I will consider mainly geothermobarometry in medium-grade pelitic rocks, including the garnet-biotite (GB) geothermometer, the Grossular-Al silicate-plagioclase (GASP) geobarometer, and the muscovite-almandine-biotite-sillimanite (MABS) geobarometer. For GB (Holdaway, 2000) experimental data and estimated biotite ΔWTi were used to optimize two exchange parameters and four biotite Margules parameters. Using stepwise linear regression, experimental vs. calculated T were constrained to lie on a line with slope of one and intercept of zero, maximizing r2. The best model involves experiments by Ferry and Spear (1978) and Perchuk and Lavrent’eva (1983), suggesting minimal viAl in the Ferry and Spear product biotite. For GASP (Holdaway, 2001), end-member experimental data do not adequately constrain the equilibrium. I used the GB model above, and allowed the end-member curve to rotate about the best-constrained part of the GASP end-member data. The end-member curve was further constrained with the kyanite-sillimanite (K-S) boundary using published chemical data on 76 pelitic schist samples from 11 localities, rejecting Low-Grs and low-An samples. The Fuhrman and Lindsley (1988) plagioclase model gives the best results. For MABS, work in progress involves 61 samples from the 11 localities which have muscovite analyses. Biotite Margules parameters were based on the GB model and McMullin et al. (1991). The MABS end-member curve was calibrated by comparison of P values determined using trial MABS data and GASP results. The P values for the 61 samples agree well with the K-S boundary, and sillimanite-bearing rocks of west-central Maine all fall in the sillimanite field. Preliminary biotite values are: GAnn = –5149198 – 412.05 T, WAlFe = –14023 + 28.14 T, WAlMg = –259582 + 308.44 T, WTiFe = 124842 – 98.67 T, WTiMg = –186148 + 271.72 T. For geobarometry, the Berman (1988, revised 1992) database was used with adjustable H and S of grossular for GASP and H and S of annite for MABS. The accuracy of currently available databases, activity models and mole fraction models is not adequate for good geothermobarometry, without further refinement. Adjustable parameters tend to compensate for error in activity models, mole fraction models and databases.

Mineralogical-chemical techniques (XRD, SEM/EDX, WDXRF) and a sequential selective extraction procedure were applied to mine-waste materials and stream sediments from the Baccu Locci stream catchment (Sardinia, Italy) affected by serious As contamination as a consequence of past mining. Results indicate that solid-state speciation of As is mainly dominated by the presence of Fe(III) hydroxides (arsenical ferrihydrites with various Fe/As molar ratios) occurring as coatings of silicate grains, in which As is contained as sorbed or co-precipitated species. Scorodite (FeAsO4·2H2O) is common too, whereas arsenopyrite is generally subordinate but, owing to its relatively rapid oxidation, environmentally significant. Moreover, some unidentified arsenates of Ca-Fe or K-Fe were also detected. Arsenic contained in these phases is slowly, but continuously, released in relatively small amounts through three main mechanisms: (1) oxidation of residual arsenopyrite to scorodite; (2) decomposition of scorodite into a hydroxide or oxide of Fe(III); (3) desorption/release from Fe(III) hydroxides. Decomposition of the unidentified arsenates is also probable, e.g. Ca-Fe arsenate → calcite + Fe(III) hydroxide + As release. The flotation tailings are widely scattered and distributed in the middle–lower Baccu Locci stream catchment, and represent the most dangerous As-generating contamination source in the study area.

The major- and trace-element chemistry of pyrite and arsenopyrite from the mesothermal Roudný gold deposits was studied by electron microprobe and laser ablation ICP-MS techniques. In total, four generations of pyrite and two of arsenopyrite were distinguished. The pyrite is enriched in As through an Fe (AsxS1–x)2 substitution mechanism. The As-rich zones of pyrite-2 (up to 4.5 wt.% As) are also enriched in gold (up to 20 ppm), lead (commonly up to 220 ppm, exceptionally up to 1500 ppm) and antimony (commonly <600 ppm, rarely up to 1350 ppm). Positive correlation of As and Au in the studied pyrites is not coupled with an Fe deficiency, in contrast to Au-rich As-bearing pyrites in Carlintype gold deposits. The As-rich pyrite-2 coprecipitated with the Sb-rich (1 –4.2 wt.%) and Au-rich (40 –150 ppm) arsenopyrite-1. The younger arsenopyrite-2 is significantly less enriched in these elements (0 –70 ppm of Au).

The chemical zonality of pyrites in the Roudný gold deposits reflects the chemical evolution of orebearing fluids that are not observed in any other mineral phases. The data available suggest relatively high activity of sulphur and low activities of arsenic and gold during crystallization of the older pyrite generation (pyrite-1). Later, after particular dissolution of pyrite-1, Au-rich As-bearing pyrite-2 and arsenopyrite precipitated. These facts suggest a marked increase in the arsenic and gold activities in ore-bearing fluids. The As-content of pyrite-2 decreases in an oscillatory manner from the core to the rim, reflecting changes in the As activity or/and in the P-T conditions. The As-bearing pyrites were formed at temperatures of at least 320–330°C, based on arsenopyrite thermometers and fluid inclusion data.

The Soufrière Hills stratovolcano on the Caribbean island of Montserrat has been erupting since 18th July 1995. An enormous amount of respirable volcanic ash has been suspended into the atmosphere by the eruptions and wind re-suspension of deposited ash. The large amount of fine, airborne particulate matter, in particular the component 10 μm equivalent aerodynamic diameter (PM10), is a cause of medical concern. Airborne levels have frequently exceeded the UK environmental standard for PM10, (50 μg/m3), although it is noted that this standard was primarily set for urban PM10. The crystalline silica in the ash is mostly cristobalite, at reported levels up to 20%. The UK government’s Chief Medical Officer, referring to Montserrat, has suggested that long-term exposure to high levels of volcanic ash could lead to silicosis. These concerns have prompted government-funded investigations into the potential toxicity of well characterized volcanic ash samples from Montserrat. Given the well established toxicity of cristobalite, particular attention was paid to the amount of this mineral in the ash samples. Three ash samples were tested: (1) a vulcanian eruption ash, (2) ash released in a domecollapse pyroclastic flow, and (3) ash from a major vulcanian explosion that was wind-transported to, and deposited on, the neighbouring island of Antigua. Comparative toxicological studies were carried out on respirable preparations of these three samples together with appropriate control mineral dusts that matched the major components of the Montserrat samples: anorthite, labradorite, cristobalite/ obsidian and cristobalite. Alpha quartz (DQ12) was the positive control. All samples, including the controls, were characterized to establish particle-size distributions, particle morphologies, and to confirm the mineralogy. Rats were challenged with 1 mg via intratracheal instillation, and groups sacrificed at three time points (1, 3 and 9 weeks). Health assessment was made by examining endpoints of increasing lung damage such as inflammation, permeability (oedema), changes in epithelium, and increase in the size of broncho-thoracic lymph nodes. The data indicate that Montserrat respirable ash, derived from dome collapse pyroclastic flows or vulcanian explosions, has minimal acute bioreactivity in the lung. The feldspar standards showed low bioreactivity, in stark contrast to the cristobalite standard that showed progressive increases in lung damage. These results suggest that either the mass of cristobalite present in the Montserrat ash was insufficient to cause an effect in the lung, or the cristobalite in the ash was, for some as yet unknown reason, markedly less bioreactive than our pure cristobalite standard.

Micro-inclusions (1 –10 μm) in 55 diamonds of cubic habit from the Udachnaya kimberlite pipe have been studied using vibrational spectroscopy. This has revealed a multiphase assemblage in cuboid diamonds from the Udachnaya kimberlite pipe. This assemblage includes carbonates, olivine, apatite, graphite, water and silicate glasses. The micro-inclusions preserve the high internal pressure and give confidence that the original materials were trapped during growth of the host diamond. The internal pressures, extrapolated to mantle temperatures, lie within the stability field of diamond and the relatively low temperatures are typical for the formation of cuboid diamonds. In contrast to previously reported data for African diamonds, the micro-inclusions in the cuboids from Udachnaya are extremely carbonatitic in composition (H2O/(H2O+CO2) ≈5 –20%) with the observed assemblage of microinclusions similar to some types of carbonatites. The low water and silica content testify that the material in the micro-inclusions of the Udachnaya diamonds was near-solidus carbonatitic melt. Vibrational spectroscopy has provided the evidence of carbonatitic melts in cuboid diamonds.

We have performed experiments to determine the extents to which Fe and H2O are lost from hydrous basaltic melts contained in Au80Pd20 and graphite-lined Pt capsules at 0.7 –1 GPa and 1300–1350°C. All experiments were performed in the piston-cylinder apparatus. In order to minimize the possibility of rupture of the AuPd capsule and to control H2O loss we used a double-capsule method. The inner welded 2 mm diameter Au80Pd20 capsule was placed inside a welded 3 mm diameter Pt capsule, the intervening space being packed with hydrous sample. Loss of FeO* from the sample was found to be ≤4% relative in both the Au80Pd20 and graphite-lined Pt capsules in experiments of up to 24 h duration. Loss of H2O is greater and it depends on the oxidation state of the starting materials and the nature of the capsule. For starting mixes fired at 1 log fO2 unit above the quartz-fayalite-magnetite (QFM) buffer at 1 atm, H2O loss from Au80Pd20 capsules averaged 9% relative. Starting mixes fired at 1 log fO2 unit below the QFM buffer at 1atm lost, on average, 32% of their H2O when run in Au80Pd20 capsules at high pressure. All samples run in graphite-lined Pt capsules experienced dramatic H2O loss, averaging 52% relative, irrespective of initial oxidation state. We conclude that Au80Pd20 capsules are suitable for high-pressure hydrous melting experiments and that the sample loses very little Fe. In order to minimize H2O-loss, however, it is important that the starting materials be relatively oxidized.

The lamproite of Gaussberg is an ultrapotassic rock where leucite, olivine and clinopyroxene microphenocrysts occur in a glass-rich groundmass, containing microliths of leucite, clinopyroxene, apatite, phlogopite and rare K-richterite.

Abundant silicate melt inclusions occur in olivine, leucite and, rarely, in clinopyroxene microphenocrysts. Raman investigations on melt inclusions showed the presence of pure CO2 in the shrinkage bubbles. On the other hand, the glass of the groundmass is CO2-poor and contains up to 0.70 wt.% of dissolved H2O, as estimated by infrared spectra. It is inferred that CO2 was released at every stage of evolution of the lamproite magma (CO2-rich shrinkage bubbles), whereas H2O was retained for longer in the liquid. At Gaussberg, CO2 seems to have a major role at relatively high pressure where it favoured the crystallization of H2O-poor microphenocrysts; the uprise of the magma to the surface decreased the solubility of CO2 and caused a relative increase in water activity. As a consequence, phlogopite and K-richterite appeared in the groundmass.

The glass composition of both the groundmass and melt inclusions suggests different evolutions for the residual liquids of the investigated samples. Sample G886 shows the typical evolution of a lamproite magma, where the residual liquid evolves toward peralkaline and Na-rich composition and crystallizes K-richterite in the latest stage. Sample G895 derives from mixing/mingling of different batches of magma; effectively glasses from melt inclusions in leucite and clinopyroxene are more alkaline than those found in early crystallized olivine. Leucite and clinopyroxene crystallized early from a relatively more alkaline batch of lamproite magma and, successively, a less alkaline, olivinebearing magma batch assimilated them during its rise to the surface.

Static lattice energy calculations have been combined with cluster expansion formalism to predict pairwise ordering interactions in the pyrope–grossular solid solution. The ordering interactions, the Js, have been then used to calculate the activity-composition relations over a wide temperature range with the help of the Cluster Variation Method. It is shown that short-range ordering in the system is driven by size mismatch. The prediction of the right signs and magnitudes of the ordering interaction energies requires separation of the mixing enthalpy into the configuration-dependent (chemical) and the configuration-independent (elastic) components. The study predicts the existence of a miscibility gap below 500°C.

The heat capacity of synthetic lazulite, MgAl2(PO4)2(OH)2, has been measured between 35 and 298 K by means of low-temperature adiabatic calorimetry. A lazulite third-law entropy (S2980) value of 204(3) J K–1 mol–1 was retrieved after extrapolation of the lazulite heat capacity by a cubic temperature function, down to absolute temperature. Identical measurements on α-Al2O3 yielded S2980 = 51.2 J mol–1 K–1 instead of the recommended 50.94 J mol–1 K–1 value. This new lazulite third-law entropy along with other phosphate entropy data either derived from low-temperature adiabatic calorimetry or experimental phase equilibria under pressure and temperature, were computed to retrieve a (S–V)P2O5 value of 57.4(2.9) to predict phosphate entropies from oxide summation. The predicted third-law entropy for trolleite, Al4(PO4)3(OH)3, amounts to 285.4(8.5) J mol–1 K–1 ~13% higher than the previously published value. We propose a new formation enthalpy from the elements of –6504.2 kJ mol–1 and a new third-law entropy of 281.7 J mol–1 K–1 for trolleite, compatible with the predicted entropy from oxide summation as well as with the published brackets on the trolleite = berlinite + corundum + water reaction.

The hydrous calcium carbonate mineral ikaite (CaCO3.6H2O) forms in nature at low temperature in carbonate- and Ca-rich waters. Ikaite crystallizes in the spacegroup C2/c, and consists of CaCO3.6H2O units with Ca ions coordinated by eight oxygens, six from H2O and two from the carbonate group. Hydrogen bonding links CaCO3.6H2O moieties to form the crystal structure.

We have used synchrotron X-ray powder diffraction at T = 243 K to refine the monoclinic structure of ikaite, and have measured unit-cell parameters of ikaite between T = 114 K and T = 293 K. Anisotropic thermal expansion in ikaite is evident, with the smallest relative increase occurring along the b direction parallel to 2-fold axes. The contribution of hydrogen bonding to thermal expansion is assessed by comparison of our data with previously published data for deuterated ikaite, ice and gypsum. Ikaite exhibits a coefficient of volume expansion intermediate between that of ice (Ih) and of deuterated gypsum (CaSO4.2D2O) between T = 114 K and T = 293 K.

The previously unknown, complex crystal structures of two fibrous ferric iron phosphate minerals have been solved using single-crystal X-ray diffraction data. The structure of a slightly arsenatian kidwellite has been refined in space group P2/c (a = 20.117(4), b = 5.185(1), c = 13.978(3)Å, β = 107.07(3)°, V = 1393.8(5)Å3, Z = 2) to R1 = 5.21%; a revision of both space group symmetry and chemical formula is proposed. The idealized formula is Na(Fe3+,M)9+x(OH)11(H2O)3(PO4)6, where M = Fe3+, Cu2+ or other metal cation, and x ≈ 0.3. The structure of a slightly arsenatian ‘laubmannite’ (as defined by Moore, 1970) has been refined in space group Pbcm (a = 5.172(1), b = 13.999(3), c = 31.083(6)Å, V = 2250.5(8)Å3, Z = 4) to R1 = 3.14%. The revised, idealized formula is (Fe3+,Fe2+,M)8+x(OH,H2O)9(-H2O)2(PO4)5, where M = Fe3+, Cu2+ or other metal cation, and x ≈ 0.1. The framework structures of both minerals are similar. Dominant building units are dimers composed of face- and edge-sharing FeO6 octahedra. Whereas kidwellite contains an additional trimer built of three corner-sharing FeO6 octahedra, ‘laubmannite’ instead contains a dimer built of two corner-sharing FeO6 octahedra. Kidwellite contains only trivalent iron, while one of the Fe sites in ‘laubmannite’ is occupied by a mixture of Fe3+ and Fe2+ in a 1:1 ratio. In both structures, the FeO6-based building units are linked via corners to PO4 tetrahedra; the M sites are located in narrow channels and have very low occupancies (~2 to 7%) and strongly distorted [6]- or [5+1]-coordinations. Close structural relations between kidwellite and ‘laubmannite’, and other fibrous iron phosphates explain observations of epitaxial intergrowths of them.

Orthorhombic edingtonite has been found coexisting with tetragonal edingtonite in a specimen from Ice River, British Columbia, Canada.

We report data on the composition and crystal structure of the orthorhombic sample. Lattice parameters are: a = 9.5341(6), b = 9.6446(6), c = 6.5108(7)Å, V = 598.68(8)Å 3. The crystal structure was refined in space group P 21212 to R1 = 1.8% using 879 observed reflections. For the first time, evidence for splitting of the extra-framework Ba site in two different sites (Ba1, Ba2), ~0.37 Å apart, is demonstrated. A comparison with the published crystal structures of tetragonal and orthorhombic edingtonite is made.

The present result supports the suggestion that the two edingtonite phases are a consequence of different nucleation phenomena and not different physicochemical conditions.

Ammonioleucite, (NH4)[AlSi2O6], and its deuterated analogue ND4-ammonioleucite (ND4)[AlSi2O6] have been synthesized in 20–150 mg amounts at 300°C and 500 MPa in 5 mm wide, 4 cm long Au capsules using Rene’ metal hydrothermal autoclaves. The resultant product consists of 20–30 mm-size single tetragonal crystals as well as 50 –100 mm wide clumps of ingrown crystals. Infrared (IR) spectra obtained from powdered samples are assigned on the basis of Td symmetry for both the ammonium and deutero-ammoniumion. They show triply degenerate vibrational bands (i.e. v3 and v4), some overtones, and combination modes from NH4+ and ND4+. While Td symmetry for NH4+ in ammonioleucite is not strictly correct due to distortion of the NH+4 molecule, the non-cubic field is not large enough at room temperature to cause a substantial splitting in the bands. However, this perturbation is documented in the IR spectra by a substantial increase in the FWHH as well as the occurrence of shoulders on the broadened bands. In contrast, at lower temperatures, the observed band splittings in the former triply degenerated states of v3 and v4 could be explained by an effective local field with D2 symmetry.

Rietveld refinement indicates that ammonioleucite, like leucite, has a tetragonal structure with space group symmetry I41/a. Here the NH4+ molecule replaces the K+ cation on the 8-fold co-ordinated W site, which has m symmetry. Substitution of NH4+ for K+ in the leucite structure results in an increase of the cell parameter a, whereas c is slightly reduced. The mean <W–O> bond length of ammonioleucite is increased in comparison to leucite from 3.00 to 3.12 Å whereas the mean <T–O> bond length of 1.65 Å remains unchanged. This results in an increase in the volume of the polyhedron hosting the NH4+ molecule as well as a decrease in distortion for structural channels parallel to the <111> direction, formed by the arrangement of the six-fold rings, on which the W cations are located. The same effect is also observed, in general, when Rb+ or Cs+ is substituted for K+ in leucite.

Silica sinter masses in the southern portion of the Pliocene Puhipuhi geothermal field of Northland, New Zealand, have recrystallized to microcrystalline quartz and moganite but many primary depositional fabrics of the sinters can still be recognized. Finely disseminated cinnabar, acicular stibnite, pyrite framboids and minor livingstonite are distributed through both massive sinter and stromatolitic fabrics with sulphide mineralization extending from fractured rocks about former spring vents into less disturbed sinter layers. The deposition of sulphides in the sinters is part of a continuum of mineralization resulting from the former hydrothermal regime and which extends to depth in the extinct geothermal system. Periodic changes in the hydrology, such as repeated fracturing following fracture sealing facilitated episodic sulphide deposition. Mercury is considered to have travelled in the liquid phase with antimony and precipitated directly as cinnabar. Remobilization of the sulphides, along with the recrystallization of the sinter masses, have produced complex textural relations. The multifaceted paragenesis of the sulphides is reflected in the range of their minor and trace element compositions revealed by electron microprobe analyses.

Five smithsonite samples from locations in Germany, Mexico and Namibia have been investigated with cathodoluminescence (CL) spectroscopy and trace-element analyses. As with other carbonates, the CL properties of smithsonite are mainly controlled by Mn2+- and Fe2+-incorporation, because these elements are the most important activator and quencher species, respectively. Additional trace elements may have either a quenching effect (Cu) or have only small or no influence (Ca, Pb). A linear correlation exists between the Mn content and the intensity of the Mn-emission band in smithsonite, which can be quantified, if the Cl intensity is related to the number of moles of Mn rather than the weight fraction. A correlation between the Cl intensity and the Mn concentration, which is valid for all trigonal carbonates, is obtained from the published results of calcite, dolomite and smithsonite. Matrix effects due to the different chemical composition of the carbonate minerals seem to be of lesser importance.

The introduction of a fifth amphibole group, the Na-Ca-Mg-Fe-Mn-Li group, defined by 0.50 < B(Mg,Fe2+,Mn2+,Li) < 1.50 and 0.50 ≤ B(Ca,Na) ≤ 1.50 a.f.p.u. (atoms per formula unit), with members whittakerite and ottoliniite, has been required by recent discoveries of B(LiNa) amphiboles. This, and other new discoveries, such as sodicpedrizite (which, here, is changed slightly, but significantly, from the original idealized formula), necessitate amendments to the IMA 1997 definitions of the Mg-Fe-Mn-Li, calcic, sodic-calcic and sodic groups. The discovery of obertiite and the finding of an incompatibility in the IMA 1997 subdivision of the sodic group, requires further amendments within the sodic group. All these changes, which have IMA approval, are summarized.