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By B. S. Butler

STUDY of the ore deposits of Colorado has disclosed, in numerous places, sharp changes in both mineralogy and metal content of the primary or hypogene deposits with change in depth. A clear understanding of the meaning of these changes is requisite to form intelligent conclusions that can be applied in the exploration of such ore deposits. This paper is an attempt to set forth some of the geologic and chemical relations of minerals that bear on this problem. The effect of the differing electrode potentials of elements on the order of oxidation and on the order of displacement of one metal by another metal in supergene sulfide deposits has been studied for many years by several investigators. The results all agree rather closely with the original Schürmann series of replacability of metal sulfides, as Wells has shown.1 So far as the writers are aware there has been little attempt from the geologist's viewpoint to correlate the electrode potentials of the elements, other than those of the common metals, with the positions and mode of combination of the elements as found in ore deposits, and in particular in hypogene deposits. Wells' discusses electrochemical activity between solutions and certain ore minerals and mentions the possibility of its effect in precipitation reactions. The senior writer for a number of years has emphasized the importance of oxidation-reduction reactions as a factor in the formation of certain hypogene ore minerals, and as the electrode potentials are a measure of the relative oxidizing and reducing power of the elements and their ions, it seems possible that a study of them may offer some suggestions on certain problems. The data at present available for such a line of attack on oxidation-reduction reactions are too far from complete to offer much help, nevertheless the table of standard electrode potentials

Jan 1, 1929

By Mark S. Childs

FRIEDENSVILLE orebody in Lehigh County, Pennsylvania, lies in the south central part of the USGS Allentown Quadrangle. Physiographically the area is located in a small reentrant-known as Saucon Valley-of the Great Valley Province into the Reading Prong of the New England uplift. Saucon Valley itself is an oval-shaped lowland eight miles long and four miles wide, surrounded by ridges except where connected with the Great Valley through a breach in the rim known as Saucon Gap. These ridges, composed of Pre-Cambrian metamorphic rocks and Cambrian quartzites, rise some 500 ft above the valley floor. They are continuous with the New Jersey Highlands. The valley lowland is immediately underlain by lower Paleozoic dolomites and limestones. This area is one of low relief having a swing of approximately 100 ft, with an average elevation of 375 ft above sea level. The entire valley, which has a water shed of about 58 sq miles, is drained by Saucon Creek. This unit flows in a northeasterly direction to the Saucon Gap, where it discharges into the Lehigh River.

Jan 1, 1957

By George H. Rupp

THE Sunrise iron mine of The Colorado Fuel and Iron Corporation is in Platte County, Wyoming, about 110 miles north of Cheyenne. It is served by the company-owned Colorado and Wyoming Railway, which connects with the Chicago, Burlington and Quincy and the Colorado and Southern railways at Guernsey, Wyoming, a distance of 6 miles from the mine. The original Sunrise claims were staked mainly by United States Army officers and soldiers stationed at old Fort Laramie, because of small showings of copper in the Carboniferous limestones that form a horizontal capping overlying the Huronian iron ore. A small copper smelter was operated for about three years at Fairbanks, now an abandoned town on the North Platte River. As many of the copper shafts and test pits near the present Sunrise mine were deepened, they penetrated the capping and encountered iron ore or gray sericitic schist, and were abandoned. Evidence of an early interest in iron ore was found when the Chicago claim was stripped for mining. A narrow, winding crevice was discovered, which led downward 20 ft. through the capping to the underlying soft red hematite, in which a room 10 by 14 by 7 ft. had been excavated. Stone hammers and wedges and a few rusted pieces of iron were found on the floor, and the evidence is conclusive that the excavation was used up to rather recent times by Sioux Indian medicine men, to provide war paint. GEOLOGY AND ORE The Sunrise district is in the Hartville uplift, an anticlinal area in which pre-Cambrian rocks similar to those of the Black Hills and the Laramie Mountains are brought to the surface. The lowest part of the pre-Cambrian series exposed is a great thickness of pink, crystalline, Huronian dolomites with thin unstratified beds of schist and quartzite. The upper part of the series consists mostly of gray or green schists but includes a few lenticular beds of jasper and a banded iron formation con-

Jan 1, 1939

By Fred DeVaney

THE coercimeter, as its name implies, is an instrument for measuring the coercive force? of magnetic substances. It was developed by Davis and Hartenheim in the Special Studies Section, Metallurgical Division. A detailed description of this apparatus may be found elsewhere.2 The coercive force determinations of magnetic materials are inter-esting because of the relationship established by Gottschalk,4 who showed a linear relationship between the magnetization coercive force and the specific surface of comminuted particles. The value of this relationship in determining grinding efficiency has been shown by Dean.3 The determination of the surface contained in the subsieve sizes has always been a difficult problem for investigators. They made approximate measurements of the surface of coarse materials by sizing on screens, but for the determination of the surface of the sub-sieve sizes it was necessary to make detailed grain counts or, elutriation tests, or to study dissolution rates. The technical literature contains many references to other methods for determining these surfaces, either by some special apparatus or by mathematical calculations based on distribution lines. Many of the methods are long and tedious, and the results of some, at least, are questionable. The turbidimeter gives quick results on ground cement. By using magnetite as the material to be ground, a simple determina-tion of its coercive force by the coercimeter, requiring 10 minutes or less, can be transposed directly and accurately into units of relative surface. This subject has been pursued further by the U. S. Bureau of Mines in cooperation with the Missouri School of Mines and Metallurgy, Rolla, Mo., and the following is a description of the results.

Jan 1, 1938

By Fred C. Bond

It sometimes happens that old knowledge is forgotten, or half-forgotten, and its rediscovery is hailed as a great new advance in technology. Autogenous grinding affords such an example. The oldest-or apparently the oldest-commercial application of continuous autogenous grinding on a large scale outside of South Africa occurred at San Juancito, Honduras, where a total of more than two million tons of silver ore were ground autogenously with complete success from 1918 to the early 1940's. The history of the San Juancito silver deposits begins in 1880 when- the New York and Honduras Rosario Mining Co. started mining silver at a rate which soon reached two million ounces of silver annually. In 1912 the Company's first mill, located in the village of San Juancito, was shut down and its equipment transferred to a new cyanide plant. This plant, constructed on a mountainside near the mine, was equipped with tube pebble mills in which Normandy or Danish pebbles were used initially.

Jan 5, 1963

By C. C. Hatch, C. R. Larsen, A. L. Mular

INTRODUCTION As part of a general project to simulate a concentrator, the Brenda Mines Limited secondary crushing plant, located near Peachland, B. C., was sampled during the summer/winter of 1975 and during the summer of 1978 to develop a digital crushing plant simulator specific to the Brenda operation. The purpose of this simulator was to study the influence of manipulable process variables on important responses, to permit study of alternative circuit configurations if desired and to perform off-line optimization. This chapter describes the methodology employed to develop the simulator (1,2) along with typical applications thereof. SECONDARY CRUSHING PLANT FLOWSHEET Figure 1 is a schematic diagram of the Brenda Mines Ltd. secondary crushing plant circuit. The 41,000 tonne coarse ore stockpile(a) is -17.8 cm oversize (3B belt) from two 2.4 m x 6.1 m double deck vibrating screens (not shown). The screens are fed by 2 conveyor belts operated in series with two 198 cm apron feeders that handle discharge from a 152 cm x 226 cm primary gyratory crusher(520 KW). The primary crusher (not shown) treats up to 2725 tonne/hr of run of mine ore. Minus 1.9 cm undersize from the primary screens (#19 belt), referred to as the primary fines, joins secondary screen undersize (#18 belt) for conveyance to fine ore bins (not shown). Feed from the coarse ore stockpile is transferred by means of vibrating feeders and two 120 cm conveyors (#6 and #7) to transfer belts #8 and #9 (Figure 1). The belts feed two secondary 2.1 m standard heavy duty cone crushers (bl and b2). Each crusher is equipped with a modified coarse mantle liner and a standard coarse bowl liner. Mantle throw is 9.2 cm; nominal close side set is 3.2 cm. Crusher .countershafts (443 rpm) are driven by single 260 KW synchronous motors (710 rpm). Discharge from the secondary cone crushers joins discharge from four 2.1 m tertiary heavy duty shorthead cone crushers (fl, f2, f3 and f4). With the exception of the cavity (modified medium mantle liner and standard coarse bowl liner; close side set is nominal .84 cm) and motor (224 KW), these machines are similar to the secondary crushers. The combined discharge is transferred from a 183 cm conveyor to #14 belt which empties into a 1452 tonne secondary screen surge bin (c). Vibrating feeders beneath the bins feed five 2.4 m x 6.1 m double deck vibrating screens (dl, d2, d3, d4 and d5) sloped at 200 from the horizontal. The upper decks are punched plates with 2.7 cm x 7.6 cm slots. Lower decks are woven wire (1.27 cm diameter) sections with

Jan 1, 1982

By G. W. Nabor, M. Mortada

The effects of anisotropic or directional permeability on the areal sweep efficiency and the flow capacity are examined. The paper points out the importance of taking directional permeability into consideration in planning a flood. It analyzes the two-dimensional flow pattern associated with the skewed line drive for a unit mobility ratio. The direct and staggered line drives are treated as special cases of the skewed line drive. Analytical expressions are developed for the areal sweep efficiency at breakthrough and the flow capacity. They are related to the spacing between like wells, the distance between a row of injectors and the nearest row of producers, and the degree of skewness of the line drive. The latter quantity is defined such that it is equal to zero for the direct line drive and equals one-half for the staggered line drive. The areal sweep efficiency and the flow capacity depend also on the orientation of the flood pattern with respect to the principal axis of anisotropy. The paper provides a simple method for determining the areal sweep efficiency and the flow capacity for a formation in which the permeability in the bedding plane is anisotropic. INTRODUCTION Directional or anisotropic permeability is manifested by the ability of the formation to conduct fluids more readily along certain preferred directions. This situation occurs in many producing formationsl-4 and is usually attributed to depositional features in which the sand grains are oriented in a preferred direction. In some cases it results from the formation of a major and a minor fracture system. 4 Directional permeability should be taken into account in many phases of the production and exploration activities. Recognizing its existence in the formation of interest and planning accordingly can lead to increased recovery and substantial savings. For instance, the areal sweep efficiency in a water flood depends to a great extent on the orientation of the flood pattern with respect to the principal axis of permeability. Anisotropic5 permeability is specified by the directions of its three principal axes and the permeability along each axis. The principal axes of permeability are mutually perpendicular. This paper deals with the areal sweep efficiency at breakthrough and the flow capacity for formations with aniscltropic permeability. The flood pattern considered consists of alternate rows of injecting and producing wells. The rows of wells are parallel and form a developed, skewed line drive which is illustrated in Fig. 1. The staggered and direct line drives are treated as special cases of the skewed line drive. PRELLMINARY CONSIDERATIONS The formations considered in this paper are assumed to be of uniform thickness and porosity. The permeability is uniformly anisotropic, with each principal axis of permeability maintaining

By W. J. Uren, Charles R. Kuzell

The industries engaged in winning minerals from the earth, because of their widespread dissemination, are faced with perhaps as wide a variety of labor-management problems as may be found in any other broad sphere of productive activity. Those problems are continually increasing in volume and complexity, and management has become aware of their growing importance. For the past quarter century at least, labor-management problems have largely been union-management problems. During this period tremendous assistance has been given labor unions through legislation and administrative and political action. In the United States, legislation favorable to unions has come about in the form of the now defunct National Industrial Recovery Act; the Wagner Act, most of which has been carried forward in the Taft-Hartley Act and the Landrum-Griffin Act; the Norris-La Guardia Act, the Wage and Hour Law, the Walsh-Healey Act, and others. The result has been to transfer from the hands of management to those who direct the affairs of the unions a large share of control over the industry and to hamper in many ways the remaining control left to management. In the United States there are many examples of the power of unions to injure whole industries seriously without regard to the interests of management, the employes, or the public. During 1958 and 1959 revelations of corruption and coercion in labor unions made before the McClellan Committee of the U. S. Senate generated considerable public sentiment in favor of legislation to protect the interests of employes and the public. However, the resulting legislation, the Labor-Management Reporting and Disclosure Act of 1959 (Landrum-Griffin Act), demonstrated quite clearly that the political power of the labor union leaders was adequate to prevent adoption of effective measures in this field.

Jan 1, 1964

By Roy Moore

THE Tom Reed Extension and Big Jim mines of United Eastern Mining Co. are situated in the Oatman district, Mohave County, Ariz., about 28 miles southwest of Kingman, the nearest railway point. Articles descriptive of the mine surface plant, mill construction, and plant operations have been written by Otto Wartenweiler1, the designing engineer; Wheeler 0. North,2 when he was assistant general manager for the company, and Earle M. Bagley, mill superintendent.3 The last article covers average costs for the full time the mill was operated. The geology of the mines is described by F. L. Ransome4 of the United States Geological Survey. Production was started in January,. 1917, and the known orebodies were exhausted in May, 1925, showing a life of seven years and five months. On account of the comparatively short life and the fact that stoping operations were confined to two orebodies, little experimenting was done with mining methods. The two orebodies were in what is generally called the Tom Reed-United Eastern vein, which occupies a fault fissure having a normal displacement of several hundred feet. Seven or eight very productive ore shoots were mined along this vein in a distance of 1 ½ miles, the two worked by the United Eastern being 1 mile apart. The maximum dimensions of the Tom Reed Extension ore shoot were height, 750. ft.; length, 950 ft.; thickness, 48 ft. The vein structure varied from a solid quartz-calcite filling to a series of parallel stringers separated by andesite. From this body, 511,976 tons of ore were mined. (Fig. 1.)

Jan 1, 1928

By W. S. Potter

THE proportions of manganese and carbon in manganese steel are familiar to all, because manganese-steel castings have been well known for a decade or more in this country. The same alloy has now become a commercial product in the wrought state, and, as not only rails and bars are rolled daily but a great variety of forged and otherwise fabricated shapes are appearing, it may be interesting to mark the progress and, perhaps, to look a little closely into the nature of this important material of engineering.

Jan 4, 1914

By Philip Drinker, R. M. Thomson

In the mining and metallurgical industries, numerous problems arise requiring determinations of solid and of liquid particles suspended in air. Frequently, these problems are of local interest and involve purely economic or operating difficulties; on the other hand, toxic effects from the inhalation or the ingestion of substances suspended in air may be a matter of concern. For checking up process improvements or for determining ventilation efficiencies in problems of this general nature, various methods have been proposed. .Although simpler methods are often satisfactory, precipitation combines several desirable features that other methods lack. This paper is, therefore, devoted to a discussion of portable alternating-current precipitators applicable to the quantitat,ive determination and microscopy of dusts, fumes, and smokes in air. Small particles suspended in gases, such as air, are referred to in the literature as aerosols or suspensoids. Of these terms, suspensoids appears to be preferable as being more nearly in keeping with words in everyday use. In problems involving air pollution by small particles—by suspensoids—it is convenient to distinguish three broad classes based on the size, the degree of dispersion, and the method by which the particles become suspended in the air. Dusts.—Particles or aggregates of particles, 150 to 1 micron in diameter, that are thrown into the air by mechanical agencies are termed dusts. Examples are silica; talc; cement; organic dusts such as hard rubber, starch, and cocoa; flocculated fume, and smoke products. Fumes.—Particles, 0.2 to 1 micron in diameter, formed from chemical or physicochemical reactions are known as fumes. Examples are ammonium chloride, lead and mercury, zinc and magnesium oxides, fogs, and acid mists. Smokes.—Particles, less than 0.3 micron in diameter, formed by incomplete combustion of carbonaceous and other substances are called smokes. Examples are the particles formed from burning tobacco, oil, tar, and gas.

Jan 1, 1925

By R. L. Skaggs, R. A. Molsberger

DARKEN1 has pointed out that in most binary liquid metal systems the thermodynamic behavior is relatively simple in the terminal regions. Between the terminal regions. the thermodynamic behavior is more complex. To describe this behavior. he has defined the stability and the excess stability as shown: Qualitatively, an inflection in the free energy of mixing curve results in a change in sign, from positive to negative, of the stability function and is associated with a phase separation. Conversely, a large, positive stability over a narrow composition range is indicative of compound formation. Darken has shown a number of binary systems where the excess stability is constant in the terminal regions and varies sharply in between. The work described in this communication was undertaken to study the variation of stability and excess stability in a binary system as a function of temperature. In addition, this work provides means for the direct comparison of previously existing equilibrium (activity) and calorimetric (molar heat of mixing) data on the Hg-Sn system. Hildebrand2 measured the vapor pressure of mercury over Hg-Sn alloys at 595°K. Calorimetric studies were made by Kawakami3 at 523°K and by Kleppa4 at 423°K. In this work, the equilibrium vapor pressure of mercury was measured over a series of Hg-Sn alloys at 453" and 503°K by use of fused salt manometer with one arm exposed to mercury vapor. Deflections of the fused salt manometer were balanced by argon pressure on the other arm. Argon pressure was subsequently measured with a dibutyl phthalate manometer. Tin activities were determined by graphical integration of the Gibbs-Duhem equation making use of the familiar Darken5 a function. The activities of mercury and tin showed positive deviation from Raoult's law at 453 and 503°K as Hildebrand observed at 595 K. In Fig. 1 are plotted log activity of mercury and tin vs reciprocal temperature. The plot contains activities obtained from calorimetric studies. Hult-gren6 has calculated activities from Kleppa's4 data, and Kubaschewski7 has similarly treated Kawakami's7 data. Presumably. in each case a regular solution was assumed. For regions where a two-phase field

Jan 1, 1970

By E. C. Harder

INTRODUCTION FEW mineral deposits have in recent years attracted such general and Widespread attention as the Brazilian iron-ore deposits, due mainly to the quantities of rich ore occurring here, in contrast to the ever-decreasing grade of ores shipped from many large producing iron-ore districts of the world. The general average grade of the iron ores shipped from the Lake Superior district' has decreased to approximately 50 per cent., natural, in recent years. The Rubio ore of Bilbao, Spain,2 in 1890 averaged 55.5 per cent. metallic iron, dried; in 1902, 52.8 per cent., While at the present time a large proportion of the ores shipped from Bilbao are obtained by reworking the old dumps. In northern Sweden, where large magnetite deposits have only in recent years been extensively developed, selective mining is even now necessary in order to obtain high-grade Bessemer ores. During the last two years the iron ores of Chile have attracted much attention on account of the activities of the Bethlehem Steel Co. and others in the Chilean iron-ore region. Many of these ores are of good grade, yielding 67 and even 68 per cent. metallic iron, but judging from the Writer's observations in this region a large proportion of them Will be found to he of non-Bessemer grade. The most important variety of iron ore in Brazil is hard, dense to specular hematite, occurring in Minas Geraes. A large number (89) of analyses of this type of ore have been averaged, 3 giving the following composition: Per Cent. Iron 69.65 Phosphorus 0.0125 Silica 0.24 Combined H,0 0.38

Jan 10, 1914

By Foster Bain

THE outstanding characteristic of the last hundred years has been the world-wide rise in the standard of living. Man's dominion over nature is increasing with an accelerating pace and more and more the forces and materials of this world are being made to serve man's necessities and his convenience. We demand both quantities and varieties of goods that were beyond the dreams, to say nothing of the reach, of our fore-fathers, and our possession of them has become so much a matter of course that they excite no remark. Literally, thousands of young folks have required an explanation of a recent popular song, "Thanks for the Buggy Ride," for the reason that their own experience does not extend back into the pre-flivver age. This transition from the use of vehicles made mainly of wood and drawn by animal power, to metal made cars propelled by mineral fuels is all but complete and the memory even of older conditions is already fading. This is symbolic of what is happening all around us. In a recent book, Dr. Frank J. Goodenough, president of Johns Hopkins University, referred to Chinese civilization as a ?vegetable" civilization meaning thereby that the Chinese depend mainly upon the plant world for food, clothing and other necessities and luxuries. Our own people did the same hardly more than a hundred years ago. In 1820, this country produced and used only 5 lb. of pig iron per capita, but a quick and enormous change was wrought in the hundred, years that followed, and in 1920 the amount was 119 times as much, or 597 lb. It has since increased even beyond this and touched a peak of 809 lb. in 1923. In that year our output was more than twice that of 1903 and nine times that of 1883. This increase in production

Jan 10, 1926

By C. Jackson, J. J. Harrington

The pH control system at Kennecott Copper Corporation's Nevada Mines Division concentrator consists of two independent systems, lime dilution and lime addition. Lime dilution is accomplished in a mixing tank where slaked lime and water are introduced proportionately. The desired dilution of the milk of lime is determined by the electrical inputs provided by eight pH probes, one per grinding section. The inputs are averaged and applied to a time base generator. The summation output of the time base generator determines the proportion of lime and water that are to be mixed and applies this input to a voltage sensitive switching device. The switching device provides a signal to one of two relays which will add either slaked lime or water, dependent upon the summation output. The entire cycle is based on a 2-min repetition rate to allow for sufficient mix time. Responsivity is controlled by maintaing a limited maximum solution level in the mix tank. Lime addition is controlled independently within each grinding section. The electrical input from the pH probe in a given section controls the solenoid valves which provide lime to each of the ball mills. The valves remain open within a time range capable of maintaining the pH of flotation feed at a given set point.

Jan 1, 1978

By Gordon E. Agar

Several correlations have been proposed to relate energy consumption and size reduction in comminution, and although these are arrived at from different starting points, it is postulated that they are all statements of the same basic concept. To test this postulate, the dry ball mill grindability of langbeinite was determined, and the results were analyzed according to the various methods. An examination ' of the energy-particle size relationships proposed in the recent past revealed that they had much in common. In fact, the conclusion was tentatively drawn that these expressions were essentially the same, even though they were arrived at from quite different basic premises. The equations attributed to Charles2 and Holmes3 were shown to re- duce to the same single equation, W - A K-3, and the simulated continuous test used by Maxson et al.4 was shown to give the best experimental value of the required empirical parameter, ß. Furthermore, the size distribution parameter a in the Schuhmann equation, y - (x/K)2, was shown to be equal to ß in many cases. The kinetic approach used by Arbiter and Bhrany5 should give the same results as the Maxson test procedure; however, the batch operation used by Arbiter and Bhrany could not produce data that would be as precise as the simulated continuous technique. To test the validity of these conclusions, the simulated continuous method was used to obtain data on the dry grinding of langbeinite. The results are discussed in terms of the various equations and approaches. APPARATUS AND MATERIAL A ball mill with internal dimensions of 17.5 cm (6 7/8 in.) in length by 19.4 cm (7 5/8 in.) in diam was loaded to 50% of its volume with balls 3.2 cm in

Jan 1, 1969

By H. O. Jahns, R. A. Greenkorn, R. E. Haring, L. K. Shallenbarger

This paper is a study of the effects of heterogeneity on flow in an analog of porous media, the Hele-Shaw model. l-3 A set of experiments in heterogeneous Hele-Shaw models showed streamlines through and around heterogeneities of various sizes, shapes and levels. (A level, we define as the ratio between the transmissibility of the heterogeneity and that of the rest of the model.) The heterogeneities were restrictions or expansions of the flow stream analogous to variations in the transmissibility of porous media. The experimental data agreed well with numerical results and with an analytical solution, which we derived for a circular heterogeneity in an infinite field. This study considers the flow-stream distortion due to the shape, size and level of heterogeneities. Size and level are much more important than shape provided the heterogeneity is not long and narrow. Our analytical solution shows that a circular heterogeneity in a large field can be replaced by an equivalent circle of either zero or infinite permeability. The radius of the. equivalent circle is a simple function of size and level of the actual circle. INTRODUCTION With the availability of high-speed computers and numerical procedures to predict reservoir behavior, we are faced with an important question. How much information about the reservoir do we need to justify the cost of the computer in any given case? To answer this question, we have to know how various reservoir parameters affect flow behavior. Reservoir heterogeneity is one of these parameters. In this study, we used a simple, two-dimensional model of porous media, the hele-shaw model, to investigate the effect of heterogeneity on flow behavior. We restricted ourselves to linear, single-phase, steady-state flow in a rectangular field with a single heterogeneity at its center. The analogy between flow in Hele-Shaw models and in porous media is easily verified. Let us first consider a homogeneous Hele-Shaw model with constant plate separation h. (The Hele-Shaw model is constructed by placing two plates, usually glass, very close together and allowing liquid to flow between them. Streamlines are made visible by introducing colored fluid into the space between the plates at a number of points across the model.) We assume a cartesian coordinate system with its origin in the middle between the plates and the z axis directed perpendicular to the glass plates (Fig. 1). The fluid flow is always in a direction parallel to the glass plates and varies from a maximum value to zero in the very small distance from the middle (z = 0) to either plate (z = h/2). For slow motion of an incompressible fluid, neglecting inertia and body forces, we have the viscous flow equation: where p is the fluid pressure, p the viscosity, and v the velocity vector with components u, v and w in the x, y and z directions, respectively. In our rase. and the derivatives of 3 with respect to x and y are small as compared with the derivative in the z direction. Therefore, approximately, with Vp and v being two-dimensional vectors in the x-y plane. Two integrations with respect to z give

Jan 1, 1965

By Forrest K. Pence

Bentonite deposits are known to occur in Texas within the Jackson group of formations. This group represents the uppermost Eocene age sediments found in the coastal plain area of Texas. It outcrops across this area of the state in a narrow band of some 4 to 20 miles width. The outcrop pattern roughly parallels the present Gulf of Mexico shore line and is some 100 miles inland from the Texas shore, Fig 1. The principal bentonite deposits are found in the areas where this outcrop pattern cuts across the south-central Texas counties of Karnes, Gonzales, and Fayette. In these deposits, the better quality bentonite is found in the lower or bottom layers of the volcanic ash deposits in which they occur. Some of these better quality benton-ite~ develop very light colors upon firing and therefore justify their being classified as "white firing." The deposits in Karnes and Gonzales Counties apparently occur in commercial quantity, whereas the white firing strata so far uncovered in Fayette County have been too thin to be classified as yet as "commercial." A study of the ceramic properties of the weathered ash in Gonzales and Karnes Counties was reported in 1941.' Commercial development of the deposit in Gonzales County, 7 miles east of Gonzales, Texas. was started earlier by the Max B. Miller Co. for the purpose of marketing the material as a bleaching clay, and this operation has developed to very sizable proportions. In recent years, this company has offered a specially selected grade of the Gonzales material as a suspending agent in glaze slips. The white firing property especially adapts the material to use in white cover coat enamels. The strata in the deposit are practically horizontal and consist from top to bottom of approximately 2 ft of soil overburden, 10 ft of brown bentonite, 2 ft of coarse white bentonite, and 4 ft of waxy white bentonite overlying a he grained sandstone. The & being made in the quarry is approximately one-half mile in length. Only the bottom 4 ft of waxy bentonite is being recovered, the upper layers being stripped and wasted, Fig 2. It may appear somewhat surprising that the very bottom strata appears to have been the one most completely altered. To confirm this, samples from top to bottom of the various strata were studied microscopically by R. F. Shurtz. Professor of Ceramic Engineering, University of Texas. His interpretation is to the effect that the lower part of the seam was deposited at a much earlier date than the top, and that the lower part was chemically altered to a considerable extent before the upper part of the seam was laid down. The conclusion to be derived from these examinations may be stated briefly to he that the alteration in these strata or parts of strata has proceeded independently of the alteration in other parts of the strata during a considerable geological period. The presence of gypsum and iron stain throughout all of the strata indicates that alteration is now proceeding more or less uniformly throughout. It is contended that the alteration of the original ash to montmorillonite is not a result of the presently operating processes. A deposit which occurs approximately 7 miles southeast of Falls City and just south of the village of Casta-howa, has been explored and leased by J. R. Martin, of San Antonio. Mr. Martin has conducted mining and marketing operations in bentonite for a period of many years and asserts that the white firing strata found in this deposit occurs in commercial quantities. His pit, which is shown in Fig 3, exposes 2 ft of soil overburden, approximately 5 ft of white bentonite having coarse texture, and approximately 5 ft of waxy white bentonite which in turn overlies a brown sandy clay. Here, as in the Gonzales deposit, the most completely altered portion is found at the bottom of the seam, as per following report of microscopic examination by Mr. Shurtz. Sample No. 1: This sample was taken from the top stratum which is one foot thick. It is grayish in color and it contains visible fossilized plants. The color is probably the result of fine carbonaceous material in the rock. Under the microscope the sample is seen to consist of glass and feldspar; the amount of glass predominating. Both these substances are slightly altered. No montmorillonite or other clay mineral can be identified definitely; however, the products of the slight alteration mentioned are probably montmorillonite or mineral gel. Sample No. 2: This sample was taken from the stratum second from the top. This stratum is fourteen inches thick. The sample is light gray. It shows numerous veinlets of greenish translucent material ranging from one-eighth inches wide down to the limit of visibility with the unaided eye. It has the smooth, sub-conchoidal fracture characteristic of some bentonites. Microscopically the sample consists mainly of aggregates of clay minerals. The birefringence of the aggregates is lower than would be expected if the

Jan 1, 1950

By George Kunz

(Butte Meeting, August, 1913.) THE manifold inconveniences resulting from the absence of a uniform standard of mass for determining the weight of precious stones have long been obvious. This lack has been keenly felt in commercial transactions, and those who have devoted time and research to the study of historic diamonds and precious stones have had frequent occasion to deplore the absence of such a standard in the past. In a paper read in Chicago in 1893, before the International Congress of Weights and Measures, held in connection with the World's Columbian Exposition, the writer suggested dividing the carat into 100 parts, and constituting a standard international carat of 200 mg. ; that is, 5 diamond carats or 20 pearl grains to a French gram, making 5,000 carats or 20,000 pearl grains to a kilogram. He also called attention to the fact that while this would depreciate the present diamond carat or pearl grain only about 2.5 per cent., it would abolish the troublesome discrepancies between the various carat-weights now in use, and could be easily explained and understood everywhere.1 The subject of the various diamond carats, their incongruity, and the resulting confusion as to the correct weights of historic gems when definite records of them are searched for, has been fully treated by me in an extensive study of this subject in The Book of the Pearl.2 To the earnest and unremitting efforts of C. E. Guillaume, Director of the Bureau Internationale des Poids et Mesures at Sèvres, is largely clue the eventual success of this eminently desirable reform, which lie has constantly urged both by articles on the subject and by addresses delivered in Paris before the International Committee for Weights and Measures.3

Jan 7, 1913

By J. A. MacLellan, John C. Bowling, J. R. Davenport, G. M. Ellis

Six months out of the year the cold is always there, and it seems to be waiting for someone to make a mistake. The simplest things can shut down a multi-million dollar plant besieged with -40°F temperatures and a 40 mph wind. It takes only one man-door improperly latched to feeze up all the pumps on the bottom floor. Someone can poke a one inch hole in an outside wall in July and six months later, the whole plant is flooded because the main water line just froze up and burst. Some important things must be remembered in plant design for cold and remote areas. For one thing, everything in these areas is more expensive due to long and difficult supply lines. Fuel is expensive and would be a major cost item even if it were not expensive, due to the extended periods of low temperatures. Building volumes should therefore be kept to an acceptable minimum. Service areas, on the other hand, must be adequate, because maintenance generally has to be conducted inside in a heated area. Supply vehicles, for instance, have to get completely inside the building to unload. If you try to unload a supply vehicle with the door open at -50°F, you won't be able to find the vehicle for fog and if you take more than 5 minutes half the water lines in the plant will freeze UP.

Jan 1, 1972