bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nigerite from Lixa, near Felgueiras, Douro Litoral province, Portugal
Authors: Tassel R. Van 
Published: December 2006

SummaryNigerite 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

SummarySix 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

SummaryThe 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

SummaryA 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

SummaryAn 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

SummaryAn 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

SummarySimple 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

SummaryThe 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

SummaryThe 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

SummarySeveral 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

SummaryNatural 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

SummaryThe 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

SummaryOlivine 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

SummaryContact 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

SummaryChemical 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

SummaryThe 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

SummaryThis 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

SummaryThe 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

SummaryIn 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

SummaryWhen 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

SummaryThe 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

SummaryIt 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

SummaryThe 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

SummaryA 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

SummaryThe 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

SummaryThe 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

SummaryHoltite, 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

SummaryThe 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

SummaryIdentification 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.