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Jan 2, 1976

By Donald A. Dahlstrom

In 1961 it became increasingly more evident that significant technological changes must be made in minerals beneficiation. The status quo in technology in today's competitive markets will not be tolerated. Higher productivity, greater recoveries and newer and better products must be sought and incorporated with lower operating costs. In other words, "when you build a new mill, don't build an old mill." Recommended reading for proof of the vital necessity of new methods and techniques is in the September 1961 issue of MINING ENGINEERING. The article by one of MBD's cherished and true veterans, E. H. Rose, is entitled "Iron Ore: The BIG Picture". Because of new beneficiation methods for iron ores, nearly 47 million tons of plus 60% iron concentrates will be produced and another 40.1 million tons of capacity will be under construction or committed. Thus in a relatively short period, 87 million tons of this high-grade iron concentrate with record low silica will be available. As Mr. Rose also points out, "in gross tons, without allowance for better grade, this is the equivalent of almost exactly two-thirds of all iron ore used for all purposes in the U.S. and Canada in the peak years of 1953 or 1957." Needless to say, improved mineral beneficiation methods have had far more reaching effects than just the production of higher grade iron concentrate.

Jan 2, 1962

By C. R. Hayward

CARLE R. HAYWARD.-I do not want it understood that I think that the conclusion that the time of tempering temperature is immaterial has been definitely proven, but since these are the first definite figures put out, I thought before continuing on more work ourselves, it would be well to present them as progress and for information. J. A. MATHEWS, Syracuse, N. Y.-I think that if Prof. Hayward would consult the paper of Profs. Barus and Strouhal,1 1885, he would find about 250 pages, mostly figures, on this subject, in which they investigated the tempering effect by electrical and magnetic methods. There are so many figures in the paper that it is very difficult reading. One point particularly brought out was that even at a low temperature, such as the boiling point of alcohol, about 60° C., there is a tempering effect, increasing up to 4 hr. One reason they obtained those results, with which the present authors are at variance, was that they started with a high-carbon steel which hardens thoroughly, whereas the steel Prof. Hayward and his collaborator used was a comparatively mild steel which does not take a great deal of hardening. About 3 years ago Mr. Stagg and I published 2 a few figures bearing on the same subject, but we used .a low-carbon alloy steel of high tempering qualities and found a great deal of improvement, particularly in ductility, by continuing the drawing up to 4 hr. We used a chrome-vanadium steel showing after heat treatment 250,000 tensile strength. On short drawing, we got almost no ductility, but by continuing to 4 hr., we raised it to 12 per cent. I believe Prof. Hayward's results are due to using comparatively mild steel, whereas Prof. Barus used drill rod and carried out a, wonderfully exhaustive

Jan 4, 1917

By J. J. Jonas, G. Gagnon

SHG zinc was extruded in the temperature range 110" to 350°C and the strain rate range 0.05 to 5 sec-1 The strain rate/flow stress/temperature results were analyzed using a power sinh stress relationship. When temperature changes due to the heat of deformation and to heat losses are neglected, the exponent of the sinh function of the stress is 5.6, and the apparent activation energy of deformation is 28 kcal per mole. When these changes are taken into account, the exponent decreases to 4.7 and the activation energy to 23 + 2 kcal per mole. The corrected stress exponent and activation energy are in very good agreement with published values obtained from creep experiments, and suggest that the hot extrusion of zinc is controlled by a mechanism involving self-diffusion. When the extrusion and creep data are compared using a Zener-Hollomon parameter and either a sinh or an exponential stress term, an appreciable offset is observed, which may be due to the difference in impurity content. For a given set of extrusion conditions the ram speed, maximum pressure, and initial temperature can also be correlated using a Zener-Hollomon parameter and a sinh pressure term. THE deformation of metals at temperatures over about one-half the absolute melting temperature has been extensively studied at creep strain rates. By contrast, relatively little work has been carried out on the behavior of metals at hot working strain rates. Most of the latter investigations have been performed using simulative methods, such as hot torsion and hot compression, in which the friction conditions and temperature rise during deformation may differ appreciably from those existing under industrial conditions. Recently, however, Wong and Jonas1 used a scaled-down industrial process to determine the stress and temperature dependence of the strain rate during the extrusion of aluminum. In such tests, the effects of friction and adiabatic heating are closer to those produced in industrial operations. Also, with regard to the testing of materials of limited ductility such as zinc, hot compression and hot torsion do not permit the attainment of true strains as large as the deformations usually applied commercially. The present study was undertaken to investigate the extrusion behavior of Special High Grade (SHG) zinc. The detailed objectives were: 1) to establish the stress and temperature dependence of the strain rate with and without a consideration of adiabatic heating, 2) to study the pressure and temperature dependence of the ram speed, and 3) to investigate the microstruc- tural changes occurring during the deformation. The last aspect of the investigation will be covered in a separate paper. The treatment described below differs from that of Wong and Jonas in that the adiabatic temperature rise during deformation is taken into account, and the calculation of the mean equivalent strain rate is based on the redundant as well as on the homogeneous work. EXPERIMENTAL PROCEDURE Rods from two shipments of continuously cast SHG zinc* were used in the investigation. The composition *Supplied by courtesy of Cominco Ltd. range of the impurities present, as given by the supplier, was: Pb: 0.0013 to 0.0023 pct, Fe: 0.001 pct max Cd: 0.0001 to 0.0006 pct, Cu: 0.0002 to 0.0005 pct, Ti: 0.0001 pct max; thus, by balance, zinc valued from 99.9963 to 99.9966 pct. The as-received rods were machined into billets having a nominal diameter of 1.56 in. and a nominal length of 1½ in.; longer billets up to 4 in. in length, were also used to investigate special aspects. The as-machined rods were annealed at 400°C for 24 hr and slowly cooled. This treatment produced a columnar grain structure, with a grain size of about $ by 2½ cm which was appreciably larger than the as-cast one. A 150-ton, direct extrusion, vertical press was used. Ram displacement and force were recorded continuously against time. A constant flow control valve permitted the maintenance of a range of preselected ram speeds up to in. per sec. The selected speed was held constant, irrespective of the required force, as long as the load developed was below the maximum available. Strain gages were used to determine the force; the gages were calibrated before and after each testing period with a 200,000-lb capacity load cell. Further details of the experimental equipment can be found in Ref. 2. The billets were preheated for 90 min in the extrusion container, which was well insulated so as to minimize temperature gradients. This period was sufficient for the billet to reach a uniform temperature at all temperatures between 110" and 350°C. A square-shoulder die having a 0.290-in. diam central hole was used. The extrusion ratio was 30 to 1. This is equivalent to a reduction in area of 96.7 pct, an elongation of 2900 pct, and a true strain of 3.4. The ram speed was varied over two orders of magnitude from 0.0027 to 0.26 in. per sec. The ram was water-cooled during most of the tests, although some experiments were conducted with a preheated, uncooled ram. All extrusions were run without lubricant, which resulted in conditions of sticking friction. EXPERIMENTAL RESULTS Stress Dependence of the Strain Rate Neglecting Adiabatic Heating. The maximum force required to extrude is given in Table 1 for each of the five initial

Jan 1, 1970

By Richard J. Robbins

Mechanical moles have developed through a tedious process of evolution. At times it has seemed that tunnel borers have been subject to the same Darwinian rules of evolution as their zoological namesakes who, despite their efficiency, are highly specialized and still restricted to soft soil conditions near the surface of the ground. HISTORICAL HIGHLIGHTS The Robbins Co. began its work in this field in 1947 with the development of a twin-bore continuous coal miner. Although these machines were used primarily in coal, two of the early prototypes were used to bore tunnels through shale. Disk cutters were first used on these machines and showed promising results as core breakers between drag-bit kerfs. In 1953, James S. Robbins and Assocs. undertook the development of a 25-ft 9-in.-diam circular tunnel borer for Mittry Construction Co. to be used at Oahe Dam in South Dakota (Fig. 1). This is believed to be the first rock tunnel-boring machine built since the end of the 19th century when short sections of the Channel tunnel were successfully bored in chalk from both the English and French shores. Another Oahe Dam machine was built in 1955, and then a series of three small-diameter machines for the company's first real experience with medium-hard and hard rock (Fig. 2) None of these three could be considered a success, although they laid the groundwork for the success that followed. Interbedded shale and limestone in Pittsburgh and hard limestone in Chicago quickly pointed up the weaknesses in these machines which were used by Perini, Dravo, and Healey. Among the problems were the high breakage rate of tungsten-carbide drag bits, too much flexibility in the drive shafts, failure of high-pressure hydraulic systems, chain-conveyor failure, and general lack of rigidity and strength. In 1956 another attempt at medium-hard and hard rock-boring proved this time to be a success and a significant turning point in the development

Jan 1, 1970

By Desio S. Oddone, Mark C. Malamphy, Irnack C. Do Amaral

Most igneous rocks, and particularly those of the basic type, contain relatively high percentages of magnetite and other iron oxides, which give them moderately high magnetic susceptibilities and make them responsible for an important percentage of the magnetic anomalies observed during the course of geophysical surveys by the magnetic method. The irregular form and high susceptibility of the igneous rocks make them readily polarizable and the position and strength of the magnetic poles formed are not always explicable by theoretical calculations of anomalies due to certain assumed forms in the normal magnetic field of the area under study. During the last four years our field work has permitted us to make detailed observations of anomalies due to igneous rocks in all the states of south Brazil. The form and position of the igneous rock at some places were fairly accurately known, which made it possible to calculate theoretical anomalies and compare them with the observed data. Some of the data we obtained have been published and additional cases are now awaiting publication. In this paper, we will present a few specific cases where the geology is moderately well known and which we believe to be of considerable value as representing typical magnetic anomalies in the south magnetic hemisphere, where the inclination of the magnetic field is very low. Although the vertical intensity is negative in the Southern Hemisphere, we have adopted the convention of plotting increase in intensity (negative) as a positive anomaly; i.e., above the x axis. This convention facilitates comparison with anomalies in the north.

Jan 1, 1940

By Albert E. Wiggin

PagE I. Early History of Boston & Montana Mill at Great Falls (1891 to 1905). 210 a. Original Mill Built in 1891.........210 b. Coarser Concentration Tried...211 c. Screen Sizing of Fine Jig Feed Introduced..211 d. Installation of Finer Grinding.......211 e. Steam Stamp Tried in Place of Blake Crushers..... 211 j. Mill Increased from Three to Six Sections........ 213 g. Tonnage Increased from 300 to 450 Tons per Section... 212 h. Round Tables Replaced by Wilfley Tables....212 I1. Hancock Jig Replaces Evans Jig...212 a. Description of Hancock Jig...213 - b. Tests Made on- Hancock Jig..213 1. Treating Natural Feed..215 2. Treating Sized Feed..215 3. Treating Classified Feed .215 c. Tests Made on Evans Jig...216 III. Richards Pulsator Classifier System...218 a. Experimental Work.....218 b. Installation of System in Section No. 4,....... 220 IV. Woodbury Classifier and Jig System.............222 V. The Great Falls System................ 222 a. As Installed at Anaconda............ 224 1. Coarse Crushing and Jigging Division...... 225 2. Hancock Jig Division........... 226 3. Fine Middling Division.......... 229 4. Table Division............. 230 5. Slime Division.........230 b. Special Features of Great ails Flow sheet....... 231 1. Development of Hancock Jig Flow Sheet..... 231 2. Development of Finishing Table Flow Sheet.... 232 3. Treatment of Coarse Middling Table Products .. 232 4. Results of Test Made on 500-Ton Section at Great Falls Mill...........234 VI. Comparison of Great Falls and Evans System at Anaconda.... 236

Jan 1, 1914

Sponsored by the Utah Section of AIME, the 1960 Annual Rocky Mountain Minerals Conference brought more than 500 members of the mineral industry to the conference rooms of the Newhouse Hotel in Salt Lake City during the period October 5 to October 7. Under the overall supervision of J. M. Ehrhorn, general chairman, and H. E. Wright, assistant general chairman, the Conference offered 14 papers of technical interest in four sessions during the first two days, and it culminated in the Exploration Symposium held on the morning of October 7. The opening session of the Conference, meeting on the morning of October 5, heard R. P. Work, utility engineer of the Mountain Fuel Supply Co., discuss the growth and economic factors related to the use of natural gas in Utah. In his paper entitled Natural Gas Market In Utah, Mr. Work emphasized the very good prospects of natural gas serving almost all parts of that state. He mentioned that recently the El Paso pipeline, built to serve the Pacific Northwest with gas from Texas, has permitted natural gas to be available to Eastern Utah, and a tentatively planned pipeline from Green River, Wyo. to Southern California will bring natural gas to the central and southeast areas of the state.

Jan 11, 1960

By George Branner

THERE is no record of the commercial production of bentonite as such in Arkansas up to the present although fuller's earth has been. mined intermittently in the state1 from 1891 to 1922. Very nearly all of this was obtained from decomposed basaltic dikes.2 Recently three bentonite deposits of close stratigraphical relationship have been identified in the Coastal Plain region of southern Arkansas, which suggests that there may be a considerable quantity of commercial material available. LOCATION AND ACCESSIBILITY The three deposits are located respectively in the SE. ;1/4 SE. ;1/4 sec. 13, T.- 2 S., R. 13 W., Saline County, the SE. ;1/4 SE. 1/4 sec. 18, T. 5 S., R. 16 W., Hot Spring County, and in sec. 22, T. 12 S., R. 19 W., Ouachita County. The Saline County deposit is 14 miles by state highway 167 south of the city limits of Little Rock and 1 mile west by dirt road. This deposit is 12 miles south of Ward switch on the C. R. I. P. Railroad and 11 miles east of Vimy Ridge by dirt road. Vimy Ridge is also on the C. R. I. P. Railroad. The Hot Spring County deposit located in the SE. ¼ SE. ;1/4 sec. 18, T. 5 S., R. 16 W. is about 100 yd. north of Durian switch on the C. R. I. P. Railroad and on state highway No. 9, 5 miles southeast of Malvern. The Ouachita County deposit has not been accurately located but lies in sec. 22, T. 12 S., R. 19 W. It is approximately 2 miles by road from Chidester on the Missouri Pacific Railroad.

Jan 1, 1929

By W. C. Ellis, M. E. Fine

INTRODUCTION IN the iron-cobalt system there are several property-composition relationships of theoretical importance. The alloys are ferromagnetic exhibiting a maximum saturation at approximately 33 at. pct cobalt;1 the interatomic distances at room temperature show large positive deviations from Vegard's rule;2 and in the region of 50 at. pct cobalt there is an order-disorder transition which has a large effect on other properties. The thermal expansion data for the system have been reported3,4.5,6 only from room temperature to 100°C, and for this temperature range a minimum in coefficient in the region of 50 at. pct cobalt is well established. 3,4,6 This paper reports the expansion properties in the iron-cobalt system for temperatures from 30 to 850°C, shows the correlation with other physical properties, and proposes an explanation for the interrelation. EXPERIMENTAL PROCEDURE The thermal expansivities of iron-cobalt alloys in 10 pct steps in composition were determined from 30 to about 850°C. The major series of alloys was prepared by induction melting from Armco iron and cobalt rondelles with the addition of about 0.6 wt pct manganese. This series was supplemented by three compositions: high purity electrolytic iron, high purity electrolytic cobalt, and an alloy of 52.1 wt pct cobalt prepared from the high purity electrolytic iron and electrolytic cobalt by vacuum-melting. The compositions of both series of alloys are given in Table I. The specimens for measurement were prepared from the cast ingots by first hot-swaging followed in most instances by cold-swaging to 0.180-in. diam rod. Some alloys in the region of 50 pct cobalt, because of inherent cold-brittleness, were swaged hot to the final diameter. The expansion specimens were approximately 2 ½ in. long with flat-ground and polished ends. Before measurement they were annealed in hydrogen for r hr at 900°C. In the apparatus used for the thermal expansivity measurements (Fig I), a modification of that designed by Hidnert and Sweeney,7 the differential expansion between the specimen and vitreous silica was measured by a dial micrometer reading to 0.001 mm. An invar fixture supported the dial gauge, and this fixture, in turn, was connected to a split invar collar which supported the outer silica tube. A pyrex "T" was placed over the outer silica tube and was sealed to the invar collar by Apiezon Q sealing compound. A movable hollow vitreous silica rod which rested on top of the test specimen slid through a flexible rubber diaphragm cemented to the top of the pyrex "T." The specimen rested on a vitreous silica pedestal fused into the outer tube and was kept centered by a silica sleeve. A non-oxidizing atmosphere was obtained by admitting hydrogen into the

Jan 1, 1948

By Irnack C. Do Amaral, Mark C. Malamphy, Desio S. Oddone

Most igneous rocks, and particularly those of the basic type, contain relatively high percentages of magnetite and other iron oxides, which give them moderately high magnetic susceptibilities and make them responsible for an important percentage of the magnetic anomalies observed during the course of geophysical surveys by the magnetic method. The irregular form and high susceptibility of the igneous rocks make them readily polarizable and the position and strength of the magnetic poles formed are not always explicable by theoretical calculations of anomalies due to certain assumed forms in the normal magnetic field of the area under study. During the last four years our field work has permitted us to make detailed observations of anomalies due to igneous rocks in all the states of south Brazil. The form and position of the igneous rock at some places were fairly accurately known, which made it possible to calculate theoretical anomalies and compare them with the observed data. Some of the data we obtained have been published and additional cases are now awaiting publication. In this paper, we will present a few specific cases where the geology is moderately well known and which we believe to be of considerable value as representing typical magnetic anomalies in the south magnetic hemisphere, where the inclination of the magnetic field is very low. Although the vertical intensity is negative in the Southern Hemisphere, we have adopted the convention of plotting increase in intensity (negative) as a positive anomaly; i.e., above the x axis. This convention facilitates comparison with anomalies in the north.

Jan 1, 1940

By Gordon E. Agar, David M. Hopstock

This paper describes the procedures and results of a series of experiments conducted to determine the depressing effect of sodium, calcium and magnesium ions on the amine flotation of quartz. It also presents an analysis of the experimental results by the electrical double layer theory. The flotation of quartz with primary amines has been practiced on a large scale in the phosphate industry for many years. Some glass sand —and recently iron ore — has also been treated by this flotation technique. These applications have been highly successful and demonstrate that a complete mastery of all the details of an operation is not needed to achieve an economic success. There are times, though, when it becomes important to recognize, both qualitatively and quantitatively, the effects of some previously ignored variables. The effects of cations on the amine flotation process, particularly those ions that contribute to water hardness and abound in sea water, are a case in point. In conjunction with the development of a cationic flotation reagent for separating quartz from apatite, it became necessary to quantify the influence of calcium and magnesium on the separation. In order to strengthen and broaden current understanding of the flotation process, the results were interpreted by means of the electrical double layer theory. THEORETICAL BACKGROUND Assume that, given the same equipment, procedure, and time, the recovery of quartz by amine flotation is a function of only the adsorption density of aminium ions in the Stern layer, i.e., that for any given adsorption density there exists only one recovery percentage. By the Stern-Grahame treatment of the electrical double layer,'-' for any ionic species in a solution in equilibrium with quartz,

Jan 1, 1969

Escalating energy costs and tough environmental standards were two major factors affecting the minerals processing area in 1978 For the most part, new startups and research and development initiatives were directed toward improving process dynamics, investigating alternative processing strategy, and lowering unit costs. In the flotation area, the trend to larger machines continued. Scientific investigation of the modeling and process control of flotation was apparent, as was the research and development of new flotation reagents.

Jan 5, 1979

By George Burrell

INTRODUCTION THE senior author of this paper, while in Colorado on other official business, made a trip to the Cripple Creek gold-mining district to get more data than are at present available regarding the composition of the gas that issues from the rock into the mines of the district. This was done at the suggestion of George S. Rice, Chief Mining Engineer of the Bureau of Mines. There are many questions of interest and importance in connection with the ventilation of the mines in the Cripple Creek district, such as the menace to life and mining of a suffocating gas entering the mines from the rock, the danger due to powder smoke (from blasting operations), and danger of continued inhalation of rock dust by the miners. This report confines itself to the first problem, the gas from the rock, and principally to one phase of this question, the composition of the gas and its effects on men and lights. A more thorough study of this and other ventilation problems is planned. That the, rock gas is a real menace is shown by the fact that miners (variously estimated from 25 to 50 by different persons interviewed) have been killed by it in the 25 years that mining has been vigorously carried on at Cripple Creek. Many men have had narrow escapes from death, some of them having been incapacitated for days. In addition, much loss of time results because at certain periods of the year or on certain days it is impossible to enter some workings. At a few mines fans force air into the workings, thus supplementing the natural ventila-

Jan 5, 1916

No true conception of the Park City mining district can be obtained without first giving consideration to the part it has played as a consistent producer of mineral wealth. Its position in this regard is almost unique in the annals of a lead silver camp. For over fifty years it has been a continuous producer of lead and silver and for twenty years it has added to the world's supply of zinc. Few camps with its productive history are so little known to the mining fraternity for the reason that its life has never been punctuated by periods of "boom" which serve to attract general attention, neither has it been the field of operation for promoters who temporarily focus attention upon their scene of action. Its history is one of legitimate mining operations. These were at first carried on by a number of smaller companies. A period of consolidation followed and at the present time the entire production of the camp is in the hands of two major companies and one smaller company. These are flanked by a number of prospecting properties, which are at this time actively engaged in the search for ores and later events will doubtless put some of them in the producing class.

Jan 1, 1925

By C. A. Stickels

In a recent paper, Held1 showed that rolling conditions can have a marked effect on the volume fraction of surface texture produced in low-carbon steel. This variation in rolling texture is reflected in the recrys-tallization texture and affects the plastic properties of the annealed sheet. The fact that roll friction can influence the surface deformation texture in iron and steel has been known for some time;'= but the magnitude of the effect has never been shown quite so clearly before. The analogous effect during wire drawing has been recognized for many year.4 Dillamore and Roberts5 examined surface textures in warm- and cold-rolled aluminum and copper. They found that when a surface texture was present it could be described as the interior texture rotated about the transverse sheet direction. The angle of rotation was a function of the type of lubrication, the amount of reduction per pass, and the temperature of rolling. The purpose of the present note is to show that surface textures in cold-rolled iron can also be described as interior textures rotated about the transverse sheet direction. Vacuum-melted electrolytic iron* was straight- rolled 90 pct at room temperature in a two-high rolling mill with 5-in.-diam rolls. Two rolling procedures were used: a) no lubrication with reductions of about 0.035 in. per pass, and b) heavy lubrication with lano-line and reductions of about 0.002 in. per pass. The final sheet thickness was 0.030 in. (110) pole figures were determined by transmission through specimens taken from the sheet surface and sheet midplane. The surface texture of the sheet cold-rolled according to procedure a is shown in Fig. l.* The shapes of the low-intensity contour lines indicate that the texture can be described as a partial fiber texture with a (110) fiber axis normal to the sheet. The approximate range of orientstions present is (011)[211] — (0ll)[100] — (011)[211]. This range of orientations is what one would obtain by rotating the interior texture 90 deg about the transverse sheet direction. The intensity of (110) and (222) reflections from planes parallel to the surface was measured after removing metal from the surface by chemical polishing. The surface texture here was confined to the outer

Jan 1, 1968

By Otto Wartenweiler

AFTER the phenomenal development of the new mine, the United Eastern Mining Co., with Mr. Frank A. Keith as President, decided to install a reduction plant. The character of the ore, closely resembling the product of other mines in the district, did not offer any particular metallurgical problems, since these neighboring mines had been operating milling plants very successfully for several years. Thus, with the general metallurgical treatment fairly well-defined, the matter of next importance was to design and construct a plant as economically as possible, that would give the best results obtainable. The ore consists of a mixture of calcite and quartz in about equal quantities with some decomposed andesite, while the average value of mill heads were calculated to be $20 plus in gold, no silver being present. The tonnage to be treated at ,the start was fixed at 200 tons, but, in view of the favorable condition of the mine, it was considered advisable to arrange facilities, for increasing the capacity to 400 tons. . While it is best in some cases to adopt a distinct independent unit system where future enlargement is contemplated, in this instance the plans worked out differently. Summarized, the treatment adopted consists of coarse crushing, coarse grinding, fine grinding and cyanidation. For coarse crushing the selection of the No. 6 size gyratory crusher was governed not so much by its capacity as by the size of the feed openings to properly receive the run-of-mine material, which was too coarse for a No. 5 crusher. To accomplish the coarse grinding to. best advantage, a careful comparison was made between the modern steel ball mill-the last word in crushing and grinding-and one of its older, and, at that time better-established, competitors, the rolls.' The following conclusion was reached: While it is possible that for the sized plant under consideration the cost of operating rolls might be a little cheaper, it is preferable to use ball mills because a simpler arrangement is possible, and1 because. the handling of, ball mills is preferred by the operator.

Jan 11, 1917

By Raymond E. Birch, Oscar M. Wicken

THE mineral magnesite, formerly the source of nearly all magnesia, now shares this role with brucite, dolomite, and the world's natural and artificial brines. The mineral magnesite is the normal carbonate of magnesium, MgCO3, composed when pure of 47.6 pct MgO and 52.4 pct CO2. It is one of the calcite (CaCO3) group of rhombohedra1 car- bonates, which also includes dolomite, CaCO3.MgCO3, and siderite, FeCO3. Magnesite does not form an isomorphous series with calcite or dolomite; consequently, these lime-bearing carbonates commonly present in magnesite deposits are there only as mechanical mixtures. Magnesite and iron carbonates form a continuous isomorphous series and therefore are inseparable mechanically. The variety of magnesite known as breunnerite is an isomorphous mixture of iron and magnesium carbonates. Magnesite may be either crystalline or amorphous (cryptocrystalline). The former, which includes breunnerite, is often termed spathic magnesite. Crystalline magnesite varies from finely to coarsely crystal- line in texture and has a hardness of 3.5 to 4. The color is white, yellowish, blue-gray to drab, red, pink, black, or mottled. It is seldom found pure but usually contains variable amounts of iron, lime, silica, and sometimes manganese. The color cannot be used as an index of purity. The cryptocrystalline variety is perhaps the more common type but the crystalline variety usually occurs in larger deposits. The amorphous type is fine grained and compact, showing no cleavage. It is usually snow white but sometimes is light to pale orange yellow or buff, owing to impurities. The fracture is conchoidal to uneven and the hardness 3.5 to 5. Silica may be present as inclusions of serpentine, quartz, chalcedony, or other minerals. The lime and iron contents are usually low. In general, amorphous magnesite is somewhat purer than the crystalline variety. The specific gravity of cryptocrystalline magnesite is 2.90 to 3.00. Pure crystalline magnesite has shown a specific gravity of 3.02 but iron

Jan 1, 1949

By M. H. Forester, John D. Cooner

ANTHRACITE ALTHOUGH the unmined anthracite will last for approximately 150 years, most of the thicker and cleaner coal beds have been almost entirely first-mined and pretty well robbed, leaving much of the present and future production to come from thin and dirtier beds. Herewith is a section of one of the dirty beds being mined in the Wyoming region [ ] This section shows that 45.8 per cent of the bed is made up of impurities and that the 45 in. of coal in the bed is in five benches, the thickest of which is 19 inches. In some localities of the anthracite region there are 14 beds of minable coal. Orderly and proper mining of the coal makes it necessary to rob or second-mine-almost all beds have already been first-mined-in sequence from the top downward. Therefore the robbing of the few remaining portions of the thicker and cleaner beds is in many instances being held up by the mining of the overlying thin and dirtier coal beds. Impurities Impurities consist of fire clay, slate, rock, and bone. The latter, which is black, contains 40 to 60 per cent carbon and often resembles good coal. In some beds there are also bands of "blue" coal, which, as the name implies, is of a bluish slaty color. Although much of this "blue" coal has a carbon content almost as high as the good anthracite, it is not

Jan 1, 1943

By A. J. Boynton

THIS paper is not the result of recent research with regard to any particular feature of iron metallurgy, blast-furnace practice or mechanical engineering. It is rather a series of notes with regard to contemporaneous progress in blast-furnace construction and operation, together with some suggestions as to changes and improvements that seem to be desirable. On April 1, 1930, a committee of the Chicago District Blast Furnace and Coke Association presented to that association a rather ambitious study of blast-furnace equipment, together with recommendations for the design of construction of a complete blast-furnace unit for the production of 1000 tons of pig iron per day. This report represented the result of months of study by members of the committee, all of whom were actively engaged in operation or design of blast-furnace plants. It is natural, therefore, that comments on the present state of the art should take this 1000-tons furnace, as recommended by the Association, as a basis for comparison with corresponding features of construction or design. See Table 1. In looking through this report at the present time, the significant difference is in the nature of the gas-washing equipment that today would be specified. In other respects, the installation would remain generally very much as it was outlined in 1930. The change in furnace dimensions would be very slight and of no especial significance, except with respect to changes in stock-line diameter, of which more will be said hereafter. The high-efficiency stove as developed by various designers is thoroughly described within this report, and few changes have taken place since. Blowing equipment shows refinement and reflects the improvement in steam engineering. Hoisting and charging equipment and ladles for the conveyance of iron and slag remain, in general, as they were in 1930. In accordance with a general tendency

Jan 1, 1935