The triple-chain pyriboles jimthompsonite, clinojimthompsonite, and probably chesterite and its monoclinic polytype occur in Lewisian amphibolite-facies ultramafic rocks near Achmelvich, N.W. Scotland. These minerals are intergrown with one another and with amphiboles in prismatic porphyroblasts up to 3 cm long, which are associated with chlorite, carbonate, magnetite and, in some cases, talc. Rocks containing triple-chain silicates have been found at three localities, in each case outcropping in a layer < 1.5 m thick. Clinojimthompsonite is the most abundant triple-chain silicate and generally forms euhedral wedge-shaped overgrowths, measuring up to 1 mm in the b-axis direction, on the {010} faces of actinolite cores. The mineral assemblages are probably of Inverian age.

The identification of the triple-chain phases is based mainly on cleavage angle, extinction angle, backscattered electron intensity and, in the case of clinojimthompsonite, on X-ray diffraction data. Microprobe analyses support the identifications. The triple-chain silicates have compositions lying in the system MgO-FeO-SiO2-H2O, with only trace amounts of other components.

The cell dimensions of the coarsest clinojimthompsonite are: a = 9.862 ± 0.002 Å, b = 27.184 ± 0.020 Å, c = 5.298 ± 0.004 Å, β = 109.61° ± 0.14° V = 1337.9 ± 1.8 Å3, and its optical properties are as follows: α = 1.600 β = 1.619 γ = 1.628 (all ± 0.001) and optic axial plane = (010). The 2Vα of clinojimthompsonite = 67 ±2°.

Back-scattered electron microscopy reveals that although substantial volumes of single-phase clinojimthompsonite are common, (010) intergrowths of Mg,Fe-amphiboles, jimthompsonite polytypes and chesterite polytypes occur locally on scales down to 0.1 µm and probably smaller, indicating considerable chain-width disorder.

The triple-chain pyriboles are not pseudomorphous after amphibole and probably grew during prograde Inverian metamorphism. Chemographic constraints suggest that they could have formed from forsterite-bearing assemblages, possibly as the result of infiltration of CO2-rich fluid. Thermodynamic calculations for associated high-variance ultramafic rocks place an upper limit of c. 600–700°C on the temperature of metamorphism.

The large number of chemically similar pyriboles and their disposition within compound prisms suggests that crystallization was kinetically controlled. A simple ‘template’ model is propesed to explain the observed patterns, in which the identity of the Mg,Fe-pyribole nucleating at any point on a preexisting actinolite or Mg,Fe-pyribole substrate is controlled by silicate-chain width and/or symmetry (ortho vs. clino), depending on the orientation of the substrate crystal face.

Synthetic end-member strontium feldspar (SrAl2Si2O8) has been studied in a diamond-anvil cell at elevated pressures up to 10.3 GPa using energy-dispersive X-ray powder diffraction. Cell parameters have been refined between ambient pressure and 6 GPa. SrAl2Si2O8 undergoes a ferroelastic phase transition from the ambient pressure monoclinic space group I2/c to the high-pressure triclinic space group I at 3.2 ± 0.4 GPa. The transition appears to be first-order and the ferroelastic and co-elastic components of the spontaneous strain tensor have been calculated.

Nearly boron-free kornerupine is locally abundant in pods or lenses of coarse-grained, non-foliated, Mg- and Al-rich rocks that occur at high metamorphic grades in early Proterozoic metapelitic rocks from the Reynolds Range, Northern Territory, Australia. This is the third reported occurrence of boron-free kornerupine worldwide. The samples consist almost entirely of coarse-grained kornerupine and its breakdown products sapphirine, cordierite, and gedrite or orthopyroxene. The kornerupine contains only 0.45 wt.% B2O3, corresponding to 0.098 B atoms per 22 (O, OH), and closely approximates 11:10:11 in terms of molar ratios of (MgO + FeOtotal):Al2O3:SiO2, with XMg = Mg/(Mg + Fetotal) = 0.874. The unusual textures and bulk compositions of the rocks in the pods are interpreted to have resulted from metasomatism and high-grade metamorphism (750 to 800° and ∼ 4.5 kbar) of precursors that may have included sedimentary Mg-rich clays. Rocks containing boron-poor, and relatively boronrich kornerupine (2.18 wt.% B2O3; XMg = 0.892) are separated in outcrop by as little as 10 m of the foliated cordierite-quartzite country rock and other rock types, suggesting that the compositions or amounts of the metasomatic fluids varied on a local scale.

The Loch Shin monzogranite is host to quartz veins bearing the sulphosalts aikinite, hammarite, lindströmite, krupkaite, gladite and pekoite, which belong to the aikinite-bismuthinite series, and represents the first significant occurrence of this series in the United Kingdom. Inclusions of the sulphotelluride tetradymite occur in krupkaite-gladite. Berryite is present as inclusions in chalcopyrite. Electron microprobe analyses reveal a range of compositions in individual crystal masses from hammarite to krupkaite in one sample, and from krupkaite to gladite in a second. Compositions between friedrichite and hammarite and gladite and pekoite are notably absent.

Within a suite of felsic-free, mica-rich alkaline ultramafic rocks of the Schryburt Lake carbonatite complex of northwestern Ontario, loparite and Ba-Fe hollandite occur in intimate association with perovskite. The host rocks have variable modal proportions of Mg-olivine, phlogopite, magnetite, ilmenite, apatite and carbonate (generally calcite) with minor Mg-salite. Thus, they correspond to ultramafic lamprophyres (i.e. aillikites), in the sense of Rock (1990) or the lamprophyric facies of the melilitite clan, in the sense of Mitchell (1993).

Perovskite is the principal titanate phase, forming both euhedral and anhedral grains, the latter showing evidence of marginal resorption. It exhibits complex zonal patterns due principally to variations in the light rare earth elements, Na and Nb. In the nomenclature suggested, they may be termed perovskite and cerian perovskite. Loparite forms as small euhedral overgrowths on corroded perovskite cores. Chemically they are essentially solid solutions of loparite, lueshite and perovskite. Consequently, they may be termed calcian-loparite, calcian niobian loparite, niobian calcian loparite, loparite and niobian loparite. Titanates of the hollandite group are rare accessory minerals whose composition closely approach that of the septatitanate BaFe2+Ti7O16.

The complex zoning of the perovskite grains has been attributed to the periodic introduction of carbonatite-derived fluids enriched in REE, Na and Nb into the silicate system during perovskite crystallization. Subsequent reaction of the early perovskite with F-bearing fluids leads to a localized environment enriched in Ti, Na, Nb and REE derived from both the fluid phase and the unstable perovskite. Loparite subsequently crystallizes from these micro-chemical environments.

Parkinsonite, ideally (Pb,Mo,□)8O8Cl2, is a new mineral from the Merehead Quarry, Cranmore, Somerset, England. It occurs as compact clusters or patches of red to purplish red bladed crystals, which have an adamantine lustre and a perfect {001} cleavage and occupy fractures and cavities in carbonate vughs in veins of manganese and iron oxide and hydroxide minerals. Associated minerals are mendipite, diaboleite, chloroxiphite, wulfenite, cerussite and hydrocerussite. Discrete crystals were not found; intergrown crystalline aggregates are the usual form of occurrence. The maximum grain size is about 300 × 100 µm, but most grains are appreciably smaller. Parkinsonite was synthesized using high purity chemicals. The measured density of the synthetic material is 7.32 g/cm3; the calculated density is 7.39 g/cm3, the difference being due to minor impurity and slight porosity in the synthetic sample. Parkinsonite is translucent. Reflectance spectra were obtained in air and in oil. Refractive indices calculated from these (at 589 nm) are for Ro, 2.58, and Re', 2.42, i.e. uniaxial negative. VHN50 is 113–133 from which the calculated Mobs hardness is 2–2.5.

X-ray studies show that parkinsonite is tetragonal with space group I4/mmm, I4̄2m, I4̄m2, I4/mm, or I422 and a 3.9922(3), c 22.514(2) Å. It has a cell volume of 358.82(5) Å3 with Z = 1. The strongest six lines of the X-ray powder diffraction pattern are [d in Å (I) (hkl)] 2.823, 2.813(100) (110,008); 5.63(85) (004); 2.251(33) (116, 0.0.10); 2.988(27) (105); 3.750(15) (006); 1.994(11) (200,118). Averaged electron microprobe analyses give the empirical formula Pb6.34Mo0.89□0.77O8.02Cl1.98 on the basis of 10 atoms [O + Cl]. The name is for Reginald F. D. Parkinson, mineral collector of Somerset, UK, who first found the mineral.

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.

Iowaite has been re-examined using new, well crystallized material from the Palabora open pit mine, Transvaal. Microprobe, carbon analyser and thermal analyses, powder and single-crystal X-ray diffraction, infrared, UV-visible and mass spectroscopic and optical studies were made. The ideal formula is (OH)16Cl2·4H2O. It is trigonal, R3̄m, a = 3.1183(9), c = 24.113(8) Å, V = 203.1(2) Å3, Z = 3/8; Dobs 2.09 g/cm3.; Dcalc 2.04 g/cm3; hardness (Mohs)=2 1/2. The interlayer Cl− ions are displaced from the threefold axis. It is uniaxial negative, with ω = 1.561 ± 0.002, ε = 1.543 ± 0.002; coloured crystals are intensely pleochroic, due to intervalence charge transfer between the Fe3+ and Fe2+ substituting for Mg2+, with O pale yellow, E deep blue-green.

Synchrotron X-ray topography was the principal perfection-assessment method employed. X-ray wavelengths were chosen that gave optimum penetration and diffraction contrast characteristics for the size of crystals examined. Two colourles transparent specimens were selected for comprehensive study. Both were of simple habit consisting of the prism {101̄0} terminated at each end by major and minor rhombohedral facets only. The larger specimen, volume ≈250 mm3, contained a moderately high but non-uniformly distributed dislocation population, totalling ≈103, all emanating from a roughly centrally located small nuclear volume. One apical region was dislocation-free. Optical microscopic observations including Nomarski interference contrast of features on one major rhombohedral facet in this region are described. The smaller specimen, volume ≈30 mm3, was remarkable for its low dislocation content, ≈20 in total, all radiating from a central point. Enhancement of dislocation image visibility relative to diffraction contrast images of severe surface damage on this crystal was demonstrated using higher-order X-ray reflections. Neither of the specimens studied in detail contained twinning or evident diffraction contrast from impurity zoning. Their lack of a microscopically visible or X-ray topographically detectable nucleating body favours a homogenous nucleation origin of these crystals.

The phase petrology of two bodies of basic granulites occurring in association with supracrustal sequences within a dextral oblique-slip shear complex in the high-grade terrain of south India, have been studied. Some metabasites are characterized by garnet + clinopyroxene assemblages such as Grt + Cpx + PI ± Hbl ± Opx ± Qtz + Fe-Ti oxide(s) which are high-pressure granulites (garnet-clinopyroxene subfacies) transitional between the intermediate-pressure granulites (orthopyroxene-plagioclase subfacies) and eclogite. Mineralogical characteristics suggest that metamorphic conditions did not reach the eclogite facies but certainly approached that level. Close spatial association of the garnetiferous varieties with garnet-free assemblages (Opx + Hbl + Pl ± Cpx) and intimate juxtaposition of anhydrous and hydrous assemblages indicate a complex interplay of variable μH2O and bulk composition, especially αSiO2. Due to variable and low closure temperature of Fe-Mg exchange reactions between coexisting pyroxene and garnet, reliable estimation of peak temperatures during this near eclogite-facies metamorphism is problematic. A combination of a garnet-clinopyroxene barometer and various temperature estimates suggests P-T conditions of 875 ± 25°C and 8 ± 1 kbar for the Mettuppalaiyam samples and 900 ± 50°C and 14 ± 2 kbar for the Kanjamalai samples. Bulk rock chemical differences in terms of SiO2-content can account for the development of similar mineral assemblages along a near adiabatic metamorphic gradient between these two localities. These assemblages represent some of the highest grade granulite facies rocks in south India. The high-pressure granulites are not in situ samples of ancient lower continental crust, but low-pressure protoliths buried at depth. Textural features suggest that the high-pressure garnet-clinopyroxene subfacies rocks evolved from an amphibolitic assemblage by formation of garnet at the expense of hornblende and plagioclase and this high-pressure assemblage underwent an isothermal decompression indicating a clockwise P-T-t path resulting from crustal thickening and exhumation. A later isobaric cooling, possibly accompanying shearing and high H2O influx (aH2O≈0.78) gave rise to the coexisting orthopyroxeneplagioclase subfacies rocks (intermediate pressure granulites).

Combustion experiments up to 1400°C were carried out with subbituminous coals from the Teruel power station, the Teruel Mining District, the Santa Eulalia coal deposit and with lignite from the As Pontes power station in Spain. The characterisations of the occurrence and distribution of inorganic matter and its transformation during combustion of these coals were carried out by means of X-ray diffraction and optical and electron microscopy. The combustion experiments show that the incorgainc transformations during the combustion of all the coals studied vary depending on the sulphur and calcium contents. The sulphur, iron and calcium contents govern the quality of anhydrite crystallisation (which takes place between 600 and 900°C Furthermore, the high calcium oxide content produces the fouling of the combustion wastes at relatively low temperatures (1200°C), prevents the occurrence of mullite and magnetite in the ashes and leads to the crystallistation of anorthite and esseneite during the colling. The comparison of the inorganic phases of fly ashes and slags from the Teruel power station with those of the experimental wastes shows that the inorganic transformations during coal combustion in the power station can be predicted by means of laboratory furnace experiments provided that the residence time in the flame and the effect of the cooling and evacuation controls of gases and particles from the power station are taken in consideration.

The concept of force of crystallization is combined with that of depression of dissolution to explain diagenetic volume-for-volume replacement in both cases, either when the pressure is increased in early sedimentary settings, or when it is diminished in a late exposure. Also, a new textural criterion is added to the three classical ones in order to recognize diagenetic volume-for-volume replacement, and calculations are carried out to estimate the speed of the replacement.

The crystal chemistry of clinopyroxene, orthopyroxene and olivine from a crushed fragment of the H5 Zaoyang chondrite has been investigated by X-ray structure refinement and detailed microprobe analysis. The meteoritic pyroxenes have cell and polyhedral volumes which compare well with such data from terrestrial pyroxenes that typically crystallize at low-pressure. Fe2+ and Mg are rather disordered in M1 and M2 sites of clino- and orthopyroxenes; the closure temperatures of the exchange reaction are 600 and 512°C respectively, which is consistent with a reasonably fast cooling rate, estimated to be of the order of 1°C/day.

The closure temperature for the intercrystalline Ca-Mg exchange reaction for clino- and orthopyroxenes is 900°C as calculated from clino- and orthopyroxene intergrowth.

The cooling rates obtained from Fe2+-Mg intracrystalline partitioning suggest a cooling of the order of degrees per day at temperatures of 600–500°C due to a strong loss of heat by irradiation.

The evolution of Fe-containing phases of carbonaceous chondrites heated under various oxidation-reduction conditions was investigated by means of Mössbauer spectroscopy. Heating of the lower petrological types of chondrites (CM2) released gases which initially produced oxidizing conditions (∼450°C) and then reducing conditions (> 700°C Phase transformation occurred rapidly (during 1–5 minutes) at all temperatures. During heating the Fe-bearing phyllosilicate phases in CM2-chondrite converted to Fe-bearing olivine, metallic iron and troilite (pentlandite). These phases resemble those of CO3, CV3 and EH-chondrites. Iron distribution resembling that of ordinary chondrites (some additional Fe2+ in pyroxene) was obtained only by heating a mixture of oxidized matter (CM2) with reduced matter (EH).

A phase transition discovered at 1050°C is probably the temperature boundary between conditions of formation of the two main components of ordinary chondrites: matrix and chondrules. Chondrules of ordinary chondrites may be formed at temperatures > 1050°C while the matrix forms at temperatures < 1050°C For the carbonaceous chondrite Kainzas (CO3) these temperatures are approximately 1000°C and < 900°C The experimental conditions determined for the evolution of chondrites do not contradict the theoretical two-component model of Wood-Anders-Ringwood and may further its development.