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By H. S. Munroe

AN elaborate discussion under this heading formed a chapter in one of the reports made by Professor Raymond as Commissioner of Mining Statistics.* In a subsequent report- was printed a paper, by Mr. William Main, Jr., of Columbia, South Carolina, containing a theoretical investigation into the effect of the velocity of impact on the effective ditty of stamps. A visit to the Lake Superior copper region last summer suggested an inquiry into the relative efficiency and economy of the enormous steam stamps of the copper-mills, as compared with the results obtained with the cant and tappet stamps commonly used in the West. The atmospheric stamp used at the Phoenix Mill promised to add interest to the inquiry, as giving an example of unusually high speed, this stamp making 160 drops per minute. In introducing his subject Dr. Raymond makes the following remarks, which are quite apropos of the present investigation : "In considering the economical application of stamping machinery, we meet, at- the beginning, with serious difficulties in obtaining accurate data for comparison. The weight and fall of stamps vary as the shoes and dies wear out; and this may lead to a change of speed also. Moreover, defects in engines, boilers, or machinery for the transmission of power, may occasion serious losses, which cannot fairly be charged to the arrangements of the stamps proper. Again, the capacity of stamp-mills is directly dependent, in some degree, upon the nature and extent of discharge, fineness of screens, and other peculiarities of the battery. Finally the hardness and tenacity of the rock crushed varies so much that comparisons between different localities cannot be implicitly trusted. The safest experiments are those made in the same mill, by changing first one and then another condition of working; but this is seldom possible for such * Mineral Resources West of the Rocky Mountains, 1871, p. 380. †- Mineral Resources West of the Rocky Mountains,, 1873, p. 345.

Jan 1, 1881

By S. M. Moos, R. E. Dugger

In reviewing available vacuum filtration equipment in this paper, several types of filters have been included which are probably not familiar to operators in the mining industry. However, it was felt that these units might be of interest in the event that an application should arise for the filtration of a product in the future that does not exist today. In addition, exposure of our industry to equipment used in other industries might have a tendency to be thought provoking and perhaps lead to the development of equipment and/or applications in our industry which do not necessarily exist at this time. Most innovations in filtration equipment have been confined to the improvement or design change of components and accessories, particularly reflecting the availability of materials of construction that have been developed. Recent developments in the application of horizontal belt filters have been innovative. The application of this unit as a substitute for or an adjunct to thickeners in a CCD circuit can certainly be innovative and perhaps provide a basis for reduction in capital and operating costs in this area. For example, mill tails are generally pumped at the highest possible density that will adequately flow. Tailings ponds and dams with their attendant design requirements are based upon this estimated water volume.

Jan 10, 1979

By F. E. Bash

About three years ago, the writer presented a paper1 on the rate of heating and cooling of a 24-in. round ingot. The present paper deals with work done on larger ingots at the plant of the Allis Chalmers Mfg. Co., Milwaukee, Wis., in August, 1919. Sufficient data on ingots of all sizes were desired to enable one to calculate in advance the rate at which any ingot could be raised to a forging temperature without injury to the steel, determining also the temperature gradient between different sections of the ingot and the length of time necessary to heat to the center. This has now been experimentally determined for 24-in. and 45-in. ignots by the writer and for a 18-in. cube by E. F. Law.2 J. F. Harper has also made tests on heat-treating temperatures on 30-in, ingots; which data are included in this paper. No attempt is made here to work out a formula for the heat penetration of steel, for too many factors are involved concerning which we have not sufficient information, as for instance, the specific heat of steel up to 2300' F. It is hoped that eventually a set of formulas will be developed so that one may calculate maximum allowable temperature differences within an ingot for any particular kind of steel and the rate of absorption of heat and temperature gradient within the ingot for a definite temperature head. EXPEEIMENTAL INGOT The ingot tested was 45 in. in diameter, having been forged into the shape shown in Fig. 1 from 54 in. diameter. Seven -in. holes were

Jan 1, 1923

By F. E. Bash

About three years ago, the writer presented a paper1 on the rate of heating and cooling of a 24-in. round ingot. The present paper deals with work done on larger ingots at the plant of the Allis Chalmers Mfg. Co., Milwaukee, Wis., in August, 1919. Sufficient data on ingots of all sizes were desired to enable one to calculate in advance the rate at which any ingot could be raised to a forging temperature without injury to the steel, determining also the temperature gradient between different sections of the ingot and the length of time necessary to heat to the center. This has now been experimentally determined for 24-in. and 45-in. ignots by the writer and for a 18-in. cube by E. F. Law.2 J. F. Harper has also made tests on heat-treating temperatures on 30-in, ingots; which data are included in this paper. No attempt is made here to work out a formula for the heat penetration of steel, for too many factors are involved concerning which we have not sufficient information, as for instance, the specific heat of steel up to 2300' F. It is hoped that eventually a set of formulas will be developed so that one may calculate maximum allowable temperature differences within an ingot for any particular kind of steel and the rate of absorption of heat and temperature gradient within the ingot for a definite temperature head. EXPEEIMENTAL INGOT The ingot tested was 45 in. in diameter, having been forged into the shape shown in Fig. 1 from 54 in. diameter. Seven -in. holes were

Jan 1, 1923

Jan 1, 1912

By T. M. Chance

THE first bituminous coal cleaning-plant to use the sand-flotation process1 was placed in operation on Oct. 1, 1925, at the tipple of the East Broad Top Railroad & Coal Co., at Mt. Union, Pa. The general principles governing the design of plants of this type and typical operating results of anthracite sand-flotation units have been previously outlined.2 I will, therefore, confine myself to a description of this particular plant and to some of the elements of design it incorporates. THE ORIGINAL MT. UNION TIPPLE The plant was installed to transfer coal from steel narrow-gage cars of 60,000 and 70,000 lbs. capacity to standard-gage equipment. The coal was hauled some 30 miles from the East Broad Top field. This coal, mined by the Rockhill Coal & Iron Co. and other operators, is a low-volatile slow-coking coal with- ash of high-fusion point. It is normally a high-grade coal that does not contain an excessive amount of free impurities, but it requires careful handling to secure a fair domestic yield, and, naturally, the need for narrow-gage transshipment increases the difficulty of the problem. The narrow-gage cars were discharged into an 8-car track hopper equipped with two feeders passing the coal to two 42-in. apron intake conveyors. Twin units were installed throughout in this original plant, two lump-and-egg shaking screens, two lump picking-tables, two egg picking-tables and two stoker conveyors. The stoker coal was loaded without cleaning. The loading tracks and booms were in duplicate and with the layout as originally installed either unit could be run independently, each unit shipping a different class of coal or both units making the same product.

Jan 2, 1926

By J. T. Ryan

FIGURES for the first 11 months of 1935 indicate that the total coal production of the United States for 1935 will be approximately 416,000,000 tons, or almost identical with the production figures for 1934. Bituminous production will show a gain of about six million tons, and anthracite production a loss of about the same tonnage, compared with the previous year. This does not take into account so-called "bootleg" anthracite coal amounting to approximately 5,000,000 tons. Twenty-nine years ago, in 1906, the production of coal was almost identical with this year's production. At that time, 626,000 men were employed in producing this tonnage, which took a toll of 2138 lives from accidents. In 1935, approximately 540,000 men were required to produce the same tonnage with an estimated loss of 1155 lives. This shows definite safety advancement in the industry, but even so accidents are still costing an average of 3c. a ton more than they should.

Jan 1, 1936

By Frank H. Reed, P. W. Henline, Harold W. Jackman

A sumMary of the consumption of coal in 1945 shows that the coke industry ac-counted for 17 pct of the total coal used. No substitute for coke and the blast furnace in the reduction of iron ore has gained sufficient prominence so far to be given serious consideration. However, while the same slot-type ovens are being built and used now as were in use a few years ago, the problem of obtaining suitable coking coals, both high- and low-volatile, has forced many operators to revamp coal-blending facilities. Until the beginning of World War 11, high-temperature ooke plants were able to secure the required high-volatile and low-volatile coals from two or three seams and from three or four mines. Thus, many of our coke oven plants were able to operate with storage bins for two coals only. The vari-pnce in raw materials was not great, and uniformity of blend was a relatively simple problem. Since the beginning of World War 11, many and important changes have taken place. Demand for all coals increased greatly. Production, though kept as near maximum capacity as possible, could not meet the demands for coal generally, and particularly for the various kinds of coal which have proved to be satisfactory for specialized uses; coals were allocated as nearly as possible in the order of greatest need; storage piling was reduced to the minimum necessary to keep plants in operation; uniformity of quality could not be maintained, and with this last, uniformity of composition of blends for coking could not be maintained. Whereas before the war producers of metallurgical coke could fill their needs from three or four mines, by the end of the war it was not unusual to find shipments to a single coke oven plant coming from as many as 30 different mines, in a single month. Since many of the mines producing both high- and low-volatile coal for high-grade metallurgical coke are rapidly nearing de-pletion, the problem of seeking new sources and of blending a number of coals in each plant for the production of high-temperature coke is facing practically every producer in the United States at the present time, and is one which will probably continue for many years to come. Midwestern byproduct coke ovens in the Chicago and St. Louis areas use annually from 12 to 15 million tons of bituminous coals which are transported 500 to 700 miles from the Appalachian coal fields of Pennsylvania, West Virginia, and eastern Kentucky. Approximately two-thirds of this coal is high-volatile bituminous. The critical transportation problem confronting the nation in 1943, and the growing scarcity of the best Appalachian coking coals, prompted the Illinois Geological Survey to propose a research program in which would be studied the coking properties of blends of low-sulphur, high-volatile Illinois coal with the high- and low-volatile coals from the eastern fields. Such blends containing Illinois coal, if substituted for the all-eastern blends normally coked,

Jan 1, 1949

By Frank D. Hoyt

BY far the most conspicuous of the Pennsylvania slate districts is that extending from the New Jersey line at the Delaware Water Gap westward almost to the Schuylkill River. This covers parts of three counties in east-central Pennsylvania: Northampton, Lehigh, and Berks. The most important development, both in geographic size and product importance, is in Lehigh and Northampton counties. The greater part of the region is underlain by only one formation-the Martinsburg, consisting of slates, clay slates, and sandy shales, all of the Ordovician period. The slate-bearing Martinsburg formation is underlain by Cambro-Ordovician limestones. Immediately overlying the Martinsburg formation is the Tuscarora quartzite of the Silurian period. The Martinsburg formation itself is divided into three distinct divisions, termed simply: the upper, the middle, and the lower members. Commercial slate has been extracted from all of these members, but the formation of greatest importance is the upper member, representing 2600 ft of the total formation thickness of nearly 11,000 ft. The upper member is commonly referred to as the "soft slate" and consists of three facies: 1) beds of blue-gray, very sandy, almost quartzitic slate, in many places, approximately a medium-coarse sand- stone with calcareous cement; 2) blue-gray sericitic slat-the dominant rock type of this member-with occasional chloritic beds; and 3) dark gray or virtually black, highly carbonaceous beds, referred to locally as "ribbons."

Jan 8, 1958

By Ihor A. Kunasz

Lithium minerals occur predominantly in pegmatites which contain mineral assemblages derived from the crystallization of postmagmatic fluids or from the metasomatic action by residual pegmatitic fluids. They have been the traditional sources of raw materials for ceramic and chemical industries. However, with the discovery of Searles Lake, brines became new sources of lithium. Indeed, the 1960s may well be referred to as the "brine decade" because several brine bodies of significant economic importance were discovered. In the United States, the brines of Clayton Valley, Nevada, presently exploited by Foote Mineral Co., and the Great Salt Lake of Utah, to be exploited by the Great Salt Lake Chemicals Corp., have been defined as major sources of lithium. Also a lithium-bearing brine has been discovered in Chile. Following the termination of the AEC purchase program in 1959, several companies such as Maywood Chemical Co., American Lithium Chemicals, and Quebec Lithium Corp. were forced to close down their operations. Nevertheless, with the development of new applications in glass ceramics, air conditioning systems, synthetic rubber, and metallurgy (aluminum potlines), the lithium industry grew steadily, and with the potential application of lithium metal in batteries and nuclear reactors, a healthy growth can be foreseen. New products and new applications are likely to stimulate exploration for expanded reserves as well as the search for new sources from which lithium could be extracted economically. Geochemistry of Lithium Lithium is the third element in the periodic table. It is the lightest of all the metals, having an atomic weight of 6.938. Its ionic radius is 0.60A and its charge is + 1. The geochemistry of lithium has been extensively studied and has been summarized by Rankama and Sahama (1950), Goldschmidt (1937), and Hortsman (1957). The distribution of lithium in igneous rocks is controlled by its size and its charge, and by the (MgO+FeO)/Li2O ratio. In the early stages of crystallization of a magma, that ratio is very large. Consequently, both magnesium and iron are removed by ferromagnesian minerals in preference to lithium which is then concentrated in the residual magma. This results in an enrichment of lithium in silicic rocks and pegmatites (Strock, 1936). Pegmatites are coarse-grained igneous rocks formed by the crystallization of postmagmatic fluids. Minerals within pegmatites may also form by metasomatism (Jahns. 1955). Genetically, the pegmatites are associated kith neigh- boring intrusives. Mineralogically, granitic pegmatites contain feldspar, quartz, and mica as the main constituents and a variety of exotic elements such as lithium, beryllium, tantalum, tin, and cesium, which may or may not occur in economically significant concentrations. Detailed studies by numerous investigators (Cameron et al., 1949, 1954; Hanley et al., 1950; Jahns, 1953, 1955; Page et al., 1953) indicate that pegmatites often exhibit an internal zonal arrangement, with each zone containing a specific suite of minerals. The lithium minerals are usually found in the intermediate zones, and although as many as 13 zones have been recognized by Cameron, a complete zonal arrangement is rarely found. Zoning of pegmatite bodies has also been observed on a regional basis. The regionally zoned pegmatite sequences exhibit mineral assemblages and complexity according to their respective distance from the granitic bodies to which they are genetically related (Mulligan, 1965). Lithium is also found in small proportions in a variety of rocks. The average lithium

Jan 1, 1975

By I. Plaskin

Interaction of sulfide minerals and native metals I with reagents in flotation is largely determined by particle-surface changes resulting from action of the medium and dissolved gases. A number of early studies were devoted to the selective action of various gases on minerals.' Mc-Lachlan' paid attention to oxygen as the most active gas affecting flotation properties of sulfide minerals. Opposing views were expressed concerning the influence of sulfide oxidation on xanthate flotation: Taggart3 recognized the positive influence of oxygen, and I. W. Wark4 rejected it. Shvedovh ffered the hypothesis of partial oxidation. As to the influence of such gases as hydrogen" and carbon dioxide on mineral floatability, opinions also differed. Effect of Oxygen on Sulfide Mineral Flotation: Research on the influence of oxygen and other gases on the floatability of sulfide minerals and native metals has been carried out at the Institute of Mining of the USSR Academy of Sciences in

Jan 1, 1960

By Evan Just

Government aid, regulation, and participation in the mineral industry are not new; they date back to the time when man first adopted communal living. Even in primitive tribal life, the obtaining of arrowhead or ceramic materials, washing of gold, or mining of copper were specialized activities, under tribal sponsorship. Later, when kingdoms, dynasties, and hierarchies developed, titles to mining properties were held by the sovereign or the state, work usually being done by slaves. Title acquisition through denouncement developed in Europe in the late Middle Ages and spread to the Western Hemisphere with the Spanish and Portuguese empires. Denouncements still recognized the rights of the sovereign in the requirement to pay royalties, which practice continues in many places today. Thus, anyone who views government participation in mineral activity as "encroachment" has no historical perspective. Only in a few countries and for a few generations have private interests enjoyed the right to exploit mineral deposits without the specific consent of the sovereign or without payment-of-royalty. Governments and the mineral industry have been linked together by other factors. Governments have had special interest in metals and minerals as stores of value and for armaments. Spanish conquests in the New World were energized by the lure of gold and silver. Pursuit of gold led to the American seizure of California in the days of the Forty-niners. The strategic importance of minerals in our own times has called for special steps to stimulate production in national emergencies and to prevent the enemy from acquiring mineral supplies. Our export controls to deny certain minerals to unfriendly countries, purchases for Government stockpile, and subsidies for domestic production are examples. Production regulation by state governments of oil and gas has become a well established routine. In brief, the mineral industry has never lacked aid, regulation, and participation by governments. The entrepreneur who wishes to explore for or develop minerals must deal with governments in most areas before he can begin, because mineral rights are reserved by them. He can proceed through discovery and de-

Jan 1, 1959

By David B. Reger

Oil and gas and their derivatives continue to be stable products in West Virginia. In the midst of the cataclysmic happenings of 1930 to 1934, which have swept away banks and practically destroyed many other enterprises of presumably nonspeculative character, the possession of a royalty or working interest in a few old oil or gas wells has prevented disaster in literally thousands of homes. These old wells yield their daily quotas of basic commodities, which the public must have. Fortunately, the facilities of disposal in the Appalachian Province are so ample and well managed that the owner of such equities may be reasonably certain that his proportionate share of existing markets will be afforded him without much effort on his part. In most cases these investments are free from encumbrance or hypothecation, therefore the main uncertainty is the date of ultimate exhaustion at the source. Generally, this is known to be fairly remote. The net result has been that individual owners part with such investments only as a last resort. In sharp contrast to the action of the small owner of wells or royalties who has prudently refrained from jeopardizing his rather certain income by drilling new wells that may be failures, or of which the product may not be needed for the moment, has been the plight of various promotional enterprises in natural gas. Many of these ventures have been operated by amateurish remote control and practically all have been overloaded from the start with bonds and debentures, which could only be satisfied in a rising and expanding market; and with operating costs that have been exceedingly high because of widely scattered producing units and large overheads. Many of these promotions are now in receivership or bankruptcy and in various instances the original units have been recaptured by former owners and have again become profitable by reason of personal operation and elimination of all forms of overhead expense. New Development In 1934, the State issued 524 permits for drilling. According to the trade journals, 553 wells were completed, with 184 oil wells, 274 gas wells and 95 dry holes (Table 3).

Jan 1, 1935

By T. W. Turk, S. A. Sass

The engineering design features of the Mercur Gold Project crushing, grinding, carbon-in-leach, bullion, reagent, and tailings disposal areas will be discussed in this paper. It presents a project overview and flowsheet along with selected design alternatives. During the engineering phase, major equipment and other features were selected to optimize design within site location and environmental constraints. The project team organization and procedures were adopted to accommodate multiple optimization studies while maintaining a tight engineering schedule.

Jan 1, 1985

By Ronald C. Whiting

SINCE the advent of what has been aptly called "chemical flotation," about 1920, the number and complexity of the various chemicals used in practice have increased enormously. Over 300 patents have been issued dealing exclusively with flotation reagents, and many of these embrace from two or three up to a score or more of specific compounds. The exact number of compounds actually finding a practical use in flotation would be difficult to determine, though the U. S. Bureau of Mines gives an annual list by groups.

Jan 1, 1938

Jan 1, 1890

By A. L. Labbe, J. J. Donoso

Hard-won experience in the operation of smelting plants has pointed the way to the most efficient design and economical operation of a baghouse system for recovery of metallurgical fumes. This paper treats of the principles governing bag filtration and the factors most directly affecting bag life. Methods for temperature conditioning of smoke previous to filtering are described and the evolution of bag shaking mechanisms is brought up to date. THE history of the bag filter process, as applied to the recovery of metallurgical fumes, goes back to 1876, when the Lone Elms Works of Joplin, Missouri, erected a two-section baghouse for filtering fumes from Scotch Hearth lead smelting furnaces. By modern standards this installation was crude, but the basic operating principles remain essentially the same today. Great progress, however, has been made in the mechanization of the process by the use of devices for mechanically and automatically cleaning bags of adhering fumes, in the use of instruments for recording and controlling the variables affecting baghouse operation, and in the conditioning of the smoke previous to filtering. The principles governing bag filtration of fumes were investigated in 1929 by A. J. Seitz of American Smelting and Refining Co., and he arrived at the following conclusions: 1. Pressure on Bags at Constant Volume: The rate at which the pressure builds up in a bag with constant volume is directly proportional to the time, with the same kind of smoke and dust burden (fig. 1). 2. Pressure on Bags for Change in Volume: With equivalent smoke and dust burden, the bag pressure increases with the square of the increase in volume. The rapid increase in pressure is due to (1) increase in volume, (2) increase in amount of dust on the bag, and (3) more intense packing of the dust at higher velocity (fig. 2). 3. Effect of Intensive Filtering on Pressure: Since the pressure builds up directly as the square of the volume, with the same smoke and dust burden, it is necessary to shake the bags in that increased ratio, and vigorously, to keep the pores of the bag open and pressure down. This increases the wear on the bags and the dust losses. 4. Effect of Shaking on Dust Losses: The losses are in direct proportion to the frequency of shaking because the loss takes place immediately after shaking, before the bag seals itself. Tests show that with hand shaking the last 20 pct of the removable dust requires seven times more shaking per unit weight of dust than the first 80 pct. 5. Effect of Fineness of Dust on Losses: The fineness of the dust particle increases the loss in two ways: (1) When the bag is clean a greater percentage of it will pass through before the bag seals itself; (2) fine material penetrates farther into the bag pores, building up pressure faster and necessitating more shaking, thereby increasing the loss. The physical principle of operation of the bag filter is simply the separation of solids from a gaseous carrier through a porous medium, and is analogous to the filtration of solids from liquid carriers. Basically, the mechanics of the process are as follows: Fume-laden gases drawn from the operating fur-

Jan 1, 1951

By G. B. Gibbs

Various semiempirical equations which relate defect-formation energies and entropies with elastic and thermal properties of a metal crystal are shown to be related by a simple model for lattice energy. An illustrative comparison of theory with experiment is made using self-diffilsion data for fee metals. SEVERAL workers have related the free energy of defect formation with elastic and thermal properties of a crystal lattice, particularly elastic bulk modulus and Debye temperature. The present note shows how the various approaches are related by a simple model for lattice energy. A comparison of theory with experiment is given using the self-diffusion parameters of fee metals. 1) A MODEL OF THE CRYSTAL LATTICE The internal energy per atom in a metallic lattice may be written U=Ui-Ue [1] where Ui and Ue refer to ion-ion interaction and valence electron energies, respectively. The volume per atom V has an equilibrium value 52 for which

Jan 1, 1968

By S. Skowronski

OvErpolEd copper, as commonly defined,- is copper which has been excessively reduced during the poling period of the refining process. Owing to its porosity, such coppcr is unfit for commercial purposes. The cause of this phenomenon is undoubtedly the lack of oxides in the copper, yet this does not completely explain it. Refined copper of the same "pitch" and "set" varies considerably in oxygen contents, and analyses of overpoled bars also show similar wide differences; moreover, it is possible to melt copper in 'crucibles so as to obtain bars that are practically free from oxygen although they show a "tough pitch" and "level set" surface. Frederick Johnson advances the following theory: The regulation of the quantity of oxygen in copper is the keynote of all copper refining. It is the presence of a well defined proportion of oxygen in the form of cuprous oxide, forming a copper-cuprous oxide eutectic, which enablcs copper to be cast free from blowholes. It seems that when oxygen is present, other gases are less soluble in molten copper; when oxygen is absent, or is present in insufficient quantity, the copper dissolves other gases, such as hydrogen and carbon monoxide, which are insoluble in the copper when solid, and, being rejected during the process of solidification, causes internal porosity and external ridges and excrescences.1 The "level set" of wire bars, etc., is entirely the result of a compromise between the occluded gases and cuprous oxide. With excess of the former the metal would be "overpitch" and spongy, while an excess of the latter would result in the metal being "underpitch" and brittle.2 The result of the absorption and subsequent expulsion of reducing gases, carbon monoxide and hydrogen,' and the effect of this action on the overpoling of copper are in dispute; the literature on the subject is full of contradictory statements and will continue to be so until better analytical methods have been developed. Sulfur, however, is tangible. The refiner can see it in his button sample and consequently attributes to it any trouble that may happen during the melting of the copper.

Jan 1, 1919

By W. J. Nelson, R. B. Nance

Detailed underground geologic mapping at a scale of 1:1200 has been carried out at the Crown II Mine of Freeman United Coal Mining Co., which operates in the Herrin (No. 6) Coal Member. The roof sequence, upward from the coal, includes (1) soft, medium -to dark-gray shale; (2) hard, black, fissile shale; (3) argillaceous nodular- bedded limestone, and (4) fine-pined, shaly, water-bearing sandstone. The first unit is highly lenticular, and any or all may be missing at a given locality. The sandstone has a sheet facies and a channel facies. The Herrin Coal is eroded in channels near the Crown II Mine. Structural features mapped at Crown II include normal and strike-slip faults and limestone "bosses." Less stable roof and wet conditions are encountered where the limestone is thin or missing or where it is broken by natural fractures or by artificial openings that intersect the water-bearing strata above the limestone. Geologic mapping of the underground workings has allowed us to predict faults, fracture zones, and channels ahead of the face for this mine. Some lithologic and structural pattern apparently are random and cannot now be projected. Conventional exploratory drilling is entirely inadequate to map faults or lithology of the roof, but it does indicate the range of lithologic variability, which can be used to project needs for roof supports. Drilling also is useful in locating channels and in mapping regional variation in thickness and facies of the sandstone.

Jan 1, 1983