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By D. R. Taylor

The use of clay granules as carriers for pesticides dates from the early 1940's and by the present day represents a business conservatively estimated at between 200 -300 thousand tons / year in the U.S. alone. Aside from economic and specific target pest efficacy advantages, the use of clay granules as pesticide carriers also delivers a number of environmental benefits which will be reviewed. Topics to be discussed will include: I) drift control (versus liquid sprays), 2) mobility (in the environment), 3) worker safety, and 4) transportation (spill) safety.

Jan 1, 1999

By S. K. Jena, S. Singh, B. Das, N. Dhawan, P. K. Misra, D. S. Rao

"Iron as an impurity in pyrophyllite ore affects pottery, ceramics and tile quality. We carried out the characterization of a pyrophyllite ore sample using optical microscopy, scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and wet chemical analysis. The study revealed the presence of 2.15% iron oxide (Fe2O3 ) along with silica and alumina as the major components, which constituted around 90% of the total sample. We carried out the removal of iron from the pyrophyllite using magnetic separation and acid leaching and found that wet high-intensity magnetic separation (WHIMS) could remove 28% of iron values while oxalic acid leaching could remove up to 99.3%. The leaching kinetics of iron removal and the effects of pulp density, acid concentration, leaching time and temperature were also investigated. The optimum conditions for leaching were found to be leaching time of 60 minutes, temperature of 90°C, pulp density of 5%, oxalic acid concentration of 0.3 M, and particle size below 100 microns. Iron dissolution from the pyrophyllite sample can be best described by the diffusion of ions through the product layer of constant-size spherical particles. The breakdown of the pyrophyllite structure was evident from the FTIR and TGA studies. The activation energy of the leaching process over the temperature range was calculated to be 43.47 kJ/mol. IntroductionPyrophyllite is a naturally occurring phyllosilicate mineral composed of aluminum silicate hydroxide [Al2Si4O10(OH)2] as the major component and often associated with other minerals such as kaolinite, mica, quartz, rutile and epidote. It occurs in fine-grained sericite schist that is quarried as pyrophyllite (Pandit et al., 2008). In India, pyrophyllite occurs mainly in Madhya Pradesh state, Uttar Pradesh state and the Keonjhar district of Odisha state (Harpavat, 1995). Pure pyrophyllite is a highly desirable material for various applications due to its unique properties. It exhibits high refractive behavior, low thermalelectrical conductivity, low expansion coefficient, low hot-load deformation, low bulk density and high corrosion resistance to molten metal and basic slag (Rieger, 1997). It is used in the ceramics, refractory, foundry, electrical-insulation, sanitary-ware, glassmaking, pesticide and rubber fields. Compared with clay, it has lower thermal conductivity and coefficient of expansion, making it more suitable for refractory applications (Harben, 2002; The Minerals Yearbook, 2011)."

Jan 1, 2015

By Ali Yalçin

The study area is located in the NW of Uluborlu (Isparta). Massive limestones and alluvial deposits form the lithological units of the study area. The average thickness of the alluvium deposit consisting mainly of light brown - red colored and fine grained clastic sediments which derived from the limestone is about 10 meters. The aim of this study to investigate the uses of this alluvial sediments as tile - brick material. For this aim, disturbed and undisturbed samples have been taken from different depths in the alluvial deposits. Mineralogical compositions have been determined by XRD and major oxide contents by XRF. Laboratory experiments have been carried out to determine the technological properties of the samples. The selected major oxide contents of samples vary between A12O3 (24.6 - 24.12 wt %), CaO (0.76 - 4.27 wt %), Fe2O3 (10.21 - 10.29 wt %), MgO2 (1.25 - 1.51 wt %). CaCO3 and MgCO3 values calculated from the geochemical analyses, are between 1.55 - 1.62 and 2.62 - 3.17 respectively. The ratios of grain size of the samples are 82 % for < 0.2 mm and 5 % for > 3 mm. Geochemical analyses and technological features of the samples indicate that these fine grained sediments of alluvial deposit are suitable in terms of uses as tile - brick material. The potential reserve of this tile - brick material has been determined as 40 million tones.

Jan 1, 2005

By Per-Martin Sandgren

LKAB&apos;s ores have specific mineralogical properties that make them especially suitable for the production of super-grade concentrates. Conditions are particularly good for this purpose at Malmberget, where a concentrate for high-purity sponge iron production has been produced for many years. Until 1978 the approximate assay was 71.2 % Fe and 0.45 % SiO2. Since then the assays have been improved by process modifications to approximately 71.5 % Fe and 0.20 % SiO2. Scope exists for still further improvement. In recent years the production of fractioned concentrates has been started. The material lies within the size range 74-125 µm and the approximate chemical analysis is 71.6 % Fe and 0.30 % SiO2. Other special products are under discussion. The Malmberget ores are also suitable for the production of high-purity direct reduction pellets with a SiO2 content below 1 %.

Jan 1, 1981

By Otis M. Clarke

The Eufaula bauxite-kaolin district in southeastern Alabama is an important source of raw material for the refractory industries in the United States. At the present time, five companies are mining and processing bauxite and kaolin from this district and a sixth company is holding substantial reserves. Mining operations are expanding, but finding new ore reserves is a major problem. The Geological Survey of Alabama sponsored geologic research in the Eufaula district to: 1) investigate the utilization of sandy kaolinS and other clays associated with bauxite-kaolin deposits; 2) find limits of the bauxite district, looking for possible extensions; and 3) study the geology of the district, looking for patterns or trends that may aid in finding new ore reserves. This work was done with the full cooperation of mining companies operating in the district and property owners. Research was aided by the U.S. Bureau of Mines and the University of Alabama. The investigation included detailed geologic mapping of mines, drilling in selected areas, and making mineral analyses of bauxite and clays. The mapping was performed primarily by pace and compass because of the complexity of the deposits studied, but aerial photographs were used to a limited extent. Drilling included both auger and core drilling. The auger drilling was limited to 100 feet, but core holes were drilled as deep as 200 feet. The term &apos;bauxite,&apos; as used here, indicates a mixture of minerals containing more than 50 percent gibbsite. Bauxitic clay is a mixture of gibbsite and kaolinite that contains more kaolinite than gibbsite. The term "kaolin" indicates a clay composed of predominantly kaolinite. Other clays in the Eufaula district are composed of kaolinite, illite, quartz, mica, and goethite or hematite.

Jan 1, 1971

By Chee Theng

"So many talks, so little time.One of the toughest challenges associated with attending the SME Annual Conference and Expo is deciding how to allocate one’s resources. After accounting for keynote and plenary sessions, committee meetings, networking events, luncheons and exhibits, attending even one of the 109 technical sessions and more than 600 technical paper presentations can be a labor of love. Many, however, managed to make it to many of the sessions, including the mineral and metallurgical processing technical session on solvent extraction, ion exchange and electrowinning.At one point, that room was seated to near capacity, with a considerable number of the audience members standing by the walls at the back. Brittany Valera of Freeport-McMoRan Inc. was one who came early and enjoyed the session in its entirety. "Everything was pretty exciting," she said. "I really liked the modular plants. I think the future of mining, just like what we talked about in there, lies in thinking about things like remote locations, lifetimes of plants, anything that would be reusable and sustainable; and lower-cost and user-friendly would be really beneficial."Michael Moats, associate professor of metallurgical engineering at Missouri University of Science and Technology, started off the session by presenting on behalf of post-doctoral student Alex Luyima, who, like many before him, had been snapped up by industry and is now working for a secondary-metals refining company in Texas. Their team studied the nucleation and growth mechanism of copper on stainless steel from synthetic acidified copper sulfate in the absence and presence of chloride ions and three commercial organic additives: Hydrostar 4208, DXG-F7 and Cyquest N-900. Currenttime data were analyzed using known models, with reference to scanning electron microscope images. Good agreement was achieved between the models and SEM micrographs of deposits at a commercially relevant current density of 30 mA/ cm2. The addition of 20 mg/L chloride was found to increase the size and reduce the number of nuclei. The addition of 2.5 mg/L of each additive did not change the mechanism, but all three reduced the size and increased the number of nuclei, leading to more uniform coverage of the substrate with smoother deposits produced in twohour electrowinning experiments. N-900 had the best deposition coverage while DXG-7 was the easiest to dissolve."

Jan 1, 2014

By R. J. Pugh

The surface chemical sites on several fillers (quartz, feldspar, calcite and granite) were studied by the adsorption of well defined acid and basic probe molecules (benzoic acid, benzyl alcohol, ethyl benzoate, pyridine and benzyl amine) from cyclohexane. The results provided a wide variation of adsorption data, emphasizing the extensive range of site heterogeneity on the filler surfaces. In addition, it was shown that the acidic probes were strongly adsorbed on all of the minerals, thus indicating that the basic surface sites dominate the acidic ones. Also, through FTIR studies with vapor-phase probes adsorbed on orthoclase, it was possible to identify the nature of specific sites and the type of bonding occurring between the filler surface and the probe molecule. These types of surface analytical techniques could give useful information for predicting the adsorption functional groups on dispersants, dyes, thickeners, etc. and could lead to enhanced interfacial bonding between the filler and the matrix.

Jan 1, 1993

By Karl O. Toppel, Jim Flaherty

The desire to minimize gaseous effluent in smelting and maximize gold yields from refractory ore are driving the nonferrous and gold refining industries to demand more and more oxygen. This, coupled with an increasingly competitive marketplace, forces the investigation of alternate methods of oxygen supply. Current progress in both the non-cryogenic and cryogenic fields is making the use of low-purity oxygen much more attractive. The benefits of on-site production are now available to most oxygen users. Historically, these on-site advantages could only be achieved by relatively large plants using high-purity cryogenic technology. The evolution of low-purity cryogenic and non­cryogenic oxygen production has added a new method of delivering on-site production. Specifically, the advent of oxygen Vacuum Swing Adsorption (VSA) technology has brought these benefits to smaller-volume customers by cost-effectively supplying oxygen requirements as low as 20 tons per day, (tpd). Low-purity cryogenic plants have also made an impact on the market, yielding cost reductions for larger-volume customers with oygen requirements greater than 70 tpd. This paper reviews the advantages and disadvantages of current supply methods for users having varying volume, purity and other requirements.

Jan 1, 1993

By Matthias Neuenschwander, Andreas Theiler, Patrick Steinle, John Singer, Martin Vogel, Diego Martini, Ömer Ündül, Markus Weh

"Quartz Dust is a major health hazard in underground works, wherever the ground contains quartz and depending on the chosen method of excavation. A research project initiated by the Swiss Tunnelling Society and realized by the Swiss Federal Institut of Technology, Zurich, established a correlation between the potential of quartz dust generation during excavation and well known geotechnical characteristics – the Cerchar Abrasivity Index CAI and the Uniaxial Compressive Strength UCS - of ten typical Swiss rocks. The results are at the center of a new guideline by the Swiss Society of Engineers and Architects on the requirements for early project stages regarding ventilation and logistics in function of the quartz dust related risk of the expected ground type of the project. The approach presented could be applied worldwide, contributing to more effective health protection as well as to better cost stability in underground works. CONTEXT Respirable quartz dust (aerodynamic diameter of particles < 10 micron) is universally recognized as a major workplace health hazard. Chronic bronchitis, silicosis and lung cancer can be caused by excessive exposure to quartz dust, as has been proved by many medical studies. Therefore, the legislations of many nations specify a maximum workplace concentration (Maximale Arbeitsplatzkonzentration MAK, Occupational Exposure Level OEL). In Switzerland, for example, the Threshold Limit Value TLV for respirable Quartz or Crystalline Silica imposed by the Federal Committee on Exposure Levels (Grenzwertkommission) is 0.15mg/m3 air. Some nations refrain from establishing a OEL because of the carcinogenic nature of quartz."

Jan 1, 2016

By Douglas R. Cook

The Ertsberg East discovery was announced by Freeport in 1979 with proven geological reserves of 45 Mt (49.6 million tons) with a grade of 2.65% copper and recoverable gold values. This recently discovered deposit is one of a cluster of skarn-type copper occurrences found within the limits of Freeport Indonesia&apos;s mining con- cession at an elevation of about 3600 m (12,000 ft) in the extremely rugged Jaya Wijaya Mountains of Irian Jaya, the Indonesian half of the island of New Guinea. The Ertsberg East lies about 1.5 km (0.9 miles) east of the Ertsberg ore body, which is also known by the Indonesian name "Gunung Bijih" or "ore mountain." For general background, the original Ertsberg ore body was first discovered by the Dutch geologist Jacques Dozy in 1938 while on a mountain climbing expedition. It was mapped and sampled by Forbes Wilson and Del Flint after a two-week harrowing trek into the mountains from the coastal swamps. A drilling program in 1967- 1968 established that the Ertsberg was a viable mining venture, containing approximately 33 Mt (36.4 million tons) of skarn-type copper ore. The deposit averaged 2.5% copper, with significant values in gold and silver. The first shipment of copper concentrates was made in December 1972, following a capital investment of $200 million. Following the routine production of ore from this deposit, it became necessary to consider additional sources of ore to extend the life of the mining operation. An exploration program was thus started with the initial objective of finding shallow or surface ores which could be blended with the material being mined at Ertsberg. Project geologist Frank Nelson was transferred from Freeport Exploration Co. to the Freeport Indonesia organization at the Ertsberg mine. However, the exploration work was the functional responsibility of Freeport Exploration. Del Flint had overall responsibility for the program from the Reno headquarters office and provided liaison with management in the USA and Indonesia.

Jan 1, 1991

By C. Newman

"Over the past decade, as conventional underground deposits have been depleted, mining operations have been forced to produce at greater depths and in more geologically and geometrically challenging conditions. As such, there has been a global increase in the application of cemented paste backfill (CPB) in tabular deposits utilizing open stope mining method with a delayed backfill placement. Despite the extensive use of CPB, many fundamental factors affecting the design of safe and economical fill structures are still not well understood. A critical issue in the design of backfilled stopes is the determination of stress states within the fill material itself as well as the surrounding rock mass. Analytical equations provide a means of quickly evaluating the effectiveness of a given design. However, in developing these equations large assumptions are implemented to simplify the design problem. It is important that one understands these simplifications as well as their effect on the overall design. This paper investigates common analytical equations utilized in the evaluation of single vertical backfilled stopes and their assumptions through comparisons to numerical modeling results. INTRODUCTION AND BACKGROUND As the mining industry continues to produce at greater depths and in more geometrically and geologically complex conditions, cemented paste backfill (CPB) has gained traction as a means of providing localized ground support in modern stope-and-fill mining operations. The application of CPB in stope-and-fill mining as a ground support material has led to the reduction of mine waste costs, while increasing both mine production and stability. In an attempt to achieve total extraction of the mining reserve, stope-and-fill mining operations often employ a primary-secondary excavation-support sequence (see Figure 1). In this practice, primary stopes are initially excavated and then backfilled in a two-stage pour; plug and final pours. During the first stage (plug), a CPB material with increased cementitious content is placed at the bottom of the stope providing a strong base from which to build a backfill structure as well as protect mine works from material breakthrough. Following placement, the backfill plug is allowed to cure to a given strength as designated by the mine design. Upon achieving the required cure strength, a less cementitious CPB material is used to backfill the remaining stope area. This is referred to as the final pour stage. With all primary stopes excavated and supported using backfill, the extraction of the secondary stopes commences as primary stopes are utilized as artificial pillars. While the application of CPB in a primary-secondary extraction-support mining sequence allows for a substantial increase in reserve recovery, it is imperative the mining personnel and planning engineers have a clear understanding of the material’s behavior and stress interaction with the surrounding rock mass to ensure the most efficient, cost-effective, and safe extraction of underground deposits."

Jan 1, 2018

By W. S. Fyfe, R. J. Puddephatt, S. Zhou

Gold is easily mobilized at temperatures within range 600-11OO°C by gases such as Cl2, CO, H2S, in gas mixtures, at low pressures. Such gases are relevant to conditions of granulite facies metaomorphism in environments of magma underplating. These observations suggest an efficient mechanism for moving gold to the upper crust during major thermal events. The efficiency of precipitation of gold at lower temperatures is related to available mineral surfaces and pyrite appears to be an excellent substrate for gold precipitation.

Jan 1, 1989

By Dennis C. Drehmel

Because of their relatively low cost, carbonate rocks are desirable in abatement of air pollution by acid gases. Although many processes and types of equipment have been proposed to control or prevent the emission of acid gases, this paper considers only three: dry-limestone injection, wet-limestone scrubbing, and chemically active fluid beds. For the dry-limestone-injection process, surface area-especially from pores in the 0. 2- to 0.3-micron range-is one of the important parameters which will discriminate between less and more reactive carbonate rocks. Marls, chalks, oolitic calcites, and other fine- grained limestones show larger-than-average surface areas and better- than-average removal efficiencies. Inert chemical impurities such as silica detract from reactivity. A dolomite is not necessarily less re- active than a calcite. For the wet-limestone-scrubbing process, dissolution rate of the carbonate rock controls the differences in stone reactivity. In this process the dolomites are less reactive than the calcites. In addition, more than 90 percent of the dolomitic impurity in Fredonia white lime- stone is inert during limestone scrubbing. Dissolution rate is also a function of particle size for large-grained carbonate rocks. Fine grinding of such rocks will increase the dissolution rate to that of a fine-grained rock. Hence the requirement of high dissolution rates may be met by some grinding of fine-grained material (e. g., marl, chalk, or other limestone) or by fine grinding of coarser grained material. For chemically active fluid beds, chalks have the best capacity to absorb both SO2 and H2S. However, most chalks are probably unsuitable for fluid beds because of high attrition rates. Because dolomites are generally more reactive than calcites with both SO2 and H2S, a dolomite would be the feed material of choice for a chemically active fluid bed.

Jan 1, 1974

By J. Slivnik, A. Stergarsek

[The site] [Z]irovski vrh uranium ore deposit is located in the extreme north-western part of Yugoslavia, some fourthy kilometers from the capital of Socialist Republic of Slovenia, Ljubljana, not far from the Italian and Austrian border. The sandstone type deposit of uranium ore with medium grade is located in a foothill of Julian Alps. The site shows some typical conditions for this region, which demand special attention in respect to the incorporation of an uranium treatment facility into environment. Among these specific conditions the following site characteristics should be mentioned: - populated area of agricultural and recreational value, - unconvenient climatic conditions with excessive rainfall and long lasting temperature inversions in the winter time, - very pure surface and underground waters which supply the drinking water reservate for large area including the capital of Slovenia, - sharp relief, - unconvenient geological structure. The choise of technology The intention to produce uranium and at the same time respecting the natural characteristics and existing uses of the site made the design of the ore treatment facility relatively difficult one. In general, there were two basic alternatives available perform the task. First alternative was to adopt the usual technological flowsheet with wet tailings disposal and with discharge of used water i.e. liquid effluents into the river. In order to prevent the negative impact of such technology on the sourrounding area sophisticated water purification installation and costly measures in wet tailings disposal e.g. impermeabilisation of large areas by concrete injections, large dam constructions, uncertain capturing of the water sources should be employed. Second alternative was to modify the usual flowsheet by employing the maximal recycling of liquid effluents to the process and to dispose the solid

Jan 1, 1980

By Ramazan Comakli, Cemal Balci, Nuh Bilgin, Hanifi Copur, Can Polat, Deniz Tumac

"Application of mechanical excavators for rock excavation in both civil construction and mining engineering fields has increased significantly in recent years. Prediction of the excavation performance of any mechanical excavators – tunnel boring machines, roadheaders, impact hammers, continuous miners and shearers for any geological formation is one of the main concerns in determining the economics of a mechanized mining and/or tunneling operation. A new portable linear rock cutting (PLCM) device was developed in the Mining Engineering Department of Istanbul Technical University and supported by The Scientific and Technological Research Council of Turkey (TUBITAK-112M859). The PLCM is used for cutting small core or block rock samples by a real-life mini disc cutter. The results from the PLCM are compared with the results obtained from the full scale rock cutting tests and theoretical model. It is found that there is reliable correlation between test results obtained from both cutting tests and theoretical model. 1. INTRODUCTION Mechanical excavators are currently the only alternatives to drill and blast due to higher production rate, increased safety, uniform muck size, less roof support, easier ventilation, continuous rather than cyclical operation, and possibilities for automatic control. The most of large civil tunneling and some mining projects are now carried out by mechanical excavators rather than drill and blast methods. Mechanical excavators can be categorized into two main groups: full-face and partial-face machines. Full-face machines such as tunnel boring machines excavate the face in one mode at the size of the cutterhead. Due to their cutting mode, the shape of the face profile by the full-face machines can only be circular. As for partial-face machines, the cutterhead is attached at the end of a boom. The face profile excavated by the partial-face machines can be from circular to horseshoe shape due to the cutting mode of the boom."

Jan 1, 2016

By Edmund W. Murphy

At the first workshop on Surface Subsidence Due to Underground Mining (1 981 ) , Yarbrough delivered a paper (1 ) describing the mine subsidence insurance program in Illinois operated as the Illinois Mine Subsidence Insurance Fund (IMSIF) . In this paper we will present claims data and describe changes that have occurred in the Illinois Insurance Code during the first six years the IMSIF has been in existence. The change in the original Illinois Public Act 80-1 41 3 that most affected the public was an amendment increasing the maximum amount of mine subsidence insurance avail- able on a structure from $50,000 to $100,000. Seventy-two counties in Illinois have been undermined for minerals, primarily bituminous coal. In Franklin County (.in the southern part of the state) 36 percent of the land area has been undermined for coal extraction. In St. Clair and Madison Counties , two counties that include the St. Louis Metropolitan area along the western border of the state, 10 percent and 7 percent of the land surface have been undermined. Most of the undermined area in the two counties is beneath urbanized land. In 34 counties, approximately 1 percent or more of the land surface has been undermined (2). The first shaft mine in Illinois was sunk in the city of Belleville (east of St. Louis) in 1842, and the mines of early vintage have initiated the majority of the mine subsidence claims. Data compiled from the first six years reveals that most Illinois mine subsidence events that affect structures occur over abandoned mines where early methods of high- extraction mining practices were used. Maps of these mines operated in the 1800s reveal irregular development of room and pillar areas and poorly defined production areas (panels). Rooms in the mines varied from 15 to 40 feet in width and the pillars varied in width from 5 to 40 feet. The pillars were often long and narrow. Recovery rates in mines that operated prior to 1900 generally averaged 50 per- cent, and extraction rates as high as 80 percent have been documented (2). Some pillar robbing occurred.

Jan 1, 1986

By Harry M. Castrantas

Caro's acid (peroxymonosulfuric acid-H2SO5) is used to destroy cyanides in tailings slurries due to its rapid reaction and low capital and operating costs. Due to its instability, Caro's acid is generated at the mine site using a hot or cold process. The majority of gold mines that use Caro's acid use the FMC hot process. In the FMC hot process, it is not necessary to cool the Caro's acid to minimize decomposition since it is used immediately upon generation. In contrast, the cold process uses a chiller to cool the raw materials and product. This paper will show, using laboratory and field data, that there is virtually no difference in Caro's acid yield between the cold and the FMC hot processes. Caro's acid yield depends on the mole ratio and concentration of sulfuric acid and hydrogen peroxide and is independent of operating temperature.

Jan 1, 1997

By S. Tuylu, D. Adiguzel, A. Bascetin, E. G. Savas, O. Ozdemir

"Paste Technology has some advantages comparing to other surface disposal methods. With this method, it is possible to pump high concentrated solid materials to very long distances without segregation problem. However, it is known from Literature that pumpability of materials is completely related to rheological properties of the materials. For this reason, in this study, the rheological parameters (e.g. yield stress and viscosity values) of the paste material prepared from Pb-Zn tailings at various solid ratios (60-85%) were obtained in order to determine the pumpability of the paste material. Additionally, slump tests, which are usually used in mining industry, was carried out. Finally, regression analysis was made between the slump values and rheological parameters of the paste material to find a correlation between two independent parameters. The results showed that there is a great correlation between the slump values and the yield stress of the material. On the other hand, there was no correlation with viscosity: ty=430.28-16.877Sv (R2= 0,94; ty: Yield Stress (Pa), Sv: Slump Value (cm)). Based on the results obtained from this study, it can be clearly concluded that the slump values obtained from a simple test can be used to predict yield stress values of paste materials. INTRODUCTION Recently, surface disposal of mining tailings has become one of the biggest problems in mining industry in terms of environmental issues. Therefore, several researches have been focused on this subject in order to find a best solution or method for this problem. These studies showed that paste technology has some advantages compared to other conventional methods. Tailings thickened to the extent show no segregation of particles during transportation, and relatively small amount of settling occur post-deposition which are often called “paste” (Cincilla et al. 1997). Paste tailing technology has two applications in the industrial area as underground paste fill and surface paste disposal. Paste tailing technology was first started to be used in Grund mine, Germany in the late 1970s (Grice, 1998). Process tailing material, water and - if needed - cement materials, which are the components of the paste, must be blended to obtain a homogenous mixture suitable for pumpability. Consistency behavior of the paste material is determined using a conventional sedimentation cone concrete test (slump). Meanwhile, the slump value of the paste must be between 200 and 250 mm for surface applications (Newman et al., 2001). Additionally, in the case of underground paste system, the optimum slump value must be between 150 and 200 mm. On the other hand, the water content and density of paste at certain slump value change depending on the amount of fine particles in the tailing sample. While moisture of the material will be high, its density will be low because of surface area of particles which increases with decrease in particle size (Meggyes and Debreczeni, 2006). For pumpability of the paste to long distances, slump value of the paste must be good enough to be accepted for use of surface paste disposal. Paste material has a yield stress because they show non-Newtonian behavior and generally is classified as a Bingham plastic fluid. (Cooke, 2008; Theriault, 2003). In addition, the appropriate viscosity value of the paste along with the yield stress must be between 100 and 250 Pa (Bascetin et al., 2013; Bascetin et al., 2014; Bascetin et al., 2015)."

Jan 1, 2016

By H. Janas

In a gas/coal outburst the gas plays an active, driving part. The proneness of coal to outbursts can be determined by means of its gas emission properties, since coal that is liable to outbursts differs from coal with normal gas emission properties in that it liberates its gas from the sorptive bond more quickly. There is a risk of outburst when the flow of metha¬ne originally desorbed by the coal is sufficient to move the loosened coal which has been broken suddenly. The violence of a gas/coal outburst can be evaluated from the distance of projection of the mass of coal. It depends on the gas pressure and on the liability to outburst of the coal at the original centre of the outburst. Both factors are complementary in their effects so that the same work is done in a gas/coal outburst when there is a high gas pressure and low proneness to outburst as when there is a low gas pressure and a higher proneness to outburst. The gas pressure in the coal increases with its gas content. Consequently it is possible to deduce the gas pressure of a coal seam from its gas content. In the Federal Republic of Germany the risk of a gas/coal outburst is thought to exist when the desorbable gas content of the coal reaches or exceeds the value of 9 m3/ton and if the specific limit value of the proneness to outburst is exeeded. The Mine Ventilation Testing Station of the Westfalische Berggewerkschaftskasse has developed a new method for determining the risk of gas outbursts immediately after taking the samples at the coal face (1), (2).

Jan 1, 1980

By Nathaniel Herz, R. J. Adamson, C. M. Romanowitz, Frank W. Jr. McQuiston, C. D. Hoyt, Robert S. Shoemaker, P. H. O’Neil

1. INTRODUCTION In this section, precious metals are defined as gold, silver, and the platinum group metals comprised of platinum, palladium, iridium, osmium, and rhodium. If the first three years of the 1970&apos;s are the criteria, gold, silver, and platinum seem destined for a bright future. Gold advanced in price from the historic figure of $35 established in 1934 to over $100 per oz (1973). For the five years 1966 to 1970, silver consumption exceeded production by about 50%. The silver price appears to be definitely on the uptrend, and a price of over $3 per oz seems probable. On this basis (at 1964 costs) the United States has an estimated 5 billion oz of unmined silver. The fresh burst of interest in platinum with a surge of renewed price strength (end of 1972) is due to the activity in the automobile emission control area, where platinum re¬mains the front runner in the catalyst area. Some international financial experts believe that governments will not rush into reform of the monetary system, and "Special Drawing Rights" (SDR&apos;s) will gain increased standing as international mone¬tary reserve assets. Gold will continue to be reviewed as the ultimate store of value and will remain the global monetary base. Devaluation of the U.S. dollar caused by imbalance of import payments over ex¬ports is the basic reason that the price of gold will likely remain above the $90 per oz figure for the balance of the 1970&apos;s. Gold and silver usually occur intimately associated, and recovery methods are often closely related; however, they were assigned sepa¬rate chapters, because the major production of each metal is from ore deposits classified as either gold or silver. For example, the gold ore occurrences in South Africa, the world&apos;s leading gold producer, have a ratio of gold to silver of approximately 10 to 1. The ores at the Homestake Mine, Lead, S.D., the largest U.S. gold producer, are predominantly gold with a ratio to silver of approximately 5 to 1. Silver in each example is a byproduct. By this same classification, the largest U.S. silver producers are the silver ores of the Sunshine, Galena, and Lucky Friday mines in the Coeur d&apos;Alene district, Idaho. However, the largest single-mine silver producer in the Free World is the Kidd Creek Mine at Timmins, Ont., where the occurrence is with sulfides of copper, lead, and zinc. Thus, the major gold production of the world is derived from those ores classified as gold ores; whereas, less than one-half of the silver production is from silver ores, and only a small percentage of the silver production is from gold ores. 2. GOLD Gold, the noblest of metals, has been mined for thousands of years. Its chemical symbol, Au, is derived from the Latin "aurum," meaning "shining dawn." A precious substance because it is one of the rarest metals, it has unique physical properties: it does not tarnish; it exceeds all other metals or alloys in malleability and ductility; it is a good conductor of electricity and is one of the most nonreactive metals. Its greatest strength is its indestructibility. It is the only metal mined at depths exceeding 10,000 ft. Since the early 1800s, its chief role has been as a medium of exchange, providing the basis for interna¬tional trade. In the past 15 years, however, gold has emerged as a useful industrial commodity. This role has been fortified by the estab¬lishment of a two-tier pricing system which maintains monetary gold prices at an established U.S. Government price, with industrial gold being priced higher by the free-market system. Occurrences and Production Native gold furnishes most of the world&apos;s production, since gold forms stable natural compounds with few other elements. Neverthe¬less, the metal is widespread with traces of it found in seawater and in the ashes of plants and animal material. Next to the native metal, the tellurides have been the most important gold-bearing minerals; these include calaverite, krennerite, slyvanite, hessite, and nagyagite. Native gold is invariably alloyed with more or less silver, but it is exceptional to find any other metal in the alloy. It is found in veins associated with quartz, calcite, alunite, other gangue minerals, and with various sulfides. Sulfide minerals in order of frequent associa¬tion are: pyrite, galena, chalcopyrite, sphalerite, arsenopyrite, tetrahe¬drite, and pyrrhotite. Small amounts of metallic gold are commonly disseminated through such sulfides. When considerable amounts of silver occur in gold, the mineral electrum is formed. In a few deposits, gold and mercury form natural amalgam. Native mercury is formed by weathering from cinnabar and other mercury minerals. Among the minerals sometimes mistaken for gold, pyrite, marcasite, and especially chalcopyrite may be men¬tioned. The flakes of biotite and other micas, especially when partially oxidized, also may imitate it closely. World gold reserves never have been estimated carefully. Esti¬mates indicate that present world reserves approximate I billion oz, of which about 60% occurs in South Africa and 20% in the USSR. World gold output is dominated by South Africa which produces two-thirds of the world&apos;s production from reserves that are adequate to maintain existing output levels. South African gold output comes from approximately 50 large underground operations that mine and mill 70 to 80 million tons of ore annually to recover 30 to 32 million oz of gold. The USSR is the second largest gold producer, followed by Canada and the United States (see Table 1). Gold production in the United States and Canada rose to high levels in the 1930&apos;s, following the increase in price from $20.67 to $35 per oz and with an abundance of good labor due to depression in other industries. Production of over 10 million oz in 1940 was behind only that of South Africa. World War II caused a precipitous drop in gold output due to the imposition of War Production Board Limitation Order L-208 issued in October 1942, which caused over 9,000 gold mines in the United States to shut down, most of which never reopened. The U.S. Treasury, which suspended purchases of newly mined gold in 1968, had been the sole buyer of U.S. produced gold since 1934. This created the two-tier pricing system, and in March 1972 the President signed into law a bill authorizing a $3 increase in the official price of gold to $38 per oz. In February 1973 the President ordered a second devaluation of the dollar, amounting to about 10% which raised the official price to $42.22 per oz. The erratic development of the gold market, which has seen the

Jan 1, 1985