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By R. G. Reddy

Chemical and structural changes occurring during the roasting of refractory gold ores were investigated. Effect of temperature on oxidation behavior of ores was analyzed using TGA, DTA and X-ray diffraction methods. The experimental results showed that the carbon in the ore has to be oxidized to a minimum value before any appreciable oxidation of sulfur occurs. Oxidation rates as a function of temperature were calculated. Optimum conditions under which a successful roasting of the refractory gold ores can be obtained are discussed.

Jan 1, 1990

By D. W. Olson

Estimated world production of natural and synthetic industrial diamond was about 630 million carats in 2004. Natural industrial diamond deposits have been found in more than 35 countries, and synthetic industrial diamond is produced in at least 10 countries. About 80 percent of the global output was produced in Ireland, Japan, Russia, South Africa and the United States. Russia and the United States are the world’s leading producers of synthetic industrial diamond. In 2004, the two U.S. synthetic producers, one in Pennsylvania and the other in Ohio, had an estimated output of 250million carats. Also in 2004, nine U.S. firms manufactured polycrystalline diamond (PCD) from synthetic diamond grit and powder.

Jan 1, 2005

By F. H. Muge

The problem of how to handle heterogeneous populations in an ore reserve global estimation arises in many geostatistical studies. In some cases it is possible to split data into different significant types of ore in such way that non-overlapping subpopulations are obtained, and a separate study is possible. In other cases the subpopulations are intermingled and a set of nested structures may model the spatial variability of the ore. Finally, one of the populations, consisting of a small proportion of high grade values of economical meaning, may disturb the structural analysis. In this paper, some methods are proposed to cope with these kind of problems and typical case studies are presented.

Jan 1, 1986

By J. R. Parga

Bacís mining is a young enterprise in Mexico that produces a pyrite concentrate rich in gold and silver. When gold and silver are associated to sulfide minerals, pre-treament such as: roasting, pressure oxidation and bioleching, is required to decompose the sulphides and thereby expose the gold and silver particles to the cyanide solution. A novel method demonstrates that the oxidation and dissolution of gold and silver in alka-line cyanide solution can be conducted simultaneously in the same autoclave in less than 90 minutes with a recovery that exceeds 96%. Factors affecting recovery efficiency such as pH, leaching time in the reactor, temperature, particle diameter, pressure, % of NaCN and pulp density were investigated.

Jan 1, 2007

By P. F. R. Altounyan, I. W. Farmer

Groundwater freezing was used to stabilise 8m thick beds of saturated and weakly cemented sands at a depth of 170m, during driving of twin 1 in 4,5.2m o.d. circular drifts from the surface to the Coal Measures through 600m of Permo-Triassic strata. Instrumentation was installed during erection of the lining in frozen and unfrozen ground to measure ground and groundwater pressures on the lining and ground temperatures up to lm into the frozen ground. Observations showed that following thawing, effective lining stresses in the frozen zone were low, indicating minimum strata disturbance during freezing and subsequent machine excavation. Groundwater pressures were lower than expected.

Jan 1, 1981

By Y. David

In 1990, the United States became only the second country (after China) to produce more than 900 Mt (1 billion st) of coal in a single year. US production of bituminous and subbituminous coal, lignite and anthracite totaled 933.5 Mt (1.029 billion st) in 1990, 5% more than in 1989. The production gains were largely due to the rebuilding of depleted coal stockpiles by electric utilities and a surge in US coal exports. Domestic coal consumption essentially remained at its 1989 level. A slight increase in electric utility coal consumption was partly offset by a decline in metallurgical coal use. The use of coal in other industries and in the residential-commercial sector remained virtually flat.

Jan 1, 1991

By James P. Cooney

The global mining industry is in the process of redefining its activity and purpose in terms of sustainable development. This process is impelling a growing number of companies to engage their stakeholders on environmental and social issues. Nongovernmental organizations (NGOs) have customarily acted as critics of the mining industry's performance. A new relationship between mining companies and NGOs is emerging in the context of sustainable development, ranging from dialogue to joint action. If positive interaction among mining companies and NGOs is to succeed, clear terms of engagement must be articulated, and measurable progress toward achieving both corporate and NW objectives must be demonstrated. The experience of Placer Dome is illustrative of the rewards and challenges of engaging with NGOs.

Jan 1, 2001

By M. A. Chandler, G. T. Adel, J. N. Richardson, E. C. Gutierrez

A rapid, bench-top analyzer has been developed to determine P2O5 content and CaO/P2O5 ratio in phosphate ores. The analyzer utilizes a portable computer equipped with a frame grabber to measure the reflective intensity (gray level) of phosphate samples placed in front of a television camera. P2O5 content is related to the average gray level of the sample, while CaO/P2O5 ratio is determined from the amount of bright material present. The sensor is currently being used to analyze flotation concentrate samples at Texasgulf's phosphate operation near Aurora, North Carolina. Sensor development along with results from laboratory and in-plant testing are discussed.

Jan 1, 1993

By H. Mercado G., J. R. Parga T

Mexico continues to be one of the main producers of silver, lead and zinc; although this leadership is ending because of the use of obsolete technologies, which is reflected in low recoveries of these processes. The country therefore requires to develop on new technologies in the field of nonferrous metallurgy, particularly be'cause it is the second most important source of foreign exchange. A novel method, presented in this paper, demostrates that refractory gold and silver can be extracted from a complex sulphide concentrate by a one stage pressure oxidation in an alkaline cyanide solution, this is achieved by simultaneous liberation_ and solubilization of the precious metals. Both gold and silver extractions are greater than 97%. Factors affecting recovery efficiency, such as: pH, lixiviation time in the reactor, temperature, particle diameter, pressure, % of NaCN and pulp density, were investigated. A summary of actual plant operations is also be included.

Jan 1, 1993

By D. G. Millette, A. J. S. (Sam) Spearing

The design of a cost effective backfill system involves many aspects and various inputs from different engineering disciplines. Backfilling is a very significant mining cost and efforts need to be made in the design stage to maximise efficiency and flexibility whilst minimising costs. The aspects that need to be considered include the following: Required fill performance underground Peak and average fill tonnage requirements Backfill scheduling in the mining cycle Material selection, testing and preliminary costing Plant design and storage needs Infrastructure requirements Implications on surface waste/tailings disposal and costs Total backfill costs In order to produce a cost effective and efficient backfill operation, a multi-disciplinary project team is required that should include the following skills and functions: Mine Planning Rock Engineering Metallurgy Mechanical Engineering Environmental Health and Safety Tailings Disposal/Waste Management This paper discusses the above and indicates important aspects that should be considered.

Jan 1, 2001

By J. Maiti, A. Bhattacherjee

A literature review on quantitative analysis of mine safely studies revealed that numerous investigators explored a wide- range of techniques, including the investigation of bivariate and multivariate statistical models. Although these researchers addressed various issues of accident causation and prevention, they, in general, did not investigate through the use of quantitative models the multivariate relationships of several factors affecting mine safety in a causal framework. In this paper, systems dynamics and structural equation modeling are presented to simultaneously represent and study the effect of policy variables related to accident prevention along with the factors causing accidents and injuries. The application of these models to a group of mines revealed that current training practices at these mines do not appear to alleviate accident occurrences. It is inferred that the use of these quantitative techniques can provide a new direction of research in mine-safety studies.

Jan 1, 2000

By M. Prud’Homme

Potash is an important natural mineral used largely as a fertilizer in the production of food and fiber. About 93 percent of all potash consumed globally is used in agriculture as fertilizer. The balance is used to manufacture potassium chemicals. Most potash is extracted by conventional underground mining methods. Solution mining is used when underground deposits are irregular and very deep. The other main production method involves the evaporation of brines in shallow salt lakes, followed by the harvesting of potassium minerals.

Jan 1, 2005

By J. D. Morgan

Introduction In 1987, the US economy continued to grow steadily, reaching an annual rate of $4.6 trillion in the last quarter. The value of domestically processed mineralbased materials rose slightly to $250 billion. The value of US metals rose sharply to more than $7 billion. Industrial minerals rose slightly to $18 billion recycled scrap was valued at $4 billion. Metal prices rose sharply toward year-end. A number of mining and metal companies experienced increased profitability, fostering more optimism about the future. Consumer demand strongly affects mining because the US economy is relatively saturated with long-lived products. Consumer, mortgage, and federal debt continue to rise. 244 million citizens already possess 170 million licensed motor vehicles and 100 million dwelling units. New car production fell 9% to 7.1 million units, but truck and bus production rose 9% to 3.8 million units. New housing starts fell 10% to 1.6 million units. Excess productive capacity exists not only in the US, but also in many other countries. Consequently, the US mineral industry is encountering stiff competition from others, as well as increasing competition from newer engi¬neered materials. Domestic production of plastics rose 9% to 25 Mt (27 million st) - on a volume basis, double all metals. Some 7% of petroleum goes to make petrochemicals including plastics. Imports of nonfuel mineral-based materials in 1987 were valued at $37 billion and exports at $24 billion. Imports supplied a significant proportion of total US consumption of several important mineral materials, including many classified as strategic and critical. In December, the Congress mandated that any major changes in stockpile goals be made only by law, and that the Department of Defense submit annually detailed stockpile supply/demand analyses. Concern about apartheid in South Africa continued, resulting in increasing interest about chromium, manganese, platinum-group metals, cobalt, vanadium, and gold. The National Critical Materials Council continued to monitor the US materials position. The Defense Production Act, authorizing priorities and allocations, supply expansions, voluntary agreements, and the National Defense Executive Reserve continues in effect through Sept. 30, 1989. Under the DPA, the US Bureau of Mines maintains the Emergency Minerals Administration. Further consultations were held with Canada to strengthen the North American defense industrial base. Coal production, 60% from open pits, rose 2% to 825 Mt (910 million st) valued at $21 billion. Nearly four-fifths was burned to generate 56% of US electricity. Exports included 42 Mt (51 million st) of metallurgical coal and 24 Mt (27 million st) of steam coal, with a total value of $3.3 billion. Domestic petroleum production fell 5% to 480 Mm' (3 billion bbl). Uranium mining, including recovery from phosphates, fell 4% to 5.9 kt (6500 st). Nonfuel minerals Major metals: Raw steel production - a major consumer of many minerals - rose 7% to 79 Mt (87 million st). Domestic iron ore production rose 11% to 44 Mt (48 million st), about 96% pelletized. Net imports, though, fell 8% to 11 Mt (10 million st). Raw steelmaking capacity fell 6% to 102 Mt (112 mil-

Jan 5, 1988

By Roy Moreby

Dartbrook Coal is currently developing a modern, high production (3.5 Mtpy) single longwall retreat coal mine in the Upper Hunter Valley of NSW, Australia. The location is a green field site, with no surface or underground mining operations ever having taken place in the initial target seams. The coal seams of the working section, floor and immediate roof average a total 20 m in thickness and contain a mixed carbon dioxide 1 methane seam gas ranging from 6.5 to 11.0 m3/t. The target seams have undergone detailed characterisation to assess hazards and quantify the controls required to minimise associated risks during mining. Risks identified during initial phases of exploration and 14 months of development include: • High gas emission during development. • Probable high longwall gas emission rate. • Medium to high propensity to spontaneous combustion • Possible carbon dioxide outbursts on geological structures • The main controls currently in place include, • Mine geometry and ventilation circuits • Exploratory drilling ahead of development • Intensive in seam pre drainage • Goaf drainage plants • Comprehensive monitoring systems • Underground environmental management plan. • Pre mining predictions of gas emission provided an indication of gas emission rates which have proven to be an under estimate. Current mine issues are; • Both surface fans are at full capacity (250 m3/s 1.4 kPa) • Both gas drainage pumps are at full capacity (2.3 m3/s) • Alternatives to extensive in seam pre drainage being investigated (surface to in seam hydro fracture) Review of mine design underway This paper describes the seam characterisation, assessment of mining hazards and summary of the management plan developed to address the risks identified. A review of current mine underground environmental performance is also provided

Jan 1, 1997

By Stephen C. Everett

Why? This is the first question that everyone asks. Why did Renison give away such a valuable asset? What is the problem with Mt Lyell? No doubt this question was asked of Denehurst regarding Woodlawn, MPI at Stawell, Golden Shamrock at Cobar, Western Metals at Cadjebut and Poseidon with the Big Pit. Whilst it is not possible to second guess the rationale behind Renison's strategic withdrawal from an operation that they considered to be uneconomic, the Renison/Mt Lyell deal has certain specific perspectives:

Jan 1, 1995

By Michael Gay

Right in the heart of Boston Harbor lies Deer Island, where a ten-year, 6 billion dollar sewage treatment plant is under construction. The 9.5 mile long, 25.5' diameter Effluent Outfall Tunnel is the center piece of this program. A Robbins double-shielded TBM is currently driving this challenging tunnel some 400 feet below sea level. This paper will discuss the set-up and operation of this Tunnel Boring Machine in driving the longest single heading tunnel ever built in North America.

Jan 1, 1993

By Alwyn Protheroe, Steve Smith, Herbert Jr. Gibson

In September of 2000, Cowin and Company, Inc., contracted with Paramont Coal Corporation to construct a large decline approximately 820 m (2,700 feet) in overall length at a grade of 8 degrees to the Lower Banner Coal Seam. This paper will discuss the methods used by the contractor and owner to overcome the unique problems required to construct this tunnel in a coal mine environment. The problems include, initial design considerations, equipment selection, ventilation, ground control, control of water in?ows, and placement of concrete.

Jan 1, 2003

By A. Cavero, M. Diaz

The annual rainfall at Minera Yanacocha's gold mining operations in northern Peru averages 1.2 meters. The influx of water into the operations is higher than losses to evaporation and by ore absorption which results in a positive water balance. To minimize water intake and maintain a balance, some special operating procedures are required, and a system involving diversion ditches, storm ponds, heap skirting and detoxification and treatment of excess water is practiced. An operation background is also reviewed at the beginning of the paper.

Jan 1, 1998

By R. D. Hansen, R. R. Klimpel

This paper discusses the influence of frother type and dosage on recovery/selectivity in coal/sulfide mineral flotation as a function of particle size. It is shown that different frother structures exhibit quite different but consistent performance characteristics depending on the underlying particle size ranges involved as well as the dosage levels of both the frother and collector. The data presented on existing commercial frothers and some new special purpose experimental frothers is used to illustrate some general operator guidelines on proper frother selection and use.

Jan 1, 1987

By Michael J. Friedel

As part of a study aimed at understanding the hydrology of in situ leach mining (ISLM), the Bureau of Mines, in cooperation with the Cyprus Casa Grande Corporation and the University of Arizona, is investigating dynamic transmissivity conditions during ISLM of a copper oxide ore deposit. Spatial and temporal variations in ore zone transmissivity during two years of ISLM operations at the Cyprus Casa Grande mine are evaluated during sixteen intervals of steady-state injection and recovery well operation. Direct inversion of an analytical hydrologic model is used to obtain estimates of transmissivity at 58 well locations during these intervals. Univariate statistical and geostatistical methods are used to describe the temporal and/or spatial relationships that exist between transmissivity and other ISLM parameters, including average well injection pressure, average sulfuric acid concentration in leach solution, and the relative configuration of injection and recovery wells. Average transmissivity during the sixteen steady-state time intervals varies between 6.00 x 10-6 m2/min. (6.46 x 10-5 ft2/min.) and 3.61 x 10-8 m2/ min. (3.89 x 10-7 ft2/min.). A trend toward decreas¬ing transmissivity is evident during two year of ISLM operations. This decreasing trend is found to correlate with a decreasing sulfuric acid concentration in injected leach solution, and suggests increasing geochemical precipitation within the deposit. Geostatistical analyses reveal a dynamic and anisotropic transmissivity structure within the target ore zone, that is dependent upon spatial and temporal changes in injection pressure and well configuration.

Jan 1, 1992