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By Joseph Hodgson

IN 1880, mining operations were commenced at the Copper Queen mine. The famous Queen orebody, which extended to the surface, was first quarried from a large open cut in the outcrop. The orebody was followed down to the 300 level with the Queen incline, and stoped. This, we believe, marks the introduction of square setting in the Bisbee district, which is still the method most generally used. Orebodies The orebodies in the Copper Queen mine occur in the limestones, and the main portion of the ore has been mined from the Abrigo, Martin, and. Escabrosa limestones. While the orebodies outcrop in the extreme western end of the mine, the general dip is to the east and south, at an angle of about 20°, although this dip is not by any means regular, being, in fact, very irregular locally. The ore is remarkable for its variableness in character, some of it being very soft, requiring a large amount of timber, and other portions consisting of extremely hard sulphides. The orebodies, in general, While remarkable for their continuity, are very irregular, both as to shape and size. The mine having been in operation so many years, and mining having been prosecuted over such a large area, the operations have caused the shrinkage of the overburden, and there is a constant movement, which is shown y large cracks and interstices in the surface rocks, which largely contribute to the very high deadwork or maintenance cost of the mine. It is surprising that for year 1913 it cost almost $400,000 just for the one item of repairs and deadwork in this property.

Jan 8, 1914

By Gerald V. Jergensen

Does an idea have merit? What does it cost to implement? Can the concept be implemented successfully? The ultimate proof is to try, then see. However, when there are many millions of dollars at stake, blindly building and trying requires considerable courage. Owners and investors in retrospect might choose other less complimentary words. So we might ask, "How might we establish the feasibility of an idea or concept before committing large sums of money to the ultimate test?" From this basic and prudent question, has evolved the engineering concept of the feasibility study. A feasibility study is simply a systematic evaluation of an idea or concept to determine the prospects for success. In a literal sense, a feasibility study considers an idea in terms of its data base, "builds" the idea on paper, "operates" that idea, calculates the cost and benefits, then measures the probable success in terms of some economic, technical or financial standard. Feasibility studies can be quite modest in scope yet provide useful insights as to the viability of an idea. A study might be initiated only to examine the completeness or validity of the metallurgical data base. Another study could be a search for a workable idea or solution to an already-identified possibly troublesome problem. In this latter case, the question, "Will it work?" may be far more important than, "How much will it cost?" Feasibility studies are sometimes global in scope, involving several dozens of specialists and examining an entire "grass roots" mining complex. Other studies may be less ambitious but equally important in examining an expansion proposal or developing new operating techniques. Studies may be commissioned to remove plant bottle-necks, solve maintenance problems and so on. The terms study and feasibility study are used interchangeably in this chapter. They denote a systematic method to examine a proposed concept or idea. DATA BASE Typically, studies are initiated with a minimum amount of specific information and a maximum number of assumptions. As the work proceeds and the data base expands, assumptions are replaced

Jan 1, 1982

By Z. F. Oszter, D. Vincent, W. K. Behrands

With the expansion of open pit operations, belt conveyors are going to be used in the 13 608 to 18 144 t/h (15,000 to 20,000 stph) capacity range, which calls for a review of some of the horsepower calculation methods. This paper presents methods (based on German research data, field tests and theoretical considerations) for the evaluation of the Ky factor in the CEMA formula for belt conveyors of large carrying capacity, which fall beyond the limits of the data given in tables in the CEMA book. (The CEMA limits are 407 N\\m (300 lb ft) and Tave = 7.3 Mg (16,000 lb). At these large loads, the impression resistance of the belting on the idlers plays a major role, which in turn influences the magnitude of the drive horse power required. An example will illustrate the order of magnitude difference of the horsepower values obtained by using a conventional calculation method and the suggested method, as well as the beneficcia1 influence of the 4-roll idler in comparison to the standard 3-roll unit for a large caving capacity belt conveyor. This paper concerns itself with the analysis of the resistance to motion of belt conveyors, emphasizing the evaluation of the frictional resistance to motion due to load and belt pressure on the idlers and the flexing resistance of the belt and material when passing over the idlers. In the case of long and heavily loaded belt conveyors, the aforementioned resistances reach extremely high values calling for close analysis of the phenomena, presently not calculable with normally used formulas. This paper establishes correlation between experimental and empirical data presenting practical formulas a tool for the designer of high-capacity belt conveyors. The application of the formula is illustrated in an example in the Appendix.

Jan 1, 1981

By T. Egleston

Although the success of metallurgical operations depends so largely on the possibility of finding proper refractory materials, which enter so prominently into the cost of their operations, it can hardly be said that our knowledge of them is in a very satisfactory condition, or even that we know very much about them, beyond a few facts which have been gathered through their use. Experience, as a general thing, is an excellent master, but the requirements of

By William G. Krantz

The increased service demands on some of the products of the National Mallcable Castings Co. prompted it about eight years ago to investigate the electric furnace, both in America and in Europe. The process had already been sufficiently developed in Europe to lead us to believe that the electric furnace would most nearly meet our requirements. After further investigation and consultation with the highest authorities on the subject, we decided upon the Heroult type as the simplest and most practicable. In 1910, we built a furnace of this type, of 300 Ib. capacity, for experimental purposes, and although it was crudely constructed the quality of the material we were able to make justified the installation of a 6-ton Heroult furnace in 1912. This furnace has three electrodes, 17 in. in diameter, uses three-phase, 60-cycle current, and is equipped with Thury regulators, which give US good regulation and a uniform load on the line even when cold melting. The power factor of the furnace is 04 per cent. Since July, 1912, the furnace has been in continuous operation, producing up to the present time over 20,000 tons of both carbon and alloy steels of varying analyses and of exceptional quality. Both cold-and hot-metal charges have been used, with a power consumption of about 150 kw-hr. per ton in the case of hot-metal charges and from 500 to 600 kw-hr. per ton in the case of cold charges. The electric energy consumed varies according to the final analysis of the steel and the amount of refining required. Too much cannot be said about the refining possibilities of the electric furnace, for no other method of steel manufacture can compete with the electric in this respect. In proper operation lies the whole secret of success. That steel has been made electrically means nothing, for when the furnace is operated under oxidizing conditions the quality is no better than that of open-hearth material; but when properly made, electric steel is as good as

Jan 1, 1916

By Parke A. Dickey

POTENTIAL differences between strata of shale and sandstone have been recognized for about 15 years, and they form the basis of the electrical logging of oil wells. Hitherto these potentials have been ascribed solely to electrochemical reactions caused by the disturbing effects of the water in the drill hole through which they are generally measured. Observations by the author in wells empty of water and in a mine shaft suggest that potential differences between sandstones and shales are natural and specific properties of the rocks, although they are modified to measurement by the disturbing effects of the water in the drill hole. The cause of these potentials probably is to be sought in the relative polar adsorptive capacities of quartz and clay particles.

Jan 1, 1944

By H. Baldauf, H. Schubert

The structure of flotation reagents is important for their adsorption on mineral surfaces and thus for their flotation effectiveness. The influence of the structure of organic depressants on the flotation of fluorite and barite with anionic and cationic collectors was investigated using a modified Hallimond microflotation cell. In addition, adsorption, desorption, and electrokinetic results were employed to further elucidate the role and the correlation of the structural parameters for adsorption and the depressing effect. As hydrophilic reagents, different aliphatic and aromatic compounds capable of forming chelates with alkaline earth materials were used. For the depressing effect, the kind, number, and position of the polar groups in the molecule, as well as the structure of the reagent films play decisive roles.

Jan 1, 1980

By E. H. Lancaster, M. E. Mitchell

A MUD-conditioning program found to be very effective for drilling and completion operations on routine field wells requiring relatively short drilling time involves a moderate alkaline-tannate-bentonite treatment resulting in an ultimate filtration rate of 10.0 cc or less (API test). Mud weight schedules are planned from pressure information on completed wells in producing reservoirs and drill-stem test data obtained on other zones not being produced at present. In general, terminal mud viscosities average 45 sec (Marsh). This value has been found to be sufficient to remove cuttings from the well bore on the average well, with the slush pumps in general use on the rigs. On field wells requiring drilling times in excess of approximately 30 days, an alkaline-tannate-lime-bentonite treatment has been effective in maintaining desirable viscosities and filtration rates with a substantial reduction in chemical costs. This system has shown particular advantage on heavily weighted muds and those with abnormal flow-line temperatures. For the most part, the chemical treatment utilized in wildcat drilling follows closely the program used on field wells, depending on depth and duration of drilling operations. Wildcat mud programs are planned from information available from various geologic and operational sources, taking into consideration the possibility of encountering mud problems of a special nature in the wildcat area. Careful planning of wildcat mud pro- grams has proved to have definite value in avoiding most serious mud problems. An analysis and recommended treatment are presented on several special. mud problems which have been encountered in the area in the past. Those problems discussed are lost circulation, blowouts, sloughing shale, excessive chloride contamination, sulphate contamination, and prevention and correction of cement contamination. Introduction Drilling-mud control in the Southwest Texas area, in general, does not involve the multiplicity of problems encountered in other coastal areas. For instance, it is rare that a mixture of problems such as lost circulation, abnormal pressure, severe sloughing shale, and others, occurs on one well within close enough limits in vertical depth not to be taken care of by a sensible casing program, together with a relatively clear-cut mud program. There are conditions such as the fairly widespread occurrence of abnormal pressure in the lower Frio and Vicksburg zones, and the tendency for sloughing shale in the Jackson section which make for rather expensive mud control. However, the availability of fairly accurate geologic and operational information makes possible a reasonable degree of standardization on mud treatment over a relatively large area. It may be said that, over most of this area where drilling is currently in progress, the natural mud made is very poor in quality, but responds readily to moderate chemical treatment to yield very good wall-building characteristics. AS far as field development drilling is concerned, the mud engineer's principal job, once the routine treatment best

Jan 1, 1949

By Robert S. Shoemaker

At this Symposium on Gold which is sponsored by The Metallurgical Society of AIME and the International Precious Metals Institute many distinguished authors will present the latest developments in the metallurgy of gold and in operating practices at mines and in refineries. It seems appropriate then, as the introduction to this volume to recall some of the history of gold and the metallurgical developments which have been accomplished, especially during the past 100 years and some of the people who have contributed so much to the metallurgy of gold. Of all the elements gold has been the most sought after since the earliest times. Perhaps the quotation from Virgil's Aeneid best describes man's desire for gold but Pliny the Elder also put it very well when he wrote in 79 A.D. that "Gold is the first of man's follies, silver the second". This quest for gold has markedly influenced man's history and through the efforts of the early philosophers and alchemists to turn base metals into gold the foundations for modern chemistry were laid. The pages of history literally teem with references to gold. Gold is the first metal mentioned in the Bible and was the source of Croesus wealth as well as the death of King Midas whose touch turned everything into gold. And of course almost everyone has heard of Jason's Argonauts and the golden fleece. They are the subject of one of the many drawings in Agricola's De Re Metallica published in 1556. The Argonauts were probably prospectors seeking the source of the placers in the region near-the Black Sea. The time was about 1200 B.C. and the placer miners recovered gold by trapping the particles in sheep's fleeces placed in sluices. After drying, the fleeces were shaken to recover the gold. Gold is not hydrophilic, or wetted by water and thus the oils in the wool aided in collecting the particles. Here we have perhaps the earliest reference to surface chemistry and the basis for concentration of gold by flotation.

Jan 1, 1984

By S. Wallden, R. Lindstrom

The electrolytic copper refining process is an excellent method for producing high-purity metal for electric conductors and other demanding applications. However, the process involves very high capital expenditure, especially the amounts of metals bound in the process. Efforts have therefore been made for many years to increase the production rate by increasing the current density, without impairing the quality of the copper. One of the approaches has been to diminish the polarization by mechanical means, while another was to "polish" the cathode surface by periodic brief reversals of the current. Reversed current electrolysis was first developed for electro- plating purposes and in 1952 Boliden AB and the Dept. of Electrochemistry at the Royal Inst. of Tech., Stockholm tested the method for copper refining with good results. However, no suitable electrical equipment for current reversal was then available. The thyristor-controlled silicon rectifier became available during the '60s and provided the scope for industrial application of the process and the first large-scale development was made by the Bulgarian copper refinery in Pirdop. Many copper refineries are now studying or adapting the reverse current process. Further lab and pilot investigations have been carried out at Boliden AB during the past 4 years and these were mainly aimed at studying the optimization of factors influencing the quality of copper. A production unit containing two tank sections with a total of 56 cells and equipped with a rectifier for cur- rent reversal has been installed and will be started during 1973.

Jan 1, 1973

By Duane E. Eubanks, David B. McDonald

The anticipated growth of western coal production over the next decade is expected to add approximately 274.3 million t/y (302.4 million stpy) to US capacity. The increased output, coming from both new mines and expansion of existing facilities, promises to bring with it a new set of problems for mine planners.

Jan 8, 1976

By Douglas R. Cook

The discovery of the gold deposits of the Jerritt Canyon district, with proven recoverable reserves in excess of 67.6 Mg (2.4 million oz) of gold, has contributed greatly to the tremendous resurgence in exploration for disseminated gold deposits in Nevada and throughout the west. The Jerritt Canyon project, including the Bell mine, is a 70130 joint venture between Freeport Gold Co. and FMC Gold Corp., both of which are wholly owned affiliates of the respective parent companies, Freeport-McMoRan Inc. and FMC Corp. The Jerritt Canyon district is located in the center of the Independence Mountains in north-central Elko County, Nevada, approximately 48 km (30 miles) northeast of the Carlin gold mine and 68 km (42 miles) north of Elko. Although the discovery of a commercial gold mine at Jerritt resulted from Freeport's exploration activities, the initial identification of a gold prospect in this area was a consequence of a program by FMC in the search for antimony. Their program was, in part, based on data in the Nevada Bureau of Mines Bulletin 61, "Antimony Deposits in Nevada." Work on the property began in 197 1 with geologic mapping followed by sampling and geochemical analyses. FMC geologists, including Robert Hawkins, Russell Hayden, and Hal Hurst recognized the striking similarity of the area to the geologic environment of Newmont's nearby Carlin gold deposit and soon focused on the gold potential. Increases in the price of gold served to stimulate interest and support for the exploration program. Geochemical samples were collected and analyzed for gold and trace elements usually associated with gold. A strong gold anomaly was found on the North Fork of Jerritt Canyon, which was called the Alchem anomaly. Drill-testing of this anomaly in 1973 revealed significant grades and thicknesses of gold mineralization in the lower portion of the Roberts Mountain formation. This initial discovery and subsequent close-spaced drilling proved the existence of several small pods of low-grade, gold-bearing material which cropped out at their up-dip edges, causing the surface anomaly. The mineralization was very encouraging, but was not, by itself, of economic importance from the standpoint of either grade or tonnage. Freeport Exploration Co. established a district office in Reno in late 1974 with responsibilities for exploration of hard minerals in the Basin and Range Province. Emphasis of the program was directed to the discovery of precious metal deposits. Enfield Bell, as District Manager for this new office, was particularly interested in the Independence Mountains and when the opportunity for a joint venture with FMC became available in 1976, it was aggressively pursued. Enfield Bell and David Stevens evaluated the FMC data and with the support of management formulated a bid in competition with 23 other companies. Freeport was selected by FMC as partner and a joint venture agreement was successfully negotiated. In mid-summer of 1976, Freeport Exploration Co. began an expanded program of detailed mapping and geochemical sampling under the direction of Bell and Stevens that led to new interpretations of the structural and alteration patterns. Hawkins' contribution during this period must be recognized since he not only was one of the original geologists assigned to the antimony and subsequently the gold investigations, but shortly after the start of the joint venture exploration, he was hired by Freeport Exploration Co. as the project geologist for the venture. Hawkins had studied the central Independence Mountains for his thesis and his understanding of the regional geology provided an excellent background for the continued exploration of the gold de- posits. His interpretation of the structure in the vicinity of the Alchem anomaly was of significant help in the Freeport exploration program. Drilling, based on this new under- standing of the geology, revealed the edge of the Marlboro Canyon ore body, which is now being exploited in the Bell mine. Although a classic bullseye geochemical target led to the discovery of the Alchem mineralization, the bulk of the reserves known today in the Marlboro Canyon area lay

Jan 1, 1985

By N. A. Richard, A. E. Austin, R. E. Maringer

AS part of a detailed study of the structure of metallic meteorites, the concentration and distribution of iron and nickel in the various phases of meteor -itic iron have been measured using an electron-probe microanalyzer. The specimen used was cut from a position about 3 in. below the surface of the Grant meteorite, a one-half-ton iron specimen (containing 9.35 pct Ni) found in New Mexico some years ago. A photomicrograph showing the general Widmanstztten structure, somewhat typical of iron meteorites, is shown in Fig. 1. The line across which the analyses were made is indicated by arrows. This area was chosen so as to evaluate the iron-nickel concentration in the three principal phases visible in Fig. 1. These phases, in the language of meteoritics, are kamacite, taenite, and plessite. Kamacite is the a-

Jan 1, 1960

By C. R. Schumacher, W. H. Moyer

Cornwall, Pa. magnetite ore, containing recoverable sulfides in the form of chalcopyrite and pyrite, has been mined continuously since 1742 1 Beneficiation of the ore was begun in 1905, at the Lebanon concentrator located six miles from the mine. At first, only magnetite was recovered, using Grondal magnetic separators. In 1907, copper minerals were recovered by means of Wilfley tables. Copper flotation, attempted as early as 1912, was finally successful in 1919. In 1940, flotation of the cobalt- bearing pyrite was begun, and Cornwall ore became the major domestic source of cobait for many years. In 1916, the Bethlehem Steel Corp. began to purchase interests in the Cornwall mine and Lebanon concentrator properties, and by 1926 had acquired complete ownership. Metallurgical practice at the old Lebanon concentrator was good, but by today's standards the plant was outdated. The flowsheet was complex, due both to the mineral content of the ore and to the low capacities of much of the equipment. As the flowsheet developed, buildings were added and the plant was spread over a relatively large area, with resulting high manpower requirements. Another disadvantage was the six-mile rail haul from the mine to the Lebanon concentrator.

Jan 3, 1966

By H. M. Conger

Kaiser Steel Corporation's Eagle Mountain mine is located in the Colorado Desert, 60 miles east of Indio, California. Iron concentrates from the mine are shipped by rail 164 miles to the' Company's steel mill at Fontana, and also to Longbeach, California for export. Temperatures are typical of the lower desert ranging from a high of 120 degrees in the summer to a low of 25 degrees in the winter. The average, annual rainfall of about two inches comes mainly as cloudbursts during the summer months. From its inception, the Eagle Mountain mine has had the problem: of breaking its mine rock. Practices followed from 1949 until 1962 were very costly, did not produce uniformly good fragmentation, and were incapable of sustaining, high production. During this period, every conventional type of explosive was tried and found to be unsatisfactory for one reason or another.

Jan 11, 1965

By O. J. Kensok

THE literature contains three previous studies of the chemical activities of Cd-Mg alloys: Trumbore, Wallace, and craigl obtained chemical activities of magnesium at 543" by performing electromotive-force measurements; Borg and irchenall calculated activities at 590°K based on vapor-pressure measurements of cadmium over Mg-Cd alloys by the Knud-sen effusion method; and Terpilouski and arcka measured the chemical activities of magnesium in the liquid state by means of electromotive-force measurements. In this study the vapor pressure of cadmium was determined over nine solid Cd-Mg alloys in the temperature range 571" to 697°K by the Knudsen effusion method. This study was prompted by the lack of precision in the data reported by Borg and Birchenall. Knudsen cells used during this study were fabricated from 0.020-in.-thick tantalum tubing. The tops and bottoms of the cells were cut from 0.010-in.-thick tantalum sheet, press-fitted, and welded in place. The orifice was drilled in the cell top and subsequently reamed to a knife-edge thickness. The diameter of the orifice was measured with a traveling microscope capable of reading 0.0001 cm. The sample was heated by means of a resistance

Jan 1, 1967

By O&apos, R. G. Meara, G. D. Coe

PRIor to the World War most of the barite used in the United States for manufacturing lithopone and barium chemicals was imported. Germany, by virtue of an abundance of high-grade ore and low labor costs, was in a position to dominate the world market. With the cessation of imports and with the war demand for barium chemicals, the barium chemical industry and the mining of barite became well established in the United States. This industry has continued to expand because of the increasing use of lithopone. In 1914 the sales of domestic crude barite was 52,919 tons and in 1934 it was 209,850 tons. Barite deposits of economic importance occur in at least 20 states, but the principal producers in 1934 were Missouri, Georgia, Tennessee, South Carolina, Virginia, California and Arizona. The main mining centers are located near the crude barite markets of the three principal marketing districts—the Pacific Coast, the Midwestern area, and the Eastern area. The Pacific Coast is supplied entirely by California, Nevada, and Arizona. The Midwestern area uses most of the Missouri crude and a small amount from the southern states. The eastern market is the chief competitive area. Practically all of the imported crude is marketed there; also the bulk of the southern crude and ground barite. In addition, this area absorbs a small part of the Missouri crude and 80 per cent of the ground barite. Besides the advantage of low delivered costs and purity of product, the imported barite has commanded a price differential because it is soft rather than hard, like many of the domestic ores. The inherent physical properties of the southern ores remain, but the purity can be controlled to a great extent by beneficiation. Simple washing or gravity concentration has sufficed in the past, but in many cases a more efficient process now becomes imperative to remove impurities not amenable to these methods. Certain deposits now being opened are of lower grade and require more precise milling conditions. In some ores, the kind of impurities has changed as the mining advanced.

Jan 1, 1938

By G. D. Coe, R. G. Meara, O&apos

PRIor to the World War most of the barite used in the United States for manufacturing lithopone and barium chemicals was imported. Germany, by virtue of an abundance of high-grade ore and low labor costs, was in a position to dominate the world market. With the cessation of imports and with the war demand for barium chemicals, the barium chemical industry and the mining of barite became well established in the United States. This industry has continued to expand because of the increasing use of lithopone. In 1914 the sales of domestic crude barite was 52,919 tons and in 1934 it was 209,850 tons. Barite deposits of economic importance occur in at least 20 states, but the principal producers in 1934 were Missouri, Georgia, Tennessee, South Carolina, Virginia, California and Arizona. The main mining centers are located near the crude barite markets of the three principal marketing districts—the Pacific Coast, the Midwestern area, and the Eastern area. The Pacific Coast is supplied entirely by California, Nevada, and Arizona. The Midwestern area uses most of the Missouri crude and a small amount from the southern states. The eastern market is the chief competitive area. Practically all of the imported crude is marketed there; also the bulk of the southern crude and ground barite. In addition, this area absorbs a small part of the Missouri crude and 80 per cent of the ground barite. Besides the advantage of low delivered costs and purity of product, the imported barite has commanded a price differential because it is soft rather than hard, like many of the domestic ores. The inherent physical properties of the southern ores remain, but the purity can be controlled to a great extent by beneficiation. Simple washing or gravity concentration has sufficed in the past, but in many cases a more efficient process now becomes imperative to remove impurities not amenable to these methods. Certain deposits now being opened are of lower grade and require more precise milling conditions. In some ores, the kind of impurities has changed as the mining advanced.

Jan 1, 1938

By E. H. Bronson

PROPERTY of Malartic Gold Fields Ltd. is situaated in the great clay belt in the northern part of the Province of Quebec. This belt represents the floor of the glacial lake Barlow-Ojibway. The clay blanket has a gently rolling, almost flat surface, with here and there projecting knobs and ridges that outline the large irregularities of the surface on which the clay was deposited. At irregular intervals glacial eskers dominate the landscape. The ore-bearing country rock is covered by strata of clay, sand, and silt to a depth varying to 40 ft. There are serious structural problems when it is necessary to place loads of unequal intensities on this surface to support buildings and machinery for a modern mining plant. Earlier mining companies and their engineers paid little attention to the science of soil mechanics, partly because they believed it unnecessary and partly because they knew little of the subject. The results are evident in some of the tottering structures in older camps. Careful analysis of soil problems is well worth-while, since cost of foundations may vary from 20 to 50 pct of the final cost of a structure. Low operating and maintenance costs can be achieved only in this way.

Jan 11, 1957

By L. W. Pommier, F. B. Brien

In order to determine the ability of cyclones with heavy liquids to preconcentrate ores, a study of the variables which govern the behavior of the solids in the apparatus has been made. To assess the test results, the cyclone products have been examined by sink and float analysis at various specific gravities and the results examined by the Tromp type curves. This analysis has allowed the development of the SG50 unit — specific gravity of the particles, 50% of which goes to overflow and 50% to underflow — rather than the d50 (size) unit used in classification. The results of tests using the closed circuit laboratory cyclone assembly with dry feed samples show the validity of the equation: Results indicate that 83% of the feed may be rejected containing 0.1% Sn. Recoveries in excess of 80% are obtained at a grade of 1.7% Sn from feed samples assaying 0.4% Sn. As water-wetted particles may comprise the plant feed, separate tests were performed to examine the effect of water in the feed material. Results indicate that the entrained water divides into two fractions, one of which is defined as free water and is rejected to the cyclone overflow, the other fraction forms an adhering envelope of water on the ore particles, altering their effective size and density. The presence of the envelope of water on the particles increases the ease with which the heavy liquid can be recovered but decreases the concentration efficiency. It is proposed that the detrimental effect of water in the cyclone may be minimized by using a higher feed pressure cx by the use of surfactants. A higher feed pressure, by increasing shearing forces, would reduce the thickness of the water envelope on the particles. The surfactants, by adsorbing on the particles and producing hydrophobic surfaces, would displace the water envelope and allow the heavy liquids to wet the modified surfaces. In both cases a larger proportion of the entrained water would report to the cyclone overflow as free water, thus minimizing the detrimental effect of water on the concentration efficiency. Additional testing is required on the behavior of water in the system; to determine the optimum particle size for the preconcentration step; to determine final particle size for optimum liberation and subsequent treatment of the products in present plants and to determine the efficiency with which the heavy liquids may be recovered from the products. For many years tin mining in Bolivia has been very important to the economy of the country. In recent years the tin content of the ore reserves has been steadily declining. An improvement in concentration efficiency is highly desirable in order to increase productivity from the present low-grade mine ores and to allow retreatment of the many millions of tons of tailings from past operations, some of which equal the present ores in tin content. A number of investigators have been or at present are working on various phases or approaches to the problem. Gravity concentration is used in Boliva today as it has been in the past to recover tin minerals from the mine ores. An objective of the work reported in this paper was to examine the possibility of treating present low-grade ores and sink-float tailings products, at a relatively coarse grind, in order to produce a higher grade feed material to the present gravity concentration plants. The possibility of using heavy liquids in cyclones to treat large tonnages with a minimum of outlay presented itself and is of particular interest since heavy liquids are now available with physical properties which lend themselves to simple recovery methods. Tests were carried out using a closed circuit laboratory cyclone assembly. It was desirable to determine the value of using the SG50 concept and Tromp curves for analyzing the cyclone concentration test results. The effects of entrained water on the behavior of ore particles in the cyclone were examined. THEORY AND TECHNICAL CONSIDERATIONS Three types of heavy liquids are available: aqueous solutions of very soluble salts, salts or mixtures of

Jan 1, 1964