Analytical transmission electron microscopy (ATEM) and X-ray absorption spectroscopy (XAS) have been used to determine the mineralogy of Pb-P deposits in the roots of the heavy metal tolerant grass cultivar Agrostis capillaris L. cv. Parys Mountain. The deposits have a pyromorphite (Pb5(PO4)3Cl)-type structure and composition although some of the Cl may be substituted by OH. Energy-dispersive mapping under the scanning electron microscope demonstrated that the majority of these deposits are present in the outer cell wall of the epidermis (the outermost layer of root cells). The phosphate composition of these grains contrasts with the phytate (C6H18O24P612−) composition of Zn-P deposits observed in similar electron microscopy studies. The physiological role of heavy metal P deposits is unclear. Heavy metal P precipitates may form actively as a tolerance mechanism to heavy metals or passively, sequestering P in a metabolically inactive form.

Diamonds from alluvial deposits near Wellington, New South Wales, have been characterized on the basis of morphological features, mineral inclusions, C isotope signatures, N content and aggregation state and internal structure. The diamonds are of two types. The larger group (Group A) is indistinguishable from diamonds found worldwide from kimberlitic and lamproitic host rocks. This group is inferred to have formed in a peridotitic mantle source in Pre-Cambrian subcratonic lithosphere. The second group (Group B) is unique in its internal structures (which show evidence of growth in a stress field and non-planar facets), has unusually heavy C isotopic compositions and contains Ca-rich eclogitic inclusions. This group is inferred to have formed in a subducting slab. Diamonds of both groups have external features (corrosion structures and polish) indicating transport to the surface by lamproitic-like magmas. The diamonds show evidence of long residence at the earth's surface and significant alluvial reworking: they are not accompanied by typical diamond indicator minerals.

Intermediate compositions along the bornite–digenite join exsolve during quenching from above-solvus temperatures. This involves vacancy clustering and cation ordering processes, and is facilitated by fast cation diffusion rates in the presence of a large (10–25%) metal vacancy population. Samples of six different compositions across the bornite–Cu9S5 join, synthesised from component elements in sealed quartz capsules, were water-quenched from 600°C and analysed using high-resolution neutron powder diffraction (HRPD). Time-of-flight spectra measured at room temperature showed all intermediate compositions had exsolved into mixtures of bornite and low digenite with a 5.0a superstructure. No evidence for the presence of any other phase was found. Variations in the lattice parameters of the exsolved bornite phase were observed for different bulk compositions across the join, and ascribed to variations in the degree of order. Bornite exsolved from digenite-rich compositions may not be fully ordered due to the much lower solvus temperatures at the Cu-rich end of the solid solution. As only slight differences were observed between the diffraction patterns of a visibly exsolved and a rapidly quenched sample of the same bulk composition, the formation of optically-visible exsolution lamellae on {100} is ascribed to a process of coalescence of sub-microscopic domains initially formed during the quenching process. The rapid kinetics of exsolution at geologically low temperatures, explains the lack of authenticated natural occurrences of intermediate compositions in the solid solution in nature, and the limited degree of stoichiometric variation observed in end-members.

The Rockeskyll complex in the north, central part of the Quaternary West Eifel volcanic field encapsulates an association of carbonatite, nephelinite and phonolite. The volcanic complex is dominated by three eruptive centres, which are distinct in their magma chemistry and their mode of emplacement. The Auf Dickel diatreme forms one centre and has erupted the only known carbonatite in the West Eifel, along with a broad range of alkaline rock types. Extrusive carbonatitic volcanism is represented by spheroidal autoliths, which preserve an equilibrium assemblage. The diatreme has also erupted xenoliths of calcite-bearing feldspathoidal syenite, phonolite and sanidine and clinopyroxene megacrysts, which are interpreted as fragments of a sub-volcanic complex. The carbonate phase of volcanism has several manifestations; extrusive lapilli, recrystallized ashes and calcite-bearing syenites, fragmented during diatreme emplacement.

A petrogenetic link between carbonatites and alkali mafic magmas is confirmed from Sr and Nd isotope systematics, and an upper mantle origin for the felsic rocks is suggested. The chemistry and mineralogy of mantle xenoliths erupted throughout the West Eifel indicate enrichment in those elements incompatible in the mantle. In addition, the evidence from trace element signatures and melts trapped as glasses support interaction between depleted mantle and small volume carbonate and felsic melts. This close association between carbonate and felsic melts in the mantle is mirrored in the surface eruptives of Auf Dickel and at numerous alkaline-carbonatite provinces worldwide.

The need in geology for in situ U-Pb age determinations of minerals is illustrated by two examples: the internal age dispersion developed within the zircon SL13 shortly after original crystallization, and the occurrence within minerals of old cores and later overgrowths. SL13 contains rare μm-sized patches of unsupported radiogenic Pb and a mainly bimodal distribution of 206Pb/238U ages otherwise. Both observations are consistent with original crystallization at 580 Ma and Pb loss at 565 Ma. Age precision is controlled by the ions counted for radiogenic Pb, and varies with instrumental sensitivity, age and U contents of the target. Laser-ablation ICPMS has similar spatial resolution and sensitivity to SIMS but consumes more sample because of much greater hole-depth in practice. Like SIMS, the measured Pb+/U+ is biased and also changes with depth so comparison with a standard mineral is necessary. Analyses of reference zircons reported here indicate that the reproducibility of Pb/U ages by ICPMS is limited by residual bias, not ion counting errors. For multipurpose ICPMS at least, the Hg background at mass 204 prohibits the measurement of 204Pb for common Pb estimation. A third micro-analytical method, ‘CHIME’, and future developments in SIMS and ICPMS are discussed briefly.

Samples of agate and quartz incrustations from different parent volcanic rocks of certain world-wide localities were investigated by EPR, CL and trace element analysis. In all agate samples the following paramagnetic centres were detected:, E′1, [AlO4]0 [FeO4/M+]0 and [GeO4/M+]0. Centres of the type [TiO4/Li+]0 and [TiO4/H+]0, which were detected in quartz of the parent volcanics, are absent in agate. Generally, the abundance of centres (silicon vacancy) and E′1 centres (oxygen vacancy) in agate is remarkably higher than in quartz. The high defect density in agates points to rapid growth of silica from a strongly supersaturated solution probably with a noncrystalline precursor.

CL microscopy reveals internal structures and zoning in agates and quartz incrustations which clearly differ from those discernible by conventional polarizing microscopy. The CL spectra of agates differ from those of quartz from crystalline rocks. At least three broad emission bands were detected in the CL spectra: a blue band of low intensity, a yellow band at about 580 nm, and an intense red band at 650 nm. The CL emission at 650 nm shows some relations to the hydroxyl or alkali content and the abundance of centres and E′1 centres. The emission intensity increases during electron bombardement due to the conversion of different precursors (e.g. ≡Si-O-H, ≡Si-O-Na groups) into hole centres. Another conspicuous feature in the CL spectra of agates is the existence of a yellow emission band centred at around 580 nm. The predominance of the yellow CL emission band and the high concentration of E′1 centres are typical for agates of acidic volcanics and are indicative of a close relationship between the two.

Tube-in-tube experiments involving a time-dependent variation of temperature or a strong thermal gradient were conducted in order to decipher the transport and transfer of Al in a closed medium along with dilute water. Results show that the solubility and the transport of Al are controlled by the alkali availability. Starting from a mixture of kyanite + quartz + muscovite at the hot end of a thermal gradient, Al is transported toward the cold end in the form of a complex with an Al/K stoichiometry close to unity. Since more Al than alkali are released by the dissolution of muscovite, an Al-rich phase (kyanite) forms in the vicinity of the starting minerals undergoing dissolution, although Al is mobile in the system. Then, the variation of the solubility of the Al-K complex with temperature leads to the formation of muscovite (+quartz) at the cold end of the thermal gradient. A quantitative interpretation of the experimental results was carried out using data from the literature on Al speciation in dilute water. Extrapolation of the laboratory data to natural rocks suggests that the diffusion of Al is an efficient transport process under medium-grade, low- to medium-pressure conditions. Therefore, mass-transfer estimates based on mass-balance analyses postulating a fixed Al reference frame should be considered with caution. Also the high fluid to rock ratio calculated from the amount of aluminosilicates occurring in veins of medium-grade metapelites is questionable because such calculations neglect the importance of the transport of Al by diffusion.

The mineral component (at least 95 wt. %) of dental enamel is hydroxyapatite (hydroxylapatite) with multiple substitutions. The biogenic origin of enamel is reflected in the unusual ribbon-like morphology of the crystals, which are extremely elongated in the c-axis direction, and their organized arrangement within the tissue. The study of enamel dissolution has been driven by the very high prevalence of dental caries. In enamel caries, the initial demineralization results in subsurface dissolution of mineral. While the surface remains intact, reversal of the lesion by remineralization is possible. Problems of understanding the physico-chemical processes in enamel demineralization include the general problems concerning the structure and chemistry of apatites formed in aqueous media. Added to these are the general problem of dissolution in an inhomogeneous porous medium and the complication that enamel apatite has a naturally variable composition which changes during demineralization. The use of model systems in caries research is illustrated by reference to X-ray absorption studies of enamel and synthetic analogues.

Wooldridgeite, ideally Na2(P2O7)2(H2O)10, orthorhombic, a = 11.938(1), b = 32.854(2), c = 11.017(1) Å , V = 4321.2(8) Å3, a:b:c = 0.3634:1:0.3353, space group Fdd2, Z = 8, is a new mineral from Judkins Quarry, Nuneaton, Warwickshire, England. Associated minerals are calcite, chalcopyrite, bornite and baryte. It occurs as equant crystals forming rhombic dipyramids; no twinning was observed. It is transparent blue-green with a very pale-blue streak, a vitreous lustre, and does not fluoresce under long- or short-wave ultraviolet light. Wooldridgeite has a Mohs hardness of 2–3, is brittle with an irregular fracture, and has no cleavage. The calculated density is 2.279 g/cm3. In transmitted light, wooldridgeite is colourless, non-pleochroic, and shows no dispersion. It is biaxial negative with α = 1.508(1), β = 1.511(1), γ = 1.517(1), 2V(meas.) = 76.2(5), 2V(calc.) = 71(10)8, X = b, Y = c, Z = a. The strongest five reflections in the X-ray powder diffraction pattern are [d(Å), (I), (hkl)]: 8.23(30)(040), 6.52(100)(131), 4.05(40)(260), 3.255(40)(262); 2.924(40)(371). Electron-microprobe analysis of wooldridgeite gave P2O5 39.37, CuO 20.24, MgO 0.24, CaO 7.73, Na2O 8.33, K2O 0.17, H2O(calc.) 24.72, sum 100.80 wt.%; the corresponding unit formula (based on 24 anions) is (Na1.96K0.03)Ca1.00(Cu1.85Mg0.04)P4.04O14(H2O)10 where the H2O groups were assigned from knowledge of the crystal structure; the infrared absorption spectrum also indicates the presence of H2O in the structure. The mineral is named for James Wooldridge (1923–1995), a fervent amateur mineral collector who discovered this mineral.

The fusion crusts of meteorites form due to heating during atmospheric entry and have mineralogies which are strongly influenced by changes in oxidation state. We have studied the fusion crusts of the most reduced primitive meteorite group, the enstatite chondrites, since they should demonstrate pronounced changes on oxidation. The fusion crusts are dominated by highly unequilibrated assemblages of sulphide, metal and oxide with compositions indicative of progressive oxidation by the reaction with atmospheric oxygen. Troilite becomes depleted in Ti, Cr and Mn, and enriched in Ni with increasing oxidation. Enrichments in the Ni-contents of kamacite and depletions in Si-content also occur with oxidation, although contemporaneous enrichments in Si within metal droplets occurs by partial melting. Assemblages dominated by Fe-oxide are found within fusion crusts as reaction rims on metal, as veins and within troilite-metal assemblages as droplets and formed by oxidation of metal during heating. Despite the evidence for large increases in redox state during heating, fusion crusts also contain lithophile sulphides indicating a high degree of disequilibrium during the atmospheric reprocessing of enstatite chondrite materials. Based on comparisons with experimental phase relations, ablation rates of 0.08–0.25 cm s−1 are predicted from the thermal gradients recorded in fusion crusts; these rates are broadly similar to those suggested for other meteorite groups.

At the Morrua pegmatite, Mozambique, alkali feldspar has replaced pollucite under low-temperature (250–150°C) hydrothermal conditions. Fluids invading a fracture system in pollucite formed round granular aggregates of (K-Rb)-feldspar in three stages: (1) a compositionally heterogeneous core of the feldspar cluster (+cookeite ± apatite) with 7–20 mol.% RbAlSi3O8, grading outward into a Rb-dominant feldspar with 66 mol.% RbAlSi3O8 (20 wt.% Rb2O); (2) an intermediate layer of non-porous, inclusion-free, end-member K-feldspar; (3) an outer layer of porous end-member K-feldspar. Feldspars of all three stages seem to be monoclinic and disordered, with metastable sanidine structure. Zoning in K/Rb, preserved on a fine scale, was formed during growth at a temperature too low for subsequent alkali-cation diffusion or (Al,Si)-ordering.

Bones from level G in the Arago cave (Tautavel, Southern France, 450 ky) were analysed using a combination of particle induced X-ray and gamma-ray emission (PIXE and PIGME) and X-ray diffraction (XRD). Human occupation and guano production by bats introduced a large amount of phosphate into the cave and as a result a decarbonated pocket was formed in the sediment, characterized by the dissolution of clay minerals, calcite and bones, and by the precipitation of phosphate secondary minerals. The Al released by clay minerals was reprecipitated as crandallite in the few remaining bones, and as montgomeryite with traces of crandallite in the surrounding sediments. Bones within the pocket have very high levels of Al, Fe, F and Zn and often have ‘diffusive’ type U-shaped concentration profiles. These profiles show that post-mortem uptake of trace elements occurred, and thus that trace element composition has to be used with care in palaeonutritional studies but is indicative of local palaeoenvironment. This uptake is complicated by a large increase in hydroxylapatite crystallinity in Palaeolithic bones compared to modern or more recent ones, as a result of the large P influx which occurred in the Arago cave after the sediment deposition.

Silvialite, ideally Ca4Al6Si6O24SO4, is tetragonal, I4/m, Z = 2, with a = 12.160(3), c = 7.560(1) Å, V = 1117.9(8) Å3, c:a = 0.6217:1, ω = 1.583, ε = 1.558 (uniaxial negative), Dm = 2.75 g/cm3, Dcalc = 2.769 g/cm3 and H (Mohs) = 5.5. It is transparent and slightly yellow, has a good {100} cleavage, chonchoidal fracture, white streak and a vitreous lustre. It occurs in upper-mantle garnet-granulite xenoliths hosted by olivine nephelinite, from McBride Province, North Queensland, Australia. The empirical formula, derived from electron-microprobe analysis, is (Na1.06Ca2.86)(Al4.87Si7.13)O24 [(SO4)0.57(CO3)0.41]. Crystal-structure refinement shows disordered carbonate and sulfate groups along the fourfold axis. Silvialite is a primary cumulate phase precipitated from alkali basalt at 900–1000°C and 8–12 kbar under high fSO2 and fO2. The name silvialite, currently used in literature to describe the sulfate analogue of meionite, was suggested by Brauns (1914).

Cathodoluminescence (CL) imaging and spectroscopy, as well as backscattered electron imaging, were used to assign the occurrence of several mineral phases and rock structures in altered nordmarkites and calcite-bearing granites from the Nb-Zr-REE deposits from Khaldzan Buregte and Tsakhir (Mongolian Altai) to three events: (1) intrusion of barren nordmarkites; (2) intrusion of small bodies of calcite-bearing granites with metasomatic alteration of the wall-rocks; and (3) alteration by F-rich fluids.

Unusual red and yellow CL caused by Fe3+ and Mn2+ emission centres were detected in microcline and albite. Fe3+ centres were also established (along with others) in quartz, zircon, and possibly in fluorite.

Magmatic and metasomatic rock structures and internal structures of the minerals coexist in the samples. The primary magmatic features were in part preserved during alteration. In contrast, the internal and the centre structures may be changed during alteration even in non-replaced mineral phases. Euhedral minerals may be formed by secondary processes as shown for lath-shaped albite. The occurrence of pseudomorphs, the inheritance of elements during replacement, and the mechanical effects of secondary minerals on earlier mineral phases during metasomatic growth are proposed as criteria for the reconstruction of the mineral succession in altered rocks. Snowball structures may be formed as a result of metasomatic alteration rather than as a magmatic intergrowth.

The structure of antimonian dussertite, (AsO4)2(OH,H2O)6, has been refined in space group R3̄m with a 7.410(3), c 17.484(4) Å, Z = 3, to R = 3.2 % and Rw = 3.7 % using 377 observed reflections with I ≥ 3 σ(I). The structure is of the alunite-type and consists of sheets of corner-sharing (Fe3+,Sb5+)O6 octahedra parallel to (0001). The substitution of Sb5+ for Fe3+, and not for As5+, is unambiguously demonstrated not only by the structure refinement but also by electron microprobe analyses and crystal-chemical considerations. The icosahedrally coordinated Ba cations occupy cavities between pairs of octahedral sheets and are surrounded by six O atoms from the AsO4 tetrahedra and six O atoms from the (Fe3+,Sb5+)O6 octahedra. The mean bond lengths for the various coordination polyhedra are As-O 1.684(3) Å, (Fe,Sb)-O 2.004(1) Å, and Ba-O 2.872(2) Å. A hydrogen-bonding network is modelled using bond-valence calculations. The dussertite sample investigated is the first member of the crandallite group found to contain substantial Sb.

Low-grade metamorphic rocks from the Meliata unit (Western Carpathians) are characterized by the presence of typical blueschist-facies minerals. In metabasalt, an early low-pressure assemblage (<0.5 GPa at 350°C characterized by muscovite and zoisite, is followed by high-pressure glaucophane, phengite, Na-pyroxene, chlorite, clinozoisite and Al-poor titanite, indicating pressures of >1.2 GPa at 450°C Na-pyroxene shows strong compositional variations between the end-members Jd4–70, Aeg10–49 and Q17–49, respectively. Phengite has high Si content of 3.5 a.p.f.u. The zoisite with Al2Fe (100[Fetot/(−2+Altot+Fetot)]) = 3–5%, is rimmed by clinozoisite, with a maximum of 75% Al2Fe, as well as being enclosed by glaucophane. The occurrence of clinozoisite, rimming zoisite, suggests that the transformation of orthorhombic to monoclinic epidote depends not only on the temperature but also on the pressure. In the studied metabasalt, retrograde phases reflecting greenschist-facies conditions are albite and chlorite. Some neighbouring metabasites may additionally contain actinolite and biotite.

A specimen of zirconolite, collected from the type locality of the mineral originally described as zirkelite at Jacupiranga, São Paulo, Brazil has been re-examined and its mineral chemistry more completely characterized. All crystals studied are metamict and display very fine lamellar oscillatory zoning (1–3 µm in width) superimposed on a sector zonation. Such zoning, observed in backscattered electron images, is primarily related to differences in the concentration of Th.

In comparison with other reported zirconolite samples from a variety of geological occurrences, Jacupiranga zirconolite has higher Ca, Th, (Nb + Ta) and lower Ti and REE, which is consistent with its occurrence in carbonatitic rocks. The compositional variation with respect to an ideal zirconolite is described by two main coupled substitutions:

Calzirtite, Ca2Zr5Ti2O16, although intergrown with zirconolite and with identical major components, shows much less compositional variability with only minor amounts of Nb and Ta substituting for Ti. Unlike zirconolite, the REE and actinide elements are not easily accommodated in the calzirtite structure.

The current definition of samarskite-group minerals suggests that ishikawaite is a uranium rich variety of samarskite whereas calciosamarskite is a calcium rich variety of samarskite. Because these minerals are chemically complex, usually completely metamict, and pervasively altered, their crystal chemistry and structure are poorly understood. Warner and Ewing (1993) proposed that samarskite is an A3+B5+O4 mineral with an atomic arrangement related to α-PbO2. X-ray diffraction analyses of the recrystallized type specimen of ishikawaite and the Ca-rich samarskite reveal that they have the same structure as samarskite-(Y) recrystallized at high temperatures. Electron microprobe analyses show that the only significant difference between samarskite-(Y), ishikawaite, and calciosamarskite lies in the occupancy of the A-site. The A-site of samarskite-(Y) is dominated by Y+REE whereas the A-site of ishikawaite is dominantly U+Th and calciosamarskite is dominantly Ca. Additionally, a comparison of these data to those of Warner and Ewing (1993) show that in several cases Fe2+ or Fe3+ are dominant in the A-site. We propose that the name samarskite-(REE+Y) should be used when one of these elements is dominant and that the mineral be named with the most abundant of these elements as a suffix. The name ishikawaite should be used only when U+Th are dominant and the name calciosamarskite should only be used when Ca is the dominant cation at the A-site. Finally, because of the inability to quantify the valence state of iron in these minerals, the exact nature of the valence state of iron in these minerals could not be determined in this study.

The crystal chemistry characteristics of a hydroxyl-fluor apatite from a recently discovered kalsilite-bearing leucitite from Abruzzi, Italy, were investigated by electron microprobe, single crystal X-ray diffraction, IR, Raman and micro-Raman spectroscopy. The apatite has exceptionally high S and relatively high Si, Sr and LREE, whereas the HREE content is negligible. The IR spectra confirm the presence of OH calculated from formula difference. A high positive correlation between Ca-site Substitution Index (CSI = 100(10-Ca)/Ca) and Tetrahedral Substitution Index (TSI = 100 (Si+C+S)/P atom/a.p.f.u.) and a systematic parallel increase in REE, S and Si indicate two substitution mechanisms, i.e. REE3+ + Si4+ = Ca2+ + P5+ and Si4+ + S6+ = 2 P5+. Site occupancy data and bond lengths, determined from structural refinements on selected samples, demonstrate that LREE and Sr show a marked preference for the Ca2 site, even though in the LREE-rich samples a partial substitution of LREE for Ca in the Cal site was observed.

Tetrahedral distances (from 1.535 to 1.541 Å.) reflect the substitution of Si4+ and S6+ for P5+, which is also confirmed by vibrational spectra. As (SiO4)4− and (SO4)2− substitute for (PO4)3−, the relative intensity of v1 Raman bands of (SO4)2− (at 1007 cm−1) and (SiO4)4− (at 865 cm−1) increase systematically, while that of phosphate decreases and the five components of phosphate v3 modes disappear. Moreover, the (PO4)3− Raman peak broadening is linearly correlated with the Si and S concentrations.

Apatite crystals are sometimes zoned with compositions varying from SiO2 = 1.15–2.07 wt.%, Σ(LREE2O3) = 0.56–1.08 wt.% and SrO = 0.58–1.02 wt.% in the core to 3.98–5.03, 4.14–6.73 and 1.97–2.17, respectively, in the rim. A sharp, strong enrichment in Sr and LREE in the rim indicate that the apatite suddenly became an acceptor of these elements in the late stages of crystallization.