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By G. S. Adisoma

To address the problem of grade estimation in a general three-dimensional shape and the uncertainty associated with the estimate, the technique of jackknifing/block kriging short-cut is proposed. A new estimator called jackknife kriging is introduced first. Through the jackknife variance, a confidence limit for the reserve grade estimate can be calculated. Unlike the kriging variance, which is more a measure of data configuration and is independent of data values, the jackknife variance reflects the true variability of the data. This approach provides a simple way to set a confidence level for global estimation of resources.

Jan 1, 1995

By James McManus

The Lornex mine is located on the Southern slope of the Highland Valley in South Central British Columbia. The large low grade deposit was discovered in 1964; stripping began in 1970, and the mill started commercial production in October of 1972. The orebody is classified as a complex porphyry type having as major constituent quartz diorite, with varying amounts of quartz, grano diorite, and porphyry. A substantial degree of alteration is evident in the host rock, and this became the key factor in major equipment selection for the grinding section. A pilot plant was constructed on the property capable of treating 100 TPD of ore. The ore was mined to be as representative as possible of the entire orebody by sinking a shaft and cross cutting the deposit underground.

Jan 1, 1975

By Yi Luo

Subsidence events occurred over inactive room and pillar (R&P) mines, including abandoned mines or sealed portions of active mines, are classified as unplanned subsidence because of their timing and distribution are unpredictable. When investigating such subsidence cases, many uncertainties exist and disputes often focused on whether the observed structural damages are caused by mine subsidence or other natural or artificial causes. However, solid evidences to identify the causes are often lacking. In order to conduct a thorough and impartial investigation, good knowledge in subsidence theories a

Jan 1, 2009

By William Bergeson

This paper presents the challenges of the Homestead Avenue Interceptor Extension (HAIE) project in downtown Hartford, Connecticut. The new 72-inch (1,830 mm) sewer pipeline project consists of installing approximately 3,010 linear feet (920 m) of PVC lined reinforced concrete pipe using pressurized face microtunneling. The entire alignment is located within soft to very soft, varved silt and clay. To the extent possible, the alignment was selected to avoid bedrock, glacial till, miscellaneous fill,buried steel piles, and utilities. Challenges for this project include low ground cover, crossing major transportation routes, and limiting settlement to prevent damage to historical buildings and critical utilities. The machine was selected for the ground conditions. Design calculations were performed for selecting the reinforced concrete pipe class and for evaluating settlement. The potential for settlement damage was evaluated using both conventional analysis and finite element analysis

By John S. Thayer, Frederick E. Brinckman, Kenneth L. Jewett, Gregory J. Olson

Interest and research in biorecovery of metals has focused mainly on cell-based metal leaching and precipitation. However, production of non-enzymatic metabolic products by microorganisms related to metals bioprocessing also deserves attention. For example, it is well known that biogenic inorganic (e. g. H2S04 ) and organic acids play a role in metal dissolution. There are other metabolic products of microorganisms which can catalyze useful metals transformations. These include methylated metabolites such as alkyl halides which can dissolve metals from ores and also reduce certain metal ions in solution to pure metallic particles. This paper describes some of our research on metal dissolution and precipitation by such metabolites. Examples include the production of high purity elemental metal particles of gold, platinum and palladium by volatile metabolic products.

Jan 1, 1989

By Natarajan K. A.

During sulphide ore grinding, electrochemical interactions between grinding medium and the minerals play a significant role in bringing out enhanced ball wear on the one hand and alter the surface property of the ground minerals on the other. The role of the flotation reagents added simultaneously during grinding with respect to ball wear as well as flotation is yet to be established. Electrochemical measurements such as rest potential, combination potential and galvanic current between sulphide mineral and ball material couples have been carried out in the presence and absence of flotation reagents to understand the nature of electrochemical interactions between ball material and sulphide mineral. Electrochemical mechanisms and models have been proposed to explain the role played by the flotation reagents during different binary, ternary and quaternary interactions with respect to ball wear during grinding.

Jan 1, 1992

By Yunsheng Yao, P. Golledge, A. D. S. Gillies

In order to investigate the explosibility of sulphide mineral dusts, sulphide ore samples were collected from five underground metalliferous mines in Australia. The mineralogical and chemical composition of the dust samples was analysed by X-Ray Powder Diffraction and Atomic Absorption techniques. Simulated post detonation fumes were produced and used in dust explosibility tests to examine the influence of the fumes on sulphide dust ex- plosions. These tests were conducted in a 20 Litre Siwek Explosion Chamber with measurement and control system that is regarded as a standard testing system worldwide for dust explosion studies. The dust mineralogical composition and dust explosibility tests indicated that the content of sulphur can not accurately predict the explosibity of the sulphide dust. The percentage content of pyrite in the sulphide dust can be a relatively reliable diagnostic criterion in evaluating the risk of sulphide dust explosions in the mining of a massive sulphide orebody. The hybrid explosion tests demonstrated that the post detonation fumes from ANFO not only decrease the lower explosion limit of the sulphide dusts, but also increase the severity of the dust explosions. The explosion pressure reaches its peak value when the fumes content in the explosion chamber is about 20 per cent by volume

Jan 1, 1997

By C. B. Rash, W. W. Fowler, Gill Montgomery

INTRODUCTION Fluorspar is the common term used for the mineral fluorite, which is naturally occurring calcium fluoride (CaF2). It is the principal source of fluorine, the most reactive of the chemical elements, from which a great variety of unique and strategically important chemicals are produced. Commercial deposits of fluorspar are widespread throughout the world, and its availability is essential to the industrial progress of all nations. GEOLOGY AND MINERALOGY In its pure form fluorspar, CaF2, contains 51.1% calcium and 48.9% fluorine, and has a sp gr of 3.18 and a hardness of 4. It is commonly a glassy mineral. colorless, white, or grayish. but may also be various shades of purple, pink, blue, green, yellow, or tan. It belongs to the cubic system mineralogically, and commonly crystallizes into cubic shapes in vugs and cavities, although most of it is massive, with interlocking crystals. Minable fluorspar deposits, in descending order of importance, occur as bedded limestone replacement deposits along fault zones; fissure-filling vein deposits; breccia filling in limestones, dolomites,

Jan 1, 1985

By D. Malhotra, R. M. Hoover

The effect of a surfactant, designated Syntex, on the wetting and spreading of hydrocarbon oil on molybdenite surfaces (faces) has been investigated experimentally through measurements of zeta potentials and factorially designed flotation tests. These studies indicate that Syntex has a positive effect in increasing molybdenite recovery in the rougher flotation circuit at the Climax mill. The analysis of experimental data using DLVO theory shows that the controlling factor in determining the magnitude of the repulsive energy barrier preventing oil from wetting and spreading on the molybdenite faces is the MoS2 zeta potential and the vapor oil droplet size. The role of Syntex in this case seems to be related to the decrease and stabilization of MoS2 zeta potential by Syntex adsorption and also to the emulsifying action of Syntex on vapor oil to provide a more favorable oil particle size.

Jan 1, 1976

By John Lovering

The Afton property is located 180 air miles East-Northeast of Vancouver and nine miles West of Kamloops, a city of 60,000 people, in South Central British Columbia, Canada. The mine is adjacent to the Trans-Canada Highway at an elevation of 2,200 feet above sea level. The orebody is a porphyry, copper deposit that has undergone supergene alteration. The-major economic minerals in the supergene zone are native copper and chalcocite with chalcopyrite and bornite in the hypergene areas. The grade is one percent with an overall copper distribution: 70% native, 25% chalcocite and 5% chalcopyrite with bornite and covellite. The ore also contains important, but variable amounts of gold and silver.

Jan 1, 1985

By John Berney-Ficklin

Large scale grinding mills can reduce both capital and operating costs for concentrators. These mills can be effectively used, but they must be free from design and manufacturing deficiencies if they are to reach their full potential and avoid costly downtime. This paper presents the evolution of today's complex grinding mill specifications and discusses the most important items to look for when buying new equipment. It emphasizes the need to monitor specification requirements during design and manufacture. It also discusses the growing trend to have grinding mills fabricated in overseas plants, and the importance of recognizing this when preparing specifications.

Jan 1, 1987

By J. Girard-Dwyer, J. Johnson, J. Whyatt

The choice of fragmentation method is one of the most fundamental aspects of mine design, and often has a major impact on the safety and economic viability of an operation. Almost exclusively, underground mining operations rely on either mechanical excavation or drill and blast techniques to extract rock. Each of these fragmentation methods has distinct advantages and disadvantages, and each is appropriate, and economic, for different mining conditions. However, the choice of fragmentation method can have a pronounced effect on the amount of damage created in the rock mass surrounding the opening. This paper reviews a number of case studies where both mechanical excavation and traditional drill and blast were used in underground mines. Ground support requirements in the mechanically excavated areas are compared to the support requirements in the blasted sections in order to demonstrate the potential safety and cost benefits of the various fragmentation methods.

Jan 1, 2003

By Miguel N. Herrera, Abbas H. Mirza, Fiona M. Doyle

The standard test methods used to determine the pyrite content of coal and mineral wastes, and their propensity to release acidic drainage, are critically reviewed. In addition to analysis of total sulfur by combustion, test methods using selective oxidation of pyrite by HNO3 and H2O2 are available. The oxidation kinetics of pyrite vary appreciably from sample to sample, and it is difficult to ascertain whether complete dissolution has occurred in heterogeneous materials. The reliability, reproducibility and suitability of different standard test methods were studied, using well characterized ore and coal pyrite samples. The kinetics of pyrite dissolution were also investigated. The results are discussed in terms of the fundamental chemical and physical characteristics of each sample, and the implications for waste characterization are considered.

Jan 1, 1992

By Greg Border

Many unique ventilation problems have been faced as Avery Island Mine's large openings have been mined. High humidity of outside air combines with the hygroscopic salt to create a corrosive atmosphere. Massive rooms preclude routine use of brattices to direct air flow to the working faces. Large amounts of explosives are consumed in single blasts. Resulting concussion pounds air control structures and ANFO ignition creates large amounts of nitrogen dioxide in single rooms. Geologic constraints confine new shafts and slopes to areas thought to be free of potential ground water hazards. Dust control techniques are limited by dry product demanded by customers. The Avery Island Mine's ventilation system has evolved to deal practically with the conditions and to dependably provide fresh air to the miners. International Salt Company's Avery Island Salt Mine, a multiple level room and pillar operation, has been mined steadily since about 1900. It is known as one of the "Five Island" salt dome mines of South Louisiana's Gulf Coast. Production from the area places Louisiana first in United States rock salt mined tonnage, according to the United States Bureau of Nines, 1982 (1). International Salt Company is a major force in U.S. salt production, as it also operates mines in Detroit, Michigan; Cleveland, Ohio; and Retsof, New York; a solar salt facility in Bonaire, Netherlands Antilles; and a solution mining plant at Watkins Glen, New York.

Jan 1, 1983

By F. Letowski

A column reactor was applied for leaching with simultaneous flotation a complex sulfide ore in ferric sulfate-solution under oxygen pressure. Elemental sulfur and the flotable, nonreacted sulfides were collected in the froth and separated from the insoluble, nonflotable gangue minerals and solid particles formed during pressure leaching. The two-stage laboratory unit, built from Corning-glass elements is described. Results of the continuous leaching/flotation experiments conducted under 20-40 psig of oxygen pressure are presented, as are supplementary batch leaching experiments with iron precipitation under 150 psig oxygen pressure. High zinc extraction to solution and near total accumulation of lead sulfate in the nonflotable fraction are easily attainable. Relatively poor flotation of pyrite is probably caused by the partial oxidation of its sulfidic sulfur to sulfate.

Jan 1, 1988

By Thomas F. Stinson

Energy-producing states see severance taxes as attractive sources of increased revenues for otherwise tight budgets. Consumers in energy-poor states, however, protest that current rates are excessive and have moved to obtain a reduction. The US Supreme Court heard two cases questioning such taxes during its 1981 term, and Congress, in each of its last two sessions, has seriously considered measures placing a ceiling on severance tax rates. Although discussions usually focus on coal severance taxes levied by Montana and Wyoming, ramifications of changes in national policy are much larger, potentially affecting mineral taxes in all states. Severance taxes yield substantial revenues in some states, as illustrated in the accompanying table. In fiscal 1980, Texas collected more than $1.5 billion from such taxes, while Louisiana, Alaska, and Oklahoma collected $525 million, $507 million, and $436 million, respectively. Oil and natural gas production were the major items taxed. While the table shows only the 10 states with the largest severance tax collections, a total of 17 states had severance tax receipts exceeding $10 million in 1980. The enormous increases in severance tax revenue between 1970 and 1980 can be seen from the table by comparing columns A and B. For the 10 states shown, revenues increased from $650 million to $3.8 billion during that period, due to a combination of higher prices, increased production, and new or increased taxes. In most states, increases in prices and production were more evident than higher tax rates. Although the revenue increase is impressive, it understates the extent of changes occurring during the past decade. Since tax collections are shown for fiscal 1980, the full impact of the decontrol of domestic oil prices is not evident. Also, taxes on natural gas reflect controlled prices. When full de-control of natural gas occurs, significantly higher revenues can be expected in gas-producing states, even if tax rates, production, and world prices remain constant. These increases in severance tax revenues, coupled with further increases expected to accompany natural gas decontrol, have produced fears that a substantial transfer of income is taking place from residents of energy-poor states to those living in energy-rich areas. Others worry that increased severance tax revenues will be used to substitute for a substantial portion of state taxes that would have otherwise been collected from firms and individuals. The resulting improvements in tax climate, it is thought, may encourage firms and workers to migrate to energy-producing states. While these issues are often portrayed as pitting energy have-nots against the haves, such is not entirely the case. Much of the original impetus for limits on coal taxes came from Texas residents, the state collecting the most severance tax revenue. One way of gaining perspective on these concerns is by examining severance taxes per capita and as a percent of state tax collections (see columns C and D in the table). When this is done, Alaska, where 1980 taxes on oil and gas production totaled more than $1300 per capita (and 35% of all state tax collections), stands out as a special case. There, the state was able to eliminate some individual taxes, place revenues in a permanent trust fund, and consider offering a rebate of some previous income

Jan 4, 1982

By Reinhold Schulze

Thiourea is being applied as an industrial leaching agent for gold and silver only in a few cases. A CIP technique was developed which eliminates most of the obstacles against its use. Mild conditions for precious metals stripping from the loaded carbon simplifies process conditions in comparison to cyanide CIP technique. Examples are given.

Jan 1, 1998

By Donald Babbitt

In 1971, during the planning and design stages of a $300 million expansion, the Iron Ore Company of Canada Ltd. through its Engineers, Canadian Bechtel Ltd., came out with a preliminary request for two (2) 10,000 LTPH belt conveyor scale systems. These Systems were to provide weighing accuracies within 2.5% of the iron ore pellets and concentrates in transit on two (2) 72" wide conveyors from the stockpiles to the ships. Each conveyor system would be fed by a rail mounted bucket wheel reclaimer, with the conveyed material moving directly to the ship loaders with no inter- mediate surge and/or storage bins between the stockpiles and the ships. The bucket wheel reclaimer discharge rates would vary from 0-9600 LTPH in cyclic periods, with the periods varying from 1-5 minutes - dependent on the level of the reclaim buckets in relation to the stockpile as well as the slewing rate of the reclaimer. There would be frequent interruptions for bucket wheel repositioning (laterally and vertically), changing ship holds, and trimming ship holds. These frequent zero flow conditions, approximately 500 per 150,000 ton ship, could last 1-5 minutes. In addition, the conveyors on which the scales were to be mounted would be over the water and subject to the wind and cold of Northern Quebec. These Systems would be in use 350 working days of the year and would load 30,000,000 LT/yr. (An average of 90,000/working day).

Jan 1, 1975

By R. H. Grau

The National Institute for Occupational Safety and Health (NIOSH) has conducted research to improve the ventilation of large-opening mines. The research has demonstrated that the ventilation of large-opening mines improves significantly by including ventilation requirements in the mine planning process and implementing some practical techniques during mining. Planning the location of long pillars to reduce the number of crosscuts between intake airways and return airways, positioning auxiliary fans in their proper locations, and establishing ventilation stoppings with minimal leakage all significantly improve the ventilation of large-opening mines. Mine operators that adopt these techniques in the mine ventilation plan will reduce mineworkers? exposure to airborne contaminants.

Jan 1, 2008

By D. C. Rotherham

The Kidston gold discoveries were originally made about 1907, and by 1934, 1.76 Mg (62,000 oz) of gold had been produced from placer and lode mining of higher grade, most¬ly oxidized gold ore. As mining in the lode ore penetrated deeper, costs increased and the world gold price stagnated. The lode or underground production averaged close to 6.9 g/t (0.2 oz per ton) Au for the 201 kt mined. No mining or development took place from 1934 until 1965. Kidston's high grade ores were exhausted by 1934. From 1965 to 1976, exploration had developed 3 Mt of about 3 g/t (0.88 oz per ton) Au. Placer Pacific acquired rights to the property in 1976 and began a geologic and engineering study of the district. It was clear that the deposit had the potential for becom¬ing a large-tonnage, low-grade producer. However, explora¬tion had to discover the tonnage and grade and engineering needed to solve the obstacles of production costs. Bulk material handling problems were addressed by Placer's wide experience in open pit mining, and the increase in work index accompanying deeper ores was handled by Placer's metallurgists. The matter of power for the operation was solved by engineering studies. These showed that power could be generated and brought in economically. The price of gold also increased after 1976, and this helped in the economic analysis. The Kidston discovery since 1976 is really a combination of good exploration geology and careful engineering plan¬ning that overcame the obstacles presented by ore characteris¬tics and the location of the deposit. The attached paper by Harry Mustard is an extract of his honors thesis and explains the deposit geology.

Jan 1, 1990