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By William P. Lohden

INTRODUCTION It is recognized that, for a variety of reasons, some companies in the mineral industry today are by no means cash-rich and, in fact, are reporting a growing proportion of long-term debt in their capital structures. A review of recent balance sheets of small, medium-size, and some larger companies, indicates that a fair number still have substantial positions in cash equivalents such as U.S. government issues and other short-term money market instruments. In part, this paper concerns itself with companies which have sufficient cash and equivalents and/or cash generation to internally finance mining projects or expansions but which, for some reason, choose to borrow funds. Misconceptions which appear to frequently underlie so-called "leveraging" decisions are explored in this paper. Also considered arc' those circumstances under which any company, including one that is cash rich, should consider borrowing for a project in an amount beyond what would otherwise be necessary based upon its internal financing ability. I do not attempt to cover the raising of equity capital in public markets in this paper. OVERALL RETURN ON INVESTABLE CASH If you approach an individual with an investment which can be financed from savings, or by borrowing at a rate higher than one is earning on savings, that individual will quickly tell you that to pay interest at a rate higher than is being earned on savings would reduce overall income. Assuming that additional investment opportunities are not currently being considered, the individual concludes that a draw-down on savings, leaving a cushion for contingencies suited to individual circumstances, is the correct financial decision. For reasons discussed later, the simple mathematical logic leading to this conclusion tends to become obscured at the corporate level. When Leveraged Studies Are Inappropriate or Premature Surprisingly, I have heard of a number of companies that could afford to finance an investment solely with internal funds, which have made DCFROR (i.e. discounted-cash-flow rate-of-return) studies not only on a 100% equity basis but also on a leveraged basis. Certainly, a leveraged study would be appropriate if additional projects were competing for more capital than was available internally. Often, however, other projects are not far enough along to warrant a leveraged study and there is some danger that a project may be undertaken because it has an estimated acceptable rate of return, on a leveraged basis, that is not ultimately earned because some of the other projects are postponed or abandoned and borrowing is less than expected. For the above reasons, until it has been determined that (1) borrowing is a reasonable certainty for a particular project and (2) the timing and amount to be borrowed has been determined within a reasonable range of accuracy, I believe it is inappropriate and misleading to calculate DCFROR for a project other than on a 100% equity basis. Even when there are several projects currently competing for funds and borrowing will be required to finance one or more of them, using the common yardstick of calculating DCFROR on a 100% equity basis is a safer method to initially evaluate and compare the attractiveness of the projects. Many companies, whether they would have to borrow or not, will reject projects that on a 100% equity basis do not meet their minimum rate of return standards. Some companies which have to borrow will undertake a project provided the project's DCFROR on a leveraged basis meets its minimum return standards. The danger of this approach is that even moderate shrinkages of estimated cash flows could plunge return below

Jan 1, 1985

By A. J. Brown

I herewith send to the Institute a sample of Pancake coal. It is rather early yet to make any estimate of the future value of the discovery; but it is certainly the most promising vein of coal yet discovered in the State of Nevada, and, I believe, the first true coal found west of the Rocky Mountains, or perhaps west of the Missouri River, unless some of the Utah coals belong to the coal measures of the Carboniferous age. The Pancake vein certainly belongs * Since the above paper was read before the Institute, some modifications in the description of the machine have been made in order that recent improvements may be embraced.—U. S. A.

By William A. Berg

Vegetation on mine wastes was an important topic at the International Symposium on Ecology and Revegetation of Drastically Disturbed Areas held at Pennsylvania State University August 3-16, 1969. This article summarizes the Symposium papers that dealt with the nutritional and physical aspects of plant establishment on mine wastes. Surface Coal Mining Spoils Germany-In toxic spoil banks created by open-cast coal mining, the material was extremely acid and low in nutrients. It sometimes contained toxic quantities of minor elements and also had a water repellency that resulted in little leaching and high erosion. However, applications of calcareous and hygroscopic ash, fertilization and deep mixing (60 cm) have promoted growth on hundreds of acres. Knobe, N., Rhine Inst. Air Pol., Essen.

Jan 1, 1970

W ill the location of the world's largest reserve of rutile, a titanium oxide mineral, in Sierra Leone, Africa, put an end to the worldwide shortage of this important mineral? According to officials of the Pittsburgh Plate Glass Co. and the British Titan Products Co. Ltd., the answer is yes. These two firms have formed Sherbro Minerals Ltd., a new company that will recover and refine the relatively rare mineral near Africa's West Coast. PPG owns 80% of Sherbro, and British Titan 20%. The rutile reserves of Sierra Leone have been reported to be larger, on a comparable grade ore basis, than existing proven reserves throughout the world. The African operation is on a strip of coastal

Jan 8, 1964

By Andrew A. Blair

THE increased importance and value of chemical analysis in connection with metallurgical operations is largely, if not entirely, due to the increased accuracy of the analytical methods used for the quantitative determination of the foreign elements always associated with the metal operated upon. This applies especially in the working of iron and steel, and to the determination of the amounts of such elements as phosphorus, carbon, and silicon. The influence of greater or smaller amounts of these elements upon the physical properties of iron and steel will be better understood when the proper experiments shall have been made upon samples whose chemical composition is known with almost absolute certainty. From the present standpoint of analytical chemistry, it is easy to see that at least one reason for the failure of many attempts to solve this problem, is the inaccuracy of the analytical methods used. Even at the present time the frequent want of agreement (over and above the unavoidable error due to manipulation) between chemists working on the same sample, leads one to think that there is still at least a choice in the methods used. It is true that very frequently a faulty method in the hands of a skilful analyst may be made to give corroborative results

Jan 1, 1876

By W. F. McDermott

This is the dawning of the computer age in process control. As 1968 drew to a close, many plants had computer installations which were being used for logging, monitoring and reporting. Today, computer usage is given serious consideration before the construction of any major minerals processing plant. Unitized automatic control of individual processes is abundant. Many plants are considering closing these control loops, i.e., allowing the computer to direct the operation of the controllers (Digital Analog Control-DAC). The next step is to make the computer itself the controller (Direct Digital Control-DDC)1 Perhaps the most important future use of computers will be in controlling interrelated operations and control units. Progress along these lines depends on the steadily improving capabilities in the field of mathematical modeling.

Jan 1, 1970

By J. P. Batcha, J. Robert Denny

Since 1964. Newmont Mining Corp. has been engaged in a systematic research and development of computer techniques for a variety of mine planning applications. The general objective of this effort has been twofold: first, to arrive at a viable near-optimum plan for mining a particular orebody and, second, to decrease the financial investment by reducing the man-hours required for mine planning. Three major phases in the evolution of Newmont's computer techniques for mine planning are discernible. In phase one, the computer's ability to duplicate manual drafting and contour mapping was developed. Obviously, all recognized geologic characteristics had to be included, and consequently the development of computer techniques for the proper incorporation of structure, stratigraphic trends, and other geological features was a significant aspect of phase one.

Jan 1, 1970

By Charles E. Carlsen

Underground construction involves all the legal problems common to the construction industry and adds a nice little group of its own. Elements which will ultimately affect contractor-owner relationship commence to form almost as soon as the owner conceives of the project. A few of these with emphasis on their application to underground construction will be mentioned. (1) During the design stage, determination must be made as to whether the specifications will be general or restrictive. To what extent will the operations of the contractor be controlled? Can he proceed to use any method of tunnel excavation that he desires and only be responsible for the end result or will specific excavation procedures be required? Can explosives be used? Under what restrictions? Are tunnel supports required? How long can the crown behind the heading remain unsupported? What kind of supports are required? What restrictions on the placement of tunnel-lining concrete will be required? Each of you could extend this list for many pages but these illustrations are indicative of decisions that must be made in advance of bidding, and the ultimate decision on each question can have a significant effect on the legal relationships that exist between the contractor and the owner. The owner wants a good job at a fair price. On the other hand, nothing is worse than having a tunnel collapse during the construction period, with its extra costs, loss of life, and delay to the entire project. If the specifications are too restrictive, increased costs of performance are bound to occur. Owners save tremendous amounts of money by obtaining a contractor who has been ingenious in devising the most economical construction procedure. Care must be taken in drafting the specifications so that the benefits of such ingenuity will not be lost. (2) HOW is the contract to be awarded? Will there be open bidding, a restricted list of bidders, or will there be negotiations with a comparatively few contractors? If it is a government project, whether Federal, state, or

Jan 1, 1970

By C. G. McLachlan

Laboratory flotation tests carried out on massive sulphide ores may not be reproduced in plant practice, and when this occurs the discrepancy can be the result of differences between laboratory and plant grinding. Results of parallel flotation tests are given to support this contention, and data show how tailing losses are affected in corresponding size zones.

Jan 4, 1951

By Carl W. Volz

NORWAY'S metallurgical development, which has extended over many centuries, is intimately associated with that country's unique topography and climatic conditions. It is a rugged mountainous country, with a most irregular shore line, bordered by thousands of islands forming a natural protection for shipping. There are an endless number of lakes, and innumerable rivers and waterfalls, many fed by glaciers and melting snow. Rainfall is abundant. Though half of the country is north of the Arctic Circle, it is warmed by the Gulf Stream, so that the average temperature is about 45°, or 20° higher than other parts of the world in the same latitude. A sub-

Jan 1, 1935

By R. J. Lytle

Geophysical exploration for engineering purposes is conducted to decrease the risk in encountering site uncertainties. Such studies are needed in construction of underground facilities. Current responsibilities, opportunities and challenges for those with geophysical expertise are defined. These include: replacing the squiggly line format, developing verification sites for method evaluations, applying knowledge engineering and assuming responsibility for crucial national problems involving rock mechanics expertise.

Jan 1, 1982

By K. S. Benson

DEPLETION is a subject of vital importance to the mining industry. Yet, in spite of its importance, its significance is not generally understood. The purpose of this discussion is to clarify the main aspects of the subject from the viewpoint of a metal mine taxpayer.

Jan 7, 1951

By H. E. Nold

THE raw materials of the ceramic industry are mostly clays. This raw material is ground, water is added and the mixture pugged into a moist, plastic, rather stiff mass. From this mass the desired units of manufacture are made (bricks, hollow building tile, sewer .pipe, etc.). These units are dried; then placed in kilns and heated until the desired degree of vitrification is obtained.1 For firing ceramic ware, two distinct types of kilns are used; namely, periodic and continuous tunnel. PERIODIC KILNS Periodic kilns are those ordinarily seen in a brick plant. They are either round or rectangular. The raw, dried, formed ware is piled or set in the kilns to depths frequently exceeding 10 ft. The kiln is heated until the ware is matured, then gradually cooled sufficiently to allow men to remove the ware; then the cycle is repeated. The time duration of the cycle may be more than two weeks.

Jan 1, 1933

By A. Stumpf, Y. Berube

An experimental apparatus for studying the aqueous oxidation of sulfide minerals is presented. The oxidation kinetics for molybdenite in solutions of caustic soda and dissolved oxygen are discussed; results of leaching experiments on chalcopyrite concentrates are given. Preliminary results on the transfer of oxygen into water are also discussed.

Jan 1, 1974

By R. M. Zimmerman

INTRODUCTION Tuff is being considered as a possible geologic median for the underground storage of commercial high level radioactive wastes by the Department of Energy (DOE). DOE has the responsibility for developing or improving the technology fir safely and permanently isolating these wastes. DOE programs must satisfy requirements established by the Nuclear Regulatory Commission (NRC) for the licensing and regulating of these storage facilities (NRC 1981). Pertinent draft NRC requirements are: 1) releases of radioactivity to the environment must be within prescribed limits and 2) emplaced canisters containing wastes must be retrievable up to 50 years following emplacement. High level radioactive wastes produce heat in storage and it is essential that the thermal/mechanical/hydrological response of the host rock will not significantly degrade either the structural performance o£ the repository or the ability of the natural or engineered barriers to retard radionuclide migration. The Nevada Nuclear Waste Storage Investigations (NNWSI) was established by DOE to evaluate the suitability of disposing of high level nuclear wastes on or near the Nevada Test Site (NTS) (NNWSI 1980). NNWSI has focused exploration and site evaluation on the tuffs of Yucca Mountain. Field testing is essential to support site characterization and repository design efforts. Preliminary studies have been conducted indicating that tuffs in G-tunnel on the NIS contain welded and nonwelded tuffs that have similar properties to those in Yucca Mountain. Thus, field testing can be accelerated. This paper discusses the issues supporting the planned field experiments in G-tunnel. Issues not related to rock mechanics are not included.

Jan 1, 1982

By C. W. Spencer, R. A. Rummel, F. N. Rhines

SPECIMENS of five cast Cu-Bi alloys, containing 4.68, 0.53, 0.043, 0.0064, and 0.0025 wt pct Bi and cast pure copper were subjected to a bend test to determine their relative ductility. Using metallo-graphlc methods the structures of the fractured surfaces were compared with those of the polished cross sections. Embrittlement was found to be associated with the presence of a second phase in the grain boundaries although, in the lower bismuth

Jan 1, 1958

By Fred DeVaney

THE coercimeter, as its name implies, is an instrument for measuring the coercive force? of magnetic substances. It was developed by Davis and Hartenheim in the Special Studies Section, Metallurgical Division. A detailed description of this apparatus may be found elsewhere.2 The coercive force determinations of magnetic materials are inter-esting because of the relationship established by Gottschalk,4 who showed a linear relationship between the magnetization coercive force and the specific surface of comminuted particles. The value of this relationship in determining grinding efficiency has been shown by Dean.3 The determination of the surface contained in the subsieve sizes has always been a difficult problem for investigators. They made approximate measurements of the surface of coarse materials by sizing on screens, but for the determination of the surface of the sub-sieve sizes it was necessary to make detailed grain counts or, elutriation tests, or to study dissolution rates. The technical literature contains many references to other methods for determining these surfaces, either by some special apparatus or by mathematical calculations based on distribution lines. Many of the methods are long and tedious, and the results of some, at least, are questionable. The turbidimeter gives quick results on ground cement. By using magnetite as the material to be ground, a simple determina-tion of its coercive force by the coercimeter, requiring 10 minutes or less, can be transposed directly and accurately into units of relative surface. This subject has been pursued further by the U. S. Bureau of Mines in cooperation with the Missouri School of Mines and Metallurgy, Rolla, Mo., and the following is a description of the results.

Jan 1, 1938

By George Haworth

ELECTRICAL illumination of shafts, stations, and haulageways has been successfully practiced for many years, but its use in drifts and stopes where mining operations are carried on has- been limited. The large underground drifts of the Tri-State field present a lighting problem that is not satisfactorily solved by the use of the carbide lamp. It has, for some time, been the policy of the Anna Beaver mine to provide ample lighting throughout the underground haulage drifts and working faces. This has, in the

Jan 6, 1928

H. M. BOYLSTON, Cambridge, Mass.-I would first like to ask what machine Capt. Bellis used to make his tests on impact strength. I have made some tests with the Charpy impact machine, the specimen being supported at both ends and nicked in the middle, and, find that the results do not always agree with those obtained by the Izod and other machines. I would also like to ask what effect the composition and heat treatment of the tool steel had on the drilling of his rifle barrels, as compared, with the heat treatment of the steel itself? I notice that the analysis of the composition of steel used shows sulphur 0.050 and phosphorus 0.065; I should like to ask how those high limits of sulphur and phosphorus came to be allowed? I have some data which lead me to feel pretty certain that those high limits make for very unsafe steel in rifle barrels. It has never been explained to the satisfaction of all of us, why the manganese is so high: 1.22 per cent. I believe several reasons have been stated; among them, that it is high in order to compensate for the high sulphur, and also to increase the elastic limit and improve other physical properties of steel. Lastly, I wish to ask whether Capt. Bellis has tried any different methods of heat-treating his steel rifle barrels? Apparently these were all heat-treated before machining; has he had any experience with heat-treatment after machining, especially after drilling? Those questions may seem somewhat outside of the range of this -paper, but they are important, and if Captain Bellis can give us any information, it will be very helpful. Dr. J. A. MATHEWS,* Syracuse, N. Y.-The same subject was discussed here last year, and the earlier papers by Dr. Carle Hayward seem to indicate that nothing was gained by the length of time of 'tempering. (It should be borne in mind that his results were based upon electrical and magnetic measurements and not upon tensile tests.) That idea has been accepted as gospel by steel workers, until late years, and particu-larly in connection with alloy steels, on which there is no question that the effect of time of tempering is very marked.

Jan 4, 1918

By Robert S. Schecter, Paul M. Bommer

This paper presents the development of and results from a computer model of in situ uranium leaching. This model uses a streamline-concentration balance approach and is useful with a wide range of reservoirs. It can be used with any type of well system, in a reservoir with or without boundaries, and with any form of descriptive kinetics. The model also includes the effects of dispersion and consumption of oxidant by minerals other than uranium. The effects of areal sweep, variable uranium concentrations, variable permeability, and the presence of oxidant consumers on uranium production are shown and discussed.

Jan 1, 1979