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By Edward H. Robie

PROBABLY nowhere in the United States or its possessions is mining development more active at present than in the Philippine Islands. Only a few years ago only one company was of any importance, the Benguet Consolidated. Now, five companies are paying dividends, five others have reached the producing stage, some seven others may produce this year, and a score or so are being actively developed. Gold production in 1933 was valued at about $8,000,000, last year at about $11,000,000, and this year an output valued at about $17,000,000 is envisaged. At the beginning of 1934 about 1750 tons of ore was being milled daily; at the end of the year, the tonnage was approximately 3400. In 1933 there were only thirteen Institute members in the Philippines; a year ago there were 27, and now there are 46. About fifteen thousand amen were employed in the mining industry last year, with mine payrolls amounting to $3,500,000. An immense amount of new machinery has been required. One difficulty has so far hindered gold-mine development to some extent-lack of adequate power. Each company therefore finds it necessary to generate its own power, and for this purpose diesel engines are generally adopted.

Jan 1, 1935

By M. J. Williams, C. P. Proctor, J. T. Crawford

The purpose of this paper is to present some data and comparisons regarding three types of Rheolaveur plants washing bituminous coal from the Pittsburgh seam. It deals only with the sections that handle coarse coal. The Rheolaveur system consists of launders or troughs in which coal and its associated impurities are conveyed by water. The impurities. being heavier than the coal, settle toward the bottoms of the launders and are drawn off through specially designed openings called Rheo boxes. Fundamentally, each plant consists of straight-sided, flat-bottomed launders of varying width and length, each launder equipped with one or more Rheo boxes for the removal of high-grauity fractions of the feed that are undesirable in the cleaned coal. Each launder has at least two longitudinal sections, the first with a slope of from 11/2 to 4 in. per foot of length, called the classification section. The single-box launder has a classification section followed by a washing section ahead of the box. A two-box launder is a single-box launder followed by a washing section and a second box. The slope of the washing section between the first and second boxes is determined to some extent by tonnage. At the end of the classification section, which may. vary from 8 to 15 ft. in length, the slope abruptly flattens out to a slope of from 92' to 1 in. per foot of length. This flatter section of the launder, called the washing section, may vary from a few feet, in a single-box launder, to 15 ft., in a two-box launder. Raw coal entering the head end of what we choose to call the "primary" launder or launders is pushed down the classification section by a stream of water entering the head end of the launder with the coal. As it strikes the washing section, of lower pitch, the velocity of flow is retarded and the heavier particles of slate, pyrite, bone, etc., take their places on the bottom and are drawn off as they pass over the Rheo boxes. The clean coal, of lighter gravity, remains on the top of the stream of

Jan 1, 1938

By C. S. Blair

The development of a geological department as an integral part of the Tennessee Coal, Iron & Railroad Co. in the Birmingham district, Alabama, in 1908 was an innovation probably unique for any mining organization south of the Ohio River. At that time a few of the oil companies were starting geological departments, but there were no geologists among the larger industrial organizations. The Tennessee Coal, Iron & Railroad Co. had been a substantial producer of pig iron for many years and was just getting a start in the manufacture of steel products from the pig iron. It had large acreages of coal land, ore land and timber land, but there was lacking the detailed knowledge of the possible mineral resources of much of its territory, and this territory at that time covered an area in the neighborhood of 500,000 acres in the states of Alabama, Tennessee and Georgia. Those responsible for the operations of the mining properties, not being familiar with the kind of help that might be expected from geologic work, were decidedly skeptical of the utility of the work. Therefore it was necessary to develop cooperation with the mining organization, by not infringing upon its functions, and by developing the work in such a manner as to demonstrate to the mining department its practical utility. In the first instance the man responsible for a mining operation is apt to assume the attitude that the geologist is a blockader, because the geologist, unfortunately, is obliged to point out difficulties in the carrying out of mining operations in the way originally planned. He points out the dangers of mining out one coal or metal seam at the ultimate expense of an upper or lower seam, and he develops structural features, such as faults and folds, which call to the attention of the mining operator difficulties in his future operations, which the latter had not anticipated. Eventually, however, the value of having these data became apparent to the Tennessee Coal, Iron and Railroad Co., and the operators not only welcomed the geological work and cooperated fully in its acquisition of essential information, but reached the point of asking assistance and advice; and complete coordination of the two activities has existed for many years.

Jan 1, 1935

By Helmer Hedstrom

The purpose of this paper is to direct attention to the importance and the usefulness of phase measurements in electrical prospecting for ore, a subject about which virtually nothing has been published. The paper describes a new field method for ore prospecting, the "Turam" method, which makes use of phase measurements, and which has been used with great success for five years. Of the principal geophysical prospecting methods, the gravimetric and magnetic methods determine the direction and strength of the static fields of force of the earth. By seismic and electrical methods, fields of force are applied to the block of ground under investigation. By these methods a third parameter can be measured, besides the direction and strength of the field; namely, the time of arrival of the applied field at the different observation points. This time of arrival has been practically the only parameter measured in seismic work, while in electrical prospecting it has generally not been considered, the measurements having been limited to determination of direction and strength of the applied field. Phase Measurements In the most widely used of the electrical prospecting methods, those using alternating current, the time of arrival of the "electrical vibration" at the different observation points can be carried out as phase measurements. The phase angle measured then expresses, in part of one "vibration," or one cycle, how much the electrical vibrations at the observation point are out of step with those close to the source of the field. A phase lag of 45", for instance, means that the alternating field in the observation point is one-eighth of one complete " vibration," or cycle, out of step behind the field at the source. If the frequency is, say, 500 cycles per second, a frequency often used in electrical prospecting, a phase lag of 45' then means that the time required for the field of force to travel from the source to the observation point is 1/8 ' /500 = 1/4000 sec. Since the phase angle can be measured with an accuracy of a fraction, say one-tenth, of a degree, and the frequency can be considerably higher than 500, it is readily seen that the time of arrival can in this way be measured

Jan 1, 1940

By C. S. Blair

The development of a geological department as an integral part of the Tennessee Coal, Iron & Railroad Co. in the Birmingham district, Alabama, in 1908 was an innovation probably unique for any mining organization south of the Ohio River. At that time a few of the oil companies were starting geological departments, but there were no geologists among the larger industrial organizations. The Tennessee Coal, Iron & Railroad Co. had been a substantial producer of pig iron for many years and was just getting a start in the manufacture of steel products from the pig iron. It had large acreages of coal land, ore land and timber land, but there was lacking the detailed knowledge of the possible mineral resources of much of its territory, and this territory at that time covered an area in the neighborhood of 500,000 acres in the states of Alabama, Tennessee and Georgia. Those responsible for the operations of the mining properties, not being familiar with the kind of help that might be expected from geologic work, were decidedly skeptical of the utility of the work. Therefore it was necessary to develop cooperation with the mining organization, by not infringing upon its functions, and by developing the work in such a manner as to demonstrate to the mining department its practical utility. In the first instance the man responsible for a mining operation is apt to assume the attitude that the geologist is a blockader, because the geologist, unfortunately, is obliged to point out difficulties in the carrying out of mining operations in the way originally planned. He points out the dangers of mining out one coal or metal seam at the ultimate expense of an upper or lower seam, and he develops structural features, such as faults and folds, which call to the attention of the mining operator difficulties in his future operations, which the latter had not anticipated. Eventually, however, the value of having these data became apparent to the Tennessee Coal, Iron and Railroad Co., and the operators not only welcomed the geological work and cooperated fully in its acquisition of essential information, but reached the point of asking assistance and advice; and complete coordination of the two activities has existed for many years.

Jan 1, 1935

By D. A. Brown, C. Lowe

"Abstract -A multi-sensor (electromagnetics, magnetics, gamma-ray spectrometry, and VLF) geophysical survey was recently conducted in the Purcell Basin of southeastern British Columbia in an area encompassing the world-class Sullivan Sedex deposit. The purpose of the survey was to geophysically characterize the known mineral occurrences and to develop strategies to enhance future mineral exploration in the basin. Follow-up investigations of geology and measurements of rock physical properties helped constrain interpretations of the geophysical data sets.Despite extraction of more than 90% of the ore from the Sullivan deposit, it is clear that the mineralization there, as well as at other Sedex occurrences surveyed, is characterized by high conductivity values, strong bedrock conductors, and elevated magnetic anomaly values. The albite-sericite alteration which accompanies this mineralization yields high potassium and low thorium-potassium ratio values. Associated Moyie gabbro is characterized by low electrical conductivity and radioelement concentrations and by high magnetic anomaly values. The study has also aided exploration for other mineral deposit types including stratabound Cu-Ag, placer gold, vein and disseminated basemetal deposits. In addition, the geophysical data have helped constrain geological interpretations of the basin."

Jan 1, 1998

By Carl E. Swartz

ALTHOUGH a number of articles appeared during the war advocating the use of cadmium in lead-tin solders, very little information of value can be found in the literature regarding the properties of solders containing cadmium. In most of the published articles the cadmium seems to have been considered merely as a partial substitute for tin in a tin-lead alloy rather than as an essential constituent of a ternary alloy. The primary object of the substitution of cadmium for tin was to lessen the amount of tin required, at a time when the latter was scarce and high-priced, and thus to produce a cheaper solder. While this object was accomplished, the new properties resulting from a change from a binary lead-tin alloy to a ternary lead-tin-cadmium alloy were not given proper consideration in many cases. For the past few years, the American Smelting & Refining Co. has been marketing a very considerable amount of cadmium in the form of lead-tin-cadmium alloys for use as solders for certain special purposes, and the successful use of these solders suggested that if more extensive knowledge were available concerning the properties of lead-tin-cadmium alloys of various compositions their field of usefulness might be materially extended. The investigation described in the present paper was undertaken to obtain this information and, by means of tests under conditions approaching those of practical use, to determine the suitability of cadmium solders for various purposes. CHARACTERISTICS AND REQUIREMENTS OF SOLDERS IN GENERAL General Physical Properties.-When cast into bars, solder should present a smooth and bright appearance free from oxide inclusions and bubbles. Ductility should be as great as possible without sacrificing tensile strength, and vice versa. Hardness and specific gravity are not of any great importance. Melting Characteristics.-The melting or solidification range is important. This statement applies both to the extent of the range and to the actual temperature at which complete solidification occurs. A rather narrow solidification range is desirable in soft solders in order that solidification may take place quickly. The solder should have high fluidity at temperatures only slightly above its melting range. For a

Jan 1, 1928

By Henry Fernald

THE accounting system or bookkeeping methods of any company are principally the concern of that company and of those who are in control of its affairs. Its published financial report is, however, primarily intended for those who are not already fully informed regarding its operations and finances. Whatever may be the advantages of standardization of accounting and bookkeeping methods, it must be admitted that a company has a certain right to handle its accounts and keep its books and records in whatever manner may seem to it best adapted to its affairs, even though such methods may differ materially from those generally adopted by others. In its financial reports it should not, however, either ask or expect that the statements it makes or the terms which it uses will be given in its case a meaning and interpretation different from that which they are ordinarily considered to have in similar reports and statements of other companies. The particular form and arrangement of such reports is a matter concerning which there may be much difference of opinion. It is of little importance whether current assets come first or last in the Balance Sheet, but it is important that there should not be included under this designation any items which are not properly current assets within the generally accepted meaning of that term. The extent to which stockholders or others interested are to be made acquainted with the full details of a company's business is a question which the proper authorities must in each case decide. It should, however, be recognized that there are certain facts regarding a mining com-pany which must be set forth in a financial statement if it is fully to cover the conditions and affairs of the company. For example, a financial, statement which does not include or is not accompanied by a statement, of the ore reserves of the company does not fully set forth its financial condition. This is true whether the absence of such a statement of ore reserves is because it is not desired to make public the figures or whether it is because the ore reserves themselves are not definitely known, or accurately measured.

Jan 1, 1928

By B. M. Larsen, T. E. Brower

IN an earlier paper1 we discussed a simple, rapid method of taking samples of liquid steel and analyzing them for oxygen, which, though possibly not absolutely accurate (as is likewise true of all other methods), certainly yields results that are satisfactorily consistent. Accordingly, samples from hundreds of heats in different shops were analyzed for oxygen, with results sufficient in number to be handled statistically and permit estimation of some general trends. Measurements were made in acid as well as in basic open hearths, throughout the refining period, to learn how stirring, blocking, adding ore or lime or sand, affects the oxygen content of the bath; we also followed the changes brought about by tapping, teeming, and deoxidizing. Some of these results, discussed in an earlier paper.2 bring out the dominant role of the carbon-oxygen reaction in regulating degree of oxidation both of metal and of slag, also the marked variability of concentration of dissolved oxygen [0] in excess of that which would be in equilibrium with carbon and with carbon monoxide at a partial pressure of one atmosphere. As a logical beginning on this complex problem, we take up in the present paper the variability of this excess oxygen, ?[O], when other factors are as constant as they ever are in open-hearth operation; namely, toward the end of the refining period, when the bath may be regarded as in the comparatively steady state it approaches in absence of disturbing factors. This condition was chosen because by that time the significant reactions, except carbon oxidation, between slag and metal have come to substantial equilibrium; this facilitates interpretation of the complex situation and thus permits more definite conclusions to be drawn. This excess concentration of oxygen, ?[0], in the metal is needed, of course, to make the steelmaking process go at a reasonable rate; alternatively it may be regarded as a measure of the virtual pressure increment above one atmosphere, or of the degree of supersaturation, of carbon monoxide in the metal. According to our measurements, the excess concentration ?[O] in liquid steel varies from about 0.009 to 0.035 per cent oxygen by weight. It is quite sensitive to change of conditions, being altered temporarily by operations such as stirring with green poles, additions of ore, lime, or sand; but as the disturbance works itself out, it resumes a level within the intermediate range characteristic of the steady state. The conditions most common in average furnace practice are covered by the following : [ ] as in a reasonably steady state-that is, when it is boiling normally, is at proper temperature with a well-shaped slag, and has been free from disturbing effects during the preceding half hour-?[O] returns from

Jan 1, 1946

By T. N. Williamson

6.3-1. Historical Development. Rotary drilling has been used in surface mining for many years. Its principal use is for primary blasthole drilling. In this use, holes in the range from 4 to 15 in. in diameter are drilled in overburden and massive ore bodies for large initial blasting operation. With properly designed shot patterns and loading, secondary blasting is seldom required. The use of rotary drilling with diamond bits for exploration is discussed in Chapter 3.1. Small rotary drillholes of approximately 2-in. diameter are employed as blastholes to shatter uncovered coal seams, but this is a minor part of surface mining drilling operations. Another minor use of rotary drills in surface mining is for placing wire saw poles in dimension stone quarries, usually accomplished with large-diameter calyx or steel shot drills. Primary blasthole drilling by the rotary method was performed with drag bits until 1949 (19). Its use in mining was only in soft formations, so that rotary drills prior to that time were found principally in overburden drilling for the surface mining of coal. In 1949 it was found that air circulation to remove cuttings resulted in increased penetration rate and prolonged life for the rolling-cutter type of bits. Prior to that time, and since their introduction in oil well drilling in 1907, water had been used for circulation with these bits. The dependence on water to clean the hole had delayed the acceptance of bits with rolling cutters in mines because of water haulage and freezing problems as well as the loss of water through cracks in the formation. After rolling cutters were introduced, subsequent improvements in tools made rotary drilling adaptable to harder formations (18). This system is now used in the hardest formations encountered in mining. 6.3-2. Principles of Operation. ENERGY. Rotary drills attack rock with energy supplied to the bit by a rotating drill stem, and infrequently by

Jan 1, 1968

By M. J. Williams, C. P. Proctor, J. T. Crawford

The purpose of this paper is to present some data and comparisons regarding three types of Rheolaveur plants washing bituminous coal from the Pittsburgh seam. It deals only with the sections that handle coarse coal. The Rheolaveur system consists of launders or troughs in which coal and its associated impurities are conveyed by water. The impurities. being heavier than the coal, settle toward the bottoms of the launders and are drawn off through specially designed openings called Rheo boxes. Fundamentally, each plant consists of straight-sided, flat-bottomed launders of varying width and length, each launder equipped with one or more Rheo boxes for the removal of high-grauity fractions of the feed that are undesirable in the cleaned coal. Each launder has at least two longitudinal sections, the first with a slope of from 11/2 to 4 in. per foot of length, called the classification section. The single-box launder has a classification section followed by a washing section ahead of the box. A two-box launder is a single-box launder followed by a washing section and a second box. The slope of the washing section between the first and second boxes is determined to some extent by tonnage. At the end of the classification section, which may. vary from 8 to 15 ft. in length, the slope abruptly flattens out to a slope of from 92' to 1 in. per foot of length. This flatter section of the launder, called the washing section, may vary from a few feet, in a single-box launder, to 15 ft., in a two-box launder. Raw coal entering the head end of what we choose to call the "primary" launder or launders is pushed down the classification section by a stream of water entering the head end of the launder with the coal. As it strikes the washing section, of lower pitch, the velocity of flow is retarded and the heavier particles of slate, pyrite, bone, etc., take their places on the bottom and are drawn off as they pass over the Rheo boxes. The clean coal, of lighter gravity, remains on the top of the stream of

Jan 1, 1938

By Toshihisa Adachi, Shosei Serata, Shunsuke Sakurai

The present state of knowledge of three-dimensional rock properties does not provide an adequate basis for evaluating the safety of under- ground structures in situ. Most of the triaxial studies reported in the past have dealt with crushing strength, but have failed to consider the intergranular behavior and triaxial strain state of rocks. Without this information, the structural competence of rocks cannot be accurately assessed. The absolute three-dimensional testing method (ATT) was conceived for the purpose of analyzing the three-dimensional states of stresses and strains in aggregate rocks under conditions commonly encountered in underground structures. In-situ stress-strain states are not simple, even in the simplest possible form of opening, excavated in a homogeneous and isotropic rock medium. In general, there are four basic stress-strain states which are present in underground openings, regardless of the complexity of their geological conditions. They are the yielded, brittle-fractured, stress-relieved, stress-concentrated states, as illustrated in the schematic diagram, Fig. 1. The ATT machine was designed to create and study all these states in the laboratory. A theory describing the aggregate behavior of rocks under these diversified states is essential to evaluate the safety of underground structures. The Griffith theory is limited to tensile failure of ductile materials and therefore does not apply to behavior of aggregate rocks under compression. The Griffith theory also fails to consider the grain boundary characteristics of aggregates, which is the determining factor of rock behavior. The Mohr-Coulomb theory of failure ignores the importance of the intergranular behavior of rocks. An application of the continuum theory to

Jan 1, 1972

By Readett D. J

Soluble salts can be removed from Bowmans lignite by water and acid leaching. The success of the removal of water soluble or acid exchangeable impurities is directly associated with the efficiency of dewatering these slurries. The filtration characteristics of a slurry at its natural pH (4.0) were poor, with a filter cake moisture of 65%. Acid treatment of the slurry at pH2 caused the filter cake moisture content to drop to 61 %. Various oils, oily surfactants and a flocculant were tested to determine the conditions for minimum filter cake moisture. A series of pilot scale filtration tests were conducted on flocculant dosed slurries with and without washing on a horizontal test unit. Moisture contents of 54% were obtained in laboratory testing using high additions of oily surfactant. For the pilot scale test work, moisture levels close to 60% were obtained with low flocculant additions, similar to results obtained in laboratory studies. Removal of soluble salts could be correlated directly to the final moisture content of the filter cake. This process of leaching followed by filtration resulted in the removal of approximately 75% (more than 80% with washing on the cloth) of the sodium chloride originally present in the lignite.

Jan 1, 1989

By C. Cigna, M. Patrucco, D. Savoca, E. Lovera

The paper deals with the activity program and the preliminary results of a research work commissioned by IReR Research Centre and Regione Lombardia to the Department of Land, Environment and Geotechnologies of Politecnico di Torino. The aim is to define measurement, analysis and control criteria for the emission of chemical and physical pollutants from non-metal mining industries, with particular reference to noise and airborne particulates. Such emissions are related to health risks and annoyance problems, both for the working crews and the neighbouring population, and so, in order to get an effective sustainability of the industry, suitable reduction methods and assessment tools are required. A simple technique for the evaluation and forecasting of both the emission levels and deriving impact has been tested at different mining and quarrying sites, considering their differences in terms of layout and exploitation method, the latter ascribed to a series of main typologies as present in Lombardia region.

Jan 1, 2005

By J. M. Callow

The selective action of oils for lustrous minerals was first disclosed by Haynes in 1860. In 1885, Miss Carrie Everson elaborated this idea and also disclosed the fact that acid increased the so-called selective action. Her patent called for oils, either animal, vegetal or mineral, also for an acid or salt. The process was tried out on a practical scale in Baker City and Leadville, in 1889, and failed: first, because, as has since been shown, of the unsuitability of the ore to flotation; and second, because the invention was too far in advance of the times. Then followed the Elmore brothers, first with their bulk oil processes and later with their vacuum method. The basic principles of oil flotation were undoubtedly covered by the above inventors, the work done since their time being merely a building up on ground work laid by them. Different kinds of oil, different quantities of oil, and all the varying degrees of agitation, were all exemplified and practiced by them in one phase or another, and the developments that have since been made are but elaborations of the fundamental principles laid down by Haynes, Everson, and the Elmore brothers. In 1902, the Potter-Delprat process was developed in Australia. In this process no oil was used, the mineral being raised by the generation of gas, brought about by the introduction of acid into the pulp. The mineral particles appeared on the surface of the separatory vessel, in the form of a scum or froth, buoyed up by minute gas bubbles attached to them. This no doubt first gave the suggestion of gaseous flotation. In 1902, also, Froment, an Italian, was granted a patent in which he combined violent agitation with oil and gaseous flotation, the gas being generated within the pulp, in much the same way as in the Potter-Delprat process. In the same year, Cattermole came out with a unique method. First, the pulp was emulsified with a small quantity of oil, by violent

Jan 1, 1916

By George G. Griswold

The Parkes process of lead refining is based on the fact that when zinc isemixed with molten lead bullion, it forms an alloy with the silver and gold. This alloy freezes at a higher temperature and is of a lower specific gravity than the lead. With proper regulation of the temperature, the alloy solidifies and floats on top of the lead bath, from which it is removed and the silver, gold, and zinc recovered. The alloy should contain the maximum amount of silver (Ag2Zn,). The usual practice is to make two additions of the zinc. The first addition gives an alloy, or zinc crust, the zinc of which is saturated and is treated for the recovery of its zinc and silver; the crust from the second addition contains an excess of zinc and is used for the first addition on the following kettle. The crust produced depends on a number of items: purity of bullion, temperature, care with which kettle work is performed, addition of zinc, pressure used in expelling lead from crust, etc. It is desirable to make the concentration of silver in the zinc crust as high as possible; otherwise an undue amount of byproducts is produced, which greatly increases the cost of refining. It was formerly considered good practice to make a concentration of 20 :1. That is to say, if the lead bullion assayed 150 oz. dorê per ton, the assay of the retort bullion recovered from the zinc crust should be 3000 oz. per ton. As a matter of fact, the concentration should never, except on bullion assaying over 300 oz., be so low, and with low-grade bullion it should be 50:1. In one lead refinery where, ordinarily, the work was good, on a bullion averaging about 200 oz. per ton, a concentration of 24:1 was common; but how it was obtained was known only to the foremen. Changes occurred, and under new foremen the kettle work fell off badly; the problem then was to bring about this greater concentration. As is customary, the refincry had a "schedule" for its 60-ton kettles, which gave the number of pounds of zinc required for all possible assays, on both the first and the second zincing. Using this schedule, high temperatures

Jan 1, 1924

By Helmer Hedstrom

The purpose of this paper is to direct attention to the importance and the usefulness of phase measurements in electrical prospecting for ore, a subject about which virtually nothing has been published. The paper describes a new field method for ore prospecting, the "Turam" method, which makes use of phase measurements, and which has been used with great success for five years. Of the principal geophysical prospecting methods, the gravimetric and magnetic methods determine the direction and strength of the static fields of force of the earth. By seismic and electrical methods, fields of force are applied to the block of ground under investigation. By these methods a third parameter can be measured, besides the direction and strength of the field; namely, the time of arrival of the applied field at the different observation points. This time of arrival has been practically the only parameter measured in seismic work, while in electrical prospecting it has generally not been considered, the measurements having been limited to determination of direction and strength of the applied field. Phase Measurements In the most widely used of the electrical prospecting methods, those using alternating current, the time of arrival of the "electrical vibration" at the different observation points can be carried out as phase measurements. The phase angle measured then expresses, in part of one "vibration," or one cycle, how much the electrical vibrations at the observation point are out of step with those close to the source of the field. A phase lag of 45", for instance, means that the alternating field in the observation point is one-eighth of one complete " vibration," or cycle, out of step behind the field at the source. If the frequency is, say, 500 cycles per second, a frequency often used in electrical prospecting, a phase lag of 45' then means that the time required for the field of force to travel from the source to the observation point is 1/8 ' /500 = 1/4000 sec. Since the phase angle can be measured with an accuracy of a fraction, say one-tenth, of a degree, and the frequency can be considerably higher than 500, it is readily seen that the time of arrival can in this way be measured

Jan 1, 1940

By N TassT, J Cyr

At the East Sullivan site, wood wastes covering the abandoned mine tailings impoundment prevent sulfide oxidation by creating an anoxic environment. The addition of coarse ligneous wastes and their high permeability favour infiltration, resulting in a water table rise that maintains most tailings under water saturation and thus provides an additional protection against sulfide oxidation. Moreover, high infiltration allows a more rapid flushing of acid prone groundwater generated prior to the cover placement, which could cause acid mine drainage over a long period of time. Finally, the pore-waters under the cover are characterised by a strong reducing potential, high alkalinity, and near neutral pHs. These conditions favour sulfate reduction and base metal precipitation as sulfides and as carbonates. Pore-water composition monitored from 1992 to 1998 showed a significant Fe2+ decrease, following cover placement. Thereafter, the restoration strategy capitalised on the alkaline and reductive properties of the waters underlying the wood-waste cover. An original treatment of acid effluents, based on the recirculation of water discharging around the impoundment through the organic cover, was implemented. In 2002, the recirculated water from May to October had a mean pumping rate of 240 m3/h, for a total volume of 800 000 m3. Data gathered near the dispersal zone from 2000 to 2002 show that despite the recirculation of acid water (pH ÿ3), the pH decreases by only one unit from 7 to 6, during the recirculation period, ie from May to November. However, alkalinity decreases from 800 to 100 mg/L-CaCO3. Despite this decrease, the alkalinity is back up to 800 mg/L-CaCO3 the following May, thanks to sulfate reduction. From 2000 to 2002, Fe2+ concentration in the pore waters near the dispersal zone is maintained below 2 mg/L. Evolution of surface water quality suggests that the contaminated groundwater flush is completed in the north and north-west area of the impoundment; the east sector is under recovery, while the south sector remains the most problematic. A wood-waste cover, besides limiting sulfide oxidation, can fill the role of alkaline reducing barrier for the treatment of these acidogenic waters, until a balance between acidity and alkalinity in the effluent is reached.

Jan 1, 2003

By Dean H. Herrick

The production of crushed stone in the United States has exceeded 1.0 Gtpy since 1987. Eighty percent of the crushed stone produced is used in the aggregate industry, accounting for over half of the quantity of natural aggregate consumed in the United States. Approximately 718 of the crushed stone produced in 1989 was limestone and dolomite followed by granite, traprock, sandstone and quartzite, miscellaneous stone, marble, shell, calcareous marl, volcanic cinder and scoria, and slate in order of descending volume (Table 1). Of the remaining 20% crushed stone produced in the United States and not used as aggregate, 12% is used in the manufacture of cement which is an important construction material. Only 8% of crushed stone is used in specialty products not associated with the construction industry. Therefore, this chapter will concentrate on crushed stone as used in aggregates, with occasional reference to other uses or to chapters which discuss specific nonconstruction uses of crushed stone. Construction aggregates are hard, essentially inert materials suitable for being formed into a stable mass by the addition of cementing or binding materials that produce a concrete by compaction, or by natural weight to produce a road or foundation fill. Aggregates are usually from 80 to 100% of the material volume of the construction masses in which they are used. Conditions necessary for a rock deposit to be developed for construction crushed stone include: Quality-should pass rigid specifications for strength and durability; Quantity-adequate volume of rock is needed to have a production life of at least 10 years, preferably 20 or more years; Market-must have adequate market to support a new crushed stone operation; Transportation-transportation cost must be competitive for the intended market; Environmental-the impacts of mining, processing and transportation of crushed stone on the environment at or surrounding the mine site must be within acceptable limits; Permitability-mining, processing and transportation of crushed stone must usually be permitted by governing agency. The following discussion will touch upon all facets of crushed stone operations from the mineral deposit and its geology to technology, uses, economic factors and end with governmental regulations of mining crushed stone. The sections are not designed to answer all questions, but rather to be an introduction to the crushed stone industry. Where more information is required, The Aggregate Handbook by Barksdale (1991) is recommended as the best general source.

Jan 1, 1994

By Brent A. D, Olsen a. H, Mayfield P. L J, Grazier P. E

Concentrates produced from MnO2 and Fe203 ore fines have been targeted as potential feedstocks for direct metallurgical processing. Prereduction of pyrolusite-rich Mn02 sands to MnO has been investigated in batch and continuous experimental bubbling fluidised beds using CO-H2 reducing gas mixtures. This process has been found to produce a high grade feedstock suitable for smelting to ferroalloys or acid digestion for chemicals production. Similarly, production of highly metallised direct reduced iron (DRI) from hematite ore fines has also been investigated in batch bubbling bed reactors. Programs to characterise the reduction kinetics, fluidisation behaviour and defluidisation phenomena for both feedstocks are currently in progress to enable optimum process conditions to be determined.

Jan 1, 1995