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By R. W. Smith, R. K. Mehta, X. P. Zheng, A. M. Raichur, M. Misra

Experimentation was per formed on the flotation of apatite and dolomite separately using anionic collectors in the presence of Mycobacterium phlei. Also, the flotation of mixtures of dolomite and apatite in the presence of anionic collectors and in the absence and presence of the bacterium were studied. It was found that M.phlei functions as a depressant for both minerals. However, it functions as a better depressant for dolomite than for apatite. Experimentation was extended to two different Florida dolomitic phosphate rocks. In this investigation a concentrate grade of less than 1.0% MgO was achieved with a 75% P2O5 recovery.

Jan 1, 1999

By A. E. Isaacson, D. B. Dreisinger, G. A. Kordosky

The U.S. Bureau of Mines is researching the application of solvent extraction technology to highly acidic (pH < 1) copper leach liquors. As increasingly complex copper ores are mined for leaching, use of highly acidic leach solutions maybe necessary to effectively recover the contained metal values. A mixture of two commercially available extractants, based on aldoximes and substituted 8-hydroxyquinoline, which has a high transfer efficiency has been identified. A synthetic leach liquor, containing 5 g/L Cu at pH 0.9 was processed utilizing the mixed extractant and a laboratory SX circuit. The loaded organic was stripped with a synthetic barren electrolyte compatible with electrowinning technology.

Jan 1, 1993

By James J. Guesk, Robert W. Reisinger, Timothy C. Richmond

A high-altitude (2,900 m [9,500 ft]) historic underground copper mine in Wyoming is discharging copper-laden water with a neutral pH into an otherwise pristine creek. The Wyoming Abandoned Mine Land program is reclaiming the site under a CERCLA deferral agreement. The clean-up goal is to reduce copper in the mine discharge so that the creek can eventually support a trout fishery. A pilot-scale passive treatment test utilizing sulfate-reducing bacteria has been conducted at the site beginning in summer 1997. Test results show significant reduction in copper concentrations in near-freezing mine water at flow rates ranging to 19 liters per minute (5 gpm)

Jan 1, 2000

By D. C. Yang, J. Ye

A comprehensive flotation study has been conducted on a Chinese fluorspar ore using the packed flotation column developed at Michigan Technological University (MTU). The results are compared with those for a conventional mechanical flotation method on the same feedstocks. Key factors controlling flotation performance of both methods are evaluated based upon a simple statistic design. The flotation concentrate produced in one stage of the packed column has 4% to 5% higher recovery and much lower silica impurity than the concentrate produced by up to six stages using a conventional mechanical cell. The results also show that the packed-column flotation process is particularly suitable for the recovery of finer fluorspar particles.

Jan 1, 1993

By B. Amadei, A. Squassabia

This paper introduces the Rock Mass Median (RMM) index, a statistical measure of the mechanical quality of a rock mass thus is obtained through a mechanistic interpretation of the Poisson stochastic process. This process is the theoretical foundation of the Exponential Model, a probability distribution successfully used in practice to describe the spacing of discontinuities in rocks. Building on the Exponential Model, a simple method to compute RMM based on a widely accepted mechanical quality index is also presented. Verification is per formed through the analysis of two sets of core samples. Hypothesis testing at the 5% level of significance supports the validity of RMM for these samples.

Jan 1, 1994

By R. S. Conti

The US Bureau of Mines (USBM) has developed an inflatable feed-tube seal (IFTS) for high-expansion foam generators. The IFTS is a lightweight, portable, rectangular inflatable bag that can be used by firefighters to rapidly seal large openings, such as those in underground mines, and to simultaneously provide a feed-tube for a high-expansion foam generator. Thus allows fire fighting foam to freely flow to the fire site and control or extinguish the fire. Studies indicated that a high-expansion foam plug will travel 183 m (600 ft) down an entry with a 4.5% rise in elevation, before leakage of foam from around the inflatable partition.

Jan 1, 1996

By C. M. Walck

The Rosebud district is located in the Kamma Mountains, southeast of the townsite of Sulphur, Nevada. Since discovery in 1989, LAC Minerals, in joint venture with Equinox Resources, has delineated a resource containing approximately 570,000 ounces of gold and 5,500,000 ounces of silver. The deposit is of the volcanic-hosted epithermal quartz-sericite type. Mineralization occurs in tabular zones in and along the hanging wall of the South Ridge fault, and in cross-cutting high-angle structures. Multiple stages of discontinuous stockwork gold-and silver-bearing quartz-calcite-clay veins cut variably clay-altered, silicified, and sericitized rhyolitic Miocene volcanic rocks.

Jan 1, 1993

By R. N. Tempel, M. Lengke

Arsenic sulfide (orpiment, realgar, amorphous AsS and As2S3) oxidation rates were measured in mixed flow reactors at pH-2 and at temperatures of 25 ° to 30 °C. The measured oxidation rates for arsenic sulfide solids by dissolved oxygen are in the range of 10-11 to 10-10 mole m-2s-1 after being normalized to final surface area. The order of arsenic sulfide oxidation rates decreases at pH-2 from amorphous AsS > realgar > orpiment > amorphous As2S3. Compared to pyrite, arsenic sulfide oxidation rates are approximately 1.5 to 15 times slower than pyrite oxidation rates at pH-2.

Jan 1, 2003

By R. R. Rollins

Field data combined with theoretical derivations were used to design a surface mining operation using explosive casting. Calculated casting results varied from 44% to 65% depending on bench height. The field tests were performed at an Eastern, contour, coal stripping operation. Results from five experimental casting shots, using a shovel and trucks, are summarized and compared to conventional mining methods. The overburden material removed by casting ranged from 35% to 65%, with an average of 50%. Fragmentation was improved, and it was demonstrated that this procedure is economically attractive, with a resultant cost savings of $0.59/m3 or $5.93/t of clean coal.

Jan 1, 1988

By Gary B. Hemphill

The 345 km long Taiwan High Speed Rail Project will connect the island’s two most populated cities, Taipei and Kaohsiung. Kaohsiung is the world’s third busiest port. The 23 km of alignment on Contract C230 requires the construction of 5,879 m of shallow mined tunnels ranging from 137 m to 1,285 m in length. All nine of these tunnels are mined using NATM methodology. Two of the tunnels, T01 and T08 are in the Toukoshan Formation. This paper will discuss the mining methods, ground support design, and the instrumentation installed to monitor and verify its effectiveness in the two aforementioned tunnels.

Jan 1, 2003

By H. J. Ilgner

Previous applications for using waste rock for backfilling in South African gold mines were reviewed and it was found that in many cases the mechanical equipment selected and the design philosophy applied did not meet the requirements. A more simplified system configuration is proposed, which allows the equipment to be relocated as mining progresses. Innovative high-intensity grinding and dense-phase pumping technology are proposed to provide a low-porosity backfill with a particle top size of 5 mm to 8 mm. According to recent rock mechanics modeling work, this comminuted waste backfill material can provide a good compromise between underground support characteristics and reliable hydraulic transportation behavior.

Jan 1, 2001

By T. E. Wilson

The length of Alaska’s coastline, combined with the presence of a significant number of fjords, encourages consideration of marine disposal of mine tailings. However, since various factors govern the viability of the submarine tailings disposal (STD) option, the decision making process is complex. An expert system, called Submarine Tailings Disposal Expert System (STADES) that will help mining project planners explore the feasibility of STD, was developed. Existing literature, supplemented by engineering recommendations, on the various aspects of marine disposal of tailings was reviewed and formed the knowledge base for the expert system. The shell used to develop the expert system was LEVEL5®.

Jan 1, 2001

By M. R. Leonard

It is estimated that between 5 and 15 pounds of solid waste are generated monthly by each individual. Finding a final resting spot for such waste is an important matter. In the "good ole days," dumps of every description and condition were available. Not so now. Almost all states have adopted and are enforcing strict regulations regarding the disposition of solid waste. Many companies, owing to the nature of their business, have potentially good waste-disposal sites available. Cleveland Quarries Company falls in this group; but in spite of our having state and county permits, opposition by the local community denied us the opportunity to provide a needed local service.

Jan 1, 1974

By Lynn B. Hales, John A. Herbst, Thomas L. Gabardi

A system for a continuous determination of the charge volume of grinding media in ball mills and SAG mills has been developed. The system, comprised of a unique measurement device and a model based Kalman filter algorithm, determines grinding media level within a mill and calculates media and liner wear rates. The signal from an instrumented washer mounted on the exterior of the mill shell is used to provide the measurement that, along with mill power and on-line models for media mechanics, result in estimates of mill parameters that can be used in media addition control strategies. Data are presented for a 12.5 x 15 ft. ball mill.

Jan 1, 1990

By K. N. (Mani) Subramanian

A 2.5 meter diameter column has been successfully used in a 100 tph flotation plant at the Harbour Lights Mine in Leonora, Western Australia, to produce a final gold bearing sulfide concentrate from the ore in a single stage. This pioneering application of column flotation cells to rougher stage was pilot tested using a 11 cm column, which demonstrated column&apos;s capability in rougher, scavenger and cleaner flotation stages. A hybrid circuit involving columns and mechanically agitated flotation cell s was adopted for the commercial installation. This paper describes pilot plant results, design of the plant flotation circuit, and early results of commercial operation.

Jan 1, 1988

By P. R. Busmann, D. J. Rogers

The Bureau of Reclamation&apos;s Syar Tunnel project included excavation of a 9.2 kilometer (5.7 mile) long, 3.6 meter (11.8 ft) diameter tunnel through gently dipping sedimentary rocks consisting of shales, siltstones, sandstones and limestone. The tunnel was supported full length with precast concrete invert segments and lightweight steel sets and lagging. Several world records for advance rate were set, including 57 meters (187 ft) in an eight hour shift and 127 meters (417 ft) in a 24 hour day. The tunneling system utilized a remanufactured and modified Robbins hardrock TBM and a 9,280 meter (30,450 ft) long, 61 centimeter (24 inch) wide, continuous conveyor system.

Jan 1, 1991

By K. S. Shivakumar, R. Bhima Rao, M. R. Patil

Liberation size can be estimated using various techniques such as grain counting, frequency curves, X-ray intensity and the mesh of grind. The present investigation deals with the estimation of the liberation size of graphite flake contained in a schistose ore from Shivaganga, India. It was observed that the flakes are liberated at from 75 to 150µm. The rougher flotation concentrate obtained after grinding the run-of-mine ore for 5 min contained 54% fixed carbon. This represented the first stage of liberation. After regrinding to <90 µm in the presence of sodium silicate and guar gum, a cleaner concentrate containing 82% fixed carbon was obtained.

Jan 1, 1998

By Levent Ozdemir, Roy H. Spitzer, Don W. Deere, John B. Blyler

This paper documents the construction of the Stanley Canyon Tunnel, the geologic conditions encountered, boreability of the rock, and the impacts of the conditions encountered on the construction. The 5.05 kilometer long (3.1 miles), 3.47 meter (11.4 feet) diameter, tunnel was driven through granites with a refurbished tunnel boring machine (TBM). Difficult ground conditions encountered included shear zones, high groundwater flows, and hard, tough, and strong rock. Detailed geotechnical studies during construction revealed that microscopic changes in the rock grain boundaries due to contact metamorphism, resulted in the hard boreability. Originally scheduled for five months, the tunnel construction required nearly three years, including periods of project shutdown.

Jan 1, 1995

By A. P. Chaves, A. Gomes

The cyanidation and adsorption processes at Fazenda Brasileiro mine were studied with the aim of increasing hydrometallurgical recovery. Technical evaluation of the processes consisted of (i) quantitative mineralogy of ore samples collected in different points of the circuit, and (ii) comparison of plant performance in the original (designed CIP) and in the modified (current CIP/CIL) circuits. An empirical correlation between process variables and gold grades in the cyanidation tailings was established. The suggested modifications in the circuit and in the operation conditions led to an increase in gold recovery, from 91 to 93.5%. Annual revenue is expected to show an increase of approximately US$ 1 million.

Jan 1, 1998

By G. E. Mellor, R. E. Lippoth, T. B. Faddies

The Little Rocky Mountains host epithermal- gold-silver bearing vein and stockwork deposits in a syenite intrusive complex. Pegasus Gold Ltd. is currently mining these oxidized deposits by open-pit methods and recovering gold and silver by heap-leach processes. A geologic program has been designed to effectively determine the basic ore characteristics; 1) mineralization; 2) oxidation; 3) structural setting; 4) lithology; 5) alteration; and ultimately, 6) the leachability of the ore. Geologic mapping, sampling, drilling, assaying, and testing are routinely used in exploration, development, production control, mine planning, and ore reserve estimations. Timely and accurate assay results are essential for the program&apos;s success.

Jan 1, 1992