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By Carmine Nappi

This article examines some important trends in East-West trade in non-fuel mineral products, in particular the recent decline in Eastern bloc exports of such products. It relates this decline to an improvement in Soviet terms of trade; a deterioration of geological and locational conditions in Soviet mineral production; an increased integration of the CMEA-countries based on a regional pooling of resources; and a surge in demand for mineral commodities in Eastern countries coupled with a slowdown in Western economic growth. Finally, it evaluates to what extent these determinants may evolve in a different direction during the eighties and thus foster East-West mineral trade. Eastern1 bloc trade in mineral products is a subject of perennial interest in the West. When exports increase, there is much talk of the dangers of dependence on the East for critical fuels and materials. When imports increase, talk turns to the danger of Soviet dependence on Western supplies. A common fear is that the USSR may not only seek to meet its own resource needs but also deny the access of Western countries to these resources. This paper, like three other recent additions to the lite5ature on Soviet foreign trade of commodities2, tries to put matters in clearer and cooler perspective. The first section evaluates the structure of East-West mineral trade and tries to identify some important trends of recent years. The second section relies on supply and demand factors, as well on the Comecon connection (the intra-Council for Mutual Economic Assistance mineral cooperation) to explain why there has been a reversal in the mineral trade trend since the end of the seventies. The last section evaluates the factors which could stimulate East-West mineral trade in the future.

Jan 1, 1986

By Majid Sarkari, Hossein Atashi, Farhad Fazlollahi

"The aim of this research work was to prepare the efficient catalyst to purify pollutant output gases such as SO2 , NO2 and CO. This catalyst, lanthanum cobaltat (LaCo03) was prepared by the proper method in the analysis laboratory of Tabriz Oil .The first materials were chosen through calcination operation and temperatures of operation related to the Tamman temperature, therefore the basis for the first material of catalyst was nitrate and aqueous and since we had no availability to lanthanum nitrate, lanthanum oxide was used to prepare the nitrate one. Before all else, the first materials of catalyst were mixed together with the equal mole proportions and then, at the lower and upper temperatures of Tanunan temperature, calcination operation was carried out. To determine the molecular structure, the XRD analysis was utilized and specified that prepared lanthanum cobaltat was sixth aqueous and had the crystal structure type Triclinic.IntroductionLaCo03 has presented a vast interest because of its special electrical, magnetic and catalytic properties [1-4]. The catalyst LaCo03 can be prepared by means of several methods such as spray drying, freeze drying and also co-precipitation [5-12]. Some methods including hydrothermal, sol gel and citrate [13] This material usually has been synthesized by ceramic method and certainly the high temperature for the calcination operation. [14]. Lanthanum catalysts have been researched because of having such an active state [15]. One of the unique properties of this catalyst is the simultaneous conversion of pollutant elements. Nowadays CO oxidation has important applications in environment protection, such as indoor air cleaning and automotive exhaust treatment. LaCoO3 is one of the most important catalysts for CO oxidation."

Jan 1, 2013

By Lætitia H. Delmau

SXFIT is the latest in a series of programs developed in our group to model solvent extraction systems of increasing complexity. SXFIT permits the user complete freedom to define the constituents from which the composition of each phase is to be specified in the data and from which all species of a model for a system are assumed to be formed. Activity coefficients in the nonaqueous and aqueous phases, water activity, apparent molar volumes of aqueous species, and solution density needed for the conversion of concentration from the molarity to the molarity scale are all taken into account by the program. Several extraction systems relevant to nuclear-waste treatment were modeled successfully using this program. As an example, the cesium extraction efficiency of the CSSX process chosen by the USDOE for cesium removal from high-level waste stored at the Savannah River Site can be predicted correctly for varying feed composition.

Jan 1, 2003

The Mining Foundation of the Southwest will hold its 15th annual American Mining Hall of Fame Awards banquet on Saturday, Dec. 6,1997 in Tucson, AZ, preceeding the Arizona Conference of SME. The Mining Foundation's Hall of Fame, located in Tucson, recognizes outstanding contributions to the mining industry by individuals and industry partners. A permanent display of honoree vitae is located at the Arizona Historical Society at 949 E. Second St. in Tucson. Each year, one living award recipient and up to two honorees from mining history are chosen by the Hall of Fame committee and the board of governors of the Mining Foundation. In 1989, the Mining Foundation also initiated a Medal of Merit to recognize outstanding individual technical and professional contributions to the mineral industry. And in 1995, an award was instituted to recognize contributions made by companies and organizations in partnership with the mining industry. This year's inductee is James R. Moffett, chairman and chief executive officer of Freeport-McMoRan Copper and Gold Inc. He will be present as guest of honor and featured speaker. The Hall of Fame will induct John V. Dorr, metallurgist and chemical engineer. Also inducted will be Frederick L. Ransome, a geologist. Medals of Merit will be awarded to Hugo T. Dummett, senior vice president, Exploration BHP Minerals, and Spencer R. Titley, professor in the Department of Geosciences at the University of Arizona. An Industry Partnership Award will be presented to the Colorado School of Mines for its continued support to the mining industry through education and research. The banquet will be held at the The Westin LaPaloma in Tucson beginning with cocktails at 6:30 p.m. Tickets are available from Clare A. Roscoe, manager, Mining Foundation of the Southwest, telephone 520-577-7519, fax 520-577-7073.

Jan 1, 1997

By William M. Brewer

Until quite recently, in fact within the past two gears, but little attention has been given to the outcrops on the west coast of Vancouver Island, and their copper-contents. During the past few months the writer has been engaged in examining and developing some of these prospects. In many respects he has found characteristics associated with these prospects which, in his experience, are unique. In the first place, nearly all the outcroppings which overlie chalcopyrite-ore along the west coast of the island are composed of a high-grade magnetite. The magnetic qualities of some of these outcrops arc so pronounced that the magnetite possesses polarity. Although the writer hinlsclf had no analyses of this magnetite made, yet from its appearance he can readily believe that analyses made for other parties, which show a yield' of 62 or 63 per cent. of metallic iron, with only traces of phosphorus and silica, are correct. At a very shallow depth, masses of chalcopyrite, yielding in some instances as high as 32.6 per cent. of copper, occur associated with the magnetite; and in one instance, which recently came under the writer's observation, a solid body of high-grade chalcopyrite, fully 4 feet in thickness, occurs Within 6 feet of ; the surface. Usually this solid sulphide-ore carries low values in gold. Probably ail average of' $2 per toil would be fairly representative. But in some instances development has determined the occurrence of narrow stringers of pyritous quartz, associated with the sulphide-ores, which yield by assay more than $20 per ton in gold. In the districts examined by the writer, the country-rock is usually crystalline limestone, with dikes of igneous rock as intrusions. Sometimes the outcrops of magnetic iron-ore are

Jan 1, 1900

By P. Venkatraman, F. S. Knoll, W. S. Kow

Froth flotation is the most widely used technique for cleaning fine coal. This practice may change, however, with the development of enhanced gravity concentrators such as the Mozley Multi- Gravity Separator (MGS). The MGS is a flowing-film concentrator that utilizes centrifugal forces to improve the separation of flotation-size particles. In the present work, a pilot-scale test program was conducted to examine the effects of feed rate, feed solids content, wash water flow rate and drum rotation speed on the performance of the MGS. The test results indicate that the MGS effectively rejects high-density minerals such as pyrite, while ultrafine ash-forming minerals are removed less efficiently. A major advantage of the MGS is that high separation efficiencies can be realized without additional grinding, flotation reagents or heavy media. This article describes the working principles of the MGS and presents data obtained from recent pilot-scale test work.

Jan 1, 1995

By T. B. Counselman

THE importance of concentration of iron ores too low in grade to be smelted direct is shown by Table I, showing 1940 ship- [ ] ments from the Lake Superior district. Canadian ores are omitted. [ ] Only in Minnesota is concentrating, other than crushing and screening, practiced at present. Tonnage produced by various methods of concentration is shown in Table 2. The curves in Fig. I show the gradual increase in tonnage of concentrated ores shipped, compared with total shipments from Minnesota. Most of the concentration work is performed on the Mesabi Range. This range is about 100 miles long, and not over 3 miles wide from the line at which the formation tapers out to a feather edge on the north to the place on the south at which, some 600 ft. thick, it is overlain with slates. CLASSES OF ORE The Mesabi Range contains three classes of iron ore. First is the unaltered taconite, or banded iron-bearing chert. It is estimated that there are some 60 billion tons of this material, which contains, roughly, 25 to 30 per cent iron. This material is virtually untouched, since no commercially successful method has yet been found for concentrating it to a grade suitable for the blast furnace. Intensive experimental work is in progress, and the problem is gradually being solved. In 1922 the Mesabi Iron Co. spent several million dollars erecting a large-scale pilot plant for concentrating and sintering the magnetic taconites on the east end of the range. An important tonnage of high-grade sinter was shipped to lower lake furnaces, proving that the taconite can be concentrated to a satisfactory grade. The costs, with equipment and methods then in use, were too high for

Jan 1, 1941

By Horace H. Emerich

PrePatory Note.—The first part of this paper was sent to me by Mr. Emrich nearly nine months ago; and I held it, waiting for the second part, which he had promised to forward soon, so that I might submit the whole to some of his former professional associates, and advise him of their criticisms and suggestions before off'ering his work to the Institute. But, five days before the second part reached me, I received by telegraph the news of Mr. Emrich's sudden death. The paper has therefore not had the benefit of such a revision by the author as might have made it ill some respects clearer and more cornplete. Nevertheless, I believe that experts in the branch of metallurgy with which it deals will find it both original and suggestive.—A. Eilers. I. Partial ReFining iN the ANode-Furnace. During my connection with one of the large New Jersey copper-refineries, and probably before that period, from 15 to 30 per cent. of the copper-bullion received was the very foul, leady blister-copper produced from lead blast-furuace matte. It had been customary to mix a small part of this blister with each charge of purer pig-copper, in the effort to dilute it as much as possible before casting into anodes; but tank-house conditions were such that I was led to try making entire furnace-charges of this blister, and refining it as much as possible in the furnace—afterwards casting to anodes and refining elec-trolytically, in tanks and solution separate from the main bulk of the purer copper. In making this experiment, notes were made, for several furnace-charges, of everything thought to have a bearing on the question, and some interesting facts were brought out, both in the furnace-working and afterwards in the tanks.

Jan 1, 1913

By R. J. Brison, W. C. Bleimeister

The International Salt Company has long been interested in finding an efficient process for the removal of impurities from rock salt, and particularly from the rock salt produced at the Detroit mine. Methods which have been used previously at the Detroit mine included both hand sorting and differential crushing in a Bradford breaker with rejection of the oversize. Neither of these methods was adequately effective. The development of a new process for removal of impurities from rock salt has been described in the preceding article." Basically, the process consists of exposure of crude rock salt to radiant heating which selectively heats the impure particles. Subsequently the heated particles are removed by adhesion to a heat sensitive-coating on a conveyor belt. This method was found to be effective in improving both the quality and appearance of rock salt by the rejection of the dark, impure particles.

Jan 8, 1960

By Alfred C. Maevis

On October 27, 1972, ground was broken for the first section of the Second Avenue Subway, a two track underground rail system that was to extend from the south end of Manhattan at Broad Street, north to the Harlem River at 126th Street, a distance of eight miles. This ground breaking was the culmination of 67 years of planning for an east side subway in Manhattan. Following the successful opening of New York City's first subway on October 1904 there was a mass planning for additional subways throughout the City. In 1905 approval was requested of the Board of Estimate for a First Avenue route and Third Avenue route. The Third Avenue route was approved but when action was not taken to start construction, the approval in accordance with the conditions under which it was given was withdrawn. Further reports and plans for an east side subway, usually to be constructed on Third Avenue, were issued in 1920, in 1922, in 1924, etc. Those of us who had worked on the Sixth and Eighth Avenue subways in the thirites and early forties left to join the armed services of World War II in the expectation that we would return and start work on designing and constructing that east side subway. The reason that much of the thrust in those years was to construct on Third Avenue was that there was a Third Avenue "EL" and business interests of the City were in favor of its demolition. This demolition was accomplished in 1955 so one of the incentives to construct on Third Avenue was removed; but an east side subway was always part of the master plan of the City.

Jan 1, 1976

By Chester Purington

PROBABLY no battleship of any great power save Japan could long remain in. the Pacific Ocean tinder present conditions, were it to depend for fuel supply on the hitherto developed coal or oil resources of any part of the adjoining lands in either hemisphere. This statement does not overlook the important but not inexhaustible oil fields of California, the bunker coals of British Columbia, nor the coals accessible and mined adjacent to Chinese water-ways. For both naval and merchant ships, however, modern practice seems to require high-grade Welsh or Pennsylvania bituminous even at great expense for transportation. Otherwise, we should not see British ships bunkering Welsh coal at Singapore nor the United States establishing a store of Pennsylvania coal at its naval base at Pearl Harbor, Hawaii. Compared with Atlantic coals, the best Miike and Nagasaki (Japanese) bunker coal, the Kailan coal of China, and the Welling-ton and Nanaimo coals of British Columbia, are dis-tinctly inferior, as one can soon learn from the chief engineers on Pacific liners. In addition to the coal used for steaming and bunker purposes, it is of increasing importance that an adequate supply of coking coal for metallurgical purposes should be made available at reasonable prices at industrial centers on the west coast of America, and at Japanese and Chinese coastal cities. The use of Chinese coking coals for smelting the iron of the lower Yang-Tse deposits is by no means so satisfactory as could be desired, while the poor quality. of Japanese coals for coking purposes is well known. If Russia, as seems not improbable, is to become a power on the Pacific in the course of the next few decades, she will doubtless develop an iron and steel industry in the Maritime Province, where an adequate and accessible supply of iron ore will necessitate a supply of coking coal.

Jan 9, 1923

By Joseph L. Gillson

BRAZIL has had an industry based on ocean beach deposits of heavy minerals containing monazite, zircon, rutile, and ilmenite for well over 40 years, but except at the very earliest period, prior to 1906, and again during World War 11, has this industry been at all comparable in size with similar operations in other countries. Limiting factors have been neither a lack of reserves nor lack of markets (except for zircon). Although poor local transportation and shipping facilities have handicapped the development in Brazil, these conditions were perhaps equally bad (when mining operations started) in the Indian State of Travancore, and in New South Wales and Queensland, Australia, in which states the principal production of beach deposits of heavy minerals has occurred. The outstanding restraints on the Brazilian industry have been the lower quality of the Brazilian minerals, the relative small size of individual deposits that were known until recently, the lack of interest of Brazilian investors in mining ventures, and the unfavorable climate for investment of foreign capital under Brazilian mining law. The lower quality of the minerals is indicated by the fact that the Brazilian monazite carries only 5 to 6 pct ThO2,*, and the ilmenite 56 1/2 pct TiO2, whiteness of the Australian zircon. An inadequate market for the abundant zircon that will be avail- able in any operation in Brazil is certainly a heavy restraint, since otherwise it could be an important byproduct. The oxide of zirconia, baddeleyite, that has come from Brazil is from other sources. 1 Since the Brazilian beach sands carry only a little rutile, that mineral has not been available as a valuable byproduct to help finance the operations.

Jan 6, 1950

By K. Hodgson, Cook. N. G. W.

Most structures are designed so that the possibility of failure is eliminated. However, some degree of failure in the rock around deep mine excavations is inevitable if mining operations are continued. The presence of failed rock constitutes a hazard the magnitude of which can be predicted by computer models from calculations of the energy change per unit area mined in stopes, or the field stress around service excavations. Empirical relationships between these calculable quantities and the incidence of rock failures and delays associated with them have been established. Experiments on the computer using different layouts enable the mining engineer to select the least hazardous of otherwise acceptable alternatives, and to predict the incidence of damage ahead of actual mining, so that appropriate measures to maintain an adequate degree of safety and productivity can be planned in advance.

Jan 1, 2014

By Martha E. Smith

INTRODUCTION Radiation is one of the many agents occurring in our environment that is capable of causing cancers. We are all unavoidably exposed to natural background radiation. If we wish to exploit the beneficial uses of radiation in medicine, industry, and for the production of electricity, some further exposures to radiation are almost inevitable. One needs to ensure therefore, that the standards of radiation protection are safely derived and one would want to understand the mechanism by which radiation might cause cancer and genetic defects. In order to study the effects of radiation one can: (1) analyze human data, (2) perform animal experiments, and (3) do molecular level experiments. Indeed all three kinds of information are needed. This paper will concentrate on the steps required to obtain some of the necessary human data regarding health effects, where the concern is about the impact and consequences of long-term low-level exposures to an agent. Such investigations require some knowledge of work histories, dose histories, health "outcomes", and the personal identification of the individual involved. Three inter-related computer systems have been developed at Statistics Canada which have been designed to permit optimal use of a number of different records for our entire country for such health related research. The development of the Canadian Mortality Data Base, the initiation of the National Cancer Incidence Reporting System, and the development of new computer linkage techniques have helped reduce the cost and increase the scale and efficiency of automated follow-up to produce statistics of sickness or death associated with radiation and other carcinogenic agents in mines. These computer systems have already been implemented, and references will be made to studies currently being conducted using these files and facilities (e.g. a study of all Ontario miners, plus various Canadian uranium, fluorospar, salt and nickel miners). We will also look at the kinds of data that need to be collected now, to improve such studies in the future. DELAYED RISKS - THE STUDY SIZE AND COST Delayed effects on human health, as for example industrially caused cancer, can in general only be detected and measured by following-up the individuals to see what eventually becomes of them. What is not generally recognized is that the relatively low levels of individual risk, about which the public is often concerned, usually requires for their detection that very large numbers of "exposed" and "control" individuals (e.g. 10,000 to 100,000 or more) be followed over a period of two or three decades to determine when they die, what they die of, and whether they contracted cancer or some other disease of special concern. Thus, it is frequently exceedingly difficult to make such investigations cost-effective so that they will be undertaken at all, and as a result very real risks to health can remain undetected or unquantified. THE MANUAL PROCEDURES Follow-up of individuals by epidemiologists has until recently been a largely manual and clerical operation. It has used a diversity of source record files; local, regional, and national. Often the tracing of people has involved letters sent through the mails and visits to institutions, physicians, municipal offices, and former neighbours. Only thus could one find out whether the individuals were dead or alive. Such studies were necessarily small, or else very expensive. Death registrations have, by tradition, provided a valuable tool for the identification of harmful influences in the environment. However, with the increasing mobility in the population, death may often occur far away from the place of exposure to such an influence. Thus, no longer will simple manual searches in a single registry office suffice to inform the investigator concerning the deaths that may have occurred in a study population, especially when that population is large. In the past, manual follow-up to locate the relevant death registration normally required some prior knowledge of the province and year of death in question, so that the alphabetic indexes could he used to direct researchers to the appropriate bound volumes of registration forms. To search manually in this fashion for any large number of death registrations, without knowing in which year or province the deaths had taken place, or even whether they had yet occurred, would be impractical, since each year in Canada there are about 170,000 deaths. DEATH AND CANCER AS SPECIAL ENDPOINTS Much of recent effort has been focused on the organization of the "endpoint" files required to do long-term follow-up studies on a national scale, because that is a function which other institutions are unable to perform due to the confidentiality laws governing the use of such information. Outside organizations generally come to us with detailed "starting" point records which relate to some specific group requiring study. We carry out these epidemiological searches on a cost-recovery basis. The analytical interpretation of results is normally

Jan 1, 1981

By Frederick B. Henderson

On 10 August 1976, The Geosat Committee was organized in Denver to institute The Geosat Program. This program is an industry backed effort to evaluate and help select optimum space remote sensing systems for geological purposes. It is believed that the recommendations of The Geosat Committee can be supported by industry as additional exploration tools which can materially benefit industry and the Nation with respect to our energy and other natural resources needs. Appended is a general summary of The Geosat Committee Organizational Meeting and general review of The Geosat Program. The Geosat Workshop Report. The Geosat Committee, and The Geosat Program will be reviewed at a special afternoon session, Friday, 3 September.

Jan 1, 1976

A. K. McCosh, Coatbridge, Scotland (written discussion*).-It is well known in Great Britain that oven operators in the United States have been able to reduce the coking time much below European standards by the employment of higher temperatures. Our linings have always been the factor that has prevented our doing the same, and it would be of much interest to coke-oven operators here if Mr. Blauvelt would give a typical analysis of the bricks his company uses for the linings of its ovens, and if he could see his way to send me a sample so that I could have the texture examined, I should personally be very much obliged. The lining brick which my company has found most successful is of a ganister variety, and has the following analysis: Silica, 80.8 per cent.; alumina and iron oxide, .17.8 per cent.; lime, 0.8 per cent.; magnesia, 0.07 per cent.; but with this brick the least carelessness on the gas regulator's part may destroy the lining. It would also be of interest if Mr. Blauvelt could give the temperatures of the air leaving these generators and also of the oven flues.

Jan 10, 1918

By C. F. Floe, M. Cohen, M. B. Bever, V. G. Paranjpe

NITROGEN is becoming recognized as one of the important elements in ferrous physical metallurgy. Several investigations indicate that nitrogen plays a significant part in such phenomena as strain aging and temper brittleness. Nitrogen is known to be a powerful austenite stabilizer and may be a useful alloying element in stainless steels. The hard-enability of steels has been found to be increased by nitrogen. The nitriding and carbonitriding pro- cesses are examples of successful industrial application of nitrogen in ferrous materials. For a complete understanding of the various roles played by nitrogen in ferrous metallurgy a knowledge of the phase relations in the binary iron-nitrogen system is essential. The literature contains a variety of iron-nitrogen phase diagrams. Those suggested by Fry, Sawyer,² Epstein and his coworkers,³,4 Lehrer,5 Eisenhut and Kaupp, and Hägg7,8 differ significantly from one another. Moreover, the most recent of these investigations dates back about twenty years. A re-determination of the entire diagram, therefore, appeared desirable. In addition to the published phase diagrams, investigations have been carried out on portions of the iron-nitrogen system. Bramley and Haywood determined the composition and temperature of the iron-iron nitride eutectoid. The maximum solubility of nitrogen in a iron was investigated by Portevin and Seferian10 and by Diikstra. 11 Several investigators have determined the crystal structure of the various iron-nitrogen phases. In fact, Eisenhut and Kaupp6 and Hägg7 based their entire phase diagrams on the results of such studies. Epstein' and Emmett12 reported lattice-parameter measurements on the E (hexagonal close-packed) phase. Osawa and Iwaisumi13 also studied the change in lattice parameters of the a, ? and E phases with nitrogen content. Brill" and Hägg7 showed that the y' phase has an ordered structure, and Hendricks and Kostingsl5 suggested a structural relation between the E and phases. In a recent investigation Jackl6 arefully studied the super-lattice reflections from the y' and phases. Experimental Procedure A large variety of experimental methods has been used by previous investigators in studying the iron-nitrogen system. These methods include thermal analysis, microscopic examination, X ray diffraction, magnetic measurements, dilatometric analysis and anelastic experiments. Thermal analysis is of low accuracy in determining changes in the solid state. This accuracy is further decreased for iron-nitrogen alloys since composition changes will occur during heating or cooling unless extreme care is taken to use a proper atmosphere. Metallographic methods are of small value . because homogeneous iron-nitrogen alloys of sufficient size can be produced only with great difficulty. The dilatometric method is open to the same objections as thermal analysis in that changes in composition may occur during heating and cooling. Lattice parameter measurements by X ray diffraction can be used satisfactorily for determining phase boundaries if cooling is fast enough to prevent structural changes. In view of the limitations of the various other techniques two methods only were adopted in this investigation, (1) X ray diffraction measurements, and (2) a controlled nitrogenizing method. The second method is an innovation for investigating the iron-nitrogen system, and will be described at length. Materials: All iron-nitrogen alloys were prepared from carbonyl iron powder of the analysis shown in table I. The average particle size was about 20

Jan 1, 1951

By T. B. Beeton

In view of the limited reserves of good-quality coking coals in South Africa, Iscor has been involved in direct reduction since the middle sixties. Since the early seventies, its interest in direct reduction was stimulated further by a swing towards' continuous casting, which, in turn, contributed to a shortage of the scrap supply for electric-arc-furnace (EAP) steelmaking. Rock engineering The First International Conference-Rock Enginet:ring and Excavation in an Urban Environmentorganized by The Institution of Mining and Metallurgy and the Hong Kong Section of the Institution, in association with the Hong Kong Institution of Engineers, will be held in Hong Kong from 23rd to 28th February, 1986. SPOTLIGHT on Gold Fields National Engineering Awards For the Gold Fields Foundation National Engineering Awards, each university affiliated to the South African Federation of University Engineering Students (S.A.F.U.E.S.) selected a candidate who, in their opinion, presented the most outstanding design project in their final year during 1984.

Jan 1, 1985

By J Kinal

Plant trials are at the best of times difficult to perform; given variations in the ore, operating practice and economic constraints placed on a plant. Testing grinding media at industrial scale adds a further level of complexity that needs to be accounted for.Laboratory test programs consistently demonstrate that altering the grinding chemistry through the application of inert grinding media has the potential to provide significant metallurgical benefit. However, prog- ressing from laboratory testing to industrial trial is often an agonisingly slow process that can lead to inconclusive results which raise more questions than give answers. There are many factors that need to be considered when conducting plant trials aimed at demonstrating the impact of inert grinding media on metallurgical performance. The decisions (or lack thereof) made during the planning stage can heavily impact on whether a statistically meaningful result is achieved. Various factors such as how the trial is conducted (dumping or purging the charge); the circuit configuration; collection of the right data; and even the human factor will affect the outcome. The authors will use examples to demonstrate the importance of proper planning and controlled operation on grinding media plant trials.

Jan 1, 2009

By Isobel Clark

Geostatistical methods of estimating ore reserves and other spatial phenomena are becoming increasingly wide spread in their use. Properly applied, Geostatistical estimation falls into two stages -- the "modelling" of the spatial variability within the study area; and the use of this spatial model to provide an appropriate estimation technique. The first stage usually consists of construction and interpretation of semi-variogram graphs, and the second is the development of the corresponding Kriging method. Because of the apparent subjectivity inherent to the first stage of a geostatistical analysis, attempts have been made to provide methods of "testing' whether a particular semi-variogram model (say) adequately represents the study area. Increasingly, the choice of model is being justified by a process known as "Cross Validation'. With this approach, the analyst uses a partial data set to estimate values at actual sampled positions. "Real" and "estimated" values are then compared in such a way that the model can be accepted or rejected. This paper discusses the process of cross validation in some detail, using case studies as examples. Some problems with the technique are illustrated and discussed.

Jan 1, 1986