Search Documents

By Robert J. Timko, Charles D. Taylor, Edward D. Thimons, Tom Mal

A test system was developed for measuring airflow in the National Institute for Occupational Safety and Health (NIOSH) ventilation gallery using a three-axis ultrasonic anemometer. The gallery was used to simulate face airflow conditions in underground mines having a blowing curtain. Airflow data collected at multiple sampling locations between the face and the end of the curtain were used to draw airflow profiles for different curtain setback distances, intake flow quantities and entry widths. In addition, methane was released at the face, measured at the sampling locations, and displayed as methane distribution in the area between the curtain and the face. Entry geometry had a significant effect on airflow patterns, and the flow patterns affected the distribution of methane in the entry. Flow measured at and parallel to the face was a good predictor of methane dilution and removal within two feet of the face.

By C J. Adams, H J. Campbell, A J. Tulloch, I J. Graham

New Zealand can be regarded as a rifted part of mineral-prospective eastern Australia. Geologically credible comparisons between selected trans-Tasman and SW Pacific geological provinces and units, especially those that contain significant mineralisation in Australia, can help provide a useful exploration framework for New Zealand. As part of a six-year Mineral Wealth of NZ and its EEZ (MWE) research programme, we have targeted selected geological units in eastern Australia for comparison and contrast with their potential New Zealand counterparts. In future years, the programme will focus on geological units in New Caledonia.

Jan 1, 2005

By J. Wagner, P. Eger, G. Melchert

In 1991, LTV Steel Mining Company decided to close an open pit taconite mine in northeastern Minnesota, using a passive treatment approach consisting of limiting infiltration into the stockpiles and wetland treatment to remove metals. Over 50 million metric tons of sulfide-containing waste had been stockpiled adjacent to the mine during its 30 years of operation. Drainage from the stockpiles contained elevated levels of copper, nickel, cobalt and zinc. Nickel is the major trace metal in the drainages, and prior to closure annual median concentrations ranged from 1.5-50 mg/L. Copper, cobalt and zinc are also present but are generally less than 5% of the nickel values. Median pH ranges from 5.0 to 7.5, but most of the stockpile drainages have pH greater than 6.5. Based on the chemical composition of each stockpile, a cover material was selected. The higher the potential a stockpile had to produce acid drainage, the lower the permeability of the capping material required. Covers ranged from overburden soil removed at the mine to a flexible plastic liner. Predictions of the reduction in infiltration ranged from 40% for the native soil to over 90% for the plastic liner. Five constructed wetlands have been installed since 1992, and have removed 60-90% of the nickel in the drainages. Total capital costs for all the infiltration reduction and wetlands exceeded $6.5 million, but maintenance costs are less than 1% of those for an active treatment plant. Since mine drainage problems can continue for over a hundred years, the lower annual operating costs should pay for the construction of the wetland treatment systems within seven years.

Jan 1, 1999

By J. David Lowell

The first part of this article is a review of industry techniques and styles during the past 50 years. It is followed by my career history during the same period. The second part covers my ideas about what works in mineral exploration. These include estimates about discovery costs, thoughts about education of explorationists, organization of exploration groups and my opinions about the relative value of exploration techniques. Evolution of exploration techniques [Table 1] shows the evolution of mineral exploration techniques and styles from 1950 to 2000. During the first half of that period, there was a progressive increase in exploration drilling. During the second half, there was a decrease in prospecting and an increase in high technology, indirect exploration and a rapid increase in discovery cost.

Jan 1, 2000

By I. D. Nock, R. M. Parkin

Paper presented at a meeting on: Artificial intelligence in the minerals sector, held in Nottingham, UK, 20 April 1993 (original title: Knowledge-based condition monitoring of cone crushers). A large proportion of the electricity used by the quarrying industry is consumed in the comminution and sizing process. In most cases aggregate processing plants operate with minimum control features resulting in limited operational efficiency. Improved control is required to increase operational efficiency with concomitant savings associated with reduction in re-circulating load and improved resource utilisation. Development work has suggested that a combination of adaptive control and process condition monitoring could improve control of comminution plants. Many commercial process control and condition monitoring systems are available, but none were deemed suitable due to the domain specific characteristics of the application. An assessment of the particular characteristics of cone crushing concluded that the application was best suited to the use of small domain specific process control combined with bespoke condition monitoring. The processing power of the control system for the project is a function not of the academic requirement, but rather the economic and practical constraints imposed by the application. As a result of the constraints a high-end PC system has been designed in preference to a workstation. Within the research project work packages are sub-divided into novel wear sensor development, knowledge based control/condition monitoring and the investigation and mathematical modelling of the wear mechanisms inherent in cone crushing. Numerous strategies were considered to implement the control system outlined. The system currently under development is a modular design which utilises intelligent novel sensors to provide a variety of data inputs

Apr 1, 1994

A survey has been undertaken of the petrography of North Island greywackes with a particular focus on the occurrence in them of smectite (swelling clay) and chlorite, two minerals that are closely associated, chemically similar, and commonly interlayered with each other. Smectite is the mineral which is a major cause of greywacke aggregatesÆ poor performance. Smectite occurs in post-metamorphic shear zones and in surface weathering profiles over greywackes. This study focuses on the petrography of fresh greywacke rocks.   The occurrence and abundance of smectite and chlorite and their relationship in greywackes is largely a function of the chemistry of the sediment and the maximum temperature that the sediment has been subjected to during diagenesis and/or very low grade (anchizone) metamorphism. Rock chemistry, particularly total iron and MgO, determines the smectite and/or chlorite content in fine-grained greywackes (argillites and siltstones) but chemistry is less influential in sandstones, where at low grades of metamorphism much of the Fe and Mg of the rock is held in unreacted detrital minerals and the mineral constituents of lithic grains.   Four zones which represent different levels of diagenesis and very low grade metamorphism, based on the crystallinity of illite and chlorite in the greywackes, and the proportion of smectite interlayered with chlorite, have been mapped in the North Island. In the anchizone smectite does not appear as a discrete mineral, it is always interlayered with chlorite. In the upper anchizone chlorite contains approximately ten per cent of smectite interlayered with chlorite. In the lower anchizone about 30 per cent smectite can occur in chlorite.   In addition to the smectite and chlorite inherent in the greywackes as the result of the thermal overprint, smectite as a discrete mineral and smectite-chlorite interlayered minerals with high levels of smectite, occur in abundance on shear zone surfaces and in alteration zones adjacent to shear zones; these are the main contributers to the high levels of smectite recorded in many greywacke aggregates.

Jan 1, 2006

By Terry J. Close

The Welcome Creek Wilderness has small, dispersed gold placers. Pockets in the 25.5 million yd3 (19.5 million m3) of alluvium along Welcome and Rock Creeks have as much as $5.61 gold/yd3 ($7.34/m3) at $500/troy oz ($16.08/g). All the alluvium averages 20.1 cents gold/yd3 (26.3 cents/m3). Because of the low average gold content large-scale placer mining would not be economically feasible. Small-scale selective pocket mining, however, may be profitable. The alluvium along the streams in the Wilderness has little apparent potential for production of sand, gravel, or stone because alternate sources are closer to markets. The four lode prospects known within the Wilderness appear to have low mineral potential. No oil, gas, uranium, or geothermal energy sources are known to be present.

Jan 1, 1982

By Richard Pizzi

Built in 1806, Boston's African Meeting House is the oldest surviving Black church building in the country. A $7 million dollar renovation was begun in 2006 to restore this historic building to its 1855 appearance and to modernize the building's accessibility, electrical and mechanical systems. As part of the restoration, an underground utility room and elevator tower, needed to provide handicap access to the Meeting House, were constructed. Extending up to 17 feet below the foundations of the abutting buildings, the utility room was constructed within one foot of some of Boston's oldest and most expensive residences. All equipment and materials had to enter the work area through a narrow alley rendering conventional methods of excavation and construction of earth support using heavy equipment unfeasible. A unique combination of micropiles, structural cap beam, internal struts and shotcrete facing was designed and constructed to provide the permanent and temporary support of the lateral loads from the earth pressures and adjacent building surcharges and the vertical loads from the elevator tower. The narrow and congested streets of the Beacon Hill neighborhood presented many day-to-day challenges for the contractor.

Jan 1, 2011

By G. L. Oldright

The studies previously made on Smelting in the Lead Blast Furnace have dealt with the custom smelter of the International Smelting Co. at Tooele, Utah,4 and on the smelter of the Bunker Hill & Sullivan Mining & Smelting Co.5 at Kellogg, Idaho. The International plant may be considered representative of the traditional custom smelter. The lead smelter of the future seemingly will have to treat increasingly richer lead charges. This feature was then stressed in describing the Bunker Hill plant.

Jan 1, 1934

By E. Marcoux, F. Lotfi, A. Belkabir, L. Maacha, A. C. Brown, S. Brunet

"Koudiat Aïcha is a small Zn-Pb-Cu deposit, enclosed in the Visean Sarhlef volcano-sedimentary series of the Moroccan Hercynian Jebilet massif. Base metal mineralization is located between a basal unit consisting of black argillite with arenite intercalations, and an upper unit composed of black argillite with locally fossiliferous calcareous units towards the top. Paraconcordant gabbro sills are present in both the upper and basal units, and the enclosing strata. Three successive phases of deformation linked to regional deformation overprint the volcano-sedimentary rocks and gabbros, as well as the sulfide mineralization.The mineral deposit includes several lenses of massive to semimassive pyrrhotite, 1 to 20 m thick, with a large halo of disseminated sulfide veinlets and sulfide nodules within a zone of intense chlorite alteration in the footwall. The ore mineralogy consists of massive to semimassive pyrrhotite with lesser amounts of sphalerite, chalcopyrite, arsenopyrite, galena, pyrite, and stannite.Lead isotope results (206Pb/204Pb averaging 18.27) suggest that the metals of the Koudiat Aïcha deposit are derived from the volcano-sedimentary host rocks. Sulfur isotopes also indicate a volcano-sedimentary origin, with bacterial reduction of sulfate (d34SCDT = -7.5‰ to -10.5‰). The conditions for sulfide meta-morphic equilibration range from 250° to 330°C (sphalerite and chlorite geothermometers). The gabbroic sills could have been a local heat source for hydrothermal circulation. Based on these geological and mineralogical features, a Besshi-type model seems appropriate for the genesis of the Koudiat Aïcha mineralization.Koudiat Aïcha est un petit dépôt de Zn-Pb-Cu, encaissé dans la série volcano-sédimentaire Viséenne de Sarhlef dans le massif Hercynien de Jebilet au Maroc. La minéralisation en métaux usuels se situe entre une unité basale d’argilite noire interlitée d’arénite et une unité supérieure composée d’argilite noire comprenant localement des calcaires fossilifères près de son sommet. Des sills de gabbro paraconcordants sont présent à la fois dans les unités basale et supérieure, ainsi que dans les strates environnantes. Trois phases de déformation successives associées a la déformation régionale superposent leurs effets sur les roches volcano-sédimentaires, les gabbros, ainsi que la minéralisation sulfurée. Ce gîte comprend plusieurs lentilles de pyrrhotite massive a semimassive de 1 a 20 m d’épaisseur au sein d’un large halo de veinules de sulfures disséminés et en nodules au sein d’une zone intensément chloritisée dans le mur du gisement. Le minerai consiste en pyrrhotite massive à semimassive avec des quantités subordonnées de sphalérite, de chalcopyrite, d’arsénopyrite, de galène, de pyrite, et de stannite. Les résultats de l’analyse des isotopes du plomb (206Pb/204Pb moyen de 18.27) suggèrent que les métaux du gîte Koudiat Aïcha proviennent des roches volcano-sédimentaires encaissantes. Les isotopes du souf¬fre indiquent eux-aussi une origine volcano-sédimentaire, impliquant la réduction bactérienne des sulfates (d34SCDT = -7.5‰ et -10.5‰). L’équilibration métamorphique des sulfures s’est produite entre 250° et 330°C (géothermomètres à sphalérite et chlorite). Les sills de gabbro pourraient avoir été la source de chaleur locale responsable de la circulation hydrothermale. Sur la base de ces caractéristiques géologiques et minéralogiques, il semble approprié d’invoquer un modèle de type pour Besshi pour expliquer la genèse de la minéralisation de Koudiat Aïcha."

Jan 1, 2008

By John P. Shubilla1, Nicholas Kyriazi

A joint effort by the Pittsburgh Research Center (PRC) and the Mine Safety and Health Administration (MSHA)3was undertaken to determine how well self-contained self-rescuers (SCSR's), deployed in accordance with Federal regulations (30 CFR 75.1714), held up in the underground environment with regard to both physical damage and aging. This report presents findings regarding laboratory-tested SCSR's in the fifth phase of testing from mid-1993to early 1996. The SCSR's were tested on human subjects and on a breathing and metabolic simulator (BMS) at PRC. These results indicate that most of the apparatus, if they pass their inspection criteria, perform satisfactorily.

Jan 4, 1996

By Madan M. Singh

This report presents the results of an investigation of inclined roof bolts, anchored over pillars, in room-and-pillar coal mines susceptible to shear failures of the roof. Although the field data do not support this contention, it is believed on the basis of analyses and other work that inclined roof bolts do offer potential under some circumstances.

Jan 1, 1978

By A Rantala, K Aberkrom, O Haavisto, P Blanz

More complex ore bodies with lowering grades increase the challenges of maintaining high throughput, energy efficiency and required particle size for optimal downstream processing in grinding circuits. Continuous and often rapidly changing characteristics of the mill feed requires constant focus to operate the circuit at optimal level. Modern process instruments, on-line analyzers, monitoring and process control systems provide attractive and managed options to increase the circuits’ capability to respond to the challenge, often in phases and in rather short time period. Furthermore, well instrumented and performing base level automation in the grinding circuit enables advanced process control (APC) strategies that utilize measurements from the whole circuit to stabilize and optimize production. In this paper alternatives for incorporating process measurements and controls to typical grinding circuits are proposed. The expected benefits to throughput, availability, energy efficiency and particle size stability are described in recent case examples.CITATION:Rantala, A, Blanz, P, Aberkrom, K and Haavisto, O, 2015. Increasing grinding circuit robustness with advanced process control, in Proceedings MetPlant 2015, pp 129–141 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 7, 2015

"Polycom, a new approach to ore processing based on pressure comminution, is obviously a very attractive alternative to conventional processing methods.Since a full-scale pilot plant was commissioned in 1986, more than 125 commercial installations, with capacities up to 1000 t/hr, have gone ahead.Already successfully used in processing cement clinker, limestone, coal, and other minerals, Polycom high pressure grinding results in:o Significantly reduced capital costs, because smaller units can be used m new installations;o Capacity increases of up to 100% in existing facilities; and o Operating economies that include energy savings of 20% or more, and reduced wear parts consumption.1. IntroductionAutogenous or semi-autogenous mills in conjunction with rod or ball mills are used with preference for ore processing. Most ball mills are of closed-circuit design and operate with mechanical classifiers (spiral or rake classifiers) or hydrocyclones. In other words, the ores undergo wet primary grinding, since slurries are required for the downstream separation stages anyway. This paper presents a new grinding system based on high pressure comminution of ores. This grinding process allows:- Energy savings of up to 20 % or more- Capacity increases of up to 100 % and more- Reduction of wear costs- Smaller units for new installation and thus- Reduced investment costsThese advantages are highly interesting for both new installations and conversion projects, particulary in cases where an increasing hardeness of the ore, i.e. rising Bond Work Index, reduces the output of the plants or where the metal assay of the ore decreases and the capacity of the existing systems has to be increased. POLYCOM high-pressure grinding rolls have established themselves with great success already for grinding cement clinker, granulated blast furnace slag, limestone, cement raw materials, coal and other materials.Meanwhile more than 250 high pressure grinding rolls have been installed worldwide. Capacities up to 1.000 t/h with roller diameter up to 2.8 m and drive units up to 2.400 kW are installed."

Jan 1, 1991

By M. F. Bucek

This report summarizes the activities performed and the results achieved during a two-phased investigation of the technical and economic feasibility of disposing of coal mine refuse underground in active mines, Three coal regions in the United States that are most severely affected by coal refuse disposal problems are identified: southwestern Pennsylvania, southern West Virginia, southwestern West Virginia and eastern Kentucky. For each region, a conceptual mine model is presented that describes the geologic conditions, mining methods, and environmental circumstances typical of that region. The model mine that was prepared for the Kanawha Region in Southwestern West Virginia and eastern Kentucky was selected as the basis for developing alternative conceptual designs of underground disposal systems in the second phase of this investigation. Procedures used in selecting the regions and in modeling typical mines are described in Part I of the report. Part II of the report describes existing methods for stowing refuse underground, presents three alternative conceptual designs of stowing system that would be appropriate for the model mine postulated in the first phase of the study, discusses technical characteristics and environmental effects relative to the various systems, and evaluates the technical and economic feasibility of the three alternative disposal system designs. Comparisons costs among systems and with costs or surface disposal are presented.

Jan 1, 1980

On July 1, 1969, the Explosives Research Center merged with the Health and Safety Research and Testing Center to form the Safety Research Center, with facilities at Pittsburgh and Bruceton, Pa. Subsequently, passage in December of the Federal Coal Mine Health and Safety Act of 1969 (Public Law 91-173) had a major influence on the activities of the new center. These activities were conducted under two main programs, Coal Mine Safety Research and Explosives Research. The Coal Mine Safety Research program was concerned primarily with two categories of hazards: health-related hazards associated with the mine environment, due to such factors as respirable dust, toxic gases and vapors, and excessive noise; and accidents due to mine fires, explosions, and roof falls.

Jan 1, 1972

By S. J. Davenport

The increased consumption and importation of fluorspar and cryolite (1)3/ in recent years, and especially the addition of fluorine compounds to drinking water in the United States, have aroused renewed interest in the properties of such compounds and possible health hazards incident to their use. It has been suggested that the issuance of a revision and elaboration of Information Circular 7311, The Hazards of Hydrogen Fluoride Poisoning in the Mineral and Allied Industries, which hay been out of print for some time, would be opportune. Fluorine minerals have been known since the Middle Ages. Fluorine was isolated in 1886 by Moisson (2).

Jan 1, 1954

By A. D. Davis, J. L. Sorensen, C. J. Webb

Environmental impacts from acidic mine drainage are growing national concerns that are particularly acute in the headwaters of the Rocky Mountain region. In the Black Hills of South Dakota, approximately one thousand mines are inactive or abandoned, most of them in the headwaters of major drainages. This paper examines the Bear Butte Creek basin, a heavily mineralized watershed with significant historical mining impacts and a surface gold mine permitted in 1997. The watershed loses its surface discharge to swallow holes in the karstic Madison Limestone. The integrity of the aquatic ecosystem was monitored with a suite of sitespecific bio-indicators. Stream surveys covered the entire reach of Bear Butte Creek from near its headwaters to the swallow holes in the Madison aquifer. Data from the stream surveys, water-quality sampling, and bio-indicator surveys clearly showed that water-quality impacts are limited mainly to Strawberry Creek and to the area of Bear Butte Creek near and downstream of the town of Galena.

Jan 1, 1999

By I. Druce, C. Li, T. Qu, J. Dong, W. Y. Xinchao, V. Nkuna

CITIC Heavy Industries has a large installed base of grinding equipment throughout Africa in different configurations, including high-pressure grinding rollers with ball mill and semi-autogenous ball crusher. The total installed power of CITIC’s mills exceeds 430 MW. In this paper, we compare several typical grinding circuits of copper in Africa with about 15 kt/d throughput based on ore properties, process selection, equipment sizing, and key equipment capital and operating costs. Actual operating performance is also introduced. The comparison for the following mine sites provides a general reference for the selection of copper grinding circuits with this approximate throughput: Kamoa-Kakula Copper Mine with high-pressure grinding rollers with ball mill circuit, and Deziwa and Sicomine Copper-Cobalt Mines with semi-autogenous ball crusher circuits

Jan 1, 2023

By N. O. Johnson

This is one of a series of-Information Circulars dealing with mining and milling methods and costs at mines in various districts in the United States. The Hog Mountain gold mining district is of the northern edge of Tallapoosa County, in the east central part of the State of Alabama. The district is equally close to Goodwater and to Alexander City, both stations on the main line of the Central of Georgia Railroad. From Alexander City the mine is reached by 13 miles of graded road, traveling in a northeast direction. In dry seasons the road is good; in wet weather it is bad but passable. Improvements are being made constantly on the road, so that in the near future the gravel road should be good under all weathered conditions.

Jan 1, 1936