bluuebunny/crossref_metadata_2025 huggingface dataset:
Australites: a unique shower of glass meteorites
Authors: Fenner Charles
Published: December 2006

It is just over a hundred years since Charles Darwin, during his great voyage, visited Sydney, New South Wales. While there, he was given, by the explorer Major Sir Thomas Mitchell, a small and curiously shaped glassy object. In his ‘Geological Observations’ (1844) Darwin figured this object and speculated as to its origin, which he suggested was volcanic. This is the first recorded reference to what are now known as australites, many tens of thousands of which have been collected from widespread localities over the whole of southern Australia.
Sapphirine crystals from Blinkwater, Transvaal
Authors: Mountain Edgar D.
Published: December 2006

Some time ago, Mr. F. C. Partridge, Mineralogist to the Geological Survey of South Africa, gave me some crystals of sapphirinc which he thought might be of interest for goniometric examination. They come from the farm Blinkwater 1037, about 47 miles NNW. of Pietersburg and 45 miles WSW. of Louis Trichardt in northern Transvaal, and were collected by him in July 1930, after he had identified some specimens of sapphirine sent to him by Mr. A. Ruskovitch of Abrasive, northern Transvaal. They occur in a coarse granitic rock rich in brown mica, and are associated with small prismatic crystals of pink corundum.

The sapphirine crystals are almost invariably tabular or platy in habit, although occasional crystals possess a rhomb-shaped cross-section. The largest crystal measures 50×35×5 mm., while the thickest one is only 7 mm. in thickness. They are generally six-sided in outline with a strong suggestion of orthorhombic symmetry.
The ‘baddelyite from Alnö’—an error
Authors: von Eckermann H.
Published: December 2006

In most mineralogical text-books the nepheline-syenite area of Alnö, on the east coast of Sweden, is given as one of the few localities of the rare mineral baddelyite, ZrO2. This information is based on a communication by E. Hussak, who claimed to have discovered the mineral in jacupirangitic varieties of the Alnö nepheline-syenites.

The present writer, being engaged with a petrological and mineralogical revision of the Alnö occurrence, earlier described by A. G. Högbom in his classic memoir of 1895, has in vain looked for the presence of baddelyite. Hussak claimed to have isolated by means of Klein's solution 0·38 gram of pure baddelyite from 100 grams of rock, as well as to have obtained characteristic ZrO2 crystals inn borax bead test. Repeated isolation tests with Clerici's solution on samples from various localities within the Alnö area, however, furnished nothing but residues of melanitic garnet.
On the relation of chamosite and daphnite to the chlorite group (With Plates XVIII and XIX.)
Authors: Hallimond A. F.
Published: December 2006

There is a close optical and chemical resemblance between chamosite, the chloritic mineral of the bedded ironstones, and daphnite, a low-temperature vein-chlorite common in some of the Cornish tin mines. New material has made it possible to undertake a fresh comparison of the two minerals: chemical analyses have been made by Mr. C. O. Harvey, chemist to H.M. Geological Survey, and a report on the X-ray measurements is contributed by Mr. F. A. Bannister, of the Mineral Department of the British Museum.

The new analysis of chamosite agrees with the simple formula previously assigned: X-ray examination of material from several localities has now established the distinctive crystalline nature of this fine-grained mineral, which differs structurally from ordinary chlorites such as clinochlore. Daphnite, on the other hand, has the ordinary chlorite structure, but the new analysis fully confirms Tschermak's original opinion that it cannot be represented chemically as a mixture of serpentine and amesite.
An electromagnetic separator for mineral powders
Authors: Evans R. C.
Published: December 2006

The use of a magnetic separator for the separation of certain ores has long been a standard commercial practice and a laboratory scale instrument applying the same principles to the separation of mineral grains from a powdered rock has been designed by Hallimond. In this apparatus the mineral grains are spread on a rotating pan which carries them below the pole pieces of one or more electromagnets, the pole pieces being so designed that the grains pass through a strongly diverging magnetic field and so are subjected to a force proportional to their susceptibility. If this force exceeds the weight of the grains they are attracted and adhere to the pole pieces. The material thus collected is periodically discharged by interrupting the magnetic field and the grains then fall through a slot in the rotating pan into a receptacle below.
Petrological application of the low-power binocular microscope
Authors: Wells A. Kingsley
Published: December 2006

In carrying out a petrological examination of pebbles collected by Mr. F. Gossling from the Lower Greensand of Surrey and west Kent, the writer has found a low-power dissecting binocular microscope an extremeIy useful piece of apparatus. The instrument, by Watson, is fitted with two pairs of objectives on a rotating nosepiece, and with two pairs of eyepieces, so that it commands the choice of four different magnifications.

The pebbles are treated in a uniform manner. After the preliminary examination of a ‘bag’ of pebbles, those selected for study are ground flat on one side, finishing on the fine carborundum plate as if for section making. Each one is then mounted on the usual 3 by 1 inch glass slide, taking care not to over-cook the balsam. If the pebbles are treated systematically in batches of six, a dozen pebbles can be mounted in less than an hour, so that the gain of time over section-making is very considerable.
The Boxhole meteoritic iron, Central Australia (With Plates XX and XXI.)
Authors: Madigan C. T. , Alderman A. R.
Published: December 2006

The Boxhole meteorite crater has been described previously. It is in Central Australia at latitude 22° 37′ 30´″ S., longitude 135° 11′ 59″ E. During the single afternoon that was spent examining this great crater, nearly 200 yards across, most of the time was occupied with taking measurements and photographs, and only a few shale-balls were found in the way of meteoritic material. Mr. Joe Webb, who lives nearby, was instructed to continue the search, and in due course he sent down to Adelaide three pieces of iron weighing respectively 17 lb. 9 oz., 1 lb. 8 oz., and 5 oz., shown in figs. 1 and 3, together with six more shale-balls. This material was purchased by the South Australian Museum. Two other small pieces of iron have been obtained by the author from other sources.
Some australite structures and their origin (With Plate XXII.)
Authors: Baker George
Published: December 2006

A number of specimens of core-like australites possess well-developed flaked equatorial zones (text-fig. 1), on which peculiar grooves and flutings are present. These markings are here referred to as ‘bubble tracks’, the term indicating their apparent mode of formation. The specimens displaying these features are round and elongate forms. The round forms vary in diameter from 34 to 41 mm., the elongate forms range in length from 30 to 75 mm., while the weights vary from 27½ to 96 grams. Australites of these sizes are of infrequent occurrence, only twenty-one having been previously recorded (9, pl. 4), (2, pl. 4), and (3, pl. 9); the illustrations of these examples show that they have comparable features, such as flaked equatorial zones and bubble tracks.
Occurrences of bavenite in Switzerland
Authors: Claringbull G. F.
Published: December 2006

Bavenite was first described from Baveno by Artini in 1901 as monoclinic crystals of prismatic habit in pegmatitic druses in granite and given the formula 3CaO.Al2O3.6SiO2.H2O. More recently, the mineral has been described pseudomorphous after beryl from Himalaya mine, Mesa Grande, San Diego County, California, by Schaller and Fairchild (1932) and shown to contain beryllium as an essential constituent. In 1933 X-ray determinations by Ksanda and Merwin indicated a unit cell with dimensions a 9·67, b 11·53, c 4·95Å, and showed the symmetry to be orthorhombic and referable to the space-group V1, Vh1, or C2v1. Revised crystallographic orientation and optical constants were also suggested by these authors.

The material about to be described is from two localities in Switzerland. Of fourteen specimens from a fissure in the rocks below the Muotta Nera, Piz del Laiblau, Val Nalps, Tavetschthal, Graubünden, selected by Mr. F. N. Ashcroft in 1935 and 1936 from a fairly large series stocked by Adolf Caveng of Sedrun, one (B.M. 1937,598) carries the mineral as roughly radiating aggregates of platy fibres of very pale brown colour in bulk.
The composite dike at Brockhill, Worcestershire (With Plate XXIII.)
Authors: Taylor J. H.
Published: December 2006

At Brockhill in Worcestershire, some 11 miles west of Droitwieh, in the valley of the river Teme, a small dike of igneous rock is intruded into the red marls and sandstones of the Downtonian Series.

The dike was figured and described by Phillips in 1848. On the Old Series one-inch Sheet 55 N.E. it was indicated as having a very limited outcrop on the eastern side of the river Teme; but a report of an excursion to Brockhill in 1874 records the presence of igneous rock on the opposite bank. The intrusion was examined during the resurvey on the six-inch scale of the New Series one-inch map, Sheet 182 (Droitwich), and is of interest both on account of its petrographic character and its remoteness from other igneous rocks. It has recently been traced by magnetic methods for a distance of over three-quarters of a mile.
New refractometers employing diamond and other minerals
Authors: Anderson B. W. , Payne C. J. , Pike J.
Published: December 2006

Direct-reading refractometers depend upon observation of the boundary between transmission and total internal reflection, when a flat surface of a specimen is placed in optical contact with the flat surface of the isotropic medium employed in the instrument. This medium is usually a heavy lead glass in the form of a hemisphere or prism. The upper limit to the range of indices which can be measured is determined by two factors: the refractive index of the medium employed in the instrument, and the refractive index of the liquid used to make optical contact between the two surfaces.

Liquids of high refractive index are essential to such instruments, and some reference to them may be conveniently made at this stage. Various pure liquids, mixtures, and melts of high refractivity have been proposed from time to time, chiefly as immersion media.
Colloidal gold as a colouring principle in minerals
Authors: Friend J. Newton , Allchin John P.
Published: December 2006

Many attempts have been made to discover the causes of the various colours displayed by minerals. If we except fluorescence and allied phenomena, the diiteren~ theories advanced may in general be grouped under one or other of the following classes:

(1)

Colour may be due to an intrinsic property of atoms, ions, or molecules. Examples are copper atoms, chromate ions, and ferric oxide molecules.

(2)

Colour is sometimes attributed to structural causes. The blue tints of certain halites have been explained in this way; but a fresh suggestion is made in this communication.

(3)

A pigmentary impurity may cause the observed colour. The colour of the ruby is believed to be caused by the presence of a red chromic oxide. The blue tint of a Yorkshire aragonite is shown later to be due to a copper salt.

(4)

Some minerals show plays of colours due to interference and/or grating effects. Labradorite and opal are cases in point. Into this group also fall minerals like bomite which become iridescent from tarnish.
Bravoite from Mill Close mine, Derbyshire
Authors: Bannister F. A , Hey M. H.
Published: December 2006

Early this year Mr. Arthur Russell brought me a small specimen of ore from Mill Close mine, Wensley, Derbyshire, for identification. An X-ray powder photograph p1. xxviii, fig. 3, showed that the mineral has the pyrite structure with unit-cell edge a 5.49 Å., and a chemical analysis of a small sample of specific gravity 4·82, yielded Ni 16·69, Fe 29·30, S 53.40% (see table 1). These data identified the specimen as bravoite, a rare mineral new to the British Isles. At a later date Professor W. G. Fearnsides interested himself in our preliminary work and kindly provided me with further specimens of bravoite and accessory minerals from the Mill Close mine. These also have been investigated.
The selenium and tellurium contents of sulphur from Krisuvik, Iceland
Authors: Friend J. Newton , Allchin John P.
Published: December 2006

The deposits of sulphur at Krisuvik, Iceland, have long been known. They were described geologically in detail by Vincent who also discussed their probable origin, but gave no chemical analyses other than rough determinations of the percentages of sulphur and matrix in various samples. From the flame spectrum Vincent thought that thallium might be present.

Apart from popular descriptions by travellers and casual references in guide-books, little attention appears to have been given in literature to these deposits in more recent years. Sporadic attempts at working the sulphur economically were made by the Danish Government during the eighteenth century and later by a Danish merchant round 1832. These were abandoned, however, owing to cost of transport. There is little likelihood of their renewal in the immediate future unless the deposits are found to contain some other element(s) of sufficient market value.
The crystal-structure of violarite
Authors: Bannister F. A.
Published: December 2006

Waldemar Lindgren described in 1924 a mineral present in nickel ores from southern Nevada which in colour, hardness, and stability differs from polydymite from Grüneau mine at Sehutzbach, between Betzdorf and Daaden in Rhenish Prussia, and yet matches so-called ferriferous polydymite from Vermilion mine, Sudbury, Ontario. He proposed the name violarite both for the mineral from Nevada and for the ‘polydymite’ from Ontario on account of the violet-grey colour of the mineral on polished sections. Lindgren assumed that the iron found in the first analysis of ‘polydymite’ from Ontario was due to admixture with pentlandite and thence deduced nickel disulphide as the possible composition of violarite. In the light of subsequent results it is relevant to mention that Lindgren and Davy's work was based upon the study of polished ore sections but not in polarized light.
Osbornite, meteoritic titanium nitride
Authors: Bannister F. A.
Published: December 2006

Nevil Story-Maskelyne described in 1870 the mineral constituents of the Bustee meteorite, which was observed to fall in 1852 near Bustee about 45 miles west of Goruckpur, India. The stone, weighing 1429 grams, now preserved in the British Museum collections, was found to consist chiefly of enstatite and diopside, and two constituents proved to be new minerals. Pale, chestnut-brown spherules of calcium sulphide, CaS, Story-Maskelyne named oldhamite and golden-yellow octahedra found embedded chiefly in the oldhamite he named osbornite. One side of the meteorite has been ground to reveal the nodules of oldhamite and a coloured lithograph in W. Flight's book ‘A chapter in the history of meteorites’ reproduces the appearance of the chief mineral constituents very well. The minute octahedra of osbornite are easily visible with a lens in the meteorite itself.
Mineral localities on the Mendip Hills, Somerset
Authors: Kingsbury Arthur W. G.
Published: December 2006

Although the Mendip Hills, as a district, have from time to time received the attention of geologists, details of the mineral occurrences are, on the whole, remarkably scarce. Mining was formerly carried on on the Hills for many centuries, but mineralogy as a science had not been sufficiently developed at the time when the mines were most active, and little interest was taken in the minerals other than those suitable or required for commercial and industrial purposes. Even in later years, when, in the course of treating old refuse and tailings left by earlier miners and of various attempts to resuscitate the mining industry, much material must have been available for examination, little attention seems to have been paid to it, or to the numerous quarries that were opened in the Carboniferous Limestone.
Observations on the alteration products of stibnite
Authors: Schoeller W. R.
Published: December 2006

In the mineralogical literature, stibnite is usually stated to change by oxidation into kermesite and finally into valentinite or senarmontire. Another alteration product is described as antimony ochre, a term loosely applied to several minerals, viz. cervantite, stibiconite, and volgerite (Dana, System of mineralogy, 6th edit., 1892, p. 203).

In my metallurgical experience with stibnite ores, I have never met with kermesite or valentinite. Whenever I have encountered altered stibnite in ores from widely separated localities, it showed a yellowish to buff coating which I took to be cervantite. After spending two years in central China where I examined hundreds of tons of stibnite ores from Hunan province, I had to purchase a specimen of kermesite from a mineral dealer in order to become acquainted with the mineral. The locality of the specimen was given as Bräunsdorf, Saxony.
The determination of ferrous iron in resistant silicates
Authors: Hey Max H.
Published: December 2006

The determination of ferrous iron in minerals, such as staurolite and kornerupine, which cannot be effectively dissolved by dilute sulphuric and hydrofluoric acids has been made possible on the macro-scale by the work of H. P. Rowledge; the mineral is fused with sodium fluoride and boric oxide at 900°C. in a sealed pyrex glass tube, the fusion cake dissolved in hot dilute sulphuric acid in a current of carbondioxide, and the solution titrated with potassium permanganate. We have met with no difficulty in applying the method on the macro-scale, but when only small amounts of a mineral are available several difficulties arise, and modifications become necessary.

The air present in the sealed tube of a Rowledge fusion, using the quantities and dimensions he specifies, is already sufficient to oxidize about 3 to 5 mg. of ferrous oxide. But when the weight of the sample is reduced to 10 mg., it is not possible to reduce the dead-space in the tube in proportion ; it can hardly be reduced below about ¼c .c. which is sufficient to oxidize 0·3 mg. or 3% FeO and is likely to be more effective in this direction than on the larger scale, since the surface of the fusion is proportionally greater.
An anorthite-epidote-garnet-hornfels from Namaqualand, South Africa
Authors: Coetzee C. B.
Published: December 2006

The present communication deals with a calc-silicate hornfels of uncommon mineralogical and chemical composition. It may be tentatively referred to the deep-seated metamorphism of a marl, and on account of the shortage of analytical data pertaining to metamorphosed sediments of the calcareo-argillaceous type, a detailed investigation of a variety of this group seems justified.

Intercalated bands of anorthite-epidote-garnet-hornfels bordered bilaterally by pyroxene-bearing gneisses occur on the farms Zandfontein, Pella, and Klein Pella in the north-eastern part of the division of Namaqualand, South Africa (cf. geological map), On Klein Pella small exposures also extend intermittingly for approximately 1·5 miles due WNW.-ESE. of the amphibolite koppie situated on the northern boundary of the farm area. The bands exhibit a gentle pinch and swell structure with maximum widths of 15 to 41 inches, and the contact with the host rock is commonly marked by an epidotic fringe ¾ inch in thickness. In some cases the anorthite-epidote-garnet-rock is penetrated by parallel lenticles of pure quartz which may attain maximum breadths of 0·8 inch.
Lamellar structure in orthopyroxenes (With Plate IV)
Authors: Henry N. F. M.
Published: December 2006

The fine lamellar structure (pl. IV, fig. 1 a and b) which is described here is very common in the orthopyroxenes of plutonic and regionally metamorphosed rocks. This structure can be seen under crossed nicols in sections inclined at a high angle to the optic axial plane (100), except on those sections which make a low angle with (001). When the main part of the crystal is in extinction, the fine lamellae stand out because their extinction position is different from that of the main crystal. Although this structure is common, it is not described in any of the widely used text-books, but several descriptions and references to it have been published in recent years. The purpose of this paper is to draw attention to the nature of this lamellar structure.
Tricalcium disilicate (rankinite), a new mineral from Scawt Hill, Co. Antrim (With Plate V)
Authors: Tilley C. E.
Published: December 2006

Tricalcium disilicate, first described by Shepherd, Rankin, and Wright in their investigations on the lime–silica and lime–alumina–silica systems has since been reported as a constituent of technical slags. An account has also been given of its occurrence as a reaction product in a glass furnace.

In the ternary system CaO–Al2O3–SiO2 the compound forms with pseudowollastonite–gehlenite and larnite–gehlenite two three-phase equilibrium assemblages, associations which are in part recorded in the technical products.

G. V. Wilson recorded the disilicate together with wollastonite and melilite in reconstituted limestone fragments enclosed in glass, while S. G. Gordon has described and presented an analysis of a slag composed of pseudowollastonite and the 3:2-compound approaching in composition that of the binary eutectic in the synthetic system.
Kalsilite, a polymorph of KAlSiO4, from Uganda
Authors: Banister F. A. , Hey Max H.
Published: December 2006

Professor Arthur Holmes has described in the preceding paper a suite of rocks from Mafuru, Uganda. During his study he observed in thin section a mineral which in optical properties is indistinguishable from nepheline. He gives chemical evidence, however, for the presumption that a potassium aluminosilicate is present in mafurite which would suggest either that the nepheline-like mineral is kaliophilite or a polymorphous form of KAlSiO4. Kaliophilite is not isomorphous with nepheline, but has similar optical properties, and the two minerals could be easily confused in thin section. They may, however, be rapidly distinguished by X-ray methods. Even minute grains insufficient for chemical analysis can be determined with certainty; so it seemed probable that an X-ray study of the nepheline-like mineral from Uganda would give additional information and decide whether or no a separation and chemical analysis of the mineral should be attempted. Professor Holmes accordingly invited me to examine his specimens and rock-sections.
Barium-felspars (celsian and paracelsian) from Wales
Authors: Spencer L. J.
Published: December 2006

In 1911 an interesting find of barium-felspars was made in the Benallt manganese mine near Rhiw in the Lleyn peninsula of Carnarvonshire. A brief preliminary note on the occurrence was given by Mr. Arthur Russell in the same year. At the same time he very generously handed over to me for crystallographic and optical description a selection of the material he had collected, while he himself made a start on the chemical analysis of the material. Chemical analyses have now, at last, been made by Miss Hilda Bennett in the Mineral Department of the British Museum, and it therefore seems time to collect together the large volume of notes on the work done in 1911.
Note on the van der Kolk method of determining refractive indices
Authors: Evans R. C. , Henry N. F. M.
Published: December 2006

It is well known that in the Schroeder Van der Kolk method of comparing the refractive index of a crystal grain with that of the material in which it is mounted, the effect can be reversed by moving the microscope sub-stage condenser, and that the position of this condenser must therefore be carefully controlled if ambiguities in the interpretation of the observations are to be avoided. This fact is mentioned in the majority of text-books and is referred to in a general manner by Wright and by Winchell. No clear explanation of the reversal is offered, however, and students are consequently inclined to forget this important limitation in the method or, alternatively, to forget in which sense the movement of the condenser influences the effect: unless a control experiment is invariably performed errors may therefore result.
Note on datolite and other minerals in a contact-altered limestone at Chapel quarry, near Kirkcaldy, Fife
Authors: Phemister James , MacGregor A. G.
Published: December 2006

The Chapel, or Charlestown Main, Limestone horizon lies in the Lower Limestone Group of the Carboniferous Limestone Series. At Chapel quarry the limestone is underlain by a thick sill of quartz-dolerite. The contact, however, is not exposed but probably lies only a few feet below the quarry floor. Other intrusions are seen in the vicinity: a very thin dike of decomposed basalt, which connects with a small ‘float’ of white trap, cuts the limestone about 30 yards north-eastwards of the point where the quarry crosses the Chapel road, and a small sill of olivine-dolerite or teschenite occurs at a horizon about 100 feet above the top of the limestone. In the quarry the limestone is about 60 feet thick. The contact-alteration described in this paper is most evident near the base of the limestone face and its extension laterally in the quarry has no relation to the outcrop of the thin dike. The alteration is therefore considered to be essentially connected with the underlying, unexposed, sill of quartz-dolerite, and, as will be shown ih the following pages, has been effected by the action of hot solutions rather than by thermal reconstruction.
Preliminary observations on the distribution of trace elements in the rocks of the Skaergaard intrusion, Greenland
Authors: Wager L. R. , Mitchell R. L.
Published: December 2006

The Skaergaard intrusion of Kangerdlugssuak, East Greenland (68° 10′ N., 31° 40′ W.) contains a series of gabbros and related rocks—the layered series—which has been interpreted as the result of fractional crystallization of a fairly normal gabbro magma (Wager and Deer, 1939). Analysis of these rocks and of some of the constituent minerals by Dr. W. A. Deer has shown a considerable and systematic variation in the major constituents (1939, table XXXVI and pp. 67–84) and it was considered therefore that it would be of value to determine the variation in some of the rarer elements.

The work of Goldschmidt and his collaborators on the distribution of trace elements in minerals (summarized in Goldschmidt, 1937) combined with our recently acquired knowledge of many crystal structures has made clearer the factors controlling the distribution of the trace constituents in minerals.
A method of tracing the temperature and oxygen-fugacity histories of complex magnetite-ilmenite grains
Authors: Bowles John F. W.
Published: December 2006

The formation of ilmenite from titanomagnetite frequently shows separate generations of production. The ilmenite products can be combined with the magnetite host to represent the intermediate stages in this development. Use of the Buddington and Lindsley (1964) geothermometer in conjunction with this method provides a number of points in the temperature and oxygen-fugacity history of a single, complex magnetiteilmenite grain.

Application of the method is illustrated by an example from the Freetown layered gabbro. A titanomagnetite exsolved granular ilmenite whilst cooling and this process ceased at 930° and an oxygen fugacity of log ƒO2 = −11·5. Further cooling and exsolution continued until the grain reached 662 °C and log ƒO2 = −19·0, producing distinct ilmenite lamellae.
A metallographic and microprobe examination of a metallic nodule from the Bondoc Peninsula meteorite
Authors: Axon H. J. , Nasir M. J.
Published: December 2006

The Bondoc Peninsula meteorite appears to be unstable and is disintegrating as the result of terrestrial corrosion. The meteorite is complex with occasional 1 to 3 cm dia. ‘Nodules’ of ‘iron-class’ material, fig. 1, within which are numerous non-metallic inclusions. These range in size from 0·5–1·5 mm and vary in shape from the extremes of angular to globular, shown in figs. 2 and 3. The metallic groundmass of fig. 1 is a polycrystalline array of kamacite grains that are equant in shape and about 3 to 4 mm dia. The boundaries between these kamacite grains are heavily invaded by corrosion product. The films of cracked schreibersite and strips of compositionally zoned taenite that are present at the kamacite boundaries each contribute about 2 % by volume and their average Ni contents are about 45 wt% and 40 wt% respectively. When these figures are combined with the average 6·2 wt% Ni, 0·75 wt% Co, and 0·02 wt% P of the kamacite the resulting bulk composition of the metal is ∼ 7·5 wt% Ni, ∼ 0·7 wt% Co, ∼ 0·3 wt% P. Nital etching reveals partially annealed Neumann bands in the kamacite, indicating a late stage reheating below about 500°C. However, the M profile method of Wood (1967) when applied to the zoned taenite yields a cooling rate of 0·1–0·5°C/Myr before this reheating event.

The angular inclusions are relatively coarsely crystalline and commonly have massive chromite and tridymite crystals, with pyroxene, anorthite, and whitlockite usually present. Most angular inclusions also contain small particles of metal (10–40 µm dia.) interstitial to the mineral phases in the depth of the inclusion. Small quantities of sulphide and phosphide are similarly located. The metal in the angular inclusions is not detectably zoned and both kamacite and taenite show a range of Ni contents that vary with particle size in the manner previously observed by Powell (1969) for a range of conventional mesosiderites. We have in addition measured the Co and P contents of this metal and find P < 0·1 wt% and the Ni and Co analyses are consistent with equilibration in the ternary Fe-Ni-Co equilibrium diagram at ∼ 450 °C.
A hydrothermal deposit from the floor of the Gulf of Aden
Authors: Cann J. R. , Winter C. K. , Pritchard R. G.
Published: December 2006

Fragments of a hydrothermal deposit, partly moulded on pieces of basalt lava, were dredged from the edge of the median valley in the centre of the Gulf of Aden. The deposit consists of two main components, manganese oxide in the form of spongy brown to hard black lumps and coatings, and friable green massive smectite. There are smaller amounts of an iron-oxide component, and mixed manganese-oxide-smectite material. Contents of the less mobile trace elements in the smectite are too low for it to have formed by alteration of basalt glass, and it is interpreted as a direct precipitate from hydrothermal solution. None of the components is enriched in Cu or Zn, or contains appreciable amounts of sulphur. If there are sulphides in this deposit, they must lie beneath the parts sampled.
The occurrence of paragonite in chloritoid schists from Stonehaven, Scotland
Authors: Baltatzis E. , Wood B. J.
Published: December 2006

Paragonite has been found in two chloritoid-chlorite-mica schists from the Dalradian, north of Stonehaven. The principal bulk-chemical constraints on the occurrence of this mineral within the chloritoid zone appear to be the ratios of soda to potash and the Al2O3 contents of the rock. The composition of paragonite coexisting with muscovite indicates a crystallization temperature of 550 °C for rocks some way above the chloritoid isograd. Although this result is supported by other mineral equilibria, the muscovite compositions suggest a temperature of 690 °C which is too high because the mineral assemblage chloritoid-paragonite is unstable above about 600 °C By combining data on the breakdown of the chloritoid-paragonite assemblage with a mineral equilibrium for the assemblage garnet-plagioclase-muscovite-biotite, it has been deduced that rocks close to the staurolite isograd crystallized at about 7·5 kb and 600 °C.
Plagioclase-alkali-feldspar geothermometry revisited
Authors: Powell Marjorie , Powell Roger
Published: December 2006

The plagioclase-alkali-feldspar geothermometer formulated by Stormer (1975) does not take into account the effect of small amounts of calcium in the alkali feldspar. This geothermometer has been reformulated using ternary regular solution model equations, and it is shown that as the Ca content of the alkali feldspar increases the temperature calculated using the Stormer geothermometer will be increasingly too high.
The structure of chloroxiphite, Pb3CuO2(OH)2Cl2
Authors: Finney J. J. , Graeber E. J. , Rosenzweig A. , Hamilton R. D.
Published: December 2006

Chloroxiphite, Pb3CuO2(OH)2Cl2, is monoclinic, space groupP21/m, witha= 10·458,b= 5·750,c= 6·693 Å, β = 97·79°,Z= 2. The structure has been refined by the method of least squares from three-dimensional Mo-Kα intensity data to a conventionalRvalue of 0·115. The structure consists of sheets of composition [Pb3CuO2(OH)2]2−, in themselves made up of the layer sequence Pb-(O, OH, Cu)-Pb, lying parallel to (01). The structure contains eight-fold PbO4Cl4and seven-fold PbO5Cl2polyhedra common in other oxychlorides, Pb6clusters and copper atoms in square planar, Cu(OH)4, coordination.
Al-rich pyroxene and melilite in a blast-furnace slag and a comparison with the Allende meteorite
Authors: Butler B. C. M.
Published: December 2006

Fassaitic diopside containing 22–23 wt% Al2O3 (approximately 41–43% calcium Tschermak's molecule, CaAl2SiO6) and melilite containing 69–43% gehlenite crystallized from a blast-furnace slag at atmospheric pressure between about 1450°C and 1250°C. The occurrence is of petrological interest because the association of pyroxene with gehlenite-rich melilite has not been recorded from experimental studies in the system CaO-MgO-Al2O3-SiO2, and because of the similarity of the compositions of both minerals to pyroxene and melilite in the Ca-Al-rich inclusions of the Allende meteorite.
Conditions of phlogopite crystallization in ultrapotassic volcanic rocks
Authors: Edgar A. D. , Arima M.
Published: December 2006

Phlogopite occurs as an early crystallizing mineral in many ultrapotassic lavas of basaltic affinities. Based on high-pressure experiments in lavas of these compositions, the early crystallization of phlogopite is controlled in large part by the bulk compositions of the liquids from which it crystallizes but also by the total pressure and by the aH2O, with early phlogopite forming under a narrow range of aH2O, less than that represented by H2O-saturated conditions. Variations in fO2 do not appreciably affect phlogopite crystallization but high aCO2 suppresses its crystallization. In ultrapotassic magmas, phlogopite will preferentially incorporate K2O, TiO2, MgO, and Al2O3 relative to the coexisting early silicate minerals, olivine and clinopyroxene, and thus, on fractionation of these minerals, phlogopite will be more effective in reducing these oxides in residual liquids. Phenocrysts and microphenocrysts of phlogopite in ultrapotassic lavas are directly related with respect to their K/Ti, K/Al, K/(K + Na), and Mg/(Mg + Fe) ratios. Textural relations suggest phlogopite may form by reaction relationships involving liquid with olivine, and/or clinopyroxene. Such relationships are supported by the experimental studies on ultrapotassic rock compositions.
Infrared spectroscopic analysis of the olivenite-adamite series, and of phosphate substitution in olivenite
Authors: Braithwaite R. S. W.
Published: December 2006

Infrared spectroscopy affords a rapid and easy method of estimating the position of a mineral in the olivenite-adamite solid solution series, and of estimating the amount of phosphate substitution in olivenites. Toman's discovery of the monoclinic symmetry of olivenites with up to approximately 20 atom % Zn/(Cu + Zn) has raised a problem in nomenclature. It is suggested that the definition of ‘cuproadamite’ be extended to cover all orthorhombic members of the series containing appreciable Cu. Studies of deuterated materials have helped to solve some of the absorption band assignments for olivenite-adamite, libethenite and related minerals.
The crystal structure of cesanite, Ca1+xNa4−x(SO4)3(OH)x · (1 − x)H2O, a sulphate isotypic to apatite
Authors: Tazzoli V.
Published: December 2006

Cesanite, Ca1+xNa4−x(SO4)3(OH)x · (1 − x) H2O, is hexagonal, space group P63/m, a = 9.446(1) and c = 6.895(1) Å, Z = 2. The crystal structure refinement, carried out by utilizing 457 independent reflections (final R = 0.021), shows that cesanite is isotypic to hydroxyapatite. The P atom of apatite is completely replaced in cesanite by an S atom; the two independent Ca sites of apatite are occupied respectively by Na and Na + Ca, the charge balance being by partial substitution of H2O for OH− although the occupancy of the (H2O,OH−) sites is not complete. The relationship between the water vacancies and the structural features of the (Ca,Na) polyhedron is discussed. A new general formula for the apatite-wilkeite-ellestadite series is proposed.
Further data on the occurrence of pectolite in kimberlite
Authors: Scott Smith Barbara H. , Michael Skinner E. , Roger Clement C.
Published: December 2006

Pectolite has been identified, using petrographic, chemical, and X-ray methods, in kimberlites from the De Beers and Dutoitspan Mines, Kimberley, South Africa and the Letseng-La-Terai Mine, Lesotho. It occurs as radiating aggregates of fibrous or acicular crystals not only in the groundmass of certain kimberlites but also in altered xenoliths included within kimberlite. The occurrence of Na-rich minerals in kimberlite is unusual. It is suggested that it can occur as an apparently primary mineral resulting from the incorporation and assimilation of foreign Na-bearing material prior to final consolidation, and/or as a secondary mineral after metasomatic introduction of Na-bearing fluids.
Mafic silicates from the nepheline syenites of the Motzfeldt centre, South Greenland
Authors: Jones A. P.
Published: December 2006

At least five successive intrusions of nepheline-bearing magmas fractionated in situ and developed repeatedly overlapping, yet distinct chemical trends in the mafic silicates. Representative electron probe analyses are given for olivine, clinopyroxene, amphibole, biotite, and aenigmatite and their variations discussed. Increasing Na with fractionation produced aegirine-rich clinopyroxene and caused Na/K in amphibole to increase from 2.4 to 7.0. Siz/Alz increased in both amphibole and in the less abundant mica. Mn-enrichment is common to all of the mafic silicates, including the olivines and it is suggested that the parent magmas were initially Mn-rich.

Mineralogically the Motzfeldt centre is evolved and similar to the other centres in the Igaliko complex. However, the Motzfeldt centre contains the most fractionated rocks (lujavrites) and is in this respect similar to the peralkaline Ilimaussaq intrusion. The compositional ranges and trends of the mafic silicates in Motzfeldt thus provide links between the uncommon peralkaline plutons and the more abundant and typical nepheline syenites.
Inclusion patterns in zoned garnets from Magerøy, north Norway
Authors: Andersen T. B.
Published: December 2006

Garnet porphyroblasts in metasediments from Magerøy crystallized during static metamorphism. They display three optical zones, each having characteristic inclusions and chemistry. The compositional zoning is related to prograde metamorphism (an inner zone, 1, and a graphite-bearing zone) and retrogression (the outer zone, 2). Inclusions of two types are present in zone 1: type 1 are equidimensional remnants of the matrix, preferentially included along planes of rapid growth; type 2 are tubular and represent recrystallized quartz grains concentrated along defects in the garnet lattice. The defects are lineage boundaries between growth segments related to screw dislocations on crystal faces. Crystal growth developed at relatively high degrees of supersaturation, but below the supersaturation required for the development of dendrites. The inclusions suggest rapid growth of zone 1, caused by heat flow from an adjacent interkinematic mafic/ultramafic intrusive complex. The graphite-bearing zone crystallized at the metamorphic peak, while the inclusion-free idioblasfic rim probably developed during retrograde metamorphism.
Uvarovite and grossular from the Fengtien nephrite deposits, eastern Taiwan
Authors: Wan Hsien-Ming , Yeh Chun-Lu
Published: December 2006

Uvarovite and grossular, the former comparatively rare, occur along the serpentinite-graphite schist contact in the Fengtien area, on the eastern slope of the Central Range of Taiwan. Uvarovite occurs as small emerald-green euhedral crystals on diopside-fels with dodecahedral crystal forms and many other modifications. Its refractive index is 1.782, specific gravity 3.702, and unit cell edge 11.912 Å. Chemical and probe analyses give average Cr2O3 contents of 11.60 wt. %; spectrographic analysis shows significant enrichment in Cr, Be, Co, Y, Sb, and La over grossular. Associated minerals include nephrite, diopside, tremolite asbestos, zoisite, and clinozoisite. Grossular is reddish-brown; large crystals, dodecahedral in form often modified by trapezohedrons, are associated with diopside, idocrase, and calcite. n = 1.746, SG = 3.636, and a = 11.866 Å. Structurally and chemically it is quite near the grossular end member. Grossular is considered to be formed from pneumatolysis associated with the intrusion of ultramafic rocks, whereas uvarovite is a replacement product of relict chromite in the original ultramafic rocks where migration of elements such as silicon and calcium from wall rocks are prominent.
Crystallization trends of pyroxenes from agpaitic phonolites (Cantal, France)
Authors: Brousse R. , Rançon J. Ph.
Published: December 2006

Ca- and Na-rich pyroxene compositions of four agpaitic phonolites from the Cantal Volcano (France) have been studied. The pyroxenes from each sample show a range of compositions between X2+ pyroxencs (with X = Ca, Mg, Fe2+) and aegirine. The main substitution, X2+ by (Fe3+ + Na+), occurs when Na-Mg = 0.5, by which time Si is already equal to 2.0. The crystallization of Fe-Na-rich pyroxenes seems to be related to the increasing peralkalinity of the environment, in which the initially high temperature was suddenly reduced. Other factors, such as the structure of the liquid, are also considered.
The obliquity of K-feldspar from schists, gneisses, and granites in the north-eastern part of the Hida metamorphic belt, central Japan
Authors: Fujiyoshi Akira
Published: December 2006

Most of 325 K-feldspars from the Hida metamorphic belt are characterized by diffuse 131 and 11 reflections. These K-feldspars are classified into eight obliquity types on the basis of the width of the 131 peak or the ratio of mean height of two outer peaks (131 and 11) to that of the middle composite peak. From the distribution of obliquity types and the microscopic characteristics of K-feldspars, this area is divisible into six zones.

The feature of each zone is shown by the frequency distribution of eight obliquity types in each zone, which reflects the strength of later retrogressive effects. The frequency distribution of Δ values in each of the types IV-VIII provides further information on later events.

The result of the K-feldspar study possibly indicates that the inversion of monoclinic to triclinic K-feldspar, characterized by the development of perthitic texture or crosshatched twinning, is sensitive to the degree of later retrogressive events. Some data on 2θ values of 04, 060 and 01 reflections in each types are presented.
The structural behaviour of tetrahedral framework compounds — a review Part II. Framework structures
Authors: Taylor D.
Published: December 2006

Tetrahedral framework compounds, as defined in this paper, generally exist as tilted and distorted versions of ideal fully expanded structures at room temperature and atmospheric pressure. How pressure, temperature, and composition (P, T, andX) affect the tilting and distortion is critically reviewed. It is shown that although the effects ofP, T, andXon the cell parameters are broadly analogous, the underlying structural changes are generally different. An important, and frequently neglected thermal effect is the apparent shortening of the framework bonds by the anisotropic thermal motion of the framework oxygens. Tilting models of framework compounds are critically examined and their failure to match the observed structural behaviour is attributed to changes in tetrahedral distortion. For quartz it appears that during compression the change in tetrahedral distortion is virtually all angular (O-Si-O angles), whereas during thermal expansion the change in distortion is in the Si-O distances. Such behaviour may typify the behaviour of many other framework compounds but the structural data needed to establish this are lacking. The review is illustrated by reference to the quartz and cristobalite analogues; to the sodalite, leucite, nepheline, scapolite, and feldspar families; and to the nitrides and oxynitrides of silicon and germanium. It is concluded that our understanding of the structural behaviour of framework compounds is still superficial and that much theoretical and experimental work remains to be done.
Eggletonite, the Na analogue of ganophyllite
Authors: Peacor Donald R. , Dunn Pete J. , Simmons William B.
Published: December 2006

Eggletonite is a new mineral, the Na analogue of ganophyllite. Type material has composition

(Na0.82K0.40Ca0.39□0.39)Σ2.00 (Mn6.61Zn0.08Mg0.16Fe0.61Al0.56)Σ8.02 (Si10.33Al1.67)Σ12.00[(O28.92(OH)3.08]Σ32.00 (OH)4.00·10.66H2O.

It occurs as prismatic crystals elongated along [100] in miarolitic cavities in nepheline syenite at the Big Rock Quarry, Little Rock, Arkansas. Single-crystal X-ray diffraction data are consistent with space group I2/a or Ia; a = 5.554, b = 13.72, c = 25.00Å, β = 93.95° Z = 2; this is equivalent to the substructure of ganophyllite. Physical properties include cleavage: {001} perfect; colour: dark brown; translucent; streak: light brown; hardness (Mohs): 3–4; brittle; observed density 2.76, calculated density 2.76 g/cm3. Optically, eggletonite is biaxial negative, with optical parameters 2Vα = 9(3)° r < ν, weak; indices of refraction α = 1.566(2), β = 1.606(2), γ = 1.606(2); pleochroism is very weak, γ ≃ β > α; α = pale brown to colourless, β ≃ γ = pale yellow brown. Principal lines in the X-ray powder diffraction pattern are (d, I/Io): 12.4, 100; 3.45, 15; 3.13, 30; 2.854, 15; 2.691, 25; 2.600, 20; 2.462, 20; 2.387, 15. The name is in honour of Dr Richard A. Eggleton, Australian National University.
Zinc- and Y-group-bearing senaite from St Peters Dome, and new data on senaite from Dattas, Minas Gerais, Brazil
Authors: Foord Eugene E. , Sharp William N. , Adams John W.
Published: December 2006

A Zn- and Y-group-bearing senaite, formulated as AM21O38 (Pb0.63Na0.46Ba0.11)Σ1.20(Ti14.64Zn1.74Y‒group REE0.70Mn0.38Nb0.20Sn0.03Zr0.03Th0.02)Σ20.9O38, a member of the crichtonite group, is a newly characterized phase associated with murataite at the St Peters Dome area, Colorado. The Zn- and Y-group-bearing senaite is uranium-free and nonmetamict, but otherwise is comparable to known senaites and davidites in X-ray diffraction pattern, symmetry, and structure. The REE distribution shows a strong dominance of Y and the Y-group REE which are present in M(1). Megascopically, the mineral is black, submetallic, and opaque; in polished section it appears to be white and moderately bright compared with murataite. Cleavage is absent but twinning on {520} is present.

Senaite and hitherto unreported zinc-bearing senaite from Dattas, Diamantina, Minas Gerais, Brazil, have the following respective structural formulas as determined by electron microprobe:

(Pb0.76Sr0.20La0.08Ce0.07Ba0.04)Σ1.15(Ti12.89Mn0.88Y0.59Zn0.12Mg0.07Nb0.03Cr0.02Th0.02)Σ20.61O38

and

(Pb0.89Ba0.15Ce0.02Sr0.02)Σ1.08(Ti14.57Zn1.76Na0.63Mn0.50Y0.28Nb0.14Mg0.04Cr0.02)Σ20.83O38