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By R. E. Muller, L. G. Martin, J. M. Stonehouse

Erratic distribution of values in free gold ore bodies presents severe problems in sorting material in large scale open pit mining. However, an intense program of modern blasting techniques and less than modern gold panning results in good sorting at Houston International's Manhattan mine. Blasting technique is important. If the sample location cannot be relocated because of blasted material movement, information acquired while drilling is useless. So short benches are critical to minimize dilution. Though not very accurate, panning allows for rapid analysis. The more accurate fire assay does not provide the needed speed. Panning can be fairly accurate and errors made are mostly on the low side. Samples of mixed and broken stockpile material are used as checks on pit procedure and to develop stockpile content in¬formation. Added tonnages discovered offset the higher labor costs of this careful sorting technique. The mine is located in central Nevada's Toquima Range in the small mining town of Manhattan, 322 km north of Las Vegas. The mine has four epithermal stockwork ore bodies that are mined in two pits. The mine problem was that conventional ore control was not separating ore from waste. Assays of 6-m blast-holes were used on 5-m centers. The blastholes were relocated by stadia survey after blasting. Holes assaying above the cutoff grade were flagged and mined as ore. This system is practical and useful in high concentration ore bodies or in evenly disseminated mineralization. But it was not practical at Manhattan because of large gold particles and small ore pocket sizes. Ore pockets were often missed when drilling a grid area for blasting. Also, large gold nuggets made assay results unreliable. The probability of a nugget being contained in an assay charge is small. So most results were low, compared to actual grades mined based on stockpile samples. When a nugget found its way into a fire assay charge, the result would be far higher than the actual grade of material represented. In addition, disturbance by blasting created problems in relocating ore. Because of these problems, the grade control program was intensified in September 1979. It successfully separated ore and waste in blocked out ore areas and located more ore in "waste" areas. Known reserves mined to date have increased up to 50% on some benches. The methods used are modern blasting techniques, detailed assaying, and traditional panning of samples collected from active mining faces. These methods allow mining flexibility, to match the variable mineral occurrence in ore bodies. The united effort of the geology and engineering departments has been important to the program's success.

Jan 12, 1980

By Houston Kempton, Tim Dyhr, Andy Davis, Mark Bloom, Connie Travers, Dave Atkins, Jeff Deen

INTRODUCTION Historical mining activities in the Robinson Mining District, in the Egan Range of east-central Nevada (White Pine County), resulted in five open pits (Veteran, Tripp, Liberty, Ruth, and Kimbley Pits), several large mine-waste dumps, and numerous underground workings developed for copper, zinc, gold, lead-silver, and manganese (Figure 1). Groundwater percolating downward through the copper sulfide ores produced a blanket-like supergene zone enriched in copper, which has been one of the primary objectives of mining since the early part of this century. To obtain permits for future operation, an EIS was conducted that evaluated future pit- lake chemistry, groundwater quantity and quality issues, transport of water and solutes subjacent to a proposed tailings impoundment, and the potential for waste dump acidification. AREA HYDROGEOLOGY The mine area is on a ridgeline draining to the Steptoe Valley to the east and to the White River Valley to the West. Precipitation in the Robinson Mining District ranges from a low of 15 cm (6 in.) per year in the valley to more than 50 cm (20 in.) per year in the surrounding mountains. Evapotranspiration exceeds precipitation, leading to a net loss of water from the basin as either surface flow or underflow to the north at Currie, Nevada (Eakin et al. 1967). The White River Valley, which lies to the south and west of the mine area, includes approximately 4,200 km2 (1,620 mi2) of the upper part of the Colorado River Basin. This valley is 112 km (70 mi) long, 32-48 km (20-30 mi) wide, and like Steptoe Valley, evaporation and transpiration exceed precipitation (Maxey and Eakin 1949). The local groundwater flow system in the Robinson Mining District and the proposed mine area is dominated by two main components: (1) a groundwater mound or high between the Ruth Pit and Murry Springs, and (2) a shallow groundwater flow divide that follows the ridge crest south of Ruth, which contains the Veteran and Tripp pits. Besides the alluvium, the main hydrostratigraphic units controlling groundwater flow are limestones, shales, and sandstones, along with the intrusive quartz monzonite stocks. Based on the piezometric surface measured in October 1993, three distinct groundwater regions were identified. In the Giroux Wash area, an apparent fault runs between WCC-G1 and WCC-

Jan 1, 1995

By A. Henchiri, G. A. Gruber

INTRODUCTION Phosphatic resources may be quantified in terms of ore tons and phosphate analyses; however, to quantify phosphate reserves it is necessary to estimate the tons and quality of phosphate rock that can be extracted from the ore. The yield and grade of phosphate rock that can recovered from sedimentary phosphate deposits are usually difficult to estimate because of variations in stratigraphy and/or mineralogy. Prospecting phosphorite ores for purposes of estimating reserves and preparing mine plans requires considerably more effort than defining ore thickness and P205 content. In Florida, for example, it is standard practice to prospect by core drilling and to subject each strata (split) to beneficiation testing, and to perform detailed chemical analyses on the beneficiated products from each strata. For a completed drilling pattern the area of influence of each hole is 2.5 acres. The number of strata per drill hole typically varies from two to five, and thus complete prospecting of a 40acre tract requires drilling 16 core holes and beneficiation testing of about 48 ore samples. Florida practice is not appropriate for all phosphorite deposits. Functional drill rigs and trained drillers may not be readily available. Water for core drilling may be unavailable and the characteristics of either the overburden or ore may require careful attention and excessive cost to obtain representative core samples. Alternate ore sampling methods include auger drilling, rotary drilling to obtain cuttings, and the excavation of trenches, pits, and shafts. Drill cuttings samples are generally the least expensive to obtain, but they are usually unsuitable for beneficiation testing because of particle size reduction during drilling. Ore samples from surface trenches and pits are expensive and may not be representative of deeper ore. Ore samples from shafts are the most expensive to obtain, but if taken properly they are reliable for use in laboratory and pilot plant testing. Regardless of the prospecting technique used, reliable estimates of the yield and grade of phosphate rock that can be extracted from an ore deposit are required: • to justify capital expenditures for a new mine • for mine design and mine planning • for beneficiation plant design • for production forecasts, quality control, and marketing. This paper describes models that predict the beneficiation response of ores from three phosphate ore deposits. The purpose of these models is to obtain maximum utilization of available prospect data with the least cost. ORE DEPOSITS Simple beneficiation models have been developed for ores from three sedimentary phosphate deposits around the Mediterranean area. The first deposit, herein described as "A" ore, is located north of the Mediterranean Sea. The second deposit, designated as "B" ore, is located east of the Mediterranean Sea, while the third deposit, "C" ore, is located south of the Mediterranean Sea. Ore "C" is from the Sra Ouertane deposit in northwestern Tunisia.

Jan 1, 1993

By James F. Archibald, Ferri Hassani, Jacques Nantel, David O. DeGagné

Operators depend upon the success of backfilling programs to ensure that mine activities run continuously (Archibald et al, 1993) where backfilling is an integral part of the mining cycle. In order to ensure that the backfill is prepared and delivered to the stope possessing the required engineering properties, as designed, and that the backfilling process is safe, mine operators at all stages of the backfilling system must be adequately trained for their tasks and be aware of how their work affects other backfilling stages, both up- and down-stream of their station. Mine operator training is primarily based on learning on-the-job from experienced supervisors or training personnel. Classroom training and the availability of reference manuals are less common. While in use by many industries for some time now, computer-based training (CBT) is becoming more readily accepted by the mining industry for a wide variety of training. It is not intended to replace on-the-job training, but to augment it. CBT offers many advantages to enhance operator learning by utilizing multimedia presentations, interactions and on-line testing to teach complex concepts and relationships. Discussions with many operations revealed that there is an industry need for a backfill guide for frontline operator training and as a reference manual for operators and mine engineers. Sponsored by the mining industry and the CIM, "Mine Backfill, An Operator's Guide" has been developed by the Departments of Mining Engineering at Queen's University and McGill University to fulfil this need. "Mine Backfill, An Operator's Guide" is an interactive multimedia package that incorporates high quality colour images, animations, sound, and video with text to review the main backfill methods employed in Canada, including hydraulic/slurry, paste and rock fill. The Guide is divided into training and reference primer sections. When in training mode, the operator is guided through a presentation of common mining and backfill practices and technologies so that he/she may become more familiar with different aspects of backfill processes. To ensure that key concepts have been learned during training, the operator will be tested after each section using a series of multiple choice and true/false questions. When in reference mode, alternatively, the operator may browse through the information in a more detailed and independent fashion through a series of interactive menus. The Guide focuses on the following main topics: resources, surface preparation, distribution, stope activities, health and safety, and quality control. Special features included in the Operator's Guide are a Buyer's Guide, a Trouble Shooting Guide, and an interactive glossary of backfill and mining terms. Concepts in interactive and computer-based learning are also reviewed in this paper.

Jan 1, 2001

By J. L. Weeks

Discussion by J.L. Weeks Discussion I wish to comment on Kissell and Sacks's paper "Inaccuracy of area sampling for measuring the dust exposure of mining machine operators in coal mines." It is well established in industrial hygiene that area sampling is not an accurate measure of personal exposure. To measure personal exposure, one must use a personal sampler. Kissell and Sacks, using data from coal mining, reached the same conclusion. This is the right answer but it is the wrong question. This issue arises because the machine-mounted respirable dust continuous monitor (MMRDCM) is being considered to monitor coal-miners' exposure to respirable dust. This device may be mounted on a continuous mining machine, and it would take a modified area sample. I refer to it as "modified" because a mining machine is not really a fixed location, as is the typical area sample. The concern with whether this machine would provide an accurate estimate of the machine-operator's exposure, however, overlooks important features of the MMRDCM. Specifically, it displays dust concentration as it occurs and at the place where it is needed, not 10 days later, as is the case with the current system. Used in this way, it allows for timely intervention to control exposure to dust and it leads to greater first-hand knowledge of specific conditions and mining practices that result in excess exposure. If one knows the dust level is excessive at the time the dust is being generated, it is possible to use known and effective methods of dust control to reduce exposure. By measuring again, one can determine whether control methods have worked. This is a generic procedure followed in any industrial process: measure, adjust and measure again. It leads to more effective and more efficient dust control and is preferred to taking a sample, waiting 10 days for the results and then trying to apply that information to a situation that no longer exists. The MMRDCM also records the dust level automatically, and it runs continuously, making it harder to tamper with. Dust monitoring in underground coal mines has been corrupted by some operators having submitted fraudulent samples (and being convicted on criminal charges because of it), weakening the credibility of the current system. The MMRDCM is, in part, a response to this corruption, and an effort to focus attention on dust levels and dust controls rather than on the perpetrators of fraud. Use of the MMRDCM is an evolutionary change from the current system. With the current system, one takes a personal sample of exposure of the "designated occupation" (DO, defined at 30 CFR 70.2 (f)), the occupation regularly exposed to the highest level of dust on a section. Typically, on sections using continuous mining machines, this is the mining-machine operator. The rationale behind DO sampling rests on some of the findings that Kissell and Sacks report. They reviewed several studies that showed that dust concentration varies with location on a mining section and that there is a concentration gradient with the highest concentration occurring closest to the face. The logic behind DO sampling strategy is that if the dust concentration at the place where it is highest is below the exposure limit, then concentration elsewhere on the section is also below the limit. In this way, one will have achieved the objective or keeping dust concentration below the exposure limit for all miners on the section by measuring the exposure of only one miner. The

Jan 1, 2003

By R. N. Chakravorty, R. J. Kolada

Introduction Spontaneous combustion in coal mining is recognized as a major hazard in terms of safety and economics. A survey by Olaf (1979) revealed that 80% of coal mine fires were caused by spontaneous combustion. Modern mining methods demand a high capital investment. Closure of a working face may then result in a huge loss. Even a short production interruption can prove expensive. Spontaneous combustion may also produce lethal amounts of carbon monoxide, thus posing a serious threat to the health and safety of underground miners. The worldwide recession in the early 1980s resulted in a number of mine closures and production cutbacks. So large stockpiles at mine sites were common. Experience has shown that stockpile fires are difficult to extinguish. Critical factors influencing spontaneous combustion There is no simple method of predicting whether a particular mining method applied to a specific coal seam will result in spontaneous combustion. Under favorable conditions of heat accumulation, spontaneous combustion can occur with any type of coal. It is known that subbituminous coals are more susceptible compared to low volatility bituminous coals, and that a high ratio of exinite increases the risk. However, the inherent moisture content of the coal and the exposed surface area may be more significant. Actual mining and ventilation conditions also strongly influence susceptibility. In practice, the experience gained with the mining method applied to a particular type of coal seam must be carefully evaluated with respect to the factors responsible for spontaneous combustion. Feng, Chakravorty, and Cochrane (1973) summarized the critical factors influencing spontaneous combustion in coal mines (Table 1). Prevention methods and strategies Mine layout is the most important factor preventing spontaneous heating. Working districts should be designed so that a particular section can be isolated on short notice without affecting production in others. Sites for preparatory seals should be identified and marked during planning. With coal seams that are highly susceptible to spontaneous combustion, the retreat method of working is preferred. This is because the gob is not subjected to a large difference in ventilation pressure. Coal pillars should be designed to resist excessive crush. The panel system of working is preferred, particularly for mining coals susceptible to spontaneous combustion. The size of each panel is calculated based on the incubation period and the rate of extraction. Controlling air leakage is also important for controlling spontaneous combustion. This is usually achieved by minimizing ventilation pressure difference, proper siting of doors, and avoiding unnecessary stopping and starting of fans. Air leakage is also reduced by sealant coating, injection of cements in cracks and crevices, and by maintaining good gateside packs. Application of inhibitors to control spontaneous combustion met with limited success. Chamberlain and Hall (1973) concluded that borate solution or Montan powder sprayed in the gob area or infused into a low rank coal would reduce the possibility of spontaneous combustion. Early detection of heating Significant research is being conducted worldwide to develop methods for early detection of heating. Monitoring combustion products during the early stage of heating is the most suitable method for detecting spontaneous combustion. The major gaseous products resulting from low temperature oxidation of coal are carbon dioxide, carbon monoxide, and water vapor. In mining operations, carbon dioxide monitoring is considered unsuitable because there are sources other than spontaneous heating from which this gas may originate. Carbon monoxide, however, is a more specific product of combustion during low temperature oxidation of coal. Over the years,

Jan 10, 1988

By Nicholas S. Lynn

Introduction Borne out of the need for reductions in capital expenditure and increased production, several new and innovative carbon systems have been developed for small precious metal heap leach operations throughout the United States. Perhaps the most important aspect of these systems is the carbon column. Though diverse in design, these columns can be categorized into three basic types. The first is known as the gravity flow type or Cortez type. As the name indicates, solution flows via gravity, throughout 4 to 6 columns which are arranged in a normally stepped con- figuration which is conventionally upflow in design. The second type, known as the vertical column, is an arrangement whereby flow is established through pressurization in an upward manner, throughout 4 to 6 columns in a vertically stacked configuration. This arrangement is typically intended for use with small portable heap leach operations and employs a semi-continuous mode thus preventing gravity from occurring. The third type and newest development in carbon columns is an arrangement whereby the solution flows throughout 4 to 6 columns placed in a side by side configuration and pressurized by a single feed pump (Figure 1). A unique aspect to the third type, is that the adsorb and desorb cycles are accomplished in the same column, due to a fixed carbon charge. An in-depth analysis is warranted due to numerous advantages of this arrangement, and is therefore the subject of this paper. Advantages and Variations One advantage to the third type of carbon column is the fact that initial capital expenditures and operating man- power requirements are reduced. Another advantage is that the system can be made fully portable up to a 0.0315 m3/s (500 gpm) capacity. Systems of this nature are operational at several sites. Above this flow rate, the system's portability is one which can be maintained, but disadvantages (i.e. larger diameter carbon column and greater weights) far outweigh the advantages. There are several variations in each of these systems which allow for unique operation. For example, carbon columns made highly portable, can be moved from unitized heap leach operations to central stripping facilities. Although this method has been used in Colorado, transportation of these units has been known to be quite cumbersome. If distances exceed 5 km (3.2 miles) then special front-end loaders are required. This limits heap locations to within 5 km (3.2 miles) of the central processing facility. Another example transports the carbon charge from the heap leach locations to a centralized processing facility; this method is quite effective. For the past 5 years one mine has employed this technique of transporting carbon in 907 kg (1 ton lots), in DOT containers, towed by company pick-ups. This operation uses a vertical column with a 907 kg (1 ton) carbon charge. A third example uses static carbon columns with fixed carbon charges. Carbon Adsorption System The carbon adsorption system (Figure 1) is fed by a single preg solution feed pump. This feed pump pushes the preg solution through all four to six fixed charged carbon columns, which are on line. The sequencing of the carbon columns is achieved using valves. Expansion of the carbon charge is dependent upon the carbon selected. The carbon typically used is a 6 x 12 mesh size, with a nominal flow rate of 0.00135 - 0.00138 m 3/s (22-25 gpm) per square foot of carbon, based on a 40% bed expansion. With 8 x 16 mesh size,

Jan 1, 1987

By Joseph M. Hans

INTRODUCTION The decontamination of a uranium mill site is principally an earth moving task. The task can be completed effectively and efficiently by selecting the proper earth moving equipment and using that equipment within its particular constraints for decontamination work. A considerable backlog of experience concerning earth moving equipment selection and use was acquired during the decontamination work conducted at the former Shiprock, New Mexico, uranium mill site. This experience was acquired by trial and error while decontaminating over a wide range of depths and different types of terrain. Many different types of excavation equipment were available to the Shiprock decontamination project because the Navajo Engineering and Construction Authority (NECA) heavy equipment operator's school was doing the decontamination work and a variety of equipment was needed for training. The equipment is described and its general use for decontamination is discussed. Its on-the-job use for decontaminating the Shiprock millsite is presented. [EARTH MOVING/ANCILLARY EQUIPMENT DESCRIPTION AND DECONTAMINATION CONSTRAINTS] Tractor-Scrapers The most commonly used scraper is the bottom-dump type because it is highly mobile and can dig, carry, and spread loads. In this type a tractor is connected with a yoke to a scraper bowl (Figure 1). The bowl is essentially a rigid box that pivots around the rear axle, opening to the front. A hardened steel knife, or bit, is attached to the leading edge of the bowl. When scraping, the bit penetrates and forces the earth overlying the bit edge into the scraper bowl as the scraper moves forward. When the bowl is full, it is closed by lowering a closure or apron against the cutting bit. The load is dumped while moving, by raising the apron and forcing the load from the bowl with a crowd, or ejector. The height of the dumped load is controlled by adjusting the bit height when dumping. Scrapers of this type generally do not have enough power to scrape up loads unassisted. Loading assistance is generally provided by a crawler tractor that pushes from the rear against the scraper's push block. Some scrapers are made self-loading by adding an additional engine for the extra power needed for the load pick up. Another commonly used self-loading scraper uses a loading elevator (Figure 2). The elevator consists of two roller chains carrying crossbars. The elevator is rotated when scraping and the crossbars cut the earth above or in front of the bowl bit, forcing the load into the scraper bowl. No apron is used on elevating scrapers. The load is dumped by partially retracting the bowl floor and pushing with an ejector. Scrapers have some undesirable characteristics when used for decontamination work. One characteristic is that a clearance space exists around the apron when it is in its closed position. Part of the load (especially sandy soils) dribbles through the

Jan 1, 1981

Disposal of solid and liquid wastes from mining and milling operations has become a focus of attention in recent years. Consequently, the geotechnical engineer is more frequently associated with design of disposal facilities. Jack Wulff, a representative of one consulting firm with experience in this field, talks with ME about the geotechnical engineer's contribution. Mr. Wulff, mine and mill waste disposal today is receiving more attention-and many more dollars-than in the past. Regulatory agencies have promulgated demanding requirements concerning mill waste (especially uranium mill waste) and specialist consultants are frequently being called in to design disposal systems. What can the experienced geotechnical engineer add to the development of waste disposal facilities? It's true that geotechnical engineers have recently become more visible in the minerals sector, but we've been around mining for a long time-as foundation engineers for mills and mine support buildings, and for geotechnical aspects of open pits, pipelines, railroads, roads, and so forth. We've also designed water supply dams, which could be considered recursors of tailings dams and other forms of disposal systems. Let me show by example what geotechnical engineering can contribute to waste disposal facility design. I recently was asked to look at several small wastewater impoundments which had failed. The design of the earth embankments appeared, at first glance, to be rather conservative. They were only about 3.4 m high, the slopes were 3 to 1 (horizontal to vertical), with about 24 m of bottom contact with the earth foundation. But there had been three episodes of dike failure in a few months, all upon initial filling. The problem was the nature of some material in the foundation that was also used as structural fill-a dispersive clay that readily deflocculated and eroded on contact with water, especially with seeping or flowing water. The design did not include the defensive measures required to use such materials confidently in water retention structures. Apparently, the designer did not recognize the potential problem posed by the unusual soil characteristics. That's the sort of engineering information fundamental to geotechnical engineering, but not necessarily a part of the civil, structural, or mining engineer's professional training or experience. This difference in expertise is not simply a matter of factual knowledge-it also affects the design process. The structural engineer can design a structure to fit the client's functional needs and can specify the materials (grade of steel, PVC, concrete, etc.) to meet the demands of the design. The geotechnical engineer's design process is somewhat different, since we work with natural materials, not man-made materials produced according to specification. We first have to establish what kinds of materials are available (usually directly from the chosen site, since importation of materials becomes expensive). Then we determine the engineering properties and characteristics and, finally, design the structure to fulfill the client's requirements within parameters dictated by available materials. In brief, the geotechnical engineer works with naturally-evolved, not man-made, materials and uses design techniques developed to accommodate that fact. Because no two sites are exactly alike in configuration, structural (geologic) characteristics, or available materials, there will be unique design and judgmental questions to be resolved on virtually every project. You said that water retention dams could be considered the precursors of tailings dams-you probably had a specific technical relationship in mind. There's a very strong carryover of methodology from earth dam design, where the technology developed and where it has become very refined. In designing a tailings impoundment or similar facility, essentially the same procedures of field sampling are involved (with a geotechnical engineer or an engineering geologist directing the program since representative

Jan 7, 1980

By David L. Rife

Introduction Our society is currently experiencing a change in civil philosophy toward US industrialization. We have become increasingly bent on the pursuit of a nirvanic state of zero risk. The money supply has become inversely proportional to its sources. And most mining companies, traditionally conservative, have become increasingly risk conscious. Rising taxes, high inflation, and decades of a steadily decreasing gross national product (GNP) - coincident with moral decay and disarmament - have eroded America's economic health. Psychology of US metal markets has shifted across the economic spectrum to disillusionment and discouragement. The sagging national economy, expanding governmental debt, and a backward mineral policy in concert with worldwide unrest and turmoil have caused great volatility in the metal markets. Congressional inaccessibility of US resources has contributed to its loss in strategic leadership and dependency on foreign suppliers and the common market. Large scale mining activities are now on the decline. And there is an overall slump in mineral exploration in this country. America now faces the sobering reality of almost total importation of 13 key mineral commodities and total dependence on foreign sources for five of them. There is a growing dependency on 21 of the 34 minerals vital to the US economy. And virtually everything needed can be imported directly from third world countries. Almost 85% of the free world's supply or production of vanadium, chromium, platinoids, manganese, and titanium - an essential to the aerospace industry - comes from South Africa. That country now plays a forefront position in supplying the West with minerals. The Soviets have become increasingly aware of this situation. They have made key moves in procuring for their own purposes major raw materials markets, particularly in South Africa. This is obviously threatening to the US' direction and brings about vulnerability to shortages and cutoffs. In spite of these developments and the overall change in the mining industry, there is good opportunity for growth ahead. The way has been paved for the smaller mining companies, particularly the more bullish of these. Smaller mining organizations possess a tight management and strong sense of direction. They can easily adapt to and cope with change. "Windows" that exist in the industry directly depend on a number of factors. These include the busi¬ness climate, market research and planning, management and human resources, applied appropriate technology, favorable hunting ground, and entrepreneurship. Mining as business Mining (and exploration) as a business is by its very nature highly speculative. It involves greater risk for a longer period of time than most other businesses. The entire mineral estate in the US continues to shrink. This is primarily because of various legislated wilderness measures. Consequently, the probability of finding an economic ore deposit in the US has decayed to less than 1%. Although the risk is high, the stakes far outweigh the gamble and are larger than most other businesses can offer. Mining properties, as investments or business opportunities, can provide effective hedges against long-term inflation because the real price for selected commodities, such as gold, may sometimes rise faster than inflation. Recessionary periods seem to provide the best climate for entering the mineral business or for a particular mining organization to expand its activities. Looking ahead and seizing opportunities during a depressed market will pay off. Property payments and royalties are likely to be lower. And the potential for an upward shift in prices for a given commodity is very positive. The decision to invest in a prom-

Jan 9, 1985

By T. B. Szwilski, R. D. Begley

Status of ISO 14000 standards. The ISO 14000 are voluntary international standards providing a frame-work that allows a company to integrate an effective environmental-management system (EMS) into its operations. The purpose of an EMS is to provide a systematic procedure to identify the environmental aspects of a company's activities, evaluate any significant impacts and use the information to set objectives and targets toward continuous improvement of the company's environmental compliance and performance. In addition to the specifications for certification, ISO 14000 can be used as a guide to develop an effective environmental-management system or for self-declaration. The International Organization for Standardization (ISO) is a worldwide federation founded in 1947 to promote the development of international manufacturing, trade and communication standards. The organization is now represented in 118 countries, with the American National Standards Institute (ANSI) representing the United States. The principal goals of the ISO is "to promote the development of standardization and related ac¬tivities in the world with a view toward facilitating the international exchange of goods and services and to develop cooperation in the sphere of intellectual, scientific, technological and economic activity." ISO develops standards with input from government and industry. Because the standards are voluntary, there are no legal requirements to pressure countries to adopt them. However, many governments, industries and US agencies are adopting the ISO standards as a requirement for business trans¬actions, thereby, compelling suppliers to adopt ISO standards. These business and market forces, which are likely to be strategic business issues in the 21st century global marketplace, are imposing the need to develop a systematic approach to environmental management. The ISO 14000 series evolved from a United Nations Conference on the Human Environment in 1972. It includes a broad range of elements: the basic environmental management system, environmental auditing criteria for internal and external auditors, criteria for environmental performance evaluation (EPE), environmental labeling criteria and life-cycle assessment methodologies. The standards comprise two categories: organization evaluation standards and product oriented standards (Table 1). The ISO 14001 specifications contain the requirements for developing an environmental-management system that may be objectively audited for certification. The ISO 14004 standard provides guidance on interpreting the ISO 14000 specifications for the development and implementation of the EMS and for coordination with the management system of the company. On Sept. 1, 1996, the American National Standards Institute (ANSI) and the Registrar Accreditation Board (RAB) signed a formal agreement to create a new entity called the National Accreditation Program (NAP). To obtain certification, a company must fulfill the requirements outlined in ISO 14001. It is required that "a third party give written assurance that a company's EMS meets all the requirements of ISO 14001." Preparing for ISO 14000 can include subscribing to voluntary environmental initiatives; learning from ISO 9000 quality-management experiences; and utilizing information from recognized training courses, publications and numerous Internet resources. Once committed to an EMS, the management should provide sufficient resources to achieve continuous environmental-performance improvement, as outlined in an environmental policy. A thorny issue now being debated concerns the potential liabilities of documenting the environmental performance of a company. General impact of the ISO 14000 EMS standards. With increasing stakeholder awareness, costly end-of-pipe pollution-control approaches and the success of ISO 9000 quality-management standards, the ISO 14000 EMS standards are being adopted by companies and governments worldwide. The United States and Canada have well-established programs. In Europe, countries differ but are firmly committed toward environmental-management standards (BS 7750, EMAS and ISO 14000). The Department of Environmental Protec¬tion of the State of Pennsylvania is using ISO 14000 as a vehicle to develop a closer working relationship with industry, and it is anticipated that this policy will eventually lead to fewer environmental site inspections for those companies with ISO 14001 certification. The Depart-

Jan 1, 1999

By W. Kemp Wait

Electronic ore sorting is a coarse particle beneliciating process which performs a function which in the past was primarily achieved through the use of hand picking belts. Photometric ore sorting is capable of separating waste from mineral bearing rock having a distinct difference in surface light reflectance levels. This type of ore sorter can be applied to gold and silver ores which are contained in quartz veining. Photometric ore sorting has been used at gold mines in South Africa as well as the Black Pinc silver mine in Montana. A new ore sorter has recently been developed with precious metal ores in mind. This ore sorter is capable of sorting ores on both photometric and conductivity sensing parameters. The first production machine has been installed at a gold mine near Beardmore, Ontario and currently is being used to process low grade waste dumps.

Jan 1, 1998

By G. Sanders

Discussion by G. Sanders The studies reported on in this paper were initiated to draw attention to the severe contamination problem in the Section 30 drilling program at Chimney Creek. The lithologic-subset sampling study reached a different conclusion from that presented in your paper, and I wish to comment on your subsequent analysis of the data and your conclusions. Request for more complete data In the section on subsampling, you mention that the subordinate lithologies were separated and sampled, yet only the dominantlithology gold value is plotted in Fig. 4. In a contamination study, the reader is interested in the assay values for the individual subsets. Please include a table of the subsample assay data in your reply. Also, please indicate which analytical methods were used to arrive at the gold values in the subsampling study. Turning barren rock into low-grade ore Figure 5 is very revealing and typical of all of the cross sections in Section 30. Note the long strings of low-grade mineralization spread out for hundreds of feet below the ore zones. There were some very high gold values found in certain contaminated fractions during the subset sampling. The conclusion, here, was that the distinctive, strongly-mineralized dolomite layer was probably loose and crumbly and continued to disintegrate during drilling. This caused salting of the unmineralized rock samples below. Missing the high-grade part of the ore body In your statistical analysis, you directly compare the reverse circulation assays to the diamond drill assays in Section 30. Two points argue against a direct comparison and suggest the differences are greater than the 3 % that you report. First, any core loss in a gold zone most likely means that the true gold values are greater. The drillers lost significant amounts of the clay-rich, Section-30 gold mineralization. Also, the initiated salt-mud system, an attempt to improve the core recovery, met with little success. Second, the practice of not sampling core geologically, but instead sampling on even 5-foot intervals, adds a deliberate dilution to the core assay values by including a portion of nonmineralized rock in the first and last samples of each high- grade intercept. The result is often a pair of low-grade assay values on either side of a high-grade gold zone. In reality, a high-grade gold zone has a very sharp assay wall that is often bounded by barren rock. This sampling method may make the diamond-drill core assays more like the reverse circulation values and may help explain the statistical similarities you found. However, it does not represent the true gold values in the high-grade parts of the deposit. You cannot deny that, by careful geological sampling of the drill core, higher and sharper assay values will be obtained. The low core recovery and the diamond-drill-core sampling method used act together to lower the diamond-core assay values. The 3% difference you found between the reverse-circulation and diamond-core assay values could be much larger when you consider what the true diamond-drill core values would be with optimum core recovery and a geologic sampling method for the core. Should statistics have been applied here? The statement "... that reverse circulation holes have overestimated the values of some ore zones and underestimated the values of others" (p. 345) is not correct. The subsampling confirmed what the cross sections hinted at in Section 30. Namely, beneath the high-grade zones, the reverse circulation holes created, by contamination, large intercepts of low-grade ore in regions of barren rock. Because the low-grade material was not there to begin with, this is not a process of overestimating low-grade mineralization. The next statement that "the average result is similar to that of the diamond drill holes" may apply to the data set numerically, but it is not true when viewed spatially on cross sections. Adjacent reverse circulation and diamond drill holes are almost impossible to correlate, high-grade zone values vary widely and many low-grade intercepts make no geologic sense. The subset sampling and cross sections presented in the first part of the paper show that the reverse circulation portion of the data set has some serious problems, as highlighted above, and should not have been dealt with statistically at all. Conclusion Each ore body is different, and each drilling method presents unique sampling problems. In this case, the diamond drill is the

Jan 1, 1994

By C. D. Anderson

"IntroductionTungsten carbide is a valuable material used in a variety of different applications, including the manufacturing of cutting tools, bearings and as a cost-efficient alternative to industrial diamonds. Both the high hardness value (Mohs 9) and scratch resistance of this material make it a valuable commodity for use in the mining industry.Usually, the production of tungsten carbide is a multistep process involving one or more of the following unit operations: hydrometallurgical digestion, solution purification, crystallization (as ammonium paratungstate), calcination, hydrogen reduction and carbon synthesis. The proposed three-step process eliminates three of these steps (crystallization, calcination and hydrogen reduction) by implementing a combination of hydro/pyrometallurgical techniques. These include alkaline pressure leaching, carbon adsorption and carburization roasting. By eliminating some of the intermediate processing steps, there is potential to reduce energy consumption and decrease overall operating costs.Methods and resultsInitially, alkaline pressure leaching with sodium carbonate (Na2CO3) was employed to selectively leach tungsten, as tungstate (WO4 2-), from an industrial Scheelite (CaWO4) flotation concentrate. Experimental variables included lixiviant (Na2CO3) concentration, temperature and residence time. Experimental constants, based on previous work, were percent solids at 13 wt% and agitation at 400 rpm (Queneau and Strathmore, 1969). Leaching results showed it was possible to extract 97% of the tungsten present. The most favorable conditions for leaching were determined: 2M Na2CO3, temperature of 180° C and a residence time of 30 minutes."

Jan 1, 2015

By Roy M. Fleming

During the decade of the 1970's, a new emphasis was placed on assuring a safe and healthful workplace for all American workers. Much of the basis for this national effort was federal legislation: the Occupational Safety and Health Act of 1970 and the Federal Mine Safety and Health Act of 1977 (amended from the 1969 Coal Mine Act). One of the agencies involved in this protection effort is the National Institute for Occupational Safety and Health (NIOSH) of the Centers for Disease Control (CDC) in the Department of Health and Human Services (DHHS). In fulfilling its mandates under the 1970 and 1977 Acts, NIOSH conducts research, experiments, and demonstrations to support and stimulate advancements in health and safety practices. Priorities for NIOSH research are established primarily through congressional mandates, requests from the Department of Labor, needs as defined by NIOSH researchers, and surveillance information. Emphasis is placed on research in the areas of toxicology, industrial hygiene, physical and chemical sciences, physiology, ergonomics, engineering, psychology (behavior and motivation), and epidemiology (industry-wide studies). The framework of the current Institute program to identify, evaluate, and control occupational hazards includes activities in surveillance, research, evaluation, and training. These activities are planned and evaluated through a system that coordinates the efforts of eight research and scientific divisions. Each division develops projects to address program areas that have been identified by NIOSH management as having highest priority. In surveillance programs, the objectives are to identify substances and agents found in a representative sample of workplaces and to collect and evaluate information on rates of disease and injury in occupational groups. Information is also collected on occupational safety and health programs implemented by industry. Estimates of worker exposures and the potential for adverse health effects are considered in setting priorities for further investigations. A related activity, which also serves to provide technical assistance to industry, is NIOSH's Health Hazard Evaluation program. On-site investigations of workplaces are made in response to worker, employer, or government agency requests. Both industrial hygiene and medical examinations are conducted, and the results contribute to identifying new problems and evaluating their significance which may have public health implications beyond the particular worksites that are investigated. Field and laboratory research projects are performed to meet several objectives: - Characterize the working environment by evaluating current and past exposure levels for workers who are included in epidemiological or medical investigations. - Develop epidemiological information to define the association between the substance or agent under investigation and the acute and chronic health effects on workers. - Determine through animal studies the parameters of an association between exposure and effect. - Investigate the etiology of disease. - Develop sampling and analytical instruments and techniques and demonstrate their application for measuring toxic materials in the workplace. - Formulate sampling strategies that will accurately and precisely indicate exposure levels. - Develop medical procedures to prevent disease and to detect the presence of disease and early indicators of disease. - Assess the technology for control of exposures, including engineering and administrative techniques, personal protective equipment, and work practices. Presently, the research program is focused on reproductive effects, neurotoxic effects, injury/trauma, lung disorders, cutaneous disorders, cardiovascular disorders, cancer, stress-related disorders, effects of physical agents, digestive disorders, and renal and other organic disorders. In studying these issues, priorities are determined by the seriousness of possible adverse health effects resulting from occupational exposures, the feasibility of studying existing records or obtaining new data, and the size of the population which is potentially affected. Where there is low level of suspicion concerning adverse health effects or where an occupational disease occurs in a variety of industrial environments, investigations are limited to gross analyses of health effects such as review of mortality patterns. In such studies, the industrial populations selected are those for which existing data resources can be utilized. Such data consists of records of occupational exposures or health status which have been maintained by the employer, the union, or Government agencies. Where a review of the available information suggests that serious health hazards exist and the existing data resources are inadequate for quantifying the relationship between the specific biological response and type and degree of exposure, prospective studies are initiated. Information derived from such research is essential for the development of sound criteria for control of industrial exposures to noxious agents. Other input to the criteria documentation process comes from searching and evaluating the literature. Criteria documents contain the recommendation of an environmental limit where information is available to support it, as well as the recommendation of work practice controls, medical evaluation, information for workers to recognize and avoid the hazard, and identification of specific research gaps. In some cases, during the criteria document preparation, gaps in knowledge are found which necessitate further research before an occupational standard can be recommended.

Jan 1, 1981

By M. Kalin, H. D. Sharma

INTRODUCTION The inactive uranium mill tailings investigated in this study are located in two mining districts, Elliot Lake and Bancroft, Ontario, Canada. The sites exhibit a mixture of surface features consisting of dry areas, with or without vegetation and areas covered with water. On the edges of the water bodies, indigenous vegetation has invaded the tailings beaches [ Typha] spp. (Tourn.) L. a dominant plant on these tailings beaches, has been studied for the uptake of radium-226 and lead-210 (Kalin and Sharma, 1981b) from the tailings. It was found that most of the radium-226 remains in the roots of the plants, and that the solubility of radium-226 in control soil differs from that in tailings. The uptake of radium226 by vegetation and other biota is related to the solubility of the element in water. Factors controlling the solubility of radium-226 in uranium mill tailings are of interest in assessing the environments effects of these wastes. Rusanova (1962) found that the soluble or extractable amount of radium from the soil is inversely related to the total concentration of calcium and magnesium in the soil. Experimental work has clarified some aspects of the leachability of radium from uranium mill tailings (Levins, et al., 1978; Wiles, 1978, and others). Halvik, et al., (1967) studied the effects of pH and chemical composition of surface water on the liberation of radium from uranium mill tailings and uranium ore. He found that an increase in pH, up to a value of pH 9, decreases the amount of radium released from the tailings and the ore. A positive effect of calcium chloride was noted on the leachability of radium. Benes (1981) reviewed the physicochemical forms of radium and its migration in water. Based on experimental work, he identifies primary factors which determine leaching of radium from uranium mill tailings. The ratio of the volume of the leaching solution to the weight of the leached sample; the composition of the leached solids and the leaching solution, and finally the pH of the leaching mixture are of importance. He emphasized that a scarcity of field data exists, which would relate experimental work to the actual situation in the tailings ponds. Inactive tailings ponds in Ontario are 16 to 23 years old, and processes which are of importance in evaluating the long term effects of uranium mill tailings in the environment can be studied. The objective of this work was to investigate the leachability of radium-226 from the tailings under field conditions. MATERIALS AND METHODS Sample Collection A description of inactive tailings sites in Ontario, where the tailings and the water for this study were collected, can be found in a report by Kalin (1981). [Typha] spp. specimens were excavated from 16 different locations along with the tailings attached to the roots of the plants. A tailings sample from the surface area, around the plant, was secured before the excavation. Tailings samples were also collected from dry areas free of vegetation in the vicinity of the wetland stand. Surface samples (depth 0-5 cm) and samples at a depth of 20-25 cm were secured. Water was collected from the shallow tailings beaches around the vegetation stands. Sample Preparation The roots of the plants were washed free of tailings with distilled water. The resulting thick slurry of tailings was allowed to settle in the wash basin for five minutes and the supernatant water was decanted. The remaining saturated tailings were brought to 400 ml volume with distilled water in a beaker. The slurry was mixed with a magnetic stirrer for two 24-hour periods. After the first 24-hours, the slurry was allowed to settle for 20 minutes and the supernatant water was removed. The remaining sediments were suspended again in distilled water (400 ml total mixture) and leached for a second 24hour period. The tailings slurries from the different locations had a solid to liquid ratio, which ranged from 0.5 to 1.4 grams of dry tailings material per millilitre. The variations in the ratios are the result of differing fractions of coarse and fine tailings on the sites. In the final leachates, the solid to liquid ratios of the samples were 0.17 (±0.1) g/ml. The pH of the surface water and the leachate was determined with an I.L. Portomatic pH meter. All the tailings samples were homogenized in a mortar and brought to dryness at 75 to 85°C. Approximately 0.5 g of tailings were

Jan 1, 1981

By B. R. Green, Ms. M. H. Kotze

Ion-exchange fibres (IEF) were prepared by the ir­radiation grafting of styrene onto polypropylene, which was then subsequently functionalized. Strong- and weak-base exchangers were prepared and evaluated Tor their ability to extract gold cyanide selectively. The IEF prepared had loading capacities similar to those of the corresponding resins and they had good selectivities for gold cyanide when contacted with a mixed metal-cyanide solution. The expected advantage of IEF over granular exchangers, that of faster kinetics, was illustrated. The strong-base Iibre in particular seemed to be very effective for the extraction of gold cyanide from dilute solutions such as return-dam waters.

Jan 1, 1990

By Wallace Jarman

Introduction As with many gravity concentration processes, pneumatic concen¬tration traces its origin in antiquity. The use of winnowing to separate chaff from grain has long been known, and such procedures were undoubtedly practiced in ancient civilizations for the concentration of ores and the separation of slag from metal whenever specific gravity, size, and shape differences were favorable. Taggart142 has reported on the use of dry rockers and dry panning techniques for use with gold ores in arid regions such as Western Australia. The present day air table was developed in the last century for this purpose. Devices and Processes Classification. All classifiers make a separation on the basis of size, shape, and specific gravity. In addition to specific gravity and size, particle shape factor is often particularly important to pneumatic processes, and advantage is taken of the fact that both flat and fibrous particles settle at velocities substantially lower than that of their equiv¬alent spheres. Another factor of importance in this process is the bulk density of the material since substances such as exfoliated ver¬miculite or partially opened fibrils of asbestos have bulk densities significantly lower than those of the pure in situ mineral. Winnowing takes advantage of all of these physical factors to affect a separation starting with a closely sized feed, and vermiculite has been separated from rock by this process.142 When air classifiers are used to size minerals, the separation will often not be perfect because heavy particles will respond similarly to somewhat coarser light particles while flat, elongated, and low bulk density particles will act as would particles finer than the cut size. An example of a classification process that also results in concentration is the zig-zag classifier"' used to separate paper from glass, metal bottles, and cans during the recycle of municipal solid waste. Application of this process to minerals showing the proper specific gravity, size, and shape differ¬ences is obvious. An important device of this type is an air-aspirated screen used to remove asbestos from its associated rock during the dry processing of that mineral.144 The raw ore is crushed and screened and the asbes¬tos removed by aspiration from the surface of the screen by virtue of its shape and low bulk density. Hindered Settling. Based on the discussion in the section on "Hindered Settling Concentration and Jigging," the use of air devices could be anticipated in desert areas or where moisture may be deleteri¬ous to the product to be separated. Such processes have three major defects: (1) dust may be difficult to contain, (2) fines are difficult to process, and (3) the process is inherently less efficient than are wet processes as may be seen from Eqs. 3 and 4 in the section on "Hindered Settling Concentration and Jigging p. 4-47." Taggart142 has reported on the use of both dry panning and a dry rocker for gold separation in and regions. The dry panning makes use of winnowing, defection on the basis of specific gravity and shape during fall, and hindered settling. Prescreened placer material is poured from one pan to another as air blows across the falling stream. The process is repeated many times with hand picking to produce a rough concentrate. Magnetic minerals are then removed, and the residue, one grain deep in the pan, is air blown. In dry rocking the gravel is sized on a steeply inclined screen with the undersize fed to a riffle box with a porous bottom which is blown from underneath."' This device was the forerunner of the present-day air table. Air Tables and Jigs.145. 146 At least nine types of these devices have been developed, all but two of them for coal. While the devices used for coal may be characterized as pneumatic jigs, pneumatic tables, and pneumatic landers,145 only pneumatic jigs survive today. The same is true for ores.'" In these devices presized particles are fed to the separator which consists of an inclined vibrating conveyor with a porous surface through which air is carefully introduced to form a fluid bed. The lighter particles are lifted by the air out of uphill conveyance and float downhill, while the heavier particles in contact with the surface are conveyed uphill by the vibrator. Typically both transverse and longitudinal slopes are used. A plan view of a Triple S air table and the type of separation made is shown in Fig. 44.147 Because of its external appearance, the device has been called an air table, although it functions essentially as a jig. However, some of the asymetrical acceleration conveying function of a standard shak¬ing table is also performed by the eccentric vibrator incorporated into this device. Low pressure air is admitted below the vibrating table surface consisting of cloth (e.g., canvas), porous plastic, woven wire, or punched metal supported on a wire mesh or grid. As with a shaking table, the device produces a concentrate, middlings, and tailings. The middlings are recycled or are subsequently treated on another concentrating device. As with many wet separations, presizing by screening is necessary. The oft-repeated admonition of Professor Richards, "Separation without classification is damnation," is cer¬tainly true here. In this way a small heavy particle which might weigh the same as a large light particle and thus report to the same place on the air table has already been removed in the sizing step. Air tables are almost universally encased with a canopy to remove dust by aspiration. Some concentration may also be achieved in this step when favorable specific gravity, size, and shape differences are present. Applications Ore Separations. Air tables were originally developed for ore separations, and they find application in and regions or where water is deleterious or inconvenient to use or remove (e.g., small tonnage materials already dried). They have been used for asbestos, bauxite, calcite, cassiterite, columbite-tentalite, diatomaceous earth, fluorite, gilsonite, graphite, kyanite, manganese minerals, mica, managite, perlite, pyrite, pyrrhotite, vermiculite, and uraninite ores. More recently, air tables have found favor in separating a wide variety of secondary materials such as abrasive grains, bone char, catalysts, fiberglass, scrap glass, scrap wire from its insulation, prills from slag, dross and coke from metal or from each other, metal from crushed crucibles, lead from plastic in old batteries, and cubic particles from flat ones. The devices also finds considerable application in the preparation of food¬stuffs. As stated before close sizing before separation is desirable, and if the specific gravity difference is slight, very tight

Jan 1, 1985

By S. Z. Galiyev

In this paper the basic approach to the present planning and quality management of open-pit ore streams is presented. This is accomplished within the framework of a unified system of information management for the administration of a geotechnological complex on open-pit development of mineral deposits.

Jan 1, 2003

By Gunther Riedmuller, Johann Golser, Peter Schubert

The paper deals with the experience of the authors to cope with tunnel projects in heterogenous and weak rocks. The procedures applied to the investigation of such areas, the geotechnical assessment, the choice of tunnelling methods, the preparation of contract documents and the main features of NATM tunnelling to adapt to these conditions are outlined.

Jan 1, 1993