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By Keith S. Liddell

he selection of mill design parameters to suit the applica­tion requirements can result in quite different operating parame­ters for each generic type of application, even though the basic mechanical layout of the mills may remain similar. The selection of the type and size of grinding media is very important to efficient and cost-effective operation, and to ensuring that the milled product achieves the required properties. Accordingly, the grinding media selection is seen as an integral part of the mill design. Consideration of the requirement for classification is important in order to achieve the optimum mill and circuit performance. This can lead to the circuit feed not being classified for a steady feed with minimal slimes and a low size reduction ratio. Feed containing on-size particles would be deslimed by open circuit classification. Closed circuit classification is performed where the feed fluctuates. The rheological characteris­tics of the circuit feed slurry can have an influence on mill performance, and needs to be allowed for. A common misconception frequently encountered is the belief that "a mill is just a mill". This is not the case with stirred types of mills, since the operating parameters selected for the mill can have a large effect on the product characteristics. For example, horizontal shaft high speed stirred mills have a com­pletely different grinding action to vertical shaft low to medium speed stirred mills, which results in large differences between the surface area produced at a given product size (Liddell, 1986). Hence, it can be misleading to apply test results or design procedures obtained from one type of mill to other types for scale-up. The Metprotech stirred mill, as applied in the mining and minerals industries, is a low to medium speed vertical shaft mill. The basic design has been discussed previously (Liddell, 1989). Currently, the largest mills that have been manufactured have an installed power of 400 kW. The largest chamber volume at this power is 6000 litres, containing IO t of grinding media. It is intended that the installed power will increase up to lMW as applications requiring larger sizes arise.

Jan 1, 1995

By Ulrich Maidl, Marc Comulada, Janosch Stascheit

"INTRODUCTION Cohesive soils are notorious for causing clogging of the cutter head and the excavation chamber of tunnel boring machines (TBMs). While clogging leads to a drastic reduction in excavation performance, it further induces higher wear of tools and other parts of the cutter head and may even prevent a controlled support of the tunnel face and, thus, lead to face collapse and excess settlements or sinkholes. Employing well-balanced soil conditioning techniques, the clogging tendency can be significantly reduced. The monitoring and control of soil conditioning as well as the timely detection of potential clogging tendencies require a close monitoring of all relevant machine parameters and measurements. To this end, a reliable and powerful Process Controlling software that gathers all machine and process-related information is a prerequisite for successful mitigation of clogging-induced problems. The remainder of this contribution is organized as follows: First, a brief introduction to the Process Controlling system PROCON is given. Afterwards, the mechanisms and mitigation techniques of clogging are discussed. Finally, an example is given how Process Controlling has been employed to soil conditioning in a tunneling project with highly clogging soils.PROCESS CONTROLLING Being both the active part and a huge measuring device, the shield machine represents the core component in mechanized tunneling. This machine comprises a manifold of complex components and devices that require constant supervision and control and, thus, is equipped with a manifold of different sensors that provide a continuous monitoring of the state and condition of the machine (Maidl & Stascheit, 2014). If these data are put into the whole context of the tunneling process, they can provide insight to the assessment and optimization of the performance and to the prediction of potential risks and hazards such as, for example, the tendency of clogging of the cutter head."

Jan 1, 2016

By D?Arcy R. George

A survey of the copper mining industry in Western United States revealed that uranium is almost universally present in the solutions resulting from leaching the waste ore dumps to recover copper. The U308 content ranges from about 2 to 15 ppm and a potential production of up to 1,000 tons of U3O8 per year is indicated. A six-week pilot plant test at the Bingham Canyon mine of Kennecott Copper Corporation showed that the uranium is readily recoverable by ion exchange techniques. The design of the new types of countercurrent ion exchange columns and operation of the pilot plant are described.

Jan 1, 1967

By D. F. Doerr, E. Blalock, D. R. Bush, K. D. Cohen

"INTRODUCTION The design, development, fabrication, and test of cryogenic breathing apparatus is part of a much larger effort funded by the National Institute for Occupational Safety and Health (NIOSH) and managed through a Space Act Agreement with the National Aeronautics and Space Administration (NASA) at the Kennedy Space Center (KSC) in Florida. This effort is designed to create cryogenically based life support equipment that is responsive to the needs of miners as required by the Miner Act of 2006. Our goal was to design and build a liquid air based self-contained breathing apparatus (SCBA) that lasted 2 hours and would be used for the egress of miners during a mining accident and be refillable while worn. Therefore, the current report describes tests of an Advanced Cryogenic Breathing Apparatus (termed the ACryoBA) designed to provide miners egressing an emergency situation with a two-hour open-circuit SCBA. The ACryoBA utilizes low pressure cryogenic liquid air instead of high pressure compressed air commonly used in most commercially available SCBA. The ACryoBA can also be self-filled from strategically placed Cryogenic Air Supply and Fill Stations (CryoASFS) initially, and thereafter on the egress route approximately every 1 hour and 30 minutes with a 30 minute air reserve. The ACryoBA evolved originally from a one hour Liquid Air Pack (LAP) developed in the 1980’s for Space Shuttle Rescue forces allowing for longer duration and cool air (Figure 1). It was used successfully for many years, through the end of the Space Shuttle Program. The first attempt at a mine egress pack was the Cryogenic Breathing Apparatus (Figure 2). It was to have a low profile, two hours of breathing, attitude independence, and a simple rapid refill while in use. The CryoBA met the two hour criteria, but with difficulty due to excessive heat leakage caused by the dual 4 liter Dewar design. Much of the stored air was lost as it vaporized faster than it could be used. However, the pack was successful in demonstrating both attitude independence and a simple rapid refill capability. The ACryoBA project was designed to continue the progression and address the deficiencies in the CryoBA. The ACryoBA pack was designed to last 2 hours. It minimizes the heat leakage with a single Dewar and thereby requires less liquid air. The single Dewar design also minimizes weight, making it much more manageable by the user (Figure 3). The ACryoBA complies with 42 CFR part 84 NIOSH certification test requirements. One critical requirement for the ACryoBA is operation in positions other than vertical for periods up to 1/4 (i.e. 30 minutes) of the rated service life of 2 hours; this was accomplished by use of new technology called the “attitude independent pickup” which is abbreviated “AIP.” The AIP, developed by BCS Life Support LLC (patent #8,899,226), has a tube going from the top flange down through the center of the Dewar. At the end it has a flexible bellows and a weighted end. Due to the flexible nature of the bellows, the pickup at the end is free to rotate and follow the liquid level around within +/- 90o of vertical."

Jan 1, 2016

By J. C. Agarwal

Major scientific discoveries cannot be programmed. New or frontier technology, however, can and should be planned. It is the vital force underlying the business strategy of a vigorous and profitable mining and metals company. Generally, a radical departure from existing technology is required to 1) Enhance the competitive value of ore reserves, i.e., to turn low grade or marginal reserves into competitive reserves. 2) To increase yield and decrease costs. 3) To decrease investment. 4) To increase mine life. 5) To improve product quality to meet market demands. The very definition of frontier technology implies that it is so different that the old plant, if already in use, will not be directly suitable to use the new technology. Therefore, a priori, we know that the commercialization of frontier technology would very likely involve new investment. The recommended technique of economic and technical analyses, I propose to call "Success Analysis.'' Simply stated, it forces us, by step- by-step procedure, to ask "what is needed to succeed in this particular project." Therefore, the first step is to identify what is meant by "success." The definition of "success" requires an agreement with top management or sponsors of the project as to what constitutes "success" in their minds as contrast to the technical people perception of "success." In general, top management would define success as meeting: 1) The technical objectives, i.e., technology being developed would produce the desired product at the acceptable quality. 2) Financial objectives, i.e., when commercialized, the project's capital cost, operating costs and return on investment are better than the projects they would normally fund. The return has to be better because new technology is inherently riskier. 3) Marketing objectives in that the project will produce product of acceptable quality in timely manner, i.e., scale-up to commercial plant would not cause undue delays in start-up and that large fix-up expenditure would not be required to protect the projected return on the investment. Many projects are started in the laboratory to develop "Frontier Technology" in mineral processing. Most of these efforts are never commercialized. There are many causes of these failures. The major causes are listed below: 1) Inadequate communication with the sponsors of the project so that project objectives are defined and agreed to by all. 2) Ill-defined technical problems. 3) Incomplete development of technology. This has two major components: a. Incorrect scale-up and engineering. b. Inadequate start-up and maintenance planning. 4) Incomplete and over-optimistic process economics. 5) Lack of understanding of the future behavior of the marketplace. 6) Failure to complete R&D effort by the time it is needed. 7) Incorrect projections of human resources required; that is, technical, managerial and operating. 8) Lack of realistic forecast of the expenditures required for commercialization of the R&D effort. These pitfalls can be avoided by comprehensive planning and the use of success analysis technique. The major elements in "Success Analysis" are: 1) Identification of the "need" for new technology. 2) Unbiased and complete scale-up engineering. 3) Acceptable economic feasibility with enough margin of error in the sale prices and operating costs to justify the inherent risks in frontier technology. 4) Timing for availability of investment capital and markets. Many failures in the development of frontier technology are preordained because the initial selection of the research project has been without adequate attention to the needs of the industry. Many very innovative hydrometallurgical processes for recovery of copper from concentrates were developed in the past twenty years. They have not adapted except to a very minor extent because they did not satisfy the success analysis criteria. The copper industry in North America needed a process to compete against high grade ores and to avoid

Jan 1, 1985

By C. Dale Elifrits

Observations made from laboratory analysis of samples of fine-grained argillaceous materials (shales) subjected to various changes in moisture content have been correlated to loss of strength in the rock material. This reaction to a change in in-situ conditions (subsequent to mining) at a mine site combined with the observed relationships of surface-disturbing subsidence features at locations where the predominant overburden material is fine-grained, provides a predictive tool for the subsidence engineer.

Jan 1, 1983

By David C. Grant

During in situ uranium mining using ammonium bicarbonate lixiviant, the ammonium exchanges with cations on the ore's clay. Mter mining is complete, the ammonium may desorb into post-leach ground water. For the particular ore studied, other chemicals (i.e., uranium and selenium) which are mobilized during the leach process, have also been found in the post-leach ground water. Laboratory column tests, used to simulate the leaching process, have shown that aluminum chloride can rapidly remove ammonium from the ore and thus greatly reduce the subsequent ammonium leakage level into ground water. The aluminum chloride has also been found to reduce the leakage levels of uranium and selenium. In addition, the aluminum chloride treatment produces a rapid improvement in permeability.

Jan 1, 1982

By G. P. Richards

RIP is the process of recovering uranium from an unclarified slime pulp which comes in contact with a moving bed of ion exchange resin, T e sand-slime separation of the acid-leach slurry is accomplished through the use of cyclones and spiral, akins type classifiers. Course sands are discarded to tailings and the combined slimes and leach liquor become the IX feed. Uranium in the IX feed is absorbed on the resin and after exhaustion the barren pulp is directed to tails, Following the uranium exhaustion cycle an eluant solution passes through the resin bed stripping the uranium from the beads, The uranium is precipitated from the clarified pregnant eluant, filtered, dried and packaged for shipment to the AEC, Normally, the ore received at the Mines Development plant is a loosely cemented sandstone containing small quantities of clay and bentonite, The ore is easily crushed and requires only a 1/3 load of rods in the rod mill to reduce the ore to grain size, Very little of the ore is recirculated by the 42" spiral classifier.

Jan 1, 1958

By S. S. Peng

To prevent mine floor heave, the mechanisms of floor heave must be fully understood. Based on the field study, the mechanisms of two types of floor heaves are analyzed in this paper. The mechanical models for the two types of floor heaves are developed. The floor heave can be predicted by the developed mechanical models and the control measures are recommended.

Jan 1, 1995

By K. T. Valsaraj, L. J. Thibodeaux

Solvent sublation, the separation process for the removal of two hydrophobic compounds (penta- and trichlorophenols) from the aqueous phase, is discussed, as is a steady-state mathematical model for fire process. Solvent Sublation "'as conducted in a continuous countercurrent mode. The underlying mechanisms, theory and experimental details on the effects of process variables on removal efficiency are reported.

Jan 1, 1994

By F. A. Camisani-Calzolari

South Africa has adopted its own code for public reporting of Mineral Resources and Mineral Reserves in 2000. The South African Code for Reporting of Mineral Resources and Mineral Reserves (SAMREC Code or Code) (SAIMM 2000) is presented here in its local and global context. The main aspects of the Code are listed and elaborated upon. The Code has been written with the participation of the major South African stakeholders in the field including Government institutions, the legal confraternity and the mining industry. The Code is modelled on, and is 90% compliant with, the Australasian Code for Reporting of Mineral Resources and Ore Reserves (JORC Code) (AusIMM 1999). The paper also elaborates on the duties and responsibilities of Competent Persons signing off resource and reserve reports and on the listing requirements of the Johannesburg Securities Exchange (JSE), formerly the Johannesburg Stock Exchange, which has officially adopted the Code. The listing requirements were updated in 2000 to incorporate the SAMREC Code and subsequently in 2002, effective 2003. The ongoing obligations of the JSE for the exploration and mining companies are being compiled and are expected to be effective from early 2004.

Jan 1, 2003

By F. L. Kadey

A discussion of fillers would not be complete without allotting adequate time to that unique and different mineral material, diatomaceous silica. Historical references to its use challenge the aesthetic aspect of man's curiosity; whereas modern scientific tools have provided a dimension of measurement that has motivated many of its more recent applications. A brief review of what is already known is in order. The diatom is a unicellular, plant-like, microscopic organism, related to the algae1. Its natural function appears to be that of a food for other marine or lacustrine organisms, The diatom's "claim to fame" from an industrial viewpoint is dependent on the fact that it secretes an opaline siliceous skeleton that must survive, chemically and structurally, the geologic processes that caused its formation in the first place; its subsequent demise, burial, consolidation, and alteration; and finally, its ultimate exploitation by man--in somewhat that order. In addition to its siliceous nature, the skeletal structure of the diatom possesses a variety of shapes, patterns, and sizes that have not only been the intrigue of microscopists for decades, but have served to set diatomite apart as an industrial mineral; and have reserved for it applications that cannot be satisfied by any other material. Its chemical inertness, its intricate structure, and its intrinsic hardness-coupled with fineness and friability-- are generally known and have accounted for its application in a wide range of filtration and filler uses. The increasing use of the electron microscope has considerably expanded our knowledge of heretofore unseen secondary and tertiary structure of submicron dimension in the diatom valve. The development of electro-sensing methods of particle size measurement which seem to supersede sedimentation and microscopic techniques has portrayed size distribution in a more realistic light. Interest in the surface chemistry of these silica structures has further strengthened our understanding for certain uses. Thus, new tools and ideas have made possible the introduction of diatomite into such sophisticated technologies as that of chromatographic supports, its improved utility in paint applications for the control of gloss and sheen, and its usefulness in the entirely new concept of "Dry Acid Concentrates." Each of these applications has been discussed elsewhere before people particularly interested in analytical chemistry, in paint, and in liquid handling, respectively, where the diatom has been a means to an end. The emphasis here, before the mining fraternity, however is on diatomite as a raw material with reference to the uses mentioned above. It is therefore toward an awareness and understanding of diatomite properties pertinent to these newer filler applications that this paper is directed.

Jan 1, 1967

By Melvin A. Jennings

Even though the title of this paper is quite long, the ideas presented herein are very simple. In fact, it occurs to me to be somewhat humble about coming before such a distinguished group with such a simple presentation. However, the application of these ideas has proven useful in at least two copper flotation plants. The purpose in presenting this paper is to inspire some interest in the great stores of data chat the Mining Industry often accumulates without making any attempt at analysis. Unfortunately, many milling engineers rely rather heavily on percent recovery as a strict measure of a concentrator's relative performance. The fallacy of this reasoning is not difficult to see since, by definition, percent recovery is a function of feed assay, tails; and concentrate grade. If copper tailing is constant, and it very nearly is for a strictly sulfide copper ore, percent recovery must fluctuate almost directly to the feed assay. The point that I wish to make here is that it is very seldom justified to compare the percent recovery figure from one period of time to another without considering the difference in feed assay. The problem of comparing results is even further complicated when the ores are of mixed oxide and sulfide mineralogy.

Jan 1, 1978

By Ian Sheppard, Kugan Kuganathan

The Mount Isa Rocky Paste Fill (RPF) was one of the five fill options investigated for the Enterprise Mine filling between June 1996 and September 1996. Co-disposal of deslimed cemented tailings (CHF) and suitably graded rockfill (RF) in certain ratios produced the rocky paste fill. The RPF behaved like a cohesive paste with very high proportion of rockfill in the mix. Several large-scale mixing trials and drop tests proved that the rocky pastefill results in a homogeneous fill mass after placement. Segregation of RF was a common problem with MIM's traditional cemented rock fill (CRF), which is a combination of CHF and RF. The segregation was eliminated and a non-segregating paste like fill was created by optimising the particle size distribution of RF, and combining the RF and the CHF in optimum ratios. In rocky pastefill, the excess water in the cemented deslimed tailings slurry is taken up by the rockfill as the surface moisture on the rockfill particles and also as pore water between the particles. This results in thickening of the CHF, and the resultant mix is a non-segregating cohesive paste, which can easily spread to any horizontal distance inside a stope at a very low surface angle. The rocky pastefill releases no free water and relatively more pervious than the standard CHF due to rockfill component. With an average cement addition of 1.5 to 2% the rocky pastefill can develop higher strengths over 1Mpa. The rocky paste fill is applicable in many situations and can accommodate a variety of coarser materials that would be available in different mine sites. This paper present the research work and the experience associated with the rocky paste fill, and gives clear design principles for any potential users.

Jan 1, 2001

By Suzanne Smith, Frank C. Fantauzzo

Introduction America's workforce is the heart of the nation's economy. The health of its members is a matter of national priority. Statistics show that the most common cause of job difficulties is excess use of alcohol or other drugs. Up to 75% of these troubled employees can be returned to productive careers at little expense and with great benefit to their industries. Of the 1.5 million private corporations in the US, only about 500 have alcohol treatment programs. Even fewer have drug abuse programs. It is time that the myths and prejudices surrounding alcohol and drug abuse are dispelled and help is offered. Corporations and labor unions are now finding that programs to treat these diseases benefit both the employees and the industry. The employee derives health and job security. The company sees increased productivity and decreased costs in sick pay and absenteeism. Unfortunately, three-fourths of the nation's 90.5 million workers are employed in establishments of fewer than 500 employees. In these settings, it is unlikely that either management or the unions will take the initiative in developing programs. Alcohol alone affects the health and productivity of nearly 8% of any workforce. This translates to more than 5 million employees in small business. These workers present an opportunity and a challenge. Alcohol abuse costs the nation nearly $116 billion annually. Seventy billion dollars is attributed to lost production. Medical expenditures related to alcohol are estimated to be nearly $13 billion. The National Institute on Drug Abuse (NIDA) estimates the cost of substance abuse to industry to be in excess of $4 billion a year. In addition to its economic impact, substance abuse has serious personal and social consequences. The mining industry experiences the same exposure as other industries to alcohol, drug abuse, and other employee problems. However, the existence of these problems poses special hazards because of the unique conditions found in mining. Mining has many safety and health hazards. Employees must have full control of their faculties and give full attention to the tasks at hand. Designing employee assistance programs An Employee Assistance Program is a cost-effective, confidential, early intervention system. It is designed to help employees

Jan 11, 1987

By Robert R. Munro

Introduction Traditional aggregate sources - riverbeds and alluvial fans - located close to developing urban centers are being foreclosed to mining. As sand and gravel reserves are depleted, nearby production plants cannot secure additional, adjacent reserves and are being forced to close down. The sand and gravel industry, in many respects, is its own worst enemy. It promotes development, street paving, home building, and industrial and commercial centers. Economics make us favor developments close to our operations. Thus, we encourage development by our neighbors, who soon become our detractors. Current Aggregate Mining Problems Urban development is not compatible with sand and gravel mining. Neighbors dislike the view of pits and quarries, and they complain about dust, noise, and trucking. In general, the neighbors are not happy being close to an aggregate source. This is reflected in land use or zoning laws. In most localities, mining requires a special-use permit. Public hearings are required before a legislative body. If a large group of opponents show up, legislators will often deny the land use. Urban areas are seeing traditional close-in sand and gravel sites becoming no longer available for industry. A parallel situation is also developing in most urban areas. That is, the not-in-my-backyard attitude toward landfills. As urban areas mature; a significant amount of change takes place in the physical makeup of a city. Streets and parking lots deteriorate and need repaving. Curbs and gutters need to be relocated. This necessitates a place to dispose of excess, or old, paving and structural material. Since landfills have become at least as difficult to permit as sand and gravel sites, they are becoming remote from urban areas. A significant portion of the structural material that needs to be disposed of is concrete and asphalt. This material is heavier than other materials. Thus, the cost of moving a large volume of very heavy material to a landfill becomes very expensive. In California, dump truck transportation is regulated by the State Public Utilities Commission through minimum rate tariffs. A rule of thumb for estimating the cost of such transportation is once the material is loaded, the extra kilometer (mile) costs $0.09/t ($0.08 per st). Thus, to haul an 18-t (20-st) road an extra 32 km (20 miles) will cost about $32. Because of its remote location, the cost of hauling aggregates to the point of use in an urban area becomes excessive - about the same as hauling the material to a landfill. Here is a classic example for synergism. If we could save the transportation cost of heavy demolition material by disposing it relatively close to the central city (its source), and at the same time provide an aggregate source close to the central city (its point of use), two difficult economic situations can be solved. Thus, the develop¬ment of recycling concrete and asphalt. Mining Concrete and Asphalt There are two methods of mining concrete and asphalt. The first is to pick up the old pavement in pieces. Thin, cracked pavement can usually be lifted from the grade with a front-end loader. It will break up into manageable-sized pieces. With heavier pavement, it is sometimes necessary to intentionally break it up with a stomper or heavy ripper. The pieces are loaded into heavy dump trucks and shipped to the crushing site. Again, a front-end

Jan 7, 1984

By Dale K. Fields

With today's technological advances in mineral processing equipment, there is an increasing demand for accurate system control. This can only come about through representative sampling. The purpose of this paper is to guide you in the selection of sampling equipment and outline design parameters for the cutters used in dry and wet sampling without adding redundant mathematical probability formulas to your files. Special attention will also be given to the equipment used in conjunction with samplers and sampling systems, such as feeders, crushers, chutes, launders, and controls.

Jan 1, 1979

By M. D. Scott

Lornex Mining Corporation operates an open pit porphyry copper mine in the Highland Valley southwest of Kamloops with a rated capacity of 43 500 TPD (48,000 TPD). It went into production in April 1972. Its concentrator consists of two grinding and flotation circuits in parallel each composed of a 6 000 KW (8,000 HP) 9,75 m (32 foot) diameter by 4,724 m (15'-6") semi-autogenous primary mill feeding two 3 000 KW (4,000 HP) 5,029 m (16.5 foot) diameter by 7,01 m (23 foot) secondary ball mills each feeding a bank of flotation cells. ,The original tailings system picked up the tailings from the flota¬tion circuits in a concrete collection box in the mill and carried the 36% solids density by weight slurry 488 m (1,600LF) through a 1100 mm (42 inch) diameter wood stave pipeline on a .46 percent slope to three 99,06 m (325 foot) diameter center drive thickeners. From the collection box under the thickeners the tailings line con¬sisted of three sections, carrying 50% solids density slurry. The first section consisted of 1460 m (4,800 LF) of 910 mm (36 inch) asbestos cement pipe for gravity flow from the thickener under flow elevation of 1252,4 m (4,109 feet) to the first pump station at elevation 1207,6 m (3,962 feet). Eight concrete drop boxes were used to limit the maximum slope on the pipeline to 0.5 percent.

Jan 1, 1976

THE PENNSYLVANIA STATE UNIVERSITY, 101 MINERAL SCIENCES BUILDING UNIVERSITY PARK. PENNSYLVANIA 16803 To the Editor: With respect to the Fenvessy and Schwab article, I offer the following: As thorough as the study may be, it still has a glaring weakness. The presumption of constant supply in face of falling demand - their "low growth" case - is just wrong. It does not allow for the rapid migration, by transfer and change of major, from former high-demand programs, such as mining, to programs that have more recently obtained the cachet of job security. The figures that are shown for rapid growth in mining engineering enrollments in the period 1970-1981 are, no doubt, correct and reflect a rapid inmigration of students into mining. A similar out-migration, which began in 1982, from mining to other engineering and science disciplines is not factored into their study. Given 1983-84 enrollments, which can already be documented, it is clear that the low-growth case will, by 1985, be 50% or less of 1981. I wish students would pick their majors on the basis of their own individual abilities and interests rather than rushing lemming-like to programs that are reputed to have jobs. In the end, students will have better jobs and careers if their college majors match their talents and we, in the academic side of things, will have a livelier and more dedicated student. Lee W. Saperstein Professor and Chairman of Mining Engineering UNIVERSITY OF MISSOURI-ROLLA To the Editor: I write concerning the recent article on future demand for graduates in the mining industry. The article is, unfortunately, inaccurate because of the erroneous assumptions it makes in its basic premises. To cite but two of these, class sizes will not continue at their current level, but will, in fact, alter dramatically as a function of the perceived immediate job market rather than the future trend, so that enrollments are already below those predicted. Secondly, it is patently wrong to assume that everyone who gets a degree in the mining field will continue until retirement to work in that field. People who do not have a job in the industry will get work elsewhere and often do not come back. Others will later move to different areas. My major argument, however, deals with the underlying assumptions and methodology of the survey itself, with the concomitant challenge to the subsequent conclusions. It is no great secret that the technological world is undergoing a dramatic revolution. Computer use is rapidly spreading to the point where the microcomputer will be an integral part of every mine engineer's desk. Such a tool, which for optimal benefit must be operated by knowledgeable mining engineers, will make mining much more of a science than the current level. To remain competitive, mines will increasingly rely on higher level deci-

Jan 1, 1984

By Virgil A. Bilyeu

The Pan American Mine, in southeastern Nevada, is about 26 miles west southwest of Pioche, Nevada, and about 266 miles southwest of Salt Lake City, Utah. The mine is located in the Comet Mining District, and since the ore occurrence is generally the same in the Comet and well known adjacent Pioche Mining Districts, the history of the two shall be considered the same. The Pioche District began about 1869 with the production of high grade gold and silver from fissure veins in the Cambrian Prospect Mountain quartzite. Peak production was reached in 1872 and then declined with sporadic production until 1924, when Combined Metals Reduction Co. shipped its first, complex sulphide ores mined from the CM bed at Pioche. Extensive ore bodies in this CM bed attracted interest in the same bed in the Comet District. Small pockets of high grade silver-lead were mined from fissures cutting the CM and other limestone beds above. Exploration in the CM beds at this time proved a large area of mineralization too low grade to be considered ore.

Jan 1, 1967