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By Howard M. Wells

The future is uncertain. In these circum- stances how can we rationally decide whether to commit funds to an investment that may or may not turn out to be successful? To date no certain answer to this problem has been found, nor is one likely to be found in the future. At best we can attempt to assess the possible outcome in terms of probability, taking into account all sources of information that may be available at the time the decision must be made. This subject is addressed with some trepidation and much humility. Any attempt to fore- tell the future is by its very nature controversial. The purpose of ' this .chapter is to present a proposed rationale for decision making under uncertainty which relates the probabilistic risk of the investment to the capacity of the firm to absorb possible unfavorable consequences if they should occur. It is not the intention to propose a cut-and-dried methodology but rather to examine the conceptual philosophy on which a methodology may be based.

Jan 1, 1979

By D. G. Krige

The problem addressed is that of estimating grade differences between sub- divisions of a new gold mining prospect when only borehole results are available. Such differential grade estimates are required in choosing the best area for initial production, and in defining the grade profile over the mine's life for purposes of feasibility studies. It is also often necessary to differentiate between the grades and hence the values of subareas, owned by separate companies, for the purpose of fixing relative share participation percentages in the new mining company. It is shown that exaggerated grade differentials will be obtained from grade estimates of the subareas based only on boreholes within each such subarea, respectively, and that it would be more realistic to apply some 'smoothing', preferably by kriging. This is feasible because the lognormal-de Wijsian model can be used to give an indication of the spatial structure for the boreholes, even where they are spaced far apart; also the degree of 'smoothing' indicated is shown to be relatively insensitive to inaccurate estimates of the relevant semivariogram parameters.

Jan 1, 1987

By Glenn L. Krum

Inflation has received much attention due to its effect on capital budgeting, associated cost overruns, and declining real profits. This study focuses on the effects of inflation on the evaluation of a mining investment and the estimation of a mining project's revenues. The study indicates that the best method for estimating future returns is the fore- cast dollar scheme. In this scheme, the metal price was held constant, and the operating costs were "inflated" along a historical regression line. The conclusion was reached by comparing the "actual" performance of a 3000 tpd (tonnes per day) lead mine model with 'its estimated performance during four time periods (1950-1960, 1955-1965, 1960-1970, 1965-1975). The individual data files for each time period and estimating method (6 files by 4 time periods) were pro- cessed by a suite of cash flow computational and investment analysis sub- routines. The analysis presumed that the mine was part of a large corporation which could utilize the expensed, development and exploration costs and any investment tax credits, in the year that they were incurred.

Jan 1, 1979

By C. D. Broadbent

Open pit blasting can be a low cost routine or a high cost bottleneck depending on geology, environment and the operator's ability to master site conditions. Because blasting is a repetitive operation, there should be ample opportunity to optimize the process; but ordinarily this optimization is rarely achieved and then only if conditions remain consistent and predictable. Often, however, and particularly with porphyry coppers, hidden differences in rock characteristics nullify the operator's best efforts. At a porphyry copper deposit being mined by Kennecott Copper Corporation, all of the following rock types occur; oxidized and fresh porphyry, altered and silicified limestone, explosion breccia, rhyolite, sandstone, shale and several others. The units can cover large areas or be limited to a few tens of feet in maximum dimension. They are rarely visible on the bench surface and often do not show up in the bench slope. Even though the blastability of these rocks varies substantially, a generally-uniform blasting pattern was formerly used with disappointing results. Secondary blasting was often required and high bottoms occurred frequently, overblasting wasted drilling time, and explosives caused excessive throw.

Jan 4, 1974

Geologists often classify ore textures on the basis of the origin of the rock in which they form and the grade of one or more minerals within the ore (Sinclair and Blackwell, 2002, pp 32-36).  Metallurgists, on the other hand, need to know how best to process the ore in order to extract the valuable minerals from it (Petruk, 2000). Geological classification has the following disadvantages:it requires the services of skilled economic geologists, of whom the supply has been dwindling for many years;it is subjective, depending on the perceptions of the individual geologists who make the classification; andit may relate only weakly to processing requirements of the ore. We describe methodology for automatic classification of ore textures from images of drill core. The images analysed are æclassifiedÆ images, in which a particular mineral (or mineral group) is assigned to each pixel. The new methodology is intended to:provide a quantitative and reproducible alternative to traditional geological texture classification,relate to process mineralogy of the ore, andimprove the ore-texture-related input to orebody domaining and geostatistical block models.

Jan 1, 2008

Various factors influence the exploration geologist or geochemist in his choice of.an analytical method for gold and other elements which may help him find the elusive gold deposit. One of the first decisions the geologist must make is the nature of sample media to collect for his survey. Needless to say there are many media available depending on the situation. These include rocks, soils, heavy mineral concentrates (from overburden drilling and panned concentrates), humus, vegetation, water, lake bottom sediments, stream sediments, etc. The choice of the sample media will depend to a large degree on the state of development of the particular project from grassroots to mine feasibility. The nature of the geological information required will affect which media and which analytical technique should be chosen for the analysis. Valid sampling from the initial sample collection, preparation and subsampling aspects may also help to determine which analytical procedure is best. Cost and turnaround time are of prime. importance to the explorationist, as it should be, however, these aspects should not be detached from receiving accurate and reliable results.

Jan 1, 1987

Australia has been an important producer of zinc minerals and metal for many years.Late in the last century Edgar A. Ashcroft, a versatile and enterprising electrical engineer proposed the treatment of zinc rich ores by roasting, followed by leaching to extract zinc, purification of the solution and electrolysis of the purified solution to produce zinc. Residues from the leaching operation were to be smelted in a lead blast furnace to recover lead, silver and gold.Ashcroft (1897-98) and (1898) has.given us a most interesting record of the attempts made at the Sulphide Corporation's plant at Cockle Creek near Newcastle, NSW, to put his ideas into practice. In spite of the best efforts of all concerned, including the use of electrolysis of aqueous chlorides and sulphates, zinc could not be deposited consistently and the project failed although lead smelting continued until 1922 (Woodward, 1965, p. 158). Based on later experience with Broken Hill materials the presence of undetected cobalt in the solutions was the likely cause of the inability to deposit zinc (Kirk and Othmer, 1956).

Jan 1, 1985

By C. W. Bildt

During many years of service in the iron and steel industry I have frequently found, as have also many other engineers, that the common devices used for feeding coal into gas-producers are not what they ought to be in order to secure the best economy. The hopper-and-cone so generally used is familiar to all, and a brief study of its action will surely satisfy everybody that this device has several serious faults. In the first place, the charging is intermittent, and depends entirely upon an attendant. When the hopper is frequently emptied, it may work fairly well, but even then it suddeinly discharges into the hot producers a large body of coal, which is often violently converted into gas that rushes into the furnace, and, as the damper for the combustion-air cannot be regulated every time the producer is charged, there will be an excess of gas, which goes up the chimney unburned. Between the chargings the quantity of gas generated decreases, and there will often be an excess of air in the furnace,

Jan 1, 1899

By R. Mohan Srivastava

In any operating mine, especially in precious metals operations, immediate improvements in profitability m readily achievable through more effective grade control. Just as the oil industry has come to recognize that enhanced oil recovery (EOR) in existing oil fields yields a higher return on investment than exploring for new oil, so too must the mining industry recognize the benefits of enhanced metal recovery (EMR). Current grade control practices are generally dismal. The very word "control" suggests a willingness to make the best of a bad situation -- as in "damage control" or "disease control" -- and a failure to perceive the opportunities for improved profit. While damage and disease can merely be controlled, success and improved profit can be engineered. This paper presents one approach to enhanced metal recovery. It shows how existing methods can be used to address the issue of ore/waste discrimination. The following sections outline the problem, describe the current state of the practice of grade control, propose an alternative approach and. illustrate the application of the proposed alternative to actual blasthole data from an operating gold mine.

Jan 1, 1992

By G. V. Lewis

"INTRODUCTORY REMARKS""I believe we need to communicate as much as possible with the industry. I don't think that we should be a body that just goes around doing dust surveys and writing nasty letters. We should get together on these problems and try and solve them as a group. I've only been with the Department a little over 12 months. I haven't visited all of your plants. I've visited most of the major open pits and I have had a chance to observe a lot of problems that you have encountered and a lot of the problems that you have brought up this morning. I thought the best thing I could do is perhaps mention a few of the approaches to the problems that my superior has suggested to me and we have discussed in the Department, and then perhaps go over a few of the evaluating problems and what we are trying to do with our dust surveys and perhaps ways and means of improving the present setup."""

Jan 1, 1976

By P. K. Ackerman, F. F. Aplan, G. H. Harris, R. R. Klimpel

Fourteen reagents that are potentially capable of chelating with a metal ion on the surface of the major copper sulfide minerals and pyrite were evaluated for their effectiveness in floating these sulfides. The reagents studied fall into the classes of mercaptobenzole mutations, thiouronium, thionocarbamates, thiourea, imidazole mutations, oximes, hydroxyquinoline and xanthogen formate. The best overall copper sulfide collector was an imidazoline (1-Hydoxyethyl - 2-Heptadecenyl), but it also proved to be an excellent collector for pyrite. Its potency as a pyrite collector can be reduced by structural alteration, but at some loss in its collecting power for the copper sulfides. The effectiveness of many of these potential collectors can be changed by minor alterations to the collector molecule and, to a lesser extent, by pH adjustment. The general order of mineral floatability with these reagents is chalcopyrite = chalcocite > covellite =bornite >> pyrite. The flotation of malachite is generally similar to that of the copper sulfides, indicating the special effectiveness of copper in the crystal lattice for collector attachment.

Jan 1, 2000

By Allan E. Hall

The use of full face boring machines in underground mining has increased considerably in recent years and over 200 raise-boring machines are now in use in the Western World. Several tunnel-boring machines have been tested notably in America, West Germany, Britain and South Africa. A relatively new concept is the blindhole borer, where the machine stands on the lower level and bores a full diameter raise upwards without the use of a pilot hole. Four of these machines have been tested to date in South African quartzites with varying degrees of success. The development of boring technology has created new problems for ventilation engineers and exacerbated several existing ones. This challenge has been met in many varying ways and this paper attempts to provide a review of the current state of the art. Technology and methods are developing at great speed in this field and therefore no final and absolute solutions can be proposed, since each machine and site pose individual problems which are best handled by local knowledge and experience.

Jan 1, 1980

By D. M. Hausen

The amenability of a given vanadium ore to any given treatment depends largely on the mineralogic combinations of vanadium in the ore. Quantitative data on vanadium mineralogy provide not only an objective basis for selection of proper treatment, but also may eliminate many time-consuming amenability studies whose results are empirical, at best. Vanadium is distributed through the interstices of mineralized sandstone ores in the form of oxidized vanadates, reduced oxides, and silicates. Oxidized vanadates, e.g., carnotite, tyuyamunite, etc., are most readily beneficiated by simple acid leaching. Reduced oxides are more slowly solubilized, but relatively amenable to most acid treatments. The layered silicates, roscoelite, mixed layered mica-montmorillonite, and chlorite, are least amenable to most acid extractions, and constitute an assemblage of vanadium- bearing clays that are common to many sedimentary deposits. Vanadium is combined principally as layered silicates in the clay fractions of many sandstone ores. Mineralogic studies in this paper are largely confined to clay minerals, and to their amenability characteristics in low pH liquors.

Jan 1, 1985

By S. K. Kawatra, R. A. Seitz

There is considerable variation in the types of coal flotation circuits in use in various parts of the world. For example, Russian plants frequently use scavenger flotation, while this is almost unheard of in the United States. The numerous circuit designs are intended to address specific problems in coal flotation, or to take advantage of the peculiarities of certain coal deposits. As a result, it can be difficult to decide which circuit is best for a given application. For this paper, coal flotation circuits were collected worldwide from many operating plants. These circuits include varying degrees of conditioning, and complexity ranging from simple rougher flotation to multi-stage split- stream processing. The design goals of each circuit are described, and the advantages and disadvantages of each are discussed. Extensive sampling campaigns were carried out in two plants with the most common types of coal flotation circuit (simple rougher, and rougher with deslimed feed). The performance of each plant was evaluated, and the benefits of more sophisticated processing in each case are described.

Jan 1, 1993

By G. Rinelli, A. M. Marabini

A wide-ranging series of experiments has been carried out on value minerals (sphalerite, smithsonite and hematite) and gangue minerals (quartz and calcite) to assess the properties of various commercially available vegetable and synthetic tannins as dispersants for these minerals in a finely ground state (<5 microns). Experiments to determine the dispersing power of each reagents on every mineral have been performed through sedimentation tests run first in water and afterwards in the presence of a collector having specific action on the mineral concerned. The tests have been extended to a wide range of dispersant concentrations, maintaining the pH and collector concentrations at the levels known to be the best for the flotation of the various minerals. By comparing the results obtained on each mineral, conclusions have been drawn on the possibility of using different classes of vegetable and synthetic tannins in the selective flotation of fine particles. These results have been related to the structure of the tanning compounds and to the surface properties of the minerals.

Jan 1, 1980

By G. R. Sawyer

Although backfilling has been in operation for many years, the methods for selecting appropriate slurry dewatering aids have, in some cases, been rather unsophisticated. This has led to many misconceptions regarding the role of the dewatering aid and its various means of application. Testing procedures employed in the correct selection of any practically applied dewatering aid must mirror the actual working processes in which they are to be used. This constraint necessitates the development of complex testing methods when applied to backfilling. The current testing procedures were scrutinized and their various merits noted. From this study a series of testing methods was evolved which incorporate the best aspects of these testing procedures with novel ideas which would eventually result in the correct selection of the dewatering aid. A major consideration in the application of any of these methods is the modus operandi of the backfilling process, and the relevance of the tests to the process. This work attempts to consolidate the testwork performed in the past and suggest new approaches in the correct selection of acceptable dewatering aids for backfilling.

Jan 1, 1988

By J. D. Steenkamp

In 2002 the commissioning of an ilmenite smelter on the North Coast of South Africa was extended by three months due to the failure and subsequent replacement of the magnesia-based refractory lining. The lining failed due to the hydration of magnesia caused by an unexpected source of water. The incident resulted in significant financial losses and a prolonged insurance claim which was settled in 2009. As magnesia-based refractories are used extensively in both ferrous and non-ferrous applications, the authors of the paper want to share the experience gained from this incident with others. The paper reviews the literature available on furnace start-up practices and explains the hydration of magnesia using available sources. The incident is studied in more detail, both technically and economically, and the costs incurred are quantified in terms of the cost of the original lining. The paper concludes with lessons learned and recommendations made for future work. The intention of the paper is to stimulate open debate regarding best practices in preheating of furnaces lined primarily with magnesia. Keywords Commissioning, hydration, start-up, magnesia.

Jan 1, 2011

By Davison GR

The cost of drilling consumables is always a large component of any mine budget. It is important that this cost be carefully examined with a view to reducing the overall cost per inetre or at least minimising its escalation.At Renison it is considered that the only way to ensure drilling costs do not rise unduly is through a total system of control from purchase to disposal.In 1979 extension of an existing drill supply service contract was carefully examined and abandoned in favour of a hybrid system. This system is providing a great deal of control over the use of drilling consumables and has maintained a relatively constant cost per drilled metre over the last five years.Current consignment stock contracts for drilling consumables are strictly specified by the Technical Services section of the Mine Department and consumables purchased under these contracts are distributed and refurbished/sharpened by a contractor.The total result of this package is individual drilling items that achieve the best cost per metre and careful distribution and maintenance to ensure maximum life.

Jan 1, 1985

By Arthur F. Johnson

Plant sites for the light metal industry must be located where ample low cost power is available. In the first half of the century hydroelectric development was the only source of this power-now the best sites have been exploited and those remaining do not promise enough water to permit year-round capacity power plant operation. In searching for economic plant sites engineers have concentrated on locations with vast water power potential. Olin Mathieson Chemical Corp. has been studying the economics of developing water power to make aluminum. However natural gas, lignite, and even atomic energy have also been considered as possible power sources for aluminum production. Economic studies have given consideration not merely to investment and production costs, but to total costs of delivering fabricated products to the market center of the U. S. When delivered costs are considered and when full account is taken of the newest techniques of mining bituminous coal and utilizing it to make electric power, one arrives at the inescapable conclusion that coal has emerged as the economic answer to American aluminum production.

Jan 4, 1955

By R. V. Lundquist

Past reports by the Bureau of Mines have described the extraction of alumina from numerous aluminum silicate materials by the lime-soda sinter process. The results from pilot-plant investigations of six materials, with alumina-to-silica mole ratios from 0.3 to 8.7, indicated a relationship between the alumina-silica ratios and the processing characteristics of the sinter. A series of laboratory tests was conducted to define this relationship. Sinter and leach tests determined that an alumina-to-silica mole ratio of 0.90 or greater resulted in the best alumina and soda recoveries while leaving the leach slurries practically free from any tendency toward gelation. The widely different chemical and mineralogic properties of the various aluminous materials used in compounding the mixes had no perceptible effect on the leaching characteristics of the sinter. The blending of low-cost, high-alumina materials with aluminum silicate materials to give an alumina-to-silica mole ratio of 0.90 or greater would improve alumina and soda extraction and minimize operating problems in the lime-soda sinter process.

Jan 1, 1970