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By J. P. Baur

The sensitivity of radiochemical techniques makes possible the study of the initial stage sulfuric acid leaching kinetics of chalcopyrite and other copper sulfide minerals. High-grade Transvaal chalcopyrite was neutron irradiated in a TRIGA reactor to produce radioisotopes copper-64, iron-59, and sulfur-35. Dissolution rates were measured in the time interval zero to 60 minutes during which time significant anomalies were observed. First, an initial period of rapid dissolution lasting a few minutes; second, an arrest or "plateau" region usually lasting from 6 to 10 minutes; third, a second period of dissolution of lesser rate than the first. The effect of solution variables such as pH, oxygen partial pressure, and ferric ion concentration at different temperatures were measured. The initial rate data were correlated by considering the rapid reaction to be due to the dissolution of surface oxidation products or the formation of an iron depleted surface layer. The data for the second slower reaction have been explained to be due

Jan 1, 1972

By Mary E. Learmont

Grinding with steel media adversely affects the flotation response of galena. Electrochemical measurements, flotation tests, and AES, XPS, and STEM examinations were employed to identify interactions between galena and mild steel. Iron oxide, hydroxide, or sulfate species that formed on the galena surface upon contact with mild steel decreased its floatability, with the time of contact and aeration condition affecting the severity of the flotation depression.. Parallel tests performed with an active metal, magnesium, indicated that floatability was also affected by the presence of a surface coating involving lead species.

Jan 1, 1984

By B. A. Wills

With the increasing need to mine lower grade ores, high energy-related costs in comminution are of major concern. Very fine grinding is needed to liberate the very fine mineral particles in these ores. Not only is this expensive but it leads to greater losses in 'slimes'. In the early 1970's, 50% of the tin mined in Bolivia, 30% of the phosphate mined in Florida and 20% of the world's tungsten were lost in this way (Somasundaran, 1979). Gravity concentration techniques become unacceptably inefficient for particle treatment below 25-50µm, and even flotation fails in the ultra-fine range. Two approaches can be adopted to try to overcome this problem. The first involves increasing the efficiency of existing equipment or developing new slimes treatment processes. Gravity devices such as the Bartles-Mozley concentrator have been developed for this purpose and good recovery has been reported from 100µm down to 5µm. Such machines, however, have relatively low throughputs, so that large areas of plant space are generally required. Flotation is rapidly growing in importance for the treatment of ultra-fine minerals traditionally treated by gravity concentration.

Jan 1, 1986

By E. R. Bauer

A primary goal of Ground Control Research, Bureau of Mines, U.S. Department of the Interior, is to develop information that can be used by the mining industry to reduce accidents and fatalities due to failure of mine roof. A specific research objective is to determine methods to detect hazardous coal mine roof. This paper reviews the existing and experimental techniques, and describes a recent Bureau of Mines contract research project that resulted in a simple technique and prototype instrument for evaluating mine roof competence.

Jan 1, 1986

By Xinyang Wang

It is believed that sulfur and volatile matter contents in coals are the main intrinsic properties to cause the self-heating of coal. Their oxidation at lower temperatures than that of fixed carbon to initiate coal's self-heating should be quantified. This study is aimed to improve the previous mathematical model developed by the authors for studying the coal's propensity for spontaneous combustion. It enhances the model's ability to consider the effects of sulfur, volatile matter and moisture contents in the coal - three important factors affecting the coal's self-heating process. Sulfur exists in coal primarily in the form of pyrite which will be oxidized rapidly under suitable conditions. Volatile matters, higher in low rank coals, are more easily to be oxidized. Heat of water condensation provides initial energy for low temperature oxidation. Heat release rates for pyrite oxidation and moisture condensation are built in the model. Finally, the simulation results in terms of time versus temperature on pyrite oxidation and moisture condensation are validated with the adiabatic testing data respectively.

Jan 1, 2013

By T. J. Close

On September 10, 1991, Secretary of the Department of Interior Manuel Lujan deleted the Silver Peak Range North Wilderness Study Area from the list of U.S. Bureau of Land Management lands in Nevada to be considered for wilderness designation. This decision was based in part on the U.S. Bureau of Mines mineral investigation of the wilderness study area which found that it has indications of precious metals resources. The following is a summary of the results of that mineral investigation. The study area lies between the Silver Peak and Dyer mining districts of west-central Nevada. The Silver Peak mining district, to the east, has a long mining history dating back to 1907 when precious-metals-bearing veins were discovered. The major producer in the Silver Peak district was Sunshine Mining Company's Sixteen-to-One silver mine. During the Bureau's study the Sixteen-to-One mine was operating; it has since been idled due to low silver prices. Precious metals-bearing veins were discovered in the Dyer district, to the west of the study area, in the 1860's. Mineral activity in Dyer district consisted mainly of prospecting. The Silver Peak study area itself has no mining history and contains only a few mining claims, but the Bureau examined 13 mineralized sites, most previously unknown and unclaimed. These sites are along two zones that cross the study area from the Silver Peak to the Dyer mining district. The two zones transect a volcanic center of fractured and altered rocks that contain epithermal veins of quartz, calcite, and jasperoid with gold, silver, and base metals. At the surface these veins are poorly defined and poorly mineralized. The more than forty veins examined in the study area are as thick as 17 feet and as long as 1,000 feet. Samples from surface exposures of these veins contained as much as 0.02 ounce per ton gold, 2.1 ounces per ton silver, 1.0 percent copper, 2.6 percent lead, and 0.4 percent zinc. Analyses of the Bureau data disclosed no vein large enough or of high enough grade to be classified a mineral resource. However, most do have indications of silver-and gold-bearing resources at depth. Subsurface exploration had to be done on the vein at the Sixteen-to-One mine to outline reserves (a vein averaging about 22 feet thick and containing 6-to 7-ounces per ton silver); the same is true of veins in the Silver Peak Range North Wilderness Study Area.

Jan 1, 1993

By Terry I. Mudder

Metal complexed cyanides in wastewaters form as a result of interactions of free cyanide with metals present in the wastewater and exhibit varying degrees of stability, toxicity, and treatability. Thiocyanate, a pollutant commonly found in cyanide bearing wastewaters, is formed through the interaction of free cyanide with sulfur containing species (i. e. pyrrhotite) both present in the wastewater. In certain industrial processes, such as the beneficiation of gold and silver, cyanide is an essential reagent. Since free cyanide, complexed cyanides, and thiocyanate are potentially toxic to humans and aquatic organisms, these compounds must be removed from wastewaters prior to their discharge into surface or ground waters serving as potential potable water sources, marine or fresh water habitats

Jan 1, 1984

By Nath S. Parate

With the extension of mining beneath residential and industrial areas, it is becoming increasingly necessary to extract coal and minerals in such a way that subsidence damage due to groundmovement is reduced to a minimum. Understanding clearly of the mechanism of subsidence development is a must in view of the environmental problems and the energy crisis today. This paper gives a simple analysis of various components resulting from subsidence and the influence of other factors on their development. An up-to-date review of the subsidence and strain profiles is presented, with particular references to the coal mining operations. The importance of this topic from mining damage to structures, buildings properties and environment in mining areas is undeniable. Field results are discussed.

Jan 1, 1982

By F. Harold Weber

On July 13, 1967 the San Bernardino County Planning Commission approved publicly a request by American Smelting and Refining Company for a zone variance to conduct a silver mining and milling operation in the Calico district, southern California, Coincidentally, on July 14 the U.S. Treasury halted its sales of silver, and the U.S. free market price quoted rose immediately from $1.30 to $1.77 per ounce. In its request to the commission Asarco stated that about 13,500 to 15,000 tons of rock would be moved daily by surface mining, including 7,000 tons of ore. The ore would be crushed to minus three-quarters inches and the silver recovered "by a chemical process." The grade of the ore was not given, but the company said that it might also recover barite as a byproduct, The operation would employ 150-160 people. Additional activity in the district includes exploration programs by Superior Oil Company and Calico Silver Mines, Ltd. History and production: In retrospect, as the price of silver began to rise in 1961 from 91 cents an ounce, and as Asarco began its exploration program in late 1964, a new era for an old bonanza silver district would seem to have begun. The Calico district has been mined for silver only on a very, very small scale since 1882 to 1896, when an estimated $12 to $20 million (perhaps 15 to 20 million troy ounces) of that metal was produced from the 50-odd mines of the district and vicinity. These mines include the Silver King, Oriental, Waterloo, Garfield, Odessa and Waterman (which is about 8 miles west of the district). Much smaller-valued amounts of barite, gold, lead, and copper also have been produced from the ore deposits of the district; and from 1884 to 1907 the region yielded about $9 million worth of borate minerals.

Jan 1, 1967

By Guillermo V. Borquez

The economics of open pit mine design are dictated by three basic elements: cut-off grade, stripping ratio and slope angle. Although these elements are functions of a number of independent parameters, they are interrelated through their influence on the overall economics. The optimum slope angle is the most uncertain element to determine, because rock mass properties are difficult to obtain. However, for preliminary estimation, the slope angle can be determined from the relationship between the probability of failure and the safety factor. The economics of the slope selected will depend on a profit versus risk judgment. In this paper, the author will present an actual case of application of this postulate.

Jan 1, 1977

By J. J. McClellenand, R. A. Jankowski

Face ventilation and water sprays are the primary controls used on continuous miner sections to protect workers from respirable coal and silica (quartz) dust. Laboratory tests were conducted by the U.S. Bureau of Mines to determine the impact on respirable dust concentrations when increasing airflow from 3000 to 9000 cfm (1.42 to 4.25 m3/sec), water flow from 15 to 35 gpm (0.057 to 0.132 m3/min) , and water pressure from 80 to 200 psi (5.52 x105 to 1.38 x106 pa). The effective limits for each control and interactions between these controls were of particular interest. Initial analysis concentrated on defining the impact of the control parameters on the respirable fraction of the feed dust, which was a blend containing 90% coal and 10% quartz. Gravimetric sampling indicated that airflow had the most significant individual impact on respirable dust levels and resulted in reductions of 99% at the operator and 57% in the return. Regression modeling was used to predict dust concentrations at the operator and in the return. Significant interactions were observed between control parameters and often, defined the level for a control parameter where increases above that level did not significantly benefit dust control. Increasing airflow to 8400 cfm (3.96 m3/sec), water flow to 25 gpm (0.095 m3/min), and water pressure to 140 psi (9.65 x105 Pa) typically provided respirable dust reductions at both sampling locations, while optimizing use of control resources. After determining these relationships for the total respirable fraction, selected filters were analyzed for quartz content to define the impact on the quartz component of the feed dust. For the individual control parameters, airflow again had the most significant impact and resulted in reductions of 98% at the operator and 26% in the return. Regression modeling of the quartz concentrations indicated that no significant interactions between control parameters were present. At the operators location, airflow was the only parameter identified as having a statistically significant reduction for quartz dust. A reduction in quartz approaching 95% was observed for increasing airflow to 6000 cfm (2.83 m3/sec). Increases above 6000 cfm had little additional impact. In the return, a linear relationship between control parameters and quartz levels was observed with reductions of approximately 27% predicted for increasing any one control parameter to its maximum level. The synergistic impact of increasing all control parameters to maximum levels resulted in a maximum predicted reduction of 81%.

Jan 1, 1991

By Dermot M. Ross-Brown

The objectives of this generic study were to use numerical modeling techniques to determine under what conditions seismic waves generated by an earthquake might cause instability to an underground opening, or cause fracturing and joint movement that would lead to an increase in the permeability of the rock mass. In general, the study showed that moderate earthquakes (up to 0.41 g) did not cause instability of the tunnel or major fracturing of the rock mass. An artificial rock-burst tremor with high accelerations, however, was found to be amplified around the tunnel, and fracturing occurred as a result of the seismic loading in salt and granite. In shale, even moderate seismic loading resulted in tunnel collapse.

Jan 1, 1981

By Bob Rautenberg, Luminita Calin

The Tunnel and Reservoir Plan (TARP), commonly known as the Deep Tunnel Project, was developed by the Metropolitan Water Reclamation District of Greater Chicago as a two-phase solution to the problem of waterway pollution and basement flooding due to sewer system backups created by the combined sewer overflows. With only one contract left before completion of the Phase I tunnels—the 12.4 km(7.7 mi.) long Little Calumet leg—the pollution control phase of the 175.7 km(109.2 mi.) long system will be 93% complete, once the Torrence Avenue tunnel project comes to an end. This paper describes the Torrence Avenue tunnel project, currently under construction by the joint venture of Kenny (Sponsor) / Kiewit / Shea. Mining of the10.4 km (34,151 feet) long and 8.3 m (27'-4") diameter mainline tunnel was completed in a record thirty-one-weeks period and the concrete lining is nearing completion. Details on the complete muck handling system, numerous mining and concrete lining records will be given.

Jan 1, 2001

By A. M. El Shafey, Ahmed W. Hussein, Ibrahim M. Gaafar, Mona M. Fawzy, Mohamed Diab, Mohamed S. Abu El Ghar

The Quaternary stream sediments of the Diit area, southern Red Sea coast, Egypt, were mineralogically studied for their content of economic heavy minerals. The study area covered approximately 450 km2 and included three main parts: Wadi and Delta Diit, as well as Diit lens. The mineralogical investigation revealed that these sediments contain considerable amounts of placer ilmenite, magnetite, zircon, sphene, apatite, garnet, and rutile. Also present, in minor or trace amounts, are uranothorite, monazite, xenotime, fergusonite, khatyrkite, and gold. The magnetic fractionation tests, supplemented with the XRD and SEM mineral analyses, indicated the presence of Fe-oxide minerals as wuestite, hematite, and maghemite accompanied with magnetite as products for hand magnet separation. Ilmenite separation was carried out using a high intensity magnetic separator at a current of 1 A, while the paramagnetic minerals (e.g., garnet, pyroxene, amphibole, epidote, monazite, xenotime, and fergusonite) were separated as magnetic fraction at a current of 3 A. The non-magnetic minerals (e.g., zircon, apatite and rutile, uranophane, uranothorite, gold, and khatyrkite) were obtained at 3 A current. On a mineralogical and geochemical basis, the present work suggests that Diit stream sediments should be considered as a potential source for Ti, Fe, Zr, Zn, and Cu after the physical upgrading processes for concentrating the minerals carrying the aforementioned economic elements.

Jan 21, 2022

By Todd S. Webster, Matthew J. Pierce, Brad D. Krumel

With the Working Shafts and Starter Tunnel under way, it became apparent this 4.7-mile, 19-foot diameter wet weather tunnel was going to live up to its name. The shaft’s pre-excavation grouting was completed, and ground water inflows were slowing project progress. As the tunnel drive was approaching 50% complete a cooperative effort was underway between the owner, engineer, and contractor to raise the base of the Retrieval Shaft by 65 feet to avoid ground water infiltration construction challenges. The tunnel alignment needed to be raised in kind. The project was behind schedule and rethinking the cast-in-place adit work was next on the agenda due to the very wet environment in the tunnel. The race was on to finish the project within the owner’s time constraints while completing multiple redesign aspects of the tunnel alignment and associated adit construction. This paper will evaluate original design criteria and actual in-route design modifications and change management to meet the owner’s just-in-time schedule needs.

Dec 1, 2022

By Ralbern H. Murray

Typical First Year Selling Price Strip Mined Western Sub-Bituminous Coal Based [Fixed Capital (1) $600 MM Construction Loan Interest $100 Working Capital $ 30 Start-up Costs $ 30 Total Capital Requirement $760 MM Annual Costs (First Year) $M/Year Coal (2) 443,550 Operating Costs(3) 53,000 Depreciation(4) 36,500 Interest(5) 45,220 After Tax Profit(6) 34, 200 Federal Income Tax (48% Rate) 31, 570 Gross Revenue Required 245,040 (Less) By-Product Sales (18, 000) Net Revenue Required 227, 040]

Jan 1, 1975

By R. A. Allwes

In-plane bending and torsion tests were conducted on full-scale masonry walls to evaluate three post-reinforcement designs. The designs were developed to minimize longwall mine subsidence damage to existing residential masonry foundations. The bending tests show that vertical and horizontal post tensioned tendons significantly increase the resistance of a masonry wall' to in-plane bending. The torsion tests reveal that post tensioned tendons increase a masonry wall's limit of deformation but do not increase its torsional stiffness. The torsion tests also show that the masonry units minimally contribute to the torsional stiffness of a masonry wall.

Jan 1, 1995

By Norman F. Schulz

The technical excellence of separation achieved in a mineral concentration process, or any other process where two constituents of any kind are physically separated from each other, is expressed uniquely and quantitatively by the Separation Efficiency: ES = (R ? Rg) where R is the percentage of the valuable constituent and Rg the percentage of the waste appearing in the concentrate. The Separation Efficiency meets all the usual requirements of a true efficiency and is independent of the nature of the process used. It can be visualized as the percentage of the feed material that, in effect, actually undergoes complete separation while the rest of the feed is distributed randomly and unchanged into the two separation products.

Jan 1, 1969

By Iwasaki I.

This article discusses the effect of physical and chemical modifications of starches on the anionic and cationic flotation of silica from oxidized iron ores and magnetite-taconite concentrates, and the results of the interaction of starch, pH, and calcium ions on the flocculation, clarification, and filtration of iron ore slimes and magnetite-taconite tailings. Starches, particularly when anionically modified, were found to be effective depressants in anionic silica flotation. British gums and dextrins were beneficial for oxidized iron ores, but none of the starches or starch derivatives appeared to have any effect on magnetite-taconite concentrates. The flocculation and filtration of iron ore slimes were most strongly affected by the level of starch, to a lesser degree by the pH, and were virtually independent of the level of calcium chloride. The clarification of iron ore slimes was complexly dependent on these three factors. The flocculation of magnetite-taconite tailings depended mainly on the level of starch, whereas their clarification depended on the level of lime. As previously reported in the literature, selective flocculation and partial upgrading of a semi-taconite could be readily attained with starch and calcium chloride.

Jan 1, 1968

By F. Habashi

Japan was a closed society until 1853 when it was forced to open to the West. Mining, metallurgical, and geological education started there around 1861 when a graduate from Yale University in USA went to Japan to organize the first School of Mines. This was followed by other metallurgists from Great Britain, France, and Germany and thousands from other disciplines. The present report is a summary of the writer's first contact with Japanese metallurgists and his visits to a number of universities and research institutions in the past years.

Jan 1, 2012