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By Douglas A. Anderson

The US Bureau of Mines, in RI 8507, has shown that blast vibrations at low frequency are more likely to cause damage and complaints than those at higher frequency. Since that publication in 1980, the Office of Surface Mining and many state and local regulatory authorities have incorporated frequency in their regulations for acceptable ground vibration from blasting. Even when frequency is not explicitly stated in regulations, it may become an issue in hearings or in court.

Jan 1, 1992

By J Steyn

Block Cave mining is one method used to extract ore from underground diamond mines as well as other massive orebodies such as copper. This necessitates the excavation of many kilometers of tunnel within the ore body. The integrity of these excavations needs to be maintained over a number of years. Most Kimberlites and weak orebodies are extremely susceptible to degradation when exposed to moisture and the atmosphere. It is therefore essential that some form of weathering protection is applied as soon as possible after exposure. Conventional methods of weathering protection such as shotcrete do not easily fit in with the production schedule, hence the need for a more efficient system that could be applied immediately after exposure and serve as a temporary support or even as a permanent support medium. The main advantages of thin sprayed liners (TSL) compared to shotcrete are the ease of application, speed of application, early strength, much reduced transportation of material, less labour intensive and cost effectiveness. Several Thin Sprayed Liners suitable for various mining environments and geotechnical conditions are available and could be well suited as additional support the undercut level development in a block cave where this may be required. TSL offer a cost effective support solution as an alternative to shotcrete in areas where the building of a support structure is not a requirement.

Jan 1, 2008

By L. M. Litz

The results of a study are presented in which gaseous oxygen was dissolved in the leach liquor at concentrations of the order of 300 parts per million. This oxygen-containing solution was injected into portions of a field being operated on a commercial basis with hydrogen peroxide as the oxidant. Comparative results indicate that were concentrations and production rates were essentially equivalent with these two oxidants.

Jan 1, 1980

By Pablo Velasco

After becoming an oil exporter in 1972, Ecuador experienced a remarkable economic upswing until 1978. However, in 1979 and 1980, a combination of only slight improvements in agricultural output and stagnating petroleum output lowered rates of real gross domestic product (GDP) expansion to 5.3% and 4.3%, respectively. In current prices, the GDP in 1980 was estimated at $11.3 billion.2 The slowdown in growth is attributable in large part to the low level of petroleum exploration in the 1972-79 period. Ecuador's production of petroleum declined 4.5% in 1980 compared with that of 1979. The consortium of Corporación Eatetal Petrolera Ecuatoriana (CEPS), the State oil company, and Texaco, Inc., operating in Ecuador's eastern jungle region was responsible for nearly all of 1980 production, The volume of total crude petroleum exports from Ecuador dropped from 44.7 million barrels in 1979 to 40 million barrels in 1980, although crude petroleum export revenues rose from $1,032 million in 1979 to $1,294 million in 1980- The latter figure represented 54% of Ecuador's 1980 merchandise exports. Crude oil exports accounted far about 46% of the value of 1979 merchandise exports. The total nonfuel mineral exports in 1980 were valued at less than $1 million.

Jan 1, 1982

By Cornelius F. Kelley

AT the Annual Meeting of the A.1.M.E. last February, Cornelius F. Kelley, chairman of the Anaconda Copper Mining Co., was presented with the Charles F. Rand Memorial Medal for "conspicuous success as administrative head of great enter- prises engaged in the production of nonferrous metals at home and abroad; for inspiring leadership of an organization that has trained able engineers for service wherever ores are mined and metals are recovered; and for enhancing the prestige of metal mining in the financial and industrial world." Mr. Kelley's acceptance speech follows: I am not unmindful of the fact that the distinction is not to be considered a personal one, but that by the language of the citation itself it is rather a recognition of the service that has been performed by the many trained men of an industrial organization that in the arts of mining and metallurgy and in the fabrication of metal products has performed a distinct service to the industry and to mankind. In that spirit, the award is accepted, and on behalf of the organization I represent and myself, I thank you and assure you that the honor is deeply appreciated.

Jan 1, 1944

By Daniel G. Di Canio

A computer based accident cost indicator model (ACIM) for estimating tangible costs of occupational injuries, illnesses, and fatalities in the U.S. mining industry is described. Studies performed to expand the scope of the ACIM to all mining sectors are presented. Validation of ACIM cost element estimation algorithms with actual costs of mining-related injuries and illnesses are presented. A study of the effect of a fatal accident on production in surface coal and metal/nonmetal mines is presented. The study is based on a sample of 15 fatalities in underground and surface mines. Evidence of significant long- term decline in postfatality production at 6 of 8 underground samples is presented. The average loss is shown to be 1.8% of annual mine production. A study of accident costs in U.S. mining from 1975 through 1981 using the ACIM is presented. The study shows that total annual costs increased from $180,000,000 in 1975 to $379,000,000 in 1981, a 15% annual increase after adjusting for inflation, with mining companies bearing 45% of the total and expected wage losses to mining families accounting for 42%. The study shows total costs of $12,400 per accident and $674,000 per fatal accident for 1981.

Jan 1, 1983

By P. W. van Deventer

?Soil quality is the capacity of a soil to function, within ecosystem and land use boundaries, to sustain biological productivity, maintain environmental quality, and promote plant, animal and human health?. In the long-term, vegetative rehabilitation of mining wastes aims at, as far as possible, the proper ecological integration of the reclaimed area into the surrounding landscape, which is sustainable and requires minimal maintenance. A certain succession pattern is therefore needed. Recent ecological concepts recognize the role of the substrate?s quality and nutrients in affecting the rates and directions of succession patterns. Although pedogenesis and eventually soil quality in mine waste are not well known, monitoring of soil quality parameters in kimberlite mine tailings reveal a remarkable establishment and or improvement of specifics oil quality indicators. During the same time the vegetative cover?s total functionality as well as reproductive ability improved. Functions of soil, and thus soil quality, can be assessed at the field, farm, ecosystem, pedosphere, and global scale. It is recognized, however, that management of soil becomes increasingly difficult at larger scales, but for demarcated mine waste sites it is possible to ameliorate and manage and assess soil functions and quality. Therefore the significance of the study is the following: soil functions and quality become inseparable from the idea of system sustainability, and are considered as key indicators of ecosystem sustainability on rehabilitated mine tailings material.

Jan 1, 2008

By K. M. Godiwalla, S. Ranganathan

The thermal state in submerged-arc furnaces (S.A.F.) producing ferro alloys is important for the conditions of both the grade of alloy produced as well as specific energy consumption. The temperature profile in the S.A.F. is affected by the endothermic chemical reactions and the rate of gas evolution. The gas evolution commences at about 900 C due to the reduction of iron in the ore. A first-principle-based 2-D model has been developed to predict the temperature profile in the furnace. In this study, four ores of different grades have been considered in order to simulate the thermal profile in the S.A.F. The influence of the composition of the ore on the thermal profile and its significance in rationalisation of charge distribution to optimise the process are discussed.

Jan 1, 2007

By Flaviani Marculano Marchesi, Silas Gambarine Soares, Elton Volkers do Espírito Santo, Felipe Fardin Grillo, Heitor Cristo Clem de Oliveira

O objetivo deste trabalho é utilizar a termodinâmica computacional para estudar as propriedades de escórias iniciais dessulfurantes utilizando misturas com diferentes fluxantes: fluorita, sodalita, borra de alumínio, B2O3 e ilmenita. A princípio, as misturas foram definidas e em seguida foram realizadas simulações para o aquecimento dessas misturas a 1350 ºC por meio do software FactSage 7.2. Assim, foi calculado o fator de dessulfuração (FDeS) para cada mistura com base nas condições de equilíbrio. As misturas contendo 5 e 10% de fluorita e 5% de sodalita foram as que apresentaram maior FDeS. Em contrapartida, as misturas com 10,15 e 20% de B2O3 tiveram os piores resultados nessa análise. Misturas da literatura também foram simuladas a fim de se obter o FDeS e relacioná-lo com a eficiência.

Oct 1, 2019

By M. J. Allan

"The paper describes the author's experiences in the startup of autogenous and semiautogenous grinding circuits gained over the last twenty years on both large and small grinding circuits. Typical phases in commissioning from construction to startup with ore are covered. The paper also describes experiences with material handling systems, slurry pumping, vibrating screens, trommel screens and pebbles crushing systems. INTRODUCTIONThe commissioning of any new mineral processing plant is an important and exciting milestone in any project. It is at this point in time that the efforts of developers, design engineers, equipment suppliers and operators culminate in a finished product. The successful completion of any project requires that the plant achieve design throughput as quickly as possible. The success of any startup can generally be anticipated by the amount of careful planning which takes place before equipment is operated. The first part of this paper describes the steps in going from construction through to introduction of ore. The organization and planning of startup activities is also covered.The second part of this paper describes some typical problem areas and past experiences in the startup of semi-autogenous grinding circuits. Semi-autogenous grinding circuits present some special challenges in the startup phase. The description of some of these problems and experiences will hopefully provide other operators with suggestions on how to avoid (or at least prepare for) these problems."

Jan 1, 1992

By J. E. Gebhardt, H. Toro, K. Y. Lee

Industrial-scale test results indicate superior metallurgical performance of column flotation compared to conventional cell flotation for copper cleaning. A technical comparison of bubble generation systems for column flotation is made. Two types of bubble generation systems are considered: the filter-cloth type spargers and the Turbo-Air® sparger, which utilizes an air-water mixture fed to the column through injection tubes. Examples of the improved technical performance available with an external sparger system are presented using data from plant tests conducted for specific applications with several different mineral ores. INTRODUCTION Column flotation is now a valuable unit operation which mineral processing engineers employ in the design and operation of flotation circuits in nearly all mineral applications. The acceptance of columns in the mid- 1980s by the minerals industry was paralleled by a rigorous approach to developing a scientific understanding of the design, scale- up, and operation of column flotation units (Finch and Dobby, 1990). Since then, column flotation has become a standard unit of the cleaning stage in many new mineral concentrator projects and has replaced older mechanical cells to improve process efficiency. The size of column cells has continued to grow from the initial 0.9- to 2.1 -meter diameter range, and it is not uncommon to find column cells today being 2.7- to 3.6-meters in diameter. With the success of the smaller units, the scale-up to larger cells has been proven and demonstrated by the performance of the large-diameter cells (Murdock and Wyslouzil. 1991). The use of columns in flotation circuits has also been accompanied by developments in modelling. control, and optimization of column performance (Lee et al, 1991). The bubble generation system is the heart of the operation of column flotation cells. The most common methods for generating bubbles can be divided into two types: the internal and external spargers. Internal spargers are typically a porous material, such as sintered glass, porous rubber or filter-cloth, or maybe a single- or multi-nozzle sparger. External spargers implies that a gas and a liquid (either water or slurry) are brought into contact outside the column and that mixture is then introduced into the column. Several types of external spargers are available today, and innovative designs for externally mounted air sparging systems have been a significant factor in the successful application of columns. Early types of bubble generation systems.

Jan 1, 1993

By R. R. Hart, B. C. Wonsiewicz, G. Y. Chin

In recent years there has been increased miniaturization of electromechanical devices to keep pace with current trends toward smaller electronic components. A major problem facing the designer, however, is the higher stresses encountered by the material as a result of shorter springs. Hence an improvement in the elastic limit, as approximated by the 0.01 pct offset yield strength, would be highly desirable. An increase of 25 pct in the yield strength, for example, will permit a 20 pct reduction in both the length and thickness of a cantilever-type spring while maintaining the same compliance. One technique of improving the yield strength that has received little commercial attention is crystal-lographic texture strengthening.1,2 Texture strengthening is expected to be most beneficial in materials of hcp structure, but considerable gain can also be expected in cubic materials. A wire with a (111) fiber texture, for example, is expected to be 20 pct stronger than randomly oriented material, and 50 pct stronger than wire with a (100) fiber texture.293 For sheet specimens with a {110}(112) texture, characteristic of many heavily rolled fcc alloys, the (111) transverse direction is expected to be the maximum yield strength direction, about 20 pct higher than that in the (112) rolling direction.' In addition, the (111) direction is the direction of maximum modulus of elasticity for most cubic alloys. A large value of the elastic modulus could be desirable in designs where stiffer springs are required. To test the above idea, a 0.090 in. (-2.3 mm) thick commercial grade A (5 pct Sn) phosphor bronze sheet, a widely-used material for relay springs, was rolled from the spring-tempered condition (60.5 pct reduction) to various additional reductions up to a total reduction of 95 pct. Subsequently, additional material was obtained with a total thickness reduction of 97.3 pct Standard tensile specimens were prepared from the sheet material with the tensile axis parallel to and at 90 deg to the rolling direction. Tests were run on an Instron testing machine at a strain rate of about 0.050 min-l. Textures were determined by the use of the reflection pole-figure technique. Data were obtained using nickel-filtered CuKa radiation and with the aid of a Siemens pole figure goniometer. The X-ray pole figure studies show an incrzasing development of the texture toward the {110}(112) ideal

Jan 1, 1970

By D. E. Buchanan

The: volatility of a motor fuel is an index to its quality and to the satisfaction that will attend its use as an internal combustion engine fuel. Natural gasoline is concentrated volatility; threfore, it is quite natural that the most important market for natural gasoline should be for blending with less volatile refinery gasolines. Progress in the art of manufacturing natural gasoline, particularly in fractionation, which has made possible the elimination of the fixed gases and lighter hydrocarbons having a tendency to gasify at atmospheric pressure and temperature, has made it possible and desirable for refiners to utilize an ever-increasing percentage of natural gasoline in their finished product. This, in turn, has enabled the industry at large with each succeeding year to supply to the consuming public a better grade of gasoline. While cracking processes and improved fractionation in refinery operation have resulted in higher yields of gasoline per barrel of crude oil refined, natural gasoline has also played a large part in this respect because it has enabled the refiner to cut deeper into the crude and still maintain proper standards of volatility by blending natural gasoline with the product from his stills. There is, of course, with even the present improved grades of natural gasoline, a limit to the percentage that may properly be used. This percentage varies with different grades of crude oil, varies according to the facilities employed at the refinery and varies according to the grade of motor fuel manufactured; therefore it is not possible to say that for a certain predetermined amount of motor fuel to be manufactured in a given area, a certain definite amount of natural gasoline will be required. It is, however, generally conceded, and statistics bear out the statement, that the average gallon of motor fuel sold in this country contains approxi-matcly 11 per cent. of natural gasoline. Isolated cases may be found where in a very few refineries during certain seasons no natural gasoline is used, while in other plants as high as 35 per cent. and 40 per cent, natural gasoline is used in certain grades of motor fuels. Production Statistics The total production of natural gasoline for 1927, including California, is estimated at 1,627,600,000 gal. This represents an increase of 20 per

Jan 1, 1928

In dealing with the pulverization and treatment of auriferous ores, it may be stated that there is not one system of treatment applicable to all classes. In the southern portion of New Zealand the ores generally contain free gold, with scarcely any impurity that is, it is found in an almost pure state, without any alloy, and its dissemination amongst the matrix is generally in tolerably coarse particles. The only difficulties the mill man has to contend with, are the economical concentration of pyrites, which in some of the lodes are rich in gold, and the extraction of the gold the pyrites contain. In some of the lodes there is what may be termed float gold, that is, the particles of the precious metal are so finely divided that it passes over the quicksilver tables, and, unless there are other appliances for saving it, this class of gold is entirely lost.Indeed it is only within the last five years that any attention has been given, in the southern portion of the colony, to saving the fine gold that has passed the amalgamating tables. In the North Island the ores are very complex there are scarcely two mines, although they may be adjoining each other, where the bullion is of the same character. On every field the gold is alloyed with silver', and in combination with other metals and mineral substances, such as copper, zinc, antimony, galenfl, iron, sulphur, arsenic, etc., and, in some instaaces, cinnabar, as in the case of the Champion lode at Tui Creek, Te Aroha. Ores of this class are extremly difficult to treat satisfactorily.

Jan 1, 1903

By A. E. Bibb, J. R. Fascia

Single-crystal wafers of zirconium have been exposed to 680°F neutral water. The single crystals were of known orientation and weight-gain data as a function of crystal orientation were obtained. These data show that all the crystal faces studied obeyed a cubic rate law out to the time of transition whereupon the crystals corroded at an approximately linear rate. The time to transition varied from 114 days for (1074) crystals to about 325 days for the (2130) faces. The epitaxial relationship be-tween metal and monoclinic oxide was found to be (0001) H (111) and [1120] 11 [101]. A black tight adherent oxide layer was formed on the crystals in the pretransition range. This black oxide was found to be monocrystalline. The white corrosion product produced after transition was found to be polycrys-talline but highly oriented. X-ray line-broadening studies found that the black oxide was a highly strained structure whereas the white oxide was relatively strain-free. These results indicate a strain-induced re crystallization or fragmentation accompanies the change from protective black oxide to nonprotective white oxide. ZIRCONIUM alloys have been used quite extensively in high-temperature aqueous environments. Alloy additions can be made to commercial sponge zirconium which enhance the corrosion resistance of the zirconium in both water and steam media, which raise the tolerance limit for certain impurities detrimental to corrosion resistance, and which reduce the amount of free hydrogen pickup during corrosion. The development of the corrosion-resistant zirconium alloys has been a long and tedious job involving trial and error methods. This technique has been necessary because of a lack of fundamental data and hence understanding of the corrosion mechanisms. The objective of the work described herein was to provide some fundamental data with respect to the aqueous corrosion of zirconium crystals as a function of the orientation of the exposed surfaces. Hg. The zirconium chunk was then cooled to below the transformation temperature (862°C) and reheated to 1200°C for 8 hr. The ultimate size of the zirconium grains increased with the number of cycles. Rapid or even furnace cooling through the transformation temperature produces a considerable amount of substructure which was intolerable in corrosion experiments as it would be in the study of any crystallographically dependent property. It was found that a high-temperature a-phase anneal for approximately 4 days reduced the substructure below the limits detectable by visual or X-ray means. Crystals so produced were carefully cut from the massive zirconium chunk and oriented by standard back-reflection Laue techniques. The crystals were then mounted in a goniometer head and, by using the three degrees of freedom available, slices on the order of 0.015 to 0.020 in. were cut parallel to any desired crystal plane. These slices were then carefully polished on both sides to produce smooth flat faces, pickled to remove about 0.002 in. per face, annealed for 1/2 hr at '750°C in a vacuum of approximately 10"5 mm Hg, flash pickled, and checked for orientation. The pickling solution was 45-45-10 vol pct HN0,-H20-HF and continuous agitation was provided to eliminate pitting of the slices. Any slice that was not within 2 deg of the desired orientation was discarded, and any evidence of substructure as indicated by the Laue spots was also grounds for discarding the sample. Thin slices were used for the corrosion tests because weight gain per area data could be obtained with only a minimum area exposed to the corrosive media that was not of the desired orientation. The thin single-crystal slices were of irregular shape and as a result the areas were determined by placing a crystal inside an inscribed square of known area, enlarging a picture of this assembly about X5, and tracing both the enlarged square and crystal with a planimeter. The zirconium used to produce these single crystals was crystal-bar grade, a typical analysis of which is given in Table I. An oxygen analysis on prepared crystals gave a concentration of 205 ppm. The hydrogen concentrations are believed to be less than 15 ppm due to the dynamic vacuum anneal given each crystal. Typical nitrogen values for zirconium treated in this manner are about 10 to 20 ppm. RESULTS AND DISCUSSION Single-crystal wafers have been exposed to de-oxygenated, deionized water in static autoclaves.

Jan 1, 1964

By Francis E. Federspiel

A mineral purvey of the Granite Chief RARE II area (A5-261), covering about 23,400 acres (9,470 ha) of Tahoe National Forest and the Like Tahoe Management Unit, was conducted by the U.S. Bureau of Mines and the U.S. Geological Survey in 1979 and 1980 (fig. 1). The investigation by the Bureau of Mines indicates that the area has a low potential for mineral resources. Samples taken from prospect pits and favorable outcrops indicate no minable quantities of precious or base metals. Placer deposits are too small and low grade to be considered a resource.

Jan 1, 1981

By Kathryn C. Sole, Owen Tinkler

"Although the first large-scale application of copper recovery by solvent extraction (SX) took place in Zambia in the early 1970s, it is only in the last decade that this technology has become widely employed in this part of the world and is now a mainstay unit operation in most copper hydrometallurgical flowsheets. The mineralogy of the ores in the African Copper Belt, and hence the characteristics of the African leach liquors, differ significantly from those in Chile and the south-western USA, where copper SX has had a long and successful history. These differences provide operators, metallurgists, reagent vendors and engineers with many challenges: new approaches are needed to adapt this technology for successful implementation in this region. This paper examines typical operating practice in the African Copper Belt, discusses differences compared with other parts of the world and looks at some of the challenges and opportunities presented by these flowsheets. INTRODUCTION Following the success of the Rancher’s Bluebird and Bagdad solvent extraction and electrowinning (SX–EW) operations in Arizona in the late 1960s, the Tailings Leach Plant at Chingola, Zambia became the first large-scale copper SX plant in the world, commissioned in 1974. Despite the equipment design now being outdated, this plant still continues to operate successfully, indicating the versatility and adaptability of this technology. Today, there are some 75 copper SX operations worldwide with cathode production above 10 kt/a. The top ten producers currently account for some 40% of the global 4.3 Mt/a SX–EW copper production. South America (predominantly Chile and Peru) is the largest copper cathode-producing region, with annual production of some 2 Mt. The Central African Copper Belt (Zambia and the Democratic Republic of Congo (DRC)) is second, with cathode production of 1.2 Mt/a and North America (USA and Mexico) third, producing close to 0.8 Mt/a Cu (Cytec data, 2014). The remaining 0.35 Mt/a comes from all other regions combined (referred to as “Rest-of-World”). Current and future operations in Zambia and the DRC are summarised in Figure 1. The industry in this region is characterised by a large number of small (3 to 20 kt/a) plants, mainly Chinese-owned, and a few very large (>200 kt/a) operations, owned by major multinational corporations. This paper examines typical operating practice in the African Copper Belt, discusses the differences compared with other parts of the world and looks at some of the challenges presented by the conditions, as well as innovations in flowsheets, reagents and operating conditions that have been introduced in these circuits."

Jan 1, 2015

By Michael J. Rinker, P. A. Tibble, M. Wiseman, R. V. Nicholson

Tailings, from an active copper-zinc operation, containing about 10% sulphur were investigated to assess the onset of acid production and potential lime requirements for treatment of drainage. Oxygen consumption rates were measured over two years to verify spatial and seasonal variations in sulphide oxidation rates. Shallow cores were collected to assess the quality of tailings porewater and to characterize solids that had been subjected to oxidation and depletion of neutralization potential (NP) for several years. Oxygen consumption data were used to quantify rates of NP depletion and onset of acid drainage from the near- surface tailings. Based on measured oxygen consumption rates and identification of NP remaining in the tailings, future lime use in the treatment plant was expected to rise significantly without mitigation. Geochemical modeling calculations were calibrated with observed oxygen consumption rates and the model results agreed well with actual lime use in the waste water treatment plant during operations. The modeling also demonstrated the benefits of lower lime demands and treatment costs after closure as a result of construction a soil cover on the acid generating tailings.

Jan 1, 2000

By F. M. Makarinsky

"SynopsisThe Kanichee open pit mine and milling complex is situated approximately four air miles north-west of Ternagami, Northern Ontario, in Strathy Township. Mining and milling production commenced in January 1974.Milling throughput currently is at a rated capacity of 500 tons per day, seven days per week. A bulk nickel-copper sulphide concentrate is produced, and is trucked daily to the smelter at Falconbridge Nickel Mines Limited, Falconbridge, Ontario, some 120 road miles from Kanichee. Concentrate grades produced are in the order of 4.0% Ni and 8.0% Cu, with corresponding recoveries of 68-70% nickel and 86-90% copper. Stage additions of 100% guar-gurn solution reagent to the flotation cells for depression of talcose minerals, proved to be the major break-through for optimizing metallurgical performance.2. HistoryThe present Kanichee Mining property is known to old-timers in the Temagami area as the former Cuniptau Mine. Several attempts were made in the mid '30's and 40's to extract the ore at a profit, but each effort resulted in failure.In 1933-36, Cuniptau Mines Development Co. Limited, later called Cuniptau Mines Limited, sank a 245-foot vertical shaft and completed 2,200 feet of lateral work on the 100-140 and the 225 foot levels. Fifteen tons of ore were sent for testwork to the Mines Branch, Ottawa, Ontario.Cuniptau Mines Limited, in 1936, milled some 3,000 tons, and the resulting concentrate was put through a pilot smelter situated on the present mine site. Metallurgically, the smelting results were not encouraging, primarily due to the high melting point of the talcose minerals in the concentrate. From the period 1937-48, minor exploration work was done by Ontario Mining Corporation, Ontario Nickel Mines Limited, and Trebor Mines Limited. During the period 1948-49, 128 diamond drill holes, totalling 40,900 feet were evaluated by Trebor Mines Limited. In 1961, the name was changed to Ajax Minerals Limited, during 1968, five diamond drill holes were sunk, totalling 1,700 feet. Since that period the property has remained idle."

Jan 1, 1975

By G. Gabra

The kinetics of acidified thiourea leaching of pyrite concentrate was investigated at temperature ranging form 20 °C to a 60 °C. The effect of various parameters on the dissolution rates are discussed. The gold extraction was found to be zero and first orders with respect to Fe (111) and thiourea concentration, respectively. The order of the reaction with respect to sulfuric acid was found to be zero. The activation energy was determined from the Arrhenius plot as 2,039 kcal mole -1 (for a freshly prepared acidic solution containing Fe (111) as the oxidant and at 800 rpm stirring speed. This relatively low activation energy value suggests that the gold extraction is controlled by a-physical phenomenon. Under optimum conditions, more than 90% of gold has been dissolved in about 30 min. and 95% in 60 min. Attempt to recover gold from thiourea solution using active carbon is also discussed.

Jan 1, 1984