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By Michael J. Howes

The nature of business in a free enterprise system is to maximise the return on an investment i.e. to maximise the wealth of the shareholders. This is normally achieved within constraints dictated by many agencies, one of which is the health and welfare of the employees. In the mining industry considerable effort has been expended in improvements in this field, however, the major problem still confronting the practicing ventilation or environmental engineer is the determination of what standards he should design for, which satisfy both the economic and health requirement s. Normally the basic health requirements are satisfied by the minimum standards defined in regulations and codes of practice. These are, however, based on an acceptance of a certain risk or lower production potential. A prime function of the ventilation engineer is therefore to financially justify and implement improvements to both standards and systems. The main purpose of this paper is to examine the basis and techniques of providing this financial justification. Changes in existing methods to achieve the same standards but at lower costs are also covered.

Jan 1, 1980

By E. A. Metz

Silicon dioxide, silica, is the most common oxide in the earth' s crust. The health effects of silicon dioxide dust have been known since Biblical times. Agricola's book, published in the mid 1500's on occupational medicine, described a lung disease that afflicted miners. He observed a disease in miners that caused shortness of breath, coughing and wasting. Add fever, chest pains and fatigue and we have the current symptom complex of silicosis. As we approached the 21stcentury, the Labor Department began an aggressive campaign to combat silicosis-a preventable disease. Unfortunately, many publications do not clearly differentiate the polymorphs of silica known to mineralogists. Crystalline silica, i.e., alpha quartz, tridymite and cristobalite need to be considered differently from the amorphous forms of silica. Freshly fractured surfaces of the silica and host specific responses will be examined. Recent research focuses on the biologic interactions of free radicals generated by mineral particles. This results in cell injury and DNA damage, in turn leading to fibrogenesis and possibly carcinogenesis. In addition to particle-cell interactions, emphasis is given to lung defense mechanisms.

Jan 1, 1998

By M. E. Mellado

In this paper, we present an a posteriori validation of a heap leaching analytical model using sensitivity analysis. The model is suitable to represent the process of heap leaching of solid reactants from porous pellets and is based on a combination of the leaching kinetics at two levels: particle and heap. The validation is simple, and a sensitivity analysis can easily be performed. The simplicity of the analysis provides insight into the control and optimization of the heap leaching process without strong mathematical complexities. The model and the corresponding sensitivity analysis include the effects of heap height, particle sizes, flow rates and several operation-design variables. Using a case study, we discuss the importance of model validation based on sensitivity analysis. We also comment on several choices for optimizing the process. We had three goals in this work: a posteriori validation, highlighting the importance of model validation and providing insight into optimization choices. We can conclude that the model has good internal logic and there are no extra variables; i.e., all of the variables in the model are necessary.

May 1, 2012

By O. H. Tuovinen, T. M. Bhatti

Microbiological leaching has been used as an alternative approach to conventional hydrometallurgical methods of uranium extraction. In the microbiological leaching process, iron-oxidizing bacteria oxidize pyritic phases to ferric iron and sulfuric acid, and uranium is solubilized from the ore due to sulfuric acid attack. If uranium in the ore material is in the reduced, tetravalent form (UIV), a red ox reaction is involved whereby uranium is oxidized to the hexavalent form (UvI) upon dissolution. In acid-leaching systems, the primary oxidant is ferric iron, which is reduced to ferrous iron by its chemical reaction with UIV. The ferrous iron thus formed is reoxidized to ferric iron by iron-oxidizing bacteria such as Thiobacillus ferrooxidans and Leptospirillum ferrooxidans. Nutritional requirements and responses to environmental extremes of acidophilic iron-oxidizing bacteria are appraised. The S-entity in Fe-sulfides is oxidized to sulfate by bacteria similar to Thiobacillus ferrooxidans and Thiobacillus thiooxidans. Pyrite and marcasite oxidation is a sulfuric acid forming reaction. Heap, dump and in situ leach techniques are feasible as bacterial leaching systems.

Jan 1, 2000

By Robert M. Mann

The Ag/S specific ion electrode has been evaluated for analysis of both free and total cyanide. Metal cyanide solutions were prepared from reagent grade compounds and by stoichiometric fixture of the metal with a potassium cyanide solution. Solutions containing Cu+1, Ni+2, Fe+2, Fe+3 and Zn+2 complexes were analyzed prior to and following EDTA pre treatment. This effort provides an understanding of the effect of each metal cyanide complex on the SIE analysis of free and "total" cyanide.

Jan 1, 1981

By James Giulianelli

Personnel at the Jet Propulsion Laboratory (JPL) are studying the technology and applications of salt-gradient solar ponds (see below) for both electrical and thermal energy generation. The brine extraction and processing site operated by the Kerr-McGee Corporation at Searles Lake, California, offers ideal conditions for economic construction of solar ponds. Furthermore, since rising conventional energy costs adversely affect the economic recovery of brine by the present process, this site was selected for a study on the feasibility of integrating the solution mining of trona (Na2CO3?NaHCO3?2H20) in the lower salt with solar ponds for heating. The major emphasis of this study was to determine whether inexpensive thermal energy available at the brine extraction site would be useful in extracting increased mineral value from the resource. The present operation, which involves the simple extraction of the complex brine and its processing at the adjacent plant, is sometimes referred to as solution mining. Since the concept discussed in this paper involves injecting a heated sodium sulfate brine to dissolve carbonate underground, the proposed scheme is referred to as "enhanced" solution mining. The subject is discussed in greater detail in a recent JPL report. (1)

Jan 1, 1981

By R. Sellaro

It has long been understood that extended occupational exposures to respirable mine dusts can lead to chronic lung disease. In underground coal mines, CWP and silicosis are major concerns. While there have been many studies aimed at understanding total dust concentrations and silica content associated with different mining conditions (e.g., locations/occupations within a mine, cutting methods, geologic strata), little research has been completed to more comprehensively characterize respirable dust (i.e., by particle composition, size distributions, shapes). This preliminary study sought to characterize dust from an underground coal mine in Central Appalachia using scanning electron microscopy with energy dispersive x-ray (SEM-EDX). Respirable dust samples were collected from various locations in the study mine, and individual dust particles were identified and classified by mineral type. A continuous personal dust monitor was also used to estimate total respirable dust concentrations during sampling. Here we report initial results of this work, and discuss advantages and challenges of particle-level characterization of mine dusts in terms of occupational health research.

Feb 23, 2014

By E. H. Smith

St. Joe Minerals Corp., a subsidiary of Fluor Corp., treats high-grade gold, silver, and copper ore at its El Indio plant at an altitude of 4 km in the Chilean Andes. The ore is complex, being a mixture of massive pyrite-enargite and quartz, both containing very fine gold and silver. Treatment produces a copper flotation concentrate containing high levels of gold, silver, and arsenic, and also dore bullion. Part of the flotation concentrate is roasted to remove the arsenic content, and arsenic trioxide is collected as a by-product.

Jan 1, 1987

By Lourens Scheepers

Mining induced seismicity and rockbursts have been part of the deep level gold mining industry in South Africa for many years. One could be forgiven for thinking that we should know everything there is to know by now to have rockbursting under control to a level that it has minimal impact on safety and production. Well, we don’t… There are things we know that we know, and they are implemented, or should be. There are thigs we know that we don’t know, and they are researched, or should be. There are things we don’t know that we don’t know, and, well, we don’t know… We know that seismicity and the associated potential for rockbursts generally increase with an increase in stress (increase in mining depth and/or mining span and creation of remnants) and proximity to faults and dykes. We know there are a number of potential sources of events in a mine; that is: mining abutments, pillar abutments, mining faces and geological structures (faults and dykes). We know there are a number of event mechanisms associated with these sources; that is: slip on a geological structure, shear through intact rock and bursting of the rock near the edge of a mining excavation. One of the tools used more and more and with increased success to identify event source mechanisms is Moment-Tensor analysis (MT). This typically assist in differentiating between three event mechanism components: volumetric deformation component, axial deformation component and slip / shear component. The insight gained from MT assist greatly in identifying the most likely event source to assist in understanding the rockmass response to mining. We know that the seismic response in our mines are mining induced (not natural). This may seem trivial, but it is important to realise that we influence the seismic response with the way we mine, and by how much we mine (extraction ratio). Therefore we put design rules and strategies in place to reduce the seismic hazard and we install rockburst support in our mining excavations. We know the seismic response to mining is influenced by the properties of the rockmass, including strength, stiffness and brittleness, but quantifying its influence is typically more difficult than expected. We know numerical modelling can improve the engineer’s understanding of the potential rockmass response associated with designed mining layouts and strategies. For our environment (narrow, tabular large area) elastic boundary element modelling remains the most convenient and practical approach, but it overestimates the stress at mining abutments and underestimates the stress further away from these abutments. Adding a crushing (based in limit equilibrium) modelling approach vastly improves the boundary element modelling ability to simulate the deformed (interpret fractured) zones and associated redistribution of stress. We don’t know how to quantify what an acceptable seismic risk is. We don’t know if we can mine remnants at an acceptable seismic risk. Some remnants are extracted surprisingly easy, others serve us with devastating rockbursts. The limit equilibrium modelling shows potential to significantly improve our ability to quantify the rockburst risk. We don’t know if large-scale preconditioning is possible and will be effective to significantly reduce the seismic risk associated with remnant and pillar mining. Research is required (and has been initiated). Vast areas of ground have been extracted historically in the South African gold fields. Most gold reserves are now in deeper ground (4000 m) and historic remnants (areas left before due to mining difficulties) as well as pillars (regional stability pillars). If we cannot find ways to extract these reserves at acceptable risk levels, the future of the South African gold mining industry is very short.

Apr 26, 2022

By V. G. Papangelakis, G. P. Demopoulos

The high temperature (180-200 OC ) pressure oxidation (02 - HzSO4) process for the recovery of gold from refractory concentrates (FeS2/FeA8S) is simulated with the aid of a computer model. The model centers on the continuous operation of a multi-stage horizontal autoclave. In particular the effects of key process parameters controlling the autogenous operation of the autoclave are critically examined. The building elements of the model are (i) the continuous particle size distribution function of the concentrate, (ii) the residence time distribution function of the slurry and (iii) the shrinking core kinetics. Conversion is calculated on the basis of the segregated flow model. For the calculation of the particle size distribution at the exit of each compartment the population balance model is employed. The effects of feed rate, feed preheating, cooling, autoclave configuration and rate limiting regime (chemical reaction vs. gas-liquid mass transfer) on the autogenous steady state operation are discussed. Finally optimum reactor design and operation criteria are indicated.

Jan 1, 1990

By James N. Grassby

Metal production has traditionally been a cyclical industry. 1977 in the base metals industry has highlighted that fact with a steady decline in the market place for base metals. Corporate aggregate planning is based on good forecasting and when changing conditions make that forecasting inaccurate, alternate analysis of schedules must be accomplished quickly. The computer is the only medium powerful enough to answer management's questions within an acceptable time frame. Worldwide communications networks now make it possible for the many multinational mining companies to arrive at coordinated corporate production plans based on similar basic data from several producing divisions. The Ontario Div. of Inco Metals Co., a unit of Inco Ltd., encompassed during 1977 14 producing mines, 2 nonproducing mines, 1 nonproducing open pit, 5 flotation mills, I smelter, 2 nickel refineries, 1 copper refinery, and an iron ore recovery plant. Several new mines are under development. Mine production approximates 63 500 tpd (70,000 stpd) from some 1000 workplaces. The need for longrange mine planning and scheduling is obvious and until recently has been satisfied by manual methods. However, while manual methods are often quite practical for a small number of mines, or for mines with relatively short lives, or for mines with only one mining method, the situation in the Ontario Div. is too complex and long-term to allow effective, timely planning by such methods. In 1967, a year after the first computer was installed in the division, work was begun on the computerization of the more than 30,000 borehole logs kept in the mines exploration files with a view to speeding up the assessment of mineral resources. Also in 1967 one of the first substantial systems developed on the main business systems computer was the monthly scheduling of development and production for all mines. This system encompassed tons productions per workplace, feet development per workplace, auxiliary and service activities and the requisite labor for each of these. These two dates are mentioned to show that concurrently with the acquisition of computers in the division there was an early understanding of the importance of automating mine scheduling and planning and of the potential for effective and useful computerization of such activities. In 1970, a pilot program was developed in one of the mines containing a large number of workplaces (350) to schedule the production on a network basis. Varying degrees of interest were shown by the individual mine engineers based on the complexity of the production planning problem at each mine. In an evolutionary process, mines were added to the system as its value became obvious in terms of time saving, flexibility, and accuracy. In 1975, the central mine engineering department decided that the system should be extended to all mines so that a complete division-wide long-range scheduling system would be available upon which to base development and production planning. This system would use basic ore data, allow the addition of scheduling commands, and calculate a schedule for the life of the mine. Many reports could be produced for each mine and all-mine summaries would also be available. The significance of the system can be stated in one phrase-speed, accuracy, and flexibility. Whereas in the past a long-range all mines schedule might have been done once a year, taking from two to three months, now it can be done in a day. The chief mines engineer can incorporate changes in input data and external constraints and call for a "new look" at the long-range schedule to assist him and mines production management in their decision-making processes. Using previous manual methods this could not be done quickly enough to be useful.

Jan 1, 1979

By Gordon M. Elliott

Health risk underlies all of today's environmental regulations. Mine Manager's are no strangers to risk, but risk in the context of mine management is not the same as risk in the context of environmental regulation. One of the risks facing the mine manager is whether the mining operations meet environmental compliance standards. These standards are defined in terms of the frequency of occurrence of adverse health effects in an exposed population (i.e., health risk). Demonstration of compliance necessarily involves mathematical modelling and selection of values for input variables. What is not immediately apparent is that the method of estimating the human health risk has a significant influence on remedy selection and the amount of money spent at suspected contaminated sites. Using a hypothetical, mining-related example, this paper illustrates the disassociation between the current deterministic approach to health risk assessment and cost-effective decision making. This paper also illustrates how the probabilistic approach to health risk assessment provides a more realistic characterization of health risk and enables mine managers to identify cost-effective remedial strategies for the site.

Jan 1, 1992

By E. Suoninen, K. Laajalehto, L. Kartio

Efficient separation of pyrite from other sulfides is of great importance for the metallurgical performance of flotation processes. In this work Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS) were used to study the surface chemistry of pyrite in depression, activation and xanthate adsorption under conditions of controlled potential. Modifications of pyrite surfaces after treatment with depressants (lime, sulfur dioxide, sodium cyanide) and after activation with metal ions (Cu, Pb) were studied. The principal adsorption product identified on pyrite was dixanthogen whose formation started at about +0.15 V and +0.25 V (vs, SHE) in ethyl and amyl xanthate solutions, respectively. Copper xanthate was formed on copper(II) activated pyrite. Activation mechanism of pyrite by copper(II) salts is likely to be electrochemical where copper occurs as copper(I) on the surface of pyrite. Effective depression is achieved by sulfur dioxide and sodium cyanide. Depression at high pH is due to formation of iron(III) hydroxides. Calcium ions do not affect the electrochemistry but adsorb on pyrite and reduce the surface sites for dixanthogen adsorption.

Jan 1, 1995

By G. Bhaskar Raju, S. Prabhakar

The amenability of column flotation for the beneficiation of fluorspar was investigated, and the overall performance of the column, flotation was compared to the performance of the existing conventional flotation cells at the plant. It was estab¬lished that improved grades and recoveries could be obtained by adopting column technology. Acidspar concentrates as¬saying 97% CaF2, suitable for HF manufacturing, can be produced by adopting two-stage column cleaning in place of multistage cleaning by conventional cells. Similarly, metspar concentrates assaying 90% CaF2, suitable for metallurgical applications, can be achieved in a single-stage cleaning by column flotation. This is an improvement over what is now being achieved using the existing conventional rougher and three-stage cleaning cells in the plant. The number of stages, i.e.,four in the acidspar circuit and four in the metspar circuit, including rougher stages, can be eliminated by adopting a three-column configuration. Thus, the cost of production, the complexity of the circuit and the power consumption can be effectively reduced with other attendant benefits.

Jan 1, 2000

By J. K. Ahlness

The Bureau of Mines investigated technologies for determining the integrity of in situ leach mining wells. A self-contained trailer-mounted well integrity testing system (WITS) was designed and built to enable rapid testing of well casings for leaks as required by environmental regulations. The WITS utilizes two inflatable packers to seal off the entire casing length or any portion thereof. Water pressure is built between the packers to the desired test pressure, and the presence or absence of casing leaks is determined by monitoring the pressure drop between the packers. A winch and steel cable are used to run the packers in and out of the well. The WITS underwent an industry field test at the Irigaray in situ uranium leaching mine near Buffalo, WY. A total of 37 wells with an average depth of 225 ft (69 m) were tested at an average rate of four wells per 8-h shift with a two-person operating crew. This represents a 75-pct time savings and an 83-pct labor savings compared to the rigid-pipe method previously used at the mine, with which a three-person crew tested an average of one well per shift.

Jan 1, 1986

By N. Duru

"Gravity concentration is still a challenging area in the mineral industry. This is mainly because of the fine size valuable mineral losses to the tailings during its application. But the recent developments in centrifugal separation methods and their mutual application with conventional separation techniques has increased mineral recoveries. In this paper, field application of conventional gravity separation methods with the combination of 2” diameter hydrocyclone cluster unit and a multi gravity separator (MGS) was discussed. Additionally, particle size distribution and chromite content of the plant streams is presented and initial laboratory test results were compared with the actual plant data throughout the paper. As expected, field data showed derivations from the laboratory tests but the combination of MGS and conventional gravity separation techniques resulted in gravity separation of -0.1 mm chromite particles. INTRODUCTION The purpose of this mineral processing plant project was to investigate the possibility of upgrading chromite ore from 12% to 48% Cr2O3 and having final tailings assay as 2% Cr2O3. For this reason, initially a set of laboratory gravity separation studies were conducted to evaluate the performance of combination of 2” diameter hydrocyclone cluster and multigravity separator. After obtaining successful results from the laboratory work, a feasibility study was initiated. Economical results of the feasibility study showed that an achievable high net present and return on investment values. Following the investment decision; engineering, equipment procurement, construction of the processing plant was completed in eighteen months. This paper focuses on the initial laboratory test work results, operational data of the 2” diameter hydrocyclones and MGS units; resulted chromite recoveries. Processed ore has the chromite associated with serpentine and olivine minerals. The chromite particles are generally in round shapes with sizes between 50 µm to 1600 µm and average size of 450 µm. The microscope images of the chromite and associated formations are presented on Figure 1.Chromite is formed in mixture with iron oxides, with varying amounts of magnesium, aluminum. The average chemical composition of the representative drill core samples of the ore deposit is given on Table 1."

Jan 1, 2017

By R. Kent Comann

Introduction This article describes ways to maximize employment potential for those looking for a job in the minerals industry. Advice on the right way to prepare a resume is followed by tips on where and how to look for a job and ways to make the best of an interview. Information on current salaries is also included. RESUME NAME: Give home and college addresses and telephone numbers, ADDRESS: if still in school. Otherwise, give home address and TELEPHONE: telephone plus business telephone number. JOB OBJECTIVE: What do you want to do? EDUCATION: List degree(s), name of college(s), location(s), and date(s) degree(s) received or to be awarded. Do not list your high school but do include postgraduate education, training, or seminars. WORK EXPERIENCE: List your most recent experience first, and the rest in reverse chronological order. Include dates (month and year) and company names. First show the entire time spent with each employer, then list the various jobs (with dates and duties) you may have had with this employer. MILITARY SERVICE: List dates, branch of service, and duties. If you did not serve, delete this section. COLLEGE ACTIVITIES: Show organizations, sports, and offices held. Only list these if you are a graduating senior, otherwise delete this section. PERSONAL DATA: List age, marital status, height, weight (optional), foreign languages spoken, professional memberships, and health (if good or excellent, otherwise do not mention it in the resume). If you prefer a certain location and would not accept a job anywhere else, list the location desired. Otherwise, do not restrict yourself. Also list special skills, hobbies, or interests that will help sell you to the company. Be brief in this section and use good judgement as to what you say. REFERENCES: Furnished on request. Resume Guidelines There are some things to remember when preparing a resume. These include: • Limit your resume to one page, unless you have a lot of experience. Then it should be a maximum of two pages. • Use 8.5 x 11 plain bond paper, white or off-white. Stay away from colored paper, odd size paper, and cute resumes. They are counter-productive. • Make certain your resume is typed professionally. Be sure to check for spelling, grammar, and typographical errors. • Have your resume reproduced by copier or printing shop. Do not use carbon copies. • Keep your sentences and remarks short and punchy. Use action verbs. • Have a good layout that is easy to read, brief, and uncluttered. Allow some white space in your resume. There are also some things you should not do when preparing a resume. These include the following: • Do not include a photograph or mention your religion, race, or sex. • Do not leave gaps of time unaccounted for in your resume. • Do not include your college transcripts with your resume or list all the courses you took in college. • Do not list all the articles you have written. Only list one or two, if appropriate for, say, a research and development job. • Do not include reference letters with your resume. Any good, prospective employer will make telephone reference checks. • Do not use "Curriculum Vitae," use "Resume." • Do not include unnecessary data such as your social security number, passport number, or PE registration number. If you are a PE or EIT, be sure to mention that in your resume. Do not mention US citizenship or US work permit unless you have a foreign education or are not a native US citizen. • Do not include present salary or salary requirements. This will come out in the interview. • Do not use the word "I" in your resume or refer to yourself in the third person. • Do not lie, distort, exaggerate, or editorialize in your resume. • Do not have your resume prepared by an outside resume service. This is unnecessary, costly, and generally not effective.

Jan 2, 1985

By T. J. Lyman, M. J. Robison, W. A. Ruemmele

INTRODUCTION The first phase of the Los Angeles Metro Rail Project consists of 7.1 km (4.4 miles) of subway and stations running through downtown Los Angeles from Union Station to MacArthur Park. Contract A171, the Wilshire/Alvarado Line, involves tunnel construction beneath 7th/Street from the 7th/Flower Station to the Wilshire/Alvarado Station. The project consists of the excavation and lininig of 3000 m (9900 ft) of twin-bore, 6.7 m (22 ft) excavated diameter, 5.5 m (18 ft) finished diameter subway tunnels. The location of the project is shown in Figure 1. The majority of the excavation passed through weak siltstone/ claystone bedrock; although, portions of each tunnel approaching the 7th/Flower Station passed through fine-grained alluvium. Both tunnels were excavated with a digger shield. The project also included the excavation and lining of 6 cross passages, 2 communication rooms and a sump, all at tunnel grade between the two bores. A program of geotechnical instrumentation and building monitoring was performed to detect and document the response of the ground and adjacent structures and facilities to tunnel excavation. The instrumentation program was also intended to provide information that would permit implementation of remedial measures, when and as required, to prevent damage to structures, facilities and utilities along the tunnel alignment. The purpose of this paper is to discuss the ground response to tunneling on Los Angeles Metro Rail Contract A171. This paper presents a description of the tunnel project, the excavation and support method used in construction, the subsurface geology, and

Jan 1, 1989

By William Gleason

While a fleet of 100 t (110 st) haul trucks were busy removing overburden from the open pit mine in the distance, a host of dignitaries, including congressmen and California state representatives, gathered for Molycorp?s official groundbreaking ceremony at the Mountain Pass Mine on April 20. The mine, recognized as arguably one of the richest rare earths deposits in the world, is at the center of Molycorps? strategic ?Mine to Magnets? plan. It aims to secure America?s future supply of rare-earth-dependent technologies by developing a strong domestic rare earth industry. Molycorp identifies rare-earth-dependent technologies as those that cannot be produced without rare earth materials. The list of these technologies is long and growing. It encompasses everything from personal electronics and batteries for hybrid cars to permanent magnet generator wind turbines and national defense applications.

Jan 1, 2011

By Donald S. Skufca

This chapter focuses attention on major factors pertaining to plant design and general arrangement of equipment. Considered are efficiency of operations, coordination of maintenance and repairs, plant testing of reagents and possible future plant expansions. The design and general arrangement of equipment considers accessibility for maintenance and isolation for repairs, minimum personnel for operations and cleanup, safe working conditions with minimum interruptions to operations. The constant introduction of new reagents requires eventual plant testing and the manner of isolating a “line” or part of the facilities to allow comparisons in the testing of new reagents is discussed. As technology improves and process changes occur, additional equipment or plant expansions are inevitable. Space for these eventualities must be considered while the general arrangement drawings are in the development stages.

Jan 1, 1986