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By William E. Ford, Edward Salisbury Dana

This section includes one distinct group, the Stibnite Group, to which orpiment is related; the other species included stand alone. Pyr., etc. - In the closed tube melts and gives a dark red liquid when hot and a red- dish yellow solid when cold; in the open tube (if heated ver slow? ) sulphurous fumes, and a white crystalline sublimate of arsenic trioxide. B.B. on ciarcoaTburm with a blue Hame, emitting arsenical and sulphurous odors. Soluble in caustic alkalies. Artif. - Realgar is frequently noted as a sublimation product from furnaces roasting ores of arsenic. Crystals are produced when arsenic sulphide is heated in a sealed tube with a solution of sodium bicarbonate. Obs. - Realgar occurs usually in veins associated with silver and lead ores. It has been found in volcanic regions as a sublimation~duct. It has also been noted as a deposit from hot spring waters. It is often rtasociate wlth orplment. It occurs at Felsi5bBnya, Kapnik and NagyAg, Hungary; Allchar, Macedonia. Binnental, Switzerland, in dolomite. In the United States, at Mercur, Utah; in the Norris Geyser Basin, Yellowstone Park, as a deposition from the hot waters. Found at the Monte Cristo millin district, Snohomish Co., Washington: the namerealga7 is from the Arabic, Rahj af gh&r,powder of the mine. Use. - Was used in fireworks to give a brilliant white light when mixed with saltpeter and ignited. The artificial material is now used for this purpose.

Jan 1, 1922

THE book covers principally the assaying of silver and gold and the determination of these values in ores, sweepings, and base metal. It seems to have been written more for the goldsmith and jeweler than for the primary producer of metals. There were approximately sixty different substances needed in the operations described and not over a dozen different types of raw material (ore, matte, crude or alloyed metal) are mentioned. The methods of separation used were essentially simple and reasonably reliable, though the processes were not sufficiently understood to permit the selection of the simplest effective ingredients, and there was a great tendency to employ complicated fluxes, with unnecessary repetition of long-continued heatings indicative of a leisurely pace of life. Practically all the processes described are based on a few chemical facts: the inability of gold to combine with sulphur, while silver and the base metals form easily fusible sulphides; the ready oxidation of base metals; and the ii- solubility of gold in nitric acid. Fluxes serve to make earthy impurities fusible, and to carry oxidizing or sulphurizing ingredients. Many of the processes of assaying had changed little up to the beginning of the present century. Even as late as 1924, when the writer took a University course in fire assaying, the crucibles, cupels, scorifiers, molds, and tongs were identical with those of the sixteenth century, though the wind furnace had a stack on it and the muffle for cupelling was gas-fired.* The fluxes were purer, but of the same essential composition. That this branch- or twig-of metallurgy had not advanced in any funda-

Jan 1, 1949

By Clarence Seyler

THE technical difficulties of cutting thin sections of coal for examination by transmitted light have hitherto restricted the investigation of the important subject of the microstructure of coal to the few possessed of the requisite skill and time. Apart from this, the method fails with anthracites and other coals rich in carbon, owing to the opacity of the material. Occasional use of the method of polishing a surface, with or without etching, has been made, but it was not until Winter1 published an account of his results that attention was seriously directed to the method. In May, 1923, a specimen of dull anthracite came into my hands; I tried Winter's method on it and the presence of megaspores and other vegetable structures became clearly visible. A preliminary notice was published by me;2 but I soon abandoned the use of Schulze's solution having found that a mixture of chromic and sulfuric acids gave far better results. In the meantime Turner and Randall, in America, had independently developed the method of flame etching, as applied to anthracite, with great success. I have spent a year studying the method of chromic etching, which gives excellent results with bituminous coals and cannels, as well as with anthracite. For anthracites, I have used the chromic method and Turner's method of flame etching, whichever was the more convenient or as a check one on the other. The polishing is done, according to metallurgical practice, by the use of a polishing machine and successively finer emery paper, followed by polishing on cloth moistened with a suspension of levigated green oxide of chromium, and a final rubbing on "selvyt" (a cotton velvet polishing cloth) moistened' with alcohol. The polished sample is examined by reflected light with a 2/3 and 1/6 in. objective. Bituminous coals usually show considerable structure, and even anthracites show it faintly in places. The sample is then etched by immersion in a boiling solution made by adding 10 c.c. of concentrated sulfuric acid to 30 c.c of a saturated solution of chromic acid; enough water is then added to dissolve

Jan 3, 1925

By W. F. Mullen, C. W. Stickler

WITH few exceptions, unit operations in the Pennsylvania slate industry in 1950 did not differ appreciably from production methods described by Behrel and Bowles2-4 several decades ago. Many traditionally picturesque but relatively inefficient hand operations continued to contribute to high operating costs in an industry in which the margin of profit, for various reasons, was admittedly low. As part of a general program in which the Pennsylvania State College has been assisting the slate industry to solve some of its problems, time and method studies were used in an effort to determine the bottlenecks of production flow. The results are as applicable to other stone industries as they are to slate. A study of the basic elements in the production of roofing slate, structural slate, and slate blackboards among selected slate producers revealed comparatively few refinements. Any marked difference in operating method was characterized largely by the available equipment, a noticeable difference in the working properties of the rock quarried by a particular company, and by either the habit thinking or ingenuity of the individual operators. With the hope that significant economies in manufacture might result, all the unit operations were broken down into elements for study and analysis. The greater part of the study encompassed those operations from the quarry rim to the finished product; however, to obtain a reasonable synthesis of time allotments per operation, several analyses of quarrying from the finish of the wire saw cut are included for reference. The complete study of quarrying made by Bowles several years ago resulted in the introduction of the wire saw into the operation; there appears to be a need for as fundamental a change in the processing of finished slate as the wire saw was in the quarrying process. Fig. 1 illustrates the flowsheet of quarried rock from the parent bed to the quarry rim with the basic elements which contribute to the difficulty of removing slate from the ground. In Pennsylvania roofing slate is produced by one of three procedures, many operations of which are quite similar. In the traditional or classical method the quarried rock is reduced by sculping and auxiliary manual treatment to workable size and then is split and dressed (trimmed to size) in the conventional shanty. Archaic as this method might appear, there are several elements that result in substantial savings over more mechanized operations. In a modified version of this method, the block is reduced by sawing and gouging preparatory to splitting and dressing in indoor stations. This method is particularly adaptable to rock which fractures unevenly by conventional sculping methods. In the third and more modern method, reduced block received from the block maker is diamond-sawed to length and finished on a production line. Fig. 2 illustrates the flow pattern in each case. In the modified and more modern plans, dressing is done on mechanically-operated trimming machines, which appreciably reduce the fatigue factor of the operator. However, it should be noted that it is advantageous for the operator to be able to control the speed of the knife to prevent breakage of certain classes of stock. In the classical plan the splitter and dresser normally act as blockmakers also and carry their eighter slabs (equivalent in thickness to eight shingles) into the shanties themselves, all of which adds to fatigue and reduced efficiency. The extremely low investment and operating expense of the classical method has undoubtedly been of paramount importance in its continuation. Production of Mill Stock The production of mill stock is accomplished by less picturesque methods than enter into the production of roofing slate but it is, in the main, relatively more efficient because of the increased use of machinery for handling and for finishing. Mill stock can be classified into two categories as far as difference in production method is concerned: structural slate and blackboards. The significant difference in operation is caused largely by the nature of the rock used for each product with the best and easiest cleaved rock being reserved for blackboards to permit the splitting of large slabs to as little as 1/2 in. in thickness. Structural stock, on the other hand, is split into panels no thinner than 11/2 in. and

Jan 1, 1952

By Joseph B. Story, John T. Clarke

A modification, of the Kelvin bridge using an inductor was used to measure the conductivities of molten sodium chloride, calcium chloride, and mixtures thereof. A capillary-type four-lead fused quartz dipping cell was constructed. The effect of a small amount of potassium chloride on the conductivity of the melt was determined. IN the electrowinning of sodium and chlorine from sodium chloride in Downs cells, calcium chloride is added to the sodium chloride in an approximately equimolar amount to permit cell operation at a lower temperature. This lower temperature improves current efficiency and ease of operation, but decreases voltage efficiency by decreasing the electrical conductivity of the melt. A knowledge of the electrical conductivity of the Downs cell melt is necessary to the understanding of Downs cell operation, for the IR voltage drop across the melt is responsible for a significant part of the electrical power consumed by the cell. The work of previous investigators on fused sodium chloride-calcium chloride mixtures was reviewed from the standpoint of consistency with the results of others on the conductivities of the pure constituents. The electrical conductivity of pure fused sodium chloride has been established with accuracy by Van Artsdalen and Yaffe,1 by Edwards, Taylor, Russell, and Maranville,2 and by Lee and Pearson.3 It has also been studied by a number of other investigators.4-13 The best values for calcium chloride are believed to be those of Lee and Pearson,3 since the sodium chloride and potassium chloride conductivity values given by them check the best literature values. A number of other investigators have also reported values for calcium chloride.'-"."' Electrical conductivity data for fused sodium chloride-calcium chloride mixtures have been reported by Sandonnini,12 Vereshchetina and Luz-hnaya,18 Ryschkewitsch,11 Barzakovskii,5 and Alaby-shev and Kulakovskaya.15 Sandonnini reports no data at temperatures lower than 850°C. The conductivity values reported by Vereshchetina and Luz-hnaya, by Ryschkewitsch, and by Barzakovskii for pure sodium chloride and for pure calcium chlor- ide vary somewhat from the literature values believed to be best and the sodium chloride-calcium mixture data of these authors and of Alabyshev and Kulakovskaya (who give no data for the pure compounds) show significant variations. In view of these facts, it seemed that an investigation of the electrical conductivities of fused sodium chloride-calcium mixtures would be worthwhile. Apparatus Bridge System—The bridge used,in this investigation is diagrammed in Fig. 1. In general, the elaborations of this bridge over the simple Wheatstone bridge were for the purposes of a) eliminating lead resistances or making them accurately measurable, and b) eliminating major capacitative and inductive effects or balancing them against each other. Lead resistances in the lower arms of the bridge were kept as low as possible by making the leads short and of low resistance wire. This could not be done in the cell arm of the bridge because of the remoteness of the cell from the other bridge components and because of the high-resistance nickel or chrome1 wires used in the cell. Since maximum sensitivity is attained when the resistances of the four arms of the bridge are equal, 50-O resistors were used in the lower arms of the bridge when fused salt conductivities were being measured, and 1000-O resistors were used when the cell was being calibrated with normal aqueous KCl solution. The cell resistance was of the order of 50 ohms with fused salts and of the order of 1000 ohms with normal aqueous KC1 solution. The resistors used were non-inductive and accurate to 50.05 pct (General Radio Co. Types 500-C and 500-H). The lead resistance between point A in the cell and point E at the measuring resistor was eliminated by using the kelvin bridge principle; that is, the voltape drop across the lead from point A to point E was divided between the cell arm of the bridge and the measuring arm of the bridge in proporation to the resistaxes in the lower arms of the bridge.

Jan 1, 1958

By Roger G. Rowe

In late 1980, Exxon Minerals Company performed rock mechanics testing on oriented 150 mm drill core from their 75Fi tonne massive sulfide deposit near Crandon, Wisconsin. Instrumented samples from depths of 300 meters indicate premining horizontal stresses in a north-south direction (parallel to pillar faces) to average 12,300 kPa, with the perpendicular plane yielding an average stress of 14,630 kPa. Rock strength versus sample size was compared using uniaxial compressive strengths from 47 mm, 95 mm and 150 mm core. Massive sulfide averaged 153,300 kPa, 139,845 kPa and 75,330 kPa respectively, while the hanging wall and foot- wall averaged 92,000 kPa, 76,560 kPa and 57,960 kPa respectively. Point load compressive strengths were calculated using formula suggested by both Hassani et al., 1980 and Broch et al., 1972. Values calculated using the Hassani formula closely resembled pre- existing point load and uniaxial compressive strengths, while values calculated using the Broch formula were 50 percent low.

Jan 1, 1982

By H. S. McQueen

The insoluble-residue method for the examination and correlation of limestones and dolomites, or other sedimentary rocks containing calcium and magnesium carbonates, originated and was developed in the laboratory of the Missouri Geological Survey. The numerous and ever-increasing problems in the field of applied geology, and the need for a tool or aid in the solution of them, led to experimental work with samples collected from deep wells, in the early part of 1924. The success attained, almost at the outset, with this method was so great that the method has now been developed from the state of the experimental to the realm of large-scale, every-day routine. In a previous paper the writer1 described the procedure in detail and the characteristics of the residues obtained from certain Paleozoic formations in Missouri. The purpose of the present paper is to discuss the economic application of the insoluble-residue method. Developmental History Within the Ozark region of southern Missouri the geologic column consists of Lower Ordovician (Canadian of Ulrich) and Upper Cambrian formations, which are composed mainly of dolomite with subordinate amounts of sandstone, shale and limestone. Chert is found to some extent in all except one of the dolomite formations. The stratigraphy of the region is complex because the dolomites have lithologic similarities, fossils are few and often poorly preserved, and identifiable horizons within the comparatively thick formations are not common. Although considerable stratigraphic work of an areal nature had been done for a period of many years by the Missouri Geological Survey, the detailed geologic succession had not, until a few years ago, been systematically worked out. The problems of subsurface stratigraphy were even more complex. This region constitutes the main ground-water province of the State of Missouri and within it wells of varying depths are drilled in order to obtain supplies of ground water. In the work of the State Geological Survey in connection with the drilling of water wells for public supplies * Published with the permission of the Director, Missouri Geological Survey and Water Resources. Manuscript received at the office of the Institute Feb. 20, 1936. Assistant State Geologist of Missouri; Missouri Geological Survey, Rolla, Mo. References are at the end of the paper.

Jan 1, 1937

By W. P. Sykes

THIS investigation was undertaken primarily to establish the relations existing between temperature and mechanical properties in molybdenum, nickel, and an aluminum-copper alloy. Molybdenum (m.p. 2500° C.) was chosen because it is partly similar to tungsten and partly similar to the common ductile metals. Also it is known to furnish, by proper treatment, a desirable material to use in studying relation of grain size and physical properties. The molybdenum used was of the quality that is drawn into wire 0.003 in. in diameter for use as filament supports in incandescent lamps; chemical analysis shows less than 0.1 per cent. of impurities. Nickel belongs to the same class as iron. Its melting point is 1450° C. and an allotropic change at about 370° C. results in a loss of magnetism above that temperature. This feature made nickel doubly valuable for the purposes of these tests. The nickel used was obtained from the Driver-Harris Co. as 0.090 in. (2.3-mm.) wire, annealed; analysis showed 99.8 per cent. nickel and 0.150 per cent. iron. Aluminum is one of the low melting-point metals. Some tensile tests at elevated temperatures have been reported by Bengough but the possibility of learning more with the low temperature and sensitive apparatus available recommended this metal. The samples marked Al are an aluminum-copper alloy; they contained 3 per cent. copper, 0.42 per cent. iron, and 0.21 per cent. silicon. The presence of the copper somewhat complicates the analysis of the results; but the action of copper in aluminum has been studied so that its influence might have been foretold, in part at least. The material and analyses were furnished by the Aluminum Castings Co. The nickel wire, which was deformed at 400° C., was drawn under a bath of molten lead and through a die, which also was immersed in the bath. A thermocouple was suspended in the molten metal to indicate

Jan 1, 1921

W. H. BASSETT,* Waterbury, Conn. (written discussion ?).-The effect of reducing gases on hot solid copper has been known for many years in the copper industry, and precautions taken to guard against it in the general practice in copper heating and annealing. In view of the statement that Bengough and Hill, in 1910, were the first to suggest the possibility of the formation of gas within the copper itself, it is interesting to note that in Harper's Magazine for April, 1904, an article, "Life and Diseases of Metals," by Professor Heyn, illustrated the effect of reducing gases on copper by a photograph, which is shown in Fig. 1. This he entitled "Copper burst asunder by disease." After referring to the effect of hydrogen on steel, he makes the following remark: "Similar symptoms of poisoning, caused by hydrogen or gases containing hydrogen (as gas for lighting purposes), are apparent in copper when exposed to red heat. Not every kind of .copper is susceptible to this poisoning in equal degree. Copper per-fectly free of cuprous oxide is entirely exempt from poisoning. Most of the various coppers of commerce, however, contain cuprous oxide, formed during the smelting process while exposed to atmospheric influences. In such coppers, containing cuprous oxide, hydrogen causes a terrible disease on the copper being heated red hot. The copper bursts asunder and is permeated by cracks. This disease is practically incurable and can be eradicated by resmelting only. The results work destructively according to the amount of cuprous oxide contained in the copper." It must have been evident to Professor Heyn, as it was to us on reading this article, that the bursting asunder of the copper was clue to the formation of steam. Practical copper heaters have known for many years that it was quite possible to produce blisters, or large gas holes, in the interior of copper plates or bars by heating to a high temperature in reducing gases. These facts, of course, do not detract from the value of the study of the action of hydrogen gas that has been made by Mr. Pilling, but simply illustrate that the practical effect of reducing gases on furnace-refined copper has long been a troublesome factor in the heating or annealing of that metal.

Jan 1, 1919

By Larry G. Hayes

Development of the Bowers-Campbell zinc deposit, located in the Shenandoah Valley two miles northwest of Timberville, Va., was commenced in 1956 by the Tri-State Zinc Co. The occurrence of lead-zinc mineralization in this area has been known for many years, but the first serious exploration program was initiated in 1951 by the geologic staff of Tri-State Zinc Co. Ordovician dolomites. The deposit is approximately 700 ft long, 100 ft wide, and 475 ft thick. Its projected plan has an elongated ovoid shape, where- as the profile appears boot-shaped with the upper portion outcropping. Vertical cross sections show the lense as having been thrust-faulted along certain bedding planes. The movement along these bedding thrusts varies greatly and in one case, has offset the deposit so as to divide it into an upper and lower orebody. The breccia lense strikes parallel to the N 34" E strike of enclosing strata.

Jan 9, 1960

By Tell Ertl, Ernest E. Burgh

INTRODUCTION THE Bureau of Mines is operating an oil-shale mine 10 miles west of Rifle, Colo., as part of its Synthetic Liquid Fuels program. The purpose of operating this mine is twofold: First, to supply oil shale to an experimental processing plant; and second, to develop practices and select methods for mining oil shale on a commercial scale at the lowest practicable cost. The second purpose-that of finding out how to mine oil shale most cheaply-entails considerable mining research. Since the drilling of oil shale probably will be one of the major items of the mining cost, factors that influence drilling speeds were investigated. One phase of the drilling program was the development of a successful hard-surfaced rock-drill bit1 that can be used for drilling long holes in oil shale without changing bits. During that phase, drilling speeds were measured and drill cuttings were collected for assay and for screen sizing. When the cuttings from the individual tests were compared, a definite relationship was shown to exist between the drilling speed and the coarseness of the drill cuttings. PROCEDURE Measurement of Drilling Speeds All drilling in the tests was done with a Model UMB-D-99W Gardner-Denver wagon drill. Round-lugged drill steel, 1 ¼ in. in diameter was used in 6, 12, and 18 ft lengths with 2 1/8 -in. Timken H-type bits hard-faced with acetylene tube borium. The tests were made in the lower adit of the Bureau of Mines oil-shale mine; the grade of the oil shale drilled ranged from 18.6 to 42.7 gal per ton. During the experiments air pressure varied between 75 and 90 psi while water pressure remained fairly constant at 75 psi. All holes were drilled almost horizontally. Each drill hole was thoroughly cleaned of cuttings after being collared. The advance of the drill along the carriage was measured and recorded as the drilling speed in inches per minute. Method of Collecting Cuttings To facilitate the collection of cuttings, each drill hole was collared in a smooth, vertical portion of the oil-shale breast (Fig 1). A galvanized-steel sheet was fastened to the breast below the area in which the hole was to be drilled. The cuttings washed out of the drill hole by the drilling water were guided by the steel sheet into a wooden box. The cuttings that remained in the drill hole after the drill was withdrawn were scraped out and placed in the same box as the cuttings washed out of the hole. After the cuttings from a 1-min. drilling interval were collected, they were placed in flat metal pans. The fines were allowed to settle and the clear water was decanted. The cuttings then were dried in the sun.

Jan 1, 1947

By Eizo Yabuuchi, Yukito Imanaga

INTRODUCTION In treatment of mine drainage, it is well known that the neutralization by calcium carbonate is far better than by slaked lime because of cheaper cost and better precipitability of its deposit. However, in case of iron ion contained in the mine drainage consists of ferrous salt, the ferrous salt must be oxidized to ferric salt before neutralization, because the ferrous salt does not react with calcium carbonate. At Yanahara Mine, during the period of 1950 through 1956, ferrous ion in the mine drainage had been oxidized to ferric ion, simultaneously neutralized by adding calcium carbonate into the aerated drainage. During the period of 1961 through 1974, after passing through many kinds of treating methods, the neutralization had been carried out by addition of calcium carbonate into the drainage after oxidized its ferrous ion to ferric by using nitrous gas as an oxidizing catalyzer. Meanwhile we had made an experiment on the oxidation of ferrous ion by utilizing iron bacteria, and developed a method which oxidized ferrous ion in large quantities briefly by cultivating and concentrating iron-oxidizing bacteria. Since 1974, we have been operating successfully for treating the drainage at Yanahara Mine by means of utilizing these bacteria.

Jan 1, 1976

By J. A. Snyder, W. L. Finlay

SEVERAL notable studies of the effects of sub- stitutional solutes have been reported. Outstanding among these for its elucidation of general principles, is the summarized work of Hume-Rothery and coworkers.1 For a systematic study of the effects of substitutional solutes on the mechanical properties of the solvent lattice, the work of Brick, Martin, and Angier² on copper; of Frye and coworkers³,4,5 on copper and silver; and of Lacy and Gensamer6 and of Austin7 on iron may be mentioned. Titanium is one of the few elements offering the possibility of a similar study of interstitial solutes since, unlike most metallic elements, it exhibits extended solid solubility for most of the interstitial solutes—hydrogen, boron, nitrogen, oxygen, and carbon. This paper reports a survey of the effects of dilute solutions of nitrogen, oxygen, and carbon on the mechanical properties of high-purity alpha titanium. Previous Work: Van Arkel and De Boer showed" that high purity titanium was quite ductile and De Boer, Burgers and Fast established".' that not only were oxygen and nitrogen very soluble in solid titanium but that, long before the limit of solid solubility of either had been reached, these interstitial solutes rendered the metal brittle. Their electrical resistance data as a function of

Jan 1, 1951

By Galen G. Waddell

Several years of rock-burst research conducted by the U.S. Bureau of Mines in cooperation with the mining companies of the Coeur d'Alene mining district, Idaho, in addition to progress made by others throughout the world, have led to a good understanding of the rock-burst problem. This paper describes conditions which have caused specific bursts, present capabilities of detecting stress buildup and bursts, control methods, and a suggested approach to analyzing any individual mine-burst problem. A rock burst is the sudden, violent release of stored strain energy in rock by some mechanism of rock failure, generally accompanied by expulsion of rock with consequent damage to the mine. A burst may be audible for only a few hundred feet, or on the surface it may sound like a sonic boom miles away. A Dictionary of Mining, Mineral, and Related Terms, U.S. Bureau of Mines (USBM)* 1968yand defines a burst as Bureau "That phenomenon which occurs when a volume of rock is strained beyond the elastic limit and the accompanying failure is of such a nature that accumulated energy

Jan 1, 1971

By Eric Jette

THE unusual physical, electrical and magnetic properties of the iron-nickel alloys has given rise to a voluminous literature. This work will be reviewed critically in "The Alloys of Iron and Nickel," a monograph of the Alloys of Iron Research Series, soon to be published. In what follows we shall therefore confine ourselves to those of the earlier investi-gations that involved the use of X-ray crystal-structure methods. The earliest X-ray work on the iron-nickel system was by Miss Andrews1. Using the powder method of X-ray analysis purely as a means of identifying the phases present, she located a region between 20 and 30 weight per cent nickel in which body-centered and face-centered phases coexisted. No lattice constants nor details of heat-treat-ment were reported. Bain2 also reported some qualitative observations. McKeehan3 made a systematic investigation over the whole of the system, giving many of his alloys four and some five different heat-treatments. In alloys furnace-cooled from 900° to 950° C. he found two coexisting phases between 0.15 and 30 per cent nickel. The precision of the lattice-constant measurements was low in comparison with what can be obtained today.. Even for alloys of the same heat-treatment, differences in the constants were often between two and ten parts per thousand. In regions where no change of lattice constant with heat-treatment should occur, differences of the same order of magnitude were found. Since the maximum change in the lattice constant of nickel with change of composition is only about 2 per cent of the constant for pure nickel, these variations in the constants for a given alloy cause the points

Jan 1, 1936

By Lloyd Pollish, Robert N. Breckenridge

SUCCESS in any underground mining operation is determined by accessibility of the orebody, which in turn is dependent upon maintenance of passage- ways to the mining zones and temporary support of the voids caused by extraction of ore. This is accomplished by one or a combination of the following methods: timbering, back-filling, pillaring, or, more recently, rock bolting. Timbering has usually been the principal means of maintaining these underground openings necessary for mining operations. Timber, however, does not prevent ground movement beyond the scope of localized sloughing, which is indicated by the gradual failing of the timber itself. Besides this, timbering has always been a costly process, and with the decline of available supplies of timber close to the mining areas, mining men have constantly sought other methods of controlling ground.

Jan 7, 1954

By Allan J. Clark

It is nearly three years since the metallurgy of the Homestake ore was discussed with considerable thoroughness, in a paper1 read before the Institution of .Mining and Metallurgy. Certain changes have been made in this period which are perhaps of sufficient interest to justify a brief description, and it is chiefly with such details and miscellanies that this paper will deal. In the circumstances, a certain amount of repetition is inevitable, but matter treated of in the former paper will be referred to here only when it is necessary for the sake of coherency. For full descriptions of equipment and technique, the former paper should be consulted. The mineralized slates and schists which constitute the ore vary considerably in composition, but the unoxidized ore, perhaps constituting the major part of the reserves, contains either chlorite or hornblende (cummingtonite), with quartz, carbonates of lime, magnesia and iron, and arsenopyrite, pyrite, and pyrrhotite. Ferrous minerals predominate, and this fact has been an important factor in determining the metallurgical treatment. With one or two exceptions the minerals noted are of relatively high specific gravity, and the ore as a whole is exceptionally heavy, many determinations giving an average specific gravity of 3.00. This high specific gravity presents one decided advantage, when the cost of treatment is compared with operations elsewhere, in that the ton, almost universally the basic unit, represents a volume probably less by 10 per cent. than that of many gold ores. On the other hand, this high gravity renders more difficult the discharge of pulp from mortars, its distribution on amalgam tables, and its transportation in launders. In the same way, as attesting the usual balance of such variations of different ores, it may be noted that the needle-like fibers of hornblende (cummingtonite), interlacing throughout the mass, render the ore more difficult to crush than would be anticipated, but on the other hand assist

Jan 1, 1916

By John V. Beall

THIS is not simply the story of how a water filled shaft was developed into a million-ton- a-year producing mine in the space of four critical years, although it is reason enough for telling it, but it is also the saga of an engineering achievement in which knowledge nurtured by years of experience in coal and ore mines was blended together and the best from each type of mining selected. The entire system of mining was detailed on maps by the mining engineering department before the shaft was unwatered, and subsequent development followed these plans nearly to perfection. The selection of machinery was particularly critical as it was necessary to push production from only a few headings in the early stages of development and metal mine machinery was being used in a coal panel-system of mining.

Jan 12, 1950

By Reinhardt Thiessen

UNDER sulfur in coal, is usually understood that form of sulfur which is combined with iron and known as pyrite. It occurs in the form of halls, lenses, nodules, continuous layers, thin sheets, or flakes, both in horizontal planes and vertical cleavage fissures. But pyrites also occur as very fine microscopic particles, or nodules, disseminated through the compact coal. This form has had but very little consideration. Finally, there is sulfur in coal in an amicroscopic form (not visible with an ordinary microscope), probably combined with the organic matter that exists -in tile coal. This form has had considerable attention from a scientific standpoint, but has probably not been recognized enough on the economic side. One or the other, or both, of these two latter forms may comprise the larger part of the sulfur content of coal, especially after it has been washed or otherwise prepared for use.

Jan 9, 1919

By William L. Lennemann

Chemistry of uranium with respect to its hydrometallurgical recovery from carnotite ores was investigated and well defined during the radium boom period between 1900 and 1920. Since that time, methods used to extract uranium from its ores have remained basically either acid leaching or sodium carbonate leaching. Until about 1950, the only practical methods known for achieving a better than 75 pct U2O3 concentrate from the leach liquors involved fundamental chemical techniques for either purifying a solution prior to the uranium precipitation, or refining a crude uranium concentrate that was produced by neutralizing a pregnant mill liquor.

Jun 1, 1956