bluuebunny/crossref_metadata_2025_split huggingface dataset:
Minor element chemistry of leucite and pseudoleucite
Authors: Henderson C. M. B. 
Published: December 2006

SummaryLeucite and pseudoleucite invariably have lower K/Rb ratios and higher K/Sr and K/Ba ratios than the groundmasses of the rocks in which they occur. The distribution of Rb, Sr, and Ba between K-rich minerals (e.g. alkali feldspars) and the liquids from which they crystallize is generally such that Rb is impoverished and Sr and Ba enriched, relative to K, in the crystallizing phase. Leucite shows the opposite relationship and this is attributed to the leucite structure being sensitive to the size and valency of the ions replacing K.
Electron-probe micro-analysis of the iron–titanium oxides in some New Zealand ironsands
Authors: Wright J. B. , Lovering J. F. 
Published: December 2006

SummaryThe electron probe was used to analyse for Fe, Ti, Mg, Al, and Mn. Vanadium could not be determined because of interference from Ti. Calcium was shown to be present only in inclusions of apatite and silicate; it does not oceur in the titanomagnetite structure.Homogeneous grains (magnetite-ulvöspinel solid solutions) do not vary greatly in bulk composition, averaging close to 61% Fe and 8 % TiO2. Inhomogeneous grains contain variable amounts of hematite-ilmenite lamellae produced by progressive oxidation of the homogeneous grains. In the early stages there is rapid build-up of titanium in the rhombohedral lamellae, which are initially relatively poor in iron. As oxidation proceeds the almost titanium-free cubic phase becomes strongly enriched in magnesium, aluminium, and manganese, while the iron: titanium ratio in the rhombohedral phase increases. The end-product may be a homogeneous titanhematite, if initial concentrations of Mg, Al, and Mn are low. Otherwise residuals of a relatively iron-poor almost titanium-free (Mg, Al, Mn)-enriched cubic phase remain in the titanhematite. The behaviour of iron and titanium agrees with recent synthetic work in the system. Some of the oxidized grains contain transparent spinel lamellae exsolved from the cubic phase. Exsolution may commence at different stages in the oxidation process, but the reason is not clear—there are no significant differences in the composition of phases with and without spinel lamellae.Analyses and normative compositions are presented for the different phases in each grain, where possible. The compositional changes accompanying oxidation satisfactorily explain the slope of the thermomagnetic curves : there is no need to invoke bulk compositional variations within a given ironsand sample.Samples from an ilmenite and a non-titaniferous magnetite concentrate were also briefly examined.
A note on varlamoffite and associated minerals from the Batang Padang district, Perak, Malaya, Malaysia
Authors: Alexander J. B. , Fliter B. H. 
Published: December 2006

SummaryA new occurrence of varlamoffite is described, and the status of this species is considered; the term is best employed for cryptocrystalline yellowish material consisting predominantly of Sn and H20 that may yield a diffuse powder pattern comparable to, or closely resembling that of cassiterite, but does yield a powder pattern identical with that of cassiterite after heat-treatment at about 1200° C. A new mineral, malayaite, CaSnSiO5, is briefly described; it is isostructural with sphene.
The origin of accessory garnet in the Donegal Granite
Authors: Hall Anthony , Tyler R. C. 
Published: December 2006

SummaryIn the Donegal Granite garnet occurs as an accessory mineral in muscovite-granties, pegmatites, and aplites. The composition of the garnet in fourteen samples of granitic rock has been determined from the physical properties and three new chemical analyses are given. All the samples examined are intermediate in composition between almandine and spessartine. The reason for the high manganese content in garnet from granites is discussed.
Kamacite plate width estimation in octahedrites
Authors: Frost M. J. 
Published: December 2006

SummaryTables are given which enable a quick estimate to be made of the true thickness of kamacite plates from measurements of the Widmanstetter figure on a single random plane. The method is applied to the following meteorites (width in mm following name): Arispe, 2·90; Brenham, 0·91; Duketon, 1·13; Henbury, 0·74; Ogallala, 1·53; Thule, 0·89; View Hill, 0·62.
The petrographic use of the spindle stage and focal-plane screening in the determination of the optical variation of some zoned minerals
Authors: Wright Hedley G. 
Published: December 2006

SummaryThe Equivibration Curve technique of Joel (1963) is used to determine the orientation of a zoned mineral on the spindle stage axis and an average value for 2V. A bracketing method enables the extreme values of each refractive index to be determined for sodium light on a single grain, using the Focal-plane Screening technique of Cherkosov (1960).
A note on the 01 spacing of some lime-rich alkali feldspars from Kangerdlugssuaq, East Greenland
Authors: Kempe D. R. C. 
Published: December 2006

SummaryThe values of 2θ 01 for some homogenized lime-rich fine microperthites from the Kangerdlugssuaq alkaline intrusion, East Greenland, are investigated and found to be consistently high when compared with the values used in the standard curves for estimating the Or content of alkali feldspars. This deviation, which is approximately proportional to anorthite content, results in anomalously low Or percentages being obtained and is ascribed to a distortion of the structure due to the unusually high calcium content of the microperthites.
The measurement of large optic axial angles with the universal stage
Authors: Munro M. 
Published: December 2006

SummaryA comparison has been made of the relative speed, accuracy, and precision of several methods of measuring large optic axial angles with the universal stage. It is concluded that a method based on the direct location of a single optic axis and the application of the Biot-Fresnel law will frequently be the most satisfactory when only the standard, low refractive index centre plate for the stage is available. If a centre plate of high refractive index is employed, however, good results can normally be obtained by using the more rapid method based on the direct location of both optic axes.
Secondary clay in Rajmahal basalts of India and its relation to palagonite-chlorophaeite
Authors: Sarbadhikari T. R. , Bhattacherjee Santi 
Published: December 2006

SummaryThe mineralogy of the green, yellow, and brown secondary constituents occurring as amygdales, irregular infillings, and replacements in the Rajmahal basalts of eastern India and commonly described under the ill-defined names palagonite and chlorophaeite, has been revised on the basis of optical, X-ray, and thermal studies. The results indicate that these coloured constituents, which have been chiefly derived by the alteration of pyroxenes, iron ores, and primary glass, belong to the clay minerals, particularly smectite and vermiculite. This brings in question the validity of the terms palagonite and chlorophaeite which, though widely current in basaltic literature, have no definite mineralogical identity. It is suggested here that they are but forms of clay.
Unit cell volumes of synthetic orthoenstatite and low clinoenstatite
Authors: Stephenson D. A. , Sclar C. B. , Smith J. V. 
Published: December 2006

SummaryCell dimensions and densities derived from least-squares refinement of X-ray powder diffractometer patterns are: orthoenstatite, a 18·2249±0·0013, b 8·8149±0·0008, c 5·1746±0·0008 Å, V 831·30±0·14 Å3, D 3·208 g/cc ; low clinoenstatite, a 9·6065±0·0011, b 8·8146±0·0007, c 5·1688±0·0006 Å, β = 108·335± 0·009, V 415·46±0·09 Å3, D 3·210 gm/cc. Because orthoenstatite transforms reversibly to clinoenstatite at high pressure and low temperature, and because a statistical test shows that orthoenstatite is less dense than clinoenstatite at the 90 % confidence level (in accord with the direction of slope of the experimental transition curve), it is no longer possible to regard low clinoenstatite as a metastable form of MgSiO3.
Residual glasses from some alkali basaltic lavas from New South Wales
Authors: Wilkinson J. F. G. 
Published: December 2006

SummaryThe glassy residua from an alkali olivine-basalt and a nephelinebasanite are respectively alkali trachytic and phonolitic in composition and contrast strongly with the compositions of the host rocks. The analysis of the glass from the alkali olivine-basalt reveals appreciable normative corundum, which is considered a consequence of the crystallization of excessive diopsidic clinopyroxene. This results in a deficiency in lime relative to alumina during the crystallization of much of the plagioclase. A consideration of the compositions of the glasses and the salic differentiates from alkaline basic intrusions indicates that the development of either trachyte or phonolite depends on differing degrees of undersaturation of the parental basic magmas.
On the oriented conversion of Ca(OH)2 to CaO
Authors: Chatterji S. , Jeffery J. W. 
Published: December 2006

SummaryIn order to study the orientational relationship between Ca(OH)2 and CaO, the transformation was carried out in stages inside an electron microscope by condensing the electron beam, and the process was monitored by electron diffraction. It has been found that at the initial stage all the hexagonal spots of Ca(OH)2 split into two ; on further heating one set of spots disappear. The remaining set of spots corresponds to the CaO structure, which has an orientational relationship to the hydroxide structure. To estimate the degree of orientation, a sample of brucite was treated in a similar way to the Ca(OH)2; a comparison shows that a high degree of orientation is preserved in the conversion of Ca(OH)2 to CaO. This observation is contrary to earlier reports.
The Barwell meteorite
Authors: Jobbins E. A. , Dimes F. G. , Binns R. A. , Hey M. H. , Reed S. J. B. 
Published: December 2006

SummaryPart of a meteorite was seen to fall on a road (52° 33′ 55″ N., 1° 20′ 23″ W.) in the village of Barwell, Leicestershire, at about 16.20 hrs G.M.T. on 24 December 1965. Fragments have been found over an area some ¾ mile long by ½ mile across, and appear to have been part of a single stone, of which 44 Kg (97 lb) have been recovered. The distribution, impact effects, and crustal morphology of the recovered fragments are described. Barwell is a moderately metamorphosed white olivine-hypersthene chondrite; a chemical analysis, with the derived Wahl norm, and a modal analysis are given, together with optical data and electron-probe analyses of the principal constituent minerals.
The dehydroxylation behaviour of amphiboles
Authors: Freeman A. G. 
Published: December 2006

SummaryThe temperature at which dehydroxylation occurs in amphiboles is thought to be largely dependent on the type of cation that occupies the M3 and M1 sites. Four amphibole types have been studied in which these sites are occupied, in various proportions, by Mg2+ or Fe2+. The temperature of dehydroxylation, in an inert atmosphere, is shown to rise with increasing Mg2+ content in these sites.
A simplified method of 2 V determination using 3- and 4-axis stages
Authors: Ehlers Ernest G. 
Published: December 2006

SummaryA method is presented for use with a 3- or 4-axis stage whereby a biaxial mineral, after being oriented into the cardinal position by means of the inner vertical, NS., and EW. axes, can be placed into an orientation suitable for measurement of the 2 V as required by the Berek method. A table of the necessary manipulations is given. The stereographic projection is only used to determine rotational corrections.
Psilomelane from India
Authors: Mukherjee Bibhuti 
Published: December 2006

SummaryMukherjee's definition of psilomelane, A3X6Mn8O16 of orthorhombic symmetry with the space group P222 and the dimensions determined for a single crystal of the Schneeberg sample, is found true for the psilomelane from Ratanpur, India. The indexing of powder data of the Ratanpur sample with the orthorhombic axes a 9·45, b 13·90, c 5·72 Å is most satisfactory.
Sideronatrite from mineralized cavities in the Rising Sun colliery, Backworth, Northumberland
Authors: Randall B. A. O. , Jones J. M. 
Published: December 2006

SummaryTwo unusual cavities at a Northumberland colliery are described. Although apparently of tectonic origin they do not seem to be related to any major fault. Sideronatrite, not previously recorded in this country, is thought to result from the alteration of the marcasite and pyrite lining the cavities by underground saline waters. These waters are the source of the baryte and gypsum that are also found in the cavities and of the salt stalactites in the disused roadways of the colliery.
Rhodonite from Meldon, Okehampton, Devonshire
Authors: Dearman W. R. 
Published: December 2006

SummaryThere are two outcrops of rhodonite rock at the same stratigraphical horizon in Lower Carboniferous rocks in the Railway Quarry at Meldon. One of these is zoned outwards from rhodonite, through calc-silicate hornfels to quartzite. Well-formed crystals occur in drusy massive rhodonite; examples have been measured and drawn.
Externally heated cold-seal pressure vessels for use to 1200° C at 1000 bars
Authors: Williams D. W. 
Published: December 2006

SummaryApparatus using cold-seal pressure vessels of molybdenum-0·5 %-titanium alloy, where each vessel is protected from oxidation by an argon gas jacket, is described. At 1000 bars pressure these vessels can be used for long runs at temperatures up to 1200° C, an increase of approximately 300° C over the range of conventional Stellite vessels. The possible use of other alloys to extend the range of this type of apparatus further is briefly discussed; pure tungsten has been shown to be too brittle.
A new British locality for beudantite: Sandford Hill, Somerset
Authors: Livingstone A. , Cogger N. 
Published: December 2006

SummaryA new British locality for beudantite [PbFe3(AsO4)(SO4)(OH)6] is recorded. The mineral is intimately associated with goethite; chemical, d.t.a., and thermogravimetric analysis data for the mixture are presented and a possible paragenesis suggested.
The petrology of the Mount Padbury mesosiderite and its achondrite enclaves
Authors: McCall G. J. H. 
Published: December 2006

SummaryThe petrography of the Mount Padbury meteorite, previously briefly recorded, is described in some detail. Both the metalliferous host material of the mesosiderite and the varied range of silicate-rich, virtually metal-free enclaves (including both familiar achondrite material and unfamiliar achondrite material) are described. Eucrite, brecciated eucrite, and a peculiar ‘shocked’ form of eucrite (resembling some terrestrial flaser-gabbros) are the calcium-rich achondrite types represented; hypersthene achondrite (including typical diogenite material and unfamiliar material) and olivine achondrite (granular aggregates of olivine not entirely similar to the unique chassignite and single crystals up to 4 in. in length) are the calcium-poor achondrite types represented. The eucrite displays more or less uniform mineralogy, but the mineral constituents are present in varying proportions, and there is a wide range of textural variations recognized. The silicate grain fragments enclosed in the metallic reticulation to form the mesosiderite host material are, significantly, entirely of minerals seen within the achondrite enclaves—plagioclase, hypersthene, pigeonite, olivine, and tridymite.These results include microscopic analysis of thin sections and polished sections, X-ray diffraction studies, optical determination of refractive indices using mineral grain mounts, and chemical analyses.The wider implications of this new and unique meteorite find are briefly considered.
On the existence of hydronium hydrates H9O+4 and H15O+7 in minerals
Authors: Kubisz Jan 
Published: December 2006

SummaryProperties and possible structures of hydronium trihydrate H9O+4 and hexahydrate H15O+7 are considered. From the 2330 minerals listed in Strunz's mineralogical tables nineteen were selected that appear to contain H+.4H2O or H+.7H2O, and the possibility of discrete H9O+4 or H15O+7 groupings existing in their crystal lattice is discussed. From a crystallochemical point of view the most probable examples of hydronium hydrate compounds are layer lattice minerals like H-montmorillonite, H-vermiculite, troegerite, H-meta-autunite, sabugalite, and hewettite.
On the preferred crystallographic orientation of garnet in some metamorphic rocks
Authors: Powell Derek 
Published: December 2006

SummaryA study of inclusions within garnet porphyroblasts demonstrates that planar inclusion bands and trails lie sub-parallel to one of the {110} planes of the host. The inclusions provide a relic of a rock fabric that existed before the growth of garnet. It is suggested that this fabric has determined the crystallographic orientation of garnet and may have arisen by the nucleation and epitaxial growth of garnet within or upon the mica lattice.
Heating experiments on gudmundite
Authors: Horrell Clark A. 
Published: December 2006

SummaryIn the absence of published experimental data on phase equilibria in the ternary system Fe-Sb-S and on the stability relations of gudmundite (FeSbS) and berthierite (FeSb2S4) , some preliminary investigations on the upper stability limit of natural gudmundite are briefly described. On heating in vacuo, As-free gudmundite broke down between 269° and 288°C, an approximate upper stability limit of 280±10°C conforming to the stability relations of the associated phases.
Anandite, a new barium iron silicate from Wilagedera, North Western Province, Ceylon
Authors: Pattiaratchi D. B. , Saari Esko , Sahama Th. G. 
Published: December 2006

SummaryAnandite is a new barium iron silicate found in the magnetite ore zone of the Wilagedera iron ore body, in the North Western Province of Ceylon. The mineral is named after the late Dr. Ananda Coomaraswamy, the first director of the Mineral Survey of Ceylon.Anandite is monoclinic, with a 5·412, b 9·434, c 19·953 Å, β 94° 52′, space group C2/c. D 3·94, hardness 3–4. Optically positive, b ‖ β, γ ∧ a 12°, β 1·855, γ > 1·88. Pleochroism: β green, γ brown. Chemical composition corresponds to the simplified formula (Ba,K) (Fe,Mg)a (Si,Al,Fe)4O10 (O,OH)2 with Z = 2. The data available indicate that the mineral has the trioctahedral structure of the brittle micas.
The pyroxenes of the alkaline igneous complexes of eastern Uganda
Authors: Tyler Ruth C. , King B. C. 
Published: December 2006

SummaryChemical analyses, some optical data, and specific gravities are given for 57 pyroxenes from the alkaline rocks of Uganda. They are members of the diopside-hedenbergite-acmite series, the more diopsidic varieties occurring in rocks of the ijolite series and the more acmitic in syenites and carbonatites. TiO2 is highest in those pyroxenes from rocks that do not contain melanite. The refractive indices and specific gravities are controlled by the Fe2+/Mg ratio in the diopsidic pyroxenes and by the Fe3+ content in the acmitic members. Paragenesis is discussed briefly.
The mechanism of oxidation in titanomagnetites: a magnetic study
Authors: O'Reilly W. , Banerjee Subir K. 
Published: December 2006

SummaryA hypothesis for the mechanism of oxidation in titanomagnetites is first put forward on the basis of new oxidation data for pure magnetite and the new model for cation distribution in titanomagnetites. Contrary to previous claims by other workers, it is shown that single-phase spinel oxidation products of titanomagnetites can only be produced under very exacting circumstances. Lowtemperature magnetic measurements on such synthetic, oxidized materials were made to show the formation of magnetite by the decomposition of the metastable oxidation products of titanomagnetites on prolonged heating at moderate (∼ 390° C) temperatures. This magnetic method of detection is more sensitive than that of normal X-ray diffraction. It is concluded that previous claims of an increase in magnetization due to the formation of synthetic single-phase, highly oxidized titanomagnetites must be due to the formation of undetected magnetite.
The crystal structure of gersdorffite
Authors: Bayliss P. , Stephenson N. C. 
Published: December 2006

SummaryGersdorffite belongs to space group P213 in the cubic system with cell dimension a 5·6885 ± 0·0003 Å and four formula units per cell. The hk0 data were measured from precession photographs obtained with Mo-Kα radiation. The structure was solved by Patterson methods and refined by least-squares techniques. This structure has complete ordering of arsenic and sulphur similar to ullmannite.
X-ray studies of natural fabrics: I. Growth-fabrics in hematite kidney ore and in fibrous calcite
Authors: Bradshaw R. , Phillips F. C. 
Published: December 2006

SummaryFibres of hematite in kidney ore are elongated at right angles to thec-axis. The fibre axis, which may be normal to a face of either of the hexagonal prisms {101̄0} or {112̄0}, may show an abrupt change of orientation along the length of a fibre. There is little preferred orientation around the length of the fibres.It is confirmed that in some calcite satin spar the fibres are elongated parallel to an edge of the cleavage rhombohedron; in other fibrous growths the elongation is either parallel to or Perpendicular toc.
A reinterpretation of monalbite
Authors: Brown William L. 
Published: December 2006

SummaryA neutron activation analysis of one of the crystals of ‘monalbite’, which was monoclinic at room temperature, shows that it contains a large proportion of potassium. It is thus not a polymorph of pure NaAlSi3O8. The contamination occurred by transfer of K through the atmosphere of the furnace from potassium-bearing ceramic materials.
On the existence of monoclinic NaAlSi3O8 s at elevated temperatures
Authors: Grundy H. D. , Brown W. L. , MacKenzie W. S. 
Published: December 2006

SummaryMeasurements from powder diffraction patterns recorded at temperatures up to 950° C for the supposed equilibrium forms of albite synthesized at 800°, 900°, and 1000° C by MacKenzie (1957) indicate that only the form synthesized at 1000° C becomes monoclinic. Single-crystal measurements on heated pure natural albite (Ab99·26) show that it becomes truly monoclinic, both in geometry and intensity distribution, at 930° C, the same temperature as for the highest-temperature synthetic form. These experiments were carried out in conditions that exclude possible contamination by potassium.
Extinction curves and equivibration curves obtained with a variable-axis spindle-stage
Authors: Villarroel H. , Joel N. 
Published: December 2006

SummaryA modification of the one-axis spindle-stage for the study of the optical indicatrix of crystal grains on the polarizing microscope is described. It allows the crystal to be rotated around axes within a range of about 40° without having to remount it. Some advantages of this variable-axis spindle-stage for obtaining extinction curves and equivibration curves (n0 curves) are illustrated.