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By E. M. Hill, D. E. Walsh, J. T. Hollow, H. K. Lin

Fairbanks Gold Mining, Inc. (FGMI) began blending and processing True North ore at their Fort Knox mill on April 12, 2001.Gold extraction subsequently dropped from 88% to 71% during the last week of April 2001. 25% of the gold values remaining in the leach tailings were gravity recoverable free gold. Significant quantities of stibnite and arsenopyrite were also identified in the tailings. In laboratory bottle roll tests, the gold extraction from a composite of leach circuit feed collected during the same period was 72.6%, when leached at an average NaCN concentration of 0.16 g/kg. The extraction increased to 82.4% and 91.7% with 0.5 g/kg NaCN, and 0.5g/kg NaCN plus 0.075 g/kg Pb(NO3)2, respectively. A passivating layer surrounding liberated gold particles and resulting from sulfide mineral dissolution, likely contributes to reduced gold recovery, which can be substantially increased by the addition of lead nitrate. Lead species remain in the solid residues after leaching and were not mobilized using Meteoric Water Mobility Procedure.

Jan 1, 2003

By I. Iwasaki

The effects of autogenous grinding and conventional grinding on the floatabilities of copper-nickel sulfides were investigated as a part of a pilot-plant development project on the differential flotation of Duluth gabbro. At the same mesh-of-grind copper, nickel, and cobalt recoveries were higher and residual sulfur in the flotation tailings was lower with the autogenously-ground pulps. With the ball-mill-ground pulps the residual sulfur in the tailings could not be lowered to the level attained by the autogenously-ground pulps even at increased levels of the collector addition. From mineralogical examinations of concentrate and tailings samples, an electrochemical interaction between grinding media and sulfide minerals was thought to have a greater effect on sulfide mineral flotation behavior than the breakage characteristics of the ore samples in these two types of mills.

Jan 1, 1981

By Jack Magtoto, Lysa Voight, Tom Martin, John Forero

SUMMARY Commitment by all parties to partnering goals established early in the contract aided Affholder, Inc. in constructing 2,360m (7,700') of soft ground tunnel in Rancho Cordova, CA. Despite two zones of known contamination, encountering a zone of loose cobbles and boulders in a matrix of flowing sand, some perched water tables and a flooded tunnel after 2 upstream safety plugs failed, the Contractor finished the work 33 days early and only 1.91% over his original bid.

Jan 1, 2007

By Q. Xu

The adsorption behavior of gold in ammoniacal solutions on to activated carbon has been studied. The gold loading capacity of the activated carbon used in the system and the recovery efficiency by the adsorption were examined. The parameters affecting the adsorption of gold on to activated carbon included temperature, agitation speed, concentration of 'cation and anion as well as that of ammonia. It was found that the maximum gold loading on activated carbon used was about 10 kg of gold per ton of carbon. The recovery of gold by the adsorption from ammoniacal solutions was dependent upon the initial gold concentration in the solution. A recovery of 98% of gold was obtained on to the activated carbon under experimental conditions after 120 hour adsorption. It was also found that the initial adsorption rate was relatively fast compared to the whole period of the adsorption. The apparent activation energy for the adsorption was measured to be 15.8 kJ/mol. It was believed that the kinetics of gold adsorption on activated carbon was controlled by pore diffusion.

Jan 1, 1995

By David Rolley

The extended weakness of dollar-denominated commodity prices during the past four years has often been attributed to, among other factors, the strong rise in the value of the dollar, and many U. S. producers have hoped for a recovery in metals and minerals prices once the dollar weakened in foreign exchange markets. The recent turnaround in dollar strength may put this view to the test quite soon. Hence a review of the role of exchange rate changes in the determination of the prices of world-traded metals and minerals may be timely. This paper has three parts. Part I reviews the recent summary record of price movements in commodity and foreign exchange markets. Part 11 reviews the distinct ways in which exchange rate changes influence the supply and demand sides of a representative commodity market. Part III then more closely examines copper and aluminum prices to highlight the potential differences in the effects of exchange rate changes for commodities whose production is dominated by geology and commodities which are processing-dominated. The paper also contemplates the likely implications of these differences for commodity prices in the case of a decline in the trade-weighted dollar. The evidence suggests that the degree of recovery for dollar- measured commodity prices may be very different for differing goods. And it may be the case that some commodities whose prices appear to have been most affected by exchange rate influences may show the least recovery in response to a fall in the trade- weighted dollar.

Jan 1, 1986

By J. E. Spencer

Mesozoic and Tertiary mineral deposits in west-central Arizona are commonly associated with Mesozoic thrust faults and Tertiary detachment faults, respectively. Quartz-kyanite rocks and pyritic quartz-sericite schists with local anomalous gold are the product of probable Jurassic argillic alteration of Jurassic volcanic, sedimentary, and plutonic rocks followed by Cretaceous thrust burial and associated metamorphism. Slivers and sheets of Paleozoic carbonates along Mesozoic thrust faults were locally sites of syn-and post-thrust mineralization. Widespread brecciation along Tertiary detachment faults resulted in increased permeability along fault zones. Elevated thermal gradients also resulted from detachment faulting and apparently caused convective aqueous-fluid circulation along detachment faults and associated Fe+Cu±Au mineralization.

Jan 1, 1988

By Alan M. Muir Wood, Gerhard Sauer

There axe two essential features of administrative practices in tunnelling in order to provide proper encouragement to innovative and economic tunnelling: first, that there should be a continuity in the decision making at all stages so that the full implications of decisions in early stages of planning and design are understood; second, that there should be appropriate provision for variation so that the greatest possible benefit can be derived from modifying the working scheme in relation to the characteristics of the ground and from study of its behaviour during execution of the work. Examples are given from the Authors[?] experience as to the benefits to be derived from the application of such principles.

Jan 1, 1981

By Mehmet Mesutoglu, Ihsan Ozkan

This study investigates the feasibility of rock bolting support in an underground coal mine gallery with a thick coal seam. The Ömerler underground coal mine working area, owned by West Lignite Enterprise of Turkish Coal Enterprises, was selected for this purpose. Longwall top coal caving is implemented as the production method in the Ömerler underground coal mine. Field and laboratory studies were conducted to determine rock mass and rock material properties, followed by experimental, empirical and numerical analyses based on the acquired data. The obtained design results were evaluated using a resin-grouted rebar rock bolting (RBR) system and steel arch support (SAS) pilot application areas. The numerical modeling results conducted using the fast Lagrangian analysis of the Continua 3D (FLAC 3D v6.0) program indicated less displacement and secondary stress change in the RBR-supported zone compared to the SAS-supported zone. In situ measurements also demonstrated that RBR provided more successful support to the roof during coal production activities. The findings suggest that RBR is a more effective solution when evaluating the feasibility of rock bolting support systems in underground galleries with thick coal seams at the Ömerler Mine. This study emphasizes the importance of more sustainable and safe support systems to enhance operational efficiency in the coal mining industry.

Mar 1, 2025

By J. A. Herbst, J. E. Bohrer, Y. C. Lo

A systematic approach has been developed to analyze a phosphate grinding circuit with a view toward determining promising alternatives for increasing mill capacity. This analysis was carried out and capacity increases were predicted in the context of detailed population balance models developed for the plant ball mills and classifier systems. Model development and verification was performed using data obtained in a series of batch tests and two plant test campaigns. The effects of feed rate, percent solids, ball size, and mill material filling, etc., on grinding were investigated in the laboratory and plant. Residence time distribution tests were also performed to determine the transport behavior in the mill. The population balance models were found to provide accurate predictions of full-scale grinding circuit performance. Based on the findings of this study, additional capacity in excess of 25% was predicted for these ball milling circuits by a proper combination of ball size change, mill dilution, and adopting screen classification in place of hydro-cyclones. These predictions have been confirmed by plant tests in which the recommended operating changes have been implemented. Understanding the effects of operating variables on breakage kinetics and the interplay between kinetics, transport, and classification has contributed significantly to increasing the mill capacity.

Jan 1, 1988

By Richard E. Gertsch

The recent upswing in mining coincided with increased environmental concern. These trends have significantly increased regulation, but have not always provided sound environmental protection. Throughout, mining has remained passive, reacting to initiatives from outside. The high road to environmental protection must be an active strategy. The mining industry must take the lead and develop an environmental program effective in price and protection. It must involve all levels of mining. The mining industry should be the real environmental activist. We have the most to gain by sound environmental protection and the most to lose if the environment decays.

Jan 1, 1991

By B. E. Davis

A technique was devised by the Bureau of Nines to recover coarse (plus 1.7 m) North Carolina phosphate now discarded as waste. Concentration utilizes the difference in particle sphericity between the relatively flat calcite and the rounded phosphate pebbles. Sizing, treatment in a continuous hydraulic classification system, and grinding upgraded a 17.0-pct-P205 reject to 24.5 pct P205 with a phosphate recovery of 63 pct.

Jan 1, 1985

By F. M. Doyle, Robert G. Robins, E. Peters

Stability diagrams for the Cu-S-H2O system have been widely applied over many years. Stability diagrams for aqueous systems generally, have been generated by computer, but with the programs for Potential-pH diagrams in particular, a common routine leads to error in multi-element systems. In this paper these errors, and some misinterpretation of diagrams are considered. In most of the published diagrams for the Cu-S-H2O system there has been no account of the sulfide complexes of copper. Here, the free energies of formation for the various species in the system have been re-evaluated for consistency, and some diagrams for the Cu-S-H2O system ( generated with the program DIASTAB Vers.5 ) are presented.

Jan 1, 1993

By Dennis Arthur Fenton

The hydrodynamic bearing was first described by, Reynolds in 1886, and has since been widely applied in motors, engines, compressors, hydroelectric turbines, and other machinery. For various reasons, the hydrostatic bearing currently predominates in the large, horizontal rotating machinery field (e.g. grinding mills). However, the current industry trend towards increasing size and energy efficiency has resulted in renewed interest in the advantages of hydrodynamic bearings. These advantages include structural improvements, reduced bearing friction, improved bearing life, improved transient characteristics, and reduced lubricant pump size and power requirements. In particular, the higher energy efficiency results in substantial savings on large machines. This paper describes some aspects of the design of large hydrodynamic bearings based on thirty years, of experience in the design of such bearings on grinding mills ranging in journal size from 2.1 m to 6.4 m, see Table 1.

Jan 1, 1985

By F. J. Menzer, E. M. Schern

The Morenci/Metcalf porphyry copper mining operation, located in southeastern Arizona, currently processes approximately 91,000 tonnes of ore per day and has copper ore reserves estimated to be in excess of one billion tonnes. Functional groups within the Geology Department (currently staffed with six professional and two support personnel) include mine geology, project geology, and hydrogeology. The primary task of mine geologists is daily preblast bench face mapping with grade and mill amenability estimates. Auxiliary duties include detailed in-pit metal distribution evaluation, mineragraphic work and flux quarry geology. Project geologists conduct exploration and preliminary development projects both within and outside the Morenci district and provide support to ore reserve block modeling and geotechnical work performed by the Morenci mine engineering group. Hydrogeologists handle exploration for and development of groundwater resources and groundwater flow modeling, mine dump leach solution penetration and recovery evaluation, and tailing dam water reclamation.

Jan 1, 1992

By Malcolm J. McPherson, Daniel J. Brunner

This paper describes an experiment conducted to investigate the law of airflow on a mechanized longwall coal face. Background to the Square Law relating frictional pressure drop and airflow is presented and deviations from this Law are discussed. The procedures used to investigate the Law of Airflow for the longwall are described and the results are presented. The results verify the Square Law relationship for airflow along a mechanized longwall face.

Jan 1, 1987

By W. K. O’Connor, J. C. White, P. C. Turner

The US Bureau of Mines is investigating the cobalt and manganese resource of the West-Central Arkansas district through field investigations, mineralogical characterization, beneficiation and hydrometallurgical tests. Located within the Ouachita Mountains, these structurally-controlled deposits occur along the axes of anticlines that form the mountain ridges. Brecciated novaculite is cemented with a mixture of manganese oxides, primarily cryptomelane and psilomelane. Cobalt is concentrated within lithiophorite, a particular Mnoxide phase. Chemical analyses of head samples reported up to 25% Mn and 0.17% Co. Magnetic separation yielded products containing up to 41 % Mn and 0.22% Co at recoveries of 95% and 93%, respectively.

Jan 1, 1993

By J. Engesser

This paper discusses the effect that water chemistry, and water treatment have on pre-fired pellet quality and bentonite-binding effectiveness. A discussion concerning the effect that water temperature, water chemistry, water treatment, and surface area have on disc filter productivity and filter cake moisture is also included. This report is a summary of the data that were presented in five previous research reports, which are listed as references in this paper.

Jan 1, 2003

NICOR Mineral Ventures, Inc. retained Neyer, Tiseo and Hindo, Ltd. to evaluate the potential effects of a planned dewatering operation at NICOR's proposed, 258-acre silica sand mining facility near South Rockwood, Michigan. The ?orebody? is a horizontally extensive, friable, quartz sandstone from the Sylvania Formation which also serves as an aquifer for some of the rural, residential development near the site. We conducted an aquifer test on the site which identified the important aquifer properties. Using these data and an analytical model, we determined that the radius of influence would be expected to range up to 6000 feet from the quarry during its final development stage. An inventory of water supply wells revealed that most wells had sufficient available drawdown and would not be adversely affected. A long-term groundwater monitoring program was recommended to monitor the possible effects at some of the closest wells.

Jan 1, 1987

By Tom B. Corry

INTRODUCTION Located approximately 48 km (30 miles) south of Dallas, Texas, use to be the site of the Superconducting Super Collider. For those of you unfamiliar with the project, this was a multi-billion dollar project taken on by the U.S. Government for the further advancement of technology, medicine, and science. Major components of the project consisted of a Linear Accelerator known as the LINAC; three accelerating rings known as the Low Energy Boosters (LEB), Medium Energy Booster (MEB) and the High Energy Booster (HEB); the East and West Campuses where the Inner Reactor Halls would have been located; and the 87 km (54 mile) main collider tunnel. Unfortunately, this all came to an end on December 6, 1993, with the termination of the project due to the Government's cancellation of funds. This paper will deal with the two of the underground contracts before the termination. These two contracts were the 1122 contract which ran from N25 to N40 and the 1130 contract which ran from N40 to N55. (See figure 1) The 1122 contract was awarded to us in July of 1992 and consisted of the excavation and support of six (6) shaft varying in diameter from 5.5 m (18 feet) to 8 m (26 feet) and ranging from 39.6 m (130 feet) to 61 m (200 feet) deep and the driving of approximately 13,100 m (.43,000 If.) of main collider tunnel. Our second contract, the 1130, was almost identical to our first

Jan 1, 1995

By Thomas H. Wake, Timothy M. Tower

A continuing trend in raise drilling is the movement toward increased automation. This paper discusses the reasons for automating a raise drill, which include labor saving, faster and smoother operation, quicker response to blocky ground, and improved data logging and diagnostics. It gives a "wish list" of features when automating a raise drill, from simple shutdown control through unattended operation. It discusses the principles involved in closed loop control of a sluggish mining machine with large inertia, and covers functions such as data logging and remote control. Results are presented from a field test on a production raise drill.

Jan 1, 1991