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By P. Venkatraman

Laboratory and pilot-scale test data have shown that the innovative feed presentation of the CrossFlow separator provides improved metallurgy when compared to traditional hindered-bed or teeter-bed classifiers. This design feature prevents excess water from entering the separation chamber and disrupting the overall fluidization flow rate within the teeter zone. Recent side-by-side industrial-scale evaluations have verified that this technology can improve overall efficiency, reduce the cut point of separation, and increase throughput capacity. This paper describes the important features that make this novel separator ideally suited for size classification and density concentration. Test data from heavy mineral, phosphate, and industrial mineral applications are also discussed.

Jan 1, 2005

By T. I. Nelson

Natural aggregates, primarily stone, sand and gravel, are recovered from widespread, naturally occurring mineral deposits and processed for use primarily in the construction industry. They are mined, crushed, sorted by size, and sold either loose or in concrete products to build roads, houses, buildings, and other structures. Smaller quantities are used in agriculture, cement manufacture, and industries employing chemical and metallurgical processes. The growth of cities, their buildings and the highways that connect them have created demand for enormous quantities of aggregates. The aggregates industry is the largest mining industry in the United States in terms of production by weight, volume and by number of active operations.

Jan 1, 2005

By J. Yuan

Ground calcium carbonate (GCC) and chemically precipitated calcium carbonate (PCC) have become important mineral-based commodities in recent years. GCC manufacturing generally requires high purity and high brightness deposits of marble, chalk or limestone as the stone source. PCC usually uses limes made from lesser quality limestone deposits. GCC products have a wide span of particle size, with a d50 size ranging from sub micrometers to as large as several inches such as those used in landscaping. PCC products are typically limited to less than 10 µm (1,250 mesh). Each PCC product has a narrowly distributed size range. GCC and PCC products tend to have higher levels of whiteness com-pared with other traditional filler and extenders, such as kaolin and talc. Published statistics of GCC production volume often vary due to the exclusion of certain size range GCC products. According to Roskill’s latest estimate, world GCC capacity was believed to exceed 56 Mt (62 millionst) during 2004 for all grades.

Jan 1, 2005

Fluorspar was not mined in the United States during 2004, although a small amount of usable synthetic fluorspar (CaF2) was produced from industrial waste streams. The majority of fluorspar consumed in the United States came from imports or stockpiled material purchased from the National Defense Stockpile (NDS). In addition, consumption is supplemented by use of by-product fluorosilicic acid produced at phosphoric acid plants. In 2004, annual production of fluorosilicic acid was 50kt (55,000 st) or about 88 kt (97,000 st) of 92 percent fluorspar equivalent. In 2004, annual production of fluorosilicic acid was 50kt (55,000 st) or about 88 kt (97,000 st) of 92 percent fluorspar equivalent.

Jan 1, 2005

By J. MacFadyen

The U.S. cement industry experienced its best year ever during 2004 in terms of production and shipments of cement. Clinker, portland and masonry cements production and shipments were up considerably. Clinker production as reported to the U.S. Geological Survey (USGS) was 87.75 Mt (96.73 million st), an increase of 5.4 percent. Gray and white portland cement production from domestic and imported clinker was estimated to be 91.6 Mt (101 million st), up 5 Mt (5.5 million st) from 2003.

Jan 1, 2005

By R. L. Virta

Four companies mined ball clay in four States during2004. They were H.C. Spinks Clay (owned by Franklin Minerals) Kentucky-Tennessee Clay (owned by Imerys),Old Hickory Clay and Unimin. Production was estimated to be 1.46 Mt (1.61 million st) valued at about $56.9 million, based on a preliminary survey of the ball clay industry. In 2003, production was 1.31 Mt (1.44 million st) valued at $56.2 million. Tennessee was the leading producer state with 61 percent of production. It was followed by Texas, Kentucky and Mississippi.

Jan 1, 2005

By A. Founie

The United States continues to be the world’s leading producer and consumer of diatomite. Production of diatomite in the United States during 2004 was estimated to be 635 kt (700,000 st). This was a 2-percent increase from 2003. The value of processed diatomite in the U.S. was about $164 million in 2004. Production was from six companies with 13 processing facilities in four states. Nevada and California were the principal producing states. They accounted for about78 percent of the U.S. production during 2004. U.S. diatomite exports were about 136 kt (150,000 st). Imports were negligible.

Jan 1, 2005

By P. A. Plunkert

Metallurgical-grade bauxite was imported into the United States from 11 countries in 2004. The principal suppliers of this 10 Mt (11 million st) of imported ore were Jamaica (33 percent), Brazil (25 percent), Guinea(23 percent) and Guyana (11 percent). The average value of imports, cost, insurance and freight (c.i.f.) U.S. ports, was $31/t ($28/st). Calcined refractory-grade bauxite imports were 165kt (182,000 st) with an average value of $146/t ($132/st), c.i.f. U.S. ports. China supplied 70 percent; Guyana, 22

Jan 1, 2005

By R. L. Virta

Six companies mined fire clay in Missouri and Ohio during 2004. Production, based on a preliminary survey of the fire clay industry, was estimated to be 398 kt(438,700 st), valued at $9.81 million. This was slightly less than the production and value figures from 2003. Missouri was the leading producer state. It accounted for more than 70 percent of the U.S. production. Consumption Domestic producers sold or used fire clay primarily for refractory applications. This application accounted for 79 percent of the market. Refractory products made using fire clay include firebrick and block, grogs, high-alumina brick and specialties, refractory mortars and mixes, and saggers.

Jan 1, 2005

By K. R. Griffin

Explosions in underground coal mines have been a serious safety concern since the advent of mining; despite significant technological advances, they are still occurring. Parameters such as barometric pressure, geological changes, and changes in ventilation can contribute to an explosion. These factors can be monitored with available and developing technologies to create algorithms that predict when explosions are more likely to occur. This paper reviews current underground atmospheric monitoring systems and related regulations around the world. In addition, suggestions for improvement and implications for explosion prevention are discussed.

Jan 1, 2011

By L. F. Delgado

Environmental and cost pressures sparked renewed interest in gravity separation. Industrial sands in Mexico are generally processed by screening, desliming, and flotation. Gravity separation with spirals was evaluated as an alternative to flotation in order to lower operating costs and decrease water pollution. Outstanding operating results are obtained in glass and foundry sand operations, plus a more competitive position for Mexican producers due to lower operating costs. Coal fines, generally recovered by flotation, have the same cost and environmental advantages when processed with spirals.

Jan 1, 1994

Researchers from the National Institute for Occupational Safety and Health (NIOSH) are developing a coal pillar rib rating (CPRR) technique to measure the integrity of coal ribs. The CPRR characterizes the rib composition and evaluates its impact on the inherent stability of the coal ribs. The CPRR utilizes four parameters: rib homogeneity, bedding condition, face cleat orientation with respect to entry direction, and rib height. All these parameters are measurable in the field. A rib data collecting procedure and a simple sheet to calculate the CPRR were developed.

Jan 7, 2020

By E. J. Sullivan

This study seeks to define the mechanism of oxyanion sorption onto surfactant-modified zeolites. Zeolites which have been treated with hexadecyltrimethylammonium bromide (HDTMA) surfactant to produce a hydrophobic surface are capable of sorbing both organic compounds as well as oxyanions such as chromate, selenate, and sulfate. Simple ion exchange and charge-balancing mechanisms do not fully explain this unusual phenomenon. The sorption of HDTMA surfactant appears to be partly ion exchange and partly sorption to non-ion-exchangeable sites. Sorption of chromate is a simple exchange mechanism with bromide, which co-adsorbs with HDTMA to form a surface precipitate. Information from this study will be used to design on-site and in situ treatment systems for contaminated water, such as filter beds and permeable barriers.

Jan 1, 1995

By E. R. Drevdahl

It has been suggested that we at the University of Arizona present a paper covering the origin, philosophy, and results of the College of Mines program in the field of computers and operations research. I have worked with the program since its beginning, and I will try to outline the developments as they have taken place. The formal development of the educational and research program in the field of Operations Research and Computer Applications at the College of Mines, University of Arizona, began in early 1957. During the year, the University offered its first formal instruction in computer programming. This was my first introduction to computers, and it did not take long to realize that this new tool had a potential that could be profitably utilized by the mining industry. In March 6f 1957, the University Computing Center began operations with its IBM 650 computer. This machine was the only computer of this size in the local area at this time, The first programming effort was in machine language and the programming cost could only be justified for repetitive-type of problems. The progress in the computer field moved very rapidly and with the development of the many compiler and assembly programs and the addition of sub routines to the computer library, the scope of problems that could profitably be investigated by computers expanded rapidly.

Jan 1, 1963

By T. B. Thompson

The Cripple Creek diatreme-intrusive complex is known primarily for its vein telluride-gold ores and, for major veins, their great vertical range (>990m). Less well-documented are the ores dispersed into the wallrocks adjacent to veins, the ores associated with hydrothermal and tectonic breccias, or mineralized zones within fluvial, lacustrine, and volcaniclastic rocks deposited within the diatreme complex. The ore-gangue minerals Here precipitated from oxidized, alkaline fluids that yielded an abundance of carbonate, sulfate, and oxide minerals along with minor base metal sulfide and precious metal telluride-s. Wallrock alteration is quite limited adjacent to veins and somewhat more extensive within hydrothermal and tectonic breccias.

Jan 1, 1991

By J. W. Shield

Refractory sulfide flotation or gravity gold concentrates are coated onto a sized support matrix and placed in a heap configuration for biooxidation. The surface coating is typically less than 0.05 in. thick and the support matrix is preferably composed of 0.375 to 0.75 in. diameter material. The exposed thin coating of sulfides reduces biooxidation rate limitations due to oxygen mass transfer. The large spaces between matrix particles reduce resistance to fluid percolation and aeration in the heap. The capital and operating costs for this biooxidation configuration are significantly less than for concentrate biooxidation in stirred tanks. After 30 to 90 days of biooxidation, sub- sequent gold recoveries exceed those seen in whole ore heap biooxidation and are comparable to recoveries obtained from stirred tank biooxidation processes. Results from laboratory and pilot testing indicate that this technology is a viable alternative for pretreating sulfide refractory gold ores.

Jan 1, 1997

By S. D. Van Nort

The Grasberg porphyry copper-gold deposit of Freeport Indonesia Inc., an 81% owned subsidiary of Freeport-McMoRan Inc., lies within the Ertsberg Mineral District in central Irian Jaya, Indonesia. The Grasberg deposit was discovered during a drilling campaign initiated in early 1988. Production at the open pit Grasberg deposit commenced in December 1989. The Grasberg copper-gold orebody is contained with a young igneous complex of dioritic composition which intrudes limestones of the Tertiary New Guinea Group. Alteration is typical of porphyry copper deposits worldwide except that higher grade primary chalcopyrite with significant gold values is associated with a centrally located zone of strong quartz stockwork.

Jan 1, 1991

By Donald T. Mylar

It is axiomatic that in designing a bulk material handling system the primary consideration is the functioning of the machines. The structure is secondary -its reasons for being are to support, enclose and provide access to the machine, for servicing. This results in a wide variety of supporting structures. Other considerations are: plant layout, local soil conditions, climate, local laws and codes, and last, but by no means least, the Customer's wishes.

Jan 1, 1971

By A. Moharana

A massive slide at Bingham Canyon wiped out a side of the pit and covered the main haul road in and out of the pit. All pre-slide mine designs and schedules were no longer valid. New designs and schedules needed to be developed quickly to provide management with information regarding the immediate post-slide production potential and the time needed to ramp back up to full production. At the time of the slide, an effort was already underway to convert Bingham?s in-house Medium Term Scheduling Process to MineSight®?s Schedule Optimizer (MSSO). One of the main reasons for doing this was to reduce the time needed to produce Medium Term Schedules at Bingham, which involves a complex shovel-based scheduling approach with shovel productivities based on shovel type and the types of mining cuts to which the shovel is assigned over each planning period. The objective of the schedule was to maximize shovel usage, satisfy mill feed requirements of four SAG mills with variable milling rates, and have flexibility in setting truck constraints. This paper will describe how the new MSSO-based mine scheduling process met the challenge of producing new schedules for Bingham in a minimal amount of time.

Feb 23, 2014

By E. Poeck, R. Garvey, U. Ozbay, K. Zhang

"A coal bump is characterized by the sudden failure of one or more pillars and an associated release of kinetic energy. Although the geologic conditions surrounding coal bumps are often similar, their occurrence and magnitude are difficult to predict. This paper presents the development of an approach to assess the potential for coal bumps in room and pillar mines through the use of energy concepts and special consideration of the interface properties between the coal and overlying rock. Back analyses were performed on the widespread collapse of a room and pillar mine with an associated 3.9 local magnitude seismic event. Pillar and mine-scale models were constructed using the distinct element method to simulate the mining stages leading up to the collapse. A variety of loading conditions, material properties, and interface properties were evaluated for their effect on unstable failure of single pillars, and the mine-scale model was used to study the evolution of failure during progressive mining. The extent of unstable failure was quantified in these models by calculating the total kinetic energy released during each mining stage. Through the parametric analysis of single pillar models, it was found that softening parameters in either the coal or the coal/rock interface can individually facilitate unstable failure of pillars, but the combination of the two in a single model produced a much higher release of energy during failure. The results of the mine-scale model further illustrated the trend as the combination of softening parameters in the coal and coal/rock interface produced a series of failures which most accurately reflected the collapse event at the mine. The method of room and pillar stability analysis demonstrated in this study effectively explores the potential for large coal bumps. INTRODUCTION The analysis of coal pillar behavior is challenging because natural variability in geologic conditions requires estimation of material strengths and predicted loads for a given mining situation. Large width-to-height (w/h) ratio pillars and deep overburden present an additional challenge, as the failure behavior of such pillars is more complex and may involve unstable, sudden collapse. Empirical methods have improved the success of coal pillar design for a wide range of conditions, but for deep cover and squat pillar geometries, less accuracy has been achieved in predicting pillar performance (Mark 2000). As with any empirical approach, more back analysis and the consideration of new variables may help improve understanding and accuracy of future designs. This paper presents a study of pillar stability through the back analysis of the Crandall Canyon Mine collapse, which occurred in August of 2007. Pillar-scale models are utilized for the calibration of material properties and assessment of potential instability under varying conditions, and mine-scale models are constructed in an attempt to reproduce widespread failure and correlate with observations at the mine. Special consideration is given to the properties of the coal and the coal/rock interface, and kinetic energy is calculated throughout the course of the simulations to gauge the level of instability when pillar failure occurs. Models were constructed using the Universal Distinct Element Code (UDEC) (Itasca, 2014)."

Jan 1, 2016