bluuebunny/crossref_metadata_2025 huggingface dataset:
Xocomecatlite, Cu3TeO4(OH)4, and tlalocite, Cu10Zn6(TeO3)(TeO4)2Cl(OH)25·27H2O, two new minerals from Moctezuma, Sonora, Mexico
Authors: Williams S. A.
Published: December 2006

Xocomecatlite and tlalocite were found at the Bambollita mine near Moctezuma, Sonora. Xocomecatlite is probably orthorhombic, and an indexed cell based on the powder data gave a 12.140 A, b 14.318, c 11.662. Based on this cell, the empirical contents are Cu36.6 Zn1.7 (TeO4)12.5 (OH)51.6 or Cu3TeO4(OH)4. Tellurate was found both microchemically and by spectrophotometry. Colour rich green (R.H.S. 132A) with pale streak, H = 4. Optically negative with α = 1.775, β = 1.900, γ = 1.920. G = 4.65.

Tlalocite is optically orthorhombic but the cell could not be indexed; only powder data are presented. Chemical analysis showed both tellurite and tellurate and led to the formula

Colour pale blue (R.H.S. 121A) with a whitish streak; H = 1, gummy and sectile. G = 4.55.

Plotting stability fields for various Te species at 25°C in terms of Eh and pH showed that TeO42−.aq can exist in nature over a wide pH range, but only under extreme conditions of oxidation.
Thermal transformation of lepidomelane
Authors: Akizuki Mizuhiko , Konno Hiroshi , Yamauchi Noriyoshi , Sunagawa Ichiro
Published: December 2006

Lepidomelane, an iron-rich biotite, was heated in air or in vacuum, or by electron bombardment, and the processes of dehydration and transformation were studied by means of X-ray diffractometry, optical microscopy, and electron microscopy. By heat treatment, vacancies are at first formed by the evaporation of water molecules and alkali ions, and they move and condense to form holes, which act as preferential nucleation sites for new phases. Other preferential sites are edges of exposed silicate sheets along microcracks, and these are decorated by a newly formed maghemite- like mineral whose a is 10.20 Å (on a hexagonal cell), so that the sites can be clearly seen even under the reflection microscope. By heating at higher temperatures or prolonged heating, various phases, olivine, hematite, magnetite, and leucite are formed, depending upon the conditions of dehydration.
The phosphate mineralogy of et-Tabun cave, Mount Carmel, Israel
Authors: Goldberg P. S. , Nathan Y.
Published: December 2006

Phosphates introduced into the et-Tabun cave as a result of human habitation, mainly as bone material, were partly dissolved by slightly acid solutions (organic acids derived from human or other animal activity). From these solutions, dahllite precipitated when the solutions came into contact with calcite. In the more weathered parts of the section, where little or no calcite occurs, the phosphate minerals formed are montgomeryite and crandallite.
Geochemical indicator of the efficiency of fractionation of the Skaergaard intrusion, East Greenland
Authors: Henderson Paul
Published: December 2006

When magmatic fractionation involves the settling and removal of crystals from the body of magma, the efficiency of the fraetionation process may be defined as the degree of separation of the solid from the liquid phase. An expression is given that relates efficiency to the amount of mesostasis, or crystallized trapped liquid, in an igneous cumulate. The uranium contents of samples from a 349-m-long drill-core of part of the lower and hidden zones of the Skaergaard intrusion are used as a quantitative indicator of the amounts of mesostasis in the cumulates. There are marked changes in the amount of mesostasis over the length of the core and the average efficiency of fractionation was 85 %.
Microstructural interpretation of some fibrolitic sillimanite aggregates
Authors: Vernon R. H.
Published: December 2006

Fibrolitic sillimanite in some high-grade gneisses from Broken Hill, Australia, shows microstructural features suggestive of compatibility with the main coarser-grained assemblage, namely: framework-silicate interfaces either meet (110)-sillimanite/framework-silicate interfaces at approximately 90° or are attached to the ends of 'fibrolite' rods; framework-silicate interfaces are deflected by 'fibrolite' grains; and interfaces of inclusions of one framework silicate in another are deflected by 'fibrolite' grains, producing irregular, rather than rounded, inclusion shapes. These criteria suggest that the 'fibrolite' in some rocks is a compatible member of the main metamorphic assemblage. Its persistence as small grains may be due to a high proportion of relatively low-energy prismatic boundaries in the fibrolitic aggregates.
Clinopyroxenes and biotites from the Centre III igneous complex, Ardnamurchan, Argyllshire
Authors: Walsh J. N.
Published: December 2006

Major- and trace-element analyses of the clinopyroxenes and biotites from the ring-intrusions of Centre III in the Tertiary igneous complex of Ardnamurchan are presented. It is shown that there are systematic differences in mineral chemistry between the eucrites, the gabbros, and the dolerites, and in particular the clinopyroxenes show an iron enrichment trend that is similar to that found in fractionated tholeiitic intrusions. The minerals from the intcrmediate rocks, the tonalite and quartz monzonite in the centre of the complex, do not show the further iron enrichment expected if these rocks had formed by continued fractionation of basic magma. On the basis of the chemistry of the clinopyroxenes and biotites, the intermediate rocks are interpreted as hybrids formed by the remelting and assimilation of country rocks into basic magma.
The crystal structure of galeite, Na15(SO4)5F4Cl
Authors: Fanfani L. , Nunzi A. , Zanazzi P. F. , Zanzari A. R.
Published: December 2006

The crystal structure of galeite from Searles Lake (California) has been determined by means of X-ray diffraction data on a single crystal. A possible structure was derived from that of schairerite on the basis of chemical and lattice analogies and was confirmed by comparison of the observed diffractometric structure factors with the calculated ones. The refinement was performed by least-squares methods employing isotropic thermal parameters and assuming that atoms related by translational pseudosymmetry exhibit equal thermal parameters. The final R value is 0·09. The cell content is 3[Na15(SO4)5F4Cl]; the space group is P31m The lattice dimensions are a 12·197(4)Å, c 13·955(10) Å The marked subcell has P3m1 symmetry and a 7·042Å, c 13·955 Å. The crystal structure of galeite consists of a three-dimensional framework, formed by coordination octahedra around Na+ ions, including tetrahedral holes with sulphur atoms at the centres. The three-dimensional framework can be considered built up by five octahedral sheets (seven sheets can be recognized in schairerite and six in sulphohalite). The very close analogies occurring in the structures of galeite and schairerite are discussed.
Base metal enrichment in volcanic sublimates and secondary alteration products from Vesuvius and Vulcano
Authors: Angus J. G. , Davis G. R.
Published: December 2006

A wide range of volcanic sublimates and alteration products from the Johnston-Lavis collection has been analysed for major elements plus copper, lead, and zinc. 'Aphthitalite' and 'natrikalite' from Mount Vesuvius and an 'alum' from the island of Vulcano all proved to be enriched in copper and selected analyses are tabulated. The process leading to copper and lead enrichment of the Vesuvian material may be vapour phase transport as chloride followed by sulphation on sublimation. It is suggested that the source of the copper found in the alum sample from Vulcano could be of interest to economic geologists.
Effect of pressure on reversible solid-solid transitions in nepheline and carnegieite
Authors: Cohen Lewis H. , Klement William
Published: December 2006

Differential thermal analysis of a rapidly reversible transition in carnegieite to 7 kbar shows the transition temperature increases from ⪝ 707°C (on heating) at I bar with initial slope ≈ 8·0 deg kbar−1 and anomalous curvature (d2T/dp2 > o), with hysteresis between heating and cooling signals that decreases with pressure. DTA of rapidly reversible transitions in nepheline shows the very subtle transition near 185°C (on heating) at 1 bar decreases with pressure to ≈ 170°C near 2-3 kbar and hardly varies in temperature up to 6 kbar; and the higher temperature transition increases from ≈ 872°C (on heating) at 1 bar with slope ≈ 25 deg kbar−1, to 5 kbar, with the hysteretic interval remaining essentially unchanged in the investigated range.
A metamorphosed, layered alpine-type peridotite in the Langavat Valley, South Harris, Outer Hebrides
Authors: Livingstone A.
Published: December 2006

A layered aipine-type peridotite, of pre-Scourian age(?), has been metamorphosed in the granulite facies then partially retrogressed to greenschist facies assemblages. Following granulite facies metamorphism of the dunite-harzburgite peridotite, granitization and metasomatism modified the peridotite by adding calcium and generated olivine-tremolite rocks. Anthophyllite-rich rocks developed from localized orthopyroxene-rich zones. The main epoch of serpentinization followed after tremolite formation and removed a portion of the calcium previously added, but with negligible effect upon the original trace-element content. Between tremolite generation and the main period of serpentinization greenschist facies assemblages formed. The layered rocks possess a repetitive, chemical variation normally attributable to basic igneous processes, although they may have formed either by vein metasomatism or by metasomatism of a disrupted layered igneous series. Twelve rock and five mineral analyses are presented, and trace element data for twenty-one rocks.
Clinoptilolite from zeolitized tuffs of Azerbaidzhan
Authors: Kashkai M.-A. , Babaev I. A.
Published: December 2006

A study has been made of a large clinoptilolite deposit in the Lesser Caucasus (Azerbaidzhan SSR). The geological conditions have been examined and a number of samples investigated by optical, electron-microscopic, chemical, X-ray, thermal, and infra-red methods. Based on these investigations and on comparison with previous literature, mineralogical, chemical, and geochemical conclusions are drawn and conditions for clinoptilolite genesis are considered.
The Mössbauer spectrum of a ferrian muscovite and its implications in the assignment of sites in dioctahedral micas
Authors: Goodman B. A.
Published: December 2006

A muscovite that contains iron almost entirely in the ferric form has been studied by M6ssbauer spectroscopy. It is established that Fe3+ ions in the sites with cis hydroxyl groups have similar parameters in both muscovite and biotite. By assuming that Fe2+ ions will also have similar parameters for these sites in both minerals the M6ssbauer results of other workers have been reinterpreted. This new interpretation, which is in complete agreement with the X-ray structural analysis of Radoslovich (1960), indicates that in muscovite the sites with cis hydroxyl groups are filled in preference to those with trans hydroxyls. These sites are occupied primarily by trivalent ions. There is possibly a preference for divalent ions by the unique sites with trans hydroxyl groups, but occupation of these sites appears to occur only when the other sites have been filled.
The geochemistry of 'charnockites' and their constituent ferromagnesian minerals from the Precambrian of south-east Sri Lanka (Ceylon)
Authors: Jayawardena D. E. De S. , Carswell D. A.
Published: December 2006

A chemical and petrographic study of charnockites and pyroxene/hornblende-bearing granulites has been undertaken, and the data used in an interpretation of the petrogenesis of these rocks. Major- and trace-element analyses of fourteen rocks are presented, together with majorelement analyses of seven orthopyroxenes, seven clinopyroxenes, two garnets, and three hornblendes. The compositions of the coexisting ferromagnesian minerals are used to obtain estimates of the likely pressure/temperature conditions of equilibration (5-7 kbar and 700±50°C of the various mineral assemblages.
A model for trace-element distribution in silicate structures
Authors: Iiyama J. T. , Volfinger M.
Published: December 2006

This paper presents an extended version of the local lattice deformation model of solid solutions (J. T. Iiyama, 1974b). It has been assumed previously that a foreign atom fixed in a crystal causes local lattice deformation, which prevents another foreign atom from occupying the deformed zone. The resulting entropy of the solid solution from this model can explain the particular behaviour of ion-exchange reactions observed with alkali and alkali-earth elements in feldspars and in muscovite. The present version assumes that the deformed zone does not prohibit foreign atoms, but that the number of foreign atoms acceptable in this region depends on the total numbers of foreign atoms already fixed in the crystal. The model is applied successfully to explain ion-exchange isotherms observed with Cs, Na, and Li in micas and permits an estimation of the apparent reaction constant of the ion exchange. This is otherwise impossible because of the lack of ideal dilute-solution behaviour in exchange isotherms even at the IO ppm range of the foreign element fixed into the crystal. It is demonstrated that the model can explain the particular behaviour of Li in sanidine.
The progressive crystallization and ordering of low-temperature dolomites
Authors: Schneider Hartmut
Published: December 2006

The progressive crystallization of dolomite has been investigated in the temperature range of 90 to 410°C by means of X-ray powder diffraction, electron microscopy, and infra-red spectroscopy.

Short-time, low-temperature experiments (≤ 145°C yielded dolomites with a high defect density. In detail, lattice faults can be described as: Random succession of more or less ordered cation domains, producing a long-range mosaic-type disorder; cation ordering may take place along <101̄0> and <112̄0> tilting and dislocation of individual CO3 groups; and irregular interstratification of dolomite layers of different chemical compositions in the crystallographic c-directions.

Dolomites produced in experiments of longer duration are composed of an interstratification of essentially two chemically different dolomite layers, of which the stacking sequence is more perfect than it is at lower crystallization degrees. Both components grow rapidly at the expense of dolomites of intermediate composition. Finally, long-term low-temperature (145°C) experiments produced two independent, coexistent dolomite phases. Within single dolomite layers cations now lie very close to their theoretical positions. CO3-tilting and dislocation decreases markedly.

Hydrothermal runs at temperatures > c. 145°C yielded one single, nearly stoichiometrie, highly ordered dolomite phase. Finally, dolomites synthesized at temperatures > c. 200°C are of an ideal chemical composition and have perfect lattice ordering.
Petrogenetic significance of some new xenolithic alkaline rocks from East Africa
Authors: Rock N. M. S.
Published: December 2006

New occurrences of xenolithic alkaline rocks from three East African volcanoes are described. Micro-ijolites and alkali pyroxenites occur in the carbonate-rich tufts and lavas of Mount Elgon; kaersutite-rich pyroxenites and a suite of fenitized basement rocks in the caldera flows of Mount Meru, and apparently unique melanocratic hortonolite nepheline syenites in the central foyaite plug of Mount Kenya. The 87Sr/86Sr ratios indicate mantle origin, and all are enriched in trace elements such as Sr, Nb, and Zr. The xenoliths from Mount Kenya are cumulate equivalents of the glassy kenyte lavas of the mountain; the pyroxenites of Mount Elgon are also cumulates whose predominant titanaugite is of identical composition to that of the host lavas. The contrast between the 'dry' Elgon pyroxenites and the 'wet' amphibole-rich types from Mount Meru is believed to reflect different CO2/H2O ratios in the volatile phase accompanying the alkaline vulcanicity. Strongly alkaline, carbonate-rich suites such as that of Mount Elgon derive from fairly dry alkali-basaltic magma under high CO2 activity by dominant pyroxene fractionation, whereas the mildly alkaline lineage seen in some areas of Mount Meru forms under more hydrous conditions in which amphibole fractionation is important. Mount Meru in addition shows a transition to rock-types typical of the strongly alkaline lineage, and this is reflected in the occurrence of relatively amphibole-poor pyroxenites with the amphibole-rich types.
Genthelvite and the helvine group
Authors: Dunn Pete J.
Published: December 2006

A plot of seventy-five new analyses of members of the helvine group and fifty-seven analyses from the literature indicates complete miscibility between the Fe and Zn members (danalite and helvine) and between the Fe and Mn members (danalite and genthelvite). The new analyses include essentially pure helvine and genthelvite (for both of which X-ray data are presented) and the nearest approach to pure danalite (86 at. % Fe). Two new localities for genthelvite, the rarest member, are reported.
Petrogenesis of migmatites in the Huntly-Portsoy area, north-east Scotland
Authors: Ashworth J. R.
Published: December 2006

Migmatites are described from the Sillimanite-potash-feldspar Zone of the aureole around the Newer Basic suite of synorogenic intrusions. The lowest-grade migmatites are trondhjemitoid (characterized by the assemblage quartz-plagioclase-biotite) or muscovite-granitoid (quartz-plagioclase potash-feldspar-muscovite-sillimanite-biotite). With increasing grade, a transition occurs to cordierite-granitoid assemblages (quartz-plagioclase-potash-feldspar-cordierite-garnet-sillimanite-biotite), which persist to the highest grades observed, where there are also noritoid migmatites (quartz-plagioclase-orthopyroxene-cordierite-biotite). The trondhjemitoids are texturally simple because the minerals did not undergo dehydration reactions. Textural immaturity and consistently cotectic modal compositions indicate that their leucosomes originated as melts. Scatter of plagioclase compositions suggests that the partial melting occurred in small closed systems. The other migmatites have more fusible compositions, so it is deduced that they also underwent partial melting. Retrograde reaction textures are used to infer the sequence of reactions, involving muscovite and biotite, by which melting proceeded during prograde evolution. Whereas the fugacity of water probably varied among spatially associated trondhjemitoid leucosomes, in the muscovite-granitoids it was constrained to an approximately constant value, at given pressure and temperature, by the buffering effect of the mineral assemblage.
Distinct cooling histories of troctolites from the Freetown layered gabbro
Authors: Bowles John F. W.
Published: December 2006

The iron-titanium oxide minerals of three troctolites from the Freetown layered gabbro have been analysed using an electron microprobe. Comparisons of the analyses of the iron-titanium minerals with the data of Buddington and Lindsley (1964) provide temperature and oxygen fugacity information relating to particular magnetite-ilmenite grains. Magnetite-ilmenite grains occurring in different silicate environments within any one single troctolite rock have equilibrated at differing times in the cooling history of that rock and this enables part of that history to be established. The partial cooling histories established for the three specimens can be clearly distinguished, and are strongly influenced by the appropriate buffer reactions.
Narsarsukite: a new occurrence in peralkaline trachyte, south Greenland
Authors: Upton B. G. J. , Macdonald R. , Hill P. G. , Jefferies B. , Ford C. E.
Published: December 2006

A flinty, spherulitic dyke of peralkaiine trachyte in a Precambrian dyke-swarm consists mainly of albite and aegirine. Within this, euhedral crystals of narsarsukite, Na2(Ti,Fe)Si4O10(F), occur as short prisms elongate parallel toc. This distinguishes them from all previously described narsarsukites, which have tabular habits. Minor phases present include micas, apatite, quartz, pectolite, nordite, and a thorium silicate. Probe analyses are presented for narsarsukite, aegirine, aibite, biotite, apatite, pectolite, nordite, and the thorium silicate.

On mineralogical and geochemical grounds it is unlikely that the narsarsukite-bearing dyke is a differentiate of supposedly mantle-derived basalt-trachyte-comendite magmas in the region. The dyke is colinear with a comendite dyke exposed at lower altitude and it is suggested that the narsarsukite- bearing dyke developed as a rhcomorphic fenite generated by reaction between quartz diorite basement and fugitive alkaline solutions from the subjacent comendite.
Lithium tourmalines from the Meldon aplite, Devonshire, England
Authors: Chaudhry M. N. , Howie R. A.
Published: December 2006

Seven chemical analyses of pink or green tourmalines belonging to the elbalte-schorl series, along with their physical, optical, and X-ray data are presented. Linear variation diagrams showing the relationship between composition and refractive indices, specific gravities, and cell parameters are constructed. Relationship between colour and chemical composition is also discussed.
The chemical evolution of glauconite pellets as seen by microprobe determinations
Authors: Velde B.
Published: December 2006

Seven samples of pelletat glauconites with varying iron and potassium contents were investigated using the electron microprobe. In-sample variation of pelletal compositions is quite important, even for samples previously separated according to grain-size, density, and magnetic susceptibility. This observation should lead to a reconsideration of previous work based upon multigrain samples.

During the evolution of pelletal material towards micaceous glauconite compositions it is apparent that iron can be added to as wellas subtracted from the bulk pelletal composition. This transfer appears to be effected when the pellet contains a multiphase mineral assemblage as well as during the evolution of a single-phase mixed layered mineral.

A schematic phase diagram is presented which attempts to describe the phase changes as a function of K, Si, and Fe variables.
Mineralogy and petrology of some Tertiary leucite-rhönite basanites from central France
Authors: Magonthier M. C. , Velde D.
Published: December 2006

The composition of the various phases present in the rh6nite-bearing leucite basanites of the southern part of the Sillon Houiller district have been determined with the electron microprobe. Clinopyroxenes show strong progressive enrichment in Al2O3 and TiO2, maximum values being 13 % and 6 % respectively. These extreme compositions are comparable to others found in feldspathoidal lavas from other provinces, and can be explained by the low silica content of the liquids they crystallized from, and high cooling-rates. Rhönite composition is similar to those previously determined in various terrestrial occurrences. The chemical compositions of the lavas differ from those of basanites, and are intermediate as far as Ca, Al, and Si contents between basanites and melilite-bearing basic lavas. The presence of rhönite can be explained by bulk composition, but is not a consequence of a particularly high Fe and/or Ti content. Xenoliths are absent from these lavas, so that there is no petrographic indication of possible contamination. It is tentatively concluded that the high K/Na ratio is primary.
A metallographic study of the disruption of the Cañon Diablo projectile
Authors: Axon H. J. , Couper W. R. D.
Published: December 2006

A metallographic investigation of macro- and micro-structures, supported by microprobe examination, has been made on similarly sized (< ca. 200 g) individual Cañon Diablo meteorites of rim or plains type. Plains type specimens show heat alteration zones of the ablation type. They are extensively cracked in a brittle manner and in some instances the cracks are penetrated by ablation melt product. In all cases the cracks are now penetrated by terrestrial corrosion. Cohenite and schreibersite are cracked in a brittle manner. By contrast the rim type specimens are remarkably free of internal cracking or corrosion penetration. Instead the cohenite, schreibersite, taenite, and kamacite are transected by slip faults or shear displacements along the line of which all phases appear to have slipped in a non-brittle manner. These specimens have all been subject to shock loading and particular attention is paid to the effects of shock on sphalerite, on cloudy taenite, and on martensitic plessite.

Plains specimens have broken from the original projectile in a brittle manner well above the earth's surface. Rim specimens have been scabbed from the rear of the projectile as it penetrated the earth's surface. Some of the rim specimens show signs of being heated by the blast of the crater-forming explosion.
Derivative structures based on the alunite octahedral sheet: mitridatite and englishite
Authors: Moore Paul Brian
Published: December 2006

It is proposed that mitridatite and englishite contain octahedral sheets of the alunite type and that their formulae are [Ca6(H2O)3(PO4)2][Fe3(OH)6(PO4)(PO3OH)]3 and [K2Na(H2O)4Ca4·5 (PO3OH)3][Al3(OH)6(PO4)(PO3OH)]3 respectively.
Experimental study of clay mineral, greenschist, and low-pressure amphibole facies in the system Na2O-Al2O3-MgO-SiO2-H2O
Authors: Triboulet Claude
Published: December 2006

Compositions concerning sodic amphiboles (glaucophane) in the system Na2O-Al2O3-MgO-SiO2-H2O have been studied at PH2O ≤ 3 kb, 380 °C < T < 700 °C. The study attempts to establish the mineral parageneses under these physical conditions as they define the clay mineral (saponite-hectorite smectite) and greenschist (chlorite-albite) facies. The occurence of sodic amphiboles is defined by compositional parameters. Glaucophane does not appear in the present investigation.

The method of ‘reaction reversal’, i.e. using precrystallized mineral assemblages to form new ones, has been used to establish the three reactions: albite + chlorite → paragonite + saponite, paragonite + chlorite → saponite + cordierite, and saponite + paragonite → albite + cordierite. In general, the clay mineral → greenschist transformation is favoured by an increase in pressure in the system studied. The amphibole present is a sodic richterite with the type substitution
Tacharanite from Tasmania, Australia
Authors: Sutherland F. L.
Published: December 2006

The mineral tacharanite has been recently re-examined by Cliff et al. (1975). They worked on material from the original locality, Portree, in Scotland (Sweet, I961) and from a few new European localities described between 1971 and 1974. None of the post-Sweet authors, however, refer to the second discovery of the mineral from Tasmania where it was identified by this writer in 1961 and recorded in a number of publications (Sutherland, 1965; Sutherland and Corbett, 1967; Sutherland and Hale 1970; Mines Department of Tasmania, 1970; Sutherland, 1973b). The first Tasmanian report was communicated to J. M. Sweet, who kindly arranged for the Department of Mineralogy, British Museum, to send the writer a small piece of the Portree material for study. As the Tasmanian find does not seem to be known in the later literature, some more detailed information on its occurrence is presented here for comparison with the European localities.
Feldspars and fluids in cooling plutons
Authors: Parsons Ian
Published: December 2006

Alkali feldspars in plutonic igneous rocks vary both in their exsolution textures and in the structural state of their components. The primary factor leading to this diversity is the availability of hydrothermal fluids during their cooling history. In many plutons feldspar variation is related to degree of fractionation as indicated by rock chemistry. The variation reflects build-up of water with magmatic evolution and implies that fluids did not circulate freely in the intrusives in the temperature range of unmixing and ordering. Experimental work bearing on the role of fluids in subsolidus changes in feldspars is reviewed, and points of overlap between crystallographic studies of feldspars and stable isotope studies are discussed.
The physical basis of mineral optics I. Classical theory
Authors: Strens R. G. J. , Freer Robert
Published: December 2006

The Helmholtz dispersion equations have been rewritten in a form that enables the optical constants of both transparent and opaque media to be calculated from their spectra. Both Helmholtz equations are used to describe the optical properties of opaque media, and to obtain values of reflectance, refractive index, and absorption coefficient. The Sellmeier dispersion equation is a special case of the dispersive Helmholtz equation applicable to weakly absorbing media (including the great majority of minerals studied in thin section): it is used to derive the wavelength-, composition-, direction-, and volume-dependence of the principal indices in mixed crystals of monoclinic or higher symmetry. The treatment can be extended to triclinic crystals.

The birefringence of transparent phases is the expression in the visible region of the pleochroism of absorption bands in the ultra-violet. The bireflectance of opaque phases depends also upon the pleochroism of bands in the visible and near infra-red, resulting in extreme sensitivity of the optics of opaque materials to changes in wavelength, composition, and structure. The optical anisotropy of both transparent and opaque phases may be calculated if the dependence of the spectra on structure can be established by measurement or by calculation from structure data. The quantitative application of Bragg's method is restricted to phases of very simple chemistry and structure (e.g. calcite and rutile), but it may be applied qualitatively to rationalize the optic orientations of phases containing only closed-shell ions of neon or argon configuration, including many pyroxenes, amphiboles, micas, and chain aluminosilicates. When open-shell (transition metal) ions enter the structure, the general rule is that the anisotropy becomes more closely related to the distortion of the coordination polyhedron about the metal ion, and for ions of formal charge ≥ 3, this source of anisotropy is usually dominant.
Bazirite, BaZrSi3O9, a new mineral from Rockall Island, Inverness-shire, Scotland
Authors: Young B. R. , Hawkes J. R. , Merriman R. J. , Styles M. T.
Published: December 2006

Bazirite, BaZrSi3O9, is one of several late-stage interstitial minerals present in the aegirine-riebeckite granite of Rockall Island. Crystals are hexagonal, probably ¯6m2, colourless, chiefly as anhedral grains. Only forms noted {10¯10} and probably {10¯14}, cleavage {0001} and probably {10¯14}. ‘Low’ and ‘high’ titanium varieties with respective mean compositions: SiO239·71%, ZrO226·38%, BaO 33·69%, TiO20·17%, SnO20·06% and SiO239·59%, ZrO226·12%, BaO 34·12%, TiO20·51%, SnO20·11%. Low and high refractive index types exist; uniaxial positive withω= 1·6751±0·0003.ɛ= 1·6850±0·0003 andω= 1·6813±0·0003, ɛ = 1·691 (deduced); probably due to differences in titanium content. Fluorescence (2537 Å), moderately strong, pale whitish blue. Space group almost certainlyP¯6c2. Cell dimensions: low R.I. variety,a= 6·7690±0·0005 Å,c= 10·020±0·001 Å; high R.I. variety,a= 6·7662± 0·0005 Å,c= 10·158±0·0010 Å. Strongest lines are 3·80 Å (100), 2·800 (100), 5·85 (35), 3·38 (35), Z = 2.Dcalc= 3·82. Related minerals, benitoite and pabstite.
Investigations on the deformation of experimentally shock-loaded biotites using X-ray single crystal diffraction techniques
Authors: Schneider Hartmut
Published: December 2006

The deformation of biotite single crystals submitted to experimental shock-pressures of about 200 and 400 kb with direction of the shock wave parallel to [001] was investigated by X-ray precession and Weissenberg techniques. The X-ray analysis reveals a ‘fracturing’ of the biotite crystals upon pressure release into relatively large lattice blocks (> 1000 Å), which increases with the degree of shock compression. Deformation is inferred to take place by gliding and/or microfracturing processes parallel to the (010) and (110) lattice planes. Chains of tetrahedra running parallel to [100] and [110] probably exert a controlling influence on shock deformation mechanisms.
The Inishdawros meta-peridotite, Callow, Ballyconneely, Connemara, Western Ireland
Authors: Ahmed A. A. , Leake B. E.
Published: December 2006

The chemistry and petrography of a meta-ultrabasic lens containing peridotite with poikilitic pyroxenes and hornblende, both of probable igneous origin, are given. The body also contains feldspathic-bearing hornblende meta-gabbros and is a tectonic fragment in hornblende-plagioclase rock belonging to the same Errismore intrusion. Chemical analyses fail to discern any appreciable systematic differentiation trend across the body despite modal variation to hornblende plagioclase layers. The high Niggli mg near the structural bottom of the intrusion suggests that this part of the Errismore intrusion is right way up, contrary to a previous suggestion.
Pumpellyite-bearing basic igneous rocks from the Lower Ordovician of North Pembrokeshire, Wales
Authors: Bevins R. E.
Published: December 2006

The first occurrence of pumpellyite in the Lower Ordovician volcanic rocks of North Pembrokeshire is reported and its form and chemistry are described. The significance of pumpellyite in relation to the grade of metamorphism attained during the Caledonian orogenic episode is discussed.
Manganoan Ilvaite from Broken Hill, N.S.W. and Ban Ban, Queensland, Australia
Authors: Plimer I. R. , Ashley P. M.
Published: December 2006

Manganoan ilvaite forms as an early retrograde metamorphic phase from calcic rhodonite in the polymetamorphosed Pb-Zn sulphide/manganese silicate rocks at Broken Hill and from grossular-andradite in a skarn at Ban Ban. Ilvaite exists as a probable metastable phase into which Mn is apparently strongly partitioned. The manganoan ilvaites analysed contain up to 13·5 % MnO substituting for FeO and this substitution shifts the 020 peak.
Linnaeite series minerals from the Kalgoorlie district, Western Australia
Authors: Ostwald J.
Published: December 2006

Five members of the linnaeite series of sulphides linnaeite Co3S4, siegenite (Co, Ni)3S4, carrollite Co2CuS4, violarite Ni2FeS4, and polydymite Ni3S4 occur in nickel-sulphide-mineralized rocks in areas adjacent to the Kambalda and Scotia deposits of the Kalgoorlie district, Western Australia. Linnaeite, siegenite, carrollite, and polydymite occur in trace amounts as disseminated grains and veinlets. Violarite is also found as disseminations but its major occurrence is in the supergene enriched zones of the ore deposits. Aspects of their mineralogy, including mode of occurrence, general mineragraphy, reflectance at 546 nm, 589 nm and 644 nm, microhardness, and electron probe microanalyses are described.
The geochemical role of primary copper-sulphur mineralization in the crystallization of the Freetown (Sierra Leone) layered gabbro
Authors: Bowles John F. W.
Published: December 2006

The separation of iron-titanium oxide droplets and the formation of olivine, in the Freetown layered gabbro, depleted the magma in iron and enriched the magma in copper. In magma injections in which the sulphur fugacity was sufficiently high, this resulted in the separation of immiscible copper sulphide droplets closely associated with the iron-titanium oxide droplets, and both were subsequently enclosed by olivine. A lower sulphur fugacity in other injections of magma suppressed the separation of the copper, which later appeared as native copper associated with euhedral titanomagnetite, and was enclosed by feldspar. Crystallization of the iron-titanium oxide droplets and subsolidus diffusion has resulted in granular exsolution of ilmenite from the droplets and lamellar exsolution of ilmenite in the euhedral titanomagnetite.
Uranospathite and arsenuranospathite
Authors: Walenta Kurt
Published: December 2006

A reinvestigation of uranospathite from the type locality, Redruth, Cornwall, shows that it is an aluminium uranyl phosphate belonging to the torbernite series but more highly hydrated than other members thereof. The composition (HAl)0·5(UO2)2(PO4)2.20H2O was derived by indirect methods and by making use of analysis by the electron microprobe, which showed an Al2O3 content 2·6% in the partially dehydrated state. Unit-cell dimensions: a 7·00, c 30·02 Å, Z = 2. Probable space group P42/n. Strongest lines of the powder pattern: 15·22 (10) 002, 7·60 (10) 004, 4·93 (10) 110, 111, 3·50 (8) 116, 200, 201.

The mineral is unstable and unless preserved at low temperature or in a humid atmosphere converts into a new phase with a loss of 10- 12H2O. This phase (HAl)0.5 (UO2)2(PO4)2.8–10H2O is identical with the mineral sabugalite. Experimental work led to the synthesis of a hydrate with the composition (HAl)o·5(UO2)2(PO4)2. 16H2O, but not to fully hydrated uranospathite. This synthetic compound also dehydrates rapidly under normal conditions, converting into the same phase as does natural uranospathite. Arsenian uranospathite occurs at Menzenschwand in the Southern Black Forest.

Arsenuranospathite proper is a new mineral found at Menzenschwand and also at Wittichen in the Central Black Forest. It forms lathlike or wedge-shaped crystals of orthorhombic symmetry. Forms: {100}, {010}, {110}, {001}. Cleavage {001} perfect, {100} and {010} good. Hardness probably about 2, ρcak2·54 g cm −3. White to pale yellow. Streak white. Fluoresces greenish in ultra-violet light with variable intensity.
Welshite, Ca2Mg4Fe3+Sb5+O2[Si4Be2O18], a new member of the aenigmatite group
Authors: Moore Paul B.
Published: December 2006

Welshite, triclinic, Ca2Mg4Fe3+Sb5+O2[Si4Be2O18],a= 10·28 Å,b= 10·69 Å,c= 8·83 Å,α= 106·1°,β= 96·3°,γ= 124·8°,P¯1 with pseudo-monoclinic cellam= 9·68(1) Å,bm= 14·77(2) Å,cm= 5·14(1) Å, βm= 101·5(2)°,c-centred, occurs as lustrous subadaman-tine, thick prismatic reddish-black crystals up to 3 mm in greatest dimension associated with roméite, adelite, swedenborgite, berzeliite, manganoan phlogopite, richterite in crystalline dolomite from Làngban, Sweden. Forms include b {010},a{100},k{130},m{110},j{021},p{111},q{121},v{131},r{¯111},s{¯121},t{¯131}, andv{¯141} (monoclinic setting). Streak pale-brown, hardness 6, specific gravity 3·77, fracture conchoidal, no cleavage,α= 1·81(1),γ= 1·83(1), 2E(obs.) ≈45°, no noticcable pleochroism.

Welshite is a new member of the aenigmatite-rhönite group and obtains from the substitution Sb5+→ Ti4+and Be2+→ Al3+in rhönite.
Manganhumite, a new species
Authors: Moore Paul Brian
Published: December 2006

Manganhumite, orthorhombic, a 10·54(1), b 21·45(2), c 4·822(9) Å, space group Pnma, Z = 4, (Mn0·68Mg0·30Fe0·01Ca0·01)7(OH)2(SiO4)3, is the manganese analogue of humite whose type locality is the Brattfors mine, Nordmark, Province of Värmland, Sweden. It is a skarn assemblage mineral and occurs with katoptrite, manganostibite, magnussonite, galaxite, etc., which replace manganosite grains in magnetite-manganosite ore.

The mineral is biaxial (+), α = 1·707(3), β = 1·712(3), 7 = 1·732(3), 2V7(obs.) = 37(4)° r > v perceptible, cleavage {010} perfect, hardness = 4, specific gravity = 3·83(5). The five strongest powder lines are 1·777(10), 2·500(7), 3·371(6), 2·628(6), and 1·525(6).
A composite tholeiite dyke at imachar, Isle of Arran: its petrogenesis and associated pyrometamorphism
Authors: Holoate Norman
Published: December 2006

This NW.-SE. dyke comprises two texturally distinct tholeiitic members. The outer (earlier) bears porphyritic plagioclases with essential olivine, plagioclase, and augite in a chloritized mesostasis; the inner carries porphyritic plagioclases in an olivine-free matrix showing ophitic and intersertal textures and disseminated varioles. The outer component had little metamorphic effect on its country-rock, but where the inner transgresses the outer to come into contact with the schistose-grits the latter are transformed to buchite. The outer component, after initial chilling, crystallized as a virtually closed system; the inner, on the contrary, shows no signs of chilling and bears evidence of crystallization as an open system. The variolitic structures in the inner component result from liquid immiscibility between droplets of acidic melt and basic host magma, the former originating as buchitic liquid caught up by the dyke magma at its contacts with mobilized country rock. Both components afford textural evidence of the immiscibility of a sulphide melt in the tholeiitic magma. The petrography and thermal behaviour of the inner dyke-member support its recognition as a probable former feeder to fissure eruption.
Ferrocarpholite associated with low-grade blueschists, northern New Caledonia
Authors: Briggs R. M.
Published: December 2006

Ferrocarpholite has been discovered at two localities in low-grade blueschists in the Diahot region, northern New Caledonia. In one occurrence (specimen 23503), ferrocarpholite was found in quartz veins associated with metamorphosed rhyolitic tufts, and at the other locality (23514) it occurs as a gangue mineral at Ao Mine associated with quartz, a variety of carbonates, and sulphide ores.
Bahianite, Sb3Al5O14(OH)2, a new species
Authors: Moore Paul B. , Carlos do Prado Barbosa  , Gaines Richard V.
Published: December 2006

Bahianite, Sb3Al5O14(OH)2-Sb3Al5(Al, Be, Si)<2O16, monoclinic, a 9·406(6), b 11·541(8), c 4·410(3) Å, β 90·94(3)°, Z = 2, space group C2/m, is a new species from the Paramirim region, south central Bahia state, Brazil. It occurs as water-worn pebbles (‘favas’) with quartz, andalusite, kyanite, diaspore, eskolaite, cassiterite, etc. Colour tan to cream, crystals in vugs colourless, tan or pale violet. Specific gravity ranges from 4·89 to 5·46 (5·26 g cm−3 for Sb3Al5O14(OH)2); hardness 9, cleavage {100} perfect, lustre adamantine, biaxial (−), 2V large, α = 1·81, β = 1·87, γ = 1·92, dispersion r > v.

The crystal structure represents a new type and is based on hexagonal close-packed oxygens. It is related to the structure of simpsonite Ta3Al14O13(OH).
Tlapallite, a new mineral from Moctezuma, Sonora, Mexico
Authors: Williams S. A. , Duggan Marjorie
Published: December 2006

Tlapallite is a new mineral found in 1972 at the Bambollita (La Oriental) mine near Moctezuma, Sonora. Also recently found in old specimens from Tombstone, Arizona. Data for type (Mexican) material: Colour viridian green RHS-128A with pale streak, H = 3, Dcalc = 5·05 g/cm3. Crystals monoclinic, class unknown. Indexing based on Ito method gave a cell: a = 11·97 Å, b = 9·11, c = 15·66, β = 90 ° 36′. Strongest lines: 11·972 Å (10), 2·985 (10), 3·540 (6), 5·946 (5), 2·887 (5), 4·731 (4), 3·372 (4), 3·282 (4). Similar data obtain for Tombstone. Chemical analysis for type material yielded the formula H6Ca2Cu3(SO4)(TeO3)4,TeO6 with Te4+:Te6+ = 4:1. However, analysis of the Tombstone material indicates a more general formula H6(Ca, Pb)2(Cu, Zn)3(SO4) (TeO3)4,TeO6. The better data from this material indicate Z = 4, Dcalc = 5·465 vs Dmeas = 5·38. Characterized by extreme birefringence, α = 1·815, β = γ = 1·960; for Tombstone α = 1·955, β = γ = 2·115.

Named from the Nahua word tlapalli, meaning paint, in allusion to its mode of occurrence at the type locality.
The high-temperature transformation of andalusite (Al2SiO5) into 3/2-mullite (3Al2O32SiO2) and vitreous silica (SiO2)
Authors: Pannhorst Wolfgang , Schneider Hartmut
Published: December 2006

The high-temperature transformation of andalusite (Al2SiO5) into 3/2-mullite (3A2O32SiO2) plus vitreous silica (SiO2) has been studied within the temperature interval from 1300 to 1600 °C by means of X-ray powder and single-crystal techniques and by infrared spectroscopy. Results are interpreted in terms of a topotactic transformation in which (011) and (01) planes of andalusite transform into (20) and (201) planes of 3/2-mullite; in this way thea- andb-axes of the two phases are interchanged. From the structural and orientational relationship between the andalusite and 3/2-mullite latrices it is concluded that the aluminium-oxygen octahedral chains, running in both structures parallel to the crystallographicc-axis, are preserved during phase transformation.
Element partitioning in ferruginous and pyritic phosphorite from the continental margin off Morocco
Authors: McArthur J. M.
Published: December 2006

Phosphorites from the continental shelf off Morocco have been analysed for major elements and Fe, Mn, V, Cu, Ni, Zn, As, Na, Sr, S, and for carbonate. In pyritic phosphorites Cu, Ni, Zn, and As are present mainly in minor pyrite and organic carbon. In ferruginous phosphorites As, Mn, and V are associated with goethite. In the ferruginous phosphorites Cu, Ni, and Zn may have been introduced in association with organic matter and pyrite during phosphorite formation and been retained during subsequent destruction of these phases by weathering. In all phosphorites Na and Sr are present mainly in carbonate-fluorapatite. Sulphur in the ferru-ginous phosphorites occurs only in carbonate-fluorapatite. In the pyritic samples it is partitioned between pyrite and francolite (carbonate-fluorapatite).
Hercynite as a breakdown product of staurolite from within the aureole of the Ardara Pluton, Co. Donegal, Eire
Authors: Atkin Brian P.
Published: December 2006

Zincian hercynite is present in pelites within the aureole of the Ardara Pluton. The hercynite is always surrounded by cordierite, garnet, or feldspar and is never in contact with quartz. From textural and chemical evidence it is apparent that the hercynite is produced by the reaction of zincian staurolite → zincian hercynite + cordierite + sillimanite. A temperature of about 725°C at pressure of about 2·6 kb and anφo2 below that defined by the Q.F.M. buffer is postulated for this reaction.
Zonal dissolution in analcime and pseudomorphs of adularia after analcime from the Lizard, Cornwall
Authors: Seager A. F.
Published: December 2006

Analcime of hydrothermal origin occurs in the gabbros and in the amphibolites and granulites. Crystals from the different rock suites display the same unusual characteristics upon dissolution: the interior is much more susceptible to attack than the outer growth zone; the former may be converted to a skeletal boxwork, and the latter may suffer extreme differential dissolution along successive narrow growth horizons. Pseudomorphs of adularia after analcime have been found in various stages of development, from partial to complete replacement. Some of the latter preserve the very delicate dissolution structures in detail. Up to fourteen growth horizons have been detected in the outer millimetre of the crystal. This demonstrates that both the growth and dissolution of analcime occurred prior to the formation of adularia, an event that has been dated.
The twin formation of tugtupite, a contribution
Authors: Petersen Ole V.
Published: December 2006

Tugtupite, space group 1, belongs morphologically to the crystal class 2m. The paper describes pseudotrigonal contact triplets recently found as freely developed individuals on two specimens donated to the Geological Museum, Copenhagen. The contact triplets, described as a symmetric twin, have the composition planes, which are also the twin planes, (10) and (01); the pseudo-threefold axis, along which the crystals are pronouncedly elongate, is [111]. The calculated reentrant angles on the two sides of the pseudotrigonal prism, the protruding angle on the third side, and the ‘central misfit’, expressed as the geometrical angles, are 178° 41′, 181° 20′, and 2° 39′ respectively. Tetragonal crystals forming pseudotrigonal twins are rare and it is emphasized that the pseudotrigonal habit has become apparent only because: the faces developed on individual I and on individuals II and III are not the same; and the proportion between the lengths of the traces of the faces (01) individual I and (01) individuals II and III in a plane perpendicular to the pseudo-threefold axis and the traces in the same plane of all other faces constituting the pseudo-threefold prism are 2:1.