Search Documents

After the close of the Revolution, settlers began to pour over the mountains, to settle in the western parts of Pennsylvania, of Virginia, to move down the Ohio into Kentucky, and in the late seventeen-eighties to settle on "the Indian side" of the river, now Ohio. With the growth of population the interest in coal increased and it was not long before the production of coal west of the mountains was larger than that east of them. Foreign nations, too, became interested in the young republic and in 1783, at the instance of the Swedish government S. A. Hermelin, an engineer, visited this country to investigate its iron industry. He made a very interesting report, not published until 1931, in which he gave many details of the iron plants in the eastern United States; apparently he was not west of the mountains, but was well informed about conditions there. He says, "that some coal near the first branches of the Schuylkill River has been mined and utilized by the blacksmiths," referring, of course, to anthracite; again that "coal mines have also been worked for several years near Pittsburg," and that "great supplies of iron ore are available at the Ohio Falls and further to the west, at Coney Creek, a part of the Green River, where there is also coal."' In 1788, Dr. Johann David Schoepf, who came to this country with the Hessian troops, visited Pittsburgh. He was an intelligent man and acquainted to some extent with minerals and methods of working them. In speaking of Coal Hill on the south side of the Monongahela he mentioned several strata of marble in the lower part and that

Jan 1, 1942

By AIME AIME

THE Hazleton district of the Pennsylvania Anthracite Region will be the scene Oct. 14 and 15 of the fall meeting of the Coal Division and the Pennsylvania Anthracite Section. Here, coal mining has been active for more than 100 years and hereabouts industrial necessity inspired the numerous inventions of the Pardees, Eckley B. Coxe, a former A.I.M.E. president, and the Marltles, who contributed much to the success of the Institute in its early days, as well as to the upbuilding of modern methods in the anthracite and bituminous industries. Headquarters will be the Altamont Hotel, Hazleton, Pa. There will be two technical sessions Friday, registration preceding the first which is scheduled for 11 a.m. to 1 p. m. The second will be called at 2:30 p.m. Saturday is reserved for mine and plant visits, with golf and tennis after luncheon for those so inclined. The ladies are cordially invited to the meeting and arrangements have been made for their participation in much of the program. The chairmen of the committees preparing for the meeting are: Donald Markle, president, Jeddo-Highland Coal Co., General Committee; R. E. Hobart, mechanical superintendent, Lehigh Navigation Coal. Co., Committee on Visits and Inspections; H. D. Kynor, general manager, Northumberland Mining Co., Committee on Programs and Papers; B. H. Stockett, general manager, Weston; Dodson, Inc., Reception Committee.

Jan 1, 1932

By J. D. Anthony

The Australian continent possesses significant reserves of a wide range of minerals, including bauxite, coal, copper, diamonds, gold, iron ore, lead, manganese, mineral sands, nickel, phosphate, silver, tin, uranium, and zinc. Australia's identified economic resources of many minerals are very large as indicated in Table 1. A sophisticated and highly experienced mineral industry is now an established feature of the Australian economy and Australia is the world's largest exporter of iron ore, alumina, mineral sands and refined lead and amongst the leading suppliers of many other commodities such as coal, lead and zinc ores/concentrates, nickel, refined zinc, tungsten concentrates and bauxite. The industry exports 70% of its production. This is reflected in the value of Australian mineral exports which have grown from about $200m in 1960/61, comprising 10% of total export receipts, to about $1265m or 29% of export income in 1970/71 to around $7061 representing 37% of Australia's total export income in 1980/81. Details of the more significant minerals are as follows: Japan (42.1%) USA (11.3%) ASEAN (6.3%) UK (5.9%) F.R. Germany (3.8%) Republic of Korea (3.4%) New Zealand (2.6%) Also see Table 2. AUSTRALIA'S MINERAL RESOURCES POLICIES Federal and State Governments' Responsibilities Australia has a federal system of government comprising six States, a self-governing Territory and a Federal Government. Under the Australian federal system the Constitution sets down the powers of the Federal Government. All powers not assigned to the Federal Government in the Australian Constitution reside automatically with the States. Certain of these broad powers result in the Federal Government having a significant influence on resources development. For example, in being responsible for economic management, the Federal Government's fiscal and monetary policies have an important effect on industry as well as on State finances. In particular, the taxation regime employed by the Federal Government is of direct importance to decision-makers in the resources industry. The Federal Government is responsible also under the Constitution for external trade matters; and international trade and commodity matters are increasingly important in Australia's international relationships. Foreign investment is another area where the Federal Government has a role to ensure that national interests are protected. This foreign investment power flows from the Federal Government's control of foreign exchange movements into and out of Australia. However, before enlarging on these and others of the Federal Government's powers and policies, it should be emphasized that the State governments, by virtue of their wide powers to regulate matters within their own boundaries, are more directly involved in the day-to-day administration and regulation of mining operations. For instance, the powers of the State governments include the responsibility-for the granting of exploration rights and mining leases, the approval of mining operations and the levying of royalties and other like charges. Administrative arrangements covering the granting of minerals and petroleum exploration and development titles vary from State to State. Before development rights are granted, State governments consider environment protection and rehabilitation aspects of development proposals. The provision of infrastructure within State borders is a matter primarily of State government responsibility. It is usual practice in Australia for State governments to construct and operate infrastructure services such. as railways, ports and electricity generation and transmission. The States may also provide certain public services such as electricity. and water, port and loading facilities, communications, health and education services which form part of the infrastructure of mining operations. In remote areas the mining companies themselves usually are expected to provide much of this infrastructure. However, the Federal Government is primarily responsible in some fields, such as telecommunications and parts of the railways network. State governments carry out preliminary exploration and geological mapping and some are directly involved in the mining of coal for power generation. The Federal Government's responsibilities in addition to economic management, taxation, international relations, foreign capital and investment, include regulation of exports, environmental matters and matters affecting the Aboriginals of the Northern Territory. FEDERAL GOVERNMENT POLICIES The continued sound development of the minerals and energy resources sector is regarded by the Federal Government as being of very great importance. However, the Government does not seek to participate directly in resource developments. It sees its role rather as that of establishing a sound economic and policy climate in which private companies can identify opportunities, seek out customers and marshall the necessary capital for the development of resource projects.

Jan 1, 1982

By W. W. Little

At the United Verde mine the 9-2D stope on the 4050 ft level is located within the north sulphide mass lying some 800 ft north of the main sulphide ore body. In 1948 it was estimated that this block contained 85,000 tons of ore at 4% copper and 9.2% zinc. The north ore body is a lenticular replacement deposit in the black schist, extending from about 100 ft above the 3750 level to a distance below the 4500 level yet to be determined. Although the mineralized zone approaches 1000 ft in length, only 300 ft is of economic importance. In width it varies from a maximum of 60 ft to about 3 ft at the north end, and is characterized by pinching and swelling in the ore zone. One of these larger swells is being mined as the 9-2D stope. Mining costs at greater depth, together with the expected grade of ore after dilution, necessitated a low cost mining method to permit profitable stoping operations. Based on the results obtained in a number of Canadian mines, it was decided to develop the ore body for stoping by the Aldermac or bench method of diamond drill blastholes; however, this plan was subsequently changed and the radial or ring method adopted. Such a method seemed to offer the advantage of large tonnages at low cost, and obviate the necessity of waste fill. This latter point was of particular importance, since the present waste system does not extend below the 3000 level.

Jan 4, 1950

By J. H. Palm

Experiments have shown12 that the formula -S = St - (St - Se')e ne [1] expresses very well the relation between the true stress S and the true form monotonic deformation of plastic metals in single tension and compression (Fig 1). St (asymptotic or final stress), Se' (threshold stress) and ne (characteristic or specific strain) are constants, the significance of which immediately follows from Fig 1. Only at the initial stages of deformation the experimental curve runs below the theoretical curve. This may be due, at least partly, to the uneven stress distribution caused by the anisotropy of the crystals. It is now obvious that a similar formula H = Ht- (Ht- He)e ne' [2] might be valid for the relation between the hardness and the strain. The hardness can be only a function of the strain and must therefore be independent on the hydrostatic tension present in the neck during straining. Hence, if Eq 2 is correct it will also represent the relation between hardness and strain in the middle section of the neck, the strain of which is generally assumed to be almost or fully homogeneous. For aluminum, copper, and several copper alloys it is indeed observed that Eq 2 agrees very well with the experimental Vickers hardness-strain relation from zero strain on up to the strain at fracture. Moreover nc' is, for several metals fairly equal to nc- Hence H = C1 + C2S [3] C1 and C2 are constants during uniform uniaxial tension. Eq 3 was also obtained for copper by Voce.3 According to Hencky's theory4 the ratio of the Brinell or Vickers hardness and the yieldstress (expressed in kg per mm2) of a non-strainhardening metal is approximately equal to 2.8. If Eq 1, 2 and 3 are correct the ratio Ht/S, must accordingly be the same for all plastic metals and be equal to 2.8. It is now experimentally established that this ratio varies between 2.7 and 3.1 with a mean value of 2.9. Taking into account that Ht and especially St can be obtained only by extrapolation from the range of rather low strains, the agreement with the theory is very satisfactory. References 1. J. H. Palm: Appl. Sci. Res. Al (1948) 198. 2. E. Voce: Jnl. Inst. of Met. (1948) 74, II, 537. 3. E. Voce: Metal Treatment (1948) 15, 53. 4. H. Hencky: Zlsch. f. angew. Math. and Mech. (1923) 3, 241.

Jan 1, 1950

By A. L. Sweetser

Experience has shown how difficult it is to obtain information regarding laboratory-tests in connection with the chlorina-tion-process for the extraction of gold from its ores, and I therefore present the following method, somewhat in detail, for the benefit of those who may desire to pursue research work in this field. The ore chosen was a partly-decomposed porphyry, extremely siliceous and comparatively soft, and of an average value per ton of from $25 to $26 in gold and $0.68 in silver. The chemical analysis gave: Fe,O,, 3.35; FeS, 1.5; MnO,, 0.75; ZuCO,, 4; A1,0,, 3.20; H,O, 0.7 ; SiO, and insol., 83.50 per cent. The ore, first crushed to pass a 5-mesh screen, was coned and quartered until a 45-lb. sample was obtained. Samples for assay and analysis, taken from this lot by means of riffles, were crushed to pass a 100-mesh screen. The original sample was divided into 10-lb. lots, of which one was crushed to pass a 10-mesh screen; another through a 12-; the third through a 20-, and the last through a 30-mesh screen. Because of the production of an excessive quantity of fine material it was deemed inexpedient to crush finer than 30-mesh size—a decision the wisdom of which is proved by the data in Table I., showing the increasing ratio of slimes, in proportion as the ore is crushed finer. In order to determine the percentage of fines in the sizes of mesh selected, a weighed sample of ore was taken from each mesh, and a sample from the 10-mesh lot was passed successively through 20-, 40- and 100-mesh screens, and the percentage remaining on each screen determined. This process was repeated with the 12-, 20- and 30-mesh lots, with the results given in Table I.

Jan 1, 1908

By T. E. Watkins, M. D. Nelson

A method of determining the lime content of drilling muds proposed by Battle and Chaney* has been examined both in the Field Research Laboratories of Magnolia Petroleum Co. and in field drilling operations. This proposed analytical method is condensed as follows: Titrate one ml of mud and one ml of mud filtrate, each with 0.02 N H2SO4, to the end point with phenolphthalein. The volume of acid in ml required for the mud titration is recorded as Pm and that of the mud filtrate titration as Pf Calculation of the lb lime/bbl mud is accomplished by use of the formula, lb lime/bbl mud = 0.6 (Pm - 1.3Pf) - 0.6 The analytical procedure outlined by Battle and Chaney was found to be quite satisfactory when reasonable precautions are used in mud sampling technique. Calculation of lime concentration by the method proposed in the above publication, however, has given values that varied as much as 100 per cent from the known lime content, for muds of either high or low solids concentration. By use of a formula, lb lime/bbl mud = 0.26 (Pm-F1.Pf), based on chemical equivalents of acid required for titration, both laboratory and field data have been satisfactorily correlated with the known amounts of lime present in the muds. In this formula a correction, F1, or volume fraction of liquid in the mud, is made for the solid content of the mud. Pm and Pf * Paper on "Lime Base Muds," presented by J. L. Battle (Humble Oil and Refining Co., Houston, Tex., and P. E. Chaney (Sun Oil Co., Beaumont Tex.), at the 1949 Spring Meeting of the Southwestern District API Division of Production, Dallas, Tex. The analytical procedure has also had wide distribution in a trade journal, Kembreak, published by the Accuracy Rig and Tool Co., Houston, Tex, †Derivation of equation lb/bbl — grams/350 ml 1 ml 0,02 N acid = 0.000741 grams of lime 1 ml 0.02 N acid/ml lime suspension = 0.26 lb of lime bbl lb of lime/bbl = 0.26 (Pm -F1, Pf ) have the same significance as in the Battle and Chaney equation. Table I shows typical data employing both formulas in calculating the lime content of various lime muds. This suggested procedure ignores lime which is in solution in the mud. The solubility of lime in water, normally about 0.5 lb per bbl, is greatly decreased by the addition of caustic soda, and, in a lime mud, it is probable that the concentration of dissolved lime is of the order of 0.1 lb per bbl. Such an amount of lime can be ignored, since it is within the range of accuracy of the method.

Jan 1, 1950

By L. S. Castleman, L. L. Seigle

THE formation and growth of intermetallic phase layers is of considerable practical importance to metallurgists interested in diffusion bonding and cementation processes and has been the subject of extensive qualitative investigation. In contrast, it is somewhat surprising that so little quantitative data have been amassed. The need for additional fundamental work was pointed out by Mehl in 1936,' and persists to a large extent to the present day. The early studies have been reviewed by Rhines,2 and his conclusions have been summarized by Lustman and Mehl3 substantially as follows: 1) All phases that are stable at the temperature at which diffusion occurs will appear in the interdiffusion of two metals; however, in some cases, certain of the phases may be too thin to be observed and identified easily. 2) The isothermal growth of intermetallic phases generally obeys a simple parabolic equation of the form X2 = Kt, where x is the thickness of the alloy layer, K the temperature dependent reaction rate constant, and t the time. 3) The rate of thickening varies with temperature according to the Arrhenius equation k = Ae -Q/RT , where k is the parabolic rate constant, A, a temperature independent constant, Q the heat of activation for the process, R the gas constant, and T the absolute temperature. Subsequently, Lustman and Mehl made a quantitative study of the laws of growth in intermediate layers in a number of binary systems, in which one of the components was either zinc or cadmium, and the other component was one of the following: nickel, copper, silver, cobalt, gold, iron, or Monel metal; the interdiffusion times used were for the most part less than 24 hr. It was found that the simple parabolic law was not obeyed in general, but that a generalized parabolic law of the form xn = kt was valid, where n was a temperature dependent constant; also,

Jan 1, 1959

By AIME AIME

As already announced in the January Bulletin, this publication will be issued during the coming year monthly instead of bi-monthly as heretofore. Among other reasons for this change, it is desired to effect thereby the earlier transmission to members of important papers, lists of candidates for membership, and other items of timely information. Spokane Meeting and Excursions. Further details of the 97th meeting of the Institute have been sent to members in the Circular of May 8, 1909. The list of those intending to go on the excursion is filling up, and since preference in position of state-room or berth is given in the order of application, members and guests who expect to accompany the party and have not yet communicated with Mr.. Theodore Dwight, 29 West 39th St., New York, N. Y., are earnestly requested to do so without delay. For convenience of the members a summary of the additional information is here presented. A special train of Pullman cars will leave Chicago about September 15. This train will be side-tracked at all places visited, and the sleepers will be available for lodging and the dining-car for meals during the entire trip, except during the Yellowstone Park tour. The general cost of the trip per member will be $300, which includes transportation, berth, and meals for the entire trip from Chicago back to Chicago, almost 6,000 miles, and the tour through. Yellowstone Park, occupying in all about 30 days. Special, accommodations on the train will be furnished at the following rates

Jun 1, 1909

The following list contains the names of members whose death notices have been printed in MINING AND METALLURGY from March 15, 1947 through March 15, 1948 Biographical sketches published in MINING AND METALLURGY are indicated in the last two columns Year of Election - Name - Date of Death - Issue Containing Biography - Page 1938 ABERNATHY, G E , (M) Feb 6, 1948 April 1948 266 1935 ARCHER, M T, (M) Oct 26, 1947 Dec 1947 633 1947 ATIKINSON, JAMES E, (S) Feb 6, 1948 June 1947 309 1940 AYRES, VINCENT L, (M) Oct 14, 1947 Jan 1948 59 1915 BABCOCK, JAMES E , (M) April 1, 1947 June 1947 309 1942 BAGGALEY, WILLIAM BLAIR, (A) Aug 28, 1947 Jan 1948 59 1897 BUIN, II POSTER, (M) Mar 9, 1948 April 1948 219 1945 BAMPFIELD, A E (M) Unknown Mar 1948 215

Jan 1, 1952

By W. S. CAYPLESS, H. O. Hofman, E. E. HARRINGTON

1. INTRODUCTION. AT the Lake Superior meeting, September, 1904, Messrs. A. Gibb and R. C. Philp presented a paper entitled " The Constitution of Mattes Produced in Copper Smelting,)' in which they concluded that ferrous and cuprous sulphides formed the chemical compound, 5 Cu2S, fee. They arrived at this inference from the observed fact that a matte containing Cu2S, 90.4, and Fee, 9.6 per cent (or, in round figures, Cu2S, 90, and Fee, 10 per cent.), did not contain any metallic copper, while one with more than 10 per cent of FeS readily dissolved copper, and with less than this amount retained copper in mechanical suspension. Although they determined the melting-points of five mattes containing from 32.6 to 80.1 per cent of copper, they did not draw a freezing-point curve, as the necessary apparatus was not available. A microscopical examination of 11 polished samples, gave them a grayish-black field of very uniform appearance, except that 5 of the specimens showed the presence of metallic copper. The object of the present investigation was to supplement the above paper by drawing the freezing-point curve of the series ferrous sulphide cuprous sulphide, and to see how the constitution could be further, revealed by microscopical work. The results obtained lead to conclusions very different from those of Gibb and Philp. While their paper bears the date 1904, it was published only in 1906.2 In the meantime, Bolles3 had presented his paper, "The Concentration of Gold and Silver in Iron Bottoms." The raw material which formed the basis of the research was a matte containing Fe, 61.68, and Cu, 11.20

Jan 1, 1907

By D. Argyriades, G. Derge, G. M. Pound

The electrical conductance of molten FeS was studied as a function of temperature and composition. It was found that stoi-chiometric FeS (36.5 pct S) shows a minimum specific conductance of 400 ohm-1 cm-1. For the Fe-rich melts the conductivity increases with increasing amount of iron to about 4850 ohm-1' cm-I at 26 pct sulfur. For the sulfur-rich melts the conductivity increases with increasing amount of sulfur until it reaches a maximum of 1300 ohm1 cm-1 for 37.4 pct S and decreases to 800 ohm-1 cm-1 for 38.3 pct sulfur. It is concluded that molten stoichiometric FeS is an intrinsic semiconductor in which the forbidden gap in the electron energy level diagram is quite narrow. Excess sulfur acts as an acceptor impurity in providing a component of positive hole conduction, while excess iron acts as a donor impurity to increase the n-type conduction. K. Bornemann and G. von Ftauschenplatl used a four-terminal, direct-current cell to study the electrical conductance of molten copper sulfide. Their measurements showed a high conductivity, of the order of 100 ohm-1 cm-" and a positive temperature coefficient. From electrolysis studies, Savelsberg2 concluded that molten Cu2S and molten FeS are electronic conductors. Further. he found that molten FeS has a high specific conductance, of the order of 1500 ohm-' cm-', and a small negative temperature coefficient. Pound, Derge, and Osuch,3 using an ac Kelvin circuit and a four-terminal cell, measured the specific conductance of molten Cu,S, molten FeS, and various mixtures. They found that the specific conductance of the solutions followed a roughly additive rule of mixtures. Yang, Pound, and Derge4 showed from electrolysis measurements that the mechanism of electrical conduction in molten Cu2S, FeS, and mattes is primarily electronic. Further, they observed that small additions of CuCl suppress the electronic conduction whereupon the system behaves ionically.

Jan 1, 1960

By J. VAN DEN BERC

Tin production and export from the Far East are still a long way off from the prewar figures. The Malayan Peninsula, which had a rather good start directly after the war largely because of stock piles found in Singapore and elsewhere, has since been hampered in the rehabilitation of its tin mines and dredging operations by material shortages and, more recently and more severely, by revolts and attacks of communist elements and gangster bands. These hindrances make working in the mines dangerous and form a daily threat against the valuable and highly vulnerable dredges. Contrary to the conditions in Malaya are those on the tin islands of Billiton, Banka, and Singkep-all in the Netherlands East Indies-where the Dutch have re-established peaceful relations with the population. Dutch efforts since the fall of 1945 have been rewarded by continuously increasing production, extension of production facilities, and return of moderate prosperity, complete safety, and all-out co-operation among the population ? native and Chinese ? to the benefit of all concerned.

Jan 1, 1949

By Marvin P. Barnes

The Sacaton open pit copper mine has recently been placed into production. Some problems have been encountered in maintaining grade control due to differences between early block estimates and actual production grade. A study was made using three methods for computing grade for 50' x 50' x 40' size blocks from exploration and development drill holes; 1) The polygonal method, 2) The inverse distance squared method, and 3) The geostatistical kriging method. The results of each were compared against a control block file created by using the assay results of all blast holes drilled in the ore over three benches of the new pit. Results indicate that the kriging technique gave better estimates for grade of individual blocks than did the other two methods for this particular deposit.

Jan 1, 1977

By Harrison Souder

In view of the proposed visit of the Institute to Cuba this winter, the following brief sketch of the principal mineral deposits near Santiago de Cuba has been prepared largely from notes taken in February, 1903, during a visit to the mines then in operation in the province of Santiago de Cuba. Westward from Cape Maysi, the most eastern point of the island, the coast is rocky and uninviting. The usual course of the steamers is well in toward the shore, and the lines of stratification of the rocks can be distinguished clearly, the presence of iron or other ores being indicated by frequent blotches of mineral stain. One is impressed with the general rugged character of the southeastern coast-line,—an almost unbroken barrier of coral-limestone bluff's, full of caves and hollows, into which the surf rushes with a roar and bursts into tall fountains of spray. Beyond rises abruptly the Sierra Maestra range, whose sharp, peaked crest-line betrays its eruptive or igneous origin. From a height of about 800 ft. near Cape Maysi, this range gradually rises to the westward, attaining its maximum elevation of more than 8,300 ft. in the Pico Turquino, beyond Santiago. A general resemblance to the mountain-ranges of southern New Mexico is noticeable. At Daiquiri, 20 miles east of Santiago harbor, the extensive

Jan 1, 1905

By C. M. Weld

(Cleveland Meeting, October, 1912.) IN the course of my professional work in China during the fall of 1907, I had an opportunity to visit the iron-ore mines at Ta-yeh in Hu-pei province (long. 114° 50' E., lat. 30° 20' N.). It occurs to me that a rescript and discussion of my notes taken at that time should be of interest, particularly as supplementing the exceedingly interesting recent paper-of Thomas T: Read on The Mineral Production and Resources of China.1 Ta-yeh is situated near the right bank of the Yangtze river. The mines are at an average distance of about 16 miles from the river-port Shi-hui-yao, which in turn is some 70 miles S-E. of Hankow. The ores are shipped to the works of the Han-Yeh-P'ing Iron & Coal Co. at Hanyang, as also very largely to the Japanese government iron- and steel-works at Wakamatsu, Japan. Smaller quantities have been exported to the Pacific coast of the United States. These ore-deposits have been briefly noticed in a number of publications, but, so far as I know, Mr. Read's description, in his chapter on the iron-ores of the Chinese Empire,2 contains the first attempt to define their geological character. In his more recent paper Mr. Read follows very closely the text of his earlier description. To quote briefly from the recent paper, he says : " The iron-ores at Ta-yeh . . . . lie along the contact between a marble and an intrusive body of a dark-gray syenitic rock." He refers to a figure which exhibits in plan, but not in section, the relative positions of the syenite, ore-bodies, and limestone. The contact is seen to trend approximately E-W., with the syenite on the north and the limestone on the south. " The syenite lies to the north of the marble, and a few miles farther north the marble again' appears, iron-ore again being present along the contact." No litho- 1 Bulletin Bulletin No. 63, March, 1912, pp. 293 to 343. 2 The Iron Ore Resources of the World', vol. ii., p. 913 (Stockholm 1910).

Oct 1, 1912

By H. H. Wade, N. F. Schulz

The large quantities of iron-bearing materials, including taconite, semi-taconite,* and other low-grade ferruginous materials occurring in Minnesota and elsewhere, constitute an important potential source of iron. Satisfactory grade and recovery of iron ore concentrate cannot ordinarily be obtained from these ferruginous materials by simple methods of beneficiation. Iron is distinctive in that the free metal and two of its oxides [magnetite (Fe2O3) and maghemite (gamma-Fe2O3) ] are strongly ferromagnetic. The successful magnetic separation of natural magnetite from taconite has already been established on a commercial scale. The iron in semi-taconite, however, occurs largely as goethite (Fe2O3-H4O) and hematite (Fe2O3) which do not respond to ordinary magnetic separation methods. Magnetic roasting converts these iron oxides to magnetite, which can, after liberation, be magnetically concentrated. MAGNETIC ROASTING Hematite undergoes a stepwise reduction when exposed at moderately elevated temperatures to a reducing atmosphere containing hydrogen or carbon monoxide: Fe2O3? Fe3O4 ? FeO ? Fe Since the desirable product in magnetic roasting is Fe3O4, the conversion is halted after the first stage by controlling the reduction potential of the gas mixture with water vapor or carbon dioxide. The reducing gas mixture must be such that the oxygen partial pressure at the solid-gas reaction interface will be maintained intermediately between the oxygen partial pressures in equilibrium with Fe2O3 and Fe3O4 at the prevailing temperature. Because of the rapid increase in decomposition pressure of Fe3O4 with increase in temperature, the practical upper limit of useful reaction temperature is about 1400°F, above which over-reduction usually occurs in atmospheres containing hydrogen or carbon monoxide. On the other hand, useful reaction rates usually occur only above 800°F. Goethite reacts similarly except that the combined water probably has to be driven off thermally before the reduction to magnetite occurs. Iron carbonate must also be decomposed thermally to an oxide before conversion to magnetite. Iron silicates are apparently not amenable to magnetic roasting. The rate of penetration of the reaction toward the interior of a given ore fragment is dependent on the chemical composition and physical structure of the solid. Most ore fragments tested here reduced satisfactorily to 1/4-in. depth in less than 14 min at 1200°F. Some very dense fragments, however, were reduced to less than 1/32-in. depth under the same conditions. Determination of the optimum temperature, gas composition, ore fragment size, or time of exposure

Jan 1, 1961

By L. G. Austin

If S (x) is the specific rate of breakage of size x and B (x, y) (see Table 1 for Nomenclature) is the cumulative breakage distribution function, the Herbst Fuerstenau2 assumption is that Inserting this assumption into first-order grinding equations it has been shown" that there are then simple analytical solutions to the grinding equations, as shown in Table 2. In this context "plug flow" is defined as all material passing through the mill in the same length of time, the residence time t. The term "n fully-mixed" means that the mill has a residence time distribution" which can be treated as if the mill were n equal fully mixed sections in series. In addition it has been shown that the assumption of Eq. 1 also leads to simple analytical solutions for closed-circuit, steady-state grinding with an ideal classifier at the mill exit returning oversize to the mill feed. The solutions are also given in Table 2, with µ as the ideal classifier cut size, C the circulation ratio, and Q (x) the size distribution of the circuit product. The specific surface area of these size distributions is where the density-shape factor k. is assumed to be constant with size. In practice, most methods of size analysis or area [ ] measurement have a finite lower limit, so that the integration is really performed from xm, to xm, For a realistic degree of grinding the value of So is dominated by the fine sizes because of the 1/x factor. Consider batch grinding of a feed of size y to y + dy. The batch grinding solution given in Table 2 is then [ ] The fresh surface area produced is the area of the fines plus the area of the original material remaining minus the area of the original material, [ ] Little error is introduced by neglecting the last term on the right-hand side since at t = 0 it is zero, and when t is significant the first term dominates because of the fine sizes produced. In addition, the form of P (x, t) for [ ] realistic values of S (x) 2t ax° is such that the major fraction of fresh surface produced is contained within the bottom 10% of weight of broken material, that is, for sizes for which P(x, t) < 0.1 (providing y is not near x.,). Thus for surface area purposes Eq. 3 can be approximated by [ ] becomes providing again that the feed sizes are coarse relative to xmi. Then the fresh area production is and W is the mass in the mill. The rate of surface production is WK, and the specific surface is Kt. From Table 2, the specific energy is mt/W so surface production per unit energy is [ ] Surface produced per unit energy input = KW/m (8) where m is the energy input of the mill. Clearly, identical reasoning applies to open-cycle, plug-flow grinding, with t replacing t, and Eq. 8 is obtained again. Considering open-cycle, fully mixed grinding, similar reasoning gives P(x) - t S(x) for surface area purposes, and

Jan 1, 1974

Rossiter Worthington Raymond, Ph.D., LL. D-1840 to 1918.-Dr. Rossiter W. Raymond, Past President, Honorary Member and Secretary Emeritus, died suddenly of heart failure at his home, 123 Henry&apos;St., Brooklyn, N. Y., on the evening of Tuesday, Dec. 31, 1918. He was one of the founders of the Institute and its second President. A Memorial &apos;Service will be held on Monday afternoon, Feb. 17. James Douglas.- The Institute suffered a second very severe loss by the death of Dr. James Douglas, Honorary Member, Past President (having served as President for two years), and in three separate respects the greatest benefactor of the Institute: first, in raising funds by volun¬tary subscription and his own personal gifts to pay the Institute&apos;s share of the money owed on the land on which the Engineering Societies Build¬ing now stands; second, as original donor to Engineering Societies Library; and third, by his bequest of $100,000 for the maintenance of the library of the American Institute of Mining Engineers. A resolution regarding the death of Dr. Douglas was passed by the Board of Directors and at the meeting of the Institute on Sept. 4, 1918, in Colorado, at which time a memorial service was held in the thea¬ter of the Hotel Broadmoor, attended by about 400 members and guests. A copy of the resolution was prepared and sent to the family. A bronze tablet is now being prepared and will be placed in the Members&apos; Room and unveiled at the February meeting. A biography and portrait of Dr. Douglas was published in the September, 1918, Bulletin. There is also placed in the Engineering Societies Library an oil portrait of Dr. Douglas which had his own approval and was presented by him. American Institute of Metals.--During the Spring of the year, plans were completed with the American Institute of Metals whereby this society became the Institute of Metals Division of the American Insti¬tute of Mining Engineers. This body was a dignified aggregation of metallurgists which had been in existence for about 11 years. A bronze tablet commemorating the American Institute of Metals is now being placed in the Members&apos; Room of the Institute, and during the year 1919 the Bulletin will bear the following title: "Bulletin of the American Institute of Mining Engineers, with which is consolidated the American Institute of Metals." Visits to Local Sections.-During the year President Jennings made visits to six of the Local Sections, on three of which occasions he was accompanied by the First Vice-president and the Secretary. First Vice-president Goodale made five visitations and the Secretary made eight.

Jan 1, 1923

Cycle, automatic, in mine hoists, LV, 17. Cylindrical furnaces, repairing partly collapsed, XXXVI, 215-222. Dacite-porphyry, San Jose, Tamaulipas, Mex., percentage composition, XXXVI, 186. DAGGETT, ELLSWORTH: The Extraordinary Faulting at the Berlin Mine, Nev., XXXVIII, [liii], 297. Daiquiri, Cuba: geology, LIII, 3, 43. iron deposits, LIII, 40. Magdalena mine, LIII, 9, 23, 24. mines, bibliography, LIII, 59. situation of mines, LIII, 42. [ ]

Jan 1, 1918