bluuebunny/crossref_metadata_2025_split huggingface dataset:
The structural formula of a hydrous amphibole
Authors: Nicholls G. D. , Zussman J. 
Published: December 2006

The majority of amphiboles conform to the general structural formula X2-3Y5Z8O22(OH,F,Cl)2, where X = Na, K, Ca, Y - Mg, Fe″, Mn, A1, Fe‴, Ti, and Z = Si, A1 or Ti. Two X ions occupy the positions filled by Ca in the ideal tremolite structure; the additional X ions are assumed to occur in the 'A' sites which are vacant in tremolite.For the amphiboles, therefore, the method most commonly adopted for deriving a formula from a chemical analysis is to assume that a total of 24 anions is present in the formula unit.
Movement of screw dislocations in hematite.(With Plates I and II.)
Authors: Seager A. F. , Sunagawa I. 
Published: December 2006

Summary
The surface structure of the basal pinacoid of crystals of hematite has been studied by phase contrast microscopy, yielding evidence of the movement of dislocations after the cessation of growth. Steps due to such movement are initiated from the centre of growth spirals, and cross the growth fronts without interrupting the growth layers. Viewed from the dislocation the step has the higher side on the left for right-handed spirals and vice versa. In the majority of cases the step is straight, but rarely it is curved or kinked. It is proposed to call such steps ‘dislocation scarps’.
The number and length of dislocation scarps vary considerably in crystals from different localities. These variations probably reflect differences in the stress history of the crystals.
The effect of 'impure' pore fluids on metamorphic dissociation reactions
Authors: Wyllie Peter J. 
Published: December 2006

Summary
Comparison of experimental data from the systems MgO-CO2-H2O (closed) and MgO-CO2-A (simulating an open system) shows that the effects of H2O and A on the dissociation of magnesite are almost identical; both behave as inert components reducing the partial pressure of CO2. The dissociation temperature at constant total pressure is lowered according to the proportion of inert volatiles in the initial vapour phase. The dissociation is completed at one temperature (univariant) in an open system but in a closed system it proceeds through a temperature interval (divariant) because the vapour phase changes composition. The amount of dissociation remains small until the upper limit of the interval is reached. More complex dissociation reactions in the systems CaO-MgO-CO2-H2O and CaO-SiO2-CO2-H2O are described; they follow similar patterns. Under closed or partially open metamorphic conditions non-reacting pore fluid components (inert) have to be treated as one additional component for application of the mineralogical phase rule. Comparison of the pattern of metamorphic parageneses with the patterns of reactions occurring under known experimental conditions may provide information about metamorphic processes. Metamorphic reactions can be represented within a petrogenetic model with axes P, T, and pore fluid composition varying between H2O and CO2.
Ferrodiorite from the Isle of Skye
Authors: Wager L. R. , Vincent E. A. 
Published: December 2006

Summary
As a preliminary to an account of the marscoite suite of the Western Redhills Tertiary igneous centre of Skye, a description is given here of one unit, the ferrodiorite. While accepting Harker's hypothesis of the hybrid origin of marscoite (1904, pp. 175–196) we consider that the ferrodiorite, with which marscoite on Marsco is associated, is not itself a hybrid, but one of the parents from which the hybrids were formed. Among Thulean igneous rocks the ferrodiorite has mineralogical and chemical affinities with Hebridean mugearites, on the one hand, and with the ferrogabbros of the Skaergaard intrusion on the other, but is probably significantly different from both.
Heat treatment of chevkinite and perrierite
Authors: Lima-de-Faria J. 
Published: December 2006

Summary
Standard heat treatments of 700° C for 3 hours, 1000° C for 1 hour. and 1300° C for 1 hour, both in a nitrogen atmosphere and in air, were applied to several samples of chevkinite and perrierite, and X-ray powder photographs were taken of the unheated and the heated materials.
Metamict chevkinites from the Urals, USSR, and from Ifasina, Madagascar, give the chevkinite phase when heated in nitrogen at 1000° C for 1 hour, but when heated in air at 1300° C for 1 hour give the perrierite phase. Perrierites only give the perrierite phase when heated in air or in nitrogen. A criterion for the identification of metamict samples of these two minerals was deduced from these experiments.
Extinction curves and 2V: a stereographic solution
Authors: Tocher F. E. 
Published: December 2006

Summary
Utilizing the Biot-Fresnel construction in reverse, the magnitude and sign of the optic axial angle of a biaxial crystal are determinable from the stereogram of the extinction curves. Refinements in the determination of the extinction curves include the use of conoscopic observations, and of crystal cylinders instead of irregular fragments or entire crystals. Direct 2V measurements on some of the material investigated by this method show that this indirect and graphical approach permits the location of each optic axis to within ¼° of its true position.
Crystal chemistry of ettringite
Authors: McConnell Duncan , Murdoch Joseph 
Published: December 2006

Summary
Crystal-chemical calculations are based on three chemically analysed samples of ettringite and their respective unit-cell dimensions and specific gravities. The large hexagonal unit cell is deduced to contain 384 oxygen atoms, 64 cations with co-ordination number 6 or more, and 48 cations with co-ordination number 4 or less. Some substitution of cations with co-ordination number 3 apparently takes place, and any excess above 192 H2O takes place in the form of substitution of (H4O4) for XO4 anionic groups. The isomorphism is extremely complex but can be generalized in simple form as 16[A4(XO4)3(H2O)12], where A represents atoms with six-fold co-ordination (Ca, Na, Al) and X represents atoms with four-fold coordination (S, Si, H4, and possibly some of the Al). It is implied that an isostructural series of silicon-containing calcium aluminium sulphate hydrates might exist, the extreme compositions of which are: 6CaO.Al2O3.3SO3.3SiO2.24H2O and 6CaO.Al2O3.3SO3.30H2O.
Pantelleritic liquids and their phenocrysts
Authors: Carmichael I. S. E. 
Published: December 2006

SummaryThe phenocrysts of four porphyritic obsidians from Pantelleria have been analysed chemically, together with the residual glasses (liquids). Three new analyses of anorthoclase (one partial analysis), two of sodic ferrohedenbergite, one of fayalitic olivine, and two of cossyrite are presented together with their optical properties, and the relationship of these phenocrysts to their liquids is considered.The experimental studies in the system NaAlSi3O8-KAlSi3O8-SiO2-H2O show that for synthetic liquids of similar composition to the normative salic constituents of the pantelleritic liquids, a potassic alkali feldspar crystallizes, whereas in the pantelleritic liquids phenocrysts of anorthoclase (Ab67–Ab61) occur. It is suggested that sodium metasilicate, which appears in the norms of all the pantelleritic liquids, may be responsible for the divergence in trend between the synthetic feldspar-liquid tie-lines and the pantelleritic feldspar-liquid tie-lines.
Electron-diffraction study of subsidiary maxima of scattered intensity in nepheline
Authors: McConnell J. D. C. 
Published: December 2006

SummaryA detailed electron and X-ray diffraction study of a suite of nephelines from a wide range of paragenetic environments indicates that, in all cases studied, additional weak maxima of scattered intensity are present. Similar intensity maxima have previously been observed and described in an isolated case by Sahama. Thermal treatment at temperatures as low as 200° C causes these maxima to become noticeably diffuse, implying a structural transformation.
Observations on the rhombic section of a zoned
plagioclase crystal
Authors: Vance Joseph A. 
Published: December 2006

SummaryA zoned plagioclase crystal from a magmatic quartz-diorite shows two generations of pericline twinning: one growth twinning, the other glide twinning. Plotting the angle of the rhombic section against composition for each set of twins gives curves indicative of an intermediate structural state with respect to the theoretical curves determined by Smith (1958). The curve for the growth twins is closer to the high structural state than that for the glide twins and supports the primary origin of the former. This curve is believed to fix approximately the lowest structural state at which primary pericline twinning can develop in magmatic rocks. The lack of coincidence of the curves for the two generations of twinning indicates partial inversion prior to formation of the glide lamellae, while the position of the curve for these secondary lamellae suggests a genetic relation to inversion. Both rhombic sections are probably relict with respect to the present structural state. The form of the curves confirms the general accuracy of Smith's curves for the maximum high and low structural states.
The ageing of sesquioxide gels. II. Alumina gels
Authors: Mackenzie R. C. , Meldau R. , Gard J. A. 
Published: December 2006

SummaryAluminium oxides occur widely in soils and are of considerable pedological significance. The ageing of alumina gels, prepared from aluminium chloride and ammonia, into crystalline hydroxides has been investigated using thermal, X-ray, infra-red, and electron-microscope techniques. At room temperature ageing is more rapid at high pH values. The structure of the original gel particles appears to resemble boehmite and ageing causes the formation of bayerite with small amounts of gibbsite. The morphology of the various mineral types is considered and a mechanism of ageing suggested.
Powellite from Traprain Law, Haddingtonshire, Scotland
Authors: Battey M. H. , Moss A. A. 
Published: December 2006

SummaryPowellite, appearing to be of primary late-magmatic origin, has been found associated with analcime, apophyllite, and calcite in a geode in phonolite. Data are: D 4·40, ε 1·984, ω 1·971, a 5·20 Å, c 11·43 Å, CaO 27·8, MoO3 61·8 (av.), WO3 11·4 (av.).
Garronite, a new zeolite, from Ireland and Iceland
Authors: Walkee G. P. L. 
Published: December 2006

SummaryA new zeolite closely related to phillipsite and gismondine is recorded from thirty localities in the Tertiary basalts of Antrim and eastern Iceland, and the name garronite is proposed. Four chemical analyses indicate a composition of NaCa2·5A16Si10O32.13·5H2O. Garronite differs chemically from phillipsite in having a very low content of potash, and from gismondine in containing less lime, alumina, and water; optically garronite is intermediate between these two zeolites.
Low-potash gismondine from Ireland and Iceland
Authors: Walker G. P. L. 
Published: December 2006

SummaryGismondine is recorded from the Tertiary basalts of the North Atlantic region, from a total of some 40 localities in Antrim and Iceland. It occupies a well-marked position in the sequence of zeolite zones in the lavas, and the characteristic associates are chabazite, thomsonite, and phillipsite. Five new chemical analyses of gismondine from these localities show a negligible content of potash, and indicate plagioclase-type substitution, giving a series ranging from near Ca8Al16Si16O64.34H2O to near Na2·5Ca5·5Al13·5Si18·5O64.34H2O. Substitution of NaSi for CaAl leads to a decrease in refringence, birefringence, and density.
Framework structures formed from parallel four- and eight-membered rings
Authors: Smith J. V. , Rinaldi F. 
Published: December 2006

SummaryFeldspars, paracelsian and danburite, harmotome and phillipsite have alumino-silicate frameworks that consist of three out of the seventeen simplest ways of cross-linking chains of the feldspar type. The four-membered rings that form the feldspar type of chain are parallel and have two adjacent tetrahedra pointing one way and the other two the other way. Chains are produced by sharing oxygen atoms of oppositely-pointing tetrahedra of parallel four-membered rings. Cross-linking of chains produces frameworks containing parallel eight-membered rings. If alternate tetrahedra in the rings point the same way, a new type of chain is produced, and there are four simple ways of joining these chains together to make a framework. If all four tetrahedra in a ring point the same way, only one structure can be developed, which has been proposed already by Barrer et al. for the zeolite Na-P1 and other members of the harmotome family. If three tetrahedra in the ring point the same way, very many simple structures can be constructed, and the seven simplest of these are described. It is suggested from comparison of cell dimensions that gismondine and, perhaps, yugawaralite may belong to this series of hypotheti- cal structures. It is also suggested that some of the complexity and confusion in the harmotome group of zeolites may arise from hitherto unrecognized members of this hypothetical group. Major angular distortions from the ideal shape occur for the naturally-occurring silicates belonging to these structural groups.
Location of argon and water in cordierite
Authors: Smith J. V. , Schreyer W. 
Published: December 2006

SummaryEvaluation of X-ray powder diffraction data shows that argon atoms (radius 1·9 Å) lie at the centres of the large holes in the cordierite structure. The reflection intensities for hydrous cordierite differ from those for anhydrous cordierite but to a lesser degree than those for argon-bearing cordierite. Although analysis is uncertain, it appears that the smaller water molecules (radius 1·4 Å) do not occupy either the centres of the six-membered rings or the centres of the large cavities. It is possible that they may be attached to the walls of the large cavities or occur partly as hydroxyl groups in the framework. Single-crystal X-ray analysis is necessary to resolve this problem.
Goyazite and florencite from two African carbonatites
Authors: McKie Duncan 
Published: December 2006

SummaryFlorencite with ω 1·653, εd 1·661, G 3·457, a 6·971 ± 0·004 Å, c 16·42±0·13 Å, and rhombohedral unit-cell contents Sr0·42Ce0·52Ca0·14Al2·83(PO4)1·77(SO4)0·10 F0·41(OH)5·24(H2O)0·85 occurs in the Kangankunde carbonatite in Nyasaland, and goyazite with G 3·386, a 6·982±0·001 Å, c 16·54±0·02 Å, and rhombohedral unit-cell contents Ba0·05Sr0·50Ce0·41Ca0·08A2·78(PO4)1·62(SO4)0·19F0·30(OH)5·30(H2O)1·18 on the Wigu carbonatite in Tanganyika. Hydrothermal decomposition experiments in the Wigu material indicate stability below 535 ± 10 °C at pH2O 200 bars and 565 ± 10°C at pH2O 2500 bars ; both minerals exhibit endothermic peaks at 630°C in differential thermal analyses. The crystal chemistry of the goyazite series is discussed in the light of the two new analyses and of newly determined unit-cell dimensions for four other members of the goyazite series. Goyazite, florencite, and gorceixite appear to have crystallized during late-stage replacement processes or under supergene conditions in carbonatites.
Some petrological aspects of order-disorder in feldspars
Authors: Marfunin A. S. 
Published: December 2006

SummaryThe results are presented of some recent feldspar studies that relate the fundamental concepts of order-disorder series to petrological problems. New diagrams have been prepared with coordinates ‘optical properties-chemical composition-structural state’. From direct observations made on natural minerals some conclusions have been reached about the sequence in which the solid-state transformations of ordering, unmixing, and twinning occur in feldspars.A study has been made of the geological distribution of different structural types of alkali feldspars in single intrusive bodies (Tertiary granite, Palaeozoic syenite, Pre-cambrian charnockite), in magmatic complexes, and in different complexes of the Ukrainian Shield and the Caucasus Geosynclinal Province.
Metamorphic pyroxenes from the Broken Hill district, New South Wales
Authors: Binns R. A. 
Published: December 2006

SummaryThe Archean rocks of the Barrier Ranges, New South Wales, show zones of progressive regional metamorphism of which the highest is characterized by orthopyroxene-bearing basic granulites. Within this zone, further increase in metamorphic grade results in a detectable change in distribution of ferrous iron and magnesium between coexisting orthopyroxene and clinopyroxene, the latter becoming relatively richer in iron. Mutual solid solution between the two pyroxene phases also appears to increase. The value of coexisting pyroxenes as indicators of metamorphic grade is thus established. There are some points of disagreement between the Broken Hill results and previously advanced theories of cation distribution in pyroxenes.
Rosasite, aurichalcite, and associated minerals from Heights of Abraham, Matlock Bath, Derbyshire, with a note on infra-red spectra
Authors: Braithwaite R. S. W. , Ryback George 
Published: December 2006

SummaryRosasite and aurichalcite occur with other copper, zinc, and also lead minerals in Masson Cavern, Rutland Cavern, and other workings in the Heights of Abraham, Matloek Bath, Derbyshire. Partial analyses of two specimens each of rosasite and aurichalcite show Cu : Zn ratios typical of the respective species. They appear to have been formed by the action of solutions containing zinc on disseminated chalcopyrite. The infra-red absorption spectra of malachite, rosasite, aurichalcite, and hydrozincite, examined by the mull technique, are shown to fall into two groups corresponding with the structural groups established by X-ray work. Twin absorption maxima at O-H stretching frequencies are present in the spectra of malachite and of rosasite.
Epididymite and milarite—alteration products of beryl from Věžná, Czechoslovakia
Authors: Černý P. 
Published: December 2006

SummaryEpididymite, determined by means of its optical properties, X-ray powder pattern, and spectrographic analysis, was found in a desilicated pegmatite near Věžná, Western Moravia, Czechoslovakia. It was formed contemporaneously with minor amounts of milarite in a late hydrothermal stage by the action of sodium-rich solutions on beryl. This is the first occurrence of epididymite and milarite as alteration products of beryl and the first findings of epididymite in any other paragenesis than that of alkaline pegmatites. The optical properties of epididymite are re-examined and older data rejected.
The chemistry and mineralogy of the olivine nodules of Calton Hill, Derbyshire
Authors: Hamad S. el D. 
Published: December 2006

SummaryChemical analyses, optical data, and cell parameters are given for olivine (Fo90·3 and Fo91·4), orthopyroxene (Ca1·5Mg89·0Fe9·5 and Ca9·8Mg88·6Fe10·6), clinopyroxene (Ca39·6Mg55·8Fe4·6), and chromian spinel from olivine nodules from the Carboniferous basalt of Calton Hill, Derbyshire. Chemical and modal analyses of the nodules and of their host rock are also presented. The distribution of Mg and Fe in the coexisting pyroxenes is fairly similar to that observed by Ross, Foster, and Myers (1954) but differs slightly in that the extension of the pyroxene tie-line intersects the Ca-Mg side of the Ca-Mg-Fe triangle. The clinopyroxene is a normal augite rather than the hydrous augite previously reported (Tomkeieff, 1928). The high chromium content of the spinel and clinopyroxene contrasts with the low value for this element in the host rock, suggesting that these minerals are not differentiates of the basaltic magma: the nodules are considered to represent fragments from a deep-seated peridotite.
X-ray study of woodruffite from Sandur ore deposits, Mysore State, India
Authors: Naganna C. , Bouška Vl. 
Published: December 2006

SummaryThe mineral woodruffite, which has so far been reported from only one locality, Sterling Hill, New Jersey, has been found to occur in the Sandur area. Its physical and chemical characters are given. Indexing of the X-ray powder photograph shows that the mineral is most probably tetragonal with a 8·42, c 9·28 Å.
The occurrence of eclogite on the Lyell Highway, Tasmania
Authors: Spry Alan 
Published: December 2006

SummaryEclogite occurring about 20 miles east of Queenstown, Tasmania, is the first example of this kind of rock to be described in detail from Australia. It has the chemical composition of a basic igneous rock and consists of garnet (A115.8Fe‴0.6Fe″10.0Mg7.3Ca5.7Si24O96) and pyroxene (Ca4.5Na2.5Mg3.7Fe″0.7Fe‴0.4Ti0.1Aliv3.7Aliv0.7Si15.3O48)with amphibole, muscovite, zoisite, quartz, rutile, and pyrite. The eclogite consists of lenticular bodies within Precambrian garnetiferous schists.
Phosphate minerals in a calculus from the reticulo-rumen of the sheep
Authors: Ellis S. E. 
Published: December 2006

SummaryBrushite occurs as radial-concentric layers of prismatic crystals deposited on baked pellets of bentonite impregnated with cobalt oxide, placed in the reticulo-rumen of lambs as a preventive of cobalt-deficiency diseases. Collophane-like whitlockite, apparently pseudormorphous after brushite, occurs underneath the brushite layers, and struvite is found as rare minute crystals between the whitlockite and brnshite layers. Analytical and physical data are given for the first two minerals and the origin of the deposit is discussed.
The determination of the calcite : aragonite ratio in mollusc shells by X-ray diffraction
Authors: Davies T. T. , Hooper P. R. 
Published: December 2006

SummaryBy measuring the integrated line intensity on a Philips' X-ray diffractometer in place of the peak intensity and by paying due regard to the ease with which aragonite converts to calcite during cleaning and grinding operations, the proportion of calcite and aragonite in a pure calcium carbonate shell can be determined to within 1% of the total in less than 30 minutes.
An X-ray investigation of synthetic pyroxenes in the system acmite--diopside-water at 1000 kg/cm2 watervapour pressure
Authors: Nolan J. , Edgar A. D. 
Published: December 2006

SummaryAn X-ray investigation has been made of synthetic pyroxenes in the system acmite-diopside, crystallized at 750° C and 1000 kg/cm2 water-vapour pressure. Lattice parameters of these pyroxenes have been determined by least squares analyses of powder diffraction patterns and show an approximately linear relationship with composition, plotted as weight per cent. A rapid X-ray method has also been devised for the determination of the compositions of pyroxenes of this series.
Order-disorder in sapphirine
Authors: McKie Duncan 
Published: December 2006

SummaryYellow sapphirine with a doubled b-axis occurs in enstatite-hornblende-sapphirine rocks at the contact between dolomite marble and yoderite-quartz-talc schist on Mautia Hill, Tanganyika. It has refractive indices α 1·725± 0·002, γ 1·732±0·002, 2Vγ66°, pleochroism a pale yellow, β pale lime green, γ pale pinkish orange, and a composition corresponding to Mg3·67Mn0·04Fe2+0·17Ti0·01Fe3+0·33Als·07Si1·75O20·00. Its unit-cell dimensions are approximately a 9·85 Å, b 28·6Å, c 9·96 Å, β 110° 30′, and its diffraction pattern exhibits diffuse streaks parallel to b*, on which lie diffuse intensity maxima representing the relics of certain types of sharp reflexions of normal sapphirine ; this is interpreted as indicative of partial MgAl ordering. The associated enstatite and hornblende have compositions Mg7·58Mn0·02Fe2+0·02Ti0·01Fe3+0·13Al[6]0·25Al0·41[4]Si7·59O24·00 and K0·04Na0·16Ca1·95Mg4·37Mn0·01Fe0·052+Ti0·04Fe0·253+Al0·42[6]Al0·91[4]Si7·09O22·24(OH)1·76respectively and are accompanied by accessory hematite and pseudobrookite. Preliminary heating experiments have demonstrated the transformation of single crystals of partially ordered Mautia sapphirine to single crystals of a defect spinel phase after 48 hours at 1287° C in air; normal disordered Panrimali sapphirine remains unchanged by similar heat treatment.