bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nickeloan pyroaurite from Leslie, Aberdeenshire
Authors: Wilson M. J. , Cradwick P. D. , Berrow M. L. , McHardy W. J. , Russell J. D. 
Published: December 2006

SummaryA nickel-bearing mineral belonging to the pyroaurite-sj~Sgrenite group has been found in a serpentinite rock near the village of Leslie, Aberdeenshire. X-ray powder diffraction data and electron-probe microanalysis indicate that the mineral has a three-layer rhombohedral structure with a probable formula near (OH)13CO3.4H2O. The mineral can therefore be described as nickeloan pyroaurite. It decomposes readily in mildly acid conditions and if inherited by serpentinite-derived soils could well be an important source of plant-available nickel.
The geochemistry of biotites from granites of northern Portugal with special reference to their tin content
Authors: Neiva A. M. R. 
Published: December 2006

SummaryBiotites from a number of granites have been analysed for major oxides and a wide range of trace elements. Their compositions are found to be typical of biotites from granite and to show element fractionation in presumed differentiation series. Estimates are made of the fugacity of oxygen and water during the crystallization of the granites. PH2O is found to increase slightly through the differentiation series, and fO2, for a temperature of 700°C is estimated to be between 10−18 and 10−12. Tin mineralization is connected with the igneous rocks and the relationship of tin in the micas to the rock compositions is described and the factors controlling the distribution of tin are discussed. The biotites have only up to 21 % of the tin of the granites. In general Sn increases in the biotites with decreasing temperature of equilibration and with increase in the degree of albitization of the granites. High Sn in biotites seems to be an indicator of potential mineralization.
A note on some Dalradian stilpnomelanes and their oxidation
Authors: Graham Colin M. 
Published: December 2006

SummaryThe widespread ferristilpnomelane in Dalradian metabasites of the south-west Scottish Highlands has usually formed by secondary oxidation of primary ferrostilpnomelane, probably during weathering. Ferrostilpnomelane oxidizes readily in polished thin sections open to the atmosphere over a period of months, and microprobe examination of the resulting ferristilpnomelane suggests a change in the role of potassium in the structure during oxidation.
A metallographic and petrological study of metal–silicate fragments in the > 1 mm size range from lunar soil 14162,80
Authors: Agrell S. O. , Axon H. J. , Goldstein J. I. 
Published: December 2006

SummaryOptical and microprobe investigations have been made on the metal and silicate portions of four particles > 1 mm extracted from the magnetic fraction of lunar soil bulk sanaple 14162,80. Three of the particles have structures and compositions similar to those encountered in the < 1-mm fraction of this bulk sample. One of the particles shows a complex arrangement of melted metal, unmelted metal, micronorite, and vitroclastic silicate material. The structure of this particle is reported in detail and its structure is explained in terms of preferential melting of metal-phosphide interfaces under the influence of shock events operating on material at a temperature of about 650°C.
Kornerupiue in metasomatic zones, Strangways Range, Central Australia
Authors: Woodford P. J. , Wilson Allan F. 
Published: December 2006

SummaryThe first known occurrence of kornerupine in Australia is described. The mineral is a minor component of a phlogopite-rich garnet-corundum-spinel metasomatic zone, which cuts mafic and ultranlafic spinel-plagioclase-orthopyroxene-hornblende rocks. The kornerupine-bearing assemblage was formed during the second major metamorphic episode that affected the terrain, probably under low-grade granulite or upper amphibolite facies conditions. Kornerupine appears to have formed at significantly lower levels ofP-Tthan those reached in the terrain during the peak of the second granulite metamorphism.
Ænigmatite from an Ægirine—Riebeckite granite, Liruei Complex, Nigeria
Authors: Borley G. D. 
Published: December 2006

SummaryÆnigmatite occurs as a trace constituent of the Ægirine-Riebeckite Granite of the Liruei Complex, Younger Granite Province of Nigeria. It is enriched in Ti and Mg and depleted in Si, Al, and Ca relative to many other ænigmatites. Relative to coexisting ægirine and arfvedsonitic riebeckite it is enriched in Ti and depleted in Fe3+. Conditions required for formation of the mineral appear to have been high Ti concentration in a peralkaline magma of low T and fo2. The composition of the Nigerian ænigmatite confirms that there is only limited miscibility between rhönite and aenigmatite although in certain circumstances the two may have a paragenetic relationship.
The halotrichite group: the crystal structure of apjohnite
Authors: Menchetti S. , Sabelli C. 
Published: December 2006

SummaryApjohnite, MnAl2(SO4)4·22H2O, is monoclinic, space group P21/c, a 6·198 (2), b 24·347 (4), c 21·266 (4) Å, β 100·28 (3)° and Z = 4. The crystal structure was determined by means of direct methods applied to X-ray data collected with a single-crystal diffractometer. At the end of the refinement, performed with least-squares method, the R index was 0·039.The SO4 tetrahedra, Al(H2O)5 octahedra, and MnO(H2O)5 octahedra are connected by a hydrogen bonding system; the only direct connection between polyhedra is by sharing of an oxygen between S(4) and Mn. In the asymmetric unit there are twenty-two water molecules, five of which lie in channels of the structure and are not linked to the cations but only to ligand water oxygens by means of hydrogen bonds.Powder data indicate a close structural relationship between apjohnite, halotrichite, and pickeringite.
Crystallinity among some hydrous aluminium phosphates
Authors: Duncan McConnell  
Published: December 2006

SummaryCompositions of nine hydrous aluminium phosphates are considered with respect to the AI, P, and H contents per 8 oxygens, and it is suggested that when the ratio (Al.P)/H is less than 0·11 (or (Al.P2)/H2 is less than 0.01) such compositions do not crystallize. Examples are bolivarite and evansite.
The Suisnish layered dyke
Authors: Parslow G. R. 
Published: December 2006

SummaryA minor picritic body at Suisnish Point, Isle of Skye, is described. The mass has a dyke-like form, and is rhythmically layered. Cryptic layering, however, is absent. From a study of the field relations, contacts, metamorphic aureole, and other physical features, it is concluded that the mass crystallized in situ (i.e. it is a true dyke) and is not an upfaulted block of pre-existing igneous rock. The main physical and chemical features of the layered units and their mineralogy are described. The problems of generating horizontal rhythmic layers in a relatively small, essentially vertical, planar intrusion are discussed. It is concluded that the surrounding country rock was maintained at a moderate temperature during, and after, intrusion of the picritic magma and that this allowed a combination of gravity settling and magma flow currents to produce a cumulate rock with characters normally only observed in much larger intrusions.
Chromite-chlorite intergrowths in peridotite at Chimwadzulu Hill, Malawi
Authors: Haslam H. W. , Harding R. R. , Tresham A. E. 
Published: December 2006

SummaryChromiferous spinel and chlorite are associated and sometimes intergrown in serpentinized peridotites at Chimwadzulu Hill. The peridotites probably crystallized from a melt under the conditions of the spinel-lherzolite facies (O'Hara, 1967) in which the stable aluminous phase is spinel. The spinel that formed was probably a chromite with some Al2O3 and MgO. At lower temperatures aluminous spinel is unstable in the presence of olivine and orthopyroxene, chlorite being the stable aluminous mineral. It is thought that the chlorite crystallized under the conditions of medium-grade metamorphism that prevailed when the rocks were emplaced, and at the same time the spinel recrystallized, depleted in Al2O3 and MgO and correspondingly enriched in FeO, Fe2O3, and Cr2O3, giving rise to the observed chromite-chlorite association.
Zoned, birefringent garnets from Thera Island, Santorini Group (Aegean Sea)
Authors: Murad Enver 
Published: December 2006

SummaryA garnetite that occurs locally in phyllitic schists exposed by the Santorini caldera consists mainly of euhedral garnet crystals showing alternating isotropic and birefringent lamellae. X-ray diffraction revealed two garnets with unit cell dimensions a of 12·052±0·002 and 11·984±0·005 Å, corresponding respectively to almost pure andradite and a granditic phase. Mean compositions determined by microprobe analysis are An97Sp1Alm2 for the isotropic and about An63Gr33Sp1Alm3 for the birefringent layers.The garnets are deduced to have been produced mainly by thermal metamorphism of the schists. Although cyclic variations in the composition of circulating fluids could have brought about the zoning, this may just as well be the result of temperature fluctuations, individual garnet compositions being indicative of the respective formation temperature.
The Lodran meteorite and its relationship to the ureilites
Authors: Bild Richard W. , Wasson John T. 
Published: December 2006

SummaryLodran is a unique meteorite consisting of roughly equal amounts of metal, olivine, and pyroxene with minor amounts of sulphide, chromite, phosphide, chrome-diopside, and a new phase with a composition close to (K,Na)AlSi5O12. Zähringer reported planetary-type rare gases in both the metal and silicates, suggesting a primitive nature. The pyroxene composition is Fs13.8with little variation. Olivine composition averages Fa12.6, but varies at least ±20 % both among grains and zoned within single grains; only the Fe-rich olivine is in equilibrium with the pyroxene. The metal probably cooled rapidly (700 K/Myr) at high temperatures and slower (30 K/Myr) at lower temperatures. Two compositional populations of chromite are found.A model for the formation of Lodran includes three steps: Formation of large olivine, pyroxene, and metal grains, with the trapping of small olivine inclusions in pyroxene and pyroxene in olivine. Equilibration and recrystallization of olivine, pyroxene, and metal, loss of alkalis and Ca; this probably occurred in a parent-body setting. And incorporation of reducing materials and mild reheating sufficient to produce the zoning in the olivine but not enough to re-equilibrate the pyroxene.Phase compositions and rare-gas concentrations in ureilites are similar to those in Lodran. In some respects Lodran appears to be a metal-rich ureilite, but the higher Fe/(Fe+Mg) ratios in the latter (Fa 21 olivine) suggest origin on separate parent bodies.The Harvard University meteorite is a mesosiderite and not closely related to Lodran.
Julgoldite, new data and occurrences; a second recording
Authors: Livingstone A. 
Published: December 2006

SummaryTwo new occurrences, in quartz dolerite, are reported for julgoldite. Physical and chemical data is presented together with indexed powder data for fifty-five reflections, fifteen of them additional to those previously reported. The julgoldite infra-red spectrum possesses the same configuration as that of an epidote or clinozoisite but with large peak shifts due to the high iron content.
Compositional range of P2/n omphacite from the eclogitic rocks of central Shikoku, Japan
Authors: Yokoyama Kazumi , Banno Shohei , Matsumoto Takeo 
Published: December 2006

SummaryThe lattice types of omphacite-diopside series clinopyroxenes were determined for 9 Japanese, 2 Norwegian, and 1 South African samples. The boundary between the compositional ranges of P and C lattice clinopyroxenes lies at about 14·5 wt. % CaO in Japanese and Norwegian samples, and the compositional gap between them is very small, if it exists. The South African omphacite has C-lattice in the compositional range of P lattice omphacite in metamorphic eclogites. These data combined with the reported electron microscope studies suggest that the omphacite—diopside series clinopyroxene has a C lattice structure above 3 to 400°C and very slow cooling after regional metamorphism is responsible for the transition to the ordered structure with P lattice symmetry.
The origin of scoriaceous rock associated with dacitic ignimbrite in the Mirannie-Mount-Rivers district, New South Wales, Australia
Authors: Nashar Beryl , White Noel C. 
Published: December 2006

SummaryFrom field and petrographic evidence, some scoriaceous rock from the upper ignimbrite horizon of the Mount Rivers Volcanic Member of the Carboniferous Dyrring Formation in the Mirannie-Mount-Rivers District, New South Wales, Australia, is believed to have a recent origin.By heating unaltered dacitic ignimbrite in a furnace it was possible to produce in the temperature range 600-1230°C changes in the rock similar to those observed in specimens of scoria collected in the field. Thus a temperature range for the alterations was established. Two possible sources of heat axe suggested as being responsible for the production of the scoriaceous rock, namely a bush fire and a lightning strike, with a preference for the former.
Crystallization trends of pyroxenes from the alkaline volcanic rocks of Tenerife, Canary Islands
Authors: Scott P. W. 
Published: December 2006

SummaryThe alkaline volcanic rocks of Tenerife comprise a compositionally continuous series of ankaramites, alkali basalts, trachybasalts, trachyandesites, trachytes, phonolites, and peralkaline phonolites. Ca-rich pyroxenes occur as phenocrysts throughout the series. They show a limited range of composition from diopside and Ti-rich samite in the basic and intermediate rocks, to sodic sahlite in some phonolites. Features of both the sahlite-aegirine and sahlite-hedenbergite trends are present. Sodic ferrosahlites occur as xenocrystal 'green cores' in phenocrysts from some basic and intermediate rocks. The latter are associated with kaersutite xenocrysts and are similar to pyroxenes in some plutonic xenoliths from Tenerife. During the formation of the 'green cores' conditions were more reducing allowing pyroxene compositions to extend through the range sahlite-hedenbergite.Aegirine-angite and Ti-rich aegirine are present in the groundmass of some phonolites and in pyroclastic boulders of nepheline syenite. The aegirines are associated with magnesioarfvedsonite and aenigmatite, and it is considered that they crystallized under conditions of low oxygen fugacity.
An occurrence of eudialyte and manganoan pectolite in a phonolite dyke from south-eastern Queensland
Authors: Carr Graham R. , Phillips Evan R. , Williams P. R. 
Published: December 2006

SummaryA phonolite dyke at Mount Goonneringerringgi, south-eastern Queensland, carries prominent pink specks of eudialyte, together with manganoan pectolite (ranging to calcian serandite), aegirine, albite, arfvedsonite, nepheline, natrolite, and analcime. This is the first confirmed occurrence of eudialyte in Australia
Chemistry of ilmenites crystallized within the anhydrous melting range of a tholeiitic andesite at pressures between 5 and 26 kb
Authors: Thompson R. N. 
Published: December 2006

SummaryMicroprobe analyses of eight ilmenites, a titaniferous magnetite, and a rutile are presented. They were synthesized at pressures from 5 to 26 kb and temperatures between 1075 and 1225°C in the anhydrous melting interval of a tholeiitic andesite from the Snake River Plain, Idaho, U.S.A. Both the Fe/Ti distribution between coexisting ilmenite and titanomagnetite at 11 kb/1075°C and the low calculated Fe3+ contents of the other ilmenites confirm previous suggestions that the fo2 in these experiments was buffered by graphite capsules to values near those generated by the wüstitemagnetite assemblage. Mn in the ilmenites (0·30-0·51% MnO) shows moderate negative correlations with both the pressures and temperatures of their formation, whilst Al (0·41-1·06 % Al2O3) shows poor positive correlations with these parameters. In contrast, the only significant trend shown by Mg in the ilmenites (2·09-5·26 % MgO) is with the position of each experimental run in the melting interval of the lava. Mg/(Mg + Fe2+) of the ilmenite decreases during equilibrium crystallization at a given pressure and appears to be controlled solely by Mg/Fe2+ distribution amongst the coexisting ferromagnesian minerals and interstitial liquid (glass).
Gmelinite and herschelite from the Ilímaussaq intrusion in South Greenland
Authors: Karup-Møller S. 
Published: December 2006

SummaryHypogene alteration of ussingite from the southern part of the Ilimaussaq intrusion in South Greenland has resulted in the formation of three associations: gmelinite-apophyllite, gmeliniteherschelite- earthy-natrolite, and earthy natrolite alone. Ossingite reacted with late magmatic fluids, producing the secondary minerals either byin situreplacement of the ussingite or in cavities, which may be up to 3 cm across.
Emeleusite: a new LiNaFeIII silicate from south Greenland
Authors: Upton B. G. J. , Hill P. G. , Johnsen O. , Petersen O. V. 
Published: December 2006

SummaryEmeleusite (Li2Na4Fe2IIISi12O30) is an orthorhombic (pseudohexagonal) mineral occurring as euhedra within a facies of a peralkaline trachyte dyke. The composition is: SiO2 70·75; TiO2 0·55; ZrO2 0·10; Al2O3 1·34; Fe2O3 12·13; MgO 0·10; MnO 0·03; Na2O 11·98; Li2O 2·78:99·76. The density is 2·775 g/cm3 (calculated) and 2·76(7) g/cm3 (determined); hardness 5–6. It is colourless, transparent, and has a glassy lustre. Emeleusite is biaxial negative with 2Va, varying from near-zero to c. 30° r » v. The refractive indices are α 1·596; β 1·597; y 1·597; with α ∥ b; β ∥ a; y ∥ c. Emeleusite can occur as interpenetration triplets with {110} as twin planes. The space group is Acam or Aba2 with a = 10·073±0·002 Å; b = 17·350±0·005 Å and c = 14·010±0·005 Å. Z = 4. Prominent powder diffraction lines are 7·001(5) 002, 4·352(10) 220, 040, 3·501(7) 004, 3·209(8) 311, and 3·090(7) 124. While the structure is as yet unknown it is suggested that it is an orthorhombic associate of the milarite group.
Partition coefficients of alkali and alkaline-earth elements between alkali feldspar phenocrysts and their lava matrix
Authors: De Pieri Renzo , Quareni Sergio 
Published: December 2006

SummaryPlots of partition coefficients (mineral/ matrix) against ionic radius of the alkali and alkaline earth elements in forty-four alkali feldspars from rhyolites and trachytes show two kinds of diagram, one for homogeneous alkali feldspars with a single peak, and the other for cryptoperthites with a wide spread of points, which cannot represent a single peak, but may probably be explicable in terms of two peaks. The difference in behaviour does not seem to be due to the chemical composition, but is apparently related to the crystallo-graphic features of the alkali feldspar structures. In particular the presence of two peaks in the diagrams of the cryptoperthites seems to be due to the existence of lattice positions suited to receive bigger ions (K, Ba, Rb) and smaller ions (Na, Ca, Sr) in the potassic and sodic domains.
Deweylites, mixtures of poorly crystalline hydrous serpentine and talc-like minerals
Authors: Bish David L. , Brindley G. W. 
Published: December 2006

SummaryAn X-ray and chemical examination of deweylites reveals that they are intimate mixtures of very poorly ordered trioctahedral 2:1 and 1:1 layer silicates. The 2:1 mineral exhibits no swelling in the presence of ethylene glycol or water and is best described as an extremely fine-grained and highly disordered form of talc, for which the term kerolite is often used. Stevensite is not a component of deweylites. The 1:1 component most closely resembles a disordered chrysotile.Evaluation of the chemical data, including values for H2O +, shows that both end-members are hydrated to various degrees. This hydration is most probably attributable to the presence of water molecules and hydroxyls associated with the large surface areas and unbalanced surface bonds. Formulae for the end-members are approximately R3Si4O10(OH)2·0·3 0·7 H2O and R3Si2O3(OH)4·0·3–0·7 H2O where R is principally Mg, but samples with more or less H2O are entirely possible due to variations in crystallinity. No specific formula can be given to deweylites as they are mixtures with variable proportions of the components. The name is useful, however, as a field or ‘box’ term, similar to the use of garnierite and limonite.
Titaniferous clinohumite from Gardiner Plateau Complex, East Greenland
Authors: Nielsen T. F. D. , Johnsen O. 
Published: December 2006

SummaryTitaniferous clinohumite occurs as a major constituent in the centres of late magmatic veins in the Tertiary ultramafic, strongly alkaline Gardiner Plateau Complex in East Greenland (69° N. and 32° W.). The complex is briefly described and an electron microprobe analysis of titaniferous clinohumite is presented. This gives the following: 38·44% SiO2, 2·99% TiO2, 4·87% FeO, 51·89% MgO, 1·3% F, H2Ocalc 1·50%, and total 100·44%. Optical data, density, and unit cell dimensions are also presented. Of magmatic occurrences, titaniferous clinohumite has otherwise only been reported in certain kimberlites and carbonatites.
Quantitative determination of analcime in pumice samples by X-ray diffraction
Authors: Parker R. J. 
Published: December 2006

SummaryA quantitative X-ray diffraction method has been successfully applied to the determination of analcime in pumice rock samples. A calibration line was constructed from spiked pumice standards (range: 0 to 42%) and the mean relative error of the standards on the calibration line was < 0·6%. The major-element compositions of the samples and standards were available, and this allowed the total mass absorption coefficients to be calculated. The latter were then used to correct the sample and standard intensities for absorption effects resulting from compositional variations. When compositional data already exist, the calculation of the total absorption coefficient provides a rapid and accurate alternative to direct measurement, or to the use of an internal standard.
The unit cell of talc
Authors: Akizuki M. , Zussman J. 
Published: December 2006

SummarySix specimens of talc studied by the electron microscope lattice-imaging and diffraction techniques were found to have the triclinic one-layer (1 Tr) structure. Since no evidence of a monoclinic two-layered structure was found in any specimen it is concluded that the 1 Tr structure is the common one for talc, and it may, moreover, be the only one. Extremely fine polysynthetic twinning and single intrinsic stacking faults were found in talc.
Kidwellite, NaFe93+(OH)10(PO4)6·5H2O, a new species
Authors: Moore Paul B. , Ito Jun 
Published: December 2006

SummaryKidwellite, NaFe93+(OH)10(PO4)6·5H2O, monoclinic, Z = 2, a = 20·61(7) Å, b = 5·15(1) Å, c = 13·75(6) Å, β = 112·64(15)·, space group A2/m, Am, or A2, is a new species that occurs in moderate abundance as a late-stage mineral associated with rockbridgeite, dufrenite, beraunite, and strengite in novaculite deposits. Colour lively pale chartreuse-green, to greenish-yellow, greenish-white, and bright yellow. H = 3, lustre silky, streak yellow, cleavage {100} perfect, habit acicular elongated parallel to [010], flattened on {100}, biaxial (−), α = 1·787(5), β = 1·800(5), γ = 1·805(5), 2V large, β∥b, not discernibly pleochroic.The mineral is moderately widespread as a replacement of rockbridgeite and beraunite from the Ouachita Mountains, Arkansas; Indian Mountain, Alabama; Irish Creek, Virginia; Waldgirmes, West Germany. A related, but apparently distinct, species is also noted from the McMahon pegmatite, South Australia, and the Sapucaia pegmatite, Minas Gerais, Brazil.