The crystal structure of carminite, PbFe2(AsO4)2(OH)2 has been refined. The mineral is orthorhombic, Cccm with a = 16.591(2), b = 7.580(1), c = 12.285(1) Å, Z = 8; the structure has been refined to a conventional R = 3.3% using 913 observed reflections [I>2σ(I)]. The structure contains stepped chains of edge-sharing pairs of Fe(O,OH)6 octahedra; these chains are linked by AsO4 tetrahedra and Pb atoms in distorted square antiprismatic co-ordination. The hydrogen bonding network in the structure has been modelled using bond valence calculations.

The crystal structure of hügelite, Pb2[(UO2)3O2(AsO4)2](H2O)5, monoclinic, space group P21/m, a= 31.066(3)Å, b= 17.303(2)Å, c= 7.043(1)Å, β = 96.492(2)°, V= 3761.6(1)Å3, Z= 8, Dcalc = 5.74 g/cm3, was solved by direct methods using data from a crystal twinned by pseudo-merohedry, and was refined by full-matrix least-squares techniques on the basis of F2 to agreement indices R1 of 3.3% calculated for 5519 unique observed reflections (|Fo| 5 ≥ 4σF), and wR2 of 6.7% for all data. Intensity data were collected at room temperature using Mo-Kα radiation and a CCD-based area detector. Hügelite is a member of the phosphuranylite group and is the arsenate counterpart of dumontite. The sheets of uranyl pentagonal and hexagonal bipyramids and arsenate tetrahedra in hügelite are oriented parallel to (100), and the interlayer contains four symmetrically independent Pb atoms, each of which is coordinated by two oxygen atoms from uranyl ions, two oxygen atoms from arsenate tetrahedra, and three symmetrically distinct H2O groups. The unit-cell volume is four times larger than that previously reported for hügelite, or expected by comparison to dumontite, Pb2[(UO2)3O2(PO4)2](H2O)5; the larger cell probably results from the accommodation of the larger As atoms (relative to P) in the structure, and consequent subtle variations in the coordination geometries of the U and Pb positions.

In recent years it has become apparent that the novel properties of nanomaterials may predispose them to a hitherto unknown potential for toxicity. A number of recent toxicological studies of nanomaterials exist, but these appear to be fragmented and often contradictory. Such discrepancies may be, at least in part, due to poor description of the nanomaterial or incomplete characterization, including failure to recognise impurities, surface modifications or other important physicochemical aspects of the nanomaterial. Herew em ake a casef or the importance of good quality, well-characterized nanomaterials for future toxicological studies, combined with reliable synthesis protocols, and we present our efforts to generate such materials. The model system for which we present results is TiO2 nanoparticles, currently used in a variety of commercial products.

Some zircons from the Hercynian Soultz granite, NE France, exhibit complex structures, with double cores and oscillatory-banded overgrowths. These glomeroporphyritic crystals are uncommon for zircons, in which synneusis has not previously been described. The cores of the zircons are considered to correspond to very quickly formed {100} or {110} prisms. These could slowly sediment in the magma chamber and cluster together while sinking. The overgrowth rims correspond to a slower growth rate.

U/Pb ion-probe dating of the cores and the overgrowth rims provided the same age of 327±6 Ma. Chemical electron microprobe analyses indicated that cores and rims have the same composition for major and trace elements.

The sinking of zircons accounts for the abnormally high percentages of zircon in the lower parts of the granite. The formation of clusters in the early stages of crystallization needs stable P/T conditions, a hot, liquid silicate melt with a high fluid content, and no other minerals crystallizing (liquidus phase).

The cerite supergroup is established and includes the cerite group (silicates) and merrillite group (phosphates). Cerite-group minerals are cerite-(Ce), ferricerite-(La), aluminocerite-(Ce) and taipingite-(Ce). The merrillite group is subdivided into two subgroups: merrillite (merrillite, ferromerrillite, keplerite and matyhite) and whitlockite (whitlockite, strontiowhitlockite, wopmayite and hedegaardite). Cerite-(La) has been renamed ferricerite-(La). The new nomenclature has been approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification.

Phase relations in the binary system anorthite-K-feldspar at 10 kbar were studied with a solid-media piston cylinder apparatus. The eutectic character of this system is confirmed, with the eutectic point located at An30Kf70 (± 3 mol%), and 1215 ± 15°C, 10 kbar. The mutual solubilities between anorthite and K-feldspar at the solidus are greatly increased at 10kbar compared with those at 1 atm. The maximum solubility of K-feldspar in anorthite is c. 5% at 1 atm, c. 18% at 10 kbar; and that of anorthite in K-feldspar is c. 3% at 1 atm, c. 7% at 10 kbar. The increased solubilities are attributed to the increase in the eutectic temperature at high isostatic pressures. The results imply increased ternary feldspar solid solutions at high pressures and support the existence of homogeneous feldspars with extensive ternary composition under high-P, T and anhydrous conditions.

Insizwaite from Waterfall Gorge, Insizwa, is a new mineral with the composition Pt1·00Bi1·35Sb0·57. The name is for the locality and is to be applied to the end member PtBi2. The analysed material is an antimonian variety. The mineral is cubic, the unit-cell for the antimonian variety has a 6·625 (2) Å, probable space group Pa3, calc. D 12·8 g/cm3. The strongest lines on the X-ray diffraction powder pattern are: 2·96 (8) 210; 2·70 (8) 211; 2·34 (5) 220; 1·99 (10 311; 1·774 (7) 321; 1·433 (5) 421; 1·277 (6) 511, 333; 1·171 (6) 440; and 0·862 (7) 731. Under reflected light the mineral is white (in air and in oil) and is isotropic. Reflectance measurements at 470, 546, 589, and 650 nm gave 61·1, 60·0, 60·6, and 61·7 %. Micro-indentation hardness values range from 488 to 540 (av. 519) kg/mm2 with a 25 g load.

New data are presented for niggliite from the type locality and for synthetic PtSn.

The crystal structure of tlapallite has been determined using single-crystal X-ray diffraction and supported by electron probe micro-analysis, powder diffraction and Raman spectroscopy. Tlapallite is trigonal, space group P321, with a = 9.1219(17) Å, c = 11.9320(9) Å and V = 859.8(3) Å3, and was refined to R1 = 0.0296 for 786 reflections with I > 2σ(I). This study resulted from the discovery of well-crystallised tlapallite at the Wildcat prospect, Utah, USA. The chemical formula of tlapallite has been revised to (Ca,Pb)3CaCu6[Te4+3Te6+O12]2(Te4+O3)2(SO4)2·3H2O, or more simply (Ca,Pb)3CaCu6Te4+8Te6+2O30(SO4)2·3H2O, from H6(Ca,Pb)2(Cu,Zn)3(TeO3)4(TeO6)(SO4). The tlapallite structure consists of layers containing distorted Cu2+O6 octahedra, Te6+O6 octahedra and Te4+O4 disphenoids (which together form the new mixed-valence phyllotellurate anion [Te4+3Te6+O12]12−), Te4+O3 trigonal pyramids and CaO8 polyhedra. SO4 tetrahedra, Ca(H2O)3O6 polyhedra and H2O groups fill the space between the layers. Tlapallite is only the second naturally occurring compound containing tellurium in both the 4+ and 6+ oxidation states with a known crystal structure, the other being carlfriesite, CaTe4+2Te6+O8. Carlfriesite is the predominant secondary tellurium mineral at the Wildcat prospect. We also present an updated structure for carlfriesite, which has been refined to R1 = 0.0230 for 874 reflections with I > 2σ(I). This updated structural refinement improves upon the one reported previously by refining all atoms anisotropically and presenting models of bond valence and Te4+ secondary bonding.

MnxZn(1−x)CO3 solid-solutions were prepared at 5°C by precipitation from metal-bearing bicarbonate solutions. The solids were identified by X-ray powder diffraction and infrared spectroscopy. Zn2+ ions substitute extensively for Mn2+ ions in the crystal lattice of anhydrous rhombohedral carbonates. Throughout the 24 h during which the experiments were conducted, the aqueous solutions remained undersaturated with respect to pure oxides, sulphates, hydroxides and hydroxysulphates. The solutions, however, were supersaturated with MnxZn(1−x)CO3 of any given composition. Besides the anhydrous rhombohedral carbonates, Zn4(OH)2(CO3)3·4H2O was precipitated from an aqueous solution with initially high Zn2+ concentration. The negative logarithm of the solubility product of Zn4(OH)2(CO3)3·4H2O was estimated theoretically to be 43.9 (25°C). Remaining saturation with respect to Zn4(OH)2(CO3)3·4H2O was calculated accordingly. The suggestion is made that hydrated zinc hydroxycarbonate is metastable under the experimental conditions used here, but that it should transform into anhydrous carbonates.

The chemical formula of fiedlerite, a rare hydrated lead halide, has been revised. The mineral is now known to contain also fluorine, and the new, correct formula is Pb3Cl4F(OH)·H2O. X-ray diffraction studies on fiedlerite from Laurion, Greece (the type locality), and from Baratti, Italy (the second known occurrence), revealed its Order-Disorder (OD) character. All structures within this OD family can be built up by layers of the same kind. The two polytypes with Maximum Degree of Order (MDO) display triclinic and monoclinic symmetry, with one and two OD layers, respectively, in the unit cell. On these grounds the nomenclature of fiedlerite has been revised, and the mineral is designated together with the polytype suffix (i.e. fiedlerite-1A, fiedlerite-2M). The crystal structures of the two MDO polytypes of fiedlerite have been solved and refined: fiedlerite-1A: P, a = 8.574(3) Å, b = 8.045(4), c = 7.276(2), α = 89.96(4)° β = 102.05(4), γ = 103.45(4), R = 0.092; fiedlerite-2M: P21/a, a = 16.681(4) Å, b = 8.043(3), c = 7.281(2), β = 102.56(4)°, R = 0.061. In both structures Pb is eight-coordinated by different ligands [CI−, F−, (OH)−, H2O] that define bicapped trigonal prisms.

Plots of partition coefficients (mineral/ matrix) against ionic radius of the alkali and alkaline earth elements in forty-four alkali feldspars from rhyolites and trachytes show two kinds of diagram, one for homogeneous alkali feldspars with a single peak, and the other for cryptoperthites with a wide spread of points, which cannot represent a single peak, but may probably be explicable in terms of two peaks. The difference in behaviour does not seem to be due to the chemical composition, but is apparently related to the crystallo-graphic features of the alkali feldspar structures. In particular the presence of two peaks in the diagrams of the cryptoperthites seems to be due to the existence of lattice positions suited to receive bigger ions (K, Ba, Rb) and smaller ions (Na, Ca, Sr) in the potassic and sodic domains.

Sea-water from Deception Island was found to contain 0·55–1·48 mg Mn 1−1 and 10·2-64·3 mg Si 1−1. Reaction of Deception Island basalt and sea-water at 190 °C and 500 bars simulated the measured water composition but leaching experiments suggest that much of the Mn etc. may derive from local volcanic ash. Mn and Mg in thermal waters at Reykjanes have concentrations compatible with equilibrium with components of montmorillonite present as an alteration mineral of average composition . However, Fe is controlled by equilibrium with sulphides. Flux calculations based on these and other data place upper limits on hydrothermal Mn input to the oceans of 5–36×1011 g yr−1 and Mn accumulation in metalliferous sediments of 2–9×1011 g yr−1.

The extended timescales involved in the decay of radioactive wastes to safe levels mean that geological disposal facilities must continue to function effectively long into the future. It is therefore essential to consider long-term climate evolution in post-closure performance assessments in order to evaluate a geological disposal system's response and robustness to a variety of potential environmental changes, driven by both natural and anthropogenic forcings. In this paper, we illustrate the multiple decay components that characterize the primary driver of climate change – atmospheric CO2 – in response to fossil fuel carbon emissions. We perform a multi-exponential analysis on a series of atmospheric CO2 decay curves predicted by an Earth system model and create an empirical response function that encapsulates the long-term (>1 kyr) removal of excess CO2 from the atmosphere. We present this response function as a simple tool for rapidly projecting the future atmospheric CO2 concentration resulting from any plausible cumulative release of CO2. We discuss the implications of the long 'tail' to this atmospheric CO2 decay curve, both in terms of future climate evolution as well as potential impacts on radioactive waste repositories.

Three natural amphibole samples collected from the former vermiculite mine near Libby, Montana. USA, have been analysed by Rietveld X-ray powder diffraction (XRPD) refinement and Fourier transform infrared spectroscopy (FTIR) in the OH-stretching region. The same materials have been analysed previously by electron microprobe analysis (EMPA), Mössbauer spectroscopy and structure refinement (SREF) single crystal X-ray diffraction (SC-XRD), which revealed that these amphiboles have a crystal chemical formula very close to an intermediate composition between winchite and richterite, i.e. AA0.5BNaCaCMg4.5M3+T0.5Si8O22(OH)2 (A = Na and/or K; M3+ = Fe3+ and/or Al). The Rietveld analysis showed the powder samples used for the experiments here to be composed only of amphibole. This in turn allowed us to use FTIR OH-stretching data to derive cation ordering on these powder samples. The three FTIR spectra are quite similar and up to four components can be fitted to the patterns. The two lower-frequency components (labelled A and B) can be attributed to a local O(3)-H dipole surrounded by M(1)M(3)Mg3 and M(1)M(3)Mg2Fe2+; (respectively), an empty A site and rSi8 environments; on the contrary, the higher-frequency C and D bands indicate the presence of an occupied A site. The FTIR OH-stretching data alone allow us to calculate the site occupancy of the A, M(1)–M(3) and T sites with confidence, as compared with previously published data. By contrast M(4)- and M(2)-site occupancies are more difficult to evaluate. This study takes advantage of the large database of well characterized synthetic amphiboles, built over the last two decades. The comparison of vibrational spectroscopy data with micro-chemical and crystallographic data reported in this study demonstrate that the FTIR OH-stretching method alone is a valuable and rapid method to derive or at least sensibly constrain site occupancy for natural amphiboles. A much more detailed cation site occupancy can be obtained by combining micro-chemical and FTIR OH-stretching data.

Confusion over the status of crichtonite is due to the fact that de Bournon included two different minerals in his species: thin hexagonal plates are indeed ilmenite, as has been generally assumed, but the much rarer steep rhombohedra with basal plane are a separate species, with a distinctive X-ray powder pattern (three strongest lines: 3·39 Å,s; 2·875,s; 2·131,S) and a composition (Fe2+,Fe3+,Ti)1·71O3 with Fe2+:Fe3+:Ti near 8:7:33. There is a rhombohedral pseudo-cell containing three oxygens, with α 23° 19′, a 7·117 Å but there is some evidence of twinning, and the true symmetry is probably orthorhombic or lower.