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By B. Cristol, G. Benier

Laboratory and pilot tests have shown that the grinding of some aluminas makes two populations appear : agglomerates’ and ultimate crystals’. Classical breakage functions (Size Mass Balance Method) aren't able to describe correctly this kind of grinding. So we have optimized a particular breakage matrix which takes into account the fact that the agglomerates can either be reduced in size or either be blown up to liberate the ultimate crystals. The models which were developed using this breakage matrix are in good agreement with the experimental results of the pilot tests. The industrial breakage functions were estimated from pilot breakage functions, using scale up prediction procedures and plant tests. The agreement between predicted and actual plant performance is excel1ent.A 20 % increase in capacity was predicted to be available by improving the grinding circuit classifier performances.

Jan 1, 1992

By Gerald M. Ellis

Introduction Gold exploration in the Dominican Republic has not received much publicity. The fact is, however, that a continuous program has been underway for some time. For the past two years, the Restauracion area of the western Dominican Republic, near the Haitian border, has been the scene of mineral exploration by the Dominican Department of Mines geologists, and later by geologists of Rosario Dominicana. The latter is a state-owned gold mining company and operator of the Pueblo Viejo open-pit gold mine. The exploration is for mineral deposits with the goal of finding another Pueblo Viejo-type deposit. Geology Exploration is being carried out in the western central Cordillera, the backbone of the Island of Hispaniola. Geology consists of quartz veins and veinlets and ramifying stringers carrying pyrite, barite, minor amounts of copper, and significant amounts of gold in places. They are associated with regional faulting in a complex of Cretaceous beds of andesites, dacites, argillites, siltstones, and shales. They are intruded by tonalites, diorites, and gabbros. Lesser amounts of zinc-lead mineralization occur in some locations. The showings appear as disseminations along the faults. To date, the work has been mostly geologic mapping - 1 to 50,000 with details on a scale of 1 to 20,000 and 1 to 10,000-stream and soil lithogeochemistry, and geophysics. Trenching and sampling were used to follow possible vein extensions. Particular emphasis has been placed on the Los Candelones district that was taken over by Rosario Dominicana. Here is where drilling has been initiated in the past months. The first hole drilled showed assays of 21 g/t (0.6 oz per st). The second hole intersected an interesting oxidized zone that reminded observers of the original Pueblo Viejo oxidized zone. A third drill hole went deeper than 75 m (246 ft), the depth to which the first two holes had been scheduled. An assay of 50 g/t (1.46 oz per st) was cut during drilling. The presence of an oxidized zone of any vertical and horizontal extent is important. This gives rise to continued exploration, as the

Jan 2, 1986

By V. McLemore

New Mexico ranks 2nd in uranium reserves in the U. S., which amounts to 15 million tons ore at 0.277% U3O8 (84 million lbs U3O8) at $30/lb (EIA, 2006). The most important deposit in the state is sandstone within the Morrison Formation (Jurassic) in the Grants district. More than 340 million pounds of U3O8 have been produced from these deposits from 1948-2002, accounting for 97% of the total production in New Mexico and more than 30% of the total production in the United States. Sandstone uranium deposits are defined as epigenetic concentrations of uranium in fluvial, lacustrine, and deltaic sandstones. Three types of sandstone uranium deposits are recognized: tabular (primary, trend, blanket, black-band), roll-front (redistributed, post-fault, secondary), and fault-related (redistributed, stack, post-fault). Several companies are planning to mine these deposits by in-situ leaching.

Jan 1, 2007

By J. Herbst, J. Groppo, A. Noble, R. Q. Honaker

"Coal and coal byproducts produced annually contain a sufficient amount of rare earth elements (REEs) to meet current U.S. demand. The REEs exist in the form of minerals, ion-adsorbed elements associated with clays, and chemically bonded elements within the organic coal matrix or host mineral. Researchers at three universities collaborated to evaluate the effectiveness of existing physical and chemical concentration processes for the recovery of the REEs. The efforts found that physical separation processes can increase the total REE content in the thickener underflow material collected from a Central Appalachian coal cleaning facility from around 300 ppm to values greater than 17,500 ppm on an ash basis. Leaching followed by solvent extraction was found to be the most effective to recover the REEs from coarse middlings materials collected from multiple coal basins, as indicated by recovery values exceeding 80 percent. Based on material characterization data and process evaluations conducted for several potential feed coal sources, economic recovery of the REEs will require byproduct production of both clean coal and REE concentrate using a process flowsheet that is unique for each source. IntroductionRecent studies initiated by the National Energy Technology Laboratory showed that U.S. coals contain significant amounts of rare earth elements (REEs), suggesting that rare earth minerals (REMs) and/or REEs can be produced as byproducts (Ekmann, 2012). According to the report, the richest source of REEs is the Central Appalachian coal. At present, there are 208 coal preparation plants located in the region consisting of areas within the states of West Virginia, Kentucky, Pennsylvania, Virginia, Alabama and Tennessee, with a total capacity of 166,495 t/h, or more than 1 Gt/y (Fiscor, 2014). If only a portion of these plants are retrofitted with advanced separation processes, the U.S. coal industry would become a significant producer of REE concentrates as byproducts. An inherent advantage of becoming a byproduct producer of REEs is that no mining cost needs to be part of the production cost."

Jan 1, 2017

By M. G. Ayat, B. C. Scott

J. Dasher Having an interest in coal slurry pipelines from a decade of arguments with Ed Wasp and crew at Bechtel about pumping thicker slurries slower, I immediately read this article and found nothing in it pertinant to the title. Ayat and Scott pumped five unidentified coals at 9% solids (50%-60% is the area of interest) in a 25-mm (1-in.) pipe around two square elbows through a 76-mm (3-in.) cyclone for up to 60 minutes and sized a large number of samples of unstated size on an unidentified wet screening device. They did not measure power consumption, discharge pressure, flow rate, or give pump tip speed or impeller diameter. They siad the cyclone had a "high" pressure drop (unmeasured) and did much of the degradation (measured) but more or less per unit of energy expended? Hargrove was not measured, so there are no data as to whether it would correlate with degradation. The authors conclude, with no attempt, correlation is "hard to establish." Please experiment before concluding. I am at a loss to know what "increasingly smaller size" means, much less what theory says such particles take "exponentially larger quantities of energy," which the authors neglected to measure. If such experiments without pertinent data or justified conclusions must be published, please attach a pertinant title. reply by M. G. Ayat The first and the last criticism of this paper is that the work is not pertinent to the title. Anybody who reads this article will immediately realize that the work describes the breakage of coal particles to finer sizes in coal slurry pipes and pumps. If this is so, why not title the work "Degradation process in coal slurry pipelines"? What could be more pertinent to this title than the investigation concerning the degradation phenomenon of coal particles in a pipe carrying a coal slurry? Mr. Dasher complains that he does not understand the meaning of the term "increasingly smaller size." The first sentence of this article defines the degradation process as "the breakage of coal particles to increasingly finer sizes." The term "increasingly finer sizes" here means successive breakage of a fine particle to finer and finer sizes. According to Hukki (Hukki, 1975), the probability of breakage is high for large particles and rapidly diminished for fine sizes. We apologize for being brief about some of these definitions. The degradation process, breakage of particles to increasingly finer sizes, is so widespread in the mineral industry that we did not feel it necessary to bore the reader with lengthy definitions of some simple terms. Mr. Dasher states that the coals examined and their original size consist are unidentified. Please look at Table I and Table 2 in the paper again where you will find the original size consist of the coals examined and their full specifications. We only named the coals A, B, C, D, and E to avoid identifying the coal seams that were more susceptible to degradation. Not identifying the name of the wet screening device used in this work has also been criticized. In our opinion, wet screening operation is such a routine and standard procedure that naming the device by which the screening is performed would serve no purpose but to promote a sales approach. This was not our intention. We did not conclude that the correlation between the degradation process and Hardgrove Grindability Index is hard to establish as Mr. Dasher writes in his letter. We stated, not concluded, that "It is reasonable to assume that some relationship between the extent of degradation and its physical properties, such as Hardgrove Grindability Index, does exist. However, any definite correlation is difficult to establish." This statement is based on other researchers work, which are clearly referenced in the article. The conclusions of this paper were based solely on the findings of the experimental work. As for the theory of comminution that Mr. Dasher asks, we would like to refer him to some basic comminution books and articles where various theories are clearly described. For example, Hukki (Hukki, R.T.,"The Principles of Comminution; An Analytical Summary," Eng. Min. 176, 106, 1975) suggests that the relationship between energy and particle size is a composite form of three laws (Bond's law, Kick's law, and Rittinger's law). A comprehensive analysis of coal breakage processes is also performed by Broadbent and Callcott (S.R. Broadbent, and T.G. Callcott, "Coal Breakage Processes, I. - A New Analysis of Coal Breakage Processes;" and "Coal Breakage Processes, II. - A Matrix Representation of Breakage," Journal of the Institute of Fuel, pp. 524-539, December 1956). These and many other relevant publications explain the relationship between the particle size and energy much better that what can be said in this short reply. We will, however, agree with Mr. Dasher on one particular point. We, too, believe that if the investigation concerning the degradation process in coal slurry pipeline were to be pursued further, one could choose to determine one or more of the variables available in the process, such as discharge pressure, power consumption, percent solid, pipe diameter, etc.

Jan 1, 1989

By Saied S. Navid, Michael A. Piepenburg, Richard F. Escandon, Robert C. Lindsay

INTRODUCTION Phase I of the Los Angeles Metro Rail Project, known as MOS-1 (Minimum Operable Segment-1), is the first phase of the 27 km± (17 mi) subway starter line. MOS-1 is currently under construction and involves approximately 6.4 km (4.4 mi) of subway, five stations, yards and shops routed through the downtown area of Los Angeles. The project will form the initial heavy rail backbone of a more extensive light and heavy rail transit system planned for the greater Los Angeles area in the future. Construction Contract A-171 is one of 4 tunnel contracts within MOS-1 and involves construction of twin tunnels running from the downtown metropolitan area west to MacArthur Park. The heavily populated and developed downtown area, potentially gassy ground conditions, and the possibility of undocumented abandoned oil wells in seismically active southern California made the design and construction of Contract A-171 a uniquely interesting project. This paper summarizes the construction history to date (December, 1988) including design geotechnical considerations, tunnel support design, as-built geologic conditions, shield tunneling performance through soft ground, and ground response. The findings presented herein may aid in the design and construction

Jan 1, 1989

By Thomas J. Peters

At the request of the U.S. Bureau of Land Management, the U.S. Bureau of Mines and U.S. Geological Survey conducted a mineral investigation of about 85,470 acres of the Diablo Mountain Wilderness Study Area, to determine mineral resources and mineral resource potential. The study area is in Lake County Oregon, about 45 miles northwest of Lakeview. Fieldwork was conducted in 1986, 1988, and 1989. Geologically, the study area lies on the northwest edge of the Basin and Range physiographic province, a region of fault block-formed mountains and basins characterized by interior drainage. Consolidated rocks are mostly Tertiary basalt and tuffaceous sedimentary rocks. Low-lying areas are covered by Quaternary alluvial-fan, sand-dune, playa, lacustrine, and landslide deposits. The principal structural features are normal faults that have large vertical offsets; these faults are typically concentrated at the margins of large horst and graben. The 34,310-acre "additional," or western part of the area was mainly studied in 1988 and borders the east shore of saline Summer Lake. In this portion of the study area there is potential for undiscovered resources of soda ash, boron compounds, and sodium sulfate as well as by-products, which include magnesium compounds, salts, potash, bromine, lithium, and tungsten associated with brines. No energy or mineral resources were identified in the study area, but brines within lake and playa sediments contain concentrations of chemical components suitable for the production of soda ash, boron compounds, and sodium sulfate. Possible by-products include potash, salts, bromine, lithium, magnesium compounds, and tungsten. Limestone from the study area could be used in the recovery process of brine components or agricultural uses. The study area includes thermal springs and lies within 2 miles of the Summer Lake Known Geothermal Resource Area. Local production of geothermal power by the binary process may be economically feasible. Soda ash, soda ash products, and boric acid are widely used in fluxing metals, and have important applications and markets in the aluminum industry in the northwest and the developing Chinese counterpart. Evaporite commodities are essential to many "backbone" industries, and to many new applications and advanced materials. Markets for brine mineral products appear to be undergoing steady and strong growth, especially in the Pacific Northwest and in Pacific Rim countries. Soda ash produced near the study area would be 55 percent closer by rail to marine export at Portland, Oregon, than trona deposits of the Green River District (Wyoming). Soda ash and a daughter product, caustic soda, and sodium borohydride will receive increased application in the bleaching of paper pulp for environmental reasons. Caustic soda, used in many industrial processes, is more environmentally friendly when derived from soda ash than when produced from sodium chloride salt, because of the absence of a chlorine by-product. Producing soda ash from brines, a type of in situ" mining, can be done with minimal environmental degradation, and mining natural soda ash is environmentally as well as economically preferable to synthetic soda ash production.

Jan 1, 1995

By Michael P. Foose

In 1994, more than 41 of the approximately 160 coal-fired, electrical- power plants within the six-state Ohio River Valley region used flue-gas desulfurization (FGD) units to desulfurize their emissions, an approximately 100% increase over the number of plants using FGD units in 1989. This increase represents a trend that may continue with greater efforts to meet Federal Clean Air Act standards. Abundant limestone resources exist in the Ohio River Valley and are accessed by approximately 975 quarries. However, only 35 of these are believed to have supplied limestone for FGD electrical generating facilities. The locations of these limestone suppliers do not show a simple spatial correlation with FGD facilities, and the closest quarries are not being used in most cases. Thus, reduction in transportation costs may be possible in some cases. Most waste generated by FGD electrical-generating plants is not recycled. However, many FGD sites are relatively close to gypsum wallboard producers that may be able to process some of their waste.

Jan 1, 1999

By C. L. Pillar

In the capitalistic system the success of a mining enterprise is measured by the rate of return on the investment and the speed by which its redemption is achieved. Exploration in search of ore deposits often results in the emergence of the lean orebody which does not meet basic company requisites. At this point a decision must be made whether to place the orebody into production or postpone production pending more favourable market conditions. The wisdom of this decision, borne out by future results, demonstrates the quality of a company's management and is instrumental in the degree of financial success it achieves. The project feasibility report must show a rate of return on the capital invested that is attractive to the company, plus its full redemption in the desired period of time, in order to bring the property into production on a sound economic basis. Mining companies have demonstrated their ability to bring the profitability of a marginal property from a point that says "no go" to a point of "go" by substantial reduction of expenditure without adversely affecting production rate or cost. Here is where the real challenge exists for today's mining engineers and plant designers; they will have to develop better ideas and concepts: ideas that will still allow maximum production at reduced capital expenditure, This is the sound way marginal orebodies can be brought into production without inflationary increases in the price of their product.

Jan 1, 1969

The criteria used to design, operate and control flotation columns are significantly different from those used for conventional flotation machines. Therefore, a computer-aided design (CAD) package for column flotation has been developed. The simulator has been set up using guidelines developed at Virginia Tech and information published in literature during the past few years. The simulator is useful for determining the proper design and appropriate operating conditions for a column cell to fit a specific set of conditions. In addition, the simulator can be used for training in column operation and for trouble-shooting operational problems. Simulation results have been found to be in good agreement with experimental data obtained using laboratory columns.

Jan 1, 1990

By K. R. Gardner, P. B. Altringer, R. H. Lien, B. E. Dinsdale

The Bureau of Mines, U.S. Department of the Interior, is investigating chemical and biological decontamination of complex wastewaters such as tailings pond water containing 280 ppm CN and 5 ppm Se as well as significant concentrations of arsenic, copper, iron, silver, and zinc. The most effective chemical procedure involves cyanide oxidation using hydrogen peroxide or sodium hypochlorite followed by selenium reduction using ferrous hydroxide. The effluent contains ?1 ppm CN and 20 ppb Se; concentrations of other - major contaminants meet National Drinking Water Standards. Preliminary research indicates that biological cyanide oxidation is possible even in highly alkaline solutions (pH 10.5) containing high cyanide concentrations; indigenous bacteria destroyed 85% of the cyanide. Exploratory research shows that other bacteria removed up to 79% of the selenium from chemically oxidized, low- cyanide water. These promising results may lead to a final processing scheme that involves a combination of chemical and biological techniques.

Jan 1, 1990

By Marcus A. Wiley, Gregory Abramov

Borehole mining (BHM) is a remotely operated method of extracting rock material through boreholes by high-pressure water jets. Figure 1 illustrates a BHM tool and fluids circulation. The tool consists of at least two pipes, one for pumping down high-pressure water, the second for delivering slurry to the surface. This article reviews the BHM process. It discusses current and new applications for borehole mining and help the readers determine if BHM is applicable in their situations. Previous articles in ME about BHM explained either a particular project (ME, April 2001, pp. 33-36) or a newest patent in this area (ME, March 1991, pp. 313-318). However, neither one provided an overview on the modern BHM technology.

Jan 1, 2004

By G. L. Dollinger, W. H. Hamilton

INTRODUCTION Design and development of new products generally proceeds through a phase of initial development and discovery based on the evolution of existing arts, followed by technical innovation and development based on both pure and applied research. The development of the mechanical tunnel boring machine (TBM) has followed a similar pattern, with the first machines closely resembling continuous coal miners. In general, however, the design of TBM's to date has been more a result of evolution and discovery than of new technical innovation, even though large sums of money have been spent on research and development. In particular, the results of experimental laboratory and field investigations have had little effect on tunnel boring machine design, and the better performance of TBM's today over those of 10 or 15 years ago, is due more to increased mechanical reliability and greater operating experience, than to improvements in penetration rates and rock fracture capability. The improvements made, have been mainly by the machine and cutter manufacturers who recognize the greater efficiency and economic advantage of utilizing large single row cutters with high load capacity along with large edge spacing. Are there any improvements to be made, therefore, in TBM performance without new and dramatic technological breakthroughs? Can TBM manufacturers design greater performance into their machines by a logical extension of the present art, and by applying what has been learned in the laboratory and field? Some, for example, believe that the kerf cutting system of boring rock is at, or close to, its opti¬mum and little improvement can be made in the present TBM concept.

Jan 1, 1979

By P. T. Bissert, L. Yan, M. D. Klein

"Federal regulations require the installation of refuge alternatives (RAs) in underground coal mines. Mobile RAs have a limited ability to dissipate heat, and heat buildup can lead to a life-threatening condition as the RA internal air temperature and relative humidity increase. The National Institute for Occupational Safety and Health Office of Mine Safety and Health Research performed heat testing on a 10-person tent-type training RA and contracted ThermoAnalytics, Inc. to develop a validated thermal simulation model (TSM) of the tested RA. The TSM was used to examine the effects of the constant mine strata temperature assumption, initial mine air temperature (MAT), initial mine strata surface temperature (MSST), initial mine strata temperature at depth (MSTD), and mine strata thermal behavior on RA internal air temperature using 117 W of sensible heat input per simulated miner. For the studied RA, when the mine strata temperature was treated as a constant, the final predicted RA internal air temperature was 12.8°F lower than it was when the mine strata thermal behavior was included in the model. A 10°F increase in the initial MSST resulted in a 7.1°F increase in the final RA internal air temperature, whereas a 10°F increase in the initial MSTD yielded a 2.5°F increase in the final RA internal air temperature. INTRODUCTION Since 2008, the Mine Safety and Health Administration (MSHA) has required the installation of refuge alternatives (RAs) in underground coal mines (1). MSHA requires that RAs provide an environment with breathable air for entrapped miners for a 96-hour period. Heat buildup inside an occupied RA is a serious concern. Without a means to dissipate the heat and humidity generated by the occupants and the carbon dioxide scrubbing system, the temperature and humidity inside RAs could lead to severe discomfort or heat stress depending on the mine ambient temperature before and during occupation of the RA. NIOSH recommended an apparent temperature limit of 95°F in its 2007 report to Congress (2). In 30 CFR 7.504, MSHA has specified a maximum apparent temperature of 95°F inside an occupied RA (3). The apparent temperature is calculated using both air temperature and relative humidity (4). Calculations could be used to determine if the air within an occupied RA will reach the apparent temperature limit. In these calculations, in order to simplify the problem, the mine temperature could be assumed to remain constant. With this assumption, the effects of the mine strata thermal mass and thermal conductivity on the heat buildup in an RA are ignored. OMSHR research has shown that the mine air and strata temperatures surrounding an RA increase when subjected to the heat of an occupied RA (5). Thus, calculations performed with the assumption that the mine temperature is constant would under-predict the resulting dry-bulb temperature and apparent temperature for a given RA occupancy. The mine air temperature has been used as the basis for RA temperature calculations. However, research has not been used to confirm that the mine air temperature is the appropriate basis."

Jan 1, 2016

By W. G. Willson

Low-rank coal (LRC) drying processes are generally categorized by operating temperature, drying environment and type of feed (either sized or ground coal). Within these broad categories, drying processes differ according to the type of drying equipment and methods of quenching and stabilizing the dried products. This paper focuses on the produce quality of various LRC drying processes including conventional low and high temperature evaporative drying and non-evaporative, hydrothermal drying. The former may be preferred if the dried product can be utilized immediately, but moisture re-absorption, spontaneous heating and fines production during handling are problems associated with longer term storage, transportation and utilization. Methods for reducing these problems are discussed. Hydrothermal processing is an advanced technology featuring high pressure, non-evaporative drying, which solves stability problems by producing a liquid fuel.

Jan 1, 1997

By J. M. Mutmansky

This paper outlines patterns of methane emission in both longwall and room-and-pillar operations and the effects that these patterns have on the decision as to whether the methane is most economically handled by ventilation alone or by means of a methane drainage system in addition to ventilation. The costs of handling the methane in the ventilation system and the costs of implementing the methane drainage system will be discussed as well as the costs related to the production of coal. The important issue of production slowdowns and gas outs will also be discussed as well as the proper response of mine management to such a situation. Suggestions concerning the keeping of production records related to methane problems will be made as well as justification for more intensive economic analysis of coalbed methane extraction and utilization.

Jan 1, 1998

By W. M. Shaver, R. Letourneau, W. R. Dengler

Dynatec Mining Limited contracted to sink a 1500 metre (4960 ft.) concrete lined shaft for Falconbridge Nickel Mines in Sudbury, Ontario, Canada. The shaft is 6.3 metres (20.5 ft) in diameter inside the concrete lining and is equipped with steel furnishings. Dynatec used the owner supplied 4.6 metre (15 ft.) diameter double-drum hoist to sink the shaft with 12.5 tonne buckets for muck removal and 4 cubic metre concrete buckets for concrete placement. One of the unique features of the shaft sinking operation is the use of a four-boom electric hydraulic drill jumbo permanently mounted in the shaft sinking stage. This paper will describe the performance obtained with the electric hydraulic drilling equipment and the high capacity muck removal and concreting equipment.

Jan 1, 1991

By C. Tsamantaki

Water-bentonite suspensions exhibit a yield stress which is defined as the minimum applied stress for flow. Considerable debate exists about the yield stress being a material property, hence different measuring methods should give similar answers, but several investigators have demonstrated that it is an engineering reality. Yield stress is normally estimated indirectly from the rheogram obtained with a viscometer following an extrapolation to zero shear rate (the dynamic yield stress), but the technique may be prone to errors because of slip flow. Direct measurements, not prone to such errors, rely on an independent assessment of the yield stress, normally carried out with the vane method (the static yield stress). In this paper results are presented and compared regarding the yield stress of 14 different water-bentonite suspensions measured using both the direct and the indirect methods. In order to obtain a wide range of yield stress values, two different types and two concentrations of bentonite at various pH were tested. Rheological data were obtained using a rotational speed viscometer and a yield stress vane measuring device. Measured vane yield stress values ranged from 5 Pa to 83 Pa. Rheological data collected with the rotating viscometer were fitted using various conventional techniques (interpolation, linear and non-linear regression analysis) as well as using a golden section yield stress search methodology based on Herschel-Bulkley model, developed in house. The vane instrument measures directly the yield stress of the suspensions and requires no further data handling. A comparison of the measured values of the yield stress with the direct and the indirect method is then made for the water-bentonite samples. Not very large differences are observed among different techniques and the variations are discussed. Similar data from literature are also analyzed and the comparison shows that differences on the various estimation methods are much larger than the differences observed in this study.

Jan 1, 2006

By Robert B. Hopler

For many years the explosives industry was a technological enigma: it was at the 'cutting edge' of some technologies and in the backwaters of others. For example, for at least the past 85 years, the industry routinely measured time to one-millionth of a second for determining the detonation rate of explosives. At the same time, however, formulations were usually hand-written in 'formula books,' such as the alchemists may have done. Also, due to the fact that the equipment had proven to be safe, many of the mixers and packing machines in use until recently were those patented in the 19th century; improving efficiency was not worth the possible risks that might be encountered. In recent years, the wide availability and portability of computers and their adaptation to specialized applications have revolutionized the explosives industry, much as it has many others. With the advent of the water-based emulsions and slurries (water gels), and the necessity to design totally new processing and delivery equipment, the opportunity arose to apply modern techniques to many aspects of the business. Table 1 lists some computer applications currently in use by explosives manufacturers and end users. The use of high-tech production controls, equipment design aids, field measurement devices and other computer applications is so pervasive in the industry today that any brief article such as this must be considered only as a broadbrush overview of the subject.

Jan 1, 1994

By J. D. Bliss

The discovery that triggered the current gold rush in southeastern Peru was made in about 1975 along the Rio Madre de Dios in Madre de Dios Department (Fig. 1). About 5000 to 10,000 miners (called chichiqueros) were working in the area as of 1990. Placer mining is the principal source of revenue for people living along the Rio Inambari and west of Puerto Maldonado. As in past gold rushes, working and living condition are harsh. Supplies are expensive, and the area has poor access compared with other areas in Peru. Food, fuel and all mining supplies are trucked over dirt roads from Cuzco, a three-to-five-day trip (Fig. 1). Some material also comes from Brazil. Many placers have a similar life cycle, beginning with small-volume mining (surface or underground). At the end of this small-scale mining, the placer is exhausted or it has a sufficient volume of gravel high enough in gold grade to be worked by large-volume methods, which lead to exhaustion of the resource. The level of maturity of a placer can be determined from its gold grade. The amount of gold production from large-volume mining can be predicted, given detailed, cumulative gold-production data on placer deposits during small-scale mining (Bliss et al., 1987). Using this general model, the authors analyzed the placers in the Rio Madre de Dios area. Small-volume mining Most placer mining in the Rio Madre de Dios area is in alluvial deposits either in or bordering the major rivers. Locally, some placer mining is in terrace deposits above the rivers. All minerals (including the subsoil) in Peru belong to the state. However, a mining claim (denuncia) is easily obtained for mineral exploitation. It is separate from property ownership.

Jan 1, 1992