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By Frank C. Aplleyard

The two calcium sulfate minerals-gypsum and anhydrite-occur in many parts of the world, and gypsum has long been of economic importance in the family of industrial minerals. Gypsum, the dihydrate form of calcium sulfate (CaSO4•2H2O) and anhydrite, the anhydrous form (CaSO4) are frequently found in close association, and it is seldom that a calcium sulfate deposit will consist exclusively of one mineral or the other. Although known gypsum deposits are extensive, anhydrite makes up the largest part of total calcium sulfate reserves. However, it has very minor economic use, and most of the following discussion will be devoted to gypsum. Calcium sulfate is one of the principal constituents of evaporite deposits, and when pure, has the following composition: [Sulfur Combined Lime Trioxide Water (CaO) (SO,) (H2O) Gypsum 32.6% 46.5% 20.9% Anhydrite 41.2% 58.8% -] Deposits of pure gypsum or of pure anhydrite which are large enough to be considered commercial have never been found because of both the metastable relationship between the two minerals, and the presence of impurities such as calcium or magnesium carbonates, chlorides, other sulfate minerals, clay minerals, or silica. As a result most mine production of gypsum will range between 85 and 95% pure. Often it is used as mined, although in certain cases, one or more forms of mineral beneficiation are employed to upgrade the product. End Uses The largest use for gypsum is based upon the unique property which calcium sulfate has of readily giving up, or taking on, water of crystallization. With the application of a moderate amount of heat in a process known as calcining, gypsum is converted to plaster of paris (the hemihydrate of calcium sulfate, CaSO4 ½ H2O) which when mixed with water will set or harden as the calcium sulfate returns to the dihydrate form. This semifinished product, usually called stucco, is then manufactured into a large variety of plasters, wallboard, and block for construction use, or into plasters for industrial applications. About 75% of the gypsum used in the United States is calcined for these purposes. Uncalcined uses of gypsum are principally as a retarder for portland cement, as a soil conditioner, as a mineral filler, and other minor industrial applications. About 25% of the gypsum mined in the United States goes into these markets; however, in less developed countries where construction and other industrial uses may be quite limited, the use of uncalcined gypsum for portland cement retarder may well be the dominant-if not the only-market for the mineral. It has often been noted that calcium sulfate constitutes the world's largest reserve of sulfur, and minor use of both anhydrite and gypsum has been made to produce sulfuric acid or other sulfur compounds such as ammonium sulfate. However, because sulfur is readily available at lower cost from other sources, use of calcium sulfate has been limited to only a few locations where it could compete economically. No such use is reported in the United States at this time. Mineralogy Anhydrite, CaSO4 because of its geologically rapid conversion to gypsum, and relatively high solubility (about 0.2 g per 100 g H2O) is not often found outcropping in climates wet enough to support abundant vegetation except on steeply dipping slopes or other places where hydrated material is continuously removed. Anhydrite rock is most often light to bluish gray in color, and under the microscope, varies

Jan 1, 1983

By Robert W. Roscoe

For over a century, St. Joe Minerals Corporation in Southeast Missouri has been sinking shafts for their lead mining operations. Upon discovery of the Viburnum Trend, or "New Lead Belt", St. Joe brought its experience and expertise in shaft sinking to the area. Eleven shafts were then sunk in an 18 year period, ending in 1972. In 1981, St. Joe began sinking a new shaft in the Trend with hand-picked employees from the four operating lead mines and service facilities. The paper describes the general history of St. Joe shaft sinking methods and equipment, focusing on the current development of the Viburnum No. 35 Shaft.

Jan 1, 1983

By Ralph W. Barbaro

In the mineral industry, the objective of a mining venture is to extract, process, and market a mineral commodity in such a manner that the profit of the venture is maximized. In a mining venture, a company normally has control over mine production scheduling, the selection and location of processing facilities (mineral beneficiation plants, smelting plants, refineries, or blending facilities), processed ore blending, and the selection of markets. The flexibility of the above factors provides many alternatives to satisfy the needs of each market with regard to quantity and quality of ore. The purpose of this paper is to present a mathematical model for determining the alternative that yields the maximum profit. Production planning is generally concerned with the best utilization of fixed resources, more specifically, with the determination of production and inventory levels to meet fluctuating demand requirements. A mine can be any source of ore such as an entire mine, a production unit within a mine, or an independent supplier. The objective of production scheduling is to determine the times at which each mine will be used and to allocate a required level of production. Production planning and scheduling problems are intimately associated with the location of new and existing mines and processing facilities. Although the location of the mines is usually fixed, there can be considerable flexibility in locating new processing facilities, in the selection of the processing plant, and in blending the ore before and after processing.

Jan 1, 1983

By Wallace W. Roepke

Four bit designs, two conical and two radial, were tested in coal against a 60° conical reference bit to obtain data on orthogonal cutting forces and primary respirable dust generation. One conical and one radial design were modified by the Bureau of Mines for these tests. Results were mixed: One radial bit used substantially lower overall cutting forces and specific energy than the other bits and was the only cutter lower on energy and most forces than the standard 60° bit. How-ever, it generated more specific and total dust than any other bit. The four bits were also tested for incendivity, with a 90° plumb-bob bit as the reference. The frictional ignition tests were designed to simulate both trimming top rock and cutting such rock during advance on-sump. Results of these tests were also mixed. The radial bits were substantially less incendive than the reference bit and caused no ignitions in either top trimming or sump modes. Only the modified mushroom-tipped conical bit caused ignitions. Bits similar to this modified design should not be used on drum-type miners in gassy mine areas; in-stead, the other types of bits tested should be used to reduce ignition potential to a minimum.

Jan 1, 1983

By L. R. Verney

A number of interrelated factors influence the economics of the sulphide smelting of copper, lead, zinc and nickel. This paper discusses these factors, mainly from a US point of view, and shows how they affect the cost of construction and operation of new and existing plants. The paper shows how metallurgical plant construction costs and the consumer price index have increased at a much faster rate than metal prices thereby making some metal mining and production operations within the USA, Canada and the EEC less profitable than operations elsewhere. This in turn inhibits new "grass roots" metallurgical developments. It is explained how retrofit of existing pyrometallurgical plants can be a more viable development than the construction of "green field" plants, especially if such retrofit improves, energy efficiencies, overall operating costs and reduces emissions of sulphur and other toxic wastes. Some aspects of metallurgical plant operation are examined, especially for copper and nickel, to show how changes in operating practices may develop in order to improve overall smelting economies, especially when developed in conjunction with objective retrofit. The paper also examines some financial aspects, especially insofar as the disparity between terms for loans offered to third world countries and the USA and the EEC are concerned and also comments upon the need, especially within the USA, for legislation to permit rapid depreciation of capital. Specific comments are made about environmental aspects, including the lack of uniformity of pollution control legislation and how environmental considerations may have some bearing of the location of future smelting operations.

Jan 1, 1983

Cement kiln dust (CKD) is a waste product generated at the rate of 4 to 12 million tons per year in the United States. The dust has considerable resource potential as a neutralizer for coal mine waste effluents and as a lime substitute in the agriculture and construction industries. However, little information has been published on the composition and characteristics of CKD, and a concern arose over the potential environmental effects of the waste when an analysis of a single sample from West Germany revealed lead and zinc concentrations of 5,620 µg/g and 16,200 µg/g, respectively. To assess the hazardous waste potential of CKD,

Jan 1, 1983

By D. M. Dabbs

A static dew point technique has been used to evaluate the solubility of arsenic in ?slag and its dependency on P02 at temperatures of 1458 and 1523K. The ferrous-ferric ion ratio of the slags ranged from 3.9 to 23.8. These values correspond to partial pressures of 02 ranging from 10-8 to 10-12 atm. The solubility of arsenic in slag was found to be independent of? P02? The data indicate that elemental arsenic exists in silicate ?slags. This result was further substantiated by mass .spectrometric analysis of doped slag specimens.

Jan 1, 1983

By Roy E. Peterson

The Bureau of Mines has been developing and evaluating methods for beneficiating the large deposits of nonmagnetic (oxidized) taconite located on the western Mesabi Range. In this segment of the research, a sample representing about 0.5 billion tons of nonmagnetic taconite from near Grand Rapids, Minn., was beneficiated using a reduction roasting, magnetic separation, flotation process. The sample contained 32.1 pct iron and 49.1 pct silica. Tests were conducted both on a bench scale and with a 1,000-lb/h pilot plant. In the bench-scale research a con-centrate containing 69.0 pct iron and 4.5 pct silica was produced with an iron recovery of 82.1 pct. In the pilot plant, reduction roasting was conducted in a 35-ft kiln using lignite as the reductant and major source of fuel. Dust from the kiln exhaust was pelletized and recycled to the kiln. The roasted taconite was beneficiated by magnetic sep-aration and flotation to produce a product containing 67.9 pct iron, 5.5 pct silica, and 69.7 pct of the iron in the kiln feed. The cyclone separation in the grinding circuit was sharpened by demagnetizing the cyclone feed in a 400-Hz, 1,000-Oe magnetic field.

Jan 1, 1983

By Paul E. Loustaunau

This report describes a project in which three structured underground coal mine equipment operator training programs were developed. The project was carried out in two parts. In the first part, a research study was conducted to determine how on-the-job training is currently conducted in industry, and to determine the overall effectiveness of current on-the-job training. In addition, the possible application of the principles of social learning theory to on-the-job training was investigated. In the second part three prototypes on-the-job training programs were developed for shuttle car operation, roof bolter operation, and continuous miner operation. These programs were carefully structured to eliminate the shortcomings of current industrial on-the-job training identified in the research study and incorporated the application of relevant principles of social learning theory. The programs are prototypes which underground coal mine training personnel can use as models to develop their own customized equipment operator training programs.

Jan 1, 1983

By Robert J. Greaves

High-resolution seismic reflection profiling can be used to evaluate detailed struc¬tural and stratigraphic features of coal pros¬pects. Since most coal prospects are relatively shallow (less than six hundred meters deep), the vertical and lateral resolution of seismic data can be significantly improved by high sampling rates in space and time. The case study present¬ed shows the effective use of seismic data in evaluation of the Wyodak coal at a prospective coal gasification site. The data were used to map the detailed structure and thickness of the coal and to search for lateral discontinuities, such as pinchouts and. faults. An important find was a paleochannel cutting across the base of the coal seam, which was later confirmed by drilling.

Jan 1, 1983

By William H. McLemore

Geologists searching for carbonate rocks suitable for chemical uses traditionally have relied on extensive laboratory testing in order to locate strata or zones that might be suitable for mining. However, when considering the significant time and costs involved in sampling and performing chemical analyses, any exploration technique whereby fewer samples and analyses are needed would be of great value. In other words, if the exploration geologist could "zero-in" on select areas, considerable time and money could be saved. In general, the major-element chemistry of carbonate rocks is determined by the abundance of the minerals present. CaO occurs with CO2 as the mineral calcite, which is the primary mineral comprising allochems, matrix and sparry cement; MgO is found in high-magnesium calcite (many calcite fossil species contain appreciable amounts of MgO in solid solution), dolomite, and chlorite; iron occurs in pyrite and in limonitic stylolites, as well as in chloritic and glauconitic clay minerals; materials containing abundant Si02 are microcrystalline quartz (chest) silt-sized quartz, and clay minerals; and Al203 is found primarily in illitic, kaolinitic, and chloritic clay minerals. The presence or absence of these minerals determines the chemical composition of the carbonate rooks.

Jan 1, 1983

By George Kachaniwsky

Until mid-1982 the Mines Gaspe copper smelter consisted of a fluid bed roaster, a reverberatory furnace, two Peirce-Smith converters of which only one was blowing at any one time, anode casting facilities, and a single contact sulphuric acid plant treating both roaster and converter gases. Reduced concentrate supplies have led to the shutdown of the roaster and, as a result, it was necessary to adapt the converter and acid plant operation to the new operating mode: green concentrate smelting with resulting lower matte grades and acid plant treatment of off-gases from only one blowing converter. Therefore, modifications were carried out to existing equipment and methods of operation and control. This paper describes the result of work done to obtain steady, maximum strength, converter off-gas flow and an efficient acid plant operation. Topics covered include: optimization of converter operation, tightness of hood and off-gas ducting, improvements in acid plant/converter communications and modifications of acid plant operation and control to cope with the fluctuations in converter gas flowrates and strengths.

Jan 1, 1983

By Gary G. Grim

The reliable performance of the coal reclaim system is essential to the continued availability of a coal-fired electric generating unit. The control of fugitive coal dust within the areas housing the reclaiming equipment is necessary not only to minimize maintenance and clean-up costs, but is also a safety and health consideration. This paper describes the reclaim system control and dust suppression systems as initially installed, the shortcomings of these systems and the steps eventually taken to correct these shortcomings.

Jan 1, 1983

By Westcott PC

The development of a coal project must pass through a number of phases, taking it from a preliminary evaluation through to detailed mine planning. For each phase the cost of data acquisition and associated mining studies increases exponentially for linear improvement in confidence levels. Within each mine planning phase there are four main activities. These are the economic ordering of reserves, the development of optimum mining strategies, mine design and scheduling and finally the estimation and analysis of costs. The development of the optimum mining strategy is one of the most critical aspects of a mining evaluation and the application of economic criteria at this stage of the project is vital to the successful generation of an optimised mine design. A recommended method is the concept of Economic Ratio (ER) which expresses the likely cost of mining from a given location in a deposit in terms of the value of the product likely to be recovered. The most economic mining strategy will be to mine areas from low economic ratio to high economic ratio within the constraints of reasonable equipment application. When selecting equipment a particular machine should not be selected solely on comparison with other machines in isolation, but the total application must be analysed. In the final selection the decision should be based on whether or not it has a beneficial effect on overall project economics. The economic assessment must take into account the time value of money, so the real cost can be determined with adequate provision for capital and operating costs over different time spans.

Jan 1, 1983

By Allen L. Frank

A portable radon diffusion chamber has been tested with electrical collection of the radon daughter nuclei for enhancement of sensitivity. The detector size was small enough to be worn suspended from the belt. With a battery-supplied high voltage the sensitivity was found to be 1.43 tracks/cm2 per pCi-hr/l of ambient radon at Sot relative humidity. The track densities on the surfaces of the CR-39 plastic nuclear track detectors were found to be non-uniform, making difficult the determination of average densities with high accuracy. The fabrication of electrets for use in the detector was investigated in accordance with published techniques with negative results.

Jan 1, 1983

By Floyd R. Hertweck

The helium resources of the United States were estimated by the Bureau of Mines to be 1,037 Bcf as of January 1, 1981. These resources are divided into four categories, in decreasing degree of assurance of their existence: (1) helium in storage and in measured natural gas reserves, which totals 211 Bcf, (2) helium in indicated natural gas resources, which is estimated at 207 Bcf, (3) helium in hypothetical natural gas resources, which is estimated to be 318 Bcf, and (4) helium in speculative natural gas resources, which makes up the remaining 301 Bcf. These helium resources are further divided into depleting, nondepleting, and stored classifications, The depleting resources are those associated with natural gasfields that are, or will be, produced for the natural gas they contain. All of the helium in undiscovered (hypothetical and speculative) natural gas resources is included in this classification. These depleting resources are estimated to contain 897 Bcf of the total helium resource base. Nondepleting resources are those in shut-in, abandoned, or otherwise nonproducing natural gasfields. Helium resources contained in nondepleting natural gas resources are estimated to total 100 Bcf. There is 40 Bcf of helium in storage in the Federal Government-owned Cliffside Gas Field near Amarillo, Tex.

Jan 1, 1983

By J. P. Matoney

The operation of a modern coal preparation plant, particularly in western Canada, is a very complex task. Most western Canadian operations are processing two or more, sometimes up to ten, different seams through the same plant. This requires a sophisticated multi-circuit plant that needs close operational control. Add the soft nature and large amounts of natural fines of western Canadian coal and you have a formidable cleaning task. To assist in the operation, programmable controllers and sophisticated control concepts are being more widely used. Two of the newest coal preparation plants in Canada have been designed by Raymond Kaiser Engineers Inc. and its Canadian subsidiary, Phillips Barratt Kaiser Engineering, Ltd. The use of programmable controllers and control systems will be illustrated by showing their application in a "typical" western Canadian coal plant. This example will cover flowsheet design, control concept systems application, and possible future uses.

Jan 1, 1983

By P. M. Brown

The Bureau of Mines is investigating a dewatering technique for coal-clay waste that uses a flocculant, polyethylene oxide (PEO). This flocculant forms strong stable flocs that can be dewatered on a static screen. A field test unit (FTU) using this technique was operated at approximately 400 gal/min, using a waste stream from the flotation circuit of a coal preparation plant. Consolidated coal-clay material con-taining 55 to 60 pct solids was produced when the flotation circuit slurries of 2.7 to 8 pct solids were treated with 0.1 to 0.3 Ib PEO per ton of solids. The FTU was also operated at 64.5 and 87.5 gal/min using a portion of the underflow slurry from the preparation plant's thickener. Consolidated coal-clay material containing 55 to 60 pct solids was produced when the thickener underflow slurries of 19 to 24 pct solids were treated with 0.08 to 0.2 Ib PEO per ton of solids. PED-treated materials continued to dewater when placed in a pit.

Jan 1, 1983

By Frederic L. Kadey

Perlite, as a volcanic glass, has been recognized since the Third Century, B.C. (Langford, 1978). The precise details of discovery often become lost in antiquity, and the variations among the stories pertaining to the more recent discovery of perlite as a material of commerce are no exception. Credit in the United States is given to a dentist who, while experimenting with tooth enamels about 1941, discovered that perlite-the rock-intumesced when subjected to heat. At about the same time it is reported that the chief geologist of Silver and Barytes Ores Mining Co. attempted to put out a picnic bonfire on the shores of Milos Island, Greece by throwing beach sand on it. The ensuing pyrotechnic display immediately conjured up in that man's mind the possibility of a new use for the volcanic rock that constituted most of the island. Very little was done with this discovery either here or abroad until after World War II. Today the name perlite is applied to both the hydrated volcanic glass, generally of rhyolitic composition, and to the lightweight aggregate that is produced from the expansion of the glass after it has been crushed and sized. Petrologically, it is defined as a glassy rhyolite that has a pearly luster and concentric, onionskin parting. Occurrences of perlite are restricted to several Tertiary to Quaternary age rhyolitic belts that trend in a generally north-south direction around the world. Commercially suitable deposits generally occur as domes of several hundred feet in height, although glassy zones in welded ash-flow tuffs and others associated with dikes and sills also have been reported. Mining is by ripping and blasting from open pits. Because of weight considerations, perlite usually is shipped to the local market area for subsequent expanding. In the United States, New Mexico leads in production with Arizona, California, Nevada, Idaho, and Colorado following in approximately that order. The principal use for expanded perlite is as a lightweight insulating aggregate in cryogenics, in plaster, concrete, and in loose fill insulation. Expanded perlite is also used in horticultural applications, and after subsequent milling and classification, as a filter aid. The United States is the world's largest producer and consumer of perlite. Table 1 shows the world production of perlite and Table 2 shows the perlite mined, processed, expanded, and sold or used by producers in the United States. Geology Composition and Morphology Any discussion of perlite must take into consideration its dual nomenclature, for it is known by the same name as both the naturally occurring rock and, after processing and expansion, as the lightweight aggregate of commercial significance. In its naturally occurring form, perlite is a rhyolitic glass that contains from 2 to 5% combined water. While perlite also can occur as andesitic or dacitic glass, these latter types are of negligible commercial significance. Table 3 lists the chemical composition of a few typical perlites (Anderson, et al., 1956; Langford, 1979). What sets perlite of commercial significance apart from other volcanic glasses is the fact that under the proper conditions of preparation-crushing and sizing-it will, when rapidly introduced into a flame of sufficient temperature, expand or "pop." All of the elements of composition contribute to the expansibility of the rock. The role of the combined water, however, is the most significant because it is believed not only to produce a fluxing effect in the softening of the highly siliceous glass prior to expansion, but it is also responsible for the explosive force of expansion through volatilization during heating. The current theory of the origin of the water in perlite is now less con-

Jan 1, 1983

By F. L. Jackson

When using perlite as an insulation, it is important to determine the requirements for different applications as this influences the processing of the perlite. In cryogenic applications, perlite properties of low density and fine particle size are desirable, while Loose fill insulation applications require similar properties and water repellency. However, in perlite insulating concrete applications, a coarser particle, of higher density, is required to provide improved compression strength. The essential properties of perlite including, particle size, density and surface treatment are discussed in relation to the various insulation applications. Also typical mineral processing and manufacturing techniques are reviewed

Jan 1, 1983