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By H. T. John

"The objective of this paper is to demonstrate how the optimum cut -off grade can be calculated for typical large tonnage openpit mines. In the examples, it is assumed that the concentrator tonnage is fixed and that there are no market restrictions. The mining rate is assumed to be variable. This is usually the situation at an operating property.ModellingA model of the ore body is required to examine alternate cutoff grade strategies. The model must be accurate in its relationship between grade and tonnage. Table I shows a typical relationship between ore tons and grade for various cut-off grades. The average strip ratio is also shown. For higher cutoff grades, the ore tonnage is decreased and the ore grade is increased. Strip ratio increases with the cut-off grade.Using the relationship between ton s and grade, and assuming a homogenous, long life orebody, a simple calculation of the optimum cut-o ff grade can be made. The objective is to maximize the present value of cash flows. For the long life homogenous orebody example this objective is satisfied by maximizing present cash flows.Cash flow is calculated by subtracting operating cost from revenue . Operating cost will increase with the cut -off grade as the strip ratio increases."

Jan 1, 1985

By F. R. Deluca

"ClassificationClassification is a combination of mechanical and hydraulic operation which separates a pulp into two portions according to their respective settling rate. The finished product, the overflow, is removed from the other product, sand, which requires further grinding.Pulp is the uniform suspension of solids in a liquid. Overflow is the fines and therefore the more slowly settling portion of the pulp which is carried over the top of the classifier by the flow of water; sand is the coarser and more rapidly settling portion of the original pulp which is discharged from the classifier by the mechanical action of the rakes or conveyed out by a ""screw"" .Selective classification is classification that has for its object the concentration of the heavy constituents of the original pulp in the sand product so that it may be ground finer than the lighter constituent.Classification is used as follows:I. To make a size separation, for example, a sand-fines separation so that each product may be given a different treatment.2. For closed circuit grinding so that the maximum size of particles entering the circuit is limited, and so that the useful work is increased by enabling the mill to operate mainly on the particles that require the reduction.3. For differential grinding of the heavy mineral constituent and the gangue. In this case, the heavy mineral is concentrated in the sand product and is reduced further, while the lighter gangue material overflows the classifier.The selection of the proper size and type of classifier is determined by the function required, the character of the ore, and the tonnage to be handled, the initial cost and the operating cost."

Jan 1, 1989

By Shoma Sinha, Nirmal K. Sinha

Deformation in a material at any temperature is known to consist of two major components - a reversible (elastic) part and an irreversible part (often called plastic). What is not universally known is the fact that at high temperatures greater than about 0.4Tm, where Tm, is the melting point in Kelvin, the reversible part includes not only elastic but also a delayed elastic (recoverable but time dependent) component. A very simple computational model is presented here for a constant-strain stress relaxation test (SRT) on the basis of a three-component constant-stress rheological equation derived from strain relaxation and recovery test (SRRT) data. It is shown that the rapid stress reduction during the early periods of relaxation when the stresses are high is governed primarily by delayed elasticity irrespective of the imposed strain level. This is in contradiction to the popular concept prevailing today. The asymptotic approach to a quasi-stable stress rate at longer times and lower stresses is, however, controlled by viscous flow (power-law creep). The validity of the theory is examined by comparing the predictions with experimental results obtained for a titanium-base alloy Ti-6246 at 0.45Tm.

Jan 1, 2004

By R. J. Twigg, S. D. Chang

"The production of heavy water, the moderator in a CANDU reactor, is examined following a flow sheet of a typical Canadian plant. The process involves the extraction and concentration of deuterium from natural water through a chemical exchange mechanism with hydrogen sulphide. Consequently, corrosion problems associated with sour environments – the use of hydrogen sulphide - are an everyday problem and have led to the development of a highly refined materials selection and testing program to prevent equipment from failing prematurely.IntroductionHeavy water is a naturally occurring compound in ordinary water and is formed from the combination of two deuterium atoms and one atom of oxygen. Deuterium is a heavy hydrogen atom which has a nucleus of on e proton and one neutron. Hence, heavy water is a combination of heavy hydrogen and oxygen and is chemically known as deuterium oxide. It looks and tastes like ordinary water but it freezes at 3.8°C and boils at 101.4°C. The molecular weight of heavy water is 20 as compared to 18 for ordinary water; the density of heavy water is ten per cent greater than that of ordinary water.Although heavy water and ordinary water exhibit only small differences in their chemical and physical properties, there are large differences in their nuclear properties, the most important of which is the neutron moderating ratio, used to measure the ratio o f the slowing down power to the neutron capture characteristics. For heavy water the ratio is 21000 and for ordinary water it is 50. This high moderating ratio is essential for achieving a high neutron economy. Heavy water is, therefore, chosen as the moderating and heat transport fluid in the CANDU reactor."

Jan 1, 1983

By J. A. Finch, J. Vergouw

"Flotation selectivity becomes progressively more difficult to achieve with decreasing particle size. One of the possible problems is agglomeration, i.e. particles clustering together. One mechanism derives from the surface charge all particles develop in water. Agglomeration driven by surface charge is known as coagulation. One form is coagulation between particles of two different minerals of opposite charge. Another is coagulation between particles of the same mineral when conditions are such that the charge approaches zero.The paper describes the method of measuring charge and a new automated settling technique for measuring agglomeration. The phenomena are illustrated with galena and pyrite. Methods of assessing the importance of agglomeration in the plant environment are still to be developed.IntroductionFine particles can agglomerate (i.e. adhere to each other) under certain conditions. This is counter-productive for any physical separation process, including flotation. One cause of agglomeration derives from the surface charge that all particles develop in water. Agglomeration due to surface charge effects is referred to as coagulation. There are two forms of coagulation. If the surface charge is brought to near zero then the force of repulsion is lost and particles coagulate. This usually applies to particles of one mineral type and the technical tenn is homocoagulation. On the other hand, if two particles have opposite charge there is an attractive force. Since the particles in this case are usually different minerals this is known as heterocoagulation.Both types of coagulation can cause minerals to be misplaced. In the case of heterocoagulation this is fairly obvious. One example that may be familiar is slime coating (fines of one mineral coating larger particles of another) But even homocoagulation can be a problem an agglomerate of the same mineral particles can entrap particles of another mineral."

Jan 1, 1997

By J. W. Cox, W S. Jones, A E. Chase

For a long time the Oil Industry has been looking for a logging tool which can determine the quality of the cement job behind casing. Older methods such as Temperature Surveys and Radioactivity Surveys might detect the presence of cement behind the casing, but short of production tests, it was impossible to tell that the producing zones were adequately sealed off from adjacent zones. A new logging method, which is called the •Cement Bond Log, operates on the principle that a sonic pulse transmitted by the casing is greatly attenuated when the casing is strongly bonded to an outer annulus such as cement. The down-hole tool consists of a source of sonic energy which is detected by a receiver situated a few feet away from the source. The amplitude of the detected energy is measured and the resulting signal transmitted to the surface where it is recorded versus depth. Amplitude is a function of attenuation and thus the log is readily interpreted.

Jan 1, 1961

By T. Guan, G. Fu, X. Zhou, L. Deng

"One kind of tailings from gravity separation of polymetallic mine contains 0.5–0.8% SnO2. The proportion of –0.037 mm size fraction of the tailings is 37.12%, and the distribution rate of SnO2 is 60.32% in it. For this tailings, two processing technology was carried out. One was felt-shaking table gravity separation in which the concentrate with a grade of 30% SnO2 at a recovery of 10% was obtained. Another was flotation-gravity separation in which the concentrate with a grade of 51.20% SnO2 at a recovery of 51.69% was obtained, but the dosage of collectors was as much as 990g/t. Therefore, the experimental research on the influence of grain size composition on the cassiterite recovery were conducted. The results show that: (1) the flotation recovery of the cassiterite distributed in +0.043 mm size fraction is only 10%, flotation recovery is not suitable for it; (2) a portion of cassiterite distributed in –0.01+0.005 mm size fraction could be recovered by flotation, but the tin flotation performance will be worsened rapidly and the dosage of collectors will be increased due to the increase of the content of –0.010 mm size fraction; (3) flotation processing is not suitable for –0.005 mm size fraction of the tailings. According to the results, a new technology has been carried out, that is discarding tailings by gravity separation-hydrocyclone desliming-flotation-gravity separation processing flow. The processing index is close to that of the flotation-gravity separation processing flow, and the collector dosage is decreased to 360 g/t by this processing technology. And, it has been achieved that the cassiterite slime is recovered economically and reasonably.INTRODUCTIONAs the density of cassiterite is higher than that of gangue, gravity separation is considered to be a low cost, pollution free, and effective process for cassiterite recovery (Wills, 2009). However, cassiterite is a kind of fragile mineral, over crushing is easy to take place and a large amount of slime is inevitably produced in the crushing and grinding of cassiterite. For the cassiterite slime exists in –0.043 mm size fraction, the efficiency of gravity separation decreases sharply. The production practice shows that, for the fine cassiterite, the recovery of tin exists in –0.043 mm +0.010 mm size fraction is about 13% through shaking table gravity separation, and the tin exists in –0.010 mm size fraction is almost impossible to be recovered by gravity separation. If flotation is adopted to recover fine cassiterite, the problems of high reagent dosage, high cost, environmental pollution, and poor economic benefit would take place. Therefore, the recovery of cassiterite slime is a worldwide problem. A key way to increase the utilization of tin resource and increase the economic benefit of tin mines is developing suitable beneficiation process for fine cassiterite."

Jan 1, 2016

By M. M. Papic

"This paper describes the Sasol coal liquefaction process, as used in South Africa. It covers coal supply, coal gasification, gas purification, Fischer-Tropsch synthesis, the major utility systems involved and the economics of the process.IntroductionThe Sasol coal liquefaction process is based on Fischer-Tropsch synthesis of liquid fuels from carbon monoxide and hydrogen, which are in turn obtained by gasification of coal with steam and oxygen. The process is shown schematically in Figure I.The first step in the process is coal preparation, in which the coal is crushed and screened to a 3-50 mm size for gasification on one side and to -3 mm size for steam and power production on the other. Oxygen needed for coal gasificatoin is produced in the air separation plant.Coal is gasified under pressure by steam and oxygen in the Lurgi gasification plant, where raw, impure gas is produced . The raw gas is first washed in a scrubber with a circulating gas liquor, heat is then recovered from it in a waste heat recovery boiler and the gas is further cooled for purification. Water-insoluble materials (tar oils) in the gas liquor are separated from aqueous solution and sent to tar refining for the recovery of tar products. The aqueous portion of the gas liquor goes to a Phenosolvan solvent extraction process, where phenols and ammonia are recovered. Water then proceeds to the effluent treatment plant.The scrubbed and cooled raw gas goes to a Rectisol gas purification plant, where all components other than hydrogen, carbon monoxide and methane are removed as completely as possible by absorption in refrigerated methanol. The acid gases (CO2, H2S) stripped from the methanol in the Rectisol unit are processed in a Stretford plant for recovery of sulphur. Regenerated methanol is returned to the process. The purified synthesis gas is passed to the fluidized-bed Synthol reactors, where Fischer-Tropsch synthesis reactions take place.The synthesis products are recovered in a product recovery unit as separate streams of decant oil containing higher-molecular- weight hydrocarbons, light oil comprised of lower-molecular- weight species, the aqueous stream containing water solubles, a C3/C4 stream, a C2 stream , a methane stream and a hydrogen-rich stream. Most of the hydrogen is recycled to the Synthol reactors; a major portion of the methane is reformed to hydrogen and carbon monoxide for recycle; the C2 fraction goes to an ethylene plant; and liquid streams proceed to the product refinery.The product refinery is used to upgrade and purify the Synthol products to specification fuels and chemicals.Sasol l, the first coal liquefaction plant in South Africa , was built in 1955. It is still operating and has a product output of about half a million tonnes per year. The Sasol II plant is in a commissioning stage and will be in full operation in 1981. It is about five times the size of Sasoll. It uses over 12 million tonnes of coal and produces more than 2 million tonnes of saleable products annually (1,2,3). The Sasol llI plant, which is a mirror image of Sasol II, is under construction and scheduled for completion in 1983."

Jan 1, 1981

By C. Ketata, M. C. Rockwell

During the operation of a mineral processing plant, the unit processes are investigated by analyzing the data extracted by means of stream sampling. The data structure is identical to the time series form. Data analysis is a crucial step in understanding the plant performance. To control the plant performance efficiently, it is very important to avoid sampling errors, which is impossible. However, it is possible to minimize these errors. The factors influencing these errors are divided into two categories: material properties illustrating its heterogeneity, and sampler features. The purpose of this paper is to study the influence of the material composition variation on sampling errors, and to compare our evaluation method with that of Gy. Note that the stream mass flowrate is assumed to be constant during the sampling process.

Jan 1, 2001

By Brian Lewis

"IntroductionThe ion exchange process is classed as a purification and concentration stage. In the uranium industry it is used to separate, and recover uranium, from a solution produced in the leach and subsequent solid washing circuit, that contains uranium as well as some impurities. The final product from this circuit is a solution, containing uranium at a 15 to 25 fold increase in concentration, with a chemical composition suitable for the ""Precipitation"" circuit.The process is a reversible chemical ""ION"" exchange, between a solution, and solid phase, with the ""resin"" being the solid phase. Various chemical changes in the solution phase will permit the resin to remove uranium from a solution or have the uranium removed from the resin back into a solution phase. The former loads uranium onto the resin, and is called the ""adsorption cycle"", and the removal or stripping is known as the ""elution cycle"".Ion Exchange resin is a semi-rigid polystyrene spherical bead, approximately 10 to 30 mesh. It is used by placing the resin in a vessel, so that a porous bed of resin is formed, through which the solution may flow.There are many different types of vessels, and systems used to hold the resin, but it is not the intention of this chapter to describe them all, but to describe two methods used in Elliot Lake. These are the ""fixed bed"", and ""moving bed"" systems, the condition of the bed during normal operation signifies the name of the system.Chemical and Physical Characteristicslon Exchange ResinThe resin used is a strange base Anionic resin, semi-rigid, and spherical in shape. The size of the wet resin is approximately 9007o between 20 and 40 mesh. Physically the beads of resin are broken early, but some have lasted over 15 years and are still in use."

Jan 1, 1989

By D. Eriksen

Zero Emission Gas power, ZEG, is a novel concept where a high temperature solid oxide fuel cell (SOFC) is integrated with a reforming reactor producing hydrogen from natural gas through Sorption Enhanced Steam Methane Reforming (SESMR). The SOFC is used as a high temperature heat source for regeneration of the CO2-absorbent. Moreover, by using part of the produced hydrogen as fuel for the SOFC, the waste heat of the process is considerably reduced. Thus, the process has a very high thermal efficiency and produces both electricity and hydrogen from natural gas. In addition, a stream of pure CO2 is produced in the regeneration step and can be deposited or used commercially. Initial cost estimates indicate a cost of electricity and a cost of hydrogen well below today's prices. A small (1kWel + 1kW H2) demonstration set-up is under construction and experimental results and related research will be presented. This set-up comprises one 2.5kWth H2 SESMR-reactor (about 0.85 Nm3/h H2) operating batchwise with dolomite as the CO2-sorbent. The reactor developed is designed like a parallel plate heat exchanger where the mixture of sorbent and reforming catalyst is packed between the heat exchanging plates. The demonstration set-up includes a 1kW SOFC operating in a continuous mode. The set¬up will therefore demonstrate continuous simultaneous hydrogen- and electricity production, but cannot demonstrate simultanuous electricity- and CO2-production. The set?up is well equipped for on-line monitoring of gas composition, flows and temperatures. This important part of the demonstration set-up is developed and provided by Christian Michelsen Research (CMR). A minor part of the project is the development of a continuous circulating fluidized bed SESMR-reactor system and in another related project the focus is on the development of more suitable sorbents. In these two projects co-operation with University of British Columbia and Lousianna State University, respectively, is highly appreciated.

Jan 1, 2005

By Claudio Rocha Rosales

"Peñoles is a mining group with integrated operations for the smelting and refining of non-ferrous metals, and it is also a chemicals producer. Peñoles is the world’s foremost producer of refined silver, metallic bismuth and sodium sulphate. It is also the leading Latin American producer of refined gold, lead and zinc. The Met-Mex Peñoles Zinc Plant commenced operations in 1973 with an annual production capacity of 105,000 t/y zinc. Since then, production capacity has increased, and at present, it stands at 240,000 t/y zinc. In this paper, the leaching process and particularly the operation of the jarosite circuit is reviewed, specifying process improvements to treat high iron calcines.INTRODUCTIONTwenty years ago the Electrolytic Zinc Plant in Peñoles was treating high quality zinc concentrates with low concentrations of iron (~7.5 wt.%) and silica (1.8 wt.%). Nowadays the quality of zinc concentrates is poor with a typical iron content of around 11 wt.% and silica at 2.0 wt.%. This has created numerous processing problems in our roast-leach-purification- electrolysis sections. In order to meet customer requirements it is necessary to find processing solutions to assure the operational continuity of the plant. These processing solutions are the focal point of this paper.REVIEW OF THE LEACHING PROCESSThe purpose of the leaching process is to recover the metals, mainly zinc, through a series of extraction stages with sulphuric acid solutions, which progressively increases the zinc dissolution. After the series of acidification stages, the solution, which is rich in iron, is sent to the jarosite circuit to separate zinc from iron (Garcia & Valdez, 1996). The first step of the leaching process is the neutral leach circuit which produces a zinc sulphate solution that is sent to the purification section for the removal of impurities such as cadmium, cobalt and copper. Then this solution is sent to the tank house to feed the electrolytic cells."

Jan 1, 2016

By Tony Lipiec, Ian Orford

"A key part of plant design is the selection of the design tonnage which is the hourly tonnage target that the equipment selection is based on. Its selection is critical for ensuring that the nominal tonnage which is critical to the financial performance of the project will be met. With deposits being developed at lower grades, higher tonnages and a higher degree of hardness variability, it is essential to ensure that the design process selects the comminution equipment which will be able to deal with the impact of this ore quality variation.Ore hardness and its variance are key factors to be taken into consideration for the selection of the design tonnage. It is well accepted that for the nominal or name plate tonnage to be consistently achieved, it is necessary to base the design tonnage on a hardness value greater than the average ore hardness of the deposit to be mined. The question is how much greater should this design value be to ensure that the nominal tonnage is met to the satisfaction of the project financial model. Standard industry practice is to set the design tonnage by:1. Select an ore hardness percentile that is greater than the average ore hardness to be the basis of the nominal tonnage. Typically either the 75th or 80th percentile value from the data set will be selected.2. Selection of a design factor to multiply by for determining the design tonnage, i.e. the design tonnage = tonnage (based on the average ore hardness) multiplied by design factor.This paper discusses the selection of the design ore hardness through the use of modelling or the use of a design factor. It further shows the impact of ore hardness variance on the capacity of the process and its ability to meet the nominal tonnage. Insight is provided as to what ore hardness percentile value should be selected balancing the shortfalls of tonnage for ores harder than the design value versus the above target production achieved for ores softer than the design ore hardness."

Jan 1, 2016

By A. H. Onur, S. Ural

"The Afsin-Elbistan coal deposit with its 3.4 billion metric tons of reserve is the biggest coal basin and one of the most important resources for electrical energy production in Turkey. The coal deposit is located north of Elbistan, Kahramanmaras Province, in southeast Turkey (Fig. 1).The Kislakoy sub-basin of the Afsin-Elbistan basin was selected as the first open cast mine to feed four power station blocks of 340 MW each. The mine is equipped with six identical bucket wheel excavators of the type Sch Rs (2300/5) 32. The annual coal demand of the power station is 18.5 million metric tons. The Elbistan basin encompasses an area of 900 km2, and its centre lies about 1150 m above mean sea level. The sedimentation took place mainly in the upper Pliocene period. The thickness of the coal bed varies from 20 m to 60 m, respectively. The basal part of the coal beds consists of clay, marl and sandy clay. These formations are overlain by gyttja, which may also occur in the form of calcareous ooze, enveloping coal beds. The thickness of the gyttja is up to 35 m (Otto-Gold, 1969). The coal of Afsin-Elbistan is soft coal and the quality has been found to vary considerably throughout the deposit. The thicknesses of the sterile intercalations vary from 0.50 m to 2.2 m and average 1 m in thickness. From the quality control point of view, the coal seam is regarded as upper seam where the gyttja formation occurs as sterile intercalations, and lower seam where the clay formation occurs instead of the gyttja (Fig. 2). The CaO content of upper Kislakoy coal is very high, grinding resistance is low and base to acid ratio of ash, that is, the ratio of acid oxides of metals to base, is greater than one (Ural and Onur, 2001). Contrary to upper Kislakoy coal, CaO content of lower Kislakoy coal is very low, grinding resistance is high and base:acid ratio of ash is smaller than one. Modified Impact Strength Index (MISI) tests are used to determine the grindability of the Elbistan coals (Ural, 1999)."

Jan 1, 2003

By John Smith

"The RTZ Corporation PLCFrom a company's point-of-view, a good investment decision is one which results in the purchase of an asset that is worth more than it costs. Thus, in order to judge the merit of an investment opportunity, it is necessary to estimate the value of the assets to be acquired.Discounted cash flow (DCF) analysis has become widely adopted by companies in assessing potential new investments. The principle is a simple one: invest in projects which have a positive net present value, and reject those which do not. However, perhaps because of its apparent simplicity, DCF analysis is frequently misused. Good practice in the use of the technique is discussed, together with several common misconceptions.Sound analysis requires sound data; thus, the valuation process relies heavily upon a wide range of specialists to provide the basic input from which cash flow forecasts can be built up. The analyst must maintain close liaison with these specialists from the outset in order to ensure that the data provided is indeed relevant and complete.IntroductionBefore turning to the main subject of this paper ""How Companies Value Properties"", it is of interest to consider first a slightly different question ""Why do Companies value Properties""? In other words, for what purposes are such valuations prepared? Certainly the commonest, and probably the most important circumstance in which a valuation is required is when the company is considering an investment opportunity. This may be the direct purchase of a property or group of properties from a third party, but could also be the opportunity to develop a new operation or expand an existing one.A very simple objective in making any kind of investment is to make our shareholders richer than they would otherwise have been. That is, to make investments whose value to shareholders exceeds the consideration required to acquire them. Thus the investment decision focusses on the difference between an asset's value and its cost.This distinction between ""value"" and ""cost"" is an important one. Study of a company's balance sheet may tell a lot about the cost of this company's assets, but very little about their value. Then again, it is sometimes argued that a business should be bought because this will result in assets being acquired for less than their replacement cost. This merely compares one cost with another, it says nothing about value."

Jan 1, 1991

By R. J. McLeod

"A new backfill plant was constructed in 1966 adjacent to the mill of Giant Yellowknife Mines. The reasons for the addition were to increase the storage capacity for sand fill, provide facilities for mixing cement with the fill for mine stope floors and provide a system for pumping fill to B -3 raise, a horizontal distance of 4700 feet from the mill. At the same time it was hoped to increase the density of the fill pumped underground.The plant consists of two only steel storage tanks of approximately 400 tons capacity of sand fill each. They are 17 feet in diameter and have conical bottoms. The cylindrical section is 28 feet high and the conical section 14 feet high. Each tank is fitted with water nozzles around the conical sections to remove solids at the required density. The water pressure on the nozzles is 150 lbs per square inch. The cyclones used to produce the sand back fill are located on top of the storage tanks. Five model Dl0B Kreb cyclones are used for this purpose. The vortex finders are 2 1/ 4 inch and the apex 1 1/4 inch. The cement silo or storage tank is located in the same building. It is a steel tank 17 feet diameter by 41 feet high with a conical bottom. The silo holds 250 tons of bulk cement, which is unloaded by air from a bulk highway carrier using 12 to 15 lbs air pressure. The cement is conveyed to the top of the silo, a distance of 70 feet from the ground by 450 lbs. of air.The mixing tank is a rubber lined steel tank 14 feet in diameter by 14 feet high. It is equipped with a Lightning Mixer supplied by Greey Mixing Equipment Ltd. The mechanism is driven by a 40 HP motor. The lower shaft is unsupported and is equipped with two 36 inch diameter axial flow turbine type rubber covered impellers. The backfill is discharged from the storage tank into the mixing tank by a 5"" x 4"" SRL-C pump powered by a 20 HP motor. A level control in the mixing tank regulates the rate of discharge of this pump through a Grinnell-Saunders automatic control valve. The cement silo is situated at such a height above the mixing tank to allow for a Rota-Lock, a small hopper and a cement feeder. The feeder is an Omega gravimetric belt type dry feeder with a Sensogram controller. The capacity of the cement feeder is 20 tons of cement per hour. The cement and backfill are mixed in the mixing tank at whatever ratio is required for the mine stope floors."

Jan 1, 1968

By Garth D. Kirkham

The Problem The Don deposit is a series of two sub-vertical zones that pose a number of challenges with respect to modeling and interpolation. The first challenge is that, based on data and observations, the mineralization and, more importantly, the grade is layered or banded and is stratigraphically controlled. The second challenge is that, due to the undulations of the deposit and extreme changes in dip, using a standard oriented ellipse to guide the estimation process is not appropriate and does not result in an estimate that is representative on a local scale. In order to solve this problem an adapted methodology of relative elevation modelling, has been devised to effectively model and estimate deposits faced with these challenges. Relative Elevation Designed for bedded seam and gridded surface With variable dip and vertical grade variability

May 1, 2013

By Art Hamilton

The Zn-Pb-Cu-Ag ore deposits of the Boundary and N-5 zones near Bathurst, New Brunswick, occur in a polydeforrned volcano-sedimentary sequence that is part of the Ordovician Tetagouche Group. Massive and disseminated sulfides are hosted by an argillaceous to cherty sedimentary sequence that is stratigraphically Wlderlain by a siliceous fragmental unit and is overlain by a feldspar-rich crystal tuff and related tuffaceous rocks. The deposits have a low iron sulfide content relative to that of most stratabound sulfide deposits of the Bathurst-Newcastle mining district. The ore is commonly associated with chlorite- and talc-rich sediments. The N-5 deposit is considered to be the fault-displaced extension of the Boundary deposit. The Boundary deposit is estimated to contain 891 000 t grading 3.31% Pb, 7.96% Zn, 0.32% Cu and 44 g/t Ag; the estimate for the N-5 zone is 330 000 t grading 3.24% Pb, 7.15% Zn, 0.33% Cu, and 37 g/t Ag. The ore is processed at 1000 tpd at the Heath Steele mill.

Jan 1, 1992

By R. G. Bradburn

"Brenda Mines Limited is a low grade open pit mining and milling operation located near Peachland, British Columbia. The mill was brought into production in late 1969 at a rated capacity of 24,000 tons per day. Tt currently treats an average of 30,000 tons per day of an ore that has an average grade of 0.130% copper and 0.030% molybdenum.Description of Crushing and Grinding CircuitsRun of mine ore is delivered to a primary gyratory crusher. The minus seven inch product is separated into plus and minus one inch fractions on two parallel vibrating screens. The fine product is conveyed directly to the mill fine ore bins, while the coarse fraction is sent to a 45,000 ton stockpile.Material from the stockpile is fed to two standard cone crushers which operate in an open circuit with five secondary vibrating screens. The minus five-eighth inch product from these screens is conveyed to the mill fine ore bins while the coarse fraction is fed to four shorthead cone crushers. These crushers operate in closed circuit with the screens."

Jan 1, 1981

By Z. D. Hora

has been no commercial production of either perlite or pumice in British Columbia. Several promising occurrences are known to exist but their development has been delayed due to difficult access and / or remote locations. The Empire Valley perlite deposit is located 120 km east of Clinton. The deposit appears to be a flat-lying volcanic flow 50 to 70 m thick that is part of an Eocene rhyolite and dacite volcanic assemblage. The Francois Lake perlite deposit occurs on the north shore of Francois Lake where perlite is part of a rhyolitic volcanic sequence. The exposure of perlite is about 13 m thick and is considered to be Eocene or Oligocene in age. The Uncha Lake perlite deposit is located about 5 km south Industrial Minerals in Canada of Uncha Lake. Perlite appears to be intercalated with porphyritic rhyolite flows that are comparable to those at Francois Lake. Showings are widespread but poorly exposed and thicknesses are unknown. The Mount Meager pumice deposit is located in the Lillooet River valley at the base of Plinth Mountain. Coarse pumice agglomerate forms a large talus slope that is undercut by the river. Unsorted, angular fragments up to 50 cm in diameter are intermixed with up to 30 per cent of sand and silt-sized particles. The exposed zone is about 200 m long and 50 m high; it is being considered as a source of lightweight aggregate.

Jan 1, 1984