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By Alfredo Menendez, Alberto Sarmentero

A B S T R A C T The Los Pijiguaos bauxite is one of the largest accumulations of trihydrate alumina ore recently discovered; it is a plateau type, with no overburden, relatively soft tertiary quartz-bearing bauxite developed on a pre-Cambrian Rapakivi Granite batholith. The deposits are found in the northwestern rim of the Guiana Shield, State of Bolivar, Venezuela, and were discovered in 1976 after a grass-roots exploration campaign. Target areas were mainly selected on the basis of geological and geo¬morpholigcal criteria, guided by correlation with known deposits elsewhere in the Guiana Shield. The vertical. lateritic profile consists of an upper concretionary zone, followed by a mottled zone, a palid zone and finally the weathered rock merging into fresh granite. The upper concretionary zone displays a cellular, pisolitic or spongy texture and contains the following minerals: gibbsite (60-90%),quartz (5-10%), hematite (5-10%), goethite (under 5%), boehmite (traces), kaolinite (traces). The gibbsite content decreases sharply downward from the lower limit of the concretionary zone and the kaolinite and quartz content increases in the underlying mottled zone. The mottled and palid zones display a pseudo rapakivi texture and quartz, kaolinite and mica are the. essential minerals.

Jan 1, 1984

By [Miroslaw] M. Hajdasinsk

The identification of the real internal rates of return (IRR's) of a project is essential for its economic evaluation. The existing methods for the calculation of IRR's are both cumbersome and unreliable, mainly because of their inability to effectively isolate the real IRR's and incapability of discovering multiple IRR's of even multiplicity. In this paper, a concept of the 'cash flow pattern tree used for isolation of the real IRR's of a project is presented. This concept, combined with the Sturm procedure for counting the real distinct zeros of a polynomial within a specified interval, leads to the development of a method and computer program for isolation and calculation of the real IRR's of a project. The method examines whether or not real IRR's exist, and if they do, isolates them within bounded and narrow intervals in a mathematically founded way. The isolated IRR's, whether simple or multiple, are subsequently calculated either directly or by means of an appropriate approximation procedure. Numerical examples assist the development of the method and the corresponding computer algorithm. Because any Net Present Value treated as a function of interest rate can easily be transformed into a polynomial, the method presented also constitutes a method for finding the real zeros of a polynomial.

Jan 1, 1986

By Jaye Pickarts, Bret Boster, Jack McPartland

Pegasus Minera de Chile, Ltda. is completing three phases of metallurgical evaluation on the Pullalli project to develop a preliminary process flowsheet. A project feasibility study is in progress. The feasibility study includes a proposed process flowsheet designed based on results from the multiple stages of metallurgical evaluation. Phases I and II of metallurgical evaluation included laboratory scale heap leach and milling cyanidation testwork on multiple drill core composites and bulk ore samples from the Pullalli Project. Phase Ill included pilot scale milling/cyanidation testwork on Pullalli drill core composites. The proposed flowsheet includes selective mining and separate processing of low grade and high grade ores. Low grade ore will be crushed and heap leached. High grade ore will be milled leached for 12 hours in an agitated cyanidation circuit. After 12 hours of leaching, sands and slimes will be separated and the sands will be washed using a counter current cyclone (CCC) circuit. Partially leached and washed sands will be added to the crushed low grade ore for heap leaching treatment and permanent placement. Partially leached slimes will be thickened in a high capacity thickener and will be processed in a CIP circuit. Leached slimes will be placed in a tailings impoundment.

Jan 1, 1996

By K. H. Al-Rawahy

Appreciation and awareness of the unique nature of mineral investment and ultimate development of a mine are crucial in promoting sustainable development. Special characteristics of mineral development include high capital intensive, long pre-production period, high risk, and the unavoidable ?economic? depletion. This paper examines ways to integrate these unique attributes of the mineral industry into the educational process, so that a properly advised and knowledgeable culture in terms of a sustainable mineral industry can be developed. Specific approaches are investigated in order to achieve this objective. These include a stochastic evaluation of a mineral investment proposal, adding a premium to the cost of capital that is used for valuation process, and internalizing incidental costs to the private cost function, thereby realizing the true (vs. apparent) marginal social cost of the proposed development. Undoubtedly, a total evaluation of any mineral project that accounts for both tangible and intangible parameters will contribute to sustainable development objectives. By incorporating the practical application of apparent theoretical topics such as risk, probability, and externality, and their relevance and impact on mineral lifecycle (prospecting, exploration, development, exploitation, use, and ultimate disposal) into the educational process, it is hoped that a generation of technocrats and decision makers that are familiar with and concerned about sustainable development will emerge.

Jan 1, 2007

By Ümit Yasar Onder, Tevfik Prof. Dr. Güyagüler

This paper describes the results of an investigation done to determine thermal properties and heat emission of coal measure rocks in Karadon district of Zonguldak Coal Colliery. In Karadon District, depth of working level is about -600 m where the heat problem arises. In the near future, workings will be at deeper levels and working conditions will be more difficult due to high heat emission. At the beginning of the paper the importance of wall rock heat emission in underground mine have been explained and then the amount of heat emission to the ventilating air has been calculated. It has been found out that the strata is the main source of heat in the mine. Therefore, geothermal gradient of the region has also been determined simply by measuring the virgin rock temperatures in different levels of the mine. All other data directly related with heat emission from different sources has been collected and has been analyzed by using a special computer package. As a conclusion, total heat and moisture content in ventilating air and heat balance has been determined for Karadon Coal Mine. In addition, some recommendations and suggestions have been made for the future works when the mine workings go to the deeper levels.

Jan 1, 1995

By Claus Becker

Waterbearing, cohesive or non-cohesive grounds with glacial stone deposits are found very often in Europe. The problem consists of destroying the boulders and supporting the face simultaneously. At the example Grauholztunnel Bern ( outer diameter 11,60 m ) the theoretical attempt of solutions for the big machines is described: destroying of the boulders with roller discs, hydraulical support of the front. The problem of coming out of stones of a certain size from the surrounding matrix will be discussed. Further diminishing to the size that can be handled by pumps is executed by a crusher, situated in the center of the machine. At the same example the theoretical attempt for headings in cohesive soil with stone deposits are shown. Surface structure of the cutting wheel and working chamber as well as controllable current movements are the solution here. The danger of clogging discs and stone crusher has to be encountered by right positioning of the tools and jetting nozzles. At the example Sewer MoosstraBe Salzburg the same problems are discussed for the Mikro-Tunnels. The pipe-jacked sewer lines have outer diameters from 485 and 805 mm. With this method, the stones have to be holed through. The wear of the cutting tools determines the [ ]

Jan 1, 1989

By L. W. Saperstein

In this paper, a number of novel hypotheses that provide a fresh perspective on the characterization of strata movements associated with longwall mining are developed by analyzing subsidence measurements with an influence-function-based computer program. Using an inverse application of the traditional influence-function technique, easily obtained surface displacements are used to analyze some of the complicated, expensive, and difficult-to- measure movements of the intermediate roof strata in a longwall panel. The primary hypothesis developed by this analysis proposes the existence of an area of partial roof caving near the edge of a panel called the "edge effect." A secondary hypothesis, interrelated with the first, promotes the importance of the effect of gate-entry closure on the observed strata movements. Both the primary edge-effect hypothesis and the secondary hypothesis concerning gate-entry closure are justified and quantified in an extensive analysis of surface subsidence that uses supporting information from related theories, design criteria, and in situ measurements. Next, the edge effect and the gate closure hypotheses are extended further and used to provide an explanation of the complex subsidence interaction of adjacent longwall panels in what is termed a "redisturbed" effect. Finally, the importance of accurately understanding these longwall strata movements for proper subsidence prediction or gate design is stressed.

Jan 1, 1988

By J. Scott McDougall, J. Herman P. Eng. Vanderlaag

An underground mine fire can seriously threaten the lives of all personnel in the mine. This fact makes fire emergency planning a high priority in the mining industry. The optimum warning alarm must be fast and able to reach all miners, regardless of their location or work activity. Current means of fire warning are varied, and include such methods as stench, telephones, and word-of-mouth (messengers). Unfortunately, none of these methods are entirely satisfactory. A novel fire warning alarm which enables instantaneous warning of all underground personnel, the Canary Nine Messenger System, has been developed by VLF Magnetic Systems Inc. in conjunction with Noranda Technology Centre and the U.S. Department of the Interior - Bureau of Nines. The warning is sent by an electromagnetic signal which penetrates through mine rock to receivers housed in the battery packs which also power each miner's cap lamp. A loud buzzer in the integrated battery/receiver unit and the flashing of the cap lamp alerts miners to incoming messages. Testing of prototype equipment has demonstrated that the transmitted signal is capable of penetrating through over a mile of mine rock and activating the receiver. This report describes the theoretical basis for through-the-rock ultra-low frequency electromagnetic transmission, and the design of recently available transmitter and receivers.

Jan 1, 1995

By A. Peppas

Perlite is a naturally occurring siliceous rock, which can be expanded from four to twenty times its original volume when heated at a temperature close to its softening point. The expanded perlite is characterized by increased sound and thermal insulating properties. However, the conventionally expanded perlite products have high porosity and low mechanical properties that limit the range of their applications in the construction and chemical industry. The present work aims at the development of new closed porous microcellular material from perlite with enhanced mechanical and physical properties to be applied in new applications, like joint compounds, functional fillers for special paint types, special blasters and mortars, artificial marble. For the production of these new materials a vertical electrically heated furnace with six different heating zones and controlled gradient temperature profile was used. The effect of major process parameters, like temperature and air flow, on the quality of the produced materials was studied using Greek perlite from Milos Island. The quality of the new products was evaluated in terms of their bulk density, compression strength, water and oil absorption, surface area and pore volume. The experimental results show that the produced materials are characterised by improved mechanical and physical properties compared to the conventionally expanded perlite products.

Jan 1, 2006

By G. D. Hood, B. E. Davis

A problem that has continued to plague the Florida phosphate industry is loss of coarse phosphate in the flotation circuit. Attempts to remedy this problem such as floating the coarse material (plus 425 µm) in a separate circuit have resulted in limited success, but recovery is still not optimum. A fundamental examination of the mechanisms involved in the conditioning of the coarse phosphate has led to results that seem to supersede common paradigms. The Bureau of Mines investigated conditioning parameters such as fatty acid/fuel oil dosage, residual clay content in the feed, conditioning time, mixing intensity, and conditioner solids content. The study revealed that the effect of all these parameters was important. However, it was discovered that contrary to common beliefs, the conditioning time affected the grade of the rougher concentrate much more than the recovery. Specifically, the longer the conditioning time, the less quartz that was floated. It was also discovered that high mixing intensity conditioners could lower the conditioning time required for good grade. Many phosphate operators use low intensity drum type conditioners. Optimizing the conditioning time, mixing intensity, and other conditioning parameters resulted in a rougher concentrate grading 30 pct P.2O5, with an attendant recovery of 95 pct.

Jan 1, 1993

By A. De Daio, D. W. Fuerstenau, P. C. Kapur

Because of its pronounced tendency to undergo visco-plastic flow, coal ground in the energy- efficient high-pressure roll mill invariably comes out as a briquetted product which must be disintegrated in a conventional type of grinding device such as the ball mill. The aggregates comprise comminuted coal particles that are apparently extensively cracked and weakened during passage of the coal through the high-pressure rolls. Their deaggregation in a ball mill in the second stage is accompanied by further grinding of the coal with a relatively small expenditure of energy. Thus in spite of energy dissipation in briquetting in the roll mill and in disintegrating the briquettes in the ball mill, significant energy savings are possible in the fine grinding of coal in a two-stage serial grinding mode, as compared to ball mill grinding alone. It has been determined that for the best results the energy invested in the two grinding stages must be apportioned in an optimal manner, the energy consumption in the ball milling step is comparable to, even in excess of, the energy spent in the high- pressure roll mill; and 20 to 50 percent energy savings might be possible in grinding coal to minus 200-mesh size by this two-step process, as compared to conventional milling.

Jan 1, 1995

By George P. Tateosian

Merchants perform a number of functions in the copper market. As a major distribution arm of the copper industry, they secure scrap and other copper bearing materials for processing into usable refined shapes. These are ultimately sold to fabricators. Merchants ' hedging and arbitrage activities help keep values in proper relationship from product to product or region to region. Through these switching and trading operations, they optimize the flow of copper from mine to consumer. And finally, merchants act as a repository for copper units during times of surplus and a stockpile from which to draw during tines of shortage.

Jan 1, 1979

By Lars A. Stålberg

"This paper will touch several of the topics covered by SDIMI 2005, including,• Sustainability indicators for the minerals industry, • Best practice of sustainable development in the minerals industry, • Social contributions,The complex issues of a company’s "sphere of influence" and "complicity" are important to every discussion of business and Human Rights. The paper will argue that to protect and promote Human Rights needs to be regarded as an integral part of sustainable development policies for the minerals industry. This implies a need for explicit inclusion of Human Rights indicators among the indicators to be applied by the minerals industry."

Jan 1, 2005

By Alan S. Peck

Chemisorbed oleate films on the surfaces of fluorite, barite, and calcite were studied by means of infrared spectrophotometry. Evidence is presented which indicates the mineral anions, i.e., fluoride, sulfate, and carbonate, are displaced from the mineral surfaces as a result of the adsorption from aqueous solutions. Also, chemisorption reactions between oleic acid and fluorite or calcite occurred spontaneously in the absence of water. Carbon dioxide was identified as a reaction product when dry calcite was contacted with oleic acid. There was no evidence of reaction between oleic acid and barite in the absence of water.

Jan 1, 1964

By John C. Wangaard

A method of raising by use of a cage has been used with considerable success at the Cary Mine, Hurley, Wisconsin, on the Gogebic Range. The Cary Mine is owned by the Odanah Iron Company, Pickands, Mather and Company, Managers. This method is known to have been used previously at Tennessee Copper and probably in other districts. The Cary Mine was engaged in deepening the main shaft from the 34th to the 37th level. To accomplish this, and to facilitate development, a ventilation shaft 930 feet north of the main shaft was sunk from the 34th to the 37th level and crosscuts were driven on the 35th, 36th and 37th levels to the main shaft location, These levels are at 200 foot verticalintervals. All of this work was done in granite and the majority of the workings were not timbered. The next step was to get a raise through from the 37th to the 36th level, and from the 36th to the 35th level, which would later be stripped to full shaft size. Several methods of raising were considered including double-compartment cribbed and two single raises interconnected at regular intervals, but the cage method was chosen as it appeared to be a safe and efficient operation. The method in general consists in the use of a drill hole between levels through which to pass a hoisting rope to raise and lower a light cage.

Jan 1, 1958

By Malcolm T. Wane

The subject matter of this paper, "Applied Rock Mechanics?," has its genesis in a recent field trip taken by the author. A more or less standard question asked at the mines visited was "How are you using the principles of Rock Mechanics to assist you in maintaining an efficient, safe, and competitive mining operation?" The question was couched in a number of different forms, but the intent was to determine whether or not a general theory based on reason and the scientific method was applied or whether the alternatives of tradition, intuition, ?common sense', revelation, ?shotgun methods' or authoritarianism were invoked. Perhaps two responses to this query will be illustrative of the general nature of the replies. At operation XYZ an extension to the known ore body has been found. The extension is of large enough size and grade that a mining scheme using load-haul-damp techniques is envisaged. Since this represents a departure from the present mining scheme, questions have arisen regarding pillar sizes, room and entry sizes and possible support requirements. A task force has been set up to expeditiously plan for these things and write the necessary specifications and requirements. The fundamental question was posed to members of this group.

Jan 1, 1971

By J. Steenkamp, A. L. Hannaford, A. N. Jones

O’Okiep Copper Co. Ltd.’s 45-kt/month (49,600-stpm) concentrator at the Spektakel mine in South Africa is comprised largely of reconditioned equipment from the old O’Okiep mill, which operated from 1940-1975. When combined with modern approaches to layout, crushing, classification, and flotation, a simple-to-operate plant was constructed at a cost of only $3.2 million.

Jan 11, 1982

By I. Andras

The paper deals with the application of artificial intelligence methods in assessing the effectiveness of longwall shield support. A fuzzy sets based method is used to derive response surfaces/curves representing the dependence between basic parameters of the shield, as the initial setting pressure and the stiffness on the response metric, i.e. the convergence and load increase during a working cycle.

Jan 1, 2008

By H. Reginald Hardy, Maochen Ge

Data analysis is one of the most important steps required for the successful application of the acoustic emission/ microseismic (AE/MS) technique. A dedicated computer software package to analyze acoustic emission/ microseismic data associated with field applications in the geotechnical area has been developed recently at Penn State University. This paper addresses the major features and applications of this computer software package.

Jan 1, 1986

By M. J. Meulendyke

Within the mineral processing Industry. a range of grinding conditions exists which include semi-autogenous grinding (SAG), rod milling. and conventional ball milling. Each of these mill environments presents a unique environment for grinding media, requiring the application of specific physical and chemical properties for optimum grinding media performance. The environments are characterized by varying degrees and combinations of abrasive, corrosive, and impact wear. An extensive test program has been conducted to determine the extent wear rates vary between these different applications. Test results are related to production results, ball size, and mill operating conditions.

Jan 1, 1989