bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evidence of shock-metamorphic effects in the Ergheo meteorite
Authors: Baldanza B. , Levi-Donati G. R. 
Published: December 2006

SummaryThe 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

SummaryYttrotungstite 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

SummaryAlkalic 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

SummaryHomogeneous 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

Summary
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

Summary
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

Summary
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

SummaryThe 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

SummaryA 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

SummaryCoexisting 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

SummaryMinute 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

SummaryCreaseyite 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

SummaryAn 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

SummaryNative 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

SummaryZ-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

SummaryThe 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

SummaryThe 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

SummaryThree-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

SummaryThe 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

SummaryZincian 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

SummarySmolyaninovite, (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

SummaryKerolites 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.
The thermal decomposition of chrysotile
Authors: Martin C. J. 
Published: December 2006

SummaryThe decomposition of chrysotile fibres heated in air has been studied in the range 100–1400°C by electron microscopy and infra-red absorption. The first observable change in the structure occurred at 580°C, where cavities started to open up between the (001) layers of chrysotile as the fibres were dehydrated, giving rise to strong low-angle diffraction. There was no evidence of any structure in the remaining material but some degree of the original atomic arrangement was preserved for the magnesium silicates, forsterite, and enstatite, later developed in certain preferred orientations. The manner of this crystallization was determined by the thermal treatment, for in samples held between 600°C and 800°C forsterite developed slowly with little further disruption of the fibre while above 800°C the remaining amorphous areas rapidly recrystallized to a mixture of forsterite and enstatite. It is suggested that the mechanisms described by other investigators to explain the development of forsterite in preferred orientations may serve simply to nucleate the crystallization and a similar mechanism to account for the nucleation of the enstatite crystallization is considered. At high temperatures a possible doubling of some of the lattice parameters of the silicates was observed.
An electron-diffraction study of a microcrystalline muscovite and its vermiculitized products
Authors: Kodama H. 
Published: December 2006

SummaryAfter approximately 50% of K from the 1–2 μm fraction of a naturally occurring microcrystalline muscovite was extracted with BaCl2 solution at 98°C electron-diffraction patterns showed a honeycomb-shaped diffuse scattering as well as intense diffuse streaks. The diffuse scattering became pronounced with increasing K-depletion. It may be interpreted in terms of a short-range order distribution of interlayer Ba ions, using an analogy to the work by Alcover et al. (1972, 1976). Since the diffuse streaks still remained after re-entry of K to the K-depleted specimen they might be related to structural disturbance, particularly in the basal oxygen arrangements, resulting from the K-extraction. Subsequent conversions of Ba-saturated vermiculitized muscovite into Na-, Mg-, and Ca-forms revealed distinct extra diffraction spots midway between two ordinary diffraction spots. They were broader than the ordinary spots and elongated along the three directions of [01]*, [11]*, and [11]*. The diffraction pattern containing the extra spots was, therefore, interpreted as a composite one made up by superimposing three independent patterns, each of which was composed of ordinary Bragg diffraction spots and extra diffraction maxima elongated in one of the three directions. This situation does not require a superlattice but modified the original face-centred lattice symmetry to a primitive lattice symmetry. However, the presence of a real superlattice should also be possible. The elongation and broadness of the extra diffraction maxima may be related to the orientation and size of coherent domains defined by a certain ordering of interlayer cationic distribution, which took place during the hydration processes including extraction and conversion.