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By Robert R. Brandom

The Boss-Bixby deposit is one of several iron deposits that occur in the Precambrian igneous rocks of southeastern Missouri. It differs, however, from all of those deposits by its significant contents of copper, cobalt, and titanium, and its close relationship with a basic igneous intrusion. Ore microscopic study of selected drill core samples has shown that the hypogene ore minerals are magnetite, hematite, chalcopyrite, bornite, covellite, ilmenite, rutile, sphalerite, cobaltian pyrite, carrollite, scheelite, and wolframite. Subsequent partial oxidation has formed martite, pseudobrookite, and anatase. Textural evidence indicates that two stages of iron and iron-titanium oxide formation were followed by the deposition of the copper-iron sulfide minerals and carrollite.

Jan 1, 1985

By J. Keith Haddock

"Introduction The Coal Valley Mine is operated by Luscar Stereo (1977) Ltd. with the Alberta Energy Company having a minority interest. The mine produces 2.0 million tonnes of bituminous thermal coal per year. Deliveries include 1.5 million tonnes to Ontario Hydro and 0.5 million tonnes to the export market via bulk handling facilities on the west coast near Vancouver, B.C. There are a number of mining methods utilized at the mine including open-pit by truck and shovel, strip mining with large draglines and stripping with scrapers. The mine is located 100 km south of Edson, Alberta. Geology The coal measures are concentrated within a 210-metre int~rval of the Paleocene section. The coal seams were originally named by the mining companies in the earliest days of development of the area and these names continue to be used today. Of the five main seams, only three are presently economic to mine based on quality, thickness and depth of cover. These are the Val d'Or, Upper Silkstone and Mynheer. The Coal Valley Mine is located in the structurally deformed foothills area of Alberta and the structure of each mining area is therefore very complex. The general bedding strike is 305 degrees azimuth but major thrust faulting and folding has extensively deformed the natural seams as a closer examination will show. The Mynheer Seam, located at the base of the coal measures, ranges in thickness from 5 m to 10 m and has numerous bentonite and shale partings. Because of inherent geological features, the Mynheer Seam has been subdivided into two zones, the Mynheer 'A' and the Mynheer 'B', and the mining of coal in these zones has necessitated the utilization of distinctly different mining methods. The structural regime of the Mynheer 'A' zone consists of an overturned asymmetrical anticline crest containing a steeply dipping major thrust fault which has raised the seam above the present topographic level. Further extensive shearing and rotation of the coal has resulted in the coal taking a 'pod' shape. The Mynheer 'B' Zone is a continuation to the southeast along strike from the Mynheer 'A' Zone. The bedding dips to the southwest at an average of 12 degrees and is interrupted at the south end by a transverse fault and to the north by its outcrop at the surface."

Jan 1, 1985

By K. C. Dean

Discarded automobiles represent the greatest single resource of reusable metals, plastics, and rubber in the United States. This report presents results of Bureau of Mines research, conducted from 1965 to 1983, on separating and recovering useful materials from the scrapped hulks, using old and new metallurgical techniques combined with standard scrapyard methods. The Bureau determined the materials composition of three composite cars designated as circa 1960, mid-1970's, and early 1980's, and used these cars to study smokeless incineration and hand-sorting techniques. In studies on treating rejects from automobile shredders, the Bureau designed a process that included air classification, water elutriation, magnetic separation, handpicking, and heavy-medium separation, and also investigated cryogenics and liquation. Complete recovery of cop-per and other metals was economically made by hand and tool dismantling, leaching, or selective melting of starters and generators. Techniques are also discussed for plastic recovery and waste tire treatment.

Jan 1, 1985

By C. M. Palencia

The Bureau of Mines evaluated the potential availability of molybdenum resources from 88 mines and deposits that account for more than 90 pct of the demonstrated resource base in market economy countries (MEC's). For each property, tonnage-cost relationships were developed that indicate the molybdenum potentially available at different average production costs, including a 15-pct rate of return on invested capital. From the 23 MEC primary deposits, 2.5 billion 1b Mo was determined to be potentially available at a price of $411b, rising to 4.7 billion 1b Mo at $8/lb. Copper price-molybdenum tonnage relationships were developed for those mines and deposits from which molybdenum can be recovered as a byproduct of copper production. This analysis showed that another 3.4 billion lb Mo is potentially available based on a copper price of $0.7511b, rising to 4.3 billion lb Mo at $l.00/lb. The United States has been the world's largest molybdenum supplier since 1924. Its remaining resources are sufficient to meet the domestic demand of 57 million lb/yr Mo (averaged for a 10-yr period) through the end of the century. Production from primary domestic mines was suspended during most of 1983 because of oversupply of materials. A major concern is the cheap molybdenum byproducts from foreign copper operations in which employment and the need for hard currency override economics in meeting production goals.

Jan 1, 1985

By D. L. Sawyer

The Bureau of Mines studied alumina extraction from uncalcined, kao-linitic clay at temperatures from 1000 to 2500 C using 20-or 27-wt-pct-HCI concentrations and with an acid-to-clay ratio of from 0.8 to 1.4 times stoichiometric. Autogenous digestion pressures ranged from atmospheric pressure to about 900 psia. Extraction of 96 pct of the alumina was obtained by HCI leaching at temperatures and leaching times that varied from 1000 C for 120 h to 2000 C for 15 min. Hydrochloric acid stoichiometry of the reaction A1203'2Si02'2H20 + 6HCI + 2AICl3 + 2Si02 + 5H20 was studied at different temperatures and leaching times in a 750-mL tetrafluoroethylene-polymer-lined autoclave. A combination of high temperature and 20 wt pct excess HCI promoted rapid and almost quantitative extraction of alumina (99 pct in some tests). Additional Bureau data obtained with 35-mL tantalum bombs and leach-ing tests with added fluoride are also provided. At high temperatures, the addition of fluoride did not result in a significant improvement over HCI alone and was deleterious to the filtering properties of the digest residue.

Jan 1, 1985

By Jon C. Volkwein

The Bureau of Mines and many member companies of the Industrial Sand Association have been working in several areas to reduce personal exposure to respirable dust. Areas investigated include ventilation, modification of hardware, moisture addition to the product, and improved housekeeping practices. Ventilation systems have been devised and shown to contain 100 pct of a tracer gas released within the hood. An industrial clean air island has been developed and shown to reduce dust levels 90 pct at the opera- tor's position, Modification of hardware on a bag filling machine has been demonstrated to reduce dust 83 pct at the machine operator's lapel. This particular development has been termed a significant advancement in the state-of-the-art of bag filling by industry representatives. Addition of moisture to dried product materials has been tested with results showing dust reductions of 90 pct are possible!, Control of the moisture addition method still needs refinement and costs may be prohibitive. Dust sampling results clearly show the benefits of housekeeping practices such as building cleaning and vacuum sweeping. Rotation of work schedules is also effective for reducing personal exposure.

Jan 1, 1985

By S. M. Hsiung

This paper presents the results of an extensive study concerning a series of roof falls in a room-and-pillar coal mine located in West Virginia. Three dimensional finite element modeling was employed to identify the possible causes for the roof falls. The effectiveness of possible roof control measures for alleviating or eliminating the adverse roof conditions is analyzed, discussed, and compared. The best mining alternatives are recommended. It has been found that large overburden depth and typical roof geology are the major reasons for the roof falls. Angle bolting may not solve the problem encountered in the mine studied. Changing the mine layout currently used in the mine appears to be the best alternative. The recommended pillar size and entry width which will eliminate the problem completely are 90 ft. x 90 ft. and 14 it., respectively.

Jan 1, 1985

By Jeffrey Y. Foley

Chromite deposits along the Border Ranges Fault in southern Alaska were investigated by the Bureau of Mines. This report, part 1 of a two- part series, describes the deposits. Part 2 describes the mineralogy and the results of metallurgical tests. Fieldwork began in 1981 and continued through 1983. Ninety-four subeconomic podifom chromite deposits in eight mafic-ultramafic complexes were investigated. Previously unreported chromite deposits at Red Mountain on Kenai Peninsula, on Kodiak Island, and near Tonsina are described. Deposits range in size from less than a thousand tons to over 1.25 million tons of contained chromic oxide (Cr203). Grades range from about 5 to 10 pct chromite. Excluding all deposits more than 10 miles from tidewater or existing roads and all deposits containing only chemical- or refractory-grade chromite, about 2,200,000 tons of Cr203 are contained in 41 hard-rock deposits. A placer deposit contains an additional 556,000 tons. These 42 deposits constitute a subeconomic indicated and inferred reserve sufficient to meet the Nation's chromite demands for about 4 yr, or the metallurgical industry's demands for over 5 yr, at 1981 consumption rates.

Jan 1, 1985

By R. W. Draves

Planning and testing in advance of the mining operation are essential. This advance work can involve physical and chemical analysis of overburden cores, field test plots, green- house studies or any of a multitude of other baseline data collection activities. This paper presents the results of Central and South West's field test plots and how they relate to topsoil substitution. Besides the obvious need for testing in advance of mining, there are the inevitable regulatory requirements. Quoting from the office of Surface Mining Regulations concerning topsoil substitution: 216.22(e) TOPSOIL SUBSTITUTE AND SUPPLEMENTS -Selected overburden materials may be substituted for or used as a supplement to topsoil if the office determines that the resulting soil medium is equal to or more suitable for sustaining revegetation than is the available topsoil and the substitute material is the best available to support revegetation.

Jan 1, 1985

By J. G. Mieczaniec

"A key element for a successful mining operation is the grinding circuit. It must be reliable, maintainable and must perform to or above design capacities for 95% of the time. Once chosen and installed major modifications are either prohibitive or very expensive. The selection of mills and drive system is probably the single most important decision made within the concentrator complex.Economic studies revealed that the optimum expansion for Lornex was a 68070 increase in plant throughput. This indicated that the new mill would have to be larger than the existing 32-foot mills.The Lornex ore has a wide range of hardness which has a great influence on mill throughput (Table 1). To smooth out the fluctuations, a blending program ha s always been in effect at the mine, coupled with ball charge control for the primary mills. As can be appreciated, an optimum balance is difficult to achieve. A sudden change to so ft ore with a high ball charge puts the mill into jeopardy with a constant speed drive.The blending philosophy would continue after the expansion, but with the addition o f a second primary crusher, it was envisaged to have the new mill process harder ore to maintain production targets. In theory, the new mill would have a proportionally larger ball charge than the existing mills.This scheme makes the new mill vulnerable for processing so ft ore for a fixed speed mill. Thus, variable speed seemed an attractive option.In early 1979 prominent mill manufacturers were invited to submit proposals for the new mill. Fixed and variable speed mills were to be considered with mill size ranging from 32-foot to 36-foot diameter. The proposals were to include the drive, ball charge, % critical speed, couplings, gears, etc. - the complete package. The recommendations were variable with most manufacturers submitting several alternatives. Recommended mill speed varied from 68% to 78% critical. The concept of variable speed was becoming more attractive, Lornex ultimately decided on a twin DC motor drive system for a 34-foot diameter mill.After start-up it was discovered that best throughput occurred at 78% mill critical speed or top speed of the drive motors. The motor speed range was adjusted upward from 186 to 200 rpm. Today the mills operate at 79% critical or a motor speed o f 193.5 rpm.Clearly the selection of the variable speed mill allowed the flexibility to optimize throughput."

Jan 1, 1985

By Paul L. Broughton

"IntroductionThe coal deposits, all of lignite rank, of economic interest in Saskatchewan are associated with the Ravenscrag Formation (Paleocene). Several Cretaceous formations have less significant lignite accumulations (Broughton, Irvine and W'hitaker, 1974). The Swan River Group (lower Cretaceous) and Judith River Formation (upper Cretaceous) have the only coalbearing strata in the shallow subsurface of central Saskatchewan. The Swan River Group coalfield is relatively small and underlies only 15 sq km of the surface approximately 40 km south of La Ronge, Saskatchewan. An estimated 36 billion short tons are within 45 m of the surface. No reserve estimates are known to have been calculated for the coal-bearing Judith River Formation exposed at the surface in the vicinity of the South Saskatchewan River valley in west-central Saskatchewan. Although no coalfields have been delineated, lignite beds up to 1.8 m thick have been intersected in test holes. The coal-bearing upper Cretaceous and lower Tertiary strata of the northern Williston Basin extends the full width of southern Saskatchewan for 650 km, and from the United States border 120 km north to 50° latitude (Fig. 1). Only the coalfields of the Ravenscrag Formation, because of their economic interest, will be considered further. There are four major coalfields. They are, from east to west: Estevan, Willow Bunch, Wood Mountain and Shaunavon (Cypress) coalfields. Cumulative lignite seam thickness for each basin is 10 -15 m (Figs. 2 and 3). The origin of each coal basin, resource calculations, seam stratigraphy, and mining activity are discussed. Regional Setting The Williston Basin is an ellipsoidal depression in the Precambrian basement, centered in western North Dakota and marginal to the exposed craton of northern Saskatchewan and central Manitoba (Fig. 1). The sediments of the basin range from Cambrian to Pleistocene in age and have a maximum known thickness of 4614 min western North Dakota. A maximum of 3200 m is recorded in southern Saskatchewan. Most structural deformation is late Cretaceous to early Tertiary (Paleocene) in age, coinciding with the Laramide Orogeny. The pre-Laramide Williston Basin, with a depocenter near Williston, North Dakota, began developing during the middle Ordovician, or possibly earlier."

Jan 1, 1985

By Mark R. Pettitt

The results of an extensive research and development program to reduce the noise generated during coal cutting are presented. The characteristics and magnitude of continuous miner coal cutting noise sources are defined. This work consisted of development of a simulated coal ,cam to facilitate above-ground coal cutting tests, noise measurements in a reverberant acoustic chamber during simulated mining operations of a continuous miner (cutting the simulated coal scam), and noise measurements in an underground coal mine during continuous miner operation. In-mine and laboratory test results were in excellent agreement for both A-weighted overall levels as well as A-weighted one-third octave band spectra. Methods to reduce coal cutting noise are presented. These methods take full advantage of the dynamic characteristics of the forces generated during coal cutting. Dynamic cutting force isolation was shown to be a very effective technique. Finally, a continuous miner was equipped with a cutter head that incorporated (among other design factors) cutting force isolation. Successful, lung term, in-mine use of the cutter head demonstrated coal cutting noise at the operator's station of less than 90 dBA and 50% coal, 50% rock cutting of less than 93 dBA.

Jan 1, 1985

By Michael J. Klishis

It was the goal of this project to develop training materials specific to two areas of the mining industry: (1) safe use and care of the self-contained self-rescuers, and (2) awareness and avoidance of electrical hazards. This report describes the development of the following training material: Instructor's modules for the OCENCO EBA 6.5, CSE AU-9A1, and PASS 700E self-contained self-rescuers; and a textbook, slide tapes, and accident case study scenarios for mine electricity, and a computer based instructional package on mine electricity and electrical hazards. The report concludes that additional efforts are needed in mine training and four recommendations are made: (a) tailor existing materials to fit specific mine sites, (b) develop and evaluate computer based instructional material, (c) develop parallel training materials for metal and non-metal mines and, (d) develop additional training materials for preparation plants and surface areas of underground mines.

Jan 1, 1985

By Jon C. Volkwein

The Bureau of Mines, Foster-Miller Inc., and Beaver Creek Coal Co. have evaluated the ability of a new system to ventilate a 40-ft-deep cut. A remote-control continuous-mining machine, in a 7-ft-thick seam, with exhausting brattice was fitted with an improved sprayfan system plus additional forward and reverse pointing sprays. Static and dynamic tests using tracer gas were conducted in a full-scale model and under-ground to measure the effectiveness of exhaust face ventilation for various deep-cutting mine and spray configurations. When compared to a lO-ft primary ventilation brattice, the extended-cut spray system consistently provided better face ventilation at all configurations up to and including a 40-ft brattice setback. The system also provided good dust protection and visibility for the machine operator. Another safety advantage is the elimination of the need to set temporary roof supports to maintain the ventilation brattice.

Jan 1, 1985

By W. M. Scheding

"There has recently been a resurgence of interest in unit flotation of mill discharges. At the Kidd Creek concentrator, this technique has been successfully applied to silver flotation in a 3050 mtpd silver-copper-lead-zinc division. The major incentive has been improved silver payment through increased overall recovery and better distribution between the sequential copper, lead and zinc concentrates. A large, but variable fraction of the silver in the ore is present as native silver and, being dense and malleable, is susceptible to overgrinding. Grinding circuit surveys showed high concentrations of silver in both primary and secondary circulating loads. Laboratory testwork confirmed that this was selectively flotable, identified the secondary ball mill discharge as the best feed stream and optimized flotation conditions. A 10 t/h pilot plant campaign confirmed that the rate of accumulation of silver was sufficient to sustain continuous production of a silver concentrate and that flotation of the whole stream was not necessary.The present 30 t/h production circuit recovers from 5 to 50% of the silver in the ore at a concentration ratio between 25 and 250. The circuit also contributes to a better understanding of ore mineralogy, as an 'on-line' indicator of elemental silver content."

Jan 1, 1985

Jan 1, 1985

By Benedicto Hadad Cintra

In an inflationary environment the need for reduced cost is a daily concern of all industries. The Du Pont do Brasil "Expanded Pattern" method has proven to be an extremely effective means of reducing costs in mining, quarrying and construction operations. Over the past years much emphasis was placed on rectangular drilling patterns where the burdens are less than the spacing. The Expanded Pattern method combining rectangular and staggered patterns, was implemented in 1971 in Brazil after extensive trials in close collaboration with numerous explosives users and Du Pont do Brasil Technical Services Engineers. The best multiple row spacing-to-burden ratio (S/B) was demonstrated to be in the 2 to 5 range and the effective spacing to burden ratio (Se/Be) was found to vary from 5 to 11. These ratios are for the interior of the blast pattern and do not hold true along the front row of holes. Geological rock properties, hole diameter and inclination, explosives energy and loading density, explosives characteristics, blast pattern geometry, bench height and delay patterns along with type and size of digging, hauling and crushing equipment must all be evaluated for each and every operation. The integration of these interrelated parameters, together with sound blasting practices are the basis for the Expanded Pattern method. Color slides and documented case histories will be presented.

Jan 1, 1985

By R. B. Lawrie

Diesel powered underground mining equipment is presently the most productive, safest and efficient equipment used in underground mining operations. The widespread application of this equipment to underground mining is restricted, however, largely because of the difficulty of controlling the diesel engine exhaust emissions. This paper briefly examines control devices currently available for underground application, and also discusses the theory and mechanics of controlling diesel missions with particulate traps and filters.

Jan 1, 1985

By Ron Hatch, M. K. Witte

"INTRODUCTIONThe proper selection of carbon for a gold carbon in pulp (CIP) circuit involves careful evaluation of several physical, chemical and economic factors. A series of evaluations are required to maximize gold recovery at the lowest capital and operating costs, whether the carbon is selected for an existing gold mill circuit or a new mill under design.Although evaluation may proceed through various stages, it is the intent of this paper to outline some of the preliminary testwork that should be carried out to screen potential carbons for a particular application.An examination of the specification sheets supplied by the various carbon manufacturers may indicate some desirable properties on which to make cursory selection. This exercise by itself will not provide the basic data needed for selecting the best carbon for a particular ore pulp and metallurgical circuit. The necessity of further metallurgical evaluation is indicated by the fact that different carbons perform differently depending on the physical and chemical nature of the leach pulp. In the case of an existing mill, actual leach slurries using mill water are available and should be used for testwork. In the case of new mills, leach pulps must be prepared to simulate the proposed circuit.Five coconut shell activated carbons were obtained from various suppliers, all reported to be 6 x 16 mesh carbons recommended for CIP circuits. A metallurgical evaluation was made utilizing two leach pulps with significantly different characteristics. This paper describes the test procedures utilized and the results obtained from the testwork."

Jan 1, 1985

By L. W. Scott

This report presents an overview of explosionproof (X-P) enclosure research being conducted by the Bureau of Mines, This report emphasizes the increasing importance of research related to the safety con- siderations of X-P enclosures used in underground coal mines. Selected topics are included that summarize results of research in the areas of electrical clearances, reliability of enclosures with windows, safety factors in X-P enclosures, potting materials, performance tests for X-P enclosures, protection against high-voltage explosions, and innovative X-P devices.

Jan 1, 1985