Major element, trace element, and REE data for metasedimentary granulites and their retrogressed derivatives formed from Archaean parent-rocks at two localities in the Lewisian complex of north-west Scotland are presented.

The metasedimentary rocks are enclosed in and intruded by metatonalites and related calc-alkaline rocks and have been highly deformed and metamorphosed along with these rocks. They are geochemically distinct from this meta-igneous suite and range from highly aluminous to highly siliceous types. Comparisons of major and trace element data with those for unmetamorphosed Archaean and post-Archaean sediments suggest that they are derived from a detrital shale-greywacke assemblage, which may have included a volcaniclastic component. High ΣREE and ΣLREE suggest that the source-rocks included fractionated felsic igneous rocks.

Evidence that depletion in the large ion lithophile elements K, Rb, Th accompanied high-pressure granulite metamorphism supports the view, based on data derived from the associated meta-igneous rocks, that depletion was effected by active fluids rather than by abstraction of a partial melt and suggests that removal of K and Th began only when a considerable reduction of Rb had taken place.

Phlogopite occurs as an early crystallizing mineral in many ultrapotassic lavas of basaltic affinities. Based on high-pressure experiments in lavas of these compositions, the early crystallization of phlogopite is controlled in large part by the bulk compositions of the liquids from which it crystallizes but also by the total pressure and by the aH2O, with early phlogopite forming under a narrow range of aH2O, less than that represented by H2O-saturated conditions. Variations in fO2 do not appreciably affect phlogopite crystallization but high aCO2 suppresses its crystallization. In ultrapotassic magmas, phlogopite will preferentially incorporate K2O, TiO2, MgO, and Al2O3 relative to the coexisting early silicate minerals, olivine and clinopyroxene, and thus, on fractionation of these minerals, phlogopite will be more effective in reducing these oxides in residual liquids. Phenocrysts and microphenocrysts of phlogopite in ultrapotassic lavas are directly related with respect to their K/Ti, K/Al, K/(K + Na), and Mg/(Mg + Fe) ratios. Textural relations suggest phlogopite may form by reaction relationships involving liquid with olivine, and/or clinopyroxene. Such relationships are supported by the experimental studies on ultrapotassic rock compositions.

X-ray diffraction, electron microprobe and STEM EDAX analyses of basalts from the South Pennines (Derbyshire) indicate that Fe-rich smectites are the dominant alteration products, occurring either as pseudomorphs or infilling veins and vesicles. Previously chlorite has been identified as the common alteration product but its occurrence is very infrequent.

Very large crystals of magnetite, up to 2 cm, are found in pure magnetitite layers in the upper zone of the Bushveld Complex. Detailed electron microprobe analysis of one of these indicates a vertical compositional zoning of Cr (a highly compatible element in magnetite) quite different from the concentric zonation often found, for example, in feldspars in intrusive rocks. It is shown that these crystals could not have grown to their present size in suspension in the magma chamber. Annealing of many small crystals into a single grain could occur either by the Ostwald ripening process at temperatures close to the liquidus or by subsolidus recrystallization. Alternatively, these grains could have formed directly from the magma by upward growth from the floor of the magma chamber, by a process analogous to crescumulate or heteradcumulate growth but in the absence of other crystallizing phases. All of these models require the observed Cr gradient to be produced during the initial crystallization event and not as a secondary effect.

Gortdrumite superficially resembles chalcocite but is more distinctly anisotropic, and is present in a vein containing ferroan dolomite and baryte which cuts dolomitized limestones from the Gortdrum Orebody of County Tipperary, Ireland. It has an empirical formula of approximately (Cu,Fe)6Hg2S5. A distinctive powder diffraction X-ray pattern has been obtained which indicates a probable orthorhombic crystal lattice with a 14.96, b 7.90, and c 24.1 Å. The reflectivity at 589 nm is 25.1 to 27.9% and the VHN10 hardness range 186 to 230.

Both Species were Found as post-Mine Minerals in the Lone Pine mine, Catron County, New Mexico. They occur encrusting ores of fluorite-pyrite with khademite and gypsum.

Wilcoxite is clear, colourless to white, H = 2, D = 1.58. Abundant as spongy masses of perfect to somewhat rounded crystals. Stubby prisms are bounded by {100}, {010}, {110}, {10}, and {01}. Triclinic P or P1 with a = 14.90, b = 6.65, c = 6.77 Å, α = 117° 26′, β = 100° 35′, γ = 80° 10′, and Z = 1. Strongest lines are 5.654(9) 110, 11, 4.908(10) 11, 4.371(6) 201, 210, and 3.384(5) 11, 111. Biaxial negative with α = 1.424, β = 1.436, γ = 1.438, 2Vα = 48°. Analysis gave MgO 6.61%, Al2O3 8.13, Fe2O3 0.46, MnO 0.13, SO3 27.50, H2O 56.40, F 3.48, total 101.24 (corr. for O ≡ F) leading to MgAl(SO4)2F·18H2O.

Lannonite is usually as chalky white aggregates of microscopic tetragonal (square) platelets; H = 2, D = 2.22. Indexed as tetragonal a = 6.84, c = 28.01 Å, and Z = 1. Strongest lines are 13.98(10) 002, 4.840(7) 110, 3.980(5) 116, and 3.456(7) 017. Uniaxial positive with ω = 1.460 and ε = 1.478. Analysis gave CaO 12.06%, MgO 4.46, Al2O3 11.06, SO3 34.40, H2O 32.00, F 9.44, total 99.45 (corr. for O ≡ F) leading to HCa4Mg2Al4 (SO4)8F9·32H2O.

Both minerals and mineral names have been approved by the Commission on New Minerals and New Mineral Names, IMA.

New analytical data for the khademite associated with these species are presented.

Eluvial pebbles from the Afu Hills, Nigeria, are largely composed of fluocerite, Ce0.50La0.28Nd0.11 Pr0.04Th0.03Ca0.02F3, with minor monazite. The fluocerite shows two types of alteration, to bastnäsite, and to bastnäsite-(La) with cerianite. Electron microprobe analyses are given for fluocerite, monazite, bastnäsite and bastnäsite-(La). The refined cell parameters of the fluocerite are a = 7.130±0.001, c = 7.2985 ± 0.001 Å. Strongest lines are 3.204 Å (100), 3.65 (45), 2.059 (45), 2.010 (45) and 3.565 (40). Space group P 63/mcm, Z = 6, Dcalc. = 6.12 g cm−3, ω = 1.613, ε = 1.609 both ±0.002, uniaxial negative. For bastnäsite a = 7.131 ± 0.002, c = 9.786±0.004 Å, for cerianite a = 5.460 ± 0.005 Å.

The first occurrence of thaumasite resulting from seawater-basalt interaction has been discovered in a drill hole on Mururoa atoll (French Polynesia, South Pacific). This sulphate-carbonate-silicate is associated with zeolites (phillipsite, chabazite, gmelinite), apophyllite, analcime, and gyrolite. In this environment thaumasite can be considered as the last mineral of an alteration sequence. It crystallized from a Ca-SO3-CO2-rich and Al-Na-K-poor fluid. The temperature of this solution is unknown, but was probably not greater than 100°C.

Infrared spectroscopy affords a rapid and easy method of estimating the position of a mineral in the olivenite-adamite solid solution series, and of estimating the amount of phosphate substitution in olivenites. Toman's discovery of the monoclinic symmetry of olivenites with up to approximately 20 atom % Zn/(Cu + Zn) has raised a problem in nomenclature. It is suggested that the definition of ‘cuproadamite’ be extended to cover all orthorhombic members of the series containing appreciable Cu. Studies of deuterated materials have helped to solve some of the absorption band assignments for olivenite-adamite, libethenite and related minerals.

Cesanite, Ca1+xNa4−x(SO4)3(OH)x · (1 − x) H2O, is hexagonal, space group P63/m, a = 9.446(1) and c = 6.895(1) Å, Z = 2. The crystal structure refinement, carried out by utilizing 457 independent reflections (final R = 0.021), shows that cesanite is isotypic to hydroxyapatite. The P atom of apatite is completely replaced in cesanite by an S atom; the two independent Ca sites of apatite are occupied respectively by Na and Na + Ca, the charge balance being by partial substitution of H2O for OH− although the occupancy of the (H2O,OH−) sites is not complete. The relationship between the water vacancies and the structural features of the (Ca,Na) polyhedron is discussed. A new general formula for the apatite-wilkeite-ellestadite series is proposed.

The mineral priderite has been examined by electron microprobe analysis and electron diffraction. The composition was approximately (K0.97Ba0.33)(Fe1.17Ti6.60Mg0.23)O16, which is in line with the observed superlattice periodicity of m = 5.88, there being inter-growths of m = 5 and m = 6 superstructures. A surprisingly high degree of lateral correlation between tunnel cations was noted.

Using solution techniques, ΔG°f(298.2k) has been calculated for schröckingerite, NaCa3UO2(CO3)3 SO4F · 10H2O, and grimselite, NaK3UO2(CO3)3 · H2O. The values are −8077.3 ±8.7 and −4051.3 ±1.8 kJ mol−1 respectively. ΔH°f(298.2k) for grimselite is −4359.0 ± 1.8 kJ mol−1. An estimate for ΔG°f of the synthetic compound Na4UO2(CO3)3(s) using previously published equilibria has been made, −3720.0±9.7 kJ mol−1. The results have been used to reconstruct the chemical environments in which these and related compounds can form. Grimselite is only stable at relatively high activities of K(aq)+ and the alkali metal carbonates containing only potassium or sodium ions have not been reported to occur naturally. This is most probably due to their relatively high solubility in water. Schröckingerite can form from solutions which are more than saturated with respect to calcite and fluorite. The close relationship of schröckingerite with gypsum, observed frequently in the field, is evident from synthetic and solution studies.

Pectolite has been identified, using petrographic, chemical, and X-ray methods, in kimberlites from the De Beers and Dutoitspan Mines, Kimberley, South Africa and the Letseng-La-Terai Mine, Lesotho. It occurs as radiating aggregates of fibrous or acicular crystals not only in the groundmass of certain kimberlites but also in altered xenoliths included within kimberlite. The occurrence of Na-rich minerals in kimberlite is unusual. It is suggested that it can occur as an apparently primary mineral resulting from the incorporation and assimilation of foreign Na-bearing material prior to final consolidation, and/or as a secondary mineral after metasomatic introduction of Na-bearing fluids.