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By H. Doi, Y. Fujiwara, K. Miyake

In order to throw light on the mechanism of plastic deformation of WC-Co alloys, compressive tests of WC-(7 to 43) vol pct Co alloys have been carried out at room temperature, and stress-micro strain relation has been investigated in detail. The analysis of the factors affecting the yield stresses reveals that the yield stresses can be predicted by modified Oro-wan's theory if one properly estimates the planar in-terfiarticle spacings. Conzpressive straining of some of the alloys by 0.066 to 0.17pct increases the decrements by a factor of as much as 3.4 to 14, whereas the corresponding increase in the electrical resistivities is less than 10 pct. The analysis of the decrement data in terms of -Gramto and Lücke theory shows that the marked increase is attributed to increased dislocation darnping itt the binder (cobalt) phase. By cornbilling the decrement data and the conzjwession duta, one obtains the relation between flow stress in shear (?t) and increase in dislocation density (p): At = const . v6 . This is interHeted to mean that the mechanism of strain hardening of CirC-Co alloys is essentially sarne as the one for dispersion strengthened alloys. The possible effect of bridge formations between the carbide particles has also been examined. OWING to the combination of hardness, strength, and other physical and chemical properties, WC-Co alloys have opened the way for unique fields of applications, the recent ones being, for instance, anvils for super-high-pressure generation apparatuses. In such applications, the alloys are frequently subjected to very high compressive stresses: these stresses may cause the alloys to deform plastically and eventually to fail. However, much remains obscure regarding the nature of the plasticity of the alloys. Evidently, the alloys owe their high strength to the hard carbide particles which frequently occupy as much as 80 to 90 pct in volume fraction, whereas the ductility required for practical applications is provided by the small amount of the binder phase between the carbide particles. When the volume fraction of the carbide phase is not very large, deformation behavior of the alloys may be described by some of the current dispersion strengthening theories. However, greatly increasing the carbide phase is thought to lead to some carbide skeleton structure or bridge formations owing to the increased chances for direct contacts between the carbide particles;1,2 this may appreciably affect the plasticity of the alloys. Regarding the effect of formation of the carbide skeleton structure, it is interesting to note the work by Ivensen et al.3 on compression tests of the alloys containing somewhat large carbide particles; they observe extensive generation of slip bands in the carbide particles after application of some preliminary compressive stresses. They interpret the results in terms of plastic deformatiot: of the carbide particles which are supposed to have formed a skeleton structure; the binder phase plays only a passive role, at least in the early stages of the deformation. That carbide crystals exhibit microplasticity at room temperature is apparent from the work of Takahashi and Freise4 and French and Thomas5 on indentation of WC single crystals. On the other hand, Dawihl and coworkers6-10 maintain that even when volume fraction of the carbide phase is very large (for instance, more than 90 pet), a very thin binder layer generally exists between the carbide particles. They interpret the results of the extensive mechanical tests in terms of the plasticity of such a layer. Gurland and Bardzil11 point out that decrease in ductility of the alloys with increase in the carbide phase is caused by the effect of plastic constraint exerted by the dispersed carbide particles. Drucker12 further develops this concept from a continuum-mechanics approach on an assumption that a continuous thin binder layer separates the carbide particles. A common feature of the studies reported so far on the plasticity of the alloys is that the information deduced is invariably qualitative in nature. Thus, very few systematic experiments for obtaining reliable and sufficiently detailed stress-strain curves of the alloys varying widely in the microstructural features have been carried out. In particular, it may be of special interest to investigate in detail the early stages of the plastic deformation of the alloys in order to shed light on the strengthening mechanism. However, such work appears to be extremely rare. Doi et al.13 recently reported a first brief account of the results of some quantitative analysis of the plasticity of the alloys in terms of dislocation theory. Their experiment was rather limited in the composition range covered (volume fraction occupied by the carbide phase: 79 to 83 pct), and thus they could not necessarily elucidate the controlling mechanism of plastic deformation of the alloys of a more general composition range. Consequently, in the present investigation, deformation behavior and some other physical properties of the alloys were investigated and discussed in more detail over a much wider composition range. SPECIMEN PREPARATION WC-Co alloys used in this experiment were prepared in cylindrical or rectangular form by sintering in vacuo compressed mixtures of tungsten carbide and cobalt

Jan 1, 1970

The dissolution kinetics of gold in iodide solutions with oxygen in an autoclave was investigated. The leaching process was described by a gas-liquid-solid heterogeneous reaction. The effect of stirring speed, temperature, partial pressure of oxygen, and concentration of lixiviants on the overall leaching rate was investigated. It was found that the dissolution of gold was limited by a heterogeneous chemical reaction. The apparent activation energy was measured to be 34.7-54.3 kJ/mol under the conditions studied. Experimental findings were in good agreement with the kinetic model proposed.

Jan 1, 1996

By R. Bakish, W. D. Robertson

IN the course of a study of stress corrosion cracking of AuCu,, it was necessary to develop new electropolishing and metallographic etching methods. The techniques are generally useful for Cu-Au alloys, including the AuCu composition in which transformation markings are well delineated. For electropolishing, the only satisfactory electrolyte and procedure that has been found1 has the composition given in Table I. The solution must be vigorously stirred while polishing and the temperature maintained in the range of 55" to 62°C. The electrolyte is very unstable and can be used only for 10 to 15 min after which its color changes and a dark-brown precipitate forms. The polishing time is between 1 and 4 min depending on the initial surface preparation. The use of a hood is recommended to avoid the danger of cyanide gas which may form at one of the electrodes even though the solution is alkaline. The optimum current and voltage conditions for vertical anode and platinum cathode are on the plateau shown in Fig. 1, in which voltage is measured across the cell terminals. At voltages below the plateau, etching of grain boundaries occurs and under some conditions, which have not been clearly defined, octahedral etch figures are observed. For general purpose grain-size determination in polycrystalline alloys, a 3 pct solution of iodine in methyl alcohol is used with excellent results. However, when it is necessary to reveal small orientation differences or concentration gradients in an alloy, the iodine etch is not satisfactory. For this purpose, a highly satisfactory etching procedure was developed during this investigation. It involves the use of the vapor given off by freshly prepared aqua regia. The solution employed is 3HC1 to lHNO, which decomposes in accordance with the reaction HNO, + 3HC1 = NOCl + 2H,O + Cl,. The polished specimen surface is held about 1 to 2 cm above an aqua regia solution for 2 to 10 sec depending on the intensity of the contrast required and the surface is not subsequently washed. The results obtained with a coarse grained cast structure are shown in Fig. 2. Subgrain boundaries in a single crystal and concentration gradients within the boundaries are developed by the same treatment with the results shown in Fig. 3. Obviously, any conclusions regarding structure-dependent properties will be modified by the pronounced heterogeneity, which is not clearly evident when more conventional methods are used. Interesting structural details are also revealed by treatment for 4 hr at 850°C in unpurified tank argon. Fig. 4 shows a pattern characteristic of orientation-dependent oxidation.

Jan 1, 1956

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Jan 1, 1938

By Rolf Andreas Lauten, Guy Kluck

"Formation of scales may have important detrimental effects in many mineral processing applications. A well-known problem is the need for frequent maintenance to remove scale from processing equipment. Another challenge may relate to encapsulation of valuable minerals in precipitating scale. In this work, we explore the ability of some crystal growth inhibitors to prevent or lower the degree of scale precipitation. In many situations pregnant leach solutions contains substantial concentrations of calcium, magnesium, sulfate and carbonate in addition to dissolved valuable elements, e.g. gold, copper, zinc. Together with non-dissolved gangue minerals, some slurries may also contain particulate gold, copper etc. During normal processing of the pregnant leach solution it may be exposed to temperature gradients or similar promoting precipitation of various scales. Valuable minerals may become entrapped in precipitates and thus become inaccessible to the lixiviant. Use of a crystal growth inhibitor may lower the degree of encapsulation of valuable elements.Using a simple model system, supersaturated with respect to gypsum, the effect of some crystal growth inhibitors on the prevention of scale is evaluated in terms of amount precipitated gypsum, the particle size of the precipitated gypsum and the carbon gold loading capacity.INTRODUCTIONGold bearing sulfide ores are often roasted or pressure oxidised prior to leaching. The purpose of this unit operation is to prevent loading the leaching circuit with sulfides that consume cyanide. Pressure oxidation or roasting chemically converts the sulfides into sulfates and at the same time, the pH of the slurry ends up in the acidic range. Typically, lime addition is the preferred means to raise the pH to around 10 where gold leaching takes place. Combination of large amounts of calcium ions from the lime with sulfate ions from the ore induces precipitation of gypsum. Compounds like calcium carbonate may also precipitate if carbonate ions are present in the slurry. Depending upon the composition of the ore, compounds like calcium carbonate and other types of scale may also precipitate on gold surfaces on the slurry particles. A layer of scale on top of exposed gold surfaces will prevent dissolution in the cyanidation that takes place during leaching. Naturally, such a precipitation may lower the gold recovery."

Jan 1, 2016

By Elwin L. Fisk

The Cordero mine is located in the Nevada portion of the Opalite Mining district that straddles the Oregon-Nevada state boundary. The mercury deposits of the district occur along the margins of the broad east-west graben valley of McDermitt Creek. The only other major producers, the Opalite and Bretz mines, on the northern margin of the graben have thus far exploited only shallow deposits within 100 feet of the surface. Through December 1965, Cordero has produced 94,680 flasks of mercury, the most of which came from the large underground cinnabar deposit. Nearly all of the mercury ore deposits in this district have been found in Miocene rhyolitic intrusives, flows, tuffs, and lake beds. These rhyolites have been argillically altered at depth and extensively silicified at or near the surface. These silicified areas or "opalite" masses were the original cinnabar-bearing outcrops.

Jan 1, 1968

By S. K. M. Chao

The increasing demand for large volumes of relatively low-cost cement has resulted in the need for an equally low-cost high-volume means for transporting that cement. It has been estimated that 20% - 25% of the total cost of cement to the buyer represents delivery expenses from the mills. For instance, during the 1972 cement shortage in the Southeastern region of the U. S., bid prices for a ton of cement delivered increased to $45 compared to $20 average at mill price, i. e. , F. O. B. plant. Much of the increase was caused by the anticipated higher cement shipping costs for longer hauling distance. The exceptionally high bid price, of course, was not the price quoted by the successful bidder. Thus, clearly, cement is not a marketable commodity unless it can be economically transported to the consumer.

Jan 1, 1975

By Nicholas Matthews, Vilem Petr

This project will report findings on the establishment of a new surface test site at the Colorado School of Mines Edgar Mine. Concerns over the blast effects on site neighbors prompted the study to be conducted. The current maximum charge weight of 20-lb was studied to ensure that all environmental effects were within the range prescribed by state and federal regulations. Geophone locations were surveyed using GPS and monitored using Instantel Minimate Plus instruments. Distances and orientation of measurement sites to the test site were varied according to the local geography and geology. Weather conditions were also observed and recorded during all tests. Neighbor complaints were recorded and taken into account during analysis. Current results show that the current charge limit results in a safety factor of over 200 for all blasting activities at the site. Data collection is ongoing and a review is to be conducted annually. These results will be presented in the future. Results are presented and discussed in the following paper. Copyright

Jan 1, 2010

By Willard Ide Pierce

The Department (formerly called State) of Tolima, which is beginning to attract considerable attention in this country on account of its mineral wealth, comprises an area of 18,415 square miles, lying between latitude 1" 34' 25" and 5" 44' 12/" N. and between longitude 74" 25' 45" and 76" 34, 25" W. from Greenwich. It is bounded on the north by the Department of Antioquia, on the east by the Departments of Cundinnmarca and Cauca, and on the south and west by the Department of Cauca. It is the most recently created of the States of Colombia, having been established by decree of April 12th, 1861, and being composed of the old provinces of Mariquita and Neiva, and of the districts Melgar, Carmen, Cunday and Santa Rosa, of Tequendama.

Jan 1, 1888

As is known to representatives on Engineering Council, the Patents Committee of Council has collaborated with the similar committee of National Research Council in developing a scheme for the improvement of the method of dealing with patents in this country. The staff of the Patent Office is itself actively engaged in this effort. Out of the report prepared by the National Research Council, and approved and adopted by Engineering Council as the report also of its Patents Committee, remedial legislation has taken form. Three hills have been introduced, known as H.R. 5011, a bill to make the Patent Office independent of the Department of the Interior or any other department, and to simplify the procedure of the Courts with reference to assessment of damages or profits for infringement of patents; H.R. 5012, a bill to establish a single Court of Patent Appeals; and H.R. 7010, a bill to increase the force and salaries in the Patent Office. Chairman Charles A. Terry, of the Patents Committee, requests that representatives of Engineering Council write to their congressmen, urging the passage of these hills and so far as convenient, request their friends to do likewise.

Jan 9, 1919

By H. J. Booss

THERE is a considerable lack of data on thermody-namic properties of hard-metal alloys. Only two papers 1,2 give mean values of specific heat in an unknown temperature range; more recently the author3 gave more detailed information on the mean specific heat in the temperature range from 20" to -190° C.. EXPERIMENTAL 1) Method—Experimental procedure followed a method suggested by Oelsen and coworkers.4 It requires samples of some 100 g of weight. The time of measurement is prolonged (30 min) but one run allows the measurement of a lot of positions on the heat-content curve. Results4 were found to be in good agreement with "best values" given by kelley,5 Kubaschewsky and Evans,6 etal.

Jan 1, 1960

The earliest suggestions that some metallic ore deposits might have resulted from seafloor volcanic exhalation seem to have been those of Elie de Beaumont in 1847 and Henry de la Beche in 1851. In 1885 Tinoco, and Bouglise and Cumenge, independently investigating-.the manto copper deposits of the Boleo district of Baja California, proposed that these had formed on the seafloor by precipitation from "hydrothermal submarine emanations". Some twenty years later the Japanese geologists Kukuchi and Tsujimoto (1904) put forward the idea that the Kuroko ore- bodies were seafloor volcanic sinter deposits and in 1919 this was re-affirmed by Ohashi. In 1909 the English geologists Thomas and MacAllister postulated a similar origin for some of the gold deposits of Mount Morgan in Queensland. Between the wars the great European economic geologists Niggli and Schneiderhohn both clearly recognized a class of seafloor hydrothermal deposits. The idea rose again immediately after the Second World War in a very clear statement by Hegeman in 1948, which was followed by contributions by Ehrenberg and Kraume and their co-workers on the submarine volcanic origin of the Meggen and Rammelsberg orebodies in 1954 and 1955 respectively. In 1955 the present writer, quite unaware of early or contemporary work on volcanic exhalative ore deposits, proposed a volcanic sedimentary/diagenetic origin for the stratiform base metal ores of SE Australia. In doing so the writer emphasized the probable importance of island arc volcanism, suggested that some "metallogenetic regions" of ancient terrains were in fact old island arc systems, that the composition of the ores might be related to the composition of the associated volcanic rocks and that such ores would be tied to volcanic stratigraphy. Ideas on relations between volcanism and stratiform ore genesis have thus been evolving over.a period of some 140 years and, beginning with the observations on Baja California in 1882, work round the rim of the Pacific has made an important contribution over a period of more than 100 years.

Jan 1, 1987

By T. Belem

In-stope backfill will cure under effective stress, which develops due to a combination of mechanical consolidation (free draining material) and ??chemical consolidation?? (self-desiccation mechanism). A good knowledge of all the drainage and consolidation characteristics of cemented paste backfill is crucial for a better design of underground backfilling sequencing. From many of the existing results and studies done by various authors, as well as the availability of some in-stope backfill pressure data measurements during and after filling, it is possible of developing a procedure of backfilling sequencing. Hence, the objective of this study is to provide a guide for underground backfilling sequencing in the view of preventing the development of excess pore pressure that will affect both the stability of the barricades and the strength development of the backfill. This will be possible by considering the interaction between consolidation/drainage rate, filling rate and binder hydration rate.

Aug 1, 2013

By H. l. Burghoff, C. H. Mathewson

THE study of the creep of metals under conditions of prolonged loading has received the attention of many investigators for several years and almost innumerable papers have been published on the various aspects of the subject. As it appeared that much could still be learned from a study of single crystals, the present work was carried out to study the effects of temperature and conditions of loading upon the properties and deformation in tension of single crystals of alpha brass containing about 70 per cent copper and 30 per cent zinc. In particular, it was hoped to obtain information from tests below and above the recrystallization temperature of the material, so that properties such as elastic limit, yield point or critical stress, and manner of deformation might be compared for tensile tests at an ordinary loading rate and for prolonged. loading. Accordingly, short-time tensile tests and creep tests were made at room temperature, 300º, 500° and 700°F. The two latter temperatures are above the lowest possible recrystallization temperature of polycrystalline 70-30 brass. PREVIOUS WORK Clarke and White1 have made creep tests of some copper-zinc alloys, including 70-30 brass, and copper-zinc-tin alloys at temperatures both below and above the recrystallization temperature of the materials considered. Hanson and Wheeler have studied the flow and fracture of single crystals of aluminum for short-time and prolonged tensile loading over a range of temperature extending from room temperature to 400°F., their experiments being made without consideration of the orientations of the test specimens. Extensive creep and fracture tests on single crystals of lead at room temperature have been made by Betty3 and by Baker, Betty & Moore.4 Results of the last-named investigation were published while the present work was in progress. Millers examined the elastic limit of zinc single crystals at and above room temperature by means of creep tests, while Miller and Milligan6 reported the results of tests designed to show the influence of temperature on elastic limit of single crystals of aluminum, silver and zinc. The behavior, of iron crystals under static tensile loading at room temperature was reported by Gensamer and Mehl7 while the present investigation was in progress. Their specimens exhibited a well-defined yield point, below which no appreciable creep could be detected. The manner of yielding proved interesting, as the shape of the creep-time curve for the iron crystals differed from the common type of creep curves. Elongation did not begin immediately, or at least was initially very slow. The rate of elongation then increased continuously and finally decreased to zero. This S-shaped type of elongation-time

Jan 1, 1941

By Ian McFeat-Smith

Despite a present, short-term economic recession, a remarkable enthusiasm exists in Hong Kong for building infrastructure including major tunnel projects. This paper provides details of current and recent bored tunnel works together with an insight into the impressive list of future underground projects planned by the MTRC,KCRC, Highways Department and Drainage Services Department for the next decade. Risks for each of these works including pipejacking, mixed face and rock tunnelling generally in Hong Kong are also identified. From this is evident that the scale and difficulty of such works continues to increase, requiring the use of more sophisticated methods of construction, the need for better methods of assessing and managing risks and for Government to utilize improved, more equitable Conditions of Contract for such major tunnelling projects.

Jan 1, 2001

By Randy R. Williams, Brian W. Wilson, George M. Filz, Marina S. W. Li, Donald A. Bruce

"In-situ wet grab sampling and post-installation coring of soil-cement structures are typically carried out for Quality Control (QC) and Quality Assurance (QA) of deep mixing (DM) schemes. Wet grab sampling and testing is used to provide data to indicate that performance requirements are being met during production, in advance of coring, which typically occurs at 28 days or later, following installation. While unconfined compressive strength (UCS) tests from wet grab samples provide good production indicators, industry practice often requires that acceptance criteria of soil-cement structures be based on UCS results from representative core samples.This paper outlines the approach adopted for field sampling and QA/QC testing carried out in highly variable subsurface conditions at a site located in northern British Columbia (BC), focusing on postinstallation soil-cement coring and strength testing for an extensive deep mixing scheme. A discussion on suitable methods of coring soil-cement structures and appropriate selection of samples for testing that are representative of the in-situ soil-cement structures is provided. This paper also discusses the selection strategy adopted for verification of strength and modulus parameters used for design, providing spatial and time coverage, as well as the acceptance criteria implemented, and provides comparisons with published industry recommendations.BACKGROUNDAn extensive deep mixing ground improvement scheme was completed for the development of a Liquefied Natural Gas (LNG) Facility to be located in Bish Cove, BC, Canada. The deep mixing scheme was implemented to treat very weak native deposits in-situ to support two mechanically stabilized earth (MSE) walls up to 20 m (66 ft) high, and their associated bulk earthworks. Within the DM area, the subsurface conditions were highly variable, ranging from deep (up to 21 m (69 ft) thick) deposits of very soft to soft clayey silt to silty clay, overlying layers of dense to very dense gravelly sand to sand and gravel, to compact deposits of silty sand (up to 15 m (49 ft) thick), overlying dense sand and gravel. Bedrock was encountered beneath the granular deposits and generally comprised granodiorite with occasional andesite dykes."

Jan 1, 2015

By R. W. Raymond

R. W. Raymond, New York City: In his paper at the New York meeting (Trans., xix., 28), Mr. Ledyard described, among other mines, the Belmont, in the county of Peterboro, Ontario, the developments of which at that time indicated, though they did not, perhaps, completely demonstrate, a deposit of high-grade Bessemer magnetite of very great extent. Mr. Ledpard said that experts estimated the quantity of ore within 100 feet of the surface at 1,000,000 tons. But the precise data upon which this estimate was based were not furnished. We are all interested in the development of fresh supplies of Bessemer ores. I think nobody who knows how enormous is the demand can seriously fear that such deposits will be exploited too rapidly. On the other hand, I need not here enlarge on the fact that a considerable number of enterprises, in which American ironmasters have been more or less interested, for the development of Canadian iron-ore deposits, have been unsuccessful, more by reason of disappointment as to the quantity of the ore and the facilities for cheaply mining it on a large scale, than as to its quality. Of course, a Canadian nine supplying the American market is handicapped at present, to the extent of 75 cents per ton, by the duty on foreign iron-ore; but this would certainly not be prohibitory in the case of a deposit sufficiently large, rich, and accessible. Or, to put it otherwise, there might easily be, somewhere in Canada, near our borders, a mine so favored that its product could be profitably

Jan 1, 1892

By J. A. Cahill, A. D. Kirshenbaum

Using an alumina or zirconia crucible with an alumina sinker or a molybdenum sinker coated with zirconium dioxide, the density of liquid iron was determined by the immersed-sinker method over the temperature range of 1800" to 2500°K. The density, with respect to temperature, is ex-Dressed by the equation Dg/cm = 8.523 - 8.358 X 10 T'K The molar Volumes and thermal coefficients of expansion were calculated. Iron, upon me1ting, was found to expand 3.5 pct. A basic knowledge of the physical properties of materials at high temperatures is becoming increasingly important. A check of the literature shows, that in spite of the importance of iron, very few measurements have been made of its physical properties in the liquid state. Density measurements have been made by Benedicks and his collaborators1g using the method of balanced columns, by Desch and smith4 using the immersed sinker method with an alumina sinker, by Lucas using the maximum bubble method5 and by Stott and endall' who used an alumina pyknometer. In the method of balanced columns, the difference in level of molten iron in two arms of a U-tube, together with the corresponding difference of pressure had to be measured. The formation of gas bubbles in one or both arms was a great source of error. These values are very erratic. They vary from 6.83 to 7.45 g per cm3 at the melting point (1805"~) and from 6.45 to 7.15 g per cm3 at 1890°K. Stott and Rendall determined the density at 1837"K, with a reproducibility of *0.2 pct. They used an alumina pyknometer fired to 1973°K. The vessel was filled in a vacuum furnace by immersion in the liquid metal. When thermal equilibrium was attained, the pyknometer was withdrawn, cooled, the ingot removed and then weighed. The chief disadvantage of the method was the difficulty of inserting the pyknometer without cracking it. The authors have been able to determine the density of liquid iron from its melting point up to 2500°K, by using the immersed-sinker method, with A1203 or ZrOz crucibles and A1203 or molybdenum sinkers coated with Zr02, Fig. 1. EXPERIMENTAL Apparatus. In these studies the source of heat was the carbon tube resistance furnace with an argon atmosphere described previously.7 Experimental runs were made using either Ala3 or ZrOz crucibles. The sinkers used were 1) pure A1a3 and 2) molybdenum coated with ZrOz. The crucible, 2 1/8 in. in diam and 3 in. high, was centered in the furnace on an Ala3 of Zr02 pedestal. The sinker, 1/2 in. in diam and 1 1/2 in. long, together with a counter weight, was suspended from an analytical balance into the melt by a molybdenum wire. Procedure. The procedure, as described previously,' consisted in measuring the weight loss of the sinker in the liquid iron while determining simultaneously the liquid iron temperature by means

Jan 1, 1962

By David A. Keys

The object of this investigation was to determine with a vertical magnetic variometer the extent of the titaniferous ore deposit that occurs not far from Ivry in Terrebonne County, Quebec, about 70 miles north of Montreal. The Ivry mine, on lots 37 and 38 of range V, Beres-ford township, Quebec, is one of the largest and most accessible to transportation of the deposits of ilmenite in Quebec. The ore consists of an aggregate of ilmenite anhedra serving as host for numerous fine plaques of hematite. No magnetite is known from any occurrence near this lot, and in this way the deposit differs from many others that contain a large percentage of magnetite with the ilmenite. The deposit at Ivry thus has much lower magnetic susceptibility than those containing abundant magnetite, and a sensitive magnetometer was necessary for the work, although a body of magnetite with ilmenite about a mile from the Ivry mine was successfully prospected with a dip needle. The principal orebody is exposed in a quarry known as the Ivry mine, from which about 16,000 tons of ore have been shipped. Small exposures of ilmenite isolated by drift serve to show the presence at the surface of some of the bodies indicated by the magnetometer, but most of the hill is covered with glacial till and second growth hardwood. At the lower levels the till gives place to fluvioglacial sands and gravels from which the forest has been cleared. The increasing thickness of the sand and gravel as the hill descends makes the tracing outward of the deposits from the rocky knob of anorthosite a difficult matter. Within the orebodies too, some masses of anorthosite persist, which may account for some local irregularities. Fig. 1 is a photomicrograph, taken by reflected light, of a typical specimen of the ore. The dark patches are hematite and the light parts are ilmenite No trace of magnetite was found. Pig. 2 is a photomicrograph of a thin section of the country rock showing the texture of the anorthosite. The mean of four analyses quoted by Robinson1 is: titaninm, 19.26 per cent; iron 45.41 per cent. The ilmenite ore is not sufficiently magnetic to deflect an ordinary compass needle, but the effects of the induced magnetism in the ore by

Jan 1, 1940

By Frank R. A. Jorgensen

Flash smelting is used to smelt a large proportion of the world's copper and nickel and some lead/zinc concentrates. Understanding the factors controlling the ignition of these concentrates is an important consideration in designing burners and maximising the throughput of the flash smelting process. The literature on the subject is briefly reviewed and techniques for the measurement of ignition temperature discussed. The mineralogy of the concentrates and the role of thermodynamics and phase diagrams in interpreting and predicting ignition behaviour are emphasised and applied to interpreting results obtained on a nickel concentrate.

Jan 1, 2002