Band 97, Heft 2-3

The crystal structure of a 5C pyrrhotite from Silberberg Mine, Bodenmais, Germany, has been determined at 120 and 293 K in space group P2 1 . The low-temperature structure refined to R = 0.0261 for 5727 data with Io > 2σ(Io) and R = 0.0354 for all 7121 data. The room-temperature structure of the same crystal refined to R = 0.0383 for 2471 data with Io > 2σ(Io) and R = 0.0550 for all 3419 data. In addition, the diffraction data of a 5C pyrrhotite crystal from Copper Cliff Mine, Sudbury, Canada, previously refined in space group Cmce, has been transformed and also refined in space group P2 1 . This structure refined to R = 0.0441 for 2701 data with Io > 2σ(Io) and R = 0.0672 for all 3843 data, which is a substantial improvement over the previous refinement. The structure is characterized by iron vacancy avoidance within a layer, and with partially occupied sites projecting on top of each other in adjacent layers. Two half-occupied sites and two sites each with occupancy of 0.88 are present in the Bodenmais structure, together with one site with occupancy of 0.28. The distribution in the crystal from Sudbury is slightly different and cannot be described with the same number of partially occupied sites. Broadly, however, the two structures are similar.

Walstromite-structured CaSiO 3 (Wal) was synthesized at 6 GPa and 1200 °C for 6 h using a cubic press, and its thermal elastic behavior was investigated at T up to 900 °C using a powder X-ray diffraction technique at ambient pressure. Within the investigated T range, all unit-cell parameters, j, of Wal varied almost linearly with T, so that we fitted the data with the equation α j = j -1 (∂j/∂T) and obtained α a = 0.92(2) × 10−5/°C, α b = 1.65(1) × 10−5/°C, α c = 0.83(1) × 10−5/°C, and α V = 3.24(3) × 10−5/°C for Wal. The magnitudes of the principal Lagrangian strain coefficients (ε 1 , ε 2 , and ε 3 ) and the orientation of the thermal strain ellipsoids, between ambient T and measured T, were calculated. The orientation of the strain ellipsoid appears constant with T variation, whereas the strain magnitudes vary significantly with T: ε 1 increases, but ε 2 and ε 3 decrease. For T > 900 °C, primitive data were collected for “parawollastonite” (Wo-2M), which led to a much smaller volumetric thermal expansion coefficient than that of Wal.

Högbomite-group minerals are complex Fe-Mg-Zn-Al-Ti oxides related to the spinel group. Their polysomatic structure is composed of spinel (S) and nolanite (N) modules. The new polysome magnesiohögbomite-2N4S (IMA 2010-084) was found in the Sør Rondane Mountains, East Antarctica. It occurs in Mg-Al-rich, Si-poor skarns, characterized by a corundum-spinel-phlogopite-clinochlore assemblage. The new magnesiohögbomite polysome formed during the retrograde metamorphic stage. Magnesiohögbomite-2N4S appears macroscopically orange red, the streak is light orange colored. Euhedral crystals are hexagonal plates or prisms with cleavage planes on {001}. The mineral is optically uniaxial (-) and pleochroic with O = reddish brown and E = pale brown. The mean refractive index calculated from reflectance data in air at 589 nm is 1.85(3). The calculated density is 3.702(2) g/cm 3 . The Mohs hardness is 6.5-7, and VHN 300 = 1020-1051, mean 1032 kg/mm 2 . The crystal structure of the new polysome magnesiohögbomite-2N4S has been solved and refined (R1 = 2.74%) from single-crystal XRD data. The crystal chemical formula is T 10 M 24 O 46 (OH) 2 where T and M represent tetrahedral and octahedral sites. The mineral is hexagonal, space group P6 3 mc (no. 186), a = 5.71050(10), c = 27.6760(4) Å, Z = 1, V = 781.60(2) Å 3 . The strongest lines in the powder XRD pattern [d (Å), I (%), hkl] are: 2.8561(4), 37, 110; 2.6120(3), 39, 109; 2.42818(16), 100, 116; 2.4160(4), 39, 1010; 2.01181(13), 50, 208; 1.54892(16), 35, 2110; 1.42785(6), 57, 220. Strongest peaks in Raman spectra are at 302, 419, 479, 498, 709, 780, and 872 cm -1 , with a broad OH-characteristic absorption around 3400 cm -1 . The mean chemical composition (wt%) is SiO 2 0.05, TiO 2 7.08, SnO 2 0.15, Al 2 O 3 66.03, Cr 2 O 3 0.02, Fe 2 O 3 0.50, FeO 4.87, MnO 0.06, MgO 18.71, CaO 0.01, ZnO 0.96, NiO 0.01, CoO 0.02, F 0.06, Cl 0.01, H 2 O 1.00, sum 99.51. The simplified formula is (Mg 8.2 Fe 1.2 Zn 0.2 ) 2+ (Al 22.7 Fe 0.1 ) 3+ Ti 4+ 1.6 O 46 (OH) 2 and ideal formula is Mg 10 Al 22 Ti 2 O 46 (OH) 2 . This mineral is a solid solution between the two ideal end-members, (Mg,Fe,Zn) 10 2+ (Al,Fe) 22 3+ Ti 2 4+ O 46 (OH) 2 and (Mg,Fe,Zn) 8 2+ (Al,Fe) 26 3+ O 46 (OH) 2 .

Hanjiangite, ideal formula Ba 2 Ca(V 3+ Al)[Si 3 AlO 10 (OH) 2 ]F(CO 3 ) 2 , is a new mineral found in the Shiti barium deposit in the Dabashan region, China. Hanjiangite was collected from lenticular witherite ore bodies and witherite-barite-quartz veins cutting carbonaceous slates. It is found as disseminations in both settings. It occurs as thin, euhedral, tetragonal, tabular crystals, and anhedral grains. Grain size commonly varies from 0.05 to 4 mm and occasionally reaches 15 mm. It is yellow-green or dark green, with one well-developed or perfect cleavage on {001}. Other physical properties are: brittle, transparent to translucent, nonfluorescent, vitreous luster, greenish white streak, hardness 4 in the Mohs scale, splintery fracture, and a measured density of 3.69 g/cm 3 . Hanjiangite is biaxial (-), α = 1.615, β = 1.655, γ = 1.700 (589 nm), and displays strong pleochroism from pale yellow-green to dark green. It is monoclinic, with unit-cell parameters refined from single-crystal X-ray diffraction: a = 5.2050(12), b = 9.033(2), c = 32.077(8) Å, β = 93.49(8)°, V = 1505.4(8) Å 3 , Z = 4, space group C2. The strongest seven lines of the X-ray powder-diffraction pattern [d in Å(I)(hkl)] are: 15.866(7)(002), 5.340(91)(006), 4.010(10)(1̅14), 3.209(23) (027), 2.676(100) (1̅110), 2.294(29)(1̅37), and 2.008(11)(2̅28). Chemical analysis by a combination of electron microprobe, HF combustion, IR absorption, thermogravimetric analysis (TGA) and crystal-structure refinement gives SiO 2 19.64, TiO 2 1.12, Al 2 O 3 11.19, MgO 0.54, CaO 4.91, BaO 34.89, V 2 O 3 9.93, Cr 2 O 3 1.75, Na 2 O 0.20, K 2 O 0.06, MnO 0.01, FeO 0.02, NiO 0.01, SrO 0.34, Y 2 O 3 0.85, La 2 O 3 0.14, Nd 2 O 3 0.26, F 1.80, Cl 0.04, CO 2 10.37, H 2 O 1.30, F=O -0.76, Cl=O -0.01, sum 98.60 wt%. The empirical formula is (Ba 1.98 Na 0.06 K 0.01 ) Σ2.05 (Ca 0.76 Mg 0.12 Y 0.06 Sr 0.03 La 0.01 Nd 0.01 )Σ 0.99 (V 1.15 Al 0.75 Cr 0.20 Ti 0.12 ) Σ2.22 [(Si 2.84 Al 1.16 ) Σ4.00 O 10 ][(OH) 1.25 O 0.77 ] Σ2.02 (F 0.82 Cl 0.01 ) Σ0.83 (CO 3 ) 2.05 based on 19 anions per formula unit. A single-crystal X-ray structure determination (sample 2005st-17) was carried out with a Smart APEX CCD system using MoKα (λ = 0.71073 Å) radiation. The structure was solved using direct methods, and refined with the SHELXTL PC (Bruker AXS Inc.) package. Anisotropic refinement using all measured independent data and reflections with I > 2σ(I) resulted in an R 1 factor of 0.08 and wR 2 of 0.20. The crystal structure is composed of alternating T-O-T and Ba 2 Ca(CO 3 ) 2 F layers. The Ba 2 Ca(CO 3 ) 2 F layer occurs between the T-O-T layers. The T site contains both Si and Al, and the O site both V 3+ and Al. The interlayer hosts not only Ba (like in chernykhite) but also Ca atoms and (CO 3 ) groups. While the coordination of the cations in the TOT layer is obvious, the coordinations of Ca and Ba in the interlayer are not straight forward. A hanjiangite has three polytypes, namely 1M-type, 2M-type, and 3T-type.

Zirconolites based on the replacement of Ti 4+ with equimolar amounts of Nb 5+ and Fe 3+ , CaZrTi 2-2x NbxFexO 7 , have been jointly refined using high-resolution neutron powder diffraction and resonant X-ray powder diffraction data, with extra information provided from 57 Fe Mössbauer spectroscopy, to determine cation disorder. The results indicate that the CaZrTi 2-2x NbxFexO 7 series adopts the zirconolite-2M polytype across the range, with the replacement of Ti 4+ by Fe 3+ and Nb 5+ located within the hexagonal tungsten bronze (HTB) layers. Mössbauer spectroscopy shows that Fe 3+ preferentially fills the Ti split (C2) site, with secondary filling of the C1 site and no observable occupancy of the C3 site. This has been confirmed by neutron and resonant X-ray diffraction. Niobium has been found to occupy both the C1 and C3 sites with no evidence for occupancy of the C2 site.

We show that the focused ion beam (FIB) technique is well suited to prepare single-crystal samples with defined dimensions and shape and excellent surface qualities for use in high-pressure experiments carried out in the diamond-anvil cell. The method allows for cutting and polishing delicate samples, including tiny, brittle, or metastable phases and thereby extends the range of materials that can be routinely probed at extreme pressures and temperatures. In addition, the technique is capable of producing electron-transparent foils from the same sample material that can be characterized on the nanometer scale by transmission electron microscopy (TEM). The application of the method to the preparation of various geomaterials is discussed with a focus on the preparation of double-side polished, transparent sample platelets for the use in Brillouin scattering experiments at extreme conditions. Using one of our FIB-prepared samples, we were able to perform direct experimental measurements of acoustic wave velocities of antigorite along crystallographic directions, which were previously inaccessible to direct Brillouin scattering measurements. At 0.6 GPa, we measure a 39% anisotropy of compressional wave velocities.

New hexagonal aluminous (NAL) phase and orthorhombic calcium-ferrite (CF) type phase are considered to be major mantle components of the mid-ocean ridge basalt (MORB) at pressure and temperature conditions in the lower mantle, which can potentially host alkali elements with large ionic radii. The high-pressure stability and elastic properties of both NAL and CF phases are therefore of fundamental importance for understanding the fate of subducted MORB. Here we report those properties of the NaMg 2 Al 5 SiO 12 system studied by means of the first-principles computation method. NAL was found to transform to the CF phase at 39.6 GPa, accompanied by discontinuities in density (+1.8%), as well as compressional wave (-0.2%), shear wave (+0.9%), and bulk sound (-1.0%) velocities. The property of subducted MORB was evaluated using these results, and the velocity contrast between pyrolite and MORB of ~ -5% was found to be quite comparable to the shear velocity anomaly observed for seismic scatterers at depths from 1100 to 1800 km. However, since the transformation of the NAL to CF phase within MORB produces insignificant increases in the seismic velocities, it would be seismologically undetectable. On the other hand, the anisotropy change associated with the phase transition is significant and could be seismically detectable using observations such as shear wave splitting measurements since the CF phase is considerably more anisotropic compared to the NAL phase.

Accessory phases are important hosts of trace elements; allanite may contain >90% of the REE in a bulk rock. The mobility and redistribution of several trace elements, notably HREE, Th, U, and Y is thus controlled by reactions involving allanite and other REE phases, as well as several rock-forming minerals. As these elements are commonly concentrated in mature clastic sediments, a suite of impure quartzite was studied. Two eclogite facies samples from the Monometamorphic Cover Complex of the Sesia Zone (Western Italian Alps) are presented in some detail, as they reveal a remarkably rich spectrum of reaction relationships that involve REE phases. Two allanite-forming reactions were inferred from textures and phase compositions (1) monazite + Ca-silicate(?) + fluid → allanite + apatite + thorite; (2) monazite + thorite + Ca-silicate(?) + fluid → Th-rich allanite + auerlite ± apatite. Petrographic observations and thermodynamic models suggest that allanite entered the HP assemblage at ~530 °C and 17-18 kbar during prograde metamorphism. In one sample, allanite is rimmed by epidote rich in Y and HREE that grew at the expense of xenotime. Two net transfer reactions were derived (3) xenotime + allanite + fluid → Y-rich epidote + apatite + thorite; (4) xenotime + allanite + fluid → Y-rich epidote + aeschynite + thorite + (phosphate?). Textural relationships and trace element analyses of coexisting allanite/monazite and xenotime/ Y-rich epidote reveal systematic partitioning of the REE. Partition coefficients for the HREE are compatible with equilibrium fractionation, whereas those for the LREE show patterns that seem to be inherited from the precursor phases, in this case zircon with variable LREE composition.

Three samples from the dumortierite group of minerals were examined with magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR): a dumortierite [c. (Al,⃞)Al 6 (BO 3 ) Si 3 O 13 (O,OH) 2 ] consisting of dark blue euhedral crystals from Madagascar (D34); a fine-grained pale blue dumortierite from Island Copper mine, British Columbia, Canada (D12); and a creamy white holtite [c. (Ta,Nb,⃞,Al)Al 6 (BO 3 )(Si,Sb,As) 3 O 12 (O,OH,⃞) 3 ] from Szklary, Lower Silesia, Poland (WPH). Restricted Hartree-Fock ab initio electronic structure calculations were performed on model clusters with the goal of matching local environments of Si atoms to peaks in the 29 Si MAS NMR spectra. The spectrum of D34 showed five resolved peaks at -95.2, -92.6, -91.3, -89.1, and -86.5 ppm with deconvoluted peak area contributions of 57, 19, 7, 10, and 7%. Electronic structure calculations, cross-polarization MAS NMR measurements and relative intensities support assigning the peaks at -95.2 and -92.6 ppm to Si2 and Si1 sites, respectively, adjacent to fully occupied Al1 sites (i.e., Q 4 Si sites), and assigning the three remaining peaks to Si sites adjacent to vacant Al1 sites (i.e., Q 3 Si sites). Due to the complexity of the dumortierite structure, clusters composed of at least the first four shells of nearest neighbor atoms to the target Si atom are necessary to model Q 4 sites. The spectrum of D12 showed two main peaks at -93 and -95 ppm, with minor peaks below -90 ppm and above -100 ppm. The spectrum of WPH showed one broad peak at -93 ppm, likely containing both Si1 and Si2 signals, and two minor peaks below -90 ppm. Single-crystal X-ray diffraction and structure refinement on D34 shows orthorhombic symmetry, Pnma, Z = 4, a = 4.6882(1), b = 11.7924(2), c = 20.1856(3) Å, and V = 1115.97(4) Å 3 with R 1 = 0.0124. Three distinct sub-sites of the face-sharing octahedral chain site Al1 were distinguished corresponding to sites with one vacancy above, with one vacancy below, and between two occupied sites; the vacancy-adjacent sites have the cation displaced to increase the Al 3+ -Al 3+ distance. Each sub-site is approximately ¼ occupied, suggesting that Al 3+ cations in individual face-sharing octahedral chains are ordered as ⃞-Al-Al-Al, although cations from chain to chain are disordered, preserving Pnma symmetry. Powder X-ray diffraction measurements were performed on both D34 and D12. The unit cell of D12 was found to be a = 4.7001(7), b = 11.785(2), c = 20.277(3) Å.

The cationic ordering in the octahedral and tetrahedral sheets of Al-rich synthetic phlogopites with composition K(Mg 3-x Al x )[Al 1+x Si 3-x O 10 ](OH) 2 (0.0 < x < 1.0) has been investigated using a combined approach of Monte Carlo simulations based on the “J formalism” (Bosenick et al. 2001; Warren et al. 2001) and 1 H, 29 Si MAS and { 1 H} → 29 Si CPMAS/HETCOR solid-state NMR spectroscopic experiments. Our results are compatible with the well-established Loewenstein’s rule of Al-Al avoidance in the tetrahedral sheets, but the Si/ IV Al and Mg/ VI Al distributions show a tendency to segregation of the excess Al atoms, and we observe a preference for VIAl and IVAl to occupy directly neighbored octahedral and tetrahedral sites. As a result the structure is separated into clusters of original phlogopite composition {K(Mg 3 )[AlSi 3 O 10 ](OH) 2 } and clusters of “eastonite” composition {K(Mg 2 Al)[Al 2 Si 2 O 10 ] (OH) 2 } that encompass a whole T-O-T layer package, although Al is solved in the phlogopite structure homogeneously on a macroscopic level.

The multi-anvil high-pressure technique is an important tool in high-pressure mineralogy and petrology, as well as in chemical synthesis, allowing the treatment of large (millimeter-size) samples of minerals, rocks, and other materials at pressures of a few GPa to over 25 GPa and simultaneous uniform temperatures up to 2500 °C and higher. A series of cell assemblies specially designed and implemented for interlaboratory use are described here. In terms of the size of the pressure medium and the anvil truncation size, the five sizes of assemblies developed here are an 8/3, 10/5, 14/8, 18/12, and 25/15 assembly. As of this writing, these assemblies are in widespread use at many laboratories. The details of design, construction, and materials developed or used for the assemblies are presented here.

Recrystallization rims are a common feature of zircon crystals that underwent metamorphism. We present a microstructural and microchemical study of partially recrystallized zircon grains collected in polymetamorphic migmatites (Valle d’Arbedo, Ticino, Switzerland). The rims are bright in cathodoluminescence (CL), with sharp and convex contacts characterized by inward-penetrating embayments transgressing igneous zircon cores. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) data and transmission electron microscopy (TEM) imaging indicate that the rims are chemically and microstructurally different from the cores. The rims are strongly depleted in REE, with concentrations up to two orders of magnitude lower than in the cores, indicating a significant loss of REE during zircon recrystallization. Enrichment in non-formula elements, such as Ca, has not been observed in the rims. The microstructure of zircon cores shows a dappled intensity at and below the 100 nm scale, possibly due to radiation damage. Other defects such as pores and dislocations are absent in the core except at healed cracks. Zircon rims are mostly dapple-free, but contain nanoscale pores and strain centers, interpreted as fluid inclusions and chemical residues, respectively. Sensitive high-resolution ion microprobe (SHRIMP) U-Pb ages show that the recrystallization of the rims took place >200 Ma ago when the parent igneous zircon was not metamict. The chemical composition and the low-Ti content of the rims indicate that they form at sub-solidus temperatures (550-650 °C). Recrystallization rims in Valle d’Arbedo zircon are interpreted as the result of the migration of chemical reaction fronts in which fluid triggered in situ and contemporaneous interface-coupled dissolution-reprecipitation mechanisms. This study indicates that strong lattice strain resulting from the incorporation of a large amount of impurities and structural defects is not a necessary condition for zircon to recrystallize. Our observations suggest that the early formation of recrystallization rims played a major role in preserving zircon from the more recent Alpine metamorphic overprint.

Evolution of concentrated Fe 2 (SO 4 ) 3 solution, a process including both evaporation of the solution and post-evaporation aging of the precipitates, was studied at 2 and 50 °C under controlled relative humidity (RH). At 50 °C and 42-47% RH, ferricopiapite [Fe 4.67 (SO 4 ) 6 (OH) 2 ⋅20H 2 O] and rhomboclase [(H 5 O 2 )Fe(SO 4 ) 2 ⋅2H 2 O] first crystallized from the starting solution, and then combined to form kornelite [Fe 2 (SO 4 ) 3 ⋅7.5H 2 O] at 42% RH or to paracoquimbite [Fe 2 (SO 4 ) 3 ⋅9H 2 O] at 46-47% RH. At 2 °C and 34-43% RH, initially crystallized ferricopiapite and rhomboclase appeared to be stable and did not proceed to form a single ferric sulfate hydrate phase over 385 days. At both 2 and 50 °C and RH ≤ 31%, an amorphous ferric sulfate formed. The amorphous ferric sulfate was preserved longer at low RH conditions, e.g., RH ≤ 11%, than higher RH, at which it slowly transformed to crystalline phases of rhomboclase and ferricopiapite, as observed at 31% RH and 50 °C. Combining the results from this study and those from our previous study at 25 °C, the ferric sulfate phase evolution at 2, 25, and 50 °C were mapped and compared. Temperature shows a strong effect on the evolution kinetics; low T may inhibit the evolution from reaching an equilibrium state. Also, an RH and T-controlled in situ X-ray diffraction (RH-T-XRD) method was used to study phase transitions of ferric sulfate hydrates at temperatures from 25 to 80 °C. A dehydration of paracoquimbite to ferric sulfate pentahydrate [Fe 2 (SO 4 ) 3 ·5H 2 O] was identified at 80 °C. The results are discussed with a previously constructed ferric sulfate RH-T phase diagram by Ackermann et al. (2009).

A specific methodology was developed to refine the complex clay mineralogy commonly encountered in soil environments. The soil examined was a Cambisol developed into a ferralitic paleosol. The sample was split into four sub-fractions of different particle sizes (<0.05, 0.05-0.1, 0.1-0.2, and 0.2-2 μm), and their respective mass contributions to the overall <2 μm clay fraction were determined. For each sub-fraction, X-ray diffraction (XRD) patterns were modeled using a trial-and-error approach based on the direct comparison of experimental and calculated profiles. Quantitative information derived from the fitting procedure for the different sub-fractions allowed for the determination of the complex mineralogy of the <2 μm clay fraction through the identification and quantification of eight clay phases. The results show that the finest and most reactive clay fraction (<0.05 μm) was totally hidden in the XRD pattern of the <2 μm fraction, the fraction commonly considered in soil mineralogical analyses. Similarly, this procedure revealed the presence of illite-smectite-chlorite and kaolinite-illite mixed-layer minerals seldom described in soil literature using classical methods. The use of this methodology improved our understanding of the pedogenesis of this soil through the identification and quantification of clay phases structural properties. The analysis of the evolution of structural parameters with particle size allowed for the detection of local modifications in the interlayer composition of expandable and hydroxy-interlayered vermiculite layers. Following this approach, key information can be derived to determine subtle changes in clay mineralogical composition that are related to microorganism and/or plant activity.

Elastic anomalies and acoustic dissipation associated with spin-state transitions of Co 3+ in Co 3 O 4 have been investigated using resonant ultrasound spectroscopy (RUS) at high frequencies (0.1-1.5 MHz) between 6 and 1107 K, and dynamic mechanical analysis (DMA) at low frequencies (0.1-50 Hz) between 127 and 775 K. Above ~800 K, the shear modulus decreases with increasing temperature and the acoustic dissipation increases. The amount of softening scales linearly with an empirical order parameter for low spin → low spin + high spin states derived from analysis of changes in unit-cell volume with temperature. The mechanism for anelastic losses is not understood but must be due to relaxation of strains coupled either to changes in spin state or to changes of cation configuration between tetrahedral and octahedral sites occurring by electron exchange. The pattern of shear modulus softening, in proportion to the spin order parameter, is likely to be general for cubic structures containing cations, which undergo spin-state transitions, such as Fe 2+ in (Mg,Fe)O. Below ~30 K, RUS data show a large softening of the shear modulus and a steep increase in acoustic dissipation due to the magnetic transition from paramagnetic to antiferromagnetic. This could be understood in terms of the influence of a symmetry breaking strain coupled to the magnetic order parameter such that cubic lattice geometry is not maintained. Possible magnetic space groups for the antiferromagnetic structure are considered through the use of the group theory.

A single-crystal X-ray diffraction (XRD) study, using a diamond-anvil cell at high pressure and room temperature, was performed on a crystal from a natural space group P2/n omphacite sample with composition very close to Jd 55 Di 45 and with a high degree of order in cation distribution. Unit-cell parameters were determined at 13 different pressures up to about 7.5 GPa. A third-order Birch-Murnaghan equation of state (BM3-EoS) fitted to the P-V data yielded V 0 = 421.43(4) Å 3 , K T0 = 122(1) GPa, and K′ = 5.1(3). The K T0 value for this sample lies between the data obtained for the two end-members jadeite and diopside, and describes a slight positive curvature trend. During the same experiment, intensity data were collected and crystal structures were refined at 5 pressures up to 7.3 GPa. Both M1 and M2 polyhedra volumes showed a slight but significant change in slope at about 4 GPa. This behavior can likely be explained in terms of tilt angle variation of TA and TB tetrahedral, which also showed a change in slope with pressure, rather than in terms of bond length compression anomaly.

We describe the first documented case of {101̅0} twinning by reflection (or by twofold rotation about [100]) or merohedry (class II) in a member of the apatite supergroup. Twinning about [100] had previously been noted for the apatite supergroup but not confirmed. Pyromorphite crystals from Puech de Compolibat, Combret, Aveyron, France, were studied by single-crystal X-ray diffraction [a = 10.0017(19), c = 7.3413(16) Å, and V = 636.0(2) Å 3 , in P6 3 /m], where twinning was confirmed with the approximate twin fraction 62:38. Subsequent inspection of the morphology confirmed the nature of the twinning. The pyromorphite crystals are typically elongate and show the faces: (21̅1̅0), ( 2̅110), (0001), (0001̅), (101̅0), (1̅010), (101̅2̅), and (1̅012̅).

Synchrotron infrared (IR) and micro-Raman spectroscopic studies have been performed on zeolite natrolites as a function of the non-framework composition at ambient conditions. This establishes the spectroscopic characterization of the ion-exchanged natrolites in the alkali-metal series both in the as-prepared hydrated (M-NAT-hyd, M = Li, Na, K, Rb, and Cs) and some stable dehydrated forms (MNAT- deh, M = Rb and Cs). The former series exhibits non-framework cation-size dependent opening of the helical channels to span ca. 21° range in terms of the chain rotation angle, ψ (or ca. 45° range in terms of the chain bridging angle, T-O2-T). For these hydrated phases, both IR and Raman spectra reveal that the degree of the red-shifts in the frequencies of the helical 8-ring channel as well as the 4-ring unit is proportional to the ionic radius of the non-framework cations. Linear fits to the data show negative slopes of -55.7 from Raman and -18.3 from IR in the 8-ring frequencies and ionic radius relationship. The spectroscopic data are also used to identify the modes of the dehydration-induced “collapse” of the helical 8-ring channels as observed in the stable anhydrous Rb-NAT-deh and Cs- NAT-deh. In addition, we demonstrate that the spectroscopic data in the hydrated series can be used to distinguish different water arrangements along the helical channels based on the frequency shifts in the H-O-H bending band and the changes in the O-H stretching vibration modes.

Atomistic computer simulations methods are used to examine the influence of Li and Al impurities on the uptake of hydrogen in forsterite. We find that Li′Mg+OH · O is more stable at the Mg1 site than at the Mg2 site and that Li + increases the ability of forsterite to incorporate hydrogen associated with magnesium sites. When both Al and Li are present, then a complex comprising a bound Al · Mg2 -Li′ Mg1 defect is highly stable. When all three impurity components are mixed together, then hydrogen will strongly partition to Si vacancies forming the hydrogarnet defect. Thus the ability of forsterite to incorporate water is likely to be intimately linked to the nuances of defect chemistry, and to concentrations of impurity elements such as Li+ and Al 3+ .

The crystal chemistry of 2M 1 micas from Bunyaruguru kamafugite (southwest Uganda) was studied by electron probe microanalysis, single-crystal X-ray diffraction, Mössbauer and Fourier transform infrared spectroscopy. Chemical analyses showed that the studied crystals are Ti-rich, F-poor phlogopites with an annitic component, Fe tot /(Fe tot + Mg), ranging from 0.15 to 0.22. Unit-cell parameters from single-crystal X-ray data are in the range: 5.3252(1) ≤ a ≤ 5.3307(1), 9.2231(3) ≤ b ≤ 9.2315(3), 20.1550(6) ≤ c ≤ 20.1964(8) Å, and 94.994(2) ≤ β ≤ 95.131(2)°. Anisotropic structure refinements, in the space group C2/c, converged to 2.77 ≤ R 1 ≤ 3.52% and 2.91 ≤ wR 2 ≤ 4.02%. Mössbauer spectroscopy showed that the studied sample has: VI Fe 2+ = 60(1)%, VI Fe 3+ = 24(1)%, and IV Fe 3+ = 16(1)%. FTIR investigations pointed to the occurrence of Fe 3+ -oxy substitutions and ruled out the presence of vacancy mechanisms. The overall crystal-chemical features are consistent with the following substitutions: tetraferriphlogopite [ IV Fe 3+ ≤ IV Al]; 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 M 3+ + IV Al]; kinoshitalite [ XII K + IV Si 4+ ↔ XII Ba 2+ + IV Al] and [ XII K + + IV Al 3+ ↔ IV Si 4+ + XII ⃞]. The estimation of the OH - content for Ugandan mica-2M 1 was obtained, for the first time, from the linear regression equation c = 0.20(2) × OH - (gpfu) + 19.93(2) derived from literature data of 2M 1 -samples with known OH − content. The orientation of the O-H vector with respect to c* was found in the range from 2.0 to 6.9°.

Menchettiite, ideally AgPb 2.40 Mn 1.60 Sb 3 As 2 S 12 , is a new mineral from the Uchucchacua polymetallic deposit, Oyon district, Catajambo, Lima Department, Peru. It occurs as black, anhedral to subhedral grains up to 200 μm across, closely associated with orpiment, tennantite/tetrahedrite, other unnamed minerals of the system Pb-Ag-Sb-Mn-As-S, and calcite. Menchettiite is opaque with a metallic luster and possesses a black streak. It is brittle, with uneven fracture; the Vickers microhardness (VHN 100 ) is 128 kg/mm 2 (range 119-136) (corresponding to a Mohs hardness of 2½-3). The calculated density is 5.146 g/cm 3 (on the basis of the empirical formula). In plane-polarized incident light, menchettiite is weakly to moderately bireflectant and weakly pleochroic from dark gray to a dark green. Internal reflections are absent. Between crossed polarizers, the mineral is anisotropic, without characteristic rotation tints. Reflectance percentages (R min and R max ) for the four standard COM wavelengths are 33.1, 39.8 (471.1 nm), 31.8, 38.0 (548.3 nm), 30.9, 37.3 (586.6 nm), and 29.0, 35.8 (652.3 nm), respectively. Menchettiite is monoclinic, space group P2 1 /n, with unit-cell parameters: a = 19.233(2), b = 12.633(3), c = 8.476(2) Å, β = 90.08(2)°, V = 2059.4(8) Å 3 , a: b: c 1.522:1:0.671, Z = 2, and it is twinned on {100}. The crystal structure was refined to R = 0.0903 for 2365 reflections with Fo > 4σ(Fo) and it resulted to be topologically identical to those of ramdohrite, uchucchacuaite, and fizélyite. The six strongest X-ray powder-diffraction lines [d in Å (I/I0) (hkl)] are: 3.4066 (39) ( 3̅12), 3.4025 (39) (312), 3.2853 (100) (520), 2.8535 (50) ( 2̅32), 2.8519 (47) (232), and 2.1190 (33) (004). Electron-microprobe analyses gave the chemical formula Ag 1.95 Cu 0.01 Pb 4.81 Mn 3.20 Fe 0.02 Zn 0.01 Sb 6.09 As 3.94 Bi 0.01 S 23.95 Se 0.01 , on the basis of 44 atoms and according to the structure refinement results. Menchettiite can be classified among the Sb-rich members of the lillianite homeotypic series, which are described with the general formula Ag x Pb 3-2x Sb 2+x S 6 . Besides the heterovalent substitution 2Pb 2+ → Ag + + Sb 3+ taken into consideration by the above formula, two isovalent substitutions relate menchettiite to the other lillianite homeotypes, i.e., Mn 2+ → Pb 2+ and As 3+ → Sb 3+ . The name is after Silvio Menchetti (1937-), Professor of Mineralogy and Crystallography at the University of Florence. The new mineral and mineral name have been approved by the Commission on New Minerals, Nomenclature and Classification, IMA (2011-009).

Adolfpateraite, monoclinic K(UO 2 )(SO 4 )(OH)(H 2 O), is a new supergene mineral from the Svornost mine, Jáchymov ore district, Czech Republic. It forms sulfur yellow to greenish yellow crystalline aggregates, up to 2 mm in diameter. Crystals are transparent to translucent with a vitreous luster, without observable cleavage. The streak is pale yellow. The Mohs hardness is ~2. The mineral shows a green fluorescence in long-wave ultraviolet radiation. Adolfpateraite is pleochroic, with α = colorless and γ = yellow (β could not been examined). It is biaxial, with α = 1.597(2), γ = 1.659(2) (β could not been measured), birefringence 0.062. The empirical chemical formula (mean of 4 electron microprobe point analyses) was calculated based on 8 O apfu and is K 0.94 (UO 2 ) 1.00 (SO 4 ) 1.02 (OH) 0.90 (H 2 O) 1.00 (water content calculated). The simplified formula is K(UO 2 )(SO 4 )(OH)(H 2 O), requiring K 2 O 10.70, UO 3 64.97, SO 3 18.19, H 2 O 6.14, total 100.00 wt%. Adolfpateraite is monoclinic, space group P2 1 /c, a = 8.0462(1), b = 7.9256(1), c = 11.3206(2) Å, β = 107.726(2)°, V = 687.65(2) Å 3 , Z = 4, and D calc = 4.24 g/cm 3 . The five strongest reflections in the X-ray powder diffraction pattern are [dobs in Å (I) (hkl)]: 7.658 (76) (100), 5.386 (100) (002), 5.218 (85) (1̅02), 3.718 (46) (021), 3.700 (37) ( 2̅02). The crystal structure has been refined from single-crystal X-ray diffraction data to R 1 = 0.0166 with GOF = 1.30, based on 1915 observed reflections [I obs > 3σ(I)]. The crystal structure consists of chains of uranyl polyhedra extended along [010], with OH - located on the shared vertex between the bipyramids. The sulfate tetrahedra decorate the outer side of the chain with bridging bidentate linkages between the uranyl pentagonal bipyramids. H 2 O groups are located on the edges of the chains on the non-linking vertex of each uranyl pentagonal bipyramid. K + atoms are located between the chains providing additional linkage of these together with H-bonds. The fundamental vibrational modes of uranyl ion, sulfate tetrahedra, and H 2 O groups were tentatively assigned in the infrared and Raman spectra. The new mineral is named to honor Adolf Patera (1819-1894), Czech chemist, mineralogist, and metallurgist.

The compressional and shear wave velocities of seven series of hydrous aluminosilicate glasses were measured by Brillouin scattering at room temperature and pressure as a function of water content. The glasses were quenched from high temperature and 0.2 or 0.3 GPa pressure. The dry end-members range from highly polymerized albitic and granitic compositions, to depolymerized synthetic analogues of mantle-derived melts. For each set of glasses, the adiabatic shear and bulk moduli have been calculated from the measured sound velocities and densities. These moduli are linear functions of water content up to 5 wt% H 2 O, the highest concentration investigated, indicating that both are independent of water speciation in all series. For anhydrous glasses, (∂V/∂P) S changes from about -0.3 to -0.7 × 10 −15 m 3 /(Pa·mol) with increasing degree of polymerization. For the same compositions, the partial molar (∂V/∂P) S of the water component changes from near zero to -0.8 × 10 −15 m 3 /(Pa⋅mol) with increasing degree of polymerization, such that dissolved water amplifies the differences in rigidity between the anhydrous glasses. This strong variation indicates that the solubility mechanisms of water depend strongly on silicate composition. A simple linear model reproduces (∂V/∂P) S to within measurement uncertainty, with glasses becoming more compressible as NBO/T decreases and as alkalinity increases. The dissolved water component also becomes more compressible as NBO/T decreases, but less compressible as alkalinity increases. In strongly depolymerized structures, water causes an increase in sound velocities even though it induces a decrease in density. The general rule according to which sound velocities correlate with density is, therefore, violated, for in these cases water dissolution results in a decrease of compressibility. Barring any strongly anomalous effect of water on configurational compressibility, the trends observed for glasses should be still more divergent for melts. Consequently, hydrous mafic and ultramafic liquids are predicted to have a very low compressibility. The shear modulus of hydrous glasses varies little with bulk composition or water content, supporting the use of a single composition-independent pre-exponential factor in models of melt viscosity.

Iron oxidation state and coordination geometry have been determined by Fe K-edge X-ray absorption near edge spectroscopy (XANES) for three sets of silicate glasses of peralkaline rhyolitic composition with different peralkalinity values. These compositions were chosen to investigate the effect of alkali content (and oxygen fugacity) on the Fe oxidation state. The samples were produced by means of hydrothermal vessels at 800 °C with oxygen fugacity conditions ranging from NNO-1.61 to NNO+2.96 log units. Comparison of the pre-edge peak data with those of Fe model compounds of known oxidation state and coordination number allowed determination of the Fe oxidation state and coordination number in all glasses analyzed. Within each group of samples, Fe tends to oxidize with increasing oxygen fugacity as expected. However, alkali content is shown to have a strong effect on the Fe 3+ /(Fe 3+ +Fe 2+ ) ratio at constant oxygen fugacity: this ratio varies from 0.25 to 0.55 (± 0.05) for the least peralkaline series, and from 0.45 to 0.80 (± 0.05) for the most peralkaline series. Moreover, pre-edge peak data clearly indicate that Fe 3+ is in fourfold coordination in the most peralkaline glasses. Extrapolation of pre-edge peak data suggests the presence of both fourfold and fivefold coordination for trivalent Fe in the other two series. Divalent Fe is suggested to be mainly in fivefold coordination in all the three glass series. The presence of minor amounts of sixfold- and fourfold-coordinated Fe cannot be ruled out by XANES data alone. XANES data suggest that the amount of alkalis also affects the Fe 3+ coordination environment resulting in a decrease in the average coordination numbers. Extended X-ray absorption fine structure (EXAFS) data of the most oxidized and peralkaline sample indicate that Fe 3+ is in tetrahedral coordination with <Fe-O> = 1.85 Å (± 0.02). This value compares well with literature data for [4] Fe 3+ in crystalline phases (e.g., in tetra-ferriphlogopite or rodolicoite) or in silicate glasses (e.g., phonolite glasses) supporting the XANES-determined coordination number obtained for the most peralkaline glasses. Calculated NBO/T ratios decrease slightly with Fe oxidation because of the higher fraction of network forming Fe, thus increasing the polymerization of the tetrahedral network.

In situ spatially resolved X-ray absorption near edge structure (m-XANES) spectra are obtained for natural Cu-In-bearing sphalerite. Copper K-edge spectral data show that, in Cu-In-bearing sphalerite, in which an excellent correlation between the Cu and In contents is noted, Cu is present in the Cu+ state. This offers indirect proof for the coupled substitution 2 Zn 2+ ↔ Cu + + In 3+ , which allows indium to enter the sphalerite structure. The study clearly demonstrates the utility of synchrotron radiation to accurately determine oxidation state in small volumes of mineral in which the concentration of the element of interest is low or very low. The study also demonstrates that good quality μ-XANES spectra can be collected on TEM foils prepared in situ at a chosen position on the surface of a polished sample using the focused ion beam-scanning electron microscope method.

Morphological quantification of the complex structure of hierarchical geomaterials is of great relevance for Earth science and environmental engineering, among others. To date, methods that quantify the 3D morphology on length scales ranging from a few tens of nanometers to several hundred nanometers have had limited success. We demonstrate, for the first time, that it is possible to go beyond visualization and to extract quantitative morphological information from X-ray images in the aforementioned length scales. As examples, two different hierarchical geomaterials exhibiting complex porous structures ranging from nanometer to macroscopic scale are studied: a flocculated clay water suspension and two hydrated cement pastes. We show that from a single projection image it is possible to perform a direct computation of the ultra-small angle-scattering spectra. The predictions matched very well the experimental data obtained by the best ultra-small angle-scattering experimental setups as observed for the cement paste. In this context, we demonstrate that the structure of flocculated clay suspension exhibit two well-distinct regimes of aggregation, a dense mass fractal aggregation at short distance and a more open structure at large distance, which can be generated by a 3D reaction limited cluster-cluster aggregation process. For the first time, a high-resolution 3D image of fibrillar cement paste cluster was obtained from limited angle nanotomography.