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By G. L. Oldright, F. S. Wartman

"In the process of smelting copper ores and secondaries in the reverberatory furnace to produce a copper matte and a slag low enough in copper content to be discarded on the dump, it is essential to the best functioning of the process that most of the iron in the material charged into the furnace be at the end in the form of sulphide in the matte or ferrous oxide in the slag. Ferric oxide and magnetite present in the charged material should be reduced to ferrous sulphide or oxide. Ferric oxide offers no difficulty in reduction, at least to the magnetite stage, because it reacts very readily with sulphides at quite low temperatures. Magnetite is less reactive and consequently more resistant to slagging, so that the furnace man must take advantage of all factors favoring its reduction in order to prevent accumulations in the furnace.In order to determine these factors more definitely, the Bureau of Mines in cooperation with the Department of Metallurgy, University of Arizona, has undertaken at the Southwest Experiment Station an investigation of the effect of various factors upon the rate of reduction of magnetite by ferrous sulphide. A previous paper's reported the nature of the reactions taking place and the effect of various physical factors when only pure sulphide and oxide were present. Since in the actual smelting operation, many other substances are also present, it seemed desirable to make a study of the effect of their presence upon the rate of reduction of magnetite by ferrous sulphide. Such a study has been made; the work done and the results obtained are described herewith.As will be shown later, it has been found that of the substances usually present in the smelting charge, silica and magnesia accelerate, whereas lime, alumina, and cuprous sulphide hinder the reduction of magnetite by ferrous sulphide.No report of a previous laboratory investigation of this subject has been found. Almost all furnace operators have made at one time or another at least qualitative ccmparisons of the effect of various changes in operating oonditions upon the behavior of magnetite in the furnace, but the conclusions derived from the experiments have never been published."

Mar 1, 1931

By Doug Anderson

Blast vibration seismograms are generally collected strictly for compliance with regulations. The peak levels (including dominant frequency) are typically all that are looked at. However, these records contain a lot more information about how a blast has performed. The seismogram is actually a record of explosive energy that was not used in fragmenting rock. The trick is to determine how to extract information that would be useful in analyzing blast performance.

Jan 1, 2013

By Sandeep K. Sharma

The U.S. Bureau of Mines has been investigating new techniques to improve the of mineral to recover water lost in the waste slurry, and to produce dewatered solid dewatering s suitable for disposal. As part of this investigation, a study was undertaken to investigate the feasibility of dewatering Alaska placer effluent. Based on the laboratory tests, preliminary field tests were conducted on three placer mines in Alaska. At these mines, the water recovered from the placer effluent (250 to 23,000 NTU) exhibited turbidities of 20 to 240 NTU. In the second year of the project, a large-scale dewatering unit was set up at a mine located in the Livengood district. The feed, at flow rates up to 935 gpm, was mixed with dilute PEO solution in a flexible plastic hose with and without static mixers. Feed to the dewatering unit generally ranged between 300 and 26,500 NTU and required PEO dosages of 0.02 to 0.14 lb per 1,000 gal to produce water from the screen underflow with turbidities of 20 to 50 NTU. During this period, a small unit was also operated at Dow rams of 10 to 25 gpm at sewn sites throughout Alaska, with the effluent from four of the sites being dewatered successfully.

Jan 1, 2010

By J. Krzyzanowska

Paper written on project work carried out in partial fulfilment of Bachelor of Engineering-Mining Venetia Mine, an open-pit diamond mining operation in the Limpopo Province of South Africa, currently has a mixed haul truck fleet consisting of Caterpillar 785B and C; 789C; modified 793D and 793D. Even in an ideal situation these trucks have different cycle times, which causes queuing at the loading area and their different speeds cause bunching on the ramps, leading to higher overall cycle times and lower productivity. This problem was identified but the root causes of the problem were not investigated and quantified. A time and motion study on the haul trucks was thus undertaken to measure actual cycle times and compare them to ideal cycle times as well as to observe any reasons for deviations. Ideal cycle times are partly evaluated on the basis of simulation and partly from production optimization expert input. Several areas that affect production were identified and these include: haul road conditions, the control room, dispatching programme and dispatching data management, as well as truck-shovel matching. The investigation was important in establishing control parameters for haul fleet operation since time spent queuing is production time lost, which defers waste tonnes to later in the life of mine, thus decreasing the tempo at which kimberlite is exposed.

Jan 1, 2007

The Oregon-Idaho graben evolved after widespread tholeiitic flood basalt volcanism associated with the arrival of the plume head of the Yellowstone hotspot beneath southeastern Oregon approximately 17 - 16 Ma. The north- to north-northeast-trending, 50 km-wide graben evolved between 15.5 and 10.5 Ma during east-west extension. The graben is part of a middle Miocene back-arc rift (1100 km long) that includes the northern Nevada rift, the Baker and LaGrande grabens, and the Chief Joseph dike swarm of the Columbia River Basalt Group. The graben ceased to be a volcanotectonic depression as the cross-cutting western Snake River plain began to evolve at approximately 10.5 Ma. At about 14.3 Ma and continuing to approximately 12.6 Ma the Oregon-Idaho graben began to break up into subbasins that were bounded by intragraben fault zones. The break up was accompanied by a change to calc-alkaline volcanism that persisted within the Oregon-Idaho graben until 8.1 Ma, approximately 2.5 million years after subsidence within the graben ceased. Three intragraben fault zones have been identified and a fourth is inferred. The easternmost, the Devils Gate fault zone, coincides with the magmatic axis of the graben at approximately 14.3 Ma. By approximately 13.5 Ma the magmatic axis had shifted to the west along the Dry Creek Buttes and Wall Rock Ridge fault zones. A diffuse magmatic axis developed at approximately 12 Ma farther to the west where the fourth intragraben fault zone is inferred. In addition to serving as conduits for the ascent of basalt, basaltic andesite, rhyodacite, and rhyolite magmas, the zones focused the discharge of large geothermal systems. The intragraben fault zones display a common evolutionary pattern. The 2 to 3 km-wide zones initially control the distribution of facies in volcaniclastic sediments and the location of basalt hydrovolcanic vents. During this stage, the fault zones may have had no surface expression other than a low elevation change on a relatively low-relief landscape. As relief developed by continued deformation along the fault zones, strike-length of individual faults increased and weakly consolidated volcaniclastic sediments, silicified sediments and hot-spring sinter, and palagonite were eroded from the uplifted blocks and deposited in neighboring subbasins. It is during this stage that the large hot-spring precious-metals bearing prospects evolved. Displacements of over 150 m on a few faults within the zones and possible reversal of the sense of displacement along the zones occurred in this final stage of development. Locally, the fault zones were remobilised during the subsidence of the cross-cutting western Snake River plain. The intragraben fault zones within the Oregon-Idaho graben illustrate the relations among syntectonic volcanism and sedimentation and the evolution of geothermal systems within continental rift systems.

Jan 1, 1995

By L. Lui, A. Cauchon, A. R. Laplante

"The gravity circuit at Les Mines Camchib Inc. consists of two pinched sluices to bleed a feed to one of two 76 cm (30"") Knelson concentrator. The Knelson concentrate is upgraded to smeltable grade with a smaller Knelson (18/30 cm) and a riffleless table. Their tails are column cyanided and washed prior to recycle to the grinding circuit. This paper details size-by-size circuit performance. The Knelsons recover around 90% of free gold (as determined by Mozley Laboratory Separator), even below 37 µm. The sluices are ineffective, with upgrading ratios around 2, but approaching unity in the fine sizes. Much of the effectiveness of the circuit lies in the high gold circulating loads in the grinding circuit, which partly atone for the poor sluice performance, and the ability of the Knelsons to recover free gold. Secondary upgrading recovers slightly above 99% of the primary concentrate gold, 90% of it in a 65% Au concentrate and the balance in a heavily loaded (10 to 20 oz/st) pregnant solution. INTRODUCTIONBackgroundThe operating performance of the mill of Les Mines Camchib Inc. has been described earlier (Laplante et al., 1989). The presence of significant chalcopyrite (1 % and up) makes flotation necessary prior to cyanidation, to limit cyanide consumption and minimize environmental impact. In 1982, the presence of very high gold circulating loads in the grinding circuit lead to the commissioning of a gravity circuit, schematically shown in Figure 1. Gravity recovery of gold has been found beneficial because it increases metallurgical recovery by 1-3% (Laplante et al, 1987), as only part of the flotation tail is cyanided, and economic recovery, because of the lower net smelter return of gold in the flotation concentrate (as compared with the gravity concentrate). The latter increase is estimated, with a net smelter return of 95%, at 1.5% when gold recovery by gravity is equal to 30%. In early 1988, a sampling program was initiated to characterize the behaviour of gold in the grinding/gravity circuit. This paper reports on the results of this study."

Jan 1, 1990

By L. W. Higley

It is estimated that well over 20 million lb of chromium and 8 million lb of nickel, plus other metal values, are diverted annually to furnace dusts, mill scale, and contaminated swarfs in the domestic stainless and other specialty steelmaking industry. Little inroad has been made toward the in-plant recycling of these wastes to reclaim the metal values. The Bureau of Mines has devised a process for recovering about 90 pct of the chromium and molybdenum and well over 90 pct of the nickel and iron from stainless steelmaking furnace dusts, swarf, and mill scale. Other metals such as manganese are also recovered. Initial laboratory results were confirmed and expanded to include a wide variation of stainless steelmaking waste mixtures. Later experiments have included specialty steelmaking wastes other than from stainless steelmaking. Significantly, the ease of technology transfer has been demonstrated by a number of industrial-sized (19-ton) commercial electric furnace heats, in which the pelletized wastes represented some 10 to 20 pct of the furnace charge, replacing part of the normal scrap charge. Results of these successful large-scale trials are presented. Some information is also presented on incorporation into the pellets of chromium-bearing particulate wastes originating from other than steelmaking production. Cost evaluation indicates the process is economically attractive.

Jan 1, 1982

By J Hall, A Gallardo, M Strizek

Mineralogy and coproponents Sino Iron, International Minerals and Austeel are in the process of developing four world class magnetite iron ore mines with multiple open pits along a 25 km strike length of Brockman Iron Formation to the south of Cape Preston on the West Pilbara coast. The close proximity of the proposed pits raises some challenging project approvals and environmental management issues relating to the impacts of dewatering at individual projects and the cumulative impacts of progressive development on local and regional groundwater resources, which includes a large fresh water aquifer system in the Fortescue River alluvium.This paper presents an outline of the hydro-environmental impact assessment process adopted and the key result that the cumulative impacts of dewatering at all four projects on the local brackish groundwater system in the basement rocks is only marginally more than the impact of any one project on its own, and that the impact on the Fortescue River alluvium aquifer is negligible. The paper also presents an outline of the proposed integrated water management approach that will involve coordinated monitoring, ongoing impact assessment and management, and reporting programs for all projects.

Jan 1, 2009

By T. A. Klinefelter

KYANITE and the related minerals sillimanite, andalusite, dumortierite, and topaz are natural aluminum silicates that can be used in production of mullite (3A1203?2Si02), a superduty refractory material. Kyanite and sillimanite are the dominant ones because of their greater abundance. The only other kyanite-group mineral presently used for mullite production is andalusite. Mullite is not an absolutely essential material as other refractories can be used in the same heat range. However, it is a highly satisfactory one. It is the only compound of silica and alumina that is stable at high temperatures. It has low thermal expansion and is very resistant to corrosive melts and to thermal shock. For these reasons mullite refractories have a much longer life than standard fire-clay refractories under the same conditions. Worldwide, excluding U.S.S.R., the refractories industry consumes about 150-000 short tons annually of kyanite group minerals and synthetic mullite.

Jan 1, 1961

By J. A. Luckmann

"SynopsisThe purpose of this paper is to introduce an innovative approach to risk management in surface mining operations, namely, positive risk. Traditionally, risk management focused on mitigating losses (negative). Positive risk, on the contrary, reverses the approach and focuses on exploiting a project’s inherent benefits (positive).The inability to accurately determine project objectives during the project planning phase and the failure to achieve those objectives during the execution phase is a major problem for any project management in the mining environment.The advance of computer aided design models for mine planning enables mining engineers to examine various options within a very short time. Employing positive risk management combined with drivers-based risk management when evaluating these options provides an ideal opportunity to investigate areas for improving the mining project’s profits. Furthermore, harnessing positive risk returns during the planning phase contributes immensely to the successful achievement of project objectives.Mining has inherent business risks, which can appear overwhelming when considering the risks associated with a mining project schedule, cost, and safety or resources, etc. The question is – how to manage risks in a surface mining environment, and what process methodologies, work methods, processes, and standards should be used when considering the surface mining risks. Applying the principles of positive risk management to manage surface mining risks is not only relevant, but definitely beneficial to mining projects and to the mining industry as a whole.It would be beneficial for risk managers and risk professionals to understand the roles of positive risk ‘drivers’, also known as ‘propitious attractors’. Identifying, analysing, estimating, and understanding the propitious attractors, their behaviour and their influence on project risk events helps considerably during the planning and execution phases. The theoretical and practical knowledge of both sides of the risk – the downside risk (negative risk) and upside risk (positive risk) – can add substantial value to any organization when downside risk is adequately mitigated and upside risk is beneficially exploited."

Jan 1, 2015

By Euler De Souza

This paper presents a study conducted to assess sillmat behaviour during undercut mining and to provide a comprehensive understanding of the effects of arching and sillmat thickness on stability. The design study investigated the effects of such parameters as stope width and height, closure strains, orebody geometry and inclination, wall roughness, fill properties and cure time on the stability of cemented sillmat during undercut mining. Arching effects have been quantified based on centrifuge modeling studies for the different mining conditions. Observations have indicated that the degree of arching is a function of stope geometry, wall roughness, fill cohesion, and wall closure. Arching effects increased with decreasing stope width, increasing backfill cohesion and frictional resistance, increasing wall roughness and with wall closure.

May 1, 2002

By A. Baldwin

This report describes the engineering feasibility and economic advantages of a unique new mining machine using cutting bits that take a constant-depth linear cut in the coal face. The studies show that this innovative new cutting concept, being developed by the Bureau of Mines, can be designed into the basic continuous mining machine. The resulting miner would be attractive to mine owners because coal could be mined with minimum generation of airborne respirable dust, substantial increases in productivity, and elimination of methane ignition due to cutting.

Jan 1, 1977

The placer mining industry of the West Coast region of the South Island is based largely around the production of alluvial gold, although other valuable minerals are also present. Since the first major discoveries in 1864-65, reported gold production has totalled around 264 t (8.5 Moz). During the past 10 years, annual production has totalled around 1460 kg (47,000 oz). It is anticipated that gold production over the next three years will continue at a level of 1400-1800 kg.   Annual gold production peaked during 1866 at approximately 17,170 kg (550,000 oz) and has not exceeded 100,000 oz since 1885. This reflects the ease with which gold was won from shallow, rich deposits that were present at many localities. Subsequently, there has been a general decline in the availability of this type of deposit, a trend that will continue in the future. This paper outlines the present state of placer mining in the West Coast region, gives some historical background to the industry and briefly predicts future trends.

Jan 1, 1997

By Joseph B. Cummings

"INTRODUCTION The property was first examined by an engineer 3/ of the Bureau of lanes in December 1942 and was later investigated by the sane engineer in January and February 1943. Prominent outcrops and underground exposures of high-grade iron ore, together with mention of sizable intersections of hematite in logs of four widely scattered churn—drill holes, indicated the possible occurrence of a substantial tonnage of iron ore at this old copper producer.From March to May 1943, detailed topographic and geologic mapping of the property was done by the Federal Bureau of Mines, the Federal Geological Survey, and the Arizona Bureau of Mines.Funds were allotted for exploration of the property by churn and diamond drilling. This work was started in December 1943 and completed in June 1944.ACKNOWLEDGMENTSIn its program of exploration of mineral deposits, the Bureau of Nines has as its primary objective the more effective utilization of our mineral resources to the end that they make the greatest possible contribution to national security and economy. It is the policy of the Bureau to publish the facts, developed by each exploratory project as soon as practicable after its conclusion. The Mining Drench, Lowell B. Moon, Chief, conducts preliminary exmination, performs the actual exploratory work, and prepares the final report, The Metallurgical Branch, P. G. Knickerbocker, Chief, analyzes samples and performs beneficiation tests. Both these branches are under the supervision Dr. R. S. Dean, Assistant Director."

Dec 1, 1946

By R. Abela

Heavy mineral sands are usually beneficiated in a spiral concentrator circuit prior to separation of heavy minerals into streams of zircon, rutile and ilmenite. The performance of the spiral concentrators is heavily affected by the presence of slimes in the rougher feed. The paper quantifies the effect of slimes content and discusses the beneficial effect of spiral feed de-sliming. The net effect of inefficient slimes removal can cause significant recovery losses of the heavy minerals present in the feed.

Jan 1, 2003

By Richard F. Flanagan, Robert H. Marshall

The Republic of Singapore’s Public Utilities Board is implementing the Deep Tunnel Sewerage System Project. The project’s deep tunnel component, 48 km of deep, large diameter sewer tunnels has been successfully completed (the works are in the defects liability period). Six International Design/Build tunnel contracts utilized eight Earth Pressure Balance TBMs ranging up to 7.23 m in diameter to deal with varied ground types ranging from deep soft clays to fresh granite. Numerous access/workshafts were constructed and using various support systems. This paper provides an assessment/overview of the tunnel contracts, tunnel excavation methods and equipment, and the shaft systems. Suggested enhancements to similar future projects are provided.

Jan 1, 2007

By Abigail Styer, Paul Holmgren, Josh Calnan

Detonating cord is a staple of the explosives industry, used widely in the civil and defense industries. Detonating cord is a thin, flexible plastic tube filled with pentaerythritol tetranitrate (PETN). It has many applications in mining, construction and military disciplines. For civil applications, it is used to connect and initiate a series of blastholes in a desired pattern. In the defense sector, it can be used as a detonating agent, a priming agent or alone as an explosive charge. Research has been done to understand the initiation and detonation physics on the detonating cord. However, its sympathetic detonation characteristics needed to be further analyzed. The sympathetic detonation of the detonating cord can lead to the poor performance of production shots in mining or civil applications and unsafe conditions in defense applications. This paper focuses on the analysis of different factors involved in the sympathetic detonation of various sizes (grain weights) of detonating cord. The variables analyzed include the minimum distance between segments of detonating cord and grain weights. These variables were analyzed by securing segments of detonating cord at measured distances apart on a steel plate and detonating them. The physical examination of the aftermath of this detonation included a qualitative recording of data. Applications of detonating cord that could be affected by this research include mining and construction blast initiation, explosives disposal, and breaching.

Fine coal is defined as material with a maximum size of 1/2 in. Various methods for separate washing of such coal are discussed briefly because separate treatment can lead to a higher overall recovery of coal or to a product having a lower ash content.A felspar jig is discussed in detail because it is the method most recently adopted in Australia, and because it has the advantages of compactness, flexibility and automatic Gontrol, with minimum operator attention. This jig has a variety of adjustable controls to enable the desired results to be obtained from a wide range of coals and the general application of each control is discussed.The only separate treatment of fine coal in the Illawarra district is by felspar jigs on Bulli seam coal.INTRODUCTIONAll reasonably large Australian collieries now win coal by mechanical methods. but while mechanization leads to more economic production of high tonnages, it also changes the characteristics of the coal won. In particular there is an increased proportion of fines, and an increased ash and moisture content. However, specifications of coal for sale have become more stringent, and consumers now require coals in a definite size range with a lower and more uniform ash content, as well as with a low and uniform moisturecontent.These factors have led to the need to wash and grade run-of-mine coal at the pithead. In' plants where the whole of the run-of-mine coal is treated in a jig, some of the fine coal in the feed is beneficiated; the extent depending on factors such as the type of coal and the feed rate. However, for dense medium treatment, fine coal must first be screened out, and there may then be no washing of fine coal at all.

Jan 1, 1961

By Laurance A. Beck

Safety is the most important aspect of haul road design. Although other aspects of road installation enter decisions on design, the safety of persons using the road has to be foremost for the duration of haul road usage. Other aspects of mad design focus on minimizing truck cycle time and fitting haul roads to the long-term configuration of the mine/quarry or construction project. Roads are often installed at high gradients for a short-term goal, but the long-term benefits are easily shown with lower gradient haul roads which provide better cycle times and lower operating costs.

Jan 1, 1995

By R WOODS

The interaction of, flotation collectors with sulphide mmerals takes place at the solid-solution interface. The electrochemistry of the processes which affect this interface are discussed. The interaction of xanthates with sulphides is an electrochemical process, xanthates being electro-oxidized to chemisorbed xanthate and dixanthogen.The role of oxygen is to provide a cathodic process to allow the anodic oxidation to occur. The hydrophobic condition of the mineral surface is brought about by the presence of the oxidized xanthate species. The action of reagents which can activate or depress the flotation of sulphides is discussed briefly.

Jan 1, 1972