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This work reports the synthesis and crystal-chemistry of ferri-clinoferroholmquistite in the system Li(2)O - FeO - Fe(2)O(3) - SiO(2) - H(2)O. Ferri-clinoferroholmquistite has a very restricted temperature stability. An almost monophase amphibole product is obtained at 500degreesC for a wide pressure range (1-7 kbar), whereas a Li-bearing pyroxene becomes predominant for T greater than or equal to 600degreesC. The X-ray powder pattern of ferri-clinoferroholmquistite was indexed in the C2/m space group. Refined cell dimensions are: a = 9.489 (2), b = 18.036 (7), c = 5.313 (3) Angstrom; beta = 101.59 (3). Infrared spectra in the OH-stretching region show the presence of a single and very sharp band at 3614 cm(-1), which is assigned to the Fe(2+)Fe(2+)Fe(2+) trimer at the OH-coordinated M1M1M3 octahedra, and a small satellite band at 3644 cm(-1) which was assigned to Li at M3. Mossbauer spectra can be fitted to three doublets assigned to Fe(3+) at M2, Fe(2+) at M1 and Fe(2+) at M3, respectively, with a calculated Fe(2+)/Fe(2+) ratio of 2/3, suggesting a composition close to the nominal one. The spectroscopic data show that synthetic ferri-clinoferroholmquistite has a strongly ordered cation distribution, in agreement with single-crystal refinements done by Caballero et al. (1998) and Oberti et al. (2000) on natural samples with related Li-rich compositions.

The Short Course on ''Amphiboles'', sponsored by the Mineralogical Society of America (MSA) and by the Accademia Nazionale dei Lincei (ANL), was held in Rome in October 2007. The aim of the Short Course was to update the scientific community on the extensive developments that have occurred over the last twenty years on many issues concerning the crystal-chemistry and systematics of the amphiboles, as well as their role in petrogenetic and environmental processes. Amphiboles are a complex but fascinating group of minerals, which are currently the focus of several investigations in the realms of geology, petrology, mineralogy, environmental mineralogy, epidemiology and even biology. During the last two decades, most of our previous concepts on the crystal chemistry of amphiboles have had to be reformulated, owing to advances in analytical techniques (especially X-ray diffraction, SIMS analysis and infrared spectroscopy), the development of new comprehensive models and the extensive study of synthetic compositions. This new situation prompted the organization of the Short Course and the preparation of a new volume of the MSA/GSA Reviews in Mineralogy series. Volume 67 (Amphiboles: crystal chemistry, occurrence and health issues) has been edited by Frank C. Hawthorne, Roberta Oberti, Giancarlo Della Ventura and Annibale Mottana, bringing together 13 comprehensive review chapters on the major issues addressed during the workshop. These chapters are focused on concepts and results more than on techniques, including advances in crystal-chemical models, classification and nomenclature. They also present challenges and results regarding synthesis, long-range and short-range ordering, geological occurrences and health issues related to the distribution of natural amphiboles in the environment. The present thematic issue of the European Journal of Mineralogy contains extensive reports on some of the open communications presented and discussed during the Short Course, which was attended by more than 50 scientists from many different countries. These contributions address the recognition and characterization of new end-members (Oberti et al., Robinson et al.), non-ambient in situ studies of synthetic compositions and the modelling of phase transitions (Della Ventura et al.), as well as strategies for the characterization of amphibole fibres (Bloise et al., Gunter et al. and Sanchez et al.). We wish to thank the Managing Editor, Christian Chopin, and the Chief Editor, Angelo Peccerillo, as well as the Special Issues coordinator, Walter Maresch, for their encouragement and patience during the collection and review of the manuscripts. Special thanks are also due to all those who contributed to the success of these many amphibole-focused initiatives. R

This study presents a cross-correlated surface and near surface investigation of two phlogopite polytypes from Kasenyi kamafugitic rocks (SW Uganda) by means of advanced Atomic Force Microscopy (AFM), confocal microscopy and Raman micro-spectroscopy. AFM revealed comparable nanomorphology and electrostatic surface potential for the two mica polytypes. A widespread presence of nano-protrusions located on the mica flake surface was also observed, with an aspect ratio (maximum height/maximum width) from 0.01 to 0.09. Confocal microscopy showed these features to range from few nm to several μm in dimension, and shapes from perfectly circular to ellipsoidic and strongly elongated. Raman spectra collected across the bubbles showed an intense and convolute absorption in the range 3000–2800 cm−1, associated with weaker bands at 1655, 1438 and 1297 cm−1, indicating the presence of fluid inclusions consisting of aliphatic hydrocarbons, alkanes and cycloalkanes, with minor amounts of oxygenated compounds, such as carboxylic acids. High-resolution Raman images provided evidence that these hydrocarbons are confined within the bubbles. This work represents the first direct evidence that phlogopite, a common rock-forming mineral, may be a possible reservoir for hydrocarbons.

A crystal-chemical investigation of vauxite, ideally FeAl 2 (PO 4 ) 2 (OH) 2 ·6H 2 O, 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 P space group, with the following unit-cell constants: a 9.1276(2), b 11.5836(3), c 6.15960(10) A, α 98.3152(10)°, β 92.0139(10)°, γ 108.1695(9)°, and V 610.05(2) A 3 . 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 H 2 O 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 ( −1 ) is compatible with the presence of two distorted PO 4 tetrahedra.

Beryllium is widely distributed in soils at low levels, but it can also occur naturally in higher concentrations in a variety of materials exploited for many industrial applications. Beryllium is also one of the most toxic natural elements and is known to be a human carcinogen. A concise account of the literature data on baseline concentrations of Be in soils illustrates the possibility of worldwide presence of areas with a high natural background concentration of Be (up to 300 mg/kg), the crustal abundance of which is generally estimated to be in the range 2-6 mg/kg. Nethertheless the number of available data is rather limited in comparison with those about other toxic elements such as Pb, Cd, Cr…This could have probabibly caused the choice of low values of concentration level as the reference ones for the definition of soil as contaminated: these values are not always realistic and applicable to large areas.As a case study we report and analyse a diffuse, unusually high (up to 80 mg/kg, average approximately 20 mg/kg), natural occurrence of beryllium in loose and poorly consolidated pyroclastic layers related to the Pleistocene activity of the Vico volcano. Additionally, the analysis of Be leachability has been carried out, providing evidence of a not negligible mobility in contrast with the scarce data presented in the literature that usually indicate beryllium as an element with low mobility in slighty acidic and oxidising surface environmental conditions. This research is proposed as a starting point for a possible possible reappraisal of beryllium geochemical behaviour and background levels, providing more realistic and flexible reference values for risk assessment and land management.

Manganese oxides are important geomaterials, used in a large number of applications. For instance, as pigments in art works or in the treatment and removal of heavy metals from drinking water. Particularly, ramsdellite [Mn4+O2] and groutellite [(Mn0.54+,Mn0.53+)O1.5(OH)0.5], because of their 2 1 frameworks that enable proton diffusion, are very important cathode materials. Manganese oxides commonly occur as crypto-crystalline and very fine mixtures of different Mn-phases, iron oxides, silicates and carbonates. Thus, proper characterization can be a difficult task using XRPD. The lack of Raman data on groutellite and the little and conflicting data on ramsdellite do not allow their proper identification by Raman spectroscopy. In this work we characterize natural mixtures of ramsdellite and groutellite by combining SEM-EDS, XRPD, FT-IR and Raman spectroscopy, to provide reference Raman spectra. Our data show that they have a typical and unmistakable spectra, allowing clear recognition. Moreover, we have investigated their laser-induced degradation. Our data show that groutellite transforms into ramsdellite, by the loss of H+ and the oxidation of Mn3+ to Mn4+, already at a very low laser power. Further increasing the laser power the formation of hausmannite [Mn2+Mn2 3+O4] occurs via the reduction of Mn cations. Our data can be used to study the discharge mechanism in cathodic battery materials, by monitoring the Mn reduction from ramsdellite to groutellite, and finally to groutite [a-Mn3+OOH]. Moreover, Raman mapping allows the study of their distribution in all the investigated samples and, indirectly, those of H+ and Mn3+, which plays a key-role in electrochemical activity of these compounds.

Manganese oxides are important geomaterials, widespread in terrestrial and Martian environments. Characterisation of the oxidation state of Mn is a central issue in science; this task has been addressed up to the present by X-ray spectroscopy or diffraction techniques. The former, however, requires access to synchrotron facilities, while the latter does not provide crystal-chemical information at the local scale. In this work, we compare a large set of Raman data from wellcharacterised samples, already published by the same authors of this paper or as found in the literature. We show a clear correlation between the oxidation state of Mn and the wavenumber of peculiar bands; octahedrally co-ordinated Mn2+ is recognised by a band around 530 cm-1, Mn3+ by a band around 580 cm-1 and Mn4+ by a band around 630 cm-1, while tetrahedrally co-ordinated Mn2+ is recognisable by a band around 650 cm-1. Strongly distorted Mn3+ octahedra are indicated by the appearance of Jahn–Teller modes. Our method allows a reliable, easily accessible tool to characterise the oxidation states of Mn in oxides, also suitable for microscale mapping. It provides a robust analytical basis for the use of these minerals as redox indicators in geology/geochemistry, in exoplanetary research or for monitoring technological processes.

High-temperature Fourier transform infrared (HT-FTIR) spectroscopy was used to characterize the deprotonation process of synthetic potassic-ferro-richterite of composition A ( K 0 . 90 Na 0 . 07 ) B ( Ca 0 . 54 Na 1 . 46 ) C ( Fe 4 . 22 2 + Fe 0 . 78 3 + ) T Si 8 O 22 W ( OH 1 . 70 O 0 . 30 2 − ) . Unpolarized single-crystal spectra were collected both in situ and on quenched samples, and heating experiments were conducted in air, at a rate of 10 °C/min. The room- T spectrum measured before annealing shows a main band at 3678 cm −1 and a minor band at 3622 cm −1 ; these are assigned to local configurations involving Fe 2+ at M (1) M (1) M (3) and facing a filled and an empty alkali-site, respectively. At 400 °C, a new band grows at 3656 cm −1 ; this is the most intense feature in the pattern at 450 °C. At T ≥ 500 °C, all peaks decrease drastically in intensity, and finally disappear at T > 600 °C. The total absorbance measured in situ increases significantly in the 25 T T range. This feature is consistent with an increase of the absorption coefficient (e) with T , the reason for which is still unclear. However, this feature has significant implications for the quantitative use of FTIR data in HT experiments. Examination of the relevant OH-stretching bands shows that iron oxidation occurs preferentially at the M (1,3) sites associated with occupied A sites. The deprotonation temperature indicated by FTIR for single-crystals is around 100 °C higher that that obtained by HT-X-ray diffraction (XRD) on single crystal by Oberti et al. (2016), whereas that obtained by HT-XRD on powders is intermediate. This unexpected observation can be explained by considering that: (1) the iron oxidation process, which is coupled to deprotonation and is probed by XRD, occurs preferentially at the crystal surface where it is triggered by the availability of atmospheric oxygen; (2) the proton diffusion, probed by FTIR, is slower that the electron diffusion probed by XRD; thus, the temperature shift may be explained by a much longer escape path for H in single-crystals than in powders. These results suggest that possible effects due to crystals size should be carefully considered in HT experiments done on Fe-rich silicates.

The crystal structure of fibroferrite, Fe(OH)SO 4 ·5H 2 O, 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 low-wavenumber ( −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 high-temperature behavior of synthetic potassic-ferro-richterite was addressed to obtain data relevant to understanding petrogenetic processes as well as to testing complementarity and mutual calibration of single-crystal X-ray diffraction (XRD) analysis plus structure refinement (SREF) with single-crystal FTIR spectroscopy. This experimental approach aims at: (1) better quantifying the onset of deprotonation, its development and the amount, if any, of relict OH at the end of the process; (2) verifying whether or not the process is homogeneous within the crystal; and (3) evaluating local changes in cation environments close to the OH dipole. In this first part of a series of two papers, we report on the crystal-chemical characterization of potassic-ferro-richterite and on a single-crystal XRD study at high T . Detailed analysis of the available data allowed us to obtain a full characterization of the bulk and crystal chemistry of the studied crystal, hence improving the unit formula suggested by Redhammer & Roth (2002). In operando H T measurements up to 1073 K showed quite anomalous behavior with respect to pargasite/kaersutites, specifically a much lower T for the onset of the deprotonation process (around 500 K), and strongly anomalous behavior of the β angle, which shows inverse slopes for protonated and deprotonated phases. “Oxo-potassic-ferro-richterite” is formed upon deprotonation and remains stable at least up to 1073 K under the conditions of this study. Structure refinements from data collected at different temperatures allowed us to detect changes in the crystal-structure geometry and in turn to decipher the way in which amphiboles with such a peculiar composition respond to increasing T and deprotonation. The thermal expansivity coefficients α (×10 −5 K −1 ) are: potassic-ferro-richterite: α a = 1.30(6), α b = 0.93(6), α c = 0.12(3), α β = −0.49(5), α asinβ = 1.34(8), α V = 2.59(2); “oxo-potassic-ferro-richterite”: α a = 1.71 (3), α b = 0.97(1), α c = 0.193(8), α β = 0.22(1), α asinβ = 1.59(4), α V = 2.74(2).

A multi-methodological study of the (K,Ca)-variety of the zeolite merlinoite from Fosso Attici, Sacrofano, Italy was carried out on the basis of electron microprobe analysis in wavelength dispersive mode, singlecrystal X-ray diffraction (at 100 K), Raman and infrared spectroscopy. Thechemical formula of the merlinoite from Fosso Attici is (Na0.37K5.69)Σ=6.06(Mg0.01Ca1.93Ba0.40)Σ=2.34(Fe0.023+Al10.55Si21.38)Σ=31.9O64·19.6H2O,compatible with the ideal chemical formula K6Ca2[Al10Si22O64]·20H2O.Anisotropic structure refinements confirmed the symmetry and the framework model previously reported (space group Immm, a = 14.066(5),b = 14.111(5), c = 9.943(3) Å at 100 K). Refinement converged with four cationic sites and six H2O sites; refined bond distances of the framework tetrahedra suggest a highly disordered Si/Al-distribution. The Raman spectrum of merlinoite (collected between 100and 4000 cm–1) is dominated by a doublet of bands between 496–422 cm–1, assigned to tetrahedral T–O–T symmetric bending modes. T–O–T antisymmetric stretching is also observed; stretching and bending modes of the H2Omolecules are only clearly visible when using a blue laser. The single-crystal near-infrared spectrum shows a very weak band at 6823 cm–1, assigned to the first overtone of the O–H stretching mode, and a band at 5209 cm–1, due to the combination of H2Ostretching and bending modes. Avery broad and convoluted absorption, extending from 3700 to 3000 cm–1 occurs in the H2O stretching region, while the ν2 bending mode of H2O is found at 1649 cm–1. The powder mid-infraredspectrum of merlinoite between 400–1300 cm–1 is dominated by tetrahedral T–O–T symmetric and antisymmetric stretches. Raman and Fourier-transform infrared spectroscopy spectra of merlinoite and phillipsite provide a quick identification tool for these zeolites,which are often confused due to their close similarity.

In this work, we address the intensity evolution of the CO2 FTIR bands of cordierite as a function of increasing T, by comparing data obtained from in situ versus quenching measurements. A natural well-characterized cordierite from Kragero (Arendal region, Norway) was studied up to 1200 °C using a heating stage fitted on a FTIR microscope. Two different oriented sections (001) and (010), respectively, were examined in order to check for the effect of the channel orientation on the CO2 release from the matrix. Spectra collected in situ show that increasing temperatures induces an increase in peak width for all CO2-related bands. The effects on the integrated absorbance A i are different for the different modes. Most notably, the integrated intensity A i of the anti-symmetric stretching mode (ν3) increases significantly up to 800 °C and then progressively decreases to 1000/1200 °C, depending on the sample orientation. Data obtained on quenched samples reveal that there is no variation in the band intensity for T

The crystal structure of calcium tartrate esahydrate, CaC4H4O6·6H2O, has been solved by the charge-flipping method from single-crystal X-ray diffraction data and refined toR= 0.021, based on 1700 unique observed diffractions. Salient crystallographic data are:a= 7.7390 (1),b= 12.8030 (2),c= 5.8290 (1) Å,Z= 2, and space groupP21212. During the refinement step it was possible to locate all H atoms by difference Fourier synthesis. The tartrate molecule has a (−)-gaucheconformation and is coordinated to two calcium ions to form infinite chains along theaaxis which alternate Ca polyhedra with tartrate molecules. The chains are interlinked by a three-dimensional network of hydrogen bonds from four water molecules surrounding the Ca ion, reinforced by hydrogen bonds from one interstitial water molecule. Micro-Raman and FT–IR spectroscopic data are provided.

Lutetium beta-tricalcium phosphate Ca9Lu(PO4)(7) was synthesized by solid-state reaction at 1200 degrees C, and investigated by means of a combination of scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectroscopies. SEM morphological analysis reveals the presence of sub spherical and prismatic micro crystalline aggregates, while EDS semi-quantitative analysis confirms the nominal Lu/Ca composition. The unit cell and the space group were determined by X-ray powder diffraction data showing that the compound crystallizes in the rhombohedral R3c whitlockite-type structure, with unit cell constants a = b = 1.04164(1) nm, c = 3.7302(1) nm and cell volume V = 3.5051(1) nm(3). The investigation was completed with the structural refinement by the Rietveld method, and discussion of the distribution of Lu within cationic sites according to the results of the Rietveld refinement. The FTIR and Raman spectra, correlated to isostructural rare earth phosphates from literature, show slight band shifts of the phosphate modes correlated to the evolving size of the rare earth elements. (C) 2018 Chinese Society of Rare Earths. Published by Elsevier B.V. All rights reserved.

The thermal dehydration of hohmannite, Fe2[O(SO4)2]·8H2O, a secondary iron-bearing hydrous sulfate, was investigated by in situ high-temperature X-ray powder diffraction and in situ high-temperature Fourier transform infrared spectroscopy. Combination of the data from both techniques allowed determining the stability fields and reaction paths for this mineral and its high temperature products. Five main dehydration/transformation steps for hohmannite have been identified in the heating range of 25–800 °C. Temperature behavior of the different phases was analyzed, and the heating-induced structural changes are discussed.

In order to clarify details of volatiles incorporation in arrojadites, two samples p\reviously characterized by X-ray diffraction and electron-microprobe (EMP) and LA-ICPMS analysis were investigated by single-crystal FTIR spectroscopy. The present study confirms and makes more quantitative previous results by single-crystal structure refinement about the presence and orientation of three OH − groups (one with partial occupancy) in the arrojadite structure. The FTIR spectra showed the presence of NH 4 + in arrojadite from Yukon, which was confirmed by EMP analysis ( ca . 700 ppm N). Micro FTIR imaging was used to check the homogeneity of OH and NH 4 + across the examined samples, as a prerequisite for the single-crystal polarized study. Based on the hydrogen bonding environment determined by structure refinement, the bands observed in the 3600–3500 cm −1 region can be assigned to the OH1 (at lower frequency) and OH2 (at higher frequency) dipoles. In the spectrum of arrojadite from Yukon several hyperfine components are resolved; these can be assigned to local Mg/ Fe 2+ octahedral configurations at the OH-coordinated octahedra. Both spectra show a very broad absorption extending from ~ 3500 to 2500 cm −1 which is assigned to the OH3 hydroxyl group. The orientation of the O-H dipoles calculated from the FTIR absorbance data are in excellent agreement with those calculated from the refined atomic coordinates, confirming the validity of the latter method also in the case of low-Z elements. Assuming the water content derived from EMP analysis, an integrated molar coefficient (polarized data) ɛ I = 63937 l/(mol□cm −2 ) is calculated for the spectroscopic quantification of H 2 O in arrojadite. For N, based on the EMP analysis, we obtain (for unpolarized data in the N-O bending region) ɛ i = 11000 ± 2000 l/(mol□cm −2 ) and ɛ I = 300 ± 60 l/(mol□cm −1 ) from integrated and linear intensity data, respectively.

We report a single-crystal Fourier-transform infrared (FTIR) study of a sample of pollucite from Maine, USA. Prior to our work, the sample had been characterized by single-crystal X-ray diffraction, neutron diffraction and electron-probe microanalysis. It is cubic Ia3d, with a crystal-chemical formula Na1.93(Cs10.48Rb0.31K0.04)Σ=10.83(Al14.45Si33.97)Σ=48.42O96·3.92H2O, and an H2O content, determined by thermogravimetric analysis, of 1.6 wt.%. The single-crystal FTIR spectrum has a doublet of intense bands at 3670 and 3589 cm–1, which are assigned to the ν3 and ν1 stretching modes of the H2O molecule, respectively. A very intense and sharp peak at 1620 cm–1 is assigned to the ν2 bending vibration. In the near-infrared region there is a relatively intense peak at 5270 cm–1, which is assigned to a combination (ν2 + ν3) mode of H2O, and a weak but well defined doublet at 7118 and 6831 cm–1, which is assigned to the first overtones of the fundamental stretching modes. A relatively weak but extremely sharp peak at 2348 cm–1 shows that the pollucite contains CO2 molecules in structural cavities. Mapping the sample using FTIR indicates that both H2O and CO2 are homogeneously distributed. Secondary ion mass spectrometry yielded an average CO2 content of 0.09±0.02 wt.%. On the basis of this value, we determined the integrated molar absorption coefficient for the spectroscopic analysis of CO2 in pollucite to be εiCO2 = 11,000±3000 l mol–1 cm–2; the linear molar absorption coefficient for the same integration range is εlCO2 = 1600±500 l mol–1 cm–1.

We report a FTIR (Fourier transform infrared) study of a set of cordierite samples from different occurrence and with different H2O/CO2 content. The specimens were fully characterized by a combination of techniques including optical microscopy, single-crystal X-ray diffraction, EMPA (electron microprobe analysis), SIMS (secondary ion mass spectrometry), and FTIR spectroscopy. All cordierites are orthorhombic Ccmm. According to the EMPA data, the Si/Al ratio is always close to 5:4; X Mg ranges from 76.31 to 96.63, and additional octahedral constituents occur in very small amounts. Extraframework K and Ca are negligible, while Na reaches the values up to 0.84 apfu. SIMS shows H2O up to 1.52 and CO2 up to 1.11 wt%. Optically transparent single crystals were oriented using the spindle stage and examined by FTIR micro-spectroscopy under polarized light. On the basis of the polarizing behaviour, the observed bands were assigned to water molecules in two different orientations and to CO2 molecules in the structural channels. The IR spectra also show the presence of small amounts of CO in the samples. Refined integrated molar absorption coefficients were calibrated for the quantitative microanalysis of both H2O and CO2 in cordierite based on single-crystal polarized-light FTIR spectroscopy. For H2O the integrated molar coefficients for type I and type II water molecules (ν3 modes) were calculated separately and are [I]e = 5,200 ± 700 l mol−1 cm−2 and [II]e = 13,000 ± 3,000 l mol−1 cm−2, respectively. For CO2 the integrated coefficient is $$ \varepsilon_{{{\text{CO}}_{ 2} }} $$ = 19,000 ± 2,000 l mol−1 cm−2.

""The structural characterization of whiteite-(CaFeMg), a natural orthophosphate from Crosscut Creek, Yukon, Canada, with chemical composition (Ca0.86Na0.05)∑=0.91(Fe0.88Mn0.02)∑=0.90Mg2.17Al1.93(PO4)4(OH)2∙8H2O obtained by WDS-EMPA, was carried out by means of single crystal X-ray diffraction. The structure was solved in the P2\\\/a monoclinic space group, with the following unit cell constants: a = 14.8700(15), b = 6.9785(5), c = 9.9268(10) Å, beta = 110.110(1)°, V = 967.31(15) Å3. Struc-ture refinement lead to the crystal chemical formula (Ca0.95Na0.11)∑=1.06Fe0.90Mg2.01Al2.05(PO4)4(OH)1.99∙8.17H2O. Phosphorus atoms display tetrahedral (PO4) coordination, while magnesium, iron(II) and aluminum display regular octahedral coordination; calcium displays a complex CaO8 coordination. MgO2(H2O)4, FeO6, AlO4(OH)2, CaO8 poly-hedra and PO4 groups are arranged such as to form a three-dimensional framework via edge- and vertex-sharing ar-rangements. Strong O-H…O hydrogen bonds contribute to stabilize the array: such interactions were also investigated by means of Libowitzky formula (Libowitzky, 1999) appli-cation, owing to the results of IR spectroscopy.""

This paper reports on the occurrence and the crystal structure of kircherite, a new member of the cancrinite-sodalite group of minerals from Valle Biachella, Sacrofano community (Rome, Latium, Italy). The mineral occurs in association with sodalite, biotite, iron oxides, titanite, fluorite, and a pyrochlore-group mineral. The groundmass of the ejectum consists essentially of K-feldspar with subordinate plagioclase. Kircherite (3 mm as largest size) is observed within miarolitic cavities of the rock and typically occurs as parallel associations of hexagonal, thin, tabular colorless to light-gray transparent crystals; it is non-pleochroic and uniaxial negative, with ω = 1.510(2) and ɛ = 1.502(2). D calc is 2.457 g/cm 3 . Kircherite is trigonal with a = 12.8770(7), c = 95.244(6) A, V = 13677(1) A 3 , Z = 1. The structure has been refined in the trigonal space group R 32, obtaining a R -value of 8.5% on 8131 reflections with I /σ I > 2. The strongest seven reflections in the X-ray powder pattern are [ d in A (I %) ( hkl )]: 3.717 (100) (3 0 0), 2.648 (100) (2 1 28; 0 0 36), 3.232 (65) (2 1 19), 3.584 (60) (1 2 14), 3.604 (53) (1 0 25), 3.799 (52) (1 2 11), 3.220 (38) (2 2 0). The single-crystal FTIR spectrum rules out OH groups and shows the presence of H 2 O and CO 2 molecules in the structural cages of the mineral. Chemical analysis gives (in wt%): SiO 2 32.05, Al 2 O 3 27.13, FeO 0.07, K 2 O 4.38, CaO 8.75, Na 2 O 13.62, MgO 0.01, MnO 0.02, TiO 2 0.01, SO 3 12.87, Cl 0.35, F 0.05, total 99.82. The empirical formula calculated on the basis of ∑(Si+Al) = 216 apfu is (Na 89.09 Ca 31.63 K 18.85 Fe 0.20 Mn 0.06 Mg 0.05 Ti 0.03 ) ∑=139.91 [(Si 108.13 Al 107.87 ) ∑=216.00 O 430.00 ](SO 4 ) 32.58 Cl 2.00 F 0.53 ·6.86H 2 O, which corresponds to the ideal formula [Na 90 Ca 36 K 18 ] ∑=144 (Si 108 Al 108 O 432 )(SO 4 ) 36 ·6H 2 O. The structure can be described as a stacking sequence of 36 layers of six-membered rings of tetrahedra along the c axis. The stacking sequence is ACABCABCABCACBCABCABCABCBABCABCABCAB…, where A, B, and C represent the positions of the rings within the layers. This sequence gives rise to cancrinite, sodalite, and losod cages, alternating along c . Sulfate groups occur within the sodalite and losod cages associated by Na, K, and Ca. H 2 O groups occur within the cancrinite cages, bonded to Ca and Na cations. Anion groups (SO 4 2− ) in sodalite cages show positional disorder, and so do consequently the extraframework cation sites related to them.

Eleven compositions along the join Na(NaMg)Mg(5)Si(delta)O(22)(OH)(2)-Na(NaCa)Mg(5)Si(8)O(22)(OH)(2) ("magnesiorichterite"-richterite) have been synthesized at T= 800-850 degrees C and P(H2O) = 0.35-0.5 GPa. The run products have been characterized by electron probe microanalysis (EPMA), synchrotron and conventional X-ray powder diffraction (XRPD), Fourier transformed infrared (FTIR) spectroscopy, and selected area electron diffraction (SAED-TEM). Nominally, the chemical variation along the join call be expressed as (B)Mg(x)(B)Ca(1-x) with 0 C2/m transformation induced by the Ca-Mg chemical Substitution are observed. The phase transition Occurs at B-site composition (X(c)) close to (B)(Na(1)Mg(0.7)Ca(0.3)). C2/m samples with a Ca content of 0.34, 0.45, and 0.54 apfu show, a significant strain tail related to local compositional inhomogeneities. This residual strain disappears Lis the amount of (B)Ca significantly increases with respect to that of (B)Mg. The transformation behavior observed here mirrors that of pyroxenes along the join diopside (CaMgSi(2)O(6))-enstatite (Mg(2)Si(2)O(6))- The Cell parameters of amphiboies with (C)Mg(5), (T)Si(8), and (W)(OH)(2) and variable A- and B-site populations follow almost linear and continuous trends, indicative of small amounts of spontaneous strain accompanying these monoclinic phase transitions and the absence of significant miscibility gaps among different amphibole groups when quenched from higher temperatures of crystallization.

The crystal structure and crystal chemistry of two natural pollucite samples, from Buckfield, Oxford County, Maine (sample M3), and from Kanzit Mawaie, Laghman, Nooristan, Afghanistan (sample N5), have been investigated by means of wavelength-dispersive X-ray microanalysis, thermogravimetric analysis, single-crystal X-ray and neutron diffraction, and single-crystal Fourier-transform infrared spectroscopy. The X-ray and neutron diffraction patterns of the two pollucite crystals show a metrically cubic unit cell [with a(M3) = 13.6914(6) angstrom and a(N5) = 13.6808(6) angstrom by neutron diffraction data; the deviation from isometry is 4 sigma(F(o)) for M3 and R(1) = 0.0693 for 31 refined parameters and 331 unique reflections with F(o) > 4 sigma(F(o)) for N5. The structure refinements show a disordered Si/Al-distribution in the tetrahedral framework. The analysis of the difference-Fourier maps of the nuclear density confirms the presence of extra-framework water molecules with oxygen sharing the Cs site (at 1/8, 1/8, 1/8, Wyckoff-16b position). However, the minima, ascribable to the proton sites, are very weak in density. Two possible proton positions, leading to a reasonable H(2)O configuration, are given, and the possible hydrogen bonding is described. Sodium is located at 1/4, 1/8, 0 (Wyckoff-24c position). The main IR absorption bands in the regions typical of H(2)O are assigned, and the presence of hydroxyls in the studied samples is ruled out. Neutron diffraction and FTIR data agree with the presence of very weak hydrogen bonds in the structure. The detailed description of the crystal structure and crystal chemistry of pollucite (e.g., Si/Al-distribution, configuration of the extra-framework content, possible hydrogen bonding scheme) reported in this study is the key to understand the high thermo-elastic stability of pollucite, the immobility of Cs at non-ambient conditions, and the extremely low leaching rate of Cs, which make this open-framework silicate a promising material with potential use for fixation and deposition of Cs radioisotopes.

We report the first Italian occurrence of yukonite, a rare hydrated arsenate of calcium and ferric iron, from Grotta della Monaca cave, S. Agata di Esaro, Cosenza, Italy. We have studied samples of cotype yukonite from the Daulton mine, Yukon, Canada, for comparison. At Grotta della Monaca, yukonite occurs in compact masses, dark reddish brown to brownish yellow in color. At the TEM scale, it consists of a chaotic assemblage of small grains (maximum dimension

The thermal behavior of synthetic richterite Na-A(B)(NaCa)(Mg5Si8O22)-Mg-C-Si-T(OH)(2), crystallized at 800 degrees C and 0.35 GPa under hydrothermal conditions, was studied by serial powder diffraction experiments using synchrotron radiation between 123 and 873 K. The a, b, and beta cell parameters show a non-linear behavior, whereas the c parameter shows a linear trend; values of the saturation temperature theta(s) are 410(3), 215(2), and 300(2) K for a, b, and asin beta, respectively. The axial expansion pattern below room temperature is alpha(b) > alpha(c) > alpha(a), whereas above room T it is alpha(b) > alpha(a) > alpha(c), the difference being related to the different saturation temperatures of the individual cell parameters. The thermal expansion was modeled following the Debye approximation for the density-of-state of phonons; the refined parameters are V-0 = 908.20 (0.04) angstrom(3), k = 1 (4), Q(0) = 32 (2) MJ, and the Debye temperature theta(D) = 586(31) K. The non-linear behavior at low T is well described without systematic differences between the data and the model. The volume thermal expansion coefficient alpha(F) changes significantly with temperature, also at temperatures higher than room temperature. It is suggested that this may occur also in other amphiboles and pyroxenes, requiring critical re-examination of the available data. A comparison of the strain tensor for the thermal expansion between amphiboles and pyroxenes shows that in amphiboles the major deformation occurs onto the (010) plane, whereas in pyroxenes it occurs along the b axis. Moreover, the major deformation on (010) in Ca-bearing pyroxenes occurs along the bond of the M2 cation with the furthermost O3 atoms, whereas in compositionally related Ca-amphiboles (i.e., tremolite) it occurs in a direction rotated by 10-20 degrees to a*, i.e., in a direction not corresponding to that of the M4-O5 bonds. It is proposed that the M4 polyhedron contributes less to the thermal deformation of amphibole than the M2 polyhedron contributes to the thermal deformation of pyroxene.

This paper describes a multi-technique approach to the complete crystal-chemical characterization of a gadolinite-(Y) sample found in a volcanic holocrystalline ejectum near the Vico lake (Latium, Italy). Gadolinite-(Y) occurs as poly-twinned crystals forming rounded short-prismatic aggregates (generally 0.1-0.3 mm in size, with the largest ever found >1 mm), associated with zircon, thorite, danburite, betafite, and tourmaline. Both the chemical and the structural characterization of gadolinite-(Y) from Vico required nonstandard procedures. After correction for (100) twinning, the structure of a crystal with unit-cell dimensions a = 4.7708(4) angstrom, b = 7.6229(7) angstrom, c = 9.8975(9) angstrom, beta = 90.017(7)degrees, and V= 359.95(6)angstrom(3) was refined in the P2(1)/c space group down to R = 2.3%. Electron microprobe (EMP) analyses failed to give accurate quantification of major elements, due to the presence of light and volatile elements as well as of rare earth elements (REE) and actinides. Secondary ion-mass spectrometry (SIMS) analysis done with accurate calibrations on well-characterized minerals allowed quantification of light, volatile, REE, and actinide elements, and also of Ca and Si. The derived chemical composition was interpreted with reference to the site-scattering values obtained from single-crystal structure refinement. The resulting unit formula is (Ca0.81REE0.66Y0.39Th0.13U0.02)(Sigma 2.01)(Fe0.292+Li0.14 Fe0.123+Mn0.02Mg0.01)(Sigma 0.58)(Si1.98Be1.09B0.81Li0.12)(Sigma 4.00) O-8(O1.20F0.51OH0.29)(Sigma 2.00,) which yields a calculated density of 4.267 g cm(-3). Fourier transform infrared spectroscopy (FTIR) single-crystal spectrum of gadolinite-(Y) shows several absorptions in the OH-stretching region that can be assigned to the different local configurations involving Ca and (REE,Y) at the A site and Be, B, and Li at the Z site. Lithium incorporation in gadolinite-group minerals is proposed to occur according to the exchange vectors: (1) Fe-x(2+) + Y-A -> Li-x + (A)(Th + U) and (2) Be-z + Fe-x(2+) -> Li-z + Fe-x(3+); the maximum amount of Li allowed in the gadolinite structure is 1.0 apfu. This work provides the first evidence that Li is a significant component in gadolinite-group minerals, particularly in geochemical environments enriched in actinides. This conclusion suggests that materials having the composition of Li-rich gadolinite may be considered as possible forms for radioactive waste disposal.

In this study, we describe the first FTIR measurements of CO2 desorption from cordierite, a microporous mineral stable up to high T conditions. To this purpose, we collected isothermal heating data on several (001) oriented sections of a well-characterized CO2-rich sample. Single-crystal slabs were heat-treated up to 1000 °C, and the intensity of the ν 3 antisymmetric stretching mode of CO2 at 2348 cm−1 was monitored as a function of time. The experimental data were modeled by using the mono-dimensional plane-sheet diffusion formalism; diffusion coefficients were plotted in the Arrhenius space and activation energies were calculated. Final data are as follows: −logD 0 = 4.2 ± 0.5 m2/s and E a = 208 ± 11 kJ/mol. Comparison with diffusion data from the literature (Lepezin and Osorgin in Rossijskaa Akademia Nauk 339:658–661, 1994) shows that at 800 °C H2O diffuses almost two orders of magnitude faster than CO2 along the structural channels of cordierite, with the difference in diffusion coefficients increasing at lower temperatures, and this implies that at lower temperatures H2O mobility is more favored compared to CO2. Therefore, the volatile contents measured in exhumed rocks may not reflect the H2O/CO2 ratio upon cordierite crystallization, and this could significantly affect the thermodynamic calculations for fluid activities or peak metamorphic conditions.

The thermal dehydration process of fibroferrite, FeOH(SO4)·5H2O, a secondary iron-bearing hydrous sulfate, was investigated by in situ high-temperature synchrotron X-ray powder diffraction (HT-XRPD), in situ high-temperature Fourier transform infrared spectroscopy (HT-FTIR) and thermal analysis (TGA-DTA) combined with evolved gas mass spectrometry. The data analysis allowed the determination of the stability fields and the reaction paths for this mineral as well as characterization of its high-temperature products. Five main endothermic peaks are observed in the DTA curve collected from room T up to 800 °C. Mass spectrometry of gases evolved during thermogravimetric analysis confirms that the first four mass loss steps are due to water emission, while the fifth is due to a dehydroxylation process; the final step is due to the decomposition of the remaining sulfate ion. The temperature behavior of the different phases occurring during the heating process was analyzed, and the induced structural changes are discussed. In particular, the crystal structure of a new phase, FeOH(SO4)·4H2O, appearing at about 80 °C due to release of one interstitial H2O molecule, was solved by ab initio real-space and reciprocal-space methods. This study contributes to further understanding of the dehydration mechanism and thermal stability of secondary sulfate minerals.

International audience; In this paper we report a crystal-chemical study of amphiboles along the nominal join richterite [ANaB(NaCa)CMg5TSi8O22W(OH)2] – ferro-richterite [ANaB(NaCa)CFe2+5TSi8O22W(OH)2], ideally characterized by direct substitution of CMg with CFe2+. Six samples were synthesized by hydrothermal techniques: the three Fe-richer compositions at 500 °C and the three Mg-richer ones at 600 °C, 1 kbar P(H2O), and internally-buffered fO2 conditions (Sergent et al. 1996). The experimental powders were studied using a combination of EMPA, FE-SEM, PXRD, and FTIR plus 57Fe Mössbauer spectroscopy. Due to crystal-size limitations, only the Fe endmember could be analyzed by EMP-WDS, while two additional Fe-rich samples could be semi-quantitatively analyzed by FE-SEM-EDS. Rietveld refinement of X-ray powder diffraction patterns show that, although a linear trend in the amphibole cell-parameters is observed, there is a significant decrease in the amphibole yield counterbalanced by an increase in clinopyroxene (cpx), up to 27 wt.%, for the Fe endmember.57Fe Mössbauer spectra could be fitted on the basis of known spectral parameters of similar amphiboles in the literature and corrected for the spectral contribution of cpx. The results show that Fe3+ is completely ordered at M(2), while Fe2+ is disordered over all available C sites; no ferrous iron is resolved at M(4). The OH-stretching FTIR spectra show complex patterns for intermediate compositions with up to eight bands; these can be assigned to the various configurations involving Mg/Fe2+ at M(1,3), locally associated with both full and empty A sites.Details of the crystal chemistry for all amphiboles in the series were obtained with the spectroscopic methods, and the resulting data were in reasonable agreement with those derived by WDS-EDS analyses for the three Fe-richer samples. For increasing Fe in the system, the amphibole composition deviates toward a sodic endmember following the exchange vector M2Fe2+M4Ca M2Fe3+–1M4Na–1, possibly due to the instability of endmember ferro-richterite for stereochemical reasons. Interestingly, along the studied series there is a general increase in the amphibole crystal size and an evolution of the crystal morphologies, from extremely acicular at the Mg endmember composition to prismatic and stubby for the Fe2+-richer compositions.

This paper reports a single-crystal unpolarized- light FTIR study in the OH-stretching region of a suite of well-characterized Ti-rich pargasites from Lherz (French Pyrenees). All amphiboles studied have fairly constant M-site composition, with Al-[6](tot) similar to 0.55 atoms per formula unit (apfia), Ti-[6] similar to 0.45 apfia, and Fe-[6](3+) similar to 0.40 apfu. SIMS and SREF data show all samples to have an 03 anion composition of OH approximate to O2- approximate to 1.0 apfu, with negligible F. The FTIR spectra show for all samples a broad absorption consisting of several overlapping bands; three main components can be recognized: similar to 3710, 3686, and 3660 cm(-1), respectively, with an asymmetric tail extending to lower frequency. Six Gaussian components can be fitted to the spectra; comparison with spectra of both synthetic and natural pargasites allows five of these components to be assigned to local configurations involving OH-O-2- at the 03 site, thus showing that coupling with an O2- anion through an A-cation significantly affects band position. Infrared spectroscopy can detect the presence of O2- in amphiboles in chemically favorable cases, i.e., in the absence of F. Moreover, the FTIR spectra show that all octahedral configurations involving Ti-M1(4+) or Fe-M1(3+) Fe-M3(3+) are associated with O2- at both adjacent 03 sites, and that Al-M3 is focally associated with OH, confirming SRO models based on structure refinement results.

We report here a single-crystal polarized-light study of stoppaniite, ideally (Fe,Al,Mg)4(Be6Si12O36)(H2O)2(Na,[]), from Capranica (Viterbo). Polarized-light FTIR spectra were collected on an oriented (hk0) section, doubly polished to 15 μm. The spectrum shows two main bands at 3,660 and 3,595 cm-1; the former is strongly polarized for E normal c, while the latter is polarized for E //c. A sharp and very intense band at 1,620 cm-1, plus minor features at 4,000 and 3,228 cm-1 are also polarized for E //c. On the basis of literature data and considering the pleochroic behavior of the absorptions, the 3,660 cm-1 band is assigned to the ν3 stretching mode and the 1,620 cm-1 (associated with an overtone 2*ν2 at 3,230 cm-1) band to the ν2 bending mode of “type II” water molecules within the structural channels of the studied beryl. The sharp band at 3,595 cm-1 is not associated with a corresponding ν2 bending mode; thus it is assigned to the stretching vibration of O–H groups in the sample. The minor 4,000 cm-1 feature can be assigned to the combination of the O–H bond parallel to c with a low-frequency metal-oxygen mode such as the Na–O stretching mode. The present results suggest that the interpretation of the FTIR spectrum of Na-rich beryl needs to be carefully reconsidered.

This paper reports a single-crystal FTIR spectroscopic study of vishnevite, ideally [Na-6(SO4)] [Na-2(H2O)(2)](Si6Al6O24), a member of the cancrinite group of feldspathoids. The study was done on several crystals from various geological occurrences. Infrared spectra show that most samples, and in particular the specimens from the holotype locality at Vishnevye Mountains (Urals, Russia), contain molecular CO2 as the main carbon species in the structural pores, while the specimens from Loch Borolan (Scotland) were found to be CO3-rich. Polarized-light measurements show that the linear CO2 molecules are oriented perpendicular to the crystallographic c axis. Structure refinement of sample Pi4 from Latium (Italy) shows usual H2O center dot center dot center dot Na center dot center dot center dot H2O sequences within the undecahedral cages; however, difference Fourier maps suggest the presence of additional protons in the channels, possibly forming OH groups. The FTIR spectra show three absorptions in the 3800-3200 cm(-1) region. The first one, at 3590 cm(-1) is strongly polarized for E perpendicular to c while the second, at 3535 cm(-1), behaves almost isotropic. These two bands are assigned to the stretching Vibrations of an asymmetric water molecule in the structural cages. The third broad absorption at 3320 cm(-1), is predominantly polarized for E vertical bar vertical bar c and is assigned to additional OH groups in the channels. Detailed microspectroscopic mapping showed several samples from Latium (Italy) to be zoned with respect to the CO2/CO3 content, thus pointing to a possible use of the volatile content of these minerals for petrological modeling.

This paper relates the in situ X-ray diffraction and FTIR high- T study of pitiglianoite from Monte Cavalluccio (Campagnano, Rome, Italy), with composition Na 4.7 K 2.6 Ca 0.1 Si 6.1 Al 5.9 O 24 (SO 4 ) 0.8 · 2H 2 O. Upon heating, the cell parameters increased in the range 25–226 °C, following paths which were best fitted by the equations a = −1 × 10 −6 T 2 + 4 × 10 −4 T + 12.821 and c = −6 × 10 −7 T 2 + 2 × 10 −4 T + 5.264, for a and c , respectively. In the range 226–403 °C, there was a strong decrease of both a and c , while for T > 403 °C there was a new expansion of the structure. The FTIR data showed a major loss of both H 2 O and CO 2 in the range 200–400 °C. The structure of pitiglianoite at room- T , before the heating run, was characterised by columns of base-sharing undecahedral cages, containing chains of alternating Na cations and H 2 O molecules, and by large channels containing sulphate groups as well as Na and K ions. Structure refinement at 457 °C showed that all water was released from the cages and that significant extra-framework K (1.4 apfu) migrated from the large channel into the cages, throughout the hexagonal tetrahedral rings. A corresponding amount of Na cations migrated from the cages into the channels; a rotation of the sulphate groups, due to the presence of Na instead of K between two sulphate groups was also observed. Refinement at room- T after the experiment showed that the thermally-induced changes were substantially irreversible. The re-hydration of pitiglianoite was prevented by the Na ⇔ K cation exchange within the pores due to the thermal treatment.

Nous presentons ici les resultats d'une etude cristallochimique d'une suite de mineraux du groupe du pyrochlore provenant de blocs syenitiques holocristallins ejectes lors d'eruptions pyroclastiques d'âge plio-pleistocene au Latium, en Italie centrale. Malgre leurs teneurs elevees en actinides, les echantillons etudies ne sont pas devenus metamictes grâce a leur formation tres recente, comme le montrent les raies bien definies et fines du spectre de diffraction X (methode des poudres). La dimension a mesuree montre une correlation avec la teneur en (Ti + Fe 3+ ) au site B de la structure. Conforme a la classification des mineraux du groupe du pyroclore de l'IMA. telle que modifiee selon la regle des 50% adoptee en 1992 ,les echantillons sont soit de la betafite, du pyrochlore ou de l'uranpyrochlore. En comparaison avec les echantillons connus des mineraux du groupe du pyrochlore, ces echantillons ont une teneur tres elevee en Ti, jusqu'a 81.3% de Ti relatif a la somme Ti + Nb + Ta, et des quantites importantes mais variables de Zr (jusqu'a 8.44% de ZrO 2 , poids) et W (jusqu'a 12.14% de WO 3 ). Certains cristaux font preuve d'une forte zonation en composition selon la substitution 3Nb 5+ + Na + ⇆ 3T14+ + U 4+ . L'accommodation de quantites tres elevees de W 6+ pourrait etre liee a la substitution couplee 2(Nb + Ta) 5+ ⇆ T1 4+ + W 6+ au site B. Les mineraux du groupe du pyrochlore au Latium contiennent des quantites importantes de terres rares (jusqu'a 7.75% des oxydes). Les traces d'enrichissements normalises a une chondrite suivent en general le trace typique d'un pyrochlore non altere, avec un enrichissement extreme en Ce et une diminution progressive vers les terres rares lourdes.

Trioctahedral mica samples, collected at Cava St. Antonio (Mt. Vulture, Italy) were studied by combining electron-microprobe and C-H-N elemental analyses, single-crystal X-ray diffraction refinement, Mossbauer and Fourier transform infrared spectroscopies. Electron-microprobe analyses show the crystals to be quite homogeneous with TiO2 similar to 3 wt % and F ranging from 0.42 to 0.59 wt% Quantitative analyses of H combined with ferric/ferrous ratios from Mossbauer data allowed reliable crystal-chemical formulae to be derived. The results suggest that the entry of both Ti4+ and Fe3+ in the structure occurs through R-oxy substitution mechanisms involving deprotonation at O(4). This inference is supported by X-ray structure-refinement results (notably the c cell-parameter. the off-centering of the M2 cation towards O(4), the bond-length distortions of the cis-M2 octahedron) obtained using anisotropic thermal parameters in space group C2/m. The amount of oxy-substitutions from both electron-microprobe and X-ray data is in agreement with carbon-hydrogen-nitrogen analyses which give an average anion composition (OH1.25O0.65F0.10). Polarized-light infrared spectroscopy shows a complex OH-stretching spectrum which is composed of several overlapping (at least five) components. These can be assigned to the main octahedral local configurations that are compatible with the chemical composition. Pleochroic Fourier transform infrared spectroscopy measurements done along the principal optical directions show that the O-H bond axis is tilted from [001] and provide the average orientation of the O-H dipole in the structure: O-H (boolean AND) alpha similar to 23 degrees and O-H (boolean AND) gamma similar to 56 degrees.

Vesuvianite, a complex sorosilicate, often contains variable (from trace-to-minor-element) amounts of H, B and F. We describe a microanalytical study of H, B and F in vesuvianite by means of Electron Probe Microanalysis (EPMA), Secondary Ion Mass Spectrometry (SIMS), and single-crystal Fourier-Transform InfraRed (FTIR) spectroscopy. Most crystals investigated are B- (up to 3.67 wt% B2O3) and F-rich (up to 2.38 wt%); H2O ranges from 0.243 to 0.665 wt%. The H data obtained by SIMS allowed us to calibrate the quantitative analysis of H2O by FTIR spectroscopy. The resulting molar absorption coefficient (epsilon(i) = 100 000 +/- 2000 L center dot mol(-1) center dot cm(-2)) is in excellent agreement with working curves available from the literature. Moreover, the SIMS data allowed us to obtain the calibration curve to estimate the B2O3 content on the basis on the FTIR absorbance: a(i) = 34000 +/- 1400 center dot B2O3 (wt%).

This paper describes a high-pressure synchrotron infrared (IR) spectroscopy study of the synthetic amphibole Na(NaMg)Mg{sub 5}Si{sub 8}O{sub 22}(OH){sub 2}. This compound has P21/m symmetry at room conditions; its IR OH-stretching spectrum consists of two main bands at 3743 and 3715 cm{sup -1}, which are assigned to the two symmetrically independent O-H groups in the P structure (sample 403, Iezzi et al. 2004a). For increasing pressure, both bands shift toward higher frequency, suggesting a shortening of the O-H bond. In addition, the two bands progressively merge to give a single, symmetric and broad absorption band at 20-22 GPa. This behavior suggests that at 20-22 GPa there is a unique O-H group in the structure, indicative of a C-lattice type. The IR data thus show that the examined sample undergoes a P21/m {leftrightarrow} C2/m phase-transition at that pressure. Upon release of pressure, the initial two-band pattern is immediately recovered indicating that the pressure-induced phase-transition is reversible, as already observed for the same kind of transition induced by temperature. By analogy with structurally related pyroxenes, and taking into account the possible crystal structural topologies of amphiboles, we suggest that the C2/m polymorph stable at high pressure is characterized by fully kinked double-chains.

We describe here the synthesis of amphiboles along the nominal Na(NaMg)Mg 5 Si 8 O 22 (OH) 2 −Na(LiMg)Mg 5 Si 8 O 22 (OH) 2 join, at 800 °C, 0.4 GPa. High amphibole yields (>90%) plus minor quartz and enstatite have been obtained at all compositions; amphibole crystals are acicular and their size rarely exceeds 20–30 × 0.5–3 μm. TEM analysis shows the presence of h+k odd reflections in all samples, indicative of a P -lattice. By similarity with closely related amphiboles from the literature (e.g., Oberti et al. 2000; Camara et al. 2003) a P 2 1 / m space group was assigned to the amphiboles synthesized here. Refined cell-parameters from X-ray powder-patterns show a linear decrease as a function of increasing Li at M4, a and β being the most affected parameters. The four infrared OH-stretching spectra all show two main bands at 3741–3748 and 3712–3716 cm −1 , respectively. They are assigned to two independent O-H groups in the P 2 1 / m structure, interacting with a strongly delocalized A Na. The spectra show in addition two minor absorptions at about 3688 and 3667 cm −1 , respectively; these bands are assigned to vacant A-sites in the structure and indicate slight departure of the nominal composition toward cummingtonite. The present work shows that one apfu of B Na can also be completely replaced by one apfu of B Li (M + ), in synthetic Na(M+Mg)Mg 5 Si 8 O 22 (OH) 2 , and that all compositions have P 2 1 / m symmetry at ambient conditions.

A great effort in X-ray imaging studies has been dedicated to the design of novel optics-detector solutions that aims in creating a compact laboratory X-ray microscopy apparatus. Based on our experience in the use of both capillary/polycapillary optical systems and LiF imaging detectors we have recently tested a new combination of these techniques. The potential of the optics both to concentrate and to shape X-ray radiation enforced by the high performances in terms of spatial resolution/dynamic range of LiF imaging detectors allows us to use very simple imaging techniques, like the contact one, particularly suitable for compact imaging systems. In this paper we present first results about high spatial resolution images of transmitted X-rays through a polycapillary semi-lens. Submicron X-ray imaging of thick geological samples was also presented and discussed. These results demonstrate the potentialities of these novel X-ray imaging system for characterization of X-rays optics and for applications in material, life and heart sciences. © 2012 Elsevier B.V.

Near-edge features of Al x-ray absorption near-edge structure (XANES) spectra in aluminosilicate compounds with mixed coordination number are usually assigned to a fourfold coordinated site contribution followed by a sixfold coordinated site contribution that is displaced towards higher energy because of the increasing ligand nucleus potentials, neglecting possible contributions due to bond distance variations and local geometrical distortion. Here we present and discuss the Al K-edge XANES spectra of synthetic micas with either fourfold coordinated Al (phlogopite), or with sixfold coordinated Al (polylithionite), as well as with mixed coordination (preiswerkite). Multiple scattering simulations of XANES spectra demonstrate that octahedral contributions may overlap the tetrahedral ones so that the lower energy structures in mixed coordination compounds may be associated with the octahedral sites. This unexpected behaviour can be described as due to the effect of a significant reduction of the ligand field strength (i.e. large local distortion and Al-O bond distances).

This paper reports on water speciation and diffusion in synthetic beryl samples treated in CO2-rich atmosphere, at 700 MPa and 700 and 800 °C, respectively. The study has been conducted by means of polarized FTIR (Fourier transform infrared) integrated with FPA (focal plane array) imaging. As expected, the infrared spectra show the presence of CO2 but also of minor H2O interpreted as resulting from moisture present in the starting materials used for the experiments. FPA-FTIR images show that H2O diffuses into the beryl matrix along the structural channels oriented parallel to [001]. Spectra collected along profiles parallel to the c-axis show subtle changes as a function of the distance from the crystal edge; these changes can be correlated to a progressive change in the H2O coordination environment in the channel, as a response to the varying H2O/alkali ratio. In particular, the data show that when 2H2O > Na+ apfu (atoms per formula unit), H2O can assume both type I and type II orientation; in the latter case, each Na cation coordinates two H2O[II] molecules (doubly coordinated H2O). If 2H2O

The crystal structure of a Th-U-rich, Y-poor hellandite-(Ce) occurring in a volcanic ejectum from Capranica (Vico volcanic complex, Latium, Italy) was refined to an R index of 1.5% for 2226 observed reflections [I > 3 sigma(I)]. Hellandite from Capranica is monoclinic P2/a with a = 19.068 (8), b = 4.745 (2), c = 10.289 (3) Angstrom, beta = 111.18 (3)degrees. The extra-framework (distorted) tetrahedral cavity, usually occupied by H in hellandite, is partially (35-40%) occupied by Be and/or Li. When this is the case, the [B4Si4O22] tetrahedral chains of hellandite are locally cross-linked to form a sheet, which is built up by the same types of rings as in semenovite but in a different arrangement. The structure refinement and the electron- and ion-microprobe analyses provide constraints on hellandite-group crystal chemistry. The presence of ([4])(Be, Li) at the Be site is coupled with the substitution of F and/or O for OH at the O5 site; the amount of extra-framework cations thus constrains the OH content in the general formula. X-ray data exclude the presence of other OH sites in the structure, in agreement with direct H determination by ion probe (1.02 H apfu + 0.98 F apfu = 2.0 apfu of monovalent anions at O5 vs. 4.5-8 apfu proposed previously). The complete chemical analysis also eliminates the need for a vacancy at the REE sites. The general formula of hellandite-group minerals is thus (Ca,REE)(8)(Th,U,Y,REE)(4)(Ti,Fe3+,Al)(2)(O,F,OHx)(4)(Be,Li)(4-x)Si8B8O44, where electroneutrality is assured by the appropriate mixing of heterovalent substituents at the M sites.

The crystal chemistry of wavellite from Zbirov (Czech Republic), ideally Al3(PO4)2(OH,F)3·5H2O, was addressed by means of a multi-methodological approach based on electron microprobe analysis (EMPA) using wave-dispersive spectroscopy, single-crystal X-ray diffraction, powder and singlecrystal infrared spectroscopy and Raman spectroscopy. The EMPA data showed the presence of significant F replacing OH in the sample studied. The structure was solved in thePcmnorthorhombic space group, with the following unit-cell constants:a= 9.6422(7),b= 17.4146(15),c= 7.0094(2) Å,V= 1176.98(10) Å3. Phosphorus atoms display tetrahedral (PO4) coordination, while Al cations display octahedral coordination. The mineral framework can be viewed as the repetition of cationic arrays made up of AlO6polyhedra, bridged by PO4groups and further joined by O–H⋯O hydrogen bonds. The single-crystal unpolarized Fourier transform infrared (FTIR) spectrum shows combination bands indicating the presence of both OH and H2O in the structure. Both FTIR and Raman spectra show a broad absorption extending from 3600 to 2800 cm−1resulting from the overlapping of several components due to the water molecules and the OH group. The frequencies observed are comparable to those expected on the basis of the Libowitzky relationship for the range ofD–H⋯Abond systems in the structure.

This paper relates an infrared (IR) (6000–2500; 1400–400 cm–1) spectroscopic study of sideronatrite, Na2Fe3+(SO4)2(OH)·3H2O. Spectra in the 600–1250 cm–1 range are dominated by fundamental S–O absorption bands. Factor-group analysis based on the space group P212121(D42) is in accordance with the observed band multiplicity. A broad and convolute absorption centred around 3400 cm–1 and a sharp band at 3605 cm–1 are observed in the 2900–3900 cm–1 frequency region. The resolution of the broad band is significantly improved at liquid nitrogen temperature; seven components can be fitted to the pattern and these can be assigned to H2O/OH molecules in the structure. All components in the broad band and the sharp absorption at 3605 cm–1 are strongly polarized for E//a, in accordance with the structure analysis results. Infrared transmission spectroscopy is a useful tool to identify these sulfate minerals occurring in specific geological environments.

"The thermal stability of sideronatrite, ideally Na2Fe3+(SO4)(2)(OH)center dot 3(H2O), and its decomposition products were investigated by combining thermogravimetric and differential thermal analysis, in situ high-temperature X-ray powder diffraction (HT-XRPD) and Fourier transform infrared spectroscopy (HT-FTIR). The data show that for increasing temperature there are four main dehydration\/transformation steps in sideronatrite: (a) between 30 and 40 A degrees C sideronatrite transforms into metasideronatrite after the loss of two water molecules; both XRD and FTIR suggest that this transformation occurs via minor adjustments in the building block. (b) between 120 and 300 A degrees C metasideronatrite transforms into metasideronatrite II, a still poorly characterized phase with possible orthorhombic symmetry, consequently to the loss of an additional water molecule; X-ray diffraction data suggest that metasideronatrite disappears from the assemblage above 175 A degrees C. (c) between 315 and 415 A degrees C metasideronatrite II transforms into the anhydrous Na3Fe(SO4)(3) compound. This step occurs via the loss of hydroxyl groups that involves the breakdown of the [Fe3+(SO4)(2)(OH)] (a) (2-) chains and the formation of an intermediate transient amorphous phase precursor of Na3Fe(SO4)(3). (d) for T > 500 A degrees C, the Na3Fe(SO4)(3) compound is replaced by the Na-sulfate thenardite, Na2SO4, plus Fe-oxides, according to the Na3Fe3+(SO4)(3) -> 3\/2 Na-2(SO4) + 1\/2 Fe2O3 + SOx reaction products. The Na-Fe sulfate disappears around 540 A degrees C. For higher temperatures, the Na-sulfates decomposes and only hematite survives in the final product. The understanding of the thermal behavior of minerals such as sideronatrite and related sulfates is important both from an environmental point of view, due to the presence of these phases in evaporitic deposits, soils and sediments including extraterrestrial occurrences, and from the technological point of view, due to the use of these materials in many industrial applications"

The crystal chemistry of sekaninaite from Dolní Bory, Czech Republic, was characterized by a multimethod approach. Particular emphasis was put on the characterization of the channel constituents (i.e. H2O and CO2). Electron microprobe analysis shows the sample to be close to the Fe endmember [XFe = Fe/(Fe+Mg) = 94%) with significant Mn (1.48 wt.%) present; laser ablation mass-spectrometry showed the presence of 0.42 wt.% Li2O. H2O and CO2 contents (1.48 and 0.17 wt.%, respectively) were determined via secondary-ion mass-spectrometry. Sample homogeneity was checked by Fourier-transform infrared (FTIR) imaging using a microscope equipped with a focal plane array detector. Single-crystal FTIR spectroscopy confirmed the presence of two types of H2O groups in different orientations (with prevalence of the type II orientation), and that CO2 is oriented preferentially normal to the crystallographic c axis. Using the Beer-Lambert relation, integrated molar coefficients, εi, were calculated for both types of H2O (εi H2O[I] = 6000±2000; εi H2O[II] = 13000±1000) and for CO2 (εiCO2 = 2000±1000).

The symmetry and crystal chemistry of a (OH,F)-rich spessartine from Junzico Xijang, Wushan Spessartine Mine, Yunxiao Co., Fujian Province, P.R. China, with composition X (Mn 2+ 2.87 Fe 2+ 0.09 Ca 0.04 ) Y (Al 1.94 Fe 3+ 0.06 ) Z [(SiO 4 ) 2.52 (OH 1.11 F 0.81 )] have been studied by single-crystal X-ray structure refinement and FTIR spectroscopy. This sample is tetragonal, space group I4 1 /acd, with a = b = 11.6347(3) A, c = 11.6449(3) A, c/a = 1.006, R all 3.1% (θ max = 55°). The two independent tetrahedra differ significantly both in terms of refined bond-lengths and site-scattering values, the latter allowing to confirm the extent of the (OH,F) substitution and to its preferential ordering at 03, the site occupied by the anions coordinated to Z2. FTIR spectra consist of a prominent peak at 3580 cm ―1 and a doublet at 3622―3632 cm ―1 . Pleochroic curves suggest assignment to a unique O―H dipole, involved in two different hydrogen bonds (O3―H···O2 and O3―H···03, the latter showing two different, O―H···H and O―H···F, configurations). The observed space group and composition imply: (a) that lowering in symmetry is related to the presence of (OH,F) 4 groups; (b) the existence of a new hydrogarnet end-member with ideal composition X Mn 3 Y Al 2 Z [(SiO 4 ) 2 (OH) 4 ] and significant F content, the first related to the pyralspite series; the sample of this work is close to its 50:50 solid solution with spessartine. Geometric considerations and the very limited increase in volume with respect to spessartine suggest that the presence of F is a requisite for the incorporation of significant amount of monovalent anions in pyralspites.

This paper reports an infrared spectroscopic study of a set of sodalite-group minerals. The specimens have been identified using a combination of X-ray diffraction and microchemical analysis. As expected, the Si/Al ratio is ∼1; the extra framework cation content is characterized by a well-defined Na ⇌ (Ca+K) substitution. The lattice parameters of the studied samples range from sodalite (sample LM11) with a = 8.889(2) A, to hauyne (sample HR3S) with a = 9.1265(2) A. The specimens, having the \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{SO}_{4}^{2-}\) \end{document} group as a dominant anion, show a clear correlation between the a cell edge and the K content. Single-crystal FTIR spectroscopy shows that hauyne and nosean typically contain enclathrated CO2 molecules, in addition to H2O and minor carbonate, while sodalite is virtually CO2-free. Detailed microspectrometric mappings show a non-homogeneous distribution of volatile constituents across the crystals, which may be related to the presence of fractures in the crystals. Because of such zoning, a relatively wide variation is observed when calibrating extinction coefficients on the basis of a bulk analytical method such as CHN elemental analysis.

Nonstoichiometric REEAl(2.07)(B(4)O(10))O(0.60) (REE = (La, Ce); Ce; Nd) dimetaborates have been crystallized and analyzed by means of single crystal X-ray diffraction. The compounds resulted to be isostructural within hexagonal space group P (6) over bar 2m (n. 189), with the following unit cell parameters: a = 4.6060(6) angstrom, c = 9.3510(8) angstrom and V = 171.81(3) angstrom(3) (La, Ce); a = 4.5960(6) angstrom; c = 9.3170(10) angstrom and V = 170.44(4) angstrom(3) (Ce); a = 4.5830(7) angstrom, c = 9.2810(14) angstrom and V = 168.82(4) angstrom(3) (Nd). The REE cations are surrounded by six oxygen atoms, making up a trigonal prismatic coordination; Al cation is surrounded by five oxygen atoms, resembling a square pyramidal coordination, while the BO(4) group displays tetrahedral arrangement. The three-dimensional framework can be described as a mica-like structure packed down crystallographic axis c, with layers of six-membered rings of B tetrahedra alternated by inter-layers REE cations and layers of Al polyhedra. A complex network of REE center dot center dot center dot O and Al center dot center dot center dot O interactions concur to stabilize the framework.