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By Robert Irvine

Exploration activity for diamonds in Canada has recently experienced a dramatic increase. Disclosure of a diamond discovery exhibiting features of a potentially economic deposit contained in a kimberlite pipe in the Lac de Gras area of Canada's Northwest Territories has sparked substantial interest in-Canada and abroad and has triggered the largest staking rush in terms of area in the history of Canadian exploration. In this paper, we report on the nature and extent of current exploration activity in Canada for diamonds (with special attention to Arctic regions), the results of this activity to date, and the context in terms of current world markets for diamonds.

Jan 1, 1995

By J. C. Franklin

The U.S. Department of the Interior, Bureau of Mines, has developed a data acquisition system to continuously monitor radon, working level, absolute pressure, temperature, relative humidity, and air velocity. Data have been taken in intake and exhaust drifts, working stopes, and sealed-off areas of positive and negative ventilated uranium mines. Radon emanation rates, ranging from 1.7- to 12.2 x 2 10-l4 Ci/cm /sec were determined in four mines. The ratios of short duration, primary fan shutdown time to radon normalization time were 1 to 2 and 1 to 4, respectively, for-negatively and positively ventilated mines. Blasting and slushing caused radon increases of 160 and 67 percent, respectively.

Jan 1, 1980

By Donald P. Spitzer, Peter V. Avotins

The flow properties of thickener underflow slurries can be characterized by their rheological parameters. Most of these slurries exhibit Bingham plastic behavior, characterized by a yield stress, to, and a Bingham viscosity, nB. Red mud is generated as a leach residue in the Bayer process. The use of new Bayer process flocculants which contain hydroxamate functional groups leads to muds which are qua1itatively considerably more fluid than muds generated with conventional polyacrylates or acrylatefamide copolymers. A variety of rheological tests confirm lower yield stresses and less extended floc structures with the new flocculants, at the same solids levels. Conversely, under given viscosity restraints, the new polymers make it possible to operate at higher solids levels, which offers major benefits in processing red muds.

Jan 1, 1992

By A. B. Holland-Batt

In the 1960s and 1970s, incremental development rather than innovation was the norm for gravity separation. However, the last 15 years have seen a number of new developments in this area. The article reviews the traditional gravity-separation techniques and then examines the newer developments such as centrifugal separators. Emphasis is placed on novel devices or improvements that offer better control or improved performance.

Jan 1, 1998

By Y. L. Su

This paper describes a case study where solutions were sought to the truck queuing that occurred at a central processing plant. Ore from three production shafts at Falconbridge Limited's Sudbury Opera¬tions is hauled by three trucking contractors to Strathcona Mill. On return trips, the classified mill tailing is carried back to the mines for backfilling. The ore feeder at the mill handles three times the tonnage designed for and the situation is not expected to improve. Excessive truck queuing and consequent mine production interruptions are therefore of great concern. During the study, stochastic models were formulated and programmed for the IBM/AT personal computer. Basic information sought from the models were truck waiting time and ore production interruptions. The existing system was tested, not only to verify the validity of the models, but also to understand the causes of the problem. Several alternatives were simulated and a simple solution selected for implementation.

Jan 1, 1986

By K. Ohga

Japan has produced 14-16 million tons of coal per year in the past several years. About half of the production comes from eight coal mines in the Ishikari coal field, Hokkaido. Most of the gassy coal mines are in this field and the average mining depth of these coal mines has already attained about 700 m from the surface. Therefore, most of the coal mines have suffered from occurrences of coal and gas outbursts. To prevent outbursts and to reduce ventilation air, gas drainage has been carried out at all of these coal mines and these have had successful results. However, the methods of gas drainage differ from mine to mine. In this report, an outline of the main methods of gas drainage are described.

Jan 1, 1987

By James R. Tompkins

This paper details the successful progression of a promising exploration property into a producing gold mine in only 35 weeks on schedule and on budget. While under construction, an extensive exploration program continued to add to the mine life through the increase in reserves, resulting in a decision to increase the mill capacity from 500 tonnes per day to 1000 tons per day while maintaining the original construction schedule. Details are provided on the unique geology at the Puffy Lake Gold Mine, development from the exploration stage through construction and ultimately to production, with a detailed flow sheet. In addition, of note is the successful change over from contract mining to the hiring of Pioneer personnel who are successfully carrying on both stope mining and development. Operating costs per ounce of gold production are projected at $185 U.S. and alternate methods of mining are currently being examined which could further reduce operating costs.

Jan 1, 1988

By C. L. Karr, D. L. Meredith, D. A. Stanley

The U.S. Bureau of Mines is currently investigating ways to combine the learning capabilities of genetic algorithms with the process control capabilities of fuzzy logic. Fuzzy logic has been successfully used for controlling a number of physical systems. However, the selection of acceptable fuzzy membership functions has generally been a subjective decision. In this paper, high-performance fuzzy membership functions are learned using a genetic algorithm, a search technique based on the mechanics of natural genetics. The membership functions learned by the genetic algorithm provide for a more efficient fuzzy logic controller than the membership functions selected by the authors for the liquid level system considered. The approach to developing genetic algorithm-based fuzzy logic controllers is demonstrated on a liquid level controller.

Jan 1, 1990

By Pradip

The selection, testing, and commercial utilization of flotation reagents is best carried out in stages through microflotation tests on pure minerals and their synthetic mixtures followed by bench-scale batch flotation tests on the ore. A systematic approach to quantitatively evaluate different reagents, in particular, through the analysis of batch flotation data, has been presented in this paper. It is recommended that the reagents are compared both in terms of their performance with respect to the recovery-time as well as the recovery-grade plots. While the former describes the kinetic aspects of reagent interaction, the latter is a measure of its selectivity for a particular separation problem.

Jan 1, 1987

By Noel N. Moebs, John L. Ellenberger

Geologic structures in mine roof rock contribute to many roof falls in Appalachian coal mines. These structures include paleochannels, scours, pinch-outs, slickensides, clay veins, and cravasse splays consisting of thinly interlaminated sandstone and shale. These structures often can be identified during, and sometimes before, development and mine projections can be revised to reduce the adverse effects of discontinuities in roof structure. Large areas of roof consisting of laminated sandstones or incompetent strata generally can be delineated from exploratory drill-hole data and the need for supplementary support can be anticipated. Because an accurate description of roof geology also provides some indication of optimum length and type of roof bolts that should be installed, this Bureau of Mines paper describes the hazardous roof structures most commonly encountered in the Appalachian coal region.

Jan 1, 1982

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 V. Rajaram

A mine fire or roof collapse may necessitate the reversal of main fans to isolate the fire or provide an escapeway. Hence, to assist the mine operator in estimating the flow and pressure during reversal, Engineers International Inc. conducted a laboratory and field study of the reverse performance characteristics of main mine fans. Laboratory tests were performed using a 2.4-m (96-in.) diam vane axial fan to establish the forward and reverse performance characteristics under controlled conditions. Subse¬quently, a field test was conducted in a Colorado oil shale mine during which two 2-m (79-in.) diam fans were reversed. The data obtained indicate that reverse performance characteristics depend on the blade angle and the hub-to-tip ratio. The quantity in the reverse mode ranged from 30% to 65% less than in the forward mode, and the static pressure was directly proportional to the square of the quantity.

Jan 1, 1987

By H. Y. Sohn, M. Pérez-Tello, J. Löttiger

An investigation of the oxidation reactions of two industrial copper mattes was performed using dflerential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) at heating rates of 20°C and 8°C/min, respectively. The temperature of incipient reaction, the total exothermic and endothermic heats of reaction and the weight change during the oxidation process were measured as functions of the oxygen concentration in the oxidizing gas, matte grade and matte particle size. The temperatures of incipient reaction measured from the DSC experiments were found to increase monotonically with all three input variables. TGA experiments showed that Cu2O and CuO CuSO4 are formed before the complete oxidation of Cu2S to CuO.

Jan 1, 2000

By M. Jaramillo

The expanded west pit of the 15 Mta (13.6 stpy) El Cerrejon mine will eventually reach a maximum depth of 270 m (890 ft). Slope-stability evaluations indicated that this depth, combined with structural complexities, would create a serious risk of footwall instability. Stabilization calls for anchoring the footwall by the installation of 9- to 33-m- (30- to 108 ft-) long multistrand steel cable bolts. For each of the 15-m- (50-ft-) high mining benches, a row of bolts is installed with variable horizontal spacing, depending on the dip magnitude. Cable bolting is now standard operating practice, and an estimated 11,800 bolts will be installed during the life of the mine. Results to date have been satisfactory in terms of the stability condition of the bolted slopes.

Jan 1, 1997

By Chris C. Sundberg, Ronald E. Heuer, Stanley L. Paul, Peter M. Douglass

Use of prestressed concrete cylinder pipe (PCCP) for pressure tunnel liners is gaining popularity with contractors, engineers, and owners. This paper presents loading considerations and a beam-spring computer model approach to tunnel liner analysis, together with ultimate strength (US) and service load (SL) procedures for liner design. The US procedure is best suited to check for adequate liner strength under extreme loading conditions. The SL procedure, based on conventional pipeline design practice, is considered more appropriate when addressing crack control and serviceability under normal working load conditions. Other design and construction considerations are discussed and a design example is presented.

Jan 1, 1987

By Thomas E. McNider

Preliminary studies were conducted at Jim Walter Resources, Inc. Blue Creek No. 3 Mine to determine the influence propane operated heaters exert on the mine ventilation system when two of three intake airshafts were heated. During initial use of the heaters, it was found that change in density caused by heating a portion of the air at two of three intake shafts altered under- ground air flow changes sufficient to be considered a violation of Part 75.322 of the Federal Coal Mine Health and Safety Act of 1969 as amended by Public Law 95.164. The primary concern was to accurately define the problem in order to derive a workable solution.

Jan 1, 1980

By S. Saklar, i. Bayraktar

The effect of the feed size distribution on the kinetic parameters in pyrite flotation was studied. The kinetic parameters of the particular sizes were determined as a function of whether other particle sizes were present. From the data, a relation between the pyrite flotation rate and the particle size distributions was obtained. It was shown that the flotation rate constant (k) is a function of the size modulus (dt) of the Gates-Gaudin-Schuhmann distribution, and its variation may be expressed as k = a • exp(b . d,) for either individual size fractions or composite feed. Parameters a and b are dependent on the particle size distribution of the feed. Specifically, parameter a increases linearly as the distribution becomes coarser. The above relationship was also tested under conditions in which the collector (KAX) dosage was varied from 130 to 278 g/t. It was shown that the established relation was not dependent on the collector dosage.

Jan 1, 2002

By J. P. Barbosa, R. V. V. Araújo, R. B. E. Trindade

Bromide stabilizes the auric or aurous ion by forming a stable complex in acidic aqueous solution. The oxidizing agent normally used for the process is bromine, which is a corrosive liquid with high vapour pressure. This is, in fact, the main reason why it has not found acceptance yet as an industrial oxidant for gold. Ferric ion with hydrogen peroxide and/or sodium hypochlorite have already proved to be effective oxidants for the dissolution of gold from a rotating disc in a bromide-containing aqueous solution. In the present work, preliminary tests with four selected ore samples were tested to evaluate the dissolution of gold with the same system already tested with the rotating disc (Br-/Fe3+/H2o2/NaCIO). Compared to the conventional cyanidation, results were superior in one instance only. The major obstacle seems to be the maintenance of a suitable potential to allow the complex formation. However, the studied system may be interesting, is in some situations it may yield better results than conventional cyanidation; therefore, further investigation seems to be worth doing.

Jan 1, 1995

By P. C. Thakur

In gassy coal mines, some methane drainage is essential for mine safety, but the ratio of total methane drained to total methane produced by the mine can vary from 10 to 70 percent. The volume of methane not captured is diluted by ventilation air and vented to the atmosphere. Since captured methane can be processed and sold, it makes sense to maximize methane drainage from coal mines. This paper describes ventilation and methane drainage schemes to achieve these goals.

Jan 1, 2003

By A. D. Davis, C. J. Webb, F. W. Beaver

The proposed National Underground Science Laboratory will be housed in the former Homestake Gold Mine at Lead, South Dakota. Uses will include underground neutrino experiments that must be shielded by several thousand feet of rock, as well as ground-water research in fracture-flow environments, and investigation of the microbiology of extreme environments. The Homestake Mine has about 300 miles of underground workings. Seepage of ground water into the mine openings is approximately 500 gallons per minute. Average annual precipitation in the northern Black Hills is approximately 28 inches per year. The majority of this becomes surface-water runoff or evapotranspiration, with little ground-water recharge because of the low permeability of the Precambrian rocks in the area. Dewatering of the workings over the 125 years of operation of the mine has influenced the subsurface hydrology of the 8,000-footdeep mine.

Jan 1, 2003