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By D. A. Knight, V. G. Medina

Kidston's 14 000 t/d mine and mill complex in Queensland, Australia, started operation in January 1985. During its first 18 months of operation, the mine produced over 7000 kg (225,000 oz) of gold, making it the largest gold producer in Australia. This paper describes the planning, logistics, flowsheet, and process for the Kidston project, and some of the problems encountered during startup and the measures taken to correct these problems.

Jan 1, 1987

By M. J. Mrugala

Typically the conventional pillar design methods consider the behavior of the pillar alone. In such analysis the contribution of the associated roof and pillar is not considered. The focus of this paper is a study of pillar behavior in the context of interaction between a different rock material sequence in the associated roof and floor. The finite difference element code FLAC (1)is used to perform modeling of pillar response to various stratigraphic sequences.

Jan 1, 2003

By James D. Bliss

Evaluation of data for three engineering variables-absorption, bulk specific gravity, and freeze-thaw durability (350 cycles)-was made for quarries in carbon- ate rocks in Oklahoma that supply aggregate. It was found that lower Paleozoic carbonate rocks (Cambrian through Devonian) are likely to make a better quality aggregate than upper Paleozoic (Mississippian to Permian) carbonate rocks. In addition, freeze-thaw durability can be forecast from absorption and is exemplary for lower Paleozoic carbonate rocks.

Jan 1, 1999

By M. Kalin, C. Steinberg

We have worked on several flooded pits from coal-mining activities in the former East Germany, as well as ones associated with hard- rock mining, including the B-zone pit discussed in the above technical paper. We found the paper to be a useful summary, but, unfortunately, it failed to give an adequate comparison of the physical limnology of the flooded pits, which is an essential component. While the title suggests that the primary focus of the review is physical limnology, it appears that it is essentially pit-lake chemistry being presented. Physical limnology requires that factors such as fetch, latitude, light penetration, relation to ground water table, methods of flooding and the physical shape of the pits be defined. These physical aspects of a pit interact with the chemical and biological processes taking place in it, all of which contribute to the character of a water body. Few of these physical aspects are presented, however. The conclusion that the authors reach suggests that meromixis may be a condition that would serve as an effective containment mechanism for contaminants in a pit. Although this may be desirable, such limnological conditions are not clearly supported by the data presented for any of the pits. These data should be summarized to facilitate comparison between the same structural units of the pit water - the epi- and metalimnion for example. The thermocline depth is a reflection of the physical forces mixing the water body, and pit dimensions affect these forces. Due to the use of different scales in Figs. 2 through 5, it is difficult to determine whether the thermocline is at the expected depth, because the fetch is not given. Moreover, the status of a water body cannot be determined unless measurements cover a period of at least one year, and depth profiles are completed to represent the entire depth of the pit. This shortcoming is most notable in the case of the Berkeley pit, where data are given for depths of only 20 and 35 m (66 and 115 ft), although the pit is reported to be 242 m (794 ft) deep. Limnological data to define the status of the pit water have to be collected at regular intervals, for the same parameters. The authors present temperature measurements for 1-m (3.3-ft) intervals, but fail to use that interval for other parameters, such as dissolved oxygen or, in some cases, for contaminant concentrations. Furthermore, the profiles for the deepest part of the pit display only part of the picture, because pits are rarely conical. Profiles can be considered to represent the status of a water body only after other stations in the pit have been monitored regularly and the consistency is determined. For example, fresh water, which can enter a pit at any depth, would interfere with the proposed meromictic conditions. Similarly, organic material at the bottom of a pit, such as the fish-waste deposited in the Gunnar pit, contribute to oxygen consumption. Oxygen depletion alone is not indicative of meromixis. It is interesting to note that the Dpit arsenic concentrations could possibly be slightly higher than the B-zone pit concentrations at depth, although this is difficult to determine accurately when a log scale is used for the D-pit and not for the B-zone pit. In our investigations, we noted arsenic removal in the B-zone pit bottom water, which was due to the formation of particles that are relegated to the newly forming sediment in the bottom of the pit. Particle-carrying contaminants form due to a combination of geochemical and biological factors and TSS contributed from erosion of the upper parts of the pit walls, whereas the settling out of particles from the water column is controlled by the physical conditions or turn over, for example. during ice cover in the B-zone pit. Although meromictic conditions for flooded pits may be desirable at decommissioning, this would depend largely on the physical conditions of the pit, because, under no circumstances, would this water be of desirable ground-water quality. Under meromictic conditions, acidity, if an environmental issue, may be reduced by microbial acid-neutralizing activity, and several heavy metals may form more or less stable sulphitic compounds. These may stay suspended in the water if conditions are such that they are not relegated to the sediments, i.e., in the absence of turnover. These processes do not take place in meromictic conditions only, but meromixis does require autochthonous and/or allochthonous organic substrate supplies, which are generated under aerobic conditions. Specific limnological (biological, chemical and physical) features of the pit lake under consideration have to be defined, such that water quality parameters can be predicted, and the objectives of the decommissioning activities, environ-

Jan 1, 1999

By David Hanson, Sean Warren, Chaparral Berry

"Coal bumps, also referred to as dynamic failure events or coal bursts (Lawson, Weakley, and Miller, 2016), continue to be a hazard in underground coal mines. While current design methods have significantly reduced the occurrence of coal bumps, they have not been completely eliminated. This paper investigates a correlation between coal compositional components, coal molecular structure, and probability of coal bumps in an effort to deepen understanding of coal behavior in an effort to reduce hazards in underground coal mines.Samples from the Penn State Office of Coal (PSOC) Department of Energy Coal Samples (DECS) were obtained for Fourier Transform Infrared Spectroscopy (FTIR) analysis using the KBr pellet method. Peaks indicative of the coal molecular structures were obtained using spectral integration software. These data, combined with published elemental data, were compared to historic bump occurrence in order to establish a possible correlation. Finally, results based on multivariate analysis of the elemental and FTIR data with bump status as the dependent variable suggest that elemental sulfur and molecular structure can be used as an indicator of bump susceptibility within the sample set considered.INTRODUCTIONThe study of coal requires consideration of multiple variables: percentages of organic and inorganic components, organic component origins, coal age, pore structure, cleat density, elemental composition, etc. Examining coal in situ increases the number of variables, such as coal depth, seam thickness, surrounding stratigraphy, and so forth. This collection of variables influences the subsequent behavior of coal simultaneously, and weighing their relative impact is a challenge for researchers. “A problem never exists in isolation; it is surrounded by other problems in space and time” (Ackoff, 1956). Having a substance such as coal that we know so much about, and yet so little, we have to ask what can be learned.An experimental study using Fourier Transform Infrared Spectroscopy (FTIR) was undertaken to determine if the chemical structure of coal contains information which may lead to a better understanding of triggers or attributes which may, in turn, lead to an increased probability of a dynamic failure event. While a full analysis of the factors driving dynamic failure are beyond the scope of this study, it is possible that a better understanding of the chemical structure of coal will lead to an increased knowledge of its inherent behavior, including its propensity to burst."

Jan 1, 2019

By Thomas J. Lien

Granitic Pegmatite deposits are the chief source of commercial feldspar, micas, lithium minerals, tantalum-columbium, beryl, and certain types of kaolin. The output from pegmatite mines in the United States is small compared to other mineral products in terms of bulk or value, and much of it comprises only minor metals and nonmetals. Nevertheless, pegmatite minerals play a vital part in our domestic industrial economy, particularly in the ceramic and electrical industries. Numerous special purpose uses also are important, even though they require small quantities of raw materials. In recent years, realizing the potential importance of the pegmatite minerals, the U.S. Geological Survey, the United States Bureau of Mines, several state Bureaus of Mines, and a few private companies have carried on extensive programs of pegmatite studies in the New England and southeastern states, in the Black Hills area of South Dakota, in the Rocky Mountain region of Wyoming, Colorado, and New Mexico, and in various parts of Washington, Idaho, Utah, Nevada, Arizona, and California. Currently, some of the pegmatite minerals such as micas and spodumene are selectively separated by the flotation process. To a lesser extent a few plants are selectively floating feldspar and quartz. Much of the credit for the above progress goes to the fine work done by U.S. Bureau of Mines (1), and companies such as Foote Minerals (2). Additional research efforts by the New Mexico Bureau of Mines (3) has successfully demonstrated selective separation of micas, beryl, spodumene, lepidolite, microlite, quartz and feldspar from a complex Pegmatite containing all these minerals. Since the nature of the mineralization of various valuable components of a pegmatite deposit is such that selective separation of some of these can be carried out at a coarse size using the Heavy Media Separation technique, it was felt that such a system should be investigated for selective preconcentration of their minerals. It was also felt that of all the :MS systems available, the DYNA WHIRLPOOL (DWP) device which allows a close control and adjustment of specific gravity should provide a means of achieving the above goal. Once the desired preconcentration of one or more of the pegmatite mineral assemblage is achieved, the available selective flotation techniques should provide effective recovery of various minerals into marketable products. This paper presents technical and economic aspects of selective preconcentration of some of the pegmatite minerals followed by selective flotation to produce marketable products.

Jan 1, 1978

By T. P. Meloy

The packed column flotation cell is an awesome separation device. Virtually unknown and untested, the packed column flotation cell is one of the ten most important developments in mineral processing of the 21st century. Though experimental and industrial data is limited, it is clear that the packed column flotation cell is two to three orders of magnitude better than the conventional flotation cell and one to one and a half orders of magnitude better than the open column flotation cell. With the modern packing taking up less than one percent of the packed column, column blocking does not occur. For a packed column operating 24 hours a day, 365 days a year, the estimated mean time between failures (MTBF) is one hundred thousand hours or roughly twelve years. With no moving parts, lower maintenance costs, lower power consumption and inherent operating stability, the packed column is a powerful separating machine. Because there is little meaningful data for comparing the packed column to the conventional flotation cell and the open column flotation cell, much of the material presented in this paper are guesstimates. They are disinterested guesstimate made by the authors after extensive theoretical work and reviewing the known facts. In the authors' opinion, no available data contradicts the guesstimate. The authors expect that there may be errors as large as three hundred percent. Even three hundred percent errors will not change the conclusions of this paper. The packed column flotation cell is a formidable separating device. To understand the problems of comparing the three types of flotation cells, consider the fact that the three cells may have different modes of separation. One of the authors, Meloy, believes that in the conventional cell, the primary particle separation takes place in the liquor with secondary separation taking place in the froth, while for open column flotation, all the separation takes place in the froth. However, he believes that in the packed column a large part of the separation may take place on the walls of the packing. If this is true, not only is the method of modeling each type of cell different, but the method of particle selection in the cell is different. This means that one type of cell may be better at differentiating between two different types of particles. There is a growing body of literature on open and packed column flotation. Suggested reading: (Clarke et al; Hucko et al; Li; Smith & Warren; and Yang).

Jan 1, 1994

By J. García, B. Arango, F. Calderón, O. J. Restrepo-Baena, A. Carreno, L. Rojas-Mendoza, J. Pérez, E. Bedoya

"Tungsten extraction is a subject of global interest due to is properties. These properties, such as its high melting point, have contributed to the development of metallurgical extraction processes that can be adapted to the particular chemical composition and mineralogy of the ore. In Colombia there is a research deficit in tungsten related areas, and especially with regard to its extractive metallurgy. In this study the physical, chemical and mineralogical characterization of a sample were performed. Subsequently, crushing and grinding were employed to reduce the material to a more convenient size, making it suitable for further concentration and metallurgical processes. Through physical concentration techniques it was obtained a concentrated ranging between 60 -70 % of WO3 content.INTRODUCTION Tungsten is a metal of great economic importance due to its excellent properties such as high density and extraordinary melting point 3422°C), which is indeed the highest of all the elements. Tungsten is primarily used in metal alloys, manufacture of special steels, coatings and catalysts; products of interest to both international and national industry. However; given that the use and economic value is determined by the percentage of tungsten in the mineral, particle size and chemical associations, it becomes essential to properly characterize the mineral to further define possible metallurgical extraction routes. The metallurgical processes for minerals enriched in tungsten may vary depending on location and the genesis of the ore body, which means that for each ore a particular set of operating conditions must be determined. This is important since process standardization can lead to misuse of the mineral resource. However, in Colombia there is a research deficit as it relates to minerals enriched in tungsten and to its extractive metallurgy. Then, there is a need to conduct studies that can lead to a better understanding of the ore, and to develop extraction processes for the metal of interest. EXPERIMENTAL A state of the art review was made in order to gain insights of the tungsten metallurgical process. Comminution was necessary with the aim to reduce the sample size; therefore the sample was taken into crushing and grinding stages. Concentration techniques such as magnetic separation, gravity and / or electrostatic were also applied. Physical, chemical and mineralogical characterization were performed by using polished sections, grain size determination, X-Ray Fluorescence (XRF) and X-ray diffraction (XRD) techniques."

Jan 1, 2015

By Lyle W. Talbotr

The DeLamar Silver Mine is a Joint Venture between Earth Resources Company, the Canadian Superior Mining Company and the Superior Oil Company. The property is a consolidation of several old operations in the district. The more widely known are the DeLamar and Sommercamp Mines. The location is 20 miles northeast of Jordan Valley, Oregon and 55 miles southwest of Boise, Idaho. The mine is on the south slope of DeLamar Mountain in the Owyhee Mountains of southwest Idaho Initial interest started in 1969 with serious exploration beginning in 1970. The feasibility study was completed in 1974, and in 1975 Mountain States Engineers were retained to design and build the plant. Processing of ore began in March of 1977 with the first bullion poured in April of that year. The plant is currently processing some 2200 TPD of ore with a grade of four ounces of silver and 0.03 oz. of gold per ton of ore. Cyanide consumption is 2.5 lb/ton, zinc consumption of 0.3 lb/ton and flocculent consumption of 0.5 lb/ton. A flowsheet is shown as Figure I. The grinding circuit is of two stage design. The primary mill is an 18 ft. dia. by 9 ft. long semi-autogenous unit. The secondary mill is a 9 1/2 ft. dia. by 15 ft. long overflow ball mill. The mill discharges are combined and sent to 15 in. cyclones for classification. Cyclone overflow reports to leaching with the underflows reporting to the ball mill. The cyclone feed pump is an 8X6 metal case pump. The primary mill has 1000 installed horsepower and rotates at 68% of critical speed. The ball mill has 700 installed horsepower and rotates at 72% of critical speed. Because the primary mill is horsepower limited the ball charge is varied to maintain the desired throughput. The mill power is held at 980-990 HP by modifying the feed rate. Four inch forged steel balls are added any time the ore feed fails to reach 100 tons per hour for four hours. During periods of extremely hard ore, the ball charge has been as high as 14 v/o and at other times the mill has operated fully autogenous for weeks.

Jan 1, 1980

By Gary MacDonald

What is the primary function of an impact assessment? Many people at the International Association of Impact Assessment?s (IAIA) annual conference said that it is time to return to the fundamentals and consider the underlying drivers of impact assessments ? human health, safety and security. This fall, managers struggling with those fundamentals will receive extra support when a new course focusing on health and socially responsible security is launched online and in British Columbia, Canada, home to many of the world?s junior miners. Now in its 33rd year, the IAIA conference recently held in Calgary, Canada, typically brings together a range of professionals who work in the impact assessment field, including academics, as well as people conducting applied disciplines, such as social and environmental performance management. It is a chance for people grappling with how to assess impacts from projects (for example, dams, mining and other extractive projects), to compare notes and to talk about developments in how to measure, track and report on them. The comments about returning to fundamentals rose as participants talked about the ongoing and increasingly recognized divergence between three main impact assessment streams: environmental, social and health (EIA, SIA and HIA, respectively). Discussions in sessions and in the corridors included calls for streamlining, for integration, for improvement and sharing of practice ? particularly in the HIA stream, where those deeply engaged in the health discipline questioned how HIAs and their intended outcome of protecting human health can be better integrated into the EIAs or SIAs that dominate the impact assessment realm. EIAs and SIAs have become the main tool, particularly from a permitting perspective for large-scale mines, but seem to leave projects with little real information about what they need to do. Human health is not the only concern re-emerging. Although not reflected at the conference, there appears to be an emerging understanding of the need to link the determinants of health with socially responsible security practices. Companies conducting independent social performance assessments for international financial institutions based on the International Finance Corporation?s Environmental and Social Performance Standards increasingly wrestle with both community health and security issues as extractive companies encounter challenging social environments around the world. Once again, the intended outcome is to better protect human health, including avoiding health impacts from conflict, abuses and violence.

Aug 1, 2013

By William Gleason

"Despite the difficult economic climate for the mining industry, more than 6,300 people joined SME for its 2016 Annual Conference & Expo in Phoenix, AZ, Feb. 21-24.Nearly every commodity has been bruised and battered during the past year, leading to one of the more difficult cycles for the industry in the past decade. Coal has taken some of the hardest hits and other commodities, such as copper and iron ore, have felt the sting of a slower growth in China and an oversupply on the market.The difficult conditions could not be ignored, but they did not deter SME from offering a forum for the industry to share knowledge, network with peers and learn about the best products and practices while visiting the sold-out exhibit hall (844 booths and 627 vendors) or while attending any of the 121 technical sessions that were offered.The current state of the industry was one of the overriding themes of the conference and during the challenging times there are often cutbacks as operations look to become leaner and more efficient, however, there is one area that cannot be cut – health and safety.The conference kicked off with a fascinating presentation from Colonel Mike Mullane, a former NASA astronaut who, in 1978, was selected as a Mission Specialist Astronaut in the first group of space shuttle astronauts. He completed three space missions and logged 356 hours in space aboard the shuttles Discovery and Atlantis before retiring from NASA and the U.S. Air Force in 1990.In his speech to a packed audience, he warned of the dangers of cutting corners to get the job done more quickly by guarding against the “normalization of deviance.”Normalization of deviance is a long-term phenomenon in which individuals or teams repeatedly accept a lower standard of performance until that lower standard becomes the norm. Usually, the acceptance of the lower standard occurs because the individual or team is under pressure (budget, schedule, etc.) and perceives it will be too difficult to adhere to the original higher standard. Their intention may be to revert back to the higher standard when this period of pressure passes. However, by getting away with the deviation from the higher standard, it is likely they will do the same thing when the same stressful circumstances arise again. Over time, the individual/team fails to see their actions as deviant."

Apr 1, 2016

By William G. Kegel

Apart from a usable product and good 'mining conditions, the greatest asset for a profitable coal mining organization is an effective mine maintenance program. The first step in achieving this is to have good mechanics-or men who want to be mechanics and are interested in knowing more about the design and control of the machines in their charge. A good mechanic's knowledge and ability result from ambition, curiosity, and determination. Starting with these qualities, the aspiring mechanic can launch his career by learning all he can about mechanics, electricity, and hydraulics. Though the path is rough, the end result is rewarding. Mining machinery probably receives as much, if not more, abuse as any other heavy equipment in use today. Considering the conditions under which much of the repair work must be done, it is essential that the mine operator has the best men and tools to perform the work. Mining machines, from their inception, have utilized the electric motor; and down through the years of mechanization, this power source has undergone many changes to better adapt it to the job. The first motors used were direct-current (d-c) motors since d-c power was the most economical power source for mining at the time of early mechanization. These motors were large open-type machines which are seldom used in modern mining. Because of the mine environment, the d-c motor has been reduced in size to better suit the application in mining machines and is now manufactured with dust-tight or explosion-proof enclosures. The d-c motor is constructed with either (or both) series and shunt fields located on the stationary part of the motor (stator) and- an armature coil wound on the rotating part of the motor (rotor). Power is supplied to the armature by brushes which are held stationary and make sliding contact with the armature. The brushes requires regular and careful maintenance because worn or defective brushes will cause heat or arcing which can destroy the motor. D-c motors can be used as d-c generators when mechanical power is supplied to them by the rotating shaft. In the case of a locomotive, this principle is used in dynamic braking. The momentum of the locomotive drives the motor and generates d-c power. The power is regulated with resistors and provides opposition to the motion of the locomotive.

Jan 1, 1981

By W. G. Pariseau

Introduction Caverns of 50 m in linear dimension at depths below 2300 m with a life of more than 25 years are proposed for the next generation of water-filled neutrino detectors. Little precedent exists for excavations in such an extreme environment, although some guidance is available from mining experience at great depths, for example, in South Africa, in Canada and at the former Homestake Mine in the U.S.A. Unlike mining for ore, there are choices available in the construction of such caverns that may mean the difference between success and failure. These choices should be informed by rock engineering principles. Recently proposed guidelines for orientation of brick-shaped caverns where the long dimension is a small multiple of the short dimension indicate that the most favorable orientation is with the long and short dimensions parallel to major and minor preexcavation principal stresses (Pariseau, 2005). Numerical analyses at reduced strength indicate some yielding at cavern walls should be expected but that an equilibrium state is quite possible and is aided by arching the back into a spherical dome when the cavern is an empty cylinder (Tesarik and others, 2002). The same indications of stability occur with brick-shaped caverns. However, the most dangerous situation occurs during the excavation sequence to final cavern dimensions. There are any number of excavation sequences that lead to the same final cavern shape, so there is an opportunity to partially optimize the sequence with construction guidelines that minimize peak stress concentrations during construction. This contribution discusses three practical excavation sequences that lead to the same brick-shaped cavern in the strong, massive Yates formation at the Homestake Mine where considerable rock mechanics data has accumulated through the years(e.g., Pariseau, 1985, Pariseau and others, 1995) and where actual mining on the 8000 Level indicates a strong possibility of successful investment in the next generation of large, deep neutrino detectors. The main results are: (1) a favorable brick-shape is one with dimensions in the same proportion as the preexcavation principal stresses (compressionpositive), and (2) favorable orientation of the most extreme but temporary shape of excavation is also best for the construction sequence. Analysis results from a mix of Homestake Mine data and possible excavation geometry illustrate the advantages of these guidelines.

Jan 1, 2006

By L. M. Lenahan, J. D. Sheets

INTRODUCTION The Raleigh-Durham International Airport (RDU) in North Carolina is the fourth largest airport in the southeast region of the United States. The Raleigh-Durham Airport Authority is currently underway with planning, designing and constructing are placement Passenger Terminal as part of the Major Capital Improvements Program at Raleigh Durham International Airport. The Terminal C Expansion and Renovation Project will replace the existing Terminal C structure with a new processor building and concourse. The project is separated into several contracts. The early stage contracts are constructing a west side storm water management facility, relocating taxiways, installing new drainage systems, installing new aircraft apron pavement, Demolition, the Central Energy Plant and Early Foundations. The later projects are the Terminal Building, Passenger Boarding Bridges, Information Technology Systems and Integration, Furniture, Furnishings & Equipment and Specialty Millwork. The Terminal Building will be constructed in two phases. Phase 1 constructs the north half of the new terminal. Airline operations will move to the new terminal at the completion of this phase. Phase 2 completes construction of the south processor building. The full build out of the project, subject to funding availability, will replace the remainder of the south concourse. The Program’s primary focus is to replace the existing passenger Terminal C with a new terminal that will provide more passenger gates and larger passenger screening, ticketing and baggage handling facilities. The planning for the New Terminal C Program began in 2002 with construction starting in March, 2003. The continuing growth of passenger airline travel in the Raleigh/Durham metropolitan area requires RDU to expand its facilities to keep up with the present and future growth within the Region. In October of 2002, the RDU Airport Authority selected Parsons Transportation Group as the Program Manager/Construction Manager to help assist in the development of the Terminal C expansion program. RDU Airport Authority selected the Seattle Washington Office of URS Corporation as the Engineer of Record for the West Side Storm Water Management Facilities. The Westside Storm Water Management Facilities Project became one of the early critical path activities of the overall RDUAA Terminal C Expansion Program. The Briar Creek Reservoir had been constructed to accommodate storm water runoff to the west of the Airport. The existing 1.5 m culvert that drained runoff from the airport terminal (area) to the reservoir was insufficient in supporting the additional flows

Jan 1, 2005

By Roy Norcross, Stephen Gos

For over 100 years Degussa has worked together with the min­ing industry not only providing quality products but also develop­ing technologies to support these products through value added goods and services. For cyanide, these technologies include leach enhancement processes such as PAL™ and Solidox™, and cyanide detoxification with peroxygen based processes such as SILOX™ and Caro's acid using our DegOX™ technology. Degussa has also made important advances in how sodium cyanide is packaged and shipped with our liquid NaCN plant joint venture with MSI, CYANCO in Winnemucca, Nevada, and our Advantage SLS™ solid to liquid cyanide delivery system. All of these innovative technologies developed to support NaCN in mining, provide value to our customers and show Degussa's commitment to Responsible Care·11.1 and dedication to product stewardship. With Responsible Care and the customer in mind, Degussa has developed Advantage CCS™ cyanide control system, which will soon be available for the North American market. Currently there are several CCS units in service installed by Degussa AG (Germany), and we are in the process of designing the next gen­eration of the CCS which should be completed by late '98. Based on our experience working with gold and silver mines all over the world, there appeared to be an opportunity to further assist our customers by providing a better more automated way to control their cyanide additions. By providing the mine with an accurate method for maintaining their desired cyanide levels in their leach circuits, we could help them avoid underdosing and the associated gold and silver losses, and overdosing the cyanide which not only wastes cyanide but may increase treatment costs as well. In the early 1990's, when we began to introduce our CCS units, there were several cyanide controllers and on-line analyzers avail­able. However, they appeared to be too complicated and not made to stand the harsh conditions inside a mill. This resulted in exces­sive downtime and poor analytical results. We also found that many units would be installed but not commissioned by the sup­plier. Based on these observations, along with filtration and con­trol problems on some existing units, Degussa decided to design its own cyanide control system based on our extensive knowledge of cyanide chemistry, using the best components available worldwide.

Jan 1, 1998

By P. J. Hyde

Cyanide is a significant contributor to the cost of producing gold. Any reduction in consumption that can be achieved through more reliable measurement and/or more efficient management of dosing rates can have a significant financial impact. An automated analyser, by its mechanical nature, is not prone to the variations of human operators, particularly notice­able from shift to shift. Reducing the standard deviation of the measurement (ie, reducing noise ), the automated measurement will give the metallurgist a truer picture of the underlying patterns of usage. The combination of automated analysis with on-line operation and a control loop provides timely information that is efficiently utilised in the management of the plant. Until the release of the Chemtronics On-Line Cyanide Analyser (OTA3000) about 12 months ago, the Australian experience with automated analysers (especially on-line) had been substantially negative. Since its release, the Chemtronics instrument has outperformed both manual titrations and other automated instruments, gaining an enviable reputation for accuracy and reliability in the process. The instrument is built around the technique ofpotentiomet­ric titrations, in which the potential of an indicator electrode is measured as a function of the volume oftitrant that is added to the sample. As the cyanide in the sample is depleted, the potential on the indicator electrode changes rapidly, producing a typical sigmoidal curve. The OTA3000 takes the first differ­ential of the curve, identifies the apex of the peak as the endpoint and reports the result in parts per million of sodium cyanide. The OTA3000 accepts the peak as valid only if it exceeds a certain minimum height. That minimum height is a programma­ble parameter and is used to optimise the relationship between sensitivity and the rejection of spurious peaks. The instrument will track cyanide trends through both positive and negative slopes of any magnitude, but it will provide a warning if it the slope becomes excessive, not because it affects the instrument but because it means that something unusual is occurring in the tanks. There are a limited number of conditions under which the instrument will produce a result of zero. In these cases the OTA3000 holds any output lines at the last valid result while it repeats the titration. This feature was incorporated for reasons of stability in a feedback loop.

Jan 1, 1995

By James W. Babcock

Introduction Geologic ore deposit models are key to any exploration program. In the search for ore deposits, the geologist first tries to understand the genesis of known ore bodies. During reconnaissance and evaluation of a prospect, a valid exploration model of a known ore body can help the explorationist focus on critical geologic attributes of the target area. Exploration models can conserve exploration funds that might otherwise be spent collecting data not critical to delineating an ore body. This article examines the benefits of using models, factors to be considered in developing models, and examples of the way recent models have evolved. New exploration concepts and techniques are developed in response to increased competition in the mining industry. New techniques can give an exploration group a slight edge that may translate into a discovery. Mine geology staffs may find previously unlooked for extensions to the ore body by applying new genetic concepts. When all appropriate techniques are applied to exploration and mining efforts, greater efficiency and increased profits may result. Before the 1950s, scientists speculated on the genesis of ore deposits and other natural phenomena. But they presented their results as if universal and final, even though they applied to only a few deposits. Because it did not provide sufficient criteria to distinguish the genetic processes, the classic conflict between hydrothermalists, epitomized by Lindgren, and nonhydrothermalists did not help the minerals explorationist much. Important information about individual ore deposits, such as age of the host rocks and mineralization, composition of the mineralizing fluids, and separation of mineralizing and nonmineralizing events in the paragenetic sequence, could not be gathered with past equipment and methods. But these early concepts of ore genesis contained excellent empirical observations, perhaps the most useful parts of these hypotheses. Through the years, prospectors have found most of the ore deposits in the world using direct observations and their collective empirical wisdom - an empirical model. The geologist's contribution becomes increasingly important after the more obvious surficial ore deposits have been discovered. In Europe and North America that time has arrived. With the introduction of sophisticated equipment and matching techniques in the 1950s in geochronology, geochemistry, geophysics, remote sensing, and computers, many previously equivocal genetic questions can be resolved. This proliferation of highly technical data has allowed the construction of many well-founded genetic models.

Jan 12, 1984

By Deepak Malhotra, William F. Riggs, Edward C. Dowling

INTRODUCTION Mining companies are In the business of making an acceptable profit on their Investments, It became obvious in the recent recession that economic profitability/viability depends on being the lowest cost producer In order to compete on a global basis. The burden of achieving this objective falls on the mineral manager. He must strive to produce a salable product in an environmentally acceptable process while continuously Improving the profit margln.(1,2) Metal prices fluctuate on a regular basis. They directly Impact revenue and hence operating philosophy. The mineral engineer needs to develop an optimum operating strategy to meet his overall objectives, One would expect that, In the modem era of complex computer models, it would be easy to develop an economic model to maximize profits and/or cash flow. Discussions with mill managers Indicate that one mine/corporation's optimum operating strategy is not necessarily optimum for another. This paper approaches the problems from basics "Economics 101" and Illustrates the complexity of developing a universal model which can be applicable to all mines. Case examples are used to illustrate the need for better communication to avoid the basic economic fallacy “that optimization of segments leads to optimization of the whole system.” TECHNICAL MODELS Technical models are a prerequisite to the development of economic models because they provide the necessary Input data to these models, The flow of material from a mine through the sale of the finished product is shown In Figure 1. The ore Is mined and milled, and the concentrate can be stored for sale or smelted and refined In-house or at a toll facility. The finished product(s) are held In Inventory until sold either through existing contracts or in the spot market. [ ] Fairly reliable technical models have been developed for mining, milling and smelter operations. Mine plans are developed to provide a good Indication of the relationship between production and cut-off grade. It is easier to change surface mine plans than plans for underground mines. However, there are limits to maximum production that can be achieved with existing equipment. It Is possible that mine benches may not be developed to handle additional equipment, even If It was purchased to enhance production. More often than not, the cut-off grade Is lowered to Increase throughput goals.

Jan 1, 1993

By Robert L. Sundeen, Richard V. Wenberg

INTRODUCTION Shotcrete can be defined as spray-applied concrete with a maximum size aggregate in excess of 9.5 mm (0.375 in.). The concept evolved from guniting, which uses smaller aggregate and generally produces concrete with poorer physical properties. The larger aggregate used in shotcrete requires less water in the mix, while offering larger bonding surfaces, thus imparting greater tensile and compressive strengths. TYPES OF MACHINES Two basic designs of shotcrete machines in general use are the wet or prehydrated zero slump and low slump type, and the dry or nozzle hydrated machines. Fig. 1 shows a typical zero-slump machine in a con¬figuration commonly used for small-volume require¬ments. The prehydrated zero-slump machine mixes exactly proportioned batches in a sealed pressurized chamber. "Slugs" of hydrated shotcrete mix and com¬pressed air are sent through a distribution hose to the nozzle where the wet mix emerges as a spray. The spray is directed onto the rock surface by the nozzle operator. The low-slump machine is similar, except that a thick slurry mix of aggregate is delivered throughout the distribution hose to the nozzle. Fig. 2 shows a typical low-slump shotcrete machine used in moderate-volume applications. The nozzle-hydrated shotcrete machine accepts a premixed "dry" (4 to 6% moisture) batch of aggregate and cement. A constant feed of this mix is directed by compressed air through the distribution hose to the nozzle. At the nozzle, water for hydration is introduced into the emerging spray. The hydrated mixture is di¬rected onto the rock surface by the nozzle operator. Fig. 3 shows a typical dry-mix machine. The major difference between the two basic machine designs is the consistency of the shotcrete quality. Pre¬hydrated machines have high degrees of consistency and produce high-strength concrete, resulting from their ability to produce exact mixtures of zero or low-slump concrete within the machine. Nozzle-hydrated machines tend to produce poorer quality concrete because of the difficulty in controlling the water content at the nozzle. Water input essentially is an art. As such it is not precise, and the shotcrete produced is of variable quality. MATERIALS HANDLING Materials handling presents a problem to either type of shotcrete machine. At times considerable quantities

Jan 1, 1982

By B. H. Kaye

Particle-size Distribution Specifications for Particulates. Feed to and finished products from size-reduction operations are defined in terms of the particulate sizes involved. It is also well to know whether the ultimate individual particle is being measured, or, if any aggregation or agglomeration of particles exists, whether this has been created by the size-reduction operation. The most complete description of a powder is given by its particle¬size distribution. This can be plotted in terms of cumulative percent oversize or undersize in relation to the diameters of particles, or it can be plotted as a distribution of the amounts present in each unit of diameter against the several diameters. It is common to employ a weight basis for percentage, but there are some data in the literature where frequency, or number of particles, is used. The basis of percent¬age, whether weight, frequency, or some less commonly used factor, should be specified, as also should be stated the diameter, its units, and preferably whether determined by sieve, settling velocity, or other¬wise. Fig. I presents two sets of distributions-ore cumulative and the other in unit intervals. The slopes of the 5-µ intervals of the cumulative curves are converted to percent per micron and plotted as a block, or histogram, from which smooth curves are derived. Powder A has a narrower, or tighter, size range for the bulk of its weight than powder B. Both materials have the same weights below and above the size marked by the arrow. Simpler treatments of distribution are possible. In some cases the significant value is the top size. Since the 100% point is dubious, some amount, as 95 or 98%, so specified, can be called top size. In other cases the percent on some sieve helps define coarseness. Merely stating that all, or all but a small percentage, passes a given sieve is inadequate for defining the true fineness or a material. Complete parti¬cle-size analysis to show the distribution is essential for most compari¬sons and calculations. Particle-Size Equations. A number of equations have been pro¬posed to correlate the quantity of a particulate material with its parti¬cle size to obtain a distribution relationship. 's 19 In the literature it is often assumed that a powder must follow some distribution, such as the Rosin-Rammler-Bennett:20, 21

Jan 1, 1985