Search Documents

By Leonard Larson

DURING several years immediately preceding the adoption of wet-charge smelting at McGill, various necessary conditions affecting this procedure, such as plant rearrangement and the metallurgical nature of the concentrate produced at the concentrator, were fully considered. Wet-charge smelting is not altogether novel to the recently reconstructed smelter at McGill. A number of years prior to this improvement, when flotation methods were initiated at the concentrator, large tonnages of wet and (at that time) sticky flotation concentrate were charged directly into the reverberatory furnaces, because of the difficulty in handling the entire tonnage in the roasters. The plant had excess reverberatory units and this surplus furnace capacity was utilized to smelt raw flotation concentrate. During the years 1927 and 1928, a number of actual operating furnace test runs were made to determine in principle the feasibility of wet-smelting operation. Results were encouraging, and in November 1932 the roasting plant was shut down. For some time thereafter the wet feed was delivered directly to the reverberatory side-charging calcine hoppers already in place. Feeding the wet material through the old calcine hoppers and charge holes into the furnace involved considerable labor, but under the conditions existing at that time it was desirable to continue wet smelting even under the handicap of this laborious procedure. The smelting plant during this period was on a curtailed production basis, operating only about 15 days per month. The alternate starting up and shutting down of the roasting plant presented a difficult problem and charging the wet material directly to the furnace entirely eliminated this difficulty. The roasting plant was never operated thereafter. EARLY PROCEDURE Fig. 1 shows the general layout of the smelting plant before the smelter was remodeled. Under this arrangement, all concentrates and fluxes except converter flux were delivered in cars to wooden storage bins, which paralleled the roaster building. The material to be roasted was dis-

Jan 1, 1938

By Ernest Darby

WHEN bronze is melted in open-flame furnaces a considerable amount of slag is formed during the melting operation. This slag may be incidental to the melting practice or it may be formed intentionally by slag-forming constituents added to the furnace charge to provide a covering for the melted metal. When this slag is removed from the furnace, it contains, in addition to the free metal carried with it by the skimming operation, a considerable amount of metal as oxide either combined or mechanically mixed with it. By the usual crushing and washing methods this metallic oxide generally goes to the tailings pile, so diluted by other foundry waste that its recovery is economically impossible. If this furnace slag is not mixed with other foundry waste, practically all of the metal oxide as well as the free metal may be recovered by some form of smelting operation. The first side of the problem to be considered is the amount of slag produced. It may not be true that the majority of foundries have no record of the amount of slag made, but it is certainly true that a very great many either have no record or pay little attention to it. Usually the collection of furnace slag for one normal week's run will be sufficient to determine the advisability of its being handled in a different manner from the crushing and concentrating generally employed. If a large representative sample of the accumulation is crushed and concentrated and the recovery compared with the results of a careful assay, it will be found that a large percentage of the total metal content was lost in the washing process. The percentage of loss will be greater than the metallic oxide content, as some free metal in extremely fine particles always is carried away in grains of slag. From such a comparison, it may be determined whether or not the slag should be melted, sold or treated as before. An example of an actual test of this kind is given below.

Jan 1, 1928

Development: Iron Ore In Peru Utah Construction Co., of San Francisco and a Peruvian Government corporation have signed an agreement for development of a large iron orebody in Peru. Most tests show 60 pct iron or better. Most of the ore is magnetite. Although ore will be shipped mainly to Eastern U. S. blast furnaces, shipments to the West Coast may develop as the orebody opens up. The construction firm indicated three American steel companies have shown interest in the project. The orebody is located 300 miles south of Lima and about 15 miles from the coast at the same longitude as New York City. Allen D. Christensen, executive vice-president of Utah Construction noted that the distance is shorter between Peru and the East Coast. The ore deposit measures about four to five miles in one direction and 10 miles in the other. As many as 15 outcroppings within these limits have been reported. Several of the outcroppings are thousands of feet long by several hundred feet wide, Christensen said. Shipments between 100,000 and 200,000 tons of ore per month are projected by the company. Cost of opening the mine to production may go over $5 million, Christensen said. It would include building of docks for ocean going vessels, housing, and heavy duty mining and processing equipment. The contract with the Peruvian government gives Utah Construction six to eight months for additional tests and a 20 year concession for mining the orebody. Peru will collect royalties on all ore. The company will also supply about 300,000 tons per year for an electric furnace to be installed by the Peruvian Government at Chimbote. No steel is produced in Peru now. Utah Construction formed the Argonaut Mining Co. last year, and was shipping iron ore from British Columbia to Japan at a rate of more than 50,000 tons a month, before winter weather decreased operations.

Jan 1, 1952

By J. D. Kalasky

Continuous mining has revolutionized the coal industry but intensified the problems of earlier mechanization. From the installation of the first miner, it was recognized that face ventilation would be one of these problems. To establish an efficient work cycle for the equipment being used, conventional mechanized mining provides four or more development faces. Continuous mining, relying on a single machine, requires only one face, although more than one can be driven alternately by the same machine. In gaseous areas mined by the older methods, the intermittent rate of exposure allows time for the face to bleed off or be cleared, and the width obtained with conventional units makes it possible to hang a brattice line almost to the face. Continuous mining increases the ventilation hazards; there is no margin of time, and very limited space. For all practical purposes, continuous miners available today can be grouped into two major types, rippers and borers. The two can be further classified, respectively, as flexible and rigid. Both types have been in operation in U. S. coal mines for the past five to ten years in a number of seams, under various conditions ranging from slightly gaseous to very gaseous. Common methods of face ventilation utilizing jute or plastic brattice material for line curtains, stoppings, and checks have so far met with success. Air volumes to operating sections are greater than for conventional mining, and specific instructions have been given to section crews stressing the precautions needed in dealing with a steady rate of gas emission and the importance of maintaining reasonably air-tight brattice to direct a good steady flow toward the face at all times. Operators of continuous miners, as well as the foreman on each section, are equipped with an approved safety lamp for gas testing. When the miner is in steady operation, tests for gas at the face are made at 15 to 30-min intervals, depending on the

Jan 1, 1960

By Robert B. McCormick

THE major use for quartz crystal is in the manufacture of radio oscillator plates and telephone resonator and filter crystals. Quartz crystal is also cut and polished as a semiprecious gem stone, particularly in the colored varieties (amethyst, Brazilian topaz, and others), and often is carved into various objects of art. Prisms, wedges, lenses and other optical parts often are made of quartz crystal, usually for special- purpose instruments. Chips and small clear crystals below 100 grams in weight, called “lascas” by the trade, are the raw material for fused quartz products. HISTORICAL BACKGROUND The Greeks believed quartz to be permanently frozen water and therefore called it krustallos, which, literally translated, means clear ice; but ages before their civilization, prehistoric man had crudely cut and polished crystals for rough charms and ornaments. About 2000 B.C., the Egyptians brought the art of cutting quartz to a high level. While there are earlier examples of crystal art that have great value, working in crystal during that period became a means of artistic and religious expression that has endured through the ages. Art museums and private collections throughout the world contain many priceless pieces. They include findings from the tombs of the earliest Egyptian rulers, as well as magnificent art objects in both clear and colored crystal encrusted with silver, gold, enamel, and precious gems of oriental and European workmanship. Pierre Curie first measured the piezoelectric effect of quartz, in 188 1, by placing a weight on the surface of a quartz crystal and measuring the resulting electrical charge, which he found was proportional to the weight applied. The following year the inverse piezoelectric effect was proved by the Curies. By applying a voltage to a piece of quartz, a measurable physical displacement occurs. The first practical application of this effect was the construction of a bimorph unit to measure voltage by measuring the amount of the displacement of the end of the bimorph. The piezoelectric properties of quartz crystal remained largely a laboratory curiosity until World War I, when a supersonic device for

Jan 1, 1949

By Frank C. Smith

The following article covers the history of a metallurgical campaign, commenced in March, 1905, at the mines of the Socorro Bold Co., in the so-called desert region of Yuma county, Arizona. The results obtained were simply a function of necessity, as will be seen from the description of the local economic conditions and the character of the ores treated. The mines and mill of the Socorro Gold Co. are located near the small village of Harrisburg, about 60 miles from Congress Junction, Ariz., which, at the time this work was undertaken, was the nearest railroad station, and from which all supplies were brought by wagon through the desert, at a cost varying from $10 to $15 per ton in addition to the railroad freights. Wood, the only available fuel, cost $7 per cord. Water for all purposes was pumped to the plant from a well in the valley about 4 miles away. Under the Arizona law, a working-shift is 8 hr. Wages were $6 per day for foremen and mill-men, $4 per day for blacksmiths and engineers, $3.50 per day for miners, and $3 per day for shovelers and trammers. The ore consisted of quartz, in which, above the 250-ft. level, the iron-minerale were largely oxidized and some free gold was visible; below that level few traces of oxidation occurred, and pyrite constituted the principal mineralizer in the quartz, together with occasional pockets of galena and a few eccentric specks of covellite. The 20-stamp mill was equipped with plates for amalgamation, and three Standard tables for concentration. The tails from the tables mere elevated by a centrifugal pump to a launder, by which they were conveyed to a 60-ton cyanide-mill for further treatment. The cyanide-mill was erected at so great a distance from the stamp-mill that a separate crew of workers and a separate power-plant were necessary. No arrangement had been made for the treatment of the concen-

Jan 1, 1907

By Harrison Schmitt

IN the practice of ore finding the geologist is continually confronted with the question of oreshoot extension, so that the general problem seems worthy of systematic investigation. This problem appears when the reserves are estimated and when the advisability of deepening the shaft comes up. Moreover, there is need for lower development cost to keep pace with cost reductions in other departments, or even to offset a rising cost of ore finding or ore following. This can be gained by close geologic control of the development; and much of the geology involved is that bearing on the downward, upward, and horizontal extensions of shoots. Furthermore, the purchase of a mine or prospect often depends directly on the question of shoot extension; because it is seldom that the ore is fully developed and the purchase price is almost invariably based largely on "possible" and geologically prospective ore. Most current methods for estimating '(possible" and the more nebulous classes of ore are crude and indecisive. In the following pages the extension of oreshoots is the major theme, although the more basic subject, the general art of ore finding, is given some space. (A) Direct Methods of Extension Prediction (I) Extrapolation and Interpolation of Shoots by Use of Conventional Geologic and Assay Plans, Projections and Cross-sections There is little need for stressing the desirability of detailed geologic plans, assay plans, projections, and cross-sections as a basis for the study and extension prediction of shoots. Underground and surface mapping, in most cases, ought to be done in exhaustive detail. All features of obvious bearing should be mapped and it is good practice to record all possible details, some of which may become significant when studied in the ensemble. It should be emphasized that the mapping should be done with an impartial mind, with interpretation reduced to the minimum. The symbols of the map can be made to distinguish observed facts from interpretation.

Jan 1, 1929

By Fred W. Gordon

The North Chicago Rolling-Mill Co., of Chicago, have four furnaces at South Chicago, built during 1881. Each furnace is 20 feet diameter of bosh, and 75 feet total height, the hearth being 11 feet diameter, and the top 15 feet 4 inches. They are blown through seven 7-inch tuyeres placed 5 feet 6 inches above the hearth level. Cubical contents, 15,000 cubic feet. Each furnace is supplied with 2 blowing engines, 84-inch blowing cylinder, and 36-inch steam cylinder, and 54-inch stroke. These two have one jet-condenser worked by an auxiliary pump. The blast for each furnace is heated by the aid of three Whitwell fire-brick stoves, each 21 feet diameter and 60 feet high. In the batteries of boilers furnishing steam for four furnaces there are 36 double-length boilers, 76 feet long, 48 inches diameter and 16,000 square feet heating-surface. The plant was designed to produce 3600 tons per week, or 900 tons for each furnace, and was fitted as above with such engines, boilers, and hot-blast stoves as were thought requisite for that production ; hence, calculated from the present make—not the least remarkable feature is the economy of construction—there are less engines, less boilers, and less hot-blast power for the iron made than at ally plant within my knowledge, or it could to-day be duplicated for less money per ton of iron made per week than could any plant now in existence, whether using fire-brick or cast-iron stoves for heating the blast. This is a practical demonstration of my assertion in a paper on fire-brick stoves, read before the Institute," that the application of fire-brick stoves in construction really lessens the first cost. In view of the statements just made, I must be most emphatic in assuring the members that nothing is strained or overburdened.

Jan 1, 1886

By Ernest Darby

WHEN bronze is melted in open-flame furnaces a considerable amount of slag is formed during the melting operation. This slag may be incidental to the melting practice or it may be formed intentionally by slag-forming constituents added to the furnace charge to provide a covering for the melted metal. When this slag is removed from the furnace, it contains, in addition to the free metal carried with it by the skimming operation, a considerable amount of metal as oxide either combined or mechanically mixed with it. By the usual crushing and washing methods this metallic oxide generally goes to the tailings pile, so diluted by other foundry waste that its recovery is economically impossible. If this furnace slag is not mixed with other foundry waste, practically all of the metal oxide as well as the free metal may be recovered by some form of smelting operation. The first side of the problem to be considered is the amount of slag produced. It may not be true that the majority of foundries have no record of the amount of slag made, but it is certainly true that a very great many either have no record or pay little attention to it. Usually the collection of furnace slag for one normal week's run will be sufficient to determine the advisability of its being handled in a different manner from the crushing and concentrating generally employed. If a large representative sample of the accumulation is crushed and concentrated and the recovery compared with the results of a careful assay, it will be found that a large percentage of the total metal content was lost in the washing process. The percentage of loss will be greater than the metallic oxide content, as some free metal in extremely fine particles always is carried away in grains of slag: From such a comparison, it may be determined whether or not the slag should be melted, sold or treated as before. An example of an actual test of this kind is given below.

Jan 1, 1928

By A. K. Knickerbocker

PRACTICALLY all underground work on the Minnesota iron ranges is done by miners working on a so-called contract wage system. This system, while it has certain advantages over the straight day's pay or company-account method of wage payment, has serious and vital defects. In view of the scarcity and demands of labor, it is important that employers of labor scrutinize their systems of wage payments carefully, not only to save losses and trouble, due to labor disturbances, but also to secure the greatest efficiency of their workmen and reduce their operating costs. It is admitted that an adequate, just, and equitable wage is the prime factor in bringing about these benefits. The wage of labor and its method of application and payment have been, and always will be, the main factors in the unrest and dissatisfaction of labor. Not only does labor want and need an adequate wage, assuming that work is adequately performed, but it wants and is entitled to a just and equitable wage. Labor must have respect for the fairness of the wage and for the fairness of the management in the application of the wage. It is conceded that the Minnesota iron miners are now, and have been, in the main paid adequately, but the inherent defects of the so-called contract system prevent any just or equitable application of this wage to the various units of the labor body. The defects of the contract system, with its obvious inequalities, favoritisms, and injustices, are cancers in the brain of labor. Every thinking miner realizes these defects and knows just what they are; the unthinking do not realize the details of the subject, but each month they are forcibly reminded of these defects through the pay envelope. As practiced on the iron ranges, however, the so-called." contract" system is not a contract and the name is a misnomer. No true contractual obligation exists.

Jan 2, 1920

By Arthur H. Redfield

The West Indies are the summits of a submerged mountain chain, the continuation of which must be sought in the mountains of central Honduras. In Haiti, the chain divides, one branch passing through Jamaica and the other through Cuba, the Cayman Islands, and the Misteriosa bank. Suess divides the West Indies into three zones: The first zone is entirely of volcanic origin and includes many recent volcanic cones. It includes the arcuate string of islands, which extends from Saba and St. Kitts to the Grenadines and Grenada. The western half of Guadeloupe belongs to this group. The second zone consists of a geanticline, of which the sedimentary rocks range from the Jurassic to the Quaternary, but consist chiefly of Lower Tertiary sediments. In the west it is broad, including the whole of the Greater Antilles; but in the east it is restricted to a narrow belt, which includes the Virgin Islands (except Anegada), Anguilla, St. Bartholomew, Antigua, the eastern part of Guadeloupe and part of Barbados. The islands that compose the third zone are flat and low. Like the second, this zone is broad in the west and narrow in the east; it includes the Bahamas, Anegada, Sombrero, Barbuda, and part of Barbados. Geologically, Florida and the plain of Yucatan may be regarded as belonging to it. Trinidad and Tobago, though geographically adjacent to the Lesser Antilles, are geologically a detached part of the South American continent. The crystalline complexes of northern Trinidad and of Barbados are a continuation, en echelon, of the crystalline axis of the promontory of Paria. The folded Cretaceous and Tertiary of the central and southern parts of Trinidad represent a continuation of the folded sedinlents of the Paria district of Venezuela. Possible Oil-bearing Areas The volcanic islands of the inner arc of the Lesser Antilles may be excluded from consideration; these include Saba, St. Kitts, Nevis,

Jan 1, 1923

By T. F. Witherbee

Success in this operation is much promoted by adhering to a definite plan. Random work is of little account. In general, anything done that will enable the blast to pass through the obstruction, providing the melted products can be got away from the tuyeres, is all that is necessary. Hence the utility of high explosives in breaking up the chilled mass in the hearth. (This, by the way, should be done with the wind on, so as to prevent the filling of the tuyeres with the usual rush of cinder following the explosion.) If from any cause it is not expedient to use explosives, the simple but very effective instrument known as the kerosene or hydro-carbon blow-pipe can be depended upon to perforate the contents of a blastfurnace hearth to any extent required. It consists, as used in the Champlain district (first by Mr. Charles H. Foote), of several pieces of gas-pipe, liberally supplied with elbows (five in number) so as to be flexible; one end being connected to a tuyere-stock and the other brought to bear upon the place to be melted out. A 1/4-inch pipe leads from the last length, or blow-pipe proper, to a reservoir of kerosene or crude oil, set high enough to overcome the blast-pressure, This 1/4-inch pipe should have a valve conveniently located to regulate the flow of oil, and also another next to the reservoir. With a good hot blast and a surprisingly small quantity of oil, this apparatus will melt, burn or mechanically dislodge anything around a blast-furnace hearth excepting firebrick and water-cooled castings or plates. It may be helped by vigorous prodding with a suitable steel bar, to detach the fused but sometimes sticky material. A very good way to operate on a chilled hearth with it, is to open up a hole from a cinder- or iron-notch to the nose of the most convenient tuyere and then make a blow-pipe of the tuyere by turning

Jan 1, 1885

By James Neale

FROM the beginning of its activities, the members of the National Production Committee have felt that the following points were essential to the success of its work: The operators must. feel that their operations were not 100 per cent. efficient; that they should be courteous and fair in their treatment of their employees; and that they should set an example of hard work and patriotic interest in increased production. Every move made must appeal to the sense of fairness of all parties concerned. The men must feel that in working more faithfully, and consequently producing more coal, they are rendering a distinct service to their Government in the time of its great need. As the workers feel that greater efficiency on their part results only in greater profits to the operators, the advantage to the operator should be lost sight of, as far as possible, and the advantage to the Government in fighting the war emphasized. Both operators and workers should know that the Government considered increased production an obligation, and opportunity for service, resting on both parties and not on the operators or the workers alone, and that both parties could very much better the efficiency of the pre-war period. Had the committee intimated that it thought the coal shortage was clue entirely to the idleness and inefficiency of the workers, its campaign would have failed, for the men would have resented the charge because only too frequently their efforts to produce more coal were thwarted by bad management; besides the operators would have lacked stimulus to better effort. On the other hand, had the impression been given that the committee thought that the coal shortage was clue entirely to bad management, the operators would have resented the charge because only too frequently their efforts to produce more coal were thwarted by the idleness and inefficiency of the workers; and the workers, having been thus indirectly pronounced 100 per cent. efficient and patriotic, would have lacked stimulus to better effort.

Jan 2, 1919

NEW YORK SECTION Executive Committee, DAVID H. BROWNE, Chairman., JOHN H. JANEWAY, Vice-Chairman, F. E. PIERCE, Secretary, 35 Nassau St., New York, N. Y. P. A. MOSMAN, Treasurer, LEWIS W. FRANCIS, BENJAMIN B. LAWRENCE. At a meeting of the New York Section, held at the Machinery Club on Jan. 19, 1916, the topic, for the evening was The Problems of the Naval Consulting Board, on which board are four prominent members of the Institute. The speakers of the evening were W. L. Saunders, president of the Institute, Dr. L. H. Baekeland, and Commander A. B. Fry, chief of staff of the New York Naval Militia. After Chairman Browne had laid before the meeting certain business matters, he introduced President Saunders, who presided during the speech making and delivered the first speech. The letter from President Wilson to Mr. Saunders and the presidents of the other national engineering societies, inviting their cooperation in a scheme for mobilizing, as it were, the industrial capacity of this country, had just been made public (see a previous page of this Bulletin) and President Saunders described in considerable detail the origin, purposes, and scope, of the work to be undertaken in this direction. Each of the five national scientific societies is to select a representative from its resident members in every State of the Union, that is, the mining engineers will have 48 representatives, likewise the electrical engineers, the chemists, the civil engineers, and the mechanical engineers. Thus, there will be a representative body or board of five members in every State, one from each of the five societies or institutes. Each committee will investigate the manufacturing and producing possibilities in its own state, and will gather information as to the capacity of every industry which may be capable of supplying things that are needed for the sinews of war. Industrial preparedness means something more than mere capacity to make shells. The field covers food, clothing, hospital equipment, motors, animals, telephones, telegraph and railway accommodations, and a myriad of small details.

Jan 3, 1916

OLIVIA'S recent revolution, by hindsight, seems to have been inevitable. The misery of the majority of the people, coupled with the economic crisis engendered by the refusal of the United States to meet Bolivian demands for a higher tin price, gave the National Revolutionary Movement party all the excuse it needed for overthrowing the government. Most of the mines in Bolivia are owned by three families. Precisely what it will mean to the United States is still a moot question. Argentina, with a mixture of Marxism, Fascism, and few twists created by the Perons, is in a position to grab off much of the tin we need. Because of the contingencies of geographical location, language and a natural simpatico, Argentina may be able to continue its efforts to oust the United States from its South American markets. Point Four aid was supposed to be given to Bolivia, but only for agriculture. Even this was entirely too slow. Mining, Bolivia's other major source of income was forgotten by the Washington planners. Primary aim of the new power will be to diminish its dependence on the world tin market. At a time when the free world is fighting a battle for control of metal, it stands a chance of losing an important source of supply. With the accent placed on agriculture and other industries, mining in Bolivia is certain to suffer. Argentina will be in a position to get the available supply of tin, make a strong ally in the world order of things, and add to its power play against the United States in South America. Ten labor groups have formed the Bolivian Central Workers Union. The first item on their list for immediate action is the nationalization of the mining and railroad industries. They also came out for agrarian revolution and diversification of industry. President Victor Paz Estenssoro has promised to appoint a committee for the investigation of nationalization of the mines. At least, this is indicative of a feeling for the need for caution.

Jan 1, 1952

By Frank Antisell

CERTAIN physical and chemical properties of copper are so intimately related that a change in variation of the physical properties indicates a certain chemical change. The standard specifications of copper of the American Society for Testing Materials are based upon physical characteristics with one exception, namely, the copper contents. The physical standard includes electrical properties, defects in the "set or casting," variation in dimensions, weight, etc. Paragraph 4 of the specifications states, " Wire bars, cakes, slabs and billets shall be substantially free from ;shrink holes, cold sets, pits, sloppy edges, concave tops, and similar defects in set or casting." Shrink holes and concave tops indicate both physical and metallurgical defects; cold sets, sloppy edges, etc., indicate physical defects only; small pit holes may be indicative of either or both physical and metallurgical defects, depending on conditions under which they originated. To the refiner, a copper casting, no matter how made, is known as a "shape," irrespective of whether it is wire bar, ingot, cake, slab, billet, etc. As practically all shapes are cast in an open mold, that is a mold without cope, the surface of the shape cools in contact with the atmosphere and has a coating of oxide. Certain phenomena of the surface indicate the adaptability of the metal for forging or rolling. The writer believes that it is much simpler to produce shapes that are metallurgically correct than those that are mechanically satisfactory. When copper is to be rolled into thin sheets or drawn into very fine wire, the slightest physical defect becomes evident. It is, therefore, of the utmost importance to, consider every characteristic of the shape and ascertain the physical and chemical relationship. Pitch and Set.-The appearance of the surface of the copper when cooled is considered as to its "pitch," or the general contour of the surface of the shape (which may vary from a concave to a convex); and the "set," or the detail appearance of the surface of the shape (the wave-like struc-

Jan 1, 1920

By R. S. Shoemaker

Mines are closed for two reasons; exhaustion of ore or insufficient price for the mineral. On the other hand, the reopening of an old mine can be the result of any one of three events; the discovery of more ore, a sudden rise in the price of the product or the use of a new low-cost method of mining or milling the ore. Examples of the latter would be the open-pitting of an orebody previously mined underground as recently happened at Tyrone, N.M., or the adoption of acid leaching of an old pit as has been done at Miami, Ariz. The unique native copper mines of the Keweenaw Peninsula of upper Michigan have not been so fortunate. These deposits, which were first worked by prehistoric Indians, have been mined continuously from the early 1840's to 1968 when the last mines of Calumet and Hecla were closed and the Ahmeek mill. still using eight Nordberg steam stamps, was shut down. There are two types of deposits from which native copper is obtained; amygdaloid, which is a lava flow, and conglomerate, a sedimentary deposit of sand, rock fragments and pebbles cemented together. "In the amygdaloid, the copper is disseminated, or distributed much like the raisins in a cake; but in the rich Calumet conglomerate, the copper is more like a malleable rope or thread cementing the pebbles together." (C. Harry Benedict. Red Metal: The Calumet and Hecla Story, (Ann Arbor, Michigan, 1952), p. 42.) These deposits produced almost all of the copper used by the North in the Civil War and were substantial contributors to the copper needs of the United States in both World Wars. Some were mined to depths of as much as 9500 ft along the dip of the vein structure and 7500 ft vertically. Few of the mines ever really became worked out, but became uneconomical because of depth, pinching of veins or grades which dropped to about 1%.

Jan 5, 1972

By W. P. Dyrenforth, W. E. Horst

Although, separating or concentrating minerals, based on differences in. their magnetic properties has been practiced for years1 the early industrial applications of magnetic separators were involved with the most highly magnetic materials. These early separators were used to concentrate magnetite, separate metallic iron from furnace products, and separate iron and brass turnings. Next, the addition of a pretreatment operation, such as roasting or calcining, to transform certain iron-bearing minerals into a highly magnetic compound that could readily be separated from the altered mineral mixture using existing magnetic separation machines was added to the flowscheme. As the number of magnetic-separator installations grew, steady development of better equipment evolved including the design and implementation of induced magnets having high-intensity fields, These developments of course greatly expanded the field of magnetic separation and made it possible to commercially separate or concentrate very weakly magnetic minerals which previously had been considered as nonmagnetic minerals. A number of different designs of magnetic separators were well developed and the unit operation of magnetic separation was gaining wide acceptance in mineral processing operations when two events occurred that dampened these developments. First, the Mesabi iron range with its direct-shipping iron ore was discovered and placed into operation. This of course significantly reduced the need for magnetic separation to meet the raw material requirements of the iron and steel industry. Second, the advent of selective froth flotation, was so successful in solving many mineral process problems that electrical concentration techniques being developed at that time, including magnetic-separation methods, were either terminated or received low priority ratings. During the past two decades interest has been renewed in the use of electrical concentration methods to solve mineral separation problems. As the direct-shipping iron ore reserves are depleted more emphasis has been placed on magnetic upgrading of lower value iron ore available throughout the world. In addition, magnetic separation techniques have found numerous applications in the non-metallic and industrial minerals industry to supplement froth flotation and thus add to the variety of beneficiation methods available.

Jan 1, 1971

By W. T. Thom

In previous classifications of coal, it has been customary to regard moisture eliminated from coal samples between 20 and 100 C. as extraneous matter, rather than as a constituent part of the coal. It seems, however, that the physical character and use properties of the low-rank coals are directly related to the amount of such moisture present, and recent chemical work has shown' that such coals contain unstable groupings which decompose between 20 C. and temperatures somewhat above 100" C., with the splitting off of moisture. According to this view, the moisture eliminated from air-dried coal below boiling point is similar in all essential respects to moisture eliminated above 100" C., and is produced by analogous reactions; and inasmuch as the moisture given off above 100" C. has always been treated as a constituent of the volatile matter of coal, it would seem that consistent usage would include as a part of the volatile matter all moisture present as an essential component of the coal as it occurs in nature. As a matter of experience, it seems clear that the general physical and chemical characteristics of the low-rank coals are largely determined by or related to the moisture, whether chemically or physically combined, present in air-dried coal; it is also demonstrable by trial that the low-rank coals cannot be satisfactorily classified on a purely chemical basis by using the moisture free form of analysis. The low-rank coals of the western United States include numerous well-defined types, many of which were referred to in a classification proposed by Ashley,2 in which the physical and use properties of the coals were made the primary basis for their systematic grouping. When testing this classification by replotting analyses of these type coals according to the Seyler scheme of classification,3 a satisfactory parallelism between use properties and chemical constitution of the dry coal was found among

Jan 1, 1925

By Gregory J. Comstock

There is a growing interest in the possibilities presented by the manipulation of metal powders, which justifies an attempt to summarize their character and potential value. A summary of this kind presents an opportunity for making a classification of metal powder products into several general types. Our present knowledge of the finer and more abstract aspects of many of the principles involved in metal powder technique is extremely limited. Any conclusions as to the ultimate value of the process will, therefore, for the present at least, be of doubtful value unless they are substantiated by its products. The number of such products is increasing. A study of their diverse and unusual characteristics; an examination of the methods by which they are made, and a consideration of the reactions that take place during their fabrication, in so far as we can define them, should afford as good an evaluation of this interesting development as it is possible to make at this time. A critical study of this kind results in a formidable list of special attributes, which apparently are characteristic of applied powder metallurgy. A comparison of these special effects with the end products and well defined limitations of the melting and casting process indicate that often they may very well be considered as being special advantages. They are subject, of course, to certain not as yet so well defined limitations of their own. Based on current products only, a necessarily condensed summary of the more striking special attributes of the metal powder process follows. Manipulation of Highly Refractory Metals The powder process presents a means of manipulating highly refractory metals, which cannot be cast and formed in the usual melting and casting process. Tungsten, molybdenum and tantalum are the classic examples of the adequacy of the metal powder process for meeting unusual conditions of this character. The development and application of these metals by means of it, and their importance in the electrical

Jan 1, 1938