bluuebunny/crossref_metadata_2025_split huggingface dataset:
A metallographic study of the disruption of the Cañon Diablo projectile
Authors: Axon H. J. , Couper W. R. D. 
Published: December 2006

SummaryA metallographic investigation of macro- and micro-structures, supported by microprobe examination, has been made on similarly sized (< ca. 200 g) individual Cañon Diablo meteorites of rim or plains type. Plains type specimens show heat alteration zones of the ablation type. They are extensively cracked in a brittle manner and in some instances the cracks are penetrated by ablation melt product. In all cases the cracks are now penetrated by terrestrial corrosion. Cohenite and schreibersite are cracked in a brittle manner. By contrast the rim type specimens are remarkably free of internal cracking or corrosion penetration. Instead the cohenite, schreibersite, taenite, and kamacite are transected by slip faults or shear displacements along the line of which all phases appear to have slipped in a non-brittle manner. These specimens have all been subject to shock loading and particular attention is paid to the effects of shock on sphalerite, on cloudy taenite, and on martensitic plessite.Plains specimens have broken from the original projectile in a brittle manner well above the earth's surface. Rim specimens have been scabbed from the rear of the projectile as it penetrated the earth's surface. Some of the rim specimens show signs of being heated by the blast of the crater-forming explosion.
Derivative structures based on the alunite octahedral sheet: mitridatite and englishite
Authors: Moore Paul Brian 
Published: December 2006

SummaryIt is proposed that mitridatite and englishite contain octahedral sheets of the alunite type and that their formulae are [Ca6(H2O)3(PO4)2][Fe3(OH)6(PO4)(PO3OH)]3 and [K2Na(H2O)4Ca4·5 (PO3OH)3][Al3(OH)6(PO4)(PO3OH)]3 respectively.
Experimental study of clay mineral, greenschist, and low-pressure amphibole facies in the system Na2O-Al2O3-MgO-SiO2-H2O
Authors: Triboulet Claude 
Published: December 2006

SummaryCompositions concerning sodic amphiboles (glaucophane) in the system Na2O-Al2O3-MgO-SiO2-H2O have been studied at PH2O ≤ 3 kb, 380 °C < T < 700 °C. The study attempts to establish the mineral parageneses under these physical conditions as they define the clay mineral (saponite-hectorite smectite) and greenschist (chlorite-albite) facies. The occurence of sodic amphiboles is defined by compositional parameters. Glaucophane does not appear in the present investigation.The method of ‘reaction reversal’, i.e. using precrystallized mineral assemblages to form new ones, has been used to establish the three reactions: albite + chlorite → paragonite + saponite, paragonite + chlorite → saponite + cordierite, and saponite + paragonite → albite + cordierite. In general, the clay mineral → greenschist transformation is favoured by an increase in pressure in the system studied. The amphibole present is a sodic richterite with the type substitution
Feldspars and fluids in cooling plutons
Authors: Parsons Ian 
Published: December 2006

SummaryAlkali feldspars in plutonic igneous rocks vary both in their exsolution textures and in the structural state of their components. The primary factor leading to this diversity is the availability of hydrothermal fluids during their cooling history. In many plutons feldspar variation is related to degree of fractionation as indicated by rock chemistry. The variation reflects build-up of water with magmatic evolution and implies that fluids did not circulate freely in the intrusives in the temperature range of unmixing and ordering. Experimental work bearing on the role of fluids in subsolidus changes in feldspars is reviewed, and points of overlap between crystallographic studies of feldspars and stable isotope studies are discussed.
The physical basis of mineral optics I. Classical theory
Authors: Strens R. G. J. , Freer Robert 
Published: December 2006

SummaryThe Helmholtz dispersion equations have been rewritten in a form that enables the optical constants of both transparent and opaque media to be calculated from their spectra. Both Helmholtz equations are used to describe the optical properties of opaque media, and to obtain values of reflectance, refractive index, and absorption coefficient. The Sellmeier dispersion equation is a special case of the dispersive Helmholtz equation applicable to weakly absorbing media (including the great majority of minerals studied in thin section): it is used to derive the wavelength-, composition-, direction-, and volume-dependence of the principal indices in mixed crystals of monoclinic or higher symmetry. The treatment can be extended to triclinic crystals.The birefringence of transparent phases is the expression in the visible region of the pleochroism of absorption bands in the ultra-violet. The bireflectance of opaque phases depends also upon the pleochroism of bands in the visible and near infra-red, resulting in extreme sensitivity of the optics of opaque materials to changes in wavelength, composition, and structure. The optical anisotropy of both transparent and opaque phases may be calculated if the dependence of the spectra on structure can be established by measurement or by calculation from structure data. The quantitative application of Bragg's method is restricted to phases of very simple chemistry and structure (e.g. calcite and rutile), but it may be applied qualitatively to rationalize the optic orientations of phases containing only closed-shell ions of neon or argon configuration, including many pyroxenes, amphiboles, micas, and chain aluminosilicates. When open-shell (transition metal) ions enter the structure, the general rule is that the anisotropy becomes more closely related to the distortion of the coordination polyhedron about the metal ion, and for ions of formal charge ≥ 3, this source of anisotropy is usually dominant.
Bazirite, BaZrSi3O9, a new mineral from Rockall Island, Inverness-shire, Scotland
Authors: Young B. R. , Hawkes J. R. , Merriman R. J. , Styles M. T. 
Published: December 2006

SummaryBazirite, BaZrSi3O9, is one of several late-stage interstitial minerals present in the aegirine-riebeckite granite of Rockall Island. Crystals are hexagonal, probably ¯6m2, colourless, chiefly as anhedral grains. Only forms noted {10¯10} and probably {10¯14}, cleavage {0001} and probably {10¯14}. ‘Low’ and ‘high’ titanium varieties with respective mean compositions: SiO239·71%, ZrO226·38%, BaO 33·69%, TiO20·17%, SnO20·06% and SiO239·59%, ZrO226·12%, BaO 34·12%, TiO20·51%, SnO20·11%. Low and high refractive index types exist; uniaxial positive withω= 1·6751±0·0003.ɛ= 1·6850±0·0003 andω= 1·6813±0·0003, ɛ = 1·691 (deduced); probably due to differences in titanium content. Fluorescence (2537 Å), moderately strong, pale whitish blue. Space group almost certainlyP¯6c2. Cell dimensions: low R.I. variety,a= 6·7690±0·0005 Å,c= 10·020±0·001 Å; high R.I. variety,a= 6·7662± 0·0005 Å,c= 10·158±0·0010 Å. Strongest lines are 3·80 Å (100), 2·800 (100), 5·85 (35), 3·38 (35), Z = 2.Dcalc= 3·82. Related minerals, benitoite and pabstite.
Investigations on the deformation of experimentally shock-loaded biotites using X-ray single crystal diffraction techniques
Authors: Schneider Hartmut 
Published: December 2006

SummaryThe deformation of biotite single crystals submitted to experimental shock-pressures of about 200 and 400 kb with direction of the shock wave parallel to [001] was investigated by X-ray precession and Weissenberg techniques. The X-ray analysis reveals a ‘fracturing’ of the biotite crystals upon pressure release into relatively large lattice blocks (> 1000 Å), which increases with the degree of shock compression. Deformation is inferred to take place by gliding and/or microfracturing processes parallel to the (010) and (110) lattice planes. Chains of tetrahedra running parallel to [100] and [110] probably exert a controlling influence on shock deformation mechanisms.
The Inishdawros meta-peridotite, Callow, Ballyconneely, Connemara, Western Ireland
Authors: Ahmed A. A. , Leake B. E. 
Published: December 2006

SummaryThe chemistry and petrography of a meta-ultrabasic lens containing peridotite with poikilitic pyroxenes and hornblende, both of probable igneous origin, are given. The body also contains feldspathic-bearing hornblende meta-gabbros and is a tectonic fragment in hornblende-plagioclase rock belonging to the same Errismore intrusion. Chemical analyses fail to discern any appreciable systematic differentiation trend across the body despite modal variation to hornblende plagioclase layers. The high Niggli mg near the structural bottom of the intrusion suggests that this part of the Errismore intrusion is right way up, contrary to a previous suggestion.
Pumpellyite-bearing basic igneous rocks from the Lower Ordovician of North Pembrokeshire, Wales
Authors: Bevins R. E. 
Published: December 2006

SummaryThe first occurrence of pumpellyite in the Lower Ordovician volcanic rocks of North Pembrokeshire is reported and its form and chemistry are described. The significance of pumpellyite in relation to the grade of metamorphism attained during the Caledonian orogenic episode is discussed.
Manganoan Ilvaite from Broken Hill, N.S.W. and Ban Ban, Queensland, Australia
Authors: Plimer I. R. , Ashley P. M. 
Published: December 2006

SummaryManganoan ilvaite forms as an early retrograde metamorphic phase from calcic rhodonite in the polymetamorphosed Pb-Zn sulphide/manganese silicate rocks at Broken Hill and from grossular-andradite in a skarn at Ban Ban. Ilvaite exists as a probable metastable phase into which Mn is apparently strongly partitioned. The manganoan ilvaites analysed contain up to 13·5 % MnO substituting for FeO and this substitution shifts the 020 peak.
Linnaeite series minerals from the Kalgoorlie district, Western Australia
Authors: Ostwald J. 
Published: December 2006

SummaryFive members of the linnaeite series of sulphides linnaeite Co3S4, siegenite (Co, Ni)3S4, carrollite Co2CuS4, violarite Ni2FeS4, and polydymite Ni3S4 occur in nickel-sulphide-mineralized rocks in areas adjacent to the Kambalda and Scotia deposits of the Kalgoorlie district, Western Australia. Linnaeite, siegenite, carrollite, and polydymite occur in trace amounts as disseminated grains and veinlets. Violarite is also found as disseminations but its major occurrence is in the supergene enriched zones of the ore deposits. Aspects of their mineralogy, including mode of occurrence, general mineragraphy, reflectance at 546 nm, 589 nm and 644 nm, microhardness, and electron probe microanalyses are described.
The geochemical role of primary copper-sulphur mineralization in the crystallization of the Freetown (Sierra Leone) layered gabbro
Authors: Bowles John F. W. 
Published: December 2006

SummaryThe separation of iron-titanium oxide droplets and the formation of olivine, in the Freetown layered gabbro, depleted the magma in iron and enriched the magma in copper. In magma injections in which the sulphur fugacity was sufficiently high, this resulted in the separation of immiscible copper sulphide droplets closely associated with the iron-titanium oxide droplets, and both were subsequently enclosed by olivine. A lower sulphur fugacity in other injections of magma suppressed the separation of the copper, which later appeared as native copper associated with euhedral titanomagnetite, and was enclosed by feldspar. Crystallization of the iron-titanium oxide droplets and subsolidus diffusion has resulted in granular exsolution of ilmenite from the droplets and lamellar exsolution of ilmenite in the euhedral titanomagnetite.
Uranospathite and arsenuranospathite
Authors: Walenta Kurt 
Published: December 2006

SummaryA reinvestigation of uranospathite from the type locality, Redruth, Cornwall, shows that it is an aluminium uranyl phosphate belonging to the torbernite series but more highly hydrated than other members thereof. The composition (HAl)0·5(UO2)2(PO4)2.20H2O was derived by indirect methods and by making use of analysis by the electron microprobe, which showed an Al2O3 content 2·6% in the partially dehydrated state. Unit-cell dimensions: a 7·00, c 30·02 Å, Z = 2. Probable space group P42/n. Strongest lines of the powder pattern: 15·22 (10) 002, 7·60 (10) 004, 4·93 (10) 110, 111, 3·50 (8) 116, 200, 201.The mineral is unstable and unless preserved at low temperature or in a humid atmosphere converts into a new phase with a loss of 10- 12H2O. This phase (HAl)0.5 (UO2)2(PO4)2.8–10H2O is identical with the mineral sabugalite. Experimental work led to the synthesis of a hydrate with the composition (HAl)o·5(UO2)2(PO4)2. 16H2O, but not to fully hydrated uranospathite. This synthetic compound also dehydrates rapidly under normal conditions, converting into the same phase as does natural uranospathite. Arsenian uranospathite occurs at Menzenschwand in the Southern Black Forest.Arsenuranospathite proper is a new mineral found at Menzenschwand and also at Wittichen in the Central Black Forest. It forms lathlike or wedge-shaped crystals of orthorhombic symmetry. Forms: {100}, {010}, {110}, {001}. Cleavage {001} perfect, {100} and {010} good. Hardness probably about 2, ρcak2·54 g cm −3. White to pale yellow. Streak white. Fluoresces greenish in ultra-violet light with variable intensity.
Welshite, Ca2Mg4Fe3+Sb5+O2[Si4Be2O18], a new member of the aenigmatite group
Authors: Moore Paul B. 
Published: December 2006

SummaryWelshite, triclinic, Ca2Mg4Fe3+Sb5+O2[Si4Be2O18],a= 10·28 Å,b= 10·69 Å,c= 8·83 Å,α= 106·1°,β= 96·3°,γ= 124·8°,P¯1 with pseudo-monoclinic cellam= 9·68(1) Å,bm= 14·77(2) Å,cm= 5·14(1) Å, βm= 101·5(2)°,c-centred, occurs as lustrous subadaman-tine, thick prismatic reddish-black crystals up to 3 mm in greatest dimension associated with roméite, adelite, swedenborgite, berzeliite, manganoan phlogopite, richterite in crystalline dolomite from Làngban, Sweden. Forms include b {010},a{100},k{130},m{110},j{021},p{111},q{121},v{131},r{¯111},s{¯121},t{¯131}, andv{¯141} (monoclinic setting). Streak pale-brown, hardness 6, specific gravity 3·77, fracture conchoidal, no cleavage,α= 1·81(1),γ= 1·83(1), 2E(obs.) ≈45°, no noticcable pleochroism.Welshite is a new member of the aenigmatite-rhönite group and obtains from the substitution Sb5+→ Ti4+and Be2+→ Al3+in rhönite.
Manganhumite, a new species
Authors: Moore Paul Brian 
Published: December 2006

SummaryManganhumite, orthorhombic, a 10·54(1), b 21·45(2), c 4·822(9) Å, space group Pnma, Z = 4, (Mn0·68Mg0·30Fe0·01Ca0·01)7(OH)2(SiO4)3, is the manganese analogue of humite whose type locality is the Brattfors mine, Nordmark, Province of Värmland, Sweden. It is a skarn assemblage mineral and occurs with katoptrite, manganostibite, magnussonite, galaxite, etc., which replace manganosite grains in magnetite-manganosite ore.The mineral is biaxial (+), α = 1·707(3), β = 1·712(3), 7 = 1·732(3), 2V7(obs.) = 37(4)° r > v perceptible, cleavage {010} perfect, hardness = 4, specific gravity = 3·83(5). The five strongest powder lines are 1·777(10), 2·500(7), 3·371(6), 2·628(6), and 1·525(6).
Bahianite, Sb3Al5O14(OH)2, a new species
Authors: Moore Paul B. , Carlos do Prado Barbosa  , Gaines Richard V. 
Published: December 2006

SummaryBahianite, Sb3Al5O14(OH)2-Sb3Al5(Al, Be, Si)<2O16, monoclinic, a 9·406(6), b 11·541(8), c 4·410(3) Å, β 90·94(3)°, Z = 2, space group C2/m, is a new species from the Paramirim region, south central Bahia state, Brazil. It occurs as water-worn pebbles (‘favas’) with quartz, andalusite, kyanite, diaspore, eskolaite, cassiterite, etc. Colour tan to cream, crystals in vugs colourless, tan or pale violet. Specific gravity ranges from 4·89 to 5·46 (5·26 g cm−3 for Sb3Al5O14(OH)2); hardness 9, cleavage {100} perfect, lustre adamantine, biaxial (−), 2V large, α = 1·81, β = 1·87, γ = 1·92, dispersion r > v.The crystal structure represents a new type and is based on hexagonal close-packed oxygens. It is related to the structure of simpsonite Ta3Al14O13(OH).
Tlapallite, a new mineral from Moctezuma, Sonora, Mexico
Authors: Williams S. A. , Duggan Marjorie 
Published: December 2006

SummaryTlapallite is a new mineral found in 1972 at the Bambollita (La Oriental) mine near Moctezuma, Sonora. Also recently found in old specimens from Tombstone, Arizona. Data for type (Mexican) material: Colour viridian green RHS-128A with pale streak, H = 3, Dcalc = 5·05 g/cm3. Crystals monoclinic, class unknown. Indexing based on Ito method gave a cell: a = 11·97 Å, b = 9·11, c = 15·66, β = 90 ° 36′. Strongest lines: 11·972 Å (10), 2·985 (10), 3·540 (6), 5·946 (5), 2·887 (5), 4·731 (4), 3·372 (4), 3·282 (4). Similar data obtain for Tombstone. Chemical analysis for type material yielded the formula H6Ca2Cu3(SO4)(TeO3)4,TeO6 with Te4+:Te6+ = 4:1. However, analysis of the Tombstone material indicates a more general formula H6(Ca, Pb)2(Cu, Zn)3(SO4) (TeO3)4,TeO6. The better data from this material indicate Z = 4, Dcalc = 5·465 vs Dmeas = 5·38. Characterized by extreme birefringence, α = 1·815, β = γ = 1·960; for Tombstone α = 1·955, β = γ = 2·115.Named from the Nahua word tlapalli, meaning paint, in allusion to its mode of occurrence at the type locality.
The high-temperature transformation of andalusite (Al2SiO5) into 3/2-mullite (3Al2O32SiO2) and vitreous silica (SiO2)
Authors: Pannhorst Wolfgang , Schneider Hartmut 
Published: December 2006

SummaryThe high-temperature transformation of andalusite (Al2SiO5) into 3/2-mullite (3A2O32SiO2) plus vitreous silica (SiO2) has been studied within the temperature interval from 1300 to 1600 °C by means of X-ray powder and single-crystal techniques and by infrared spectroscopy. Results are interpreted in terms of a topotactic transformation in which (011) and (01) planes of andalusite transform into (20) and (201) planes of 3/2-mullite; in this way thea- andb-axes of the two phases are interchanged. From the structural and orientational relationship between the andalusite and 3/2-mullite latrices it is concluded that the aluminium-oxygen octahedral chains, running in both structures parallel to the crystallographicc-axis, are preserved during phase transformation.
Element partitioning in ferruginous and pyritic phosphorite from the continental margin off Morocco
Authors: McArthur J. M. 
Published: December 2006

SummaryPhosphorites from the continental shelf off Morocco have been analysed for major elements and Fe, Mn, V, Cu, Ni, Zn, As, Na, Sr, S, and for carbonate. In pyritic phosphorites Cu, Ni, Zn, and As are present mainly in minor pyrite and organic carbon. In ferruginous phosphorites As, Mn, and V are associated with goethite. In the ferruginous phosphorites Cu, Ni, and Zn may have been introduced in association with organic matter and pyrite during phosphorite formation and been retained during subsequent destruction of these phases by weathering. In all phosphorites Na and Sr are present mainly in carbonate-fluorapatite. Sulphur in the ferru-ginous phosphorites occurs only in carbonate-fluorapatite. In the pyritic samples it is partitioned between pyrite and francolite (carbonate-fluorapatite).
Hercynite as a breakdown product of staurolite from within the aureole of the Ardara Pluton, Co. Donegal, Eire
Authors: Atkin Brian P. 
Published: December 2006

SummaryZincian hercynite is present in pelites within the aureole of the Ardara Pluton. The hercynite is always surrounded by cordierite, garnet, or feldspar and is never in contact with quartz. From textural and chemical evidence it is apparent that the hercynite is produced by the reaction of zincian staurolite → zincian hercynite + cordierite + sillimanite. A temperature of about 725°C at pressure of about 2·6 kb and anφo2 below that defined by the Q.F.M. buffer is postulated for this reaction.
Zonal dissolution in analcime and pseudomorphs of adularia after analcime from the Lizard, Cornwall
Authors: Seager A. F. 
Published: December 2006

SummaryAnalcime of hydrothermal origin occurs in the gabbros and in the amphibolites and granulites. Crystals from the different rock suites display the same unusual characteristics upon dissolution: the interior is much more susceptible to attack than the outer growth zone; the former may be converted to a skeletal boxwork, and the latter may suffer extreme differential dissolution along successive narrow growth horizons. Pseudomorphs of adularia after analcime have been found in various stages of development, from partial to complete replacement. Some of the latter preserve the very delicate dissolution structures in detail. Up to fourteen growth horizons have been detected in the outer millimetre of the crystal. This demonstrates that both the growth and dissolution of analcime occurred prior to the formation of adularia, an event that has been dated.
The twin formation of tugtupite, a contribution
Authors: Petersen Ole V. 
Published: December 2006

SummaryTugtupite, space group 1, belongs morphologically to the crystal class 2m. The paper describes pseudotrigonal contact triplets recently found as freely developed individuals on two specimens donated to the Geological Museum, Copenhagen. The contact triplets, described as a symmetric twin, have the composition planes, which are also the twin planes, (10) and (01); the pseudo-threefold axis, along which the crystals are pronouncedly elongate, is [111]. The calculated reentrant angles on the two sides of the pseudotrigonal prism, the protruding angle on the third side, and the ‘central misfit’, expressed as the geometrical angles, are 178° 41′, 181° 20′, and 2° 39′ respectively. Tetragonal crystals forming pseudotrigonal twins are rare and it is emphasized that the pseudotrigonal habit has become apparent only because: the faces developed on individual I and on individuals II and III are not the same; and the proportion between the lengths of the traces of the faces (01) individual I and (01) individuals II and III in a plane perpendicular to the pseudo-threefold axis and the traces in the same plane of all other faces constituting the pseudo-threefold prism are 2:1.
A study of iron-bearing rutiles in the paragenesis TiO2-Al2O3-P2O5-SiO2
Authors: Putnis A. , Wilson M. M. 
Published: December 2006

SummaryHydrothermal ruffles from a suite of rocks at Mount Perry, Queensland, have been studied in thin section, by electron microprobe analysis, and by transmission electron microscopy. The iron-bearing rutiles, while originally singte-phase, are found to exsolve a sequence of iron-rich precipitates on experimental annealing, with hematite being formed as the stable equilibrium precipitate. Experiments at different temperatures and annealing times enable a time-temperature-transformation plot to be drawn for the exsolution process. The kinetics of this process are used to conclude that the rutiles formed below about 450 °C.
Relations between the spectral reflectance and the chemical composition in the magnetite-ulvöspinel series
Authors: Halfen B. 
Published: December 2006

SummarySpectral reflectances and chemical compositions of twenty-eight different grains of exsolved titanomagnetite were measured. Relations between reflectance and composition were established by calculating best-fit planes (Kummell, 1879) for the reflectance at 499 and at 617 nm. These were then transformed to expressions from which the contents of Ti and Mg can be estimated. Even though these estimates are not as accurate as microprobe values, the method is still a useful tool in the study of chemical variation in exsolved titanomagnetites.