Niccolite and other nickel-bearing minerals have been found in magnetite-rich ore at Lady's Rake Mine [NY 8063 3414] in the North Pennines 5.5 km NW of Langdon Beck, Teesdale, Co. Durham. Associated ore minerals include galena, sphalerite, chalcopyrite, pyrite, and pyrrhotite. Similar magnetite-rich ores, in places bearing ugrandite garnets, have been located at two nearby localities, though without nickel minerals. Petrographic study indicates that this unusual assemblage developed in a skarn environment, probably related to the intrusion of the Whin Sill. Field evidence suggests an association with the Teesdale Fault system. Electron microprobe analyses show that Lady's Rake niccolite is near to end-member composition: analyses of other North Pennine niccolites show up to 25 at. % substitution of S and Sb for As.

Potassium pargasite containing 3.19 wt. % K2O was found in a skarn from the islet of Einstödingen, Lützow-Holm Bay, East Antarctica, together with some high potassium pargasitic amphiboles. A positive correlation is shown between Fe2+/(Mg+Fe2+) and K/(K + Na(A)) ratios in pargasitic amphiboles suggesting that the increase of Fe2+ serve to stabilize high-K pargasites under the metamorphic conditions of the granulite facies.

Re-interpretation of the significance of phase assemblages present in two sequences of rocks having experienced similar burial diagenesis allows one to establish that the change of oxidation state of iron in sediments could have the effect of changing the smectite content of the mixed layer mineral. This is used to explain an almost isothermal change in the composition of a sequence while others do not show such a rapid change. An indicator of the reaction is seen in the composition of the chlorite present in the rocks which is iron-rich and alumina-poor compared to chlorites in rocks showing a slower rate of change in the smectite content of the mixed-layered mineral. In order to reveal such a relation, one must make an analysis of the clay mineral assemblage, especially in the number of phases present during the course of diagenesis.

Fluid flow through a fractured granite core and leaching experiments on granite powder (at constant temperatures of 50 and 100°C and during cooling from 100 to 50°C) indicate that the dissolved silica content of the fluids originates from the dissolution of feldspars and phyllosilicates. The dissolution of quartz is not ruled out but it should be a minor phenomenon. The precipitation of quartz may control the dissolved Si content during constant temperature leaching. During cooling from 100 to 50°C chalcedony, alumino-silicates, and chlorite are all capable of precipitation, possibly leading to some clogging or sealing of fissures.

Endoskarns formed where a swarm of diorite dykes have intruded calcite marble at Redcap Creek include an inner melilite-dominated, a wollastonite-dominated, and an outer massive tilleyite zone in contact with marble. The massive tilleyite is unusual in that it is coarse-grained (prisms 2–15 cm in length) and its deep grey colour contrasts with the lighter coloured varieties described elsewhere. A chemical analysis gives a formula close to ideal, with only minor substitution of Al, Ti, and Mg. Refined unit cell parameters are in close agreement with those quoted in the literature. The skarns have clearly formed by transport of Si, Mg, Fe, Al, and Ti from the igneous rocks, and Ca in the reverse direction from the marble. Activity diagrams derived from experimental data are most useful in interpreting the zonal sequence of endoskarns, and preliminary results suggest mass transfer at low Xco2 and temperature of the order of 800°C or higher for the formation of the massive tilleyite.

The absorption spectrum of Ti3+ in quartz is typical for that element in an octahedral site, except for the high oscillator strength of the band which indicates intensive charge transfer, most likely between a substitutional Ti4+ and an interstitial Ti3+. The biaxial anisotropy of the band is similar to that of octahedral Fe2+ in the same crystal, suggesting the same site for the Ti3+, an interstitial site at the intersection of the threefold axis with two twofold axes. The dynamic nature of the Ti and Fe ions is indicated when the crystal is subjected to X-irradiation and then to bleaching treatment with UV-light or heat. Ti(IV) ions are acceptors of electrons donated by Fe2+ during X-irradiation. This is indicated by increase of the 2.4 eV band intensity with decrease in the Fe2+ band intensities and appearance of Fe3+ charge transfer bands in the UV-region. Heat and UV-light treatment decrease the Fe3+ CT bands and increase the Fe2+ crystal-field bands along with decrease in the 2.4 eV band related to titanium.

Diagenetic illitic clays from seven North American bentonites of Ordovician, Devonian, and Cretaceous ages and from three subsurface North Sea sandstones of Permian and Jurassic ages have been examined by X-ray diffraction (XRD) and transmission and scanning electron microscopy (TEM and SEM). XRD indicates that the clays from the bentonites are randomly and regularly interstratified illite/smectites (I/S) with 30–90% illite layers, whereas the clays from the Jurassic and Permian sandstones are regularly interstratified I/S, with 80–90% illite layers, and illite respectively. TEM of shadowed materials shows that randomly interstratified I/S consists primarily of mixtures of elementary smectite and ‘illite’ particles (10 and 20Å thick respectively) and that regularly interstratified I/S and illite consist mainly of ‘illite’ particles 20–50 Å thick and > 50 Å thick respectively. Regularly interstratified I/S from bentonites and sandstones are similar with regard to XRD character and particle thickness distribution. These observations can be rationalized if the interstratified XRD character arises from an interparticle diffraction effect, where the smectite interlayers perceived by XRD, result from adsorption of exchangeable cations and water or organic molecules at the interfaces of particles generally < 50Å thick. A neoformation mechanism is proposed by which smectite is converted to illite with increasing depth of burial in sedimentary rocks, based on dissolution of smectite particles and the precipitation/growth of ‘illite’ particles occurring within a population of thin phyllosilicate crystals.

Multi-packer hydraulic tests and radioactive tracer experiments carried out in boreholes in the Carnmenellis granite have shown that the flow of water through the rock is largely confined to narrow zones separated by zones of very low permeability. Correlation of the hydraulic data with geological data from oriented cores has shown that most of the flow is associated with discrete geological features, including pegmatitic and other veins, and elvan (quartz-feldspar porphyry) dykes, characteristic features of the granite of the area. Joints have also been found to conduct water, particularly in the upper 250 m of the granite. The permeability of the granite has been found not to be simply a function of fracture frequency, long sections of highly fractured rock having no associated flow under test conditions. While flow paths have been found to become less frequent with depth, flow rates do not vary over the depths studied, the highest flow rate recorded at the site being associated with a vein at 637 m. Water-conducting fractures have been found to have certain preferred orientations which vary with depth. A set striking 155°C is particularly well developed in the upper 250 m of the granite. This orientation is significant in that it is parallel to the cross-courses in the nearby mineralized belt with which the younger (Tertiary) mineralization tends to be associated and from which thermal brines issue into several local mines. These fractures are also approximately parallel to the maximum horizontal stress which affects the granite and which appears to be responsible for the selective opening of joints of certain orientations.

Microprobe analyses of the halogen contents of apatites from two samples of amphibolite-facies schist from Connemara, Ireland, have been used to calculate the fugacity ratios fHCl/fH2O and fHF/fH2O using the experimental data of Korzhinskiy. The results imply fugacities for both acids in the range 0.03 to 0.1 bars, but whereas for the lower grade rock fHF > fHCl, the migmatitic sample gives fHF⋍fHCl. An independent estimate of fHF/fH2O from the biotite composition in one sample is in acceptable agreement with the result obtained from apatite.

Textures and relict mineralogy in the Dalradian gneisses from the southern contact aureole of the Glen Doll diorite trace the development of three stages of metamorphism through regional and contact metamorphic phases. Regional metamorphic stage I is characterized by the stability of sillimanite+muscovite; recognition of a subsequent regional metamorphic stage II of lower grade is based on textural criteria, the stability of kyanite and staurolite + quartz, and geothermometry/geobarometry. The breakdown of zincian staurolite occurred under the conditions of contact metamorphism (stage III). Textural evidence from the outer part of the contact aureole suggests that zincian staurolite broke down by the following oxidation reaction:

zincian staurolite + muscovite + quartz + O2 → andalusite + Zn-rich spinel + magnetite + biotite + H2O.

Various stages of completion of this reaction have been observed in different parts of a sample. Predominance of magnetite over Zn-rich spinel (⩽ 14 wt. % ZnO) as a breakdown product can be explained by the initial breakdown of Fe-staurolite component + muscovite + quartz+O2 to form andalusite+biotite+magnetite. These product phases were joined by the Zn-rich spinel when sufficient Zn-staurolite component had concentrated in the unreacted staurolite. Rare local examples where Zn-rich spinel is dominant over magnetite may reflect lower O2 fugacity and/or higher initial Zn contents of the staurolite.

Zn-rich staurolite occurs in a pelitic gneiss from the Uvete area, central Kenya. The rock was metamorphosed to staurolite-kyanite grade during the Mozambique metamorphism. Microprobe analyses of the staurolite gave the following values (in wt. %): SiO2 26.2–27.3, Al2O3 52.4–53.5, FeO 8.3–9.2, MgO 2.2–2.6, and ZnO 6.0–7.5. Cell dimensions are a = 7.874(± 0.003), b = 16.620(±0.006), c = 5.656(±0.002) Å and β = 90.00 (± 0.002)°. Optical properties are 2Vz = 82–85°, α = 1.742 (±0.002), β = 1.747(±0.002) and γ = 1.753(±0.002). The optical dispersion is moderate and r > v. Density is 3.83(±0.01) g/cm3. Infra-red absorption spectra were also recorded. The cation correlation suggests that the principal substitutions in the staurolite are Zn ⇆ Fe in the tetrahedral sites in the hydroxide sheet and Al ⇆ Mg in the octahedral sites.

Vivianite specimens from various world localities yield X-ray powder patterns of two types: one corresponds with that shown by synthetic Fe3(PO4)2 · 8H2O and is not readily distinguished from that of barićite; the second shows reflections of monoclinic vivianite and triclinic metavivianite along with reflections of a bobierrite-type phase. The triclinic phase occurs as two twin-related lattices with twin plane 110 being the structural equivalent of 010 in the monoclinic phase. The relationship of the bobierrite-type lattice to the other two has not been established. The ternary pattern is produced by some coarse-grained vivianites on natural oxidation. Finer grained vivianites oxidise to an X-ray amorphous state without passing through a triclinic intermediate.

Four size fractions have been separated and studied in eight samples of Cambrian greywackes, ranging from non-metamorphic to low metamorphic grade. Chemical study included analyses of each size fraction and comparison with the whole rock analysis. Mineralogical study involved analyses of individual crystals using microprobe (> 6 µm) and STEM (< 6 µm). This showed that in each fraction, a progressive homogenization of the mineralogical composition occurred during the development of metamorphism; that chemical transfers especially of Fe-Mg and K-Na, occurred between fine and coarse fractions and that recrystallization in fine and coarse fractions was simultaneous.

Hydroxyl-bastnaesite-(Nd), the Nd- and OH-dominant new member of the bastnaesite group, has been found in the red karstic bauxites near Nikšić, Montenegro. It occurs as whitish, irregular aggregates of crystals usually 100–200 µm in diameter. Hexagonal with the cell dimensions a = 7.191 and c = 9.921 Å, with Z = 6. The strongest lines of the X-ray powder diffraction pattern (d, I, hkl) are: 4.95 80(002); 3.596 79(110); 2.911 100(112); 2.077 29(300); 2.042 51(114); 1.914 30(302). The mineral is uniaxial positive, ω 1.715, ɛ 1.81; Dcalc 4.89 g/cm3.

Electron probe analysis, using garnet, apatite and synthetic glass standards, combined with thermogravimetric and evolved gas analysis, gave Y2O3 0.2, La2O3 27.1, Ce2O3 0.3, Pr2O3 8.5, Nd2O3 31.5, Sm2O3 4.4, Eu2O3 1.3, Gd2O3 1.4, CaO 0.3, F 3.3, H2O 2.26, CO2 20.63, sum 101.19, less O = F 1.39, total 99.80%. This analysis calculates to (Nd0.41La0.36Pr0.11Sm0.06Gd0.02 Eu0.02Ca0.01)Σ0.99(CO3)1.03[(OH)0.55F0.38]Σ0.93, or ideally, (Nd,La)CO3(OH,F), with Nd > La and OH > F.

Diffusion into the rock matrix is potentially an important retardation mechanism for nuclides leached from an underground radioactive waste repository in a fractured hard rock. A technique for measuring the intrinsic diffusion coefficient and rock capacity factor is briefly described. Simple solutions to migration model equations are used, together with diffusion results and typical hydrogeological parameters, to estimate the impact of matrix diffusion on radionuclide migration. It is shown that retardation factors in excess of 100 and reductions in the peak concentration by 3–4 orders of magnitude are possible for non-sorbed ions, which would otherwise be carried by the flow and not retarded at all.

The results of a microstructural study by backscattered scanning electron microscopy and a microchemical study using X-ray microprobe analysis of phyllosilicate intergrowths from sandstones, shales, metagreywackes, and low-grade schists are presented. The microstructural study revealed that the intergrowths thicken and become more coherent with metamorphic grade; the intergrowths change from incoherent to coherent in the anchizone. The increasing coherency is mirrored by an increase in the crystallinity indices of the illites/phengites. Chemical analysis of the individual intergrowth phases was difficult in the sediments and no systematic compositional variations were recorded. However, clear compositional trends with increasing metamorphic grade emerged in the phengites from the metagreywackes and schists, but in the chlorites only slight compositional changes were recorded.

The crystal structure of botallackite, Cu2(OH)3Cl, monoclinic, a = 5.717(1), b = 6.126(1), c = 5.636(1)Å, β = 93.07(1)°, V = 197.06(5)Å3, space group P21/m, Z = 1, has been refined to an R index of 3.8% for 350 observed (4σ) reflections, measured with Mo-Kα X-radiation on an automatic four-circle diffractometer. The structure consists of sheets of edge-sharing Cuϕ6 (ϕ = unspecified anion) octahedra of composition Cu2(OH)3Cl; these sheets are // {100}, and are joined by hydrogen bonding between oxygen and chlorine anions, thus accounting for the perfect {100} cleavage and the platy habit of botallackite.

A sequence of sedimentary rocks from the Lower Chalk to the Oxford Clay has been studied as part of a reasearch programme into the feasibility of the disposal of low- and intermediate-level radioactive wastes in argillaceous strata. The preservation of aragonite in such rocks suggests that little groundwater movement has occurred through the bulk of these clays and this would imply that most groundwater movement is likely to occur along any fractures that may be present. Such fractures may interconnect with adjacent aquifer units along which most transport of radionuclides would occur. In these sediments the presence of smectitic clay minerals would strongly influence their retention of radionuclides by sorption and ion-exchange reactions. Compaction, calcite cementation, calcite dissolution and the diagenesis of biogenic silica have influenced the porosity and permeability of the rocks. These processes have also controlled the chemistry of many pore surfaces in contact with groundwater and these in turn will affect groundwater chemistry, and the nature of interactions with transported radionuclides.

Chemical analyses for ganomalite from Franklin, New Jersey, and Jakobsberg, Nordmark, Sweden, imply that Mn is an essential element and that the formula is Pb9Ca5MnSi9O33, with Z = 1 for the hexagonal unit cell. Preliminary crystal structure data confirm that Mn and Ca are ordered, as implied by the chemical analyses. Ganomalite is hexagonal, space group P3, with a = 9.82 and c = 10.13 Å. Occurrences of samples from both localities are described, together with analytical data for macedonite from Jakobsberg.

The lead silicate minerals from Franklin, New Jersey, occurred in two separate assemblages. One of these is characterized by esperite associated with hardystonite and occasional larsenite. The second assemblage can be considered as two parts: one consists of margarosanite, barysilite, nasonite, and ganomalite; the other contains roeblingite and hancockite, together with a number of highly hydrated phases. Chemical analyses indicate that these species conform to their theoretical compositions. There are no simple lead silicates at Franklin; all are compound silicates of Pb with Mn, Zn, and Ca.