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By Donald A. Cranstone

"This paper provides a bird's eye view of the pattern of gold discoveries since 1823, the year of Canada's first gold find, up to 1983. Within this 160-year period, more gold was discovered in Canada during the last ten-year period (1973-1982) than during any previous decade. The record suggests that the potential for further major gold discoveries is high, which bodes welt f or the future of Canadian gold mining.IntroductionCanada has an impressive history as a gold producer. Since 1921 we have occupied second or third place among the world 's gold producing nations, after South Africa and most of the time the U.S.S.R. Canadian gold production over the last hundred years has added up to some 6 per cent of all-time world production.The sharp rise in the price of gold in the 1970s led to a surge of gold exploration, which in turn resulted in the discovery of significant quantities of gold in Canada. How do these recent discoveries rate in comparison with those of the more distant past? For example, are the quantities of gold in notable discoveries of recent year s, such as Hemlo and Detour, in the same league with the amounts of gold discovered around 1910 in the Porcupine and Kirkland Lake district s of Ontario? Can the combined gold content of the recent discoveries be likened to that o f the almost 40 major Canadian gold deposits, along with numerous smaller ones, discovered in Canada during the 1920s and 1930s? What are the implications of the more recent gold discovery record for future rate s of gold discovery in Canada?This paper attempts to glean answers to such questions from an overview of the period that begins in 1823, the year of Canada's first gold discovery. Gold deposits come in two major types: placer deposits and lode deposits in solid rock . Placer gold is distributed in sand and gravel. Gold in solid rock occur s mostly in gold ore filling fissures."

Jan 1, 1985

By R Gilbertson, N Freeman

Metallurgical accounting is key to the control and production planning process of any mining operation. This is even more crucial for complex operations involving mining, concentration, smelting, refining and marketing. The tracking of multiple metal product and contaminant components through the operation can improve process predictability and inventory management. Appropriate use can be made of æhigh quality dataÆ for strategic reserve utilisation, mining operations, milling operations, etc. This information enables the optimisation of all aspects of the mining and processing operations. This case study discusses a metal balance implementation for WMCÆs Olympic Dam operations; a large integrated mining, concentration and refining operation, which used an existing off the shelf statistical data reconciliation package developed for the oil industry. It was extended to track and balance the metal co-products across the entire integrated mining, mineral processing and refining plant. The key benefits discussed are tight integration with existing data collection systems, formalisation of previously informal processes, and leveraging the development and support available for a widely used package. The project provided a solution for the site metallurgical balance spanning the mine and processing plant. The solution facilitates a bridge between the planning and production worlds, using a common data model across the site.

Jan 1, 2002

By M K. Singh

Mining is nothing but an art - besides being a science - of extracting valuable minerals from the womb of the mother earth. In this gigantic task, a large number of machinery and equipment are employed judiciously. Wire ropes play a vital role in lifting or hoisting men and materials under hostile/adverse working conditions and constitute a major item of investment on machinery/equipment. The economy of using a wire rope is a concern for engineers, users and the planners. The economic use of wire ropes for mining purposes largely depends on the following factors;Mechanical design considerations - which include tensile strength of wires, elasticity, resistance to abrasion and crushing, fatigue values, static and dynamic loads on wire ropes, factor of safety, fleet angle, etc. Metallurgical consideration - Composition and heat treatment of wire materials, defects like inclusions and voids, surface quality factor, lubrications, micro structural parameters. Operational consideration - Seizing and cutting of rope, storage, care and maintenance, cutting back, etc. Environmental consideration - Temperature and humidity, pit condition, dust, corrosive atmosphere, etc. In the present paper, an attempt will be made to suggest steps for achieving optimum economy while using the wire ropes for extraction of precious minerals and coal keeping in view the points noted earlier. Once technical viability is established, economy is the ultimate consideration for an industry for safe hoisting of men and material.

Jan 1, 2000

By Scott Tzcrner

WITHIN recent years people have begun to realize the importance and significance of the mining and allied industries. The leading part the engineer plays in civilization is becoming recognized. However accurate quantitative knowledge of the industrial importance of mining is still seldom possessed except by those close to this business. It is true that there are a few who go to the extreme and represent the whole progress of civilization as a reflection of man's gradual mastery of mineral utilization, but on the whole, the magnitude of the-industry is underestimated. In this paper I shall call attention briefly to the importance of mining in the United States, in Canada, and in the world. Ordinarily, the annual primary mineral production of the United States is about $5,500,000,000. The average for the last 5 years has been a little over that, but last year, sadly enough, it was less than 31/4 billion. Just now, we are on the decline, and have been for the last two years. In Canada, the 5-year average was about $268,000,000, and last year it was 227 million. Due in part to gold mines (in 1930, for the first time, Canada's gold production exceeded that of the United States), the Canadian average is holding up better than ours. Average world mineral production over the last -5 years has been estimated at about $12,000,000;000 whereas in 1931 it was less than than 8 billion.

Jan 1, 1932

By R. W. Coburn

The results of field experiments on wells which required stimulation indicated that engineered well-completions will cause an increase in ultimate recovery at reduced costs. Techniques and tools have been developed which can be used to establish well conditions most conducive to successful stimulation. Cementing, perforating and treating are bound together so completely that the success of one phase is completely dependent on the .effectiveness of the preceding phase. A method of determining the efficiency or effectiveness of any given well-stimulation treatment has been derived. Pressure behaviour during a treatment can be analyzed to yield the total percentage of the formation which has been treated.

Jan 1, 1960

By Éder Domingos Oliveira, Carlos Antonio Morais, Ruberlan Gomes Silva

The objective of this study is to assess the impact of different reagents, such as limestone, lime, magnesium oxide, and sodium hydroxide, in experiments carried out in the single purification step and in two consecutive purification steps by raising the pH of a rare earth sulfuric liquor with the aim to remove or reduce the impurity concentrations in the rare earth sulfuric liquor. The choice for the best purification condition was made based on the minimum loss of rare earth elements (REEs), reagent consumption, and residue generation. The exploratory experiments show that it takes place in the two consecutive purification steps, the first one consists in dosing the limestone pulp until it reaches a pH of 3.5 followed by an addition of a lime pulp reaching a pH of 5.0. Under this condition, the results were a total removal of Fe3+, PO4 3− , and Th4+ ions and a reduction of 99%, 87%, and 37% w/w in the Al3+, UO2 2+, and SO4 2− concentrations, respectively, in the purified rare earth liquor. Furthermore, the lowest REE losses (8.3% w/w) and reagent consumption (4.3 kg/m3 ) and also a low residue generation (7.5 kg/m3 ) were observed in this condition. Despite reaching similar results regarding impurity removal, the experiments done with the addition of limestone, lime, magnesium oxide pulps, and sodium hydroxide solution in the single purification step, where the pH was raised to 5.0, presented higher REE losses (64.9%, 42.5%, 44.8%, and 60.9% w/w, respectively) and a higher residue generation (43.2, 25.1, 11.1, and 13.6 kg/m3 , respectively). This occurred due to the co-precipitation of salts containing rare earth elements in their composition. The experiments conducted with limestone, lime, and MgO resulted in a higher consumption of reagents, while the same result was observed when NaOH was used (4.3 kg/m3 ). In the experiments carried out with the addition of magnesium oxide and sodium hydroxide, the respective purified rare earth liquors presented a high concentration of magnesium, sulfate, or sodium, which could impact the quality of the marketable rare earth salts, whereas the salts obtained under the best condition observed in this study seem to be amenable for use as raw material in an attempt to obtain rare earth products with an acceptable chemical quality.

By Willard P. Ward

SOME TIME in the year 1874 or 1875, I conceived the idea that spiegeleisen might be made -in a blast furnace from ores that were not carbonates, and which did not contain both manganese and iron in the same ore. Up to this time, such ores had formed the basis of all the spiegel that had been produced; and all the ferromanganese that was on the market before 1875 was made in crucibles, and cost about 00 per ton, for 80 per cent. Mn. I consulted the great steel metallurgist of the day, Alexander Holley, who listened attentively to what I had to say, and told me he did not think my plan was practical, so I abandoned it for the time being. But I was so stubborn that I could not get the notion out of my head. It seemed to me that a good metallurgist should be able to work the thing out in some way. I had already had some experience in smelting refractory lead ores in Utah, and was young and not lacking in self confidence, so after waiting a bit, I got Anton Eilers, the best all-around metallurgist I knew, and J. H. Bramwell, the best iron blast-furnace man I knew, both intimate friends of -mine, to come to my place in Bartow County, Georgia, and look over things. They remained for several days, and made all the examination they thought necessary; and they also advised me to give up the project, and either to keep the furnace running on car-wheel iron or to blow it out. After my talk with Holley, I improved my plant in several ways. I closed the top of the furnace, put in a hot-blast stove, a steam boiler and a Weimer blowing-engine which gave me blast enough, at a pressure high enough for all the requirements of, the furnace, and which I could bring up to a temperature of 600° to 700° F.

Jan 1, 1921

By L. C. IlsLey

In January, 1922, a conference relative to trailing cables for use with permissible mining machines was held at the Pittsburgh Experiment Station of the U. S. Bureau of Mines. At this conference it was recommended that the bureau take steps to investigate the rubber-sheathed type of cables and to bring about the establishment of a list of approved cables. Effective until such time as a complete investigation could be made, the bureau asked the several manufacturers holding approvals for mining machines to recommend cables for use with their machines. In general the cables recommended were tentatively approved. Due to the lack of available personnel, no actual tests of cables were made until mid-1927. Meanwhile a field investigation of trailing cables was made at 20 mines of three coal companies in western Pennsylvania, and samples of cables were obtained from the manufacturers for laboratory tests. Twenty-five samples of the concentric-type cable, representing the product of five manufacturers, were obtained for the tests. These cables were of four sizes, as follows: 3 cables of No. 2 B & S gage, 17 cables of No. 3 B & S gage, 3 cables of No. 4 B & S gage, and 2 cables of No. 6 B & S gage.

Jan 1, 1929

By C Gypton

This paper gives some insights into what to look for when reviewing feasibility studies. The review by a third party is an important element of the risk management process and may be the last remaining opportunity to uncover errors, or identify and reduce project risks on paper before they are converted to financial disappointments, steel and concrete monuments to process failures or cost overruns. The mining industry has had a spotty record in the area of estimating initial capital costs and operational performance, even though the standard of feasibility studies is generally acknowledged to have improved in the last decades. Third party reviews rarely have the luxury of enough time and unlimited funds, so where should the reviewers focus their efforts to be most effective? Assuming that the project already apparently meets investment criteria, the authors suggest where and how to look among fundamental project parameters for signs that serious flaws exist that have the potential to become project killers. We also give advice on how to review cost estimates without becoming lost in the details. The paper is supported with numerous actual examples.

Jan 1, 2003

By R O’Sullivan, D Taylor, J G. McLellan, B Miller

The Mount Isa copper deposit is located adjacent to the city of Mount Isa, Queensland, and lies within a series of Palaeoproterozoic to Mesoproterozoic Superbasins. The deposit is hosted almost entirely within the Urquhart Shale (US), a unit of the Mount Isa Group sediments and part of the Isa Superbasin. The copper mineralisation is separated into two distinct orebodies: the X41 mine (1100 and 1900 orebodies) and the Enterprise mine (3000 and 3500 orebodies). The orebodies are situated in the hanging wall of the major controlling structures, the Paroo Fault, which has juxtaposed older basement Eastern Creek Volcanics against the younger Mount Isa Group sediments cf 1655 ± 4 Ma. Conjecture remains over the exact timing of this thrust event. However, it is clear that inflections on the Paroo Fault have a close association with the orebodies and are an important structural feature in the mineralisation of the Mount Isa copper deposit.The life-of-mine is reducing steadily and new geomechanical modelling techniques were employed to target structurally controlled mineralised zones in three dimensions. Following a structural review of the mine using underground mapping, structural data and core shed observations, a conceptual 3D mine model was constructed utilising existing data modelled in MineSight®. This conceptual model included all the main lithological units and structures. The conceptual model aimed to test the effects of deformation on the main lithological and structural components of the system and attempted to highlight areas of anomalous stress and strain that may indicate a higher likelihood of fluid focusing and mineralisation potential. This project was focused on testing the latter stages of a D3 event (NE–SW compression) and D4 event (SE–NW compression), which are considered to be responsible for the current location of the mineralisation.The fully coupled 3D finite element analysis models resulted in highlighting anomalous patterns of stress and strain and subsequent fluid flow as a result of the two deformation events. The NE–SW D3 simulation provided the best correlation with the known distribution of mineralisation. This event also indicated several areas on the Paroo Fault and within the US that have potential to host further areas of mineralisation. The SE–NW D4 simulation provided less of a correlation with known mineralised zones. However, this event may have been responsible for post mineralisation re-mobilisation of copper on a relatively small scale. Areas of maximum shear strain, shear stress, volumetric strain and fluid flow correlated well with areas of minimum principal stress and provided the best overall match with known mineralised zones. Furthermore, several additional highlighted areas provide a high potential for further discovery of copper mineralisation. Recent exploration drilling north of the Enterprise mine 3000 orebody, utilising geomechanical modelling as part of the targeting criteria, intersected copper mineralisation, providing further validation of the modelling results.CITATION:McLellan, J G, O’Sullivan, R, Miller, B and Taylor, D, 2014. Geomechanical modelling of the Mount Isa copper deposit – predicting mineralisation, in Proceedings Ninth International Mining Geology Conference 2014 , pp 197–206 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 18, 2014

By Akram Marseet, Andrew J. Petruska, Rik Banerjee

Underground mine roof bolting is a crucial operation for miners’ safety and mine sustainability. Since roof bolting is a manual or human-supervised operation, miners’ safety is at risk due to dust or rock falls. Traditional machine learning algorithms have shown limitations to detecting drillable areas, mainly due to harsh lighting conditions. The authors propose an adaptive deep-learning framework for autonomous roof bolting. The proposed framework is based on implementing a binary semantic segmentation algorithm on color images to classify pixels that belong to rock from those that belong to non-rock. Significantly, the proposed framework implements deep learning semantic segmentation on images from traditional and neuromorphic vision sensors in underground mines. The performance of the proposed model shows an impressive accuracy level of at least 98% at a low number of training epochs with smooth learning curves. The high accuracy enables the implementation of autonomous roof bolting, greatly improving miners’ safety and operational efficiency while reducing human exposure to safety hazards. This research will advance the use of deep learning in mining automation and has the potential to revolutionize the traditional mining industry.

Feb 1, 2024

By A. V. Hooker, E. J. Coggeshall

"The Bureau of Mines for some time advocated the firing of all blasts in coal mines as single shots, and this method of firing is the general practice in American bituminous-coal mines. All single shots can be fired with permissible single-shot units so designed that they will not ignite mixtures of methane and air.If several shots in a face are fired singly it is necessary to return the face after each shot. In some mines having steeply pitching coal seams, this may be dangerous or even impossible, under these conditions shots are usually fired simultaneously.Several shots cannot be fixed simultaneously with permissible single-shot blasting units, and safe types of multiple shots blasters are not readily available. This means that the firing of multiple shots in gassy mines is usually accompanied by the possibility of gas ignition as the blast occurs.Tests have been made at the Pittsburgh Experiment Station to determine the possibility of developing safe types of multiple-shot units suitable for such use, or of applying other type safely in gassy sections of mines where firing shots singly is impracticable.The tests may be divided into the following four groups:1. Tests to demonstrate hazard in the use of existing types of multiple-shot units of the portable generator type.2. Tests to show the electrical characteristics of multiple-shot generator units relative to the possibility of preventing igniting sparks and of modifying the design and application of such units in furthering safety."

Mar 1, 1935

By Jensen B, Ofori P, He Y, White E, Stanmore B, Brien M, O&apos

As part of a large AMIRA project, an on-line moisture meter was installed at two mine sites in Central Queensland. This project investigated the factors which control the moisture content of coarse (>0.5 mm) coal from the centrifuges used in conventional coal preparation plants. It was placed immediately after the first centrifuge to isolate the factors pertaining to one machine and its feed.The meter was found to be accurate and precise when compared with manual and mechanical sampling methods. The Grubbs estimator technique indicated that its precision is better than 0.3 per cent at the 95 per cent confidence limit.It has been identified that:1. the variability of the measured moisture contents of coarse coal can be described by normal distributions. Standard deviations of about 0.6 per cent are common; and2. the treatment of the coarse coal on the drain and rinse screens immediately prior to the centrifuge can affect the final moisture content.

Jan 1, 1995

By T. H. Yang, Q. K. Wang, T. Song, J. W. Zhou

The grinding circuit can be one of the most important mineral processing circuits in plants. Along with the application of large-scale milling machines, the design and optimisation of the operation strategy for grinding circuits is more complicated. An in-house grinding process simulation tool was developed to mass balance, model fit and simulate crushing, grinding and classification circuits. An industrial grinding and classification circuit in a copper mine was modelled, and the modelling parameters were verified by a particular group of plant survey data. To justify the prediction ability of the fitted models, the model predictions under different operation conditions were compared with another group of plant survey data. Then the model predicted the effects on the circuit of changing operating conditions. Circuit analysis of the comminution process for water feed to a SAG mill, water feed to sump, the rolling speed of a SAG mill and the percentage of ball filling in a SAG mill was put into practise, based on the simulation results. The simulation results can be used to help plant operators understand the features of the comminution process and may help to build a knowledge library for process control. Keywords: Process modelling, grinding, comminution, circuit analysis

Jan 1, 2020

By Peter A. Hacquebard

Recent drilling programs have shown that the in-situ coal resources of Nova Scotia are very substantial. The grand totals of the measured, indicated and inferred categories amount to 232 m, 646m and 993 m tons, respectively. This vast quantity of coal occurs essentially in five main fields: Sydney, Mabou, Port Hood, Pictou and Springhill. The largest resources (84% of the total) occur in the submarine area of the Sydney coalfield. With a 65% recovery rate, there are at present 150m tons of proven, recoverable coal in Nova Scotia. At a predicted maximum annual production of 5 m tons, this amount equals a lifespan of 30 years. However, additional drilling, particularly in the Sydney offshore area, holds promise of increasing the recoverable reserve tonnage to at least 350 m tons. This figure may be compared with the 484 m tons production obtained during 191 years of mining (from 1785-1976). The geological appraisal of the remaining coal resources in the five fields mentioned is presented in three-dimensional diagrams, per individual seam and corresponding reserve area. In addition, the submarine extensions of the Sydney and Mabou coalfields are discussed in light of results obtained from off shore oil exploration wells. The terminology and standards of coal resource calculations are pointed out, and the phenomenon of seam splitting and its prediction from geological data is illustrated. The availability in Nova Scotia of either thermal or metallurgical coal is considered in relation to rank and sulphur content. This paper was presented in June 1977 at the 90th Annual Meeting of the Mining Society of Nova Scotia. The coal resource estimates, however, have been updated to include the results obtained with the offshore drilling in the Sydney Coalfield to November 1977.

Jan 1, 1979

By Zheng-qi Guo, De-qing Zhu, Feng Zhang, Jian Pan

Iron mainly exists as the magnetite and fayalite, while copper is primarily dispersed in the form of fine matte particles in the copper slag, which is difficult to recover by conventional separation techniques. In this paper, the feasibility of an integrated technological route to improve beneficiation of copper and iron components from copper slag through the modification of molten slag was investigated, and the results shows that: the copper grade of rougher copper concentrate was increased from 6.43 to 11.04%, iron recovery from magnetic separation was increased significantly from 32.40 to 63.36%, and other evaluation indexes were changed slightly, in comparison with unmodified copper slag. Meanwhile, the grains of the target minerals in the modified slag grew considerably to a mean size >50 lm after slow cooling. Ultimately, the beneficiation efficiency of copper and iron was improved because of the ease with which the target minerals were liberated.

Mar 1, 2017

By Bartho J. Admiraal, Antoine Feddema

Pneumatic sinking of caissons has been established from mid-19th century. The technique of pneumatic sinking has been applied on many projects for underground construction up to depths over 20m below groundwater level since that time. Volker Staal en Funderingen, a known deep foundation contractor in the Netherlands, was awarded two contracts in 2015 for sinking in total 2 caissons in Hamburg (Germany) to large depths (over 30 m (100 ft) and two projects near Amsterdam (the Netherlands). The latter concerned two gate chambers for the world’s largest sea-lock, one of them was 55x81 m2 (180x266 ft) to a depth of 25.5 m (84 ft), which would mean a world record for pneumatic sinking! But with depths and dimensions like these, the deployment of personnel is the main limiting factor for production, despite all developments to date. It was decided to develop a remote controlled process, including the necessary equipment and monitoring systems. Monitoring not only the kinematics of the equipment in the working chamber and the production parameters related to the excavation but also of the structural behaviour of the sea-lock gate chambers was essential for approval of this innovative execution method. The lay-out and the sizes of the largest caisson the structural integrity was extremely critical for torsion and bending moments. A displacement controlled execution by the observational method was therefore required. In engineering a new approach for modelling the semi-continuous failure mechanisms of the soil was needed to understand the sensitivity of the excavation process and to define limit values for the execution. In the paper these structural and geotechnical issues will be explained together with the experiences during the execution.

May 1, 2022

Under the sponsorship of the U.S. Department of Energy, a project was completed in 2005, which studied the use of a special pneumatic capsule pipeline (PCP) system, driven by linear induction motor (LIM), for transporting minerals and/or mine wastes. In this study, the pipeline is a rectangular tube of 1m × 1m cross section. The capsules are similar to railroad cars running on small rails imbedded in the tube. A LIM is placed AT the entrance of the tube to transfer power electro-magnetically from the LIM to capsules. The capsules going through the LIM, propelled by the electromagnetic field generated by the LIM, move faster than the air and hence impart energy into the airflow. This in turn pushes the capsules in the tube forward. When the tube is long (say longer than 10 km), additional LIMs may be needed along the tube to serve as booster pumps. An advantage of using LIMs instead of blowers as used in ordinary PCPs is that capsules can pass through the LIMs unhindered. This enables the use of booster pumps for long tubes. It also enables PCP to achieve much higher cargo throughput than that of PCPs using blowers, thereby reducing unit cost ($ per ton-km). Advantages of using capsules with steel wheels running on steel rails in the tubes including: (1) contact friction is only about one-fifth of that using rubber tires, thereby conserving energy, (2) capsules can run at a much higher speed than those using rubber tires without overheating and damaging the tires, and (3) rails make capsule motion control simple; they restrict lateral movement of capsules, and make branching easy-by using standard rail crossing equipment. This advanced PCP system combines the advantages of LIM with the advantages of rails, resulting in a super-efficient tube system having throughputs an order of magnitude greater than that of conventional PCPs, and having an energy efficiency better than railroad transport. Analysis shows that the system is highly cost-effective when throughput is high-at least 5 million tons per year. The system is most suitable for long-distance transportation of minerals (including coal and flyash) and wastes (including both mine wastes and municipal solid waste).

Jan 1, 2014

By H. R. Stahl

FIVE mills are operated in Southeast Missouri by the St. Joseph Lead Co.; these have a total rated capacity of 24,300 tons per day divided as follows: Federal, 12,000 tons; Leadwood, 4800 tons; Desloge, 3600 tons; Bonne Terre, 2400 tons; and Mine La Motte, 1500 tons. These concentrators are similar in a general way, differing mainly in size and type of equipment and in minor variations in flow sheet. No attempt is made rigidly to standardize procedure in the various mills in spite of a general similarity in the ores. Each mill may be regarded as a separate laboratory in which new ideas and changes may be tried. A generalized description of the process is given, noting important differences in procedure at the various plants. The concentration process may be divided into five main stages: dry crushing, wet grinding, desliming and classification, tabling, and flotation.

Jan 1, 1947

By E. P. Pfleider

Important economic planning by industries, companies, financial firms and governments is predicated on estimates of future growth potential. Prior to the passage of the Taconite Amendment by the people of the State in November 1964, various admittedly conservative forecasts were made of the future of Minnesota's iron ore industry. Since that date, 3 new taconite plants are under construction, 2 are being expanded, one has just gone "on stream," and a seventh is in the design stage. These plants have a total capacity of about 35 million tons of pellets annually. The pessimism of 1964 today is being replaced by unbounded optimism. In the light of such recent developments, it becomes essential to update forecasts related to production, employment and capital investments. New projections show 50 to 58 million tons of pellet production from Minnesota by 1975. This tonnage, together with some 6 to 8 million of natural ores, should provide an annual full-time employment of 15,000 by the mining companies, plus 700 in related railroad and power producing activities and 1000 in plant construction. Total capital investment in new plants should reach $1.5 billion by 1975 and $2 billion by 1990. These current estimates indicate that the conservative goals as set in 1964 for the year 1990 should actually be achieved by 1975 or 1980. BACKGROUND Various forecasts1,2,3 have been made of the future consumption and production of iron ores within the United States. The most recent of these is by Harrison,1 delivered at the American Mining Congress meeting in Las Vegas in October. His estimates reflect the latest iron ore developments on a world wide front as well as the accelerating trend toward pellets. Minnesota's Natural Resources council prepared a detailed report in 1964 outlining the various factors that affect the future of Minnesota's iron ore industry. It presented estimates predicated on the

Jan 1, 1967