bluuebunny/crossref_metadata_2025 huggingface dataset:
Pyroxene relations in two Hawaiian hypersthene-bearing basalts
Authors: Muir I. D. , Long J. V. P.
Published: December 2006

A preliminary account is given of an optical and electron-microprobe investigation into the pyroxene relations of Hawaiian hypersthene-bearing lavas. It is shown that the clinopyroxene jackets to the phenocryst hypersthenes consist of strongly zoned augite, not pigeonite as formerly believed; the compositional range of this pyroxene is approximately the same as that of the groundmass augite phase. Groundmass pyroxene relations are complex; in one case two distinct pyroxene phases, augite and pigeonite occur, in the other all compositions lying between augite and pigeonite are encountered.
Non-coaxial quartz- and mica-girdles in lineated quartzites from the Broken Hill District, New South Wales
Authors: Phillips F. C.
Published: December 2006

Non-coaxial quartz- and mic-girdles in lineated quartzites from the Broken Hill District, New South Wales, are described and discussed.
Oriented overgrowth of hematite on beta-alumina
Authors: Segnit E. R.
Published: December 2006

An alkali-alumina-silica slag from the interior of a kiln used for the firing of refractories was found to contain recrystallized mullite, corundum, and beta-alumina. Isolated areas of the slag were also rich in iron oxides; in these areas beta-alumina crystallized from the melt as hexagonal plates, and at a later stage small hexagonal plates of bematite grew on the 0001 face of the beta-alumina plates in a regular fashion.
Chemical analysis of olivines by the electron microprobe
Authors: Smith J. V. , Stenstrom R. C.
Published: December 2006

Thirty-one natural olivines, of which 25 had been previously analysed by wet chemical methods, have been analysed for Mg, Fe, Mn, Ca, Ni, and Co by electron-microprobe techniques. The totals of the olivine molecules Fo, Fa, etc., calculated from the above metals vary from 97·6 to 101·5 with a mean of 99·6%. Twenty-one of the specimens had been used previously by Yoder and Sahama to prepare a determinative curve between mole per cent. Fo and the lattice spacing d130. Yoder and Sahama had found that the data for natural olivines showed large random displacements from a straight line, and that the best straight line deviated for low Fo values from that for synthetic olivines. A plot of Fo determined from the microprobe vs. d130 corrected for lattice expansion caused by Ca and Mn shows no systematic deviation between natural and synthetic specimens, and only small deviations from the best continuous curve (maximum 4% in Fo assuming no error in d130). The maximum contents found for Mn, Ca, Ni, and Co were 3·2, 0·54, 0·33, and 0·03%, respectively. For these minor constituents, some of the wet chemical analyses agreed very well with the microprobe results while others showed large deviations. Although the substitution of Ca is small, it can affect considerably the determination of mole per cent. Fo from d130.

After specimen preparation and calibration have been carried out, microprobe analyses for most major and minor (but not trace) elements in common silicates can be made with an accuracy of about 0·5 to 5% of the amount present in about one minute for each group of three elements. Although standard chemical methods applied to large homogeneous samples will retain their fundamental reference value, microprobe techniques with their high spatial resolution, relative freedom from contamination problems, high speed, and moderate to good accuracy promise to revolutionize analytical programmes in mineralogy and petrology.
Nigerite from Lixa, near Felgueiras, Douro Litoral province, Portugal
Authors: Tassel R. Van
Published: December 2006

Nigerite occurs in pegmatite as hexagonal crystals enclosed in mica or in association with lithiophilite, apatite and vivianite. Absolute hexagonal parameters are a 5·67 and c 13·88 Å. Powder data are given. Forms and present besides the well-developed {0001}. Density 4·25. Refractive index 1·80, birefringence about 0·005, negative optical character. The chemical composition is studied by means of chemical, X-ray fluorescence and optical spectrography methods.
Titanomagnetites from a differentiation sequence, analcime-olivine theralite to analcime-tinguaite
Authors: Wilkinson J. F. G.
Published: December 2006

Six titanomagnetites from a differentiated alkaline intrusion have been studied using microscopie, chemical, and X-ray techniques. The titanomagnetites are homogeneous; with differentiation their FeO and TiO2contents decrease, and Fe2O3increases. The titanomagnetite course of crystallization extends from close to the ulvöspinel-magnetite join, near to ulvöspinel, towards magnetite. The recalculated normative compositions of three titanomagnetites indicate that they are essentially Fe3O4-(γ-FeTiO3)-(γ-Fe2O3)solid solutions. The changing chemistry of the titanomagnetites is ascribed primarily to variations in the chemistry of the magma during differentiation.
Aspects of the geochemistry of arsenic and antimony, exemplified by the Skaergaard intrusion
Authors: Esson J. , Stevens R. H. , Vincent E. A.
Published: December 2006

The distribution of As and Sb in a series of Skaergaard rocks and some of their minerals has been investigated using neutron activation analysis, and the geochemical behaviour of these elements during the fractionation of a basic magma is discussed.

It is concluded that As3+ is probably accepted into octahedral lattice sites usually occupied by Fe3+, Mg2+, Ti4+, and Al3+, and that there is also some substitution of As5+ for Si4+ and Al3+ in tetrahedral sites. There is a strong tendency for the element to concentrate in both interstitial and late-stage liquids.

Sb seems to show a marked preferential entry into early (magnesian) olivines, as in the case of Ni. The analytical results indicate that the substitution of Sb3+ for Fe2+ probably accounts for most of the Sb in silicate and oxide minerals. The tendency for Sb to concentrate in the residual Skaergaard liquids is less marked than in the case of As, but greater than in the cases of V, Cr, and Ni.

As and Sb have also been determined in four chondritic meteorites, in which the As/Sb ratio ranges from 8·5–12·4. Analyses for As and Sb in the standard rock powders G-1 and W-1 have also been made.
A chlorite–corundum roclc from Mount Painter, South Australia
Authors: Oliver R. L. , Jones J. B.
Published: December 2006

A rock from the Mt. Painter area, South Australia, consists essentially of corundophilite (anal., X-ray) and corundum, with accessory boehmite, sapphirine, cordierite, muscovite, and rutile. The rock probably crystallized at 500 to 700°C under 20 000 Ib/in.2 pressure, boehmite being formed by retrogressive metamorphism at 120 to 280° C.
Measurements of spectral reflectivity of manganese oxides
Authors: Nichol Ian , Phillips Roy
Published: December 2006

An accurate and highly sensitive method for the measurement of reflectivities incorporating a photomultiplier and a direct-reading galvanometer is described. The high sensitivity of the technique permits the determination of spectral reflectivities as opposed to ‘white’ light reflectivities, the latter values being subject to variation according to the type of apparatus used in their determination. The absolute spectral reflectivities of pyrite determined by the method are in good agreement with those quoted by some previous workers. Spectral reflectivities in air and oil and refractive and absorption indices are given for wavelengths from 430–650 mµ for manganese oxide minerals.
Porphyroblastic adularia from Shimabala, Zambia
Authors: Mallick D. I. J.
Published: December 2006

An unusual occurrence of adularia as a porphyroblastic mineral in an Upper Pre-Cambrian marble from Zambia is described, and optical and chemical data given. The presence of good cleavages oblique to the crystal faces indicates that the latter are hemi-orthodomes and high index pyramids, although the crystals are of simple form.
Solubility of basalt under atmospheric conditions of temperature and pressure
Authors: Nashar Beryl , Basden Ralph
Published: December 2006

Simple laboratory experiments involving the contact of distilled water with crushed olivine-basalt over several months under atmospheric temperature and pressure conditions have shown that constituents are dissolved from the basalt and upon evaporation the solutions deposit crystals of carbonates, smectites, and zeolites. The results bear out the observations and conclusions previously made in the field that solutions depositing secondary minerals in Tertiary basalts in New South Wales are extraneous and cold. It is also suggested that as the assemblage calcite-montmorillonite-heulandite can form in the vesicles of basalts under such conditions it should not be included in the zeolite facies of metamorphism.
The alkali feldspars of the Ardara pluton, Donegal
Authors: Hall A.
Published: December 2006

The alkali feldspars in the Ardara pluton are microcline- and orthoclase-microperthites. Their compositions have been determined by the 20 X-ray method, both before and after homogenization. The bulk compositions are very rich in potassium as a result of postmagmatic recrystallization of the alkali feldspar. There is no significant variation in either the bulk composition or the composition of the potassic phase in different parts of the intrusion. The structural state of the feldspars has been studied by measurement of 2V and obliquity of the potassic phases, and the reciprocal lattice angles α* and γ* of the potassic and sodic phases in selected crystals. Most of the specimens contain near-maximum microcline, but there is a decrease in the obliquity of the potassic phase at the eastern end of the intrusion. This can be related to the subsequent intrusion of the Main Donegal Granite.
A new method for the absolute measurement of reflectivity
Authors: Bradshaw P. M. D. , Phillips R. , Smith R. A.
Published: December 2006

The theory of a new method for the determination of reflectivity at truly normal incidence is described. A parallel light beam falls on the specimen after passing through a glass cube with semi-silvered diagonal mounted at the centre of an optical goniometer. The various reflected beams are measured by a photomultiplier fixed to the telescope of the goniometer. Experiment has proved the validity of the method and the spectral reflectivity of pyrite in air and in oil has been investigated.
BeO in pegmatitic cordierite
Authors: Newton Robert C.
Published: December 2006

Several cordierites from pegmatites were found by emission spectroscopy to contain as much as 0·7 wt. % of BeO. Structural crystallographic considerations suggest that the beryl molecule, Be3Al2Si6O18, may have appreciable solubility in the structure of cordierite. Some hydrothermal experiments carried out on this assumption indicated about the same amount of BeO substitution in the magmatic temperature range as is shown by the pegmatite cordierites. The natural BeO-bearing cordierites have distinctive infra-red absorption properties, which are reproduced in the synthetic solid solutions.
Properties of the Al–Fe–Mn epidotes
Authors: Strens R. G. J.
Published: December 2006

Natural Al-Fe-Mn epidotes are divided into Al-Fe and Al-Fe-Mn series.

In the Al-Fe series,a, b, andcincrease steadily over the range 0 to 0·9 Fe3+per formula unit, and more slowly at higher Fe contents. Index variation diagrams show the reverse trend, with indices increasing moderately fast over the range 0 to 0·85 Fe, and faster at higher Fe contents.

In the Al-Fe-Mn series,bincreases almost linearly over the range of (Fe, Mn) contents, with Mn causing a larger increase than Fe, whilstaandcincrease over the range 0 to 0·9 (Fe, Mn), and then decrease. This curious behaviour is accounted for by the application of crystal field theory. The indices increase linearly over the range 0·8 to 1·5 (Fe, Mn), the optic axial angle depending on (Fe, Mn) content and the ratio Mn/(Fe, Mn).

Thermal and mechanical properties (conductivity, thermal expansion, specific heat, compressibility, and hardness), electromagnetic properties (dielectric constants, conductivity, magnetic susceptibility), and thermodynamic data (S) are also summarized, and estimates given where experimental data are not available.
Amphibole compositional space
Authors: Phillips R.
Published: December 2006

The basic formula of an amphibole is completely defined by stating the number of sodium atoms in X positions and the numbers of aluminium atoms in Y and Z. These three numbers are coordinates in a compositional space that can easily be represented. The alkali amphiboles are re-defined as having at least one atom of sodium in X in the basic formula unit. A systematic nomenclature for the calciferous and alkali amphiboles is suggested using existing end-member names.
X-ray study of deformation lamellae in olivines of ultramafic rocks
Authors: Challis G. A.
Published: December 2006

Olivine crystals showing {100} deformation lamellae between crossed polars show spots streaked out transversely to 00l layer lines in X-ray oscillation photographs. Compositional inhomogeneity is ruled out by optics and electron microprobe analysis. Structurally controlled gliding on {100} (plane of greatest atom density) in the direction [001] (close-packing direction) is deduced on analogy with deformed metals. Mechanism of lamella formation is discussed in terms of superincumbent load; but it is concluded that pressures due to crystal growth are mainly responsible.
Metasomatism of cherts on the north-west margin of Dartmoor, Devonshire
Authors: El Sharkawi M. A. , Dearman W. R.
Published: December 2006

Contact metamorphic and metasomatic effects are described in the black radiolarian cherts of Lower Carboniferous age occurring at varying distances from the margin of the Dartmoor granite in the neighbourhood of Meldon, near Okehampton, Devon.

Development of biotite by contact metamorphism is over-printed by metasomatic conversion of chert to coarse-grained calc-silicate hornfels. Changes are localized and controlled by structural planes including faults and joints. Earliest effects are scapolitization giving black-and-white calc-flinta by local addition of calcium and subtraction of silicon. The same trend in transfer of elements is maintained in later phases: wollastonite-diopside reaction zones may enclose cores of black-and-white cale-flinta and are in turn replaced by wollastonite-grossular and grossular reaction zones marking the sites of main channels for migration of mineralizing fluids. Finally, veins with datolite-diopside, datolite-grossular-idocrase, and datolite-grossular-zeolite assemblages were formed in the altered cherts. Tin was available with aluminium and ferric iron during metasomatic changes in which garnet developed.

Some chemical transfer may be reciprocal changes with interbedded limestones, but appeal is made to external sources for the later metasomatizing agents.
A new polytype of taaffeite–a rare beryllium mineral from the granulites of central Australia
Authors: Hudson D. R. , Wilson Allan F. , Threadgold Ian M.
Published: December 2006

Chemical and single crystal X-ray studies have shown the existence of a 9-layer polytype of taaffeite. The parameters of the hexagonal unit-cell are a 5·675 Å, c 41·096 Å (arh 14·085 Å, α 23·24°). The oxide composition of the mineral is Al2O3 71·44, MgO 15·76, FeO 6·78, BeO 5·50%. It is pale olive green, with refractive indices ω = 1·739, ε = 1·735, and a specific gravity of 3·68.
Li2Zr(WO4)3, a wofframite-type compound
Authors: Chang Luke L. Y.
Published: December 2006

The compound Li2Zr(WO4)3 has been synthesized. It has the monoclinic wolframite-type structure with cell dimensions a 4·78Å, b 5·70 Å, c 4·96 Å, and β 92° 10′. The univalent and tetravalent cations are randomly arranged in the divalent cation sites in the wolframite-type lattice.
Harmotome from Korsnäs, Finland
Authors: Sahama Th. G. , Lehtinen Martti
Published: December 2006

This paper describes a harmotome from the Korsnäs mine in Finland, which occurs in the same open cavity as the yellow apophyllite previously reported in this journal. The harmotome is always twinned according to the morvenite and Marburg laws. Chemical composition, optical properties, X-ray powder pattern, and single crystal data are given.
The decomposition of struvite
Authors: Whitaker A.
Published: December 2006

The subaerial decomposition of struvite has been investigated at room temperature (21±2° C), from which it has been concluded that the decomposition product is newberyite. X-ray power patterns of newberyite, both from a diffractometer and Debye-Scherrer cameras, are given. Comparison of these patterns with other newberyite patterns suggest that the camera pattern is more reproducible; this may be due to grain orientation in the diffraetometer mounts.
Micro-forms of hay-silica glass and of volcanic glass
Authors: Baker George
Published: December 2006

In view of recently reported microtektites in deep-sea sediments north-west, south-west, and south of Australia, attention is drawn to the occurrence of minute forms of hay-silica glass among the products of incineration of opal-bearing vegetation in haystacks, and to the minute forms of volcanic glass ejected in lava fountains. These terrestrial micro-forms of glass have properties within the range of those for the fossil glassy bodies named ‘microtektites’. It is possible that the fusion of opal contained in silica-accumulator plants during fierce, prehistoric forest, bush, and grass fires in Australia generated micro-forms of glass that became readily airborne and drifted away in up-currents. Carried by the south-east Trades, they would ultimately descend over the Wharton Basin in the Indian Ocean. Strong to violent northerlies and north-easterlies (Brickfielder Winds) would carry them over the ocean south and south-west of Australia. Thus they could contribute to the deposits of bodies of glass regarded as microtektites in deep-sea sediments. Many microbodies of glass in the Wharton Basin could have had their origin in the Javanese volcanic eruptions.
Subsolidus crystallization behaviour in the system KAlSi3O8–NaAlSi3O8–H2O
Authors: Parsons Ian
Published: December 2006

When gels and glasses of alkali feldspar composition are crystallized hydrothermally below their solidus the crystals present when crystallization is incomplete do not have the same Na:K ratio as the starting material but bear a relation to the starting material analogous to that between crystals and liquids coexisting at the liquidus. This effect has been investigated in the temperature range 700–850 °C at water-vapour pressures between 5000 lb/in.2 and 30000 lb/in.2 Fractionation and normal zoning of crystals may, in principle, occur within fixed bulk compositions held under isothermal, isobaric conditions.
The cell parameters of the arfvedsonite–eckermannite series, with observations on the MgO and total iron content of amphiboles
Authors: Kempe D. R. C.
Published: December 2006

The cell parameters of 35 members of the arfvedsonite-eckermannite series and catophorites (17 from the literature, 18 newly determined) are presented and an attempt made to relate them to chemical composition. In general, all parameters (includingβ, obtuse) decrease from arfvedsonite to eckermannite, but for different reasons:a,b, andβ(very slightly) as the Mg: Fe2+ratio and F increase;cas Fe3+decreases. The apparent decrease inaandbwith high Li is coincidental, due to its strong correlation with F, which varies inversely With (OH). In addition,bis increased by high Ca and slightly reduced by high A1.

Also, the empirical and calculated curves relating MgO and total iron as Fe2O3(weight %) with the Mg ratio, 100 Mg/(Mg + Fe2+Fe3++ Mn), for all amphibole groups are given, as a rapid method of obtaining an estimate of the Mg ratio.

The full lists of possiblehklvalues for an arfvedsonite and an eckermannite are enumerated up to 45° 2θ, Cu-Kα, to illustrate the difficulty in indexing X-ray photographs and diffractometer charts of this group.
Can Ti4+replace Si4+in silicates?
Authors: Hartman P.
Published: December 2006

It is argued on crystal-chemical grounds that Si deficiency is compensated by the entering of Al, Fe3+, or Ti4+, in this order of preference, into tetrahedral sites. It is pointed out that Ti4+occurs in tetrahedral coordination in exceptional circumstances only, while Fe3+relatively easily takes a tetrahedral coordination.
Studies in the system BaO–Al2O3–SiO2 III. The binary system sanbornite–eelsian
Authors: Lin H. C. , Foster W. R.
Published: December 2006

The system sanbornite-celsian has been investigated by the quenching method, and the results compared with earlier studies. The system is essentially a simple binary eutectic system with little or no solid solution. The eutectic is located at a composition of 69% sanbornite and 31% celsian (by weight) and at a temperature of 1227±3°C. No evidence for substantial solid solution of celsian in sanbornite, as reported in previous work, was found. Paracelsian, a naturally occurring polymorph of celsian, was not encountered in the study.
The origin of myrmekitic intergrowths and a comparison with rod-eutectics in metals
Authors: Shelley D.
Published: December 2006

A review is given of the metallurgical literature relating to the formation of metal rodeutectics, which are texturally similar to myrmekite. Since no satisfactory explanation for rodeutectics has been advanced, a comparison is made with myrmekite. It is proposed that this intergrowth develops as a result of the constriction of quartz during its recrystallization and inclusion in an expanding blastic growth of plagioclase, and the forces involved lead to the prolongation along the growth directions of quartz in the form of rods with a relatively small surface area (i.e. with circular cross-sections). Possible forces that could produce the same geometry in metal intergrowths are those that result from the relative contractions of the two components during freezing; in all cases for which quantitative data are known, the metallic rods have a greater contraction on freezing than the host substance. Examples of myrmekite and myrmekite-like intergrowths in the Constant Gneiss are described in relation to their particular origin. Two factors, the lack of proportionality of qtartz to feldspar and the intimate association of myrmekite with myrmekite-like intergrowths, support the proposed mechanism of constriction of pre-existing quartz.
Manganese-bearing silicate minerals from metamorphosed manganese formations of India. I. Juddite
Authors: Roy Supriya
Published: December 2006

The manganiferous amphibole juddite has been reported by a number of workers from metamorphosed manganese formations of India. The mineral is developed at the contact of pegmatite and gondite, and associated characteristically with blanfordite (manganoan aegirine-augite) and winchite (manganoan richterite-tremolite). The range of the refractive indices of the mineral and the orientation of the optic axial plane normal to (010) suggest the mineral to be of magnesioriebeckite composition. The 100 Mn2+:(Mn2++Mg+Fe2+) and 100 Fe3+:(Fe3++Alvi+Ti) ratios plotted in the glaucophane-magnesioriebeckite diagram show that eight out of nine analyses (eight new) are grouped under magnesioriebeckite composition range. It may thus be concluded that the juddites generally refer to (manganoan) magnesioriebeckite compositions. In some cases, however, the composition of juddite shows considerable departure from ideal magnesioriebeckite composition and the juddite and winchite (manganoan tremolite-richterite) show evidences of compositional transition, indicating partial miscibility. The juddites have been formed by the interaction of pegmatitic fluid on manganese ore, gondite, and other country rocks such as mica schists and diopside-forsterite marble.
A study of some iron meteorites of the Gibeon association
Authors: Axon H. J. , Smith P. L.
Published: December 2006

The macroscopic features of a number of Gibeon meteorites have been reviewed and selected specimens have been examined in more detail by metallographic, microprobe, and X-ray diffraction techniques.

A number of specimens appear to have been reheated by man and in these cases reheating temperatures are indicated. Specimens that show no signs of artificial reheating are discussed in relation to the form, distribution, and structure of the kamacite, daubréelite, and troilite. X-ray examination of the kamacite reveals partly annealed shock damage. Small monomineralic inclusions of daubréelite appear to be concentrated in the non-octahedral kamacite and show no signs of alteration By contrast all the troilite has been remelted and has dissolved contiguous plessite and daubréelite. The remelting of troilite appears to have been induced by shock at temperatures below about 450°C.
Holtite: a new mineral allied to dumortierite
Authors: Pryce M. W.
Published: December 2006

Holtite, a new mineral allied to dumortierite, occurred as pebbles with stibiotantalite and tantalite on an alluvial tin lease near Greenbushes, Western Australia, and is named after the late H. E. Holt, Prime Minister of Australia.

The mineral is orthorhombic with a 11·905 Å, b 20·355 Å, c 4·690 Å, space group Pmcn, weak supercell 2a, 2b, c developed. Crystals are elongated along c, D 3·90 ± 0·02, hardness 8½, fluorescent. Optical properties α 1·743−1·746, mainly yellow, ‖ [001], β 1·756−1·759, colourless, γ 1·758−1·761, colourless, 2Vα 49−55°, r < v. X-ray powder data are given.

Chemical analysis gave SiO2 20·30, Sb2O5 4·61, Al2O3 46·43, Ta2O5 11·24, Nb2O5 0·76, Fe2O3 0·27, MnO 0·05, TiO2 0·09, BeO 0·05, B2O3 1·82, Sb2O3 13·89, H2O+ 0·38, H2O− 0·08, sum 99·97%. On a water-free basis the unit cell contains Al24·5Sb2·56‴Ta1·36Sb0·76vNb0·16Fe0·10‴Be0·05Ti0·03Mn0·02B1·40‴Si9·09O66·85. Compared with dumortierite, 4[(A1,Fe)7BSi3O18] or 4 (X11O18), the holtite unit cell contains approximately 4(X10O17).

Type material is preserved at the Government Chemical Laboratories, Perth, Western Australia.
A metamorphosed pyroxenite at Nero Hill, Central Tanzania
Authors: Haslam H. W. , Walker B. G.
Published: December 2006

The pyroxenite of Nero Hill has been metamorphosed under relatively low water pressure at the centre and higher water pressure at the margins. Thus a central pyroxenite consisting of diopside, hypersthene, oligoclase, garnet, and a little hornblende grades outward into a hornblende-cummingtonite amphibolite.
Composition and orientation of clinopyroxene lamellae in Bushveld-type orthopyroxene from the Greenhills ultramafic complex, Bluff Peninsula, Southland, New Zealand
Authors: Mossman D. J.
Published: December 2006

Identification of clinopyroxene lamellae in Bushveld-type orthopyroxene from the Greenhills Ultramafic Complex has been made on the basis of partial analysis by electron microprobe as well as by unit cell determination by prolonged exposure to X-rays of single crystals of orthopyroxene. Lamellae averaging Ca42Mg47Fe11 in composition with an approximate unit cell a 9·79, b 8·90, c 5·29 Å, β 106° 14′, occur in orthopyroxene Ca2Mg67Fe31 with unit cell a 18·28, b 8·85, c 5·20 Å. The Greenhills lamellae are of orientation identical to those described by Hess (1960), which share c and b axes with host orthopyroxene.
Evidence of shock-metamorphic effects in the Ergheo meteorite
Authors: Baldanza B. , Levi-Donati G. R.
Published: December 2006

The Ergheo meteorite was inspected both by transmitted and reflected light in order to look for evidence of shock metamorphism by petrological observations. The stone is a well-recrystallized olivine-hypersthene chondrite that shows features of severe fracturing, prominent veining, and diffused cracking. The presence of several shock-transformed components is described in some detail. Ergheo is a meteorite that suffered particularly by shock in full agreement with Heymann's (1967) and Turner's (1968) statements.
Yttrotungstite
Authors: Davis R. J. , Smith G. W.
Published: December 2006

Yttrotungstite occurs at Kramat Pulai mine, and at Tapah, Kinta, Perak, Malaysia, as yellow earthy material and as monoclinic laths, elongated along [001], flattened, and always twinned, on {100} to pseudo-orthorhombic symmetry, and frequently bevelled by {110}; crystals are very rarely terminated by {101}. γ = [010], α:[001] = 26°, probably in β acute, and 2Vα ≃ 68°. A thermal weight loss curve and an infra-red absorption spectrum are given and discussed. Accessory minerals include raspite and stolzite.

The yttrotungstite unit cell has a 6·95, b 8·64, c 5·77, β 104° 56′, space group P21/m; cell contents are (Yt, Ln, Ca, Mg)2(W, Al, Si, Ti, Fe)4(O, OH)14(OH)2·2H2O. Indexed X-ray powder data are given. Microprobe studies show that Al and Si replace W and are concentrated in zones showing larger values of a sin β (6·75 Å instead of 6·72 Å) but with no other appreciable difference in cell dimensions. Crystal structure studies show that the structure consists of WO6 octahedra sharing non-opposite edges in zig-zag chains running parallel to [010]. Yttrium is in approximately trigonal prismatic coordination between the chains, with the water molecule as a seventh neighbour at one prism face. The water molecule is accommodated in the angle between zig-zags in the WO6 chains; it is probably hydrogen bonded to chain oxygen atoms, and becomes coordinated to the yttrium by a shear between chains away from strict close-packing of the oxygen atoms. The shear is related to the change in a sin β in (Al, Si)-rich zones; arguments based on this and on details of the chemical analysis suggest that SiO4 replaces WO6 with a local oxygen deficit.

Oxygen atom peaks on partial Fourier difference syntheses for our data for yttrotungstite are only slightly larger than the troughs in the syntheses due to experimental error. Methods of testing the significance of the positive peaks are described in an appendix.
Feldspar relations in Icelandic alkalic rhyolites
Authors: Sigurdsson Haraldur
Published: December 2006

Alkalic rhyolites with peralkaline affinities, bearing quartz and potassic feldspar phenocrysts, are described from Iceland for the first time. Evidence from electron-probe analyses of feldspar phenocrysts indicates crystallization in or near the thermal valley of the system SiO2-Or-Ab. Icelandic acid volcanic rocks are subdivided into alkalic rhyolites, belonging to transitional and alkalic basalt lineages, and the mildly calc-alkaline rhyolites of tholeiite lineages.
Preparation of glass standards for the use in X-ray microanalysis
Authors: Smellie J. A. T.
Published: December 2006

Homogeneous glasses for the use as standards in electron-probe microanalysis were prepared as an alternative to natural minerals, oxides, and pure minerals. Homogeneity was achieved by careful grinding, mixing, and fusion of powders of known composition. Fusion was carried out under vacuum using a molybdenum boat. This method avoided bubbles and contamination and made it possible to achieve temperatures high enough for final mixing to occur during the fusion process. Nine glass beads each containing six to seven oxides were subjected to careful micro-probe examination. A statistical analysis of the results showed that for each element there was no significant difference in composition between the spots measured. As the analysing spot was of diameter 0·8 µ, this showed that the glasses were homogenous on a sub-micron scale.
Granulite facies metamorphosed basic dykes
of the Torngat Mountains, Labrador
Authors: Morgan William C. , Taylor Frederick C.
Published: December 2006

In the Four Peaks region of Labrador
Precambrian hornblende granulite facies
metamorphosed basic dykes discordantly cross the
foliation of garnet-hornblende-pyroxene granulites
with sillimanite-garnet-biotite-quartz-feldspar
gneiss. Most of the dykes are schistose or banded,
but some are massive and undeformed with
blastophitic textures. Mineral analyses are given
for the equilibrium assemblage in one analysed
clinopyroxene-orthopyroxene-amphibole-garnet-plagioclase-
quartz blastophitic dyke. Dyke intrusion occurred
after formation of the host rock foliation, while
the metamorphism was about 1400 Myr ago.
Differences among low Ceylon
zircons
Authors: Vance E. R. , Anderson B. W.
Published: December 2006

Low Ceylon zircons showing an optical
absorption band at 5200 Å appear to have suffered
more radiation damage than other low Ceylon
zircons. Very heavy fission-fragment irradiation
failed to lower the density of each of two low
Ceylon zircons significantly, although the
specimens were rendered completely amorphous.
Further fission-fragment irradiation experiments
indicated that low Ceylon zircons showing a
previously reported anomalous absorption spectrum
have been heated late in their geological
histories.
A metallographic study of some
hexahedrites
Authors: Axon H. J. , Waine C. V.
Published: December 2006

Large samples of the hexahedrites
Scottsville, Indian Valley, Okano, Puripica, and
Hex River Mountains from the British Museum
Collection and a sample of Lombard have been
prepared for metallographic examination and
details of their structures have been mapped with
the aid of a specially constructed
X-Y plotting device
that is geared to the stage of a metallurgical
microscope. The following elements of structure
have been studied and an attempt has been made to
discuss the circumstances under which they were
formed: clear etching and frosty etching kamacite,
decorated Neumann lines, giant rhabdites, plate
rhabdites, rhabdite clusters, microrhabdites,
cohenite or decomposed cohenite, and troilite
(which in some instances is recrystallized or
remelted). In general the range of structural
effects is similar to that previously reported for
the Angra dos Reis hexahedrite (Min. Mag. 1971,
38, 94–101). The variations
of structure are discussed in relation to nickel
content and trace element chemistry of the
meteorites.
Alkali feldspars from part of the Galway granite, Ireland
Authors: Wilson J. R. , Coats J. S.
Published: December 2006

The structural states of alkali feldspars from the eastern end of the Galway Granite show transitions from orthoclase to microcline as a result of late deformation. Analyses of twenty samples for SiO2, Al2O3, TiO2, Fe2O3, CaO, Na2O, K2O, S, Cu, Zn, Ga, Rb, Sr, Ba, and Pb agree with previously determined orders of entry of elements into the ‘alkali site’. A relationship between this order of entry and the melting points of feldspar end-members is discussed.
A silica-deficient pyroxene in iron ore sinters
Authors: Dyson D. J. , Juckes L. M.
Published: December 2006

A minor phase in iron-ore sinters has been synthesized and identified as a clinopyroxene with the approximate formula Ca1·0(Ca0·14Al0·60Si1·08)O6. This composition shows that it consists largely of the hypothetical Tschermak's molecule, M2+SiO6. The small size and sparse distribution of this phase in most iron-ore sinters has previously hindered analysis.
Coexisting hornblende and cummingtonite from the Khetri copper belt, Rajasthan, India
Authors: Das Gupta S. P.
Published: December 2006

Coexisting hornblende and cummingtonite in an amphibolite near Peliwali have been analysed. The rock formed by Fe-Mg addition and Ca removal from pre-existing amphibole quartzites within the altered wall rocks surrounding sulphide lodes. The amphibole compositions are controlled by the bulk composition of the rock. The Mg/(Mg+Fe2+) ratio of the hornblende (0·66) is only slightly higher than that of the cummingtonite (0·64).
Peraluminous sapphirine as a metastable reaction product in kyanite—gedrite—talc schist from Sar e Sang, Afghanistan
Authors: Schreyer Werner , Abraham Kurt
Published: December 2006

Minute crystals of pure Mg-sapphirine approximating (Mg3.23Al4.74)vi(Al4.69Si1.31)ivO20, and thus having more aluminous compositions than the hitherto accepted 7:9:3 end member, were formed together with Mg-cordierite and corundum along narrow zones of the schist through reaction of the pre-existing high-pressure assemblages kyanite-gedrite and kyanite-talc. These sapphirines are considered to be metastable intermediate products growing under the influence of the structurally similar host mineral kyanite. Under equilibrium conditions they continued to react with kyanite to form the stable assemblage cordierite-corundum. Peraluminous sapphirines including those most recently synthesized may be metastable phases under all conditions of crystallization.
Creaseyite, Cu2Pb2(Fe,Al)2Si5O17-6H2O a new mineral from Arizona and Sonora
Authors: Williams Sidney A. , Bideaux Richard A.
Published: December 2006

Creaseyite was first noted in specimens from Tiger, Arizona, and was then found at Wickenburg, Arizona, and Caborca, Sonora, prior to description. It is an oxide zone mineral occurring with wulfenite, willemite, mimetite, chrysocolla, wickenburgite, and ajoite. The composition is [Cu2Pb2(Fe,Al)2Si5O17-6HaO]. Colour Agathia green (R.H.S. 142B) with pale streak, H = 2½, Dmeas = 4.1, calc. 4.01. Crystals are orthorhombic with a 12.483, b 21.395, c 7.283. Z = 4.2Vγ 69° meas; α 1.737, β 1.747, γ 1.768.
Argentian mercurian tetrahedrite, a new variety, from the Chiprovtsi ore deposit, Western Stara-Planina mountains, Bulgaria
Authors: Atanasov Vassil At.
Published: December 2006

An electron-probe microanalysis of tetrahedrite occurring together with the latest-deposited pyrite-cinnabar association in the Chiprovtsi lead-silver deposit yielded more than 16 wt. % Ag and more than 18 wt. % Hg. X-ray powder examination established an extremely large unit-cell edge, a 10.64±0.01 Å. Vickers microhardness 223 to 237 kg/mm2. The chemical formula derived on the basis of the analyses made is quite near to Cu6+(Cu+, Ag+)4(Hg,Zn)2(Sb,As)4S13. There is not any antiparallelism between Ag and Hg in tetrahedrite. The name proposed for all stages of simultaneous isomorphic replacement along the Cu+-Ag+ and Cu2+-Hg2+(Zn2+,Fe2+) directions is argentian mercurian tetrahedrite. The upper limits of the Ag and Hg content are expected to be Cu6Ag4Hg2(Sb,As)4S13. It is the six copper atoms (Cu4+;Cu22+), sited in the Laves’ polyhedra, that are replaced by Ag+ and Hg2+ respectively.
Native nickel from the Jerry River, South Westland, New Zealand: an example of natural refining
Authors: Challis G. A.
Published: December 2006

Native nickel of composition Ni 96.3 %, Fe 1.77 %, and Co 0.69 % was found as tiny flakes up to 0.75 mm across in a heavy mineral concentrate from stream sediments in the Jerry River, South Westland, New Zealand. The locality is approximately 13 km downstream from the original locality for awaruite (Ni2Fe), and it is shown that the nickel content of detrital grains increases with distance from the source of the awaruite in serpentinites of the Red Hills Range. It is proposed that the native nickel has been derived from awaruite by leaching of iron.
Some observations on Assarsson's Z-phase and its structural relations to gyrolite, truscottite, and reyerite
Authors: Gard J. A. , Mitsuda T. , Taylor H. F. W.
Published: December 2006

Z-phase was obtained hydrothermally at 120 °C by decomposition of Al-substituted tobermorite and by reaction of lime and colloidal silica. X-ray and electron diffraction show that the structural element is hexagonal, with a 9·65, c 15·3 Å, and good {0001} cleavage. Reversible water loss and lattice shrinkage occur on heating, the layer thickness (c) decreasing to 12.1 Å at 400 °C. For material in equilibrium with air of normal humidity, the composition is probably between CaO. 2SiO2. 1·7H2O and CaO. 2SiO2. 2H2O; Z = 8 for the structural element. New t.g. and infrared absorption data are presented; the infra-red spectrum closely resembles that of gyrolite, but OH ions attached only to Ca appear to be absent. Conditions of formation are discussed; if Z-phase has any stability field, it is below 120 °C. Crystal structures for Z-phase, gyrolite, and truscottite are suggested, based on the known structure of reyerite.
Cookeite and diaspore in the Back Creek pyrophyllite deposit near Pambula, New South Wales
Authors: Loughnan F. C. , Steggles K. R.
Published: December 2006

The occurrence of cookeite, a di/trioctahedral chlorite of composition (Al3.95Fe0.02Mg0.01Li0.81)(Al0.74Si3.26)O10(OH)8, in the Back Creek pyrophyllite deposit near Pambula is described. The mineral is restricted to a relatively narrow zone near the centre of the deposit and although diaspore is also present in this zone the two have not been found in intimate association, it is concluded that the introduction of lithium has been the principal factor controlling development of the cookeite.
Difference in spectral reflectivity between grains of homogeneous and exsolved titanomagnetite
Authors: Halfen B.
Published: December 2006

The spectral reflectivities of homogeneous and exsolved titanomagnetites of the same chemical composition were measured in air and in oil. The reflectivities of the two kinds of titanomagnetite are closely similar in the blue part of the spectrum, but become increasingly different when proceeding towards the red end. The refractive indices (n) and the absorption coefficients (k) were calculated from the reflectivity values. The n-values of the two kinds of titanomagnetite show a pattern of separation similar to that of the reflectivity values. Regarding possible differences between the k-values no reliable conclusions could be drawn. Some possible explanations of the observed separations are discussed.
The crystal chemistry of the amphiboles. III: Refinement of the crystal structure of a sub-silicic hastingsite
Authors: Hawthorne F. C. , Grundy H. D.
Published: December 2006

Three-dimensional counter-diffractometer data and a full-matrix least-squares method have been used to refine the crystal structure of a sub-silicic hastingsite in the space group C2/m. The chemical composition of the amphibole is with ceil parameters a = 9·8659(4), b = 18·0139(8), c = 5·3545(2)Å, and β = 105·082(1)°. Unit weights were used throughout the refinement and the final R-factor for 1263 observed non-equivalent reflections was 4.1%. The mean tetrahcdral bond length for aluminous amphiboles varies linearly with the total amount of tetrahedral A1. Curves are derived relating individual mean bond lengths with A1 occupancy. The positional disorder on the A-site of the aluminous amphiboles appears to be partly related to the amount of substitution of A1 into the T(2) tetrahedron.
Laboratory duplication of comb layering in the Rhum pluton
Authors: Donaldson Colin H.
Published: December 2006

The changes in olivine morphology and grain size upwards through comb-layered olivine eucrite and peridotite varieties of harrisite in the Rhum layered pluton are systematic, from abundant small granular crystals, to fewer and larger hopper crystals, to highly elongate branching crystals, which are preferentially elongate along the a axis and perpendicular to the plane of the layering. These changes have been reproduced in the laboratory by cooling water-bearing melts (P = 5 kb) of harrisite at 14 and 30 °/hr. These cooling rates represent maximum values for natural crystallization of comb-layered harrisite. Other experiments suggest that the oriented branching olivines in the rock crystallized at 30–50 °C supercooling. The results indicate that continuous, rather than abrupt, changes in the degree of supercooling and supersaturation of the magma can cause formation of comb layers. They also indicate that while field relations point to growth of most comb layers along a thermal gradient in the magma, this is not an essential condition for comb layer formation. Growth could be along a compositional gradient instead. During crystallization of a comb layer, both nucleation rate and the number of crystals suspended in magma close to the layer are essentially zero. Conditions initiating and terminating comb layer formation and the origin of the rapid vectorial crystallization are discussed. It is suggested that some comb layers could form without change in degree of supercooling, due to rapid removal of crystals suspended in the magma causing the enhanced growth rate and branching style of growth of the remaining crystals. Multiple origins of comb-layered rocks may therefore be possible.
A zincian högbomite and some other högbomites from the Strangways Range, Central Australia
Authors: Wilson Allan F.
Published: December 2006

Zincian högbomite has formed by hydrous alteration of spinel and biotite in a lens of highly aluminomagnesian sapphirine-bearing granulite-facies rocks. The högbomite forms chestnut-brown {0001} flakes 1 mm across. ε = 1·827, ω = 1·852 (− 0·002). Analysis: BeO 0·10, SiO20·65, Al2O3 59·69, TiO2 5·37, Ga2O3 0·23, Nb2O5 0·01, Fe2O3 5·24, SnO2 0·06, NiO 0·04, ZrO2 0·03, MgO 7•69, Sc2O3 0·01, CoO 0·11, ZnO 3·08, FeO 17·52, In2O3 0·05, MnO 0·12. The pattern of d-spacings is anomalous. Other högbomites from the region have exsolved from cordierite or titaniferous opaque oxides.
On the occurrence of smolyaninovite in the Mount Cobalt deposit, in north-western Queensland, Australia
Authors: Smith L. K. , Han K. N. , Lawson F.
Published: December 2006

Smolyaninovite, (Co, Ni, Ca, Mg)3 (Fe, Al)2 (AsO4)4. 11H2O, has recently been recognized in the mineralized region around Mount Cobalt, Queensland. It is a soft polycrystalline earthy yellow-brown material, is probably the weathering product of cobaltian arsenopyrite or alloclase, and shows para-magnetic properties.
The nature of kerolite, its relation to talc and stevensite
Authors: Brindley G. W. , Bish David L. , Wan Hsien-Ming
Published: December 2006

Kerolites from Goles Mountain (Yugoslavia), Wiry (Poland), Madison Co. (North Carolina), and Kremze (Czechoslovakia) are compared with talc and stevensite. Chemical analyses give a composition for kerolite near R3Si4O10(OH)2.nH2O with R mainly Mg and n about 0·8–1·2. Infra-red data and dehydration-rehydration experiments suggest that the additional water is partly surface-held hydrogen-bonded molecular water, lost up to about 300 °C and easily recoverable, and ‘water’ held as surface hydroxyls, lost at temperatures up to about 650 °C and less easily recoverable. The surface area of kerolite from North Carolina by nitrogen absorption measurements is 196 m2/g.

X-ray data show broad basal reflections, a basal spacing (after Lorentz-polarization correction) of about 9·6 Å and a crystallite size of about five structural layers, which is consistent with the large surface area. Two-dimensional hk bands indicate a randomly stacked layer structure with b ≈ 9·14 Å and a crystallite ‘diameter’ of about 150 Å. The basal spacing shows no expansion in water and no thermal contraction up to 500°C. A partial and irregular swelling with ethylene glycol is obtained only after prolonged cxposure (several weeks). In both respects, kerolites differ from stevensite. Kerolites come close to talc in structure and composition but differ in having a highly random layer arrangement, a slightly enlarged basal spacing, which could be due to misfit of layers caused by random stacking, and weaker interlayer bonding.

Kerolite is considered to be a useful varietal name for this talc-like mineral in agreement with the views of D'yakonov and of Maksimovic. It cannot be defined as serpentine + stevensite.