bluuebunny/crossref_metadata_2025_split huggingface dataset:
The occurrence of platinoid bismuthotellurides in the Merensky Reef at Rustenburg platinum mine in the western Bushveld
Authors: Kingston G. A. 
Published: December 2006

SummaryFour different palladium and platinum bismuthotellurides, one containing major mercury, have been identified in the ore from Rustenburg mine on the Merensky Reef. The composition of each phase was determined by electronprobe microanalysis, and X-ray powder data are presented for three of these phases. Quantitative spectral reflectivity values at 470, 546, 589, and 650 mμ were obtained on areas of 1–10µ. Similar phases have been located in the ore from Union mine.Two of these phases are shown to be moncheïte and kotulskite. From two electronprobe microanalyses, kotulskite is shown to be Pd(Te,Bi). The other two phases are new minerals: analysis of one of them gives the composition (Pd,Pt)(Te, Bi)2, containing 23·1% Pd, 1·8% Pt, 50·8 % Te, 14·2 % Bi, with strongest X-ray powder lines at 2·92 (10), 2·10 (6), 2·02 (3), and 1·54Å (3), and cell parameters a 3·978±0·001, c 5·125±0·002; it is probably isostructural with moncheïte, and an isomorphous series may exist between them; the name merenskyite is proposed for this mineral, after Dr. Hans Merensky who was mainly responsible for discovering the platinoid bearing ‘reef’; it is commonly intergrown with kotulskite. For the second new phase (Mineral A), no X-ray data could be obtained, but a single electron-probe microanalysis gave a composition of Pd 27·8 %, Hg 12 %, Te 38·5 % and Bi 1·6 % suggesting the empirical formula (Pd,Hg)(Te,Bi).
A new Czechoslovak occurrence of stokesite
Authors: Černý P. 
Published: December 2006

SummaryThe third occurrence of stokesite was discovered in a desilicated pegmatite at Věžná, Western Moravia. In this locality, stokesite accompanies columbite, cassiterite, and stibian pyrochlore-microlite, in a miarolitic cavity of albite. The X-ray data and the optical properties of the Věžná stokesite agree well with those observed by previous authors.
The alkali feldspars from microsyenitic dylces of southern Greenland
Authors: Scharbert H. G. 
Published: December 2006

Summary26 b-axis oscillation photographs of alkali feldspars of microsyenitic dykes of Southern Greenland are presented. The crystals are rather restricted in composition (Or42·4 to Or35·3) but are rather rich in Ca (up to 14 % An). The range of variation of the optic axial angles, 2 V 45° to 71° (exceptions up to 87°), puts the crystals between sanidine-anorthoclase cryptoperthite and orthoclase microperthite, as classified by Tuttle (1952).Since the syenitic magma cooled down rather rapidly some peculiarities in the structural state of the alkali feldspars are to be expected. The potassium-rich phase is (nearly) monoclinic. According to the values of the reciprocal lattice angles α* and γ* the sodium-rich phases can be divided into three groups: high-temperature pericline-twinned and high-temperature albite-twinned phases, high-temperature pericline-twinned and low-temperature albite-twinned phases, and high-temperature pericline-twinned and low-temperature albite-twinned phases with nearly identical values of the reciprocal lattice angle γ*.
Graphite in natural and experimental carbonate systems
Authors: Gellatly D. C. 
Published: December 2006

SummaryGraphite occurs in the Darkainle nepheline syenite complex, Somali Republic, as small drop-like grains in an altered ankeritic carbonatite; it has been recorded previously from carbonate-bearing nepheline syenites and kimberlites. Experimental evidence indicates that siderite decomposes to a stable association of magnetite and graphite within the PT ranges 500 to 10 000 bars and 455 to 745° C. The graphite in carbonatite and other alkaline igneous rocks may have been formed similarly by the decomposition of siderite or iron-rich carbonates.
The feldspars of the Rosses Granite Complex, Donegal, Ireland
Authors: Hall A. 
Published: December 2006

SummaryAn examination has been made of the composition and structural state of the feldspars in each of the units of the Rosses granite complex. The compositions of the plagioclases are systematically related to the compositions of the rocks, but the alkali feldspars are much more uniform as a result of postmagmatic recrystallization. In the granites both alkali feldspar and plagioclase are in low-temperature structural states, but alkali feldspar phenocrysts from one of the porphyry dykes associated with the complex show a higher-temperature state.
The analysis of molybdates and tungstates
Authors: Easton A. J. , Moss A. A. 
Published: December 2006

SummaryThe estimation of molybdenum and tungsten when present together has proved difficult, as is indicated by the large number of methods put forward for their determination. Many of the methods given are for one or other of these elements only, a note often being added that the presence of the other invalidates the method. The estimation of molybdate and tungstate in the mineral powellite has been briefly described by one of the authors (A. A. M.): molybdate and tungstate were precipitated as oxinates (Mo,W)O2(C9H6ON)2 and the molybdate (MoO4″) determined by measurement of the optical density at 230 mµ of a solution containing molybdate and tungstate. The amount of tungstate present was then estimated by difference. The property of the molybdate ion, MoO4″, to absorb strongly in the ultra-violet has been further investigated and it has been found that, if a wave-length of 240 mµ is chosen and the proper precautions taken, the MoO4″ ion can be estimated without significant interference by the WO4″ ion. Methods are given for the analysis of the common molybdate and tungstate minerals, together with results obtained during the course of this investigation.
Clinopyroxenes from the Square Top intrusion, Nundle, New South Wales
Authors: Wilkinson J. F. G. 
Published: December 2006

SummaryDespite a wide range in parent rock compositions, from analcime-olivine theralite to analcime-tinguaite, clinopyroxene phenocrysts in the Square Top intrusion show limited compositional variation. The crystallization trend of the pyroxenes (principally sahlites) lies approximately parallel to the diopside-hedenbergite join of the pyroxene quadrilateral, and in addition reveals slight enrichment in acmite. The limited iron enrichment in the pyroxenes (and in olivine phenocrysts in the theralites and tinguaites) stemmed from progressively more hydrous liquid fractions whose ferric/ferrous iron ratios increased during differentiation.
The weathering of biotite in some Aberdeenshire soils
Authors: Wilson M. J. 
Published: December 2006

SummaryThe weathering of biotite in some freely drained soils developed from a biotite-rich quartz gabbro near Strathdon, Aberdeenshire, has been studied. Using a combination of X-ray, chemical, differential thermal, infra-red, and optical techniques, it was found that the biotite weathers to an intergrade aluminous vermiculite-chlorite together with zones of kaolinite and gibbsite. The crystallographic axes of biotite and included kaolinite are common and parallel and it is proposed that both kaolinite and gibbsite zones crystallized epitaxially within opened out cleavage spaces of the host biotite. The development of kaolinite and gibbsite in this manner could have occurred relatively quickly and the significance of this with regard to generalized pedogenic weathering reactions of biotite is discussed.
Experimental studies of apatite crystallization in parts of the system CaO-P2O5-H2O at 1000 bars
Authors: Biggar G. M. 
Published: December 2006

SummarySolid-liquid-vapour phase equilibria for the join Ca(OH)2-Ca3(PO4)2-H2O at 1000 bars are determined in the temperature range 700 to 950°C. The isobaric invariant equilibrium portlandite + hydroxyapatite → liquid on the join Ca(OH)2-Ca3(PO4)2 involves a liquid with the composition 96 wt. % Ca(OH)2, 4 wt. % Ca2(PO4)2 and occurs at 765°C. The isobaric invariant equilibrium portlandite + hydroxyapatite + vapour → liquid on the join Ca(OH)2-Ca3(PO4)2-H2O is encountered at 735°C, and involves a liquid containing 92 wt. % Ca(OH)2, 4 wt. % Ca3(PO4)2, and 4 wt. % H2O. The apatites are shown by X-ray diffraction techniques to vary in composition with changes in the bulk composition from which crystallization occurred.The apatite liquidus is steep; apatite is the first mineral to crystallize from calcium-hydroxide-rich liquids containing as little as 4 wt. % Ca2(PO4)2 (1·8 % P2O5) at temperatures as low as 735°C in the presence of vapour at 1000 bars pressure; and rapid crystal settling of apatite was experimentally noted. These observations suggest that concentrations of apatite in carbonatites are the result of crystal accumulation from liquids relatively poor in P2O5.
Paragenesis of the metasomatic actinolite-bearing rocks from the Khetri copper belt, Rajasthan, India
Authors: Das Gupta S. P. 
Published: December 2006

SummaryIn the south-eastern part of the Khetri copper belt, actinolite occurs in association with alteration assemblages resulting from the Fe-Mg metasomatism that accompanied sulphide mineralization, and more commonly with albite-bearing rocks formed by albitization of quartzites and schists near granitic rocks. Within the latter occur many coarse, massive, and unoriented aggregates of actinolite crystals, individuals being commonly more than 10 cm long. Locally fluorite-bearing veins oecur within granitic and albite-quartz rocks. The actinolite is pleochroic from pale pink to green; γ: [001] = 26°; γ = 1·642 ± 0·003; 2Vα = 80°. The composition of the analysed actinolite closely compares with those published in the literature excepting in (OH), which is low. The mineral assemblages, formed by metasomatic replacement of pre-existing rocks, are equivalent to those of albite-epidote-amphibolite facies. The metasomatic fluid was apparently rich in Ca, F (indicated by fluorite), and oxygen (indicated by magnetite, ilmenite, and hematite).
The mineralogy of the potassium-barium feldspar series. II. Studies on hydrothermally synthesized members
Authors: Roy N. N. 
Published: December 2006

SummaryMembers of the KAlSi3O8-BaAl2Si2O8feldspar series have been synthesized by hydrothermal methods. Although the products are too finely crystalline for complete detailed study, some X-ray and optical measurements have been made, together with some electron-diffraction observations.The results presented confirm the existence of high structural states over the greater part of the series, and suggest that a simple solid-solution series is formed between the end-members at high temperatures.
Phosphates and other minerals in pegmatites of Rhodesia and Uganda
Authors: Gallagher M. J. 
Published: December 2006

SummaryIn the rich mineral assemblage found in the pegmatites of Rhodesia and Uganda are members of the amblygonite-montebrasite series with α 1·592–1·615, γ, 1·612–1·638, the highest values corresponding to montebrasite, Li1·98Al2·00 (P1·95O7·90)(OH1·90F0·20); apatite with up to 8·8 per cent MnO; heterosite (new analysis) and other manganese-iron phosphates; and a variety of niobium-tantalum and uranium minerals.
Genthelvite and bertrandite from the Cairngorm Mountains, Scotland
Authors: Morgan W. C. 
Published: December 2006

SummaryA zinc-rich helvine (genthelvite) has been found with bertrandite in miarolitic cavities in adamellite at Coire an Lochain in the Cairngorm Mountains. The genthelvite occurs as green or brown tetrahedral crystals of sp. gr 3·58±0·01. It is isotropic, n 1·742±0·003, a 8·133±0·005 Å. Bertrandite crystals are pale brown with sp. gr. 2·60±0·01; biaxial negative with 2V 75°, and α 1·590, β 1·603, γ 1·613, all ±0·003.
Garnets as indices of progressive regional metamorphism
Authors: Nandi Kamal 
Published: December 2006

SummaryGarnets undergo readjustment of ion-assemblages under external mechanical and thermal stresses; this adjustment favours those paths that annul the very cause to which it is due. Metal ions in garnets being replaceable, with rising metamorphism garnets become reluctant to accommodate ions of larger ionic radii.Data from recent literature on chemical analyses of garnets from rocks belonging to different grades of regional metamorphism reveal that the (FeO + MgO) content of garnet varies linearly with (CaO + MnO) content. As the Fe/Mg ratio does not vary appreciably, a fair estimate of metamorphic grade can be made from a knowledge of (CaO + MnO) or of (FeO +MgO) individually or even, with less confidence, of FeO or MgO alone. From the study of the available data it is found that (CaO + MnO) and (FeO + MgO)/(CaO + MnO) provide the best indicators of progressive metamorphism. Cell edges of garnets decrease progressively with increasing metamorphism and this may also be used as a fairly good index of metamorphism. When cell edges are plotted against (FeO + MgO)/(CaO + MnO), a hyperbolic curve is obtained.
Measurement of the modal composition of a granitic rock powder by point-counting, infra-red spectroscopy, and X-ray diffraction
Authors: Bradshaw P. M. D. 
Published: December 2006

SummaryA rapid method for determining the mode of a four-component powder (microcline, orthoclase, plagioclase, and quartz) was sought to aid the interpretation of geochemical results. An accuracy of about ±5 % (absolute) was required. Three methods were tried : point counting proved too long as well as destroying the sample; infra-red spectroscopy was not sufficiently accurate for this particular type of rock powder; X-ray diffraction proved the most rapid and, although less accurate than point counting, was within acceptable limits and had the advantage of giving additional information about the composition of the feldspars.
Methods for the chemical analysis of meteorites: II. The major and some minor constituents of chondrites
Authors: Moss A. A. , Hey M. H. , Elliott C. J. , Easton A. J. 
Published: December 2006

SummaryPure dry chlorine at 250 to 350° C is shown to have no action on the principal silicate and phosphate phases of meteorites, but reacts quantitatively with the sulphide and phosphide phases and with kamacite; taenite does not react if it contains more than about 20 to 25 % Ni; some rare meteoritic minerals have not yet been tested. Volatile chlorides (including SiCl4) distil, and non-volatile chlorides can be leached out with water. Based on these observations, a method has been devised and applied to the analysis of a number of chondrites and to the purification of olivine and pyroxene separated by physical methods. The amount of Si present in the metal of enstatite chondrites, and the distribution of P, Ga, Ge, Ti, Cr, Mn, Ca, and Mg between oxidized and non-oxidized phases can readily be determined, and some results are presented. From the limited data so far available, Co appears to be concentrated in kamacite; gallium in the metallic phase is mainly in the taenite; germanium is strongly siderophile in the common chondrites but some is present in the silicate of the enstatite chondrites; titanium is markedly chalcophile in the enstatite chondrites, less so in the common chondrites, and the same applies to chromium; phosphorus is present as phosphide in the enstatite chondrites, but as phosphate in the hypersthene chondrites.
The Woodbine meteorite, with notes on silicates in iron meteorites
Authors: Mason Brian 
Published: December 2006

SummaryThe Woodbine meteorite, ploughed up in Illinois in 1953, is a fine octahedrite with numerous inclusions of silicate minerals. The minerals present include kamacite, taenite, troilite, schreibersite, orthopyroxene (Fs6), diopside, olivine (Fa4), plagioclase (An9), and graphite. The chemical analysis is: Fe 73·06, Ni 9·08, Co 0·15, P 0·47, C 0·21, FeS 1·65, SiO2 8·55, TiO2 0·02, Al2O3 0·53, Cr2O3 0·03, FeO 0·49, MnO 0·03, MgO 5·19, CaO 0·34, Na2O 0·29, K2O 0·02, sum 100·11. Woodbine is compared with other meteorites of similar composition. The silicate material has chondritic composition, and is quite different from the silicate material of the mesosiderites, with which some of these meteorites have been classed.
Chemical study of pyroxenes from the charnockitic rocks of Kondapalli (Andhra Pradesh), India, with emphasis, on the distribution of elements in coexisting pyroxenes
Authors: Leelanandam C. 
Published: December 2006

SummaryThe chemical analyses, structural formulae, and trace element data are presented for 18 orthopyroxenes and 9 clinopyroxenes from the charnockitie rocks of Kondapalli, Andhra Pradesh, India. The chemistry of these pyroxenes is discussed and conclusions are drawn. The data are compared with the similar data available for the pyroxenes of the charnockites of the type area near Madras, some 200 miles south of Kondapalli. The element-distributional relationships between the coexisting pyroxenes are discussed and inferences are made regarding the temperature of crystallization of charnockite pyroxenes.
Vlasovite: a second occurrence and a triclinic to monoclinic inversion
Authors: Fleet S. G. , Cann J. R. 
Published: December 2006

SummaryVlasovite, Na2ZrSi4O11, previously reported as monoclinic by Pyatenko and Voronkov from an occurrence in the Kola Peninsula, Russia, has been found in rocks from Ascension Island in a triclinic twinned modification. The obliquity is very slight (α and γ, differ from 90° by less than 1°), and X-ray photographs show arrays of paired spots corresponding to diffraction by different parts of the crystal related by the twinning operation, reflexion across (010).On heating, this vlasovite is found to transform to the monoclinic variety at 29° C. The phase change has been followed on a single-crystal X-ray heating camera, and the obliquity is found to have successively smaller values as the crystal is heated from temperatures below room temperature to 29° C. The obliquity is characteristic of the particular temperature over the transformation range and is not affected by thermal history.The transformation appears to be a displacive one, similar in some respects to α → β tridymite and α → β cristobalite, and some information has been obtained by X-ray structural investigations about the nature of the atomic movements involved.
Some manganese oxide pseudomorphs
Authors: Davis R. J. 
Published: December 2006

SummaryPyrolusite pseudomorphous after manganite occurs at Serro do Navio, Amapa, Brazil. It consists of wedges, flattened on (100) and elongated along [010], twinned on (011) and showing forms d{210}, , b{010}, and f{021} (all indices referred to manganite, in the setting of Dana, 7th edn). The difficulty of distinguishing between pyrolusite pseudomorphous after manganite and after groutite is discussed and also the possible existence of the latter. The distinction was made here by measuring the twinning angle between the pyrolusite lattices using (0kl) precession photographs. Specimens of manganite intergrown with pyrolusite are described and their relative orientations determined. On heating, manganite partly decomposes to a monoclinic phase, a 9·9 Å, b 5·73 Å, c 4·89 Å, β 98°, space group I2, Im, or I2/m.
X-ray data on some calcium-iron-oxygen compounds
Authors: Hughes H. , Roos P. , Goldring D. C. 
Published: December 2006

SummarySynthetic mixtures of CaO and Fe2O3 fired in air at temperatures in the range 1180° C to 1240° C in some cases lost oxygen and formed ferrous-iron-bearing compounds. Samples after firing were examined by incident light microscopy and X-ray diffraction; new powder data are presented for the phases reported. In addition to α-Fe2O3, CaFe2O4, and Ca2Fe2O53. four distinct phases have been identified. These are and two forms of , described previously by Braun and Kwestroo (1960). The likely compositions of these phases are given.
The olivine, pyroxene, and metal content of chondritic meteorites as a consequence of Prior's rule
Authors: Mueller Robert F. , Olsen Edward J. 
Published: December 2006

SummaryThere is an important corollary to Prior's rule to the effect that as the state of oxidation of meteorites is increased the quantity of olivine increases relative to pyroxene and metallic iron. We have derived a rigorous parametric expression for this corollary and find that, as in the case of the quantitative interpretation of the rule itself, there is in this case also a fair correspondence to the observational data, so that the validity of the rule is further supported.
An exceptionally large chondrule in the Parnallee meteorite
Authors: Binns R. A. 
Published: December 2006

SummaryA giant chondrule, nearly 4 cm in diameter, has been found in the Parnallee meteorite, and is described, with analysis. An estimate of the composition of the partly devitrified groundmass falls within the known compositional range of chondrule glasses. The bulk composition of the chondrule is very close to the bulk composition of the meteorite excluding metal and sulphide.
The hydroxyl-stretching region of the biotite mica spectrum
Authors: Wilkins R. W. T. 
Published: December 2006

SummaryAn interpretation of part of the hydroxyl-stretching region of the infra-red absorption spectrum of biotite is proposed. A consideration of band shapes enables the interpretation to be quantified and tested against a series of natural biotites. The equation derived may be used to determine the atomic ratio Mg2+/(Mg2++Fe2+) in biotites but the necessary assumptions and simplifications make it unlikely that the method will be very useful in practice.
The petrochemistry of some Lewisian granitic rocks
Authors: Bowes D. R. 
Published: December 2006

SummaryThe chemical compositions of eighty granitic rocks from the Lewisian of the North-West Highlands of Scotland, particularly from the Gairloch district, are set out in relation to geological occurrence and their normative proportions of albite, orthoclase, quartz, and anorthite compared with experimental data relating to the systems NaAlSi3O8-KAlSi3O8-SiO2-H2O and KAlSi3O8-NaAlSi2O8-CaAl2Si2O8-SiO2. The field of composition for these Lewisian rocks moves from Ab-Q-rich for autochthonous granites to Ab = Or = Q (approximately) for parautochthonous granites to Or-rich for intrusive granites. This trend is related to the varying roles of mineral solubility under stress, selective melting, and potassium metasomatism.
Trace elements in pyroxenes and amphiboles from ultramafic rocks of the Urals
Authors: Borisenko L. F. , Борисенко Λ. Φ. 
Published: December 2006

SummaryThe minor elements Li, Sc, V, Cr, Co, Ni, Ga, Rb, and Sr have been determined in a number of diopsides and horneblendes from ultramafic rocks of the Gussevogorsk, Baranchinsk, and Nizhne-Tagilsk massifs in the Urals. Actinolite and anthophyllite are rare contact metamorphic products ; they too were analysed. The diopside and hornblende from the earlier-formed rocks, richer in olivine, contain more Cr and less V and Ti than those from the later-formed rocks.