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By D. M. S. Bhatia

The intimate association of iron formation and massive sulfide deposits has been documented by many investigators (McAllister, 1960; Hutchinson, 1972). In a classic example of such an association four distinct facies (oxide, carbonate, silicate, and sulfide) were identified in an Algoma type iron formation occurring in Paleozoic rocks, but exhibiting physical features (banding) and chemical composition (SiO2 + A1203 + Fe2O3) typical of Precambrian iron formations. The geochemical variation of the iron formation was studied by analyzing 62 samples for Si, Al, Fe, P, S, and CO2. Following a model proposed by James (1954), the geochemical and mineralogical variation of the iron formation can be used as an excellent tool for the exploration of massive sulfide deposits.

Jan 1, 1981

Train services through the Channel Tunnel linking Britain and France where scheduled to be fully restored in February 2009 following several months of repairs after a major fire in the tunnel on Sept. 11, 2008. A lorry caught fire on a shuttle train carrying heavy goods vehicles bound for France through the 50-km- (31-mile-) long northern tunnel. The fire, that spread to other vehicles, raged for about 16 hours. The extreme temperatures of up to 1,000º C (1,832° F) caused extensive damage to about 600 m (2,000 ft) of the 7.6-m- (25-ft-) diameter tunnel?s concrete lining, approximately 11 km (7 miles) in from the French entrance. The Channel Tunnel operator, Eurotunnel, awarded the repair con-tract, estimated to be between ?50 to 60 million, to a consortium of Freyssinet, Eurovia Travaux Ferroviaires (ETF) and Vinci Energies. Freyssinet was appointed to look after the civil engineering works, while ETF would be responsible for track and overhead wire restoration and Vinci Energies responsible for other equipment. The technique of hydrodemolition, which uses high-pressure water jets to remove concrete from various structures, was specified as the method to remove the fire damaged concrete. Freyssinet subcontracted the concrete removal to the specialist hydrodemolition and industrial cleaning contractor Philip Lasserat.

Jan 1, 2009

By J. C. Squire, E. W. Baker, G. A. Sullivan, G. W. Flathers

A mine collapse severs communication with trapped miners. Landlines are crushed and commercially available radios cannot penetrate hundreds of feet of dense, conductive earth without the use of regenerative repeaters that may also be crushed. This paper describes a proof-of-concept device that uses seismic P-waves, instead of radio waves, to allow communication of a code that represents prearranged messages, including the safe haven location identifier, number of people and air quality, from trapped miners to aboveground rescue units. The transmitter designed is about 0.03 m3 (1 ft3) in size and can broadcast for four hours from its 27-kg (60-lb) battery pack. The receiver consists of a geophone and a 2.5-kg (5.5- lb) signal conditioning unit attached to a laptop computer, which displays the communication signal in real time. Testing in a bituminous coal mine with an MSHA representative revealed the device was able to transmit through 271 m (890 ft) of overburden, at 0° and 12° from vertical, using 500 W of power.

Jan 1, 2009

By F. W. Petersen

Slurry reactors are being used extensively throughout the chemical, biochemical and mineral processing industries. This paper describes the interaction between fine ore particles and granular porous adsorbents such as activated carbon and ion-exchange resins in a stirred tank reactor. Gold and silver cyanides were used as adsorbates to detect changes in the mass transfer characteristics of the adsorbents, which were ashed to determine the loading of ore particles. A simple kinetic model incorporating film diffusion, intrapanicle diffusion ~d the adsorption equilibrium, was used to interpret kinetic data and to estimate the effect of slurry conditions on the diffusion parameters. It was observed that the equilibrium loading of fines in the adsorbents was independent of their concentration in the slurry. Furthermore, the presence of these panicles inside an adsorbent decreases the effective diffusion of gold or silver cyanides into the adsorbent matrix. When fine suspended solids are present in the reactor, a decrease in the effective availability of the superficial surface of the pre-saturated adsorbent panicles for mass transfer from the liquid phase was observed. This newly defined surface availability factor was dependent on the concentration, panicle size, and the zeta potential of the fine particles in suspension.

Jan 1, 1993

By F. A. Gates, Bengt Samuelson, James E. Edmunds, S. McCune, Neil Hario, Norman L. Weiss, J. M. Bertram, A. M. Cavaliere, F. M. Jr. Stephens, D. D. Chiang

DESIGN BASIS Size of Project The size of the project generally is expressed in tons of ore milled per day, but company policies differ widely in this respect with a few adhering to this set figure but many expecting the design capacity to be liberal. To some companies that follow the latter practice a 25,000-tpd milling plant that cannot reach 30,000 or 35,000 tpd with¬out major additions is a disappointment. The engineers responsible for planning the operation must know what is intended. Other projects are sized according to the tonnage of product rather than of mine ore; examples are iron ore mills that express size in terms of tons per year of pellets or high-grade concentrates, heavy minerals plants in tons per year of rutile or ilmenite, cement plants in barrels per year, potash in tons per year of muriate, phosphate in tons per year of washer rock and flotation concentrate, and others. However, tons per day milling rate is also the common denominator in most of those instances because the major equipment has to be selected on that criterion. Equally important are operating schedules, particularly the number of operating days per week and shifts per day for ore delivery, crushing, grinding, and processing. Hours per shift also are an impor¬tant factor in design, particularly in the case of ore delivery, and the lost time expected for maintenance, cleanup, inspection, preventive maintenance shutdowns, and many others, has to be taken into ac¬count. Frequently, the ore deposit will vary in hardness and grade to such a degree that the capacity of the mill will vary widely from year to year and cannot be expressed as a fixed figure, but rather as an average over a calculable period, such as ten years, or as a specific daily capacity over the first two years, next four years, etc., or some similar projection. A good example of this kind of situation is Asarco's Mission operation 15 miles southwest of Tucson, Ariz., described by Weiss and Vincent,1 where the major rock types differed widely in hardness, so that a change in the proportion of these types in the mill feed could have imposed difficult design problems if a constant tonnage rate had been expected. Expected Life The life of a mining operation depends upon the size of the deposit and the rate of mining. The latter is a policy decision based on an economic analysis2 which, in turn, is based on many factors. From the point of view of mill planning, the estimated life of the operation determines many criteria and affects many decisions on strength of structures and degree of protection of men and materials, the quality of the materials-handling and process machinery, the type of delivery systems for ore to the mill and concentrates to the smelter or market, environmental considerations, and many others. Costly installations that may be excellent investments for a 20-year project may be waste¬ful for a 5-year operation. An example is the comparison of different methods of crushing or grinding. Take single- vs. multiple-stage grind¬ing-the former may be found more economical for a 5-year operation, and the other, more costly method more economical for a 15- to 20-year life. Mining and Ore Transportation The mining method and the means of transportation of the ore to the first crushing stage have far-reaching effects upon mill design, particularly the crushing sections, and upon site selection (see Chapter 2, Situation of Mill). Consequently, mill design cannot advance until the mine planning has reached at least tentative decisions concerning these important matters, or reach the final stages until much is known about the ore that may be expected month by month and year by year for a reasonable period. Methods of ore transportation used in over 90 underground and open-pit mines are listed briefly in Section 32 (Table 1), and more detail is found later in this section and in Section 10, Storage and Transport. These methods include surface railroad, trucks, conveyors, surface skips, underground skips, and tramming from hoist or tunnel. In surface mining, transportation of the uncrushed ore by rail or truck to the primary crushing plant-conveniently located for lowest overall cost-is most common. Rail transportation provides low perton-mile costs. Truck transportation, though in some cases less eco¬nomical, is more flexible and more adaptable to mountainous terrain; furthermore, recent improvements have reduced the operating costs to keep trucks competitive on low-grade ores. The design of the primary crushing plant will be essentially the same whether delivery is by truck or rail, but the location of the plant is subject to more rigid restrictions in the latter case because of grade limitations, and these in turn may adversely affect the selec¬tion of the mill site as well. The influence of truck haulage in reducing the stripping ratio in open-pit mines is an added reason for predicting a minor role for rail transportation in the future. The use of conveyors to transport ore from the pit to the milling plant involves (in most cases) crushing the ore to a reasonable size (10 to 20 in. maximum with today's crushers) before conveying. The Twin Buttes system3 which went into operation in late 1969, utilizes primary crushers (two) and conveyors to receive rock waste, ore, and low-grade stockpile material from trucks, then transport them to the appropriate destination. Flexibility is dependent upon the porta¬bility of the primary crushers. In the face of this development, inclined skip hoists are no longer important to the mill designers. Underground mines generally pose fewer problems of design; these will be discussed in Chapter 2. Character of Deposit The degree of homogeneity of the ore in various parts of the mine is an important factor. The characteristics that concern the millman (approximately in order of importance) are: hardness, assay, metallurgical response, size distribution,4 and moisture content. Under metallurgical response may be included degree of oxidation, mineral¬ogy, clay content, and reagent consumption, as well as process re¬sponse in general. Short-term variations-hour-to-hour, day-to-day, or even week-to-week-make operation of the plant more difficult, require greater flexibility of process design and, perhaps, also require more instrumentation and manpower. Uniformity of the ore in the characteristics noted previously and

Jan 1, 1985

By J. C. Franklin

The U.S. Department of the Interior, Bureau of Mines, has developed a data acquisition system to continuously monitor radon, working level, absolute pressure, temperature, relative humidity, and air velocity. Data have been taken in intake and exhaust drifts, working stopes, and sealed-off areas of positive and negative ventilated uranium mines. Radon emanation rates, ranging from 1.7- to 12.2 x 2 10-l4 Ci/cm /sec were determined in four mines. The ratios of short duration, primary fan shutdown time to radon normalization time were 1 to 2 and 1 to 4, respectively, for-negatively and positively ventilated mines. Blasting and slushing caused radon increases of 160 and 67 percent, respectively.

Jan 1, 1980

By F. Dakubo

"Solvent extraction of copper pregnant solution (PLS) obtained from ammonium peroxodisulfate assisted leach was modeled using response surface methodology. Mixing speed, pH, reagent concentration and organic to aqueous (O/A) ratio were selected for testing. A pitched blade mixer was used in the experiment. Mixer speed contributed significantly to copper extraction significant, while pH had minimal effect on copper extraction. The response model developed has an R2 = 0.97 and Adeq precision of 28.3. A parallel kinetic comparing study using a straight blade Rushton turbine in a turbulent regime of mixing showed no difference (p-value =0.308) between peroxodisulfate assisted leach PLS and conventional ferric/sulfuric acid leach PLS- the power draw data support this conclusion. INTRODUCTION High arsenic chalcopyrite concentrates are a problem to the smelters all over the world due to high arsenic gas emissions during smelting. Therefore leaching is often the alternative for extracting the copper in these concentrates if dilution with low arsenic concentrate is not possible. High-pressure autoclave leaching is used. Alternatively, the use of stronger oxidants such as peroxodisulfate has been proposed [16, 18]. There is a concern brought up by the hydrometallurgy community about the faith of the organic extracting reagent coming into contact with stronger oxidant residue in the pregnant leach solution (PLS) and hence the efficiency of such extraction process. This work, therefore, looks to answer such concerns. PLS generated from leaching of chalcopyrite concentrate with the peroxodisulfate ion was used in this solvent extraction experiment. As a liquid-liquid extraction, solvent extraction involves contacting the aqueous PLS with organic extractant via mixing. Mixing is known to increase the interfacial area for mass transfer by decreasing the diffusion path length (Jussi et al.1997). EXPERIMENT Instruments and Reagents Reagent grade Acorga 5910 reagent was used in the experiment was supplied by Cytec (Current name Solvay), Ammonium peroxodisulfate and sulfuric acid were reagent grade obtained from Amazon. Apparatus The solvent extraction tests were carried in a 2000 ml plastic cylindrical reactor equipped with four 0.5” baffles. In the hypothesis test, the reactor was a 4000 ml cylindrical reactor with four 1” thick baffles arranged evening in the reactor. Comparison between peroxodisulfate and ferric leach PLS via hypothesis test"

Jan 1, 2018

By J. E. Murphy, L. A. Walters, F. H. Nehl, G. B. Atkinson

The US Bureau of Mines investigated the selective electrowinning of Ag and Au from cyanide solutions contaminated with Cu with the goal of decreasing the amount of Cu codeposited. Decreasing Cu codeposited will reduce refinery costs. Direct current was applied to the cell in pulsed and square wave voltages at 0.7 A h/150 mL of solution. Times tested for each cycle ranged from 1 to 10,000 msecs. Graphite, lead and stainless steel were evaluated as electrode materials. Square wave electrowinning at 70°C (158° F) gave the best separation of Ag and Au from Cu. Applying 2.5 V during the duty cycle, 0.0 V the rest of the period, a duty cycle of 10% to 30%, and a period of 100 msecs to 1000 msecs gave the following results: Ag concentrations decreased from 34 µg/mL to 0.1 µg/mL. Au concentrations decreased from 54 µg/mL to 0.2 µg/mL and Cu concentrations remained almost constant at 560 µg/mL.

Jan 1, 1995

By P. Diehl

The increasing public interest in a useful framework for an assessment and classification of mineral resources (1) is documented by the recently published international classification scheme of the United Nations (1979) and the revision of the classification system of USBM/USGS (2) (1980). Moreover, various classification systems are currently discussed by the mining industry. In spite of major improvements in respect of the concepts, definitions, and taxonomy of ore classification, it has been recognized that the recent practice to classify mineral resources does not create truly reproductible results, i.e. an assessment to the various categories which is free from personal bias or corporate interests. Following are geostatistical methods proposed for a standardization and quantification of various terms in ore classification. After critical review of present practices, we will establish a precise link between the classical terms such as "measured", "indicated", and "inferred" reserves and the geostatistical concept of estimation errors. Moreover, we will demonstrate, how the basic criteria of economic feasibility, geologic assurance and recovery can be taken into account by geostatistics. A specific algorithm will be proposed to block out and to classify reserves according to the degree of geologic assurance. . We will also show computerized methods which perform complete classification procedures, and will also exemplify them with typical case studies.

Jan 1, 1982

By R. Weinstein, R. Snoby

There are many advantages to upgrading coal with dry jigging technology. The most obvious is the lack of process water, which eliminates the need for fines dewatering and slurry confinement. Dry jigging eliminates the clean coal moisture penalty associated with wet processing. Particulate emissions are virtually nonexistent due to inclusions of fabric dust collectors on all modern dry jig plants. Due to the environmentally kind nature of dry jig plants, installation permits are often measured in days, not months. Coupled with all these advantages there has been a fundamental advance in dry jigging efficiency. All of these advantages have renewed the coal industry’s interest in dry jigging. But, air jigging isn’t right for every application. There are limitations due to particle size, particle shape, moisture, and near gravity content. This paper explores the evolution of dry jigging; reviews parameters important for determining the suitability of dry jigging; compares historical performance data as measured by imperfection, against results from modern dry jigging technology; and presents actual data from modern dry jig installations.

Jan 1, 2006

By Ch. R. V. S. Nagesh, Ramesh Naidu Mandapati, Venkata Swamy Nalajala, Tondepu Subbaiah, Naga Jyothi Kothamasu

Leaching studies of magnesite obtained from Tamilnadu Magnesite Limited, Salem, have been carried out using hydrochloric acid leaching and percentage of magnesium chloride recovered was estimated. The variables considered in this study were the following: duration of leaching, volume percentage of hydrochloric acid, temperature, and pulp density. Percentage recovery of magnesium chloride increased with duration of the leaching, volume % of concentrated hydrochloric acid, and temperature. Percentage recovery of magnesium chloride decreased with increase of pulp density. The optimum conditions found to be pulp density (10%), hydrochloric acid concentration (30%), duration of leaching (2 h), and temperature (348.15 K). Iron was removed by treating the leach liquor with hydrogen peroxide and by raising the pH to 3.5–4. The purified leach liquor was subjected to spray drying for producing high pure magnesium chloride.

Jun 7, 2022

By E. C. Ekedahl, R. J. Heath

Introduction Potassium, together with nitrogen and phosphorous, is an essential nutrient required for growth. Since all living things need potash, the major demand for potash - about 95% of the total - is as a fertilizer. Agricultural productivity has increased dramatically in recent times. This increase in crop yields requires substantial amounts of added nutrients to keep the soil fertile. It follows then that potash will always be in demand. There is no substitute. Other fertilizers that contain phosphorous (P) and nitrogen (N) are complementary and not competing products. Fireplace ashes (pot-ashes) have a relatively high potassium content. Their value as a fertilizer had been recognized for centuries. But today's potash industry did not begin until deposits of potassium-rich ore were discovered and exploited in Europe during the 19th century. Canadian potash development Potash in Saskatchewan was first recognized in 1943. It was discovered as a byproduct of an oil exploration program. But it was several years later before the existence of a major commercial deposit was acknowledged, and not until 1951 that the first attempt at development occurred. That attempt was unsuccessful. The shaft flooded and was abandoned. It did, however, demonstrate the need for new technology to penetrate the waterlogged Blairmore layer. This was eventually developed and the first mines were brought into production in the early 1960s. Once the technology was available, and the extent and quality of the potash beds became known, a number of companies proceeded to develop mines. By 1970, seven mines were in operation and three more were nearing completion. Combined, total capacity then was 7.6 Mt/a (8.4 mil¬lion stpy) K20. At that time, world potash consumption was about 15 Mt/a (16.5 million stpy). This increase in supply from Canada produced a large potential surplus that shattered the prevailing balance between supply and demand. Although world demand increased steadily throughout the 1960s and early 1970s, it was several years before world supply and demand were again in balance. Saskatchewan capacity has been expanded a number of times. It now stands at 10.7 Mt/a (11.7 million stpy) K20. Actual production has not approached this figure, however. Two new mines in New Brunswick have recently been built with a combined annual capacity of 1.2 Mt (1.3 million st) K20. Total Canadian capacity of about 12 Mt/a (13 million stpy) now amounts to 30% of world capacity. Central offshore marketing organization Canadian Potash Exports Ltd. (Canpotex) was created in 1970 as the offshore marketing organization for Canadian producers. Canpotex is owned by Saskatchewan producers and is their exclusive marketing organization for offshore business. Each company handles its own sales in Canada and the US, but all sales to other markets are handled through and by Canpotex. The Saskatchewan industry has an ore body of a size and consistency unmatched anywhere in the world. Large efficient mines have production costs that compare favorably with other producing countries. On the minus side, Saskatchewan is remote from most major markets. It therefore needs the ef¬ficiencies that stem from one organization that coordinates all offshore shipments and minimizes distribution costs. Agriculture guides potash market In the period following World War II, potash was a classic growth industry. World demand increased each year from 1945 to early 1970s. Since then, demand has been more erratic. Some years show substantial increases, but are followed by significant declines. For about the last decade, the pattern has been unclear and future demand has become correspondingly difficult to predict. North America and Europe together account for about 40% of the world potash consumption. In both areas, farming is characterized by surplus production, declining crop prices, and expensive government support programs. Under those circumstances, farmers respond by minimizing input costs. Fertilizer is one of the items they reduce. Potash is retained in the soil. It is possible to reduce potash application with no immediate deterioration in crop yield. The lower yields occur only when potash levels are depleted. So, farmers can econo-

Jan 12, 1987

By R. L. Virta

Six companies mined fire clay in Missouri and Ohio during 2004. Production, based on a preliminary survey of the fire clay industry, was estimated to be 398 kt(438,700 st), valued at $9.81 million. This was slightly less than the production and value figures from 2003. Missouri was the leading producer state. It accounted for more than 70 percent of the U.S. production. Consumption Domestic producers sold or used fire clay primarily for refractory applications. This application accounted for 79 percent of the market. Refractory products made using fire clay include firebrick and block, grogs, high-alumina brick and specialties, refractory mortars and mixes, and saggers.

Jan 1, 2005

By C. I. Walker

"Understanding the influence of slurry particle size on wear is essential to maximising the life of centrifugal pumps operating in mineral processing plants and for hydrotransport duties. Particle size influences not only the wear rate but also the wear pattern in pumps. Complicating the situation is the different relative wear rate for different pump parts depending on particle size. A simple Slurry Wear Type (SWT) number based on particle size and size distribution is proposed as a means for categorising slurry pump wear patterns and optimising pump application and material selection. INTRODUCTION The wear of centrifugal slurry pumps in mineral processing and hydrotransport can be quite severe and is one of the major cost concerns of plant operators. Some typical worn slurry pump parts made from high chrome white iron are shown in Figure 1. Erosion wear rates of up to 2 mm/day are not uncommon [1].Centrifugal slurry pumps are required to handle solid-liquid mixtures with a very wide range of particles extending from sub-micron size clay through to 200mm and larger cobbles. Particle size distribution can also vary widely from uniform and narrow (such as graded sand) through to very broad (such as grinding circuit slurries). Slurry particles may also undergo size change due to attrition during the pumping process. The major wearing parts in a slurry pump are the impeller, side liners and casing liner. These are shown with reference to a Warman® MC centrifugal pump in Figure 2. While many particle properties (including size, shape, hardness, density and concentration) influence pump wear, this work will consider only the effect of particle size as it is the major determinant of wear characteristics. Particle size influences the wear pattern, material performance and relative component wear rate in centrifugal slurry pumps. SLURRY WEAR TYPE (SWT) BASED ON PARTICLE SIZE Soil and grain size classification systems abound. Many have different limits to the ranges for a particular classification, albeit not too"

Jan 1, 2018

By C. A. Fleming, C. J. Ferron, E. S. Makande, P. Mason

Several small mines are producing refractory gold concentrates in Zimbabwe and, owing to the small scale of most of these operations, their output is processed in a central custom roaster in Kwekwe. Owing to the wide variations in the feed to the roaster, the efficiency of the old Edwards roaster is deemed unsatisfactory with gold recovery from concentrate as low as 70%, and alternative processes were evaluated to improve this situation. Various processes for oxidizing refractory arsenopyrite/pyrite concentrates to liberate gold prior to cyanidation are known. In practice, only two have to date met with wide industrial acceptance, pressure oxidation and roasting. Owing to the ·high arsenic and antimony levels of some concentrates in Zimbabwe, the only viable roasting alternative would be two-stage air-roasting of concentrates in two reactors, as practiced at Giant Yellowknife, Campbell Red Lake and New Consort. This process, however, creates an arsenic disposal problem, and produces gas of fairly low SO2 content, requiring a large gas handling system for acid production. On the other hand, there are currently four commercial pressure oxidation plants treating refractory gold ores (McLaughlin, Mercur, Getchell and Goldstrike) and three treating concentrates (Sao Bento, Porgera, Campbell). One other concentrate oxidation plant is being constructed (Con), and several more are being considered.

Jan 1, 1992

By L. Arbore

Introduction Mine operators are interested in energy conversation in two ways. With our finite sources of energy, we are concerned for future generations. In addition, as mine operators, we want to minimize energy costs. Moving material represents a substantial amount of the energy used in mining operations. Wheeled vehicles are used extensively to move materials. And they derive all their energy from fuel. Energy is also required to overcome the vehicle's inertia, and internal and external frictional forces. Included in the vehicle's frictional forces is its suspension. Tires are an important part of this suspension. What influence do tires have on the overall fuel consumption of the vehicle? Does tire construction affect this influence? As far back as 1896, it was apparent that tires were a factor in fuel consumption. A test was devised in France using a coal-fueled steam-driven auto. The test measured whether there was any fuel savings with the new pneumatic tires rather than of the then commonly used solid tires. The result was a 28% savings in water and a 29% savings in coal on pneumatic tires. Today, the pneumatic tire is accepted, but there are differences in present constructions. Tire Construction: Bias vs Radial There are basically two types of tire construction, bias and radial. Bias tires have been around for about 60 years. Radial tires are more recent. They were developed to improve a tire's ability to withstand higher speeds and loads, as well as to improve tire life and vehicle handling. Another advantage of the radial tire is its lower rolling resistance. This characteristic results in lower fuel use by a vehicle. This has been demonstrated with passenger cars and over-the-road trucks. It is now being demonstrated with earthmoving equipment. A basic description of both types of tire construction should now be reviewed: The casing of a bias-ply tire is made up of crisscrossed textile plies or layers. The cords of these plies run on a bias, from bead to bead. The cords of each ply run on an angle relative to the cords of the adjacent plies. As the tire rolls and deflects, the angle between the cords changes, like the blades on scissors (Fig. 1). The cords of one ply pull one way, and the adjacent ply pulls another, straining each other. This movement generates heat. Since the same layers of cords wrap around under the tread, they

Jan 9, 1984

By T. K. Bundtzen, C. B. Green

Exploration expenditures in Alaska last year amounted to $8.9 million. This was comparable to 1985's $9.1 million. Development expenditures dropped 29%, $24.3 million in 1986 vs. $34.1 million in 1985. The exploration industry is restructuring and stabilizing after the loss of major mineral firms during the last few years. These included Anaconda Minerals, Asarco, Hecla Mining, Enserch Exploration, Phillips Minerals Division, Exxon Minerals, Noranda Inc., General Crude, Mohawk Oil & Gas, Inspiration Development, Teton Exploration, and St. Joe Minerals Division. Some of these companies were mineral subsidiaries of oil companies and were either dissolved or redirected to programs outside of Alaska. However, recent entry exploration firms include Echo Bay Mines Ltd., Long Lac Minerals, and Exvenco. They are busy evaluating prospects and mineral developments in the southeastern panhandle. In the 1970s, about $254 million was spent on Alaska mineral exploration. Of this, about 5% ($12 million) was for nonmetallics and coal, about 26% was directed at precious metals ($66 million) mainly gold, and 69% ($175.3 million) for the base metals zinc, copper, molybdenum, tin, tungsten, and nickel. Since the early 1980s, trends have reversed. Of the nearly $196.3 million spent from 1981-1986, 48% has been for precious metals ($94.3 million) and 40% on nonmetallics and coal. In the last two years, nearly 70% of the Alaskan exploration dollar has been spent in search of precious metals. Three gold skarns were explored during the year - the Nixon Fork project in western Alaska (Battle Mountain Mining Co.), the Nebesna and Rambler lodes of the northern Wrangell Mountains (Nebesna Mining Partners), and the Zackley project near Paxson in southcentral Alaska (Nerco Minerals). Nearly 7.6 km (25,000 ft) of diamond and rotary drilling were conducted on these three properties. Aspen Exploration announced that significant gold mineralization was found under the Nome coastal plain in western Alaska. Meridian Minerals joint ventured with Resource Associates of Alaska, exploring precious metal

Jan 5, 1987

The Newmont Boddington Orebody (NBO) is a large, diffuse Au/Cu orebody in Western Australias South-West corner with approximately 20Moz Au in current Reserves. The current sulphide Resource is reported after calculation with the non-linear estimation technique Uniform Conditioning to account for the mining selectivity being smaller than the average drillhole spacing. Simulation of Au grade is also run over the entire orebody reviewing risk and uncertainty. There are differences in results from the two methods. These have been investigated and the lessons learned of the influencing parameters and effect of technique alone, are helpful for applications to other orebodies.

Jan 1, 2010

By Bruce F. Bohor

Silica sand has been mined in Illinois from the St. Peter Sandstone since the turn of the century, especially in the area around Ottawa on the Illinois River in the north-central part of the state. Production of this sand, consumed mainly by the glass and foundry industries but also sought after for many other uses, has grown with the economy, and last year's output in Illinois exceeded 4,000,000 tons. Such an important commodity was given the early attention of the Illinois State Geological Survey, and a very complete report was issued in 1928, authored by J. E. Lamar. The mining and processing of the sand has changed very little during the intervening 40 years, so that much of Lamar's data and descriptions are applicable today. More recently, the stratigraphy of the St. Peter Sandstone in north-central Illinois has become better known from the work of Willman and Payne (1942). The present authors have borrowed generously from Lamar's publication, and we wish to acknowledge the contribution of both of these studies to our work.

Jan 1, 1969

By George J. Allen, Laura A. Allen

Introduction This section of the text presents a general review of the different types of concentrate marketing contracts. Too often the marketing strategy is ignored in the design phase of the project and the producer is left to the mercy of the buyer. Many items such as concentrate grade, impurity levels and moisture content of the concentrate my enhance, or severely restrict the producers ability to make a profit it. Close attention should be paid to the design of the concentrator which can improve the quality of the concentrates, thus the ability to increase the rider of potential buyers can be enhanced. Difficult at best, is the position of the miner who only has one outlet available for its production. Obviously, the trade offs must be evaluated. For example, concentrate grade vs recovery and grind/filtering capacity vs moisture of the concentrate all must be weighted against freight cost to a potential buyer. In addition, the above considerations must be weighed against the capital cost to the miner. This chapter is intended to highlight important articles that are included in short and long term agreements and to give a new miner/producer some insight into hat my or my not add value to the product. Unless the miner sells the product directly to a consumer such as a gold, or silver producer, or to a large enough operation that has a totally intergrated system to make a finished product, most miners are forced to sell to buyers who ultimately will refine and market the product. Types of Contract Agreements There are many types of contract agreements just as there are colors in the rainbow, however, most contracts fall into three basic categories. (1) Smelter Schedules: Designed for the small producer, the odd lot of concentrate, smelter flux and precious metal ore. Albeit custom smelters are becoming fever by the day, because of pollution control requirements and financial difficulties, most remaining custom smelters have a smelter schedule. A smelter schedule is a posted list of charges and conditions that the smelter will buy material from a seller. Smelter schedules exist for copper, lead, zinc, silver and gold (Handbook for Small Mining Enterprises, Montana Bureau of Mines). (2) Short Term Custom Contracts: Large mine producers frequently use Short Term Contracts where the seller has the buyer frame a contract that is tailored to the sellers’ production. The short term contract my be as long as one year. A spot sale qualifes as a

Jan 1, 1986