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By George B. Pryde

Dear Sir: Yours of July 23rd, relative to my appointment on the Safety Committee in connection with the Rocky Mountain Coal Mining Institute. As you say in your letter, "The duty of this committee is to draft suggestions as to safer mining practices with the idea of preventing disasters in coal mines." Much has been written and many suggestions made on this same subject, and it is very hard to put up further recommendations than have already been made. The disasters you mention in your letter unquestionably have direct reference to coal mine explosions, which from time to time still occur in this and other countries. As far as our Western mines are concerned, you know that sprinkling and shot firing by electricity have been very extensively carried out. Notwithstanding these precautions; we have had a few rather serious disasters in the past in these mines. I do not care to place any blame or responsibility on the companies having these disasters, but it is a fact that in each and all of them, after careful investigation has been made, that the human element has had more or less bearing on the accidents happening. From most reports that we gain, either directly or indirectly, it is very evident that investigation shows after an explosion that the rules governing one or both of the above safety measures have been somewhat carelessly or negligently carried out. Much has been written and read about rock dust sprinkling, but it is questionable if this method is doing a great deal toward the eliminating of disasters. While it is true it may have the effect of preventing propagation, still I do not believe anyone claims for it a sure preventative against initial explosions. I had occasion not long ago to visit a mine, after an explosion, in which dust barriers were supposed to be hung, and from indications it was quite evident that the dust barriers had been in operation, but they did not prevent the explosion from reaching all open parts of the mine. It is also true that profuse scattering of rock dust throughout a mine would have a beneficial effect, but there is a question arises here as to whether the sprinkling by rock dust or the spraying by water, if available, is the most effective. I am satisfied that if all coal mines are kept well sprinkled and all open workings maintained in a thorough moist condition, that the biggest factor in a coal mine explosion is in this way eliminated. There is no doubt but what the use of permissible powder, particularly if shot by electricity, has had a very marked effect on the number of disasters in mines, and if this method of shooting was energetically carried out there would be a difference in the number of explosions, both minor and Major, all over the country. Some of the recent explosions have taken place where no shooting was being done, but there is no denying the fact that the other ingredient, namely, coal dust, entered in the elements very extensively. We have read and heard of hydraulic cartridges and other patents (substitutes for powder) that were being worked out for the purpose of

Jan 1, 1923

By John Skelton, E. J. Harvey

Seepage runs (stream flow measurements in a short time at many points in a basin,) and stream flow records are used to locate losing areas in stream basins in the Missouri Ozarks. The terrane consists of dolomitic limestone and sandstone of Ordovician and Cambrian age. Side-looking radar imagery emphasizes variations in topography and reveals two types of drainage basin topography, rough and smooth (deeply dissected and slightly dissected basins). In the deeply dissected basins (rough ones), main streams and tributaries generally gain. In the slightly dissected basins (smooth ones), the streams lose a part or all of their flow. Logan Creek, a tributary of Black River in the southeastern Ozarks, loses much of its storm runoff and all of its dry weather flow. East and West Forks of the Black River, north of Logan Creek, gain water through most of their main stems. On radar imagery Logan Creek basin has a light uniform tone and smooth texture in contrast to the darker tone and rough texture of the East and West Forks. The contrast is due to the difference in degree of dissection. Therefore, radar imagery may be useful in suggesting gaining or losing streams (or reaches of streams).

Jan 1, 1973

By Lawrence K. Jetter, Robert F. Mehl

SOME advances have been made recently in the theory of the kinetics of precipitation from metallic solid solution despite the complexities of the problem, but there is surprisingly little quantitative information available on rates of precipitation with which to test present theory or upon which to build new theory.? Attempts to measure rates of precipitation have been beset with difficulties which originate both in the anomalies that attend the changes in the properties selected for measurement, as, for example, in electrical conductivity or mechanical properties, and also in the complexities in the structural changes in some systems, as in the aluminum-copper system. If the functional relationship between the quantity of precipitate and the value of the selected property is uncertain, measurements of that property are obviously of uncertain utility in determining absolute rates of precipitation. If the precipitating system passes through one or more transition stages, the interpretation of measured rates lacks definiteness; in such cases, it is necessary to measure the rate of reaction in each separate stage, if the rate measurements are to have any significance from the kinetic point of view.* These difficulties cannot be wholly avoided, for at least in some measure they are characteristic of the process of precipitation from solid solution, but they can be minimized both by the selection of a simple system and by the use of a method of measurement relatively free from anomalous behavior. The present paper reports dilatometric measurements on the rate of precipitation of silicon from the aluminum-rich solid solution in the aluminum-silicon system-a study that approaches the desiderata of simplicity. The aluminum-silicon system offers advantages from these points of view: there are no known anomalies in the property changes accompanying precipitation ;2,3,4 there are no known transition stages; the precipitate is an element, not a compound, and both matrix and precipitate are cubic, and while the structures are not identical (the solid solution is face-centered cubic and the precipitate is diamond cubic), the system at least approaches the ideal case of a crystal precipitating from a matrix of the same crystal type-the ideal case which Becker5 assumed in treating the precipitation process theoretically. The dilatometric method, while not free from disturbing effects, as the subsequent dis-

Jan 1, 1942

By W. S. Hui, M. G. Silva-Valenzuela, H. Wiebeck, F. R. Valenzuela-Diaz, B. B. Michel

Biodegradable polymer microcapsules have been used as a control sustained release system with many applications. Studies reveal that the incorporation of nanoparticles improves matrix properties, even more so if the clay is modified. The objective of this work was to compare microcapsules of poly (succinate-co-butylenelactate) (PBSL) reinforced with Brazilian clay, composed of smectites and kaolinite, in its natural (MMT/K) and modified (O-MMT/K) forms. Nanocomposites and microcapsules were synthesized by emulsification-diffusion of solvent and solvent diffusion methods. Its characterization was then performed by scanning electron microscopy (SEM), stereo microscopy and wide-angle X-ray diffraction (XRD). The results reported corroborate that PBSL/OMMT-K form an intercalated montmorillonite and kaolinite nanostructure, capable of generating uniform spherical microcapsules with diameter values smaller than that of PBSL/MMT-K, reaching 5–10 lm. DRX indicates that there was a real change in the clay structure. The incorporation of modified clay showed an improvement in surface quality and the strength of microcapsules, making it possible to produce smaller sizes.

Mar 1, 2018

By Keith A. Heasley

In the past, numerous displacement-discontinuity (DD) models of stratified rock masses have been proposed using a homogeneous isotropic elastic overburden. In this paper, it is postulated that a laminated overburden model might be more accurate for describing the displacements and stress in these stratified deposits. In order to investigate the utility of using a laminated overburden in a DD model, the fundamental mathematical basis of the laminated model is presented and graphically compared with the fundamental behavior of homogeneous isotropic elastic overburden and with field data. Specifically, the stresses and displacements surrounding an idealized longwall panel as determined from the laminated overburden model are presented and compared with results from the homogeneous isotropic overburden and with measured abutment stress data. Also, the remote displacements and surface subsidence as calculated by the laminated overburden model are compared with homogeneous isotropic calculations and with measured subsidence data. The results of this investigation show that the laminated overburden is more supple, apt to propagate displacements and stress further, and better able to fit observed data than the classic homogeneous isotropic overburden. Ultimately, it is suggested that the laminated model has the potential to increase the accuracy of displacement and stress calculations for a variety of mining situations.

Jan 1, 1996

Cyclone Process for Heavy Metals Decontamination of Sediments

Sep 13, 2010

By Michael Karmis, Syed Muhammad Tariq, Zeshan Hyder

This paper analyzes the blast design for lime stone quarries of two major cement plants in Pakistan. The production blast of these quarries was resulting in excessive boulders production. At some instances, the rate of boulders production was approximately 10%-15% of the main production blast i.e. if a round of main blast gave around 4000 tons of material; almost 400 to 500 tons of that material was in the shape of massive boulders. This gave rise to increased operating costs requiring boulders collection, drilling and secondary blast.

Jan 1, 2012

By R. I. Iacobescu, Y. W. Chiang, A. Van Audenaerde, R. M. Santos, T. Van Gerven, P. Knops

In this work, we explore a novel mineral processing approach using carbon dioxide to promote mineral alterations that lead to improved extractability of nickel from olivine ((Mg,Fe)2SiO4). The precept is that by altering the morphology and the mineralogy of the ore via mineral carbonation, the comminution requirements and the acid consumption during hydrometallurgical processing can be reduced. Furthermore, carbonation pre-treatment can lead to mineral liberation and concentration of metals in physically separable phases. In a first processing step, olivine is fully carbonated at high CO2 partial pressures (35 bar) and optimal temperature (200 °C) with the addition of pH buffering agents. This leads to a powdery product containing high carbonate content. The main products of the carbonation reaction include amorphous colloidal silica, chromium-rich metallic particles, and iron-substituted magnesite ((Mg1- x,Fex)CO3). Carbonated olivine was subsequently leached using an array of inorganic and organic acids to test their leaching efficiency. Compared to leaching from untreated olivine, the percentage of nickel extracted from carbonated olivine by acid leaching was significantly increased. It is anticipated that the mineral carbonation pre-treatment approach may also be applicable to other ultrabasic and lateritic ores.

Jan 1, 2014

By John Ralston, Stephen Grano, Yongjun Peng, Daniel Fornasiero

"A specially designed mill which allowed the control of pH throughout grinding was used to study the effect of rgrinding conditions on galena flotation and galena separation from pyrite. The various reactions occurring on the mineral surface were investigated by a range of techniques, including OH- addition to maintain the grinding pH, EDTA extraction, XPS and ToF-SIMS measurements.Galena flotation and galena separation from pyrite were strongly dependent on the metal oxidation species produced on galena and pyrite surfaces under different grinding conditions. Iron oxidation species depressed both galena and pyrite flotation, whilst lead oxidation species activated pyrite but had little effect on galena. Optimum galena flotation and galena selectivity against pyrite were achieved by selecting grinding conditions that enabled lead and iron oxidation production to be controlled."

Jan 1, 2003

By C. P. PERIN, DONALD BELCHER

T HE production of pure iron by electrolyzing solutions of its salts has been the object of scientific curiosity and research for about 80 years; and in the last two decades a realization of the unusual physical and chemical qualities of electrolytic iron has turned the attention of chemists and metallurgists toward a commercial application of this accumulated knowledge. Thus Burgess and Hambuechen in America, . Cowper-Coles in England, and Fischer in Germany- devised methods, more or less successful, for the electrolytic refining of iron, but none of these processes has yet attained large-scale operation. During the war some interesting ,work was done in France and England on building up worn or defective machine parts by electrodeposition of iron. It remained for the Société "Le Fern in France to carry on the process commercially. For six years Les Fonderies et Forges. de Sainte-Maire et Gravigny and the works of Bouchayer & Viallet at Grenoble have manufactured pure-iron boiler tubes in competition with established practice. The French process originated in the researches of Anthelme Boucher in 1910, and was, not put into operation until several years of experimentation had passed.

Jan 1, 1921

By Guillermo Velarde

Dado que la flotación seguida por la fundición/ refinación es la única vía de procesamiento del cobre, se buscó una alternativa que trate con suficiencia los sulfuros de leyes marginales dentro del CUT-OFF de una concentradora. En ese sentido, el presente texto señala que la energía solar se convierte en una herramienta que ayuda a lixiviar minerales con poca pirita y obtener una temperatura de proceso que magnifica la recuperación del cobre en especial de la calcopirita, etc. Asimismo, la influencia cuantitativa de la temperatura en la recuperación de los sulfuros primarios, transicionales y secundarios de cobre, la velocidad de calentamiento de la pila, las temperaturas de proceso que puede alcanzarse, las pérdidas de calor en el periodo no soleado del día, el balance térmico de la pila y otros indicadores económicos de viabilidad, etc. son presentados como resultados de pruebas diversas a nivel de laboratorio e industrial.

Oct 21, 2015

By S. W. Hurlbut

12.4 Application of Research Findings. After the findings of research have been evaluated and approved, there remains the problem of translating them into practical usage. It frequently happens that this is the more difficult phase of the research project. Hitherto, the problems have been largely associated with material objects and scientific laws. When the findings of research are implemented in the field, the human factor becomes the most important element bearing on success or failure. From this point on, the attitudes and reactions of people of all kinds are involved, and just how they are involved and their relation to successful implementation is the subject of the remainder of this section. 12.41. Management Attitudes. To engage in research at all implies management backing to a degree. But this could be dictated by overall company policy or by just some executives in the hierarchy of management. The existence of research per se does not necessarily mean that there is a solid, unanimous echelon of management executives who sincerely believe in the fruits of research, who have an earnest desire to make breakthroughs, and who have a willingness to take calculated risks. Under the ideal condition of complete management backing, translating the results of research into practice is greatly facilitated. If management accepts the results of research as valid, the order is given, or it has been established by precedent that those results will be implemented. The rest of the organization will have grown to accept the fact that this is so, and that the results must be given a fair trial in the field. However, this ideal condition probably exists but rarely, and it is against a background of incomplete, or partial, management backing that most results of research must be implemented. At the present time, the climate for research in the mining field is less than perfect but is improving rapidly as the realization grows within the industry that the way toward taking its proper place in the Space Age is by applying to mining the philosophy and techniques of research that made the Space Age possible.

Jan 1, 1968

By J. L. Carr, A. K. Smith, C. C. Jobes, G. T. Homce

"Underground continuous mining machines pose a difficult safety challenge since their operators generally work in close proximity to these machines in very restricted spaces. Intelligent software for use with magnetic proximity detection systems has been shown to accurately locate workers around mining machinery in real time. Calibrating these systems requires the manipulation of a lot of data to determine the calibration constants. Researchers have developed software to analyze, convert, and visualize data acquired during this calibration process to more accurately model magnetic fields and their interaction with the environment. This paper details the background, development, and operation of the resulting application software focusing on the utility of the graphical user interface to visualize the magnetic field calibration data. The refined data developed by this process can then be utilized by the proximity detection system to more accurately identify the location of miners working in an underground mining environment. INTRODUCTION Roughly half of the electricity consumed in the United States is produced with coal, and roughly one-third of all US coal production comes from underground mines [1]. Over the last century underground mining health and safety has seen a continuous and dramatic improvement. However, machine-related injuries and fatalities continue to be a major safety concern [2]. Every year, hundreds of miners are severely injured while operating underground mining equipment, and 39 miners have been killed in striking/pinning accidents involving continuous mining machines (CMMs) since 1984. CMMs, such as the one shown in Figure 1, are large mobile machines that are used to mechanically cut coal in an underground mine. These machines weigh approximately 40 to 50 tons, have hydraulically articulated appendages, and are capable of moving at speeds up to six feet per second [3]. Modern CMMs are remote-controlled, yet the operator and other miners are often in close proximity to the machine. Recent research by the National Institute for Occupational Safety and Health (NIOSH) reveals that the locations workers take relative to the CMM are usually influenced by visibility requirements and safety concerns [4]. The Mine Safety and Health Administration (MSHA) estimates that at least 28 fatalities involving CMMs since October of 1984 may have been prevented with proximity detection technology [5]. MSHA further estimates that proximity detection could prevent 20% of all deaths throughout the industry [6]."

Jan 1, 2016

By John W. Wagner, Robert K. Willardson

Single crystals of Pbl-xSnxTe have been grown from nonstoichiometric, cation-rich melts with the objective of producing as-grown, bulk material containing carrier concentrations ranging from 1016 per cu cm to 1018 per cu cm. Three specific crystal composi-tions were investigated in detail; x = 0.00, 0.10, and 0.17. Pull rates of from I to 3 mm per hr were used. Single crystals were successfully pulled from melts containing as little as 30 at. pct Te. Hall coefficients, resistivities, and carrier mobilities of these materials were determined. The relationship between the composition of the melt and the carrier concentration in the as-grown crystal has been studied for the three crystal compositions of interest. BULK single crystals of Pb,-,Sn,Te have previously been grown from stoichiometric melts.1,2 Such crystals are p-type and have relatively high carrier concentrations ranging from -9 x 1018 per cu cm for PbTe to -8 x l020 per cu cm for SnTe at 77°K. These carrier concentrations result from deviations from stoichiometry (lead vacancies) in the as-grown crystals. Since lower carrier concentrations are desirable for electrooptic device applications, these crystals are usually subjected to long-term, isothermal anneals.' This paper reports on the growth of Pbl-xSnxTe single crystals from nonstoichiometric melts with the primary objective of producing as-grown material containing relatively low (1016 to 1018 per cu cm) carrier concentrations and also reports on the general characteristics of these crystals. The phase relationships in the Pbl-xSnxTe systems are such that materials solidifying from nonstoichiometric, cation-rich melts will have smaller deviations from stoichiometry than materials grown from stoichiometric melts. Fig. 1 is the T-x phase diagram for PbTe in the vicinity of the stoichiometric composition.3 A crystal grown from a stoichiometric melt will solidify at a melting point maximum at which the solid will contain -0.5002 atom fraction of tellurium. PbTe single crystals grown in our laboratories from stoichiometric melts have carrier concentrations of 9 x 10" per cu cm, indicating that the excess tellurium in the crystals is as expected from this phase diagram. However, growth of PbTe from a lead-rich melt will result in material having a more nearly stoichiometric composition. Although the addition of Sn to the melt shifts the solidus curve further toward the tellurium-rich side,4 the general discussion given for PbTe applies to the Pbl-xSnxTe systems as well. EXPERIMENTAL Single crystals of Pb1-xSnxTe have been grown in our laboratories from nonstoichiometric, cation-rich melts using the Czochralski technique and boric oxide liquid encapsulation. The details of the growth apparatus and growth technique have been reported in a previous paper on growth of these alloys from stoichiometric melts.2 In the present study, three specific crystal compositions were investigated in detail; x = 0.00, 0.10, and 0.17. Growth of alloy crystals from nonstoichiometric melts requires considerable care, and good quality single crystals were obtained in this study only by optimizing the mechanical and thermal stability of the growth system and by using pull rates of from 1 to 3 mm per hr (Pbl-xSnxTe crystals are easily pulled from stoichiometric melts at rates of from 5 to 10 mm per hr). The liquid encapsulation technique was found to yield near-ideal conditions, since the B2O3 layer increased the thermal stability at the growth interface, permitted easy attainment of near-ideal thermal gradients, and dampened vibrations at the melt surface. The hygroscopic character of the B2O3 was a slight problem and vacuum heat treating was necessary to completely remove the water from the boric oxide. During initial growth, the seed diameter was reduced and a narrow neck (1 to 2 mm diam) of several millimeters length was grown. The latter steps were found to be necessary for the growth of single crystals, i.e., if either of these two requirements were

Jan 1, 1970

By M. Hopf

The use of water-cooled copper components as sidewall elements of submerged arc furnaces and other pyrometallurgical applications has become increasingly common. The high cooling efficiency of copper has made it possible to increase the service life of furnace refractories when compared to conventional refractory linings. However, even the self-healing effect of ?freezing? worn areas of the lining does not necessarily protect the copper coolers against wear or corrosion completely. In order to avoid furnace explosions, various methods have been used to monitor the wear of coolers. Unfortunately, these have not been able consistently to identify localized wear. Thos Begbie (South African) and SAVEWAY (German) jointly developed technology to embed a line sensor into the copper cooler during the casting process. This system allows an exhaustive monitoring of the copper cooler. A SAVELINE sensor is placed inside the copper-cooling panel between the water-cooling passage and the hot face of the panel. The sensor follows the meandering shape of the cooling water channels. In the first instance, the sensor provides analogue information as the thickness of the copper reduces. Secondly, this wear signal will be confirmed by a signal of interruption if the sensor is washed away. Because of the structure of the sensor, a self-diagnosis is possible and indications can be confirmed (double proofed).Subsequent to the manufacture of some test pieces, coolers for a large submerged arc furnace were manufactured. The sensorized coolers have been installed at the intermittent surface (slag line) where the largest amount of corrosion has been encountered. The system has been operating since December 2005 in what is considered one of the largest submerged arc furnaces in South Africa. Keywords: Pyrometallurgy, furnace, copper coolers, freeze lining, monitoring, Saveway

Jan 1, 2006

By A. H. Leuschner, P. J. Kruger, J. Kruger

INTRODUCTION This paper deals with some practical aspects of the use and interpretation of dosimetric methods for assessing the exposure of workers to natural uranium. Consideration must be given not only to the scientific value of the method of dosimetry, but also to the practicality of the method in the particular working environment. It is generally accepted (IAEA, 1976) that uranium does not present a hazard during the mining and extraction processes up to the final concentration stage, that is precipitation as ADU or calcining to the oxide. Further processing (e.g. conversion to oxides, fluorides, etc.) is generally associated with the nuclear industry. It is customary for uranium processing facilities to be managed according to industrial norms rather than according to those applied for the purpose of radiation protection. This is mainly because of the large quantity of material to be processed and the fact that uranium is considered to be of a low radiotoxicity. Although ventilation is used to some extent, provision is not made for the same level of protection as would be required in a radiochemical facility. It is typical in such a plant to find that the process itself may be enclosed and ventilated, but the ventilation is inadequate to cope with an accidental release of material. The working environment is poorly ventilated, sometimes only by natural ventilation, and one frequently finds areas with high airborne dust levels, designated as mandatory respirator areas. Protection of personnel is dependent on personal protective equipment. Radiation protection is not of prime concern and personnel are not specifically trained in this subject. It is in this type of environment that acceptable monitoring procedures and personnel dosimetry must be established. The effectiveness and practical application of the dosimetry must also be judged against this working environment. DOSIMETRIC TECHNIQUES The methods available for assessing personnel exposure, whether it be in terms of chemical or radiological hazard, include urinalysis, faecal analysis and [in vivo] monitoring. Faecal analysis does not present itself easily as a method for routine use. Techniques for [in vivo] monitoring have been developed recently and as expensive instrumentation is required, it is not generally available. That leaves urinalysis as a dosimetric technique for routine use, and it is probably for this reason that urinalysis is still widely used. Guidelines for the interpretation of urinalysis results, as originally provided by Neuman (Neuman, 1950), are still used in practice, even though it has become clear that this method has severe limitations as regards the assessment of the dose as a result of the intake of class W or class Y compounds (Alexander, 1974). Typically a level of 300 µg [U/C] urine can serve as an indicator of an acute exposure (above which chemical damage to the kidneys may occur) and a level of 100 µg [U/C ] urine can serve as an indicator for an investigation. Such levels are determined and are used in conjunction with several factors, such as mode of intake (ingestion or inhalation), solubility of compound (D, W or Y), means of intake (acute or chronic), environmental monitoring results and frequency of urine sampling. Since the ICRP concept for internal radiation limitation changed from that of the critical organ, i.e. the single organ of greatest significance under the circumstances, to that of effective dose equivalent, i.e. account being taken of the total risk due to the exposure of all tissue, the maximum permissible organ burden (MPOB) was replaced as secondary dose limit by the annual limit on intake (ALI) (ICRP, 1977). The ALI values are calculated from the committed dose equivalents of the various organs, and are used to determine organ burdens, which are then used to interpret the dosimetric results. Using the ICRP model (ICRP, 1979), a comprehensive calculation was made by Johnson (Johnson, 1980), giving organ burdens and excretion data in terms of intake for acute and chronic exposures for different categories of uranium compounds. The question arises as to what extent the direct measurement of intake can be utilised as a method of dosimetry. This will require a method of personal intake measurement for each individual worker, with both ingestion and inhalation being taken into account. A measurement of

Jan 1, 1981

Recycling and Recovering Fine Particles from Auto Shredding Residue (ASR/SR) to Conserve Raw Materials and Protect Environment

Sep 13, 2010

By Francis O. Blackwell

There are few industries in which power is more important to successful operation than mining, and none in which it is so difficult to ohtain power cheaply. Fuel is usually expeusive in mining districts, ana the ma chinery may be widely scattered and located in places difficult of access. The work is often so intermittent and variable as to prevent the economical use of steam. Mining operations are likely to exhibit accumulations of comparatively small and inefficient engines, numerous boilers and long lines of wasteful steam-pipes. Conlpressed air, as a means of transmitting power, is so handicapped by losses in the compressors and piping that it is limited to short distances and to the operation of apparatus requiring power, without regard to cost. To-day, electricity is rapidly replacing other methods of power-distribution, primarily because it is practically independent of distance. By selecting a potential proportional to the length of transmission, the cost of electric conductors and the e5ciency are the same for all distances within reasonable limits. For instance, a given amount of power can be delivered either 528 ft. away at 100 volts, or 50 miles at 50,000 volts, with the same total of copper per H.P. and with exactly the same loss of power in the transmissioo-circuk. This independence of distance permits the selection of the place most advantageous for power-development as a site for an electric power-plant, and the co~~centration there of the generation of all the power required within a radius of many miles. The powel.-site may be at a fall of water, if one is available, or a steam-plant can be built where fuel and supplies are cheapest, or where suflicient water is available for boiler-feed and condensing purposes.

Jan 1, 1904

By M J. Daniel

Comminution is the science of size reduction of brittle materials. It is integral to mineral extraction and is one of the most energy intensive processes in the mining industry. There are a number of tests used to quantify the strength of ore, which are then used to size the AG / SAG mill in circuit design. The calculated energy utilized for breakage in these devices is based on the assumptions that the materials treated are of average shape and that the processing equipment is designed to break the ore as efficiently as possible under the given operating conditions. In drop weight tests, it was found that shape significantly influences the measured rock strength. Controlled experiments with variations in blends of rock shape show that mill throughput increases with the addition of weaker shaped rocks.

Jan 1, 2012

By R M. Briggs

Kapowai Caldera Complex (KCC), located 10 km west of Tairua (eastern Coromandel Peninsula), is a late Miocene composite collapse caldera, formed during eruption of several small and large volume andesitic rhyolitic ignimbrites. Numerous epithermal Au-Ag mineral deposits and associated alteration zones at the KCC are related to caldera (rhyolite lava domes, intracaldera faults) or regional structures (faults). The main epithermal deposit exposed in the central KCC is associated with an E-W striking structural boundary fault that cuts the Welcome Jack rhyolite dome. Propylitic (calcite - chlorite) and sericitic (quartz - sericite) alteration haloes surround this deposit. Sporadic zones of sericitic alteration are also exposed within and on the margins of the Bulls Run rhyolite dome complex. Epithermal systems post-dated emplacement of these rhyolite domes, but were controlled by them. Propylitic alteration of ignimbrite in the floor of the Kapowai and Kauaeranga valleys is related to the major NE-trending Kapowai Fault which extends SW to south of Thames. Alteration along this fault pre-dates alteration associated with the rhyolite lava domes. Numerous sericitic and propylitic altered welded ignimbrite, rhyolite and andesite lava lithic fragments have been sampled from intracaldera ignimbrites, and although no direct source is known, they infer the presence of buried epithermal systems. Repeated epithermal activity at the KCC is inferred by the exposed epithermal deposits/alteration zones and the older buried geothermal systems. Silicic caldera volcanoes are considered to be critical volcanic environments for epithermal Au-Ag mineralisation in Coromandel, but are highly variable and need detailed stratigraphic, structural, petrologic, and geophysical studies to characterise them.

Jan 1, 1999