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By Colonel Oattis E. Parks

The quantity of coal recovered by diamond coring techniques is not sufficient in many instances to make meaningful coking and/or ash fouling tests. Quantities in excess of that obtained by conventional coring techniques, usually in amounts exceeding 500 pounds, has been designated bulk sampling. During the past three years, AMAX Coal Company has utilized five methods of bulk sampling. It was our desire to obtain a bulk sample that was diagnostic of the seam by the most expedient and economical method. From the beginning all of our efforts have been directed to methods which would extract the required coal from slim boreholes which provide quick and inexpensive access to the coal seam, regardless of depth, terrain and accessability. In our efforts and investigation several large diameter cores have been taken from thick coal seams at relatively shallow depths in easily drilled rocks. On the other hand, for deeper thin seams multiple large diameter coring is more expensive and time consuming. It is somewhat less expensive when multiple cores are taken from a single slim borehole utilizing deflection coring, although considerable skill is necessary.

Jan 1, 1973

By B. Pesic

This is an extension of the work on recovery of silver and manganese from Ag-Mn ores, and recovery of silver and gallium from flue dust from phosphate industry. Carbon adsorption was considered as the most adequate method for recovery of silver from thiourea leach solutions. For this reason it was decided to examine the characteristics of adsorption of silver on activated carbon. Coconut hard shell activated carbon was used for this study. Ag(TU)2C1 complex was dissolved into thiourea solution to give 2 gpl stock solution. Thy studied parameters were: loading isotherms at 25°C, 35°C, and 45°C, initial kinetics as a function of thiourea concentration, temperature, pH, N2, and O2. It was found that the loading capacity of carbon for silver and thiourea was 137-150 mg/g and 514 mg/g, respectively, at 25 °C.

Jan 1, 1986

By W. Clark Ashby

Productivity is a fascinating concept. Like motherhood or apple pie, we know it as a good thing. Just what it means is not so clear. To a coal miner we assume it means tons of coal hauled from the mine. To the company president it means profit after capital, labor, and other costs have also been reckoned. To the government economist it means output in a balance of payments. What does it mean to the biologist, and can reclamation really be productive? In this paper we discuss productivity from a biological viewpoint, give some yield data for various types of reclamation plantings, and discuss how our demand for or acceptance of differing kinds of productivity is tied up in bigger questions of land use, environmental stability, and resource allocation.

Jan 1, 1981

By George R. Stephans

The Climax Mine is a panel caving mine which has had a long history of incidents of severe ground control problems. The nature of the ore deposit, which lends itself to the caving meth- of of production, a1 so makes the mine susceptible to large scale stress concentrations which are referred to as ?weight? problems. These problems have increased with increased production and also with expansion to deeper mine levels. During the past twenty years the mine has had to learn to cope with these problems in order to remain in operation. A number of practical guidelines and useful techniques have emerged from these efforts. The purpose of this paper is to share a few of these ideas. The Mine is located near Leadville, Colorado on the continental divide at an elevation of 3450 meters. The ore body is a large low grade deposit of disseminated molybdenum sulfide. It measures about 1200 to 1600 meters in diameter and it had an original depth of about 660 mters. The Mine has been in operation since 1918 and the massive nature of the ore body together with its blocky, highly fractured condition made it natural for the caving system to have been adopted for production at an early date. Open pit mining was started in 1973. The total plant has a capacity of more than 50 thousand tons per day, and more than 400 million tons of reserves at an average grade of 0.310 percent molybdenum disulfide remain to be produced.

Jan 1, 1982

By E. Ashworth

A thermistor probe has been developed to measure in situ temperature profiles underground. A full description of the probe is given. Data collected from the probe has been used to compare the actual profiles with those predicted from a finite element analysis using laboratory measured thermal properties of the different rock types. This comparison indicates the applicability of laboratory measured parameters in modeling the real conditions. Factors such as applied pressure, moisture content and anisotropy on laboratory measurements is discussed.

Jan 1, 1983

By F. L. Wilke

A model is presented to minimize the winning costs per shift within the different sections of a potassium mine by liner programming and to simulate the other areas to get all costs in order to comp re different production strategies. he model is based on a a given total layout of the underground mining which is considered to be fix during the planning period. Room-and-pillar mining is assumed to be used. Potassium extraction is done by drilling and blasting. Transportation of the raw material to sectional crushers is done by scoop-trams where it is crushed to coarse-grains which allow further transportation by conveyor belts to the hoisting shaft or to a bunker. When production is stopped, the continuously working factory is supplied by means of this bunker. Starting from a desired composition of the raw material the model has to keep the given total. demand of raw material per shift, to minimize the winning costs, to keep the capacity constraints of the equipment and to determine the planned output of production of the sections per shift. Costs of the areas which follow the extractions are added to extraction costs in order to allow a comparision of costs of several alternatives of production. Optimization in extraction and assignment of scoop-trams to sections is done by linear programming. The other areas of the mine are treated by simulation. The model output is a schedule of the calculated costs broken down into costs of processes, equipment, and kinds of costs. This proceeding enables to compare different ways of production.

Jan 1, 1979

By F. C. Eberhardt

Systematic planning of underground work is increasingly important in this era of advancement of rapid underground excavation techniques. The day when planning consisted of deciding which men would shovel and which would push wheelbarrows - and the answer to any problem was more men - has faded into the past. The modern underground constructor faces economic and competitive conditions which demand exacting planning, logistics and scheduling; the most efficient operating methods and equipment known; and realistic, comprehensive, analytical risk evaluation with adequate contingencies or other protection. Proper planning to cover all these elements - plus one other element: old fashioned "good luck" - will insure a successful underground project. Underground work, because of its inherent characteristics, is among the most risky types of construction. The forecasting of underground conditions is at this time only educated predictions based on sometimes faulty data, insufficient data, or no data at all. The predicted conditions of numerous operations have deviated far from the actual conditions encountered. Opportunities for error exist in profusion seldom present for surface operations. Other than this unusual risk factor, the planning for underground work does not differ greatly from planning for surface work. In planning and starting an operation there is seldom available the information or time to thoroughly analyze all unknowns. It then becomes necessary to develop a plan predicated on assumptions and trade-offs that appear to be safe and economical and to add time and cost contingencies that will provide some degree of protection. On competitively bid fixed price work, choice of markup on estimated

Jan 1, 1974

By Walter von der Linden

On April 14, 1975, Consolidation Coal Company began to operate a longwall face in their Shoemaker Mine using shield supports. This was the first time that shield supports were used in the United States (1) 1/. Shortly thereafter, Kaiser Steel Corporation started a shield longwall face at their York Canyon Mine (2). From October 1975 through May 1976, three more longwall faces were commissioned in mines located in south-western Pennsylvania and northern West Virginia. In June 1976, four installations had completed their first panel and two installations had completed the subsequent move to the second panel where coal production is now well under way. During this time (April 75 to June 76) the total number of shield support face operating months, including moving time, was 40 and the combined face advance was approx. 17, 000 feet (5200 m) with face lengths varying from 450 - 550 feet (137 - 168 m). While the shield support experience in the U.S. is still limited on the basis of time and mining parameters, the operating results of all faces have been very satisfactory. New record 24 hr production figures were set and - far more important - long term production figures could be sustained on an impressively high level even when taking face moving time into account. The purpose of this paper is to review the performance of shield type supports in the U.S. and to assess their value as longwall supports for U.S. underground mining conditions with regard to roof control, maintenance, operator convenience, safety and productivity.

Jan 1, 1976

By J. F. Brune

"Re-occurring face ignitions in U.S. coal mines are concerning and require a closer look at air quality monitoring systems and practices employed in these mines. The explosion disaster at the Upper Big Branch mine in West Virginia in 2010 caused 29 fatal injuries and was largely caused by inadequate water sprays and inadequate ventilation monitoring. In this comparison, the author compares ventilation system monitoring in Australian, German and U.S. underground coal mines and makes recommendations for improvements and best practices. Mines in Germany and Australia are adhering to more stringent requirements for monitoring air quality and quantity and for monitoring water spray systems on cutters to prevent frictional ignitions. Air quality should to be monitored for sufficient oxygen, toxic gases, explosibility and for fire gases indicating a potential fire. Ventilation monitors must also confirm that sufficient quantities of air are available. Fully automated, continuously recording atmospheric monitoring and alarm systems are established practices in Germany and Australia and should be mandated for U.S. mines as well, in addition to the current, regular spot inspections of the ventilation system by certified mine examiners. BACKGROUND: METHANE EXPLOSIONS, FACE IGNITIONS AND NEED FOR AIR QUALITY MONITORING Accumulations of methane in face areas of underground coal mines frequently lead to ignitions that can cause burns, traumatic injuries and, in the case of the 2010 Upper Big Branch disaster, cause major explosions with multiple fatalities. Table 1 shows the number of reported face ignitions in U.S. coal mines between 2010 and 2014, based on statistical data published by MSHA (MSHA 2010 – 2014). Although there appears to be a downward trend in such ignition incidents over time, ignitions continue to occur with some regularity; and each ignition may cause a potentially catastrophic mine explosion.Per regulation, all U.S. coal mining machinery, continuous miners and longwall equipment, is outfitted with continuously monitoring methane sensors wired to cut power to the equipment as the methane level exceeds 1%. Face ignitions keep occurring because these sensors are usually not positioned in sufficiently close proximity to the coal cutting drums or to the freshly exposed coal face where the methane is most likely released. Therefore, methane may accumulate in explosive concentrations near the coal face and the cutting drums long before the gas concentration reaches the 1% level near the monitor and creates an alarm."

Jan 1, 2016

By Douglas F. Stevenson

Your committee doesn't assign any easy topics to us speakers. How do you define "successful" in what is essentially a losing game? I am reminded of the fellow who returned from a one-week vacation in Las Vegas, and proudly stated, "I only lost $150." To him, that was "success." I am afraid that workers' compensation is a losing game for employers, too, and success has to be defined in terms of how much or how little is lost. We have no chance of producing a profit for our employer. We will narrow down to some suggestions about conducting a workers' compensation program at the plant level, but first I want to discuss the general legal, social and legislative climate in which your plant program operates. Workers' compensation is a statutory program with its general parameters established by the legislature. These parameters are then amplified by the boards and commissions established to administer workers' compensation. What influences the legislature and the boards and commissions as they establish the framework in which we must function?

Jan 1, 1986

By Sheldon P. Wimpfen

Back in 1970 Congress passed the National Mining and Minerals policy Act, which had as one of its basic tenets to rely on a strong and stable private minerals industry for the development and production of our mineral resources. Since then, a substantial amount of legislation has been introduced that impacts on the minerals industry. Although most of the bills proposed are not passed into law, each bill affecting minerals and mining is given careful review by the Bureau of Mines. Comment is forwarded with the object of being helpful to legislators by providing our assessment of the probable impact of each bill proposed along with suggestions to improve them. Actually few bills introduced become law. For example, in the 93rd Congress 4,260 bills were introduced in the Senate and 17,690 in the House. In the final accounting there were passed 123 private laws and 649 public, 3 percent of the bills introduced. There would be little merit here in attempting to analyze each mineral-related bill that was proposed. Many are similar and aim at making a certain aspect of our minerals activity fit needs. So, to simplify the task the many bills have been grouped by subjects. Slide 1 shows the principal topics and the number of related bills introduced. Putting it altogether, there are 26 principal subjects and almost 200 bills. And these numbers are probably off somewhat, as this accounting was made early in December.

Jan 1, 1976

By G. Pan

Although geostatistical techniques have been widely accepted as the standard methods for reserve calculations in the mining industry, the production data of many mines frequently differ from geostatistical estimations based on exploration and development drilling. The discrepancies in recovered metal amounts, commonly in the range between 10% and 30%, are related to different factors. Major causes vary from mine to mine. A common cause, however, is the ignorance of important geological constraints in reserve modeling. Three major factors appear to be related to such an unfortunate fact: 1) modelers are over-confident on geostatistical techniques, 2) it is difficult to establish geological models, and 3) mine schedules are too tight to allow detailed geological modeling work. Defining mineralization envelopes has been a major effort in geological modeling. Past experiences have showed that geological modeling is much mo~ demanding than the choice of sophisticated kriging estimators. Since building envelopes for complex ore bodies can be extremely tedious and time-consuming, computerized approaches are badly needed for mine modelers. A comprehensive procedure reported here is referred to as probability-assigned constrained kriging (PACK), which includes a built-in method for defining 3-d mineralization envelopes. The modeling technique is fast and accurate for complex precious metal deposits. The technique is demonstrated on a gold deposit. The estimation results are compared with blast-hole based production panels, showing that the estimated tonnage is 2.2% larger than the actual production and the average grade is 2.6% lower.

Jan 1, 1994

By J. Diaz

"Antioquia region, in Colombia, is considered one of the areas with the highest mercury contamination in the world due to its use in gold recovery through artisanal mining, emissions to the environment between 100 and 150 tonnes of mercury are estimated by year. Therefore it became necessary to develop a project in which it was proposed aim to empower traditional artisanal mining community, or in different areas, such as gold mining in the region of Antioquia, in the implementation of safe mining practices and environmentally sustainable, from the introduction of clean technologies, in order to prevent or mitigate the impacts generated by traditional mining on the environment and the communities involved. In order to achieve this training to traditional mining community developed and technical visits to artisanal mining were performed in order to optimize operating processes and promote safe mining practices. In the project more than 1400 artisanal miners were trained.INTRODUCTION In the developing world, a combined 30 million individuals extract more than 30 different minerals using rudimentary techniques. Gold is the preferred mineral extracted by artisanal operators due to its high unit value and its market price, which has increased almost sevenfold over the last decade (Veiga et al, 2014). The artisanal gold mining sector in Colombia has 200,000 miners officially producing 30 tonnes Au/a. In the Northeast of the Department of Antioquia, there are 17 mining towns and between 15,000 and 30,000 artisanal gold miners (M. Veiga, 2010) (Upme, 2014). This production, however, has caused environmental problems, including high levels of river siltation and mercury pollution (Veiga et al, 2014) (UPME, 2007) (Cordy et al., 2013). The mercury contamination in Colombia by artisanal gold mining has been recognized by a number of researchers and local authorities for over a decade estimated that the annual mercury emissions from artisanal gold miners in Colombia in 2007 were between 50 and 100 tonnes, however given recent gold value increases and gold rush activity, current mercury emissions are likely much higher. Colombia is likely the world's 3rd largest source of mercury emissions from AGM after China (240 to 650 tonnes of Hg/a) and Indonesia (130 to 160 tonnes of Hg/a) (Telmer and Veiga, 2008) and is the world's highest per capita mercury polluter (M. Veiga, 2010)."

Jan 1, 2016

By V. Aghazadeh, E. Bidari, M. Aazami

In this study, mineralogical and microanalysis characterization, as well as diagnostic leaching and cyanidation tests, were performed to gain a better understanding of the refractory nature of the arsenical zone of a Carlin-type gold deposit and also to evaluate possible treatment routes to maximize gold recovery. The results obtained showed that only 56% of the ore’s gold content is amenable to direct cyanidation. The majority of the remaining gold was found as submicroscopic gold and in association with sulfide minerals, such as orpiment, pyrite, and sphalerite. It was also found that despite the abundance of silicate and carbonate minerals in the arsenical zone, they do not play a key role in the refractory nature of the ore, and gold can be liberated from such minerals by appropriate grinding. The analyses further revealed that orpiment dissolves readily during cyanidation, and this dissolution retards the kinetics of gold extraction. Pyrite and sphalerite were generally found to occur in fine network texture and in association with quartz. Flotation of such auriferous sulfides may be difficult due to their oxidized surface. Fine grinding (−20 μm) was found to be partially effective in improving gold extraction.

May 28, 2020

By Jessica M. Wempen, Dallan J. Coons, Bailey S. Simmons, Michael K. McCarter

Gate-road yield pillars are subject to increases in stress as the longwall face advances toward the pillars. Increases in pillar stress can be inferred by measuring roof/floor convergence surrounding the pillar. This paper presents a case study of convergence measurements surrounding a two-entry gate-road yield pillar in the head gate of a coal mine. Convergence was measured over a six-month period, as the longwall face approached and passed the pillar. Measurements were collected at eight locations surrounding the pillar: four locations in the travelway and four locations in the beltway. In addition to convergence stations, the pillar was instrumented with an array of seismometers. In future analysis, convergence measurements will be compared to seismic interpretations. This study reports on the geology and geometry of the longwall panel, the roof and rib support, the change in convergence over time, and the physical properties of coal and parting. Additionally, the convergence measurements are compared to pillar safety factor distributions derived from a finite element model. The convergence measurements contribute to the knowledge of when yield pillar abutment loading, caused by the encroaching longwall, is first detected. Knowing when abutment loading begins to yield the pillars can help define when standing secondary roof supports are required for head gate entry support.

By A. Anttila, S. Persson

The grinding mill is probably the most common unit operation in mineral processing. There is, however, much that can still be done in the way of optimization. This paper discusses the results of a well-controlled pilot-scale test in which the performance of a tumbling mill equipped with a conventional rubber lining and lifter bars was compared to a tumbling mill equipped with a smooth rubber lining of the magnetic type. The results indicate that the smooth lining is about 14% more effective with respect to energy consumption. By optimizing the size of the grinding media, the mill capacity can be increased in many grinding operations. In this specific case, grinding with a -20-mm ball charge required 26% less grinding energy than grinding with a -30-mm ball charge. The energy savings can, in most cases, be converted to an increase in capacity. The wear of the grinding media is difficult to assess over a short test period, but the results suggest that the wear is somewhat less when a smooth lining is used. A determination of the wear of the linings was not included in this study, but it is generally accepted that the use of magnetic linings reduces the lining costs dramatically. Computer simulation using the Millsoft code developed by Mishra et al. confirms and explains the increased effectiveness of comminution when a smooth lining and smaller grinding balls are used.

Jan 1, 2000

By T. J. Close

The Silver Peak Range North Wilderness Study Area was deleted from the list of US Bureau of Land Management lands in Nevada to be considered for wilderness designation. This decision was based in part on the US Bureau of Mines mineral investigation of the wilderness study area which found indications of precious- and base-metal-resources. The study area lies between the Silver Peak and Dyer mining districts of west-central Nevada. The Bureau examined 13 mineralized sites, most of which were previously unknown and unclaimed. These sites are along two zones that cross the study area from the Silver Peak mining district to the Dyer mining district. The two zones transect a volcanic center of fractured and altered rocks that contain epithermal veins of quartz and calcite with gold, silver, and base-metals. At the surface, these veins are poorly defined. Exposures of the more than forty veins examined were as thick as 17 ft and as long as 1000 ft. Samples from these veins contained significant amounts of precious- and base-metals-as much as 0.02 oz per ton gold, 2.1 oz per ton silver, 1.0% copper, 2.6% lead and 0.4 % zinc. No vein large enough or of high enough grade to be classified a mineral resource was disclosed by the sample data. However, most do have indications of precious- and base-metal-resources at depth. Subsurface exploration of some of the veins is recommended.

Jan 1, 1995

By K Martin, C. J. Nelsen, J. L. Schutz, S. R. Maynard

Investigations in the Ortiz Mountains have revealed the relationship of igneous activity and gold mineralization to the Tijeras-Canoncito Fault System (TCFS). The northeast-trending TCFS passes through the southeastern part of the Ortiz Mountains where its principal structure is the asymmetric Ortiz Graben. Several fault blocks, containing up to 305 m (1000 ft ) of Eocene Galisteo Formation, comprise the graben that has up to 1220 and 610 m (4000 and 2000 ft) of stratigraphic separation on its southeast and northwest sides, respectively. Intrusions in the Ortiz Mountains can be subdivided into two petrochemical types: an older calcalkaline suite and a younger alkaline suite. The calc-alkaline rocks are characterized by extensive sill, dike, and laccolithic bodies of latite-andesite intrusives and at least one younger (?) granodiorite stock at Candelaria Mountain. The alkaline rocks consist of a large nepheline-bearing augite-monzonite stock, a latite-porphyry hypabyssal plug, the Ortiz diatreme (vent breccia), and trachytic-latite dikes radial to the diatreme. K-Ar age determinations suggest the older suite to be 34 +/-2.2 million years while the younger alkaline rocks range from about 30 to 26 million years. Gold mineralization in the Ortiz Mountains occurs in five distinct environments: brecciapipes, skarns, veins, porphyry-like stockworks, and placers. Lode mineralization is associated with the alkaline suite of intrusive rocks postdating the Ortiz diatreme and predating most of the trachytic-latite radial dikes.

Jan 1, 1991

By William V. Robinson

The Iron Ore Company of Canada mines, processes and ships crude iron ore, concentrate and pellets from the rich ore bodies of the Labrador Trough area in the extreme north-eastern part of Canada, some five hundred miles from Montreal (see figure 1). There are three main sites of activity. At Schefferville, approximately 12 million tons a year of crude ore (chiefly limonite) are mined, crushed, screened and shipped to Sept-Iles. At Labrador City, 40 million tons of specular hematite are mined annually for processing into 17 million tons of concentrate. Of this, 9 million tons are converted into pellets. All product 1s shipped to Sept-Iles. At Sept-Iles, on the north coast of the St. Lawrence, a six million ton per year concentrator and pellet plant process much of the Scheffervllle ore into high-grade pellets. Also at Sept-Iles are the company's administration offices stockpiles and shipping facilities. The Terminal facilities can berth and load a 250,000 ton bulk carrier at 19,000 tons per hour.

Jan 1, 1975

By Ning Wang, Tengfei Guo, Wanyan Li, Hanjie Wen, Hannian Gu, Zehai Li

Bauxite residue (red mud) is an alkaline waste derived from the industrial process for extraction of alumina from bauxite ore. Some bauxite residues contain considerable concentrations of critical metals, for example, rare earth elements. Lithium in red mud was also reported as a potential resource. In the current study, a Li-rich red mud was leached using acetic acid to investigate the leaching behavior of lithium followed by neutralizing with hydrochloric or oxalic acid. By neutralizing red mud using diluted hydrochloric acid (0.01 mol/L), 58.04–60.27% of lithium was leached using 25% acetic acid at 95 °C for 60 min. In the meantime, more than 95% of sodium and 85% of calcium were also dissolved in the leachate solution. While oxalic acid (0.5 mol/L) was used to neutralize red mud prior to acetic acid leaching, lithium performed lower leaching efficiencies (42.41–46.88%) in comparison of using of hydrochloric acid–neutralized red mud. Nevertheless, these leaching efficiencies of lithium were close to that of calcium and much higher than those of sodium under the condition. In this study, 25% (v/v) of acetic acid, at 85 °C for 60 min, was demonstrated as optimum conditions for lithium extraction from oxalic acid–neutralized red mud using acetic acid. The results would be useful and of interest for lithium recovery and purification from red mud.