Band 96, Heft 5-6

A comparative study of the equation of states of hydrous (0.4 wt% H 2 O) and anhydrous San Carlos olivine (<30 ppm H 2 O) was conducted using synchrotron X-rays up to 11 GPa in a diamond anvil cell (DAC) at ambient temperature. Both samples were loaded in the same high-pressure chamber of the DAC to eliminate the possible pressure difference in different experiments. The obtained compression data were fitted to the third-order Birch-Murnaghan equation of state, yielding a bulk modulus K 0 = 123(3) GPa for hydrous olivine and K 0 = 130(4) GPa for anhydrous olivine as K 0 ′ is fixed at 4.6. Therefore, 0.4 wt% H 2 O in olivine results in a 5% reduction in bulk modulus. Previous studies reported bulk modulus reduction by water in olivine’s high-pressure polymorph (wadsleyite), to which the transformation from olivine gives rise to the seismic discontinuity at 410 km depth. The new data results in a reduction in the magnitude of the discontinuity by 50% in vP and 30% in vS (for 1:5 water partitioning between olivine and wadsleyite) with respect to anhydrous mantle. Previous knowledge of the influence of water on this phase transition has been in opposition to a large amount of water [e.g., 200 ppm by Wood (1995)] existing at 410 km depth. Calculation of the seismic velocities based on newly available elasticity data of the hydrous phases indicates that the presence of water is favorable for the mineral composition model (pyrolite) and seismic observations in terms of the magnitude of the 410 km discontinuity.

Cathodoluminescent (CL) textures in quartz reveal successive histories of the physical and chemical fluctuations that accompany crystal growth. Such CL textures reflect trace element concentration variations that can be mapped by electron microprobe or laser ablation-inductively coupled plasmamass spectrometry (LA-ICP-MS). Trace element maps in hydrothermal quartz from four different ore deposit types (Carlin-type Au, epithermal Ag, porphyry-Cu, and MVT Pb-Zn) reveal correlations among trace elements and between trace element concentrations and CL textures. The distributions of trace elements reflect variations in the physical and chemical conditions of quartz precipitation. These maps show that Al is the most abundant trace element in hydrothermal quartz. In crystals grown at temperatures below 300 °C, Al concentrations may vary by up to two orders of magnitude between adjacent growth zones, with no evidence for diffusion. The monovalent cations Li, Na, and K, where detectable, always correlate with Al, with Li being the most abundant of the three. In most samples, Al is more abundant than the combined total of the monovalent cations; however, in the MVT sample, molar Al/Li ratios are -0.8. Antimony is present in concentrations up to -120 ppm in epithermal quartz (-200-300 °C), but is not detectable in MVT, Carlin, or porphyry-Cu quartz. Concentrations of Sb do not correlate consistently with those of other trace elements or with CL textures. Titanium is only abundant enough to be mapped in quartz from porphyry-type ore deposits that precipitate at temperatures above -400 °C. In such quartz, Ti concentration correlates positively with CL intensity, suggesting a causative relationship. In contrast, in quartz from other deposit types, there is no consistent correlation between concentrations of any trace element and CL intensity fluctuations.

Krotite, CaAl 2 O 4 , occurs as the dominant phase in an unusual Ca-,Al-rich refractory inclusion from the NWA 1934 CV3 carbonaceous chondrite. Krotite occupies the central and mantle portions of the inclusion along with minor perovskite, gehlenite, hercynite, and Cl-bearing mayenite, and trace hexamolybdenum. A layered rim surrounds the krotite-bearing regions, consisting from inside to outside of grossite, mixed hibonite, and spinel, then gehlenite with an outermost layer composed of Al-rich diopside. Krotite was identified by XRD, SEM-EBSD, micro-Raman, and electron microprobe. The mean chemical composition determined by electron microprobe analysis of krotite is (wt%) Al 2 O 3 63.50, CaO 35.73, sum 99.23, with an empirical formula calculated on the basis of 4 O atoms of Ca 1.02 Al 1.99 O 4 . Single-crystal XRD reveals that krotite is monoclinic, P2 1 /n; a = 8.6996(3), b = 8.0994(3), c = 15.217(1) Å, β = 90.188(6), and Z = 12. It has a stuffed tridymite structure, which was refined from single-crystal data to R 1 = 0.0161 for 1014 F o > 4σF reflections. Krotite is colorless and transparent with a vitreous luster and white streak. Mohs hardness is ~6½. The mineral is brittle, with a conchoidal fracture. The calculated density is 2.94 g/cm 3 . Krotite is biaxial (-), α = 1.608(2), β = 1.629(2), γ = 1.635(2) (white light), 2V meas = 54.4(5)°, and 2V calc = 55.6°. No dispersion was observed. The optical orientation is X = b; Y ≈ a; Z ≈ c. Pleochroism is colorless to very pale gray, X > Y = Z. Krotite is a low-pressure CaAl 2 O 4 mineral, likely formed by condensation or crystallization from a melt in the solar nebula. This is the first reported occurrence of krotite in nature and it is one of the earliest minerals formed in the solar system.

The crystallographic complexity of “hexagonal” or “intermediate” pyrrhotites (Fe 1-x S with 0.125 > x > 0.080) is a long-standing and challenging problem. Integral (e.g., 5C) and non-integral NC type structures found within this group at ambient temperatures are characterized by sharp but complicated electron diffraction patterns, which were found to be interpretable in terms of a translation interface modulation (TIM) superstructure. Transmission electron microscopy (TEM) dark-field images obtained using superstructure reflections show dense arrangements of stripes, which can be interpreted as arrays of closely spaced anti-phase domain boundaries (APB). The displacement vector at the interface is R = 1/8[001] of a metrically hexagonal 4C superstructure cell and the involved translations are solely confined to the Fe sublattice. The vacancy arrangement of the APB-free monoclinic 4C-pyrrhotite serves as a base of the TIM superstructure and therefore NC structures can be regarded as two super-imposed ordering phenomena relating to the arrangements of individual vacancies and APBs, respectively. APBs are chemically non-conservative and govern the higher Fe/S ratios of intermediate NC-pyrrhotites. If oriented strictly parallel to (001) the APBs can be regarded as completely filled Fe double layers within the 4C stacking sequence. However, direct imaging of APBs shows waviness and variable disorder on mesoscopic scales, yielding essentially aperiodic structures. A high degree of self-organization among APBs has been observed within apparent diffusion profiles around exsolved troilite lamellae and along interfaces with 4C-pyrrhotite, where complicated eightfold node arrangements occur. Our TEM observations indicate that all NC-type pyrrhotites can be treated by the TIM approach and that the concepts of polytypism and polysomatism in pyrrhotite are not fully capable in representing the observed structural complexities.

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 Mössbauer spectroscopy. EPMA data yielded the following ranges: Al 2 O 3 (8.7-10.1 wt%), MgO (19.6-20.6 wt%), FeO (5.7-6.5 wt%), TiO 2 (5.9-7.5 wt%), K 2 O (8.9-9.7 wt%), Na 2 O (0.4 -0.6 wt%), and fluorine (3.4-4.1 wt%). Mössbauer investigation indicated: VI Fe 2+ - 60%, VI Fe 3+ - 10%, IV Fe 3+ - 30%. X-ray analysis indicated the 1M polytype, with cell parameters in the range a = 5.3208-5.3376, b = 9.2210-9.2464, c = 10.1227-10.155 Å, β = 100.157-100.194°. Structure refinements using anisotropic displacement parameters were performed in space group C2/m and converged to 2.01 ≤ R 1 ≤ 3.51, 2.00 ≤ wR 2 ≤ 3.51%. The micas have no VI Al 3+ and Na is probably partitioned over both interlayer and octahedral sites. Major substitutions are OH− ↔ F − , and the Ti-oxy substitution: VIM2+ + 2(OH)− ↔ VI Ti 4+ + 2O 2- + H 2 ↑. Accordingly, the structural features of the studied micas encompass those typical of both fluorophlogopites and micas affected by Ti-oxy substitution.

We have carried out equilibrium molecular dynamics simulations of CaAl 2 Si 2 O 8 (anorthite) liquid as a function of pressure (up to 160 GPa) and temperature (2500 to 6000 K) within density functional theory. Along the 3000 K isotherm, the Ca self-diffusivity varies most (decreasing by two orders of magnitude between 0 and 50 GPa), whereas the self-diffusion coefficients of Al, Si, and O vary anomalously- they initially increase with pressure, reach the broad maxima (around 5 GPa), and then decrease upon further compression. The calculated melt viscosity also shows a weak anomalous behavior with a local minimum around a similar pressure. Temperature suppresses the dynamical anomalies as well as the overall pressure variations. Therefore, the curvatures of the diffusivity (viscosity) isotherms change from a concave (convex) shape at 3000 K to a convex (concave) shape at 6000 K. We find that anorthite liquid is much more mobile than silica liquid because of its high content of non-bridging oxygen atoms (NBO) and oxygen triclusters (O3). The predicted pressure variations can be associated with structural changes consisting of the pressure-induced maximum in the abundance of pentahedral states (fivefold Al/Si-O coordination) and rapid increase in the O3 abundance. Finally, our predicted first-principles results compare favorably with the available experimental data.

In the western part of the Singhbhum Shear Zone (SSZ), East Indian Shield, borosilicate-bearing veins of variable thickness (tens of micrometers to 1 m thick) are hosted in kyanite-quartzite and kyanite-mica schist. The veins have been classified into three types, which are, from oldest to youngest, generation I (tourmaline), II (dumortierite + tourmaline), and III (tourmaline) veins. Alkali- and Mg-rich tourmaline [X Mg = Mg/(Mg + Fe) = 0.68 ± 0.09; X = Na, Ca, K, □ (vacancy) = 0.40 ± 0.12] is the sole borosilicate in generation I veins, which have been folded in response to regional deformation. Generation II veins were emplaced along shear bands (1 mm to 1 m thick) developed parallel to the axial planes of these folds. Long axes of fibrous dumortierite and prismatic tourmaline of generation II veins are oriented along the shear bands and have been bent around lenticular remnants of host kyanite-quartzite. Generation III veins have a dendritic pattern, crosscut generation II veins and show aggregates of fibrous to acicular tourmaline. Prismatic tourmaline in generation II veins is optically zoned with a green tourmaline core that is variably replaced and rimmed by blue tourmaline. Fibrous to acicular tourmaline in generation III veins is comprised up of blue tourmaline with compositions similar to the rim composition of prismatic tourmaline in generation II veins. Green and blue tourmaline is aluminous (Al total >7 apfu) and alkali-deficient (X = 0.71 ± 0.08). High Y Al content, high X, low XMg (0.19 ± 0.10), and excess cation charge indicate tourmaline in generation II veins is rich in an “oxy-foitite” component. Foitite-rich tourmaline in generation III veins has tetrahedral Al and a slightly lower Mg-content and X than those of generation II veins. Optical zoning in prismatic tourmaline corresponds to an abrupt compositional change with paragenetically older green tourmaline having higher Al and XMg, but lower alkali content in the X-site than the blue tourmaline rim. The compositional variation in green and blue tourmaline can be explained by a combination of coupled substitutions represented by AlO[R(OH)] -1 and Al(NaR) -1 , where R = (Fe 2+ + Mg). Pseudosections in the system Na 2 O-K 2 O-Al 2 O 3 -SiO 2 -H 2 O constructed from bulk chemical compositions of the studied rocks and the P-T slopes of two isochors computed from brine-rich inclusions trapped in quartz grains indicate that borosilicate formation in generation II and III veins occurred within 4.1 ± 0.5 kbar and 377 ± 21 °C. The mineral assemblages and textures suggest that the borosilicate-bearing veins formed from infiltration-driven alteration of host kyanite-quartzite and kyanite-mica schist along structurally controlled conduits by more than one batch of chemically distinct boron-rich aqueous fluids.

The montmorillonite dissolution in saline solutions that mimic synthetic lung fluids (SLF) was investigated to gain knowledge on the clearance mechanisms of inhaled clay particles. Dissolution rates were measured at pH 4 (macrophages) and 7.5 (interstitial fluids) at 37 °C in flow-through reactors. The effect of organic acids was investigated through the addition of lactate, citrate, and glycine (0.15, 1.5, and 15 mmol/L). Lactate or glycine does not markedly affect the montmorillonite dissolution rates at pH 4, but at pH 7.5 there exists a slight inhibitory effect of lactate on the dissolution, probably due to a reduction in the number of reactive surface sites caused by lactate adsorption. Citrate enhances the dissolution rate by 0.5 order of magnitude at pH 4 and more than 1 order of magnitude at pH 7.5, thus indicating the prevalence of the ligand-promoted over the proton-promoted dissolution mechanism under these experimental conditions. The kinetic data were used to estimate the reduction in size of an inhaled clay particle. At pH 7.5, a particle 500 nm in diameter could be reduced 25% in the presence of citrate, whereas the reduction in saline solution would only be 10% after 10 years. Ligand adsorption was measured in batch experiments at pH 2-11 and EQ3NR was used to model the capacity of the ligands to form soluble species of Al. Citrate, glycine, and lactate adsorb onto montmorillonite under acidic conditions, up to 23, 26, and 60 μmol/g, respectively. However, only citrate can complex the released aqueous Al at pH 4 and 7.5, which contributes to enhance dissolution rate and prevents precipitation of gibbsite at pH 7.5. The enhancement of the dissolution rate in acidic citrate solution very likely comes from the formation of surface complexes between the ligand and the edge surface of montmorillonite. In neutral conditions the effect may be also due to the decrease of the activity of Al 3+ by formation of aqueous Al-citrate complexes.

Metal removal and neutralization of acid mine drainage (AMD) in treatment systems is often controlled by addition of alkaline reagents and metal hydrolysis reactions. To overcome the disadvantage of high cost by conventional treatments, the use of paper mill wastes was evaluated as an alkaline additive to treat AMD at sites within the Iberian Pyrite Belt (IPB) through batch experiments in the laboratory. Paper wastes include three by-products from kraft pulping in a nearby mill: green liquor dregs, slacker grits, and lime mud. When paper mill wastes interacted with AMD, the initial pH increased up to circumneutral values and enhanced greatly the metal removal, reaching average ratios of up to 100% for Al, 98% for Fe, and 66% for Zn (major elements) and 100% for As, Cr, and Cu, 84% for Cd, and 75% for Ni (minor elements). After reaction, gypsum and poorly crystalline Fe-Al oxy-hydroxides and oxy-hydroxysulfates were the main precipitates identified by X-ray diffraction and scanning electron microscopy. Trace metal uptake is mainly attributed to co-precipitation and/or adsorption onto the newly formed Fe-Al precipitates. Geochemical modeling of solutions using the PHREEQC code predicted supersaturation of the observed phases. The experimental results were optimized with the PHREEQC code and combined with the annual production of each waste to quantify the extent of a possible treatment at field-scale. According to our estimations, the system proposed is able to treat effectively an annual total volume of 11.6 hm 3 , which is equivalent to a mean discharge of 368 L/s. Green liquor dregs alone would be able to treat 86% of the total volume. This result demonstrates the possibility of using alkaline paper mill wastes for treatment and restoration of worldwide natural resources extremely contaminated by AMD such as the IPB.

The mineral fettelite, [Ag 6 As 2 S 7 ][Ag 10 HgAs 2 S 8 ], has been recently structurally characterized. On the whole, the structure can be described as a regular succession of two module layers stacked along the c-axis: a first module layer (labeled A) with composition [Ag 6 As 2 S 7 ] 2- and a second module layer (labeled B) with composition [Ag 10 HgAs 2 S 8 ] 2+ . Here we report an integrated high-temperature single-crystal X-ray diffraction (HT-SCXRD), differential scanning calorimetry (DSC), and complex impedance spectroscopy (CIS) study on a sample of fettelite from Chañarcillo, Copiapó Province, Chile. DSC and conductivity measurements pointed out that fettelite shows a ionic-transition at about 380 K. HT-SCXRD experiments confirmed the phase transition toward a disordered phase having a trigonal symmetry with the a and b unit-cell parameters halved. In the HT-structure, the disorder is located in the B layer where the Ag-Hg cations are found in various sites corresponding to the most pronounced probability density function locations of diffusion-like paths. This indicates that at least two polytypes could exist for fettelite, the ordered, monoclinic RT-structure (space group C2), and a fast ion conducting, trigonal, disordered HT-form (space group P3̄m1) with a and b parameters halved. The two unit-cell types (corresponding to two different polytypes) could be also found in nature. Slightly different chemical compositions for different fettelite samples (e.g., different Ag/Hg ratios) could play a crucial role as driving forces for different unit-cell stabilizations.

The crystal structure of walstromite, ideally BaCa 2 Si 3 O 9 , was refined with data from single-crystal X-ray diffraction on a natural specimen from the type locality Esquire No. 8 claim, Big Creek, Fresno County, California, U.S.A. It is triclinic, with space group P1̄ and unit-cell parameters a = 6.7335(2), b = 9.6142(3), c = 6.6859(2) Å, α = 69.638(2)°, β = 102.281(2)°, γ = 96.855(2)°, and V = 396.01(2) Å 3 . The only previously published structure for walstromite was based on photographic film intensity data collected from synthetic BaCa 2 Si 3 O 9 (Dent Glasser and Glasser 1968). Due to uncertainty in oxygen positions, the reported final R-factor was 0.16. The current refinement yielded an R-factor of 0.030 with the inclusion of anisotropic displacement parameters. Walstromite is a Ba-Ca cyclosilicate characterized by Si 3 O 9 three-membered rings. It is related to the important calcium silicate group of minerals, especially to CaSiO 3 -walstromite, through the substitution of Ba into one of the three distinct Ca sites. Joswig et al. (2003) suggested that the structural changes caused by the replacement of Ba 2+ by Ca 2+ are minimal and that walstromite is isomorphic with CaSiO 3 -walstromite, but topologically different from high-pressure wollastonite-II (Ca 3 Si 3 O 9 ). Our study demonstrates that wollastonite-II and CaSiO 3 -walstromite are identical phases, and are isostructural with walstromite. This isomorphism implies that the high-pressure CaSiO 3 phase may be a potential host for large cations in deep Earth environments.

Relationships between cathodoluminescence spectra and trace element contents of hydrothermal α-quartz including hydrogen species are characterized for crystals from Gigerwald (Switzerland) and Rohdenhaus (West Germany) grown under highly different physico-chemical conditions and related to growth fabrics visualized by classical cathodoluminescence microscopy. Distinct emission bands at 395, 448, 503, 569, and 648 nm determine the spectral characteristics of cathodoluminescence images. Aluminum, Li, and H are the most important trace elements as determined by LA-ICP-MS and IR spectroscopy, reaching up to 6000 μmol/mol Al 3+ , 3300 μmol/mol Li + , and 5000 μmol/mol H+. Germanium, B, and Na are present at less than a few μmol/mol concentrations. A large amount of H is present in structurally bound water. AlOH-defects are also common, whereas LiOH- and SiOH-defects play only a minor role. Fast grown zones contain Li + and H + concentrations too low to compensate the charge deficit if all measured Al substitutes for Si 4+ in the quartz structure. This indicates the occurrence of intrinsic defects such as oxygen deficiency centers, which are assumed to affect the luminescence properties. Lithium abundances correspond to [AlO 4 |Li]-defects, correlated to the unstable intensity at 395 nm, but the correlation is different for both localities. This is inconsistent with a simple causal relationship between Al-Li-centers and the emission at 395 nm. Conversion of [AlO 4 |Li]-defects to [AlO 4 ] 0 -defects by natural irradiation is a possible explanation for this discrepancy. The increase of the intensity at 648 nm is not proportional to SiOH concentration as suggested in the literature, indicating that other precursor defects such as peroxy-linkages are more important. The decay of the intensity at 395 nm is much more rapid than the increase at 648 nm, excluding a coupling between these processes. Trace element incorporation in slowly grown hydrothermal quartz crystals is a direct function of fluid chemistry and temperature for a specific growth sector. Because quartz grows during extended periods of hydrothermal activity, changes in trace element inventory as visualized by cathodoluminescence may identify significant changes in growth conditions, which likely remain unrecognized during sample characterization with conventional microscopy.

Since the first report of triple-chain silicates in 1977, there has been considerable uncertainty about their formation in nature, primarily concerning whether they are stable minerals or an intermediate step in the formation of other chain or sheet silicate minerals. The lack of thermochemical data and relevant experimental studies for any triple-chain silicate has impeded establishment of their thermodynamic stability relative to other minerals. Here we combine recently reported thermochemical data for a sodium-analog of the triple-chain silicate clinojimthompsonite (Na-cjt) with existing data for various common minerals (i.e., enstatite, talc, anthophyllite, and chrysotile). We also present new experimental data to show that Na-cjt should form stably at typical metamorphic conditions of 0.2 GPa and 450 °C. Ion-activity vs. pH diagrams calculated at 100-300 °C and 0.1 GPa show that Na-cjt could form by reaction between primary igneous minerals (enstatite, forsterite) in oceanic harzburgite and seawater at temperatures up to 300 °C. However, formation of Na-cjt from harzburgite that has been altered to talc and chrysotile is not expected to occur, except at the unusually high pH conditions observed for forearc serpentine mounds. Estimates of the thermochemical properties of the Na-free end-member clinojimthompsonite [Mg 10 Si 12 O 32 (OH) 4 ] suggest that it also should form from the primary mineralogy of harzburgite at temperatures and Si concentrations typically observed for various oceanic hydrothermal and geothermal systems, but probably not from ultramafic rock already hydrated to serpentine.

The position of the spinel-post-spinel phase transition in Fe 3 O 4 has been determined in pressuretemperature space by in situ measurements using a multi-anvil press combined with white synchrotron radiation. Pressure measurement using the equation of state for MgO permitted pressure changes to be monitored at high temperature. The phase boundary was determined by the first appearance of diffraction peaks of the high-pressure polymorph (h-Fe 3 O 4 ) during pressure increase and the disappearance of these peaks on pressure decrease along several isotherms. We intersected the phase boundary over the temperature interval of 700-1400 °C. The boundary is linear and nearly isobaric, with a slightly positive slope. Post-experiment investigation by TEM confirms that the reverse reaction from h-Fe 3 O 4 to magnetite during decompression leads to the formation of microtwins on the (311) plane in the newly formed magnetite. Observations made during the phase transition suggest that the transition has a pseudomartensitic character, explaining in part why magnetite persists at conditions well within the stability field of h-Fe 3 O 4 , even at high temperatures. This study emphasizes the utility of studying phase transitions in situ at simultaneously high temperatures and pressures since the reaction kinetics may not be favorable at room temperature.

The first comprehensive PVT description of ε-Fe is presented by collecting the complete data set of previous experiments on ε iron, covering a pressure and temperature range of 6-306 GPa and 293-2255 K, respectively. A single set of equation of state parameters, which is able to cover the entire pressure and temperature range has been determined. The root mean square misfit of the residuals is 1.17 GPa for the PVT version of the Birch-Murnaghan equation of state. The equation of state uses an absolute reference frame (T = 0 K and P = 0 GPa) and follows a path, which eliminates the pressure effect on the volume coefficient of thermal expansion and the temperature effect on the pressure derivative of the bulk modulus. The calculated temperatures, which reproduce the PREM density, bulk modulus, and bulk seismic velocities at the inner core boundary, are 4640, 4070, and 3980 (±230) K, respectively, indicating that no light elements are necessary in the inner core. The calculated density deficit for the outer core at 4000-4600 K ICB temperatures is 4.4-3.5%.

We have carried out X-ray diffraction and Mössbauer spectroscopy measurements on the spinel phase g-Fe 2 SiO 4 (ringwoodite) at ambient temperature and pressures up to 66 GPa using diamond anvil cells. At pressures above 30 GPa, a previously unknown structural phase transition to a rhombohedrally distorted spinel phase has been observed (space group R3̄mR). Mössbauer spectroscopy measurements reveal two different Fe 2+ sites at high pressure with an abundance ratio of 3:1, in agreement with the two crystallographic sites occupied by the iron in this distorted spinel structure. The unit-cell volume of the low-pressure spinel phase as a function of pressure results in a bulk modulus of K 0 = 197(3) GPa using the second-order Birch-Murnaghan equation of state, and K 0 = 201(8) GPa and K′ = 3.7(7) when using a third-order equation of state. The pressure evolution of the unit-cell volume and the Mössbauer hyperfine parameters are in good agreement with previous studies, which were limited to a lower pressure range.

Change in configuration and structure with composition are important components of thermodynamic and transport properties of most aluminosilicate melts, but the complex interactions, particularly in metaluminous and peraluminous compositions, are not yet well understood. In this paper, we present high-resolution 27 Al and 17 O MAS and 3QMAS NMR data on several calcium and potassium aluminosilicate glasses prepared at several SiO 2 isopleths, ranging from peralkaline to peraluminous compositions. In all calcium aluminosilicate glasses, the V Al content increases with increasing Al content, while the NBO content decreases (in one series, below the limit of detection), consistent with other recent NMR studies of calcium aluminosilicate glasses. An increase in V Al content per total Al is also observed as the glass approaches the calcia-silica binary. In the potassium aluminosilicate glasses, NBO is directly quantified for the first time in metaluminous and peraluminous compositions; V Al is below the detection limit. We discuss possible mechanisms for the incorporation of alumina into the melt structure and show how changes in the V Al content as a function of composition may be used to eliminate mechanisms that do not fit the observed data. We also explore reactions, which show the difficulty of explaining the NBO present on the metaluminous join with only the observed V Al, implying the necessity of multiple reactions producing NBO in such compositions.

δ-Al(OD) 3 powders were synthesized from Al(OD) 3 bayerite at 4 GPa and 523 K using a cubic press apparatus. Neutron powder diffraction analyses of δ-Al(OD) 3 at ambient conditions revealed that the crystals are orthorhombic with space group P2 1 2 1 2 1 , not Pnma as reported previously based on X-ray diffraction data. The P2 1 2 1 2 1 δ-Al(OH) 3 structure contains seven independent atoms in the asymmetric unit, including one Al, three O, and three H atoms. The initial lattice parameters and the atomic positions of both Al and O were taken from previous X-ray structural analyses of the Pnma structure, while the positions of H were determined in the present study using ab initio calculations to (1) give the least energy among trial structural models for P2 1 2 1 2 1 δ-Al(OH) 3 , (2) accurately reproduce the measured lattice parameters of δ-Al(OD) 3 , and (3) show reasonable energetic relations between the Al(OH) 3 polymorphs; namely, gibbsite is stable at ambient pressure, δ-Al(OH) 3 has the lowest enthalpy at pressure greater than 1.1 GPa, and both bayerite and η-Al(OH) 3 are metastable over the entire pressure range. Furthermore, we found that the structure of δ-Al(OH) 3 obtained from ab initio calculations is in good agreement with that derived from a Rietveld refinement of δ-Al(OD) 3 , based on the present powder neutron diffraction data. The δ-Al(OH) 3 structure possesses one relatively long and two short O-H···O hydrogen bonds. Ab initio calculations also reveal that δ-Al(OH) 3 with space group P2 1 2 1 2 1 transforms to another high-pressure polymorph with space group Pnma at around 67 GPa, and that the two short hydrogen bonds in δ-Al(OH) 3 become both symmetric through the P2 1 2 1 2 1 to Pnma transformation, in which the protons are located at the midpoints of the O···O hydrogen bonds.

Electrical resistivity of synthetic nanocrystalline (30-40 nm crystallite size) and a crystalline natural sample of geikielite MgTiO 3 has been measured at simultaneous high pressure and high temperature up to 6 GPa and 800 K, respectively. The temperature dependence of the electrical resistivity of both the synthetic and natural sample obeys the Arrehenius behavior in the temperature range between 3 and 800 K and pressure range up to 6.0 GPa. The activation volume of the electrical conduction for coarse crystalline natural sample of geikielite is almost twice that of the synthetic nanocrystalline geikielite indicating the increase of activation volume with the crystallite size. The activation energy for the electronic conduction decreases from 0.39 eV at room pressure to 0.25 eV at 6.0 GPa for natural geikielite, and 0.68 to 0.225 eV in the same pressure range for synthetic geikielite. The pressure dependence of the activation energy of geikielite sample is found to obey the following expressions ΔE (eV) = 0.39 - 0.026(1) P + 0.0036 P 2 for natural sample, and ΔE (eV) = 0.68 - 0.080 (2) P + 0.0007 P 2 for synthetic sample, where P is pressure in GPa. We observe a crossover from extended state type conduction to hopping conduction at 4.0 GPa and 350 K for nano-crystalline geikielite. However, there is no such change of conduction mechanism observed for the natural geikielite at high pressures and high temperatures. The present study reveals the phase stability of nano-crystalline geikielite and natural geikielite up to mantle pressure and temperature conditions, viz. 6 GPa and 800 K, and no phase transition or decomposition is observed in the sample.

The density of liquid iron sulfide (FeS) was measured up to 3.8 GPa and 1800 K using an X-ray absorption method. The compression curve of liquid FeS was fitted using the Vinet equation of state. The isothermal bulk modulus and its temperature and pressure derivatives were determined using a nonlinear least-squares fit. The parameter sets determined were: K 0T = 2.5 ± 0.3 GPa at T = 1500 K, (dK 0 /dT) P = -0.0036 ± 0.0003 GPa/K, and (dK 0 /dP) T = 24 ± 2. These results suggest that liquid FeS is more compressible than Fe-rich liquid Fe-S.

Cranswickite is a newly recognized mineral of composition MgSO 4 ·4H 2 O from Calingasta, San Juan Province, Argentina (IMA2010-016). Cranswickite is monoclinic, space group C2/c, a = 11.9236(3), b = 5.1736(1), c = 12.1958(3) Å, β = 117.548(2)°, V= 667.0(1) Å 3 , Z = 4, d obs = 1.917 g/cm 3 , and d calc = 1.918 g/cm 3 . The mineral occurs0 as a soft white vein filling in a metasedimentary rock. The atomic structure has been determined by direct methods and refined by Rietveld analysis of powder diffraction data. The atomic structure consists of chains of corner-sharing magnesium-containing octahedra and sulfate tetrahedra similar to the structure of pentahydrite. All the water molecules directly coordinate magnesium in the structure. The five strongest lines in the powder X-ray diffraction data are [dobs in angstroms (I) (hkl)]: 5.259 (100) (200), 3.927 (46) (112̄), 3.168 (45) (113̄), 4.603 (29) (111̄), 2.570 (23) (311). Infrared and Raman spectra are very similar to the spectra measured from starkeyite. The chemical composition of cranswickite is the same as starkeyite MgSO 4 ·4H 2 O, but starkeyite has an atomic structure where two sulfate tetrahedra and two Mg(H 2 O) 6 octahedra share corners to form a four-membered ring and not a chain as in cranswickite. The new mineral is named in honor of Lachlan M.D. Cranswick (1968-2010), an Australian crystallographer who helped to developed and maintain the Collaborative Computational Project No. 14 in Powder and Small Molecule Single Crystal Diffraction (CCP14).

Ambrinoite, ideally (K,NH 4 ) 2 (As,Sb) 8 S 13 ·H 2 O, occurs as a rare sulfosalt species in the Triassic evaporitic formation of Gessi (gypsum) outcropping near the hamlet of Signols (Oulx, Susa Valley, Torino, Piedmont, Italy). The new species is associated with sulfur and orpiment; in the same occurrence galkhaite, stibnite, and enargite were also identified. Ambrinoite occurs as aggregates of tabular crystals up to 1 mm in length. The color is red, with an orange-red streak; the luster is vitreous to resinous. The mineral is transparent; its microhardness VHN (10 g) = 30 kg/mm 2 , corresponding to a Mohs hardness of about 2. Electron microprobe analysis gives the empirical formula [K 1.43 (NH 4 ) 0.42 Na 0.02 Tl 0.01 ] Σ=1.88 (As 5.82 Sb 2.18 ) Σ=8.00 S 13.22 ·1.2H 2 O, close to stoichiometric [K 1.5 (NH 4 ) 0.5 ] Σ=2 (As 6 Sb 2 ) Σ=8 S 13 ·H 2 O; the calculated density is 3.276 g/cm 3 . Micro-Raman spectroscopy confirmed the presence of water and ammonium cation. Ambrinoite is triclinic, space group P1̄, with a = 9.704(1), b = 11.579(1), c = 12.102(2) Å, α = 112.82(1), β = 103.44(1), γ = 90.49(1)°, V = 1211.6(3) Å 3 , Z = 2. The strongest X-ray powder diffraction lines [d in Å (I) (hkl)] are: 10.78 (100) (001), 5.79 (55) (02̄1), 4.23 (35) (102), 5.31 (34) (1̄02), 5.39 (32) (002). Its crystal structure has been solved by X-ray single-crystal diffraction on the basis of 2667 unique reflections, with a final R = 0.035. It is formed by two kinds of modules: slabs (110) PbS of modified PbS archetype (type A slabs) and openwork slabs with channels accomodating (K,NH 4 ) + cations and H 2 O molecules (type B slabs). Its structure can be described as an order-disorder (OD) structure, built up by two different kinds of layers. Taking into account only the short (As,Sb)-S bonds, (As,Sb)S 3 triangular pyramids form double chains similar to those described in other natural and synthetic compounds, among which its homeotype gillulyite, as well as gerstleyite. Ambrinoite belongs to the hutchinsonite merotypic family. It is probably the product of late-stage hydrothermal fluid circulation. The name of this new mineral species (IMA 2009-071) honors Pierluigi Ambrino (b. 1947), the mineral collector who kindly provided us with the studied specimens.

We present the first single-crystal Raman spectra of the mineral schafarzikite FeSb 2 O 4 from the Pernek locality of the Slovak Republic. In addition, Raman spectra of the natural mineral apuanite Fe 2+ Fe 4 3+ Sb 4 O 12 S, originating from the Apuan Alps in Italy, as well as spectra of synthetic ZnSb 2 O 4 and the arsenite mineral trippkeite (CuAs 2 O 4 ) are presented for the first time. The spectra of the antimonite minerals are characterized by a strong band in the region 660-680 cm -1 with shoulders on either side, and a band of medium intensity near 300 cm -1 . The spectrum of the arsenite mineral is characterized by a medium band near 780 cm -1 with a shoulder on the high wavenumber side and a strong band at 370 cm -1 . Mode assignments are proposed based on the spectral comparison between the compounds, symmetry modes of the bands and prior literature. The single-crystal spectra of schafarzikite showed good mode separation, allowing bands to be assigned to the symmetry species of A 1g , B 1g , B 2g , or E g .

A nomenclature for tourmaline-supergroup minerals is based on chemical systematics using the generalized tourmaline structural formula: XY 3 Z 6 (T 6 O 18 )(BO 3 ) 3 V 3 W, where the most common ions (or vacancy) at each site are X = Na 1+ , Ca 2+ , K 1+ , and vacancy; Y = Fe 2+ , Mg 2+ , Mn 2+ , Al 3+ , Li 1+ , Fe 3+ , and Cr 3+ ; Z = Al 3+ , Fe 3+ , Mg 2+ , and Cr 3+ ; T = Si 4+ , Al 3+ , and B 3+ ; B = B 3+ ; V = OH 1- and O 2- ; and W = OH 1- , F 1- , and O 2- . Most compositional variability occurs at the X, Y, Z, W, and V sites. Tourmaline species are defined in accordance with the dominant-valency rule such that in a relevant site the dominant ion of the dominant valence state is used for the basis of nomenclature. Tourmaline can be divided into several groups and subgroups. The primary groups are based on occupancy of the X site, which yields alkali, calcic, or X-vacant groups. Because each of these groups involves cations (or vacancy) with a different charge, coupled substitutions are required to relate the compositions of the groups. Within each group, there are several subgroups related by heterovalent coupled substitutions. If there is more than one tourmaline species within a subgroup, they are related by homovalent substitutions. Additionally, the following considerations are made. (1) In tourmaline-supergroup minerals dominated by either OH 1- or F 1- at the W site, the OH 1- -dominant species is considered the reference root composition for that root name: e.g., dravite. (2) For a tourmaline composition that has most of the chemical characteristics of a root composition, but is dominated by other cations or anions at one or more sites, the mineral species is designated by the root name plus prefix modifiers, e.g., fluor-dravite. (3) If there are multiple prefixes, they should be arranged in the order occurring in the structural formula, e.g., “potassium-fluor-dravite.”

This paper focuses on the determination of the speciation in calcium-silicate glasses from Raman spectra and describes in detail the statistical method to determine quantitatively the speciation from collected spectra. We developed a novel statistical method employing optimization technique to determine the number of active species and partial spectral contributions for overlapped spectra. This method allows deconvoluting overlapping spectra from spectral data such as UV-vis, Raman, X-ray, photoelectron spectroscopy (XPS), or other. We treat spectral methods that have absolute and relative information. By viewing the data as noisy or uncertain, we put all steps to deconvolute spectral data on a unified statistical approach, which allows to model spectral data with more realism. The suggested method enables us to calculate from overlapping spectra directly the individual contributions of each active component (species) present in the system without making any assumptions on the shape or peak positions of the components in individual spectra. To determine quantitatively the speciation in calcium silicate glasses, we have collected Raman spectra of the glasses in the range of 45 to 52 mol% SiO 2 . The spectra are strongly overlapped, and therefore, cannot be directly deconvoluted. Therefore, spectra were deconvoluted using our statistical approach. This lead to the discovery of partial spectra, which can be attributed to contributions of three different species. In addition, we have determined the equilibrium constant for the reaction 2Q 2 ↔ Q 1 + Q 3 (1) where logK 2 is found to be 1.15 ± 0.1, being in good agreement with available NMR study.

Icosahedrite, ideally Al 63 Cu 24 Fe 13 , is a new mineral from the Khatyrka River, southeastern Chukhotka, Russia. It occurs as dark gray-black anhedral to subhedral grains up to 100 μm across, closely associated with spinel, diopside, forsterite, nepheline, sodalite, corundum, stishovite, khatyrkite, cupalite, and an unnamed phase of composition AlCuFe. Icosahedrite is opaque with a metallic luster, possesses a gray streak, and is brittle with an uneven fracture. The density could not be determined. For quasicrystals, by definition, the structure is not reducible to a single three-dimensional unit cell, so neither cell parameters nor Z can be given. In plane-polarized incident light, icosahedrite exhibits neither bireflectance nor pleochroism. Between crossed polars, it is isotropic. Reflectance percentages (R min = R max ) for the four standard COM wavelengths are 62.3 (471.1 nm), 60.6 (548.3 nm), 58.1 (586.6 nm), and 56.0 (652.3 nm), respectively. The X-ray powder pattern was indexed on the basis of six integer indices, as conventionally used with quasicrystals, where the lattice parameter (in six-dimensional notation) is measured to be a 6D = 12.64 Å, with probable space group Fm3 5̄̄. The four strongest X-ray powder-diffraction lines [d in Å (I/I0) (n 1 ,n 2 ,n 3 ,n 4 ,n 5 ,n 6 )] are: 2.006 (100) (420 042), 2.108 (90) (422̄ 2̄22), 1.238 (30) (604̄ 064), and 3.41 (25) (311̄ 1̄11). Average results of 34 electron-microprobe analyses gave, on the basis of total atoms = 100, the formula Al 63.11 Cu 24.02 Fe 12.78 Si 0.03 Co 0.01 Ca 0.01 Zn 0.01 Cr 0.02 Cl 0.01 . The simplified formula is Al 63 Cu 24 Fe 13 , which requires the mass fractions Al 43.02, Cu 38.60, Fe 18.38, total 100.00 wt%. The new mineral is named for the icosahedral symmetry of its internal atomic structure, as observed in its diffraction pattern. Both the new mineral and mineral name have been approved by the Commission on New Minerals, Nomenclature and Classification, IMA (2010-042).

Here Mars and Moon are used as “natural laboratories” with Moon displaying lower oxygen fugacities (~IW-1) than Mars (~IW to FMQ). Moon has lower concentrations of Ni and Co in basaltic melts than does Mars. The major sulfides are troilite (FeS) in lunar basalts and pyrrhotite (Fe 1-x S) in martian basalts. This study focuses on the concentrations of Ni, Co, Cu, and Se. We chose these elements because of their geochemical importance and the feasibility of analyzing them with a combination of synchrotron X-ray fluorescence (SXRF) and electron microprobe (EPMA) techniques. The selenium concentrations could only be analyzed, at high precision, with SXRF techniques as they are <150 ppm, similar to concentrations seen in carbonaceous chondrites and interplanetary dust particles (IDPs). Nickel and Co are in higher concentrations in martian sulfides than lunar and are higher in martian olivine-bearing lithologies than olivine-free varieties. The sulfides in individual samples show very large ranges in concentration (e.g., Ni ranges from 50 000 ppm to <5 ppm). These large ranges are mainly due to compositional heterogeneities within individual grains due to diffusion and phase separation. Electron microprobe wavelength-dispersive (WDS) mapping of Ni, Co, and Cu show the diffusion trajectories. Nickel and Co have almost identical diffusion trajectories leading to the likely nucleation of pentlandite (Ni,Co,Fe) 9 S 8 , and copper diffuses along separate pathways likely toward chalcopyrite nucleation sites (CuFeS 2 ). The systematics of Ni and Co in lunar and martian sulfides clearly distinguish the two parent bodies, with martian sulfides displaced to higher Ni and Co values.