bluuebunny/crossref_metadata_2025_split huggingface dataset:
An improved technique for producing thin rock-sections
Authors: Bishop A. C. 
Published: December 2006

SummaryThe preparation of thin rock-sections using a modified high-speed surface grinding machine is described. The machine is fitted with a new type of jig designed to hold ¼ in. thick glass slides to which the rock slices are mounted for grinding. The machine operates automatically once a cut is set and the large size of the jig enables fifteen 3 in. × 1 in. sections to be produced at one grinding operation without the constant attention of an operator.
Cobaltic hydroxide in nature
Authors: Hey M. H. 
Published: December 2006

SummaryNatural cobalt hydroxide is CoO.OH, not Co(OH)2 as has recently been asserted; for this mineral the name heterogenite has priority. Copper, frequently present, may be in solid solution as (Co,Cu)(O,OH)OH, or may be as finely divided malachite; for cuprian heterogenite, the name schulzenite has priority.
β-Ferric oxyhydroxide—akaganéite
Authors: Mackay A. L. 
Published: December 2006

SummaryA new mineral, akaganéite, has been found in limonite deposits and has been shown to be identical with synthetic β-FeOOH. It contains no chlorine. The micro-morphology of β-FeOOH as it occurs as akaganéite and as it is produced by a solid-state transformation from FeCl2.4H2O , by the hydrolysis of dilute FeCl3 solutions, and by the hydrolysis of very concentrated FeCl3 a solutions, has been studied, chiefly by electron microscopy and diffraction. Some modes of colloidal association of the particles of β-FeOOH are described.
The origin of stannite by replacement of cassiterite in the Turkaňk zone of the Kutná Hora ore deposit
Authors: Novák F. , Blűml A. , Tacl A. 
Published: December 2006

SummaryThe trace-element assemblage of the cassiterite of the Turkaňk and Rejsy zones of the Kutná Hora mining district are typical of a hydrothermal sulphide-cassiterite formation. Polished section studies show replacement of cassiterite by pyrrhotine, with stannite as am intermediate zone.
The identity of almeriïte with natroalunite
Authors: Hoyos de Castro A. , Alías L. J. 
Published: December 2006

SummaryTwo specimens of almeriïte from the type locality have been examined by chemical analysis, d.t.a., and X-ray powder photography and shown to be identical with natroalunite. A little illite and kaolinite are present as impurities. X-ray powder data for natroalunite are presented.
Amphiboles from the Younger Granites of Nigeria. Part I. Chemical classification
Authors: Borley G. D. 
Published: December 2006

SummaryThe Younger Granites of Nigeria contain varied assemblages of iron-rich ferromagnesian minerals in which amphiboles are an important component. Eighteen of these amphiboles (separated from rocks belonging to nine complexes) have been chemically analysed and the results are presented and discussed. The amphiboles are shown to fall into two groups, a lime-alkali group (comprised of ferrohastingsite of general formula NaCa2Fe″4Fe‴Al2Si6O22(OH)2) and an alkali group (of general formula (Na, K, Ca)2.5–3.0(Fe″, Fe‴)5(Al, Si)3O22(OH)2). The alkali amphiboles are characterized by their extremely low magnesia content, by the presence of Li and F (both in significant amounts), and are of specialinterest because of the unusual amount of ZnO they contain. Optical properties of the amphiboles have been determined but it has not been found possible to use these properties to determine accurately the chemical composition of the alkali amphiboles. It is suggested that, according to current classifications of amphiboles, the analysed alkali amphiboles should be called riebeckitic arfvedsonites or arfvedsonites. The relationship between the hastingsites and the alkali amphiboles is not yet clear.
Amphiboles from the Younger Granites of Nigeria. Part II. X-ray data
Authors: Frost M. T. 
Published: December 2006

SummaryThe cell parameters of fifteen arfvedsonites and four ferrohastingsites were determined using powder and diffractometer techniques and a least squares method of computation. Methods are proposed of distinguishing between calcium- and sodium-rich amphiboles, and between iron-rich and iron-poor varieties of these two groups, by their powder data. Within the arfvedsonite group the b parameter was found to increase with increasing Ca, Fe″, and (OH) and to decrease with increasing Na, F, and Li. The c parameter was found to decrease with increasing F and increase with increasing (Fe‴+Al+Ti). The parameters a, β, and a sin β all tended to increase with increasing Ca, Fe″, and F content. The cell volumes were found to vary with the b parameter. The ferrohastingsites were found to have much larger cell parameters than the arfvedsonites. An attempt was made to explain these variations from structural considerations.
The occurrence of magnesian pyroxenes and magnetite in porphyritic acid glasses
Authors: Carmichael I. S. E. 
Published: December 2006

SummaryThe problem of magnesian pyroxenes in acid liquids is considered in the light of new analyses of pyroxene and magnetite phenocrysts. It is suggested that the early precipitation of titaniferous magnetite, which will strongly deplete the liquid in iron, will decrease the iron:magnesium ratio of the pyroxene components in the liquid. Accordingly the iron:magnesium ratio of a pyroxene precipitating from an acid liquid may vary over a wide range depending upon the presence or amount of early magnetite.
A differential thermal study of the chlorites
Authors: Phillips Wm. Revell 
Published: December 2006

SummaryDifferential thermal analysis alone appears inadequate as a tool for distinguishing the many chlorite varieties; however, this process is capable of yielding much valuable information about the chlorites. The 7 Å septechlorite structure may be easily distinguished from the normal 14 Å chlorite structure. Two stages of dehydration, oxidation of ferrous iron, and structural collapse appear as endothermic and exothermic peaks on the D.T.A. chlorite curves. Septechlorites show only one, large dehydration stage, which leads directly to the structural breakdown. Iron oxidation accompanies the initial dehydration in both structural types, and the temperature at which dehydration begins is noticeably lowered by increasing ferrous iron content of the chlorite variety.
Lamprophyre dykes from Argyll
Authors: Gallagher M. J. 
Published: December 2006

SummaryIn the Carboniferous-Permian dyke-suite north of Loch Sunart, Argyll, a complete gradation is displayed from olivine-dolerite to camptonite. The dolerites are more numerous than the camptonites, and dykes of monchiquite are rare. A small number of minettes and allied lamprophyre types of Devonian age are also present. New analyses of biotite and diopside from a minette and of augite and hornblende from a camptonite are presented, with optical data, and the classification of the dykes briefly discussed.
Simpsonite and stibiotantalite from Benson pegmatite mine, Mtoko, Southern Rhodesia
Authors: von Knorring O. , Hornung G. 
Published: December 2006

SummaryA new occurrence of the tantalum minerals simpsonite and stibiotantalite is described from a lithium pegmatite at Mtoko, Southern Rhodesia. Optical, chemical, and powder X-ray data are given and the formula of simpsonite is considered; a new formula is proposed.
The Dehydration of Chrysotile in Air and under Hydrothermal Conditions
Authors: Ball M. C. , Taylor H. F. W. 
Published: December 2006

SummaryChrysotile fibres, and also single crystals of lizardite, were dehydrated hydrothermally, and the resulting pseudomorphs studied by X-ray rotation photographs. The initial products are normally forsterite and disordered material; talc forms more slowly. At water pressures up to 600 kg/cm2, both forsterite and talc show strong preferred orientation. At higher pressures the talc is oriented but the forsterite tends to be unoriented. The orientation of forsterite formed at 550° C and 500 kg/cm2differs from that found when chrysotile is dehydrated by heating in air. The orientation relationships suggest that, in the dry reaction, the forsterite orientation is controlled mainly by the octahedral layers of the chrysotile, while in the hydrothermal reaction it is controlled mainly by the tetrahedral layers. This does not support the generally accepted mechanism for the dry reaction. New mechanisms are suggested, for both dry and hydrothermal reactions, similar to that already suggested by us for the dehydration of brucite. The formation of talc in the hydrothermal reaction, and of enstatite in the dry reaction above 1000°, are also discussed. The dehydration of talc, to give enstatite, has also been studied using single crystals, and the mechanism of this process is briefly discussed.
Some natural analcime solid solutions
Authors: Wilkinson J. F. G. 
Published: December 2006

SummaryChemical, optical, and X-ray data are presented on three analcimes from a differentiation sequence, olivine-theralite to analcime-tinguaite; compared with the ideal analcime composition, they reveal replacement of NaAl→Si. Optical and X-ray data on these minerals accord reasonably well with analcimes possessing similar compositions, and synthesized in the sub-solidus region in the NaAlSiO4-NaAlSi3O8-H2O system.
Note on a chrome and two manganese garnets from India
Authors: Sastri G. G. K. 
Published: December 2006

SummaryMineralogic data on a chrome garnet, a spessartine, and a spandite from India are presented. The chrome garnet, named hanléite by Fermor, carries 89·7 % uvarovite, and is not a distinct mineral. The end-member compositions of the manganese garnets, recast from their chemical analyses, lend support to the existence of calderite and blythite as garnet end-members.
Melting relations of Tertiary granitic rocks in Skye and Rhum
Authors: Brown G. M. 
Published: December 2006

SummaryThe results of reconnaissance melting experiments on Tertiary granophyres and Torridonian arkose at 1000 kg/cm2 water-vapour pressure show that the melting behaviour of these rocks can be viewed in relation to the synthetic system NaAlSi3O8-KAlSi3O8-SiO2-H2O. By analogy with this system, P-T curves are constructed for Skye granophyres and, viewed in relation to the stability of tridymite, the depth and temperature of emplacement are estimated. Further estimates of the likely depth of magma generation, and the behaviour of the country rocks at that level, lead to the conclusion that most of the Tertiary granitic rocks were produced through partial melting of Lewisian basement rocks, the heat being provided by the basic magmas available during this volcanic episode. Subsidiary amounts of granitic magma were similarly derived from higher levels, within the Torridonian arkose group, and evidence is provided for the depth and temperature at which these, together with tridymite-bearing metamorphosed arkose in Rhum, were produced.
The högbomite polytypes
Authors: McKie Duncan 
Published: December 2006

SummarySingle crystal X-ray examination has shown that högbomite forms a series of polytypes, designated nH or nR, with hexagonal or rhombohedral lattices and hexagonal unit-cell dimensions a 5·72 Å, c 4·6 × n Å. The polytypes arise by variation, in a manner as yet undetermined, of the stacking sequence of approximately close-packed oxygen layers with interstitial cations on fourfold and on sixfold sites; the composition of 1/nth of a unit-cell may be represented as R2+1.0_1.6T4+0.2-0.4R3+3.7-4.3O2-7.6-8.0(OH)-0-0.4,, where R2+ = Zn, Fe, Mg, and R2+ = Fe, Al. The polytypes so far observed are 4H, 5H, 6H, 15H, 15R, and 18R. Minerals structurally related to högbomite are nigerite (3H) and taaffeite (4H). A new occurrence of högbomite, polytype 5H, with composition Ti1·7Fe1·6Mg6·3Al18·8Si0·2O40, is described from a spinel-free paragenesis in a magnesian skarn at Mautia Hill, Tanganyika. Another new occurrence in an aluminous xenolith in the Cashel gabbro in Co. Galway, Ireland, is recorded. X-ray powder data are given for two of the polytypes.
The kinetics of the low→high transformation in albite I. Amelia albite under dry conditions
Authors: McKie Duncan , McConnell J. D. C. 
Published: December 2006

SummaryThe transformation was followed in Amelia albite powders by variation in 2θ131−2θ13̄1 with time under isothermal conditions at various temperatures in the range 920°–1080°C. The activation energy of about 74 kcal mole-1 is rather larger than that obtained for the ordering process in synthetic NaAlSi3O8 under hydrothermal conditions.
An unusual distribution of precipitates in a diamond
Authors: Shah C. J. , Lang A. R. 
Published: December 2006

SummaryThe central region of a type 1 stone was found by optical and X-ray topographic examination to be densely populated with small inclusions. The X-ray studies indicated that these were precipitates formed after growth of the stone. Precipitate sizes fell into two groups, 1 µ or less, and around 5 µ. Many cases of decoration of grown-in dislocations by these precipitates were observed.
Some Observations on Igneous Ferrohastingsites
Authors: Borley G. , Frost M. T. 
Published: December 2006

SummaryNine ferrohastingsites from the Younger Granites of Northern Nigeria and five from the nepheline-bearing rocks in the Marangudzi complex of Southern Rhodesia have been analysed chemically and their optical properties and unit-cell parameters determined.All the minerals have compositions that can be expressed by the formula NaCa2(Fe″Mg)4Fe‴Al2Si6O22(OH)2, but the Nigerian minerals differ from those of Marangudzi in their lower alumina contents, generally greater degree of iron enrichment, lower potassium, and more variable fluorine contents. These differences are considered to reflect the differences in composition of their respective parent rocks. The compositional similarities between some hastingsites and barkevikite are commented upon and the pleochroism of barkevikite is briefly discussed.Refractive indices of the analysed hastingsites have been plotted on the optical curves of Tröger. It is suggested that such curves are of limited use and that variations in unit-cell parameters might be a more useful method of determining the iron contents of hastingsites.The variation in cell parameters with variation in chemical composition of the analysed minerals is also discussed.
A simple single-axis rotation apparatus
Authors: Hartshorne N. H. 
Published: December 2006

SummaryThe apparatus enables a small crystal to be rotated through 360° about an axis parallel to the stage of a polarizing microscope, while immersed in a liquid of known refractive index. Angles of rotation are measured on a graduated drum to the nearest degree. The working distances separating the crystal from the objective and the condenser are sufficiently small for wide-angle interference figures to be obtained. The crystal is easily mounted and centred.
The stereographic projection: a procedural revision in crystallography
Authors: Oppenheim M. J. 
Published: December 2006

SummaryObjections are raised to the custom of reversing the pole of projection when dealing with lower crystal faces, for some points so projected no longer retain their natural interangular relations. Instead, lower face normals may be replaced by their antipodal points; these antipodal points are then projected in the usual manner, with suitable symbols. The resultant stereographic projection not only portrays all crystal faces within the primitive circle but is also strictly angle-true.
Direct stereographic determination of the optic axes from a ,few extinction measurements: a progressive elimination technique
Authors: Tocher F. E. 
Published: December 2006

SummaryA new method of determining the optic axes from a few extinction measurements is presented. It is based on the progressive elimination of those parts of the stereogram in which it is obvious that the optic axes cannot lie. It has two applications: as a valid method in its own right, if applied systematically; and as a reconnaissance technique. The second application permits, for example, the recently presented trisogon technique to be rapidly and economically applied over a very small fraction of the stereogram instead of over its whole area.
The spectrochemical determination of feldspars within the field microcline-albite—labradorite
Authors: Fraser W. E. , Downie G. 
Published: December 2006

SummaryTwo spectrochemical methods of feldspar determination are described: one based on the flame spectrophotometer; the other on the quartz spectrograph. For the first method, unknown feldspars are dissolved in a mixture of hydrofluoric and perchloric acids and diluted to 1 : 104. Percentages of Or and An are determined by comparison with dissolved feldspar standards at the same dilution; percentages of Ab are estimated by difference. For the second method, unknown feldspars are burned, unadulterated, in the cathode of the spectrograph arc and a visual estimation is made of the intensities of the following lines: Na5688, Na5683, Ca4455, Ca4435, Ca4425, K4047, K4044, Ca3644, K3447, Na3303, Na3302, and Ca3159. The estimated intensities are then substituted in two empirically determined functions:(ICa4455+ICa4435+ICa4255+ICa3644+ICa3159)−4/3(INa5688+INa5683+INa3303+INa3302)and (3INa5688+3INa5683+2INa3303+INa3302)−43(4IK4047+3IK4044+2IK3447) .From the algebraic values of these two functions, the compositions of the unknown feldspars, expressed as percentages of Or, Ab, and An, are read directly from a chart based on results obtained from feldspar standards of known chemical composition.
A zinc phosphate analogue of analcime: kehoeite
Authors: McConnell Duncan 
Published: December 2006

SummaryKehoeite, a hydrated zinc aluminate-phosphate, produces an X-ray powder diffraction pattern with interplanar spacings similar to those of analcime, viséite, and pollucite. The diffraction maxima appear to be compatible with a cubic (or pseudocubic) lattice witha13·7 Å. It is concluded that kehoeite is essentially isostructural with analcime and that its framework is composed of linked tetrahedra: (AlO2)−, (H3O2)−, and (PO2)+, as was found to be the case for viséite, which contains (SiO2) in addition. Calculations of the density, the number of oxygens in the unit cell, and the chemical composition are consistent with the structural formula Zn5·5Ca2·5(H2O)32[(Al16P16(H3)16)O96].
Kyanite produced in a granitic aureole
Authors: Lobjoit W. M. 
Published: December 2006

SummaryAn occurrence of kyanite in the inner aureole of a granodiorite intrusion is described from south-western Ghana. Greenschist facies phyllites have been elevated to the amphibolite facies and the regional strike of these country rocks has been disrupted by the intrusion, so that clear evidence is available of the time relationships. It is concluded that the kyanite crystallized as the result of the forceful intrusion of the granodiorite, probably under epizonal conditions.
Some orthopyroxenes from Scottish metamorphic rocks
Authors: Howie R. A. 
Published: December 2006

SummaryChemical analyses, cell parameters, and optical properties are presented for seven Scottish orthopyroxenes: four from Harris, two from Scourie, and one from Belhelvie, Aberdeenshire. The compositions range from En83·6 to En55·5. Six of the orthopyroxenes are from pyroxene granulites or related rocks and the other is from a plagioclase-hypersthene hornfels: the latter mineral is notable in having 7·21% Al2O3, causing a considerable contraction in the a and b cell parameters. The alumina content of orthopyroxenes is briefly discussed. Analyses are also given for olivine and diopsidic augite from a South Harris ultrabasic gneiss and for two enderbitic pyroxene gneisses from Scourie.
A hydraulic stage: an aid in counting mineral grains
Authors: Humphries D. W. 
Published: December 2006

SummaryA hydraulically operated microscope stage is described and constructional details are given. The stage is foot-operated, which leaves both hands free for continuous focusing of the microscope and the operation of a mechanical counting device. A further advantage of the hydraulic stage is that unmounted grains (or small fossils) can be moved smoothly and without relative movement between individual grains. The rate at which grains (or small fossils) can be counted is thus greatly increased.
The oriented transformation of aragonite into calcite
Authors: Dasgupta D. R. 
Published: December 2006

SummaryThe oriented transformation of aragonite to calcite has been studied by X-rays. The [100], [110], and [001] directions of aragonite become [101̄0], [011̄0], and [0001] of calcite. The transformation was completed by a re-orientation of the CO3 groups about the [001] direction of aragonite through an angle of 30°, different rows of CO3 being turned in opposite directions, together with a displacement along the same direction. The layers of Ca ions also are shifted along the basal plane of calcite so that their arrangement perpendicular to the [0001] direction of calcite becomes ABCABCA… instead of ABABABA… as in aragonite.
Arthurite, a new copper—iron arsenate from Cornwall
Authors: Davis R. J. , Hey M. H. 
Published: December 2006

SummaryThin apple-green crusts on several specimens from Hingston Down Consols mine, Calstock, Cornwall, proved to consist of a new mineral, alone or intimately mixed with pharmacosiderite (which it closely resembles), or with an unidentified mineral of the alunite-beudantite group having a 7·04, c 16·6 Å, or with both. The new mineral, for which the name arthurite is proposed, for Sir Arthur Russell and Mr. Arthur W. G. Kingsbury, who independently collected material and suggested that it might be new, gives X-ray powder photographs with their three strongest lines at 4·28, 4·81, and 6·97 Å ; the photographs could be satisfactorily indexed on a monoclinic unit-cell with a 10·09, b 9·62, c 5·55o Å (all ± 0·01 Å), β 92·2° ± 0·2° and containing [Cu2Fe4(AsO4)3(OH)7.6H2O]. Chemical analysis on 1·1 mg gave: CuO 16·8, Fe2O3 32·4, As2O5 34·3, H2O 16·5 % (reduced to 100 % after deduction of 27·4 % quartz) ; sp. gr. 3·2 (calc. 3·07). Under the microscope arthurite is pale olive-green and very finely granular; n 1·78, birefringence low to moderate.
The lattice parameters of high-temperature triclinic sodic feldspars
Authors: Carmichael I. S. E. , MacKenzie W. S. 
Published: December 2006

SummaryThe lattice parameters of twenty calcium-bearing anorthoclases and potassium-bearing acid plagioclases have been determined by powder methods. The 201̄ spacing of the homogenized anorthoclases gives a good measure of the Or content irrespective of the amount of calcium present ; this spacing combined with α* (010): (001) may be used to determine the ternary composition of homogeneous feldspars more potassic than approximately Or15. The lattice parameters of feldspars less potassic than Or15 cannot be used for the determination of their ternary composition.
Rhythmic amphibole overgrowths in appinites associated with explosion-breccias in Argyll
Authors: Bowes D. R. , Kinloch E. D. , Wright A. E. 
Published: December 2006

SummaryTremolite and actinolite form rhythmic overgrowths over hornblende in appinites associated with pipes of explosion-breccia and represent growth under alternating physical conditions arising from increase of gas pressure and its explosive release. The number of overgrowths present in each appinite mass is related to the number of explosions required to breach the particular structural trap that hindered the upward movement of the volatiles.