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By D. R. East

Recent experiences within certain sectors of the international mining industry suggest an underestimation of the environmental risk associated with the design of mine waste management facilities. These experiences show that the technical and managerial challenge of responsible mine waste management is not always fully appreciated. Unfortunately, the image of the mining industry's environmental performance is negatively impacted by a relatively few number of failures. This negative view overrides the many positive contributions made by the majority of mining companies. The fact that these failures continue to occur to this day in both developed and developing countries is indeed remarkable, and indicates a degree of risk-taking approaching unacceptable levels. The design requirements for tailing storage facilities are, in many cases, more demanding than those of conventional water dams, because seepage of fluids which contain dissolved metals may pose a greater threat than the mere loss of water.

Jan 1, 1999

By L. B. Rothfeld

This paper presents preliminary results of a Bureau of Mines study of potential costs of compliance with the federal Resource Conservation and Recovery Act for copper heap and dump leaching. Specifically, estimates are given for the cost of compliance with possible technology standards that would require the use of liners and closure caps regardless of terrain and underlying geology and hydrology. This cost is compared to the co lit of compliance with present state requirements for terrain a typical of those found at existing copper leach sites in the Southwestern U.S.A. Incremental compliance costs are found to widely exceed screening criteria used by the Environmental Protection Agency to denote significant economic impact.

Jan 1, 1993

By Neil Williams

The brecciated dolostone-hosted (Mississippi Valley-type) and associated shale-hosted stratiform Pb-Zn deposits at McArthur River occur adjacent to a major syndepositional fault, the Emu fault. Base-metal zoning, mineral parageneses, and Pb and stable isotope ratios indicate that both types of deposits formed contemporaneously from metalliferous brines that flowed into the host sediments from the Emu fault. Derivation of brines from underlying evaporitic sediments is suggested. Geochemical evidence indicates that the mechanism of ore formation was sulfate-reduction coupled with oxidation of organic matter. The textural relationships of stratiform sulfide mineralization to diagenetic dolomite concretions, chert blebs, volcanic glass shards, and inter-ore breccia beds, indicate that the reactions proceeded diagenetically within about 100 m of the sediment/water interface.

Jan 1, 1979

By Ronald Ludchak

Since coal has been designated as the short-term answer to the threatening world energy crisis, improved surface mining techniques, along with improved extraction and handling equipment, are needed to increase the amounts that can economically be mined by open pit methods. A dwindling supply of low cost oil and gas have dictated a major rethinking of our energy sources and their use. New methods for open pit coal mining have to be found to increase coal production and to meet more stringent reclamation laws. Modern twin-engine elevating scrapers can play a vital role in meeting these needs. They are readily available, with short delivery times, from several experienced manufacturers of earthmoving equipment. Recent developments of the elevator system have extended its working range to include many of the materials commonly encountered in open pit mining. The paper deals with the advantages of using twin-engine elevating scrapers in the performance of various mining tasks. These tasks range from utility work to the major task of using the scrapers as a primary stripping toot and, of even more importance, a stripping- reclamation tool for, with scrapers, the overburden can be moved and redeposited in the same strata sequence or soil horizon as in its natural state. A recap of current applications of the elevating scraper will be presented, along with proposed uses.

Jan 1, 1975

By W. J. Schlitt

Introduction Heap and dump leaching are low-cost metal production techniques that are gaining in popularity among gold and copper producers. However, the flow of solution in heaps and dumps has received little attention in the literature. This is unfortunate since solution flow is one of the few parameters subject to operator control. Thus, solution management may well influence both operating costs and plant performance. Costs aside, there are two important aspects of solution flow to be considered -the metallurgical and the hydrological. Some of the metallurgical factors have recently been discussed (Jackson and Ream, 1980; Schlitt, 1984; Schlitt and Nicolai, 1987). These cover solution application rates and methods, irrigation rates, leach-rest cycles, and nonvertical solution flow. According to Caldwell and Moss (1985), however, the hydrological aspects may be more significant than the metallurgical ones. In particular, a phreatic surface will form when excessive flow leads to an accumulation of water and the associated buildup of pore pressure within the rock pile. Such internal flooding can either originate at the foundation or at some other zone of very low permeability. The latter condition gives rise to an impounded volume of solution, i.e., a perched water table (see Whiting, 1985). Caldwell and Moss point out that a rising zone of saturation is probably the most common cause of dump failures. Of course, such failures have even occurred in heaps that were carefully prepared for leaching (Milligan and Engelhardt, 1984). Thus, flooded conditions and perched water tables represent an important safety consideration as well as having an impact on metallurgical performance. The following sections describe a case history in which a perched water table developed within a copper leach dump. The description includes background information, solution flow rates, and metallurgical data. Then this situation is compared to one involving normal drainage. Description of the leach system The leach dump in the case history is located at a shutdown open pit copper mine. It was built in two lifts, with the second added some 20 years after the first. There is little detailed information available on the initial lift. It was built with rail¬hauled waste and was generally less than 30 m (100 ft) high at the crest. The area available for leaching was about 120 m (400 ft) wide and more than 380 m (1250 ft) long. The dump surface was prepared for leaching by dozing ponds approximately 12 m by 12 m by 2.5 to 3.0 m deep (40 ft by 40 ft by 8 to 10 ft). The ponds were leached by flooding with barren leach solution returned from a scrap iron cementation plant. Based on mill feed at the time, the average waste grade was probably close to 0.4% Cu. The first lift leached well. It accepted high flows, which together with the waste grade, produced a rich pregnant leach solution (PLS). Old records indicate a PLS of "50 lb Cu/ 1000 gal," or about 6 g/L. As later drilling would indicate, such a high tenor led to dissolution of considerable scrap iron that was returned to the dump. The iron then hydrolyzed and settled out on the pond bottoms. In addition, the waste settled substantially so that the unleached crest was 3.0 to 4.5 m (10 to 15 ft) above the ponded area. Eventually, the leachable copper was extracted and the dump became less permeable. Thus, the PLS tenor dropped until it became uneconomical. About ten years later, mining resumed and the decision was made to add another lift to the dump. This was done without giving much thought to a subsequent leach operation. Hence a 24-m (80-ft) lift was built on top of the original dump. The surface of the latter was not prepared in any way, e.g., by leveling and/or deep ripping, prior to over-dumping. Examination of subsequent drill cuttings indicated that the new lift contained about 0.2% Cu, with chalcopyrite and chalcocite (50:50) being the predominant copper minerals. Most of the chalcocite occurred as rimming on the abundant pyrite, with the pyrite to chalcopyrite ratio estimated at 10 to 1. The use of 100- and 120-ton trucks for haulage caused some waste compaction during emplacement. In addition, the host rock itself was relatively soft, being a porphyry intrusive material that was partially altered to clay. As a result of the initial compaction and clay swelling, the rate of water percolation from the new leach ponds was slow and the ponds often contained considerable standing water. Even frequent ripping failed to provide a sustained improvement in the percolation rate. The poor surface permeability was exacerbated by hydrolysis of iron salts which settled as a layer on the pond bottoms. Partly as a result of the permeability problems, metallurgical performance was not up to expectations. These had been based on laboratory tests which showed about 20% copper solubilization in two weeks. Continued copper extraction in the tests also suggested that a substantial percentage of the copper would eventually be recovered. However, the PLS grade in the actual operation peaked briefly at about 0.48 g/L Cu (4 lb Cu/1000 gal), then declined to a range of only 0.24 to 0.36 g/L Cu (2 to 3 lb Cu/1000 gal). The poor leaching was traced to a lack of oxidation of the sulfides. There were two principal observations supporting this conclusion. First, there was no evidence of any heat being generated within the dump. As discussed elsewhere (Schlitt and Jackson, 1981; Hiskey and Schlitt, 1982), pyrite oxidation is quite exothermic and the high pyrite content of the waste should have led to an increase in the temperature of the leach solution as it percolated through the rock pile. Second, there was no sign of any natural convective air flow through the dump.

Jan 1, 1987

By C. L. Pillar

In the capitalistic system the success of a mining enterprise is measured by the rate of return on the investment and the speed by which its redemption is achieved. Exploration in search of ore deposits often results in the emergence of the lean orebody which does not meet basic company requisites. At this point a decision must be made whether to place the orebody into production or postpone production pending more favourable market conditions. The wisdom of this decision, borne out by future results, demonstrates the quality of a company's management and is instrumental in the degree of financial success it achieves. The project feasibility report must show a rate of return on the capital invested that is attractive to the company, plus its full redemption in the desired period of time, in order to bring the property into production on a sound economic basis. Mining companies have demonstrated their ability to bring the profitability of a marginal property from a point that says "no go" to a point of "go" by substantial reduction of expenditure without adversely affecting production rate or cost. Here is where the real challenge exists for today's mining engineers and plant designers; they will have to develop better ideas and concepts: ideas that will still allow maximum production at reduced capital expenditure, This is the sound way marginal orebodies can be brought into production without inflationary increases in the price of their product.

Jan 1, 1969

By M. J. Gilbey

Cross passageways between adjacent tunnels in passenger rail or transit systems may be used during train fire emergencies to evacuate passengers to points of safety in the non-incident tunnel. Rescue trains can be brought into the non-incident tunnel to remove passengers to expedite evacuation times as compared to walking along bench walls to the nearest egress stairs. In cases of multiple train emergencies, the required ventilation capacities can result in high pressure differences between the incident and non-incident tunnels. These pressure differences can make it difficult or impossible for a normal person to open doors of a cross passageway between adjacent tunnels. If opened, the velocity of the airflow through an open cross passageway can reach levels high enough to impede passenger evacuation. This paper describes the analysis of this problem for a sample rail tunnel. A ventilation concept that mitigates the problems of high cross passageway door opening forces and high velocities through open cross passageways is presented.

Jan 1, 2009

By G. V. Henderson

The San Gabriel Valley contains some of the richest and most extensive sand and gravel deposits in California. Operating quarries within the San Gabriel area mine more than 15 million tons of high quality aggregate per year. This represents about 45 percent of the total mined in the greater Los Angeles area, one of the nation's largest aggregate markets and producing regions. Popular opposition to continued aggregate production in the San Gabriel Valley is high, especially in the city of Irwindale where 40 per-cent of the city's property is made up of "excavated holes," some 150-200 feet deep. Reclamation of 70 years of mining is now an almost impossible task. Zoning regulations have the effect of depleting these vast reserves rapidly by changing the definition of total reserves to include only "legally minable reserves." All but two or three of the aggregate mines now operating will be depleted or zoned out of business by the year 2000. Some studies indicate that there will be no aggregate mining operations by 1995. Recent studies show a drastic change in land use patterns within this valuable mineral resource area over the past 20 years. The San Gabriel Valley is a classic example of the lack of adequate regional planning with regard to urban development in MRA's and represents a "too little, too late" effort by local government and industry.

Jan 1, 1978

By N. Bat, N. Sarantsatsral

Blasthole sampling practices were investigated at the Erdenet copper and molybdenum mine in Mongolia to address grade reconciliation issues. The goal of the study was to determine if the particle size distribution (PSD) of blasthole cuttings was accurately reflected in the samples. The study additionally examined if the measured grade was related to the particle size of samples. Using a sector sampler specifically designed to collect samples for the study, six large samples were collected from three blocks following a specialized protocol. Each sample was split into nine size fractions, ranging from larger than 12 mm to smaller than 63 µm. Copper and molybdenum grades were determined for each of the size fractions. For comparison, nine samples were collected from the same blocks following the standard mine sampling protocol. These samples were also split into the same nine size fractions. As with the other samples, grades were determined for each of the size fractions. The results showed that the PSD in the samples collected following the standard operating procedure varied significantly from sample to sample. This variation was much lower for the samples collected following the specialized protocol. Loss of fines was also indicated in the standard mine sampling process. These observations suggest that the standard sampling protocol did not consistently capture the PSD. The copper and molybdenum grades increased as particle size decreased, regardless of the sampling protocol used. This observation underscores the importance of the PSD of a sample being representative of the true PSD. Given the low number of samples in the study, it is not a strong conclusion that the standard sampling protocol captures the PSD inconsistently. However, it could be taken as a caution. On the other hand, the grade versus PSD relationship is more certain, given that it was observed regardless of the sampling method used.

Feb 1, 2017

By Shular R. Scudamore

There was a time when heavy-duty apron feeders were built to last almost forever. The machines were heavy and built to maintain certain expected longevity and reliability. Increasing emphasis on return on capital leads to cost-effective designs. Costs can be increased or decreased, depending on customer specifications and the design philosophy of the feeder manufacturer. Specifiers can make important contributions to cost effectiveness. To do so, this article describes what should be known about planning with a supplier for heavy-duty apron feeders. There are several factors that should be considered, including capacity, characteristics of material carried, length, method of feeder loading, degree of lift, hopper opening, pan construction, and type of drive. Today's apron feeders are built in various sizes and with a variety of components to handle heavy, lumpy, or abrasive materials that can ruin lighter feeders. Careful feeder selection is important if it is to provide a controlled feed rate, absorb huge impacts, be used with long hopper openings, and have a relatively low power-perton capacity. Variations in systems and materials demand that each feeder be designed for its application, drawing on a wide range of components. Therefore, certain factors must be considered before final specifications are drawn. Capacity The design and application of an apron feeder is based on how material passes through a given system over the feeder into processing machinery. The processing machinery's capacity governs other equipment and productivity of the flow. From this basic information, related sizes of upstream equipment can be determined. Of these, the apron feeder acts as the "mouth and neck of the bottle." No more will pass than the mouth and neck will accommodate. Everything in the apron feeder design, from dimensions to power, is based on processing machinery. Material Considerations Are Vital Just as the nature of materials to be crushed or screened affects capacity and productivity of a crusher or a grinding mill, so does it affect capacity and performance of a feeder. Lump size must be identified closely so the pan width can be selected to accommodate the maximum lump with room to spare. For example, a lump size of 760 mm (30 in.) indicates a pan width of 1.5 m (60 in.) While two times the maximum lump is considered minimum width, if the maximum lump

Jan 12, 1983

By Richard C. Neavel

Among the many compositional parameters used to judge the quality of a steam coal is the fouling factor of Attig and Duzy1 [% base in ash % acid in ash X % Na20] in ash. The higher the fouling factor, the more likely the heat transfer surfaces of the boiler will acquire a deleterious deposit of sintered ash. While examining the elemental composition of ash from various size and gravity fractions of coals from Illinois, we noticed that variations in the fouling factor were attributable mostly to variations in the sodium content. Further, sodium content was essentially the same in all sink-float fractions from a given coal. In other words, sodium was related neither to the ash nor to the organic material. We therefore concluded that the sodium was most likely in the pore water, which was approximately a constant proportion of all fractions. This led to the supposition that the sodium might be removable through water extraction. This supposition tended to confirm the observations of Daybell,2 Daybell and Gillham,3 and Gluskoter and Ruch4 that much of the sodium in coals existed as water soluble sodium ions. In passing, it should be noted that most sodium in Western U.S. coals (i.e., Wyoming, North Dakota, Montana) is not water soluble, but rather is fairly strongly held in association with the organic material (ion-exchanged).5 Because data reported in the literature were not very conclusive about the typical proportions of sodium that might be removed by water extraction, and because there were few data indicating extraction rates, and finally, because our calculations showed a favorable economic incentive to lower sodium contents, we initiated an experimental program to investigate water extraction of sodium from Illinois coals.

Jan 1, 1976

By JIAQI JIN, Joe Milbourne, Maoming Fan

Gold is very important to support the financial system, and to be used in industries of the jewelry, high-tech fields such as electronics and aerospace, etc. Gold is mainly extracted from three types of ores: primary ore (vein gold), placer (alluvial gold) and associated ore. Cyanide was widely used in gold ore flotation to depress gangue minerals and leaching/cyanidation. The process of extracting gold from gold ore, its separation and flotation concentrate, specifically through a technique called cyanidation or cyanide leaching. This method, which has been dominant since the 1970s, utilizes a dilute solution of cyanide to dissolve gold from the ore. While effective, the use of cyanide raises environmental and safety concerns due to its high toxicity. Cyanide spills can have severe environmental consequences. This has led to the exploration of alternative, environmentally friendly reagents. This paper discusses processing results using the alternative flotation depressants such as sodium sulfite (Na2SO3), etc. to produce a goldrich flotation concentrate for sale to a smelter or as feed to an alternative leaching agent. and methods to extract gold from ore without relying on cyanide.

Feb 22, 2026

By Greg Border

Many unique ventilation problems have been faced as Avery Island Mine's large openings have been mined. High humidity of outside air combines with the hygroscopic salt to create a corrosive atmosphere. Massive rooms preclude routine use of brattices to direct air flow to the working faces. Large amounts of explosives are consumed in single blasts. Resulting concussion pounds air control structures and ANFO ignition creates large amounts of nitrogen dioxide in single rooms. Geologic constraints confine new shafts and slopes to areas thought to be free of potential ground water hazards. Dust control techniques are limited by dry product demanded by customers. The Avery Island Mine's ventilation system has evolved to deal practically with the conditions and to dependably provide fresh air to the miners. International Salt Company's Avery Island Salt Mine, a multiple level room and pillar operation, has been mined steadily since about 1900. It is known as one of the "Five Island" salt dome mines of South Louisiana's Gulf Coast. Production from the area places Louisiana first in United States rock salt mined tonnage, according to the United States Bureau of Nines, 1982 (1). International Salt Company is a major force in U.S. salt production, as it also operates mines in Detroit, Michigan; Cleveland, Ohio; and Retsof, New York; a solar salt facility in Bonaire, Netherlands Antilles; and a solution mining plant at Watkins Glen, New York.

Jan 1, 1983

By W. E. Sabina

In the short period of one mans? career we have seen specifications for bulk material handling systems and equipment grow from two or three pages to as much as two or three volumes for a single contract. The old 'short form' described what the purchaser expected the equipment to do. The long form does the same but also includes nut, bolt, and lockwasher depth of detail. What are the events that led to this proliferation of verbiage, and does it benefit the buyer in the final analysis? Is there a better way to purchase complex equipment while ensuring the highest quality for the dollar spent?

Jan 1, 1986

By Steven J. Schafrik, Michael Karmis, Zacharias Agioutantis

3-D or pseudo 3-D visualization of orebodies and mining related processes such as loading and tramming, are now commonly used by the mining industry. An approach is presented that can aid the engineer in creating the visualizations necessary for accurate presentations for use in public relations, safety training, production projections, reclamation plans, etc. It is shown that the creation of such digital representations of mining environments are independent of the mining package used to create the original mine design. Once a proper model has been created, any view of the areas is possible. These views can be taken from any number of stationary points or entered into an animation showing the progress of a mining construction. The paper focuses on the presentation of the steps used to accomplish the visualization and an example is for a quarry fill placement project.

Jan 1, 2002

By Paul I. Eimon

Mineral exploration involves the selective collection, organization, evaluation, and interpretation of geologic and economic data. The sources for such data are original field observations and existing documented information of various types (publications, reports, maps, company files, etc.). As exploration data are accumulated, their storage, organization, indexing, and J retrieval is key to exploration progress. Initial use of computers by mineral exploration groups indicates that data can be meaningfully handled by machines. A computer system makes possible: 1) the storage, manipulation, collation, and selective retrieval of data; 2) the utilization of data banks developed by geologic service groups and available at relatively low cost; and 3) the retrieval of stored data more rapidly, completely, and effectively than by manual systems. Profitable utilization of these capabilities is conditioned by several factors, particularly by the information selected for the system data base and by the design of the computer system itself.

Jan 1, 1968

From a vast army of workers to gargantuan machines to immense volumes of material being moved, almost everything about the Port of Miami Tunnel (POMT) project points to tunneling on a massive scale. Almost.The star of this underground and underwater show is a Herrenknecht tunnel boring machine (TBM,) nicknamed ?Harriet? by a local Girl Scout troop. With her 12.9-m- (42.3-ft-) diameter cutting head and a total length of 139 m (457 ft), Harriet is boring through thousands of cubic meters of clay, dirt and sand, which is often mixed with coral and other materials, to create two 1,280-m (4,200-ft) traf?c tunnels connecting Watson Island and the Port of Miami (Dodge Island) beneath Biscayne Bay, FL. But in the midst of all of the oversized equipment and machines, a strong contender for the best supporting nod goes to a relatively tiny machine: the Brokk 400. Bouygues Civil Works Florida crews are using the compact, remote-controlled and electric-powered machine to excavate five cross passages between the twin traffic tunnels. The pas-sages will be essential to the safety of people who drive their vehicles under the bay every day.

Sep 1, 2013

By Georgene Renner, Chee Theng, William Gleason

"In February 2018, drawn in part by the states’ proud mining heritage, SME took its Annual Conference & Expo to Minneapolis, MN for the first time. More than 5,000 people and 554 exhibitors converged on the Minneapolis Convention Center for three days of networking, exhibiting and technical sessions.The state’s mining legacy, one that continues today, is fueled in large part by its vast iron ore resources in the northern part of the state. The historical significance of the mines in the Mesabi Range, otherwise known as the Iron Range north of Lake Superior, cannot be understated. “Mining is a way of life here,” said U.S. Congressman Rick Nolan of Minnesota’s 8th Congressional District. A native of the Iron Range, the three-term U.S. congressman was one of the featured speakers of the opening keynote session. “We like to think we contribute enormously to the well-being of this country and the world. We were the source of the iron ore and steel that helped win two world wars. And we like to think that we are part of the progress that has taken place in the United States ever since.” Nolan kicked off the keynote sessionthat focused on innovation and its part in the mining industry. The session included Rene Aquilar, vice president of corporate affairs and sustainability, Antofagasta Minerals Group; Bob Anderson, vice president for research and development, 3M; Rolf Weberg, executive director, Natural Resources Research Institute, University of Minnesota-Duluth and Christopher Beck, executive vice president and president, Nalco Water. The panel session looked at U.S. and global minerals production, and the importance of the United States to maintain a major role in the minerals industry, both as a producer and as a technology leader. The panel also touched on the global mining industry and the issues that impact mining around the world. Sustainability, the use of water in mining and earning a social license to operate were among the topics discussed by the panel.Speaking of the importance of mining, Nolan conceded that talking about the benefits of mining to the crowded auditorium at the SME conference might be akin to a preacher speaking to the choir, but, following the adage that all politics are local, he continued to illustrate his point by emphasizing the importance of mining to the Great Lakes.“A study by Homeland Security concluded that 13 percent of the nation’s GDP comes out of Lake Superior through the locks at Sault Ste. Marie and most of that is iron ore,” said Nolan. “That study found that, if those locks fail, it would create a national depression. It would put millions of people out of work. That ore and those minerals supply the steel mills, the auto industry, the heavy industrials. They are the heart of our economy. The study concluded that if the states that make up the Great Lakes were a nation, it would be the fourth largest economy in the world.”"

Jan 5, 2018

By O. E. Wheeler

The term "finite element analysis" is heard and seen in print a great deal these days; a few words on what precisely it is are in order. In the broadest sense, finite element analysis is an application of an idea developed by a nineteenth century mathematician named Rayleigh. His basic idea was to decompose any problem in mathematical physics into a large number of simpler problems, solve the simpler problems, and then put those solutions together to form an approximation to the solution of the original problem. The scheme works nicely because of two features: first, much of the difficulty in solving practical problems of mathematical physics stems from irregularities in the boundaries and the simpler problems can be chosen with regular boundaries and second the smaller problems are solved for small physical areas where simple approximations of the solution do not differ much from the true solution. In the narrower sense, in which we are now interested, finite element analysis is a technique of using imaginary simple structural elements to construct analytical models of real structures. A direct parallel with the Rayleigh approach exists since the "finite elements" have simple boundaries and are restricted to simple behavior within a single element. Although the correspondence between Rayleigh's ideas and finite element analysis is now widely recognized, the computational tool, as it has developed over the last thirty years, comes not from the discipline of physics but rather from that of structural engineering. It is interesting that it came not from the traditional research community, the universities, but instead from working

Jan 1, 1974

By Joe D. Mitzel

The Indian Head fine has been in existence since 1922. For over 56 years there have been North Dakota people mining coal at this same location. The area affected will fit inside a circle 5 km in diameter, and the coal is lignite. The seam thickness has varied from 2.4 m to 3.65m, and the overburden from 6 m to 30 m in depth. me Lignite coal which is being mined at the Indian Head Mine is from 15.8 x l0 6 to 16.7 x 10 6 J per kg; it has a moisture content of 33 to 38%; an ash content of 5 to 10%; and a sulfur content of from 0.5 to 0.7%. The moisture content and the fact that we crush the coal co a top size of 14 cm x 0, are two of the characteristics or the product which cause it to freeze and remain inside of the railroad cars on the slope sheets. The market for the coal initially was almost entirely local coal sales. That is, coal was sold to people in the area who used the lignite to heat their homes, stores, offices, schools, and churches. Back in the early 1920's, there were no stoker-fed boilers, or pulverized fuel boilers, as we have in today?s marketplace. Basically, all of the coal was sold as lump coal, pieces about 30 to 35 cm square, to be used in furnaces: and nut coal with a top size of about 7.5 cm to 10 cm to be used in the old kitchen cookstove. All of the coal fines, less than 5 cm, were screened out and layed onto a pile. There was no market for the smaller sizes of the lignite coal. It has been our experience that when the coal is in lumps or chunks larger than 7.5 cm to 10 cm, there is a very slight possibility of freezing. That is the chunks themselves freeze, but by their nature, they do not cling to one another or form large masses of frozen material which are difficult to remove from the slope sheers of the railroad cars.

Jan 1, 1980