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The occurrence of metallic minerals in Australia to the time of the proclamation of South Australia as a Colony in 1836 was unknown. It is, therefore, perhaps, surprising that British settlers arriving in the Coromandel included among their number a German scientist Johannes Menge who had been appointed by the South Australian Company to the post of Mine and Quarry Agent and Geologist on 1 July 1836. His instructions were to `explore the natural productions of the Colony above and below ground and to superintend the working of quarries of stone and slate, the boring for water, metal, lead, coal and other mines at a salary of ú150 per annum for one year and for as much longer as the Company require your services not however exceeding five years'. In the event, he was to have little influence on those matter.

Jan 1, 1993

By George B. Quaye

Conventionally, roadways in South African collieries are 6 to 7 m wide. This dimension is chosen so as to allow maneuvrability of appropriate mine machinery and equipment, to meet production requirements and to ensure roof stability. Over the last two decades, a great deal of research effort has been expended to understand the behaviour of roadways in different strata within this width range. The results have improved the understanding of the strata behaviour to such an extent that 6 m wide roadways are developed with a high degree of confidence. With the advancement of technology and the quest to mine at a lower cost, some mines in South Africa have started considering the benefits of other types of mine machinery that will require much wider roadways to ensure optimum productivity. The roadways required will have to be about 10 - 14 m wide. The challenge confronting these coal mining companies is the potential instability that might be associated with such wide roadways. This dilemma is aggravated by the fact that, apart from theory, nothing is known about the expected behaviour of such wide roadways. This led to experimentation at a selected site in a South African coal mine where 10 m and 14 m wide roadways were developed and monitored. This paper highlights the experimental procedure adopted, discusses the results obtained, compares the prediction of elastic theory to reality and set the precedence towards understanding the behaviour of wider roadways in South Africa.

Jan 1, 2001

By F. Qunfei, W. Laijun, X. Lyu, A. Cosmos, L Huijuan, Z. Jinggang, G. Yao

In this paper, four cyanide-utilising bacteria strains were isolated from a gold mine tailings pond, in the Hexi gold mine (Shandong), China. Based on the analysis of 16S rRNA gene sequence, four strains were identified as Aeromonas hydrophila strain C1, Bacillus mojavensis strain C3, Shewanella oneidensis strain C2, and Aeromonas media strain C4. Based on the cyanide detoxification efficiencies results of the four strains, Bacillus mojavensis C3 had the highest detoxification rate and was selected to assess its efficiency to detoxify cyanide in gold mine tailings at different pH (9.5, 10.5, and 11.6) using cyanide as the sole carbon and nitrogen sources. Strain C3 was capable of detoxifying 46.5mg/L of cyanide-containing gold mine tailings at all tested pH ranges at 30oC, 196 rpm after 15 d. The amounts of cyanide detoxified were 87.5%, 84.1%, and 73.5% at initial pH 9.5, 10.5, and 11.6, respectively. The highest cyanide detoxification was observed at pH 9.5. The viable cells growths in the samples were 5.7E+09CFU/mL, 4.9E+09CFU/mL, and 2.7E+09CFU/mL at pH 9.5, 10.5, and 11.6, respectively. Free ammonia concentrations were observed as a byproduct of the biodetoxification process. The residual ammonia concentration in the sample was observed at 0.35 mg/L, 0.33 mg/L, and 0.62 mg/L at pH 9.5, 10.5, and 11.6, respectively. The highest residual ammonia concentration was noticed at pH 11.6. The amount of cyanide removed by mixed culture strains C3 and C4 was 94.6% and showed a residual free ammonia concentration of 2.6mg/L, as biodetoxification byproduct after 120 h. The pure culture Bacillus mojavensis strain C3 and its mixed culture strains exhibited higher potential to detoxify cyanide-containing gold mine tailings at alkaline pH values and could be cultivated to detoxify gold mine effluents at large-scale. Keywords: Bacteria strain, cyanide, detoxification efficiency, gold mine tailings

Jan 1, 2020

By Z. Levinson, R. Dimitrakopoulos

A mining complex is an engineering system where raw materials are extracted from several mines, processed, transported, and sold to the market. The uncertainty and local variability of material grades and their locations within the related mineral deposits are critical for determining the optimal life-of-mine extraction sequence, destination policy, operating modes, and capital investment decisions, which define the production schedule of a mining complex. Infill drilling is used to further characterise a mineral deposit and reveals information that changes the representation of the resource model and potentially the resulting optimal long-term production schedule. A self-learning reinforcement learning approach is proposed to determine the optimal drilling locations that maximise the net-present value of the long-term production schedule and the associated financial forecasts by adapting the schedule to additional information. A case study at a copper mining complex demonstrates a $70 M increase in project value by collecting drilling information with a $1 M budget.

Sep 1, 2021

By Jr. Hawk

The power generation industry may be required to reduce CO2 emissions if regulations related to global climate change are enacted. Coal-fired generation, which emits 82% of the power sector CO2, would be a likely target for CO2 reduction. Compliance with the Kyoto protocol will require a 30% reduction from the projected year 2012 emission level even with moderate load growth. This paper describes an analysis of power industry CO2 reduction options and their costs to assess how a generator would make compliance decisions under a mandatory CO2 emissions reduction program. Carbon sequestration, fuel switching and new plant construction are considered.

Jan 1, 1999

By A. H. Kaksonen

Numerous reactor designs for biological sulfate reduction have been reported. Fluidized-bed bioreactors (FBR) can efficiently retain biomass and allow high mass transfer and reaction rates. This work reviews the development of various sulfate-reducing FBR processes for treating acidic metal- and sulfate-containing waters and recovering metals from bioleaching liquors. The FBR process performance was evaluated with continuous flow experiments under various operational conditions: fluidization rates, influent pH values, metal, sulfate and salt concentrations, hydraulic retention times, electron and carbon sources, and temperatures. Substrate utilization and sulfide inhibition kinetics were determined with batch FBR-kinetic experiments. An artificial neural network (ANN) model was used to predict the performance of the FBR. Sulfate-reducing bacteria (SRB) were characterized in FBRs with molecular and culture-based approaches with the aim to gain a better understating of the bioprocesses. Based on the studies, FBRs are well suited for the combined removal of metals, acidity and sulfate from water.

Jan 1, 2010

By R. J. Matetic, J. Noll, C. Zhou, J. DuCarme, M. Reyes, J. Srednicki

"In April 2016, the U.S. Mine Safety and Health Administration (MSHA) began requiring the use of continuous personal dust monitors to monitor and measure respirable mine dust exposures to underground coal miners. Mines are currently using the PDM3700 personal dust monitor to comply with this regulation. After the PDM3700’s implementation, mine operators discovered that it interfered with proximity detection systems, thus exposing miners to potential striking and pinning hazards from continuous mining machines. Besides the PDM3700, other electronic devices were also previously reported to interfere with proximity detection systems. MSHA sought the aid of the U.S. National Institute for Occupational Safety and Health (NIOSH) and mining industry stakeholders to determine how the PDM3700 and some other electronic devices and proximity detection systems interact with each other. Accordingly, NIOSH investigated existing standards, developed test protocols, designed experiments and conducted laboratory evaluations. Some interferences were observed to be caused by electromagnetic interference from some electronic devices, including the PDM3700. Results showed that there was no significant interference when the PDM3700, as well as other electronic devices, and the miner-wearable component of the proximity detection system were separated by distances of 15 cm (6 in.) or greater. In the present study, it was found that the PDM3700 and the personal alarm device needed to be at least 15 cm (6 in.) apart in order for them to be used simultaneously and reduce potential interference. IntroductionUnderground coal miners are exposed on a daily basis to a variety of hazards, such as coal dust exposures, high noise levels, roof and rib falls, potential for fires and explosions, and operating and working with heavy machinery. One of the hazardous jobs is that of operating or working near a continuous mining machine. According to U.S. Mine Safety and Health Administration (MSHA) statistics, 44 miners had been fatally struck or pinned by a continuous mining machine since 1984. In an effort to prevent future striking and pinning fatalities from occurring, proximity detection systems have been developed and are required on all operating continuous mining machines in underground coal mines, with the exception of full-face continuous mining machines, by 2018 (MSHA, 2015a)."

Jan 5, 2018

By P. A. Hacquebard, M. P. Avery

"Gondwana coal deposits are widespread and are known to occur in four continents. They are present in Brazil, India, South Africa, and Australia. From coal petrographic examinations and a detailed literature survey, it is interpreted that Gondwana coals are present also in Canada and the United States. Laurasia, or Northern Hemisphere, coals occur in the United States, Canada, and Europe. They form the main coal producing fields of the world. Megascopically, Gondwana coals have a uniform, micro-banded appearance, with a dull lustre; Laurasian coals are bright and have distinct bands of vitrain and clarain. Petrographically, Gondwana coals, compared to Laurasian coals, are lower in vitrinite, but higher in inertinite, particularly in semifusinite. Mineral matter averages 16% in Gondwana coals and 5.7% in Northern Hemisphere coals.Gondwana coals are characterized by thick seams that terminate through lithification (Versteinerung), whereby coal passes laterally into shale. Laurasian coal seams are thinner and terminate by splitting and digitation.Vitrinite/inertinite ratio data indicate deposition of the Gondwana coals in dry marshes under strong oxidizing conditions. The Laurasian coals originated in wet marshes in a reducing environment. As deduced from fossil plants and fossil spores, temperate and near arctic conditions apply for the Gondwana coals. A tropical and subtropical climate is indicated for the Laurasian deposits. The Gondwana coals were formed under allochthonous conditions. They derived from vegetation that drifted into the peat bogs. The Laurasian coals are autochthonous and originated from vegetation that grew and was buried in the peat bogs. The Gondwana coals are Late Carboniferous and Early Permian. The Laurasian coals are entirely Late Carboniferous."

Jan 1, 2004

By O. Celep, H. Deveci, Ersin Y. Yazici, F. Ahlatci

"There are increasingly stricter environmental regulations imposed for use of cyanide leaching for the extraction of gold from ores. Alternative lixiviants to cyanide, preferably with low toxicity, have been extensively studied. Thiosulphate has emerged as one of the most suitable alternative leaching agent in place of cyanide due to its low toxicity and technical attributes e.g. fast leaching kinetics, high gold extractions from carbonaceous ores in particular. High solubility of most copper minerals in cyanide solutions results in low gold extractions due to excessively high consumption of cyanide. In contrast, low reactivity of copper minerals in thiosulphate solutions makes thiosulphate leaching potentially suitable alternative for treatment Cu-bearing gold ores. The extraction of gold/silver from a copper-bearing pyritic gold concentrate (62 g/t Au, 110 g/t Ag and 0.3% Cu) in thiosulphate solutions was investigated in this study. The concentrate is composed of predominantly quartz (25%) and pyrite (32.7%) as well as sphalerite (5.37%), galena (2.12%) and anglesite (1.13%). Other minor minerals are arsenopyrite, chalcopyrite, covellite and bournonite. Previous studies by the authors indicated that the concentrate did not respond well to cyanide leaching (i.e. 45-46% Au/Ag at 1 g/L NaCN). The effects of concentration of ammonia (0.2-1.5 M NH3), thiosulphate (0.1-0.75 M S2O3) and copper (0-20 mM CuSO4) on the extraction of gold and silver over 8 h. was investigated. Increasing the concentration of thiosulphate and ammonia substantially improved the rate and extent of gold leaching while high copper levels produced an adverse effect particularly at low concentration of thiosulphate (i.e. 0.1 M). Complete extraction of gold was achieved under suitable conditions. In contrast to gold, silver extractions remained consistently at low levels (i.e. 28%). These findings demonstrated that thiosulphate leaching could be used to achieve acceptable levels of gold extraction from the copper-bearing pyritic gold concentrate."

Jan 1, 2018

By David F. Gearhart, Mark Van Dyke, Heather Dougherty, Ted Klemetti, Gabriel S. Esterhuizen

"Coal mine longwall gateroads are subject to changing loading conditions induced by the advancing longwall face. The ground response and support requirements are closely related to the magnitude and orientation of the stress changes, as well as the local geology. This paper presents the monitoring results of gateroad response and support performance at two longwall mines at a 600-ft and 2,000-ft depth of cover. At the first mine, a three-entry gateroad layout was used. The second mine used a four-entry, yield-abutment-yield gateroad pillar system. Local ground deformation and support response were monitored at both sites. The monitoring period started during the development stage and continued during first panel retreat and up to second panel retreat. The two data sets were used to compare the response of the entries in two very different geotechnical settings and different gateroad layouts. The monitoring results were used to validate numerical models that simulate the loading conditions and entry response for these widely differing conditions. The validated models were used to compare the load path and ground response at the two mines. This paper demonstrates the potential for numerical models to assist mine engineers in optimizing longwall layouts and gateroad support systems.INTRODUCTIONThe need for roof stability in coal mine longwall gateroads places significant demands on the gateroad ground support system. The variable loading conditions associated with the approaching longwall face can cause excessive ground deformations that need to be accommodated by the support system. In coal mines in the United States several different types of supports are used to maintain the stability of gateroads. The supports may include grouted roof bolts, cable bolts, and roof trusses as intrinsic support. Standing supports include timber cribs, engineered timber props, and various types of cement-based cribs. The intensity of support is governed by the expected geologic conditions and the expected stress changes that will occur during longwall mining. At present, the design of ground support for gateroads is largely based on local experience. In-mine trials are usually conducted when new support technologies become available or ground conditions dictate a change in the support system. The research reported in this paper has the objective to assist mining engineers in evaluating alternative gateroad supports and to design suitable support systems for the local ground conditions."

Jan 1, 2018

By John J. Sammarco, Alan G. Mayton, Elaine N. Rubinstein

Researchers from the National Institute for Occupational Safety and Health (NIOSH) developed a light-emitting diode (LED) area luminaire called the Saturn and conducted a laboratory study using a Fletcher High Dual-boom Mast Feed (HDDR) roof bolting machine. The Saturn luminaire was designed to (1) enhance floor illumination to enable better detection of trip hazards in the interior spaces of a roof bolter and (2) reduce glare that has typically been an issue of concern on roof bolters. This paper reports on the results of achieving the second objective. The existing roof bolter lighting was the baseline and was compared with three versions of the Saturn luminaire relative to light intensity (100%, 75%, and 50%). Discomfort and disability glare data were obtained from 30 participants that comprised three age groups. Discomfort glare perceptions were obtained using the De Boer rating scale, and disability glare was quantified by using Mars Letter Contrast Sensitivity tests. Discomfort glare was reduced at least 3 levels with all Saturn versions. Also, a predictive model was used to estimate discomfort glare, and the results were similar. Disability glare was the least for the Saturn’s 50% intensity, and all Saturn versions had significantly less disability glare than with the baseline lighting. Veiling luminance was calculated and used as another indicator of disability glare. Veiling luminance was 28 to 42 times greater with the baseline lighting as compared with that of the Saturn lighting. Lastly, visibility levels were calculated. The Saturn versions were 4 to 6.5 times better in terms of visibility level.

By C. B. Huntress

"We have ourselves to blame in the steel industry for our condition." These words were addressed twelve days ago by James A. Farrell, President of the United States Steel Corporation, to his "comrades" at a meeting of the American Iron and Steel Institute. They carry a note of challenge to all industry, and particularly to the coal industry, where they point the way to the pressing need for operators everywhere to get their feet under one table. It is that note which I would stress to all producers. You have yourselves to blame for your condition. True, there are inter-district competition and competition of substitute fuels, but they'll always be with us, more or less, and the only sensible, sane course is to remove the evils within our respective districts, which can be done only by constructive effort along cooperative lines. It's the same story in Alabama, the same in Illinois and elsewhere. The larger number of the men gathered here are at the front, as it were, in the business of mining coal. They are the men who are doing a remarkable operating job. And naturally, the sessions of this annual meeting treat of news from the front, of technical problems. But, as in actual warfare, those at the front are often uninformed of developments in the rear. They keep on fighting without fully sensing the significance of a disaster at headquarters. You've played your eighteen holes today and evidenced the efficiency of your technique in the, production of coal. It is not amiss to take advantage of this moment, the nineteenth hole, to ponder over what it's all about. After all, what do improvements in the art of mining mean if business policies engulf you in red ink? To the extent that mechanization is a factor in increased overhead, which in turn increases the pressure to produce regardless of market demand, it only aggravates our troubles unless there is the controlling influence of coordinated effort.

Jan 1, 1931

By S. M. Bradshaw, E. Charikinya

"Microwave induced cracks have the potential to enhance metal recovery from coarse sphalerite particles in heap leaching operations by creating new crack surface areas for lixiviant and enhancing value mineral exposure. The mode of fracture and the extent of mineral exposure due to microwave induced cracks have not yet been investigated. The objective of this study was to determine the extent of particle damage and mineral exposure in microwave treated particles. This was done using X-ray computed tomography (XCT) and image analysis techniques. XCT analysis was conducted on small (–5+4.75 mm), medium (–16+9.5 mm), and large (–25+19 mm) sphalerite ore particles before and after microwave treatment (MT). Geometrical properties, such as volume and surface area of each mineral phase in each particle was determined from the XCT reconstructed images using VGStudioMax image analysis software. These geometrical properties were used to calculate the interfacial areas of sulphide mineral grains in microwave treated particles before and after MT. The ratio of specific interfacial area after MT to specific interfacial area before treatment was used as an indicator of the degree of preferential grain boundary fracture. The results showed significant grain boundary fracture after MT at all sizes. For small sized particles, about 31% of the interfacial area was lost compared to 23 and 16% for medium and large particles, respectively. The results also showed an increase in the degree of mineral grain exposure of 28, 26, and 15% for small, medium, and large particles, respectively, after MT. These results provide experimental evidence supporting improved mineral exposure due to MT. INTRODUCTIONFor some years it has been suggested that microwave treatment (MT) of ores might result in preferential grain boundary fracture that would have benefits such as improved grain exposure and particle weakening. (Kingman, 2006). Most of the experimental work investigating the application of microwaves to mineral processing flow sheets has focused on assessing the benefits of applying microwave technology to flow sheets consisting of size reduction and mechanical flotation cells (Kingman et al., 2004). Experimental studies have shown that coarse crushing during tertiary grinding of microwave treated ore resulted in a better liberated coarser flotation feed (Scott, Bradshaw, & Eksteen, 2008). It has been suggested that improved liberation in milled flotation feed, was due to the presence of grain boundary fracture in microwave treated particles. However, this improvement in coarse particle liberation does not necessarily translate to a significant improvement in downstream flotation recovery (Kobusheshe, 2010). This is as a result of the size limit to the flotation of coarse material, due to detachment forces acting on particle-bubble aggregates, which increase as the particle size increases (Jameson, 2012). Current conventional, mechanically agitated flotation cells are not designed to float coarse material (Jameson, 2012). Hence it has been difficult to show the downstream processing benefits of applying microwaves to ores processed by comminution followed by flotation (Kobusheshe, 2010). It is clear from investigations carried out so far that inappropriate downstream exploitation of microwave treated ore would fail to realise a meaningful process benefit (Kobusheshe, 2010; Ali & Bradshaw, 2011)."

Jan 1, 2016

By J. Burrows

The Chamber of Mines of South Africa is an association of major mining corporations, gold mines, coal mines, diamond mines and other metalliferous mines. It looks after those interests of its members which can best be handled on a co-operative basis. The Chamber's activities include the engagement of labour; the negotiations of all labour matters, including minimum wage rates, with recognised trade unions and associations; the carrying out of advanced technological research; representing the industry in dealings with the government and the administration of miners' training colleges and rescue training stations. Subsidiary companies of the Chamber handle matters such as the refining of gold and other metals; the processing and marketing of uranium and the marketing of Krugerrands. The thirty-two gold mines members of the Chamber of Mines of South Africa produce approximately 694 tons of gold per annum. To achieve this they employ 430000 persons and break about 8400 kilotons of rock per month. The working revenue is approximately 4 225 million US dollars per annum and the annual working profit is approximately 2 050 million US dollars. The electric power consumed by the gold mining industry is 1650 MW, about 20% of the total power produced in South Africa, and the annual costs of this power is approximately 200 million US dollars per annum. It is estimated that about 25% of this power is used for ventilation and refrigeration appliances. Thus the annual power costs for ventilation and refrigeration is approximately 50 million US dollars. The gold bearing reef is a narrow tabular deposit situated at varying depths throughout the gold fields. The weighted mean rock breaking depths and, virgin rock temperatures range from 1 700 - 9 000 ft (520 - 2 740 m) and 68 - 113°F (20 - 45°C) respectively. The maximum virgin rock temperature at which mining currently takes place is 130°F (54.5 C). Obviously at such depths and temperatures and with such a large labour force the provision of an acceptable environment is critical and to achieve this 59 000 000 cfm (28 000 m3/s) of air is downcasted during the main shift and 122500 tons (430 MW) of refrigeration are provided. Legislation in South Africa requires that on metalliferous mines when more than 1000 persons are employed underground during any one shift the manager shall appoint one or more ventilation officers. The legal responsibilities of the ventilation officers are concerned mainly with the measurement and control of dust. In practice, this is not the main part of their work and ventilation personnel perform many other duties such as measuring and controlling the distribution of air, checking the performance of fans and cooling plants, planning air and refrigeration requirements and, more recently, measuring and controlling noise and illumination levels. Ventilation personnel are specialists who provide management with advice on all matters relating to the mine environment. At the present time there are 506 persons engaged as ventilation personnel in gold mines and a further 1744 persons are employed in gold mine ventilation departments in a non-technical capacity, for example as construction workers, filter cleaners, fire patrollers, etc.

Jan 1, 1980

By Emilio Giuseppe Sarno Severi

Mining and Petroleum Similar Industries ?Asset Intensive ?Exposed to market volatility ?Highly Risky Operations ?Scarcity of Experienced and Trained resources ?Operating in diverse countries with different cultures ?Increasing Environmental and Safety Regulations

Nov 1, 2011

By ALFRED T. BARR

In certain areas of the New Cornelia pit, considerable secondary blasting is necessary to reduce oversized boulders, formed from primary blasting, to pieces which will pass the 41/2-cu yd dippers on the shovels. Some of the boulders are 'dobied, but when time permits they are blockholed and blasted. In most instances one hole drilled to a depth of 2 to 3 ft and blasted with 1/3 to 1/2 of a stick of powder will break a boulder satisfactorily. Blockholing is normally done by using a jackhammer of the 55-lb class, 1-in. round drill steel, and detachable steel bits, 2-in. gauge when new. A bit change is usually made after the completion of each hole. The use of light drilling equipment in blockholing is desirable, both from the standpoint of safety and ease of doing the work, and when it was seen there was a possibility of using a lighter jackhammer through the use of tungsten-carbide bits and at the same time get at least the same drilling efficiency as with the standard equipment, it was decided to test tungsten-carbide bits. The claims for long life of the bits and footage drilled before resharpening gave hopes of eliminating much of the delay time in changing bits which is unavoidable with the use of steel bits. and thus gain in actual drilling time.

Jan 1, 1949

By Charles H. Thurman

THE data given herein were first included in a paper read before San Francisco Section, A.I.M.E., in October 1940, and are applicable to conditions existing until the gold-dredging industry was temporarily suspended by Order L-208 of the War Production Board in the fall of 1942. There is no doubt that gold dredging will be resumed at some future time, and on a scale equivalent to that of the recent past, but the cost data given herein will be affected to some extent by conditions existing at that time, and by labor rates and prices for materials then prevailing. DRAGLINE VS. BUCKET-LINE Dragline dredges should not be considered for mining large areas of low-grade placer gravel. In such deposits a dragline operator with a 5-cu. yd. dragline would be doing well to maintain an operating cost of 6¢ per cu. yd., while a bucket-line dredge with buckets no smaller than 7 cu. ft. each could be operated for less than 4¢ per cu. yd. By operating costs, I mean only field charges such as direct operating and overhead, which includes pay roll, power or fuel, repairs and maintenance, insurance, land clearing and general expenses, but not including such items as prospecting, depletion, depreciation of equipment, State Franchise Tax, or Federal Income Tax. It is not to be inferred that a dragline dredge cannot make a profit in small low-grade deposits, where the extent of a given property is too small to justify the use of the more costly bucket-line dredge. Consider small deposits of 10¢ gravel. It is obvious that a deposit of 5,000,000 cu. yd. of such gravel could not be mined profitably with a new, 7-cu. ft. bucket-line dredge, costing upward of $250,000, and with operation costs at 4¢ per cu. yd., paying for land or royalties out of earnings; nor could a new combination 5-cu. yd. dragline and washing plant, worth upward of $125,000 and working at 6¢ per cu. yd., make a profit. These comparisons are made because the hourly capacity of both types of dredges is nearly the same. The bucket-line dredge averages 93 per cent operating time in 24 hr., as against about 80 per cent or less for the dragline dredge. These percentages of operating time are important factors in making a comparison of this kind. The bucket-line dredge has greater efficiency in cleaning soft bedrock, usually characteristic of dredging deposits, and a 7-cu. ft. bucket-line dredge can be efficient to a total digging depth of 80 ft. (65 ft. below water, 15 ft. above). A 5-cu. yd. dragline dredge is limited to about 30 ft. of efficient digging depth, 5 ft. of which could be above water. In small areas of gravel not over 30 ft. deep, a 5-cu. yd. dragline dredge could make a profit where a bucket-line dredge could not do so. As an example: compare the dredging of 3,000,000 cu. yd. of 10¢ gravel 28 ft. deep with bucket line, costing 4¢ per cu. yd., and with a 5-cu. yd. dragline dredge operating at 6¢ per cu. yd. Because of small yardage, new equipment is not warranted, therefore we can assume that the dredges of both types are used equipment, fully depreciated. Dismantling, mov-

Jan 1, 1945

By F. Boudreault, M. J. Scobie, J. Szymanski, C. Hendricks

The development of new stoping methods and more effective control over dilution, recovery and fragmentation depends on improved accuracy in blasthole drilling. The mechanisms and factors which control accuracy are poorly understood. Canadian blasthole stoping and the practices adopted for monitoring and controlling drilling accuracy are reviewed. The techniques and problems associated with blashole set-up and trajectory surveying are discussed. Four new blasthole trajectory survey systems are evaluated on the basis of their performance in recent underground trials. Conclusions are drawn as to the technological developments required so that more precise control over drilling accuracy can be achieved.

Jan 12, 1992

By P O. Koons, R J. Norris, S C. Cox

 The Southern Alps is an active oblique collisional zone which has a characteristic wedge-shaped geometry above a low-angle ductile shear zone. The Main Divide region is a relatively low strain zone above this ductile shear zone, and is _deforming principally along steeply dipping strike-slip faults. Extensional fractures are common at a high angle to the regional structural trend. These steeply dipping structures act as conduits for gold-bearing fluids from depth, and small mesothermal gold deposits have formed at several structural levels including the near-surface region. Gold has also been deposited in a meteoricmetamorphic fluid mixing zone near a conductive thermal anomaly on the western slopes of the mountains. These various gold deposits and their well-constrained structural and tectonic settings can be used as analogues for larger, deeper-eroded mesothermal gold deposits in the Mesozoic Otago Schist belt. High level Miocene veins in NW Otago have formed beneath the main divide of the initiating Southern Alps. Late metamorphic gold-bearing veins formed as fluid escaped from the ductile-deforming crustal root beneath Mesozoic mountains.  

Jan 1, 1997

By William R. Yernberg

In October 1999, Liebherr-America, Liebherr Construction and Liebherr Mining Equipment held anopen house at its Newport News, VA, plant. The open house was held to celebrate the company’s50th anniversary and to demonstrate the new TI 272mining truck. Attending the open house members of the media, vendors and company representatives from all over the world. In his introductory comments, company president Peter Eller announced Liebherr’s dedication to expanding its presence in North America. Liebherr now has 30 dealers across the United States. As part of the open house, a brief history of Liebherr was presented, beginning with its creation in1949. Liebherr engineering and sales representatives were available to answer questions.

Jan 1, 2000