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By Edgar S. Burkhardt

In mining, the process of comminution starts at the pit and ends at the classifiers. The first machine that breaks or comminutes ore is the primary crusher. There are many types of crushers, but the one most commonly used in large tonnage plants is the gyratory so discussion is restricted to this type of machine. See Figure 1. The primary crusher is the most important piece of comminution machinery in the plant because every ton of ore processed by the concentrator must pass through it, as shown in Figure 2. Most plants can operate if a secondary crusher or a mill is shut down, but if the primary crusher stops, the whole concentrator goes down. It is, therefore, important that the machine be able to produce sufficient ore to keep the concentrator running without hesitation. The plant designer first considers the required daily capacity and an estimate of the size of the ore from the pit. To this he adds an availability factor to compensate for delays due to shovels, trucks and rou- [ ] tine maintenance at the crushing station. This factor is based on experience and can be on the order of 75% (1). With these figures, he determines the hourly capacity required of the primary crushing station to keep the concentrator supplied. See Table I.

Jan 1, 1982

By A. M. Gaudin

It is only in recent years that substantial progress has been made in developing a physico-chemical picture of the solid state. The molecular concept, so useful in dealing with gases, was naturally carried over to the field of crystalline solids; it has resulted in the firm implanting of erroneous concepts that only now are being eradicated successfully. Two simply written and effective books on the subject are Crystal Chemistry by Stillwell' and An Introduction to Crystal Chemistry by Evans. A more complete treatment of the subject is available in a book by Wells. The monograph by Hucke14 also touches on a subject most easily perceived by reference to the brief introduction by Bragg; that master of the field. These texts make it clear that while some solids are built of molecules, many are built of ions, others of atoms connected in the form of giant molecules, and still others of cations and electrons. The various lattices in which these entities are systematically arranged, the joint use of several of these entities, and the transitional character of some of the bonds make for the great variety of crystalline solids. The purpose of this paper is to point out a most important corollary of present views on the structure of solids. In this connection the classification of solids in Table I is helpful.

Jun 1, 1955

By Carl Henrich

A.. S. DWIGHT, New York, N. Y.-Mr. Henrich's paper is rather inconclusive as to the role that alumina really plays in slags. He gives a number of interesting instances of high alumina, with conclusions that he draws from the analyses, in the light of what he knows of the accompanying conditions, but the information given is hardly sufficient to permit intelligent criticism of these conclusions, for it is well known that the slag composition is not the only factor that can produce some of the furnace results favorable or disastrous, as the case may be, which he records. As a matter of fact, most metallurgists who have wrestled with this problem in connection with the smelting of lead and copper ores, usually arrived at some sort of a working hypothesis which met the local conditions fairly well, and then, being busy men, were inclined 'to leave the theoretical question very much as Mr: Henrich leaves it when he says: "A question with which I purpose dealing at some future time." It is unfortunate that in the Golden Age of the smelting industry in the West, when we were all dealing with large tonnages of complex ores, often containing large percentages of alumina in combination with other. refractory elements, the smelting companies were not generally equipped for research as they are today, and much experience that might have been,

Jan 4, 1917

By B. Kopelman, C. C. Gregg

THE reduction of tungstic oxide to tungsten metal powder by hydrogen is a process by which one might expect the resultant metal powder to he porous. In- deed, sponge iron, prepared by rcduction of the oxide in a reducing gas, is generally accepted as quite porous. with pores large enough to be seen readily under the optical microscope at relatively low magnifications. However, any pores that may exist in tungsten metal powder are not resolved by the optical microscope, and apparently, not even by the electron microscope. Fig r shows commercial tungsten powder magni- fied at I0,000 X by the electron microscope,' both etched and unetched. In an earlier paper by one of the authors,* the existence of ports in tungsten powder was required to explain adequately the particle size changes occurring during the reduction of tungstic oxide. The inability to detect these pores under the electron microscope at 10,000 X implies that these {pores} are of a size of 100 A units or less. (This in itself is by no means proof that pores above 100 A would not exist, since polishing effects on the specimen might smear up holes of such small magnitude). If, then, these pores are less than IOO A. and of the order of molecular size, then the density of the metal powder should be

Jan 1, 1949

By Henry S. Poole

This field is geologically of much interest. It is small, hut with some seams of unusual thickness, the main one being as much as thirty-eight feet thick. The quality of the seams, as also of the associated beds of shale and sandstone, in several instances changes to a remarkable degree within short, distances. The strata dip at inclinations that carry the coal to depths of 3000 feet or more; heavy faults cut up the district, and the New Glasgow conglomerate, of disputed age, separates it from the Upper Carboniferous measures, in which no seams of workable thickness are known. This coal-field offers to the geologist much ground for study and peculation. The commercial value of the field is affected by its restricted area, the varied quality of its coal, and its advantageous position in the mainland, with railway connection and home markets, offset by the physical difficulties which make the cost of production high. It has been so long a habit with us to speak of our resources of coal as boundless, that any adverse comments, or insinuations that avoidable loss in working is a national loss, hare hitherto fallen on idle ears. While it is not my purpose to underrate the riches we do possess, yet I deem that no good end is served by echoing exaggerated estimates which encourage a national indifference to wasteful

Jan 1, 1886

By Anders Carlson

NOTABLE advances have been made in the evaluation of oil-reservoir rocks from information furnished by core analysis. Among the physical data employed, per-meability is of primary importance. It may be assumed that the permeability of a core sample, considered as a property inherent to the nature of the porous medium only, is not markedly altered by the coring opera-tion, therefore some degree of accuracy is justified in the laboratory determination of permeability constants by means of homo-geneous flow media. To provide that such relatively simple determinations be sus-ceptible to duplication and consistent inter-pretation should prove advantageous in the prediction of subsurface flow conditions involving nonhomogeneous fluids. The air permeameter seems to fill most satisfactorily the need for rapid and fairly accurate determinations. Instruments that are similar in design and operation have come into general use. However, this has not resulted in an encouraging uniformity in the results obtained. Recognizing the value of reducing measured values to a common quantitative standard, the authors have sought to determine possible reasons for undue discrepancies and means for their elimination. This paper will be specifically concerned with three factors, which appear to be of some importance in the establishment of consistent permeability values: (I) design and operation of the permeameter, (2) preparation and mounting of the sample, (3) type of flow created in the sample.

Jan 1, 1940

By M. K. Barnett

[ ] ENGINEERING research consists, broadly speaking, in the investigation of the effect of the variations in a number of factors on some property of a product or characteristic of a process. The unambiguous description of the product or process requires that the property or characteristic be expressible in quantitative terms. For the purpose of practical control, it is likewise desirable that the independently variable factors governing the product or process be quantities, although this ideal goal is not always attained. Maximum efficiency-i.e., the attainment of the maximum amount of reliable, useful information relating to the influence of the factors on the property of the product or characteristic of the process, for the least expense-is an important requirement for the satisfactory operation of a research organization. Obviously, a necessary condition for the attainment of maximum efficiency is an adequate knowledge of the specialized field in which the experimental research lies. While necessary, this condition is not sufficient. Proper attention must also be given to the general principles of experimental design together with the modem methods for the analysis and evaluation of experimental data. The present discussion is confined to a single design, the so-called "factorial" design. This design is of special interest in that it attains its goal, maximum efficiency, by directly departing from the

Jan 1, 1947

By Paul E. Queneau, H. J. Roorda

Cobalt consumption will increase during the next decade at an average rate at least equal that of nickel. In the past, use of cobalt has at times been curtailed by lack of availability or by high price. In the future, output of cobalt derived from copper ores and iron sulfides will continue to grow and output of cobalt from nickel ores will be greatly increased. There should therefore be an adequate supply of this metal at a reasonable price. Nickeliferous limonites constitute by far the largest known terrestrial reserves of cobalt. A process has been conceived, based upon selective reduction and aqueous chlorination for treatment of such ores. The proposed procedure permits good extraction of the ore's cobalt content, comparable to that of the nickel, and is adaptable to large-scale, automated unit operations. Chlorine leaching of the ore enhances its value as a potential source of iron and chromium. Over four thousand years ago, cobalt pigments were employed for decorative purposes in some glass and glazes of Egypt and Persia, and by 1000 B.C. they were widely used in the Middle East.' " However, prior to 1914, virtually no cobalt was produced as metal and ceramics remained the largest consumer of the element as oxide. During World War I cobalt-containing high-speed steels came into their own and the metal's merit in magnet steels was established.

Jan 1, 1971

In accordance with the requirements of By-Law LX,- I beg leave to submit herewith the report of the Library Committee for the year 1916. The activities shown by the sale of the Institute's publications during the year are somewhat larger than last year, due principally to the increased sale of special editions on account of the larger sale of the Posepny and Emmons Volumes, owing to increased advertising and to the reduction in price of the Emmons Volume. The sales were distributed as follows: Sale of Transactions $3,237.07 Sale of Special Editions 1,722.50 Sale of Bulletins and Pamphlets 2,263.95 Total $7,223.52, The Institute library has now been merged with the libraries of the. other three Founder Societies and is known and administered as the Library of the United - Engineering Society. When this merger, was effected, a proviso was made that the books contained in the Institute library up to the date of the merger were still to be considered as the individual property of the Institute, and this arrangement applied also to the libraries of the other two Founder Societies. At the time that the American Society of Civil Engineers joined as a fourth Founder Society, they immediately turned over their entire library to the United Engineering Society, relinquishing all property rights in the books entirely.

Jan 2, 1917

By Bernard Kopelman, C. C. Gregg

THE reduction of tungstic oxide to tungsten metal powder by hydrogen is a process by which one might expect the resultant metal powder to be porous. In- [ ] deed, sponge iron, prepared by reduction of the oxide in a reducing gas, is generally accepted as quite porous, with pores large enough to be seen readily under the optical microscope at relatively low magnifications. However, any pores that may exist in tungsten metal powder are not resolved by the optical microscope, and apparently, not even by the electron microscope. Fig I shows commercial tungsten powder magnified at 10,000X by the electron microscope,1 both etched and unetched. In an earlier paper by one of the authors,2 the existence of pores in tungsten powder [ ] was required to explain adequately the particle size changes occurring during the reduction of tungstic oxide. The inability to detect these pores under the electron microscope at 10,000 X implies that these pores are of a size of 100 A units or less. (This in itself is by no means proof that pores above 100 A would not exist, since polishing effects on the specimen might smear up holes of such small magnitude). If, then, these pores are less than 100 A, and of the order of molecular size, then the density of the metal powder should be

Jan 1, 1948

By E. Gybbon Spilsbury

In the course of the persistent and rapid advance of our country towards the goal she has set for herself, of commercial and manufacturing supremacy, there stand out certain periods or cycles of prosperity or depression, succeeding one another with a comparative regularity as to their ultimate trend, but of varying lengths and intensities. I might compare this course to that of a railroad between two points at different levels, with intervening mountain ranges and valleys, the up-grades climbing towards the final upper terminal of prosperity, while the down-grades retard the ascent, and tend to return to the valleys below. Just at the present time we are evidently at the bottom of one of these valleys, and, before starting to climb the next divide, it may be prudent for us to look into the condition of our rolling-stock, and especially into that of our brakes, and see what the experience of our downward journey has taught us, and whether we are properly equipped for the new upward advance which now lies before us. Probably no previous period of the same duration has produced in all branches of mining and metallurgy improvements SO many and so various as have the last ten or twelve years. Not that they have brought forth any such startling and revo-

Jan 1, 1898

By David Swan

No mystery shrouds the discovery of chromium. The indefatigable French chemist Vauquelin, in reporting his discovery of this chemical element to 1'Institut National in 1798, concluded his discourse with the statement: "I place before the eyes of the Institute a small quantity of chromium and several of its most re- markable combinations." Working with the so-called "red lead of Siberia, Vauquelin not only prepared numerous chemical compounds of the new metal, but he reduced the oxide to the metallic state. These chemical compounds possessed a variety of remarkably distinctive colors; so, acceding to suggestion, Vauquelin named the new element chrome (chromium), a derivative of the Greek word chroma, meaning color. Siberian "red lead" (crocoite) was not plentiful; however, it was not long before Vauquelin's prediction was realized that the chemical compounds of chromium would become useful in the arts when sources of chromium became more readily available. Although chrome-iron ore (chromite) became obtainable in France, the United States and elsewhere during the early part of the nineteenth century, it is interesting to note that from 1828 to about 1860, Maryland, Pennsylvania, and others of the eastern United States furnished almost the entire chrome-ore requirements of the world. Several countries each in turn have since dominated for certain periods the supply of chromite. In recent years, the largest tonnages have come

Jan 1, 1953

By Dean S. Rogers

The conventional role of exploration, development and grade control is examined in this paper within the context of the many and varied types of gold occurrences which are found at the Dome Mine. The account endeavours to trace the development of the total ore evaluation process, from diamond drilling through the exploration and drifting stage, to the stope development and planning phase of the operation, with an emphasis on sampling techniques and assaying procedure. The concept of ore reserve calculations is developed and the practice of grade control is described. In summary, the role of the geological, the engineering and the mining department is presented in relation to the contribution each has to make in the evaluation and exploitation of ore from one of the world's classic Archean gold deposits.

Jan 1, 1985

By Robert Greenwood

The advent of the space age and its promise of interplanetary flight has prompted new ideas for propulsion systems that will allow maximum energy with minimum fuel weight. The use of cesium as the source of energy for such rocket flights has been found desirable. Theoretical efficiency of a rocket fuel is measured in terms of specific impulse, defined as the number of pounds of thrust per pound of propellant consumed per second. Specific impulse is usually expressed in seconds (the number of seconds for which one pound of fuel would produce one pound of thrust) although it is really a measure of total energy, not of power. The most sophisticated chemical fuels have a specific impulse of 300 to 400 sec; liquid hydrogen heated by nuclear reactor has a specific impulse of 1000 to 1200 sec. Specific impulses as high as 20,000 sec, however, are theoretically attainable with the ion rocket, in which free cesium ions are accelerated across a voltage drop and ejected at high velocity.' Characteristics of the system have been sketched by Boden. The desirable properties of an ion propellant are: 1) low ionization potential, 2) low boiling point, and 3) high atomic weight. Alkali metals best fulfill these requirements, and Table I indicates the superiority of cesium. The use of heavy complex ions such as UCl; is ruled out by their instability and other disadvantages.

Jan 5, 1960

By Eric S. Cheney

The often-heard question "How can we interest young geologists and engineers in AIME?" is virtually the same as "How can we interest young geologists and engineers in the glamorous mining industry?" Many persons would reply that AIME and industry should improve their image by various devices aimed at high school students and teachers, boy scouts, and even grade school children. For more immediate results, I suggest that we concentrate our efforts at the professional level on students already identified as geol¬ogists and engineers. Why does our glamorous profession appear distinctly unglamorous to most of the engineers and geologists currently in college and graduate school? The answers seem quite simple to me. First, the profession talks almost exclusively to itself, seldom to the engineering or geologic public, and almost never to the lay public. Second, the industry has been overly conservative in all aspects of recruiting during an especially competitive and affluent period. Consequently, mining has taken a terrific public drubbing from preservationists who still portray its leaders as robber barons. SME and AIME have, of course, various commendable programs for enticing student interest, including student membership, the low dues for this membership, the somewhat reduced prices at which students can attend AIME meetings and buy AIME volumes, and the large number of AIME Student chapters on campuses. Obviously, more active encouragements are needed.

Jan 1, 1971

By G. H. Clevenger

Discussion of the paper of ALLAN J. CLARK presented at the San Francisco meeting, September 1915, and printed in Bulletin No. 103, July, 1905, pp. 1381 to 1398. G. H. CLEVENGER, Palo Alto, Cal.-Since the precipitation of extremely dilute solutions as regards cyanide presents one of the greatest problems of zinc-dust precipitation, I should like to ask Mr. Clark the minimum concentration in cyanide of the solution from which it is possible to precipitate satisfactorily the gold with zinc dust in Homestake practice. A. J. CLARK.-For a day's work about 0.015 per cent. That is precipitating a very low-grade solution, very low in alkalinity. It requires probably 0.2 lb. of zinc dust to the ton. JOHN A. FULTON, Melones, Cal.-At the Melones mine, we have been working very low-grade rock for a number of years, the process being amalgamation and concentration up to the last year. The value of the ore increased so that we had to supplement the concentration with a sand and slime plant. Classification was a problem, since to install classifiers would mean tearing the mill all to pieces. We are therefore making use of a Wilfley table for this purpose. The amount of wash water is increased and a stream of fresh water is also run into the feed box at the

Jan 12, 1915

EUGENE COSTE, ? Calgary, Alta.-Evidently in Argentine they have a petroliferous province just east of the Andes where very much the same conditions exist as are found on the east side of the Rocky Mountains and in the plains adjacent. It strikes me, though, that the same mistake is being made in Argentine in the exploration for oil as was made in Alberta, Canada; viz., drilling the wells too .near the seepages in the belt in the eastern part of the petroliferous province, too near the mountains. This same mistake was made in Alberta, with disastrous results; viz., only fissure production was found. The strata so near the mountains are tilted at a very strong angle, such as is described in this paper, and the dislocations are intense. On the other hand, we have found that when we get 100 or 200 mi. away from the mountains we get into oil and gas belts which are very prolific. So far our fields in Alberta have been gas, but in Wyoming, as you know, they get many thousands of barrels a day. I have no doubt that conditions in Argentine are exactly similar but that they have so far kept too near the mountains and that they want to explore the belts farther east to obtain better results.

Jan 4, 1919

By W. H. Bassett

THE subject assigned is rather a broad one but it, is doubtless expected that it will be dealt with as applying to metals and alloys and not to the ob-taining of metals from their ores. The liberty will further be taken of confining the matter discussed to copper and some of the copper alloys. Everyone is familiar with copper, at least everyone who attends the meetings of the A. I. M. E., so no gen-eral description of the metal is necessary. There are still to be recognized two classes of copper and each of these has some sub-divisions. The two general classes are electrolytic and fire-refined copper. Since there is some misunderstanding about these materials, definitions are in order. Electrolytic is just what the name implies. It may and it should be very pure but with high current densi-ties or very impure anodes, or both, impurities such as antimony, tellurium and lead may be carried over to the, cathode. Any one of these, or a combination in which they occur, are alike fatal to good working quali-ties in the resulting metal. Of course, these metals are not supposed to be deposited with copper, but slimes containing them may be 'occluded. in the deposited cop-per or held in rough cathodes if not washed with suffi-cient thoroughness.

Jan 5, 1927

By John Eash

DURING recent years nickel has had an increasingly important role as an alloying element in the copper-tin bronzes. Nickel additions not only produce better casting alloys but also make alloys whose properties can be varied by precipitation hardening; thus leading to increased commercial application of copper-nickel-tin alloys. Recent investigations have indicated a decrease in the solubility of tin in the alpha phase as the annealing temperature is lowered and as the nickel content is increased within certain limits. A further change caused by the nickel additions is produced in the excess phase of the copper-tin bronzes. The alpha plus delta eutectoid is replaced by a clear precipitated constituent in the alloys containing up to 15 per cent tin and not less than 1 per cent nickel. This paper has a dual purpose. The first is to present a new determination of the alpha-phase boundary in alloys containing from 0 to 20 per cent nickel, together with the liquidus and solidus temperatures above that field. The second purpose is to give the equilibrium conditions existing in alloys exceeding the alpha phase containing up to 31 per cent tin and 5 per cent nickel, so that the disappearance of the alpha plus delta eutectoid constituent may be explained. After considering the earlier investigations of the related alloy systems and the experimental procedure used in this investigation, the alloys will be discussed in groups as separate quasibinary systems containing constant amounts of nickel. The systems considered contain 0, 1, 2, 3, 5, 10 and 20 per cent nickel. The straight copper-tin system was reinvestigated in order to establish a foundation on which to build the remaining material. The 1 per cent nickel alloys studied give the relations existing in the region of the eutectoid transformation between the copper-tin system and the 2 per cent nickel copper-tin system which has been investigated in detail. The thorough examination of the latter system was made since 2 per cent of nickel is representative of the commercial additions to the cast bronzes and also because it is sufficient to produce

Jan 1, 1932

By John T. Eash, Clair Upthegrove

During recent years nickel has had an increasingly important role as an alloying element in the copper-tin bronzes. Nickel additions not only produce better casting alloys but also make alloys whose properties can be varied by precipitation hardening; thus leading to increased commercial application of copper-nickel-tin alloys. Recent investigations have indicated a decrease in the solubility of tin in the alpha phase as the annealing temperature is lowered and as the nickel content is increased within certain limits. A further change caused by the nickel additions is produced in the excess phase of the copper-tin bronzes. The alpha plus delta eutectoid is replaced by a clear precipitated constituent in the alloys containing up to 15 per cent tin and not less than 1 per cent nickel. This paper has a dual purpose. The first is to present a new determination of the alpha-phase boundary in alloys containing from 0 to 20 per cent nickel, together with the liquidus and solidus temperatures above that field. The second purpose is to give the equilibrium conditions existing in alloys exceeding the alpha phase containing up to 31 per cent tin and 5 per cent nickel, so that the disappearance of the alpha plus delta eutectoid constituent may be explained. After considering the earlier investigations of the related alloy systems and the experimental procedure used in this investigation, the alloys will be discussed in groups as separate quasibinary systems containing constant amounts of nickel. The systems considered contain 0, 1, 2, 3, 5, 10 and 20 per cent nickel. The straight copper-tin system was reinvesti-gated in order to establish a foundation on which to build the remaining material. The 1 per cent nickel alloys studied give the relations existing in the region of the eutectoid transformation between the copper-tin system and the 2 per cent nickel copper-tin system which has been investigated in detail. The thorough examination of the latter system was made since 2 per cent of nickel is representative of the commercial additions to the cast bronzes and also because it is sufficient to produce

Jan 1, 1933