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By D. M. Avant, A. J. Solomon, S. M. Pickering, W. R. Fox

Introduction Most high purity silica is produced from crystalline quartz, generally from sand. However, there is a small area of southern Illinois where a porous, friable white chert rock is found that is very different in physical form from quartz sand. This microcrystalline material, commonly referred to as tripoli, is more easily ground to micron sizes than sand. Although of similar Moh's hardness, microcrystalline tripoli is less abrasive than either ground quartz sand or many synthetic abrasives. Location The southwestern corner of Illinois is underlain by extensive deposits of very porous chert; in some places the material is quite white. Two companies, Illinois Minerals Co. and Tammsco Inc., mine and process this white material. The Illinois Minerals plant is located at Elco, and the Tammsco plant is in Tamms, IL. Both companies mine from various locations within a 10-mile truck haul of their plants. Production from this district has been continuous since at least 1915. Malvern Minerals Co. mines and processes a generally similar microcrystalline, friable novaculite near Hot Springs, AR. Geology The southern Illinois white tripoli area is on the southern flank of the Illinois Basin. The commercial silica zone is a facies of the Clear Creek chert of Lower Devonian Age. To the north, where it occurs deep in the basin, the Clear Creek is a siliceous limestone. In the mining area, thin overburden has allowed access by surface ground water, which has leached away the carbonate content and left a quite pure silica residue. Fossils characteristic of sea bottom deposition, such as brachiopods and trilobites, are occasionally encountered in mining. The structure of the mining area is poorly known, due to infrequent outcrops. Strata in most mines are inclined at dips of 5° to 20°. There appear to be occasional high angle normal and reverse faults, but these are seldom of any significance in mining. The friable white silica zone mined in the Clear Creek chert is overlain by dark brownish-red chert and siliceous shale. Exploration drilling to date has not encountered the base of the microcrystalline tripolitic zone. Chemical content Leaching by ground water solution has removed virtually all the carbonate from the original siliceous limestone. Impurities encountered are red to yellow iron oxides, aluminous clays, and occasional black manganese oxides. The silica has no detectable formula water. A typical chemical analysis and physical properties are listed in Tables 1 and 2. Mineralogy and crystallinity Southern Illinois friable tripoli appears amorphous under the polarizing microscope. No crystal structure and only occasional, vague, patchy anisotropism is evident. However, the material gives an excellent quartz X-ray diffraction pattern. Thus, so far as X-ray mineralogy is concerned, the material is clearly

Jan 1, 1987

By James Boyd

JAMES BOYD 29.1-STAFF-AND-LINE ORGANIZATION Industrial organizations are established primarily to coordinate the activities of many individuals working toward a specific goal. In mining, the goals can vary widely, and the skills necessary to reach them likewise will vary from operation to operation. It is essential to keep in mind the principal point that an organization embodies the necessary skills which supplement each other and achieve a given objective. Those who direct such an organization are grouped together as "management" and accept the responsibilities for the regulation, administration, supervision and guidance of the enterprise. Those who comprise the "administration" and have supervisory authority are referred to as the "executives." In the early days of mining it was common for one executive to exercise virtually complete control over the entire organization, and direct its operation from a central office. However, the science of management has advanced significantly since then. Mining organization administration now allocates increased authority and flexibility to those in direct-line responsibility, and organizes competent people in specialized fields to provide supervisors with guidance where it is needed in day-to-day operations. Few mining companies today are confined to one operation. Therefore, highly developed skills can be provided in the staff which assists management. This is known as staff-and-line organization, illustrated, in general, in Fig. 29-1. Each operation requires diverse skills for the carrying out of specific functions. The acquisition and training of those with such skills is an important operation in assembling organizations. An organization normally is modified to accommodate individuals rather than being a "hard and fast" mold into which people are fitted. The modern manager is inclined to organize to minimize central direction, with delegation to line executives, providing staff whose day-to-day operations, in cooperation with line executives, coordinate a continuing drive toward the organization's objectives. The staff officers, therefore, tend to become what could be described as parts of the president's brain, dealing with specific areas requiring certain skills. They do not necessarily direct operations, but watch them to be sure that the skills which they have themselves developed can be transmitted to line operations by persuasion rather than by direct authority. The elements of management requiring staff assignments are: 1. Planning, which, at staff level, is only a coordinating activity. Planning is done at all levels in the organization. 2. Engineering. 3. Finance. 4. Control. 5. Personnel and industrial relations, which set personnel policies, including salary plans and the means of handling relations with the unions. 6. Research, which, in a modern organization, is essential to progress and needs to be overseen at the top. 7. Legal staff to see that all operations of the company are provided with sound legal advice, and that the company's policies stay within the law.

Jan 1, 1973

By Malcolm J. A. Swallow

In June 1997, Mount Polley Mining Corp., a division of Imperial Metals Corp., completed an 18-kt/d (20,000 stpd) gold-copper mine in central British Columbia. Fast-track construction and extensive off-site construction were combined with an aggressive project schedule to build the mine in one year. This was three months ahead of schedule and 7% below the original budgeted cost of C$123.5 million (US$86 million). The Mount Polley Mine was the first of a crop of new open-pit mines in British Columbia. The Mount Polley deposit has been explored since the mid-1960s when it was known as the Cariboo Bell property. From 1988, Imperial Metals completed drilling and metallurgical testing on the deposit. This led to a positive feasibility study and the issuing of a Mine Development Certificate in 1991. The project was later shelved due to falling metals prices and the strength of the Canadian dollar. In late 1994, Imperial merged with Bethlehem Resources Corp., bringing a strong project team to the company. The deposit was then re-evaluated, ore reserves revised and additional metallurgical testing was performed. The result was a revised project plan. It indi¬cated that a financially feasible gold-copper mining op¬eration could be constructed at Mount Polley operat¬ing at 18 kt/d (20,000 stpd). In May 1996, an agreement was reached with Sumitomo to jointly fund and develop the project. By early 1996, final plans and permits were being prepared for construction, scheduled to begin in June 1.996. On-site work commenced on May 28th, 1996 following lifting of the road restrictions. Mount Polley Mining acted as its own project manager. Construction was completed in June 1997. Plant runup took place in July and full production began in August. Through the use of off-site construction and the careful selection of contractors who cooperated to complete some 12 major contracts, it was possible to reduce the mine and mill construction time from 16 to 13 months. Off-site construction for all possible aspects of the work and the use of used milling equipment allowed significant savings in overall capital costs of construction. Total costs for the mine, mill and tailings dam equated to C$6,100/t/d of throughput. The mill design incorporates several innovative features that will aid maintenance and allow flexibility of operation. The operation is designed as a closed system and meets the latest environmental standards. Concentrate is shipped by truck to the port of Vancouver. Revenues for the mine come from the mine's production of about 3.1 t/a (100,000 oz/year) of gold and 10.8 kt/a (24 million lbs/year) of copper during the first four years of the 12-year mine life.

Jan 1, 1998

By Donovan F. Symonds

INTRODUCTION The selection of the optimum coal preparation plant flowsheet is a vital part of the development of a new plant or the expansion of an existing facility. Selection of an inappropriate flowsheet or individual equipment items can result in costly production losses, or needless expenditures or redundant or oversized equipment. The accuracy of the flowsheet selection process is, like most decisions, heavily dependent upon the amount, reliability, and quality of the database. A flowsheet which is based on simple borehole information from an area that has experienced little or no previous mining activity must necessarily include significant allowances for uncertainties. However, a plant which is to be built at an existing mine with good information on run-of-mine (ROM) coal quality, as well as bulk washability data and accurate projections of future quality, can be optimized. The following chapter will describe the processes which should be followed to select the most appropriate flowsheet for each unique operation. They include: 1. Examining and adjusting the washability database to reflect the ROM feed. 2. An evaluation of clean coal specifications. 3. Selection of the level of washing required. This includes no washing, if the coal is already at the desired specification, all the way through to complex total washing circuits for metallurgical grade coals. 4. Selection of the appropriate circuit such as dense medium bath vs. Baum jig. The most appropriate circuit is generally determined on the basis of economics. An approach for performing the evaluation will be desired. 5. The steps that need to be followed to develop a balanced plant flowsheet. ADJUSTING WASHABILITY DATA It is not unusual to have as many as 10 to 20 sets of washability information available for a particular mining property. These may be a combination of core and bulk samples or all bulk samples. In the latter case, they may also be face and/or ROM samples. It is necessary to reduce all of this information to a single set of washability data that is representative of the mean feed to the proposed preparation plant. This set is used to compare the clean coal yield and quality characteristics of the various flowsheet options. The term "representative" has some serious negative connotations. It is recognized that ROM coal quality will vary throughout a mine. However, over a period of 250 to 350 days per year, certain trends can be established. If possible, this "representative" sample should be close to the coal quality of the mean daily sample in terms of raw ash and sulfur contents, clean coal yield, and clean coal ash and sulfur content. If possible, this sample should be within the

Jan 1, 1991

By J. B. Gwiazda

Introduction Thick seams constitute a considerable portion of Polish coal reserves. In producing mines and those under construction, the reserves where the height is more than 4.5 m (15 ft) total about 24v0 of all the hard coal reserves. The reserves that are under urban and industrial areas can be extracted using stowing methods for surface protection. About 50v0 of thick seam reserves can be extracted by caving methods. Thick seam mining methods Thick seams are usually extracted by multilift methods. There are some methods of thick seam mining that generally can be divided into caving and stowing methods. The stowing method is more expensive, but must be used when mining to protect surface features. The more known methods of thick seam mining include: • extraction of thick seam in ascending order with stowing; • thick seam mining in descending order with consolidated stowing; • thick seam mining with gob consolidation; • thick seam mining in descending order with roof caving; • sublevel caving thick seam mining system; and • thick seam mining system using an artificial roof. • Thick seam mining with introduction of an artificial roof The most advantageous method of thick seam mining is the method using an artificial roof. The artificial roof usually consists of wire mesh. Such wire mesh must be durable and must prevent small rock fragments from passing through. The mesh is usually made of steel properly protected against corrosion. The artificial roof is placed on the coal floor of the top slice (Fig. 1). Caving rock falls on the artificial roof and is thus separated from the coal. The next slice is extracted under the artificial roof. The producing face of the next slice must progress within 10 m (33 ft) behind the front of the first slice. As the second producing face progresses, the wire mesh moves down on the coal floor and may be used as an artificial roof for the next slice. Thus, one artificial roof allows the extraction of several consecutive slices. Application of the artificial roof allows for clean extraction and reduces coal losses. It also eliminates the hazard of spontaneous combustion. Introduction of the artificial roof has been limited due to a lack of artificial roof laying equipment. Manual laying of wire mesh is a labor-intensive operation, and it delays face progress, resulting in poor productivity. To eliminate these problems, artificial roof laying equipment was designed at the Polish Central Mining Institute. The support and the method of laying operation is covered by a patent. Artificial roof laying powered support To extract thick seams using an artificial roof; four-leg shield supports with lemniscate linkage were developed (Fig. 2). This shield is used in the first top

Jan 1, 1988

By T. W. West

INTRODUCTION This paper presents an assessment of conventional flotation technology. In addition it presents some ideas which can be used to change the perception of what may be done with conventional flotation equipment to maximize its efficiency. Perspective of Conventional Flotation Technology 1. Flotation in many coal preparation plants is defined as something between a necessary evil and a non-viable concept because: -Too much art is required on a continuous basis to achieve uniformly acceptable results. -It is expensive, the capital cost in dollars per ton of circuit feed for flotation and dewatering is high. -It is a difficult process to use when SO2 reduction governs system design and equipment selection. -It creates a product (fine coal froth) that is difficult to dewater in the presence of BTU/lb as-received pressures. -It is a difficult process to control from a management standpoint, there are no dependable set points to rely on. 2. Many froth cell circuits are 0.5m x 0 (nominal 28 M x 0) feed which is sourced from screen/cyclone underflows. The original intent was to obtain maximum yield at acceptable product quality and moisture using disc filters. (See Figure #1) 3. An alternate to conventional flotation and its perceived to be limits of efficiency, capital costs, etc. is to move towards such developing flotation technologies as column flotation, reverse flotation, and microbubbles. A lot of work is being done to move these concepts thru pilot stages into full scale, commercial plant operation. The majority of the coal producers and coal preparation plant designers view these concepts as being in the development/pilot plant stages. OBJECTIVES Based on the preceeding comments of the perspectives of the coal producers and plant designers, the options are limited. They can make do with what they have available to them in the way of industry standard equipment and practices or they can move forward with developing technology. I feel there is a third option: what can we really do today with what is available to us, without reinventing the wheel? APPROACH 1. When processing coal against ash and SO2 restrictions, the fine clean coal stream can be the best stream on the clean coal conveyor due to the release by size and the ability to create a high BTU/low sulfur (dry basis) product. 2. Targets: -Consistent raw coal size consist in the plant feed . -Do not put pyrites in the froth cells. -Adjust criteria defining good flotation away from yield towards maximum BTU recovery at minimum ash. -Limit the froth cell feed size consist to 0.15 mm x 0 (nominal 100M x 0). -Establish and maintain a correct, consistent percent solids in the froth cell feed. -Select flotation reagents with care. -Introduce reagents in the proper sequence.

Jan 1, 1988

By W. Haupt, M. Thormé, H. J. Ertle, K. Reim

Though Germany has a very old mining history, her experience in uranium mining only started in the late sixties. Today in the Federal Republic of Germany (FRG) there are only 5 small mines in the exploration stage, namely Menzenschwand and Müllenbach in the Black Forest and Mähring, Popenreuth and GroBschloppen in northern Bavaria. In all these exploration mines much development is required to define shape and size of ore bodies. Mining engineers, government authorities and environmentalists alike are very much concerned about environmental safeguards and protection of mine workers against radon and its daughter products. Miners are affected by internal and external radioactive exposure. In general the external [f3]- and [µ] -exposures can be considered as small in comparison to the internal exposure and are therefore not discussed in this paper. The internal exposure is caused by the inhalation of radon and its daughter products and is relevant to the lung as the critical organ. The nobelgas radon is inert and does not from compounds with other elements easily. Contrary to the physical half-life of 3,8 days the biological half-life of radon is only 10 to 20 minutes. During the rentention time in the body only approximately 1 % of the long-lived decay products are retained in the system (SCHOGER, 1976). In this connection is it important that the radon resorption as well as the radon secretion varies individually and depends to a large extent on the age of the person (SCHOGER, 1960). RENOUX et al. (1978) have determined that the greatest part of the a(-activity in the air is attached to aerosoles with a diameter of 0,4/14. The radiation exposure of the lung by radon is negligible if compared with the exposure by short-lived decay products. For this reason one has introduced the concept of the potential [o](-energy (P) of the short-lived radon decay products, which means the total [ct]-energy, which is produced when an atom decays in the decay-series down to the long-lived lead-210. [ ] The unity of the potential [o]-energy concentration in the SI-system is 1 j/m3 air. In radiation protection however a specific unit is used namely the working level (WL): [ ] The WL-unit, though internationally recognised has not been introduced officially in Germany. Because of the large amount of tunneling still to be done in the FRG, the various mines departments responsible for safety and health in mining ask searching questions such as: - What are the laws governing radon emanation in tunneling? - Can workers be adeguately protected against radiation hazards? - How should one drive through high grade uranium ore? - What happens if the ventilation system breaks down?

Jan 1, 1981

By Henry N. McCarl

From the earliest use of crushed and broken stone as landfill for eroded gullies in trails and roads, to the mixing of sand and gravel with cement to make concrete, men and women have found mineral aggregates to be useful materials in satisfying human wants. Crushed stone, sand and gravel, volcanic cinders, pumice, manufactured lightweight aggregates, slag, cinders, expanded perlite and vermiculite, and a great array of recycled materials such as grog (broken or crushed brick) and fly ash have served as mineral aggregates. These materials have provided bulk and strength in portland cement concrete, bituminous concrete, road base, fill, concrete block, and plaster and stucco finishes. Mineral aggregates provide many special characteristics such as compressive and tensile strength, surface textures, weight and density, thermal and acoustical insulation, abrasion resistance, and impermeability to various concrete products and mixes. While most materials used as mineral aggregates are consumed on the basis of their low unit values, the large volumes extracted in the United States each year make them one of the most valuable mineral resources in current production. In 1960, US production of construction aggregate was just over a billion tons per year (Meyer and Zelnick, 1991). Two decades of accelerated interstate highway, residential, and commercial construction brought the total annual production of mineral aggregates to roughly 1.4 Gtpy by 1970 and just over 1.6 Gtpy by the late 1970s. General economic and related construction slowdowns in the early 1980s saw annual US production of aggregates fall to below 1.1 Gt in 1982, and then rise to just over 1.7 Gtpy in 1990, a new peak in mineral aggregate production and use. Per capita annual consumption of mineral aggregates was approximately 5.68 t/capita in 1960, 6.89 t/capita in 1970, rose to a high of 7.25 t/capita in 1979, and has since settled to just under 7 tpy for every man, woman, and child counted in the United States Census of 1990. The value of these materials came to approximately $9 billion in 1990. During the period 1960-1990, roughly half of all mineral aggregates were used in the construction of residential, commercial, and industrial structures, and the remainder was consumed in highways, bridges, and other transportation facilities such as railway roadbeds, airports, and water-related projects (Meyer and Zelnick, 1991). During the period 1988-1992, public works (highways, waterway projects, road maintenance, etc.) represented closer to 60% of annual mineral aggregate demand with residential and non-residential construction approximately 40%. The growing market share of public works projects has been mostly due to the dramatic slowdown in residential, commercial, and industrial construction during the 1988-1992 period.

Jan 1, 1994

By Palmer C. Sweet

Kyanite. andalusite, and sillimanite are anhydrous aluminum silicate minerals, and they have the same chemical formula, Al2SiO3. Dumortierite and topaz are also classified as aluminum silicates although they contain boron and fluorine respectively. Mullite (a rare mineral named for its discovery site, the Scottish island of Mull) is produced when kyanite, andalusite, or sillimanite are heated. Synthetic mullite, also classified as an aluminum silicate, is formed by melting alumina and silica, bauxite, and kaolin or alumina, kaolin, and kyanite, depending on the type of synthetic mullite desired. These materials are either sintered in rotary, periodic, or tunnel kilns, or fused in an electric arc furnace. The world's largest producer of kyanite is the United States. Domestic kyanite is presently produced from one company at two sites in Virginia; Kyanite Mining Corporation mines kyanite from Willis Mountain and adjacent East Ridge in Buckingham County in the central Piedmont province of Virginia. Internationally, kymite is produced in Australia, Brazil, India, Kenya, Sweden, and Zimbabwe; the former USSR also produces kyanite (Fig. 1). Andalusite is produced by Piedmont Minerals Company, Inc. in the Piedmont province near Hillsborough, NC. Andalusite is also produced in France, India, the Republic of South Africa, and Spain (Fig. 1). Sillimanite is produced in Australia, Brazil, India, Spain, and the Republic of South Africa; the former USSR is also thought to be a major producer (Fig. 1). Some of the countries produce only for domestic use. Synthetic mullite, made by sintering and by electric arc fusion, is produced by Mulcoa (Mullite Company of America) in Andersonville, GA, and by Washington Mills Electro Minerals Corporation in Niagara Falls, NY. Annual world production of kyanite, andalusite, sillimanite, and synthetic mullite is approximately 672 727 tons (Potter, 1988). GEOLOGY Mineralogy Kyanite is a blue to light-green, triclinic mineral that occurs in long, thin-bladed crystals and crystalline aggregates in gneiss, schist, and pegmatites. The mineral has a hardness of 5 parallel to the long axis of the crystal and a hardness of 7 across the crystal. Andalusite is a yellow, brown, green, or red orthorhombic mineral that occurs in thick, almost square prisms in schist, gneiss, and hornfels. Gem quality andalusite exhibits a strong pleochroism; brownish-green in one direction and brownish-red perpendicular to it. Andalusite also occurs in placer concentrations where it has weathered out of rock. Sillimanite is a brown, pale-green, gray, or white orthorhombic mineral that occurs in long, slender, needlelike crystals in schist and gneiss. Chemical and Physical Properties Chemical and physical properties of kyanite, andalusite, and sillimanite are noted in Table 1. Kyanite is the only mineral that irreversibly expands when heated (calcined to produce mullite) and may offset the shrinkage of most ceramic or refractory ingredients when heated.

Jan 1, 1994

By Keith G. Papke

Industrial-mineral mining started early in the history of the State when salt was extensively mined for use in processing gold and silver ores, and borates were produced to meet most of the world's needs. After this start, industrial-mineral production grew slowly until World War II, mostly because of the remoteness of the State and the small population. Nevada now has a large and varied industrial-mineral industry. In 1983, 14 principal commodities were produced from 48 deposits; the total value of these materials was 168 million dollars. Nevada ranks first in domestic production of barite and magnesite; second in diatomite, gem stones, and lithium; third in fluorspar; and sixth in gypsum. Other materials produced are carbonate rocks, cement, clays, decorative and crushed stone, light- weight aggregate, perlite, pyritic soil additive, salt, sand and gravel, and silica. From 1978 through 1982 barite was the most important commodity; in 1983 diatomite surpassed barite in value of production. Most of the Nevada production consists of high-value commodities that are consumed out of the State. Approximately 430 significant deposits with 20 principal commodities are present in Nevada. This abundance can be attributed to the numerous and diverse geologic processes that have been operative. Seven major modes of origin have been identified: hydrothermal activity, sedimentation, combined hydrothermal activity-sedimentation, evaporative precipitation, brine formation, extrusion of igneous rocks, and alteration by ground water. The hydrothermal type accounted for 39 percent of the deposits, the combined hydrothermal-sedimentary type for 28 percent, and the sedimentary type for 13 percent. Nevada diatomite production is about 200,000 short tons/year valued at 30 million dollars. In 1984 three companies operated in Nevada producing diatomite from six open pits and processing it at four plants - one plant producing filter-grade materials and the others adsorbents and fillers. The diatomite occurs in about 60 areas, almost all in the western one-third of the State. The diatomites were deposited in long-lasting, fresh-water lakes in topographically closed valleys formed by basin-and-range faulting. About 85 percent of the barite mined in the United States is produced in Nevada. In 1981 the high point of production,-2.5 million short tons of bedded barite was produced from about 30 open-pit mines. About 120 significant bedded-barite deposits are known in Nevada; 38 of these have had past production of more than 25,000 short tons. The deposits are associated with marine siliceous rocks of Cambrian through Devonian age and occur in a zone about 300 miles long and 60 miles wide. Abundant evidence supports the theory that the bedded barite is of exhalative sedimentary origin.

Jan 1, 1987

By Jasinder S. Jaspal

The United States has very large coal reserves in seams that are less than 1065 mm (42 in.) thick. These reserves are often not mined because of the difficulty of working in low heights and, in most cases, the seams are beyond the technical or economical limits. It is estimated that the remaining reserves in 355 to 710 mm (14 to 28 in.) thick seams that are not faulted or intruded, dip less than 15° and under a cover of 610 m (2000 ft) or less are nearly 910 Gt (1 trillion st). This is a very large percentage of coal reserves in the United States (Unrug, 1985; DuCarme et al., 1990). The US Bureau of Mines is attempting to develop new techniques for mining 150 to 1065 mm (6 to 42 in.) thick coal seams. Research has focused on existing thin seam mining techniques, testing of small- and full-scale physical models of the Bureau's slot mining concept and computer modeling of the full-scale process. In 1986, only 21 % of the total US coal production came from -1065 mm (-42 in.) thick seams. Of that, 355 to 710 mm (14 to 28 in.) thick seams share of production was minimal, probably 5% or less (Mayercheck et al., 1990). This shows that the thin seams, particularly the seams 355 to 710 mm (14 to 28 in.) thick, have not been mined to the extent of the available reserves. Thin seam coal, generally, is of premium quality. As thicker seams are depleted, the mining of thin seams could become more important. Thus, there is a need to develop technology to mine these seams (J. Farinelli et al., 1987). A successfully applied technology could change reserve categorization. In the Appalachian Plateau there are 417 Gt (460 billion st) in 355 to 1065 mm (14 to 42 in.) seams. This represents nearly 9.2% of the US remaining reserves (Unrug, 1985). At depths of 152 m (500 ft) or less, the Appalachian Plateau has about 214 Gt (236 billion st) of reserves in 355 to 1065 mm (14 to 42 in.) thick seams. Other mining areas also have substantial coal reserves in this seam thickness category. Those, however, are not as attractive for mining as the Appalachian Plateau. In the past, most of the reserves of the Appalachian Plateau region were partially worked by contour and highwall auger mining. It is estimated that these mining systems had left some 40,230 km (25,000 miles) (Readers Digest, 1987) of unreclaimed highwalls. The Bureau recognized this situation. In FY1987, the agency initiated a research project to develop anew technology for mining thin seams of the Appalachian Plateau.

Jan 1, 1992

By Calvert D. Iles

Open-pit mines in the US and throughout the world are typically characterized by increasing operating costs and decreasing ore grades. Thus, companies must continue to improve their use of human and technological resources to remain competitive in the marketplace. Duval Corp. has historically been very sensitive to mining costs, in part because of relatively low grade copper-molybdenum ore bodies. These concerns have resulted in three haulage system generations at the 218 kt/d (240,000 stpd) Sierrita-Esperanza open-pit mine south of Tucson, AZ. Each generation has exceeded the performance of the one replaced. The latest system of portable crushers and conveyors reduces hauling costs by combining both hardware and technique. Savings are achieved not only bysubstituting conveyors for haul trucks, but also by permitting the crusher-convey or system to closely follow mining as the pit deepens and/or mining areas change location. The Duval system is capable of easy and inexpensive relocation in varying site configurations in relatively short time periods. Its implementation in active mining areas results in minimum disruption to both the mine operation and mine design. This haulage concept allows the mining engineer maximum freedom to design an open pit for profit rather than for equipment. Maximum savings with a portable system are achieved by minimizing truck haulage costs. At Sierrita, for example, the yearly estimated operating cost savings for each thousand feet of +10% truck ramp replaced by conveyors is about $1 million per portable crusher. A savings of $30 million could be achieved fora three-portable system overa 10 year period simply by reducing the average truck Iiftto the crusher by 30 m (100 ft), There is also the added capital expense of buying trucks to cover the additional 30 m (100 ft) of lift. Relocation costs are an important consideration in a portable system. Direct costs can become a significant operating expense if frequent relocations are necessary to take full advantage of potential haulage cost savings. A site preparation cost of $375,000, for example, would add an additional operating cost of 2.8¢/t(2.5¢/st) for a system handling 13.6 Mt/a (15 million stpy), assuming one move a year, In addition to the direct cost of site preparation, such as installation of retaining walls, apron feeder slots, and equipment pads, there is the cost of site renovation after abandonment. Indirect relocation costs, while less tangible and more dependent on specific mine design and scheduling, can be of significance. A slowdown in the mining rate or a less efficient mining plan can result from a site not being immediately available for mining after abandonment. Conversely, mining in narrow areas can be adversely affected if two or three month lead times are required for site preparation.

Jan 4, 1983

By Don Fisher, Jean Juilland

Introduction A section of the Federal Land Policy and Management Act of 1976 specifies the procedure for areas the US Bureau of Land Management manages that have wilderness qualities. In part, FLPMA specifies that within 15 years of its approval, the Secretary of the Interior shall review roadless areas of 20 km2 (5,000 acres) or more and roadless islands of public lands identified during the inventory as having wilderness characteristics described in the Wilderness Act of 1964. Further, the Secretary shall report to the President his recommendation as to the suitability of each area or island for preservation as wilderness. However, before any recommendations for, wilderness designation, mineral surveys shall be conducted by the US Geological Survey and the US Bureau of Mines to determine if any mineral values are present. And finally, a Presidential recommendation for wilderness designation becomes effective only if so provided by an Act of Congress. BLM Inventory Procedures To fulfill these legal requirements, BLM is inventorying the land it manages for wilderness qualities. Since the law sets special provisions for Alaska, BLM included in its inventory only the public lands it manages in the conterminous US. In 1980, after public input, BLM picked 967 areas to be considered as Wilderness Study Areas. All of the selected WSAs are in 11 western states and the areas total about 97,128 km2 (24 million acres). From these 967 areas, through its multiple-use planning system, BLM is making initial recommendations of areas to be considered suitable for preservation as wilderness. Those WSAs that BLM initially considers suitable for wilderness preservation will have mineral surveys conducted by the USGS and the USBM, to determine mineral values. Based on these mineral surveys and other resources information including wilderness qualities, the Interior Secretary will report to the President his recommendations on the WSAs suitable for wilderness preservation. To make the initial recommendation of suitability, BLM managers will need information about geology, energy, and mineral (GEM) resources as well as information about other resources. BLM has begun a GEM assessment program to provide its managers with that information. This program is designed to provide information for a WSA suitability decision process that aims to supply minimum necessary GEM information. In essence, the program will provide preliminary assessment of the mineral potential for each WSA. Assessing the WSAs To accomplish this, a two-phase program was designed. In phase one, only existing data are collected and used. In phase two, new data are generated and added to existing data. Phase two begins only if BLM geologists, mining engineers, or managers consider the information provided in phase one as inadequate. This avoids unnecessary work and expenses and allows the program to proceed without undue delay. Figure 1 shows the two-phase process, including BLM's GEM in-

Jan 10, 1983

By N. S. Dalal, V. Castranova, K. Van Dyke, V. Vallyathan, J. H. Kang

Previously we reported crushing or grinding crystalline silica results in silica-based free radicals on the particulate surface which can generate hydroxyl radicals in aqueous solution (1). Now we find that freshly ground silica is more cytotoxic to and a more potent activator of alveolar macrophages than similarly sized aged silica. Since the United States Department of Labor estimates that over 1.25 million American workers may be exposed to freshly ground crystalline silica arid nearly 60,000 may be at risk of developing some degree of silica-based occupational lung disease, then this is hardly a trivial problem. Occupations of concern include workers who come in contact with silica including miners of soft and hard minerals, stone quarry workers, glass workers and even millers who stone grind flour. Acute silicosis is manifested by inflammation, alveolar lipo-proteinosis, and the rapid development of respiratory disability that depending on the dose of silica can produce chronic silicosis which takes 20 - 40 years to develop. It is demonstrated by the appearance of concentric hyalinized nodular lesions and progressive development of dyspnea(3). Certainly the free radicals produced on the surface of freshly ground crystalline silica play a most important role in producing the acute and chronic symptoms of silicosis. When respirable-size freshly- ground silica (0.1 -- 5 microns in diameter) enters the deep alveolar spaces in the lung and contacts an aqueous environment, hydroxyl radical are generated and cellular damage is bound to occur. We have found that freshly ground silica can cause lipid peroxidation and lysis of erythrocytes(1). The objective of this investigation was to further elucidate the enhanced toxicity of freshly ground versus aged silica. It can be deduced from the data that not only is freshly ground silica more cytotoxic to alveolar macrophages but it is a more potent stimulant of these phagocytes. However the mere characterization of toxicity is not entirely helpful if there is not a useful means to detoxify the cause of the damage. We have identified an aqueously soluble substance that can be used in high dilution to detoxify the SiO(•) and Si(•) type of free radicals. This is the organosilane known as Prosil 28 (R). We have found that coating of the freshly ground silica can effectively reduce its toxicity. The importance of this observation is that such a coating could be used with water cooled drills. This may partially detoxify silica at the point of generation of the free radical, i.e., the generation of the fresh silica dust itself. Such a coating could be used in great dilution 1:103 or 1:104. The coating would be long lasting, inexpensive and should be non-toxic because of the great dilution.

Jan 1, 1991

By Jim Oehler

The US minerals industry, as well we know, has been hit hard by the recent recession and is faced with what is projected to be a slow recovery. Even so, there was an underlying feeling of optimism at American Mining Congress' International Mining Show in Las Vegas, NV, Oct 11-14. More than 25,000 people attended during a particularly rough financial year, dispelling fears that attendance would dip sharply below 1978's 30,000 plus tally. The equipment expositionheld every four years-was the largest show of its kind this year in the Western Hemisphere in terms of exhibit space, providing an extensive view of mining-related equipment. In addition to the nearly 700 exhibits occupying more than 445 hm2 (11 acres), 20 technical sessions were held covering topics ranging from minerals availability and the state of the mining industries to communications, computers, and accounting. Government officials were well represented, with six US senators and five US representatives participating in various convention functions. Sen. Paul Laxalt (R-NV) was the keynote speaker at the welcoming luncheon. Other senators involved in the show included Howard W. Cannon (D-NV), Pete V. Domenici (R-NM), James A. McClure (R-ID), Frank H. Murkowski (R-AK), and Steven D. Symms (R-ID). Representatives on the program were Joseph M. Gaydos (D-PA), Guy Vander Jagt (R-MI), Don Young (R-AK), Jim Santini (D-NV), and Ceil Heftel (D-HI). There were also many international vistors at the show, including exhibitors from Australia, Austria, Canada, England, Finland, Sweden, South Africa, and West Germany. Equipment Highlights Equipment and services featured at the exposition ranged from aerial mapping to wire rope. Aisle space alone between exhibits exceeded 8 km (5 miles). And the companies represented ranged from small businesses to large corporations. Some of the company products described here are representative of the many exhibitors in attendance. Atlas Copco's extensive display of rock drilling and tunnel and shaft boring equipment featured its Boomer H-201, the newest addition to its line of underground drifting rigs; the ROC 306, a new track-mounted, high pressure down-the-hole drill rig; a new hydraulic surface crawler drill, the ROC 712H, designed for small and medium-size holes in quarries and small open-pit mines; a computerized analysis system, CARE (see page 1570), designed to project productivity and operating costs for various mining operations; several electro-hydraulic loaders, including the new rail bound LM E60 and LM E80, and two Hagg-loaders-the 7HR and 10HR-that use two digging arms to rake and guide muck; a mechanized blasthole charging system; rock bolting equipment and its new Swellex roof bolting method; Sandvik Coromant drill steel and bits; and its new Jarva R200 raise boring machine.

Jan 11, 1982

By D. T. Iseley, David Bennett, Christopher Norris

The microtunneling test program is one of three main elements of the research project, "Trenchless Construction: Evaluation of Methods and Materials to Install and Rehabilitate Underground Utilities." The other elements of this project include an evaluation and demonstration of horizontal directional drilling technology and pipeline rehabilitation systems. The research is a Corps and Industry cost-shared project funded under the Construction Productivity Advancement Research (CPAR) program. The laboratory partner is the U.S. Army Engineer Waterways Experiment Station (WES), Geotechnical Laboratory. The industry partner is the Louisiana Tech University's Trenchless Technology Center. Industry participants are contributing over half the total cost of this research. The overall objective of the CPAR program is to improve productivity in the U.S. construction industry, thereby enhancing the competitiveness of the U.S. industry in domestic and overseas markets. The Corps and other federal and state agencies will benefit by realizing reduced costs, enhanced safety and better products and services as the products of this research program are developed, tested, and pushed into the market place. The microtunneling demonstrations and evaluations were performed during September and October 1992 at a specially constructed test facility built at WES in Vicksburg, MS. The test facility is 104 m (340-ft) long, 5 m (16-ft) wide, and 4 m (13-ft) deep. It was constructed, ironically, by first excavating a trench into which 6 different types of soils were placed and compacted in approximately 18.3 m (60-ft) long sections. The soil profiles include a lean silty clay (loess), a dry sand, highly plastic buckshot clay, wet sand, clay gravel and silt. The interfaces between soil profiles were sloped to simulate mixed face conditions as the machines exit one zone and enter another, and provided challenges to ground control and alignment and grade control during these transitions. Moisture and density tests were performed on all materials in each lift to assure uniformity. Horizontal inclinometers and 3 levels of settlement plates were installed at key locations in the test bed. The settlement plates and rods and the horizontal inclinometers, together with surface survey points, provided data to evaluate settlement and heave along the test section. Penetration resistance was measured in each section of the completed test bed. Strain gages were installed in 8 of the 0.6 m (24 in.) diam. Hobas pipe sections to measure strains in the pipe as it was being jacked into place. Steering jack loads, jacking thrust loads, and cutterhead torque were also measured during the drives. The results of these tests will be used together with other information to develop guidelines for conducting feasibility studies and selecting proper methods compatible with anticipated conditions.

Jan 1, 1993

23.1-SOURCE, POWER-SYSTEM ELEMENTS A. J. T HUM Basic considerations in providing power for mine production and collateral operations are: 1. Mining operations of any size normally use electric motors for driving all equipment except mobile service units. 2. The electricity for power may be purchased or self-generated, depending on the location, size and specific operating circumstances of the individual property. 3. The major elements of the power system will be the source, either an incoming transmission line from a utility in the case of purchased power or the power plant if self-generated. Energy for the power plant may be water, hydrocarbon fuels, waste heat or nuclear, which will govern the type of prime mover selected. 4. The electricity normally is generated in the form of alternating current and must be distributed to the points of usage. This usually requires a primary substation for transformation to suitable voltages and secondary substations at points of usage throughout the operations, The power is delivered from the primary to the secondary substations over transmission lines or cables, depending on distances, voltages and local conditions. 5. At the points of use, there will be starting and protective devices for each motor. In some instances, direct current will be needed and rectifiers of various types can be used to provide it. 6. The entire electrical system requires suitable switching and protective devices to prevent damage to the equipment in case of power failues or faults; also, in most cases, sufficient metering to establish the demand and amount of electrical energy consumed. 23.2-PURCHASED POWER A. J. THULI 1. Where public-utility or government-generated power is available, it usually is advantageous for the mine owner to purchase rather than generate. Purchased power generally will be cheaper and more reliable than operating a small generating plant except in some cases where waste heat is available as the source of energy and can be used to supply all or a portion of the power requirements. 2. If it is decided to purchase power, the owner usually must participate in the cost of constructing the connecting line from the closest existing utility line to his point of usage. If the connected load is less than 1,000 lip, it probably is best to let the utility provide the primary substation. For larger connected loads the owner can obtain a more favorable "primary voltage" rate if he provides the primary substation to receive the incoming power and transform it to the distributing and usage voltages. 3. The cost of purchased power usually is made up of a demand charge, deter¬mined by the maximum amount of power the customer takes during any 15-min period throughout a month, and a graduated energy charge for the kilowatt-hours consumed-that is, so much for the first block of energy based on the demand,

Jan 1, 1973

By G. Swartz, R. J. Brison, R. A. Wyman, J. P. Vandenhoeck, S. E. Khalafalla

Magnetic fluids are commonly composed of ultrafine submicron particles of magnetite (Fe3O4) dispersed in either a kerosene or a water carrier medium with oleic acid as a protective colloid. The unique property of these fluids is that when the magnetic particles are attracted to a magnet the carrier medium moves along with the particles so that the liquid also appears magnetic. The availability of a fluid whose gross behavior changes sharply in a magnetic field without affecting its rheologic characteristics is becoming critical for many technologic applications. About two gener¬ations ago suspensions of relatively large, micron-sized ferromagnetic particles in oil proved useful in clutches, brakes, and dashpots. These were called magnetic clutch materials, and their viscosities were highly dependent upon the applied magnetic field, in contrast to true mag¬netic fluids which retain their fluidic characteristics under all applied fields and field gradients. While the term "ferrofluid" was used by Rosensweig and Kaiser&apos; to designate a magnetic colloid composed of a dispersed magnetic ferrous material, the more general term, "mag¬netic fluid," is preferred. This is because these fluids may contain ferro- or ferrimagnetic substances, such as cobalt, nickel, gadolinium, dysprosium, or magnetic ferrites in carrier liquids, such as hydrocar¬bons (kerosene), silicones, water, fluorocarbons, etc. Preparation of Magnetic Fluids Magnetic fluids were first prepared by Papell and Faber, at the NASA Lewis Research Center, Cleveland, Ohio, by tumbling ferrite materials for several weeks in a carrier medium (such as kerosene) and a dispersing agent (such as oleic acid) with steel balls. Rosensweig et al.1 compared the stability of their ferrofluids obtained from both metallic iron and the magnetic oxides of iron, Fe3O4 and yFe2O3. They found that, although the saturation magnetization of iron is 3.5 times greater than that of magnetite, its colloidal solutions deterio¬rated much more rapidly. The iron particles were undoubtedly rapidly oxidized to a nonmagnetic state due to the enormous surface area of these colloidal particles. Because the properties of these fluids are highly dependent on particle size and may acquire opposite characteristics by small incre¬ments in that size, more controllable methods of preparation have been developed recently by Khalafalla and Reimers.6 In one method metastabilized pyrophoric wiistite is ground to colloidal size in a kerosene oleic acid mixture, and then it is disproportionated to colloi¬dal magnetite and iron at temperatures just below the eutectoidal temperature of wüstite stability (570°C); thus, t < 570°C 4 FeO t > 570°C Fe + Fe30, (1) Because of its antiferromagnetic characteristics, the precursor wüstite is much easier to grind than magnetite. Another method3 avoids grinding entirely and utilizes a peptiza¬tion technique from ferrous materials in the molecular state of aggrega¬tion. This latter procedure has resulted in preparation of strong fluids at considerable savings in cost.

Jan 1, 1985

By E. F. Schnitzer, C. Lidstone, D. Cramer, P. J. Wampler

The River Island mining site is located at approximately river mile (RM) 15 on the Clackamas River, a large gravel-bed river in northwest Oregon. During major flooding in February 1996, rapid channel change occurred. The natural process of meander cutoff, slowed for several years by dike construction, was accelerated by erosion into gravel extraction ponds on the inside of a meander bend during the flood. In a matter of hours, the river cut off a meander and began flowing through a series of gravel pits located on the inside of the meander bend. The cutoff resulted in a reduction in reach length of approximately 1,100 m. Erosion by bed lowering, knick point retreat and lateral erosion of upstream river banks occurred quickly. Within two days of the peak flow, 3.5 hectares of land and 105,500 m3 of gravel were eroded from the river bank just above the cutoff location. Much of this gravel moved a short distance downstream into the excavation. Reach slope increased from 0.0022 to approximately 0.0035 in the cutoff reach. Between 1996 and 2003, the knick point from the meander cutoff has migrated 2,290 m upstream, resulting in increased bed load transport, incision, and local lowering of the water table. In 1993, prior to the meander cutoff, transects were surveyed in the River Island reach upstream of the cutoff location. Resurvey of these transects and aerial photo analysis indicates that 96% of the knick point migration occurred during the first winter following meander cutoff. Connection of the flowing river to the off-channel ponds has had minimal effect on water temperatures in the mainstem Clackamas River. It is likely that this minimal change in temperature will decrease as ponds are isolated from active river flow by gravel bar deposition. Fish net-ting in spring 2002, suggests that salmonid use of the pond in the spring is minimal. The most abundant native species netted were large-scale sucker and northern pikeminnow. The most abundant non-native species netted was brown bullhead. Early regulation by state and federal agencies did not adequately evaluate potential impacts to the river and the floodplain; nor did it evaluate future impacts related to geomorphic processes and sediment transport. New permit evaluation methods, currently implemented by both Oregon and Washington, incorporate 1) river dynamism through historic river migration analysis; 2) stability of human structures in light of river dynamics; and 3) sediment transport and its impact on channel stability and dynamics. The gravel pit capture at River Island highlights the potential risks of mining in an active secondary channel of a large gravel-bed river. Mining deeper than the depth of the adjacent channel, within the active migration zone, may increase off-site impacts. In locations where multiple gravel excavations are present within the meander zone, a comprehensive reclamation and restoration plan should be developed which provides long-term channel stability within the natural variability of the entire river reach.

Jan 1, 2006

By William E. Foreman

Editor&apos;s Note: For purposes of uniformity throughout this book, Coal Preparation, 5th Edition, the editors have advocated the use of the U.S.A. Sieve Series of testing sieves (see Table 6-2) as the testing sieves of modem choice. The adoption and use of the U.S.A. Sieve Series and its forerunner, the Tyler Standard Screen Scale, has for over seventy-five years introduced uniformity into reports; has simplified the comparison of results; and has provided control for operation of modem coal preparation circuits. While a full explanation of the differences, and more importantly the similarities of these two measuring systems cannot be stated here, it is felt that a brief clarification of terms is in order. The difference between the U.S.A. Sieve Series and the Tyler Standard Screen Scale Sieve Series is the identification method. Tyler Screen Scale sieves are identified by mesh designation with the width of opening varying by the square root of two, or 1.414 times the width of opening in the previous sieve. The U.S.A. Sieves are identified by openings in millimeters or microns and also arbitrary numbers which do not necessarily mean the mesh count; this series uses width of opening variations in the order of approximately the ratio of the fourth root of two, or 1.189. Tyler Standard Screen Scale and U.S.A. Sieves can be used interchangeably, and to avoid confusion the nameplate of all Tyler Screen Scale sieves show the U.S.A. Number, while all U.S.A. Sieves show Tyler Screen Scale mesh equivalent numbers on the nameplate. INTRODUCTION Sizing is the process of separating mixed mineral particles into groups of particles all of the same size, or into groups in which all particles range between definite maximum and minimum sizes. This chapter applies the modem mechanical screen and the liquid-solid cyclone (hydrocyclone) to the process of sizing solid particles as applied to coal preparation. Screening is a mechanical process that separates particles by size. Modem coal preparation is made possible by efficient sizing. Sizing of coal is defined in terms of the opening through which an individual particle will or will not pass, or as two openings, the larger of which passes the particle and the smaller of which retains the particle. Screening accomplishes sizing by passing coal of a wide range of sizes through a series of screens, each of a decreasing size. The individual screen discharges are then directed into different screen products for subsequent sale or processing. Screening in modem preparation plants is done for the following reasons: 1. Removal of fine coal before a size reduction step. 2. Size separation of the coal into a coarse and fine fraction for sized products or for processing in coarse and fine coal circuits. 3. Recovery of heavy media from heavy media coal cleaning circuits.

Jan 1, 1991