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By Samuel S. Adams

Economic concentrations of potassium are essentially limited to thick, stratigraphic sections of marine evaporites. These deposits were precipitated through the evaporation of sea water in restricted epicontinental seas or in grabens related to continental margin rift systems. Following deposition the deposits were subjected to diagenesis and varying degrees of metasomatism and structural deformation. The origin and characteristics of potash deposits are easier to study and interpret than those of most ore deposits because the phase chemistry of the salt systems is known and the approximate composition of the ore-forming fluid (sea water) can be inferred with confidence. It is particularly helpful that the temperature and pressure of deposition approximated that of present earth surface conditions and the pertinent mineral assemblages can readily be duplicated in the laboratory. The study of these comparatively simple salt deposits provides examples of the practical advantages of understanding the genesis of an ore deposit. These observations, in turn, illustrate the importance of pursuing research on the more complicated magmatic, hydrothermal, and ground-water systems as a means to the more successful exploration for and exploitation of the deposits they have produced. It is the purpose of this paper, therefore, to discuss certain aspects of salt deposit geology as they contribute to exploration and mining through some understanding of ore formation. References to field examples and chemical relations in the salt systems are brief. All examples are more fully discussed, however, in the references cited.

Jan 1, 1970

By Roy L. Klein

The production of synthetic fuels from coal has been pioneered by South Africa. South Africa made a decision in 1975, due to the threat of an oil embargo, to proceed with the construction of Sasol Two, then followed by Sasol Three. South Africa has large coal but little indigenous petroleum reserves. The indirect coal liquefaction process used by Sasol since 1955 is the only commercially demonstrated method available for producing transport fuels from coal. The new plants consume 27 million tons per year of coal from a single mine that now produces transport fuels in sufficient quantities for energy independence.

Jan 1, 1983

By J. W. Cooksley

Pyrometasomatic zones are a type of replacement deposit, normally in a carbonate rock unit, which consists of a zoned, coarse-grained, generally iron-rich mixture of calcium and magnesium silicates. These zones or rock masses are also called ?skarn,? and ?tactite?. They are formed as a result of the interaction of a shallow intrusion of magma with a carbonate or calcareous host rock and are considered to be of hydrothermal origin. Three environments of pyrometasomatic deposits are depicted in Figure 1. Of course, the interaction takes place at high temperatures. Pyrometasomatic zones are categorized as calcic or magnesian, depending on whether the intrusive interacts with a limestone or a dolomite. Common pyrometasomatic zone minerals are garnet, epidote, quartz, calcite, wollastonite, actinolite, hedenbergite and diopside. Pyrometasomatic zones are of considerable economic importance because they contain ore deposits of tungsten, molybdenum, copper, lead, zinc and iron. According to Rose and Burt (1979), the chronological sequence in the formation of a ?typical? pyrometasomatic deposit is as follows: 1. Shallow intrusion of magma at 900-700°C into carbonate sediments.

Jan 1, 1981

During the past year a number of significant advances in geostatistics have been published. These were presented at the 13th APCOM Symposium in Clausthal, Germany and at a NATO Advanced Study Institute on Geostatistics in Rome, Italy. Of greatest importance is the work that has been done in establishing methods which correctly predict the cutoff grade-tonnage curves, and the average grade of ore-tonnage curves for deposits in which ore and waste are intermingled. Grade-tonnage curves based on estimates made from widely spaced exploration data have been found to underestimate the grade of ore and overestimate the tonnage present. This problem has been remedied by the calculation of conditional probability distributions for the unknown grade of a block. Another advance has been made in the field of geostatistical estimation for deposits in which a trend is present. Previously a technique known as universal kriging has been used, which involves much subjective judgement as to the trend fitted. A new technique, generalized increments, allows computer estimation of such deposits with much less subjective judgement. Computational efficiency of geostatistical methods has continued to improve to a point where a geostatistical estimate can be obtained for little more than the cost of any other computerized method.

Jan 1, 1976

By Hasan Nizamoğlu, Z. Abidin Sarı, Aslıhan Demiraslan, M. Deniz Turan, Tolga Depci

In this study, recovery of copper from solid material (obtained by leaching of chalcopyrite with oxalic acid in the presence of hydrogen peroxide) with a copper oxalate structure was carried out selectively using HCl. The chemical composition of the solid was as 29.3%, 9.7%, and 13.3% for Cu, Fe, and S, respectively. Selective recovery of copper by degrading the copper oxalate structure with a low-solubility product (Ksp = 4.43 × 10−10) was performed by conventional leaching in the presence of HCl. The optimum leaching conditions were determined as 5 M of HCl concentration, 318 K of leaching temperature, 120 min of leaching time, 25 ml/g of liquid–solid ratio and 400 rpm of stirring speed. Under these conditions, approximately 77% of copper and 3% of iron were taken into the solution. According to the characterization of the leach residue that was obtained, the oxalate structure was degraded. Moreover, the results of XRD analysis showed that the sulfur (S) and cubanite (CuFe2S3) phases were mostly observed in leaching residues, and this was supported by the SEM-EDX data. Based on the results, it may be stated that selective copper extraction can be obtained from a chalcopyrite concentrate by a two-step leaching method using a conventional hydrometallurgical technique.

By Bijan Taheri, Behrouz Maghsodi, Monireh Heshami, Reza Kohan

A common problem recently encountered with the increase in the rate of input feed at Enrichment Plant 2 of the Sarcheshmeh Copper Complex is the loss of value to the tails, translating to lower recoveries. The feasibility of the direct transfer of part of the high-grade concentrate from rougher stages to an appropriate position along the circuit was studied, and two positions were proposed for direct transfer of the concentrate. One position was the feed flow into cleaner cells, and the other was the feed flow into the recleaner cell. The results indicated that transferring the concentrate from the first unit of the rougher stage to the feed flow into the cleaner cells was feasible, with no limitations, while the second position required the installation of a set of hydrocyclones. It was found that the transfer of concentrate to the proposed positions not only addressed the problem of limited cell capacity, resulting in debottlenecking of the circuit, but also improved metallurgical separation efficiency up to 1.4%.

By H. Hinds

Plant testing of DuPont's Activator Technology in the vat leach circuit of the Homestake mine shows increased gold recoveries of 3-5%. Activators are catalysts of gold dissolution in cyanide solution. DuPont received the patent for this technology in January, 1996. The test was run in the west sand plant alternating control and activated vats to reduce the variability in head grade and cyanide consumption. Activated vats had gold in the preg solutions earlier, higher gold recovery, and lower gold residuals. Activator addition did not adversely affect mill operations or the environment. Optimization of the technology continues.

Jan 1, 1997

By J. B. Gwiazda

S.S. Peng The highlights of this paper are : • The shield supports with lemniscate links will exert a tangential force on the roof strata, causing unnecessary and harmful roof movements, thus damaging the roof structure. The principal source of the tangential force is the horizontal movement of the point O, the pivotal joint between the canopy and the caving shield. When the support height is changed during setting, the point O will move along a curve upward and rearward toward the gob. As a result, it produces a vertical movement, causing the roof to move up a distance of ?d, and a horizontal movement toward the gob, creating vertical fractures in the roof. • The major purpose for employing the lemniscate-link system is to protect the hydraulic legs against the action of the bending moments induced by the tangential force that causes deformation or destruction of the legs. • Based on these two points, the author suggested that, in order to eliminate the harmful effects of the lemniscate-link system and strengthen its advantageous features, a shield support with a new design of that mechanism has been developed. With the new design, the conventional rigid lemniscate links are replaced by hydraulic rams. When the pressure inside the rams reaches a certain level, the ram will yield.

Jan 12, 1986

By Robert F. Droullard

The U. S. Bureau of Mines (USBM) has investigated instrumentation and methods for measuring exposure to radon daughters in underground mine atmospheres. Both personal and area monitors have been studied through in-house and contract research. A field study in uranium mines identified some reliability problems that required additional work for the personal dosimeter systems. Improved versions of continuous working level detectors have been developed and tested for use as area monitors in underground mines. Test results for the personal and area monitors were satisfactory for underground mine applications.

Jan 1, 1981

By Heiner J. Sander

Stanford University operates the National Research Facility which is located at the Stanford Linear Accelerator Center (SLAC) in Menlo Park, California. In order to improve and allow for enhanced experiments, the current facilities required expansion. A1500 foot long tunnel (20 ft wide by 21 ft high) and a 220 foot long underground cavern (49 ft wide by 32 ft high) were excavated through the Ladera Sandstone formation which is an intermediate geo-material with week rock properties. The overburden between surface and crown of the structures varies from 10 to 80 feet. The underground structures were excavated according to the principles of the NATM (New Austrian Tunnel Method). This paper addresses the challenges that were encountered during the construction phase of the project and how construction issues were resolved mutually by the owner, engineer and contractor. The implementation of geotechnical instrumentation, recorded data and interpretations, soil conditions and behavior encountered during construction are also presented.

Jan 1, 2008

By R. N. Chakravorty

Spontaneous combustion presents a very serious hazard to both safety and economics of mining operations. Notwithstanding considerable research that has been done over the years to present and control spontaneous combustion the risk still exists. Consequently, this problem poses a major challenge to mine safety researchers; new and improved techniques are constantly being developed to deal with this major hazard. This paper reviews the current practices to prevent and control spontaneous combustion in coal mine operations highlighting new developments in this area. Research and development work presently being carried out in Canada to' deal with this problem is also discussed which includes monitoring, inertization and application of biotechnology.

Jan 1, 1988

By D. W. Gentry

Introduction Until recently, there were many jobs for mineral engineering graduates. Traditionally, minerals-related career paths available to university graduates stem from rather standard offerings in the disciplines of mining, metallurgy, petroleum, geology, geophysical engineering, and mineral economics. Within each discipline, there exists many career opportunities. In fact, until fairly recently, the most difficult decision for most graduates was choosing among all the available alternatives. Unfortunately, this relative state of euphoria changed quickly and dramatically within the minerals sector. Within two or three years, graduates from minerals-related engineering disciplines found it exceedingly difficult - and then almost impossible - to secure employment in the minerals sector upon graduation. At the same time, there were dramatic reductions in production requirements and, ultimately, mine closings. This resulted in massive layoffs and often termination of professional personnel possessing significant and valuable industrial experience. Obviously, this worsened an already bad employment picture for those hoping to begin a career in minerals. Certainly, there is no universal agreement on what the future offers for the US minerals industry or the career opportunities associated with it. However, there are a number of considerations that deserve study by students, faculty, administrators, and industrial personnel before minerals-related career paths are chosen. Where Will the Jobs Be and How Many? Everyone is aware that the minerals industry is very cyclic. It is not surprising then that job opportunities for new graduates also fluctuate. Typically, there is a two-to-four year lag between industry's engineering manpower needs and the academic community's ability to produce this talent. Due to the response lag, there will necessarily be years when supply and demand do not match. Employment Projections It is extremely difficult to anticipate what the key career paths might be within the next few years. Considerable speculation remains with respect to whether activity in the US minerals sector over the short-, intermediate-, and long-term will improve, remain status quo, or further deteriorate. However, some information pertaining to the prospects for career opportunities in mining engineering was offered by Tingley and Ghose (ME, Sept. 1983, p. 1274) from a study performed by Fenvessy and Schwab. Results from this industry-sponsored survey suggest that the US will experience 700 more mining engineers than needed in 1985, 1300 in 1990, and 1800 in the year 2000. These conclusions were based on the assumptions that future graduate levels remain flat and demand increases 3.6% annually. Educators quickly argued that depressed job markets, coupled with university student mobility, would negate the assumption of flat mining graduate levels in the immediate future. Student Mobility Student mobility from one engineering discipline to another is high. This is perhaps best demonstrated by the tremendous growth in programs such as computer engineering and computer science at the expense of enrollments in the more traditional engineering programs. The ability and willingness of students to quickly change engineering disciplines in response to existing and perceived job market demands have created significant student, faculty, and resource dislocations within universities nationwide. This has resulted in problems for university faculty and administrators responsible for effective use of

Jan 2, 1985

By Edward M. Dowey

The concrete lining for a long 8.05 km (5 mi) section of New York City Water Tunnel No. 3 was cast in place. The contractor, Grow-Perini-Skanska, placed over76,841 m3 (100,505 cy) of concrete, pouring 24 hours per day, 5 days per week. The concrete was dropped 204 m (670 ft) to the tunnel level, transported by rail to a concrete remixer and pump, and placed in 146.3m (480 ft) of full circle forms. Some of the many challenges include the sheer magnitude of the job, navigating through drifts, a raise and curves, dealing with ground water inflows, and placing the concrete within time limits.

Jan 1, 2001

By Jonathan G. Price

Silver-copper-lead deposlts in Precambrian, Permian, and Cretaceous red-bed sequences near Van Horn, Texas, have the following features In common: (1) mineralization controlled by steeply dipping fractures in sandstones, (2) lack of ore In overlying and interbedded limestones, (3) absence of igneous intrusions, (4) sulfide ores without typical hydrothermal gangue minerals, and (5) associated arsenic, molybdenum, zinc, and cadmium but not gold. Ore was probably deposited along fractures by reaction between low-temperature, oxidizing, metal-rich ground waters and sulfide-bearing waters or rocks. Detailed mapping and studies of fracture patterns indicate that mineralization occurred during Basin and Range extensional deformation, thereby postdating major Trans-Pecos igneous activity.

Jan 1, 1983

By J. S. Meyer

Although salmonid fishes (including Pacific salmon and trout) have only intermediate sensitivity to copper (Cu) for traditional toxicity endpoints (survival, growth, and reproduction) and thus do not ?drive? the freshwater Cu criteria (e.g., see species-sensitivity ranking in US EPA 2007), Cu concentrations as low as 1 to 2 µg/L have been reported to impair olfaction (the sense of smell) in salmonids in laboratory experiments using dilute fresh water (see references in Meyer and Adams 2010 and DeForest et al. 2011). Olfaction is crucial to predator avoidance, recognition of kin, and reproductive synchronization (Baldwin et al. 2003); and Cu is of general ecotoxicological concern because it can be present in acid/mine rock drainage, industrial and municipal effluents, agricultural runoff, and urban stormwater runoff (Meyer et al. 2007). Therefore, there is public concern that the current regulation of Cu in surface waters is not stringent enough to protect salmonid fishes against olfactory impairment (e.g., OSU 2007; Pearson 2007). Because the toxicity of metals to aquatic organisms is a function of water chemistry [e.g., acute toxicity of Cu generally decreases as pH, water hardness (Ca2+ + Mg2+), alkalinity, and dissolved organic carbon (DOC) concentrations increase; Meyer et al. 2007], hardness-based freshwater criteria for metals are lower at lower water hardness. The recently-developed biotic ligand model (BLM) explicitly takes into account all four of those water chemistry parameters and the concentrations of other major inorganic cations (Na+, K+) and anions (Cl-, SO42-) to predict the acute toxicity of cationic metals (e.g., Ag, Cd, Cu, Ni, Pb, Zn) to aquatic organisms; and the BLM has been adopted by the U.S. Environmental Protection Agency (US EPA) to calculate acute and chronic national freshwater criteria for Cu (US EPA 2007). Consistent with observations of Cu toxicity to aquatic organisms, BLM-based Cu criteria generally are lower at lower pH, water hardness, alkalinity, and DOC concentrations. Therefore, although threshold concentrations for olfactory impairment by Cu can be low in dilute fresh waters, the corresponding hardness-based and BLM-based Cu criteria for the same waters also tend to be low. This leads to a logical question: Are Cu criteria already protective against impairment of olfaction in salmonid fishes, thus obviating the need to decrease those criteria even lower to protect against adverse effects to this physiological/ecotoxicological endpoint? Herein, we demonstrate that in all studies conducted to date, the US EPA?s BLM-based freshwater Cu criteria would have been protective against olfactory impairment in salmonid fishes, but the US EPA?s hardness-based criteria would not always have been protective. This distinction is important because all 50 States in the USA still use hardness-based Cu criteria in their water quality standards, and only some of the States allow use of the BLM to calculate site-specific Cu criteria. Additionally, in the absence of empirical results for calibration of a saltwater Cu-olfactory model, we demonstrate that a proposed unified freshwater-saltwater Cu-olfactory BLM predicts the US EPA?s current saltwater Cu criteria would be protective against olfactory impairment caused by Cu in sea water.

Feb 27, 2013

By W. Bakiewicz

The Lower Indus Basin deposits form a substantial unconfined alluvial aquifer of excellent quality. This aquifer contains basically highly saline groundwater, overlain in places by considerable amounts of freshwater whose origin can be traced to the present and historical courses of the River Indus. In the past the main source of groundwater recharge has been direct river seepage and water tables were generally deep. Since the establishment of a perennial irrigation regime however, deep percolation from the increased irrigation supplies has predominated and the water-table has risen to within a few feet of the surface. The river system itself is being progressively developed for irrigation and very shortly a situation will arise where the entire low winter flow will be utilised. Fresh groundwater will then be exploited to supplement the surface supplies, and at the same time a drainage system, mainly based on wells will be used to stabilise the water-table at safe depths. This paper discusses some of the methods used to ensure optimum-economic development of the fresh groundwater and describes the general design philosophy evolved by the authors firms for both irrigation and drainage wells, with respect to both well configuation and operation. Water quality standards are discussed in as much as they affect subsequent use of the groundwater. A few particular aspects are considered, including that of the values of the relevant aquifer constants, the construction of wells and the determination of screen losses. A major problem solved during the Lower Indus Project investigations has been the design of wells to-produce fresh water from layers overlying saline water. This solution is also discussed.

Jan 1, 1967

By M. García-Vásquez

In Peru, the third destination in worldwide exploration based on expenditure, mining conflicts have spread dramatically over the last decade. Mining companies need to create new initiatives to avoid social conflicts and strengthen the social capital needed to keep mining in a country with proven mineralogical riches. This document provides information about a research project that explored the opinions and experiences of a resource many times overlooked by companies: the human resource. Over 30 surveys were conducted among professionals working at mines in the Peruvian mining industry, in different departments and from different organizational levels. Mining employees acknowledged that they play an important role in the development of company-community relationships and gave their impressions about initiatives implemented by international mining companies in Peru. Mining employees also provided their recommendations to succeed in a location where cultural differences have not been properly considered.

Jan 1, 2011

By Wm. I. Weisman

Sometimes in assessing where we are and where we are going it is informative to take a look at where we have been. Whether or not it adds to our understanding of the present, I think it may be interesting to review some of the past history of our industry. As a starting point I chose to use the famous Paley Commission Report, formally known as "The U. S. President's materials Policy Commission -Resources for Freedom."(l) The Paley Commission report said "Fluorspar is an essential raw material for the steel, aluminum, and chemical industries." Of course this statement is still true. It also said, "United States known reserves of fluorspar would be sufficient for some 15 years at present rates of consumption--about 426 000 short tons in 1960. Projected consumption for 1975, however, is several times as great, and reserves in other free countries do not appear adequate to supply United States deficiencies during the next 25 years." This simply demonstrates how even the most learned and competent people can observe all the facts avail-able to them at a given time and yet be unable to predict the future very accurately. We all know that reserves in other countries are more than adequate to supply the United States today, 25 years since the report was published. In fact, the report estimated free-world reserves at something over 36 million tonnes (40 million short tons). Contrast this with 246 million tonnes (271 million short tons) estimated as total world reserves from the section on fluorspar from Commodity Data Summaries of 1974, published by the Department of the Interior. (2) The Paley Report discusses other matters pertaining to fluorspar that are still of interest, such as improving mining methods. Furthermore, it certainly did a good forecasting job in noting that greater recycling should become possible in the aluminum industry in regard to fluorine lost in wastes and also concerning the substitution of fluorspar in the steel industry by other fluxing materials. It also suggested that non-fluorine containing propellants should be investigated as a replacement of those containing fluorine as a conservation matter. Some discussion was devoted to recovering the fluorine content of phosphate rock, which is being practiced today, but was in its infancy in 1950.

Jan 1, 1978

By Ted DePooter, Mun Wei Leong, Chad Frederick

Downtown Bellevue Tunnel (DBT) is part of Sound Transit’s $3.7 billion, 14-mile light rail transit system from downtown Seattle, across Lake Washington, to the cities of Mercer Island, Bellevue, and Redmond. The tunnel was the first Sound Transit East Link project and posed significant construction risk. This paper discusses implementation of design changes to the soft ground tunneling method, implementation of several technologies such as the use macro-synthetic fiber initial shotcrete lining, use of spray-applied waterproofing, and use of shotcrete for the final tunnel lining. These efforts allowed for significant time and cost savings to the project.

Jun 13, 2021

By A. C. Lyons

Foreword Sir William Halcrow and Partners are responsible for the design of the Ahmed Hamdi Tunnel as Sub-contractor to the Contractor, Osmac, a joint venture formed by the Arab Contractors, Osman Ahmed Osman and Company of Cairo, and Tarmac International of London. Throughout the paper the term "Client" refers to the Employer, the Ministry of Housing and Reconstruction, which latterly became the Ministry of Development and New Communities of the Arab Republic of Egypt. At the time of writing of this paper only a few hundred metres of the tunnel have been driven, but the design is substantially complete. Introduction The Ahmed Hamdi Tunnel, which is at present under construction, will be a two-lane tunnel crossing beneath the Suez Canal approximately 15 km north of the town of Suez at El Shallufa. It will become the first permanent connection across the Canal since 1967 and is visualised by the Egyptian Government as an early step in the development of the Sinai Desert along the eastern bank. The tunnel will carry pipelines for treated water and electric power cables to assist in this development. The tunnel, which will be 1640 m in length, is being driven through hard clay and mudstone using a tunnel shield fitted with hydraulic excavators. The primary lining is being constructed with precast, bolted reinforced concrete segments with an internal diameter of 10.4 m. The road deck structure and the walls of the air supply ducts beneath it are formed with precast, reinforced concrete units erected immediately behind the shield.

Jan 1, 1979