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By John R. Bartels

This report discusses an improved method for rerailing underground railcars devised in a joint effort by the Bureau of Mines and Hoesch MFD. This improved method utilizes a lightweight hydraulic ram with hand-pump activation to move a bridge-mounted roller carriage in conjunction with steel-reinforced air-lift bags. This method provides a lightweight portable system in which only two workers are required to perform the mine car rerailing operation. Because of the very narrow confines in underground mines, use of overhead cranes and other surface rail techniques is not possible. This new system is designed for very low profile work, and provides the necessary lifting force from light- weight compressed-air bottles.

Jan 1, 1985

By A. W. Randall

Geological Aspects of Ore Reserve Estimates of Pine Point District Zinc- Lead Deposits, N.W.T. Zinc-lead ores of the Pine Point District, Northwest Territories, Canada are hosted in paleokarst cavities within a Middle Devonian carbonate barrier complex. Of the nearly 100 deposits found, most are irregularly distributed along two main regional stratigraphically controlled trends. The ores, which occur predominantly as open space filling, form deposits most of which average one million tonnes in size with an average grade of 10% combined zinc plus lead. Geological features related to karsting control not only distribution of deposits but also their shape, size and grade. The higher grade ore in these deposits generally occurs in a relatively small core area. Consequently, accuracy of reserve estimation is dependent on drill hole density and understanding of karst geometry. Several case examples will be reviewed to demonstrate the relationship between shape, size and grade of deposit, geological reserves and drill hole density, along with a discussion of geological ore reserve estimation methods.

Jan 1, 1985

This publication summarizes the research (in-house and contract projects) programmed by the Bureau of Mines for fiscal year 1985 (October 1, 1984-September 30, 1985) under its Health and Safety Technology Program. The objective of these projects is to provide an ordered and sequenced advance toward the Bureau's overall goal of providing the system technology required to create a more healthful and safer working environment for the Nation?s mining and minerals processing workers.

Jan 1, 1985

Safe operation and system integrity are two important properties of a mine hoist electrical system. Previous methods used to assess these systems, though rare, have involved extensive downtime and required skilled personnel. The recommended design considerations presented in this report are for a proposed automated system that will perform real time measurements, calculations, and recordings of pertinent performance data. Included are equipment installation and test procedures to be used with the system. The report also contains descriptions of the hoist performance criteria, and how they are to be collected.

Jan 1, 1985

By Mark S. Sanders

This report discusses the development and testing of prototype gloves for underground mining work. An analysis of HSAC hand-finger injuries revealed three high-risk jobs: laborer, mechanic, and roof bolter. Laboratory tests of dexterity and protection were performed using six off-the-shelf gloves. Two prototype gloves were developed. Both were Kevlar-cotton blend knit gloves. One had polyvinyl "Ks" screened on the palm and fingers, and a hand pad sewn into the palm. The other prototype had the palm and fingers coated with a sol id layer of polyvinyl and had no hand pad. Field tests revealed that the solid-coated gloves were preferred by workers, but that the polyvinyl melted when working with hot drill steels.

Jan 1, 1985

This Bureau of Mines investigation addressed two primary issues of air velocity measurement in mines: the determination and use of correction factors, and the development of guidelines for the selection of a suitable site at which the measurements should be taken. Other facets of the investigation included a comparison of measurement methods and devices, and aircourse cross-sectional area measurement. The study consisted of theoretical, laboratory, and in-mine investigations. The measurement devices included in the experimental phase were vane anemometer, vortex shedding anemometer, a prototype thermoan-emometer, smoke tube, and oil of wintergreen sprayer. The measurement methods included single-point centerline, timed-point traverse, continuous traverse for the anemometers, and various distances and cloud positions for the smoke tube and oil of wintergreen devices. The study resulted in guidelines for measurement site selection that are applicable to most inmine situations. It also showed that the use of correction factors is problematic. There are many potential pit-falls and there are cogent arguments against using certain correction factors. However, generalized correction factors were developed that can be successfully applied in routine ventilation work, provided that their use is properly understood.

Jan 1, 1985

By Dean H. Ambrose

This Bureau of Mines publication summarizes the status of mine electrical equipment reliability research. Failure rate data were estimated from theoretical, laboratory, and field studies. Tables are presented listing reliability characteristics of molded-case circuit breakers, undervoltage relays, ground check monitors, cables, motors, and control circuitry. Application of failure rate data is shown in tables listing maintenance scheduling intervals of components and components that are most sensitive to the probability of hazardous voltages on power distribution systems in the mines. Complete, accurate, and appropriate failure rates on mine equipment are of the utmost importance for reliability evaluations.

Jan 1, 1985

By J. T. Kline

This paper will present a review of the underground leaching of remnant copper mineralization left as a result of the block cave mining operation at the Lakeshore Mine in Casa Grande, Arizona.

Jan 1, 1985

By R. Altman

A Brookfield viscometer fitted with a stainless steel bob was used to measure the viscosity of industrial lead blast furnace slags between 1126 and 1298°c. Slag oxidation state was characterized by first annealing the? slag samples at 750°c in sealed copper tubes in order to precipitate magnetite crystals. The magnetite concentration was then measured on an Outokumpu Saturated Magnetic Analyzer. Using an Arrhenius-type equation, a viscosity model was developed by regression. The equation below accounted for 75% of the variability in the data used to generate the regression coefficients and, on average, could predict viscosity within ± 12% of the measured value. The greatest difficulty encountered in measuring viscosity was due to the occasional presence of solids in the slag which caused, at times, erroneously high viscosity measurements. Precautions to minimize this problem are outlined in the text.

Jan 1, 1985

By Daryl R. Tweeton

The Bureau of Mines is investigating possible applications of geophysics to monitor leachate during in situ mining. Tomographic reconstruc-tion of seismic or electromagnetic crosshole data appears applicable. The tomographic program BOMTOM (Bureau of Mines tomography) was written and then used to investigate reconstructions with synthetic travel time data. The calculations confirmed that without constraints, crosshole data do not provide unique solutions. The solution is not determined solely by the data, but is also influenced by the velocity guesses starting the iterative solution procedure. The effectiveness of constraints in combatting nonuniqueness was examined. The requirement that the velocity not vary laterally at the top and bottom of the pixel grid was effective. This constraint is realistic when the top and bottom of the grid represent dry and saturated re-gions, respectively. Limiting the maximum velocity improved reconstructions, but may not be applicable in practice. BOMTOM uses the simultaneous iterative reconstruction technique (SIRT) with straight ray paths. The program is efficient in use of memory, and can be run on a personal computer. A source code in FORTRAN is listed. A source code in BASICA and compiled executable codes in both languages are available from the Bureau's Twin Cities (MN) Research Center.

Jan 1, 1985

By A. J. Fejes

The purpose of this Bureau of Mines report is to provide mining industry personnel and regulatory authorities with a subsidence-reference list and annotated bibliography that will aid them in locating subsidence information and in developing their own subsidence information sources. Over 700 references are listed in the Bureau's subsidence information center bibliography; approximately 600 of these references were obtained for assessment. Of these 600 references, 167 were selected to be rated, categorized, and annotated. All literature referenced in this report was published prior to 1984. Table 1 is a cross - referenced index that classifies and rates selected references with respect to specific keywords. References are rated not on quality of content but rather on applicability to given subject areas. Appendix A is an annotated bibliography of the references listed in table 1 and provides further information of each article to aid the user in selecting articles for specific areas of subsidence technology. Appendix B is a copy of the subsidence information center bibliography.

Jan 1, 1985

By Howard Keele

"The Whitewood Mine near Edmonton, Alberta, is owned by TransAlta Utilities Corporation and operated by Manalta Coal Ltd. Approximately 2 million tonnes of sub-bituminous coal is supplied annually to the Wabamun Generating Plant. A high water table, high groundwater pressure, and structural folds contribute to stability problems in the fine-grained overburden. Significant increases in coal recovery have been achieved in recent years through improvements in water management and mining methods. Agricultural capability of the post-mining landscape has also been improved following the completion of mining/ reclamation activities. Introduction The Whitewood Mine, located to the north of Lake Wabamun and seventy kilometres west of Edmonton, Alberta, is owned by TransAlta Utilities Corporation and operated by Manalta Coal Ltd. Figure 1 shows the location of the Whitewood Mine with respect to the city of Edmonton. The mine presently supplies two million tonnes annually of sub-bituminous ""C"" coal to the 582-megawatt Wabamun Generating Plant located adjacent to the mine. The area is characterized by a high water table-, rolling coal seams and an overburden that consists of muskeg, clay and various sedimentary layers of sand, gravel and fine-grained sandstone. These distinctive characteristics require careful attention in order to not only meet the coal delivery requirements of the Wabamun Generating Plant but also to do so economically. Historical Background A small-scale underground coal mine was opened in the Wabamun area in 1910 by the Conner Coal Mining Co. Ltd. Underground operations were continued by several operators until 1948 when the Alberta Coal Co. Ltd. opened a strip mine which was subsequently taken over by the Alberta Southern Coal Co. Ltd. in 1951. The small-scale strip opera"

Jan 1, 1985

By Gary L. Hundley

The Bureau of Mines has devised and demonstrated an ammoniacal sulfate leach process for recovering nickel and cobalt from low-grade domestic laterites. Solvent extraction of cobalt, one of the process steps, requires the reduction of hexammine complexes of C03+ to C02+ in an ammo-niacal leach solution. Previously, reduction was accomplished using cobalt metal shot in a column. This report presents experimental results and an economic evaluation comparing two alternate techniques with the shot column: (1) an electrolytic reduction cell with an extended surface area cathode and (2) direct electrowinning from purified leach solution using a cell with a fluid bed cathode. The second alternative eliminates the conventional solvent extraction-electrowinning steps. The costs of the three methods, based on the requirements of a pro-posed commercial-sized plant, including all unit operations, were deter-mined by the Bureau's process evaluation group. The operating costs for the shot column, $1.19/kg Co, and for electrolytic reduction, $1.20/kg, are essentially the same, but the cost of direct electrowinning, $3.77/ kg Co, would eliminate this method as a practical alternative. The cap-ital cost of approximately $14.4 million for reduction in a shot column is much higher than the approximately $4.4 million for electroreduction.

Jan 1, 1985

By Keith L. Harris

Economic activity in the United States picked up in the third quarter, according to the latest estimate released by the Department of Commerce. Real gross national product (GNP)--the Nation's output of goods and services--grew at a seasonally adjusted annual rate of 4.3%, or $17.6 billion, compared with a rate of 1.9% for the second quarter of 1985 and 1.6% for the third quarter of 1984 (table 1). The 4.3% rate is one percentage point above the preliminary estimate reported in the August/September issue of Minerals and Materials. Most of the upward revision was due to the change in business inventories and Government purchases, while the figure for net exports was revised downward substantially. The 4.3% growth bettered by 1.5% the average rate of growth in GNP from 1974 through 1984 and was 1.1 % above that of the period from 1975 through 1984 and 0.7% above that of 1980 through 1984. Of importance to the minerals industry was the $14.4-billion growth in personal consumption expenditures, $10.2 billion of which was for durable goods (especially domestically produced automobiles) and the growing residential investment. The net export deficit continued to grow, however, and investment in nonresidential structures, producers' durable equipment, and business inventories declined. Prices, as measured by the GNP fixed-weighted price index, increased at an annual rate of 3.1% in the third quarter, compared with 3.9% in the second quarter. The slower rate of inflation resulted mainly from a decline in energy prices, following second-quarter increases. Fourth-Quarter Prognosis Many of the economic data available for October and November indicate that the economy is growing modestly and will continue to grow over the next 3 to 6 months. The composite index of leading indicators, designed to predict economic activity within 3 to 6 months, rose 0.3% in October, the sixth consecutive monthly advance, according to the Department of Commerce. Six of the 11 available leading indicators were positive: Stock market prices rose, as did sensitive material prices, credit outstanding, and manufacturers' new orders for consumer goods and materials; initial claims for unemployment insurance decreased, and firms were getting slower delivery of goods. Four of the indicators were negative: Business formations, homebuilding permits, contracts and orders for plant and equipment, and money supply all declined. The average hours worked per week, already at a high level, remained unchanged.

Jan 1, 1985

By William A. Vogely, Robert T. Deacon, Walter J. Mead

Oil and gas together are the most important energy sources consumed in the United States. In 1983, 67% of total energy consumption was represented by these two resources (43% was oil and 25% natural gas), while coal accounted for only 23% of U.S. energy use. All other sources (hydroelectric, nuclear, geothermal, wood and other waste products) accounted for only 10% (U.S. Department of Energy, 1983, p. 1). In this chapter we address the issue of regulation in the oil and natural gas sectors of the U.S. energy industry. In addition, we analyze the cartel characteristics of the Organization of Petroleum Exporting Countries (OPEC). If OPEC is an effective cartel, then U.S. oil as well as substitute energy prices, production, and consumption will be affected by cartel action. Further, as the nation learned in the 1970s, major changes in oil prices produced major disturbances in other sectors of the U.S. and world economies. Consequently, it is important to determine whether the roughly ten-fold increase in nominal prices that occurred in the 1970s was the result of cartel action, the result of normal economic forces adjusting to the fact that the world was running out of cheap oil, or some combination of the two. Furthermore, the presence of OPEC- associated oil price increases is related to regulations that were imposed on the energy sector during the decade of the 70s. THE RATIONALE FOR GOVERNMENT INTERVENTION Economists have traditionally judged the state of an economy to be efficient if it is impossible to improve the welfare of any one member of society without harming someone else. Any economy that satisfies this condition is said to be Pareto efficient, after the Italian economist Vilfredo Pareto who first gave rigorous attention to such questions (see Chapter 4.10). It is easy to see why an economy that fails to satisfy this condition could not be efficient; by definition, it would be possible to alter the allocation of resources in a way that improves everyone's welfare.' Much of the appeal of this weak efficiency criterion is that it avoids comparisons of levels of well being among different individuals. The cost of such generality, however, is that in any given economic system a wide array of different Pareto efficient states will typically be attainable. In the simple Robinson Cursoe economy of the undergraduate textbook, for example, efficiency could just as easily be attained in the case where most of the island's resources are owned by Friday as in the case where they are under Crusoe's control. However, the distribution of welfare among the two inhabitants would obviously be quite different in the two situations. Such equity issues cannot be settled on objective or scientific grounds. To decide which distribution of welfare is socially "best" an explicit value judgment is needed. It is useful to keep in mind the preceding distinction between efficiency and equity issues when analyzing the role of government in a market economy. Decentralized market processes will not necessarily result in a distribution of welfare that society considers just. For this reason a potential role for government lies in the redistribution of income among individuals. In some circumstances, however, market pro-

Jan 1, 1985

By John S. Brock

INTRODUCTION The Oxford Dictionary says that the word "promoter" has usually been used in an opprobrious sense since at least 1876. This popular image of mining promoters is of cigar-chomping shysters and Brooklyn-Bridge vendors, improving their standard of living with the aid of funds raised through the sale of stock to little old ladies. It is unfortunate that mining promoters are considered crooks until they can prove their integrity and honesty by finding a mine. A common rule of thumb states that for every 1,000 prospects, 100 come to be drilled, and one becomes a mine. However, it is also a statistic that there have been mining promotions, where money raised has gone elsewhere than into the ground; Junior exploration companies can be handy vehicles for unscrupulous financial activity. One must remember though that every stock exchange has had its share of sound mining promotions that, because of the one in 1,000 odds, have failed for legitimate reasons. The promoter must be able to rationalize the worth of a mineral discovery which, on an industry- average basis, probably cost more to find than the discounted value of its net return, which return is not an assured percentage of invested capital, and furthermore, is ultimately from a wasting asset. So, it is easy to understand why the promoter must constantly justify the credibility of his operation to his grubstakers during the course of the "five phases of exploration," those being (1) euphoria, (2) disillusionment, (3) search for the guilty, (4) punishment for the innocent, and (5) distinction for the uninvolved. The promoter with the exploration organization that does not have the benefit of positive cash flow, by definition for the sake of this article, works for a promotional outfit, a Junior Company, that must raise its exploration budget from a variety of sources. Promotion, as discussed here, will not entirely refer to the formation and operation of a joint- stock company but rather to the overall methods of raising risk capital for mineral exploration ventures from outside sources. THE NECESSITY OF PROMOTION In Canada, the publicly financed Junior Company has had an enviable record of mine-finding success. In the Province of British Columbia alone, the discovery of fifteen out of twenty-four mines has been as a result of the activity of the Junior Company (B. C. & Yukon Chamber of Mines, 1977). In the Province of Ontario, one research study indicated that between 1951 and 1974 the 'Juniors' spent only 28 percent of the total exploration funds but were responsible for 62 percent of all economic discoveries (Freyman, 1978). The reasons for the success of the Juniors are tied to a variety of factors, the main one being personal initiative based on incentive. In other words, the principals, or their employees have 'a piece of the action.' The smaller companies can operate faster and more efficiently than their larger counterparts. The Junior Company is also destined to take some bigger risks, the 'long shots,' many of which efforts by virtue of the Junior's perseverance coupled with a touch of 'ore is where you find it' philosophy, result in major discoveries. The individuals, syndicates, private and publicly financed Junior Companies, because of high costs of exploration and development, cannot hope to finance most mineral prospects all the way to production. Exceptions do exist, those being the lower capital cost, small, high-grade deposits. Private investors and publicly financed Junior companies, therefore, can usually afford to finance most exploration through the initial drill-testing stage. The major resource company will enter a mining deal with a Junior Company usually by way of option or joint venture agreement, and will finance to production to earn an equity in the prospect or the Junior Company or both. The conventional lending institutions, banks and government agencies, will usually only participate through loaning a portion of capital

Jan 1, 1985

By Andrew Cecala

The Bureau of Mines performed tests to compare the effectiveness of steam and of water sprays to reduce respirable dust levels at mineral processing plants. By applying 0.22 wt pct water vapor as steam to product material, a 64-pct respirable dust reduction was recorded. By applying the same amount of moisture with water sprays, only a 25-pct dust reduction was recorded. By increasing the moisture content up to0.5 pct using water sprays, the dust reduction was increased to 55 pet, which was still less than the dust reduction achieved by adding less than half that amount of water in the form of steam.

Jan 1, 1985

By J. A. Herbst, H. R. Cooper, R. J. Brison, R. W. Harper, K. P. Ananthapadmanabhan, W. C. Hellyer, B. H. Bergstorm, D. M. Hopstock, H. Rush Spedden, W. C. Hellyner

Scope of Section The physical characterization of an ore or mineral mixture in such detail that mineral processing may be effectively applied to create more useful products is one part of the technology of sampling and testing. In addition, the evaluation of the multitude of separation processes, both physical and chemical, combined with ancillary opera¬tions and performed on samples at a laboratory scale, is another part of the testing procedure. Although analytical techniques provid¬ing quantitative determinations of elemental compositions are an im¬portant and necessary supplement to any testing program, that field of endeavor is a well-developed, separate entity beyond the scope of this Section. Sampling procedures cover the practice of selecting representative quantities of test materials in the field to evaluate mineral deposits, and extend to techniques of obtaining process samples in slurry and bulk ore as part of process evaluation. The same techniques are appli¬cable, of course, to standardized methods of metallurgical accounting. Sampling is also an important facet of successful on-line measurement of slurry properties such as assays and particle size in the practice of automation. However, the sampling methods in this case can be different from those needed for precise testing and accounting pur¬poses. Sampling was well defined in Taggart's Handbook as "the opera¬tion of removing a part convenient in size for testing, from a whole which is of much greater bulk, in such a way that the proportion and distribution of the quality to be tested (e.g., specific gravity, metal content, recoverability) are the same in both the whole and the part removed (SAMPLE). The conditions of the more stringent definition, that the sample shall be completely representative of the whole as regards all aspects save bulk, are practically never fulfilled when heterogenous mineral mixtures are sampled." Taggart's Handbook of Mineral Dressing, Section 19, "Sampling and Testing," continues to be a very useful compendium of principles and techniques, particularly as applied to manual methods for han¬dling samples. In the intervening years since its last revision, substan¬tial progress has been made in both the theory and the techniques; thus, this current contribution is designed to be an extension of the earlier work, yet complete enough to provide procedural guidelines to methods of continuing validity. Although basic principles of testing remain unchanged, the meth¬ods of applying those principles have undergone great change. New testing equipment has become available, yielding a greater precision of results. Testing methods have been refined which, in many cases, allows for a valid scale up of flowsheet designs without the necessity of costly pilot or prototype plant development. Justification for a Sampling and Testing Program* The proper evaluation of a mineral property is a complicated process. It often is done on a team basis with the exploration geologist, mining engineer, mineral process engineer (extractive metallurgist), economist, and product utilizer (ceramist, chemical engineer, chemist, metallurgist, etc.) all represented. The mineral processing engineer is a key member because he can provide a go no-go answer to the question, "Can this ore be processed economically?" In addition, his judgment on the response of even the initial sample to processing can be an invaluable guide to the proposed process and its mutations. Since the capital investment and operating costs are so sensitive to the type of process used, the judgment of the mineral processing engineer forms an important part of the early evaluation of the profitability of a new mining venture. This early estimation of the processing approach is all the more important since, for some metalliferous ores, the capital investment for mill, smelter, water supply, and tailings disposal exceeds the cost of the mine. At present, for commodities such as coal, the reverse is true. There is a smaller capital investment for the coal preparation plant than for the mine. In general, both the capital and operating costs escalate very rapidly in the following order: gravity concentration of alluvial deposits (e.g., dredging), gravity concentration of lode ores, flotation, simple hydrometallurgical processes, and complicated hydrometallurgical and pyrometallurgical processes. The latter two processes may cost 100 to 1,000 times more per ton treated than processing of a simple alluvial deposit. This dictates that the valuable mineral be concentrated as much as possible to minimize the total tonnage treated in the more expensive operations. Within each of these ore-processing categories there is a wide range of process sophistication and hence of capital and operating costs. Perhaps the greatest variations are in the chemical processing of ores. These range from the simple leaching of a copper waste dump to very sophisticated hydrometallurgical processing of ores in increasing order of cost. Because the overall cost of a mining venture is so sensitive to the process selected, it is essential that the mineral¬ processing engineer evaluate the ore in the initial stages of the development of an ore body. As better samples become available, he must continually revise his estimate of the process to be employed. The sampling and testing process must be a necessary and continuing activity throughout the life of a project. One fundamental aspect of nearly all mineral deposits is the inherent variability of the mineral assemblage and composition. A utopian goal of any processing plant is to have the process so flexible and so well-defined that an automatic process control system can optimize the economic recovery at all times. Since this is rarely possible, a continuing or at least a periodic testing program is desirable. Variables to be considered are: 1) Ore body inconsistencies. 2) Zonal variations. 3) Feed variations from mining plan or methods. 4) Variable performance of processing units due to wear. 5) Seasonal or other changes affecting processing conditions such as water quality, temperature, etc. 6) Changing market conditions for product quality or byproducts. 7) Technological advances in processing methods or equipment. 8) Increasing demands for environmental control. 9) Changing economics of competitive processes, of supplies, of capital investment vs. labor costs, etc. Sampling Procedures Preliminary Guidelines for Sampling Ore Deposit Studies. t At a very early stage, it is essential that the mineral processing engineer receive a sample of the ore. This may be a portion of the diamond drill core or a split from the trench, pit, churn drill, channel, or sheet sample. Even a grab sample may have some value, but it should be selected by the mining engineer or exploration geologist to be as representative of the ore body as possible within his best judgment. The sample delivered to the process engineer should have been subjected to as little prior crushing as is practical since fine sizes are difficult to concentrate. In addition, finely ground ores are readily oxidized and thus may give misleading test results. Furthermore, ground samples may make it impossible to eval¬uate either the comminution or the coarse-gravity concentration pro¬cesses. For an initial evaluation, a good deal may often be learned from a sample of only a few pounds if that is all that is available. To obtain the maximum information from a sample, its selection should be carefully discussed with the mineral processing engineer. In addi¬tion to being as representative as possible, the mineralogically distinct samples should be carefully segregated rather than composited. Since drastically different processes are often needed to process samples of differing mineralogy, considerable care and time must be exercised during this sample collection step. The segregation of samples showing gross mineralogical differences, such as the oxide caping on a sulfide deposit or a laterized zone, is easy. It is the more subtle changes in mineralogy that can often elude the field man. Yet these differences are often sufficient to dictate that an entirely different type of process be used. Obviously, the selection of these initial samples for ore testing and mineralogical studies requires that it be done by a man of consider¬able experience and judgment. While the mining engineer or field geologist is collecting these samples, he should also note and convey to the processing engineer such details as water quality and availabil¬ity, terrain, potential mill location, tailings-disposal areas, case of transportation, etc. As the property is developed with additional drill holes, adits, etc., larger and more representative samples will be required to develop the ore-processing flowsheet more adequately. If pilot-plant studies are required, a very large sample may be necessary. Though the type and amount of sample collected for flowsheet development investigations vary widely, gathering a representative sample of the ore body is a prime requisite for any process development effort. The process developed for any given ore body is only as reliable as the sample on which the flowsheet was based¬

Jan 1, 1985

By Willard C. Lacy

Rather than attempting to present a summary of the many and highly varied papers that have been presented at this symposium on sampling and grade control, I will attempt to extract the general philosophy of analysis and approach, and attempt to identify the trend of future developments. First, the term "sampling" is used with its broadest connotations. A sample consists of a representative portion of a larger mass, and must represent the mass not only in the grade of contained metals or minerals, but also in all other respects in terms of mineralogy and mineral quality (1, 5), deleterious materials, recoverability of economic components, physical behavior, geophysical response (I), and even archaeological and environmental aspects (7, 11). The sample must be taken from a locality and in such a manner and quantity that it is representative of the larger rock mass. This calls for complete and accurate geological control and an understanding of the nature and distribution of the contained chemical and physical elements and a record of the effectiveness of the different sampling methods. Second, value of a given mass of ore material is based upon its profitability - the difference between recoverable value and costs to achieve recovery, beneficiation and sale. There is a strong movement in mining geology control toward more complete analysis in determining cutoff grades and in grade control, as illustrated by the kriging of metallurgical recovery factors as well as grade at the Mercur Mine (8). To achieve a "profit- ability factor" as a guide for economic mining practice requires further integration of: 1) the value of contained metal or mineral, 2) percentage recovery of values, 3) dilution of ore with waste rock, 4) addition to, or loss of value as a consequence of by-product materials or deleterious components, 5) cost of producing a saleable product plus mini- mum profit to justify the effort (cutoff), and 6) cost of land restoration (7, 11). All these parameters vary with the rock type, rock structure, mineralogy, depth, geometry, mining and metallurgical methods, but they must be sampled and analyzed if sampling and grade control are to reflect profitability. A wide variety of deposits has been presented at this symposium; each deposit with its own problems and special solutions. Deposits containing high unit-value components, e.g. precious metals and diamonds, present special problems in the obtaining of accurate samples and generally require statistical analysis control methods or may disregard or modify occasional high or occasional low values, based upon experience (12 ) Grade control may be accurate for the long term but may vary for the short term. Bulk sampling is always essential. Deposits containing metals or minerals with low unit value are very sensitive to transport costs, and they are often very sensitive to small amounts of deleterious components or differences in physical or chemical behavior. Problems of sampling and grade control change with the genetic type of deposit, with the stage of deposit development and with the size of the information base. Precious metal epithermal deposits (2, 6, 8), because of rapid vertical zonation and erratic lateral distribution of values, have always been difficult to evaluate and maintain grade control and ore reserves. On the other hand, evaluation and grade control are relatively easy in bulk-low- grade deposits (4, 13). However, these deposits generally have a low margin of profit and are sensitive to mining and beneficiaton costs, price fluctuations and political costs. Industrial mineral deposits (5) often must be evaluated on the basis of their behavior, rather than by chemical analysis. Environmental impact generally increases with the scale of the operation, but certain elements or minerals have especially high impact effects (7, 11). In the exploration phase there is no production control of sampling procedures and careful geological observations are particularly essential. The greatest number of problems is related to the oxidized outcrop where the chemical environment of the ore body has changed and the contained values may have been enriched, depleted or values left unchanged (2, 6). Present evidence suggests that gold values may be very mobile under certain conditions (2, 6) and stable under others. Everything must be sampled in detail. Principal values and by-product or deleterious elements may vary dependent upon their position within the soil profile. Such factors as geomorphic position, erosion rate, vegetation, climate, etc., may affect the interpretation (1, 3). During the development phase it is equally easy to overtest, to have "paralysis by analysis," as to undertest (3, 6). Bulk samplng and testing are

Jan 1, 1985

By W. W. Roepke

The Bureau of Mines has developed an interactive computer program that enables mine operators and others to identify the effect of cut-ting system changes on relative dustiness at the face. The program, which simultaneously evaluates machine parameters, coal seam parame-ters, and operator-controllable parameters, was developed for use on any microcomputer using BASIC programming language. The program allows the user to change one or more of the cutting system parameters at a time to see how these changes affect relative dustiness. A complete program listing and flowchart are included along with operating in-structions and sample outputs. An example showing how to use the program is also included.

Jan 1, 1985