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By Keith A. Heasley

At this point in time, approximately 800 M tonnes (880 M tons) of coal are mined each year in the United States. Forty percent of this coal or approximately 320 M tonnes (350 M tons) is taken from underground coal mines, and from this subtotal 16% or 50 M tonnes (55 M tons) is from longwall panels (1). If, for the sake of argument, an aver- age extraction thickness of 1.5 m (5 ft), an aver- age extraction ratio of 50 percent and an in situ density of 1360 kg/ms (85 lb/ft3) for this coal are assumed, then the 320 M tonnes (350 M tons) of underground coal translates to over 310 km2 (76,000 acres) that is undermined each year. Con- sidering that the total U.S. production of under- ground longwall coal to date is approximately 345 M tonnes (380 M tons), then a total of approximately 165 km2 (41,000 acres) (considering 100% extraction) has been directly undermined by longwall coal production in the United States. If the angle-of- draw is considered, the total area affected by longwall subsidence in the United States is probably twice the above value or 330 km2 (82,000 acres) . In the future, a number of other miscellaneous factors seem likely to multiply the number of potentially damaging situations that occur due to longwall coal mining. First, the overall production of coal in the United States is expected to gradually increase. This factor is further com- pounded by both the fact that the percentage of the overall production due to underground mining is bound to increase, since the vast majority of U.S. reserves (68%) are only recoverable by underground methods, and the fact that the percentage of the underground production of coal that is recovered by longwall mining is drastically increasing (1). Finally, as the nicest underground reserves are depleted, the remaining reserves will tend to be deeper, which increases the affected surface area, and under denser population concentrations, which increases the likelihood and severity of possible damages. Overall, considering the number of factor which are biased towards increasing the amount of undermined acreage, it appears that there must certainly be a corresponding increase in the number of possible damaging situations due to longwall-induced, ground subsidence.

Jan 1, 1986

By Valerie Kollonitsch

Functional mineral pigments are used in large quantities in paint, paper, plastics, rubber, textiles, agriculture, and several other industries. U.S. consumption in 1969 is estimated at over 5 million tons a year, valued at nearly $150 million, as shown in Table 1. Originally extender pigments were employed only to lower cost. They were thought of merely as adulterants to replace more expensive prime pigments and binders. However, over the years their role has become better understood, and today their main functions are: - Increasing strength, stability, and service life. - Improving surface properties. - Enhancing application and processing properties. - Extending prime pigments. - Controlling viscosity and package stability - Lowering overall costs of the finished product. The principal minerals used as functional pigments are kaolin, ground calcium carbonate, talc, and asbestos. Other minerals include barytes, attapulgite, diatomite, mica, ground silica, wollastonite, and nepheline syenite. Several synthetic products, including precipitated calcium carbonate; precipitated, gel, and fumed silica; alumina trihydrate; and barium sulfate, compete with mineral products. They are more expensive, but often have more closely controlled particle size or other properties because they can be tailor-made according to the requirements. This paper covers only natural products selling for $10 or more a ton, approximately the lower limit for pigment grades. Data refer only to consumption in pigment applications. For example, such applications as filter aids for diatomite are not included. Key properties of the major mineral pigments are given in Table 2. It is important to note that these properties are primarily physical rather than chemical. In general, these products are sold to performance specifications for what they can do rather than on chemical composition specifications on what they contain.

Jan 1, 1969

By E. Neumann

With fuel costs unstable but escalating, solid fuels are playing an increasingly larger part in industrial concerns. Coal, petroleum coke and wood are examined from a burner system design viewpoint and from operational experience in kilns, hot gas generators, etc. The burner of today must also handle multi-fuel tasks and allow immediate, painless switching from one fuel to the next as well as the simultaneous burning of two or mope fuels. The paper discusses the principle of burning alternate pulverized fuels as well as the practice both in the United States and around the world.

Jan 1, 1983

By L. Yan, D. Yantek

Federal regulations require refuge alternatives in underground coal mines to sustain life for 96 h while maintaining an apparent temperature below 35 °C (95 °F). Research by the U.S. National Institute for Occupational Safety and Health (NIOSH) has shown that heat and humidity buildup is a major concern with refuge alternatives because they have limited ability to dissipate heat, and high internal air temperature and relative humidity (RH) may expose occupants to heat stress. The heat transfer process within and surrounding a refuge alternative is complex and not easily defined, analytically or experimentally. To investigate heat and humidity buildup in refuge alternatives, NIOSH conducted multiple in-mine, 96-h tests on a 10-person tent-type refuge alternative, a 23-person tent-type refuge alternative and a six-person metal-type refuge alternative. The results show that when moisture was introduced to represent perspiration and respiration from miners (wet tests), the average temperature at midheight increased by 10.5 °C (18.9 °F) and the RH approached 88 percent for the 10-person tent-type refuge alternative; the average temperature at midheight increased by 9.4 °C (16.9 °F) and the RH approached 94 percent for the 23-person tent-type refuge alternative; and the average temperature at midheight increased by 7.7 °C (13.9 °F) and the RH approached 95 percent for the sixperson metal-type refuge alternative. For the dry tests, where no moisture was introduced, the average internal temperature increased by 12.6 °C (22.7 °F) for the 10-person tent-type refuge alternative, by 10.3 °C (18.5 °F) for the 23-person tent-type refuge alternative and by 8.4 °C (15.1 °F) for the six-person metal-type refuge alternative. These results may provide refuge alternative manufacturers and mine operators with guidelines and considerations for evaluating temperature profiles for portable refuge alternatives. The information may then be used to make decisions on occupancy ratings and heat mitigation strategies based on the thermal environment in which the refuge alternatives will be installed.

Jan 10, 2018

By C. Zhou, J. Srednicki

Electronic systems have been increasingly used in underground mines to improve mine safety. These electronic systems emit electromagnetic (EM) energy which can adversely impact the performance of other electronic systems nearby and thus should be characterized. Researchers at the National Institute for Occupational Safety and Health (NIOSH) characterized the magnetic fields emitted from devices that can potentially interfere with the performance of proximity detection systems (PDSs) and compared the emission levels of these devices to the susceptibility of PDSs. In this paper, we present our measurement results pertaining to this effort. Particularly, magnetic fields emitted from the different orientations of a powered air purifying respirator (PAPR) and two lite trackers are evaluated based on the RE101 protocol specified in the MIL-STD-461G standard. The results show that both devices emit strong magnetic fields which strongly depend on the orientation of the devices. At some frequencies, the maximum emission levels from the two devices exceed both the emission limit given in MIL-STD-461G and the maximum magnetic fields that a PDS can withstand without a failure. The results and findings in this paper can help the mining industry better understand electromagnetic interference (EMI) underground and provide critical scientific data that support mining-specific recommendations to address EMI-related challenges.

Feb 1, 2023

By D. Buranek, J. G. Wulff, F. W. Gifford

I. INTRODUCTION During the past few years, the state of the art of disposal of solid and liquid waste products from uranium mining and milling operations has experienced some rather interesting and significant changes. Some of these changes have resulted from technological advances in the milling operations and in the engineering aspects of the actual design and construction of the disposal facilities. However, the most significant changes, at least those which have had the greatest impact on the comparative cost and economics of modern disposal systems, have been environmental requirements and regulatory controls, which have become increasingly stringent in recent years. Without delving into the details of the myriad of new laws and regulations which now control the uranium industry, it can be stated with reasonable confidence that one of the principal purposes of more rigid state and federal controls over this industry is the basic desire to promote safer, more reliable and longer term means of effectively controlling and disposing of the potentially objectionable waste products resulting from uranium mining and milling operations. It is difficult to take issue with these basic goals because their need was spawned by past lack of awareness and inattention on the parts of both government and industry to the long term environmental problems and potentially hazardous conditions which can be created by limited planning and ill-conceived or poorly controlled and executed disposal practices. On the other hand, despite the good intentions of those who developed and those who are administering the regulatory controls now in effect, the basic danger exists that overgeneralization of the approach to disposal problems and overrestriction of the potentially acceptable solutions for uranium mine and mill waste disposal could have a significant, adverse economic impact on the mining industry and the ultimate consumers of their products. The regulatory pendulum, which perhaps swung too far toward lack of controls over uranium mill waste disposal in the 1940's, could now well be headed too far in the opposite direction, that is toward over-regulation in the form of restrictions based on technically unrealistic or weakly supportable

Jan 1, 1980

By U. Schoepf

Economic and at the same time environmentally acceptable mining of small vertical ore bodies and veins to great depths has always been a challenge for miners. The Bauer cutter system, widely used in civil engineering, has been further developed for applications in exploration and mining, to a sustainable system for selective mining with a focus on small vertical ore bodies and veins, as well as residual ore in open pit operations. Current situation of conventional mining of small ore bodies and vertical veins Small ore bodies and vertical or near-vertical ore veins often pose a challenge to the mining industry. The relatively small size of the ore deposit over great depths or lengths, with only limited exposure to the surface makes economical mining difficult. Open pit mining of such ore bodies must either be terminated early because of the high stripping ratio and the enormous environmental impact or is unprofitable from the very beginning. The required massive stripping of waste rock leads to high material hauling times and costs, intensive roadway and bench construction and maintenance, possible safety hazards due to heavy vehicle movement, pit wall stability risks, intensive surface water management and massive waste dump requirements. In addition, it can be assumed that increasingly extensive rehabilitation measures will be required in the future after mine closure. Particularly in vertically oriented magmatic and hydrothermal deposits the technical, economic and environmental limits for further pushbacks, to extend the open pit depth, can lead to an early end of mine life even if a significant quantity of residual ore is left behind. Going underground is only a viable option in a limited number of mines with very high ore values and volumes. The high development cost of an underground mine, as well as the higher underground mining costs, often prevent further mining to greater depths.

Feb 1, 2023

The mining and minerals extraction industries have often been demonized by the public as industries that put profits and production before people. It is true that the inherent danger of the work has led to more fatal accidents than anyone associated with the industry would care to remember. But, in stark contrast to what has often been said, the truth of the matter is safety is now the top priority of every miner, from the face of the longwall to the executive boardroom. Without safety, nothing else matters. This message was told and retold by representatives from some of the world?s top mining and petroleum companies from Oct. 11-13 during the inaugural Safety and Reliability in the Mining and Resources Industries Conference in Calgary, Canada. The meeting was hosted jointly by the Canadian Institute of Mining, Metallurgy and Petroleum (CIM) and the Society for Mining, Metallurgy, and Exploration (SME). It was the first of a series of conferences to focus on these important topics. Next year, the conference will be held in Minneapolis, MN from Nov. 13-15.

Jan 1, 2011

By Erik Westman, BEN WESTON, SETAREH GHAYCHI AFROUZ, KATHRYN DEHN

This study investigates the changes in seismic velocity of rockmass before and after three major seismic events to determine any potential identifiable precursory velocity changes associated with these events. Induced stress measurement is one of the challenging tasks in deep underground mining, with extreme impacts on the safety and stability of the mine. This study used p-wave passive seismic tomography to image the velocity redistribution within a rockmass, which can indicate induced stress level changes in the rockmass and detect the velocity changes that might precede a major seismic event or a rockburst. The ultimate goal of this research focus is to develop another tool for the deep-mining community that will help to increase safety and efficiency. For this purpose, the hypothesis of conventional mechanics, which implies induced stress at the hypocenter (as inferred by the p-wave velocity) increases until the seismic event occurs, is evaluated. It is found that the p-wave velocity did not increase at any of the three hypocenters prior to the seismic event occurring; however, the p-wave velocity did increase in the closest “zone center” for two of the three events. 

By A. Jolly, A. R. Kumar, T. Novak

"Coal dust in an underground mining environment has always been a health and safety issue, especially with longwall faces. Efforts to integrate a flooded bed scrubber within a longwall shearer are underway at the University of Kentucky (UK) in order to reduce worker exposure. Small scale physical modeling, along with numerical modeling and full-scale experimentation, are engineering tools being used by the authors for simulating operating conditions underground. Recent advances in affordable 3D printers offer a means for fabricating accurate, scale models for obtaining timely insights prior to building large, expensive test setups. Comparing scale-model results with those of numerical modeling, such as computational fluid dynamics (CFD), lends guidance and confidence in a proposed design. This paper discusses the small scale physical modeling of a longwall shearer with an incorporated flooded-bed dust scrubber in its operating environment. A tracer gas was used in the model in lieu of dust to measure dust-capture efficiency. Results obtained from the physical model are presented and compared with those of CFD model. The small scale model and the CFD results demonstrate good agreement. Dust capture results show the usefulness of the approach in advance of actual design implementation. INTRODUCTION Dust generation is an undesirable, but innate, byproduct of all mining processes. It is particularly problematic in underground coal mining, where coal dust poses potential hazards from two fronts – health and safety. Coal workers’ pneumoconiosis (CWP), commonly referred to as black lung, is a chronic lung disease that results from the long-term overexposure to respirable coal dust. Although the prevalence of CWP has steadily and significantly declined over the three decades following the Federal Coal Mine Health and Safety Act of 1969, a study by the National Institute for Occupational Safety and Health (NIOSH, 2008) indicates that significant health hazards associated with respirable dust still exist within the coal mining industry. In addition to being a health hazard, coal dust can also create a potentially catastrophic safety hazard. Dust that is not captured or removed at its source is suspended and transported throughout a mine by the ventilation airstream. This float dust is subsequently deposited on all mine surfaces along its travel path. Without adequate application of rock dust to these surfaces, forces from a localized methane ignition can reintroduce settled coal dust into the airstream creating an explosive mixture. Therefore, capturing and removing coal dust at its source mitigates the probability of two major hazards that continue to plague the mining industry."

Jan 1, 2016

By V

"Recent regulations, as well as a general aversion to central dust collectors within the Powder River Basin Coal user’s community, have created a need for an alternate method for eliminating airborne dust. This paper addresses the capital expenditure as well as the cost of ownership of an integrated point source air cleaning system in comparison to a central collection system. This assessment was conducted by comparing the cost to purchase and operate a central dust collection system and integrated air cleaner system on a typical multiple transfer point application. The central dust collector consists of a negative pressure blower, a series of filter bags, a collection hopper, a screw conveyor to place collected material back into the material stream, and a series of ducts to pull air and dust from individual pickup points. The point specific integrated air cleaners consists of a negative pressure blower to pull dust and air from an application point through a bag-less filter media located at the application point. The agglomerated material is then redeposited into the material stream at point of use without the need for ducting or a central material hopper. The assessment yielded a 54% reduction in capital expenditure and a 26% reduction in operating costs for the same application when using individual dust filters as opposed to a central system. In addition to the lowered cost, there are reductions in risk associated with the elimination of ductwork and the central containment enclosure for collected explosive dust. By the conclusion of this paper, the reader will have a better understanding of the quantifiable differences between a central dust collection system and a set integrated air cleaner systems. BACKGROUND Spillage has always been a problem in the bulk solids handling industry. As long as there have been conveyors, there has been spillage. Spillage is material that falls off a conveyor belt and creates a hazard in the environment around a conveyor belt."

Jan 1, 2016

By S. D. Rosenthal

"This paper will share my ‘shift in career direction’ journey from corporate mine engineer, with 31 years of mining various commodities with a wide range of responsibilities in a variety of countries, to the world of academia. There are times in one’s career that a change is required, albeit perhaps not as drastic of a change as moving to teaching. This paper will share how the transition arose, the decision to make the change, the challenges of the first year in academia, and the journey within academia going into the second year. INTRODUCTION As a graduate of the Montana College of Mineral Science and Technology (Montana Tech) with a B.S. Mining Engineering degree in May of 1982, my first job with Utah International in the Farmington area took me back to my home state of New Mexico. Some of you will remember that the early 1980’s was not a period of prolific opportunities for mining engineers; given low commodity prices, especially for copper (for example, Anaconda Company had been taken over by Arco and was in the midst of closing down its Butte operations). Coal was good and the learning opportunities abounded with Utah (which became BHP and then BHP Billiton). Gold was taking off in the mid to late 1980’s thanks to use of cyanide and heap leaching technology improvements, coupled with deregulation of the gold price, so I ventured off to work in the gold industry with a (then) junior Canadian company called Barrick at a new acquisition of theirs known as Goldstrike. That same gold surge was causing a shortage of iron ore mining engineers in Australia so after a few years in Nevada, I uprooted the family and left for a little town in the Pilbara of West Australia, known as Newman, to work in the iron ore industry with BHP Iron Ore. An initial short overseas posting turned into six plus years before transferring to BHP’s Indonesian steam coal mines in Kalimantan on the island of Borneo. BHP was going through a rough period following some ill-fated projects (Magma copper purchase, Beanup and HBI) and was reviewing assets and staffing so internal opportunities became scarce. Employees were encouraged to ‘leave the company and find work elsewhere.’ So, off I go to Argentina to try copper mining in the Andes with Minera Alumbrera. This short stint in South America was followed by a move to another mining town, Morenci, Arizona, and a posting with Phelps Dodge (now Freeport McMoran). After 12+ years without living close to snow we moved to the Denver area in a new position with Newmont Mining Corporation. Along the way I became a Professional Engineer (Nevada) and completed a Masters in Project Engineering and Management. After 11 years with Newmont, I moved to Butte, Montana where I accepted a position as Assistant Professor of Mining Engineering."

Jan 1, 2015

By Turan Uysal, Ramazan Aydogmus, MURAT ERDEMOGLU

The paper investigates the effects of calcination for thermal activation and intensive milling for mechanical activation on aluminum recovery by acid leaching of pyrophyllite ore enriched via attrition scrubbing and froth flotation. The study compares these methods in terms of energy consumption and aluminum recovery, concluding that mechanical activation is more economical and environmentally friendly.

Nov 1, 2023

By Barrie A. Wigmore

There are two aspects of financing western coal development -- whether there is going to be enough money to finance the prospective large development of the industry, and the specific techniques of raising money for that development. To take the first question of whether there is going to be enough money around to finance your industry, I think it is quite clear that the restrictions on the development of western coal are going to be non- financial. Environmental impact problems are creating the greatest delay in coal mine development, at the moment; but getting enough personnel, mining equipment, railroad equipment, and failure of the Department of Interior to act on leasing federal coal lands all appear likely to create significant bottle- necks in the development of western coal -- larger bottlenecks than financing. Financing appears straightforward for the industry. There are many projections of the financing required to meet Project Independence goals. The National Academy of Engineers estimated that development of 500 million tons per annum of western coal would be necessary by 1985 to meet the Project Independence goals which might require $20 billion of capital spending. It is generally agreed that 500 million tons a year is not a realistic possibility. Carl Bagge?s estimate of production of 250 million tons a year by 1983 appears a more reasonable projection. Development

Jan 1, 1976

By Wayne S. Cavender

The geochemical association of arsenic and gold in epithermal precious metal deposits of the Basin and Range province is well documented, and in this paper I wish to discuss the evaluation and utilization of this element association for geochemical gold exploration. In 1961-62, I conducted an exploration program on lands controlled by Getchell Mine, Inc, and centered about the Getchell gold mine itself, Besides exploring for new gold deposits, the program was to evaluate these lands for potential deposits of any type; thus, a multi-phase program encompassing a number of exploration methods was conducted. I shall not elaborate on the process of designing the program or of integrating the various methods, but for gold exploration, geochemical methods were determined to have the best potential. This paper is based on that effort. Figure 1 shows the exploration area, which covers the northern half of the Osgood Mountains in eastern Humboldt County, Nevada. The Getchell $line is on the east flank of the range and is about 40 miles northeast of Winnemucca.

Jan 1, 1964

By T. Tomioka

1. An Overall View of the Japanese Ferroalloys Industry 1) Depressed Demand for Ferroalloys: In Japan consumption of ferroalloys in the last ten years has decreased, although there has been some fluctuation from year to year. During this term production figures of the steel industry, which are closely related to consumption of ferroalloys, are as follows: Shipment of steel products for the domestic market has declined gradually from 69 million tons in 1979, which was the peak year for steel production, to 60.3 million tons in 1982 and 60.4 million tons in 1983, the level of 1978. In addition, exports also have been a downward trend since 1976, which was the peak year with tonnage of 34 million tons, to 28 million tons in 1982 and 31 million tons in 1983.

Jan 1, 1984

By L. M. Pero

The paper summarizes aspects of the recent literature on mineral development in the Third World. The emphasis is on publications covering agreements between host governments and mining companies.

Jan 1, 1985

By Charles O. Frush

This paper presents a summary of the current employment practices with respect to recent graduates in Mining Engineering, as observed at the Colorado school of Mines. Because our experience is limited to our own group of students it prob¬ably does not correspond exactly to that experienced at other mining schools, but because the Colorado School of Mines graduates approximately 15 per cent of the men in this field our experience is probably representative. We have chosen to limit the information presented here to that pertaining to the period since July 1, 1960. This corresponds to the experience with the class of 1961 and to the experience of the class of 1962 up to the end of the first semester of the senior year. There were 36 mining engineering degrees given in 1961 In a class numbering 43 senior. We expect to give 30 first degrees in 1962 in a class numbering 44 seniors.

Jan 1, 1962

By John E. Bailey

The advent of Nuclear Energy has caused a phenomenal growth in the uranium mining industry. To keep abreast of this surge the mining industry has located many ore bodies, determined the best types of mining adaptable to this particular type of ore and developed a highly specialized type of operation. But, has the mining industry gone far enough in the planning? Has ?built-in? safety been included in the efficient methods of operation? Preplanning safety in the mining industry, as in all industries, takes engineering and ingenuity combined with the experience and cooperation of all concerned. A system of mining can be planned on a map and it will look good. However, when the actual mining takes place, conditions may be such that deviations from the original plans may be required because of excessive water faults or other conditions encountered. With safety we may also be required to change, to conform to the characteristics of a particular operation. People in the mining industry are well aware that loose back has killed miners each year. This condition occurred in practically all types of mines. The condition is not new to us. It is also known that explosives, haulage, machinery and conditions common to all types of mining have taken a heavy toll of human life in mining. In addition to these hazards in the uranium mines, the hazard of radon is also present, Radon is a radioactive gas liberated from ores containing radium. This gas is released into the active workings by the blasting or breaking up of the ore. Sometimes it is caused by radium contaminated water seepage from abandoned workings or from the ore body itself. Until the action of this gas on the human was known, many miners were affected. Un- less adequate precuations are taken to protect the people in these mines,, they may be exposed to this hazard, Health researchers made a study of this substance to determine how it would affect the health of the men, They also studied men who had worked in previous years, in mines known to have contained radioactive materials. All of this research contributed to the present knowledge of radon and its daughter products. It is not flammable nor explosive, but, if allowed to enter the body through the respiratory organs it can cause serious damage. Mines have been operated in the past and are still being operated, which were known to contain explosive and noxious gases, indicating that this problem can be controlled. Several states have instituted laws that make it mandatory to provide adequate ventilation and use of monitoring devices to limit radon and its daughter products to a maximum of 300 micro-microcuries per liter of air. This is considered a safe limit for sustained periods of human exposure. While the findings of research do not prove conclusively that the inhalation of excessive radon or its daugher products cause lung cancer, indications point to this as a possibility, particularly radium A and radium C1 of the daughter products. The threshold limits set by law in most uranium producing states are believed to be safe. In a few years, when tests and data now in the process of collection by interested state officials and laboratories is complete, these limits may be found to be ready for revision. Studies such as these take time. At present, the limits that are used are based upon estimates. The permissible limits of exposure to radon and daughter products include a large safety factor. It is considered that a good supply of fresh air delivered to the working places, adequate dust control, the sealing of unused or abandoned workings, the removal of mine water which is generally contaminated and a safe waiting period after blasting, will hold to a minimum the dangers from this source. There are, of course, problems accompanying each of these procedures. For example, the ventilating of untimbered raises and bringing fresh, uncontaminated air to the working places may be a problem. However, a good mining man can solve these problems as they apply in each particular operation. From the information available at the present time, the daughter products containing polonium and emitting alpha radiation, may be a health hazard. Fortunately, the half life of most of the daughter products is short, however, radium D has a half life of 22 years and presents a problem of contamination in the storage of old tailings. So we can see that failure to comply with the accepted good mining practices may have harmful effects on the health of miners. It is gratifying to note the interest in this potential hazard by the officials in the uranium ore producing states, who are making extensive studies and keeping records of the men who work in this type of mining. This all provide information necessary for preplanning safety. By contrast, little has been accomplished to control the injuries and deaths from some other factors connected with most underground mining operations. I would like to discuss briefly one of the hazards which take an annual toll in our underground mines, this is falls of back and walls. This problem or hazard is present, and will be

Jan 1, 1958

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