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By Ian Mitchell, Peter Faganl, Paul Haddad, Rob Dunne

During the gold cyanidation process, cyanide can be lost from the leachate by various chemical routes. The products of these cyanide losses include base metal cyanide complexes, thio­cyanate and cyanate. These losses are particularly important when treating pyritic or cupriferous ores since the two most sig­nificant cyanic ides, in order of importance, are sulfides and cop­per bearing minerals (I). Cyanidation of pyritic minerals results in the formation of thiocyanate. The problems caused by cyanide soluble copper minerals are well known to the gold processing industry and have been reviewed by several authors (e.g. 2, 3). An important consider­ation, especially with a number of more recent leaching tech­nologies, is the effect of the CN :Cu mole ratio, R, on the gold leaching kinetics. In order to efficiently leach cupriferous ores, it is important that R is maintained at a level that allows suffi­ciently rapid leaching without excessive use of cyanide. The optimum value for R in a fixed leaching system would appear to lie between 3 and 4. This is based on the early observations that the leaching rate is very slow when R is below 3, with a rapid increase in the leaching rate above 3 (2, 3,4). The leaching rate increases gradually when R is greater than 4 (4). The major Cu(I)-cyanide complex in this range of R values is the [Cu(CN)J]2· species. It has been postulated that leaching occurs due to either uncomplexed cyanide or the fourth ligand in [Cu(CN)4]3·, since the stepwise formation constant for this complex is very small (2, 3). An additional consideration when leaching cupriferous ores is the oxidation of cyanide by Cu(II) minerals, resulting in the formation of cyanate. It has also been reported that both sulfide minerals (5) and activated carbon (6, 7) catalyse the oxidation of cyanide to cyanate. From the above discussion, it is important for the leaching con­ditions to be carefully controlled when treating pyritic and cuprifer­ous ores in order to achieve efficient and economically viable leach­ing. For example, large concentrations of thiocyanate in the leachate would reveal large cyanide losses and thus indicate the need for a pretreatment step to oxidize the sulfides. Alternatively, a low R value would indicate slow leaching kinetics and consequent low gold recoveries, indicating the need for increased cyanide dosage.

Jan 1, 1996

By M. Robb, S. J. Bate, M. Boisvert

The never-ending quest for gold-bearing ore deposits is a primary industry in Canada, employing people of widely differing expertise. The exploration models for gold deposits are generally geologically complex and the targets have relatively small cross-sectional areas. These problems are compounded in Canada by the minimal outcrop exposure in most mineral provinces and the high percentage of water-covered areas. Naturally the chances of successfully delineating an economic gold deposit are very much greater if all parties involved can act as a team of explorationists constantly confemng amongst themselves particularly as the applicable disciplines generally overlap and complement each other. Three case histories (see Figure 1) are presented to illustrate this philosophy with emphasis placed on the role of the geophysicist in translating the exploration model as defined by the geologist into physically measurable parameters and identifying target areas with similar characteristics. The Conwest-Miminiska property in Ontario is a grassroots exploration play. Additional ore reserves needed to be delineated on the Salmita property in the Northwest Territories. At Laura Lake, near Chapais, Quebec geophysical methods were employed to trace thin high-grade mineral intersections under deep overburden and severe cultural interference.

Jan 1, 1989

By J G. Dunn, S M. Thurgate, A C. Chamberlain, P Franzmann, M Jeffrey, L J. Warren, G E. Poinen, T Williams

Gold has always fascinated mankind. From Tutankhamen's mask to the huge nuggets that have been found in the Australian outback, gold has quickened the pulse and fevered the eye. But in recent years, governments around the western world have shown a singular lack of interest in research into gold processing, with many programs being cut. There are some notable exceptions, fortunately, and this paper summarizes a large research effort that is well supported by the Australian government and the Australian gold industry. The AJ Parker Cooperative Research Centre for Hydrometallurgy is an unincorporated joint venture between the CSIRO Division of Minerals, Murdoch University, Curtin University of Technology and the Western Australian Department of Minerals and Energy. The Australian Mineral Industry Research Association (AMIRA) is the Parker Centre's broker for generic R&D contracts with industry. Each of the partners makes available staff, students and equipment to further the work of the Parker Centre, and the Australian Government provides additional funding. The Parker Centre is nearly five years old and has grown spectacularly in that time. There are now about 30 full-time-equivalents of effort from 50 scientists and engineers, as well as about 40 postgraduate and honours students. The fundamentals of the key operations in hydrometallurgy are studied in three programs: leaching (which includes pretreatment by roasting etc), precipitation (or crystallisation), and surface processes (which includes solid/liquid separation, adsorption, solvent extraction, etc). A large part of the Parker Centre's R&D is directed towards gold processing technology. In Australia, a dramatic increase in gold production, from about 30 to nearly 300 tonnes per year (1977-1997), has been made possible largely as a result of a brilliant metallurgical innovation, the carbon-in-pulp process. However, falling head grades eg 2.56 to 1.84 g(Au)/t over the last 10 years, and environmental concerns, are squeezing profit margins. There is increasing pressure to reduce costs, and the Parker Centre program is focussed on providing the scientific understanding required to do this. A selection of research highlights will be given, to indicate the depth and breadth of the R&D at the Parker Centre.

Jan 1, 1997

By D. Vavadakis

Abandoned bauxite surface mines in the Parnassos area may be rehabilitated using bauxite residues as filler. The objective of this study was to estimate the percentage of precipitation that may infiltrate through the bauxite residues to the lower geological formations when they are disposed off in mine open pits. Two scenarios were investigated simulating: a) available field tests, and b) a demonstration test that was planned to be performed in an abandoned open pit close to the Aluminium of Greece plant. It was indicated that the annual infiltration from bauxite residues disposed off in the demonstration test for the most probable scenario is very low, equal to 13.17mm corresponding to 3.1% of the annual precipitation. Furthermore, it was estimated that the annual percolation from the field tests is approximately 4.4%, very close to the infiltration values measured in the field tests for the same period.

Jan 1, 2006

By Glenn P. Jones

Laterization of syenite and other rocks in north Alabama produced material which was picked up and carried by streams to southeast Alabama. These streams deposited the aluminum rich material in the sinkholes of a karst topography developed on the Clayton Limestone. Measurement of the bearing of the long axis of each deposit in the Screamer area, along with plotting the location of these deposits on a map, indicate a depositional pattern controlled by local fractures or solution zones in the Clayton Limestone. The sinkholes and channels dictated the original structure of the deposits. Additional structure changes have resulted since compaction of the deposits by continued solution of the underlying limestone. The original material in these deposits was enriched by the removal of silica to form bausite and bauxitic kaolin during deposition and compaction. Subsequent ground water action has reintroduced silica into the deposit leaving a core of bauxite.

Jan 1, 1972

The US Bureau of Mines' dictionary of mining terms defines productivity as "the efficiency with which economic resources (men, material, and machines) are employed to produce goods and services." Or, the relationship between the physical outputs and the physical inputs used to produce those outputs. As demand for mine materials dropped, mining companies and equipment manufacturers discovered that ratios between the inputs and the final products were disproportionate to the profits realized. Some companies are fighting for survival. The US, while still the most productive country in the world in absolute terms, is looking over its shoulder as other industrialized nations continue to exceed its yearly productive growth rate. According to John Belcher, Jr., of the American Productivity Center in Houston, TX, the US has seen a steady decrease in productivity growth since the mid-1960s. During the post World War II period, the US labor productivity growth rate was 3.2% annually. The slowdown began in 1965 and by the mid-1970s, the country's annual growth rate was 1%. By 1978, labor productivity growth ceased to gain at all and from 1978 to 1980 a 2% decline occurred. Solutions to the productivity decrease are increasing product prices or improving productivity. By increasing prices, though, the producer runs the risk of pricing himself out of the competitive market. To maintain an acceptable profit level, prices must increase proportionately higher than required to offset production cost increases, Belcher says. Many companies are turning to in-house productivity improvement programs as an answer to increased costs and declining profits. These programs are geared toward management commitment and employee awareness of what productivity means. Companies are finding ways of measuring productivity levels in financial reporting, budgeting, and planning. Organizational teams have been formed to coordinate activities and oversee product management, and improve productivity of materials and capital investments. This special issue of Mining Engineering examines productivity in the mining industry. First, there are articles about various, and different, factors that affect productivity in each of ME's five main readership areas - exploration, mining, processing, coal, and industrial minerals. There is also a look at mining industry productivity from the manufacturer's view. The next section of this special issue is devoted to some topics that affect all areas and sectors of mining: research, management practices, computers, maintenance, and energy management. Then follows case studies in exploration, coal, and iron and steel. These studies provide examples of practices and strategies used by companies and operations to boost productivity.

Jan 11, 1983

Semiautogenous (SAG) ball mills are being increasingly used today for the coarse grinding of a range of ores, including gold, copper and iron. Larger mines are demanding mills with larger throughputs. This has led to some remarkable developments in mill diameters and installed powers. Conventional design principles - mills with trunnion bearings - have reached their limitations. This article describes one SAG mill with a slide-shoe arrangement and Krupp Polysius' Combiflex twin drive. In August 1997, the world's largest SAG mill with a slide-shoe arrangement was commissioned in Queensland, Australia, operating as a wet mill. The inside diameter is 10.4 x 5.1 m (34 x 17 ft) effective grinding length. The 1.36-ktlh (1,500-stph) SAG mill is driven by two Combiflex drives (twin drives with 2 x 5,500-MW or 7,375-hp installed motor power) in conjunction with a girth gear (outside diameter 11,890 mm or 468 in.). Commissioning of the SAG mill was completed with no notable technical difficulties. The plant runs continuously except for planned maintenance stoppages and process-specific reasons. As this article is written, the machine has been in operation for about 8,000 hours without major problems.

Jan 1, 1998

By Michael S. Kucker, Robert A. Robinson, Harvey W. Parker

Ground deformations are of major concern during tunneling, especially in downtown environments, since they have a significant impact on the costs and practicality of tunneling. This case history describes soil and groundwater conditions and ground behavior during the construction of twin transit tunnels for the Downtown Seattle Transit Project (DSTP). The tunnels were excavated through complex glacial soils ranging from hard glaciomarine drift to flowing sand. The tunneling process was greatly facilitated by the prediction of soil layer positions to an accuracy of ±0.6 m (2 ft). Tunneling was complicated by the presence of over 500 temporary tiebacks and by disturbed ground overlying an operating railroad tunnel. A variety of ground improvement techniques were used to successfully minimize settlements, which ranged from 1 cm (0.4 in.) in glaciomarine drift to 6 cm (2.4 in.) in flowing sands. Ground improvement techniques included compaction grouting, chemical grouting, jet grouting, and eductor well systems.

Jan 1, 1991

By K. Ohga, V. J. Hucka

The presence of methane gas in mines creates hazards of explosions, fire and suffocation. Under certain conditions the occurrence of methane also poses a danger of gas and coal outbursts. Consequently, prevention of gas and coal outbursts in coal mines requires a sound knowledge of methane gas occurrence in mine workings. However, the direct method of determining methane content of coals developed by the U.S. Bureau of Mines is time and labor consuming for measurement, a new transportable methane tester was developed for Japanese coal mines. The instrument automatically measures emission gas from coal samples in the underground and also records and stores the data. Back on the surface, the tester can be connected via a RS 232 port to a PC computer for methane content estimation. Details of this technique are described here. Results on methane content determined in Japanese and U.S. western coal seams are discussed, as well.

Jan 1, 1991

By Craig Cina

Transporting goods from producers to consumers is a fundamental part of the US economy. The demand for transportation closely reflects the economic health and well-being of the nation's industrial, commercial, and agricultural sectors. The inland waterway barge industry has traditionally played a key role in transporting needed commodities to industries on an economical basis. Barges account for 10% of the domestic intercity tonnage carried by all transportation modes. Water carriers operating on inland waterways hauled more than 450 Mt (500 million st) of cargo in 1980-up from 428 Mt (472 million st) in 1970. Inland Waterway Shipments Metallic and nonmetallic minerals comprise one of the largest commodity groups moved on inland waterways. As illustrated in Table 1, metallic and nonmetallic mineral shipments accounted for more than 69 Mt (77 million st), or nearly 15% of all commodities shipped in 1980. Putting this tonnage in perspective, coal and petroleum represent the two largest commodities moved on inland waterways. In 1980, petroleum and petroleum products accounted for 138 Mt (152 million st), or 28% of all commodities shipped. Similarly, coal represented 120 Mt (132 million st), or 25% or all commodities shipped. Even though shipments of metallic and nonmetallic minerals are smaller than coal and petroleum, they still account for a sizeable portion transported. The inland barge industry moves a variety of metallic and nonmetallic minerals ranging from manganese ores to building cement. Minerals transported by barge include: • iron, copper, bauxite, and manganese ores for metal production; • lime and limestone for construction and electric utility scrubbers; • phosphate rock, natural fertilizers, and gypsum for agricultural needs; • sand, gravel and crushed rock, clay, asphalt, tar, and pitches, and building cement for construction purposes; and • a host of other minerals to meet industrial needs. A few mineral commodities are responsible for a large proportion of waterborne mineral shipments.

Jan 10, 1982

By Viggo C. Bertelsen, David G. Hammond

LOCATION AND EXTENT OF BART TUNNELS The San Francisco Bay Area Rapid Transit District (BART) during the past six years has become the Owner of 23.5 miles of single-bore tunnels. The tunneling experience gained while working closely with our Engineer and Contractors in the design and construction of these major transit facilities provides a basis for our "Owners" viewpoint. The 23.5 miles of tunnels are divided into two categories. Fifteen and one-half (15-1/2) miles of tunnels were constructed in soft ground underlaying the downtown areas of San Francisco, Oakland and Berkeley. Eight (8) miles of tunnels were built in "hard ground" in the hills separating Oakland and Berkeley from Contra Costa County and in the San Francisco hills on the Mission Line. Location of tunnels within the BART system are shown on Figure 1. The tunnels comprise 15.7% of BART's 75-mile dual track system. Their 176 million dollar costs (excluding rail, electrification or ventilation features) are 12.4% of the system's total estimated cost of $1.4 billion. The tunnels constructed in soft ground were shield and boring machine driven with ground support provided by steel liner rings. The exterior diameter is 17 foot, 6 inches in the majority of tunnels; however, on two tunnels with a 500 foot radius of curvature, the diameter was 18 feet. BART awarded 14 contracts for soft ground tunneling. The work was accomplished under free air or compressed air depending upon the ground water and soil conditions, safety requirements, and considerations for protecting adjoining property from damage either from the de-watering operations or settlements due to excavation. The tunnel bores, except on curves, were normally parallel being spaced at 32 foot centers on the Mission

Jan 1, 1997

By Liuhuai Ding

Background of Ocean Mining Research Inspired by the 1970?s deep seabed mining activities of other nations, China started ocean mining research work within the framework of the International Law of the Sea Treaty (UNCLOS) and the subsequent establishment of the International Seabed Authority in the 1990?s. This work has been carried out mainly with the cooperation of the Changsha Research Institute of Mining And Metallurgy. We have been committed to this work to fulfill our responsibilities and obligations as a Pioneer investor under UNCLOS and also to support the much needed development of deep-sea technology in China. Exciting recent advances by Nautilus Minerals in the development of seafloor massive sulfide deposit exploitation has led us to a new perspective of ocean mining and some re-evaluation of ocean mining economics. This has provided us with an opportunity to support more efforts in ocean mining research. We will not delay the development of our ocean mining system and corresponding technology, although commercial mining in the deep-sea area may not occur for many years.

Jan 1, 2008

By Steve Kral

The power industry throughout the world is in the midst of a significant transition that will result in a major restructuring. Deregulation of utilities in the United States is continuing, resulting in increased competition among power providers. The traditional ways that electric power is globally bought, sold and delivered will also change. However, according to the Department of Energy's (DOE) Pat Godley, one thing is clear: "Those who provide the power during the 21 st century will be those who are willing to change - those who are willing to accept new ways of doing business and willing to employ new technologies." Godley is assistant secretary of fossil energy with DOE. Her comments came during the opening remarks at the Fourth Annual Clean Coal Technology Conference, held in Denver, CO, Sept. 5-8, 1995. The conference was sponsored by DOE and the Center of Energy and Economic Development. Under the theme "Global Opportunity," more than 300 coal and utility executives spent three days discussing the new face of the electric-power industry throughout the world and the new, mostly clean coal technologies (CCT) that will be available to power providers.

Jan 1, 1995

By Sibley C. Burnett

Early attempts to apply superconductivity to the beneficiation of kaolin required very large refrigerators to remove the heat generated during rapid charging and discharging of the magnet. In the early 1990's, Advanced Cryo Magnetics, Inc. developed and patented methods to reduce this pulsed heating by a factor of fifteen. Small, helium refrigerators and cryo-coolers are now used. Along with savings in electric power, superconductivity allows operation at higher magnetic fields and greatly improves separation process efficiency. New designs offer enormous reductions in weight, size and capital cost as compared to older copper magnets. Application of this technology to minerals other than kaolin is emerging.

Jan 1, 1999

By Mark W. DeLawyer

The base of the stone quarry still stands today, as imposing as any Mavan temple or Egyptian pyramid. For 80 years it has been a reminder to those who must sweat to earn a wage. There are no plaques to indicate its impressive history. Rather, it stands as a towering monument to the masons and stone cutters who built it-a testimony in stone to that most demanding and back-breaking of industries. Take your imagination back to the limestone quarries at Split Rock, near Syracuse, NY. The sound of an occasional steam drill and the mighty roar of a dynamite explosion herald progress. The ring and crash of a hundred sledge hammers are music in the calloused hands of the quarry men. It is a symphony of man against nature. Hundreds of sweat-soaked men break up the blue Onondaga limestone for the "sodi ash," the popular name for the quarry owner, the Solvay Process Co. Nearby, expert stone masons fit mammoth 454-kg (1,000-1b) blocks of cut stone into place, building the foundation for what may have been, back in 1902, the world's largest stone crusher. Consider for a moment, a modern stone quarry. The business is now essentially one of machine against nature. The shovels, drills, conveyors, and locomotives help make the quarry of today a profitable venture. Now consider the quarry of the early 20th Century. Anyway you look at it, a tougher, more demanding life would be difficult to imagine-12 hours a day, all kinds of weather, breaking up tons of rock that had been drilled, blasted, or pounded from the bowels of an uncooperative earth. Before proceeding, it might be prudent to briefly describe the history of the Split Rock quarries. Before the purchase of the quarry lands by the fledgling Solvay Process Co. in 1889, the quarries already had a reputation literally chiseled in stone. Most of the municipal buildings in Syracuse were made of it, as well as over half of the Erie Canal, including the engineering marvel of the time, the Montezuma Aqueduct. This was where the Canal passed not only through, but in some

Jan 11, 1982

By E. R. Slatick

The northern and central Appalachian coal basin in the eastern United States has been the source of about two-thirds of the nation's coal output during the 20th century. This region includes parts of Pennsylvania, Ohio, Maryland, West Virginia, Virginia and eastern Kentucky. It covers about 130,000 km2 (50,000 sq miles) of the Appalachian coal basin and ranks as one of the world's most important coal production regions (Fig. 1). The coal industry's heyday in northern and central Appalachia has passed. This was due to competition from other fuels and low-sulfur coal produced in the West and because of the declining use of coking coal for steelmaking. Nevertheless, the region still plays a vital role in US coal production. It currently produces about 40% by weight of the nation's coal (its share is about one-half when measured by the energy content of the coal), contributes substantially to electricity generation and serves as the mainstay of US coal exports.

Jan 1, 1995

By Mark A. White

Surface mining of multiple seams by mountaintop removal and contour mining is complex in Appalachia. Arch of West Virginia, a division of Apogee Coal, has made its operations state-of-the-art to cope with this challenge. Arch of West Virginia moved into the heart of coal mining in Appalachia when Arch Mineral acquired coal reserves and coal operations in the southern West Virginia counties of Logan and Wyoming. These reserves were initially developed at the turn of the century as underground operations. Today, though, they are mined using mountaintop removal and contour mining. The steep slopes in the mountains of Appalachia generated a method of mining referred to as contour mining. During the late 1960s and early 1970s, contour mining was introduced at these operations using front-end loaders with bucket capacities of more than 7 m3 (10 cu yd) that could load 45-t (50-ton) end-dump trucks.

Jan 1, 1995

By M. Makarenko

The sandstone type Devladivske uranium deposit is located within the limits of Eocene pale-ovalley filled with alluvial sediments. Mineralization with uranium content up to 0.1% forms several ore beds divided by redox barriers. In the period 1962-1983 the deposit has been exploited over an area of 918000m2 by in situ leaching (ISL) using drillholes with a depth between 35 and 100m. During mining operation about 200,000 t of H2SO4, 6,300 t of HNO3, and 15,000 t of NH4NO3, have been pumped in the ore body. In 1983, the groundwater pollution aureole had a length of 4.5 km and a width of 400-600 m. There is a hydraulic connection between the uranium-bearing aquifer and both the upper and lower ones. The technological solutions used for ISL caused partial contamination of these horizons. After mining completion, dilution of the residual technological solutions with "pure" natural waters took place through gaps in impermeable sediments between aquifer horizons. Calculation of self-purification process kinetics shows that the sulfate ion pollution aureole will disappear approximately after 120-150 years at a distance up to 2.0-2.5 km from the western margin of the deposit. This means that there is no risk for contamination of the river Saksagan? that flows at a distance of 17km from the deposit.

Jan 1, 2005

By Pieter Barendsen, Olivier Dubugnon

INTRODUCTION There are three fronts on which development efforts are being concentrated to extend the application domain of Tunnel Boring Machines (TBM), which is potentially very large - Assessment of a reliable prediction method, including machine-rock interaction and geological characterisation, so that the boring system can be designed properly and the costs remain in the predicted range for each given tunnel project. - Development of lighter, more flexible and more controllable machines to be applied in shorter, deeper tunnels or roadways, such as required in mining. - Reduction of cutter and machine costs when excavating hard rocks or difficult grounds, in developing improved tool materials, cutting geometries and tunnelling systems. The above three lines of development have a common, critical requirement: to have a reliable set of design rules to optimize the machine specifications from the knowledge of rock and geological parameters and working requirements. This optimization can only be done if a model sufficiently sophisticated is made available, able to take into account the numerous factors influencing the TBM advance , and being interactive enough to achieve the optimization.

Jan 1, 1985

By A. L. Putz, G. Ladouceur, A. R. Laplante

A laboratory centrifugal concentrator was used to evaluate two gravity circuit configurations treating a flash flotation concentrate at a Canadian gold mill. The Initial circuit consisted of a 76 cm (30 Inch) plant Knelson Concentrator (PKC) for coarse gold removal. Later, a hydroseparator and spiral were Installed, with the hydroseparator underflow feeding the spiral and the spiral tailings plus hydroseparator overfiow reporting to a 51 cm (20 Inch) PKC. Gold recovery In the 76 cm PKC averaged 45%. Gold was recovered consistently In all size fractions greater than 38 µm, where recovery dropped to 22% for the -38 µm material. Changing the circuit to Include the hydroseparator and spiral decreased the Knelson unit recovery to less than 17%. The decrease was attributed to the spiral which recovered much of the free gold ahead of the Knelson and to changes In the mill feed (free gold portions were finer and less abundant). The spiral demonstrated erratic behaviour although It still recovered significant coarse gold (+75 µm) yielding unit recoveries of 18-44%. Although mechanical difficulties were experienced with the 76 cm PKC, Its performance was superior to that of the hydroseparator, spiral and 51 cm PKC configuration. Much of the gold In the ball mill recirculating load was found to be too coarse for significant recovery In the flash flotation cell and should be recovered by gravity from the cyclone underflow or ball mill discharge. The LKC proved to be a successful device to evaluate gravity recoverable gold content. Dilution of test samples with silica further enhanced this methodology.

Jan 1, 1993