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By Wilson Blake

A mathematical model based on the finite element method of stress analysis has been used to describe the behavior of the western wall of the Kimbley Pit as its slope was steepened from 45 degrees to 57 degrees. Theoretical stress changes because of slope modification are slight except at the toe of the modified slope. Magnitudes of stress created are small when compared with the strength of a competent rock. Resulting displacement patterns point out the need for determining the in situ state of stress at a site prior to excavation or modification. A comparison of model results with field measurements shows that, in general, the model has described the measured behavior of the west wall of the Kimbley Pit remarkably well.

Jan 1, 1968

By H. Knorre, A. Griffiths, J. Loroesch

Introduction Hydrogen peroxide is known to the mining industry as a powerful oxidant. able to attack and to destroy cyanide, the most important leaching reagent (Knorre and Griffiths, 1984; Griffiths, 1988; Griffiths, 1988). [ ] The most recent development, however, is the use of H2O2 as an oxidant in the cyanidation of precious metals. This application may appear to be a contradiction to the above mentioned detoxification process. This can, indeed, be the case if certain conditions are not considered carefully. Degussa has developed a new process to enable the application of H2O, in this field without having any detrimental effect on the cyanide. The incentive to seek an oxygen supplier like H2O2 instead of air was the fact that one of the most important conditions for the fast dissolution of gold is the presence of physically dissolved oxygen in the pulp (Kydryk and Kellog, 1954; Warstell, 1987). [ ] Complete gold recovery within a reasonable leaching time may only be achieved if the pulp is saturated with dissolved oxygen. Gold losses in leach operations mainly occur due to the following reasons: In some cases, the saturation of oxygen in the pulp cannot be achieved by aeration due to the difficulty to transfer oxygen from the gaseous into the liquid phase. This happens, for example, in pulps with a high viscosity. In such cases, even violent aeration only results in a low concentration of dissolved oxygen in the pulp. In any case, the starting phase of leaching requires the highest amount of oxygen. Therefore, it is especially important to raise the dissolved oxygen level to saturation in the starting phase. Peroxide assisted leach process (PAL) The intention of the process is to introduce oxygen in a liquid form. As a result of intensive research work, it could be shown that hydrogen peroxide can be used as a source of oxygen in the leaching of gold ores. To avoid side reactions, the following conditions must be applied: Hydrogen peroxide must be diluted before it is added to the pulp. The dosage of H2O, must be properly regulated based on the oxygen level of the pulp. An important part of the continuous O, control is a special oxygen electrode, which resists the extremely abrasive action of the pulp.

Jan 1, 1990

By R. Gong, R. Bhaskar

[Full-scale laboratory experiments were performed to evaluate the effect of ventilation and water spray pressure on the potential dust capture efficiency of a ventilation system comprised of blowing ventilation and an underboon scrubber. The tests were performed for a 1.52-m (5-ft) roof height and 2.36 m-3/s (5000 cfm) blowing ventilation volume, and a 2.44-m (8-ft) roof height and 4.72 m3/s (10.000 cfm) blowing ventilation volume at three face positions of the miner. The scrubber suction rate was varied for the tests to study the effect of scrubber flow rate on capture efficiency. The airflow patterns and scrubber efficiency were determined by performing tracer gas tests. Tracer gas was released through a manifold placed in front of the rotating miner drum. The gas was sampled in a grid fashion using a real-time multi-point gas sampling system. The capture efficiency of the scrubber was evaluated based an the peak gas concentration of the gas laden air drawn through the scrubber and the amount of gas passing, through the scrubber as a fraction of the gas released at the face. The data were analyzed to yield scrubber peak concentrations, potential exposures at various operator locations and the gas removal percentage (GRP). The underboom scrubber appears to work best in the end sump position, relative to the start sump and start slab positions. The capture efficiency scrubber was higher for 2.44-m (8-ft) roof heights compared to 1.52-m (5-ft) roof heights. The data also showed that the scrubber air discharged behind the mining machine may be drawn into the face area by the action of the blowing ventilation system, resulting in recirculation.]

Jan 1, 1994

By H. Wu, V. Izaxon

Intensive ventilation is required during the excavation of a mine opening and the subsequent exploitation of the mineral resources. The exchange of heat between the ventilation air and the rock mass has a major influence on the thermal regime of a mine, especially in the initial segment of the airway. In frozen ground, heat flow into the rock mass from the ventilation air can result in the eventual thawing of the permafrost, which can result in roof-rock instability. This paper presents a mathematical analysis of the dispersion process of ventilation-induced heat by thermosyphons placed on the surface of the mine. The principal uses of thermosyphons in the Arctic are to reduce the ground temperature to prevent potentially unstable permafrost from thawing and to increase the bearing strength of the material. The mathematical model of the physical problem, generally known as "the Stephan problem," takes into account the varying thermo-physical properties of air and the frozen and thawed rock mass, the thermal properties of the freeing fluid in the thermosyphons and the phase change of water. Finite-difference techniques were employed to determine the temperature isotherms around the thermosyphons. It was found that two rows of thermosyphons on a 10- x 10-m grid provide an acceptable design spacing for reducing the ground temperature around the mine airway.

Jan 1, 1997

By D. Leppert

Mr. Garrett brings up several interesting points with respect to the proposed API specification for "nontreated bentonite." However, although not explicitly stated, these specifications are being written based strictly on bentonites from the Wyoming/South Dakota area. Other sodium bentonites may be suitable for use as drill mud but will be unacceptable since the specifications are designed for Wyoming bentonites. Regardless of the API's intent that its specifications are intended only as guidelines, they are generally adhered to on an international basis and, for practical purposes, might as well be chiseled in stone. Estes (1986) notes that the quality of bentonite available from Wyoming producers has steadily declined since the early 1960's. The plastic viscosity: yield point (PV:YP) ratio was included in the current API 13A specification primarily to prevent excessive polymer treatment of lower quality bentonite to make drill mud. However, with development of polymers designed to control YP, this specification cannot ensure that only high-quality bentonites are used for drill mud. Nor will the new specifications for untreated bentonites. Other sodium bentonites are available. Bentonite produced in southeast Oregon demonstrates superior performance characteristics without addition of polymer or other chemicals. However, the exceptionally high purity of these deposits leads to a relatively high YP:PV ratio since the naturally high YP probably results from the higher purity and smaller particle size of this bentonite (Rath. 1986 and personal communication). These bentonite; typically have a smectite component exceeding 90% (Rath, 1985), compared with 70% to 75% smectite for typical Wyoming bentonites, as determined by X- ray diffraction and tests for colloid content. As evident from the accompanying table, the untreated Oregon bentonite has excellent rheological properties, though different from Wyoming bentonites due to the high purity. Additionally, this bentonite reacts well with polymers typically used in the oil industry, making it eminently suitable for use in a low-solids mud system. The extremely low grit content, less that 0.5% on a 75 mm (200-mesh) wet sieve, greatly exceeds the standards set for Wyoming bentonite. Optimum rheological properties are obtained at a higher moisture content than Wyoming bentonites. At 10% moisture, API 13A maximum, the clay is overdried, again reflecting the high smectite content. In summary, the specifications proposed by the API Task Group will ensure that only Wyoming producers can supply "nontreated bentonite to the oilfield since specifications are

Jan 1, 1990

By Norman Weiss

The purpose of this paper is to relate progress in the engineering field called Minerals Beneficiation to undergraduate and graduate education in our colleges and universities. So mach has been written recently about the education of scientists and engineers that I've had to struggle against the temptation to repeat what has been often said before, particularly because man like Robert Mehl of Carnegie Tech, Antoine Gaudin of MIT, H. M. Davis of Penn State, and John Vanderwilt of Colorado School of Mines have recently written many quotable paragraphs on the subject. In the matter of progress, the rapidity of proliferation in the area of physical and chemical beneficiation is convincing proof that this is indeed a lively art, and having been a millman for 35 uninterrupted years I prefer to lean on personal observations to some extent, rather than on statistics and charts v culled from the journals. I propose in this paper to talk first about the progress we've made in our branch of the mining industry in the last 3 decades--particularly in the last few years--and try to show that future progress will depend upon the quality of education and capacity for research possessed by our colleges. The second part will deal with some of the problems the colleges encounter in trying to fulfill these responsibilities.

Jan 1, 1959

By Gordon M. Pugh, David G. Rasmussen

INTRODUCTION Square-set timbering of stopes developed from stull support methods because veins too wide for stulling were being mined. In general, the void caused by the stoping of the ore is filled with a system of interlocking timbers. Timber framework supports the wall rock, the mining operations, and provides access. A timbered stoping method can be used in all widths of veins at any dip. The timbering can be normal and parallel to the planes of the walls or at angles to these planes. Irregularly shaped ore bodies can be worked by timbered methods. Pinching or swelling of the vein will not adversely affect the method. Timbered stoping is especially advanta¬geous where weak ground is encountered in the vein or the wall rock. The ground is unsupported only until timber sets are stood. These stopes can be filled with sand or waste when desirable. The customary method of developing a square-set timbered stope with haulage drifts above and below and timbered raises on each endline is shown in Fig. 1. The drifts are timbered the full stoping length. The raises have two compartments with the manway and timber slide in one compartment and the chute in the other. The drifts and the raises cannot be widely spaced as handling timbers is an important consideration. Stoping can begin immediately above the drift timber and continue in both directions and upward from the raise. Breasting down each blast round for only one timber set laterally is the common practice. The blasted ore falls to a lower floor where it is slushed or trammed to the chute. Drilling can proceed on the upper floor while broken ore is being removed from the stope. As shown in Fig. 2, square-set timbering may be used in cut-and-fill stopes to support the back and walls until fill is added. There are various ways of developing an ore block for timbered stoping. Fig. 3 depicts the situation for the main haulage in the vein with an intermediate drift separated from it by a sill pillar. The ore is slushed into the chute connecting the two drifts. The situation in Fig. 4 is identical to that in Fig. 3 except that no sill pillar is used. In Fig. 5, the haulage drift development is done in the footwall with crosscuts driven to intersect the ore body. The intermediate drift development is above the crosscuts with a minimal sill pillar. The main bottleneck in timbered stoping is in the timbering process. Drilling in the stope is generally held up while timbering is done. Two or three men are re¬quired to do the timbering and an additional one or two men are needed to transport and raise or lower the tim¬ber. Good organization is essential to timbering. Skill must be exercised in standing the timber to support the ground and still maintain good production. COSTS AND PRODUCTIVITIES Development and stoping costs are presented in Tables 1 through 7 for the situations in Figs. 3 and 5,

Jan 1, 1982

By Vincente M. Jr. Lim, Brain W. Lawrence

Underground mining operating costs consist pri¬marily of direct costs such as labor, supervision, ma¬terials, and supplies, plus indirect costs. The material and supply costs vary substantially between mines but commonly range from 35 to 60% of the total direct costs. As part of the preparation of accurate operating cost estimates for a project, information must be as¬sembled to select the material and supply items and to determine the quantities of these items that will be required. Cost data then can be incorporated with the estimated material and supply requirements to determine the total material and supply costs for the project. Estimated quantities will vary considerably between mining projects depending upon factors such as the type of material being mined, the mining method, the equip¬ment selected, drilling and blasting techniques, mucking and haulage methods, ground support requirements, number of men employed, etc. Valuable information often can be obtained from suppliers and manufacturers, including data on current operating practices for similar projects, recommenda¬tions for the specific project, and preliminary cost quota¬tions. However, quotations obtained for estimates are generally higher than the prices paid at the time of purchase. Mines operating in the area, or those mining under similar conditions, also can provide essential design information, but it often is difficult to obtain cost information from the operators. Estimated costs for the most common major items of underground materials and supplies are presented in the accompanying tables. They represent current costs or cost ranges and are intended to be used only as a guide when preparing budgetary estimates for materials and supplies. Cost data were obtained mainly from suppliers and manufacturers, with up to three quotations being ob¬tained for each item whenever possible. In most cases, as noted in the table footnotes, prices were based on quantities representing normal requirements for me¬dium-size mine operations. Every attempt was made to assure accuracy. However, the cost for most items, especially those with multiple sources, can deviate sig¬nificantly for various reasons such as geographical loca¬tion, current market conditions, quantities ordered, size of the customer (which could influence the ultimate quantities purchased), and the ability of the purchasing department. It is also for these reasons that the actual amount individual mines are now paying for specific items may vary from the estimated cost in the tables. The cost for specific sizes of items that do not appear in the tables often can be factored from the data pre¬sented. Costs for many items can be converted easily to a unit that sometimes is more basic, but not as com¬monly used, such as from a length to a weight unit. Other items not listed, such as repair parts for equip¬ment, will involve contact with suppliers to determine specific recommended requirements and to obtain costs for these items as related to each individual project. Costs are expressed in terms of US dollars as of 1978 unless otherwise specified. All measurements, sizes, and weights are expressed in conventional units (i.e. feet, inches, pounds) ; applicable metric conversion fac¬tors follow each table. Costs are represented for drill steel and bits; mining explosives; blasting caps; blasting supplies; ground sup¬port items; ventilation equipment; utility pipe, utility hose, and accessories; mine track and accessories; tires for underground equipment; lubricants and fuels; and miscellaneous supplies.

Jan 1, 1982

By Anthony Harding, Rodolfo D. Aradas, Juan M. Fernandez, Darío Tsingas

"The adoption of tunneled combined sewerage interceptors and outfalls leads to design linings which are often subject to internal pressures that are larger than the external pressures, resulting in significant tension loads. The need to meet stringent durability conditions for the normal design life of 100 years often drives client specifications to require a double pass solution with a cast in situ secondary concrete lining. However, improvements in concrete technology and the need to seek efficiency in terms of time and costs, have driven designers to consider single pass segmental linings. The Riachuelo Sanitation project in Buenos Aires is subject to these constraints both upstream and downstream of a sewage treatment plant. This paper describes how the challenges of up to 2 bar pressure differential have been addressed by careful analysis of soil structure interaction to ensure that the full benefit of external ground pressure is realized, resulting in a more optimal design for the constructor both in terms of cost and time. INTRODUCTION The construction of long sewerage interceptors and outfalls is becoming an increasingly common piece of infrastructure for modern urban cities facing a large water front and estuarine conditions, which are under a significant environmental burden imposed by decades of sustained growth. Such works intercept most of the distributed sewage discharges to then divert them to a central treatment point from which it will be finally diffused via an outfall into a water body capable to accept these discharges under acceptable environmental conditions. Depending on the magnitude of the sewage load to be handled, the configuration of the urban environment and the conditions of the receiving water body, both in terms of oceanography forces and seabed conditions, these schemes will vary in length, conveyance capacity and design and construction requirements. When conditions permit, the current trend is the execution of long outfalls using flexible solutions (such as the use of HDPE pipes) which usually require some form of concrete ballasted weights to resist off shore dynamic forces when directly laid over the sea bed. However, this concept faces limitations when the conveyance requirements indicate the need for large diameters (typically above 3000 m) and also when the outfall needs to avoid deep features off shore such as navigation channels. When this occurs, tunneling, particularly segmentally lined tunnel constructed by TBM emerges as the most feasible approach for large diameter, long deep outfalls. The operating conditions often result in internal pressures that are larger than the external pressures, resulting in significant tension loads in the lining. The need to meet stringent durability conditions for the normal design life of 100 years often drives client specifications to require a double pass solution with a cast in situ secondary concrete lining."

Jan 1, 2016

By B. R. T. Simoneit

The formation of petroleum is normally thought of as a geologically lengthy process, involving the accumulation of organic matter, its gradual burial, diagenetic breakdown via geochemical reactions, maturation, heating within a 75-150'C "oil window" induced by normal geothermal gradients in the subsiding basin, and slow product migration into structural traps (Tissot and Welte, 1984, Hunt, 1979). The entire process can take millions of years and, indeed, most oil reservoirs probably formed in this manner. How-ever, today in sedimented, submarine rift basins (Fig. 1), Cl to >C40 hydrocarbons with the chemical and physical properties of crude oil are forming in demonstrably much shorter time by rapid thermal maturation of immature organic matter in hydrothermal regimes that are unusually high for sedimentary basins (Brault and Simoneit, 1988a, b; Didyk and Simoneit, 1988; Kawka and Simoneit, 1987; Peter et al., 1988; Simoneit, 1983; 1984; 1985a,b; 1988; Simoneit et al., 1984; 1987; 1988).

Jan 1, 1989

By W. M. Ma, Daniel W. H. Su, K. Centofanti, Yi Luo, W. L. Zhong, Syd S. Peng

5.1 INTRODUCTION There are several types of surface ground disturbances, each of which is immediately transmitted to surface structures and causes damage of various forms, depending on the location of the structures in the subsidence basin. Many criteria have also been proposed for defining the potential structural damage. All of these topics will be discussed in this chapter. 5.2 TYPES OF GROUND DAMAGES There are two types of ground damage, continuous and dis¬continuous, that could inflict damages to surface structures. Dis¬continuous ground damage is open fractures of various degrees. Four types of fractures are commonly seen (Brauner, 1973b): 1. Fissures or cracks. Cracks are the most common form of ground damage and range from completely closed to several feet wide. Surface cracks are most prominent when the ratio of mining depth to mining height is smaller than 30 to 50 times mining height. Cracks initiate parallel to, but ahead of the moving long¬wall face at some intervals when the depth-to-mining height ratio is less than 25 to 30. As the face continues to move, they open up and then close gradually, and in most cases eventually close up completely when the face moves farther away. Sometimes when the depth-to-mining height ratio is larger, cracks may initiate be¬hind the face and go through the same cycle. Cracks are also more likely to occur in the hill when the face is moving in the uphill direction. Cracks also occur at or near both sides of the panel edges. Those cracks tend to remain open permanently. When the surface is covered with grass or other vegetation, cracks of less than 1 to 2 in. wide usually do not penetrate it and become invisible on the surface. 2. Steps. A step may occur when the longwall face stops abruptly if the mining depth-to-mining height ratio is less than 20. Steps may also occur along the panel edges. Steps also range from a few inches to a few feet in width and depth. If planes of weakness are oriented favorably, ground will slide along these planes and form steps on the surface. 3. Cave-in pits. These result from local collapse of the ground from the mine level to the surface when the mining depth is less than 150 ft and occur mostly above abandoned mined lands. They may be as large as 40 ft wide and deep. 4. Bumps (compression ridges). Bumps result from ground compression and occur mostly near panel center some time after mining. Bumps of up to 4 ft, but mostly 1 to 2 ft, have been identified. Continuous ground damage refers to the formation of the sub¬sidence basin where continuous nondestructive ground deforma¬tions occur. As mentioned earlier, continuous ground deforma¬tions associated with a subsidence basin include subsidence, slope, curvature, displacement, horizontal strain, twisting, and shearing. 5.3 TYPES OF SURFACE STRUCTURAL DAMAGES Both continuous and discontinuous ground disturbance cause damage to surface structures. A. Structural Damages Due to Discontinuous Ground Disturbance 1. Fissures or cracks. Open cracks can cause dislocation of surface structure if the gaps are sufficiently large so that the struc¬tural elements cannot resist but fail. On the other hand, minor cracks affect only the appearance, and not the structural integrity. 2. Steps. When a surface structure is located on a step, some portions of the structure lose support and become overhung. In the case of a residential house, there will likely be many open frac¬tures in the overhung portions, followed in severe cases by sepa¬ration of the superstructure at the edge of the step. 3. Cave-in pits. If the caved-in pit is larger than the surface structure, the structure will drop into the pit and become unstable. If the caved-in pit is smaller than the surface structure, the struc¬ture may either become overhung or lose support in some portions. In either case, it is unsafe for use. 4. Bumps (compression ridges). Bumps will disrupt roadways or house floor. If located under supporting members of the struc¬tures, it may cause damages. B. Structural Damage Due to Continuous Ground Disturbances 1. Subsidence. Pure subsidence or uniform subsidence over an area does not cause any structural damage. However, if it becomes a topographical low area, it may be flooded with water and make the surface structures unusable. It must be noted that the flat bottom area at the center of the final supercritical subsidence basin does not reach that position suddenly. Rather, as shown in Fig. 3.1, it is subjected to the dynamic surface deformation asso¬ciated with the traveling subsidence basin before it is left behind to be part of the flat-bottom area. Therefore any structure located at the center of the final supercritical subsidence basin must be able to resist the dynamic surface deformation in order not to be dam¬aged. 2. Slope. Ground slope will induce tilting of the structure. Tall structures with small base areas, such as water towers, chimneys, and power transmission towers are most sensitive to ground slope. If the ground slope is such that if after tilting the center of the gravity of the tilted structure falls outside the base area, it will topple, but this seldom occurs. Ground slope will change the designed slope of a buried trans¬portation pipeline, either increasing or decreasing the original slope depending on whether the ground slope coincides with or opposes the original slope. There are maximum allowable final slopes for various types of transporting materials. Ground slope also affects highways and railways. There is a maximum allowable final slope for a railway because tractive effort increases 1/1000 of its weight for every increase of 1/1000 in grade. 3. Curvature. There are positive (convex) and negative (con¬cave) curvatures. When a surface structure is located on a positive curvature, both ends become unsupported, followed by bending upward at the midportion. The top portion is subjected to more severe stretching than the lower one. As a result, vertical cracks with a wider gap at the top occur at the window, door frames, on the walls, and at -the wall joints. V-shaped cracks appear at the

Jan 1, 1992

By G. E. Wasson

Coal in most refuse ponds including those owned by Consolidation Coal Company can be recovered by froth flotation techniques. Laboratory studies show that the flotation conditions required for coal recovery varied greatly from pond to pond. The variables found to be most important for high coal recovery and low product ash were: a) the amount and type of flotation reagents and b) the degree of conditioning before flotation. Coal recovery at a rate of 0.504 kg/s (2 tons/hr) was demonstrated at a pond site employing a mobile froth flotation unit.

Jan 1, 1988

By L. M. Gochioco

The Seismic Interactive Interpretation Workstation (IIW) integrates various sets of geophysical and geological data to form a network of information which is stored in a database. Computer models are generated from known drillhole information and later correlated with the processed seismic data. Seismic color processing adds another dimension to the interpretation process. Complex trace attributes provide better definition of subtle features not easily observed from black and white sections. Utilizing the computer workstation, the explorationist gains valuable insight and conducts more intelligent interpretation of seismic data through a more comprehensive network of data analysis.

Jan 1, 1989

By R. J. Watters

Many rock sass classification systems exist' to assist the engineer in assessing the rock support requirements for underground design. Our ongoing research in this area is directed at attempting to utilize the fractal dimension and the acoustic emission' response of the tuffs at Yucca Mountain, Nevada to further aid in rock mass classification. The Topopah Spring' member, the proposed nuclear waste horizon, is characterized by welded and partly welded tuffs, exhibiting a wide range in moduli, strength, porosity and degree of fracturing. Differentiating between the different' types of porosity can be extremely difficult if not impossible. An attempt was made to correlate the acoustic emission response with the porosity of the sample. Events and the peak amplitude may offer a means-to distinguish between, fracture porosity and pore porosity. In addition-, fractal dimension were calculated for several fractures in densely welded tuffs. Two techniques for calculating fractal dimension were-applied' to describe-fracture geometry and roughness. Fractures in-welded-tuff were-found to be relatively smooth.

Jan 1, 1989

By Sheldon P. Wimpfen

Sand and gravel has been, and will continue to be, our principal construction material. Most of us are familiar with the patterns of past growth. Today we will examine the present status of this vital industry. We shall also attempt to look into the future to see where it is going and to evaluate the constraints that are being imposed. Natural aggregates are among the lowest in value of all bulk industrial minerals. From the processing point of view, sand and gravel production is relatively simple since the products are sized materials obtained from a deposit of satisfactory physical soundness. They can be used either loose or bound to provide bulk, strength, or protection. One of the main uses of coarse aggregate is in concrete as a filling material. As a general rule, the coarse aggregate constitutes about three-quarters of the volume of concrete. The other main use for aggregate is as a roadstone or roadbase to provide protective and stabilizing bulk beneath the road surface. Also it is used in a mixture with petroleum products as the wearing course on top. The sand and gravel industry is geographically widespread. In general, the output of operations is directly proportional to the amount of construction in any area. A wide variety of other aggregates compete with sand and gravel, including crushed stone, blast-furnace slag, clinker, and artificial and natural lightweight materials.

Jan 1, 1972

By J. M. Cases

Diffuse - reflectance Fourier - transform infrared spectroscopy, Hallimond tube flotation and microelectrophoresis have been utilized to investigate the reactions involved in the adsorption-abstraction of K-amylxanthate on finely ground galena and pyrite. In order to work under well-controlled conditions both minerals were wet ground in a specially built laboratory stainless steel or iron mill. Four surface products were found to be formed on galena: monocoordinate lead xanthate, non-stoichiometric lead xanthate, dixanthogen, and amyl carbonate disulphide. Only dixanthogen was observed on pyrite after using stainless steel rods, while ferric iron xanthate was found when iron rods were utilized.

Jan 1, 1989

By S. Ford

The introduction of recent advances in molecular biology into the field of microbial ecology has made available a powerful set of analytical tools for dissecting the structure of microbial communities in natural environments. The use of these approaches, many of them based on DNA-DNA hybridization enables the researcher to assess the occurrence of specific DNA sequences among the natural bacterial flora (Ford and Olson 1987). These techniques promise to have wide application as tools for monitoring the spread of introduced microorganisms (Trevors, 198'): Ford and Olson. 1987) and have been used to examine the response of bacterial communities to environmental contaminants and stressors (Barkay and Olson. 1986. Olson and Ford. 1986. Olson. Ford and Lester 1987) The occurrence of heavy metal resistance among microorganisms has been discussed as a possible tool for the detection of pathfinder elements employed in mineral exploration (Olson and Barkay 1986). In addition, the occurrence of heavy metal resistant bacteria may be utilized in protocols for assessing the occurrence and biological impact of contamination occurring as a consequence of mining operations. In this context the use of DNA hybridization technology enables the investigator to directly quantify the number of heavy metal resistant bacteria by the use of genetic probes specific for those resistance genes. The implementation of a strategy for detection of heavy metal resistance genes by hybridization technology is dependent on the availability of data on the genetic systems which encode resistance The availability of extensive DNA sequence data on mercury resistance genes (Brown et a11986. Barrineau et al 1984) has lead us to use gene probes specific for mercury resistance within natural bacterial populations as a model system for investigating the response of these bacterial populations to the occurrence of mercury In the environment.

Jan 1, 1988

By H. W. Renner

The paper industry is an $80 billion/year business that is the largest consumer of industrial minerals. Paper industry generally refers to paper and paperboard products, including pulp mills. Grades and uses of paper and paperboard are very diverse, including such things as napkins, paper plates, corrugated boxes, magazines, newsprint, currency, and copier paper. Only about 40% of paper utilizes industrial minerals as fillers or coating materials. Minerals are used for both functional and economic reasons. Most often, minerals such as kaolin clay and calcium carbonate are used to improve print quality, brightness and opacity of paper. The minerals can be added as fillers into the paper in the wet end of the papermaking system, or can be applied as part of a coating to the paper. Coated papers are the highest quality paper, being used for magazines, advertising brochures and annual reports. Common uses for filled uncoated paper are books, copier paper, envelopes and many of the Sunday newspaper advertising inserts.

Jan 1, 1993

By R. Fields

Nevada is primarily known today for its nation-leading production of gold and silver. However, industrial mineral production continues to play an important role in providing construction materials to help make the state the fastest growing in the United States. Aggregate production in Nevada was about 20 million tons in 1991. Most of that was used in construction in the fast-growing Las Vegas area. The state leads the nation in the production of barite and mined magnesite and has significant production of lithium carbonate, diatomite and gypsum. Other industrial minerals produced in the state include specialty clays, silica, lime and dolomite and relatively small production in salt, perlite and dimension stone. Industrial minerals operations are subject to state and federal permitting requirements, especially in the areas of air and water quality and mined land reclamation. As in all segments of the mineral producing industries throughout the nation, the amount and complexity of regulations affecting industrial minerals has increased significantly in recent years. Nevada is no exception.

Jan 1, 1993

By R. Z. Pyrih

Uranium tailings at Cotter Corporation's Canon City, Colorado Mill were moved to a double-lined impoundment, but uranium and molybdenum salts remaining in the fractured bedrock underlying the old tailings ponds seeped into groundwater. Fluor Daniel GTI recommended an in situ geochemical fixation remedy, flushing Best Sulfur Products' calcium polysulfide reductant into the subsurface with clean water. Residual metals became immobile, trapped in the bedrock. Fluor Daniel GTI designed and implemented the process on ten acres with high metal concentrations. Cotter is operating and monitoring the system, which can be expanded to "hot spots." The original remediation time was estimated at less than five years.

Jan 1, 1998