bluuebunny/crossref_metadata_2025 huggingface dataset:
An X-ray Examination of decomposition products of chrysotile (asbestos) and serpentine
Authors: Hargreaves A. , Taylor W. H.
Published: December 2006

Many of the experiments described in this paper were made in the course of an examination of problems arising in connexion with technical uses of fibrous asbestos, undertaken about three years ago at the request of Dr. W. Francis, at that time Director of Research for Messrs. Turner Brothers Asbestos Company Limited, Rochdale. We have recently been able to investigate in a little more detail certain points which seemed likely to be of fairly general interest, and we now present our results in the hope that they may be of use to other researchers in this field. We are indebted to Dr. Francis and his colleagues for valuable discussions on questions arising in the course of the work, and to the Directors of Messrs. Turner Brothers for financial assistance in connexion with the earlier experiments, and for permission to publish this paper.
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.
The cell dimensions and space-group of pinnoite
Authors: Stadler H. P.
Published: December 2006

Pinnoite, first described by Staute in 1884, is straw-yellow, granular to faintly fibrous. It occurs in the upper kainite layers at Stassfurt, and is found associated with earthy boracite from which it is freed by washing with water. The analysis corresponds to the formula MgO.B2O3.3H2O, and Staute assumes the mineral to be an alteration product of boracite, 6MgO.MgCl2.8B2O3. Groth classes pinnoite together with CaO.B2O3 as a hydrated metaborate. This assumption does not seem justified, as will be pointed out later.
The identity of minervite and palmerite with taranakite
Authors: Bannister F. A. , Hutchinson G. E.
Published: December 2006

The abundance of the well-known potassium aluminium silicate minerals, orthoclase, microcline, and muscovite, stands in striking contrast with the rarity of the little-known potassium aluminium phosphate minerals. The only one of these which occurs as distinct crystals and which has yielded a satisfactory formula is minyulite, KAl2(PO4)2(OH,F).4H2O. This mineral was first described by E. S. Simpson and LeMesurier from Western Australia in 1933 and an examination of well-crystallized specimens from South Australia by L. J. Spencer et alii was published in 1943. Spencer's paper included X-ray single-crystal and powder data for minyulite. X-ray, optical, and specific gravity data were also determined at that time for a few other hydrous potassium aluminium phosphate minerals from the British Museum collections. These included palmerite from guano deposits in a large cavern, Monte Alburno, near Controne in Salerno, Italy, presented by E. Casoria who described the mineral in 1904, and taranakite from the Sugarloaves, near New Plymouth, Taranaki, New Zealand.
The nomenclature of the halloysite minerals
Authors: MacEwan Douglas M. C.
Published: December 2006

The name ‘halloysite’, first used in 1826 by Berthier, is derived from that of Omalius d'Halloy, who found the mineral in Angleur, Liége, Belgium. In 1935, Mehmel discovered that there were two distinct substances included under the name halloysite, one of which contains loosely bound water and shows a 10 Å. basal reflection on an X-ray diagram, the other none and shows a reflection at about 7 Å. Mehmel preserved the name halloysite for the hydrous mineral, and for the product of its dehydration he proposed the name ‘metahalloysite’. Both substances may occur naturally (though this may not have been known to Mehmel at the time). Previous to this work it had been suggested by Hofmann, Endell, and Wilm that the 10 Å. material on dehydration at a low temperature gave kaolinite. Mehmel showed that this was wrong; and that the error was due to the similarity of the X-ray diagrams of kaolinite and metahalloysite. Hofmann and co-workers, and Mehmel, all tacitly assumed that the name halloysite was correctly applied to the 10 Å. material rather than the 7 Å. material.
Cuspidine from dolomite contact skarns, Broadford, Skye
Authors: Tilley C. E.
Published: December 2006

Cuspidine was first described by Scacchi (1876) in the ejected blocks of metamorphosed limestone at Vesuvius, but a detailed and systematic morphological description of well-terminated crystals was given first by vom Rath (1883) from material at Cozzolino in Resina, Vesuvius. The monoclinic character of the spear-shaped crystals was then established with a:b:c = 0·7243:1:1·9342, β = 89° 22′, and twins on (100) giving = 1° 16′. Scacchi (in Arzruni, 1877) had earlier indicated the possibility that cuspidine he had described as orthorhombic was monoclinic and twinned when he recognized a re-entrant angle of 178° 42′ on the cleavage truncating the acute ends of the crystals.
Pyrophanite from the Benallt mine, Rhiw, Carnarvonshire
Authors: Smith W. Campbell , Claringbull G. F.
Published: December 2006

Pyrophanite was recorded by one of us in a recent paper as one of the minerals occurring at the Benallt manganese mine in the vein from which material for the chemical analyses of the new manganese-rich chlorite, pennantite, was separated. As this was only the third record of pyrophanite in the world it seems necessary to give, very briefly, the evidence for its identification.
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.
On tilleyite and its associated minerals from Carlingford, Ireland (With Plates XI and XII.)
Authors: Nockolds S. R. , Vincent H. G. C.
Published: December 2006

The mineral tilleyite was first discovered by Larsen and Dunham in thermally metamorphosed limestones from the contact zone at Crestmore, California. It is associated there with merwinite, wollastonite, spurrite, and gehlenite, and the rock is traversed by streaks of idocrase with grossular. The amount of tilleyite in these rocks was apparently small, but in certain thermally metamorphosed limestones from Carlingford it is abundant and some specimens are practically pure tilleyite-rocks, it has been possible, therefore, to make a more detailed optical and chemical examination of this mineral. The tilleyite occurs as subidioblastic crystals when abundant, or as rounded grains in calcite-rich rocks, or as irregular plates.
Subcalcic ferroaugite from Mount Arthur, East Griqualand
Authors: Poldervaart Arie
Published: December 2006

In recent years the clinopyroxenes of the system clinoenstatite–diopside–hedenbergite–clinoferrosilite have received a great deal of attention. As research in this field advanced, the need for a balanced and generally acceptable subdivision of the system has made itself increasingly felt. Hess (1941) proposed a classification for these clinopyroxenes, which was subsequently extended by Benson (1944).
The relationship of orthopyroxene to pigeonite
Authors: Poldervaart Arie
Published: December 2006

Interest in the orthopyroxene series is evidenced by the great number of publications on that subject which appeared in the literature. Correlations of the chemical composition and optical properties were attempted by Winchell (1923, 1933), Walls (1935), Henry (1935), and Hess and Phillips (1940). The nomenclature of the series was discussed by Winchell (1923), Alling (1936), and Hess and Phillips (1940). The obscure phenomena exhibited by certain orthopyroxenes in polarized light, attributed by some to twinning, by others to exsolution, was noted by a great many petrologists, of whom are mentioned here Lewis (1908), Holmes and Harwood (1928), Guimarães (1933), Scholtz (1936), Hess and Phillips (1938, 1940), Kuschke (1939), Wager and Deer (1939), Nel (1940), Walker (1940, 1943), Walker and Poldervaart (1940, 1941), Edwards (1942), Henry (1942), and Poldervaart (1944, 1946).
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.
Pyroxenes, amphibole, and mica from the Tiree marble
Authors: Hallimond A. F.
Published: December 2006

The Tiree pink marble, a fine-grained, severely crushed limestone with evidence of earlier coarse crystallization, is exposed in several small areas up to 100 feet across on the farm of Balephetrish near the north coast of the island of Tiree in the Hebrides. It contains a remarkable quantity of dark silicate minerals and has discordant contacts with the adjacent Lewisian gneiss. The precise nature of its relation to the gneiss, and mode of emplacement, have been much discussed. The writer has been permitted to consult accounts of the literature, by Mr. V. A. Eyles, and of the petrography, by Sir Edward B. Bailey, and is also indebted to those authors for discussion of the problems. At the suggestion of Sir Edward Bailey the present work was undertaken as a contribution to the study of this problem from the mineralogical point of view. Most of the determinations were made in 1938, but it was not possible to complete publication at that time.
Excursion to Penrith and the north-west
Authors: Dunham K. C. , Hollingworth S. E.
Published: December 2006

Mineral localities in north-western England were visited during the second excursion organized by the Society in recent years, from April 14 to 18, 1947, the headquarters being the George Hotel, Penrith. Members taking part included: The President, W. Campbell Smith (London), O. J. Adamson (Oslo, Norway), W. Anderson (Newcastle), F. A. Bannister (London), D. W. Bishopp (Dublin), C. E. N. Bromehead (London), G. F. Claringbull (London), T. Deans (London), W. A. Deer (Cambridge), K. C. Dunham (London), N. R. Goodman (Nova Scotia and Oxford), G. S. Gowing (Stockton-on-Tees), S. E. Hollingworth (London), W. Hugill (Stoke-on-Trent), H. Neumann (Oslo and Leeds), C.W. Pegg (London), F. H. Rathmann (U.S.A.), P. L. Rumsby (London), R. D. S. Shrimpton (Slough), J. H. Taylor (London), E. A. Vincent (Durham), L. R. Wager (Durham), Miss D. E. Wisden (Southampton). Dr. Claringbull undertook the administrative arrangements.
The occurrence of an orthorhombic high-temperature form of Ca2SiO4 (bredigite) in the Scawt Hill contact-zone and as a constituent of slags (With Plates XV and XVI.)
Authors: Tilley C. E. , Vincent H. C. G.
Published: December 2006

Recent research on the polymorphism of calcium orthosilicate has broadened and to some extent modified the picture of the phase relations of this substance as presented in the pioneer studies of Day and Shepherd (1906) and Rankin and Wright (1915). These investigators recognized three distinct forms, α, β, and γ, related by transformation as follows: α⇄β at 1420° C. and β⇄γ, at 675° C. The high-temperature α form was described as monoclinic or triclinic and intimately twinned, the β form orthorhombic, and the low-temperature γ form as probably monoclinic. The optical properties of these α and β forms as reported are so closely similar that were it not for the twinning, regarded as diagnostic, the two forms would be distinguishable only with difficulty. This optical similarity was later found to be paralleled by a close agreement of the X-ray powder diffraction patterns of the two phases early noted by Hansen (1928) and confirmed among others by Insley (1936).
Earlier stages in the metamorphism of siliceous dolomites (With Plates XVII and XVIII.)
Authors: Tilley C. E.
Published: December 2006

In the progressive thermal metamorphism of siliceous dolomites, tremolite and calcite are usually considered the earliest of the new mineral phases formed by reaction of the primary materials, dolomite and quartz. An early formation of forsterite has also been recorded, as, for example, in the dolomitie zones of the Durness limestone surrounding the Tertiary Beinn an Dubhaich granite of Skye. In this aureole, however, the relation of forsterite to tremolite has hitherto not been closely investigated. As Bowen has pointed out in his systematic study of the progressive metamorphism of siliceous limestones and dolomites, a first formation of forsterite from dolomite and quartz could not rank as an equilibrium reaction since forsterite and quartz can have no stable coexistence. Tremolite has accordingly been regarded as the first metamorphic product in an equilibrium series of reactions of increasing decarbonation affecting siliceous dolomites in an advancing higher temperature environment at any given pressure.
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.
An improved polarizing microscope. III. The slotted ocular and the slotted objective
Authors: Hallimond A. F. , Taylor E. Wilfred
Published: December 2006

Measurements with the petrological microscope may be divided into those made with the orthoscopic and those with the conoscopic arrangements. It was early realized that if the micrometer scale or compensator was inserted in the focal plane of the ocular, the same apparatus would serve for measurements of both kinds, provided that a Bertrand lens was available. The method was described by A. B. Dick as early as 1888 in a form of microscope which has remained popular with many workers up to the present time. Additional slots at the level of the focal plane of the ocular were cut through the mount and the upper part of the microscope tube. Most European manufacturers, however, continued to provide only the usual slots in the lower part of the tube.
On rashleighite, a new mineral from Cornwall, intermediate between turquoise and chalcosiderite
Authors: Russell Arthur
Published: December 2006

The mineral here described was at first considered to be an iron-rich variety of turquoise and was described by myself as such when this paper was read before the Society in 1937. At that time only a partial analysis had been made; since then Dr. J. A. Smythe of King's College, Newcastle-upon-Tyne, has most kindly undertaken at my instigation careful analyses of the mineral from both of its localities, Bunny mine, St. Austell, and Castle-an-Dinas wolfram mine, St. Columb Major. As a result of these two analyses, which are in close agreement, it is evident that the mineral is a new one, intermediate between turquoise and the two minerals chalcosiderite and andrewsite, and forming a middle member of what is probably an isomorphous group.
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.
Pyroxene from the Squilver dolerite, south Shropshire
Authors: Blyth F. G. H.
Published: December 2006

The andesine-dolerite of Squilver Hill, situated nearly 3 miles due north of Bishops Castle, has been described in another place. This somewhat coarse-textured rock, with a distinctive greenish-blue colour, contains up to 20 per cent. of a fresh monoclinic pyroxene as crystals of irregular shape, many of which are about a millimetre in length. The rest of the rock consists of saussuritized plagioclase, some interstitial chlorite and prehnite, and accessory apatite, sphene, magnetite, and ilmenite; the unaltered nature of the pyroxene is noteworthy.
Ships' loadstones
Authors: Bromehead C. E. N.
Published: December 2006

From the beginning of classical times it was well known that the mineral conveniently called loadstone, whether magnetite in the strict sense or some other compound, attracted or, better, adhered to iron ; also that this property was imparted to a piece of iron in contact with a loadstone, so that a chain of disconnected iron rings could be suspended from it. This action aroused such wonder that many superstitions gathered round the stone which was reckoned throughout tlle Middle Ages as a gem. A genuine economic value was given to loadstone when the further discovery was made that a suitably shaped piece of the stone, or of iron touched with it, if free to move, would always aline itself approximately north and south.
On the delimitation of diorite and gabbro and related rocks
Authors: Ellis S. E.
Published: December 2006

There is general agreement as to the basis on which most major igneous rock-types are defined despite some difference of opinion as to quantitative limits. This is not true of diorites and gabbros (or of their hypabyssal and volcanic equivalents) in distinguishing between which at least four different criteria are in current use.
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.
Notes on the mineralogy and geochemistry of zinc
Authors: Neumann Henrich
Published: December 2006

The ionic radius of zinc (0·83 Å.) is identical with that of divalent iron (0·83 Å.) and nearly the same as that of magnesium (0·78 Å.). One would therefore expect zinc to be mineralogically closely related to iron and magnesium. It is, however, well known that this is not the case. An examination of a list of the zinc minerals which have so far been described shows that only in a few cases are the corresponding isomorphous ferromagnesian species known. As a rule zinc minerals and iron-magnesium minerals with corresponding chemical formulae are entirely different in their crystal-structure.
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.
The constitution of some Egyptian clays
Authors: Gad G. M. , Barrett L. R.
Published: December 2006

The Egyptian clays under consideration are obtained from two different localities. The Aswan clays are mainly concentrated in the neighbourhood of Aswan town in Upper Egypt and the Sinai kaolins from the Sinai Peninsula. The Aswan clays, namely: red Aswan clay, white Aswan clay, and siliceous Aswan clay, are transported clays, while Aswan kaolin is a residual clay. The Sinai kaolins are of obscure origin but most probably are transported clays. As is shown later, these are alunite-bearing clays not previously recorded in Egypt.
Alteration of the properties of bentonite by reaction with amines
Authors: Jordan John W.
Published: December 2006

The affinity between certain organic compounds and clays has been known for many years. Lloyd reported the adsorptive capacity of fuller's earth for alkaloids in 1916 without theorizing extensively about the mechanism. Smith reacted organic bases and their salts with bentonite and presented evidence that the reaction was one of base-exchange or metathesis, while Hauser has discovered that certain organic compounds of bentonite have the property of swelling and dispersing in organic liquids. This paper reports observations on the rather striking conversion of bentonite from the hydrophilic to the organophilic condition and proposes a mechanism to explain the observed phenomena.
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 type

montmorillonite ⇋ 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.
Experimental formation of chlorites from montmorillonite
Authors: Caillère S. , Hénin S.
Published: December 2006

One of the problems which occupy the mineralogist as well as the geologist or pedologist is the mechanism of the formation and evolution of minerals in nature. In this general connexion we have been trying to clarify the possibility of passing from montmorillonite to chloritic minerals. Already in a previous work we showed that on precipitating magnesium with ammonia in the presence of montmorillonite, a substance is obtained which shows certain of the characteristics of vermiculite and chlorite. Having thus shown the possibility of passing from one type to the other, we wished to clarify the mechanism of the change. We wanted to know what are the conditions of the transformation, and then to follow the montmorillonite from the moment when it was in equilibrium with the solution of magnesium chloride to the end of the alteration. Finally, it had to be established to what extent the product obtained resembled or differed from the standard minerals. These different points will be considered in succession.
Cymrite, a new barium mineral from the Benallt manganese mine, Rhiw, Carnarvonshire
Authors: Smith W. Campbell , Bannister F. A. , Hey Max H.
Published: December 2006

Among the specimens collected at the Benallt manganese mine in 1944 by Dr. A. W. Groves and myself was one (B.M. 1944,48) from the 60-foot level in no. 1 ore-body which showed on a face of dark, compact manganese ore colourless plates up to 7 mm. across and about ½ mm. thick. These plates proved to be uniaxial and negative with perfect basal cleavage. Heated in an ignition tube the fragments decrepirated, gave off water, and became pearly, white, and opaque. Qualitative tests showed Ba, Al, and SiO2 to be present. Preliminary X-ray photographs revealed hexagonal symmetry, but could not be matched with those of any known mineral.
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.’
Silica percentage as a factor in igneous-rock classification
Authors: Wells A. K.
Published: December 2006

In previous editions of Hatch's ‘Petrology of the igneous rocks’ including the last two, for the revision of which the writer was largely responsible, historical precedent was followed and the main lines of classification were based on variation in the silica percentage. In preparing for the new post-war edition considerable thought has been given to this matter. The weakness of the scheme has become increasingly apparent to the writer, and it is now obvious that no juggling with the selected ranges of silica percentage chosen to delimit the ‘acid’, ‘intermediate’, and ‘basic’ categories can result in a workable, logical scheme. Silica percentage as a basis of rock classification must be abandoned for the reasons discussed below.
Correlation of the Mohs's scale of hardness with the Vickers's hardness numbers
Authors: Taylor E. Wilfred
Published: December 2006

Mineralogists have long been accustomed to describe hardness with the aid of a scale devised by Friedrich Mohs, who lived from 1773 to 1839. The test is qualitative, each mineral in the scale being capable of scratching those that precede it, but the ten minerals have held their ground as a useful representative series with which it is now interesting to compare another method of estimating hardness.
Observations on the colouring of pink and green zoned tourmaline
Authors: Bradley J. E. S. , Bradley Olive
Published: December 2006

This investigation was concerned with two aspects of the colour-zoning in tourmaline: firstly, the origin of the green and pink colours ; secondly, the reason for the apparent incompatibility of these two forms. Much of the previous work on the colour of tourmaline has involved the use of emission spectra. This method provides information as to which elements are present; it does not, of course, indicate which of the twenty or so elements identified is responsible for the colour, although it may be possible to infer this. Absorption spectra, on the other hand, are directly concerned with colour. They have been employed quite extensively in Germany, and more recently in Russia, but the earlier data and instruments were often inadequate. The last decade has seen marked improvements in the technique of absorption spectroscopy, particularly in the development of photo-electric methods for the quantitative recording of spectra, and the method is likely to prove one of increasing value.
Ferrous chamosite and ferric chamosite
Authors: Brindley G. W. , Youell R. F.
Published: December 2006

In a previous paper (Brindley, 1951) chamosites from a number of localities were examined, and their structure was shown to be of kaolin-type. Furthermore, it was shown that many of the variations in X-ray powder diagrams of chamosites can be accounted for by the existence of two kaolin-type structures, one hexagonal and one monoclinic, with simply related ceil dimensions.
An X-ray method for studying orientation of micaceous minerals in shales, clays, and similar materials
Authors: Brindley G. W.
Published: December 2006

Micaceous minerals, such as the micas, the chlorites, and most clay minerals, usually develop as thin lamellae parallel to the crystallographic basal plane (001). In sedimentary deposits these lamellae tend to lie parallel to the bedding plane and in slates parallel to the cleavage. Their degree of orientation is likely to vary with the conditions of formation of the material, and in the case of slates Bates (1947) has shown that it is closely related to their fissility. In relatively coarse-grained materials the degree of orientation may be studied directly by suitable microscopic techniques, but with fine-grained materials X-ray methods must be used, and even with coarser-grained materials the use of X-ray methods may have advantages, especially if a scanning technique, such as that described by Thewlis and Pollock (1950), is employed.
Gyrolite
Authors: Mackay A. L. , Taylor H. F. W.
Published: December 2006

The mineral gyrolite was discovered in Skye by T. Anderson in 1851. He showeditto be ahydratedcaleiumsilicateofapproximate composition 2CaO.3SiO2.3H2O. Subsequently gyrolite has been found in other localities, and has been prepared hydrothermally by Flint, McMurdie, and Wells. The ratio of lime to silica found by Anderson appears well established, but various values of the water content have been reported and more recent analyses approximate to 2CaO.3SiO2.2H2O. X-ray powder measurements were given by McMurdie and Flint, a but no crystallographic or other investigations of a detailed character have been reported.
The mineralogy of the antimony oxides and antimonates
Authors: Mason Brian , Vitalian Charles J.
Published: December 2006

During an investigation of stibiconite and cervantite (Vitaliano and Mason, 1952) we examined many specimens of antimony ochre. The commonest mineral in these specimens proved to be stibiconite, but others were found, and to establish their identity it became necessary to study the secondary products as a group. The mineralogy of these oxygenated secondary antimony minerals presents unusual problems on account of their earthy and often inhomogeneous nature. Our experience indicates that without X-ray powder photographs it is difficult to establish the true identity of much of this material. The purpose of this paper is to present the results of our investigations and to provide more adequate descriptions of some little-known species.
The pumpellyite mineral series
Authors: Coombs D. S.
Published: December 2006

The bluish-green epidote-like mineral, pumpellyite, was first described by Palache and Vassar (1925) from the copper-bearing amygdaloidal lavas of the Lake Superior region. It has since been reported from many parts of the world in rocks which have undergone low grades of metamorphism, especially types such as amygdaloidal spilites and diabases (Burbank, 1927; Waldmann, 1934; Tsuboi, 1936; Quitzow, 1935, 1936; Klein, 1939; Laeroix, 1942; Seether, 1942; Zavaritsky, 1944:; Korzhinsky, ]944; de Roever, 1947a, b; Kvasha, 1950) and in glaueophane-schists and even eclogites in which pumpellyite is often associated with lawsonite (Irving, Vonsen, and Gonyer, 1932; Quitzow, 1935, 1936 ; Lacroix, 1942 ; Switzer, 1945 ; de Roever, 1947a, b, 1950). W. P. de Roever (1947a, 1950) has suggested a pumpellyitic facies of metamorphism as a lower-grade equivalent of his lawsoniteglaucophane subfacies, characterized by high confining pressure, but subordinate shearing stress and thermal influence, and passing into unmetamorphosed rocks.
An occurrence of harmotome in north-west Ross-shire
Authors: Waterston Charles D.
Published: December 2006

The minerals to be described were found by Dr. Duncan M. Morison, of Edinburgh, and the writer in a small quarry having a national grid reference of 29/076184, which is at present being excavated for road surfacing material. The quarry is situated on the east side of the coast road between Lochinver and Ullapool at a point ¼ mile south-west of the southern margin of Loch an Arbhair (called Loch a' Choin on early editions of the Ordnance Survey sheet 101) and ¾ mile south-west of the bridge carrying the Lochinver-Ullapool road over the river Kirkaig, the course of which here marks the boundary between the counties of Sutherland and Ross.
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 granophyre from Coire Uaigneich, Isle of Skye, containing quartz paramorphs after tridymite (Plate XIII)
Authors: Wager L. R. , Weedon D. S. , Vincent E. A.
Published: December 2006

The narrow belt of granophyre lying to the west of Blaven in the Isle of Skye showed so admirably the effects of chilling that a series of specimens was collected by one of us (L.R.W.) and found to contain, in the chilled marginal rock, phenoerysts of tridymite, now inverted to quartz. In the Thulean Tertiary igneous province former tridymite is known from certain acid lavas, for example, the Tardree rhyolite (von Lasaulx, 1877) and certain Icelandic liparites (Hawkes, 1916), and from metamorphosed arkoses adjacent to basic igneous intrusions (Harker, 1908, 1932), but it has not previously been noted in the intrusive acid rocks. In addition to phenocrysts of tridymite inverted to quartz, there is present in the groundmass of the unchilled granophyre a second generation of inverted tridymite crystals, surrounded by a final stage of quartz and felspar which has crystallized with normal microgranitic textures. Some of the textural features resemble those of the normal Skye granophyres, while others resemble certain metamorphosed arkoses.
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.
The identification and determination of plagioclase felspars by the X-ray powder method
Authors: Goodyear J. , Duffin W. J.
Published: December 2006

There appear to be few published data correlating X-ray powder patterns of chemically analysed plagioclase felspars with composition. Tuttle and Bowen (1950) have examined the powder patterns of low-temperature and high-temperature modifications and find that pure albite from Amelia, Virginia, when heated for ten days at 1050° C., gives a powder pattern identical with that of synthetic albite. They have not given, however, complete data over the whole range from An0Ab100 to An100Ab0. Claisse (1950) selected six reflections from the powder patterns of eight plagioclases of composition extending over the complete range, and plotted line separations against composition determined optically, but did not distinguish between high- or low-temperature forms.
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.
Crystallization of pyroxenes in an iron-rich diabase from Minnesota
Authors: Muir I. D.
Published: December 2006

The Beaver Bay diabase forms an irregular sill-like intrusion about 3000 feet in thickness exposed over a distance of approximately six miles from Split Rock to Beaver Bay on the north shore of Lake Superior, Minnesota. It is intrusive into the Keeweenaw volcanic series above the Duluth gabbro to which it is almost certainly related. It is the largest of many such sills in this region and includes several petrographic facies grading from troctolite, through olivine-gabbro, normal gabbro, and ferrogabbro to red granite.
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.
Zoisite-amphibolite with corundum from Tanganyika
Authors: Game P. M.
Published: December 2006

The most striking rock now described occurs in the Northern Province of Tanganyika Territory, just west of the Great North road, and south of the track from Longido to Engare Naibor. A small group of specimens was collected by Mr. A. G. Clough of Industrial Minerals Ltd., and presented to the British Musemn (Natural History) in 1952 (B.M. 1952,133). The outcrops occur in the highly metamorphosed Basement Complex which forms small hills (The Matabatu Mountains) descending, at their margin, by step-faulting to a peneplaned surface cut out of much younger, unconformable volcanics; the faulting in the marginal area of the basement rocks forms the eastern side of the Rift Valley. The basement rock adjacent to the zoisite-amphibolite is usually anamphibolite with conspicuous large, brown-red garnets. The occurrence of this garnet-amphibolite is usually an indication of the proximity of the zoisite-amphibolite.