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By Kelly F. Bailey

The issue of regulating non-asbestiform varieties of the amphiboles actinolite, tremo1ite, and anthophyllite to the same degree as asbestos has been studied in detail by the National Stone Association. The ramifications of such a regulation, and the over simplistic regulatory definition of a fiber, are enormous not only for the aggregate industry and its users, but also for the nation. Evaluation of the health, geological, mineralogical, technical, economic and legal issues do not support an "asbestos-like" regulation of non-asbestiform minerals. The adverse consequences of regulating non-asbestiform varieties of actinolite, tremolite and anthophyllite like asbestos would be magnified many times if a similar standard for generic mineral fibers were promulgated.

Jan 1, 1988

By J. A. Frew, R. M. Glen

Recovery of galena and sphalerite from fine grained lead-zinc ores by flotation normally requires re-grinding to achieve economic recoveries at acceptable concentrate grades. Re-grinding aims to reduce the coarse valuable mineral particles to a size where they float more readily and to liberate the composite valuable particles so that the gangue in these composites does not dilute the concentrate. Besides changing particle size and liberation, re-grinding changes the surfaces of the minerals and thus may alter the rate that mineral particles of a given size and liberation float. A method was developed to apportion the total change in recovery after re-grinding between changes in size and liberation and changes in flotation rates. The flotation behaviour of minerals, before and after re-grinding, was measured by floating samples of plant streams under controlled conditions in a laboratory cell. Results from several industrial lead-zinc circuits indicated that the change in behaviour observed fell into three different categories. It is concluded that the method will indicate whether the focus for optimization of existing plant should be on comminution or flotation, and it will help determine the path for laboratory testing in designing new regrind circuits.

Jan 1, 1995

By Jeffery H. Stricklin

Jim Walter Resources operates five underground coal mines with longwall faces in operation in four of the mines. Due to high air velocities (1000-1200 fpm) needed for methane control together with the friability of the coal, dust control on JWR longwalls offers unique challenges. We have tested many innovative measures to reduce respirable dust concentrations on longwalls with varying degrees of success. These measures include the "shearer clearer" system, different drum water spray configurations, sprays on the longwall belt, stageloader and crusher sprays, wetting agents in the spray water system, and homotropal ventilation. Water infusion of deactivated horizontal methane drainage holes in longwall panels is now being evaluated. A study was completed in November 1986 where water was infused into two horizontal de-gas holes. Personal gravimetric samplers were used to measure respirable dust concentrations and showed a significant reduction in the infused zone. A more in depth study will be conducted. This paper will describe the dust control measures presently used on JWR longwalls, give the results of past studies, and discuss new methods proposed to control longwall dust.

Jan 1, 1987

By K. E. Doud

An unusually pure grade of rutile and several grades of aplite rock are produced in a unique mining and mineral dressing operation in Hanover County, Virginia. The ore body is an aplite rock of gnessic structure, having a sari ace exposure extending over several hundred acres, heavily leathered and containing rutile, ilmenite, and other titanium and iron minerals. The physical nature and mineral composition of the ore body has permitted the use of a relatively economical and unusual processing circuit. The flowsheet was designed to take full advantage of the remarkable liberation of the minerals at relatively coarse rinds. It permits flexibility in changing the product mix, and maintains high levels of purity in both rutile and aplite rack. The mineral processing is discussed in some detail below.

Jan 1, 1962

By Paul M. Keyser

Flotation columns continue to offer improved metallurgical and economic advantages over other flotation methods. Pilot testing at Ozark-Mahoning Co. in Rosiclare, IL led to installation of one 2.3-m-diam (7.5-ft-diam) column for zinc roughing and one 1.1-m-diam (3.5-ft-diam) column for zinc cleaning. This circuit replaced one stage of mechanical roughing-scavenging followed by two stages of cleaner flotation. General Column flotation continues to make inroads into applications traditionally dominated by mechanical flotation cells. For example, columns are becoming more visible as rougher flotation devices. At Royal Mountain King Mine in California, two 2.9-m-diam (9.5-ftdiam) columns are used for rougher flotation of carbon from a gold ore (Orlich et al., 1992). In addition, work performed at BRGM in France demonstrated the superiority of column flotation over mechanical flotation with respect to design of new plants (Morizot et al., 1991). The primary reasons for this acceptance of columns are a general improvement in design, scale-up and operation, as well as improvements in sparger design and performance. With these advances, the full benefits of column flotation can be realized. The benefits of properly designed, aerated and operated flotation columns include lower capital costs, reduced operating costs, fewer processing stages and improved metallurgical performance.

Jan 1, 1993

By R. D. Archibald

Currently, around 100 million tons of construction materials and aggregates are shipped annually by rail. And recently, producers are looking much more carefully at rail not only to reduce fixed costs through increased volume, but also to eliminate operating headaches, such as increasing community pressures about trucks on the road, noise and dust. Many producers are uncertain as to how to enter the rail shipping business since railroads have historically been reluctant to ship small quantities short distances. This article provides strategies to help producers examine and pursue moving their rock by rail.

Jan 1, 1995

By George A. Hoffman, Richard J. Proctor

INTRODUCTION We will discuss here only the subway construction phase; that is, two to five years at a given location--not the long-term analysis. We also will compare some tunnel construction methods used for BART and in Los Angeles. Typically, urban planners and engineers try to balance a new mass transit system to include tunneled subways, cut-and-cover construction in city streets, and elevated guideways. Their decisions are based on many factors, most of which can be quantified. But there are some socio-economic-environmental factors which are almost intangible, or nonquantifiable, and these are rarely included in the final report for a rapid transit system. There are two reasons for this: First, it is difficult to evaluate disruptions and psychological inconveniences to individuals and to the community during the construction period, and even more difficult to assign costs because the valuations are always subjective. Second, the rapid transit project capital costs are given in the final report and the public knows them; but the intangible social costs are borne by the affected neighborhood community, not the entire city, and as such they are "hidden costs," which in fact may add as much as 25 percent to the total system cost.

Jan 1, 1974

By H. Bernatowicz

The Nucoalyzer (On-Line Nuclear Analyzer) is a new method recently made comercially available for monitoring the elemental composition of a process stream. Applications for the Nucoalyzer include grading ore on a conveyor belt before or after it has gone through primary crushing, monitoring the slurry being transported in a pipe to the concentrator, and monitoring the stream of concentrate or the tailings from the concentrator. The Nucoalyzer may also be used at the smelter to monitor elements in the feed that include copper, sulfur, iron and silicon where a uniform feed is desired. The advantage of the Nucoalyzer over most other techniques are (a) it performs the measurement directly on the process with no sampling necessary, (b) the analysis can be performed on streams of particulate and slurries, and (c) the system does not have to make contact with the material it measures. These Nucoalyzers are operating at coal fired power plants and several more are about to be placed in service. This paper discusses the principles of operation of the Nucoalyzer, our experience in the field, application of minicomputers to data reduction, and potential applications in the ferrous and non-ferrous industries.

Jan 1, 1982

By Joseph Alexis

Humphreys Engineering Co. has been associated with mining and milling since the turn of the century, but its greatest contribution to the industry was development of the Humphreys spiral concentrator in 1943. Few devices in the history of mineral beneficiation have been so uncomplicated. The spiral concentrator has no moving parts and requires no power except that needed to deliver slurry to the feed box, a requirement common to all concentrating devices. Although Humphreys Engineering Co. produces several models of spiral concentrators, the one -commonly used for coal cleaning is Model 24C-6 which has a flatter pitch than most other models. The spiral concentrator consists of a spiral conduit with a modified semicircular cross section. A slurry containing 20-35% solids by weight is fed to the feed box at the top of the spiral and flows downward. The heavier refuse particles concentrate along the inner side of the slurry stream and the lighter coal moves to the outside. The coal spiral has six complete turns-each turn consists of three 120°-sections and each section has a refuse port at the lowest point of the channel. The Humphreys spiral concentrator separates minerals in accordance with their physical properties (primarily specific gravity and particle shape). Aside from pumping slurry to the distributor, no energy is required to produce clean coal since the separating action is controlled by gravity. As slurry flows down the spiral channel, each particle is subjected to a centrifugal force, tangential to the channel. This force piles slurry on the outer rim of the spiral until the flowing stream reaches an equilibrium between outward centrifugal force and downward gravitational force. Once established, the stream position is relatively constant. In any flowing stream, differential velocities are present within that stream (the slowest fluid levels nearest the channel surface and the fastest layers at the center). As the channel curves, the lower slurry levels, retarded by friction, have much less centrifugal force and tend to move sideways toward the inner radius of the channel. As the bottom layers move inward along the bottom of the channel, the upper layers must move outward to maintain equilibrium. This cross sectional rotation separates the minerals and moves those of highest specific gravity toward the inner radius where they drop through refuse ports (see figure on following page). The simplicity of the spiral concentrator is apparent in operation. After tonnage, slurry volume, and percent solids of the feed have been determined-generally with laboratory testing-the operator's main concern is simple adjustment of the splitters located in the refuse ports. These splitters control the amount of refuse collected and, generally, once properly set they need little attention unless grade conditions drastically change or trash builds up and hinders laminar flow. Spiral concentrators are not overly sensitive to changes in pulp densities, variances in grade, or parti¬cle size and shapes. All these conditions may fluctuate over fairly wide ranges without adversely affecting recovery and product grade. In certain applications, desliming may improve recovery.

Jan 8, 1980

By Haydn H. Murray

The three major catalyst markets that utilize industrial minerals as raw materials are petroleum refining, chemical processing, and emission control. Because of economic, competitive, and regulatory pressures, catalyst producers are pushed to develop products with improved performance to meet changing environmental standards. Also, refiners are demanding new families of cracking catalysts that will crack residual fuels. In 1987, worldwide cracking catalyst sales amounted to $457 million (Occelli, 1988a). Recently enacted federal and state laws to improve air quality have prompted strong growth for environmental catalysts, which in 1989 accounted for more than a third of the $1.9 billion catalyst market in the United States (Farrauto, Heck, and Speronello, 1992). A catalyst is a material that promotes or enhances a chemical reaction but does not itself enter into the reaction. One of the more important mineral groups used as catalysts is clays. The first recorded use of clay as a catalyst was its use in the dehydration of alcohol (Bondt et al., 1797). Clay minerals that are used as catalysts are kaolinite, halloysite, smectite, palygorskite, and sepiolite. Minerals used as catalysts, catalyst supports, or as a raw material to make zeolites are kaolinite, halloysite, sodium montmorillonite, calcium montmorillonite, hectorite, palygorskite, sepiolite, talc, calcined kaolinite, gibbsite, chlorite, and titanium dioxide.

Jan 1, 1994

By Robert J. Auber, Thomas R. Scotese

The West Leg Interceptor is part of a new sanitary sewer system in the southwest suburbs of Cleveland. The first two construction contracts were excavated in glacial soils varying from hard tills to pressurized silts and flowing sands. These soil and groundwater conditions were locally problematic during shaft and tunnel excavations and final lining construction. A variety of solutions were developed primarily during construction. During the WLI-1R Contract, subgrade pressures, continued ground losses, and displacements necessitated extra eductor wells and modified inverts for stabilization of shafts. At the WLI-2Contract, one shaft excavation in similar ground required only one extra well. In the WLI-1R tunnel, localized inflows of groundwater, silt, and sand through the geotextile fabric were stopped by cement grouting. In one WLI-2 connector tunnel, damage to the TBM flood doors combined with wet, flowing silt and sand led to ground losses, surface settlements, plugging, patching, and chemical grouting. The concrete lining in the main WLI-2 tunnel required remedial work to improve watertightness at joints.

Jan 1, 1999

By S. K. Palm

Volatility is a fact of life in the mining industry. Prices of and demand for mineral products are among the most volatile of those for any product. The volatility of these markets wreaks havoc on both corporate management and the personal lives of mining people. Yet, until recently, it has been difficult to assess the impact of volatility on business strategy. This paper discusses how mining firms can profit from market volatility through an operations strategy that stresses operating flexibility. The foundation for our strategy analysis is the observation that a mine is analogous to a stock option. Techniques based on those developed to value stock options have recently been extended to the field of mine valuation. The insights provided by option pricing are very valuable in the development of mine operating strategy.

Jan 1, 1986

By G. R. Tostengard

Gold plant performance during the start-up period, which extends until capacity production is sustained, has a major impact on the internal rate of return and the net present value of gold projects regardless of mining and processing configurations. The start-up period experiences substandard production, extra expenses, and sometimes reduced recovery. This results in lost profits, a portion of which are recouped at the end of the life of the mine. Poor start-up performance can put projects into financial jeopardy. The gold mining industry regularly experiences start-ups ranging from good to poor. Problem areas, which affect start-up performance, include shortcomings in ore reserve sampling and testing, equipment design and installation, untrained plant operators, inability to cope with problems which arise, and organization of the maintenance program. An investment, equal to 0.5% to 1.0% of plant capital cost, in programs to prepare for start-up, in advance, is recommended. Investment in such a program will make a good start-up possible. Without it the best result which can normally be expected is a fair start-up. Developers of new gold mines are urged to compare the cost of this investment with the anticipated increase in project net present value. Funds for this investment should be included in feasibility studies.

Jan 1, 1988

By Gerhard Sauer, Heimo Gold

The main advantage of the New Austrian Tunneling Method over conventional drill and blast techniques, TBMs and shields is its outstanding flexibility. Many different support concepts help to cope with all but the most adverse conditions. A considerable variety of unique additional support measurements provide a functional tool when dealing with particularly difficult conditions or restricting requirements. The resulting adaptability of NATM with respect to geometric and geologic changes is a cornerstone to providing an economic design and to a safe and unhindered execution of the tunnel work. To take best advantage of this flexibility and to emphasize its cost-saving capacity, NATM explicitly extends the design period into the construction phase. In accordance with corresponding ground classes or other anticipated conditions, a number of basic support categories and an array of additional support measurements are established during the actual design phase. The decision for applying a particular support category at a specific location and for necessary additions to the given support scheme, however, is regularly made on site after each advance, and is determined by the key persons involved in the construction. Contract documents must reflect this approach to facilitate the execution of the work and to curtail construction costs. Biased distributions of risks, however, can adversely effect the envisioned benefits. Consequently, the respective responsibilities of engineer, contractor, and client need to be redefined.

Jan 1, 1989

The US Geological Survey (USGS) held a one-day workshop at its Denver, CO facility to inform the public of the status of its National Mapping Program. In addition, the agency wanted to obtain information from topographic map users on what their needs are. The agency wants to know what the topographic map user wants. The USGS faces the challenge of keeping up with the changing needs of the nation. In the last few years, the agency has changed dramatically to meet these needs. For example, the "new" USGS incorporates mineral-information specialists from the former US Bureau of Mines and also uses the expertise of former National Biological Service employees. These areas complement the agency's traditional strengths in mapping, geology and water re- sources. The stated mission of the USGS's National Mapping Division is to "meet the nation's need for basic geospatial data, ensuring access to and advancing the application of these data and other related ears science information f& users worldwide." To accomplish this goal, the USGS publishes topographic maps, including shaded-relief editions of areas of special interest (state maps and national parks); photo image maps; satellite image maps; geologic maps and hydrologic maps. The geologic maps include geologic quadrangle maps, oil and gas investigation maps and charts, and coal investigations maps. The familiar 7.5-minute series topographic maps are the most widely used. The 7.5-minute- (1:24,000-scale-) format mapping was begun in 1935.

Jan 1, 1998

By Edward S. Plotkin

The tunneling construction industry faces a new challenge in endeavoring to comply with the multitude of regulations and standards of the Occupational Safety and Health Administration and to work following accepted and experienced tunneling practices. Tunnel inspections appear to be gaining in priority. The national OSHA inspection activities reported for the year 1976 in the construction industry are as follows: 989 Inspections 45 As result of Accidents 186 As result of Complaints 605 General 153 Follow Up 34% Were found to be in compliance 714 Citations were Issued 1,825 Violations were found (201 of which were serious; 1573 were non-serious; 51 were imminent danger. There were no recorded failures to abate a violation in our industry.) The five general priorities by which a company would be scheduled for an inspection in descending order are: imminent danger situations, reports of fatal accidents or catastrophies, inspections in response to valid employee C( taints, inspections of work places covered by National Emphasis Program NEP, (OSHA's NEP has been designed to impact on any industry having a very high injury or illness rate) and finally random inspections of work places covered by OSHA. The following criteria in selecting companies for random inspections is used by OSHA.

Jan 1, 1979

By D. S. Ramey

In-situ leaching of the oxidized copper mineral resource at the San Manuel mine has proven to be a technically and economically viable method of copper extraction. Although this leaching method has been modeled to predict future production capabilities, the expected magnitude of the ultimate recovery from any portion of the present mine is not fully understood. A closely controlled test has been designed, constructed, and is now operating to determine the rate and magnitude of copper recovery. The test, initiated in June 1992, is scheduled to operate for approximately 18 months. This paper presents an overview of the test design and current results.

Jan 1, 1993

By José A. Matar Ibañez

Geologic terranes in Argentina include potential mineralized environments from localized younger Precambrian cratonic outcrops through Paleozoic sequences, generally in the northwest or under younger cover, to the Mes[o] zoic-Cenozoic Andean Systems in western and southern Argentina. Argentina is self sufficient or nearly so in many metallic, nonmetallic, and energy commodities, and exploration in each of these categories is ongoing. Present production of precious metals (silver and gold) is important, and many recent discoveries of base metals, precious metals, alloy metals, and other mineral categories have been made. Economic trends, geologic environments, and commodity types important in actual exploration are described, and it is emphasized that extensive areas showing attractive alteration, geochemical, and geological anomalies, especially of porphyry, cordilleran vein, and epithermal characteristics, remain to be fully evaluated.

Jan 1, 1986

By John P. Norton

Microcystaline silica has been mined in Illinois from the Clear Creek formation since the turn of the century, especially in the area around Tamms in Alexander County, in the southernmost part of the state. Production of this silica, consumed mainly by the abrasives and coatings industries but also sought after for many filler/extender uses, has grown with the economy with several new applications overshadowing traditional markets in recent years. Such an important commodity was given the early attention of the Illinois State Geological Survey and a very complete report was issued in 1953 (Report of Investigations No. 166), authored by J. E. Lamar. The mining and processing of the silica ore has changed very little since the first reported production in 1906, although emphasis has been placed on the production of the finer sized grades to meet newer market requirements. Industrial Mineral Notes 40, published by the Illinois State Geological Survey in June 1970, describes a method by which a less than 1-micron fraction could be commercially produced from the readily available finest commercial grade presently being marketed (99% minus 10 microns). The finer grades exhibit to a lesser degree the reinforcement, high flatting efficiency, thickening and dry brightness properties associated with the synthetically produced silicas. It is expected that the extremely fine grades of microcrystaline silica will become accepted in the markets that now use a combination of precipitated silica and less expensive extender/filler minerals such as kaolin or calcium carbonate.

Jan 1, 1976

By Karl O. Toppel, Jim Flaherty

The desire to minimize gaseous effluent in smelting and maximize gold yields from refractory ore are driving the nonferrous and gold refining industries to demand more and more oxygen. This, coupled with an increasingly competitive marketplace, forces the investigation of alternate methods of oxygen supply. Current progress in both the non-cryogenic and cryogenic fields is making the use of low-purity oxygen much more attractive. The benefits of on-site production are now available to most oxygen users. Historically, these on-site advantages could only be achieved by relatively large plants using high-purity cryogenic technology. The evolution of low-purity cryogenic and non­cryogenic oxygen production has added a new method of delivering on-site production. Specifically, the advent of oxygen Vacuum Swing Adsorption (VSA) technology has brought these benefits to smaller-volume customers by cost-effectively supplying oxygen requirements as low as 20 tons per day, (tpd). Low-purity cryogenic plants have also made an impact on the market, yielding cost reductions for larger-volume customers with oygen requirements greater than 70 tpd. This paper reviews the advantages and disadvantages of current supply methods for users having varying volume, purity and other requirements.

Jan 1, 1993