Search Documents

By Frederick B. Henderson

The US Environmental Protection Agency (EPA) has tried many regional and laboratory efforts to develop measurement and monitoring techniques using environmental remote sensing technologies. In 1997, the agency established the Advanced Measurement Initiative (AMI): This is a eadquarters-level program, operating under the auspices of the EPA Office of Research and Development. The program is one result of the April 30,1996 White House Conference on Advanced Monitoring of the Environment. The EPA was encouraged to work with other federal agencies to leverage its remote sensing capabilities and use them to improve the efficiency, cost-effectiveness and flexibility of environmental measurement and monitoring for regulatory compliance and reinvention. During the fall of 1996, the EPA and the Department of Energy developed an interagency effort to broaden the use of governmental technologies for environmental measurement and monitoring. In addition, the EPA and the National Aeronautics and Space Administration (NASA) conducted joint workshops on the use of NASA remote sensing and other technologies for water quality and pollution applications. In the meantime, the EPA proceeded with an industry-proposed workshop to explore ways to cooperatively examine new research and to develop commercial remote sensing systems. It also examined how these systems might become accepted by the EPA in the regulatory and compliance processes. In particular, industry was interested in where new remote sensing capabilities might fit in with EPA's efforts at regulatory reinvention. Historically, the mining and petroleum industries have been reluctant to experiment with or use environmental remote sensing. They were concerned with the unknown liability from potential discovery of previously unknown environmental problems. Moreover, resource industries have been reluctant to use remote sensing for environmental applications where the EPA did not accept such data or information as part of the compliance process. Acceptance by the EPA of these advanced measurement and monitoring technologies (AMMT) will be a major reason for industry's increasedd use of remote sensing in environmental "applications for regulatory compliance. In July 1997, the EPA Office of Research and Development hosted at the Colorado School of Mines a stakeholders workshop on the AMI program and industry-government collaboration. The workshop's aim was to demonstrate the usefulness of AMMT technologies for environmental applications. Stakeholders included the mining and petroleum industries; environmental services companies; state environmental agencies and local governments; remote-sensing, value-added companies and data suppliers. The workshop used specific technologies and applications as a way to develop collaborative demonstration projects for several AMMT technologies covering different environmental problems. The workshop focused on the use of highly sensitive hyperspectral (very narrow spectral bands), geographic information systems and surface mapping to identify active acid-producing mine dumps and wastes from benign wastes at Leadville, CO. NASA's advance infrared imaging spectrometer (AVIRIS) was the instrument used. It was developed at California Technology's Jet Propulsion Laboratory. The EPA, the US Bureau of Land Managment (BLM), the US Geological Survey and several environmental service contractors sponsored the overflight and data evaluation. The AVIRIS study demonstrated reliability (95% correct surface mineral identification) and cost-effectiveness of this technology to accurately map and discriminate active acid-producing mine wastes from benign wastes. It could also predict which streams would be effected by acid and toxic mineral drainage. The BLM'said that the AVIRIS overflight could save it $500,000 a year in surface sampling costs at Leadville. The AMI workshop further outlined five 1997 funded AMI projects of potential interest to the mining industry. They were: ? Mine waste characterization using remote sensing methodologies at Asarco's Ray Mine in Arizona. ? Predictive emissions development and testing in

Jan 1, 1997

By Richard H. Oitto

With increased interest and urgency for coal mine safety and the passage of the Federal Coal Mine Health 'and Safety Act, the Bureau's research effort in roof control has been greatly expanded. One new project, the subject of this paper, concerns improving conventional roof bolting and has been involved with the effects of different variables on the performance of roof bolt expansion anchors. These include types of expansion anchor, rock type at the anchorage horizon, borehole roughness, rate of torquing a roof bolt to set the anchor, installed tension, bolt length, and relative humidity fluctuations. For this work, two types of experiments were carried out. One was concerned with tension loss in bolt-anchor assemblies and simulated anchor performance in a static roof. The other dealt with anchor slippage as tension was increased and simulated anchor performance in an active roof. Trials were made in the laboratory under controlled conditions so that factors suspected of affecting expansion anchor performance could be selectively studied. Because of the natural variability in rock and the fact that most expansion anchor components are essentially rough castings or forgings, the experiments were designed to permit using analysis of variance techniques for analyzing data. Thus, in this paper, "significant" means statistically significant.

Jan 1, 1972

By D. S. Choi

The paper contains a subsidence measurement taken over a room and pillar panel of a mine located in northern West Virginia. A total of 72 monuments were used to determine a three dimensional view of mine subsidence. In addition, the results of measurements were used to compute ground strains with the use of a numerical model.

Jan 1, 1982

By I. Melik-Gaykazov, N. N. Melnikov, V. A. Fokin, S. P. Reshetnyak

Kola Mining Institute has been carrying out investigations of the possibility to steepen the walls of the Kovdor open pit with the design depth of 600 m. Steeping (up to 60°) wall angles is done by double height (24 and 30 m) benches with vertical slopes. One of the safety factors of mining with such walls is choosing the width of the safety berms preventing against rock falling from the slopes into the pit working area. The test on rock falling from 24 m benches has shown that vertical slopes are not more dangerous compared to the inclined(60-75°) ones.

Jan 1, 2003

By Brian Burdett, Terry I. Mudder, Robert T. Richins, James A. Stevenson, Michael M. Botz, Alan L. Wilder

The first Cyanisorb process was constructed in 1991 at the Golden Cross Mine in Waihi, New Zealand to recover cyanide from CIL tailings. The Golden Cross operation consists of an open-pit and underground gold mine with a conventional crushing, grinding and CIL circuit with Merrill Crowe zinc precipitation for gold recovery. Prior to disposal in the tailings pond, slurry tailings are stripped of cyanide at a pH of approxi­mately 7.5 using the Cyanisorb process. Mill throughput is approximately 2,500 tons per day (TPD), and CIL slurry tailings average 37% solids with a specific gravity of 1.27. CIL tailings WAD cyanide average 150 mg/L. The Cyanisorb process recovers approximately 85% of tailings WAD cyanide, produc­ing a slurry effluent with approximately 20 mg/L WAD cyanide. A second Cyanisorb process was commissioned at the NERCO DeLamar silver mine in southwest Idaho in May, 1992. The ore milling and silver recovery operation consists of crushing, grinding, a CIP circuit and Merrill Crowe zinc precipi­tation for silver recovery. Cyanide recovery is from clarified tailings with WAD cyanide ranging from 3 50 mg/L to 600 mg/L, producing an effluent with less than 30 mg/L to 60 mg/L WAD cyanide. Due to the presence of zinc-cyanide complexes in mill tailings resulting from the Merrill Crowe process, cyanide is stripped at a pH of approximately 5.5.

Jan 1, 1995

By G. Deschenes, M. Fulton

The New Britannia Mine processes a qumtz-carbonate gold ore containing 4.63 git Au at a rate of 2,200 tpd. The ore contains approximately 3 .0% arsenopyrite, 2. 7% pyrite and the rest is gangue minerals. Eight to ten percent of the gold is refractory to leaching. Two years ago, New Britannia Mine experienced cyanidation problems. Gold extraction was not stable and occasionally decreased significantly. Preliminary test work, at laboratory scale and in the plant, indicated that lead nitrate addition was beneficial. A laboratory study was initiated to evaluate the level of control of the parmneters (grinding size, dissolved oxygen, pH, free cyanide and lead nitrate) to optimize the efficiency of the process. It was found that lead nitrate addition is required to alleviate the effect of metallic sulphides. This addition causes a significant increase in the gold leaching kinetics and a reduction in the cyanide consumption. The optimum system appeared to be: leaching for 24-30 hours at pH 11.8, 50 git lead nitrate, 250 ppm NaCN and 8 ppm 02. The gold extraction was 89.8% with grinding at 89%-74Fm (leached tail at 0.48 git). Cyanide and lime consumption are 0.40 kglt NaCN and 1.9 kglt respectively. Following the incorporation of lead nitrate, overall gold extraction was increased from 89.2% to 91.1 % but no change was noticed in cyanide consumption. The gross profit is $CDN 988,000 per year.

Jan 1, 1999

The Chinese city of Shanghai is one of the fastest growing in the world. To keep up with the growth, two tunnels, three-lanes each, are being built beneath the Yangtze River to connect Shanghai with the Changxing River Island. To complete such a large project, Herrenknecht Tunneling Systems was brought in to construct the largest tunnel boring machine (TBM) in the world. The first Herrenknecht S-317 Mixshield has a diameter of 15.43 m (50.62 ft). It was built to construct one of the two 7.2-km (4.5-mile) tunnels. The tunnels are part of the Changjiang Under River Tunnel Project and will be at depths of up to 65 m (213 ft) beneath the Yangtze River in Shanghai-Pudong. These two tunnels are to be opened to traffic in April 2010, in time for Shanghai to host the World Expo. More than 20 million people live in the Shanghai area. The area itself has been growing at an extremely rapid pace for more than a decade and is in need of more space. The search extended beyond the natural limits of the Yangtze River Delta. As part of its incredible growth, 500 new vehicles are registered every day. The new tunnels will connect the Changxing River Island, with a population of approximately 600,000 people to the road traffic network. A bridge construction will also provide a traffic link between Changxing Island and the large island of Chongming.

Jan 1, 2007

By R. D. Grove

The control of Florida phosphate flotation plants is largely based on the visual observations of experienced operators, both in recognizing good and bad froth conditions and in making judgments about the composition of feed, concentrate and tailing streams. Chemical analyses lag the process by at least two hours and, therefore, only assist in recalibrating the operators' vision when major deviations occur. An image analysis system was developed by IMC Fertilizer to improve the accuracy and precision of the composition estimation process. It still relies on the operator taking a representative sample, but provides a measurement in about 15 minutes after that sample is obtained. Background The search for a quick and inexpensive technique for estimating phosphate flotation stream composition continues. There have been attempts at using "wet chemistry," nuclearmagnetic resonance, neutron activation, X-ray diffraction and other techniques reported on in the past several years. None of these have yet found its permanent place in the flotation plants of the Florida phosphate industry. IMC attempted to use wet chemistry to provide 7.5-minute estimates of final concentrate insol and tailings BPL. This was aborted after 36 months of plant operation due to the high operating costs for chemicals and an operator. There was also no significant economic improvement in the plant's operation. Another factor was the necessity to limit these crude analyses to only a few process streams, which were insufficient to achieve improved plant operation.

Jan 1, 1993

By D. F. McCarthy

INTRODUCTION Mined underground chambers specifically designed for the purpose of storing liquefied petroleum gas (LPG) at ambient temperatures have been in use for over thirty years. The first caverns were developed by Warren Petroleum of Tulsa, Oklahoma, in 1948, for its plants in Texas. The basic concept of an LPG-storage cavern is to create a space in an impervious formation at a depth sufficiently below the water table so that if any movement of fluid occurs the ground water will enter rather than the gas escape from the cavern. In the past, the primary reason for LPG storage underground has been its attractive cost advantages over steel storage on the surface. At current prices the cost of storing 7.949 ML (50,000 barrels) would be equivalent, whether stored on the surface or underground; whereas 79.494 ML (500,000 barrels) of storage underground costs only one-fifth of surface storage. It is usually uneconomical to excavate less than 79.494 cu m (50,000 barrels) of storage space. The fixed costs - engineering, mainshaft and ventilation shaft - are a substantial part of the total cost, whereas the incremental costs for excavating additional storage are relatively low. Recent concern over the hazards posed by the handling and storage of LPG and liquefied natural gas (LNG) has led to a new interest in the underground storage of these gases. Underground storage offers the following advantages: safety, security, low initial cost, low maintenance cost, operating, cost, minimum land require-

Jan 1, 1981

By N. S. P. Kumar

INTRODUCTION Development work at Carr Fork Mine of Anaconda Copper Company in Tooele, Utah commenced in August 1974. A decision to install an underground gyratory crusher for primary crushing run-of-mine ore and waste was made in 1976. Higher throughput rates, larger reduction ratios and greater flexibility in terms of meeting immediate and expanded production needs were the main reasons for selecting the gyratory crusher over the jaw crusher. UNDERGROUND MATERIALS HANDLING Underground crushing and conveying system was designed for a capacity of 16,300 mtpd of ore and waste on a 2-shift, 5-day week basis. Engineering and design of crusher complex was performed by Anaconda engineers at Carr Fork. Figure 1 represents the longitudinal section of mine showing the general materials handling system. Mine area is trackless except for materials and production haulage which is run on rail track on both 1200 and 970 levels. Ore from stopes and waste rock from development headings are handled by 3.8 cu m (5 cu yd) Jarco scoops and dumped into 2.4 m (8 ft) diameter ore and waste passes at the 1200 level. The material gravitates down to the 970 level where it is loaded into 12 cu m (420 cu ft) ASEA mine cars using side loading chutes. The muck train, consisting of 15 to 18 cars and two 27 mt General Electric trolley locomotives, is hauled over a distance of 2,300 m (7,550 ft) to

Jan 1, 1981

By T. D. Rourke, E. J. Cording, O&apos

INTRODUCTION Detailed investigation of a 60-ft-deep excavation in a mixed profile of sands and stiff clay was performed by the University of Illinois for the Washington Metropolitan Area Transit Authority (METRO). The work was coordinated through DeLeuw, Cather and Co., the General Engineering Consultant of METRO. Instrumentation was concentrated in a portion of braced excavation for the Gallery Place Station near the intersection of 7th and G Street. The early construction date, the 60 ft depth of cut, and the proximity of large buildings formed the basis for selection of this site as the focal point of observation and measurement. A history of lateral and vertical displacement is provided wherein movements which occurred during excavation to the full depth of cut and, subsequently, during station construction and the removal of braces are described in detail. Observations of preloading and the consequent brace loads and wall displacements are described. The effect of temperature change on brace loads is discussed and the measured apparent earth pressure for the 60-ft cut is provided. The paper discusses the relationship of lateral displacements of the cut wall to the construction procedure, and compares the lateral wall displacement with both lateral and vertical movement in the surrounding soil mass. Based on observed movement, the method by which displacement was predicted for a nearby 82-ft-deep excavation is described. The performance of the 82-ft-deep excavation has been summarized elsewhere (2).

Jan 1, 1974

By Philip U. Santacroce, James H. Meinholz

INTRODUCTION The Milwaukee Metropolitan Sewerage District (MMSD), is a special purpose sub-regional agency that provides collection and treatment services for sanitary wastewater for an area of 420 square miles (1088 km2) in 27 municipalities in the Milwaukee, Wisconsin metropolitan area. During its almost 75 years of existence, it has constructed 464 km of intercepting sewers, the majority in tunnel, and two sub-regional secondary wastewater treatment plants. The present program, the $1.7 billion Milwaukee Water Pollution Abatement Program, was started in 1977 and developed from ongoing internal planning, the Federal Clean Water Act and court judgments. Elements of the Program include improvement and expansion of the two treatment plants; rehabilitation of older in-place sewers; building new interceptors and relief sewers and providing capacity for high volume storage in approximately 32 km of deep, large diameter rock tunnels; reducing combined sewer overflow; and disposal/utilization of the solids that remain after the treatment process. The construction phase of the Program accounts for $1,105,900,000 within 335 separate construction contracts, 211 let to date, and covers a span of 15 years, starting in 1979 and running through 1994. Conveyance System construction cost is estimated to be $650,000,000 or about 60 percent of the total. Through December 1986, in terms of dollars, the total construction program is about 38 percent complete with Conveyance at 34 percent complete.

Jan 1, 1987

By William G. Fischer

Basic laboratory tests initiated the. Rock Mechanics program. The stress-strain curve, modulus of elasticity, Poisson's ratio, the uniaxial rock strengths, Mohr's envelope, the stress at failure, and creep were investigated. A series of underground problems were then approached using this information; and various field measuring devices, most of which were developed by the Bureau of Mines. Initially, stress concentrations near mine openings were evaluated using the stress relief technique. This required an accurate determination of the pre-mining stress field. Later, stress concentrations associated with the cave line .sere studied. After about thirty stress reliefs over an appropriate time interval the effects of one type of mining could be compared against another. The microseismic technique was used to investigate a possible application of warning devices near the cave line. A study of mane reorientation was made Problems related to the shape and size of pillars and barriers were studied. Partial extraction mining systems were evaluated. The effectiveness of roof bolting patterns were examined. Control of roof stresses was attempted. A new system of mining in heavy ground has been developed using the information secured in the Rock Mechanics program without this system, mining in more than one instance would Nave been next to impossible. Indeed; from this one discovery alone, the Rock Mechanics program has paid off in improved safety as well as in dollars.

Jan 1, 1964

By D. Elroi

This paper addresses the sharing of 2D and 3D data between GIS and mine planning software. Two-dimensional (2D) data, and now three-dimensional (3D) data as well, can be formatted such that both types of software can use, exchange, and display the same datasets. This increases the ability to share data between such groups as environmental, exploration, and mine planning. It overcomes shortcomings of mine planning software in areas of open database connectivity, spatial analysis, and data input and output. It also helps to overcome shortcomings of GIS software in the areas of geologic modeling, three-dimensional interpolation, and visualization.

Jan 1, 1998

By Andrew Chegwidden, Tara Wilk

Construction of Shaft 17B-1, a part of The New York City water supply system, required an excavation of approximately 38 m (123 ft) through water-bearing overburden soil and more than 152 m (500 ft) of gneiss bedrock to make a connection to Water Tunnel No. 3. Ground freezing was the specified method to provide temporary earth support and ground water control for the overburden material. The ground freezing process relied on a supplemental geotechnical investigation and comprehensive laboratory testing of the frozen soil to evaluate the potential long-term creep behavior of the soil and the elimination of a temporary lining system. This paper describes that process as well as the drilling and installation methods of the ground freezing system. Additionally, the methodical system of excavation and insulation is discussed that permitted a safe and timely excavation followed by the installation of the permanent concrete liner.

Jun 13, 2023

By James E. Kolesar

An essential prerequisite to expanding the application of longwall mining techniques in the United States is the development of a better understanding of the mechanics of rock mass deformation near the mined seam, in the inter- burden and at the surface. The results of studies of this type will provide a basis for the development of empirical and/or numerical modeling techniques to predict the rock mass response to mining both near and far from the mined seam. This will lead to improved gate and panel design, resulting in maximum recovery, increased productivity, as well as provide a mechanism for assessing likely surface effects induced by long- wall mining. Presented here is the instrument plan to be used at Kitt Mine No. 1 in the study of rock mass response to two adjacent longwall panels.

Jan 1, 1982

By Rasik H. Raythatha

Calcium carbonate is perhaps the most widely used mineral in the world. With total consumption of all calcium carbonate exceeding over 25 million tom per year, within this class of filler, a relatively smaller segment of precipitated calcium carbonates (PCC) is often misunderstood as a commodity product and bundled in the same category as ground calcium carbonate. However, each material has a distinctly digerent role and characteristics. Precipitated calcium carbonates are used to influence specific performance in a specific application whereas ground calcium carbonate is used primarily to reduce cost in many applications. In this paper, attempts are made to demonstrate the role of nano-fine-PCC in improving shear-thinning characteristics of common and specialized sealants and automotive underbody coating and how such "nano-particle" cal- cium carbonate properties can be exploited to process PVC plastics while reducing overall cost. We also review the role of precipitated calcium carbonate as "nano" material and why it must be viewed as a specialty additive.

Jan 1, 2003

By A. L. Mula

Pasaremos revista brevemente a 10s fundamentos de 10s ciclones, considerando un ciclón típico. Los datos gráficos disponibles en la literatura han sido convertidos en ecuaciones matemáticas por conveniencia. Se suministran los procedirnientos preliminares para seleccionar y diseñar tanto los ciclones como las bombas, y se facilita con algún detalle un ejernplo de cálculo para un hipotético circuito de molienda. En general, debe consultarse a 1os proveedores de ciclones y bombas para determinar un disefio definitivo. Algunos suministradores de ciclones emplean normalmente computadores digitales para el diseño definitivo con objeto de asegurar una gran precision.

Jan 1, 1982

By William Hustrulid

INTRODUCTION The Idarado mine lies high in the San Juan Moun¬tains on the divide between the Uncompahgre and San Miguel Rivers and consists of a consolidation of a number of old and prominent mining properties through which course some famous and very produc¬tive veins. Among the better known are the Smuggler, Tomboy, Montana-Argentine, Black Bear, Liberty Bell, Virginius, Flat, Barstow, and Japan, as well as many others. Most of these veins have been extensively mined over the past century and in the last three decades the Montana-Argentine and Black Bear veins have been the backbone of the Idarado mine; therefore, the descrip¬tion of the veins is limited to them. Access to the mine is through either the Treasury tunnel, whose portal is below Red Mountain Pass on US Highway 550 at an elevation of 3244 m (10,643 ft), or the Mill Level tunnel entrance 3.2 km (2 miles) east of Telluride, CO, at an elevation of 2761 m (9060 ft). The Treasury tunnel intersects the Black Bear vein 2643 m (8670 ft) from the portal and the Mill Level tunnel intersects the Argentine vein 2179 m (7150 ft) from the portal. Mining is by shrinkage stoping from slusher sublevels. The size of the scope blocks varies somewhat, but the standard size is 67 to 76 m (220 to 250 ft) long and 61 to 76 m (200 to 250 ft) high. The mine ranks either first or second in Colorado in yearly production of gold, silver, copper, lead, and zinc. It is 9.6 km (6 miles) from the Red Mountain plant to the Pandora plant, via interconnecting drifts and raises. There are engineering offices at both plants as a matter of convenience. The Red Mountain plant in¬cludes the company general offices, warehouse, carpen¬ter and machine shops, and mine change room. The Pandora plant consists of the mill and assay office, ma¬chine shops, and mine change room. The flotation mill has a capacity of 1632 t/d (1800 stpd), making a bul¬lion product and separate concentrates of lead, copper, and zinc. HISTORY OF THE MINE The Montana-Argentine vein was first extensively worked by the Tomboy Gold Mines Co., Ltd., a British concern. This company mined the stoped areas above the Ophir level between 1910 and the late 1920s and most of the stoped areas above the 2100 level between 1900 and the late 1920s. Gold was the principal ore metal mined. The area between the Revenue and Ophir levels was mined chiefly by the Revenue Mines Co. between 1900 and 1910. The ore was worked from the Revenue tun¬nel, which portals in Canyon Creek. Gold and silver were the chief metals recovered. The stopes between the 1700 and Revenue levels, as well as some higher stopes, were mined by Telluride Mines Inc. during the 1940s. The Mill Level tunnel was driven by that company from 1945 to 1948. Lead and zinc then became economically more important than the precious metals. In 1953, Idarado purchased Telluride Mines, which merged with the parent company in 1956. The Black Bear vein was first extensively worked by the Black Bear Mining Co. in the 1900s and by the Colorado Superior Mining Co. from about 1914 until snowslides at the mine camp [altitude 3750 m (12,300 ft)] terminated the company's operations in 1924. Leasers operated at intervals until 1934. The Treasury tunnel, formerly the Hammond tunnel, had been started before 1900 and reached the 1646-m (5400-ft) mark early in the 1900s, at which time activity lagged until the late 1930s. In the early 1940s, Idarado extended the Treasury tunnel from its heading at 1646 m (5400 ft) to the Black Bear vein and established a raise connec¬tion with the 600 level, the lowest level in the old mine. Since completion of initial work in the mid-1940s, systematic development of the mine, both in the driv¬ing of new headings and the utilization of older open¬ings, has resulted in the present extensive network of workings. GEOLOGY Introduction The oldest rocks of the area are the Precambrian metamorphic rocks, the Uncompahgre formation which are massive quartzites, some phyllites and slates, and dolomitic or limestone beds. West-dipping Paleozoic and Mesozoic strata lie on the Uncompahgre formation. These units are separated by a major angular uncomformity from overlying, essentially horizontal, Tertiary formations that include the basal Telluride conglomerate and several thousand feet of overlying volcanic rock. Intrusive rocks, mostly Tertiary in age, are common in the area, and are in the form of dikes, stocks, and sills. Dikes are very closely associated with some of the ore veins (Mayer). Description of Veins The Black Bear and Argentine veins range from 0.6 to 7.6 m (2 to 25 ft) in width, but in most places are 1.5 to 2 m (5 to 7 ft) wide. They vary in character from a well-defined tabular structure between sharp "frozen" walls, or gouge seams, to an irregular zone of quartz and quartz-sulfide stringers. Many gouge seams within the veins make the veins blocky and loose. Common gangue minerals in the veins include quartz, pyrite, rhodonite, chlorite, sericite, clay minerals, epidote, calcite, adularia, rhodocrosite, fluorite, and specularite. Quartz constitutes 60 to 70% of the veins and varies widely in character, ranging in color from clear through white, gray, and green, to amethyst. Chlorite, sericite, the clay minerals, and fine-grained quartz are common alteration products of the vein walls and of wall rock fragments in the veins. Epidote is an altera¬tion of the dike or, less commonly, of tuff-breccia. Calcite, adularia, fluorite, and rhodocrosite, which are wide¬

Jan 1, 1982

By R. C. Freas

Imported products and materials have been in the news over the last several years in a wide variety of industries. Certainly the mining and industrial minerals industry has not been exempt from this. Cement imports have received considerable attention in the press and a number of written articles. We are also seeing imported aggregates particularly along the gulf coast and east coast of the United states. We are now hearing increasing talk of bringing high brightness calcium carbonate from offshore sources into the U.s. domestic markets. This paper takes a look at the location of these sources, factors affecting their acceptance by U.S. industry and presents a general cost comparison of offshore and domestic calcium carbonate. In addition, the market response of U.S. suppliers and the impact of imports is also discussed.

Jan 1, 1989