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By K. A. Natarajan, M. K. Yelloji Rao, P. Somasundaran

The bacterium Thiobacillus ferrooxidans triggers the surface modification of sulfide minerals to provide hydrophilicity or hydrophobicity for the flotation of sphalerite and galena. The effects of initial cell concentration, period of biotreatment and pulp density on the floatability of the minerals are discussed. With galena, flotation enhancement obtained through sulfuric acid treatment was retarded by biotreatment at all cell concentrations due to chemical effects. Such a decrease occurred for sphalerite only at cell concentrations sufficiently high for bacterial attachment to the mineral surface. The variables affecting surface modification (and, thus, flotation response of the minerals) include the cell concentration used for bacterial conditioning, the period of biotreatment and the pulp density. Although bacterial growth during biotreatment was observed even in the absence of nutrients, such growth was more common in the sphalerite suspension than in the galena suspension. Cell protein estimations suggest that more cells are attached on galena than on sphalerite. Probable reaction mechanisms associated with bacterial modification are discussed.

Jan 1, 1993

By Lynn B. Hales, Randy Ynchausti, Jeffrey D. Mckay

Many consider rougher flotation control to be more of an art than a science. Some have even thought it impossible to make process control decisions and changes without human interaction. Controlling flotation bank pulp levels to maintain consistent pulling rates in the face of changing feed slurry flow rates, varying mineral types, and inconsistent reagent additions can be daunting. However, an advanced supervisory control strategy was installed on the plant floor to control an industrial rougher flotation circuit with little or no operator interaction. Plant staff monitored the flotation circuit under supervisory control and reported benefits of up to 4% improvement in copper recovery above that achieved with an older supervisory control strategy. To accomplish this work, a novel use of instrumentation to solve a flotation bank pulp level control problem was employed, a new implementation approach was used to correct some flaws in the older approach, and careful attention was paid to a few key process control principles. This paper discusses important aspects of these activities.

Jan 1, 2000

By Joseph E. Worthington

The announcement of a high-grade ore intercept near Wenatchee, Chelan County, WA, by Asamera Minerals in 1983 triggered widespread interest in this old gold mining district. The district has a long history of exploration and production and was actually one of the few underground gold mines that operated in the post World War I1 years in the US. Gold occurs in a north-trending structural zone in folded and faulted Eocene arkose intruded by andesite and dacite dikes having dates in the 42 to 50 m.y. range. Ore has been mined selectively from ladder veins perpendicular to the trend, from the south end of the trend near Squilchuck Creek. These veins narrow and silicification becomes pervasive northerly where wider zones were caved later in the operation. Recent discoveries at "B" reef at the north end are also in wide zones of silicified arkose. The gold lodes originally cropped out as prominent silicified and iron-stained ridges that were described in the early days as "reefs." The early discoveries were made in out- crop about a hundred years ago, and two claims, the Gold King and Macbeth lodes, covering the most prominent out- crops on the north side of Squilchuck Creek, were staked in 1885 and patented shortly thereafter. A five stamp mill was erected in 1894, but failed to liberate gold for amalgamation. The two patented claims were acquired in 1934 by J. Keegan, who carried out limited exploration and shipped small amounts of flux ore to Tacoma during the next few years. There was no substantial exploration or development of the claims, however, for several years after that time, and ownership of the claims eventually passed to a series of trusts administered by a bank in Seattle.

Jan 1, 1990

By Zhengbin Cheng, Wenguang Lu, Baoqi Sun, Jiaying Tang

This paper studied the flotation separation of feldspar, zircon and kyanite from quartz with a mixture of cationic and anionic collectors. Tests show that collector mixture has specially good effect, using it, the separation of these three silicate minerals from quartz can be successfully achieved at the natural pH value of tap water in the absence of any acid, fluoride and other inorganic reagents. The properties and characteristics of collector mixture were analysed. By means of IR-spectra, ESCA and AES, the action mechanism between collector mixture and minerals was throughoutly studied.

Jan 1, 1995

By Kurt Bryan, O&apos

The crushing and milling of mineral bearing ores can now be accomplished more efficiently through the application of WaterFlush technology. WaterFlush crushing has reduced capital and operating costs for the processing of a lead/zinc ore in South America. Similar benefits can be expected in the processing of other ores. WF cone crushers offer improved performance over conventional cone crushers. Performance improvements include the ability to crush wet and sticky ores, increased reduction ratios and greater production of flakier and finer products.

Jan 1, 1989

By Mark Rybak

On August, 31, 2006, Tropical Storm Ernesto hit the City of Richmond, Virginia. The Battery Park area was hit particularly hard, as flooding forced an evacuation of the area. A large sinkhole collapsed a sewer line in the Battery Park area, blocking the pipe and causing more serious flooding. This case history describes the fast track design, bidding, and construction of an emergency tunnel to bypass the collapsed sewer. Innovative value engineering, tunneling and shaft sinking methods, and final lining design all contributed to the success of this project. The storm inundated Richmond, Virginia with up to twelve inches of rain in some areas causing widespread flooding and damage. One of the hardest hit areas of Richmond was Battery Park. A major trunk sewer in the Battery Park area collapsed causing local combined sewer and storm-water flooding. The collapsed sewer was an 8'-3" wide by 9'-6" high arch sewer that was constructed in the nineteen twenties and later filled over with municipal solid waste and a soil fill cap to current elevations. A sinkhole was created in the area of collapse approximately sixty feet deep and one hundred feet in diameter causing the existing arch sewer to become blocked. As a result of this blockage contaminated flood waters reached depths in low lying areas in excess of twenty five feet. [ ]

Jan 1, 2008

By D. L. Sober, D. Ince, T. V. Vasudevan

Separation of dolomite from Florida phosphates was achieved by first conditioning the feed with fatty acid at pH 10 followed by reconditioning at pH 4 or below, before flotation. Observed selectivity of this two-stage conditioning process was attributed to the amount as well as changes in the nature of adsorbed collector species upon reconditioning. In this paper, bench-scale flotation results of optimizing the major process parameters, such as reconditioning pH and collector dosage, for upgrading natural high dolomitic phosphate samples from Florida are discussed.

Jan 1, 1991

By Richard R. Klimpel

In this paper, the old and the new commercially available reagent chemistries for the improved flotation of sulfide minerals will be summarized. The reagent classes discussed are those that meet three criteria: 1) they are being commercially used and/or large scale plant tested in North America in the last few years; 2) they are clearly different in chemical structure than commonly used commercial reagents of the last few decades and are not simply mixtures of existing reagents and/or simple changes in cation, alkyl group size, etc. and 3) the structural formulae are clearly specified in the public literature.

Jan 1, 1994

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

An extensive geotechnical monitoring program was used to assess ground and liner behavior, provide input to a Disputes Review Board, and verify design assumptions during construction of the Mt. Baker Ridge Highway Tunnel along I-90 in Seattle, Washington. The stacked-drift tunnel liner was constructed with twenty-four 2.9 m diameter concrete-filled drifts forming a semi-flexible compression ring, followed by excavation of the 19.4 m diameter soil core. Instrumentation data was used for monitoring hillside stability, liner deflections and loads, impacts on adjacent highway tunnels, for back analyzing soil properties, and for helping to limit construction-induced settlements to about 6 cm.

Jan 1, 1987

Safety is the No. 1 concern of any drill contractor or mine operator. Everyone in the industry knows a safe site helps stabilize operational costs and enables higher productivity. When it comes to exploration drilling, research has proven a majority of injuries are caused by the mishandling of coring rods. A driller helper will typically handle up to 50 rods per shift or up to 15,000 rods per year. With an annual 340 t (750,000 lb) in rods managed by hand, the risk of serious injury is extremely high. Because of this, the top request from the exploration industry is diamond rod handling. The Boart Longyear 4200 surface exploration drill, slated for release in 2009, will give the industry a hand-free, operationally safe rig.. Developed through the collaboration of its global drilling services and products divisions and targeted at the 1,200-m (3,900-ft) NQ market, the upcoming Boart Longyear 4200 surface exploration drill features the safest and most flexible rod management sys-tem in its class. The rig includes the industry?s first, truly hands-free rod handling system. This increases operator safety on the jobsite. In addition to the rod handler, the rig also features many new innovations that boost productivity and rig efficiency while minimizing the risk of downtime due to component failure or operator error. Boart Longyear has also included an intelligent PC-based operating system designed to allow complete drilling control as well as diagnostics reporting for the rig.

Jan 1, 2009

By Roshan B. Bhappu, Sukhendu L. Barua

The economics of developing and operating small precious metal mines are unique and require much more scrutiny than larger mines since a limited tonnage must carry a heavy burden of capital investment as well as operating cost per unit ton to be mined and processed. Moreover, potential operators of small mines do not have the required expertise available to critically evaluate the technical and economic aspects of their projects. In this paper, the authors have attempted to provide technical and economic guidelines for developing and operating small precious metal mines. Capital and operating cost estimates as well as return on investment are provided for various scenarios utilizing different mining and processing techniques.

Jan 1, 1987

By M. Bidart, V. Sawyer, M. Saunders Macdonald

A number of open pit gold mines in Nevada extract ore from areas that are below the natural groundwater elevations. This necessitates dewatering, which requires a method for the disposal of the extracted water. Some of these open pits extend well below, the water table with dewatering volumes greater than 10,000 gpm (38,000 L/min). Some mines with large volumes of dewatering water have constructed reinfiltration basins to reintroduce the water into the groundwater system at a point some distance from the pits. This paper presents an overview of the state of the art of reinfiltration projects, including the permit process for such projects in Nevada. The paper includes the necessary engineering considerations.

Jan 1, 1997

By R. M. Carland, F. F. Aplan

Six natural zeolites were evaluated for their ability to selectively remove heavy metal cations from solution. Ion selectivity was found to be Pb+2>Zn+2>Ni+2 and Cu+2>Co+2 from their respective solutions. The presence of K+, Ca+2 and Mg+2 in the actual waters to be used may seriously interfere with the ion exchange and elution of cations from zeolites. Zeolites were found not to be effective in removing precious metals from their cyanide solutions.

Jan 1, 1995

By C. Ostrowski, Z. Fajklewicz, K. Jakiel

Results of the application of the micro-gravity method in predicting rock bursts and rock mass deformations are discussed. Research was done in the Daisy black coal mine, Upper Silesia, Poland, during 1979-1980. At that time, microgravity investigations helped increase the safety of coalbed exploitation in progress. During the first stage of exploitation, a mining shock of 107 J energy was predicted in a region where 40 miners worked.

Jan 1, 1987

By M. C. Rockwell

There are about 1.8 Mt (2 million st) of discarded dolomitic-limestone tailings from the Gays River lead/zinc mining operation in Nova Scotia currently stockpiled in a tailings pond at the mill site. Neutralization effectiveness similar to an agricultural grade limestone and low contents of residual metals make the tailings a potential source of soil conditioner material for the local market. However, the fine particle size, 98% passing 147 pm (about 100 mesh), and a moisture content of 20% make their handling, shipping, and application to soils difficult. The tailings were agglomerated into small hard pellets with various amounts of soil nutrients, moisture content less than 13%, and pH values ranging from 6.5 to 8.7.

Jan 1, 1987

By R. H. Grau

The National Institute for Occupational Safety and Health (NIOSH) has conducted research to improve the ventilation of large-opening mines. The research has demonstrated that the ventilation of large-opening mines improves significantly by including ventilation requirements in the mine planning process and implementing some practical techniques during mining. Planning the location of long pillars to reduce the number of crosscuts between intake airways and return airways, positioning auxiliary fans in their proper locations, and establishing ventilation stoppings with minimal leakage all significantly improve the ventilation of large-opening mines. Mine operators that adopt these techniques in the mine ventilation plan will reduce mineworkers? exposure to airborne contaminants.

Jan 1, 2008

A study was undertaken to determine the effects of five industrial frothers on the relationship between entrainment recovery and water recovery. The experiments were conducted using a Batequip rectangular 60L steel flotation cell that was run in parallel with the first cell in a copper/silver prefloat rougher circuit. The concentration of the frothers ranged from 2.5 to 8.4 g/t. The experiments were repeated at three different froth depths. A power function was found to fit this relationship with no discontinuity in the relationship caused by the changes in frother type and concentration and froth depth.

Jan 1, 2002

By W. G. Pariseau

Equivalent elastic properties of discontinuously jointed rock masses are computed using a non-representative volume element(NRVE) approach within a three dimensional finite element program. Joint persistence, defined as the percentage of a joint plane that is actually occupied by joint material, is used in the NRVE computations as a step towards greater realism in stability analysis of mine openings. Persistence p is also the probability that a segment of a joint plane is occupied by joint material. Computations reveal a threshold phenomenon in jointed rock mass moduli similar to that observed in percolation theory. A rapid decrease in moduli occurs above a critical value pc(about 0.6). A detailed analysis of the well-known solution for stress about a circular opening in isotropic, elastic ground illustrates the effects of joint set orientation, spacing and persistence. Although stable “on average”, joint segment failures reveal a threat to stability and point towards rational design of reinforcement or support of discontinuously jointed rock masses.

Jan 1, 2003

By James M. Prudden, E. P. Jucevic

The Divide mining district occupies the center of a Tertiary caldera hosting the famous Divide silver lode and the crosscutting Gold Mountain mines. The northwest-southeast trending silver lode hosted ore with typically a 100:1 silver:gold ratio, high molybdenum content and argillic alteration dated at 16.5 m.y. within the Fraction Tuff. The east-west trending Oddie Rhyolite flow dome at Gold Mountain experienced possibly several periods of resurgence with repetitive silicification, brecciation and attendant precious metal deposition forming stockwork type mineralization. Silver-gold ratios average 10:1 for the mineralization phase of this 16.4 m.y. intrusive event. Similar chalcedonic mineralization registering a 3:1 silver:gold ratio cements conformable breccias within the Oddie Rhyolite basal flows unconformably overlying the Siebert Tuff on the northern flanks of Gold Mountain. Gray and red chalcedonic breccia matrix in the King Tonopah member of the Fraction Tuff contains a 50:1 silver :gold ratio.

Jan 1, 1990

By Vernon Miller

In 1986, a subsidiary of Echo Bay Mines Ltd. purchased the McCoy property, 55 km (35 miles) southwest of Battle Mountain, NV. Echo Bay then launched a two-year, $1 15-mil lion capital program to build a mill to extract gold and silver from high-grade ore mined in two open pits - the original McCoy pit and a more recent discovery, the Cove. Engineering on a new mill began in 1987 with the facility coming on line in 1989. It was comprised of a semiautogenous (SAG) mill and ball mill grinding, leaching, flotation, counter current decantation (CCD) and Merrill-Crowe processes. The mill started up on McCoy ore, a rocky material that settled very well in the new CCD thickener system. Production levels were maintained at about 7.2 kt/d (8000 stpd). The situation changed as the McCoy ore played out and increasing amounts of material from the Cove pit-with its oxide, sulfide and carbonaceous ore - were fed to the mill. The problem was the high clay content of the Cove ore. The new ore immediately created production problems, mainly loss of control on the CCD thickeners. With the McCoy pit slated to be shut down in early 1991, it was essential to find a way to efficiently process the Cove ore. Initially, the only way to regain control of the thickeners was to slow down the processing rate and increase flocculant usage, thereby getting the solids to settle in the thickeners. But this had its cost. Production dropped to about 5.9 kt/d (6500 stpd), additional operators were needed and flocculant costs, on occasion, would reach an unacceptable $80,000 per month. Overfloccing led to viscous

Jan 1, 1993