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By H. A. Doerner

The Rare and Precious Metals Station of the U. S. Bureau of Mines has investigated several cases in which widely divergent amounts of molybdenum were reported by a number of custom laboratories to which quartered portions of the same sample had been sent for analysis . On an oxidized lead ore containing considerable vanadium and a little molybdenum , the amount of the latter reported ranged from 3.14 to 0.24 per cent M003 . The high results were due to the fact that vanadium was estimated with , and reported as , molybdenum . When analyzed by the method described in this paper , 0.15 per cent Moog was found, which is a fair agreement with the lowest figure previously reported . In another and more unusual example , a fine- grained rock containing considerable graphite was submitted for analysis . As a white residue could not be obtained by treating this material with acid , several chemists decomposed the ore by a prolonged fusion with soda ash and nitre and leached the melt with hot water in crder to insure the dissolution of any and all the molybdenum present . After precipitating and filtering the silica from the solution , acetic acid , ammonium acetate , and lead acetate were added to precipitate lead molybdate . The solution contained phosphorous derived from the ore , which precipitated as lead phosphate . The latter was mistaken for , and reported as , molybdenum. As two different chemists used essentially the same procedure , their results , although incorrect , checked . Other chemists using different methods found no molybdenum . From these and other instances it is evident that reputable and conscientious assayers may make serious errors in determining molybdenum, and even duplication of results by different chemists does not necessarily insure against error . The elements most likely to cause trouble are vanadium, tungsten, uranium , arsenic , antimony , titanium, tin , phosphorous , and chromium . The precautions necessary to eliminate these and other impurities vary with the type of ore and the method of analysis . Most texts present methods of limited application and omit or fail to emphasize adequately such precautions . No one method can be given that will best fit every case , but the following procedure has been selected as being the simplest reliable method for such occasional determinations of molybdenum in an ore as are encountered in customs work.

Sep 1, 1930

By W. C. Phalen

"The Phosphate Rock Market:Indications, in the fertilizer market, point to a prosperous condition, caused chiefly by the growing demand for all classes of fertilizer material in spite of a shortage of supplies. Both of these conditions have been caused by the war. The shortage in phosphate rock is being relieved as production increases, but the supply has not caught up with the demand for this spring's trade, at least. Reports from Florida are to the effect that more than half the necessary quota of laborers are at work. This may not appear to be a very good showing, but even this situation is en¬couraging because there is a larger force now at work than has been the case for some time, and it is steadily, though slowly, increasing. Some of the producing companies are conducting advertising campaigns to get laborers back to the phosphate fields and attractions in the way of better housing and living conditions are being offered.Producers are far more confident about the situation than they were two months ago, and though the shortage will not be met before the end of 1920, theme is a surplus accumulating over what is going out on existing contracts.Quotations are now being offered on all Florida rock excepting land pebble and this, it is expected, will be soon quoted.Quotations on Florida rock per ton are as follows:"

Jan 1, 1920

By D. C. Rotherham

The Kidston gold discoveries were originally made about 1907, and by 1934, 1.76 Mg (62,000 oz) of gold had been produced from placer and lode mining of higher grade, most¬ly oxidized gold ore. As mining in the lode ore penetrated deeper, costs increased and the world gold price stagnated. The lode or underground production averaged close to 6.9 g/t (0.2 oz per ton) Au for the 201 kt mined. No mining or development took place from 1934 until 1965. Kidston's high grade ores were exhausted by 1934. From 1965 to 1976, exploration had developed 3 Mt of about 3 g/t (0.88 oz per ton) Au. Placer Pacific acquired rights to the property in 1976 and began a geologic and engineering study of the district. It was clear that the deposit had the potential for becom¬ing a large-tonnage, low-grade producer. However, explora¬tion had to discover the tonnage and grade and engineering needed to solve the obstacles of production costs. Bulk material handling problems were addressed by Placer's wide experience in open pit mining, and the increase in work index accompanying deeper ores was handled by Placer's metallurgists. The matter of power for the operation was solved by engineering studies. These showed that power could be generated and brought in economically. The price of gold also increased after 1976, and this helped in the economic analysis. The Kidston discovery since 1976 is really a combination of good exploration geology and careful engineering plan¬ning that overcame the obstacles presented by ore characteris¬tics and the location of the deposit. The attached paper by Harry Mustard is an extract of his honors thesis and explains the deposit geology.

Jan 1, 1990

By W. E. Keck

THE flotative properties of the principal minerals in Michigan's potential iron ores have been investigated to develop methods of bene-ficiation for the ores. One of these minerals, magnetite, is of considerable importance as a source of iron. Study of its flotation was similar to that of hematite1, another iron mineral in these potential ores. The present research consisted essentially of: (1) a survey of the literature on mag-netite flotation, (2) the preparation of pure magnetite, (3) the develop-ment of laboratory procedure and (4) flotation experimentation. Literature an Magnetite Flotation.-For the purpose of this discussion, the results of previous work on the flotation of magnetite can be sum-marized as follows. The mineral has been floated with pine oil2, and it has also been separated from synthetic mixtures with silicates by the use of the same reagent2. Magnetite and apatite in iron-ore slimes have been separated by flotation of apatite with sodium palmitate3. These data were utilized in the present investigation. Preparation of Magnetite.-The pure mineral was prepared from the magnetic-separator concentrate of an iron ore (obtained from the Wither-bee Sherman Corporation, Port Henry, N. Y.). This concentrate was slowly comminuted with laboratory rolls and pulverizer to pass 65 mesh and was then tabled several times. Tabling yielded a relatively coarse magnetite concentrate, tailing and slimes. The two latter materials were rejected insofar as the present work is concerned, and treatment of the magnetite (table concentrate) was continued by separating it into -65 + 200 and -200-mesh sizes. Separation of the sizes was made by first dry screening and then wet screening. The -200-mesh material was rejected to eliminate possible introduction of error into flotation

Jan 1, 1937

By J. F. Blandy

IN October last, I was call upon to examine a copper deposit in the South Mountain, near the Pennsylvania and Maryland boundary. The specimens shown me contained oxides and carbonates with native copper, and were similar to some that had been described to me some years ago as existing at the Luray Gap in Virginia. An examination of Rogers's Report on the Geology of Pennsylvania, led me to expect to see his so-called "Primal Formation," such as exists throughout the southeastern district of the State. I was therefore much surprised on arriving at the summit of the Western Maryland Railroad to find myself on familiar ground. Instead of the "Primal" as I had known it in Southeastern Pennsylvania, I soon decided that the rocks were identical with the "Lake Superior Copper Formation." My visit was unfortunately a short one, part of two days, and in that time I had to pass over a good many miles, but I saw sufficient to convince me that instead of the Lake Superior Copper Formation being a local geological feature, it would have to be considered as a widely extended series of rocks. I was unable to even approximately estimate the thickness either of the trap zone or other members, schists and slates, of the series. In an article on the Copper Range of Michigan, prepared by C. P. Williams and myself in 1862, and published, in vol. xxxiv of the American Journal of Arts and Sciences, we endeavored to divide that range into zones, according to the character of the traps. The limited nature of the explorations at that time made this work very imperfect. Subsequent explorations have confirmed my notes then

Jan 1, 1879

By S. F. Shaw

IN 1913, the Tiro General mine, at Charcas, S.L.P., Mexico, which had been making from 125 to 150 gal. of water per min., was allowed to become flooded, after all the pumps had been removed, and in 1918 the problem of unwatering it came up for solution. There are two vertical shafts, the Tiro General, 1390 ft., and the San Fernando, 1225 ft. in depth, with five connecting levels between them. The San Fernando shaft had been partly retimbered, while the Tiro General had been newly timbered from the collar to, 1090 ft. in depth. It had been possible to place guides in only one compartment of the Tiro General, from the collar to the seventh or 850-ft. level, to which it was necessary to lower the water before station pumps could be installed. Soundings indicated that compartments in the Tiro General were open to 1082 and 428 ft., and in the San Fernando shaft to 471, 488, and 586 ft. The water had risen to a point 140 ft. below the collar of the Tiro General shaft. PUMPING EQUIPMENT The steam plant at the Tiro General shaft includes one 300-hp., one 150-hp. and one 100-hp. Erie City water-tube boiler, and two 160-hp. Heine water-tube boilers. All but one of these boilers were supposed to be in good shape, but it was soon discovered that six years of idleness in a climate that is foggy for several months of the year had left them in poor condition. The compressed-air plant comprises one Nordberg cross-compound compressor with piston displacement of approximately 2500 cu. ft. of free air compressed to 96 lb. per sq. in.; and another Nordberg cross-compound with piston displacement of 1235 cu. ft. of free air, to the same pressure.

Jan 2, 1920

By Kim H. Shikaze, John R. Hawley

"Even though acid mine drainage is an old problem, particularly in coal mining areas, its appearance in the form of a major environmental hazard in the hardrock mining districts of Ontario was unexpected. The yellow and amber coloured wastes that characterize an acid mine drainage situation were first noted by the Ontario Water Resources Commission in the uranium mining Elliot Lake district. Problems of a similar nature were also noted in the copper-lead-zinc camp at Manitouwadge, the nickel camp at Sudbury and at numerous isolated base metal properties, both in and out of the Province of Ontario.Without exception, when acid mine drainage type effluents were evident, the specific companies involved worked sulphide or sulphide-associated ores. Without exception, the ore bodies contained quantities of iron sulphide (in various mineralogical forms) and, without exception, the milling circuits serving these operations were such that the iron sulphides were rejected to the tailings areas as waste.Once in a tailings area and after a varying period of time, iron sulphides react to form water soluble salts which, when discharged in the effluents from the tailings area, can affect stream chemistry and stream ecology.It is not unusual that the minerals pyrite, marcasite and pyrrhotite (all iron sulphides) react to form a stable oxide under atmospheric conditions. The law of stability of rocks and minerals, for instance, states that rocks and minerals are stable only in the environment of their formation and, as the environment surrounding them changes, the rocks and minerals tend to change to other species which are relatively more nearly stable under the conditions of the new environment (a). Under atmospheric conditions, iron oxide exhibits a greater stability than iron sulphide."

Jan 1, 1971

THE problem of reaction rates in the open-hearth process is essentially that of trying to form a fairly clear picture of the "chemical mechanisms" in the bath. Quantitative data on reaction rates would not be very useful even if they were available; however, what few , approximate data there are, can be used in combination with data given in Chapters XVI and XVII to sketch a picture of the "chemical mechanics" of the open-hearth process that is consistent with essentially all the present available evidence. The result may later be found incorrect in many details but even so it will illustrate certain useful methods for obtaining a clearer understanding of the process. As discussed in the last portion of Chapter XIII chemical reactions in general involve the following factors: 1. The reacting molecules are mixed together in space in such fashion as to favor collisions among them. 2. A certain number of collisions occur per unit time among the reagent molecules, depending on their concentration and on temperature. 3. A certain percentage of these collisions result in reaction, these being the collisions between those molecules possessing at the moment energy levels above certain minimum values. The temperature factor enters mainly through (3), and its effect is very marked. (What is called temperature is really the mean energy content of all the molecules of the substance involved; at any one temperature a certain proportion of the molecules will have much higher energy content than the mean value.) Various reaction rates measured at around room temperatures have been found to be speeded from 1.6 to 4.0 times by an increase of only 15 to 20°F., simply because increasing temperature produces a rapidly increasing percentage of molecules with energy levels above the minimum needed to produce chemical reaction in a collision.

Jan 1, 1944

By J. Stoll

In May 1998, Hanson Aggregates Midwest, as an outcome of mine planning, offered a 10-acre tract of land containing the famed fossil-bearing Silica formation, to the City of Sylvania, OH. in the form of a 99-year lease agreement. The Olander Park System, and Ohio code park operating within Sylvania Township, was then approved by Hanson and the City to manage and fund the park. All parties signed the lease in August of 1999. In November 2001, local residents voted to fund the park by a margin of 2 to 1. The park will consist of a shallow (approx. 20 ft.) former cement production quarry that is 700 ft. long by 300 ft. wide. Hanson’s motivation and vision for the park was fivefold: 1) the site was located away from long-term reserve access; 2) it would serve nicely as buffer property for the active quarry; 3) it had become an area of illegal dumping by locals in the past; 4) trespassing and safety issues would be limited by allowing supervised usage; and 5) the shallow outcropping contains the world famous, fossil-bearing Silica shale. Hanson will supply shale to the park perpetually via stripping activities in the process of uncovering quality construction aggregate limestone and dolomite reserves. Thousands of enthusiastic fossil hunters have already combed throughout the shale in their quest for “treasures”. The park’s master plan also features nature trails, picnic areas, a fossil-themed play area, amphitheater, visitor’s center and gift shop. Given the natural and people resources that Sylvania Fossil Park will have to offer, Hanson is confident that it will become the premier invertebrate fossil hunting site in the United States. It will also remain a solid community relations vehicle for years to come.

Jan 1, 2003

By Sterling G. Valentine

Until within late years, the preparation of sulphurous ores for the blast-furnace has received comparatively little attention. After the first improvement made on the old style of heap-roasting and roasting between walls, there has followed an almost general adoption of the Gjers kiln or some modification thereof, and the majority of iron-masters have seemed perfectly satisfied with so much progress. However, the Westman kiln was developed in Sweden, and other gas-roasters for sulphurous ores have been since constructed. They are in use on the continent of Europe and in America to a limited extent. The following experiments were made in order to furnish additional information as to the proper conditions for the elimination of sulphur from ores where it is present as sulphide of iron, FeS2 I desire here to acknowledge the Kindness of Dr. Franklin Menges, of the laboratory of Pennsylvania College, at Gettysburg, Pennsylvania, for lending his valuable aid in carrying out a part of these experilnents and analyses. In the first series of these experiments, pure, roughly-pulverized pyrites crystals were used, containing 53.42 per cent. of' sulphur. They were made with a view to determine the effect on pyrites, of heat alone, in various degrees of intensity and duration, air being altogether excluded. The heats at a low temperature were made in glass combustion-tubes, sealed at the end, where the pyrites to be tested were placed, and with only a small opening at the opposite end. Although not allowing circulation, this arrangement still permitted a part of the evolved sulphur to escape. The heats at high temperatures were made in Hessian and graphite crucibles, tightly luted, every precaution being taken to exclude air. The temperatures attained are given approximately, and are as nearly correct as it was possible to estimate them, using Pouillet's scale as a guide.

Jan 1, 1890

By George Smith

TWELVE years ago, the Director of the United States Geological Survey addressed to the Secretary of the Interior a letter calling attention to the government's need for liquid fuel for naval use and pointing out that the rate of increase in demand was more rapid than the increase in production.1 This letter, in a way, inaugurated the policy of public oil-land withdrawals, which was well founded in its primary purpose of protecting the oil industry and highly desirable in its immediate effect of checking the over-development of that day in California. Unfortunately, however, through delays in legislation, this policy may be regarded now as having outlived both its intent and its usefulness. In 1908, the country's production of oil was 178,500,000 bbl., and there was a surplus above consumption of more than 20,000,000 bbl. available to go into storage.: In 1918, 10 years later, the oil wells of the United States yielded 356,000,000 bbl.-nearly twice the yield of 1908-but to meet the demands of the increased consumption more than 24,000,000 bbl. had to be drawn from storage. Nor is this all of the brief comparison. In 1918, our excess of imports over exports of crude petroleum was nearly 33,000,000 bbl. whereas in 1908 we exported 3,500,000 bbl., which was net, as we had not begun to import Mexican oil. In this period, the annual fuel-oil consumption of the railroads alone has increased from 16,871,000 to 36,714,000. bbl.; the annual gasoline production from 540,000,000 gal. to 3,500,000,000 gal. This record may be taken not only as justifying the earlier appeal for Federal action, but as warranting deliberate attention to the oil problem of today.

Jan 1, 1920

By Aloys H. Wohlrab

[THE conditions that govern the selection of a suitable type of detachable bit for the small isolated mine, for rock work and tunnel contracting and for the large mine are quite dissimilar, therefore intelligent recommendation of a particular make of detachable bit must involve consideration of many factors. Small, isolated mines may find advantageous a detachable bit that a larger mine cannot afford to use, because of more efficient conventional steel sharpening and steel-distribution practice, but a small mine may of be able to adopt the practice of larger mines because of necessary capital expendites for equipment for detachable-bit sharpening and shanking. The perfect detachable bit, suitable for all conditions, has n yet been developed. CONVENTIONAL DRILL BIT IN USE That drilling speed increases as the hit gauge decreases is well known, but since small-hole drilling is the exception rather than the rule the rate of such increase is probably not so generally recognized. Tests married out by Holman Brothers Limited1 with 7/8-in. show that when bit sizes are reduced from. 1 ½ in. 1 3/8 in., and 1 3/16 in., to 1 3/8 in., 1¼ in., and it' in., respectively, the volume of the hole is15 per cent less and the drilling speed 4q per cent higher. Recent tests by the United States Bureau of Mines2,3in hard, uniform basalt showed that a reduction in average gauge from 2.077 to 1.826 in., a difference of 0.251 in., gave an increased drilling speed of 65 per cent. The limits to which a drill hole may be extended depend upon the loss in gauge. Since the conventional bit with 5° and 14° clearances did not possess sufficient reaming edge to permit the smaller gauge changes that were required for small-hole drilling, experiments were made in bit construction with a view to correcting this deficiency. This resulted in the adoption of the full reaming cross bit (having full Carr characteristics) by some mines.4 In order to drill holes having a minimum taper from the collar to the bottom of the hole, full reaming center-hole cross bits with 90° cutting angles, 5° and I4° wing tapers, forged on 7/8-in. quarter-octagon drill rods, are used in the conventional drill-steel practice at Hollinger. In the steel shop close attention is given to the condition of the dies and dollies, which, combined with a rigid inspection of the finished bit, ensures as nearly a perfect bit as can be forged economically. Shop practices and costs have been discussed in earlier papers.5,6 The method by which the radii for the special dies used for forging bits of different gauge diameter are obtained so that the points and reaming edges cut circles of the same diameter has been discussed by Hibbert.7 REQUIREMENTS FOR DETACHABLE BIT FOR HOLLINGER Under these circumstances, it was apparent that it would be difficult to introduce a detachable bit that could successfully compete with the conventional bit already in]

Jan 1, 1942

Joseph E. Thropp, Jr., Indiana Harbor, Ind.:—To what do you attribute the fact that in some localities the by-product coke sells at a premium over the ordinary bee-hive coke for foundry use ? If the cell-structure is preferably soft and rather thick in coke for foundry use, as I understand it, do you mean that by-product coke has soft and thick cell-walls ? William H. Blauvelt, Syracuse, N. Y.:—As I say in one of the paragraphs of my paper, the tendency seems to be towards the manufacture of foundry- and furnace-coke under somewhat different conditions. The development of the best cell-structure in coke, of course, has not reached perfection, but we are making progress, and we are inclined to believe that under ordinary conditions the best furnace-coke, that is, coke with the hard cell-wall and the well-developed cell, is produced at fast coking-time and high heats, whereas the best foundry-coke seems to be produced at somewhat lower heats. In one of our plants we are making furnace-coke in 16-hr. coking-time, and foundry-coke in 20-hr. time. Foundry-men want the strong, tough coke. I think the furnace-men present will agree that the best furnace-practice requires a hard coke, with a well-developed cell-structure. Replying to the question as to the reason for higher prices being realized for by-product foundry-coke than for bee-hive coke, of course, the immediate reason is that it suits the foundry-men better. Perhaps one cause may be that we are able, by the selection of coals, which is not usually practicable at bee-hive plants, to get a quality and analysis best suited to foundry-work, with high carbon-content, and with cell-structure and physical strength especially suited to the foundry-men's ideas.

Jan 1, 1913

By Lester G. Morrel

THE RICH and varied occurrences of metallic ores in Australia, extensive nickel deposits on New Caledonia and phosphate rock on several widely scattered small islands were important aspects of the economy of the South Pacific area. Relatively small quantities of gold and nonmetallic minerals produced in New Zealand, Fiji, and the Territory of Papua-New Guinea remained important to the domestic economies of these islands, but had little importance to overall world mineral supplies. The value of mineral commodities produced in this area in 1964 was estimated at $658 million,3 compared with $585 million in 1963. The year's greatest commodity gains were in bauxite and aluminum, beryl concentrate, manganese ore, nickel smelter products, tin, and coal. Annual increases were recorded in virtually all countries and possessions in the area except Papua-New Guinea, where the drop in output of alluvial gold accounted for a decline of about $160,000. Mineral industry activities in Australia overshadowed those in all other parts of the South Pacific in 1964. Outstanding developments were the sales contract negotiations and physical preparation for exploiting the rich iron ore discoveries in Western Australia, the initiation of domestic crude oil production, the commissioning of two new steal mills and an alumina refinery and a start on the new alumina-aluminum project based on Cape fork bauxite deposits. The principal mineral development in 1864 in New Zealand was the progress on plans of the Newzealand Steel Co. to use indigenous iron sans as the resource base for a local steel industry. In New Caledonia, additions and expansion of the nickel mining and smelting facilities continued throughout the year. Plans for extensive geophysical studies were announced by the Government Geological Departments of British Solomon Islands and Fiji.

Jan 1, 1966

By Tomoyuki Moritani, Atsuyuki Mizuno

A concentration of manganese nodule varies areally from 0 to 30 kg/m2 in the central-eastern deep sea bottom of Central Pacific Basin with depth of 5,600-5,900m, but generally it is low, mostly of the abundance order from 0 to less than some kilograms per square metres through the bottom. A high concentration over about l0kg/m is localized to the northwestern basin, besides "St. 414 Deep Sea Hill" and “GH 76-1 Trought”, and also it is likely related with the substratum of deep sea clay. Nodules are tentatively classified into nine types of Sr, SPr, SEr, Db, Ss/SPs, ISs, IDPs and V, in terms of morphology and surface feature. The types may be related with internal structure, nuculeus, mineral composition, chemical composition, occurrence and areal distribution, and might have resulted from various environmental factors of nodule genesis. The abundance of nodule at each station shows the interesting relation with acoustic records by 3.5KHz and seismic reflection profilings. In both the records, thick transparent layer over about 45m thick yield neither any nor significant amount of nodule. The layer less than 45m relates with abundant nodules up to 30kg/m2, though it yield also very little nodule in some cases. The relation suggests that the formation of nodule most likely could be related with the accumulation rate of the post-middle Eocene sedimentary sequence to some extent and also with other controlling factors. The relation can lead us to the tentative delineation of distribution of nodule deposits in the area. The comparative-consideration with the deposits in GH 74-5 area, just east- ward of the present area, shows the areal peculiarity of nodule genesis in deep sea bottom. The results of chemical analyses will be discussed elsewhere.

Jan 1, 1976

By M. Yavuz

Multiple Criteria Decision Making (MCDM) is one of the most considerable branches of Operation Research. MCDM refers to making decisions in the presence of multiple, usually conflicting, criteria. The problems in MCDM are classified into two categories: Multiple Attribute Decision Making (MADM) and Multiple Objective Decision Making (MODM). However, very often the terms MADM and MCDM are used to mean the same class of models and mostly confused in practice. Usually, MADM is used when the model cannot state in mathematical equations and otherwise MODM is used (Hwang and Yoon, 1980). Decision-making (DM) is extremely important stage in Mining Engineering like other engineering branches. Every mining engineer makes several decisions in daily mining applications. Most of the decisions made by mining engineers are completely instinctive according to their past experiences and there is not any DM method applied in DM process. Analytic Hierarchy Process (AHP) is one of the well-known techniques solving the decision problems. The AHP is very simple, and understandable method especially non-numerical data considered in DM process. Equipment selection is one of the prominent problems of mining engineering. Mining engineers have to make difficult decisions when equipment selection stage. As the decisions in the equipment selection have radically influenced the economic life of any mining scenario, these are considered as complex MADM problem. So, the decision maker can evaluate the subjective criteria in the problem of equipment selection. The decision maker wants to maximize more than one objective criterion for equipment selection stage. Among the number of alternatives, the most suitable equipment must be selected according to objectives and alternatives. MADM applications can help the decision maker to reach the optimal solution for the equipment selection. In the mining industry, MADM methods can be applied for the equipment selection because it is a process that includes subjective and objective criteria affecting the selection of equipment among the alternatives.

Jan 1, 2007

By G. A. Kosick, M. Freberg, L. A. Kuehn

"Highly variable and higher than forecast lead miff feed grades were problems experienced at the Polaris Concentrator. Limited flotation capacity and poor operating flexibility prevented the plant operators from overcoming these difficulties, and resulted in grades and recoveries which were lower than necessary.Two column cells were integrated into the lead circuit in an effort to give the operators the tools they required to achieve the best grades and recoveries possible, regardless of the miff feed grade. Installation of the column cells increased lead concentrate grade from 76% to 79.3% Pb, and increased lead recovery from 9/% to 91.3% Pb.This paper reviews the design, development and operation of column flotation cells in the lead circuit at the Polaris Mine.IntroductionThe Polaris Concentrator was constructed in 1980 on a barge in Trois Rivieres, Quebec, and towed to its pre sent location on Little Cornwallis Island, Northwest Territories, about 1450 km from the North Pole. The plant presently treat s about 2800 mtpd of new feed with average feed grades of 3010 Pb, 13% Zn and 5% Fe. Current production averages 36 000 tonnes of lead concentrate and 220 000 tonnes of zinc concentrate annually.The barge design and min e location dictated that the concentrator .be compact with very little unused floor space. As a result, flexibility was limited in terms of expanding the plant.Mill feed grades were highly variable and above forecast and the lead flotation circuit was found to be under capacity. This caused continued overloads in the lead cleaning circuit, resulting in low concentrate grades and recoveries. It was evident that an increase in lead flotation capacity and flexibility was necessary. The existing floor space did not allow for the installation of additional conventional flotation cells, but one alternative was the installation of column cells."

Jan 1, 1988

By Minoru Fujita, Ian M. Johnson

"A helicopter-borne geophysical survey was flown in 1978 over selected areas on Kyushu Island, Japan. The principal sensors were a moving source electro-magnetic system and a magnetometer. Maps of apparent resistivity were generated from the EM data. Based on the resistivity signature of known deposits within the survey areas, targets were selected for ground follow-up. Drilling of one such target in late 1980 resulted in the discovery of a gold deposit from which full production will begin in the summer of 1985. The deposit contains a minimum 120 tonnes (3.86 million ounces) of recoverable gold and is the largest in Japanese history. The deposit is in a geological setting previously unsuspected of hosting precious metal deposits. The case history suggests a preferred exploration strategy which might be employed in other similar geological environments.IntroductionThe Hishikari area is located some forty-five kilometres north of Kagoshima city, Kagoshima Prefecture, Kyushu Island, Japan (Fig. I). The area and its environs is one with a number of gold deposits which have been worked with varying results since the late 1800s. The large st deposit in terms of recovered gold is the Ohkuchi (or Oguchi) Mine (Fig . 2) which was recently closed due to exhaustion of reserves. The Ohkuchi Mine started production in 1896. A total of 22.2 tonnes (714 ,000 ounces) of gold, with an average ore grade of 13.6 grams/tonne (0.39 ounces/ton), was extracted over the Life of the mine.In an attempt to discover new deposits , the Metal Mining Agency of Japan (MMAJ) carried out a regional geologic mapping program of the area between 1975 and 1977. This was followed by a helicopter-borne electromagnetic and magnetic survey. The airborne survey was flown by Scintrex and the compiled results presented to MMAJ in early 1979."

Jan 1, 1985

By Porter W. Shimer

As is well known, cast-iron borings are a mixture of small particles of iron with more or less of finely divided graphite, separated from thc surfaces of these small particles during the process of boring. The amount of graphite thus mechanically mixed is, in all cases, quite large enough to cause serious difficulty when the problem is to obtain an average sample of a given lot of borings for carbon determination. This difficulty arises from the necessity of obtaining a uniform mixture of the heavy and comparatively coarse borings with the finely divided and light graphite, and of removing a sample for analysis without disturbing the uniformity of this mixture. It was first sought to overcome this difficulty by having the horings made very fine, so that they might have more nearly the size of the particles of graphite. It was not practicable, however, to secure this uniformity of size, since much of the graphite is in the form of the finest dust. At all events, the duplicate determinations of rarbon in these fine borings, made with every precaution by combustion in oxygen, frequently showed differences too large to be accounted for in arty other way than by imperfect sampling. Very coarse borings were also tried with the idea that the graphite separated from these large and heavy pieces would perhaps be inappreciable ; but it was found that quite enough was separated to vitiate the results. Various methods of mixing were tried, both in the bottle and on glazed paper ; but in all these mixtures it mas found that duplicate samples seldom colitained the same proportion of the mechanically mixed graphite; and when they did, there could be no certainty that it was the true proportion. All this was shown many times over by the failure of duplicates to agree closely, the differencheing sometimes so much as 0.20 per cent. It was finally clear that nothing was to be hoped from these methods. Even if we could secure a perfect mixture containing in every part its due proportion of graphite, it would run a great risk of being destroyed the moment a spatula was inserted to remove a sample: for the least agitation causes some of the graphite to fall through between the coarser borings.

Jan 1, 1886

By Robert Keeney

AT the beginning of the use of the electric furnace, for the manufacture of calcium carbide and ferro-alloys, experimental work was conducted in it upon the production of steel from iron ore. Stassano performed two series of experiments in Italy, the first1 during the years 1898 to 1902, and the second2 in 1908. For many years steel and wrought iron have been produced directly from ore on a small scale in the forge, crucible, and reverberatory furnaces; but the difficulties attending the operation of these combustion processes have prevented their adoption to any great extent. The combustion

Jan 2, 1914