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By Simon C. Dominy, Alwyn E. Annels, Paul Wheeler, Suzanne P. Barr, G. Simon Camm

Abstract-Narrow veins are an important world-wide source of silver, tin, uranium and particularly gold. To potential financiers, this style of mineralization is viewed as high risk because of the often relatively small resource involved and high cost of estimation. In many cases diamond core drilling will not enable resource estimation beyond the inferred and indicated categories. Exploratory underground development is required to define measured resources. The definition of geological and grade continuity are major factors in narrow vein assessment. A measured resource must be based on strong geological and grade continuities. Narrow veins, generally less than 3 m wide, are complex geological phenomena, which commonly display unpredictable geometry and grade distribution. Variations in structural continuity, dip, strike, width, mineralogy and specific gravity are common. Veins may be composite, with ore-grade mineralization restricted to a specific structural domain. Branches, intersections and braided zones are common features. Potentially high-grade zones are often localized within ore shoots, which are surrounded by barren/low-grade regions. Resources must be determined as closely as possible to reality and reflect the distribution of the commodity in the rock. Estimation has three main requirements: (1) geological study to determine orebody nature; (2) estimation of tonnage and grade, and (3) the presentation of this information using a classification that is clear, unambiguous and bankable. Estimation methods employed are either classical or geostatistical; however, classical methods are often used because of the difficulties in applying geostatistics. Grades generally show a strong positively skewed distribution testifying the presence of high-grade values. Problems exist in the applicability of cutting outlier values risking over- or underestimation of grade. It is generally believed that where resource estimates are in error, poor geological control is usually the cause. Overestimation can lead to the closure of a mine through lost revenue and capital. An understated estimate can result in an opportunity missed for profit and/or greater economies of scale. Definition of reserves involves the consideration of economic and engineering data, to decide which part of the resource is economically mineable. Geology plays a similarly important role at this stage in the assessment of likely mining method, dilution, recovery etc. Throughout resource/reserve estimation, it is crucial that the amount and quality of the data and the geologist’s experience are relevant. The impact of geological understanding on estimation is often undervalued or assumed to be of lesser importance than finding grades and tonnages. This paper discusses the geology of narrow vein deposits and the importance of geology in their evaluation.

Jan 1, 1997

By John P. Capp

After World War II the Bureau of Mines studied methods of producing synthesis gas including a plan to gasify coal in place. Consequently, under a cooperative agreement with the Alabama Power Co., Bureau engineers directed a series of experiments that were carried out on the property of the Alabama Power Co. at Gorgas, Ala. The purpose of underground gasification of coal, regardless of method used, is to obtain the energy contained in the fuel for use on the surface, without mining in the usual sense of the term. Underground gasification can be described as (1) a process where coal, in place, is consumed by partial combustion with air, oxygen, steam, or any combination of these to produce a low calorific value gas (80 to 300 Btu per cu ft) or (2) a complete combustion process in which air is used to produce a gas containing carbon dioxide, nitrogen, and considerable thermal energy.

Jan 1, 1963

By John P. Capp

After World War II the Bureau of Mines studied methods of producing synthesis gas including a plan to gasify coal in place. Consequently, under a cooperative agreement with the Alabama Power Co., Bureau engineers directed a series of experiments that were carried out on the property of the Alabama Power Co. at Gorgas, Ala. The purpose of underground gasification of coal, regardless of method used, is to obtain the energy contained in the fuel for use on the surface, without mining in the usual sense of the term. Underground gasification can be described as (1) a process where coal, in place, is consumed by partial combustion with air, oxygen, steam, or any combination of these to produce a low calorific value gas (80 to 300 Btu per cu ft) or (2) a complete combustion process in which air is used to produce a gas containing carbon dioxide, nitrogen, and considerable thermal energy.

Jan 1, 1963

By K. B. Nowels

"INTRODUCTION For the last several years the oil industry has been turning more and more toward conservation arid the study of related production problems. It is generally conceded that ultimate recovery is increased by holding the natural gas in thy sand which is net needed in lifting the oil. The retained gas lowers the viscosity and surface tension of the oil and helps flow the oil from the sand. Lewis states that ""while the operator can not control the original conditions of energy and resistance in the sand, he can partly control the efficiency of expulsion. As it is the energy contained in the compressed and absorbed gas rather than the oil that is exhausted, it is but logical to judge the efficiency of a producing method largely by the relative quantities of gas produced with each barrel of oil. If by a change in method the producer lessons the proportion of gas with each barrel of oil, he should increase the total recovery- of oil correspondingly, even if the rate of production is temporarily reduced somewhat.""The effect of ""pinching in"" or controlling the flow of oil wells in an effort to lessen the proportion of has never been definitely known. The general belief has been that ""pinching"" a flowing well causes the oil and gas volumes to be reduced proportionately, maintaining the same gas-oil ratio as before the reduction in flow was made. Studies of gas-oil ratios in many fields have shown that much gas has been wasted, insofar as its effectiveness in oil production is concerned. Swigart and Bopp carried."

Oct 1, 1927

By G. W. Jones

"INTRODUCTION As part of its work in promoting safety, the Bureau of Mines is investigating various means of eliminating or mitigating the explosion hazards of combustible gases encountered in mining and industry. Information has been obtained and a procedure developed whereby the explosibility of many complex gaseous mixtures may be calculated in a rather simple manner without the necessity of performing laborious laboratory experiments. An earlier publication 3/ described the method of determining by calculation the limits of inflammability of gaseous mixtures, including methane, hydrogen, carbon monoxide, nitrogen, carbon dioxide, and oxygen. The information published in the above report permitted calculation of the limits of inflamnability of such gases as are liberated by mine fires, gases from explosives, automobile exhaust gases, gases present after mine explosions, blast-furnace gas, and other gases of similar type.Gases liberated in certain potash mines in the western part of the United States sometimes contain ethane, in addition to the gases named. An investigation was made to obtain data from which the limits of inflammability of such gaseous mixtures could be determined by calculation. 4/Similar data have been Published covering all types of natural gases containing wide ranges of concentration of nitrogen and carbon dioxide.5/"

Dec 1, 1944

By R. C. Troxell

Alternative methods of analyzing data acquired by the Morenci copper concentrator process control instrument-computer system are presented. Experimental measures of ore characteristics, for proposed feed forward control, are introduced. These include on-line indexes of ore hardness, ore density, ore dusting, and ore color. Comparison of metallurgical results before and after computerized process control implementation, allowing for differing ore grades, oxidation, hardness, and fineness of grind, also is described.

Jan 1, 1979

By J. J. Taute, S. J. Archer

"BASF Mining Solutions has developed a new-generation copper solvent extraction reagent that offers significant benefits over standard extractants currently available to the industry. As the name suggests, the new hightemperature (HT) extractant can be used at a higher operating temperature, but also exhibits significantly lower degradation rates, greater copper-toiron selectivity, and is totally nitration-proof compared with the standard extractants. Pilot-plant trials have also shown that lower aqueous-inorganic entrainment can be achieved. This paper investigates the technoeconomic benefit of using the HT extractant as an alternative to the standard extractant in a high-temperature application. The results of the technical evaluation showed that the use of the HT extractant reduces the extractant addition requirements and bleed volume from copper electrowinning; this smaller bleed requirement further reduces acid and limestone consumption, leading to a reduction in valuable metal losses. The results of the economic evaluation showed that the use of the HT extractant represents significant cost savings over that of the standard extractant. IntroductionCurrent solvent extraction (SX) reagents employed for the extraction of copper from typical pregnant leach solutions (PLS) at ambient conditions function well with minimal long-term effects on the extractant’s performance (Taute et al., 2015). This performance, however, deteriorates at elevated temperatures due to the degradation of the reagent’s hydroxyoximes. The degradation mechanism, acid-catalysed hydrolysis of the oxime, is accelerated by high temperature. This has a knock-on effect where the increase in degradation products increases the organic viscosity, leading to increased entrainment, crud formation, and ultimately to an increase in SX reagent consumption (Bender, Emmerich, and Nisbett, 2013).SX reagents also show an increase in the co-extraction of iron as the ferric concentration in the PLS increases. Co-extracted iron is transferred to electrowinning (EW) during stripping of the loaded organic and can adversely affect EW current efficiency. Iron in the EW circuit is typically managed by bleeding the electrolyte; however, this can lead to excessive consumption of EW reagents such as acid, cobalt, and mist-eliminating surfactants. The electrolyte bleed can also affect upstream consumption of reagents, such as lime, due to the high acid concentration recycled to leach."

Nov 1, 2018

By R. R. Sayers

The contemplated use of dichloro-difluorco methane in domestic and commercial refrigerating appliances and in air-conditioning equipment for public buildings and possibly homes, brims attention to the health hazards involved in a wide potential exposure of the public to vapors of another new product, and for the first time to vapors of an organic fluorino compound. The objective in the development of this new refrigerant, however, has been the mitigation of health and explosion hazards in automatic refrigeration, and accordingly these factors have been given primary attention. Early in the development, the Bureau of Mines as requested to make a laboratory study of the toxicity and potential hazard, and it was ca the oasis of the results is of this work and the results of a preliminary investigation made in another laboratory6 that the compound has been selected for commercial use. The investigation conducted by the Bureau of Mines is still in progress, enough information has been obtained to indicate the order of the toxicity and the magnitude of the health hazards involved in the use of dichloro-difluoro methane as a refrigerant. The following is a summarized report of the work completed to date:

Jan 1, 1930

By C. H. Johnson

This paper on the out-and-fill method of mining is one of a series on mining methods published by the United States Bureau of Mines. It has been compiled chiefly from recent publications of the bureau describing in detail mining methods and costs at various mines. Other sources of information were the technical press, the Transactions of the American Institute of Mining and Metallurgical Engineers, the Mines Haudbook, and company reports. References other than those mentioned in Table 1, which lists the mines entering into this discussion and gives general data regarding them, are given in the body of the paper. The authors wish to acknowledge the kind assistance of many operating officials, either through correspondence or in the course of numerous visits to their mines. DEFINITION OF CUT-AND-FILL STOPING The out-and-fill method of stoping is that method in which relatively small sections or slices are taken successively from the lower surface of a block of ground by open-stoping methods, the broken ore being removed and each section filled with waste material before the next is mined. This definition excludes shrinkage stoping, even with subsequent filling; it excludes square-set and fill methods; it excludes the Mitchell slice method, which may be classed as underhand square-setting; it excludes the systematic use of stull sets and filling, which is a variation of square-setting; it excludes any method involving the caving of the ore, walls, or overburden during the process of extraction, although caving may be allowed to take place when the waste fill is withdrawn for use in other stopes; and it excludes any open-stope method without filling. Through variations, which will be discussed later, the cut-and-fill method merges into shrinkage stoping, open stoping, or square-setting. The use of casual timber support, such as props, stulls, or timber cribs for holding up weak portions of the back does not constitute a change from cut-and-fill to square-set mining.

Jan 1, 1933

By M. R. Swaan, G. J. Stewart

"ABSTRACTThe application of failsafe techniques to ask the ""What if"" questions about any process has been well established in the chemical industry for many years. The unusual number of fatalities that occurred in Ontario during 1986-87, prompted Inco management to look at the Fail Safe techniques as a method of improving safety performance.INTRODUCTIONOne of the major areas at any time for potentially disastrous accidents is the shaft, where all men and materials must travel. In April 1987, Inco's Thompson Mine's first Fail Safe Team was established to look at its shaft operations. The initial group of eight people was made up of hourly equipment operators, mine foremen, engineering, maintenance and the superintendent. This group took the name of Shaft Risk Analysis Team or SRAT.The many tasks or jobs that are performed in a shaft prompted the team to divide the work under six major headings; slinging, moving men, skipping, dewatering, shaft inspections and moving materials. Each of these areas contained many different tasks which are interrelated. The only way to understand this interrelationship was to flow chart the steps that actually occur in getting any job done.The flow charting is done by the foreman and operators using existing standard manuals and their experience of what actually takes place. In many cases, it soon became apparent that they had been ""working around"" many problems created by their standards. Fine tuning of these flow charts takes place at the weekly meetings, where input from all involved leads to a better understanding of the actual job being analyzed and its potential hazards. Two major points need to be emphasized in getting good flow charting at a mine:I. It must never be blame oriented or you will never discover how the jobs are actually done and hence you won't know what to improve.2 . All team members must have equal voting rights in deciding how to put the charts together so that they have ownership of the finished product. It is far too easy to end up with amanagement view of the way it should be. Many different techniques or methods are being employed to improve the tasks and reduce the risks associated with any job once the basic flow chart is established. The ones found to be the most useful are highlighted."

Jan 1, 1989

On 26 August 1971, the Bureau of Mines, through the Spokane Mining Research Center at Spokane, Washington, approved initiation of the evaluation of oscillatory energy toward enhancing flow of polymer into shale. The effort was an outgrowth of work performed under Bureau of Mines Contract H0210055, "Feasibility Study of Surface Impregnation equipment for the Chemical Stabilization of Coal Mine Structures," wherein feasibility of the impregnation concept was expressed and the detailed design of a machine for impregnation of coal mine roofs with polymer (under static pressure head) accomplished. Under these efforts, the potential enhance¬ment of polymer uptake into the shale thru superposition of oscillatory energy on the static impregnation pressure was suggested. A proposal for investigation of this phenomena entitled "Feasibility Study of the Application of Oscillatory Energy as an Aid to Afford Chemical Stabilization" was presented to the Bureau whereupon a three month program for initiation of investigation was approved.

Jan 1, 1972

By M. I. Brittan

Discussion Dr R. E. Robinson (Fellow): The author must be congratulated on a very meticulous and self-contained piece of work. It is indeed a pleasure to read a paper that is so clearly and systematically laid out, and where the conclusions and the testwork conducted have been so clearly described. The paper is complete in itself, which makes it very difficult for someone who is not intimately involved in the whole Torco project to make any comments on its content. However, two points that, strictly speaking, fall outside the scope of the paper are of considerable interest. The first relates to the particle size of the material treated. In the paper, the testwork is confined to one standard particle size (minus 60 plus 100 mesh). The essential feature of the paper is to indicate that the rate-controlling reaction in the whole segregation process is the rate of reaction of the ore particles with the reducing agent and the hydrogen chloride. One wonders, therefore, to what extent this relatively slow rate of reaction is affected by the particle size of the ore itself. One imagines that the reaction must take place by contact of the hydrogen chloride with the surface of the mineral particles, and it is reasonable to suspect that the rate of diffusion of the copper ions to the surface is a relatively slow process and is thus the limiting factor in this particular rate of reaction. It is possible, for example, that the improvement obtained, when the ore is subjected to reducing conditions before the chlorination, is due to a breakdown in the crystal structure of the original particle. This breakdown is brought about by the reduction and by the consequent increase in surface area available for reaction with hydrogen chloride. Can the author indicate whether any work has been done along these lines, and whether it has been established that the reaction depends on the surface area available? The second point relates to the application of this kinetic study to the actual operation of a Torco reactor. It was once planned to feed the sodium chloride, together with the reducing agent, into the top of the segregation chamber. In the paper, the author mentions that it has now been established that the segregation chamber behaves, to all intents and purposes, as a fluidized bed, and that there is, therefore, a rapid evolution of gas in the lower regions of the chamber, which, it is imagined, displaces the gas phase rapidly. Since the reaction between sodium chloride, water vapour, and the aluminium silicates in the ore is extremely rapid, one wonders how much of the hydrogen chloride produced is removed from the reaction zone before it has had time to react with the copper minerals. The extremely low consumption of sodium chloride (which is a vital feature of the Torco process) must depend on an extremely rapid circulation of the hydrogen chloride gas to all the ore particles in the segregation chamber. One wonders, therefore, if a system for the introduction of the sodium chloride into the bottom regions of the chamber might not result in even greater efficiency in the utilization of sodium chloride. ProC D. D. Howat (Fellow): All of us who have been concerned with the study of chemical reactions at high temperatures are keenly interested in kinetics and are well aware that this is not an easy study experimentally. Dr. Brittan is to be congratulated on the development of neat experimental methods and for his full discussion of the results obtained. Although the segregation process for the extraction of copper from oxide and silicate ores has been known for almost fifty years, the fundamental chemical and physical changes involved have been little understood and the fundamental data are very scanty. The work now in progress at A.A.R.L., together with that sponsored by the Anglo American Corporation in other research institutions throughout the world, is bound to produce new fundamental data and a much more complete understanding of this rather fascinating process. It is already apparent that some of the old and well-worn chemical reactions that were postulated to occur, just cannot take place in the way which was formerly accepted. Dr Brittan's work, carefully conducted and thoroughly analyzed as it has been, still leaves us with one great outstanding problem. The thermodynamic data and the possible reactions set out in Table I (page 281) of his paper leave us asking, in complete despair, how can copper be converted into a volatile chloride in the presence of HCl, CO and carbon at temperatures about 800°C? The thermodynamics all combine to show that copper should be reduced to metal as the first step in the process. This brings us right up against the second problem. If copper were reduced to the metal how would HCI convert it to the volatile chloride? On top of these problems is the unknown reason for the very high speed of reaction between CO, HCI and the ground copper ore. Still further into the region of the unknown is the reaction by which gaseous hydrochloric acid is produced in the actual process. Perhaps Dr Brittan is feeling grateful that he doesn't have to try to explain this reaction-at this stage of the research programme at least. The results very clearly show that both CO and HCl gas are essential for rapid production of the volatile copper chloride. Dr Brittan states that 18 minutes were required to attain 83 per cent extraction with HCl gas alone and this was reduced to 4 minutes when CO was

Jan 2, 1970

By D. Harrington

This circular presents part I of a review of the literature on effects of breathing dusts, with special reference to silicosis, largely in the minim; and allied industries. The literature on this subject is so extensive that no attempt has been made to include all published material but only to assemble some of the more outstanding data on several aspects of the subject. Parts II and III will deal with prevention and treatment of dust diseases and some of the economic and legal aspects of dust diseases in industry, with special reference to mining. Dust diseases arc much before the public at present, and there is good reason to believe that the information on the subject available to the layman is extremely meager; even those rated as experts usually have a more or less theoretical conception of the diseases, their causation, remedies, and prevention, rather than actual experience with them. Until recently little attention has been given to prevention, and the usual attitude of the engineer, upon whom the main reliance for prevention ultimately must devolve, has been to let "sleeping dogs lie" or, more definitely, to "let well enough alone." However, the "laissez faire" attitude no longer is tenable, and in the past few years numerous conditions have caused those engaged in industry, including mining, to bring the subject before the public with a view to ascertaining the facts upon which to formulate remedial measures, primarily preventive.

Jan 1, 1935

By D. S. Robertson

More than 700,000 feet of diamond drilling was completed in the Blind River area between 1953 and 1958. Much of this drilling was at depths which are still not usual in North America. However, as the tendency is to deeper holes, factual data from the Blind River operation may well provide information of value in future programs. Rates of drilling decreased with in-creasing depth, but uncommonly good rates (an average of over 50 feet per day over more than 4,000 feet of hole) were achieved with proper engineering and care. Costs varied as contractors and geologists became familiar with the area Hole deviation in the Blind River area was locally severe and control of the hole trace became a major problem. Careful surveying was necessary and found to be highly re-liable. It was found that control of the hole trace above 1,500 feet was much more difficult than at depths below 1,500 feet. This is explained by the mechanics of the drilling operation. Various methods of controlling hole deviation were attempted and,

Jan 1, 1962

The principal activities of the Bureau of Mines Explosives Research Center from July 1, 1962, to June 30, 1963, are described briefly in part 1. Part 2 gives short abstracts of publications that appeared during fiscal year 1963; in general, the research reported in these publications antedates the report period.

Jan 1, 1965

By J. R. Cahoon, H. W. Paxton

The possibility of using unidirectionally solidified, two-phase alloys as an approximation to fiber composite materials is investigated. The short-term me.chanical properties and failure modes of unidirectionully solidified A1 (rich)-Cu alloys containing ap -Proximately 0, 17.5, and 27.7 vol pct of 0 phase 'fibers" are determined at temperatures from 25" to 500" and compared with those obtained for conventionul SAP alloys. In a previous publication,' hereafter referred to as I, the possibility of understanding some of the room-temperature mechanical properties of unidirectionally solidified castings was explored. For Al(rich)-Cu and Al(rich)-Mg two-phase alloys over a substantial range of compositions, the yield and ultimate strengths and common ductility measures were very adequately predicted from the principles of fiber strengthening4 and the analysis of ductility outlined by Gurland and Plateau." The results obtained in I suggest the possibility of using unidirectionally solidified, two-phase alloys to simulate fiber composite materials where the inter-dendritic second phase or constituent acts as the reinforcing material. Recent attempts concerning the fabrication of fiber conlposites have concentrated on producing composites with a good bond between fiber and matrix and with very long fibers so that their maximum contribution to the strength of the composite may be realized. However, these objectives are difficult to attain in practice and present fabrication processes are either extremely laborious or costly.13 The slow, unidirectional solidification of eutectics has received considerable attention as a method for producing composite materials. 5,6 This method can fulfill both of the above objectives but it is currently laborious, expensive, and has the additional disadvantage that the volume fraction of reinforcing phase cannot be easily varied. On the other hand, unidirectionally solidified, two-phase alloys, also with a good bond between the phases, are relatively easy to make and the volume fraction of reinforcing "fibers" can be easily varied by changing the average composition of the alloy. The disadvantage of the cast alloys is that the mechanical effectiveness of the "elongated interdendritic reinforcements" (EIR)* may be reduced due to their rela- tively short lengths, the w factor in Eq. [2] of I. However, if the EIR have a high strength their contribution can be considerable. For composite materials containing discontinuous cylindrical fibers of various lengths the ultimate strength is given by1 where it is assumed that the composite fractures when the fibers fail. In Eq. [I], a, is the stress in the matrix just prior to failure of the composite, Vf is the total volume fraction of fiber reinforcing constituent, Vf(l+) is the volume fraction of fibers whose lengths exceed the critical length, I,, which is defined as the shortest length of fiber in which the stress can build up sufficiently to break the fiber. af is the fracture strength of the fiber material, w is a factor accounting for the discontinuity of those fibers whose lengths exceed I,, 1-/d is the average aspect ratio of those fibers whose lengths are shorter than I,, and t is the shear stress in the matrix at the fiber-matrix interface. The factor w is dependent on the length of the fibers and also on whether deformation of the matrix occurs plastically or elastically. However, for a given length of fiber, w is smaller when elastic deformation of the matrix is assumed.' It is of interest to consider the properties of simple unidirectionally solidified, two-phase alloys at elevated temperatures in view of the possibility of using suitable modifications for high temperature service. Knowledge of the creep behavior of these materials is still rudimentary (although under active investigation) and the present paper concerns itself with short time tensile properties of some alloys similar to those investigated in I (i.e., unidirectionally solidified Al(rich)-Cu alloys). Unidirectionally solidified alloys containing 5.6, 17, and 23 wt pct Cu were tested parallel to the direction of solidification at temperatures from 25" to 500°C. In the present investigation, the alloys were homogenized for 2 days at 535°C giving a matrix of homogeneous a phase (5.2 wt pct Cu) and an interdendritic constituent (EIR) which was completely Q phase (53 wt pct Cu). EXPERIMENTAL Alloys of nominal composition 5.6, 17, and 23 wt pct Cu (containing approximately 0, 17.5, and 27.7 vol pct 8 phase, respectively, after homogenization at 535°C) were prepared by melting 1200 g of A1 (99.99 pct) in a high purity graphite crucible and adding the appropriate amount of freshly cleaned copper chips (99.9 pct). The molten alloy (at 700°C) was poured into a preheated graphite mold (also at 700°C) and the ingot unidirectionally solidified by impinging water on the steel baseplate of the mold. The alloy was degassed immediately

Jan 1, 1970

By H. Colijn

Weight may be defined as the gravitational attraction or earthpull on a body (mass). Thus, from a practical viewpoint, a scale or other form of weighing device is a mans for determining mss. Weighing devices fall into two principal categories: (1) gravimetric; and (2) non-gravimetric or nuclear devices. At present, after many centuries of use, the effect of gravitational force as a meas¬ure of mass in industry and commerce remains by far the most common method for mass (weight) determination. Non-gravimetric methods are just becoming established in the industry. The general trend is toward weighing materials on the Trove. The predominant advantage of continous weighing over batch weighing operations is its ability to handle large tonnages without interrupting the material flow. The accuracy and reliability ability of continuous weighing equipment have improved greatly over the past decade. However, static weighing equipment still outsells continuous weighing equipment, because it is considered more accurate. Batch weighing can also produce a continuous weighed delivery through automation where the process requires it. In caparison with continuous weighing devices, such as belt scales, the batch-type scales have same inherent advantages affecting their accuracy. For example, weighing 300 lbs. per minute on a belt scale may mean that only 3 lbs. will be on the scale mechanism at one time. In order to obtain a scale accuracy of 1/2%, the sensitivity must be at least 1/2% of 3 lbs. or 1/4 oz. On the other hand, a batch scale may discharge a 300 lbs. load every 60 seconds through a timing mechanism. An accuracy of 1/2% can be easily obtained with a sensitivity of 1/2% of 300 lbs. or 24-oz.

Jan 1, 1970

By S. H. Ash

THE INUNDATION of anthracite reserves in the Eastern Middle field of Pennsylvania affects the life of the anthracite industry in this field; it also influences the economic status of people, communities, and industries that depend wholly or in part upon anthracite for their livelihood. The trends of production and of employment in the anthracite-mining industry in this field are downward, and they probably will continue in this direction. The reserves have been depleted to the extent that the end of the active life of the industry as a. major economic factor is approaching. By removing the water in those pools where it can be done economically, the future of this industry may be extended somewhat.

Jan 1, 1950

By C. D. Rowe, H. S. Mitri, J. Malki, I. Vennes

Ore extraction at great depths creates high stresses around mine openings, which can result in violent rock failure in one of various forms of strainburst. This is especially true with strong and brittle rocks, which can store a large amount of strain energy that is suddenly released at failure. The strength and brittleness of rocks have been extensively investigated in the past. The most widely accepted method for the determination of rock burstability is the strain energy storage index obtained from a non-destructive uniaxial load–unload test. However, the results of this method are not always conclusive, showing less repeatability when the target test load is changed. This study concerns itself with the introduction of microscopic analysis as a tool to help validate the strain energy index results when burstability cannot be warranted based on mechanical property tests alone. In this study, two types of rocks, namely, basaltic komatiite (BK) and felsic norite (FNOR) obtained from Canadian underground mines are examined. The selection is based on the premise that felsic norite is known to be burstable from the mine experience, whereas basaltic komatiite is not necessarily burstable. A total of 60 mechanical properties tests were conducted including uniaxial compressive strength, Brazilian tensile strength, and load-unload tests. Laboratory tests on FNOR consistently exhibit high burstability; however, the results for the BK tests are not conclusive. To seek explanations for the mechanical rock behavior, 18 thin sections were examined with optical microscopy and image analysis. The findings show the tested BK specimens are dominated by alteration products, and all primary igneous minerals are lost. There is minor quartz, garnet, carbonate minerals, talc, and serpentine, which give the rock its ductile properties. The FNOR specimens are found to be relatively fresh and supported by a strong network of plagioclase with minor pyroxene, biotite, and secondary micas, explaining the higher stiffness. This study demonstrates how optical microscopy can complement mechanical property tests to evaluate burstability of rocks.

May 4, 2025

By M. C. Malamphy

A general description of the activities and results of bauxite investigation by The Bureau of Mines at its bauxite project in Saline and Pulaski Counties, Ark., has been given in Report of Investigations No. 4251. The factual data obtained during the project are reported in a series of Reports of Investigation beginning with No. 4251, of which this is the fourth. The data are accompanied by maps showing the location of holes drilled and the deposits developed. Each area upon which work was done is reported by half townships. Each bauxite deposit investigated was assigned a name and a number for ready reference and identification, and its location and name are shown on the appropriate half-township map. The description of each half township is followed by a description of each deposit developed in that half township. The 14 half-township maps and 77 detail maps of the bauxite deposits in this series of reports give the locations and numbers of all the holes drilled on the project except the deep holes drilled to test the geophysical anomalies. The locations of those holes show on Figure 13 in Volume 1. The descriptions of the deposits developed are followed by complete detailed logs of the drill holes. Many of the widely spaced exploratory holes did not discover bauxite of minable thickness and grade. The pertinent information obtained from the widely spaced exploratory drill holes has been summarized and tabulated, and a table for each half township-is given with the discussion covering that area.

Jan 1, 1948