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By S. G. Axen

Design of wells for in-situ leaching is based on individual mining operation and ore deposit requirements. Major design considerations are well flowrate, depth, fluid composition, expected well life, mine operating plan and cost. A large variety of downhole equipment, materials of construction, contract services and methods of well completion and stimulation are available. A generalized design procedure which allows the engineer to optimize well design for a particular ISL application is described.

Jan 1, 1988

By Edward Burris, Terry Gorsuch, Joseph M. Hans

INTRODUCTION In any large earth-moving operation, good planning and management are necessary to complete the operational tasks promptly and successfully. When an earth moving operation is complicated by radioactive contaminants, normal earth moving techniques and procedures must be modified. Any planning and management, therefore, must include the radiological aspects of the operation. It was found that the radiological aspects dominated most of the planning and management activities and were extended to all facets of the decontamination work at the former Shiprock uranium millsite. These planning aspects are discussed and their use to develop a work plan is described. The management aspects are discussed and their use to establish a management structure are also presented. PLANNING Some method of procedure, formulated beforehand, was necessary to govern the decontamination work at the former Shiprock uranium millsite. This procedure was expressed in the form of a work plan which served several listed purposes. 1. It defined the work to be done and the sequence it would follow. 2. It was used as a yardstick to measure progress. 3. It was used to assign organizational responsibilities. Several factors were considered to aid in the development of the plan. These factors are discussed below: Goals It was established that radiation exposure was occurring to persons working at the millsite, and in an around the community of Shiprock, from airborne radioactive mill wastes and radon-222 exhaling from the tailings piles. The goal set for the decontamination work was to reduce on-site exposures to levels acceptable for the millsite occupants. The attainment of this goal would also have a substantial impact in reducing off-site exposures. The objectives necessary to achieve the goal were consolidation and containment of the wastes. The former objective implies decontamination of the millsite and environs, and the later implies stabilization of the wastes. In practice, a total and complete decontamination of the millsite and contaminated environs would be very difficult and costly. The costs for decontaminating them could be high enough that an alternative method might be more cost-effective for reducing human exposures (i.e, move the affected people away from the source). The interim guide "Radiological Criteria for the Decontamination of Inactive Uranium Millsites" was used for the decontamination criteria (EPA 74). Briefly, the criteria state that off-pile decontamination should be effective enough to reduce the net above ground exposure rate to less than 10 [u]R/hr for unrestricted use of the affected area. When decontamination cannot readily be achieved, the exposure rate levels could be relaxed to 40 [u]R/hr; however, the affected area has to be restricted. The second objective, waste containment, means isolating the wastes from the biosphere. Since no method of containment was available at the beginning of the millsite decontamination effort, temporary containment (interim stabilzation) became the objective. The tailings pile and decontamination wastes would be covered with clean fill. The interim stabilization should last from 5 to 10 years until the final disposition of the wastes will occur. The goal, therefore, would be achieved by decontaminating the off-pile areas to less than 10 uR/hr where practical. The decontamination wastes would be used to plate the surface of the tailings pile and would be covered with clean fill. Radiological Survey The radiologial survey is the key factor for planning a decontamination activity. The survey should delineate the spread and depth of the contaminants relative to the decontamination criteria. Surface wastes, in general, can be evaluated for spread and depth with reasonable radiation survey equipment. Subsurface wastes on the other hand can be missed entirely, as happened during the radiation survey at the Shiprock site, although numerous exploration holes were bored and dug. The survey results can be used to define areas that may not be amenable to decontamination because of complications or safety reasons. For example, no decontamination of the bluff base was to be attempted because of the possibility the bluff might collapse on the personnel and equipment. Contaminated bottoms of decant ponds on the flood plain were not removed because they would be slurried by ground water. Slurry removal was deemed inefficient because the contaminants would be scattered and no equipment was available for its transport. In summary, the radiological survey defines the boundaries of the decontamination work and provides

Jan 1, 1981

By Stanley Ferguson

Since 1978, the Colorado Department of Health has become involved in specific investigations of possible radiation hazards among nonminers in Colorado communities. In each instance, the improper disposal of mill tailings has precipitated concerns and allegations of radiation hazards. This presentation is a brief summary of the findings, to date, of 4 such investigations involving tailings disposal problems in Canon City, Denver, Durango and Grand Junction, Colorado. Canon City In the summer of 1979, allegations of excessive cancer incidence were made at public hearings concerning an application for a Radioactive Materials License submitted to the Colorado Department of Health by the Cotter Corporation for a uranium mill at Canon City. Canon City is the site of a uranium mill operated since 1958 by Commonwealth Edison. Local residents accumulated figures and calculated rates suggesting a 2-fold excess in total cancer mortality. These rates were not adjusted or standardized for demographic varibles. A review of cancer mortality data and computation of age standardized rates for years 1950 through 1977 showed that Canon City's cancer mortality rates were within expected limits, actually lower than rates for the State of Colorado or the United States. The first slide shows rates for every fifth year, 1950 through 1975. Further, an analysis of Canon City cancer incidence data from the Colorado Central Cancer Registry revealed that 1979 incidence rates were not significantly different from Colorado rates, with the exception of prostate cancer. The next slide shows age standardized incidence rates for lung, colon, breast and prostate cancer. Data were also reviewed for leukemia, myeloma, lymphoma and cancers of the thyroid stomach, uterine certix, ovary, kidney, bladder-and brain, however, small numbers of cases prevented meaningful rate calculation. 1980 data are presently being analyzed. None of the data yet examined support allegations of radiation-associated cancer in Canon City. Denver In February of 1979, the Department of Health became aware of a number of radium mill tailing deposits in the Denver metropolitan area, remnants of the radium milling industry of the early 1900's. Several of the deposits were situated so as to possibly contribute significantly to radiation exposure of a small number of people over a period of several decades. The Department developed protocols for radiation surveys, dosage estimates and, for a small number of persons, body burdens determinations and peripheral blood lymphocyte cytogenetic studies. The results of this investigation suggested no measurable biomedical impact as a result of the radium deposits. Durango In October of 1979, a physician residing in Durango, Colorado released information from a preliminary analysis of lung cancer data suggesting an incidence rate several times expected in that city. The data were presented at a meeting of a citizen's group concerned about the possible health hazards of 2 uranium mill tailing deposits located in the south end of the city. Since cancer incidence data generally do not exist in most of western Colorado, a team of epidemiologists was dispatched to Durango to work with local physicians and hospitals in conducting an epidemiologic study of selected cancers for the period 1969 through 1978. After case-finding and record abstracting were completed, it was determined that sufficient data were available for study of only 3 sites: lung cancer, breast cancer and leukemia. The next slide shows age standardized incidence rates for these 3 sites for 1969-1978 for Durango and the State of Colorado. There are no significant differences in these rates. The data did show a geographic peculiarity with regards to the relative proportion of tumor types near the tailings deposits as opposed to away from the deposits, however, this finding is based upon very small numbers of cases and may represent only the random excursion of rates based upon small observations. This investigation suggests that if a carcinogenic hazard is present, it is too small to be detected by the study method employed. Grand Junction The Department of Health has been involved in the Grand Junction mill tailings problem for several years. In 1966, the Department issued an order terminating the practice of free public access to a 55-acre pile of uranium mill tailings. Prior to this order, an estimated 300,000 tons of material was removed. Of this amount, an estimated 50,000 tons was presumably used in residential and commercial construction. Despite many allegations of cancer and birth defects excesses in Grant Junction since the mid 1960s, the first epidemiologic study of cancer was conducted in the spring of 1977. Data from the Colorado Central Cancer Registry were analyzed and reported to the Executive Director of the Department of Health in June of that year. The findings of the first and preliminary study were an unexplained excess of acute leukemia and chronic myelocytic leukemia. The excess was based upon small numbers but was present across all age groups. No increase in chronic lymphocytic leukemia was evident.

Jan 1, 1981

By S. Kesler

Rössing Uranium Limited has operated since 1976 a large open pit uranium mine and extraction plant at a remote site in the Namib desert, South West Africa/Namibia. The geology (Berning, I., et al. Economy Geology) and the technical aspects concerning mining, grade control and metallurgy have previously been described (Rössing Uranium, Mining Magazin and Whyllie, R.J.M. "Rössing Uranium reaches rated production", World Mining). The improvement of leach 'extraction has been reported in 1984 (Kesler, S.B. et. al. "Uranium extraction at Rössing") and the installation of a central process control system has been described (Kesler, S.B. et al. "The introduction of a central process system at Rössing"). At the beginning of 1983 a decision was made to develop a computer system for metallurgical plant optimisation which included mass and volumetric balances, analytical assays for up to 5 chemical elements and the costs for the major consumables. Within 10 months this computer system was developed and implemented. A large number of test runs were made and computer studies were undertaken. The metallurgical division now has a scientific tool for production; planning for actual comparison with plant results and for strategic investigations and decision making.

Jan 1, 1986

By Duane B. Jorgensen

The two calcium sulfate minerals, gypsum and anhydrite, occur in many parts of the world, and gypsum has long been of economic importance in the family of industrial minerals. Gypsum, the dihydrate form of calcium sulfate (CaSO, . 2H20) and anhydrite, the anhydrous form (CaSO,) are frequently found in close association, and it is seldom that a calcium sulfate deposit will consist exclusively of one mineral or the other. Although known gypsum deposits are extensive, anhydrite makes up the larger part of total calcium sulfate resources. Although it has very minor economic use, it is important to the understanding of gypsum deposits and is referred to frequently in the following discussion. Calcium sulfate is one of the principal constituents of evaporite deposits, and when pure, has the following composition: [ ] Deposits of pure gypsum or of pure anhydrite which are large enough to be considered commercial have not yet been found because of both the metastable relationship between the two minerals, and the presence of impurities such as calcium or magnesium carbonates, chlorides, other sulfate minerals, clay minerals, or silica. Most gypsum produced ranges from 80 to 95% pure and beneficiation is normally limited to selective mining or quarrying or upgrading by crushing and screening during mill processing. END USES The largest use for gypsum is based upon the unique property which calcium sulfate has of readily giving up, or taking on, water of crystallization. With the application of a moderate amount of heat in a process known as calcining, gypsum is converted to plaster of paris, the hemihydrate of calcium sulfate (CaSO4 ½ H2O), which when mixed with water will set or harden as the calcium sulfate returns to the stable dihydrate form. This semifinished product, usually called stucco, is then manufactured into a large variety of plasters, wallboard, and block for construction use, or into plasters for industrial applications. About 75% of the gypsum used in the United States is calcined for these purposes. Uses of uncalcined gypsum are principally as a retarder for portland cement, as a soil conditioner, as a mineral filler, and other minor industrial applications. About 25% of the gypsum mined in the United States goes into these markets; however, in other countries with building practices different from those in the United States and Canada, relative usage varies widely. Calcium sulfate deposits are the world's largest sulfur resources; minor quantities of gypsum and anhydrite have been used to produce sulfur or sulfur compounds. This use is accompanied by a unique site-specific set of economics because sulfur is generally available from non-gypsum sources at lower cost.

Jan 1, 1994

By Ray E. Harris

All of the major raw materials (silica, soda ash, limestone, and feldspar) needed to manufacture most grades of glass are found in Wyoming. Additional advantages for the manufacture of glass include the state's geographic location, a well-developed transportation network, a favorable tax structure (no corporate or personal-income tax), and low energy costs. Inadequate local markets and prohibitive transportation costs to other markets have been the major obstacles to developing a glass industry in Wyoming, the least- populated state in the nation. The Rocky Mountain region only recently became a major market for glass, especially for the Colorado Front Range and Utah's Wasatch Front. Currently, changing costs of the production of glass, an increased market for con- tainer glass in the Colorado Front Range, and innovative production and transportation ideas (e.g., production of selected types of glass and bulk shipments of specification-glass pellets) favor developing a glass plant in Wyoming. Thus, the Wyoming State Geological Survey (WSGS) and other state agencies have been conducting studies and contacting investors in an effort to attract a glass-manufacturing plant to the state. Between 1987 and 1993, three locations of silica-sand and -rock deposits were studied in Wyoming (Cassa, Plumbago Creek, and John Blue). Funding was provided by the WSGS operating budget and local and state Department of Commerce economic- development grants. The reports on these areas were released between 1988 and 1993. In 1988-89, a California-based company conducted additional drilling and feasibility studies and prepared to construct a glass plant in Cheyenne, using the Cassa silica source. However, due to losses incurred by some of their other investments, the company did not proceed. In 1997, the Wyoming Science, Technology, and Energy Administration (STEA) contracted a market study for glass manufactured in Wyoming, using information provided by the WSGS. The STEA contacted several major glass producers, and a major glass-producing company began feasibility studies in January 1998, for the construction of a glass plant. In June 1998, bids to supply brown beer bottles to the Budweiser brewery northeast of Fort Collins, Colorado, were submitted by at least two companies that were considering glass-plant sites in Wyoming.

Jan 1, 1999

By R. K. Mehta

An electrochemical coal oxidation model involving heterogeneous kinetics is presented. This model was tested by collecting current transient data on three coals assaying different ash content under varying operating conditions such as particle size, temperature, and % solids. In all cases, the model fitted the data very satisfactorily. Three intrinsic rate constants, namely mass transfer coefficient of Fe(II) Ions diffusing from solution to the anode (kma), mass transfer coefficient of Fe(II) Ions diffusing from solution to the coal surface (kmc), and chemical rate constant for coal oxidation with respect to Fe(III) at coal surface (k), were calculated. It was interesting to note that in this system, the mass transfer at anode was as important as the chemical reaction at the coal surface. The validity of this model was further demonstrated through a comparison of the activation energy of coal oxidation: firstly, by utilizing calculated chemical rate constant and assuming Arrhenius' type of relationship: secondly, by utilizing conventional approach using limiting current values. The comparison revealed that agreement was quite close. This kinetic analysis is useful because such a model can be used in predicting the intrinsic rate constants so that the relative importance of mass transport can be rationally analyzed.

Jan 1, 1991

By J. C. Emerick

Preliminary investigations have shown that wetland-based treatment systems can be an effective and relatively inexpensive control strategy for mine drainage pollution in eastern coal mining regions. This strategy also has potential for western mining regions, although too few systems have been installed in the west to permit general evaluation of the concept for western climates. The construction of prototype systems is encouraged for some situations. Wet-land environments have the capability of removing metals by natural geochemical and biological processes, including precipitation, filtration, ion absorption, and biological uptake and accumulation. Data presented for natural wetlands receiving mine drainage show removal of iron and other metals, and high accumulation of metals in soils and plants.

Jan 1, 1988

By B. Cavender

Investments in new technology are often intended to improve the production or cost performance of existing operations. The economics used to justify these projects can be flawed, however, if they do not adequately consider the potential benefits of the alterative: the fully optimized use of the facility's present equipment and personnel. While new technology can be effective, dramatic improvements in production performance can also be achieved through the rigorous application of standard industrial engineering and operations management practices. An intermediate approach may also be effective: many basic improvements In the mine or plant necessary to support new technology will be equally effective when implemented for the facility's present operators. Firms who optimize their present operations are able to save the capital and avoid the risk associated with new technology. These firms will also be able to capitalize more quickly on new technology when it is implemented.

Jan 1, 1999

By R. RAMSDEN

The deep South African gold mines rely on refrigeration to provide a safe working environment. Chilled water, which is produced in large central refrigeration plants, is distributed throughout mines In insulated pipes. In view of the high cost of the insulation materials and recent regulations which prohibit the use of certain insulation materials, a careful examination of the actual benefits of insulating chilled water pipes was undertaken. The objective of the investigation was to produce general guidelines regarding the use of insulation, but the results of numerous studies have shown that the use of insulation is extremely site specific and thus no general guidelines can be given. To assist ventilation engineers with studies on insulation requirements for their cooling systems a computer program has been developed. This paper describes the personal computer program which contains the same user friendly interface as developed for other COMRO programs. Is fully menu driven and incorporates a comprehensive HELP facility which provides background information and assistance with the selection of input data. The effects on the ventilation air and chilled water temperatures from not insulating chilled water pipes in certain areas are calculated. Air leakage, heat flow from the surrounding rock to the ventilation air and heat flow from the ventilation air to the water flowing in chilled water pipes are taken into account. A simple cooling system is considered in which cold water is distributed over a distance of 1 000 m through pipes to a single air cooler. The influences of changes in the temperature of the chilled water and ventilation air, as well as air leakage on the insulation requirements are determined.

Jan 1, 1991

By Paul J. A. Lever, Robert H. King

Human operators, geological conditions, equipment changes, mining sequences, and roof conditions are some of the continually changing operating conditions that drive a dynamic mining environment. These dynamic characteristics make it difficult to automatically analyze mining data because attributes change as the mining environment changes. Mine monitoring systems could provide mine managers with much more useful information than they do presently, if automatic analysis were possible. Automatic analysis of sensor data is also key to autonomous mining systems. This paper describes artificial intelligence (AI) and sensor fusion based sensor data analysis techniques developed over the past four years. These techniques were used to classify machine operating events by continuously monitoring machine power usage in a continuous miner section at an under- ground coal mine. The result is a report similar to an industrial engineering time study. First, numerical pattern classification techniques broadly identify operating events. However, domain knowledge about inter-machine and intra-machine interactions is necessary to identify and refine dynamic event boundaries. By implementing AI and sensor fusion based techniques we are able to classify machine events more accurately and recognize more specific events. These techniques could easily be applied to many different mining sensor data applications

Jan 1, 1993

The effect of the chemical composition of pulverized bituminous coal particles on their physical transformation during the initial stages of combustion has been investigated. The results suggested that cenosphere formation does not require extensive thermal decomposition of the coal particles. The vitrinites in the bituminous coal softened earlier and developed larger cenospheres than the othe macerals. The coal particles swell to a higher extent during combustion than in pyrolysis; however, the cenospheres formed in the former process experienced a higher extent of fragmentation. The development of microporosity occurred predominantly after the resolidification of the swelled char particles. The type of macerals originally in the coal did not significantly affect the microporosity of the chars. Conversely, the morphology and anisotropy of the chars were strongly dependent on the maceral composition of the coal.

Jan 1, 1986

By Walter C. Jr. Sherman

6.1-SOIL MECHANICS WALTER C. SHERMAN, JR. 6.1.1-DEFINITION Soil mechanics is concerned with the behavior of soils in relation to the design, construction and performance of engineering works. In this context, soils include all uncemented materials, such as, gravels, sands, silts and clays, either naturally or artificially deposited, and, under certain conditions, weakly cemented, badly broken or weathered rocks. Many types of mine wastes have physical properties similar to those of soils and thus are amenable to analysis by the principles of soil mechanics. The principles of soil mechanics are used to solve such problems as the stability of various types of structures with respect to failure of the supporting soils, determination of soil pressures and deformations in the design of foundations and retaining structures, analyses of seepage and under seepage, and stability with respect to sliding of excavated and natural slopes and embankments. 6.1.2--SOIL PROPERTIES Soils are classified on the basis of index properties, such as, particle-size distribution and plasticity characteristics. The Unified Soil Classification System1 used to classify soils for engineering purposes is shown in Table 6-1. Other physical properties important from an engineering standpoint include natural water content, density, permeability, shear strength and compressibility. Physical properties are evaluated on the basis of carefully conducted laboratory tests. Procedures for laboratory testing are presented by Lambe. 2 Soils, either of natural or artificial deposition, are complex three-phase materials consisting of solids, water and gas (usually air or water vapor). One of the most important principles in soil mechanics is based on the concept of effective stress in the soil-water system. A stress, a, applied to a saturated soil is taken partly by the soil particles (effective stress, a'), and partly by the water in the voids (neutral stress or pore water pressure, u,) so that a' = a - u,. Only the effective stress affects the mobilization of frictional resistance between soil particles. In partially saturated soils, the pore-water pressure is negative due to capillary effects. The effective stress relation remains valid for small negative pore pressures, but anomolies arise if the soil is significantly unsaturated. In this case, the pore pressure is commonly assumed as equal to the pore air pressure, u,, so that [ u' = u - u..] 6.1.3--SOIL EXPLORATIONS Soil explorations are carried out by borings or test pits. Hvorslev3 has reviewed procedures and boring requirements, such as, type, depth and spacing employed. In general, soil strata are logged and representative exploratory samples are recovered for classification purposes and for determining the subsurface soil profile, which is constructed utilizing also knowledge of the geology of a site. Undisturbed samples are recovered if the properties of the undisturbed soil are required, as generally is the case. The undisturbed soil sampler consists of a thin-wall tube

Jan 1, 1973

By R. Chandramohan, Landon Jackson, C. Meinke

Understanding constraints within the raw battery material supply chain is essential for making informed decisions that will ensure the battery industry’s future success. The primary limiting factor for long-term mass production of batteries is mineral extraction constraints. These constraints are highlighted in a first fill analysis which showed significant risks if lithium-ion batteries are used to fully support vehicle electrification and intermittent energy storage. Nickel, lithium, cobalt and graphite reserves risk 100 percent depletion with significant consumption of known resources. Furthermore, more than 700 new critical mineral mines will need to be developed to meet the required production rates for decarbonization by 2050. Demand for critical minerals will outpace mine development timelines even as improvements are made to battery energy density and compositions. Governments and the private sector need to align themselves on decarbonization goals to establish cooperative agreements on the critical mineral supply chain by reducing the barriers to entry and increasing exploration efforts. Additional measures must also be taken to reduce the demand for critical minerals. Policy such as incentivizing public transportation and biking infrastructure can be exploited to drastically reduce the mineral demand placed on the mining industry.

Feb 1, 2025

By A. Probst, N. Moores, J. A. Finch

In 1994, McGill University and INCO Ltd. (Sudbury operation) initiated the transfer of technology originally developed to detect levels in equipment ranging from flotation columns to thickeners. A conductivity probe was installed in a concentrate thickener to monitor the mud line and the solids load. The probe consisted of a vertical tube with 32 equally spaced electrode rings connected in pairs to give 31 conductivity cells. Conductivity was measured as a function of depth to produce a conductivity profile. From the conductivity profile, the mud line and the percent solids can be inferred. The probe was installed in October 1994, and it has been successfully detecting profiles since then. This paper includes a description of the incidents that occurred and the experiences gained during this technology-transfer process. Discussed is probe installation and startup; software modifications to accommodate both operating conditions and the needs of the operators; and calibration procedures to adjust to changes in performance as a consequence of long-term use. Also included are preliminary observations of the still-in-progress last stage, i.e., signal interpretation and use to facilitate operation, particularly by providing early reaction to upstream disturbances.

Jan 1, 1999

By Ralph E. Weeks

Utilization of true in situ technologies for mining copper in Arizona will involve a complex environmental permitting process. This process is a key factor in determining the feasibility, costs, and implementing time frames required for development of this innovative mining method. The regulatory structure in Arizona is presently changing due to enactment of the Environmental Quality Act (EQA) of 1986 and development of new aquifer protection rules and regulations. The Bureau of Mines has reviewed the comprehensive hydrogeologic characterization, ground water monitoring, mechanical integrity testing, well construction, contingency planning, and other regulatory elements that will serve as mechanisms to assure protection of ground water resources. The purpose of this paper is to inform the domestic copper industry of the significance of the new Arizona regulatory structure and its implications for prospective in situ operators.

Jan 1, 1988

By C. L. Elmore

This paper describes a new development in the cyanidation of gold ores, which we expect will result in a major improvement in the way many gold ores are treated. The process has evolved through work at Hazen Research, Inc. for Kamyr, Inc. and in brief, the consists of utilizing oxygen rather than air in the carbon-in-1 each (CIL) process. We refer to this improved process for all ores amenable to cyanide leaching as carbon-in-1each with oxygen or CILO.

Jan 1, 1988

By Jessica Elzea, Haydn Murray

The term bentonite was first proposed in 1898 by Knight, a year after he had named this clay taylorite, because taylorite had been previously used for another mineral. The name taylorite was after the Taylor ranch, the site of the first mine, near Rock River, WY, and the name bentonite is from the Benton Shale in which the clay was thought at that time to occur. The Benton Shale was, in turn, named after Fort Benton, MT, located more than 640 km miles north of Rock River. Early in the 20th century, several geologists recognized that bentonite, mainly in beds in Cretaceous and Tertiary rocks, originated from transported volcanic materials. This recognition led to definitions based on origin, the one most widely quoted and generally accepted by geologists is the following definition by Ross and Shannon (1926): "Bentonite is a rock composed essentially of a crystalline clay-like mineral formed by devitrification and the accompanying chemical alteration of a glassy igneous material, usually a tuff or volcanic ash; and it often contains variable proportions of accessory crystal grains that were originally phenocrysts in the volcanic glass. These are feldspar (commonly orthoclase and oligoclase), biotite, quartz, pyroxenes, zircon, and various other minerals typical of volcanic rocks. The characteristic clay-like mineral has a micaceous habit and facile cleavage, high birefringence and a texture inherited from volcanic tuff or ash, and it is usually the mineral montmorillonite, but less often beidellite." The difficulty in applying the foregoing definition to bentonite as an industrial mineral commodity is that it is based on origin and is restricted to an ash, tuff, or volcanic glass parent material. Therefore, deposits consisting of the clay minerals required by this definition, but having uncertain origin or parent materials, cannot properly be called bentonite. Furthermore, many deposits in the western United States and in other countries that have formed from rocks other than the types required by the definition are being mined and sold as bentonite. Perhaps the best definition of bentonite as an industrial mineral is one given by R.E. Grim in a plenary lecture at the International Clay Conference (AIPEA) at Madrid, Spain, June 27, 1972. According to this redefinition, which will be used in this chapter, bentonite is a clay consisting essentially of smectite minerals (montmorillonite group of some usages), regardless of origin or occurrence. This definition solves the problem of the difference between the geologic and industrial usages of the term and overcomes the difficulty in assigning a name to smectite clay that formed from igneous rock other than ash, tuff, or glass, or those of sedimentary or uncertain origin. However, bentonite, when used with this meaning is still a rock term (consisting of more than one mineral), and it will not be possible to distinguish it from fuller's earth in many instances. One way of classifying bentonite is based on its swelling capacities when wet or added to water. Bentonite having sodium (Na+) as either the dominant or as an abundant exchangeable ion typically has very high swelling capacities and forms gel-like masses when added to water. Bentonite in which exchangeable calcium (Ca++) is more abundant than other ions has much lower swelling capacities than sodium varieties. Some calcium types swell little more than common clay, and most crumble into granular masses in water. Intermediate calcium-sodium bentonites, the so called mixed types, tend to swell moderately and to form gels of lesser volumes than equal masses of the sodium type bentonite. Because of the general relationship of swelling and exchangeable ion characteristics bentonite is commonly divided into the high swelling or sodium, low swelling or calcium, and moderate swelling or intermediate types. The term sub-bentonite (Davis et a]., 1940) is used inconsistently in industry for the low or moderate swelling varieties. The authors believe the use of this term should be discouraged because of its implication of low quality or low value and the lack of a mineralogical or use basis for it. In the United States bentonite is also classified by geographic location and the uses for which it is sold. Inasmuch as most of the low swelling calcium type occurs in states bordering the Gulf of Mexico, this variety is commonly called Southern bentonite. The largest high swelling sodium bentonite deposits and the major producing districts are in Wyoming and adjacent states. Therefore, this bentonite is commonly called the Wyoming or Western type. Such terms as drilling mud bentonite, foundry bond bentonite, and taconite bond bentonite relating directly to use are applied in marketing. Other terms including high and low yield bentonite, high and low gel bentonite, and high and low strength bentonite are also used to distinguish different grades. The varied classifications notwithstanding, bentonite occurs in so many different varieties that some cannot logically be classified according to any of the foregoing groupings. One of these types is hectorite, which is a high swelling lithium-bearing variety of smectite occurring mainly in California and adjacent states. It is, therefore, not a Wyoming type, and it occurs even farther west than the so called western bentonites. Others are bentonites having magnesium (Mg++) or hydrogen (H+) as the most abundant or dominant exchangeable ion. These types are neither sodium nor calcium varieties, and apparently some are low swelling, whereas others have rather high swelling capacities. Still another type of bentonite, the so-called potassium type, K-bentonite, or metabentonite, occurs in Ordovician and other Pa-

Jan 1, 1994

By Frank Hagar, George M. L. Robinson

INTRODUCTION Mine waste monitoring and management is essential when the industry is being required to accept the environmental liability for all generated, stored and disposed solid and hazardous waste. Environmental regulations mandate the operator to minimize waste production while requiring the operator to cleanup existing contamination. Since these requirements are being enforced, many operators do not have a clear under- standing, whether their existing operation will or could be required to adopt remedial plans to mitigate off-site contamination impacts. The following methods, using conventional and advanced geostatistical methods, provide a tool to make appropriate assessments whether existing or potential contaminant issues are present. BACKGROUND Generated solid wastes from mining operations are currently exempt from Solid Waste Disposal Act (SWDA) Sub- title C (RCRA), statutes and promulgated regulations, however, compliance with SWDA Subtitle D statutes and regulations is required. In order for the mining operator to be exempt from hazardous waste regulations, the operator must demonstrate that generated waste does not have hazardous waste characteristics. In many instances the operator will be able to use statistical tools and their existing data to determine whether their site could be a potential hazardous waste liability. METHODS The following statistical and geostatistical methods can be used to determine whether existing wastes could be a regulatory concern. The following presents a brief discussion of standard statistical methods and discusses, in greater detail, how advanced geostatistical tools can be used to define potential waste issues. The following will discuss how data can be screened, "Data Filtering and Reporting"; how data can be evaluated using "Conventional Statistics"; followed by a detailed discussion o f "Geostatistical and Estimation Techniques" and "Statistical Modeling". Data Filtering and Reporting Data filtering is the simplest, but potentially the most powerful statistical tool because data can be easily sorted to meet regulatory reporting requirements. Filtering includes unions and intersections of data such as date, maximum and minimum values of one or several variables. Using the data base presented in "Mine Waste Data Base Management Procedures", Robinson and Hagar, 1987, an example of a filter group is presented.

Jan 1, 1987

By William M. PhD. Schafer

The net acid generation (NAG) pH method is an important analytical tool that supplements static and kinetic tests for assessment of the acid generation risk of rock samples. This method is useful because it is simple, rapid and cost-effective; it combines features of the static and kinetic tests; and it can be conducted at mine assay labs. The NAG pH test is particularly effective for operational testing programs used to classify, selectively handle, and route potentially acid-generating waste rock. The NAG pH procedure is based on a 24 hour oxidation of a pulverized rock sample with hydrogen peroxide and subsequent measurement of the sample's pH. If the NAG pH is below a critical value, determined empirically, then the sample has the potential to generate acid in the field. The critical NAG pH value is typically within the range of 3 to 4.5, but the exact relationship between NAG pH and potential acid generation should be determined individually for each mine site, based on comparison with results of acid base accounting, humidity cell tests, and mineralogical analyses. Calibration and use of the NAG test for predicting ARD risk at several mines are described in this paper.

Jan 1, 2000