Volume 94, Issue 10

The origins and near-surface distributions of the ~250 known uranium and/or thorium minerals elucidate principles of mineral evolution. This history can be divided into four phases. The first, from ~4.5 to 3.5 Ga, involved successive concentrations of uranium and thorium from their initial uniform trace distribution into magmatic-related fluids from which the first U 4+ and Th 4+ minerals, uraninite (ideally UO 2 ), thorianite (ThO 2 ), and coffinite (USiO 4 ), precipitated in the crust. The second period, from ~3.5 to 2.2 Ga, saw the formation of large low-grade concentrations of detrital uraninite (containing several wt% Th) in the Witwatersrand-type quartz-pebble conglomerates deposited in a highly anoxic fluvial environment. Abiotic alteration of uraninite and coffinite, including radiolysis and auto-oxidation caused by radioactive decay and the formation of helium from alpha particles, may have resulted in the formation of a limited suite of uranyl oxide-hydroxides. Earth’s third phase of uranium mineral evolution, during which most known U minerals first precipitated from reactions of soluble uranyl (U 6+ O 2 ) 2+ complexes, followed the Great Oxidation Event (GOE) at ~2.2 Ga and thus was mediated indirectly by biologic activity. Most uraninite deposited during this phase was low in Th and precipitated from saline and oxidizing hydrothermal solutions (100 to 300 °C) transporting (UO 2 ) 2+ -chloride complexes. Examples include the unconformity- and vein-type U deposits (Australia and Canada) and the unique Oklo natural nuclear reactors in Gabon. The onset of hydrothermal transport of (UO 2 ) 2+ complexes in the upper crust may reflect the availability of CaSO 4 - bearing evaporites after the GOE. During this phase, most uranyl minerals would have been able to form in the O 2 -bearing near-surface environment for the first time through weathering processes. The fourth phase of uranium mineralization began ~400 million years ago, as the rise of land plants led to non-marine organic-rich sediments that promoted new sandstone-type ore deposits. The modes of accumulation and even the compositions of uraninite, as well as the multiple oxidation states of U (4+, 5+, and 6+), are a sensitive indicator of global redox conditions. In contrast, the behavior of thorium, which has only a single oxidation state (4+) that has a very low solubility in the absence of aqueous F-complexes, cannot reflect changing redox conditions. Geochemical concentration of Th relative to U at high temperatures is therefore limited to special magmatic-related environments, where U 4+ is preferentially removed by chloride or carbonate complexes, and at low temperatures by mineral surface reactions. The near-surface mineralogy of uranium and thorium provide a measure of a planet’s geotectonic and geobiological history. In the absence of extensive magmatic-related fluid reworking of the crust and upper mantle, uranium and thorium will not become sufficiently concentrated to form their own minerals or ore deposits. Furthermore, in the absence of surface oxidation, all but a handful of the known uranium minerals are unlikely to have formed.

Tazieffite, ideally Pb 20 Cd 2 (As,Bi) 22 S 50 Cl 10 , is a new mineral from the high-temperature fumaroles of the Mutnovsky volcano, Kamchatka Peninsula, Russian Federation. It occurs as tiny, slender, needleshaped crystals, up to 400 μm long and 10 μm across, generally forming fibrous aggregates. Tazieffite is closely associated with greenockite, galena, mutnovskite, kudriavite, and Cd-rich cannizzarite. Other minerals spatially associated are pyrite, anhydrite, and cristobalite. Tazieffite is silvery-gray in color, occasionally with a magenta tint when it forms aggregates of extremely fine needles. It has a black streak and metallic luster. In plane-polarized incident light, tazieffite is weakly bireflectant and weakly pleochroic from dark gray to a blue-gray. Between crossed polars, the mineral is weakly anisotropic, without characteristic rotation tints. Reflectance percentages measured in air (R min and R max ) for a single grain are 33.9, 34.1 (471.1 nm), 32.8, 33.0 (548.3 nm), 32.4, 32.6 (586.6 nm), and 30.9, 31.1 (652.3 nm), respectively. Electron microprobe analyses yield the following ranges of concentrations: Pb 41.88-44.14 (avg. 42.90), Cd 0.87-1.16 (avg. 1.03), Sn 0.31-0.69 (avg. 0.48), Bi 20.43-22.94 (avg. 21.90), As 8.64-10.73 (avg. 9.66), S 16.10-17.48 (avg. 16.58), Se 0.82-1.28 (avg. 1.04), Cl 2.39-2.77 (avg. 2.63), Br 0.09-0.15 (avg. 0.12), I 0.27-0.58 (avg. 0.42). The empirical chemical formula, calculated on the basis of 44 cations, is Pb 20.06 (Cd 0.89 Sn 0.39 In 0.02 ) Σ1.30 (As 12.49 Bi 10.15 ) Σ22.64 (S 50.08 Se 1.28 ) Σ51.36 (Cl 7.18 I 0.32 Br 0.15 ) Σ7.65 . Tazieffite is closely related to the halogen-sulfosalt vurroite, Pb 20 Sn 2 Bi 22 S 54 Cl 6 , both from a chemical and structural point of view. It represents the (Cd,As)-dominant of vurroite, according to the coupled heterovalent substitution Sn 4+ + 2S 2- → Cd 2+ + 2Cl-. The crystal structure of tazieffite was refined in the space group C2/c to R = 0.0370 for 4271 reflections with I > 2σ(I). Unit-cell parameters are a = 8.3520(17), b = 45.5920(92), c = 27.2610(55) Å, β = 98.84(3)°, with V = 10257(4) Å 3 , and Z = 4. The structure of tazieffite consists of lozenge-shaped composite rods made of coordination polyhedra of Pb around an octahedrally coordinated (Cd,Sn,Pb) position, interconnected into layers parallel to (010). These layers are separated by ribbons of As and Bi in distorted octahedral coordination. The ribbons form wavy, discontinuous double layers of the PbS archetype. Lone electron pairs of As and Bi are accommodated in the central portions of the PbS-like layers. The possibility that small amounts of NH 4 + are incorporated in the crystal structure of tazieffite is discussed. The name of this new mineral species (IMA 2008-012) honors Haroun Tazieff (Warszawa, May 11, 1914-Paris, February 6, 1998), famous Belgian/French volcanologist, who was a pioneer in the field study of volcanoes and devoted his life to the study of volcanic gases.

Idrialite from Skaggs Springs, Sonoma County, California, was studied by microbeam and bulk analyses; the former include micro X-ray diffraction (μ-XRD), electron microprobe (EMP), and micro Fourier transform infrared (μ-FTIR) spectroscopic analyses, and the latter include powder XRD analysis, thermogravimetry-differential thermal analysis (TG-DTA), and carbon isotope analysis. Careful observation under a stereo-microscope clearly disclosed that the examined sample is composed of yellow and brown parts. The yellow parts were identified as idrialite with high crystallinity, whereas the brown ones were confirmed as amorphous matter by μ-XRD. Furthermore, the μ-FTIR spectra revealed that the yellow and brown parts contain hydrophobic and hydrophilic compounds, respectively. EMP analysis showed no chemical zoning and homogeneous distribution of S-bearing molecules in the yellow parts. TG-DTA disclosed that the present idrialite of the yellow part left no residue on heating up to 740 °C; this thermal behavior is similar to that of the other natural organic matter in liquid states such as petroleum and crude oil. The carbon isotopic composition was analyzed using an elemental-analyzer isotopic-ratio mass spectrometer (EA/IRMS). The δ 13 C value of the idrialite is -24.429 ± 0.090‰ (vs. V-PDB), which is akin to carbon isotopic compositions of the typical higher-plant triterpenoids contained in sedimentary organic matter. Both the yellow part (idrialite) and brown part (amorphous organic matter) occur on the coexisting minerals (opalline silica, metacinnabar, and siderite); the textural relationship indicates that the organic matter precipitated after crystallization of the associated minerals. Thus, it is suggested that the organic molecules were migrated by hydrothermal fluids and then separated into hydrophobic (idrialite) and hydrophilic (amorphous organic matter) molecules during the cooling process. Following the separation, idrialite was crystallized and then the amorphous organic matter was precipitated at the final stage of the hydrothermal activity.

This study reports new spectroscopic and structural data of fibrous amphiboles from the volcanic area of Biancavilla (Sicily, Italy) that generated interest because of an anomalous increase of pleural mesothelioma of inhabitants. Each of the four samples is made of loose fibers, which show an edenite-winchite (fluorine) compositional trend, with significant tremolite component. Small amounts of iron (3.6-6.0 wt% FeOtot) were identified in all samples, and the Fe 3+ /Fe tot ratios were evaluated by Mössbauer spectroscopy: two samples are characterized by Fe 3+ /Fe tot ratios between 50 and 70%, and the other two have Fe 3+ /Fe tot ratios higher than 90%. The OH-stretching region was investigated by FTIR, and no absorption bands were observed. Structural investigation was carried out by X-ray powder diffraction using the Rietveld method. Cell parameters, positional parameters for all the atoms, and site scattering for M1, M2, M3, M4, A, and A(m) were refined. The most important differences with respect to prismatic fluoro-edenite are the decrease of β, a, and c with decreasing Ca content, A-site occupancy, and tetrahedral Al content, respectively. By combining chemical, spectroscopic, and structural data, possible site occupancies were obtained. In particular, it was found that Fe 2+ is distributed between M1 and M2 sites; moreover, for the two samples enriched in Fe 2+ , it is also present at M4. Fe 3+ is generally ordered at M2 site; however, for the two samples enriched in Fe 3+ , minor amounts are partially disordered between M1 and M3 sites. For the Biancavilla amphibole fibers, the large compositional variation observed in every sample makes the classification very difficult, so that the regulatory agencies would not classify as “asbestos” the whole mineral series, because of the large components of edenite and winchite in addition to tremolite. Many common features were found with respect to amphibole fibers from Libby, Montana, including Fe contents and oxidation state. Preliminary results of in vitro toxicological tests on Biancavilla fibers confirmed their high reactivity, and suggest that the samples with the highest Fe 2+ contents induce a rapid start to cell mortality.

The iron oxides hematite, magnetite, and goethite were studied with density functional theory to establish a consistent set of structures for both the bulk mineral and key surfaces, characterize surface relaxation, and predict and test calculated scanning tunneling microscopy (STM) images. Spinpolarized, plane-wave pseudopotential calculations were carried out on recognized terminations of the hematite (0001) and goethite (010) surfaces and on two terminations of magnetite (111), derived from bulk structures optimized with the same simulation parameters. In the bulk, geometry optimizations having different spin configurations were compared, to find that even without an on-site Coulomb correction, the expected spin states were found to have lowest energy: antiferromagnetic in hematite and goethite and ferrimagnetic in magnetite. However, magnetite shows a conducting minority spin. All four surfaces showed structural relaxation consistent with previous work. The ½-monolayer termination (octahedral and tetrahedral Fe) of magnetite (111) underwent slightly more relaxation than the ¼-monolayer termination, with consequently lower surface energy. A calculated STM image for ¼-monolayer magnetite is compared to an observed image at positive bias and suggests that the tetrahedral Fe dominates the image. STM images are predicted for hematite and goethite to aid interpretation of future experimental work.

Cr 3+ -bearing clinozoisite along the join Ca 2 Al 3 Si 3 O 12 (OH)-Ca 2 Al 2 Cr 3+ Si 3 O 12 (OH) was synthesized using cold-seal pressure vessels at P H ₂ O = 0.35 to 0.40 GPa and T = 500 °C and a piston-cylinder apparatus at P H ₂ O = 0.8 to 1.5 GPa and T = 500 to 800 °C. Gel-starting materials of Ca 2 Al 3-q Cr 3+ q Si 3 O 12.5 composition with q = 1.00, 0.75, 0.50, and 0.25 were employed to maximize the yields of clinozoisite. Mass fractions of clinozoisite in the experimental products with q = 0.50, 0.75, and 1 were about 70 to 90% along with lesser amounts of eskolaite, garnet, and quartz. Clinozoisite crystallized from the gel with q = 0.25 was associated only with zoisite. The crystal structures of clinozoisite in four runs, containing 0.28, 0.49, 0.50, and 0.62 Cr apfu were refined using X-ray powder diffraction data and the Rietveld method. The amount of Cr 3+ at the octahedral M3 and M1 sites ranged from 0.37(1)-0.16(1) to 0.25(1)-0.12(1) apfu, respectively. Corresponding K D = (Cr 3+ /Al) M1 /(Cr 3+ /Al) M3 values range between 0.57 and 0.73. The M2 site contained only Al. The KD values, and published results for intracrystalline partitioning in epidote and piemontite, show that the preference of Cr 3+ for M1 is stronger than that of Fe 3+ and Mn 3+ in spite of the fact that most Cr 3+ is partitioned into M3. Unit-cell parameters of clinozoisite increase with increasing Cr 3+ . Variations in macroscopic unit-cell parameters can be related to variations in the local M3-Oi and M1-Oi distances.

Kumtyubeite, Ca 5 (SiO 4 ) 2 F 2 -the fluorine analog of reinhardbraunsite with a chondrodite-type structure-is a rock-forming mineral found in skarn carbonate-xenoliths in ignimbrites of the Upper Chegem volcanic structure, Kabardino-Balkaria, Northern Caucasus, Russia. The new mineral occurs in spurrite-rondorfite-ellestadite zones of skarn. The empirical formula of kumtyubeite from the holotype sample is Ca 5 (Si 1.99 Ti 0.01 ) Σ2 O 8 (F 1.39 OH 0.61 ) Σ2 . Single-crystal X-ray data were collected for a grain of Ca 5 (SiO 4 )2(F 1.3 OH 0.7 ) composition, and the structure refinement, including a partially occupied H position, converged to R = 1.56%: monoclinic, space group P2 1 /a, Z = 2, a = 11.44637(18), b = 5.05135(8), c = 8.85234(13) Å, β = 108.8625(7)°, V = 484.352(13) Å 3 . For direct comparison, the structure of reinhardbraunsite Ca 5 (SiO 4 ) 2 (OH 1.3 F 0.7 ) from the same locality has also been refined to R = 1.9%, and both symmetry independent, partially occupied H sites were determined: space group P2 1 /a, Z = 2, a = 11.4542(2), b = 5.06180(10), c = 8.89170(10) Å, β = 108.7698(9)°, V = 488.114(14) Å 3 . The following main absorption bands were observed in kumtyubeite FTIR spectra (cm -1 ): 427, 507, 530, 561, 638, 779, 865, 934, 1113, and 3551. Raman spectra are characterized by the following strong bands (cm -1 ) at: 281, 323, 397 (ν 2 ), 547 (ν 4 ), 822 (ν 1 ), 849 (ν 1 ), 901 (ν 3 ), 925 (ν 3 ), 3553 (V OH ). Kumtyubeite with compositions between Ca 5 (SiO 4 ) 2 F 2 and Ca 5 (SiO 4 ) 2 (OH 1.0 F 1.0 ) has only the hydrogen bond O5-H1···F5′, whereas reinhardbraunsite with compositions between Ca 5 (SiO 4 ) 2 (OH 1.0 F 1.0 ) and Ca 5 (SiO 4 ) 2 (OH) 2 has the following hydrogen bonds: O5-H1···F5′, O5-H1···O5′, and O5-H2···O2.

The liquidus temperatures of the Skaergaard intrusion can be estimated for the layered series from plagioclase compositions. Plagioclase saturation in one-atmosphere melting experiments on evolved North Atlantic basalts is a function of An content (mol%) and can be described by an empirical linear relationship [T (°C) = 899 + 3.6 An; 1σ = 20 °C]. This relationship predicts a total crystallization interval for the intrusion of ~150 °C. Plagioclase crystallized in the Hidden Zone (An 71 ) at 1155 °C, at the base of the Lower Zone (An 66 ) at 1137 °C, and finally in the Sandwich Horizon (An 30 ) at 1007 °C. These temperatures are in good agreement with previous estimates based on melting studies of suitable chilled margin rocks and gabbros from the Skaergaard intrusion and liquid line of descent modeling. Our temperature estimates, however, are markedly lower (by up to 60 °C) than recent temperature estimates based on an extrapolation of high-pressure experimental data for the Kiglapait intrusion to Skaergaard emplacement conditions. Proposed variations in magmatic pressure during Skaergaard evolution and reasonable estimates of magmatic water contents do not alter these conclusions.

There are many challenges associated with collecting, processing, and interpreting high-energy XAS data. The most significant of these are broad spectra, minimal separation of edge positions, and high background owing to the Compton tail. Studies of the Sb system are a particular challenge owing to its complex bonding character and formation of mixed oxidation-state minerals. Furthermore, in environmental samples such as stream sediment containing mine waste, different Sb phases may coexist. Ways to overcome these challenges and achieve accurate and useful information are presented. Our investigations used Sb K-edge X-ray absorption near-edge spectroscopy (XANES) to elucidate Sb geochemical behavior. Several Sb mineral spectra are presented, including Sb sulfosalts, and contrasted based on the different hosting and coordination environments around the Sb atom in the crystal structure. These comparisons lead to the recognition of how the different hosting and coordination environments are manifested in the shape of the Sb mineral spectra. In fact from the shape of the spectra, the occupation of the Sb atom in a single or in multiple crystallographic sites, regardless of whether multiple phases are present in the sample, is discernible. Furthermore, we demonstrate that quantitative information can be derived from the XANES region using linear combination fitting of the derivative spectra, rather than the energy spectra. Particularly useful to the advancement of Sb research is the demonstration that a significant amount of information can be gained from the Sb K-edge XANES region.

The γ-tricalcium phosphate phase (γ-TCP), γ-Ca 3 (PO 4 ) 2 , is a high-pressure polymorph of tricalcium phosphate with a potential important implication as the reservoir of rare-earth elements and very large lithophile elements in the deep mantle. In situ synchrotron X-ray diffraction measurements of the γ-TCP phase have been carried out using a diamond-anvil cell to 40.29 GPa at room temperature, with a methanol-ethanol mixture as the pressure medium. The pressures in the measurements have been determined by using gold metal as the internal pressure calibrant. The third-order Birch-Murnaghan equation of state fitted to the experimentally defined unit-cell parameters suggests for the γ-TCP phase a density of ρ 0 = 3.461(1) g/cm 3 , an isothermal bulk modulus of K T = 100.2(13) GPa, and first pressure derivative of K′ T = 5.48(16). When K′ T is fixed at 4, the derived K T is 113.1(12) GPa.

We investigate the effect of the lattice topology (ideal hexagonal rings vs. ditrigonal rings) and cluster size of model clusters (three-ring vs. seven-ring clusters) on the nature of benzyl alcohol adsorption on kaolinite surfaces using quantum chemical calculations with an emphasis on the equilibrium configuration, binding energy, and NMR chemical shielding tensors. The optimized structure of benzyl alcohol adsorbed on the tetrahedral layer of kaolinite varies according to the type and size of model cluster. While the calculated binding energy varies with the level of theory and the basis sets used for the calculations, the binding energies between benzyl alcohol and seven-ring clusters are smaller than those between benzyl alcohol and three-ring clusters partly due to the edge hydrogen for the latter. The results also indicate a stronger binding energy between benzyl alcohol and octahedral surfaces than between benzyl alcohol and tetrahedral layers. Although the calculated binding energies for seven-member rings with varying lattice topologies are rather similar, the detailed optimized structures are distinct, demonstrating the effect of lattice topology on the nature of adsorption. The optimized structures and binding energies indicate that an intermediate degree of hydrogen bonding is dominant for the three-member silicate rings and that the interaction between the benzene ring and basal O atoms in the seven-member rings is characterized by a weak hydrogen bond and dispersion force. The calculated 17 O isotropic chemical shieldings of some basal O atoms decrease up to ~4-5 ppm after the adsorption (with an estimated uncertainty of ~2 ppm). Since the high-resolution 17 O 3QMAS NMR spectroscopy of layer silicates yielded a resolution of 1-2 ppm for the basal oxygen sites in the layer silicates in previous work, the NMR technique may be useful in exploring the nature of adsorption between organic molecules and silicate surfaces, whereas further computational studies on the effect of the basis sets, the surface coverage, and the types of diverse organic molecules with larger model clusters for surfaces remain to be explored.

The crystal structure of a naturally occurring pyrrhotite from the Copper Cliff North Mine, Sudbury, Canada, has been determined in the space group Cmce (formerly Cmca), and the positions and occupancy of the Fe and S atoms have been refined, together with their anisotropic atomic displacement parameters, to a conventional R value of 0.072. The summed occupancies of the Fe and Ni atoms [8.908 (Fe + Ni) per 10 S] are compared with the chemical composition, as determined by microprobe analysis, the latter giving a formula of Fe 8.892 Ni 0.115 S 10 or 9.007 (Fe + Ni) per 10 S. The structure has cell dimensions of a = 6.893(3) Å, b = 11.939(3) Å, and c = 28.63(1) Å. The S atoms are hexagonally close packed and adjacent Fe-S octahedra share faces that are perpendicular to the c direction. The Fe atoms in adjacent face-sharing octahedra also have the closest Fe-Fe interatomic distances. Some Fe atoms have partial occupancies, and together with the fully occupied sites, they add up to 71.26 (Fe + Ni) atoms per 80 S atoms in the unit cell, as compared with 72 atoms per 80 S atoms for Fe 9 S 10 . The distribution of Fe in the partially occupied layers is different from that previously postulated for Fe 9 S 10 , with vacant sites present in two of the 10 layers. The partially occupied Fe sites are present in all the remaining cation layers, and there are therefore no cation layers containing completely filled atomic sites. Space group symmetry constrains the partially occupied cation sites to project on top of each other along the c axis, similar to the distribution of partially occupied sites in Fe 11 S 12 (6C pyrrhotite).

We calculate here the basal peak profiles of Na-rectorite (regularly interstratified Na-illite-smectite) with two different scattering origin choices, one based on the octahedral cationic plane and the other on the basal oxygen plane of the tetrahedral sheet. Our calculation shows that the scattering origin of the octahedral cationic plane, which has been often used in previous diffraction models, is ineffective for profiling the measured peak skewness and irrationality. Alternatively, the calculation using the scattering origin of the basal oxygen plane better mimics the measured peak profiles and provides more reliable crystallite thickness distributions for Bertaut-Warren-Averbach analyses. This origin is also useful for demonstrating the scattering sequence, the layer chemistry heterogeneity, and the effect of the crystallite margin on rectorite scattering.

This work presents a comparative study of Roman and modern slags, which represent the same type of mining waste but which were produced at vastly different times. The natural laboratory in which both materials are found is São Domingos, one of the most emblematic of Portuguese mining districts in the Iberian Pyrite Belt (IPB). The methodology included: (1) detailed studies of the mineralogy and geochemistry of both materials with a reflected-light optical microscope, scanning electron microscope (SEM), electron microprobe analyses (EMPA), and bulk-rock analyses; (2) MELTS thermodynamic software to quantitatively test fractional crystallization of both glassy matrix types; (3) TWQ-v. 2.32 software for performing internally consistent thermometric calculations; and (4) a modified Community Bureau of Reference (BCR)-sequential extraction procedure applied to the chemical speciation of potentially toxic elements. The combination of petrologic studies and sequential extraction leaching may be used to evaluate and predict pollution impact on the environment. We conclude that a 2000 year time gap has not produced an important modification to the base-metal extraction system as reflected by the petrologic similarity of both slags and that, considering the total mass of modern slags, the transfer rate of metals to the environment over the next 2000 years will be ~6.7 t/year of Fe, 1 t/year of S, 81.1 kg/year of Zn, 55.5 kg/year of Pb, 6.5 kg/year of Cu, 0.7 kg/year of As, 31.2 g/year of Sb, and 18.3 g/year of Cr. The results demonstrate the pollutant potential of the slags within this IPB mining district as revealed by the spoiled state of the fluvial courses in the region.

Ferrihydrite is a key reactive nanoparticle in the Earth surface environment that regulates nutrient and metal cycling in marine, lacustrine, and groundwater settings; yet its genesis is unknown and there is no mechanistic explanation of its nanostructural nature. We develop a model, based on established aqueous precipitation theory, for rough-surface phases growing by accretion of monomers under fast diffusion conditions. The model is entirely defined in terms of a minimal set of necessary microscopic (molecular-scale) characteristic parameters. It is applied to ferrihydrite where the needed microscopic parameters are constrained by some of the mineral’s known physico-chemical properties. Our model qualitatively reproduces the main nanostructural properties and known precipitation kinetics of ferrihydrite, predicting that ferrihydrite will be nanometric in size, will have a narrow particle size distribution (standard deviation width equal to a fraction of the average particle size), and will typically precipitate from supersaturated conditions within times ranging from a fraction of a second to several days, under normal environmental-proxy conditions. The model also suggests that different metastable structures of ferrihydrite having similar rough surfaces would kinetically compete during nucleation and growth to coexist in the final product, as observed by Janney et al. (2000a, 2001).

The crystal chemistry of sursassite, simplified formula Mn 2+ 2 Al 3 Si 3 O 11 (OH) 3 , from six different localities [(1) Falotta, Switzerland, (2) Woodstock, New Brunswick, Canada, (3) Kamisugai, Japan, (4) Kamogawa, Japan, (5) Molinello, Italy, and (6) Gambatesa, Italy] was studied using electron microprobe analysis (EMPA), Fourier transform infrared spectroscopy (FTIR), and single-crystal X-ray diffraction methods. The structure has two symmetry independent Mn sites. The Mn1 site is seven coordinated by O and hosts, in addition to Mn 2+ , up to 20% Ca, whereas Mn2 has octahedral coordination and is strongly selective for Mn 2+ . In the simplified formula, three smaller octahedral M sites are occupied by Al. However, M1 also accepts significant amounts of divalent cations, such as Cu, Mg, Fe, and Mn, whereas M2 is occupied exclusively by Al. The unit-cell parameters of sursassite are a = 8.698-8.728, b = 5.789-5.807, c = 9.778-9.812 Å, β = 108.879-109.060°, V = 465.7-470.0 Å 3 , the space group is P2 1 /m. Structure refinements converged to R1 values of 2.15-6.62%. In agreement with bond-valence analyses, at least three OH groups, depending on the concentration of divalent cations at M1, are found at the O6, O7, and O11 positions. However, the bond-valence sum at O10 is always low, thus partial hydroxylation is assumed at O10 to maintain charge balance. Owing to the influence of divalent cations at M1 in sursassite the hydrogen-bond systems in sursassite and isostructural macfallite are different. The FTIR spectrum in the region of OH-stretching vibrations is characterized by three strong bands at 3511, 3262, and around 2950 cm -1 , the latter being broad. The band at 2950 cm -1 is assigned to strong hydrogen bonds between O6 and O10 (O6···O10 = 2.66 Å). Residual difference-Fourier peaks in the refinement of the Kamogawa and Molinello (specimen 1) crystals indicated less than 5% pumpellyite intergrowth.

Ivanyukite-Na-T, Na 3 [Ti 4 (OH)O 3 (SiO 4 ) 3 ]·7H 2 O, ivanyukite-Na-C, Na 2 [Ti 4 O 2 (OH) 2 (SiO 4 ) 3 ]·6H 2 O, ivanyukite-K, K 2 [Ti 4 (OH) 2 O 2 (SiO 4 ) 3 ]·9H 2 O, and ivanyukite-Cu, Cu[Ti 4 (OH) 2 O 2 (SiO 4 ) 3 ]·7H 2 O, are new microporous titanosilicates found in a natrolitized microcline-aegirine-sodalite lens in the orthoclase-bearing urtite at the Koashva Mountain (Khibiny Massif, Kola Peninsula, Russia). The minerals occur as well-shaped colorless (ivanyukite-Na-T), paleorange (ivanyukite-Na-C), pale-blue (ivanyukite-K), and green (ivanyukite-Cu) cubic crystals (up to 1.5 mm in diameter) grown on microcline, vinogradovite, sazykinaite-(Y), natrolite, and djerfisherite. The minerals have vitreous luster and white streak. They are transparent and non-fluorescent. The Mohs hardness is estimated as ~4. The minerals are brittle. Cleavage is perfect on {100} (ivanyukite-Na-C, ivanyukite-K, and ivanyukite-Cu) or on {1011} (ivanyukite-Na-T), fracture is stepped. Density, measured by the sink/float method in heavy liquids, ranges from 2.60 (ivanyukite-Na-C) to 2.70 g/cm 3 (ivanyukite-Na-T, ivanyukite-K, and ivanyukite-Cu), whereas calculated densities are: 2.58 (ivanyukite-Na-T), 2.39 (ivanyukite-Na-C), 2.69 (ivanyukite-K), and 2.46 g/cm 3 (ivanyukite- Cu). Ivanyukite-Na-T is uniaxial (+), n ω = 1.76(1), n ε = 1.85(9) (589 nm), and the other minerals are isotropic, n = 1.73(1). Chemical analysis by electron microprobe gave (wt% for ivanyukite-Na-T, ivanyukite-Na-C, ivanyukite-K, and ivanyukite-Cu, respectively): Na 2 O 7.46, 5.19, 0.27, and 0.17; Al 2 O 3 0.07, 0.21, 0.18, and 0.07; SiO 2 23.75, 25.47, 23.16, and 24.80; SO 3 0.00, 0.00, 0.00, and 0.20; K 2 O 5.89, 6.34, 7.09, and 6.81; CaO 0.21, 0.14, 0.95, and 0.23; TiO 2 38.89, 37.81, 36.14, and 38.36; MnO 0.05, 0.33, 0.68, and 0.28; FeO 0.54, 2.17, 0.37, and 0.73; CuO 0.00, 0.00, 2.21, and 6.81; SrO 0.00, 0.00, 0.19, and 0.00; Nb 2 O 5 2.99, 2.90, 3.62, and 3.02; BaO 0.14, 0.00, 0.00, and 0.00; H 2 O (by the Penfield method) 19.00, 19.15, 25.00, and 21.50; total 98.99, 99.71, 99.86, and 98.97. The empirical formulae (based on Si+Al = 3 apfu) are (Na 1.82 K 0.95 Ca 0.03 Ba 0.01 ) Σ2.81 [(Ti 3.68 Nb 0.17 Fe 0.06 Mn 0.01 ) Σ3.92 (Si 2.99 Al 0.01 ) Σ3.00 O 14.59 (OH) 1.37 ]·7.29H 2 O (ivanyukite-Na-T), (Na 1.17 K 0.94 Ca 0.03 ) Σ2.14 [(Ti 3.32 Fe 0.21 Nb 0.15 Mn 0.03 ) Σ3.71 (Si 2.97 Al 0.03 ) Σ3.00 O 12.89 (OH) 2.87 ]·6.01H 2 O (ivanyukite-Na-C), (K 1.16 Cu 0.21 Ca 0.13 Na 0.07 Sr 0.01 ) Σ1.58 [(Ti 3.49 Nb 0.21 Mn 0.07 Fe 0.04 ) Σ3.81 (Si 2.97 Al 0.03 ) Σ3.00 O 13.19 (OH) 2.75 ]·9.32H 2 O (ivanyukite-K), and (Cu 0.62 K 0.43 Na 0.04 Ca 0.03 ) Σ1.12 [(Ti 3.48 Nb 0.16 Fe 0.07 Mn 0.03 ) Σ3.74 (Si 2.99 Al 0.01 ) Σ3.00 O 12.88 (OH) 2.88 (SO 4 ) 0.02 ]·7.21H 2 O (ivanyukite-Cu). Ivanyukite-Na-T is trigonal, R3m, a = 10.94(2), c = 13.97(4) Å, Z = 3. Other minerals are cubic, P4̅3m a = 7.856(6) (ivanyukite-Na-C), 7.808(2) (ivanyukite-K), and 7.850(7) Å (ivanyukite-Cu); Z = 1. The strongest lines in the powder X-ray diffraction pattern [d bs (Å) (I obs ) hkl] are: 7.88(100) (011), 3.277(60)(014), 3.175(80)(212), 2.730(50)(220), 2.607(70)(303), 2.471(50)(124), 1.960(60)(044), 1.916(50) (135) (ivanyukite-Na-T); 7.88(100)(100), 4.53(30)(111), 3.205(80)(211), 2.774(30)(220), 2.622(40)(221, 300), 2.478(40)(310), 1.960(30)(400), 1.843(30)(330, 411) (ivanyukite-Na-C); 7.85(100)(100), 3.91(20)(200), 3.201(80) (211), 2.765(20)(220), 2.602(30)(221, 300), 2.471(40)(310), 1.951(30)(400), 1.839(30)(330, 411) (ivanyukite-K); 7.87(100)(100), 3.94(20)(200), 3.205(80)(211), 2.774(20)(220), 2.616(30)(221, 300), 2.481(30)(310), 1.960(30) (400), 1.843(30)(330, 411) (ivanyukite-Cu). The crystal structure of ivanyukite-Na-T [trigonal, R3m, a = 10.921(3), c = 13.885(4) Å, V = 1434.2(7) Å 3 ] has been solved from highly mosaic crystal and refined to R1 = 0.147 on the basis of 723 unique observed reflections. The crystal structures of ivanyukite-group minerals are based upon a 3-dimensional framework of the pharmacosiderite type, consisting of four edge-sharing TiO 6 -octahedra interlinked by SiO 4 tetrahedra. The framework has a 3-dimensional system of channels defined by 8-membered rings with an effective channel width of 3.5 Å (calculated as the distance between O atoms across the channels minus 2.7 Å). The channels are occupied by Na + and K + cations and H 2 O molecules. The infrared spectra of the ivanyukite group minerals show 14 absorption bands caused by vibrations of Si-O and Ti-O bonds, molecular water, and (OH) - groups. Ivanyukite-Na-T formed as a late-stage, hydrothermal phase of ultra-agpaitic hydrothermalites; ivanyukite-Na-C is produced by partial hydration of ivanyukite-Na-T, and both ivanyukite-K and ivanyukite-Cu are produced by partial hydration of ivanyukite-Na-T and natural cation exchange of Cu for Na near dissolved djerfisherite and chalcopyrite grains. Nomenclature of the ivanyukite group is based on the dominant extraframework cation and symmetry of the crystal structure. The minerals are named in honor of Gregory Yur’evich Ivanyuk, Russian mineralogist and petrologist, head of the Laboratory of Self-Organized Mineral Systems in the Geological Institute of the Kola Science Centre of the Russian Academy of Sciences, for his contributions to the petrology and mineralogy of banded iron-formations, alkaline, and alkaline-ultrabasic massifs.

Spinel is often used as a magmatic indicator of crystallization processes, without considering the effects of metamorphic alteration on spinel geochemical features. Serpentinized mélanges in the southern Urals host different kinds of disseminated to massive chromitite mineralization. In mélange environments, intense metamorphic alteration above 300 °C leads to major changes in chromite chemistry and to the growth of secondary phases such as ferritchromite and chromian-chlorite. Based on textural and chemical analyses, mélange-hosted Kalkan chromitites exhibit a hydration and oxidation reaction that can explain the formation of ferritchromite and chromian-chlorite from chromite and serpentine: Textural analyses fit well with the proposed reaction and show that it usually proceeds very close to completion. The degree of alteration of chromite into ferritchromite is controlled by the initial chromite to serpentine ratio. In chromitites, high ratios prevent complete transformation of chromite into ferritchromite. The most likely environment for such reaction is a prograde metamorphic event post-dating serpentinization of the Kalkan ophiolite, possibly related to emplacement within an accretionary wedge.

The Alamo Complex consists of structural-metamorphic domes surrounded by low-grade metasedimentary rocks of Upper Proterozoic to Lower Cambrian age that form part of the Schist Graywacke Complex (Central Iberian Zone, Spain). Tourmaline is ubiquitous throughout the domes, in which it occurs in tourmalinites, psammo-pelitic schists, quartzites, gneisses, migmatites, leucogranites, aplo-pegmatites, and quartz veins. Overall, tourmaline compositions can be described within the four component system schorl-dravite-foitite-magnesiofoitite, with K 2 O < 0.23%, low Ca contents, Mg/(Mg+Fe) = 0.25-0.71 and X/(X+Na) = 0.18-0.43, where X = vacancies in the X site. Field relations and petrographic observations, combined with tourmaline 40 Ar/ 39 Ar data, provide evidence of intense boron metasomatism affecting this region. Tourmaline 40 Ar/ 39 Ar step-heating spectra for Cambrian-Ordovician orthogneisses are complex, yielding a pseudo-plateau age of ~370 Ma that is interpreted to reflect Variscan rejuvenation of older tourmaline. Tourmaline 40 Ar/ 39 Ar data for mylonitized and folded tourmalinites yield disturbed spectra with pseudo-plateau ages of ~355-342 Ma that are unsuitable for precise age determination. These ages, however, are consistent with published ages (340-350 Ma) for the second Variscan deformation (D 2 ). Tourmaline from fine-layered tourmalinite and metasedimentary rocks yield well-defined plateau ages of 317 and 315 Ma, respectively, recording an additional metasomatic event concomitant with anatexis and evolution of B-bearing granites, pegmatites, and hydrothermal fluids. The different tourmaline-forming stages reflect significant boron cycling within the continental crust of the Central Iberian Zone, driven by deformation, metamorphism, and magmatism during the Variscan orogeny. Boron-rich aqueous fluids related to Cambro-Ordovician magmatism are considered to be the primary source of boron.

The new mineral kushiroite, belonging to the pyroxene group, was first discovered in a refractory inclusion in the CH group carbonaceous chondrite ALH 85085. The chemical formula is Ca 1.008 (Mg 0.094 Fe 0.034 Al 0.878 )(Al 0.921 Si 1.079 )O 6 , containing 88% CaAlAlSiO 6 and 12% diopside components. We identified the exact nature of kushiroite by micro-Raman spectroscopy and electron backscatter diffraction (EBSD) analyses. The results are consistent with those obtained from the synthetic CaAlAlSiO 6 pyroxene, thus indicating a monoclinic structure (space group C2/c). Although CaAlAlSiO 6 has been one of the most important hypothetical components of the pyroxene group, it is here for the first time established to be a naturally occurring mineral. We named this pyroxene with >50% CaAlAlSiO 6 component kushiroite, which was recently approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA2008- 059). The name is for Ikuo Kushiro, Professor Emeritus at the University of Tokyo, Japan, and eminent experimental petrologist, for his outstanding experimental investigations on silicate systems involving the Ca-Tschermak component. There is no obvious evidence for impact in this inclusion. We suggest that metastable crystallization of this pyroxene took place from refractory melts in the solar nebula. Coexisting grossite-bearing refractory inclusions in the type specimen ALH 85085 show 26 Mg excesses with inferred initial 26 Al- 27 Al ratios between 2.1 × 10 -6 to 3.9 × 10 -5 , providing evidence that condensation, melting, and crystallization took place in the solar nebula when 26Al was still extant.

Calcium Tschermak’s pyroxene (CaTs), CaAlAlSiO 6 , is well known as an important component in pyroxene. It is a member of the Ca clinopyroxene group in which Al dominates in the M1 site. Pyroxenes with more than 80 mol% CaTs were observed previously in Ca-,Al-rich refractory inclusions (CAI) from five carbonaceous chondrites. This study re-investigated the near end-member CaTs in the Allende and Murray chondrites. Electron backscatter diffraction (EBSD) is used to establish that its crystal structure is monoclinic, C2/c; a = 9.609 Å, b = 8.652 Å, c = 5.274 Å, β =106.06°, V = 421.35 Å 3 , and Z = 4. Its EBSD pattern is an excellent match to that of synthetic CaAlAlSiO 6 with the C2/c structure. MicroRaman is also carried out to confirm the crystal structure. The Allende CaTs, with 46.00 wt% Al 2 O 3 and 97 mol% Al in the M1 site, has the formula Ca 1.02 (Al 0.97 Fe 0.01 Mg 0.01 ) Σ0.99 (Si 1.00 Al 1.00 ) Σ2.00 O 6 . It occurs as micrometer-sized crystals along with melilite, hibonite, perovskite, spinel, corundum, Ti 3+ -rich pyroxene, and grossular in a fluffy Type A CAI. It is probably a secondary phase resulting from the alteration of gehlenitic melilite. The CaTs in Murray, with a formula Ca 0.98 (Al 0.81 Mg 0.16 Ti 4+ 0.04 ) Σ1.01 (Si 1.11 Al 0.89 ) Σ2.00 O 6 , occurs with hibonite and Al-rich diopside in a glass-free refractory spherule. This sample formed by solidification of a once-molten droplet early in the history of the solar system.

A series of X-ray absorption spectroscopy (XAS) experiments were made to determine the structure and stability of aqueous REE (La, Nd, Gd, and Yb) chloride complexes to 500 °C and 520 MPa. The REE 3+ ions exhibit inner-sphere chloroaqua complexation with a steady increase of chloride coordination with increasing temperature in the 150 to 500 °C range. Furthermore, the degree of chloride coordination of REE 3+ inner-sphere chloroaqua complexes decreases significantly from light to heavy REE. These results indicate that steric hindrance drives the reduction of chloride coordination of REE 3+ inner-sphere chloroaqua complexes from light to heavy REE. This results in greater stability and preferential transport of light REE 3+ over heavy REE 3+ ions in saline hydrothermal fluids. Accordingly, the preferential mobility of light REE directly influences the relative abundance of REE in rocks and minerals and thus needs to be considered in geochemical modeling of petrogenetic and ore-forming processes affected by chloride-bearing hydrothermal fluids.

Grossmanite, Ca(Ti 3+ ,Mg,Ti 4+ )AlSiO 6 with an end-member formula CaTi 3+ AlSiO 6 , is a new member of the Ca clinopyroxene group, where the trivalent cations are dominant in the M1 site with Ti 3+ being the dominant trivalent cation. It occurs as micrometer-sized crystals along with spinel and perovskite in a melilite host in Ca-,Al-rich refractory inclusions from the Allende meteorite. The mean chemical composition determined by electron microprobe analysis of the type material is (wt%) SiO 2 27.99, Al 2 O 3 24.71, CaO 24.58, Ti 2 O 3 10.91, TiO 2 6.68, MgO 4.45, Sc 2 O 3 0.43, V 2 O 3 0.19, ZrO 2 0.13, FeO 0.08, Cr 2 O 3 0.03, sum 100.20. Its empirical formula calculated on the basis of 6 O atoms is Ca 1.00 [(Ti 3+ 0.35 Al 0.18 Sc 0.01 V 3+ 0.01 ) Σ0.55 Mg 0.25 Ti 4+ 0.19 ] Σ1.00 (Si 1.07 Al 0.93 ) Σ2.00 O 6 . Grossmanite is monoclinic, C2/c; a = 9.80 Å, b = 8.85 Å, c = 5.36 Å, β = 105.62°, V = 447.70 Å 3 , and Z = 4. Its electron back-scatter diffraction pattern is an excellent match to that of Ti 3+ -rich pyroxene with the C2/c structure. The five strongest calculated X-ray powder diffraction lines are [d spacing in Å, (I), hkl] 2.996 (100) (2̅21), 2.964 (31) (310), 2.581 (42) (002), 2.600 (28) (1̅31), 2.535 (47) (221). The name is for Lawrence Grossman, a cosmochemist at the University of Chicago.