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By David J. Raden

INTRODUCTION Economic deposits of phosphate are found at shallow depths (80 ft.) in central and northern Florida (Figure 1) where they have been mined since the late19th century(l).The present (1978) mining rate is approximately 40 million short tons per year of product (called “phosphate rock1”), which represents approximately 80% of the total U.S. production and 30% of the world production. The principal use of Florida phosphate is for the manufacture of fertilizer. There are 10 major mining companies and 20 active mines in Florida at the present time, strip mining approximately 5000 acres per year. The ore, known as "matrix," consists of gravelly clayey sands containing phosphate minerals (principally carbonate fluorapatite), quartz, and clay minerals. The clay to phosphate ratio is generally about 1:1 by weight and the sand to phosphate ratio ranges from, 1:1 to about 3:1. Mining is done by large electric draglines, which strip and cast the sandy overburden soils, generally 10 to 40 feet deep, and remove the matrix, generally 10 to 25 feet deep. Dragline bucket capacities are generally 20 to 45 cubic yards, but range up to 65 cubic yards. Mining cuts are usually 300 to 500 feet wide and up to several thousand feet long. The ore is cast into an earthen sump where high pressure water guns are used to slurrify it. Centrifugal pumps move the slurry through a pipeline to a beneficiation plant where the phosphate rock is separated from the waste sand and clays.

Jan 1, 1979

By E. D. Williamson

DURING the wartime rush to prepare the glass necessary for the needs of our army and navy, the problem of the temperature control of the annealing kilns became most serious. The narrow limits of strain allowable (all the specifications called for less internal strain than the average of the previously used German glass) made necessary a very exact procedure and the methods had to be used on a much larger scale than theretofore. At the Charleroi plant of the Pittsburgh Plate Glass Co., the members of the staff of the Geophysical Laboratory, which was cooperating with the company, had occasion to study the methods available, and reached a number of conclusions (many of them by no means new except in their application) that may interest and assist those who have to meet similar problems in other fields. The following is a short account of the essential features of the system of temperature control evolved, along with a rather abridged statement of the reasons that led to the adoption or rejection of various schemes.

Jan 8, 1919

By E. C. Barfield, D. G. McCarty

Two-dimensional analyses offer considerable promise in providing the basic information required to effect more precise control of petroleum reservoir performance. This paper describes a method for conducting some engineering analyses of this type using a high-qreed digital computer. The general approach is to (I) develop a representative numerical model of the reservoir and (2) employ a suitable numerical technique to solve the basic equation of flow and to develop the required engineering information for the particular case represented by the model. This technique has been used to calculate pattern performance in connection with several field projects involving water injection into oil reservoirs. This type of analysis involves sequentially (I) calculating the pres-' sure distribution in the reservoir and (2) tracking the progress of the interface between the displaced and displacing fluids in a step-wise manner to provide a depletion history of the operation. The particular analysis presented in this discussion is subject to the restriction that the mobility of the displaced and displacing fluids be equal and assumes that the fluids are incompressible and that gravity and capillary pressure do not affect the shape of the flood pattern. Complete two-dimensional .flexibility is maintained with regard to definition of reservoir rock and fluid characteristics, placement of physical restrains and boundary conditions, investigation of flow characteristics in the reservoir, and movement of the displaced and displacing fluid interface. The results of these studies indicate that the highspeed digital computer is well suited for conducting reservoir performance studies in two-space dimensions and that dependable numerical techniques are available for making such analyses. INTRODUCTION One of the problems facing petroleum engineers is that of providing more precise engineering control over reservoir operations at all stages during the depletion cycle. The most direct approach to this problem is to simulate the reservoir with some type of physical or mathematical model and use the information developed from the behavior of the prototype to predict the performance of the actual reservoir. This principle is, of course, not new, and a variety of simulation techniques have been developed to provide information on the behavior of oil and gas reservoirs. One straightforward refinement of present reservoir analysis techniques is the progress from one-dimensional reservoir models to those where the reservoir can be represented in two- and three-space dimensions. Multidimensional reservoir analyses are desired in order to show not only what is happening in the reservoir but in addition to show where in the reservoir the various phenomena of interest are occurring. Thus far, two-dimensional analyses have been confined predominantly to potentiometric and electrolytic model studies. However, when large numbers of wells are involved and where large-scale models are required, such problems become very tedious and instrumentation problems become acute." It is possible through use of numerical methods and general purpose digital computers to avoid many of the instrumentation difficulties and to relax some of the restrictions of previous techniques. The purpose of this paper is to discuss some recent experiences with the use of high-speed digital computers for predicting pattern performance in fluid injection operations and to describe the numerical procedures which have been used for making such analyses. THE NUMERICAL MODEL The problem of representing the reservoir with an appropriate numerical model is composed of at least two important considerations. The first requires that an adequate description of the reservoir mechanism be formulated in the form of the basic differential equation describing the process. The second consideration is definition of the physical characteristics of the reservoir. The latter requires that representative basic data be obtained, examined, and interpreted to provide sufficient detailed definition of the pertinent physical properties throughout the system. The Differential Equation One of the basic assumptions made for the purpose of performing the two-dimensional studies being dis-

By M. N. Short

It is almost self-evident that the student of geology depends for his education in geology only in small measure upon his own observation. His chief sources of information are lectures and personal instruction from teachers, and the geological literature. Of these, the literature is by far the most important. The total geological knowledge available to the geologist of today is substantially that which is on the printed page, and no more than that. There are many geologists of outstanding rank who during the course of a busy and useful professional career have accumulated valuable geological knowledge. This, however, is never available to the profession, owing to the disinclination of these geologists to write or to the refusal of their employers to allow the results of their work to be published. With the passing of these geologists, their accumulated knowledge is irretrievably lost. In many mining districts the operating companies are not averse to the publication of geological information gathered by their engineering and geological staffs, but for various reasons this information is not published. However, when a public survey geologist goes into the district this information is placed at his disposal and eventually is published. But for the intervention of a disinterested public scientist, this information would have been buried in company files. In the last analysis, the teachers themselves depend largely upon the printed page for the knowledge they pass on to the student. Without geological literature, then, the instruction of geological students would be almost impossible. There is no .question that, as a whole, geologists who are on the public payroll have to their credit far more contributions to literature than have either teachers or professional geologists, whether the latter be independent or in the employ of private corporations. The very fact that geologists are upon the public payroll places them under obligation to make available to the public the results of their endeavors. They must either prepare these results for publication or they must furnish data or otherwise aid their colleagues to publish their results. The success or failure of a public geological survey depends entirely on the

Jan 1, 1935

By M. N. Short

It is almost self-evident that the student of geology depends for his education in geology only in small measure upon his own observation. His chief sources of information are lectures and personal instruction from teachers, and the geological literature. Of these, the literature is by far the most important. The total geological knowledge available to the geologist of today is substantially that which is on the printed page, and no more than that. There are many geologists of outstanding rank who during the course of a busy and useful professional career have accumulated valuable geological knowledge. This, however, is never available to the profession, owing to the disinclination of these geologists to write or to the refusal of their employers to allow the results of their work to be published. With the passing of these geologists, their accumulated knowledge is irretrievably lost. In many mining districts the operating companies are not averse to the publication of geological information gathered by their engineering and geological staffs, but for various reasons this information is not published. However, when a public survey geologist goes into the district this information is placed at his disposal and eventually is published. But for the intervention of a disinterested public scientist, this information would have been buried in company files. In the last analysis, the teachers themselves depend largely upon the printed page for the knowledge they pass on to the student. Without geological literature, then, the instruction of geological students would be almost impossible. There is no .question that, as a whole, geologists who are on the public payroll have to their credit far more contributions to literature than have either teachers or professional geologists, whether the latter be independent or in the employ of private corporations. The very fact that geologists are upon the public payroll places them under obligation to make available to the public the results of their endeavors. They must either prepare these results for publication or they must furnish data or otherwise aid their colleagues to publish their results. The success or failure of a public geological survey depends entirely on the

Jan 1, 1935

By S. H. Cathcart

Price, production and drilling operations exceeded any year since 1930. A top price for crude of $2.55 was maintained from May 1 to November 6 and increased activity about coincides with that period. The average crude price for the year was: Bradford, $2.46; Kane-Butler, $2.34; Southwest Pennsylvania, $2.13. Production for the year exceeded 15 million barrels, an increase of about 2 million barrels over 1933. That this increase was more than justified by market demand is indicated by a reduction of 892,000 bbl. in stocks for the year. Two classes of data appear on Table 1, which are differentiated by footnote references. Where possible the .figures were obtained from individuals and companies that, from long acquaintance and varied contacts, are most capable of supplying an estimate where an estimate is necessary. The remaining data represent a rather careful compilation from all available published records (see p. 378). Drilling operations and production as summarized by the Oil City Derrick are as shown on Table 2.

Jan 1, 1935

By J. Gurland

A method of measuring the degree of contact between grains of 1 phase in multiphase alloys is derived. It is shown that the number and the areas of contacts between grains can be determined by metallographic analysis. Relations between the area of contact, the dihedral angle, and the mean free path of spherical grains are developed. It is often desirable to interpret the mechanical behavior of alloys in terms of structural features observed under the microscope. A quantitative description of microstructures of multi-phase alloys requires consideration of geometrical and topological factors such as the amount, size, and shape of grains and the continuity of the constituent phases. The number and dimensions of grains may be metallographically determined by applying the methods described by Smith and Guttman1 and by Fullman2 in their papers on the measurement of particle size and internal boundaries in opaque bodies. The present work intends to show that the same methods can be used to evaluate some of the parameters of phase continuity; namely, contiguity, number of contacts, and areas of contact of grains of 1 phase. Application of these concepts may be found in such problems as the calculation of electrical conductivity of 2-phase alloys, or the evaluation of the length of fracture path through grains of a brittle phase more or less dispersed in a matrix. I. DEFINITION The following definitions and derivations are based on 2-phase alloys, of which the units of the microstructure are grains. Contiguity is defined as the average fraction of surface area shared by 1 grain of a phase with all neighboring grains of the same phase. In a 2-phase alloy of constituents A and B, the contiguity of phase B is given by: where Cb is the contiguity of phase B aBß is the average area of contact between a grain of phase B and adjacent grains of phase B, aAB is the average area of contact between a grain of phase B and adjacent grains of phase A. The contiguity is a measure of the average degree of contact between grains of phase B in the 2-phase mixture. The ratio varies from 0 to 1 as the distribution of phase B changes from a completely dispersed to a fully agglomerated structure. Smith and Guttman1 have shown that the relative areas of 2 kinds of interfaces in a volume are directly proportional to the number of interfaces of each type intersected by a random line. The lines can be drawn on metallographically prepared surfaces as long as these are random sections through the sample. The contiguity ratio of phase B then becomes: Cb = 2NBB/NAB + 2N BB [2] where: NBB is the number of interfaces between grains of phase B intersected per unit length of random line. Nab is the number of interfaces between grains of phase B and grains of phase A intersected per unit length of random line. The factor 2 arises in Eq. [2] because each interface B-B is associated with 2 grains of B-phase, whereas the interface A-B involves only 1 grain of B-phase. The calculations of contiguity do not require any assumption as to volume fraction, particle size, or particle shape. Fullman2 gives an expression for the determination of the mean free path between particles. The mean free path PB between grains of phase A, i.e., through grains or agglomerates of phase B, may be found from the relationship: PB =2fB/NAB [3] where fB is the volume fraction of phase B. The calculation of the mean free path is independent of grain shape and grain size distribution. The calculation of the number of contacts and of contact area requires assumptions of grain shape, grain size, and contact shape. In the case of uni-

Jan 1, 1959

By SAM A. LEWISOHN

IT is popular today to dramatize in a journalistic spirit, some particular factor among the causes of unemployment. Naturally the time chosen for such emphasis is usually when the factor in question is temporarily a particularly active one. A few months ago, in the unemployment then current, we saw largely the results of a healthy acceleration in changes in processes, greater efficiency, a more intensified use of labor-saving devices, perhaps also a change in products. So we have been hearing a great deal about the influence of mechanization on unemployment, the so-called technological unemployment. Many talk as if this kind of unemployment were a wholly new phenomenon, for- getting that it is a constant process in a growing industrialism, though it sometimes becomes more pronounced. At other times one would think that seasonal unemployment is the only type of unemployment, and then again the fashion changes and we hear .about nothing except cyclical unemployment. Every few years there seems to be a different fashion in labelling the germ supposed to be the cause of unemployment.

Jan 1, 1929

By C. K. Leith

MANGANESE is one of the minerals which is principally consumed in countries other than those of origin. Nearly 85 per cent of the pro-duction is used by the United States, England, Germany and France, and roughly a third of the total is used by the United States alone. On the other hand, over 85 per cent of the world production comes from Brazil, Russia, India, the Gold Coast of Africa, and the Sinai Peninsula. It follows from this fact that practically all manganese moves across international boundaries in raw or alloy form, and much the larger part of this movement is for considerable distances and is ocean borne. There is no indication that any one of the principal consuming countries can develop even approximately adequate supplies of its own. Under abnormal war conditions, with high prices and changes in metal-lurgical methods, only 35 per cent of the needs of the United States was met from local sources, and under our recent tariff only 11 per cent. There are thousands of manganese deposits scattered about the world, but only a very few which can figure largely in supplying requirements on a modern scale. The known reserves, together with highly probable extensions and explora-tions now under way, indicate no shortage from a world standpoint for many decades to come. The production and marketing of manganese is going steadily into fewer and stronger hands. The steel in-dustry uses over 90 per cent of all the manganese mined, and is acquiring control of a considerable part of the production in all of the principal fields-the Germans in Nikopol, the English in India and Gold Coast, the Americans in Georgia, India, Gold Coast and Brazil. Some of the controlling companies are of international scope. Concentration of commercial control is a notable tendency. A natural consequence is the growing un-easiness of smaller consumers the world over about their ultimate supplies and desire to know more definitely how and where manganese supplies will be controlled in the future. The sources of supply are few enough to warrant the belief that more or less monopolistic ele-ments of control are not impossible.

Jan 5, 1927

By E. F. Kingsbury

ONE of the well-known and important uses of the noble or precious metals has been for electrical contacts. In fact, the elements of this group, comprising gold, silver and the six platinum metals, have been called "noble" because of their ability to resist- heat and corrosion, properties which were early found to be of importance in good contacts. Of these, platinum and its iridium alloys, palladium, and silver, have been extensively used. In recent years the electrical industry has been responsible for about one-eighth of the total consumption of the platinum metals in the United States. Information is not available as to what part of this one-eighth has been used for contacts but it is certainly an important one. SUBSTITUTES FOR PLATINUM During the past 20 years a considerable number of contact alloys have been proposed in the patent literature largely with the aim of more or less replacing platinum by gold or silver, and some of these alloys are finding increasingly widespread application as the reliability of their performance becomes established.. From even the partial data at hand it appears that this substitution by the less precious metals has replaced at least one-half of the amount of platinum that the entire electrical industry would otherwise be consuming at the present time.

Jan 1, 1928

By Dan Crackel, G. G. Ramos, Mark Heisel

INTRODUCTION Feasibility studies indicated that a cratering type stoping method was best suited to the character of the first ore block at Carr Fork. This method known as vertical crater retreat (VCR) has since been modified to a combination cratering and deck blasting using VCR drop raises for initial undercut development . The modified form retains many of the advantages of VCR while allowing high tonnage production blasts which have offset many of the disadvantages. FIRST CONCEPTS AND PREMISES Geologic Considerations The Steep Highland Boy (SHB) skarn orebody, the first of several blocks being developed, is a steeply dipping 70° to 90° limb of a syncline, with a width averaging 25 m (82 ft). The bed has a consistent east-west strike length of over 400 m (1300 ft) and extends from the surface to depths of over 1000 m (3300 ft). The footwall is highly fractured quartzite and the hanging wall grades from garneti te to limes tone and hornfe 1s. Because of the limestone in the hanging wall, the hanging wall appears more competent than the footwall. The ore is garnetite with lenses of massive sulphide and magnetite. The quartzite footwall is highly fractured not only because of the bedding but also due to the folding and intrusion of the quartz monzonite. This irregular footwall outline of some stopes in- creases the likelihood of excessive dilution. The principal ore mineral is chalcopyrite with some bornite. The garnetite ore is quite variable in terms of compressive strength and drillability. In addition to the sulphide and magnetite lenses, it is transected by clay- altered dikes and major and minor north-east faults. TABLE (1) gives the range and mean strengths of the rocks. Investigating Mining Methods Initial consideration of a suitable mining method centered around maximum safety and efficiency with minimum potential dilution. The following major methods were considered and investigated. Cut and fill mining was eliminated because of low productivity, the cost and problems associated with providing fill, and the relatively unsafe nature of the method. Sublevel caving was rejected due to the unpredictable cavability of the waste and the geometry of the ore body. Conventional sublevel or blasthole methods require excessive development, as fan and ring drills are limited to efficient drilling in the 18 to 25 m range (60 to 80 ft). Mining downdip with equipment drilling small diameter holes would have required eight separate extraction/drill horizons with crosscuts and associated excavation in the main ore block. The use of down the hole (DTH) machines cap- able of drilling 165 m (6g in) diameter holes

Jan 1, 1981

THE second operation in the art of casting, and one of the greatest importance, is that of melting and thoroughly liquefying the materials of which you wish to make your casting. On this operation depends the whole outcome of your intentions and the perfection of your work. Without it, even though you had a great abundance of moulds and vast quantities of bronze, your desires, labor, and expense would all be in vain. In this operation I find on consideration that, in addition to experience, there are three necessities-perhaps indeed four-that must be provided without fail. The first is the furnace or other agent which contains the fire and the metal brought together. The second is the wood or charcoal which is the necessary and proper nutriment of the fire, from whose virtues are derived the greater or lesser forces which, according to their kind, are ready to effect what is required. The third is to have the materials disposed to easy fusion by means of corruption, alloying, or by their own nature. The fourth, as the motivating cause of the whole, could perhaps be listed as the first-this is the ingenuity and good judgment of the worker, together with the bodily exertions not only of himself but also of his helpers in addition. For, besides a certain ordinary caution, it is necessary to pay particular attention, first, to see that the furnaces, machines, ladles, hearths, refineries, and other kinds of instruments or similar vessels be made so as to dispose the metals for melting, and, when melted, that they easily maintain them so. These should also be prepared in such a way that they cannot be injured by the fire, for if they should be damaged the operation would fail. In order to do this, it is first necessary that you arrange the instruments with forethought and action so that the power of the fire can operate. Fire operates on things only when brought together with them in long-continued operation, or when driven by a great force of wind. It burns many things and softens others, but it makes the metals as liquid as water.

Jan 1, 1942

C. A. Stetefeldt, San Francisco, Cal. (communication to the Secretary): In view of Mr. Louis's statement that the balance and weights employed in his experiment were '(by no means first-rate," the results can scarcely be entitled to weight. And if a slight variation in specific gravity were to be accepted as proof of the existence of allotropic modifications, we should be obliged to conclude that every metal existed in such modifications. When the observed specific gravity of an alloy (as is often, and perhaps generally, the rase) differs from the calculated one, it seems more reasonable to explain the difference (apart from errors of determination) by assuming that actual chemical combination takes place between some atoms of the metals. MR. Louis (communication to the Secretary): In reply to the criticisms with which Mr. Stetefeldt has favored me, I beg to point out to him that, in the first place, I do not myself attach very much weight to the results I have obtained. I merely claim to have pointed out that amorphous gold obtained from dissolving up the alloy with silver has a higher specific gravity than common gold—a result corroborated by the quoted results of Rose. At any rate, it is easy to repeat my observations, and I hope this may be done by men who have better opportunities than myself for this investigation. Surely it is worthy of attention from assayers at the mints. I am not prepared to say that I should regard slight variations in specific gravity as absolute proof of allotropism, but I do consider

Jan 1, 1894

By E. Mcl. Tittmann

Deep-seated human instincts urge us to positively mark the passage of time. We celebrate the passage of each year. Years give way to decades, and decades to half centuries and centuries. At all these mileposts we are inclined to pause, take a look around and catch our breaths before embarking on the next leg. We are at such a point now and this meeting I am sure will give direction to the road ahead into the decade of the seventies. In looking around at this point, 1973, it is obvious to all of us that the environment in which we must mine, mill, smelt and refine lead and zinc has radically changed. These changes have, of course, occurred over a long period of time. They have, however, all been in the same general direction. They have all had the same motivation. The period of greatest contrast is probably the fifteen years just before World War II and the fifteen years following the end of that war. I thought that I might review briefly with you what seems to me to be four of the more important changes that have developed since World War II that profoundly affect our activities in the lead and zinc industry. I mentioned before that all these changes have been in the same direction; that is, they have all tended to restrict our freedom of action in pursuing our objective of producing lead and zinc on a competitive basis at a profit. Consequently, in discus- sing them you may think that I am merely viewing with alarm. This is not the intent. This is merely supposed to be an objective analysis. I think it appropriate before discussing these trends in de- tail to examine the position of lead and zinc today.

Jan 1, 1970

By Richard D. Dick

The Los Alamos National Laboratory was involved in an oil shale fragmentation research program in cooperation with a Consortium of industrial companies to investigate the feasibility of using modified in-situ (MIS) recovery of oil from oil shale. Field tests were conducted at the Anvil Points Mine, Colorado, in the thick oil shale beds of the Green River formation. Part of the program included obtaining data about fragmentation by instrumenting the tests with accelerometers, velocity gauges, and the CORRTEX technique (Continuous Reflectometry for Radius versus Time Experiments). Some of the rock motion data from accelerometer and velocity gauges is presented, along with some conclusions. In addition, the signal recording system is briefly explained. The CORRTEX technique is discussed, and some results on explosive performance and stem behavior using the method are discussed.

Jan 1, 1984

By Philip Bucky

THE general conception of a mine model is that of a three-dimensional object representing the mine workings, the orebody and the country rock of a particular property. Its chief uses have been to make it easier to understand the mine and to serve as a basis for the arguing of legal questions. Fayol endeavored to use mine models in a different way and to all students of subsidence "Fayol's dome theory" is of decided interest. We have more recently the suggestion of Young and Stoek of the University of Illinois, who1 suggest the use of models as a means of studying the problem. Prof. Henry Briggs, of the University of Edinburgh and Herriott Watt College, also makes use of models to determine the effects of bending at the edges of extensive workings.2 It is interesting to note that civil engineers are taking a decided interest in the application of models and the principles of dynamic similarity to the solution of their problems. The Proceedings of the American Society of Civil Engineers for 1930 contain an elaborate article by Benjamin F. Groat,3 who says, in his opening remarks: "Every engineer should know and understand that a model constructed in accordance with Newton's theory of similarity is not only the means for reproducing the complexities of flow, or other mechanical action, on a small scale, but that models may be made the best means of designing works of great magnitude. In the present state of knowledge, a properly constructed and properly tested model will answer the difficult questions of hydrodynamics much more quickly and accurately than the most profound mathematical analyses." A study of P. W. Bridgman's book on Dimensional Analyses leads one to arrive at the same conclusion.

Jan 1, 1931

By David White

THE search for potash salts in the great "Red Beds? region of the Southwest, conducted for several years by the U. S. Geological Survey, the work being carried on for a part of the time in coöperation with the Bureau of Economic Geology and Technology of the University of Texas, has resulted in the discovery, within shafting depth, of potash salts, apparently of workable thickness and commercial quality, and prob-ably of great extent. Definite information is lacking as to the exact thickness of the potash beds, the size and boundaries of the areas underlain by workable strata, and the locations of the deposits richest and most favorably situated for exploitation. Briefly to review the salient features, of the general situation: We have in the great Red Beds region of the southwestern United States, embracing portions of central Kansas, western Oklahoma, eastern New Mexico, and northern and western Texas, .a series of sandstones. shales, anhydrite beds, clays and limestones, which; through an interval of 1000 ft., more or less, carry beds of salt, estimated by Darton1 to contain over 30,000 billions of tons of rock salt. It is the greatest known salt field of the world. At some points the intercalated beds of rock salt, one of which is reported by the driller to exceed 300 ft. in thickness, aggregate, accord-ing to the drillers' records, over 1000 ft. The sedi-mentary strata are similar in composition to those carrying the potash deposits of western Europe, and they were laid down at the same time and under condi-tions which, in many respects at least, were similar The stratigraphy and character of the beds are des-cribed by Darton2 and a, part of the area and the reported aggregate thicknesses of salt are shown, with some revision after Darton, in the accompanying map Fig. 1. The assumption that in the great areas of shallow evaporation basins spread over -the vast base-level region of saline deposition in the Southwest during Permo-Triassic time, potash salts were in some places, and at different stages, thrown down in crystalline deposits associated with the beds of rock salt, anhydrite, and gypsum, is, geologically speaking, more than reason-able. They are to be expected, and the conviction that they are probably present has long been held both in the Texas Bureau of Economic Geology and Tech-nology, under Dr. J. A. Udden, and in the- U. S. Geological Survey. Accordingly, for many years, efforts to determine whether potash deposits are present in this region have been made, though under very great difficulties, such as insufficient funds for boring, hack of drilling on private initiative in the more promising regions, hack of interest at first on the part of the drillers and companies, and, hater, inadequacy both of the methods of boring and of the sampling, to reveal in definite terms the thickness-of any saline stratum of given composition.

Jan 4, 1922

By H. C. George

The Wisconsin Zinc District, or the Upper Mississippi Lead and Zinc District as it is often called, lies in the southwestern corner of Wisconsin, in Grant, Iowa and Lafayette Counties, and it includes adjoining parts of Illinois and Iowa. The district is about 70 miles long, north and south, and about 40 miles wide, east and west. It lies wholly within what is geologically known as the non-glaciated area of the Upper Mississippi Valley. HISTORY OF THE DISTRICT The district was first opened up as a lead producer in 1822. From this time until 1860, about 205,000 tons of cog lead (galena) and washed lead (galena) was produced from shallow crevices and openings. From 1860 to 1900, about 74,500 tons was produced, and since that time, from 5000 to 7000 tons has been produced annually. Since 1900, most of the lead concentrate produced has been as a byproduct of the zinc mines. The first zinc ores were mined about 1862. These were the carbonate ores, locally known as "drybone." Very little zinc blende was mined in the district, previous to 1875. The zinc blende ores mined from 1875 to 1900 were mostly of the high-grade, hand-cobbed, sheet-ore class, which usually contained from 45 to 60 per cent. metallic zinc Such mines as the "Sallie Waters," "Quinlin," 'Lead Mine," "Benton Blende," and "Ida Blende," located near Benton, Wis., were mines which produced ores of this type, during this period. The mines located at Highland, the "Coker Mine" located at Livingston, Wis., and the "Opencut Mine" located at Shullsburg, Wis., were mines that were heavy zinc carbonate producers, previous to 1900. The production of zinc ores in the district from 1862 to 1890 was about 283,500 tons, mostly zinc carbonate, with a probable average metallic zinc content of 30 per cent. From 1890 to 1903, the production

Jan 1, 1918

By A. F. Daily

Free World consumption of diamonds of all types closely follows the fluctuations of the business cycles in the large industrialized countries, particularly the U.S. Sustained purchasing by this country for stockpiling purposes has been a major factor in Free World demand for crushing bort and industrial diamonds, and it has been for this reason that investments in larger plants have been made by all major diamond mining companies during the past few years. For the purposes of this study, the diamonds produced in the Congo and elsewhere in the Free World are divided into three types:

Jan 5, 1961

By H. V. W. Donohoo

Exploration in 1955 was marked by a trend toward large-scale programs using a number of geophysical techniques. These programs were initiated both to locate new mineral districts and to bring individual prospects into production. All 14 companies replying to the author's questionnaire include geophysics in the general exploration routine whenever it is applicable, and five companies carry on extensive geophysical programs. Nearly all report that company personnel perform the surveys. In addition to these firms there are the many smaller operators who contract much of their geophysical work. There are indications that the volume of such contracting is sizable.

Feb 1, 1956