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By J. N. Philbrook

As with most industries, mining must now include in its plan of operation mechanisms to address a project's environmental impact. New regulations have focused attention on the potential environmental impacts of industry, particularly the handling of wastes. Modifications are currently being proposed to the Bevill Amendment. And development is ongoing of Resource Conservation and Recovery Act (RCRA) Subtitle D regulations specific to mining wastes. The result is a growing concern on the part of lenders, developers, buyers and owners regarding acquisition and ownership of mining properties. One of the most effective tools in managing the regulatory requirements is an environmental audit. An environmental audit can be a literature review to determine regulatory requirements. The audit can also take on the form of a phase-one site assessment. This is a limited investigation to determine whether there are specific

Jan 1, 1991

Degussa's PAL-system (peroxide assisted leach) has been proven to be more economical than the conventional cyanidation technique. Significant in- creases in the gold recovery have been reported, accompanied by savings in cyanide. Accelerated extraction kinetics and modified reagent demands necessitate a redesign of the conventional cyanidation plant. The South African Osprey Mine is presented as an example of a successful PAL-application. Based on the plant and laboratory data it is shown that the redesign of the flowsheet can be an important factor for the effectiveness of a metallurgical plant. In the case of the Osprey Mine, the PAL-technology all ows a modification of the current preoxidation-ClPcircuit to two separate CIL-plants to treat run-of-mine ore and old tailings dumps. A doubling of the throughput is possible without enlargement of the plant. This innovation in the field of gold extraction, the combination of the PAL-process with a redesign of the metallurgical plant, can be considered as a basis for a more profitable gold mine.

Jan 1, 1991

By James R. Boulton

Fire detection using Carbon Monoxide sensors is based on the assumption that a rise in the level of Carbon Monoxide in the atmosphere over a fixed, predetermined ambient level is indicative of a fire. The method is simple, reliable, and effective in those mines where the only source of CO is from undesired combustion. Ambience for this purpose is defined as that level of the gas that is present on a day to day basis whose source is not a fire. In a diesel powered mine the level of CO can and does vary so widely from hour to hour and minute to minute that the selection of a predetermined, fixed level represents a compromise between sensitivity and reliability. The compromise is a best of both and worst of both situations and the computer system often resembles the little boy who cried wolf instead of a state of the art early fire monitoring and detection system. Cyprus Coal personnel have developed method of determining the ambient level of CO in the atmosphere on a real time basis and using that dynamic ambient level to determine whether or not a fire exists in the mine. The method has been given the name of Wave Trend Crossing.

Jan 1, 1991

By R. D. Doepker, P. L. Drake

The dissolution of metals from various metal- mine tailings has been studied through a series of submerged tailings batch tests at US Bureau of Mines laboratories. Tailings selected for this study included both reactive (as determined by column leaching studies) and benign tailings. Metal mobilization in aerated (97% saturated with oxygen) samples appeared to be consistently greater than metal dissolution from stagnant (79% or 70% saturated with oxygen) waters. In the early weeks of the study, sulfate concentrations increased with solid-liquid contact time, while calcium dissolution remained early constant. Metal concentrations varied in relation to solid-liquid contact time and aeration. Leachate pH appeared to be nearly independent of solid-liquid contact time for basic tailings. Reactive tailings having both a submerged and a surface component demonstrated increased metal mobility.

Jan 1, 1991

By L. M. Nuelle

Rare earth element (REE)-and gold-bearing breccia pipes are a potentially significant economic target in the Pea Ridge iron ore mine, Washington County, Missouri. The Pea Ridge deposit is one of eight known volcanic-hosted iron ore deposits in the Middle Proterozoic St. Francois terrane, which are similar to the Olympic Dam-type deposits of Australia. The iron orebody is steeply dipping, tabular-shaped, and cuts across the host rhyolite. The footwall of the deposit is zoned from the massive apatite-bearing magnetite core outward to heterolithic breccia, pseudobreccia, specular hematite zone, to an extensive silicified zone. The hanging wall is zoned from the massive magnetite core outward to a heterolithic breccia, pseudobreccia, and an amphibole skarn zone. The REE-rich breccia pipes cut through the various lithologies along the footwall at or near contacts. They are typically 60 m long, 15 m wide, and extend at least 120 m vertically. The pipes are comprised of fragments of rhyolite host rock, massive magnetite zone, specular hematite zone, and silicified zone rocks supported in a matrix of rock flour, barite, feldspar, monazite, apatite, chlorite, xenotime, and, locally, gold. Total REE oxide content of samples of the ground mass material, which are not diluted with lithic fragments, average about 20 weight percent. Grades from working faces in the mine are lower and average about 12 weight percent. Gold distribution is erratic, but concentrations are as high as 371 parts per million.

Jan 1, 1991

By Andrew L. Mular, Richard R. Klimpel

Optimization strategies of possible interest to mineral processing are reviewed and typical strategies initiated in processing plants to date are discussed. Both On-Line and Off-Line optimization procedures have been employed by industry, assisted either by operators or by digital computers. In every case, dollar benefits have accrued.

Jan 1, 1991

By Richard H. Granhom

Detonation pressure, or Chapman-Jouguet pressure, is an intrinsic property of an explosive, and like detonation velocity, is an indicator of explosive performance. Pressure and velocity are also important for calibrating computer codes and for other calculations such as the stress imparted to rock or metal by an explosive. The detonation pressures, P~cj, of many "ideal" explosives have been measured indirectly by recording some hydrodynamic flow variable other than pressure, with P~cj being inferred from hydrodynamics and the assumed Chapman-Jouguet equations. One such method is the difficult and expensive "aquarium technique''.] Commercial explosive manufacturers generally rely on estimates of P~cj generated by computer codes not explicitly designed for non-ideal explosives typically used in commercial applications. Over the last decade, U.S. national and government laboratories have developed in-situ gauge techniques such as the manganin gauge, for direct measurement of detonation pressure. Manganin is an alloy of copper, manganese and nickel, and is ideally suited for use as a pressure transducer because its electrical resistance changes with pressure, but is nearly constant with changes in temperature. A simplified manganin gauge technique adapted for use at a commercial test site is described and some initial results from measurements on commercial emulsion explosives are presented.

Jan 1, 1991

By A. J. Partos

Table 4, Page 311 Table 4 Experimental Parameters from Straight Line Interpretation of Mohr Failure Envelope [ ]

Jan 1, 1991

By Katherine H. Walton

The research affiliate projects of the Continental Shelf Division of the Marine Minerals Technology Center concentrate on the development of technologies and methodologies for the exploration 4 and assessment of nonfuel continental shelf mineral resources within the U.S. Exclusive Economic Zone. Three of the FY 1990-91 research grants are summarized below. Scientists at the Center for Applied Isotope Studies at the University of Georgia have developed ?An Advanced Design for a Seafloor Gamma Isotope Mapping System? for the rapid collection of data on seafloor sediments. This system is designed to detect gamma radiation emitted by naturally occurring radioactive elements found in marine sediments. This data can be used to study seafloor lithology and has direct application in marine mineral surveys. The purpose of this study has been to redesign and calibrate the system for marine mineral survey work. Recent modifications of the sled design, gamma radiation detector, and supporting software have resulted in considerable improvements in sensitivity, functional operation, and data acquisition.

Jan 1, 1991

By Lawson F

Synthetic calaverite (Au Tez) has been prepared and its physical properties checked.Simple flotation tests indicate that the recovery of calaverite should be possible using n-butyl or sec-butyl xanthate collectors under approximately pi I neutral conditions with a copper sulphate activator.Roasting calaverite in air at moderate temperatures resulted in its decomposition with the formation of elemental gold and tellurium dioxide.In alkaline oxygenated cyanide solutions, both gold and tellurium tend to dissolve. At pHs less than 14, about 50 per cent of the tellurium remains as elemental tellurium; however in very strongly alkaline solutions, essentially all of the tellurium is converted to the soluble tellurite ion (TeOl-).However, even at high pHs, the solubility of gold in the cyanide solution is still low due almost certainly to passivation effects.

Jan 1, 1991

By Michel Grenier, Gopal Kunchur, Stephen Hardcastle

This paper presents the findings of a dust study in a typical fluorspar processing plant. The primary purpose of this study was to identify employees and occupational groups exposed to high dust levels and determine compliance with personnel regulations for regular and extended work shifts. The range of airborne concentration of respirable silica and fluoride compounds in specific areas and on personnel was determined. State of the art dust monitoring equipment and tracer gas techniques were used to measure dust concentration, pinpoint dust sources and map major airflow trends in the mill. Results of the survey indicated silica dust concentrations in excess of permissible limits being produced mainly by crushers at the south end of the building. Tracer gas releases and gas chromatographic analysis further showed that prevailing south to north air currents tended to carry and spread dust produced by the crushing operations throughout the process plant. Airborne concentrations of fluoride compounds measured during the study were always well below the prescribed threshold limit value (TLV) for the contaminant. Recommendations, including a mechanical exhaust ventilation system on crushers and transfer points, scheduled preventive maintenance on existing bar sprays and wearing of personal protective equipment were made which significantly improved the work environment. Further testing conducted after Installation of the dust extraction system revealed significant improvements in most areas of the mill.

Jan 1, 1991

Good morning ladies and gentlemen. It gives me great pleasure to talk to you today about a pet subject of mine, on when to mill and when to leach gold ores. According to Gold Fields Mineral Services of London, gold production in the United States in 1989 amounted to about 8.5 million ounces (259t), an increase of 29 per cent over 1988 and 67 per cent over 1987. The U. S. Bureau of Mines reports that from the major producing states of Nevada, California, Montana, and Alaska, some3.2million ounces of the 1989 production were produced from milling gold ores and 2.3 million ounces from heap or dump leaching. Ap- proximately 45 million tons of ore were milled and 140 million tons of ore were heap or dump leached.

Jan 1, 1991

By Mwaba CC

Ok Tedi Mining Ltd has been using flotation for the production of copper/gold concentrates from a complex copper sulphide ore for several years. During this period, much effort has been devoted to metall- urgical treatment of the ore. This paper examines some of the mineralogical aspects of the sulphide minerals in the ore using the electron microprobe analyser. Results have revealed the complexity of the copper sulphide minerals and in particular, chalcocite. Analysis of both plant and laboratory flotation products has provided further insight into the effects of mineralogy on the flotation of copper and iron sulphides. A significant observation is that some of the pyrite minerals apparently exhibit natural floatability. The implications of the mineralogical characteristics of the sulphide minerals on the flotation of the ore are also discussed.

Jan 1, 1991

By Corby G. Anderson

Since 1985, the Sunshine Mining Company has used a patented nitric-sulfuric acid pressure leaching system for production of silver and copper from a refractory sulfide ore body. To better understand this novel process, a program of lab scale testing was undertaken to quantify the effect of system variables on silver recovery. Some of the factors studied include temperature, agitation, acidity, vessel pressure, particle size, percent solids and oxidizer amount. In turn, this knowledge will be applied in actual plant practice to upgrade reaction time, increase concentrate throughput, raise silver recovery and lower reagent costs. A discussion of plant process changes resulting from lab scale testing is included.

Jan 1, 1991

By Clarke DS

The igneous intrusions in SE Papua New Guinea are part of a sub-volcanic to plutonic, high-K calc-alkaline to shoshonitic suite. High-K andesitic to dacitic intrusives on Misima and Woodlark Islands, and shoshonitic intrusives in Milne Bay and the eastern Owen Stanley Ranges are related to late Cenozoic andesitic volcanism. Both suites are associated with epithermal Au-Ag deposits and weak porphyry Cu-Au mineralisation. All significant alluvial and lode gold occurrences in the region are spatially related to intrusions. Intrusions in the D'Entrecasteaux Islands and near Mt Suckling are core plutons related to basement doming, and appear to have no association with either volcanism or hydrothermal mineralisation. The core plutons are not petrochemi:ally distinct from the volcano-re:-ed Intrusions.

Jan 1, 1991

By Bengt H. Fellenius

It is a truism that in the design of pile foundations one must consider both capacity and settlement. As to capacity, most basic text books contain simple methods of design of capacity of single pile. More sophisticated methods are the subject of many journal papers. However, methods for design considering settlement of pile foundations are scarce. (Most confuse settlement with the movement due to load-transfer?the transfer of load from the pile to the soil). Furthermore, for both capacity and settlement, most methods include several simplifying assumptions regarding soil layering and neglect the effect of the frequently occurring fill and excavations, as well as changes of the groundwater table and pore pressure distribution. Therefore, the methods may provide qualitative results, but not quantitative. Because of this situation, pile design often appears as somewhat of a guessing game and a very subjective?and risky?occupation. This need not be. Pile foundation design is controlled by three factors: capacity, strength, and settlement requirements and these have been combined in a method called "the unified design of piles and pile groups considering capacity, settlement, and negative skin friction" (Fellenius, 1984; 1989), which method is summarized in this guide.

Jan 1, 1991

New Celebration Gold Mine is located 35 km SE of Kalgoorlie, Western Australia, in the Archaean Kalgoorlie-St Ives Greenstone belt. The leases total 119 sq kms and arepart of a joint venture between Newmont Australia Ltd (as manager) and Mt Martin Gold Mines N.L. Mining commenced in August, 1986 and is now producing over 115,000 ounces of gold per annum. A variety of gold mineralisation styles with a total resource of 23.5 million tonnes at 2.19g/t are associated with shear zones at New Celebration. Gold production is co-ordinated from 7 open pits with others planned to com- mence soon. A large scale underground trial mining operation has com- menced with a decline on the hanging wall of the main producing orebody, Hampton Boulder. Millfeed produced is classified on the stockpile according to grade and metallurgical performance and blended tomaximise throughput while main- taining grade through a CIL treatment plant currently operating at 1.7 million tonnes per year.

Jan 1, 1991

By Joseph M. Denk, Gary J. Wirth

This paper summarizes a three phase face ventilation study which was conducted from September 1989 through March 1990 to determine face area methane liberation patterns on two extended longwall sections. The coal seam being mined was considered gassy and the mine liberated an average of 14.4 million cubic feet per day (cfd) or 0.41 million cubic meters per day (cmd) of methane through the mine fans. The mine also used an extensive underground degasification program to recover up to 13.4 million cfd (0.38 million cmd) of methane. Data was collected while the longwall sections were mining from the beginning, middle and end of panel extraction to determine the relationship between the methane liberation and extent of longwall retreat. As expected, methane concentrations did increase from the headgate (intake) to the tailgate (return) side of the longwall face and peak concentrations were detected above the shearer as it passed a methanometer location during mining. There were significant differences in the methane liberations due to the location of the active face within the longwall panel. Results from this study could be used to determine a minimum design face air quantity for an extended longwall section operating under similar conditions.

Jan 1, 1991

By Majorkiewicz A

Engineering of gold treatment facilities complete with infrastruc- ture in a remote location such as Papua NewòGuinea present unique problems to the design team. Site location, topography, ground conditions and infrastructure are some of the major hurdles to overcome when setting out on the design of such plants. This paper discusses two such plants, located in two distinctly different areas of Papua New Guinea and the solutions evolved in order to design successful operating facilities.

Jan 1, 1991

By O E. Crenwelge

Seismograph measurements are usually made near blasting operations solely for the purpose of monitoring compliance with governmental regulations. However, recordings of seismograph signals have far greater potential than this, if the proper procedures are used for analyzing the transient data.

Jan 1, 1991