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By C. P. Haller, S. J. Aresco, R. F. Abernethy

The Bureau of Mines has been active in promoting the purchase of coal for Government use under specifications that define the requirements in terms of heating value of the coal, expressed in British thermal units, and the composition as shown by proximate analyses. To these, when required, are added the ash- softening temperature of ash, the free-swelling index, and the hardgrove grind- ability index. Under most of these specification contracts the bidders guarantee the quality of the coal, and that guaranteed by the successful bidder becomes the standard of his contract. The deliveries are sampled in accordance with instruc- tions issued by the Bureau of Mines; the samples are analyzed in the Bureau laboratory to determine whether the coal is of the quality guaranteed by the con- tractor and, if it is not, a price adjustment is made. Analyses of the delivered coal and tipple samples (samples collected at mine tipples as coal is being loaded into railroad cars or trucks) provide valuable data for use in evaluating future bids. In addition, the continuous sampling of coal as delivered is a check on the practical results obtained in burning the coal. The Government purchased approximately 5-1/4 million tons of coal in fiscal year 1953. In connection with these purchases, the Bureau analyzed 11,435 samples. These are published for the use of Government officials and the public. A series of publications has been completed on coal analyses by States, or, where production is small in any one State, by groups of adjacent States. In addition to analytical data showing composition and quality of coals of the States, the publications con- tain brief descriptions of the geological structure of the coal basins, typical mining conditions in the various districts, the principal economic data of the industry, and the relationship of mine or channel samples to delivered and tipple samples. The present publication covers many States but deals only with the analytical data of the coals. Previous publications in this series are: Bulletin 516, Analyses of Tipple and Delivered Samples of Coal (Collected During the Fiscal Years 1948 to 1950 Inclusive); Report of Investigations 4934, Analyses of Tipple and Delivered Samples of Coal (Collected During the Fiscal Year 1951); Report of In- vestigations 4972, Analyses of Tipple and Delivered Samples of Coal (Collected During the Fiscal Year 1952). Following are the Bureau of Mines technical papers published by States, with their numbers: Alabama, 347; Alaska, 682; Arizona, California, Idaho, Nevada, and Oregon, 696; Arkansas, 416; Colorado, 574; Illinois, 641; Indiana, 417; Iowa, 269 and 706; Kansas, 455; Kentucky, 308 and 652; Maryland, 465; Michigan, North Dakota, South Dakota, and Texas, 700; Missouri, 366; Montana, 529; New Mexico, 569; Ohio 344 (and Bulletin 499); Oklahoma, 411; Pennsylvania Bituminous, 590 (Supplement 645); Pennsylvania Anthracite, 659; Tennessee, 356 and 671; Utah, 345; Virginia, 365 and 656; Washington, 491 (Supplement 618); West Virginia, 405 and 626; and Wyoming, 484.

Jan 1, 1955

By C. Arthur Carlson

"It now becomes my privilege and duty to call to order this fifty-first meeting of the Rocky Mountain Coal Mining Institute. "I bid you a hearty welcome and I know by your attendance at these meetings you will gain a great deal of valuable information, as well as have a wonderful time. "We have been very ably represented by Mr. John H. Emrick as General Chairman, assisted by our good friend Mr. Fred W. Whiteside, our secretary and treasurer. I know they have worked very hard in selecting the various committees, who in turn - by the looks of our program have gone all out to prepare material that should be of great interest to us. I trust we will be attentive to the subjects presented and freely enter into the discussions, also relating our problems and experiences. I am sure this will prove both profitable and beneficial to all present. "The main purpose of these conventions is to become acquainted with each other, renew old acquaintances, talk over our problems, and have a little fun and relaxation from our every day routine. "Let us not forget the manufacturers, the distributors, the operators, or the press because it is through their splendid support that this organization is successful. "Since our last meeting we have gained many new members, whom we especially welcome. We are sorry to have lost a few. I am mindful, at this time, of two very good members from my home state who have passed away, Walter Wetzel, a former president of this institute, and Lee Alger, at the time of his death, Vice-President from Utah. We also lost very recently our assistant Secretary-Treasurer, Everret Davis. These men contributed a great deal to the institute and the coal industry in general. I am sure they are greatly missed by all who knew them."

Jan 1, 1955

By BUREAU OF MINES

This report is submitted in accordance with the provisions of the Synthetic Liquid Fuels Act of April 5, 1944 (30 U.S C. 321-325, as amended), which require that: "The Secretary of the Interior shall render to Congress on or before the first day of January of each year a report on all operations under this Act." Owing to the broad scope of the content and the diversity of interests represented, the Annual Report for 1953 has been divided into two separate publications. Each has been published by the Bureau of Mines as a Report of Investigations, and the respective titles follow: R. I. 5043, Part I - 011 From Coal. R. I. 5044, Part II 011 From 011 Shale. - Identical in each report, the introduction summarizes research progress made in 1953 under the entire Synthetic Liquid Fuels program. A free copy of each of these publications may be obtained by a written request to the Bureau of Mines, Publications Distribution Section, 4800 Forbes Street, Pittsburgh 13, Pa. The R. I. number and title of the publication desired should be indicated.

Apr 1, 1954

By BUREAU OF MINES

This report is submitted in accordance with the provisions of the Synthetic Liquid Fuels Act of April 5, 1944 (30 U.S.C. 321-325, as amended), which require that: "The Secretary of the Interior shall render to Congress on or before the first day of January of each year a report on all operations under this Act." Owing to the broad scope of the content and the diversity of interests represented, the Annual Report for 1953 has been divided into two separate publications. Each has been published by the Bureau of Mines as a Report of Investigations, and the respective titles follow: R. I. 5043, Part I - Oil From Coal. R. I. 5044, Part II - Oil From Oil Shale. Identical in each report, the introduction summarizes research progress made in 1953 under the entire Synthetic Liquid Fuels program. A free copy of each of these publications may be obtained by a written request to the Bureau of Mines, Publications Distribution Section, 4800 Forbes Street, Pittsburgh 13, Pa. The R. I. number and title of the publication desired should be indicated.

Apr 1, 1954

By W. A. Boyer

HOISTS for metal mines are seldom designed for H one particular depth. They are intended for an ultimate load and depth with a given speed but are first used to hoist from a shallower depth, gradually working to the ultimate as development progresses. Sometimes the mine is not worked on the upper levels because of the kind and grade of ore, the mining of which depends on market conditions. In this case the hoist may be used in the same working shift to lift ore, for example, from the 1200 and the 4400-ft level. This means that the safety factor of the rope should be considered not only when it hoists from the greatest depth, but also when it hoists from the upper levels. According to present safety factor standards, a hoisting rope can have ample safety margin when hoisting from the lower or lowest level and still be shy of sufficient safety margin when hoisting from the upper levels. This will be shown by curves presented in this paper.

Jan 10, 1954

By J. Visman

FOR more than 25 years evaluations of coal cleaning units have appeared in many publications, and during this time considerable progress has been made in developing the theory and techniques of calculating washery results. A variety of characteristics have been defined over the years, many receiving general recognition during the first post-war Coal Preparation Conference in Paris in 1950. Coal preparation has become a science, and the approach to preparation problems is being revolutionized. Formerly, for example, if a coal operator wanted to know the performance of a given cleaning unit for a particular grade of his run-of-mine, he either shipped a carload to the manufacturer for a test run or relied on a report of a test carried out on a coal similar to the one he intended to clean. In modern practice the expensive, time-consuming test work generally can be avoided if the washability curves of the coal in question and the error curve of the cleaner are known. Normally a guarantee can be given on the strength of this information. General acceptance of modern standards has thus reduced the need for pilot-scale models of existing types of coal cleaners. Needless to say, the method requires exhaustive and accurate information on the cleaning unit and on all the additional circumstances affecting its results, in- formation that ultimately can be secured only from actual tests made in the laboratory or in the washery.

Jan 10, 1954

MODERN mining is based on drilling--everything else stems from that. U. S. and Canadian mining companies and suppliers of mining equipment are constantly seeking new techniques and tools for increased drilling efficiency. Ultimate goal is increased bit-against-rock time. Just how important their efforts are can be seen through a legitimate extension of available statistics. In Canada some 70 million ft of drilling per year is required. While the number of feet actually drilled in the U. S. is unknown, it is possible to compare U. S. and Canadian mineral production, excluding oil and coal. In the U. S. mineral value was $4200 million and across the border $836 million. Taking into account the number of drilled feet required to produce Canada's total, the U. S. total would be 365 million ft in 1953. A saving of 14 per ft would reduce over- all metal and nonmetal mining costs some $3.65 million per year. This does not take into account other indirect savings. Methods have changed and there have been structural and metallurgical advances in blasthole practice in the last ten years. The Editors of MINING ENGINEERING in the articles on the following pages present the most significant innovations coupled with results in the field. Environment plays an important role in selection of materials and equipment -but while unanimity does not exist throughout the industry in reference to drilling problems, a definite trend is evident. For the story of that trend read the articles on the following pages.

Jan 9, 1954

By Reno H. Sales

EVERY mine manager, mine geologist, and every prospector in the field who appraises the future of mining properties does so on the basis of a theory of ore deposition whether he recognizes this fact or not. Wherever the ultimate value of a mine or prospect is dependent upon undeveloped ore, any estimate by an engineer or geologist necessarily involves a theory of origin of the deposit. In view of these facts the importance of a thorough understanding of the genesis of ore deposits cannot be overestimated. It well may be that the greatness of our country will depend upon finding reserves of natural resources as yet undiscovered. The genesis of ore deposits offers a fascinating field for study and investigation. This is attested by the large number of geologists who have written at length on the subject. For progress made toward a better understanding of ore genesis we owe much to Kemp, Lindgren, Ransome, Vogt, Emmons, Spurr, Graton, and a host of others. Within my own experience, I have attempted to apply in practice the various concepts and theories that have been advanced by these men.

Jan 5, 1954

By H. C. Hamontre

The liquid-level gage described in this report is an instrument designed to locate liquid levels in wells rapidly and accurately and, with auxiliary equipment described, to follow moving liquid levels automatically. The depth at which the instrument makes contact with the liquid in a well is indicated at the surface by a depth meter on the cable to which the instrument is attached. When the gage is used to follow a surging moving level, the liquid depth is indicated continuously at the surface. This report contains a description and illustrations of the gage and outlines the operating procedures. The instrument is 1-3/4 inches in diameter and approximately 6 feet in length and may be operated through 2-inch tubing. The gage consists essentially of a float that moves upward with respect to the rest of the assembly, causing a change in the flow of electric current from the surface when the liquid level is reached. The instrument has been tested under a variety of conditions and has been found to be sensitive to changes in liquid level of 1/2 inch. Its accuracy is limited principally by the accuracy of the wire-line depth indicator used. It is not affected by pressure or temperature, and it can be run in open hole or under pressure through a lubricator. It employs only one electric circuit and can be run on an Amergraph single-conductor cable (type 1-H-0) ,

Jan 1, 1954

By K. F. Anderson

The increasing number of oil-productive reservoirs in the Ellenburger formation has emphasized the need for information pertaining to the hydrocarbon recoveries that may be obtained from such reservoirs. Most of the space available for accumulating hydrocarbons in the Ellenburger formation is derived from fractures, which makes it difficult to estimate reserves or probable recoveries. The Ellenburger reservoir in the Big Lake field was selected for study because it is one of the few near-depleted reservoirs in the area. The experience gained in operating and developing this reservoir has been and should continue to be a helpful guide to operators both in predicting recovery and establishing methods of development and operation In similar reservoirs. Development and production data were gathered from different sources. The writers have compiled and interpreted these data to estimate the ultimate recovery of hydrocarbons. In addition to the estimates of ultimate recovery, the report contains sample calculations and estimates of theoretical recovery based on different methods of operation. The calculations presented in this report indicate that the Ellenburger reservoir is 95 percent depleted and that the ultimate recovery of hydrocarbon liquid from the oil reservoir and gas cap combined will he 4-0 barrels per gross acre-foot of reservoir rock. An estimated 32 barrels of condensate per gross acre-foot of reservoir rock in the gas cap has been recovered, and the estimated ultimate recovery of crude oil will be 47 barrels per gross acre-.foot of rock in the crude-oil reservoir.

Jan 1, 1954

By C. E. Schwab

A lead-zinc orebody, in fairly strong quartzite and with a dip of 35" to 60°, is block-caved by use of scrams in a stair-step pattern up the ore footwall. Scram linings to handle coarse muck and permit the use of folding scrapers are developed by the use of end-grain wooden blocks to reduce maintenance and keep operating cost to a minimum. THE Bunker Hill mine, since its discovery in 1885, has steadily produced a high grade of lead-silver-zinc ore. By the end of 1952 over 21,000,000 tons of this high-grade ore had been produced by square-set mining, and reserves in the mine continue to be very satisfactory both as to quantity and grade. For many years prior to 1941, mine production and mill capacity had been 1200 tons of feed per day. Closely adjacent to the mill, and stored behind dikes, coarse jig tailings had been impounded during the time preceding the advent of fine grinding and selective flotation. When manpower became short in 1941 and sink-and-float preconcentration was proved successful, mill capacity was increased to 1800 tons per day to treat these jig tailings economically. By 1946, because the supply of jig tailings was limited, underground exploration was started to discover and prove ore reserves of low-grade material which could be mined by an appropriate bulk mining method. During the years of square-set mining many possible areas of low-grade mineralization had been observed. One chosen for the first exploration work was sufficiently remote from active mining areas so that subsidence, if an ore-body were proved, would cause no problem. Also, old adits and workings were still open and in good enough condition so that exploration in the mineralized zone could be started with a minimum of preparatory work. In 1948 an orebody was proved of sufficient tonnage, of a grade about 2 pct Zn, 0.5 oz Ag, and 1.0 pct Pb. It was decided to use block-caving, the only appropriate mining method by which this grade of ore could be economically recovered. Exploration for additional reserves in other areas of the mine is continuing, but ultimate results are not known at this time. With more sink-and-float capacity, larger ball mills, and more flotation machines, mill capacity was increased to 3000 tons per day, permitting the mining of ore in the square-set area at a maximum rate not usually achieved, because of the scarcity of labor. Increased mill capacity also permits block caving and the mining of jig tailings at variable rates to keep mill feed up to 3000 tons per day. Fortunately the three types of feed are amenable to the same mill circuit and reagents for recovery of Pb and Zn. For example, during the first 10 months of 1952 square sets produced 827 tons per day, block-caving 1421 tons per day, and jig tailings 643 tons per day, an average daily production of 2891 tons for all three products. Exploration had proved the existence of an ore-body 1000 ft long and 165 ft wide in horizontal section, see Fig. 1. Company engineers were concerned only with the vertical extension, about 300 ft, from an old level to the surface. Much of this almost outcropped, Fig. 2. The ore lies in the hanging wall of a major fault of the Bunker Hill mine, standing at 65" in one end of the zone and separated from the fault by a wedge of waste, see Fig. 3. This wedge pinches out near the center of the zone, at which point the ore dips 45", lying nearly on the fault, Fig. 4. The remaining portion lies on the fault and conforms to the fault dip of 35", Fig. 5. Open-pit mining for the top of the ore was considered, but since the ore zone dipped into and under the mountains, adverse waste-to-ore ratios precluded use of this method. The ore occurs in massive quartzite of sufficient strength to support untimbered drifts, crosscuts, and raises. Zones of weakness in the quartzite are bedding, jointing, and small faults or slips. The mineralization, which occurs as small stringers of sphalerite and galena as well as pyrite, creates another line of weakness. The mineral veins or veinlets in themselves are high-grade. Their size and regularity and the amount of barren quartzite by which they are separated determined the limits of mineable ore, which are all assay limits except for the one determined by the major fault. Block 1 Without any background of caving in this type of quartzite, engineers selected the first block on the very steep end of the zone. Compelling reasons prompted this decision. The steep portion of the ore in Block 1 was of the lowest grade, so that if difficulties were encountered no very valuable ore would be lost, while the experience gained might be applied in mining the remaining blocks. A block 200x200 ft was laid out, with four scrams spaced 50 ft apart for drawing and placed at a right angle to the strike. Finger raises were placed in a 25-ft interval grid pattern, with flat undercutting done by crosscuts at the undercut level 25 ft above

Jan 1, 1954

By Jean Scott, G. A. Collins, G. W. Hodgson

WHILE it is well known that trace metals in crude •oils and distillates have been a matter of deep concern to refining engineers because of the damage done .by the metals to cracking catalysts and refractories (8, 5), the trace metals in crude oils may be of great benefit in correlation studies and in origin studies. During the geological processes in which the oil is formed from •animal and vegetable life, the hydrocarbons are subjected to a host of inter-related reactions, both physical and chemical. It has been well demonstrated that the lighter materials, certainly the short-chain paraffin hydrocarbons, are degradation products of the heavier molecules, and it might be concluded that for correlation studies it would be advisable to direct attention as much as possible not to the degradation products of the large molecules but to the large molecules themselves. Be this as it may, the methods at •hand to conduct the study are not particularly precise and, in the past, attention has centred on the simpler small molecules, as evidenced by the great mass of work involving distillation and chromatography with painstaking separation of the simpler 'front-end' hydrocarbons.

Jan 1, 1954

By R. G. Nelson

The mechanical properties of low-hafnium, arc-melted, Kroll-process zirconium are presented. The effect of temperature on the ultimate strength, yield strength, proportional limit, elongation, hardness, Young's modulus, electrical resistivity, and impact strength are shown, The effects of cold work and annealing on the tensile properties, bend radius, and formability, as determined by cupping tests, are also given, Tensile properties are compared, in part, to those obtained on earlier graphite-melted zirconium and on crystal-bar zirconium. INTRODUCTION The commercial production of high-purity, low-hafnium bearing zirconium has been achieved, and this metal is becoming available for industrial use. However, there is little published information regarding the physical and mechanical properties of this product; and, since there have been many improvements in the production and arc-melting techniques of zirconium in the past 3 years, it was considered advisable to present the properties of the vastly improved zirconium representative of current production.

Jan 1, 1954

By J. W. Watkins

This report describes in detail methods of making corrosion tests and chemical analyses that have been used extensively and satisfactorily in a study of plants in which various surface, waters and brines are conditioned and used for water flooding, brine disposal, and reservoir-pressure maintenance in Kansas, Oklahoma, and North Texas. The tests and analyses described were designed and adapted for use in the field in determining the relative corrosive and plugging tendencies of waters from various sources conditioned by different methods. Although the described methods were developed and used in testing oil-field waters in the Midcontinent oil-producing area of the United States, these same methods should be equally applicable to testing oil-field or highly mineralized waters throughout the world. Many of the methods used have been discussed by the writer (1)2/ previously, and some of them have been used for similar work in other laboratories. Early in the development of the practice of the subsurface injection of brines for disposal and increasing the recovery of oil, it became evident that different methods of chemical treatment and conditioning equipment would have to be devised to sustain desired injection rates into water-input wells. These changes became necessary because the highly mineralized waters produced with petroleum from deep formations became chemically unstable when pumped to the surface, owing to loss of dissolved gases as pressure and temperature dropped to atmospheric and to the contact with atmospheric oxygen at the surface.

Jan 1, 1954

By Robert H. Merrill

This report contains a summary of the various studies made to determine the structural design of the production mine area of the Oil-Shale mine, Rifle, Colo. Prior to this investigation, it had been determined from a study of the geology, the structure of the deposit, and mining costs that the deposit should be mined by open stoping. The problem remained to determine the maximum safe roof span, the optimum extraction ratio, and the size of the pillars. These factors were determined from a study of the geologic structure of the deposit, the physical properties of the oil shale, and the magnitude and distribution of the stress around proposed underground openings. The latter was determined from both theoretical calculations and model studies. Safe roof spans, pillar sizes, pillar contours, and optimum extraction ratios were calculated from elastic theory and the physical properties of the mine rock. Safe roof spans, pillar sizes; and time effects were determined by Wright and Bucky by testing mine models in a centrifuge. The models were made from rock specimens taken from the proposed mine roof and pillars. The results from both studies agreed.

Jan 1, 1954

By C. H. Riggs

This report of a petroleum-engineering study of the Flat Rock oil field, Osage County, Okla., describes the geology, reviews the production history, and estimates remaining oil reserves. The Flat Rock field in the southeastern corner of Osage County approximately 6 miles northwest of Tulsa. Okla., was discovered in November 1904. The field was one of the first of many Bartlesville-sand fields developed in eastern Osage County during the early part of the 20th century. Although substantial oil reserves remain in the pressure depleted sands in some parts of the field, their economic recovery by water flooding will require careful consideration of the many factors involved.

Jan 1, 1954

By M. L. Brashears

IN the last 15 years industrial use of ground water has more than doubled, and in 1951 amounted to 5 billion gallons per day. A similar sharp increase in the utilization of ground water for irrigation and public-water supply occurred in the same period. In many areas rapid increase in withdrawal from wells has taken place almost entirely unhampered by regulatory control and with little or no integration of effort. As might be expected, the chief interest in many regions has been maximum production rather than sustained perennial yield. As a result, widespread depletion of underground reservoirs and deterioration of the quality of the water stored in them has taken place in many areas, even though total pumpage in the United States is far below ultimate potential. Of even more concern is the fact that excessive withdrawal has drawn salt water into the reservoirs beneath many heavily populated centers along the Atlantic, Gulf, and Pacific coasts, causing costly abandonment of pumping plants.' Many hydrologists expect that consumption of water will rise rapidly in the near future, and some predict that industrial requirements will more than double in the next decade.2,3 Thus it appears likely that the draft on many already heavily pumped underground reservoirs will be greatly increased and the search for additional sources of usable ground water intensified in years to come. In view of this, industry as a whole will be forced more and more to recognize the potentialities and limitations of ground-water reservoirs and to utilize them more effectively to prevent costly water shortages and disruption of production. Through painful experience, some industries are already well aware of the need for effective water utilization, and have managed individually or through joint effort to check trends threatening to deplete underground reservoirs completely or to impair the quality of the water. Various remedial measures have been used to bring about successful management of local or regional ground-water resources. Of these, replen-ishment of aquifers by recharge wells or basins has played an important role in overcoming some ground water problems. Artificial recharge of underground reservoirs by water spreading has been practiced successfully in the United States for many years. In the West it has become an important method of salvaging flood run-off for irrigation of crops and maintenance of public water-supply reserves, and it is used to some extent in parts of the East. Artificial recharge by means of wells, on the other hand, is a relatively new development. Until recently it was employed in only a few areas, principally along the East coast. For the last few years, in the ever increasing search for additional water supplies, industry has had greater recourse to this method. Utilization of recharge wells to control the temperature and quality of underground water supplies is also being considered seriously. Operation of recharge wells, like water spreading, is governed largely by local conditions. It requires water relatively low in turbidity, whereas in some areas water spreading has been used successfully with water of high turbidity and silt content. However, water spreading must be employed in large areas and can be carried on effectively only where aquifers crop out at the surface. Recharge wells can be used in limited space. Recharge wells are similar to production wells except that the water flows in the opposite direction. Thus any water-bearing bed that will yield water to wells may be recharged by wells. Often, however, the water available for recharge is of a different character and temperature from that existing in the ground-water reservoir and if transmitted directly underground from a recharge well to a production well might require expensive or difficult treatment before it could be used. Fortunately the physical characteristics of reservoir beds, which control the movement and behavior of ground water, are generally not homogeneous. Moreover, the movement of ground water is very slow because of the frictional resistance of the reservoir beds. By taking full advantage of hydrologic and geologic conditions, it is therefore possible in many instances to bring about favorable changes of temperature and dilution as the water moves from the recharge wells underground to the production wells. Furthermore, if the natural quality or temperature of ground water is unfavorable for industrial purposes, recharge wells may be used to introduce water of more favorable quality or temperature into the ground-water reservoir. When water is discharged into a recharge well, the head in the well is increased. Because of this, a cone of elevation is produced on the water table or the artesian pressure surface in the area surrounding the well. The cone of elevation is similar to the cone of depression produced around a pumping well except that the apex of the cone is above the water table or artesian pressure surface. Thus if a recharge well and a production well tapping the same water-bearing bed are close together, as would be the case at many industrial plants, some of the water discharged from the recharge well would be drawn into the production well within a short time. Under such conditions it is apparent that water of unfavorable temperature and chemical characteristics should not be used for recharging. The more important ground-water reservoirs in the United States often consist of alternating layers of impermeable beds and porous material that will yield water readily to wells. Physical characteristics of individual beds in a ground-water reservoir may not persist over great distances, the impermeable layers grading into beds that will yield large quantities of water. Thus the water-yielding material in underground reservoirs, whether large or small,

Jan 1, 1954

By Samuel H. Dolbear

THE value of a mine is basically dependent on its capacity to yield profits. Since the ore must be mined, treated, and sold, some of it in various future years. there is a risk involved as to future costs, selling price, and working conditions. It cannot be expected that the economic condition existing at the time of valuation will continue unchanged for long periods in the future. During the past 20 years, mineral production in the United States has been conducted under a changing economy in many respects more exacting than that applied to other businesses. There have been increased production incentives, technical aid, exploration of privately owned mineral deposits by government at federal expense, and liberal loans for development and equipment, with risk partially assumed by government.. Some of these benefits have been counterbalanced by price ceilings, consumption controls, and stimulation of competition from foreign producers who have been offered the same advantages extended to American operators. For the present, mines will operate under a government policy directed toward reducing federal aid and control. The tenure of this change will depend upon future elections and the status of foreign relations. War and threat of war are now of the most vital significance to the mineral industries. Other factors which influence cost of production, markets, and price of mine output might be classified as Acts of God or Acts of Government. In some countries expropriation and the difficulty of exporting earnings or investment returns are risks that must be considered by foreign capital. Recognizing that this retards American investment in foreign countries, the Mutual Security Agency offers insurance against such expropriation and guarantees the convertibility of capital and profits. Since it is impossible to predict with certainty either cost of production or selling prices of metals for long periods, some assumptions must be made as to profits in the future. The basic assumption must be that the price of the company's product will vary in proportion to changes in operating cost. There is often a lag in this reaction, however, for prices of minerals are generally more sensitive to declines and less sensitive to increases than are costs. This reflects in part the resistance of labor to downward wage revision and a corresponding alertness in realizing its share of price advances. Some labor contracts include automatic adjustments to metal prices. Notwithstanding the complexity of the, problems involved and the difficulty of weighing their effect on value, such risks may be appraised with reasonable accuracy and a rate of earnings adopted that is compatible with the risk. It is, of course, possible to revert to a yardstick of value such as the commodity dollar, which has been advocated from time to time, but while revaluation in 1933 disturbed public confidence, the theoretical gold dollar continues to be the standard of greatest stability. Its gain or loss in purchasing power is reflected ultimately in cost of production and selling price of the mine product. At present 35 dollars are allocated to one ounce of gold. Measurement of Risk In the application of the Hoskold and most other formulae, a yearly dividend rate commensurate with the risk involved is set aside out of annual earnings. If the risk is great, this rate may be 15 to 25 pct of the amount invested. The remainder is placed in a sinking fund invested in safe securities such as high grade bonds or conservative equities, and the interest or dividends from these securities are added to the sinking fund. The sum of these sinking fund payments and the compounded interest at the end of the mine life is taken as the value of the mine. Admittedly the decision as to the size of the risk rate is the most difficult element in valuation and one requiring the most exacting consideration. It is necessary to look years ahead in an effort to determine future costs, market prices, demand, competition which may develop, including that of substitutes, and other influences common to the mine and to the region in which it is situated. Another phase of risk is the enactment of unfavorable legislation, taxes, and what appears to be an alarming spread of nationalization and expropriation. Capital is sometimes borrowed from the government to finance strategic production. Such loans may be collectable only out of production and involve no liability otherwise. Valuation in these cases must recognize the effect of such a reduction in liability. Offsetting some of these risks are the possibilities of mechanization and other cost-reducing discoveries, improvements in mining and treatment methods, new uses for minerals and metals, and normal growth of markets. In this paper, the terms risk rate, dividend rate, and speculative rate are synonymous. Safe rate and redemption rate are also used interchangeably. These alternatives are used here because they are commonly found in the literature on mine valuation. In Michigan, the State Tax Commission has long employed a risk rate of 6 pct in its valuation of iron mines. There the outline of reserves is well established and operating costs and conditions are based on adequate experience. The following comment on rates appears in the report of the Minnesota Interior commission on Iron Ore Taxation submitted to the Minnesota Legislature of 1941.1 Most engineers agree that 7 percent for the specu-lative rate is "an absolute minimum". C. K. Leith in

Jan 1, 1954

By W. T. Turrall, M. J. Cook

A discussion of modern developments in beneficiation of fine sizes of anthracite, this paper includes a description of the plant flowsheet, an analysis of operating results, and a summary of fundamentals of mineral separation relative to plant operation. DURING the past several years Lehigh Naviga-tion Coal Co. has installed equipment at Tamaqua and Lansford collieries for cleaning and sizing No. 4 buckwheat —3/32 + 3/64 in. and for recovering and cleaning flotation coal —20 + 200 mesh at Tamaqua colliery. Papers describing some of these installations have been presented to AIME. At Coaldale colliery, however, methods used to clean fine coal were inadequate and inefficient. Management decided upon a thorough investigation of all existing processes before building a plant to treat the combined three sizes mentioned. Investigation, carried out on company property and at other plants, entailed a study of hydrotators, hydroclassifiers, tables, spirals, flotation machines, methods of screening, and methods of dewatering. On the basis of this investigation a flowsheet was designed which necessarily excluded many processes in use, and the writers wish to emphasize that no criticism is implied by omission of processes or machines. A determining factor in selection of many machines was the policy of standardizing equipment wherever possible. Flowsheet and Operational Data The first principle to be considered in designing of any plant is efficiency of cleaning as related to laws of classification. Beneficiation of coal may be described as separation of two materials having different specific gravities. Although there is an inherent ash content even in the purest coal which slightly affects its specific gravity, it is recognized that many particles are true middlings. The percentage of these particles allowable in the final product depends upon the ultimate ash, or specifications of the consumer. Richards in his study of free settling and hindered settling classification' determined that particles of equal size and different specific gravities had unequal settling velocities. He also determined a definite size relationship for equal settling velocities with free settling and hindered settling conditions. Considering the design of machines used to clean No. 4 and No. 5 buckwheat, it may be assumed that both free settling and hindered settling conditions exist and that ratio of size for practical operations is between the established values. The essential factor is that the more efficiently and closely sized the feed is maintained, the more nearly perfect the resulting separation. Flowsheet design was governed primarily by factors related to the 1200 to 1500 tons per hr feed to the main plant. It should be stressed that because of the many sources of supply from mine and stripping, the physical characteristics of this feed varied considerably. The most significant influence was varying percentage of fines, necessitating that all machines be capable of operating under maximum peak load during periods of surge. Since cleaning practice is a wet process, about 9000 gal per min containing 14 to 15 pct solids, or 350 tons per hr, must be treated. This slurry contained all the fines, or —3/32 in., but also percentages of oversize, up to 1 % in., dependent on spills or breaks in screen jackets, a not uncommon occurrence in preparation plant practice. The flowsheet developed is shown in Fig. 1. Circled numbers represent points of sampling. Table I gives operational data including size, ash by size, composite ash, rate of flow in gallons per minute, percent solids dry weight, and average tons of solids per hour. It should be noted that these results are subject to human error in sampling practice. Detailed information reported is a representative evaluation of plant operation.

Jan 1, 1954

By D. S. Kingery

Efficient transportation is necessary to complement modern mechanized mining methods. The increasing trend toward high-capacity face loading equipment has demanded equally efficient haulage methods; this has been met by increasing mine-car sizes, using larger locomotives, and increasing haulage speeds, all requiring properly installed and maintained haulage roads specifically designed for this type of traffic. The recommendations and specifications included in this circular were made to point out salient factors important to the proper construction and maintenance of track haulage roads and to serve as recommended standards for track installation and maintenance. GLOSSARY OF TERMS USED Haulageway. - The track, walkway, trolley wire, feeder lines signal end telephone lines, signals, telephones, support, and drainage of the entry referred to. Subgrede. - The base upon which the ballast is laid.

Jan 1, 1954