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By L. A. Panek

When rock is subjected to a load it is deformed. Ordinarily this is observed in a mine as the displacement of one point with respect to another-the deflection of the roof, which may be observed as a convergence between roof and floor; or the extrusion of material from the rib, which may be observed as a decrease of the distance between the rib and the post of a timber set. The effect of excessive pressure may be a rockburst if the rock is strong, or it may be "squeezing" ground if the rock is "soft". Some desirable effects of high stress (high in relation to strength) are the caving of roof in a longwall mining operation, the caving of ore in block caving, and the decrease in mechanical energy required to break down the mineral seam in a retreating pillar-robbing operation. In any case, whether the observable effect of rock load is desirable or undesirable, it is a displacement, and depends on the following four factors:

Jan 3, 1961

Robert T. Hill, Washington, D. C.: Having studied very minutely the geology of the district referred to by Prof. Branner, I beg to state that his quotation of my classification of the Cretaceous deposits of Arkansas is not the one which I originally gave,* nor is it the one which has since been published and is now generally accepted.? I did not assign ally of the Cretaceous formations of Arkansas to the " middle Cretaceous,"

Jan 1, 1898

By Joseph L. Jernegan

THE Whale Lode occurs in the main range of the Rocky Mountains, Park County, Colorado Territory, at Hall Valley. It has been opened up and worked to some extent by the Whale Mine, situated some 11,300 feet above the level of the sea. The mine, with 700 feet of the lode on either side of the discovery shaft, is the property of the Hall Valley Silver-Lead Mining and Smelting Company. The adjacent country rock is a compact, fine-grained gneiss ; its general strike is about north and south, dipping steeply to the west. In the immediate vicinity of the mine, the strata are very nearly vertical. The gneiss incloses numberless veins of a reddish granite, in which the feldspar largely predominates over the quartz and mica, the latter oftentimes being scarcely perceptible. As a general rule these granitic veins seem to more frequently follow the lines of stratification of the gneiss than otherwise. They are of varying width, some large, some small; the larger are from 5 to 6 feet wide. Gash veins of feldspar and quartz are also of very fre¬quent occurrence. The general trend of the lode is about northeast and southwest, intersecting the country rock at about an angle of 45° to its stratification. It dips to the northwest at an angle of 65°. I am unable to state accurately how far this lode has been traced upon the surface, but it is at least well known to extend entirely through the mountain upon which the mine is situated, and is traceable over the ridge by a hollow extending for some distance along the surface, in which the lode crops out. This hollow in the surface rock has probably been formed through decomposition of the vein matter by atmospherical influences. The width of the crevice is variable, generally between 5 and 10 feet; the pay vein varies from an inch, or less, to 36 inches. The vein is generally accompanied both on foot and hanging walls by a whitish, semi-decomposed rock, composed of quartz and decomposed feldspar, and in some places-where the process of decomposition has not reached as advanced a stage-a light-greenish or black mica. This rock, therefore, is in places composed of all the constituents of gneiss, and is undoubtedly nothing more or less than the same in a decomposed condition. It is often very strongly impregnated with iron pyrites, generally crystallized in minute cubes, and it is probably owing to the presence of this min-

Jan 1, 1875

THERE are, as I have heard, varying opinions among men experienced in minerals as to whether silver has its own mineral [i.e., occurs native] or not. Mineralogical reasons and the authority of the majority persuade me that it has, not only because I have seen the natural material separate but also because I know that in mines of gold, copper, lead, and other metals pieces of pure metal are found without admixture, and I have heard that pieces of silver, gold, and copper have been found that had been reduced to their ultimate purity by natural causes. This is also confirmed by a German, Georgius Agricola, who says* that in a mine in Saxony a piece of metallic silver was found so large that the Duke who was prince and patron of the place had a whole dining table of square German style made from it without its being enlarged or worked on by any human artifice except for the tripod legs, and he often boasted that in this he surpassed the greatness of the Emperor. In truth I have never seen any metal except copper that was brought out from the mine pure and without any mineral, but I think that such a thing is indeed possible, since I believe in the greatness and power of Nature, who strives toward no other goal than perfection and purity. Indeed most of the minerals that I have seen have not been without admixture, not only of their earth but also of other metals, and this is more true of that which I have heard called silver than of any of the others. I except the silver that is mined in Schio in the region of Vicenza. These doubts, therefore, are not born without some shadow of apparent reason. As I told you above I believe that silver may have and does have its own mineral, for every substance that is converted into metal can exist pure by itself in its own species, as it also exists separately even though it be mixed with others, since it is seen that in each ore its metal is generated in a single body. Therefore it happens many times that whoever speaks of the ore of silver in one breath, without distinction, speaks of that of all the other metals, because there are few ores that are not mixed. But because the most noble things always have the prerogative of including in their name that of the others, where there is gold or silver the ores are not called

Jan 1, 1942

By William A. Johnson

THE fundamental role of diffusion in many reactions occurring in solid metals has long been recognized, and there have been careful measurements of rates of diffusion in numerous alloy systems, but our understanding of the atomic mechanism by which diffusion occurs is scarcely in an advanced state 1-3 It is doubtful that this mechanism can ever he directly ascertained, rather, all imaginable mechanisms must be examined and the one that is in best accord with such data as can be obtained from suitably chosen experiments should be selected Because of its relative simplicity, diffusion in a system containing only one kind of atomic species-commonly called self-diffusion-is of considerable theoretical interest It may be expected that diffusion theory will not be advanced appreciably until a wide variety of diffusion experiments-of which diffusion in a chemical concentration gradient and self-diffusion are two important types-are carefully performed and inter-compared Aside from the purely theoretical interest in self-diffusion measurements, such studies will be of considerable engineering importance The rate of any process in a pure metal requiring the movement of atoms, of which recrystallization and creep are two familiar examples, will be understood more readily with the aid of self-diffusion data † Self-diffusion implies the diffusion of something into its exact counterpart, the detection of such a process is patently impossible, and it is-necessary to substitute for it the diffusion of one isotope (in this case radioactive) into another isotope (in this case stable) of the same chemical element There is, however, no reason to suppose that a radioactive atom will not diffuse at the same rate as its stable isotope, for all of the isotopes of the same element have exactly the same chemical properties, neither the difference in nuclear energy nor the difference in mass would be expected to exercise an important influence in this phenomenon In this sense, self-diffusion may be thought of as the diffusion of radioactive atoms down a radioactivity concentration gradient, just as usual diffusion is the diffusion of one kind of atone down its chemical concentration gradient The first measurements of self-diffusion ii ere made by von Hevesy4-6 using the radioactive lead isotope thorium B in ordinary lead The recent development of means for producing artificial radioactive elements has made possible similar measurements on gold,7,8 copper,2,9 and zinc 10 11 Many of the data that have been obtained are rather poor, and no adequate reason has been given for their poorness, it appears, however, that the unsatisfactory results are characteristic of the particular experimental procedure employed, and not of self-diffusion measurements in themselves The experimental technique that has yielded the poorer results is the deposition of a thin layer of radioactive atoms on the surface of a specimen and the determination of the rate of inward diffusion

Jan 1, 1941

By Glenn C. Waterman, Scott Hazen

3.1-1. Purpose. Development drilling is directed towards determining the grade, volume, and three-dimensional outline of a mineralized zone previously located by exploration. It is distinguished from exploration or reconnaissance drilling, which has as an objective the discovery of new mineralized areas. A development drilling and bulk sampling program should furnish the following information: 1. Geology of the mineralized zone. 2. Quantitative data on grade and tons of material within pertinent cutoff limits. 3. Physical size and shape of the deposit. Areas underlain by waste as well as ore. 4. Mineralogica1 and metallurgical characteristics of the ore. 5. I1hysical characteristics of the ore. 6. Hulk samples for metallurgical testing and grade check. 7. Data on other factors that could affect mining operations, such as ground water, ground conditions, etc. 3.1-2. Procedures. There are numerous methods and techniques that are used to acquire pertinent data on a potential ore deposit. The total cost and accuracy of a development program depends on significant evaluation of the geology, proper selection of a drilling method, thorough analysis of sample data, and accurate evaluation of all the information. Knowledge of the geology of the mineral deposit is important in planning the development testing program and in evaluating the data obtained from such a program. Exploration work usually provides some significant information on the general size, shape, thickness, grade, and geology of the deposit. In some cases no further data are needed; in many cases geological complexities suggested by the preliminary work require further geological study. Of considerable importance may be the following:

Jan 1, 1968

By J. W. Craig, H. L. Walker

Industry has for many years recognized the dependence of certain mechanical and physical properties. as well as workability, upon grain size variations in brass. Although the dependence of properties upon grain size has been recognized there are not many instances where a planned program of testing has been conducted and where the only intentional variable has been grain size. In particular the literature is limited with respect to the effect of grain size on the endurance limit, though there are many industrial applications where the brasses are subjected to cycles of repetitive stresses. Literature A number of the physical and mechanical properties of a given brass sheet, in the annealed condition, will depend upon: (I) The ready-to-finish grain size before final rolling, (2) the percentage deformation by cold working, and (3) the time and temperature of annealing. The first and second variables affect the recrystallized grain size, and the third variable affects the coalesced grain size. Gibbsl has shown the effect of two different ready-to-finish grain sizes upon the tensile strength and hardness of deep drawing brass strip after a definite amount of cold rolling. The smaller the ready-to-finish grain size, the higher the tensile strength and hardness, but with lowered ductility, Gibbs also demonstrated, for a given time and temperature of anneal, that the tensile strength, hardness, and elastic limit are higher for the smaller ready-to-finish grain size, but the elongation is lowered. Townsend and Greena112 have reported data which show that cold working increases the tensile strength, hardness, and load carrying ability of deep drawing brass sheet under reversed stress. Greenall and Gohn3 have reported data which show that the smaller grain sizes have higher tensile strength and hardness properties, and the data also show that increased cold working increases the tensile strength and hardness properties of deep drawing brass sheet. Kommers4 has reported data for tests of brass of known ready-to-finish grain size, a specific amount of cold reduction, and annealed at different temperatures above and below the recrystallization temperature. Kommers' results indicate that annealing below the recrystallization temperature does not change the tensile strength and hardness properties, but the endurance limit may be increased from 22,000 to 28,000 psi. The increased endurance limit is explained as resulting from the reduction of internal stresses by a stress-relief anneal. Burghoff5 and associates have reported data on creep tests, over

Jan 1, 1949

By J. T. Michalak, H. W. Paxton

The recovery of the initial flow stress of poly-crystalline iron is characterized by a) a logarithmic time dependence; b) an increasing activation energy with increasing recovery; c) an increased ?,ate and fraction of recovery with decreased temperature of deformation; and d) an increased rate with increased deformation. Isochro)ml studies of the recovery of single crystals revealed more sluggish recovery. The original flou3 stress of single crystals could be regained by recovery anneals at 800"or 900°C. ThE great majority of the theoretical treatments and experimental studies of strain-hardening have been concerned with the close-packed lattices.' Very little effort has been expended on the bcc structure so that the theory of work-hardening of this lattice is essentially nonexistent. The limited amount of experimental data resulting from the direct studies on silicon-iron,2 low-carbon steel,3 and purified irons4"7 does not as yet permit a detailed analysis of the strain-hardening. Studies concerned with the effects of annealing following deformation have been few in number," have been somewhat limited in extent, and have had the disadvantage of using irons containing a substantial impurity content. The present research was undertaken to augment the limited knowledge we have of the characteristics of a bcc metal as regards strain-hardening and recovery from the strain-hardened state. The recovery of the flow stress has been employed since it was felt that the stress associated with the hardened state gives at least a fair qualitative description of the state of the imperfections causing the hardening. The study was concerned primarily with the recovery of flow stress following strain-hardening of polycrys-talline, zone-melted iron as a function of the amount of deformation, the temperature of deformation, and the time and temperature of the recovery anneal. A limited investigation of the recovery of the initial flow stress of single crystals of this same material as a function of the recovery temperature was also conducted in conjunction with the Lambot X-ray technique." MATERIAL The zone-melted iron used in this investigation was obtained through the courtesy of the American Iron and Steel Institute and Battelle Memorial Institute. The analysis, as given by the supplier indicated a maximum impurity content of 0.02 wt pct excluding those impurities listed in Table I. (The actual impurity content is very probably less than this since detection limits were considered as the amount of a particular impurity level.) Also listed in Table I are the interstitial impurity contents of the iron at various stages of experimental work indicating that these im-

Jan 1, 1962

The following are excerpts from the report of the Treasurer of the United Engineering Society, for the year ending Dec. 31, 1915. Finances Due to the growth of the activities of the United Engineering Society, it was found desirable early in the year to consolidate the various accounts and financial records of the Society and of the Library, heretofore kept separately, and to have all the data pertaining to the building and its operation in the charge of one individual. An assistant secretary especially assigned to this work has been appointed, and a separate office has been established. The Finance Committee has had all of the records brought fully to date and has prepared a new set of account books to meet the new conditions. The Real Estate Account now includes the following items: Land $ 540,000.00 Building 1,050,000.00 Equipment 33,171.16 Founder Societies, Preliminary expenses 24,000.00 Total $1,647,171.16

Jan 4, 1916

By Robert Glass Cleland

THE DEVELOPMENT of the Phelps Dodge copper and railroad interests began in one era of the company's history and continued unbroken into the next. Yet the two eras themselves were strikingly dissimilar and represented marked differences in the company's activities, corporate structure, and personnel. From its organization in 1834 almost to the end of the first decade of the twentieth century, the partnership known as Phelps Dodge was directed, managed, and controlled by the family dynasty established by Anson Greene Phelps. The last two directing partners of this three-generation-old regime assumed control of the company's affairs in 1879 when the economic revolution that followed the Civil War was well under way.' They lived in an age of gigantic undertakings, gigantic enterprises, gigantic combinations, gi- .

Jan 1, 1952

By Nicholas Chlumecky

To date information is somewhat limited concerning the strength and bearing capacity of floor strata, which is of great importance where proper roof control is desired. If the bearing strength of strata is not known, the support may be excessively strong in relation to the support capacity of the floor, with the result that strong props sink into the floor strata, giving them dubious value as a roof support. The method described is used to determine how tests are made on dry rock to determine the required support area for the base of props or other structures which may rest on rock strata in mines. Relationships were established for the bearing capacity of rocks which were subjected to loads by means of bearing areas of various sizes ranging from 0.09 sq cm (.014 sq in.) to 700 sq cm (108.5 sq in.). This permits the evaluation of the bearing capacity of rocks by testing small areas for the de- termination of the capacity of larger areas.

Jan 3, 1968

By H. L. Hinds, L. L. Trautman

The refining of precious metals from steel wool cathodes is completed by direct fire smelting or acid treatment of the cathodes to dissolve the steel wool followed by fire smelting. To further the refining of the cathodes, the Miller process and the Wohlwill process are used.

Jan 1, 1984

By Alfred Siegel

Mineral pigments give color, opacity, or body to paint, stucco, plaster, mortar, cement, linoleum, rubber, and similar materials. They must be finely divided, substantially insoluble, and generally inert for such uses. Inorganic pigments may be grouped somewhat arbitrarily as follows: A. Natural mineral pigments dug from the earth. 1. Those consisting mostly of iron oxides, such as hematite and limonite. 2. Those containing large amounts of clay or noncoloring matter, such as ocher, sienna, umber, and colored shales. 3. Those whose color is not due to iron oxide, such as Vandyke brown (including sap brown, an alkali extract of Vandyke brown), graphite, and terre verte. B. Synthetic pigments. 1. Those containing iron oxide as the essential coloring matter, such as "pure" reds, yellows, and blacks, and Venetian reds. 2. Those not containing iron oxide, but rather such compounds as lithopone, zinc white, titanium white, ultramarine, Prussian blue, and the like. Only groups A and B-1 are discussed here. All the pigments in those two categories, except Vandyke brown, sap brown, and some of the carbonaceous slates, contain, as their essential color constituents, one or more compounds of iron; namely, an oxide-limonite (2Fe2O3.H2O to Fe2O3.4H20), hematite (Fe2O3), or magnetite (Fe2O3.FeO). Man's first permanent coloring materials were earth pigments-the ochers, iron oxides, and various iron-stained clays. The caves occupied by prehistoric man and the arts of the ancient Chaldean, Egyptian, and Cretan civilizations bear mute witness to this and also testify to the beauty and permanence of earth colors. As the Roman era developed, earth pigments were pushed from their pre-eminent position by white lead and red lead and in the Middle Ages by zinc oxide. Today, of course, the number of acceptable pigments is very large and on a value basis the group of natural and synthetic earth pigments stands forth with $16,000,000 per year; it is surpassed by titanium, lead and zinc pigments. Of this sum,21 natural pigments supplied 31 pct of the tonnage and 16 pct of the value of the total finished pigment in 1957, the remainder representing the tonnage and value of sales of the synthetic iron oxide colors. The average value of finished natural pigments in 1958 was $80.62 per ton. The average value of manufactured pigments in the same year was $202 per ton. Of the 60,000 tons of manufactured colored pigments sold in 1958, the reds comprised 76 pct of the market and the yellows 20 pct. The reds furnished 68 pct of the value and the yellows 24 pct. Of the finished iron oxide pigments (natural and manufactured) sold in 1958, the reds dominated the market with 66 pct of the quantity and 63 pct of the value; yellows supplied 17 pct of the quantity and 20 pct of the value, and browns furnished 11 pct of the quantity and 10 pct of the value. The average value of the reds was approximately $152, and the average value of the yellows $190 per ton. The highest valued pigment in 1958, with almost 12 pct of the total tonnage and 21 pct of the value of the iron oxide pigment market, was manufactured red from calcined copperas valued at $286 per ton.

Jan 1, 1960

By Henry U. Ross

The behaviour during reduction of iron-ore pellets and sinters was investigated. Several methods for the preparation of agglomerates and their reduction were tried. Commercial agglomerates from world-wide sources as well as experimental samples were tested. The effect of coke additions to pellet and sinter plant feeds was given special consideration. An analysis of the test results has helped to explain many of the phenomena associated with the reduction of iron-ore agglomerates such as swelling, loss in strength and wear resistance, changes in porosity, changes in mineralogy and the formation of metallic iron and slag. A double-layer pellet with all of the coke concentrated in the core proved particularly interesting. Although large quantities of coke showed that partially reduced agglomerates containing metallic iron could be produced in the laboratory, the problem of producing reduced pellets and sinters by the existing agglomerating processes still remains.

Jan 1, 1977

By Carl D. Broadbent

In 1956, Kennecott Copper Corp. instituted a slope mechanics program. Its objective was to obtain effi-ient and safe pit slopes. Since then, Kennecott has onducted a great deal of research into the area, most otably at the Kimbley Pit. This paper, which describes the transitional work at this period and draws from the pertinent experimental work done by others, paves the way for the next step of the program: refining the design process and applying it for profit. The goal of slope mechanics is to achieve efficient and safe pit slopes. In the case of ultimate mine slopes, the objective is to minimize the stripping ratio by steepening the slopes to their maximum stable limit. On the other hand, the inclination of working slopes is normally established by operating space requirements and the function of slope mechanics should be the continuous surveillance of slope conditions to assure long-term stability and provide timely warning of impending slides so that corrective measures may be incorporated in production planning. In 1956, Kennecott instituted a program to provide

Jan 1, 1970

For the US coal industry, 1978 was a nightmarish recurrence of 1977 as the United Mine Workers strike cut into production during the first three months of 1978, followed by the strike against the Norfolk and Western Railway during the summer and early autumn. Coking coal production was floored by the one-two punch of environmental constraints on US coke ovens and competition from low-cost, high-quality imports. At the same time, US ex orts of coal fell to their lowest level since 1962. And in the face of all of this, steam coal consumption was sluggish as utilities burned huge amounts of oil to conserve coal stockpiles during the UMW strike. This was followed by decreased electrical demands due to mild summer weather in many parts of the country and dramatically improved availability of hydroelectric power.

Jan 5, 1979

By H. W. Ahrenholz

Seven weeks of 1971 were devoted to a nationwide coal walkout resulting in lost production of some 70 million tons and leaving 1971 coal production at about 550 million tons. Compounding the problem, consumption of coal in 1971 by electric utilities rose by about 5% to 336 million tons. In the mean- time, numerous contracts were awarded for coal R&D including $24.8 million given by the Office of Coal Research to Bituminous Coal Research for the construction of a coal-to-gas pilot plant using the BIGAS process. Exports declined mainly due to Japan's decrease in steel production and to that country's increase in coal imports from Canada and Australia. The advances in equipment design and mining procedures made 1971 a noteworthy year. Introduction of the variable pitch I dipper, the trend toward wheeled vehicles, the greater use of scrapers in reclamation and battery-operated vehicles and oscil-mining, and the increased activity in the areas of ventilation and dust control were given widespread approval. There were also strides made in computerization, longwall mining, roof bolting, rock dusting, mine haulage and methane detection.

Jan 2, 1972

By H. N. Wolcott

AMONG the many cases of replacement of one mineral by another, that of quartz or silicates by pyrite, or even other sulphides, is not uncommon, but the reverse of this process does not appear to have been recorded, even if it has been observed. It, therefore, seemed to the writer that the case described below was worthy of record. FIG. I.-GROUND MASS OF CHALCOPYRITE (C) CONTAINING ROUNDED GRAINS OF PYRITE (P) SHOWING DIFFERENT DEGREES OF REPLACEMENT BY QUARTZ (Q), AND ALSO QUARTZ VEINLETS CUTTING THROUGH THE PYRITE. (PHOTOGRAPHED BY REFLECTED LIGHT.) The specimens described in this paper were obtained by R. B. Morton of Idaho Springs, Colo., from the Old Town Mine, in Russell Gulch, and are in the collection of Cornell University, where the writer studied them. In the rough, the specimens appeared to consist largely of chalcopy- rite, with some grains of tetrahedrite. The polished surface of some of

Jan 6, 1917

By A. K. Sinha, K. M. Sinha

Several studies concluded by various agencies (Coal Outlook, 1982; Malhotra, 1977) indicate that both the national and international markets for utility coal, which have been growing in recent years due to the uncertainties in petroleum supplies, will continue to grow in the foreseeable future. The areas where the Gemand for utility coal is projected to increase sub- stantially lie close to the midwestern coal fields, in the southeastern US, and in western Europe. Illinois has all the elements necessary to become an important exporter of thermal coal (Library of Con- gress, 1981) provided the coal is desulfurized to meet the environmental restrictions. Because of its high energy content, Illinois Basin coal, if desulfurized, has great potential for competing in the utility markets both nationally and internationally. Sulfur in coal occurs in organic and inorganic forms. The inorganic sulfur in Illinois coal is almost exclusively pyrite. The pyrite can be liberated by grinding and removed from the coal by such techniques as froth flotation. The Illinois Basin coals reportedly contain (Gluskoter and Simon, 1968) an average of 3.57% sulfur. Out of this, 2.06% is pyritic, 0.08% is sulfate, and 1.46% is organic sulfur.

Jan 1, 1986

By Warren E. Wilson

PRESENT-DAY design of launders is essentially an art depending to a marked degree upon the experience of the designer, whose problem is that of determining the dimensions of a conduit that will transport the pulp within the physical limitations of the plant and in the most economical manner. This paper has been prepared in an effort to place launder design upon a more scientific basis. A method is developed from elementary principles and presented in a form that may be used directly by the designer in determining launder dimensions.. The equations that are developed are believed to represent an advance over older ones, in that they give due consideration to all the pertinent variables, either including them in the analysis or showing that they may be neglected within the limits of applicability of the equations. Experimental data from several sources are used in evaluating the coefficients that are not determined in the mathematical analysis. On the basis of the material presented, it is concluded that launders may be designed with a much greater degree of accuracy than previously believed possible, when due consideration is given to all the factors involved in the problem. However, a great deal of work still remains to be done in the laboratory before a complete answer to all the questions in launder design can be made available. HISTORY OF LAUNDER DESIGN Among the references1-11 are cited accounts of many experiments that have been conducted in an effort to advance the knowledge of the flow of liquid-solid mixtures in flumes and pipes. With three notable exceptions, this work was carried on in such a manner that the results have limited value in solving the general problem, since not all the pertinent variables were measured and controlled. The exceptions are found in the works of Blue,6 Gilbert,7 and Blatch,11 who exercised great care in controlling and measuring all the significant quantities involved in the experimentation. It is notable that much of the work done by men directly connected with the mineral industries1-4 lacks somewhat in completeness, owing apparently to preconceived notions concerning the factors that determine the flow. For example, many measurements on flow in pipes and flumes carrying liquid-solid mixtures determined only the slope and percentage of solids, with no mention of size of particles, depth of flow, roughness of channel or specific gravity of solids. Material in current handbooks8,9 and textbooks is based largely on the experimental work cited above. Although most discussions of the topic-include statements that the results to be obtained by using the data presented are limited by the fact that all variables have not been considered, it is

Jan 1, 1943