I. Grey, R. Hochleitner, A. R. Kampf, Stephanie Boer, C. MacRae, J. Cashion, Christian Rewitzer, W. G. Mumme
Abstract. Manganrockbridgeite, Mn22+Fe33+(PO4)3(OH)4(H2O), is a new member of the rockbridgeite group, from the Hagendorf-Süd pegmatite, Oberpfalz, Bavaria. It occurs in association with frondelite, kenngottite, hureaulite and hematite. It forms compact intergrowths and clusters of shiny greenish black blades up to 200 µm long and 20 µm wide but only a few micrometres thick. The crystals are elongated on [100] and flattened on {001}, with perfect cleavage parallel to {001}. Individual thin blades are green in transmitted light and red under crossed polars. The calculated density is 3.40 g cm−3. Manganrockbridgeite is biaxial (+/-), with α= 1.795(5), β= 1.805(calc), γ=1.815(5) (white light) and 2V(meas.) = 90(2)∘. The empirical formula from electron microprobe analyses, Mössbauer spectroscopy and crystal structure refinement is (Mn1.072+Fe0.692+Fe0.163+)Σ1.92(Fe3+)2.88(PO4)3(OH)3.64(H2O)1.44. Manganrockbridgeite has monoclinic symmetry with space group P21/m and unit-cell parameters a=5.198(2), b=16.944(5), c=7.451(3) Å, β=110.170(9)∘, V=616.0(4) Å3 and Z=2. The crystal structure was refined using both laboratory and synchrotron single-crystal diffraction data. Whereas other rockbridgeite-group minerals have orthorhombic symmetry with a statistical distribution of 50 % Fe3+ / 50 % vacancies in M3-site octahedra forming face-shared chains along the 5.2 Å axis, monoclinic manganrockbridgeite has full ordering of Fe3+ and vacancies in alternate M3 sites along the 5.2 Å axis.
{"title":"Manganrockbridgeite, Mn2+2Fe3+3(PO4)3(OH)4(H2O), a new member of the rockbridgeite group, from the Hagendorf-Süd pegmatite, Oberpfalz, Bavaria","authors":"I. Grey, R. Hochleitner, A. R. Kampf, Stephanie Boer, C. MacRae, J. Cashion, Christian Rewitzer, W. G. Mumme","doi":"10.5194/ejm-35-295-2023","DOIUrl":"https://doi.org/10.5194/ejm-35-295-2023","url":null,"abstract":"Abstract. Manganrockbridgeite,\u0000Mn22+Fe33+(PO4)3(OH)4(H2O), is a new\u0000member of the rockbridgeite group, from the Hagendorf-Süd pegmatite,\u0000Oberpfalz, Bavaria. It occurs in association with frondelite, kenngottite,\u0000hureaulite and hematite. It forms compact intergrowths and clusters of shiny\u0000greenish black blades up to 200 µm long and 20 µm wide but only a few micrometres thick. The crystals are elongated on [100] and flattened on\u0000{001}, with perfect cleavage parallel to\u0000{001}. Individual thin blades are green in\u0000transmitted light and red under crossed polars. The calculated density is\u00003.40 g cm−3. Manganrockbridgeite is biaxial (+/-), with\u0000α= 1.795(5), β= 1.805(calc), γ=1.815(5)\u0000(white light) and 2V(meas.) = 90(2)∘. The empirical formula from\u0000electron microprobe analyses, Mössbauer spectroscopy and crystal\u0000structure refinement is\u0000(Mn1.072+Fe0.692+Fe0.163+)Σ1.92(Fe3+)2.88(PO4)3(OH)3.64(H2O)1.44.\u0000Manganrockbridgeite has monoclinic symmetry with space group P21/m and\u0000unit-cell parameters a=5.198(2), b=16.944(5), c=7.451(3) Å,\u0000β=110.170(9)∘, V=616.0(4) Å3 and Z=2.\u0000The crystal structure was refined using both laboratory and synchrotron\u0000single-crystal diffraction data. Whereas other rockbridgeite-group minerals\u0000have orthorhombic symmetry with a statistical distribution of\u000050 % Fe3+ / 50 % vacancies in M3-site octahedra forming face-shared\u0000chains along the 5.2 Å axis, monoclinic manganrockbridgeite has full\u0000ordering of Fe3+ and vacancies in alternate M3 sites along the 5.2 Å\u0000axis.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47757543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pete Williams, Frédéric Hatert, Marco Pasero, Stuart Mills
{"title":"IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) – Newsletter 72","authors":"Pete Williams, Frédéric Hatert, Marco Pasero, Stuart Mills","doi":"10.5194/ejm-35-285-2023","DOIUrl":"https://doi.org/10.5194/ejm-35-285-2023","url":null,"abstract":"","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135568816","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. To provide a tool for fast estimation of the Fe3+ content in Ca2(Al, Fe3+)3Si3O12(OH) epidote grains, including in thin sections and crude-rock samples, we applied Raman spectroscopy to 33 areas from 15 natural samples with Fe3+ ranging from 0.22 to 1.13 atoms per formula unit (apfu), the chemistry of which was independently determined by wavelength-dispersive electron microprobe analysis (WD-EPMA). The Raman spectra were collected from the very areas subjected to WD-EPMA. We have analysed both the OH-stretching region (3215–3615 cm−1) and the spectral range generated by the framework vibrations (15–1215 cm−1). Similarly to the IR spectra, the Raman peaks in the OH-stretching region shift toward higher wavenumbers with increasing Fe. However, the quantification of Fe3+ based on OH-stretching Raman peaks can be hindered by the multicomponent overlapping and significant intensity variations with the crystal orientation. Among the Raman signals generated by framework vibrations, the position of four peaks (near 250, 570, 600, and 1090 cm−1) exhibit a steady linear regression with the increase in Fe content (in apfu). However, the peak near 250 cm−1 attributed to MO6 vibrations also depends on the crystal orientation and therefore is not always well resolved, which worsens the accuracy in Fe-content determination based on its position. The peaks near 570, 600, and 1090 cm−1 arise from Si2O7 vibrational modes, and although their intensities also vary with the crystal orientation, all three signals are well resolved in a random orientation. However, among the three Si2O7-related signals, the 570 cm−1 peak is the sharpest (peak width <10 cm−1) and is easily recognized as a separate peak. Hence, we propose to use the position of this peak as a highly reliable parameter to estimate the Fe content, via the linear trend given as ω570=577.1(3)-12.7(4)x, where ω is the wavenumber (cm−1) and x is Fe content (apfu), with accuracy ± 0.04 Fe3+ apfu. The peaks near 600 and 1090 cm−1 may be complementarily used for the Fe estimate, based on the following relations: ω600=611.6(2)-13.8(4)x and ω1090=1098.8(3)-13.5(5)x. Analyses of the effect of Sr as a substitution for Ca and Cr at the octahedral sites indicate that contents of Sr <0.12 apfu do not interfere with the quantification of Fe via the ω570 (x) relation, whereas Cr >0.16 apfu leads to overestimation of Fe; Cr presence can be recognized however by the broadening of the peaks near 95 and 250 cm−1.
{"title":"Optimal Raman-scattering signal for estimating the Fe3+ content on the clinozoisite–epidote join","authors":"M. Nagashima, B. Mihailova","doi":"10.5194/ejm-35-267-2023","DOIUrl":"https://doi.org/10.5194/ejm-35-267-2023","url":null,"abstract":"Abstract. To provide a tool for fast estimation of the Fe3+\u0000content in Ca2(Al, Fe3+)3Si3O12(OH) epidote grains,\u0000including in thin sections and crude-rock samples, we applied Raman\u0000spectroscopy to 33 areas from 15 natural samples with Fe3+ ranging from\u00000.22 to 1.13 atoms per formula unit (apfu), the chemistry of which was\u0000independently determined by wavelength-dispersive electron microprobe\u0000analysis (WD-EPMA). The Raman spectra were collected from the very areas\u0000subjected to WD-EPMA. We have analysed both the OH-stretching region\u0000(3215–3615 cm−1) and the spectral range generated by the framework\u0000vibrations (15–1215 cm−1). Similarly to the IR spectra, the Raman peaks\u0000in the OH-stretching region shift toward higher wavenumbers with increasing\u0000Fe. However, the quantification of Fe3+ based on OH-stretching Raman\u0000peaks can be hindered by the multicomponent overlapping and significant\u0000intensity variations with the crystal orientation. Among the Raman signals\u0000generated by framework vibrations, the position of four peaks (near 250,\u0000570, 600, and 1090 cm−1) exhibit a steady linear regression with the\u0000increase in Fe content (in apfu). However, the peak near 250 cm−1\u0000attributed to MO6 vibrations also depends on the crystal orientation\u0000and therefore is not always well resolved, which worsens the accuracy in\u0000Fe-content determination based on its position. The peaks near 570, 600, and\u00001090 cm−1 arise from Si2O7 vibrational modes, and although\u0000their intensities also vary with the crystal orientation, all three signals\u0000are well resolved in a random orientation. However, among the three\u0000Si2O7-related signals, the 570 cm−1 peak is the sharpest\u0000(peak width <10 cm−1) and is easily recognized as a separate\u0000peak. Hence, we propose to use the position of this peak as a highly\u0000reliable parameter to estimate the Fe content, via the linear trend given as\u0000ω570=577.1(3)-12.7(4)x, where ω is the wavenumber\u0000(cm−1) and x is Fe content (apfu), with accuracy ± 0.04\u0000Fe3+ apfu. The peaks near 600 and 1090 cm−1 may be complementarily\u0000used for the Fe estimate, based on the following relations: ω600=611.6(2)-13.8(4)x and ω1090=1098.8(3)-13.5(5)x. Analyses of\u0000the effect of Sr as a substitution for Ca and Cr at the octahedral sites\u0000indicate that contents of Sr <0.12 apfu do not interfere with the\u0000quantification of Fe via the ω570 (x) relation, whereas Cr\u0000>0.16 apfu leads to overestimation of Fe; Cr presence can be\u0000recognized however by the broadening of the peaks near 95 and 250 cm−1.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41732551","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. The coupling behaviour of H+ and trace elements in rutile has been studied using in situ polarised Fourier transform infrared (FTIR) spectroscopy and laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) analysis. H2O contents in rutile can be precisely and accurately quantified from polarised FTIR measurements on single grains in situ. The benefits of this novel approach compared to traditional quantification methods are the preservation of textural context and heterogeneities of water in rutile. Rutile from six different geological environments shows H2O contents varying between ∼ 50–2200 µg g−1, with large intra-grain variabilities for vein-related samples with H2O contents between ∼ 500 and ∼ 2200 µg g−1. From FTIR peak deconvolutions, six distinct OH absorption bands have been identified at ∼ 3280, ∼ 3295, ∼ 3324, ∼ 3345, ∼ 3370, and ∼ 3390 cm−1 that can be related to coupled substitutions with Ti3+, Fe3+, Al3+, Mg2+, Fe2+, and Cr2+, respectively. Rutile from eclogite samples displays the dominant exchange reactions of Ti4+ → Ti3+, Fe3+ + H+, whereas rutile in a whiteschist shows mainly Ti4+ → Al3+ + H+. Trace-element-dependent H+ contents combined with LA–ICP–MS trace-element data reveal the significant importance of H+ for charge balance and trace-element coupling with trivalent cations. Trivalent cations are the most abundant impurities in rutile, and there is not enough H+ and pentavalent cations like Nb and Ta for a complete charge balance, indicating that additionally oxygen vacancies are needed for charge balancing trivalent cations. Valance states of multivalent trace elements can be inferred from deconvoluted FTIR spectra. Titanium occurs at 0.03 ‰–7.6 ‰ as Ti3+, Fe, and Cr are preferentially incorporated as Fe3+ and Cr3+ over Fe2+ and Cr2+, and V most likely occurs as V4+. This opens the possibility of H+ in rutile as a potential indicator of oxygen fugacity of metamorphic and subduction-zone fluids, with the ratio between Ti3+- and Fe3+-related H+ contents being most promising.
{"title":"A framework for quantitative in situ evaluation of coupled substitutions between H+ and trace elements in natural rutile","authors":"Mona Lueder, R. Tamblyn, Jörg Hermann","doi":"10.5194/ejm-35-243-2023","DOIUrl":"https://doi.org/10.5194/ejm-35-243-2023","url":null,"abstract":"Abstract. The coupling behaviour of H+ and trace elements in rutile has been\u0000studied using in situ polarised Fourier transform infrared (FTIR)\u0000spectroscopy and laser ablation inductively coupled plasma mass spectrometry\u0000(LA–ICP–MS) analysis. H2O contents in rutile can be precisely and\u0000accurately quantified from polarised FTIR measurements on single grains in\u0000situ. The benefits of this novel approach compared to traditional\u0000quantification methods are the preservation of textural context and\u0000heterogeneities of water in rutile. Rutile from six different geological\u0000environments shows H2O contents varying between ∼ 50–2200 µg g−1, with large intra-grain variabilities for vein-related samples\u0000with H2O contents between ∼ 500 and\u0000∼ 2200 µg g−1. From FTIR peak deconvolutions, six distinct\u0000OH absorption bands have been identified at ∼ 3280, ∼ 3295, ∼ 3324,\u0000∼ 3345, ∼ 3370, and\u0000∼ 3390 cm−1 that can be related to coupled substitutions\u0000with Ti3+, Fe3+, Al3+, Mg2+, Fe2+, and Cr2+,\u0000respectively. Rutile from eclogite samples displays the dominant exchange\u0000reactions of Ti4+ → Ti3+, Fe3+ + H+, whereas\u0000rutile in a whiteschist shows mainly Ti4+ → Al3+ + H+.\u0000Trace-element-dependent H+ contents combined with LA–ICP–MS\u0000trace-element data reveal the significant importance of H+ for charge\u0000balance and trace-element coupling with trivalent cations. Trivalent cations\u0000are the most abundant impurities in rutile, and there is not enough H+\u0000and pentavalent cations like Nb and Ta for a complete charge balance,\u0000indicating that additionally oxygen vacancies are needed for charge\u0000balancing trivalent cations. Valance states of multivalent trace elements\u0000can be inferred from deconvoluted FTIR spectra. Titanium occurs at 0.03 ‰–7.6 ‰ as Ti3+, Fe, and Cr are preferentially\u0000incorporated as Fe3+ and Cr3+ over Fe2+ and Cr2+, and V\u0000most likely occurs as V4+. This opens the possibility of H+ in rutile as\u0000a potential indicator of oxygen fugacity of metamorphic and subduction-zone\u0000fluids, with the ratio between Ti3+- and Fe3+-related H+\u0000contents being most promising.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41836087","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Demouchy, M. Thieme, F. Barou, B. Beausir, V. Taupin, P. Cordier
Abstract. We report a comprehensive data set characterizing and quantifying the geometrically necessary dislocation (GND) density in the crystallographic frame (ραc) and disclination density (ρθ) in fine-grained polycrystalline olivine deformed in uniaxial compression or torsion, at 1000 and 1200 ∘C, under a confining pressure of 300 MPa. Finite strains range from 0.11 up to 8.6 %, and stresses reach up to 1073 MPa. The data set is a selection of 19 electron backscatter diffraction maps acquired with conventional angular resolution (0.5∘) but at high spatial resolution (step size ranging between 0.05 and 0.1 µm). Thanks to analytical improvement for data acquisition and treatment, notably with the use of ATEX (Analysis Tools for Electron and X-ray diffraction) software, we report the spatial distribution of both GND and disclination densities. Areas with the highest GND densities define sub-grain boundaries. The type of GND densities involved also indicates that most olivine sub-grain boundaries have a mixed character. Moreover, the strategy for visualization also permits identifying minor GND that is not well organized as sub-grain boundaries yet. A low-temperature and high-stress sample displays a higher but less organized GND density than in a sample deformed at high temperature for a similar finite strain, grain size, and identical strain rate, confirming the action of dislocation creep in these samples, even for micrometric grains (2 µm). Furthermore, disclination dipoles along grain boundaries are identified in every undeformed and deformed electron backscatter diffraction (EBSD) map, mostly at the junction of a grain boundary with a sub-grain but also along sub-grain boundaries and at sub-grain boundary tips. Nevertheless, for the range of experimental parameters investigated, there is no notable correlation of the disclination density with stress, strain, or temperature. However, a broad positive correlation between average disclination density and average GND density per grain is found, confirming their similar role as defects producing intragranular misorientation. Furthermore, a broad negative correlation between the disclination density and the grain size or perimeter is found, providing a first rule of thumb on the distribution of disclinations. Field dislocation and disclination mechanics (FDDM) of the elastic fields due to experimentally measured dislocations and disclinations (e.g., strains/rotations and stresses) provides further evidence of the interplay between both types of defects. At last, our results also support that disclinations act as a plastic deformation mechanism, by allowing rotation of a very small crystal volume.
{"title":"Dislocation and disclination densities in experimentally deformed polycrystalline olivine","authors":"S. Demouchy, M. Thieme, F. Barou, B. Beausir, V. Taupin, P. Cordier","doi":"10.5194/ejm-35-219-2023","DOIUrl":"https://doi.org/10.5194/ejm-35-219-2023","url":null,"abstract":"Abstract. We report a comprehensive data set characterizing and\u0000quantifying the geometrically necessary dislocation (GND) density in the\u0000crystallographic frame (ραc) and disclination density\u0000(ρθ) in fine-grained polycrystalline olivine deformed in\u0000uniaxial compression or torsion, at 1000 and 1200 ∘C, under a confining pressure of 300 MPa. Finite strains range from 0.11 up\u0000to 8.6 %, and stresses reach up to 1073 MPa. The data set is a selection\u0000of 19 electron backscatter diffraction maps acquired with conventional\u0000angular resolution (0.5∘) but at high spatial resolution (step\u0000size ranging between 0.05 and 0.1 µm). Thanks to analytical\u0000improvement for data acquisition and treatment, notably with the use of ATEX (Analysis Tools for Electron and X-ray diffraction)\u0000software, we report the spatial distribution of both GND and disclination\u0000densities. Areas with the highest GND densities define sub-grain boundaries.\u0000The type of GND densities involved also indicates that most olivine sub-grain\u0000boundaries have a mixed character. Moreover, the strategy for visualization also\u0000permits identifying minor GND that is not well organized as sub-grain boundaries\u0000yet. A low-temperature and high-stress sample displays a higher but less organized GND density than in a sample deformed at high temperature for a similar\u0000finite strain, grain size, and identical strain rate, confirming the action\u0000of dislocation creep in these samples, even for micrometric grains (2 µm). Furthermore, disclination dipoles along grain boundaries are identified\u0000in every undeformed and deformed electron backscatter diffraction (EBSD) map, mostly at the junction of a\u0000grain boundary with a sub-grain but also along sub-grain boundaries and at\u0000sub-grain boundary tips. Nevertheless, for the range of experimental\u0000parameters investigated, there is no notable correlation of the disclination\u0000density with stress, strain, or temperature. However, a broad positive\u0000correlation between average disclination density and average GND density per\u0000grain is found, confirming their similar role as defects producing\u0000intragranular misorientation. Furthermore, a broad negative correlation\u0000between the disclination density and the grain size or perimeter is found,\u0000providing a first rule of thumb on the distribution of disclinations. Field\u0000dislocation and disclination mechanics (FDDM) of the elastic fields due to\u0000experimentally measured dislocations and disclinations (e.g., strains/rotations and stresses) provides further evidence of the interplay\u0000between both types of defects. At last, our results also support that\u0000disclinations act as a plastic deformation mechanism, by allowing rotation\u0000of a very small crystal volume.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43192760","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. A large number of lepidolites K(LixAl3−x)[Si2xAl4−2xO10](OH)yF2−y and Li-muscovites K(LixAl2-x/3□1-2x/3)[Si3AlO10](OH)yF2−y were synthesised by a gelling method in combination with hydrothermal syntheses at a pressure of 2 kbar and a temperature of 873 K. The nominal composition ranged between 0.0≤x≤2.0 and 0.0≤y≤2.0, i.e. from polylithionite K[Li2.0Al][Si4.0O10](OH)yF2−y over trilithionite K[Li1.5Al1.5][AlSi3.0O10](OH)yF2−y to muscovite K[Al2.0□][AlSi3.0O10](OH)yF2−y. 1H, 19F, 29Si and 27Al magic-angle spinning nuclear magnetic resonance (MAS NMR) and 27Al multiple-quantum magic-angle spinning (MQMAS) NMR spectroscopy has been performed to investigate the order and/or disorder state of Si and Al in the tetrahedral layers and of Li, Al, OH and F in the octahedral layer. The synthetic mica crystals are very small, ranging from 0.1 to 5 µm. With increasing Al content, the crystal sizes decrease. Rietveld structure analyses on 12 samples showed that nearly all samples consist of two mica polytypes (1M and 2M1) of varying proportions. In the case of lepidolites, the 1M / 2M1 ratio depends on the Li/Al ratio of the reaction mixture. The refinement of the occupancy factors of octahedral sites shows that lepidolites (1.5≤x≤2.0) represent a solid solution series with polylithionite and trilithionite as the endmembers. In the case of the Li-muscovites (0.0≤x≤1.5), the 1M / 2M1 ratio depends on the number of impurity phases like eucryptite or sanidine depleting the reaction mixture of Li or Al. There is no solid solution between trilithionite and muscovite; instead, the Li-muscovite crystals consist of domains differing in the relative proportions of muscovite and trilithionite. The overall composition of the synthesised micas which consist of two polytypes can be characterised by 29Si, 1H and 19F MAS NMR spectroscopy. The Si/Al ratio in the tetrahedral layers and thus the content of [4]Al were calculated by analysing the signal intensities of the 29Si MAS NMR experiments. The Li content xest was calculated from the measured tetrahedral Si/Al ratio of the 29Si MAS NMR signals. The calculated Li contents xest of samples between polylithionite and trilithionite agree with the expected values. The F-rich samples show slightly increased values and the OH samples lower values. Lepidolites with only F (x = 1.5 to 2.0, y = 0.0), but not lepidolites with only OH (x = 1.5 to 2.0 and y = 2.0), were observed after synthesis. With decreasing Li content, x≤1.2, Li-muscovites containing mostly hydroxyl (y>1.0) are formed. It was possible to synthesise fluorine containing micas with a Li content as low as 0.3 and y = 0.2 to 1.8. The 19F and 1H MAS NMR experiments reveal that F and OH are not distributed statistically but local structural preferences exist. F is attracted by Li-rich and OH by Al-rich environments. The quadrupolar coupling constant which represents the anisotropy of the Al coordination is low for polylithionite with CQ=1.5 MHz and increases to CQ
{"title":"Cation and anion ordering in synthetic lepidolites and lithian muscovites: influence of the OH ∕ F and Li ∕ Al ratios on the mica formation studied by NMR (nuclear magnetic resonance) spectroscopy and X-ray diffraction","authors":"Lara Sulcek, B. Marler, M. Fechtelkord","doi":"10.5194/ejm-35-199-2023","DOIUrl":"https://doi.org/10.5194/ejm-35-199-2023","url":null,"abstract":"Abstract. A large number of lepidolites\u0000K(LixAl3−x)[Si2xAl4−2xO10](OH)yF2−y\u0000and Li-muscovites K(LixAl2-x/3□1-2x/3)[Si3AlO10](OH)yF2−y were synthesised by a gelling method in combination with hydrothermal\u0000syntheses at a pressure of 2 kbar and a temperature of 873 K. The nominal\u0000composition ranged between 0.0≤x≤2.0 and 0.0≤y≤2.0, i.e. from polylithionite\u0000K[Li2.0Al][Si4.0O10](OH)yF2−y over\u0000trilithionite\u0000K[Li1.5Al1.5][AlSi3.0O10](OH)yF2−y to muscovite K[Al2.0□][AlSi3.0O10](OH)yF2−y. 1H, 19F,\u000029Si and 27Al magic-angle spinning nuclear magnetic resonance (MAS\u0000NMR) and 27Al multiple-quantum magic-angle spinning (MQMAS) NMR\u0000spectroscopy has been performed to investigate the order and/or disorder state of\u0000Si and Al in the tetrahedral layers and of Li, Al, OH and F in the\u0000octahedral layer. The synthetic mica crystals are very small, ranging from\u00000.1 to 5 µm. With increasing Al content, the crystal sizes\u0000decrease. Rietveld structure analyses on 12 samples showed that nearly all\u0000samples consist of two mica polytypes (1M and 2M1) of varying\u0000proportions. In the case of lepidolites, the 1M / 2M1 ratio depends on\u0000the Li/Al ratio of the reaction mixture. The refinement of the occupancy\u0000factors of octahedral sites shows that lepidolites (1.5≤x≤2.0)\u0000represent a solid solution series with polylithionite and trilithionite as\u0000the endmembers. In the case of the Li-muscovites (0.0≤x≤1.5),\u0000the 1M / 2M1 ratio depends on the number of impurity phases like\u0000eucryptite or sanidine depleting the reaction mixture of Li or Al. There is\u0000no solid solution between trilithionite and muscovite; instead, the\u0000Li-muscovite crystals consist of domains differing in the relative\u0000proportions of muscovite and trilithionite. The overall composition of the synthesised micas which consist of two\u0000polytypes can be characterised by 29Si, 1H and 19F MAS NMR\u0000spectroscopy. The Si/Al ratio in the tetrahedral layers and thus the content\u0000of [4]Al were calculated by analysing the signal intensities of the\u000029Si MAS NMR experiments. The Li content xest was calculated from\u0000the measured tetrahedral Si/Al ratio of the 29Si MAS NMR signals. The\u0000calculated Li contents xest of samples between polylithionite and\u0000trilithionite agree with the expected values. The F-rich samples show slightly\u0000increased values and the OH samples lower values. Lepidolites with only F\u0000(x = 1.5 to 2.0, y = 0.0), but not lepidolites with only OH (x = 1.5 to 2.0\u0000and y = 2.0), were observed after synthesis. With decreasing Li content, x≤1.2, Li-muscovites containing mostly hydroxyl (y>1.0) are\u0000formed. It was possible to synthesise fluorine containing micas with a\u0000Li content as low as 0.3 and y = 0.2 to 1.8. The 19F and 1H MAS NMR\u0000experiments reveal that F and OH are not distributed statistically but local\u0000structural preferences exist. F is attracted by Li-rich and OH by Al-rich\u0000environments. The quadrupolar coupling constant which represents the\u0000anisotropy of the Al coordination is low for polylithionite with CQ=1.5 MHz and increases to CQ","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47074832","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. Grey, R. Hochleitner, Christian Rewitzer, A. R. Kampf, C. MacRae, R. Gable, W. G. Mumme, E. Keck, C. Davidson
Abstract. Pleysteinite, [(H2O)0.5K0.5]2Mn2Al3(PO4)4F2(H2O)10 ⚫ 4H2O, is the aluminium analogue of benyacarite, from the Hagendorf-Süd pegmatite, Oberpfalz, Bavaria, Germany. It was found in specimens of altered zwieselite, in association with nordgauite, fluellite, rockbridgeite, pyrite and columbite. Pleysteinite occurs as isolated and small aggregates of colourless, stubby prisms that are typically 10 to 30 µm wide and up to 100 µm long. The crystals are flattened on {010} and bounded by {111}, {100} and {001} planes. The calculated density is 2.34 g cm−3. Optically, pleysteinite crystals are biaxial (+), with α=1.566(2), β=1.580(2), γ=1.600(2) (measured in white light) and 2V(meas.) = 80(1)∘. The empirical formula from electron microprobe analyses and structure refinement is [(H2O)0.50K0.50]2(Mn1.20Mg0.49Fe0.272+Zn0.05)∑2.01(Al1.63Fe0.203+Ti0.194+)∑2.02(Al0.56Ti0.444+) (PO4)4.02[F0.58O0.31(OH)0.11]2(H2O)10 ⚫ 3.92H2O. Pleysteinite has orthorhombic symmetry, with space group Pbca and unit-cell parameters a = 10.4133(8) Å, b=20.5242(17) Å, c=12.2651(13) Å, V=2621.4(4) Å3 and Z=4. The crystal structure was refined using single-crystal data to wRobs=0.054 for 1692 reflections with I>3σ(I). The crystal structure contains corner-connected linear trimers of Al-centred octahedra that share corners with PO4 tetrahedra to form 10-member rings parallel to (010). K+ cations and water molecules are located in the rings. Additional corner-sharing of the PO4 tetrahedra with Mn(H2O)4O2 octahedra occurs along [010] to complete the 3D framework structure.
{"title":"Pleysteinite, [(H2O)0.5K0.5]2Mn2Al3(PO4)4F2(H2O)10 ⋅ 4H2O, the Al analogue of benyacarite, from the Hagendorf-Süd pegmatite, Oberpfalz, Bavaria, Germany","authors":"I. Grey, R. Hochleitner, Christian Rewitzer, A. R. Kampf, C. MacRae, R. Gable, W. G. Mumme, E. Keck, C. Davidson","doi":"10.5194/ejm-35-189-2023","DOIUrl":"https://doi.org/10.5194/ejm-35-189-2023","url":null,"abstract":"Abstract. Pleysteinite,\u0000[(H2O)0.5K0.5]2Mn2Al3(PO4)4F2(H2O)10 ⚫ 4H2O, is the aluminium analogue of benyacarite, from the\u0000Hagendorf-Süd pegmatite, Oberpfalz, Bavaria, Germany. It was found in\u0000specimens of altered zwieselite, in association with nordgauite, fluellite,\u0000rockbridgeite, pyrite and columbite. Pleysteinite occurs as isolated and\u0000small aggregates of colourless, stubby prisms that are typically 10 to 30 µm wide and up to 100 µm long. The crystals are flattened on\u0000{010} and bounded by {111}, {100} and {001} planes. The calculated density is 2.34 g cm−3. Optically, pleysteinite crystals are biaxial (+), with α=1.566(2), β=1.580(2), γ=1.600(2) (measured in\u0000white light) and 2V(meas.) = 80(1)∘. The empirical formula from\u0000electron microprobe analyses and structure refinement is\u0000[(H2O)0.50K0.50]2(Mn1.20Mg0.49Fe0.272+Zn0.05)∑2.01(Al1.63Fe0.203+Ti0.194+)∑2.02(Al0.56Ti0.444+)\u0000(PO4)4.02[F0.58O0.31(OH)0.11]2(H2O)10 ⚫ 3.92H2O. Pleysteinite has orthorhombic symmetry, with space group\u0000Pbca and unit-cell parameters a = 10.4133(8) Å, b=20.5242(17) Å, c=12.2651(13) Å,\u0000V=2621.4(4) Å3 and Z=4. The crystal structure was refined\u0000using single-crystal data to wRobs=0.054 for 1692 reflections with\u0000I>3σ(I). The crystal structure contains corner-connected\u0000linear trimers of Al-centred octahedra that share corners with PO4\u0000tetrahedra to form 10-member rings parallel to (010). K+ cations and\u0000water molecules are located in the rings. Additional corner-sharing of the\u0000PO4 tetrahedra with Mn(H2O)4O2 octahedra occurs along\u0000[010] to complete the 3D framework structure.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48329195","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Thierry Decrausaz, M. Godard, M. Menzel, F. Parat, E. Oliot, Romain Lafay, F. Barou
Abstract. Earth's long-term cycling of carbon is regulated from mid-ocean ridges to convergent plate boundaries by mass transfers involving mantle rocks. Here we examine the conversion of peridotite to listvenite (magnesite + quartz rock) during CO2 metasomatism along the basal thrust of the Semail Ophiolite (Fanja, Sultanate of Oman). At the outcrop scale, this transformation defines reaction zones, from serpentinized peridotites to carbonated serpentinites and listvenites. Based on a detailed petrological and chemical study, we show that carbonation progressed through three main stages involving the development of replacive textures ascribed to early stages, whilst carbonate (± quartz) veining becomes predominant in the last stage. The pervasive replacement of serpentine by magnesite is characterized by the formation of spheroids, among which two types are identified based on the composition of their core regions: Fe-core and Mg-core spheroids. Fe zoning is a type feature of matrix and vein magnesite formed during the onset carbonation (Stage 1). While Fe-rich magnesite is predicted to form at low fluid XCO2 from a poorly to moderately oxidized protolith, our study evidences that the local non-redox destabilization of Fe oxides into Fe-rich magnesite is essential to the development of Fe-core spheroids. The formation of Fe-core spheroids is followed by the pervasive (over-)growth of Mg-rich spheroids and aggregates (Stage 2) at near-equilibrium conditions in response to increasing fluid XCO2. Furthermore, the compositions of carbonates indicate that most siderophile transition elements released by the dissolution of primary minerals are locally trapped in carbonate and oxides during matrix carbonation, while elements with a chalcophile affinity are the most likely to be leached out of reaction zones.
{"title":"Pervasive carbonation of peridotite to listvenite (Semail Ophiolite, Sultanate of Oman): clues from iron partitioning and chemical zoning","authors":"Thierry Decrausaz, M. Godard, M. Menzel, F. Parat, E. Oliot, Romain Lafay, F. Barou","doi":"10.5194/ejm-35-171-2023","DOIUrl":"https://doi.org/10.5194/ejm-35-171-2023","url":null,"abstract":"Abstract. Earth's long-term cycling of carbon is regulated from\u0000mid-ocean ridges to convergent plate boundaries by mass transfers involving\u0000mantle rocks. Here we examine the conversion of peridotite to listvenite\u0000(magnesite + quartz rock) during CO2 metasomatism along the basal\u0000thrust of the Semail Ophiolite (Fanja, Sultanate of Oman). At the outcrop\u0000scale, this transformation defines reaction zones, from serpentinized\u0000peridotites to carbonated serpentinites and listvenites. Based on a\u0000detailed petrological and chemical study, we show that carbonation\u0000progressed through three main stages involving the development of replacive\u0000textures ascribed to early stages, whilst carbonate (± quartz) veining\u0000becomes predominant in the last stage. The pervasive replacement of\u0000serpentine by magnesite is characterized by the formation of spheroids,\u0000among which two types are identified based on the composition of their core\u0000regions: Fe-core and Mg-core spheroids. Fe zoning is a type feature of\u0000matrix and vein magnesite formed during the onset carbonation (Stage 1).\u0000While Fe-rich magnesite is predicted to form at low fluid XCO2 from a\u0000poorly to moderately oxidized protolith, our study evidences that the local\u0000non-redox destabilization of Fe oxides into Fe-rich magnesite is essential to\u0000the development of Fe-core spheroids. The formation of Fe-core spheroids is\u0000followed by the pervasive (over-)growth of Mg-rich spheroids and aggregates\u0000(Stage 2) at near-equilibrium conditions in response to increasing fluid\u0000XCO2. Furthermore, the compositions of carbonates indicate that most\u0000siderophile transition elements released by the dissolution of primary\u0000minerals are locally trapped in carbonate and oxides during matrix\u0000carbonation, while elements with a chalcophile affinity are the most likely\u0000to be leached out of reaction zones.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44053777","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Majzlan, Alexandra M. Plumhoff, M. Števko, G. Steciuk, J. Plášil, E. Dachs, A. Benisek
Abstract. Many natural secondary arsenates contain a small fraction of phosphate. In this work, we investigated the olivenite–libethenite (Cu2(AsO4)(OH)–Cu2(PO4)(OH)) solid solution as a model system for the P–As substitution in secondary minerals. The synthetic samples spanned the entire range from pure olivenite (Xlib=0) to libethenite (Xlib=1). Acid-solution calorimetry determined that the excess enthalpies are non-ideal, with a maximum at Xlib=0.6 of +1.6 kJ mol−1. This asymmetry can be described by the Redlich–Kister equation of Hex= Xoli⋅Xlib [A+B(Xoli−Xlib)], with A=6.27 ± 0.16 and B=2.9 ± 0.5 kJ mol−1. Three-dimensional electron diffraction analysis on the intermediate member with Xlib=0.5 showed that there is no P–As ordering, meaning that the configurational entropy (Sconf) can be calculated as -R(XolilnXoli+XliblnXlib). The excess vibrational entropies (Svibex), determined by relaxation calorimetry, are small and negative. The entropies of mixing (Sconf+Svibex) also show asymmetry, with a maximum near Xlib=0.6. Autocorrelation analysis of infrared spectra suggests local heterogeneity that arises from strain relaxation around cations with different sizes (As5+ / P5+) in the intermediate members and explains the positive enthalpies of mixing. The length scale of this strain is around 5 Å, limited to the vicinity of the tetrahedra in the structure. At longer length scales (≈15 Å), the strain is partially compensated by the monoclinic–orthorhombic transformation. The volume of mixing shows complex behavior, determined by P–As substitution and symmetry change. A small (0.9 kJ mol−1) drop in enthalpies of mixing in the region of Xlib=0.7–0.8 confirms the change from monoclinic to orthorhombic symmetry.
{"title":"Thermodynamic and structural variations along the olivenite–libethenite solid solution","authors":"J. Majzlan, Alexandra M. Plumhoff, M. Števko, G. Steciuk, J. Plášil, E. Dachs, A. Benisek","doi":"10.5194/ejm-35-157-2023","DOIUrl":"https://doi.org/10.5194/ejm-35-157-2023","url":null,"abstract":"Abstract. Many natural secondary arsenates contain a small fraction of phosphate. In\u0000this work, we investigated the olivenite–libethenite\u0000(Cu2(AsO4)(OH)–Cu2(PO4)(OH)) solid solution as a model system\u0000for the P–As substitution in secondary minerals. The synthetic samples\u0000spanned the entire range from pure olivenite (Xlib=0) to\u0000libethenite (Xlib=1). Acid-solution calorimetry determined\u0000that the excess enthalpies are non-ideal, with a maximum at Xlib=0.6 of +1.6 kJ mol−1. This asymmetry can be described by the\u0000Redlich–Kister equation of Hex= Xoli⋅Xlib [A+B(Xoli−Xlib)], with A=6.27 ± 0.16 and B=2.9 ± 0.5 kJ mol−1.\u0000Three-dimensional electron diffraction analysis on the intermediate member\u0000with Xlib=0.5 showed that there is no P–As ordering, meaning\u0000that the configurational entropy (Sconf) can be calculated as\u0000-R(XolilnXoli+XliblnXlib). The excess vibrational entropies\u0000(Svibex), determined by relaxation calorimetry, are\u0000small and negative. The entropies of mixing (Sconf+Svibex) also show asymmetry, with a maximum near\u0000Xlib=0.6. Autocorrelation analysis of infrared spectra\u0000suggests local heterogeneity that arises from strain relaxation around\u0000cations with different sizes (As5+ / P5+) in the intermediate\u0000members and explains the positive enthalpies of mixing. The length scale of\u0000this strain is around 5 Å, limited to the vicinity of the tetrahedra in\u0000the structure. At longer length scales (≈15 Å), the strain is\u0000partially compensated by the monoclinic–orthorhombic transformation. The\u0000volume of mixing shows complex behavior, determined by P–As\u0000substitution and symmetry change. A small (0.9 kJ mol−1) drop in\u0000enthalpies of mixing in the region of Xlib=0.7–0.8 confirms\u0000the change from monoclinic to orthorhombic symmetry.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45145174","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. Lykova, R. Rowe, G. Poirier, H. Friis, K. Helwig
Abstract. The new mckelveyite group mineral alicewilsonite-(YCe), ideally Na2Sr2YCe(CO3)6 ⋅ 3H2O, was found at Mont Saint-Hilaire, Quebec, Canada, and subsequently at the Saint-Amable sill, Quebec, Canada, and the Khibiny Massif, Kola Peninsula, Russia. Alicewilsonite-(YCe) crystals are commonly hemimorphic pseudotrigonal and pseudohexagonal and show barrel-shaped, saucer-shaped, spindle-shaped, cone-shaped, columnar, tabular, and platy habits. They are usually up to 2–3 mm in size with some larger crystals reaching 2–3 cm. The crystals often form stacked or parallel growth aggregates and rosettes. Alicewilsonite-(YCe) colour varies from pale yellow to yellow, lemon yellow, green yellow, orange-yellow, pale green to green, pale grey to grey, green grey, beige, and colourless. The streak is white; the lustre is vitreous. The cleavage is fair to indistinct, parallel to (001). The Mohs hardness is 3. Dcalc is 3.37 g cm−3. Alicewilsonite-(YCe) is optically biaxial (+), with α=1.554(3), β=1.558(3), γ=1.644(2), 2V (calc.) = 26∘, 2V (meas.) = 20(3)∘ (589 nm). The IR spectrum is reported. The composition (wt %, average of six analyses) is Na2O 7.42, CaO 0.72, SrO 21.49, BaO 1.41, Y2O3 8.52, La2O3 5.93, Ce2O3 9.52, Pr2O3 0.59, Nd2O3 1.75, Sm2O3 0.46, Gd2O3 0.83, Dy2O3 1.65, Ho2O3 0.34, Er2O3 1.21, Yb2O3 0.64, CO2 29.33, H2O 6.13, total 97.94. The empirical formula of the holotype calculated on the basis of six cations is Na2.11Ca0.11Sr1.83Ba0.08Y0.67(Ce0.51La0.32Pr0.03Nd0.09Sm0.02Gd0.04 Dy0.08Ho0.02Er0.06Yb0.03)Σ1.20(CO3)5.88 (H2O)3.00. The mineral is triclinic, P1, a=9.0036(6) Å, b=9.0175(6) Å, c=6.7712(5) Å, α=102.724(2)∘, β=116.398(2)∘, γ=60.003(2)∘, V=426.46(5) Å3, and Z=1. The strongest reflections of the powder X-ray diffraction pattern [d,Å(I)(hkl)] are 6.07(31)(001), 4.372(100)(120, 2‾1‾1, 11‾0), 4.037(25)(1‾11, 1‾2‾1, 210), 3.201(25)(121, 2‾1‾2, 11‾1), 2.831(67)(1‾12, 1‾2‾2, 211, 1‾21, 21‾0), 2.601(39)(030, 3‾3‾1,3‾01), 2.236(24)(2‾4‾1, 2‾21, 4‾2‾1). 2.019(23)(003, 2‾22, 2‾4‾2‾, 420). 1.9742(24)(032, 3‾03, 3‾3‾3, 331, 03‾2, 301). The crystal structure, solved and refined from single-crystal X-ray diffraction data (R1=0.055), is of the weloganite type.
{"title":"Mckelveyite group minerals – Part 2: Alicewilsonite-(YCe), Na2Sr2YCe(CO3)6 ⋅ 3H2O, a new species","authors":"I. Lykova, R. Rowe, G. Poirier, H. Friis, K. Helwig","doi":"10.5194/ejm-35-143-2023","DOIUrl":"https://doi.org/10.5194/ejm-35-143-2023","url":null,"abstract":"Abstract. The new mckelveyite group mineral alicewilsonite-(YCe),\u0000ideally Na2Sr2YCe(CO3)6 ⋅ 3H2O, was found\u0000at Mont Saint-Hilaire, Quebec, Canada, and subsequently at the Saint-Amable\u0000sill, Quebec, Canada, and the Khibiny Massif, Kola Peninsula, Russia.\u0000Alicewilsonite-(YCe) crystals are commonly hemimorphic pseudotrigonal and\u0000pseudohexagonal and show barrel-shaped, saucer-shaped, spindle-shaped,\u0000cone-shaped, columnar, tabular, and platy habits. They are usually up to 2–3 mm in size with some larger crystals reaching 2–3 cm. The crystals often\u0000form stacked or parallel growth aggregates and rosettes.\u0000Alicewilsonite-(YCe) colour varies from pale yellow to yellow, lemon yellow,\u0000green yellow, orange-yellow, pale green to green, pale grey to grey, green\u0000grey, beige, and colourless. The streak is white; the lustre is vitreous.\u0000The cleavage is fair to indistinct, parallel to (001). The Mohs hardness is\u00003. Dcalc is 3.37 g cm−3. Alicewilsonite-(YCe) is optically biaxial\u0000(+), with α=1.554(3), β=1.558(3), γ=1.644(2), 2V (calc.) = 26∘, 2V (meas.) = 20(3)∘ (589 nm).\u0000The IR spectrum is reported. The\u0000composition (wt %, average of six analyses) is Na2O 7.42, CaO 0.72,\u0000SrO 21.49, BaO 1.41, Y2O3 8.52, La2O3 5.93,\u0000Ce2O3 9.52, Pr2O3 0.59, Nd2O3 1.75,\u0000Sm2O3 0.46, Gd2O3 0.83, Dy2O3 1.65,\u0000Ho2O3 0.34, Er2O3 1.21, Yb2O3 0.64, CO2\u000029.33, H2O 6.13, total 97.94. The empirical formula of the holotype\u0000calculated on the basis of six cations is\u0000Na2.11Ca0.11Sr1.83Ba0.08Y0.67(Ce0.51La0.32Pr0.03Nd0.09Sm0.02Gd0.04\u0000Dy0.08Ho0.02Er0.06Yb0.03)Σ1.20(CO3)5.88 (H2O)3.00.\u0000The mineral is triclinic,\u0000P1, a=9.0036(6) Å, b=9.0175(6) Å, c=6.7712(5) Å, α=102.724(2)∘, β=116.398(2)∘, γ=60.003(2)∘, V=426.46(5) Å3,\u0000and Z=1. The strongest\u0000reflections of the powder X-ray diffraction pattern [d,Å(I)(hkl)] are\u00006.07(31)(001), 4.372(100)(120, 2‾1‾1, 11‾0), 4.037(25)(1‾11, 1‾2‾1, 210),\u00003.201(25)(121, 2‾1‾2, 11‾1),\u00002.831(67)(1‾12, 1‾2‾2, 211, 1‾21, 21‾0), 2.601(39)(030, 3‾3‾1,3‾01), 2.236(24)(2‾4‾1, 2‾21,\u00004‾2‾1). 2.019(23)(003, 2‾22, 2‾4‾2‾, 420). 1.9742(24)(032, 3‾03,\u00003‾3‾3, 331, 03‾2, 301). The crystal\u0000structure, solved and refined from single-crystal X-ray diffraction data\u0000(R1=0.055), is of the weloganite type.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43803131","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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