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By James W. Baxter

State geological surveys promote sound procedures for evaluation of mineral resources before development-procedures that protect the environment and accrue maximum benefit to citizens. Sophisticated laboratories have been equipped for geophysical, geochemical, petrographic, and mineralogic characterization of materials to assist citizens in land-use planning and optimum development of natural resources, activities clearly within purview of the state. Proper use of these facilities in support of exploration in a competitive, free-enterprise system should be based on achieving ultimate benefits to the public, but, in general, should not entail competition with commercial laboratories.

Jan 1, 1982

By William R. Wessels

This report describes a field survey and laboratory investigation into the causes of failure of resiliently clad screen decks applied to coal preparation plants. Blinding of screen deck perforations and delamination of the resilient cladding are studied and mechanisms responsible for these failure modes are hypothesized. A laboratory test program to simulate the mechanisms was begun and abandoned when it became apparent that meaningful test results would require a substantially redirected effort. No meaningful test data was obtained from the laboratory simulation.

Jan 1, 1982

By John R. Parker

Work places of an underground coal mine are required (30 CFR 1719) to be illuminated while self-propelled equipment is used. Permissible machine mounted systems have been developed and applied satisfactorily to many mining operations. However, some low seam and thin seam equipment has been difficult to illuminate because reliable, direct current systems and compact, low output, low glare luminaires were not available. This program resulted in the design and prototype construction of compact, low glare luminaires and AC and DC power systems, particularly suited to resolving illumination problems on low and thin seam mining equipment. Design objectives were based on enhancing the prospects for thin seam illumination solutions through definition of a product which could challenge markets enjoyed by higher glare luminaires and through reduction of technical risks associated with any new product development as well as the MSHA certification process.

Jan 1, 1982

By George C. Reynolds

INTRODUCTION The overall importance of the minerals industry during the next 20 years was highlighted In "The Global 200 Report to the President" (Barney, 1982) in the following terms: "The industrial and agricultural processes that are taken for granted today would be severely disrupted of any one of dozens of critical minerals ceased to be available in dependable, reasonably priced supply. Supply in turn has become highly energy intensive and international In scope ...... because resources are not uniformly distributed geographically, political considerations (also) become an Important determinant of price and trade patterns." In attempting to determine Australia’s contribution of bauxite raw materials to the world of the future, this paper necessarily also concerns itself with the alumina and aluminium industry to which it supplles the raw material. It is an industry which is energy intensive, International in scope and heavily influenced by political considerations. The aluminium industry has shown a remarkably rapid growth during the past 20 years (Fig. 1).

Jan 1, 1982

By G. D. Bates

INTRODUCTION The Magmont mine is a joint venture of Cominco American Inc. (operator) and Dresser Minerals, Inc. The mine-mill operation is located approximately 160 km (100 miles) southwest of St. Louis, MO, in what is commonly referred to as the "Viburnum Trend.” The Magmont mine is designed for a production rate of 3810.2 t/d (4200 stpd) on a 5-day week, three shifts per day basis. Initial production began in 1968. The mine is open stope, room-and-pillar, and essentially horizontal along the trend of the ore body. Briefly, the main geological structure can be described as a brecciated graben bounded by reverse faults. The ore body in cross section is shaped like a bell curve with some lateral extension at the lower part. Presently outlined ore is 609.6 to 762 m (2000 to 2500 ft) in width and 2133.6 m (7000 ft) in length. The ore varies in thickness from 4.87 m (16 ft) on the fringes to an average of 27 m (90 ft) in the high ore areas bounded by the reverse faults. Lead is the primary metal with zinc and copper secondary. MINE DESIGN The basic design of open stope, room-and-pillar mines has been described by several writers and need not be repeated here. (Anon., 1970; Bullock, 1973; Casteel, 1972; Christiansen et a]., 1970; and Lane, 1964) This discussion covers the mining sequence as applied to the particular problems at the Magmont mine, the use of equipment, and deployment of the work force. In the upper portion of the Magmont ore body is a layer locally called the False Davis shale. This layer lies below the true Davis shale, is normally interbedded with dolomite, is of varying thickness, and if mineralized, is included in the top pass of the mining sequence. In thick ore areas this layer will be 2.13 to 2.43 m (7 to 8 ft) in thickness and will occur in the upper portion of the pillars. Due to its incompetency the presence of this False Davis layer is of primary concern in mine planning and operation. Mining areas are divided into three basic groups by ore thickness. First are areas of ore up to 6.09 m (20 ft) in thickness. These areas are below the False Davis shale and are mined single pass with drill jumbo. Second are those areas up 13.71 to 15.24 m (45 to 50 ft) in height. The first 4.87-111 (16-ft) Pass is taken at the top of the ore and the back and pillars secured. Benching the lower portion(s) in 4.57 to 4.87-m (15 to 16-ft) passes is then done with either a drill jumbo drilling horizontally or a crawler drill drilling vertically. Normally these areas are below the Table 1. Productivities per Manshift False Davis shale. These areas may also be mined by back slashing, or overhand benching, where the first 4.87-m (16-ft) pass is taken at the base of the ore and successive 4.87- m (16-ft) passes are taken upward. A minimum amount of back slashing is done at Magmont since it requires repetition of roof control on each pass and roof control is the single largest stoping cost at Magmont. Ore left to provide a working platform oxidizes and is coated by oil spills thus reducing metallurgical recoveries. The third mining area is over 15.24 m (50 ft) in height UP to a maximum of 40.23 m (132 ft) and will encompass the False Davis shale. These areas are mined by first driving +15% inclines to the top of the ore body. The top pass is mined and the back is bolted and roof mats installed as a matter of standard practice to minimize roof problems as mining progresses downward. Once the back and pillars on the top pass are secured, benching begins on successive passes with either the drill jumbo or crawler drill. Pillars on all successive passes below the top pass are secured as necessary. While benching progresses below the top pass, the pass at the base of the ore body is mined leaving a sill of 4.57 to 7.62 m (15 to 25 ft) in thickness to be removed with the crawler drill in a retreating manner. Rooms are mined on a 1.57 rad (90") grid pattern to insure alignment of pillars where multiple passes are taken. Pillars are designed on a 17.98-m (59-ft) spacing with rooms up to 10.66 m (35 ft) in width. Heading widths are wide enough for the mobile equipment to turn without additional allowance for curves. The result is a flexible layout which provides a maximum number of headings available for high extraction rates and grade control. PRODUCTION Incentive Bonus Incentive bonuses play an important part in the mine production at Magmont. Production crews are trained to perform only one of the mining functions of drilling, blasting, mucking. or roof bolting. This specialization, or functionalization, is augmented by development to open all possible stoping areas as early as possible in the life of the mine. This insures that each crew will have enough headings to perform its specialty. The incentive bonuses increase exponentially as output increases. The lucrative incentive bonus coupled with the specialization of the production crews and proper mine development have combined to give the high productivities shown in Table 1. Development crews perform all mining functions in their area. The incentive bonus is paid on a per foot basis, Crews on different shifts working the same heading share equally in the bonus proportional to their contract hours worked.

Jan 1, 1982

By Victor F. Hollister

North American ophiolite complexes are known to contain significant volcanogenic sulfide only in the following five areas: Newfoundland; Quebec; Applegate, Oregon; Rogue, Oregon; and Orca, Alaska. Most North American ophiolites, including the Baltimore, Kings-Sierra Nevada, and Del Puerto complexes, and those associated with the Franciscan, Trinity, eastern Oregon, and Cache Creek groups lack significant volcanogenic sulfide. The characteristics of sulfide-bearing ophiolites are: (1) manganozls cherts, and (2) fine, carbonaceous clastics inter- calated with pillow basalt and chert. It is suggested that sulfide- bearing ophiolite complexes developed in a restricted basin environment, such as is now present in the Gulf of California; whereas sulfide-poor ophiolites, formed in midocean, rises distant from land masses. Sea floor oxidation makes the typical midocean ridge configuration not conducive to sulfde preservation, whereas spreading centers bounded by land masses are more likely to produce anoxic physiographic lows favorable to sulfide accumulation.

Jan 1, 1982

By A. B. Holland-Batt

The application of Reichert spirals and cone concentrators within the South African mineral industry is discussed, and the procedures used in the acquisition of design data are outlined. Computing techniques developed by Mineral Deposits Limited for the processing of test data for use in the design of production circuits are described.

Jan 1, 1982

By Steven J. Schatzel

Gas drainage through surface bore-holes has been the conventional means of methane control for U.S. longwall gobs. However, these vertical boreholes are becoming so costly, and the surface rights so difficult to obtain, that the Bureau of Mines is developing underground gob gas drainage as an alternate means of methane control for U.S. longwalls. Holes are drilled into the roof over the panel and on retreating longwalls, towards the working face from a location inby the face. As the longwall retreats, an increasing portion of the hole intercepts the fracture system over the caved gob. A surface exhauster maintains a vacuum on a pipeline parelleling the panel and draws the methane mixture out of the mine. Auxiliary systems of gob gas drain-age during longwall mining will be essential for an increasing number of coal mines. Deep and gassy mines often find ventilation insufficient for adequate dilution of methane in bleeder entries. Although this cross-measure method of degasification has been used successfully in Europe, some of the European techniques cannot be directly applied to U.S. mines. This is the first study of its kind in this country.

Jan 1, 1982

By Walter W. Lilly, Issa S. Oweis

Application of rock engineering in geotechnial consulting practice considered herein is in areas of: (a) bedrock verification for foundation support, (b) bearing capacity and settlements, and (c) excavations. A routine geotechnical investigation usually provides data on depth to rock, rock classification, and rock quality. In cases of rock outcrop, such outcrops are mapped for geologic structures and rock mass description. In addition, the regional geology and the general aspects of the groundwater regime are usually known from either published literature or previous experience. The predominant technique for ground and site investigation are usually drilling and geologic reconnaissance. Other techniques involving seismic and geophysical soundings, borehole camera, and oriented cores are used by by no means routine. Performing laboratory strength and compressibility tests is often made to be considered as routine. The use of the point load test is gaining increasing use in the United States and would, perhaps, become a routine field or laboratory test due to its simplicity and, more importantly, its relatively low cost. The purpose of this paper is to describe cases where mostly routine investigation and testing were used to arrive at engineering decisions. Bearing Capacity and Settlements The allowable bearing values for foundation support on rock is usually dictated by local building codes which presumably should reflect local experience. The interpretation of the code, however, can present a problem, especially if the interpretation is made by a designer under the delusion of knowledge in rock engineering. For

Jan 1, 1982

By G. T. Adel

This paper presents the highlights of a general-purpose simulator for mineral processing plants that is being developed at the University of California, Berkeley. The state-of-the-art structured design methodogy based on a top-down design approach is being used to construct a modular and completely structured simulator such that it is independent of the unit operation models and routines. The simulator provides for two levels of operation allowing prebuilt or user-built simulation flowsheets depending upon the degree of computer knowledge expected of the user. The philosophy used in designing this simulator appears to be unique in the field of flowsheet simulation. The paper also includes a mini-example demonstrating the usage of the simulator.

Jan 1, 1982

By A. Koursaris, H. M. Friede, A. A. Hejja

The features of smelting slags from South African prehistoric sites and of related cinder material are described. Chemical analyses of twelve slag samples found in the Transvaal, Swaziland, and Botswana are reported and discussed. An attempt is made to establish a relationship between these slags and the ores collected at the Early Iron Age site of Broederstroom, which date between AD 350 and AD 600. The liquidus temperatures of29 slags were determined by the use oh hot-stage microscope. The major mineral phases of 16 slags were identified by X-ray diffraction and microscopic examination. It appears that the slags investigated were formed at temperatures below 1250°C or - in some cases - at temperatures only marginally in excess of 1250°C.

Jan 1, 1982

By Constance F. Acton

This paper presents an overview of -- the carbon-in-pulp process for gold and silver recovery as seen in the early 1980's. Traced back to its origins in the mid-nineteenth century the process development through the present state-of-the art is described. The process technology and equipment design are described in detail for the carbon-in-pulp process. A typical process flowsheet is given with a description of appropriate design criteria. Technical advantages and disadvantages as compared to the traditional countercurrent decantation process are discussed including some illustrative comparisons of capital and operating costs. A summary of currently operating carbon-in- pulp plants throughout the world is given with an insight into future developments in this industry.

Jan 1, 1982

By Michael Hood

Subsidence profiles above two adjacent panels in Illinois are compared with pro- files predicting subsidence behavior obtained using the (i) National Coal Board (NCB, 1975) method, (ii) the profile function method and (iii) the influence function method. The NCB method predicts the maximum subsidence values at the center of the troughs accurately, but, the overall shapes of these predicted profiles do not match the profiles from the measured data well. Consistent values for the angles of draw were measured but these angles were different in the transverse (average value 43 degrees) and in the longitudinal (average value 17.5 degrees) directions. Time dependent subsidence effects are shown to be small but measurable. These displacements continue at a linear rate for at least a 12 month period. A comparison of measured horizontal distances, interpreted as horizontal strain, and the NCB predictions for strain shows that the peak measured strains are greater by a factor f about four than the predicted strains. The relationship between surface curvature and strain is investigated. Problems associated with calculation of surface curvatures from vertical displacement data are highlighted and a recommendation is made for future studies to consider direct measurement of this parameter. Surface curvatures above a moving face are found to be about three times less than the curvatures at the stationary end of the panel. On the other hand, a hyperbolic tangent profile function is shown to serve as an accurate predictive tool for subsidence behavior in two adjacent longwall panels at Old Ben Number 24 mine in Illinois. This function predicts not only the vertical displacements but also the surface curvatures above both panels. Influence functions are shown to be more problematic, although potentially more flexible, in their application than the profile functions.

Jan 1, 1982

By J. Absil, H. Dreissen

Upgrading low-concentration ores is of increasing importance today. The heavy medium cyclone process, due to strong centrifugal forces, effectively separates particles varying only slightly in specific gravity but widely in size. The paper discusses separation efficiency, assessment of that efficiency, and the influence of such factors as medium solids. The operating results of nine heavy medium cyclone plants, each handling a different mineral, are reported.

Jan 1, 1982

By Ronald R. Bauer

Wollastonite is a little known industrial mineral of the silicate group. The largest and purest known deposit in the free world is being mined and beneficiated in Millsboro, New York by NYCO, A Division of Processed Minerals Incorporated. The associated garnet and diopside are separated from the wollastonite using dry high intensity magnetic separators. Beneficiated wollastonite is used extensively as an additive and filler in the ceramic, paint, refractory, and wallboard industries. Wollastonite acts as a functional filler due to its unique chemistry and physical acicularity.

Jan 1, 1982

By Reichman J, Chapman G

The features of seam gas drainage from the point of view of mathematical modelling are outlined and discussed: 1. The use of conventional single phase gas reservoir simulator for very simplified modelling. 2 Alteration of a conventional petroleum reservoir simulator into a specialised simulator for seam gas drainage. 3. Application. of a conventional petroleum reservoir simulator for modelling of seam gas drainage by the way of pseudo-functions and sacrifying one dimension.

Jan 1, 1982

Significantly reduce respirable dust exposures of longwall shearer operators when cutting out at the headgate. Approach As a result of Bureau research, a ventilation curtain is recommended to be mounted between the stage loader and the coal rib to more effectively prevent the ventilation air from blowing across the shearer drum as it cuts out at the headgate. Some mine operators already employ this method of reducing dust, but a vast majority do not. How It Works One source of extreme concentrations of respirable dust for longwall shearer operators is the shearer headgate drum as it cuts through into the headgate entry. As the drum cuts into the entry, it is exposed to the primary ventilation airstream. The high velocity air passes through and over the rotating drum, picking up large quantities of dust.

Jan 1, 1982

By Bruce H. Baker

Studies of used or unused refractory materials are excellent examples of applied mineralogy in industry. Refractory materials are mineral substances containing ceramic or chemical bonding systems. Knowledge of the mineral composition, bonding, and textural relationships often explains the resulting physical property values of a refractory and contributes to the interpretation of refractory wear mechanisms occurring in steel plant service.

Jan 1, 1982

By Robert L. Sundeen, Richard V. Wenberg

INTRODUCTION Shotcrete can be defined as spray-applied concrete with a maximum size aggregate in excess of 9.5 mm (0.375 in.). The concept evolved from guniting, which uses smaller aggregate and generally produces concrete with poorer physical properties. The larger aggregate used in shotcrete requires less water in the mix, while offering larger bonding surfaces, thus imparting greater tensile and compressive strengths. TYPES OF MACHINES Two basic designs of shotcrete machines in general use are the wet or prehydrated zero slump and low slump type, and the dry or nozzle hydrated machines. Fig. 1 shows a typical zero-slump machine in a con¬figuration commonly used for small-volume require¬ments. The prehydrated zero-slump machine mixes exactly proportioned batches in a sealed pressurized chamber. "Slugs" of hydrated shotcrete mix and com¬pressed air are sent through a distribution hose to the nozzle where the wet mix emerges as a spray. The spray is directed onto the rock surface by the nozzle operator. The low-slump machine is similar, except that a thick slurry mix of aggregate is delivered throughout the distribution hose to the nozzle. Fig. 2 shows a typical low-slump shotcrete machine used in moderate-volume applications. The nozzle-hydrated shotcrete machine accepts a premixed "dry" (4 to 6% moisture) batch of aggregate and cement. A constant feed of this mix is directed by compressed air through the distribution hose to the nozzle. At the nozzle, water for hydration is introduced into the emerging spray. The hydrated mixture is di¬rected onto the rock surface by the nozzle operator. Fig. 3 shows a typical dry-mix machine. The major difference between the two basic machine designs is the consistency of the shotcrete quality. Pre¬hydrated machines have high degrees of consistency and produce high-strength concrete, resulting from their ability to produce exact mixtures of zero or low-slump concrete within the machine. Nozzle-hydrated machines tend to produce poorer quality concrete because of the difficulty in controlling the water content at the nozzle. Water input essentially is an art. As such it is not precise, and the shotcrete produced is of variable quality. MATERIALS HANDLING Materials handling presents a problem to either type of shotcrete machine. At times considerable quantities

Jan 1, 1982

By Sterling J. Anderson

To define the technical competence and capabilities of a nonexplosive excavation concept, the Bureau of Mines conducted reduced-scale laboratory tests of a mechanical excavation tool called a rock splitter. Hydraulically actuated splitters, capable of generating both radial and axial loads on a predrilled hole, were designed and fabricated. Through paired variable testing and drifting simulation, reduced-scale splitter performance was evaluated in concrete. Testing proved that the rock splitter is capable of excavating within the highly confined drift set-ting and that it offers a distinct advantage over splitters that can generate radial loads only.

Jan 1, 1982