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By R. S. Wagner, W. C. Ellis

A new mechanism of crystal growth involving oapor, liquid, crnd solid phases explains many observations of the effect of implurities in crystal growth from the vapor. The role of the impuuitq is to form a liquid Solution with the crystalline tnalerial to be grown from the vapor. Since the solution is n prefevred site for deposition firorti the uapor, the liquid becorrles supersaturated. Crystal growth occurs by precipitatzon from the supersaturated liquid crt tlie solid-liquid zntevfnce. A crystalline defect, such as a screw dislocation, is not essetztial for VLS (vapor -liquid-solid) growth. The concept of the VLS mechanism is discussed in detail with reference to tire controlled growth of silicon crystals using gold, platinum, palladium, nickel, silver, or copper as an implurity agent. RECENTLY a short communication' described a new concept of crystal growth from the vapor, the VLS mechanism. In this paper we present a detailed description of the process and its application to the growth of silicon crystals and we discuss its relevance to existing concepts of .'whisker" crystal growth. Crystal growth from the vapor is usually explained by a theory proposed by Frank2 and developed in detail by Burton, Cabrera, and Frank.3 In this theory a screw dislocation terminating at the growth surface provides a self-perpetuating step. Accommodation of atoms at the step is energetically favorable, and is possible of much lower supersatu-ration than required for two-dimensional nucleation. Crystals of a unique form resulting from aniso-tropic growth from the vapor are "whisker" or filamentary ones. Such crystals have a lengthwise dimension orders of magnitude larger than those of the cross section. For most filamentary crystals both the fast-growth direction and directions of lateral growth have small Miller indices. The special growth form for a whisker crystal implies that the tip surface of the crystal must be a preferred growth site. sears4 proposed that, according to the Frank theory. a whisker contains a screw dislocation emergent at the growing tip. Such an axial defect provides a preferred growth site and accounts for unidirectional growth. The hypothesis was extended by Price. Vermilyea. and Webb," still implying the presence of a dislocation at the whisker tip. They postulated that impurities arriving at the fast-growing tip face become buried while those arriving on the surface of slow-growing lateral faces accumulate and thereby hinder growth. These considerations led to a whisker morphology. There is increasing evidence that most whisker crystals grown from the vapor are dislocation-free. Webb and his coworkers6 searched for an Eshelby twist7 in zinc? cadmium, iron. copper, silver, and palladium whisker crystals. They found unequivocal evidence for an axial screw dislocation in only one element, palladium. However, not every palladium crystal examined contained a dislocation. Observations with the electron microscope have failed to show dislocations in whisker crystals of zinc, silicon.9 and one morphology of AlN.10 Since many whiskers are completely free of dislocations, an axial dislocation does not appear to be required for whisker growth of many substances. A significant advance in understanding whisker growth has been a recognition of the need for impurities. This requirement has been clearly demonstrated for copper,11 iron,13 and silicon9-1 whiskers. For silicon, detailed studies proved conclusively that certain impurities, for example, nickel or gold, are essential. Another pertinent phenomenon which has received little attention is the presence of a liquid layer or droplets on the surface of some crystals growing from the vapor. Crystals in which this has been observed include p-toluidine,14 MoO3,15 ferrites,16 and silicon carbide.'" The liquid layers or globules were considered to be metastable phases, molecular complexes, or intermediate polymers originating from condensation of the vapor phase. The possibility has been suggested that the halide being reduced is condensed at the tip18 or adsorbed on the surface11 of a growing metal whisker, for example copper. The literature on whiskers discloses illustrations of rounded terminations at the tips. These appear. for example, on crystals of A12O3,19,20 sic,21 and BeO.22 For BeO, Edwards and Happel suggested that during growth of the whisker the rounded termination consisted of molten beryllium enclosed in a solid shell of BeO. A recent paper9 on the growth of silicon whiskers contains many observations pertinent to an understanding of the mechanisnl of whisker growth. These observations are summarized as follows. 1) Silicon whiskers are dislocation-free. 2) Certain impurities are essential for whisker growth. Without such impurities the silicon deposit is in the form of a film or consists of discrete polyhedral crystals.

Jan 1, 1965

By David Firewick, Daniel Stewart, Richard Rein

Panel caving of the Henderson orebody began in August, 1976. Fifty months later, on September 10, 1980, the cave zone appeared on surface as a steep-walled cavity positioned directly above the initial cave area. Although surface survey data revealed the development of a slight depression over the production area, surface inspection by geologists, three days prior to breach- ing, resulted in no evidence of impending glory-hole development. Geologic factors such as rock contacts and alteration-zone boundaries had little influence on the location of the initial glory hole. Since initial breakthrough, the glory-hole shape and growth have not directionally followed caveline advance because of topography and faulting. Based on periodic data, mine production has resulted in immediate growth of the Henderson glory hole.

Jan 1, 1984

By Theodore J. Hoover

WHAT are the chief branches of the mining engineering profession today? In an effort to analyze the structure of the profession, for practical purposes, a quantitative study has been made of the membership of the A.I.M.E., and is herein reported for the first time. In spite of the effect that a long history and a relatively small group of professional workers have had in limiting specialization in mining engineering, there has nevertheless grown up a wide variety of specialties in this field. More than a hundred different kinds of engineers were discovered among the titles given by Institute members in the Directory, ranging from "advisory engineer" and "American engineer" down to "wire-rope engineer" and "works engineer." How should all these titles be defined and interpreted? How many of them should be relegated as meaningless or confusing? What are the relationships among the remaining useful designations? Should some of them be grouped as "metallurgical" or "chemical," or under some other head?

Jan 1, 1935

By T. Leser, A. W. Jenike

The problems of caving and underground subsidence can be considered as the failure of a highly compacted rock and its subsequent flow in the form of broken rock. The problem is complex because the propagation of failure and flow have to be considered simultaneously; the yield strength of the virgin rock and the broken rock are different; and, while under certain conditions it is sufficient to consider the virgin rock as homogeneous, the density and the yield function of broken rock are both pressure and time dependent. A study of the failure and flow of solids with a pressure dependent yield function has been published recently by Jenike.' In this paper the density of the broken rock is assumed to be only time dependent and the consequences are examined in the case of one-dimensional vertical subsidence into an initial cavity. The following describes an attempt to develop a tool which, in combination with other tools, may lead to mathematical solutions of real problems of caving and subsidence. STATEMENT OF THE PROBLEM An underground cavity of horizontal cross section 4 = 1 and height 6 is assumed to exist at some depth below the surface. At the time t = 0 rock above the cavity fails and completely fills out the cavity with expanded broken material. With passing time the broken rock consolidates and subsidence proceeds continuously upuard in a vertical shaft. The phenomenon is one-dimensional (see Fig. 1). The problem consists of finding the displacement and the velocity with which the frlmt of the subsidence (wave front) moves upward as a function of the time and of the rock properties. DIFFERENTIAL EQUATIONS CONTROLLING THE PHENOMENON With the assumptions that the broken rock is a continuum and that the subsidence occurs continuously, we can apply the one-dimensional differential equation of contitiuity (conservation of mass) and the equation of preservation of momentum The latter equation is replaced by an assumed relation based on experience, which takes care of the

Jan 1, 1962

By Paul Sterling

1. INTRODUCTION. THE general impression regarding the preparation of merchantable anthracite is that it is confined to a colossal, grimy structure, called a "coal-breaker." This name is misnomer; for the desired result is not to break the coal, but to prevent its being broken. Preparation may be said to begin at the face of the chamber, with the mining and loading of the coal. Local conditions vary, not only in the same field or basin, but also in the same mine, so that there is no fixed empirical rule governing the method of blasting or cutting coal. Tests should be made, when possible, to determine the explosive, or the mechanical coal-cutter, which will produce the largest percentage of what are locally known as " lump " and " prepared sizes " of anthracite. The prepared sizes are those mostly consumed for domestic purposes. All other sizes might be called by-products of the anthracite industry; for they are not especially desirable, being the degradation resulting from the mining and handling of a brittle or laminated material. Being low in volatile combustible matter, anthracite burns most successfully when nearly of a uniform size, permitting the easy passage of air through the voids. This accounts for the large number of sizes into which the coal is separated. Table I. gives the various sizes, the diameter of ring over and through which each size is made, and the usual purpose for which it is employed.

Oct 1, 1911

By Gerald Edmunds, R. K. Waring, E. A. Anderson

Brass is liable to failure under the combined influence of stress, certain corrosion media, and time, a phenomenon commonly termed season cracking or stress-corrosion cracking. The consequences of this are serious in applications of brass generally, including the important field of cartridge cases. Cartridge cases (70 Cu: 30 Zn) that fail from this cause may allow the escape of gas from the gun breech, a hazard to the shooter, and may not eject, thus temporarily putting the gun out of action. In loaded cartridge cases, the stress present is partly residual from the, drawing and necking operations and partly applied by the insertion of the projectile. Ammonia, present as a decomposition product of smokeless powder, air and moisture constitute corrosive media. The prevalence of season cracking has been reduced considerably, but not eliminated, during the past quarter of a century by low-temperature annealing to relieve stresses residual from fabrication, a method suggested by Diegel 38 yr. ago(I).2

Jan 1, 1945

By AIME AIME

COMMITTEES. LOCAL COMMITTEE.-R. C. Crawford, Chairman; Harrison W. Craver, Secretary; Julian Kennedy, Taylor Allderdice, E. W. Pargny, Charles L. Miller, W. H. Rea, S. A. Taylor, M. E. Wadsworth, W. A1. Henderon, A. C. Dinkey, W. L, Jones, E. L. Messier, George Mesta, J. H. Jones, G. H. Riley, S. L. Goodale, D. W. McNaugher. LADIES' COMMITTEE.-Mrs. Taylor Allderdice, Chairman; Mrs. Julian Kennedy, Mr. R. C. Crawford, Mrs. E. M. Herr, Airs. J. W. Marsh, Mrs. T. A. Mellon, Mrs. G. P. Bassett, Jr., Airs. D. M. Clemson, Mr. Charles L. Miller, Mrs. V. L. P. Shriver, Mrs. W. A. Bostwick, Mrs. A. C.. Dinkey, Mrs. A. P. Childs, Jr., Mrs. F. R. Dravo, Mrs. Hermon Griffin, Mrs. W. H. Nimmick, Mrs. F. H. Lloyd, Mrs. S. G. Cooper, Mrs. S. H. Church, Mrs. E. N. Ohl. The Institute Headquarters was established at the Hotel Schenley, where a bureau of information was maintained for the benefit of the visiting members and guests of the party during the time of the meeting. TECHNICAL SESSIONS. The first session, held Tuesday evening, Mar. 1, 1910, in the large lecture hall of the Carnegie Institute, was called to order by Harrison W. Craver, Secretary of the Local Committee. Mr. Craver introduced Dr. John A. Brashear, who extended to the members and guests a hearty welcome to the city of Pittsburg, to which David W. Brunton, President of the Institute, responded. The following papers were presented in oral abstract by the authors: Biographical Notice of Dr. Charles B. Dudley, by Dr. R. W. Raymond, New York, N. Y. Biographical Notice of William Metcalf, by Col. II. P. Bope, Pittsburg, Pa. Development of Hindered Settling Apparatus, by Robert H. Richards, Boston, Mass. (Illustrated by lantern-slides.) A Few Mining Districts in the Argentine Republic, South America, by Z. S. Beyl. (Illustrated by lantern. slides.)

Apr 1, 1910

By E. J. Schmitz

The following abstract of an unpublished treatise, prepared by me, on the geological formations and minerals of the State of Alabama, is deemed of interest to the Institute. This State, called after the river of the same name (which, formed by the junction of the Coosa and the Tallapoosa, waters, with its tributaries, more than half the State), is divided by its main watershed into a larger southern district, sloping south and southwest, and drained into the Gulf of Mexico, and a smaller northern district, sloping generally north and west, and drained into the Tennessee. Geologically the State may be divided (according to historical geology) according to the different formations it exhibits, among which I include the Azoic, the existence of which in Alabama has been doubted by some; or it may be divided (according to structural geology, as closely related to topography) into a north and northwestern, a middle, and a southern zone.

Jan 1, 1884

By J. A. Herrick

For a long time, especially in Europe, heavy pieces of forging, such as cannon, armor plates, marine shafting, etc., have been steadily augmented in size, more particularly since steel has been substituted for wrought iron. To keep pace with these forgings several very large hammers have been, from time to time, erected. The most powerful and thoroughly appointed of all now in operation is that designed and built by Messrs. Schneider & Co. at their' works at Creusot, and it is the design of this communication to give to the members of the Institute a concise description of this remarkable piece of mechanism, which I have taken from an article published in the Annales Industrielles. This hammer is rated nominally at 80-tons power, but its capacity is, in reality, far greater, as will be seen by the comparative figures given later. The complete plant, comprising the hammer, the cranes, the furnaces, and the building which shelters the whole, is distin-

Jan 1, 1880

By A. D. Hodges

The process to be described, whatever other merits (or demerits) it may have possessed, certainly proved a financial success under the conditions of the locality where it was introduced and where a refining process had been sought previously in vain. I have ventured to bring it to the notice of the Institute in the hope that it may prove of some interest as a solution of a practical problem, such as is often presented to the metallurgist in the remote mining regions of the West. The method was used first at the Lyon Mill at Dayton, Nevada, and has been adopted at other tailings-mills on the Cornstock. These mills treat two classes of tailings: "sand," or; material which has passed previously through the pans of the ore-mills; and " slimes," or the fine clayey material which, coming from the battery, is too light to settle in the tanks inside of the mills but is

Jan 1, 1886

By J. A. Herrick

FOR a long time, especially in Europe, heavy pieces of forgings, such as cannon, armor plates, marine shafting, etc., have been steadily augmented in size, more particularly since steel has been substituted for wrought iron. To keep pace with these forgings several, very large hammers have been, from time to time, erected. The most powerful and thoroughly appointed of all now in operation is that designed and built by Messrs. Schneider & Co. at their works at Creusot, and it is the design of this communication to give to the members of the Institute a concise description of this remarkable piece of mechanism, which I have taken from an article published in the Annales Industrielles. This hammer is rated nominally at 80-tons power, but its capacity is, in reality, far greater, as will be seen by the comparative figures given later. The complete plant, comprising the hammer, the cranes, the furnaces, and the building which shelters the whole, is distin-

Jan 1, 1880

By Benjamin C. Allen

The surface tensions of liquid chromium and manganese were determined by a modification of the dynamic drop-weight method and found to be, respectively, 1700 * 50 and 1100 * 50 dynes per cm at their melting points. Molten drops were formed LITTLE is known about the surface tension of liquid chromium and manganese, even though they are technologically important metals and widely used in steelmaking. In the past, direct determinations have been hampered by their high reactivity on the lower end of a vertically held rod inductively heated under argon. The technique essentially reproduced surface tensions reported for liquid nickel and zirconium using static drop-shape methods. and vapor pressure. In this work, surface tensions were measured by the drop-weight method, using induction heating under argon. EXPERIMENTAL WORK Chemical analyses of rods used are given in Table I. Chromium rods were prepared from iodide-process crystals which had been are-melted, hot-extruded, warm-swaged, and centerless-ground.'

Jan 1, 1964

NEW MEMBERS The following list comprises the names of those persons who became members during the period of Oct. 10, 1917, to Nov. 10, 1917. ABEY, HIROSHI Min. & Met. Engr.. Mitsubishi Co., Tokio, Japan. BARNETT, WALTER W., Assayer & Chem., Seoul Min. Co., Tul Mi Chung, Chosen, Korea. BATES, WILLIAM S Min. Engr., Anaconda Copper Min. Co., Butte, Mont. BENDELARI, ARTHUR E Mgr. of Mines, Eagle Picher Lead Co., Picher, Okla. BERKEFELD, PAUL C Mining Engr., 2901 Piedmont Ave., Berkeley, Cal. BILLINGS, It. S Mgr., Sheep Trail Pyramid Mines Co., Kingman, Ariz. BILLWILLER, C. J., JR Mgr. Nitrate Agencies, Ltd., Iquique, Chile. BLUM, EDWARD H., Engr., Asst., to Pres., The Atlantic Refining Co., 3144 Passyunk Ave., Philadelphia, Pa. BORDEN, GAIL, Vice-Pres. & Treas., American Safety Explosive Co., 50 East 42d St., New York, N. Y. BRESLIN, THOMAS F Min. Engr., Cebu, Cebu, P. I. BURKE, JAMES M., Efficiency Engr., Calumet & Hecla Mining Co., Calumet, Mich. CANTON, WILLIAM R Met., Nevada Consolidated Copper Co., McGill, Nev.

Jan 12, 1917

By K. P. Gupta, P. C. Panigrahy

The stabilization of the R, a-Mn, and 0-Mn phases have been studied in the Mn-Ti-Fe and Mn-Ti-Co systems. Iron and cobalt both appear to stabilize the (Mn-Ti) R phase to almost the sarne extent. The R-phase region was found to extend from the lowest e/a to slightly beyond the maximunz e/a limit known for this phase. But, while iron appears to stabilize the a-Mn phase, cobalt tends to stabilize the p-Mn phase. In the two systems manganese appears to get replaced by iron and cobalt in each of the mentioned phases. The instability of the a-Mn phase in the Mn-Ti-Co system and the /3 -Mn phase in the Mn-Ti-Fe system cannot be explained on the basis of adverse size effects because atomic diameters for both iron and cobalt (C.N. 12 at. diam) are ziery similnr and not much different from manganese which they replace. Qualitatively, the reason for the stability of the a-Mn and the p-Mn phases can be traced to the more favorable e/a ratio prevailing in the respective systems and to a competing tendency between the two phases. In transition metal alloy systems the o, p,P, R, a- Mn,' and p-Mn2 phases have been claimed as electron compounds. A large volume of work has been done to establish the criterion for the formation of the o phase but until very recently practically no systematic work was done on the a-Mn and the /3-Mn phases. A recent investigation on the P-Mn phase3 indicates the e/a criterion for p-Mn phase stabilization. Since the R phase was first known to appear only in certain ternary systems1 no detailed work was then possible for this phase. The R phase has been recently discovered as a binary intermetallic compound in the Mn-Ti~ and Mn-si~-' binary systems. The existence of binary R phases opens up the possibilities of studying the effect of alloying elements on the stabilization of the R phase. Of the two binary systems possessing an R phase, the Mn-Ti system appears to be more interesting because at a suitable high temperature it is possible to find the three electron compounds, the a-Mn, p-Mn, and R phases, side by side and it is possible to study the effect of a third transition element on these three electron compounds. For the present investigation iron and cobalt, so called B elements for the formation of electron compounds, have been used as the third element to study the stabilization of the a-Mn, P-Mn, and R phases. EXPERIMENTAL PROCEDURE The alloys were prepared by using 99.9 pct pure electrolytic Fe and Mn, 99.5 pct Co, and crystal bar titanium, supplied by Semi Elements Inc., New York and Gallard Schelsinger Mfg. Co., New York. Weighed amounts of the components were melted in recrystal-lized alumina crucibles in an inert atmosphere (argon) high-frequency induction melting unit. Titanium was made into fine chips for easy dissolution and a special charging procedure was adopted to avoid contacts of titanium chips with the alumina crucibles. Up to 20 at. pct Ti, the maximum titanium content in the investigated alloys, there was no visible sign of reaction of titanium with the alumina crucibles. With a careful control of melting time and temperature the losses were minimized and were always found to be below 0.1 pct. Because of such small and almost constant weight losses, the alloys were not finally analyzed. The alloys were wrapped in molybdenum foil and annealed in evacuated and sealed silica capsules at 1000" * 2°C for 72 hr and subsequently quenched in cold tap water. Annealed samples were examined metallographically and by X-ray diffraction. For all high manganese alloys oxalic acid solutions of various concentrations and 1.0 pct HN03 solution were found suitable as etching reagents. Best contrast between the a-Mn and the R phases could be obtained by using freshly prepared 60 pct glycerine + 20 pct HN03 + 20 pct HF solution. For high iron and cobalt containing alloys, especially for alloys containing the a-Fe, y-Fe, and P-Co phases, 15 cc HNOJ + 60 cc HC1 + 15 cc acetic acid + 15 cc water solution was found to be the best etching reagent. All X-ray diffraction work was carried out (using specimens prepared from annealed powders) with a 114.6 mm diam Debye-Scherrer camera using unfiltered FeK radiation at 25 kv and 10 ma. All calculations for X-ray diffraction work were carried out using an IBM 7044 digital computer RESULTS AND DISCUSSION The two ternary systems, MnTiFe and MnTiCo, were investigated near the manganese rich end, Figs. 1 and 2, and show some common features. In both alloy systems large extensions of narrow R phase regions occur at almost constant titanium contents. At titanium contents higher than that of the single phase R-phase alloys, the same unidentified X phase was found in both ternary systems. The extensions of the X phase close to the Mn-Ti binary indicate that this phase could be the TiMns phase. Too few X phase diffraction lines were present in the diffraction patterns to make positive identification of the X phase. In contrast to this similarity the two systems show opposite behavior in the extensions of the a-Mn and 8-Mn phase regions; while iron tends to stabilize the a-Mn phase, cobalt

Jan 1, 1970

By T. P. Meloy

In a recent paper, Gaudin and Meloy1 derived a size distribution function for single, impact fracture. Mular2 extended the use of this size distribution to describe the output of carefully controlled grinding experiments. As it stands, the function is difficult to compute. Consequently, a series of tables of the function are presented below: where M(x) is the cumulative fraction finer than size x when x is particle size. Weight percents are tabulated for the single parameter, r, in three different size ranges: from 0 to 1, from 1 to 10 and from 10 to 100. Tables I, II and III are cumulative percent finer and Tables IV, V and VI are for weight percent passing screen size x, retained on the screen below. A number of conditions from the table are plotted in Figs. 1 and 2. Fig. 1 is a plot of the cumulative percent finer vs. size, and Fig. 2 is the weight per-

Jan 1, 1963

By J. W. Stewart

ONE of the postwar problems posed for mineral engineering educators is the desire of some mature student veterans to finish their college education under the G. I. Bill of Rights as quickly as possible, a desire that is quite understandable. Not only have they lost several years of education, which they wish to make up as quickly as possible, but many are married and have families and want to become productive as soon as possible in order to support their families properly. The obvious solution to this problem, if it really is serious, would appear to be a continuation of the wartime Accelerated Program, as it was carried on in most colleges and universities. As a matter of fact some schools are known to have continued their wartime programs in one or another form. To ascertain just what our mineral engineering schools generally are doing to meet this postwar problem, last April a questionnaire was sent to administrative officers at colleges and universities

Jan 1, 1946

By Charles R. Keyes

the leaching of near-by rocks, had had no other result than to bring out from obscurity three certain features of practical lmport, all the labor of that controversy would have been well expended. These three points are : (1) a clear distinction between the vadose and the profound zones; (2) a determination of the manner in which the latter may be invaded by conditions of the former; and (3) an establishment of the general truth of the lateral-secretion theory when vadose conditions prevail, and of the. ascension-theory under profound conditions. In the practical consideration. of ore-deposits these generalizations are fundamental. Their wider application must be productive of great industrial advantages. Of first importance in the broader scientific survey of ore-genesis is the recognition of a sharp distinction between vadose and profound conditions. To many who listened to Professor Posepny's remarkable paper, read at the Chicago session of the Institute during the Columbian Exposition in 1893, this seemed, as Dr. S. F. Emmons has already observed, its most valuable and suggestive feature. Notwithstanding Posepny's implications to the contrary, and his vigorous berating of Sandberger's views, the immediate and lasting .effect of the . argument was really to strengthen greatly Sandberger's position. For it completely and sharply separated the lateral-secretionists from the ascensionists, raising the sphere of the former bodily above the line of permanent water-level and at the same time confining .the sphere of the latter to regions below that horizon. A little later, Professor Van Rise showed in some detail how meteoric waters may deeply invade the profound zone and carry vadose conditions into it. The zonal limitations of two great and apparently opposed agencies being thus definitely fixed, it is found that neither of the theories based thereon is susceptible of general application. If the generalizations of the lateral-secretionist be propounded solely for vadose conditions, we are able to agree with all of his more-important contentions; while there is general acquiescence in the views of the ascensionist if their application be restricted to the profound zone. Of the ore-bodies of the world that are mined to-day, the majority are essentially vadose in origin, and probably originated

Jul 1, 1910

By Richard P. Rothwell

A REFERENCE to the geological map of Alabama shows the coal- measures of that State to form three distinct fields. The Coosu, or most easterly, contains about one hundred square miles ; the Cahaba, or middle field, which is also the most southern true coal in the United States, contains about 230 square miles ; and the Warrior field, which contains in the State of Alabama some 5000 square miles, is the southern extremity of the great carboniferous deposit, which extends through Pennsylvania, West Virginia, Kentucky, Tennessee, and Georgia. But very little has yet been done towards developing those coal- fields, partly owing to the absence of all commercial manufacturing enterprise in the South under slavery, and partly owing to the want of capital and the disturbed condition of the South since the war. During the past three or four years I have devoted a large part of my time to the examination of the coal and iron ores of this range,

Jan 1, 1874

By B. M. O Harra, George M. Fowler, R.E. Illidge

The Tri-State district comprises an area of about 2000 square miles in southwestern Missouri, southeastern Kansas, and north- eastern Oklahoma. The part that is in and contiguous to Missouri is still sometimes designated as the Joplin district (Fig. I). Early Operations Mining operations in what is now the Tri-State district date from about 1848 and have been continuous to the present. Apparently the first discoveries of ore were made about the same time near the present sites of Joplin, Oronogo, and Granby. Lead minerals were found at grass roots, probably in shattered rock in shallow excavations, then these minerals were followed in shear zones to deeper horizons. The mining of zinc followed. Before 1874, zinc ore was worthless and discarded as waste. According to published records, the total production of lead to that date was 49,000 tons of metal from 70,000 tons of concentrates. Production The a.ggregate ore production from the Tri-State district was recorded at intervals

Jan 1, 1943

By George M. Fowler, B. M. O Harra, R. E. Illidge

The Tri-State district comprises an area of about 2000 square miles in southwestern Missouri, southeastern Kansas, and north- eastern Oklahoma. The part that is in and contiguous to Missouri is still sometimes designated as the Joplin district (Fig. I). Early Operations Mining operations in what is now the Tri-State district date from about 1848 and have been continuous to the present. Apparently the first discoveries of ore were made about the same time near the present sites of Joplin, Oronogo, and Granby. Lead minerals were found at grass roots, probably in shattered rock in shallow excavations, then these minerals were followed in shear zones to deeper horizons. The mining of zinc followed. Before 1874, zinc ore was worthless and discarded as waste. According to published records, the total production of lead to that date was 49,000 tons of metal from 70,000 tons of concentrates. Production The a.ggregate ore production from the Tri-State district was recorded at intervals

Jan 1, 1943