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By George M. Leonard

Mineral commodities on National Forest System lands contribute to the nation's well being. Access to these commodities is dependent on public perceptions of the effects of mineral operations on other resources. An outlook is described which the Forest Service believes is essential to the minerals industry if it plans to continue seeking minerals on National Forest and Grasslands.

Jan 1, 1991

By Barbara J. Arnold

The Electric Power Research Institute (EPRI) and six EPRI-member utilities are sponsoring research to define relationships between coal properties and coal handling behavior. Deratings and outages caused by plugged chutes or bunkers or frozen coal can cost utilities millions of dollars annually in lost energy production as well as in manpower to restore coal flow. There is also the added expense of maintaining redundant equipment to assure a continuous coal feed to the boiler, a common practice for utilities. Over the past two years, researchers at CQ Inc. and Iowa state university have collected and analyzed coal samples to develop a coal handleability index for utilities to use when specifying coals for their power plants. These coal samples cover ranges in ash content, rank, grindability, size distribution, and moisture content--properties that affect the handling behavior of coals. Other properties, such as the washability and ash composition, are measured as well. Over the remaining two years of the project, all of these analyses will be correlated to handling behavior, measured using a triaxial shear tester that determines the strength of a coal under compression. An index will be developed and validated at host utility power plants.

Jan 1, 1991

Coeur d'Alene Mines is a precious metals producer which is dedi- cated to growth through it's exploration and acquisitions efforts. We foster and support these activities by providing our staff with long-term financial support, the encouragement to proceed with their projects and ideas, and a firm belief that we will be successful. Coeur's corporate headquarters are located in beautiful, historic Coeur d'Alene, Idaho. Our main mining operations are Rochester, locate near Lovelock, Nevada, Coeur Mine,located near Wallace, Idaho, and Thunder Mountain, located in central Idaho. Our Ken- sington Gold project is located about 45 miles north of Juneau in southeast Alaska. We have exploration offices located in Reno, Nevada, and Santiago, Chile. At this time, Coeurd'Alene Mines produces precious metals from mines located in the United States. Our Rochester open-pit opera- tion, which is 100 per cent owned and operated, is located in Nevada. Presently, this operation produces 5.5 to 6 million ounces of silver per year and 60-70,000 ounces of gold. We move 65,000 to 70,000 tons of rock per day of which about 23,000 tons is ore. The ore is crushed, stacked on permanent heaps and leached. The recovery is by Merrill-Crowe. Although the average grade is rela- tively low, 1.4 ounces per ton silver and 0.012 ounces per ton Au, the operation is very low cost. Our cost of production is less than $4.00 per silver equivalent ounce. Rochester is anunusual operation in that the crushed rock stacks without much compaction and the ores are easily leached. The final height on our heaps will be about 220', and overall recovery will be about 55 per cent of the silver and about 85 per cent of the gold. Reserves at Rochester are expanding and are now adequate for at least fifteen years of opera- Tion.

Jan 1, 1991

By G. Heiken

On the Earth's Moon, obvious hazards to humans and machines are created by extreme temperature fluctuations, low gravity, and the virtual absence of any atmosphere. The most important other environmental factor is ionizing radiation. Less obvious environmental hazards that must be considered before establishing a manned presence on the lunar surface are the hazards from micrometeoroid bombardment, the nuisance of electro-statically-charged lunar dust, and an alien visual environment without familiar clues. Before man can establish lunar bases and lunar mining operations, and continue the exploration of that planet, we must develop a means of mitigating these hazards.

Jan 1, 1991

Mining of the Martha Hill epithermal gold deposit via open pit methods will excavate a pit to 15 m below sea level. Regular geotechnical evaluations of pit slopes have taken place. Details of the various components of these evaluations, including geological structure, material strength, and groundwater, are covered. Pitwall geological structures are represented clearly on pit floor grade control maps with the dominant sets being steeply dipping strike fractures. Cross cutting shears are common. Material strength is reflected by the oxidation status of the hydrothermally altered host rocks, with weaker material occurring in partially oxidised ground. Regional groundwater is generally high, particularly on the north-eastern side of the pit, where it has been little affected by de-watering. Geological structures appear to control the flow of groundwater in the proximity of pitwalls and require draining by the introduction of horizontal drains. An overview of pit slope design is given. Slopes are designed for overall slope stability, allowing for the occurrence of minor interbench failures.

Jan 1, 1991

By James C. Barker

Alaska's expansive continental shelf represents future opportunities for marine mineral development. Although today's metal prices and subsidized foreign mineral production continue to discourage industry investment in marine exploration worldwide, the longer term outlook is one of increasing costs on-shore with a dwindling land-base available on which to search for and extract minerals. Likely, the generations of the 21st century will increasingly recover their minerals from the sea-floor. Though largely unexplored, Alaska potentially represents a major port ion of the U.S. marine resources. Several factors demonstrate this. First, the Alaskan OCS is huge; 74% of the entire United States' continental shelf lies off of Alaska, and 54% of the U.S. coastline is Alaskan. Combined with the jurisdiction waters of the Soviet Far East, the Bering-Chukchi shelf is one of the world's largest tracts of shallow water. Second, Alaska is situated at the northwestern terminus of the mineral-rich American cordillera. From Chile to Alaska, major on-shore deposits of precious and base metals, ferroalloys, and industrial minerals are found in the tectonically disturbed belts of the cordillera. In 1988, the western U.S. cordilleran states produced 70% of this country's mineral output (excluding construction materials). Throughout the cordillera's entire 10,000 mile length, the rock units strike largely parallel to the coastline, but in Alaska they extend directly offshore and onto the continental shelf. Consequently, the mineral-rich terranes off of Alaska have a much more complex interaction with coastal and lit-

Jan 1, 1991

By John E. Frost

Duval's (now Battle Mountain Gold Co.) copper and gold deposits in the Battle Mountain District in Nevada are in two subdistricts - Copper Basin and Copper Canyon - about 18 km (11miles) apart. Location of the two subdistricts is shown in Fig. 1. The two centers of mineralization have distinctive geologic and ore characteristics that required different innovative approaches to exploration and development. Nearly all of the copper from Copper Basin has been recovered by heap leaching. Because of relatively high gold and silver values in the Copper Canyon ores, a significant part of the sulfide copper ores has been recovered by a conventional flotation mill at Copper Canyon. Recently, this mill has been converted to the recovery of gold that is mined from zones peripheral to the copper deposits. Prior to Duval's entry, small amounts of copper, gold, silver, lead, zinc, and antimony had been mined in the district over a nearly 100 year period, beginning in 1866. The bulk of the $13 million total production to 1962 was derived from copper and gold lode ores and gold placers. Duval's interest in Battle Mountain-arose directly from a submittal by Asarco, which controlled key claims in both the Copper Basin and Copper Canyon subdistricts. Asarco acquired its holdings in the district in 1959 and undertook limited exploration until mid-1961. At that time, the company decided to dispose of its interests. Duval was invited to evaluate Asarco's properties and accepted. On Dec. 6 and 7, 1961, J.E. Frost, R.C. James, R.W. Sayers, and H.A. Schmitt, representing Duval, and K. Richard and E.W. New- man, representing Asarco, visited Copper Basin and Copper Canyon. Frost concluded that the properties were of considerable interest and prepared, by Jan. 12, 1962, a voluminous report recommending that Duval acquire and explore Asarco's properties. Furthermore, he recommended a large initial exploration program that included not only geologic mapping, geochemistry, and geophysics, but also the extensive drilling that was to involve, as the first phase of exploration, 49 drill holes in Copper Basin and 21 drill holes in Copper Canyon. Following property agreements between Duval and Asarco, and Duval and several other claim owners, geologic mapping, geochemical surveys, and drilling began in August 1962. Exploration drilling was completed in July 1964 and engineering studies in April 1965. Development of the Battle Mountain properties was authorized in July 1965, and production commenced in the first quarter of 1967. Because of the unusually high oxide copper content of the ore bodies, particularly in Copper Basin, a much larger than typical proportion of the copper in the deposits has been recovered by heap leaching. The generalized geology and ore zones of the Copper Basin are as shown in Fig. 2 and of Copper Canyon in Fig. 3.

Jan 1, 1991

A knowledge of airway friction factor (K-factor) is necessary to designing mine ventilation systems for least cost and optimum effectiveness. The friction factor used must be accurate and reliable to estimate correctly roadway resistances and pressure sources for required flows. Though the resistance to flow offered by mine airways has been an object of study over the last half century, no accurate relation has yet been established from which the prediction of the resistance of a projected airway can be made. In Kentucky, only limited and incomplete data on local K-factors are available. Therefore, there is a need for field investigations to determine these values in-situ for existing mining conditions. The author describes a study concerning K-factor that was carried out in ten coal mines, located in eastern and western Kentucky. The results of these investigations are presented in both tabular and graphical form.

Jan 1, 1991

By P. D. Rao

The combination of high moisture and low heating value has restricted most low-rank coal (LRC) usage worldwide to mine-mouth power generation. Coals from Usibelli Coal Mine and the Beluga coal field have a heating value of approximately 8,000 Btu/lb and 28% moisture. Hydrothermal treatment (at 275 to 352'C) of lump coal from Usibelli Coal Mine and Beluga coal field enhanced the heating value of the coal, on an equilibrium moisture basis, from 8,000 Btu/lb to nearly 12,000 Btu/lb. The product coal with high heating value and 0.2 % S is an environmentally acceptable premium fuel. The Hardgrove grindability index of the coal is greatly improved, further enhancing its value. Increase in hydrothermal drying temperature promotes vesiculation of resinite. Vitrinite reflectance increased to 0.72 and vitrinite was subjected to widespread visiculation resulting in a coke like structure indicative that the material went through the fluid stage.

Jan 1, 1991

Crushing and grinding activity in 1989 followed the rapid pace of the mineral industry. Use of existing installations, demand for expanded capacity, and implementation of entirely new operations contributed to a high level of activity. At the 1989 SME-AIME Annual Meeting in Las Vegas, NV, the crushing and grinding session focused on wear materials in crushers and mills. Another session joined the process control group in its simulation-modeling and control of crushing and grinding circuits. Both sessions addressed the optimization in operating effectiveness. Specific subjects covered grinding media wear of forged and cast grinding balls and rubber lined mill liner wear. Also, the Semi Autogenous Grinding (SAG) Mill Conference in Vancouver in September 1989 provided a valuable update on the progress of SAG operations in recent years. Operationally, gold grinding and roasting circuits were implemented in 1989. Freeport McMoRan Gold started up two operations in Nevada. Two other circuits, both using SAG mills, are scheduled to start in 1990. These will be in Nevada and British Columbia. Elsewhere in gold, additional capacity continues to be brought onstream, both domestically and worldwide. In copper, expansions continue to call on additional crushing and grinding units. The unrest at Bougainville in Papua New Guinea has fueled a continued, strong demand for comminution in the copper sector. Specific equipment installed or started in 1989 included the ac variable frequency drive SAG mills in Australia, Alaska, and Papua New Guinea. Also, the gearless drive SAG mill in Chile provides tremendous flexibility in terms of mill speed. The trend toward moveable in-pit crushers continues -even at established operations.

Jan 1, 1990

A new classification of subduction related (epithermal- / mesother-mal) gold mineralisation styles based on the tectonic framework they occur in, has been found helpful in practice. It offers a ratio-nalisation of exploration efforts during all stages of work.Methodology on the ground during first pass- and follow up explo-ration which has been found effective for the various mineralisa-tion styles is being briefly outlined.

Jan 1, 1990

By J. P. Bunch

As the number of environmental laws continues to steadily increase and the economic penalties for contamination problems become more severe, environmental management represents an important management function within today's U. S. mining industry. The economic impact to a mining company for contamination is not only realized in legal fees and fines but also in the cost of doing normal business. For example, a mining company with contaminated property applying for a loan may be refused because of a lending institution's reluctance to finance due to liability concerns. Or, an insurance company may decide to greatly increase its annual premiums because of existing or potential contamination problems. One of the main duties of the environmental manager is to seek ways to reduce these types of problems by eliminating contamination or by knowing what problems exist and designing corrective measures to prevent the situation from worsening.

Jan 1, 1990

By N. S. Dalal, B. Jafari, F. H. Y. Green, V. Vallyathan

"INTRODUCTIONThe mechanistic details of the biological events leading to coal workers pneumoconiosis (CWP) are not yet fully understood, despite several decades of extensive epidemiologic1.2 and laboratory studies.2-6 Epidemiologic studies1.2 have shown, for example, that the incidence and severity of CWP differ markedly in the different regions and mines at comparable exposures, but laboratory investigations2-6 have demonstrated only partial correlation of the epidemiologic data with the differences in the mineral composition and the rank of coal mined. In particular, while epidemiologic data indicate1.2 direct correlation of the· prevalence and severity of CWP with the rank (i.e., % carbon content) of coal, this correlation has not been established by laboratory4'6 and animal exposure3 studies. In order to explain these results, in 1980 Artemov and Reznik' suggested that perhaps they arise from the fundamental differences in the surface properties of the coal. dusts inhaled by the coal miners and those used in the laboratory studies: while the miners inhale freshly fractured coal particles, henceforth called the 'fresh' coal dust, the laboratory studies generally utilize 'aged' coal dusts (i.e., dusts that have been stored for many days or even longer). Reznik and Artemov' used electron spin resonance (ESR) spectroscopy to show that the mechanical crushing of some Soviet Union coals generated organic free radicals and that the concentration and the decay times (hence the reactivity) of these radicals were higher for the coals of higher ranks. Since some of the radicals decayed within a few minutes in air, the authors surmised that while these radical species could lead to certain specific pathogenic reactions at the sites of mining operations, this might not be the case in the laboratory studies, due to the conventional use of 'stored' dusts which would be expected to contain significantly smaller free radical concentrations. This is consistent with the recent findings that, standardized, aged coal dusts exhibit minimal cytotoxicity. 8While the above mentioned work of Artemov and Reznik7 did suggest a possible new clue to the pathogenesis of CWP (i.e., the role of the coal based free radical species), no direct biological/cytotoxicity data were provided to show that 'fresh' coal dusts were, indeed, more pathogenic than the 'stale' ones. Because of the rather significant implications of the Artcmov-Reznik hypothesis to the understanding of 1hc biochemical mechanism and, hence, the strategies for the eventual containment of CWP, we have initiated a comparative study of the free radical formation and cytotoxicity properties of freshly crushed coal ·particles. As done by Artemov and Reznik, 7 we have used the ESR technique as the direct method of measuring the concentration and decay kinetics of the coal based free radicals. Our preliminary ESR studies on two Pennsylvania coals, a bituminous (carbon content 72 % ) and an anthracite (95 % carbon) coal, have confirmed the Artemov-Reznik finding that the crushing-induced free radical sites are higher on the coals with higher carbon content (i.e., higher rank).9-11 In the present work we describe our more recent results of a parallel study of the time dependence of the decrease in the free radical content of a freshly made anthracite dust (as measured via ESR) and that of the dust's cytotoxicity potential as measured by the extent of hemolysis of (sheep) erythrocytes. We have also investigated the effects of free radical scavengers on the cytotoxicity potential of the dust and deduce that indeed the free radicals could play a significant role in the initial events in the mechanism of the cytotoxic effects due to the inhalation of coal dust inhalation."

Jan 1, 1990

By R. W. Adams

A new process has been developed for leaching zinc sulphide concentrates at atmospheric pressure using air or oxygen plus nitrogen dioxide in dissolved or gaseous form as? an oxygen carrier. The process is flexible and can cope with variations in the degrees of retention and regeneration of dissolved nitrogen dioxide in the leaching phase. By controlled addition of concentrate a leach solution with low residual nitrate concentration can be produced. Following separation by filtration of unleached solids and elementa1 sulphur and conventional oxidation/precipitation of dissolved iron, the leach liquor can be treated with metallic zinc to remove the remaining nitrate and other meta111c impurities such as copper, cadmium and cobalt to provide a solution suitable for electrolytic recovery of zinc. Pilot scale testing of the process .has given zinc recoveries in the high nlnet1es, production of a hi.gh grade jarosite-free Pb/Ag residue (50% Pb.) and a saleable high grade of elemental sulphur. .A wide range of concentrates can be treated containing substantial levels of lead and copper as well as zinc. Indicative cost estimates suggest that the new process is competitive with alternative procedures such as pressure leaching.

Jan 1, 1990

By Donna L. Anderson

This U.S. Bureau of Mines report discusses the status of a laser-based guidance system to provide position and heading feedback and closed-loop control of tramming maneuvers for a continuous mining machine. The system has been developed and tested at the Bureau, and is now being prepared for underground experiments. The system hardware includes laser scanners, a sensor communication network, and host computer hardware. The system software includes a position and heading computation module and a tram control module. The description of the software includes discussions of laser data acquisition, error compensation methods, position and heading determination, safety checking for continuous miner tramming, and closed-loop tram control. The accuracy of the laser scanner's data, the reliability of the lasers in a dusty environment, and the system's accuracy on tracking the position and heading of the continuous mining machine are shown in the results of experiments performed at the Bureau. Conclusions are stated based on these experimental results, and further work to improve the system performance and prepare for underground testing is discussed.

Jan 1, 1990

By M. B. Cortie, J. H. Potgieter

An account is given of the production of three types of experimental high-chromium duplex stainless steel. The alloys had chromium contents of 22, 29, and 35 per cent. The partitioning of the main alloying elements between the austenite and ferite phases was determined, and the effect of the alloying elements chromium, nickel, and molybdenum on the mechanical properties and corrosion resistance of the duplex stainless steels is summarized. The phase compositions of the different duplex stainless steels were measured by different techniques, and the values obtained were correlated. The cracking occasionally observed during the thermo mechanical processing of these alloys was studied, and is explained as being the result of known embritlement processes.

Jan 1, 1990

By P. A. Mingione

"AEROPHINE@ 3418A is a unique sulfide mineral promoter produced by Cyanamid, based on phosphine (PH3) chemistry. It has proven effective as a collector for the sulfide minerals of copper and particularly lead (galena), as well as for secondary gold and silver values. AEROPHINE 3418A has widest application as a Cu and/or Pb collector for complex ores of Cu-Zn and Pb-Zn, which frequently have significant quantities of associated precious metal values. Advantages shown in the use of AEROPHINE 3418A are improved selectivities against Zn- and Fe-sulfides, increased precious metals recoveries, reduced total collector consumptions for Cu and/or Pb flotation, and increased flotation kinetics leading to higher recoveries of these values. Operating plant, pilot plant and laboratory test data from treating different ores are presented, demonstrating the advantages in use and preferred application of AEROPHINE 3418A.INTRODUCTIONCyanamid operates the only phosphine and phosphine derivatives plant in North America, located in Niagara Falls, Ontario. Specialty chemicals manufactured at this facility are used in many diverse applications, including solvent extraction reagents and textile flame retardants. A unique phosphine-based sulfide mineral promoter, AEROPHINE 3418A, is also produced. The origins of AEROPHINE 3418A promoter date back to the 1960's, when it was established that sulfide mineral collectors based on phosphine chemistry demonstrated efficacy. This new collector chemistry was found to provide flotation performance differing significantly from those of more traditional thiol collector chemistries such as xanthates, dithiophosphates, mercaptobenzothiazoles, thionocarbamates and those with xanthogen groups. Some of the advantages ultimately demonstrated by AEROPHINE 3418A promoter compared to these traditional collectors include:"

Jan 1, 1990

By J. F. Peterman, M. C. Roberts

The success of any industrial mineral project requires an accurate forecast of the demand fir the material as well as accurate projections of costs and prices. This paper develops a general method of predicting mineral requirements and applies it to the case of graphite. The basic method is to explain graphite consumption in each of its major uses by the output and manufacturing technology of the using industry. Once these underlying factors are determined, they can he projected to establish future requirements. This forecast is critical to the evaluation of a new source of supply, such as the graphite resources of Upper Michigan.

Jan 1, 1990

Mineral resource and ore reserve estimation is a challenging and demanding field, requiring application of professional knowledge, skill and experience of the highest order. If the many potential hazards and pitfalls are to be avoided however, there are two other requirements which are of equal, if not greater importance:

Jan 1, 1990

By Draper J. J, Lang S. C

Regional geological mapping and facies analysis of the Late Devonian to Early Carboniferous Keelbottom Group of the Burdekin Basin have resulted in a depositional model representing six siliciclastic-carbonate facies. The six facies represent alluvial fan, braidplain delta, siliciclastic shoreline, siliciclastic shallow marine, restricted siliciclastic/carbonate shelf, and carbonate shoal depositional environments. These facies are identified in the Star beds which are equated with and included in the Keelbottom Group in this paper. Facies are repeated throughout the Group, as a result of two transgressive-regressive cycles.The first transgression recognised in the Keelbottom Group began in the mid-Famennian, and followed deposition of the Late Devonian Dotswood Group. It was marked by the deposition of Siliciclastic Shoreline facies in the basal Myrtlevale Formation, which was succeeded by Siliciclastic Shallow Marine facies at the peak of the transgression. The return of Siliciclastic Shoreline facies in the upper part of the Myrtlevale Formation marked the onset of the first regression, which resulted in the progradation of Braidplain Delta facies from the northwest of the basin. During the peak of this regression, deposition in the western part of the basin was dominated by Alluvial Fan facies.

Jan 1, 1990