Search Documents

By T. Velea

The most widespread methods for producing metallic copper are smelting of copper sulphide concentrates (which generates various types of polluting substances) and the hydrometallurgical route which consists of leaching in sulphate and chloride media (usually employing high temperature, high-pressure and special equipments). This paper presents a process, called VEPE, which consists of oxidizing copper sulphide concentrates in weak alkaline media (Na2C03 orland NaOH solutions), under low pressure and with air sparging. The oxidized concentrate contains less than 0.4% S. Copper is recovered from the oxidized concentrate by the standard leaching-solvent extraction-electrowinning route, with a total efficiency of 98% extraction. The proposed technology could represent a good opportunity to recover copper from sulphide concentrates in a clean, simple and profitable way.

Jan 1, 2007

By G. R. Parslow

U, Fe, Mn, Ni, Cu, Zn and Co data for the sediment in both Key and Seahorse lakes, which overlie portions of known economic uranium deposits in the region, are presented. With the exception of U, Fe and Mn, the elemental distributions can be considered anomalous, in a statistical sense, in both lakes. The U values are of particular interest in that Key Lake is not anomalous, whereas Seahorse Lake is markedly anomalous. Tentative correlations made with background data from other surveys in an attempt to differentiate between anomalous and background values indicate that deviations from linearity in a distribution, and not absolute mean or maximum values, are indicative of anomalous samples within the distribution.

Jan 1, 1979

Rock engineering has now been practised as a discipline for about50 years, and many sophisticated methods of analysis for use in rock engineering design have been developed. However, analysis is only a tool for use in engineering design, and rock masses are often so complex that realistic modelling of them, even with sophisticated methods of analysis, is impossible. At the other end of the scale, rock mass classification methods have been developed to quantify the rock mass. These ?numbers? are now widely used for assessment of stability of underground and surface excavations in rock, for the determination of rock support requirements, and for the estimation of rock mass strength and deformation properties. In considering these areas, the two concepts?design, and prediction of behaviour?will be dealt with. The discussion will be introduced by a consideration of the characteristics of the rock mass, which will highlight the variability in its properties and hence the uncertainty in the behavioural parameters. Examples of real projects will be used to illustrate the discussion.

Jan 1, 2003

By Arthur A. Center

WAR demand- motivated developments in the zinc industry during 1942. Stocks of Prime Western were built up and High-Grade remained tight. The Prince The Prime Western stocks are expected to be cut down and the demand for High-Grade more easily filled as the Depue reflux plant of the New Jersery Zinc Co. increases - production. Subistition of steel for brass in artillery shell cases will have a considerable effect on the zinc situation of the country one estimate of the saving in zinc in 1943 by this substitution being a little under 100,000 ton, of metal. The metal saved will, of course be High-Grade. If the substitution occurs, the present tight situation in High-Grade may be entirely relieved as new production comes on the market and zinc may find itself approaching a situation as comfortable as that of lead provided the supply of zinc-hearing raw materials is sufficient to keep all reduction plants tip to capacity production. The premium price of the per pound of zinc over set quotas which went into effect early in 1942, helped to bring about the new lead-slag-fuming plant and other new sources of raw materials.

Jan 1, 1943

By Klaus Rabensteiner, Klaus Chmelina

"INTRODUCTION Urban tunneling is often related with special geotechnical risks. Typical causes are difficult (hydro)geological conditions, a very low overburden and the presence of critical and vulnerable (infra)structures in the influence zone of the construction (e.g. existing tunnels, roads and pavements, sewer pipes, gas and power lines, landmarked buildings, historic monuments). To manage these risks appropriately, an early detection and warning of unexpected behavior of the affected geotechnical objects ground and tunnel, as well as existing structures are mandatory. To accomplish this, the design and execution of a dense geotechnical monitoring program is of high importance. In more detail, this means specifying and performing a systematic and continuous acquisition, processing and analysis of monitoring data to support decision making. In recent years the development of new automatic sensors and (wireless) data transfer techniques and the general trend towards an automatic acquisition of monitoring data has led to an enormous increase of data production frequencies and volumes. In order to handle this data explosion efficiently, information systems and geo-databases have been developed and used successfully in many projects. They represent IT tools that support the different tasks of a given geotechnical monitoring program including data acquisition, transfer, check, processing, backup, analysis, distribution, reporting and, last but not least, alarming. Meanwhile, some tools already have developed the capability to connect to other theme-specific databases used in the project and, thus, serve as a central data management system for all kind of digital data produced. This makes possible the implementation of further useful functions and services supporting tunneling tasks such as machine control, tunnel simulation, geological prediction, process optimization, etc. where data from different engineering disciplines must be combined and processed in an integrated way. In the following chapters our aim is to describe how monitoring data management, geotechnical monitoring, alarming and reporting are organized and technically implemented at the metro project Cityringen in Copenhagen (Denmark). We want to highlight the specific role and tasks of the used tunnel information system in the project, and particularly inform on the most relevant challenges."

Jan 1, 2016

By K. H. Coats

This paper describes an approximate technique for handling the problem of percolation of evolved gas upwards through the oil column in computer simulation of natural depletion. This technique has been incorporated into a general model for simulating three-phase flow in one, two or three dimensions. The mathematical model for perfonning these calculations is described in detail in a separate article. 1 While vertical gas percolation occurs during natural depletion in a reservoir of any configuration, it is especially pronounced in the pinnacle reel or bioherm. The reel may have an areal extent less than one section with a thickness of up to 800 It. The upward percolation of evolved gas often limits the time step in calculations as little as one day. Using this small time step, computer expense for a single 30- to 40-year simulation on even a one-dimensional basis has exceeded 92,000. The method described here for handling the percolation allows time steps of 60 days or more (depending on reservoir size and production rate), resulting in a considerable reduction in computing expense. The method also allows calculations in which secondary gas caps build up in tight zones of the oil column below the main gas cap. The validity of the method is indicated in connection with an example pinnacle reef field. Calculated results using a 2-day time step (where the method in question is not needed and not invoked) are compared with results using the method and a 60-day time step. The comparison shows good agreement. Results from one- and two-dimensional simulations of the reef are presented along with the corresponding computing times on the CDC 6600 computer. A three-dimensional simulation was also performed and the required computing time is given. INTRODUCTION A general analysis for simulating three-dimensional, three-phase flow in reservoirs has been developed. 1 In applying this model to reservoirs undergoing natural depletion, a time-step restriction was encountered due to the flow of evolved gas upwards through the oil column and toward the gas cap. A remedy for this problem has been incorporated in the analysis and is described here. The time-step restriction is encountered only in calculations which include flow in the vertical or near vertical direction. The restriction occurs to some extent in reservoirs of any geometrical configuration, but it is especially pronounced in the pinnacle reef or bioherm where the ratio of thickness to areal extent is unusually large. This paper describes the problem, a method of handling it, incorporation of the method in the three-dimensional, three-phase model, and, finally, a test of the method's validity in an application to an example pinnacle reef reservoir. THE PROBLEM During the early stages of reservoir depletion, pressure falls below bubble point in progressively lower regions of the oil column. Continuing production results in evolution of dissoived gas throughout the oil column. This gas then percolates upwards toward the top of the reservoir. If the gas encounters a sufficiently low permeability zone in its travel upward, then it can accumulate and form a secondary gas cap. If no zones are encountered which are tight enough to hold gas against the gravity forces, then the gas travels on until it reaches the top of the sand or the main gas cap. Numerical simulation of multiphase flow in reservoirs is generally performed with time steps such that the flow of a fluid into or out of a block in one time step is a fraction (considerably less than one) of the total amount of that fluid present in the block. Use of a time step where the time step's

Jan 1, 1969

By P. Campbell, E. M. Gardy, L. Hachkowski

Introduction The efficient process control of a uranium mill and its associated mining operation requires a nearly continuous knowledge of the uranium concentration in the ore. Generally, the approach is to use laboratory assays of grab samples from the mill feed belt. In some cases, elaborate and expensive systems have been used to ensure random sampling, but even with these systems, mass-balance discrepancies still exist. There is a requirement for an on-line instrument that can give a prompt, accurate analysis of a large portion of the feed stock. The authors have recently evaluated a laboratory system that achieves these goals using neutron activation and delayed neutron counting. The development of the on-line uranium ore analyzer is a consequence of previous work done at the Whiteshell Nuclear Research Establishment (WNRE) (Campbell et al., 1978 and 1981), and is based on the emission of delayed neutrons after the neutron irradiation of fissionable materials. The mechanism of delayed neutron emission has been described (Keepin, 1965), but briefly is as follows. The fission fragments resulting from irradiation are in an excited state. Certain of these delayed fission products, precursors, decay to a more stable state by the emission of a delayed neutron. The delayed neutrons can be divided into six groups with effective half-lives ranging from 0.2-55 sec. It is important to note that more than 50% of the delayed neutrons are emitted within the first 6 sec after irradiation; this has an influence on the design of the analysis instrument. Measurement Cycle The measurement cycle involves a neutron irradiation, a delay time, and a counting period. The laboratory demonstration model of the ore analyzer comprises a californium-252 neutron source, a source chamber, a pneumatic transfer facility, and a neutron irradiation and counting module (Fig. 1). The ore sample is placed in the irradiation chamber. The neutron source is transferred to the center of the chamber for a 5-sec irradiation while the helium-3 thermal neutron detectors are switched off. As the source returns to the storage chamber, the detectors are switched on and the delayed neutrons counted. The total assay cycle is 16 sec. The current instrument design calls for the ore to be cut from the main belt every 16 sec by a mechanical arm and dropped into the analyzer directly, or via another belt. The cycle starts when there is a sufficient mass of ore in the irradiation chamber to depress a switch and stops when the delayed neutron count is finished. The ore is then dropped through the bottom of the analyzer chamber and returned to the main belt. The counts from each cycle are accumulated and the data reduced to give the desired information. Key for Fig. 1 A-Helium-3 neutron detector B-Wax moderator for neutrons C-Irradiation chamber D-Funnel for receiving ore E-Gate F-Transducers G-Biological shield for neutron source H-Transfer tube for neutron source I-Neutron source J- Microprocessor K-Accumulator for hydraulics L-Control panel M-Electro-hydraulic servo valve to control movement of the source N-Electro-hydraulic proportional valve to control movement of the gate O-Hydraulic power unit Irradiation and Counting Equipment Irradiation of the ore is achieved using a 1 X 10 7 neutron*s-1 californium-252 neutron source. The source is contained in an iron capsule and pneumatically transferred between the irradiation/counting and storage chambers. The irradiation/counting chamber possesses 12, 600-mm (24-in.) long helium-3 thermal neutron detectors embedded in an annulus of wax (Fig. 1). Two sets of six detectors are each interfaced to a preamplifier, amplifier and single-channel pulseheight analyzer system, and the two systems are connected to a scaler. A special timing unit controls the transfer of the source and the on and off switching of the detector assembly, in sequence with the movement of the source. Results and Discussion In the experimental demonstration, using the 107 neutron.s-1 source, a 10% uranium ore was measured to ± 10% (2o total error) in 10 cycles and ±6% (2o) in 100 cycles. Since a larger source was not available, it can be statistically predicted that a 109 neutron-s-1 source could be used to measure a 0.1% ore to ± 10% (20) in 10 cycles. The uranium can occur as discrete nonhomogeneous particles in the ore, and the error caused by such a distribution of particles is ± 4% (2o), as determined by

Jan 1, 1984

By J. S. Whatley

The properties, origin and industrial uses of kaolin clay are briefly reviewed. The general waterwashed beneficiation process is described. Yost aspects of filtration and solids-liquid separation as practiced in the kaolin industry are mentioned along with devices that are currently in the developmental stage. The paper focuses heavily on the well known art of rotary vacuum filtration, including general construction and operating details. Devices under investigation that might be used to mechanically or electrically dewater clay slurries to higher cake solids levels than can be achieved with rotary vacuum filters are described briefly.

Jan 1, 1986

By JOEL H. SWARTZ

During a series of resistivity measurements carried out in 1929 and 1930 a number of questions arose concerning the effect of topography on the character of the curves and the depths attained , the ratio of true depth to certain radii interpreted as representing depth , etc. To answer these questions it was decided to undertake a series of experimental investigations on artificial strata . It is the purpose of the present paper to present the results of the studies thus undertaken .

Feb 1, 1931

By C. A. Johnson, K. F. Unrug

The identification of the major subsidence areas in the Eastern Kentucky Coal Field has been made to distinguish the subsidence phenomena on the basis of geographical location. Further, this identification process is based upon selected critical geological, topographical, and mining features in the coal fields. The proposed identification of the regions is derived from a comparison of the subsidence potential in a particular area. The most likely severe subsidence areas are compared to those with the probable low subsidence severity. The combination of certain geological and mining parameters involved allows for the derivation of a classification of the subsidence potential.

Jan 1, 1986

By Paul C. Hyndman

The U.S. Bureau of Mines investigations of the three subunits (fig. 1) of the Homestead RARE II area (No. 6291) revealed no evidence of mining activity or mineral deposits in the area. The Iron Dyke Mine, 3 mi (5 km) outside the study area produced ore between 1916 and early 1982 from a volcanogenic massive sulfide deposit in the Permian volcaniclastic Hunsaker Creek Formation of the Seven Devils Group. The Hunsaker Creek Formation does not crop out in the RARE II area, but extends into the area beneath Miocene flows of Columbia River Basalt. The abundant basalt in the area could be used as aggregate or dimension stone, but equivalent deposits exist closer to markets. INTRODUCTION Location and Access The Homestead RARE II area (fig. 1) encompasses 6260 net acres (253U ha), in three units, of the Wallowa-Whitman National Forest in Baker and Wallowa Counties, Oregon. Two small units of 160 and 300 acres (65 and 120 ha) are 5 mi (8 km) north and east of the main study area. Homestead, Oregon, on the Snake River, is about 3 mi (4 km) south of the two small areas, and about 3 mi (4 km) northeast of the main study area. Peripheral access is provided by State Highway 86, U.S. Forest Service Road 39, and ancillary roads and trails.

Jan 1, 1983

By L. A. Cisternas, R. I. Jeldres, C. Cruz, P. A. Robles

"Previous studies have shown that the floatability of chalcopyrite in seawater at highly alkaline conditions is significantly affected by the presence of clays. The reason is that the species of calcium and magnesium present in seawater under those conditions may act as a bridge between the surfaces of clay and chalcopyrite, generating massive aggregates that then depress. In this context, the objective of this work is to analyze the impact of pretreated seawater with low amount of calcium and magnesium ions on the recovery of a sulphide copper mineral with high kaolinite content as clay. The seawater pre-treatment is done by the addition of sodium hydroxide in a high carbon dioxide environment. The chemical reactions realized under these conditions lead to the formation and precipitation of calcium and magnesium species that are subsequently removed by vacuum filtration. The pre-treated seawater is then used in flotation tests at pH 11 for copper sulphide, where the mineral is synthetically prepared by mixtures of chalcopyrite, kaolinite, and quartz. When comparing the flotation results for different types of water, including seawater and pre-treated seawater, a significant effect is observed: as the seawater hardness decreases, which comprises the calcium and magnesium ions, the recovery of chalcopyrite is increased. However, the effect is markedly enhanced in the presence of kaolinite. Therefore, the results indicate that sodium hydroxide and carbon dioxide are able to remove different species of calcium and magnesium from seawater and could improve the chalcopyrite recovery with high kaolinite content. INTRODUCTIONIn many cases, mineral deposits are found in arid areas with little access to water resources. Water is a fundamental element to carry out the unit operations that achieved the separation of valuable minerals (especially in concentration operations). Seawater has acquired an interesting role in recent years (Cisternas and Moreno, 2014); in fact, it seems to be one of the few viable options to ensure the sustainability of the mining industry in arid zones. At present, there are numerous experiences of industries that use or have used this resource, either by submitting the seawater to a desalination treatment by reverse osmosis or by applying it directly, without desalting. The latter case may involve significant economic benefits (for example, by avoiding the investment of building a desalination plant) and in some cases some operational benefits. A positive aspect is that in general terms the foaming in the saline medium is much more efficient compared to fresh water (Quinn et al., 2014; Castro et al., 2010). Some reports show that the foaming doses required to achieve a certain quality of bubbles are remarkably reduced, reaching exceptional cases such as Xstrata's Raglan concentrator, where it did not even include foaming to carry out the operation. This fact is quite promising, considering that some researchers have stated that controlling the quality of bubbles and foam could float minerals through coarse particles. This would lead to multiple benefits, such as energy savings by avoiding excessive grinding and a lower presence of fine ore that causes major problems in water recovery operations by gravitation (such as thickening) and in tailings management. However, seawater also causes significant challenges in multiple operations (Jeldres et al., 2017, 2016; Castro et al., 2010), as for example in minerals with high clay content (Uribe et al., 2017). In fresh water, the presence of clays minerals in ores is already a major problem in the flotation stages since the operation becomes difficult to be controlled, and operators are commonly forced to increase the consumption of reagents because the collectors are deposited on the clays' surfaces reducing froth stability (Farrokhpay and Bradshaw, 2012). Sometimes the use of rheology-modifying reagents should also be incorporated since the pulps become more visc"

Jan 1, 2018

By K. Thambi

Environmental rehabilitation has increasingly become a central concern in the regulatory and fiscal landscape governing South African mining operations. A key issue within this domain is the extent to which mining entities may claim tax deductions for expenditures incurred in fulfilling their environmental rehabilitation obligations. The Supreme Court of Appeal's decision in Sishen Iron Ore Company (Pty) Ltd v Commissioner for the South African Revenue Service [2025] ZASCA 16 addresses pivotal questions regarding the tax treatment of such expenditures. The judgment offers authoritative clarification on the interpretation of the Income Tax Act 58 of 1962—specifically sections 11(a), 11(c), and 36(11)(e)—as they pertain to mining activities and the environmental responsibilities imposed under the Mineral and Petroleum Resources Development Act 28 of 2002. This commentary critically examines the multifaceted implications of the Sishen ruling, highlighting the intersection of statutory interpretation, operational realities, and environmental accountability within South Africa’s mining sector.

May 8, 2026

By C. N. Harman

Steel is the most versatile material which has made the progress in every aspect on this earth possible. There are hundreds of varieties of steel because for each application it has to be made with specific properties to get the most optimum usage. It is well known that the basic constituent of steel is iron. But it is the proportion of other elements in it, which give each type of steel certain specific properties. These elements are added in liquid iron inform of Ferro alloys to get the desired composition and properties. Thus, Ferro alloys are important additives in the production of steel. It can be said that no steel can be made without use of one or more of the several Ferro alloys. They form the backbone of steel. Thus, the Ferro alloys industry is vitally linked for its growth and development to that of the steel industry. Ferro alloys industry in India has never been globally competitive, despite its rich ore deposits and low-cost manpower, essentially due to a) Insufficient availability and high cost of electric power b) Increasing ores and reductants cost c) Non-availability of low ash, low phos. coking coal in the country for the production of desired coke with low ash, and low phos. contents, making import of such coke at a high cost imperative d) High-cost and insufficient infrastructural facilities (both road and rail) for rapid transportation of ore from mines to plants e)Stiff competition from producers and exporters of Ferro alloys in other countries like South Africa, Kazakhstan, China, Russia, Australia etc. due to global trade agreement which has made drastic reduction in customs duty on imports necessary. f) Wide fluctuations in the International price of Ferro alloys depending on demand versus supply. To over come these challenges plus adhering to stringent pollution control norms innovations are inevitable in the process technology, and plant equipment design, along with frequent changes in product mix, to be more cost-effective. An attempt is made in this paper to address the innovations that took place in the past and those that further need to be made, considering the future of this industry.

Jan 1, 2007

By K. Viking

The vibratory characteristics of full-scale sheet piles, vibratory driven into the ground, have so far not been described systematically in detail. This paper concerns the preliminary results of a series of full-scale field tests where both the driveability and induced ground vibrations have been continuously monitored. Furthermore, the results of measured ground vibration levels have been measured at two different sites characterised as having hard and easy driving conditions. In the light of the presented results, the paper briefly discusses how the complexity of a driveability and vibration prediction can be subdivided into three parts, namely, vibrator-, sheet pile-, and soil-related parameters, all of which significantly affect both the driveability and induced ground vibrations.

Jan 1, 2000

By E Ferrow, R Herbert, M E. Malmstr, M Fuchs

The study of microbial sulfide oxidation and oxidation rates of tailings requires the use of sterile control samples in laboratory experiments for comparison purposes. The need for sterile tailings sand is also apparent in the study of microbial communities and processes. This study compares six different methods with regard to sterilisation efficiency and investigates chemical and mineralogical changes in the samples as the result of sample treatment. In addition, the effect of sterilisation on mineral weathering rates is also studied. The efficiency of the different methods with regard to sterility is estimated by most probable numbers (MPN) of both sulfur and iron oxidising bacteria. The sterilisation methods that were compared are: washing with sterile water, washing with ethanol, applying antibiotics, repeated heating to 70¦C, autoclaving, and γ-irradiation. There are several possible drawbacks with the different methods, including the risk of an applied chemical acting as a substrate for micro-organisms in the system, and the risk of altering the tailings. The results show a substantial difference in sterilisation efficiency between the treatments. For example, autoclaving, repeated heating, ethanol and irradiation efficiently kill micro-organisms, rendering an undetectable amount of bacteria after one month of incubation, whilst washing with water exhibits virtually no microbiological effect, with a bacterial content comparable to the control. The use of antibiotics for sterilisation ranks intermediate: the lag-phase was twice as long in the antibiotics treatment compared with the controls. X-ray diffraction, optical and electron microscopy, M÷ssbauer spectroscopy, and mineral magnetism indicate no significant change in the bulk mineralogical composition. However, X-ray photoelectron spectroscopy analyses show that with some of the treatments, sulfides are partially oxidised, as indicated by the formation of sulfate and partially û oxidised sulfur species at the tailings surfaces. Aerated batch weathering experiments performed on sterilised tailings samples and untreated controls indicated that while the initial rates of element (S, Fe, Cu, Zn, Mg, Na, K, Ca) release may differ between the samples, over the course of ~100 days of experiment at pH 2 and room temperature, the rates declined toward a similar value for all samples. To conclude, there does not appear to be one perfect method for tailings sterilisation. Autoclaving and heating damage the mineral grain structure and oxidise the sulfide surfaces. Ethanol, antibiotics and rinsing greatly alter the pore water chemistry through the washing procedure. In addition, ethanol and denatured antibiotics might serve as a substrate and also, in the case of antibiotics, adhere to mineral surfaces thus obstructing chemical reactions. Irradiation seems to be the preferable method on an overall basis, although the formation of surface Fe3+ was suggested by M÷ssbauer spectroscopy.

Jan 1, 2003

By Hugo Villanueva

En la actualidad, el supervisor de mina busca optimizar las operaciones de minado para mejorar la productividad del yacimiento minero. Sin embargo, la información recibida sobre minería sin rieles es escaza, así como la experiencia en este sistema. Por ello, el supervisor se limita a esta forma incipiente del sistema. En este sentido, el objeto del texto es otorgar a los supervisores una herramienta que les permita programar o corregir alguna anomalía del sistema de operación a través de una breve descripción del sistema de explotación, standars de operación, definición del standard, cálculo de las asignaciones, standard de las fases principales y el standard de excavación.

Nov 20, 1978

By D. R. Young

Drilling exploration over the Wesizwe Platinum Limited?s Pilanesberg Project has identified the Merensky Reef at depths varying from 594 m to 1 552 m depth. Merensky Reef thickness varies from 0.05 m to 3.63 m and contains PGE(4) mineralization above a cut-off grade of 1.0 g/t over intersection widths of 0.95 m to 2.63 m. Four distinct facies types have been identified over the property, viz.1) Normal Merensky Reef, generally 1.2 m thick, bounded by thin top and basal chromitite layers and composed of upper feldspathic pyroxenite and lower feldspathic olivine pegmatoids containing base metal sulphide mineralization overlying poikilitic anorthosites. 2) Single chromitite Merensky Reef, generally0.15 m thick and usually devoid of internal silicate material, overlying variable stratigraphy containing significant base metal sulphide mineralization. 3) Detached Merensky Reef, generally1.0 m thick, bounded by thin top and basal chromitite layers and composed of feldspathic pyroxenite or pyroxenite containing base metal sulphide mineralization overlying Merensky Pyroxenite. 4) Normal footwall Merensky Reef, generally 1.8 m thick, bounded by thin top and basal chromitite layers and composed of feldspathic pyroxenite containing base metal sulphide mineralization overlying norites also containing significant base metal sulphide mineralization. The PGE(4) content?s (g/m2) distribution for the global intersection data appears to be lognormal, and conversion to lognormal space produces a near normal distribution which could be interpreted as a compound lognormal distribution. The mean PGE(4) contents estimated by these three different distributions are the same, and thus do not impact on the contained metal. Data for the Normal Merensky Reef facies type are sufficient to indicate that a normal distribution is followed for this facies type, and therefore does not need to be transformed to log space for estimation of the mean and the 90% confidence limits. A global evaluation based on all of the data is compared with a facies-weighted evaluation. The latter method is noted to provide a better definition of the associated estimation errors and thus potential classification of Mineral Resources. A valuation of $20.95 for Inferred and $41.90 for Indicated PGE(4) ounces is applied to both of the evaluations and compared. The global evaluation is considered to over-value the project by approximately 40%, thus indicating that valuations based on global summary sampling data that have a compound distribution may be materially flawed, and that cognizance of the underlying geology is crucial for unbiased valuation.

Jan 1, 2006

By D. A. Lindsey

Gravel lithology affects the quality of aggregate because different rock types in gravel have different physical and chemical properties. The lithologic composition of alluvial gravel reflects the composition of its source terrane and the variable effects of weathering and transport on each rock type. This report discusses lithologic controls on aggregate quality in the mountain-front environment of the Colorado Front Range. Lithologic controls on aggregate quality of gravels were evaluated using pebble count data. Gravel lithology along the Front Range shows both temporal and regional variation. The principal variable in gravel lithology is quartz plus quartzite, of which quartzite is commonly more abundant. Large quantities of metaquartzite derived from the mountain front southwest of Boulder, Colo., were dispersed northeastward during deposition of the oldest Front Range gravels. Average quartz plus quartzite is greatest in the oldest gravels. Aggregate quality is probably enhanced by large quantities of quartzite. Abundant volcanic rocks in gravel may enhance aggregate quantity, but such occurrences are local in extent. Abundant sedimentary rocks in gravel, mainly sandstone near the mountain front, may decrease aggregate quality.

Jan 1, 2002

By F. E. Brantley

Research was undertaken by the Bureau of Mines to assess the technical feasibility of smelting cement-copper precipitate in an electric furnace to produce commercial-grade copper. The blister-grade copper produced in smelting was refined by gaseous oxidation and reduction methods to rive a product equal in quality to fire-refined copper. The cement copper used in the study was typical of the material produced in commercial operations. The sample product was received in a partially oxidized state and analyzed 77.5 percent Cu, 3.4 percent Fe, 0.8 percent Pb, 0.05 percent Ni, 0.6 percent Sn, and 0.9 percent S. Smelting tests were made on the precipitate using laboratory-size induction and electric-arc furnaces. Three types of furnace linings were tested during, the investigation: Carbon, including graphite; clay-graphite; and silicon carbide. Although all proved satisfactory, either carbon or graphite was preferred because of their superior refractory properties and low permeability to molten copper. Copper recoveries in the induction and arc smelting tests averaged 92 percent in commercial-grade metal assaying 99.8 percent copper. Refining the molten copper by oxidation and gaseous reduction or by chlorine lancing increased the purity to plus 99.9 percent.

Jan 1, 1961