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By Andrew B. Crichton

THE oft repeated statements of the United States Geological Survey and the Bureau of Mines that the coal reserves in the United States are sufficient for 3000 yr have given us all a sense of security hard to disturb. If we discount that statement 66 pct, which to the uninformed seems drastic, we would still have 1000 yr supply, and why should mortal man worry about the difference between 1000 and 3000 yr supply of coal. That is exactly the attitude which many who should be better in- formed have taken toward the problem. A recent brochure "How Strong is America," by the New York Herald Tribune, states there is "no end to coal * * The truth is staggering * * U. S. has enough coal to last 4000 years." What the statement actually means is that the calculator got as high as 4000 yr and decided it was pointless to go on. The President's ERP Committee on Natural Resources and others in high places continue to assure the country of our superabundance of coal. In the past few days the “Wall Street Journal" carried an item from Director Boyd of the Bureau of Mines saying that within a hundred years we would need to triple our annual coal production of 6oo,ooo,ooo tons, making it 1,800,000,000 tons annually, and at that rate we had coal reserves sufficient for 1000 yr. In my humble opinion, we cannot now or ever produce 1,800,000,000 tons annually, be- cause we do not have the reserves in the producing districts to do it. Past reckoning in geology may be, as in the Psalms, a thousand years are as yesterday, but the future must be considered more realistically, and "a thousand years" is really a "heck" of a long time. In most developed areas, mining engineers can count the coal reserves in terms of a hundred years or less, and in some important areas now producing large annual tonnages in much under fifty years. They think when they hear of thousands of years coal reserves, reference is made to distant fields and "the fields are always green far away." The estimates of our coal reserves upon which we are relying were made in 1907 under the direction of Marius R. Campbell, Director of the United States Geological Survey. It is apparent this work was not well done. It was necessarily based on rather meager data because of the little development and prospecting as of that date. There were mistakes in the correlation of seams, and they assumed the continuity of thick seams throughout large coal bearing areas where coal often did not exist. The overstatement of coal bearing areas in the Campbell figures are common. The 1907 survey includes all coals over 14 in. in thickness to a depth of 3000 ft. The total coal reserves according to Campbell were 3157.2 billion tons. The production and mining losses that year would amount to -570 million tons and

Jan 1, 1948

By L. H. Schwartz, S. K. Lahiri, M. E. Fine, D. Chandra

WHILE the yield stress of solution treated Fe-Cu alloys increases rapidly with aging, a precipitate has only been directly observed in overaged samples.'-" This precipitate is essentially pure fcc copper, the E phase. Hornbogen2 suggested that the initial hardening is due to clustering of copper atoms in a bcc iron matrix. Hornbogen was not able to obtain direct confirmation for such bcc clusters by either X-ray diffraction or electron microscopy; however, he did observe analogous clustering in Fe-Au alloys7 where the scattering factor difference between iron and gold is more favorable than that for iron and copper. Fujii, Nemoto, Suto, and Monma4 recently observed diffuse electron diffraction scattering in a 2.5 pct Cu alloy aged at 500°C: for 30 hr. They suggested that part of the diffuse SCattering was due to a modulated structure of 26 to 42 wavelength parallel to the (110) matrix plane. This disappeared with further aging. However, 30 hr at 500°C is well beyond the peak strengthening in this alloy which occurred at less than I hr at 500oc.4 By transmission electron microscopy they could not distinguish between quenched samples and samples aged to maximum strength. The purpose of the present investigation was to try to obtain further confirming evidence for a precipitation stage preceding the formation of the fcc E phase. Change in Young's modulus was selected for study be- EXPERIMENTAL PROCEDURE The Fe-1.67 at. pct Cu alloy was supplied by the U.S. Steel Corporation in the form of a hot forged rectangular bar. The carbon and nitrogen contents of this alloy were 70 ppm and less than 10 ppm, respectively. The samples for Young's modulus measurements were made by cold swaging to & in. diam and cutting to 2 in. lengths. Tensile test samples 1 in. long were prepared by cold rolling to a thickness of 0.012 in. and then machining to gage dimensions of 0.5 by 0.012 in. For Mijssbauer studies, foils 1 mil thick were prepared by cold rolling. During fabrication the alloy was given intermediate anneals at 845OC followed by quenching. The specimens after preparation were solution treated at 1000°C (y field) or 845°C (a field) for 1 to 2 and 5 to 6 hr, respectively, in a dynamic vacuum of about 2 x lom6 torr. The tensile and modulus specimens were drop-quenched into iced brine through an aluminum foil which vacuum-sealed the bottom of the furnace tube. The MOssbauer foils were drop-quenched into helium gas cooled by passing through N2 (liq) in a copper coil. The grain diameter of the modulus and tensile specimens was between 0.025 and 0.035 mm. The samples were aged from 400" to 500°C in a dynamic vacuum of 2 x 10-6 torr and cooled by pulling into a water-cooled portion of the vacuum system. The dynamic Young's modulus was measured at room temperature using electrostatic excitation and detection of longitudinal vibrations.' Neglecting any length change during the aging, (this is expected to be comparatively small), the fractional change of Young's modulus (?Et)/Eav, is equal to twice the fractional change of the resonant frequency (?ft)/fav . ?ft =ft —fo where fo and ft are the resonant frequencies of a specimen before aging and after aging to time t. The measured f's, approximately 51,000 cps, were corrected to 25°C for any variation in the ambient temperature. The tensile tests reported were carried out at room temperature in an Instron with a 1000 lb full scale load cell. The flow stress reported herein corresponds to a strain of 0.002. The Massbauer spectra were taken in a constant acceleration model AM-1 NSEC spectrometer. The

Jan 1, 1970

By D. B. Jugle, J. B. Darby

The equilibrium solubility limits of the transition elements Ti, V, Cr, Fe, and Co in liquid tin were determined in the temperature range from 827" to 1211°K. Since the equilibrium concentration of Ti, V, or Cr in liquid tin is moderately dilute in the temperature range investigated, the solubility data were employed to estimate the partial molar enthalpy and the partial molar excess entropy of solution for the three solutes in liquid tin. The reference state s for titanium or vanadium were selected relative to the solute in an intermetallic compound. The thermodynamic quantities for chromium were calculated relative to pure chromium. RECENT experiments1 have shown that the rate of solution of several transition elements in liquid aluminum can be qualitatively predicted from a knowledge of the temperature dependence of the solvent-rich liquidus. In order to extend the analysis to binary tin systems,' it was necessary to know the equilibrium solubility of several of the first-long-period transition elements in liquid tin. Since solubility data for the tin-rich portion of binary systems are meager, the present investigation was undertaken to determine the equilibrium solubility limit of Ti, V, Cr, Fe, and Co in liquid tin in the temperature range from 850" to 1200°K. EXPERIMENTAL PROCEDURE A useful technique3 to determine the equilibrium solubility of a solute in a liquid-metal solvent consists essentially of placing a pure solute in contact with a pure solvent and allowing sufficient time for equilibrium to be attained at the temperature of interest. Subsequently, the solvent is removed and the equilibrium solute concentration in the solvent is determined by an appropriate analytical procedure. The technique can be applied very successfully to relatively simple systems such as the copper-germanium system.3 However, in many binary systems of transition elements with tin, several intermediate phases are known to exist and precipitation of the phases from solution, in solubility experiments, can lead to an erroneously large solubility. The difficulty was avoided in the present work by equilibration of the most solvent-rich intermediate phase with the pure solvent over a range of temperatures. The compounds employed in this investigation, and the temperature range over which each compound is in equilibrium with liquid tin are listed in Table I. No stable intermediate phases are reported in the chromium-tin system4 and, therefore, pure chromium was utilized as the solute. The stoichiometric compounds were prepared by arc-melting on a water-cooled copper hearth in a helium-argon atmosphere. The elemental tin employed in.this investigation was 99.998 pct pure, and typical lot analyses of the transition elements were reported elsewhere.' A sample of an appropriate solute, in the form of a button and in sufficient quantity to exceed the equilibrium solubility, and the pure tin solvent were placed in a high-purity recrystallized-alumina crucible. The crucible and contents were placed in a horizontal furnace under a high vacuum (10-6 torr) and held at temperature for periods varying between 24 and 72 hr. A water-cooled quench tank, partially filled with diffusion-pump oil, was attached close to one end of the

Jan 1, 1970

By R. E. Head

SOME mixtures of sulphide and oxide ores from the Tintic district in Utah are of a sufficiently good grade to be shipped to the smelter without beneficiation. In mining this type of ore, however, a material tonnage of ore of a similar composition but of lower grade is obtained. It is a question of economics whether such ore should be shipped with a certainty of a small return or concentrated if that would yield a sufficiently increased return to amortize plant construction and upkeep and yield a higher rate of profit than at present. It may be assumed that the tonnage of this borderline ore is constantly increasing and that eventually it will attain such proportions as to justify plans for milling on a relatively large scale. Under existing conditions, the producer of mixed sulphide and oxide ores is not greatly concerned about the physical characteristics of his ore or of its mineralogical complexities, since his contract with the smelter calls for payment on the basis of chemical analysis. When concentration is contemplated an entirely different picture is presented. Percentages of valuable metal content must then be considered in terms of minerals, for it is in the form of minerals that recoveries are made and losses sustained. In describing the performance of a given flotation mill and reagent combination, it may be stated as a generality that a specific percentage recovery of valuable elements is made. Technically, however, the concentrator is really constructed and the reagents are selected to recover the valuable minerals. These considerations must be given prominence in discussing border- line ores from the Tintic district because of their physical characteristics and mineralogical composition. Because of these peculiarities they may be justly termed complex, since their lead, silver, and copper contents are each represented by two or more minerals of different chemical composition and presenting widely divergent physical properties. This paper sets forth the results of a microscopic study of a type of borderline ore from the Tintic district that is now being treated by direct smelting. A

Jan 1, 1938

By Terry J. Close

In 1992, as part of the U.S. Bureau of Mines Idaho Land Assessment Program, the Western Field Operations Center investigated the mineral resources of the 30,300-hectare Elk Summit study area. The area is in the Clearwater National Forest, adjoining the Selway-Bitterroot Wilderness in Idaho County. Idaho. The study area is underlain by granitic and metasedimentary rocks. Associated with these rocks are road metal (stone) resources, black sand mineral placer resources, and thermal water resources. Also present are abundant sand and gravel. Two of the five sites examined during the Bureau study have road metal (stone) resources, one has black sand mineral resources, one has thermal water resources. The fifth site is a black sand mineral placer occurrence. There is no evidence of petroleum or coal resources. Idaho County records indicate that 38 mining claims, mostly black-sand placer, have been located in the study area, Twenty-three of the claims are current. Workings consist of a few pits and trenches at the placer, and two borrow pits. The only mineral commodity produced from the area was about 1,500 tonnes of stone excavated from the Savage Pass and Swamp Creek borrow pits along the Elk Summit road, north of Hoodoo Lake. The stone was used to surface the road; these stone resources will continue to be used as needed.

Jan 1, 1993

By David C. Grant

A laboratory technique for simulating in-situ uranium mining was developed and used to determine the effects of leaching variables on permeability, uranium recovery, leach solution interaction with the ore-aquifer environment, and post-leach chemical leakage. In particular, ammonium bicarbonate, the commonly-used leach solution, was examined in great detail. Agitation leach tests were conducted to examine the effect on ammonium sorption and desorption of clay content, solution and clay ammonium levels, pH, and the type and concentration of other anions and cations in solution. Initial column tests were performed to determine the degree of ore-aquifer interaction that could be expected for various leach solutions; sulfuric acid, and ammonium, sodium, and potassium bi-carbonates. Subsequent tests examined various methods to restore the ores by lowering the post-leach chemical leakage. The restoration tests examined the use of reducing agents (e.g., ammonium bisulfite, sodium bisulfite; and sodium sulfite), ore blocking and stabilizing agents (e.g., sodium silicate, aluminum chloride, and magnesium-calcium salt).and ammonium displacement agents (e.g., aluminum chloride and lanthanum chloride-sulfate)

Jan 1, 1980

By C. M. Boss

Throughout the Lake Superior Basin each of the great ironranges, from which vast quantities of iron-ore have been, and are now being mined, presents characteristics differing from each and all of the others. One of the most peculiar of these varying features is found in the dikes of the Gogebic range. From an economical standpoint this feature of the dikes has been studied by our practical mining men more than any other geological phenomena in connection with the deposits of merchantable iron-ore. In the greater portion of our mines these dikes appear to form the riffles in the sluice of the ore formation, against which the particles of iron oxide are deposited in the process of concentration out of the quartzose matrix which is termed the ironbearing formation. In composition these dikes are apparently of a dioritic formation, more or less altered and decomposed, comparatively soft, and sometimes almost steatitic. While frequently showing something of a cleavage in the direction of their pitch, they are devoid of parallel laminæ, and when broken assume the form of irregular angular fragments. They are generally of nil ashy grey color, but sometimes at great depth are found to be quite dark, almost black, and of a very hard massive nature, showing radial or fibrous crystallization. Practically all of the dikes thus far discovered in the iron formation are approximately at right-angles with the dip of the formation, and the greater number of them have an average easterly dip of from fifteen to eighteen degrees. Sometimes, however, they are folded in such a manner as to form long synclinal basins; but while their western or initial extremity is fre-

Jan 1, 1898

By Clarence R. Claghorn

Few facts relating to the Bernice anthracite coal-basin have been published in our Transactions, and little is known among engineers in general of the character and composition of the coal found in that basin.

Jan 1, 1889

"During the development of a mining project, samples are taken for metallurgical tests. The sample can be a composite sample made of material from a selection of various drilling products or a sample from a mining test. It can be also a sample from an existing plant in order to investigate process enhancement. This sample can represent several tonnes of material which are analysed and split for use in various tests.In the current case, a composite sample of gold ore is dedicated to a Gravity Recoverable Gold (GRG) test. The properties of interest are the head grade of gold, the size distribution of the material, and the gold assay per size class. The sample is mixed and a sub-sample is taken to measure the feed properties: the size distribution and the gold assay per size class. The remaining material of the sample is subject to the first stage of concentration using the laboratory Knelson concentrator. The concentrate is analysed in its entirety, while a sample of tailings is taken for the same analysis. The remaining part of tailings is subject to grinding to feed the second and third stages of concentration. Similar sampling is performed at each stage.The concentration performances are analysed in light of these measurements. But what is the accuracy of the measurements of the properties? Pierre Gy’s theory of sampling, associated with a heterogeneity model built using the GRG test results, will answer this question. The current paper presents, through a real example, the calculation of the errors of the measurements of size distributions and gold assays performed during the GRG test. The uncertainties of the concentration performances and liberation size estimate are then calculated and their impact on the results interpretation is analysed.INTRODUCTIONDuring the development of a mining project, samples are taken for metallurgical tests. The sample can be a composite sample made of material from a selection of various drilling products or a sample from a mining test. It can be also a sample from an existing plant in order to investigate process enhancement. This sample can represent several tonnes of material which are analysed and split for use in various tests. In order to take into account the ore variability in terms of gold deportment, it is recommended to perform variability studies (Dominy, Murphy, & Gray, 2011, Dominy, 2013) using samples representing various horizons or years of production. But for a given ore type, it can be necessary to perform many tests with different operating conditions (Brochot, 2012a). In that case, the variability of the samples is not due to the heterogeneity of distribution of the deposit, but only on the heterogeneity of constitution of the primary sample. The level of confidence associated with the estimated performance parameters is directly linked to the overall error (including sampling error) of the measurements performed during the tests."

Jan 1, 2016

By Charles T. Holland

The tonnage produced on mechanized automated retreating longwall faces in the United States is growing rapidly. This time last year some 14 faces were operating, and in addition to that, three were known to be down looking towards revision or repairs before being placed back in service. These, it is believed, are now in service. It is estimated at the present time, therefore, that somewhere between 20 and 25 faces are being operated in the country. A survey made last year by the School of Mines, West Virginia University, indicated that longwall mining in general has been beset with a great many problems, some more serious than others. The problems that we propose to discuss here are those pertaining to roof and floor trouble in the tailgates. Longwalls are operating in this country at the present time under an overburden ranging from 200 feet to nearly 3000 feet. Main and tailgate entries are operating in panels of up to five each, with the width of the pillars between these entries varying from 20 to 50 feet. Face lengths are running from 270 feet to 670; actually a face 800 feet long should be possible. The most economical face is often spoken of as being around 450 feet.

Jan 1, 1969

By Philip E. Niebuhr

A procedure, which can be performed in the field by nonanalytical personnel, is given for sensitive spot tests for detecting tellurium or selenium. The expressed need of a field test for detecting small amounts of tellurium, which may be accompanied by relatively large amounts of selenium, has led to the development of this method. Tellurium search has been impeded by the lack of a satisfactory test from the standpoint of sensitivity and specificity. A quantitative laboratory method exists, but it is expensive and relatively laborious. Several other qualitative tests are known, but they require unstable solutions, which must be freshly prepared for use, and a greater variety of laboratory equipment. The particular advantages of the test described are its simplicity and the stability of the reagents required, there-fore is is well adapted for field use. Also, this test was found to be of practical use in the analytical laboratory when screening samples, thereby reducing analytical costs. The roughly quantitative interpretation of the results can save time by indicating the approximate size of the sample taken for a quantitative determination.

Jan 1, 1962

By Martin Williams

During the coming decade, many of the first generation of ‘super-pit’ gold and base metal mining operations in North and Latin America will reach the end of their economic lives. The closure of such pits in a manner which is environmentally sustainable presents a considerable challenge to the minerals industry. Pit closure often results in the partial or total inundation of formerly dewatered mining operations, and the resultant formation of lakes. The development of techniques for predicting, and controlling, the chemistry, groundwater discharge characteristics and long term hydrospheric impact of these lakes has become a critical aspect of pit closure planning. In this sense, the paper point out that Sleeper Mine was the first of a new generation of open pit gold mines developed in Nevada, USA. The closure of the Sleeper pit exemplifies the use of a range of pragmatic approaches to pit flooding, with applicability to mine closure at many other sites throughout the Américas.

Apr 22, 2003

By Jayson Ripke, Peter Amelunxen, Brandon Akerstrom, Fernanda Solís

It is commonly known in the industry that one of the key challenges for a greenfield project, such as Capstone Copper’s Santo Domingo project, is the obtention of samples for metallurgical testing and subsequent plant design. To face this challenge, the Santo Domingo project completed 169,692 meters of drilling. The material collected has been used for a variety of analysis including the economic recovery of iron, which contributes significant economic value to the Santo Domingo business case. Composite and variability samples, covering the main geological units considered in the life of mine (LOM) plan, were selected for bench and pilot scale testwork. Davis Tube Tests, small scale Low Intensity Magnetic Separation (LIMS) tests and a pilot utilizing a 48 in (1.2 m), diameter magnetic separation drum were completed. The testwork demonstrated that the Santo Domingo ore could achieve iron concentrate grades of 65% Fe - suitable for blast furnace, and 67% Fe - suitable for Direct Reduction, primarily by concentration of magnetite. The outcomes of this work have informed the iron concentrator plant design and scale up.

Feb 1, 2025

By J. Mattern

Performance monitoring, operational practices and ongoing collection of geologic data in open pit slopes all provide valuable information for quantifying potential steepening of subsequent slopes. Mining at the Goldstrike open pit has been ongoing since the early 1980’s, with its share of slope instabilities. In areas where slopes have remained stable, consideration has been made for potential slope steepening of final walls. With the proper available equipment, steepening of bench face angles via pre-split blasting is not an uncommon method for steepening of inter-ramp slope angles. As an alternative at Goldstrike, the commonly used Modified Ritchie Criteria for empirical catch bench width has been adjusted resulting in quantified, rock specific formulas for bench width and rock fall berm placement. The result is an inter-ramp slope angle increase of 2 degrees on a 300m high slope, without the necessary purchases and procedural changes that would be required for pre-split drilling and blasting. The result has shown significant net benefits through reduction in mined waste tons and an increase in gold reserves. Location The Goldstrike open pit is located on the Carlin Trend gold belt in northeastern Nevada USA (Figure 1). The mine has produced over 43 million ounces (1.2M kg) of gold during the past 30 years. Engineering Geology Stratigraphy Figure 2 is a stratigraphic section of the rocks in the Goldstrike open pit. Quaternary alluvium and Miocene materials typically are poorly indurated stiff soils and are not present in all locations. Bedrock units consist of siltstones, mudstones, sandstones and cherts. From top down the major units exposed in the open pit are the Vinini Formation, the Rodeo Creek Unit, and the Popovich Formation. In general, rock mass strength increases with depth.

Jan 1, 2019

By Fisher N. I

Disequilibrium ratios (U3O8/eU3O8), which assess the degree to which gamma activity represents the uranium content of a sample, have been measured on a representative set of samples from the ore zone of a carnotite ranium deposit located at Yeelirrie, Western Australia. A statistical analysis has been performed to investigate the dependence of the ratios on lithology and on the location of the sample in the orebody. The analysis indicates that dependence on lithology and on position across the orebody is negligible. Samples from the western end of the orebody and those from below the water table level tend to have slightly lower ratios than samples from other positions, although these trends are small compared with a large random variation in the data. The large random variation could result from some redistribution of the daughter isotopes of uranium within the orebody. On the basis of the results from all the samples, the estimated deficiency of uranium relative to radium in the ore zone of the deposit is 11 per cent.

Jan 1, 1980

By R. A. Williams

Surface and electrochemical techniques have been used to describe the surface chemistry of ferrosilicon powders, as a function of pH and electrochemical potential, for conditions typical of operating DHS plants. The practical consequences on the likely corrosion behaviour and associated electro- kinetic particle-particle interactions (which affect stability to sedimentation) in the suspension, are discussed.

Jan 1, 1987

By Viktor Tokle, C. W. Dawson

The Devico directional core drilling system and its capabilities are described, with reference to other directional drilling technologies and the advantages and disadvantages of these systems. The advantages and disadvantages of a number of borehole navigation systems are also presented. A discussion of the applications of the technology follows, illustrated by case histories. Finally, the environmental impacts and benefits of the technology, in comparison to more conventional systems, are presented.

Jan 1, 1999

By Edward Wisser

The Pachuca silver district, situated about 100 kilometers northeast of Mexico City (Fig. l), covers roughly the southeastern half of the Sierra de Pachuca. The latter is a mountain range with northwest trend, and forms a part of the northeastern rim of the topographic basin known as the Valley of Mexico. The length of the Sierra proper is about 50 km., its greatest width about 9 km., and it rises to a maximum of 600 meters above the general level of the basin floor. The Pachuca district consists of two contiguous subdistricts, the Pachuca area and the Real del Monte area. The center of the Real del

Jan 1, 1937

By Dan J. Van Roosendaal

A closely spaced grid of survey points was installed over the tensile zone of a longwall panel in southern Illinois and monitored daily during subsidence to document the complex ground-surface movements associated with dynamic subsidence. Vertical and horizontal displacements were used to calculate maximum tilts and principal strains within the grid. The dynamic nature of subsidence is made evident by changes in both the direction and magnitude of maximum tilts and principal strains. The maximum tilt (smax) of 0.036 and maximum tensile strain (Emax) of 0.027 were measured after subsidence and were oriented transverse to the longwall panel. Observations of surface fracturing were correlated with strain determinations to estimate a surface strain at incipient cracking (E;) of 0.006 to 0.009. Using shallow inclinometers, a linear variation of horizontal displacement with respect to depth was observed, suggesting a neutral¬axis bending mechanism for near-surface deformation. Horizontal displacements transverse to the longwall panel reduce to zero at a depth of 40 feet. A linear relationship between strain and curvature was used to estimate ground-surface curvatures associated with Emax (0.00068 ft-1) and E; (0.00015 to 0.00023 ft-1). The curvature estimates are consistent with published results.

Jan 1, 1986

By B. M. Kunar

It is well known that job-related hazards and individual factors influence occupational injuries. However, research involving coalminers has been limited. This case-control study assessed the relationships of job-related hazards and individual/life style factors with injuries among underground coal miners. It compared 245 cases with at least one injury during the previous two-year period with 245 matched controls with no injury. The data were gathered via personal interview and analysed using the conditional logistic model. The significant risk factors were materials handling (adjusted OR 5.15), poor environmental/working conditions (2.63), geological/strata control-related hazards (2.35), lack of formal education (3.00), sleep disorders (1.86), alcohol consumption (2.32), disease (2.23), having a large family (5.40), and risk-taking behaviour (9.40). Machine-related hazards, sleep disorders and alcohol consumption primarily affected workers aged less than 45 years; whereas, environment/working condition-related hazards, presence of disease, smoking, risk-taking behaviour and large family size were more likely among workers aged 45 or over. Keywords: Occupational injuries, sleep disorders, job hazards, alcohol, coal miners

Jan 1, 2010