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By Chris Campbell-Hicks

Methods used for assay of gold values in resource estimation, grade control or downstream processing are based almost entire­ly on Fire assay or Aqua Regia techniques. Both these tech­niques frequently produce spurious results. The mechanism of error is explained. Major decisions are made based on this often flawed data. This is what our operating budgets and projected cash flows are based on. Project economics demands metallur­gical accountability for performance predicted. Accountants and more astute members of the board are often not sympathetic to gold out-tum from plant production which is occasionally or consistently less than that predicted. Equally importantly, better than budgeted gold out-tum, resulting from under assaying will produce reconciliation or accounting problems (surplus cash flow) often denying correct timing of expansion or acquisition. Both these scenarios can be avoided if 'real world' extractable gold values are presented to financial managers at all stages. Such extractable gold results are now possible, and compared to fire assay and aqua regia, the assays are faster, cheaper, simpler and more accurate.

Jan 1, 1996

By V. I. Lakshmanan, Chris Dodson

Refractory gold ores or concentrates are pretreated in general by physical, chemical and biological oxidative pretreatment processes prior to cyanidation for the economic recovery of gold. The thermal treatment processes generally include fluid bed pro­cessing(!>, chemical with pressure<') or atmospheric (Caro's< ·'>, 3 Nitrox1')) pretreatment leaching and physical with ultrafine grinding!"). Roasting and aqueous pressure oxidation pretreat­ment methods have several commercial applications (Homestake, Barrick) and biological oxidation methods have recently found industrial applications in Africa. The roast pretreatment methods to treat refractory sulphide ores or concentrates transform iron sulphides generally to a porous iron oxide matrix assisting the lixiviant cyanide to effectively diffuse the calcine for cyanidation and hence with improved gold recovery. Jha and Kramer<') made an extensive review of roasting chemistty and practice to tt·eat refract01y gold ores. Industrially two stage pretreatment roasting is generally employed. During the first stage roasting is carried out under oxygen deficiency conditions to provide a low arsenic calcine, mainly magnetite and in the second stage magnetite is trans­formed to haematite under oxidizing conditions.

Jan 1, 1998

By David Lunt, Evan Kirby, Peter Mason, Ian Ritchie

The treatment of refractory gold ores, in particular the "competing" technologies and their relative advantages and economics, has become a major segment of most mineral technology oriented conferences in recent years. A common theme is the increasing refractory nature of gold ores being treated. This is despite ores such as those at Kalgoorlie having required roasting for liberation since the last century. Papers on refractory gold treatment have examined the characteristics of refractory ores and the causes of reduced recovery (eg La Brooy 1994), the available technologies and their relative economics eg Litz 1990), and the selection of a suitable process route (eg Nicholson 1993, Weston 1994). The most comprehensive collation of data on such processes is provided in the different editions of Randol. A variety of classifications and definitions of "refractory ore" have been published. Due to the many factors which can impact on the recovery of gold it is perhaps not feasible to develop a universal characterisation that can be applied to all gold bearing rocks. La Brooy et al have provided the framework for characterisation shown in figure 1.

Jan 1, 1995

By A. Anderson, G. May, C. Kubank, S. Meik

The Kori Kollo operation is owned by Empresa Minera Inti Raymi S.A., a Bolivian mining company. Inti Raymi is an eighty-five percent owned subsidiary of Battle Mountain Gold Company (BMGC). The remainder of Inti Raymi is held by Zeland Mines S.A., a Bolivian mining company. The project is located near the village of La Joya, approximately 220 km south of La Paz, and 40 km north west of Oruro on the Bolivian altiplano. Inti Raymi started a heap leach operation in 1985. By 1988, following several expansions, 4,000 tonnes per day of oxide ore were being treated. At this time drilling was started to delineate the larger sulfide orebody. A feasibility study for the development of this deposit was completed in 1990, and following project approval, the engineering design was started later that year. During this period orders were placed for the major items of mechanical equipment. In July 1991, Minproc Engineers Inc. was awarded a firm price contract to design and construct the 14,000 tonne per day sulfide ore process facility.

Jan 1, 1993

By M. Kavvadas

Geotechnical design using Factors of Safety recommended by Codes of Practice is based on largely unknown ?margins of safety?, usually without consideration for the importance of the project (i.e., potential consequences of failure) directly or explicitly. On the contrary, probabilistic modelling can be a useful tool in risk management as it provides the means to measure the risk to be managed. This is achieved by calculating the probability of failure associated with a specific design, i.e., by relating the classical factors of safety with the corresponding probability of failure and by using a cost optimization procedure to achieve ?optimal? designs, accounting for the expected costs in case of catastrophic failure. This paper describes the methods used to calculate the probability of failure and its correlation with the classical Factor of Safety using sampling techniques and a simplified method based on the moments of the factor of safety considered as a random variable. These procedures are illustrated in an example which investigates the stability of a slope.

Jan 1, 2005

By Vitaly T. Borisovich

Mining economics courses have been taught in Europe for more than two centuries and in the United States for most of this century. They are the mineral industry&apos;s version of engineering economics offered by industrial engineering departments. In the 1930s, mineral economics first appeared in American mining schools. This subject goes beyond the deposit and the mine. It examines the economic aspects of mineral resources in general and the individual mineral industries in particular. In 1947, the first degrees in mineral economics were granted in the United States. There are mining and geological engineers who specialize in mining economics. But it has rarely become a separate degree program. Rather, in this country and several others, a graduate student in a mining department or school will include economics in his course work. Then the person writes a thesis or dissertation on a mining economics topic. One exception is found in Moscow at the Department of Geoeconomics of the Moscow Geological and Prospecting Institute (MGPI). To place this program in perspective, some background is needed on education in the Soviet Union.

Jan 1, 1991

By C. Menidiatis

The first cement plant of TITAN Cement Co was founded in Elefsis in 1902. It was the first cement industrial facility to operate in the Balkans and in the Eastern Mediterranean region. Currently have four cement plants in Greece producing 5.4 million tons per annum, and 25 ready-mixed concrete sites producing 1.4 million m3 annually. It has a total of 20 quarries, 14 of which are producing materials used in the making of cement while the remaining six produce aggregates used in the production of ready-mixed concrete. All plants in Greece are accredited for ISO 14001. The restoration of quarries began in 1976 at the company?s limestone quarry of the Patras plant, and was soon extended to all quarries. At that time, a department responsible for all environmental issues was established. To date, over 700.000 shrubs and trees have been planted and maintained at quarries, plants and ready-mixed concrete facilities, while over 100,000 trees have been donated to municipalities, communities, customers and to the Greek state.

Jan 1, 2002

By R. Markovic

The objective of this research study was the investigation of heavy metal removal from wastewaters of the "SARAKA" stream by using low-cost materials. These wastewaters flow into Krivelj River and through the network of existing rivers into regional water reservoirs. Sawdust, cardboard and fly ash were used as reactive materials in laboratory studies. Sawdust was obtained from oak and fir-wood while fly ash from heating station Bor, bitter-oak and oak. Experiments were carried out using real Saraka stream wastewaters and the degree of removal for iron, copper, manganese and zinc was investigated. The content of these heavy metals in Saraka stream wastewaters was under the limit of III and IV class of water (Law on Water - Official Register of the Republic of Serbia). Parameters such as flow rate of water, pH and effluent volume, contact time between water and reactive material, etc, were monitored during the experiments. All used materials give satisfactory results for iron and other heavy metals removal; the highest degree of removal was obtained by using fly ash.

Jan 1, 2006

At present, increasing focus of public perception is placed on the environmental and social benefits, risks and impacts of metals and metal-bearing products. To address these issues, the concept of product stewardship has recently been introduced into the political debate. In this paper, results from a survey of existing environmental and social reporting practice in the copper mining, smelting, refining and fabricating industry are presented. In this context, particular emphasis is placed on the reporting practice regarding products and product performance over the life cycle. In a few companies there has recently been a shift towards adopting product stewardship principles and putting them into action. As part of an ongoing exercise within the Non-Ferrous Consultative Forum on Sustainable Development sponsored by the International Copper Study Group (ICSG) key issues of interest to the non-ferrous metals sector are being addressed. The Forum, for example, has developed a series of principles, criteria and indicators that could form the basis for a voluntary, industry-lead product stewardship scheme. Current achievements and way forward of this product stewardship initiative will be presented.

Jan 1, 2003

By Suresh K. Bhatt

Appalachian coalfields have been the predominant source of quality coals since the inception of commercial mining in the United States. In a broad sense, Appalachian coalfields can be considered those east of the Mississippi River, representing about 55% of total US coal production. In this special feature on Appalachia in MINING ENGINEERING, emphasis is given to the four coal-producing states of Pennsylvania, West Virginia, Virginia and (eastern) Kentucky. These four states produce more than 90% of the coal from the total Appalachian region, or about 40% of the total US coal production. Historically, Appalachia has been the principal source of coal for domestic industries and for export. There have been numerous fluctuations in the Appalachian coal industry during the past 20 years. Appalachia was affected by cyclical and structural changes in various industries, particularly the US steel industry, and changing world coal markets. It was also the region of more mine worker labor stoppages than other parts of the country. In general, the factors that affected Appalachian coal production over time are identical to those that determined changes in coal production nationally.

Jan 1, 1995

By R. Bouzaiene

In the paper presented by F.W. Brackebusch on the “Basics of paste backfill systems,” paste fill was presented as a backfill process that offers many advantages over other alternatives such as hydraulic fill and rockfill. It was observed, however, that the mechanics of paste-fill transportation in pipelines is not fully understood and that the success of its implementation in practice depends on the precise control of the proportions of fines, aggregates and water in the mixture. The author emphasized the necessity for laboratory and full-scale testing to determine the suitability of a material to be used as paste fill. Although experimental testing is definitely an important operation in the design of a reliable paste fill, advances in the understanding of the fundamental laws that govern paste flow in pipelines are equally relevant. Ideally, the results of such efforts would provide predictive models for the rheology of the paste and the corresponding pumping-energy requirements. In an attempt to achieve this objective, an ongoing research program has been active at McGill University’s Department of Mining and Metallurgical Engineering.

Jan 1, 1995

By Elias Apostolidis

Since 500 B.C. Mt. Penteli has been famous as white marble production site, which provided the birthstones for the construction of Athens Acropolis and Parthenon. The Aloula quarry belongs to ?Dionyssomarble S.A.?, a commercial and industrial marble company, which retreated after 1940. Disturbance in the site was minimal since then. In July of 1994 the reclamation started by a group of quarry workers from Paros, already familiar with traditional marble quarrying techniques, unchanged from antiquity to 1940. The project was complete in 1997. Our main objectives have been to show respect to the area and the art of people, to let nature guide our choices, to use only local stone as a construction means, to imitate the old construction rules and to turn the land use into amenity and civilization. Aloula quarry will become a site restored for amenity and civilisation, including ancient quarrying techniques. The restored quarry is already open to the public, though to a small number of visitors, and soon will become an amenity park and an open space museum of the ancient quarrying art.

Jan 1, 2002

By X. Zhu

Establishment and monitoring of revegetation in areas affected by mining activities is quite often a difficult task. The efficiency of the scheme applied can be substantially improved by using simple adequate indicators so that progress and trends can be plotted, elucidated and assessed over time. Sustainable revegetation management indicators should take into account soil quality and area characteristics, as well as social, economic and political aspects. In the present paper an interactive prototype Spatial Decision Support System (SDSS) is presented. The system, based on methodological studies, has been designed to identify and interpret indicators that can be used for the evaluation of revegetation efficiency. It provides a platform for formulating indicators describing biophysical, socio-cultural and economic processes during the entire revegetation period. It integrates modular assessment, database management sub-systems and Geographical Information System (GIS). It is structured in a way that takes into account the project environment, soil quality, land characteristics, data acquisition control, output engines and spatial analysis. The output generates visual quality diagrams and interactive attribute quality maps that elucidate revegetation issues.

Jan 1, 2007

By J. Finch, W. Petruk, R. G. Pinard

An investigation was conducted to determine the minimum number of samples that must be studied by image analysis of polished sections to characterize a mill product and determine the apparent mineral liberation. It was found that a representative polished section cannot be prepared from an unscreened sample that has a wide size range of particles. Similarly, individual screened fractions are not representative of the sample because minerals are partitioned during screening, and the quantities of soft brittle minerals are increased in fine grained fractions, whereas the quantities of hard minerals are increased in coarse grained fractions. It is assumed that results obtained by combining data for a series of narrow size range screened fractions (one Tyler size range) are representative of the sample, and relatively accurate apparent mineral liberation data can be obtained for a mill product by analyzing each fraction and combining the data. Somewhat less accurate data would be obtained by analyzing a series of screened fractions that have a wider size range of particles (five Tyler size ranges).

Jan 1, 1987

By R. Venugopal, T. C. Rao, J. P. Barnwal, K. Udaya Bhaskar

The performance characteristics of a multigravity separator for the recovery of heavy minerals of lead, zinc, copper and silver from a lead rougher-flotation concentrate were studied. Factorially designed experiments were carried out on three operating variables, i.e., the amount of wash water, the drum inclination and the drum rpm, of a multigravity separator. The experiments were carried out at two levels of each variable. With the experimental data, regression equations were developed for different metal grades and recoveries. The analysis revealed that drum speed has a major influence in determining the heavy-metal grade and recovery. Drum inclination is the next most important variable, with the amount of wash water being the least important. A concentrate containing 40% lead, 9.4% zinc, 1.5% copper and 1,400ppm silver was obtained with recoveries of 74.8%, 65.9%, 64.1% and 53.2%, respectively. Finally, the predicted values of grades and recoveries at intermediate levels are compared to actual experimental data to test the validity of the equations developed.

Jan 1, 2000

By D. Limpitlaw, E. M. Hoadley

The minerals sector plays a significant role in the development of many Southern African economies. In the Southern Africa region, as in other developing regions, economic development is seen as the key contributor to poverty alleviation and social upliftment. The significant economic contribution of the minerals sector may be reduced by negative impacts on the biophysical environment and on the communities where mines operate. A critical variable in determining the net contribution of mining companies to SD is the degree of transparency with which the companies operate. Transparency is increasingly emphasised as an essential aspect of good governance and SD, but it is also difficult to establish, and is a sensitive issue for mining companies as they compete with each other for minerals sales. Transparent reporting could ensure that the interests of all stakeholders are addressed as company data is subject to informal ‘auditing’ by any interested party. This paper assesses published reports of five companies over a number of years to establish whether it is possible to make an assessment of the companies’ contribution to SD.

Jan 1, 2005

By Selamet G. Ercelebi, Mahmut Yavuz

An inherent aspect of longwall mining is moving the equipment from a mined-out panel to a newly developed panel. Moving times may be reduced by detailed preplanning. A very useful tool for planning is MS Project. Using MS Project, one can efficiently plan, manage and coordinate a project from conception to conclusion. The critical path analysis identifies potential critical activities which may cause excessive time delays. Changes to the tasks on the critical path can have significant impact 0.n the completion of a project. Assigning additional resources to these tasks (either moving labor from other tasks to critical tasks or providing labor overtime work) may reduce the move time. Simultaneous activities are the candidates for moving the labor from an activity to another. Each time a change is made, the critical path should be recalculated. MS Project quickly recalculates schedules and lets you see how changes in one part of the project will affect the overall plan. In this fashion it is possible to minimize the longwall move time.

Jan 1, 2002

By Thomas H. Koenning, James R. Boulton

The coal mined by Cyprus at the Shoshone mine near Hanna, WY is highly susceptible to spontaneous combustion. Spontaneous heatings have occurred in the gob of several of the longwall panels and, in some cases, following roof falls. Prevention and detection methods have evolved over the years as more has been learned about the occurrences. Seal design and construction have progressed to reduce air leakage into the gob. Pressure balancing has been successful as a supplement to good workmanship in reducing leakage. Early heating detection has improved as knowledge has been gained. Prior methods of detection relied upon thermocouples detecting a temperature change. Later a gas chromatograph was used to analyze gob gas samples. Initially the products of combustion (POC) were relied upon for detection. Most recently, lack of oxygen depletion in the gob has been used as an early warning of problems. Examples are presented to illustrate the evolution of spontaneous combustion control at the Cyprus Shoshone coal mine. Methods have been developed which minimize the oxygen concentration in the gob and reduce the potential for spontaneous combustion.

Jan 1, 1997

By M. Niinae, Y. Nakahiro, T. Wakamatsu

In some cases, the extraction and separation efficiency of metals with a combined extractant are better than those with either extractant alone. However, the extraction and separation efficiency of metals with a combined extractant are not always better than those with either extractant alone. As part of the fundamental studies on the extraction and separation of metals with combined extractants, the extraction and separation efficiency of Au and Fe(III) added as an oxidizer in the leaching of Au from a sulphuric acid solution containing thiourea, and the extraction and separation efficiency of Nd and Sm from hydrochloric acid and sulphuric acid solutions were examined. The combined extractants for Au and Fe(III) were di(2-ethylhexyl) phosphosphoric acid (D2EHPA)/tri-n-butyl phosphate (TBP), D2EHPA/trioctyl phosphine oxide (TOPO). tri-n-octylamine (TOA)/TBP and TOA/TOPO, and those for Nd and Sm were D2EHPA/TOA. D2EHPA/TOPO. 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHPNA)/TOA and EHPNA/TOPO

Jan 1, 1994

By Joseph B. Alberts, David D. DiPonio, Francis B. Manning

From 1996 to 2001, Wayne County and 13 suburban Detroit communities constructed the Downriver Regional Storage and Transport System (DRSTS) to improve area water quality, protect public health and alleviate basement flooding. The project consisted of a 10-mile long storage and transport tunnel, a pump station at the existing wastewater treatment plant, 9 miles of relief sewers (6 in tunnel and 3 in open cut). The work was separated into 10 contracts. Due to hydraulic design requirements and other constraints, the tunnel profile was located generally 65 feet below ground surface within a soft to medium clay strata which skimmed along the top of a very dense glacial till “hardpan” overlaying bedrock. Boulders within the tunnel bore were recognized as a significant, but indeterminate risk. This paper presents a case history of the owner’s contracting strategy for risk assumption and management of the boulder impacts on the project. Actual conditions encountered during construction and contractual adjustments made to address problems are reviewed, and recommendations for future contracts are included.

Jan 1, 2003