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By · J. B. Boisvert, O. Leuangthong, T. Acorn

Optimizing final pit limits for stochastic models provides access to geologic and economic uncertainty in the pit optimization stages of a mining project. This paper presents an approach for optimizing final pit limits for a highly variable and geologically complex gold deposit. A heuristic pit optimizer is used to manage the effect of geological uncertainty in the resources within a pit shell with multiple uncertainty rated solutions. The uncertainty rated pit shells follow the meanvariance criterion to approximate the efficient frontier for final pit limits. Stochastic dominance rules are then used in a risk management framework to further eliminate sub-optimal solutions along the efficient frontier. This results in a smaller set of final pit shells that could be further analyzed for production scheduling. Additionally, the original solutions are analyzed for changes in the mining limits and two regions are targeted as potential regions for further exploration.

By M. K. Sichone

Anglo Platinum?s Waterval smelting complex based in South Africa operates the Anglo Converting Process (ACP) that produces SO2 offgas. This SO2 offgas is treated in a double-contact, double-absorption acid plant allowing for conversion efficiencies higher than 99.90 %. The catalytic converter used in the acid plant to convert the SO2 to SO3 is a 4-bed reactor loaded with a combination of cesium-promoted and conventional vanadium pentoxide catalysts. In June 2008 there was a shutdown, in which one of the main activities was to screen the catalyst. Before this shutdown, the operator would control the converter pass temperatures manually, via the SCADA, especially during plant start-ups after which some of the automatic temperature controllers were used. After the shutdown, the control philosophy was revisited and all temperature controllers were put on auto mode during plant start up. Furthermore the set points of the pass inlet temperatures were reduced to maximize conversion in the first two passes. The result has been a reduction of SO2 emissions, from a daily average of 50 ? 70 ppm to as low as 20 ppm for similar sulphur dioxide and oxygen concentrations. Further work has been done to maintain high bed temperatures in the third and fourth passes at low SO2 strengths by splitting the gas stream between pass 1 and 2 thus increasing the SO2 content in the gas to pass 2. This increases the temperature of the gas exiting the second pass, which results in higher temperatures in passes 3 and 4. Comparison of the converter performance prior to and after the changes is made. The benefits of partially bypassing the first pass to increase the SO2 content in the gas to the second pass are shown. Conclusions and scope for further work have been drawn from the comparisons.

Jan 1, 2009

By F. H. Gunnell, W. C. Dunham

"INTRODUCTION The Treasure Hill mines, situated in Dry Canyon, Ophir mining district, Tooele County, Utah, together with several other properties in the district, examined were examined by Frank L. Wideman, an engineer, the Bureau of Mines, in September 1942.In April 1945, development drilling was started on the Treasure Hill mines, which are operated under lease from the Madison Mines Co. The project was continued in 1946 and terminated in 1947.While the Bureau of Mines project was in progress, the Morgan and Fullion tunnel workings were surveyed by Bureau engineers.ACKNOWKEDGEMENTSIn its program of investigation of mineral deposits, the Bureau of Mines has as its primary objective the more effective utilization of our mineral resources to the end that they make the greatest possible contribution to national security and economy, It is the policy of the Bureau to publish the facts developed by each project as soon as practicable after its conclusion. The Mining Branch, Lowell B. Moon, chief, conducts preliminary examinations, performs the actual investigative perk, and prepares the final report. The Branch, O. C. Ralston, chief, analyzes samples and performs beneficiation tests. The work here described was under the direct supervision of Paul T. Allsman, chief, Salt Lake City Division, Mining Branch."

Jan 1, 1948

By Richard C. Moore

The U.S. Bureau of Mines contracted a study to review the air and water monitoring requirements of five Federal environmental acts (the Federal Water Pollution Control Act, the Safe Drinking Water Act, the Clean Air Act, the Surface Mining Control and Reclamation Act, and the Resource Conservation and Recovery Act) and to compile information on the currently available monitoring instruments. A literature review of the acts and their associated regulations was conducted to determine applicability to the mining industry as well as any air and water monitoring requirements. In addition, an industry search and literature review was performed to assess the instrumentation available to comply with the monitoring regulations. Based on this research, the instruments are classified by general applicability to air, surface water, or ground water monitoring, then catalogued by monitoring parameters. A discussion is provided on recommended and innovative monitoring techniques.

Jan 1, 1981

A new mine has begun production of antimony ore and concentrates in Serbia, Yugoslavia. The mine is operated by the mining and metallurgical enterprise "Aajaca." Initial production is running at approximately 45 thousand tons of ore per year, yielding about 1,500 tons of concentrate. The mine is located on the mountain Kopaonik-Raiceyoj Gori. It is planned to expand production eventually to approach the level of 300,000 tons of ore per year. This level will be a significant addition to the world supply of antimony and will place Yugoslavia among the world's major producers. Currently the United States produces only about 6 percent of its primary requirement for antimony. COBALT -Anglo American Corporation, Ltd. reportedly is considering restarting the Tenke-Fungurume copper-cobalt project in Zaire. Construction on the project was suspended in January because of inadequate financing and political uncertainties. Technical feasibility and financing on a smaller scale than previously envisioned are now being considered. However, an increased copper price may be necessary before any decision to proceed is made.

Jan 1, 1976

This is the initial issue of STATE MINERAL SUMMARIES. This publication provides estimated data and summaries of mineral activities at the State level for 1988. Most of the estimates are based on nine months data. These summaries have been prepared in cooperation with State geological surveys or related agencies. Individual State summaries are published separately as State Mineral Industry Surveys and copies can be obtained from the appropriate State Activities field office.

Jan 1, 1989

By Christopher Snee

??care has to be taken that the design is driven by sound geological reasoning and rigorous engineering logic rather than by the very attractive images that appear on the computer screen.??Hoek 1999 Design of a cavern is inextricably linked to the engineering geology of the site. The importance of sound geological reasoning will be illustrated by transportation projects in New York City where there are proposals for at least 11 caverns. These caverns have been the subject of advanced exploration techniques and geological interpretation but even so the raw data falls short of the sophistication of modern numerical methods. This paper will give geological explanations for the engineering characteristics of the rock in New York City which will provide guidance for practitioners when approaching cavern design in New York and elsewhere.

Jan 1, 2008

By A. G. Spencer

"The horsepower required to drive large grinding mills has increased dramatically during the past ten years. Limitations on the amount of power which may be transmitted by a single gear and pinion have resulted in the application of multimotor drives, with consequent loadsharing problems. It has also sparked the development of some entirely new drive concepts. In addition, the severe demands made upon the electrical system during the acceleration period have required that the selection of motors and electrical system design be closely coordinated. Moreover, the installation of such large process units results in downtime being very costly. The equipment selected and the plant maintenance philosophy must therefore be such as to minimize the risk of unscheduled downtime."

Jan 1, 1972

By S. D. Dladla, S. Ramsamy

The majority of the tailings dam operations in South Africa will be required to comply with the new Global Industry Standard on Tailings Management (GISTM) within the next one to three years, depending on the dam classification and the requirements of the respective investors and insurers. With up to 72 auditable requirements, the implementation of the Standard needs careful planning and prioritization. This paper focuses on the practical steps to GISTM compliance for tailings facilities in operation in South Africa. The discussions are based on current practices, South African regulations, and industry standards requirements. The possible changes in dam classifications and the associated requirements are presented.

Jun 2, 2022

By R. L. Virta

Four companies ? H.C. Spinks Clay Co., Inc., Imerys, Old Hickory Clay Co., and Unimin Corp. ? mined ball clay in four states in 2013. On the basis of preliminary data, production was 1 Mt (1.1 million st) with an estimated value of $47 million. Production increased by 3 percent in tonnage from 973 kt (1.1 million st) with a value of $45.1 million in 2012. Tennessee was the leading producer accounting for 64 percent of domestic production, followed by Texas, Mississippi and Kentucky. About 67 percent of total ball clay production was airfloat, 22 percent was crude or shredded and 11 percent was water-slurried.

By R C. A Minnitt

The two methods for calibrating the parameters K and (alpha) for use in Gy’s equation for the fundamental sampling error (FSE), the duplicate sampling analysis (DSA) and the segregation fractionalised analysis (SFA) are described in detail. A case study using identical broken reef material from a Witwatersrand-type orebody is calibrated using the DSA and SFA methods and the results are compared. Classically, the form of Gy’s equation for the FSE raises the nominal size of fragments given by dN to a power of 3. Gy’s formula is a theoretical formula applicable in the case when fragments are randomly collected one by one, which is obviously never the case. This is because the fragment shape factor (f) and the granulometric factor (g) were introduced to take care of this anomaly. More recent formulae, such as those suggested by François-Bongarçon and Lyman, are empirically based formula. A later modification of Gy’s formula raises dN to the power ? (alpha), the latter term being calibrated with the coefficient K in the DSA and SFA methods. The preferred value of ? (alpha) for low-grade gold ores used by sampling practitioners in the mining industry is 1.5. A review of calibration experiments for low-grade gold ores using the DSA and SFA methods has produced values of K that vary between 70 and 170 and values of alpha in the range 0.97 to 1.30. The average value for alpha is found to be 1, rather than 3 as originally proposed in the classic form of Gy’s equation or the industry preference for 1.5. It is suggested that for low-grade gold bearing ores, the equation for the FSE should raise dN to a power of 1. Such an equation for the variance of the combined FSE plus the grouping and segregation error, now referred to as the short-term component of the quality fluctuation error (QFE1), greatly simplifies the characterisation of gold ores, which now only requires the calibration of K for a given mass and established fragment size. The implications for the heterogeneity test from the generalised equation are that provided the fragments have been screened to within a narrow size range, any particular size will return a value for K that is acceptable for use in the sampling nomogram.CITATION:Minnitt, R C A, 2017. A generalised form of Gy’s equation for gold ores – empirical evidence, in Proceedings Eighth World Conference on Sampling and Blending , pp 331–350 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2017

By H. B. Hill

Virtually from the date of its discovery in December 1928 the Oklahoma City oil and gas field, Oklahoma County, Okla., has attracted national and international attention. The history of the field has been associated closely with rules and regulations pertaining to production control and proration practices. Early development was rapid, and Oklahoma City soon attained the distinction of being the first major field in which the producing wells were over a mile in depth. Before the structural features of the reservoir had been disclosed every outpost well was considered a "wildcat", so complex appeared the underground geology. The wells not only were deep and the reservoir pressures high, but the production from the early wells was a high A.P.I. gravity oil, accompanied by large volumes of gas. Several "blow-outs" and fired occurred during the early development, and the close proximity of these now unusual events to a large city gave the field much publicity, both local and national. Later, when its production threatened to demoralize the market for oil and its products, the Oklahoma. City field again attracted wide publicity. The then little understood geology of the underground reservoir and the diversity of ownership of the land overlying the producing structure made orderly development and production difficult to enforce. Proration was enforced with difficulty, and the rate of production from the field continued to increase until, on August 4, 1931, martial law was declared in all prorated fields of the State, and most of the wells in the Oklahoma City field wore shut in. On October 9, 1931, permission was granted to reopen and produce the wells in the Oklahoma City field. The order permitting production of the wells provided that during the period beginning October 10 and extending to October 20, 1931, all wells in the field that had not produced more oil than specified under the earlier proration orders and that had been shut in for the required 65-day period were permitted to produce 5 percent of their last potential during that 10-day period.

Jan 1, 1936

By E. P. Youngman

Titanium ranks as one of the more abundant elements, is widely distributed, and occurs in concentrated form in numerous deposits. This substance was discoveres 140 years ago; but despite the efforts of metallurgists and chemists to find a place for it in industry, only within the last 10 or 15 years has the increased use of titanium pigments provided any extensive outlet for titanium ores. Even to-day titanium is confined to a few highly specialized industrial applications. The metal itself is now quoted regularly in trade journale, but scarcely yet can it be said that the production or use of the metal. has progressed very far beyond the laboratory stage. Ferroalloys containing the element were largely used for a time, especially in connection with the manufacture of Bessemer steel rails; but as American rail- ways adopted open-hearth rails in preference to Bessemer rails, the demand for the alloys in the rail manufacture gradually dwindled into insignificance. New outlets for ferrotitanium have been found in the steel industry; and the production of titanium alloys, both in the United States and in Europe, has increased in recent years. By far the largest use of titanium at the present time, however, is in pigments. The manufacture of titanium white began in Norway, but at present the United States is the leading producer. One of the two companies now operating in the United States is also the leading factor in European production. Although titanium occurs, in many minerals, the principal commercial sources are rutile (the natural oxide, Ti02) and ilmenite (iron-titanium oxide, FeO. TiO2). The latter is a coal-black mineral, but it is the one used in the manufacture of the titanium white of commerce, as well as in the manufacture of ferroalloys and arc-lamp electrodes. Rutile, the natural oxide, is not pure white and, being less common in nature, costs more; it is, therefore, reserved for use in the manufacture of titanium chemicals employed in relatively small amounts in dye works and bleacheries and for sundry minor purposes. This paper summarizes the titanium industry, with special reference to its economic aspects. It is offered as a survey of current trade literature and as a digest of material in the files of the bureau and is presented in response to numerous inquiries from prospective producers as to ways and means of exploiting deposits. (At present, much of the ilmenite consumed in this country comes from overseas, principally from British India..). A forthcoming circular, devoted to deposits of titanium-bearing ores, deals with foreign and domestic sources of supply.

Oct 1, 1930

By Robert Torbin

The objectives of the Continuous Shaft Lining (CSL) System are to reduce the costs, safety hazards, and time currently required in lining mine shafts with concrete. The CSL will line machine bored shafts downward from the shaft collar on a continuous basis using an inverted, pressurized slipforming technique. The technique for slip-forming downwards has been demonstrated and refined under this program. The approach taken involved laboratory scale testing of key features of the CSL concept. These feature tests included concrete distribution, concrete sealing, concrete slipforming and development of a reliable concrete mix. Based on these results, a full scale above-ground test facility and CSL were designed and fabricated. The objectives of these tests were to demonstrate the viability of the basic concept; to establish operating limits; and to provide input data and information for the design of a second generation shaft lining system. The results of the program have led to a CSL design and operational philosophy which will need to be tested in an underground environment before industry will accept the technology. However, the next generation CSL promises to meet all the original program technical objectives.

Jan 1, 1983

By C J. Kruger, E le Roux

Anglo American Platinum has adopted a strategy of Best Practice Principles (BPP) for sampling, mass measurement, analysis and metal accounting for more than a decade now. When new plants are designed, the most suitable sampling equipment and sampling protocols are implemented and material flows and plant layouts are designed around sampling strategies. A few years ago, a crushing plant for a high-grade matte stream was commissioned.The design called for the high-grade material to be crushed to 95 per cent passing 2 mm and the design allowed for a single cutter primary Vezin sampler, increments taken from a gravity flowing stream at regular intervals, whilst filling a tanker for the pneumatic offload at our base metal refinery. This was a single point of sampling and analysis that would measure the wanted output from our smelting complex and the input to our refineries. In addition, the design incorporated the functionality to collect increments in an ‘interleaved’ fashion from the Vezin sampler for internal precision checks.The metal accounting strategy for Anglo Platinum is the ongoing measurement of all inputs, outputs and stock levels for all our operations for platinum group metal (PGM) and base metal (BM) content. Included are yearly stocktakes, usually done on 1 February every year, across the smelters and refineries (at least the base metal refinery). A trend was developing in the accounting period immediately following the introduction of the new crushing and sampling facility, whereby the absolute difference between the physical stock and theoretical stock (PGMs predominantly) increased for the two respective sites on an ongoing basis. The smelter (sender) showed an increase in physical stock compared to the theoretical stock and the base metal refinery (receiver) showed that their theoretical stock increased against their physical stock. Because of this anomaly, an additional stocktake was held in September for the period in question and it was confirmed through the physical stock measurement results, that the PGM accounting problem was indeed pointing towards the evaluation of the high-grade matte stream.This paper showcases parts of the process that took place to explain the poor accountabilities for the respective sites. Previous results from the sampler ratification process (of the interleaved sampling design) were analysed again, a physical inspection was carried out on the sampling system again and the sampler performance was monitored (quality control parameters) for the period.From these investigations, it was found that airflows present inside the Vezin introduced the sampling bias and a change in sampling protocol was introduced as well as physical changes to the sampling equipment were made to eliminate the airflow and thus the bias conditions significantly. The accounting period which followed, after a phased upgrading process, showed that the accounting between our smelter and base metal refinery had been restored to within statistical limits (difference between physical and theoretical stock below five per cent relative to theoretical stock).CITATION:Kruger, C J and le Roux, E, 2017. Pitfalls in Vezin sampling for finely crushed materials, in Proceedings Eighth World Conference on Sampling and Blending , pp 151–158 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2017

By S. J. Schatzel, J. D. Addis, V. Gangrade, L. L. Chasko, C. A. Hollerich

A ventilation study using tracer gas was conducted at a western US coal mine. The objective of the study was to evaluate the movement of longwall face air exchanges between the face and worked-out area and to document the presence or absence of face airflow pathways between these locations. The mine operator uses a bleederless longwall ventilation system with a back return and a blowing mine ventilation system. The study was conducted on an active panel and included both underground and surface monitoring sites. The study used sulfur hexafluoride (SF6) released as a slug on the longwall face and in the front of the gob inby the face. The velocity of the tracer gas movement in the gob was 0.019 m/s (3.7 fpm). The rate of movement for the overall tracer gas slug averaged about 0.0091 m/s (1.8 fpm). A separate tracer gas test initiated with the release of SF6 into the legs of the first shield showed the existence of more than one pathway of face air in the general direction from the headgate towards the tailgate corner. Maintaining adequate ventilation air on longwall faces is important for worker safety and for the dilution of methane emitted from the face and caved gob. A more detailed characterization of longwall system air and gas movement allows a mine to better assess its ventilation design for controlling gas on the face and in the gob.

By John D. Rockaway

Failure of the mine floor supporting coal pillars frequently occurs when the subcoal strata include "underclays" or other low strength strata. The failure process has been studied to define the response of these materials to applied coal pillar loads and to determine the applicability of bearing capacity analysis to evaluate unsafe conditions. The study has been accomplished through an investigation of both the intact and insitu geotechnical properties of the subcoal strata and through the installation of floor movement monitoring instrumentation. The results of these studies have indicated that both the shear strength of the underclay and the stratigraphy of the subcoal strata must be considered in the analysis. The shear strength was the major controlling factor determining the ultimate load carrying ability of the materials, but the thickness and stratigraphic position of the weak layers influenced the mechanism of the failure process. The methods of bearing capacity analysis were used to define pillar stability that included provisions for taking into consideration a two-layer system. Conditions assumed for a coal mine where a weak underclay overlies firmer strata. The results of the analysis compared very well with observed mine conditions, indicating marginal conditions in areas of the mine which later experienced pillar support failure. In addition, a "heave factor" was derived to predict potentially unstable floor conditions in the mines studied in detail.

Jan 1, 1979

By H. W. Gillett, A. E. RHOADS

In its study of methods for reducing metal losses in the non- ferrous metal industry, the Bureau of Mines has conducted a long series of experiments on electric brass melting and collected much data on the experiments of others. Reports bearing on this work that have already been published by the Bureau of Mines are Bulletin 73, "Brass-furnace practice in the United States," and Bulletin 77, "The electric furnace in metallurgical work." A comprehensive report describing the design and operation of all types of electric brass furnaces and showing their performance in experimental tests on a commercial scale is in course of preparation. However, commercial tests of several new and promising types of furnaces are still under way, the results of which should be included in any general discussion of the subject. For this reason it has seemed desirable to issue a preliminary bulletin giving the data on a type of furnace developed in one stage of the bureau's work.

Jan 1, 1918

By G. E. McElroy

The Coeur d'Alene minim, district of Shoshone County, Idaho, has been one of the largest and most active lead-silver producing districts in the United States for the last 40 years. The mines of the district enjoy exceptional natural advantages with respect to ventilation in that the veins apex high on mountain sides and are most often developed to considerable depths, up to 2,000 feet, by adit and crosscut tunnels under conditions that develop large natural draft pressures; the increase of temperature of the rock with increase of depth from surface in at a low rate; and the average surface temperatures are low. These natural conditions have, in the main, resulted in well-ventilated mines with low temperature conditions throughout. However, where the development has been carried to considerable depths below the lowest level of surface entry, natural-draft ventilation has proved inadequate, and mechanical ventilation systems have been installed on the three largest mines of the district. Local conditions, more particularly those in dead-ended working places, have also required auxiliary ventilation by will fan-pipe units in these and other mines. A particular feature of the district is the number of exceptionally long crosscut tunnels that have been driven to provide entry to vein systems from low points adjacent to milling and transporta¬tion facilities. Three of these tunnels are approximately 2 miles long, and lengths of 3,000 to 8,000 feet are quite common.

Jan 1, 1931

By R. H. Nafziger

Owing to the growth of alloy steel production and its influence on tramp element levels when recycled, foundries have expressed concern regarding the quality of scrap used to prepare iron castings. Reliable and current information was unavailable on the amount of tramp elements contained in iron castings over time. Accordingly, the U.S. Bureau of Mines, in cooperation with the American Foundrymen's Society (AFS), analyzed cast iron samples from participating foundries throughout the United States on a quarterly basis to ascertain possible trends. Each sample was analyzed for 28 elements to determine if changes had occurred as a function of several input variables. This bulletin describes the research and presents analytical results and evaluations over a 5-3/4-year period from January 1981 to September 1986. Results show that iron casting compositions are changing with respect to a few tramp elements such as arsenic, cobalt, chromium, tin, and zinc over the period. Changes in charge compositions probably are responsible. Significant variations between zones also were observed with aluminum, arsenic, cobalt, chromium, copper, and manganese.

Jan 1, 1990