DOIUrl":"10.1007/s00269-022-01201-w","url":null,"abstract":"<div><p>The equation of the state of a natural elbaite sample has been investigated at room temperature and up to 21.1 GPa for the first time using in situ synchrotron X-ray diffraction in this study. No phase transition is observed on elbaite over the experimental pressure range. The pressure–volume data were fitted by the third-order Birch-Murnaghan equation of state (EoS) with the zero-pressure unit-cell volume <i>V</i>_<i>0</i> = 1540.7 (6) ų, the zero-pressure bulk modulus <i>K</i>_<i>T</i>0 = 114.7 (7) GPa, and its pressure derivative <i>K</i>'_T0 = 4.2 (1), while obtained <i>V</i>₀ = 1540.1 (4) ų and <i>K</i>_T0 = 116.4 (4) GPa when fixed <i>K</i>'_T0 = 4. Furthermore, the axial compressional behavior of elbaite was also fitted with a linearized third-order Birch-Murnaghan EoS, the obtained axial moduli for <i>a</i>-axis and <i>c</i>-axis are <i>K</i>_a0 = 201 (4) GPa and <i>K</i>_c0 = 60 (1) GPa, respectively. The axial compressibilities of <i>a</i>-axis and <i>c</i>-axis are <i>β</i>_a = 1.66 × 10^–3 GPa⁻¹ and <i>β</i>_c = 5.56 × 10^–3 GPa⁻¹ with an anisotropic ratio of <i>β</i>_a: <i>β</i>_c = 0.30: 1.00, which shows an intense axial compression anisotropy. The potential influencing factors on the bulk moduli and the anisotropic linear compressibilities of tourmalines were further discussed.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2022-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4088373","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High-pressure behaviour of stellerite: single-crystal X-ray diffraction study","authors":"Yurii V. Seryotkin","doi":"10.1007/s00269-022-01205-6","DOIUrl":"10.1007/s00269-022-01205-6","url":null,"abstract":"<div><p>The high-pressure (H<i>P</i>) behavior of natural stellerite |Ca_4.00Na_0.16 (H₂O)₃₂| [Al_8.16Si_27.84O₇₂] has been studied by single-crystal X-ray diffraction using a diamond-anvil cell under pressures up to 4.5 GPa, with a 4:1 ethanol:water mixture and paraffin as pressure-transmitting media. The changes in the structure of stellerite at high pressures, especially the STI framework deformation, are similar to those in Na-rich stilbite |Ca_4.00Na_1.47 (H₂O)₃₀| [Al_9.47Si_26.53O₇₂]. Both stilbite and stellerite udergo pressure-induced hydration, in which H₂O molecules first occupy partly vacant sites and then the initially vacant positions. Some difference in the behavior of the two minerals is due to the presence of Na⁺ cations in stilbite. Sodium occupies positions in the 10-membered ring and prevents H₂O molecules from penetrating near the ring center. Meanwhile, both stellerite and stilbite can fill the initially vacant sites in the 8-membered ring at high pressures. The pressure-induced changes, including the reduction of H₂O sites in the cation coordination and a total number of H₂O molecules, are less significant in Na-bearing stilbite than in stellerite.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2022-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5124420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thermal annealing of fission and ion tracks in epidote","authors":"Wagner M. Nakasuga,&nbsp;Weixing Li,&nbsp;Chien-Hung Chen,&nbsp;Trevor A. Dumitru,&nbsp;Vladimir A. Skuratov,&nbsp;Rodney C. Ewing","doi":"10.1007/s00269-022-01200-x","DOIUrl":"10.1007/s00269-022-01200-x","url":null,"abstract":"<div><p>Fission tracks are used for geologic age-dating and for the reconstruction of thermal histories of Earth’s upper crust. However, there remains a gap in the understanding between the atomic-scale annealing mechanism of latent (unetched) fission tracks and the observations of etched tracks at the micrometer scale. This is because the structure of latent fission tracks is lost during the leaching process. We have conducted the first comparison of the thermal-annealing behavior of latent and etched tracks in epidote, using transmission electron microscopy (TEM) and optical microscopy, respectively. For high-resolution TEM observations, we used ion tracks instead of fission tracks to control the density of tracks, and we demonstrated that latent ion tracks are amorphous in epidote. The reduction in diameters of latent tracks is insignificant after thermal annealing at 800 °C for 24 h, indicating that the track diameter does not appear to change substantially until the final stage of annealing. The optical observations show that the parallel etched ion-induced tracks have a lower track density reduction rate at or below 500 °C and an accelerated reduction rate above 500 °C as compared with randomly oriented fission tracks. However, the two types of tracks display a comparable thermal-annealing behavior as evidenced by the fit of the two curves for the normalized density of ion and fission tracks as a function of temperature with the same equation but with different fitting parameters. Thus, ion-induced tracks can be used to simulate fission tracks in epidote and provide a basis for understanding the annealing of latent and etched tracks.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2022-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00269-022-01200-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5118509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"In-situ high-pressure and high-temperature spectroscopic studies of phengite in ultrahigh-pressure eclogite: implications for water transport during ultra-deep continental subduction","authors":"Xuejing He,&nbsp;Li Zhang,&nbsp;Hiroyuki Kagi,&nbsp;Joseph R. Smyth,&nbsp;Kazuki Komatsu,&nbsp;Xiaoguang Li,&nbsp;Jing Gao,&nbsp;Li Lei","doi":"10.1007/s00269-022-01196-4","DOIUrl":"10.1007/s00269-022-01196-4","url":null,"abstract":"<div><p>Pressure and temperature responses of natural phengite [K_0.93Na_0.03(Al_1.46Mg_0.45Fe_0.09)(Si_3.59Al_0.39Ti_0.02)O₁₀(OH_1.94F_0.06)] in ultrahigh-pressure eclogite from the main hole of the China Continental Scientific Drilling Project (CCSD), the Dabie-Sulu orogenic belt have been studied using in-situ high-pressure mid-infrared and high-temperature Raman spectroscopic measurements up to ~ 20 GPa and 800 °C, respectively. Linear positive pressure dependences were observed for the infrared absorption bands associated with the aluminosilicate vibrations up to ~ 19 GPa, indicating the steady compression of the structure framework. The frequencies of the O–H stretching doublet bands, initially at 3601 and 3626 cm⁻¹, displayed linear downshifts up to 16.6 GPa at − 2.02 and − 2.72 cm⁻¹/GPa, respectively, implying high stability of the hydroxyl groups under compression. In the high-temperature Raman spectra, the bands initially centered at 265, 420, 703 cm⁻¹, and the O–H stretching modes at 3620 cm⁻¹ exhibited modest linear negative shifts with increasing temperature up to 800 °C. Comparisons between experimental results of the present study and those of the previous studies make it plausible that phengite with a higher Si content, i.e., a higher tetrahedral Si/Al ratio, would have higher stabilities under both high pressure and high temperature, and is likely to transport water to greater depths during subduction processes.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2022-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00269-022-01196-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4902527","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On the crystal-chemistry of meyerhofferite, CaB3O3(OH)5·H2O","authors":"G. Diego Gatta,&nbsp;Giorgio Guastella,&nbsp;Silvia C. Capelli,&nbsp;Davide Comboni,&nbsp;Alessandro Guastoni","doi":"10.1007/s00269-022-01199-1","DOIUrl":"10.1007/s00269-022-01199-1","url":null,"abstract":"<div><p>The crystal structure and crystal chemistry of meyerhofferite, ideally CaB₃O₃(OH)₅·H₂O, was investigated by a multi-methodological approach based on titrimetric determination of boron, gravimetric determination of calcium, determination of fluorine by ion selective electrode, determination of water content by heating, other minor elements by inductively coupled plasma atomic emission spectroscopy, along with single-crystal synchrotron X-ray and neutron diffraction. The concentration of more than 50 chemical elements was measured. The combination of these techniques proves that the composition of meyerhofferite approaches the ideal one (i.e., (Ca_1.012Mg_0.003) (B_2.984Si_0.001)O₃(OH)₅·1.018H₂O), with only a modest fraction of Mg (with MgO ≈ 0.03 wt%) replacing Ca, and with Si the only potential substituent of tetrahedral B (with SiO₂ ≈ 0.02 wt%). The content of REE and other minor elements is, overall, not significant, including that of fluorine as a potential OH⁻ substituent (i.e., &lt; 0.01 wt%). These findings have some relevant geochemical and technical implications, here discussed. The X-ray and neutron structure model obtained in this study prove that the building units of the structure of meyerhofferite consist of: two BO₂(OH)₂ tetrahedra and one BO₂(OH) triangle, linked by corner-sharing to form [B₃O₃(OH)₅]²⁻ rings, and distorted Ca-polyhedra (with CN = 8, CaO₃(OH)₄(OH₂)), linked by edge-sharing to form infinite chains along [001]. The B₃O₃(OH)₅ rings are connected to the Ca-polyhedra chains by corner- and edge-sharing, on two sides of the chains. These heteropolyhedral chains, made by Ca-polyhedra and B₃O₃(OH)₅ rings, are mutually connected through hydrogen bonding only, giving rise to the tri-dimensional edifice of meyerhofferite. The neutron structure refinement showed no evidence of static or dynamic disorder pertaining to the H sites; their libration regime was found to be significantly anisotropic. At least seven of the nine oxygen sites of the structure are involved in H-bonding, as <i>donors</i> or as <i>acceptors</i>. The role played by the H-bonding scheme on the physical properties of meyerhofferite is discussed.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2022-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00269-022-01199-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4698423","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thermodynamic properties of geikielite (MgTiO3) and ilmenite (FeTiO3) derived from vibrational methods combined with Raman and infrared spectroscopic data","authors":"Michael H. G. Jacobs,&nbsp;Arie P. van den Berg,&nbsp;Rainer Schmid-Fetzer,&nbsp;Jellie de Vries,&nbsp;Wim van Westrenen,&nbsp;Yue Zhao","doi":"10.1007/s00269-022-01195-5","DOIUrl":"10.1007/s00269-022-01195-5","url":null,"abstract":"<div><p>We present a model for the lattice vibrational density of states of MgTiO₃ (geikielite) and FeTiO₃ (ilmenite) that predicts thermodynamic properties, in agreement with observational data. The model is based on Kieffer’s method combined with spectroscopic data. For both substances experimental data sets are influenced by non-stoichiometry. For geikielite that affects the volume, whereas for ilmenite volume and bulk modulus are affected. We show that Kieffer’s method enables predicting bulk moduli in pressure–temperature space. We demonstrate that intrinsic anharmonicity or electronic effects significantly affect the heat capacity of ilmenite, whereas that is not the case for geikielite. We use Kieffer’s method to derive multiple-Einstein models, from which we demonstrate that thermodynamic properties are insignificantly influenced by dispersion in Grüneisen, mode-q and anharmonicity parameters for both substances. We show that our results enable predicting thermodynamic properties and shear modulus of the solid solution formed from geikielite and ilmenite. Geikielite and ilmenite are added to our thermodynamic database for the system MgO–SiO₂–FeO, to enable modeling phase stability and physical properties of titanium-rich reservoirs in the Earth’s Moon.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2022-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00269-022-01195-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4389716","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Crystal structure and investigation of Bi2TeO6·nH2O (0 ≤ n ≤ ({raise0.5exhbox{$scriptstyle 2$} kern-0.1em/kern-0.15em lower0.25exhbox{$scriptstyle 3$}})): natural and synthetic montanite","authors":"Owen P. Missen,&nbsp;Stuart J. Mills,&nbsp;Michael S. Rumsey,&nbsp;Matthias Weil,&nbsp;Werner Artner,&nbsp;John Spratt,&nbsp;Jens Najorka","doi":"10.1007/s00269-022-01198-2","DOIUrl":"10.1007/s00269-022-01198-2","url":null,"abstract":"<div><p>The crystal structure of montanite has been determined using single-crystal X-ray diffraction on a synthetic sample, supported by powder X-ray diffraction (PXRD), electron microprobe analysis (EPMA) and thermogravimetric analyses (TGA). Montanite was first described in 1868 as Bi₂TeO₆·<i>n</i>H₂O (<i>n</i> = 1 or 2). The determination of the crystal structure of synthetic montanite (refined composition Bi₂TeO₆·0.22H₂O) has led to the reassignment of the formula to Bi₂TeO₆·<i>n</i>H₂O where 0 ≤ <i>n</i> ≤ <span>({raise0.5exhbox{$scriptstyle 2$} kern-0.1em/kern-0.15em lower0.25exhbox{$scriptstyle 3$}})</span> rather than the commonly reported Bi₂TeO₆·2H₂O. This change has been accepted by the IMA–CNMNC, Proposal 22-A. The PXRD pattern simulated from the crystal structure of synthetic montanite is a satisfactory match for PXRD scans collected on both historical and recent natural samples, showing their equivalence. Two specimens attributed to the original discoverer of montanite (Frederick A. Genth) from the cotype localities (Highland Mining District, Montana and David Beck’s mine, North Carolina, USA) have been designated as neotypes. Montanite crystallises in space group <i>P</i><span>(overline{6 })</span>, with the unit-cell parameters <i>a</i> = 9.1195(14) Å, <i>c</i> = 5.5694(8) Å, <i>V</i> = 401.13(14) ų, and three formula units in the unit cell. The crystal structure of montanite is formed from a framework of BiO_<i>n</i> and TeO₆ polyhedra. Half of the Bi³⁺ and all of the Te⁶⁺ cations are coordinated by six oxygen atoms in trigonal-prismatic arrangements (the first example of this configuration reported for Te⁶⁺), while the remaining Bi³⁺ cations are coordinated by seven O sites. The H₂O groups in montanite are structurally incorporated into the network of cavities formed by the three-dimensional framework, with other cavity space occupied by the stereoactive 6<i>s</i>² lone pair of Bi³⁺ cations. While evidence for a supercell was observed in synthetic montanite, the subcell refinement of montanite adequately indexes all reflections in the PXRD patterns observed in all natural montanite samples analysed in this study, verifying the identity of montanite as a mineral.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2022-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00269-022-01198-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4389717","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}