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By Dale R. Ralston, Roy E. Williams, Gerry V. Winter, George L. Bloomsburg

Aquifer. A formation, group of formations, or part of a formation that contains sufficient satu rated permeable material to yield significant quan tities of water to wells and springs. Artesian. Synonymous with confined; see ground water, confined. Capillary fringe. The zone immediately above the water table in which all or some of the interstices are filled with water that is under less than atmospheric pressure and that is continuous with the water below the water table. Conceptual model. A conceptualization of a field hydrogeologic framework that facilitates the development of analytical field testing procedures. The results of the test(s) may force changes in the initial conceptual model. Conductivity, hydraulic. Replaces the term "field coefficient of permeability." The volume of water at the existing kinematic viscosity that will move in unit time under a unit hydraulic gradient through a unit area measured at right angles to the direction of flow, if the porous medium is isotropic and the fluid homogeneous. Confining bed. A body of "impermeable" material stratigraphically adjacent to one or more aquifers; its hydraulic conductivity may range from nearly zero to some value distinctly lower than that of the aquifer. Flow, steady. Any point where the magnitude and direction of the specific discharge are constant in time. Flow, uniform. At every point the specific discharge has the same magnitude and direction. Flow, unsteady. At any point the magnitude or direction of the specific discharge changes with time. Fluid potential. The mechanical energy per unit mass of a fluid at any given point in space and time with respect to an arbitrary state and datum; the fluid potential is proportional to the head. Ground water, confined. Ground water under pressure significantly greater than atmospheric; its upper limit is the bottom of a bed of distinctly lower hydraulic conductivity than that of the material in which the confined water occurs. Ground water, perched. Unconfined ground water separated from an underlying body of ground water by an unsaturated zone. Ground water, unconfined. Water in an aquifer that has a water table. Head, static. Height above a standard datum of the surface of a column of water (or other liquid) that can be supported by the static pressure at a given point. Homogeneity. Hydrogeologic properties are identical everywhere. Hydraulic gradient. Change in static head per unit of distance in a given direction. Hydrostratigraphic unit. A body of material having considerable lateral extent and comprising a geologic framework for a reasonably distinct hydrogeologic system. Isotropy. Condition in which all significant properties are independent of direction. Porosity. Property of containing interstices or voids; may be expressed quantitatively as the ratio of the volume of its interstices to its total volume. Porosity, effective. Interconnected pore space available for fluid transmission; expressed as a percentage of the total volume occupied by the interconnecting interstices. Potentiometric surface. A surface that represents the static head along a particular specified surface or stratum. Specific retention. Ratio of the volume of water that the rock or soil, after being saturated, will retain against the pull of gravity to the volume of the rock or soil. Specific yield. Ratio of the volume of water that the rock or soil, after being saturated, will yield by gravity to the volume of the rock or soil. Storage, specific. The volume of water released from or taken into storage per unit volume of the porous medium per unit change in head.

Jan 1, 1986

By Bruce E. Holbein, Dennis K. Kidby, Ann L. Huber

World gold production figures and the processes used for gold production indicate a high dependence on both cyanide leaching and carbon adsorption metallurgies. Problems associated with the use of carbon in the treatment of refractory ores as well as economic and environmental considerations associated with the use of cyanide point to the advantages that can be realized through the use of more efficient gold adsorption media and with cyanide recovery. We have developed a process termed AurosaveTM-1 which provides a number of advantages through the use of a new synthetic robust gold adsorption medium, termed Vitrokele TM V-911. This process allows further recovery of gold from a variety of ores and allows for a simplified process for use not involving thermal regeneration or high pressure elution. We have also developed a cyanide recovery process termed Cyanosave ™ which uses Vitrokele TM V-911 and allows efficient recovery of cyanides from decants or tailings and re-use of recovered cyanide. This obviates the high chemical expenses for cyanide destruction where environmental issues require such water and tailings management.

Jan 1, 1998

By C. Anastasiadis

The wettability of sandstone was investigated using the technique of dielectric spectroscopy in the frequency interval 1kHz-1MHz. The natural wetness of the material was modified to get two different sets of samples, one with sea-water wetness and the other with crude oil wetness. Measurements showed that the electric responses of water-wet and crude oil-wet samples were markedly different beside the fact that the dielectric response of both groups of samples obeys a general fractional power law. The dispersivity, of the complex permittivity component that expresses the material loss with respect to the electric field was found to be the most suitable parameter to check the wettability of the samples.

Jan 1, 2005

By L. S. Leal Filho, L. A. F. Barros, S. M. Assis

Zeta potential determinations and microflotation tests (with starch, sodium oleate and flotigan EDA-B) versus pH, pCa and pMg were performed with apatite and typical silicate minerals that occur in Brazilian phosphate ores: schorlomite, diopside, quartz and micas. Unlike quartz and micas, schorlomite and diopside were depressed by cornstarch during anionic flotation with sodium oleate (pH 1 9). The selectivity of the separation apatite/quartz and apatite/micas by flotation with sodium oleate was adversely affected by the presence of calcium (pCa) and magnesium (pMg) in flotation pulp. Solubility/cation exchange capacity of micas is an important source of dissolved calcium and magnesium in the system.

Jan 1, 2002

By Y. David

In 1990, the United States became only the second country (after China) to produce more than 900 Mt (1 billion st) of coal in a single year. US production of bituminous and subbituminous coal, lignite and anthracite totaled 933.5 Mt (1.029 billion st) in 1990, 5% more than in 1989. The production gains were largely due to the rebuilding of depleted coal stockpiles by electric utilities and a surge in US coal exports. Domestic coal consumption essentially remained at its 1989 level. A slight increase in electric utility coal consumption was partly offset by a decline in metallurgical coal use. The use of coal in other industries and in the residential-commercial sector remained virtually flat.

Jan 1, 1991

By David Whitehead

My qualification to speak on the globalization of the the mining industry comes from having worked in the industry in Europe, North and South America, Africa and Australasia in positions ranging from exploration geologist to chief executive. For about a third of my career I have lived and worked in the Southern Hemisphere. And for much of the rest of my career I have been involved in or responsible for activities in the Southern Hemisphere. This has given me the opportunity to experience globalization from the sharp end, as it were. This means speaking English with an Australian accent, Spanish with a Chilean accent, French with a West African accent and Dutch with an English accent. My topic is globalization, especially of the mining industry from a Southern Hemisphere perspective and specifically the experience and history of Gencor in that context. First, I will say a little about what globalization means to the southern part of the world: How and why the South differs from the North and how the challenge of globalization affects a south-based company differently than a northern one. I will also detail how Gencor has made significant progress in globalizing through the acquisition of mining assets from Shell. As Fig. 1 shows, I have divided up the world into northern and southern components, rather than hemispheres. The southern world comprises mainly countries that have emerged from the status of economic - if not political - colonies of nations such as England, Spain, Portugal, France, the Netherlands and, surprisingly, Italy and Germany. I have not considered the Indochinese and Arabian peninsulas in my southern world. The emergence of the. former is still in its early stages while the latter is clearly a part of the northern economic system. Large parts of Africa and South America are geometrically in the Northern Hemisphere but economically in the southern world. The reverse is the case for the IndoPersian peninsula. With the distinguished exception of Australia and South Africa, most of these countries nationalized their mining industries and mineral patrimony after attaining political independence. A major element of the globalization of the mining industry is related to the privatization of the mining industry in these countries and to the opening up of their min¬eral patrimony to non-national exploitation. The Southern Hemisphere is the watery part of the world. It is almost three quarters ocean as against a slight preponderance of land in the north. Economically, ocean areas have only a fraction of the productivity of land, except in a few oil-rich areas like the Gulf of Mexico and the North Sea. The consequence is that even on an economically level playing field we would expect the south to generate only about one third of the world's economic product.

Jan 1, 1997

By Zong-Xian Zhang, Charlie C. Li

It has been observed that the rock debris of a strain burst event are often in the mode of tensile fracture. Seismic waves could create tensile fractures in the material nearby reflecting surfaces, such as at the boundary of the fracture zone and the rock surface of an underground space. The fractured rock could be ejected to the space when the seismic waves are powerful enough. The average ejection velocity of the ejected rock is a measure of the magnitude of a burst event. The ejection velocity is directly associated with the released energy from the seismic waves and with the strain energy stored in the rock prior to the burst. In some cases, the seismic wave induced tensile fracture and the energy conversion occur in successive moments during bursting. In this paper, tensile fracture caused by seismic waves is investigated through an 1D model. The relationship of the average ejection velocity of the ejected rock in a rockburst event is analytically established with the energy of the seismic waves and the strain energy stored in the rock.

Apr 26, 2022

By James Y. Oldshue, Paul M. Kubera

Ore processing requirements in the gold industry are similar to those in other sectors of the minerals industry. In all cases, the processes revolve around the handling of large volumes of ore slurry, incorporating either physical processing or chemical processing steps which are related to distinct mixing application classes as defined in Table 1. From this standpoint, the complexity of the applications range from the simple (blending, solid suspension, etc.) to the complex (e.g., multi-phase reactor systems). The large volume of material to be processed dictates the large equipment size which is characteristic of this industry, and the often remote locations place a premium on both mechanical and process reliability.

Jan 1, 1992

By Howard M. Graff

The Inland Steel Company operates five underground iron mines in the Lake Superior District. The two largest of these, from the standpoint of productive capacity, are the Sherwood Mine in Iron River and the Bristol Mine in Crystal Falls, both on the Menominee Range of Michigan. It is at these two mines that we have had our principal experience with belt conveyor installations underground, .At the Sherwood Mine, which has an annual capacity of about 450,000 tons, the first conveyor belt installationwas made in 1947 when conveyors were installed in the main haulage drifts on the 1200 ft, level, It was estimated at that time that approximately 5,000,000 tons would be mined from the stopes above the 1200 ft, level and. that if all this material could be moved to the shaft by belt conveyor, the entire cost of operation, including maintenance and the amortization of the equipment, would be about $,05 per ton, which was slightly more than half of what the cost would have been by conventional tramming methods employing locomotives and cars. Now, ten years later, the 1200 ft, level is almost completely mined out and we have actually removed. 5,200,000 tons and. the average cost of transporting this material to the shaft by belt conveyor has been $.095 per ton. Since there has been a substantial increase in hourly rate of pay and also in the cost of materials since 1947, we feel that the anticipated savings were very nearly realized., The 1200 ft, level installation at the Sherwood consisted of two 36" trunk line conveyors 815 feet long and 380 feet long, respectively, deliverying ore to the shaft. These in turn were fed. by three lateral 36" conveyors which paralleled the sides of the orebody, These gathering conveyors passed under draw points to which ore was brought from the stopes by mea S of scrapers or shaker conveyors, Shaker conveyors were used for a number of years in conjunction with the conveyor belt system of haulage but it was finally concluded that with this particular type of ore, the maintenance on shaker conveyors was excessive. Therefore, more recently, we have gone back to scrapers for the shorter distances and. are using belt conveyors in the scraper drifts for the longer distances. After this belt system had been in operation for about three years, it had proved to be so successful that it was decided to proceed with the same system or. a new level to be opened up 200 feet below. Instead of sinking the shaft and driving a horizontal drift to the orebody on the 1400 ft, level, an inclined conveyor drift was started near the shaft at the 1200 ft. level and driven downwards toward, the orebody at a slope of 15 degrees. The conveyor installed in this inclined drift is 36" wide, 990 feet long, is powered. by a 100 hp motor, and is capable of delivering 300 tons per hour to the 1200 ft, level shaft pocket. It is fed by lateral horizontal conveyors on the 1300 ft? 1400 ft., and 1425 ft, sub levels. Wien the inclined drift was started, the rock was scraped from the breast directly to the rock pocket at the shaft. As the distance increased., double scraping was employed, until the advance had reached 350 feet, At this point a portion of the final conveyor was installed, with a scraper slide near the breast, T e drift was then advanced be scraping on to the conveyor until a sufficient distance had been driven to permit the installation of an additional 200 feet of conveyor. This proved to be a very efficient and economical means of moving the development rock to the shaft and obviated the need of using cars or an inclined skip way, At the present time 85 percet of tie entire mine output is being mined below the 1200 ft, level and is delivered to the shaft via the inclined conveyor. The system appears to be working as well and as economically as did the conveyor systemonthe 1200 ft, level.

Jan 1, 1958

By R. F. Holub, E. Franco, T. B. Borak, K. J. Schiager

INTRODUCTION According to a recent analysis by Schiager et al.(1981), inhalation of radon daughters continues to contribute the largest risk from exposure to radioactive materials in underground uranium mines. The American National Standards Institute (1973) has published a concensus standard for radiation protection in uranium mines. According to this standard, a monitoring system for radon daughters must be capable of measuring the annual accumulated exposure in working level months within an uncertainty interval of 50% at the 95% confidence level. To satisfy this criterion, uranium mining companies in the USA have adopted a procedure consisting of single or periodic measurements of the air concentration of radon daughters. All of the measurement methods sample a known volume of air through a filter. After a specified delay interval, the filter is analyzed for radioactivity. The exposure rate from total airborne potential alpha energy in units of working level (WL) is estimated from the measured activity on the filter. For control purposes, this measurement establishes whether or not a work area is safe for occupancy by miners. For routine dosimetry, the concentration estimated from the grab sample is assigned to the appropriate work area. It is then assumed that the concentration of radon progeny is equal to the average of the two measurements at the beginning and end of the specified interval. Meanwhile, the work locations and exposure times of each miner are recorded on the daily time card and verified by the shift supervisor. Most cards provide space for 15-minute time intervals. The exposure in working-level hours (WL-hr) for each shift is obtained by summing the time spent in a given location multiplied by the exposure rate (WL) assigned to that location.The exposure of an individual miner to radon progeny is summarized on a weekly basis and commonly reviewed each month. These values are then accumulated in units of working level- months (WLM) during the calendar year. EVALUATION TECHNIQUE AND RESULTS The evaluation of grab sampling methods for monitoring exposure to radon progeny is presented in two sections. The first section examines each method individually according to accuracy, precision, and uncertainties attributed to human errors. The second section includes an analysis of procedures which are common to all measurement methods. The ultimate goal is to determine whether a specific measurement method, or grab sampling in general, can fulfill the criterion that the annual accumulated exposure of each miner be known to within ± 50% at the 95% confidence level. In addition it is essential that the above criterion be satisfied at an acceptable cost to the mining company. The results of each testing procedure are presented in terms of the contribution of the relative uncertainty in the estimates of cumulative WLM. Each of these are then combined to form a figure of merit for the complete monitoring system. The method of combining statistical uncertainties and interpretation of the results is subject to some debate. However, since all of the tested parameters enter into the final computation of WLM multiplicatively, we have used the commonly accepted procedure of combining the squares of the relative uncertainties. We have also assumed that each of the uncertainties is derived from independent random variables and the covariance of any two variables is zero. A description of each grab sampling measuring method is given in Table 1. Also included is the equation used to compute WL from the measured quantities. Accuracy (U A) Our definition of accuracy is based on the uncertainty inherent in any method which attempts to estimate potential alpha energy without unambiguously determining the concentration of the three unknown radioisotopes, RaA, RaB and RaC. (For simplicity, the RaC and RaC' nuclides are referred to in combination as RaC.) The inherent uncertainty strongly depends on the mixture of these three components at the time of measurement.

Jan 1, 1981

By C. A. Young

Previous experimental results have shown that an increase in temperature and/or oxygen concentration leads to an increase in the hydrophobicity of fluorite (CaF2) with adsorbed oleate. Subsequently, ex-situ Fourier transform infrared (FT-IR) transmission studies suggested that this increase in hydrophobicity was the result of double-bond reactions between adjacent oleate species adsorbed at the fluorite surface. Now an in-situ FT-IR study on single crystals of fluorite has been used to monitor this phenomenon using internal reflection spectroscopy (IRS) with the crystals serving as reactive internal reflection elements. The double-bond reaction has been correlated with in-situ adsorption density measurements. These results demonstrate that only the first chemisorbed oleate layer undergoes the double-bond reaction at an appreciable rate. However, multilayers of precipitated calcium oleate in the case of fluorite appear to react minimally even for oxygen saturated solutions at elevated temperatures.

Jan 1, 1991

By A. I. Kogut

Impurity minerals in fluorspar ores and concentrates from a deposit in Southern Africa have been studied by reflected light, transmitted light, and cathodoluminescence microscopy. The principal impurities are quartz, calcite, aegirine, apatite, ankerite, magnetite, goethite, and synchysite [Ca(La,Ce,Nd)(CO3)2F]. Cathodoluminescence microscopy was found to be very useful in studying the character of the fluorite and especially for recognizing the presence of apatite and calcite impurities. Fluorite exhibits blue, calcite shows yellow, and apatite has white, light purple, and pink cathodoluminescence. The cathodoluminescent character of apatite varies with its geological environment and position in the orebody. The results of this microscopic study show that phosphorus present in fluorite concentrates occurs principally in binary locked apatite-fluorite particles. Successive fluorite cleaner concentrates contain progressively smaller amounts of locked apatite-fluorite particles. Free apatite has been effectively partitioned to the final tailings.

Jan 1, 1995

By R. W. Smith, D. Clare

The removal of metals from an acid mine drainage (Leviathan Mine, Alpine County, California) water by precipitate flotation was investigated. The Leviathan waters vary from about pH 4.0 to pH <2.0and contain from about 2,000 to about 12,000 ppm SO42-.The main multivalent metals present in solution are Fe, Ca, Mg, Al and Mn. Both Cu and Co are present in small amounts. The pH was adjusted with lime. The collector used was either sodium oleate or tall oil. The sodium oleate was used as a function of pH to establish optimum flotation conditions and the tall oil was used only at the optimum pH. Dow Froth 250 was used as a frother. In some test additional Cu was added to the system. Excellent recovery of Fe and Cu were achieved at optimum pH. The process achieves results comparable to precipitation and filtration without as much problems with screens blinding because of less material to filter.

Jan 1, 2004

By M. C. Rockwell

There are approximately 1,800,000 t of discarded dolomitic-limestone tailings from the Gays River lead/zinc mining operation in Nova Scotia. Neutralization effectiveness similar to an agricultural grade limestone and low contents of residual metals make the tailings a suitable source&apos; of soil conditioner material for the local market. However, the fine particle size, 98% passing 147µm, and a high moisture content make their handling and application difficult. Agglomeration of the tailings into relatively small hard pellets was investigated and difficul¬ties were overcome. Pellets with a range of pH values and various amounts of soil nutrients and moisture content less than 10% were obtained, from tailings containing 20% initial moisture, through the addition of less than 15% selected materials.

Jan 1, 1985

By William W. Wellborn

Abrasives are substances both natural and synthetic that are used to grind, polish, abrade, scour, clean, or otherwise remove solid material usually by rubbing action (as in a grinding wheel), but also by impact (pressure blasting). Facts about the discovery, early use, adaptation, and development of abrasives prior to the 20th century are few. From the sparse, earliest information that is available, it would appear that the science of abrasives began when, to fashion his tools, man began to select certain kinds of rocks in preference to others because of their peculiar properties. There is evidence that stones were sawed by some sort of grinding machine as early as 4000 BC in Egypt. The real expansion of abrasives use coincided with the beginning of metallurgy in the Middle East around 2000 BC. The earliest confirmed use of abrasives for grinding metal comes from a steel dagger found along with a sharpening stone which was dated at about 1500 BC. Natural and manufactured abrasive substances play an important role in fashioning and finishing numerous products with a wide variety of end-use applications. The mining and preparation of crude, natural abrasives for their markets and the manufacture of synthetic and other abrasive materials contribute significantly to the US economy (Table 1). In addition, just as sawing to specific dimensions enhanced the value of the Egyptian stone, the use of abrasives in fabrication of modem products, and the addition of abrasives to others, add value. GENERAL CONSIDERATIONS The most important physical properties of materials that qualify as abrasives are hardness, toughness (or rigidity), grain shape and size, character of fracture (or cleavage), and purity (or uniformity). To fabricate bonded abrasive products such as grinding wheels, additional considerations include stability under high heat and bonding characteristics of grain surfaces. The economic factors of cost and availability are always important. No one singular property is paramount for any use. For some applications extreme hardness and toughness are needed, as in diamonds for drill bits. For other uses, factors of greatest importance are hardness and ability to break down slowly and, in the process, develop fresh cutting edges when grains become worn. In garnet sandpaper, for example, highly cleavable, friable, or extremely tough grains are not desirable. For other uses, extreme hardness may be objectionable. Abrasives for dentifrices and for glass-cleaning soaps are cases in point. For the most efficient uses in more critical applications, different types of abrasives are rarely completely interchangeable. While crushed quartz and garnet are both used in sandpaper, the two abrasives are not at all interchangeable in their applications. In the final analysis, the choice of a high-grade abrasive depends upon the quality and quantity of work performed by the abrasive per unit of cost. Initial cost of an artificial abrasive may be much greater than that of a natural abrasive, but the artificial mineral may do so much better work and do it so much faster that the ultimate cost is less. It is for this reason that artificial abrasives have largely replaced natural abrasives.

Jan 1, 1994

By V. Prabhu, D. Mantha, R. Reddy

Secondary copper blast furnace slag was treated with carbon to derive the conditions for maximum recovery of copper with a minimum simultaneous reduction of iron oxide. Experiments were carried out to study the effect of temperature, carbon and CaO additions to the slag on the efficient recovery of copper. A two-stage reduction process was also employed to study the efficiency of copper recovery and the results were compared with those of single-stage reduction. The maximum recovery of copper in alloy phase was obtained with 5 % initial carbon in the slag, 2% CaO addition to the slag and at a reducing temperature of 1573 K. Higher grade of the alloy phase with respect to copper was obtained by employing a two-stage reduction process. The results obtained in this study are comparable to those of the earlier research on the recovery of copper from reverberatory furnace discard slags.

Jan 1, 2004

By Harold Gibson

The mechanisms leading to the impact of airborne dust particles onto bluff flow obstacles have been extensively reported [1] and widely applied in dust measuring instruments (e.g., impactors) and in dust collecting devices (e.g., filters and scrubbers). If the human head is regarded as a bluff body, particles from dusty flowing air can impact onto the face by virtue of those mechanisms. While a great deal has been researched and written on the nuisance caused to human beings by the entry of dust particles into the body by inhalation through the nose and mouth, there appears to be nothing reported in the scientific literature about the irritation which can be caused by the impact of dust onto the face. And yet there is sufficient evidence to suggest that in certain working environments and under certain conditions, the problem is indeed a real (albeit subjective) one. In the coal mining industry, underground workers are exposed to conditions, involving dust-creating production and handling processes on the one hand and high ventilation rates demanded by the gassy nature of the environment on the other, in which the problem can exist. At the coal face, for example, the movement of powered roof supports ("chocks") can release bursts of dust formed by the crushing action of the supports, which in turn is entrained into the moving air and impacts onto the faces of miners working just downstream. The dust in question contains a large proportion of coarse particles which, while still fine enough to remain airborne for appreciable distances downstream of the point of release, are coarse enough to produce sen¬sation on impact with the skin. Adverse subjective response of workers to such irritation could damage morale and productivity. We have performed laboratory and field experiments to investigate the psychophysical and physiological responses of human subjects to dust impacting onto the face and into the eyes. Since this appears to be the first systematic investigation into these questions, the aim has been to construct a useful scientific framework from which to allow characterisation of the problem of such "fly-dust", and, ultimately, the development of methods for monitoring and controlling it. The main results of our research are given here; the theoretical and experimental details will be presented at greater length elsewhere.

Jan 1, 1980

By R. C. Bunge

The selective flotation of semi-soluble salts with fatty acids is often negatively affected by the interaction of the potential determining cation with the ionic surfactant in bulk solution. This problem can be avoided by floating at low pH which involves the emulsification of the collector. The research presented here focuses on the influence of the Ca2+ ion on the flotation of fluorite with palmitic acid at low pH. Our results show that the surfaces of collector emulsions are dominated by precipitation phenomena similar to those encountered in bulk. In turn, fluorite in palmitic solution at intermediate pH displays surface properties similar to those of the collector by itself. This may be due to two alternative mechanisms (i) adsorption of bulk precipitate on the fluorite surface or (ii) the formation of a bilayer of surfactant ions on fluorite. Possibly, both mechanisms occur simultaneously.

Jan 1, 1993

By Guillermo P. Salas

The Consejo de Recursos Naturales No Renovables of the Mexican government entered into an agreement with the United Nations in 1964 for the mineral exploration of a large area in Estado de Sonora, Mexico. The agreement called for a systematic exploration for copper in northern Sonora based on photogeologic mapping, aerial reconnaissance, and geochemical stream sediment sampling. The UN-CRNNR investigations resulted in the detection of anomalous copper values in sediment from the Arroyo Cruz de Cafiada. The anomaly was followed upstream to its source, which ultimately proved to be the La Caridad ore body (see Fig. 1). Soil copper and molybdenum values were found over a large area, and further detailed geologic and geophysical investigations were instituted of the anomalous area. David Coolbaugh was largely responsible for the follow-up work. An induced polarization (IP) survey found a roughly circular region of "highs" that coincided with a high soil copper anomaly. The circular anomalies ringed the topographic feature that ultimately was found to contain the Caridad ore body. Soil geochemical copper response over the ore body was subdued, because the soils were derived from a leached capping, whereas leaching in fringe areas that contained less veining was less intense. The ore body was also ringed by the typical high pyrite zone, and this was the anomaly detected by the IP survey. The UN began drilling in the fall of 1966. Eleven holes tested the IP-Cu geochemical high, but none were of commercial interest. The project was returned to the Consejo and was reviewed in the field by G.P. Salas and V.F. Hollister. It was found that the leached capping had not been tested by the past activities, and the Consejo elected to explore that area in 1967. The capping was evaluated by Salas and Hollister and drilling by the Consejo began in 1967. Commercial grade ore intercepts were found in the first hole. The Consejo drilled nine holes, of which eight were commercial. At least 90.7 Mt (100 million tons) of 0.8% copper were indicated by the Consejo in eight holes. The lesson learned in this discovery is that evaluation of leached capping is an important guide to exploration. The general-

Jan 1, 1991

By James H. Boettcher

Inflation and increasingly complex tax laws in the United States combined with rising national ism overseas have made the structuring of viable financing plans which meet the requirements of the various parties involved equally important in determining project success as the design of an efficient mining plan or selection of the optimal size equipment. Whereas the use of computerized analysis to design and evaluate the technical parameters of resource ventures is well accepted, computerized evaluation of the investment criteria (qualitative and quantitative) of the various parties to the project (mining firm, financial institution, product buyer, host government, etc.) is a more recent application which can make a material impact in strengthening project economics. By identifying the objectives of the parties and critically evaluating and testing them with the technical and economic/financial constraints on the project the sponsors can design a financial structure tailored to the attributes of the deposit. A myriad of new financial techniques have evolved for financing natural resource ventures, from "Commodity-backed bonds" to tax based limited partner- ships, but in every case the structure of the financing mechanism depends on carefully matching the parameters of the financial structure with the economic characteristics of the project and the objectives of its sponsors. This presentation outlines a methodlogy for computer based project evaluation in the design and structuring of stronger financial plans for natural resource ventures.

Jan 1, 1982