Porosity occlusion has been studied in a granodiorite rock from the Peruvian Coastal Batholith. The texture of the granodiorite is characteristic of Cordilleran I-type rocks, and the textural relations and modelled crystallization path within the quaternary An-Ab-Or-Qz system indicate alkali feldspar was the last major phase to start crystallizing. In thin section, alkali feldspar crystals occur both as large anhedral ‘plates’ containing numerous inclusions, and small interstitial cuneiform ‘pockets’. The alkali feldspar pockets are interpreted as late stage nucleation and growth of new crystals in pores that became isolated from the larger crystals during the latter stages of crystallization. Their geometry therefore mirrors that of the pores immediately after isolation.

From the modal abundance of the interstitial pockets, and taking into account contemporaneous growth of the other major phases, it is suggested that crystallization in isolated pores involved solidification of the final 3–4% of liquid. Alkali feldspar growth on the rims of the large anhedral plates prior to pore isolation is evidence for the localised (mm-cm scale) diffusion of chemical species within the interconnected melt phase. However, Rayleigh number calculations indicate that the separation of melt from crystals by compositional convection is unlikely to have occurred during interstitial crystallization.

Reaction textures including corona structures in granulites from the Proterozoic Long Range Inlier of western Newfoundland are spatially associated with a Silurian (0.34 Ga) mafic intrusion, the Taylor Brook Gabbro Complex. They comprise, in metabasites and tonalitic gneiss, coronal orthopyroxene and plagioclase on garnet and, in metapelites, cordierite and spinel formed at the expense of sillimanite, garnet and quartz. Although generally interpreted to indicate near-isothermal decompression (ITD) following regional metamorphism, which in the inlier occurred at ˜1.10–1.03 Ga, these features appear to be absent elsewhere. Therefore they are interpreted to be products of contact metamorphism (near-isobaric heating – IBH) within the thermal aureole of the gabbro. Thus, there is a ˜0.7 Ga difference (i.e. mid-Proterozoic vs. mid-Silurian) between the age of the regional metamorphic mineral assemblages and the contact aureole assemblages. The observation that classic ITD features occur in this aureole environment underscores the fact that P-sensitive reactions can progress during IBH as well as by pressure release.

Vaughanite, idealized formula T1HgSb4S7, is a very rare primary constituent of the Golden Giant orebody of the Hemlo gold deposit, Hemlo, Ontario, Canada. It was found in two polished sections from one drill core; as a 450 by 300 µm aggregate associated with pääkkönenite, stibnite, realgar, and native arsenic; and as a 40 µm anhedral grain associated with stibarsen and chalcostibite. Vaughanite is opaque with a metallic lustre and a black streak. No cleavage was observed but parting, produced by indentation, was detected as a series of weak parallel traces. It is brittle, with an even, occasionally arcuate, fracture. VHN25 is 100–115, mean 104. Mohs hardness (calc.) = 3−3½. In refected plane-polarized light in air the bireflectance is weak to moderate; the pleochroism is also weak, from a somewhat greenish grey to slightly darker bluish grey. Anisotropism is moderate to strong, with rotation tints in shades of green, yellow, purplish brown to brown. Reflectance spectra and colour values are tabulated. The colour in air is light grey. Internal reflections are rare but are arterial-blood-red on indentation fractures. X-ray studies have shown that vaughanite is triclinic with refined unit-cell parameters a 9.012 (3), b 13.223 (3), c 5.906 (2) Å, α 93.27 (3)°, β 95.05 (4)°, γ 109.16 (3)°, V 659.46 (80) Å3, a:b:c = 0.6815 : 1 : 0.4466 and Z = 2. The space group choices are P1 (1) or (2), diffraction aspect P*. The five strongest lines in the X-ray powder pattern [d in Å (l) (hkl)] are: 4.343 (30) (), 4.204 (100) (), 3.313 (60) (130), 2.749 (40) (, 131) and 2.315 (30) (, 122). The average of five electron microprobe analyses gave T1 18.3 (2), Hg 17.5 (2), Sb 43.4 (3), As 1.1 (1), S 20.5 (5), total 100.8 wt. %, corresponding, on the basis of total atoms = 13, to T10.98Hg0.95(Sb3.90As0.17)Σ4.07S7.00. The calculated density is 5.56 g/cm3 for the empirical formula and 5.62 g/cm3 for the simplified formula. The mineral is named for Professor David J. Vaughan.

A rich vein of silver and silver-lead sulphosalt minerals was discovered in 1906 in the Meerschaum Mine, on the Sunnyside goldfield at Mt. Wills, in northeastern Victoria. Andorite, miargyrite, tetrahedrite (freibergite), owyheeite, and argentian gold are the main silver-bearing minerals present, and sphalerite, pyrite, arsenopyrite, and covelline also occur in the vein.

The vein was probably emplaced under epithermal conditions from ore fluids accompanying the intrusion of the Mt. Wills granite. The main silver-bearing minerals were probably deposited at temperatures ranging from about 350 ° to below 300 °C.

Semi-aquatic and native plants collected from a mining site in the Iberian Pyrite Belt were analysed. Semi-aquatic plants showed enrichment of Cu (1.2—11 times), Zn (1.3—6 times), Pb (5—8 times) and As (24—1300 times) relative to typical concentrations in plants of the same species growing at uncontaminated sites. Translocation factors indicate limited internal metal transportation from roots to shoots. Infrared spectroscopy identified aromatic and aliphatic C-H (CH2) groups, S-O complexes and kaolinite in semi-aquatic plants.

The crystal chemistry of tapiolite is more complicated than previously recognized. Perusal and synthesis of relatively recent publications reveals a ‘hidden’ story about tapiolite, one that: (1) permits quantification of the effects of Mn, Fe3+, Ti (and Sn) upon the unit-cell parameters of maximally ordered tapiolite; (2) shows that the effect of Nb = Ta substitution upon unit-cell parameters is insignificant; (3) casts doubt on the usefulness of heating experiments for accurately evaluating cation order in tapiolite; (4) suggests that rutile exsolves from tapiolite upon heating in air at lower temperatures than previously established; (5) shows that the maximum solubility of TiO2 in FeTa2O6 tapiolite during the later stages of crystallization of granitic pegmatites is ∼1 mol.%; (6) shows that the heating paths for at least some natural tapiolite samples are not necessarily linear, consisting of two sequential steps; (7) sheds doubt on the usefulness of unit-cell parameters as quantitative measures of long-range cation order, Q, in tapiolite; but (8) does show that the intensity ratio I011/I110 can provide an accurate and reasonably precise measure of cation order in tapiolite.

A sample of levyne-Na from Dunseverick, Antrim, Northern Ireland, UK, has been characterized from the crystal chemical and structural point of view. Its mean crystal chemical formula, calculated on the basis of 54(Si+Al), is Na7.72Ca4.62K1.31Sr0.08Mg0.02(Al19.55Si34.45O107.50)·50.5H2O. Levyne-Na is associated with erionite-Na whose chemical formula is Na6.08Ca0.8 5K2.55Mg0.16(Al10.41Si25.59O72.13)·30.6H2O, calculated on the basis of 36(Si+Al). Their compositions are consistent with those of levyne/erionite inter/overgrowth reported in the literature. The structural analysis, carried out by the Rietveld method on laboratory parallel-beam X-ray powder diffraction data, is in good agreement with the chemical composition representing a significant improvement with respect to the available data so far. Extra-Framework (EF) cations are allocated at four sites, Ca1, Na3, K4 and Na5 with partial occupancy. Water molecules are distributed among five sites. Possible coexistence schemes of cations, forced by the avoidance of short contacts are proposed and validated by bond valence analysis.

Sub-greenschist facies metamorphism has produced unusual subcalcic, Fe-rich actinolitic amphiboles in meta-dolerites from the Glenrock Station area, NSW. They show edenite, riebeckite, ferri-tschermakite and Ti-tschermakite coupled substitutions. Their high Fe content is attributed to high aFe2+ and aFe3+ in the fluid phase produced during the breakdown of clinopyroxene, hornblende, magnetite, and ilmenite. The high aFe2+ led to Fe led to Fe2- occupying the B site, resulting in the formation of subcalcic amphiboles. Variation in aFe2+, aFe3+, aMg, aSi, aAl, and aCa, in different domains resulted in the crystallization of chemically inhomogeneous amphiboles.

The crystalch emistry and crystal structure of naturalky anite crystals from the Eclogitic Micaschists Complex of the Sesia-Lanzo Zone, Western Italian Alps, have been investigated by means of optical microscopy, wavelength dispersive X-ray microanalysis, and single-crystal X-ray diffraction. The association of kyanite + garnet + phengitic-mica + chloritoid suggests that the eclogite-facies stages occurred at P ≤ 2.1 GPa and T ≤ 650ºC. Kyanite grains are large (cm-sized) porphyroblasts grown dynamically during one of the deformational events related to the subduction of the Austroalpine continentalcr ust. Under the polarizing microscope, kyanite grains show almost homogeneous cores, whereas rims are sometimes symplectitic aggregates of quartz and kyanite, confirming at least two stages of growth most likely related to the multistage deformational history of these rocks. Chemical analysis shows that Fe3+ is the major substituting cation for Al3+, ranging between 0.038 and 0.067 a.p.f.u.

The single-crystal X-ray diffraction investigation of the kyanites shows severely textured patterns on the (h0l)*-plane. Such evidence is not observed in the unwarped diffraction patterns on (0kl)* and (hk0)*. The most significant difference between the structuralp arameters refined in this study, with respect to those of previously published unstrained gem-quality crystals, concerns the displacement parameters. The anisotropic displacement ellipsoids of all the atomic sites are significantly larger than those previously described, and systematically oriented with the largest elliptical section almost perpendicular to [010]. The larger ellipsoids in the kyanite crystal investigated here reflect the displacement of the centre of gravity of the electron distribution, rather than an anomalous atomic thermal motion. The magnitude and orientation of the displacement parameters and the textured/strained diffraction pattern may be the result of two combined effects: (1) that the kyanite crystals are actually composed of several blocks; (2) the crystals are affected by a pervasive residual strain, as a result of tectonometamorphic plastic deformations and re-crystallization.

Corkite associated with plumbojarosite and goethite occurs in gossan and iron-formation at Black Mountain and Broken Hill, Aggeneys. Electron microprobe analyses indicate that there are two groups of corkite present in the area; one with high Cu and low (PO4)3− and the other with low Cu and high (PO and the other with low Cu and high (PO4)3− contents. This can be explained in terms of the general formula contents. This can be explained in terms of the general formula AB2(XO4)2(OH)6, where the incorporation of divalent ions in the B site is accompanied by the exchange of trivalent anions by divalent ones to retain charge balance. Complete solid-solution is inferred between (SO4)2−and (PO4)3− end members, indicating that the jarosite and beudantite groups form part of the same solid-solution series. The distribution of Zn in corkite also reflects the regional distribution of zinc grades in the area, becoming more zinc-rich from west to east. New X-ray diffraction parameters are also presented which update existing data.

Based on geological studies, 141 rock analyses and 5 trace element analyses of metabasites, the present paper deals with the rock association, chemical features, protolith formation and the original tectonic settings upwards through the Lower Proterozoic metamorphic strata in the Dabieshan-Lianyungang area, in the south-east of the North China Platform. The results of the study indicate that the lower and middle parts of the metamorphic strata comprise terrigenous clastics, phosphoritic and aluminous sedimentary formations which formed under stable continental margin conditions. In the middle-upper part a calc-alkaline volcano-sedimentary formation under the active continental margin was developed. The Lower Proterozoic meta-strata of sedimentary-volcanosedimentary origin from bottom upwards suggest that the tectonic evolution of the south-eastern margin of the North China Platform is a process from stabilization to mobilization. This process suggests a northward subduction of the Yangtze Plate under the North China Plate during the later part of the early Proterozoic.

Sampleite from Jingemia Cave, Watheroo (30° 16′ S. 116° 00° E.), 190 km north of Perth, Western Australia is derived from the alteration of copper sulphides in contact with guano deposits. Associated minerals are atacamite, weddellite, and gypsum on goethite and manganese-oxide-coated friable quartz rock. Birnessite, halite, dolomite, taranakite, todorokite, apatite, and malachite are also present.

The sampleite occurs as platy spheroidal aggregates to 0·3 mm with D 3·20±0·01, α 1·625 ∥ [010], β and γ 1·674, all ±0·002, α Turquoise Green 41d to Light Blue-Green 39d, β and γ Benzol Green 41 to Venice Green 41b, absorption α < β = γ, 2Vα 5–10°. Chemical analyses are given.

Cu3(PO4)2·3H2O, a corrosion product reported on artifacts, is believed to be sampleite. A further occurrence of sampleite has been recorded from Brookton, 120 km ESE. of Perth. The structurally related mineral lavendulan has been reported from five Western Australian localities.

Major- and trace-element data are presented for basic dykes intruding the Eastern Red Hills district of the Tertiary igneous centre of Skye. In addition to a group of transitional basic intrusions, members of two other distinctive suites have been identified: (1) a series of basic alkaline intrusions (akin to the ‘Beinn Dearg Type’ of Harker, 1904), with characteristic high alkali contents, distinctive values of K2O/(K2O + Na2O) and rare-earth-element (REE) patterns similar to those of many of the Tertiary lavas of north Skye, and, (2) tholeiitic dykes, with low concentrations ofK2O, Ti/Zr values of c. 100, and flat REE patterns similar to those of the so-called Fairy Bridge magma type (Mattey et al., 1977). From these data and a consideration of the time relationships of the various components of the Skye Centre, agreement is found with Thompson et al.'s (1972, 1980) model of a mantle thermal anomaly which generates the magmatic sequence: transitional basic magmas, giving way to olivine-bearing tholeiitic magmas (at the culmination of the anomaly), and, finally, late-stage basic alkaline magmas at the end of the activity.

Supposed 'merlinoite' crystals from Monte Somma, Vesuvius (Italy) and Fosso Attici, north of Rome (Italy) represent highly twinned coherent intergrowths between merlinoite and phillipsite on a submicroscopic level. The MER (Immm, a ≈ 14.1, b ≈ 14.2, c ≈ 9.9 Å) and PHI (P 21/m, a ≈ 9.9, b ≈ 14.3, c ≈ 8.7 Å, β = 124.8°) frameworks of similar composition are assembled from identical tetrahedral units, though with a different connectivity. Coherent intergrowth and twinning of the two frameworks lead to P42/mnm pseudosymmetry, which is diagnostic of the intergrowth. Under ambient conditions merlinoite has Immm symmetry or I4/mmm if twinned. a low-symmetry model of space group P121/m1 (a ≈ 14.2, b ≈ 14.2, c ≈ 10 Å, β = 90°) allows structure refinement and quantification of the two frameworks.

Upon in situ dehydration to 250°C the evolution of the unit-cell volume of the Monte Somma merlinoite/phillipsite intergrowth displays an intermediate trend between previously studied pure merlinoite from the Khibiny massif (Russia) and Ba-rich phillipsite.

The Monte Somma crystal studied by temperature-dependent single-crystal X-ray diffraction methods also contained a subordinate chabazite inclusion with no coherent structural relationship to the merlinoite/phillipsite framework. Thus, the modification of the chabazite framework on dehydration could also be studied.

The validity of Haüy's great law of the rationality of intercepts — better known as the law of rational indices—or its equivalent, the law of homogeneity of arrangement of the ultimate particles in a crystalline structure, has as yet never been seriously called into question : nevertheless, in the crystals of the telluride of gold, calaverite, we find characters which are to all appearance at variance with this law. As far as the author is aware and can ascertain, no difficulty of a precisely similar kind has ever been encountered before. Certain substances do, indeed, display the so-called optical anomalies; but these are, as was first established by Mallard, in reality in strict accordance with the actual crystalline arrangement.

If a drop of strong solution of potassium bichromate, placed upon a microscope-slide, be observed under the microscope as it crystallizes, and if the drop be sufficiently thin, it will generally be found that the following events take place: The first crystals make their appearance at the edges of the drop and after growing rapidly for a short period as branching fibres, they begin to grow quietly in the form of plates or flattened rods presenting the characteristic form of the crystals of this substance. These crystals continue to grow uniformly, but after a short period, at a distance from the growing crystals, and at some spot where the drop is thin, a fresh crystalline growth starts suddenly from a point, and extends with great rapidity in all directions in the form again of branching needles and fibres.

The Cairnsmore of Carsphalrn igneous complex (1) is the smallest of the larger Caledonian intrusions of the Southern Uplands of Scotland. The intrusion is composite, consisting of a central granite, followed by successive zones of granite-tonalite hybrid, tonalite, and basic hybrids. The complex began with the intrusion of a gabbro. When this was crystallized, but still at a high temperature, the tonalite was emplaced. This intrusion of tonalite produced a series of hornblende-hybrids. The hybridization of the original gabbro attendant on the injection of the tonalite is the result of a 'partial magma' of potash-felspar, quartz, and volatiles. The final intrusion of granite took place while the tonalite was still incompletely crystallized, and resulted in the formation of a zone of acid hybrid rocks. The three biotites that have been analysed occur in the granite, tonalite, and hornblende-hybrid respectively.

A new method of determining the optic axes from a few extinction measurements is presented. It is based on the progressive elimination of those parts of the stereogram in which it is obvious that the optic axes cannot lie. It has two applications: as a valid method in its own right, if applied systematically; and as a reconnaissance technique. The second application permits, for example, the recently presented trisogon technique to be rapidly and economically applied over a very small fraction of the stereogram instead of over its whole area.