bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stability of Al2SiO5 solid solutions
Authors: Strens R. G. J. 
Published: December 2006

SummaryAn ideal solution model has been used to calculate the effect of the substitutions on the stability fields of the Al2SiO5 minerals. The results show that divariant assemblages of andalusite+sillimanite and sillimanite + kyanite solid solutions can coexist over ranges of 0·1 to 0·4 kbar at 527° C, but that kyanite+andalusite would be stable over a much narrower range. On adding (Fe, Mn)3+ to the system, the andalusite/sillimanite curve can be considered to rotate about the invariant point, first eliminating the sillimanite field, and then penetrating the kyanite field. Wide zones of viridine+sillimanite and viridine+kyanite are thus formed.In view of the ease with which epitaxial nucleation occurs in the Al2SiO5 system, it is considered that extensive metastable growth of andalusite, sillimanite, and kyanite is improbable in nature. Metastable persistence is likely to occur in dry systems, or in the presence of an ‘armour’ of the stable phase, but reaction of millimetre-sized crystals should be completed in geologically short times when aqueous or silicate liquids are present. The combination of the effects of metastable persistence and solid solution seems adequate to account for essentially all the examples of kyanite + sillimanite and kyanite + andalusite, and for many sillimanite +andalusite assemblages. In addition, if small supersaturations develop during metamorphism, simultaneous growth of andalusite + sillimanite could occur over a restricted temperature range.
Copper in various phases of several olivine-hypersthene and olivine-bronzite chondrites
Authors: Hey M. H. , Easton A. J. 
Published: December 2006

SummaryDeterminations of Cu in separate phases of three olivine-hypersthene and one olivine-bronzite chondrites show that it is very strongly concentrated in the taenite; appreciable amounts are present in the olivine, less in the pyroxene plus plagioclase; it is probable that the copper found in the ‘unattracted, attacked’ fraction is present as metallic copper, and that very little is present in the sulphides.
Electronprobe analyses of stannite and related tin minerals
Authors: Springer G. 
Published: December 2006

SummaryQuantitative electronprobe microanalyses have been made of stannite from various localities. It was found that in general this mineral corresponds in composition to the formula Cu2FeSnS4. However, noticeable deviations in the ratio of the metals can occur and considerable concentrations of zinc may be present.Some tin minerals related to stannite have also been analysed, namely hexastannite, mawsonite, and an apparently hitherto unknown mineral to which the name rhodostannite is given.
A former association of enstatite and kyanite
Authors: Chinner G. A. , Sweatman T. R. 
Published: December 2006

SummaryAn enstatite-cordierite-sillimanite-quartz rock from a pyroxenegranulite facies terrain in southern Rhodesia gives evidence of at least two stages of recrystallization : an early, high-pressure recrystallization to form the assemblage enstatite-kyanite-quartz, and a later, ‘retrogressive’ recrystallization during which kyanite inverted to sillimanite, and cordierite was formed by reaction. The rock itself has ratios of R2+ : Al : Si that are virtually those of cordierite ; the recent data of Schreyer (1967) may thus be applied to the occurrence. The early kyanite-enstatite recrystallization occurred under pressures in excess of 10 kb, corresponding to depths greater than those of the continental Moho.
Chemical variation in tourmalines from South-west England
Authors: Power G. M. 
Published: December 2006

SummaryForty-eight samples of tourmaline from the granitic rocks of south-west England have been analysed by emission spectrography for Fe, Mn, Mg, Ca, Ti, Na, F, Li, Sc, V, Cr, Co, Ni, Cu, Ga, Rb, Sr, Zr, Sn, and Sc. The tourmaline reflects the fractionation trends of the rocks from which it comes in the proportion of Mg, Ca, Ti, and certain trace elements it contains and is considered likely to have been a primary product of the magma. Textural evidence that indicates a later development is interpreted as recrystallization, possibly at low temperature, with little change in chemical composition. Hydrothermal tourmaline has a distinctive chemical composition, being higher in Mg, Ca, Sr, and Sn and lower in Fe, Mn, and F and also tending to have a higher Cr, V, Ni, and Sc content. The chemical composition of the tourmalines is used to show that some quartz-tourmaline rocks are the product of extreme fractionation and are not completely tourmalinized granites. Parti-coloured tourmaline is shown to be the result of hydrothermal growth.
The stability of tobermorite in the system CaO-SiO2-H2O at elevated temperatures and pressures
Authors: Speakman K. 
Published: December 2006

SummaryHydrothermal studies in the silica-rich region of the CaO-SiO2-H2O system have given information on the stability field of tobermorite. At saturated steam pressures tobermorite is unstable relative to xonotlite (C6S6H) above 140 °C but between 10 000 and 40 000 lb/in.2 (69 and 276 N/mm2), the decomposition temperature is raised to 285±5 °C. Tobermorite is stable at all compositions between C/S = 0·67 and 1·0 up to this temperature and has a formula close to C5S6H5. Variable compositions reported earlier are thought to be mixtures rather than lime-rich or silica-rich tobermorites.Data have also been collected on the equilibrium assemblages below C/S = 0·67 and between C/S = 1·0 and 1·5 involving truscottite, gyrolite, xonotlite, foshagite, and hillebrandite.
Colour in charnockites
Authors: Oliver R. L. , Schultz P. K. 
Published: December 2006

SummaryMicroprobe analysis of leached and unleached varieties of a charnockitic rock from Madras supports the contention of Howie (1964) that the characteristic dark greenish colour of such rocks is contained mainly in fine (chloritic ?) veinlets cutting the feldspar and quartz, though a certain amount appears to be contained in exsolved sodium feldspar. Leaching of the darkish colour of the charnockitic rock has not affected the crystallographic state of the potassium feldspar.
The related layered minerals ganophyllite, bannisterite, and stilpnomelane
Authors: Smith Marie Lindberg , Frondel Clifford 
Published: December 2006

SummaryTwo monoclinic minerals formerly classified as ganophyllite have been differentiated on the basis of single-crystal X-ray data. True ganophyllite occurs at the Harstig mine, Pajsberg, Sweden (a, 16·60 ± 0·05 Å;b, 27·04 ± 0·08 Å;c, 50·34 ± 0·15 Å;β, 94° 10′ ± 10′; space groupA2/a), at the Benallt mine, Caernarvonshire, Wales, and in Aroostook County, Maine. Bannisterite, a new mineral, occurs at Franklin, New Jersey (a, 22·20 ± 0·07 Å;b, 16·32 ± 0·05 Å;c, 24·70 ± 0·08 Å;β, 94° 20′ ± 10′; space groupA2/a) and at the Benallt mine, Wales. Both minerals have similar pseudocells:a, 5·53 Å;b, 3·3 Å;c, 25 Å;β, 94° The chemical analysis of ganophyllite from the Harstig mine, Sweden, is: SiO2, 39·67 %; Al2O3, 7·95; Fe2O3, 0·90; MnO, 35·15; CaO, 1·11; MgO, 0·20; PbO, 0·20; K2O, 2·70; Na2O, 2·18; Li2O, trace; H2O, 9·79; total, 99·85. The chemical analysis of bannisterite from Franklin Furnace, New Jersey, is: SiO246·20 %; Al2O3, 4·74; MnO, 23·02; FeO, 6·40; ZnO, 4·67; CaO, 1·52; MgO, 1·99; Na2O, 0·29; K2O, 1·21; H2O, 9·74; total, 99·78.Both ganophyllite and bannisterite show a structural resemblance to stilpnome-lane from Deer Isle, Maine, in projection on selected zones. All three have a micaceous cleavage parallel to {001} in the orientations here taken. Stilpnomelane is triclinic, pseudotrigonal, and pseudomonoclinic. In the triclinic cell,a=b, 22·05 Å ± 0·06 Å;c, 17·70 ±0·06;α, 124° 49′;β, 95° 58′;γ, 120° 00′ (angles ± 5′). In the trigonal subcell,a′, 3·2 Å;c′, 36·4. Small distorted trigonal subcells for ganophyllite havea′, 3·38 Å;c′37·7, and for bannisterite havea′, 3·264 andc′, 37 Å.
The mineralogy of the potassium-barium feldspar series III: Subsolidus relationships
Authors: Gay P. , Roy N. N. 
Published: December 2006

SummaryFurther data are presented on the properties of natural and synthetic members of this series. Cell constants have been determined for over 50 specimens across the composition range; the activation energy for a low-high transformation in an intermediate hyalophane has been evaluated as 101·5 ± 5·0 kcal/mole; additional single crystal studies have revealed complexities not previously reported.Although there remain many detailed problems to be resolved, the present studies allow some suggestions concerning the nature of the relationships within the series. Problems of nomenclature and subsolidus relations are discussed together with some structural implications.
Synthesis and study of diaboleïte
Authors: Winchell R. E. , Wenden H. E. 
Published: December 2006

SummaryDiaboleïte has been synthesized between 25 and 100° C at atmospheric pressure and approximate water vapour partial pressures of 14·7 lb/in2. Under similar conditions at 170° C cumengéite appears to be the stable phase produced from a diaboleïte composition. Synthetic diaboleïte is much simpler morphologically than the natural mineral but the hemimorphic symmetry is more clearly demonstrated morphologically in the artificial specimens. A comparison of X-ray powder data for natural and synthetic diaboleïte shows almost exact detailed correspondence in line position and intensity between 0 and 180° 2θ. The cell dimensions obtained from X-ray powder data are a 5·869 ± 0·002 Å and c 5·495 ± 0·003 Å.
The crystal structure of gersdorffite (III), a distorted and disordered pyrite structure
Authors: Bayliss P. , Stephenson N. C. 
Published: December 2006

SummaryThe crystal structure of gersdorffite (III) has been examined with three-dimensional Weissenberg X-ray diffraction data. The unit cell is isometric with a 5·6849 ± 0·0003 Å, space group PI, and four formula units per cell. This structure has the sulphur and arsenic atoms equally distributed over the non-metal atom sites of pyrite. All atoms show significant random displacements from the ideal pyrite positions to produce triclinic symmetry, which serves to distinguish this mineral from a disordered cubic gersdorffite (II) and a partially ordered cubic gersdorffite (I). Factors responsible for the atomic distortions are discussed.
Ferrian chlorospinel from Carneal, Co. Antrim
Authors: Sabine P. A. , Sergeant G. A. , Young B. R. 
Published: December 2006

SummaryA Tertiary dolerite plug at Carneal, Co. Antrim has been contaminated by Chalk with the production of calc-silicates and related minerals. In a larnite-spinel-rock the spinel is of the unusual ferrian variety. It has the composition The spinel, which is brown, has: n, 1·862; D, 3·97; a, 8·1905 Å. A chemical analysis and powder data are given, the implications of experimental data are briefly discussed, and the nomenclature is reviewed.
The mineralogical characteristics of calcium-iron olivines
Authors: Wyderko Marta , Mazanek Eugeniusz 
Published: December 2006

SummaryFor the estimation of the properties of calcium-iron olivines in ironore sinters, synthetic mixtures of CaO, FeO, and SiO2 were prepared and melted; the obtained olivines were then examined microscopically and by X-ray powder method. The investigations allowed to state, that with the increase of the basicity of sinters, the relation of Fe : Ca in olivines decreases, which causes the change of their physical, optical, and röntgenometric properties.
Oriented transformations in the system MnO-O-H2O
Authors: Dent Glasser Lesley S. , Smith Ian B. 
Published: December 2006

SummaryExtensive studies on oriented reactions in the system MnO-O-H2O have revealed surprising symmetry changes, which we have been unable to explain. Orientation relationships are often complicated, but where interpretation is possible, the results support the idea that orientations are controlled by the oxygen frame-work and that considerable migration of manganese occurs.
Subsolidus phase relations in the system ZnWO4-ZnMoO4-MnWO4-MnMoO4
Authors: Chang Luke L. Y. 
Published: December 2006

SummarySubsolidus phase relations in the systems ZnWO4-MnWO4, ZnWO4-ZnMoO4, MnMoO4-ZnMoO4, and MnWO4-MnMoO4, were investigated by using the quenching technique. A complete series of solid solutions forms in the system ZnWO4-MnWO4 above 840° C, whereas limited solid solubilities were found in the other three. The various limits of solubility are, at 620° C, 4·0 mole % ZnMoO4 in ZnWO4 and 4·0 mole % ZnWO4 in ZnMoO4, 13·0 mole % ZnMoO4 in MnMoO4 and 12·0 mole % MnMoO4 in ZnMoO4, 9·0 mole % MnMoO4 in MnWO4 and 6·0 mole % in MnWO4 in MnMoO4; and at 1000° C, 15·0 mole % ZnMoO4 in ZnWO4 and 15·0 mole % ZnWO4 in ZnMoO4, 36·0 mole % ZnMoO4 in MnMoO4 and 29·0 mole % MnMoO4 in ZnMoO4, 15·0 mole % MnMoO4 in MnWO4 and 27·0 mole % MnWO4 in MnMoO4.Subsolidus phase relations in the system ZnWO4-ZnMoO4-MnWO4-MnMoO4 were studied at 900° C. The solubility of molybdenum in the (Zn,Mn)WO4 series increases from both end members to a maximum of 27·0 mole % at the composition Mn35Zn65. Both molybdates also have limited ranges of solid solutions, and a three-phase region occupies the central portion of the system defined by three points with compositions of 41 mole % ZnMoO4, 26 mole % MnMoO4, 33 mole % MnWO4; 57 mole % ZnMoO4, 10 mole % MnMoO4, 35 mole % MnWO4; and 27 mole % ZnMoO4, 34 mole % MnWO4, 39 mole % ZnWO4.
On the infra-red spectrum and thermal decomposition products of thaumasite, Ca3H2(CO3/SO4)SiO4.13H2O
Authors: Kirov G. N. , Poulieff C. N. 
Published: December 2006

SummaryThe infra-red spectrum of untreated thaumasite Ca3H2(CO3/SO4)SiO4.13H2O, as well as the spectra and X-ray diffraction patterns of thaumasite heated in air at 200, 360, 550, 725, 800, 900, and 1150° C were investigated. The release of CO2 and H2O upon heating was followed. It was established that thaumasite changes between 200 and 550° C to a glass-like, amorphous state. Ca2SiO4-polymorphs and anhydrite are formed upon heating at temperatures up to 800° C. From 900° C calcium silicosulphate and anhydrite are the thermal decomposition products. These results are used in the assignment of the IR-absorption bands under 1400 cm−1 of untreated thaumasite, which are shown to be of a composite nature, i.e. attributable to overlapping vibrations of both sulphate and silicate tetrahedra.
Oligoclase-andesine phenocrysts and related inclusions in basalts from part of the Nigerian Cenozoic province
Authors: Wright J. B. 
Published: December 2006

SummaryThe Benue trough is a graben structure containing folded Upper Cretaceous sediments. Mid-Tertiary to Recent rift-valley type vulcanicity in and near the trough was mainly basaltic (in the north at least), salic lavas being now represented mainly by a few eroded plugs. The Nigerian rocks are regarded as a practically extinct sub-province within a larger Gulf of Guinea alkaline province, dominated by the voluminous and still active vulcanicity of the Cameroun rift. The two structures have the same trend as other graben features further south along Africa's western margin.Large sodic plagioclase crystals in a basalt plug within the Nigerian sub-province have rounded edges and more calcic overgrowths. They probably crystallized at deep crustal levels but are unaccompanied by any of the mafic phases that normally crystallize from basalts under high pressure. However, spinel crystals and olivine nodules found in a nearby plug indicate that the complementary mafic assemblage may be found not far away. Sparse published data on phenocrysts and inclusions in the Jos Plateau lavas offer some support for this suggestion.Crystallization of sodic feldspars in basalt may have a bearing on the independent genesis of salic liquids, while apatite and magnetite inclusions in them suggest a possible link with carbonatites.
The variation of the 01 reflection in plagioclases
Authors: Hamilton D. L. , Edgar A. D. 
Published: December 2006

SummaryThe position of the 01 X-ray reflection in albite varies with the degree of Al/Si ordering. This is also true for binary plagioclases but the 01 reflection for high-temperature plagioclases is constant and therefore independent of anorthite content. For plagioclases of ternary composition grown in a hydrous silicate melt, the position of the 01 reflection gives a good estimate of the orthoclase content when a determinative curve is used that was originally drawn from data on high-temperature synthetic binary alkali feldspars.
X-ray data, optical anisotropism, and thermal stability of cobaltite, gersdorffite, and ullmannite
Authors: Bayliss P. 
Published: December 2006

SummaryData are presented from cobaltite (CoAsS), gersdorffite (NiAsS), and ullmannite (NiSbS) for cell size, compositional zoning, mineralogical association, X-ray diffraction powder intensities, and optical anisotropy. The presence of powder X-ray diffraction reflections 001 and 011 are related to the crystal structure type. The amount of distortion from cubic symmetry is related to the 001 reflection intensity and also to the optical anisotropism strength. These properties are related approximately to the thermal stability of the distorted crystal structure. This thermal stability increases with the substitution of cobalt for nickel, which decreases the cell size. An order-disorder change occurs before the distortion release in non-cubic gersdorffite (P1) with a large cell size, whereas only a distortion release is observed in cobaltite (Pca21) and non-cubic gersdorffite (P1) with a small cell size. Glaucodot (Co,Fe)AsS converted to cobaltite at 620 C. No evidence was found to relate optical anisotropism of pyrite to deviations from cubic symmetry.
The Siena meteorite: Mineralogy and Chemistry
Authors: Baldanza B. , Levi-Donati G. R. , Wiik H. B. 
Published: December 2006

SummaryThe principal data are collected about the fall and the distribution of the fragments of the Siena, Italy, meteorite (11·6°E., 43·1°N.). A complete individual, weighing 110·55 g, is described in some detail. Crust morphology, mineralogical composition, and structure were studied. Optical data were established by microscopical analysis and both thin and polished sections were observed. Compared with available electron-probe analysis they are found in good agreement. The chemical analysis is Fe 12·93, Ni 1·39, Co 0·09, FeS 5·46, SiO2 37·10, TiO2 0·14, Al2O3, 3·91 FeO 11·46, MnO 0·35, MgO 23·81, CaO 1·63, Na2O 0·90, K2O 0·16, P2O5 0·44, H2O+ 0·10, H2O− 0·00, Cr2O3 0·56, total 100·43. Siena is an ordinary chondrite, with relatively ambiguous characteristics and evident features of recrystallization and metamorphism.
The determination of multiple correlations between several variables, with especial reference to the correlation of physical properties and chemical composition
Authors: Hey M. H. 
Published: December 2006

SummaryIf the true values of a number (n) of variables are exactly related by one or more (m) equations but all experimental values are liable to experimental error then, provided the errors of measurement can be assumed to be symmetrically distributed about a zero mean, provided the relations are linear, and provided the assessed probable errors of measurement of the several variables remain in constant ratio from one set of measurements to another, the best estimate of the relations derived fromNsets of measurements will be given by the latent vectors corresponding to themsmallest latent roots of then-square matrix whose terms are Σwiξijξik(summed from (summed fromi= 1 toi=N) for alljandkfrom 1 ton, wherewiis the weight of theith set of measurements and ξijis the standardized value of theith measurement of thejth variable measured from its weighted mean.It is also shown that the alleged inconsistency of the maximum-likelihood estimate of the variance in such a case is simply a confusion of the root-mean-square residual with the root-mean-square normal residual.An Autocode computer programme has been written to carry out the necessary operations for correlating the physical properties and chemical properties of an isomorphous series of minerals using this procedure.
Study of minerals from the pegmatites of the Nellore mica-belt, Andhra Pradesh, India Part I. Microcline perthites
Authors: Babu V. R. R. M. 
Published: December 2006

SummaryThe obliquity values of microcline perthites are nearer to maximum microcline type, indicating that they have less than 10% Ab in their lattices, apart from exsolved albite. The perthites are classified based on form as stringlet, string, film, vein, and replacement types. It is concluded that stringlet and string perthites are formed by exsolution along contraction cracks, followed by film as a result of decrease in rate of cooling and increase in water vapour content of the pegmatites, whereas vein and replacement perthites are formed last, by replacement when the pegmatites crystallized in a closed system. Based on the chemical composition of microcline perthites, a temperature of 600 °C is arrived at for unmixing of feldspar to give rise to microcline perthite.
Electrostatic energy for ion clustering in intermediate plagioclase feldspar
Authors: Smyth Joseph R. , Smith Joseph V. 
Published: December 2006

SummaryElectrostatic calculations estimated the energy of hypothetical ion clustering in intermediate plagioclase feldspars. The calculated energy appears too great to allow segregation of Ca and Na atoms into domains upon annealing without a corresponding movement of Al and Si from an original disordered structure. The calculated energy may be sufficiently small that Ca and Na atoms can disorder partially without movement of Al and Si upon heating a low-plagioclase to high temperatures.
Kaersutite-bearing plutonic xenoliths from Tristan da Cunha, South Atlantic
Authors: Le Maitre R. W. 
Published: December 2006

SummaryThe xenoliths, which are gabbroic in character, consist of kaersutite, titanaugite, plagioclase, and iron ore in variable amounts. Biotite and olivine are also occasionally present. New analyses and trace element data are given for two xenoliths and their coexisting kaersutite, titanaugite, and plagioclase. After discussing several possible origins with the aid of a principal latent vector variation diagram, it is concluded that they represent the accumulation of phases that crystallized from the Tristan magma at depths between 5 and 25 km. Evidence is also presented to show that the parental Tristan magma may be of trachybasalt composition.
A Mössbauer study of biotite weathering
Authors: Rice C. M. , Williams J. M. 
Published: December 2006

SummaryFresh and weathered biotites have been studied using Mössbauer, chemical, and X-ray analytical techniques. In the Mössbauer spectra the complete interference of both low-spin ferric lines by one of the high-spin ferrous lines and the existence of high-spin ferric iron in the weathered biotite has been demonstrated. In view of this interference, which appears to be common, allowances must be made in spectral interpretation if chemical analysis reveals ferric iron to be present in detectable amounts. Hypothetical extension of the weathering trends observed suggests that high-spin ferric iron is the only stable iron species in the end product.During weathering marked loss of ferrous iron occurs, whereas the ferric iron content remains approximately constant. As a result of the instability of ferrous iron in the weathering environment there is a significant rearrangement of the octahedral layer.
Petrofabric analysis of a large microporphyritic chondrule in the Parnallee meteorite
Authors: Dodd R. T. 
Published: December 2006

SummaryOlivine microphenocrysts in a large microporphyritic chondrule in the Parnallee chondrite show a linear preferred orientation of the long (β = c) axes, which is thought to reflect flowage of a partly crystalline parent magma. The orientation pattern is somewhat disturbed by post-crystallization fracturing.