bluuebunny/crossref_metadata_2025 huggingface dataset:
Orientation of the boundaries of out-of-step domains in anorthite
Authors: Ribbe Paul H. , Colville Alan A.
Published: December 2006

The orientation of the boundaries of out-of-step domains in ‘transitional’ anorthite has been deduced from the direction of elongation of the diffuse X-ray reflections h + h + l = 2n + 1 in selected precession photographs. The reflections are elongated normal to which is in the zone and contains the body-centring vector (a+b−c)/2. The structure is presumed to be perfect parallel to . Atoms in essentially identical, primitive anorthite-like domains are related across the out-of-step domain boundaries by body-centring vectors. Increasing diffuseness of the h + k + l = 2n + 1 reflections indicates progressively smaller domains (more frequent domain boundaries), and when thesereflections disappear, the structure has become body-centred on the average.
Compact chlorite associated with lizardite from New South Wales, Australia
Authors: Golding H. G. , Bayliss P.
Published: December 2006

Segregations of compact chlorite from ultramafic belts in New South Wales have been examined using chemical, X-ray, differential thermal, and electronprobe techniques. The chlorites vary from pennine to sheridanite. Some segregations occupy the central zone in metasomatic sequences of altered chromite, chlorite, and lizardite; but others may have formed at junctions of serpentinite and rodingite.
Perryite in the Kota-Kota and South Oman enstatite chondrites
Authors: Reed S. J. B.
Published: December 2006

Electron-microprobe scanning pictures and quantitative analyses of the nickel silicide perryite in the Kota-Kota and South Oman enstatite chondrites are given. Comparative data for the narrow perryite lamellae in the Horse Creek iron meteorite are included. Perryite in these meteorites lies within the limits 75–81% Ni, 3–7 % Fe, 12–15 % Si, 2–5 % P.
Onoratoite, a new antimony oxychloride, from Cetine di Cotorniano, Rosia (Siena, Italy)
Authors: Belluomini G. , Fornaseri M. , Nicoletti M.
Published: December 2006

Onoratoite, a new antimony oxychloride Sb8O11Cl2 from the antimony mines of Cetine di Cotorniano, Rosia (Siena, Italy), is triclinic with lattice constants a 18·92, b 4·03, c 10·31 Å, α ≃ γ ≃ 90°, β 110°. Density 5·3 meas., 5·49 calc. The needle-like crystals are elongated on [010] and show as prominent form {001}. Other forms present are {100}, {201}, {401}, {412}.

The new mineral is optically biaxial negative, extinction angle small and variable from 0° to 14°. Orientation β:[100] ca. 8°; α:[001] ca. 12°; γ:[010] 0 to 14°. Refractive indices are 2·26 > γ > 2·23, 2·23 > β > 2·18. Birefringence γ-β 0·024 (meas.).

The stability field of onoratoite has been investigated by systematic thermo-gravimetric and differential thermal analysis of antimony oxychlorides and by a direct study of equilibrium relationships in the system SbCl3-Sb2O3-HCl-H2O. The probable mechanism of formation of onoratoite is discussed.

Onoratoite is named in honour of the Italian mineralogist Ettore Onorato.
An experimental study of ordering in sodium-rich alkali feldspars
Authors: Parsons Ian
Published: December 2006

Variations in the value of 2θ131 – 2θ13̄1 of two anorthoclase feldspars of compositions Ab95Or5 and Ab90Or10 were investigated by hydrothermal crystallization of gels for long periods in the temperature range 500–950 °C, at water vapour pressures up to 15 000 lb/in.2. The results are compared to those obtained by MacKenzie (1957) for pure albite. It is shown that the variation in 2θ131 – 2θ13̄1 is largely the result of Al-Si order-disorder and that at 700 °C and above the magnitude of the variation in the anorthoclases suggests that the degree of order is like that in albite, but at lower temperatures, particularly below 600 °C, the variation is less, and the anorthoclases are less ordered than albite at the same temperatures. At 600 °C and above the rate of attainment of equilibrium is the same for all three compositions. Below 600 °C Ab95Or5 behaves differently to albite. At low temperatures the equilibrium degree of Al-Si order in mixed Na-K feldspars is a function of composition as well as of temperature of crystallization.
On the electrolysis of molten basalt
Authors: Oppenheim M. J.
Published: December 2006

The effects to be expected from the interaction of possible electric currents at depth with bodies of basaltic magma have been investigated experimentally. Trough-shaped molten specimens were produced in the surface of basalt blocks by heating from above ; the melts were electrolysed and the products analysed chemically.

Si, Al, Ti, P, Fe2+, and probably Fe3+are concentrated towards the anode, apparently in the form of drifting lattice remnants; oxygen gas is liberated. Na, K, Ca, Mn, and Mg ions concentrate towards the cathode.

Relatively to basalt, the cathodic product is an alkaline and femic rock with normative nepheline and a more acid plagioclase. The anodic rock is distinctly calc-alkaline and salic, with normative quartz and a plagioclase that is more basic. The precise ‘rock-type’ developed depends on the amount of electricity passed, but the trends are distinct. In that increasing basicity and alkalinity (cathodic rocks) are accompanied by both increasing Na/K and Mg/(Fe2++ Fe3+) ratios (which ratios decrease with decreasing basicity and alkalinity) the electrolytic series developed from a basalt magma appears to have few counterparts among natural rocks.
Cell dimensions of olivine
Authors: Louisnathan S. J. , Smith J. V.
Published: December 2006

Cell dimensions obtained from X-ray powder photographs of twenty-four natural olivines and one synthetic forsterite have been related to the cation contents by a new statistical procedure developed by M. H. Hey. Unlike conventional statistical analysis, which assumes error only in one parameter, this procedure simultaneously considers the estimated errors in all variables.

Linear terms in Ca, Mn, Mg (or Fe(≡ 1-Mg-Ca-Mn)) satisfactorily account for the cell dimensions, and there was no need to invoke a term in Mg2. Since there are three cell dimensions and three chemical unknowns, it is theoretically possible to estimate the major cations in olivine just from the cell dimensions. However, the coefficients for Mn and Fe are so similar and the ranges of Ca and Mn are so small that the technique would be impractical.

Data for ideal (Mg,Fe) olivines were estimated by adjusting the cell dimensions by linear extrapolation from the cell dimensions of tephroite and monticellite. A simple chemical term was sufficient to account for each cell dimension. The linear relation between cell volume and Mg is consistent with the complete disorder of Mg and Fe revealed by parallel single-crystal X-ray studies.

The cell dimensions of a synthetic fayalite deviate significantly from those of natural fayalites after correction for the effects of Ca and Mn substitution in the latter: some structural or chemical difference, probably involving ferric iron, is indicated.

No superstructure lines have been found, in contradiction to Eliséev's data.
The metallographic structure of the iron meteorites Arltunga, Kopjes ,Vlei, Murnpeowie, Braunau, and Rancho de la Pila
Authors: Axon H. J.
Published: December 2006

From a metallographic examination it is suggested that Rancho de la Pila is a shock-hardened octahedrite; Murnpeowie is a cosmically reheated meteorite of unusual composition; Kopjes Vlei may have been produced by the reheating of a shock-hardened hexahedrite either cosmically or on earth; Braunau shows signs of preterrestrial reheating but Arltunga is a nickel-rich ataxite with no signs of metabolic alteration.
Mineralogical note on the chrome-chlorite (kämmererite) and chrome-garnet (uvarovite) from the chromite deposits of Kalrangi, Orissa, India
Authors: Chakraborty K. L.
Published: December 2006

The geological set-up, chemical composition, physical and optical properties, and X-ray data of one sample of chrome-chlorite (kämmererite) and of a chrome-garnet (uvarovite) from Kalrangi chromite mines, Orissa, India, are presented here. Chrome-bearing solution contributed in the formation of both the minerals in the hydrothermal stage. It is suggested that the garnet is an intermediary form between uvarovite and pyrope.
Cation and anion substitutions in the humite minerals
Authors: Ribbe P. H. , Gibbs G. V. , Jones Norris W.
Published: December 2006

The humites are structurally analogous to olivine wherein the replacement of four oxygen by four (F,OH) anions in the slightly distorted, hexagonal close-packed array is balanced by the replacement of one tetrahedrally coordinated Si by a tetrahedral void, according to the general formula Mg2xSix-1O4x-4(F,OH)4 where x = 3, 5, 7, 9. In humites the key structural units are not ‘olivine and sellaite (or brucite) layers’, as previously assumed, but are zigzag chains of edge-sharing octahedra, just as in olivines. It is shown that for humites and olivines alike the unit cell parameters a, b, and d001/n and the cell volume (normalized to one-half the mean anion-anion distance along the normal to (001)) vary linearly with the average radius of the octahedrally coordinated cation in the chain.

Substitutions of (F,OH) for O and vacancies for Si have second-order effects on the unit cell parameters, causing a linear decrease of the normalized cell volume with increase in F/O ratio in the synthetic series forsterite-humite-norbergite. Comparison of the crystal structures of forsterite and norbergite shows that the polyhedral distortions in norbergite are smaller than in forsterite in accord with the decreased number of shared edges: the fluorines in norbergite are bonded to three Mg atoms whereas all anions in forsterite are bonded to three Mg and one Si atom.
On the origin of translation lamellae in olivine
Authors: Gibb Fergus G. F.
Published: December 2006

Translation lamellae in olivine crystals are generally considered to be a result of mechanical deformation of pre-existing crystals but a recent hypothesis suggests that they may be formed during the latter stages of olivine crystallization in olivine-rich rocks due to the stresses imposed by mutual interference. Olivine crystals showing well-developed translation lamellae occur in the ultrabasic dykes of south-west Skye and it is demonstrated that these lamellae are unlikely to have been formed by mutual interference. Possible origins of the lamellae are considered and it is concluded that they are most likely to have been formed by tectonic deformation at elevated temperatures prior to the intrusion of the dykes.
Kaersutite from San Carlos, Arizona, with comments on the paragenesis of this mineral
Authors: Mason Brian
Published: December 2006

A 230 g kaersutite xenocryst from basalt at San Carlos, Arizona, has the composition SiO2 40·10 %, TiO2 4·44, Al2O3 14·53, Fe2O3 3·24, FeO 10·05, MnO 0·14, MgO 11·00, CaO 11·06, Na2O 2·99, K2O 1·62, H2O + 0·73, H2O − 0·10; D = 3·28; α 1·680, β 1·700, γ 1·715; a 9·858 Å, b 18·063 Å, c 5·315 Å, β 105° 14′. Kaersutite occurring as xenocrysts in basic volcanic rocks and tuffs, and as a phase in garnet-pyroxene xenoliths from such rocks, is probably of upper mantle origin, and may be the important potassium-bearing phase in this region.
Temperature control and calibration in quench furnaces and some new temperature measurements in the system CaO–MgO–Al2O3–SiO2
Authors: Biggar G. M. , O'Hara M. J.
Published: December 2006

Techniques associated with temperature control and measurement in quench furnaces are described and a study made of calibration problems. Systematic temperature errors as great as 30°C in published results from separate laboratories are explicable. A comprehensive redetermination of temperatures of invariant equilibria in systems containing CaO, MgO, Al2O3, SiO2, Na2O, Fe-O2, has been initiated and the results to date are presented, including approximate determinations of three invariant equilibria in the system CaO-MgO-Al2O3-SiO2 involving liquid, monticellite, spinel, and two of merwinite, periclase, and forsterite, which are important in the melting of magnesia refractories, and precise determinations of the three newly recognized invariant equilibria involving liquid, spinel, diopside, and two of forsterite, melilite, and anorthite.
Axinites from the contact skarns of the Meldon aplite, Devonshire, England
Authors: Nawaz Chaudhry M. , Howie R. A.
Published: December 2006

Chemical analyses, optical properties, and specific gravities are presented for nine axinites. A reciprocal substitution relationship is demonstrated between Mg and Mn2+, and a linear variation diagram is constructed between refractive indices and the (Fe2++Fe3++Mn2++Ti) ions calculated on the basis of 16(O,OH). The composition of these axinites is independent of the composition of their host rocks; their colour appears to be independent of the Fe2+/Mn2+ ratio for the range of iron and manganese values of the specimens investigated.
Further detail on the crystal structure of zussmanite
Authors: Lopes-Vieira A. , Zussman J.
Published: December 2006

Mineral data and a brief outline of the structure for zussmanite (ideal formula

KFe13Si17AlO42(OH)14)

have been published previously. This paper describes the determination of the crystal structure and presents and discusses the results. The structure consists of rhombohedrally stacked layers of Fe-(O,OH) octahedra to each side of which are attached rings of six (Si,Al)-O tetrahedra. These composite layers are linked to one another by rings of three (Si,Al)-O tetrahedra, and by potassium atoms, the latter in positions analogous to those in a mica. There is some evidence of disorder of the layer stacking. Interatomic distances and angles, and valency balance, are discussed.
The chemistry and cell parameters of omphacites and related pyroxenes
Authors: Edgar A. D. , Mottana A. , Macrae N. D.
Published: December 2006

In an attempt to correlate the chemical compositions and cell sizes of omphacites and related pyroxenes, the cell dimensions of fifty-five analysed pyroxenes have been determined, or taken from the literature. Twenty-two of the chemical analyses are new, nineteen of them being done by electron microprobe. Approximately two-thirds of the total number of analyses may be considered first class, the remainder are of doubtful or unknown quality. Cell parameters, determined by X-ray powder diffraction methods, have errors of 0·1 % for the majority of samples, although for some samples taken from the literature errors are unknown.

The majority of methods of recalculating omphacite analyses into their end-member molecules are unsuitable for correlation of cell constants with chemistry, mainly due to the impossibility of graphical representation of more than three end-member molecules, and to the non-stoichiometry of these molecules. Using a modification of Tröger's (1962) method of recalculating chloromelanite analyses the present analyses have been recalculated into the diopside-jadeite-acmite and diopside-jadeite-hedenbergite molecules and compared with their determined cell parameters. Because of the gradations in all parameters between these end-member molecules, determination of compositions based on the cell parameters (a, b, c, vol, orβ) can only be made within wide limits. However, using a method of projection of compositions from the acmite and hedenbergite apices to the diopside-jadeite join the ratios of diopside to jadeite can be determined for most samples to within ±5 mol%. As there are the most important constituents of most omphacites, this method permits an approximate estimation of omphacite compositions. From a knowledge of the cell sizes of the omphacite a rough indication of the conditions of formation of its host rock may also be obtained.
Phase relationships in the join Ca(OH)2–CaCO3–Ca3(PO4)2–H2O at 1000 bars
Authors: Biggar G. M.
Published: December 2006

Phase equilibria involving calcite, apatite, portlandite, liquid, and vapour were determined at 1000 bars. Calcite, apatite, and portlandite melt at 654 °C to form a liquid of composition (wt %), Ca(OH)2 53 %, CaCO3 46 %, Ca3(PO4)2 1 %. With water present melting occurs at 635 °C to form a similar liquid with a low water content. The X-ray diffraction patterns of the equilibrium apatites were not significantly different from synthetic hydroxyapatite.
Relations between cell dimensions, chemical composition, and site preference of orthopyroxene
Authors: Smith J. V. , Stephenson D. A. , Howie R. A. , Hey M. H.
Published: December 2006

Cell dimensions have been measured from correctly indexed powder patterns of thirty natural and two synthetic orthopyroxenes. The natural specimens (mostly metamorphic) contain exsolved phases largely avoided during microprobe chemical analysis. Linear regression analysis between the cell dimensions and Mg, Al, Ca contents (ignoring minor elements) was quite unsatisfactory until a term in Mg2 was added. Two separate regression analyses for the ranges Mg 0–0·5 and 0·5–1 using only Mg, Al, and Ca were satisfactory. Olivine yielded satisfactory regressions for the whole range without a term in Mg2 (Louisnathan and Smith, 1968). The difference between olivine and pyroxene results from absence of site preference by Mg and Fe in olivine compared to strong preference in pyroxene revealed by electron density and Mössbauer studies (Bancroft, Burns, and Howie, 1967; Ghose and Hafner, 1967).

The data were recalculated by means of a new best-fit procedure developed by Hey in which the errors in the chemical and physical parameters are considered simultaneously.

Earlier measurements of a and b for plutonic pyroxenes are consistent within possible experimental uncertainties with those given here; however a and b data obtained by Kuno and by Hess on volcanic specimens are considerably higher by variable amounts. Although there are uncertainties in the Ca content and its effect on a and b, the larger dimensions probably result from lower site preference as indicated by Mössbauer studies.

Prediction of Mg, Ca, and Al from just the cell dimensions is only moderately accurate even for metamorphic orthopyroxenes.
Epitaxic relations between coexisting pyroxenes
Authors: Tarney J.
Published: December 2006

Many examples of epitaxic relations between coexisting pyroxenes are found in the picritic dykes that cut the Lewisian gneisses of the Lochinver area, Sutherland. In some dykes augite forms oriented overgrowths on the (100) face of orthopyroxene; in others orthopyroxene forms similar overgrowths on augite. A number of unusual variants of the first case are described together with a complex ‘induced’ twinning found in the augite overgrowths. Analyses of the coexisting pyroxenes suggest that the overgrowth relation has been facilitated by increased solid solution between the pyroxenes, so reducing the crystallographic misfit along the c-axis. However, crystallization of the pyroxenes in an ordered sequence rather than simultaneously also seems to have been an important factor.
Tavistockite and bialite discredited
Authors: Embrey P. G. , Fejer E. E.
Published: December 2006

Specimens of tavistockite fall into two groups: true tavistockite from the George and Charlotte mine, Tavistock, Devon, and wavellite from the Stenna Gwyn mine, St. Austell, Cornwall. Both were sold as tavistockite by the discoverer, Richard Talling.

Tavistockite proper is a fluorapatite, as shown by optical and X-ray examination, and the alumina and water in the original analysis are certainly derived from kaolinite with which the apatite is intimately associated.

The published optical properties attributed to tavistockite were determined by E. S. Larsen on Stenna Gwyn material, and are those of wavellite.

Re-examination of a portion of Buttgenbach's type bialite, which he related to tavistockite on optical grounds, shows it to be wavellite.
Thermal investigations on alunite and its mixtures with quartz and dickite
Authors: Kashkai M.-A. , Babaev I. A.
Published: December 2006

The thermal decomposition of alunite and of mixtures of alunite with dickite or quartz or both has been studied, and X-ray determinations of the products at various stages of the decomposition have been made. Between 600 and 700°C the product from alunite is a mixture of anhydrous alum and amorphous alumina; between 700 and 770°C the anhydrous alum breaks down into aluminium sulphate and alkali sulphate; then in the prominent 850°C endothermic reaction three-quarters of the sulphate is lost, leaving a mixture of alkali sulphate and γ-alumina. The area of the 850 °C endothermic peak may be used as a measure of the percentage of alunite in alunitized rocks (alunite-quartz-dickite mixtures).
A high-temperature X-ray study of the equilibrium forms of albite
Authors: Grundy H. D. , Brown W. L.
Published: December 2006

Complete lattice parameters have been determined at a series of temperatures up to 950 °C using a furnace on a powder diffractometer for six synthetic supposed equilibrium albites, a nonequilibrium albite, two natural albites, and a heat-treated natural albite. The supposed equilibrium albites were prepared hydrothermally by MacKenzie (1957) for long periods of time and reached or nearly reached a state of no further change at their temperatures of synthesis between 500 and 1000 °C. A crystal of natural albite and three crystals of heat-treated natural albite were studied by high-temperature, single-crystal methods on a Buerger precession camera up to 1000 °C for comparison.

The lattice angles for each albite decrease smoothly with increasing temperature; the a-axis and the volume increase smoothly with increasing temperature. The rates of change increase with increasing temperature. The c and in some cases the b-axes appear to decrease initially in the range 25–300 °C and then subsequently increase. The thermal dilatation is highly anisotropic—the change in a is about twice that in b and about six times that in c over the whole range 25–850 °C. The effect of a temperature rise on the lattice parameters of the albites is very similar to the effect of the substitution of potassium on the room-temperature parameters.

Plots of α* against γ* for each albite at a sequence of temperatures up to 950 °C fall on nearly straight parallel lines, all albites becoming less oblique (triclinic) with increasing temperature. Of the equilibrium albites, only the one synthesized at 1000°C becomes monoclinic below the melting point. The ratio d010/d001 or c*/b* is a measure of order in the albites and does not vary with temperature. The similar behaviours of this ratio and of other lattice parameters as a function of the temperature of synthesis confirms the two-step ordering process in albite.
A comparison of gel and glass starting materials for phase equilibrium studies
Authors: Biggar G. M. , O'Hara M. J.
Published: December 2006

A method of preparing compositions suitable for phase equilibrium studies in systems containing CaO-MgO-Al2O3-SiO2-Fe-O2-Na2O employing a gelling technique is described. The subsolidus assemblages obtained from the recrystallization of some of these gels and from the recrystallization of devitrified glasses of the same composition are compared. It is not yet clear whether either starting material has any advantage as the gels may retain early formed metastable phases and the glasses may fail to nucleate stable phases.
Relationships among 2:1 layer silicates
Authors: Whittaker E. J. W.
Published: December 2006

The relationships between the 2:1 layer silicates are discussed in terms of the charge balance between the ions occupying X, Y, and Z sites. This brings out the relationship of glauconite to the illites, and clarifies the reason for the ideal occupancy of the Y sites in montmorillonite. It not only shows hectorite, saponite, and sauconite to be tri-octahedral smectites, but also shows vermiculite to be a tri-octahedral analogue of the illites. Apparently anomalous differences in permitted compositions of the di-octahedral and tri-octahedral micas are explained in terms of mismatch between the tetrahedral and octahedral layers, and it is shown that ephesite is to be regarded as a tri-octahedral common mica, not an analogue of margarite. Anandite is the nearest known naturally occurring equivalent to a tri-octahedral analogue of margarite, but the true analogue is a barium magnesium mica synthesized by Frondel and Ito.
Physical properties of synthetic and natural pyroxenes in the system diopside–hedenbergite–acmite
Authors: Nolan J.
Published: December 2006

Unit cell dimensions and refractive indices have been determined for synthetic pyroxenes in the system CaMgSi2O6-CaFeSi2O6-NaFeSi2O6, which have been crystallized and annealed on the nickel-bunsenite (Ni-NiO) oxygen buffer curve at 700 °C and a total pressure of 2 kb. The data presented confirms the many postulates that a complete solid solution series does exist in the subsolidus region of the ‘ternary’ system. The unit cell dimensions show an almost linear change with composition between the end members. The determined cell parameters for a series of analysed natural alkali pyroxenes have been compared with the data for the synthetic pyroxenes and close agreement was found between both sets of data. The variation of the unit cell dimensions and refractive indices has been examined in relation to the possible ionic substitutions taking place in the pyroxenes.
Olivine recrystallization textures
Authors: Ragan Donal M.
Published: December 2006

Mosaic olivine textures, with straight triple grain boundaries meeting at angles of 120°, are common in dunites. This is a well-known feature of annealed metals, and is the result of grain-boundary migration during recrystallization in which the system tends toward a state of minimum interfacial energies. Geometrically similar textures are present at the boundaries between such mosaic grains and strain-banded relict olivine grains. The unstrained mosaic grains make angular projections into the strained grains exactly at the junctions between the deformation bands. These are interpreted to be triple junctions with the two differently oriented bands acting as separate grains, and thus also due to recrystallization.
An X-ray investigation of the thermal decomposition of portlandite
Authors: Brett N. H.
Published: December 2006

The thermal decomposition of portlandite, Ca(OH)2, has been studied in air and in vacuum using X-ray single-crystal techniques. In air, the crystals were decomposed in situ on the goniometer arcs whilst X-ray reflections were simultaneously recorded. The transformation to CaO was not accompanied by topotaxy; this is attributed to the high nucleation rate of CaO crystallites in air. When Ca(OH)2 single crystals were decomposed under vacuum (and subsequently exposed to X-rays), some orientation of the CaO crystallites occurred. These results are compared with those of previous workers using electron-diffraction techniques. Decomposition of Ca(OH)2 single crystals commences at ∼ 450 °C in air and at ∼ 230 °C in a vacuum of 10−6 mmHg; reaction commences at crystal edges and surface defects, the reaction boundary moving inwards to the centre of the crystal. This observation is consistent with a homogeneous mechanism of decomposition.
On the oriented transformation of Ca(OH)2 to CaO
Authors: Datta N. , Chatterji S. , Jeffery J. W. , Mackay A. L.
Published: December 2006

The conversion of Ca(OH)2 to CaO has been studied by X-ray diffraction techniques. When Ca(OH)2 crystals are heated in vacuo the conversion is oriented, but not when they are heated at atmospheric pressure. This difference is attributed to the lowering of the decomposition temperature in vacuo and consequent lower thermal vibration.
Quantitative determination of water in granites by infra-red analysis
Authors: Aucott J. W. , Marshall M.
Published: December 2006

Two methods using nujol and hexachloro-butadiene mulls are described to analyse the water content of powdered granite samples. The nujol mull analyses were carried out on a Unicam SP 100 spectrometer using the silica content of the rock as an internal standard. The hexachlorobutadiene mull analyses were done by a twin-path Unicam SP 200 spectrometer, using hexachlorobutadiene as the internal standard. The broader and more pronounced V1 vibrational mode (3450 cm−1) is ratioed to a standard of known composition. Comparisons are also made between absorption due to free water (V1 = 3450 cm−1) and combined water (V3 = 3680 cm−1) in aplites, biotite granite, and chlorite schists.
The application of scanning electron beam anomalous transmission patterns in mineralogy
Authors: Jones M. P. , Gavrilovic J.
Published: December 2006

It is possible with a standard Geoscan microanalyser to produce back-scattered electron pictures that resemble Kikuchi patterns but which are produced by a different mechanism. These effects have been called scanning electron beam anomalous transmission (SEBAT) patterns and they are produced by the interaction of a parallel scanning beam of high-energy electrons with a crystalline sample. The patterns are excellent indicators of the crystallographic perfection and orientation of samples and can provide information about the lattice dimensions of solid, bulk specimens. The same specimens can, if necessary, be chemically analysed in the same instrument.

In order to produce the patterns the electron beam must be deflected through a minimum angle of approximately 20° and, on existing instruments, the beam covers an area of about 2 × 2 mm during such a deflection. Minor modification of the authors' microanalyser has reduced the scanned area to 0·5 × 0·5 mm and attempts are being made to reduce this even further.

In favourable circumstances the technique enables the mineralogist to determine, rapidly and easily, the crystallographic structure and orientation of large, bulk specimens. Examples are given of patterns that have been produced from cleaved, as grown, and polished mineral faces. The degree and nature of the crystallographic damage produced during mechanical polishing of a galena crystal are illustrated.
A metallographic and microprobe study of the Brenham pallasite
Authors: Axon H. J. , Yardley E. D.
Published: December 2006

A metallographic study has been made of the macroscopic and microscopic features of the Brenham pallasite. The microprobe has been used to investigate the condition of kamacite inter-faces with second kamacite grains, olivine, schreibersite, troilite, and taenite and of taenite interfaces with olivine. The results indicate that grain-boundary migration of nickel may be important in these structures.
The Credo and Fenbark meteorites, new finds of common chondrites from north-west of Kalgoorlie, Western Australia
Authors: McCall G. J. H. , Cleverly W. H.
Published: December 2006

Two new finds of stony meteorites north-west of Kalgoorlie are described, and the masses covered by brief petrographic descriptions.
Comments on ‘Kaersutite from San Carlos, Arizona, with comments on the paragenesis of this mineral’ by Brian Mason
Authors: Prinz Martin , Nehru C. E.
Published: December 2006

Electron probe analyses have been made of eight kaersutites from San Carlos, Arizona, and one from Kakanui, New Zealand; also of olivine, clinopyroxene, ilmenite, and spinel from San Carlos. There is not as yet adequate evidence that the kaersutite is an upper mantle phase.
Segregation and cation-ordering in sjögrenite and pyroaurite
Authors: Taylor H. F. W.
Published: December 2006

A specimen from Långban, Sweden, was found to consist largely of sjögrenite in which segregation and ordering of the metal cations had occurred, yielding an intergrowth of regions of two main types with compositions probably of or near Mg2/3Fe1/3(OH)2(CO3)1/6(H2O)0·4 and Mg12/13Fe1/13(OH)2(CO3)1/26(H2O)0·8. To a smaller extent segregation had proceeded further, giving regions probably approximating to the end-member Mg(OH)2.H2O. It is suggested that the names sjögrenite and pyroaurite be used for the 2H- and 3R- polytypes of this structure irrespective of Mg:Fe ratio, segregation, or cation ordering.
Electron microprobe analyses of chlorine in hornblendes and biotites from the charnockitic rocks of Kondapalli, India
Authors: Leelanandam C.
Published: December 2006

Chlorine is estimated in nine hornblendes (0·13–1·12%) and nine biotites (0·19–0·62%) from the Kondapalli charnockites for the first time, using the electron microprobe. The data obtained suggest that these Kondapalli minerals are unexpectedly and unusually rich in Cl, which is well equilibrated in the five available coexisting hornblende-biotite pairs.
Study of minerals from the pegmatites of the Nellore mica-belt, Andhra Pradesh, India Part III—Biotite
Authors: Babu V. R. R. M.
Published: December 2006

The biotites in the pegmatites are Fe2+ type. X-ray analyses indicated that they are 1M or 3T polymorphs. In the colour of the biotite iron plays an important role. From the Fe/(Fe+Mg) ratios, the analysed biotites are assumed to have crystallized between 760 and 500 °C.
On the X-ray identification of amblygonite and montebrasite
Authors: Moss A. A. , Fejer E. E. , Embrey P. G.
Published: December 2006

Previous investigations have been confined to individual members or to small compositional ranges of the amblygonite-montebrasite series. The present study is a survey based on twenty-two specimens in the range Amb14Mon86 to Amb92Mon8 (1·8–11·8 % fluorine), and indicates that the fluorine content may be related both qualitatively and quantitatively to differences in the X-ray powder patterns. Fully indexed powder data to d = 1·68 Å and derived cell parameters are given for four members of the series. There is no evidence of a break in the continuity of the series. The first British occurrence of both amblygonite and montebrasite is reported from a pegmatite vein in aplite at Meldon, Okehampton, Devonshire.
Staringite, a new Sn–Ta mineral from north-eastern Brazil
Authors: Burke E. A. J. , Kieft C. , Felius R. O. , Adusumilli Maria S.
Published: December 2006

Staringite, (Fe,Mn)0·5(Sn,Ti)4·5(Ta,Nb)1·0O12, occurs as inclusions in tapiolite from pegmatites at Seridózinho and Pedra Lavreda, Paraiba State, NE. Brazil. An indexed powder pattern is presented. The mineral is tetragonal with a 4·742 Å and c 9·535 Å, and most probably has a ‘trirutile’ structure. Electron-microprobe analysis yielded Ta2O5 21·5%, Nb2O5 1·8, SnO2 73·3, TiO2 0·03, FeO 3·7, MnO 0·3, sum 100·6%. Dcalc 7·17. Micro-indentation hardness (load 100 g) 1033–1187 kg/mm2; reflectivity at 470 nm (R0) 12·8 to (R′e) 14·5%, at 546 nm 12·1–13·9, at 589 nm 12·0–13·7, and at 650 nm 11·8–13·6; staringite is uniaxial positive.
Harmotome from the Tokatoka district, New Zealand
Authors: Black Philippa M.
Published: December 2006

Harmotome, associated with analcime, is described from andesite dykes at Rehia and Maungarahu in the Tokatoka district, New Zealand. The Maungarahu harmotome has the composition: (Na1·03K0·23)(Ba1·54Ca0·18)Al4·66Si11·31 12·39 H2O; physical properties: α 1·498, β 1·503, γ 1·506, 2Vγ 75–82° β:[001] 28° D 2·378; and cell constants: a 9· 906±0·006, b 14·119 ±0·003, c 8·712±0·007 Å, β 124° 57′ ± 3′. The harmotome is Ba-poor, and 2 Na+ has substituted for Ba2+ on a valency basis. Analcime associated with the Maungarahu harmotome has chemical composition: (Na15·16 K0·03Ca0·09)Al15·52Si32·47 15·93 H2O and physical properties: n = 1·483, D = 2·257, a = 13·708 Å. The zeolites are believed to have crystallized from Na and Ba-rich alkaline solutions at approximately 200°C The source of the Ba is baryte concretions in adjacent limestones.
Formation of the hour-glass structure in augite
Authors: Strong D. F.
Published: December 2006

A study of augite in over three hundred thin sections of mainly alkalic rocks permits the distinction of two main types of hour-glass structure. The common ‘swallow-tailed’, sometimes skeletal augite crystals are found in the fine-grained groundmass of many rock types, and it is suggested that rapid crystallization alone accounts for their formation. Hence, this type of hour-glass structure has been called ‘quench hour-glass’. The hour-glass structures of larger augite crystals of porphyritic and coarse-grained rocks are commonly described as hour-glass ‘zoning’, as they result primarily from compositional differences between the different sectors. These were formed under conditions of relatively slower cooling than the ‘quench hour-glass’, and thus cannot be explained in the same way. They are thought to have formed by a process involving adsorption of impurities on a particular crystal face so as to impede growth of these faces, producing an initial skeleton of hour-glass form, which is completed by later crystallization of augite richer in FeO, Na2O, TiO2, and Al2O3. This hypothesis also explains the patchy zoning of other augite crystals, casting doubt on some petrogenetic interpretations of such zones as core zones.
Porphyritic plagioclase–hornblende–pyroxene granulite from charnockitic rocks of Chipurupalli, Visakhapatnam district, Andhra Pradesh, South India
Authors: Rao K. S. R. , Rao A. T. , Sriramadas A.
Published: December 2006

An unusual occurrence of porphyritic plagioclase-hornblende-pyroxene granulite (porphyritic basic charnockite) has been observed within the ‘Charnockite region’ of the Eastern Ghats of the Precambrian formations of India. From the X-ray and chemical data the phenocrysts are considered to be augite phenocrysts. Based on petrographic and chemical evidence it is inferred that the basic charnockites of Chipurupalli area in Visakhapatnam district are formed from tholeiitic magma as a gabbroic mass under deep seated plutonic conditions. The gabbroic mass has been recrystallized as plagioclase-hornblende-pyroxene granulite due to later metamorphism, leaving most of the phenocrysts unaffected.
Cognate xenoliths in the Tertiary uhrabasic dykes of south-west Skye
Authors: Gibb Fergus G. F.
Published: December 2006

A group of ultrabasic dykes occurring in south-west Skye is typified by often abundant and diverse ultrabasic xenoliths composed of essentially the same minerals as the dykes. The xenoliths, which vary considerably in shape and size, are in sharp contact with the host rocks and exhibit no evidence of remelting by, or reaction with, the dykes. Although extensive axial concentration of olivine occurred in the dykes during intrusion, the xenoliths appear to be randomly distributed throughout all but the extreme margins of the dykes and often exhibit a preferred orientation. The orientation and distribution of the xenoliths are attributed to the suppression of rotation and axial migration of the xenoliths during the emplacement of the dykes because of the relatively high viscosity of the suspending medium.

The ultrabasic xenoliths, unlike many of those occurring in basalts, kimberlites, etc., are considered unlikely to represent primary upper mantle material and it is suggested that they were probably derived by the disintegration of layered ultrabasic rocks genetically related to the dykes and hence are of cognate origin.
Paragenesis of staurolite in pelitic
schists of Kishangarh, District Ajmer,
India
Authors: Lal R. K. , Shukla R. S.
Published: December 2006

The staurolite-bearing schists of the area
were metamorphosed in the staurolite-kyanite zone
of the amphibolite facies. The various assemblages
of the pelitic schists are represented in the AKF
and Thompson's AFM diagrams. Within the
PT conditions of
stability of staurolite, this mineral develops in
pelitic schists that have a high
Al2O3
(excess)/(K2O+FeO+MgO) ratio
so that the plots of analyses lie above the
muscovite-garnet join in the AKF diagram. The
three-phase field of staurolite-kyanite-biotite in
the AFM diagram migrates towards the lower FeO/MgO
side with increasing oxidation ratio and thus
staurolite-bearing rocks are not necessarily
restricted to pelitic schists with high FeO/MgO
ratio as is commonly believed. On the other hand,
the three-phase field shifts towards the higher
FeO/MgO side with increasing grade of metamorphism
assuming oxidation ratio and pressure to be
constant, thus reducing the composition field of
staurolite schists in the AFM diagram.
On the electrolysis of basalt, II:
experiments in an inert atmosphere
Authors: Oppenheim M. J.
Published: December 2006

The recently described electrolysis of
molten basalt (Oppenheim, 1968) gave indefinite
results with regard to the behaviour of iron.
Repeating the experiments in an inert atmosphere
has shown that ferric iron moves towards the
anode, and ferrous iron to the cathode. All
metallic ions of valency three and more are now
seen to be concentrated towards the anode, with
relative enrichments in decreasing order:
Fe3+, P, Ti, Si, and Al; and
oxygen gas is released at the anode. Metals of
valency one and two are concentrated towards the
cathode with relative enrichments in decreasing
order: Na, Fe2+, K, Ca, Mn,
and Mg.

The series expected to be differentiated
within a magma consequent upon its electrolysis is
redefined. The absence of natural analogues
suggests either the non-operation of suitable
electric currents within magmas, or the
destruction of their effects by convection,
fractional crystallization, or both. An
electrolytic process is feasible at the
mantle-core boundary, leading mainly to deposition
of iron on the core and release of oxygen
upwards.
Reactions in the system
CaO-MgO-SiO2-H2O.
Hydrothermal treatment of some compositions on the
joins
Ca3Si2O7-Mg3Si2O7
and
Ca2SiO4-Mg2SiO4
Authors: Speakman K.
Published: December 2006

The effects of hydrothermal treatments on
gel mixtures and synthetic minerals in the
C3S2-M3S2
and
C2S-M2S
regions of the CaO-MgO-SiO2
system have been investigated. The products formed
in the temperature range 180-350°C at pressures up
to 220 N/mm2 were identified.
The reactants generally behaved as simple mixtures
of binary silicates and their products agreed well
with existing data for reactions in the
CaO-SiO2-H2O
and
MgO-SiO2-H2O
systems. An unidentified phase that resulted from
the hydration of åkermanite could be a new
compound in the quaternary
CaO-MgO-SiO2-H2O
system. There was no evidence to indicate that a
magnesium analogue of kilchoanite can be formed
from materials that are isostructural with
γ-Ca2SiO4.
Optical data on some authigenic feldspars
from Western Australia
Authors: Glover J. E. , Hosemann P.
Published: December 2006

Authigenic envelopes up to 0·18 mm thick
on clastic potassium feldspar grains from arkoses
and subgreywackes of the Devonian Nannyarra
Greywacke have been examined with the four-axis
universal stage. The plane of the optic axes is
parallel to (010) in some segments of individual
envelopes and normal to (010) in others, and the
range of 2Vα over all
envelopes is from close to 0° to 65°. The optics
are ascribed to modifications of potassium
feldspar corresponding to high-and low-sanidine
and orthoclase.
The Mössbauer spectra of several micas and
related minerals
Authors: Hogg C. S. , Meads R. E.
Published: December 2006

Well-resolved Mössbauer spectra of several
dioctahedral and trioctahedral micas have been
obtained and subjected to detailed computer
analysis. Most of the spectra can be resolved into
two ferrous quadrupole doublets and one ferric
quadrupole doublet. In dioctahedral micas, ferrous
iron is seen to occupy the larger, more symmetric
octahedral site in preference to the smaller, less
symmetric site, confirming predictions made on the
basis of structure alone. In trioctahedral micas
there is still a tendency for ferrous iron to
occupy preferentially the more symmetric
octahedral site even though the two octahedral
sites are no longer distinguished by size. A
lithium-rich biotite gives a spectrum typical of
that expected from a mica with a zinnwaldite
structure, but the spectrum of a more
authenticated zinnwaldite could not be resolved
sufficiently for detailed structural
interpretation. The spectra of pyrophyllite and
talc give results that can be related to the
corresponding micas by considering their
respective structural differences. In none of the
micas studied was there evidence of ferric iron in
tetrahedral coordination. The ferrous: ferric
ratios obtained from the Mössbauer spectra do not
always agree with the chemical values. In several
cases the spectra show more ferrous iron than
found chemically. It is suggested that the
spectral values are more accurate, oxidation on
chemical analysis being the most likely source of
error.
Grandidierite from Cuvier Island, New
Zealand
Authors: Black Philippa M.
Published: December 2006

Grandidierite has been found in hornfelses
around a diorite stock on Cuvier Island. Physical
properties and electron microprobe analyses are
given for two Cuvier Island and two Madagascan
grandidierites. The Cuvier Island grandidierite
has crystallized under conditions of the
K-feldspar-cordierite hornfels facies at
temperatures of approximately 600°C. and pressures
(Pload) of less than 300
bars.
On the occurrence of varlamoffite at the
Sardine tin mine, North Queensland,
Australia
Authors: Taylor R. G. , Morgan W. R. , Phillips D. N.
Published: December 2006

A new occurrence of varlamoffite is
described, and the results of chemical analysis,
differential thermal analysis, and infra-red
spectrographic analysis are presented. It is
suggested that varlamoffite is of secondary origin
resulting from the attack of meteoric waters on
stannite.
Pyroxenes from non-carbonaceous chondritic meteorites
Authors: Binns R. A.
Published: December 2006

Chemical, optical, and X-ray data are presented for pyroxenes from a representative selection of chondrites. The Mg-Fe pyroxenes originally crystallized above 1000-1200 °C as the protoenstatite-protohypersthene polymorph, and inverted on cooling to the polysynthetically twinned clinoenstatite-clinohypersthene polymorph. In most chondrites the latter became converted to orthopyroxene during recrystallization at temperatures ranging up to 900 to 950 °C. The contents of certain minor elements changed during the clino-ortho inversion. Ancestral protoenstatiteprotohypersthene may have been slightly non-stoichiometric. Accessory Ca-rich pyroxenes are discussed briefly.
Pyroxene and biotite from the charnockitic rocks of Garbham area, Srikakulam district, Andhra Pradesh, India
Authors: Bhattacharyya C.
Published: December 2006

Chemical analyses and optical properties of ten orthopyroxenes, two clinopyroxenes, and six biotites (partial analyses) are presented from basic to intermediate charnockites of the Garbham area. The orthopyroxene is hypersthene to ferrohypersthene and the clinopyroxene is sahlite. Biotite has secondarily formed from pyroxene, particularly orthopyroxene, as a result of injection of potassic fluid in the basic charnockite. By combining the data of Srikakulam with those from other areas of the world it is shown that during the transformation of pyroxene to biotite in charnockitic rocks, in general, Mg and Fe2+attain near-equilibrium distribution between orthopyroxene and biotite as well as between clinopyroxene and biotite. The magnesium distribution coefficient (KD) of coexisting orthopyroxene and biotite is found to increase with the increase of temperature of biotite formation. A tentative geothermometric scale has been proposed plotting temperature of biotite formation against magnesium distribution coefficient of coexisting orthopyroxene and biotite. According to this scale, biotite in basic and semibasic charnockites from Garbham has formed between 285 and 465 °C.
Application of the muscovite-paragonite geothermometer to a staurolite-grade schist from Sulitjelma, north Norway
Authors: Henley K. J.
Published: December 2006

The occurrence of coexisting paragonite (containing 0·70 % CaO) and muscovite (containing 0·16 % CaO) in a staurolite-grade paragonite-muscovite-hornblende-garnet-biotite schist from Sulitjelma enables an estimate to be made of the temperature of recrystallization, using an extension, based on crystal chemistry considerations and available analyses of muscovites and paragonites from metamorphic rocks, of the experimentally determined solvus in the K-Na white mica system into the Ca-K-Na system. This temperature of recrystallization is approximately 550–70 °C and is consistent with the experimental data on the coexistence of staurolite and quartz in the system Fe-A1-Si-O-H (Richardson, 1968).