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By Atmesh K. Sinha

Death and injury rates in mining have been the highest of any industry; the injury severity rates in mines have also been the highest. Tentative figures reveal that 1971 was the best year yet for the bituminous coal indus¬try with the lowest number of fatal accidents. Nevertheless, 177 men were killed at a frequency rate of 0.76 per million man hours. Coal mine accident statistics have been described at various times as unacceptable and intolerable and recently resulted in the enactment of massive legislation. The 1969 Coal Mine Health and Safety Act was passed by Congress "to improve the working conditions and practices in coal mines and to prevent accidents and occupational diseases originating in the coal mining industry." The prevention of accidents in coal mines is the statutory responsibility of mining engineers and the moral responsibility of all who have any part to play in mining coal. The questions to be answered by these men may well be - What are the reasons for the high accident rate? Are the mines as safe as they can be? Are our mines sufficiently manned to insure proper supervision of production cycles and safety requirements? Are our plans for safety committees, safety campaigns, and safety inspections sufficient? Are they producing the results intended? If not, how can these be reorganized to have a greater impact? What is the real cost of an accident? What are the immediate and long-term plans for further improvements? These questions are in no way exhaustive, and the answers are not easy. There are many aspects of mine safety, and any one of them can be the subject of a lengthy discussion. The aim of this paper, therefore, is to limit the analysis to documented fatal electrical accidents in mines so that meaningful conclusions for improvement in electrical accident-experience statistics can be made. In doing this, it is also the intention to emphasize areas of missing information and propose a few suggestions for better hazard analysis.

Jan 1, 1972

By A. Kaina

The San Luis deposit is one of the few documented gold deposits on a detachment surface. This paper presents mineralogic and geochemical data that was gathered to characterize the mineralization, classify the ore deposit, and provide details of the ore forming process. Included are data on the paragenesis; alteration-mineral assemblages major and trace element geochemistry, and fluid inclusions. The San Luis deposit occurs on the western slope of the Sangre de Cristo Mountains adjacent to the San Luis Basin about 5 miles northeast of the town of San Luis in Costillo County, south-central Colorado. Mineralization was discovered in the district in the early 17th century. Production began in 1890 on lead-silver ores from which the district took the name the old name of "El Plomo". From 1897 through 1934 gold was intermittently produced. Battle Mountain Gold Company took an option on the property in 1987 and proved on ore body comprising an eastern block that has 1,277,300 t ore at a grade of 1.68 g/t and a western block of 9,744,000 t with a grade of 1.34 g/t. Production began in 1990. A companion paper by Benson (1994) describes the San Luis district and the ore body, hence the reader is referred to this or Robert and David (1990) for details of the geology from which the following is summarized.

Jan 1, 1994

By James A. Jessop

The Bureau of Mines is investigating the use of geophysical methods to determine rock mass characteristics, particularly rock quality, lithology, and fracture parameters that are important for determining the feasibility of in situ leaching operations. As part of this research, two Bureau-developed crosshole geophysical systems are described that can be used for site investigation and rock mass characterization. Results are given for performance tests at field sites in Arizona and Texas and for correlations between the crosshole seismic data with fracture frequency, rock quality, and lithologic variation. Recommendations are made for using elastic waveform propagation characteristics and dynamic elastic properties for improving rock mass characterization in the geomechanical assessment of in situ leaching deposits.

Jan 1, 1990

By J. V. Belke

There are many aspects of a grinding mill supply and installation that can result in the mill not operating as intended, resulting in unplanned shutdowns, poor reliability and headaches for all concerned. One of the largest aspects, both in criticality and physical mass, is the mill foundation; if not properly specified, designed and constructed the mill operation will be compromised. The mill foundation starts with the design specification and loading diagram supplied by the mill builder. The importance of understanding these documents and how to apply them is critical for the start of any mill project. When designing mills with a GMD the foundation must be properly modeled to ensure that all interactions of the mill and motor structures, foundation and subsurface strata behave in the intended fashion. All of the previous efforts can be laid to waste if the construction of the mill foundation is poorly handled. Mill foundations are typically the most massive concrete structure at a processing plant and can easily cause nightmares for inexperienced contactors. This paper explores some of the more important facets along the lifecycle of the grinding mill foundation.

Feb 23, 2014

By R. H. King

Suboleski and King (1990) analyzed the reasons for the dramatic increase in underground coal mine productivity during the last 10 years. This paper examines whether this increase can be extended. The paper forecasts whether the mix of technological, procedural and other factors that produced the increase will change in the future. The forecast is based on the base case and spreadsheet production model described in the previous paper.

Jan 1, 1991

By V. K. Gupta

The experimental results of some wet batch and continuous grinding experiments carried out in a 40 x 40 cm grate discharge ball mill have been analyzed for the variation of the grinding rate parameters, Si, with various operating conditions using a linearized population balance model. The wet grinding tests were carried out under conditions which were very similar to those encountered in the actual practice in plant operation. Well distributed -4 and -20 mesh feeds of two complex pyritic ores were used. The volume-percent solids in the pulp ranged from 30-40, the particle load from 5-8 kg, and the solids feed rate from 70-1 10 kg/hr.

Jan 1, 1981

By B. J. Scheiner

The Bureau of Mines, U. S. Department of the Interior, is conducting research on a dewatering technique for fine particles generated during the mineral beneficiation process that will recover a portion of the water now being lost using conventional waste disposal methods and significantly reduce the time required for land reclamation. The technique utilizes a flocculant, polyethylene oxide (PEO), that forms strong stable flocs that can be dewatered rapidly on static and/or rotary screens. In field tests, phosphate clay waste has been dewatered from a nominal 2.5 percent solids to greater than 20 percent solids. In other field tests, coal-clay waste has been dewatered from a nominal 3 percent solids to greater than 55 percent solids, in addition, small-scale continuous tests have shown that bentonitic clays can be dewatered from 12 percent solids to 40 percent solids.

Jan 1, 1983

Geostatistical literature has been dealing with recoverable reserve estimation techniques for the last 30 years. There have been well established support correction techniques (Le. affine correction, indirect log-normal correction, etc.) to deal with volume -variance relationship globally in determining what will be the reserves above a cutoff grade during mining. Kriging has become the accepted technique in the mining industry for ore reserve estimation. Many large companies are using this method for gold and copper deposit modeling. In general, the estimates coming from kriging are smooth. The variances of the block grades estimated by kriging are often lower than the material that will be mined selectively. As a result, kriging tends to under estimate reserves at high cutoff grades and overestimates them in low cutoff grades. It is necessary to perform additional steps after kriging if the goal is to determine recoverable reserves at some cutoff and not the in situ resources. In the mining industry, it is becoming more and more common for the low grade heap leach projects to consider whether the higher grade portion of a deposit may be processed by a mill at higher profits. Similarly, a concentrator -refinery operations are implementing heap leach -SX-EW option for the lower grade portion of their deposit. These options are making it very critical to estimate the low and high end of the grade distributions more accurately. Ore reserve estimation is normally done by using widely spaced exploration data which has very small size support (Le. core samples). Selective mining is carried out on ore control that is based on closely spaced blasthole data normally averaged into larger polygons based on some cutoff grade. Estimated grades from exploration data need to reflect the variability of the grades of the selectively mined units if they are used without further adjustments to predict recoverable reserves.

Jan 1, 1997

By S. R. Hutchins

Several refractory sulfide and carbonaceous gold ores were examined to determine whether microbial pretreatment could be used to enhance gold recovery. Test samples were biologically leached using unique, thermophilic microorganisms to solubilize iron sulfide minerals. Gold recovery from sulfide ores and concentrates was enhanced following pretreatment with the thermophiles; responses varied widely for the individual materials. Although bioleaching had little effect on the preg robbing characteristics of the carbonaceous gold ores, cyanidation of the bioleached residues yielded higher gold recoveries than cyanidation of the native ore. By combining bioleaching with abiotic processes designed to inhibit preg robbing, gold recoveries of 83-98% were obtained from carbonaceous ores yielding 10-50% gold recovery by direct cyanidation.

Jan 1, 1987

By P. A. Cornejo

Blastings always generates induced vibrations through seismic wave, these are lost energy from the blasting and therefore causing the disturbance of slopes and structures near the blast source. Most of the components of an open pit mine have to reach a physical stability, especially during its closure process. Aiming to develop a vibration prediction model using the historical records from an open pit mine located on Peru, this research has two main focuses depending on the distance from the blast source to the structure: to protect the final slopes and to protect the villagers houses. Both are based on the Devine model of the Square Root Scaled Distance (SRSD) to predict the Peak Particle Velocity (PPV). The Mid field model, where is found mainly final slopes from the pit, limited by the failure criteria of McKenzie based on the geo mechanical properties of the rock mass. The Far field model ranges distances where are located the most community households, limited by the German rule DIN 4150 for highly sensitive structures. Both scenarios resulted on a distribution abacus to limit the weight of used explosives to get the best operational advantage and structure safety.

Mar 2, 2022

By R. Tamir

This paper will describe the benefits of utilizing the decision support system, DSS to support the methodology of structured decision-making in the mining environment. It will outline the layers of the mining related decision making – 1. Creation of “one truth” situational awareness utilizing 2. existing planning, ERP, operational and monitoring agents, a. Expressing plan verse performance across mining phases and functions compared with the actual and trends to evaluate performance. b. Creating alternate courses of action and the implications up and downstream. 3. It will review the current condition were although a multitude of technologies resolve multi variable issues they do not interact in a way that assists decision makers throughout the organization in making high-quality decisions that will push the overall performance envelope. 4. The paper will show the benefits of integrating military methodologies to resolve multi variable complexed issues (operational, financial and other), operating in changing environments in order to meet time sensitive objectives with restricted resources. This is achieved by creating a shared situational awareness thru incorporating information from a multitude of data generating agents, creating COA, selecting the appropriate and turning it into a plan. The paper will discuss the implementation and suggest a path.

Feb 1, 2023

By H. O. Harju

Inco acquired majority interest in the nickel laterite concessions in eastern Guatemala in 1960 and, through its subsidiary Exmibal, extensively explored the deposits until 1965 to define the site for project development on the north shore of Lake Izabal. This paper outlines the exploration methods used to evaluate the Guatemalan laterite deposits.

Jan 1, 1979

By E. D. Attanasi, J. H. DeYoung

Several factors contributed to continued declines in mineral-exploration activity in the US in 1985. Low metal prices and, what appears to be worldwide chronic excess capacity in copper, molybdenum, lead, and uranium, have resulted in mineral-exploration expenditures remaining anemic. Economic recovery could result in a healthier mining industry and more cash flow to fund exploration. This is because general economic activity and US mining industry activity have historically been closely linked. However, as the worldwide economic recovery has expanded, the mining sector has continued its downward slide. New cuts in industry exploration budgets in 1985 shocked those who thought the exploration situation could not become worse. Some personnel and equipment had been redirected from base metals exploration to precious metals in the past few years. Last year, continued reductions in exploration sent many professionals out of the mining industry. Recent staff reductions or consolidations of operations were made by Noranda, Chevron, Molycorp, and other exploration companies. The latest data from the Society of Economic Geologists (SEG) summary of exploration statistics show that professional staff at year end in major US exploration companies (domestic and foreign operations) fell from 2355 in 1981 to 1868 in 1983 and 1277 in 1984. By the end of 1985, two economic trends were established that could improve the future profitability of mining and hence exploration. First, the price of crude oil began a decline. If sharply reduced energy prices increase worldwide economic expansion, the substantial excess capacity in some of the base metals industries could disappear, and prices could improve. Furthermore, if energy price declines reduce mining and processing costs significantly, metals may recapture some lost markets. The decline in oil revenues has already encouraged some oil-producing countries, such as Venezuela, to look toward development of mineral resources to earn foreign exchange for debt repayment. Second, the decline of the dollar by 21% during 1985 could also help US producers meet foreign competition. During 1985, industry restructuring continued as many oil companies sold off mining subsidiaries and minerals properties. Gold, silver in new discoveries Precious metals continued to dominate the announcement of new discoveries and exploration projects in 1985. A review of domestic exploration and development activities reported in several industry journals shows that 60% to 80% of these projects were directed primarily at precious metals, particularly gold. Base metals exploration activities frequently involved polymetallic deposits with gold or silver values. Because much of this exploration was done on identified targets (on-property exploration), the decrease in wildcat or grassroots (off-property) exploration may be more substantial than indicated by reductions in total exploration activity. Significant gold discoveries in 1985 included several in Nevada, among them the Genesis property of Newmont (near the Carlin mine), Goldfields' discovery of the Chimney deposit in Humboldt Co., and Freeport's discovery of two mineralized sites near Jerritt Canyon. Gold exploration continued to be focused in the western US and Alaska, but gold production starts at the Haile mine in South Carolina, and the Ropes mine in Michigan as well as Amselco's feasibility studies on deposits near Ridgeway, SC, are evidence that gold exploration is not limited to the West. The dominance of gold projects in exploration is not limited to the US, as demonstrated by gold dis¬coveries and exploration projects in Australia, Brazil, Canada, the Caribbean region, China, Guinea, Ivory Coast, South Africa, the South Pacific islands, and Thailand. From the standpoint of US metal miners, it is perplexing that worldwide exploration and development is also taking place in copper, zinc, tungsten, and other metals with depressed prices. During 1985, the US Geological Survey's efforts to map the sea floor of the Exclusive Economic Zone shifted from the Pacific Coast to the deep water areas of the Gulf of Mexico and to areas off the coast of Puerto Rico and the Virgin Islands. An atlas containing sea-floor maps of the west coast area was published as US Geological Survey Miscellaneous Investigations Series Map 1-1792. Results of the 1985 surveys are expected to be published by January 1987. Exploration trends - Statistical evidence Data from the SEG showed continued decline in the US mining industry's exploration expenditures through 1984. The share of US companies' domestic exploration expenditures directed toward base and precious metals has increased from 51% to 84% from 1980 to 1983 and to 86% in 1984. US mining companies spent about $0.67 of each exploration dollar in 1984 in the US. However, this represents an increase from earlier years. The 1983 data also show that firms spending more than $5 million on exploration accounted for 77% of exploration expenditures. Since 1981, the Bureau of Land Management (BLM) has been assembling data on claims and an-

Jan 5, 1986

By T. Panhorst

Evaluation of through-deck blasthole sample reliability at the Lone Tree gold mine revealed a non-systematic bias in the sampling system. Ore is primarily hosted within the Powerline fault zone. Clay gouge, present in the fault zone and typically enriched in gold content, forms agglomerates during blasthole drilling leading to a segregation error during sampling. Replicated samples split from blasthole cuttings piles show through-deck samples to be either significantly enriched or depleted by 1.5 standard deviations or more from the mean gold content of their respective cuttings pile quality of through-deck samples correlates strongly with quantity of clay present.

Jan 1, 1999

By James N. Orlich

Meridian Gold Company's Royal Mt. King mine (RMK), a subsidiary of FMC Gold Company, is located approximately 40 miles east of Stockton, California on the western edge of the historic mother lode belt. Gold ore at RMK is associated with a series of northwest trending fault zones hosted in either meta-volcanic or meta-sedimentary rock types commonly referred to as greenstone sulfide and carbonaceous phyllite. Mineralogy studies show gold in both ore types to occur primarily as electrum in the form of 1 -20 um inclusions in pyrite with varying amounts of free milling gold. In carbonaceous ores, gold was not found to be closely associated with carbon. At the start of the current mining operation, three major ore resources were identified. North Pit and Gold Knoll pits were the major greenstone reserves while Skyrocket Pit contained over 60% of the total reserves as carbonaceous ore. Since North Pit and Gold Knoll were to be the first areas mined, the mill began operation in February 1989 with a flowsheet designed for greenstone ores with a carbonaceous expansion anticipated after depletion of the greenstone reserves.

Jan 1, 1992

By Charles R. Marek

There is an ever-increasing need for quality construction materials to provide the necessary housing and transportation facilities required for the protection and movement of people and goods. By the year 2000, requirements for housing in the United States will have doubled due to population growth. Requirements for transportation facilities in this same period will also have increased substantially. Further, all existing facilities for both housing and transportation will require substantial maintenance of one form or another. Aggregate is the basic material of the construction industry. There is some occurrence of aggregate source material in virtually every state of the United States, and in every country in the world. United States reserves of commercially useable aggregate have never been systematically estimated and are probably so vast as to be incalculable.1 However, in many areas its existence is largely negated by inaccessibility. Often it is lodged deeply or intricately in the earth or it is too distant from markets to offer a desirable "return on investment" under the present economic structure. Other factors that prevent its utility are the occurrence of small scattered deposits that individually are too small to justify the necessary capital investment for exploitation and collectively are too widely disseminated; also, the aggregate nay be deficient in certain desired chemical or physical qualitites.1

Jan 1, 1974

By M. W. Harmer

Laboratory test work, pilot plant testing and plant experience with wet, fine mesh screens is discussed. High frequency, low amplitude, fine mesh, wet screens were installed on the 6th cleaner concentrate stream. These screens produce a 60% oversize recovery split of the molybdenite concentrate that is of leached equivalent quality. The undersize stream is leached with 'hot ferric chloride to remove Pb and Cu contaminates before roasting or shipment to sulfide customers. This plant modification is a good example of using existing technology in an unconventional flow sheet to yield significant cost savings.

Jan 1, 1990

By S. M. Hsiung

Chain pillar design formula under weak roof condition was developed by statistically analyzing the results from the three dimensional finite element parametric analyses. The parameters such as mechanical properties of the roof and floor strata, overburden depth, panel width and length, and coal strength were incorporated in the formula. A conversion formula which transfers a rectangular chain pillar into a square chain pillar of equal strength is proposed. The influence of high in-situ horizontal stresses, which are often encountered in the coalfield, on chain pillar stability is also discussed.

Jan 1, 1984

Considerable attention has been given to the restoration of low-level radioactive (<1000 pCl/g) sites contaminated during the early years of the atomic energy program. Current clean-up activities which involve the relocation of contaminated soils to licensed disposal sites have been shown to be very costly due to the large volumes of soils which must be excavated, transported and stored. Recent characterization studies conducted at Virginia Tech suggest that the volume of soil requiring disposal can be greatly reduced using mineral processing techniques such as classification, density separation and froth flotation. This article discusses the application of these technologies for soil remediation and describes a conceptual flowsheet for treating soil samples from two contaminated sites.

Jan 1, 1997

By G. Ahuja

Tests were conducted to investigate the effects of cyclone geometry, operating conditions, and particle size on magnetite classification. The effects of these parameters on the partition curve for narrow size fractions were studied using a 25mm diameter cyclone cleaning -150 µ m coal. Additional tests were run to investigate the effects of geometry and operating conditions on the slurry, solid, and water splits. The relationship between the relative density of the underflow stream and the relative density of separation was also investigated. This paper presents the results from this study.

Jan 1, 1994