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The use of solid state detector and radioisotope x-ray source for x-ray fluorescence analysis is illustrated by analysis for iron, copper, zinc, tin, and lead in about 700 samples taken from Australian mineral process streams. Limits of detection based on counting statistics (3 standard deviations) range from 0·001 to 0·004 per cent by weight element. The analysis accuracy was usualIy between 2 to 10 per cent (rms) of the mean element concentration and was determined by comparison with assays supplied by mineral companies. In most cases the main cause of error appears to be due to this assay and not the x-ray fluorescence technique.Some potential fields of application of solid state detector and radioisotope x-ray source for analyses in the mineral industry are indicated.

Jan 1, 1974

By Hans W. Brodbeck

The Advisory Conference on Tunnelling of the OECD, held in Washington, D.C. in June 1970, has established the following definition: "Tunnelling refers to the construction by any method of a covered cavity of predesigned geometry whose final location and use are under the surface, whose cross-sectional area is greater than 2 square metres". (1) The definition makes clear that the term includes all types of underground construction, be it in hard rock, soft ground, under mixed conditions, underwater, etc. Small-sized tunnels in rock therefore constitute but one part of the tunnelling scene. With an ever-growing urbanisation taking place in industrialized as well as developing countries, the demand for small-sized tunnels is, however, rapidly increasing and requires a far-reaching mechanization of excavation and support functions. This trend is accentuated by the fact that small-sized tunnels are far more labor-intensive than large ones, and, with wages raising at a much faster rate than costs for plant and equipment, this will accelerate the introduction of new tunnelling systems. SMALL-SIZED ROCK TUNNELS The main field of application for a tunnelling system for small sized hardrock bores is thus defined. It is in fact the numerous relatively short tunnels required under cities and other populated

Jan 1, 1974

By Rolland L. Blake

The Bureau of Mines is concerned with extracting minerals from residual geothermal brines after their heat content and some demineralized water have been recovered. This literature study is based on a survey of the literature and discussions with individuals knowledgeable on various aspects of the subject. This report examines the potential of the domestic geothermal mineral resources, considers the technical problems involved, and outlines possible effects on the environment from reservoir fluid withdrawal and reinjection. Geothermal resources in the Western United States were extensively explored during the 1960's. Limited development operations included exploratory drilling and operating wells producing hot brine, separating steam for experimental electric power generation, and recovering minerals in solar evaporation ponds or in extraction plants. Interest in the recovery of minerals and salts from geothermal fluids waned because of corrosion and scaling problems and low or no market value of the mineral products. Most of these problems can be controlled with existing technology and careful planning of processes and equipment. Extracting geothermal minerals is technically feasible, but the problems of low or no market value for major mineral products, and insufficient amounts of more valuably major products, make mineral recovery uneconomical at present.

Jan 1, 1974

By R. R. Schehl

The Bureau of Mines analyzed the structure of a high-grade metallurgical coke, carbonized at different temperatures in the range 500° to 1,000° C, through X-ray diffraction studies. Growth in the crystallite size with increasing coking temperature was calculated from profile analysis and compared with values obtained from the radial distribution function. The carbonization temperature appeared to have little influence upon the stack height, whereas the layer diameters more than doubled in size between 500° and 1,000° C. These results are comparable to those obtained from other studies of poorer quality cokes.

Jan 1, 1974

By B. W. Madsen

Experimental results obtained from large scale (7 tons), long-term (500 days) leaching of low tenor copper sulfide ores were interpreted by a geometric model involving the movement of a reaction zone through the ore fragments. The postulated leaching mechanism involved mixed kinetics and included diffusion of the reacting species through the host rock and a chemical reaction at the surface of the mineral particles. Ore properties which were considered were ore particle size and shape, grade of ore, and mineral content. Excellent agreement between the mixed kinetic model and the laboratory leaching results was obtained when minus ½ inch ore particles were not included in the leach. Also, a satisfactory prediction of copper recovery from plus ½ inch ore with a different particle size distribution was made; however, it was necessary to modify the shape factor in the model. Predictions of copper recovery from an ore sample which included the minus ½ -inch fine fraction and leaching for 460 days was 56.5 percent, and the recovery from leaching was 47.0 percent. The presence of fines caused channeling and uneven solution distribution and inhibited the leaching rate.

Jan 1, 1974

By R. G. Bottge

To better understand those factors which increase mining costs in Alaska, a Bureau of Mines study was conducted to compare the estimated costs of operating a 100,000-tpd open pit copper mine located on a hypothetical ore body in the Lake Clark area, Alaska, with the costs of mining a similarly sized hypothetical copper ore body near Tucson, Ariz. The information derived should be beneficial to the State and Federal governments in appraising the potential for development of large, low-grade porphyry copper deposits in south-central Alaska. Conventional mining and concentrating methods were assumed, and capital and operating costs were derived using flowsheets and standard costing methods. The total price required for copper mined in Alaska and Arizona was $1.12 and $0.63 per pound, respectively, plus or minus 20 percent. These values were obtained assuming no leaching of low-grade copper, recovery of gold, silver, and molybdenum as byproducts, 100-percent equity financing, and a 12 percent discounted cash flow rate of return. The average domestic and international prices for copper in July 1973 were $0.60 and $0.916 per pound, respectively. The existence of a developed transportation and power system in Alaska would have reduced capital and operating costs subs tantially. The required price for copper would have declined from $1.12 to $1.05 per pound, plus or minus 20 percent.

Jan 1, 1974

By D. D. Bolstad

This report describes the construction and use of a direct-reading azimuth protractor (DRAP) by the Bureau of Mines for measuring fracture orientations in mines, tunnels, or other excavations having a magnetic environment. The DRAP allows a rapid and simultaneous measurement of dip and azimuth of dip of a fracture plane. The instrument is rugged, lightweight, and easily constructible from standard hardware items. The DRAP can measure dip to within ±0.5° and azimuth of dip to within ±5° of corresponding values obtained with a Brunton compass.

Jan 1, 1974

By J. W. Mahar, E. J. Cording

INTRODUCTION In exploration for rock tunnels, the geology should not only be described, but its effect on excavation and support assessed. It is not an easy task to correlate exploration results with support and excavation requirements, even when the exploration program is detailed and geologic conditions are relatively well known. Many of the significant geologic features are subtle and their effect is difficult to interpret from exploration results. However, in similar geologic settings, there are specific geologic features which will cause recurring support problems. Such features should be actively sought out when exploring in a given geologic setting. In blocky and seamy rock, the primary features controlling performance are the joints, shears, and shear zones. This paper describes the effect of such features on the formation and movement of rock wedges in tunnels driven in foliated metamorphic rocks in Washington, D. C. and New York City. In both areas the foliation commonly forms a N-S striking plane of weakness along which major shear zones, shears, and joints have formed. In addition, the structural history of the two areas has been similar, so that there are similarities in the orientation and character of the other major joint sets and shear zones in the rock mass. The observations were made in tunnels ranging from 10 to 70 ft in width and excavated at depths ranging from 80 to 800 ft. Most of the tunnels described were deep enough to be located in unweathered rock, or in rock only slightly weathered along joints and shears. Variations in the planarity, filling, spacing, and attitude of joints, shears, and shear zones accounted for significant differences in the

Jan 1, 1974

By Donald R. Johnson

Apparatus developed by the Bureau of Mines for thermal analysis of oil shale was used to determine the thermal properties of shortite. Dissociation of shortite near 470° C occurs as an endothermic reaction that could consume significant quantities of heat in the oil-shale retorting process that produces shale oil. The shortite dissociation products undergo other thermal reactions that would not affect the retorting process. These reactions include crystal inversions near 365° C and 425° C and melting and decomposition endotherms above 500° C. Two separate reaction route for fusion and decomposition of the shortite decomposition products are dictated by the presence or absence of CO2 around the sample.

Jan 1, 1974

By William Detty

An architect representing the Atlanta office of the Brick Institute of America periodically presents a slide lecture to interested groups entitled "The First 10,000 Years of Brick". The title signifies the fact that brick, man's oldest manufactured building material, has been around for quite some time and will continue to be utilized by architects and builders in the foreseeable future. This is not to say that the brick industry can rest on its laurels and ignore the competition presented by newer more innovative products. The industry will have to be equally inovative and market oriented in order to maintain its market share of the predicted construction boom between now and the year 2000. The implication is made, however, that brick can be produced under rudimentary conditions and that the desire to use the product has been long standing. In addition, history has sham that there has been plentiful clay available to produce the product. This paper is an attempt to assess the climate in which the brick industry will operate during the next 26 years. An analysis of regulatory conditions affecting the manufacture of the product will be followed by an assessment of the materials environment in which the industry will be operating. These factors are then reconciled with a projected demand for the product to determine the ability of the industry to satisfy future demand for brick. From a mineral point of view this paper will address itself generally to the availability of and demand for clay. However, other than a brief overview of the uses of other specific types of clay, it will concentrate on the clays utilized in the production of structural clay products, specifically brick.

Jan 1, 1974

By Roshan B. Bhappu

Stimulated by current $0.80 to $1.20 per pound price tag of copper, considerable interest and activity have been generated in the copper mining camps throughout the world, and especially in the Southwestern United States and Northern Mexico copper belt. Under these economically favorable conditions, many of the marginal oxide-copper deposits, as well as newly discovered prospects, are under scrutiny for possible exploitation. For both the known deposits and new prospects, the big question facing the mine operator is the selection of the best method for processing these economically attractive oxide-copper deposits. Several variations of the hydrometallurgical processes are currently available for treating oxide-copper ores which can be mined by the open-pit method. Basically, these processes involve preparing the ore for application of an acid solution, applying the solution to the ore, and recovery of the metal from the pregnant solution. Dump leaching, heap leaching, vat leaching, agitation leaching and, in more recent times, in situ leaching or solution mining in combination with well established cementation process or the newly developed solvent extraction-electrowinning system have all been employed or have been investigated for the recovery of copper from oxide ores. Of these processes, dump, heap and vat leaching have been successfully practiced for treating oxide-copper ores. Agitation leaching is a relatively newcomer and has been adopted from the experiences of uranium and gold processing. Finally, the inplace leaching technique is the latest process to be suggested for possible treatment of oxide-copper ores.

Jan 1, 1974

By Edward H. Opitz

Much has been written recently about the Henderson Mine Project in Colorado being developed by American Metal Climax, Inc. To briefly recap the project, AMAX has an ore body, containing about 300 million tons of proven and probable molybdenum ore which is located under Red Mountain on the eastern slope of the Continental Divide. The mill, however, will be located on the western slope in the Williams Fork Valley where water and space for waste disposal are more available. AMAX will carry the ore by remote controlled trains from a gathering level underground at the mine, through a ten (10) mile tunnel under the Continental Divide and thence along a five (5) mile surface railroad to the mill site. One of the more challenging facets of the project is the western portion of the ten (10) mile tunnel being driven by Dravo Corporation through difficult ground conditions, downgrade, toward the Continental Divide. The tunnel is a 16'-6" wide by 15' high horseshoe, which runs in a straight line and drops at a constant three percent (3%) grade from the West Portal to the ore zone. Dravo's portion is anticipated to be about 6 1/2 miles long and includes permanent pumping stations located every 4,900 linear feet (lf) permanent rectifier stations every 12,5001f, and one (1) 1,560 ventilation shaft. The western portion of the tunnel lies in the Idaho Springs formation, a mixture of gneiss and schist with some granitic intrusions. Toward the Continental Divide a transition into Silver Plume Granite is expected to occur. Preconstruction geologic information indicated the Idaho Springs and Silver Plume formations to be basically competent with some faulted and altered areas. It

Jan 1, 1974

By Fathi Habashi

Chalcopyrite can be readily leached with HNO3, but the recovery of elemental sulfur does not exceed 50% under the most favorable conditions. Preheating at 500°C in a slightly reducing atmosphere increases the recovery of elemental sulfur to about 65%. Chalcopyrite can also be treated with HNO3 in a pressure reactor at 110°C to solubilize selectively the copper while iron remains in the residue as an oxide. The recovery of elemental sulfur also improved when preheated chalcopyrite is treated in this way. Stainless steel should be an adequate material of construction.

Jan 1, 1974

By F. A. Olson, S. L. Pohlman

A unique method of measuring weight loss as a function 3 of time, with a sensitivity of 10-5 grams, while leaching copper minerals with a flowing acid leach solution has been developed. Kinetic results obtained coupled with visual and microprobe analyses show topochemical reaction for the leaching of chrysocolla with sulfuric acid. The kinetics follow a shrinking core model and show ion diffusion through a product layer, chemical reaction at the unreacted core interface and mass transfer through the boundary layer as being important.

Jan 1, 1974

By Tuncel M. Yegulalp, Peter G. Zambas

In planning an underground room-and-pillar mine, the selection of the shaft or portal location and the orientation of the main haulage arteries is of paramount importance, particularly in view of the high dependence of the cost of truck haulage on the proper definition of these parameters. In an effort to facilitate this selection a computer program was written which, by relating the truck characteristics to the areal configuration of the property or ore body, derives the volume-weighted total fuel and time requirements for hauling ore from every panel within the property to a specified portal or shaft location through a predetermined gridwork of haulage drifts. By varying the size and orientation of the gridwork and the location of the portal or shaft access, an infinite number of configurations can be investigated. The results of this analysis can be plotted to indicate the optimum conditions.

Jan 1, 1974

By Lee M. F

The Lady Loretta lead-zinc-silver mineral isation of north-west Queensland was discovered first by Placer geologists in 1968 as a result of a geochemical soil survey. The stratigraphic position, mineralisation and rock associations of the deposit are very similar to those of the Mount Isa lead-zinc-silver orebodies. Aspects of the exploration history, geo- chemistry and structural geology of the Lady Loretta deposit, are discussed. A geometric model of the Ore Horizon is given.

Jan 1, 1974

By William E. Hole

The sand and gravel industry provides an enormous quantity of materials vital to the maintenance of low-cost construction. There has been little effort to conserve this valuable natural resource. In fact, existing regulations which affect sand and gravel operations act more to waste these materials than to conserve them. Another factor affecting the industry is new legislation requiring the reclamation of worked-out pits. Although such legislation creates many administrative headaches for a sand and gravel operator, there exists the possibility through such legislation of gaining some conservation measures that could be helpful to the industry.

Jan 1, 1974

By Lulie H. Crump

Salient information on reserves, production, and consumption of fuels and energy by State are summarized in this Bureau of Mines publication. The data are broken down by fossil fuels (coal, petroleum, and natural gas) and hydropower and nuclear for the major consuming sectors: Household-Commercial, Industrial, Transportation, Electric Power and Miscellaneous. In addition, total energy consumption in the Nation in 1972 is compared with consumption in 1971 and 1973 (preliminary data).

Jan 1, 1974

By D. M. Doyle

"The Strathcona Concentrator operations, the application of control systems in the crushing, flotation and tailing fill sections, and current and future computer control concepts are described in this paper.The computer has been used for reporting and monitoring roles and operating the on-stream analyzer since start up of the mill in 1968, while over the past twenty months, it has been used for process control. The systems which have been developed include:1. The blending of pentlandite concentrate with pyrrhotite concentrate to produce a special product of constant nickel analysis.2. The blending of cement with tailing fill to produce backfill of consistent cement content.3. The supervisory control of xanthate, frother and pH to the flotation circuits to maintain the nickel copper concentrate grade within narrow limits.IntroductionThe Strathcona Concentrator is currently treating 7,200 tons per day of an ore which contains nickel associated with the minerals pentlandite (28 -32% Ni) and pyrrhotite (0.3 -1.0% Ni). The ratio of the nickel minerals varies from 4 to 15 parts of pyrrhotite to 1 part of pentlandite over the orebody. The production of a high grade concentrate re4uires the separation of this small quantity of .oentlandite from the much greater proportion of pyrrhotite and gangue and is complicated by the presence of two pyrrhotite minerals differing in nickel content, floatability and magnetic susceptibility."

Jan 1, 1974

By M. E. Wadsworth, A. E. Lewis, R. L. Braun

Experimental results obtained in laboratory leaching studies of primary copper sulfide ore in sulfuric acid systems pressurized with oxygen are interpreted by a computerized geometric model involving the movement of a reaction zone through the ore fragments. Physical properties of the ore, including size, shape, and mineral content, are considered. The leaching mechanism involves mixed kinetics and includes a surface reaction within a moving reaction zone plus pore diffusion of dissolved oxygen through the reacted portion of the ore fragment to the reaction zone. The results are applicable to conditions that would exist in nuclear solution mining or similar processes in which the ore is converted into rubble and then inundated by a leach solution adequately supplied with oxidants. Experimental results at 90°C are correlated with the model, which includes temperature-dependent parameters.

Jan 1, 1974