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By R. J. Wagner, G. H. Gronhovd, A. J. Wittmier

The paper describes the results of a series of full-scale boiler tests run to determine the ash fouling characteristics of a North Dakota lignite as a function of sodium content of the coal. Four levels of sodium were investigated and rate of fouling was determined both by boiler performance and by specially constructed probe equipment. Discussed is information on chemical and physical properties of the ash deposits. The vast lignite deposits in North Dakota are becoming increasingly important as a source of low-cost fuel for power generation. A new 200-megawatt lignite-burning plant located near Stanton, N.D., was placed in operation early in 1966. Another 172-mega-watt unit in the same area is scheduled for operation late in 1966, and plans have recently been announced for a 212-megawatt unit to be in operation by 1970. If these plants show good performance, western North Dakota could become a major power production center for a large geographic area in the upper midwest. One of the problems associated with the use of lignite in power boilers is its tendency to form troublesome ash deposits on boiler tube surfaces. This problem varies considerably from one lignite-fired boiler to another and is dependent upon such factors as source of lignite, boiler design, load factor, tube metal temperatures, and soot-blowing practices. This report presents data on sodium content* variation in a North Dakota mine, describes the results of a series of tests performed to determine the relationship between ash fouling tendencies and the sodium content, and tells how the mining company and electric utility have coordinated their operations to reduce the ash fouling problem. GENERAL BACKGROUND Until recent years it was generally assumed that North Dakota lignite from a given mine had qualities peculiar to that mine, but that within the mine, the lignite was quite uniform. In 1959, the Otter Tail Power Co. installed a 53.5-megawatt lignite-burning unit at its Hoot Lake plant, Fergus Falls, Minn. Shortly after the unit was put into operation, it was noted that at certain times under high load conditions, ash fouling problems were quite severe, but not consistent or predictable. Each time fouling occurred in the unit the position of the loading shovel at the mine was noted. Within two years it became apparent that there were certain areas in the Knife River Coal Mining Co. mine at Beulah, N.D., where the lignite apparently had a high fouling tendency for the Hoot Lake unit. Results from analyses of the coal did not show large differences in moisture percentage, ash percentage, heating value, or ash fusion temperature between the highly troublesome and less troublesome coals. After three years of operation, the troublesome areas had been quite well defined and the mining company started a procedure of bypassing these areas when load conditions at the plant were high and then returning to the troublesome areas to load the lignite during the summer months when peak loads were lower. It was noted that the lignite from the areas which caused severe fouling under high load conditions produced much less fouling at the lower summer loads. However, bypassing certain areas in the strip pit caused the mining company to disrupt their continuous loading schedule, which in turn upset their continuous stripping schedule and made for less efficient mining operation. Meanwhile, at the Hoot Lake plant, the number of soot blowers on No. 2 boiler had been increased from 30 to 55, and a very rigorous blowing schedule had been adopted resulting in soot blowers operating at least some part of 21 hrs per day. Fouling problems continued, with a resulting reduction in plant economy and reliability. During this period the Federal Bureau of Mines Coal Research Laboratory at Grand Forks, N.D., had initiated various research programs relating to the study of lignite ash and ash fouling problems. One project was a survey in which full seam samples were obtained from various locations in all the major

Jan 1, 1968

By Jacques Nantel

"The molybdenite property of Brynnor Mines Limited, Boss Mountain Division (wholly-owned subsidiary of Noranda Mines Limited), is situated approximately 360 miles northeast of Vancouver on the east slope of Takom-kane mountain in British Columbia's Cariboo District. Orebodies at the deposit fall into two categories; quartz breccia, and veins and stringers. The development of the breccia ore zone was started in June, 1964. The bulk of the ore is being mined from the stringer ore zone. The ore-body has been divided into 100-foot stopes and pillars. A sub-level blasthole method is used and the broken ore is handled in drawpoints and scram drifts. The development, drilling, blasting and handling of the ore are reviewed. The future pillar recovery operation is also analysed. The paper is also concerned with a scheduled shaft sinking program."

Jan 1, 1970

By Christoph Muller, Geoffrey Liggins, Mohan Hensman

Modern commercial blasting is as much a technical process as it is a business one. As with most processes both aspects of blasting are driven by and generate new data. The time-critical nature of commercial blasting in mining and construction projects, dictate the timely exchange of information so as not to impede production or commerce. Up-to-date information about the blast to be undertaken can help suppliers: meet customers’ expectations to address challenging ground conditions; react to a market where quickly changing orders occur regularly; and address as-drilled blast patterns as opposed to baseline plans. “Real-time” data exchange into and out of the blasting process supports the whole-of-mine data management that the industry is migrating to.

Jan 1, 2010

President John T. Atkins on behalf of The RMCMl officers and Executive Board, invites you and your family to attend The 80th Regular Meeting and Convention of 'The Rocky Mountain Coal Mining Institute to be held at Marriott's Mark Resort, Lionshead Village in Vail, Colorado JUNE 24 - JUNE 26, 1984

Jan 1, 1983

By Roger J. Daniel

Major interest and investment in southern Africa's west coast diamond deposits have resulted in the development of various tools for sampling and mining in the varied geological conditions encountered. Namco's project progression from sampling to mining is discussed with particular reference to the ROV technology employed for both phases of the operation. The Namrod sampling tool was mobilised in June 1995 and following extensive sampling resulting in resource definition, detailed research, design, and engineering was undertaken to develop the NamSSol mining system in conjunction with SubSea Offshore Ltd., a Dresser Industries company. Mining operations commenced in early 1998. History of the background to the development leading to design criteria, engineering considerations, operational parameters and discussion of field performance are presented. The innovative systems employed by Namco represent significant developments in a rapidly expanding technological field.

Jan 1, 1998

By David Arana

The use of gas-water dispersion of a molten material flow onto a vibrating surface is developed as a process to minimize water pumping requirements, minimize the risks of explosions, and minimize the post solidification dewatering and fines handling equipment requirements. The process uses existing vibration transport technologies and common plant utilities. Plant trials using the smaller footprint and the progressive molten particle cooling time have yielded encouraging results. The results are analyzed and reported.

Jan 1, 2006

By John M. Tinsley, Calvin D. Saunders, H. K. van Poollen

In the past few years much con-sideration has been given to the evaluation of the effect of hydraulic fracturing on the productivity of wells. Generally, these studies included the evaluation of fracturing materials, fracture extension and formation damage due to the use of various fracturing fluids. Only little consideration has been given to the characteristics, and in particular the flow capacity, of the fracture itself and its effect on well productivity. This paper presents the results of laboratory investigations pointed toward fie evaluation of the efficiency of various fracrures with special emphasis on the flow capacity of these fractures. Data presented in this paper are the results of both an electrical model study and physical testing. Under consideration are (I) effect of overflush, (2) premature production of well after treatment, (3) "tailing-in" with coarse sand near the end of the treatment, (4) effect of propping agent size and concentration, (5) reduction in effective frac-ture permeability caused by formation caused by formation fines, silt and clays, and (6) effect of various fluids on formation strength and competency. The results of this investigation indicate that the flow capacity of a fracture is affected by any or all of the various parameters mentioned above. The authors believe that a better understanding arid utilization of these factors should result in more efficient formation fracturing. INTRODUCTION Hydraulic fracturing has become almost a standard practice of many companies for stimulating production from old and new wells. Although most companies utilize this service, techniques of application vary widely between companies and areas. Probably too often when a well in an area responds favorably to a particular technique all future wells in the same area are treated in a similar manner. Possibly a modification of the technique would result in a further production increase. Variables, of which many are extremely difficult to evaluate from field results, hamper the selection of procedure changes. Attempts are being made by a number of organizations to analyze statistically treating techniques from production data. This is a very worthy and necessary approach but very possibly laboratory investigations may aid in evaluating some of the variables which tend to affect the results of a fracturing treatment. Some of the factors cannot be studied from practical field experience and only laboratory tests can show the possibilities which might exist. One of the factors which appears to be of major concern today is the flow capacity of the created fracture and how it can be changed. Papers on this general subject have been primarily concerned with the size of propping agent and the extent of fracture. Papers have also been written on the possible permeability damage to formations by fracturing fluids. In addition, it might be possible that another type of flow restriction is prevalent. This would be a restriction of flow through a sand-packed frac- ture caused by foreign materials integrating within the propping agent. This paper presents preliminary data obtained in an attempt to evaluate the effect of some factors affecting flow through sand-packed fractures. No attempt is being made to offer a fracturing technique adaptable to all areas and conditions, but to furnish data tending to show the possible effects which might be caused by variations in procedures and materials. PROPPING AGENT PERMEABLLITIES A hydraulically induced fracture containing sand as a propping agent may theoretically be classified as a packed-sand system. The flow of fluids through such packed systems has been the subject of much research. Although there have been numerous methods proposed for the evaluation of such systems, most writers agree on the general properties affecting their flow capacity or permeability. These properties include porosity, particle size, sphericity and the roughness of the particle. In some methods of evaluation . the particle size and sphericity terms are combined to produce an equation which is a function of the surface area of the particles. In this study the permeability of various fracturing sands was both measured and calculated. The apparatus for the permeability measurements consisted of a 52-in. Lucite tube with a 2.5-in. ID. A screen and drain plug were fitted in the bottom of this tube to retain and hold the sand in place while allowing fluid flow. Two pressure taps consisting of thin, highly perforated

The performance of the Australian Mining Industry over the past 10 years using key indicators of production, revenue, aftertax return investment, together with key cost elements, market changes and ore reserves is briefly reviewed. The elements of competitiveness are discussed forthe industry and the effects of Government charges and policies relating to existing operations are outlined. There is a demonstrated need for improvements in competitiveness in direct and indirect costs and for improved access to resources for the mining industry to continue to grow and add to Australia's economic growth.

Jan 1, 1987

By P. A. Plunkert

Metallurgical-grade bauxite was imported into the United States from 11 countries in 2004. The principal suppliers of this 10 Mt (11 million st) of imported ore were Jamaica (33 percent), Brazil (25 percent), Guinea(23 percent) and Guyana (11 percent). The average value of imports, cost, insurance and freight (c.i.f.) U.S. ports, was $31/t ($28/st). Calcined refractory-grade bauxite imports were 165kt (182,000 st) with an average value of $146/t ($132/st), c.i.f. U.S. ports. China supplied 70 percent; Guyana, 22

Jan 1, 2005

By Michael Hamilton

Mineral resources have been identified at two properties in the Ten takes RARE II area (table 1). Commodities consist of copper and silver. The deposits, in the northwest part of the study area, are hydrothermal and associated with fissure veins that developed along northwest-striking faults within the Precambrian Purcell Lava. In addition to the identified resources, there is high potential for additional copper-silver resources at these properties and moderate potential for copper-silver-lead-zinc-bariun resources at five others (table 2) in the portion of the study area that is underlain by the Purcell. There is no evidence that significant mineralization occurred in strata above or below the Purcell.

Jan 1, 1983

By B. F. Westfall

Throughout the 1960's and 1970's world trade grew rapidly, reaching a peak of USS1.8 trillion in 1980. Since then the world recession of the early 1980's shrunk trade to about US$1.6 trillion. The reduced cash flow to developing economies made it difficult to service their huge international debts, Nowadays lenders are reluctant to grant Third World countries additional credit. The shortage of export financing, plus trade barriers set up by developed countries, is further inhibiting international trade. Therefore, countries are turning to new and creative alternatives to financing imports of consumer as well as of investment goods. Non-cash transactions, including different forms of countertrade, are rapidly growing alternatives to traditional trade financing patterns. In 1983 about 30% of international trade, or close to US$600 bill ion, were presumably done by non-cash transactions, up from barely 2% in 1976. By year 2000, half the world trade is likely to be conducted on basis of barter. As of mid-1984 some 88 nations used countertrade regularly and Governments of at least 15 Latin American countries had arranged or mandated commercial countertrade.

Jan 1, 1986

By Charles F. Stack

The A. P. Green Refractories Co. operates clay mines in ten states. Eight of these states have reclamation laws with which we have to comply and indications are that the U. S. Congress will pass a federal surface mining reclamation act in the near future. These regulations, in addition to the value of land in most areas, dictate that mining and reclamation be considered as a single operation. In many instances the land may be more valuable after properly planned mining and reclamation than before. Refractory clay, commonly called "fire clay" is defined as a siliceous clay rich in hydrous aluminum silicates, capable of withstanding high temperatures. It is deficient in iron, calcium, and alkalies and approaches kaolin on composition. Refractory clay is much more limited in occurrence and usage than common clay or shale. During 1971, common clays and shales were mined in 47 states with a total production of 45 million tons. Fire clay production was reported in 22 states with a total production of only slightly over 3 million tons.(1) Many of these producing areas are extremely limited in extent and production. Several are contained within a one or two county area. This reflects the unique geological conditions required for the formation or development of fire clay. The major fire clay producing areas in the United States are shown in Figure 1.

Jan 1, 1974

PRESIDENT MOSES: I thank you, Mr. Emrick. Mr. Shubart would like to supplement your paper with another article. SECRETARY SHUBART: My paper really should not supplement Mr. Emrick's paper, because I secured some data from him, I knew Mr. Emrick had had a great deal of experience in shearing and I thought he could give you some useful data. (Here Mr. Shubart read the following:) "For the past two years, there has been considerable discussion among coal mining men concerning the advantages of a shearing cut in addition to the undercut, in mine work. We have had a number of requests for information on sheared coal. We were asked questions like these: What percentage increase in lump can be obtained from sheared coal? What has been the experience of mine men who have employed the shearing cut? Is the shearing cut a means of increasing the lump content? If so, is it increased to such an extent as to warrant the installation of shearing machines? Upon investigation it was found that no one could give us any definite information on the subject as no one had weighed separately the grades of coal produced from' the shearing cut. With a view of getting this information first-hand, the Goodman Manufacturing Company built up a shearing machine to be used in experimental work only. The officials of the Troy Coal Company were eager to share in the expense of obtaining this information, so that in May of this year we shipped to their mines our first type 319 shearing machine. The Troy Coal Company operates a mine at Troy, Illinois, in the No. 6 seam and produces about 275 tons daily. The coal seam averages five and one-half feet in thickness. Previous to the arrival of the shearing machine the coal was undercut six feet deep by a' Goodman Shortwall Machine. To break down the coal required two shots in the entries and three in the rooms. The percentage of lump measured over two-inch screens, averaged 58.2 per cent. The conditions of the mine were very favorable for obtaining accurate weights on the amount of lump and slack coal run over the shaker screens. The shearing machine easily cut the entire tonnage of the mine so that all coal dumped into the railroad cars had been produced from a shearing cut, in addition to an undercut. Accurate records were kept of the railroad weights and front this data the percentages of lump and slack were computed. During the month of June the percentage of lump produced over two-inch shaker screens was 69.9 per cent. This result demonstrated that the introduction of the shearing cut had increased the percentage of lump twenty per cent. The entries were driven ten feet wide and the rooms thirty feet wide The shearing cut was made near the center of the face in all places. A hole was drilled in each rib and the coal shot down with one-half the powder required when the places had been undercut only. The coal was broken down to the back of the cut so that very little pick work was necessary to load it out. The benefits derived from the shearing cut were as follows: 1. Increased percentage of lump, thus increasing the average price of coal per ton. 2. Preservation of a tender top due to the decreased amount of explosive used. 3. Facilitated handling of coal by the miner thus increasing the tonnage per man. 4. Eliminated coal yardage in entries and crosscuts of ten feet or less in width for the reason that the shearing cut provides a loose end from which to shoot the coal. This applies to the union fields only, as the non-union mines do not pay for coal yardage. Based on a price of $2.50 for lump coal and $1.25 for slack coal, the average price per ton was increased

Jan 1, 1926

By R. T. Artz, Simpson. O. V.

"INTRODUCTION The provision of escapeways from coal mines is a moral and, in most States, a legal obligation of mine owners and operators. The obligation is not always fulfilled because of the hope that no occasion will ever arise requiring the use of such facilities, and, as time passes without the need for using them, a false sense of security is born in the belief that ""it can't happen here.""The disastrous fire in a mine in Ohio on July 5, 1944, again focused attention on the importance of escapeways in averting disasters and made it clear that one or more dependable exits must be provided from a mine and parts thereof where men might be trapped by being cut off from the regular travel route. This matter of always-having available travelable exits has been advocated for many years by the United States Bureau of Mines."

Aug 1, 1948

In this paper, a number of novel hypotheses that provide a fresh perspective on the characterization of strata movements associated with longwall mining are developed by analyzing subsidence measurements with an influence- function-based computer program. With this influence-function technique, easily obtained surface displacements can be used to determine some of the complicated, expensive, and difficult to measure movements of the immediate roof strata in a longwall panel. The primary hypothesis developed by this analysis proposes the existence of an area of partial roof caving near the edge of a panel called the "edge effect." A second hypothesis, interrelated with the first, promotes the importance of the effect of gate-entry closure on the observed strata movements. Both the primary edge effect hypothesis and the secondary hypothesis concerning gate-entry closure are justified and quantified in an extensive analysis of surface subsidence that uses supporting information from related theories, design criteria and insitu measurements. Next, the edge effect and the gate closure hypotheses are extended further and used to provide an explanation of the complex subsidence interaction of adjacent longwall panels in what is termed a "redisturbed" effect. Finally, in the conclusions of this paper, the importance of accurately understanding these longwall strata movements for proper subsidence prediction or gate design is stressed.

Jan 1, 1986

Though the mining industry is beset with problems-a broad slump in metal prices, a rash of acquisitions and takeover attempts, rising capital costs, and an aggressive Canadian energy program-there was an under-current of optimism at the 1981 AMC conference that's been missing at industry meetings in recent years. The industry anticipates a turnaround in the 1980s, buoyed perhaps by the new spirit of cooperation from the Reagan administration. For the first time in years, it appears that Washington and the mining industry share mutual goals for developing the nation's resources. A number of prominent Reagan officials were on hand during the three-day conference in Denver, September 28-30, to reassure conferees that restrictions plaguing energy and minerals development would be eased. Interior Secretary James Watt and other government speakers promised cooperation in bringing balance to federal public lands policies, a review of regulations that have hampered the industry, and prompt action on domestic minerals policy. Daniel N. Miller, Jr., assistant interior secretary for energy and minerals, said, "It is our intent to dismantle the overhearing bureaucracy that has stifled mineral and energy exploration. We know that Interior's rules have shackled the mining industry in recent years, and we know that those rules must be eased." Miller noted that the administration will not permit mining on national park lands or wildlife refuges, but added that "we must assess a variety of uses of public lands ... we will restore lands to multiple use where practical." EPA administrator Anne Gorsuch assured industry representatives that the administration intends to work within environmental laws and with Congress to review and revise water, soil, and air pollution policies. "We have a strong commitment to see that there are major mid-course corrections" of air regulations, Gorsuch said. Support from these "new friends in Washington" will be crucial in light of the serious problems pressuring the industry. Copper prices have plunged to almost three-year lows and prices for molybdenum, gold, and silver have slumped. Earnings are down and today's high interest rates prevent a quick turnaround. Companies are on edge after the recent takeovers of Kennecott, St. Joe Minerals, and Texasgulf Though the companies may benefit from the major injection of capital that large energy firms can provide, many observers fear the new parent companies won't be willing or able to survive the cyclical metal markets. Arco and Gulf Resources, for example, have been criticized for closing Anaconda's Montana copper facility and the Bunker Hill unit in Idaho, respectively. Canada's national energy program has brought additional pressure on the industry. This policy, which emphasizes Canadian majority ownership of the country's energy sources, resulted in acquisition of Texasgulf's Kidd Creek lead-zinc-silver complex by Canadian and French interests. In response, the American Mining Congress adopted two resolutions on takeovers. One calls for the US government to review laws regulating tender offers and takeovers "to better ensure that principles of fairness and sound investment policy govern such transactions.'' The other asks the government to demand "fairness and reciprocity" as a basis for US policy governing international trade in minerals and investment relations with other countries. AMC's shopping list included four other priority goals, aimed primarily at the Interior Department: • Prompt implementation of Interior's efforts to bring order and balance to rules governing access to public lands for exploration and development. • Statement by the President of a comprehensive and coherent domestic minerals policy. • Amendment of the Clean Air Act to remove impediments to productivity and barriers to economic development that are not necessary to essential goals of the act. • Development of new approaches to better achieve worker health and safety in the most cost-effective manner without penalizing productivity. Almost 6000 mining industry executives attended the 1981 convention-the largest in AMC's 84-year history. As in years past, the conference offered a wide spectrum of presentations-nearly 100 papers in 26 sessions-ranging from commodity forecasts to the latest technical achievements. New Administration Stockpile Goals The minerals availability session included a presentation on management of the minerals stockpile by Paul K. Kruege r of the Federal Emergency Management Agency. Krueger notes that rather than providing incentives for development of a domestic raw materials industry, the government has "a history of providing disincentives to industry." In mining industries, he adds, the rate of productivity growth has been -6% over the last six or seven years. Krueger feels there will be a major change under the Reagan administration. In March 1981, FEMA began the first purchase program for the national defense stockpile in over 20 years. The stockpile is sadly out of balance, Krueger adds. Stockpile materials are

Jan 12, 1981

By Lewis M. Haupt

Discussion of the paper of Mr. Granger, presented at the New Haven meeting, February, 1909, and published in Bulletin No. 25, January, 1909, pp. 1 to 37. LEWIS M. HAUPT, Philadelphia, Pa. (communication to the 'Secretary*) :-This subject is of great interest to me, and I am noting progress and conditions as a test of my own judgment in advocating what I believed to be the nearer, cheaper and better route at Nicaraugua. I have as yet learned nothing to change my views, or modify the convictions which led me to retire from the Commission; but that is not the issue to-day. Our government is committed to the Panama route, and is bound to " make good." There are many points presented by Mr. Granger which seem to me worthy of very serious consideration. But when all is said there remains the risk of seismic convulsions, to which either form of canal is subject; and I fail to see that the risk would be reduced by making the cut deeper, with greater surcharge of lateral pressure upon the side walls. A severe earthquake in the rainy season would doubtless close either type of canal. One of the arguments in favor of the Panama route most insisted on, was that Nature had provided good natural harbors at its termini. Recalling this, it has interested me to note that the cost of creating the necessary harbors is estimated at $27,000,000. Mr. Granger refers to this, and quotes the Board's report to the effect that, on the Atlantic side, it will require 5 miles of jetties to " make an excellent harbor out of a wretched one." The vulnerable part of Mr. Granger's paper seems to me to lie in the admission that the plant required is still in the embryonic stage, and that at least one machine should be built and tested " to demonstrate that the theoretical strains and forces work out in practice exactly as expected." This, how-

Jul 1, 1909

By ALBERT E. HALL, Arno C. Fieldner, Alexander L. Field

As a safeguard against excessive clinker troubles, specifications for the purchase of coal can be drawn to include the "softening" or "fusing" temperature of the ash. The value of such information has been recognized by the Bureau of Mines and has induced the bureau to investigab~ laboratory methods of determining the fUSIbility of coal ash, and the bearing of the results on clinker formation in fuel beds. The bureau realized that the fusibility of a mixture of oxides and silicates snch as is comprised in coal ash ,'aries according to the conditions under which tests are made, and that in the absence of any generally accepted method, no agreement is to be expected among tests made in differ«:-nt laboratories. Indeed, Marks a has recently called attention to differences as great as 3900 C. that were obtained with the same sample of ash by two different laboratories. Therefore if a fusion-temperature clause is to have any place in specifications for coal, a standard m('thod of t('sting should be adopted in order to insure comparable results by different laboratories and to obtain the softening or fusing temperature of the ash unde:'r conditions similar to those of a fuel bed. After a consistent method has been devised for obtaining comparable:' results at different laboratories, there will remain the correlation of these results with those from the burning of coal in furnaces before the value of fusibility tests in coal specifications can hE' finally determined.

Jan 1, 1918

By C. Kremer Bain

DURING the past several years of diamond drilling in Washington County, Mo., the St. Joseph Lead Co. has discovered a concentration of commercial lead-zinc ore at four different points within an area of 36 square miles. The largest and to date the most promising group of these orebodies is located in the Indian Creek area. It was considered to be of sufficient value to warrant development. The Indian Creek area is in the center of the northern half of Washington County, 11 miles northwest of Potosi, Mo., the county seat. The location is readily accessible from Potosi by car or truck over the all-weather Missouri State Highway No. 114. The topography is one of rolling relief, varying from an elevation of 700 ft above sea level on Mineral Fork and Indian Creek to a maximum of 1176 ft at High Point Tower. It is divided in equal halves between the drainage to Mineral Fork and to Indian Creek. The shaft site at 1060 elevation is on the divide between the two drainage areas. The Indian Creek side is rough and heavily wooded, with only a few cultivated clearings. The slopes to Mineral Fork are more gentle and rounded, with much of the area cleared for farm land. Most of the surface is covered with Potosi and Eminence formations, which show little evidence of any structure. Ore structure was worked out by extensive diamond core drilling, with holes varying in depth from about 700 to 1300 ft. As of Oct. 1, 1950, 218 prospect holes had been drilled within the 36-square mile area. The ore is disseminated galena with considerable accompanying sphalerite in the Bonne Terre forma-tion in the shape of irregular blanket-type deposits. The main controlling structural feature of the outlined mineral zone is a buried pre-Cambrian rhy-olite-porphyry ridge extending partly through the Bonne Terre formation, which laps against the por phyry and also covers it. The mineralized zone parallels and forms an irregular halo around the porphyry ridge and is concentrated in the Bonne Terre formation where the La Motte sandstone is cut out by the porphyry ridge. This is a very common mineral occurrence in the southeastern Missouri lead belt district. The La Motte sandstone, which normally underlies the Bonne Terre formation, is thus cut out entirely. In this area the Bonne Terre is usually about 275 to 320 ft thick, the La Motte varying in thickness from zero up to 400 ft. Commercial concentrations of ore are indicated at several places, the most notable being at the shaft site where an orebody at least 4000 ft long with widths of 500 to 600 ft has been outlined. The total thickness of mineralized rock reaches 150 ft in some holes, although total ore thickness runs from 8 ft to about 60 ft, often in more than one layer. Preliminary Planning Ore reserves as outlined lend themselves to open-stope mining with trackless haulage and mobile loading machines and drilling equipment. This type of equipment has proved to be very efficient during recent years in the company's lead belt operations. After a study of bids for shaft sinking and an estimation of comparative costs, it was decided that the shaft would be sunk by St. Joseph Lead Co. personnel using company equipment. Since the plant site is about 26 miles from the company's nearest lead belt operations, it was necessary to plan a complete surface plant, including mill, shops, office, change room, and warehousing facilities. Immediately following the filing of an application for a certificate of necessity, a headframe was selected for which detailed drawings were already available. The order was placed for fabrication so that it could be delivered and erected in time to serve for sinking the shaft. This eliminated the expense of a temporary headframe. Drilling was started on two churn drill holes near shaft location, and two 1000-gpm deep well pumps

Jan 1, 1954

By S. K. Ash

In arriving at economic losses in coal mining due to accidents, a statistician is confronted with many difficulties on account of the lack of information relative to nonfatal accidents. For comparative purposes the ex¬ perience of those countries, States, or companies that keep complete records can be drawn upon and an extimate can be arrived at whereby one State can be compared with another, or one mine compared with another in the same district. Such a comparison for the United States has been compiled by the United States Bureau of Mines. It will be observed in Table 1 that the cost per ton for accidents in the State of Washington for the year 1927 is higher than for any other State, with the exception of Georgia and North Carolina, with a small combined tonnage of 130,089 tons. (The figures for coal production in Table 1 are taken from Bulletin 319, 1930, of the United States Bureau of Mines.) The reasons why the cost of accidents in Washington might be higher than the average are on account of physical conditions such as steep pitches, faults, igneous intrusions, highly explosive coal-dust, extremely friable coals, presence of gravel and water, very gassy coal beds, rugged topographic conditions, inherently bad roof and floor, thick beds, and heavy cover. The nature of the coal beds requires the use of preparation machinery. The mines are often deep, and topographic conditions are such that long and fast haul¬ age becomes necessary. All of these factors not only tend to cause high cost of production, which is manifested largely in a. lower than average daily pro¬ duction, per man, but..they.also affect to some degree a tendency toward a higher than average cost for accidents.

Nov 1, 1931