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By H. A. Wheeler

It may surprise some of our members to learn, that, among the industries based on the mineral resources of the United . States, clay now ranks third, being exceeded in value of product only by pig-iron and coal. The present annual value of clay-products exceeds the value of the outputs of gold or silver, and also exceeds the combined values of copper, leacl, zinc, aluminum, mercury, antimony and nickel. These facts are shown in Table I. which gives the statistics for the year 1902 :

Jan 1, 1905

By Harold A. Linke

The following article presents notes and data compiled and computed by the writer for use in the determination of: size and slope of mill launders, details of junction boxes and downspouts, and distribution of pulp. It also includes pulp formulas, volume of discharge through bushings, paths of discharging streams, banking of turns and curves. In the design of a concentrating mill, the draftsman usually considers launders to the extent of providing ample "head" for transmission of pulp from one department of the mill to another. The superintendent of construction aims to build his launders wide and deep, and on a slope steep enough to ensure positive flow. So launders are laid generally on too steep a slope, with the result that the repair gang works to maintain launder bottoms and sides against the erosive action of the conveyed pulp. To this end many kinds of liners have been devised: concrete, mastic, white iron, glass, rubber. True, the reduction of slope to the point where a pulp will flow with minimum wear, will minimize labor and expense; but when the desired slope is not predetermined, the millman hesitates to readjust his launder slopes by cut-and-try methods. To the end that the desired size and slope may be found readily, the writer has: (1) conducted experiments with pulps of different specific gravity, screen analysis and dilution; (2) gathered a few graphic data from standard reference works (such as Peele's Mining Engineer's Handbook and Taggart's Handbook of Ore Dressing); (3) computed several tables; and compiled results that have proved dependable for Utah Copper ore. It is quite possible that the following tables and graphs may not be applicable to all ores, but it is hoped that they may prove helpful, even in slight degree, in alleviating a portion of the trouble and migraine of some other millman. Launder Slopes The main object in the study of launder slopes is to provide grade steep enough to prevent "sanding" by a safe margin, and to avoid

Jan 1, 1943

By Harold A. Linke

The following article presents notes and data compiled and computed by the writer for use in the determination of: size and slope of mill launders, details of junction boxes and downspouts, and distribution of pulp. It also includes pulp formulas, volume of discharge through bushings, paths of discharging streams, banking of turns and curves. In the design of a concentrating mill, the draftsman usually considers launders to the extent of providing ample "head" for transmission of pulp from one department of the mill to another. The superintendent of construction aims to build his launders wide and deep, and on a slope steep enough to ensure positive flow. So launders are laid generally on too steep a slope, with the result that the repair gang works to maintain launder bottoms and sides against the erosive action of the conveyed pulp. To this end many kinds of liners have been devised: concrete, mastic, white iron, glass, rubber. True, the reduction of slope to the point where a pulp will flow with minimum wear, will minimize labor and expense; but when the desired slope is not predetermined, the millman hesitates to readjust his launder slopes by cut-and-try methods. To the end that the desired size and slope may be found readily, the writer has: (1) conducted experiments with pulps of different specific gravity, screen analysis and dilution; (2) gathered a few graphic data from standard reference works (such as Peele's Mining Engineer's Handbook and Taggart's Handbook of Ore Dressing); (3) computed several tables; and compiled results that have proved dependable for Utah Copper ore. It is quite possible that the following tables and graphs may not be applicable to all ores, but it is hoped that they may prove helpful, even in slight degree, in alleviating a portion of the trouble and migraine of some other millman. Launder Slopes The main object in the study of launder slopes is to provide grade steep enough to prevent "sanding" by a safe margin, and to avoid

Jan 1, 1943

By J. K. Lovrien

A Link-Belt roller-bearing conveyor system was in- stalled recently at the Gross-Marble mine of the Oliver Iron Mining Co. at Marble, Minn., for removal of overburden and lean ore. The material, consisting of clay, sand, gravel, and glacial boulders. is excavated by an electrically operated walking dragline equipped with a 10 cu yd bucket working from a boom approximately 150 ft long. This machine loads into a receiving hopper of a rail-mounted screening plant in 45 second cycles. A manganese steel apron feeder under the receiving hopper delivers to an elliptical grizzly, from which the oversize boulders and extraneous material, by way of an apron conveyor, arc loaded into refuse haulage trucks.

Jan 12, 1951

By T. H. Janes

NATURAL abrasives of some type are found in all countries of the world. In order of their hardness the principal natural abrasives are diamond, corundum, emery, and garnet, which are termed high grade, and the various forms of silica, including pumice, pumicite, ground feldspar, china clay and, most important, sandstone. The properties qualifying materials for use as abrasives are hardness, toughness, grain shape and size, character of fracture, and purity or uniformity. For manufacture of bonded grain abrasives such as grinding wheels, the stability of the abrasive and its bonding characteristics are also important. No single property is paramount for all uses. Extreme hardness and toughness are needed for some applications, as in diamonds for drill bits, while for other purposes the capacity of the abrasive to break down slowly under use and to develop fresh cutting edges is of greatest importance, as with garnet for sandpaper. In dentifrices, soaps, and metal polishes, of course, hardness and toughness are objectionable.

Jan 10, 1954

By Thomas M. Barczak

The resultant load vector is the representation of the forces applied to a longwall roof support element by caving strata into a single, quantifiable measure of support resistance. The relatively complex kinematics of the shield support prohibit a determination of support resistance simply by summation of leg forces. A method is being investigated by the Bureau of Mines to determine the resultant load vector by instrumenting supports with pressure transducers and strain gages to measure leg, canopy capsule, and lemniscate link forces. This concept has been laboratory tested in the Bureau's Mine Roof Simulator. Functional relationships among variables have been assessed, and confidence intervals have been established for prediction of the resultant load vector parameters.

Jan 1, 1984

By W. C. Lacy

THE Cuajone porphyry copper deposit is the northernmost of a group of three deposits in southern Peru controlled by the Southern Peru Copper Corp.-Toquepala, Quelleveco, and Cuajone- all within a 20-mile belt. Although small pockets of high-grade copper oxide ores were worked in the Cuajone area in the 19th century, it was not until 1939 that its potentialities as a disseminated deposit were recognized by O. C. Schmedeman. An exploratory drilling program was begun in December 1942 and continued until early 1945. The program was revived in November 1952 and completed early in 1954. Early exploration was by diamond drilling. Later exploration was predominantly churn drilling, with diamond drilling used only for wildcat holes.

Jan 1, 1958

By Joseph Perry

MAGNESITE is found in 22 California counties, but many of the deposits are too small or too impure to be of commercial value. Several of sub-stantial size and quality were entirely exhausted by wartime operation. At present, three properties comprise the only known workable deposits in the state. Of these, the Western mine and the Patterson mine have been known and worked for many years, and have been described in con-siderable detail in various publications, therefore need only brief mention here, because of their proximity to the Bald Eagle mine. The latter, recently developed, is unusual in type of ore deposit, plant design and operation, as well as products made, and very little has been written concerning it. WESTERN MINE The Western mine, 32 miles south of Livermore, Calif., was formerly operated by C. S. Maltby. It has been a consistent producer for many years.1 The ore is of amorphous variety, occurring along fracture zones in serpentine. The veins vary greatly in width, the average being perhaps 8 ft., with the maximum indicated in one early stope of 40 ft.; 2 ft. is considered the minimum for economical mining. The strike of the veins is predominantly north and south, with dip to the west varying from 40° to 75°. Walls are well defined and as a rule firm and easily supported, Veins range in length from a few hundred feet to 1000 or more. Their maximum vertical extent is about 350 ft., but many run less. Early mining consisted of open-cut and glory-hole work on the larger outcrops. This was followed underground by a modified shrinkage system, the waste and low-grade horses being removed by hand sorting on the tramming levels and transported to surface dumps. Filled-stope mining is used now, in order to eliminate the handling of waste, which has

Jan 1, 1938

By R. F. Bell, L. W. Eastwood, R. W. James

Among those concerned with the annealing and heat-treating of aluminum and aluminum alloys, it is well known that after co1d-working a coarser grain is usually produced by slow heating than hy more rapid heating. Consequently, for the control of the grain size produced by annealing or heat-treating cold-worked aluminum and aluminum alloys, the heating rate is of considerable practical importance. References in the current literature on the effect of heating rate are numerous, but it appears neither necessary nor desirable to give here a review of the former nark done on this subject. It became evident during some preliminary work on the recrystallizn-tion of aluminium and aluminum alloys that the effect of heating rate depended upon the type of microstructure of the metal. This observation led to the following study of the relationship of the type of microstructure of the alloy to the effect of the heating rate. Materials Investigated Analyses of the aluminum and aluminium alloys investigatted are given in Table 1. Three classes of material are listed, as follows: Class I.— Belonging to the first class are pure aluminium and aluminium containing a second constituent that is soluble in the aluminium matrix at

Jan 1, 1939

By R. F. Bell, R. W. James, L. W. Eastwood

Among those concerned with the annealing and heat-treating of aluminum and aluminum alloys, it is well known that after co1d-working a coarser grain is usually produced by slow heating than hy more rapid heating. Consequently, for the control of the grain size produced by annealing or heat-treating cold-worked aluminum and aluminum alloys, the heating rate is of considerable practical importance. References in the current literature on the effect of heating rate are numerous, but it appears neither necessary nor desirable to give here a review of the former nark done on this subject. It became evident during some preliminary work on the recrystallizn-tion of aluminium and aluminum alloys that the effect of heating rate depended upon the type of microstructure of the metal. This observation led to the following study of the relationship of the type of microstructure of the alloy to the effect of the heating rate. Materials Investigated Analyses of the aluminum and aluminium alloys investigatted are given in Table 1. Three classes of material are listed, as follows: Class I.— Belonging to the first class are pure aluminium and aluminium containing a second constituent that is soluble in the aluminium matrix at

Jan 1, 1939

By A. S. Grove, C. T. Sah, E. H. Snow, B. E. Deal

A summary of- several recent investigations in to the properties of the metal-oxide-silicon system is presented. A major portion of these studies makes use of the MOS capacitance-z)oltage method of' analysis. The particular areas of investigation which are reported include: 1) a general survey of the electvical properties of thermally oxidized silicon surjbccs; 2) a study of ion migration through silicon dioxide films ; 3) measurements of electron and hole mobilities in surface inversion layers; 4) a study of impurity redistribution due to thermal o.ridatiotz; and 5) measurements of the rates of oxidation oj-heavily doper7. silicon. THE importance of the metal-oxide-semiconductor (MOS) system in the semiconductor industry is well-known. In addition to its importance in the "planar" device technology,' the MOS structure is now also used in the fabrication of active solid-state devices. Consequently, extensive efforts have been made recently to obtain a better understanding of the characteristics of this system. A summary of some studies of the MOS system conducted in our laboratories during the past year is presented. For the most part these studies used silicon as the semiconductor, along with silicon dioxide and aluminum as the other two components of the system. Since the MOS capacitance-voltage method of analysis was used extensively in these studies, we will first briefly describe its nature and consider some of the possible causes of deviation of experimental observations from the simple theory. We will then outline the various related areas of investigation carried out in our laboratories and will briefly indicate some of the results. It should be noted that the purpose of this paper is merely to provide a brief summary of MOS studies. More detailed discussions of the various areas of investigation are given in the references cited. PRINCIPLES OF THE MOS C-V METHOD OF ANALYSIS' A sketch of the MOS structure is shown in the upper portion of Fig. 1. In this case the insulating film is Si02 and the semiconductor p-type silicon. If a large negative bias is applied to the metal field plate, holes are attracted to the silicon surface. The silicon then behaves much like a metal and the capacitance measured is that of the oxide layer alone, Co. If a small positive bias is applied to the aluminum, holes are repelled and a region depleted of majority carriers is formed at the silicon surface. This depletion I-egion adds to the width of the dielectric and the measured capacitance begins to drop. With increasing positive bias, the width of the electrical depletion region increases. At some large positive bias an inzevsion regiotr is formed at the surface and additional charges induced in the silicon appear in the form of electrons in this narrow inversion region. Thus the depletion-region width approaches a maximum value and, consequently, the capacitance reaches a minimum value and then either levels off or rises again depending on the measurement frequency and the rate of equilibration of the minority carriers in the inversion layer.3 Band diagrams, along with the corresponding charge distributions, are shown in Fig. 1 for the above bias conditions. If minority carriers cannot accumulate at the surface to form an inversion region, the depletion-region width continues to increase with increased positive bias and the capacitance drops toward zero as in a reverse biased p-n junction. The effect of a work-function difference $hs between the metal and the silicon, and of surface charges per unit area Qss located at the oxide-silicon interface, is simply to attract charges in the silicon much like the applied bias. It can be shown that this results in a parallel shift of the capacitance-voltage characteristic along the voltage axis by an amount corresponding to AV = -$bIs + Qss/Co. Theoretical curves have been calculated4 giving the capacitance of the MOS structure C normalized to the oxide capacitance Co vs the quantity VG here VG is the voltage applied to the metal field plate. In Fig. 2 such calculations are shown as points for a particular oxide thickness and bulk impurity concentration for a p-type semiconductor. (For an n-type semiconductor the curves would be mirror images of these.) All three cases, i.e., low frequency. high frequency, and depletion, are indicated. Also shown in the figure are recorder tracings of the characteristics of actual devices. These characteristics have been shifted along the voltage axis to compensate the effect of surface charges and work-function difference. It is evident that agreement between experiment and theory is good. The nature of this shift along the voltage axis is

Jan 1, 1965

By W. E. Keck, Paul Jasberg

THE flotative properties of the principal minerals in Michigan's potential iron ores have been investigated to develop methods of beneficiation 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 magnetite flotation, (2) the preparation of pure magnetite, (3) the development of laboratory procedure and (4) flotation experimentation. Literature on Magnetite Flotation.-For the purpose of this discussion, the results of previous work on the flotation of magnetite can be summarized 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 Witherbee- 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 This paper describes a part of a general investigation into the flotation of Michigan's potential iron ores. A comprehensive discussion of the status of these ores and of the reasons for research on their Rotation beneficiation is available in mimeographed form on application to the Michigan allege of Mining and Technology, Houghton, Michigan. Manuscript received at the office of the Institute Nov. 12, 1936. Printfed without author's corrections. Subject to revision.

Jan 1, 1937

By Irving Lipkowitz

While the light metals are recognized generally as a distinct group in technical literature, economic classifications and data usually still treat them as part of the nonferrous group of metals. However, the economic characteristics of the light metals also differ markedly from those of other nonferrous metals. The distinctiveness of the light metals, as, a group and individually, becomes evident when their growth, since World War II is compared with that of other metals, as in Table 14.3.1. The growth of light-metals production has been much sharper than that of other metals. A weighted average for the light metals shows an increase of 112% during the 1958 to 1968 period. This compares with a 62% increase in the "All Primary Metals" component of the Federal Reserve Board Index of Industrial Production. The contrast was even sharper during the next six years (1968-1974), with light metals production up another 50% as against a 21 % increase in the FRB Primary Metals production index. The most important reason, however, for considering light metals separately is the trend and pace of technological change and not their distinctive statistics. Technology both creates and demands increasingly sophisticated materials. As technology advances and as all the world makes more extensive use of advanced technology, the importance of the light metals is likely to accelerate rapidly. There may be a profound clue to the future in the fact that light metals were predominant among the materials used in the construction of the Apollo 11 spacecraft. In determining what materials to use for the spacecraft and its equipment, the National Aeronautics and Space Administration (NASA) has explained that it did not look to "some of the more exotic metals" and relied instead on "generally proven materials." Accordingly, it apparently used a wide variety of metals, including precious metals, rare earths, special steels, copper, and light metals. What seems particularly significant is that, in seeking performance, NASA relied as heavily as it did on the light metals. Materials breakdown estimates show that aluminum accounted for over 75% of the materials used, titanium for another 5%, and magnesium was also used. Thus, light metals accounted for over 80%' of the materials used for the Apollo 11 spacecraft. The light metals are also unique in their availability. They rank high in abundance among the elements in the earth's crust. Aluminum is the third most abundant element, after oxygen and silicon, with magnesium ranking eighth, and titanium ninth. Among the structural metals, aluminum is the most abundant in the earth's crust, iron is second, magnesium third, and titanium fourth. This potential availability of light metals provides strong incentives for continuing improvements in process technology, because of two major national problems: (1) there is

Jan 1, 1976

By A. W. Allen

THE technological study of the treatment of gold and silver ores has been largely responsible for the phenomenal strides which have marked the progress in this branch of metallurgy during recent years. In no other application of science to industry is system more imperative at every stage; correct formulation of result is only second in importance to efficiency of operation. Progresss in method has been largely the result of individual initiative, aided by the work of technical journals and metallurgical societies. There still remains a field for profitable discussion, and it is my intention to deal with some inconsistencies of expression common to a number of writers on the subject; and also to draw attention to the false impressions created by a statement which may, possibly, be only unintentionally misleading. I also take the opportunity of tracing the source of both metallurgical and economic result; and to question the desirability of the methods usually employed in arriving at a final statement. In the first place, I wish to deal with the question of extraction. This term may mean anything or nothing, and it is often used to mislead. In a report of a mining engineer as to the result of operations subsequent to the remodeling of a treatment plant prominence was given to the statement that the extraction had amounted to 91 per cent. On examination it was found that only a small percentage of the so-called extraction was calculated on actual bullion return, a proportion being figured from the gold left in the zinc boxes, and not recovered. In addition to this, a proportion of the extraction was said to be due to gold in concentrate. As there was no concentrating apparatus on the property and as concentration did not form a part of the scheme of treatment the matter was investigated, with the result that the concentrate, of lower gold content that the original ore, was found to be the result of an inefficient pumping system which failed to provide for the whole of the battery product delivered to it. The balance was stacked and, although itself of no marketable value, the gold content was allowed to form a basis of extraction figures.

Jan 7, 1914

By T. A. Rickard

In " The Genesis of Certain Auriferous Lodes "* Dr. Don makes a reference to a curious vein-formation known as the "Indicator," which characterizes a portion of the Ballarat mining district,, in Victoria, Australia. During 1890 and again in 1898 I had an opportunity of making a few notes, which, although somewhat belated,t may be worth adding to the observations recorded in the Transactions of the Institute. The country of the Ballarat gold-field consists of the Lower Silurian slates and sandstones, which also enclose the reefs of Bendigo; but it is noteworthy that the successive anticlinal folds, and accompanying saddles of quartz, which distinguish Bendigo are not characteristic of Ballarat, the geological structure of which presents greater complexity. That part of the district known as Ballarat East became famous early in its history on account of the large nuggets which were found in the alluvium, and subsequently it became further known because of a peculiar persistent black seam, traversing the bed-rock underlying the alluvial deposits, which was found to be associated with rich bunches of gold-ore, not only in the gravel that capped it at the surface but also in the quartz-veins which crossed it underground. The name of " Indicator " was early given. In 1871 Mr. Morgan Llewellyn directed attention to it as influencing the distribution of the gold. In the government quarterly report for December, 1888,

Jan 1, 1901

By L. R. Velho, N. A. D. Parlee, J. Gani

THE unsteady-state type of gas-liquid metal diffusion cell1 has found considerable application.2"4 Cells of this general design can function as steady-state cells if allowed to operate long enough to reach steady state. This report tells of some success in the adaption of this type of cell for steady-state work, using the 0-Ag system in which the mass transfer of the gas "species" is basically controlled by diffusion in the liquid. The gas, e.g-., O2, is maintained in the cell tube'-3 at 1 atm pressure, Fig. 1, by buret and sensitive oil manometer. The gas, after diffusing through the stagnant metal, escapes at the annular metal surface around the tube at a lower constant partial pressure, in this case that of O2 in slowly flowing air, 1 atm.

Jan 1, 1970

Charles T. Malcolmson, Chicago, Ill.:—Mr. Blauvelt's admirable paper is a valuable contribution to the literature on briquetting of coal in this country. It should have a special significance for those interested in the commercial development of the coal-briquette industry. I believe that the data included in Mr. Blauvelt's paper will be particularly useful because they represent costs taken from a briquette-plant in actual operation. There are several points touched on in Mr. Blauvelt's paper which may bear comment in the way of emphasis rather than of criticism. In the first place, he has stated a fact which becomes axiomatic to any one who has had any experience in the design, building, or operation of coal-briquette plants, and that is, that the press is only one factor in the successful opera-

Jan 1, 1911

By Austin Park

More metal at a lower profit continued to be demanded from the mining industry during 1969. Correspondence with U.S. and Canadian mining districts and a study of the mining literature indicate that, a large majority of the mines are keeping pace and rising to the challenge. Continued research and better understanding of pneumatically applied concrete for roof and wall support was of top interest. Many mines are changing mining methods for the adaptation of load-haul-dump units. The most recent adaptation being the use of these units in cut- and-fill stoping and in various types of development headings. Boring methods and use of two- or three- boom drilling jumbos mounted on rubber tires for versatility continues to be the favorite approach to the demand for rapid excavation.

Jan 1, 1970

POSITIONS VACANT (Under this heading will be published notes sent to the Secretary of the Institute by members or other persons.) General manager .for a pyrite mine in Virginia, with experience in the mining and particularly in the washing of pyrite, required. Salary at start, $250 per month with perquisites. No. 28. Assayer and cyanide man for a Costa Rica plant. Salary $100. No. 29. Mine manager to develop gold-mining property in Witwatersrand, Transvaal. Salary £2,000 to £4,000, according to the experience and ability of the engineer. No. 31. Mine superintendent for a mine in Arizona containing copper, gold, silver ore. Will have entire charge of operation and development. Salary to start, $200 per month with perquisites. No. 32. .Mining engineer to make complete report and suggest necessary machinery for development and operation of a placer property; also to examine a copper property. Both properties in Peru, South America. No. 34.

Jan 4, 1915

By A. V. Henry

THE kaolins of the southeastern United States were known to civiliza-tion as early as the latter part of the eighteenth century-and yet the GEORGIA PRODUCTION UNITED STATES PRODUCTION IMPORTS Fig. 1.-KAOLIN PRODUCTION AND IMPORTS. commercial history of Georgia kaolins may be said to begin in the year 1900. The U. S. Bureau of Mines reported for that year a production of 6885 tons of "miscellaneous" clays in Georgia. A comparison of these figures with those of 1934, when the production rose to 284,556 tons (65 per cent of the domestic production), indicates the growing economic and technologic importance of this raw material. Fig. 1 clearly shows that a part of the increase is due to a normal growth in the use of kaolinitic clays and a part is due to replacement of clays formerly imported.

Jan 1, 1937