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By Marlin J. Veesaert

Urban quarries offer one of the greatest opportunities for profit in nonmetallic mining with limited financial risk-if properly evaluated, planned and developed to meet market needs. Location, with respect to market, is the prime consideration. Geologic considerations and quality of rock are nearly as important. Cost factors and return on investment (ROI) are the principal financial considerations. Risk of capital is determined by weighing all factors that should be considered and how well judgments are based on information acquired. It is a simple, true axiom of business that an investment must be founded on amount of capital required with its expected return plus profit, expertise required to operate, and time involved. Urban quarries generally offer excellent stone product market opportunities. Costs of land with mineral containment and processing operations are much greater than in rural areas. Environmental problems have become increasingly severe. Competition from other quarries in the market area is usually directly proportional to the profit attractiveness. Risk of capital (initial, developmental and operational) can be evaluated and reduced only by thorough analysis of the entire situation. Time and money expended on planning and preliminary investigations probably represent the most productive investment of available company resources. Basic Reasons to Establish a Limestone Quarry Profit Motive: Certainly the dominant and overriding motive must be that of attaining a reasonable profit. In certain situations a quarry firm may acquire land, necessary rezoning (if required), and satisfy all of the other prerequisites preparatory to beginning operations but delaying the actual development.

Jan 1, 1980

By A. A. Smith, J. S. Smart, A. J. Phillips

The preparation of a sufficient quantity of high-purity copper for extensive laboratory use in the study of impurity effects has been an integral part of a research program in progress at the Central Research Laboratory of the American Smelting and Refining Co. for the past several years. Initially the degree of purity desired was that necessary to meet two essential requirements for experimental accuracy: (I) no impurity was to be present in the copper in an amount capable of producing a detectable effect on the properties to be studied, (2) even the minor changes in propertties caused by the addition of extremely small amounts of individual elements were to be measured without significant interference from contaminants. In the course of the investigation, evidence has accumulated to justify the conclusion that this copper is of exceptional purity; in fact, no impurity can be detected by any chemical method or spectrographic technique known to the authors. The present paper describes the method of production of the copper and presents some of its properties. Preparation oF High-purity Copper The elimination of impurities from commercial electrolytic copper is accomplished by a three-step purification process. The first operation consists of an electrolysis through a purified CuSO4-H2SO4 electrolyte using bagged anodes, low current density (5 amp. per sq. ft.) and low tem- perature (25°C max.). The electrolyte is prepared from commercial Cu2SO4 and is purified by heating the solution and adding I gram Fe as Fe2(SO4)3 to each 100 grams dissolved copper; sufficient hydrated oxide of copper, prepared from Cu2SO4 and NaOH, is supplied to precipitate Fe(OH)3, which carries down arsenic, antimony, tin, selenium, tellurium and other minor constituents. Silver and remaining traces of lead are removed by addition of Na2S to the acidified filtrate, which is then reatered after standing hot overnight. The cold solution is made up to 30 grams per liter Cu and 150 grams per liter H2SO4 and introduced without addition agents into the electrolytic system, which consists of a double row of hard-rubber battery boxes with the inside webbing and partitions removed, arranged in seven steps of ascending height. Electrolyte is uniformly supplied to the two highest cells by glass siphons operating from a constant-level reservoir, and flows by gravity through the bank of seven cells, entering each at the bottom and leaving at the top. Glass air lifts continuously supply the returning liquid to the constant-level reservoir for recirculation. Each cell contains three 4 3/4 by 4 3/8 by 1-in anodes cast from high-quality electrolytic wirebar copper, various lots of which have been used with equal success. The anodes are pinned to sheet copper hangars shaped to prevent crawl of the electrolyte to the multiple-wired bus bars—which would result in fouling of the contacts—-and hang inside wool flannel bags stretched over open wood frames. The deposit

Jan 1, 1941

By A. J. Phillips, A. A. Smith, J. S. Smart

The preparation of a sufficient quantity of high-purity copper for extensive laboratory use in the study of impurity effects has been an integral part of a research program in progress at the Central Research Laboratory of the American Smelting and Refining Co. for the past several years. Initially the degree of purity desired was that necessary to meet two essential requirements for experimental accuracy: (I) no impurity was to be present in the copper in an amount capable of producing a detectable effect on the properties to be studied, (2) even the minor changes in propertties caused by the addition of extremely small amounts of individual elements were to be measured without significant interference from contaminants. In the course of the investigation, evidence has accumulated to justify the conclusion that this copper is of exceptional purity; in fact, no impurity can be detected by any chemical method or spectrographic technique known to the authors. The present paper describes the method of production of the copper and presents some of its properties. Preparation oF High-purity Copper The elimination of impurities from commercial electrolytic copper is accomplished by a three-step purification process. The first operation consists of an electrolysis through a purified CuSO4-H2SO4 electrolyte using bagged anodes, low current density (5 amp. per sq. ft.) and low tem- perature (25°C max.). The electrolyte is prepared from commercial Cu2SO4 and is purified by heating the solution and adding I gram Fe as Fe2(SO4)3 to each 100 grams dissolved copper; sufficient hydrated oxide of copper, prepared from Cu2SO4 and NaOH, is supplied to precipitate Fe(OH)3, which carries down arsenic, antimony, tin, selenium, tellurium and other minor constituents. Silver and remaining traces of lead are removed by addition of Na2S to the acidified filtrate, which is then reatered after standing hot overnight. The cold solution is made up to 30 grams per liter Cu and 150 grams per liter H2SO4 and introduced without addition agents into the electrolytic system, which consists of a double row of hard-rubber battery boxes with the inside webbing and partitions removed, arranged in seven steps of ascending height. Electrolyte is uniformly supplied to the two highest cells by glass siphons operating from a constant-level reservoir, and flows by gravity through the bank of seven cells, entering each at the bottom and leaving at the top. Glass air lifts continuously supply the returning liquid to the constant-level reservoir for recirculation. Each cell contains three 4 3/4 by 4 3/8 by 1-in anodes cast from high-quality electrolytic wirebar copper, various lots of which have been used with equal success. The anodes are pinned to sheet copper hangars shaped to prevent crawl of the electrolyte to the multiple-wired bus bars—which would result in fouling of the contacts—-and hang inside wool flannel bags stretched over open wood frames. The deposit

Jan 1, 1941

By I. C. White, G. H. Ashley, J. A. Bownocker

Among the rich mineral deposits of the great Appalachian field, the Pittsburgh coal bed stands pre-eminent. Other coal beds may cover a wider area, or extend with greater persistence, but none surpasses the Pittsburgh seam in economic importance and value. It was well named by Rogers, and his able assistants of the First Geological Survey of Pennsylvania, in honor of the city to whose industrial growth and supremacy it has contributed so much. Whether or not the prophetic eye of that able geologist ever comprehended fully the part which this coal bed was to play in the future history of the city that gave it a name we do not know; but certain it is that the 7 ft. of fossil fuel, which, in Rogers' time, circled in a long black band around the hills and, overlooking the site of Pittsburgh from an elevation of 400 ft. above the water of the Allegheny and Monongahela, extended up the latter stream in an unbroken sheet for a distance of 200 miles, has been the most potent factor in that wonderful modern growth that has made the Pittsburgh district the manufacturing center of America, and that bids fair to continue until it shall surpass every other district in the world, even if it does not now hold such primacy.' The Pittsburgh coal bed stands today as probably the largest contributor of wealth of any single mineral deposit in the world. If it is not, what other deposit is? It has contributed to Pennsylvania alone more than 2,500,000,000 tons of high-grade coal worth nearly $4,000,000,000; since 1910, it has added more than $2,500,000,000 to the value of Pennsylvania's mineral output. In 1920, this bed2 contributed 127,227,000 tons of coal as follows: Pennsylvania, Pittsburgh district........................ 38,245,000 Connellsville district................................. 34,095,000 Weatmoreland-Ligonier district........................ 16,107,000 88,447,000 West Virginia, Fairmont district........................ 15,571,000 West Virginia-Ohio, Panhandle No. 8 district............. 21,128,000 Maryland-Potomac (Est. one-third of production)......... 2,081,000 38,780,000 Total........................................... 127,227,000

Jan 1, 1927

By Homer W. Riley

ANTHRACITE SMALL power-driven, toothed, cast-iron rolls were used first to break anthracite in 1844. Prior to that time, men with hammers, who stood on perforated cast-iron plates, broke the large lumps into commercial sizes. In order to convert run-of-mine into the various sizes required by the anthracite industry, about 20 million tons must be broken, annually, into smaller sizes. This phase of anthracite preparation is of major importance, because the degradation accompanying reduction in coal sizes should be kept at a minimum. The exclusive use of toothed rolls for that purpose indicates that comminution by rolls is the best solution of the problem. Many improvements have been made in tooth design, but the most important was a reduction of the peripheral speed of the rolls from 1000 to 300 ft. per minute. The higher speed was based upon and approximated the velocity of a falling piece of coal when it entered the rolls, Exhaustive roll tests at the slower speed showed that the same size reduction could be affected with less degradation. The adoption, therefore, of slow-speed, compound geared rolls, especially for breaking the larger sizes, became quite general after 1912. A high-speed roll is shown in Fig. 1 and a slow-speed roll in Fig. 2. Anthracite Crushing Problems.-Crushing anthracite presents the problem of selecting a series of rolls that will produce the greatest percentage of the prepared sizes of nut and over. The size distributions to be expected are shown in Table 1. Coal breaking and crushing practices in anthracite breakers involve the use of equipment for comminuting the following classes of material: 1. Run-of-mine-plus 6 ½ -in. coal. 2. Sized coal-steamboat, broken, egg, stove, nut, and pea. 3. Flat coal--coal that is flat and hence not suitable for the market. 4. Bone--a piece of laminated coal and slate, crushed for the purpose of reclaiming the coal. 5. Breaker refuse, reduced to a size suitable for flushing into a mine for back-filling purposes.

Jan 1, 1950

By M. R. Campbell

Coal is the geological product of entombed vegetal tissues. This view of its origin led Stopes and Wheeler to define it as "mummified plants." They evidently intended this term to be used in a broad way and to mean the preservation of the organic material, as such, regardless of the means employed to accomplish the purpose. The term " coal" should be regarded, therrfore, as broadly generic, and applicable to all accumulations of vegetal tissues as soon as they are covered and protected either by water or by earthy material. In this sense peat should be regarded as the first stage of coal formation and the term coal should include the resultant products of transformation in all other stages of the process until they have lost all resemblance to the original matter from which they were derived. If this idea of the development of coal is accepted and it is admitted, as the geologists claim, that the forces which produced this transformation of the coal have been active since vegetation began to grow upon the land, and are still in operation, it is obvious that somewhere in the world there are all gradations of this material from peat just forming in the swamps of today to graphitic anthracite which presumably marks the most advanced stage that can be recognized with certainty as belonging to the series. Some of these coals, particularly those occurring in the upper part of the series, are fairly well known because they are the ones that are most widely distributed and have been mined and utilized most extensively. On the other hand, the coals in the lower part of the series are but little known because they are not so abundant and, owing to their relative inefficiency, have been only slightly exploited and utilized, especially in regions where the better coals are abundant. The result of these conditions is that much research work has been done on coals of the higher ranks and a great body of facts regarding their physical and chemical properties and the uses to which they are best adapted has been accumulated, but little information is available regarding the coals of the lower ranks. Many able scientists, particularly chemists, have attempted to bring some order of the chaos of coals of various compositions and uses by

Jan 1, 1930

By Thomas E. Leontis

INTRODUCTION THE importance of magnesium alloys in the manufacture of aircraft engines has been realized for many years. A concentrated effort has been exerted in the laboratories of the Dow Chemical Co. to develop magnesium-base alloys with improved properties at elevated temperatures whereby greater advantage can be taken of the inherent lightness of these materials. In an earlier publication,1 attention was called to the superior tensile properties and resistance to creep of cerium-containing magnesium alloys at temperatures up to 700°F. More recently, additional data on magnesium-cerium alloys have been furnished by Murphy and Payne.2 The present paper deals with the mechanical properties of sand-cast magnesium alloys containing zinc, at temperatures up to 500°F. The study includes binary Mg-Zn† alloys containing up to 10 pct zinc and several ternary and some polynary alloys based on the Mg-1Zn,†Mg-3Zn, Mg-4.4Zn, Mg-6Zn, and Mg-10Zn binaries. The compositional variation in the tensile properties, hardness, and creep at room and elevated temperatures, and in the electrical conductivity at room temperature has been determined. The results of these tests show that many zinc-containing magnesium alloys exhibit resistance to creep at elevated temperatures significantly higher than that of present commercial magnesium alloys, but lower than that of alloys of the magnesium-cerium type. In addition, they have high tensile properties at room and elevated temperatures and high conductivity. This combination of mechanical properties and conductivity indicates that these alloys should be given serious consideration for commercial applications involving exposure to temperatures higher than those to which present commercial magnesium alloys can be taken safely. LITERATURE The properties of sand-cast magnesium alloys containing zinc as a principal alloying element have not been investigated very extensively, especially at elevated temperatures. The following remarks, which are confined to sand-cast alloys, will serve as a summary of the most important references on this phase of magnesium metallurgy. The first recorded determination of the tensile strength of binary Mg-Zn alloys as a function of zinc content was reported by Aitchison.3 Similar studies, including the measurement of elongation and hardness, have been performed by Gann and Winston,4 Dumas and Rockaert,5 Haughton and Prytherch,6 and by Spitaler, the last being reported by Beck.7 A slight superiority in the tensile strength of chillcast Mg + 8 Zn alloy over the sand-cast alloy was noted by Maybrey 8 That alloys of magnesium containing 5 to 12 pct zinc

Jan 1, 1948

By Richard W. Smith

Kyanite, long known to occur in Georgia, did not excite coimmercial interest until about 1930. Investigation1 revealed two main types of deposits: (1) separate kyanite crystals embedded in mica schist; and (2) crystal aggregates of kyanite associated with quartz in small and very irregular veins. The second kind at first sight appeared to be the best source of supply. Large boulders or dornicks of kyanite with more or less quartz were found on the surface at many places throughout the Piedmont and Highland sections of the state, but prospecting failed to disclose a sizable vein. These dornicks seem to be a surface accumulation from small veins or lens-shaped masses not more than one or two feet thick, and with a horizontal extent of not more than a few feet. 'rile larger surface accumulation of kyanite dornicks, where not too badly stained by iron oxide, may prove to be marketable, but it is extremely doubtful whether a vein large enough to mine will ever be found. In 1932 deposits of the kyanite-mica schist were known to occur in two places northwest of Clarkesville, in Habersharn County. In 1934, at the request of and in cooperation with the Georgia Geological Survey, the United States Geological Survey made a thorough investigation2 of the deposits and found that the two known areas of kyanite-mica schist in Habershain County were but a part of an unsymmetrical, U-shaped belt (Fig. 1) with a western limb extending into Rabun County and somewhat longer than the eastern limb. The total length of the belt is about 30 miles. The width of outcrop ranges from 100 ft. to 1/4 mile or more. Deposits of kyanite-mica schist of very doubtful commercial importance were found in several other counties. Only the deposits of this kyanitc-mica schist belt in Habersham and Rabun counties will bc discussed in this paper. Geology The kyanite-mica schist of Habersham and Rabun counties occurs near the northern cdge of the Piedmont Upland in metamorphic rocks of pre-Cambrian age3. These rocks probably were deposited as sedimentary

Jan 1, 1938

By Richard W. Smith

Kyanite, long known to occur in Georgia, did not excite coimmercial interest until about 1930. Investigation1 revealed two main types of deposits: (1) separate kyanite crystals embedded in mica schist; and (2) crystal aggregates of kyanite associated with quartz in small and very irregular veins. The second kind at first sight appeared to be the best source of supply. Large boulders or dornicks of kyanite with more or less quartz were found on the surface at many places throughout the Piedmont and Highland sections of the state, but prospecting failed to disclose a sizable vein. These dornicks seem to be a surface accumulation from small veins or lens-shaped masses not more than one or two feet thick, and with a horizontal extent of not more than a few feet. 'rile larger surface accumulation of kyanite dornicks, where not too badly stained by iron oxide, may prove to be marketable, but it is extremely doubtful whether a vein large enough to mine will ever be found. In 1932 deposits of the kyanite-mica schist were known to occur in two places northwest of Clarkesville, in Habersharn County. In 1934, at the request of and in cooperation with the Georgia Geological Survey, the United States Geological Survey made a thorough investigation2 of the deposits and found that the two known areas of kyanite-mica schist in Habershain County were but a part of an unsymmetrical, U-shaped belt (Fig. 1) with a western limb extending into Rabun County and somewhat longer than the eastern limb. The total length of the belt is about 30 miles. The width of outcrop ranges from 100 ft. to 1/4 mile or more. Deposits of kyanite-mica schist of very doubtful commercial importance were found in several other counties. Only the deposits of this kyanitc-mica schist belt in Habersham and Rabun counties will bc discussed in this paper. Geology The kyanite-mica schist of Habersham and Rabun counties occurs near the northern cdge of the Piedmont Upland in metamorphic rocks of pre-Cambrian age3. These rocks probably were deposited as sedimentary

Jan 1, 1938

By C. T. Eddy, R. W. Drier

The conductivity of copper wire is of prime importance to the electrical industry and consequently to the copper refiner and wire manufacturer. Annealed copper wire has a higher conductivity than hard-drawn wire, but, on the other hand, its tensile strength is lower. In an attempt to explain the reasons for these changes in properry. or at least to study the conditions existing in these two types of copper wire, the experiments described here were carried on in the Department of Metallurgy of the Michigan College of Mining and Technology This is only a partial and preliminary report on some of the work done to date on a research program of which the object is an intensive study of copper. It is offered with the hope that, though it is not an exposition of the most rigorous of conclusions, the general trend of inferences which may be drawn will be of value and interest. Effect of Direction of Drawing In 1928 some work was done on hard-drawn copper wires to determine whether wire drawn in a continuous machine (that is, all in one direction) would have a different structure from wire that had a reversal in direction at some stage of the drawing process. The diffraction spectra obtained indicated that as the position of the wire rayed approached the core, a preferential crystal orientation existed, and that the closer to the core the more preferred was the orientation. The data obtained partly corroborated the work done by Schmidt and Wassermanl and by Clark.2 Samples Used in Following Investigation The samples selected for use in both the diffraction work and the resistivity measurements were taken from Nos. 6, 8, 10 and 12 gage

Jan 1, 1930

By M. F. Trice

Pyrophyllite is a hydrous aluminum silicate (A1²Si4O10(OH)²)1 that, occurs in both the foliated and the massive forms. The foliated variety resembles talc in that it has a greasy feel, a pearly luster, perfect basal cleavage, and usually is white, although in some deposits apple green, gray, brown, russet, and nearly black specimens may be found. The massive deposits of pyrophyllite yield pearl gray to light tan aggregates, some of which are so friable that they may be crushed with the hands into a fine gritty powder. Frequently specimens of the massive variety are studded with crystals of radial structure. The mineral has a specific gravity of about 2.7 and a hardness of 1 on Mohs' scale.' The chemical composition of commercial pyrophyllite reflects the mineralogy of the deposits, which, according to Stuckey12 contain pyrophyllite and quartz, together with chloritoid, sericite, and a few other minerals of negligible importance. The latter, he says, ('are noticed in but small quantities to the extent they might occur as accessory constituents of an igneous rock or as products of regional metamorphism or weathering. . . . Quartz is abundant everywhere except in the very best grades of pyrophyllite." Analyses of specimens from several deposits are listed in Table 1, showing that the silica content varies from 57 to 73 per cent and the alumina from 22 to 33 per cent. Oxides of iron and the alkaline metals are collectively present, with one exception, to an extent of about 1 to 1.5 per cent. Sources At present, North Carolina is the only commercial source of pyrophyllite, although the mineral has been found in small quantities in many parts of the world. The North Carolina deposits are in the "Carolina Slate Belt," which traverses the center of the state in a southwesterly direction. This belt varies from 8 to 50 miles in width. Two major deposits of pyrophyllite lie along its eastern boundary, in what is known as the Deep

Jan 1, 1942

By M. F. Trice

Pyrophyllite is a hydrous aluminum silicate (A1²Si4O10(OH)²)1 that, occurs in both the foliated and the massive forms. The foliated variety resembles talc in that it has a greasy feel, a pearly luster, perfect basal cleavage, and usually is white, although in some deposits apple green, gray, brown, russet, and nearly black specimens may be found. The massive deposits of pyrophyllite yield pearl gray to light tan aggregates, some of which are so friable that they may be crushed with the hands into a fine gritty powder. Frequently specimens of the massive variety are studded with crystals of radial structure. The mineral has a specific gravity of about 2.7 and a hardness of 1 on Mohs' scale.' The chemical composition of commercial pyrophyllite reflects the mineralogy of the deposits, which, according to Stuckey12 contain pyrophyllite and quartz, together with chloritoid, sericite, and a few other minerals of negligible importance. The latter, he says, ('are noticed in but small quantities to the extent they might occur as accessory constituents of an igneous rock or as products of regional metamorphism or weathering. . . . Quartz is abundant everywhere except in the very best grades of pyrophyllite." Analyses of specimens from several deposits are listed in Table 1, showing that the silica content varies from 57 to 73 per cent and the alumina from 22 to 33 per cent. Oxides of iron and the alkaline metals are collectively present, with one exception, to an extent of about 1 to 1.5 per cent. Sources At present, North Carolina is the only commercial source of pyrophyllite, although the mineral has been found in small quantities in many parts of the world. The North Carolina deposits are in the "Carolina Slate Belt," which traverses the center of the state in a southwesterly direction. This belt varies from 8 to 50 miles in width. Two major deposits of pyrophyllite lie along its eastern boundary, in what is known as the Deep

Jan 1, 1942

By H. J. R. Way

THE work to be described was undertaken at various periods from 1937 to 1939 on the Busia gold field, in the eastern province of Uganda. It was decided to examine the possibility of reef prospection by the resistivity method, for it was not known how far the usually disintegrated nature of most reefs in the ubiquitous laterite near the surface would obscure indications obtained by resistivity traverses. The work at the commencement was therefore largely experimental, but the results obtained thereby were satisfactory, and a survey was started at the Government closed area at Amonikakine. With the limited time and resources at the writer's disposal, it was not possible to complete the survey to his satisfaction or to follow up exhaustively all the geophysical indications, but some of the results of the experimental work and the survey were of sufficient interest to be worth recording; in particular the relation between the width of reef, electrode separation and shape of the curve, and the interference effect of constant separation curves over zones of float are significant and useful. Three new veins were located, but only one contained sufficient gold to warrant detailed prospection. This was called the Geophysical reef, and was uncovered over a strike distance of 1140 ft., and there are indications that it extends over a distance of 1990 ft. These results and the recommendations consequent therefrom were embodied in a special report to the Uganda Geological Survey. HISTORY OF THE FIELD The Busia field is in the southeastern corner of Uganda near the Kenya-Uganda border, and is about 17 miles north of the northeastern corner of Lake Victoria. Gold was first discovered in the area in the stream beds by Davies1,2 in 1932. Subsequently numerous small alluvial claims were worked by prospectors and the area was prospected for reef by a company for periods varying from three to nine months, but was finally abandoned, as the results were considered unfavorable. Further prospecting by the Geological Survey in 1935-1936 under Davies3 and later under the writer4 uncovered three reefs with sufficient gold values to be of economic interest. These were finally taken over by a company known as Borderland Syndicate, which still owns the area, and from September 1937 to the end of 1941 about 13,000 oz. of gold was extracted from reefs of the area proved by the Geological Survey. Opencast mining operations are still proceeding (February 1943). The Amonikakine area lies to the immediate north of that of Borderland Syndicate. A certain amount of prospecting had been done when the writer started work there. As a result of his report, this area was taken over by another syndicate, but little further work was accomplished before it ceased operating because of difficulties of wartime working.

Jan 1, 1944

By Samuel M. Cassidy, John A. Garcia

In some districts of the bituminous coal field the problem of constructing bulkheads to seal off water under pressure is becoming increasingly important. Recently this matter has been brought very much to the front by the loss of a large Illinois mine due to failure of a bulkhead that separated it from several old, flooded mines. As this great misfortune has provoked much inquiry about proper bulkhead design, it is felt that a description of the successful and extensive water-sealing practice at three mines that have different natural conditions will be of considerable interest to those connected with properties having a present or future water problem and to engineers that may have to design safe bulkheads of economical construction. These three mines are the Saxton and Dresser, near Terre Haute, Ind., and the Hegeler, near Danville, Ill. All three have water conditions that make it necessary to regularly seal off all worked-out sections of the mine, and there are considerably over a hundred bulkheads in each. AS far as the writers know, these three mines are the only ones in the bituminous coal fields of the United States with anything like so large a number of water seals and experience, although a number of other mines are known to have a few bulkheads. More detail will be included herein on the Saxton mine than on the others, as the writers are more familiar with it. General Mining System All three of the mines use the same general panel room-and-pillar system, which consists of rooms turned both ways off room entries and a solid block of coal left on all sides of the completed panel except on the cross-entry side, where a heavier pillar is pierced by two entries for haulage and air. On completion of the panel the two entries arc sealed and the panel is then isolated from the rest of the mine. Owing to water conditions, no pillars are pulled; recovery inside the panel barrier pillars is approximately 65 per cent.

Jan 1, 1938

By Samuel M. Cassidy, John A. Garcia

In some districts of the bituminous coal field the problem of constructing bulkheads to seal off water under pressure is becoming increasingly important. Recently this matter has been brought very much to the front by the loss of a large Illinois mine due to failure of a bulkhead that separated it from several old, flooded mines. As this great misfortune has provoked much inquiry about proper bulkhead design, it is felt that a description of the successful and extensive water-sealing practice at three mines that have different natural conditions will be of considerable interest to those connected with properties having a present or future water problem and to engineers that may have to design safe bulkheads of economical construction. These three mines are the Saxton and Dresser, near Terre Haute, Ind., and the Hegeler, near Danville, Ill. All three have water conditions that make it necessary to regularly seal off all worked-out sections of the mine, and there are considerably over a hundred bulkheads in each. AS far as the writers know, these three mines are the only ones in the bituminous coal fields of the United States with anything like so large a number of water seals and experience, although a number of other mines are known to have a few bulkheads. More detail will be included herein on the Saxton mine than on the others, as the writers are more familiar with it. General Mining System All three of the mines use the same general panel room-and-pillar system, which consists of rooms turned both ways off room entries and a solid block of coal left on all sides of the completed panel except on the cross-entry side, where a heavier pillar is pierced by two entries for haulage and air. On completion of the panel the two entries arc sealed and the panel is then isolated from the rest of the mine. Owing to water conditions, no pillars are pulled; recovery inside the panel barrier pillars is approximately 65 per cent.

Jan 1, 1938

THE great development of the mines and metallurgical works of this country during the last few years, accompanied as it has been by the investment of enormous sums of money in purchasing lands, and in the erection of improvements, requires that advantage should be taken of the accumulated knowledge of engineers, superintendents, and' others, in mastering &he problems which are constantly presenting themselves for our action. Among those may be mentioned the consideration of more economical systems of mining in our coal and metal-liferous mines, improved methods of transportation above and below ground, unwatering and ventilating mines, the mechanical preparation of coal and other minerals, the various metallurgical processes, and, in fact, every question tending to the attainment of two great objects : 1st. The more economical production of the useful minerals and metals. 2d. The greater safety and welfare of those employed in these industries. In European countries, where the arts of mining and metallurgy have long been the subject of the most careful study, no means have been found so effectual in attaining the end above proposed as the free interchange of experience among those actually engaged in these industries, and this object has been accomplished, mainly, through the medium of institutes, associations or societies, composed of those engaged in these occupations, and by the periodical publication of essays or papers, communicated to such societies by their members. I t must be evident to all practical men that the interchange of the varied experience of those engaged in such occupation in this country could not fail to advance very materially the desired objects; it is, therefore, proposed to establish an American Institute of Mining Engineers, which will hold its meetings periodically in the great mining and metallurgical centers, where works of interest, such as mines, machine shops, furnaces, and other metallurgical works, can be inspected, and the members exchange their views, and consult for mutual advantage upon the difficulties encountered by each; these transactions or proceedings, when published, would form a most valuable and greatly-needed addition to our professional literature. I t is proposed that a meeting of those sympathizing with the object above mentioned shall be called for the purpose of organizing such an association, the place and time of meeting being Wilkes-Barre, Pa., and the month of April or May. Communications indicating the opinion and wishes of all, both as to these points, and also as to the organization and objects of the Institute, will be gladly received by any of the undersigned, and a notice of the date of meeting, which will be arranged to suit the greater number, will be duly communicated. Any

Jan 1, 1933

By Richard McCaffery

WHEN we began the study of blast furnace slags we limited our work at first to a study of those slags containing only lime, alumina and silica. On our paper1 on some of the results of this first work, the solubility of sulfur in slags containing no magnesia was reported and the question of sulfur solubility and slag viscosity discussed. There has been, for a long time, a very great difference of opinion among metallurgists as to he effect of magnesia in blast furnace slags, and the literature is full if expressions of the most contrary opinions on the subject. As a result, our next publication' developed the constitution of slags considered as a four-component system, silica-alumina-lime-magnesia, and advanced an explanation of slag structure which accorded with the facts and with scientific theory. The present paper continues our study of the general subject of slags. As blast furnace slags are included in the silica-alumina-lime-magnesia system, which is a particular case of four-component solutions, we have determined that there are 22 components Table 1), which may enter into the silica-alumina-lime-magnesia system and that 10 or 12 of these components may be present in blast furnace slags which are within the ordinary ranges of composition. To cave a very definite conception of the behavior of these components in a slag, we have developed the theory of the cooling of a four-component solution from the liquid state to the solid and the conclusions that we obtained have been made use of in this paper. On account of the importance of the four oxides and 18 compounds which enter into the silica-alumina-lime-magnesia system, some method of calculating the percentages of the various compounds that are present in the slag when the percentages of the oxides are given, seemed very desirable and we develop L method later herein for doing this, and finally we give illustrations of the composition of a wide series of blast furnace slags and show some applications of these composition data.

Jan 1, 1927

By Henry D. Hibbard

A NOTED ordnance engineer once said to a friend, in speaking of the production of great steel guns, "How is it? We design our guns with a factor of safety of eight, and the guns burst." The vague way in which internal stresses and strains in iron and steel are often considered and spoken of makes it worth-while to examine them, as to their nature, their causes and results, how they may, for useful purposes, be advantageously dealt with, and how, when detrimental or dangerous, they may be reduced or kept within harmless proportions. Rankine defines ?strain " as a change of form or dimensions of a solid or liquid mass produced by a stress. This definition seems not intended to cover strains due to internal stresses, and it will help us in the present inquiry to consider strain as a tendency to change as well as an actual change of form. Internal strains in iron and steel are the result of stresses within the mass of the piece, some parts pulling and others pushing in resistance to them; or, in other words, some parts are in tension and some in compression, each part striving to relieve itself from strain and make the piece assume a form in which all parts are at rest. Subdivision, so that each part could relieve its strain by motion relative to the other parts, would, if carried out far enough, practically obliterate strain. The internal strains we are now to consider are not those due to the stresses of the service which the piece is rendering, either alone or as, a part of a structure, which may be termed service-strains, but those which originate or at least are contained in the piece itself. Internal stresses in a piece of metal are, like action and reaction, always equal and in opposite directions. The stresses

Sep 1, 1906

By Forbes Rickard

Gilpin County, the cradle of mining in Colorado and the Cornwall of North America, is too well known to need much introduction; get, for the benefit of those not familiar with the district, it may be well to premise that it comprises a tract of country of about 122 square miles, lying between the counties of Jefferson, Boulder and Clear Creek, and hounded on the west by the main range of the Colorado Rockies. It is located centrally in the State, 40 miles west from the city of Denver. During the 38 years since the first gold-discovery, Gilpin county has contributed about eighty million dollars in gold and silver to the world's supply of these metals. Many mining districts have had their rise and decline in half this time; but, very far from being exhausted, this mining district is still in the ascendant; its output is increasing (it was $3,600,000 for the year just closed), and it was never more prosperous nor productive than to-day. Taken generally, there does not exist anywhere in the world so great a number of permanent veins within so small an area as in this district. Gilpin is practically a " poor man's camp." Its veins, with few exceptions, outcrop at the surface. In the oarlier---days of the camp these outcrops were worked in many instances by sluice-mining; particularly is this the case with regard to the veins of the Russell gulch. Discoveries are still made in the heart of this district, and the productive area is every year extending its limits. The districts of Yankee Hill, Hawkeye and Pine Creek, which used to be isolated, are now part and portion of the one gold-field of Gilpin county. Within the last year sensationally rich gold-discoveries have

Jan 1, 1899