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By E. M. Frizzell

In an effort to economically and efficiently enhance the erosion control aspects of present surface coal mine reclamation practices, the US Bureau of Mines has recently completed a two-phase research program wherein irrigation strategies and equipment developed under the first phase were field tested on three surface coal mine sites. The fundamental basis for the use of irrigation as a reclamation tool is to provide the plant moisture requirements as a supplement to prevailing natural precipitation, and thereby support the natural growth of drought-hardy native vegetation. Portable solid-set irrigation equipment and several irrigation strategies were tested on large 6-ha (15-acre) sites in Montana, Wyoming, and New Mexico. Results of these tests will be presented which include daily irrigations, precipitation levels, soil moistures, climatic data, and density cover and biomass of the native plants.

Jan 1, 1987

By L. Stas

The authors have been interested in stress measurements in the rock mass for a long time. This paper describes the development of new apparatus for stress measurements in a rock mass. The principle of stress measurement by this device is based on the relief method as applied on the conical shaped surface of the bottom of a borehole. The design started based on the experience of K. Sugawara and Y. Obara who have been using the compact conical borehole over-coring system (CCBO). The conical shape of the strain gauge probe CCBO makes the fixation of the probe in borehole easy and, also, makes the measurement of stress in independent directions possible. The principle of the measuring method, the preparation of the borehole, the design of the probe for continuous measurement of stress during the course of overcoring are described. Also, a simplified version of the probe for long term monitoring of stress variations in the rock mass by means of the inserted body method and the initial laboratory results and in-situ testing of the development sample are described. Additionally, testing was done regarding the possible glues in relationship to the creep effect for this case.

Jan 1, 2006

By A. Perelli Cippo, R. Granata, D. A. Bruce

During the last few years, significant advances continue to have been made in aspects of grouting technologies used for ground treatment in advance of tunnelling. In permeation grouting, fundamental researches have continued into improving the penetrability characteristics of cement-based grouts. The twin advantages of field regrinding normal grouts to reduce cement particle sizes, and incorporating special additives into stable grouts, are now being systematically exploited in major soft ground tunnelling projects in Europe. The methodologies of jet grouting continue to be developed with special attention being paid to qa/qc issues, reducing unit production costs, and improving predictive capabilities for subsequent settlements.

Jan 1, 1993

By Steve Hansen

Heap leach mining has long been an economical method for mining oxide copper ore, and with the U.S. Bureau of Mines' discovery of a way to economically strip gold and silver from carbon, it has become the standard in the gold and silver indus­try as well. Sulfide leach in copper recovery has always been a byproduct of oxide leach mining, although the methods and recovery rates have increased with technology. SX-EW has kindled a new interest in large deposits and dormant dumps of low grade sul­fide ore. Gold ore bio-oxidation was developed in the 1980's, but not tried on a large scale until US Gold built the Tonkin Springs Mine. This mine was dedicated to the large scale production of low grade sulfide ore that could be recovered through the newly discovered bio-oxidation method. On a small scale the method worked, but as time went on, problems with the process were costly and recovery was poor. US Gold did not have the finan­cial backing to perfect the process, and the mine was closed in 1990. Since that time, Newmont Gold Company has taken the lead and has dedicated a lot of resources to the perfection and implementation of this method. Some small mines have discov­ered that if they can use this technology they may be able to dou­ble and triple current ore reserves, because they will be able to mine deposits previously considered not to be economical.

Jan 1, 1998

By S. S. Hsieh

As part of a program to address the long-term need to ensure adequate supplies of domestic phosphate raw materials, the Tennessee Valley Authority (TVA) has conducted considerable research on dolomitic phosphate rock beneficiation. The discovery that alkyl diphosphonic acids act as phosphate mineral depressants led to the development of several processes involving a carbonate flotation step for the effective beneficiation of these problem ores. Most recently, a partial deoiling process in which the reagent consumption is greatly reduced has been developed. The reduction is achieved because part of the initial feed is beneficiated without passing through the separate carbonate flotation step. Using this method, a phosphate product containing 30.6-30.9% P2O5 and 0.7-0.8% MgO was obtained from a Florida dolomitic phosphate pebble that contained about 23% P2O5 and 2.0% MgO. The P205 recovery was 80.8-86.5%.

Jan 1, 1991

By Keith J. Henley, Nicholas C. Clarke, Paul Sauter

A detailed investigation of the stability in cyanide solutions of native gold and gold-silver tellurides in a flotation concentrate from the Golden Mile, Kalgoorlie, has been undertaken to assess whether leaching under different conditions can be used to quantify the distribution of Au between native gold and gold-silver tellurides, as suggested by, for example, Chryssoulis and Cabri (1990). The leaching was carried out on +20 µm native gold and gold-silver tellurides separated from a high-grade flotation concentrate and then diluted with barren quartz. The material leached assayed 270 ppm Au and 118 ppm Te and the leach conditions used were:- Stage 1: Leaching in dilute cyanide (0 .1 % ) at pH 9 .5 for 24 hours to dissolve native gold but not gold-silver tel­lurides. Stage 2: Leaching the residue from Stage 1 in strong cyanide (2%) and pH 12.5 for 96 hours to dissolve gold-silver tellurides.

Jan 1, 1995

By L. M. English

A basic model was developed to help assess methane control needs for the longwall mining of coal in gassy areas. Rather than depending on reservoir and rock mechanical theories, it uses an empirically determined gas emission rate as an input, and it operates on the assumption that, within a specific region and zone, gas emissions will be relatively equivalent for uniform incremental volumes of gob created by mining. The computer program divides longwall panels into segments, keeps track of the face advance and generates emission rates and volumes for both the entire panel and for individual zones within the panel by summing values for all undermined segments. This model can aid in the determina¬tion of the number, size and location of vertical wells or other methane-control applications that are needed for gob gas control.

Jan 1, 2000

? The U.S. depends on minerals for economic growth and development, and for national security and defense. ? Public lands are an important, long-term source of essential minerals. ? Access to public lands for mineral exploration and development has become more difficult as large tracts of land have been designated for other uses. ? Mineral-bearing areas on public lands are routinely withdrawn or restricted from development before comprehensive resource inventories and economic assessments have been made.

Jan 1, 2011

By S. C. Brown, R. C. G. Oliveira

Surface wettability, or contact angle, dictates a number of multiphase ensemble interactions that influence particulate dispersability and adhesion behavior (e.g., filler compatibility] in addition to a number of other phenomena including biocompatibility and bulk powder segregation. The wettability of particulate surfaces significantly impacts nearly all process industries; however, the available techniques to access this quantity are either relative, or tedious-and are application or industry specific. In this study, key features of existing techniques have been combined to design an improved method to delineate particle wettability that is simple, versatile and capable of providing reproducible measurements in an industrial environment.

Jan 1, 2003

By Rodney H. Sergent

After being forgotten or ignored for nearly 100 years, the ability of bromine chemistry to extract gold from ore has been rediscovered. While bromine chemistry is similar to chlorine, there are some important differences. Bromine in its elemental form is a dense, fuming, red liquid. Elemental chlorine is a gas and requires a substantial amount of equipment to handle, store and deliver to solution. Bromine has an advantage in its ability to rapidly and completely oxidize heavy metals to water soluble halide salts. The first patent for use of bromine chemistry for gold extraction was issued in 1881 (1). By 1895, work done in Colorado concluded well roasted ores required approximately 1-1/2 lbs/ton of elemental bromine for superior extraction of metals (2)). At that time, bromine was deemed to be cost effective vs. chlorine even though it was more expensive on a pound basis than chlorine. The advent of cyanide technology virtually eliminated both chlorine and bromine from consideration for leaching of ores. Cyanide was so inexpensive that it made deposits requiring unique technologies unattractive for mining. Only since the deregulation of gold price has bromine/chlorine technology been considered for those ores not amenable to cyanide. While chlorine has found its way into the pretreatment steps, bromine is just beginning to realize its niche in the marketplace.

Jan 1, 1998

By R. L. Grayson, G. Mishra

Introduction Many old underground mines have been developed extensively into reserves requiring large numbers of workers to maintain and rehabilitate lengthy track haulages and/or belt conveyor systems. Often, large numbers of fans are required to maintain minimal airflows in areas where poor conditions and huge leakages prevail. Problems that beset one such coal mine and projects undertaken to restore it to potential profitability are presented. Brief history The Vesta No. 5 mine was opened in 1908. Drift development began near the Monongahela River, which was the primary avenue for shipping metallurgical coal to coke ovens in Pittsburgh. Over the ensuing 75 years, the main haulage entries were developed a distance of 16.1 km (10 miles) to the present mining area. Track haulage was used to transport coal from working sections to the river loading facility. As haulage distance and areas of high water influx increased, management decided, in 1973, to construct an underground conveyor belt system. The project spanned 36 months and culminated in a system of 22 flights, ranging from 205.7 to 1767.8 m (675 to 5800 ft) long. Six intake and eight return entries were developed as the mains were advanced. These entries provided adequate ventilating capacity over the years, but as extensive gob areas progressed and roof conditions deteriorated, the entries became inaccessible and more resistant to airflow. By 1981, five fans were being used to circulate 943.9 m3/s (555.5 cfm) of air through the mine. An average of 6440 t (7100 st) were produced from 20.8 continuous miner unit shifts and 2.7 longwall unit shifts each day in 1981. The ratio of support to production personnel was 1.94. To maintain the outby 16.1 km (10 miles) of haulage, 110 personnel were used. The average cost per ton was $43.54 ($39.58 per st), resulting in excessive bottom-line losses. The mine possessed a rather promising reserve, mostly in lease, of good quality, medium-sulfur metallurgical coal, but it also had a number of formidable operating problems. Operating problems Contributing factors toward relatively low productivity and high costs were the conditions of the track haulage, conveyor, and ventilation systems. Productivity was affected greatly by downtime associated with the conveyor system, which lacked adequate access for making splices or other repairs. Many areas within the conveyor belt entry itself required more

Jan 1, 1988

By K. N. Han

A kinetic model for the batch leaching of various metals using different lixiviants was developed. The overall material balances for the reactants and products at the solid/ liquid interface were formulated for various types of heterogeneous reactions at the interface. The solutions to these mass balances are identified analytically, as well as numerically. Applications of these numerical solutions to various leaching systems using rotating discs or powders are discussed. The metal-dissolution systems addressed include cobalt, nickel and copper in acid, cyanide and ammoniacal solutions.

Jan 1, 1996

By Ahmed A. El-Saie

To reduce the problem of overbreak and its associated added costs, a new technique is proposed to make a slot around the tunnel profile in hard rock. The Finite Element Method was used to investigate the effect of the slot on the stress field and deflection of the tunnel core. Beam theory was also applied to calculate the stresses and deflections of a slotted tunnel for several different slot depths.

Jan 1, 1981

By J. Wagner, P. Eger

Although lifetime estimates for sulfate reduction based on total substrate carbon typically range from 20 to 30 years, field and laboratory experiments showed that rates of sulfate reduction decreased over time as readily available organic material was consumed. When the rate of acid input exceeded the rate of sulfate reduction, alkalinity was removed from the substrate, the pH decreased and metals increased. Output pH increased from 4 to more than 6 after the system was shut down for several weeks and the rate of acid input was reduced. Successful long-term treatment requires a design based on the input pH and the long-term organic decomposition rate.

Jan 1, 2002

By J. E. Wennen

Screens serve several important functions in CIL and CIP processes for gold extraction. One important screen application known as interstage screening allows slurry to be continuously transfered through a series of CIL or CIP tanks while retaining activated carbon in the tank. In some cases, this has been accomplished by using airlifts to carry slurry containing activated carbon to an external screen which separates carbon as oversize and returns it to the tank by gravity. The undersize slurry advances to the subsequent tank. More recently this has been accomplished using launder screens and Kambalda type screens. These are essentially static screens that rely on air blasts or mechanical sweepers to clear carbon away from the screen surfaces.

Jan 1, 1998

By R. Hogg, A. C. Maffei, D. T. Ray

Based on standard population balance models for agglomeration and size reduction processes, a simplified model has been developed to describe simultaneous growth and breakage in the flocculation of agitated suspensions. The results of semi-batch flocculation tests have been used for estimation of the model parameters and empirical relationships have been obtained to describe the effects of process variables and to establish scale-up criteria. Application of the model to the design, operation and control of continuous flocculation processes is discussed.

Jan 1, 1990

By Ian Corrans, Gary Johnson, John Angove

The Activox™ process is a new method for the pre­treatment of refractory gold ore concentrates prior to cyanidation. The process has been developed in Western Australia, and relies on a combination of fine grinding and pressure oxidation to achieve the destruction of sulphide minerals and the liberation of encapsulated gold. The process operates under much more moderate conditions than those that would typically be used for conventional pressure oxidation of similar concentrates. This results in significantly lower capital and operating costs being achievable.

Jan 1, 1993

By C. J. Ferron

Gold occurrence in operating plant tailings ranges from gold in solution, fine free gold, gold associated with sulphides/arsenides/tellurides and gold occluded within iron oxides or arsenates and silica gangue. This paper briefly presents various alternatives to reprocess gold tailings, with examples. These include the use of centrifugal gravity separators, CIL, magnetic separation, flotation and pressure oxidation.

Jan 1, 1993

By Photios G. Ioannou, Guillermo F. Salazar, Herbert H. Einstein, Yeong W. Kim

The MIT tunneling group has developed, over the past decade, a number of decision support tools for the geologist and engineer, planner and designer, owner and contractor involved in underground construction. These computer based tools can be used in the planning and exploration stage of a project, in predesign and design, in construction planning and during construction. Tasks as different as optimizing information collection during exploration and during construction, as selecting major design alternatives in predesign and modifying design during construction, as providing cost and time estimation and considering social and physical environmental constraints, can be handled. Output can be in the form desired by the user ranging from geologic profiles (cross sections) to management reports.

Jan 1, 1987

By Nathaniel Arbiter

In attempting to assess the contributions of Antoine Gaudin to the profession which he illuminated for almost a half-century, we will need to examine a very broad canvas. He was active in three significant areas: as a teacher; in research, both through his own endeavors and those of his students; and as a consultant to the mining industry and to the Government. Beyond these specific contributions, there was the major personal influence he had on scores of students, friends, and colleagues in the profession. If a single measure of the man's contribution is to be found, it will be the extent and direction in which he influenced the practice of his profession. To find this we should examine the state of miner- al processing when he began his activities in the 1920's, the progress which has taken place over the past half-century, and the part his activities played in this advance. However, there is a provocative and broader examination which I have chosen to make instead. This is to examine the past century in mineral processing through the lives of three men who, by common agreement, stand on the heights, both in teaching and in their contributions to industry: Robert H. Richards, Arthur F. Taggart, and the man whose memory we honor this evening, Antoine M. Gaudin. Their careers, by coincidence, cover just a century. This is also AIME's first century, and the first century of mineral industry education in the United States. In fact, mineral processing itself on any significant scale in the country encompasses only a century and a quarter. BEGINNINGS OF PRACTICE IN THE U.S. Before the 1840qs, U.S. mining, except for coal and iron ore, was on a small scale and was confined to the eastern states, with processing practically nonexistent. The 1840's saw the beginning of Michigan native copper production, including ore dressing; the 18501s, iron ore production in Minnesota; and the 18601s, lead production and processing in Missouri. But the most explosive event was the California gold rush after 1848, which not only brought tens-of-thousands of fortune hunters to the West, but also catalyzed broad mining activities and processing within the following decades. This was not only in Calif-

Jan 1, 1976