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By P. S. Roller

P. S. ROLLER,*College Park, Md.-The author introduces the idea of a grind limit, or lower size limit of the particles formed directly by grinding, and this is stipulated to be 0.70 micron. I wonder where all the particles come from that lie between the resolving power of the microscope and 0.7 micron, which are seen under a microscope in examining a sample of grind? There is also introduced the idea of excess fines; this is all right in itself but the author's quantitative definition seems to be virtually impossible to justify, and, moreover, is obscure. Just why E, the excess fines, should he defined as the distance between an F line and a y line is hard to follow, and just where the distance should be measured does not appear to be stated, as it should be since the F and y lines intersect and the distance between will depend upon where that distance is measured. The basis of the presentation is the relation of log weight against log size that was "discovered" by Schuhmann. While this relation is implied to fit, the only evidence that I can see is a slightly irregular line in Fig. x between 2 per cent and 18 per cent by weight and then a precipitous drop at 18 per cent away from any sort of straight line. Some of the conclusions are rather startling. It is stated that E, the excess fines, remains constant for all the comminution products of any particular material, except that it may decrease for some coarse crusher products. No reason is given for this assertion. One would, on the contrary, expect that excess fines, if such a concept is permissible, would generally vary with different conditions instead of being constant. Again, "as much net energy is required to reduce a ton of quartz to particles of the grind-limit diameter (namely, of course, 0.7 micron) by grinding as is required to melt the quartz." This would require many data to prove, but no proof is given; any consideration would reveal the impossibility of such a result. Still further, ore samples "ground to widely different sizes, and with different circulating loads and different size distributions or product, show the same production of new surface area per revolution of the mill, when this grind limit is used." This statement is confuted by ordinary experience, which teaches that grinding efficiency varies generally with the condition of material. For example, the cushioning effect of fines is widely accepted, while the inefficiency of a ball mill when the feed is too coarse is also well known. R. SCHUHMANN, JR.," Cambridge, Mass. Contrary to Mr. Bond's stand, there is a great deal of miscellaneous experimental evidence that comminution does not stop at around 0.7 micron, nor does it cease consuming energy at that point. Comminution is in fact recognized as an important method of producing colloids., Mechanical comminution methods were used by von Weimarn6 to produce colloidal dispersions of a variety of solids, including the minerals chalcocite, galena, hematite, stibnite. Utzino7 gives average particle sizes ranging from 0.02 to 0.09 micron for colloids produced by mechanical comminution of several crystalline solids. Andreasen and Berg' have ground

Jan 1, 1941

By P. S. Roller

P. S. ROLLER,* College Park, Md.-The author introduces the idea of a grind limit, or lower size limit of the particles formed directly by grinding, and this is stipulated to be 0.70 micron. I wonder where all the particles come from that lie between the resolving power of the microscope and 0.7 micron, which are seen under a microscope in examining a sample of grind? There is also introduced the idea of excess fines; this is all right in itself but the author's quantitative definition seems to be virtually impossible to justify, and, moreover, is obscure. Just why E, the excess fines, should be defined as the distance between an F line and a y line is hard to follow, and just where the distance should be measured does not appear to be stated, as it should be since the F and y lines intersect and the distance between will depend upon where that distance is measured. The basis of the presentation is the relation of log weight against log size that was "discovered" by Schuhmann. While this relation is implied to fit, the only evidence that I can see is a slightly irregular line in Fig. I between 2 per cent and 18 per cent by weight and then a precipitous drop at 18 per cent away from any sort of straight line. Some of the conclusions are rather startling, It is stated that E, the excess fines, remains constant for all the comminution products of any particular material, except that it may decrease for some coarse crusher products. No reason is given for this assertion. One would, on the contrary, expect that excess fines, if such a concept is permissible, would generally vary with different conditions instead of being constant. Again, "as much net energy is required to reduce a ton of quartz to particles of the grind-limit diameter (namely, of course, 0.7 micron) by grinding as is required to melt the quartz." This would require many data to prove, but no proof is given; any consideration would reveal the impossibility of such a result. Still further, ore samples "ground to widely different sizes, and with different circulating loads and different size distributions or product, show the same production of new surface area per revolution of the mill, when this grind limit is used." This statement is confuted by ordinary experience, which teaches that grinding efficiency varies generally with the condition of material. For example, the cushioning effect of fines is widely accepted, while the inefficiency of a ball mill when the feed is too coarse is also well known. R. SCHUHMANN, JR.,* Cambridge, Mass.-Contrary to Mr. Bond's stand, there is a great deal of miscellaneous experimental evidence that comminution does not stop at around 0.7 micron, nor does it cease consuming energy at that point. Comminution is in fact recognized as an important method of producing colloids.5 Mechanical comminution methods were used by von Weimarn6 to produce colloidal dispersions of a variety of solids, including the minerals chalcocite, galena, hematite, stibnite. Utzino7 gives average particle sizes ranging from 0.02 to 0.09 micron for colloids produced by mechanical comminution of several crystal-line solids. Andreasen and Berg8 have ground

Jan 1, 1941

By M. Sagisaka

The purpose of this study is to obtain carbon dioxide emissions by copper production systems and quantitative merit to use copper scraps in Japan. Electrolytic copper and sulphuric acid originating from the refining gas are produced in the system. In this study, the inventories such as the fuel consumption of the unit processes and the in-house electricity generation were obtained from published papers and public statistical data. The following observations were made based on the Life Cycle Assessment (LCA) method: (1) Carbon dioxide emissions from the production of electrolytic copper and sulphuric acid in the system are about 1.0 kg and 0.4 kg/kg-product respectively. The carbon dioxide emissions attributable to the transportation of copper concentrate correspond to 20% of the total emission. This emission is higher than that of zinc because the metal content in the concentrate is lower than zinc. (2) The carbon dioxide emissions from the system decrease with the recycling of copper scrap to the converting process because the consumption of copper concentrate is reduced. The reduction is estimated to be 0.18 kg-CO2/kg-Cu at the point of 0.1 kg-scrap/kg-blister Cu. This corresponds to 9% reduction for the present system. However, this recycling leads to the decrease of sulphuric acid by 450x103 tonne at the point. The recycling of scrap should be evaluated not only from the reduction of carbon dioxide emissions, but also in terms of sulphuric acid demands as well as advantage of waste management.

Jan 1, 2003

By M. H. Kotze, M. J. Virnig, G. Steinbach

Earlier work at Mintek on the development of gold-selective resins culminated in a plant-manufactured batch of the first generation of Minix resin. A subsequent pilot-plant campaign at a South African gold mine identified some problems with that resin. These included lower capacity and selectivity for gold compared with the laboratory prototype, and a slow but progressive loss in capacity as the resin was eluted and reloaded cyclically. These problems were overcome by chemical modification of the resin structure. Examples of these improvements are presented. The commercialization of a new resin for a new metallurgical application presents problems, which are exacerbated by the initial lack of demand for the resin because the process is unfamiliar to the mining industry. Progress in the commercial development of Minix is discussed in this context.

Jan 1, 1993

By Robert A. Bauer

Two basic types of subsidence occur in Illinois: pit and sag / trough. Pits develop over mines less than 165 feet deep and where relatively incompetent strata are found over the mines. Sag subsidence is found over mines as shallow as 75 feet and more generally over mines of greater depths. The percentage of subsidence and angles of draw associated with sag subsidence appear to be controlled by the rock properties at each specific site. The percentage of subsidence and angles of draw are smaller where the sites are not affected by geologic structures. An investigation to determine if a time factor based on the time interval from the date of mining to the subsidence events has shown that simple correlations with time, percent extraction, average pillar stresses, and pillar dimensions is not evident in Illinois.

Jan 1, 1982

By W. A. Ver Wiebe

UNder the impetus of new demands caused by the defense program, the oil and gas industries of Kansas established new records during the year 1941. In all, 2113 wells were drilled, which compares favorably with the record total drilled in 1937. These 2113 tests resulted in 1446 oil wells, 76 gas wells and 592 dry holes. In all three categories there was an increase over the previous year, but unfortunately the most marked increase was in the dry holes. Nearly 80 per cent of the increase must be allocated to the drilling 01 unsuccessful tests. This was partly because of the increasing difficulty of finding new reserve areas and partly because of the erratic character of the production in the Arbuckle dolomite, which is now the main producing zone. Closer analysis of the totals reveals that western Kansas accounted for 1634 tests, of which 1186 were oil wells, 34 were gas wells and 415 were dry holes. The total potential initial daily production uncovered by the successful wells amounted to 1,691,000 bbl. of oil and 508,000,000 cu. ft. of gas. Both figures indicate a considerable decrease when compared with the proceeding year; in 1940 the respective figures were 2,128,000 bbl. and 1,289,000,000 cu. feet. In eastern Kansas a total of 479 wells were drilled. Among these, 260 were oil wells accounting for a daily initial potential production of 45,662 bbl. The new gas wells numbered 42 and added 290,438,000 cu. ft. per day to the gas potential production of the state. The remaining tests, 177 in number, were dry. It is interesting and significant that almost half (791) of the total wells drilled in western Kansas were drilled by the independent operators. Among the large companies the Cities Service Oil Co. drilled 169 wells; the Stanolind Oil and Gas CO., 101; the Skelly Oil Co., 80; the Continental Oil Co., 99, and the Shell Petroleum Co., 63 wells. In eastern Kansas the independent operators drilled 406 out of the total of 479 wells. Among the major oil companies the Cities Service Oil Co. drilled 38; the Phillips Petroleum Co., 13, and the Sinclair-Prairie Oil Co., II wells. The figures on relative percentages of dry holes to successful oil or gas wells are revealing. In western Kansas approximately one third of all wells drilled by the independent operators were dry holes. The major oil companies drilled approximately 844 wells in western Kansas, of which 678 were successful in finding either oil or gas. It thus appears that the major companies fared much Getter than the independents. In eastern Kansas the major companies drilled 73 wells of which 63 were successful in finding commercial quantities of oil or gas. No less than 286 wildcat tests were put down in western Kansas and 72 in eastern Kansas, or 358 in all, during 1941. Considerably more than half of these were drilled by independent operators; zoo in western and 66 in eastern Kansas. An exploratory hole % mile or more from production is regarded as a wildcat well in Kansas. On a percentage basis, approximately 75 per cent of all wildcat wells were failures; only 25 per cent found oil or gas in western

Jan 1, 1942

By W. A. Ver Wiebe

UNder the impetus of new demands caused by the defense program, the oil and gas industries of Kansas established new records during the year 1941. In all, 2113 wells were drilled, which compares favorably with the record total drilled in 1937. These 2113 tests resulted in 1446 oil wells, 76 gas wells and 592 dry holes. In all three categories there was an increase over the previous year, but unfortunately the most marked increase was in the dry holes. Nearly 80 per cent of the increase must be allocated to the drilling 01 unsuccessful tests. This was partly because of the increasing difficulty of finding new reserve areas and partly because of the erratic character of the production in the Arbuckle dolomite, which is now the main producing zone. Closer analysis of the totals reveals that western Kansas accounted for 1634 tests, of which 1186 were oil wells, 34 were gas wells and 415 were dry holes. The total potential initial daily production uncovered by the successful wells amounted to 1,691,000 bbl. of oil and 508,000,000 cu. ft. of gas. Both figures indicate a considerable decrease when compared with the proceeding year; in 1940 the respective figures were 2,128,000 bbl. and 1,289,000,000 cu. feet. In eastern Kansas a total of 479 wells were drilled. Among these, 260 were oil wells accounting for a daily initial potential production of 45,662 bbl. The new gas wells numbered 42 and added 290,438,000 cu. ft. per day to the gas potential production of the state. The remaining tests, 177 in number, were dry. It is interesting and significant that almost half (791) of the total wells drilled in western Kansas were drilled by the independent operators. Among the large companies the Cities Service Oil Co. drilled 169 wells; the Stanolind Oil and Gas CO., 101; the Skelly Oil Co., 80; the Continental Oil Co., 99, and the Shell Petroleum Co., 63 wells. In eastern Kansas the independent operators drilled 406 out of the total of 479 wells. Among the major oil companies the Cities Service Oil Co. drilled 38; the Phillips Petroleum Co., 13, and the Sinclair-Prairie Oil Co., II wells. The figures on relative percentages of dry holes to successful oil or gas wells are revealing. In western Kansas approximately one third of all wells drilled by the independent operators were dry holes. The major oil companies drilled approximately 844 wells in western Kansas, of which 678 were successful in finding either oil or gas. It thus appears that the major companies fared much Getter than the independents. In eastern Kansas the major companies drilled 73 wells of which 63 were successful in finding commercial quantities of oil or gas. No less than 286 wildcat tests were put down in western Kansas and 72 in eastern Kansas, or 358 in all, during 1941. Considerably more than half of these were drilled by independent operators; zoo in western and 66 in eastern Kansas. An exploratory hole % mile or more from production is regarded as a wildcat well in Kansas. On a percentage basis, approximately 75 per cent of all wildcat wells were failures; only 25 per cent found oil or gas in western

Jan 1, 1942

By Edgar F. Cruft

It is sometimes said that "mines are made, and not found". I rather doubt that the exploration geologist would be overly sympathetic to that statement, and, of course, like most one-liners it is only partly true. As an explorationist who has been involved in building his own company over the last ten years, and by necessity has become a financier, I can appreciate what real grains of truth are in that statement, however. Because technical people are seldom taught financing in their basic training, and because they are usually not involved in it until at quite a senior level in their careers, the whole field often acquires a certain mystique. The engineering professions have too often believed financing is the province of the accountant or financial executive and just as we in the technical world are often too quick to bristle if the latter try to tread on our domain, the opposite can just as easily be true. Unfortunately, this is another example of a compartmentalized individual, and that is one thing the successful financier cannot be.

Jan 1, 1979

By A. P. Cook

Methane drainage on a mine-wide scale is a relatively new technology to South African coal mines. Shallow seams and apparently low methane contents have been assumed to result in less methane problems than experienced in other countries. The introduction of deeper mines however, has now resulted in methane drainage taking on a higher priority. Methane contents in the region of 12 m3\t have resulted in one colliery introducing drainage as a ventilation support. Although a low seam permeability initially indicated reduced potential for drainage, early borehole flows of 90 m3\m\year have since increased to 450 m3\m\year. Rapid inflow of methane into goafs and sealed areas from seams surrounding the main production seam at another colliery have warranted extensive evaluation of the methane properties of these seams with the projected introduction of predrainage from surface. Methane pressures in excess of 1000 kPa and contents in the region of 10 m3\t again give methane volumes suitable for drainage. Coal seam drainage ahead of mining is becoming more significant and is likely to see an increase in the near future. INTRODUCTION Methane gas is an everpresent hazard associated with underground coal mining. Safe working levels of methane in the mine atmosphere are normally maintained by ventilation practises, ensuring sufficient dilution of the gas. However in some cases the ventilation must be assisted by methane drainage, either from the mined seam, or from adjacent seams and strata, or from goafed areas. South African collieries have practised only limited methane drainage until now. Relatively shallow mining depths, and apparently low in-seam methane contents have been assumed to result in fewer problems with methane than are the normal for other countries. This is now being shown to not necessarily be the situation. Work carried out by the Coal Mining division of COMRO (Cook and Erwee, 1991) indicates South African production coal seams have very similar methane retention properties to those of coals in other countries, with seam gas contents of up to 12 m3/t. This awareness, as well as greater mining depths, and higher degrees of mechanisation, has resulted in higher priority being given to methane emission problems throughout the industry. Increased levels of safety, as well as possible commercial applications, are the main reasons for the interest now being shown in methane drainage. Not only is there possible applications in the present production coalfields, but South Africa has vast areas of coal reserves which are presently non-mineable, now being seen as possible alternative energy sources. Limited methane drainage is practised within the industry, but only on collieries that have identified specific methane problems that can be alleviated by drainage. Historically this has been restricted to surface drainage of longwall goafs, reducing emissions onto the faces. More recently, horizontal in-seam holes have been drilled, until now for bord and pillar sections, but the results are being evaluated for later application to shortwall faces. Adjacent seams pose problems at some sites and vertical and cross measure boreholes are now being considered.

Jan 1, 1993

By P Murthy, Z Guan, P Townson

In this paper, we introduce a methodology to optimise mining equipment operation in terms of the conflicting concerns of productivity and availability. We also introduce the concept of damage points and equipment dutymeters. These provide the mine management with tools to monitor the success of such optimisation. Since we have quoted the results of an on-going Australian Coal Association Research Program (ACARP) project, the apparent focus of this article is on draglines. However, the concept is equally applicable to other equipment. Mining is the type of business that requires a large investment in capital infrastructure and equipment to produce a product that is sold at a relatively low unit cost. In such a business, the key to competitiveness lies in achieving the full realisation of capital investment ie sustained production at high levels. Some of the concepts outlined in this paper are essential components of this picture.

Jan 1, 2000

Most types of nuclear power reactors use uranium dioxide fuel. Power reactors using natural uranium dioxide'fuel are of special interest to countries such as Australia that have their own uranium supplies. A wide range of uranium dioxide powders can be fabricated and the ideal one flows readily, presses without the need for binders or lubricants, sinters to the required density and gives low reject rates at all fabrication stages. Sinterable uranium dioxide is usually produced via the ammonium diuranate route. The A.A.E.C. is aiming to demonstrate production of nuclear grade uranium dioxide from Australian concentrates, improving technology where possible. Details are given of the dissolution, solvent extraction, precipitation, filtration, drying, and calcination-reduction steps. Solvent extraction from sulphate media is also under study with a view to developing a process to produce a nuclear grade product at the mine treatment plant site,

Jan 1, 1969

By William T. Griswold

Few metals or industrial minerals can boast a better growth record over the past fifteen years than the borates. This period of growth occurred before the influence of any large-scale use in plastics or high-energy fuels. These new developments not only provide expanding markets, but the programs related to their development are generating research information that will lead to many other new uses. The most dynamic growth areas for refined products of boron or borates are in the acid, the oxide and the reduced forms, such as the metal and the hydrides. Expanding requirements for these products will modify the emphasis on the use of naturally occurring sodium borates. Any borate from which boron can be economically extracted will become a potentially important ore. This is particularly true of the calcium borate, colemanite. Only one large deposit in the Western World has ever been developed where the principal economic minerals are sodium borates, This factor alone would discourage any exploration program directed solely toward the discovery of these ores; on the other hand, ample exploration opportunities for calcium borates exist in the desert regions of California and Nevada. It is therefore reasonable to restrict a program to this region, in spite of geologically favorable areas in foreign countries such as Turkey, Argentina and Chile.

Jan 1, 1959

By Hokuichiro Ohmachi

INTRODUCTION Metallic minerals have been formed only through complex geologic processes which took place at certain stages of the earth's histrory. Their concentration, abundance, and distribution are, therefore, restricted geologically, and very small in global scale. Ore is a mineral deposit or mineral concentration from which metals can be economically extracted by the contemporaneous technology. By this definition, several factors should be considered before any mineral deposit is regarded as an ore. The grade of mineral concentration and the scale of the reserve are most important. Demand for the metal and its price are the other factors. Advancement of technology in mining and extraction are also vital. Copper, for example, is now commonly extracted from the ores containing less than 0.3% of the metal. However, in the 1700's the common minerable grade was about 13%, and in the 1900's between 5 to 2.5%. This decrease in minerable grade is a function of not only the demand for copper, but also technological progress in mining and metal extraction in this case. Availability of ores has recently been subject to political factors, which were not the primary concern in the past. The petroleum of the Middle East is the prominent example. The metallic minerals are classified into three categories. The first one is the minerals free from these factors mentioned above. Iron and manganese belong to this category. The second category include aluminum, copper, nickel, cobalt, titanium, lead and zinc. These metals can be provided by the future progress in technology which enables the use of lower grade deposits. The third one represents the metals whose occurrence is geologically limited, and, thus, subject to the political factors. Niobium and tantalium are the example. In this article, I discuss these minerals in detail to give an outline of the factors which brought their concentration, distribution and availability. SELECTED MINERAL CONCENTRATIONS Iron Major iron ore deposits are the features of the relics of ancient continental crusts. They are found in all the continents where the Precambrian rocks expose. They do not occur in the oldest rocks (3,000my old) nor in the youngest ones (600my old). They are sedimentary rocks, normally, exhibiting alternations of bands of iron oxides (magnetite and hematite) or iron silicates (especially greenalite), and bands of silica, variously described as jasper, quartzite and chert. The best known banded iron ore deposits exist in the Lake Superior region of the North America, and their distribution extends at intervals to Labrador of Canada. Other examples occur in the U.S.S.R. Brazil, Venezela, India, the mainland China, and southern and western Africa (Liberia and Guines) (Table 1). Recently large deposits have been discovered in the Hammersley region of the western Australia, and northern and central region of Brazil. These ore deposits were originally formed in shallow seas where simple but abundant life existed. After the deposition, enrichment processes , related to tropical weathering, have brought about wholesale removal of silica to produce the deposits of best quality. Ores with 50-60% iron represent the best products in the Precambrian fields. Since local reserves of this high grade ores approach to exhaustion, benefication processes have been used effectively to upgrade much leaner ores (for example, taconite with 20-25% iron in Minesota, U.S.A.). There are two other types of iron deposits. Ironstone, a sedimentary rock containing goethite, chamosite and siderite, first appeared in early Paleozoic times in the stratigraphic record, and reached its Zenith in the Jurassic. Similar bedded iron deposits are found in the belt from the Cleveland Hills to Oxford in England, and in the "minette" oolitic ores of Alsace-Lorraine in Luxenburg and France. The iron content of these ironstones seldom exceed 30%, but they usually contain calcite and are self-fluxing. They also have phosphorous as undesirable impurity. Because of the grade and impurities, they require more fuel than the Precambrian ores. The third type of iron ore is associated with igneous activity and consists of magnetite and some hematite, and apatite. This deposit is believed to be a product of magmatic differenciation. It occurs in Kiruna of Arctic Sweden. The iron ore, therefore, present no global shortage problem. They extend to considerable depths. Their concentration is largest among the metals. If low grades were treated, the resource can be stepped up much substantially. Manganese Manganese is a ferro--alloy metal, thus, essential to the manufacture of sound steel. Manganese comes from manganese oxide and silicate ores. Many minerals contain manganese, but only a few oxides, silicates, and, in some places, carbonates (rhodecrosite) are mined as ore. Types of manganese deposits are bedded, massive,

Jan 1, 1982

By E. L. Smyth, A. Button

The apparent absence of significant Tertiary auriferous palaeoplacers in the Yilgarn Block of Western Australia can be explained by the dissolution of the placer gold into the highly saline, acid, oxidising ground waters which currently occur in upper portions of the palaeochannels proximal to the gold sources. The dissolved gold has then been redeposited in redox fronts further downstream. The placer gold is preserved in more distal portions where the ground waters are reducing. Exploration for these placers can be effective using the gravity contrasts that exist between the Tertiary sediments and the Archaean bedrock and SIROTEM which can detect the highest salinity zones which occur in the deepest parts of the channels. Final assessment of the gold content of the sediments must be determined by drilling.

Jan 1, 1989

By John Vanderwilt

THE value of molybdenum as a ferroalloy has been known for many years. For a long time, however, the metal was used only on a small scale in the iron industries, because the known source of supply appeared inadequate and the cost to the consumer was not stabilized. The world's production of molybdenum prior to 1914 was only a few thousand pounds per year and even during the war period annual production was only about 800,000 lb. Production during 1929 and 1930, however, was over 4,000,000 lb. per year and that of 1931 promises to be of the same order of magnitude. This remarkable increase in production is due primarily to the development of a large molybdenite deposit at Climax, Lake County, Colo., which has accounted for 80 per cent of the world's production of molybdenum during the past two years. Based on conservative esti-mates, the deposit at Climax has the capacity to maintain its 1929 and 1930 rate of production for 100 years or more. The production of molybdenum ores has been established on a new basis-in recent years as compared with the period during and before the world war. During the earlier period, production came from small deposits and the cost to the consumer fluctuated. At present, production comes from a few large deposits and the price is not only lower but also fairly constant. In recent years the price of molybdenum has consistently dropped as consumption increased. The present price is $0.95 per pound of molybdenum in ferromolybdenum and $0.80 for molybdenum in calcium molybdate. Before and during most of the war, Australia, Norway, and a few other foreign countries were the chief producers, while at present the United States is producing over 90 per cent of the world's production. With molybdenum available at a moderate cost, the steel industry has been adopting more and more the use of molybdenum as an alloy addition. A relatively small demand for molybdenum exists in the chemical and electrical industries, but the recent large increase in con-sumption has in large part been by the iron and steel industries, which

Jan 1, 1932

FOLLOWING the presentation at the annual meet-ing of the paper "Recent Developments in Classi-fication," by A. M. Gaudin and W. L. Remick, the discussion presented below took place: H. N. Spicer : I haven't been able to study this paper closely, but I would like to ask 'Mr. Remick something regarding the work done by the mechanical classifier. The screen test given here would appear to show that the classi-fier did very, very poor work. The 44 per cent efficiency calculated from this equation is much lower than any ordinary operation. Nothing is stated regarding the de-tails. of the operation, the slope of the classifier, the dilu-tion, the speed, and such other factors that influence results. I would also like to know something of the material that was worked. The Manhattan schist that I have seen them digging out of the subways is of a flaky nature, so that in any classifier, you might get the factor of fine flakes floating over. Was the same material used in the hydrotator test? The screen tests vary a whole lot. Mr. Remick: You will notice the Dorr classifier han-dled the circulating load. This classifier naturally was run in closed circuit. I should like to be pardoned for quoting from Mr. Bates' paper of last year on "Classifica-tion in the Witwatersrand Mills." In this report only two efficiencies were given for the so-called straight type Dorr classifier. One was 44.6 per cent and the other 61.6. I don't know whether or not an average should be taken for the proper performance. I assume that that test was performed under better conditions, yet the efficiencies av-eraged only 53.1 per cent. I am afraid I am taking the words out of Professor Taggart's mouth, but he has told me that the Dorr classi-fier at Columbia is not the proper size to work with the Hardinge mill with which it is connected. This indicates only the inadvisability of putting commercial sized mat chines in a school laboratory. You cannot, he says, get the proper tonnage from the Hardinge mill to work the Dorr classifier and get the best results. Mr. Bates' results show higher efficiency with the lower capacity. Now, on the other hand, I assume that the classifier described in Mr. Bates' paper was probably run at the proper capacity.. It is a rather puzzling question.

Jan 4, 1927

By R. J. Davidson, N. Schoeman

SYNOPSIS The paper describes each of the stages in a carbon-in-pulp (CIP) or carbon-in-leach (CIL) plant, and details the steps that can be taken to achieve effective carbon management by referring to practices at the Daggafontein CIP plant. This approach was adopted because of the difficulty in summarizing current carbon management in the many varying operations in South Africa, Daggafontein being chosen as a high-tonnage dedicated well-run plant of recent design. Because of the major role played by the consumption of carbon in the operating costs of CIP and CIL plants, an attempt is made to develop a series of indexes based on quality parameters and price that can be used as a guide In the selection of carbon.

Jan 1, 1991

By G. Barbery

A review is given of the present applications of random sets and integral geometry in fragmentation and liberation models of ores and minerals. Although attempts have been made in the past to apply such mathematical techniques to the comminution of solids, it is shown that it would not result in major progress. In liberation modeling, it is demonstrated that the approach can lead to fruitful results. Following a recent paper by Davy (1984), a model of liberation prediction is developed that can be calibrated for ore texture and breakage using image analyzers. The model is demonstrated for the case of a Poisson polyhedra ore texture and monodisperse fragment size. The model enables prediction of the complete composite particle distribution and thus is valuable for integration of ore breakage models with minerals separation models.

Jan 1, 1988

By William T. Schneider, Taylor Cole

Drilling in West Texas during 1941 was more active than in any year since 1937, a total of 2325 wells having been drilled. Pre-Permian exploration was the greatest in the history of the area; 106 wells tested pre-Permian formations during the year. Wildcatting reached the peak since 1937, with 135 wildcats, of which 20 per cent were producers. The wells were drilled to a greater average depth than in any previous year. Slim-hole drilling was the common practice, using drilling equipment that is largely portable. Because of deeper drilling, more attention was paid to mud fluids, especially the use of materials to reduce water filtration. There has been slight improvement in the protection of the pay horizons while drilling by the use of reverse circulation, and drilling-in with oil as well as low water-filtration muds. The practice of setting and cementing the oil strings through the producing formation and perforating opposite the pay zones has increased in the fields producing from sands. It is doubtful whether this practice is of unusual value in dolomitic limestone fields. There have been few if any technological improvements in obtaining necessary information on the pay sections penetrated, by coring, core analyses, better sampling, and more detailed drilling time. However, more operators are beginning to realize the necessity of good samples. For a proper study of the reservoirs in West Texas, it is essential that better samples be obtained, that more core analyses be run, and that better methods of obtaining drilling time be initiated. It should be noted that increased drilling speeds and slim-hole drilling have tended to reduce coring and core recovery and have not aided in obtaining good subsurface samples. In fact, fast drilling speeds and slim-hole drilling have reduced the cost of drilling operations, but with the sacrifice of much needed subsurface information. Larger quantities of slower-reacting acid are being used per well. There has been improvement in shooting, in that a greater number of quarts per foot have been used and an attempt has been made to concentrate the shots opposite the pay zone. The use of mud logging to determine the characteristics of the pay section increased considerably over the year 1940. There has been a slight increase in obtaining reservoir information in the new fields, such as bottom-hole sampling, bottom-hole pressures, and records of gas, oil, and water withdrawals. However, there is great need for more data on these subjects, particularly accurate information regarding gas and water volumes. There are three repressuring projects and a fourth is nearly ready for operation in the Kermit field. There is one repressur-ing project in the Payton field and one in the North Ward field. So far, the gas-injection projects have not shown very impressive results. As yet, there are no water-flooding projects or water-disposal projects in West Texas. Not including gathering lines within the fields, 222 miles of feeder pipe lines were

Jan 1, 1942

By Taylor Cole, William T. Schneider

Drilling in West Texas during 1941 was more active than in any year since 1937, a total of 2325 wells having been drilled. Pre-Permian exploration was the greatest in the history of the area; 106 wells tested pre-Permian formations during the year. Wildcatting reached the peak since 1937, with 135 wildcats, of which 20 per cent were producers. The wells were drilled to a greater average depth than in any previous year. Slim-hole drilling was the common practice, using drilling equipment that is largely portable. Because of deeper drilling, more attention was paid to mud fluids, especially the use of materials to reduce water filtration. There has been slight improvement in the protection of the pay horizons while drilling by the use of reverse circulation, and drilling-in with oil as well as low water-filtration muds. The practice of setting and cementing the oil strings through the producing formation and perforating opposite the pay zones has increased in the fields producing from sands. It is doubtful whether this practice is of unusual value in dolomitic limestone fields. There have been few if any technological improvements in obtaining necessary information on the pay sections penetrated, by coring, core analyses, better sampling, and more detailed drilling time. However, more operators are beginning to realize the necessity of good samples. For a proper study of the reservoirs in West Texas, it is essential that better samples be obtained, that more core analyses be run, and that better methods of obtaining drilling time be initiated. It should be noted that increased drilling speeds and slim-hole drilling have tended to reduce coring and core recovery and have not aided in obtaining good subsurface samples. In fact, fast drilling speeds and slim-hole drilling have reduced the cost of drilling operations, but with the sacrifice of much needed subsurface information. Larger quantities of slower-reacting acid are being used per well. There has been improvement in shooting, in that a greater number of quarts per foot have been used and an attempt has been made to concentrate the shots opposite the pay zone. The use of mud logging to determine the characteristics of the pay section increased considerably over the year 1940. There has been a slight increase in obtaining reservoir information in the new fields, such as bottom-hole sampling, bottom-hole pressures, and records of gas, oil, and water withdrawals. However, there is great need for more data on these subjects, particularly accurate information regarding gas and water volumes. There are three repressuring projects and a fourth is nearly ready for operation in the Kermit field. There is one repressur-ing project in the Payton field and one in the North Ward field. So far, the gas-injection projects have not shown very impressive results. As yet, there are no water-flooding projects or water-disposal projects in West Texas. Not including gathering lines within the fields, 222 miles of feeder pipe lines were

Jan 1, 1942