On the nature of withamite from Glen Coe, Scotland (With Plate IV.)

1938 ◽  
Vol 25 (162) ◽  
pp. 119-124 ◽  
Author(s):  
C. Osborne Hutton
Keyword(s):  
Satisfactory Agreement ◽  
Geological Survey ◽  
Fine Grained ◽  
Andesitic Rock

In 1824 Henry Witham discovered a beautiful red epidote mineral in the lavas of Glen Coe, Argllshire, which was described by Brewster under the name withamite. An analysis was made by Coverdale of obviously highly impure material, but later a more complete one was carried out by Heddle on carefully hand-picked mineral. Heddle admits, however, that his analysis shows ‘by no means a satisfactory agreement with the composition of epidote’, and from his figures it would seem very likely that his analysed material was also impure. In the Glen Coe Geological Survey Memoir no further data were recorded of this mineral, Heddle's analysis and description merely being quoted.The writer visited Glen Coe and collected material in a cutting on the new road, approximately 5½ miles west of King's House (Geological Survey, sheet 53), where it is fairly well exposed. It occurs in a fine-grained, rather altered andesitic rock, as narrow veinlets up to 120 mm. in length and 50 mm. in width ; also as infillings of vesicles. The veinlets may be straight or highly irregular; in the former case they possibly follow joint-planes, for the rock will often fracture along such a plane, producing one or two surfaces covered with the red epidote mineral. The vesicles vary greatly in size from approximately 0·3 to 70 mm., and in the larger ones calcite is a common associate.

scholarly journals II.—Additional Note on the Correlation of the Rocks associated with the Devonian Limestones of the Hindu Khoosh

1903 ◽  
Vol 10 (2) ◽  
pp. 52-53
Author(s):  
C. A. McMahon
Keyword(s):  
Geological Survey ◽  
Joint Paper ◽  
Red Sandstone ◽  
Fine Grained ◽  
Additional Note ◽  
Sandy Clay ◽  
Cricket Ball ◽  
Devonian Age ◽  
Dark Blue ◽  
Fossiliferous Limestone

Since the publication of the joint paper by Mr. W. H. Hudleston and myself on “Fossils from the Hindu Khoosh,” in which the Devonian age of well-preserved fossils found in the limestone member of a series in Chitral was demonstrated, my attention has been called by Mr. T. H. Holland to the fact that the series in Chitral agrees very closely with the rocks known to the Geological Survey of India as the infra-Trias, and described, for the last time, in Hazara by Mr. C. S. Middlemiss.The Chitral series consists of three principal formations:— (1) A lower bed of conglomerate with rounded to subangular pebbles, varying greatly in size up to 3¼ inches in diameter, lying in an indurated, fine-grained matrix of slaty grit or arenaceous mudstone. The pebbles consist of limestone, slates, sandstones, and quartzites, with rounded, white quartz-pebbles, which recall the ‘eggs’ of the Blaini conglomerate of the Simla area. (2) A middle band described by my son, who made a hurried visit to the place, as red sandstone; and (3) an upper bed of grey, dark-blue, and creamcoloured fossiliferous limestone.In Hazara the system of rocks known to the Geological Survey as the infra-Trias, on account of its position unconformably below the Trias, consists in the same way of a lower conglomerate, a middle sandstone series, and an upper limestone formation. These rocks, originally referred to by Wynne and Waagen, were described in fuller detail by Middlemiss in 1896.According to Middlemiss, the conglomerate is composed of sub-angular pebbles of slates and quartzites, usually of about the size of a cricket ball, but varying from mere pebbles to larger lumps, and set in a fine purple sandy clay or shale.

III.—Notes on the North-Western Region of Charnwood Forest

1915 ◽  
Vol 2 (12) ◽  
pp. 545-554 ◽  
Author(s):  
T. G. Bonney
Keyword(s):  
Lava Flow ◽  
Lava Flows ◽  
Geological Survey ◽  
Western Region ◽  
Fine Grained ◽  
The Third ◽  
The North ◽  
North Western

Charnwood Forest, since 1891, the date of the last paper by Canon E. Hill and myself, has been investigated by the Geological Survey. Though part of their map and the accompanying memoir have not yet been published, the general results of their work have been announced by Professor W. W. Watts, by whom most of it was executed. As we stated at the time, we were far from being satisfied with some important points in our own conclusions; so that since my return to Cambridge I have studied my specimens and slices from the north-western region, which had presented to us the more serious difficulties. In 1891 I had been led to regard the characteristic rocks of Peldar Tor and High Sharpley as lava-flows, but considered the dominant rocks of Bardon Hill to be mainly pyroclastic. Professor Watts, however, maintained the intrusive character of the first and second, while taking the same view as myself about the third. The lava-flow hypothesis had appeared to me the more probable, because I doubted whether a mass so large as the Peldar-Bardon porphyroid, if intrusive, could have maintained throughout a texture so uniformly fine-grained, and I had found in the Bardon quarries fragments of it embedded in rock which I then supposed to be a somewhat altered tuff, closely related to the High Sharpley lava.

On the relation of chamosite and daphnite to the chlorite group (With Plates XVIII and XIX.)

1939 ◽  
Vol 25 (167) ◽  
pp. 441-465 ◽  
Author(s):  
A. F. Hallimond
Keyword(s):  
Low Temperature ◽  
Simple Formula ◽  
British Museum ◽  
The Other ◽  
Geological Survey ◽  
Chemical Analyses ◽  
X Ray ◽  
Fine Grained ◽  
New Material ◽  
Crystalline Nature

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.

I.—Hapalocrinus Victoriæ, N.S., Silurian, Melbourne, and its Relation to the Platycrinidæ

1897 ◽  
Vol 4 (8) ◽  
pp. 337-345 ◽  
Author(s):  
F. A. Bather
Keyword(s):  
Iron Oxide ◽  
Geological Survey ◽  
Fine Grained ◽  
The Matrix

The specimen herein described was sent me by Mr. T. S. Hall, M.A., of Melbourne University. It was found by Mr. F. P. Spry in a rock of supposed Silurian age, at the Yarra Improvement Works, near Prince's Bridge, Melbourne, in November, 1896. The matrix is a fine-grained micaceous sandstone, of a dark purplegrey, weathering yellowish. It often contains crinoid columnals, such as were long ago noticed by the Geological Survey of Victoria, and were figured by W. Blandowski as “Cyatocrinites (probably)pinnatus”; but neither from here, nor from any other Silurian rock of Australia, has a crinoid crown hitherto been recoi-ded. The remains of the crinoid are in the form of an impression, coloured red by iron-oxide; all calcareous matter has been dissolved away. The counterpart of the impression has not been preserved. The specimen was studied by means of wax squeezes; the drawing (Plate XV) represents such a squeeze; and the description follows the drawing.

scholarly journals Dinoflagellate cyst stratigraphy of the Lower Cretaceous Jydegard Formation, Bornholm, Denmark

1984 ◽  
Vol 32 ◽  
pp. 145-161
Author(s):  
Stefan Piasecki
Keyword(s):  
Lower Cretaceous ◽  
Geological Survey ◽  
Dinoflagellate Cysts ◽  
Dinoflagellate Cyst ◽  
Fine Grained ◽  
Fault Block

Two Danish Geological Survey boreholes in the Lower Cretaceous fine-grained R0dbjerg Member (Jydegard Formation) in the Nyker fault-block on Bornholm have yielded dinoflagellate cysts which can date the sequence as latest Ryazanian to earliest Valanginian. Two dinoflagellate zones are identified, a lower Gochteodinium villosa Zone and an upper Pseudoceratium pelliferum Zone. The age assignment is in agreement with previous ostracod datings. One new dinoflagellate cyst species, Mendicodinium rugarum, is erected and one monospecific genus and the species is emended, Lagenorhytis- L. delicatula. The morphology and distribution of Sentusidinium pelionense, Cantulodinium speciosum and aff. Chlamy­dophorella nyei are discussed.

Application of an image management system in microscopy

1992 ◽  
Vol 50 (2) ◽  
pp. 1052-1053
Author(s):  
Richard S. Chemock
Keyword(s):  
Data Storage ◽  
Cost Savings ◽  
Image Data ◽  
Analytical Techniques ◽  
Operational Mode ◽  
Fine Grained ◽  
Image Recording ◽  
Primary Output ◽  
Capacity Data ◽  
Image Management System

One of the most common tasks in a typical analysis lab is the recording of images. Many analytical techniques (TEM, SEM, and metallography for example) produce images as their primary output. Until recently, the most common method of recording images was by using film. Current PS/2R systems offer very large capacity data storage devices and high resolution displays, making it practical to work with analytical images on PS/2s, thereby sidestepping the traditional film and darkroom steps. This change in operational mode offers many benefits: cost savings, throughput, archiving and searching capabilities as well as direct incorporation of the image data into reports.The conventional way to record images involves film, either sheet film (with its associated wet chemistry) for TEM or PolaroidR film for SEM and light microscopy. Although film is inconvenient, it does have the highest quality of all available image recording techniques. The fine grained film used for TEM has a resolution that would exceed a 4096x4096x16 bit digital image.

Use of fractals to describe microstructures of porous thick-film platinum electrodes

1992 ◽  
Vol 50 (1) ◽  
pp. 314-315
Author(s):  
Steven D. Toteda
Keyword(s):  
Fractal Dimension ◽  
Power Plants ◽  
Electrical Response ◽  
Cubic Phase ◽  
Platinum Electrodes ◽  
Fine Grained ◽  
Impedance Response ◽  
Platinum Particles ◽  
Energy Surfaces ◽  
Highly Porous

Zirconia oxygen sensors, in such applications as power plants and automobiles, generally utilize platinum electrodes for the catalytic reaction of dissociating O2 at the surface. The microstructure of the platinum electrode defines the resulting electrical response. The electrode must be porous enough to allow the oxygen to reach the zirconia surface while still remaining electrically continuous. At low sintering temperatures, the platinum is highly porous and fine grained. The platinum particles sinter together as the firing temperatures are increased. As the sintering temperatures are raised even further, the surface of the platinum begins to facet with lower energy surfaces. These microstructural changes can be seen in Figures 1 and 2, but the goal of the work is to characterize the microstructure by its fractal dimension and then relate the fractal dimension to the electrical response. The sensors were fabricated from zirconia powder stabilized in the cubic phase with 8 mol% percent yttria. Each substrate was sintered for 14 hours at 1200°C. The resulting zirconia pellets, 13mm in diameter and 2mm in thickness, were roughly 97 to 98 percent of theoretical density. The Engelhard #6082 platinum paste was applied to the zirconia disks after they were mechanically polished ( diamond). The electrodes were then sintered at temperatures ranging from 600°C to 1000°C. Each sensor was tested to determine the impedance response from 1Hz to 5,000Hz. These frequencies correspond to the electrode at the test temperature of 600°C.

Amorphous silica coating on α-alumina particles

1995 ◽  
Vol 53 ◽  
pp. 210-211
Author(s):  
J. W. Mellowes ◽  
C. M. Chun ◽  
I. A. Aksay
Keyword(s):  
Amorphous Silica ◽  
Heterogeneous Nucleation ◽  
Homogeneous Nucleation ◽  
Silica Coating ◽  
Full Density ◽  
Optimal Conditions ◽  
Fine Grained ◽  
Alumina Particles ◽  
Complete Mullitization ◽  
Powder Compacts

Mullite (3Al2O32SiO2) can be fabricated by transient viscous sintering using composite particles which consist of inner cores of a-alumina and outer coatings of amorphous silica. Powder compacts prepared with these particles are sintered to almost full density at relatively low temperatures (~1300°C) and converted to dense, fine-grained mullite at higher temperatures (>1500°C) by reaction between the alumina core and the silica coating. In order to achieve complete mullitization, optimal conditions for coating alumina particles with amorphous silica must be achieved. Formation of amorphous silica can occur in solution (homogeneous nucleation) or on the surface of alumina (heterogeneous nucleation) depending on the degree of supersaturation of the solvent in which the particles are immersed. Successful coating of silica on alumina occurs when heterogeneous nucleation is promoted and homogeneous nucleation is suppressed. Therefore, one key to successful coating is an understanding of the factors such as pH and concentration that control silica nucleation in aqueous solutions. In the current work, we use TEM to determine the optimal conditions of this processing.

Interfacial structures of dissimilar materials joined by capacitor-discharge welding

1994 ◽  
Vol 52 ◽  
pp. 534-535
Author(s):  
C. P. Doğan ◽  
R. D. Wilson ◽  
J. A. Hawk
Keyword(s):  
Rapid Solidification ◽  
Fusion Zone ◽  
Dissimilar Materials ◽  
Solidification Process ◽  
Weld Interface ◽  
Capacitor Discharge ◽  
Fine Grained ◽  
Iron Aluminum ◽  
Conductive Ceramics ◽  
Capacitor Discharge Welding

Capacitor Discharge Welding is a rapid solidification technique for joining conductive materials that results in a narrow fusion zone and almost no heat affected zone. As a result, the microstructures and properties of the bulk materials are essentially continuous across the weld interface. During the joining process, one of the materials to be joined acts as the anode and the other acts as the cathode. The anode and cathode are brought together with a concomitant discharge of a capacitor bank, creating an arc which melts the materials at the joining surfaces and welds them together (Fig. 1). As the electrodes impact, the arc is extinguished, and the molten interface cools at rates that can exceed 106 K/s. This process results in reduced porosity in the fusion zone, a fine-grained weldment, and a reduced tendency for hot cracking.At the U.S. Bureau of Mines, we are currently examining the possibilities of using capacitor discharge welding to join dissimilar metals, metals to intermetallics, and metals to conductive ceramics. In this particular study, we will examine the microstructural characteristics of iron-aluminum welds in detail, focussing our attention primarily on interfaces produced during the rapid solidification process.

TEM/AEM characterization of fine-grained clay minerals in very-low-grade rocks: Evaluation of contamination by empa involving celadonite family minerals

1996 ◽  
Vol 54 ◽  
pp. 694-695
Author(s):  
Gejing Li ◽  
D. R. Peacor ◽  
D. S. Coombs ◽  
Y. Kawachi
Keyword(s):  
Electron Microscopy ◽  
Volcanic Rocks ◽  
Analytical Electron Microscopy ◽  
Metamorphic Rocks ◽  
New Mineral ◽  
Chemical Compositions ◽  
Low Grade ◽  
Fine Grained ◽  
Depth Analysis ◽  
Mineral Aggregates

Recent advances in transmission electron microscopy (TEM) and analytical electron microscopy (AEM) have led to many new insights into the structural and chemical characteristics of very finegrained, optically homogeneous mineral aggregates in sedimentary and very low-grade metamorphic rocks. Chemical compositions obtained by electron microprobe analysis (EMPA) on such materials have been shown by TEM/AEM to result from beam overlap on contaminant phases on a scale below resolution of EMPA, which in turn can lead to errors in interpretation and determination of formation conditions. Here we present an in-depth analysis of the relation between AEM and EMPA data, which leads also to the definition of new mineral phases, and demonstrate the resolution power of AEM relative to EMPA in investigations of very fine-grained mineral aggregates in sedimentary and very low-grade metamorphic rocks.Celadonite, having end-member composition KMgFe3+Si4O10(OH)2, and with minor substitution of Fe2+ for Mg and Al for Fe3+ on octahedral sites, is a fine-grained mica widespread in volcanic rocks and volcaniclastic sediments which have undergone low-temperature alteration in the oceanic crust and in burial metamorphic sequences.

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