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By J. D. Bennett

The degree of injury and days lost from work due to an injury are examined for selected electrical sources, occurring in conjunction with falls of the injured miner or with selected machinery, that could have been eliminated by use of diesel equipment. Although the number of electrical source injuries that could have been prevented is small relative to the total number of injuries during the period examined, many lost-time injuries could have been precluded and thousands of days lost from work could have been avoided.

Jan 1, 1984

Traditionally, production volume has been considered the major determinant of cost. As volume increases, total cost increases but unit cost decreases. This concept has been so widespread in industry that many of the tools used to analyze costs are based on production volume as the sole measure of activity and driver of unit cost-fixed and variable costs, cost-volume-price and breakeven analysis, contribution margin, flexible budgets, and others. Clearly, volume is a driver of cost. It is important in both a tactical sense (to the manager at an operating mine) and a strategic sense (as one determinant to the firm's overall cost position). However, many other factors influence costs as well, even though they have not been studied to the same extent. For example, production managers know that their costs will be reduced if the workforce does not have accidents. Safety costs are to a large extent independent of volume. Other cost components increase as volume increases, such as some environmental charges. Some costs may or may not reflect volume changes. Maintenance, for example, may appear as either a fixed or variable cost, as can operating labor in facilities that are highly automated. In the strategic sense, where the firm is selecting a strategy to pursue competitive advantage and increased profitability, all costs are variable. This reflects both the strategic intent and the long-term time frame associated with strategic positioning. Tactically, on a month-by-month basis, some costs are essentially fixed. Cost driver analysis must therefore consider the relevant time frame.

Jan 1, 1999

By Jerome F. Machamer

Ninety percent of manganese is used as an alloying element in steel. Smaller amounts are used in dry-cell batteries, in aluminum and bronze alloys, and many other uses. The element has several oxidation states, and oxidation-reduction reactions control its chemical behavior. Manganese, in primary minerals such as rhodochrosite, rhodonite, and braunite, is in a divalent oxidation state, and manganese in secondary minerals, such as pyrolusite and cryptomelane, is in a quadrivalent state. Virtually all manganese ore production comes from three types of sedimentary manganese deposits. First, lenticular beds of manganese carbonate or carbonate-silicate rock in Early Precambrian volcano-sedimentary complexes in South America and Africa have been major sources of manganese ore. Second, laterally extensive beds of mangano-silicate and manganiferous carbonate minerals in certain banded iron formations are major sources of commercial ore and constitute the largest resource of manganese. Finally, manganese accumulations deposited in marginal to epicontinental basins are the largest source of current manganese ore production. Residual deposits resulting from the destructive weathering of rocks with a low manganese content have been, but are no longer, important sources of manganese ore. Most deposits have been altered to some extent by super- gene oxidative processes, and are economic because of that alteration. Outcrops of manganese ores are invariably oxidized and can be very deceiving as to the character of the underlying material. Nearshore facies of epicontinental basins, and nearshore age-equivalents of metalliferous black shales are among the targets for new manganese exploration. Very high-grade manganese occurs in sedimentary deposits altered by metamorphic and metasomatic processes.

Jan 1, 2001

By Peter W. Scott

The Caribbean islands, with their very diverse geology, are a source of several industrial minerals both for their own domestic consumption and for export. The geology of the Greater Antilles, which comprises Cuba, Hispaniola, Puerto Rico, and Jamaica has a Mesozoic or pre-Mesozoic basement overlain by sediments and volcanics, the latter being dominantly island arc in character. Later granitoid intrusions were emplaced. Obduction of ophiolites also occurred variously from the mid- Cretaceous to the Palaeogene. Thick accumulations of limestones surround the older strata, along with Neogene and younger sediments. The Lesser Antilles islands form an arcuate chain, mainly of volcanic rocks of calc-alkali or sub-alkaline affinity with some younger limestones and siliciclastic sediments. Trinidad and Tobago have closer similarities with the South American continent in their geology. Tobago has a metamorphic complex, juxtaposed with a volcanic-plutonic complex, and limestones. Trinidad has very thick Cretaceous to Recent exposed sedimentary sequence. The current exploitation of industrial minerals in the Caribbean is dominated by construction raw materials (mainly sand and gravel, limestone, and cement), although there is extraction of gypsum, silica sand, marble, clay (almost entirely for construction use), pumice, and natural asphalt. Salt is obtained from solar evaporation of seawater. Limestone of high purity and high brightness, gypsum, pumice, and high-density igneous rock have potential for further development of their markets, particularly ex- ports. Potential new and undeveloped industrial-mineral resources include residual and sedimentary kaolin, bentonite, zeolites, magnesite, and talc. Cuba could be a source for many industrial minerals in the future.

Jan 1, 1999

By R. D. Lama

Coal mining is one of the major sources of methane release to the atmosphere by human industrial activities and is believed to contribute to -30% of the total methane emissions from industrial activities. In 1993, world saleable black coal production, attained almost 3.5 billion tonnes from which around 65% was produced underground. Coal in underground mines can contain high quantities of methane and some deep coal seams have methane content as high as 50 cubic meters per tonne of coal. Gas is re- leased during coal mining from the mined seam and in a higher degree from the neighboring unmined seams and gas bearing strata which are fractured as mining advances. This paper de- scribes a study which was undertaken to estimate the extent of methane emissions from coal mining in the world. Measured emission related data were collected from most underground coal producing countries in the world. The data included methane flows in the ventilation system, methane flows in gas drainage system, in-situ gas content, methane utilization and coal production. More comprehensive data were collected from a range of gassy and non-gassy Australian mines. Residual gas content of samples from run of mine were also measured. Using the Australian data, mathematical expressions were established to evaluate methane emissions as a function of coal production and in-situ gas content for other mines. These emission models were then used to evaluate the emissions for the countries or coal basins without measured emission data. Trends in methane emissions from underground mining for the year 2000 and beyond were also estimated.

Jan 1, 1997

By Carl F. Austin

The subject of strata control in mining can be approached from both static or loading concepts or from dynamic or impulsive loading concepts. The fracture process itself appears to be primarily a dynamic process as is the gross creation of fractures through the use of impact, stress wave passage or in more general terms, the use of explosives. This paper presents experimental results which indicate that the understanding of the fracture behavior of rock that has been, established in the open literature is not always appropriate. In particular, the results of this experimental program have shown very interesting differences between the formation of fractures in rock and the formation of fractures in other materials such as metals and plastics which are often used as models for rock behavior studies Fracture patterns and causes of dynamic fracturing in various rock and artificial materials are presented.

Jan 1, 1965

By P. W. Hynes

Tg Soda Ash has operated a shortwall mining system in the Green River, Wyoming trona district since August. 1982. The system has proven to be highly productive. In an effort to reduce the relatively expensive development mining and Improve mine planning flexibility, a method to mine the return air tailgate during the shortwall retreat was tested beginning In April, 1987. As of June. 1988 four shortwall panels had been completed utilizing the advancing tailgate, producing over 815,000 tons.

Jan 1, 1989

By Christian F. Baiz

Industrial minerals can have similar financing requirements to those needs of metaliferrous and coal mining projects. Although, one may see many similarities in the fundamentals of the various risks that must be evaluated in lending to any specific project, one of the outstanding differences is the understanding of the many different markets that these industrial minerals represent. There are in excess of 30 principal industrial minerals ranging in terms of annual production from the largest quantity such as sand and gravel, to possibly the smallest quantity of production of a legitimate industrial mineral which may be defined as industrial and rough gem diamond. If we assume that it is necessary to finance independent projects of ore bodies of industrial minerals for development, the financing techniques are similar to the fundamentals that we would use for financing coal projects or metaliferrous deposits. Therefore, let's begin by redefining project financing in the traditional banking or private sector area, and then in the later development of this paper, we will apply these techniques to industrial minerals in general and cite it with several specific examples.

Jan 1, 1982

By Neil B. Prenn

Drill-hole contamination has been a problem for many years. Contamination of rotary drilling has been well documented. More recently contamination in wet reverse circulation drilling has been noted by Echo Bay and others at the 1991 AIME annual meeting. Mine Development Associates (MDA) has worked on a number of projects at which contamination of drill-hole samples has occurred. Properties are commonly acquired with drilling accomplished by other companies and at times the only records of the drilling program are the drill-hole logs and assays themselves. Identification of contaminated zones is sometimes difficult to determine. Most geologists and engineers in the industry are aware of the magnitude of the problem, as contamination is a relatively common problem with wet reverse circulation drilling. MDA has developed a computer program to help determine if contamination has occurred when using reverse circulation drilling, based on cumulative distribution curves and by a process we call decay analysis. Most deposits are not homogeneous throughout the deposit, but exhibit a characteristic drop-off or decay of assay values around higher-grade drill-hole intercepts. Using graphs of this characteristic decay and cumulative frequency distribution, we can use the program to help determine contamination in several ways. This paper will discuss the use of decay analysis at three gold deposits where contamination is known to have occurred. In one of the deposits decay analysis was used, successfully to determine if contamination had occurred, while in the other two the decay analysis was used to verify our decay analysis procedure.

Jan 1, 1992

By E. T. Sugar

English China Clays, the world's largest producer of China Clay, has its main production capacity in the South-West of England, where a complex of pits, refining plants, dryers and ports covers an area of approximately 100 square kilometres. The possibility of a computerised information network was first considered in 1980. The system was required to provide information at the central level and also at local plant level to improve co-ordination and control. Immediate access by any authorised user, and flexibility of interrogation were important aims. A small micro-based prototype system was implemented in 1981, and later that year development of the mainframe system commenced. This latter system will provide at least one terminal in every works location and will allow inter-communication of laboratory test data as well as detailed stock levels and production data. An integrated system for order processing will allow stock levels to be monitored in relation to anticipated requirements. The system has been developed by the Data Processing Department using the IDMS database package running on an ICL ME29 mainframe. It was decided to use microcomputers as terminals, which although more complicated because of protocol emulation allows stand-alone applications to be run on the same equipment. Those applications concerning Production Planning are outlined in the paper. Communication on the network is by synchronous transmission over dedicated lines. All data is stored on the central database with terminals accessing it in a star configuration. The system is currently partially implemented with 30 available screens at 18 separate worksites.

Jan 1, 1986

By J. W. Mahar, E. J. Cording, F. L. Gau

INTRODUCTION The Washington, D.C. rapid transit system (METRO) when completed will consist of 98 miles of double track rail. Fifteen miles will be tunneled in rock and 12 large underground rock chambers will be constructed at station locations. The University of Illinois is under contract to Metro to provide observations and instrumentation services in the initial phase of construction. The work is coordinated through DeLeuw, Cather & Co., the General Engineering Consultant to Metro. The program is designed to monitor construction conditions as well as to provide information useful for the design of future rock tunnels and rock chambers in the Metro system. This paper presents the results of observations in the rock tunnels constructed to date. Most of the observations are in a 5000-ft-long, 30-ft-wide, double track tunnel in downtown Washington, D.C. Observations were also made in single track tunnels, shafts, enlargement areas, and pilot tunnels, and are being made in a large rock chamber 700 ft long, 76 ft wide, and constructed at shallow depth in a schistose gneiss. One of the major objectives of the observational program was to determine the orientation and character of joints and shear zones and to evaluate their effect on support requirements for various tunnel orientations and configurations. The consistency of geologic features throughout the Washington area has made the results of the initial study applicable to evaluation of support requirements on future tunnel contracts. The first section of this paper summarizes the geologic conditions in the tunnel and their effect on overbreak and rock movement.

Jan 1, 1997

By J. H. Calder, J. C. Hower

Three lithotypes of Phalen coal from Cape Breton County, Nova Scotia, Canada, were subjected to a modified Hardgrove grindability index (HGI) test. The testing scheme differed from conventional (ASTM D-409) Hardgrove testing by, in one case, repeating the test three times prior to removing the -200-mesh fine coal from the Hardgrove mill, and, in a second test, removing fines after each of three successive Hardgrove tests. Only the first stage of the latter testing scheme actually conforms to the standard HGI test. All processed samples were analyzed petrographically by a combined maceral/microlithotype analysis. The increase in the percentage of coal ground to -200 mesh increases through the 60- to 180-mesh fractions for each of the lithotypes for the following two apparent reasons. First, with progressive grinding, more of the oversize material is close to 200 mesh (75 µm), creating a "pool" of particles ready to be ground to -200 mesh, and, second, the removal of fines from the system at each step eases the grinding at the successive step. The fines retained system shows the influence of buffering of further grinding by the particles retained in the grinding mill. The Phalen lithotypes and the series of Central Appalachian coals, evaluated previously by Hower and Wild (1994), differ in that an increase in vitrite and a decrease in trimacerite is observed in successive -200-mesh fractions in two of the Phalen lithotypes. This is the opposite of the trend observed in the slightly lower-rank Central Appalachian coals.

Jan 1, 1998

By W. R. Ernst

A method for the removal of nickel and vanadium contaminants from spent HDS catalysts involves pretreating the catalyst with H2S followed by the extraction of the metals with an acidic solution of ferric ion. The ferric ion solution alone removes significant amounts of active ingredients cobalt and molybdenum; however, after pretreating the catalyst with H2S, the extraction becomes more selective for the removal of Ni and V.

Jan 1, 1986

By J. F. Rakszawski, Robert P. D'Orazio

The use of cyanide in the processing of gold has been documented for over a century. It is still one of the more effective methods of isolating gold, as witnessed by the fact that in 1987 cyanidation was used in the processing of 91.5% of the gold produced in the United States.

Jan 1, 1990

By Ray W. Ballmer

Historically, Bingham is a rail pit, starting with steam locomotives in 1906 and converting to electric locomotives in 1923. Ore production was maintained through an effective utilization of available rail equipment. From time to time as it became necessary to deepen the pit and as stripping ratios increased, various studies were made on alternate material haulage systems. Utilization of diesel locomotives, conveyor belts, and trucks have all been subjects of study, however, conversion from rail haulage utilizing electric locomotives could not be justified. Because of the gradual decline in ore grade, a program was approved in 1963 to raise ore production to 108,000 tons per day. This was designed to return copper production to the 1950 level. Attainment of this production level by expansion of the rail system had definite limitations and built-in inflexibility. Track and trolley wire relocation causes shovel down time in excess of that required for normal maintenance. Instability of the dumps and the resulting additional track maintenance increases greatly as the volume of waste material to be handled daily expands.

Jan 1, 1965

By Mortimer J. Richardson

Dredging can be traced to early times where it may have been derived by the Phoenicians prior to the 4th century B.C. The first tangible design drawings of a bucket ladder (BL) dredge can be found in the collections of Leonardo da Vinci (1452-1519), which he produced when he was attempting to create better methods of channel and port dredging. The perfection of the system did not commence until after the invention of the steam engine in the early 1800's; providing the impetus to progress from man-powered mud mills, horse drawn along polders or dikes in the Netherlands, England, France and Germany, to steam-driven. In the 1860's following the various gold rushes in the U.S., Australia, New Zealand, Siberia and South America, with placers in particular, efforts were begun to apply mechanization to achieve deeper digging. There is a recording of a dredge being installed to mine gold in Montana in the 1860's but did not include a processing system. Then in the 1880's in New Zealand, some practical engineers developed a system that is said to be the first bucket ladder mining (BL/M) dredge for mining gold placers. In studies of the New Zealand gold dredging experience, it is estimated that some 500 dredges were built to mine gold between the 1880's and 1942. A careful analysis of the data, however, shows that very few were profitable. The technology appeared to stagnate in the early part of the century. Two of the BL/M dredge design engineers left New

Jan 1, 1992

By T. L. Brekke, T. R. Howard

Stability of an underground opening can be defined in several ways. To geologists and engineers that are used to working in geological environments where the major parts of the works after careful scaling can be left unsupported during the construction period as well as during operation, any rock mass behavior that requires reinforcement, support or lining may be regarded as a stability problem. To colleagues excavating underground openings in geological environments that require continuous use of reinforcement or support and lining "stability problems" are often associated only with those parts of the work where "standard" construction procedure and method of reinforcement or support and lining is inadequate, and special measures therefore needed. In either case, a major objective is to assess the stability problems correctly -as far as possible at the planning stage -- and choose methods for excavation and reinforcement or support that will bring the opening safely and as economical as possible through the problem areas. INTRODUCTION It is not uncommon that stability problems associated with faults or seams have been described as "unexpected." This term has unfortunately been used to indicate that no one knew that the fault or seam existed prior to excavation. A careful review of documented cases where serious stability problems have occurred revealed that the existence of these zones most often was known, but that their behavior was incorrectly assessed prior to or during construction. Miscalculations have been made in terms of the type and magnitude of loads that developed, and in particular in terms of the time-dependant behavior.

Jan 1, 1997

By J. P. Vandenhoeck

Sizing devices used commercially are unfortunately not 100% efficient, the splits that can be obtained are usually inferior to the results obtained in the laboratory. Often the capital and operating costs of equipment capable of high sizing efficiency cannot be justified by the economics or requirements of the process. To reconcile the desired sizing efficiency needed to obtain optimum process requirements with the sizing efficiency of equipment economically practical, it is often necessary or desirable to predict the gradation and weight splits of the products obtained based on the expectant efficiency of the contemplated sizing device or method. The less efficient the sizing device one must employ, the more important it is to know the results that may be expected for the establishment of the optimum flow sheet and the more difficult it becomes to estimate the results accurately. Air classification equipment which sizes materials by opposing the drag force created by an air stream acting on a particle with a combination of gravitational, inertial or centrifugal forces are substantially less efficient than, for example, a laboratory sieve analysis. Air classifiers allow oversize material to contaminate the fine fraction and leave undersize material in the coarse fraction. The techniques employed to predict the gradation and weight splits obtained from air classification outlined below are adaptable to other sizing devices less than 100% efficient such as screens, sifters and wet classifiers.

Jan 1, 1965

By H. Nakazawa

Galvanic contact, occurring between electricall y conducting minerals in flotation pulps, may affect the nature of mineral surfaces and influence their floatabilities. Rest potential and galvanic current measurements were made on an electrode combination of pyrite and pyrrhotite under nitrogen, air and oxygen aeration conditions, and the results were correlated with their oxygen-consuming characteristics and flotation behaviors. The galvanic contact improved the floatability of pyrrhotite, but adversely affected that of pyrite. Auger electron spectroscopy, x-ray photoelectron spectroscopy and scanning electron microscopy indicated that the formation of hydroxide or oxide and sulfate species of iron on pyrrhotite decreased whereas that on pyrite increased when these minerals were held in contact. An electrochemical mechanism was proposed for the observed behaviors.

Jan 1, 1985

By P. F. Hara, O&apos

Stratabound Proterozoic precious metal mineralization in central Arizona is associated with felsic and adnesitic to mafic volcanic rocks and sediments derived from these rocks. Hydrothermal fluids associated with felsic volcanism form gold mineralization within hotspring vent complexes or within asymetric basins, which flank the vent complexes and are filled with tuffaceous sediments. Massive to semi-massive sulfide copper-zinc systems associated with felsic volcanism may locally contain small gold occurances either laterally or vertically zoned from the ore. In andesitio to mafic rocks, zinc-lead-gold-silver-copper bearing mineralization and gold mineralization are both associated with feruginous sulfide bearing cherts. The partitioning of gold into these specific geologic environments may be related to variations in temperature and composition of the hydrothermal fluid and the depth of the seawater-sediment interface below sea level during the mineralization event.

Jan 1, 1988