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By Robert L. Davidoff, Rodney D. Rosenkranz

In order to determine copper resource data and production costs for major market economy mines and deposits, the Bureau of Mines has performed detailed engineering and economic analyses on 271 of the world's most significant copper deposits. At the demonstrated resource level, copper potentially recoverable from these deposits is estimated to be 325 million metric tons, 180 million tons of which would be from Pacific Rim countries. Chile has the largest known copper resources of any country and accounts for nearly 45 percent of the copper avail- able from Pacific Rim countries. At $1.00 per pound, in January 1981 dollars, an estimated 80 million metric tons of copper are potentially economically recoverable from Pacific Rim deposits. At this same price, analyses indicate that these deposits could economically produce about 2 million metric tons of copper per year. Sensitivity analyses reveal that if operating costs were to decrease 25 percent, with copper at a price of $1.00 per pound, total copper economically recoverable from Pacific Rim countries could increase by about 10 percent; a 25 percent increase in operating costs could lower economically recoverable copper by 50 percent. Analyses also indicate that byproduct prices are important. If byproduct revenues increased 25 percent, at a copper price of $1.00 per pound, an additional 2 million metric tons of copper could be recovered; if byproduct revenues decrease 25 percent, about 5 million metric tons less of copper metal would be available. Since the January 1981 date of this study, inflation and decreases in copper and byproduct prices have greatly affected the profitability of the world copper industry. Many producing mines have curtailed or suspended production, and development of many non- producing deposits has been postponed.

Jan 1, 1982

By J. C. Bayles

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Jan 1, 1906

By Carl Henrich

The Ducktown copper-mines are located in the southeast corner of Tennessee. The name Ducktown was originally given to a district occupying the southeast corner of Polk county, which in turn occupies the southeast corner of the State. Fig. 1 is a map of the vicinity of Ducktown, taken from the topographical surveys of the United States Geological Survey. The Ducktown district is bounded on the east by Cherokee county, North Carolina (the boundary-line between the two States running here a little east of north along the western slope of Pack mountain), and on the west by the eastern foot-hills of Little Frog mountain. On the north, Stansbury mountain, really a chain of low mountains or hills, forms the dividing-line between Ducktown and Turtletown districts. On the south, the Ducktown district extends beyond the Ocoee river to the Georgia State line.. This line, in going west, gradually recedes southwards from that river into the foot-hills of Big Frog mountain, the highest mountain of the neighborhood, which rises about 4300 feet above sea-level, while the surface of the Ocoee river, where it leaves the Ducktown district, is less than 1500 feet above sea-level. It will be seen from this description, and from a study of the map, that the Ducktown district occupies the northern part of a kind of basin, bounded on the east by Pack mountain and on the west by Little and Big Frog mountains. Between these mountains the Ocoee river, draining the basin, cuts its way to the Hiwassee and the Tennessee rivers in a narrow gorge, through the crystalline slates and schists, which from their excellent exposure in this Ocoee gorge have received the local

Jan 1, 1896

By Wilhelm Borchers

IN all special branches of the chemical and metallurgical industries, in which large electric furnaces became necessary for carrying out new processes or for the improvement of old ones, the development of the electric furnaces took place on much the same lines. The endeavors to make a success of a new idea brought forth many ingenious designs, which, however, almost without exception, furnished the proof that the safest and shortest way to practical success is the utmost simplicity of construction of the necessary apparatus. Our knowledge of the qualities of materials for building electric furnaces and of the constituents of the furnace-charges, especially their electric conductivity and their chemical affinity . towards one another at high temperatures, is still far from being complete, and from this fact we must conclude that the smaller the number of elements in the construction of a furnace, the fewer the number of unreliable factors both in the construction and in the operation of the electric furnace. This conclusion deserves special attention when an electric furnace for making steel has to be chosen from the constantly growing number of inventions, inasmuch as the chief con¬stituent of steel, the element iron, is a substance which in its liquid phase has so great an affinity fir those elements which are to be removed from the charge, that it is very difficult to comply with the following conditions: 1, to beat the refining-slag to the highest point of its chemical activity ; to prevent the iron from entering the slaw, or, where this cannot be done, to make it enter so that it finally appears in the end-product

Jan 1, 1910

By Arthur L. Christenson, Clarence E. Jackson

IN the establishment of the relationship between weldability and hardenability, two methods have been employed in correcting for the grain growth produced in the heat-affected zone: first, the hardenability calculated from chemical composition1 may be corrected to the grain size observed in an actual weld,2 or, second, a hardenability test may be made on the steel quenched from a temperature high enough to produce a grain size comparable to that found in the heat-affected zone.3 In order to obtain grain sizes in the end-quench hardenability bar comparable to those resulting in the base metal from the welding cycle, a quenching temperature of 2100°F. has been used. In studies of the end-quench hardenability specimen quenched from 2100°F. instead of from a lower temperature of 1700°F., it is important to ascertain the relative cooling rates for various distances along the bar. It is a question as to whether the cooling occurs at the same rate or whether there is any significant difference from the standard cooling-rate curve published by Jominy and confirmed by others.4,5 This paper reports experimental evidence concerning the effect of quenching temperature on the cooling rates in the end-quench hardenability test. The effect of quenching temperatures on cooling rates has been studied by a number of investigators.6,7 French has considered this effect from both theoretical and experimental aspects. In French's studies on complete quenching of spheres and rounds, an increase in the quenching temperature caused an increase in the cooling rate at 720°C. at the center of the specimen. The center cooling velocity also has been shown to be dependent upon the surface per unit volume for the type of specimens studied; the velocity of cooling increases with an increase in the surface per unit volume. Three methods of indicating the rapidity of cooling of a body of metal during a quenching operation have been proposed: I. The time it takes for the metal to cool from the quenching temperature to a temperature halfway between the quenching. temperature and the temperature of the quenching medium (half-temperature time): Grossmann, Asimow and Urban7 justify the use of this criterion by the fact that the half-temperature time includes the temperature and time of incubation as well as the zone of formation of pearlite and, further, the data so derived accord very closely with experimental values. 2. The time interval the metal remains in a given temperature range; for example,

Jan 1, 1943

By C. S. Blair

THE development of a geological department as an integral part of the Tennessee Coal, Iron & Railroad Co. in the Birmingham district, Ala-bama, in 1908 was an innovation probably unique for any mining organ-ization south of the Ohio River, At that time a few of the oil companies were starting geological departments, but there were no geologists among the larger industrial organizations. The Tennessee Coal, Iron & Railroad Co. had been a substantial producer of pig iron for many years and was just getting a start in the manufacture of steel products from the pig iron. It had large acreages of coal land, ore land and timber land, but there was lacking the detailed knowledge of the possible mineral resources of much (of its territory, and this territory at that time covered an area in the neighborhood of 500,000 acres in the states of Alabama, Tennessee and Georgia. Those responsible for the operations of the mining properties, not being familiar with the kind of help that might be expected from geologic work, were decidedly skeptical of the utility of the work. Therefore it was necessary to develop cooperation with the mining organization, by not infringing upon its functions, and by developing the work in such a manner as to demonstrate to the mining department its practical utility. In the first instance the man responsible for a mining operation is apt to assume the attitude that the geologist is a blockader, because the geologist, unfortunately, is obliged to point out difficulties in the carrying out of mining operations in the way originally planned. He points out the dangers of mining out one coal or metal seam at the ultimate expense of an upper or lower seam, and he develops structural features, such as faults and folds, which call to the attention of the mining operator diffi-culties in his future operations, which the latter had not anticipated. Eventually, however, -the value of having these data became ap to the Tennessee Coal, Iron and Railroad Co., and the operators not only welcomed the geological work and cooperated fully in its acquisition of essential information, but reached the point of asking assistance and advice; and complete coordination of the two activities has existed for many years.

Jan 1, 1933

By William Hurst

Muskat's depletion performance equation is here derived considering the expansion behavior of the reservoir hydrocarbon system and a simple fractional-flow equation. This nietkod of derivation leads logically to the two extensions that follow. The first of these is concerned with gravity segregation in a depletion-drive reservoir. The second is concerned with including an empirically determined tern? for water influx in the performance equation. The more general equation for gravity segregation when there is a primary gas cap and empirically-determined water influx is stated for completeness. These equations have been found useful in reservoir performance calculations in Eastern Venezuela. A discussion on the methods of solving these equations follows, and considers firstly the effect of taking finite intervals in the numerical integration, and sec-ondly, methods of incorporating the time functions involved in segregation in with the expansion behavior. The paper concludes with a brief general discussion on further extensions to the depletion performance equation. INTRODUCTION The two fundamental sources of energy by which oil is produced from a reservoir result from pressure depletion inside the boundaries of the reservoir and fluid encroachment across the boundaries of the reservoir. The wells in either case form low pressure outlets through which oil and gas may be produced by the expansive force of the reservoir fluids and associated encroaching fluids. When the reservoir pressure is higher than the bubble-point pressure of the oil, so that there is no free gas in the reservoir, these expansive forces are the only ones available for the production of oil. However, when the reservoir pressure is less than the bubble-point pressure of the oil, free gas is vaporized as the pressure falls. With both oil and free-gas phases present, the additional forces of gravity and capillarity may operate on the gas-oil system, as they have previously operated on the oil-interstitial water system. Gravity tends to segregate the free gas from the oil due to their density difference. Capillarity opposes and eventually balances gravity as the more extreme free gas and oil saturations are reached, preventing the independent move- ment of free gas until it is above a certain saturation, and the independent movement of oil when it is below a certain saturation. The type of depletion performance equation chosen for predicting the future performance of a reservoir depends on the amount of past history available. When the reservoir is somewhere past the halfway mark in depletion, some form of decline curve is often used. With less past history, material balance equations which incorporate empirical factors based on the past performance are often used. When, however, the amount of past history is small, the Muskat depletion performance equation will usually be used. The distinguishing feature of this type of equation is that empirical factors based on the over-all or macroscopic reservoir behavior are almost or entirely absent. Each parameter affecting the reservoir performance is ascribed an independent set of values based on measurements made on laboratory samples; that is, incorporating microscopic empirical factors. In establishing Muskat-type depletion performance equations, it is necessary to consider the reservoir as consisting of a number of associated blocks, in each of which the saturations and pressures may be considered uniform, and in each of which all substances have uniform pressure-volume characteristics. Thus, a primary gas cap can usually be considered as one block and an aquifer as another. Gravity segregation may be negligible for practical purposes when the rock and oil properties are adverse and/or the dip or thickness of the reservoir is too small. In this case the whole oil leg may be considered as one block, except in very large reservoirs. In very large reservoirs the fluid and rock properties may vary enough, particularly in the dip direction, for it to be necessary to divide the oil leg into a number of blocks, in each of which the relevant quantities may be considered uniform. When gravity segregation of the oil and free gas is not negligible, it is necessary to consider the space occupied by the initial oil leg as divided into two blocks, a secondary gas cap and an effective oil leg, in each of which saturations may be considered to be uniform. The total volume of these two blocks is thus constant, but the secondary gas cap grows continuously at the expense of the oil leg. Muskat1 derived depletion performance equations for the basic case of an oil reservoir with closed boundaries and without segregation, and for the case of an oil

By Theodore Simons

During the last half century a great amount of ingenuity and energy has been devoted to the invention of appliances for the recovery of valuable minerals from very fine sands and slimes. The reason for this is that in almost every dressing plant the greatest losses of values, considered relatively as well as absolutely, occur in the treatment of slimes. The natural aim of mill operators to minimize these losses has in recent years received another impetus, from the fact that the gradually diminishing occurrence of high-grade ores makes a more intense recovery of values from existing resources absolutely necessary for profitable operation. The results of such attempts are found in the appearance of a great number of machines and appliances which make it profitable to-day to rework old clumps, containing the tailings of older processes. A constantly growing difficulty of obtaining skilled labor and the increase in wages made it prohibitory to employ those types of machines which required much attention, and in the middle of the ninieteenth century the various concentrating tables of the percussion type, which automatically discharge their products, began to take the place of the intermittent tables, on which, when the bed had reached a certain thickness, operation had to be stopped in order to allow the skimming by hand of the separate layers formed on the table. In the course of years, two general types of machines evolved for the treatment of fine sands arid slimes: The so-called concentrators and vanners, on the one hand, and the buddles and round tables on the other.' For the profitable treatment of the very finest slimes, round tables have as a last resort proved more satisfactory and econoillical than other machines. In recent years they have agaiu become the subject of close inves-

Jan 1, 1914

By Chas. B. Dudley

WHILE working, during the summer of 1877, upon the "Chemical Composition and Physical Properties of Steel Rails," the results of which are given in my report with this title, I was struck with the surprising wear which some of the rails, which would ordinarily be called soft rails, had endured. At that time I knew of no chemical measure of softness except low carbon, and I found that a number of rails with low carbon had endured as high or higher tonnage, with apparently as little loss of metal by wear, as those with higher carbon. My own work on steel rails that summer did not embrace any definite experiments as to the amount of metal worn off the rail per million tons which had passed over it; and so I could get no more definite answer from that work, to the question at the head of this paper, than was given by comparing the appearance of the worn section of the rail with its tonnage. This comparison, however, served to arouse in my mind the query, whether the commonly received opinion as to the relation between the hardness and wearing power of steel is correct, as applied to steel rails. This opinion, if I am right, is: the harder the steel, the better will be the wear, and the limit of hardness is simply one of safety ; hard, brittle steel being, of course, more liable to break than soft, tough steel. The query, although aroused, did not bear any immediate fruit, and, as will be evident to any one reading it, the report above referred to was written with the commonly received opinion in mind. Since that time I have collected a little information upon this subject, which I should be glad to submit to the Institute, if for no other purpose, for the sake of arousing attention, and directing study to the question of hardness versus wear in steel rails. Before making known this information, however, permit me a few words in reference to hardness. How shall we measure the hardness of steel ? Of the various ways of getting indications as to the hardness of steel, which are known, three will serve our present purpose. These are: 1st. High carbon. It is generally agreed, I think, that at least within proper limits, the greater the amount of combined carbon in a piece of steel, the harder the steel, and I need not do

Jan 1, 1879

By Franklin Moeller

CONSIDERING the really short time that has elapsed since hydro-metallurgical processes of extracting copper from ores have been extensively developed, and the large scale on which this method is practised at Ajo, the successful operation of the plant must excite the admiration of every visitor. The application of the mechanical unloader to the purpose for which it is employed at Ajo is but an extension of the use for which it was originally designed, some 20 years ago, for unloading iron-ore vessels at the lower lake ports. At a time when the maximum output of a single machine, with men shoveling the ore into buckets, did not exceed 40 tons per hour, G. H. Hulett invented and constructed a mechanical unloader with a bucket of 10-ton capacity. This machine was of the steam hydraulic type, and it is still in operation after nearly 20 years of service. Several more machines of the same type were built, but the difficulties of power transmission, and the rapid development of electrical machinery, soon led to the adoption of electrically operated machines, and practically all of the later installations have been thus equipped. This electrically operated unloader has proved so well fitted for the work that the design of the lake boats has been practically revolutionized, with special view to the ease and rapidity of unloading. It is now possible to unload a 12,000-ton vessel with four machines in a little over 2 hr. This has necessitated an increase in the capacity of the machine, and the largest yet built handles an average load of 17 tons, with a possible maximum of 20 to 21 tons.

Jan 8, 1918