The 2M1-phlogopite from the potassic gabbronorite (Black Hill, Australia) has been studied by electron microprobe and single-crystal X‑ray diffraction analyses. The crystal-chemical formula was (K0.95Na0.01)(Al0.15Mg1.27Fe2+1.16Fe3+0.04Ti4+0.38)(Si2.85Al1.15)O10.76F0.11Cl0.03OH1.10. The structural analysis has shown that the crystal has the cell parameters a = 5.352(1), b = 9.268(1), c = 20.168(1) Å, and β = 95.10(1)° and exhibits symmetry lowering from the ideal space group C2/c to C1. An octahedral cation ordering pattern was revealed from the refined site-scattering powers. Specifically, using the scattering species Mg vs. Fe, it was found that the M1 site at z = 0 was occupied principally by Mg (~77%) and subordinately by Fe (~23%), whereas that at z = 0.5 was completely occupied by Fe; the M2 sites at z = 0 displayed ~88% Mg and ~12% Fe, whereas those at z = 0.5 were occupied by ~86% Fe and ~14% Mg. The analysis of geometrical features shows that the Ti uptake in the structure via the Ti-oxy mechanism induces structural distortions of different extents on the z = 0 and z = 0.5 layers, with stronger effects for the layer at z = 0. Minor chemical and structural differences, instead, affect the T sheets at z = 0 and z = 0.5.

3T trioctahedral micas are rarer than it is thought. This is likely due to the occurrence of apparent polytypism, so that 1M polytype twins result in a diffraction pattern simulating a 3T periodicity [1, 2]. Most of the 3T trioctahedral micas found in nature to date belong to muscovite-polylithionite-annite system [3, 4, 5, 6]. X-ray diffraction studies on these micas have often reported partial tetrahedral ordering and/or different patterns of octahedral ordering [3, 6]. In the present work, a 3 T trioctahedral mica from Kasenyi (south west Uganda) kamafugite was studied via Electron Probe Microanalysis (EPMA) and Single Crystal X-ray Diffraction (SCXRD). Main EPMA data gave: SiO2 = 38.7(2), Al2O3 = 13.08(9), MgO = 20.4(2), TiO2 = 4.8(1), FeOtot = 5.51(9), Cr2O3 = 0.90(7), K2O = 9.64(5), Na2O = 0.29(1), BaO = 0.15(5) and F = 0.13(5) wt%. The analysed crystal may be classified as a Ti-rich, F-poor mica with a composition intermediate between the annite and phlogopite end members. Anisotropic single crystal X-ray refinement was performed in the <i>P</i>3<sub>1</sub>12 space group and converged to R1 = 4.34 and wR2 = 3.33 %. Unit cell parameters were: a = b = 5.3235(3) and c = 30.188(2) Å. Mean bond length distances of M1, M2 and M3 follow the pattern M1 = M2 < M3, suggesting partial octahedral cation ordering. Conversely, mean bond lengths of T1 and T2 point to a disordered cation distribution over tetrahedral sites. Finally, the overall crystal chemical features indicates the occurrence in the studied sample of the following substitution mechanisms: tetraferriphlogopite; Ti-oxy and Al, Fe3+, Cr-oxy; Al, Fe3+-Tschermak; kinoshitalite and XIIK+ + IVAl3+ « IVSi4+ + XII. Such substitutions are the same as those found in 1M-2M1 coexisting micas from the same rock sample [7].

A 3T mica polytype from Kasenyi (south west Uganda) kamafugite was studied by Electron Probe Microanalysis (EPMA), Single Crystal X-ray Diffraction (SCXRD), micro-Fourier Transform Infrared Spectoscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS) in order to characterize its crystal chemistry and the relationships with samples from the same rock but showing different stacking sequence. EPMA data gave: SiO2 = 38.7(2), Al2O3 = 13.08(9), MgO = 20.4(2), TiO2 = 4.8(1), MnO = 0.03(3), FeOtot = 5.51(9), Cr2O3 = 0.90(7), NiO = 0.11(5), SrO = 0.03(3), ZnO = 0.04(3), ZrO2 = 0.01(2), K2O = 9.64(5), Na2O = 0.29(1), BaO = 0.15(5), F = 0.13(5) and Cl = 0.01(1) wt%. The analysed sample may be classified as a Ti-rich, F-poor mica with a composition in the phlogopite- annite join end members. X-ray photoelectron spectroscopy provided Fe2+/Fe3+ and O2- /OH equal to ~ 0.75 and 7.14, respectively, which are in agreement with the results of previous Mössbauer investigation on the BU1 sample and with the structural formula of the studied crystal. Infrared spectra showed, in the OH- stretching region (~ 3740-3600 cm-1 cm-1), a shoulder at ~ 3660 cm-1 which is assigned to MgMgFe3+-OH--K-O2- local configurations. No evidences of vacancy substitutions were observed. Single crystal X-ray refinement using anisotropic displacement parameters was performed in the P3112 space group and converged to R1 = 4.34 and wR2 = 3.33 %. Unit cell parameters are: a = b = 5.3235(3) and c = 30.188(2) Å. Geometrical and chemical considerations point to a disordered cation distribution over T1 and T2 tetrahedral sites, whereas partial cation ordering characterizes the octahedral sites with M1 = M2 ≠ M3. Tetrahedral bond/edge lengths distortion and angle variances parameters evidence more distorted polyhedra in 3T polytype than those found in coexisting 1M and 2M1 polytypes. Finally, the overall crystal chemical features indicates the occurrence in the studied sample of the following substitution mechanisms: tetraferriphlogopite [IVFe3+ IVAl]; Ti-oxy [VIM2+ + 2 (OH)  VITi4+ + 2 (O2–) + H2] and Al, Fe3+, Cr-oxy [VIM2+ + (OH)  VIM3+ + O2– + ½ (H2)]; Al, Fe3+-Tschermak [VIM2+ + IVSi4+  VI(Al3+, Fe3+) + IVAl3+]; XIIK+ + IVAl3+  IVSi4+ + XII.

The results of a combined electron probe microanalysis, single-crystal X‑ray diffraction, and Fourier transform infrared study of a crystal of armstrongite from Khan Bogdo deposit (Gobi, Mongolia) are reported. Major element analysis provided (wt%): CaO 9.2(1), ZrO2 20.9(2), and SiO2 62.5(2). Significant concentrations of REE (0.45 wt%) were also detected. From single-crystal structural refinement, armstrongite resulted monoclinic [space group C2/m, a = 14.0178(7), b = 14.1289(6), c = 7.8366(3) Å, b = 109.436(3)°, V = 1463.6(1) Å3, Z = 4] and twinned with two individuals rotated around a twin twofold axis parallel to [100]. The analyzed crystal was refined up to R = 3.3% (Rw = 2.9%). The structural refinement showed that the investigated armstrongite has only two water groups per formula unit consistent with the infrared analysis. Indeed, the occurrence in the infrared spectrum of the armstrongite (here reported for the first time) of two bending vibration bands at about 1640 and 1610 cm–1 testifies to the presence of two water groups environments. The results of this integrated approach converged to the following empirical formula (based on Si = 6 atoms per formula unit): (Ca0.96Ce0.01Yb0.01)Zr0.99Si6O14.97·2.02H2O. Finally, the studied mineral shows a framework density (FD = 21.86) lying in the range of zeolites and microporous heterosilicates with tetrahedral-octahedral frameworks. The determined crystal chemical features are relevant for the possible employment of this mineral or of its synthetic analogs for technological applications.

Abstract In the present work, crystal chemical variations between 1M and 2M1 phlogopites coexisting in the same rock sample from kamafugite of Kasenyi (southwest Uganda, west branch of the East African Rift) were explored by electron probe microanalyses, single crystal X-ray diffraction and Mo¨ ssbauer spectroscopy. Chemical analyses revealed close similarity both within and between the two polytypic arrangements as well as high TiO2 (*4.9 wt%) and Al2O3 (*12.9 wt%), and low Cr2O3 (*0.8 wt%), F (*0.3 wt%) and BaO (*0.2 wt%) con- tents. Room temperature 57Fe Mo¨ ssbauer investigation proved that the studied mica is a tetraferriphlogopite with: IVFe3? = 19(1) %, VIFe2? = 58(1) %, VIFe3? = 23(1) %. Single crystal refinement showed that both polytypes have narrow range of variation in terms of some relevant unit cell parameters and similar values in terms of mean bond lengths, mean atomic numbers and distortion parameters. Similar substitutions were active in the structure of the 1M and 2M1 studied phlogopites. However, in 2M1 poly- types the oxy-type substitutions were found to occur to a greater extent. Comparison of unit layer of 1M mica (in the 2M1 setting) with that of the 2M1 ones showed that the 2M1 polytypes are affected to different extent by relative shifts of the upper and lower triads of octahedral oxygens along the ±b directions. This effect did not cause any symmetry lowering in the T-O-T layer of the studied samples.

In the present work, the crystal chemistry of natural Tiphlogopites from alkali-rich igneous rocks from the Central Fields of Bunyaruguru and Katwe-kikorongo (Southwest Uganda) has been investigated. The host rocks are characterized by olivine – melilitite and olivine – kalsilite – nepheline – clinopyroxene assemblages [1]. The phlogopites from the former rock are labelled BU (specifically, BU1, BU3 and BU4) whereas those from the latter are labelled KK (in detail, KK8 and KK13). All samples underwent chemical (Electron Micro Probe Analysis, EMPA), structural (Single Crystal X-ray Diffraction, SCXRD) and spectroscopic (FTIR) investigation. EMPA yielded the following ranges: MgO (17.87-21.48 wt%), FeOtot (5.40-9.22 wt%) and TiO2 (4.59-7.05 wt%) for BU samples whereas MgO (17.98-18.51 wt%), FeOtot (8.17-8.86 wt%) and TiO2 (6.02-6.49 wt%) for KK crystals. SCXRD analyses showed the coexistence of both the 1M and the 2M1 polytypes within the same sample. The BU3 mica is an exception because, to date, only crystals belonging to the 2M1 polytype have been found. Average cell parameters are a = 5.33, b = 9.22, c = 10.22 Å and = 100.06° for the 1M whereas a = 5.33, b = 9.23, c = 20.22 Å and = 95.08° for the 2M1 phlogopites. Structure refinements using anisotropic displacement parameters were performed in space group C2/m for 1M and C2/c for 2M1 samples and converged at 1.63 R 4.64 %, 1.96 Rw R Rw 4.41 % for the two polytypes, respectively. Micro-FTIR provides insightful informations about octahedral cationic environments, the substitution mechanisms trough which cations enter the mica structure and the hydrogen orientation [2-4]. The samples so far analyzed display, to different extent, fine structure in the OH- stretching region. In terms of substitution mechanisms this implies that the samples contain different combination of M3+-Tschermak, M3+- oxy substitutions, whereas they are not affected by M3+-vacancy substitutions. Indeed the bands at about 3620 and 3535 cm-1, which correspond to Al3+Al3+-OH and Fe3

The crystal chemistry of 2M1 micas from Bunyaruguru kamafugite (southwest Uganda) was studied by electron probe microanalysis, single-crystal X-ray diffraction, Mössbauer and Fourier transform infrared spectroscopy. Chemical analyses showed that the studied crystals are Ti-rich, F-poor phlogopites with an annitic component, Fetot/(Fetot + Mg), ranging from 0.15 to 0.22. Unit-cell parameters from single-crystal X-ray data are in the range: 5.3252(1) ≤ a ≤ 5.3307(1), 9.2231(3) ≤ b ≤ 9.2315(3), 20.1550(6) ≤ c ≤ 20.1964(8) Å, and 94.994(2) ≤ β ≤ 95.131(2)°. Anisotropic structure refinements, in the space group C2/c, converged to 2.77 ≤ R1 ≤ 3.52% and 2.91 ≤ wR2 ≤ 4.02%. Mössbauer spectroscopy showed that the studied sample has: VIFe2+ = 60(1)%, VIFe3+ = 24(1)%, and IVFe3+ = 16(1)%. FTIR investigations pointed to the occurrence of Fe3+-oxy substitutions and ruled out the presence of vacancy mechanisms. The overall crystal-chemical features are consistent with the following substitutions: tetraferriphlogopite [IVFe3+ ↔ IVAl]; Ti-oxy [VIM2+ + 2 (OH)− ↔ VITi4+ + 2 (O2−) + H2↑] and Al, Fe3+, Cr-oxy [VIM2+ + (OH) − ↔ VIM3+ + O2− + ½ (H2)↑]; Al, Fe3+-Tschermak [VIM2+ + IVSi4+ ↔ VIM3+ + IVAl]; kinoshitalite [XIIK + IVSi4+ ↔ XIIBa2+ + IVAl] and [XIIK+ + IVAl3+ ↔ IVSi4+ + XII□]. The estimation of the OH− content for Ugandan mica-2M1 was obtained, for the first time, from the linear regression equation c = 0.20(2) × OH− (gpfu) + 19.93(2) derived from literature data of 2M1-samples with known OH− content. The orientation of the O-H vector with respect to c* was found in the range from 2.0 to 6.9°.

In trioctahedral micas, polytype 2 M1 occurs less frequently than 1M one. For such a reason, trioctahedral 1M-polytype has been extensively studied up to date whereas studies on 2 M1-polytype are relatively rare. In several cases 2 M1-micas have been reported as coexisting with 1M-micas [1, 2, 3, 4, 5]. Other studies were focused on the characterization of phlogopite-annite 2 M1 micas with peculiar composition [6, 7, 8, 9, 10]. The crystal chemistry of 2 M1 micas from Bunyaruguru (south west Uganda) kamafugite was studied by Electron Probe Microanalysis, Single Crystal X-ray Diffraction, Mössbauer and Fourier Transform Infrared spectroscopy. To the best of our knowledge, this is the first integrated crystal chemical study of phlogopite from Ugandan kamafugites, and was undertaken to get an insight into the crystal chemistry of the trioctahedral mica 2 M1-polytype. Chemical analyses showed that the studied crystals are Ti-rich, F-poor phlogopites with an annitic component, Fe<sub>tot</sub>/(Fe<sub>tot</sub> + Mg), ranging from 0.15 to 0.23. Unit-cell parameters from single crystal X-ray data are in the range: 5.3252(1) < a ≤ 5.3307(1), 9.2231(3) < b ≤ 9.2315(3), 20.1550(6) < c < 20.1964(8) Å and 94.994(2) < β ≤ 95.131(2)°. Anisotropic structure refinements, in the space group C2/c, converged to 2.80 < R1 ≤ 3.56 % and 2.91 < wR2 ≤ 4.08 %. Mössbauer spectroscopy showed that the studied sample has: VIFe2+ = 60(1) % , VIFe3+ = 24(1) % and IVFe3+ = 16(1) %. FTIR investigations pointed to the occurrence of Fe3+-oxy substitutions and ruled out the presence of vacancy mechanisms. The overall crystal chemical features are consistent with the following substitutions: tetraferriphlogopite; Ti-oxy and Al, Fe3+, Cr-oxy; Al, Fe3+-Tschermak; kinoshitalite and XIIK+ + IVAl3+  IVSi4+ + XII. The estimation of the OH<sup>-</sup> content for Ugandan mica-2 M1 was obtained, for the first time, from the linear regression equation c = 0.20(2) x OH- (gpfu) + 19.93(2) derived from literature data of 2 M1-samples with known OH- content. The orientation of the O-H vector with respect to c* was found in the range from 2.8 to 12.6°, consistently with literature values [11].

Phosphates are among the most complex and variegated compounds in the entire mineral kingdom. Currently the total number of distinctive phosphate species is about 300 and most of them contains hydrogen as OH, H2O or in HPO4 2- group. Hydrogen bond has a central role in stabilizing the hydroxy-hydrated phosphate (HHPh) structures because it supplies the additional bond-valence (0.1 - 0.3 vu) contribution to the anions. Hence the (PO4) groups can link easily to all other interstitial cations (Huminicki & Hawthorne, 2002). For this reason, most HHPhs are characterized by the presence of complex tridimensional networks of O-H…O hydrogen bonds, which connect the polyhedral units making up a three dimensional framework. Consequently, the dimensionality of the structural unit is controlled primarily by the amount and role of hydrogen in the structure (Hawthorne, 1998). This could explain the observed correlation between the position in the paragenetic sequence of pegmatitic phosphates, and the amount of H2O in their formula (Fisher, 1958). FTIR spectroscopy is a powerful tool for the study of hydrogen in minerals, but HHPhs are rather challenging to study because of their complex structures. Moreover, due the high OH/H2O contents, these minerals show extremely intense IR absorptions in the OH region. In this work, we describe the results obtained by IR spectroscopy in different spectral regions of selected phosphates (veszelyite, whiteite, vauxite, paravauxite, metavauxite, augelite, wardite, wavellite, lazulite, arrojadite). O-H and hydrogen bonds orientation were studied by single crystal polarized light m-IR-spectroscopy, and experiments at HT- and LT were performed to study phase transitions and dehydration mechanisms with the aim of defining the thermal stability of these minerals. Finally, some applications done by using the novel FPA-FTIR imaging methods are presented. Fisher D.J. 1958. Pegmatite phosphates and their problems. Am. Mineral., 43, 181-207. Hawthorne F.C. 1998. Structure and chemistry of phosphate minerals. Mineral. Mag., 62, 141-164. Huminicki D.M.C. & Hawthorne F.C. 2002. The Crystal Chemistry of the Phosphate Minerals. In: Kohn M.L., Rakovan J. & Hughes J.M. Eds., Phosphates Geochemical, Geobiological, and Materials Importance. Rev. Mineral. Geochem., 48, 123-254.

The crystal structure of fibroferrite, Fe(OH)SO4•5H2O, was studied by means of single-crystal X-ray diffraction and vibrational (FTIR and Raman) spectroscopies. The new diffraction data allowed to successfully locate eleven H positions and to completely define the H bond system that ensures the cohesion of the Fe-O-S chains in the fibroferrite structure. Infrared and Raman spectra are presented for the first time for this compound and commented on the basis of the crystal structure and literature data for sulfate minerals. Both FTIR and Raman spectra show, in the fundamental water stretching region, a very broad absorption extending from 3600 to 2600 cm−1; peaks at 3522, 3411 and 3140 cm−1 can be resolved in the Raman pattern. The bands present in the lowwavenumber (<1300 cm−1) region are assigned on the basis of the literature data for similar substances, and the observed multiplicity is in agreement with a symmetry reduction of the sulfate ion in the structure of fibroferrite.

The aim of this work is to investigate the efficiency of the phyllomanganate birnessite in degrading catechol after mechanochemical treatments. A synthesized birnessite and the organic molecule were grounded together in a high energy mill and the xenobiotic-mineral surface reactions induced by the grinding treatment have been investigated by means of X-ray powder diffraction, X-ray fluorescence, thermal analysis and spectroscopic techniques as well as high-performance liquid chromatography and voltammetric techniques. If compared to the simple contact between the birnessite and the organic molecule, mechanochemical treatments have revealed to be highly efficient in degrading catechol molecules, in terms both of time and extent. Due to the two phenolic groups of catechol and the small steric hindrance of the molecule, the extent of the mechanochemically induced degradation of catechol onto birnessite surfaces is quite high. The degradation mechanism mainly occurs via a redox reaction. It implies the formation of a surface bidentate inner-sphere complex between the phenolic group of the organic molecules and the Mn(IV) from the birnessite structure. Structural changes occur on the MnO6 layers of birnessite as due to the mechanically induced surface reactions: reduction of Mn(IV), consequent formation of Mn(III) and new vacancies, and free Mn2+ ions production.

The existence of a lot of worldwide pentachlorophenol-contaminated sites has induced scientists to concentrate their effort in finding ways to degrade it. Therefore, an effective tool to decompose it from soil mixtures is needed. In this work the efficiency of the phyllomanganate birnessite (KBi) in degrading pentachlorophenol (PCP) through mechanochemical treatments was investigated. To this purpose, a synthesized birnessite and the pollutant were ground together in a high energy mill. The ground KBi-PCP mixtures and the liquid extracts were analyzed to demonstrate that mechanochemical treatments are more efficient in removing PCP than a simple contact between the synthesized birnessite and the pollutant, both in terms of time and extent. The mechanochemically induced PCP degradation mainly occurs through the formation of a surface monodentate inner-sphere complex between the phenolic group of the organic molecules and the structural Mn(IV). This is indicated by the changes induced in birnessite MnO6 layers as a consequence of the prolonged milling with the pollutant. This mechanism includes the Mn(IV) reduction, the consequent formation of Mn(III) and new vacancies, and free Mn2+ ions release. The PCP degradation extent is limited by the presence of chloro-substituents on the aromatic ring.

Several diffraction studies on coexisting 1M and 2M1 polytypes have been carried out to date [1, 2, 3, 4, 5, 6] in order to draw informations on their differences by comparing unit layer structure and/or the crystal chemical details of the two polytypic forms. Some of the quoted studies contain implications on polytype formation in micas [1, 2]. In the present work, the crystal chemistry of 1M and coexisting 2M1 micas from Kasenyi (south west Uganda) kamafugite was investigated by Electron Probe Microanalysis, Single C rystal X-ray Diffraction and Mössbauer spectroscopy. The aim of the present study is to compare crystal chemical and unit layer structural features of the coexisting polytypic forms and to make comparisons to literature data. EPMA investigation yielded similar composition for 1M and 2M1 polytypes. They are Ti-rich, F-poor phlogopites with an annitic component, Fetot/(Fetot + Mg), of about 0.14. The room temperature Mössbauer spectrum of the sample yielded three Fe-species: V I Fe2 + = 58(1) % , V I Fe3 + = 23(1) % and I V Fe3 + = 19(1) %. A typical crystal chemical formula is: (K0 .9 6 Na0 .0 4 Ba0 .0 1 )(Mg2 .2 9 Al0 .0 9 Fe2 + 0 .2 1 Fe3 + 0 .0 8 Ti0 .2 8 C r0 .0 4 Ni0 .0 1 )(Si2 .8 7 Al1 .0 6 Fe3 + 0 .0 7 )O1 0 .6 5 F0 .0 5 OH1 .3 0 . Average cell parameters are a = 5.326, b = 9.224, c = 10.231 Å, β = 100.06° for polytype 1M and a = 5.325, b = 9.223, c = 20.206 Å, β = 95.08° for polytype 2M1 . The interatomic distances are similar for the two polytypes and consistent with the relevant site chemistry. The comparison among atomic coordinates of 1M and 2M1 micas from this study and from the literature in the 2M1 setting evidenced a remarkable agreement between all atomic coordinates, with the exception of the y values of the octahedral oxygen atoms. Specifically, the difference between y values was 0.004 in the study samples, 50 times the estimated standard deviations. Similar differences were found for the literature data [1].

A crystal chemical study of narsarsukite from the Murun alkaline massif, Russia has been carried out combining single crystal X-ray diffraction, electron microprobe analyses, micro-Fourier Transform infrared spectroscopy and X-ray photoelectron spectroscopy. The narsarsukite single crystals are tetragonal (space group I4/m) with unit cell parameters: 10.7140(1)  a  10.7183(2) Å and 7.9478(1)  c  7.9511(1) Å. The XPS analysis showed that Fe occurs in the mineral as Fe3+, whereas the FTIR spectrum evidenced that the studied sample is anhydrous. The Murun narsarsukite has average crystal chemical formula: Na2.04K0.01(V5+0.01Ti0.74Zr0.01Al0.01Fe3+0.22Mg0.01)1.00Si4.00(O10.74F0.23OH0.03) 11.00. Structural disorder at octahedral and interstitial sites was modeled and discussed also in consideration of the main substitutional mechanism Ti4+ + O2- ⟷ Fe3+ + (F-, OH-) active in the structure of the mineral.

Iron oxides are transition metal oxides of paramount importance for their technological applications. Their synthesis can be performed by a variety of methods, most of which are chemical methods. Hematite, α-Fe2O3, can also be produced from iron sulfates by heating them sufficiently in air. In this work we have employed the thermal decomposition method to obtain hematite from the dehydration of fibroferrite, FeOH(SO4)·5H2O, a secondary iron-bearing hydrous sulfate. The study was performed via Rietveld refinement based on in-situ synchrotron X-ray powder diffraction combined with thermogravimetric analysis and mass spectrometry. The integration of the data from these techniques allowed to study the structural changes of the initial compound, determining the stability fields and reaction paths and its high temperature products. Six main dehydration/transformation steps from fibroferrite have been identified in the heating temperature range 30-798 °C. In the last step of the heating process, above 760 °C, hematite is the final phase. The temperature behavior of the different phases was analyzed and the heating-induced structural changes are discussed.

The structures of tokkoite, K2Ca4[Si7O18OH](OH,F) and tinaksite, K2Ca2NaTi[Si7O18OH]O from the Murun massif (Russia) were refined from single-crystal X-ray diffraction data in the triclinic space group P 1: Average crystallographic data are a≈10.423, b≈12.477, c≈7.112 Å, α≈89.92°, β≈99.68°, γ≈92.97°, V≈910.5 Å3 for tokkoite; a≈10.373, b≈12.176, c≈7.057 Å, α≈90.82°, β≈99.22°, γ≈ 92.80°, V≈878.5 Å3 for tinaksite. The substantial similarities between the geometrical parameters of the tokkoite and tinaksite structures led us to conclude that the two minerals are isostructural. However, major differences of tokkoite with respect to tinaksite are larger lattice constants, especially concerning the b parameter, longer <M–O> distances, especially <M1–O>; larger values of the M1–M3 and O20–O2 bond lengths, and a stronger distortion of the M1 polyhedron. Mössbauer analysis showed that significant trivalent iron is present, VIFe3+ 40.0(7)% in tokkoite and 12.8(3)% in tinaksite. It is confirmed that 2Ca2þ (M1þM2) +(F, OH)(O20) ↔ Ti4þ (M1) +Naþ(M2) +O(O20) is the exchange reaction that describes the relation between tokkoite and tinaksite. In addition, this exchange reaction causes local stress involving mainly the M1 site and its interaction with the M2 and M3 sites.

A crystal-chemical investigation of vauxite, ideally FeAl2(PO4)2(OH)2 6H2O, from Llallagua (Bolivia) has been performed using a multi-methodological approach based on WDS-electron microprobe, single-crystal X-ray diffraction, and vibrational spectroscopies (Raman and FTIR). The structure was refined in the triclinic P1 space group, with the following unit-cell constants: a 9.1276(2), b 11.5836(3), c 6.15960(10) Å, a 98.3152(10)°, b 92.0139(10)°, g 108.1695(9)°, and V 610.05(2) Å3. The vauxite structure is based on a building unit oriented parallel to the c axis and composed of a chain of Fe2 and Al2 edge-sharing octahedra and two chains of corner-sharing P2 tetrahedra and Al1 octahedra, interconnected via corners and P1 tetrahedra. Neighboring building units are interconnected by Al3 octahedra and via Fe1 octahedra. The framework is completed with two non-coordinated water molecules. The latter, together with the two hydroxyl groups and the other four coordinated water molecules, form a complex hydrogen bonding network whose interactions further compact the whole framework. Both FTIR and Raman spectra show, in the H2O stretching region, a broad absorption consisting of several overlapping components due to the six water molecules plus the OH groups. The band multiplicity observed in the low-wavenumber region (o1400 cm–1) is compatible with the presence of two distorted PO4 tetrahedra.

A general method to synthesize conjugated molecules with a benzofulvene core is reported. Up to four conjugated substituents have been introduced via a three-step sequence including (1) synthesis of 1,2-bis(arylethynyl)- benzenes; (2) exo-dig electrophilic cyclization promoted by iodine; and (3) cross-coupling reaction of the resulting bisiodobenzofulvenes with organoboron, organotin, or ethynyl derivatives under Pd catalysis. Structural aspects of the new compounds are discussed.

A full characterisation of micas requires complete chemical analysis, including the determination of light elements, combined with Mössbauer spectroscopy or any technique suitable for the determination of ferric and ferrous iron contents, and crystal structural analysis (SCXRD). In this context, the SIMS technique is essential for a deeper understanding of the crystal chemistry of mica owing to its capability of precise and accurate quantification of light elements, i.e., H, Li, B, F, .... The role of SIMS is here outlined in the investigation of the complex crystal structure of mica, with new data on a set of volcanic samples, and their comparison with those from literature on trioctahedral micas from volcanic areas of Southern Italy. The importance of SIMS micro-spot (in-situ) analysis is here emphasized as a modern approach to gain insight into physico-chemical processes that affect grain-to-grain or intra-grain chemical variability in complex mineral structures.

A suite of Ti-bearing garnets from magmatic, metamorphic and carbonatitic rocks was studied by Electron Probe Microanalysis (EPMA), X-ray Powder Diffraction (XRPD), Single Crystal X-ray Diffraction (SCXRD), Mössbauer spectroscopy and Secondary Ion Mass Spectrometry (SIMS) in order to better characterize their crystal chemistry. The studied garnets show TiO2 varying in the ranges 4.9(1)-17.1(2) wt.% and variable Fe3+/ΣFe content. SIMS analyses allowed quantification of light elements yielding H2O in the range 0.091(7)-0.46(4), F in the range 0.004(1)-0.040(4) and Li2O in the range 0.0038(2)-0.014(2) wt%. Mössbauer analysis provided spectra with different complexity, which could be fitted to a number of components variable from one (YFe3+) to four (YFe2+, ZFe2+, YFe3+, ZFe3+). A good correlation was found between the Fe3+/ΣFe resulting from the Mössbauer analysis and that derived from the Flank method (Höfer & Brey, 2007). X-ray powder analysis revealed that the studied samples are a mixture of different garnet phases with very close cubic unit cell parameters as recently found by other authors (Antao, 2013). Single crystal X-ray refinements using anisotropic displacement parameters were performed in the Ia-3d space group and converged to R1 in the range 1.63-2.06 % and wR2 in the range 1.44-2.21 %. Unit cell parameters vary between 12.0641(1) and 12.1447(1) Å, reflecting different Ti contents and extent of substitutions at tetrahedral site. The main substitution mechanisms affecting the studied garnets are: YR4+ + ZR3+ ↔ ZSi + YR3+ (schorlomite substitution); YR2+ + ZR4+ ↔ 2YR3+ (morimotoite substitution); YFe3+↔ YR3+ (andradite substitution) with ZR4+ = Ti; YR4+ = Ti, Zr; YR3+ = Fe3+, Al3+, Cr3+; ZR3+ = Fe3+, Al3+ and YR2+ = Fe2+, Mg2+, Mn2+. The 2YTi4++ ZFe2+ ↔ 2YFe3+ + ZSi4+, the hydrogarnet substitution [(SiO4)4-↔ (O4H4)4-], the F– ↔ OH– and the YR4+ + XR+ ↔ YR3+ + XCa2+, with YR4+ = Ti, Zr; YR3+ = Fe3+, Al3+, Cr3+; XR+ = Na, Li also occur. The garnet crystal chemistry and implications in terms of nomenclature and classification (Grew et al., 2013) are discussed. Antao S.M. 2013. The mystery of birefringent garnet: is the symmetry lower than cubic?. Powder diffr., 28(4), 281-287. Grew E.S., Locock A.J., Mills S.J., Galuskina I.O., Galuskina E.V. & Hålenius U. 2013. Nomenclature of the Garnet Supergroup. Am. Mineral., 98, 785-811. Höfer H.E. & Brey G.P. 2007. The iron oxidation state of garnet by electron microprobe: Its determination with the flank method combined with major-element analysis. Am. Mineral., 92, 873-885.

The crystal structures of tobelite and NH4+-rich muscovite from the sedimentary rocks of the Armorican sandstones (Brittany, France) have been solved for the first time by single crystal X-ray diffraction. The structural study was integrated by electron probe microanalyses, X-ray photoelectron and micro-Fourier transform infrared spectroscopy. The crystals belong to the 2M2 polytype with the following unit-cell parameters: a = 9.024(1), b = 5.2055(6), c = 20.825(3) Å and β = 99.995(8) for tobelite and a = 9.027(1), b = 5.1999(5), c = 20.616(3) Å and β = 100.113(8)° for NH4+-rich muscovite. Structure refinements in the space group C2/c converged at R1 = 8.01%, wR2 = 8.84% and R1 = 5.59%, wR2 = 5.63% for tobelite and NH4+-rich muscovite, respectively. X-ray photoelectron spectroscopy revealed nitrogen environments associated either to inorganic (B.E. 401.31 eV) and to organic (B.E. 398.67 eV) compounds. Infrared spectra showed, in the OH- stretching region (3700-3575 cm-1), two prominent bands, centered at ~ 3629 and ~ 3646 cm-1, and two shoulders at ~ 3664 and ~ 3615 cm-1 which were assigned to Al3+Al3+-OH- arrangements having OH- groups affected by different local configurations. In addition, a series of overlapping bands from about 3500 to 2700 cm-1 characteristic of the NH4+-stretching vibrations, a main band at ~ 1430 and a shoulder at ~ 1460 cm-1 which were associated to the NH4+ bending vibration (ν4) were also present. The ammonium concentration was semi-quantitatively estimated in both crystals from the absorbance of the OH--stretching and NH4+-bending vibrations in the infrared spectra. Additional estimate was obtained for the NH4+-rich muscovite by considering the normalized peak area between K2p3/2 and N1s in the X-ray photoelectron spectrum. The obtained values were also in agreement with those derived from the interlayer spacing in the simulated X-ray powder diffraction spectra. The results of this integrated approach converged to (K0.18Na0.01NH4+0.62)Σ=0.81 (Al1.98Fe2+0.02)Σ= 2.00(Si3.19Al0.81)Σ= 4.00O10.00OH2.00 for tobelite and to (K0.46Na0.03Ba0.01NH4+0.36)Σ=0.86 (Al1.98Mg0.01Fe2+0.01V3+0.01)Σ=2.01(Si3.13Al0.87)Σ=4.00O10.00F0.08OH1.92 for NH4+-rich muscovite.

Two mineral clays of the montmorillonite group were tested as sorbents for the removal of Rare Earths (REs) from liquid solutions. Lanthanum and neodymium model solutions were used to perform uptake tests in order to: (a) verify the clays sorption capability, (b) investigate the sorption mechanisms and (c) optimize the experimental parameters, such as contact time and pH. The desorption was also studied, in order to evaluate the feasibility of REs recovery from waters. The adsorption–desorption procedure with the optimized parameters was also tested on a leaching solution obtained by dissolution of a dismantled NdFeB magnet of a hard-disk. The clays were fully characterized after REs adsorption and desorption by means of X-ray powder diffraction (XRPD) and X-ray photoelectron spectroscopy (XPS); the liquid phase was characterized via Inductively Coupled Plasma–Optical Emission Spectroscopy (ICP–OES) analyses. The experimental results show that both clays are able to capture and release La and Nd ions, with an ion exchange mechanism. The best total efficiency (capture 50%, release 70%) is obtained when the uptake and release processes are performed at pH = 5 and pH = 1 respectively; in real leached scrap solutions, the uptake is around 40% but release efficiency is strongly decreased passing from a mono-ion system to a real system (from 80% to 5%). Furthermore, a strong matrix effect is found, with the matrix largely affecting both the uptake and the release of neodymium.

This study reports a petrographic and crystal chemical analysis of three types of micas (yangzhumingite, light brown phlogopite and dark brown phlogopite) found in a lamproitic dyke at the Kvaløya Island (North Norway). The study was carried out integrating different analytical techniques: electron microprobe, single crystal X-ray diffraction, inductively coupled plasma mass spectrometry, Mössbauer and micro-Fourier Transform infrared spectroscopy. Kvaløya yangzhumingite (second occurrence in nature) was characterized for the first time in detail via single crystal X-ray diffraction. The different mica types are distinguishable on the basis of the VIFe and Mg versus Si content. Yangzhumingite composition is intermediate between those of KMg2.75(Si3.5Al0.5)O10F2 and KMg2.50Si4O10F2 synthetic compounds reported in the literature. Light and possibly dark brown phlogopite is a Mg-rich fluorotetraferriphlogopite, the latter having a greater Fe content. The infrared spectra of yangzhumingite and the light brown phlogopite show the occurrence of OH- absorption bands respectively at: ~ 3586 cm- 1 which correlates well with the measured F content; 3707 cm- 1 and 3686 cm- 1 assigned mainly to 3Mg2 +-K+-OH- (phlogopitic) environment. Structural analyses, performed only on yangzhumingite and light brown phlogopite show that both samples are 1M polytypes with the expected space group C2/m. Crystal chemical details are compatible with the following major substitution mechanisms: 2XIIK+ + VI[] ↔ 2XII[] + VIR2 + (where R2 + = Mg, Fe), OH- ↔ F- for yangzhumingite and 2VIR2 + ↔ VITi4 + + VI[] (Ti-vacancy), OH- ↔ F- for light brown phlogopite. All three types of micas formed at relatively constant low pressure, but over a large temperature range in equilibrium with a grain boundary fluid that underwent significant changes in composition during reaction progress. Light brown phlogopite cores and dark brown phlogopite rims formed during crystallization from the lamproitic magma, while yangzhumingite formed as a result of reactions between the already formed phlogopite and the highly reactive fluid that was derived from the volatile-rich lamproite magma.