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By Sarkis G. Ampian

Crystalline silica (quartz, cristobalite, and tridyrnite) is regulated by the Mine Safety and Health Administration (MSHA) and Occupational Safety and Health Administration (OSHA) because of its potential for causing debilitating but nonmalignant lung diseases. In 1987, the International Agency for Research Against Cancer (IARC) conducted a review of the health literature and concluded that crystalline silica was a probable human carcinogen. As a result of this finding, OSHA was required to regulate crystalline silica under its Hazard Communication Standard (HCS). The standard requires that all materials handled by OSHA-regulated facilities be labeled according to the requirements of RCS and that workers receive proper training on the handling of the material if the crystalline silica content equals or exceeds 0.1 weight percent (0.1 %). MSHA currently is considering enacting its own RCS. This will be similar to OSHA's RCS. If the standard is enacted, most mineral producers will have to determine the respirable monitor filter and bulk crystalline silica contents of their ores and products so that workers and/or customers will know whether they are in compliance with the 0.1% HCS and/or the OSHA permissible exposure level (PEL) of 50 µg for an 8-hour workday for respirable crystalline silica as determined from monitor samples. Two major concerns with the RCS are the widespread occurrence of crystalline silica in nature and the suitability of current technology for routinely determining crystalline silica concentrations at the 0.1 % RCS level. Most ores are extracted from silica-bearing deposits and it is a common constituent of rocks and soils. OSHA's RCS will have the greatest impact on the producers of crushed stone, diatomite, dimension stone, gravel, industrial sand, perlite, pumice, pyrophyllite, sand, and talc because these materials frequently are shipped directly from the mill to the customer. MSHA's RCS would affect nearly all mineral producers. Those producers that have crystalline silica present in concentrations near the 0.1 % cutoff point will have the most difficulty with the analysis. Crystalline silica can be quantified at the 0.1 % level by X-ray diffractometry in simple systems containing one, two, and possibly three minerals if (1) none of the accessory minerals has X-ray diffraction reflections that coincide or overlap with those of crystalline silica and (2) the standard has a particle size distribution and crystallinity similar to those of the sample. In some instances, it may not be possible to determine the crystalline silica content of a sample with any degree of certainty using the recommended regulatory protocol. In all cases, it is recommended that a qualified mineralogist identify the minerals in a sample prior to any regulatory analysis. Additionally, the uncertainty as to whether some silica polymorphs should be classified as crystalline or noncrystalline and the suitability of metastable high-temperature standards, such as cristobalite and tridyrnite, for regulatory analysis at ambient temperatures should be addressed further. This overview is written both to highlight these problems and to serve as a guide for analysts, regulators, and industry personnel who are involved in the crystalline silica issue. It also covers some of the difficulties and/or shortcomings in quantifying crystalline silica, such as the ubiquitous mineral quartz, in the workplace.

Jan 1, 1992

By Ashish Ranjan Kumar, Barbara Arnold, Luis Sanchez Gonzalez

The health and safety of miners is critical in the industry. Prolonged exposure to dust-laden air results in irreversible ailments like pneumoconiosis that have a severe impact on their lives. Operations use various personal protective devices (PPEs) to alleviate their exposure to respirable dust. Powered Air Purifying Respirator (PAPR) is one such device that uses high- efficiency filters and positive pressure masks to shield miners from airborne contaminants. Used in the medical and other industries, these respirators efficiently protected healthcare workers during the COVID-19 pandemic. Recently, the mining industry has shown a growing interest in adopting this PPE to ensure safe working conditions for the miners. We present an introduction to the PAPRs and discuss their dust capture efficacy in this manuscript.

Feb 1, 2025

By Harry E. Brownlow

The United States Bureau of Mines contracted Norecol to prepare a report identifying the regulatory processes associated with metal mine development in British Columbia using the Snip Mine as a case study. The intent of this study is to assist industry and regulatory agencies in developing understanding as to differences in objectives, perspectives and operating methods. The case study will be incorporated into a larger report summarizing the comparative advantages and disadvantages of metal mine permitting in British Columbia and Alaska. The purpose of the report is to identify the development schedule and permitting process at Snip which will assist the U.S. Bureau of Mines in suggesting improvements in environmental review and permitting processes for mine developments. The report provides an abstract of the environmental assessment review processes in Canada and the Mine Development Review Process in British Columbia and provides an understanding of the linkages between policy, legislation, and environmental review.

Jan 1, 1992

By B. J. Arnold

Coal blending inherently means homogenizing a mixture of coals so that, overall, the properties of the blend meet some specifications for maintaining power plant performance and emission requirements. In common practice, however, coal blending is at best coal mixing. If necessary, more sophisticated blending systems can produce a more homogeneous feed by using accurate weighing devices and on-line coal analyzers coupled with sampling systems. Blending can be accomplished at the mine, on stockpiles, and from bins, bunkers, and silos.

Jan 1, 1994

By William A. Hustrulid

The subject of surface mine development is large. This section covers the fundamental concepts involved in both the open pit mining of thick or steeply dipping deposits as well as the strip mining of thin, shallow, and relatively flat-lying seams or beds. Design involves the marrying of geometries, ore and waste characteristics, equipment, and economics so that the desired result is achieved. Generally, there are many possible combinations from which to choose. For example, extraction over a short time period requires one strategy while quite another is applied for longer times. Variations in supply and demand require some flexibility of operation. Customer requirements impose certain constraints regarding the set of possible designs. Over recent years, planning and operating considerations for surface mining imposed by environmental requirements have increased markedly. There have, at the same time, been enormous advances made in the design aids available to the mine planner. Computer simulation of the various options, whether it be for mine design or equipment selection, provides detailed information for decision making in real time. A significant challenge to the engineer/planner is how to best use the aids avail-able. Because of the widespread use of commercially available and in-house computer software by industry, this section does not deal with the details of planning (for basic coverage of mine development, see Section 7). Rather, some of the basic concepts are stressed. The principles involved in equipment sizing and selection are discussed. A highly important but sometimes over-looked aspect of planning, haul road design, is also covered. For surface mining operations of the future, in-pit crushing and conveying will become even more important. Some of the considerations for application evaluation are included. The section concludes with some future concepts for surface mining.

Jan 1, 2008

By E. Swartzman

This paper presents a general re-view of the various methods of briquetting coals, with and without the aid of a binder, with special reference to the production of a suitable briquette from Nova Scotia 'fines' for re-blending with industrial coal. From the economic and technical viewpoints, either small stoker-sized briquettes made with about 4 per cent asphalt in standard low-pressure double-roll presses, or briquettes made without binder in high-pressure double-roll presses, appear to be the most reasonable solution at present.

Jan 1, 1959

By Floyd G. Anderson

This report reviews and summarizes information on prevention and suppression of dust in mining, tunneling, and quarrying published in the United States from 1961 through 1967. Unpublished pertinent data developed or assembled by the Bureau of Mines during this period also are included.

Jan 1, 1969

A Discussion of the papers of James Gayley, on "The Application of Dry-Air Blast to the Manufacture of Iron" (see Trans., XXXV., 746, 1022, also pp. 315 and 745 of the present volume, and of J. E. Johnson, Jr., on "The Physical Action of the Blast-Furnace," p. 454. Chas. B. Dudley, Altoona, Pa.:—I am not a blast-furnace man, and this always puts me at a disadvantage because I cannot go into the details of the making of iron and steel. I have not the experience, and have to take the statements of other people, so what I say regarding the subject of this paper is not in the sense of an expert. When I first heard of Mr. Gayley's experiments, I said to myself, a I fear they will result in failure, since, apparently, Mr. Gayley has forgotten one chemical fact, namely, that carbon does not combine with oxygen in the absence of mater-vapor." This fact which was so astonishing when it was first brought out some years ago, and which those who are interested may find in the Journal of the Chemical Society of London, for 1885, page 349, and 1894, page 611, led me to think that the drying of the air would be a mistake. The general subject of the influence of water-vapor on chemical action is a large one; but the special point in which we are, for the moment, interested, namely, the influence of water-vapor on the combustion of carbon, was especially treated by Mr. H. B. Baker, in the papers referred to. Apparently, however, as the result of Mr. Gayley's experiments, we are to learn that the amount of moisture still left in the desiccated air is sufficient to secure perfectly satisfactory combustion. In thinking over Mr. Gayley's paper, it occurred to me that there were two alternatives, either of which might be chosen, namely, we might dry the air as Mr. Gayley does, or possibly we might, in a very much easier way, simply saturate the air at a constant temperature, and thus get uniform working and

Jan 1, 1906

By Frank T. Sisco

SHORTAGES of metals and minerals and substitution of less critical materials for those in which a virtual famine exists received detailed and frank discussion at a recent conference in Washington called by Robert E. McConnell, director of the Conservation Section, Office of Production Management. Representatives of the large engineering societies in the United States and O.P.M. department heads participated in the discussion. To open the session Mr. McConnell called upon Zay Jeffries, chairman of the O.P.M. Advisory Committee on Metal Conservation and Substitution, to summarize the present situation. Dr. Jeffries touched briefly on the status of metal shortages, which has already received considerable attention in the popular press, and said that much of the present difficulty was caused by the too-hasty substitution-without sufficient con¬sideration of the immediate conse¬quences-of metals having ordinarily a small yearly consumption, for those having a much larger annual consumption. As a result, all the alloying metals used in alloy-steel manufacture have become scarce, with the exception of molybdenum; further¬more, despite a reserve of 11,000 tons of molybdenum in this country and despite a normal consumption of only about 3500 tons and a prospective annual production rate of 21,000 tons by October, a shortage of molybdenum is possible before this war is over.

Jan 1, 1941

By M. W. Von Bernewitz

The Bureau of Mines receives frequent requests for information on the treatment of mercury ores, but as its own and almost all other publications on mercury are out of print, the Bureau has prepared this circular on the metal for the prospector and operator of small mines and plants. Mercury, commonly though improperly termed ?quicksilver?, is the only common metal that is liquid at ordinary temperatures. Mercury is used in the amalgamation of gold and silver, in power boilers, explosives, friction-less bearings, laboratory apparatus, lamps, medicine, paint, rectifiers, and for ?silvering.? The last mentioned is being superseded by silvering with silver. The use of mercury boilers may increase when they are thoroughly understood, but amalgamation is -being replaced to some extent by the use of corduroy and other collecting mediums, such as jigs and flotation cells.

Jan 1, 1937

By Catherine C. Kilgore

The Bureau of Mines investigated the availability of fluorspar (CaF2) from 36 U.S. and 50 foreign mires and deposits in 13 countries. Only 6 U.S. properties are considered to be economic, as 29 domestic deposits were found to have an average total cost of production that was uneconomical at a breakeven (0-pct) discounted-cash-flow rate of return (DCFROR). The 50 foreign properties evaluated represent at least 55 pot of demonstrated fluorspar resources located in market economy countries and China. Al I evaluated foreign operations were found to be economic to marginally economic in January 1984 dollars when compared against published prices for each country. Reserves for 56 properties totaled 97 million metric tons (mt) (recoverable Ca F,) from demonstrated ore resources of 344 million mt that contained 123 million mt CaF2. The average total cost needed to cover all costs over the life of each operation was determined for all recoverable fluorspar products. Comparisons of ruining, beneficiation, and transportation costs per metric ton of fluorspar concentrate illustrate advantages between countries. Of the three countries with the greatest fluorspar production, China, with its high-grade, low-cost operations had the lowest weighted-average total cost of production ($38/mt concentrate), Mexico was next, at $54/mt concentrate, and benefited in U. S. dollar terms from the devaluation of the peso. The Republic of South Africa needed an average of $90/mt of concentrate to cover all costs of production at its large low-grade deposits.

Jan 1, 1985

By Margaret E. Harris

The formation of nitrogen oxides, the decay of carbon monoxide, and the concentrations of residual hydrocarbons in the secondary combustion zones of propane-air and methane-air flames were studied in three enclosed burners designed to simulate gas appliances such as space and water heaters. The effect of thermally or chemically perturbing the combustion gases above these flames was determined theoretically and by means of factorial experiments. The concentrations of air pollutants and the flame temperatures were measured, and the effects of ingress of secondary air into the primary and secondary combustion zones, flame stability, burner port surface, and simulated recycling of combustion gases were noted. Based on this study, four principles were derived that, applied to gas appliance design, will insure minimal emissions of these air pollutants: 1. Oxides of nitrogen can best be kept low by depressing peak temperatures to about 3,050° F. 2. If this is not possible, then the secondary combustion zone should be cooled rapidly to this temperature. 3. Carbon monoxide concentrations can be limited by rapid induction of secondary air. 4. Hydrocarbon concentrations can be controlled by designing for well-seated, stable flames. In addition, empirical reaction rates were derived that predict the concentrations of nitrogen oxides and carbon monoxide in the primary and secondary combustion zones.

Jan 1, 1970

By Jian Zhou, Shuai Huang, Wenqin Xi, Kun Du

The deep oceans harbor a wide variety of mineral resources that are characterized by their abundance and high quality. Nations worldwide are actively pursuing the exploration and extraction of these resources. This paper provides a concise overview of the mineral resources found in the deep sea, highlighting the challenges associated with their exploitation. Furthermore, it presents a comprehensive analysis of the historical development of deep-sea mining technology and equipment, offering valuable insights into this field. By examining the current issues and obstacles faced in deep-sea mineral extraction, this study concludes that the future of deep-sea mining lies in the direction of automation, intelligence, and standardization. Additionally, it identifies the key technological advancements that need to be achieved in order to overcome the challenges associated with deep-sea mining.

Jan 5, 2024

By F. Calizaya

A booster fan is an underground fan installed in series with a main surface fan and used to boost the air pressure of the ventilation air passing through it. To accomplish this objective, the fan is installed in a permanent stopping and equipped with airlock doors, a monitoring system, and interlocking devices between main and booster fan controls. The stopping and doors are used to prevent flow recirculation, and the monitors to ensure safe operation of the fan. A booster fan, properly sized and sited, can be used to create safe work conditions and allow the extraction of minerals from areas that would otherwise be uneconomic to mine. In deep and large mines with heavy emissions of air contaminants, the required quantities of air can only be supplied by using high pressure fans. These fans will inevitably induce significant losses of fresh airflow through the stoppings and doors. For well defined ventilation circuits, booster fans can be used to decrease the main fan pressures and reduce the leakage flows. However, this will require a good understanding of the correct ventilation practice, from planning to operation and maintenance of booster fans. The objective of this study is to investigate the conditions under which booster fans can be used safely and efficiently in underground coal mines. Specifically, the study is directed at (1) collecting reliable information on airway resistances and flow requirements from two large U.S coal mines, (2) collecting fan performance data from one or more existing coal mine where booster fans are used regularly, (3) monitoring the performance of booster fans in a laboratory model and an experimental mine, (4) developing a booster fan selection method to assist the ventilation engineer at the planning stage, and (5) training six M.S. or Ph.D. graduate students in advanced mine ventilation.

Jan 1, 2010

By D. C. Myntti

An open pit mining equipment maintenance program, in order to be successful, must have many active segments covering the full range of equipment selection, trained personnel, repair facilities, preventive maintenance programs, warehousing, interdepartmental cooperation, paperwork and effective communications. The mine maintenance program is required to protect company assets Which are units of equipment generating revenue. The program should result in reduced unscheduled equipment downtime, increased equipment productivity rates, and decreased unit operating costs. Current maintenance problems; maintenance effectiveness and future projections on equipment maintenance are discussed. Equipment maintenance is big business and the maintenance department is a full-time partner in the mining venture.

Jan 1, 1978

Coal research and related activities in 1964 by the Bureau of Mines resulted in many advances in the production, preparation, and utilization of this valuable natural resource. Mining research during the year was marked by work on hydraulic mining, coalbed degasification, mine drainage control, mine sealing, strip-mine rehabilitation, and quenching of mine-refuse fires. Bureau research continued to produce information leading to increased safety in underground mining. Such research included roof and rib control via bolting and bonding, pressure monitoring of coal and mine rock during mining operations, and development of safety devices for detecting conditions leading to roof falls. Other safety work was continued on methane detectors, coal-dust suppression, and mine ventilation equipment and techniques. Mine explosion and explosives research, mine equipment and materials, safety rule modernization, and safety education and training of mine workmen were continued. Coal storage and preparation work in 1964 ranged from freezeproofing of lignite for rail shipment, through washability studies of coals and washing equipment, to research on new ways to remove ash and sulfur from coal. Electric power production, which accounts for a major portion of the market for coal, received further study. Unique power generation systems, including coal-burning gas turbine and megnetohydrodynamic generators, were intensively investigated. Conventional power systems were improved through continuation of work on furnace performance, powerplant stack gas purification, and engineering and boiler water service.

Jan 1, 1965

By Charles V. Jude

This U.S. Bureau of Mines report presents a review and evaluation of existing and new backfilling materials and methods for their applicability to the problem of gate road stress reduction in deep retreat longwall coal mines. Candidate backfill materials include pulverized coal combustion fly ash, flue gas desulfurization, and fluidized bed combustion by-products from coal-fired electric power generation plants. Properties of both backfill and its component materials are presented, with particular emphasis on the unconfined compressive strength and elastic modulus of backfill mixtures. Hydraulic mix designs discussed in this report include high-water content slurry and low-water content paste fills. Three gate road stress-transfer-modification concepts are proposed to reduce abutment stresses in gate road systems. The first concept, packwalling, involves packwall construction behind the headgate shield inby the face and adjacent to the headgate pillars. The second concept, gob-filling, involves infilling a strip of gob inset from and parallel to the headgate using paste injection methods patterned after a technology recently developed in Europe. In the third concept, entry-filling, slurry fill methods are used to fill abandoned gate roads and crosscut entries inby the face.

Jan 1, 1995

By Gus Van Weert, Samuel A. Bolorunduro, David B. Dreisingerm

"As deposits of high-grade base metal sulphides become depleted, attention must be focused on the treatment of complex sulphides, which contain significant fractions of precious metals such as gold and silver. Acid pressure oxidation is a promising process for these materials and the recovery of silver and gold will improve the economy of the process. Gold can be recovered from the oxidised residues, however, silver is incorporated into the jarosite specie and the cyanidation of the resulting residue yields very low recovery.Pressure oxidation of various complex sulphides was carried out at 110-150°C in sulphate media with additions of potassium iodide under conditions similar to industrial autoclaving. The resulting residues were subjected to cyanidation. High recovery of silver, up to 98%, was achieved because its incorporation into lead-hydronium jarosite during the pressure oxidation was minimised, while its deportment into the cyanide-soluble silver iodide was favoured. Silver recovery decreased slightly at high temperatures (140° and 150°C) because of the enhanced stability and kinetics of lead-hydronium jarosite, but this could be overcome by increasing acidity and iodide concentration of the autoclave slurry."

Jan 1, 2003

By Yuzhe Zhang, Xiaodi Huang, Xinli Wang, Bowen Li, Matthew Andriese, Xin Yan, Jiann-Yang Hwang, Zhiwei Peng

Using a TM0n0 cavity system as the main reactor, an integrated process was developed to find the best condition for waste tire rubber to absorb microwaves. The penetration depth was the main character for determining the best condition. The penetration depth is defined as the distance from the surface into the materials at which the traveling wave power drops to from its value at the surface. The waste tire powder was irradiated by two different microwave frequencies, including 915 and 2466 MHz. The study was conducted with same powder size and atmospheric condition. The effects of temperature and microwave frequency were analyzed based on the experimental data. The main trends are higher the temperature, the absorption will be better and the higher the frequency, the better the absorption will be.

Mar 1, 2017

Editor?s note: Each year, Mining Engineering features an industrial minerals review. Several people put in a fair amount of time in developing the material for this issue, all the while doing their own jobs. Thank you to the industrial minerals annual review editor, to the Industrial Minerals and Aggregates Division technical committee chair and vice-chairs, and to the authors of the individual commodity profiles. Jim Norman, member SME, of Tetra Tech, is the industrial minerals annual review editor. Rajesh Raitani, member SME, of Cytec Industries Inc., is chair of the Industrial Minerals and Aggregates Division?s Technical Committee. The technical Committee vice chairs include: ? Vishal Gupta, member SME, of FlSmidth, Agricultural Materials. ? Candace Trimble, member SME, of Oil- Dri Corporation of America, and Bradley Van Gosen, of the U.S. Geological Survey, ceramics and refractory materials. ? Stanley Krukowski, member SME, of the Oklahoma Geological Survey, chemical raw materials. ? Russell Winn, member SME, of R.E. James Gravel Co., chemical raw materials. ? Justin Zdunczyk, member SME, of Plum Creek, construction materials. ? Jerry Gauntt, member SME, of Golder Associates, fillers and pigments. ? Michael Cheshire, member SME, of Los Alamos National Laboratory, sorbents, filters and process aids. ? Rajesh Raitani, member SME, of Cytec, Industries Inc., specialty minerals. Their help makes possible this June industrial minerals issue. On behalf of ME readers, the editors thank them.

Jul 1, 2013