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By A. Davaliev, K. Hrkovic, V. Pavlovic

On the territory of Macedonia in South Yugoslavia primary and dory gold occurences were known since ancient times. Remnants of numerous goafs and remainders of washaries on river terraces and alluviums date right back to the times of Phillip II and his son Alexander of Macedonia and from Roman times, as well as from the Middle Ages witness exploitation of primary and secondary gold. More recent explorations on primary and secondary gold occurrences date from the period between two World Wars. Over that period a number of private companies, each on their own jointly, carried out gold exploration, particularly of alluvial occurrences on rivers emptying into River Vardar, starting from Skopje to the Greek frontier. The latest gold explorations carried out In the alluvium of River Konjska date back in 1976, and in 1978 old terraces of River Konjska were explored. The Visibility Study was prepared on possibilities of exploitation of gold from River Konjska alluvium. In the paper are collected the basic date an all known primary and secondary occurrences of gold, the results of the latest explorations, and the study itself. To-date geological explorations and analyses show very interesting potentionality of River Konjska and River Vardar alluvium, which proves continuing of he further explorations. For the moment, it is necessary to re-explore more complete view of the deposit. After that it will be possible to make complete techno-economical estimation of the auriferious alluviums and the conditions of the evaluations of the alluvial gold. 1. REVIEW OF PRIMARY AND SECONDARY GOLD DEPOSITS IN MAOEDONIA,YUGOSLAVIA 1.1. Primary deposits Scarse data are available for primary gold deposits in Macedonia` being unadequate for clear

Jan 1, 1988

By Stephen B. Castor

The rare earth elements (REE) which include the 15 lanthanide elements (Z = 57 through 71) and yttrium (Z = 39) are so called because the elements were originally isolated in the late 18th and early 19th centuries as oxides from rare minerals. Most REE are not as uncommon in nature as the name implies. Cerium, the most abundant REE (Table 1), comprises more of the earth's crust than copper or lead. Many REE are more common than tin and molyb¬denum, and all but promethium are more common than silver or mercury (Taylor, 1964). Promethium (Z = 61) is best known as an artificial element, but has been reported in very minute quantities in natural materials. Lanthanide elements with low atomic numbers are generally more abundant in the earth's crust than those with high atomic numbers. In addition, lanthanide elements with even atomic numbers are two to seven times more abundant than adjacent lan¬thanides (Table 1) with odd atomic numbers. The lanthanide elements traditionally have been divided into two groups: the light rare earths (LREE), lanthanum through eu¬ropium (Z = 57 through 63); and the heavy rare earths (HREE), gadolinium through lutetium (Z = 64 through 71). Although yttrium is the lightest REE, it is usually grouped with the HREE to which it is chemically and physically similar. The REE are lithophile elements (elements enriched in the earth's crust) that invariably occur together naturally because all are trivalent (except for Ce+4 and Eu+2 in some environments) and have similar ionic radii. Increase in atomic number in the lanthanide group is accompanied by addition of electrons to an inner level rather than the outer shell. Consequently, there is no change in valence with change in atomic number, and the lanthanide elements all fall into the same cell of the periodic table. The chemical and physical differences that do exist within the REE group are caused by small differences in ionic radius, and generally result in segre¬gation of REE into deposits enriched in either light lanthanides or heavy lanthanides plus yttrium. The relative abundance of individual lanthanide elements has been found useful in the modelling of rock-forming processes. Comparisons are generally made using a logarithmic plot of lanthanide abundances normalized to abundances in chondritic (stony) meteorites. The use of this method eliminates the abundance vari¬ation between lanthanides of odd and even atomic number, and allows determination of the extent of fractionation between the lanthanides because such fractionation is not considered to have taken place during chondrite formation. The method is also useful because chondrites are thought to be compositionally similar to the original earth's mantle. Europium anomalies (positive or negative departures of europium from chondrite-normalized plots) have been found to be particularly effective for petrogenetic modelling. REE were originally produced in minor amounts from small deposits in granite pegmatite, the geologic environment in which they were discovered. During the second half of the 19th century and the first half of the 20th century, REE came mainly from placer deposits. With the exception of the most abundant lanthanide el¬ements (cerium, lanthanum, and neodymium), individual REE were not commercially available until the 1940s. Since 1965, most of the world's REE have come from two hard rock deposits: Mountain Pass, United States, and Bayan Obo, China. GEOGRAPHIC DISTRIBUTION OF REE DEPOSITS More than 70% of the world's REE raw materials come from three countries: China, the United States, and Australia. China emerged as a major producer of REE raw materials during the 1980s, while Australian and United States market share decreased dramatically (Fig. 1). Table 2 gives recent annual production figures along with estimated reserves by country, and Fig. 2 shows loca¬tions of significant REE mining. MINERALS THAT CONTAIN REE Although REE comprise significant amounts of many minerals, almost all production has come from less than ten minerals. Table 3 lists minerals that have yielded REE commercially or have po¬tential for production in the future. Extraction from a potentially economic REE resource is strongly dependant on its REE miner¬alogy. Minerals that are easily broken down, such as bastnasite, are more desirable than those that are difficult to dissociate, such as allanite. In general, producing deposits contain REE-bearing min¬erals that are relatively easy to concentrate because of coarse grain size or other attributes. For more thorough discussions of REE¬bearing minerals see Mariano (1989a) and Cesbron (1989).

Jan 1, 1994

By John D. Hanifin, C. Kevin Moon, Eric C. Wang

Value Engineering on Connecticut DOT’s Walk Bridge selected the trenchless option for utility relocation to address the channel crossing’s environmental concerns. The design and construction considerations of the twin micro-tunnel drives and associated shafts are presented. Key challenges included vertical alignment selection to achieve minimum one-tunnel diameter stable cover within thin glacial till underlying extremely soft clay, limited choice of pipe and joint materials meeting stringent non-metallic conduit requirements, thermal grout backfill application, and the close proximity of temporary trestle piles. Mitigation measures were developed for potential point loading pipe damage from remnant boulder fragments in the annular space.

Dec 1, 2022

By D. H. Carlson, J. H. Johnson, C. F. Renders

Research was conducted at a western coal mine on a wide variety of underground mining vehicles to develop testing procedures for portable instrumentation monitoring of tailpipe concentrations of diesel particulate matter (DPM), carbon dioxide (CO2) carbon monoxide (CO) and nitric oxide (NO). DPM was measured using the Emissions Measurement Appa¬ratus (EMA) developed by Michigan Technological University (MTU), and an ECOM-KL five-gas analyzer was used to measure gaseous tailpipe concentrations. Baseline concentrations of the tailpipe pollutants were measured using vehicle systems to load the engine. Concentrations before and after the water scrubber were measured and water scrubber efficiencies were estimated by calculation. Field measurement procedures were established. Heavy-duty vehicles with automatic transmissions were loaded using the torque converter to stall the engine. Consistent engine loading for light-duty vehicles with manual transmissions involved placing the transmission in neutral and adjusting the throttle to maintain a constant engine speed of 2,500 rpm. Tailpipe CO2 concentrations for Caterpillar 3306 and 3304 engines were compared to laboratory CO2 data from Caterpillar and MSHA to help determine if engine settings were correctly adjusted for operation at high altitudes. (Perfect agreement between the mine vehicle tailpipe and laboratory measurements would not be expected because of the differences in the test conditions.) DPM concentrations for light-duty vehicles ranged from about 20 to 160 mg/m3, and one light-duty vehicle averaged near 1,000 mg/m3. DPM concentrations for heavy-duty vehicles ranged from about 55 to 200 mg/m3. Widely ranging DPM concentrations for a particular vehicle type reflect the state of maintenance, fuel rate settings and different engine loading procedures as well as differences between samples collected upstream and downstream of the waterscrubber. The calculated DPM removal efficiencies due to the water scrubber varied considerably between vehicles, ranging from 13% to 51%. Calculations indicate that, under worst-case conditions, very large reductions in DPM may be required to meet the proposed DPM PEL of 0.15 mg/m3, even on vehicles with water scrubbers. In-mine ambient air studies, which are needed to actually measure the impact of the tailpipe concentrations on the work environment and the effect of mine ventilation on the dilution of DPM were not done in this first set of tests.

Jan 1, 2000

By Scott G. Britton

Planning is a management tool used to solve problems and provide data and decision alternatives for company growth, profitability, and direction. Strategic planning is defined as the efforts needed to accurately measure the risks of obtaining a result from future actions given a finite number of outcomes. The techniques of strategic planning are being applied more and more to underground mine design as a result of the fierce market conditions underwhich the industry is facing today, and the conditions they will likely face in the future. The objectives of strategic planning are centered on the ability of the operator or company to manuever its limited resources to the best position available under the given future scenarios. This paper briefly examines the most popular techniques for accomplishing these objectives, how these techniques fit into the current mine management decision-making, and what results to expect from these techniques in planning efficient underground mines.

Jan 1, 1985

By William J. Miles

From a historical perspective, bentonite is the common rock term for various uses and applications. Its name originates from water-based muds near Fort Benton used for lubrication of wagon wheels during the 19th century migration to western territories (which are presently part of the United States) when the pioneers ran out of axle grease. From a clay mineralogy perspective, bentonite is composed primarily of montmorillonite, an expandable magnesium aluminum silicate clay mineral. When magnesium occupies an octahedral structural site that usually contains an aluminum atom, a negative charge is created. In order to neutralize negative charges, cations are drawn to the interlayer surfaces between clay mineral sheet structures. Modem applications for bentonite depend on the sodium or calcium cation populations and other characteristics of the clay mineral. When sodium is the dominant cation, the material is called sodium bentonite, also known as swelling bentonite, western bentonite or Wyoming bentonite. When calcium or magnesium is the dominant cation, the material is called calcium bentonite, also known as non-swelling bentonite w southern bentonite.

Jan 1, 2012

By R. D. Beard

Puerto Rico lies within the remnants of a deformed Cretaceous island arc system in the northeastern Caribbean. The Island can be divided into three broad geologic provinces: the Central Volcanic-Plutonic Province (Lower Cretaceous to middle Eocene), and the Northern and Southern Limestone Provinces (early Oligocene to middle Miocene). Known precious metal deposits are generally small and occur in veins and shear zones within Lower and Upper Cretaceous volcanic and plutonic rocks. Some Tertiary igneous rocks are also mineralized. Selected indications of disseminated lithology-controlled mineralization could represent larger deposits. Associated metals in some deposits include copper, zinc, and lead. At present, tax policies, population density, political outlook, and lack of proven significant precious metal deposits discourage the establishment of a metal mining industry.

Jan 1, 1993

By K. Häge

"Die Nachhaltigkeit der Braunkohlengewinnung in der öffentlichen Wahrnehmung wird nur weiter erfolgreich kommuniziert werden können, wenn durch konkretes Handeln glaubhaft gezeigt wird, dass die offenen Fragen fair und solide beantwortet werden. Dazu gehören insbesondere die neue innovative technische Lösung sowie das sensible Interessenmanagement. Die Braunkohlenindustrie hat gelernt, dass Offenheit und nicht zuletzt das beständige Bemühen um den Meinungsaustausch mit ihrem Umfeld wichtige Elemente sind. Der in Jahrzehnten erworbene Schatz an Glaubwürdig-keit ist eine Basis, auf der die Braunkohlenindustrie ihre Zukunft gestalten kann. Darüber hinaus sind politische Rahmenvorgaben erforderlich. Das öffentliche Interesse an einer sicheren und preiswerten Energieversorgung unter Einschluss der Braunkohle ist unverzichtbar. In diesem Kon-text kann dann die Braunkohle die an sie gerichteten Fragen der Ökonomie, der Ökologie und der Sozialverträglichkeit auch mit Hilfe von Indikatoren beantworten.ABSTRACTThe discussion of the sustainability of lignite mining can only be continued successfully if the indus-try acts in a practical manner and demonstrates trustworthiness by responding fairly and reliably to open questions. This includes new and innovative technical solutions as well as the sensitive management of interests. The lignite industry has learned that openness and the constant effort to exchange viewpoints within their environment are all essential elements. The credibility that has been gained over the decades is the foundation on which the lignite industry can build its future. Beyond that a framework of political guidelines is necessary. Public interest in a secure and inex-pensive energy supply that also includes lignite is indispensable. In this context, the lignite industry will then be able to answer the questions which are directed at them and concern the economy, ecology, and social tolerability also by indicators."

Jan 1, 2005

By Michael Schultz, Gregory Sanders

The City of New Haven is planning to construct the Downtown Storm Sewer Infrastructure Improvement project to mitigate on-going stormwater flooding in the Long Wharf District. The proposed project includes a 685 cubic feet per second (cfs) stormwater pump station and a 3,200 linear feet (975 meter) long tunnel segment with an internal diameter of 120-inches (3.05 meters). This paper presents the aspects of the final design and the use of the cloud-based data management software to make better data-informed decisions. The software was used to create a spatially aware database of the subsurface conditions, as well as improve visualization and analysis of the soil properties.

Dec 1, 2022

By Georges E. Vaillant

Air pollution control in primary aluminum smelter . Various processes are known for air pollution in electrolysis plants. Mainly two systems have to be taken into consideration: -Treatment of concentrated gases collected directly from hooded pots. This is normally achieved by either dry or wet process. This is not the object of this paper as these processes have been already described. -Treatment of low concentrated fumes. A certain amount of gaseous and solid fluoride (35 % of total fluor pollution) goes out of the hooded pot. Gases commonly called secondary fumes are generally treated by wet process. The object of 'this paper is to describe two plants with specific treatment for secondary fumes. 1/ A plant in operation in Vlissingen (Netherlands) for PECHINEY. 2/ Presentation of tests carried out by a specialized Company. The results of such tests have been used for the design of the scrubbers presently under construction for ALUMINIO ESPANOL San Ciprian (Spain).

Jan 1, 1978

By R. P. Stahura

In many ways, conveyors are the lifeline of mining and processing operations. Like arteries in the human body, they continuously supply materials to and carry finished products and waste away from vital on-going operations. And like arteries, when the conveyors are running with less than maximum efficiency and productivity, it spells serious trouble for the operation's overall health. Inefficient conveyors suffer carryback, leading to the build-up of materials on idlers and other expensive components. They spill and leak material at loading zones and conveyor transfer points, causing accumulations that can damage the belt, wear moving components, and increase both clean-up labor and maintenance expense. They wander or mistrack, spilling material and endangering personnel and conveyor components including the belt itself. And through these inefficiencies, they multiply the operation's hidden costs. These added expenses are created in lost production, increased downtime for service and maintenance, and the cost of the replacement of prematurely worn equipment. In addition, the attitude that inefficiency is "good enough" is recognized elsewhere in the organization; as a result, other departments relax or operate at less than peak performance. Quality goes down and with it employee morale.

Jan 1, 1992

By Barrie Butt, V. S. Znamensky

The opportunity for an exploration geologist to follow a successful exploration project through the feasibility, financing, construction, development, and exploitation phase is rare. In addition, it is not often that the exploration geologist can be present during the mining of a deposit to explain why certain actions were taken or interpretations made, and to find out how these interpretations turned out in actuality. At the Woodsreef chrysotile asbestos mine in New South Wales, Australia, mining has been- in progress for seven years and the writer of this chapter has been intimately associated with the project during the five years of exploration and seven years of exploitation. The Woodsreef mine has had major production problems, the majority of which have stemmed from the unique characteristics of the ore body and fiber. Because of the latter feature, much research has been undertaken by Woods- reef and other scientific organizations in Australia, England, and Canada regarding the Woodsreef fiber. The answers to some of the problems have negated some accepted concepts of asbestos ore milling and led to the development of new techniques. Some of these new techniques include the adoption of microscopic fiber counts as a routine procedure, the modification of accepted evaluation procedures, the development of new machines for dedusting fibers, and the recognition of a fiber with a unique milling behavior pattern and, possibly, properties. The problems experienced can be broadly divided into those associated with the geology and the physical properties of the fiber. It is possible that the same features may manifest themselves in other deposits around the world, and if they can be recognized during the exploration stages, a feasiblity evaluation may be just a little closer to the actual. The Woodsreef chrysotile asbestos deposit (latitude 30°24' S, longitude 150°44' E) is located 80 km north of Tamworth, NSW, Australia. The mine has been in production for six years and has a present scheduled mining rate of 33.11 Mt/y. An eight rock line mill treats an average of 7000 t/day, after beneficiation, and yields fiber grades in the range of group 4 to group 6 with some floats. The estimated re- serves of 30.56 Mt, with an ore to waste ratio of 1:3.0, are contained in two main zones that are designated the North and South zones. Mining started in the South Zone in 1972 and then, be- cause of the higher ore value, moved to the North Zone in 1975. Presently, there are two distinct open cuts referred to as the South and North pits that will eventually be worked together. The Woodsreef mine is owned by Woodsreef Mines Ltd. and is operated by Chrysotile Corp. of Australia Pty. Ltd., and is one of only two producing asbestos mines in Australia. The second mine is at Baryulgil, (latitude 29°13' S, longitude 152°37' E), and is operated by a subsidiary of Woodsreef Mines Ltd. This operation produces about 500 t/y for a captive market. An exploration program is being conducted in the area surrounding this small producer with a significant degree of success. The concepts developed during the exploitation of the Woodsreef deposit are being incorporated in the evaluation of the Baryulgil area, and if the Baryulgil deposit proves to be eco- nomic it is hoped that this approach will eliminate some of the major crises that have beset the production at Woodsreef during the first four years of operation. The purpose of this chapter is to describe the Woodsreef deposit, and more important, to

Jan 1, 1986

By Javad Sattarvand, Frimpong Kwaku Asare

The safe evacuation of miners during an emergency in the shortest amount of time is one of the most essential features of a mining operation. Despite advancements in mine evacuation research, the usage of mine vehicles during evacuation has not been considered. The majority of recent studies have been done on miners’ evacuation on foot. Mathematical formulations including Minimum Cost Network Flow (MCNF) models, Dijkstra's algorithm, Floyd-Warshall algorithm, and Ant Colony Optimization models have been used to solve mine evacuation problems. These models, which concentrate on determining the shortest escape routes during the evacuation, have been found to be computationally expensive and may not offer the best solutions in some cases. The goal of this paper is to incorporate light vehicles in the evacuation process using a mixed-integer programming approach. The methodology aims to minimize the total time required to evacuate the mine, ensuring minimal exposure of the miners to the adverse conditions that triggered the evacuation.

Jun 25, 2023

By V. C. Lo

The major cost in comminution is energy consumption, which can be as high as 50 percent of the operating cost. Improvements in plant operations have resulted in up to a 15-percent reduction in energy usage (kwh/t). These improvements have been made through optimization of grinding efficiency and use of expert model-based control systems. Optimization involves the determination of the levels of the critical operating conditions that result in the most efficient breakage of ore in the mill. These optimal levels are identified through plant/laboratory testwork and computer simulation using advanced process models. Model-based expert control achieves the maximum performance from the grinding circuit by identifying the characteristics of the ore in the mill with an optimal on-line estimator. Using this information, the control system dynamically determines the operating point that will yield the optimal performance. Two industrial applications of grinding circuit optimization and model-based control are presented to demonstrate the power of this new technology.

Jan 1, 1995

By Charles A. Ramsey, Kathleen S. Smith, Philip L. Hageman

We developed a statistically based strategy for sampling the surficial material of mine-waste dumps for use in screening and prioritizing historic dumps on abandoned mine lands. This sampling strategy entails the collection of a representative composite sample from individual dumps and allows for regional or watershed-based assessments. One 30-inment dump-composite sample collected using this sampling strategy contains as much information, relative to average value, as 30 individual grab samples at 1/30 of the analytical cost.

Jan 1, 2000

By Heinz Hoberg, Fred Ulrich Schneider, Rudolf Diegel

The risk of contamination of dumped tailings and ground water by coal flotation reagents has been investigated by using the 14C-radiotracer method for adsorption and desorption measurements. The results indicate, that a high amount of the reagent components adsorbed on the tailings if there was no coal in the pulp. In coal flotation however a competitive adsorption behaviour could be observed, with the effect that only a low quantity of reagents adsorbed on the tailings. Mobilization tests showed, that only small quantities of reagents could be desorbed by rinsing water. Therefore the contamination of ground water should be low.

Jan 1, 1995

By Al. Valero

This paper quantifies in universal units (energy units), the annual decrease in the mineral endowment of the planet. This is done for some important extracted non-fuel minerals, namely aluminium, cobalt, chromium, copper, gold, lead, uranium and zinc and is compared with the depletion figures of conventional fossil fuels. The results of this study reveal that each year, the decrease of the global non-fuel mineral bonus provided by Nature is 2 to 3 orders of magnitude greater than the loss associated to the burning of fossil fuels. Particularly for 2008, the depletion in mineral wealth of the studied commodities was about 20 times greater than that of fossil fuels. The assessment methodology is based on the Second Law of Thermodynamics. It quantifies the useful energy (exergy) required to concentrate a mineral from a completely dispersed state in the crust, to the conditions of composition and concentration found in the mines. Exergy can be a useful measure for quantifying the mineral depletion caused by man, as it takes into account the main physical features that make minerals valuable: composition and concentration. This analysis enhances and puts numbers to the importance and necessity of material reuse and recycling.

Jan 1, 2011

By Todd Minoski, Matthew McElhinney, Mark Mazzella, Morgan Sears, Craig Compton

The National Institute for Occupational Safety and Health (NIOSH) is staffed with Engineers, Geologists, and Field Technicians conducting a variety of ground control research. The mission of the ground control teams within the Mine Systems Safety Branch (MSSB) is to eliminate ground failures leading to mineworker injuries and fatalities. Advancing the science behind ground control relies heavily on conducting mutually beneficial research at participating mines which is detailed in specific references throughout the paper. The ground control teams have several types of field instruments at their disposal to measure the ground response in underground mines. These include borehole pressure cells (BPCs), vibrating wire stress meters (VWs), hollow inclusion cells (Hi-Cells), roof and rib extensometers, load cells, and convergence meters. These instruments are used to measure changes in pressure, strain, and displacement within the underground environment. Instrumentation data is collected automatically using intrinsically safe or MSHA permissible dataloggers if required. Information is transmitted to the dataloggers using approved cable to distances of 200–1,000 ft. depending on the type of datalogger being used. Once mining is completed, the dataloggers are retrieved and brought to the surface, providing in-mine data to mine management and engineers for the conditions currently being encountered in a particular mine. This data, in conjunction with geologic data and stress mapping, can be used to validate numerical models. The practical application of these models is extremely important for mine management and engineers, particularly when faced with more challenging mine environments. Insight gained from applying these models can be used to make better engineering-based judgments for areas that will be mined in the future. The impact of such applications can result in a reduction of ground-fall accidents and injuries as well as generally safer working conditions.

Feb 1, 2024

By L. B. Paterson

Mining Engineers throughout the world have an appreciation for the importance of the role of the Blasthole Drill in one of the primary elements of the mining process. This paper highlights areas that could influence the overall cost effectiveness of that process of breaking rock and how equipment is designed and configured to meet that challenge. Factors influencing drill productivity and overall cost effectiveness are addressed, both in the Mine Environment and on the Blasthole Drill.

Jan 1, 1999

By K. F. Unrug

The concept of bolting mine roofs to prevent roof falls was initiated in the 1950's and was quickly accepted by the mining industry because it was inexpensive, effective and convenient. The principle regarding roof bolting were that: a) the loose and fragmented rocks were suspended from or clamped to more competent surrounding rock and b) generally, by clamping several layers of thin and laminated strata, a more competent monolithic beam is created.

Jan 1, 1991