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By P. E. J. Pitfield, S. D. G. Campbell

The regional shear zone runs along or near the southern margin of the Chinhoyi greenstone belt. It hosts four of the seven mines in the southern part of the belt with recorded production above 100 kg Au, including the top two current producers. Displacement occurred in the late Archaean, producing a shear zone with a trend ranging from northeast at Golden Kopje to east at Muriel. The orebodies at the two mines formed synchronously with the shearing and show strong but contrasting structural controls on mineralisation. The Golden Kopje orebodies plunge to the southwest, parallel to the intersection of curved foliation with discrete shear planes and sub-perpendicular to local stretching lineations. The Muriel orebodies plunge steeply west but parallel to local stretching lineations. The greatest fluid flow during mineralisation of the shear zone was along either the intersection of fabrics (Golden Kopje) or the extension direction (Muriel). There is no unique relation between the orebodies and the extension or shear direction. Where earlier mining has not established the directions of the oreshoots it is essential to understand the possible structurally controlled geometries of orebodies before planning a drilling programme to evaluate their potential

Apr 1, 1996

Development of Grindability Tests Based on Direct Measurement of Energy Nowadays, for the characterisation of the grindability different grindability indices - Bond-work index (Wi), Hardgrove Grindability Index (HGI) or Zeisel specific grindability (Wt) - are used. Generally, the grindability tests are carried out under relatively simplified circumstances, in a special dry batch mill with defined feed size material until prescribed conditions are reached at room temperature. However, in the fine- and ultra fine grinding, which is a frequent task (fly ash, tailings, alumina, etc), a fine material (<50 - 200 ¦m) is usually ground down to the few micrometers. The conventional grindability testing methods and apparatuses (Bond-, Hardgrove-, Zeisel-processes) for their determination, although, are not suitable directly to measure the grindability of such fine materials, since the maximal particle size of the feed material (0.5 - 3 mm) to be tested is much higher. One of the important goals of the research carried out in our Institute was to develop the novel grindability testing methods, which are suitable for the fine and ultra fine grinding, and additionally provide the possibility for the fast determination of the grindability. In order to realise the above aim the conventional Bond- and Hardgrove- mills were modified in order to directly measure the grinding work. In particular, the Hardgrove-mill was equipped with a simple torque-meter (load cell). The Bond-mill was rigged with a digital electric power measurer. The systematic experiments were carried out parallel in both mills using the conventional and the developed methods. Finally the results of both were compared. The measuring results have proved that the Bond-work index can be determined based on the developed methods. The new grindability testing methods were applied successfully in several industrial research tasks for the determination of the specific grinding energy and the Bond-work index. These methods can be also used in the industrial practice for the control of the grinding process.

Sep 13, 2010

By R. D. Joseph

This report deals exclusively with roof-fall accidents that occurred during 1955 and 1956 in both anthracite and bituminous-coal mines throughout the United States. The report stems from a cooperative study conducted by the Bureau of Mines and the Roof-Control Committee of the Coal-Mining Section, National Safety Council. The study includes an analysis of individual accident reports, sets forth the measurable factors, and compares such factors with a representative sample of average data from 39 anthracite mines and 117 bituminous mines (appendixes A and B). Particular emphasis is placed on fatal roof-fall accidents with respect to their causes, locations, and the methods of support used at the point of occurrence. INTRODUCTION The purpose of the report is to classify all measurable details of the occurrences of roof-fall fatalities so that the material presented will assist those promoting safety and will serve as a manual for those whose principal duty is inspection of mines.

Jan 1, 1958

The Round Hill gold-scheelite deposit is located three kilometres from Macraes Flat and approximately 60 kilometres due north of Dunedin, New Zealand. A mining feasibility study is currently being undertaken on the deposit by BHP Minerals (New Zealand) Limited, who are the managers and operators of a Joint Venture with Home Reef Mining Limited. BHP has a 70 per cent equity in the project area.

Jan 1, 1987

By D. Tsweleng

In the Evraz Highveld production process, iron ore is prereduced in rotary kilns prior to charging into submerged arc furnaces (SAFs). Owing to the highly aggressive slags that are formed within the combustion zones of these kilns, chrome-oxide-containing lowcement castables have been used for some years in the kiln lining. Due to concerns around the potentially harmful effects should Cr(V1) be present in the spent linings, Highveld and its suppliers of kiln castables devoted time to developing alternative chrome-free lining materials. Such materials needed to be cost-effective and ensure good performance and improved kiln availability. This paper discusses all the parameters surrounding this development. Keywords Low-cement castable, chrome-oxide free, chrome (VI), titaniferous magnetite ore, rotary kiln, submerged arc furnace, open slag bath furnace, Evraz Highveld Steel & Vanadium Limited.

Aug 1, 2013

By Ned Baker

Details are given of a Hydride Fuel System to provide 5 kg of HZ to fuel a Caterpillar 3304 engine previously modified to operate on hydrogen fuel and intended to power an underground mining vehicle. The Fuel System was installed onto the engine and the Engine/Fuel System tested under cold start conditions and a full range of engine loads and speeds. Refueling tests were also performed. The fuel system tested will support full engine power and allow delivery of at least 3/4-power on a continuous basis, from cold start conditions.

Jan 1, 1983

By David Smith, Bernie Martin

The Queens Bored Tunnels consist of 11,000 feet of 19'-6" inside diameter tunnels mined through rock, mixed face and dense glacial till, constructed with bolted gasketed one pass reinforced concrete liner. The tunnels are to be excavated with a pressurized face TBM, either EPB or slurry. The construction of the tunnels will require ground stabilization in the mixed face area, instrumentation and monitoring of railway infrastructure, underpinning of bridges, relocation and protection of utilities, demolition of some industrial buildings, construction of open-cut approach tunnels and emergency exits and vent plants. The purpose of this paper is to describe the scope of work, the suggested methodology and the proposed construction schedule.

Jan 1, 2005

By Thomas J. Peters

Tungsten, silver, lead, zinc, and placer gold occur in the Cucamonga B RARE II area (no. B5174). A strata-bound, scheelite-bearing zone at the Blue Diamond prospect (fig. 1, no. 1) contains an estimated 16,000 tons (15,000 t) of identified, subeconomic resources averaging 0.16 percent tungsten trioxide (W03). There is a high potential for discovering additional tungsten resources at this property. The California-Hercules prospect (fig. 1, no. 5) ha; a mineral occurrence which contains an estimated 1,000 tons (900 t) of tactite averaging 1.3 oz silver per ton (45 g/t), 0.75 percent lead, and 0.72 percent zinc. Another occurrence, at the Blew Jordam Prospect (fig. 1, no. 4) has an estimated 100 tons (90 t) of tactite averaging 10 oz silver per ton (340 ,/t), 3.75 percent zinc, and 2.3 percent lead. There is a moderate potential for discovering silver, lead, and zinc resources at these prospects, which are in metamorphic pendants. There are a few lode gold prospects in the area (fig. 1, nos. 3, 11, 14) are on geologic structures which parallel the San Andreas Fault, northeast of the area. These deposits are not well exposed and have been historically unproductive. Placer gold in area B occurs locally in the beds of intermittent tributaries to Lytle Creek (fig. 1, nos. 10, 12, 13) in concentrations as high as $1.17 per cu yd ($1.53/cu m, at a gold price of $450 per troy oz). The deposits have no significant volume, but could be utilized for recreational panning and suction dredging. In the Cucamonga C RARE II area (No. C5174) placer gold occurrences locally contain as much as $1.23 per cu yd ($1.61/cu m). However, gravel containing the gold appears to be limited to stream beds, and does not occur in sufficient quantity to constitute resources. Recreational panning and dredging also may occur in this area.

Jan 1, 1983

As the theme of this conference is æRediscover OtagoÆ it would seem appropriate to revisit the era of the gold rushes and subsequent mining industry which rapidly advanced settlement and economic prosperity for Otago, and left permanent reminders in the form of historic mining sites, many of which are now encompassed within the Otago Goldfields Park. I have been invited to give a paper at this conference on the subject of æHistoric Goldfields of Central OtagoÆ. As well as having a working involvement with historic areas through my employment with the Department of Conservation, I have a personal interest in the early goldmining industry of Central Otago as my grandfather came out from Scotland in the 1890s to help construct gold dredges on the Molyneux. My grandfather made headlines in the local paper in 1920 when he believed he saw a New Zealand otter at Island Block near Beaumont - but that's another conservation trail that I will not pursue any further today! For this paper I intend to divide my time to cover the following topics. Firstly, I would like to sketch a mental picture of the characteristics that make up the Central Otago landscape, and the general perception that early miners must have had when viewing this foreign land. Then I would like to briefly discuss the changes and the consequences in the early gold rush to Central. Finally, I would like+ to discuss the establishment of the Otago Goldfields Park, which I will illustrate with several slides.

Jan 1, 1992

By David K. Hylbert

This study investigated roof falls in room-and-pillar drift coal mines in eastern Kentucky and utilized geologic methods for predicting roof conditions in advance of mining. In the Highsplint mine, the roof was classified in four categories or conditions: Condition A and B (Laminated Shale), Condition C (Rolling Sandstone with Shale in Pockets) and Condition D (Zone of Major Sandstone Roll(s)). Structure contour and isopach maps of the Darby coal bed and associated immediate roof rocks were used to project axial trends of the sandstone roof. Trend mapping in the mine and on outcrop provided more detailed control for roof projections.

Jan 1, 1978

By G. Ward Wilson

Waste rock and tailings may be combined through intimate blending to create new materials with superior physical and hydraulic properties. The new material, termed Co-Mix, has high shear strength characteristics, low compressibility, low hydraulic conductivity, and a high water retaining capacity. Co-Mixed tailings and waste rock may be used to construct cover systems, internal barriers and seals, confinement structures and full depth waste repositories. Field scale test trials using Co-Mixed blends of waste rock, tailings and slag have been constructed at the Copper Cliff Mine in Sudbury, Canad. These lysimeters will be used to evaluate the performance of the new material for cover systems that may potentially be constructed on the tailings impoundment upon closure. In this sense, the paper point out the construction of the lysimeters with respect to expected field performance during the spring snow melt period and summer to produce cover systems for closure.

Sep 12, 2005

By R. Q. Shotts

Factors of geological structure and occurrence of coalbeds, plus the resulting mining conditions, have required more care in preparing coals in Alabama than in most other districts almost since mining Alabama coals began. For this reason, literature on these coals may be interesting to those in areas where prime coals have been mined out, and thinner and less regular beds must now be exploited. This literature review has been arranged in order of subject matter. Some references have been listed more than once, but each separate review is limited to the material pertaining to the subject matter being discussed. For those seeking specific information, the authors have indicated which items repeat material and which items are most complete or specific. Geology, preparation, and carbonization of coal have been reviewed the most frequently.

Jan 1, 1963

By Jean R. Garcia, Paulo J. R. Albuquerque, Renato P. Cunha, Osvaldo Freitas Neto

"Abstract Results obtained from in-situ load tests carried out on drilled displacement piles sunk in a porous, lateritic and unsaturated soil deposit, are analyzed in this paper. Three slow-maintained load tests were performed on deep instrumented piles with a diameter of 0.37 m and around 12 m long. The soil deposit consists of a superficial, silty clay “porous” layer 6 m thick, with an average standard penetration blow count (NSPT) of 4 and cone tip resistance and sleeve friction (qc and fs) of 1.5 MPa and 48 kPa, respectively. Under this layer there is a residual stratum 10 m thick, geotechnically consisting of a “porous” clayey silt with an average NSPT of 7 and qc and fs of 2.4 MPa and 202 kPa, respectively. The water table was reached at a depth of 17 m below ground level. The results of the field load tests yielded a maximum pile load (average for the tests) of 1428 kN, which is twice as high as corresponding experimental values from standard bored piles with similar geometric conditions. Exhumation of one of the tested piles was carried out after the test, in order to check integrity and shaft conditions. Numerical finite element analyses, using the commercially available French Code LCPC Cesar®, were performed in order to back-analyze the geotechnical soil parameters for a post execution pile condition. The results permitted a better understanding of the improvement of the subsoil given the intrinsic execution characteristics of this particular pile. It was also possible to note that drilled displacement piles have great potential to become an economically viable solution in tropical soils, given the enhanced behavior of such piles when compared to alternative (cheaper) techniques. In fact, it has several advantages which should make it a key foundation type in the Brazilian market in the future.IntroductionMost buildings in tropical soils use, as the main type of foundation, deep bored or auger type piles. These types of foundations can be performed in various ways, for example with or without soil extraction, with or without bentonite mud and so on. Two main processes maybe formulated: the first execution process is typified by bored pile types, continuous flight auger piles etc., which do not cause excessive soil displacement during excavation. With respect to the second process, one could mention, amongst others, driven piles (precast concrete or steel), Franki piles and drilled displacement piles, which do displace the soil during excavation by pushing the soil laterally around the hole in order to allow either the penetration of the pile or the excavator auger."

Jan 1, 2014

Real Time and In Situ Measurement of Elemental Composition Using Lasers

Sep 13, 2010

By Francis J. Kelly

This Bureau of Mines study was made to obtain and present facts concerning the production and marketing of rare-earth metals and thorium in the Central and Southern Rocky Mountains (Arizona, Colorado, New Mexico, Utah, and Wyoming, referred to in this report as the region) and to review the current demand for these elements in the United States. Little or no published information was available on the marketing practices for these commodities. As a result of many inquiries from industry, potential prospectors, and the general public, the various factors of resources, production (present and potential), marketing, and consumption have been investigated, and the results are set forth in this report. Material concerning occurrences and deposits is from published references detailed in the bibliography.

Jan 1, 1962

The Ross Goldfield is a unique gold resource. From its discovery in 1865 there was a growing understanding of the geology of the deposit as mining moved from the surface at Jones Flat in the south to underground extraction at Ross Flat further north. Multiple layers of gold-bearing gravels were penetrated in deep shafts and six rich gold-bearing bottoms were worked. The ultimate bottom on the Old Man Group gravel surface has never been reached either at Jones Flat or at Ross Flat. Mining at Ross Flat was ultimately halted by uncontrollable flooding, by escalating costs and by a shortage of labour during the First World War. Mining at Jones Flat recommenced in the late 1980s and attention has once again been drawn to the potential magnitude of the resource at Ross Flat. Research of historic literature shows that there is potential for a bulk gold grade of 400 mg/m3 in a volume of 82 million cubic metres of gravels which lie in a basin between Jones Flat and north Ross.

Jan 1, 1993

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.Low-sulfidation epithermal gold mineralisation at Ridge Mountain occurs within the Oligocene to Miocene volcanic rocks comprising andesite, porphyritic dacite and diatreme breccia. A diatreme breccia complex with a NE–SW elongated orientation covers an area of 3.0 × 1.7 km. Four main stages of mineralisation were identified, comprising: E–W- to NW–SE-trending quartz-chalcedony veins with disseminated pyrite, chalcopyrite and gold. N–S- to NNE–SSW-trending breccia veins with quartz matrix and disseminated pyrite and accessory sphalerite, galena, chalcopyrite and gold. NE–SW-trending quartz and calcite veins with disseminated pyrite and accessory sphalerite, galena, chalcopyrite and gold. ESE–WNW- to ENE–WSW-trending quartz veins with disseminated pyrite. This stage is only mineralisation that is hosted by diatreme breccia and clearly postdates.Quartz veins of the first, third and fourth stage are less than 2 m wide. Only breccia veins of the second stage are up to 10 m wide. Gold is present in all stages as microscopic inclusions in quartz and sporadically in pyrite. Macroscopic gold can be seen in the first and second mineralisation stages. Gold commonly occurs in association with sphalerite, galena and chalcopyrite in the second and third mineralisation stages.CITATION:Kucera, J, 2015. Diatreme breccia-hosted epithermal gold deposit at Ridge Mountain, eastern Mindanao, Philippines, in Proceedings PACRIM 2015 Congress, pp 587–592 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By Michael Zachariah, Art Miller, David Kittelson, Gib Ahlstrand

This report describes an investigation in which we used iron-doped diesel fuel to generate metal-bearing diesel particles and a subsequent analysis of the particles using transmission electron microscopy (TEM) and energy-dispersive spectroscopy (EDS). For this study, DPM was generated by a 1.5-L diesel engine and the fuel was doped with ferrocene to enhance the level of iron in the system. The exhaust particles were collected on TEM grids and analyzed using the Philips CM12 TEM/EDS instrument. Results show that when the iron-to-carbon (soot) ratio (Fe/C) in the engine is low, the exhaust particles have morphologies similar to those for the undoped case, but at a threshold Fe/C value of 0.013 (for this engine), homogeneously nucleated metallic nanoparticles are formed and begin agglomerating. The number and size of these nanoparticles increase with level of doping. Metal-bearing particles that span a wider size range are also formed. Agglomeration of metallic and carbon particles is observed in two distinct modes: attachment of iron primary particles (5–10 nm in diameter) to carbon agglomerates, and coagulation of iron agglomerates (20–200 nm in diameter) with carbon agglomerates. Results of this work imply that as new engine technologies reduce soot levels in the engine and/or levels of trace metals in the fuel are increased, the generation of metallic nanoparticles may ensue, creating a potential health concern. Keywords: Nanoparticles; Particulate emissions; Metallic particles; Metal emissions

By H. F. Yancey

About 65 percent of the more than 400 million tons of coal produced annually in the United States is mechanically cleaned to remove the inorganic impurities before being sent to market. The impurities, principally shale and clay with some pyrite, average about 20 percent of the raw coal treated. Nearly 95 percent of the tonnage is treated by wet processes, in which water, suspensions of solids in water, or occasionally calcium chloride solutions are employed. Difference in density of coal and impurity is the basis of these processes. Of major importance in the separation is the competency of the impurities, that is, the resistance of the impurities to size disintegration in water. In general, the impurities are more resistant in geologically older coals or those in effect made older by metamorphism. If the impurities suffer reduction in particle size when immersed in water, the separation of organic from inorganic material becomes more difficult, Recently the Scientific Department of the National Goal Board (Great Britain) undertook fundamental research into the interaction of shale and water and also developed an empirical method of assessing shale breakdown or disintegration. 6

Jan 1, 1962

By John C. Machisak

INJURY DATA and experience at coal mines in the United States for 1956 and 1956 are presented in this publication with a minimum of interpretation and comment because of the numerous tables required to afford detailed comparisons between the 2 years. Corresponding table., for 1955 and 1956 follow in consecutive order under the following general sections: (A) General injury experience: Tables I to II: contain current data on number of fatal and nonfatal injuries, frequency and severity rates, and average severity. (B) Selected injury data: Tables 12 to 77: Contain current data on causes of injuries, distribution of injuries by part of body injured, clays of disability, extent of hand and machine loading, experience by employment and production groups, and various other operating factors and physical conditions related to the occurrence of injuries at the Nation's coal mines. (C) Injury experience, by States: Tables 78 to 87: Contain data on injuries, injury rates, employment, cause of injuries, aid severity rates by States. (D) Major disasters: Table 88: Contains data on major disasters, 1947 -56. A major disaster is defined as a single accident in which, or as the result of which, five or more persons are killed instantly or died at any time thereafter. (E) Historical coal-mine-fatality experience: Tables 89 to 93: Contain data on fatalities and their causes at bituminous-coal and anthracite mines from the earliest records through 1956.

Jan 1, 1960