bluuebunny/crossref_metadata_2025_split huggingface dataset:
An X-ray study of the crystal-structure of antigorite (With Plate V)
Authors: Aruja Endel 
Published: December 2006

Antigorite is a lamellar variety of serpentine, and is supposed to be a dimorphous form of chrysotile, which is finely fibrous. Its chemical composition is approximately H4Mg3Si2O9, which is taken as the basis of calculations here.This study was undertaken primarily because it was hoped that knowledge of the structure of antigorite would throw some light on that of chrysotile. Certain similarities between the two structures have been established, namely in the c(7·3kX or 14·6kX), and b(9·2kX) directions. There are two main differences, however. Firstly, imperfections which cause line broadening in the X-ray pattern of chrysotile, are absent in antigorite (apart from certain ‘streaks’). Secondly, the a(43·4kX) axis of antigorite is approximately eight times longer than the corresponding axis in chrysotile. A complete determination of the structure has not been achieved, but the X-ray pattern has been described, and some suggestions made as to the explanation of the peculiarities observed. A further study of the outstanding questions is in progress.
Myrmekite in graphic granite and in vein perthite
Authors: Spencer Edmondson 
Published: December 2006

This paper describes the occurrence of myrmekite in a graphic quartz-microcline-rock from the mica-bearing pegmatites of Kodarma, Bihar, India. The myrmekite has grown out from the quartz-mierocline junctions into the potash-felspar with the appearance of having replaced the latter. The two are in optical and crystallographic continuity and, owing to the large ‘single crystal’ character of the microcline, definitely oriented sections can readily be prepared. A detailed study of these sections shows that the myrmekite has been formed by the segregation and coalescence of microperthitic albite formerly held in solid solution in the potash-felspar. Successive stages in this process of segregation can be observed.These sections also provide evidence of the paragenetic relationship between the quartz rods, the vein perthite, and the body microcline. This is supplemented by additional evidence from graphic granites and vein perthites obtained from other localities.
Barium-felspars from Broken Hill, New South Wales (With Plate XIV.)
Authors: Segnit E. R. 
Published: December 2006

At two localities on the outskirts of the township of Broken Hill—near the De Bavay shear zone, and at ‘The Piggery’—W. R. Browne reported unusual rock types rich in barium. His statement is accompanied by an analysis by H. P. White (analyst to the Mines Dept.) of one of these rocks, which contains 9·23% BaO. Subsequently S. R. Nockolds and E. G. Zies examined the felspars of the rock analysed by White with a view to ascertaining whether they are barium-containing varieties.In view of the very high barium content of some of the occurrences now being investigated, much higher than that of the rock examined by Nockolds and Zies, a further mineralogical investigation was undertaken with the results recorded below. The rocks under examination were light-coloured gneisses containing up to 15% BaO. They are distributed as lenses and streaks in an acid gneiss. A specimen of the latter rock was analysed and found to contain only 0·09% BaO. The barium was found to occur in four felspars, one being a new variety of celsian. The minerals studied were celsian, calciocelsian, hyalophane, and barium-plagioclase. A careful search was made for other barium silicate minerals such as sanbornite, but none was found.
Pennantite, a new manganese-rich chlorite from Benallt mine, Rhiw, Carnarvonshire
Authors: Campbell Smith W. , Bannister F. A. , Hey Max H. 
Published: December 2006

The manganese ores of the Benallt mine are pervaded by an orange-coloured mineral which occurs very poorly crystallized as patches and small specks in the matrix. Less commonly it occurs as minute flakes in the ore and sometimes as a constituent of very thin veins which traverse the ore. In some specimens the mineral is better developed. It then shows a good cleavage and resembles in appearance in thin section a weakly pleochroic mica or chlorite. Patches of this mineral in the matrix frequently enclose very small rounded garnets which are believed to be spessartine.In 1932 Dr. A. F. Hallimond examined some sections of ore from the old Benallt mine for Dr. C. A. Matley and suggested that one of the constituent minerals might be a manganiferous chlorite.
Bustamite from Treburland manganese mine, Cornwall, and its paragenesis. (With Plate XV)
Authors: Tilley C. E. 
Published: December 2006

Bustamite forms an important constituent of the manganese ores of the Treburland mine near Altarnun, Cornwall. The rediscovery of this mineral locality is due to Sir Arthur Russell, who has already presented an account of the rhodonite and tephroite of the mine (Proc. Min. Soc. 1944, p. xix). Since then the writer has noted bustamite and bementite from the same locality (ibid. 1944, p. xxvi), and it is the purpose of the present paper to discuss the composition and paragenesis of this bustamite.Rhodonite and tephroite form the chief silicate constituents of the manganese ores exposed On the dumps adjacent to the old Treburland mine shaft, but bustamite-bearing assemblages are not uncommon.
A contribution to the study of luxullianite
Authors: Wells Maurice Kingsley 
Published: December 2006

Lxullianite is well known, at least by name, in this country, and indeed it enjoys an international reputation among petrologists. Its general characters have been described by Bonney and Sir John Flett, while reference to the type is to be found in most standard text-books on petrology. It is, however, a rock of outstanding interest and deserves fuller description and illustration than have yet been accorded it.The preparation by Mr. A. V. Weatherhead of a large set of thin sections for teaching purposes has given the writer an opportunity of making a more detailed examination of the micropetrology of the rock, with special reference to the manner of the replacement of the several original components.
Variation in the structure of zircon
Authors: Stott Vaughan H. , Hilliard Alfred 
Published: December 2006

In the course of an investigation on refractory materials, in which the identification of minerals by their X-ray diffraction patterns had a prominent place, an interesting observation was made on a zircon of gem quality which was lent to us by the courtesy of Mr. B. W. Anderson.It may be recalled that the existence of three allotropes has been postulated in order to explain the considerable variations of physical properties which are found when comparing different specimens of zircon. In particular, densities ranging from 3·95 to 4·86 have been observed, the density of zirconium silicate, calculated from X-ray measurements, being 4·71.
Extinction in X-ray crystallography
Authors: Lonsdale Kathleen 
Published: December 2006

Extinction is the increase in absorption that is to be expected when Bragg reflection of X-rays takes place in single crystals, and the corresponding decrease in intensity of reflection observed.The increase of absorption was directly observed in 1914 in two ways. Using the ionization spectrometer, W. H. Bragg found that the amount of radiation transmitted by a crystal section was notably decreased when the transmitted beam had suffered reflection from a set of crystal planes.
Crystals of artificial cassiterite
Authors: Frankel J. J. 
Published: December 2006

The crystals of artificial cassiterite, described below, were produced by volatilization of South African low-grade tin ores. In the sinter-pot method employed, air was blown through a charge of alternate layers of coke and of a 12 % metallic tin concentrate mixed with fine coke. This charge was placed above a basal layer of previously ignited coal. Occasionally sodium chloride was mixed with the concentrate to remove tin as chloride as well as oxide fume. The air-flow was carefully controlled to prevent slagging and was maintained until the evolution of copious fumes of tin oxide, and at times of chloride, ceased.Optical pyrometer readings on the charges during the experiments gave temperatures of 1050°C. approximately, but it is certain that this value is a grave under-estimate of the actual temperatures in the interior of the sinter-pot.
Chemical Analysis of ullmannite from New Brancepeth, Co. Durham
Authors: Smythe J. A. 
Published: December 2006

The first occurrence of this mineral in Britain was announced by L. J. Spencer who found it in the great baryte-witherite vein at New Brancepeth, near Durham. It was found later by Sir Arthur Russell in the witherite vein at Settlingstones, Northumberland.Spencer proved the presence of antimony in considerable quantity and of sulphur, and returned the nickel as 27·87 %, a quantity which agrees well with the accepted formula, NiSbS; the specific gravity was given as 6·70. In view of the rarity of the mineral and its scientific interest, a complete analysis was deemed advisable, and I have carried this out on a specimen from New Brancepeth, which came into my hands not long after its discovery.
The geochemistry of radiogenic strontium
Authors: Ahrens L. H. 
Published: December 2006

The important influence that the radioactive decay of the radio-elements uranium and thorium has had on the geochemical distribution of lead is now well appreciated, but little is known about the possible geochemical implications of the radioactivity of rubidium.Like its alkali metal homologue potassium, rubidium is β radioactive and slowly disintegrates into a stable isotope of strontium: small quantities of strontium have therefore been accumulating in various minerals since the earth's crust first consolidated. This paper will describe firstly, the abundance of radiogenic strontium in the earth's crust as a whole, and secondly, the distribution of radiogenic strontium in various minerals and rocks, in particular those which are of igneous origin.
A simple method for the measurement of the refractive indices of the felspars
Authors: Robins Olive 
Published: December 2006

The method described is one that can be used to measure the refractive indices of minerals when no refractometer is available. The readings are consistent to ±0·002 and are in reasonable agreement with those obtained using a refractometer.The principle of the method is to mix two liquids with different refractive indices. One of these is a typical immersion liquid with a very low volatility. It must have a refractive index greater than that of the mineral under investigation. The other, more volatile liquid has a refractive index less than that of the mineral. The two liquids selected must be miscible in all proportions, but must not react together. The mineral is completely immersed in a mixture of the two liquids.
The lattice parameters and interplanar spacings of some artificially prepared melilites
Authors: Andrews K. W. 
Published: December 2006

A laboratory investigation in connexion with some blast-furnace slags, led to the preparation of the five synthetic melilites for which X-ray data are provided. The five compounds represent gehlenite, åkermanite and three members of the intermediate series of solid solutions, corresponding to 25, 50, and 75 % of åkermanite.The binary system gehlenite–åkermanite was studied by Ferguson and Buddington, who established relationships between refractive indices, density, and composition and determined solidus and liquidus curves. The crystal structure of the melilite group of compounds was investigated by Warren, who showed that the structure was based on a tetragonal lattice.
Two olivines from south african melilite-basalts
Authors: Mathias Morna 
Published: December 2006

The separation and analysis of the olivine phenocrysts from the Spiegel river and Klaasvoogds melilite-basalts was undertaken in order to ascertain whether the olivines contain significant amounts of Ca2SiO4in their constitution in view of the fact that the closely allied rock-types, alnöite (Bowen, 1922) and the basalt from Shannon Tier, Tasmania (Tilley, 1928), are known to contain monticellite, and that Taljaard (1936) has tentatively identified monticellite in one of the melilite-basalts from the Sutherland district, Cape Province.The Spiegel river melilite-basalt from the Riversdale district of the Cape Province was first described by Corstorphine (1898). Petrographic descriptions of the rock have been given by Rogers and Schwarz (1898), Rogers and du Toit (1903), Rogers (1905), Wagner (1914), du Toit (1926), Taljaard (1936), and Holmes (1936).
On the occurrence of anatase in sedimentary kaolin
Authors: Nagelschmidt G. , Donnelly H. F. , Morcom A. J. 
Published: December 2006

It has been shown recently by Brindley and Robinson that anatase could be recognized by X-ray diffraction technique in fireclays from Scotland and Yorkshire which contained from one to two per cent. of titanium dioxide. These authors remark that the anatase appeared to be of a fineness comparable to the kaolin mineral which was the main constituent, and although kaolinites from various sources throughout the world were examined, in no case was either anatase or rutile detected.The object of this note is to draw attention to the presence of anatase in the sedimentary kaolins of Georgia and perhaps South Carolina, U.S.A. According to Smith 115 kaolin samples from Georgia had on an average 1·13 % of TiO2 by chemical analysis. The values ranged from 0·5 to 2·2 % of TiO2. This is in marked contrast to most primary kaolins; those of Cornwall and Devon, for instance, have as a rule below 0·2 % of TiO2.
Dickite from the Witwatersrand gold mines
Authors: Frankel J. J. 
Published: December 2006

The occurrence of dickite in the gold-bearing rocks of the Witwatersrand system was first reported by Mr. H. C. M. Whiteside. In addition, among the many mineral samples given to me by students of the Witwatersrand Technical College, Johannesburg, were several dickite specimens from mines all along the Witwatersrand area. Dickite may therefore be regarded as fairly widespread in the rocks of at least the Main-Bird series, although not in large quantity.The only occurrence of which a detailed record is available is that from the Daggafontein mine. Little is known of the other samples except from the immediate mineral associations. It is, however, clear that all the occurrences are of hydrothermal origin.
Transformation of minerals of the montmorillonite family into 10 Å. micas
Authors: Caillère S. , Hénin S. 
Published: December 2006

In his work on the mineralogy of soils colloids G. Nagelschmidt, suggests the possibility of a reversible change of the typemontmorillonite ⇋ illite ⇋ muscovite.We have attempted to establish experimentally the existence of this transformation following fixation or departure of the potassium from between the fundamental structural sheets of the mica type. The initial material was montmorillonite from Camp Bertaux, Morocco, separated from its impurities by sedimentation. As it was evident a priori that the alteration of montmorillonite into illite necessitates (1) saturation of the base-exchange capacity of the minerals by potassium, and (2) the departure of the layers of water from between the structural sheets of the montmorillonite, we finally, after several attempts, were led to make use of the following technique.
Plagioclases from Sultan Hamud, Kenya
Authors: Game P. M. 
Published: December 2006

The plagioclase which forms the subject of this investigation was presented by Dr. C. Stansfield Hitchen, director of the Kenya Geological Survey, who has kindly sent the following note of its occurrence:‘The pale-green transparent felspar described in this note was found on the western slopes of a hill named Kioo, about 14 miles due north of Sultan Hamud station, Machakos district, Kenya Colony. From a description given by Messrs. D. Lyall and P. Cull, who found the mineral, it appears to have occurred in a small vein-like pegmatite sandwiched between parallel plates of decomposing mica. Towards the periphery of the enclosing mica plates the transparent felspar graded into opaque cream-coloured felspar of more normal appearance. The clear material was somewhat shattered and broke with many fragments on removal. The occurrence suggests a deuteric or possibly hydrothermal origin. Kyanite-gneisses occur in the vicinity.’
High-order plates for the microscopic examination of mineral grains
Authors: Smithson Frank 
Published: December 2006

For the examination of grains with high birefringence the usual types of wedge or plate often fail to give clear indications of optical sign. In such cases plates up to the 20th order on Newton's scale (relative retardation about 10μ) may be employed.Determination of sign of length of a crystal—A detrital crystal of zircon (length positive, i.e. slow) about 300-400μ thick observed between crossed nicels in conjunction with a 15-20th-order plate will illustrate this test. When the length of the crystal is parallel to the fast direction of the plate (fig. 1 A) there is compensation, and colour bands are seen. Without the plate, or with the crystal rotated through 90° (fig. 1 B), only high-order whites are seen. A crystal of high birefringence with length negative (e.g. a bipyramid of anatase) will give colour bands in position B, and none in position A.
A re-examination of churchite
Authors: Claringbull G. F. , Hey Max H. 
Published: December 2006

In the course of a study of certain cerium minerals, a spectrogram of churchite was taken and it was noticed that the cerium lines were barely visible, whereas the yttrium lines were very strong. We therefore decided to re-investigate this species.Churchite was originally described by A. H. Church in 1865, and named by C. G. Williams in the same year. The specimens were collected by R. Talling from an unnamed locality in Cornwall. It has only been analysed once, by Church, who showed it to be a hydrated phosphate of rare-earths and lime; his quantitative data have been recalculated and included in table I. Church obtained qualitative reactions for the cerium group of rare-earths, and for cerium itself, but made no attempt to determine the ratio of cerium to yttrium earths; he assumed a mean molecular weight for the rare-earths which would correspond to R2O3 324, essentially a mixture of cerium earths with but little yttria, but did not adduce any evidence for this assumption.
Note on the occurrence of beryl and löllingite at the New Consols mine, Stoke Climsland, Cornwall
Authors: Embrey P. G. 
Published: December 2006

Specimens of the minerals beryl and löllingite were found by me among material collected in the summer of 1950 and the spring of 1951 for work on the distribution of trace elements in the New Consols mine, Stoke Climsland, Cornwall. Unfortunately, I was unable to collect further material, and in the case of the 1ö11ingite its presence on a specimen was recognized only after the mine had been abandoned and become flooded. This locality for the two minerals seems worthy of record in view of the small number of reported occurrences in Cornwall.The beryl was found in specimens from a pegmatite vein, approximately 2 feet thick and dipping steeply southwards towards the main granite boss of Kit Hill, which was intersected 222 yards from the engine shaft by a south cross-cut at the 52-fathom level.
A new review of the chlorites
Authors: Hey Max H. 
Published: December 2006

The chlorites form an extensive isostructural series with a high degree of isomorphous substitution, within which it has always been difficult to define or delimit species; until recently, owing to the lack of adequate X-ray studies; several structurally distinct species were included with the group, further complicating the problem. The group comprises aluminosilicates of magnesium and iron (ferrous and ferric); a few contain appreciable amounts of chromium, nickel, or manganese, and one (pennantite) contains manganese as a major constituent.The first step towards the understanding of the relations of the chlorites was taken by G. Tschermak (1890, 1891), who divided them into two groups: the orthochlorites, with compositions between (Mg,Fe")2Al2SiO5(OH)4 and (Mg,Fe")2Si2O5(OH)4, and the leptochlorites, with compositions not explicable on this basis, and in general richer in trivalent ions (often including considerable Fe"′) relative to silicon and divalent ions. The two orthochlorite end-members have the composition of amesite and serpentine respectively, but it is now known that neither of these two minerals has the chlorite structure.
A simple monochromator
Authors: Vincent H. C. G. 
Published: December 2006

An easily constructed apparatus, giving illumination by light of any chosen colour, and of adequate purity in a narrow spectral region, has been made and found satisfactory in the determination of the optical properties of crystals.Light of high intensity is focused on an adjustable slit, rendered approximately parallel by means of a lens, and passed through two hollow prisms containing alpha-monochloronaphthalene. In the widely divergent spectral beams the microscope moves along a calibrated arc and any desired wave-band of reasonable purity may be selected. The apparatus is illustrated in the accompanying diagram (fig. 1) and photograph (fig. 2).A small carbon arc (A) using direct or alternating current gives adequate intensity, allowing for a narrow setting of the slit, with corresponding purity of the monochromatic beam.
The identity of jurupaite and xonotlite
Authors: Taylor H. F. W. 
Published: December 2006

Jurupaite was discovered at Crestmore, California, by A. S. Eakle in 1921. The mineral was found in a quarry which was rapidly being enlarged, and Eakle stated that it was probably represented only by the one specimen which he had collected. He showed that it was a hydrated calcium silicate containing magnesia, with the composition 2(Ca,Mg)O. 2SiO2. H2O, the ratio of lime to magnesia being approximately 7 : 1.This specimen passed into the keeping of Professor A. Pabst, who kindly made a portion available to the writer. He confirmed that it was unlikely that any other specimen existed. The jurupaite consisted of rosettes of white needles or fibres, about a centimetre in diameter. A brown discoloration was observed on the exposed outer surfaces of the specimen, but not on freshly cut surfaces. Calcite was present in contact with the jurupaite.
The orthoclase-microcline inversion
Authors: MacKenzie Wm. Scott 
Published: December 2006

The association of orthoclase and microcline in the same rock has been commented on by many writers, and from these occurrences attempts have been made to deduce the relative stability of these two low-temperature forms of potash-felspar. Ahnost all investigators have concluded that nlicrocline is the lower-temperature modification, but difficulties in explaining the relationship of adutaria to orthoclase and microcline have been encountered.The identification of the monoclinie potash-felspar in association with microcline is almost always based on optical properties, viz. straight extinction in the zone [010] or the absence of visible multiple twinning.
An occurrence of a regular mixed-layer clay-mineral
Authors: Heystek H. 
Published: December 2006

About twelve miles south-east of Burghersdorp in the Cape Province, South Africa, the unusual clay reported in this paper was first discovered on the farms 'Groenvlei' and 'Kuilfontein'. Later deposits were also uncovered on the farms 'Kapokkraal' and 'Kleinhoek'.The clay-mineral appears to be of a very unusual type, namely, a regular mixed-layer clay-mineral (1:1 hydrous mica and montmorillonite). The mode of origin of the clay is also of interest in that it appears to be produced from a shale by hydrothermal alteration, due to intrusion of dolerite sheets.