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By Gregory Owen Lewis

The use of gravity concentration as a means of recovering the 'free' gold component from alluvial and milled ore products is widely used and is receiving increasing attention, particularly with the introduction of the centrifugal-type concentrating units. Because of ever-increasing mining and processing costs and a decline in the gold price, it has become important that the recov­ery efficiency from concentrates is improved so as to increase the yield of bankable gold from this primary recovery step. This paper outlines an alternative hydrometallurgical approach aimed at achieving overall gold recoveries in excess of 98%, together with the elimination of any secondary residue streams which, in the case of conventional treatment methods, require re-processing. An adaptation to the Minataur™ Process technology is being applied with the proposed method, incorpo­rating the pre-treatment of the concentrate, oxidative leaching of the pre-treatment residue, followed by precipitation of a high­purity gold. This route is seen to have application in all scales of operation. Selected results from laboratory-scale testwork are presented to highlight the discussion.

Jan 1, 1998

By X. M. Yuan

In the flotation of Zn-Pb ores, sphalerite is floated following copper sulfide activation. In this type of sulfide ore, pyrite is commonly treated as a gangue, and poor selectivity between sphalerite and pyrite/quartz is often reported. But pyrite may also appear in association with gold, and flotation of such auriferous sulfides is of great importance in many countries (e.g. South Africa, Australia). In the cationic flotation of sulfide ores with dodecyl amine, sphalerite can be floated while depressing quartz and pyrite. While in a well-aerated pulp in the presence of lime (especially after oxidation with H2O2) the cationic flotation of pyrite is depressed, oxidation of pyrite in the presence of Na2S makes it floatable with amines even in very alkaline environment.

Jan 1, 2002

By Claus Becker

The new, 2.600 m long pipe under the river Elbe in Hamburg/Germany required for 2 traffic lanes, emergency lane and space for utilities a boring diameter of 14,20 m(46,6 ft). According the geology (glacial deposits consisting of clay, sand and marl, all containing big boulders) a Slurry-Shield with crusher was selected. With a minimum cover of 7 m and a maximum pressure of 5,6 bar extensive ground treatment was necessary to make the drive feasible. The machine contains a lot of new developments. The drive was finished in spring 2000 so all experiences can be reported. A special risk sharing contract avoided completely litigation.

Jan 1, 2001

By E. Medina, W. Callupe, R. Sharon

Slope stability in Barrick’s Pierina Mine open pit is significantly influenced by the structural geology, the variably argillized rock mass, and locally by perched groundwater. Development of an extensive surface water diversion network continues at Pierina, which is necessary to minimize highwall and adjacent natural landslide movement and erosion during the wet season. Slope movements are effectively monitored using optical survey methods, strobe light extensometers, gap monitors, and piezometers. The slope stability program at Pierina is focused on improving the understanding of the stability mechanisms in order to ensure continuous safe operating conditions. Priorities are placed on developing an accurate detailed engineering geological model, enhancing groundwater depressurization, and optimizing highwall controlled blasting procedures.

Jan 1, 2003

By Brian H. Zelenko, Patricia M. Perry

INTRODUCTION The environmental requirements of the next section of Washington, D.C. METRO subway tunnels present unique challenges to the Contractor. The 14th Street Tunnels contract includes twin 975 m (3200 linear ft) soft ground tunnels. A stringent environmental soil and groundwater monitoring and free product recovery program was specified by the owner. A project-wide dewatering program hinges on satisfactory completion of the environmental requirements. Implementation of the Contractor's environmental program is discussed, including the pros and cons of the program, as they relate to progress of the project. Environmental issues on tunneling projects have become an important part of the urban tunnel construction process. Delays associated with environmental issues can have a major cost impact on tunneling projects. This paper will discuss the first of five Washington Metropolitan Area Transit Authority (WMATA) tunnel and station contracts awarded in 1994. These contracts are part of WMATA's Fast Track Plan to complete the original 166 km (103 mile) system by 2001. As such, stringent environmental requirements have been specified as a part of these contracts to limit delays associated with local regulators in order that the tunnels may be constructed on schedule.

Jan 1, 1995

By M. Ericsson

The extractive industries consist of five major sectors: - Mining equipment and services - Dimensional stone - Industrial minerals - Aggregates - Metal mining These industries produce some finished goods but mostly semi-finished products as they feed into other industrial sectors: Basic metals, fabricated metals, construction, chemicals, dyes and pigments, inorganic chemicals, fertilizers, rubber and plastics and non-metallic mineral products. These are the major down-stream industries in this study. Taken together with the extractive industries they form the mineral resource based cluster. The mineral resource based cluster is a substantial part of the Finnish economy: It employs 211 000 persons, 39% of the number of employees in industry. The cluster?s exports account for 20% of industry exports. Value added is 34% of total value added in industry. Investments reach 35% of total industry investments.

Jan 1, 2003

By Charles Ronkos, Jeffrey Edwards, Brian Brodsky

The Marlin gold-silver deposit is in western Guatemala, 15 kilometers south of a major transform fault that separates the North American and Caribbean plates. A district-scale, northwest-trending graben controlled deposition of a greater than 1200 meter thick upper Tertiary quartz latite to rhyolite volcaniclastic sequence. These volcanics were subsequently intruded and unconformably overlain by a small intermediate, latite to andesite, volcanic complex. Classic low-sulfidation, quartz-calcite-adularia veins and stockwork formed a 2.2 million ounce gold deposit, in association with late-stage andesite dike swarms, along a west-northwest striking normal fault on the eastern flank of the volcanic complex.

Jan 1, 2005

By Rolando V. Cuaño

For geostatistical applications, heterogeneous spatial phenomena are better modeled as mixtures of populations. However, the modeling of the constituent populations can become complex. The alternative mixture model offers a simplified approach to the w modeling problem. The model is applied and tested on the Walker Lake data set. Compared to the univariate ordinary kriging model, the alternative model generates less biased block estimates.

Jan 1, 1996

By Raphael Mourad, Colin R. Phillips

Fluorescence, radioluminescence, phosphorescence and thermoluminescence in TLD 100 and 700 are discussed and compared. The energy budget in thermoluminescent material is presented in general terms. Results of measurements of radioluminescence, phosphorescence and thermoluminescence in LiF:Mg irradiated with [a] radiation, using simple facilities, are presented. The calculated energy budget in the exposed chips using [a] radiation is compared to published data using [y] irradiation.

Jan 1, 1981

By M. A. Candia

Stability analyses were performed on the La Libertad, Nicaragua existing tailings embankment in order to determine the conditions for the minimum buttressing required for stability of the dam as a short term measure. Two critical sections, shown in Figure 1, were investigated under static, drained and undrained conditions for existing and modified geometries. The existing geometries reflect the "as built" topography of the dam, and the modified geometries reflect the implementation of a toe berm to buttress the slope. For these geometries drained and undrained conditions as well as different elevations of the toe berm were evaluated against a factor of safety.

Jan 1, 1996

By K. N. Han, P. B. Queneau, Bruce W. Cavender

Measures of metallurgical performance, such as recovery rates or mass balances, are frequently based on point estimates of operating conditions in the system of interest. Because the processes being measured are dynamic, a range of uncertainty accompanies each measurement; this uncertainty is reflected in the accuracy with which the calculated result describes the true metallurgical performance. In stochastic modeling, a range of probable values is used in place of a point estimate to describe each variable. The calculated result takes the form of a distribution, delineating both the magnitude and probability of potential outcomes.

Jan 1, 1993

By L. J. Drew

The plate tectonic setting, regional geology, and certain aspects of the economic geology of the iron-rare-earth-nio-bium ore bodies at Bayan Obo, Inner Mongolia, China, were studied by a team of geologists from the Tianjin Geologic Research Academy and the U.s. Geological Survey between 1987 and 1989. These ore bodies were formed by hydrothermal replacement of Middle Proterozoic dolomite in an intracontinental rift setting. A variety of veins and/or dikes that have a carbonatite-like mineralogy cut the footwall clastic rocks and migmatites. A stockwork of veins occurs at several locations in the footwall. The hanging wall is a shale that has been converted to a K-metasomatite and has microcrystalline potassium feldspar as its principal constituent. This shale served as a sealing caprock that contained the chemical solutions that reacted with the dolomite and that created the enormous concentration of mineralized rock in an 18-kilometer-long syncline. The rocks that host these ore bodies and the associated mineralized areas occur today as roof pendants in granitoid rocks of Pennian age that were emplaced during a continent-to-continent collision during that period.

Jan 1, 1991

In September, a fleet of 363-t (400-st) Liebherr trucks became operational in Brazil and have already begun moving iron ore in Para state. Prior to the arrival of the the trucks the Brazilian fleet relied on trucks up to 218 t (240 st). With the addition of the 363 t (400 st) trucks, the fleet has since experienced the high productivity offered by Liebherr T 282 B trucks.

Jan 1, 2010

By J. Loredo

The region of Asturias, located in the northwest of Spain, has an extensive mining history; coal, gold, zinc, lead, copper, cobalt, mercury, iron, manganese, fluorspar and others have been extracted from the antiquity. In the Asturian Central Coal Basin, the closure of all open pit coal mines and their restoration, the progressive closure of underground coal mines that is happening from the 1980?s, and the restoration of spoil heaps, provides post mining lands for alternative uses. In relation to metallic mining, the abandonment of all mercury mines without restoration in the 1970´s, has left significant quantities of wastes and mining works. More than thirty years later most of them remain without restoration. In these sites the legacy of the historical mining activities is apparent in the form of shafts, galleries and transversals, old mining installations and spoil heaps. Mine wastes have eventually become important Hg and As pollution sources, resulting in a widespread contamination of the surrounding soils and surface waters. Abandoned mines of other metals such as copper, cobalt, iron, etc. and industrial minerals such as fluorspar, have also left a mining legacy to take into consideration. In this context of declining mining areas, some remedial options have been applied to specific areas resulting in alternative uses as pastures, agro-forestry, industry and socio-cultural activities.

Jan 1, 2008

By J. D. Miller, P. L. Sibrell

The nature of surface sites for the adsorption of gold from alkaline cyanide solutions has been investigated using samples of synthetic, highly-oriented pyrolytic graphite (HOPG). This HOPG material offers an idealized graphite structure enabling the independent study of the graphitic basal-plane sites and the edges, or defect sites, of the graphitic planes. Radiochemical and X-ray photoelectron spectroscopic experiments independently demonstrated that gold adsorption was much higher on the edges (defects) of the graphite planes than on the planes themselves. These results suggest that site-specific adsorption is prevalent in the adsorption of gold by graphitic carbons (including activated carbon, carbon black and graphite) and that most of the favored sites are at edge defects in the graphite crystal structure.

Jan 1, 1993

By J. S. Long

A finite-difference model using a digital computer was constructed to assist in the water management of a proposed oil-shale mining operation in the Piceance Basin in Colorado. The presence of ground water is both a detriment and a benefit for development of the resource. On one hand, dewatering is required because permeable zones are present in and above the oil-shale sequence, and rich oil shale at the proposed mine is as much as 457 m (1500 ft) below the water table. On the other hand, ground water is the most feasible source of water for processing the oil shale. A ground- water model was constructed to simulate the development of an environmentally acceptable water-management system that will satisfy both the mine-dewatering requirements and the water-supply requirements for processing. The ground-water model discussed in this chapter was constructed for the Rio Blanco Oil Shale Co. (RBOSC) by International Engineering Co., Inc., a subsidiary of Morrison-Knudsen Co. The model was applied to evaluate dewatering and water control systems for several open-pit mining plans initially investigated to develop Federal Lease Tract C-a. A collateral application of the model analyses was to project effects of the proposed dewatering operation on the regional ground-water regime in connection with a permit acquisition program by RBOSC. Subsequently, RBOSC has completely changed its mine development plan and has adopted modeling and related techniques more suitable for study of that plan and dewatering operation. The authors of this chapter are solely responsible for the contents and conclusions.

Jan 1, 1979

An insufficient hydrologic data base exists for most large and small coal basins in Alaska owing to the lack of need in the past to collect data. The runoff process is insufficiently understood which is complicated by specifically northern phenomenon, and the lack of understanding of hydrologic relationships in permafrost environment. This paper presents an understanding of the hydrologic effects of frozen ground and presents methods by which the influence of surface mining upon the hydrologic balance can be analyzed.

Jan 1, 1988

By Jouko Suominen

The basic development of various mining equipment has been strongly influenced by two objectives; improving economic results and safety aspects. Both of these factors contribute to increased requirements of mechanization and automation in different parts of mining processes. When we are limiting the discussion the crushing circuits, automation has two dimensions, one being the component automation, or intelligence, the other being automation of complete processes. Both of these subjects are closely tied up, the former being a condition for the latter. The key technologies of crushing automation are transducers, programmable logics and computer software. Also equipment technology continually faces new challenges, which result even in totally new product families. One example of this kind of development area the track-mounted, integrated crushing systems, where design criteria have been simple control, unmanned operation, and flexibility in changing requirements. This crushing system, or philosophy, offers excellent possibilities for new concepts in various underground and open pit applications, connected with automatic process control. Following presentation is a summary of aspects, of haw a crusher manufac¬turer sees the development of automa¬tion as an integral part of equipment technology and development.

Jan 1, 1989

By L. S. Jen

The seven most important base and precious metals produced in Canada are copper, nickel, lead, zinc, molybdenum, gold and silver. Because much of Canada's mineral production is exported in the form of concentrates, it is of special interest to keep track of the production of these various concentrates and the capacity utilization of the concentrators producing them. Annual data surveys on individual concentrators, coupled with the interactive capabilities of the computerized mineral product ion system through a custom-tailored, fairly low-cost computer system configuration are used for ongoing monitoring. Rapid analysis of concentrator production can be carried out on a disaggregated basis that allows policymakers to see specific reasons for significant changes over the years.

Jan 1, 1986

By Ralph P. Hackl

Biooxidation processes for treating arsenical and other types of refractory gold ores are touted by many as being simple, inexpensive and environmentally friendly. One of the advantages claimed by proponents of biooxidation is that arsenic is disposed of as insoluble ferric arsenate which is suitable for long term disposal in tailings ponds. However, there is considerable controversy as to the stability of ferric arsenate with respect to re-dissolution of arsenic. In particular, there is concern that the amorphous ferric arsenate produced at low temperature is not stable, especially at the alkaline pH's required for cyanidation. There is a general lack of published information on the stability of arsenical bioleach tailings. Past work on ferric arsenate stability has usually involved purely chemical systems and the use of synthetically prepared precipitates. Upon completing the Salmita bioleach pilot plant campaign (Hackl and Wright, 1989) the author had the opportunity to test the stability of the arsenical bioleach/cyanide tailings which were produced. This paper summarizes the results of that work.

Jan 1, 1990