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The Macraes Mining Company Limited was listed on the New Zealand and Australian stock exchanges in January 1990, and the proceeds of the float were used to purchase a 70 per cent interest in the Macraes Gold Project, previously owned by BHP Gold Mines (NZ) Limited. Macraes Mining has had a 30 per cent interest in the project since May 1984, when it was incorporated. Project financing in the way of a gold loan was secured in February 1990 and construction commenced shortly afterwards. The mine construction activities were completed within nine months and the mine commenced operations in October 1990.

Jan 1, 1991

By Michael D. Justason

...a global perspective... In March of 2000, the Japanese Geotechnical Society added "Rapid Load Testing" to their national standard for pile testing. In the year 2000. it is estimated that there will be more than 500 "Rapid Load Tests" on foundations around the world. ...so what is a "Rapid Load Test", and why is it gaining acceptance and popularity?

Jan 1, 2001

By Patrick Pelletier Jr., Pierre-Alexandre Bossé, Gianni Bartolacci, Ian Orford, Steve Parent

"Over the last decades, many authors have shown the importance of froth in the flotation process. Mineral recovery is related to froth recovery and flotation. Selectivity is affected by froth characteristics, especially structure and loading. The characteristics of froth textures could therefore be used for diagnosing flotation.Machine imaging, especially image texture analysis, allows on-line measurement of important froth characteristics and process state classification. The measured characteristics include froth texture, loading and stability indicators. To extract information from images, texture analysis tools are used as well as a block-matching algorithm (BMA). For process state classification, images are analyzed with the same tools and clustering is done with multivariate data analysis algorithms.Two case studies, Brunswick Mine Concentrator Cu/Pb circuit and LaRonde Mine Zn circuit, are presented to show that these indicators may be used for diagnosis and control. The influence of manipulated variables on measured froth features is shown as well as the relationship between froth characteristics, mineral recovery and flotation selectivity.INTRODUCTIONImaging is a way to depict abstract characteristics of a scene or an object; it is often related to other types of scientific observations, chemical component concentrations, for example (Geladi and Grahn, 1996). In this paper, the scene is flotation froth. Imaging can be especially useful in applications where it is difficult to obtain the measurements needed for process analysis – froth flotation, for example."

Jan 1, 2006

By William S. Heckman

a. When to use: high surcharges, vertical capacity required, limit noise and eliminate vibrations, low headroom, eliminate vibration induced settlements. b. Advantages: eliminates impact noise and vibrations, high section modulus if required, vertical load bearing capacity; corrosion resistant, easy to apply facing for use as a permanent wall, adapts to complex wall layouts, would allow top- down construction, very high uplift resistance. c. Disadvantages: spoil disposal, not water tight, cannot penetrate rock and most obstructions, soil can erode between the piles if surface water and ground water are not controlled, hard to install reinforcing beams over 409 long; subject to high negative skin friction loads, high grout takes in rubble and organic soils. e. Relative cost to other systems: 30% to 50% more expensive than driven soldier piles and lagging except when surcharge loads are involved, or the pile cannot be driven due to noise and vibrations. About the same cost as a sheet pile system. Very competitive if high vertical load must be supported by the wall.

Jan 1, 1997

By Peter B. Dowden, Robert A. Robinson

Boulders, frequently found in tunnels excavated through soils, can pose major problems for full face TBMs in terms of slowing or halting the tunnel advance, cutter damage, and abrasive wear. The paper aims to consider the problem as a whole, from the geological characteristics of boulder sites, to the appropriate physical design of theTBM, and its operation in boulder-laden soils. In addition, visualization of boulders and other subsurface obstructions by seismic methods and ground penetrating radar are reviewed. The paper will assist the construction planner in assessing the risks and preparing appropriate specifications.

Jan 1, 2001

By J. S. Roberts

"Campbell mines has been in operation since 1948. Part of the process consists of roasting of a flotation concentrate which contains arsenopyrite.At present operation level the milling rate averages about 850 t.p.d. and about 48 t.p.d. of concentrate is roasted. The gas emissions at present contain between 3 and 3.5 t.p.d. of arsenic trioxide, about2 - 2.5 t.p.d. of particulate matter and between 19 - 25 t.p.d. of sulphur dioxide. The particulate is extremely fine calcine dust and it assays about 4 oz. Of gold per ton.Until 1974 the gas was discharged untreated through a 125' stack.UntreatedThe decision was made in 1972 to erect a gas treatment plant, construction ran through 1973 and operation began in 1974. The cost of the installation was about 1.3 million dollars.On investigation the process technology, it was apparent that the plant operated by giant Yellowknife for the same purpose was the model we should study. I would like to acknowledge the fine cooperation we had from giant, the plant that emerged is very similar to theirs and incorporates some improvements suggested by them and based on their operating experience.The plant is designed to remove arsenic and solid dust and it has no provisions to remove sulphur dioxide.We depend upon the 125' stack to assure adequate dilution. Because of the nearby airport the stack cannot exceed 125'. A stack burner is provided that can ""y used to heat the stack gas and carry it higher into the atmosphere when there is an inversion condition.The removal of arsenic from hot gas is fairly simple. The sublimation point is about 425°f, a few degrees above this point the arsenic is a gas and a few degrees below it condenses into a solid form. The arsenic could have been removed by simply dropping the temperature below the condensation point and collecting all the solids in a baghouse. This would have removed the possibility of recovering the gold in the calcine dust and would have produced an impure and more bulky arsenic material to be placed in safe storage. The decision was made to collect the solid dust in a hot electrostatic precipitator operating above the sublimation point and subsequently lower the temperature below the condensation point and collect the arsenic in a baghouse."

Jan 1, 1976

By P. A. Hagerty

Biological treatment of metals-impacted water using sulfate reduction is a viable means of treatment that has been applied in pilot and full scale at numerous projects. One of the fundamental challenges with this type of treatment is the selection of an appropriate substrate to support the sulfate reduction process long-term. The substrate degradation products provide a carbon source and an electron donor for metabolism by sulfate-reducing bacteria and consequently organic characteristics are critical; however, the physical attributes of the substrate are equally critical to an efficient and optimized substrate mix. This paper explores the affect of particle size (a.k.a. grain size) of several substrate mixes on the treatment efficiency of sulfate reducing treatment systems. Substrate selection can be separated into two phases of evaluation, the primary selection phase and the secondary optimization phase. The primary selection phase considers such fundamental attributes as source availability, economics, bioavailability and longevity. These fundamental activities are conducted in order to identify potential candidate ingredients of the substrate mix which are regionally available, economically viable and consistent with the biogeochemical aspects of the project. Recent work has been conducted in the development of testing protocol for organic substrates to quantify bioavailability (Martinez Hernandez et al. 2010, Place et al. 2006) as part of the primary selection phase. Once the substrate ingredients have been selected based on the primary criteria, the mixture of these ingredients is then developed based on an optimization process, including consideration of the substrate ingredient?s particle size distribution.

Jan 1, 2011

The geologist is often called upon to give judgment on the possibilities of reviving a former mining field presumably worked out as far as the evidence then available indicated. From time to time, scarcity and consequent high prices of metals has led to there-examination of many old fields. The possibility of resuming investigation on them where the practical miner ceased work, even where he had the aid of the trained geologist, has long since disappeared.Means of access to mines have been removed and water fills the workings. Hence an indirect mode of attack becomes essential.This method depends mainly on past history, and may be described as a reaching out by faith supported by shrewd guessing from the known to the unknown. Apart from whatever general intelligent observations may be made in situ of the evidence of former mining activity, the method depends largely on the examination of the past history of the field as revealed in the official records, company reports, plans of underground workings, local newspaper accounts, and the testimony of practical miners formerly employedon the field, the' reliability of which has to be carefully sifted. The matter derived from the examination of these sources must next be rigorously collated and correlated where possible. When the review of all individu!1l features and aspects has been completed, tentative and speculative conclusions may be drawn which, though not verifiable before the event, will usually prove to be more serviceable guides in exploratory operations than mere "blind stabbing."As an actual illustration of what is involved in the mode of procedure outlined above, the following is the description of an investigation in which the writer took part.In 1937, during the course of the Commonwealth Aerial, Geological and Geophysical Survey of Northern Australia, a detailed geological investigation was undertaken of the Croydon gold field, situated near the south-eastern. extremity of the Gulf of Carpentaria in North Queensland.The history of the field briefly is as follows: It was discovered in 1885, reached its peak of production 1896, declining thereafter till 1906, when operations ceased. The total production was about 1,000,000 ounces of gold bullion, containing approximately 40 per cent. of silver. The gold bullion was won from flat-dipping quartz reefs, which yielded an average of 2.oz. to the ton, and the maximum depth to which production occurred was 500 feet. Subsequent prospecting below this depth failed to locate further ore.In consequence of the inaccessibility of the mines and the almost total masking of the' surface by alluvium, the investigation of future possibilities became largely an. office ,study, which was conducted under the following headings:-1. Recording of factual data of each mine separately.

Jan 1, 1950

By Burton Scott

A device for detecting carbon monoxide at ppm levels is described which is based on the measurement of infrared absorption at 4.65 microns. The unique feature of the nondispersive infrared instrument is contained in the optical design which includes a confocal cavity, increasing the effective optical path length by a large factor, thus greatly reducing the required package size. The cavity has the effect of reducing the total amount of radiation passing to the detector, but at the same time increasing the percent attenuation observed when adding CO, by a factor called gain. The radiation is chopped by a filter wheel which contains narrow band filters at 4.0 and 4.65 microns. The resultant signal produced by the pyroelectric detector is demodulated by the electronics to product an automatic gain control signal, proportional to the total radiation, and a difference signal, proportional to the CO present. Tests of a breadboard model are described which show cavity gains of 10 with noise levels equivalent to 2 to 10 ppm CO.

Jan 1, 1975

By Edwin F. Shorey, Richard F. Coon, Steven B. Fradkin

Crosstown Interceptor Phase IA is the first deep tunnel element of the Milwaukee Inline Project. The tunnel contract includes 6,492 meters (m) of 9.1-m-diameter tunnel, two access shafts, and partial lining for structural purposes. The work also includes grouting to be performed as directed by the engineer to provide groundwater infiltration control in lined and unlined reaches of the tunnel. This paper summarizes infiltration observations, progress of the grouting work, and its potential application to the remainder of the Milwaukee project.

Jan 1, 1987

Recently, work was carried out by the Shotcrete Working Group to study anisotropy in steel fibre reinforced shotcrete using strain-controlled, compressive strength testing methods. The shotcrete materials used and specimen preparation procedures as well as testing methods are described. The test results are discussed and it is concluded that, because of the anisotropic nature of fibre reinforced shotcrete, it may be worthwhile investigating the degree of such anisotropy in practice using strain-controlled, strength testing techniques.

Jan 1, 2001

By Les Gutzwiller

Fan applications in the mining industry have changed during the last 70 years. In 1922, J.R. Robinson authored a technical volume entitled Practical Mine Ventilation. At that time, atmospheric control had only recently shifted from natural to mechanical. The large, mechanical draft fans that were used then were centrifugal. The fans ran at low speeds, about300 rpm. Most were steam-engine driven. In the late 1920s and early 1930s, mines became larger, increasing the pressure and volume requirements of the fan equipment. Axial fans were designed to run at much higher speeds (710 to 880 rpm) and were driven by electric motors. They were also smaller and less expensive to install than the cumbersome centrifugal units. However, changes in mining have resulted in progressively higher static-pressure requirements. So centrifugal fans are once again proving to be a good choice.

Jan 1, 1999

By G. Coombs, L. Meade, J. Welshimer

Industrial Minerals commodity profiles are continued from May's Annual Review issue. Diatomite G. Coombs, Manville Sales Corp. Growth in US diatomite production continued to lag in 1986. The US Bureau of Mines estimated that 580 kt (640,000 st) were produced last year. This is a 1%0 growth over 1985. The cumulative growth from the 1982 low point is 4.4%. Present production, though, is still only 90% of the high tonnage of 1979. The industry will see increased competitive activity with the start-ups of two new mines and production facilities in California and Oregon. US production has come primarily from Lompoc, CA, Bassalt, Clark Station, and Lovelock, NV, and Quincy, WA. New production, probably with capacities of 45 kt/a (50,000 stpy) each, have started near Burney, CA, and Vale, OR. Eagle Picher's new, full-line filter aid and filler plant at Celatom, Vale, OR, was dedicated in August. The plant uses diatomite from the Celatom mining district in Juntura, OR. Grefco's new filter aid and filler plant near Burney, CA, was ready in July. It produced flux calcined products through a single kiln and can handle both bag and bulk shipments. The operations are in Shata County with the plant and mine at the same site. Manville Specialties Group is moving its Filtration and Minerals Division headquarters and research staffs to Lompoc, CA. The move is intended to strengthen response and performance by locating research, marketing, and production close together. Diatomite is processed in three methods: natural, calcined, and flux calcined. The natural is dried to remove water and is particle size classified. Calcined or straight calcined products have been sintered to modify particle size or permeability. Flux calcination, or flux sintering, has a stronger influence on permeability and also benefits color. The unique structure of diatomite is used in a range of particle sizes from fine paint fillers, to coarser filter aids, to granular aggregates. Dimension stone L. Meade, Geomapping Associates Ltd. 1986 was another good year for dimension stone production. The trend toward using marble, granite, limestone, sandstone, and slate has created an increasing demand. According to US Bureau of Mines 1986 estimates, 1.1 Mt (1.2 million st) of dimension stone, with a value of $173 million, was produced by 200 companies. This is an increase from 1985, where 220 companies produced 1 Mt (1.12 million st) valued at $172 million. The increased production volume and decreased unit value is due to the competition from imports. The net import reliance in 1986 was 68% compared to 62% in 1985. The value of imports was $374 million in 1986 versus $295 million the year before. In an effort to maintain their market share, domestic finishers, particularly in the granite industry, continued to upgrade plants and machinery during 1986. In addition, offshore dollars have financed a number of fabricating facilities in North America that will finish imported rough stock. It is hoped that this increased domestic production capability will capitalize on a devalued US dollar. The trend has been for growth in stone usage and market. This trend is continuing with increased public awareness and desire for natural stone in buildings. The area of greatest market growth is expected to be in residential and interior decorative stone usage. Use of sophisticated, automated equipment has made the cost more affordable. Now lobbies, foyers, and specialty rooms are being clad in stone. Dolomite J. Welshimer, National Lime & Stone Co. About three-quarters of dolomite production is used as construction aggregates and 10% to 20% is sold or used as an industrial mineral. Total limestone and dolomite consumed for chemical and metallurgical purposes is about 136 Mt/a (150 million stpy). Sales of industrial dolomitic products were somewhat stronger in 1986 than levels recorded in the early 1980s. Some of the sales' strength, however, can be attributed to reductions in the number of active mining and processing operations. The industry will probably undergo further consolidation by the end of this decade. This will be due primarily to the continued softening in demand by the steel industry. Dolomitic limestone deposits being mined for raw materials for the steel, glass, and refractory in¬dustries are generally 54% calcium carbonate and 45% magnesium carbonate by weight. Impurities composed of silicon, aluminum, iron, sulfur, and phosphorous, represent less than 1%. The heaviest concentration of high purity, surface mineable dolomite in the US is in northwestern Ohio. Crushed and sized dolomitic limestone is a basic raw material for the iron and steel industry. It is also used as feed stone or lime kilns. Soft-burned lime is a popular raw material for BOF steel production. It is also used extensively in insulating glass fiber manufacturing. A related material, hydrated

Jan 6, 1987

By F. E. du Plessis, P. De Waal

Through the development of innovative in-line mineral quantification sensors, the possibility has arisen to apply modern control theory to implement automatic process control for electrostatic high tension (“HT”) roll separators. A pilot-scale set-up was constructed to enable continuous tests to be carried out. A typical dry mill feed was continuously pre-heated and separated with a modern lab scale HT roll machine. The mineralogy as well as mass-flow of the non-conductor stream was quantified in-line, and the combined streams were re-circulated in an endless loop by a combination of vibration feeders and a bucket elevator. A fractional factorial experiment was executed to determine the most significant control parameters of the HT roll separator. Then a multi-input, multi-output dynamic model of the HT electrostatic separator was extracted by the application of standard system identification techniques for automatic control. The most important control variable to ensure a stable product grade could be identified. This allowed a robust single-input, single-output controller to be implemented. The process variable and set-point was mineral grade and the control variable was electrode voltage. Roll speed was manually adjusted while the mineral grade was kept on set-point by the control system. The roll speed, where maximum mass flow and therefore maximum yield was produced on-grade, could therefore be rapidly determined. Atmosphere humidity and ore temperature served as disturbances. Some other adjustable parameters were kept constant during the experiments, namely feed mineralogy, splitter settings and feed rate. Delivery of maximum yield, with a controlled grade, can improve production while reducing the burden of complex manual tuning. Manual tuning previously involved coping with multiple parameters with uncertain cross coupling influences on the end result. Even the end result was typically only known after completion of mineral assays. Automatic grade stabilisation and yield optimisation for a HT roll separator bank requires in-line measurement of mineralogy and mass flow, as well as the implementation of a robust process control system.

Jan 1, 2005

By C. R. Summers, J. N. Murphy

In response to the Coal Mine Health and Safety Act of 1969, mandatory noise standards have been developed that specify time-noise limits of mine personnel exposure. Most affected by elevated noise levels is the pneumatic roof bolter operator, both in terms of levels near or in excess of 115 dbA and in terms of length of exposure. Therefore, the principal emphasis of this Bureau of Mines report is on pneumatic drill noise control. It is not the intent of this report to suggest any drill redesign; instead, methods are suggested to reduce the noise level by complementing existing machines. An integral muffler system and a separate muffler system were tested in an attempt to lower pneurnaric drill noise levels. Pneumatic drills, when new, operate at about 115 dbA when drilling in sandstone. Using the drill muffler systems, it was possible to decrease the noise level of a 115 -dbA s rope drill to approximately 100 dbA.

Jan 1, 1974

By B. P. Faulkner, M. Weinecke

Svedala started a development program in 1997 to develop a process to convert waste tires into valuable commodities. A review of numerous approaches revealed short-comings in the various approaches either process, mechanical, combination of factors, or trying to emphasis the production of low value products. A market study revealed that a process that could produce a good grade of carbon black would be economically feasible. This paper discusses the laboratory and pilot plant development and commercial plant design.

Jan 1, 2001

By Rodrigo Jerez

Advances in inexpensive computer automation led to the development and use of a computerized ore control system at the Cyprus Copperstone Gold Mine near Parker, AZ. These new ore control practices improved accuracy, performance and productivity of the ore control effort. An automated system for data collection, including bar coding of blasthole samples, laboratory analysis, data management, grade estimation, cut delineation and ore zone stake out, plays a major role in ore control practices. This is of particular interest because of the large amount of blasthole information being processed, analyzed and reported daily. Copperstone Gold management has been progressive toward new, efficient methods regarding ore reserve estimation, long-term mine planning, short-term mine planning, ore control and surveying. Technological advances, including powerful personal computers, applicable mine planning software and surveying instrumentation, have become readily available and affordable. The computerized ore control procedures used at Copperstone include sample data collection, laboratory automation and computerized data management. These have reduced the time to complete ore control on a blast pattern by 50% to 75%. The final product - ore control - is generated in a more timely and accurate manner.

Jan 1, 1991

By G. D. Buson

Driefontein Consolidated Limited has a proud history in the South African gold mining industry dating back to March 1945 with the formation of the West Driefontein Gold Mining Company. The reclamation gold plant at West Driefontein was originally built as a uranium recovery plant in 1970. With the collapse of the uranium oxide yellow cake market, the uranium plant was closed in 1988and successfully converted into a gold plant, recovering gold from repulped tailings dams1. The West Driefontein Reclaim plant utilized milling, leaching, conventional rotary vacuum filtration and cementation to recover the gold at a rate of 200,000 dry tons per month. The No. 1 tailings dam (at a head grade of 0.8 Au g/t) began to near the end of its life during 1996, and the next slimes dams to be treated, the No. 2tailings dam (at a lower head grade of 0.56 Au g/t) was found too marginal for reprocessing using the filtration technology. Alternate technologies were investigated, particularly the carbon-in-pulp (CIP) plant based on the Anglo-American Corporation (AAC) pump-cell technology at the Vaal Reefs Exploration and Mining Company?s East gold plant which was operating profitably at lower head grades2. The AAC pump-cell technology is based on the carousel mode of operation2. The suitability of CIP technology for the West Driefontein Reclaim plant was investigated using a pilot plant pump-cell supplied by Kemix The data gathered were utilized in sizing a full scale AAC pump-cell plant. This plant was motivated, built and commissioned on the 22nd of November 1996. Incorporating 6 eighty cubic metre AAC pump-cells. The West Driefontein Reclaim plant initially treated repulped slimes dam material. A subsequent change of feed material to current arisings (from the main gold plant) occurred in1997 in order to convert mills for waste rock treatment. Currently the reclaim plant treats a combination of current arisings and waste rock (milled at the reclaim site). The new CIP plant replaced twenty-seven rotary vacuum filters. A comparison between the filters and CIP in terms of operating costs was undertaken, as well as a performance analysis of the CIP plant to determine its flexibility in terms of variation of the throughput, pulp density, gold input, leaching efficiency prior to CIP, and the rate of carbon movement.

Jan 1, 1999

By James M. Franklin

Research on modern hydrothermal systems provides quantitative measures of the processes of formation of hydrothermal fluids and of precipitation mechanisms from them. Studies of ancient deposits provide new information regarding volcanological processes that are related to the deposits, as well as data on their spatial and temporal compositional variations. Mew exploration guidelines result from both aspects of research. The most fundamental requirement for large metalliferous hydrothermal systems is an abundant heat supply for the upper two kilometers of the crust. This heat may come from a focused heal source (shallow-level subvolcanic intrusion), but ambient heat also may have provided enough energy for the reactions necessary to effect leaching of metals, especially where heat flow is particularly high (i.e. very large or high-temperature magmatic source, such as ultramafic environments). For most VMS systems, the majority of the metals were derived through leaching from footwall strata; in addition interstratal fluids may enter subvolcanic intrusions during episodes of magma a chamber "cracking," engendering some '?magmatic" component in the hydrothermal system. Direct contributions of metalliferous magmatic fluid also may be significant from arc-related or back-arc felsic or alkalis systems. These latter contributions may form exceptionally high - grade portions in some deposits. Subvolcanic intrusions, which are excellent indicators of high heat flow and may have been the direct driving mechanisms for some stems undergo two stages of alteration: On intrusion emplacernent. fluids may rapidly enter and react with their mesostatic portions, evident in the sills in the Middle Valley. High temperature interactions caused albitization and destruction of oxides and sulfides, releasing metals. During terminal hydrothermal stages, the metalliferous fluid collapsed into the intrusions, forming disseminated and vein sulfides.

Jan 1, 1998

By E. F. Schnitzer, P. J. Wampler

During 1996 and 1997, Oregon experienced flooding on a scale not seen in many years. Some gravel pits located near rivers experienced erosion and, in several cases, breaches between the gravel pit and the river. Initial evaluation of several sites that experienced breaches indicates that impacts to the river system are complex and vary significantly from site to site. The impacts to the adjacent river system may be viewed as both positive and negative. Several floodplain-mining sites in Oregon located in areas of historic river flow have reverted to active riverbed. In many cases, state and federal fisheries biologists and university researchers see the resulting increase in channel complexity and habitat as favorable. The Oregon Department of Geology and Mineral Industries – Mined Land Reclamation Program (DOGAMI-MLR) is performing additional studies of the impacts to the off-channel areas that resulted from the 1996 floods. More data is needed to make sound floodplain decisions regarding mining.

Jan 1, 1999