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"Located in Madison River Canyon, about 14 miles by road from Norris, Mont. Built in 1907 by Madison River Power Co.DAM: Rock filled wooden crib structure, 183 ft. long, 34 ft. high or 44 ft. to top of flashboards.SPILLWAY: 140 ft. long, equipped with flashboards 10 ft. high.PIPE: One 10-foot and one 12-foot wood-stave pipe, 7,515 feet long.PRESSURE: One pressure chamber, 32 ft. high, 30 ft. wide and 81 ft.CHAMBER: long, built of concrete.PENSTOCKS: 4 9-foot steel penstocks about 200 ft. long, one for each wheel.WATER WHEELS: 4 double horizontal, center discharge, Sampson special 44-inch turbines, 3,600 h-p., at 100 ft. head. Speed 300 r. p. m„ direct connected to generators.GENERATORS: 4 G. E., W. C., 2,250 k-w., 4,000 volts, 300 r. p. m., 3 phase, 60 cycles, alternators, with exciters mounted on same shaft.TRANSFORMERS: 12 G. E., W. C., 900 k-w., 60 cycles. High tension voltage 23,100, 34,650, 46,200; low tension voltage 4,000, 3,800, 3,600. Now operating at 46,200, delta connected. They can be connected Y for 40,000, 60,000 or 80,000.OPERATION: This is the principal plant of the whole system and carries most of the load."

Jan 1, 1913

By Samuel G. Lasky

The writer has been interested in determining the mineralogic dis-t,ribut.ion of silver in the base-metal ore of thc Ground Hog mine of the Asarco Mining Co. in the Central mining district of New Mexico.' This ore consists of a varitextured mixture of sphalerite, chalcopyrite, galena and pyrite in a quartz gangue. The average ore contains 14 per cent of zinc, 9.5 per cent of lead, 5 per cent of copper, and 10 oz. of silver per ton. Generally it is accepted that the silver in ores of this type, in which no definite silver minerals can be recognized, is contained in the base-metal minerals. Published assays of pure mineral specimens from many districts show that each of the base-metal minerals contributes in some degree to the total silver content of the ores, and to determine the proportionate amount contributed by each mineral in any specific ore it has been the practice to assay selected specimens of each mineral, the purity of which has been determined microscopically. There being no such assays available for the Ground Hog ore, and it being impracticable to have enough of them made to give average results, the writer resorted to a mathematical attack upon composite assays of large quantities of ore and concentrates. Surprising results were obtained, and it is the threefold purpose of this paper to present these results, to describe the mathematical method used, and to point out the value of using this method even when assays of pure specimens are available. Value of the Mathematical Method The obvious way of attacking the problem would be to separate cleanly large quantities of ore into its component minerals and then to determine the average silver content of each mineral by assay of representative samples. Since an absolutely clean separation is not feasible, it has been the practice, as mentioned above, to assay pure specimens of the different minerals. No one will contend seriously that the silver content of a base-metal mineral is constant throughout any particular deposit, and it will

Jan 1, 1935

By Samuel G. Lasky

The writer has been interested in determining the mineralogic dis-t,ribut.ion of silver in the base-metal ore of thc Ground Hog mine of the Asarco Mining Co. in the Central mining district of New Mexico.' This ore consists of a varitextured mixture of sphalerite, chalcopyrite, galena and pyrite in a quartz gangue. The average ore contains 14 per cent of zinc, 9.5 per cent of lead, 5 per cent of copper, and 10 oz. of silver per ton. Generally it is accepted that the silver in ores of this type, in which no definite silver minerals can be recognized, is contained in the base-metal minerals. Published assays of pure mineral specimens from many districts show that each of the base-metal minerals contributes in some degree to the total silver content of the ores, and to determine the proportionate amount contributed by each mineral in any specific ore it has been the practice to assay selected specimens of each mineral, the purity of which has been determined microscopically. There being no such assays available for the Ground Hog ore, and it being impracticable to have enough of them made to give average results, the writer resorted to a mathematical attack upon composite assays of large quantities of ore and concentrates. Surprising results were obtained, and it is the threefold purpose of this paper to present these results, to describe the mathematical method used, and to point out the value of using this method even when assays of pure specimens are available. Value of the Mathematical Method The obvious way of attacking the problem would be to separate cleanly large quantities of ore into its component minerals and then to determine the average silver content of each mineral by assay of representative samples. Since an absolutely clean separation is not feasible, it has been the practice, as mentioned above, to assay pure specimens of the different minerals. No one will contend seriously that the silver content of a base-metal mineral is constant throughout any particular deposit, and it will

Jan 1, 1935

The writer has been interested in determining the mineralogic dis-t,ribut.ion of silver in the base-metal ore of thc Ground Hog mine of the Asarco Mining Co. in the Central mining district of New Mexico.' This ore consists of a varitextured mixture of sphalerite, chalcopyrite, galena and pyrite in a quartz gangue. The average ore contains 14 per cent of zinc, 9.5 per cent of lead, 5 per cent of copper, and 10 oz. of silver per ton. Generally it is accepted that the silver in ores of this type, in which no definite silver minerals can be recognized, is contained in the base-metal minerals. Published assays of pure mineral specimens from many districts show that each of the base-metal minerals contributes in some degree to the total silver content of the ores, and to determine the proportionate amount contributed by each mineral in any specific ore it has been the practice to assay selected specimens of each mineral, the purity of which has been determined microscopically. There being no such assays available for the Ground Hog ore, and it being impracticable to have enough of them made to give average results, the writer resorted to a mathematical attack upon composite assays of large quantities of ore and concentrates. Surprising results were obtained, and it is the threefold purpose of this paper to present these results, to describe the mathematical method used, and to point out the value of using this method even when assays of pure specimens are available. Value of the Mathematical Method The obvious way of attacking the problem would be to separate cleanly large quantities of ore into its component minerals and then to determine the average silver content of each mineral by assay of representative samples. Since an absolutely clean separation is not feasible, it has been the practice, as mentioned above, to assay pure specimens of the different minerals. No one will contend seriously that the silver content of a base-metal mineral is constant throughout any particular deposit, and it will

Jan 1, 1935

By Samuel G. Lasky

The writer has been interested in determining the mineralogic dis-t,ribut.ion of silver in the base-metal ore of thc Ground Hog mine of the Asarco Mining Co. in the Central mining district of New Mexico.' This ore consists of a varitextured mixture of sphalerite, chalcopyrite, galena and pyrite in a quartz gangue. The average ore contains 14 per cent of zinc, 9.5 per cent of lead, 5 per cent of copper, and 10 oz. of silver per ton. Generally it is accepted that the silver in ores of this type, in which no definite silver minerals can be recognized, is contained in the base-metal minerals. Published assays of pure mineral specimens from many districts show that each of the base-metal minerals contributes in some degree to the total silver content of the ores, and to determine the proportionate amount contributed by each mineral in any specific ore it has been the practice to assay selected specimens of each mineral, the purity of which has been determined microscopically. There being no such assays available for the Ground Hog ore, and it being impracticable to have enough of them made to give average results, the writer resorted to a mathematical attack upon composite assays of large quantities of ore and concentrates. Surprising results were obtained, and it is the threefold purpose of this paper to present these results, to describe the mathematical method used, and to point out the value of using this method even when assays of pure specimens are available. Value of the Mathematical Method The obvious way of attacking the problem would be to separate cleanly large quantities of ore into its component minerals and then to determine the average silver content of each mineral by assay of representative samples. Since an absolutely clean separation is not feasible, it has been the practice, as mentioned above, to assay pure specimens of the different minerals. No one will contend seriously that the silver content of a base-metal mineral is constant throughout any particular deposit, and it will

Jan 1, 1935

By D. G. Brubaker

IN the history of geophysical exploration by the electromagnetic method many procedures and types of equipment have been used. Source arrangements for surveying on the ground have included long wires grounded at both ends, large loops laid on the ground, small horizontal loops, and vertical loops of moderate to small sizes. Receivers have ranged from simple direction-finding coils to combinations of coils and a bridge circuit to measure quantities related to both amplitude and phase of the received signal. Primary considerations in choosing a survey method are effectiveness, speed, and economy. In work on the ground in which locating and out- lining conducting bodies is the objective, methods using a vertical coil and a simple direction-finder have been found the most satisfactory. Mason1 and his associates applied such a method by setting up a vertical source loop, fed with low frequency alternating current by an engine-generator set. With a direction-finding receiver they surveyed lines along the ground in the plane of the loop, taking measurements at each station of the azimuth and inclination of the magnetic field direction. Deviations of this direction from the normal direction, that is, from horizontal and perpendicular to the traverse line, indicated a conducting body. Recent advances in design of light-weight generating equipment have encouraged using this and similar methods.

Jan 7, 1957

By A. R. Rosenfield, G. T. Hahn

The effects of adding 0.025 volume fraction of uniformly dispersed Tho2, particles (particle size -380A) to iron have been examined. The two-phase alloy is shown to have a lower transition temperature and higher cleavage stress than either the base metal or a solid-solution alloy (Fe-3Si). Enhanced cleavage resistance is thought to be a consequence of particles limiting the effective slip distance of dislocations and thus the ability of Pile-ups to act as stress concentrations. Further calculations predict that the highest cleavage strengths are attained with uniform dispersions, where the particle size is kept small (-250A) and the volume fraction is relatively large (-2 to 3 pct). ALTHOUGH a fine dispersion of second-phase particles is known to impart strength to an alloy, the possibility that it might also impart ductility has only recently been explored. Outstanding progress has been made in the production of ductile tungsten alloys containing Tho21,2or (Hf, Zr)C,= but the contribution of the dispersion to ductility has neither been optimized nor fully analyzed. The basis for such an analysis has now been developed1,5 and is discussed briefly below. Experiments on iron are also described that attempt to isolate one of the possible ductilizing mechanisms and test its effectiveness. In analyzing these experiments, it is important to remember that cleavage obeys a stress criterion, and that either a lower ductile-to-brittle transition temperature or a higher cleavage stress is evidence of enhanced resistance to cleavage. DUCTILIZING MECHANISMS Slip Blockage. Cleavage fracture of polycrystals may be initiated at the intersection of a slip band (or twin) and a neighboring grain or a large (-1 to 5 µ) particle. The slip band generates a stress concentration at its head, and either the grain boundary fractures, the particle fractures, or cleavage is initiated in a neighboring grain. Experimental evidence for this viewpoint is found in metallographic studies8-8 and from the observation that cleavage is usually preceded by yielding.8-11 The potency of a slip band as a stress concentrator

Jan 1, 1968

By F. Lawson, N. A. Sareyed-Dim

A rotating disk of iron precipitant in a high temperature batch reactor has been used to study the kinetics of precipitation of nickel from low concentration aqueous solutions. Under inert atmosphere conditions, for temperatures up to 150°C, the rate of nickel deposition at pH25°C of 5 to 6 is controlled both by the rate at which nickel ions reach the surface and the rate of chemical reaction at the surface. However, the presence of oxygen in the atmosphere above the reacting system increases the nickel deposition rate dramatically. It is suggested that under the experimental conditions used, hydrogen atoms are adsorbed on both the iron and nickel, thus reducing the number of sites available for the cementation reaction. Oxygen acts as a depolarizer for hydrogen.

Jan 1, 1977

By M. Muskat, R. D. Wyckoff, H. G. Botset

The flow of liquids through porous media is known to follow Darcy's law which states that the velocity of flow is proportional to the pressure gradient. This law is but a statement of the facts obtained from experimental studies and is, therefore, uncontroversial. It should be men-tioned, however, that it applies only when the flow is viscous in nature and that at excessive velocities which tend to produce turbulence, the velocity is proportional to some power of the pressure gradient, the exponent ranging from 1 to 0.5 as the degree of turbulence increases. However., experiments with media having permeabilities corresponding to those of actual producing horizons show conclusively that the actual flow of liquids in a producing horizon must be viscous except perhaps in the immediate vicinity of a well producing at a high rate. Therefore, one is justified in assuming Darcy's law to hold for cases of practical interest, as will be implicitly assumed in this discussion Given this basic law of flow it is possible, theoretically to obtain solutions to any problem of viscous flow of dead liquids1 by the usual methods of potential theory. However, problems of practical interest often present such complex geometrical configurations of sources and sinks (driving sources and output wells) as to make the analytical solutions extremely difficult or even impossible. It is useful, therefore, to note that Darcy's law is precisely equivalent to the law of electrical conduction, so that the pressure distribution in steady state porous flow of liquids is exactly the same as the potential distribution in an electrical conducting medium.2 This analogy permits the use of electrical models wherein the potential distributions may be measured with far greater facility and accuracy than is possible in actual fluid-sand models. Such electrical models were used in determining the pressure distribution about complex arrays of wells, an example of which will be shown later in the discussion of the 5-spot flood. One phase of the porous flow problems which is of considerable practical interest involves the tracing of an advancing fluid front. Thus,

Jan 1, 1933

By B. J. Scheiner, A. G. Smelley

The Bureau of Mines, US Department of the Interior, is conducting research on a dewatering technique for fine particles generated during the mineral beneficiation process that will recover a portion of the water now being lost using conventional waste disposal methods and significantly reduce the time required for land reclamation. The technique utilizes a flocculant, polyethylene oxide (PEO), that forms strong stable flocs that can be dewatered rapidly on static and/or rotary screens. Infield tests, phosphate clay waste has been dewatered from a nominal 2.5% solids to greater than 20% solids. In other field tests, coal-clay waste has been dewatered from a nominal 3% solids to greater than 55% solids. In addition, small-scale continuous tests have shown that bentonitic clays can be dewatered from 12% solids to 40% solids.

Jan 1, 1985

By L. Eaton, A. W. Last, J. L. Stevens

COPPER ore from Kennecott Copper's Ray mine, about 60 miles southeast of Phoenix, Ariz., is concentrated at the company's mill at Hayden, some 18 miles south of the mine. The Hayden mill is currently treating 16,000 tons of ore per day by flotation, using raconite, a crude butyl xanthate, as a collector for the sulfide copper minerals and lime as a pyrite depressant.1 The ore contains significant amounts of nonsulfide copper minerals, but recovery of these values has been low. The Hayden mill is now being modified to provide for treatment of future ores by leach- precipitation-flotation (L-P-F). This modification, costing about $5 million, is expected to reduce the loss of nonsulfide copper values and improve overall copper recovery by an additional 2 lb per ton of ore.

Jan 11, 1957

By S. H. Ash

Safety records in the mineral industry for 1954 will do well to hold their own as compared with 1953, because of the poorer rate in the coalmining branches, even without the recent mine explosion at the No. 9 mine of the Jamison Coal & Coke Co., Farmington, W. Va., that killed 16 persons. .The cause of that disaster has not yet been ascertained. The metal-mining branch appears to have improved its record over the last year, however. Health Diesel equipment continues to be favored in non-coal mines. Equipment includes locomotives, trucks, tractors, and muckers. Of major concern and interest is the establishment of a new threshold limit for oxides of nitrogen-5 ppm as compared with 25 ppm. This gas is the most harmful component of diesel-engine exhaust gas

Jan 3, 1955

By Nathaniel Herz

IN the operation of any ore processing plant, no matter what beneficiation process or combination of processes may be used, certain fundamental figures are regularly needed for essential records and accounting. These include amounts of ore treated and products made, with their assays, as well as quantities of labor and supplies used, with their cost. Usually labor and supplies are broken down and allocated to certain operations by the accounting department, and resulting tabulations are available for study by the milling plant management. However, to avoid too many minor details that would make these reports cumbersome and involved, much information that could be useful to the plant operator is often consolidated in such a manner as to have lost a considerable part of its value. To clarify this point, it may be stated that top management is most concerned with production figures and cost of production, while the plant operator is also interested in quantities of labor in man- hours and amounts of supplies used. Due to varying unit prices of labor and supplies, comparisons on a dollar basis alone are often misleading. With rising unit costs of the past few years now about twice as high as they were a few years ago, constant study of quantities involved is required to improve efficiency and productivity.

Jan 6, 1957

By C. S. Smith

The partial persistence of grain size and grain shape on melting and resolidifying crystalline substances, as well as the general effects of pre-solidifi-cation and of superheating on nuclea-tion rate, have been attributed to the presence in the liquid of crystalline impurities bearing some structural relation to the principal solid and hence capable of serving as nuclei for its crystallization. That such lattice matching does sometimes occur is well established, but it is surely improbable that a compound possessing both high-temperature stability and the requisite structural similarity should be naturally available in almost every system. It is now suggested that a mechanism for producing appropriate nuclei exists in the crystallization of all but absolutely pure substances. Impurities can he of many kinds. Some will give rise to compounds that are less soluble in the solid crystal than in the liquid. A . crystal forming from a melt or solution containing these will be supersaturated in some degree, and the foreign atoms will commence to segregate during or after solidification. They do not necessarily form pure, unstrained, crystals of the precipitating compound with its normal composition and structure. Generally—at least in the metallurgical examples that have been most studied —the first recognizable nuclei have lattice coherency with the surrounding matrix and have practically the same crystal structure and lattice spacing as the material in which they form, differ- ing only in composition. An extremely thin oxide layer formed under appropriate conditions on or in a solid metal will tend to be coherent with the metal lattice, and the first few atom layers of the oxide in contact with the metal will differ in both composition and structure from massive crystalliue oxide. It will resemble the metal more closely than the oxide. If it did not subsequently change on melting, such an oxide film would constitute an almost perfect "template" or two-dimensional matrix to hold a few atoms of the primary metal in the exact array needed to form a nucleus for solidification. Any precipitating material will adopt the correct spacing over a few atom diameters, and with appropriate substitution of other atoms of the correct sizes a precipitate can match the parent lattice over large areas of cohererlce without excessive strain. In metals, the componentsof a host of oxides, silicides, borides, nitrides, carbides, sulphides, and other compounds are always present in minute amounts. Some of these will be eliminated because of extreme insolubility in the liquid, while others will remain soluble in the solid; occasionally, however, particles will be formed in the solid by coherent precipitation—not of pure substances, but of whatever assortment of atoms best satisfies the joint requirements of availability, affinity, and appropriate average atom size. Of these, many will disappear on melting, but a few will persist unmelted as little rafts of complex composition, maintaining in the liquid a surface of the exact geometry needed to nucleate the solid on subsequent cooling. Their number and size distribution will determine the resulting grain size; the dimensions of the largest will determine the degree of undercooling that can occur before solidification commences. A similar process may operate in the case of phase transformations in solids. The coherent precipitation of supersaturated minor constituents in a low-temperature phase should facilitate the nucleation of this phase on subsequent cooling after transforming into another phase at higher temperatures. At first sight this hypothesis may seem little different from the older ones. It should therefore be emphasized that it does not depend on chance to provide the right compound to form a nucleus, but postulates that every crystal, containing minute amourlts of any of a wide range of impurities, automatically engenders particles having the correct surface structure to serve as nuclei for subsequent solidification. It could operate in any system, metallic, organic, or inorganic. The suggested mechanism is closely analogous to the production of antibodies from antigens in living organisms—indeed, it was a description of the matrix theory of this process that suggested to the writer its crystalline analogue.

Jan 1, 1950

By L. S. Kolbert, C. H. Baab

Introduction In June 1981, the Electric Power Research Institute (EPRI) issued a report titled "Control Systems in Coal Preparation Plants" to determine the status of instrumentation and automation systems in the coal preparation industry. EPRI concluded that the control systems presently being employed in the US coal preparation plants "are relatively primitive compared with those in other mineral processing industries; and analytical instrumentation is virtually non-existent." With tighter specifications on the quality of steam coal, interest is increasing in more sophisticated control systems. One type of device that is currently assisting the preparation plant operator optimize and control the coal cleaning process is nuclear based instrumentation. Nuclear instrumentation includes methods for measuring weight, level, and density as well as for performing elemental analysis on coal. Major Features and Benefits of Nuclear Measurement and Analysis Systems There are many features and benefits of nuclear instrumentation. The major benefit is that nuclear instrumentation is non-contacting. The measuring heads do not contact the process materials. This enables measurements of corrosive, abrasive, or high temperature materials with no loss of performance, reliability, or useful life. Also, there are no moving parts to wear or be fouled by dust or corrosion. Installation is simple and inexpensive. For instance, density gauges are simply clamped onto existing pipe runs. Weigh scales and level switches usually require nothing more than welding brackets to customers' equipment. Once installed, routine maintenance can be performed without interrupting the process. Thus, nuclear instrumentation is highly reliable and easily installed and maintained. The operating life of the instrumentation is virtually unlimited. Principle of Operation Nuclear belt weigh scales, point level switches and density gauges all operate on the gamma-ray transmission principle. A beam of gamma radiation from a radioisotopic source is projected through the process material either on a belt, in a vessel, or in a pipe. Opposite the source is a radiation detector whose electrical output is proportional to the intensity of the radiation it absorbs. Gamma radiation is part of the same electromagnetic spectrum that encompasses light, infrared, and x-rays. In many respects, gamma radiation behaves much like light. However, it is far more penetrating and can be transmitted through considerable thickness of materials that are opaque to visible light, e.g., several inches of steel. Types of Nuclear Instrumentation in Coal Preparation Plants There are four types of nuclear instrumentation presently being employed in coal preparation plants. They are: •Belt Weigh Scales •Point Level Switches •Density Gauges •Coal Analysis Equipment. Each type of instrumentation has a number of potential applications within the plant. What follows is a discussion of three different types of devices and their applications. Weigh Scales In coal preparation plants, weighing instruments are used for measuring material throughput, totalized weight, and batch weight on conveyor belts and other transport equipment. They are also used on drag chain conveyors, vibrating conveyors, and screw conveyors. Weighing is important for receiving the run-of-mine coal, controlling mass flow, scheduling production, and loading and shipping the washed coal to market. There are two basic types of weighing instruments: gravimetric and nongravimetric devices. Gravimetric devices are units which measure the pull of gravity on the material being weighed. Nongravimetric devices are not dependent on the force of gravity on the sample. Nuclear weigh scales are the most prevalent nongravimetric devices used. The nuclear weigh scale works on the same basic principle as other nuclear gauges. The greater the quantity of material placed in the path of a radiation beam, the more radiation will be absorbed by the material. In weigh scales, Cesium 137 source is generally placed above the moving stream of material so that the radiation is directed through the material. An ion chamber radiation detector is on the opposite side of the material. The radiation passing to the detector generates a signal which is inversely proportional to the weight of the material present. This signal is amplified and integrated with the speed of the process flow yielding the weight. The weight is indicated and can be totalized for throughput, batch control, etc. In conclusion, radiation weighing methods have become well established in the coal preparation industry throughout the world. As mentioned before, this device finds its most

Jan 1, 1985

The Duluth Engineers' Club was formally organized on the evening of Aug. 5, 1918, at a meeting .attended by over l00 members of the several engineering professions. W. G. Swart, a member of our Institute, was elected the first President of the Club. At the organization meeting, an opportunity was given, to Alfred D. Flinn, Secretary of the United Engineering Society, to outline the assistance that is being rendered to the Federal Government in the present contingency by members of the engineering profession. Membership in the Duluth Club is to be open to mining engineers on the iron ranges as well as to the residents of the city of Duluth.

Jan 10, 1918

By Alan Stanley

THE Maclntyre Development of National Lead Co. is located at Tahawus, N. Y., in the heart of the Adirondack Mountains. Operations involve the mining and concentrating of a titaniferous iron ore to produce ilmenite and magnetite concentrates. A general description of the operation and metallurgy has been given by Frank R. Milliken.1 Pigment plant production demands that the MacIntyre mill produce a 44.7 pct. TiO2 ilmenite concentrate. To achieve the required ilmenite grade and tonnage it is important that the table concentrate grade be closely controlled. Unfortunately, however, the titaniferous orebody which feeds the Maclntyre mill is not uniform. Ore dressing characteristics vary from one end of the orebody to the other, and from one level to the next.. The changeable nature of the mill feed precludes a single adjustment of the equipment for long periods of time. Thus the operators must constantly watch the equipment to insure a uniform concentrate from the fine and coarse tables and Wetherills, or dry magnetic separators. Chemical assaying of mill products requires about 4 hr from the time the sample is taken until assay results are obtained, and this is available only on a two-shift basis. The ore may change rapidly, even several times during a shift, so that assay results lose most of their control value by the time they are reported to the mill operating crew. Members of the crew have therefore tried to evaluate the table and Wetherill concentrate by visual inspection, since through long experience the shift operators, under most circumstances, can gage closely the grade of the mill products. However, there are times when the, physical nature of the ore is radically different from normal. Under these conditions visual inspection is of no value, and at such times final ilmenite as low as 43 pct TiO2 has been produced and shipped before the assay results have been received. The specific gravity method of assaying for TiO2 has been attempted to eliminate the shipping of ilmenite below normal grade as well as to help control day to day and hour to hour mill production. Table I shows the minerals found in the Maclntyre ore along with their average weight proportions and specific gravities. The first two products considered for the specific gravity method were fine and coarse table concentrates. It was reasoned that these products were essentially ilmenite with the higher specific gravity gangue minerals. Since they were always produced the same way, and the desired grade of TiO2 was always constant, the specific gravity of these materials would increase or decrease as the amount of ilmenite increased or decreased. Thus for table concentrates which assayed 40 pct TiO2 a constant gravity would invariably be obtained, and as the TiO2 value changed the specific gravity would change in direct proportion. The third product considered was Wetherill ilmenite. It was assumed that a desired grade of 44.7 pct TiO2 would also always contain the same amount and type of gangue minerals along with the ilmenite, and thus would always have the same specific gravity. As the TiO2 value of the ilmenite concentrate changed so would its specific gravity. Dr. Kenneth Vincent, chief metallurgist of the Baroid Division of National Lead Co. at Magnet Grove, Ark., ran specific gravity tests on 17 samples of the desired products. The lowest specific gravity reading assayed the lowest in TiO2 and as the specific gravity increased the trend was for the TiO2 assay to increase, see Fig. 1. Since these results warranted further investigation, a 500-g capacity Torsion balance and 250 ml Le Chatelier specific gravity bottles were obtained. [ ] Shift samples of fine table concentrate, coarse table concentrate, and final ilmenite were tested. Each sample was split and 85 g weighed on the Torsion balance. The Le Chatelier bottle was filled with water to a zero mark. To avoid wetting the neck of the bottle it was found necessary to do this

Jan 1, 1952

The curve of Fig. 3 for pyrite requires modification. There 11% a range of pH values from 6.2 to 7.8 for which no cyanide is required to prevent contact. From 7.8 to 11.3 a small amount of cyanide is required, with a sharp maximum of 20 mg. per liter at pH=9.6. The mistake arose from considering too few solution compositions (17 were considered) in constructing the curve. Subsequent work with other collectors indicates that the corrected curve is typical for such systems; it illustrates the further development of the dip in the pyrite curve of Fig. 5.

Jan 1, 1938

By O. A. Kiehn, C. A. Born, F. N. Bender

Development of the flotation reagent scheme at Climax Molybdenum Company's mine at Climax Colorado is reviewed. Features of the mineralogy, milling practice and background of reagent changes are outlined. Special attention is given to the hitherto unpublished details of the application of depressants for copper and lead impurities. The present rougher flotation reagent scheme utilizes a neutral hydrocarbon oil, low in unsaturates and wax, as collector with a sulfated coconut oil emulsifier and pine oil frother. Lime and sodium silicate are used as rougher conditioning and slime dispersant agents. Chalcopyrite and galena impurities are depressed in both rougher and cleaner plants by stage addition of Nokes reagent and sodium cyanide to yield a metallurgical grade molybdenite concentrate containing greater than 90% molybdenite and less than 0.5%, 0.1% and 0.05% iron, copper and lead impurities, respectively.

Jan 1, 1976

By Rudolph G. Wuerker

THE scarcity of values of tensile strength of rocks has been explained by the lack of successful testing procedures. In the case of mine rock a description is given' of the difficulties encountered in testing a cylindrical specimen, such as a core, by conventional methods. Over a period of years the following method has given definite and reproducible results with the weakest as well as with the strongest rocks. It does not completely supersede the use of cores with special fixtures but is a supplement in all cases where cores cannot be obtained, as from soft rocks, or in cases where it is less expensive to prepare test specimens by cutting them out of the rock instead of drilling cores. Principle and equipment are the same as for the test for tensile strength of hydraulic-cement mortar.' The test specimen, Fig. 1, has the shape of a briquet. While in the original cement mortar test the briquet is cast in a special mold, it is prepared from rocks in different ways, depending on how easily they can be cut and shaped. Soft rocks, which cannot be core-drilled with a carboloy or diamond bit, are simply hand-cut. Only two dimensions need be watched. The first is the 1-in. diam at the narrowest cross-section of the briquet. The other critical measure is the radius of curvature of the waistline, as the roller supports in the grips have a fixed distance. This radius is ground out of the solid by means of a carborundum grinding wheel having a 3/4-in. radius. Medium hard rocks can be core-drilled with a carboloy bit. The resulting core can be used for nondestructive sonic testing first, and after that for any destructive test. By using an EX-bit and by carefully placing the coreholes, preferably by using a tenplate such as shown in Fig. 1, it is possible to obtain from the rock a punched sample from which numerous tensile briquets can be made. The outside radius of the EX-bit differs from the radius of curvature of the briquet by 1/8 in., but this still permits placing and aligning the specimen in the grips. In the case of bedded rocks the core might have bedding planes normal to the plane of the briquets, and rocks can be tested in any arrangement of the bedding planes desired. Hard rocks, limestones, igneous, and metamor-whic rocks can only be diamond-drilled or diamond-cut. Here the method of getting the tension briquets by accurate placing of EX-drill holes is especially economical. The tops of the briquets made from hard rocks cannot be rounded; they are straight cuts made with a diamond cut-off saw and rounded off on a polishing wheel. Results: As long as specimens broke over the waistline the results were considered acceptable. Further statistical treatment of the tests' showed a satisfactory percentage of standard deviation. The tensile strength values obtained by this method do not represent true values because of the stress concentration caused by the curvature of the side of the piece and because of the closeness of the grips. The ratio of maximum to average stress at the plane of failure has been determined to be about 1.75." All tensile strength values listed in Table I are corrected accordingly. To avoid this stress-concentration, if there are a sufficient number of cores, tensile strength can be measured by imbedding the cores in mortar in the two outer briquets in the gangmold.4 Strain-Measurements: The applicability of the briquet specimens for strain observations was tested in the case of sandstone and shale. Two element Rosette SR-4 strain gages were used. Young's modulus and Poisson's ratio, both in tension, were computed and found to be different from those in compression, determined during the same test series and from the same rock, see Table I. References 1 L. Obert, S. L. Windes. and W. I. Duvall: Standardized Tests for Determining the Physical Properties of Mine Rock. U. S. Bur. Mines R.I. 3891 (1946). 2 Test for Tensile Strength of Hydraulic-Cement Mortar, ASTM Standard C 190-44. S F. O. Auderegg, R. Weller, and B. Fried: Tension Specimen Shape and Apparent Strength. Proc. ASTM 11939) 39, pp. 1261-1269. 4 API Code 32.

Jan 1, 1956