Search Documents

By David B. Brooks

I gratefully acknowledge the help of a number of American and Canadian geologists, in both federal surveys and in private firms, who took the time to discuss this problem with me. Hans Landsberg and Bruce Netschert also followed the study with interest and encouragement. In their 1961 monograph, THE FUTURE SUPPLY OF THE MAJOR METALS, Bruce Netschert and Hans Landsberg noted that identified potential resources (that is, known but submarginal resources) of lead and zinc were much lower relative to reserves (that is, known and supermarginal resources) than was the same ratio for other metals.1/ Put another way, it seemed that for such metals as iron, manganese, copper, and aluminum, slightly more favorable economic conditions or modest advances in technology would greatly increase reserves by permitting the exploitation of vest quantities of leaner or deeper or otherwise less valuable mineral deposits. But for lead and zinc, Netschert and Landsberg concluded that either: "(1) there is relatively little material below present cutoff grades; [or] (2) such material exists, but for some reason there are no data.? 2/ This situation, which they called "the lead-zinc anomaly" has been subsequently discussed by other authors. The purpose of this paper is to carry the discussion further by examining the evidence in favor of (1) and (2) and by advancing a third alternative.

Jan 1, 1967

By D. Baker

Alternative material handling methods are allowing material handling operations to be performed with increased cost savings. This allows for higher production levels with better returns. RAHCO International Inc.'s Continuous Mining Excavator (CME) has recently received a lot of attention due in part to its operating efficiency, flexibility, and associated low operating costs. The CME is designed to perform three primary functions. These include material excavation, sizing and loading operations. In many applications, a drilling and blasting process can be eliminated. The CME was developed originally in 1985 for open pit coal mining. See figure I. Since this time, it has been proven an effective system for excavating many other types of materials including friable and sticky materials. It has also been shown to suitably handle hard rock in certain site conditions.

Jan 1, 1998

By Ramesh Malhotra

Overseas coal trade has increased from 169 to 274 million metric tons (tonnes) between 1970 and 1983, representing a 3.8% average annual rate of growth. Metallurgical coal accounts for nearly 61% of the international coal market while steam coal's share is about 40%. By year-end 1983, the U.S. was the single largest coal exporter at 77 million tonnes, followed by Australia, 56 million tonnes; Poland, 35 million tonnes; South Africa, 28 million tonnes; USSR, 27 million tonnes; and Canada, 17 million tonnes. Coal exports can play a more significant role for one country than another country. For instance, in the U.S., coal exports accounted for only 9% of total coal demand in 1984 while in Australia, exports accounted for 53% of that country's total coal demand. Of all the major coal exporters, only U.S. exports accounted for less than 10% of total consumption in 1984. Japan is the largest importer of coal, 73.8 million tons in 1983. Although the majority of Japan's imports are metallurgical coal, steam coal imports into Japan increased seven-fold between 1978 and 1983, from 2 to 14 million tonnes. Australia is the leading exporter of both metallurgical and steam coal to Japan, accounting for 47% and 55% of Japan's coal imports, respectively. Since 1978, South Africa has developed into a major steam coal exporter to Japan, increasing its market share from 7.9% to 18.8%. The U.S., which was not even a player in Japan's steam coal market in 1978, has made inroads and accounts for 6.7% of Japan's steam coal imports. However, this translates into only one million tonnes. In the European coal market, for the most part, the U.S. is the leading supplier of metallurgical coal and South Africa is the major supplier of steam coal. The U.S. was not even a factor in the European steam coal market in 1978 and has made inroads during the last six years at the expense of Poland and South Africa. From 1978 to 1983, the U.S. has increased its market share in steam coal exports to France from 0.2 to 28%; Spain, 0 to 52%; Italy, 0 to 43.5%; Denmark, 0 to 19%; Germany, 0.5 to 16%; and the Netherlands, 0.6 to 45%, respectively. The use of coal (solid fuels) as a fuel to produce electricity has had increasing signficance for most of the countries analyzed between 1978 and 1983. The flip side to this is that oil has lost its share of this market during this time period. Of all the countries selected, only France reported a decline in coal's share of total electricity production. This is a reflection of France's ambitious nuclear program.

Jan 1, 1986

By Howard R. Postovit, Bonnie C. Postovit

Raptors are birds of prey. In recent years, these birds have become highly regarded and have been given protection under various state and federal statutes. Surface coal mining can have both negative and positive impacts on raptors. Mitigation strategies and enhancement techniques can be implemented to alleviate negative impacts. The success of habitat reclamation will determine the long-range impact of mining on raptors.

Jan 1, 1989

By Alberto S. Nieto

The general role of geology in the location of different types of large underground chambers is discussed. Aspects of structure, rock type and state of stress are discussed at some length. Some practical implications on stability of observations about the attitude, spacing and persistence of structural features are made. Characteristics and likely problems inherent to rock types (igneous, metamorphic, and sedimentary) are discussed. Observations regarding the uniformity of stress conditions within a physiographic province are presented. The influence of stresses parallel to the chamber axis on wedge movements is briefly discussed.

Jan 1, 1983

By G. S. Austin

New Mexico produced 83% of domestic potash and 27% of domestic consumption in 1992. The potash industry of New Mexico produces sylvite (KCI), langbeinite (K2SO4-2Mg(SO4)2), and artificial K2SO4. Average sylvite grade in New Mexico today is about 14%. The average grade of langbeinite is 8-10% Kp. Commercial potash occurs in the middle or McNutt Member of the Salado Formation (Upper Permian Ochoan Series). The 120-m-thick McNutt Member dips about 1° east and contains 11 of 12 potential ore zones in the Salado. The mineralogy and proportion of clay minerals, up to 7% of the ore, influence optimum milling procedures and ore grade cutoff.

Jan 1, 1994

By H. Y. Sohn, H. K. Lin

The leaching of primary porphyry chalcopyrite ore under simulated solution-mining conditions was studied using a packed-bed reactor. A mathematical model incorporating the intrinsic leaching kinetics of chalcopyrite and pyrite grains, the pore diffusion of dissolved oxygen within the ore fragments, liquid-solid mass transfer, and the effect of fluid flow and axial dispersion was formulated and tested for the overall leaching process. The dependence of oxygen solubility on ionic strength of the solution was also incorporated into the model. Satisfactory agreement between model pre- dictions and experimental data was obtained. The model can also predict the rate of the leaching process under different temperatures, oxygen pressures, solution flow rates, and different size distributions of ores.

Jan 1, 1991

By Samuel S. M. Chan

Rock surrounding mine openings frequently is an impermeable type such as shale or granite. Most rock, however, has joints, bedding planes, cleavage planes, or other potential discontinuities. Permeability to fluids (gas or liquid) may exist via natural joints or fractures in an otherwise impermeable rock. In the mining situation, tectonic and induced tensile and shear stresses may be great enough to cause joints to open or fractures to develop in previously solid rock. The rock, as a result, becomes less self-supporting and may - require artificial support such as rock bolts or timber. Simultaneously, as fractures develop, permeable paths may be created. If fluid can be injected into a previously solid and impermeable rock mass, a logical conclusion is that a fracture (crack) flow path must be transmitting that fluid. The U.S. Bureau of Mines Laramie (Wyo) Energy Research Center has been evaluating results of in-situ oil shale fracturing (hydraulic or explosive) and retorting experiments by. a fluid (air) injection , and borehole air flow profile logging technique since 1956 (1, 14, 15). In the oil shale case, it is imperative to know the location and flow capacity (permeability) of natural fractures, if they exist, and induced fractures that inter-connect vertical wellbores at depths of fifty to several hundred feet. By injecting air into one wellbore in a system of several wells and measuring input volume and pressure while simultaneously measuring the output of other wellbores, the minimum areal extent of interconnecting permeable fractures can be determined. Exact locations (depths) of fractures and individual fracture flow capacities between wellbores can be determined by air flow profile logging (14, 15). Knowledge of fracture locations and permeability is essential to rational experimental in-situ retorting design.

Jan 1, 1973

By Mohammed Sakr

The empirical relationship between torque measured during installation and pile capacity has gained a wide acceptance in the helical pile industry in the last few decades. This paper presents a theoretical model developed to estimate torsional resistance of cohesive soils to helical pile installation. The proposed torsional resistance model was then used to establish torque factor, Kt, a factor that is widely used in the industry. The results of the study indicated that the Kt factor is a function of the load path (i.e. tension or compression), pile geometry and soil properties. The assessed Kt factors in tension and compression were validated by the results of 74 installation records and full-scale helical pile load tests. A parametric study was also performed to qualitatively assess the relative importance of different parameters that affect the Kt factors.

Aug 1, 2013

By Stephen P. E. Redmond

A 15 km water supply tunnel is being constructed in Buenos Aires, Argentinata expand the capacity of the existing system. Two 4.3 meter diameter Earth Pressure Balance (EPB) tunneling machines operating at times from the same shaft on a congested work site and advancing through sedimentary deposits underlying this wonderful city pose interesting challenges. As of January 1999approximately 50% of the tunnel has been excavated. Combined machine production rates of 1026 m/month have been achieved. Presentations made in prior proceedings can be referenced for details of the overall Project scope and for details of the tendering process. The purpose of this paper is to compliment those presentations by addressing now the execution of the work.

Jan 1, 1999

By Mark J. Logsdon, Barbara Basse

Mississippi Valley Type Pb-Zn deposits are widespread in the midcontinent U.S. and have been mined from the 1800's to present. Some tens of thousands of acres of mined land in the Tri-State District have been designated as Superfund sites as a result of surficial mine wastes and ground waters with elevated levels of metals. EPA considers the surficial mine wastes to be hazardous and a major source of acid mine drainage fAMD) that degrades water resources and threatens human health and the environment. To mitigate potential risks at one site near Galena, Kansas, a group of mining companies who had been identified by EPA as Potentially Responsible Parties IPRPs) proposed subgrade disposal of the mining wastes in shafts and subsidence features. However, this proposal was challenged by the Agency on grounds related to AMD and the potential for degradation of ground water quality. The PRP team developed a program of materials characterization, laboratory-scale leaching, and finally large-scale, pilot testing in the field. Static and dynamic leaching tests at both laboratory scale fusing artificial rainwater under both variably and fully saturated conditions) and field scale (using pH 4.5 ground water) showed that the surficial wastes do not produce acidic leachate and are not a long-term source of metals. Laboratory chemical and mineralogical tests show that the mine wastes contain substantial carbonate, but very limited iron sulfides, consistent with the leach test results. EPA "characterization" tests fEP Toxicity and TCLP) compare very poorly with tests simulating the expected leaching conditions. While these tests would classify the surficia1 wastes as "hazardous, they do not characterize the behavior of the high-volume, low-concentration, coarse-grained materials with respect to environments and disposal options of interest. To be meaningful, characterization of mining wastes must be performed in a manner that simulates the environmental conditions that are actually of interest with respect to a specific decision, such as subgrade disposal in the saturated zone.

Jan 1, 1991

By W. H. McDonald, D. D. Carr

The use of stone in building construction predates written history. From the time that stone was first used, builders have constructed stone buildings predominately from local or regional materials. However, since World War II, the stone business has become increasingly global. For example, French limestone is now sold to builders in the United States, and American granite is shipped to Japan. The internationalization of architectural and construction firms has encouraged this trend. Differences among nations in trade practices, environmental demands and the level of knowledge of dimension-stone characteristics make international trading in stone a risky and potentially disastrous business for unwary participants.

Jan 1, 1997

By Frederick Bradley Henderson

This study was initiated to investigate the occurrence of cinnabar in the oxidation zones of some mercury sulfide deposits. Seven mines or mine districts were visited and samples were taken from both the oxidation and primary zones of these deposits in order to compare their mineralogies and assess Vie chemical changes that took place during oxidation. As a result of the study of these specimens, several limiting factors are suggested for the chemical environments and processes active in both the deposition and oxidation of mercury sulfide deposits. The Mt. Jackson mine, near Guerneville, California (location map, fig. 1), was studied in some detail and forms the basis of this paper. The mine has not heretofore been described in detail in the literature. The Mt. Jackson mine is considered typical of mercury sulfide deposits occurring at the faulted boundaries of serpentinite bodies and enclosing sediments. Such mines are common in the California and Oregon Coast Ranges? Specimens collected by the author from the New Idria and New Almaden districts, the Mt. Diablo, the Culver Bear, and the Buena Vista mines in California, and the Opalite district (Cordero and Bretz, mines) on the Oregon-Nevada border were studied for comparison with the Mt. Jackson samples. The mine description, maps and sketches were composed from field maps kindly provided by Francis Fredericks, consulting geologist to the Sonoma Quick-silver Mine Inc. during the author's visit in 1962. Additional information was obtained from the company maps and minor corrections and interpretations were added by the author.

Jan 1, 1965

By Kenneth J. Reid

The application of computers for control purposes in hydrometallurgical processes is not as well-established as in mineral processing plants. This is not only due to the comparatively new development of large-scale application of hydrometallurgy and the relatively small number of operating plants, but also due to some of the basic dynamic characteristics of hydro- metallurgical processes., Basically there is little difference in the development and application of digital control techniques in hydrometallurgical plants from those techniques widely in use throughout the chemical process industry and in nonslurry applications; particularly for those cases involving liquid streams only, the primary sensing elements are essentially the same. On-stream X-ray fluorescence analysis is a well-established method for determination of metal content in the process streams, and standard equipment is used for the measurement and control of pH, flow, density, temperature, pressure, and other variables. Nevertheless, the high proportion of corrosive slurry streams at elevated temperature and pressure poses a challenge to the instrument engineer concerned with developing long-life, reliable instrumentation. One major difference and potential problem area in developing control systems for hydro- metallurgical processes is related to the very long time constants which are common in the larger plant. In these circumstances, it is important to define the overall control objectives very carefully and be prepared to allow for considerable drift in intermediate variables. In larger projects with many control loops the general advantage of lower costs compared to conventional analog instrumentation can be confidently expected. Also in most cases, the process analysis necessary to design and specify a comprehensive computer control system and the increased operator involvement in implementing digital control systems yield additional benefits due to the increased understanding of the dynamic characteristics of the process.

Jan 1, 1979

By J. J. Gusek

The Riley Pass strip mine is an abandoned uranium-bearing lignite deposit in Harding County, South Dakota, covering about 150 acres of highwalls, pit floor and mine spoils exhibiting elevated levels of radioactivity. Six reclamation design alternatives were developed, ranging from doing nothing to reclaiming to approximate original con-tour. The alternatives were evaluated for expense, site stabilization, and mitigation of public safety hazards. A comparative economic evaluation on three of the alternatives was completed for the Forest Service in selecting an alternative and substantiating federal funding requests. This evaluation included economic impacts associated with physical and radiologic health hazards, affects on recreational users, socioeconomic impacts and environmental improvement.

Jan 1, 1995

By R. Riding

Degussa Corporation's peroxide-assisted leaching (PAL) process was evaluated in the batch concentrate leach circuit at Hecla Mining Company's Republic Unit. The product leached in this batch circuit is a high grade gold-silver sulfide (predominately pyrite) flotation concentrate. The primary objectives of the test program were to determine the effects of dilute hydrogen peroxide addition on leaching kinetics, sodium cyanide consumption and precious metals recovery. The results of the testing demonstrated that using dilute hydrogen peroxide produced the following benefits: - 1. Batch leach time requirements decreased by 80%. - 2. Sodium cyanide consumption in concentrate leach reduced by 55%, which translated to an overall plant reduction of 20%. - 3. In the concentrate leach process, gold recovery was increased by 1 to 2%. Because of the excellent metallurgical results achieved with the use of dilute hydrogen peroxide, as well as an economic incentive, PAL has become standard practice in the concentrate leach circuit operation. A complete description of the Republic PAL plant evaluation and performance is provided in this paper. In addition, process chemistry considerations in regard to the role of hydrogen peroxide are discussed.

Jan 1, 1992

By M. Fan

Dry coal separation technology has particular advantages in the applications in arid and cold regions, or low rank coal separation. The hazardous pollutants in low rank coals can not be efficiently removed by conventional wet coal separation processes because a considerable amount of porose and easily friable low rank coals suffer serious particle size degradation problems in water. In this paper, a novel dry coal separation method with a vibrated air-fluidized bed of magnetic fly ash and magnetite is put forward for dry coal beneficiation. The magnetic fly ash used in this study was derived from fly ash obtained as a byproduct of coal combustion. The vibration?s effect on the uniformity and stability of a magnetic fly ash air-fluidized bed was studied. The 6×0.5 mm dry coal separation results with a vibrated air-fluidized bed of magnetic fly ash and magnetite showed that the probable error E value of separation is 0.06-0.08 t/m3.

Jan 1, 2009

By M. R. Bowie, J. M. Barker, J. S. Hingtgen

Techniques of testing perlite require a combination of art and science. The modifications made to the perlite Corp. vertical laboratory furnace include addition of instrumentation, flowmeters, vibrators, automatic feeders, and regulators. The basic testing sequence consists of expanded density, furnace yield, compacted density, percent sinkers, and compaction resistance. These tests are modified versions of those specified by the Perlite Institute. This sequence is designed as a preliminary evaluation of a material's suitability for horticultural-aggregate end uses rather than a detailed measure of filtration capability.

Jan 1, 1988

By N. Economou

Temporary local seismic networks were installed in western Crete, in central Crete, and on Gavdos, an island south of western Crete, in order to image shallow seismically active zones of the Hellenic subduction zone. Data acquisition was divided in four campaigns through the years 1996 to 2001. More than 4000 events in the magnitude range between 0.5 and 4.8 were detected and localized. The resulting hypocenter distribution allows the localization of seismically active zones in the area of central Crete from the Mediterranean Ridge to the Cretan Sea. The comparison of the hypocenter distribution and the structure has allowed intraplate and interplate seismicity to be distinguished. A southwards dipping zone of high seismicity within the Aegean lithosphere is found south of central Crete in the region of the Ptolemy trench. Between 20 and 40 km depth beneath central Crete, the Aegean lithosphere appears to be seismically inactive. Especially for the year 2001, 1560 events were localized, by the seismic network installed on Messara, central Crete. Most of the seismic events were located, as expected, in the South region of central Crete. National Observatory of Athens (NOA) maintains a permanent seismic network in Greece. In this work a comparison of the earthquake epicenters obtained from both the NOA network and the BOCHUM-TUC network is presented.

Jan 1, 2006

By Walker Ian W., John D. Gow

The paper describes the exploration and development activity associated with a series of open pit gold deposits in the Laverton region of Western Australia with an aggregate resource base of 4 million tonnes at a grade of about 3 grammes per tonne. In September 1988, Hill Minerals N.L., now a wholly owned subsidiary of Ashton Mining Limited, completed the purchase of the Cork Tree Well treatment plant from Austwhim. This CIP plant had a rated capacity of 235,000 tonnes per annum, and is located within the Hill Minerals Laverton Project area. Ore is trucked by haulage contractors from each open pit mine to the central treatment plant at Cork Tree Well. Studies were completed and a plant expansion undertaken lifting throughput to 500,000 tonnes per annum. A contract was let for this expansion in November 1988, and construction completed in April 1989. Concurrent with the above project development work, heap leach metallurgical studies are being undertaken on low grade mineralisation associated with higher grade ore zones at several of the open pit mines, notably King of Creation and Craiggiemore. It is anticipated that heap leaching will provide a useful adjunct to gold production from milling higher grade ores.

Jan 1, 1989