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This chapter summarizes data on crude mineral production for the United States, its island possessions, and the Common- wealth of Puerto Rico. Included also are tables that show the principal mineral commodities exported from and imported into the United States and that compare world and U.S. mineral production. The detailed data from which these tables 'were derived are contained in the individual commodity chapters of volume I and in the State chapters of volume II of this edition of the Minerals Yearbook. Although crude mineral production may be measured at any of several stages of extraction and processing, the stage of measurement used in this chapter is what is normally termed "mine output." It usually refers to minerals or ores in the form in which they are first extracted from the ground, but customarily includes the production of auxiliary processing at or near the mines.

Jan 1, 1978

By S. Schina

Part of the Imittos Western Peripheral Motorway in Athens is the twin road tunnel in the vicinity of American College, with 20m excavation diameter. In the paper, the environmental and other requirements, the geometry and the geological – geotechnical characteristics of the rock formations in the construction area are given. Information regarding the modeling and analysis methods that are used for the design of the temporary support, the final lining and the wedge and slope stability analysis is described thoroughly. Finally, the results of the analyses are compared with these of measurements and general remarks during the construction of the tunnels.

Jan 1, 2001

By Allison

During the 1980’s, laboratories opened throughout the United States to serve the analysis needs of a rapidly growing asbestos abatement industry. The samples analyzed were either collected during the abatement of known asbestos-containing materials or were suspect asbestos-containing construction materials. Many asbestos analysts received minimal training and used analytical protocols that were industry specific. False positives (reporting a sample as containing asbestos when none is present) went unnoticed or had minor repercussions. The mindset of the industry was to err on the conservative side – it would be better to identify a non-asbestos fiber as asbestos than visa versa. With growing public awareness of the health hazards of asbestos, other materials began to be tested for asbestos content. Rock and ores began to be tested for naturally occurring asbestos by these laboratories using the same protocols or an in-house protocol. Analysts were given no additional training and accreditation, in most cases, it was not required. With no consistency in sample collection, testing protocol or expertise in analysis, significant discrepancies in final results can be expected. If we further complicate this scenario with misidentification of naturally occurring look-a-likes for asbestos, expensive false positives are likely. To avoid the repercussions of misidentification of naturally occurring chrysotile asbestos from look-a-like fibers in rock and ores, correct sampling and analysis protocols with more stringent scientific diagnostic criteria are needed.

Jan 1, 2005

By Walter I. Paniagua

A housing complex of 76 buildings is being constructed in the city of Morelia, in western central Mexico; the buildings are 5 levels high, with a shallow concrete slab foundation. Soil conditions include a soft clay stratum, with up to 8 m depth, in a highly seismic area. Pile foundations and micro-piles were considered, but discarded due to economic factors. The alternative of soil improvement with rigid inclusions was used. An FEM (Finite Element Method) analysis was conducted to determine the diameter, spacing, length and arrangement of the inclusions. Construction was implemented with traditional methods: soil boring, and mortar tremied with pipe and the aid of a sock to contain the material (no steel reinforcement was used). So far, 46 buildings have been built, and level measurements for 18 buildings have been recorded since 2006, with resulting good behavior in both total and differential settlements.

Jan 1, 2008

By Jian Li

Developing the Generation IV nuclear reactor is an international collaborative effort. One of the most promising Gen IV nuclear reactor designs is the supercritical water (SCW) concept, in which the water coolant runs at about 625 oC at the outlet. Under this temperature and high pressure condition, the cooling water is at supercritical state, which poses significant demand for both in-core and out of core materials. High-temperature mechanical properties, corrosion resistance and radiation damage are some of the key challenges. At present, no single commercial material can meet all the requirements of the severe SCWR conditions. Corrosion experiments per-formed under SCW condition yield various kind of corrosion modes, some are very challenging to characterize using conventional techniques. A combination of various advanced characterization techniques proofed to be essential to understand the root cause of materials? degradation.

Jan 1, 2010

By Marilia S. de Magalhaes

Keywords: sinter, characterization, agglomeration, iron ore Iron ore sinters are the main burden of blast furnaces for pig iron production. The evaluation of these agglomerates is very important due to their properties affect indirectly the productivity and costs of production of the steel industry. In the sintering plants, the standard procedure of sinter assessment has been carried out by particle size control, bulk chemical analyses, tumbler and/or shatter tests and determination of reduction degradation and reducibility indexes. Microscopy techniques have just been applied to characterize sinters produced in pilot conditions, however, these techniques, the classical ones and the less traditional, allow enhancing the industrial sintering process assessment. For investigation of the phases, microstructures and fabric, reflected-light and scanning electron microscopy(backscattered electrons images) were used; for micro analytical chemical examination, energy-dispersive X-ray spectrometry; for Kikuchi patterns registers, electron backscattering diffraction. In addition to the microscopy techniques, the magnetic behavior was depicted by means of magnetic susceptibility measurements. Iron ore sinters are made up by hematite, magnetite, silicoferrite of calcium and aluminium and silicates. These phases develop either during sintering or, in some proportion, represent remnants of ores and fluxes; this is the case of some hematite and Mg-bearing silicate, respectively. From the magnetic susceptibility results, three different behaviors were determined, which are directly related to the magnetiteproportion in the samples. The phase association and proportion, the sintering conditions andthe quality assessment are some features appraised by such procedures, which reveal themagnitude of this proposal in sintering plants.

Jan 1, 2005

By Bertram Price

Libby, Montana is the site of a large vermiculite deposit that was mined between 1920 and 1990 to extract vermiculite for commercial applications such as insulation, gardening products, and construction materials. The Libby vermiculite deposit also contains amphibole minerals including tremolite, actinolite, richterite, and winchite. Historically, Libby mine workers experienced high exposures to amphibole structures, and, as a group, have experienced the health consequences of those occupational exposures. It has been suggested that Libby residents also have been and continue to be exposed to amphibole structures released during the vermiculite mining operations and therefore are at increased risk for disease. The Agency for Toxic Substance and Disease Registry (ATSDR) conducted two epidemiological-type studies of residents living in Libby and the surrounding areas to assess these risks. The Environmental Protection Agency (EPA) collected and analyzed exposure data in Libby and used those data to project risks of asbestos-associated disease for Libby residents. The EPA has placed the Libby Asbestos Site, which includes the mine and the town of Libby, on its National Priority List of hazardous waste sites in need of clean up. This article presents a review of the exposure studies conducted in Libby and an analysis of health risks based on the data collected in those studies. Libby mine workers have experienced elevated levels of asbestos-associated disease as a consequence of their occupational exposures to amphibole structures. Libby residents? exposures typically are substantially lower than mine workers? historical exposures, and the health risk projections for residents are, accordingly, substantially lower. © 2007 Published by Elsevier Inc. Keywords: Libby; Montana; Vermiculite; Amphibole minerals; Asbestos; Asbestos-associated disease

Jan 1, 2007

By S. E. Phillipson

During the course of evaluations by the Mine Safety and Health Administration’s Roof Control Division, the controls on ground instability were investigated at surface and underground limestone mines throughout the eastern and southern United States. Structural geologic features, including joints and faults, were identified by basic geologic mapping as primary controls on highwall and back instability in surface and underground limestone mines. By comparing the spatial orientation of discontinuities and internal angle of friction with the orientation of highwalls on a stereonet, the potential for sliding, toppling, and raveling failures was evaluated in a semi-quantitative fashion. Structural geologic mapping identified faults and joints, which dismembered the back and were associated with ground instability, in underground mines. This paper documents the importance of recognizing structural geologic controls on ground stability in limestone mines, advocates basic geologic mapping as a critical component of ground control programs at surface and underground limestone mines, and provides examples of simple stability evaluations using the stereonet method.

Jan 1, 2006

By G. M. Molinda

Ground Penetrating Radar (GPR) is being investigated for the potential to determine roof hazards in underground mines. GPR surveys were conducted at four field sites with accompanying ground truth in order to determine the value of GPR for roof hazard detection. The resolution of the current system allows detection of gross roof fractures (>63 cm (s1/4 in) zone) or rider beds in coal measure roof. Data quality is not yet sufficient to detect small bed separations or subtle lithologic changes in the roof. Differences in data quality are discussed, as well as suggestions for collecting improved data.

Jan 1, 1996

By Patrick Bermingham

The advancement of hydraulic impact hammers has followed the general advancement of hydraulics. The construction industry has been revolutionized by the application of hydraulics in excavators, cranes and, of course, in the hydraulic vibratory driver/extractor, which has become a standard tool. The innate ability to move a large mass with a very small displaced volume has given hydraulic power the advantage over previous power mediums. Recent development of more specialized and complex seal configurations and compounds has greatly improved the reliability and permitted the use of higher pressures in hydraulic systems.

Jan 1, 1987

By Luis Alberto Medina

La característica principal de la composición de un cuerpo mineralizado es la heterogeneidad, dado que sus elementos no son iguales. En ese sentido, la prueba de heterogeneidad en el mineral de Cerro Verde, es una guía para la geología, mina, metalurgia y laboratorio químico, que busca optimizar los protocolos de muestreo y minimizar errores en las muestras tales como: Error Fundamental; Error de Segregación, generado por una muestra o submuestra cuando es cuarteada; Error de Extracción, generado por una muestra pequeña o insignificante colectada o tomada, y Error de Preparación, producido por la pérdida excesiva de finos. De acuerdo al estudio, el presente trabajo señala que la heterogeneidad de cobre total, cobre soluble en ácido y cobre soluble en cianuro, desarrollada para el mineral de Cerro Verde, es baja, lo que permite un manejo operacional sencillo para el muestreo con protocolos más simples, mientras que el parámetro más heterogéneo es el cobre soluble en cianuro y el protocolo podría ser afectado en el error fundamental.

Sep 13, 2001

By Steve Cole

"The economic and strategic importance of PGE bearing deposits is fuelling renewed exploration and development efforts in the precious metals mining sector.This paper presents a review of the various techniques used in the processing of PGE bearing ores, from primary benificiation to processing routes for the different flowsheets that have been developed amongst current producers. Recent innovations such as preconcentration of ore using gravity separation, recent trends in flotation circuit design and the development of hydrometallurgical routes for the direct treatment of flotation concentrates without the need for smelting will be discussed. Data from recent projects will be presented to illustrate common characteristics of PGE ores and concentrates.INTRODUCTIONThe six platinum-group elements (PGE): ruthenium, rhodium, palladium, osmium, iridium and platinum, together with gold and silver, are considered to be ""precious"" metals. The recent spike in platinum and palladium prices coupled with the projected increase in demand for the metals has fuelled a spate of exploration and new projects in the PGE sector. Historically primary producers of PGE metals have controlled the flow of information relating to the mining and processing of these ores into the public domain. Very little published information relating to individual operations and processes is available in comparison to the abundant literature relating to other metals.The purpose of this paper is to provide a general overview of the issues relating to the processing of PGE ores. Each topic discussed could easily be the topic of a paper or book and so in many cases only the surface of the topic will be scratched. An attempt has therefore been made to provide as many references as possible.This paper discusses the classification and location of PGE ores, the mineralogical factors that affect recovery of PGE's, methods currently used for recovering PGE's and process trends in PGE metallurgy."

Jan 1, 2002

By I. Liebman

The Bureau of Mines conducted experiments on coal dust explosion suppression. The investigation took place on a beltway in the double-entry of the Bureau's Experimental Mine. Using conditions that simulate those in a working mine, the investigation showed that a coal dust explosion can be readily initiated in a conveyor belt entry. Also, the explosion can spread into adjacent entries through opened crosscuts (stopping destroyed by explosion) to propagate for long distances even though the adjacent entries are rock dusted in compliance with regulations. Passive water barriers (water-filled tubs) were found to be effective in suppressing explosions on a beltway; however, barrier efficiency was reduced by opened crosscuts. The study indicated that the beltway barrier should be the distributed type consisting of continuous rows of water-filled tubs covering long distances along the entry. A plan is outlined for the installation of a water barrier system in a working coal mine for the protection of a beltway.

Jan 1, 1981

By Roberto Antoniolli

"IntroductionSINCE ancient times, the precious metals have played an important role in influencing the course of history. Silver and gold happened to occur, although in small amounts, in those countries where the early civilizations developed. Their persistent brightness certainly amazed the primitive people, who also found it easy to shape them into ornaments •and implements. Ever since then their properties have made them seem desirable possessions.Use of precious metals as money was the natural consequence of man's desire for them. The possibility of changing an ornament into a tool or food at any time, and the ease with which such medium of exchange could be carried and hidden, further increased the demand for the two metals.Silver was probably discovered after gold and copper, and was undoubtedly found by prehistoric man as native silver. The oldest silver articles have been discovered in Chaldean tombs and date back to 5000 B.C. The earliest ascertained producers of silver were Asia Minor and the Iberian Peninsula. The Romans worked deposits in Spain, Britain, and France. In the Middle Ages, some silver was extracted from German deposits, and near the end of the Middle Ages systematic workings were carried on at Freiberg, Schneeberg, and Joachimsthal (1).Before the discovery of the New Continent, the Aztecs and Toltecs in Mexico, and the Incas in Peru, had made extensive use of silver. In the 16th century the Mexican deposits became the largest source of the world silver."

Jan 1, 1954

GARY STUBBLEFIELD RMCMI PRESIDENT 1993-1994 on behalf of the RMCMI Board of Directors and Officers of The Rocky Mountain Coal Mining Institute cordially invites you and your family to attend the 90th Regular Meeting and Convention June 26 thru 28, 1994 Snowmass Resort, Colorado

Jan 1, 1993

By Benoit Virollet

Over the last 10 years the diameter of unbraced, unlined and unanchored circular shafts has grown dramatically in many parts of the world. This progress has taken place through improvements in: construction methods; concrete rheology; and design capabilities. Excavation equipment has become more precise in terms of operator control and ability to correct alignment of digging elements leading to better alignment tolerances. Also contributing to the increases in shaft diameters is the evolution of design models. A better understanding of soil structure interaction is being incorporated into the analyses in terms of radial soil stresses and imposed loads on the shaft. This paper provides an overview of the recent progress made in circular shaft construction, the primary design considerations, and some innovative uses of efficient arc elements to develop unsupported structures of other shapes. In addition, a summary of recent circular shafts constructed worldwide is provided.

Jan 1, 2006

By R. C. Burton

One of the major problems encountered with recirculatory breathing apparatus presently used by mine rescue teams is that the inspired air becomes uncomfortably, and often dangerously, hot. This is also true with self-rescuers. It is well known that man can tolerate very high dry-bulb temperatures if the wet-bulb temperature is low, but not vice- versa. The maximum tolerable, wet-bulb temperature is about 42 °C (108 °F). A continuously inhaled wet-bulb temperature above this value can cause irreversible damage to the throat and lung tissue, and wet-bulb temperatures close to it cause extreme discomfort (1) and seriously retard the capability of the man to perform useful work. A theoretical analysis, combined with experimental results, has shown that it is the carbon dioxide absorbent that is the major cause of high wet-bulb temperatures of the inspired air in the Siebe Gorman Proto 4, and in the Draeger BG 174 apparatus, both of which are used by rescue teams on South African mines (2). In the Proto 4 apparatus, the absorbent for the carbon dioxide is soda lime (calcium hydroxide). The German Draeger BG 174 also uses this absorbent but under arduous conditions such as in hot environments (50 °C, 122 °F), the use of an alkali absorbent cartridge is recommended which consists mainly of caustic soda (sodium hydroxide). Lithium hydroxide is used in some apparatus in the United States. It is clear that different absorbents will produce different quantities of heat and moisture for a given rate of absorption of carbon dioxide. The proportion of this heat and moisture which is transferred to the user depends upon how much can be removed from the recirculating air between the absorbent and the mouthpiece. This paper discusses the present methods of heat removal and describes the design and test results of a prototype evaporative cooler.

Jan 1, 1980

By Robert Jakiel

The following paper is being presented to provide an understanding of the Deep Soil-Cement Mixing (DMM) performed at Contract C09A7 at the Fort Point Channel Site (FPC), for the I-90/I-93 Interchange of the Central Artery/Tunnel Project (CA/T), Boston, MA. The paper is written as a summary of the DMM from the DMM Contractor's perspective. The summary provides technical information and practical observations that are currently considered to be state-of-the art knowledge within the soil mixing industry. The observations and information are being provided by Robert L. Jakiel, Chief Engineer of SMW Seiko, Inc., who was the DMM Project Manager and Project Engineer for the A7 Joint Venture at FPC. The DMM was started in April of 1996 and completed in December 1999. The various acronyms and terminology used to describe the soil mixing are found in a section at the end of the paper.

Jan 1, 2000

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 Patrick R. Taylor

In the search for the development of more "environmentally friendly" and more intensive waste disposal approaches to meet more and more stringent environmental regulations, thermal plasma-based processes? are considered one of the most promising alternatives to well-established technologies such as incineration. This paper presents an overview on the research and development status of thermal plasma-based waste remediation technologies. The properties of thermal plasma are described. Due to its unique feature of high-energy intensity and super high temperature, thermal plasma is particularly capable of destroying organic-containing wastes. Its potential and promising application to waste remediation may include: treatment of incinerator ashes; metallurgical dusts (especially, electric arc furnace dust); medical wastes; radioactive wastes; and other Resource Conservation and Recovery Act (RCRA) listed hazardous wastes. Many research institutes and vendors have been involved in the development of thermal plasma-based waste treatment-technology encouraged by the cleanup programs supported by the Environmental Protection Agency (EPA), the Department of Energy (DoE) and the Department of Defense (000). More recently, thermal plasma-based waste treatment technologies (sometimes called plasma-enhanced pyrolysis) are focused more and more on not only just destroying organic wastes but also on how to practically, and economically recover energy contained in the organic waste materials in addition to the recovery of metals in order to offset the high operating costs.

Jan 1, 2003