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By E. D. Attanasi, J. H. DeYoung

Although fraught with problems of completeness and comparability, statistical measures of mineral exploration in the United States point downward for 1985 and 1986. Exploration expenditures in the US domestic and Canadian companies have dropped steadily from a 1981 peak of about $400 million to about $190 million in 1985, according to a recent survey of exploration statistics by the Society of Economic Geologists (SEG). These totals have been adjusted to account for differences in the estimated coverage of exploration activity by each year's SEG survey. This survey is now supported by the US Bureau of Mines and the US Geological Survey (USGS). The drop in current dollar amounts does not take into account the effects of inflation, which would make the decline even more substantial. Metals Economics Group of Boulder, CO reported in its Mine Development Bimonthly that announced exploration budgets for 1986 indicated an even larger drop for the past year. Worldwide expenditures for companies covered by the report dropped from about $800 million to $750 million from 1984 to 1985 and plummeted to about $600 million in 1986. Exploration activity has been declining since about 1981. This has been due in large part to low prices for base and ferrous metals. Exploration budgets of mining subsidiaries of oil companies have plunged as parent companies try to conserve cash in the face of the sharpest decline in oil prices in nearly 40 years. Mining subsidiaries of petroleum firms that were either liquidated or divested recently include Anaconda (Arco), Getty Mining (Texaco), and Cyprus Minerals (Amoco). Exploration expenditures in Canada increased in 1984 in regions where gold is a traditional target. But there was little change in 1985, based on preliminary statistics from a federal government report (Energy, Mines and Resources Mineral Bulletin MR 211, 1986). Claim staking in Canada dropped 23% from 1983 to 1984 and declined slightly in 1985. Diamond drilling increased in 1984 to the record levels of 1980 and 1981. The ratio of exploration to development expenditures in Canada, however, fell from a 1981 peak of 0.9 to about 0.5 in 1984. The report also indicated that, since 1981, there has been a massive write-off of reserves with high production costs. Reserve levels of all major metals were down since 1981. Precious metals exploration accounts for an increasing share of total mineral exploration. For example, the SEG data show that 90% of 1985 US exploration expenses by domestic mining companies were devoted to base and precious metals, compared with only 51% in 1980. The restructuring of the mining industry has been accompanied by a decrease in response to the last two SEG annual surveys, but the trend towards precious metals was already established in earlier years. Trade journal reports suggest that the reduction of long-term interest rates has encouraged the mining industry to make cost-reducing capital investments in existing mines to maintain competitiveness. This is consistent with the observations that metals explorations in 1986 was characterized not by announcements of "grassroots" discoveries, but by on-property exploration on identified mines or prospects. In an effort to cut costs, gold mining companies have been following up on low cost production opportunities in their prospect inventories. Short-term, low risk, heap leach operations that can produce rapid returns on investment have been pursued. Specific exploration projects are covered in the individual state sections of this Annual Review. Even though economic growth continued steadily through 1986, the domestic mining industry has

Jan 5, 1987

By C. R. Jenkins, G. S. Taylor

Three sedimentation ponds had their performance evaluated before and after installation of modifications. Each pond had a floating baffle installed, two had siphon outlets, and one had a floating outlet device. Baffles inhibited short circuiting, and the outlet devices retarded flow following a rainfall event and drained the pond, creating a large storage volume to maximize detention time. Total suspended solids and settleable solids tests were measured on samples of influent and effluent to evaluate pond performance. Particle size analyses were conducted on samples containing measurable amounts of solids. Performance improved in each pond, with baffles providing the major improvement.

Jan 1, 1987

By Paul E. Richardson, Edwin E. Maust

Cyclic voltammetry and surface potential (photovoltage) measurements have been carried out on galena electrodes in sodium tetraborate solutions with added HC1 and NaOH to adjust the pH over the range 2 to 13. The first technique shows that the surface species formed on moderate anodic polarization and reduced on subsequent cathodic polarization are the same over the entire pH range. At anodic potentials, a soluble metal species and excess sulfur are formed; at cathodic potentials, sulfur is reduced to a soluble species. More importantly, excess surface sulfur is formed spontaneously under zero current conditions in alkaline solutions. This has been shown to occur on both polished surfaces and on virgin surfaces produced by in situ cleavage under the electrolyte. The photovoltage gives some insight into the charge and potential distribution at the galena surface. This is found to depend on past electrochemical history and the n- or p-type semiconducting character of the electrode and is interpreted in terms of changes in the surface stoichiometry that occur during reduction or oxidation. The effect of surface stoichiometry on subsequent xanthate interactions is discussed.

Jan 1, 1976

By V. Ciribeni, R. J. Ferretti, C. de Arrieta, E. E. Rossi

The relationship between collector concentration and the solution pH at which flotation occurs is discussed for different minerals. When flotation results are plotted as log of the concentration against pH, the values define areas of total, partial or no flotation. The experiments were performed in three different conditions: a) floating with the same solution used for conditioning; b) floating with water at the same pH as the conditioning solution; and c) floating with water at pH = 7. In each case, the results obtained are quite different. It is suggested that the presence of a second layer of collector reduces flotation over some domains in the graphs. These domains are called depression areas.

Jan 1, 1992

By Steven W. Hunt

"A paper called “Global Experience with Soft Ground and Weak Rock Tunneling under Very High Groundwater Heads” was presented at the North American Tunneling 2006 conference (Holzhäuser et.al 2006). It summarized global experience with earth pressure balance (EPB) and slurry shield tunneling on nine projects that encountered groundwater heads ranging from 6 to 11 bar. Since then, additional projects have been completed with groundwater heads ranging from 7 to 15 bar. Of these, the high pressure tunneling experience on the Lake Mead Intake No. 3 project in Nevada and on the Eurasia Tunnel (Istanbul Strait Crossing) had the greatest lengths of tunneling at face pressure over 7 bar. Experience with sustained pressurized face tunneling at groundwater heads over 7 bar and risk management observations are the focus of this paper. INTRODUCTION High groundwater head, particularly at 7 bar or more, is a major challenge when tunnelling in high permeability ground and on drives long enough to require cutter changes. It has a strong impact on design and operation of Tunnel Boring Machines (TBMs) in order to protect the main bearing from contamination, prevent excessive groundwater inflow, ensure face stability and enable access to the cutterhead and excavation chamber for maintenance. During the past 20 years, TBM manufacturers and suppliers have made tremendous improvements that allow tunneling at groundwater pressures to 17 bar or more. The most significant risk with high pressure tunneling is generally that of excavation chamber access and potentially the cutterhead for cutter changes, cutterhead repairs and TBM maintenance. Hyperbaric interventions are possible and safety variances have been approved for saturation dive interventions at pressures as high as 17 bar (Lake Mead Intake No. 3). While high pressure hyperbaric intervention equipment is available and safety approvals can be obtained at many locations, few contractors consider the cost and risk of hyperbaric interventions over 7 bar to be acceptable as the primary means of excavation chamber access. Experience with high pressure tunneling prior to 2006 was summarized in a paper entitled “Global Experience with Soft Ground and Weak Rock Tunneling under Very High Groundwater Heads” (Holzhäuser et.al 2006). That paper provided information on 9 projects: South Bay Ocean Outfall, San Diego; Channel Tunnel (French Side), France; Storebaelt Tunnel, Denmark; 4th Elbe Tunnel, Germany; Wesertunnel, Germany; Westerschelde Tunnel, Netherlands; St. Petersburg Red Line, Russia; Nara Prefecture Water Conveyance Tunnel, Japan; and Tokyo Wan Aqua Line Tunnel, Japan – see Table 1."

Jan 1, 2016

By George W. Toth

This chapter describes the development of a computer code which rapidly estimates the cost of producing coal from either surface or underground mining situations. The computer code, termed the coal production cost (CPC) code, was developed under an NUS corporate research grant and was based on the findings of several coal mining and cost research analyses performed by NUS over a three-year period. The studies which served as the primary basis for the CPC code were the coal mining cost models developed by NUS for the Electric Power Research Institute. These models were designed for use in manual analyses and have been published by EPRI (Toth, 1977; and Stinnett, 1977).

Jan 1, 1979

By Marek Niec

Native sulfur deposits in Poland occur in Upper Miocene strata on the northern (platform) border of the Carpathian foredeep. Systematic exploration since 1953 has resulted in the discovery of seven stratifom-stratibound sulfur-bearing limestone deposits that together contain about 0.6 billion tons of demonstrated sulfur reserves and about 0.5 billion tons of inferred and hypothetical resources. One open pit and three Frasch mines are currently in operation; another is under construction and one has been abandoned. Total production is about five million tons per year from ore containing on the average about 25% sulfur. Field, isotope, and micropaleontological data indicate that the sulfur-bearing limestone was formed through the bacterial reduction of gypsum in the presence of methane discharged from source beds and traps in the Carpathian foredeep. Subsequent recrystallization of the sulfur-bearing limestone, tectonic activity, jointing, karstification, and partial leaching of the sulfur has transformed the sulfur deposits and has altered the thickness and content of the sulfur-bearing strata, and their porosity and permeability, affecting the productivity and water consumption of the sulfur wells. Caputerized borehole logging techniques and geostatistical reserve estimates are used in mine planning. Great environmental impact constrains the development of sulfur mines.

Jan 1, 1992

By D. R. Nagaraj

The practice of nonsulfide minerals flotation can be best characterized as an evolutionary blend of scientific theory and art. Although extensive fundamental studies have been carried out in the past several decades, and significant theoretical aspects have been developed, plant practice has developed the art form, often ahead of the theory, which is somewhat in contrast to sulfide minerals flotation. Several excellent review articles have been published in the past highlighting both the theoretical aspects and plant practice. An overview of nonsulfide flotation is presented here. Major differences in sulfide and nonsulfide flotation are highlighted. An assessment of the state of nonsulfide flotation, recent advances made in flotation processing, and industry needs are also given.

Jan 1, 1999

By D. J. Frey

While costs of most commodities and services have increased markedly over the past 25 years, the cost of electricity has steadily declined. One of the reasons for this price decline is the improved efficiencies of generating plants which is shown in Fig. 1. 1,2 Another reason for this is the decline in coal production costs. Efficiencies for the best plant increased from about 32 percent in 1540 to about 40 percent in 1962 and then decreased slightly to 38 percent in 1965. The increase in efficiency for all plants (US average) has been even more notable, progressing from less than 15 percent in 1940 to about 32 percent in 1965. The chief reason for the improved efficiency is the change in operating steam temperatures. These increased about 12 F per year until 1200 F was reached in 1962. At this high temperature excessive corrosion of super-heater and reheater tubes was experienced and steam temperatures were dropped back to 1050 F and even 1000 F in some cases. To successfully compete against other energy sources for generating electricity, this corrosion problem must be solved so that operation at higher temperatures and thus, increased efficiencies will be possible.

Jan 1, 1967

By Michael Schmalzel

Freeport-McMoRan Copper & Gold, Inc. (FMI) will soon begin copper production from the Dos Pobres and San Juan deposits near Safford, Arizona. Ore reserves total 615 M tons grading 0.36% copper, predominantly as chrysocolla. Copper extraction will be by leaching with sulfuric acid. Fluor Canada Ltd. provided EPCM services to design an ore handling and conventional SWEW facility capable of producing a nominal 240 million pounds per year of cathode copper. The ore handling facility will process 114,000 tons per day of ore through three-stage, open-circuit crushing followed by agglomeration and product placement on the permanent leach pad. Stacking of ore on the leach pad will utilize Terra Nova Technologies' "Super Portable" mobile stacking system. The stacking system fleet consists of 13 self- propelled, crawler-mounted mobile conveyor units, each with 72-inch-wide belting and a capacity of 6,800 tons per hour, including ten 250-foot-long portable conveyors, a horizontal feed conveyor, a 285-foot-long horizontal conveyor and a 220-foot-long radial stacker. PROJECT BACKGROUND Project History The Safford Leach Project is located in the Safford mining district in Graham County, Arizona, approximately eight miles northeast of the town of Safford and 170 miles east of Phoenix. The 3,360-acre property is located in the Gila River Valley, immediately south of the Gila Mountains, at elevations between approximately 3,000 and 5,400 feet above sea level. The Safford Leach Project is comprised of the Dos Pobres and San Juan deposits, two of five known copper ore deposits in the Safford mining district.

Jan 1, 2008

One of the major objectives of cost analysis is to enable the manager to predict the financial outcomes of decisions. To accomplish this, the future costs and benefits of alternative courses of action must be determined. If care- fully used, information about past financial performance can be helpful in this analysis despite the fact that, by definition, financial reporting information is historical. In many cases, both revenues and costs need to be estimated for decision- making. For the production manager, additional revenue is a result of increased throughput or recovery of valuable material from the stream of mined material. A reduction in operating cost, although similar to a revenue increase in its financial impact, is estimated using slightly different techniques. Generally, the estimation of cost is more difficult than the estimation of revenue. Most cost estimates have two components: an estimate of fixed costs and an estimate of variable costs. As discussed in chapter 5, the total cost of an activity during a specified period can be expressed as: Total cost = (Variable cost per unit of activity) x (Units of activity) + Fixed cost or TC = VX+F

Jan 1, 1999

By Zhang Youdi

A two-step approach has been developed for surface mine short term planning by the authors. The first step is mid term control and planning by the use of Goal Programming. This step gives optimal results for mid term planning (i. e. yearly or quarterly mine plan) as well as a macro control for short term planning (i. e. monthly or weekly plan.) The second step of the approach deals with short term production scheduling by the application of CAD technique and Systems Simulation. An interactive color character graphic design system has been developed with a software package. The menu-driven and module- structured package provides sufficient functions for surface mine short term planning and makes the model very flexible and user-friendly. This model has been applied to a large surface coal mine for short term planning optimization. Satisfactory results have been obtained. It is concluded that for complicated mining conditions this two-step combined approach gives an optimal control of mid term planning, makes the short term planning easier to avoid blindness; it has been proven that the Goal Programming is a powerful tool for solving multi-objective decision-making problems; guided by GP mid term planning, the CAD technique and simulation software package for short term planning are able to be concentrated on their practicality and flexibility.

Jan 1, 1992

NIOSH is conducting research to reduce the silica dust exposure of workers at surface coal mines. One goal of this research is to evaluate the relationship between drilling parameters, rock strata and silica dust generation. This study involved measuring blast hole emission dust from a rotary drill rig which required sampling high concentration dust (>400 mg/m3) for silica content in a high velocity airstream. To measure dust initially, traditional sampling methods using personal sampling instruments were attempted in and around the shroud area of the drill with no success. Variations in the dust cloud concentrations under the shroud, the condition of the shroud and its orientation over the hole, and ambient air conditions prevented consistent and accurate dust measurements from being obtained. Amore consistent dust cloud is necessary for accurate measurements. An area of the drill’s dust collector system that consistently draws the emitted airborne dust from the hole is the collector tube. This tube connects the drill collector’s vacuum and dust filtration system to the shroud area. Assuming the collector system is working as designed, sampling from the collector tube would enable more consistent and accurate samples to be taken. However, current personal samplers are unable to sample in the concentrations and velocities experienced in the collector tube, so another method had to be devised. To achieve the desired results, an in-stack cascade cyclone was used. Preliminary field testing shows positive results.

Jan 1, 2003

By Bruce R. Sutherland, Jim B. Ramsden, Gerry L. Bolton

Conductive metal powders are important building blocks for today's micro-electronic circuitry. Formulated into inks, they provide the interconnects needed to complete a complex integrated circuit and the means to enter the world of miniaturization. Traditionally, the inks have been based upon expensive metals such as silver, palladium, platinum and gold because of their excellent electrical conductivity and resistance to corrosion and oxidation. The use of a copper based ink, as an alternative to precious metal inks, recently has received considerable attention. Instability in the prices and limited supply of certain precious metal systems have driven up production costs, making the development of a lower cost copper system more attractive to manufacturers. However, lower production costs are on1 y real ized if performance and reliability can be maintained. While the development has been driven by cost, copper does offer some significant performance advantages over noble metal systems: conductivity as good as silver and 4W better than gold; leach resistance better than silver and equal to gold; stability at high frequencies better than gold or silver; strong film bonding characteristics; and compatibility with most solders. These benefits, however, do not come without cost. The inherently reactive nature of pure copper, while providing unique performance properties, makes it difficult to process. Unl i ke precious metals which can be fired in air, copper would oxidize and so requires special furnaces and atmospheres. Despite these difficulties, the transition from precious metal thick film systems to copper is gaining momentum. Manufacturers of high density, high performance circuitry are exploring the performance advantages of copper over gold and silver and the manufacturers of consumer products are considering the potential cost savings of copper over silver-palladium. Sherritt has developed a fine copper powder for this industry. Through association with the ink manufacturers, it has been found that performance properties of the ink vary with the physical and chemical characteristics of the powder. Production Process The production of very fine copper powders at Sherritt is based upon the disproportionation of cuprous ions as outlined in Equation [1] (1).

Jan 1, 1990

By R. Addison, P. V. Avotins, E. Martinez, L. A. Haas, D. K. Mortenson, E. EI-Shall, R. D. Kulkarni, M. D. Flavel, S. Chong

Mineral processing activities in general reflected the economic ills of 1981 and early 1982, but in some areas the depressed state of the industry resulted in increased activity. As were all aspects of the minerals industry, processing plant operations were severely affected by the recession-prone economy, by sagging prices for primary metal products-copper, molybdenum, nickel, iron, manganese, and especially uranium-and numerous shutdowns and layoffs. Copper production by major producers in Arizona and Utah was severely curtailed; Amax, the major US molybdenum, producer did considerable belt-tightening; and the uranium industry was in a state of disaster. Even the precious metal superstars-gold and silver-were affected, with a steady decline throughout the year in world market prices. Perhaps hardest hit have been newly developed properties, particularly in the uranium industry, and old-line properties where historical development impacts today. No longer can such properties afford the luxuries, for example, of a long haul distance between mine and plant or continued use of antiquated facilities. Surprisingly enough, the very state of the economy has caused increased activity in some sectors of the mineral processing industry. In mill design, although large projects have been tabled, smaller projects have gone on, with innovations in design, often for cost-saving reasons, that will affect future designing approaches. Economic restrictions are impacting on mill flowsheets as researchers look for improvements and better, less expensive techniques. Other unit processes-hydrometallurgy, pyrometallurgy, concentration, materials handling-are impacted by the need for a better, less costly product. Although at the end of the first quarter of 1982, no major environmental legislation had been enacted, rumors persist that there will be a loosening of some of the stricter standards, both in the requirements themselves and in the time allowance for implementation. The year had seen some relaxation in how current legislation and standards are administered. For example, in OSHA (Occupational Safety and Health Administration) operations, there has been a shift toward voluntary checking of industry compliance with work rules, rather than emphasis on agency inspections. However, the industry continues to view environmental factors as having major influence on future operations and efforts to design for environmental safety are becoming almost as important as the processes themselves. Throughout the industry there has been a further focussing on project management, recognizing the necessity for tight control of budgets and schedules-and the systems used to effect them. Materials Handling Review prepared by A. T. Yu, ORBA Corp. The frenzy of coal export activities has continued into 1981. Many modern export terminals are now in construction while others have either been held up or cancelled. Economics and environmental permits have been some of the major problems. Currently under construction are terminals in Newport News, VA; Charleston, SC; and Baltimore, MD. Expansion of existing facilities at Mobile, AL, and New Orleans, LA, is also well under way. A wide variety of systems and components are being used. They include traveling shiploaders, tunnel and bucket wheel reclaim¬ers, stackers and high line trippers, and bottom and side dump-type car dumpers. Manufacturers from Japan and Europe have been participating along with domestic suppliers. As an attempt to avoid environmental problems, a system of loading and unloading coarse coal

Jan 5, 1982

By Miguel N. Herrera, Abbas H. Mirza, Fiona M. Doyle

The standard test methods used to determine the pyrite content of coal and mineral wastes, and their propensity to release acidic drainage, are critically reviewed. In addition to analysis of total sulfur by combustion, test methods using selective oxidation of pyrite by HNO3 and H2O2 are available. The oxidation kinetics of pyrite vary appreciably from sample to sample, and it is difficult to ascertain whether complete dissolution has occurred in heterogeneous materials. The reliability, reproducibility and suitability of different standard test methods were studied, using well characterized ore and coal pyrite samples. The kinetics of pyrite dissolution were also investigated. The results are discussed in terms of the fundamental chemical and physical characteristics of each sample, and the implications for waste characterization are considered.

Jan 1, 1992

By Eugene R. Palowitch, Albert W. Deurbrouck, Thomas H. Parrsons

INTRODUCTION Hydraulic concentrators utilize the physical characteristics-size, shape, and specific gravity-of particles suspended in a fluid medium to effect a concentration of desired quality. Fine-coal concentrators include generally those devices which are used to clean roughly 3/4, in. (9.5 mm) top-size coals. While this size designation is somewhat arbitrary, it is consistent with current practice although some fine- coal concentrators can treat coarser coals effectively. A variety of devices have been and are currently being used to wash fine coals and include: dense media cyclones, wet concentrating tables, hydrocyclones, jigs, spirals, launders, and upward-current classifiers. As launders and upward-current classifiers have been replaced by more efficient devices, they no longer warrant consideration as fine-coal washers. And as fine-coal jigs were addressed with the Baum jig under Part 1, Section 2, and heavy media cyclones and hydrocyclones were addressed under Part 2, Section 1, of this Chapter, only the wet concentrating table and the spiral concentrator will be discussed here. WET CONCENTRATING TABLES History The current wet concentrating table evolved from continuous belt concentrators which utilized a flowing film of water to recover heavy metals. In these devices the heavier concentrate moved up the inclined plane of the belt while the lighter impurities were washed away by water flowing down the belt. The natural outgrowth of the continuous belt concentrator was the vanner, a vibrating endless belt which was first developed about 1860 by Hartwig. Later models of the vanner, such as the Frue, incorporated oscillation in a plane transverse to the direction of the water current. Excellent descriptions of these washers are found in The Cleaning of Coal, by Chapman and Mott.80 Further development of tables included the circular stationary table (Linkenbach), the multiple round table (Anaconda-Evans), the bumping table (Campbell), and finally the differential-motion table which is now used extensively for cleaning fine coals.

Jan 1, 1991

The Waste Isolation Pilot Plant (WIPP) is a geologic repository for disposal of transuranic waste and is operated by the US Department of Energy. The repository is located at a depth of 655 min the Permian age salt beds of the Salado Formation. The exhaust air from the facility is independently monitored by the Environmental Evaluation Group to verify compliance with regulatory release limits for radioactive materials. A May 1995 video inspection of the exhaust shaft identified fluid migration into the uppermost 25 m of the shaft. Since then, water has been observed flowing in from cracks in the shaft lining between 16and 25 m below surface level at an estimated rate of between 5 and15 m3/d. This water inflow has not only negatively impacted the equipment in the shaft, associated duct-work and monitoring equipment located at the top of the shaft, but also challenged efforts to verify compliance at the WIPP. This paper provides an analysis of these effects.

Jan 1, 2004

By James Donald Forrester

JAMES DONALD FORRESTER 32.1-EXAMINATIONS The field examination of a mineral deposit or mining enterprise requires a comprehensive effort to determine all natural and man-made factors bearing upon the problem to be resolved by the investigation. Therefore, the purpose to be served by an examination must be fully understood before the engineer assumes responsibility, and before actual field work starts. A clear understanding facilitates planning the approach to the project for maximum efficiency and thorough acquisition of information. It follows, of course, that the engineer has the necessary knowledge and experience to discharge satisfactorily the professional obligations attending the project. Some studies are in herently more complex than others, and the requirements of the problem are not always the same. Some examinations require the detailed investigation of large operating or nonoperating mines or, possibly, of mining districts; others involve more or less reconnaissance studies; and still others rela¬tively small undeveloped mineral occurrences. Likewise, the primary objective of some analyses may be the evaluation of a mineral deposit or a mining property, whereas in other projects the major objective may be guiding mining or drilling work in the discovery of new or hidden ore bodies and mineral-bearing structures. Thus, the possible range of any given examination may extend in varying degree through one, or more, of the following types of procedures: 32.1.1--GEOGRAPHIC ENVIRONMENT Studies of geographic environment should be made to ascertain the general physical situation in the area under consideration and to identify those correlative factors hearing on the, findings resulting from the field examination. This commonly will include determinations of: A. Location of the field area with respect to the state and county in which it occurs and, if feasible, a record of the township, range and section with reference to the principal meridian, and base line (or lines) that apply. For examinations in foreign countries, or in regions outside the continental United States, it is desirable that the field locality, in each instance, be identified with reference to the boundaries of some form of political entity essentially comparable in character to the divisions used in the United States. B. Distances from existing communities and related service centers, via: 1. Roads, both improved and unimproved. 2. Railroads. 3. Navigable waterways. 4. Airports. C. Topographic relief as it will influence the selection of 1. Pit site or positions of underground mine portals or shaft sites, including dump areas. 2. Mill site, including tailings disposal area.

Jan 1, 1973

By A. K. Bakshi

In cold regions, rinsing of spent cyanide from leach heaps is stopped during winter and is resumed again after the snow melts. The effect of this idle time on the overall removal process was studied in this experiment. Samples were collected for rinsing tests from one heap at a gold mine near Fairbanks, Alaska. Continuous and interrupted rinsing of this sample were carried out in test columns. The rinse solution was analyzed at regular intervals to determine the rate of cyanide removal from the solids. It was found that total cyanide concentration per rinse cycle for interrupted rinsing test was higher than for the corresponding continuous rinsing test. As a result, interrupted rinsing required less rinsing cycles than continuous rinsing.

Jan 1, 1995