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By Frederic P. Dewey

THE Bureau of the Mint of the United States Treasury maintains 13 offices for the purchase of gold-bullion, and this paper describes an investigation to establish the reasonable differences in the assay-results at the various institutions which may be commercially allowable in the settlements between them. Beginning with the comparative assay of proof-gold at the Philadelphia mint and the Utrecht mint, which shows 0.00002 as the closest agreement now possible, eight tables of comparative results, taken from the regular work of the service, are given. These tables begin with very fine gold, produced in an electrolytic refinery, showing close agreement. in the assay-results, and follow through decreasing gold fineness and . increasing amounts and complexity of base metals to very impure and complex bars produced at cyanide-mills, some of which give widely-varying results. Next is given a series of results on samples, prepared and sent out to various laboratories in the service, to test the influence of different metals and various combinations upon the' agreement of the assay-results; 11 samples were sent out and each one was assayed from 44 to 71 times, making a total of 623 assays. To these are added 107 assays of identical samples of coin-gold. On a previous occasion,' I have endeavored to show the degree of accuracy that may be expected in the ordinary everyday analysis of various materials, and on another occasion2 I

Aug 1, 1909

By E. E. White

(Cleveland Meeting, October, 1912.) IN, August, 1911, I read a paper before the Lake Superior Mining Institute' on surveying and sampling diamond-drill holes. The present paper gives a more thorough description of these methods, together with a few changes and notes suggested by further experience. Since August, 1911, the methods, used constantly by the Cleveland-Cliffs Iron Co., have been developed to a higher degree of efficiency, and have given great satisfaction. Until a few years ago but little attention was paid to the determination of the actual course of drill-holes, to the accurate sampling and analysis of the material, or to the scientific location of the drill-holes. It has now been common practice for several years in many districts to test the inclination of drill-holes by etching glass tubes with hydrofluoric acid, but the direction of deviation from the vertical has not often been determined. Methods of determining the direction by means of a compass were first developed in connection with drilling in Victoria. The latest method used on the Rand in South Africa has been recently described by John I. Hoffman.2 In the same paper Mr. Hoffman describes an ingenious method of wedging-off a drill-bole so as to start new holes at several successive points. By this means a hole can be deflected in any desired direction, and the curvature can be controlled to a considerable extent, provided the rock is soft enough to permit the hole to be wedged off. Unfortunately, in the Lake Superior district, the jasper iron-formation is so hard that it is very difficult, if not impossible, to do this. I tried to deflect one hole so as to avoid drill-rods stuck in the hole, by using a 1 Proceedings of the Lake Superior Mining Institute, vol. xvi., pp. 100 to 120 (1911). 2 Recent Practice in Diamond-Drilling and Borehole Surveying, Bulletin No. 91, Institution of Mining and Metallurgy (Apr.. 11, 1912).

Nov 1, 1912

By EDWARD B. DURHAH

(San Francisco Meeting, UCtober, 1911.) THE refinery at the San Francisco Mint takes the bullion purchased by the receiving department, and carrying more than 200 parts of precious metals in 1000, or, in mint parlance; over 200 fine, and separates and refines the various metals contained therein, using electrolytic processes exclusively. Bullion containing silver is treated in cells charged with a nitric electrolyte. These cells produce fine silver and leave a residue rich in gold. The residue from the silver-cells, together with crude gold-bullion, is treated in cells having a chloride electrolyte. These produce fine gold and leave a residue containing silver chloride. The latter is reduced to the metallic state with zinc and is then treated in the silver-cells. The various waste solutions and the wash-waters, after being freed from the bulk of their precious metals, still contain copper and other metals. These are removed by scrap-iron, and are then treated in the copper-cells, having a sulphate electrolyte. These cells produce pure copper, and collect a residue containing lead, some gold and silver, and all the metals of the platinum group that were in the bullion. This residue is relatively small, and is melted into bars and stored until sufficient accumulates to warrant treating it for platinum, etc. The refinery occupies three large and three small rooms. The large ones are, a melting-room, 30 by 34 ft.; a cell-room, 39 by 46 ft.; and a wash-room, 30 by 33 ft. The small rooms are used as foreman's office, laboratory, and generator-room, respectively. The methods here described are those in use in December, 1909, when notes for the present paper were taken.

Oct 1, 1911

By George J. Young

DR . JOHN A . CHURCH, in his treatise on the Comstock Locle 1 gave a full and clear account of the conditions of the mine during the period of greatest activity. The difficulties in the way of deep mining at that time were excessive water and high temperature. The drainage of the mines taxed the financial resources of the mining companies, and the high temperatures restricted the capacity of the miners for underground labor. In spite of these difficulties exploratory work was continued until the financial burden of removing the water became too great. The companies then restricted the work to the upper levels. The years 1883 to 1886 marked the period of cessation of deep mining. For 12 years thereafter mining was confined to the levels above the Sutro tunnel; and, while the question of drainage was more or less agitated, nothing of importance was done until the formation of the Comstock Pumping Association in 1898. Since that time successive levels have been drained until, at present, on the north-end mines, a depth of 700 ft. below the Sutro-tunnel level has been reached. Mining is now carried on in the Ophir mine from the 1,700- to the 2,200-ft. levels, and a winze is being sunk to make connection with the 2,300-ft. level (the 2,450 ft. of the C. & C. shaft). In 1903-the Ward Shaft Association was formed to undertake the draining of the Central and Gold Hill group of mines, and at the present time a depth of 2,500 ft. has been reached in the Ward shaft. The situation at the Ward looks promis¬ing, and the 3,000-ft. level may be reached in the near future. It is proposed to establish a large pumping-station on this level, and then begin the opening of known ore-bodies and the prospecting for new ones. The main factors which have contributed to the successful solution of the drainage problem are the Sutro tunnel, the use of the hydraulic elevator as a sinking-pump, the concentration of pumping-units, and cheap electrical power. The question of high temperature and its control still remains as a minor but important problem. The temperatures encountered in the new workings are as great as those in the earlier periods. The Comstock was considered the hottest group of mines in the world, and I am not aware of similar conditions in any other mining-district. A water-temperature as high as 160° F. has been reported from the Ward shaft, and temperatures below the Sutro tunnel are very high in many instances.

Nov 1, 1909

By H. F. Moore

DURING the last six years, there have been many extensive investigations of the fatigue of metals. The major work of 'these investigations has been the determination of constants for fatigue strength of wrought ferrous metals; but during the past year or two there have become available considerable test data on the fatigue strength of certain nonrferrous metals, including copper, brass, bronze, nickel, copper-nickel alloys, aluminum and aluminum alloys, magnesium and magnesium alloys. It is not proposed to give here extensive quantitative tables of test results; for such tables, reference is made to the published data of various laboratories. The following general conclusions, however, seem to be fairly well established: 1. The phenomenon known as "fatigue" of metal really a progressive fracture of metals. A minute (probably submicroscopic) crack is formed in the metal, the internat stress, is intensified at the ends' of the crack, and under successive applications of load the crack spreads like a minute hacksaw cut until there is not enough sound metal left in the cross-section of the piece to stand the load. applied, and then failure occurs suddenly. 2. For wrought ferrous metals, there is .a limiting intensity of stress (as computed by the ordinary formulas of mechanics of materials) below which, a metal is able to withstand an indefinitely large number of repetitions of stress without failure. This limiting stress is known as the "endurance limit or the fatigue limit.? For reversed flexure, the endurance limit for. wrought ferrous metals is usually not far from 50 per cent. of the ultimate tensile strength.

Jan 1, 1925

By H. S. COOLEY

TO talk about a "factor of economy" in connection with the wire ropes used in mining practice may be coining a new phrase. If such be the case it needs no other apology than that economy in wire rope usage is so bound up with the factor of safety as to justify a similarity in naming that makes one suggest the other. At the latest Wire Rope Research Conference, held under the auspices of the A. S. M. E., Re- search Committee and Engineering Foundation, data were introduced covering mine ropes working under

Jan 1, 1930

By Raymond F. Gray, Victor J. Hoffman, Richard J. Bagan, Harold L. McKinley

The first indication of tungsten in the Bishop area was the discovery of scheelite concentrations in a gold placer operation in the ( since named) Tungsten Hills in 1913. After early intermittent production, the deposits of the district were slowly discovered and developed. The Pine Creek mine, located in 1916 and under the direction of Union Carbide Corporation since 1935, became the principal producer in the district. By the end of 1965, the total production of the district had reached 3,450,932 units of WO3, 17,071,242 pounds of molybdenum, and 19,599,110 pounds of copper. The topography of the district is characterized by its extreme relief, ranging in elevation from 13,986 feet to about 4400 feet in the Mount Tom quadrangle. The present topography is the result of the uplift and erosion of the Sierra Nevada and the great subsidence of the Owens Valley with its related deposition and volcanism. The general structure of the pre-Tertiary rocks consists of a series of tightly-folded metasedimentary and metavolcanic rock remnants surrounded by exposed plutons ranging in composition from hornblende gabbro to alaskite. The metasedimentary rocks consist of low- to intermediate-grade metamorphic equivalents of fine-grained sediments deposited during the Paleozoic era in a miogeosynclinal environment. Later volcanics were deposited in a eugeosyncline. The ore bodies in the Bishop district consist of scheelite-bearing tactite formed by the pyrometasomatic replacement* of calcareous sediments along the contact with an acidic granitic intrusive. A number of the metasedimentary remnants have had tungsten deposited along their edges.

Jan 1, 1968

By N. H. Emmons

In the United States the value of gold- and silver-ores is everywhere reckoned in ounces troy of the metal per " short ton " (2000 lbs. avoird.) of the ore. In the case of silver, which fluctuates in market value, the New York quotation on a given day must be known, in order to determine the gross value of an ore at that date. In Mexico the assay is reported 'in kilogrammes of silver or grammes of gold per metric ton. As everyone is aware, this is practically a percentage system, 1 kg. of silver per metric toll (1000 kg.) being 0.1 per cent., and 1 gramme of gold per metric ton, 0.0001 per cent. The notation is simple and convenient for both assayer and miner.* The Mexican government purchases at an unvarying price for silver, payable in silver, and at a fixed price for gold, payable in gold if the seller insists, but preferably in silver at about the rate of exchange between U. S. gold coin and Mesican silver coin. The value of silver is $40.915 per kilogramme in Mexican silver dollars. That of gold is $675.416 per kilogramme in gold coin. The mints do not, as a rule, issue gold dollars, as the government keeps them to pay the interest on the national debt. Almost all bullion containing a considerable percentage of gold is shipped to foreign countries (principally the United States) to be refined. The Mexican mint receives for refining and coining no bullion which is not at least .950 fine in gold and silver, separately or

Jan 1, 1902

By Paul M. Tyler, Colin G. Fink

THE field of rare metals is so broad that progress can be reported upon many important fronts. Not satisfied with the 92 elements that Mendeleeff and his followers have accepted as legitimate, scientists are trying now to complicate matters by making new elements. Enrico Fermi announced the fabrication of "Element 93". Uranium, instead of being allowed to disintegrate slowly according to its normal habit, was bombarded with neutrons until some of them seemed to have stuck in the nucleus. To understand just what is alleged to have happened all one has to do is to line up the elements in their usual order of ascending atomic weight and imagine, as physicists do, that each atom is a little solar orbit comprising a central mass or planet about which other masses revolve like satellites. Ordinary hydrogen, being very light, consists of only one positively charged proton center, with only one positively charged electron revolving about it. Other atones are progressively more complicated until we come to uranium, which has a relatively big center and 92 particles revolving around it.

Jan 1, 1935

By M. D. Cooper

IN spite of the uncertainty in the bituminous coal industry during 1933, progress worth recording has been made. Along with other industries, coal has felt the effects of business stagnation, but even in the worst weeks of the past four years, .the total production of bituminous coal in the United States was seldom less than half the production in some of the best weeks of the more prosperous years, a record better than that of many industries. However, the competition of other fuels and sources of power, together with the increased efficiency in the use of coal, has brought anxiety to producers. This has resulted in pressure for reduction of costs, not always by the wisest means. On the other hand, the effort to survive has directed increasing interest toward research, a wholesome development in a difficult situation. Wages, limitation of hours of labor, and the NRA have occupied much time and thought. Following a period .of wage cutting paralleling price cutting, the industry found itself rather suddenly faced by the President's Agreement, followed in due course by the Code, and then in many places by the agreement with the United Mine Workers. Although there is still some uncertainty in regard to the detailed working out of the new arrangements, there seems to be an honest endeavor by the signatories to the Code and Agreement to work them out in a straightforward manner.

Jan 1, 1934

By H. H. Moss

OXYACETYLENE .cutting has experienced rapid development in the last few years and greater advances and expansion and broader application may be expected in the immediate future. Marked changes in cutting practice may be expected as a result of the advances in metallurgical science that have produced special alloy steels with properties requiring different cutting techniques than for ordinary low-carbon steels. Much current attention is being directed to those problems of modified cutting practices. Cutting has thus ceased to be merely a shaping problem. It is rapidly coming to have a predominantly metallurgical aspect. The problem is no longer how to cut a given shape, but how to cut a given steel. The answer

Jan 1, 1936

By DR. SAMUEL B. CHRISTY

? THE man is always greater than his work.? The training of the men who are to develop the mineral resources of the world is the most important problem connected with mining engineering. It becomes ever more important to civilization as the mineral wealth of the earth approaches exhaustion. I have therefore decided to consider a few of the more important problems arising in the training of the mining engineer, and especially those arising in America. THE PECULIAR NATURE OF MINERAL WEALTH. Mining and Agriculture are the two fundamental arts. Without the latter our existence would be precarious; without the former, our civilization impossible. Agriculture furnishes that regular supply of food and raiment which leads to the growth of large communities in which cultivated leisure first becomes possible; while raining furnishes the metallic thread from which is woven that complex fabric we call civilization. But in these two arts the conditions for success are widely different. Most of the crops that the farmer reaps may be harvested year after year, and the proper fertilizers being added, he may continue the annual harvest indefinitely, while, as a result of cultivation, his farm becomes yearly more valuable. But the crop the miner reaps can be harvested but once in the history of the race. Our mineral wealth has taken unknown ages to mature in the bosom of the earth. The ripened fruit can be plucked but once. There are no fertilizers for worked out mines. It never pays to work over a mine that has been

Sep 1, 1905

By John D. Ridge

Here are summarized 162 papers, published between 1933 and 1967, that deal with various aspects of ore genesis. Emphasis is placed on additions to, or modifications of, ore-formation theory, no matter what type of deposit is discussed. More space is given to papers on the formation of base-metal sulfides solely because more papers are written on this subject. The final conclusion is reached that a chemically and geologically sound theory for the genesis of ore deposits can be built around the concept of concentration of ore e’ements in a magmatically produced ore fluid and around such surface processes as may act to concentrate economically valuable materials from rocks of any origin exposed at the surface.

Jan 1, 1968

Jan 1, 1885

By S. S. PRENZ

Discussion held at the sessions of the Canal Zone meeting, November, 1910. [SECRETARY'S NOTE.-As a result of this discussion, an expression of opinion covering all points of unanimous agreement was adopted and signed by members of the Institute party as individuals. This statement, which was printed in the Bulletin of December, 1910, is reprinted below, as an introduction to ,the detailed report of the discussion. It should be clearly understood that it does not constitute an official declaration by the Institute, the rules of which forbid any such action. At the New Haven meeting of February, 1909, a free discussion of the plan of the canal took place, in which the critics of the present scheme had full opportunity to state their views. That discussion was continued at considerable length in the newspapers ; but the Institute was never committed to either side. In this latter instance, the situation is precisely similar. Certain members and guests of the Institute, having had the advantage of later developments and of personal inspection, have expressed the conclusions at which they have arrived on their own responsibility ; and these conclusions are published by the Institute, subject to further discussion, like any other part of its proceedings. The general statement referred to contained a promise that the full discussion, of which it was a result, would be subsequently printed ; and this promise is fulfilled, so far as practicable, in the subjoined report, concerning which I beg to offer the following explanations: 1. It is made up of the remarks of the members of our party, as subsequently written out and mailed to the Secretary. 2. In editing these contributions, I have condensed the material considerably by cutting out much repetition of opinions and phrases ; and in such excision, I, frankly confess, the authors whose communications were delayed, have been the sufferers. Nevertheless, there is a good deal of repetition left, as there must be, when so many persons had talked so much, and come to agreement upon so many points. 3. It has been found impossible to preserve in this report the actual order of the free and informal oral discussion represented. Consequently the several contributions have been arranged in alphabetical order under the names of their authors. References to "preceding speakers," etc., must therefore be construed as referring to other speakers, preceding or following.-R. W. R.] S. S. PRINZ AUGUST WILHELM, AT SEA, November 14, 1910. We, the undersigned, members and guests of the American Institute of Mining Engineers, after a visit to the Isthmus of Panama, and inspection of the work of the United States Isthmian Canal Commission, and after full discussion of our individual impressions, find ourselves in unanimous agreement as to the following conclusions:

Jan 1, 1911

By Persifor Frazer

1. SMOKE PREVENTION. Report of Select Committee of House of Commons (1843). Nuisance considerably abated in Leeds (Wm. Backerd, July 13, 1843, 239 pages). A synoptic index, p. 211, gives, in alphabetical order, the digest of every subject taken up. 2. FUEL : ITS COMBUSTION AND ECONOMY. D. Kinnear Clark, C. E. 24mo, 1354 pp. Crosby Lockwood & Co., London (1880). Includes abridgement of treatise on combustion of coal and prevention of smoke, by C. W. Williams, A.I.C.E. 3. DIE RAUCHSCHÄDEN IN DEN WÄLDERN DER UMGEBUNG DER FISCALISCHEN HÜTTENWERKE BEI FREIBERG. Dr. J. v. Schröder, Professor in Tharand, and Dr. A. Schertel, Vorstand des Hüttenlaboratoriums zu Freiberg. Royal 8vo, 27 .pages, 19 pages of tables and a map. Ernst Maukisch, Freiberg (1884). (Aus dem Jahrbuch für das Berg- und Huttenwesen, 1884.) In 1861, Reich and Stockhardt examined the extent of injury to vegetation by the Muldner works. Needles and twigs of pine showed in 100,000 parts : Pb, 5 to 50 ; As, 3.3 to 14.3 ; S02, 62 to 120. In the top twigs, 5 to 8 ; needles, 10 to 16 ; thicker twigs, 10 to 22 ; thinner twig-ends, 17 to 54 of lead. Lead greater in amount in sickly twig-ends with few needles ; also in the bark than in the naked wood of the trunk, which had hardly a trace ; also in the part turned toward the works than on the opposite side. Pb and As diminished in the vegetation with distance from the smelter ; and the same with regard to the soil. Fresh snow was collected, and SO, As, and Pb detected in it.

May 1, 1907

By A. J. WADHAMS

THE relative importance of things is a fascinating subject for thought. As we look about us we realize the Creator of all things has provided the metals for our use, each in the quantity needed-iron in vast quantities gold in small quantities. Had gold been given us in the quantities of iron, the mechanical age mould Eave been very different. You may find some pleasure in running over in your mind this question of the quantity available of an element and man's need of it in the scheme of things. Nickel in this sense is a middle group element. It was not essential to man's early development. Its usefulness dates back only about one hundred years. The quantity available to man has increased as his needs in- creased. On two occasions more nickel became available than was needed and on both of these occasions the ex- cess was soon absorbed by new and useful developments.

Jan 1, 1929

By William H. Bassett

RECENTLY it has become the custom of retiring presidents to talk of the relations of the Institute to its membership and its constituency- and it seems a good precedent to follow. Past-president Smith reviewed our relations to materials and to society in general. Mr. Bradley spoke of the value and use of our publications and of our educational duties. My message will be in regard to the coordination of our various groups of member interests and of service to industry. This Institute has, within its organization, four divisions and fourteen technical committees--each interested in a separate put very definite subject, and each covering a phase of mining engineering interest. These vary from geology and the geophysical methods of prospecting, to the physics of the structure of metals, truly "from the mine to the consumer"-from the preparation for mining to the final use of that which has been mined.

Jan 1, 1931

By Pierre de P. Ricketts

Having had occasion while in Europe during the past summer to visit some of the foreign mints and assay offices connected with the same, I thought a brief description of the general process of coining employed, and such items connected with assaying as were new, might prove interesting to the Institute. The principal foreign mints are: the Royal Mint, London; and the mints in Paris, Brussels, Utrecht, Berlin, Vienna, Copenhagen, St. Petersburg, Stockholm, Madrid, Milan, Rome, and Constantinople. My time only permitted my visiting a few of the principal and largest given in the list, and for a description of the remainder I am indebted to the kindness of Mr. James M. Napier, who in company with the deputy master, and chemist of the Royal Mint, made a complete inspection of all the European Mints in 1870.

By Pierre de P. E. M. Ricketts

HAVING had occasion while in Europe during the past summer to visit some of the foreign mints and assay offices connected with the same, I thought a brief description of the general process of coining employed, and such items connected with assaying as were new, might prove interesting to the Institute. The principal foreign mints are: the Royal Mint, London; and the mints in Paris, Brussels, Utrecht, Berlin, Vienna, Copenhagen, St. Petersburg, Stockholm, Madrid, Milan, Rome, and Constantinople. My time only permitted my visiting a few of the principal and largest given in the list, and for a description of the remainder I am indebted to the kindness of Mr. James M. Napier, who in company with the deputy master, and chemist of the Royal Mint, made a complete inspection of all the European Mints in 1870.

Jan 1, 1876