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The key-note of good writing, as of good manners, is B natural. Sincerity is the first requisite for effective writing. When a man says what he knows or believes, he is likely to be interesting, because each human being possesses an individuality, a point of view, or a range of sympathy that makes him different from his fellows. To say or to write what you do not think, for the mere sake of talking or writing, is a verbal exercise that must be performed with extraordinary skill if it is to be attractive. Affectations are rarely attractive, rarely effective. To be natural is to be yourself, not a poseur; to give the reader the best of yourself, instead of re-warming the baked meats of yesterday. Quotations-which are second-hand thoughts-will serve occasionally when the thing you want to say has been said so well by another that it would be waste of energy to try to say it better; gut, as a rule, the utterance of the writer himself is more interesting than the quotation, because the writer brings something of himself to bear on the subject, and for the moment is more in touch with the reader than any dear departed author. Therefore, say things as best you can in your own way, neither in borrowed words nor in the phraseology that mimics another. Write as if you were speaking to a person whom you desire to persuade or convince. You will then write better than you speak, because, in the first place, you can be more deliberate, and, secondly, you can revise what you have written. Speaking and writing are similar mental acts, with a difference: the difference between eating food raw and eating it cooked. Some kinds of food gain nothing by being cooked; likewise some kinds of utterance are not bettered by being written down first; but most expressions of thought, especially

Jan 1, 1931

By K. L. Williamson, P. W. Dugan

INTRODUCTION In recent years there has been increased social awareness and government attention directed toward the mining industry. The growing influence of the Occupational Safety and Health Administration (OSHA), the Mine Safety and Health Administration (MSHA), and the Environmental Protection Agency (EPA) has resulted in volumes of regulations governing a multitude of health and safety aspects of mining and milling. These regulations naturally have had an impact on new plant design and in some cases have necessitated retrofitting of existing plants. This paper will not examine the regulations governing the industry, since they are a matter of public record, but rather will address two specific health considerations, dust and noise, and their influence on the design of crushing and screening plants. DUST AND NOISE CONCEPTS Dust is generally defined as finely divided solids which may become airborne without any physical or chemical change except fracture. Since the purpose of comminution circuits is to reduce the size of solids by fracture, a percentage of the material is normally reduced in size to a point where it can easily become airborne. The major cause of dust becoming airborne is the air induced by falling material. When granular material falls through a distance, the induced (or entrapped) air rushes out available openings, carrying with it the fine particles that have become suspended. For this reason, the major points of dust generation are the points where the material is falling: chutes, transfer points, screens and equipment feed and discharge points. The expected dust concentration in an area is a function of the degree of size reduction (i.e., finer particles are more readily carried by air currents than heavier particles) and the volume of air that is induced. The measured dust concentration values for various operations agree with this

Jan 1, 1982

By Lawrence P. Bonicatto

The steel industry's increased demand for higher grade pellets has caused the pellet producers to investigate methods of upgrading their product and the Hanna Mining Co.'s Groveland plant on the Upper Peninsula of Michigan is no exception. The low grade iron deposit is a complex mixture of magnetite and hematite with chert, quartz, jasper and various iron silicates.1 Beneficiation is by Humphrey spirals and anionic flotation of the iron minerals.2 Flotation of the spiral tailings makes up about 75% of the concentrate, while a minor amount of concentrate (less than 3%) is produced in magnetic circuits. The concentrate is pelletized at the rate of 1.6 million tpy. The initial concentrating facilities were constructed in 1958 and the concentrate was marketed as sinter feed until a pelletizing plant was added early in 1963. Grade improvement soon became a high priority research project, and several methods of concentration were investigated.

Jan 3, 1968

By G. F. Comstock

These notes should be considered as a further discussion of Mr. S. W. Miller's paper on "Some Structures in Steel Fusion Welds."l In that paper and the resulting discussion, several conflicting opinions were expressed as to the identity of the needles or small crystals present in oxyacetylene and electric welds. An interesting specimen of an electric weld examined by the writer seems to afford new evidence regarding the needles, that may be worth presenting at this time. The specimen consisted of a piece of 3/8-in. (9.5-mm.) steel plate, about 21/4 by 13/4 in. (5.7 by 4.5 cm.) in size, on which some iron had been deposited by arc-welding to a depth of about 3/16 in. (4.7 mm.). The weld appeared to be a very good one, with no noticeable break or boundary between the plate and the deposited iron. Sections for microscopic examination were cut in three planes at right angles to each other through the deposited metal, two of these sections also extended through the steel base. After polishing in the usual way, the microscope showed that the deposited metal was full of very small, round, gray, oxide spots, while the steel plate contained quite a number of alumina inclusions and a little slag. The sections were etched with nitric acid in ordinary alcohol, and structures similar to those described by Mr. Miller were then displayed. Fig. 1 shows the typical appearance of the deposited metal, which was quite uniform in all three of the planes examined. The round dark-gray spots are oxides, and the pale angular crystals are evidently what Mr. Miller called cem-entite and Mr. Jeffries martensite, while Mr. Ruder and Professor Boyls-ton think that they might be nitride. The boundary between this structure and the steel base was sharply defined under the microscope. Fig. 2 shows the structure of the plate just under the weld; this is almost martensitic and resembles a coarse-grained casting. This coarse cast structure soon became finer as the distance from the weld increased, finally becoming very fine, with numerous small particles of sorbite. This very fine structure, shown in Pig. 3, became coarser in turn and finally merged into the original normal structure of the steel plate, shown

Jan 1, 1920

US 4,141,854-Method of resolving water-in-oil emulsions from the organic solvent extraction of uranium from an aqueous ore leach solution The emulsion is treated at optimum temperature with a water-soluble acrylamide copolymer which contains 5-50% by weight of a lower alkyl substituted tertiary aminoethyl methacrylate or quaternary ammonium salts thereof The emulsion is broken, enabling recovery and reuse of the organic portion of the emulsion A M Pavilcius and M A Latko, assigned to Nalco Chemical Co Feb. 27, 1979 3 pp (252-301 1W) Filed: 12-14-77 (860,542). US 4,142,952-In the recovery of copper from an ore leach solution, the solution is contacted with a water-immiscible organic solvent containing 5 to 20 g/L of o-hydroxyaryloxime and 2 to 20 times the weight of the o-hydroxyaryloxime of nonylphenol The loaded solvent phase is separated from the aqueous phase and stripped with sulfuric acid Copper is recovered rapidly and in high yield from aqueous solutions containing high copper concentrations R F Dalton, as¬signed to Imperial Chemical Industries Ltd Mar 6, 1979 6 pp (204-106) Filed 1-3-77 (756,067). Priority: United King¬dom, 1-30-76 (3788/76), 6-15-76 (24722/76), and 10-21-76 (43711/76). Same- British 1,549,615, dated Aug. 1, 1979 US 4,148,631-In the recovery of nickel and cobalt from a mixed sulfate ore leach solution, both metals are extracted by means of a cationic extractant, the loaded extractant treated with an aqueous chloride or thiocyanate solution to back extract the cobalt, and the cobalt then recovered by solvent extraction or ion exchange with an anionic extractant Recovery is effected in a relatively few extraction steps. F Babjak, V A Ettel, and K. R Dymock, assigned to Interna¬tional Nickel Co , Inc, Apr. 10, 1979 6 pp (75-101 BE) Filed¬7-27-78 (928,401). Priority- Canada, 12-28-77 (293,967) US 4,148,813-An improved extractant for use in the recov¬ery of nickel and cobalt from an ore leach solution comprises a water immiscible organic solvent system containing solubilized mercaptide ions, e g , dodecanethiol. Cobalt and nickel mercaptides solvated in the organic phase are easily stripped in the presence of carbon monoxide and an aqueous alkaline solution A. S. Rappas and J. P. Pemsler, assigned to Ken¬necott Copp

Jan 1, 1980

By W. Rostoker

A STUDY of the titanium-oxygen system' involved an associated series of measurements of the lattice parameters of the a and TiO phases. The results permit some interesting deductions which are herein reported. A comprehensive survey of the physical PI-operties of the phases in this alloy system has been made by Ehrlich.2 However, only impure titanium was available at that time, so that some revision of his measurements is to be expected. The lattice parameters were calculated from the high angle lines of Debye-Scherrer patterns taken in a 14 cm camera and using filtered CuKa radiation. The specimens were prepared largely by crushing and screening of lump samples which had been quenched from elevated temperatures. Only in the case of low oxygen contents was it necessary to resort to filing and annealing. The results of the lattice parameter studies are graphically presented in Figs. 1 and 2. It will be seen that oxygen produces a pronounced distortion of the c parameter of the a phase (hexagonal close-packed). The trend is in general agreement with Ehrlich's work, although the divergence of actual parameter values strongly suggests that his titanium was very impure. It will be noted that the a phase of titanium can tolerate the unusually high saturation solubility of about 34 atomic pct 0. By virtue of this unique effect, it is possible to make a calculation of the effective atomic diameter of oxygen when dissolved in a lattice with metallic bonding. This has not been possible before. Ehrlich's2 density measurements demonstrated that oxygen occupies interstitial positions in the a lattice and the trend of the lattice parameters would certainly support this. In a hexagonal close-packed unit cell the largest interstitial positions lie at (2/3, 1/3, 1/4) and (2/3, 1/3, 3/4). Accordingly, if both of these positions were occupied, the ratio of titanium to oxygen would be 1:1. The extrapolated c parameter may be taken as between 4.93 and 4.99?. The a parameter appears to reach a constant value of 2.955? at low oxygen contents. The distance of the center of a titanium atom site from the [vc2/16+a2/3-1.448] Then the atomic diameter of the oxygen atom is represented by the function: where the radius of the titanium atom is 1.448A,

Jan 1, 1953

By E. G. Dean

A method of top slicing has been devised at the Miami Copper Co.'s mine at Miami, Aria., which differs radically in some ways from the customary methods of top slicing. The area of that section of the orebody in which top slicing is used is about 800 ft. square. The ore, while for the most part soft, is, nevertheless, considerably harder than the capping. The latter is siliceous, seldom containing any clay or other binding material, and breaks into fine particles so that it runs like sand if given the opportunity. Because of these facts, and because the ore is above the average grade of the mine ore, it has been mined by top slicing. Haulage levels are opened up 150 ft. apart, vertically, with two sub-levels between at 50-ft. intervals, to facilitate the putting up of ore chutes. These sublevels are used during slicing for distributing air in the ventilation system. On the haulage level the drifts are spaced on 50-ft. centers, and raises along these drifts are also spaced on 50-ft. centers, except the incline raises as hereafter noted. The raises are cribbed where necessary. Where the wear will be excessive, 1/4-in. iron plates are spiked to the top of every third set of cribbing, for its protection. When top slicing was first used, an attempt was made to carry a slicing face from fifty to several hundred feet long. Timber and other supplies were brought in through long drifts from an auxiliary shaft. Great difficulty was experienced in keeping these drifts open, the side pressure breaking the posts and the top weight breaking both caps and posts. Furthermore, the men could not work efficiently while these drifts were being repaired. The slicing faces advanced irregularly, due to varying conditions, and in many ways the results were not all that could be desired. It was then decided to divide the slicing area into blocks 200 ft. square and this was later changed to 250 ft. square. At the center of each block a two-compartment raise is put up as a supply raise, the compartments being 2 ft. 6 in. and 4 ft. by 4 ft. 4 in., the smaller being used as a manway. Station sets of 12 by 12 timber with

Jan 1, 1917

By Roy C. Kirkman

It is with great pleasure that I read Mr. Howard M. Wells article in the December 1978 issue of MINING ENGINEERING entitled: "Optimization of Mining Engineering Design in Mineral Valuation." Mr. Wells very adequately presents the case and point that there are a great number of variables which must be analyzed during an economic evaluation of an FUND RESOURCE, such as copper or uranium.

Jan 4, 1979

By Willard L. Cumings, Benjamin L. Miller

The Camaguey brown iron-ore deposit covers the top of Sari Felipe hill, the nearest point of which lies 14 miles NW. of the city of Camaguey. While there are several low flat-topped hills in the vicinity covered with a more or less continuous mantle of brown iron-ore, the deposit of San Felipe hill is the only one of any size and importance, and the name " San Belipe district" is proposed for the region. The deposit extends in a NW-SE. direction for a distance of about 10 miles, with an average width of 5 miles. The location is shown in Fig. 1, a sketch-map of the eastern part of Cuba. Fig. 2 is a map of the San Felipe district. 2. Description. The district is mentioned by Spencer,' who says: " The Cubitas iron-ore fields are situated from 12 to 15 miles north of Camagueg City, in the province of Camagueg.....Within an area measuring roughly 10 miles east and west and 4 miles north and south, there are several flat-topped mesas rising 300 to 400 ft. above the level of an almost featureless plain which extends for many miles in all directions except toward the north." With the exception of the discrepancy in his statements .as to the distance from Camaguey and the area of the hill, which is over 50 sq. miles, his description is a very good one. Kemp2 has the following to say of ores in Camaguey Province:

Jan 1, 1912

By Marcel R. Daly

In a preceding paper1 the writer has pointed out some apparent relationship between the distribution, on the surface of the globe,, of the known hydrocarbon deposits and the disposition of the principal zones of deformation of the earth's body (geosynclines). He wishes to present some further remarks on this subject. Petroleum deposits, or their derivatives or descendants, are found through the whole range of sedimentary strata, from the pre-Cambrian to the Quaternary. For instance, the prc-Beltian (Shuswap) series of the Canadian Cordillera are interbedded with limestones which are sometimes rich in carbonaceous matter (Sicamous limcstone); and the Beltian system of the same region contains layers of argillitcs and dolomitic limestones which are equally high in carbon content.2 This carbon may be interpreted as the last remnant of hydrocarbons previously contained in the rocks. On the other hand, the actual formation of hydrocarbons under conditions that would eventually permit their deposition in modern sediments is conceded by some geologists.3 Between these two extreme limits, bitumens are found indifferently in all sedimentaries. Thcy constitute a continuous series, some kind of a large family, whose individual members may be entitled to a community of origin and probably represent the different stages of evolution of the primitive, parent matter. The kinship between petroleum and such substances as asphalt, ozocerite, manjak, grahamite, albertite, etc., is well known; and E. H. Cunning-gam-Craig has recently shown how intimately shale fields and oil fields are connectcd.4 For this reason, no distinction is made in the present

Jan 1, 1918

By William Campbell

In the olden days the making of alloys was an art, and the secrete of the craft were jealously guarded. To-day it has become a science, though the old ideas in regard to the secrets and formulæ are dying hard. Modern progress may be attributed to scientific research and testing of materials, and the substitution of chemical analytical control for " cook-book " methods. We know to-day a great deal about the constitution of alloys, the reasons of the change in structure and physical properties by heat and mechanical treatment; and this new knowledge is due for the most part to the physical chemist and metallographist, who have shown us that alloys are simply solutions, and as such obey definite laws. The application of the theories of solutions and of the phase rule tells us what ought to happen when our alloys are in a state of equilibrium. The working-out of the temperature-composition diagram (thermal diagram) for numerous alloys has thrown a light on the structure and constitution which has dispelled most of the darkness in which we labored before the advent of metallography. The work began with the determination of the freezing-point curves, and here the research of Le Chatelier,' Gautier,2 Roberts-Austen,3 and the other pioneers broke the ground. Next the physical chemists, Tammann,4 Rooseboom,5 Bancroft,6 and their colleagues, showed us the complete thermal diagram and its meaning. Then the researches of Heycock and Neville7 on the Cu-Sn series and of Shepherd 8 on the

Jan 1, 1913

By R. Steinitz, L. Seigle, R. Resnick

THE rates of growth of the carbide phases MC and M2C in the Ta-C and Cb-C systems have been measured at various temperatures and the results used to estimate the rate of carbon diffusion within the inter metallic phases. Sheets of high-purity tantalum (50 ppm Cb, <25 ppm Ti, 10 ppm Fe, 5 ppm Cr, <50 ppm Mo, W, and all other metals, 15-75 ppm O2, 10-30 ppm N2, and 10-30 ppm C) approximately 1/4 by 1/2 by 0.020 in. were heated to temperatures between 1800" and 2700°C in a carbon resistor furnace under an atmosphere of argon plus sufficient methane to maintain an excess of carbon at the sample surface. The thicknesses of the carbide layers, illustrated in Fig. 1, were measured with a filar micrometer and plotted logarithmically as a function of time. Fig. 2 is a typical plot for the TaC phase. The points may be represented within experimental error by lines with slope equal to 1/2; therefore the growth of the layers may be described by the usual expression X = kt1/2, where X is the layer thickness, t is the time, and k is a temperature-dependent constant. From these data and compositions at the phase boundaries, it is possible to estimate values for the diffusion coefficients of carbon in each phase, assuming that layer growth occurs by carbon diffusion alone, and that the dif-fusivity is not a function of composition within each

Jan 1, 1965

By Roy Moore

THE Tom Reed Extension and Big Jim mines of United Eastern Mining Co. are situated in the Oatman district, Mohave County, Ariz., about 28 miles southwest of Kingman, the nearest railway point. Articles descriptive of the mine surface plant, mill construction, and plant operations have been written by Otto Wartenweiler1, the designing engineer; Wheeler 0. North,2 when he was assistant general manager for the company, and Earle M. Bagley, mill superintendent.3 The last article covers average costs for the full time the mill was operated. The geology of the mines is described by F. L. Ransome4 of the United States Geological Survey. Production was started in January,. 1917, and the known orebodies were exhausted in May, 1925, showing a life of seven years and five months. On account of the comparatively short life and the fact that stoping operations were confined to two orebodies, little experimenting was done with mining methods. The two orebodies were in what is generally called the Tom Reed-United Eastern vein, which occupies a fault fissure having a normal displacement of several hundred feet. Seven or eight very productive ore shoots were mined along this vein in a distance of 1 ½ miles, the two worked by the United Eastern being 1 mile apart. The maximum dimensions of the Tom Reed Extension ore shoot were height, 750. ft.; length, 950 ft.; thickness, 48 ft. The vein structure varied from a solid quartz-calcite filling to a series of parallel stringers separated by andesite. From this body, 511,976 tons of ore were mined. (Fig. 1.)

Jan 1, 1928

By Robert Mehl

THE mechanical behavior of metals and alloys is presumably conditioned by two factors; namely, the crystalline symmetry and the interatomic forces. Considerable attention has been given to the first of these factors through the recent advances in X-ray .technique. It is the purpose of the present paper to call attention to the importance of the second of these factors, to point out promising methods of investigation, and to present some pertinent data. Plastic deformation takes place by-slip along atomic planes.1 This slip may be inhibited in a number of ways: by the interatomic forces of cohesion which bind the atoms rigidly in a lattice structure, which in pure metals is usually of high symmetry; by lattice distortion caused by solid ,solution formation or by mechanical strain; by the intercrystalline boundaries where slip is restrained by the non-registration of the atom planes in adjacent crystallites;2 and by the presence of small hard particles which serve to "key" the slip along the atom planes.3 In pure metals, and perhaps also in solid solutions, the atom planes, of easiest slip are those exhibiting the greatest density of atomic population and the greatest interplanar distance4 and apparently can now be predicted from the analysis of the lattices. Concerning the interatornic forces, which resist this slip by holding the atoms firmly together, little is known. Most textbooks on physical metallurgy, following the work of Bot-tone,5 correlate the hardness of the pure metals with the atomic volume;.

Jan 1, 1928

By H. W. Hardinge

Disregarding for the present the economic side of a new device, let us turn to that feature of the conical pebble-mill which is of interest from a scientific point of view, and consider the device as a puzzle in which the theories of the cylindrical type of mill have been increased. Many articles have been written on the theory of the tube-mill, and explanations have been made which do not explain ; but these have evolved suggestions of practice which have resulted in changes in the tube as to length, diameter, feed, discharge, speed of rotation, rotation on hollow trunnions, rotation on rings, and changes in the operation as to quantity and size of pebbles, charge of load above or below the axis, crushing by causing the larger pieces of the material of the charge to act as grinders, whether crushing is abrasive or impactive, etc. The practical worker in crushing. is first interested in the endeavor to reach an econonlic means of accomplishing a desired end; but the improvements in crushing-practice have been largely left to the manufacturer of machinery, who, as a rule, has little, if any, knowledge of the specific requirements— such as granulation, sizing for concentration without pulverizing the metals, instead of pulverizing the rock or gangue; the metals being the more friable, while the rock is tough and not so easily disintegrated. A reversal of this practice is the aim of sliming direct for cyanidation or pulverizing for cement, etc. In the ordinary cylindrical mill, having a diameter of 4 or

Jan 1, 1909

By J. D. Davis, A. C. Fieldner

The older coal chemist had a much simpler conception of coal than we have today. To him coal was a mineral composed essentially of carbon, hydrogen, oxygen, nitrogen, sulfur, ash, and water, in various proportions. His studies on the constitution of coal were directed along the conventional lines of proximate and ultimate chemical analyses and making deductions from these data without any real appreciation of the fact that coal is a conglomerate of various chemical compounds, including many of the most complex structures known to organic chemistry. The view of the modern coal chemist is well expressed by Franz Fischer,&apos; who says that while proximate and ultimate analyses are important both from the scientific and technical point of view, they tell the chemist no more concerning the number and kinds of chemical compounds that constitute coal than the reader would learn of the contents of a book if told that the printed contents consisted of 15 per cent. of the letter "e," 5 per cent. of the letter "n," 1 per cent. of the letter"g," 4 per cent. of the letter "b," etc. As the reader must have the grouping of letters into words and words into sentences, so the chemist must have the grouping of atoms into molecules and the proportion of each molecular compound in the coal aggregate before he acquires an adequate knowledge of the constitution of coal. Modern investigators2 are laying the foundation of a new chemistry of coal based on the biochemistry of plants and the chemical changes involved in processes of fermentation and decay. As

Jan 1, 1925

By Thomas H. Leggett

In speaking of the mining and economic conditions prevailing at the present time on the Rand, it is not my intention to go into the details of the mining practice, since this has been already well described both in the Transactions&apos; and elsewhere,2 but rather to take a more comprehensive view of the industry and its surroundings as a whole, marking its general development and the lines of its future progress. In a paper entitled Deep-Level Shafts on the Witwaters-rand, with Remarks on a Method of Working the Greatest Number of Deep-Level Mines with the Fewest Possible Shafts,&apos; presented to this Institute in August, 1900, I drew attention to the great cost of sinking the very deep vertical shafts that were then being seriously proposed as necessary for the development of the deeper areas, pointing out the strong advisability of working this ground by means of inclines to be sunk from the existing shafts of from 3,000 to 4,000 ft. in vertical depth. In this paper it is stated (p. 975): &apos;" In short, practice upon the Rand now tends towards fewer vertical shafts and more underground inclines, especially for the very deep mining about to be undertaken." In consequence, the 6,000-ft. vertical shafts, at one time so much discuesed, have never been started, and they do not now seem likely ever to be. The necessity of placing all deep shafts further apart in order to make them control and exhaust larger areas was also dwelt upon. This economy wae vitally necessary for both

Jan 1, 1909

By Oscar Lachmund

DURING the driving of the main haulage level at the Copper Mountain mines of the Canada Copper Corpn., Ltd., near Princeton, B. C., some very rapid driving was clone, though no claim for a world&apos;s record is made. Conditions, however, were unfavorable for economical operations. The cost of power was high, for the fuel was of poor grade; besides, during the time the work was in progress, very little other power was needed so that most of the power cost was charged against the footage. The FIG. 1.-DRIFT ROUND USED IN MAIN HAULAGE LEVEL, COPPER MOUNTAIN, B. C. transmission line consisted of No. 4 galvanized iron wire with the result that the line loss was considerable. The voltage transmitted was about 30,000. The plant was operated under a lease, which was due to expire about the same time this work was supposed to be completed; an extension was refused, therefore speed was most important. The plans called for a straight adit 2900 ft. (884 m.) in length. At a point 2800 ft. (853 m.) from the portal, two raises were to be put up to the next nearest workings, a difference in elevation of about 800 ft. (243 m.). One of these was to be a two-compartment hoistway and the other a zigzag ore pass, or muck run. A location for these raises had been determined by a number of diamond-drill holes, but the material to be penetrated by the alit was not known. It seemed imperative to get the tunnel work completed as rapidly as possible, in

Jan 3, 1919

By Charles Austin

IT has long been known that plain high-carbon steels may be susceptible to graphiti-zation below the A, critical, but no data have been available to indicate what factors cause and tend to inhibit graphite formation. Two recent publications1,2 have shown that the factors controlling graphitization below the A, are different from those operating above the A, inversion where commercial graphitization of malleable iron begins. Furthermore, for plain high-carbon steels graphitization below the critical point does not appear to be related to ordinary chemi-cal analyses. Many years ago it was recorded&apos; that the rate of graphitization at subeutectoid tem-perature is not a maximum just below the A, critical, but at some lower temperature, which Austin and Norris have shown to be about 670°C. Indeed, work done in our laboratory has demonstrated that it is im-possible to spheroidize certain steels in the temperature range of 650° to 710°C. with-out the formation of considerable amounts of graphite. However, if the temperature is maintained just below the A, (720°°C,) these same steels may be completely sphe-roidized at constant temperature. In previous studies1,2,4 on 1 per cent plain carbon steels graphitization was en-countered during prolonged tempering. The limited number of steels studied did not provide sufficient data to permit adequate study of the factors controlling this graphi-tization. Accordingly, a limited statistical investigation was undertaken, utilizing 18 steels of similar chemical analyses, fur-nished by four steel companies, who also supplied information regarding the history of manufacture.

Jan 1, 1940

By W. W. Little

At the United Verde mine the 9-2D stope on the 4050 ft level is located within the north sulphide mass lying some 800 ft north of the main sulphide ore body. In 1948 it was estimated that this block contained 85,000 tons of ore at 4% copper and 9.2% zinc. The north ore body is a lenticular replacement deposit in the black schist, extending from about 100 ft above the 3750 level to a distance below the 4500 level yet to be determined. Although the mineralized zone approaches 1000 ft in length, only 300 ft is of economic importance. In width it varies from a maximum of 60 ft to about 3 ft at the north end, and is characterized by pinching and swelling in the ore zone. One of these larger swells is being mined as the 9-2D stope. Mining costs at greater depth, together with the expected grade of ore after dilution, necessitated a low cost mining method to permit profitable stoping operations. Based on the results obtained in a number of Canadian mines, it was decided to develop the ore body for stoping by the Aldermac or bench method of diamond drill blastholes; however, this plan was subsequently changed and the radial or ring method adopted. Such a method seemed to offer the advantage of large tonnages at low cost, and obviate the necessity of waste fill. This latter point was of particular importance, since the present waste system does not extend below the 3000 level.

Jan 4, 1950