bluuebunny/crossref_metadata_2025_split huggingface dataset:
The mineralogy and chemistry of the nickel carbonates
Authors: Isaacs T. 
Published: December 2006

SummaryNickel carbonate occurs in nature as a hexahydrate (hellyerite) and as a hydroxyhydrate (zaratite), but the anhydrous species is only known as an artificial product. All of the compounds show anomalous properties that have led to confusion in the literature.Only the calcite structure was found for NiCO3; hydrothermal conditions appear to be essential for its synthesis, and a variation in cell size was found with changes in duration or temperature of synthesis, or both.Hellyerite probably is [Ni(H2O)6]CO3, which would explain its ease of decomposition and rarity in nature. Zaratite is not a single mineral, but a composite of amorphous and fibrous components. The conditions under which NiCO3might be expected to occur are discussed. Nickel bicarbonate formed in the reactions to produce NiCO3; its X-ray diffraction pattern, indicating cubic symmetry, analysis, and optical properties are given.The behaviour of nickel in these compounds is best explained in terms of crystal field theory.
Determination of 2V from one extinction curve and its related n0 curve
Authors: Joel N. 
Published: December 2006

SummaryFrom the extinction curve of a biaxial crystal mounted on a spindle stage (or one-axis stage goniometer), the related n0 curve can be derived and drawn on the stereogram. The n0 curve is the equivibration curve—or constant-refractive-index curve—that goes through the projection P0 of the spindle-stage axis. After the principal diameters (maximum 2η and minimum 2ζ) of the no curve have been measured, the angle 2V may be calculated by means of the formula cos V = sin ζ/sin η. This method can also be used for determining—or refining—the directions of the principal axes α, β, γ.
The nomenclature of the natural alloys of osmium and iridium
Authors: Hey M. H. 
Published: December 2006

SummaryAn historical review of the nomenclature of the natural Os-Ir alloys suggests that the most suitable names are: For the cubic alloys, osmiridium (Steffens, 1824), i.e. osmian iridium; and for the hexagonal alloys, iridosmine (Breithaupt, 1827), i.e. iridian osmium, for alloys with 20% or more Ir, and native osmium for the very rare alloys with little or no Ir. Iridosmine may, if desired, be divided into two varieties, nevyanskite and sysertskite, following Rose and Haidinger.
A new incident illuminator for polarizing microscopes
Authors: Smith F. H. 
Published: December 2006

SummaryThe customary illumination by a ‘coverglass’ inclined at 45 degrees is replaced by a double reflection. The beam from the horizontal collimating tube is first reflected from a highly reflecting mirror at the back of the unit, then downward from a coverglass placed at the top of the unit. With this arrangement the coverglass is inclined at less than 22½ degrees to the axis of the microscope, with a similar reduction of the angle of incidence. The correction ratio for rotation by upward passage of light through the coverglass is now reduced from 6:5 to the almost negligible value 21:20. There is a corresponding improvement in the homogeneity of extinction over the microscope field.
Olivine composition determination with small-diameter X-ray powder cameras
Authors: Jambor J. L. , Smith Charles H. 
Published: December 2006

SummaryOlivine composition can be rapidly and accurately obtained by using standard (Straumanis-mounting) 57·3 mm X-ray powder cameras. A determinative curve based on analysed natural olivines has been constructed by plotting the mol. % Fo against the spacing of back-reflection line 174. The regression equation for the composition range Fo100 to Fo30 isFo (mol. %) = 4151·46−3976·45 d174using Fe-Kα1 radiation. The fayalite end (Fo30 to Fo0) of the determinative curve shows a relatively sharp break from a straight-line relationship of d-spacing versus composition. Practical applications of the determinative curve are briefly presented.
Statistical analysis of X-ray data for olivine
Authors: Agterberg F. P. 
Published: December 2006

SummaryA diagram of the relationship between d174 and % forsterite in olivines is presented in fig. 1 of the preceding paper by Jambor and Smith. In this note, statistical aspects of Jambor and Smith's data are considered in detail and compared to equivalent data by Yoder and Sahama (1957). This analysis leads to the conclusion that the relationship of mol. % Fo and d174 or d130 can be expressed as a straight line for Fo > 30 %. Olivines with Fo < 10 % are not related to this straight line.
A siereographic construction .for determining the optic axes of a biaxial crystal directly ,from a few extinction measurements
Authors: Joel N. 
Published: December 2006

SummaryIt is possible to determine the directions of the optic axes of a biaxial crystal mounted on a spindle stage—and hence the angle 2V and the directions of α, β, γ—from only four measured extinction positions. The method is a generalization of the one proposed by Tocher (1962); but in the present procedure it is not necessary to determine first the optic axial plane.
Reyerite
Authors: Chalmers R. A. , Farmer V. C. , Harker R. I. , Kelly S. , Taylor H. F. W. 
Published: December 2006

SummaryReyerite from the original locality in Greenland has been re-examined using chemical analysis, infra-red absorption, X-ray powder and single-crystal diffraction, and thermal weight-loss curves. The unit cell is trigonal with a 9·74, c 19·04 Å, and the space group is probably P3¯. The unit cell contents are probably best represented as KCa14(Si24O60)(OH)5.5H2O, with some minor replacements. The molecular water is lost reversibly below 400° C. There are indications that the crystal structure is based on Si6O18 rings resembling those in beryl, but linked into sheets by additional tetrahedra.Reyerite closely resembles truscottite, a mineral found originally in Sumatra, but there are distinct differences, especially in the infra-red pattern. It is not yet certain whether or not the two minerals should be considered as distinct species. Synthetic preparations examined resembled truscottite more closely than reyerite.
Spurrite from northern Coahuila, Mexico
Authors: Temple A. K. , Heinrich E. Wm. 
Published: December 2006

SummarySpurrite-bearing contact-metasomatic mineral assemblages occur with a few of the many rhyolite stocks intrusive into Georgetown (Cretaceous) limestone in the Encantada district of northern Coahuila, Mexico. The contact-metasomatic suites are found associated only with rhyolites that solidified within the thick Georgetown limestone. Rhyolites that penetrated through the limestone have sharp contacts commonly marked by perlitic contact breccias. The structural form of all the rhyolites indicates intrusion under high pressure.Three distinct contact-mineral suites have been recognized: Foliated garnetwollastonite rocks occur adjacent to the rhyolite, whereas spurrite is only found further from the intrusive. The inner side of the spurrite-bearing zone is characterized by foliated spurrite-garnet-periclase rocks, whereas the outer side of the spurrite zone consists of a massive, coarse-grained, spurrite-rankinite-periclase rock, which has a sharp contact with the outermost foliated marble zone. At one location, massive spurrite occupies ‘dikes’ radial to the intrusive, which are post-dated by wollastonite-bearing gehlenite-diopside rocks.It is concluded that the stages of rhyolite emplacement include: First, preliminary high-pressure structural site preparation accompanied by intrusion of rhyolite and metasomatic introduction of Si and Al into preheated cap rock. Then crystallization of the metasomatic zone, under conditions of upward pressure exerted by the rhyolite, to give the features of the spurrite zone; followed by conversion of the inner side of the spurrite zone to a wollastonite-bearing assemblage.
Conical extinction curves: a new universal stage technique
Authors: Joel N. , Tocher F. E. 
Published: December 2006

SummaryNew generalized extinction curves, derived from wave-normals located on a circular cone, are presented. They may be used with the universal stage for the accurate location of up to all three of the indicatrix axes, α, β, γ, of any biaxial crystal, or the optic axis of any uniaxial crystal.
Epidotes of the Borrowdale Volcanic rocks of central Borrowdale
Authors: Strens R. G. J. 
Published: December 2006

SummaryEpidote and clinozoisite are widely distributed in the andesitic lavas and tuffs of the Borrowdale Volcanic Series. Four main types of occurrence may be distinguished, namely quartz-epidote vein fillings; ‘Shap type’ veins, bordered by pink reaction zones rich in SiO2, Na2O, and K2O; autometasomatized lavas and tuffs; and tuffs subjected to alkali metasomatism. Epidote alone formed in the quartz-epidote veins; clinozoisite is found with epidote in the other types of occurrence.Epidote and clinozoisite formed in vesicles at pressures of 10–280 kg/cm2, at temperatures of 300–550° C; epidote associated with pre-Bala mineral veins formed in the range 130–550° C at 1000 kg/cm2; epidote around the Caledonian granites probably formed up to 600° C at about 2000 kg/cm2. Clinozoisite crystallized together with epidote in the vesicles, demonstrating a gap in the clinozoisite-epidote solid solution series. Early formed epidote in vesicles is more strongly coloured than late epidote, although the compositions of the earliest and latest fractions are identical.
A petrographic and geochemical study of back-veining and hybridization at a gabbro-felsite contact in Coire Dubh, Rhum, Inverness-shire
Authors: Dunham A. C. 
Published: December 2006

SummaryField, petrographic, and chemical data are presented which make it possible to follow the course of back-veining of felsite by a gabbro ring-dyke. The remelted felsite back-veined the chilled margin of the gabbro, then acidified the partly crystalline basic mush within the chilled zone and finally mixed with the mainly liquid basic magma farther inside the dyke to produce hybrids of marscoitic aspect. Spectrographically determined trace-element data, with data on some major elements, illustrate these changes. The veins are shown to have a composition nearer the ternary minimum in the system Ab-Or-Qz-H2O than the parent felsite, while culminations of soda and iron in the acidified gabbros and hybrids suggest that metasomatism has accompanied the mixing of the partly liquid end members. This study confirms the earlier suggestion that the gabbro post-dates the felsite.
Amphiboles in alkaline rocks of Koraput, Orissa
Authors: Bose Mihir Kumar 
Published: December 2006

SummaryThe chemistry and optics of the amphiboles in alkaline rocks of Koraput, Orissa, India, are described. The variation in chemical characters of the amphiboles is consistent with the variation in rock composition. With progressive fractionation the mineral shows increasing replacement of magnesium by iron while Ca is not affected by such replacement. The trend in variation is comparable to that in pyroxenes of alkaline basaltic magmas. The entry of Ti into the structure of amphibole appears to be favoured by alumina activity and concentration of Ti in the magma. Optical characters vary with the iron : magnesium ratio and titanium content of the mineral. The water content of the magma had an important influence on the composition of the mafic minerals in the rocks.
Wairauite—a new cobalt-iron mineral
Authors: Challis G. A. , Long J. V. P. 
Published: December 2006

SummaryA new cobalt-iron mineral of composition close to CoFe has been found associated with awaruite (Ni3Fe) in the Red Hills serpentinites of the Wairau Valley, South Island, New Zealand. The name wairauite, after this locality, is proposed. Electron-probe analysis of the small grains so far discovered has shown that the nickel content is very low (0·5 ± 0·1 wt. %). Wairauite is optically very similar to awaruite but a tendency to form euhedral grains (octahedron and cube) and a slightly lower refiectivity are an aid to identification. No X-ray data are available at present, but it is suggested that the structure may correspond to that of the ordered CsCl type of the synthetic alloy of the same composition.
A study of the hydrothermal growth of ruby
Authors: Butcher J. , White E. A. D. 
Published: December 2006

SummaryExperiments have been conducted to determine the optimum conditions for the hydrothermal growth of ruby. The solubility of corundmn in various solutions has been determined and compared with the respective growth obtained in each medium. The discrepancy between solubility and effective growth is discussed.The need for a high degree of chemical purity has resulted in the development of platinum liners for the autoclaves. The effects of impurities and of other factors on the growth of ruby crystals have been studied. The crystal habit of hydrothermal ruby is also described.
The unit-cell of aenigmatite
Authors: Kelsey C. H. , McKie Duncan 
Published: December 2006

SummaryRedetermination of the unit-cell dimensions as a 10·406 Å, b 10·813 Å, c 8·926 Å, α 104° 56′, β 96° 52′, γ 125° 19′, has shown that the hitherto accepted unit-cell of Gossner and Spielberger (1929) is in error. The morphological unit-cell of Palache (1933) is related to the new unit-cell, to a high degree of precision, by the transformation Palache → Kelsey-MeKie [001∕01½½∕½00]. Fifteen published and two new analyses indicate that the unit-cell contents approach Na+4 [Fe2-10- Ti4+2] Si4+12O2-40. The common twin axis constitutes the diad of a pseudo-monoclinic cell, the (010) plane of which is dimensionally closely related to that of pyroxenes and amphiboles. It is suggested that the aenigmatite structure is based on silicate chains of pyroxene type cross-linked by Ti4+ and Fe2+ on distinct 6-fold sites, with Na+ on sites of higher coordination number. Aenigmatite from volcanic in contrast to that from plutonic parageneses is often submicroscopically twinned and may be inverted from a high temperature monoclinic polymorph.
Microscope accessory plates and colour blindness
Authors: Tocher F. E. 
Published: December 2006

SummaryThe ordinary quartz wedge is adapted for use by the colour blind by the superposition of a two-colour isotropic auxiliary plate. A birefringent plate of suitable retardation may also be used in conjunction with the same auxiliary plate to replace the standard sensitive tint plate. In both cases, diagnostic colour changes are replaced by relative intensity changes.
Theory of Immiscibility in Mineral Systems
Authors: Mueller Robert F. 
Published: December 2006

SummaryThe theoretical basis for the stability of binary and quasi-binary solutions is discussed with special emphasis on miscibility relations. Solutions of the distribution equations are presented for the case of two and three coexisting regular solutions and this model is used to illustrate the energetics of miscibility relations. The same principles are then extended to give a qualitative interpretation to sequences of mineral assemblages consisting of pyroxenes, amphiboles, micas, and feldspars. A formulation is presented for the intrinsic stability of a solution, which depends on the presence or absence of an excess free energy of mixing, and the extrinsic stability of a solution, which depends on the standard free energy of the component end members.
The transformation of groutite (α-MnOOH) into pyrolusite (MnO2)
Authors: Lima-De-Faria J. , Lopes-Vieira A. 
Published: December 2006

SummaryThe transformation of groutite (α-MnOOH) by heating has been studied at 300° C in air, by single-crystal and powder X-ray methods. At this temperature groutite transforms topotactically into pyrolusite (MnO2), the a, b, and c axes of groutite becoming respectively the a, b, and c axes of pyrolusite (in pyrolusite b = a). At various stages of the transformation other weak and diffuse spots were observed on X-ray oscillation photographs, which could not be ascribed to pyrolusite. Some of these extra spots fit well to an α-Mn2O3 structure (isostructural with hematite), with c 14·3 and a 4·9 Å; the other few spots could not be identified.The transformation of α-MnOOH into MnO2 is explained by a homogeneous mechanism, with migration of protons and electrons to the crystal surface. A detailed interpretation of this mechanism is presented on the basis of the close-packing characteristics of these two structures.
A new universal stage extinction technique: the determination of 2 V when neither optic axis is directly observable
Authors: Tocher F. E. 
Published: December 2006

SummaryA new universal stage extinction technique is presented. It is based on the special case of coplanar and conical extinction curves where an optic axis lies on the wave-normal locus. It may be used in favourable circumstances to determine 2V when neither optic axis is directly observable.
Four new uranium–lead ages from Cornwall
Authors: Pockley R. P. C. 
Published: December 2006

SummaryFour new isotopic U/Pb ages from Cornwall are reported. The Pb206/U238 and Pb207/U235 ages for each specimen are concordant. The Pb206/U238 ages are : South Terras mine 225 ± 5 million years (Myr.), Redruth Area 124 ± 4 Myr., Wheal Owles mine 58 ± 3 Myr., and South Terras Area 62 ± 3 Myr. Cell sizes, calculated from X-ray powder photographs, decrease with decreasing ages of the specimens, indicating a progressive increase in the oxidation states of the uranium present. It is concluded tentatively that at least two periods of mineralization affected south-west England at about 290 Myr. and 225 Myr., and that a final event occurred at about 60 Myr. Whether this final event involved the remobilization of older uranium with loss of lead, or the introduction of additional uranium, or a combination of both effects cannot be established from this evidence. No unique explanation has been made for the 124 Myr. age.
Pumpellyite in Snowdonian soils and rocks
Authors: Jenkins D. A. , Ball D. F. 
Published: December 2006

SummaryDetrital grains, noted during the mineralogical examination of certain Snowdonian soils, have been identified as varieties of the mineral pumpellyite : the source of one variety has been located in dolerites exposed in the area, and the identity of this variety confirmed by X-ray analysis.
The calciferous and alkali amphiboles
Authors: Phillips R. , Layton W. 
Published: December 2006

SummaryAn attempt is made to systematize the nomenclature of the calciferous and alkali amphiboles. The compositions of end-members can be plotted on a simple diagram, which can also be used to display the affinities of the naturally occurring minerals after deriving a basic atomic formula according to the rules given. The composition of an amphibole can in some cases be expressed quantitatively in terms of solid solution of two or three pure end-members.
Polythermal metamorphism of limestones at Kilchoan, Ardnamurchan
Authors: Agrell S. O. 
Published: December 2006

SummaryJurassic limestones occurring in a screen between two ring dykes are shown to have undergone two periods of thermal metamorphism; the first characterized by a high ratio of CO2:H2O and the second by a high ratio of H2O:CO2in the vapour phase. The first metamorphism produced minerals characteristic of Bowen's decarbonation series. Some of these minerals became unstable in the second metamorphism and (OH, F) bearing minerals were produced. A stage of fracture-controlled replacement veins with mineral assemblages which indicate a varying CO2:H2O ratio in the vapour and a general falling temperature sequence terminate the metamorphic history. Three new minerals, rustumite (Ca3Si2O7.Caterminate (OH)2), dellaite (Ca12Si6O22(OH)4), and kilchoanite (Ca3Si2O7), of which the last has previously been described, are characteristic of the second episode of metamorphism.
Ultrabasic eruptives with alnöitic-kimberlitic affinities from Malaita, Solomon Islands
Authors: Allen J. B. , Deans T. 
Published: December 2006

SummaryA detrital assemblage of magnesian ilmenite, pyrope, chrome-diopside, rutile, and zircon has been traced to outcropping ultrabasic alkaline rocks, hitherto unknown in the Melanesian region. Analyses and descriptions of these ‘kimberlite indicator minerals’ are given. The host rocks comprise alnöite, an alnöite breccia with calcite matrix, and a magnesian ankaratrite, which are described, with chemical analyses. Emphasis is laid on the abundance of ultrabasic inclusions and xenocrysts and the replacements and transformations they have undergone. Malaita Island promises to contribute significantly to the understanding of the relations between alnöite, melilite basalts, and kimberlites.
Re-investigation of clino-ferrosilite from Lake Naivasha, Kenya
Authors: Bown M. G. 
Published: December 2006

SummaryThe clino-ferrosilite from the lithophysae in an obsidian from Lake Naivasha, Kenya, originally examined by Bowen (1935), has been shown to be substantially pure FeSiO3, with about 5% MnSiO3 in solid solution. It has the same space-group, P21/c, as clino-enstatite and pigeonite. The unit-cell dimensions are a = 9.718 Å, b = 9·088 Å, c = 5·239 Å, β = 108° 27′. These do not conform to the scheme proposed by Brown (1960): reasons are given why this was not unexpected.
The origin of three garnet isograds in Adirondack gneisses
Authors: Buddington A. F. 
Published: December 2006

SummaryThree isograds may be drawn, indicating increasing grades of metamorphism in the northern Adirondack area, based on the development of garnet successively in biotite-quartz-plagioclase paragneiss, metadolerite and metagabbro gneiss, and in syenite and quartz syenite orthogneisses. Changes in the accompanying minerals show that this is an order of increasing temperature. Rocks of similar chemical composition, suitable for the development of garnet, occur in each grade of metamorphism and geologic studies indicate adequate temperature and depth for the development of garnet even where it is not present. The degree of development of garnet in rocks of similar chemical composition, in even as high a grade as the pyroxene-granulite subfacies, is widely variable. All of the data are consistent with an hypothesis that the successive development of a garnetiferous facies for each of the different kinds of gneisses mentioned required special conditions that facilitated the kinetics of the reaction, such as temperature in excess of that for equilibria, in order for the garnet reaction to proceed. The data are not conclusive as to whether certain non-garnetiferous facies of amphibolites are due to the physical conditions (such as high partial pressure of H2O for the prevailing temperature and load pressure) or to non-equilibria.
The kyanite isograd in Glen Clova, Angus, Scotland
Authors: Chinner G. A. 
Published: December 2006

SummaryMineral data from Glen Clova, Angus, suggest that the development of kyanite in graphite-bearing staurolite mica-schists, treated in terms of a Ca-free system, involved decrease of staurolite and a decrease in biotite MgO:FeO ratio. A kyanite isograd may be defined in Glen Clova as the locality where kyanite joins the assemblage staurolite-garnet-biotite-muscovite-plagioclase-quartz-graphite, the biotite having mol. , although the persistence of this identical assemblage over some 600 metres introduces some uncertainty of interpretation. It is suggested that the reaction staurolite+quartz → garnet+kyanite is unlikely to be a common reaction in nature and that its use to subdivide the amphibolite facies is unjustified.