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By S. Chander

A mineral or metallurgical process uses various inputs, such as ores, energy and other raw materials, to make different products that fulfill societal needs. The processing of raw materials has changed in recent years due to the increased complexity of processing low-grade ores, intensifying competitiveness and greater constraints. For process improvement, various plant optimization and process modifications must be conducted under environmental, social, political and economic constraints. Processing research and education's success in meeting the process industry's future needs depends on an adequate balance between micro- and macro-engineering approaches. In its simplest form, macro-engineering is concerned with the "big picture," while micro-engineering requires looking at a subset of the process. So macro-engineering may be defined as an investigation of the larger or "whole" system to achieve the desired goals. And micro-engineering may be viewed as a quantitative investigation of a subset of the process, to determine cause-and-effect relationships within the subset. Two different approaches might be used in macro-engineering analysis. In one, the big picture may be viewed without a detailed knowledge of the subunits. With this approach, statistical tools are used to relate input and output parameters. Also, actual plant data or analog models might be used to obtain the desired information. The usefulness of such an approach increases with problem complexity. To attain the desired goals using the second, "model-based," approach, a detailed knowledge of the subunits is often useful and their interactions may be considered. In complex process analysis, the first of these approaches is more useful since less information is needed. However, it is also less exact and more likely to fail if there are significant changes in conditions and interactions. The second approach, on the other hand, is more exact, with greater predictive ability within the narrow subset being considered. Consequently, it is difficult and costly to conduct.

Jan 1, 1992

By Garrett R. Hyde, Aleksandar Stojsic

Introduction Economic pressures in the international marketplace have spurred advances in almost every facet of flotation. New developments have occurred in flotation chemicals, flotation machines, and in the application of automated process control technology to grinding and flotation. Many of these advances are the results of concerted efforts to apply the knowledge obtained from basic flotation research over the past 15 to 20 years, to develop industrial technology for the more efficient separation of sulfide minerals in real ores. Mining company executives and equipment manufacturers are being called on to make decisions for incorporating some of this technology into present operations. This discussion is limited to two developments now at the stage of being engineered into industrial scale operations. They are control of the electrochemical environment or redox potential of the slurry, and control of bubble size in column flotation. Potential economic impacts are noted. Froth flotation Froth flotation makes use of differences in the surface properties of finely ground minerals to obtain separation. If the mineral surface is water repellent, the mineral particle will stick at the air-water interface of a bubble and float. If a mineral surface is not naturally water repellent, a chemical collector is added to the slurry to make it so. The collector must adsorb on, and make water repellent only the mineral to be recovered, not the gangue minerals. To achieve this degree of selective adsorption, chemical modifiers may have to be added to the slurry. Modifiers include pH regulators, activators, and depressants. Electrochemical control One of the most significant developments in recent years in the area of mineral processing technology is the recognition that collector adsorption of sulfide minerals is an electrochemical process. Consequently, flotation of these minerals depends on the electrochemical or redox potential of the system. Many of the modifiers used to control various flotation processes are actually potential controlling reagents. For example, the role of well known depressants, such as cyanide, sodium hydrosulfide, and sulfur dioxide, is essentially to

Jan 7, 1987

By S. K. Kawatra, S. K. Valluri, S. J. Root

Carbon dioxide, a by-product of combustion reactions, is a greenhouse gas linked to climate change. At Michigan Technological University, we have studied the capture of CO2 using alkali scrubbing solutions in a pilot scale packed bed counter-current scrubbing column. To do this, we have simulated flue gas by combining streams of CO2 and compressed air. Real flue gas has impurities such as CO, SO2, and NOx, and has lower levels of O2 than our simulated flue gas. In order to study CO2 capture from a real flue gas, the Department of Chemical Engineering worked with the Facilities department to install a pilot scale scrubbing column in the Michigan Tech steam plant. Experiments were conducted using a sample stream of the flue gas from the boiler in the steam plant. Data collected from these experiments were compared to the data collected from identical experiments conducted on simulated flue gas in the lab. The capture efficiency of the real flue gas scrubbing column is discussed in this paper. BACKGROUND The most common equipment used to separate CO2 from a flue gas stream is a counter-current packed-bed scrubbing column. The department of Chemical Engineering at Michigan Technological University has two such pilot scale columns. In order to study the effect of impurities found in real flue gas, one is installed in a controlled laboratory using a simulated flue gas created by mixing CO2 and compressed air. This column will be used to establish a baseline for percent capture analysis and is displayed by figure 1. The second scrubbing column is identical to the first, and is installed in the Michigan Tech central energy plant. The plant produces up to 130,000 lb/hr of 80 psig steam to provide hot water and heat for campus buildings. A typical wintertime load burns around 25,000 SCFH of natural gas; this load releases 1.4 metric tons of CO2 per hour. The flue gas the steam plant produces is roughly 7.5% CO2 by volume. In order to study CO2 capture from this flue gas, a tap has been installed on the main exhaust duct which draws a sample of the flue gas into the pilot scale scrubbing column. Figure 2, a simplified diagram of the steam plant, shows that the tap was installed between the economizer and the stack condenser.

Jan 1, 2019

By H. Knorre, A. Griffiths, J. Loroesch

Introduction Hydrogen peroxide is known to the mining industry as a powerful oxidant, able to attack and to destroy cyanide, the most important leaching reagent (Knorre and Griffiths, 1984; Griffiths, 1988; Griffiths, 1988). CN- + H202 => OCN- + H2O The most recent development, however, is the use of H202 as an oxidant in the cyanidation of precious metals. This application may appear to be a contradiction to the above mentioned detoxification process. This can, indeed, be the case if certain conditions are not considered carefully. Degussa has developed a new process to enable the application of H2O2, in this field without having any detrimental effect on the cyanide. The incentive to seek an oxygen supplier like H2O2 instead of air was the fact that one of the most important conditions for the fast dissolution of gold is the presence of physically dissolved oxygen in the pulp (Kydryk and Kellog, 1954; Warstell, 1987). 2 Au + 4CN- + 1 /2 O2 + H2O => 2 [Au(CN)2]- + 2 OH Complete gold recovery within a reasonable leaching time may only be achieved if the pulp is saturated with dissolved oxygen. Gold losses in leach operations mainly occur due to the following reasons: • In some cases, the saturation of oxygen in the pulp cannot be achieved by aeration due to the difficulty to transfer oxygen from the gaseous into the liquid phase. This happens, for example, in pulps with a high viscosity. In such cases, even violent aeration only results in a low concentration of dissolved oxygen in the pulp. • In any case, the starting phase of leaching requires the highest amount of oxygen. Therefore, it is especially important to raise the dissolved oxygen level to saturation in the starting phase. Peroxide assisted leach process (PAL) The intention of the process is to introduce oxygen in a liquid form. As a result of intensive research work, it could be shown that hydrogen peroxide can be used as a source of oxygen in the leaching of gold ores. To avoid side reactions, the following conditions must be applied: • Hydrogen peroxide must be diluted before it is added to the pulp. • The dosage of H2O2, must be properly regulated based on the oxygen level of the pulp. • An important part of the continuous 02-control is a special oxygen electrode, which resists the extremely abrasive action of the pulp.

Jan 1, 1989

L.R. Bower In regard to the paper by J.B. Gwiazda, it makes a highly technical approach to show that the µ factor used by designers of lemniscate-guided roof supports has never really been confirmed as a maximum and assumes that convergence is vertical. Also, the paper does not appear to take into account deflection of structures, which occurs when the lemniscate and base members are fully loaded to their maximum stress level, nor the front to back line of the support in relation to differential roof to floor movements caused by strata movements under pressure. It is not unusual for differential movements to be slightly diagonal to the line of the support, particularly in faulted areas and on gradient faces. The paper also does not take into account consolidation of fines immediately above and below the support. Generally speaking, any differential movement is from face to waste and under these conditions the µ of 0.3, which appears to be an international standard, has worked in practice. However, if the face end of the support is lower than the waste end, then the µ of 0.3 can be considerably increased, giving rise to the damage mentioned in the paper. The ideal design should aim for a slightly forward bias in the lemniscate guide so that the last increment of setting is toward the face, tending to close any fissures that may have developed during the support advance cycle. The support should also be fitted with positive set valves to ensure that a high setting load density is attained to minimize bed separation. As far as powered supports are concerned, convergence is irresistible and all powered supports converge at their rated yield load. A similar principle can be applied to the differential roof to floor movements to drastically reduce the very high forces that would otherwise be applied to the lemniscate structures and pins and that, in turn, are transferred to the base arrangement and floor loading. Any differential movements are usually catered for by the 0.3 µ factor or deflection of structures in the lemniscate guide arrangement and consolidation of the floor. The floor loading, due to differential movement, is in addition to the support convergence load and requires additional bearing area to avoid possible floor penetration. Some seven years ago, Fletcher Sutcliffe Wild Ltd. (FSW) introduced a lemniscate-guided shield support where the lemniscate linkage is connected to the roof bar through two horizontally converging rams to allow differential movement to take place above a given rated figure. This is a known force and can be guarded against, whereas with rigid connections the forces, as yet, are unconfirmed. By careful design, a horizontal force in excess of 6 MN (60 tons) opposes differential movements for a total ram loading of only 2.5 MN (25 tons), or 1.25 MN (12% tons) each. This principle can considerably reduce the length and weight of the support in comparison with a rigid pin-type structure ; also, the yield load rating can be increased without affecting the lemniscate forces. The graph shows the tensile and compressive forces in a lemniscate linkage of a support with and without hydrostore. These forces react into both the roof beam and base members and, as can be seen from the support height to linkage load graph, a considerable reduction in these reactions is gained by the use of the FSW patented hydrostore system. Floor loading is considerably reduced under maximum µ conditions, and by allowing the roof bar to move with the strata, some degree of improvement to strata control is achieved in line with the assumptions in the paper. In practice, these movements have only been in the region of a few millimeters, which, in turn, reflects on the improvements to strata control by the addition of positive set valves. Supports to this design of both 450- and 280-t (496-and 309-st) rating have been successfully used in the United Kingdom for several years, negotiating many faulted areas without one single reported need for repair or maintenance. This includes supports left unattended during the year-long strike, proving the reliability of the system.

Jan 8, 1986

By Gary Krix

The Amdel Thickener Interface Gauge (TIG) provides continuous on-line measurement of the level of the liquid/solid interface in thickeners and Counter Current Decantation (CCD) washers. Unlike other interface level measurement systems, the TIG also determines the span of the transition zone. The transition zone is the region between the clear liquid overflow zone and the compressed solids zone. The Thickener Interface Gauge determines the level of the interface by measuring the natural radioactivity of the solids in the thickener tank using an array of up to twelve detectors mounted vertically in a stainless steel probe. All solids contain low levels of natural radioactivity while the liquid phase generally does not. The concentration of natural radioactivity at each level in the thickener therefore depends on the concentration of solids. The radiation emitted by the solids is converted to electrical pulses by the detectors in the probe and the pulse-rate provides an accurate measurement of the density. A typical count-rate profile is presented in Figure 1. The vertical axis indicates the depth in the tank referenced to the surface of the liquid. The horizontal axis indicates the count-rate measured by the TIG probe, this count-rate is proportional to the density and can be used to determine the settling rate. The count-rate at the top of the graph is relatively low, this region corresponds to the clear overflow zone which contains virtually no solids. Moving down the vertical axis the count-rate increases dramatically at the level of the transition zone where the solids content increases with the depth in the tank. In this region the settling conditions of the solid particles change from free settling to compression. Moving further down the vertical axis the count-rate reaches a plateau where the count-rate remains relatively constant although there are often small fluctuations, this region corresponds to the solids compression zone. The liquid/solid interface as measured by the TIG corresponds to the depth at which the count-rate crosses the target count-rate which is generally selected to be midway between the liquid count-rate and the compressed solids count-rate. The length of the TIG probe is selected to cover the typical operating range of the liquid/solid interface in the thickener or washer. If, for example, the minimum bed level is 3.0 metres below the surface of the liquid then the probe length is selected to extend 30 metres below the surface. The TIG probe can include up to twelve detectors and the se are spaced over the measurement range. For small measurement ranges of around one metre 4 to 6 detectors would normally be used while for larger measurement ranges of three metres or more twelve detectors would be supplied.

Jan 1, 1993

By G. P. Hand

Graphite usage in the United States during 1994 was fairly strong. The hearty showing of the domestic economy, along with sound performances from the major industries that use graphite, helped make 1994 a solid year for the graphite industry. Supply Virtually all natural graphite is imported into the United States, as there is no domestic production. The primary producers are Brazil, Canada, China, Madagascar, Mexico, Mozambique, Sri Lanka and Zimbabwe. Mozambique is a new producer. It is now supplying a high-carbon, large-crystallite flake in large quantities. Sri Lanka continues to experience problems with one of its two mines, closing operations in December 1994. The synthetic graphite used domestically was produced primarily in the United States as a byproduct of electrode production. Synthetic graphite was also imported from Switzerland for specialized applications. The purified graphites/carbons, such as Desulco and ThermoPURE materials, were also produced domestically. There was a sufficient supply of all types of graphite to meet domestic demand.

Jan 1, 1995

By Gary Beerkircher

WaterFlush Technology and WaterFlush crushing offers significant operational ben­efits in gold milling operations. WaterFlush crushing is the technology that Nordberg Inc. has developed, tested and proven in an actual operation during the 1980's. Patents have been obtained for both the process and the apparatus of implementa­tion. WaterFlush involves volumetric process controlled water flow into the ore feed cav­ity of a WF cone crusher. While the addition of water in itself is not new, the con­trolled amount of water coupled with the WF crusher operating parameters are revolution­ary. The WF crusher is a specially designed version of Nordberg's Omnicone crusher oper­ating at higher speeds, with a reduced ec­centric throw and higher horsepower capabil­ity. The results are increased capacity, higher crushing energy input and a finer crusher product. The WF crusher product is a slurry containing 40-60% solids by weight.

Jan 1, 1990

By Milton E. Wadsworth, Jeffrey S. Thompson

The effect of an activator on gold dissolution in clear solution is examined using a rotating disk gold electrode. Steady state polarization curves for anodic dissolution of gold and cathodic reduction of oxygen indicate that the dissolution rate increases in the presence of the activator. The activator enhances gold disso­lution under standard cyanidation conditions; however, optimum activator concentration at the maximum dissolution rate is a function of the cyanide level. In the presence of an activator, the gold dissolution mechanism is controlled by surface kinetics and may be explained by a metal dissolution over-potential model. The dissolution rate with activator is higher than the dissolution rate at a higher cyanide concentration but without activator. The dissolution rate measurements indicate that 3 PPM of activator in a 500 PPM NaCN solution provides a higher dissolution rate than 1000 PPM NaCN alone. Activator technology may be a cost-effective means to reduce cyanide concentration.

Jan 1, 1998

By Warwick Hoffmann, Robin Batterham, David Conochie

CRA has been actively involved in developing a bacterial oxidation process for the treatment of low grade, refractory gold resources. Success in this application is dependant on the design of large, energy efficient reactors. It was identified at an early stage, that the conventional, bottom sparged bioreactor is inherently inefficient because air must be compressed to a pressure above that at the bottom of the tank. This inefficiency increases as the size of the reactor increases. CRA has developed a novel approach to the aeration problem. In this, venturi aeration is used to aspirate air into a liquor stream. The stream is then reintroduced at the top of a draft tube bioreactor. The advantages found with this technique include · low energy requirements and high oxygen utilisations. From results at the 30 m3 scale, we predict an energy usage of -500 kWh/t sulphur oxidised at a scale of 1000 m3.

Jan 1, 1993

By J. Searls

The potash review arrived too late to appear in the June issue. Potash is a general term that includes several water soluble potassium salts: potassium chloride (muriate of potash), potassium sulfate (sulfate of potash), potassium magnesium sulfate (sulfate of potash-magnesia), potassium nitrate (niter) and sometimes potassium carbonate. Potassium carbonate was the original potash when it was leached from wood ashes and dried in large, cast iron pots to black-to-gray crystals (ash) to form "pot ash." "Pearlash" was potash roasted to white crystals. In modern terminology, the great preponderance of "potash" is the mined forms. It is estimated that 95% of the potash mined around the world is used as fertilizer. In 1840, Justus von Liebig demonstrated to the scientific community the importance of potassium to the growth of plants. But there was no low-priced source of potash available at that time. In the winter of 1851-1852, minable potash was discovered near Stassfurt,

Jan 1, 1991

By D. W. Dew, D. M. Miller, P. C. van Aswegen

The bacterial oxidation (BIOX®) process for pre-treatment of refractory ores for gold recovery is marketed by BIOMIN Technologies S.A. The process was originally developed by GENMIN who are still providing testwork, design and commissioning assistance to BIOMIN. This process offers an alternative to the more conventional roasting or pressure oxidation techniques with the following advantages: • Greatly reduced capital costs for small to medium size plants. • A relatively flexible and easily controllable process requiring relatively unskilled labour for operation. • Improved gold recovery. • A process that is environmentally friendly. The principal disadvantage of bacterial oxidation is the relatively slow kinetics compared to pressure oxidation and roasting, a plant residence time of 4 to 5 days typically being required to obtain complete liberation of gold from refractory sulphide minerals. Bacterial activity is also slow to recover from disruptions such as air supply failure or contamination by toxic species such as cyanide. Optimum plant performance depends on judicious management and sound training of operators.

Jan 1, 1993

By Steve Kral

It is agreed in mining and regulatory circles that a safe and healthy working environment for underground miners is the major challenge for mine operators. Underground mine ventilation is complex. And it is becoming even more difficult as mines become larger, deeper and more complicated. At the Seventh US Mine Ventilaton Symposium, a group of mine ventilation experts from industry, government and academia attempted to solve some of the problems in ventilating underground mines. The meeting, sponsored by the Underground Ventilation Committee of SME and the University of Kentucky, was held in Lexington, KY June 5-7, 1995. Andrzej M. Wala, symposium chairman, commented that previous mine ventilation symposiums have focused mainly on work in North America. The 1995 symposium, however, broadened its borders to include several international papers. Of the 77 papers presented and bound into the Proceedings volume, 25 are from operations and research centers outside of the United States and Canada.

Jan 1, 1995

By Fathi Habashi

CRYSTALLIZATION from aqueous solution is a simple and old method for the recovery of metal values from leach solution. Practically all the methods for the recovery of aluminum from clay are based on the crystallization of an aluminum salt from the leach solution. Differences in solubilities may be used to advantage for separating two metals from the same leach solution. The classical method of Marignac (1866), which makes use of the difference in solubilities of K2TaF7 and K2NbOF5 to separate niobium from tantalum, has been used successfully in the manufacture of these metals (Fig. 10-1). The slurry containing the metal oxides is dissolved in 70 % hydrofluoric acid, diluted, and heated near boiling. A potassium salt is added in sufficient quantity to form the complex fluorides of the niobium and tantalum present. The solution is filtered and allowed to cool. At room temperature most of the tantalum salt crystallizes out while the niobium remains in solution.

Jan 1, 1970

By K. C. Kane, D. L. Meredith, B. E. Davis, D. A. Stanley, O&apos

Computer control of the minerals beneficiation process is limited by a lack of adequate sensors to provide information on the current state of the process. Recent reduction in the cost of image acquisition and powerful inexpensive computers make use of computer vision as sensory input in process control a possibility. In the phosphate industry, the amount of apatite in phosphate tailings is estimated by inspection. For machine vision, a simple 256 x 512 color image of the tailings was captured via an inexpensive color video camera on an IBM PC. Initially, the image is converted to gray scale and displayed on an EGA color monitor. A program was written which identifies the different constituents of the sample by analyzing the gray scale levels for the digitized picture. In other instances the minerals are identified by their relative color intensities. The amount of each constituent is determined with good accuracy from the area it occupies on the image.

Jan 1, 1990

By John J. Gillis

There is an ongoing battle to gain general acceptance of fossil fuel byproducts as safe, economical and useful agro-industrial materials. Despite that, the US ash industry is witnessing a steady growth in the volume of coal burned, along with the production of greatly refined, higher-quality ash particulates. There are two principal reasons for this. Economics have caused an increasing number of US electric utilities to convert from oil-burning to coal-burning. And the Federal government has tightened specifications on fly/bottom ash production quality. Hence, it must be noted that new and more stringent Federal regulations were implemented in 1980. The resultant ash particulates are finer, more compact, and less heavy than in previous years. Additionally, the first shift from oil to coal in the US was initiated in December, 1979 by the New England Power Co. in Massachusetts. Coal is the most widely-distributed fuel in the US. And it is found in 38 states. The wide availability of this fossil fuel and its general cost-efficiency, coupled with the undaunted move of US electric utilities toward nuclear power, are major factors affecting the current statistics on ash generation (65.4 x 106 million tons). Interest in the use of coal in power plants is creating a unique ash disposal and use situation for ash producers as well as the Federal government. There are growing quantities of fly/bottom ash residue. Ash producers must decide how this byproduct can be dealt with effectively and profitably. At the same time, government agencies such as the US Environmental Protection Agency (EPA), are commissioned by Congress to assure that solid, liquid, or gaseous material released into the environment is not harmful or offensive to human health and the environment. Additionally, the Federal government is often responsible for establishing and enforcing guidelines and standards governing the use of recycled materials. Several standards and guidelines governing the properties and use of ash in the US have been established by governmental agencies as well as by the ash industry itself. Of these, some have been developed for ash use by a specific federal agency. Others apply to the entire industry. The following is a brief identification of the major specifications for fossil fuel ash: • US Corps of Engineers - These specifications were first established in 1957. They delineate the physical and chemical requirement for pozzolans used in mass concrete. These specifications applied only to Corps of Engineers' concrete construction projects for locks, dams, and other mass concrete projects until 1977. At that time, a joint effort between the American Society for Testing and Materials and the Federal government produced a modified specification that is now generally applied. The Corps of Engineers' ash, however, retained certain aspects of its specifications for its own use, particularly in the area of handling and shipping fly ash to its own projects. Prior to transporting the fly ash to the corps, all potential sources for the ash must be inspected and approved as a supply source. All silos must be filled, sealed, and tested before the ash is released for shipment. The normal test period for the ash is seven days, although several testings may require up to 28 days. Once the fly ash has been released, it can only be shipped to US Corps of Engineers' projects. All shipments are made with a government inspector present during loading. After a truck or railcar is loaded, the silo is resealed until the next shipment. This procedure requires three silos, and a minimum of 454 t (500 st) each should be considered for each storage unit. All silos are strictly committed to Corps of Engineers' use and are not available for other commercial shipments. • US Bureau of Standards - This Federal agency maintains a standard testing sample of nearly every product used in the US. The accuracy of the fly ash chemical analysis is measured by a regular cement and concrete reference laboratory (CCRL) inspection and based on test results from a standard sample of cement. • US Bureau of Reclamation - This agency pioneered several projects using fly ash and required Federal Standard Certification for pozzolans. • American Society for Testing and Materials (ASTM) - This nongovernmental organization began preparing standards for fly ash sold and used in the cement and concrete industry in 1947, at the urging of ash marketing firms. Current standards define chemical and physical requirements and is entitled, "Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Portland Cement Concrete (C 618-80)." • State Highway Specifications - Led by Alabama, many states are moving toward permitting - and in some cases requiring-the use of fly ash in portland cement concrete and with lime for base stabilization projects for roads and highways. • Federal Aviation Administration (FAA) - The FAA acts in an advisory capacity. It has final approval on design specifications for airport construction projects. The agency has established a set of guidelines permitting the use of fly ash, and has approved several fly-ash-specific designs. The most current FAA fly ash projects

Jan 8, 1984

By Liam Findlay

Optimizing a production schedule with semi-mobile in-pit crushing & conveyance (IPCC) requires integrating extraction sequence, destination policy, crusher relocation, conveyor layout, and truck fleet investment decisions. An integrated stochastic optimization framework is proposed to produce long-term schedules for mining complexes using multiple semi-mobile IPCC systems. The optimizer selects the crusher locations and designs the conveyor routes from anywhere in the mines. The stochastic framework considers simulated multi-element orebody realizations and manages associated risk. A hybrid metaheuristic based on simulated annealing and evolutionary algorithm is implemented for the optimization. The method is demonstrated using an iron ore mining complex.

Jun 25, 2023

By D. A. Newman

The accurate prediction of mine profitability is essential for success in the present minerals market as is the ability to quantify the influence/of variations in revenues and costs on cash flow. A menu based spreadsheet template has been developed to determine annual cash flow, maintain depreciation schedules, and estimate labor and operating expenses. Sensitivity analyses may be conducted to determine the effect of productivity upon mining costs and the effect of selling price escalation upon rate of return. The advantage of this approach is that it can be used by a wide variety of professionals without extensive computer experience.

Jan 1, 1988

The Newmont Boddington Orebody (NBO) is a large, diffuse Au/Cu orebody in Western Australias South-West corner with approximately 20Moz Au in current Reserves. The current sulphide Resource is reported after calculation with the non-linear estimation technique Uniform Conditioning to account for the mining selectivity being smaller than the average drillhole spacing. Simulation of Au grade is also run over the entire orebody reviewing risk and uncertainty. There are differences in results from the two methods. These have been investigated and the lessons learned of the influencing parameters and effect of technique alone, are helpful for applications to other orebodies.

Jan 1, 2010

By David R. Baughman, Ray V. Huff, Paul D. Chamberlin

ISL Ventures, Inc. (ISLV) is developing a process for recovering gold and silver from ores using a chloride-hypochlorite lixiviant. The leach solution, composed of water, NaCl and NaOCl, is maintained at a pH of about 7. At this pH most base metals are not leached. This is important for deposits that contain cyanide-soluble copper. An inhibitor can be incorporated to slow the decomposition of the oxidant. This paper reviews the history of development, presents details of the chemistry and indicates the nature of deposits, which we believe to be amenable to production using the process.

Jan 1, 1999