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By Spencer R. Titley

Nearly three decades of intense research, corresponding with a period of unparalleled discovery and the advent of scientific advances and hypotheses of ore formation, has resulted in a great body process-focused research concerning how ore deposits form. The development of process models and their application has proceeded more or less in step. Discoveries have been made in mineralized regions such as provinces and districts but generally without a comparably developed understanding of why provinces and ore bodies exist and, except in general terms, where ore deposits are within districts and regions. The process of discovery is still referred to as search and exploration budgets are heavily weighted toward exploration drilling.

Jan 1, 1995

By Jinxing Ji

Several fundamental aspects related to the nickel electrowinning from chloride electrolytes have been addressed in this paper. The thermodynamic study includes the activity coefficient of the hydrogen ion and the speciation diagram of NiCI2 solutions. The activity coefficient of the hydrogen ion (YH+) was calculated and estimated experimentally using a combination glass pH electrode. It was found that YH+ was greater than one in concentrated NiCl2 solutions and increased significantly with increasing NiCl2 concentration. The speciation diagram for NiCl2 solutions was plotted with YH+ and the effect of the ionic strength on the equilibrium constants being taken into account. It was discovered that the predominant nickel species in the acidic region were Ni2+ and NiCI+ in 0.937 M NiCl2 solution at 25°C. Electrodeposition tests demonstrated that higher Nit' concentration in the electrolyte improved the current efficiency of nickel electrodeposition (CENi). The additions of H3BO3, and NH4Cl increased very little the current efficiency of nickel electrodeposition at pH 1.5 and temperature 60°C. However, the addition of sulfate decreased the current efficiency of nickel electrodeposition. Nickel electrodeposition was also found to be a steady-state process since the amount of acid added to the electrolyte at a constant pH increased linearly with time during galvanostatic electrodeposition. The cathode surface pH during nickel electrodeposition was measured using a flat-bottom combination glass pH electrode and a 500-mesh gold gauze as cathode. The cathode surface pH was found always to be higher than the pH in the bulk electrolyte, and if the current density was sufficiently large, it would eventually reach a level causing precipitation of insoluble Ni(OH)2(s) on the cathode surface. Rotating disc electrode studies revealed that the rate of nickel electrodeposition was first order with respect to the activity of nickel ion and zero order with respect to the activities of chloride and hydrogen ions. The rate of hydrogen evolution was found to be first order with respect to the activity of hydrogen ion and to be zero order with respect to the activities of nickel and chloride ions. These findings indicate that nickel deposition and hydrogen evolution proceed independently.

Jan 1, 1995

By L. F. Zeiler

In the past, health concerns in coal mines have primarily centered on those elements which have been essentially inherent to the mining environment. These would include respirable coal mine dust, respirable crystalline silica, excessive noise levels, and diesel exhaust particulates. Commercially-available chemical products are prevalent on mine property. These potentially toxic materials are chemical formulations that can degrease, clean, and lubricate metal parts, separate coal from rock in float/sink operations, and aid in roof consolidation, among other uses. As the general public has become more aware of the hazards of chemical exposures, miners have likewise become more concerned about working with an ever-expanding variety of chemical products on the job. Often, product or chemical specific hazard communication training is inadequate or ineffective, and miners do not know exactly what the ingredients are in the products they handle, or the health hazards involved with their use or misuse. Currently, the Mine Safety and Health Administration (MSHA), by law, enforces 1972 Threshold Limit Values (TLV). MSHA is making preparations to adopt new personal exposure limits for enforcement. The values given throughout the article are 1994 TLV's and are not enforcement standards, but are used for discussion purposes. They reflect the current scientific thinking regarding personal exposure to these chemical agents. An overview of these products is presented, and the potential health hazards associated with their use are discussed. Controls needed to prevent overexposures, such as proper handling procedures and personal protective equipment, are covered. Methods used to collect and identify contaminants are presented.

Jan 1, 1995

By John F. Papp

Based on a review of historical domestic and international chromium metal production capacity, production, consumption, trade, and trade literature, world annual chromium metal production capacity in 1995 was estimated to have been 38,300 metric tons, a drop from 43,500 tons in 1994. World chromium metal production and consumption were estimated, on average from 1984 through 1992, to have been 21,000 tons per year. U.S. consumption was estimated, on average over the same time period, to have been 6,200 tons per year. The major world chromium metal producers between 1984 and 1995 were China, France, Germany, Japan, Russia, United Kingdom, and United States. From 1984 through 1992, world trade averaged 8,400 tons per year. Germany and the United States accounted for over 75 percent of imports on average during the same time period. U.S. chromium metal import value rose from under $1 per kg before 1964 to over $6 per kg in 1993. Over the same time period, prices rose from about $4 per kg to about $10 per kg. Chemical specifications have become more stringent. Detailed chromium metal trade, prices, value, chromium metal chemical specification, and production capacity by country are reported. A shift in trade patterns was anticipated as Japan exits production and displaces Germany as the second largest importer and as Russia increases its role in world trade.

Jan 1, 1995

By Charles W. Perdue

This U.S. Bureau of Mines report considers, from a psychological perspective, the perceptual process by which miners recognize and respond to mining hazards. It proposes that if the hazard recognition skills of miners can be improved, mining accidents may be reduced to a significant degree. Prior studies of hazard perception in mining are considered, as are relevant studies from investigations of military target identification, pilot and gunnery officer training, transportation safety, automobile operator behavior, research into sensory functioning and visual information processing. A general model of perception is introduced, and selected concepts from the psychology of perception that are applicable to the detection of mining hazards are reviewed. Hazard recognition is discussed as a function of the perceptual cues available to the miner as well as the cognitive resources and strategies employed by the miner. The development of expertise in responding to hazards is related to individual differences in the experience, aptitude, and personality of the worker. Potential applications to miner safety and training are presented.

Jan 1, 1995

By Y. C. Guan

The dissolution behavior of silver and copper form their elemental states and Ag/Cu alloys in ammoniacal solutions has been studied using rotating disc electrodes. The variables studied included concentration of ammonia, oxygen partial pressure and rotating speed of the disc. The results have been interpreted in terms of the mixed potential theory. The effect of local current resistance on the overall current has also been examined as a part of the governing theory of the dissolution. It was observed that the dissolution potential and the rate of dissolution were very much affected by the composition of the alloys.

Jan 1, 1995

By W. M. Hart

The current Automatic Data Acquisition system developed by some support manufacturers makes it possible to continuously monitor and record changes in leg pressure and advancing ram stroke in every shield, and shearer position at any moment during the mining operation. In order to effectively use the massive data obtained from this system for improving production and maintenance managements as well as providing better roof control at a longwall face, the research currently conducted jointly by West Virginia University and Cyprus-Amax Coal Co. attempts to develop a Longwall Management System for mine operators. The LMS software package runs on a MS Windows NT environment and consists of four sub-systems: (1) Data Interpretation and Analysis; (2) Production Management; (3) Maintenance Management; and (4) Ground Control. This paper presents the details of each sub-system.

Jan 1, 1995

By R. D. Irvine

Enhanced concern for protection of the environment and attendant actions by environmental regulatory authorities in support of this concern are influencing to varying degrees the demand and supply of a range of industrial minerals in a number of jurisdictions. These influences take a variety of forms. In this paper, the author seeks to delineate certain broad trends which are occurring relative to industrial minerals and the environment and then, through a series of examples, outline opportunities, developments, and impacts respecting a number of industrial minerals produced and consumed in Canada and the United States.

Jan 1, 1995

By W P. Player

The legislative operating environment, or the mineral regime, that a country has to offer is one of the key determinants that a company wanting to invest in an area takes into account in formulating its investment decision.   The New Zealand Government recognises this and the importance of getting the regime right in order to provide for continuing investment in mineral exploration and mining in New Zealand . In recent years, the Government has given considerable attention to developing legislation which provides for investment to take place; for those making the investments to have a stable, fair and open investment environment with government intervention only when considered absolutely necessary because other approaches are not working; and for the people of New Zealand to know that investment must meet acceptable health and safety standards and have acceptable impact on the environment. Also of key importance is having a clearly defined mining regime which includes rules on how to obtain a permit and rules in respect of ongoing permit compliance, rights to develop a mineral resource and permit conditions (in particular, the royalty regime). In New Zealand , these matters will all be addressed in what are referred to as 'minerals programmes'.   The Crown Minerals Act 1991, which is the legislation governing the allocation and management of permits for Crown owned minerals, requires that the Minister of Energy prepare minerals programmes. Minerals programmes establish the policies, procedures and provisions that the Minister shall follow in exercising his or her functions and powers under the Crown Minerals Act. Minerals programmes set out the principal reasons for and against adopting these policies, procedures and provisions and also restrictions on prospecting, exploration and mining for Crown owned minerals. Essentially minerals programmes define the mining regime for the minerals to which they apply, other than the taxation regime, environmental and health, safety provisions, land access matters and general matters concerning the investment climate.

Jan 1, 1995

By P. E. Fox, R. S. Cameron

"The QR gold deposit lies in the Cariboo plateau region of central British Columbia. The deposit was discovered in 1977 and since then a mineable reserve of 1.3 million tonnes grading 4.7 g/t Au has' been outlined in three separate zones. Soil sampling of glacial tills followed by diamond drilling of favourable host rocks proved to be key exploration techniques.The deposit is situated in the southern Quesnel terrane along the eastern fringe of the Intermontane Belt which here comprises a sequence of basic and intermediate volcanics and a series of stocks of alkaline affinity; generally diorite, monzonite and syenite. Hornfels and epidote-rich ferromagnesian exoskarn and sulphide-rich mantos have developed in a metamorphic aureole formed around a central diorite stock. Gold-rich zones lie along the outer periphery of the aureole where bodies of gold-bearing epidote-rich skarn and auriferous mantos rich in epidote and pyrite have formed in beds of calcareous tuffite lying at the top of a thick basaltic sequence. The deposit is regarded as' a subclass of gold skarn deposits. Diagnostic features are its association with alkalic intrusive rocks in a subvolcanic setting and the presence of oxidized, epidote-rich mineral assemblages.IntroductionThe QR gold deposit lies within the Cariboo plateau region of central British Columbia, 58 km southeast of Quesnel. The deposit, owned by Kinross Gold, was discovered during a regional reconnaissance program by Dome Exploration (Canada) Limited and Newconex Canadian Exploration in 1977. Considerable exploration and development has been done since that time. Mineable reserves of 1.3 million tonnes grading 4.7 g/t Au have been outlined to date in three zones."

Jan 1, 1995

By D. J. Turk

Faced with decreasing production from the gold heap leach operation, Robinson implemented a drilling and blasting program on the leach pads in 1993. This program offset some of the negative effects of low ore permeability and short circuiting of leach solution that resulted in lower than optimum recoveries. The drilling and blasting program created new solution flow paths and increased gold recovery. Production and pulp assays at depth intervals, prior to and following drilling and blasting, reveal the degree of short circuiting and benefits of the program.

Jan 1, 1995

By Vynne J. F

Drill monitors for rotary blasthole drills have been available to the mining industry since the 1970s. The early monitors were pen strip chart recorders that were developed for the oil drilling industry and adapted to mining. They recorded drilling parameters such as depth, pull-down pressure, torque, RPM, and hailing air pressure. While these recorders could generate a large volume of paper, the amount of useful data was minimal. The data was not summarised and required an engineer to interpret the chart traces. Being a mechanical recorder, the devices were also susceptible to frequent failures. Modem electronics, and the development of the personal computer and its associated software have radically changed the type of instrumentation that is now available for blasthole drills. Perhaps more important is what can be done with the data. The PC allows the logged data to be analysed, summarised, and a variety of reports to be generated. The reports can be customised to meet the specific requirements of the mine and reduce the amount of time that is required to interpret the data. There is also an increased awareness in the mining industry of the importance of production drills. Blasthole drills have typically been the piece of production equipment that received the least amount of attention in a surface mine. Management focussed on the trucks and shovels or draglines. This situation is changing, and therefore the benefits that can be derived from monitoring drill performance are being recognised. Potential economic benefits of installing drill monitors have been documented in previous papers (Peck and Vynne, 1992). Mines are finding that pay-back periods of less than twelve months and rates of return in excess of 30 per cent are not uncommon. These benefits include the following: 1. Reduced overdrilling; 2. Increased rate of penetration; 3. Helping to locate coal seams; 4. Identification of weak and strong zones; 5. Reduce geophysical logging; 6. Optimising blasts; 7. Improved fragmentation and diggability; 8. Decreased coal dilution; 9. Increased bit life; 10. Reduced maintenance costs; 1 I . Improved accuracy of data and reports.

Jan 1, 1995

By E. M. Williams

The U.S. Bureau of Mines recently conducted a limited-scope study on the use of lineament analysis and electromagnetic geophysics to better identify the surface expressions of faults at the Cimmaron Mine near Raton, NM, an operating longwall mine in the York Canyon mine complex. Two normal faults were encountered by the mine, one during gate road development and drilling and another only through drilling. The potential ground control problems and offsets associated with these faults will severely impact long-range development plans, so it is essential to know the lateral extent of these faults within the coal reserves. The surface topography at the site is fairly rugged, yet outcrop exposure is poor. There is no obvious visible geologic evidence to indicate that the faults identified at depth extend to the surface. Both the geophysical and remote sensing techniques provided information on the presence and extent of important geologic structures which could not be gained just from drilling and surface outcrops. The geophysical surveys also were invaluable in confirming the presence of subsurface geologic structures in the vicinity of the lineaments assumed to be associated with the faulting.

Jan 1, 1995

By Henley S

The year 2000 is not very far ahead - only five years. It should not be hard to forecast what will happen between now and then, because the technologies that will be in practical use then should all be at least in embryo existence now. There has been a historical trend for the mining industry to work ever more difficult and ever more marginal deposits. There are clearly a few exceptions and major discoveries, but the industry is becoming heavily dependent, at both the exploration and the mining stages, on technological innovation to retain acceptable profit margins. With the new exploration and mining technologies come requirements for additional computing support. Computing technology further allows the potential integration of a wide variety of different types of data to help the explorationist to build and test exploration strategies, or to help the miner to design and schedule mining operations.

Jan 1, 1995

By J. H. White

It is hypothesized that the Hotelling Valuation Principle (HVP) can determine the value of developed gold reserves using simple methods and easily obtained data. This paper reports the results of an empirical test of this hypothesis. Using publicly available data from North American gold companies, we obtained data for V, R, p, and c and ran a simple linear regression using equation (1.1) as the definition of the dependent and explanatory variables. By examining the value of the coefficients of the resulting regression equation, we can draw conclusion as to whether or not the HVP can be confident1y used as an estimator of the value of developed gold reserves.

Jan 1, 1995

By G. A. Parkison

The sequential copper analysis method is a particularly useful technique to semi-quantitatively define the geologic, mineralogic, and metallurgical types and zonations commonly associated with porphyry-type copper deposits. The method is based on the partial dissolution behavior displayed by the prevalent copper minerals malachite, chrysocolla, chalcocite, and chalcopyrite to solutions containing sulfuric acid and sodium cyanide. Results from sequential analyses of the sample and analytical residue using sulfuric acid followed by sodium cyanide and then aqua regia solutions when compared with conventional total copper analyses can determine the amounts of leachable oxide minerals, leachable secondary sulfide minerals, and primary copper minerals, respectively. Sequential assay analytical results and interpretation are presented for copper deposits in Chile, Mexico, and the United States.

Jan 1, 1995

By C. L. Molina

The U.S. Geological Survey (USGS), in cooperation with the Bureau of Land Management (BLM), Geological Survey of Wyoming, and U.S. Bureau of Mines (USBM), will produce an estimate of the amount of available coal in an area about 55 Ian (35 miles) south of Gillette, Wyo., where the Wyodak coal bed is 8-27 m (25-90 ft) thick. Available coal is coal that actually is accessible for development under current regulatory, land-use, and technologic conditions. Local coal-development considerations include roads, ranches, railroads, pipelines, power lines, wildlife and archaeological sites, alluvial valley floors, cemeteries, and the Hilight oil and gas field and gas plant. Some of these considerations would be mitigated so that surface mining may proceed; others presently preclude mining in their vicinity.

Jan 1, 1995

By J. G. Schofield, C. G. Tan, R. J. Ord

"Most electric furnaces in the nickel and copper smelting industries are still fitted with conventional electrode holders which consist of water-cooled electrical contact clamps and a pressure ring. The water cooling exerts a significant cooling effect on the electrode column. The importance of controlling the temperature of the Soderberg electrode paste at the contact clamp area is examined, using in-plant experience and computer simulation of the paste melting and baking process. In addition to the effect of water-cooling, the effect of other variables, including the mantle air temperature, the electrode current, the furnace freeboard temperature and the electrode slipping rate are discussed. Ways in which the variable heating conditions in the paste melting zone can be controlled are outlined.IntroductionIn most non-ferrous electric smelting operations, the breakage of Soderberg electrodes is an infrequent, isolated occurrence. Occasionally, however, a rash of breakages may be experienced on a particular furnace for what appears to be no obvious reasons. The extent of the breaks may not exhibit a uniform pattern; sometimes the break may be less than half a metre above the electrode tip; at other times it may be at or just below the roof level. The latter type of break is, of course, the most dangerous since it is closest to the non-baked, weak portion of the electrode paste column. No matter where the breaks occur, they result in abnormal furnace power, charging and tapping conditions and loss of production while the new electrode section is slipped and baked. On a six-electrode furnace, breakage on one electrode has the immediate effect of reducing the total furnace power by one-third. On a three-electrode furnace, the effect is more drastic, one half of the power being lost."

Jan 1, 1995

By Fathi Habashi

The behavior of pyrite, covellite, and arsenopyrite during leaching is different from other sulfides due to the presence of the disulfide ion, Sl. Arsenopyrite contains in addition, the diarsenide ion, Asl. The disulfide ion undergoes auto-oxidation in high acidity leading to elemental sulfur and sulfide ion formation: The sulfide ion may oxidize further by oxygen to elemental sulfur if high acidity is maintained. In neutral medium, the disulfide ion does not undergo auto-oxidation but oxidizes to thiosulfate then to sulfate: This leads to the two overall reactions observed experimentally: In acid medium and in neutral medium Covellite and arsenopyrite behave similarly.

Jan 1, 1995

By S. Davis

It has been accepted almost as dogma that sampling contributes most of the error to fluctuations in gold fire assays. Differences in assay results on pulp material from the same sample interval are frequently regarded as evidence of the presence of the so called "nugget effect" or relatively coarse gold particles. It is true that if coarse gold particles are present they contribute to substantial sampling fluctuations, but while the process of sampling is probably the major source, the analytical process cannot -be completely ignored as a possible contributor to erratic assay results. In order to maintain a stable assay process, the analytic part of the system must be kept in control as well as the sampling and preparation part. One way of monitoring the performance of the analytic system is to systematically assay standard material whose sampling characteristics are carefully controlled. Gold assay standards are not prepared nor can they be prepared to account for both sampling and analytical errors. It is not possible to send coarse material to a lab for preparation (which includes both the processes of comminution and splitting) followed by fire assay, to make inferences only about the fire assay process. Because most gold ores are very heterogeneous, sampling errors would in most cases completely mask the contribution of the analytical errors. Assay standard material is prepared only to assess the accuracy and variability in the fire assay process.

Jan 1, 1995