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By Ken Santini, Ronald R. Bauer, Joseph R. Copeland

Wollastonite, named after W.H. Wollaston, an English chemist and mineralogist, is a calcium metasilicate having the chemical formula CaSiO2. Although it is a unique mineral, wollastonite has a short history of industrial use. Wollastonite is the only naturally occurring, nonmetallic, white acicular mineral. Its acicularity is the main reason for its ascendancy in the late 1970s and 1980s as a reinforcing filler and as a replacement for short-fiber asbestos and short-fiber milled fiberglass. Wollastonite is used in applications ranging from bowling balls to automobile fenders, from ceramic tile to automobile brakes, and from thermal insulation board to protective industrial coatings. The United States is the largest producer of wollastonite, with China, India, and Finland as the other three major sources. The United States, Europe, and the Far East are where most of the production is consumed. Geology Mineralogy and Physical and Chemical Properties Wollastonite, a member of the pyroxenoid mineral group, has the theoretical composition of 48.3% CaO and 51.7% SiO2. Iron, manganese, magnesium, or strontium may substitute for some of the calcium. Commonly associated minerals include garnet, diopside, calcite, quartz, epidote, apatite, and sphene. Some of the physical properties of wollastonite are listed in [Table 1]. Wollastonite is largely chemically inert; however, it can be decomposed in concentrated hydrochloric acid. Some wollastonite will fluoresce under shortwave or longwave ultraviolet light, or both, with colors ranging from pink-orange to yellow-orange and, more rarely, bluish green. In addition, wollastonite may show phos¬phorescence. Because of its unique cleavage properties wollastonite breaks down during crushing and grinding into lath-like or needle-shaped particles of varying acicularity. This particle morphology imparts high strength and is therefore of considerable importance in many of the markets for wollastonite. The acicularity of particles is defined by their length:width, or length:diameter, ratio (i.e., aspect ratio). Individual particles, even the smallest ones, commonly ex¬hibit an aspect ratio of 7:1 or 8:1 and have an average diameter of 3.5 gm. Low aspect ratio products (powder wollastonite, or milled grades) with 3:1 to 5:1 aspect ratios are used as general fillers, in ceramics, and in metallurgical fluxing. High aspect ratio products with ratios of 15:1 to 20:1 are used as functional fillers for rein¬forcing thermoplastic and thermoset polymer compounds and as a replacement for asbestos. The dry brightness and whiteness of wollastonite are also important in determining its suitability for certain filler and ceramic applications. When pure, the mineral is brilliantly white, but impurities may color it cream or gray. Brightness is determined by measuring the reflectance of finely ground powder against a stan¬dard that is assigned a brightness of 100. Magnesium oxide and barium sulfate are the two standards used. G.E. brightness, a term used in North America, refers to brightness measured with a Gen¬eral Electric reflectometer. Commercial wollastonite products usu¬ally have a G.E. brightness ranging from 85 to 95. The Hunter method is also used to measure the brightness of wollastonite. Loss on ignition (LOI), another important property in determining applications for wollastonite, is the amount of volatile matter driven off when the mineral is heated to 1 000°C. Com¬mercial wollastonite products have an ignition loss ranging from 0.5 to 2.0%. Wollastonite's naturally high pH of 9.9 (10% water slurry) is of major importance to its use in the coatings industry. Coatings formulators use milled grades as a pH stabilizer in interior and exterior PVA (polyvinyl acetate) and acrylic latex paints. There are two polymorphs of calcium silicate: wollastonite, a low-temperature form, and pseudowollastonite, a high-temperature form. Conversion of wollastonite to pseudowollastonite occurs at about 1 120°C and results in an increase in the coefficient of expansion and a color change. Pure white wollastonite may change to a cream tint or to various shades of red or brown. This color change is thought to be due to the presence of iron and/or strontium.

Jan 1, 1994

By M. E. Gershon

Software for coal blending has gained a lot of recent attention as micro-computer programs have come on the market. Some of this software is appropriate and some is not. This paper looks at the types of models being used and points out the strengths and weaknesses of each. Recommendations are then made concerning the level of detail required for these programs, relating this concern to the various ways in which coal companies are using these programs. A checklist of company requirements for these programs and available pro-gram-features provides an aid in matching the program to the company.

Jan 1, 1988

By Chris Mark

In the wake of the Crandall Canyon mine disaster, the U.S. Congress asked the National Institute for Occupational Health and Safety (NIOSH) to study the safety of deep cover pillar recovery operations in the US. The legislation defined ?deep cover? to be greater than 1,500 ft, but NIOSH is also evaluating mines at depths greater than 1,000 ft when multiple seam interactions are encountered. By these definitions, there about 35 active mines that engage in deep cover pillar recovery, in the states of UT, CO, VA, WV, and KY. To date, NIOSH has documented ground conditions and ground control experience at nearly all of them. This paper provides an overview of current deep cover pillar recovery practice. Specific ground control issues that are discussed include: Pillar and barrier pillar design, ? Coal bumps, Thick seam pillar extraction, and ? Multiple seam interactions.? INTRODUCTI

Jan 1, 2009

By Yousef Ghorbani, Abolfazl Danesh, Fatemeh Kazemi, Ataallah Bahrami, Morteza Abdollahi, Mohammad Raouf Hosseini

This study aims to investigate the effects of the operational variables on the concentrate grade, recovery, separation efficiency and kinetic parameters of the copper flotation process. The results indicate that concentrate collecting time and pulp density were the parameters with the greatest effects on the concentrate grade. Considering copper recovery, the concentrate collecting time, collector dosage and pulp density were the most significant variables, in decreasing order of importance. The separation efficiency was found to be mainly influenced by the concentrate collecting time. This study can be helpful in identifying the parameters with the most effects on flotation performance and, consequently, the overall process efficiency, including recovery and separation efficiency. Such an outcome can be used as a decision-based tool to apply the necessary changes in a real-life industrial operation in a more effective way to improve the quality and quantity of the flotation concentration.

By Glenn M. Boyce, Timothy R. Coss

Microtunneling first appeared with some regularity in the United States in 1987. Until then, only Japan and Germany utilized this method of construction. Its high costs initially limited its application to special situations. The last ten years have seen the use of new pipe materials, new machines, new cutterheads, new techniques, and an average growth of30 percent each year. This paper documents the growth and changes that have occurred with microtunneling. Based on current industry practices and advances from abroad, this paper postulates what the next ten years may hold.

Jan 1, 1997

By Y. Topkaya, R. E. Johnson, D. Buttinelli, B. R. Palmer, A. Geveci, L. Stoppa, C. Lupi, F. Pochetti

Representative samples of a composite mixture of three typical Cu/Zn complex sulphide ores, namely Black-, Yellow- and Altered-ore, from the Cayeli deposit in Turkey, were used for leaching tests in 2.2 M FeCl3, or 1 M CuC12-2 M NaCl solution in the temperature range from 313 K to 363 K (40O to 90O C), with and without the presence of an organic solvent for elemental sulphur, such as CCl4. The leaching rates of copper and zinc were quite high, as expected, in FeCl3 solution and complete recovery of both metals was obtained at the highest temperature when the solvent was present. However in CuC1, solution, extraction yields of the order of 95% only for Cu and Zn were achieved and the positive effect of the solvent was not clearly shown. The kinetics curves of Cu leaching by FeCl3 indicated a model of reaction rate depending on the particle surface, as in a chemically controlled reaction, in tests with the presence of CCl4. Without the solvent, or in CuCl2 media, the model of the diffusion controlled reaction seemed to prevail. Values of apparent activation energy, in both of the leaching processes, were determined and compared with those reported in literature.

Jan 1, 1993

By R. M. Hays

Jan 1, 1980

By William K. Brown

Are the results of an exploration program worth the cost? This is a question I suspect many of you are familiar with and, theoretically at least, it is an easy question to answer. The answer, of course, lies in comparing the future earnings stream the program is expected to generate, to the present value of the cost of carrying it out. While historical costs can be determined without much difficulty, estimating the value of a future earnings stream involves all sorts of assumptions regarding future costs, metal prices, inflation rates and an appropriate discount factor; and in the context in which the question arises, requires additional assumptions about mineral deposits which have yet to be discovered. As a practical matter, this kind of approach isn't likely to produce a very convincing answer; certainly not one convincing enough to satisfy a skeptical audience; nor one likely to temper the illusions of recent converts to mineral exploration, who are convinced that if enough money is spent, profitable discoveries will inevitably follow. Within broad limits, however, I believe it is possible to analyze the costs and results of gold exploration in the U.S.A. over the past 20 odd years in a useful manner. And while such an analysis is imperfect, it will provide some insight into this fascinating subject.

Jan 1, 1983

By James S. Goff, Stephen J. Navin, Wesley W. Moulton

The White River Shale Oil Corporation (WRSOC) is developing a prototype oil shale facility on Federal Lease Tracts Ua and Ub located in northeastern Utah. This paper covers the successful driving of 1,525 m (5,000 ft) of dogleg downgrade decline with a 70-ton Paurat Roadheader mining machine and a conveyor muck-handling system. Ground support is with rock bolt and shotcrete; welded wire mesh is optional. The Upper Decline of 3.89 m by 8.69 m (12.75 ft by 28.5 ft) was mined through the Uinta Formation sandstones and shales in 210 days. The sandstones have a compressive strength in the 48 MPa (7,000 psi) range with a few bands of shale up to 137.8 MPa (20,000 psi). Green River Formation dolomitic marlstone with some sandstone lenses was mined in the Lower Decline 3.89 m by 5.64 m (12.75 ft by 18.5 ft) in 175 days. The Green River marlstones are tough massive formations ranging up to 206.8 MPa (30,000 psi). Roadheaders for use on steep slopes must be modified to accommodate the particular problems associated with mining downdip. The paper concentrates on the application of Roadheaders to steep slopes and the problems of mining tough materials such as marlstone. The paper also shows the advantage of using the method of excavation on long drives.

Jan 1, 1985

By W. Bassow

In June 1972, when the United Nations convened its historic Conference on the Human Environment, only 24 countries had established government agencies with environmental responsibilities. Of these, 11 were in the industrialized world, 13 in the Third World. By 1985, the number had dramatically surged to a world-wide total of 145, with the greatest growth among the developing countries to 110, an increase of almost 1000%.

Jan 1, 1988

By Salvatore] [Parand

Deep well disposal is a much used and abused term which is the panacea for wastewater disposal in some minds and creates near hysteria in others. It can be the answer to a difficult waste disposal problem, or if improperly employed, can create more problems than it solves. My purpose in this presentation is to focus on the value and limitations of deep well disposal as expressed by New York State's experience and policies. To he sure, I feel a place for such practices docs exist if adequate safeguards are utilized. I shall give a broad brush approach to New York's legislative, geologic and operational concerns and speak briefly on some case histories. I shall not delve deeply into the technological details since I am not an expert in mining exploration or well drilling.

Jan 1, 1973

By E. J. Donovan, O&apos

The use of Dynamic Analysis techniques in the design of conveyor systems is extremely limited. The most frequent use of the technique is in large and expensive systems where the emphasis is on insurance against failure caused by catastrophic tension waves. This paper sets out to illustrate a much wider range of applications where dynamic analysis has been successfully employed. The examples chosen deal with identification and correction of dynamic low tension problems, the variability in take-up movement as other system parameters change, the requirement for proper tuning of starting controls and finally the absolute necessity for a complete understanding of the entire system when specifying brakes for critical applications. The intent of the paper is to get designers to view a conveyor as a system of interacting flexible components rather than as a single rigid body.

Jan 1, 1993

By J. Hazen, R. Jenner

This project was developed at the PCS Phosphate Mine in Aurora, NC. This site includes a surface mining operation, beneficiation plant and chemical processing facility located in the coastal plain of eastern North Carolina. The phosphate ore being mined at this operation is a 10 to 12 meter (35 to 40 foot) thick colloidal deposit located approximately 30 meters (100 feet) below the ground surface. The ore is pumped to the beneficiation facility where it is separated into clay, sand and concentrate streams. The concentrate product is utilized at the chemical plants to produce a wide range of products including fertilizer, industrial phosphates and animal feed products. The Cyclone Dike Builder (CDB) project developed a technique for dewatering the beneficiation tailing sand stream and providing innovative placement for dike construction. Future material balance requirements at the PCS Phosphate mine required an improvement in tailing sand placement technique to accomplish strategic objectives. The water volume of the sand slurry forces significant quantities of sand out of the dike profile during deposition. PCS Phosphate and MetPro Supply of Florida developed a mobile high-density hydro-cyclone station to remove most of the water and significantly increase the density of the sand being placed for dike construction. This high-density sand slurry is then effectively controlled using minimal heavy equipment operation.

Jan 1, 2004

By David B. Ashley

Risks in underground construction are often viewed as technical in nature; "running ground, " "squeezing ground" and "chimneys" are terms that appear in construction managers' nightmares, and occasionally in their underground projects. Financial consequences of these and other project risks are reviewed. Special attention is paid to sources of cost overruns. From this study a structure evolves for setting priorities for risk management actions; these actions can also be tested for impact and potential effectiveness. Finally, case study reviews of six underground projects indicate the "state of the practice" for financial risk management.

Jan 1, 1983

By K. C. Carriere

INTRODUCTION The purpose of this paper is to introduce the reader to basic control strategies for solid/liquid separation in mineral processing and to indicate some of the implementation difficulties to be encountered, without becoming overly involved in details of process, equipment or software. It is assumed that the reader has some familiarity with control systems and with dewatering processes, since exploration of these topics would require considerably more length. The paper is organized into three parts: first a general discussion on the need for control of dewatering processes and of the general criteria involved, next a more detailed elaboration on control strategies for the various unit operations, and finally a case study showing a specific approach towards such a project. Motivation & Objectives The justification for implementing any control system in an industrial plant is to improve operations and thereby to increase profitability. Without this motivation, the system will likely be perceived as unnecessary and will decline into disuse, an expensive and troublesome monument to someone's ill-conceived ideas. However, when a control strategy is correctly conceived, implemented and integrated into operations, it can provide significant advantages in operating ease and efficiency, and a handsome return on investment. In general terms, the objectives in establishing a control system are: • stabilization of process disturbances maintenance of product quality • maximization of throughput • dearer definition of process • protection of personnel and equipment A successful control strategy must address at least some of the above criteria. However, the most important requirement is a commitment on the part of plant personnel and management to start up, operate and maintain the system, and to upgrade it to reflect current process status and operational philosophy. Process Applications In this paper, control strategies will be explored for the most common methods of dewatering of mineral pulps. These unit operations include: drying, centrifuging, filtering and sedimentation. While the first three are important, they do not tend to be as complex as sedimentation, and thus will not be as exhaustively treated. Sedimentation is very widely applied, not

Jan 1, 1986

By K. Morsy, S. S. Peng

A new method of pillar stability evaluation was proposed. The unique feature about the method is that it estimates two types of stability factors for the pillar. The first stability factor is to measure how much the applied stress at that point is smaller than its strength, and the second stability factor is to predict whether or not the pillar will fail violently. The strain-softening behavior of coal pillars was simulated by the Drucker-Prager yield criterion. A new algorithm that simulates the strain-hardening behavior of the gob was used. A numerical technique to estimate the local mine stiffness (LMS) was introduced and verified by both numerical and analytical methods. A case of massive pillar failure in a room-and-pillar mine was used to define the stability limits for the proposed method.

Jan 1, 2003

By John E. Urbanic, William D. Faulkner, Robert W. Ruckel

Guidelines are presented for the selection, handling and regeneration of activated carbon used in gold recovery operations. The guidelines are based on Calgon Carbon Corporation's own investigations and experience gained in working with gold mine operators all over the world. Gold adsorption rate and adsorption capacity are shown to be independent variables thereby requiring testing of both properties when selecting activated carbon. Means of measuring these properties are provided. Historical activity tests on activated carbon are shown to be minimally useful in selecting carbon for gold recovery. Proper thermal regeneration techniques to maximize recovery of adsorption rate without weakening the carbon structure are suggested. Simple positive means of measuring efficiency of regeneration are presented. The subject of hardness measurement as a predictor of "in process" abrasion is discussed. The cost/benefit issue of carbon activity level is addressed.

Jan 1, 1986

By Surendra K. Mishra

Recent land ban act has put pressure on industry to decontaminate the waste streams before they could be discharged. However, for both metal and organic contaminated wastes, there are commercial incentives to recover usable resources. Recent technology developments have helped meeting such objectives. This paper reviews developments in treatment technologies for industrial wastes. Major chemical groups used in waste treatment are summarized.

Jan 1, 1994

By John A. Shuster

INTRODUCTION Controlled ground freezing for mining and construction applications has been in use for over a century. Despite the great technological evolution which has occurred during this period, ground freezing is still used on projects today with much the same basic technology as that used originally over 100 years ago. Major developments have occurred in the separate fields of frozen soil mechanics, refrigeration, and heat transfer analysis. However, except for a few projects in Europe and Asia, these developments have not been combined to upgrade ground freezing techniques to their potential level. In view of this situation, it is believed desirable to examine the art of ground freezing in light of recent technical developments, together with highlights on some of the apparent advantages, disadvantages and economics of the various alternative approaches. The purpose of this paper is to attempt such an examination, with particular emphasis on the practical application of presently available technology. GENERAL ADVANTAGES AND DISADVANTAGES Ground freezing may be used in any soil or rock formation, regardless of structure, grain size or permeability; however, it is best suited to soft ground rather than rock conditions. Freezing may be used for any size, shape or depth of excavation and the same physical plant can be used from job to job despite wide variation in these factors.

Jan 1, 1997

By Marvin A. Ph. D. Friedman

The following paper describes an overview of evaluations for assessing the potential hazards associated with handling newly developed reagents used in the mining industry. Important factors in determining the risk and hazard associated with handling a particular chemical include hazard identification, dose-response assessment, exposure assessment, and risk characterization. The hazard evaluation step involves collecting and evaluating appropriate toxicology information on a chemical. This can include a comparison of the structure of a developmental chemical with that of a material with known toxicology information. Acute toxicology data, including oral, inhalation, and dermal LD50 values, eye and skin irritation data and sensitization or allergic potential information are typically generated for new chemicals. Environmental and in-vitro genetic toxicology data (e.g. Ames test) are also used to evaluate new mining reagents.

Jan 1, 1994