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By A. Atrafi, L. Barroilhet

The top size of particles in the flotation of potash ores, which can be as large as 4 mm, exceeds by far the top size in other flotation plants. It is then understandable that while long chain amines are used in the flotation of fine fractions (below 0.8 mm) of potash ores the coarse particle flotation also requires an extender oil. While new and very promising fluidized-bed flotation machines (e.g. HydroFloat) constitute a significant development in the flotation of coarse particles, in the area of extender oils, as reviewed in 2007 by Strathdee, Gotts and McEachern, there have been no new developments to replace the industry standard asphaltene-based carcinogenic extenders. This situation first of all results from the experimental problems that arise when water-soluble minerals like sylvite are to be tested in saturated brine. Both oils and longchain amines are water/brine insoluble. The oil with the amine dissolved in it can however be emulsified and then used as an extender oil. Such oil droplets must wet KCl particles and the emulsion must be stable to avoid handling problems. In this paper we test the use of the phase inversion technique as a method of studying wettability of KCl particles by the oil in saturated brine, and the effect of amine dissolved in this oil on the wettability. The results show that this relatively simple technique can be used to characterize the wettability of fine KCl particles by the tested oil and to determine the effect of added amine on it, and so it can be useful in selecting proper extender oils.

Jan 1, 2016

By B. Simser

Noranda?s Brunswick mine is a 10 000 t/d producer of lead-zinc-copper-silver ore that has been in operation since 1964. Mining of this multiple lens deposit is primarily by blasthole stoping techniques between 400 m and 1200 m below surface. The combination of a high overall extraction ratio, an overall steeply dipping tabular shape, and high horizontal stresses (twice the vertical) have elevated the induced stress regime to levels comparable to much deeper operations. Improved mine design, and a better understanding of how the rock mass responds to mining in high-stress environments is essential to improve overall recoveries and maintain safety. Seismic monitoring has proven to be an essential tool at Brunswick, for both short-term safety of workers, and long-term strategic planning. Practical case studies illustrate how seismic data, particularly source parameter information, can be used to measure the rockmass response to mining and improve mining layouts in difficult regions. As the global trend continues toward mining in deeper, higher stress environments (e.g., South African Witswatersrand Basin, Sudbury Basin) and as local extraction and thus ground stresses continue to increase in existing deposits, seismic monitoring will play a critical role in mining safely and economically.

May 1, 2004

By G. F. Trainor

At the Canadian Natural Resources Limited (CNRL) Horizon Mine they use Wenco International Mining Systems Ltd (Wenco) Fleet Management System to monitor and control their production fleet with the goal of increasing operator productivity and safety, and raising dispatcher awareness and control. Amongst the broad productivity goals CNRL wanted to achieve with help from the system was a very specific need to blend ore at the truck level. CNRL uses 25m x 25m block geological model information to represent their complex ore body. Wenco's High Precision GPS application, BenchManager provides precise graphical actual-vs-design operator feedback and system integration. Together the two companies advanced the BenchManager product to meet CNRL's needs by using live camera feeds to compare activity with data collection that ultimately lead to changes in the algorithm to include enhanced GPS indicators and the support of a GLONASS assisted solution generating distance and bearing information.

May 1, 2011

By M. Okada

Consumption of refined copper in Asia, especially in China and India, has soared, and the copper price is at its historic height. New smelters and refineries have been built in the region with state-of-the-art technology to meet the unprecedented demands. Supply of copper concentrate, on the other hand, has fallen short of the growing demand for concentrate by the smelters and refineries with expanded production capacities. The shortage of copper concentrate is attributable to the delay in the mining development, caused by the prolonged price slump of before 2005. The mismatch between supply of concentrate and smelting and refining capacities may cause disorderly movement of copper price, and hamper the sound development of the industry. The recent high copper price may prompt substitution with alternate materials. With electrical and thermal conductivity and workability, copper is one of the most customer-friendly materials. It is regrettable for both customers and suppliers if the high copper price would become an impediment to promoting copper use. Some outdated and environmentally unfriendly facilities still operate. In view of recent lower-grade copper concentrate with higher sulfur content, these facilities must reform their equipment to environmental-responsive one. The current level of per capita consumption of refined copper in Asia shows that the demand of copper will further grow. It is necessary to realize stable supply of refined copper and stable copper price, to help developing countries including China and India to economically take off. Hence, it is essential that the development of the copper industry be accompanied by environmentally friendly facilities, and harmoniously increased capacities between mining and smelting and refining.

Jan 1, 2007

By R. Matusewicz

The key drivers for the copper smelting industry are a complex mix of economic and "human" factors which combine to drive technology in new directions and can provide a strong indication of future industry trends. Recent examples have been the drive to achieve increased scale of production and resultant cost efficiencies by using a single furnace high intensity smelting vessel, and the broad acceptance of Top Submerged Lancing (TSL) technology for this duty. The development and adoption of continuous converting processes to counter the increased pressures faced by the Peirce Smith converting process is another example of the need for innovation. This paper discusses the merits of the continuous converting process, describes how the Ausmelt TSL batch converting process has been adapted to the new Ausmelt Continuous Copper Converting (C3) process in response to these industry trends and examines the Ausmelt continuous converting flowsheet options available to the end user.

Jan 1, 2007

By M. J. Merwin

Heat treated seamless tubular products are processed in a fashion that can be easily modified to produce dual phase microstructures, through the implementation of intercritical soaking prior to quenching. Dual phase steels are known to possess low yield strength compared to tensile strength. The steel line pipe market is interested in low yield-tensile ratio materials for application in reel barge pipe laying operations. In the current work compositions of commercially produced material already in use for the line pipe market were examined and dual phase microstructures were successfully developed. The microstructure and properties of the materials were found to be stable over the range of intercritical temperatures employed. Tempering temperature and, somewhat unexpectedly, small chemistry differences were found to have the largest influence on properties. Excellent toughness performance was observed in samples tempered at temperatures in excess of 550°C. Tempering in this temperature regime produced materials with strength suitable for application as API X60 line pipe. A difference in tensile strength between steels of similar chemistry was observed, and is not fully understood at this time. Welding performance was considered through simulation of three regions of the heat-affected zone. Neither intercritical temperature, nor tempering temperature, were found to have a significant influence on the heat-affected zone properties. The peak temperature achieved in the thermal cycle was the only significant factor. The hardness of the heat-affected zone was found to increase continuously with increasing peak temperature. While toughness was found to be low for both partially-transformed and coarse-grain heat-affected zones, the toughness of the fine-grained heat-affected zone was substantially better. Based on the results found in this laboratory study, a limited production trial is expected.

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 William G. Pariseau

"This contribution describes linkage of stress concentration at the face of tabular excavations, for example, longwall coal mine panels, at a meter scale to surface subsidence at a kilometer scale. Joints are considered according to orientation and spacing at an intermediate scale. A new dual-node, dual-mesh technique based on first principles uses a multi-scale technique that allows for computing whole mine surface subsidence while also allowing for computational details of stress, strain and displacement about main entries and pillars, panel entries, and bleeder entries. The technique is implemented in a conventional continuous Galerkin finite element program that has been in use for many years.The advantage of the dual-node, dual-mesh technique is the capability to do a whole mine analysis that takes into account interaction between all sections of a mine where stress transfer over long distances is often the rule rather than the exception while at the same time allowing for details of stress concentration at working faces where caving is initiated and subsidence begins. The technique, outlined recently during ARMA 2014 (Pariseau, 2014), is applied to an underground coal mine in central Utah where mines are developed from outcrops in steep canyon walls. Meshes contain over 10 million, three-dimensional nodes; runtimes are typically overnight, as a practical matter. Results compare favorably with mine subsidence measurements made over a period of several years and show the capability of this new technique to provide useful design guidance for tabular deposits such as underground coal mines. The role of variability or uncertainty in strata properties is illustrated in element safety factor distributions about development, bleeder and main entries and pillars. Such details are new in this contribution. Energy tracking for mine-induced seismicity is also new. Results show a high correlation between number of events and failed elements and suggest a simple index to mine induced seismicity."

Jan 1, 2015

By John Eggert, Paul Benford

"Since 1982, Placer Dome Inc. -Dome Mine has steadily increased mill throughput. Tonnage has increased from a nominal design capacity of 3000 short tons per day, attained in 1985, to 4130 stpd by the end of 1992. Many minor and major circuit adjustments were tried to maximize tonnage.Having utilized most conventional means of increasing tonnage, further increases required a newer approach. This paper discusses the Dome experience in the development and implementation of an expert system.The Comdale/C system was chosen for a controlled trial. The criteria for acceptance were: increased tonnage had to be sufficient to pay for the system; the increase had to be visibly sustainable and the mill operators had to be willing to accept the system.The criteria for purchase were met during the trial and the system was purchased. The system continues to perform well. The tonnage throughput increase has been sustained while operator acceptance remains high.IntroductionPlacer Dome Inc. -Dome Mine is Canada's oldest operating gold mine. The mine was among the first established in the Porcupine camp in what is now Timmins, Ontario. The City of Timmins is located approximately 500 miles or 800 kilometres north of Toronto. Figure 1 shows a map of the province of Ontario and the mine location.In 1912, milling began at a rate of 350 short tons per day. With two minor exceptions, milling has been continuous since this time. The first of these shut downs was in 1918 during the first world war. The war created labour shortages which forced the mine to stop production for more than a year. The second was in 1930 when fire destroyed the mill."

Jan 1, 1994

By George Brien, O&apos

The history of the lighting of mine workings dates back to the early part of the 18th century, when small candles known as tallow dips, were used. These were set or held in a lump of wet clay. When looking for gas the flame of. the candle was reduced to a mere glimmer by surrounding the wick below the flame with clay. The candle was then very cautiously raised from the floor toward the roof, the observer screening the brighter portion of the flame with his hand and watching for the first appearance of the pale blue cap above the flame, even at that time, known to indicate the presence of gas. When this appeared the candle was lowered quietly and its flame extinguished before attempting to drive out the gas. A very common and dangerous practice adopted at that time was to get rid of the gas by firing it. This was done by a person selected for his nerve rather than for his caution. Dressed in a? suit of dampened sackcloth or leather, this man well termed a "fireman", would lie prone on the floor of the roadway and light the gas above him by raising his candle fastened to the end of a long stick. If he survived, which was not always the case, he would withdraw promptly to fresh air after the flame had passed over him.

Jan 1, 1924

By G. A. Gross

"The Soviet Union has enormous reserves of iron ore in many different kinds of deposits that are widely distributed in this vast land area. The present iron ore industry is based mainly on deposits in Precambrian cherty iron-formation at Krivoy Rog, Kursk and Murmansk. Extensive reserves of both naturally enriched hematite ore and magnetite iron-formation in these areas alone could sup-ply all the domestic ore required for several hundred years.Many contact metasomatic magnetite deposits discovery in recent years in the eastern Ural Mountain belt and east of the Kusnetsov basin in Siberia are being developed, with ore reserves measured in billions of tons. Oolitic limonite-chamosite-siderite ores of Cretaceous and younger age at Kerch on the Black Sea and around the east and southern perimeter of the West Siberian basin constitute some of the largest concentrations of iron in the world. These sedimentary ores are low grade, of poor quality and difficult to beneficiate. Banded jasper magnetite and hematite iron-formation in volcanic rocks of Devonian age in Kazakhstan and along the Mongolian border are of special geoloica1 significance.Iron deposits in the Krivoy Rog and Kursk areas were examined and a large number of geologists discussed their work on deposits in many other parts of the Soviet Union during the writer's seven-week study tour of mines and research institutes in Moscow, Leningrad, Novosibirsk in Siberia and Kiev in the Ukraine. The descriptive geology of iron deposits of useable ore and of marginal material has been well documented in the course of systematic work and a large number of scientists are studying fundamental problems on the origin and treatment of iron ore."

Jan 1, 1967

By S. D. Anitha Kumari, T. G. Sitharam

"The huge urbanisation of the world cities have invariably resulted in enormous requirements of development in transport and other facilities. As the surface space available for the construction of these infrastructural facilities is found to be inadequate, underground space is widely used recently for this purpose. However, to understand the behaviour of these underground structures through experiments under various loading conditions is not practically feasible. Hence numerical methods have widely been used to model these structures and predict their behaviour. The underground structures generally rest on soil or rock. Depending upon the properties of the material surrounding the tunnel, the deformation pattern and the stress contours vary. If the tunnels are placed on soft ground at a shallow depth, the presence of existing structures will add to the stresses and strains developed. In the case of densely populated cities, tunnelling operation may result in huge damages if the settlements are not within the desirable limits. This may in turn lead to the collapse of the tunnel along with adjoining structures. So the determination of stress levels associated with the yield of wall due to excavation is very important and necessary supports and reinforcement should be provided. Numerical simulations using discrete element method (DEM) and finite element method (FEM) have been done to understand the stress variation around single and twin tunnels. Studies are also done to quantify the improvement of stability on the introduction of lining around the tunnels in a weak cemented soil mass like sandstone.INTRODUCTIONMost of the life line facilities which include pipelines for electricity, water, communication, sewage, gas, roads, metro, utility tunnels etc in modern urban areas are underground structures. Infrastructure development is crucial for any city and sustainable development urges for underground constructions. Accordingly, there is already a great demand for tunnels to be constructed in difficult and crowded urban settings. This results in the fact that a large number of risk factors are associated with tunnels in these densely populated urban areas. These constraints pose threats to tunnel construction and also demands for minimal disturbance to the public and to the surrounding utilities. One of the most important factor to be considered while designing an underground structure is its stability with respect to the surrounding medium and adjoining existing structures. In this study, a comprehensive presentation of the numerical modeling of single and twin tunnels adopting two different methods is presented."

Jan 1, 2015

By W. J. Wolfe

"Quartz Hill is a large, low- to moderate-grade quartz vein stockwork porphyry molybdenum deposit, discovered in 1974 during a regional stream sediment geochemical reconnaissance survey of southeast Alaska conducted by United States Borax and Chemical Corporation. Mineralization is localized in the upper parts of an Upper Oligocene (30 Ma) composite quartz monzonite stock which is emplaced discordantly into older Cretaceous to Early Tertiary terrain of the Coast Range igneous metamorphic complex of the northwest North American Cordillera. Subsequent fault-controlled, complex multi-stage intrusion, concentrated in the core of the Quartz Hill stock, produced successive pulses of hydrothermal alteration and molybdenum mineralization at about 27 Ma. Overall, the deposit is tabular and flat-lying and well suited to open pit mining. The 0.05% MoS2 grade limit covers an area of approximately 1500 m by 2750 m and extends to a maximum depth of 520 m below surface. Details of grade distribution show two separate lobes of higher grade material within the larger low-grade deposit.A ten year program of exploration drilling, underground development, sampling and metallurgical testwork led to a 1983 feasibility study based on a resource of 1600 million tonnes grading 0.127% MoS2 at a 0.08% MoS2 cutoff The large size of the deposit and its homogeneous grade distribution, typically showing gradual outward decrease of grade, makes in pit grade selection practical at several cutoff levels. Cominco Ltd. now reports a Probable Resource of 210 million tonnes averaging 0.22% MoS2 with a further Possible Resource of 1100 million tonnes averaging 0.12% MoS:z. At low molybdenum metal prices which have persisted for 10 years since the molybdenum price spike of the late 1970s and early 1980s, the Quartz Hill deposit is sub-economic."

Jan 1, 1995

By M. Behrouz

Thermal power plants convert thermal energy due to nuclear reactions or the combustion of coal, gas, heavy oil, or some other hydrocarbon to electrical energy. They consist of a variety of equipment, such as boilers, turbines, generators, cooling towers, and auxiliary equipment. Any factor that affects the equipment efficiency affects the overall efficiency. Analysis of the cooling tower and raw water using the Langlier Saturation and Ryznar Stability Indices showed that the cooling water at Sarchesmeh was slightly scaling with respect to silica. Cold lime softening was found to be a cost-effective method to produce cooling water with adequate properties to reduce the cooling water make up from 85 to 70 m3/h and blow down rate from 35 to 20 m3/h.

Jan 1, 2007

By E. S. Moore

In order that a logical conclusion may be reached regarding the possible occurrence of commercial iron deposits in Canada it is necessary to consider some important producers found elsewhere on this continent. A study of such deposits reveals the fact tl:~at a number of distinct types are producing large tonnages of ore. These types may be classified according to origin and occurrence as follows: (1) Bedded sedimentary deposits. (2) Contact metamorphic deposits. (3) Residual ores. (4) Lenses in metamorphic rocks and m some cases of uncertain origin. In addition to the types listed there are other deposits which have contained or do contain considerable ore and they either have not been worked on a large scale or they have been nearly exhausted. These include the following types: (1) Magmatic segregations. These are mostly titaniferous magnetites. (2) Dikes of magnetite of igneous origin. (3) Bog and lake ores in glacial drift. (4) Black sand placers.

Jan 1, 1925

By Neil Campbell

"The Pine Point area is on the south shore of Great Slave Lake, 510 air miles north of Edmonton and J JO miles south of Yellowknife, N.W.T. The occurrence there of lead and zinc was reported in J 899 by R. Bell (5) of the Geological Survey of Canada, and in the following years several claims were staked and some prospecting was done. In 1928 Atlas Exploration Co. took over the property containing the discovery occurrences. In 1929 The Consolidated Mining and Smelting Company of Canada Ltd. (""Cominco"") and Ventures Ltd. participated with Atlas in forming the Northern Lead-Zinc Co., which, under the direction of J. M. Bell, carried out 24,499 feet of drilling in the discovery and surrounding areas. Two shafts and many surface pits were also sunk. This work showed that the discovery deposits contain about 500,000 tons of lead-zinc ore, but no new orebody was found.In 1936 D. F. Kidd (11) drew attention to the highly significant space relations between the base-metal discoveries at Pine Point and the projections of certain major Precambrian faults mapped earlier by C. H. Stockwell. Geological work by Cominco in 1940 and subsequent years suggested the presence of mineable deposits within a belt of land including part of the area of earlier field work and extending far beyond it. Between 1946 and 1954 exploration financed by Cominco and Ventures Ltd. included 182,950 feet of diamond drilling, 383 feet of sinking, and 240 feet of drifting, raising, and crosscutting. This work was successful in finding substantial quantities of new ore in places where bedrock is completely concealed.The topography is one of low relief, characterized in many places by swampy muskeg and shallow, marl-bottomed ponds. The area where ore has been found is generally higher ground which, though not well drained, is comparatively dry. It is also marked by raised beaches and a few sand dunes overgrown by small spruce and pine. Bedrock is generally overlain by a variable thickness of hard, glacial boulder clay. This in turn is covered by silt, sand, and gravel, probably deposited from the waters of Great Slave Lake, which formerly extended many miles beyond its present southern shore."

Jan 1, 1949

By Elizabeth Wademan

Recessions Eventually End ??Companies aggressively cutting production and inventories ??these will come in-line with demand ??U.S. home inventories are declining ??Housing becoming more affordable ??Global trade recovering after collapsing ??Lower oil prices should act as a stimulus Protracted Deleveraging Process Beginning ??Era of leverage-driven consumption is over ??Greatest destruction of consumer wealth since WWII ??Consumers will no longer be able to substitute capital gains for savings ??Shift towards savings will be a headwind to economic growth ???Paradox of Thrift?

May 1, 2009

By C. A. Ingram

The Cigar Lake ore body is a high-grade uranium deposit situated within water-saturated sandstone. In order to extract the uranium ore remotely, ensuring minimal radiation dose to workers, and also to access the ore from stable ground, the Jet Boring System (JBS) was developed. This method of mining involves drilling a pilot hole up through a frozen ore body and utilizing a high-powered water jet to mine out cavities. During the mining process an ultrasonic sensor will be used to provide feedback to the operator, who is located beneath the ore body, as to the dimensions of the cavity. However, more precise data is required to determine final shape, volume, and location of the cavity for mine planning purposes. Selecting a device that will provide sufficient range data in the challenging environment will be vital to optimizing the mining process. Major issues include fog build up and flying debris during mining, and an environment that is wet, dark, and cold A test cavity has been designed and constructed at the Saskatchewan Research Council (SRC) so that a study comparing three different technologies, as prospective candidates for the survey system, can be conducted. The devices being evaluated include a Senix ultrasonic sensor, an MDL Cavity Auto-Scanning Laser System (C-ALS), and a MESA Time of Flight (ToF) camera. The ultrasonic sensor is known to provide range data in foggy conditions but has low accuracy. The C-ALS has been developed for surveying remote cavities but is expensive and does not provide reliable data in fog. The ToF camera provides a high volume of data in a short time period, with potential to provide accurate information in extreme conditions, but has not been tested in a mine cavity application. Iterative closest point (ICP) registration is applied in an attempt to create a 3D point cloud from the scan data and to also compute rotation and translation of the ToF camera. This paper presents an overview of the challenges involved in conducting a survey within a JBS mined cavity, the analysis used to determine the suitability of each device, and the data collected from the test cavity.

Aug 1, 2013

By E. Krause, V. G. Papangelakis, S. Garg, R. Mahadevan, E. Edwards

"Bioleaching uses iron and sulfur-oxidizing bacteria to extract base metals from sulfide minerals. As bioleaching involves breaking the iron-sulfur bonds by ferric attack, the biologically mediated rate of iron oxidation is recognized to play a key role in influencing the overall kinetics. In this study, we investigate the catalytic ability of an indigenous AMD culture for oxidizing Fe(II) in solution. This culture was subsequently adapted on pyrrhotite tailings (0.6% Ni) by gradually increasing the solids loading. Results from this study show that such an adaptation reduces the initial lag phase in the biotic oxidation of Fe(II), thereby allowing for a higher Ni extraction when compared to experiments with an un-adapted culture at a similar solids loading. The use of adapted cultures also helps to reduce the residence time for bioleaching of Ni from pyrrhotite tailings. INTRODUCTIONAs the world demand for pure base metals grows; the mining industry is increasingly faced with the burden of processing lower grade ores and mining waste streams in order to recover the occluded metal VALUES ((Watling, 2006). The extractive metallurgy of nickel from sulfide minerals focuses on using a combination of mineral processing, pyrometallurgical (smelting) and hydrometallurgical techniques to extract Ni from its ore bodies.Pyrrhotite (Fe1-xS) is commonly found in association with pentlandite and chalcopyrite in sulfidic Ni ores, such as those found in Sudbury, Ontario, and in Russia, e.g. Norilsk. The vast majority of this pyrrhotite needs to be removed using mineral processing techniques, in order to minimize the Fe and S contents of the concentrates that proceed on to smelting. If all pyrrhotite were left in the concentrate, much more slag and SO2 would be produced, and the smelter throughput would be limited. Beneficiation of Ni sulfide ores leads to the rejection of unwanted constituents as mining wastes, which may still contain extractable amounts of Ni (Edgar Peek et al., 2010)."

Jan 1, 2012

By I. M. Marshall

A review of technical literature covering Canadian mining emphasizes the advancement and changes that have been made in mining practice. However, current technical publications rarely outline basic principles or state definite rules that govern profitable mine operation. it may be argued that the broad principles of mining have long a go been outlined in various handbooks, text-books, and periodicals, and that these principles never alter. This is in great part true, but modern machinery, improved meta1-lurgical practice, and other advances, have in part modified these principles or changed the manner of their application. Many engineers hesitate to state specific rules, because it is so easy to quote an exception to a rules that any such statement appears to lose weight upon its very utterance. The exception to rules, and the reluctance to formulate rules, has forced such maxims as "the only rule in mining is the point of a pick," and "gold is where you find it". As an illustration of rules and their exceptions, one might quote the time-honoured maxim that a mill should not be built before a shaft has been sunk on a property in point of fact, Canadian mining history is replete with examples of wasted capital where a mill was built before a shaft had been bottomed. Y et this past year has seen a property enter profitable production whereon the building of the mill was started before the shaft was sunk. Instances such as this should not be accepted as evidence that a rule has been overthrown, but rather as an exception to the rule. The case cited pays tribute to the application of the diamond-drill combined with the correlation of sound geology. Incidentally, both these features emphasize a modern trend in the development of Canadian mining properties-a trend that is perhaps worthy of further comment. It is such trends that affect the principles of mining or modify their application. It is with such that this paper deals, at ]east in part. It is hoped that the statement of principles and the opinions herein outlined will be of sufficient interest to arouse discussion.

Jan 1, 1939