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By Robert V. Pierce

In the last few years, much study has been devoted to increasing stoping efficiency. The reasons for this are shortage of manpower, shorter working hours, operating regulations, and shortages of essential materials. More efficiency in mining methods is needed to offset these adverse factors. In the past, attention has been centered upon haulage, hoisting equipment, mill flowsheets, etc., but recently the spotlight has been focused on the cost of stoping and the cost of handling materia,ls. Scrapers and scraper hoists have thus assumed greater importance. In order to make it possible for certain ore bodies to be mined at a profit, it has been necessary to apply assembly-line practices to the streamlining of mining methods. All cycles of the mining operation must balance, and the sooner broken ore is removed from the working face, the sooner another round can be started. Since the introduction of scraper hoists in metal mines more than thirty years ago, much progress has been made in their design and application. Alert operators are now constantly watching for methods in which to apply scrapers. The saving of: manpower in development work and the changing of mining methods that once employed manual handling of materials are increasing vital wartime tonnages. Essential ores from newly discovered ore bodies are moving rapidly from stopes to reduction plants—because it is now possible to develop an ore body and place it in production with a minimum of manpower and development work. Today, speed is one of the prime essentials of mining. Everywhere, there is a concentrated effort to use experienced miners in breaking rock, in timbering, and in carrying out the various phases of mining that require many months of training. Much effort is being made to mechanize the working places because experienced men naturally prefer to work where the majority of materials are handled mechanically. In line with this policy, many new men are being taught the details of scraper work, because even green men can quickly become acquainted with scrapers and thereby release older heads to perform the more skilled phases of mining. In some places it has been found economical to change from .one system of stoping to another that more readily allows the application of mechanical muck-handling equipment. Where blocks are worked faster, the cost of materials, time, and labor is cut drastically. This favorable situation allows more manpower to remain on straight breaking and timbering—or straight production mining. Moreover, when blocks are mined faster, more floors can often be mined vertically before the mucking or wheel floor is moved. This results in several direct savings. There are cases where it has been proved that by working a given block faster more area, longitudinally or vertically, could be mined at one time, thus permitting the reduction of development cost. (Fig. I.)

Jan 1, 1943

By Robert V. Pierce

In the last few years, much study has been devoted to increasing stoping efficiency. The reasons for this are shortage of manpower, shorter working hours, operating regulations, and shortages of essential materials. More efficiency in mining methods is needed to offset these adverse factors. In the past, attention has been centered upon haulage, hoisting equipment, mill flowsheets, etc., but recently the spotlight has been focused on the cost of stoping and the cost of handling materia,ls. Scrapers and scraper hoists have thus assumed greater importance. In order to make it possible for certain ore bodies to be mined at a profit, it has been necessary to apply assembly-line practices to the streamlining of mining methods. All cycles of the mining operation must balance, and the sooner broken ore is removed from the working face, the sooner another round can be started. Since the introduction of scraper hoists in metal mines more than thirty years ago, much progress has been made in their design and application. Alert operators are now constantly watching for methods in which to apply scrapers. The saving of: manpower in development work and the changing of mining methods that once employed manual handling of materials are increasing vital wartime tonnages. Essential ores from newly discovered ore bodies are moving rapidly from stopes to reduction plants—because it is now possible to develop an ore body and place it in production with a minimum of manpower and development work. Today, speed is one of the prime essentials of mining. Everywhere, there is a concentrated effort to use experienced miners in breaking rock, in timbering, and in carrying out the various phases of mining that require many months of training. Much effort is being made to mechanize the working places because experienced men naturally prefer to work where the majority of materials are handled mechanically. In line with this policy, many new men are being taught the details of scraper work, because even green men can quickly become acquainted with scrapers and thereby release older heads to perform the more skilled phases of mining. In some places it has been found economical to change from .one system of stoping to another that more readily allows the application of mechanical muck-handling equipment. Where blocks are worked faster, the cost of materials, time, and labor is cut drastically. This favorable situation allows more manpower to remain on straight breaking and timbering—or straight production mining. Moreover, when blocks are mined faster, more floors can often be mined vertically before the mucking or wheel floor is moved. This results in several direct savings. There are cases where it has been proved that by working a given block faster more area, longitudinally or vertically, could be mined at one time, thus permitting the reduction of development cost. (Fig. I.)

Jan 1, 1943

By Arthur F. Taggart

The following notes represent significant excerpts from a mass of records of experimental work done in the ore-dressing laborattory at the Columbia School of Mines during the years 1926 to 1928 inclusive. Classification of Experimental Work The experiments performed may be grouped for purposes of description under the following general headings: I. Collecting agents. a. A method for quantifying collecting effect. b. Coating with undissolved collecting agents (oils). c. Action of dissolved collecting agents. II. Frothing agent's. a. A method for quantifying frothing effect. b. Relation between frothing effect and chemical composition. III. Inorganic reagents. a. Methods of studying the effects of these reagents. b. Effect on slime dispersion. c. Effect on sulfides. Summary of the Origins of Present-day Flotation Practice The first practicable, foolproof method of froth flotation was described in U. S. Patent 835120, issued in 1906 to Sulman, Picard and Ballot, and in the equivalent patents in other countries. A number of less simple methods of producing the same result had been described previously in patent publications and otherwise.' The reagents specified in all of these early patents were "oils" and, in addition, some inorganic substance, usually an acid. The quantities of reagents recommended and added were enormous when compared with those used today.

Jan 1, 1930

By Ellis Clark

THE mining town of Pribram is situated in Central Bohemia, on the western slope of the Heiliger Berg, 30 miles southwest from Prague. Birkenberg, the village in which most of the shafts and ore-dressing establishments are situated, is built on a mountain of the same name. It is about a mile from Pribram, is 1700 feet above the sea, and is surrounded by graywacke rocks of Silurian origin, which are intersected by greenstone dikes, and in the southerly, southeasterly, and southwesterly direction are bounded by granite. The graywacke formations consist on one side of graywacke sandstone and quartzite, and on the other of graywacke slates. These last are separated from the first in the immediate vicinity of the mines by a graywacke seam converted into clay. For many years this so-cal led clay seam (lettenkkluft) was considered as a boundary of the ore deposits in both zones of graywacke. The graywacke formation is divided according to its hardness, structure, texture, and color, into fine, coarse, compact, slaty, whitish-gray, reddish-gray, and black graywacke. The, miner divides the formation into four divisions. The first or lowest division, which is in contact with the granite, consists of a fine-grained dirty gray slate; the -second is a very fine to a very coarse schist, white to reddish-gray in color, and rich in quartz, but containing little mica; the third consists of a slate with a contused cleavage, which has a dirty gray, dark gray, and very often black color and is often graphitic in its composition ; the fourth consists of a fine to coarse-grained graywacke schist, of a grayish-white or reddish-gray color, and rich in quartz. The cleavage in all four divisions strikes from northeast to southwest, and the dip is sometimes northwesterly, sometimes southerly, and often vertical. All four zones are cut through by a great number of diorite and greenstone dikes and chimneys. The thickness of these dikes, which are of

Jan 1, 1881

By M. E. Tyrrell, Alan H. Goode

The application of a simple, two-dimensional computer technique for evaluating rock burst potential in cut-and-fill stopes was investigated. The principal purpose of the study was to compare the effectiveness of high-modulus fill and destressing as aids in the control of rock bursts. Two conclusions that are probably of general applicability are drawn. First, high-modulus fill is ineffective as a means of increasing the mine stiffness and acts to control rock bursts only if it supports enough load to reduce substantially the stresses on the unmined vein material. Second, destressing is most effective if it is performed when the vein material is near the point of failure.

Jan 1, 1975

By John V. Beall

There was optimism on 14th Street on April 22, Earth Day. We only have the report second hand because the demonstration conflicted with another appointment. Fifth Avenue was closed to vehicular traffic from 14th Street to the Park for a few hours and the crowd that showed up to promenade rivaled anything that can be imagined, even one at a country fair in Merry Old England. Certainly the domestic animals were there and the costumes were wild-as they are almost any day on 5th Avenue. However, the mood was friendly, happy and optimistic according to one of our neighbors who filmed and taped interviews with some of the characters. People think the air is going to be clean, and the water pure in the future. Land is going to be treated with respect. Even if the demonstration temporarily fouled the streets with litter, it served the purpose of dramatizing awareness. In talking to our friend about his experiences we didn't miss the opportunity to sound out his impression of whether or not people recognize that no group of people nor industry has a monopoly on pollution.

Jan 1, 1970

By O. C. Wheeler

The activity in exploration and in the acquisition of prospective oil lands that reached such a high level in Colombia during 1936 gained momentum and reached unprecedented proportions during 1937. Both national and private lands were taken up. In the Magdalena Valley above Puerto Berrio, leases on large tracts of private lands are held by Richmond (Standard of California), Shell and Texas. Tropical also owns leases covering a block of acreage in this area near Honda. From Puerto Berrio to El Banco most of the acreage is of national ownership, and concessions covering parts of this area have been granted to Tropical, Socony Vacuum, Shell and others, while applications for additional concessions are pending. Latterly leases on private lands below the Lebrija River have been taken out by Shell and Richmond. In the drainage basins of the Meta and Guaviare Rivers of the Llanos region of eastern Colombia, several of the major companies have carried on geological exploration and it is understood that some private properties have been leased or optioned. Under Colombian law, subsoil rights are reserved to the nation on all lands that passed from Government ownership after Oct. 28, 1873. Private titles antedating that day carry both surface and subsurface rights. Conditions under which lands may be acquired, explored and

Jan 1, 1938

By Philip D. Shelton

INTRODUCTION Traditional design of support for permanent underground mine excavations place great emphasis on the magnitude of the maximum radial load which a specific support or lining must sustain. However, this depends upon so many factors that reliable prediction in advance of excavation is very difficult except in strong-self supporting ground. Some of the factors affecting the loads acting on a support are illustrated in Table 1. [ ]

Jan 1, 1984

By T. H. Aldrich

(San Francisco Meeting, October, 1911.) THERE are two conditions generally prevailing upon the earth-those within atmospheric influence, tending towards oxidation, and those away from atmospheric influence, tending towards reduction. Practically all mineral substances from mines of any depth are in a reducing condition. Since the cyanide process, in order to dissolve silver or gold, requires that the prevailing conditions under which it operates shall be oxidizing, and the materials usually acted upon being of a reducing character, it becomes necessary to supply oxygen to the solution carrying the cyanide. This oxygen is usually supplied through the medium of dissolved air in the solution, or through the medium of various chemical compounds, which upon combining with the solution or the ore give off a part of their oxygen. Strange as it may seem, practically all mineral substances are partly soluble in water, especially water carrying alkali or cyanide. The greater the surface exposed and the finer the material is ground, the greater will be the rate of dissolving of the reducing agents from the ore into the cyanide solution. In most cases, if the solution carrying the ore particles is agitated with air, the air will dissolve into the solution faster than will the reducing-agents; but in some cases the reducing-agents will dissolve more rapidly on account of easy solubility or greater surface exposed. It is a dissolving race between the oxygen from the air and the reducing-agents from the ore, and if the reducing-agents predominate, cyanide will not dissolve the gold from the ore. In many cases it will dissolve some of the gold, because in a mass of irregular shape some of the gold particles might be exposed upon the outside surface of a particle of rock;' but if the solution had to penetrate through cracks, the side-walls of which were lined with reducing-agent-

Feb 1, 1912

Nationalization of the coal mining industry in Great Britain was one of the first pieces of major legislation enacted by the post-war Labor Government in 1964. It followed a long period of economic depression with high unemployment and bad industrial relations in the coal mining industry during the 1930's, and shortages of coal during the last war. Upon nationalization, the National Coal Board took over control of the industry in 1947 and so became the biggest single employer of labor in the western world. As well as the coal mines themselves, it assumed responsibility for a great variety of other assets including coke ovens, byproduct plants, land, houses, railways and shipping wharves.

Jan 6, 1964

By RUSSELL C. FLEMING

THE important advances that have been made of recent years in mining and milling methods and in mechanical equipment at mines need no re- telling, but there has been a remarkable growth in one type of equipment which has gone nearly unnoticed. That is the increasing use of storage-battery locomotives underground. Since the war the number of these locomotives and their field of use have increased tremendously; their growing acceptance represents an al- most complete reversal of opinion from an earlier period when they were generally looked upon as in- adequate for the strain of mine service. At the time when storage-battery powered units were first making their bid for recognition, the use of power in haulage had already passed through several phases; hand tramming, rope haulage, compressed air locomotives, even gasoline locomotives, had all been used, ending finally in the general adoption of the electric trolley locomotive for practically all power-haulage requirements. It was, and is, conceded that the trolley loco- motive met more adequately the varied and severe conditions of mine service than any previous type of haul- age unit. Subsequent developments have had to endure comparison and surpass in performance that type of haulage before changes would be considered.

Jan 1, 1930

The total estimated production of coal in the United States during the first century and a quarter of mining is shown in Table 20. This is the total of the production of the various states already shown in the various tables, and is believed to be the first statement of this sort made. No such table prepared from limited data can be accurate, but it is the writer's opinion that the totals shown are less than those actually produced. It was thought that this study would enable a reasonably accurate account of the movement of coal down the Ohio and Mississippi Rivers to be written. The searches made have shown that at this time the data do not exist from which such a study can be made, but some of the facts collected may be useful to future students.

Jan 1, 1942

By R. S. Archer

SILICON is one of the most important elements in the metallurgy of aluminum. It is always present in small amounts in the ordinary grades of "pure" aluminum, and hence in all alloys made therefrom. Within the last few years binary alloys containing up to 13. per cent, of silicon have come into extensive use for castings. Silicon is also added, beyond the amount present as an impurity, in alloys containing one or more other elements such as copper, manganese, magnesium and nickel. The binary aluminum-silicon alloys are not yet heat treated to any extent in commercial practice, although, as will be shown, their properties are affected to a very considerable degree by heat treatment. There are other aluminum alloys that develop higher strength, but the special characteristics of the silicon alloys may well lead to the application of heat-treating processes on a commercial scale. The role of silicon in the heat treatment of aluminum alloys is more important than would be indicated by consideration of the binary alloys alone, because many of the alloys that are heat treated in regular commercial practice contain some silicon in addition to that derived from the aluminum ingot as an impurity. Among these may be mentioned the heat-treated 195 alloy castings, and the wrought alloys 258, Special 178 and 51S of the Aluminum Co. of America, and the German wrought alloy, Lautal. It is the purpose of this paper to present the results of experimental work and the conclusions derived therefrom regarding the heat treatment of the binary aluminum-silicon alloys. The products heat treated included forgings, chill castings and both "normal" and "modified" sand castings.

Jan 1, 1927

By Frederic Carter

THERE have been many attempts to prove that platinum was known to the ancients, but since no traces of the metal have been found in the relics of early times, it must be concluded that it had not been known to them. As far as records go, it was actually first discovered in the 16th century in a Spanish mine on the Pinto River in South America; from which source it received its name of Platina del Pinto (little silver from the Pinto). It was more or less of a rarity and was a subject of interest to a few chemists only, until the year 1822 when the metal was first discovered in Russia. In 1819 there had been noticed in the washings of the gold sands of the southern part of the Ural Mountains, grains of a heavy white substance, but it was not until three years later that this substance was found to contain platinum. While at first the amounts of platinum brought from the Urals had been meager, prospecting soon disclosed rich deposits extending over a considerable area, and nuggets from 10 to 20. lb. were by no means rare. This discovery assured to chemists an ample supply of platinum for their crucibles, etc. The ore is now found in various parts of the world but the richest deposits are still found in the Ural Mountains. The platinum of commerce is obtained entirely from alluvial deposits at depths varying from 6 to 40 ft. The sand and gravel of former river beds are subjected to a series of screenings and washings to effect the separation of the ore. Actually, probably all gold-bearing gravel beds of the world contain platinum, and it is more than likely that large quantities of platinum ore have been thrown away with the black sand washings from gold placer deposits. This is especially true of the alluvial deposits of the Pacific Coast in California and Oregon. Platinum ore is usually found in the form of rounded or, flattened grains of "sand," and occasionally in irregular lumps of the size of peas. Large nuggets are very rare. The ore has a metallic luster and is distinguished by its steel gray color, but shows light gray streak when rubbed on a hard white surface; it has a high specific gravity, 16 to 19; is infusible in the hottest blast furnaces, and insoluble in any single acid. Platinum ore is a complex body consisting of the metal in combination with varying proportions of the other members of the platinum group; iridium,

Jan 1, 1928

By E. W. Parker

THE anthracite region, from which there is produced annually about 80,000,000 tons, or approximately 15 per cent. of the total coal supply of the United States, has a combined area of a little less than 500 sq. mi. The total area occupied by the bituminous fields (including the sub-bituminous and lignite fields) is in the neighborhood of 400,000 sq. mi., so that 15 per cent. of the total output comes from this small area of only a little more than 0.1 per cent. of the coal-producing territory. of the United States. The productive anthracite area is divided into a series of basins or troughs, roughly parallel, extending. in a northeast-southwest direction through the. Counties

Jan 1, 1921

By C. K. McArthur

THE subject of classification is so broad that this discussion is confined to what the author believes is of prime importance in connection with proper grinding and classification. The years passed have witnessed many noteworthy changes in fine grinding and classification, which have been accompanied by a readjustment of ore-dressing flowsheets for the preparation of better ground and/or sized products at an expenditure of less power, steel and maintenance than formerly. Nowhere in the industry is more being done in the way of experimental work to lower costs than in grinding circuits, because, at best, grinding costs are high. Recent years have indicated that, on the average, finer grinding has a real application. Without careful preparation of the process feed, no operation can be highly efficient or successful. In an earlier paper, the findings of an extensive survey at representative concentrators were presented1. Also, in the year of 1935, a technical discussion was given by Dr. J. V. N. Dorr (Some Notes on Classification Trends in America) before the Chemical, Metallurgical and Mining Society of South Africa In both papers mentioned, much has been said regarding flowsheets, grinding and classification. The author is very familiar with these papers, having had considerable to do with the actual operation of the flowsheets, as well as large mills and classifiers in the work described. Some data from the second paper have been included in the following discussion. Circulating Load In this particular paper it seems advisable to deal with the classification phases of the work that to a major extent govern the success of any closed-circuit grinding unit. The question has often been asked in connection with a closed circuit: "What circulating-load ratio should be carried?" This is really an

Jan 1, 1937

By Hoyt Gale

RECENT work on borate deposits near Kramer, in the extreme southeast corner of Kern County, California, is of special interest to those who are making a study of the mode of origin of the borate minerals colemanite and ulexite. A valuable clue to the mode of origin of colemanite in its present known deposits is given in a paper by W. F. Foshag1, of the United States National Museum. Colemanite is found in or near original deposits of ulexite, from which it is supposed to have been derived by a change in the rate of movement or the character of the ground water. Indications that an alteration of this sort had produced colemanite were first recognized by the writer' in specimens collected in the Kramer district in 1920, and sent to W. T. Schaller, at U. S. Geological Survey, for identification. The identity of the two borate minerals in these specimens was not at once determined, but the relations of the minerals as seen in the specimens afforded a manifest clue to the origin of the deposits. Similar specimens were obtained by the writer from deposits in death Valley soon after he had examined the deposits near Kramer. After studying the specimens submitted to him Dr. Schaller wrote as follows: "I have finally positively identified the boron minerals you sent me with your letter of Sept. 27. The `white fibrous mineral like ulexite' is ulexite; the harder nodules' in the clay are colemanite, apparently formed from the ulexite as a result of leaching, with recrystallization in place-a theory that Foshag is working on." The present paper is a report on the facts observed at. the deposits near Kramer, and some general observations on the geological relations noted, which, unfortunately, still form only a very incomplete record.

Jan 2, 1926

By R. E. Head

Under existing economic conditions, the treatment of gold ores occupies an outstanding position in metallurgical activity. The increased price of gold has automatically brought about a reclassification of old dumps and low-grade orebodies, and many that formerly were considered valueless are now being vigorously investigated and worked. This situation has developed problems that have taxed the ingenuity and ability of metallurgists to the utmost. Some gold ores give a high extraction of gold by standardized methods of treatment; other ores of apparently similar character yield but a relatively small percentage of their gold when treated by the same processes. Surface Contamination The experience gained by microscopic study of numerous gold ores and tailings has shown that there are pronounced differences in the physical characteristics of the minerals composing them, more especially of the gold. Repeated studies of tailings from flotation and cyanidation of gold ores has established the fact that surface contaminations on gold particles are often directly responsible for high gold losses; comparison of gold particles isolated from flotation concentrates and the resulting tailings have showed that the clean gold has been recovered and the tarnished or contaminated gold invariably lost in the tailing. Obviously, it is not possible to make such a comparison of gold ores treated by cyanidation, as the clean gold has been taken into solution; but when the gold found in cyanide tailing has a tarnished or coated surface, one may infer, with a reasonable degree of certainty, that the clean gold has been extracted. This premise is supported by experimental evidence obtained by isolating particles of tarnished gold and exposing them to cyanide solution in small parting cups. In one such experiment, tarnished gold particles picked from a cyanide tailing showed but slight evidence 01 dissolving at the end of 27 days. In this test, a cyanide solution of 1.6 11). per ton was used and the leach solution was decanted arid renewed every

Jan 1, 1939

By R. E. Head

Under existing economic conditions, the treatment of gold ores occupies an outstanding position in metallurgical activity. The increased price of gold has automatically brought about a reclassification of old dumps and low-grade orebodies, and many that formerly were considered valueless are now being vigorously investigated and worked. This situation has developed problems that have taxed the ingenuity and ability of metallurgists to the utmost. Some gold ores give a high extraction of gold by standardized methods of treatment; other ores of apparently similar character yield but a relatively small percentage of their gold when treated by the same processes. Surface Contamination The experience gained by microscopic study of numerous gold ores and tailings has shown that there are pronounced differences in the physical characteristics of the minerals composing them, more especially of the gold. Repeated studies of tailings from flotation and cyanidation of gold ores has established the fact that surface contaminations on gold particles are often directly responsible for high gold losses; comparison of gold particles isolated from flotation concentrates and the resulting tailings have showed that the clean gold has been recovered and the tarnished or contaminated gold invariably lost in the tailing. Obviously, it is not possible to make such a comparison of gold ores treated by cyanidation, as the clean gold has been taken into solution; but when the gold found in cyanide tailing has a tarnished or coated surface, one may infer, with a reasonable degree of certainty, that the clean gold has been extracted. This premise is supported by experimental evidence obtained by isolating particles of tarnished gold and exposing them to cyanide solution in small parting cups. In one such experiment, tarnished gold particles picked from a cyanide tailing showed but slight evidence 01 dissolving at the end of 27 days. In this test, a cyanide solution of 1.6 11). per ton was used and the leach solution was decanted arid renewed every

Jan 1, 1939

By W. W. Wirth

RESEARCH looking toward the reduction of the cost of roof support by substitution of longer-life materials for wooden timber is fully justified by the fact that roof support is an important element of all production costs. Permanent or semipermanent roof support will reduce the expense of timber-maintenance crews during steady operations, but even more markedly during idle periods. The management, therefore, is faced with the important problem of timber renewals, which in times of regular operation are frequently obscured by more urgent problems of production. Increased use of timber in the Anthracite Region of Pennsylvania is caused mainly by increased percentage of coal obtained from robbing areas, which requires more timber for safety than develop-ment work, and maintenance of long haulageways through crushed ground despite the fact that less coal is transported over them. The timber reserve in the immediate vicinity of the mines has been depleted to such an extent that it is necessary to secure 70 per cent of the timber requirements from distant sources. Originally, mine timbering in this region was done by largely utilizing round props or legs with round collars. The whole cross section of the tree from which timber was cut was utilized by forming the joints between the legs and the collars with saw and adze, using plank or round saplings for lagging behind the legs and over the collars to prevent material falling between them. The Mine Inspectors' report of 1898 records an important digression from the use of round timber, when two tunnels at the Babylon colliery, near Pittston, Pa., were timbered with 12 by 12-in. square timber sets with mud sills, through quicksand for distances of 425 and 160 ft., respectively. The timbers were lagged with 3-in. plank to control sand.

Jan 1, 1940