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By A. D. Mah

To assist Bureau of Mines research in extractive metallurgy and to add to the thermodynamic data base useful to others, energy calculations were made for 63 reactions relating to investigations on the production of anhydrous aluminum chloride from chlorination of clay.

Jan 1, 1982

By Stanley G. Hutton, Robert Brubaker

"It has long been recognized that mining workers subjected to high levels of hand-transmitted vibration may suffer from vibration-related complaints. Prolonged exposure to whole-body vibration may also result in adverse effects. In this study, the effects of vibration on mining workers are examined. Previous work documenting the occurrence of vibration-related disease is reviewed. From this work, it is apparent that operators of hand-held pneumatic rock drills are exposed to a significant risk of developing vibration disease. Vibration levels recorded on the rock drills now in use are presented and shown to exceed levels recommended by a proposed ISO standard.IntroductionThe possible harmful effects of exposure to excessive vibration levels have long been recognized, particularly among operators of hand-held tools. Numerous cases have been reported of a vasospastic disorder commonly known as vibration white finger disease (VWFD), which was a term coined by the Industrial Injuries Advisory Council in Scotland in 1970(1 ), Those suffering with the disorder have frequent vasospastic attacks in which the fingers, hand and, in advanced cases, the lower arm turn white and numb, usually after a cold stimulus. Advanced stages of VWFD have been reported in which the skin becomes ulcerated and gangrenousm. The incidence of the disease has been particularly serious in the forest industry due to the extensive use of chain saws. However, in recent years, the introduction of antivibration saws has resulted in a significant reduction in the occurrence of the disease.In a recent report for the Canadian Department of Supply and Services - Energy, Mines and Resources, Hutton & Brubaker considered the effects of vibration on workers in the mining industry. In this report, the physiological and medical effects of vibration were considered, relevant vibration standards were discussed, previous vibration measurements were documented and field measurements carried out. In the present paper, the results recorded in this study will be summarized, together with results that have been previously published relating to vibration levels existing in the mining industry."

Jan 1, 1982

By Robert W. Waytulonis

The Federal Bureau of Mines contacted 29 organizations--mine maintenance departments and equipment manufacturers--concerning service experience and construction of diesel exhaust-gas water scrubbers. Scrubbers are used primarily on mobile diesel-powered mining equipment subject to 30 CFR 36. Because the scrubbers cool exhaust gas and act as flame arresters, their failure would compromise safety in underground mines. Scrubber maintenance problems and frequency and modes of failure were identified, and construction materials and techniques were evaluated. Three failed scrubbers were randomly selected from two cooperating mines, and their modes of failure were determined. In conjunction with failure analyses, mine water and scrubber water solution samples were chemically analyzed to characterize corrosive properties. Sludge and mineral deposits and different types of corrosion and metal fatigue were identified as problems leading to scrubber failure. The corrosion process is explained; maintenance practices, construction materials, and manufacturing methods that could be used to reduce premature failures and allow longer effective scrubber life are identified; and basic changes in scrubber design are suggested. If type 304 stainless steel is used throughout the scrubber and regular maintenance is performed, long, dependable service can be expected. Other materials such as 304L, 316, or other more exotic steel alloys may be necessary under certain conditions.

Jan 1, 1982

By M. Splaine, C. E. Dohm, S. J. Browner

As the grade of the gold (head grade) in the ore supplied to a reduction plants falls, the efficiency of recovery of the metal drops. This is not simply due to a fixed grade lost in the residue, since the residue grade is itself a function of the head grade. A multi-disciplinary approach was used in the construction of a model to represent the relationship between head grade and recovery efficiency. The model is a physicochemical one based on (i) the reaction characteristics of cyanidation, (ii) the milled-ore selection characteristics of gravity concentration, and (iii) the nearly log normal distribution of gold grades and particle sizes in ore reserves. The model was used to set sound target levels for recovery efficiency for a given head grade at a given plant, against which the performances of the plant equipment can be judged for control purposes.

Jan 1, 1982

By S. McMurray

INTRODUCTION Towards the end of the 1890s the attention of a prospector by the name of Thomas Cullinan was drawn to the occurrence of alluvial diamonds east of Pretoria. Persistent prospecting work by Cullinan led to the loca¬tion of the source of these diamonds-a kimberlite pipe on the Elandsfontein farm. Cullinan eventually acquired the property in 1902, and during an extensive evaluation program outlined the largest diamondiferous pipe in South Africa on which the Premier mine was established. Worldwide attention was drawn to this mine in 1905 when the Cullinan diamond, which weighed 3106 carats and is by far the largest gem diamond ever discovered, was recovered. Premier mine operated with varying success until 1932 when the worldwide depression forced it to close. In 1945 the mine was reopened and since then has been a major producer of gem and industrial diamonds. During the early 1950s exploratory drilling revealed that below the 370-m level the pipe had been completely cut off by a younger gabbro sill. This sill has created major mining and metallurgical problems but the existence of vast reserves of high grade ore below it justi¬fied the establishment of virtually a new mine below the sill. Detailed planning of below-the-sill mining is nearing completion and the development of the first mining block (the L1 block) is well advanced. A full discus¬sion of this block follows. GEOLOGY OF PREMIER MINE Pipe Morphology and Country-Rock Geology As can be seen in Fig. 1, Premier mine is an elon¬gated oval shape with a long axis of 900 m on the surface and a short axis of 450 m. The pipe has a surface area of 32 hectares which decreases progres¬sively with increasing depth, so that 500 m below the surface the area is reduced to 22 hectares. The contact between the kimberlite and the surrounding country rock is sharp, with an average angle of dip of 1.48 rad (85°). From the surface down to approximately 350 m, the country rock is a felsite which grades downwards into a norite. In general both rock types are hard and massive, the felsite in particular being poorly jointed. This characteristic combined with other factors results in an extremely stable open pit, and near-vertical side¬walls are currently being maintained. The norite in general is competent but is heavily jointed in some areas resulting in very blocky ground which creates localized tunnel support problems. In the southeastern area below the sill a zone of highly altered and very unstable norite, which has also created localized sup¬port and development difficulties, lies adjacent to the pipe contact. Kimberlite Geology The Premier pipe is a complex multiple intrusion which contains in the region of 15 separate types of kimberlite, most of which are volumetrically insignifi¬cant. On a simplified basis three major types can be identified which correspond to three separate phases of intrusion. They are: Brown Kimberlite: This represents the first phase of intrusion and now occupies the eastern part of the pipe. In plan the brown kimberlite has a crescentric shape resulting from the intrusive relationship with the younger gray kimberlite which lies to the west. The brown kimberlite increases in relative area with increas¬ing depth which is a favorable factor for future mining operations since this kimberlite is the richest area of the mine, having an average grade of 70 carats/ 100 t. Below the sill this rock disintegrates extremely rapidly when exposed to air or water, to form a fine gravel-like material. This characteristic is due to a high montmorilonite clay content. As is common with clay minerals of this type, water can be absorbed into the crystal lattice with a resultant increase in volume which causes the physical decomposition of the rock. The presence of this decomposing kimberlite was a major factor governing the choice of a mining method, as well as development and tunnel support techniques. Gray Kimberlite: This is the most abundant type and represents the second major phase of intrusion. The diamond content is variable depending on the amount of waste rock dilution, and in general the rock is stable and non-decomposing. At the time of formation of Premier, the surface rock type was Waterberg quartzite, a rock formation which has subsequently been removed from this area by erosion. The explosive extrusion of the gray kimberlite caused extensive brecciation of this rock and while the kimberlite was in a mobile state huge masses of quartz¬ite, amounting to tens of millions of tons, slumped into the pipe. This quartzite became concentrated in the central area of the mine and has been a major mining problem throughout the history of Premier since, due to the irregular distribution of the quartzite, effective selective mining has never been possible. The quartzite is therefore extracted with the ore and has a significant dilution effect on the overall grade. Black Kimberlite: In the western part of the pipe a circular, pluglike body of kimberlite is intruded into the gray kimberlite. This plug consists mainly of a hard, dark-colored rock known as black kimberlite, but also contains a number of minor kimberlite variet.ies as well as nonkimberlite carbonate dikes. The Gabbro Sill The sill averages 75 m in thickness and within the confines of the pipe consists of 52 million t of rock. On average the major dip is 0.34 rad (20°) to the northeast which is across the short axis of the pipe, the range of dip being from near horizontal up to 0.52 rad (30°). Due to the pronounced dip, the sill is encount¬ered over a vertical distance of 175 m with the highest upper contacts on the 355-m horizon and the lowest bottom contact on the 530-m horizon.

Jan 1, 1982

By Frank G. Horino, V. E. Hooker

INTRODUCTION The determination and use of mechanical properties of rock in engineering and rock mechanics are rapidly developing. Many of these properties are determined on intact rock specimens; thus, their application and repre¬sentation of rock mass properties may be limited. How¬ever, relative information often provides useful guidance in the solution to mine design and stability problems. Summarized in this chapter are some of the stan¬dardized techniques and procedures currently used to obtain these mechanical properties. Typical applications of the use of these properties are also presented. Stan¬dardized techniques include those advanced by the American Society of Testing and Materials (ASTM), International Society of Rock Mechanics (ISRM), US Bureau of Mines (USBM), Canadian Dept. of Mines and Technical Surveys, South African Institute of Min¬ing and Metallurgy, and other individual investigators. Information on the mechanical properties of rock and the behavior of the rock under a given system of stresses represents a necessary part of the information for rational engineering design for any given mining op¬eration. The mining method, the type and extent of sup¬port, the extraction ratio, the overall dimensions of the mine, and the orientation of the rooms and pillars are all decisions that are influenced by the mechanical prop¬erties of the ore, roof, and floor material under various stress systems and the magnitude and direction of the in situ stresses (Hooker, Bickel, and Aggson, 1972). Initial mechanical property information regarding a structure or mine property is generally obtained by two basic techniques: (1) static and dynamic property tests are conducted on intact and fractured rock specimens of exploratory drill core, and (2) dynamic properties are obtained by borehole logging techniques. When mining access becomes available, and as the mining horizon is expanded, additional information can be ob¬tained to verify preliminary mine design values. This chapter presents some of the standardized tech¬niques and equipment currently used in obtaining me¬chanical property data in the laboratory. The properties considered are: (1) uniaxial compressive strength of intact rock core specimens, (2) uniaxial compressive strength of rock cores containing planes of weakness, (3) triaxial compressive strength of intact rock core specimens, (4) triaxial compressive strength of cores with a plane of weakness, (5) Young's modulus, (6) Poisson's ratio, (7) density or apparent specific gravity, (8) modulus of rupture, (9) indirect tensile strength, and (10) creep characteristics. Where possible, an at¬tempt will be made to evaluate each property measure¬ment in relation to the problems of rock mechanics and application of results. TEST SPECIMENS The selection and care of drill core for laboratory testing require some consideration. It is recognized that laboratory-determined properties are not necessarily rep¬resentative of an in situ rock mass property. However, relative information between beds or zones of interest is still valuable information in selecting mining horizons and preliminary design criteria. To provide statistical data the number of drill core samples selected to repre¬sent each of the areas of interest should be from a mini¬mum of three to a maximum of ten test specimens. A judgment must also be made on site as to whether the recovered drill core should be wrapped and sealed in plastic to preserve moisture. On the one hand investiga¬tions of air-dried and saturated specimens have shown that moisture significantly affects the elastic properties and strengths of many rock materials (Obert, Windes, and Duvall, 1946; Colback and Wiid, 1965); on the other hand it is apparent that most core drilling is done with water which may saturate the specimen to a greater extent than in the in-situ condition. Whether or not the decision is made to retain the moisture, the core should be delivered to the laboratory as soon as possible after recovery for subsequent specimen preparation and testing. Specifications Shape: The shape of the specimens influences lab¬oratory testing in two ways: (1) time and cost of sam¬ple preparation and (2) strength of the material. Cy¬lindrical specimens of drill core are by far the least time-consuming to prepare for static or dynamic labora¬tory testing. In addition, the cylindrical shape lends it¬self to a more uniform stress distribution throughout the sample than other shapes, such as rectangles and hexa¬gons. The compressive strengths of various shapes have been studied (Grosvenor, 1963, and Price, 1960), and results indicate that the cylindrical specimens usually provide the highest strength for a given height-diameter ratio. However, reduction in strength from a cylindrical shape to a rectangular in situ pillar is not regarded as significant in relation to other considerations such as planes of weakness in a pillar or safety factors in the design process. Length-Diameter Ratio: The length-to-diameter ra¬tio, LID, has a significant effect on the compressive strength. Various recommendations have been made to use standard LID ratios ranging from 2 to 2.5 to 3 (ASTM, 1975c; ISRM, 1972). However, past work by others such as Obert, Windes, and Duvall (1946) has shown that excellent results can be obtained using LID ratios from 2 > (LID) > >/s. In selecting an LID ratio for testing, one should keep in mind the amount of material available for testing. In many instances, this may be limited. Thus, a shorter specimen such as 1: 1 LID may be necessary to provide enough test data for statistical analysis of results. Sec¬ond, it may be desirable to obtain elastic constants dur¬ing the test. This generally requires instrumentation such as linear variable differential transformers (LVDTs) or strain gages near the center of the specimen. In this case, an LID of 2.5 or 3 is desirable so that the instru

Jan 1, 1982

By Rex C. Bryan

An application of geostatistics to financial decision analysis is the linking of reserve parameters estimation precisions to a mine economics computer program calculating profitability. The estimates of economic reserve parameters are obtained by the kriging method, while precision are calculated by a technique more akin to the polygon method. To indicate the effect of the variables probability distribution on a distribution of profitability, their values are sampled by a Monte Carlo technique and entered into a mine economics modelling program developed by T. R. Ellis. The distribution of profitability calculations are in essence, a superior method of sensitivity analysis. The method is applied to a roll-front uranium deposit in the Powder River Basin, Wyoming.

Jan 1, 1982

By Sam Rosenblum

The anomaly ratio is obtained by dividing the analyzed value of an element by the anomaly threshold value of the element. The sum of anomaly ratios for all anomaly elements in a sample may be compared with similar sums for other samples, so that samples having the greatest anomaly- ratio totals can be recognized easily. In partial or full suites of ore elements the we of anomaly ratios is more meaningful than use of analyzed value because the ratios quickly indicate how use of analyzed values because the ratios quickly indicate how anomalous some elements are, and call attention to samples and

Jan 1, 1982

By Robert L. Sundeen, Richard V. Wenberg

INTRODUCTION Early rock-bolting practice usually consisted of ran¬domly installing bolts, using hand-held drilling equip¬ment such as air-leg mounted sinkers or stopers. As bolting technology evolved, the practice of installing uniform bolt patterns was developed, utilizing random bolt installation as required within the uniform pattern. The uniform rock-bolting technique, when used as the principal method of rock support, requires drills and jumbos designed specifically for rock bolting. This equipment is similar to conventional face drilling machines, except that the jumbos can orient the drills to obtain any necessary bolting angle; often, this means bolts may be installed at or near perpendicular to the centerline of the drift or stope opening. Fig. I shows a typical rubber-tired rock-bolting jumbo of the type commonly used in drifts and room-and-pillar mining. Modern rock-bolting jumbos are capable of drilling the required holes, inserting rockbolts, and torquing them to proper levels. Jumbos also are available for use with resin-anchored bolts. Probably the most unusual of this type utilizes a rotating bolt turret that carries the rock drill, resin charging unit, and the bolt in a single mechanism. Once the turret is loaded with the resin and bolt, further manual effort is not re¬quired. Drilling and bolt placement are accomplished by the operator from a station remote from the bolt site. Fig. 2 shows this turret device. Roof-bolting jumbos are available mounted on rail, crawler, or rubber-tired chassis. Various types of rock drills are used. Depending upon the type of rock, these may include rotary, percussion, or rotary-percussion drills. Fig. 3 shows a typical rail-mounted jumbo. CONDITIONS INFLUENCING APPLICATION General Rock Conditions Rock-bolting generally is applicable in moderately hard to hard rock. No particular type of rock is ex-

Jan 1, 1982

No noticeable international economic recovery occurred during the first half of 1982. Industrial production continued to fall in the United States, Canada and Italy and to hold steady in France. Modest increases in production occurred in Japan, England and Germany, although some decline took place from March to April. The U.S. mining industry has been more severely affected by the world recession than the U.S. economy. This is not immediately obvious when comparing the U.S. mining industrial production index from 1981 to 1982, which decreased 8.5 percent, as compared to a 7.1 percent decline for total domestic industries. However, "mining" industry statistics in the U.S. national economic accounting system include petroleum and natural gas as well as minerals. When metal mining is isolated, the decrease in production from 1981 to 1982 is 19.3 percent. If metal mining production continues to perform at the same rate during the third and fourth quarters of 1982 as during the first half of the year, declines from 1981 levels will be quite severe. Aluminum will have declined 22 percent, copper 18 percent, iron ore 24 percent, lead 3 percent, steel 29 percent, titanium 2 percent and zinc 25 percent.

Jan 1, 1982

By Richard H. Bares

The general or macroclimate of the study sites in western North Dakota is characterized by rapid and sometimes extreme daily and day-to-day temperature fluctuations, rainfall patterns which are erratic in spatial and temporal distribution and intensity, generally low relative humidity, plentiful sunshine, nearly continuous air movement, and a relatively short frost-free period. Of particular relevance to plant growth and productivity is the mosaic of microclimates: these microclimates are affected by landform (convex and concave surfaces); exposure; slope angle, length and aspect; soil color, texture and surface cover (litter), and vegetation cover. The most critical plant growth governing factor in this region is available water. It is determined principally by water input (precipitation) and water loss (evapotranspiration) which is increased by high temperatures, wind, and poor litter and vegetation cover. While spring and fall precipitation is generally gentle and soil-soaking summer rains frequently come in the form of intensive, soil-washing, localized convective thunderstorms of short duration. Due to the convective nature of these storms, summer rainfall is particularly affected by regional topography; southwest slopes and crests often receive more rainfall since these storms usually move in a northeasterly direction. The water loss due to runoff and consequent soil erosion arc major problems resulting from such "cloudbursts". Previous fall precipitation (September - October) when added to current seasonal precipitation (March - August) was found to be significantly correlated (r-.93) with plant production. Winter precipitation (snowfall) is relatively light as the prevailing weather is dominated by dry polar air masses from the north. The nearly continuous wind is responsible for removing snow from open exposures and depositing it in depressions and windbreaks. Although the winter precipitation is not a large component of the total annual precipitation, conservation of that which does occur would contribute to plant production during the following growing season. Generally clear skies over the region facilitate receipt of abundant sunshine at the earth's surface. While good for early season soil warming and plant photosynthesis, this abundant sunshine coupled with long days and nearly continuous wind is responsible for evapotranspiration exceeding precipitation by an average of six inches between June' and September. On a local (micro) scale, the water deficit is most severe on the southern exposures which receive the most direct (most effective) solar radiation and therefore are warmer than other exposures. On a broader scale, it was found that ambient temperature extremes were slightly but significantly greater in the town of Beulah in the Knife River Valley than at the upland test sites, This may have been due to the difference in topography and/or the "urban heat island" effect. It is known that air temperatures in large cities may be 2° to 4°C higher than that of the surrounding countryside. It is also well known that basins, depressions or valleys are sinks for cold air masses and are often subject to frosts not occurring on adjacent upland sites.

Jan 1, 1982

By William Petruk

The development of automatic image analysers brought the application of image analysis into process mineralogy because the analysers can measure parameters more easily, quickly and accurately than by manual grain counting techniques, and can also collect data unobtainable by manual grain counting. Data from ore specimens and mill products are used to predict and to define the behaviour of minerals during processing. The analyses are generally performed on the basis of either surface areas or linear intercepts of grains in polished or thin sections, and the data are computer processed to give mineral quantities, liberations, size distributions, and characteristics of middling particles. For analysis, the minerals must be detectable and discriminatable from each other. An image editor is usually used when minerals are not easily discriminated. In addition BSE-8EM photographs have been used where the silicate minerals could not be discriminated from the mounting media. Methods of analysis, typical results, and their applications are discussed.

Jan 1, 1982

By Charles J. Hass

INTRODUCTION Deformation measurements are some of the simplest and most useful measurements that can be made by the mining/rock mechanics engineer in assessing the sta¬bility of openings in rock. A number of tools and tech¬niques are presently available. This chapter will de¬scribe the most common instruments, their application, and present the equations needed for data reduction. MECHANICAL STRAIN GAGE Description of Instrument A mechanical strain gage of the Whittemore type shown in Fig. I is a useful instrument for measuring deformations of pillars, sidewalls, and roofs of under¬ground mines. Measurement gage lengths typically range from 51 to 254 mm (2 to 10 in.), and the dial indicator reads to 0.0025 mm (0.0001 in.). The instru¬ment measures the deformation between precision gage points which are anchored in the rock. The anchor points are typically grouted in small holes drilled 12.5 mm (1/2 in.) or so deep into the rock. Strain a is calculated from the measured deformation AL with the equation [ ] where L is gage length. A necessary accessory for the instrument is a master bar normally made from invar steel having a low co¬efficient of thermal expansion. This bar allows one to check the instrument for changes in the mechanical zero point and to correct for temperature effects on the measuring instrument. The instrument is available from Soiltest, Inc. for a cost of approximately $340; the cost of the master bar is approximately $55; and nonreusable brass inserts which are anchored in the rock are nominally priced at $0.27 each. All prices are for 1978. Applications Two classes of applications may be considered, one where only one measurement direction is involved and the second where three measurement directions are em¬ployed. Applications where only one measurement di¬rection is necessary include: monitoring crack or frac¬ture separation or shear movement with anchor points on opposite sides of the discontinuity; measurement of vertical strain in a pillar or sidewall; and measurement of steel support deformations with anchors in the steel members. The more general application involves a strain ro¬sette consisting of three measurement directions which for convenience are oriented 1.04 rad (60°) apart to form an equilateral triangle as shown in Fig. 2. Strains in the three measurement directions [ ]

Jan 1, 1982

By William F. Eichfeld, Robert J. Wenzel

INTRODUCTION The phrase "subsidence control planning" can refer to the use of specific mining methods and-specialized techniques to control subsidence events or it can refer to planning for subsidence by predicting its magnitude and timing and further planning mitigation strategies. In the first case the objective is actually subsidence prevention while in the second it is a design procedure that seeks to maximize the use of both surface and subsurface resources. Neither technology is well developed at this point. The purpose of this presentation is to briefly outline the Department of Energy's Subsidence Program. This program is, in general, bases on the premise that subsidence control technology, by any definition, can be accomplished only through a thorough and rigorous understanding of subsidence phenomena. This understanding must come from many well planned and executed studies of stress redistribution and strata deformation as they occur during mining activities. There is presently considerable incentive to improve our subsidence engineering capabilities due to the desire for increased coal utilization with acceptable environmental impact. Considerable research in this area is being sponsored by federal and state governmental agencies, universities, and the coal industry. Federal sponsorship has been borne by the Department of Energy, the Bureau of Mines, the Office of Surface Mining and the U.S. Geological Survey for the most part. These agencies have carried out basic research in their laboratories and have contracted with other organizations for additional work. At this time most of the available resources are directed toward contract research, especially in DOE. It is the DOE research plan which will be addressed here.

Jan 1, 1982

By D. Y. Geng, Syd S. Peng

This paper analyzes the effects of geology and mining methods on surface subsidence factor, angle of draw and angle of critical deformation based on the results of 40 longwall subsidence profiles in the Northern Appalachian coalfield. Several equations were derived to show the relationships between those parameters. Furthermore, the equations were transferred and plotted in the form of several monographs for convenience of applications.

Jan 1, 1982

By Terry G. Richard, Vernal H. Kenner, Sunder H. Advani

This paper presents and discusses the results of thirty-one fracture toughness tests on Pennsylvanian Age Clay Shale. Two different orientations for this anisotropic material were studied and two series of tests were conducted, namely, 1. a test series to determine the effect of moisture content on fracture toughness, and 2. a test series to study mixed mode fracture. Increased absorbed moisture is found to reduce fracture toughness. Several analyses of mixed mode failure are found to give varying non-conservative predictions of failure stress intensity level.

Jan 1, 1982

By K. N. Clark, N. B. Carter, C. G. Thomas, V 7. 0 / 300 dpi

A statistically designed, experimental study showed how gangue minerals, flux additions, fineness of grind, firing temperature, and time affect the properties of acid pellets made from a Western Australian hematite ore. Alumina has less effect than silica and lime, but interactions between the six variables occur, which influence abrasion index, reducibility, and cold compression strength. Finer grinding has little influence on reducibility but improves the other two properties. The major variable is firing temperature, which interacts with all other variables to affect pellet properties. Calculations based on the data show the implications for straight-grate pellet plants and optimum hood temperature ranges.

Jan 1, 1982

By Thomas R. Smith

This paper covers oil shale resources in those countries that border the Pacific Rim. The major known resources around the Pacific Rim occur in the Western United States, Australia, the People's Republic of China, (PRC) and the Thailand/Burma region. The location of these deposits is shown in Figure 1. In 1965, the U.S. Geological Survey estimated world oil shale deposits of over 4 quadrillion tons having a potential oil yield of over 2 quadrillion barrels. If all this were extracted, it could meet the world's entire energy needs far into the future. However, the Survey also estimated the spent shale waste could cover all of the surface of the world to a depth of about 10 feet. Thus, for this and many other technical and economic reasons, it does not appear to be feasible to develop a large portion of the world's oil shale resources in this century; nor will shale in itself solve our energy problems. Nevertheless, shale oil and other ' synthetic fuels are expected to play an important role in new energy supplies in the longer term. WHAT IS OIL SHALE OR SHALE OIL? The term "oil shale" is sometimes a misnomer, in that the rock is often more of a limestone or siltstone than a shale. The common link between resources termed “oil shale" is that they all contain an insoluble substance cal led kerogen (which is from the Greek words for waxmaking). Kerogen is a form of organic carbon derived from a variety of plants ranging from algae to higher plants. When heated sufficiently, the kerogen generates hydrocarbons called shale oil, a form of synthetic crude oil that in most cases is lower in hydrogen content than conventional crude oil. The amount of oil in oil shale is relatively small --roughly 10 percent (by weight) in the richer shales. To upgrade this synthetic oil to usable products, additional processing is necessary. This brief sketch gives an idea of what this different, but significant, form of hydrocarbon is like. ENVIRONMENTS OF DEPOSITION Most oil shale deposits fall into three environments of sediment deposition: 1ake (called lacustrine), sea (marine) and river (fluvial-deltaic). In each case, the deposition of oil shales took place in quiet water environments where plant life, particularly algal plants, could flourish and, after dying, be deposited in unoxygenated water where the kerogen precursors would be safe from destruction by oxidation. The oil shales that were deposited in large lake basins (lacustrine) have attracted the most attention for development over the years. They often have multiple seams, deposited in a cyclic nature with extensive areal distribution and rapid vertical changes in kerogen content. Grades are moderate to high, ranging from 80 to 200 liters per tonne. Rundle in Australia and the Piceance Creek Basin in Colorado are examples of this type. Both deposits represent large volumes of oil shale in small areas which could provide the large volume of feedstock needed for future commercial operations. The stratigraphic sections of these two deposits feature thick oil shale seams with average grades of 80 - 125 liters/tonne conducive to both open pit, and underground operations. However, the rock strength of the Rundle shale is not sufficient to - support underground mining. On the other hand, the Colorado deposits, being more carbonate in nature, are sufficiently strong to support either type of mining depending on the overburden to ore ratio. These latter types of deposits will likely provide the first target for development of a commercial industry. The marine type is characterized by extensive areal distribution with relatively thin seams. The grades are generally low to moderate, ranging from 50 to 120 liters per tonne. The marine oil shales are common worldwide, and their attractiveness for mining is dependent on the overburden to ore ratio. Because of their widespread areal distribution, their in situ resources can be quite large. The Toolebuc Formation in Central , Queensland, Australia is a good example of this type of deposit being 7-10 meters thick over an extensive area. The Julia Creek deposit with its favorable overburden-to-ore ratio is being studied for possible development. In a fluvial-deltaic environment, there are many small lakes or bogs associated with rivers in which a very pure type of oil shale called torbanite could form. Torbanites are very high grade containing up to 75 percent hydrocarbons. The known occurrences are generally small lenticular deposits associated with coal seams. Even with the high grades, it is not likely that any of the known deposits would warrant commercial development because of their small size. The torbanite deposits in New South Wales, Australia were processed prior to World War I1 near the town of Glen Davis. However, today's known resources of this type are not large enough to warrant a commercial plant.

Jan 1, 1982

By R. M. Giegerich

"This paper begins with a brief history of Madawaska Mines, a brief description of the geology, mining methods and equipment, and the historical development of 7/8-in. tapered drilling equipment. It then outlines the performance characteristics and inherent problems of the traditional 12-degree, tapered connection, blade-type insert bits. Service-free (Unipass) button-type insert bits are presented as a possible solution to these problems. The paper concludes with an analysis of button bit performance to date.Brief History of Madawaska MinesMadawaska Mines Limited, near Bancroft, Ontario, is in Faraday Township, Hastings County, approximately 100 miles northeast of Toronto and 100 miles west of Ottawa.The mine re-opened in 1976committed to 1,500 tons per day to provide approximately 600,000 pounds of yellowcake (U3O8) per year to A.G.I.P. (an Italian government agency) under the joint ownership of Federal Resources Corporation, Salt Lake City (51%), and Consolidated Canadian Faraday Limited (49%). At present, the mine is producing approximately 2 pounds per ton (.1% U3O8) at the rate of 60,000 pounds per month. The mine employs about 400 employees.Brief Description of Geology, Mining Methods and EquipmentGeologyThe Grenville metasediments of the mine area are chiefly paragneiss, amphobolite and some carbonate (marble) rocks, which were intruded by a basic rock, altered to a metagabbrometadiorite. These formations are generally concordant, striking east to northeast and dipping 45 to 60 degrees to the south. Locally, the metagabbro is often discordant. The above group of rocks (mixed hybrid gneisses) forms the hanging wall of the south-dipping Faraday granite sheet and was intruded by nepheline syenite, syenite and granite. The ore occurs in the granite-syenite-pegmatite dykes that are probably genetically related to the Faraday granite. The ore shoots are erratically distributed within the pegmatite bodies, mainly on the hanging or footwalls but also medially. Their size varies from 50 to 350 feet in length, 5 to 40 feet in width and 50 to 200 feet in height. The ore occurs most frequently in a medium-grained granite or syenite, well hematized with 10 to 30% mafic crystals of pyroxene, amphibole and/or relics of the host rock."

Jan 1, 1982

By Thomas R. Stauffer

The principle that conventional schemes for taxing petroleum or mineral resources are "inefficient" is illustrated using simulation calculations tested against an "ideal" system. Inefficiency is defined as the relative success in maximizing expected government revenues from the resources. Most systems fail because: 1) they leave oil in limbo, i.e. unproduced because of excessive fiscal burden; or 2) they unnecessarily increase the variance in the explorationist'c, rate of return by undertaxing large fields and overtaxing smaller but infra-marginal fields. This increases his discount rate and reduces taxable surplus. An "ideal" tax system is specified which maximizes government revenues while minimizing risk to the operator. Two criteria are developed: 1) the tax falls to zero on fields which yield only the minimum necessary rate of return ("marginal" fields); and 2) the after-tax present value of all fields is the same for all fields above a threshhold size. In particular, marginal fields, while contrib- uting little to expected values, do contribute to reducing variance and hence risk praemia by distributing the exploration costs over a higher probability of successful outcomes.

Jan 1, 1982