Search Documents

By Thomas A. Simpson, Tunstall R. Gray

The Birmingham district first produced steel from Alabama hematite ores in 1899. Since then, the district generally produced more than 6.0 million gross tons of ore a year to the late 1950's. Production has declined since then to an annual rate of about 1.5 million gross tons. Reserves calculated for the district are sufficient to last many years. Mining in the district is now confined to Woodward Iron Company's Vance and Pyne mines. The rocks exposed consist of about 15,000 feet of consolidated Paleozoic sediments with a thin veneer of unconsolidated Cretaceous sediments in the Vance area. The district is characterized by a distinctively parallel and subparallel, slightly arcuate series of faults and joint systems. In view of available information, it seems reasonable to conclude that the Birmingham red ores are of sedimentary origin, modified to a small extent by diagenetic replacement after original deposition.

Jan 1, 1968

By R. M. Douthwaite, G. Birkbeck

The effect of grain size and specimen dimensions on the occurrence and magnitude of a yield point drop in pure iron has been examined. The tests were done at room temperature. The results indicate that gain size is the critical factor determining whether a yield drop occurs. The specimen diameter:gain size ratio does not influence the magnitude of the yield drop for the range of gain size and specimen diameters investigated. HUTCHINSON,' petchY2 and worthington3 have investigated the grain size dependence of the upper yield stress (uUYP) and the yield point drop, ouyp - aLYP, in Armco iron, mild steel, and Si-Fe, respectively. These authors used center-annealed wires to avoid stress concentration from specimen shoulders and to ensure uniformity of the applied stress. Coarsegrained specimens show no yield point drop; the yield point drop then increases as d-'I2 increases (where d is the grain diameter). These results can be understood in terms of Petch's analysis2 in which the magnitude of amp depends on the strain rate in the (limited) number of grains deforming plastically at the upper yield point. If N grains per unit volume are undergoing plastic deformation, the strain rate in the deforming grains is l/Nd3 times higher at the upper yield stress than when the whole specimen deforms homogeneously. If N is constant and independent of grain size at uUyp, then all the grains are deforming when ~d~ = 1, so there is no yield point drop. At finer grain sizes, the yield point drop is given by: where AU, is the friction stress increase corresponding to a tenfold strain rate increase. Christ, Smith, and Burton studied the upper yield point in 0.050-in.-diam wire specimens prepared from zone-refined iron. Each end of the 2; -in. specimens was soldered to a & -in. diam steel ball and the load applied through the two balls. There was a yield point drop in specimens with grain diameters less than 0.1 mm; no drop was observed in specimens of grain diameter greater than 0.1 mm that were free from veining substructure, but specimens of grain diameter 0.129 mm, annealed in the y range, showed an upper yield point. and this was associated with the presence of a veining substructure in these specimens. Christ et al. suggested the upper yield point occurs when more than a specific number of grains fill the specimen cross section so a multiplicity of slip is required to initiate plastic deformation. Table I summarizes the published data on the grain size at which the yield drop disappears. On the basis of this data the ratio of specimen diameter:grain diameter = 5 to 27 appears to be the critical value for the occurrence of a yield point drop. Thus, petch2 interprets the appearance and magnitude of the yield point drop in terms of the limited number of grains deforming plastically at uuyp, whereas Christ et a1. consider that the occurrence of the yield drop depends on the ratio specimen diame-ter:grain diameter. The published data cover a wide variety of materials so some variation between the results is to be expected, but the size range covered in the data of Table I is rather limited. In an attempt to discover whether the specimen diameter:grain size ratio or the grain diameter is critical in determining

Jan 1, 1969

By Gordon MacVean

THE adoption of rock dusting, as a safety measure, has made notable progress in the West Virginia coal mines since May, 1925. At that time there were but two mines in the State that were thoroughly rock dusted, mines No. 2 and No. 12 of the Boone County Coal Corp., at Sharpless. Since then it is probable that 75 per cent of the coal operators in the State have given consideration at one time or another to rock dusting. This growth of interest followed the meetings of the various mining institutes all over the country, during the summer of 1925, at which papers were presented, drawing the attention of the coal mining operators to the merits of this safety measure. Yet outside of the experience with rock dusting at the Old Ben Coal Corp., of Southern Illinois, and the Carbon Fuel Co., of Rains, Utah, there had been no actual occurrence in the coal mines of the United States, which could be taken as positive evidence of the efficacy of rock dusting in the prevention of the propagation of coal dust explosions. The U. S. Bureau of Mines, however, had run innumerable tests under conditions which closely approximated actual coal mining conditions and had clearly shown that rock dusting was effective.

Jan 1, 1926

By L. E. Young

IT has been said the British Empire was built on British Coal. In all the postwar planning for Great Britain the necessity for producing cheap coal and the prosperity of the coal industry are given first consideration. On Jan. 23, 1945, there was released in London a "Report to the Colliery Owners" which had been awaited with great interest. This was entitled "A Plan for Coal" and was the recommendation of Robert Foot, chairman of The Mining Association (Colliery Owners), prepared at their request. Presentation of the "Plan" at this time is particularly significant as it is an answer to the demand for nationalization of the coal industry by the Labour Party and at the same time is a carefully considered program for postwar reconstruction, prosperity, and stability. In the words of Mr. Foot, If the coal industry for the first ten years after this war is to find itself in a situation similar to the one it occupied for the ten years following the last war, with its record of disputes, strikes, stoppages, short-time working, unemployment, and, with it all, a completely insufficient margin of profit, and all the insecurity and instability in our basic industry that was brought with them, it is goodbye to any real prospect of full employment, social security, and high standard of living. To present an elaborate review of the conditions which have brought to a crisis the unfortunate situation in the British coal industry is here unnecessary, but certain of the salient points

Jan 1, 1945

By A. Aly Selim

A computer model was developed to calculate the fragmentation cost for in situ leaching operations as a function of the blast design and deposit parameters. The model is based on blasting an ore zone only or an ore zone plus overburden by either a coyote blast or a vertical blasthole system. The model calculates the blast design parameters and the fragmentation cost based either on a user input powder factor value or on a powder factor calculated by the model as a function of the overburden height and the ore zone thickness. Examples of blast design parameters calculated by the model are the number and spacing of blastholes for a vertical blasthole system and the number and spacing of crosscuts for a coyote system. The model also calculates the total amount of explosives, the detonating cord length, and the number of primers. The cost of blasthole drilling can be calculated by the model based either on purchasing and operating a drill or on a user input value of the contracted cost of drilling. Application of the model to an example ore deposit showed that the vertical blasthole systems were more economical than the coyote system when there was no overburden and the deposit had an average ore thickness less than 45 meters. With no overburden and ore thickness greater than 45 meters, the vertical blasthole system was either more or less expensive than the coyote system depending on the number of levels used in the coyote system. With overburden, the coyote system was less expensive than the vertical blasthole system for blasting either the ore only or the ore plus the overburden. A coyote blast will usually produce larger particle sizes than a vertical blasthole system. Larger particle sizes can result in lower copper recoveries so that a less expensive coyote blast may not improve the overall economics of an in situ leaching operation. Blasting the ore zone only was generally less expensive than blasting the ore plus the overburden by either blasting system. Also, for the example considered, the coyote system costs were less sensitive to changes in overburden thickness and powder factor while the vertical blasthole system costs were less sensitive to changes in ore thickness.

Jan 1, 1977

By A. Goldberg, T. E. Tietz, J. E. Dorn

Introduction The concept that the flow stress for plastic deformation of metals in the work hardening range is a function of the instantaneous values of the strain, strain rate and test temperature was promulgated by Ludwick' many years ago. This thought has been more or less a guiding principle throughout the immediate period of development and growth of mechanical metallurgy. It has been tacitly assumed or knowingly applied to many investigations on the plastic behavior of metals. Spurred by the theoretical interest and practical importance of the plastic behavior of metals, many investigators have attempted to determine empirical, semi-empirical, and theoretical equations2-l8 relating the flow stress with the strain, strain rate, and temperature. Although the applications of such equations have been extensive, the experimental verification of the existence of a mechanical equation of state is weak. Furthermore, some of the available evidence on plastic flow appears to suggest that no simple functional relation between stress, strain-rate, strain and temperature can exist. The mechanical equation of state demands that Where a = true stress = loadlinstantaneous area e = true strain _ Instantaneous gauge length ~ initial gauge length i = true strain rate T = temperature This formulation implies that da is an exact differential. Therefore the flow stress (a) is a function of the instantaneous values of the strain (c) the strain rate (i) and the temperature (T), independent of the previous mechanical or thermal history. Having reached a certain strain, strain rate, and temperature, by any path whatsoever, a definite and fixed value of the flow stress should be obtained. One check on the validity of the mechanical equation of state is easily obtained. Consider the following three tests on the stress-strain curve at constant temperature: A. Strain at rate :I B. Strain at rate it C. Strain at rate 11 to el and continue test at &. A graphical representation of possible results of such tests are shown in Fig I. If, for strains greater than el, test (C) data coincide exactly with the data from test (B), as shown in Fig ra, a limited verification of the mechanical equation of state is obtained for the range of strain rates from il to iz. But if the data from test (C) differ from those of (g) beyond strain t\ where the strain rate is changed from il to k2, the mechanical equation of state is not

Jan 1, 1949

By AIME AIME

THE autumn is the time that nearly all the special groups within the broad field of the Institute's activitives chose for their own special meetings. The big annual meeting in New York in February has its own special advantages, but to realize them involves sacrificing others. A meeting of a smaller group with the subjects brought up for discussion much more closely limited to a single field of interest has some advantages that a big general meeting cannot possibly have. And so the custom has gradually developed of having these smaller meetings in the autumn, at con¬venient places, so the men will not have to travel too far from the job to be present. Sometimes the meetings have for their field of interest a single phase of mineral technology, and are called divisional, and at other times they cover a diversity of topics that are locally important in that geographical area, and are then called regional meetings. Of the five meetings to be held this fall, four are divisional and one regional. Two of the divisional meetings are to be held in the same place at the same time, but with programs so arranged that they do not conflict.

Jan 1, 1930

AIME 1953 DIRECTORY SUPPLEMENT OFFICERS AND COMMITTEES OF LOCAL SECTION; COUNCIL OF SECTION DELEGATES Linwood Thiessen, Chairman H. D. Vaughan, Vice-Chairman John H. Melvin, Secretary EXECUTIVE COMMITTEE L. E. Thelin, Connecticut J. B. Cunningham, Arizona W. L. Penick, San Francisco G. L. Yates, Kansas DELEGATES Adirondack - C. DeWitt Smith '54 Alaska - Robert 11. Chapman, ?54 Arizona J. B. Cunningham, '53 Black Hills - Sidney M. Runke, '54 Boston -R'. Schuhmann, Jr. ?54 Carlsbad Potash - W. P. Wilson, '54 Central Appalachian - Charles T. Holland, '54 Chicago - H. A. White, '54 Cleveland - Milton Tilley, '54 Colorado - J. Paul Harrison '54 Columbia - Harold Kirkemo, '54 Connecticut - Lewis E. Thelin, ?53 Dallas - Kenneth F. Anderson, '54 Delta - Roy S. Sullins '54 Detroit - F. P. Bens, '53 East Texas - Joseph A. Morris, '54 El Paso Metals - E. M. Thomas, '54 Florida - W. O. McClintock '54 Fort Worth - Ray Elner, '51 Gulf Coast - H. E. Treichler, '53 Kansas - G. L. Yates, '53 Lehigh Valley - H. R. Gault '54 Lima, Peru - R. P. Koenig, ?54 Lou-Ark - A. H. Crawford. '53 Mexico - W. G. Kane, '54 Mid-Continent - J. H. Beesley, '53 Minnesota - J. R. Stuart, '54 Montana - F. W. Strandberg, '53 Nevada - Albert Silver,'53 New York - P. Malozemoff, '54 North Pacific - A. H. Mellish, '54 North Texas - K. F. Anderson, '54 Chio Valley - J. H. Melvin, ?53 Oklahoma City - Charles Miller, '53 Oregon - T. C. Matthews, '54 Penn. Anthracite - D. C. Helms, '54

Jan 1, 1953

By Dever C. Ashmead

Anthracite was first mined in the Wyoming Valley and sold as an article of commerce in 1808. As some preparation has always been necessary to make it ready to burn, the preparation of anthracite must date back over a hundred years. Two vital factors have determined to a large extent the degree and the method of anthracite preparation. These are, first, the character of the beds worked and the methods by which they are mined and, second, the equipment used and practices followed in the burning of the coal. It is not the intention here to go deeply into these phases of preparation as a paper of no mean length could be prepared on the history of either. Rather, the intention here is to point out the main considerations and to show the influence they have exerted on the preparation of anthracitc. Mining Methods and Their Relation to Preparation In the beginning of the nineteenth century, the coal beds were virgin with the possible exception of some outcroppings that had been worked, to a slight extent, by the Indians. It is known that the American aborigines had a, knowledge of the use of this fuel, because when the Wyoming Valley was purchased from them, in 1754, they mentioned the fact that, by selling the land, they would lose their coal. Real mining of anthracite began about 1808 when Judge Jesse Fell, of Wilkes-Barre, discovered that the "common stone coal of the valley" could be burned in an open grate. For some years thereafter mining was conducted near the surface. The working p1aces were driven narrow; only the best of the coal was selected and the remainder was left in the ground. Only the lumps could be used, as no market existed for other sizes. As time passed, however, it became necessary either to go farther into the ground or to widen the working places. When these places were widened, falls of roof were apt to occur, making it necessary

Jan 1, 1922

By C. W. Dunham

FOR discharging and diffusing the gases from the reverberatory furnaces and converters the Morenci Reduction Works has been provided with one of the largest reinforced concrete chimneys ever built. It is 612 ft. high from the bottom of the foundation to the cap at the top, and has a minimum diameter of 24 ft. inside the lining near the top and 38 ft. 10 in. at the bottom. Its estimated capacity, at the elevation of 4338 ft. above sea level, is about 1,000,000 cu.ft. of gas per minute at a temperature of 500° F. and an atmospheric temperature of 90°. Under these conditions the draft will be at least 3 in. of water at the flue inlet. The gases enter the chimney through a steel balloon flue 33 ft. high and 15 ft. wide, the bottom of which is 19 ft. above the ground.

Jan 1, 1942

C. N. FEnner, New York City (communication to the Secretary) : A possible explanation of some of the' phenomena of amalgamation cited by Mr. Bayliss and others has occurred to me. We know that if, to a quantity of mercury, gold and silver are added until a putty-like paste is formed, and if this mass is spread on a flat surface and pressure is applied, a more fluid portion of the mercury will be squeezed out from the rest, carrying gold and silver with it. The proportion of gold to silver will depend, I think, upon various causes and conditions—the relative chemical affinity which gold and silver have for mercury; the amount of pressure used; the presence of other metals:

Jan 1, 1898

By R. S. Shoemaker, F. W. McQuiston

CARLIN GOLD MINING COMPANY 1974 Operating Data to October MINE LOCATION: 40 miles from Elko, Nevada ORE DESCRIPTION: Gold with minor amounts of mercury occurring in siltstone and carboniferous limey shales. TYPE OF MINE: Open pit ORE HAULAGE TO MILL: By trucks up to a distance of 12 mi1es MILLING CAPACITY: 2500 tons per day ORE GRADE: 0.20 oz per ton oxide ore 0.25 oz per ton carbon type ore PRODUCTS: Gold bullion 993 fineness, by product quicksilver RECOVERIES: Oxide ore 887'0 Carbon ore 83% POWER FOR GRINDING: 7 Kwh/T POWER, other than grinding: 14 Kwh/T WATER SUPPLY: Pumped from wells 2- 112 miles through 13,000 ft of 8" buried pipe 6 ft underground. Consumption 0.60 tons of new water per ton of mill feed. TAILINGS: By 10" woodstave pipe a distance of 2500 ft to mine waste filled dam. RUNNING TIME: 10 ft x 10 ft mill on oxide ore, 98% 7 ft x 8 ft mill on carbon ore, 937'0 Principal causes of lost time, power outages and problems of feeding gaseous chlorine to carbon ore agitators. LABOR, TONSIMAN SHIFT: See detailed data sheet ILL BUILDING DESCRIPTION: Framed structural steel with sandwich type walls of marine plywood, then packaged pre - fabricated insulation and outer sheeting of galvanized corrugated steel.

Jan 1, 1975

By Louis W. Huber

The Liberty tunnels extend through a very steep hill in Pittsburgh (locally called Mount Washington) for a distance of slightly over a mile. The two tunnels parallel each other and are 59 ft. apart, center to center (Fig. 1) They are for vehicular traffic, and in each there is ample space for two lines of vehicles. Northbound traffic, toward downtown Pitts- burgh, is confined to the east tunnel and southbound traffic to the west tunnel. The South Hills residential district is separated from downtown Pittsburgh by Mount Washington, a steeply rising escarpment south of and adjacent to the Monongahela River. The Mount Washington district immediately south of the Monongahela River has been reached, for many

Jan 1, 1927

By Sir Albert E. Kitson

The manganese ore deposits of the Gold Coast, British West Africa, occur in very ancient rocks, of both sedimentary and metamorphic types. In certain respects they have a strong resemblance to those of India and Brazil, as contrasted with those of Tertiary age in Georgia, but in this paper no careful comparison with them can be made. Viewed from the present condition of the manganiferous rocks, the oldest deposits are in the sediments. Later than these are the progressively metamorphosed representatives of these sediments. Youngest are the products of decay and degradation with the concentration of manganese oxide in the rocks of both groups. The oldest occurrences are in argillaceous and siliceous phyllites and slates, which show only a moderate degree of metamorphism. They belong to a series which also includes mudstones, sandstones, grits, conglomerates and subordinate limestones, with tuffs and lava-flows, largely of basic types. This has been named the Birrim System. Its age is unknown, for no definite fossils have been discovered in it. Since these non-fossiliferous strata at many plaees are of a character which in many parts of the world are suitable for the preservation of fossils, and which contain them, it is assumed that the Gold Coast deposits are pre-Cambrian. These rocks of the Birrim System have normally a northeast-southwest strike, and are folded, but not to any very great degree except in certain belts. From the Eastern Province of the Gold Coast they may be traversed diagonally across their strike for upwards of 600 miles, to the extreme northwestern corner of the Northern Territories. Thence they probably extend much farther into French territory.

Jan 1, 1927

By E. C. Bain

THE more familiar compositions of iron-carbon-chromium1 and the iron-carbon-tungsten2 systems have been investigated with a degree of thoroughness which has permitted the construction of their three-dimensional equilibrium diagrams; and it is probable that these equilibrium diagrams are sufficiently accurate for the present metallographic needs. Strangely enough, in spite of their importance, the alloys of iron, carbon and manganese apparently have not been investigated in the same systematic manner, and so far as is known, no three-component equilibrium diagram for this system is available. Even iron-carbon-nickel alloys3 have been studied rather more thoroughly; for these the solidus and liquidus surfaces have already been determined, but the solid transformations in this, as in the manganese system, have not been reported systematically. The present paper deals with the constitution at equilibrium of a series of 36 iron-carbon-manganese alloys of commercial purity limited by 1.5 per cent carbon and 15 per cent manganese, a range of compositions including most of the manganese steels. The temperature range of melting has not been determined, nor has the high-temperature (delta iron) ferrite equilibrium been included in the study, it being considered that the more important characteristics of the manganese steels are their ordinary transformations in the solid state. The delta iron region is almost certain to be a small tetrahedron not very different in magnitude or contour from that in the iron-carbon-nickel diagram. It is probably true

Jan 1, 1932

By Wayne A. Greenwalt

A method that determines venture participation when the decision maker's level of risk aversion varies according to venture profitability and risk investment is presented. The decision maker's fundamental aversion to risk is established by the selection of a desired working interest for a venture that anticipates only a discounted payout.

Jan 1, 1982

By N. J. Grant, Per Knudsen, J. T. Blucher

The fatigue behavior of three SAP alloys was studied in ternzs of strain rate and temperature, at high strains. The k values in the modified Manson-Coffin equation, Nk4 = C, were less than 0.5 under all test conditions, and change with strain amplitude for the lower-oxide alloys at about 2 pct strain. Lowest k values were near 0.25. Strain rate had no effect on life at 80 F, but had an increasingly greater effect with increasing temperature above 500". Life decreased with decreasing strain rate, above 500"F, and with increasing temperature. Ductility at fracture in a tension test was indicated to be an important factor in determining 1ife in these big+-strain tests with the SAP alloys. INEVITABLY, in the course of mechanical tests at elevated temperatures, particularly if significant time at temperature is involved, there are large changes in structure; these changes make it difficult to relate behavior patterns over ranges of temperature or strain rates at high temperatures. Such changes are to be expetted in low cycle fatigue at low strain rates and high temperatures. Accordingly, it was of great interest to examine the low cycle fatigue behavior of SAP / an aluminum oxide dispersion-strengthened aluminum, a type of alloy which had shown unusual structure stability to temperatures as high as 1000" to 1150°F and resisted recrys-tallization essentially to the melting temperature.'j3 Since the matrix is pure aluminum, there are no complications of averaging, agglomeration, or phase solution. It was also desirable to check the Manson-Coffin equation4?' for the SAP alloys, namely N~E~ = , where ep is the total plastic strain amplitude, k and C are constants, and N is the number of cycles to failure. Here, too, was an opportunity to check the roles of temperature and strain rate with a very stable material. Tavernelli and coffin6 had concluded that k had a value of about 0.5 for many alloys and C was equal to ~/2, where E is the fracture ductility determined from a static tension test. The results were obtained from low-temperature tests where creep and diffusion processes are unimportant. Manson7 found k = 0.6 fitted his data reasonably well; however, in later analyses of a large amount of low cycle fatigue data generated at room temperat~re@"~ he found k to vary from 0.6 for short lives to 0.21 for long-life fatigue tests. In the latter studies,89g Manson separated the total strain range into elastic and plastic components when he found that k was influenced by the nature of the strain. The use of EL (total strain) instead of EP (total plastic strain)4'5 makes a difference in the resultant k value. The ratio of changes with temperature, strain rate, and strain; further, there are the problems in the determination of the elastic strain. Based on these considerations, and the improved fit of points in a plot of by Wells and Sullivan,' is also utilized in these studies. Anderson and wahl,14 using commercial 1100 aluminum, and Blucher and Grant,15 using 99.99 pct pure aluminum, found an increase in life with increasing test temperature. Anderson and Wahl were the first to report low cycle fatigue results from SAP materials. With increasing temperature, the role of strain rate becomes more important. In this regard, care must be exercised to differentiate between frequency (wherein strain rate may vary from zero to a maximum in each cycle, sinusoidally, for example), and constant strain rate, as used in the present study, in a saw-tooth type cycle; in the latter case, the frequency is not specified but can easily be calculated from the strain and strain rate data. It has generally been found that life in low cycle fatigue tests decreases with decreasing frequency16 or with decreasing strain rate at elevated temperatures.15 Coffin,17 reviewing Eckel's work,16 also reported that k increased with decreasing frequency for acid lead, yielding values from 4.0 at a frequency fo 6.6 cycles Per day to 1-46 at a frequency of 7440 cycles per day; the value of k decreased to 0.58 at a frequency of 2.38 x lo6 cycles per day. EXPERIMENTAL PROCEDURE Three SAP alloys, of two nominal compositions, were tested. Alcoa supplied XAP 005 as 2-in.-diam extruded bar, of nominal composition A1-7 wt pct A1203. The Danish Atomic Energy Commission supplied SAP 930 (A1-7 wt ~ct Ala3) and SAP 865 (A1-13 wt pct Al&) manufactured by Swiss Aluminium Ltd., in the form Of $-in.-diam extruded rod. Metallographic comparison of the structures of XAP 005 and SAP 930 showed the former to have a more uniform oxide distribution. Button-head specimens were machined in the longitudinal direction of the bar with 0.4 in. gage length by 0.2 in. diameter, with a fillet radius of j-B in. After machining, the specimens were electropolished in a 1 to 4 mixture of perchloric acid to methanol to remove all machining marks. All test bars were in the as-extruded condition. The fatigue tests were performed on a hydraulically activated, axial strain machine, with complete reversal of strain.15 Test conditions were:

Jan 1, 1969

By E. D. Gardner

FIFTY years ago the Utah Copper enterprise at Bingham was just getting under way. An epic in metal mining was in the making. Throughout the West the bonanza deposits were approaching exhaustion and most ore still went direct to smelter. But concentrators were shortly to be constructed for treating milling grade ores, and most important, the pilot plant for the Utah Copper enterprise was being built that year at the mouth of Bingham Canyon. The same decade was to see development at the Inspiration mine in Arizona of the most important new mining method for 50 years to come—undercut block caving. Although the average grade of ore being mined has been declining for 50 years, and wage rates and prices of supplies have been greatly increased, the mining industry has continued to grow and to prosper. Technology has advanced to a point where minerals can be mined under the most severe conditions. The hardest rock can be drilled and broken and the heaviest ground handled. Large or small, an ore-body can be mined successfully, at any desired rate of production. It is possible to pump great volumes of water and to ventilate the most extensive workings; air conditioning has made practicable the mining of ore where the rock temperatures are beyond those that can be borne by man. Mining today in the U. S. is a huge earth-moving operation. In 1953 nearly 2 billion tons of material were mined for direct use or for processing. Stripping at open-cut mines totaled about 1.7 billion cu yd. Table I gives relative tonnages of the branches of the mineral industry in 1953. In addition to the solid materials moved, 350 million tons of petroleum and 340,000 tons of gas were produced in 1953. Fifteen million tons of salt and 5 million tons of liquid sulphur were pumped from wells. An appreciable amount of copper was recovered by leaching old mine workings and dumps. Total value of minerals produced in 1953 was $14.4 billion: oil and gas $7.6 billion, coal $2.6 billion, nonmetallics $2.4 billion, and metals $1.8 billion. Formidable problems face some branches of the industry today, especially pertaining to increased output tons per manshift. The time has come when these problems should be reappraised. With current wage rates, the industry no longer can afford to pay men to do manual labor. It should be recognized, also, that the miner is a skilled worker; efforts to promote the dignity of his calling and his pride of accomplishment have yielded beneficial results. Mineral deposits occur under widely varying conditions. In most instances the degree of support needed by the roof and walls is the deciding factor in selection of an underground mining method. The degree of support needed, in turn, is governed by natural physical characteristics of the ore and its enclosing rocks. Mine operators, of course, learn to judge ground by observation, and an experienced mine boss generally can anticipate what will happen following any given mining operation. A more scientific approach, however, would be advantageous in most cases. More should be known about the strength of the ore and the enclosing rocks, more about stresses set up in the ground when ore is removed, and more about the mechanics of moving ground. Better understanding would work both ways: first, favorable rock conditions could be fully utilized for more efficient mining, and second, hazards of rock falls could be minimized, loss of ore in mining reduced, and expenses caused by ground pressures and subsidence lowered. In general, mining comprises breaking the ore or rock in place, supporting the mine workings, and transporting the ore to the surface. This latter is a materials handling problem. Ventilation, of course, must be provided, and the mines must be kept free of water. Development work at some places is the most important cost item in extracting ore. Drilling and blasting remain the usual practice for breaking ore or rock from place except, of course, at block-caving mines. The drilling and blasting practice at a mine must fit the mining method. In laying out mining procedures attention is being given to

Jan 1, 1956

By AIME AIME

C. H. BENEDICT, chief metallurgist of the Calumet and Hecla Consolidated Copper Co., has pioneered for nearly half a century. Noted for his ammonia leaching process, lie has Iong been responsible for all Calumet and Hecla mill, concentrator, and reclaination plant flowsheets. His influence has spread far beyond his own organization. lie is dean of Lake Superior metallurgists and has contributed greatly toward raising his specialty-the country over-to an honored profession; not merely an honored profession but a profitable one for industry and the public. The leaching process which he developed in 1912 has, since 1915, produced for Calumet and Hecla 250,000 tons of copper from waste tailings at a cost per pound, in 1929, below five cents. It has yielded profits of $35,000,000. In the war just ended, this process proved the only one adaptable to the recovery of copper from gilding-metal¬clad steel strip, and Calumet and Hecla treated more than 50,000 tons of such scrap for the Government.

Jan 1, 1945

By VERITAS

THE most concentrated industry of major character in the United States is that of the Ford Motor CO., which is to say Henry Ford. Its sole function is to supply the public with a cheap motor car which it does to the extent of two million or so per annum. In doing this, a relatively small profit per unit is multi- plied to an enormous aggregate per annum and has resulted in the creation of one of the greatest industrial fortunes of the world. The industrial and sociological consequences of .this are bound to be immense. On the physical side the production of two million automobiles means the consumption of two or three million tons of materials, chiefly metals, in the 'direct form of the finished product', and a huge additional tonnage of coal and other things that ,are consumed en route, and also the labor of many thousands of men. In the development of a business on this scale it was but natural that the Ford Motor ,Co. should seek to supply itself with the raw 'materials it needs, and they being so largely coal and metals the company is brought into close contact with the mining and metallurgical industries. It is a huge consumer of - steel. It is the fourth largest consumer of copper. It is a large consumer of lead, tin, aluminum and zinc. The mining and metallurgical industries have, therefore, good reason to learn to know Henry Ford, his personality, his thoughts and his policies.

Jan 1, 1924