bluuebunny/crossref_metadata_2025 huggingface dataset:
The reciprocal role of alumina in reaction series
Authors: Brammall Alfred
Published: December 2006

Inquiry into this feature was stimulated by a reasonable doubt concerning the reality of the immiscibility gap in the clinoenstatite-diopside series. The existence of this gap was first suspected by Sosman and Asklund, and the identity of the gap with the composition field of the hornblendes has recently been suggested by Kennedy, whose comparative study of hornblende and pyroxene composition engaged statistical methods applied in the first instance by Asklund.
The paragenesis of kyanite-eclogites
Authors: Tilley C. E.
Published: December 2006

In Haüy's original definition of eclogite, the presence of kyanite as an accessory constituent was recognized, and it is apparent that he was familiar with examples from the Sau Alps and Styria. The best known of eclogites—those of the Bavarian Fichtelgebirge (e.g. Silberbach, Weissenstein, and Eppenreuth)—contain significant kyanite interspersed among the omphacite grains or associated with accessory quartz and muscovite in the rocks. Of these rocks rather extended descriptions have been published. Analyses of the minerals and the rocks themselves belong to an early date and do not reach the standard of modern analyses. Later, Drill (1902) published a systematic account of these Bavarian eclogites and has added an analysis of an eelogite with kyanite from Unterpferdt near Silberbach and an analysis of a garnet from a Silberbach eclogite.
The paragenesis of Cookeite and hydromuscovite associated with gold at Ogofau, Carmarthenshire
Authors: Brammall A. , Leech J. G. C. , Bannister F. A.
Published: December 2006

This paper describes occurrences of cookeite (not previously recorded as a British species) and hydromuacovite, associated with auriferous pyrite and arsenopyrite, blende, galena, carbonates, and free gold at Ogofau, on the left bank of the river Cothi, half a mile ESE. of Pumpsaint, Carmarthenshire.

The hillside around Ogofau is scarred with opencast workings and trenches reputed to be an 'ancient gold mine' dating back to Roman times. Though the mine is described as 'disused' on the Ordnance Survey map (six-inchcs/mile, Sheet XVII, NW.), these surface workings have been exploited for free gold intermittently within the last fifty years, and recent development work (by the Roman Deep Holdings,Ltd.) from a shaft sunk in 1910 is approaching the producing stage.
An integrating micrometer for the geometrical analysis of rocks
Authors: Dollar A. T. J.
Published: December 2006

This instrument is a microscope stage-micrometer for the quantitative estimation of one to six different kinds of constituents in a substance, by the Delesse-Rosiwal method. It is intended, primarily, for linear micrometrie analysis in petrography, but has similar uses in mineralogy, chemistry, and metallography. Economic applications include the volumetric evaluation of components in building stones, road-metals, sSlid fuels, refractories, and slags.

The object of this new design is to combine speed and accuracy in operation with a particularly compact construction, mechanical simplicity, and strength. Special consideration has been given to the wear and cleansing of bearings, the definition of scale-divisions and zero-marks, and the rigidity of all supports for moving parts.
Two new pyroxenes included in the system clinoenstatite, clinoferrosilite, diopside, and hedenbergite
Authors: Deer W. A. , Wager L. R.
Published: December 2006

Two monoclinic pyroxenes from the Skaergaard Halvoen intrusion, Kangerdlugssuak, East Greenland, have been separated and analysed. They occur in a strongly differentiated gabbro complex which ranges from a hypersthene-olivine-gabbro at the base to a fayalite-quartz-gabbro of unique composition at the top. The differentiation has proceeded with a steady increase in iron and a corresponding decrease in magnesia, while the other major oxides remain relatively constant throughout. The clinopyroxenes in the lower horizons are in equilibrium with labradorite, normal olivine and hypersthene, and are fairly normal varieties as shown by the following optical properties:—

(1)

… α 1·672, β 1·678, γ 1·701, 2V 42°, γ: c 39°, sp. gr. 3·34.

(2)

… α 1·695, β 1·702, γ 1·722, 2V 43°, γ: c 41° sp. gr. 3·38.
Francolite from sedimentary ironstones of the Coal Measures
Authors: Deans T. , Vincent H. C. G.
Published: December 2006

The sedimentary iron ores of Britain all contain small amounts of phosphorus which is generally present in the colloform mineral collophane. In a rather uncommon class of oolitic ironstones recently described from the Yorkshire coalfield, a crystalline phosphate was found which has now been identified as francolite and forms the subject of this paper. These oolitic ironstones occur in the immediate roofs of coal seams, are of freshwater origin, and consist of ooliths of kaolinite and isotropic clay in a groundmass of chalybite. During the later stages of their diagenesis, francolite, associated with quartz, calcite, pyrite and blonde, and much kaolinite, crystallized within the ooliths (fig. 1) and in the shrinkage cracks (fig. 2) of the ironstone, and sometimes replaced the ooliths and groundmass. The francolite is present in all of the three oolitic ironstone occurrences described from Yorkshire, and also in the similar rock from Derbyshire in the Geological Survey's collection of iron ores. Details of these localities are given in the ironstones paper. The writer has also found similar francolite in an ironstone nodule from a parting in the Mühlenbach coal seam of south Limburg, Netherlands. Although not recorded, it may be expected to occur in some of the black-band ironstones and other rocks closely associated with coal seams. The following account is based entirely on material from Robin Hood quarry, Thorpe-on-the-Hill, 4 miles south of Leeds.
Some new and little-known meteorites found in Western Australia
Authors: Simpson Edward S.
Published: December 2006

When some publicity was given recently in the press to the Gundaring and Kumerina finds, which are described below, Mr. G. E. Willard called upon me in regard to a meteorite which had fallen on Dalgaranga sheep station (27° 45′ S., 117° 5′ E.). He stated that when he was a manager of this station in 1923 he found a crater measuring 75 yards across at the top, 50 yards at the bottom, and 15 feet deep. The surface of the country was ‘hard conglomerate’ (laterite?—E. S. S.), and pieces of rock up to one cubic yard were pushed up out of the hole, as if there had been an explosion. The NW. side had been thrust upwards more than any other, indicating that the meteorite came from the SE. In and around the crater Willard found ‘a hatful’ of small ragged pieces of iron like the Henbury (Central Australia) fragments. These original specimens unfortunately had since been mislaid, but he was able to secure for me from the present manager of the station a 40-gram piece.
The Kaalijärv meteorite from the Estonian Craters
Authors: Spencer L. J.
Published: December 2006

Kaalijärv is a crater-lake on the estate Kaali (järv = lake in the Estonian language) at 58°24′N., 22°40′E. Known in German as Sall, this locality is 20km. NE. of Arensburg (= Kuresaare) on the Baltic island of Oesel (= Saaremaa). On the level agricultural country a thickly wooded knoll 6–7 metres high is seen. Inside there is a crater 15½ m. in depth, the circular rim of which measures 92–110 m. across. The lake at the bottom is about 60 m. across. The rock of the district is horizontally bedded Silurian dolomite with a covering of glacial deposits. The rim of the crater consists of fragmentary materials, and the steeper inner slopes show the beds of dolomite dipping outwards as a dome at angles of 30–40°. Near by, on an area of ¾ sq. km., are five other smaller craters similar in character, and at least three other depressions that have been filled with stones collected from the tilled fields.
Merosymmetry versus merohedrism
Authors: Rogers Austin F.
Published: December 2006

While crystal classes based upon symmetry furnish a clear-cut classification of crystals free from ambiguity and uncertainty, there are cogent reasons for recognizing the larger groups called systems.

It is important to recognize crystal systems, not only on account of physical properties, but also on account of the difficulty of assigning some crystals to their appropriate class. For example, a crystal consisting of a tetragonal prism and a pinakoid may belong to any one of seven classes. For the time being it is placed in the tetragonal system. When it is carefully investigated and its symmetry determined it may be assigned to the proper class.

Contrary to statements that have been made, we can have, and do have, a two-fold classification in geometrical crystallography—the thirty-two classes based upon symmetry, and the six systems based upon properties that certain classes have in common.

In the opinion of the writer the most satisfactory set of names for the crystal classes is the one based upon names of general forms. These names of Groth are comparatively simple, consistent, and lend themselves to international usage.
The adinoles of Dinas Head, Cornwall (With Plate XI.)
Authors: Agrell S. O.
Published: December 2006

Dinas Head is a small promontory adjoining Trevose Head, some five miles west of Padstow on the north coast of Cornwall. Petrographical attention was first drawn to it by Howard Fox, who in 1894, noted the development of albite-rich rocks between greenstone and slate, and he concluded that the rock was an adinole. He also noted the peculiar spherulitic development of albite giving some rocks an igneous appearance, but, on account of the fine banding preserved in these rocks, he concluded that they were metasomatized sediments. This conclusion was subsequently supported by McMahon and Hutchings. The Memoir of the Geological Survey of the Padstow and Camelford district agrees with Fox as to the origin of the adinole, and points out the exceptional thickness of its development when compared with other greenstone-slate contacts.
Some minerals from the leucite-rich rocks of the West Kimberley area, Western Australia
Authors: Prider Rex T.
Published: December 2006

In the investigation of a suite of leucite-lamproites from the West Kimberley area of Western Australia, carried out in the Department of Mineralogy and Petrology, Cambridge, during the period 1937–38, a number of unusual minerals were noted. Three of these were isolated and analysed and two of them proved to be new species. The present paper deals mainly with the three minerals analysed. They are—

(l)

Magnophorite, a new amphibole allied to katophorite.

(2)

Wadeite, a new potassium-zirconinm silicate.

(3)

Titaniferous phlogopite.

The leueite-bearing rocks occur at a number of isolated volcanic vents, nineteen of which have been examined and mapped by Dr. A. Wade. They have in every instance broken through sedimentary déposits of Permian age. Considerable diversity is to be seen in the rock types developed, but they are all characterized by high potash, magnesia, and titania, with low alumina and soda. Analyses of some types which indicate the general chemical character of these rocks are given in table I.
Tektites and silica-glass (With Plates XVI and XVII.)
Authors: Spencer L. J.
Published: December 2006

The natural glasses recognized as tektites are characterized by their acidic composition, the silica percentage ranging from 68 to 80. Their origin is still a debatable point. Within this range glasses are known which have undoubtedly been produced by the fusion of siliceous terrestrial materials in the intense heat developed when large iron meteorites have struck the earth's surface; while others of the same origin show silica ranging up to 98 per cent., that is, an almost pure silica-glass.

From a collection of 84 chemical analyses of tektites taken from the literature, only 36 (many of them due to A. Lacroix) give data for the specific gravity and refractive index which presumably were determined on the same sample of material as that analysed. These are reproduced in table I (arranged in order of silica percentages) and plotted in figs. 1 and 2. Corresponding with the range in SiO2 from 68·00 to 80·73% there is a nearly uniform decrease in d (2·498–2·339) and n (1·526–1·4867). The specific refractivity, K = (n−1)/d, varies from 0·2050 to 0·2107 (0·2258 in the case of no. 29 with the abnormally high n 1.5380).
A new method for the preparation of thin sections of clays
Authors: Weatherhead A. V.
Published: December 2006

Thin sections of clays are not easily prepared by the routine petrographic methods. The chief difficulties are due to the extremely fine texture of the clays and to the soft and plastic nature of these materials. These difficulties are only too well known, and, although in some cases they have been partially overcome by impregnation in vacuo, it is safe to assume that really little work has been accomplished in the microscopic examination of clays on account of the difficulty of producing satisfactory thin sections. The writer has attempted to extend the scope of the microscopic investigation of clay rocLs by means of the technique outlined below.

The method has been devised in response to an appeal by a friend, who, working in a laboratory at a well-known pottery works and thus connected with the clay industry, desired a method that would make possible the examination of thin sections of clays under high powers with polarized light.
A note on crystallographic calculations
Authors: Hey Max H.
Published: December 2006

In the course of work on the Barker index of determinative crystallography, a number of interesting problems have arisen owing to the selection by a few workers of unusual sets of fundamental angles for their computations. Most of these problems have been of no general application, but One appears to have a wider interest and may prove of practical value in dealing with crystals having curved or striated faces that only admit of accurate measurements along one zone.

This problem was to compute the angles and elements of a monoclinic crystal, using as fundamentals the angles from b(010) to any three faces e, f, g (of known indices) not in the zone [010], and no pair of which are co-zonal with b(fig. 1).
On maucherite (nickel-speiss, placodine, temiskamite) (With Plate XXIV.)
Authors: Peacock M. A.
Published: December 2006

Nickel-Speiss (Nickelspeise), an impure arsenide of nickel obtained as a by-product in the manufacture of smalt, has long been known as a source of distinct crystals representing a definite chemical compound. Such crystals were already analysed by Döbereiner (1823), who concluded that the material was an artificial form of niccolite, NiAS. Later analyses showed that the composition of the crystallized furnace product approaches Ni3As2, a compound unknown in nature at that time.

A substance corresponding to the crystallized nickel-speiss, but thought to be of natural origin, was first described by Breithaupt (1841), who named the material Plakodin (πλăκώδης, broad) in allusion to the tabular habit of the crystals. These were said to have occurred in the Jungfer mine at Müsen in Westphalia, associated with chalybite and gersdorffite and to have been salved by a smalt-works official from a shipment of ores.
Optical properties of olivines from Ubekendt Island, west Greenland
Authors: Game P. M.
Published: December 2006

The olivines, which are the subject of this note, were obtained from a series of basaltic lavas and dikes on Ubekendt island, which lies off the west coast of Greenland in latitude 71 ° N., longitude 54 ° W.

The optical properties of the olivines were investigated in order to determine any range in composition; such variations might have been expected in the very thick lava series. From this aspect, however, the results are disappointing, the composition range being small. However, it is thought that the results may have a certain interest in showing the relative accuracy obtainable in the measurement of refractive indices and optic axial angles. The usual determinative methods have been slightly varied. It is the purpose of this note to describe these variations and to compare the relative speed and scope of the method used with those obtained by other methods.
The identity of ‘eggonite’ with sterrettite
Authors: Bannister F. A.
Published: December 2006

During the X-ray study of a new phosphate mineral, not yet published, the usual comparison was made with cell-side measuremerits of related minerals. One of these is ‘eggonite’, a rare hydrous aluminium phosphate said to occur on silver ores at Felsőbánya, Hungary. Rotation photographs of ‘eggonite’ are different from those of the new mineral, but yielded dimensions close to those of sterrettite, a new mineral from Fairfield, Utah, described last year by Larsen and Montgomery. These authors generously presented a specimen of sterrettite to the British Museum, and rotation photographs taken in the Mineral Department not only give cell-dimensions close to those published but also identical with those of ‘eggonite’. A brief account of this identification is now given not only to justify abandoning the mineral name ‘eggonite’, but also to place on record a European occurrence of a rare mineral so far described from only one American locality.
A nomogram for the law of direction-cosines
Authors: Tomkeieff S. I.
Published: December 2006

If α, β, and γ are the three angles between a line passing through the origin and the three rectangular co-ordinate axes, then the equation connecting them is as follows:

cos2α+cos2β+cos2γ = 1.

This is the law of direction-cosines of a line.

Substituting (cos 2α+1)/2 for cos2α, &c., we get:

cos 2α+cos 2β+cos 2γ = −1.
The chemical composition of leucoxene in Cainozoic bauxite from Boolarra, Victoria
Authors: Edwards A. B.
Published: December 2006

During a petrological examination of samples of bauxite from Boolarra, in south Gippsland, Victoria, it was noted that some specimens of the bauxite, which is largely derived from Tertiary olivine-basalt, contained numerous grains of yellow-brown to amber-yellow leucoxene. The leucoxene is clearly pseudo-morphous after ilmenite, residual particles of ilmenite being enclosed in many of the leucoxene grains. Most of the leucoxene grains are opaque, but occasional grains are translucent to transparent, though isotropic. Some of them show parallel markings suggestive of cleavage, but probably a residual structure from the replaced ilmenite. In view of the highly aluminous nature of the enclosing rock, there seemed some possibility that this mineral might be the little-known aluminium titanate, xanthitane. It was thought, therefore, that if a pure sample of the mineral could be prepared, a chemical analysis would establish its identity.
An X-ray study of diamonds artificially prepared by J. B. Hannay in 1880 (With Plate X.)
Authors: Bannister F. A. , Lonsdale K.
Published: December 2006

During the course of a general investigation by one of us (K. L.) of diamonds from various sources, using X-ray analytical methods, the inquiry arose as to whether so-called artificial diamonds had ever been examined in this way. It was found that there was, in the Mineral Department of the British Museum, a glass slide bearing 12 minute specimens, labelled as being diamond, artificially prepared and presented by Mr. J. B. Hannay in 1880, presumably the remainder of those investigated by Prof. N. Story-Maskelyne, and referred to in a letter to the Editor of The Times which appeared in that paper on February 20, 1880, as follows:

Sir,—A few weeks since I had to proclaim the failure of one attempt to produce the diamond in a chemical laboratory. To-day I ask a little space in one of your columns in order to announce the entire success of such an attempt by another Glasgow gentleman.
Notes on some minerals either new or rare to Britain
Authors: Russell Arthur
Published: December 2006

On June 6, 1940, Mr. John Blackwood of Leadhills, while searching for gold in the alluvial wash at the head of the Shortcleuch Water, Leadhills, Lanarkshire, a spot which has for many years been the happy hunting ground of Mr. Blackwood and John D. Weir, Leadhills' two most persistent and successful gold winners, was lucky enough to discover a water-worn mass of gold in quartz weighing 501·2 grains, by far the largest and richest specimen that has been found within the memory of those living in the district. The specimen (plate I) was found while removing a mass of rock at a depth of about 3 feet, the exact spot being a few yards from the east bank of Shortcleuch Water, about midway between the ruined Lowther Cottage (wrongly shown on the six-inch Ordnance map, Lanarkshire 49 NE., as Lauder Cottage) and the junction with the Windgate Burn (Windgate Foot).
An X-ray study on the crystal-structure of gümbelite
Authors: Aruja Endel
Published: December 2006

Dana classifies gümbelite in the kaolin division under pyrophyllite, and expresses the view that it may be an impure pyrophyllite. The present study, however, has shown that the unit cell of gümbelite is very similar to that of muscovite. Also the chemical analysis reveals a Closer similarity to muscovite, particularly to a variety called hydromuscovite.
An unusual occurrence of bedded thenardite
Authors: Spencer Edmondson
Published: December 2006

A peculiar occurrence of anhydrous sodium sulphate, thenardite, has recently been discovered below the salt crystallizing pans at Didwana, Jodhpur State, India. Here salt (NaCl) is crystallized out by evaporation in open pans from brine obtained by sinking wells alongside the pans, to a depth of about 15–20 feet below the surface. The land surface consists of very fine sandy silt and the salt-pans are made by cutting shallow depressions about 120 feet long by 85 feet wide, a low ridge of silt about 2 feet high and 3 feet broad being left between them. The pans are cleaned out at the beginning of the salt season (February-March): the brine from the wells is run into them to a depth of 1 to 2 inches and the salt crystallizes out by evaporation.
Banalsite, a new barium-felspar from Wales
Authors: Smith W. Campbell , Bannister F. A. , Hey Max H.
Published: December 2006

In 1941 the Home Ore Department of Iron and Steel Control, Ministry of Supply, took over the old Benallt manganese mine at Rhiw in the Lleyn Peninsula, Carnarvonshire. A new shaft was sunk and a new mine was developed among and mainly below the old workings. It was in one of the old workings of Benallt that Mr. (now Sir) Arthur Russell discovered in 1911 the well-crystallized specimens of celsian and paracelsian recently described by Dr. L. J. Spencer.

Dr. A. W. Groves of the Mineral Resources Department of the Imperial Institute and geologist to the Home Ore Department had had a sharp look-out kept for the reappearance of the barium-felspars in the new workings, and when thin bands of coarsely crystallized but compact, white ‘sparry’ minerals were found in one of the ore-bodies he sent specimens to the Department of Mineralogy of the British Museum for investigation.
Boracite from a boring at Aislaby, Yorkshire
Authors: Guppy E. M.
Published: December 2006

Cuttings from their Eskdale no. 2 boring, Aislaby, near Whitby, at a depth of 4095–4100 feet from the surface were presented to the Geological Museum by the D'Arcy Exploration Co. Limited, in response to a request for a specimen from the Permian Saliferous Series which might contain polyhalite, a mineral already recorded by Professor C. E. Tilley from this boring (Min. Mag., 1943, vol. 26, p. lvii). The cuttings were examined by Dr. J. Phemister who found no polyhalite in them, but a small quantity of a mineral which he thought was probably boracite. In response to a request for additional material the company very kindly supplied further cuttings from depths in the bore between 4090 and 4160 feet.
The X-ray pattern of low-temperature cristobalite
Authors: Jay A. H.
Published: December 2006

Cristobalite is found as the first product in the conversion of quartz following a high-temperature heating, and it constitutes a large percentage of the crystalline material in most manufactured silica bricks. It is present also in fireclay products, the amount being dependent upon the nature of the raw material and the conditions of firing. In the majority of these products the cristobalite is only poorly developed, i.e. the crystals are only perfect over distances of the order of about 1 × 10-6 cm. This value is derived from the diffuseness of the high-order reflections on the X-ray powder photograph. On the other hand, the crystals of cristobalite are well developed in the hot face of an open hearth silica roof-brick.
The lattice parameters of α-alumina and chromic oxide
Authors: Jay A. H. , Wilde W. T.
Published: December 2006

During the course of a study of the interaction of certain pure refractory oxides at high temperatures it became necessary to obtain accurate values for the lattice parameters of α-alumina and chromic oxide. Values obtained by previous workers, listed in table I, did not attain a greater accuracy than one part in 2000, whereas the use of large-diameter powder cameras calibrated with quartz now yield lattice parameters accurate to at least one part in 30,000.

Samples of the calcined oxides were examined in a 19 cm. diameter powder camera, alumina with cobalt Kα radiation and chromic oxide with chromium Kα radiation. Results are given in tables II and III.
Banalsite crystals from Wales
Authors: Smith W. Campbell
Published: December 2006

Banalsite, the new orthorhombic barium-felspar, was described from coarsely crystalline but massive material found as thin bands traversing manganese ore at the Benallt mine, Rhiw, Carnarvonshire. Up to the time of the reading of the paper which announced the discovery of the mineral no crystals had been found except two showing indications of faces seen in a thin section of one of the veins. The only other indications of crystal form were lines of black inclusions seen in thin section within the irregular boundaries of crystals forming the vein-material. Now I have been fortunate to find, in a specimen recently collected by Dr. A. W. Groves from no. 5 ore-body in the Benallt mine, a small cavity containing minute crystals of banalsite.
Notes on the mineral deposits of the Teign valley, Devon
Authors: Ramsden J. V.
Published: December 2006

Research into the history of the old mines suggests that two mineralized fissuring systems intersect in central Devon, often carrying commercial ore-bodies. The older of these is the east-west system usually carrying copper, iron, or tin, which has been extensively worked in west Devon, but is less developed on the eastern flank of the Dartmoor granite massif.

The younger north-south series, characterized by its lead and silver ores and baryte is particularly well developed in the Teign valley. This band of mineralization can be traced from the north of Scotland through Brittany and Spain to Algeria. In Devon it appears to be divided into three main fissure bands:

1.

Combe Martin to Plymouth.

2.

North Molton to Spreyton, with a possible extension south of the Dartmoor granite.

3.

Molland to Newton St. Cyres and the Teign valley.
A magnesian chamosite from the Wenlock Limestone of Wickwar, Gloucestershire
Authors: Bannister F. A. , Whittard W. F.
Published: December 2006

The Little Avon river rises on the scarp slope of the Cotswolds near Hawkesbury, 14 miles north-east of Bristol, and flows in a westerly direction over Mesozoic strata, until half a mile south-east of Wickwar it cuts through the Triassic mantle and exposes to view three inliers of Wenlock Limestone (Whittard & Smith, 1944, p. 65 and map). The West Gloucestershire Water Company was interested in the valley as a possible site for an impounded reservoir, and as part of a preliminary survey a trial-shaft was sunk into the Wenlock Limestone of the southernmost inlier situated near Sturt Bridge. The shaft penetrated 28 feet of dolomitized siltstones and crinoidal limestones, and at a depth of 4 feet it entered a band of calcareous chamositic siltstone averaging 9 inches in thickness. The shaft had been completed and the sides boarded before we heard it had been sunk; the hand-specimens were therefore obtained from the tip-heaps, but there is no doubt that all the material originated from the same horizon.
The shape of reflections on X-ray, single-crystal photographs (With Plates X and XI)
Authors: Lonsdale Kathleen
Published: December 2006

In the early days of X-ray crystallography the study of the atomic and molecular structure of crystals was of primary importance. It was more necessary to know the arrangement of the atoms in, say, rocksalt, quartz, diamond, or graphite, than to know the exact distances apart of the atoms, or the small deviations from the mean atomic structure which may result from heat movements, eccentricity of growth, mechanical distortion, and other factors.

Now, however, the range of problems is widening, and X-ray methods are being used as a research tool by many workers whose main interest is in other branches of science. It is necessary, therefore, to point out that the familiar Bragg law, nλ = 2d sin θ, which relates order of spectrum n, wave-length λ, crystal spacing d, and diffraction angle θ in an ideal crystal, though still of course applicable, must be applied with some caution to crystals which are not ideal in either structure or texture, and which may be of irregular or eccentric shape.
On the petrology of the ultrabasic and basic plutonic rocks of the Isle of Rum
Authors: Tomkeieff S. I.
Published: December 2006

The Isle of Rum contains one of the most interesting assemblages of plutonic rocks of Tertiary age in the British Isles. The pioneer work of Macculloch and the later exploratory efforts of Judd and Geikie were followed by an admirable account of the rocks by Harker, given with his usual lucidity and precision. In 1938 I spent a fortnight on this island, and this paper—the outcome of my visit—aims merely at supplementing Harker's petrographical description by certain quantitative data in respect of the ultrabasic and basic rocks found there and of recording certain observations relating to the igneous tectonics.

The earliest phase of igneous activity on Rum was the eruption of doleritic and mugearitic lavas. As shown by Bailey the eruptive phase of igneous activity was followed or accompanied by the formation of a ring-fault and two subordinate vents iufilted with explosive breccia and intruded by felsite. The space inside the ring-fault was then intruded by a banded peridotite-allivalite complex and later by eucrite in the form of a semicircular ring-dike and associated sheets. Finally, a granophyre boss was intruded along the western side of the ultrabasic-basic complex.
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.
Baryte and fluorite from Loch Bruicheach, Beauly, Inverness-Shire
Authors: Russell Arthur
Published: December 2006

Loch Bruicheach (One-inch Ordnance Survey of Scotland, popular edition, sheet 37; Six-inch Inverness-shire, sheet 18) is situated 7½ miles (about 9 miles by road) south-west of Beauly and is best reached by taking the road from that town to the keeper's house at Clunevackie and thence by a track to within about half a mile of the actual locality, a low cliff bordering the north-east shore of the loch. Attention was apparently first directed to the locality about the year 1884 by a Mr. John Ross, one of Lord Lovat's gamekeepers, and Mr. Thomas D. Wallace of Inverness, having received through him specimens from there of baryte and a mineral which he, Mr. Wallace, recognized as resembling fluorite, visited the spot with Mr. Ross in May 1885. In August of the same year Mr. Wallace gave a description of the occurrence in the pages of this Magazine, and in July 1886, also in this Magazine, there appeared a note and analysis of the fluorite by Professor W. Ivison Macadam of Edinburgh, who in collaboration with Mr. Wallace proposed for the mineral, without any sort of justification, the name bruiachite. Macadam's analysis of the fluorite was very inaccurate and showed only 10% of fluorine.
The structure of kaolinite
Authors: Brindley G. W. , Keith Robinson
Published: December 2006

A possible structure for kaolinite was first put forward by Pauling (1930) in a paper dealing generally with the structures of layer-type minerals, chlorites, micas, &c. He suggested that the structure consisted of a sheet of Si–O tetrahedra arranged in a hexagonal network with a superposed sheet of Al–(O,OH) octahedra, the two together forming a layer of composition Al2Si2O5(OH)4 (fig. 2). Ross and Kerr (1931), from a detailed microscopic study of the kaolin minerals, concluded that the symmetry of kaolinite is ‘probably monoclinic’. The first attempt at a detailed structure analysis was made by Gruner (1932a) from X-ray powder photographs. The reflections, some 40 altogether, were indexed on the basis of a monoclinic cell with a 5·14, b 8·90, c 14·51Å., β 100° 12′.
The atomic structure of fluor-apatite and its relation to that of tooth and bone material. (With Plates XVI-XVIII.)
Authors: Beevers C. A. , McIntyre D. B.
Published: December 2006

It is well established by X-ray crystal analysis that the mineral constituent of bone and of the enamel and dentine of teeth is essentially hydroxy-apatite Ca5OH(PO4)3, and that hydroxy-apatite has a structure differing only in small details from that of the well-crystallized mineral fluor-apatite Ca5F(PO4)3. The main difference, and in fact the only fully established one, between the two structures is that the hydroxy-apatite has a slightly larger unit cell than that of the fluor-apatite. The structure of the latter has been determined by Náray-Szabó, and by Mehmel who finally agrees with Náray-Szabó. We have made what is probably a more accurate determination of the structure, using more extensive X-ray data.
The rapid separation and determination of barium, strontium, and calcium in rocks and minerals
Authors: Osborn G. H.
Published: December 2006

Calcium is one of the most widespread and abundant of metals, coming fifth on the list of elements and third among the oxides of the outer lithosphere; it is an essential constituent of a great many rock-forming minerals and is, therefore, almost always present in rocks. Barium and strontium come very much lower in the list of abundance of elements, but nevertheless barium is extremely widespread and occurs in most rocks, igneous, metamorphic, and sedimentary, while strontium is also very widespread. It has been stated that the average content in igneous rocks of both of these elements is of the order of 0·05%.
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.
Pyroxenes from the Lower Carboniferous basalts of the old Pallas area, Co. Limerick
Authors: Ashby D. F.
Published: December 2006

The most complete succession of Carboniferous rocks found in Co. Limerick crops out in the Limerick basin, which is situated between Limerick and Tipperary. The zonal ranges of the chief lithological divisions of the Lower Carboniferous rocks have been determined, and two volcanic episodes, represented by the Lower and the Upper Volcanic Groups, are now known to have occurred early in S1 and early in D1 times. The porphyritic pyroxenes have been isolated from representatives of the lower group, which ‘constitute a graded series of olivine-basalts, trachybasalts, trachyandesites and trachytes, comparable with the Lower Carboniferous Scottish suite. Among the olivine-basalts, all the Scottish types have been recognised, with the exception of Craiglockhart type and mugearite.
Studies of mineral sulpho-salts: XIII—Polybasite and pearceite
Authors: Peacock M. A. , Berry L. G.
Published: December 2006

These two minerals are analogous silver compounds with similar pseudo-hexagonal monoclinic form and similar compositions: polybasite, 8(Ag,Cu)2.(Sb,As)2S3, and pearceite, 8(Ag,Cu)2S.As2S3. Cu replaces Ag in considerable and varying amounts in both minerals, and in polybasite there may also be substantial replacement of Sb by As. However, the rather numerous existing analyses do not indicate continuous chemical variation from arsenian polybasite to pearceite, and therefore it is proper to recognize the two minerals as distinct species rather than end-members of a series.
Whitlockite from Sebdou, Oran, Algeria
Authors: Bannister F. A.
Published: December 2006

During the course of recent work on minyulite (KAl2(PO4)2 (OH,F).4H2O) X-ray, optical, and density data were obtained for several hydrous K-Al phosphate minerals. These included one specimen of a soft white compact mineral labelled by P. Pallary as minervite from Sebdou, Orau, Algeria, which was presented in 1940 to the Trustees of the British Museum by Major M. Connolly. Minervite was originally described and analysed in 1895 by A. Carnot from Minerva grotto, Fauzan, dép. Hérault, France. In the same year Carnot also described the same species from Tour-Combes grotto, Misserghin, Oran. Sebdou is some 80 miles SSW. of Oran and geological maps show there a patch of Pliocene on late Jurassic. No doubts were entertained that the specimen under discussion belonged to the same species as minervite from Misserghin, since the geological formations of both localities are closely related.
Excursion to Durham and the northern Pennines
Authors: Dunham K. C.
Published: December 2006

The decision of the Council to organize an excursion, the first since the Jubilee of the Society in 1926, arose from an invitation presented by Dr. A. E. J. Vickers, on behalf of Imperial Chemical Industries Ltd., to visit the anhydrite mine at Billingham. During the excursion the opportunity was also taken of visiting mineral localities in the northern Pennines (west Durham and Cumberland) under the leadership of Professor Wager and the writer. Accommodation was arranged in Durham at University College (by kind permission of the Master), and here, housed in the ancient castle, members enjoyed a comfortable stay. Transport each day was by private coach. The excursion was organized by Dr. G. F. Claringbull; the thanks of members are also due to Mr. E. Myers, secretary of the north-east section of the Society of Chemical Industry for his help in making local arrangements.
Ankerites and chalybites from the northern Pennine orefield and the north-east coalfield
Authors: Smythe J. A. , Dunham K. C.
Published: December 2006

Ankerites from the Northumberland coalfield were first described, with chemical analyses, some ten years ago (Hawkes and Smythe, 1935), when it was found that examples from veins exposed on the coast near Hartley and from sludge from nearby coal-washeries showed a remarkable uniformity in composition. The operations of the collieries concerned cover an area roughly 6 × 6 miles, and range from the Beaumont to the High Main Seam. In order to ascertain whether this uniformity is maintained over a wider area, five additional samples of ankerite from veinlets in rocks of Coal Measure age, and one from partings in the Lower Carboniferous Scremerston coal have been examined. The Coal Measure rocks cut by the veinlets have been proved to contain substantial proportions of ferriferous carbonates, while for comparative purposes two examples of rocks of similar age with carbonate but unaccompanied by ankerite veinlets have been investigated. The range in composition of ankerites in the coalfield has proved to be small.
The occurrence of artificial kalsilite and allied potassium aluminium silicates in blast-furnace linings
Authors: Rigby G. R. , Richardson H. M.
Published: December 2006

The contour and dimensions of a typical blast furnace are shown in fig. 1. The shell of the furnace consists of riveted steel plates, inside which is a lining of firebricks varying in thickness about 2–3½ feet. Molten iron collects in the crucible or hearth at the bottom of the furnace and is periodically run off through a hole in the side of the furnace known as the tap-hole. The hearth is lined with firebrick both around the sides and along the floor, the total thickness of brickwork below the hearth in fig. 1 being 3 feet 9 inches.
An improved polarizing microscope. II. All-purposes model
Authors: Hallimond A. F. , Taylor E. Wilfred
Published: December 2006

In the description of an improved polarizing microscope, recently published by the present authors, provision was made for the use of polarizing film in place of calcite prisms, and the consequent changes in the design of the substage and tube were discussed. The model then described was, however, of smaller size than is required for some patterns of Fedorov stage now in use, and a larger stand wan under consideration. For technical reasons this could not be produced at the same time as the smaller instrument, and it was therefore necessary to postpone the description which forms the subject of the present supplementary paper. The changes involved are mainly dimensional, the optical and manipulative arrangements being in principle the same as in the smaller model, but the general standard of equipment in details such as stage racks, ball-bearing stage, and interchangeable bodies is on a scale corresponding with that in the largest existing types of stand.
Flavus or blavus: a difficulty in understanding early descriptions of minerals
Authors: Bromehead C. E. N.
Published: December 2006

While studying some of the early works on minerals I came across an obvious difficulty: several minerals, amongst which lapis-lazuli is the most startling, are described in Latin as flavus, yellow or flaxen-coloured, not blue. This error has been copied into a book in English. The solution is less obvious than the difficulty, and it may therefore be worth while to put it on record for other workers on similar lines.
The occurrence of nigerite, a new tin mineral in quartz-sillimanite-rocks from Nigeria
Authors: Jacobson R. , Webb J. S.
Published: December 2006

A new tin mineral, which has been given the name ‘nigerite’, was discovered in June 1944 during au investigation of the tin-bearing pegmatites of Kabba Province, central Nigeria. The chemical and physical properties of nigerite have been determined by F. A. Bannister, M. H. Hey, and H. P. Stadler, and their results will be published in the next number of this Magazine. Dr. Hey's analysis shows SnO2 25·33, Al2O3 50·91, Fe2O3 11·90, ZnO 4·51 %, &c., and the unit-cell contents are given by the formula (Zn,Mg,Fe″)(Sn,Zn)2(Al,Fe‴)12O22(OH)2.
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 survey of the micas (With Plates VII–IX)
Authors: Tolansky S. , Morris Pamela G.
Published: December 2006

In a group of earlier publications details have been given of the application of multiple-beam interference methods to the study of mica. The characteristic structure of this mineral is exhibited by the Fizeau fringes which are produced when one side of a mica slip is silvered and placed against a similarly coated optical flat. The fringes show that the surface is violently contorted and crossed by cleavage steps, the heights of which appear to be integral multiples of the crystal-lattice spacing perpendicular to the basal plane of cleavage. If, however, a mica slip (thickness circa 1/100 mm.) is silvered on both sides then fringes of a totally different appearance are observed. It is frequently found that, despite the distortions on the surface, the Fizeau fringes are large areas of uniform illumination bounded by cleavage ‘lines’.
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.