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By Louis W. Cope

Mongolia is known in western countries as the location of rich dinosaur fossil fields. However, the country is even richer in mineral resources. The Ministry of Industry and Trade reports 6,000 mineral occurrences of 80 metals and minerals. Mongolia has already attracted much foreign investment in the mining sector. Mining is the country’s largest industry. It is responsible for 17 percent of the gross domestic product, 65 percent of industrial output and 57 percent of export earnings.

Jan 1, 2006

By Robert W. Yokom

As the search for new sources of energy and minerals leads to more remote areas of the country - and the world - the need to plan for adequate housing and community facilities for the construction and operations workforces and their families takes on an importance equal to the mining and processing facilities themselves. A corollary to the need for planning is the increasingly crucial need for development companies to devise effective strategies for dealing with the local communities impacted by these projects. Experience has amply demonstrated the high price to be paid for failure to learn this lesson, a price measured in lost productivity, confrontation with local communities, labor turnover, mental health and other social and eocnomic problems. In Sweetwater, Wyoming, a new industrial activity caused the population to double from 18,000 to 36,000 between 1970 and 1974. During that period industrial productivity fell 25 to 40 percent, cost overruns on the principal new industrial facility exceeded 33 percent, annual employee turnover rates climbed above 100 percent, the local mental health clinic workload increased nine times and complaints to the local law enforcement agency increased 60 percent.

Jan 1, 1981

By Ronald L. Wiegel

In the 2000 page Handbook of Mineral Dressing by A. F. Taggart, the subject of material or metallurgical balances is covered in only six pages of eve-straining type. Although Taggart's work was compiled before 1945, and there has been significant progress since then in most areas of mineral processing, the practicing metallurgist's approach to metallurgical balances remains exactly the same as described in those six pages. There are several portions of Taggart's text appropriate to introduce the subject of this paper which I would like to quote: "Milling Calculations. Computations of per¬formance in milling are complicated by the fact that it is a continuous rather than a batch operation, that the quantities of solid materials handled are large and usually mixed with water, hence difficult or impos¬sible to weigh. Fortunately it is possible to determine many facts concerning perfor¬mance without knowing weights, if the value of various constituents is known in some common unit, e.g., the content of some par¬ticular metal or mineral, or of water, or some ingredient soluble therein, or of par¬ticles of a particular size or falling within some particular size range, or the like."

Jan 1, 1979

By Konstantinos Komnitsas, Evangelos Petrakis, Emmanouil Varouchakis

During the modeling of grinding systems, population balance modeling (PBM) which considers a constant breakage rate has been widely used over the past years. However, in some cases, PBM exhibited some limitations, and time-dependent approaches have been developed. Recently, a non-linear framework which considers the traditional linear theory of the PBM as a partial case was introduced, thus allowing the estimation of product particle size distribution in relation to grinding time or the specific energy input to the mill. In the proposed model the simplified form of the fundamental batch grinding equation was transformed into the well-known Rosin–Rammler (RR) distribution. Besides, the adaptability and reliability of the prediction model are among others dependent upon the operating conditions of the mill and the adjustment of the RR distribution to the experimental data. In this study, a series of grinding tests were performed using marble as test material, and the adaptability of the non-linear model was investigated using three loads of single size media, i.e., 40, 25.4, and 12.7 mm. The results indicate that the proposed model enables a more accurate analysis of grinding, compared to PBM, for different operating conditions.

Jun 24, 2023

By Ana E. Bohé, Georgina De Micco, Juan P. Gaviría, FEDERICO J. POMIRO, Gastón G. Fouga

Chlorination and carbochlorination processes have industrial applications in metallurgical activity for extraction and purification of uncommon metals such as rare earth elements (REE). This study reviews the chlorination and carbochlorination reactions of light REE (LREE) oxides with chlorine considering the thermodynamic, stoichiometric, and kinetic aspects of the reactions. Lanthanides between lanthanum to gadolinium were considered as LREE, in agreement with previous literature, and the results were detailed in this review. LREE were analyzed taking into account their oxidation states and were divided into three groups accordingly. The results presented show that, although the LREE are chemically similar, their behaviors during the reactions with Cl2 and Cl2–C, and the different LREE-O–Cl compounds formed, have particularities. It was observed that gadolinium, in both thermodynamic calculations and experimental results, presents some differences, and it can be considered intermediate between light and heavy REE; i.e., reactions between LREE2O3 and Cl2(g) begin at approximately 250 °C, except for Gd2O3 that begins at 327 °C. The present work will contribute to a better understanding of the chemistry of LREE oxides and Cl2 under different conditions and the products obtained in the LREE–O––Cl2(g) and LREE–O–C–Cl2(g) systems.

Oct 15, 2021

By John Keefner, Charles Kocsis, Kyle A. Scalise

Geotechnical modeling of mines is crucial for understanding the many factors that can pose potential hazards or limit production opportunities. The process of back analyses for modeling is often used, but in many instances, the back analyses can be cumbersome and time inefficient.While thesemodels and back analyses may be accurate, these types of back analyses may not be ideal to be used at mines and by engineers because the process is so time-consuming. This paper introduces event-based back analyses that utilize prior events to create more accurate models while eliminating large modeling time because the models are back analyzed from previous events. The completed analyses supply a more detailed insight into the potential hazards at Round Mountain, an open pit operation, as well as provide a better understanding of how improper risk analysis results in missed opportunities. The more we understand about mining activities and processes through modeling, the safer and more productive mines will be.

May 24, 2021

By C. D. Hebert, M. R. King

The 56,000' (17 km) long San Vicente Aqueduct Pipeline tunnel is being constructed using precast concrete rings to act as preliminary ground support through two sections of the bored tunnel with lengths of 9,450' (2.9 km) and 33,700' (10.27 km).The six segment bolted trapezoidal ring was manufactured using a combination of steel fiber reinforced concrete and self compacting concrete in vertical moulds. This paper briefly describes the design and function of the segments, and reviews the development stages of the concrete mix, and the advantages and disadvantages of the adopted manufacturing method.

Jan 1, 2007

By F. N. Siddiquie, Mohd Shaif, Rajiullah Khan, Juned Alam

Manganese ore bodies of Banswara Mn belt were classified into stratiform and stratabound types, based on their mode of occurrence, distribution, and their chemical characters. These ore bodies generally composed of braunite, pyrolusite, cryptomelane/ psilomelane, wad, etc. The stratiform-type Mn ore bodies are conformable with the associated host rocks (Mn phyllite, etc.) and occurred in the form of layers, bands, etc., which are variable in their shape and size. These ore bodies are also strongly folded with the enclosing host rocks. The others, which are stratabound-type Mn ore bodies, also showed an intimate association with the associated host rocks. These types of ore bodies occurred in thin layers, pockets, lenses, stringers, etc. The classified ore bodies are confined with Kalinjara formation of Aravalli Supergroup of Paleoproterozoic age. The ore bodies are structurally controlled and well associated with phyllite, schist, limestone, quartzite, etc. The stratiform-type ore bodies constitute a marginal to low Mn grade and are also characterized by lower Mn content (26.19–39.24%) along with the Mn/Fe ratio of 7.16–12.23, while the stratabound-type Mn ore bodies are rich in Mn (35.92–49.64%) along with the higher Mn/Fe ratio of 14.15–23.97. However, the poor Mn grade along with high siliceous impurities of Banswara Mn deposits is subjected to them for intermittent mining activities in the past and, consequently, did not attract the scientific and industrial community for the evaluation of these resources. Therefore, the authors attempted this study in a scientific and systematic manner (mode of occurrence/distribution and possible methods for evaluation/exploration) to evaluate the potential of existed and newer Mn deposit resources in the Banswara Mn belt. The whole findings would be very much helpful for exploration/ mining geologist along with other concerned, to completely evaluate these Mn deposits in the future.

Aug 16, 2021

By C. G. Clifton

The Oatman District produced approximately 2.2 x 10 6 ounces of gold and 0.8 x 10 ounces of silver between 1897 and 1942. A total of 3.8 x 10 tons of ore averaging 0.58 O/T gold and 0.17 O/T silver was extracted from eight major orebodies and a number of lesser deposits. Oatman lies at the center of a trachyte-latite-rhyolite volcanic complex which contains at least one resurgent caldera. The orebodies are typical epithermal quartz-calcite + adularia lode deposits which are very deficient in sulfur. Ore deposition has occurred within dilatant zones on faults which radiate from a common point within-the complex. Fischer-Watt Mining approached the Oatman District with an integrated exploration program utilizing four basic procedures to define the characteristics of past productive areas the results of which were applied to unexplored portions of the vein system. These procedures, listed in their order of usefulness, in defining known and prospective mineralized zones are: vein contouring, detailed alteration mapping, fluid inclusion temperature determinations, and geochemical sampling.

Jan 1, 1980

By David Hopkins, Steve Klein, Bradford Townsend, Ed Sum, Derek Penrice

INTRODUCTION The Transbay-Caltrain Downtown Extension (DTX) Project involves the construction of an approximately 1.5-mile rail line that will extend Caltrain commuter service and the future California High Speed Rail system into downtown San Francisco. The underground rail extension will be constructed by mined tunnel and cut-and-cover methods. Tunneling challenges include difficult ground conditions, low rock cover, the presence of historic buildings along the alignment, and the large tunnel span, ranging from approximately 50 to 65 feet. Three mined tunnel construction methods were evaluated: the Stacked Drift Method, the New Austrian Tunneling Method/Sequential Excavation Method (NATM/SEM), and Tunnel Boring Machines (TBM). This paper describes the challenges presented within the mined tunnel section, and summarizes the evaluation of tunneling methods that led to the selection of NATM/SEM. PROJECT OVERVIEW The existing Transbay Terminal opened in downtown San Francisco in 1939. This facility is antiquated, and does not meet current building seismic safety standards or the transportation needs of the Bay Area. For these reasons, San Francisco voters approved Proposition H in 1999, which proposed to construct a new or rebuilt regional transit center at the site of the existing terminal and extend Caltrain commuter rail ser-vice to the new transit center. The new transit center is the hub of the Transbay Transit Center (TTC) Program, which will greatly enhance regional transit service by providing connectivity for six Bay Area transit providers at one facility. The program will be the largest inter-modal centerwest of New York City. The TTC Program is comprised of two major projects, the Transit

Jan 1, 2007

By Youngtak Ko, Wonnyon Kim

Korean contract Mn-nodule field in the NE equatorial Pacific is composed of seven sectors showing average water depths of 4,513 - 5,025 m. Of the various factors controlling the property of Mn-nodules, water depth has a potential linkage to chemical composition, shape and abundance of nodules. To clarify such a possibility, we review more than 20 years of research data in one of the northern sectors (hereafter KR1) where there is a marked contrast in water depth. High-resolution seabed mapping clearly separates a northern part from a deeper southern part, cutting across the middle of the KR1. In terms of nodule occurrence, manganese nodules in the deeper north are comparatively larger (2-4 cm) with rough surface (t-type) and discoidal shape (D-type), while those in the south are generally small (<2 cm) with smooth surface (s-type) and irregular shape (Itype). In addition, the nodules in the north have higher metal contents including Cu, Mn and Ni. Such connections of water depths to nodule occurrence and metal contents are commonly observed in the Korea licensed Pacific nodule fields. However, the relation between nodule abundance, size and water depth may be a different story. In KR1, nodule abundance and size are probably controlled by morphological features especially in the north. Seamounts in the north continuously provide rock fragments as new nuclei for the nodules. As a result, the nodules can not grow larger than 2 cm and show the shapes of newly formed nodules (i.e., smooth surface and irregular shapes). Such an interpretation is supported by anomalously high backscattered intensities in the side-scan sonar image map of the north, which possibly reflects a younger generation of magmatic activity.

Sep 1, 2014

By R. B. Toombs

In describing the Canadian mineral industry in a world setting, this paper examines the industry from four points of view. First, mineral industry growth is related to trends in economic activity thereby providing a measure of the industry&apos;s importance in the Canadian economy. To give perspective to the Canadian scene, reference is made to economic trends in several of the world&apos;s leading mineral producing and mineral consuming countries. The Canadian mineral industry is next examined in terms of its major developments of the past 20 years and the resultant size, structure, and production diversity of 1964. The position of the Canadian mineral industry in the world industry is then analyzed by tracing changes in mineral supply and demand patterns. Growth of the Canadian industry depends greatly on expansion of export markets because three fifths of the value of production is accounted for by exports. Finally, attention is directed to the outlook for the Canadian mineral industry. Problems facing the industry are surveyed, and an appraisal is made of economic policies that have encouraged industry growth. A forecast of mineral production value in 1970 is included.

Jan 1, 1964

By L. J. Buter, D. J. Collins

Introduction FMC&apos;s Paradise Peak gold mine was discovered by staff geologists in July 1983. Located south of Gabbs, in western Nevada, the deposit contains about 11 Mt (12 million st) of ore grading at 3.6 g/t (0.105 oz per st) of gold and 129 g/t (3.75 oz per st) silver. It is estimated that the ore contains 34 t (1.1 million oz) of recoverable gold and 933 t (30 million oz) of recoverable silver. The 3.6 kt/d (4000 stpd) mill began operation April 14, 1986, just 18 months after Davy McKee completed a feasibility study and construction, and two-and-a-months ahead of schedule. It also came in about 10% under budget at a cost of about $100 million. Crushing Run-of-mine ore is delivered from the mine in 45-t (50-st) haul trucks to a 272-kt (300,000-st) capacity open air stockpile. Ore is reclaimed using 5 m3 (7 cu yd) front-end loaders that feed a 91-t (100-st) hopper equipped with a 610- x 610-mm (24- x 24-in.) grizzly. A 1.4- x 11-m (54-in. x 35-ft) apron feeder delivers ore from the hopper by way of a vibrating grizzly screen with 127 mm (5 in.) openings to a 1- x 1.3-m (43- x 51-in.) Rexnord jaw crusher. Crushed material is conveyed to a 1.8- x 4-m (6- x 14-ft) Link Belt vibrating screen equipped with a 50-mm (2-in.) manganese grizzly bar deck. Screen oversize is fed to a 1.7/0.6-m (5.5 ft) Rexnord standard cone crusher. Product from this crusher joins the -50 mm (-2 in.) screen undersize and is conveyed to a 136-t (150-st) surge bin. Three hydraulically driven belt feeders deliver ore from the ore bin to three 2 x 6 m (7 x 20 ft) Link Belt single-deck tertiary screens fitted with 6 x 25 mm (0.25 x 1 in.) slotted polyethylene screens. Screen undersize - -6 mm (-0.25 in.) rock - is conveyed to a 3.6-kt (4000-st) ore storage bin. Screen oversize is delivered by way of a conveyor to a 91-t (100-st) surge bin. From this bin, two belt feeders feed ore to two 1.7 m (66 in.) Rexnord Gyradisc crushers, which are in closed circuit with the tertiary screens. Design features include magnetic protection for tramp iron removal and sloping floors and pump sumps for ease of clean up. Dust scrubbers keep the working environment clean and in compliance with state dust emission regulations. Grinding Two 1 x 4.5 m (3.5 x 15 ft) belt feeders deliver ore from the fine ore bin to a conveyor belt that feeds it to the 5 x 7 m (16 x 22 ft) Allis-Chalmers ball mill. The conveyor belt is equipped with a Merrick weightometer. This controls feed rate to the ball mill by speed control on the hydraulic motors driving the feeders. The 2.6 MW (3500 hp) powered mill grinds 3.6 kt/a (4000 stpd) to an average grind of 85% -75 µm (-200 mesh). The mill is in closed circuit with four 660 mm (26 in.) Krebs cyclones. Three of these are normally in operation while one is a standby. Warman pumps feed the cyclones through a cyclone distribution manifold. The cyclone underflow returns to the ball mill, which has a 300% average circulating load. Mill discharge pH is 11, and that is obtained through pebble lime addition to the feed belt. Cyclone overflow is sampled using a Heath & Sherwood two-stage sampler. It then flows to a 27-m-diam (90-ft-diam) Eimco thickener. Thickener overflow is returned to the grinding circuit, while underflow at 50% solids is pumped to the leaching circuit. Grinding-circuit design features include a steeply sloped floor for ease of clean up, an open area over the pumps for maintenance accessibility, and a ball hopper with a self discharge bottom to speed ball addition. Other features include a mill liner handler and an air clutch that connects the mill motor to the mill.

Jan 12, 1986

By D. Loring, J. Almgren

Climax Molybdenum Company’s Henderson Mine is a large panel caving molybdenum mine located about 43 miles west of Denver, Colorado. Three Joy M120-72-880 fans are installed in parallel on the No. 1 exhaust shaft. Throughout the mine’s history, ventilation changes such as the completion of the No. 5 exhaust shaft have decreased the utilization of these fans. To optimize fan performance they have been run with the full complement of 16 blades, down to as few as four blades. Since the completion of ventilation upgrades associated with the Henderson 2000 project, one surface fan has been operated under normal conditions with 10 or 12 blades. With the completion of a new network model of the Henderson ventilation system, a tool was built to develop fan curves for possible future fan configurations and predict future fan performance. This paper describes the tool and its use at Henderson.

Jan 1, 2007

By J. A. Botín

NPV is a static measure of project value which does not discriminate between levels of internal and external risk in project valuation. Due to current investment project?s characteristics, a much more complex model is needed: one that includes the value of flexibility and the different risk levels associated with variables subject to uncertainty (price, costs, exchange rates, grade and tonnage of the deposits, cut off grade, among many others). Few of these variables present any correlation or can be treated uniformly. In this context, Real Option Valuation (ROV) arose more than a decade ago, as a mainly theoretical model with the potential for simultaneous calculation of the risk associated with such variables. This paper reviews the literature regarding the application of Real Options Valuation in mining, noting the prior focus on external risks, and presents a case study where ROV is applied to quantify risk associated to mine planning.

Jan 1, 2012

By Stephen A. Orr

Underground mining is a dynamic art and science with a diverse set of design, production, and economic criteria that must be considered before selecting an optimal method to extract the ore. While all methods can be technically classified as either self-supported, supported, or caving, the multitude of subsystems and existing variations bear witness to the fact that each orebody is unique and, as such, justifies an individual approach to optimize mineral extraction. In this sense, underground mining is an art. The ability to evaluate the unique characteristics of each ore body and utilize sound engineering principles to design the optimal system constitutes effective method selection. The task by no means ends at this juncture, however. Subsequent implementation requires an ability for modification. Very rarely are all the facts available to make a concrete decision prior to development of the resource. As a result, the risk of a wrong decision can never be eliminated. This requires a significant degree of flexibility with each method. Each unit of exploration, development, or exploitation work contributed to a deposit enhances knowledge of the ore body. The best mining methods are those that correctly account for the known parameters but provide an allowance for change at minimal cost and adapt to unanticipated conditions.

Jan 1, 2008

By Guodong Li, Chenlin Wang, Zibiao Yu, Bo Xu

Abandoned coal mines have many underground space resources, such as roadways, shafts, and gobs. Among them, abandoned roadways are the best gas storage space for underground compressed air energy storage (CAES). However, CAES caverns have high air pressure and strict sealing requirements. Therefore, the stability and sealing of abandoned roadways under high internal pressure must be analyzed. Afterward, the suitability of abandoned roadways used for CAES caverns should be evaluated. In this study, the numerical simulation software FLAC3D was used to calculate the stress, deformation, plastic zone volume, and pore pressure of surrounding rock in an abandoned roadway under 10 MPa internal pressure. The influence of buried depth, surrounding rock grade, and in situ stress state on roadway stability and the effect of surrounding rock permeability on roadway sealing were analyzed. Results showed that the stress, displacement, and plastic zone volume of surrounding rock were affected by high internal pressure when the buried depth was less than 300 m, but high internal pressure had little effect on them when the buried depth was more than 300 m. The suitable range of buried depth was more than 300 m. The optimal choice of surrounding rock grade was I and II, followed by grades III, IV, and V. The optimal choice of in situ stress state was σH > σh > σv, followed by σH > σv > σh and σv > σH > σh. The sensitivity of the stability evaluation parameters was ranked in descending order as follows: buried depth, surrounding rock grade, and in situ stress state. When the surrounding rock permeability was less than 1 × 10− 14m2, the 24-h air leakage rate of the roadway was less than 1%. The suitable range of surrounding rock permeability was less than 1 × 10− 14m2.

May 23, 2023

By R. D. Auten

This paper is primarily a report on the process of using oolitic aragonite, as received from Marconi& Ocean Industries, Ltd. without further processing, for a major portion of the raw feed to a rotary kiln producing cement clinker. Oolitic aragonite is a high purity calcium carbonate material, dust free, with the appearance of a course, white sand. It is farmed when under the right conditions of temperature ocean currents, and ocean floor topography. The calcium carbonate will precipitate into small spherical particles on the ocean floor. These oceanic conditions are correct to cause precipitation of the calcium carbonate near Ocean Cay in the Bahama Island chain. The present growing deposit near Ocean Cay is in the billions of tons and is mined by a relatively shallow-operation hydraulic dredge. The aragonite thus formed is en orthorhombic crystaline form of calcium carbonate with a specific gravity of approximately 2.9. At a temperature of 505°C. (940F), the aragonite converts to the hexagonal crystal of calcite with a specific gravity of 2.6 to 2.7. This change in specific gravity weakens the structure of the particles but the individual pieces are still fairly hard. When the material is then calcined at 900°C (1650°F), the particles retain their shape but become soft and will break up under finger pressure.

Jan 1, 1978

By Erich J. Jacob

In the past 15 years the enforced improvement of the public traffic systems caused a boom in urban tunnel construction. In 1961 the City of Paris started to build the Express-Metro. Of the 47 km long double-track line crossing the city center, nearly 45 km are in operation since 1971. Still missing is here only an about 2.6 km long connecting stretch, which is under construction now. From 1963 to 1969 the 21.8 km long Victoria Line was built in London as extension of the existing network,. A little later, in the years 1965 to 1973, the City of Hamburg supplemented its subway network by the construction of a 16.8 km long line between the Boroughs of Billstedt and Stellingen. Also in 1965 the City o Munich started to build a subway system of 54 km f length. Thereof a stretch of 16.2 km could be taken into operation in 1972 shortly before the Olympic Games. These are only some of the better known projectsas examples of the activities in European cities. In nearly all cities with more than about ½ million inhabitants subsurface traffic lines were begun or supplemented. Furthermore, numerous undercuts or other subsurface structures were built. The Ij Tunnel in Amsterdam and the new Elbe Tunnel in Hamburg may be mentioned, both structures finding international attention.

Jan 1, 1976

By R. C. Burtan

Long before recorded history, man began to dig into the earth&apos;s crust in a never ending search for useful materials. It is well known that more than half of the earth&apos;s crust is composed of silicon dioxide (SiO2), also known as silica. Silica and silica-containing material have a great many uses in modern society. This material, however, is potentially an extreme health hazard. Silicosis: Not a New Disease Centuries before the Christian Era, Hippocrates wrote of a lung disease common to those who mined in hard rock. He was obviously describing silicosis. It is also apparent from ancient writings that the Egyptians were aware of this malady. Dioscorides also wrote on this subject in the fifth century B.C. It is undoubtedly the oldest and best studied of the occupational lung diseases. Silicosis was certainly described by Agricola in his De Re Metallica published in 1556. Here he described lung disease among hard-rock miners. The original document was written in Latin and then translated in 1912 by Hoover and Hoover. One of these translators was Herbert L. Hoover, a former US president who once made his living as a mining engineer. More recently, there are numerous references in medical literature in the 19th and 20th centuries relating silica exposure to silicosis. There are specific references to mining in hard rock, as well as to sandblasting and a host of other industrial exposures. In 1919, Winslow described standards for measuring the efficiency of exhaust systems in polishing shops using sandblasting. These standards were equally applicable in the mining industry. As early as 1920, Winslow explored the efficiency of certain devices used to protect sand-blasters against the dust hazard. These devices were equally applicable in the hard-rock mining industry. The medical community recognized the silica health hazard in the early 1900s. Middleton described the illness in the British Medical Journal in 1929. He noted the danger to health at that time. D. Hunter mentions in his book, The Diseases of Occupations (1969), the monumental work of Merryweather in 1936, in which he surveyed the silicosis risk in Great Britain. He showed statistically that the average employment length of sandblasters who ultimately died of silicosis was 10.3 years, compared to 40.1 years for all fatal cases, irrespective of occupation. Sandblasting and hard-rock mining and drilling, obviously, are very hazardous occupations. Weil and Zisking of Tulane University wrote in 1975 that "it was known as early as 1935 that the course of silicosis is much more rapid in sandblasters than in miners or foundry workers. This can be explained by the fact that sandblasters are exposed to an almost pure siliceous dust containing high concentrations of respirable particles within the range of 1 to 3 micron size." Protecting the Worker The medical community recognized in the early 1900s the need for proper protective equipment for all of those who worked with siliceous materials. Middleton, writing in 1929, said: "The worker is then protected by a close fitting helmet with an air feed, much as in the case of an underwater diver. In spite of these precautions, cases of silicosis among sandblasters are being met with today. It is a matter for serious consideration whether a substitute, such as steel or iron grit, could not be used to replace the siliceous grit as the abrading material." C. E. A. Winslow, a professor of public health at Yale School of Medicine, and others wrote of the need to protect sandblasters by

Jan 7, 1984