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By William B. Potter

It is a time-honored custom in this, as in other kindred bodies, for the retiring President on giving place to his successor, after a year of official duties which have been the means of directing his attention in a more than usual degree to the work and interests of the Association, to report the results of his observations from this outlook, and the thoughts that may be suggested by the view. In looking out over the many fields of activity within the range of this Institute, the attention may be arrested by special features marking recent progress and development, or such as by their meager outline or lack of important detail stand in less pleasing contrast, or. even form unsightly objects in the view. It may be that the special field and particular work in which one is engaged will, when observed from the more distant standpoint, or in the light of the whole outlook of the profession, assume a different aspect or develop features of new interest and importance. In this way some special object may suggest to the observer a, fitting theme for the occasion. To others, again, an outline of the whole view may seem a more useful subject for study and review. All fields are examined and the wide horizon of the whole profession scanned to note and report whatever is new in knowledge and practice—the new permanent bench-marks that appear near the horizon designating ground definitely located; the stakes which mark reconnoissance into new territory, and even the prominent objects that faintly appear through the mist of the distant atmosphere, and which may serve later on as points of attachment for the advancing lines of survey into the unknown. And besides these, there is the progress of the work in older and nearer fields—what has been attempted, what accomplished,

Jan 1, 1889

By Thomas V. Mullen

Some 146 kt (4.69 billion oz) of gold have been mined throughout history. Of this, 70% has been mined in this century alone, with 17% produced from 1985 through 1996 (Fig. 1 and Table 1). Until the mid-19th century, placers were the chief source of gold. Advancements in mining, metallurgy and geological thinking have resulted in underground mining (first of veins plus stockworks and later of Rand-type deposits) becoming the principal source of gold. With the demise of the South African deposits and the move towards lower grade ores, the primary source of gold will be from disseminated deposits exploited through large, open-pit mines. For the past 200 years, there has been a fairly constant ratio of about 31 g (1 oz) of gold to each person alive. If this ratio is to be maintained, annual gold production will have to rise from about 2.3 kt/a (73.9 million oz/year) to more than 3.1 kt/a (99.7 million oz/year) by the year 2000. To effect this increase, an unforeseen breakthrough in exploration or metallurgy is needed. Barring this, there will be pressure for an increase in the price of gold. This article traces the historical production of gold from 4000 B.C. - the earliest record of gold mining - to today and relates this 6,000-year record to advances in geological thinking, mining engineering and extractive metallurgy. It also proposes that man's thirst for gold, reflected in the price he will pay for gold, and his ability to find, mine and refine gold have combined to effect an equilibrium based loosely on the historical ratio of 31 g (1 oz) of cumulative gold production per each man or woman alive.

Jan 1, 1998

By Ernesto Villaescusa, Andres Brzovic

Rock masses of the primary copper ore at the El Teniente Mine are very competent and massive. The rock mass contains almost no open discontinuities. Nevertheless, there is a high frequency network of small discontinuities coupled with widely spaced faults. A data collection campaign designed to characterize the rock structure was recently implemented. The results show that conventional analysis in terms of discontinuity frequency does not predict differences between two studied sectors. However, when an empirical definition of a weak discontinuity is applied, appreciable differences between the two sectors appear in terms of discontinuity frequency and predicted in situ block size distributions. These differences are in accordance with actual observations at the mine site. Due to the geological features of the primary copper ore, rock mass classification schemes cannot be readily applied to characterize these rock masses.

Jan 5, 2007

By B Arthur, K Sexsmith, D Hockley, S D

At the proposed Crandon Project, mill tailings would be depyritised for upland disposal. The resulting pyrite concentrate would be disposed of in the underground workings as a cement-amended paste backfill. In the long term, the underground workings would be flooded and the potential for the paste backfill to generate acid would be limited. However, while the mine is operational, there is potential for oxygen ingress to the backfill that may lead to sulfide mineral oxidation and acid generation. A series of humidity cell tests were completed to assess the potential for groundwater contamination. To assess effects of surface area on oxidation, the humidity cell tests were conducted on moulded cubes of paste backfill. The tests were terminated at different intervals, and the cubes were dissected and examined mineralogically. Various leach extraction procedures were also used to assess the progress of oxidation and secondary mineralisation within the paste backfill. The test results showed that: the cement amendment significantly contributes to acid neutralisation and results in a lag in excess of one year before the onset of acidic conditions (in comparison to less than three weeks for the pyrite concentrate); the depth of oxidation in the paste backfill is restricted to about 1 mm after 107 weeks of testing; and secondary minerals form a distinct ærindÆ at the surface of the paste backfill. The results indicate that acid generation in the backfilled stopes would be minimal. The importance of including the surface area effect in the testing (ie using moulded cubes) is clearly demonstrated.

Jan 1, 2003

Evolutionary changes to the original sizer concept are mild when compared to those which have taken place in the engineering standards embodied in today's commercially available machines. This paper examines the principles of sizer operation and reviews the development trends in new applications for this unique screen type.

Jan 1, 1978

By Eugene Guccione

Before answering the question raised in the title, let's briefly consider how East-West trade is viewed within the entire US political spectrum. Essentially, there are four major schools of thought: (1) The Peaceful-Coexistence School. Advocates of this school call themselves free-traders and hold to the premise that: (a) trade benefits all parties involved, hence it is the best tool to achieve peace; (b) US trade barriers should be removed, and the quicker the better; and (c) negotiations, cultural exchanges, and political compromise should be used extensively.

Jan 9, 1974

By Ross Glanville

INTRODUCTION The Optimum Production Rate (OPR) is one of the most important parameters in the evaluation of a mineral deposit. The OPR can also be expressed as the Optimum Mine Life (OML) in years since the expected mine life is determined by dividing the OPR per year into the estimated ore reserves. Unfortunately, very little time and effort has been directed towards the determination of the OPR. Instead, "rules of thumb" are often applied to select a mine life without due consideration of the economic implications of such a selection. A "justification" for a particular production rate is often based on a pre-conceived arbitrary requirement for a mine life of 5, 10, or 15 years, for example. In this paper it is demonstrated that such arbitrary selections for high-grade/low-tonnage mines (such as many underground gold/silver deposits) often lead to sub-optimal results. In fact, an apparently uneconomic deposit at an arbitrary production rate may be economic at the OPR. Consequently, investment opportunities may be overlooked if one analyzes mine properties based on arbitrary production rates. This paper analyzes the interrelationships of variables such as production rates, capital and operating costs, cut-off grades, discount rates, metal prices, etc. The analysis shows that the OML for high-grade/low-tonnage deposits is often in the range of two to four years. Although such mine lives intuitively appear too short to many individuals, it should be noted that, in the past, much of the mining industry became familiar with the economics of large scale mining operations. The rules of thumb developed for such large scale operations should not be applied to high-grade/low-tonnage mines such as many of the underground gold deposits. DEFINITION OF OPTIMUM PRODUCTION RATE The OPR is selected on the basis of maximizing the net present value of the after-tax cash flows. However, as discussed later in this paper, the production rate selected for a particular mine may be somewhat higher or lower than the theoretical OPR as a result of other variables such as: 1) the probability or expectation of additional reserves being discovered 2) the likelihood of being able to custom mill nearby deposits owned by others 3) the configuration or attitude of the orebody, which may place upper limits on the production rate 4) the residual, or salvage values, of the mine/mill facilities COMPARISON BETWEEN DIFFERENT PRODUCTION RATES For an orebody with definite physical cutoffs*, or boundaries (such as faults or unconformities), the total ore reserves at different production rates may be identical. Consequently, for such an orebody, varying production rates result in differing mine lives. Although the metallurgical recoveries, the mine dilution, and other similar physical parameters may vary slightly at different production rates, the major differences are the capital costs and operating costs per ton. The ramifications of these differences are especially important at low production rates (up to approximately 1000 tons per day), but can also be significant at higher production rates.

Jan 1, 1985

This paper deals with innovative techniques that have enabled personal computers to be used on the mine site to define, develop and manage an ore body resource, while being aware of the consequences to the environment. The same set of personal computer tools that are used for resource estimation, once the province of expensive workstations, can also be used by geologists, mining engineers, surveyors and environmentalists, in managing the whole mining process, including production, grade control, monthly reconciliation and stockpile management through to tailings the management, mine rehabilitation and the due diligence process of mine closure.

Jan 1, 1996

By Bryan J. Lane, Paul N. Worsey

The recommended maximum explosive weight for boulder blasting using internal charges is 0.1 O-kg/m” (3.5 oz./yd) (Olofsson, 1988). Normally this charge results in excessive scattering and flyrock, creating increased liability for the operator, especially in congested areas. An alternative technique using smaller explosive charges is being developed at the University of Missouri - Rolla. It is designed to reduce boulder scatter, flyrock and fumes and allows shooting in close proximity, using common blasting products.

Jan 1, 1999

By H. D. Jacobs

The Bureau of Mines developed a concentration method to upgrade and utilize marginal natural or direct-shipping iron ores and fine-grained lean iron ores. Presently these ores receive little beneficiation and accordingly have low iron-silica (Fe-Si02) ratios. Ore samples were roasted with equal weights of solid reductant at 1,100° C for 1 hour to metallize the iron and for an additional hour at 1,200° C to promote grain growth. Concentration was effected by crushing and screening techniques and/or wet magnetic separation. Sized concentrates (minus 4 plus 35 mesh) derived from crushing-screening processes contained from 80 to 85 percent iron that was 90 percent metallized. Iron-silica ratios as high as 12:1 and iron recoveries from 75 to 94 percent were obtained. The sized concentrates were judged suitable for use as blast furnace feed. Minus 200-mesh metallized concentrates derived from roasted minus I-inch plus 8-mesh ore fractions and magnetically concentrated contained 90 percent Fe and 4 percent or less Si02, chemically qualifying them as feed for electric furnaces. Roasting minus 8-mesh ore with hydrogen, then magnetically concentrating it, produced iron concentrates containing 57 percent to 67 percent Fe and 3.6 percent to 8.4 percent Si02. The concentrates having Fe-Si02 ratios ranging from 8:1 to 12:1 were considered adequate for use as blast furnace feed. Overall iron recoveries for the 12 ores tested ranged from 56 percent to 94 percent with an average iron recovery of 86 percent.

Jan 1, 1969

By D. H. Chambers

Digestion studies were undertaken to develop a method for the rapid dissolution of high-temperature ferroalloy scrap. Laboratory tests showed: (1) dissolution of alloy scrap with ferric ion as the leaching agent was a moderately rapid method of digestion; (2) the dissolution process can be considered as a typical reaction of a metal with chlorine gas, although evidence was obtained to show dissolution as a two-step process, one step as the reduction of ferric ion by the soluble alloy constituents and the other as the oxidation of ferrous ion with chlorine gas; and (3) the attack of ferric ion on the alloy was a function of alloy composition, ferric to ferrous ion ratio, and area of contact between leach solution and alloy. The exceedingly complex nature of alloy compositions and dissolution products generally precluded satisfactory analytical determinations. Results of moderate accuracy were obtained using complex modifications of standard analytical and spectrographic techniques.

Jan 1, 1968

Magnetic separation using particle rotation in a continuously rotating magnetic field offers very low to insignificant non-magnetic particle entrapment, and precise magnetic fractions. The precision of rotating magnetic field separations makes the method ideal for dry laboratory magnetic analysis work, where conventional laboratory magnetic separators can give misleading or uncertain data. The very low entrapment characteristics make the method ideal for entrapment-critical separations within the diamond exploration industry or in gold recovery. A single wet rotating magnetic field (RMF) unit is able to achieve a cleaner separation (at similar or better recovery rates) than a three-stage separation using conventional wet drum separators. The RMF separator is able to work effectively at particle sizes below 50 ¦m, and RMF separation could, at least in theory, be used down to single domain particle sizes. Rotating magnetic field (RMF) separation is carried out by magnetically spinning the particles at frequencies up to 300 Hz. The particle rotation itself may be used to roll the particles out of the separator. At angular velocities of 100 Hz, magnetic flocs are unable to form, and any entrapped particles are energetically expelled. In an RMF separator, the outer drum can be stationary while the inner magnet rotor rotates, allowing, for example, the injection of cleaning water underneath the separating magnetics to help remove small suspended non-magnetic particles.

Jan 1, 2000

By Perring CS, Vearncombe J. R, Ho SE, Groves DI

Large Late Archaean greenstone belts in Western Australia, Canada and Zimbabwe, contain abundant mesothermal gold, volcanogenic massive base-metal sulphide, and komatiite-associated Ni-Cu mineralization. These greenstone belts are similar in many respects to convergent and accretionary plate margins found in the Pacific rim; modem environments which are cor-respondingly rich in gold and base-metal mineralization. The giant gold placer deposits of the Late Archaean Witwatersrand Basin (the world's largest gold producer) formed in a foreland or retro-arc basin; in a similar tectonic setting to much modem placer mineralization around the Pacific. Gold and volcanogenic base-metal sulphide mineralization are abundant in Late Archaean terranes and the Pacific rim because1. gold mineralization is a product of convergent margin tectonics, and 2. accretion in convergent margin orogens provides the best chance of preserving base-metal mineralization related to submarine volcanism.It is therefore likely that the abundance of gold and base-metal sulphide mineralization in the Late Archaean reflects the widespread growth and sta-bilization of continental crust via tectonic processes broadly similar to those operating in the present Pacific basin.

Jan 1, 1990

Standards in the public reporting of resources and reserves in Australia have dramatically improved since the implementation of the Australasian Code for Reporting of Mineral Resources and Ore Reserves (The JORC Code) in 1989. Whilst the JORC Code states clearly that Mineral Resources and Ore Reserves are imprecise calculations and should be treated as estimates, there is strong evidence that many people regard them as fact, including some accountants, directors, auditors and investors. Mineral Resources and Ore Reserves are key inputs in the valuation of a mining company and the determination of financial performance. Geological knowledge is the foundation upon which Mineral Resources, Ore Reserves and investment decisions are made, however this information carries with it substantial uncertainty. Case studies and company reports have established that errors derived from inadequate geological inputs have led to reduced profitability in operating mines and in extreme cases the premature closure of mine operations. Whilst there are many causes of mine closure and reduced profitability, including commodity prices and exchange rates, the cumulative effect of all geological uncertainty contributes significantly to the erosion of the credibility of mining within the investment community. There are a number of methods used to characterise and model uncertainty in Mineral Resource and Ore Reserve estimation. Empirical mining indexes, sensitivity analyses, Monte Carlo simulations and Conditional simulations are used to identify and estimate geological uncertainty, notably the quantification of uncertainty in grade and tonnage estimates. These techniques have not generally been applied to estimating geological uncertainty associated with key Ore Reserve inputs such as appropriate mining technique, equipment selection, production rate, mining dilution, stability requirements, materials handling, metallurgical processing, product quality and waste storage. New software tools are needed to model the entire mining process with all its geological and other interdependencies, enabling all uncertainties to be separately identified and estimated. By its very nature, mining involves the assumption of significant technical, financial, political, environmental and social risk. Success comes by understanding and managing these risks and consequently the mining industry will never choose to reduce the level of geological uncertainty to nil. The ultimate aim of improved identification and estimation of geological uncertainty is to quantify inputs into the Ore Reserve process, allowing a company to assess the risks and manage these accordingly. This approach is relevant to feasibility studies for new projects as well as life-of-mine planning through to the weekly schedule at existing mines.

Jan 1, 2003

By Keith Sutherland

AEROFLOAT 25 is a complex mixture of free cresylic acid with aryl substituted dithiophosphoric acids, sulphides, disulphides, etc. Its complete composition has not been published by the makers or patentees. It is prepared1 by the reaction between phosphorus pentasulphide and carefully selected cresylic acid. We have been informed that this acid contains no phenol and very little cresol, and that it is rich in the higher alkyl phenols, particularly the xylenols. The reaction between a phenol ROH and phosphorus pentasulphide may produce compounds of the following type:2 (i) RO S P Diaryldithiophosphoric acids RO SH (ii) R-SH Thiophenolic compounds (iii) R-S-R Diaryl sulphides (iv) R-S-S-R Diaryl disulphides (v) Substituted thianthren compounds Except for the simplest type, the thiophenols (ii), the boiling points of these compounds lie above 300° C. The amounts of the thianthren compounds formed from the five xylenols (if all these are present) will vary according to the position of the substituents. In an attempt to ascertain something of the nature of the reagent, fractional distillation under atmospheric pressure was undertaken. At the outset, hydrogen sulphide was freely evolved, and-particularly below 200° C.-the fractions had the strong odor characteristic of the

Jan 1, 1939

This work was instituted to investigate the microscopic structure of brown coals by means of microtome sections cut from them. It was found to be essential to impregnate the coal with some material prior to cutting, because of its powdery and crumbly nature. Of a number of impregnating materials tried, e.g., glycerine gum, gelatine, by far the most satisfactory was paraffin wax. Samples of brown coals for section cutting must be moist. When obtained, they should be put immediately into air-tight tins, and, if they are not to be used for some time, it is desirable to keep them under water containing a small amount of formalin. If the sample is allowed to dry in air, it becomes too hard to be cut. It cannot be softened again even by prolonged soaking in water.PREPARATION OF COALSmall rectangular, blocks were cut from the sample with a chisel and a strong scalpel. The largest block prepared was 3·2 x 2·5 x 0·6 cm. The faces of the block from which sections were to be cut were approximately levelled before treatment. The block was then painted carefully on all sides with two coats of warm aqueous agar, approximately 2 %. This prevented crumbling and breakage of the block during treatment. When the agar was set, the block was placed in water, and all the air removed with a vacuum pump. The water was replaced first by alcohol, then by chloroform, by the usual step transference of a series of liquids, in each of which the block was placed for 24 hours: Ethanol %, 10, 20, 30, 50, 70, 85, 95, 100 (three changes); Ethanol-chloroform, 3: 1, 1: 1, 1 : 3, chloroform pure (three changes) '. The blocks were then embedded in paraffin of melting point 56-58°C. Fresh...

Jan 1, 1947

By Oliver C. Ralston

A definite field of usefulness has developed for the brine-leaching processes of removing lead from ores and other products, so this paper reviews the developments, both in practice and in research, that have taken place since the publication of two earlier papers on this subject.' Several commercial plants are now in operation and a number of semi-commercial test plants have been operated in an effort to determine the limitations of brine leaching and to compare the results with other forms of treatment. Briefly, the brine leaching of lead depends on the fact that lead chloride and lead sulfate are soluble in saturated sodium-chloride solutions. In dilute brines, the solubility of the lead salt is less than in pure water; but in the strong brines, the solubility is greater than in pure water due, supposedly, to the formation of a double sodium-lead chloride. This is seen in Fig. 1, which shows the results of M. Demassieux2 on the solubility of lead chloride in sodium-chloride solutions of different concentrations and at three temperatures. The curves are not those given by Demassieux but are calculated from his results in order to convert them to units common in metallurgical work. The right-hand branch of each curve shows that if the solution is kept in contact with solid sodium chloride the lead chloride can be almost entirely displaced from solution, but that brines which are saturated with sodium chloride, but are not in contact with the solid salt, have a very high solubility for lead chloride. The diagram gives the analysis of the solution in grams of lead per liter, although the substance actually in solution is lead chloride. At 100" C. as much as 100 gm. of lead per liter can be obtained; but at lower tem-

Jan 1, 1924

By Theodore Simons

During the last half century a great amount of ingenuity and energy has been devoted to the invention of appliances for the recovery of valuable minerals from very fine sands and slimes. The reason for this is that in almost every dressing plant the greatest losses of values, considered relatively as well as absolutely, occur in the treatment of slimes. The natural aim of mill operators to minimize these losses has in recent years received another impetus, from the fact that the gradually diminishing occurrence of high-grade ores makes a more intense recovery of values from existing resources absolutely necessary for profitable operation. The results of such attempts are found in the appearance of a great number of machines and appliances which make it profitable to-day to rework old clumps, containing the tailings of older processes. A constantly growing difficulty of obtaining skilled labor and the increase in wages made it prohibitory to employ those types of machines which required much attention, and in the middle of the ninieteenth century the various concentrating tables of the percussion type, which automatically discharge their products, began to take the place of the intermittent tables, on which, when the bed had reached a certain thickness, operation had to be stopped in order to allow the skimming by hand of the separate layers formed on the table. In the course of years, two general types of machines evolved for the treatment of fine sands arid slimes: The so-called concentrators and vanners, on the one hand, and the buddles and round tables on the other.' For the profitable treatment of the very finest slimes, round tables have as a last resort proved more satisfactory and econoillical than other machines. In recent years they have agaiu become the subject of close inves-

Jan 1, 1914

By G. Pan

The production data of many mines have not reconciled geostatistical estimations based on exploration and development drilling. The discrepancies in recovered metals are sometimes as large as 30%. A number of factors are responsible for such unpleasant outcomes. A major cause, however, is the lack of geological controls in the implementation of geostatistical techniques. Geological modeling establishes geological constraints and mineralization/ore envelopes. Geological constraints are usually established through drill hole interpretation. Mineralization and ore envelopes have been delineated manually based on assay grades. The issues associated with manual methods are: •Time requirements . •Inconsistent dilution. •Uncontrollable implementation variance. Although the time issue may not be a big concern for some companies, the other two have been responsible for many undesired estimation errors. A new geostatistical approach described in this study is designed on the basis of indicator and ordinary kriging. The central component of the method is the procedure for automatic delineation of mineralization and ore envelopes. The method, referred to as probability assigned constrained kriging (PACK), is demonstrated on a Carlin-type gold deposit. The estimation results are compared to blast-hole based production panels, showing that the estimated tonnage is about 2.1 % higher than the actual production, and the average grade is about 2.4% lower.

Jan 1, 1995

By E. J. Gleim

A list of permissible mine equipment, tested and approved previous to January 1, 1942, was published In Bureau of Mines Information Circular 7207.3/ The present list covers additional equipment approved during the calendar year 1942. The items have been numbered to indicate the order in which each type of machine or device was approved in its particular classification. Thus, Information Circular 7207 gives four air compressors on the Bureau's active list, and the present circular gives the fifth to be approved. Items 90 and 94 under Loading; Machines land Conveyors also appear in Information Circular 7207. These numbers are repeated hero to show that approval was granted during 1942 for additional voltages on machines previously listed one voltage only. Equipment listed in these circulars is approved by the Bureau of Mines only when found upon inspection and test to comply with minimum standards of safety as outlined in schedules prepared on the basis of many years of experience in dealing with safety problems of the coal-mining industry. The use of such equipment in mines known to be gassy, as well as in those which may become so, is earnestly recommended in the interests of safety. This circular is published so that the industry may be kept informed as to the many types of machines, devices, and lamps that arc available for reducing explosion and other hazards incidental to coal mining. The present paper and Information Circular 7207 together give the complete list of all available permissible .Mine equipment.

Jan 1, 1943