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By F. C. Turin, T. L. Friend, A. G. Mayton, J. S. Jaspal, W. J. Wiehagen

This paper describes the serious injuries that have occurred to bulldozer operators working at domestic coal, metal and nonmetal mines in the United States. A serious injury is defined as one that results in either a fatality or in lost work time. Examined were 873 injury records compiled by the Mine Safety and Health Administration (MSHA). The time period covered was 1988 through 1997. These injuries resulted in 18 fatalities and 31,866 lost work days. All of these injuries occurred to dozer operators while they were performing common production tasks. An injury classification system was developed to code the narrative information that describes the circumstances surrounding the injuries. Jolts and jars accounted, for 604 or 70% of the serious injuries to bulldozer operators, and jolts and jars accounted for 75% of the workdays lost. Vertical jars comprised the largest set (354 incidents) of jolting and jarring injuries. In more than half of these incidents, the operator was backing up the dozer. Working near an edge carries significant risk for fatal injuries. Of 116 incidents where the dozer fell over an edge, rolled over or fell into a hidden void, 14 (12%) resulted in fatal injuries. In cases where the dozer operator either jumped or was thrown out of the cab in a fallover or rollover, seven out of 17 of the operators were killed. This study finds that further reductions in injury risk would require more widespread use of seat belts; consideration (and maintenance) of the seat and seat suspension systems that might reduce injury risk from jolts and jars; research interventions to assess the effect of alternative engineering designs to dampen or isolate the effects of shock and vibration; and continued attention to skilled performance, i.e., the integration of hazard awareness, recognition and response with dozer operational skills.

Jan 1, 2003

By William Paul Robinson

I would like to first summarize the relevant health information relating to the workers and general populations around uranium mining as a basis for understanding the hazards associated with these operations and their available remedies. This discussion will summarize the literature on Radon and its daughters, among the most toxic uranium decay products. Second, I will discuss waste handling in the uranium industry: past, present and future, discussing exploration, mining, and milling and the volumes of water and solid and gaseous wastes which are associated with these various phases of uranium operations. This paper will also include a discussion of the various past and present materials handling technologies and their responsiveness to the concern for uranium waste isolation. I will then conclude with a summary of recent modifications in the relevant standards as applied to uranium mining and milling. Joseph Wagoner, a research epidemiologist with the U.S. Public Health Service has summarized the literature on uranium mining and its health effects in his written testimony as a commissioned witness in British Columbia Royal Commission of Inquiry into Uranium Mining in January of 1980, entitled Uranium, The U.S. Experience: A Lesson in History.1 Briefly summarizinq his report, as early as 1546, miners of uranium bearing ores in Central Europe were reported to have unusually hiqh frequencies of fatal lung disease2. As early as 1879, the real nature of pulmonary disorders among these miners was first diagnosed to be malignant neoplasia or lung cancers. Of 655 miners dying between 1875 and 1912, 40% or 276 of these Central Europe miners died of lung cancer.4 By 1939, it was reported that lung cancer mortality rate for miners in these Central European mining districts was several times (9.7 per 1000) higher than that for similar populations in Vienna, Austria (0.34 per 1000). Thus, before uranium mining began in the U.S., there was a considerable body of information linking uranium mining to lung cancers. The U.S. experience can be summarized in Table 1 also from Wagoner's B.C. Testimony.1 This table shows that through 1978, 205 respiratory cancer deaths have been observed among white underground uranium miners in the

Jan 1, 1980

By Steve Tadolini

Underground roof falls can have devastating effects on the safety of operations personnel, and equipment, and seriously impact production. Immediate steps are usually taken to danger off and secure the area while clean-up efforts are designed and implemented. A critical step, often overlooked due to production demand, is the determination of - why the roof fall occurred so that additional occurrences can be avoided in future developments or what measures can be taken to identify areas that have similar ?symptoms?? Forensic engineering includes the investigation of materials, products, structures or components that fail or do not operate/function as intended. The authors define forensics in ground control engineering as the study of evidence discovered while examining underground roof falls by applying expert observational techniques and established mining engineering principles to determine the probable cause, hypothesize solutions, and design engineering safeguards to prevent reoccurrences. Simply stated, the primary steps in the forensics of underground roof fall techniques are: ?Assess regional and local conditions prior to the event. ? Assess post-event conditions. ? Hypothesize plausible ways in which the pre-event conditions became the post-event conditions. ?Search for evidence that either denies or supports the various hypotheses. ?Apply engineering skill to relate the various facts and evidence into a cohesive scenario of how the event may have occurred. This paper details the proposed technique by utilizing a roof fall case study that required the examination of five primary factors: mine design parameters, excavation geology, method of excavation, method of support, and mining cycle times.

Jan 1, 2009

By V. K. Kollipara

Dust dispersion characteristics in mine airways are important for developing engineering controls for dust and explosions. Authors here have used CFD modeling approach to analyze the dust dispersion characteristics in mine airways. The technique was initially validated with the published field experimental data. The results obtained were in a reasonable agreement. CFD validation results show that in a single entry the dust concentration decreases exponentially as a function of distance. Finer particles can travel up to a distance of 350-400 m away from the source. Parametric studies indicate that air velocity and input dust concentration has significant influence on dust concentration distribution. CFD modeling was then applied to study the dust dispersion characteristics in a room-and-pillar mine layout. Preliminary results show that dust concentration distribution is highly dependent on the airflow patterns and air velocity distribution. The distribution is not exponential until the velocity in the travel way becomes uniform. Data developed in this study may be used to design mine layouts and engineering controls for dust control and explosions.

Jan 1, 2011

By Larry DeGraff

With the increase of new mine development in the past several years, many coal mines have decided to self- perform the design and construction for their slope development projects. The development process of determining the proper configuration is challenging, and a major economical consideration. Greenbrier Smokeless Minerals engineering staff and consultants, along with DSI/American Commercial, developed a support configuration that was best suited for their slope. The developmental process took into consideration the length of slope, depth of slope at the high-wall transition, economics of a single or multiple entries, waterproofing, stresses on the steel supports and lagging during the backfilling operation. This paper describes the developmental concept of using a single entry, side by side configuration, using steel ?Banjo String? supports with steel plank lagging, to develop a long term permanent installation in a cut and cover application.

Jan 1, 2009

By William G. Fischer

Equations developed by an early researcher in subsidence, F. Martos of Budapest, Hungary, have been slightly modified to produce effective equations for predicting the time-dependent nature of Green River trona mine subsidence. Following the initial study, a survey was run to check the results twenty years after mining of the area had been completed. The final results were within a few centimeters of the value that had been projected. Mining conditions in the Green River area are ideal for this sort of study with trough type subsidence being the surface manifestation of high extraction underground room and pillar caving operations.

Jan 1, 1986

By N. Arbiter

During the first four decades of flotation practice, close to 200 machine designs were patented, although only about a score were ever used commercially. By the end of that period, the rigors of use had resulted in obsolescence of most pneumatic cells, with a few mechanical cells dominating the field. After World War II, newer designs began to appear but most were modifications in varying degrees of older designs with special features added. Of the dozen or so most recent developments, almost all are pneumatic, relying on compressed air instead of impellers for motive power, although in several cases pumps supplement compressors. Table 1 lists a few of the more fully documented new cells, with their significant characteristics, along with similar characteristics of a widely used mechanical cell. New designs in general are emphasizing: bubble size control; in several cases, methods for delivering feed directly to the froth; methods for introducing and dispersing air through nozzles, eductors, packed beds, or permeable walls; and variable cell volumes, relative to capacities, ranging from very small, with less than a second of retention time, to the largest, with retention times of over 20 min. An important question is the extent to which any of the newer designs are based on locating weaknesses in current mechanical cell designs and then using these as a starting point for innovations. In the present study, the key subprocesses which must take place in a cell are outlined; mechanical cells are analyzed to establish where weaknesses may exist; and then alternative subprocesses are considered which could effect improvements. COMPONENTS FOR CELL DESIGN It is assumed that mineral surface chemistry has been modified as necessary to provide optimum potential floatability. While the cell process may affect this to a degree, cell design is primarily concerned with actualizing the existing potential floatability. The cell design problem is to provide more effectively for the following: 1) Dispersion of air to obtain an optimum bubble size distribution at an optimum ratio of air volume to feed volume. 2) A hydraulic environment which permits most effective contact of potentially floatable particles with bubbles: [Table I - Cell Comparisons* Cell Type Mechanical Column Deister Miller ASH No. of units Multiple Single Single Single Retention time min.10/20 17/27 3.8 ca. is Capacities mt/m3s 0.022/0.066 0.066/0.20 0.11 10.4 st/ft3d 1/3 0.3//0.9 m5.0 469 Air hold-up % 15/20 20 n.a. 50/80 Air escape velocity m/s 0.015/0.0200.020/0.025 n.a. n.a. ft/m 3/4 4/5 n.a. n.a. * References: Mechanical (Harris, 1976,1985), (Bassarear, 1985); Column (Travis, et al. 1987); Deister (Zipperian and Christophersen, 1985); ASH (Air-Sparged Hydrocyclone) (Miller 1989).]

Jan 1, 1989

By Dennis Dolinar

Improperly designed support systems have led to unplanned roof falls in longwall tailgates. To prevent such falls requires appropriate support and adequately designed support systems. The National Institute for Occupational Safety and Health (NIOSH) is currently developing a standing support design methodology based on the ground reaction curve. To design the support system with this methodology requires a quantitative assessment of the ground and support interaction, which is developed from instrumented test sites installed in longwall tailgates. To compliment and expand the field data results and to optimize the support design, numerical modeling is also conducted. The models are calibrated from the test site data. In the present study, data was obtained from a longwall tailgate in the Illinois basin. The test site was located in the Herrin No. 6 coal seam at a depth of 500 ft. At the site, the immediate roof was a weak shale overlain by a competent limestone. Above the limestone, sandstone formed the intermediate roof. The floor consisted of a weak underclay. In the study, the performance and interaction with the surrounding rock mass of two different standing supports, an engineered crib and a conventional 4-point wood crib were monitored. The two cribs have similar load-displacement characteristics at least through 6 in of displacement. Beyond 6 in, the engineered crib becomes unstable and begins to strain soften and shed load. The measurements and developed ground reaction curves indicated that the tailgate at the mine was a low convergence environment until well inby the face. Because the convergence was well below their capacity, both supports provide more than adequate levels of support to the tailgate. Significant convergence and support loading did not occur until 90 to 100 ft inby the face. The results of this study were also compared with results from similar studies conducted in the Pittsburgh seam to further advance the development of the ?ground reaction curve? based support system design.

Jan 1, 2009

By Ruifeng Li, Yanghui Ren, Hua Gao

"Since entering the new century, China’s coal industry has witnessed the rapid development, and provided a reliable energy supply for the national economic and social development. But after the “golden decade” of rapid development, the coal industry now is facing overcapacity, low industrial concentration and production efficiency, high pressure of production safety and environmental protection and other prominent issues. Based on defining the connotation of highly-efficient recovery of coal resources, this paper established the relevant 8 indicators to reflect the highly-efficient recovery level of coal resources, summarized the present situation of China's coal resources recovery and the main problems, analyzed the development environment of China's coal industry under the new situation, and finally put forward the strategic measures to promote highly-efficient recovery of coal resources in China.1. Background Coal is the main energy in China. Since entering the new century, China's coal industry has made significant progress, and the level of production safety, resource recovery rate and mining mechanization increased significantly, which provided a reliable energy supply for the rapid development of the national economy. However, due to the changes of China's economic environment, slow growth of energy demand and other factors, some prominent contradictions in the coal industry have significantly restricted the healthy development of the industry. The first problem is serious overcapacity. In the past few years, 16 industries including coal, electric power, chemical and others have invested in coal mines. It is reported (Han 2016) that only during the nine years from 2005 to 2014, the fixed assets of coal industry increased totally more than 3.3 trillion RMB, which brought a large number of production capacity. Affected by the slowdown of economic growth and energy structure adjustment, Chinese coal demand has reached the peak platform and caused the overcapacity of coal supply, so shutting down the backward capacity is the most important task in the future. The second problem is the low efficiency of coal production. There are about 4.3 million coal mine workers in China, and the annual coal production per capita is less than 900 tons, while it was reported (EIA 2016) that the annual production per capita in the United States is more than 10 thousand tons. The third problem is that the green coal resources are not rich. Among the 1.53 trillion tons proven reserves, only about one third are green coal resources in accordance with the principle of ""safety, technology, environment and economy"". The coal resources with high quality and easily mining conditions are not abundant."

Jan 1, 2017

By S. Zamna, M. E. Defoe, Franklin T. Davis, Earl Rau, Yarroll. Warren H., Paul D. Chamberlin

This section contains a description of the ore processing methods of the walled industrial minerals that are not described in major sections of the book. Table I contains the production figures for each of these commodities in the United States and the world. Specifications for concentrates or final mineral product are also summarized as well as prim for them at the time the section was written. In each chapter an attempt has been made to provide the reader with information on the common commercial mineral or minerals involved with the commodity, some of the uses. the processes used to recover and concentrate the minerals, as well as geographical areas where these process are utilized.

Jan 1, 1985

By Mritunjoy Sengupta

The Green River formations in the Western U.S.A. contains vast amounts of petroleum reserves in oil shale deposits. Exploitation of this petroleum reserve calls for large scale mining of the oil shale. Applicable mining methods include conventional underground mining using roan and pillar, sub-level caving and block caving; underground insitu retorting of oil shale and open pit mining. Roam and pillar mining offers one of the most economic methods of underground mining of oil shale. A 2.4 x l09 litre per year (50,000 barrels per day) of crude oil production would require a daily oil shale production of 100,000 tomes per day from underground operations. For this large production, a highly mechanized room and pillar mining muld utilize large capacity diesel equipment such as 85 tonne trucks and 8m front end loaders. The total air requirements of an oil shale mining operations can. be as high as 28443/s. Ventilation planning for such a large scale underground mining operation presents a formidable task. The major objectives of providing ventilation air to underground workings are to dilute airborne .dust and diesel fumes to harmless levels, and to insure that the mine environment is compatible with the health and safety of mine personnel. Regulation of air velocities and air temperatures is a major factor in mine environmental control. Colorado State law requires that a minimum of 0.047m3/s of fresh air be supplied for each kW of diesel power operating underground. Additionally, 0.047m3/s of fresh air must be supplied for each underground employee, and a minimum air velocity of 0.15m/s must be maintained in all working places. It is desirable to exceed this minimum velocity in order to prevent stratification of ventilation air. Moreover, Colorado law also stipulates the maximum allowable concentration of noxious gases mine air, below: ? C02 - 0.5% by volume, 5,000 ppm. ? CO - 0.005% by volume, 50 ppm. ? Oxides of Nitrogen - 0.0025% by volume, 25ppm. ? Nitrogen Dioxide 0.005% by volume, 5 ppm. This paper examines ventilation requirements for the underground mine, with respect to air quality requirements and distribution of air in mine workings in light of the above regulations. Analyses were made for sane typical mining plans to determine airflow resistance or pressure drops and fan horsepower requirements. In addition, the possible occurrence of high concentrations of toxic gases, was examined. Expected temperature levels in mine workings were approximated.

Jan 1, 1980

By Bryce T. Tripp

Utah produces a wide variety of industrial rock and mineral commodities, valued in 1998 at $534 million (28 percent of the total non-fuel mineral production of Utah). Major commodities produced in 1998 include: halite; potash and magnesium chloride; Portland cement; sand and gravel; car- bonates including lime, limestone, and dolomite; phosphate; crushed stone; clays; perlite; gypsum; and sulfur and sulfuric acid. Commodities produced in lesser amounts include: diatomite; pumice; silica; lightweight aggregate; gemstones, ornamental stone, and mineral and fossil specimens; byproduct sulfur and sulfuric acid; silica; and building stone. The years 1993 through 1998 were a period of steady growth in industrial rock and mineral production. However, some commodities have grown much more rapidly than others. The robust western U.S. economy has stimulated production of construction-related commodities like sand and gravel, raw materials for Portland cement, lime, and building stone, resulting in exploration for raw materials, development of new quarries, and expansion of existing plants. Noteworthy specific developments include: (1) opening of new aggregate operations and buyouts of small aggregate operations by large national and international firms, (2) expansion of a lime operation and two cement plants, and (3) development of several new gypsum mines. The future of the industrial minerals industry in Utah looks promising despite a more restrictive regulatory environment and a growing anti-development attitude among its citizens. While Utah has become less pro-development than it was prior to the 1990s, it is still moderate compared to strongly anti-development states, so companies have some motivation to choose Utah in their strategic mineral development plans. As long as the western states' economies continue to grow, Utah's industrial minerals industry should thrive.

Jan 1, 2001

By Murali M. Gadde

Perimeter mining is a special form of very productive partial extraction method practiced at some mines in the United States. In the Illinois Basin mines where all major coal seams have weak underclay in the immediate floor, experience shows that any long-term ground control issues will arise due to floor failures rather than instability of the coal pillar itself. While there is a significant amount of work done on floor stability associated with regular pillars, no work has been done so far on the stability of perimeter pillars. This paper reports the results of a comprehensive study that was conducted for the first time on floor stability during perimeter mining in the Illinois Basin mines. A special plate template, which mimicked a common perimeter pillar configuration was created to conduct in-situ bearing capacity tests at five mines in three states of the Basin. Additionally, because of the complex shape of pillars created in perimeter mining that defies any closed-form solution, floor bearing capacity was studied using three-dimensional nonlinear numerical modeling. Based on these in-situ and numerical studies, some guidelines are provided for perimeter pillar stability analysis.

Jan 1, 2009

By M. L. W. Tuttle, B. R. Berger

Our study focuses on the geology, hydrology, and geochemistry of a variety of molybdenum (Mo) porphyry systems. The systems are either high fluorine, granite, Climax-type, systems (e.g. Mount Emmons/Redwell Mo deposit, Colorado and Questa Mo deposit, New Mexico) or low fluorine granodiorite systems (e.g. Buckingham Stockwork Mo deposit, Battle Mountain, Nevada and Cannivan Gulch Mo deposit, Montana). The water quality of streams, natural springs, mine discharge, and ground water from drill holes were assessed in the region of these deposits. The ultimate goal of our study is to understand the environ-mental behavior of these Mo porphyry systems in the context of geologic setting, hydrologic regime, and climate.

Jan 1, 2004

By C. J. Hall

The simplest natural ventilation cycle is similar to a Joule or Brayton cycle. This comprises two reversible adiabatic processes in the shafts and constant pressure processes underground and on surface. The thermal efficiency of such a cycle is given by the temperature increase in the downcast shaft divided by the absolute temperature of the air at the bottom of the downcast shaft, and is independent of the temperature increase underground. This efficiency is comparable to the Carnot efficiency, which is the greatest possible value between constant temperature reservoirs, source and sink. Two variations of the Joule cycle are investigated, using numerous work examples. In the first, dry air is used as the working substance, a fan is provided at the top of the upcast shaft, and various mass rates of flow are used with frictionless shafts and a constant resistance value in the horizontal mine workings. The lost work less the fan work gives the natural ventilation work, and this divided by the enthalpy increase in the workings gives the thermal efficiency. The thermal efficiency increases dramatically with mass rate of flow, although the enthalpy increase remains constant. This appears to violate the second law of thermodynamics, since the frictionless case has a Carnot efficiency. When the lost work is added to the enthalpy increase, however, the efficiency decreases slightly from the Carnot value, to conform with the second law. This increase in efficiency with mass rate of flow is often referred to as the reheat effect, although the air is not heated. The second investigation is similar to the first, except that the air entering the downcast shaft contains a small amount of water vapor, and there is evaporation in the mine workings only, until the air entering the upcast shaft is saturated. There is, of course, condensation in the upcast shaft. In this case, it is not possible to calculate the Carnot efficiency, but the thermal efficiency is 20 to 40% of the similar dry air values. This decrease is much more than can be accounted for by the larger value of specific heat for water vapor. In addition, the natural ventilation work is almost constant with increased mass rate of flow, and the thermal efficiency based on heat addition tends to decrease. The thermal efficiency based on heat and lost work decreases in conformity with the second law. The reasons for the differences in behavior between dry and moist air are not readily apparent.

Jan 1, 1991

By Jun Han

Coal has been mined in the Kailuan mining area for more than 130 years. The remaining reserves consist of, in large part, coals that would have been considered economically unminable or technically not feasible by the previous generations. Some of the current operations have to resort to overmining because the lower seams had been extracted in the past. This paper deals with the feasibility and proper layout of mining roadways of overmining carried out in the No. 5 seam of Qianjiaying coal mine of Kailuan mining area using numerical and physical simulation. FLAC2D was used to investigate the characteristics of stress and displacement in the overburden after extraction of the lower seams. It also analyzed the proper layouts of gateroads in the upper seams, i.e. locating them in the stress-relief zone of the gob so that their stability can be easily maintained. In addition, a two-dimensional physical model was constructed for investigation of damages to the upper seams due to mining of the lower seams. Finally, based on the results of investigations, proper gateroads layout was designed and successful extraction was implemented for panel 1357 in the No.5 seam.

Jan 1, 2009

By Richard M. Bennett

Twelve linear test foundations were constructed over an advancing longwall panel in southern Illinois, six were located along the centerline, and six in the maximum tension zone. One footing in each set was a control foundation constructed according to conventional practice. It suffered severe damage. Footings with reinforcing bare and post-tensioning had much smaller elongations, with the post-tensioning preventing cracking of the footing. Footing-soil interface treatments of plastic-on-sand and plastic-on-soil served to reduce damage. The addition of steel fibers to the footing had about the same effect as an interface treatment. Sill plate construction (butt-jointed versus lap-jointed) appeared to significantly affect the behavior.

Jan 1, 1986

By M. Tirmarche, J. Brenot, J. W. Piechowski

INTRODUCTION Statistical analysis of results obtained by workers survey is very often limited to the determination of the collective dose and mean annual values. This information is not sufficent by itself for radiation protection purposes since the cumulative exposure of a worker during his working life is not taken into account. A more complete analysis would be obtained by considering both: [ ] These two notions are different. The former depends on the evolution of the protection with time and is related to annual limits (ICRP, 1977 and ICRP,1977 a). The second depends mainly on the works performed during the period of survey, the interference of protection evolution is weakened. So it is useful to foresee how the individual average annual doses would be when considering survey periods of 5, 10 years, or more. STUDIED POPULATION In order to analyse the two previously mentionned notions it is necessary to follow up a well defined population of workers which is continuously exposed to the radiological hazards on a long enough period. The selected population is that of the workers of the French uranium mines always present during the 1971-1979 period (9 years). The number of individuals is 937. The radiological hazards are: 1. exposure to radon and short-lived daughters 2. exposure to long-lived ore dust 3. external irradiation. The workers of the uranium mines are exposed to these radiological risks in different ways according to the work performed. It is therefore necessary to subdivide the population into more homogeneous groups with respect to the radiological risks. Three groups are considered: - Group 1 : 227 individuals whose radon and dust exposures are always nil - Group 2 : 449 individuals whose radon and (or) dust exposures are different from 0 every year - Group 3 : 261 individuals represent a mixed category. Some features of these groups are given in table 1. [ ] The 937 followed individuals represent approximatively the half of the whole population of the French uranium mines. Taking into account the procedure adopted to select the studied population, it appears clearly that this population is not representative of the whole miner population. DOSIMETRIC RECORDS Three risk indicators are considered .Individual annual exposures to radon and its shortlived daughters. They are determined by ambient monitoring based on radon concentration measurements and recording of the times elapsed in the various workplaces. For each worker the annual exposure is represented by the mean annual air concentration and is expressed as a fraction of the maximum annual concentration (MAC). Given the administrative arrangements and the effective state of equilibrium between radon and its daughters, the maximum annual concentration is practically equivalent to 1 Working Level = 2.08 x 10- 5 jm-3. (UNSCEAR, 1977). . Individual annual exposures to long-lived ore dust which are also expressed in fraction of the maximum annual concentration. . Individual annual doses of external irradiation (X and [y] rays) expressed in mSv (= 10-3 Sievert). Irradiation monitoring is based on use of individual film badges.

Jan 1, 1981

The only good news in the exploration sector in 1982-a year plagued by low metal prices and weak demand-was precious metals. Gold in particular remained in the forefront, as it has for at least the past three years. The reason for this is partially due to gold's seeming resilience to conventional supply side factors-such as new production-that normally influence many other metals. Also, with projected production costs of about $6.40-$9.65/g ($200¬$300/oz), modest deposits with average grades can offer an early return on capital investment and good profit potential. Keeping escalating capital costs for new mining ventures within reason has shifted gold exploration efforts in recent years. Many mining companies are seeking relatively low grade, modest tonnage, near-surface gold mineralization. This, of course, leads to lower development costs using open-pit mining methods. Recent refinements in the carbon-in-pulp recovery process also has enhanced the economics of such deposits. Slumping economic conditions certainly played a key role in shaping exploration activity last year. Nearly every major mineral-producing state recorded exploration slowdowns. In Alaska, for example, development expenditures approached the level of exploration spending for the first time in the state's history. This not only reflects major companies' decisions to move toward production but also the economic slowdown. The worldwide recession stopped Nevada's exploration and mining boom "dead in its tracks," said John Schilling, state geologist. The year was one of layoffs and closings for the state's mines and exploration offices, he reported. Similar trends were noted in most other states, especially in the West and Southwest. In the Pacific Northwest, however, exploration appeared to continue at a relatively good pace considering the metals market. In the mining geophysical community, recent advances in telecommunications and microprocessor technology are continuing to provide a positive impact. Many geophysicists have begun using satellite digital communication links to access computer systems from remote sites where using a microcomputer would be difficult. There were also major contributions made in exploration geochemistry last year. Highlights include progress in formulating mineral deposit models, geochemical exploration in glaciated and arid environments, and publication of many informative books. The following state-by-state summary and articles on geophysics and geochemistry provides a detailed view of exploration events throughout the US in 1982.

Jan 5, 1983

By Peng Gao

Coal-based reduction followed by magnetic separation is an innovative technology used in processing refractory iron ores. Given that size is essential to the separation of the metallic iron from the gangue, the morphology of metallic iron particles and their evolution during coal-based reduction are investigated in the present work. The size of the metallic iron particle increased from 128.76 µm to 565.70 µm when the reduction time increased from 20 min to 60 min at 1,225° C and C/O (i.e., the amount of coal addition in terms of the gram-atomic ratio of the fixed carbon in the coal added to the combined oxygen in iron oxides) of 2.5. Based on our microstructural and metallographic analysis, the iron ore reduction process can be divided into three stages: (1) metallic iron particle formation, (2) iron oxide reduction and metallic iron assembly and (3) metallic iron particle growth. Almost all iron oxides are reduced to metallic iron in the second stage. These newborn metallic iron particles are energetically active and able to assemble and grow, and are eventually separated from the gangue. The large metallic iron particles benefit the subsequent magnetic separation process.