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By Danqing Gao, Brijes Mishra

Spatial variance of rock properties is an important characteristic of rock which addresses the heterogeneity of mechanical and physical properties and their effect on underground mining. Assessing spatial variance can be useful for both locating potential difficult grounds and performing reliability analysis in the mining support system. This study shows a microscale numerical model for rock material based on continuum mechanics. To consider the spatial correlation factor of mechanical properties in realistic rock mass, this study introduces a spatial correlation concept into the traditional type III extreme value distribution model. Based on the improved microscale random model, we conducted a series of numerical uniaxial compressive tests and one longwall mine model to investigate the progressive failure of rock. The results show that spatial correlation factor can significantly affect the load-deformation curves and fracture patterns. The spatial variance model was applied to a longwall mine that included several cutting sequences to observe the influence of the spatial variance on roof behavior. The cohesion and friction random fields induced failure that propagated randomly through the immediate roof in different entries. The results showed that the spatial variance provides an accurate prediction of erratic roof falls in coal mines.

Jul 20, 2020

By V. T. McLemore

"Production of industrial minerals remains important to the rural economy of New Mexico. In 2014, 226 active mines and mills were registered in New Mexico and included four coal, eight potash, 11 metal, 33 industrial mineral and 170 aggregate and stone operations. New Mexico leads U.S. domestic production of potash, perlite, zeolite and travertine. Other production includes aggregate, humate, pumice, gypsum, salt, common and fire clay, scoria, limestone, fly ash, cement, magnetite, silica and decorative stone. New Mexico also has the potential for additional production of industrial minerals. One company is exploring for garnet. Cretaceous black sandstones in the San Juan Basin have drawn interest for titanium, rare earth elements (REEs), niobium and zircon, and other REE deposits are being explored. REE-thoriumuranium veins have been found in the Gallinas, Capitan and Cornudas Mountains and Laughlin Peak-Chico Hills. Exploration for beryllium has occurred in the Ojo Caliente No. 2, Cuchillo Negro and Victorio mining districts. Companies also are examining high-calcium limestone and high-magnesium dolomite for potential development, while aggregate continues to be important in urban areas and along highways. IntroductionIndustrial minerals and rocks are literally the building blocks of our way of life. They are an exceptionally diverse and vital group of raw materials that underpin almost all aspects of human activity, infrastructure and standard of living. Industrial minerals and rocks are used in the manufacture of many products, from ceramics to plastics to refractories to paper. Although industrial minerals permeate nearly every aspect of daily life, their presence and their roles are typically invisible. A widely used definition of industrial minerals and rocks is “any rock, mineral, or other naturally occurring substance of economic value, exclusive of metal ores, mineral fuels, and gemstones: one of the nonmetallics” (Bates, 1975). This definition includes the important construction materials sector as well as specialized industrial minerals, but complex interactions between consumer industries produce a number of apparent anomalies to this definition. Some metals are included as industrial minerals because their use is industrial rather than as a metal. Sulfur is now predominantly extracted as a byproduct of cleaning natural gas, one of the world’s major energy fuels.Production of industrial minerals has been and remains important to the rural economy of New Mexico. Industrial minerals constitute nearly 41 percent of the more than $3.1 billion generated by mineral production in New Mexico in 2014 (Table 1). In 2014, 226 active mines and mills were registered in New Mexico and included four coal, eight potash, 11 metal, 33 industrial mineral and 170 aggregate and stone operations (New Mexico Mining and Minerals Division, 2015a). New Mexico leads U.S. domestic production in potash, perlite, zeolite and travertine. Other industrial minerals production from New Mexico includes aggregate, humate, pumice, gypsum, salt, common and fire clay, scoria, limestone, fly ash, cement, magnetite, silica and decorative stone. Additional production statistics can be found in Harben et al. (2008). Major industrial mineral districts are shown in Fig. 1."

Jan 6, 2017

By John E. Dreier

The Pachuca-Real Del Monte district, Hidalgo, Mexico (Figure 1) has produced roughly 1,500,000,000 oz Ag., 6,000,000 oz Au. and minor Pb., Zn, and Cu from about 100,000,000 tons of ore since discovery early in the 16th century. Production has come from epithermal vein deposits that have been up to 8 km in length, 650 m in vertical extent and 45 m in width but which averaged 200-400 m in length and vertical extent and 2-4 m in width. Ore deposits occur through-out an area about 12 km E-W by 10 km N-S (Figure 2) and between the elevations of 2000 and 2800 m above sea level. The deposits occur as shoots in the veins and terminate laterally where the veins narrow, upward where the veins pinch out and downward where the veins decrease in silver con-tent to below the cut-off grade; the veins are known to extend 500 m below the bottoms of the ore bodies and probably extend to much greater depths. The district lies wholly within a mid-to-late Tertiary volcanic rock sequence that is made up principally of andesite and dacite lava flows and flow-breccias. Although the bottom of the sequence is not exposed in the district, stratigraphic constructions indicate the volcanic rocks to have an aggregate thickness of 2000 to 2500 m. Structurally, the area is characterized by gentil warping and normal faulting of the volcanic rocks. Pre-ore modifications to the volcanic rock sequence consisted mainly of faulting along west-trending, south-dipping normal faults and north-trending high-angle faults.

Jan 1, 1978

By Changjiang Li, Jun Yang, Qiang Fu, Xu Chang, Xing Wu, Yubing Gao

With the development of underground mining, the deformation of roadway floor has increasingly become a major constraint on the safe and efficient production of coal mines. To address the floor deformation that was caused by massive stress concentration in roadway, an innovative method based on deep-hole directional tensile blasting technology is put forward. By taking No.122108 working face in Caojiatan Coal Mine as engineering background and analyzing the mechanism of deformation, a numerical simulation and field test are carried out to verify the effect on deformation control of this technology. It is found that the deep-hole directional tensile blasting technology can actively control the fracture position of the roof in the gob area and cut off the stress transmission path, so as to relieve the stress in the roadway. And since different blasting parameters have different impacts on the stress relief effect, a numerical simulation is implemented and it is found that the stress relief effect is the best when blasting depth is set to be 32 m and the blasting angle be 60°. By applying the optimal blasting parameters to the field engineering test, it can be seen that the deep-hole directional tensile blasting technology could effectively reduce maximum stress value and stress field range of the both sides of the roadway, and make the stress field far away from the roadway, thus effectively controlling the deformation of the roadway floor. The deep-hole directional tensile blasting technology can effectively solve the problem of roadway floor deformation and can be safely applied to engineering sites.

Jun 13, 2023

By J. Alderman

In modern industry, cost and productivity concerns and environmental concerns are sometimes incompatible, but at other times only appear to be incompatible. Surface disposal of wastes from coal preparation plants appears to be an area of the production system with little opportunity for initiating measures which cut costs and concurrently benefit the environment. However, improving the recovery efficiency of fine coal circuitry can cost-effectively reduce the plant waste environmental burden by a substantial amount. Studies at Jim Walter Resources indicate that fine-coal waste measuring 50% ash contains over 50% recoverable, marketable coal. Modifications to the plant circuitry which reduce the amount of misplaced coal in the fine-coal waste stream could substantially reduce the volume of fine waste disposed aboveground. Studies at Jim Walter Resources indicated that episodic overloads of the vacuum filters in the fine-coal circuits at the preparation plants were a source of misplaced coal in the fine-waste stream of the cleaning plants. To improve the filtration rate and reduce overload episodes, conventional rotary blowers were replaced with high pressure air blasters on most of the filters. Subsequent testing indicated that measurable benefits can be derived from this modification.

Jan 1, 1990

By Hasan Sevim

This paper summarizes recent developments in modeling of underground coal slurry haulage networks for determination of optimum design and operating parameters. The model presented here is based on a stochastic dynamic programming formulation, applicable in any typical room-and-pillar and/or longwall mining configuration commonly practiced in the United States. The formulation and the structure of the model is general enough to handle design problems involving more than one face and mining method. Given the stochastic operating characteristics and a system layout, the model can be used to determine the equipment configuration and operating regimes that minimize the overall unit cost of coal haulage.

Jan 1, 1983

By G. T. Daware, M. J. Chaddha, S. P. Masurkar, P. G. Bhukte, A. Agnihotri

JNARDDC has evaluated bauxite deposits of India from the geo-technological point of view. During the evaluation studies, it was observed that bauxite deposits are associated with saprolite resources. During bauxite mining, various low-grade materials such as saprolite, laterite and low-grade bauxite are generated. These materials typically have low-alumina, high-iron oxide and high-silica content. Owing to their inferior quality, these materials cannot be used for alumina production and hence remain unutilized at the mine site. For the present study, the saprolite samples were collected from the Western Ghats bauxite deposits in India. The sintering studies were conducted on saprolite granules using a variety of parameters. The sintered granules were characterized, and their properties determined. The test results showed that bulk density, apparent density, porosity and refractoriness (PCE 1645–1659 °C) of the aggregates were within the range of refractory specifications. The feasibility tests carried out at the refractory industry indicated that the developed aggregates are suitable as refractory material and can substitute for calcined clay. Currently, high-purity clay resources used in the refractory industry are limited and fast exhausting; therefore, the industry is likely to face an acute shortage of raw materials, which will become more critical in the future. Therefore the sintered granules (aggregates) developed from saprolite, which is a mining waste, provide a low-cost, eco-friendly solution for the fast-exhausting resources of the high-purity clays. The developed process may change the Indian bauxite mining scenario because saprolite may substitute as a potential raw material for the refractory industry.

Apr 12, 2021

By L. A. Alcorn, H. E. Camargo, G. Gwaltney

"One of the most pervasive diseases in the mining industry is noise-induced hearing loss. The exposure of miners to noise levels above the permissible exposure level results in hearing loss in approximately 80% of coal miners by retirement age. In this context, the U.S. National Institute for Occupational Safety and Health (NIOSH) is conducting research to develop noise controls for longwall mining systems, which are used to extract half of the national underground coal production.From field measurements, previous research determined that the dominant sound-radiating components at the shearer of a longwall system are the two cutting drums used to remove coal. Due to the dimensions and complexity of longwall mining systems, the NIOSH project developed a validated finite element model of the cutting drum to use in predicting the sound radiated by the drum due to the excitation forces experienced in underground operations. This same model will be used to develop engineering noise controls for the drum. The excitation forces arise from the interaction of the cutting bits and the coal and are transmitted to the cutting drum through the bit holders. Due to the adverse conditions at the face, and a lack of instrumentation approved for underground use, the operational coal cutting forces have not been assessed before. To this end, NIOSH, in collaboration with Michigan Technological University, developed a self-contained, intrinsically safe instrumented bit to measure these forces.This paper describes the development of the instrumented bit and the measuring of operational coal cutting forces at three working coal mines. The measurements revealed that the forces have a flat spectrum, representative of the impact nature of these forces, up to around 100 Hz. Above this cutoff frequency, the force magnitude decreases at a rate proportional to the inverse of frequency squared."

Jan 1, 2014

By B. T. Mirabile, D. Tang, Y. Luo, S. S. Peng, C. T. Holland

Knowledge of local coal mine roof geology is critical to the design of a safe and suitable mine structure. An automated drill control and data collection system has been designed for a J.H. Fletcher twin-head roof bolter. Drilling parameters collected during the drilling process can be used to interpret geologic features intercepted in the mine roof. The drill and data collection system have been tested in both laboratory and underground settings. Visualization of certain drilling data has shown good correlation with geology drilled. A quantitative prediction model was developed using drilling parameters examined with data visualization. The quantitative model was tested using laboratory drilling data.

Jan 1, 2004

By Jack M. Campbell

The regulatory process by which governmental authorities acknowledge and, in turn, permit the location, construction, and operation of large scale energy-related facilities has become extremely detailed in recent years. One example of the detail that is entailed in the regulatory process is the number of permits that must be acquired by operators prior to the construction and operation of energy-related facilities. It has been estimated, for example, that 75 permits are required prior to the opening of a new coal mine in Pennsylvania while 50 are required in Kentucky. From the perspective of facility owners and operators the regulatory process often appears overly complex and may be perceived as a constraint to the corporate decision making process. From the perspective of those responsible for administering regulations, the process is perceived as a mans by which public desires - pursuant to social objectives such as environmental protection and occupational safety - can be achieved. As a result of conflicting organizational interests, the clash between energy facility owners and operators and their regulators appears to be inevitable. Furthermore, the resolution of this conflict lies in the tradeoff between objectives and the costs of regulation. The balance of objectives and costs is a subject of the political process and not a topic of consideration in this paper. This paper is concerned with the actual administration of regulations, that is, the implementation of that which arises from the interplay of organizational interests. The paper assumes that environmental control laws will not likely be repealed, that regulations to implement the intent of these laws are here to stay and thus the paper seeks to assess how regulations are administered at various levels of government pursuant to objectives. The paper hypothesizes that the administration of objectives (or policy) has an impact on decision making which affects energy facility decision; making while recognizing the fact that regulatory policy cannot be totally divorced from administration, this paper proceeds

Jan 1, 1977

By John Hillman

The reconstruction of the British mining industry which began shortly after nationalisation in 1947 continued until well into the 1950s with the support of the Government. This support diminished as plentiful supplies of cheap oil from the middle East made many coalmines un¬economic. The planned rundown which followed was foreshadowed in the 1965 White Paper which outlined the financial measures to speed the closure of uneconomic collieries. The decline appeared likely to continue into the 21st century as the role of coal in UK energy requirements became less and less significant. This policy was well on course in 1973 when the oil crisis led to a complete reappraisal of the position. A Government examination in 1974 of the coal industry then supported the National Coal Board's general strategy of major capital investment as set out in its 'Plan for Coal' (1). Plan for Coal aimed at halting the intended decline in the industry's capacity and restoring it to 120 million tons of deep mined output in 1985. The Plan proposed action along the following lines (a) increase output by major Investment in construction at existing collieries with sufficient reserves to give 13 million tons per annum extra output (b) invest in extending the life of existing collieries by gaining access to additional reserves, to give 12 million tons per annum extra output © by sinking new mines, produce an extra 20 million tons per annum. Figure 1 shows the contribution (2) expected from each of the three sources up to 1990/1. The measures taken were expected to offset the inevitable exhaustion of existing pits and provide the additional 40-42 million tons capacity needed to restore annual output in 1985 to 120 million tons. Parallel to this programme for expansion of deep mined output, opencast mining was to produce 10-15 million tons per annum. A recent review however, indicates that new mines are likely to yield only 10 million tons per annum by 1985, mainly owing to the need for public inquiries into proposals for new mining and the resultant fact that planning approval takes 'much longer than originally expected. Nevertheless the objective of 120 million tons deep mined output by 1985 is still considered achievable of means of a greater contribution from existing mines. This programme was originally estimated to cost 2,-56 million dollars at March 1974 prices, out revised estimates of the cost of Plan for Coal indicate that it may now exceed 6,960 million dollars at mid-1977 prices. Plan for Coal includes a substantial investment in new and reconstructed coal preparation plaints. At mid-1977 prices more than 322 million dollars Ls so be invested in coal preparation projects in the UK, at the rate of, about 70 million dollars a year. This rate 3f capital expenditure has been maintained over the past three years and covers investment in a wide range of coal preparation coals for the power station, coking and domestic markets.

Jan 1, 1978

By C. Clark, J. Seymour, D. Benton

"National Institute for Occupational Safety and Health NIOSH is conducting research on jackleg use and related accidents in underground metal mines. This paper provides an analysis and overview of jackleg drill usage, accidents, operational characteristics, and alternatives, based on information from injury reports, legacy research, stakeholder input, and published literature. Jackleg drills are involved in more ground fall accidents in underground metal mines than any other drill. Jackleg-related injuries are most prevalent at the face in the course of installing initial ground support. Alternatives to jacklegs for drilling and bolting under incomplete support in narrow underground openings are not yet available. Small mechanized bolting equipment needs to be developed to address jackleg-related accidents and improve safety at mines where jacklegs are being used. JACKLEG DRILL Description The term “jackleg drill” is a generic name for a class of handheld, rotary, percussion rock drills that are equipped with an attached reaction leg to provide stability and thrust for the drill (Figure 1). All of the drill and leg controls are located near the operator’s handle at the rear of the head portion of the drill. Jacklegs are classified according to the bore size of their pneumatic pistons which normally range from 6.03 to 8.26 cm (2.375 to 3.25 in) [Kurt, 1982; Clark, 2012]. Jacklegs typically weigh 460 N (103 lbs), but their weight can approach 535 N (120 lbs) after they are fitted for operation with drill steel and air and water hoses [McKibbin and Clark, 2001]. In underground mines, jackleg drills are commonly used to drill 3.8-cm (1.5-in) diameter holes 1.83 m (6 ft) deep in rock. Application The jackleg drill is primarily used in underground mines when the size of the ore body, the ground conditions, or the mining method do not permit large openings to be mined using mechanized equipment (e.g., narrow vein mining). Jacklegs are used to drill blast-holes for explosives and also holes for installing ground support. These versatile drills are used in nearly all phases of mining including exploration, development, production, and maintenance [Kurt, 1982; Williams et al., 2007; Chen and McKinnon, 2012]. The jackleg is used to drill holes in rock using drill bits attached to hollow steel bars called drill steels (rotary percussion drilling). After the hole is drilled, the jackleg can be used to install different types of ground support components, depending on the ground conditions and the specific ground support measures that are needed. For example, the jackleg can be used to install expansion-anchor rockbolts or resin-grouted rockbolts using the drill’s rotary-motion feature. On the other hand, the jackleg can also be used to install friction-type Split-Set™ rockbolts using the drill’s percussion (hammer-motion) feature. As shown in Figure 1, various washer-like bearing plates can be installed along with these bolts to provide additional ground support and to help secure surface control products, such as wire mesh and shotcrete that are in turn used to retain small, loose material between the bolts [Clark, 2012]."

Jan 1, 2016

By R. R. Klimpel

The efficiencies of plant scale comminution processes are often evaluated by various indices that are calculated and/or measured somewhat independent of the performance of any associated downstream froth flotation processes. In order to compare some specific comminution factors such as energy utilization, media consumption, equipment utilization time, etc. comparisons of comminution efficiency independent of flotation behavior are appropriate. However, as more and more detailed plant level information is gathered on the joint and highly interactive nature of comminution and froth flotation, it is becoming increasingly obvious that knowing and using simple efficiency indices are not enough. What is needed are more performance related measures of the efficiencies of the combined size reduction -froth flotation system for effective plant level economic optimization to occur. The purpose of this paper is to present some examples of important interactions that influence the joint efficiencies of size reduction and froth flotation processes.

Jan 1, 1998

By T. J. DeMull

The business of heap leaching requires accurate forecasting of metal production from the heaps. Business forecasts typically follow a format that project periodic (monthly, quarterly, or annual) product shipments based on anticipated operating results, e. g., tons of ore placed, grade of ore, and rate of leach extraction. Since revenue and cash flow are dependent on the metal production stream, forecasts of metal production are very important for project evaluation and business planning purposes. Nevertheless, production forecasts, particularly for new heap leach projects, have been prone to errors. The present paper identifies some of the pitfalls that would be encountered in preparing production forecasts for new heap leach operations and provides a checklist of considerations to assist in preparing a forecast. Also, the paper presents a case study of copper production forecasting used for the Sanchez Project, a heap leach operation located near Safford, Arizona, that is presently under development by AZCO Mining, Inc.

Jan 1, 1995

By James E. Lawver

The agriculture industry has made great strides during the past decade to increase agriculture yields through increased use of fertilizers. Increased use of fertilizers may prevent or at least delay mass starvation due to the alarming increase in world population. Phosphate was added to soil as a plant nutrient in the forms of calcined bones at least 2 000 years ago, (1) and man has used phosphate minerals as a source of fertilizers in one form or another for at least 100 years. During 1977 the world produced about 116 million metric tons of phosphate rock, with about 86% used for fertilizers and another 4% for animal feed supplements. More than three-fourths of the total production comes from the United States, Morocco, and the Soviet Union. From a mineral beneficiation point of view, the major sources of phosphate rock and the methods of beneficiation can be classified as follows. Marine deposits not containing appreciable carbonate minerals, marine deposits requiring a francolite carbonate mineral separation, igneous deposits not containing appreciable carbonate minerals, and igneous deposits, requiring an apatite carbonate mineral separation.

Jan 1, 1978

By James R. Dunn

The mineral industry" has made and will continue to make important contributions to the growth of our economy. However, the industry is presently under continuous and increasingly severe attacks by organizations and individuals interested in the preservation of our environment. Yet neither the public interest value of preservation nor the public interest value of our mineral industry is known. In the absence of such values, judgments about best land use where minerals are involved are nearly always made on emotional grounds. An example of the sort of problem that has been created is in the New York Metropolitan Area. Because of institutionally-created shortages stemming largely from zoning decisions and building over deposits, the effective cost of fine aggregate delivered at dockside at Manhattan rose from $2. 65/cubic yard in July, 1969, to $4.10/cubic yard in May, 1970, this in spite of approximately ;l0,000 years of reserves on Long Island. The cost of fine aggregate for New York City alone has "Increased over $S million annually within one year, with the cost increase for the Tri-State Metropolitan Area (coastal Connecticut, New Jersey, and New York)" exceeding $10 million annually. The ab0ve situation has created a cost increase which is clearly the result of non-conservation of a mineral resource. That is, in readily measurable values, it Is costing the public about $10 million per year because good conservation practices were ignored-a public-interest loss. Admittedly, this is not the whole story because the public is simultaneously obtaining other values from the land surface that would otherwise have had to be dedicated, temporarily to be sure, to mineral recovery-a public-interest gain. However, the point is that we do not know where the balance lies-the net public interest value; it may lie one way for deposits zoned out of existence by a growing suburb, another for areas designed as permanent greenbelts, and still another for areas under new highways

Jan 1, 1971

By P. W. Finck

Detailed mapping, using a large diameter diamond-drill in conjunction with high resolution reflection seismics, has increased known resources of kaolin clay and glass-grade silica sand from scattered deposits generally < 1 km2 to large areas of Cretaceous valley fill up to 130 m thick. Detailed chemical and physical analysis of drill core is presently underway. Silica sand deposits intersected in this study are up to 99.4 % SiO2 without beneficiation. Light grey to white kaolin clays identified by XRD and DT A have concentrations values (without beneficiation) up to 47.28% SiO2, 37.44% Al2O3, 0.45% Fe2O3, 0.49% K2O, 0.07% Nap, 0.07% CaO and 0.39% MgO.

Jan 1, 1996

By L. A. Alcorn, H. E. Camargo, G. Gwaltney

"Una de las enfermedades más extendidas en la industria minera es la pérdida de audición inducida por el ruido. La exposición de los mineros a niveles de ruido superiores a los niveles de exposición permisibles resulta en la pérdida de audición de aproximadamente el 80% de los mineros del carbón a la edad de jubilarse. En este contexto, el Instituto Nacional para la Seguridad y Salud Ocupacional (NIOSH, por sus siglas en inglés) está realizando investigaciones para desarrollar controles de ruido aplicados a los sistemas de minado de tajeos largos. Este método de minado es usado para extraer la mitad de la producción nacional de carbón subterránea. A partir de las mediciones en campo, se determinó en investigaciones anteriores que los componentes dominantes que generan sonido en el cizallador de un sistema de tajeos largos son los dos tambores de corte utilizados para extraer el carbón. Debido a las dimensiones y complejidad de los sistemas de minado de tajeos largos, el proyecto NIOSH desarrolló un modelo de elementos finitos validado del tambor de corte para utilizarlo en la predicción del sonido generado por este debido a las fuerzas de excitación experimentadas en las operaciones subterráneas. Este mismo modelo se utilizará para desarrollar controles de ingeniería para el ruido del tambor. Las fuerzas de excitación surgen de la interacción de la broca de corte y el carbón, y se transmiten al tambor de corte a través de los sujetadores de brocas. Debido a las condiciones adversas en el frente y la falta de instrumentación aprobada para uso subterráneo, las fuerzas operativas de corte de carbón no han sido evaluadas anteriormente. Para este fin, NIOSH, en colaboración con la Universidad Tecnológica de Michigan, desarrolló una broca instrumentada autónoma con seguridad intrínseca para medir estas fuerzas. Este artículo describe el desarrollo de la broca instrumentada y la medición de las fuerzas operativas de corte de carbón en tres minas. Las mediciones revelaron que las fuerzas tienen un espectro plano, algo característico de la naturaleza del impacto de estas fuerzas, hasta alrededor de 100 Hz. Por encima de esta frecuencia "cutoff", la magnitud de la fuerza disminuye a una razón proporcional al cuadrado de la inversa de la frecuencia."

Jan 1, 2014

By T. J. Close

On September 10, 1991, Secretary of the Department of Interior Manuel Lujan deleted the Silver Peak Range North Wilderness Study Area from the list of U.S. Bureau of Land Management lands in Nevada to be considered for wilderness designation. This decision was based in part on the U.S. Bureau of Mines mineral investigation of the wilderness study area which found that it has indications of precious metals resources. The following is a summary of the results of that mineral investigation. The study area lies between the Silver Peak and Dyer mining districts of west-central Nevada. The Silver Peak mining district, to the east, has a long mining history dating back to 1907 when precious-metals-bearing veins were discovered. The major producer in the Silver Peak district was Sunshine Mining Company&apos;s Sixteen-to-One silver mine. During the Bureau&apos;s study the Sixteen-to-One mine was operating; it has since been idled due to low silver prices. Precious metals-bearing veins were discovered in the Dyer district, to the west of the study area, in the 1860&apos;s. Mineral activity in Dyer district consisted mainly of prospecting. The Silver Peak study area itself has no mining history and contains only a few mining claims, but the Bureau examined 13 mineralized sites, most previously unknown and unclaimed. These sites are along two zones that cross the study area from the Silver Peak to the Dyer mining district. The two zones transect a volcanic center of fractured and altered rocks that contain epithermal veins of quartz, calcite, and jasperoid with gold, silver, and base metals. At the surface these veins are poorly defined and poorly mineralized. The more than forty veins examined in the study area are as thick as 17 feet and as long as 1,000 feet. Samples from surface exposures of these veins contained as much as 0.02 ounce per ton gold, 2.1 ounces per ton silver, 1.0 percent copper, 2.6 percent lead, and 0.4 percent zinc. Analyses of the Bureau data disclosed no vein large enough or of high enough grade to be classified a mineral resource. However, most do have indications of silver-and gold-bearing resources at depth. Subsurface exploration had to be done on the vein at the Sixteen-to-One mine to outline reserves (a vein averaging about 22 feet thick and containing 6-to 7-ounces per ton silver); the same is true of veins in the Silver Peak Range North Wilderness Study Area.

Jan 1, 1993

By S. K. Kawatra

A high calcium fluid-bed combustor ash has been shown to be an effective binder at dosages of 1 to 2% of the magnetite concentrate weight. Magnetite pellets 1.3 cm (1/2 inch) in diameter were produced with dry crushing strengths greater than 22.3 Newtons/pellet (5.0 pounds force/pellet), which is comparable to the results produced using conventional bentonite binder. The effectiveness of fly-ash-based binders was considerably improved when calcium chloride was added as an accelerator. Addition of calcium chloride at a rate of 0.1 to 0.2% of the total powder weight increased the strength of dried pellets by as much as 22% compared to the strength of pellets made using fly-ash without accelerators.

Jan 1, 1997