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By A. G. Lylie

Introduction At the Britannia Mining and Smelting Company's mill, the equivalent of 2,500 to 2,800 pounds of copper sulphate crystals per day is made from copper which is precipitated from the mine-water. This copper sulphate is used in the mill for the recovery of sphalerite by2 flotation. From 1932 until 1936 it was produced by exposing the precipitate to air for thirty days and then dissolving the oxidized copper with dilute sulphuric acid. In 1936, the flotation of sphalerite was discontinued and, when it was resumed in 1947, steps were taken to try to improve the former method. The present paper outlines the way in which this was done, and describes the plant and procedure by which copper sulphate is now being made, and by means of which an appreciable saving is being effected. Aboratory Tests The previous work had established that the precipitate, which consists mainly of metallic copper, must be oxidized before the copper would dissolve in dilute sulphuric acid. Various methods for oxidizing it were tried but in the early laboratory work the only suitable one found was to heat the precipitate to 600°C. and hold it at this temperature for two hours. When this was done, approximately 90 per cent of the copper became soluble in .acid. This percentage was considered satisfactory for practical purposes, but the cost of roasting was prohibitive because only a small amount of roasted precipitate was required each day.

Jan 1, 1951

By Davood Moradkhani, Maryam Rasouli

"The present study reports solvent extraction and separation of zinc from concentrated nickel sulfate solution. In our previous study, Zn and Cd in cold filter cake (CFC, 45-55% Zn, 11-16% Cd, and 2.5-4% Ni) were extracted by alkaline leaching followed by electrowinning processes respectively. The strip solution from electrowinning process, was a pregnant liquor solution (PLS) containing 16.8 g/l Ni and 4.2 g/l Zn. In this work, PLS is subjected to the solvent extraction process for separation of traces of Zn from high grade nickel. The zinc free raffinate containing 16.6 g/l Ni sulfate solution will flow to nickel electrowinning plant for cathode production. Di-(2-ethylhexyl) phosphoric acid (D2EHPA) is the organic phase used in this study. The effects of various parameters such as organic phase concentration (10- 40 % v/v), pH (1.5-3), and temperature (25 and 45°) are investigated. Zinc over nickel separation factor increases by increasing pH from1.5 to 3. The results show that 98.7% of Zn was loaded at25°C O/A ratio of 1, pH 3, and 10% vol. D2EHPA. A 10 M NaOH is used for pH control. However, replacement of pH controlling agent with ammonia solution (25%. v/v) results in interesting observations. Ammonia addition, reduces the solubility of Ni2+ cations in solution. Nickel starts to precipitate from raffinate in a crystalline bluish-green form. The obtained crystals are characterized by XRF and identified to be nickel-bearing analog of boussingaultite, a rare sulfate mineral of nickel with chemical formula of Ni (NH4)2(SO4)2.6H2O. The crystallization rate of crystals is studied. It is a slow precipitation process with 75% in 4 days.INTRODUCTION Annually, many hydrometallurgical processes such as electrowinning, solvent extraction and leaching are applied to waste filter cakes in Zanjan, Iran. These additional processes on filter cakes are critical from both environmental and economic points of view. CFC (cold filter cake) is a toxic but valuable filter cake (45-55% Zn, 11-16% Cd, 2.5-4% Ni, and 0.2-1.5% Cu) produced in many zinc production plants. Our research group at Research and Engineering Company for Non-ferrous Metals (ReCo.), developed a series of hydrometallurgical methods for extraction of zinc, cadmium and nickel from CFC (Moradkhani, & Rasouli 2012). The recovery of zinc and cadmium with alkaline leaching and electrowinning was successfully studied. The strip sulfate solution from cadmium electrowinning unit, contains high concentration of nickel with some traces of zinc impurity. This pregnant liquor solution (PLS) was analyzed and reported to contain 16.8 g/l Ni and 4.2 g/l Zn. In this work, PLS is subjected to the solvent extraction process to separate Zn from nickel (Fig. 1). The organic phase stripping solution containing 4.2 g/l zinc and 200 ppm nickel can be circulated and used in the acidic leaching step. This generates nickel solution with high purity suitable for nickel cathode production."

Jan 1, 2017

By A. P. Page, G. E. Alexander, L. L. Sirois, A. A. Winer

A knowledge of the electrical surface characteristics of minerals is all-important in the choice of treatments to up-grade and beneficiate them. At their solid-liquid contacts, there are transfers of ionic species, which for insoluble oxide minerals are the H+ and OH-ions. The adsorption density of these ions can be detected by carrying out potentiometric titrations, and this paper describes the automation of such an apparatus. The details are discussed fully and the validity of the method is demonstrated by flotation tests.

Jan 1, 1969

By Peter Wells, Gordon Marrs, Dominic Fragomeni, Warren Holmes, Daryl Macnamara

"LocationThe Strathcona mill ofFalconbridge Limited is located in Onaping, Ontario, 50 km northwest of Sudbury.GeneralOre from the Falconbridge mines in the Sudbury Basin (Strathcona, Fraser, Onaping, Craig and Thayer Lindsley mines) is processed through the Strathcona mill with 8500 t of nickel ore and 1500 t of copper ore being treated daily. Current capacity is -3 Mt of ore at 1.8% Ni, 1.9% Cu combined grade. Custom feeds are also processed. The valuable minerals in the ore are pentlandite (FeNi)9S8, chalcopyrite (CuFeS2) with some cubanite (CuFe2S3) and very minor nickel sulphides/ arsenides. Cobalt is present mainly in solid solution in pentlandite. There are small but economically important concentrations of precious metals including platinum, palladium gold, and silver. The common non-sulphide gangue minerals are feldspar, quartz, mica, talc, and chlorite while pyrrhotite (Fe7S8) is the major gangue sulphide. The pyrrhotite contains between 0.6% and 1.2% nickel in solid solution and additional nickel as exsolved pentlandite in micron sized blebs. The nickel and copper ores are batch-crushed in a two stage dry crushing plant and then ground in separate circuits. Concentration by flotation and magnetic separation produces a nickel concentrate assaying approximately 16% nickel plus copper and a copper concentrate assaying 30% copper and 0.4% nickel. The nickel concentrate is trucked as a slurry to the Falconbridge smelter while the copper concentrate is trucked as filter cake to the Kidd Division of Falcon bridge"

Jan 1, 2000

By A. Y. Smith, R. J. Allan, E. H. W. Hornbrook, R. W. Boyle, W. Dyck

"HYDROGEOCHEMICAL METHODS in the Canadian Shield can be based on analyses of the following :(1) spring waters and their precipitates;(2) stream and river waters;(3) lake and muskeg waters;( 4) ground waters from drill holes, wells, faults, etc.;(5) waters issuing from diamond drill holes, faults, shear zones, etc. into mine workings and open pits; also analyses of precipitates associated With these waters.The first four can be utilized in both reconnaissance and detailed surveys. The last is suitable only for detailed work.For hydrogeochemical methods of prospecting to be effective, the following conditions must be present. 1. Natural waters must come into contact with mineral deposits and remain in contact with them long enough for the solution of detectible amounts of ore, gangue or indicator elements. 2. Dispersion patterns must be present in the hydrologic systems in order to trace the elements back to their source. These patterns may take the form of trains (e.g., increasing amounts of elements upstream toward t he source (s), Figure 1 ) or halos (e.g., increasing amounts of elements in bodies of water toward the source (s), F igures 2 and 3)."

Jan 1, 1971

By James R. Hein

Manganese nodules form at the sediment surface of abyssal plains throughout the global ocean at water depths of about 4000-6500 m. The nodules form a continuum from purely hydrogenetic (all metals from seawater) to purely diagenetic (all metals from sediment pore waters), which will determine which metals of potential economic interest are enriched in the nodules. Another important factor in metal enrichment is whether diagenesis in the bottom sediment is oxic or suboxic. There are several nodule fields in the deep ocean that have received much attention with regards to economic potential, the most important being the Clarion-Clipperton zone (CCZ) in the NE Pacific, where the International Seabed Authority (ISA) has signed 12 contracts for exploration areas, each spanning 75,000 square kilometers. Those nodules are rich in nickel (mean 1.3 wt. %), copper (mean 1.1 %), and manganese (28%), with moderate amounts of cobalt (mean 0.2%), molybdenum (587 g/t), and lithium (129 g/t). A conservative estimate is that there exists 21,100 million dry tonnes of nodules in the CCZ, yielding more manganese, twice the nickel, three times the cobalt, and four times the yttrium than the entire land-based reserve base (economic plus marginally economic plus subeconomic reserves) for each metal. Total rare-earth elements (REEs) as oxides average 0.09% in CCZ nodules, a potential byproduct even at that grade because the heavy REE complement averages 26%, compared to less than 1% for the large land-based carbonatite REE deposits. The price for HREEs is much greater than for the light REEs. For comparison, the REEs in deep-ocean ferromanganese crusts are 3 to 5 times greater than nodules and the HREE complement averages 18%. Of the 12 CCZ contracts, 7 are with States (China, France, Germany, Japan, Korea, Russia, and a group of States (IOM); and 5 are with companies: G-Tec Sea Mineral Resources NV, Nauru Ocean Resources Inc. (NORI); Tonga Offshore Mining Ltd (TOML), UK Seabed Resources Ltd (Lockheed UK), and Marawa Research and Exploration Ltd. Three other nodule fields that have received attention are in the Peru Basin, which has nodules very rich in manganese (34%) and lithium (mean 311 g/t), the Penrhyn Basin (Cook Islands Exclusive Economic Zone), with nodules very rich in cobalt (mean 0.4%); and the Central Indian Ocean Basin (CIOB), where India has an exploration contract with the ISA. CIPB nodules have mean nickel, copper, and manganese contents of 1.1%, 1.0%, and 24% respectively.

May 1, 2013

By L. F. Haven

"The desirable shovel speed-torque curves are described, along with the characteristics of the more important electrical components used to approximate these curves. A particular shovel regulator system combining these components is discussed in detail and some of the advantages and disadvantages of the system are given.INTRODUCTIONIN 1959, STATIC CONTROL was for the first time successfully applied, installed and operated on a mining machine in North America. Since that time, a great deal has been learned about this control by the people maintaining these machines as well as by the de-signers.In 1961, the first SCR (Silicon Controlled Rectifier) or thyristor control system was installed on an excavator. This control differed from the earlier static control in that thyristor excitors supplied the generator fields directly. The development of thyristors of a sufficient rating to supply amounts of phase-controlled power to the generator fields eliminated the bulky Mag. Amp. -Rectifier combination previously used."

Jan 1, 1969

By V. Aprahamian, G. B. Harris, C. W. White, M. Tangen

"In 2005, the Royal Canadian Mint (RCM) commissioned a new silver electrorefining circuit. This circuit was intended to operate with a minimal electrolyte bleed for the control of copper. However, by the time of start-up, the levels of copper-rich silver doré to electrorefining had increased, and despite partial pyro-conversion in a small Top Blown Rotary Converter (TBRC), copper concentration in the silver anode still averaged 7.5%. This necessitated frequent replenishment of the electrolyte with fresh silver nitrate since copper displaced dissolved silver during electrolysis, and therefore requiring a robust copper bleed treatment step in order to maintain cathode silver flake purity at 99.99%. The originally-installed bleed treatment system could not meet the RCM’s needs. A thorough review of known technologies, however, did not indicate one capable of handling the copper load, and resulted, therefore, in the development of a novel copper hydrolysis approach for removal of copper as an insoluble basic nitrate salt, and recovery of the associated nitric acid for re-use in the circuit. Laboratory-scale trials showed reproducible results, and existing equipment was subsequently modified.INTRODUCTIONIn 2005, the introduction of a new silver electrorefining circuit at the Royal Canadian Mint (RCM) initiated changes in the way customer silver, collected from the gold doré circuit, was processed. These circuit changes were discussed in a recent paper (Aprahamian, 2015). A wastewater treatment plant had not been budgeted at the time, and this represented a significant constraint when considering the introduction of a wet processing circuit. After a review of various options, a turnkey silver electrorefining circuit was purchased from a European firm. Initially, enough cells were ordered to produce 2 million oz of fine silver (999), with the option to increase to 5 million oz. The selected equipment was based on a Moebius cell design combined with a silver grain pressure dissolver to produce make-up silver nitrate solution. Additionally, an evaporator/hydrolysis unit included in the package appealed to the Mint Refinery, on the basis that it offered a simple way to bleed dissolved copper in electrolyte without generating effluent."

Jan 1, 2016

"Option pricing is used in finance for valuing options to buy (or sell) shares at some future date because it provides a convenient framework for quantifying values subject to uncertainty. As one of the main sources of uncertainty in mining is the price (sales) of the metal, this approach can also be used for valuing mining projects.The first part of this paper reviews options and option pricing; the second part presents the approach developed by Brennan and Schwartz (1985) for using option pricing to value natural resources. Several applications of this methodology have been published; these are described. From a mining point of view, the assumptions made by Brennan and Schwartz are too simplistic. The weaknesses are discussed with a view to improving an apparently promising new way of assessing the value of projects. IntroductionThe collapse of the British merchant banking group, Barings, has highlighted the risks that can be incurred by speculators and arbitragers in the futures and options markets. But this negative attention on futures and options should not make us forget their positive aspects. They can provide producers and consumers of metals with more predictable sales prices. The introduction of the new traded average price options, TAPOS, by the London Metal Exchange in January 1997 is a response to this need. Equally important, the theory that the finance industry has developed for valuing options provides an interesting framework for valuing mineral projects as well. While this paper was being revised, the South African gold mining house, JCI, announced that it was using a methodology based on option pricing for valuing the mineral rights to deeplevel gold resources (see Box 1)."

Jan 1, 1997

By Arthur. H. Winckers, Stephan L. Chryssoulis

"The deportment of gold in residue samples of cyanide leach tests of David Bell ore from level 6A block 13 was established using a comprehensive quantitative mineralogical approach. In every test the feed was first pre-aerated for 4 hours, followed by 48h cyanidation. Test no. 2 was done without lead nitrate and yielded a residue assaying 3.03g Au/t. In test nos. 4 and 9 lead nitrate was added before pre-aeration at 0.03kg/t and 0.3kg/t respectively yielding residues of 1.04 and 0.81 g Au/t.The mineralogical approach employed to establish the deportment of gold involved superpanning, to preconcentrate the free gold and assaying of the tailing fraction to determine the gold associated with quartz. It was thus determined that without lead nitrate added 47.2% of the lost gold is in the form of residual free gold particles less than 20 µm in size. It is this form of gold which is under represented in the residues of leach tests with lead nitrate added.Having eliminated coarseness of gold particles as a factor for lower recovery, it was determined that the residual gold particles have extensively contaminated surfaces. Amongst the deleterious surface contaminants identified: S, As, Ag, Sb and Hg, the two most harmful are S and Hg because of their concentration on the surface and rate of accumulation.Mercury and Ag are minor constituents of native gold at David Bell (average composition Au: 78.9 wt%, Hg: 18.5 wt% and Ag: 2.6 wt%) and they become enriched on the surface of residual gold particles because of their slower rate of dissolution in cyanide. The other elements absorb onto the gold particles from solution.The beneficial effect of lead nitrate was documented by comparative surface analysis of gold from residue samples of 48 hour leach testing with and without lead nitrate added and from time dependent (0-2 hour) leach tests in the presence and absence of lead nitrate. Lead nitrate accelerates the dissolution of gold by performing the following functions: (i) catalytic effect on the cyanidation of gold by accepting electrons; (ii) reaction with surface sulphur to form PbS which is then removed by oxidation; (iii) catalytic reaction on amalgam and Ag facilitating the cyanidation of Hg and Ag thus slowing down their build up onto the dissolving gold particles and (iv) the precipitation of sulphide sulphur from solution thus minimizing its build up on the surface of dissolving gold particles which is believed to facilitate the access of cyanide ions."

Jan 1, 1996

By Carlos Rebolledo, Nelson Parra

Arsenic is an unresolved problem in the mining industry considering the fact that most of the new copper deposits have high arsenic contents; stricter environmental restrictions for handling, transporting and processing complex materials are expected and stable abatement of arsenic is not extensively applied. In 2018 Chile produced 24.5% of the total copper from concentrates and in the future copper production in Chile is expected to increase, mainly associated with production of concentrates that will also contain more arsenic. China has set an import benchmark of maximum 0.5% for arsenic content in copper concentrates and this value is expected to be more restrictive in the future. On the first day of 2018 China banned the importation of scrap. Blending practice has been a business option, but it is not sustainable in the future, as “normal” copper concentrates become less and less clean. By the end of 2018, Chile formulated new regulations, increasing the capture of SO2 and arsenic to 95%. In order to comply with these regulations Chilean smelters had to make large invest large amounts of money. Disposing of arsenic as a stable residue is a pending issue. EcoMetales is a 100% subsidiary of Codelco and provides the mining industry with environmental solutions. It has a plant near Calama in Chile that treats flue dust from smelters, refinery effluents and acid solutions from acid plants. EcoMetales is fully committed to contributing to the solution to the arsenic problem. Currently we are developing four main projects: 1) Concentrates treatment. A PLCC project considering the treatment of 200 ktpy of copper concentrates with arsenic from the northern district of Codelco; 2) EPAS DET project considering the treatment of 700 m3/d of weak acid solution with arsenic from the of El Teniente devision of the Codelco acid plant; 3) Borras project, considering the recovery of valuable metals (Cu, Ag, Ge, Pb) from the flue dust leaching plant; 4) Tailings project, considering the recovery of metal values from tailings. The purpose of this work is to present the trends and treatment processes for arsenic handling in the copper mining industry with a focus on the scorodite process. INTRODUCTION Between 2000 and 2015 the global copper concentrates production has grown from approximately eleven to fifteen million metric tons per year. Chile produced 26.5% of the total copper from concentrates and in the future copper production in Chile is expected to increase, mainly as a result of the production of concentrates (Figure 1)

Jan 1, 2019

By J. Gordon Parr, D. A. Whitaker, G. A. Yorko

High purity alloys of zinc with 25 per cent to 50 per cent aluminum, have been prepared. Mechanical properties of the as-cast and heat-treated alloys have been related to constitution, determined by x-ray diffraction and microscopic methods. Investigations include the effects of aging and of small nickel additions on the properties of the alloys.

Jan 1, 1960

By Horatio Sam-Aggrey, Margot Hurlbert

Small Modular Reactors (SMRs) have been touted as having the potential to spearhead a nuclear renaissance. Proponents of this view cite the relative advantages of SMRs over larger nuclear plants as reason for their optimism. Some of these merits include potential economies of mass production deriving from modular factory production, enhanced safety features, the ability to locate reactors in remote areas, and reduced requirements for technical workforces to install and maintain SMRs. Despite the optimism surrounding SMRs, nuclear power is still a contentious issue for many Canadians. The growth of nuclear power remains adversely affected by concerns over issues such as: the health and safety consequences of nuclear power generation, environmental impacts, proliferation of nuclear materials, terrorism, and radioactive waste disposal (Organisation for Economic Co-operation and Development (OECD) and Nuclear Energy Agency (NEA), 2010). Personal values, past nuclear accidents, and lack of trust in the industry are other factors influencing attitudes toward nuclear energy (IAEA, 2005). In Canada, three main areas where SMRs could be used have been identified. These include: a. Traditional, on-grid power generation, especially in provinces looking for zero-emissions replacements for CO2-emitting coal plants. B. Remote off grid communities that currently rely on diesel or fuel oil power generation. There are 279 off-grid communities in Canada, many of them being Aboriginal communities (NRCan, ND). Notably, all communities in each of Canada’s three territories qualify as remote. C. Resource extraction sites, such as mining and oil and gas extraction sites. Many of Canada’s principal producing mines and active mineral exploration projects are located within close proximity of Aboriginal communities. Any proposed implementation of small nuclear plants would, require the support of the local population, which is largely Indigenous in the northern regions. The possible deployment of SMRs raises important issue relating to consultation and accommodation of Aboriginal concerns regarding potential SMR deployment. This is especially pertinent given Canada’s pending implementation of the provisions of UNDRIP. One of the provisions of UNDRIP that has attracted a lot of attention is the one on Free Prior and Informed Consent (FPIC). Drawing on previously published information, this paper discusses some of the challenges posed by FPIC for the deployment of SMRs. The next section outlines the provisions of FPIC and its implementation in the Canadian context. Section 3, details some of the challenges posed by FPIC to the deployment of SMRs, while Section 4 provides some concluding comments.

Jan 1, 2020

By Jean Robitaille

La découverte du gisement du puits Penna a nécessité une révision complète de tous les circuits du concentrateur Laronde pour permettre, premièrement, l?adaptation du procédé à la nouvelle minéralogie et deuxièmement, l'accroissement du tonnage de 1800* à 4500 t/j. Aux circuits existants de broyage, de flottation du cuivre, de cyanuration et du charbon en pulpe, les circuits suivants furent greffés : broyage semi-autogène, flottation du zinc, manutention des concentrés (épaississage, filtration, entreposage et chargement automatisé), décantation à contrecourant et précipitation au zinc, destruction des cyanures et remblai en pâte. Cet article se veut une revue des différentes étapes du projet d'agrandissement du concentrateur qui se sont effectuées par phases progressives de 1997 à 2000. De plus, une description des nouvelles technologies sélectionnées et implantées est présentée.

May 1, 2001

By H. H. Bleakney

The merit of reduction-in-area as a criterion of quality in metals is shown to lie in its influence on breaking stress, but the virtue of elongation is not easy to find. In order to assess the value of elongation, either as a measure of quality or as a guide to design, it will be necessary to separate the overall de-formation occurring in tension tests from the localized deformation associated with localized reduction in area. The obstacles to a successful solution of this problem have been shown to be more formidable than is generally appreciated, and a new solution to the problem has been suggested. This solution involves a de-vice by which an electric circuit is broken when the particular value of strain is reached that is to be taken as the point of separation between general and localized deformation. The report presents results from a number of tests on both low-carbon and alloy steels. These results indicate that the selected criterion of separation is accurately identified by the proposed method; that it

Jan 1, 1962

By Kremena Dedelyanova

The paper presents research of mechanism for the creation of air bubbles in vibratory a column flotation machine. Factors are discussed that influence the increase in the duration of the bubble in the area of contact with the mineral particles. Formulas are derived for the parameter effect of vibrations, applicable to the design of flotation machine. The collision efficiency of the bubbles in a vibratory column flotation machine is determined.

Aug 1, 2013

"An unparalleled growth in the Canadian coal industry in 1970 coincided with increasing awareness by Canadians of their environment and their geography with its accompanying transportation factors. R and D on coal moved with greater emphasis toward solving problems in these areas as well as continuing with strong interest in coal preparation, carbonization, combustion, ""weathering'', spontaneous ignition, storage, exploration and geology. Long-range ""basic"" research was not forgotten in that work continued on coal-based carbons, coal chemistry and agrobiological uses for coal. This paper reviews the status of these many areas of coal research at the beginning of the seventies and takes note of some of the more significant legislation and projects brought to the author's attention. No attempt is made to itemize or to describe in detail all the worthwhile projects, many of which are reported elsewhere."

Jan 1, 1971

By H. Tsuruta, A. Fujibayashi, I. Sumi, A. Murao, R. Murai

Injection of biomass into blast furnace as alternative reducing agent is so effective for the purpose of mitigation of carbon dioxide emissions from steel industries, because biomass is considered to be carbon neutral raw materials. Certain amount of Palm Kernel Shell (PKS) is abandoned after Palm oil extraction process. To use as a reducing agent of blast furnace, PKS was carbonized and classified by 100 mesh sieve. To examine the gasification behavior of PKS carbide under the blast furnace conditions, several combustion experiments were conducted using hot model experimental furnace. The experimental results showed that the gasification efficiency of PKS carbide increased as the quantity of volatile matter increased. This tendency is the almost the same for the pulverized coal, so carbide of PKS can be used at blast furnace at appropriate amount of volatile matter that can be controlled by carbonization condition. In addition, the pressure drop of the furnace tends to decrease because the amount of ash in PKS carbide may be smaller than that of pulverized coal. PKS carbide is a suitable reducing agent in that respect.

Jan 1, 2015

By W. E. Roscoe

The probability of making an exploration discovery in Canada can be calculated from Derry's (1970) data on exploration expenditures and number of discoveries over the last nineteen years. Considering an average exploration "try" to be $30,000, the probability of a discovery with one try has decreased tenfold from about 0.01 in 1951 to 0.001 in 1969. A plot of these probabilities can be extrapolated to the future, giving a 1969-71 three-year average probability of 0.00096 with 90 per cent confidence limits of 0.00042 and 0.00153. Using this probability, various calculations can be made, such as (1) the probability of making at least one discovery for any given exploration expenditure, (2) the probability of ultimate ruin or survival of the exploration investment process and (3) the expected value of an exploration investment. There is a critical minimum amount per discovery that must be re-invested in exploration, no matter how large the original investment is, for exploration to survive at all in the long run. Currently, this critical minimum is $31,200,000 with 90 per cent confidence limits of $19,600,000 and $71,400,000.

Jan 1, 1971

By W. E. Coates

The social ecology of surface mining in urban areas is illustrated by a case study of a recent application for the opening of a new gravel pit in the city of Guelph, including the design of a progressive extraction-rehabilitation sequence for the property, investigation of the ecological impact of the proposed operation, history of the application procedure for a zoning change and the relationship of the operating plan to provincial legislation controlling surface mining.

Jan 1, 1972