Search Documents

By R. P. Benson, D. H. MacDonald, D. R. McCreath

1 - INTRODUCTION The Canadian Shield is well known as being among the older exposed areas of the earth's surface. Except for local zones, its extent from the Arctic to central North America is characterized by strong and durable crystalline rocks. It is generally regarded as highly competent for tunnelling and underground excavation and, as a result, many openings are excavated in it with minimal temporary support. If hydraulic efficiency is not a factor, tunnels do not usually require continuous concrete linings. A high percentage of the crystalline rocks of the Shield are of metamorphic origin and as such one of the dominant characteristics is their foliation. Zones of sheared or faulted rock are common in the Canadian Shield, particularly in association with foliation. These zones may be created during the late stages of the metamorphic process, leaving shear zones as an integral feature of foliated rock. As foliation is a preferred direction of weakness, deformation and rupture during subsequent tectonism may also create parallel shear zones. These "foliation shear zones", as described by Deere (1973), are an adverse feature of the otherwise durable rocks of the Canadian Shield. The zones may range from faults of major proportions to seams only a fraction of an inch thick. If fault gouge or alteration products exist in the zone the strength of the rock mass may be great1y reduced. As foliation is usually continuous, large unstable wedges of rock may be created if the opening is subparallel to the foliation. The effect on the construction of underground openings in terms of excavations, support and scheduling can be significant.

Jan 1, 1974

By F. C. Loughnan, Shane B. Sadleir

Bauxite is currently produced at three centres in Australia: - Weipa in northern Queensland; Gove on the northeastern tip of Northern Territory; and in the Darling Range near Perth, Western Australia. At each of these centres the bauxite is of Tertiary age and occurs as blanket-like, lateritic crusts in which gibbsite is the predominant mineral. Development was essentially in situ although possibly the deposits, particularly at Gove, are in part of transported origin. All of the deposits formed from quartz-rich parent rocks with those at Weipa and Gove being derived from kaolinitic sands while in the Darling Range, granite and other crystalline rocks of Precambrian age immediately underline the lateritic bauxite.

Jan 1, 1984

By James M. Reichman

Waterjet assist of mechanical cutters has been demonstrated in a variety of laboratory studies as well as on field equipment. As this technique becomes more widely accepted, it will be necessary to develop methods of minimizing the horsepower and water requirements. In machines such as roadheaders, continuous miners, and longwall shearers, the use of waterjet assist can be optimized through the development of phasing valves. Phasing valves will allow only the cutters in contact with the rock to be assisted. Since only 30 - 40% of the cutters are in contact with the rock, the saving power is significant. Flow Industries has developed a phasing system for use on roadheading machines. This system allows the operator extensive control of the angle of assist as well as the quadrant being assisted. This system could be greatly simplified for production machines and adapted for use in continuous miners and longwall machines.

Jan 1, 1985

By Hiroyuki Kawata, Toshiyuki Ueno, Mikio Yamazaki

INTRODUCTION For the construction of several kinds of structures which pass through under railways, we have recently developed an effective and new tunnel construction method, aiming at more secure train operation during the construction as well as the rationalization in the construction works for such structures. Most important in carrying out the construction works for the structures under railways is how to maintain the safe operation of trains. For such construction works, temporary supporting structures and supplemental works have been often applied, for which high cost and long period for the construction have been required. While, this new tunnel construction method has the feature that it is capable of constructing definitive structures for various purposes, which, at the same time, acts as the temporary supporting members for protection of railways. Therefore, this method is now drawing much attention in that higher safety of train operation, low construction cost, and shorter construction period are accomplished, minimizing the period required for slackening the train speed during the construction works.

Jan 1, 1979

By K. G. Sutterer, P. T. Wang, R. Sweigard

One possible alternative for the disposal of flue gas desulfurization (FGD) by-products is to use it as backfilling support material in highwall mine adits. The finite element method was used to analyze the variation in stresses and displacements within and around a highwall adit backfilled with FGD materials. The engineering properties of the rock material and the optimum mix of the FGD materials were obtained from laboratory tests. Finite element analyses show that, for the case in question, the roof displacement would decrease about 48% and the peak stress could be decreased by about 58%. The study indicates that fairly weak FGD materials can eventually lead to the stability of backfilled highwall adits.

Jan 1, 1998

By L. Yuan, J. H. Rowland III

"In 1995 and 2003, the Mine Safety Health Administration (MSHA) conducted surveys to determine the number of atmospheric monitoring systems (AMS) being used in underground coal mines in the United States. The survey reports showed data for the different AMS manufacturers, the different types of equipment monitored, and the different type of gas sensors and their locations. Since the last survey in 2003, MSHA has changed the regulation requirements for early fire detection along the belt haulage entries. As of December 31, 2009, point-type heat sensors were prohibited for use for an early fire detection system; instead carbon monoxide (CO) sensors are now required. This report will examine the number of AMS currently used in underground mines in the United States to see if there is a change in their use. The locations and parameters monitored by AMS are also discussed. INTRODUCTION The last survey conducted by the Mine Safety and Health Administration (MSHA) on atmospheric monitoring systems (AMS) used in underground coal mines in the United States (US) was in 2003 [1]. The survey report states that since 1995 there had been a steady increase in the use of AMS in underground coal mines as the technology of CO sensors was improved by manufacturers. AMS had become more reliable and some CO sensors could be purchased with the capability to discriminate between the CO produced from a fire versus CO produced from diesel equipment. This increase in reliability had reduced the number of false alarms and the response time. The faster response time to a developing fire allowed for the miners to take the necessary action to put out the fire or exit the mine. It should also be noted that at the time of last MSHA survey, some mines still used point-type heat sensors to detect the presence of a fire on conveyor belts. This detection method works by measuring the temperature of the air around the sensor. As a fire starts to develop, smoke and hot gases are produced from the combustion process, and the air is heated up. Once the air and gases reach a designated temperature detected by the point-type heat sensor, a fire alarm signal is generated. Studies have shown that the response times for detecting the presence of a fire using CO sensors are much shorter than using point-type heat sensors [2]. Finally, since the last MSHA survey, regulations have changed on the type of automatic fire detection systems permitted to be used in conveyor belt entries. As of December 31, 2009, point-type heat sensors are not permitted to be used for fire detection in underground coal mines in the US; instead CO sensors are required as a replacement (30 CFR 75.1103-4). This study will examine how the changing of the above regulations has impacted the use of CO sensors in underground coal mines in the US compared to their use based on the last MSHA survey. Importantly, in the previous MSHA survey, the data was recorded for producing and non-producing coal mines. In this study, only the data from the producing coal mines was recorded. Data was collected from a total of 235 coal mines for this study with the help of the MSHA district offices."

Jan 1, 2017

By Tom F. Deems

The term ball clay is applied to plastic sedimentary clays that have a high content of kaolinite and that possess white firing properties and high green strength (Mitchell and Stentiford, 1973). However, the name ball clay is not derived from any specific property of the clay. Instead, it comes from the original method of production in southwestern England (Scott, 1929). From open pits, the clay was cut into cubes with hand tools. The sides of the cubes were about 220 to 250 mm (9 to 10 in.) and weighed 14 to 16 kg (30 to 35 lb.). The eventual rounding of the corners with handling before sale gave rise to the term ball clay. Ball clays provide the workability and green strength required by the whiteware section of the world's ceramic industry. The main applications are in the sanitaryware, tile and tableware sectors. Each, though, requires particular technical properties in the ball clay component. The clay has to be as white firing as possible for all applications. However, for sanitary-ware, the rheological properties are most important. For tableware, fired whiteness and freedom from specking are the main criteria. Tiles need a reasonable green strength but the clay also needs to be cost-effective. The technical properties of the individual clays in any deposit depend on the clay mineral assemblage. This, in turn, depends on the geological formation of the deposits. Hence, it is the latter that largely determines the market sector for which the clay blends from a particular deposit are suited. Formation of ball clays Ball clays are formed from three main components - kaolinite, micaceous minerals and quartz - while carbonaceous material is also often present. The crystallinity of the kaolinite and mica varies. There are also occasional minor occurrences of feldspar, chlorite, montmorillonite andmixed. layer minerals. Marcasite, siderite and anatase also occur in small amounts. The properties of the clay depend on its mineralogical composition and its particle size distribution, particularly in the lowest size ranges. The original source rocks and the environment of deposition of the clay are the controlling factors. The importance of weathering processes in the formation of ball clays has long been recognized (Bristow, 1968). The diversity of source rocks produces considerable variation in the clay minerals formed. Therefore, each deposit is unique, with time-related variation within it. The greatest development of a weathering mantle takes place in a tropical climatic environment. Plant remains confirm that most ball clay deposits were formed under hot and wet conditions. Sedimentation of the clays had to be in fresh or low salinity water or clay minerals detrimental to whiteware manufacture would have been formed. Fresh water traps for the ball clay, sand and lignite sequences depended -on tectonic features, such as basin development along fault zones or lakes and lagoons on the edge of a large scale embayment. These factors for Devon ball clays were discussed by Vincent (1983). The combination of suitable source rocks, tropical climate, significant fresh water sedimentary environment

Jan 1, 1997

By Paul L. Russell, Charles O. Hook

While the oil shale resources of the US are becoming increasingly known, few people in this country are aware of the extensive worldwide occurrence of this resource. Two recent international conferences* confirmed the growing worldwide interest in oil shales, both as future and current energy sources. The 1981 conference noted the difficulty in characterizing worldwide oil shale resources because of lack of common terminology in reporting both assay value and resource potential. Assay value is variously reported as: •US gallons per short ton; •Imperial gallons per metric ton; •Liters per metric ton; •Liters per cubic meter; •Weight percent oil; and •Volume percent oil. Oil shale resources are variously reported in barrels, short tons of oil shale, metric tons of oil shale, and cubic meters of shale oil. Worldwide petroleum shortages sparked interest in alternate energy resources including oil shales. While petroleum supplies appear to have stabilized, at least for a while, high costs are affecting the balance of payment index of many countries, resulting in a continued search for local energy resources. Kerogen is the organic constituent of oil shale and may be the most abundant form of hydrocarbon on earth, possibly exceeding coal occurrences and far more abundant than naturally-occurring petroleum resources. Oil shale, by one name or another, is widespread and is known to exist in more than 38 countries (Table 1). Oil shale industries have existed in at least 14 countries at one time or another. Many predated the Drake oil discovery in Pennsylvania in 1859, and most were unable to compete with natural oil; these operations either converted to its use or closed. At the present time shale oil is being produced on a commercial scale only in the USSR and in China. Only very rough estimates of grade and quantity are available for most of the worldwide shale occurrences since only a few deposits have been thoroughly explored. The Green River Formation of Colorado, Utah, and Wyoming is an exception. For many years this oil shale deposit has been described as the largest single concentration of hydrocarbon material in the world. With increasing world interest, larger deposits may yet be found. In 1965, the US Geological Survey published an in-place world oil shale estimate. This study, while made some 16 years ago, is still a reasonable order-of-magnitude estimate. Although exploration and evaluation are underway and a few oil shale deposits have been appraised, information on which to evaluate most worldwide oil shale occurrences has improved little since 1965. Table 2 presents an order-ofmagnitude estimate of in-place world oil shale resources. Total US resources and Green River Formation

Jan 1, 1982

By Harry H. Posey, John Woodling, Miriam L. Renkin

Natural acid drainage is generated from pyritic rock underlying 17 percent of the upper Alamosa River basin. About one-third of these acid producing rocks have nil carbonate buffering capacity; there the streams carry significant acid plus dissolved Al, Cu, Fe, and Zn. In part of the basin, aquatic life is limited by the natural acid drainage. In the four miles where the Alamosa flows through pyritic rock the river grows toxic to trout. Inhospitable conditions continue downstream for at least another four miles. The waters become refreshed, naturally, through metal dilution, metal oxide and hydroxide precipitation, and acid neutralization. Water quality fluctuates in seasonal cycles. Dissolved metals and acid, which are generated year-round by weathering, are stored over winter in the unsaturated zone in the retained water and in soluble metal- sulfate minerals that form by evaporation of acid-metal waters. Seasonal discharge variations cause metal concentrations and pH to shift in the trunk stream; the acid drainage source streams, however, shift only slightly by season. In early spring, metal concentrations and metal loads increase as metals and acid are flushed from the unsaturated zones by melting snow. Peak metal loads occur at this time, and precede peak flow by up to two months. Other metal load peaks occur during peak flow and monsoon flow, even though metal concentrations are diluted at that time by precipitation. In late spring and thereafter, discharge of neutral pH water wanes, so trunk stream pH falls and metal concentrations return to previous high levels. Metal concentrations appear to be low from November through January when dilution from precipitation is lowest, but rise in February to near peak yearly concentrations. In years with high monsoonal flows, metal-laden waters apparently flush from the unsaturated zone and metal concentrations remain low from about October through January. In years with low monsoonal flows, however, metal concentrations in October and November at least are higher.

Jan 1, 2000

By Greg T. Saretzky, Wilson G. Ward

A comprehensive hydrologic study was completed far the waste rock dump at Equity Silver Mine, BC. Characterization of the hydrologic system included geologic structure. topography, surface hydrology and groundwater systems. The results of the study conclude that the cover system is restricting net infiltration to approximately 5%. However, significant discharge continues to occur from the perimeter of the dump. A three dimensional seepage analysis was carried out to illustrate the influence of groundwater discharge associated with the regional topography and geologic structures. The results of the modelling program show that groundwater discharge occurs from the waste rock dumps when high recharge rates are specified for the surrounding topography- This groundwater discharge strongly influenced by the high hydraulic conductivity assumed far the fractured bedrock. The modelling results are considered preliminary and field drilling and piezometer installation is being conducted to determine the groundwater regime in the vicinity of the waste rock dump.

Jan 1, 2000

By C. S. Vender

Knife River Coal Mining Company's Beulah Mine is a multiple seam lignite operation located in western North Dakota. The mine began production in 1963 with annual production at 450,000 metric ton and now produces 2.2 mm ton. As development progresses, operations have advanced into more complex geologic areas. Various techniques have been analyzed to maximize coal recovery in a cost effective manner. Additional studies are on-going to determine what changes will be implemented as we encounter deep wet sands in the reserve area.

Jan 1, 1991

By I. Casasbuenas, K. A. Nguyen, E. I. Ngoma, H. Kim, D. Borja, J. H. Park, R. A. Silva, S. Choi

"This study aimed to determine the optimum operating parameters of a continuous bioleaching system to leach arsenic (As) from mine tailings using a mixed mesophilic bacterial culture. The microbial consortium, previously adapted for effective growth at high pulp density and metal concentrations, was mainly composed of Leptospirillum ferriphilum, and Acidithiobacillus caldus. The mine tailings, collected from the Janggun mine (South Korea) contained 11% (w/w) of As. The tests were performed in a laboratory-scale unit composed of three reactors connected in series following a cascade configuration. Agitation speed, air supply, solid concentration, residence time and temperature were systematically optimized by assessing the leaching activity. Several parameters were monitored on a daily basis, including the As released into solution, iron oxidation rates, pH, cell concentration, dissolved oxygen and redox potential. Overall, improvement of oxygen transfer, by optimizing the agitation speed and air supply, presented the most tangible impact on the leaching performance. The highest As leaching efficiency observed in this study was 82%, which supports the feasibility of the process. INTRODUCTION Worldwide, around of 65 billion tons of mine tailings are produced every year (Jones & Boger, 2012). These materials comprise the waste minerals produced after ore beneficiation. Mine tailings usually contain heavy metals (e.g., Cobalt (Co), Lead (Pb), Zinc (Zn) and Arsenic (As) (Falagán, Grail, & Johnson, 2016; Nguyen, Lee, Park, & Lee, 2014). The exposure of these materials to the environment can produce serious health damage and environmental degradation (Martin, Dowling, Pearce, Sillitoe, & Florentine, 2014). Mine tailings management represents a major issue in South Korea. There are more than 1,000 abandoned mines containing stockpiled mine tailings within the territory (Choi, Park, Hong, Park, & Kim, 2013; Kim, Kim, Ahn, Ko, & Lee, 2005; Lee, Lee, & Kim, 1998). These tailings comprise high concentration of arsenic. Therefore, the Korean Government has directed its efforts to developing eco-friendly technologies, for the arsenic detoxification of mine tailings Continuous bioleaching is explored as a remediation technology (Borja et al., 2016). The present study aimed to develop a mixed mesophilic bacterial culture for optimal growth at high metal and solid concentration; and optimize the operating conditions of a continuous bioleaching unit. This investigation forms part of a larger study aimed to develop a bioleaching technique to treat Janggun mine tailings (Borja et al., 2017; Ngoma et al., 2017)."

Jan 1, 2018

PT Freeport's Mine in Irian Jaya, Indonesia uses a number of 500m long vertical ore passes to transfer ore from the open pit to the mill. The current tonnages moved are in the order of 125 ktpd and this will be increasing to 240 ktpd. This amount of falling rock generates high pressures in the ore bins, when ore feed is terminated the pressure is no longer constrained resulting in back blasting of materials and air up the ore passes. Three methods were tested to try and eliminate or reduce this problem; recirculation of the entrained air, widening of the orepasses and relieving the pressure of the back blast. The final method proved to be the most effective in the short term. As a long term solution the orepasses are currently undergoing widening.

Jan 1, 1998

By James A. Barclay

Results of investigations over approximately the last 10 years by the Bureau of Mines and others on technology for recovering cell-grade alumina from domestic nonbauxitic resources such as clay, anorthosite, alunite, dawsonitic oil shale, coal ash, and coal shale are reviewed. It is concluded that, although many innovative techniques have evolved from this effort and have been shown to be technically feasible, energy and economic considerations will prevent any of the processes from competing with the Bayer process under normal conditions. Based on the Bureau's experience, some variation of clay-HCI leaching, HC1 gas sparging crystallization has the greatest potential as an alternative to the Bayer-bauxite process.

Jan 1, 1984

By H. Evans

It is well known that iron-ore pellets are considered one of the best blast-furnace burden materials used today. The demand for pellets is demonstrated by the increase in pellet output from one million tons in 1955 to approximately 37 million tons in 1964. This growth continues as new plants are placed on-stream each year. The consumer generally specified (1) the acceptable content and range of chemical constituents, (2) a minimum strength determined by some standard testing procedure, (3) the size range of pellets, and (4) perhaps a measure of reducibility.

Jan 1, 1966

By Rick Bearce, Minsu Cha, Mike Mooney, Yuanli Wu, Lisa Mori

"Proper soil conditioning is critical for effective earth pressure balance (EPB) TBM tunneling. Chamber pressures can reach 3-5 bar yet the vast majority of testing is performed under atmospheric conditions. This paper illustrates how pressure influences foam stability and conditioned soil behavior, and how atmospheric test results must be viewed in the context of expected chamber pressures. Torsional shear strength, compressibility and abrasivity of foam conditioned sand were found to be ideal when the void ratio was above the ASTM-determined maximum void ratio, achieved by sufficiently expanding the soil grain structure with foam, herein when the foam injection ratio at pressure exceeded 45%. Otherwise, the engineering properties of foam conditioned sand were not ideal, i.e., appreciable torque and abrasivity, low compressibility. INTRODUCTION Proper soil conditioning is critical for effective earth pressure balance (EPB) TBM tunneling. The formation soil at the cutterhead must be transformed into a highly compressible, low shear strength and low permeability medium within the excavation chamber to allow effective EPB performance. This behavior must be maintained for a certain residency time while the soil is in the chamber and screw conveyor. The vast majority of published studies on conditioned soil behavior have been performed under atmospheric conditions (Quebaud et al., 1998; Bezuijen et al., 1999; Psomas and Houlsby, 2002; Vinai et al. 2008; Thewes et al., 2012; Peila, 2014); however, the desired soil behavior must occur under chamber pressures that can reach 5-7 bar. The influence of pressure on conditioned soil is significant and is dramatically different than behavior under atmospheric pressure (Williamson et al., 1999; Mori et al., 2015). This paper illustrates how pressure influences conditioned soil behavior and how atmospheric test results must be viewed in the context of expected chamber pressures. The influence of pressure on foam bubble size (including with time) is shown through digital image analysis. The influence of pressure on foam half-life is also investigated. The compressibility, shear strength, and abrasivity of conditioned soil under pressure is presented and explained in terms of density, soil and air compressibility and porosity."

Jan 1, 2016

By Ezra L. Kotzin

Foundry sands used to make molds and cores have been very important to foundrymen since metal casting began hundreds of years ago. They are now used in two basic ways, either in an uncured green state, grain-bonded with clay, or in a set cured state achieved with sand that, mixed with resins or oils, is cured by baking or by chemical reaction. The term sand, as generally used in foundry applications, may best be defined as material composed of granular particles of mineral matter, ranging in size from 0.5 to 2 mm in diameter. The particulate nature of the material may be the result of natural disaggregation or result from crushing and screening of rock or ceramic materials; crushed and screened products are sometimes referred to as "manufactured sand." Based on their origin, the raw materials for foundry sands will vary in grain shape, grain composition, relative surface, grain size, and grain distribution patterns. These properties, in addition to their chemical analyses, sintering point and expansion characteristics play an important part in the choice of sands used as the base molding or core aggregate in metal casting. Sands with different origins may be blended to produce specific compositions and grain size distributions. Early raw material requirements based on silica sand were simple, but as sand/core/mold technology became more sophisticated and binder technology continued to be developed, the physical properties of foundry sands became more critical. Silica sand is composed of quartz, along with, in most cases, small amounts of feldspar, mica, clay, and other common minerals. Although silica sand is still by far the most widely used base material in production of molds and cores used in metal casting, other natural mineral sands have their own unique characteristics and fill an important niche in special applications. As a result, the term sand, as applied to raw materials used in metal casting, has been logically extended to include granular materials composed of a group of minerals other than quartz. With increased use in advanced foundry technology, natural sands composed predominantly of zircon, chromite, staurolite, or aluminum silicate minerals and of granularized chromite or olivine, have become more than just alternate materials and are now commonly classified as sands when the grains are sand-sized. Foundry sand may therefore be considered under two categories: silica sands and non-silica sands.

Jan 1, 1994

By D. E. Ranta, G. H. Giroux, A. W. Randall, D. A. Barr

Zinc-lead ores of the Pine Point District, Northwest Territories, Canada, are hosted in paleokarst cavities within a Middle Devonian carbonate barrier complex. Of the nearly 100 deposits found, most are irregularly distributed along two main regional stratigraphically controlled trends. The ores, which occur predominantly as open space filling, form deposits most of which average one million tonnes in size with an average grade of 10% combined zinc plus lead. Geological features related to karsting control not only distribution of deposits but also their shape, size and grade. The higher grade ore in these deposits generally occurs in a relatively small core area. Consequently, accuracy of reserve estimation is dependent on drill-hole density and understanding of karst geometry. Several case examples will be reviewed to demonstrate the relationship between shape, size and grade of deposit, geological reserves and drill-hole density, along with a discussion of geological ore reserve estimation methods.

Jan 1, 1992

By Gürkan Bacak

Study area is located on the NorthWestern of Yatagan-Yenikoy and placed in the units of the crystaline Menderes massif of Eagen, Turkey. Stratigraphically gneissic, migmatitic and metagranitic rocks are found at the base. Garnet schists, phyllitic rocks lie unconfirmitelly upon the basement rocks. Permian aged marbles can be observed as diferrent sized lenses within the schists. Triassic, Jurassic and Cretaceous aged gray colored dolomites and pure crystaline calcite bearing marbles lie upon the Permian aged schists. Neogen series, mainly composed of conglomerates, claystones, marl and limestones unconformly cover the other basement series, mentioned above. Pure calcite bearing marble occurances are found at 2 locations in the study area. These are known as Berber Quarry and Kavuk Quarry. Samples numbered as N7, N8, NA from the Berber Quarry, mineralogically composed of Calcite (97-99%)+iron oxide (1-3%) and chemically contain CaCO3 (97,98%), Fe2O3 (0.5-1%), SiO2 (0.025%) N9 and N10, sampled from the Kavuk Quarry-mineralogically composed of Calcite (94,95%)+iron oxide (2-3%)+albite-Quartz (1-2%) and chemically contain CaCO3 (92-93%), SiO2 1.49%, Fe2O3 0.42%. Especially in plastic and paint sector albite and quartz are unwilling minerals due to their hardness. Approximatelly 1/20 of the study area (87.500 km2) contains industrial calcite occurances. Moreover about 100 billion Tons geological, 1.86 billion tons runable (possible) calcite reserve calculated. It can be expected the calcite quality will be increased with depth. During the running stage of the quarries over burden removel and hand sorting processes will positive affect of the quality.

Jan 1, 2005

By Raymond L. Jones

With the inauguration of the open pit operation in Bagdad, plans were formulated for a large scale leaching operation. Dump stockpiling was started almost immediately, but actual production was not initiated until the spring of 1961. Like all neophytes, we started something about which, on a commercial scale, we knew next to nothing, either dump preparation or leach procedure, and as a consequence, we are still paying the piper. True, we had been through an extensive laboratory pilot program, but it soon became apparent that there was considerably more to increasing solution volumes than simple multiplication. Had we initially possessed our present acumen, the Cyprus Bagdad plant could be operated more efficiently and at a better profit. During the past several years, the art of dump leaching of copper has improved in many ways, primarily because of the application of scientific principles gleaned from general mining practice. Rigid pH control and the use of atomic absorption techniques for rapid," accurate assaying have probably played a leading role in this respect, although we cannot overlook the other sophisticated electronic controls lending improvement to acid addition and pumping, better piping materials, and lastly, the more efficient use of our pregnant liquors. Thin too, the years of experience have given us a greater understanding of dump behavior in general; and, we can, to a greater extent, measure, predict, and avoid some of the idiosyncrasies inherent in every dump. However, it is my firm belief that we will still be confronted with unexplainable dump behavior as long as we are involved in leaching. We have found our dump to be a wonderful money bank, but one that is capable of yielding a wildly fluctuating profit.

Jan 1, 1975