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By Guerry H. McCullen, Bruno Despujol

Quartz and phosphate grains from concentrates and ores from Atlantic Coastal Plain sediments often are wholly or partially coated by humates. Coatings were studied in situ using infrared microscopy, by transmission Fourier transform infrared of extracts, and scanning electron microscopy. The 14C age of the coatings is about 20,000 years, much younger than the mineral substrates. Coatings on double flotation concentrates indicate that the conditioning pH may be too low, allowing coated quartz grains to follow phosphate grains through beneficiation. Organic matter from coatings may contribute to processing problems as well as affect final product quality.

Jan 1, 1999

By Heribert F. Broicher

As of 1998 German companies have been engaged in research and development of LIF analyzers for rock identification, i.e. for the fingerprinting of rock by the analysis of laser-induced fluorescence (LIF). Test work in Germany, Sweden and South Africa showed the potential of this new technique, which operates online and in realtime (1). In 2003 the Finnish company IMA Engineering Ltd Oy commenced building and marketing LIF analyzers under the trade name OreSpex. Today, one OreSpex analyzer has been installed in the Kiruna Mine, Sweden to check the phosphorus content of train loads. In 2004 a second OreSpex analyzer was built for dilution control in the Argyle Diamond mine, Australia. In 2005 another LIF analyzer will be used for test work in various mines in the US. The principles of the technology and status of ongoing work are presented.

Jan 1, 2005

By James S. Browning

The principal uses of fine ground mica are as filler in wallboard joint cement, as a filler and surface coating for roofing, as an ingredient in paints, and in oil well drilling mud. The mineral has other uses in the manufacture of rubber, wallpaper, plastics, welding rods, electric insulation, house insulation, and textiles, and as an annealing agent in metal treatment. In recent years, more than 999 percent of the domestic mica produced has been scrap and flake mica (mica which does not meet specifications for sheet mica and is used for producing fine ground mica). There has been a continued increase in mica production for, several years, the 1963 production of scrap and flake mica totaling 117,251 tons.

Jan 1, 1966

By K. M. Belingheri, M. E. Smith

Pinson Mining Co. operates a conventional mill and two heap leach operations in north-central Nevada. The latest of these heap leach operations, the Preble project, is a low-grade, low-tonnage property made profitable through several innovative capital reduction techniques. Rapid return on investment was a prime factor in design. To facilitate this, fast-track design and construction techniques were employed. The project is a seasonal 1.5 kt/d (1 700 stpd) crush/agglomerate heap leach plant using both clay and plastic leach pads. Construction and startup were achieved through cooperative arrangements between local contractors and in-house construction personnel, with few items put out to bid. An interactive approach to design minimized lost time and construction costs.

Jan 1, 1987

By J. L. Ellenberger, P. W. Jeran

A deep longwall coal mine was instrumented with a three-dimensional microseismic system in order to help determine the exact strata mechanics associated with the rock failure, redistribution of stress and the associated gob formation from the longwall. Overall, 5,000 well calibrated seismic events were recorded during the mining of the panel. Analysis of these events showed a close correlation between the seismic activity and advance rate, and that the majority of the recorded seismic activity occurs in the immediate area of the advancing longwall face.

Jan 1, 2002

By W. M. Schafer

The risk that water quality will be degraded by mining activity can be evaluated using risk analysis techniques. Water quality impacts can occur where water-rock interactions with tailings, waste rock, or leached ore lead to increased loading of constituents into surface or groundwater. Constituent loads contributed by mining facilities are determined by the migration route and chemical evolution of mine water. Mass load contributions from mines can be determined by estimating the prototype pore water in contact with mining waste, predicting the rate and timing of flow, assessing the degree of geochemical attenuation, and modeling chemical mixing with natural surface or groundwater. Mining facility siting and design measures can alter the chemical evolution of mine water by varying the quantity or quality of flow. Stochastic risk management techniques provide a powerful tool for quantitatively identifying the environmental consequences of various siting and design alternatives.

Jan 1, 1998

By C. C. Harvey

Based on resource studies in many developing countries, four categories of industrial clay resources are recognized as precursors to development strategies. Category I: High quality, high technology clays requiring major investment for large tonnage international markets. Category 2: Unique specialty clays requiring advanced technologies for small tonnage niche markets. Category 3: Lower technology, moderate quality clays, predominantly to supply local markets. Category 4: Low quality clays requiring little or no processing. Projects with Categories 1 and 2 clays require extended development times (green field to investment decisions) with significant pre-development investment, while projects with Categories 3 and 4 clays require shorter development timetables and lower levels of investment.

Jan 1, 1998

By Frank S. Hicks, Y. Charles Guan, Glenn A. Gruber

This paper describes a two-part program funded by the Florida Institute of Phosphate Research and performed by Jacobs. The first part of the program was to examine the application of ultrasonic treatment to clean phosphate particle surfaces. Florida phosphate pebble and rougher flotation feeds were treated in an ultrasonic trough to remove clays. Also, the de-oiling of rougher concentrates by ultrasonic treatment was tested. In order to improve the clay removal efficiency, viscosities of primary cyclone overflow from six beneficiation plants were studied in the second part of the program. Viscosities for different samples at the same clay % solids vary significantly, and increase exponentially with clay % solids content for the same sample. A method of controlling cyclone operation using on-line viscosity measurements and pump box level sensors is proposed to logically improve primary cyclone performance.

Jan 1, 2002

By P. F. Mataich

When the subject of plant computers is brought up most people visualize the computer's controlling the entire plant with very little operator intervention. Actually, this picture is true today in only a limited number of cases and will certainly not be true in the minerals industries for many years to come. There are several ways in which a plant computer can significantly contribute to improving plant operation and closed loop control is only one of these. First of all, what are the basic ingredients for good plant control? For good plant control, two requirements must be met. First, the operator must get good information feedback from the process and then he must know what action to take in response to this information. Control information can be obtained through instruments, laboratory analyses, or through simple visual observation. If it is timely and accurate and the operator knows how to use it, then we have the makings of a good plant control system. The computer can be of help in both these areas by getting good data back to the operator and in helping to develop a good control scheme for the plant.

Jan 1, 1966

By H. W. Newcomen, D. R. Brox

Assessments of the stability performance of open pit highwalls have traditionally been based on consideration of surface movement rates. Although generally accepted in industry, this approach presents challenges for establishing appropriate threshold values to allow for safe mining operations and does not address the issue of total strain. Surface movement monitoring data from a limited number of open pit mining operations in North and South America has been evaluated in terms of highwall strain, rock mass quality and inferred mechanism of instability. Threshold strain levels for key stages of highwall stability proposed from previous work have been reviewed and are generally endorsed based on evaluation of additional data. An empirical highwall strain criteria for the assessment of highwall stability performance is postulated based on the observed trends in highwall strain data from the case histories presented.

Jan 1, 2004

By A. A. Terchick

It has been reported in the literature that there is a substantial economic incentive for removing sulfur from coal. Therefore, U. s. Steel initiated an investigation to determine the feasibility of lowering the sulfur content of its Pittsburgh-seam coal. Preliminary crushing and washability studies on a representa-tive sample indicated that substantial sulfur reductions could be attained. Figure 1 shows the effect of the top size of a given coal sample on the sulfur content of the float-l.45 specific-gravity fraction of coal. At a top size of 3 inches, the raw-coal sulfur content of 2.32 percent was reduced to 1.64 percent. Crushing to a top size of 20 mesh reduced the raw-coal sulfur to 1.25 percent. Below a top size of one inch, the sulfur content decreased rapidly as top size was decreased. Figure 2 shows the effect of specific gravity of separation on pyritic sulfur. Normally this coal has an organic-sulfur content of approximately 1 percent. As expected, pyritic sulfur was reduced as the separating gravity was lowered for all the various size fractions shown. The rate of decrease in pyritic sulfur was gradual above 1.45 specific gravity, but great below 1.45. Greater sulfur reductions were attained on the coarser sizes with decreasing

Jan 1, 1971

By Robert J. Russell

The importance of grinding as a unit operation in all industry has caused much effort to be expended toward improving the facility with which grinding can be done. Endeavor has continued nearly 100 years to formulate laws governing crushing and grinding. This has not been without controversy. However, grinding is an experimental science and our useful knowledge originates in experience. The recorded experience is grinding history. Today, many types of size reduction equipment, each with variations, are available to industry. Frequently, more than one type of grinding equipment will meet a requirement of grinding. However, an economic evaluation of installation and operating costs generally indicates a preferred type. The selection of grinding equipment requires' a consideration of the purpose in grinding, the characteristics of the material to be ground, equipment available for grinding, and the manner in which it can be applied best.

Jan 1, 1960

By Rustu S. Kalyoncu

Rainbow colors of roofing granules, adorning the roofs of buildings from single family units to largest office buildings, have their origin in the roofing shingles as burlap soaked with tar appearing as early as the 1700s. Dusting of talc and mica on the coated surfaces, to keep roofing from sticking to itself in storage, represents an early improvement to the original construction product. Sometimes, colored, natural mineral dusts were added as color pigments within the dusting material, for initial color. Prolonged exposure to sun caused the asphalt to become brittle, and it eventually cracked and leaked. Search for solutions to cracking and subsequent leaking problems eventually led to the use of crushed mineral granules on asphalt coated shingles. This provided the impetus for further growth in the asphalt roofing industry. Application of a layer of crushed mineral on the asphalt coating minimized the coating deterioration from exposure to ultraviolet light, thus significantly improving the shingle life. In the 1900s, screened waste from slate quarries was the most commonly used granule in asphalt roofing products. Records indicate the use of coarse slate screenings for asphalt roofing as early as 1906. As the asphalt roofing industry further developed, other naturally colored minerals, such as silica sand, quartz, mica, feldspar, talc, slag, granite, rhyolite, and oyster shells were used on roofing surfaces. Later on, a number of manufactured granular materials, such as crushed brick and tile, fire clay, and white porcelain were used. The first artificially colored roofing granule was produced in 1914 by running molten slag into a solution of alkaline metal silicate, which was absorbed by the porous slag. Various colors were obtained by adding pigments to the silicate coating and by subsequently heat treating the granules. In 1922, another technique was developed in which green slate granules were saturated with copper sulfate solution and heated to 760°C to form copper oxide. Since then, many other granule coloring processes have been patented, one of the most significant being the sodium silicate coatings introduced around 1975. Granules as used in construction (specifically roofing materials) are defined as natural or synthetic-mineral grains smaller than gravel and larger than sand in particle size. They are used primarily for protective and decorative purposes on the weather- exposed surface of asphalt composition roofing. Development of artificial coloring techniques has made it possible for the roofing industry to provide asphalt roofing shingles in a wide variety of colors complementing the color and style of buildings. Roofing granules, as we see today, are the products of long technological evolution.

Jan 1, 1994

By M. A. Greenwood

The total value of coal, FOB mine, consumed in the United States was $21 billion in 1985. Roughly $6 billion was spent to transport coal from the mine to the consumer by rail. This indicates the impact railroad transportation has on the competitiveness of U.S. coal as an energy resource. Actually, this is just the tip of the iceberg. When you consider the largest U.S. reserve of coal, the Powder River Basin, which is possibly the lowest cost coal in the U.S., or maybe even the world, the transportation cost is the overriding factor in developing competitive pricing. Rail transportation costs from Powder River can be multiples of 2, 3, or even 4 times the cost of coal FOB mine. About sixty percent of all U.S. coal is shipped by rail. In the case of Powder River Basin coal and many other reserves there are no current alternatives to rail. Are there feasible alternatives to rail transport?

Jan 1, 1986

By J. H. Calder, J. C. Hower

Three lithotypes of Phalen coal from Cape Breton County, Nova Scotia, Canada, were subjected to a modified Hardgrove grindability index (HGI) test. The testing scheme differed from conventional (ASTM D-409) Hardgrove testing by, in one case, repeating the test three times prior to removing the -200-mesh fine coal from the Hardgrove mill, and, in a second test, removing fines after each of three successive Hardgrove tests. Only the first stage of the latter testing scheme actually conforms to the standard HGI test. All processed samples were analyzed petrographically by a combined maceral/microlithotype analysis. The increase in the percentage of coal ground to -200 mesh increases through the 60- to 180-mesh fractions for each of the lithotypes for the following two apparent reasons. First, with progressive grinding, more of the oversize material is close to 200 mesh (75 µm), creating a "pool" of particles ready to be ground to -200 mesh, and, second, the removal of fines from the system at each step eases the grinding at the successive step. The fines retained system shows the influence of buffering of further grinding by the particles retained in the grinding mill. The Phalen lithotypes and the series of Central Appalachian coals, evaluated previously by Hower and Wild (1994), differ in that an increase in vitrite and a decrease in trimacerite is observed in successive -200-mesh fractions in two of the Phalen lithotypes. This is the opposite of the trend observed in the slightly lower-rank Central Appalachian coals.

Jan 1, 1998

By David R. Reid, Lawrence W. Talbot

INTRODUCTION In the mining industry, timing in land acquisitions can be of the essence. In order to secure promising lands, deals are often negoti- ated quickly and evidenced by letters of intent containing what the parties feel are the essential terms of the deal. In some cases, a company is willing to acquire land only if it can lock up a number of promising properties, and so a "non-binding" letter of intent is used to formalize the essential terms, while leaving the company without legal liability. Later, the letters of intent will be sent to a lawyer to prepare a formal acquisition agreement. Many times, how- ever, especially in a land acquisition rush, another company will attempt to better the deal prior to the execution of that formal agreement, and the first company will be forced to rely on the initial letter of intent, only to find out to its chagrin that it has no deal In other cases, the company holding the desired property is another mining company, and the negotiation of an option or joint venture is the only way the first company can acquire an interest in the desired land. In order to make its offer more attractive, it may have to reveal confidential or proprietary information about the property or the surrounding lands. Here, too, letters of intent are often used to formalize the essential points of the agreement. Once again, however, prior to the execution of a formal joint venture agreement, the transaction may collapse and the letter of intent prove to be only that. In this paper, the authors examine the dangers associated with the use of letters of intent and the specific provisions courts look for to find a binding contract, and consider how to increase the

Jan 1, 1988

By P. Somasundaran, S. E. El-Mofty

A comparison of the IMC Anionic Process and the CLDRI Process, based on pilot plant testing of waste pebble by Jacobs Engineering is presented. Estimated costs for constructing and operating a beneficiation plant utilizing dolomite flotation are given. Research to develop practical flotation processes for removing dolomite from low-grade phosphate rock has been a high priority for the Florida Institute of Phosphate Research. The Institute funded the above pilot plant programs in 1998 and 2000. The Florida Phosphate industry currently deals with the increasing dolomite content of ore reserves by practicing selective mining. Heavy media separation plants installed at two mines to remove dolomite from pebble are not being operated. The flotation separation of dolomite from waste pebble requires that the flotation feed be ground. Grinding liberates the mineral species and produces particle sizes small enough to be floated. Only two dolomite flotation processes, the IMC Anionic Process and the CLDRI Process, have been successfully demonstrated on flotation feed that has not been deslimed after grinding. Deslimed flotation feed, relative to undeslimed feed, has improved flotation performance and reduced reagent consumption. However, for the above mention processes, undeslimed ground feed increases the yield of concentrate because the phosphate desliming losses are avoided.

Jan 1, 2002

By Dae S. Young, Eleonora Widzyk-Capehart

A quantitative estimation of the size distribution of rock fragments is extremely important in mining, metallurgy and other geotechnical fields. This paper presents a new approach to the analysis of fragmentation. The method combines the practicality of digital image processing of the rock surface with the theoretical volume calculations based on the principles and laws of fractal geometry. The final volumetric distribution curve is compared with the results from traditional sieving indicating close agreement.

Jan 1, 1996

By W. Kemp Wait

Electronic ore sorting has been in use for over 15 years at many mining operations worldwide. Photometric ore sorting, which operates on the basis of measuring light reflectance levels of a rock surface, is in use at various locations on ores such as limestone, magnesite, gold, talc, spodumene, tungsten and coal. Radiometric sorters have been employed on uranium deposits in the western U.S.A. as well as at certain South African go1 d mines where preconcentrating gold is achieved using uranium association as a detector. A new ore sorter, employing two sensing parameters has been developed. Utilizing both photometric and conductivity sensing modes, this system has application to many gold ore types of North America. The first production machine has been installed at a gold mine near Beardmore, Ontario for the purpose of preconcentrating ore both from waste dumps from past production as well as within the ongoing mining operation.

Jan 1, 1987

By Bernard J. Reddy

This paper describes in detail the economic forces affecting cobalt supply, demand, and prices. The major factors that will determine the growth or decline in the use of cobalt in each of its applications are discussed. The flows of cobalt from mine to refinery are described on a company-by-company basis. The paper concludes with a discussion of how the characteristics of the supply and demand sides of market interact to determine cobalt prices.

Jan 1, 1986