Search Documents

By Frederic Dewey

IT IS common to blame irregular assay results upon volatilization and much has been written upon the subject, but there is no. real evidence that, in a properly conducted assay, the loss of either gold or silver by volatilization is sufficient to affect appreciably the result, even when, arsenic or antimony may be present. Bulk assays of flue dust from assay muffles have been published, but the data given are totally insufficient to even approximate the volatilization from a single assay; and such figures as we have indicate the volatilization to be extremely small. Diligent search in the literature and wide inquiry among assayers and instructors have failed to produce a single case where the litharge volatilized in making an assay has been collected and assayed for gold and silver. Having attempted to do this, with most indifferent success, I am not surprised that this has not been done. While various textbooks give volatilization as a cause of loss in cupellation, it may safely be said that in the rare cases where this volatilization is sufficient to affect appreciably the result it is due to excessive temperature. Percy1 says "The loss of silver by volatilization during cupellation is very slight (unless the temperature has been much too high), and may be disregarded." This statement is repeated by the Beringers2 and Smith,3 who includes gold with silver. Mitchell4 says the litharge fume rarely contains over one ten-thousandth of silver. Campredon5 says that at a proper temperature no silver is lost by volatilization.

Jan 2, 1920

By Stephen Taber

Introduction.............................. 62 Asbestiform Minerals.......................... 63 Chemical and Mineralogical Relations............... 63 Physical Properties........................ 64 Types of Asbestos............................ 65 Origin of the Fibrous Structure...................... 66 Views of Previous Investigators.................... 66 Discussion of the Evidence.................... 67 Conclusions........................... 69 Origin of Cross-fiber Veins....................... 71 Chrysotile Veins......................... 72 Structural Features of Cross-fiber Veins............... 78 Veins of Crocidolite and Other Fibrous Amphiboles........... 83 Origin of Slip-fiber........................... 84 Origin of Mass-fiber........................... 86 Discussion............................... 87 IntRoduCtion The term asbestos, as commonly used, includes half a dozen minerals all having a well-developed fibrous structure, but differing in chemical composition and in some of their physical properties. In its strict application the name is limited to the fibrous varieties of the monoclinic amphiboles. Commercially, however, the most important of the asbestiform minerals is chrysotile, a fibrous variety of serpentine. About 95 per cent. of the asbestos used in manufacturing is chrysotile, and it commands a much higher price than any of the other fibrous minerals now on the market. Although the production of asbestos has increased rapidly in recent years, comparatively little has been published concerning its origin. The present paper is preliminary in its nature, and therefore does not pretend to exhaust the subject. The ideas herein developed are the result of field investigation, laboratory experiments in the growth of fibrous

Jan 1, 1918

By AIME AIME

THE Chairman of the Iron and Steel Division for 1945 is one of the most versatile and best-known men in this industry, with wide experience in research and operations and in handling both the men and the materials that are used in enormous quantities. Erle G. (Doe) Hill was born in Santa Ana, (alit, April 21, 1890 and graduated (Bachelor of Science) in mining and metallurgy from the University of California in 1913. For the next five years lie held a variety of jobs as miner, foreman, and null superintendent in gold, silver, copper, and quicksilver mines in the West and in Mexico. As Doe was an individual endowed with an exceptional amount of horse sense, he left the West in 1918, to become instructor of mining engineering and ore dressing at Carnegie Institute of Technology, and while in that post did considerable consulting work as a geologist and mining engineer. In 1920, still possessing the same common sense. he got out of mining engineering and geology and became associate professor of metallurgy at the University of Pittsburgh, a position he retained for nearly ten years.

Jan 1, 1945

By Henry D. Hibbard

FoR the purpose of this paper all steels will be divided into two divisions: effervescing and non-effervescing. This classification must be borne in mind as many statements true of one class are not true of the other. Effervescing steels are those that effervesce in the molds, evolving large volumes of gases, which, in escaping, throw up a spray of molten particles of steel and give the molten metal in the mold a rapid stirring or churning motion until it freezes, or, at least, becomes pasty. This effervescing is intended and proper. The non-effervescing steels, which are more or less completely killed, should not evolve any gas in the molds. Many years ago the writer proposed to call the two classes of steels evolution and solution steels, depending on whether the gases in the molds are evolved or kept in solution, but the present designations seem to be better. In America, at least, effervescing steels are in a class by themselves and include steels made for boiler, tank, and ship plates, steel pipe, soft steel wire, wire nails, soft machincry, and structural steels. These are all low-carbon steels with less than 0.40 per cent. carbon. Low-carbon steels that do not effervesce but are killed are also made; these are put into ingots and castings but they are outside the limits of this paper. Effervescing steel is cast into square or slab molds, either top or bottom poured. Most of the effervescing steel is made in the basic open-hearth furnace, though much is made by the acid Bessemer process and a little is made in the acid open-hearth. It is not made by the crucible or electric-furnace process, in which the volume of gas required cannot be produced in the steel and evolved from it in the mold to give the effervescence desired. Any steel ingot, when teeming is finished, is of a certain size or volume. Leaving out of consideration for the moment the lessening of the over-all dimensions of the ingot through contraction due to loss of heat, the ingot may be placed in one of three classes: It may settle, losing in volume; it may stand, that is, remain constant in volume; it may rise, that is, increase in volume. Into which class an ingot will fall depends on the gases of the steel,

Jan 1, 1920

By E. M. Wise, T. E. Kihlgren, N. B. Pilling

SYSTEMATIC data are presented on the relation of composition of nickel silvers to color, tarnish resistance, hardness and liquidus temperatures, for alloys containing up to 30 per cent nickel and 50 per cent zinc, further modified at certain nickel and zinc contents by 0 to 8 per cent of tin and 0 to 10 per cent of lead. Attention has also been directed, using a still more limited range of alloys, toward a study of tensile properties and such casting properties and characteristics as fluidity, shrinkage and pressure tightness. In some of these, rather broad ranges of composition are dealt with; in others, it has been expedient to focus attention on the Federal Specification 20 per cent nickel silver casting alloy, WWP-541.

Jan 1, 1935

By Richard H. Rein, John Chipman

Liquid slags of the system SiO2-Ca0-MgO-A1~03 were equilibrated with liquid Fe-Si-C alloys in graphite or Sic crucibles at 1600°C in pure CO gas at atmospheric pressure, and the silicon content of both phases determined. Ternary slugs of the systern SiO2-CaO-A12O3 were also studied at 1550°C. The silicon content of the metal phase saturated with both graphite and SIC is 22.0pct at 1550°C and In the iron blast furnace, as in nearly all carbon-reduction processes, some silicon is transferred from slag to metal. The importance of this reaction is enhanced by its indirect effect on the transfer of sulfur from metal to slag, and this has stimulated a comprehensive research program on the equilibrium distribution of silicon between slag and metal. Earlier studies'-3 of this same problem provided data for calculation of the thermodynamic activities4 of the components in SiO,-CaO-A1,O3 slags. 22.4 pct at 1600°C. The temperature at which the phases cristobalite, gvaphite, $ SiC, liquid slag, Fe-Si-C alloy, and CO gas at 1 atm pressure can coexist in equilibrium was found to be 1533°C. The results agree well with earlier studies. They are shown graphically as lines of constant silicon cmtent in the metal which also are lines of constant SiO, activity in the slag.

Jan 1, 1963

By W. Hurst

What is entailed here is the extension of the sinzplified material balance formulas to encompass interference between oil fields. As previously reported, the ex-plicitness as so revealed for the cunzulative pressure drop as a function of all factors contributing to its change in the material balance equation, is now transcribed through the inter-conzmunicating aquifer to effect an increased pressure drop on an adjoining field by interference. Such is performed by mathematical analyses and the application of the Laplace transformations. What is accomplished is that the reiteration problems previously associated with interference studies are nullified, since volumetric changes for the fluids in situ are automatically adjusted by the explicitness so expressed, and what pertains to the superposition principle applies only to the impeded water drive upon a su.bject field, which is likewise incorporated in the over-all pressure drop that results. The mathematics treats with the rigorous solution of the problem, as well as with methods easily amenable to numerical interpretation by the practicing engineer. In all cases, however, what is deduced for areal extents, reveal interference between wells when time becomes large that further substantiate the analyses. Probably of equal significance, all variables and for/nation characteristics are accounted for. This applies to the differences in PVT analyses that occur from field to field and the physical parameters associated with the lithology of the reservoirs. The latter is deduced from a rigorous interpretation of the unsteady-state flow problem for sands of different permeabilities in series. Thus, what purports to be a trial-and-error calculation to include variations in sand conditions within the intercommunicating aquifer to define water drive has little importance compared to the designation of such paranzeters at the reservoir to constitute the essential criteria. INTRODUCTION In a recent publication, the reader has been introduced to the simplified material balance formulas,' It has been shown that the complexities formerly associated for identifying and determining reservoir pressure in the material balance relationship can be resolved by treating with the Laplace transformations, the inversion of which reveals pressure as an explicit function of all factors contributing to its change. For an under saturated oil reservoir, this constitutes an integrated effect from the inception of production; and for a saturated oil reservoir, such represents a survey traverse. However, what is most important, for the first time we are able to express the pressure change in a reservoir directly to the oil, gas and water produced, and to the physical parameters of the formation, in the same manner that reservoir pressure has served in the past to define well interference — which opens up this avenue of endeavor for investigating interference between oil fields. The occurrence of interference is by virtue of the juxtaposition of two or more oil reservoirs producing in the same aquifer. Thus, in any one field, the extended production so incurred creates a pressure lowering in the field, as well as in the aquifer, which can now be transcribed by these simplified material balance formulas to the adjoining reservoir to observe the increased pressure change so induced. These effects are retroactive from field to field, to reveal a pressure drop far in excess of normal depletion to evidence the interference pattern that can result. Such is the purpose for the present undertaking — to develop the mathematical physics treating with this phenomenon of interference between oil fields, employing the simplified material balance formulas. Since Ref. 1 often will be referred to in the text, it is identified as "The Simplification", in the same connotation that another paper has been referred to as the "Laplace Trans-formation. However, the amount of material to be covered in these passages is substantial; therefore, the total emphasis will be placed upon developing these fundamental ideas treating with interference rather than attempting to offer work curves, which always can be prepared. For the practical application of these simplified material balance formulas that form the framework of the present development, the reader will find a comprehensive treatment in the Appendix of Ref. 1, illustrating a factual field example. In essence, what is proposed by this presentation is to make available to the practicing engineer a simplified means to treat with interference between oil fields, independent of the complex machine computations that have attended such undertakings in the past. As the problem unfolds, a common pattern will be discernible, whereby the many reiteration processes that previously required computing devices are eliminated.

By M. C. Leverett

THE dynamic behavior of a multiple fluid system is completely describable in terms of driving forces and resistances to flow. The latter are proportional to the vis-cosity of the fluid under consideration and inversely proportional to a property of the system termed the " effective permeability" to that fluid, a property therefore defined by this relation. Since three phases are usually present in oil reservoirs, it is essential to know the effective permeabilities to the several fluid phases, and the relationship between the composition of the fluid in the pore space and that of the flowing stream, in order to handle satisfactorily certain problems of oil production. In this regard, there are many unknown factors and parameters, and many that can be evaluated only indi-rectly. However, it is expected that work along lines similar to this present under-taking will help materially in solving these problems. Previous workers in this field have inves-tigated the two-phase systems, water-gas,1 water-oil2 in unconsolidated sands, and water-gas3 in consolidated sands. The ex-tension of the study of the flow of hetero-geneous fluid systems from two to three phases involved only slight changes in technique. The apparatus used in the present work, except for slight changes to be described, was that used by Leverett in his water-oil experiments.2 Correlation and interpretation of data were made by methods analogous to those used in two-phase work. The relative permeability to a phase-the effective permeability divided by the permeability of the system to a homogeneous fluid-was employed through-out in correlating the rate of flow of that phase with the composition of the pore space. Quantitative measurements of two inde-pendent physical properties of the system were required to determine the composition of the pore space. As in the two-phase work, the fraction of water was determined electrically. The gas fraction was deter-mined by measuring changes in volume accompanying measured pressure changes. Suitable account was taken of the solubility of the gas in the liquid phases, and of the vapor pressure of the water phase. Since this work was exploratory in nature, no attempt was made to obtain highly accu-rate numerical results. Reasonable precision and reproducibility were sought.

Jan 1, 1940

A. Blainey (Ministry of Supply, Atomic Energy Research Establishment. Hnrtoell. England)—With ref- erence to the published work of Hausner et al. on the powder metallurgy of zirconium, it will be of interest to summarize briefly the results of preliminary work we have carried out on this subject at A.E.R.E., Harwell. For the early experiments we used zirconium

Jan 1, 1953

By Adrien Berton

FOR nearly a century, the Corocoro deposit has been renowned among geologists from the fact that it shares with the Lake Superior deposits of the United States the distinction of being the only important copper districts where native copper is worked commercially. The Corocoro district, named after the city of Corocoro, the capital of the Province of Pacajes (Department of La Paz, Bolivia) is situated towards the western edge of the Bolivian high plateau, at an altitude of a little over 13,000 ft. The most interesting part of the district is that immediately surrounding the city of Corocoro, at a distance, by railway, of 65 miles from La Paz and 210 miles to the Chilean port of Arica on the Pacific Coast. The climate of the region is that of the semi-desert, dry and relatively cold, with big differences of temperature between day and night. The rainy season begins in December and ends in March. The cupriferous lodes of Corocoro have not attracted as much interest as the silver mines of Potosi but they have been known for a long time. In the precolonial period the Indians were using the charquis, or natural native copper sheets, to make small brass objects, and the beautiful pale green brochantite of the outcrops as a source of green pigments. During the colonial period, the oxidized ores of the outcrops were worked for copper, which was used by the mint at Potosi for making currency. The native copper ores were neglected because the Spanish miners were at a loss how to concentrate and smelt them. About 1830, work by rudimentary processes, which were improved little by little, was begun on the native copper ores. The total production of native copper in the following hundred years amounted to 100,000 tons. This native copper, which was remarkably pure, was much appreciated on the European markets before the introduction of electrolytic copper. It was useful for making special ornamental brass or bronze and the granular concentrates of native copper, called barrilla, containing 80 to 85 per cent copper were suitable for making copper sulfate by direct oxidation and subsequent leaching with sulfuric acid.

Jan 1, 1936

By George B. Clark

THE " Munroe effect" of shaped explosive charges was discovered by Charles E. Munroe more than 50 years ago (in 1888), but it was not until World War II that it was put to any practical use. Both Allied and Axis armies used the principle effectively in bazooka projectiles, artillery projectiles and in fixed shaped charges. The first two were used primarily to combat tanks and other armor and the latter to assault pillboxes and other fixed concrete emplacements. Many engineers and others who saw the military application of the jet effect of shaped charges believed application would be possible in many industrial fields where blasting is used, such as mining and quarrying. Some work has already been done on the problem of making shaped charges applicable to mining operations. Experimentation conducted at the National Tunnel and Mines' was directed primarily along the lines of use of shaped charges for secondary blasting in connection with long-hole stoping methods. Experimentation initiated earlier and conducted by the author2 at the University of Utah on a more scientific basis was directed at revealing the basic principles of the functioning of shaped charges, as well as the feasibility of using them in mining operations after the principles of their operation had been clearly defined. It was found that: (I) a given design of charge required an optimum standoff to make it most effective, either in penetrating solid rock or steel (see Fig 3); (2) for a given design of charge there exists an optimum ratio of charge diameter to charge height above which the increase in effectiveness of the charge decreases rapidly (see Figs 4 and 5); (3) partial confinement has the effect of making charge performance much more consistent; (4) the higher power and higher velocity explosives tested are much more effective than relatively low-strength explosives; and (5) shaped charges may be adaptable to mining operations in secondary breakage and drilling blasting holes. Fig I is a diagrammatic sketch of the action of a shaped charge for two types of cavities, while Fig 2 shows the approximate manner in which the jets are believed to be formed when an explosive wave encounters the cavity, approaching it from the top. The experimentation already completed has laid the foundation for further research in the study of shaped charges. Standoff effects, effect of the strength of explosives and other features have been fairly well established. Such elements in the design of shaped charges as (I) geometry of cavity liners, (2) relative horizontal dimensions of explosive column, (3) effect of

Jan 1, 1947

By R. L. Wiegel

The generation of operating information for mineral beneficiation processes has become more sophisticated as a result of the use of improved laboratory analytical techniques, some of which provide multiple component assays, as well as the introduction and gradual industrial acceptance of process sensors for the measurement of flow, density, size, and chemical composition. In general, however, the mineral processing engineer's ability to tie together this wealth of information has not kept pace with these developments. In fact, in almost all existing plants, the metallurgical inflow-output balance, wed to indicate current process performance, is still being calculated from only a small portion of the information routinely available. There is substantial activity in the development of techniques for using all available process information to significantly improve the reliability of the metallurgical balance. While the use of these improved techniques does require access to computing facilities and a slight change in perspective on the part of the mineral processing engineer regarding the inviolability of process information, there are numerous practical benefits to be derived from their application. In addition to summarizing some of the concepts basic to these techniques, this paper describes the experience of the author in applying one of these advanced metallurgical balance techniques to a variety of pilot plant and commercial plant flowsheets during the past eight years.

Jan 1, 1983

By M. H. Forester, John D. Cooner

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

Jan 1, 1943

By Gloyd M. Wiles

Since D. C. Jackling was famous for his adeptness at organizing and training teams of operating personnel, the subject of mine management is particularly appropriate for a Jackling Lecture. In fact, it is doubly appropriate because in very basic ways Jackling's career changed the nature of the tasks and challenges facing a mine manager. Management of mines, of course, is the art of finding and winning minerals economically from the earth's crust, and it involves the use of all the engineering sciences. But also of prime importance is a skill which is not yet a science-the area of management often referred to as human engineering. Since expenditures on staff and labor may well involve more than 50% of the direct costs of operating a mine, ability at human engineering is just as important as the ability to plan and put into effect the most efficient operating procedures.

Jan 5, 1962

By M. J. Bradley, P. H. Dike

THE art of melting nonferrous metals, in smelting, casting, and in compounding of alloys, is highly dependent on a knowledge of the temperature of the metal. This knowledge may reside in the experience and judgment of the melter, or it may be based on measurement by suitable instruments. It-is our purpose to discuss briefly the instruments available for such measurements, and more at length the present, practice in molten metals, without recommendation. In the limits of time and space allotted, we can do little more than mention the available methods of measurement that are directly applicable in this field. In the 1939 edition of the Metals Handbook, issued by the American Society for Metals, pages 285-310, there is a more extensive discussion of pyrometry than can be attempted here, which should be referred to for details we must omit. For reasons that will appear, thermoelectric pyrometry will constitute the major portion of our discussion of the subject, only limited attention being given to radiation or optical pyrometry. METHODS OF MEASUREMENT THERMOELECTRIC PYROMETRY A thermocouple consists of two dissimilar wires, or a wire inside a tube of a dissimilar material, joined together at one end, which is placed in the region or medium where the temperature is to be measured, while the other ends are connected through suitable lead wires to a voltage-measuring device, which may be a millivoltmeter or a potentiometer. An electromotive force is generated in the circuit, which is proportional to the difference in temperature between the hot junction and the junctions of the lead wires to the measuring instrument. If this latter temperature is maintained constant, the e.m.f. measured varies only with the temperature of the hot junction. Every thermoelectric pyrometer is calibrated for a particular cold-junction temperature such as 0°F., 32°F. or 75°F., but usually it is more practical to compensate instrumentally over the probable range of cold-junction temperatures than to maintain the junction at the particular temperature for which the instrument was calibrated. Thermocouple Materials Only a very few pairs of metals are in frequent use for pyrometric measurements. The most generally used are iron-constantan for temperatures up to 1500°F. in oxidizing and up to 1800°F. in reducing atmospheres and chromel-alumel, which may be used in oxidizing atmospheres at temperatures up to 2400°F. for intermittent service. The accuracy of the latter deteriorates rapidly at temperatures above 2200°F. Platinum vs. platinum-rhodium thermocouples may be used up to a temperature of 3000°F , but they are easily contaminated by slow absorption of

Jan 1, 1946

By C. W. Clark, J. H. Schloen

Two papers have been written previously concerning operations at the Montreal East plant of Canadian Copper Refiners Limited. The first one,1 written in 1932, described silver-refinery operations at the time for producing silver and gold bullion from tankhouse anode slimes; the second,2 published in 1933, consisted of a description of the entire plant. Since publication of these papers the refinery has become the world's largest producer of refined selenium. The first selenium was produced in August 1934. Tellurium production on a commercial scale followed in October 1935. This paper will deal with selenium and tellurium production and also with present operations in the silver refinery. Blister cakes from Hudson Bay Mining and Smelting Co., Flin Flon, Manitoba, and commercial anodes from Noranda Mines Limited, Noranda, Quebec, are refined at Montreal East. Both these bullions have unusually high gold, selenium and tellurium content. The average assay of raw slimes produced from domestic and Noranda anodes is about 40 per cent Cu, 3600 oz. per ton Ag, 800 oz. per ton Au, 22 per cent Se and 3.7 per cent Te. EARLY SILVER-REFINERY OPERATIONS From the start of operations in 1931 until July 1934, the raw slimes were oxidize-roasted at 700° F. in a Nichols-Herreshoff furnace, acid¬leached with tankhouse discarded foul electrolyte (20 per cent H2SO4), filtered and charged directly to the doré furnace for refining to doré metal. This is the customary method for treating tankhouse anode slimes but was not suitable at the Montreal East plant because of the high selenium and tellurium content of our slimes. In the acid-leaching process about 50 per cent of the selenium and tellurium in the roasted slimes was dissolved in the electrolyte. These elements were recovered with the copper as a sludge in a small electrolytic

Jan 1, 1938

By N. V. Hansell

The preparation of low-grade iron-ores by concentration, whether or not followed by an agglomeration of the concentrate, has in the United States only recently been recognized as a metallurgical process of vast economical importance for its iron indust.ry. This importance of the process lies not only in the fact that it makes possible the use of ores heretofore discarded on account of their low iron-content or their too high percentage of elements deleterious in the iron industry, but also in its produetion of a raw material for the blast-furnace that is more uniform in its physical character and chemically purer, with a higher iron-content, than the general run of natural ores. When mixed in the burden of the furnace, it lowers the amount of coke and fluxing-stone required per ton of pig-iron produced. The furnace-operations become more regular and more easily controlled. The pig-iron is of higher quality and more uniform in character. In brief, it is becoming recognized that the beneficiating of the natural iron-ore, even if it makes the furnace-ore higher in cost per unit of iron entering into the burden, may mean a lowering of the production-cost of the pig-iron and an improved product. At the present time, the Lake Superior district furnishes about 80 per cent. of all the iron-ore yearly produced in the United States. If the Southern States arc exempted the percentage runs as high as 93 per cent. These ores are showing a steady decrease in grade from year to year. For the past 10 or 15 years this falling off in the average grade has been about 0.5 per cent. a year. The lowered grade of ore means an in-

Jan 1, 1913

By Marcus Grossmann

THIS paper offers for consideration certain somewhat radical modifications in the iron-carbon diagram, these modifications being the result of the presence of notable amounts of alloying elements. When only small amounts of alloys are present, 'the standard iron-carbon diagram (Fig. 1) can be used with but insignificant changes; when larger amounts of Chromium, Per Cent FIG. 1.-IRON-CARBON DIAGRAM. FIG. 2.-IRON-CHROMIUM DIAGRAM. alloys are present, however, it assumes a distinctly altered appearance. No comment is offered for the present except to call attention to the delta area, A4BM, which represents a region of mixtures of austenite and delta iron, just as area A3SP represents mixtures of austenite and alpha iron.

Jan 12, 1926

I HAVE previously demonstrated to you as well as I knew how in what way ores are treated and then how the separated metals are brought to their pure and ultimate limit of perfection by means of smelting and other artificial fires; all except gold, which remained incorporated in the silver. Because the method used for the others does not serve for this, and if indeed it did serve it would be a great labor and could not be done without a great loss of the thing, it is therefore necessary to proceed with the practice of another art if you wish finally to extract gold from the bonds of the intrinsic substance of silver, for it exists bound and scattered in this like the soul in the body of living creatures. In this, unlike the other works where you make direct use of the vigor of the fire, you use a substance that is like water, drawn by the force of fire from a very powerful composition of two materials. This is a very marvelous thing to consider as a liquor because of its powerful effects. It is made by artificial distillations and it has an acid property and the power of corroding and reducing into itself silver and any other metal placed in it, with the exception of gold. Nothing is apparent in it except a pure water. It is indeed a very ingenious thing for which we must be greatly indebted to that philosopher, alchemist, or whoever else was its discoverer. The silver that contains gold is put in this water, and from its former quiet state you will see it change as if forced to combat and breathlessly devour and consume that silver in itself and change it into water. This happens in a very short time and with very little help from the heat of the fire. All the gold that was united in the silver you will see like sand at the bottom, and when the water is taken off by decantation it will freely give you all the gold without any loss. Nor is it so ill-mannered as to fail to restore the silver to its place if you wish; and though it seems to have consumed and spoiled it as it was before, it returns it to you without loss. Since the process of this art is a very useful thing for anyone who knows

Jan 1, 1942

By K. Stout, E. Van Eeckhout, L. Friel

Previous research at the Montana College of Mineral Science and Technology indicated that it is practical and economically feasible to place stiff back- fill in a cut-and-fill stope. This backfill would reduce wall closure and high stress buildup in pi1llars, thus alleviating rockburst potential. Three ;topes from the Sunshine Mine, of the Coeur d’Alene Mining District, were chosen for a test verification of this concept. Although the first stope was lever mined beyond the initial cut (for economic reasons), some vibrating wire stressmeter results were obtained and found to compare favorably with numerical predictions. Some other instrumentation devices were built and tested, but never installed .

Jan 1, 1984