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The structural model and chemical composition of vlasovite from the Burpala massif (Russia) have been determined using X-ray diffraction methods and electron probe microanalysis. The crystal structure has been refined in the sp. gr. Cc to R = 1.4% (Rw = 1.8%) with the following unit-cell parameters: a = 11.0396(3) A, b = 10.1042(2) A, c = 8.5696(2) A, β = 100.307(1)°, V = 940.48(4) A3, and Z = 4.

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 groupP1̄. Average crystallographic data area≈ 10.423,b≈ 12.477,c≈ 7.112 Å, α ≈ 89.92°, β ≈ 99.68°, γ ≈ 92.97°,V≈ 910.5 Å3for tokkoite;a≈ 10.373,b≈ 12.176,c≈ 7.057 Å, α ≈ 90.82°, β ≈ 99.22°, γ ≈ 92.80°,V≈ 878.5 Å3for 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 thebparameter, longer distances, especially ; 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 2Ca(M1+M2)2++ (F,OH)(O20)–↔ Ti(M1)4++ Na(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 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 (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). 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 showed that the sample studied is anhydrous. The average crystal chemical formula of the Murun narsarsukite is: Na2.04K0.01(V0.015+Ti0.74Zr0.01Al0.01Fe0.223+Mg0.01)1.00Si4.00(O10.74F0.23OH0.03)11.00. Structural disorder at octahedral and interstitial sites was modelled and also discussed in consideration of the main substitutional mechanism Ti4+ + O2– ↔ Fe3+ + (F–, OH–) active in the structure of the mineral.

The crystal structure of hohmannite, Fe3+2[O(SO4)2]·8H2O, was studied by means of single-crystal X-ray diffraction (XRD) and vibrational spectroscopy. The previous structural model was confirmed, though new diffraction data allowed the hydrogen-bond system to be described in greater and more accurate detail. Ab initio calculations were performed in order to determine accurate H positions and to support the experimental model obtained from XRD data. Infrared and Raman spectra are presented for the first time for this compound and comments are made on the basis of the crystal structure and the known literature for sulfate minerals.

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.

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.

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 Kvaloya Island (North Norway). The study was carried out integrating different analytical techniques: electron microprobe, single crystal X-ray diffraction, inductively coupled plasma mass spectrometry, Mossbauer and micro-Fourier Transform infrared spectroscopy. Kvaloya 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 VI Fe and Mg versus Si content. Yangzhumingite composition is intermediate between those of KMg 2.75 (Si 3.5 Al 0.5 )O 10 F 2 and KMg 2.50 Si 4 O 10 F 2 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 3Mg 2 + –K + –OH − (phlogopitic) environment. Structural analyses, performed only on yangzhumingite and light brown phlogopite show that both samples are 1 M polytypes with the expected space group C 2/ m . Crystal chemical details are compatible with the following major substitution mechanisms: 2 XII K + + VI [] ↔ 2 XII [] + VI R 2 + (where R 2 + = Mg, Fe), OH − ↔ F − for yangzhumingite and 2 VI R 2 + ↔ VI Ti 4 + + 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.

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) A, b = 109.436(3)°, V = 1463.6(1) A 3 , 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.

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 bis-iodobenzofulvenes with organoboron, organotin, or ethynyl derivatives under Pd catalysis. Structural aspects of the new compounds are discussed.

The determination of the oxidation state and structural role of transition metals in minerals is a crucial challenge. XPS has proven to have a great potential in probing the site distribution and chemical states of Fe and Ti transition elements, provided that the right method to process the spectra is used. XPS spectra of these elements have the 2 p core level region usually rich of features but the choice of the method for background removing can seriously affect the results of the quantitative analysis. Single crystals of brookite (TiO 2 ) and natural micas (phlogopites) are investigated to examine the effect of background subtraction on Ti2 p and Fe2 p signals. The backgrounds used are: the “Linear” background; the traditional “Shirley” background; three different Tougaard-like backgrounds; and the more recent “shape parameter, κ” method. In the case of the studied natural micas, the Fe chemical state proportion (Fe 2+ /Fe tot ) obtained with the corrected spectra varies by 10%. It is shown that TiO 2 oxides are not suitable as standard for octahedral Ti 4+ signal in the studied micas. The “shape parameter, κ” method proves to provide supplementary information useful for a full interpretation of XPS signals.

The structure, structural disorder and chemistry of miserite from the charoite-bearing rocks of the Murun massif (Russia) and from alkaline-syenite pegmatitic rocks of the Dara-i-Pioz massif (Tajikistan) were investigated employing a combination of electron microprobe, single crystal diffraction and micro-Fourier transform infrared spectroscopy analysis. Chemical analysis of the sample investigated by X-ray diffraction evidenced that Dara-i-Pioz miserite has a greater REE concentration than Murun miserite (~0.22 vs. 0.05 apfu, respectively) and also contains Y (0.14 apfu), which is absent in Murun miserite. The occurrence of a band at about 1,600 cm−1 testified to the presence of H2O in miserite at hand. Structural analyses yielded average cell parameters of a = 10.092, b = 16.016, c = 7.356 A, α = 96.60°, β = 111.27° and γ = 76.34°. Anisotropic structural refinement in space group P $$\bar{1}$$ converged at similar values for the analyzed samples (R ~3.4, R w ~3.8 %). An interesting feature shown by both the miserite specimen is the presence, revealed by difference Fourier analysis, of a disordered part of the structure. This turned out to be due to the flipping of the tetrahedra belonging to the isolated [Si2O7]6− diorthogroups, one of the two radicals (the other is [Si12O30]12−) characterizing the miserite structure. The sixfold and seven-vertex Ca polyhedra linked to the inverted diorthogroups show variation in coordination number with respect to those of the ordered structure.

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 3 T mica polytype from Kasenyi (southwest Uganda), kamafugite, was studied by electron probe microanalysis (EPMA), single-crystal X-ray diffraction (SCXRD), micro-Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) to characterize its crystal chemistry and the relationships with phlogopites from the same rock but showing different stacking sequence and to get insights into factors affecting polytypism in Ugandan phlogopites. EPMA data gave: SiO 2 = 38.7(2), Al 2 O 3 = 13.08(9), MgO = 20.4(2), TiO 2 = 4.8(1), MnO = 0.03(3), FeO tot = 5.51(9), Cr 2 O 3 = 0.90(7), NiO = 0.11(5), SrO = 0.03(3), ZnO = 0.04(3), ZrO 2 = 0.01(2), K 2 O = 9.64(5), Na 2 O = 0.29(1), BaO = 0.15(5), F = 0.13(5), and Cl = 0.01(1) wt%. The analyzed sample may be classified as a Ti-rich phlogopite. X-ray photoelectron spectroscopy provided Fe 3+ /Fe 2+ and O 2− /OH equal to ~0.75 and 7.14, respectively, which are in agreement with the results of previous Mossbauer investigation on the BU1 phlogopites from the same rock and with the structural formula of the studied crystal. Infrared spectra showed a shoulder at ~3660 cm −1 in the OH − stretching region (~3740–3600 cm −1 ), which is assigned to MgMgFe 3+ -OH − -K-O 2− local configurations. No evidences of vacancy substitutions were observed. Structure refinement based on single-crystal X-ray diffraction data was performed in space group P 3 1 12 using anisotropic displacement parameters and converged to R 1 = 4.34 and wR 2 = 3.33%. Unit-cell parameters are: a = b = 5.3235(3) and c = 30.188(2) A. 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 high-charge cations preferentially located as expected on M2 and M3. Tetrahedral bond length distortion and angular variance parameters describe more distorted polyhedra in 3 T polytype than those found in coexisting 1 M and 2 M 1 polytypes. Finally, the overall crystal-chemical features indicate the occurrence of the following substitution mechanisms in the studied sample: Ti-oxy [ VI M 2+ +2(OH) − ↔ VI Ti 4+ +2(O 2− )+H 2 ↑] and Al, Fe 3+ , Cr-oxy [ VI M 2+ +(OH) − ↔ VI M 3+ +O 2− +½(H 2 )↑]; Al, Fe 3+ -Tschermak [ VI M 2+ + IV Si 4+ ↔ VI (Al 3+ , Fe 3+ )+ IV Al 3+ ]; XII K + + IV Al 3+ ↔ IV Si 4+ + XII □ tetraferriphlogopite [ IV Fe 3+ ↔ IV Al].

The 2 M 1 -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 (K 0.95 Na 0.01 )(Al 0.15 Mg 1.27 Fe 2+ 1.16 Fe 3+ 0.04 Ti 4+ 0.38 )(Si 2.85 Al 1.15 )O 10.76 F 0.11 Cl 0.03 OH 1.10 . The structural analysis has shown that the crystal has the cell parameters a = 5.352(1), b = 9.268(1), c = 20.168(1) A, and β = 95.10(1)° and exhibits symmetry lowering from the ideal space group C 2/ c to C 1. 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.

The crystal structures of tobelite and NH 4 + -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, and X-ray photoelectron and micro-Fourier transform infrared spectroscopy. The crystals belong to the 2 M 2 polytype with the following unit-cell parameters: a = 9.024(1), b = 5.2055(6), c = 20.825(3) A, and β = 99.995(8)° for tobelite and a = 9.027(1), b = 5.1999(5), c = 20.616(3) A, and β = 100.113(8)° for NH 4 + -rich muscovite. Structure refinements in the space group C 2/ c converged at R 1 = 8.01%, wR 2 = 8.84% and R 1 = 5.59%, wR 2 = 5.63% for tobelite and NH 4 + -rich muscovite, respectively. X-ray photoelectron spectroscopy revealed nitrogen environments associated either with inorganic (B.E. 401.31 eV) or 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 that were assigned to Al 3+ Al 3+ □-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 NH 4 + -stretching vibrations, a main band at ~1430 and a shoulder at ~1460 cm −1 that were associated to the NH 4 + -bending vibration (ν 4 ) were also present. The ammonium concentration was semi-quantitatively estimated in both crystals from the absorbance of the OH − -stretching and NH 4 + -bending vibrations in the infrared spectra. An additional estimate was obtained for the NH 4 + -rich muscovite by considering the normalized peak area between K2 p 3 / 2 and N1 s in the X-ray photoelectron spectrum. The obtained values are 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 (K 0.18 Na 0.01 NH 4 + 0.62 ) ∑=0.81 (Al 1.98 Fe 2+ 0.02 ) ∑=2.00 (Si 3.19 Al 0.81 ) ∑=4.00 O 10.00 OH 2.00 for tobelite and to (K 0.46 Na 0.03 Ba 0.01 NH 4 + 0.36 ) ∑=0.86 (Al 1.98 Mg 0.01 Fe 2+ 0.01 V 3+ 0.01 ) ∑=2.01 (Si 3.13 Al 0.87 ) ∑=4.00 O 10.00 F 0.08 OH 1.92 for NH 4 + -rich muscovite.

In the present work, crystal chemical variations between 1M and 2M 1 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 Mossbauer 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%) contents. Room temperature 57Fe Mossbauer 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 2M 1 studied phlogopites. However, in 2M 1 polytypes the oxy-type substitutions were found to occur to a greater extent. Comparison of unit layer of 1M mica (in the 2M 1 setting) with that of the 2M 1 ones showed that the 2M 1 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 study, it has been highlighted that SIMS data in association with high - quality structural data and information derived from other complementary techniques allows the crystal chemical properties of " diffi cult " mineral phases to be successfully established. Moreover, a SIMS study of inhomogeneous samples at the micrometer scale can provide insightful relationships between their crystal chemistry and the volcanological processes to which they have partaken

The crystal chemistry of 2M1 micas from Bunyaruguru kamafugite (southwest Uganda) was studied by electron probe microanalysis, single-crystal X-ray diffraction, Mossbauer 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) A, 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%. Mossbauer spectroscopy showed that the studied sample has: VI

The crystal chemistry of Ti-rich phlogopite from deposits of the oldest activity (∼740 ka) of Mt. Vulture, Potenza, Italy, was investigated to identify the substitution mechanisms in Ti-rich phlogopite and to determine its potential as a geohygrometer. Substitution mechanisms were determined by electron probe microanalysis (EPMA), single-crystal X-ray diffraction (SCXRD), Mossbauer spectroscopy, and micro-Fourier transform infrared (FTIR) spectroscopy. Magnetite and sanidine from the mica-rich host rocks were also analyzed. Use of the biotite-magnetite-sanidine geohygrometer in these volcanics (essentially trachytic-phonolitic ignimbrites) is exploited.

The iron sulfate Na 3 Fe(SO 4 ) 3 studied here has been obtained as a high-temperature (HT) product (~400 °C) from the thermal decomposition of sideronatrite from Sierra Gorda (Chile) having composition Na 2 Fe(SO 4 ) 2 (OH)·3H 2 O. The structure determination was carried out using synchrotron X‐ray powder diffraction. Structural data refined by the Rietveld method, up to R p = 11.95%, are: space group R 3, lattice parameters a = b = 13.6231(1) A and c = 9.0698(1) A, V = 1457.76(2) A 3 , and Z = 6. The structure of Na 3 Fe(SO 4 ) 3 can be described in terms of FeO 6 octahedra connected to sulfate tetrahedra by corner-sharing to form infinite chains [Fe(SO 4 ) 3 ] ∞ , running along c . These chains are joined together by Na atoms to build up a three-dimensional network of strong (Fe-O-S) and weak (Na-O) bonds. The topological relationships of Na 3 Fe(SO 4 ) 3 to the structure of some analog minerals are also discussed.

ab S tract The kinetics of the Fe-oxidation/deprotonation process in a natural Fe-rich phlogopite from Mt. Vulture (Potenza, Italy) was studied under isothermal conditions by in situ high-temperature singlecrystal X-ray diffraction. Isothermal annealing experiments were performed at five temperatures in the range 640–750 °C on five crystals with similar chemical composition and lattice parameters. The Fe-oxidation/deprotonation process at high temperature occurs with a reduction of unit-cell parameters and cell volume. The changes in unit-cell parameters measured at high temperature and during cooling show that the same degree of Fe-oxidation/deprotonation process was achieved at all temperatures. Changes in unit-cell parameters with temperature and time show that the kinetics of Fe-oxidation/ deprotonation in phlogopite follows an exponential law, and the temperature dependence follows the Arrhenius relation. A kinetic analysis was performed and good agreement was obtained with the onedimensional diffusion model. An apparent activation energy of 195(4) kJ/mol was determined.

Very high temperature, Ca-rich alkaline magma intruded an argillite formation at Colle Fabbri, Central Italy, producing cordierite-tridymite metamorphism in the country rocks. An intense Ba-rich sulphate-carbonate-alkaline hydrothermal plume produced a zone of mineralization several meters thick around the igneous body. Reaction of hydrothermal fluids with country rocks formed calcium-silicate-hydrate (CSH), i.e., tobermorite-afwillite-jennite; calcium-aluminum-silicate-hydrate (CASH) — “cement” phases - i.e., thaumasite, strätlingite and an ettringite-like phase and several different species of zeolites: chabazite-Ca, willhendersonite, gismon-dine, three phases bearing Ca with the same or perhaps lower symmetry of phillipsite-Ca, levyne-Ca and the Ca-rich analogue of merlinoite. In addition, apophyllite-(KF) and/or apophyllite-(KOH), Ca−Ba-carbonates, portlandite and sulphates were present. A new polymorph from the pyrrhotite group, containing three layers of sphalerite-type structure in the unit cell, is reported for the first time. Such a complex association is unique. Most of these minerals are specifically related to hydration processes of: (1) pyrometamorphic metacarbonate/metapelitic rocks (natural analogues of cement clinkers); (2) mineralization between intrusive stocks and slates; and (3) high-calcium, alkaline igneous rocks such as melilitites and foidites as well as carbonatites. The Colle Fabbri outcrop offers an opportunity to study in situ complex crystalline overgrowth and specific crystal chemistry in mineral phases formed in igneous to hydrothermal conditions.

Metasideronatrite was obtained as the first dehydration product of sideronatrite, Na 2 Fe(SO 4 ) 2 (OH)·3H 2 O, from Sierra Gorda, Chile. The crystal structure of metasideronatrite was solved by direct methods and refined by full-matrix least-squares to R = 0.039, using 574 independent reflections with I > 3.0σ(I). It is orthorhombic, space group Pbnm, with a = 7.3959(8), b = 16.0979(15), c = 7.1607(8) A, V= 852.5(2) A 3 , Z= 4. The crystal-chemical formula derived from this structural study is Na 2 Fe(SO 4 ) 2 (OH)·H 2 O. The backbone of the structure is the same as that in sideronatrite: infinite [Fe 3+ (SO 4 ) 2 (OH)] 2- chains of interconnected octahedra and tetrahedra parallel to the c axis. These chains are linked primarily by Na atoms to build a 3-dimensional network of strong (Fe-O-S) and weak (Na-O) bonds. Another prominent feature of the structure is the arrangement of distorted (NaO 5 H 2 O) octahedra, which alternately share one edge and one face to form columns parallel to the [Fe 3+ (SO 4 ) 2 (OH)] chains. Subsidiary intra-chain bonds are provided by H atoms belonging to OH - groups shared by adjacent Fe octahedra, and to the unique water molecule shared between two adjacent (NaO 5 H 2 O) octahedra. At normal conditions of relative humidity (RH) and temperature (i.e., RH > 60% and T < 40 °C), metasideronatrite rehydrates rapidly to sideronatrite. The structure solution has allowed us to: (1) investigate the strong relation between sideronatrite and metasideronitrite; (2) elucidate the mechanism involved in the transformation of metasideronatrite into the order/disorder (OD) structure of sideronatrite; and (3) get insight into the stability of this mineral from the valence-matching principle applied to the main structural unit [Fe 3+ (SO 4 ) 2 (OH)] 2 and Na + interstitial species. The weak hydrogen bonds and the particular arrangement of the face-sharing adjacent [NaO 5 (H 2 O)] octahedra are the main factors affecting the stability of metasideronatrite.

The structural evolution of a trioctahedral mica from Cava St. Antonio, Mt. Vulture, Potenza, Italy, has been studied in the temperature range 100–1023 K using in situ single-crystal X-ray diffraction techniques. The sample used shows a Ti-rich composition close to the phlogopite-annite join with the following crystal-chemical formula: (K0.85Na0.11Ba0.03)(Al0.17Mg1.98Mn0.01Fe0.292+Fe0.373+Ti0.18)(Si2.75Al1.25) O10.66(F0.13OH1.20Cl0.01). In the present study, the chemical and structural changes and the deprotonation process involved during heating have been characterized. Analysis of the data showed that a , b , and c cell parameters expand almost linearly up to 823 K, while the β angle remains constant. A sharp decrease in the unit-cell dimensions was observed at 873 and 1023 K. Linear trends obtained during reversal experiments from 1023 K to room temperature demonstrated the irreversibility of these events. Structure refinements of single-crystal XRD data collected at 100, 200, 298, 473, 673, 873, and 1023 K converged to 2.14 ≤ R (%)≤ 8.47, 2.47 ≤ R w (%) ≤ 10.83. In the temperature range 100 673 K, the thermal expansion along the c direction is mainly due to interlayer thickness dilation. The tetrahedral ring approaches the ideal hexagonal shape with increasing temperature to match the expanding octahedral sheet. In the range 873–1023 K, a strong shrinking of the interlayer is associated with the shortening of the M1-O4 and M2-O4 distances and to the consequent reduction of octahedral thickness. Such structural features indicate the occurrence of Fe oxidation process, involving loss of structural H, which is responsible for a phase transition. Mossbauer spectroscopy supported this hypothesis.

A suite of Ti-bearing garnets from magmatic, carbonatitic, and metamorphic rocks was studied by electron probe microanalysis (EPMA), X-ray powder diffraction (XRPD), single-crystal X-ray diffraction (SCXRD), Mossbauer spectroscopy, and secondary ion mass spectrometry (SIMS) to better characterize their crystal chemistry. The studied garnets show TiO 2 varying in the range of 4.9(1) to 17.1(2) wt% and variable Fe 3+ /∑Fe content. SIMS analyses allowed quantification of light elements yielding H 2 O in the range 0.091(7)–0.46(4), F in the range 0.004(1)–0.040(4), and Li 2 O in the range 0.0038(2)–0.014(2) wt%. Mossbauer analysis provided spectra with different complexity, which could be fitted to several components variable from one ( Y Fe 3+ ) to four ( Y Fe 2+ , Z Fe 2+ , Y Fe 3+ , Z Fe 3+ ). A good correlation was found between the Fe 3+ /∑Fe resulting from the Mossbauer analysis and that derived from the Flank method. 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. Single-crystal X-ray refinement using anisotropic displacement parameters were performed in the Ia 3 d space group and converged to 1.65 ≤ R 1 ≤ 2.09% and 2.35 ≤ wR 2 ≤ 3.02%. Unit-cell parameters vary in the range 12.0641(1) ≤ a ≤ 12.1447(1) A, reflecting different Ti contents and extent of substitutions at tetrahedral site. The main substitution mechanisms affecting the studied garnets are: Y R 4+ + Z R 3+ ↔ Z Si + Y R 3+ (schorlomite substitution); Y R 2+ + Z R 4+ ↔ 2 Y R 3+ (morimotoite substitution); Y R 3+ ↔ Y Fe 3+ (andradite substitution); in the above substitutions Y R 2+ = Fe 2+ , Mg 2+ , Mn 2+ ; Z R 4+ = Ti; Y R 3+ = Fe 3+ , Al 3+ , Cr 3+ ; Z R 3+ = Fe 3+ , Al 3+ . Minor substitutions, such as 2 Y Ti 4+ + Z Fe 2+ ↔ 2 Y Fe 3+ + Z Si, (SiO 4 ) 4− ↔ (O 4 H 4 ) 4− , F − ↔ OH − , and Y R 4+ + X R + ↔ Y R 3+ + X Ca 2+ , with Y R 4+ = Ti, Zr; Y R 3+ = Fe 3+ , Al, Cr 3+ ; X R + = Na, Li also occur.

Fluorophlogopite, a new F-dominant mineral of the mica group, was found at Monte Calvario, Biancavilla, lower southwestern flanks of Mt. Etna volcano (Catania, Sicily, Italy). The mineral occurs in autoclasts of gray-red altered benmoreitic lavas, primarily associated with fluoro-edenite, alkali-feldspars, clino- and ortho-pyroxenes, fluorapatite, hematite, and pseudobrookite. It was formed by metasomatism of the original lava rocks from very hot fluid enriched in F, Cl, and other incompatible elements. Fluorophlogopite occurs as very thin laminae with a diameter of 200 to 400 pm. Main physical properties are pale yellow in color; yellowish-white in thin section; vitreous to resinous luster; transparent; non-fluorescent; Mohs' hardness 2-3; brittle and malleable; perfect cleavage on {001}; biaxial (-), alpha(calc) = 1.5430(8), beta = 1.5682(5), gamma = 1.5688(5) (lambda = 589 nm); 2V(meas) 17(2)degrees; (alpha = acute bisectrix perpendicular to (001); nonpleochroic; D-calc = 2.830 g/cm(3) (using empirical formula and single-crystal unit-cell parameters), D-calc - 2.842 g/cm(3) (using empirical formula and powder cell constants). Infrared spectrum did not show a significant absorption band in the OH-stretching region (3800-3600 cm(-1)) confirming that the F content of the fluorophlogopite from Biancavilla is close to the stoichiometric value. Unit-cell parameters from X-ray powder-diffraction data (114.6 rum diameter Gandolfi camera, CuK alpha) are a = 5.305(2), b = 9.189(3), c - 10.137(4) angstrom, beta = 100.02(3)degrees. These data agree with those obtained by single-crystal X-ray studies on a very thin (similar to 15 pm) fluorophlogopite crystal, i.e., Monoclinic (1M polytype); Space Group C2/m; a = 5.3094(4), b = 9.1933(7), c = 10. 1437(8) angstrom, beta = 100.062(5)degrees, V= 487.51(6) angstrom(3), Z= 2. Structure refinements using anisotropic displacement parameters converged at R = 3.50, R-w = 4.37, R-sym = 3.72%. Electron microprobe analysis performed on the same crystal used for X-ray investigation gave: SiO2 = 45.75(39), TiO2 - 1.05(5), Al2O3 = 9.60(19), MgO = 27.92(30), MnO = 0.16(3), FeOtot = 1.25(6), BaO = 0.09(5), K2O - 8.22(11), Na2O = 0.61(30), Cl = 0.02(1) wt%. Secondary Ion Mass Spectrometry (SIMS) was used to estimate light elements [Li2O = 0.30(1) and H2O = 0. 16(2) wt%] and fluorine content [F - 8.69(24) wt%]. The new mineral fluorophlogopite and its name were approved by IMA-CNMMN (2006/011).

Volcanic activity at Mt Vulture lasted throughout the Middle Pleistocene and produced SiO2- undersaturated volcanics. Deposits from the Monte Vulture stratovolcano have been classified into four subsynthems and clustered into the Barile Synthem. In the present investigation, trioctahedral micas from the uppermost units (the Ventaruolo Subsynthem) of the Barile Synthem are considered. The samples are labelled VUT187. The phlogopitic micas were separated from the host rock (an olivinefoidite) and underwent chemical (electron microprobe analysis - EMPA and C-H-N), structural (singlecrystal X-ray diffraction) and spectroscopic (Mössbauer) investigations.The EMPA yielded: MgO (17.62–21.89 wt.%), FeOtot (5.98–9.78 wt.%), TiO2 (1.81–3.92 wt.%) and Al2O3 (14.47–17.98 wt.%), with H2O contents = 2.86 (±0.42) wt.% determined by C-H-N analyses. Mössbauer investigation provided [VI]Fe2+ = 12.6%, [VI]Fe3+ = 87.4%. The chemical and structural data are consistent with the occurrence of Ti-oxy, [VI]M2+ + 2(OH)– ⇋ [VI]Ti4+ + 2O2– + H2, and M3+-oxy substitutions, [VI]M2+ + (OH)– ⇋ [VI]M3+ + O2– + 1/2H2, with M3+ = Fe3+, Al3+. In particular, Fe3+-oxy substitution has affected the Fe2+/Fe3+ ratioin the studied sample. This is probably due to the fact that interaction with underground water or a hydrothermal system may have altered the oxygen fugacity and raised the Fe3+ content of VUT187 phlogopite with respect to magmatic values.

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.

The iron sulfate FeOHSO 4 studied was obtained as a dehydration product of metahohmannite Fe 2 (H 2 O) 4 [O(SO 4 ) 2 ] during a synchrotron real-time powder diffraction experiment. As quoted in the literature, FeOHSO 4 has iron atoms octahedrally coordinated with two hydroxyl groups and four sulfate O atoms, while each hydroxyl group is bonded to two iron atoms. This compound is commonly described in the orthorhombic system with space group Pnma , lattice parameters a J = 7.33, b J = 6.42, and c J = 7.14 A ( a J , b J , and c J are the Johansson lattice parameters), and Z = 4. However a preliminary Rietveld refinement of the pattern at about 220 °C using the structural model from the literature yielded a poor fit of the observed data and a final R p value of about 23%. A careful analysis of the calculated powder diffraction pattern showed unexpected peaks, not observed in the experimental trace, for h = 2 n + 1, while sharp reflections for h = 2 n seemed to point to different lattice constants and space group. The recognition of the order-disorder character of the FeOHSO 4 compound was the key to successfully interpreting the unexpected features of the experimental powder pattern and the misfit with respect to the calculated pattern. In fact, FeOHSO 4 belongs to a family of OD structures formed by equivalent layers of symmetry Pbmm . Only two MDO (Maximum Degree of Order) polytypes are possible. MDO1 results from a regular alternation of stacking operators 2 1/2 and 2 −1/2 , and yields an orthorhombic structure with space group Pnma and lattice parameters a J = 7.33, b J = 6.42, and c J = 7.14 A. MDO2 results from the 2 1/2 |2 1/2 |2 1/2 ... sequence of symmetry operators and yields a monoclinic structure with space group P 2 1 / c , a M = 7.33, b M = 7.14, c M = 7.39 A, and β = 119.7°. The analysis of one-dimensional stacking disorder was performed by fitting the observed XRPD pattern with a calculated intensity curve generated by DIFFaX. The disorder model was investigated by taking into account a probability matrix for the occurrence of OD layer sequences. The best fit ( R p = 0.009) to the observed powder pattern was obtained with a 61:39 ratio of monoclinic and orthorhombic polytypes for a fully disordered OD layers sequence.

The crystal chemistry of Ti-rich trioctahedral micas of plutonic origin, cropping out at Black Hill (South Australia) has been investigated by combining electron microprobe analysis, single crystal X-ray diffraction, Mossbauer spectroscopy and X-ray photoelectron spectroscopy. Chemical analyses have shown the samples taken to be quite homogeneous and Ti-rich (TiO2 ≈ 7 wt.%). Mossbauer investigation yielded Fe2+/Fe3+ ≈ 30. X-ray photoelectron spectroscopy analysis seems to suggest the occurrence of three Ti species: octahedral Tr4+(60%), octahedral Ti3+(26%), and tetrahedral Ti4+(14%). The analyzed sample belongs to the 1M polytype and the relevant crystal data from structure analysis are: a = 5.347(1) A, b = 9.261(2) A, c = 10.195(2) A, β = 100.29°(1). Anisotropic structure refinement was performed in space group C2/m, and converged at R = 2.62, Rw = 2.80. Structural details (the c cell parameter, the off-center shift of the M2 cation towards 04, the bond-length distortions of the cis-M2 octahedron, the interlayer sheet thickness, the projection of K−O4 distance along c*, the difference outer- inner) support the occurrence of the Ti-oxy substitution (VIR2+ + 2(OH)− ⇌ Ti4+ + 202− + H2) in the sample. Analysis of structural distortions as a function of the Ti content revealed that the positions of the oxygens 03 and 04 are displaced in opposite senses along [100]. This produces an enlargement of the M1 site with respect to the M2 site and a shortening of the interlayer distance. This trend seems to be in common with other Ti-rich 1M micas of plutonic origin.

The title complex, [Ir2(C18H13FNO2S)4Cl2]·C7H8, was crystallized from dichloromethane solution under a toluene atmosphere. It is a dimeric complex in which each of the two IrIIIcentres is octahedrally coordinated by two bridging chloride ligands and by two chelating cyclometalated 2-(4-benzylsulfonyl-2-fluorophenyl)pyridine ligands. The crystal structure analysis unequivocally establishes thetransdisposition of the two cyclometalated ligands bound to each IrIIIcentre, contrary to our previous hypothesis of acisdisposition. The latter was based on the1H NMR spectra of a series of dimeric benzylsulfonyl-functionalized dichloride-bridged iridium complexes, including the compound described in the present work [Ragniet al.(2009).Chem. Eur. J.15, 136–148]. The toluene solvent molecules, embedded in cavities in the crystal structure, are highly disordered and could not be modelled successfully; their contribution was removed from the refinement using the SQUEEZE routine in the programPLATON[Spek (2009).Acta Cryst.D65, 148–155].

A stereoselective synthesis of tetrasubstituted 2,3-dihydrofurans was carried out in n-butylpyridinium tetrafluoroborate ([bpy(+)][BF(4)(-)]) as solvent. The reaction proceeds smoothly in one step starting from simple materials such as aldehydes and beta-ketosulfides of benzothiazole. A comparison between several ionic liquids (ILs) is presented, and the role of the benzothiazolyl moiety is discussed. Workup proved to be very easy and recycling of IL possible.

A crystal chemical study was undertaken on a melanite crystal from the pyroclastic deposits of Colli Albani (Lazio, Italy), a Middle-Late Pleistocene volcanic complex belonging to the Roman Perpotassic Province. Previous investigations by electron-probe microanalysis and X-ray topographic methods have shown that melanite from Colli Albani is affected by both sector and concentric zoning. In the present study, we focus on the crystal chemistry of the sector zoning using a combination of Mossbauer spectroscopy, electron probe microanalysis and single crystal X-ray diffraction methods. Electron probe microanalyses show the occurrence of minor chemical differences, especially in the Al and Ti content between non-equivalent {121} trapezohedron and {110} rhombic-dodecahedron growth sectors. Structural analyses are carried out on three crystals fragments taken from the (110), (011) and (121) sectors of the same macrocrystal. We find that the slight chemical difference between the growth sectors produce detectable effects on bond distances: the Y-O distance is significantly shorter and the Z-O distance greater in {121} than in the {110} sector. Two doublets are fitted to both RT and LNT Mossbauer spectra and assigned to octahedral Fe 3+ (∼ 93%) and to dodecahedral Fe 2+ (∼ 7%). As far as the crystal chemical behaviour is concerned, two kinds of heterovalent substitutions seem to affect the melanite structure, i.e. M 2+ (Y) + M 4+ (Y) ⟷ 2M 3+ (Y), morimotoite substitution, with M 2+ = Mg, Mn; M 3+ = Al, Fe; M 4+ = Ti, Zr, and Ti 4+ (Y) + Fe 3+ (Z) ⟷ Si 4+ (Z) + Al 3+ (Y), schorlomite substitution. The former occurs in both growth sectors, {121} and {110}, the latter only in the {121} sector. These results seem consistent with the more rapid growth of {121} sector according to a “layer by layer” mechanism, as revealed by the X-ray topographic investigation.

The crystal chemistry of trioctahedral micas-1 M from Mt. Vulture phonolitic-trachitic ignimbrites has been investigated by single crystal X-ray diffraction, microprobe analysis and plasma emission spectroscopy. Chemical analyses have shown that Mt. Vulture trioctahedral micas belong to the phlogopite-annite join, with minor component of kinoshitalite-ferrokinoshitalite solid solution. In addition, samples with remarkably different Mg/Fe ratio can coexist in the same volcano-stratigraphic level, Fe-rich samples having also higher Ti content. The crystal structure of all of the analysed samples is affected, to varying degrees, by structural disorder, due to ± b /3 slips of octahedral sheet along the [0 1 0], [3 1 0] and [3 −1 0] directions. The latter has been reported in the literature for a handful of cases. In the present work, for the first time, the disorder has been successfully interpreted and managed in the structure refinement. It is demonstrated that it leads to desymmetrization of the TOT layer and therefore of the whole structure, with reduction of symmetry from C 2/ m to C 2. For the sample mostly affected by disorder (17 %) the R -factor drops from 9.97% ( C 2/ m ) to 2.74 % ( C 2). The chemical and geometrical features show that Mt. Vulture micas are homo-octahedral, even if some structural details suggest a preferential partitioning of Ti at M2 sites. However the mechanism of Ti incorporation in the structure seems to be different in Mg-rich and Fe-rich samples. For the former the Ti-vacancy substitution mechanism seems to hold: \(2^{VI}Mg^{2}{+}\ {\longleftrightarrow}\ ^{VI}Ti^{4{+}}\ {+}\ ^{VI}[]\) For the latter, the occurrence of Li, as detected by emission spectroscopy plasma measurements, structural evidence and charge balance considerations suggest the following novel substitution mechanism, \(^{VI}Ti^{4{+}}\ {+}\ ^{VI}Li^{{+}}\ {+}\ O^{2{-}}\ {\longleftrightarrow}\ 2\ ^{VI}M^{2{+}}\ {+}\ OH^{{-}}\) , to be active in the structure.

A single garnet crystal of kimzeyite from Anguillara Sabazia, Sabatini Volcanic District (Rome), has been studied by electron probe microanalysis (EPMA), single crystal X-ray diffraction (XRD) and Raman spectroscopy (RS). X-ray intensities for the structure refinement were collected by means of both a conventional four circle diffractometer (CD) and an area detector (AD) diffractometer. Salient crystallographic data from AD measurements are: a = 12.397(4) A, V = 1905.24 A 3 , μ= 25 cm −1 , crystal dimension ∼ 40 μm, D x =3.83 g cm −3 . The chemical analyses allowed to ascertain that Ca, Ba, Fe, Al, Mg, REE, Zr, Si and Ti are present in the structure. The transition element distribution is: Fe 3+ (Y) ≪ Fe 3+ (Z), and Ti as Ti 4+ occurs only at Y. No hydrogen atoms were detected. The problem of the correct distribution of Ba and REE (essentially Eu and Gd) is dealt with, but not fully solved in the present study. Because of the very small amount of sample available and of the strong dilution of Ba and REE (∼0.03 and 0.02 atoms per formula unit respectively) the correct distribution of these atoms over the X and Y sites is problematical. The radius ratio rule and electrostatic requirements suggest Ba at X and REE at Y. From these principles, the following site distribution can be deduced: Ca 2+ and Ba 2+ at X; Mg 2 +, REE 3+ , Zr 4+ , Ti 4+ , Fe 3+ at Y; Si 4+ , Al 3+ , Fe 3+ at Z. On the other hand, structural details and the best fit between EPMA and XRD site populations indicate REE at X and Ba at Y. Bond strength theory arguments support this hypothesis. The main substitution mechanisms can be summed up as follows: 1) Ti 4+ (Y) + Fe 3+ (Z) ↔ Si 4+ (Z) + M 3+ (Y) [schorlomite substitution]; 2) Zr 4+ (Y) + M 3+ (Z) ↔ Si 4+ (Z) + M 3+ (Y) [kimzeyite substitution]; 3) Mg 2+ (Y) + Zr 4+ (Y) ↔ 2M 3+ (Y) [morimotoite-like substitution], where M 3+ = (Al, Fe). In addition, following the bond strength theory indications, another mechanism which possibly involves the X and Y sites is also taken into account: 4) REE 3+ (X) + Ba 2+ (Y) ↔ Ca 2+ (X) + M 3+ (Y).

A detailed protocol for the resolution of the Betti base [i.e. 1-(alpha-aminobenzyl)-2-naphthol] was investigated and the absolute configuration of the two isomers was established by means of an X-ray diffractometric study. A series of optically active derivatives was also prepared. The list includes the N-benzyl- and the N,N,O-trimethyl derivatives. The N,N-dimethyl derivative was prepared in racemic form by means of the Betti reaction and was resolved into the two enantiomers with an extremely easy and efficient procedure. The O-methyl derivative was prepared in a racemic form and subjected to resolution. The configuration of each base was determined by correlation with the configuration of the Betti amine. (C) 1998 Elsevier Science Ltd. All rights reserved.

Muscovite, KAl2(AlSi3O10)(OH)2, is a common rock-forming mineral in igneous and metamorphic-rocks, sediments, hydrothermal alteration and ore deposits. The site between two adjacent T-O-T (tetrahedral-octahedral-tetrahedral) layers is shared between K and NH4 in all proportions leading to the building of the "ammonium micas". In this work three tobelite crystals were investigated in terms of major and minor constituents by electron probe microanalysis (EPMA) and in terms of nitrogen, for the first time at authors' knowledge, by secondary ion mass spectrometry (SIMS). The objective was that to gain information on the presence and amount of NH4 in this matrix. The lack of standards did not allow us to provide quantitative results at the ion microprobe. Nevertheless, the SIMS data agree qualitatively with constraints resulting from EPMA analyses and charge-balance crystal chemical considerations. The results of this study emphasize the capabilities of SIMS in the in-situ analysis of N and point out the possibility to develop reference materials (standards) for quantitative SIMS analysis of nitrogen in mica.

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"

Fluorine is an important proxy for magmatic differentiation processes in the shallow parts of volcanic plumbing systems. Fluorphlogopite is one of the more important fluorine carriers in magmatic rocks. In the present study, a full crystal chemical investigation of fluorophlogopite 1 M from Piano delle Concazze, Mt. Etna volcano, Italy, is carried out. The fluorophlogopite occurs in a benmoreitic lava from prehistoric volcanic activity at Mt. Etna (post-caldera forming phase of the “Ellittico” eruptive center; ~15 ka BP). It is primarily associated with fluorapatite covered with amorphous SiO 2 and crystallized during syn/post-eruption pneumatolytic stages. The mica sample studied here is among the most Fe- and Ti-rich fluorophlogopite found in nature. EPMA data yielded the following mean chemical formula for this mineral ( K 0.83 Na 0.13 ) ( Fe 0.44 2 + Fe 0.09 3 + Mg 2.18 Al 0.05 Ti 0.23 Mn 0.01 ) ( Al 0.92 Si 3.08 ) O 10.64 ( Cl 0.01 F 1.35 ) . Structure refinements on four fluorophlogopite crystals, performed in space group C 2/ m , converged at R = 0.03–0.04, with cell parameters in the ranges a = 5.323–5.324, b = 9.219–9.222, c = 10.116–10.119 A, β = 100.1–100.3°. Major substitutions are OH − ↔ F − ,M 3+ -oxy ( VI M 2+ +OH − ↔ VI M 3+ +O 2− ) and Ti-oxy substitution: VI M 2+ +2(OH) − ↔ VI Ti 4+ +2O 2− . The fluorophlogopite from Piano delle Concazze exhibits the shortest c -parameter with respect to other fluorophlogopites found in nature. The short c parameter is essentially due to the absence of the hydroxyl group in favor of F − and especially of O 2− and to the thus increased attractive interaction between the interlayer cation and the anion content (F − , O 2− ) located at the O4 site. A comparison with other natural fluorophlogopites (namely from Biancavilla, Etna and Presidente Olegario, Brazil) show intermediate crystal-chemical features for the Piano delle Concazze fluorophlogopite. Particularly at Etna, differences in the chemical composition of the crystallized fluorophlogopites could be related to the various extent of enrichments by transfer of a gas phase achieved in specific parts of the volcanic plumbing system.

This study reports the first crystal chemical database resulting from a detailed structural investigation of trioctahedral micas found in xenolithic ejecta produced during the AD 1631, 1872 and 1944 eruptions, three explosive episodes of recent volcanic period of Vesuvius volcano (Southern Italy). Three xenolith types were selected: metamorphic/metasomatic skarns, pyrometamorphic/hydrothermally altered nodules and mafic cumulates. They are related to different magma chemistry and effusive styles: from sub-plinian and most evolved (AD 1631 eruption) to violent strombolian with medium evolution degree (AD 1872 eruption) to vulcanian-effusive, least evolved (AD 1944 eruption) event, respectively. Both xenoliths and micas were investigated employing multiple techniques: the xenoliths were characterized by X-ray fluorescence, inductively-coupled plasma-mass spectrometry, optical microscopy, X-ray powder diffraction, and quantitative energy-dispersive microanalysis; the micas were studied by electron probe microanalysis and single crystal X-ray diffraction, The mica-bearing xenoliths show variable texture and mineralogical assemblage, clearly related to their different origin. Based on the major oxide chemistry, only one xenolithic sample falls in the skarn compositional field from the Somma-Vesuvius literature, some fall close to the skarns and cumulate fields, others plot close to the syenite/foidolite/essexite field. A subgroup of the selected ejecta does not fall or approach any of the compositional fields. Trace and rare earth element patterns show some petrological affinity between studied xenoliths and erupted magmas with typical Eu, Ta and Nb negative anomalies. Strongly depleted patterns were detected for the 1631 metamorphic/metasomatic skarns xenoliths. Three distinct mica groups were distinguished: 1) Mg-, Al-rich, low Ti-bearing, low to moderate F-bearing varieties (1631 xenolith), 2) Al-moderate, F- and Mg-rich, Ti-, Fe-poor varieties (1872 xenolith), and 3) Al-, Ti- and Fe-rich, F-poor phases (1944 xenolith). All the analyzed mica crystals are 1M polytypes with the expected space group C2/m. Micas from xenoliths of the 1631 Vesuvius eruption are phlogopites characterized by a combination of low extent of oxy-type and variable extent OH- --> F- substitutions, as testified by the range of F concentration (from similar to 0.20 to 0.80 apfu). Micas from xenoliths of the 1872 Vesuvius eruption exhibit structural peculiarities typical of fluorophlogopites, i.e. OH- --> F- substitution is predominant. Micas from the xenolith of the 1944 Vesuvius eruption display features typical of oxy-substituted micas. The variability of the crystal chemical features of the studied micas is consistent with the remarkable variation of their host rocks. Micas from 1631 nodules are related to metasomatic, skarn-type environment, deriving from the metamorphosed wall-rocks hosting the magma reservoir. The fluorophlogopites from the 1872 xenoliths testify for strongly dehydrated environmental conditions compared to those of the 1631 and 1944 hosts. Finally, magma storage condition at depth, associated to a decreasing a(H2O) may have promoted major oxy-type substitutions in 1944 biotites.

The present work concerns the determination of the cation site populations and crystal chemical formulae of some Ti-rich silicate garnets. The samples come from Mt. Vulture, a volcanic complex located on the east side of the Lucania Apennines (south Italy). Mossbauer spectroscopy (MS) has been used in order to obtain the iron site occupancies. Two different models for interpreting the Fe2+ peak positions in the Mossbauer spectra are compared, and some methodological aspects are discussed. The derived iron distributions have then been combined with the data obtained by electron probe microanalysis (EPMA) and single-crystal X-ray diffraction analysis (XRD) to obtain consistent crystal chemical formulae for these compounds.

Trioctahedral micas from kamafugitic lavas of Presidente Olegario (Brazil) are Ti-Fe-bearing fluorophlogopites. They were investigated using a combination of electron probe microanalysis (EPMA), single-crystal X-ray diffraction (SCXRD), and Mossbauer spectroscopy. EPMA data yielded the following ranges: Al2O3 (8.7–10.1 wt%), MgO (19.6–20.6 wt%), FeO (5.7–6.5 wt%), TiO2 (5.9–7.5 wt%), K2O (8.9–9.7 wt%), Na2O (0.4 –0.6 wt%), and fluorine (3.4–4.1 wt%). Mossbauer investigation indicated: VIFe2+ ~ 60%, VIFe3+ ~ 10%, IVFe3+ ~ 30%. X-ray analysis indicated the 1 M polytype, with cell parameters in the range a = 5.3208–5.3376, b = 9.2210–9.2464, c = 10.1227–10.155 A, β = 100.157–100.194°. Structure refinements using anisotropic displacement parameters were performed in space group C 2/ m and converged to 2.01 ≤ R 1 ≤ 3.51, 2.00 ≤ wR 2 ≤ 3.51%. The micas have no VIAl3+ and Na is probably partitioned over both interlayer and octahedral sites. Major substitutions are OH− ↔ F−, and the Ti-oxy substitution: VIM2+ + 2(OH)− ↔ VITi4+ + 2O2− + H2↑. Accordingly, the structural features of the studied micas encompass those typical of both fluorophlogopites and micas affected by Ti-oxy substitution.

Selected phlogopite flakes from Mt. Vulture in southern Italy were studied using a combination of single-crystal techniques: electron microprobe analysis (EMPA), secondary ion mass spectrometry (SIMS), single-crystal X-ray diffraction (SCXRD), and micro-X-ray absorption near-edge spectroscopy (XANES). The latter technique was employed to analyze the structure of the Fe-K absorption edge over the region from 7080-8100 eV and to determine Fe{sup 3+}/{Sigma}Fe at a micrometer scale, albeit with large error bars due to known effects of orientation on pre-edge energy. The annite component, Fe/(Mg+Fe), of the samples studied ranged from 0.16 to 0.31, the Ti content from 0.11 to 0.27 atoms per formula unit (apfu) and the Ba content from 0.03 to 0.09 apfu. SIMS analysis showed H{sub 2}O (wt%) = 1.81-3.30, F (wt%) = 0.44-1.29, and Li{sub 2}O (wt%) = 0.001-0.027. The intra single-crystal chemical variability for major/minor elements (Mg, Fe, Al, Ba, Ti, and K) was found particularly significant for samples VUT191{_}11 and PG5{_}1, less significant for the other samples of the set. SIMS data relative to crystals VUT187{_}24, VUT191{_}10, VUT191{_}11, and VUT187{_}28 showed a noteworthy variation in the concentrations of some light elements (H, Li, and F) with coefficient of variation CV (as 1{sigma}%) up to {approx}18% formore » H{sub 2}O. The analyzed micas belong to the 1M polytype. Structure refinements using anisotropic displacement parameters were performed in space group C2/m and converged at 3.08 {

A natural Fe- and Ti-rich phlogopite-1 M of volcanic origin with an average composition (K 0.86 Na 0.08 Ba 0.04 ) (Mg 1.97 Al 0.17 Mn 0.01 Fe 0.29 2+ Fe 0.37 3+ Ti 0.19 )(Si 2.72 Al 1.28 )O 10.66 (OH 1.22 F 0.12 ) was studied using in situ low/high temperature neutron powder diffraction and the full-profile Rietveld refinement technique. Data sets were collected at 10, 298, 673 and 873 K on the D2B high resolution diffractometer at the ILL (Institute Laue-Langevin) Facility. The cell parameters expand linearly from room temperature up to 873 K [α a = 1.43(5) · 10 −5 K −1 , α b = 1.47(4) · 10 −5 K −1 , α c = 1.99(19) · 10 −5 K −1 , α V = 4.90(12) · 10 −5 K −1 ]. Site-occupancy refinements show that in the octahedral sheet Ti and Al tend to order into the M2 and M1 sites, respectively. As a consequence, Fe 2+ and Fe 3+ are preferentially ordered at the M1 and M2 sites, respectively. The H position was accurately refined at 10 K. The large components of the atomic displacement tensor of H suggest that hydrogen disorders over two symmetry mirror-related sites, around the average position ( x ,1/2, z ). Hydrogen can also act as an “atomic probe” of the Al—Si distribution over the tetrahedral sites. A comparison with the high-temperature results previously obtained using single-crystal X-ray diffraction on the same sample shows that, in the present study, dehydrogenation/oxidation processes involving hydroxyl group coordinated to Fe 2+ have occurred at a very modest rate, as confirmed by FTIR spectroscopy measurements.

The crystal chemistry of red phlogopites from Mt. Vulture (Italy) ignimbrites has been studied by electron microprobe, secondary ion mass spectrometry (SIMS), single crystal structural investigation and Fourier transform infrared (FTIR) spectroscopy. The analysed phlogopite has Fe/(Fe + Mg) ∼ 0.35, TiO2 (wt%): 2.8–5.0 and H2O (wt%): 1.24–3.37. Infrared spectra revealed the presence of bands due to the NH 4 + and H2O stretching and bending vibrations. The samples belong to the 1M polytype. The bimodal behaviour of several structural parameters allows red micas to be clustered into two distinct groups: K+ ↔ NH 4 + , H2O and M3+-vacancy substitutions dominate in the first group; M3+,4+-oxy, in the second group. It has to be pointed out that quantitative analysis of hydrogen (via SIMS) together with the characterization of the local environment of the anionic site (via FTIR) are fundamental in assessing the correct structural formula and the substitution mechanisms in micas.

Volcanic activity at Mt. Vulture lasted about 750 ka and produced SiO2-undersaturated volcanic rocks that can be classified as old (similar to 700 ka), intermediate (similar to 600-550 ka), and young (similar to 130 ka). The intermediate deposits consist of pyroclastic falls and flows and lavas with compositions ranging from phonolite to foidite. A recent revision of the stratigraphic setting allowed these deposits to be classified into one synthem (the Barile Synthem) and further subdivided into four subsynthems (Toppo S. Paolo, Rionero, Vulture-S. Michele, and Ventaruolo). In the present investigation, trioctahedral micas from sample VUT191 in the Vulture-S. Michele Subsynthem are considered. The host rock has modal diopside (20.2%), analcime (22.8%), plagioclase (27.8%), hauyne (5%), phlogopite (8.9%), and magnetite (6.3%). The micas were studied using chemical (EPMA, C-H-N, SIMS), structural (SCXRD), and spectroscopic (Moessbauer) methods. EPMA of 36 crystals from thin sections and 6 discrete crystals selected for the structural analysis showed remarkable compositional variability, as follows (in wt%): SiO2 = 33.14-38.01, Al2O3 = 15.56-20.45, MgO = 13.02-20.81, FeOtot = 6.34-14.08, TiO2 = 2.34-6.02, K2O = 6.03-9.48, Na2O = 0.50-0.78, and BaO = 0.89-4.06; all crystals proved to be phlogopite. Elemental C-H-N analyses yielded H2O = 2.86 +/- 0.36 wt%. The water content was also determined by SIMS on two single crystals, labeled VUT191_2 and VUT191_19, which yielded values of 3.81 +/- 0.12 and 1.72 +/- 0.08 wt% H2O, respectively. Moessbauer investigation showed that all the iron in VUT191 mica is octahedral with Fe2+= 25.5% and Fe3+= 74.5%, confirming that Vulture micas are particularly Fe3+-rich, as also found from previous investigations. Structure refinements using anisotropic displacement parameters were performed in space group C2/m and converged at 1.89 Ti-VI(4+) + 2O(2-) + H-2] and M3+-oxy [M-VI(2+) + (OH)(-) M-VI(3+) + O2- + 1/2H(2), with M3+ = Fe3+, Al3+] substitutions. The second group consist of samples in which vacancy-bearing mechanisms, 2 M-VI(2+) Ti-VI(4+) + (VI)square and 3(VI)M(2+) 2(VI)M(3+) + (VI)square occur.

Mt. Vulture trioctahedral micas-1M mainly consist of phlogopite-annite solid solutions with a minor component of brittle micas. However, both Li-free and Li- and F-rich compositions may coexist in the same volcano-stratigraphic level. We report the results of electron microprobe analysis (EMPA), secondary ion mass spectrometry (SIMS), and single-crystal X-ray diffraction (SCXRD) for three crystals (LC7-27Go, LC7-3Go, and LC7-1R) that are representative of both compositions. EMPA and SIMS showed that sample LC7-1R is richer in TiO2 , Li2O, and F and poorer in H2O than the other samples. Structure reÞ nements using anisotropic displacement parameters for the three samples, performed in space group C2/m, converged at 3.46 ≤ R ≤ 4.34, 3.89 ≤ Rw ≤ 4.39. When considering bond distances, the three samples can be described as homo-octahedral whereas mean atomic numbers suggest that only LC7-1R is meso-octahedral. SigniÞ cant differences occur among the samples for some distortion parameters commonly used for micas. In particular, LC7-1R displays higher values of BLDM2, shiftM2 and lower values of ΔK-O4 and tK-O4 than those of samples LC7-3Go and LC7-27Go. These differences are ascribed to F- and Ti-substitutions. Cation distributions were obtained by combining EMPA, SIMS, and SCXRD data after analysis of the effect of normalization schemes commonly used in mica formula recalculation. In LC7-3Go and LC7-27Go, Ti is incorporated according to the Ti-Tschermak mechanism, whereas more than one Ti-substitution mechanism occurs in LC7-1R. For the latter sample, octahedral vacancies are present leading to a complex substitution pattern and complex structural distortions related to the special octahedral compositions that were determined. Keywords: Analysis, chemical (mineral), EPMA and SIMS investigation, crystal structure, trioc- tahedral micas -1M, major and minor elements, Ti-F-bearing phlogopites, trace elements and REE, Li-bearing micas, XRD data, single-crystal structure reÞ nement

Different analytical and structural methods (Electron Probe Micro-Analysis, Single Crystal X-ray diffraction, X-ray Photoelectron Spectroscopy, Mössbauer spectroscopy) were combined to fully characterise the crystal chemistry of natural Ti-bearing garnets from Colli Albani (Lazio, Italy). The study of the relevant complex crystal chemistry ( large number of cation substitutions affecting the three independent X(8-fold), Y(6-fold) and Z(4-fold) crystallographic sites and Fe and Ti transition elements exhibiting several oxidation states and coordination environments) benefited from the multi-technique approach. Electron probe microanalysis provided elemental composition of the analysed samples, which have low Ti-content (TiO2 in the range 1.99 - 3.48 wt %) and slightly different Fe/Al ratios. For all samples, two doublets were fitted to room temperature Mössbauer spectra and assigned to Fe3+(Y) (approximately 95%) and Fe2+(X) (approximately 5%). Up to three doublets (Ti3+(Y), Ti4+(Y), Ti4+(Z)) were fitted to XPS spectra and yielded direct evaluation of Ti site population. XPS technique confirmed its potential for the study of speciation of Ti in minerals.