bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrodialysis of mineral silicates: an experimental study of rock-weathering (With Plate XIII.)
Authors: Hla Tha 
Published: December 2006

Palmer's investigation of the chemical and mineralogical aspects of soil-forming processes was restricted to comparative chemical analyses of the weathered shells and the essentially unaltered cores of certain spheroidal basic boulders from Wahiawa in the Hawaiian Islands.The present writer describes an experimental approach to the general problem of rock-weathering on lines suggested by Dr. A. Brammall:(a)Electrodialysis of eight typical rock-forming mineral silicates, each of which was dialysed separately after having been ground to an impalpable powder and analysed in detail.(b)Assessment of the effect of dialysis by comparing the composition of the unaltered mineral with that of the slime left in the mineral-chamber when dialysis was virtually at an end.(c)X-ray and kathode-ray tests on three of these minerals and the corresponding slimes, to ascertain whether colloidal end-products associated with, or coating, particles of unaltered mineral had integrated to form one or other of the specific ‘crystalline colloids’ identifiable in soils and clays.
Note on the determination of the orientation of section planes of meteoritic irons
Authors: Terpstra P. 
Published: December 2006

Recently Dr. M. H. Hey published in this journal a method to construct graphically a projection showing the relation of two etched surfaces M and N to the crystallographic axes of a mass of the Gibeon meteoritic shower. Upon those faces could be distinguished the traces of four octahedron planes 0l, 02, 03, 04 which are inclined at the following angles, measured clockwise from the intersection [MN] of the etched surfaces: on surface M 22°, 62°, 98°, and 135° and for the same octahedron planes on surface N 106°, 38°, 150°, and 86°, respectively.The two faces M and N are at an angle of 84° one to the other. Hey's solution of the problem is based on a reversal of the Goldschmidt construction for drawing crystals from the gnomonic projection.
An improved polarizing microscope
Authors: Hallimond A. F. , Wilfred Taylor E. 
Published: December 2006

In recent years there has been little essential change in the design of the petrological microscope. F. E. Wright directed attention to the improvement that could be obtained by using a full-sized condenser with a large polarizer, but the high cost of the latter seems to have restricted its use to a few special models.With the introduction of ‘polaroid’, a thin, intensely pleochroic film mounted between glass disks, this restriction no longer holds. A polarizer can be supplied of sufficient size to cover an ordinary Abbe condenser, while the analyser no longer requires the compensating lenses which usually accompany a calcite prism, with the indirect result that the definition of the interference-figure is improved.
Nigerite, a new tin mineral
Authors: Bannister F. A. , Hey M. H. , Stadler H. P. 
Published: December 2006

The discovery of nigerite, a new tin-bearing mineral, by R. Jacobson and J. S. Webb claims more than the passing interest of an addition to the few known species containing appreciable tin. Nigerite is the first mineral to be discovered in which both tin and aluminium are essential constituents. Its chief interest to mineralogists lies in its close relationship to minerals like spinel and corundum based on a close-packed or nearly close-packed assemblage of oxygen ions.Samples of nigerite submitted to us for investigation consist of brittle, lustrous, brown, weakly magnetic, hexagonal plates up to 5 x 2 mm. in size but mostly much smaller. These samples also contained grains of cassiterite, columbite, gahnite, sillimanite, quartz, andalusite, and chrysoberyl, which were easily separated by hand-picking.
An interferometric examination of synthetic mica (With Plate X)
Authors: Tolansky S. , Morris Pamela G. 
Published: December 2006

A recent report has appeared describing a process developed in Germany for the production of a crystal described as synthetic mica. The details are given for a process used at Ostheim and reference is also made to a Siemens–Halske technique. Through the courtesy of Mr. Kendall of Metropolitan-Vickers we have secured a few small samples of the Siemens-Halske material. This is reported to be a fluor-phlogopite with the chemical composition KMg3AlSi3O10F2 and free from water of constitution. Claims made by the manufacturers stated that the synthetic material exhibits the cleavage characteristics of natural mica.The few samples we have obtained have areas somewhat less than a square centimetre and we have selected thin cleavage flakes and submitted them to intefferometric examination with the multiple-beam technique.
X-ray studies of halloysite and metahalloysite
Authors: Brindley G. W. , Robinson Keith , Goodyear J. 
Published: December 2006

This paper concludes the account of our experiments on halloysite and is to be read in conjunction with the two previous parts, to which frequent reference will be made.The effect of heat-treatment on metahalloysite was examined with the primary object of ascertaining if a recrystallization or ‘kaolinization’ of metahalloysite could be achieved.
The densest and the least dense packings of equal spheres
Authors: Melmore Sidney 
Published: December 2006

Of the results which have so far been achieved by study of the packing of equal spheres one of the most remarkable, both by reason of its simplicity and of its fundamental importance, was that announced by Barlow in 1883. He called attention to the fact that equal spheres can be most densely packed in two ways, one possessing cubic symmetry and the other hexagonal (fig. 1).Already in 1862 Tait had investigated the piling of marbles of equal size and had noticed that ‘there are two obvious ways of constructing the layers, and two of applying layer to layer’: nevertheless his two densest arrangements are in fact identical. He saw that the cubic structure could be begun either upon a square base or a triangular base but failed to perceive the possibility of the hexagonal arrangement.
An optical and X-ray examination of the basic-slag mineral silicocarnotite
Authors: Riley D. P. , Segnit E. R. 
Published: December 2006

Blue pleochroic crystals obtained from basic slag were first described by Carnot and Richard. They published a chemical analysis, some of the optical properties, and a brief description of the forms they observed. The crystals were stated to be orthorhombic, with a composition of 5CaO.P205.SiO2. Several authors later described similar crystals. None, however, gave a thorough account of the optical properties. These various papers were summarized and discussed by Kroll, who accepted Carnot's formula, but concluded, from Bücking and Linck's examination, that the material was monoclinic. Kroll applied the rather unfortunate term ‘silico-carnotite’ to these crystals.The present work shows that silicocarnotite occurs in only one modification–orthorhombic. The crystals drawn by Bricking and Linck and described as monoclinic are, in fact, identical with our orthorhombie crystals.
Clinozoisite from Camaderry Mountain, Co. Wicklow
Authors: Johnston R. W. 
Published: December 2006

The clinozoisite to be described is found in veins traversing a metamorphosed basic intrusion exposed at the top of Camaderry Mountain, Glendalough, Co. Wicklow. This intrusion is a small boss of Lower Palaeozoic age which has been metamorphosed both by earth movement and by the intrusion of the Leinster granite. The rock exposed is now an amphibolite (fig. 1) within which are found the veins carrying clinozoisite with albite and a little prehnite, sphene, and tremolite. These veins, which are up to an inch in width, were probably introduced during the late stages of the basic intrusion as veins of lime-rich plagioclase.Preliminary examination under the microscope shows that the clinozoisite is well crystallized, fresh, and free from inclusions. The colour in the hand-specimen is grey-white; in thin section it is colourless. Individual crystals are found up to 5 mm. in length. Twinning and intricate zoning are common.
The Wherry mine, Penzance, its history and its mineral productions
Authors: Russell Arthur 
Published: December 2006

If the visitor standing at Wherry Town on the south-western end of the esplanade at Penzance looks seaward he will observe at low tide at some distance from the shore a low scaweed-clothed rocky shoal (fig. 1), and from his now very conventional surroundings it is difficult to realize that upon this shoal, always surrounded by water, there existed many years ago a rich tin mine, unique in the boldness of its conception, romantic in the extreme in its situation and execution, and withal the effort of a poor working miner.Very fortunately in the year 1790, during the hey-day of its career, this remarkable mine was examined by a very competent observer in the person of John Hawkins (1761 ?-1841), F.R.S., of Trewithen, Cornwall, and Bignor Park, Sussex, and it is to him that we owe most of the details concerning its mode of working, &c. The Wherry mine and its history have always fascinated me, as they must have many others, and in re-telling the old story I have endeavoured to collect all the known facts, both as to the mine itself, its mode of working, and its mineral productions, and in so doing pay tribute to its gallant and resourceful originator Thomas Curtis.
Goethe's interest in British mineralogy
Authors: Hennig John 
Published: December 2006

Johann Wolfgang von Goetiie (1749-1832), the bicentenary of whose birth at Frankfurt-on-Main will be commemorated on August 28, 1949, gave us extensive accounts of the development of his studies in optics, botany, and meteorology; with regard to the history of his studies in mineralogy and geology, his most concise statement is his essay ‘Geology, in particular that of Bohemia’. This essay, written in 1817, starts with three quotations. The first is in English:What is the inference ? Only this, that geology partakes of the uncertainty which pervades every other department of science.The source of this quotation still remains to be discovered. At the end of this essay, Goethe said that he was:fortunate in obtaining a series of minerals from all the principal countries. Herr Mawe, the mineral merchant in London, provided me with a most satisfactory collection from Cornwall, and to Herr Ritter v. Giesecke I am indebted for an important addition to my collection of English stream tin and Malacca tin. All these materials have now been well arranged in my collection, but my plan to write something conclusive on this subject could not be carried out, as so many other things I should have liked to do in the scientific field.
The decomposition of biotite in the soil
Authors: Walker G. F. 
Published: December 2006

A noticeable feature of many of the soils of north-east Scotland is the presence in them of glistening yellow flakes of decomposed biotite. The light-reflecting property of this material catches the eye even though the flakes themselves are often of very small size.An analogous process to the breakdown of biotite as reported below occurs in the soil-clays of the area, and the present study was undertaken primarily in order to throw light on the mineralogical nature of the clay fractions of the soils, since the large amounts of anmrphous material associated with the soil-clay minerals renders less satisfactory the direct approach. The mineralogy of the soil-clays will be dealt with in a separate communication.
The surface structure of crystals
Authors: Seager A. F. 
Published: December 2006

C . W. Bunn and H. Emmett have observed the spreading, of multi-molecular layers on growing crystals of artificial compounds, and have suggested that deposition takes place on the high-index surfaces at the edges of the layers. Their work led the author to examine crystals of several mineral species for evidence of the mechanism of growth, and this account is the result of a preliminary survey of the growth structures found.So many growth structures could be seen with the naked eye or with a hand-lens that it was decided to use low magnifications in order that comparatively large areas of the crystal faces could be examined and photographed at one time. A metallurgical microscope with a prism reflector and 1-inch objective was used for the observations and most of the photography. This work is qualitative rather than quantitative, but it is intended to carry out a quantitative examination of the same specimens later.
An improved polarizing microscope. V. The ore-microscope
Authors: Hallimond A. F. , Wilfred Taylor E. 
Published: December 2006

Examination in reflected polarized light is now widely used in metallography as well as for mineral sections. The recent introduction of graded diamond abrasives has overcome most of the difficulties in polishing that have previously hindered the widespread use of this important method.The present instrument (fig. 1) has been designed to give the best available control over the conditions of illumination and extinction, and to provide for the complete analysis of the reflected elliptically-polarized beam. A robust stand of normal grade suitable for general research purposes and works control is provided with a stage rack, reflector unit, and the usual polarizing equipment. It may be adapted for transmitted light by the addition of the detachable substage shown on the right of the figure.
Cheralite, a new mineral of the monazite group
Authors: Bowie S. H. U. , Horne J. E. T. 
Published: December 2006

A Green mineral akin to monazite, derived from the State of Travancore in southern India, was investigated chemically during the first world war by the Imperial Institute, London, and was found to be exceptionally rich in thorium and uranium. No description of this unusual 'monazite' has hitherto been published.The high content of radioactive elements in this mineral led the State Geologist, Mr. Venkitarama Mahadevan, to have a deposit opened up in 1945, in readiness for an assessment of the radioactive mineral resources of Travancore. At the invitation of the former Dewan, Sir C. P. Ramaswami Aiyar, K.C.S.I., K.C.I.E., this assessment was carried out by Dr. C. F. Davidson early in 1946.
Some data on synthetic aluminous and other pyroxenes
Authors: Segnit E. R. 
Published: December 2006

Although detailed experimental investigations have been carried out on the lime, magnesia, and ferrous pyroxenes, relatively little attention has been devoted to synthetic studies of the group involving replacements by ions of higher valencies. In the present study, determinations have been carried out on the limits of solid solution of alumina in pyroxenes in the system CaSiO3-MgSiO3-A12O3. Determinations of the solubility of ferric oxide and titania in diopside were also made.Pure calcium carbonate, magnesia, silica (crushed and washed rockcrystal), alumina, ferric oxide, and titania were used for the preparation of the mixtures. The constituents in their requisite proportions were fused together four or five times with intervening crushing of the quenched glass. The product was an homogeneous glass free from crystalline material.
The hydrated calcium silicates riversideite, tobermorite, and plombierite
Authors: McConnell J. D. C. 
Published: December 2006

In a recent paper Taylor has shown that three distinct hydration levels exist within the ‘calcium silicate hydrate (l)’ group of artificial preparations (Taylor, 1953a, p. 168). The individual hydrates may be distinguished from the position of the 002 reflection in X-ray powder photographs. The d spacings corresponding to the three hydrates of this group examined during the present investigation are 14.6, 11.3, and 9.6 Å. These hydrates have H2O : SiO2 molar ratios of approximately 2.0, 1.0, and 0.5 respectively.A recent examination of the minerals crestmoreite and riversideite (Taylor, 1953b) has shown that both these minerals are intimate inter-growths of members of the above hydrate series with the mineral wilkeite. Both the artificial preparations and the crestmoreite-riversideite intergrowths have failed to provide material suitable for detailed optical study.
Spectrographic and X-ray data on some fluorites from the Transvaal, South Africa
Authors: Steyn J. G. D. 
Published: December 2006

The fluorites of the Transvaal occur in different rock-types, viz in the dolomite of the Transvaal System, in acidic rocks (red granite and granophyre of the Bushveld igneous complex and Rooiberg felsites), and in alkalic rocks. The purpose of this study was to determine:(1) What minor elements are present in selected fluorites.(2) What the effect of these elements is on the respective cube-edges.(3) Whether these elements have any geological significance.Fluorite displays a wide range of colour; both colourless and distinctly coloured specimens were examined. Differently coloured varieties could in some instances be taken from the same sample. The choice of coloured varieties in the different rock-types was nevertheless limited. Only light-coloured fluorites occur in the dolomite, whereas the alkalic rocks yielded only very dark purple specimens.
The significance of tridymite in igneous and metamorphic petrogenesis
Authors: Black George P. 
Published: December 2006

Physico-Chemical data clearly show that the presence of tridymite in a rock indicates the prevalence not only of high temperatures, but also of relatively low pressures during the formation of that rock. Whereas many authors (e.g. Shand, 1927; Larsen, 1936) have used tridymite as an indicator of temperature, the importance of tridymite as an indicator of pressure has been largely overlooked.Although the presence of tridymite is by itself sufficient to enable the pressure, and hence the depth, at which a rock formed to be estimated within certain limits, the presence of tridymite in association with some other pressure-or temperature-indicating mineral allows much closer limits to be set.
The Rev. William Gregor (1761-1817), discoverer of titanium.
Authors: Russell Arthur 
Published: December 2006

In view of the important uses to which the metal titanium has been applied in recent years, it seems fitting that some tribute should be paid to its Cornish discoverer, the Rev. William Gregor, and with this end in view I have collected the following facts concerning this now almost forgotten distinguished early chemist.The Rev. William Gregor, M.A., chemist and mineralogist, was the younger son of Francis Gregor, member of an old Cornish family of Trewarthenic, Cornelly, CornwalI. Born on December 25, 1761, he was educated at Bristol Grammar School, and it was while there that he first developed a taste for chemistry.
The hydration of larnite (β-Ca2SiO4) and bredigite (α1-Ca2SiO4) and the properties of the resulting gelatinous mineral plombierite
Authors: McConnell J. D. C. 
Published: December 2006

In this paper the formation of a gelatinous hydrate phase from the natural dicalcium silicate minerals larnite and bredigite is described. Detailed study of the gel so formed indicates that the process of hydration is a solid reaction which is effeeted by diffusion. The preferred orientation of the hydrate phase suggests that the hydration is facilitated by a relationship between the structure of the anhydrous silicate and that of the hydrate phase produced.In this investigation the variations in density, mean refractive index, and chemical composition of the natural gels have been determined and the characteristics of the adsorbed water studied by isothermal dehydration and rehydration. In discussing the mechanism of hydration it has been assumed that this obtains at constant volume. This assumption is based on the study of gel pseudomorphs after single crystals of larnite and bredigite in thin section.
Disordered structural states in the dehydration of goethite and diaspore
Authors: Lima-de-Faria J. , Gay P. 
Published: December 2006

Summary
Single crystal X-ray studies of the dehydration of goethite to hematite at low temperatures show that satellite reflections occur close to the hematite diffraction spots. At higher temperature these satellites are replaced by diffuse intensity regions, which disappear on further heating. The satellites are situated on each side of hematite spots on reciprocal lattice lines parallel to the c*-axis of the hematite; their spacing corresponds to a periodicity in direct space of about 32 Å. A similar phenomenon is observed on the dehydration of diaspore to corundum, with a spacing for the satellites of about 39 Å.
The mode of occurrence of the satellites, both in position and intensity, could correspond to a sinusoidal or square-wave structure amplitude modulation along the c-axis of the hematite and corundum crystallites, before dehydration is complete.
The Wairarapa Valley, New Zealand, Chondrite
Authors: Battey M. H. 
Published: December 2006

SummaryThe Wairarapa Valley hypersthene-olivine chondrite, found about 1863, has been analysed with the following result: SiO2 35·72, TiO2 0·11, Al2O3 2·91, Cr2O3 0·48, FeO 12·42, MnO 0·28, MgO 23·28, CaO 1·73, Na2O 0·96, K2O 0·20, P2O5 0·31, Fe 12·61, Ni 1·50, Co 0·04, FeS 5·46, Cl 0·07, H2O+ 1·05, H2O− 0·48, less O for Cl 0·03; total 99·58 %. D. 3·65. The phases present are kamacite, taenite, plessite, troilite, magnetite, chromite, olivine Fa16, bronzite Fs15, possibly enstatite, plagioclase An25, and (?) maskelynite An9. The structures of the silicate phases and those disclosed by etching the metal phase are illustrated and described.
Optical determination of aegirine-augite with the universal stage
Authors: King Basil C. 
Published: December 2006

SummaryThe accurate determination of α:[001] and 2V in members of the aegirine-augite series often presents difficulties owing to strong absorption and dispersion, especially as high angles of tilt on the universal stage are often involved. Both of these angles depend on the location of α, and this operation is the one most subject to error.An alternative procedure is the determination of A:[001], the angle between an optic axis and [001]. This angle is very easily and accurately determined and varies systematically with composition. It can be derived from the values for α:[001] and 2V, while conversely values of α:[001] and 2V can be obtained from A:[001] by reference to standard curves.
Quartz after tridymite in an acid intrusion from Mull
Authors: Skelhorn R. R. 
Published: December 2006

SummaryThe occurrence of tridymite, now inverted to quartz, in a craignurite (allied to granophyre) from Craignure, Mull, is described. An account of the field occurrence and petrology and a new analysis of the craignurite are given. The significance of the occurrence of tridymite is discussed in the light of recent experimental studies.
Strontium in plagioclase feldspars from four layered basic masses in Somalia
Authors: Butler J. R. , Skiba W. 
Published: December 2006

SummaryThe petrological and structural characteristics of four layered basic masses in Somalia are described. Sr contents of feldspars from three of the masses are similar for comparable An contents; Sr varies between 1000 and 1850 p.p.m. and tends to increase as An decreases from An68 to An48. In feldspars from the other mass Sr also increases with decreasing An content (An74 to An56), but is at a much higher general tenure (1650 to 2350 p.p.m.). It is concluded that the four masses were not all part of the same layered intrusion.
Low-temperature thermal effects in natural volcanic glasses due to strain
Authors: Ewart A. , Fieldes M. 
Published: December 2006

SummarySharp exothermic peaks occurring at about 90° C during D.T.A. treatment of natural volcanic glasses are described and are shown to be due to release of external strain. This is probably triggered by loss of surface water. No systematic variation in strain could be found in glass of different geological histories, but strain is found to decrease during natural weathering of volcanic glasses. Differences in weatherability of natural glasses may be related to degree of surface strain.