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By P. Somasundaran

Flotation of oxide minerals is controlled by a number of factors, such as surface potential and solubility of the mineral, concentration and type of various inorganics, properties of the collector, pH, ionic strength and temperature. The role these factors play depends on the mechanisms of adsorption of the collector inorganics or polymer additives. The major mechanisms include electrostatic interactions, chemical adsorption, chain-chain interaction between adsorbed collector species and modifications of the surface by inorganics. In real systems, flotation is, however, markedly affected by various other processes, including aging of the minerals, surface precipitation of the collector on the mineral and associative interactions between various collector species leading to highly surface active, for example, ionomolecular complexes. These effects are reviewed here with selected examples.

Jan 1, 1999

By Paul T. Allsman, Paul F. Yopes

17.1--CURRENT AND FUTURE STATUS OF SURFACE MINING PAUL T. ALLSMAN AND PAUL F. YOPES 17.1.1--CURRENT The history of surface mining essentially is one of mining coal, copper, iron and aluminum ores, of placer mining gold and tin, and of pits and quarries producing clays, gypsum, phosphate rock, sand, gravel and stone. Table 17-1 is a summary of the estimated world and United States production of crude metallic and non¬metallic ores and coal in 1969. It includes estimates of the quantities produced by surface-mining methods. Two-thirds of the 10 billion tons are mined from the surface, ranging from a third of the coal. 57% of the metallic ores, and nearly all clays, stone, sand and gravel. Production by surface methods in the United States, parallels that of the world with one exception: about 90% of the copper and iron ore is mined from the surface, whereas elsewhere only about half the copper ore is surface mined. In Canada, surface mining of the Athabasca tar-sand deposits is a recent large-scale unique operation. In surface mining of coal and, to a lesser extent, metallic ores, much waste is stripped, but in nonmetallic pits and quarries the ratio between waste and ore usually is small. Assuming that the stripping ratio for surface mining in the

Jan 1, 1973

By J. S. Hu

FTIR spectroscopy has been used for the characterization of adsorbed oleate at the fluorite surface. It has been found that modest changes in the adsorption density at high temperature and high oxygen potential do not provide a satisfactory explanation for the significant increase in the hydrophobic character of the system under similar conditions. Rather, FTIR spectroscopic measurements suggest that chemical interaction between adsorbed oleyl groups occurs at high temperature and/or oxygen potential and accounts for the increased hydrophobicity. Specifically, the intensity of the =CH bond of the adsorbed oleate diminishes at high temperature and/or high oxygen potential. Such a phenomenon was not observed in control tests with the calcium oleate soap. For extensive reaction at the fluorite surface, the presence of a new surface species has been identified. These results indicate that the fluorite surface catalyzes an oxidation and/or polymerization reaction between adsorbed oleyl groups which results in a more hydrophobic structure at the fluorite surface.

Jan 1, 1986

By S. Middlemiss

The Indentation Fracture technique is being developed as a tool for use in comminution and mineral liberation analysis. Fracture toughness measurements for a number of mineralogical materials were made and comparisons were drawn between these and properties measured with the Ultrafast Load Cell drop weight apparatus. The technique has also been used as a probe to quantify differences in fracture properties at different areas in the microstructure of a material. In both a Utah limestone and a South African quartzite, material near a grain boundary fractures very differently to that in the bulk. Ongoing work is ultimately aimed at producing a comprehensive fracture model for a multi-mineral system based on its micro-fracture characteristics.

Jan 1, 1994

By Robert M. Becker

The evaluation of in situ rock stresses from measurements of the change in diameter of a borehole that is stress-relieved by overcoring has become a common practice. Generally the stress evaluation has been based on isotropic relations whereas rock in varying degrees is anisotropic. A plane elasticity solution for a circular hole along one axis of an orthotropic medium has been adapted to evaluation of in situ stress. The necessary elastic parameters for this evaluation may conveniently be obtained from static tests on the overcore in conjunction with a consistent orthotropic thick-wall cylinder solution. The method and equations for the laboratory and field evaluations are summarized and illustrated.

Jan 1, 1968

By Ihsan Berk Tulu, Mark Alexander Van Dyke, Deniz Tuncay, Ted M. Klemetti

Bleeder entries are critically important to longwall mining for the moving of supplies, personnel, and the dilution of mine air contaminants. By design, these entries must stay open for many years for ventilation. Standing supports in moderate cover bleeder entries were observed, numerically modeled, and instrumented by researchers at the National Institute for Occupational Safety and Health (NIOSH). The measurements of the installed borehole pressure cells (BPCs), standing support load cells and convergence meters, and roof extensometers are presented in this paper in addition to the numerical modeling results and visual observations made by the NIOSH researchers in the bleeder entries. The results include the effects of multiple panels being extracted in close proximity to the instrumented site as well as over one and a half years of aging. As expected, standing supports closer to the longwall gob showed the greatest load and convergence. The roof sag appeared generally independent of the proximity to the longwall gob. The BPC readings were driven by both the proximity to the gob and the depth into the pillar. The results of this study demonstrated that the entry roof can respond independently of the pillar and standing support loading. In addition, the rear abutment stress experienced by this bleeder entry design was minimal. The closer the mine development, pillar, or supports are to the gob, the greater the applied load due to rear abutment stress.

Jan 7, 2021

By C. O. Brawner

Approximately 7 billion tons of soil, rock and ore are currently being excavated in open pit mines and quarries on the North American continent at the present time. As the depth of excavation increases and the grade of ore being mined reduces, the safety and economy of the stability of the pit slopes becomes increasingly important. The magnitude of the potential influence on economics can be appreciated from the results of recent full scale field studies by Kennecott Copper Corporation at the Kimbley pit near Ely Nevada (Merrill, 1968). This pit was originally excavated with an average wall slope of 45°. Based on detailed studies it appeared that a slope of 610 would be stable. Subsequent excavation to this slope proved the original pit could have been steepened by 16° during production.

Jan 1, 1968

By Robert A. Bauer

Introduction A longwall mining demonstration currently in progress in the Herrin (No.6) Coal Member near Benton, Illinois, involves the extraction of three adjacent panels by the longwall method. The first panel was completed in May, 1977. The Illinois State Geological Survey is involved in this project for two reasons: (1) to detail the geology of the roof and relate the geologic features to the behavior of the roof during mining operations, and (2) to study the nature and occurrence of coal balls (carbonate petrifactions of peat) encountered during this demonstration. General Geology of Area The stratigraphic sequence of beds immediately above the No. 6 Coal in this area, ranging from oldest to youngest, is: gray shale (Energy Shale Member), black carbonaceous shale (Anna Shale Member), and argillaceous limestone (Brereton Limestone Member) (figure 1). In some areas of the mine, where one of these units may rest directly on the coal, one or more of the members is absent from the stratigraphic sequence. The nature of roof for the area is shown in figure 2. It is greatly exaggerated in the vertical direction. The Walshville Channel, 11.3 km west of this mine, was a river at least in part deposited at the same time as the coal. The gray shale wedge on top of the coal, which thins away from the channel, is thought to represent an overbank deposit of mud from the channel. The next layer deposited on top of the gray shale, and on the coal not covered by gray shale, is the black carbonaceous shale, believed to represent a mud deposited in a brackish environment. The area where the roof lithologies change rapidly from one shale to

Jan 1, 1977

By Dolf Vos

The balling section of the pelletizing plant at Hoogovens IJmuiden consists of 7 balling drums. Each with an average capacity of 100 tons of green pellets per hour. The balling drums are equipped with rotating scrapers and water-spraying systems. The scrapers are installed in order to restrict the growth of the race to a certain thickness. The spraying system is used to adjust the desired value of the moisture-content of the rewetted ground ore, the pellets and the race. The desired value is the value by which the balling- process is stable, good pellets are formed and surge occurs within certain limits. In October 1980 the construction of one of the balling drums has been modified. The rotating scraper was removed and the inner wall of the drum was supplied with a rubber-lining. In 1982 a second balling drum has been rubber- lined. At the same time the Tyler vibrating screen of this balling circuit has been replaced by a roller(bed)screen. By the end of 1983 all 7 balling circuits will be equipped with rubber-lined drums in combination with roller(bed)screens. The combination of these two modifications will improve the quality and the screen analysis of the green pellets, moreover resulting in savings on energy- and maintenance costs. This paper describes the influence of a rubber- lining on the balling process and the green pellet quality by carrying out in-plant testruns in November/December 1980. The testrun results have been compared with the results of a not modified balling drum.

Jan 1, 1983

By S. F. Willey

The difficulties encountered in justifying replacements for over-age mobile mine equipment at the Gay Mine are common to most mining operations. More critical management reviews, resulting from ever rising capital expenses, increased such difficulties. These increased difficulties are especially apparent to those who are primarily operators and are not statisticians, mathematicians, or computer oriented. The Gay Mine is located 17 miles east of the town of Fort Hall in southern Idaho. This open pit operation annually supplies the J. R. Simplot Company and the FMC Corporation with 1.5 MM - 2.0 MM tons of phosphate ore. Stripping ratios average approximately three bank cubic yards of waste per ton of ore mined. The mobile mine equipment fleet consists of ten 24 yard scrapers; twenty-one 30-50 ton end dump trucks; four 32 42 yard shovels; fifteen dozers in the D-8 and D-9 classes; and three road patrols. Equipment replacement is based on the results of evaluations made on individual units. Authorization of capital expenditures for equipment replacement is dependent upon a favorable profitability index (true rate of return on investment) plus a favorable payout time. The system is based on cash flows and requires the determination of (1) the net cash outflows in the form of capital expenses plus (2) the expected cash inflows resulting from reduced expenses and depreciation tax credits. After adjustments for taxes and the time value of money, the net amounts are used to calculate the required indices. The basic elements for the system related to the replacement of mobile mine equipment include: (1) the determination of dollar penalties to be expected from the continued use of aging equipment; (2) the selection of equipment that will provide the greatest return on the investment dollars; (3) the quantification of the expected savings; and (4) the calculations of the prescribed indices. Inadequacies inherent in previous evaluating methods led to the search for more

Jan 1, 1972

By A. G. Provost

On April 3, 1981, Harrison Western Corporation was awarded a contract by Amax Alloy - A Division of Amax Inc., to sink the Henderson #5 ventilation shaft. The project was located on the Henderson Mine site 88 kilometers west of Denver near the town of Empire, Colorado (Figure I). The Henderson No. 5 Shaft, located in an Alpine environment at an elevation of 3145 meters, was a 9.8 meter diameter concrete lined shaft with a total depth of 793 meters. Work started and continued with Harrison Western employees until January 15, 1982. At that time, Amax made the decision to continue the shaft-sinking with their own labor, and with Harrison Western providing supervision under a management service contract. Shaft sinking continued under this arrangement to October 1, 1982, at which time Amax put the Henderson No. 5 project on standby status until further notice.

Jan 1, 1986

By Mark C. Williams, Thomas P. Meloy

Particle shape characterization is a complex task made more difficult because of the human eye's sophisticated recognition of shapes, giving rise to the assumption that shape analysis is considered a simple problem. Further exacerbating the problem is the question of whether particles have a general shape. Old and new shape measuring techniques are discussed, particularly the new image analysis methods techniques such as Fourier, Haar, Walsh and Delta. Problems with the current image analysis equipment and future research equipment needs are presented.

Jan 1, 1989

By Brian F. Taylor

The Mexican fluorspar industry is faced with and will face serious problems, some of their own making and others beyond their control. However, they still offer the most secure source of fluorspar for North American' consumers. Since 1975, even in light of declining markets, they have, increased then production capabilities' as shown in Table #1. In analyzing Table #1, we note that Compania Miners Rio Colorado has closed down due to their ore reserves being exhausted. Fluorita de Rio Verde expanded their acid grade fluorspar capacity in anticipation of additional North American business. Campania Miners Las Cuevas presumably increased capacity to meet their North American contractual commitments and to supply their own hydrofluoric acid plant (Fluorex) at Juarez, Mexico. Historically, the Mexican fluorspar industry has relied on the United States as the mainstay for their sales. As shown in Tables #2 and #3, the Mexican share of the United States market has moderately decreased. However, as noted in Table #4 the volume loss is substantial as explained below.

Jan 1, 1985

By V. Miller

C. Hertzler The difference of means of milling characteristics by rock and ore type is tested in a statistical manner in the paper. The null hypothesis being tested is that the sample means of two different populations are equal. It is assumed that the null hypothesis is true when performing the test. Because of this, acceptance of this hypothesis leads to the conclusion that the sample means of the two different populations are equal (or there is no significant difference between the sample means), not that the samples come from the same population, as the author asserts. Rejection of the null hypothesis leads to the conclusion that the sample means of the two different populations are not equal. A P value for this test is reported in Table 2 and is incorrectly identified as the probability that the two samples came from different populations. Actually, what was recorded was 100(1 - p) where p is the usual p-value. The usual p-value measures, on a scale of zero to one, the extent to which the data agree with the null hypothesis. It is the probability of observing a value of the test statistic (Z score) that is at least as contradictory to the null hypothesis as the one computed from the sample data (McClave and Dietrich II, 1982). The author makes no mention of the fact that were these tests to be conducted together, the chances of determining that the null hypothesis is not true when it is really true are increased considerably (Snedecor and Cochran, 1980). This is a multiple comparisons problem and should be dealt with accordingly. The usual methods involve adjusting the level of the individual tests. Table 2 reports an incorrect 100(1 - p) value in the comparison of concentrate grades for other rock types with .30 to .69 % Cu vs other rock types with .70 + % Cu; 86 % should be 98.6 %. Although the article can be criticized for poor data presentation and discussion of that data, the point the author makes regarding the use of these statistics in the ore reserve estimation process is well taken. It does not appear that inaccuracies in the statistical interpretations have hindered that usefulness. References McClave, J.T., and Dietrich, II, F.H., 1982, "Statistics," Dellen Publishing Co., San Francisco and Santa Clara, CA, 766 p. Snedecor, G.W., and Cochran, W.G., 1980, "Statistical Methods," The Iowa State University Press, Ames, IA, 561 p. Reply by V. Miller After reading Ms. Hertzler's comments, it appears that the differences noted were basically semantics. If the paper is ever presented at a math symposium, some changes will be needed. When deciding the best way to present the data to mining engineers and geologists, I decided that presenting the probability that the two sample groupings came from different populations (reverse to the Null hypothesis) was easier and would require less verbage to explain. Hence, the 100(1 - p) difference which was noted. Ideally, I would have preferred to give the recovery and concentrate grades, then comment which ones had significant differences. Unfortunately, Kennecott Corp. did not grant permission to publish the ore body's actual recoveries and concentrate grades. The conclusion is that there was, as expected, a relationship between the ore's geologic properties and the metallurgical properties, and by determining this relationship, the overall mineral model was greatly improved.

Jan 8, 1984

By Lorraine B. Burgin

The extensive lead time to develop most Arizona copper deposits commenced with initial production efforts before the turn of the century, when the first attempts were made to recover gold and silver and later copper from the high-grade vein deposits of the territory. Each of these discoveries, prospects, and early operations had its own lead time and life cycle as economic production was attempted. Because prices of the metals fluctuated and the higher grade material was depleted, economics forced operations to close and companies to fail. Renewed interest in the property because of improved conditions, different interpretation of the geologic structure, or new promotional ability frequently resulted in the formation of yet another company to finance the exploration and, hopefully, the development of the property. This cycle of renewed activity and subsequent abandonment was and is common, accounting for many lead times and for the long period of time from the initial location of claims to large-scale production. In order to gain a perspective on the lead-time interval necessary to achieve development of a large-scale operation, the histories of several major Arizona mines were examined, rather than a simple listing of discovery and production dates of many mines to arrive at a statistical average. The Miami, Castle Dome, Copper Cities, San Manuel, and Twin Buttes properties were studied, and as much data as possible obtained on the Pinto Valley, Esperanza, Sierrita, Pima, and Mineral Park-Ithaca Peak properties.

Jan 1, 1974

By R. DasGupta

The dissolution behavior of gold in ammoniacal solutions at 75°C has been investigated. The variables investigated include concentration of lixiviants, pH of the solution and various oxidants. The anodic dissolution of gold was studied in the absence of oxidants using the potentiodynamic polarization technique. The cathodic reaction of oxidants was studied on a platinum electrode. Tafel polarization tests were also performed to determine the dissolution rate. The overall dissolution of gold in ammoniacal solutions was examined using a mixed potential theory. A comparative study on the role of cupric am mine, oxygen, hydrogen peroxide, sodium hypochlorite as oxidants for the dissolution of gold in ammoniacal solutions has been carried out.

Jan 1, 1996

By T. Bui

The shut-off value for a panel cave mine determines when a draw point will be shut-off and mining will cease from that draw point. Using a shut-off value strategy for a panel cave mine is similar to using a cut-off value strategy for an open-pit mine. This paper will discuss how to choose an appropriate shut-off value strategy that an engineer can use when planning a panel cave mine to increase the net present value (NPV) of the project. Using a shut-off value equal to the mining and processing cost will provide the total mining reserves for a panel cave mine given a specified footprint. When the net present value analysis method is used to compare one design to another then using a shut-off value greater than the mining and processing cost will generate a higher NPV. This strategy will replace the marginal ore at the top of a draw column with higher grade ore at the bottom of newly opened draw points. A draw column is broken material which sits above a draw point and it is mined to a specified height above the draw point. This height is called the height of draw (HOD). Varying the shut-off value over the life of the mine can increase the NPV even further. This strategy would have a high shut-off value during the early stages of a mine and low shut-off value during the later stages. If the shut-off value is too high then too many tonnes would be left behind the draw point and the overall value of the mine will be decreased. Also with a high shut-off value then the production target may not be maintained due to too many draw points closing too soon.

Feb 23, 2014

By J. L. Huiatt

The U.S. Bureau of Mines and Great Salt Lake Minerals and Chemical Corp. developed a froth flotation process for concentrating potassium salts from Great Salt Lake solar evaporites containing about 5 percent K. The crude evaporites, which were predominately halite (NaCl) with smaller amounts of kainite (KCl.MgSO4.2.7H20) and schoenite (K2SO4MgSO4.6H20), were conditioned in a saturated brine solution, thus converting nonfloatable kainite to the floatable mineral schoenite. Schoenite was then selectively floated with a medium-molecular weight fatty acid. Continuous small-scale pilot plant testing indicated that 80 percent of the potassium could be recovered from the crude evaporites in flotation concentrates assaying about 11 percent K.

Jan 1, 1975

By Robert T. Chapman

Many of us are privileged in that we have witnessed the transition from mining methods used in the first quarter of the twentieth' century to those practiced today. In the late Twenties, for example, many mines still used hand mucking methods. In the middle Thirties, more than one large metallurgical limestone quarry still used the 4 cubic yard railway steam shovel formerly in use at the Panama Canal. Mules could occasionally still be found underground, where they provided the-main-source of motive power. Within the last decade, and even within the past five years or less, great improvements have been made in blast-hole drilling, ore loading, and ore hauling equipment. Industrial demand for minerals can be expressed in exponential terms as compared to that at the turn of the century. Even marine mineral resources are receiving accelerated attention. One overall result is that larger and lower grade orebodies can be exploited at a profit. This profit must be made despite, for example, a static monetary price for gold, and despite the continual cost escalation involving labor, materials, supplies, and equipment. Accordingly, the application of the necessary degree of knowledge and judgment required to meet production, cost, and profit goals is paramount.

Jan 1, 1966

By Bror Nyman

Wide settlers are a way to decrease the linear velocities of advancing liquid phases. It has, however, been found unnecessary to risk a proper settler performance by building shallow settlers in order to avoid a so-called interface turbulence due to a too big difference between the linear velocities of the organic and the aqueous phase. This conclusion has been reached from tests using a large transparent settler model, where the behaviour of a clean interface between two advancing liquids has been investigated. Also in a more realistic case, making an organic in aqueous or an aqueous in organic dispersion to move between the liquid phases, no obstacle has been found to use a somewhat more deep and correspondingly ore slowly t10wing aqueous phase. Based on above findings, support can be given to a new trend to build the settlers slightly deeper than what has been typical for the so-called low-profile design. In this way, it is much easier to avoid an excessive air introduction and other severe difficulties, like those caused by crud moving from one stage to another. It is further shown, how gravity can be used to slow down and distribute a dispersion being fed into a settler of a VSF unit. Entrainment levels have been found to be reduced by a careful design of primary dispersion distributors and picket fences of the settler. Finally, it is demonstrated, how outlets from the side of the settler can be used to simplity interstage pumping and to decrease the rotation speed of any pumping device.

Jan 1, 1996