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By Chee Theng

"Keep calm and carry on mining. That has long been the conventional wisdom in the mining industry, a largely cyclical one that has weathered roller-coaster booms and busts. But in the years from 2002 to 2016, an unprecedented steep rise in commodities prices that lasted a decade and then took a sharp turn downward had made it hard for gold and silver miners to stay the course.“The last 15 years highlighted some of the structural and inherent challenges that our industry has, from product price uncertainty to long lead times to the capital intensity of our business,” said Mitchell Krebs, president and chief executive officer of Coeur Mining, who was the luncheon speaker at the American Exploration & Mining Association’s 122nd Annual Meeting held Dec. 5-9, 2016, in Reno, NV.Looking back, Krebs said, “We were given this enormous gift of a commodities super cycle, and the industry kind of blew the opportunity.” While gold prices rose 319 percent and silver prices rose more than 200 percent over the 2002 to 2016 period, the XAU index of 30 gold and silver mining companies’ stock prices went up by only 20 percent.Entering 2016, precious-metals prices have made a comeback, with gold rallying strongly from a six-year low at the start of the year. This time, the industry is ready. Companies are leaner and meaner, with lower costs, reduced debt and an increased focus on higher grades and quality ounces. Although opportunities were missed in the past, the industry has got its act together and is now well positioned to take advantage of a price upswing and even to show profits when prices fall, as they did in August 2016, pushed down by a strong dollar."

Feb 1, 2017

By Patrick Doig, Ross Webb

The Bradshaw Section 5A Interceptor involves the construction of two miles of 108-inch, finished diameter tunnel in dry soils. Excavation is generally by Lovat TBM with ribs and lagging support. The tunnel is beneath a recreational parkway and stringent measures have been enacted to preserve the parkway and minimize disruption to the neighborhood. Apart from these constraints, the project would have been unremarkable but for the intervention of CalOSHA and the local fire department who ordered extraordinary fire protection measures. The paper discusses the cause and effect of these measures and comments on the potential repercussions for other projects.

Jan 1, 1999

By Muhammad I. Kabir

A new minitest of in situ uranium leaching processes at reservoir conditions is proposed. The test which consists of a single observation/ production well and two observation wells is designed to permit the evaluation of both restoration and leaching parameters. It is shown that by using a straight forward history matching procedure, sometimes called a type curve analysis, both the rate of leaching and the ultimate uranium recovery can be evaluated based on the results of the test. Type curves are presented for the case in which the reaction rate is kinetically controlled and there are no other minerals competing for oxidant. Other situations can be approached using the same techniques as those presented here.

Jan 1, 1981

By J. H. Hammarstrom, S. M. Fortier, W. C. Day, S. J. Ryker, R. R. Seal

"The United States’ supply of critical minerals has been a concern and a source of potential strategic vulnerabilities for U.S. economic and national security interests for decades (for example, see Strategic and Critical Minerals Stockpiling Act, 1939). More recently, with the rapid increase in the types of materials being used in advanced technologies (Fortier et al. 2018a), and geopolitical events surrounding the supply of rare earth elements (Ting and Seaman, 2013), among other developments, the critical minerals issue has again achieved a high level of visibility within the U.S. government (Executive Order 13817 (2017)).In this paper, the U.S. Geological Survey (USGS) provides an overview of its ongoing focus on critical minerals through the agency’s core competencies in mineral information, mineral resource assessments, geologic and topographic mapping, geophysical surveys and mineral resource research. Aspects of the multifaceted critical minerals issue addressed here include:• Identifying minerals that meet the definition of “critical” provided in Executive Order 13817.• U.S. net import reliance for critical mineral raw materials.• Current status of domestic critical mineral resource assessments.• Current status of topographic and geologic mapping, and geophysical survey coverage of the United States.• The Earth Mapping Resources Initiative (Earth MRI) to support future critical mineral exploration.• Critical mineral potential of waste streams from extractive industries.Identifying minerals as criticalU.S. government agencies and other organizations use a number of existing definitions and criteria to identify a mineral or mineral material as critical, strategic or otherwise important. The executive order defined a “critical mineral” to be “(i) a nonfuel mineral or mineral material essential to the economic and national security of the United States, (ii) the supply chain of which is vulnerable to disruption, and (iii) that serves an essential function in the manufacturing of a product, the absence of which would have significant consequences for our economy and national security.” This definition is broadly consistent with that defined by the National Research Council (NRC, 2008) and may be summarized as “essential in use” and “subject to disruption of supply.” Virtually all of the dozens of critical minerals studies conducted since the 2008 NRC report have used some variation of this same definition (Hayes and McCullough, 2018)."

May 1, 2019

By Robert J. M. Miller

Thank you Mr. Chairman. For more than 15 years a debate has been taking place among students of massive sulphide deposits as to the origin of these deposits. Prior that time it was widely accepted that the deposits were of hydrothermal, epigenetic and even replacement origin (Wilson, 14). Kinkel, Knight, Stanton and others advanced hypotheses which would explain the, formation of the deposits by different, largely syngenetic, volcanogeric processes. I was fortunate in having become involved in exploration for these deposits at about the time the debate was beginning and thus had an opportunity to apply with some success, some of the new and old ideas for formation of massive sulphide deposits. The deposits which I will discuss today are all located n northwestern Quebec, in the Abitibi orogenic belt. Mattagami Lake Mines is about 100 miles due south and Noranda's Horne Mine about 200 miles south of James Bay. In 1959 I prepared a talk which was presented to the 1960 CIM Convention calling attention to the spatial and possible genetic relationship between the ore sulphides of the Mattagami Area, Quebec and the tuffite, as well as the structures which controlled the ore. In this present paper I would like to cover the following points: (1) The general criteria used by the epigeneticists to support their contention that the deposits were formed after the enclosing rocks.

Jan 1, 1973

By Hubert E. Risser

At the outset of a discussion on the adaptability of Illinois coals for use in iron and steel production, it is perhaps well to define terms. ?Adaptability? as used in this context, means that a coal can be, adapted to use within a given technological and economic framework. For a coal to be adaptable, to use in the manufacture of metallurgical coke within the present technological and economic framework, it must possess, among other things, at least the following characteristics: 1. The coal must be capable of producing, alone or in combination with other coals, a coke that can meet at least a minimum standard of required performance in the present-day blast furnace. The coke must have sufficient strength, stability, hardness, and freedom from impurities to make it suitable. 2. If the coal in its raw form does not meet these requirements, it must be amenable to beneficiation or upgrading so that the requirements can be met. 3. It must be available in uniform quality and in sufficient quantities to meet the need. 4. Use of the coal must be economically attractive. If its quality is equivalent; to that of the coals with which it must compete, it must be no more expensive than they. If It is better, a premium price may perhaps be demanded. If, in any respect, it is the least bit less suitable, the cost must be lower to offset its disadvantages.

Jan 1, 1961

By D. D. Gertenbach

"The successful commercialization of a pressure oxidation (POX) process for recovering metal values, including gold, copper, zinc, nickel and molybdenum, is the result of a carefully planned development program. The initial task involves developing one or more conceptual flowsheets, including the POX autoclave and downstream purification and recovery steps. A laboratory program is completed to determine the technical viability of the flowsheets, define the operating parameters for each step and provide information for an initial economic assessment of the process. The process is then confirmed during a continuous pilot plant program, providing engineering design data and other information for the commercial design. A well-thought-out development program has been shown to be critical for reducing the risk of commercializing POX processes. Experiences developing POX processes for refractory gold ores and copper concentrates are briefly discussed. IntroductionPressure oxidation (POX) has become a common commercial operation for processing sulfide-bearing feedstocks. These feedstocks include gold ores and concentrates; copper concentrates; nickel concentrates and mattes; zinc concentrates; and molybdenum concentrates. Drivers for the development and commercialization of POX processes include:• The high cost for pyrometallurgical processing of sulfide ores, much of which is attributed to environmental controls.• The motivation to implement safe and more environmentally attractive alternatives for sulfide ores.• The need to process increasingly difficult ores with complex mineralogy.• Improvements made over the last 25 years in POX equipment design and experience operating commercial POX plants.Although the capital and operating costs for commercial POX processing can be high, this technology is capable of rapid oxidation of most sulfides and arsenic minerals in the feed, with little noxious gases and environmentally stable iron arsenate and other iron compounds in the POX residue (Marsden and House, 2006).In POX operations, sulfides are oxidized to either sulfates or elemental sulfur in an autoclave at elevated temperature and pressure with oxygen gas. An example is the overall oxidation reactions of chalcopyrite when sufficient oxygen is present, shown in the following reactions:"

Jan 1, 2016

By R. L. Peyton

Risk analysis is used extensively in many engineering applications. Although its use in the field of dam safety has been limited in practice, it has received considerable attention in recent years in the dam safety literature. Thus far, it has been shown that risk analysis in the evaluation of existing dams has the potential for providing a more rational basis for decision- making because of its focus on the direct issues--likelihood of failure, likelihood of loss of life, and risk cost of damages. It provides for a logical balance between the risk a dam imposes and the degree to which rehabilitation is required, compared to traditional evaluations based on somewhat arbitrarily chosen design events applied to large classes of dams. Dam owners could benefit by optimizing the cost of remedial measures. Downstream landowners could benefit by minimizing the likelihood of flood damages. However, it is also clear that significant technical and policy issues remain to be resolved before risk analysis in dam safety is accepted and routinely implemented in engineering practice. An obvious and important potential application of risk analysis is its use by the state regulatory agency as an in-house evaluation tool, or even as part of regulatory policy, in the implementation of its state dam safety program. Adoption of such a policy would have an important impact on the mining industry. .Although no state dam safety programs are known by the writers to have officially incorporated risk analysis into their regulations, there appears to be considerable interest in the concept. In recent surveys 47 states agreed that the development and promotion of a risk assessment methodology for state dam safety programs should be encouraged (Tschantz, 1983; Tschantz, 1984). The issue has also received important attention within the Association of State Dam Safety Officials (1986). One state-Illinois-proposed regulations during 1986 to allow risk analysis to justify lower spillway requirements for existing dams (Illinois Department of Transportation, 1986). At the Federal level, the National Research Council has found risk analysis especially appropriate for assessing dam safety at high-hazard dams (National Research Council, 19851, the Bureau of Reclamation has published guidelines for incorporating risk analysis into their dam safety grogram (U.S. Department of the Interior, 1986), and the Federal Emergency Management Agency has recently sponsored workshops and supported research related to risk analysis in dam safety (Federal Emergency Management Agency, 1985a ; Federal Emergency Management Agency, 1985b; - - McCann, et. al., 1985a, 1985b).

Jan 1, 1986

By R. W. Bartlett

I first met Milton Wadsworth in 1951 as an eighteen year old junior taking his mineral processing course at the University of Utah. He guided my senior thesis, evaluating the then new polymer flocculants on settling uranium leached ore pulps. This was before ion exchange and solvent extraction. After my military service and a brief working stint at Kennecott he supervised my PhD work. He encouraged me to be active in AIME and its constituent societies, where both of us have been directors of AIME and presidents of TMS. He has been a consultant for research groups that I have managed. Above all, he has been my mentor and friend for nearly 45 years. Thus, I am honored and particularly pleased to receive 5MB's Wadsworth Award.

Jan 1, 1996

By T. Hackett

Western underground coal reserves are tremendous, but recovery in western seams can be poor because of mining problems caused by deep cover, geologic anomalies, and thick seams. For instance, many seams contain a rock parting too thick to be extracted economically with the coal. This forces the operator to mine the coal above or below the parting. Subsequently, the rock pressures induced by mining make the part left difficult or impossible to extract by standard mining methods. Because upper and lower parts of the seam are frequently of minable thickness, the presence of rock partings can result in a significant loss of coal. Given a longwall recovery of 60 pct and equal thickness for the two parts of the seam, overall recovery is reduced to less than 30 pct if one part only is mined. The coal left in place is unavailable to meet the nation's energy needs, or to produce revenues for coal companies or government. [ ] Multi-slice longwall mining has the potential to recover the portion of split seams that are now left in the mine. Using superimposed standard longwalls with chain pillars, overall recovery could be doubled, depending on panel and pillar widths. Using a combination of advancing and retreating longwalls in descending slices, overall recovery could be improved to more than 80 pct. Because of the potential for improved recovery, the Bureau of Mines is analyzing the ground control factors affecting multi-slice longwall under western mining conditions and is conducting field trials at a planned multi-slice operation.

Jan 1, 1987

By James J. Guesk, Robert W. Reisinger, Timothy C. Richmond

A high-altitude (2,900 m [9,500 ft]) historic underground copper mine in Wyoming is discharging copper-laden water with a neutral pH into an otherwise pristine creek. The Wyoming Abandoned Mine Land program is reclaiming the site under a CERCLA deferral agreement. The clean-up goal is to reduce copper in the mine discharge so that the creek can eventually support a trout fishery. A pilot-scale passive treatment test utilizing sulfate-reducing bacteria has been conducted at the site beginning in summer 1997. Test results show significant reduction in copper concentrations in near-freezing mine water at flow rates ranging to 19 liters per minute (5 gpm)

Jan 1, 2000

During the past year a number of significant advances in geostatistics have been published. These were presented at the 13th APCOM Symposium in Clausthal, Germany and at a NATO Advanced Study Institute on Geostatistics in Rome, Italy. Of greatest importance is the work that has been done in establishing methods which correctly predict the cutoff grade-tonnage curves, and the average grade of ore-tonnage curves for deposits in which ore and waste are intermingled. Grade-tonnage curves based on estimates made from widely spaced exploration data have been found to underestimate the grade of ore and overestimate the tonnage present. This problem has been remedied by the calculation of conditional probability distributions for the unknown grade of a block. Another advance has been made in the field of geostatistical estimation for deposits in which a trend is present. Previously a technique known as universal kriging has been used, which involves much subjective judgement as to the trend fitted. A new technique, generalized increments, allows computer estimation of such deposits with much less subjective judgement. Computational efficiency of geostatistical methods has continued to improve to a point where a geostatistical estimate can be obtained for little more than the cost of any other computerized method.

Jan 1, 1976

By Ben W. Burdett

The operation of an electrolytic refining tank house is an art as well as a science. If the electro-refining industry is to progress, a better understanding of the refining process is necessary. This would help to reduce the amount of training necessary to produce competent tank house operators who, in turn, would be able to increase both quantity and quality of the tank house product. To aid in understanding this process, quantitative relationships between the critical tank house variables must be established. The inherent major contributor to inefficiency in most tank houses is short circuits. By quantifying the effect of short circuits on each of the other variables in the system, as well as their effect on over- all system performance, better decisions regarding manpower allocation can be made. Current distribution under short circuit conditions, which has always been somewhat of a mystery, can be studied in detail. The relative importance of electrolyte balance, proper anode-cathode spacing, low contact resistance at points of electrical connection, and other system variables can be determined, With a better understanding of these variables, the steps necessary to increase current efficiency are more easily defined. Relationships between most of these variables are described in qualitative terms in the literature, but quantitative relationships between tank house variables have never been established. A realistic mathematical model of the tank house could be used to test the effect of variations in a single variable on other variables in the system, and thus define the quantitative relationships between tank house variables. It is not the purpose of this paper to establish these relationships, but to describe a recently developed model that can assist in their establishment. A computer program implementing this model has been applied to examine the effect of short circuits on overall current distribution. Some of the results are given here as examples of the utility of this program.

Jan 1, 1973

By W. G. Lawrence

The rapid development of science and technology in Russia has been the result of well laid plans since 1918. At that time the Institute of Silicates was established is Moscow and later the establishment of similar more specialized institutes for the study of cement, glass, refractories, construction ceramics, electrical ceramics, building materials and asbestos provided the necessary research facilities for studies related to all types of ceramic inorganic materials. The' Institute of Ceramics and the Institute of Silicate Chemistry, Academy of Sciences, USSR, were founded in Leningrad. The work now going on in these various research' institutes covers every branch of silicate science and ceramics The impetus behind such establishment of special¬ized laboratories is no doubt due to the 5-year plans and the necessity of improving the scientific knowledge regarding the materials being used and the products being manufactured.

Jan 1, 1960

By Chaoxun Zhao, TAIYOU LI, JIAQI JIN, Jan D. Miller, Chen‑Luh Lin

A large portion of the energy consumed in copper concentrators is used to reduce the particle size of the feed by crushing and grinding. The cost of metal production could be reduced if low-grade particles of cm size were removed prior to further processing. Two copper sulfide ore samples (3 × 1 cm) from Arizona were analyzed by micro X-ray computed tomography (Micro-XCT) to determine the grade of copper sulfide in each particle. For copper ore sample A, a significant number of particles contained very low amounts of copper, while some particles had copper sulfide grains of mm size. Based on Micro-XCT, it was expected that 85% of the copper for sample A could be recovered at 65% of mass rejection during preconcentration by sorting. However, in sample B (a different copper ore), distribution of copper sulfide was dispersed primarily in each ore particle, so for the particle size class of 3 × 1 cm, liberation of copper sulfide and gangue minerals was not significant. In view of the XCT results, dual energy (DE) X-ray radiography was used as a basis for sorting. Previous DE X-ray radiography of a drill core sample demonstrated that this rapid detection method can be used to identify rich or poor Cu-bearing coarse particles. Pilot scale X-ray sorting of sample A (10 × 1 cm) showed 31% rejection of a 0.08% Cu gangue product with a corresponding recovery of 90% copper.

Nov 30, 2021

By R. H. W. Chadwick

We in Kennecott are well aware that Alaskans are interested in the progress of our project at Ruby Creek. We would very much like to be able to present you with a final report at this time and tell you about a new mine. I'm afraid, however, that it will be several years at best before such a report can be made. This, then, is an interim report to describe briefly some of our findings to date, and to acquaint you with some of the problems, both geologic and economic, which must 5e resolved favorably before we can talk about a mine. There are several things about this project which make it unusual and interesting to those of us who have been connected with it. Firstly, there is the fundamental importance to Alaska, in the present stage of its economic history, of any undertaking which offers promise of turning a natural resource into a competitive export product. I am sure all of us would get a lot more satisfaction out of having a part in bringing in a new mine in Alaska than we would out of adding another one to the long list in, say, Arizona.

Jan 1, 1960

By Alex Stewart

Most iron bearing ores treated by the R=N Direct Reduction Process yield products lower in phosphorus than the initial ores. The sulfur is also removed and generally is in the range of 0.02 to 0.05 percent in the final R=N product, independent of the sulfur content of both the ore and carbon fuel used. The mechanism and thermodynamic justification of the principal reactions leading to the removal of both phosphorus and sulfur and the control of sulfur in the iron concentrate produced are discussed and supported by the results of laboratory experiments. In substantially all iron ores (containing up to 4% sulfur as sulfate) and solid carbon fuels (containing sulfur from 1 to 8%) tested, the rejection of sulfur has been in the order of 90-95%, with not more than 0.02 0.05% sulfur in the final metallic iron product. With respect to phosphorus-bearing iron ores ranging up to 0.70% P205, the rejection to tailings has been in the order of 70-95%, resulting in not more than 0.03 - 0.07% phosphorus in the final product.

Jan 1, 1958

By Yinan Zhang, Yi Luo

The widely used R70 method is modified to measure the self-heating propensity of low-rank coals. This modified R70 method enables the introduction of controlled amount of moist oxygen into the reaction vessel. Three coal lumps were collected from three different locations in a surface mine in the Powder River Basin. The coal samples were tested in oxygen flow with controlled moisture content under adiabatic condition. By measuring the relative humidity at the exhaust exit point of the testing setup, the flux and cumulative wetting heat that is consumed by coal samples can be determined. Through a better way of determining the coal’s specific heat, the total heat, including heat of wetting and coal’s oxidation heat, required to raise coal to a given temperature can be determined. Then, the contribution of heat of wetting at the different stages of the testing is quantified. The effects of evaporative heat through a group of tests have also been quantified. From this research, a better understanding of the effect of wetting heat on inducing low-rank coal’s spontaneous combustion can be acquired.

Nov 30, 2022

By Juan J. Monsalve, AMAN SONI, Nino Ripepi, Richard Bishop

The design and strength of pillars are important parameters while implementing the room-and-pillar mining method in a limestone mine. The process becomes complex with the presence of the karst voids which are frequent phenomena in a carbonate rock formation. The karst system is a network of cavities that along with an omnipresent fracture network may lead to ground control issues in a limestone mine. The objective of this study is to provide a safe and reliable alternative design for a pillar in a case study mine for safe and efficient ore recovery. This research is a continuation of a previous study aimed at studying the effect of karst void on the strength of the same limestone pillar. It was assessed from the calculated pillar strength and the estimated redistributed stresses that the pillar is capable of countering more stress than is currently imparted on it. Numerical modeling studies combining in situ stress determination and excavation sequencing were used to estimate the existing stresses on the pillar. Different possibilities of modification to existing pillar design were simulated using Distinct-Element Modeling (DEM) to determine a better design. Discrete fracture networks (DFNs) were included to imitate the effect of the presence of discontinuities. An effort is also made to understand the variation of pillar strength with height for karst-affected pillars using two different constitutive models. This study serves as a preliminary investigation in terms of improving the future design of pillars and also while recovering old pillars prone to karst formation.

Jan 30, 2023

By Kunzo Amano

Fully-bonded rock bolts have been widely used in construction sites and mines in recent years. The purpose of this investigation is to prove the effectiveness of rock bolt supports in unstable ground through in-situ tests and numerical analysis. 2. MEASUREMENTS AND PROCEDURES OF IN-SITU TESTS The fully-bonded rock bolts as the mine road¬way supports were tested in the Fukasawa mine which is located in the northeast district of Japan (Fig. 1). The Fukasawa mine (one of the Kuroko mines) started the production in 1973, and the present monthly production is slightly less than 20,000 tons. The ore deposit which exsists at about 400 m depth is divided into several small lenticular shaped bodies. They are distributed apporiximately 1500 m in NW-SE direction and 700 m in NE-SW direction. The hanging wall is basaltic lava and the footwall is tuff. The rocks surrounding the ore bodies are soft but relatively intact, so the trackless mining system has been adopted from the beginning of the development.

Jan 1, 1982