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By Frederic P. Dewey

The Bureau of the Mint of the United States Treasury maintains 13 ofEces for the purchase of gold-bullion, and this paper describes an investigation to establish the reasonable differences in the assay-results at the various institutions which may be commercially allowable in the settlements between them. Beginning with the comparative assay of proof-gold at the Philadelphia mint and the Utrecht mint, which shows 0.00002 as the closest agreement now possible, nine tables of comparative results, taken from the regular work of the service, are given..These tables begin with very fine gold, produced in an electrolytic refinery, showing close agreement in the assay-results, and follow through decreasing gold fineness and increasing amounts and complexity of base metals to very impure and complex bars produced at cyanide-mills, some of which give widely-varying results. Next is given a series of results on samples, prepared and sent out to various laboratories in the service, to test the influence of different metals and various combinations upon the agreement of the assay-results ; 11 samples were sent out and each one was assayed from 44 to 71 times, making a total of 623 assays. To these ire added 107 assays of identical samples of coin-gold. On a previous occasion,' I have endeavored to show the degree of accuracy that may be expected in the ordinary everyday analysis of various materials, and on another occasion,2

Jan 1, 1910

By Kenneth E. Hay

Researchers from the U.S. Bureau of Mines conducted a field study to assess the safety of remotely controlled mobile roof supports (MRS) in a retreat pillar mining operation, Data were collected to provide the Mine Health and Safety Administration with criteria needed to develop guidelines for MRS use and to determine if precursors could be identified that would alert miners to imminent roof falls. Two test sites at which two different support methods-MRS's and posts were used and were monitored to obtain information on entry stability. Pressure transducers and string pots were installed on all four MRS's to obtain loading and displacement information. and roof bolt load cells. sonic probes, extensometers, and survey targets were installed in the surrounding entries to obtain information on ground behavior. Results showed a larger increase in roof bolt loading and roof movement when MRS's were used, especially in the intersection area. Roof bolt loads in the entries showed decreases in load when the MRS's were set and increases up to 11,1 kN (2,500 lbf) when the MRS's were unloaded. Unloading of one MRS in a pair did not significantly increase load on the other. MRS's I and 2 usually had the higher loads, with these loads increasing as the pillars on each side were being mined. MRS 3 normally had lower loads than I and 2: however, it also experienced some very high loads when in the last position near the pushout. MRS 4 usually had the lowest loads, primarily because it was located near the solid pillar that was not being mined.

Jan 1, 1995

By Mark Springett

The problems inherent in sampling low- grade deposits have long been recognized. As economic grades become lower with increasing metals prices and improvements in recovery technology then the previously difficult sampling problem has consequently become even more demanding. The breakdown of the sample process and error is illustrated by describing in the remainder of the paper some sampling practices that have been utilized on mining and exploration properties and by describing some problems that have been encountered, providing a series of cautionary tales to those involved in any aspect of mine or exploration sampling.

Jan 1, 1983

By Christopher Mark, Gregory M. Molinda, Timothy M. Barton

The Coal Mine Roof Rating (CMRR) was first presented at this Conference nine years ago. Since its introduction, the CMRR has been incorporated into many aspects of mine planning, including longwall pillar design, roof support selection, feasibility studies, and extended cut evaluation. It has also become truly international, with involvement in mine designs and funded research projects in South Africa, Canada, and Australia. The purpose of this paper is to bring the mining community up to date with recent improvements and applications of the CMRR. The most important new development is a streamlined process for determining the CMRR from exploratory drill core. Just three types of information are now required: •Fracture spacing (or RQD) •Uniaxial compressive strength (or axial Point Load Testing) •Diametral Point Load Testing The moisture sensitivity adjustment has also been changed, and new research has related the immersion test to slake durability. Most recently, the CMRR has been implemented in a computer program, which can be obtained from NIOSH free of charge. The program facilitates calculation of the CMRR from either underground or drill core data. Values from many locations can be saved in a single file, and an interface with Autocad allows CMRR contour plots to be integrated into mine planning.

By C. E. Fivaz

SYNOPSIS Tribute is paid to J.S. MacArthur and the Forrest brothers for their invention. The opinion is expressed that the successful application of their process, not only saved the gold-mining industry on the Witwatersrand from stag¬nation for an indefinite but probably prolonged period, but also made a major contribution to the economic growth of the country in the twentieth century. A background is given of the activities of prominent chemists who researched the solubility of gold in cyanide solution prior to the MacArthur-Forrest invention. An account is given of the invention and patenting of the cyanidation process, and of the golden rule that the patentees laid down for themselves, which came close to wrecking the invention. The South African gold-mining scene from the discovery of gold on the Witwatersrand in 1886 up to 1890 is sketched. An account is given of how, when unoxidized ores were first encountered, the recovery efficiency dropped alarmingly, gold shares were sold on an unprecedented scale, and doom and despondency seized the town of Johannesburg. The complete turnabout in the fortunes of the South African gold-mining industry after the introduction of the cyanidation process in 1890, the steady rate of increase in production after the Anglo-Boer War, and its effect on the South African economy are described. A brief look is taken at the effect of gold mining on secondary industry. The deportment of the gold that is not dissolved from the ore by the cyanidation process is illustrated. Some thoughts are expressed on what can be done to increase the gold recovered by cyanidation.

Jan 1, 1988

By W. D. Johnston, T. P. Thayer

THE minerals that collectively are known as chromite form an isomorphous series of the general formula (Mg,Fe) 0. (Cr,Al,Fe) 203. So wide is the range in chemical composition in this group that chrome ore consisting entirely of the mineral chromite may range from less than 30 pct to more than 60 pct Cr203. The most comprehensive published data on the chemical com- position of chromite are by Stevens,62 who made complete analyses of 52 samples of chromite concentrate from many localities in North, Cen- [ ] tral, and South America. These samples were mechanically purified to remove associated silicates and might be regarded as the cleanest chromite that could be obtained by any mechanical milling process. Fig 1 shows the predominant zone of isomorphism, within the triangular prism of composition defined by the mineralogical end members of the series, wherein his analyzed samples fell.

Jan 1, 1949

The Bega granite at Whipstick, N.S.W., consists of a granite metasomatically altered to leucogranites and a spessartite-granite. The ore occurs in pipes controlled by jointing and shows evidence of post-depositional tectonic forces.The principal ore minerals are molybdenite and bismuthinite, with minor amounts of uraninite, pyrite, gold, bismuth, joseite A, joseite B, tetradymite, chalcopyrite, arsenopyrite, and skutterudite. The gangue minerals are microcline, albite, quartz, muscovite, and spessartite, with fluorite, chlorite, magnetite, and biotite as accessory minerals.The intrusion of granite was followed initially by ascending metasomatic fluids which penetrated along joints to be trapped in the domed roof of the intrusion to form the leucocratic granite. Iron-manganese-rich fluids metasomatically altered the granite to a spessartitegranite which is associated with the later deposited ore.Quartz veins and dykes of varying composition post date the ore deposition.

Jan 1, 1968

By Dennis W. Boehm

The building boom of the late 1970's and early 1980's has all but used up most of the better sites across the more populated metropolitan areas of the United States. This means that current buildings and other types of structures are being founded on more marginal sites. The use of marginal sites has placed ever-increasing quality control on the installation of the deep foundation systems utilized for these sites. Several remedial techniques are available for the repair of the deep foundation systems. These include minipiles, compaction grouting and jet grouting. Eight case histories are cited where these methods have been utilized to repair deep foundations.

Jan 1, 1999

By G. H. Glos

There was a time when an occasional failure of a tailings embankment was considered an acceptable risk associated with mining activities. This is not the case anymore. A major tailings failure today could result in the indictment of mine officials, huge fines and a possible site closure due to the loss of operating permits. As a result of this changed operational environment, tailings disposal facilities must be operated with these potential consequences in mind. Physical controls for tailings embankments are prohibitively expensive. However, the nuclear industry has developed a system of administrative controls as an alternative to physical controls. Administrative controls may be defined as control of actions, through organizations and management, using written procedures, record keeping, review and audit to assure operation of a facility in a safe manner (10 CFR 50). Administrative controls can reduce the cost of operating tailings impoundments, as well as increase the level of confidence in these facilities.

Jan 1, 1999

By Shaoxian Song, Ling Xia, Hongqiang Li, Yubiao Li, Yunliang Zhao, Shaobing Xie

Since human daily demands for fresh water have been increased significantly, the supply of fresh water for the mining industry, especially froth flotation, should be considerably reduced. In addition, stricter environmental standards have been implemented in many countries to reduce the risks due to the disposal of wastewater, many flotation operators have to seek more efficient ways to utilize the limited fresh water sources. Recycling water with high concentrations of impurities is a normal strategy for most of the mineral processing plants; however, water quality should be carefully considered to guarantee a smooth flotation process. Recently, the application of seawater in flotation has attracted much attention due to its availability and abundance rather than fresh water. However, the influencing mechanisms due to the application of seawater in flotation have not been fully understood especially the reactions between mineral particles and bubbles in the presence of high concentrations of cations and anions. This would impede the application of alternatives to fresh water in the flotation. Therefore, this paper reviews the current water sources and the technologies for water recycling in the flotation process. Specifically, the life cycle of water in flotation was proposed. In addition, the strategies including high pulp density flotation as well as the most promising alternatives to fresh water have been discussed in details, with the related mechanisms being demonstrated.

THE solid nonmetallic inclusions present to some extent in all commercial steels have been variously designated. In early references they were usually called slag inclusions, and this terminology is still retained to some extent. On the premise that all nonmetallic matter produced in a metallurgical process is slag, this can be justified. We have come to think of slag, how- ever, in a more restricted sense, and calling these particles slag inclusions is further objectionable because it fosters the erroneous concept that they are actually incorporated portions of furnace slag. Rarely is this true. The term sonims (coined from solid nonmetallic impurities) was proposed many years ago but never came into common use. In general, the term non- metallic inclusions seems to be satisfactory and adequate. NATURE AND CONSTITUTION OF NONMETALLIC INCLUSIONS From the standpoint of origin, inclusions fall naturally into two classes: (1) those occurring as a result of reactions taking place in the body of molten or solidifying metal and (2) those resulting from mechanical incorporation of refractories or other materials with which molten steel comes in contact. The former are by far the more numerous and have been called indigenous, natural, or native inclusions. The latter are by their very nature sporadic in occurrence and have been called exogenous, accidental, adventitious, or foreign inclusions. They are often referred to as the "slag-stringer" type, though here also the material is not likely to be furnace slag. Substances Found in Inclusions. Nonmetallic inclusions are composed principally of oxides and sulfides but carbides and nitrides sometimes play an important role. In the case of indigenous inclusions the reactions by which these particles are precipitated from molten or solidifying steel may be caused by: (1) oxidation such as may occur during refining or during tapping and teeming, (2) deoxidation by added alloys, (3) change

Jan 1, 1951

By John D. Sullivan

A DISCUSSION of the developments of the past decade in the field of refractories, and the effect of these developments on the performance and life of open-hearth furnaces, is perhaps best introduced by reference to Fig. 1. This shows the most important types of refractories doing into various parts of the furnace, together with their cost, and remarks on their use. It has been estimated that half of the refractory makers market comes from the iron and steel industry, and something like one-third of all refractory brick used finds its way into open-hearth furnaces. To melt steel, a furnace capable of withstanding temperatures close to 3000 deg. F. is required. The furnace is assembled of various refractory materials selected by experience and economic considerations. Furnace structures today, from a refractory standpoint, are considerably different from a quarter century ago. Furnace operators, interested in the performance of refractories, care little how they are made or where they come from so long as they give reasonable service. But, the entire history of the refractory is important and technical knowledge of the ceramic materials used in making the refractory is necessary to the manufacturers, so that the proper article gets into the hands of the ultimate consumer.

Jan 1, 1936

When the mining and milling of 1100 copper orebody commenced at Mount Isa a satisfactory grade of copper concentrate was difficult to produce. The major concentrate contaminants were fine pyrite and silica, particularly in the minus 10 microns fraction. Studies of the 1100 orebody showed that much of the fine grained pyrite and a proportion of the silica present in the ore contained carbonaceous matter in the form of complete or partial rims and as internal carbon films disseminated throughout grains. The hydrophobic surface property of the carbonaceous material resulted in inherently flotable fine pyrite and siliceous particles.The addition of a 60:40 mixture of nigrosine and dextrine, initially to a prefloat concentrate of the inherently flotable carbonaceous material and finally to the total copper flotation feed, successfully controlled the flotation rates of the carbonaceous pyrite and silica. The objective of a 25 per cent Cu concentrate grade was then achieved without decreasing copper recovery.

Jan 1, 1971

By Markus Reuter, Antoinette van Schaik

In this paper the link between process metallurgy, classical minerals processing, product centric recycling and urban/landfill mining is discussed. The depth that has to be achieved in urban mining and recycling must glean from the wealth of theoretical knowledge and insight that have been developed in the past in minerals and metallurgical processing. This background learns that recycling demands a product centric approach, which considers simultaneously the multi-material interactions in man-made complex ‘minerals’. Fast innovation in recycling and urban mining can be achieved by further evolving from this well developed basis, evolving the techniques and tools that have been developed over the years. This basis has already been used for many years to design, operate and control industrial plants for metal production. This has been the basis for Design for Recycling rules for End-of-Life products. Using, among others, the UNEP Metal Recycling report as a basis (authors are respectively Lead and Main authors of report), it is demonstrated that a common theoretical basis as developed in metallurgy and minerals processing can help much to level the playing field between primary processing, secondary processing, recycling, and urban/landfill mining and product design hence enhancing resource efficiency. Thus various scales of detail link product design with metallurgical process design and its fundamentals.

Jan 1, 2014

"Horizontal grinding mills have been used in the mining industry for more than a century, and due to their operational and maintenance simplicity they remain a widely used technology for various stages of comminution. The relative ‘efficiency’ of horizontal grinding mills compared to other comminution equipment is often debated, and efforts to improve the energy efficiency of these mills is an on-going area of attention for process engineers.The discharge arrangement design affects the material transport characteristics within a horizontal grinding mill. Material transport plays a significant role on efficiency of horizontal grinding mills. The magnitude of benefits that can be achieved with efficient material transport in AG/SAG mills has been demonstrated in a Greenfield milling operation at Mirabela Mineração’s SantaRita Nickel operation in Brazil. This grinding circuit was commissioned in October 2009, which was designed as a typical SABC circuit to grind 4.6 mtpa (575tph) to produce a P80 of 125um with 10-12% ball charge in SAG mill. The nameplate design capacity has been achieved in few days in ABC circuit without grinding media in SAG mill, and has been operating in ABC mode. The through has gradually increased to an average of 800 tph and recently 7% ball charge has been introduced to increase the throughput to +900tph.This paper investigates improved material transport using Outotec’s TPL™ (Turbo Pulp Lifter) technology and the opportunities this technology presents when designing horizontal grinding mills. Operational data, with particular reference to energy and throughput optimization, is presented."

Jan 1, 2013

By J. J. Montoro

The influence of blasting on the excavators’ efficiency, defined as mucking rate (amount of rock mucked per unit time) and mean bucket load (amount of rock loaded in each bucket operation), is investigated. Rock characteristics, blasting parameters (drill pattern, explosive energy, and charging), and the excavator’s performance (truck loading time and number of buckets to fill a truck) were monitored in eleven blasts in an open pit iron ore mine. ANFO, ANFO/emulsion blend, and watergel were used in the blasts and the powder factor was varied between 0.98 and 1.45 kg/m3. The mean bucket load is mainly affected by the bucket size, which is independent of the blasting parameters. Besides the relation with the mean bucket load, the mucking rate was found to be positively correlated with the explosive energy, whereas no significant correlation with the rock properties was found. The analysis of the data, together with other published works, suggests a non-monotonic relation of the mucking rate with the powder factor, with a maximum mucking rate at a certain powder factor. This is especially true when the useful work of the explosive per unit rock volume is used rather than the classical mass powder factor and when only the amount of explosive above grade is considered.

Jan 1, 2007

By Forrest T. Moyer

[The safety record of the nonmetal mining industry during 1965 way worse than that of 1961 in all general measures s of injury experience except for a slight improvement in the number and frequency rate of nonfatal injuries Work fatalities in 1965 totaled al and occurred .it a frequencyrate of 0.29 and a severity rate of 1,711 per million man-hours of worktime. The fatality total was seven oven higher than to 1964 and the injury ratess increased d 32 and 28 present, respectively Thin total. of 2,172 nonmetal injuries u- in 1965 was 3.4 less than in 1964 and the frequency rate per million ion man-hours worked declined percent to 22.73 from: 23.14 in 1964. However, the 1965 nonfatal severity rate of 1,339 per million man-hours worked was 15 percent our the: d.96,1 rate of 1,160, This increases was largely attributable to two more permanent total and nine more permanent partial injuries. in 1965 than in the proceeding year. The average severity all injuries in 1965 was 132 days, 1-I. or charged per injury or 25 days more than in 1961. Injury experience in the nonmetal mining industry, including and excluding officeworkers, for the a-year period 1961-65 is shown in table 1. The average number of men working, on active days in 1963 was 48,429, or 635 fewer than in 1961. However, mines and mills, wore active an average: of 5 days more for a total of 277 in 1965, and each worker averaged 2,245 hours compared to 2', 190 hours in 1961. As a result, aggregate worktime of 108.7 million man-hours increased 1 percent over the 1964 total of 107.4 million hours.]

Jan 1, 1970

By Donald A. Brobst

Barite, the sulfate of barium, occurs in many geological environments in sedimentary, igneous, and metamorphic rocks. The commercial deposits of barite may be classified into three major types. 1. Vein and cavity fillings that occur in rock fractures, along bedding planes, and in various solution structures. 2. Bedded deposits in which barite occurs as the principal mineral or cementing agent in stratiform bodies in sedimentary rocks. 3. Residual deposits occurring in unconsolidated material formed by the weathering of preexisting rocks. The geologic characteristics of each type of deposit are of fundamental importance to the successful search, development, and economic use of barite deposits.

Jan 1, 1980

By Ziyad Abunada, David O’Connor, Abir Al-Tabbaa

"Abstract Contaminated land remediation using soil mix technology (SMT) is a relatively recent development which has been shown to be a cost effective and versatile system with numerous environmental advantages over other remediation techniques. The added complexities and variability associated with contaminated sites has escalated the need for field trials, field monitoring and specific QC measures to be undertaken for this setting and was the rationale behind project SMiRT (Soil Mix Remediation Technology). The main aim of project SMiRT was field validation, testing and assessment to provide stakeholder confidence in SMT and increase its uptake for land remediation in the UK. The field trials involved the treatment of 800 m3 of soil, through applying six different remediation techniques with four different SMT systems and introducing over thirty binders and binder compositions with a range of installation methodologies. Various issues were faced during the installation process and which were addressed on site. This paper presents some aspects of early age field observations, field monitoring, in-situ testing, coring and laboratory testing of cored samples and highlights some lessons learnt, providing valuable information on the issues that need to be addressed for this application of SMT.IntroductionAlthough soil mix technology (SMT) was developed in the 1960s in Japan and Sweden for geotechnical applications, its potential in geo-environmental applications became evident more recently the 1980s in the US and in the 1990s in Europe, having since increased to provide a range of remediation systems (Al-Tabbaa and Evans, 2003; Al-Tabbaa et al., 2011). The most common applications to date have been (a) the construction of low permeability containment walls or cut-off walls to contain a contaminated site; (b) stabilisation/solidification (S/S) treatment, with cementitious binders, for physical and chemical encapsulation of contaminants in soils and (c) the installation of permeable reactive barriers (RPBs), which are permeable walls that intercept the groundwater flow and remove contaminants from it, by mixing special additives with the native soil. Contaminated land remediation using SMT is a cost effective and versatile approach with numerous technical and environmental advantages over other remediation techniques. These advantages include the use of simple and well established techniques and equipment, speedy implementation, applicability to sites of any size and to multiple contaminants, elimination of off-site disposal, low risk and low emissions. There is a lack of competing alternative technologies that offer the same level of versatility and economic, environmental and social benefits, under current environmental legislation constraints. In addition, most currently available contaminated land remediation techniques are only partially effective, and are relatively contaminant-specific. This makes SMT a promising and timely contender to lead the market place in offering a cost-effective, efficient and low risk solution to contaminated soil and groundwater remediation and has resulted in a range of recent innovations."

Jan 1, 2014

By Rosana Silva Xavier

Compósitos magneto-elétricos (ME) combinam fases magnetostrictivas e piezoelétricas e podem ser utilizados na geração de energia a partir de vibrações e campos magnéticos presentes no ambiente, sendo também aplicáveis em sensores de campo magnético e em redes de sensores sem fio. Neste trabalho, um compósito ME foi processado pelo método cerâmico com 15 vol% CoFe2O4 (ferrita de cobalto) como fase magnetostrictiva e 85 vol% BaTiO3 como fase piezoelétrica. É mostrada a relação entre os parâmetros de processamento/sinterização e a microestrutura do compósito ME, com três tipos diferentes de arranjo das fases: particulado (obtido por dois diferentes métodos) e em camadas. Foram compactadas pastilhas dos compósitos para sinterização nas temperaturas de 1.200ºC, 1.300ºC e 1.400ºC por 4h, sendo que ocorreu a fusão da pastilha sinterizada a 1.400ºC. As amostras sinterizadas foram observadas em microscópio eletrônico de varredura (MEV), onde foram analisadas as características de porosidade, tamanho de grão e a distribuição das fases na microestrutura. Foram realizadas também análises cristalográficas por difração de raios-X (DRX), de espectroscopia RAMAN e de espectroscopia de energia dispersiva (EDS). Foram relacionados os parâmetros de processamento utilizados com os resultados obtidos.

Aug 8, 2018