Search Documents

By R. Bainbridge

"IntroductionTHE LEAD SMELTING Department of The Consolidated Mining •and Smelting Company of Canada, Limited (Cominco), at Trail, B.C. treats materials from numerous sources for the recovery of lead, •and, of secondary importance, for the .recovery of sulphur as S02• The Department's sintering section has a .capacity of 1,500 tons daily. This section is being replaced by •a new charge-•handling and sintering plant with a daily capacity of 2,000 tons of finished sinter. Materials handled in the sintering section comprise concentrates, ores, and fluxes from Company mines and from 'custom' (independent) producers, together with intermediate products from various plants of Cominco'•s Metallurgical Division, all of which must be treated to, make up a chemically balanced charge of a predetermined lead content for the sintering plant.As received, 80 •per .cent of these materials are finer than 200 mesh, and one-quarter of the tonnage (dry basis) is a slurry .at 30 to 40 per cent moisture. This slurry, a -residue from the electrolytic zinc operation, was, for many years, partially dried before being mixed with other dry materials to make up the sinterplant charge.Some experimental work carried out in 1937 indicated that the metallurgy of the sintering operation could be improved by adopting a technique of 'wet-mixing' followed by controlled drying and nodulizing."

Jan 1, 1953

By M. Dupuis

Recently, a new approach to controlling alumina feeding in a H.H. cell has been proposed [1, 2 and 3]. This approach, labeled In Situ aluminium cell control, is based on a correlation between the slope of the cell voltage during a no feed observation period and the dissolved alumina concentration in the bath. Once the dissolved alumina concentration has been estimated, a primary calibration surface uniquely relating the dissolved alumina concentration and the anode-cathode-distance (ACD) to the cell voltage is used to estimate the cell ACD. Once both the alumina concentration and the ACD have been estimated at the end of the observation period, a PID controller can be used to regulate the rate of alumina feeding using only the normalized cell voltage to calculate the error between the estimated dissolved alumina concentration and a target value. The In Situ aluminium cell control algorithm has now been tested with the Dyna/Marc [4, 5 and 6] cell simulator demonstrating that it should be possible to control a H.H. cell in this manner with less variation in the dissolved alumina concentration and other process variables producing a prediction of improved cell current efficiency and power efficiency.

Jan 1, 2011

By S. Feinstein, I. Reznik, Y. H. Hatzor, O. Shitrit, Y. O. Rosenberg, H. J. Vinegar, S. Nguyen

"We report the effects of porosity and total organic carbon (TOC) content on the mechanical behavior of organic-rich chalks, based on laboratory measurements. The organic-rich chalks are from the Senonian Ghareb and Mishash formations. This deposit is an immature oil-prone source rock, about 300 meters thick, situated at shallow depths (several hundreds of meters) in the Shefela basin in central Israel. The study is based on core data collected from the Zoharim borehole.Three main phases comprise the bulk volume of this rock: 1) carbonate mineralogical phase (predominantly calcite); 2) pores (mostly saturated with brine); and 3) solid organic phase (type IIS kerogen). The mechanical effects of porosity (23-45%) and TOC (4-19%) are evaluated based on bulk incompressibilities vs. volumetric fractions analysis. Volumetric fractions of mineralogical and organic phases were obtained by porosity, density and TOC measurements. Saturated rock bulk moduli were measured through ultrasonic velocity measurements. Saturated rock bulk moduli correlate best with the sum of kerogen and pore volume fractions, rather than each of them separately. The volumetric fractions were also used to define the range of bulk modulus of the organic-rich chalk, using the Hashin-Shtrikman upper and lower bounds. Based on Marion's Bounding Average Method (BAM), the normalized stiffness factor of the chalk averaged at w=0.197, indicating a soft pore geometry. Using the average normalized stiffness factor, the BAM predictions showed excellent match with the saturated rock bulk modulus and the sum of kerogen and pore volume fractions. Based on our findings, it is inferred that kerogen grains do not support the solid skeleton but are distributed between the minerals grains. We also propose here a straightforward approach for calculating the Hashin-Shtrikman bounds, based on TOC and porosity measurements. The mechanical effects of porosity and TOC indicated here are very important for the understanding of the influence of immature kerogen presence in highly porous chalks, as the Ghareb and Mishash formations."

Jan 1, 2015

By M. Pearson, J. Irvine, L. Mercer, P. Lauzon

Severe service ball valve performance has a direct impact on the mechanical availability of high pressure oxidation and leach plants. The primary function of these valves is to isolate the autoclave for maintenance. Valve failure has historically contributed significantly to the maintenance downtime of these process plants. An understanding of the root causes of valve failures is the first step in increasing the reliability of the severe service ball valves. A rigorous failure analysis practice has been developed by Hatch for investigating refractory failures in furnaces and kilns based on Kepner-Tregoe methodology. The method has also been modified for valve failure analysis. From a root-cause failure tree analysis of each of the valve components, a list of all potential valve failure mechanisms was developed for ranking and evaluation, along with recommendations for further valve development. The purpose of this paper is to present the reader with the modified Kepner-Tregoe method and examples of this analysis.

Jan 1, 2004

By P. Su

Friction stir spot welding of a range of Mg-alloys is investigated (AZ91, AZ31, AM50 and AM60). The peak temperatures during friction stir spot welding of all Mg-alloys are close to their solidus temperatures. Also, the apparent material viscosity of Mg-alloy sheet is lower than that when Al-alloy sheet material is spot welded. This is important since it means that the widths of the stir zones forming during spot welding of Mg-alloy sheet are smaller than those when Al-alloy sheet is welded (when identical welding parameter settings are applied). These lower apparent viscosity values must be taken into account during numerical modeling of the Mg-alloy spot welding process. The efficiency of energy utilization is very low when Mg-alloy sheet is spot welded and is of the same order as that when fabricating Al-alloy sheet. The energy generation contributions of the rotating pin and the tool shoulder are investigated. When the spot welding operation is carried out without the application of a dwell period, the contribution made by the rotating pin vis-à-vis energy generation is around 66%. The contribution made by the tool shoulder increases to about 65% when a dwell period of four seconds is incorporated during the spot welding operation. This increase results from a longer contact time between the tool shoulder and material within the stir zone, The failure load during overlap shear testing increases when the bonded area and the energy input increase during spot welding. Sample failure initiates from unbonded regions and from discontinuities at the edge of the stir zone. The formation tendency of discontinuities is increased when Mg-Alloy sheet is spot welded because of the limited deformation characteristics of the base material at lower temperatures.

Jan 1, 2006

By Alan Bauer, Melvin A. Cook

Measured detonation pressures of "prills and oil" (94/6 ammonium nitrate/fuel oil) and three of the new "slurry" blasting agents are presented and compared with computed, ideal detonation pressures and with detonation pressures expected from the measured detonation velocities. Results seem to show that the peak pressure in the detonation wave in these cases is the Chapman-Jouguet pressure and that no "spike" exists in these detonation waves. The absence of the Zeldovich-von Neumann "spike" is noteworthy in view of the very long reaction zone lengths of these mixtures. The measured detonation pressure of one of the slurry blasting agents (DBA-3") under steel confinement ( 172 kilobars) is shown to be considerably greater than the ideal detonation pressure of 75 per cent gelatin dynamite (p. = 135 kilobars) despite the fact that the detonation was still somewhat non-ideal in "DBA-3," its computed ideal detonation pressure being 180 kb. The popular 94/b AN /FO blasting agent exhibited a detonation pressure of only 13.5 kb in 5" paper tubes, but 37.5 kb in 5"• steel pipe compared with a computed ideal pressure of 40 kb.

Jan 1, 1961

By F. S. Thurner

This paper, a description of the new ore-unloading and stockpiling facilities at the Sydney Works of DOSCO Steel Limited, deals with a new approach to arrive at the most economical solution to combine ore unloading facilities for common bulk carriers and for different types of self-unloading vessels. Also discussed is the design and installation of a 1-mile-long steel-cord belt conveyor sys-tem with a most modern type of mobile belt conveyor stacker, along with automatic and semi-automatic controls for the entire ship-unloading and stockpiling operations.

Jan 1, 1968

By C. B. Ndimande, C. Ntsele, M. Lisso, L. Arlow

"In the processing of UG2 platinum ore, stirred milling technologies are dominating regrind applications that require grinding the particles to P80s’ in the region of 45 µm. For this application stirred mills are 30–40% more energy efficient and require a smaller foot print compared to traditional tumbling mills. In this work a study was carried out using a batch pin mill and three scales of Stirred Media Detritors. A laboratory scale pin mill, a pilot scale Stirred Media Detritor with an installed power of 18.5 KW and two industrial scale Stirred Media Detritors in continuous operation, with an installed power of 355 KW and 1,100 KW were used. The industrial scale SMDs were in the secondary grinding section of a mill floatmill float (MF2) UG2 processing plants. The tests were focused on assessing the effect of feed rate and percent solids on power consumption and product fineness at lab scale, floatation response of the SMD product at pilot scale and on an industrial scale, the effect of feed rate on energy consumption and product fineness. The measurements obtained were feed flow rates, mill power and from the samples cut, particle size distribution of both feed and product. Specific energy was observed to increase with increasing percent solids over the 30wt% to 80wt% studied. Floatation response tests of the pilot scale SMD products show improvement in grade. Specific energy and reduction rations are observed to decrease with an increase in feed rate.INTRODUCTIONThe purpose of comminution in most mineral processing applications is to liberate the valuable minerals from gangue so that they can be recovered in subsequent separation stages. Most precious and base metal plants treat low grade fine-grained ores which require a higher degree of size reduction to yield the necessary degree of liberation (Partyka & Yan, 2007). Many authors have shown that the relationship between product size and grinding energy consumption is exponential, the finer the product from the comminution device, the higher the energy consumption (Gao & Weller 1993; Napier-Munn, Morell, Morrison & Kojovic, 1996; Jankovic, Valery & La Rosa, 2003). The suggested reason for this kind of relationship is that smaller particles have fewer flaws and higher strength than larger particles. Particles with fewer flaws and higher strength require higher energy for breakage to occur. One of the challenges most plants face is that of efficient energy utilisation in the liberation of the mineral from these complex ores. Conventional tumbling mills are not energy efficient in fine and ultra-fine grinding applications because some of the energy is spent on moving the charge and does not go directly into breakage. Stirred mills have been found to be about 30% to 40% more efficient and require a smaller foot print compared to traditional tumbling mills for regrind applications that require product size with P80s’ in the sub 45 µm regions (Radziszewski & Allen, 2013). Stirred mills are able to produce fine product because they can achieve a high number of stress events per unit time and volume compared to tumbling mills (Kwade, 1999a). To minimise energy usage without compromising product quality, the mining industry has adopted stirred milling technologies for fine and ultra-fine grinding (Radziszewski & Allen 2014; Kwade, 1999b). The south Africa platinum group metal (PGM) industry alone had over 40 stirred media mills installed by 2011 (Rule, 2011). Of that 40, 13 were in the ultra-fine grinding (UFG) application and the rest in main stream inert grinding (MIG)."

Jan 1, 2016

By Gerry Doeksen

The paper deals with three case studies: (a) the handling of wet concentrates (5 to 8 per cent moisture) through feed bins; (b) the handling of the same product in rail cars; and (c) the handling of dry concentrates (less than 0.5 per cent moisture) through feed bins. In each case, the paper discusses the problems of rat-holing. In each of cases (a) and (c), there is a discussion on the consequent extreme variations of feed rates coming from the feeders, making automation of process control difficult to impossible. Currently available bin-flow theory and flow property tests are used as aids in redesigning the bins. The paper concludes with illustrations of the final results after the redesigned hoppers were installed and tested. There is also a discussion on the advantages of the new mass-flow bins on adjacent feeder performance.

Jan 1, 1970

By Clifford S. Gibson

THESE troubled times suggest three reasons for maximum effort to control silicosis: (1) To keep to a minimum the ever-increasing burden occasioned by past deficiencies in this respect. (2) To effect the greatest production with maximum efficiency, which means at the least cost. (3) To preserve man-power in every way. Good control of the silicosis problem aids these aims. Inadequate control hampers all three. Insofar as our knowledge goes, silicosis in Ontario mines is caused by the inhalation of finely particulate quartz. It follows, therefore, that removal of dust containing this mineral automatically erases the cause. The achievement of this ideal is the aim of the mine operator. His best tool to this end is ventilation. This paper discusses mine ventilation from the viewpoint of dust control and it is hoped that in so doing there may result a better understanding of the part played by air in silicosis prevention. No attempt will be made to treat the subject fully. Instead, there will be presented certain salient aspects culled from field observations, the data in all cases referring to gold mines, unless mention to the contrary is made.

Jan 1, 1942

By R. Therrien, L. Gosselin, J. Raymond

ABSTRACT: The ground-source heat pump is a low-carbon technology that uses the earth’s renewable geothermal energy to heat and cool buildings, with an ef?ciency 3 to 4.5 times that of conventional systems. These high performances are achieved by exchanging heat with the earth using a ?uid that is groundwater, surface water or closed loop water. Expensive installations, such as water wells or buriedcoils, are however necessary to transport the ?uid in and out of the earth, making ground-source heat pumps more costly than conventional systems. Installation costs can be reduced in mining environments due to the abundance and the accessibility of resources to be used with heat pumps. Examples of system design calculations using data from the Mouska and Doyon mines in Abitibi show signi?cant installation cost savings using dewatering mine water or ground heat exchangers installed below oxidizing waste rocks. Ground-source heat pump technology is reviewed and scoping calculations are presented to illustrate how such systems can be installed in mining environments.

Jan 1, 2010

By F. S. Thurner

"This paper describes the engineering and construction activities of the ""design-build"" project awarded to the joint venture of Foundation-Comstock-Janin for the construction of the plant and wharf facilities, camp site, power plant and all supporting services. As a member of the Foundation Group of companies at that time, Fenco actecl as consulting and design engineers for the project. Particular emphasis is given to the problems which adversely affected design and construction activities due to prevailing arctic conditions and the remote location of the project. The paper also describes the approach taken in the investigation of the site and soil conditions as well as the selection of the special structures for the 225,000-toncapacity fibre storage building, the wharf structure for 50,000-dwt vessels, and the 1,000-tph-capacity reclaiming and ship-loading facilities . It further covers the logistics problems and the scheduling activities related to the short duration of the shipping season, and the transportation of equipment and mate1•ials by sea as well as by air."

Jan 1, 1976

By E. Brouillette

Difficult operating and mining conditions such as low visibility, difficult roadbeds, fast cycling, small openings, and sharp corners create high demand for LHD manoeuvrability and operator dexterity. Operator experience and patience is especially solicited to fill the bucket rapidly and efficiently and performance can be particularly affected by the skill level of individual operators. Teleoperation and automated loading are viewed as options to improve overall equipment and operation performance in certain mining conditions. Comparative statistical measurements of autoloading performance in different production environments at Noranda demonstrate an increase in bucket filling efficiency and a reduction in filling variance, allowing LHD operation to be more consistent and within manufacturer specifications. Consequential cost savings and productivity increases are demonstrated to be transferable to other mining situations.

May 1, 2003

By Fr. -W. Bach

In the past years the enormous weight saving potential of magnesium sheet has been demonstrated by various research projects all over the world. It has been shown magnesium flat products can benefit automotive, aviation, machine tool and consumer electronics industries. Major material problems such as poor formability, corrosion resistance and high production cost still inhibit the application of magnesium sheets in large scale production. The present contribution outlines achievements in casting and rolling technology. The authors developed an adapted strip casting process in which near-net-shape rolling feedstock of several wrought alloys has been produced. During the rolling process, various parameters were varied in order to modify the microstructure and surface quality of sheet. Several temperature cycles, strains, lubricants, roll surface structures and roll coatings have been analyzed. The sheets were examined and tested in deep-drawing experiments. Suitable rolling schedules have been developed for standard and modified wrought alloys. The study concludes with an overview of current industrial solutions and an estimation of the potential cost savings that might result from the adaptation of the process that has been developed.

Jan 1, 2006

By E. Lee Cameron

The old mine workings on four barite-fluorite veins of the Lake Ainslie district, Nova Scotia, were opened recently and channel sampled. The samples were then forwarded to the Ore Dressing Laboratories, Bureau of Mines, Ottawa, for chemical analyses. Following the analyses, the sample rejects were combined to form bulk samples, representing ore from each vein, for small-scale batch test work. Tonnage samples from the veins, for pilot mill testing, were submitted when requested by the Bureau. The results of the analyses on the channel samples showed that there are two grades of ore in the di strict, represented, for test purposes, by the Trout River vein and Johnson vein ores. Small-scale and pilot-plant test work was undertaken on both these ores. The Trout River ore is amenable co concentration but, because of the high-barite-co-fluorite-co-calcite ratio, a fluorite concentrate was not obtainable from the Johnson vein ore as received. However, Johnson ore blended in a 1 :1 ratio with Trout River ore gave a mill feed that was readily concentrated. The test work on these ores showed that the following concentrates are obtainable : (a) A barite concentrate, with a recovery of 85 to 95 per cent of the available barite, analysing 93 co 96 per cent BaS04, 4 co 6 per cent CaF,, and 0.5 co 2 per cent CaCO3. (b) A fluorite concentrate, with a recovery of 80 co 85 per cent of the available fluorite, analysing 94 to 97 per cent CaF, , 1 to 3 per cent BaSO., and 1 to 3 per cent CaCO3

Jan 1, 1945

By C. Jay Hodgson

Hydrothermal systems form on land where and when an impermeable cap-rock unit ( either natural or self-sealed) , a permeable aquifer. and permeable discharge and recharge channels (cross-stratal permeability) develop in an anomalously hot part of the crust. A consideration of the relationship between magmatic and tectonic events in volcanically active areas indicates these conditions arise during: (1) the resurgent doming stage of the resurgent caldera cycle; (2) following movement on the bounding faults of tilted fault blocks ; and (3) as a result of hydrothermal boring associated with the intrusion of major sills. On the assumption that the submarine hydrothermal systems which deposit volcanogenic massive sulphide ores are comparable to subaerial hydrothermal systems, it is suggested that: (1) the horizon of mineralization corresponds to the time period when conditions favour the development of hydrothermal systems, as outlined above; (2) exploration for Cu-rich Cu-Zn-Pb or Cu-Zn ores should be directed to paletopographically high areas near discharge conduits , whereas exploration for Cu-poor ZnPb ores should concentrate on paleotopographically low areas down slope from conduits; (3) deposits with stringer zones lying above normally permeable units may be underlain by regionally extensive weakly mineralized and altered zones (self-seal caps) ; (4.) in the absence of a self -sealed cap, the ore horizon may be underlain by a naturally impermeable unit (e .g. a fine clastic sediment) ; (5) the condition of cross-stratal permeability may be evidenced by features such as dykes. alignment of vari ous magmatic and hydrothermal phenomena, abrupt thickness changes in stratiform units indicative of ponding against syn-volcanic faults, and fault-scarp slump deposits; (6) the condition of high heat flow may be evidenced by near-surface magmatism and steep thermal gradients preserved in metamorphic mineral assemblages.

Jan 1, 1977

By R. E. Ray

"As real estate for new development in urban settings becomes scarce, commercial high rises are being constructed above open passenger rail tracks and vehicular roadways. Rail and roadway overbuilds are treated as tunnels requiring emergency ventilation systems for train or automobile and truck fires. The value of floor space in residential and office towers poses challenges to engineers responsible for designing fan rooms and shafts for tunnel ventilation systems within the towers. This paper describes a case study of the unique incorporation of tunnel ventilation fan plants in the overbuild structure of a passenger railyard and an adjacent roadway.INTRODUCTIONTunnel ventilation systems are required for passenger rail and transit (subway) tunnels by the NFPA 130 Standard for Fixed Guideway Transit and Passenger Rail Systems, and the NFPA 502 Standard for Road Tunnels, Bridges, and Other Limited Access Highways requires tunnel ventilation systems for vehicular (road) tunnels. Passenger rail and transit (subway) tunnels are typically ventilated with a series of shafts placed longitudinally along the tunnels to provide piston relief for normal train operations and emergency ventilation of train fires utilizing reversible axial flow fans. The shafts are incorporated in dedicated ventilation buildings that house the tunnel ventilation fans and starters, switchgear to power the fans and other equipment and systems in the building, Programmable Logic Controllers (PLCs) to control fan operation with Supervisory Control and Data Acquisition (SCADA) software, and HVAC fans and ductwork to ventilate the spaces in the building. These ventilation buildings may also provide access to the tunnels below with ingress/egress stairs for use by first responders and firefighters entering the tunnels and train or transit system passengers exiting the tunnels in an emergency. A photograph of a passenger rail ventilation building that encompasses four tunnels is shown in Figure 1."

Jan 1, 2019

By E. Godin, M. Rigaud, S. C. Panigrahy, I. Malinsky

"RésuméDes boulettes de concentres d'hématite spéculaire à basse silice ont été produites en substituant la bentonite par de la tourbe, adéquatement traitée, additionnée d'une faible quantile de soude caustique durant le boulettage. La réductibilité de telles boulettes et leur gonflement pendant la réduction ont été évacues, en utilisant quatre mélanges gazeux différents, formes de H2 - CO - N2.L'influence du pouvoir réducteur du gaz utilise, sur le gonflement des boulettes, à été mis en évidence. Quelles que soient ces conditions réductrices, les propriétés mesurées sur les boulettes liées a la tourbe sont comparables aux propriétés obtenues avec des boulettes traditionnelles liées à la bentonite.ABSTRACTAdditions of peat moss and small quantities of NaOH during balling of low silica specular hematite concentrates have eliminated the need to use bentonite as a binder. The reducibility and swelling of such pellets have been evaluated using four different gas mixtures, consisting of H2 - CO -N2. The influence of the reducing power of the gases, on the swelling behaviour of pellets has been documented. Under the different reducing conditions, this new type of pellets exhibit properties similar to the ones obtained using bentonite."

Jan 1, 1987

By J. P. Morris, J. T. Novak, E. A. Sarver

"A variety of reagents are utilized in coal preparation, but aside from performing their desired function relatively little is known about the behavior of these reagents within the processing circuits. Where exactly do reagents go once dosed? In this paper, we present preliminary results of partitioning studies on frother (i.e., MIBC) and collector (i.e., diesel) chemicals commonly used in coal flotation, and examine implications for water management (e.g., in closed-loop systems). Additionally, we discuss the usefulness of such data in predicting environmental transport and fate of chemicals – which is currently a top priority for industry.INTRODUCTIONThe purpose of coal preparation is to upgrade mined coal into more valuable products. Since coal is primarily used as a fuel source for electricity generation, product specifications are typically contracted to minimize unwanted constituents that detract from the overall heat value (e.g., ash and moisture) or that add to environmental pollution or other problems like corrosion at a power plant (e.g., sulfur) (Pitt & Millward, 1979). Failure to meet specifications results in a financial penalty for the coal producer (Szwilski, 1986), and thus preparation processes have evolved to simultaneously optimize recovery of valuable “clean” coal with rejection of mineral matter and moisture. In addition to advancements in equipment and circuitry, development and application of various chemical reagents has dramatically improved the performance of coal preparation processes.Contemporary preparation plants typically include multiple circuits that can be categorized by the size of particles they process: coarse, intermediate, and fine/ultra-fine (Figure 1). Coarse and intermediate circuits generally rely on size classification and gravity separations (e.g., dense-media cyclones), and do not require significant chemical reagents. However, fine and ultra-fine circuits often use froth flotation to separate coal from impurities, which requires chemical additives (Table 1). The primary additives include collectors, which coat the surface of the coal particles to render them (more) hydrophobic and thus more likely to attach to air bubbles and float; and frothers, which aid in the formation and stability of the froth that will accumulate the floated coal particles. Modifiers are also commonly added to flotation circuits to regulate pH in instances where coal or impurity characteristics may change water chemistries (Laskowski, 2001). Following flotation, coagulants and flocculants are often utilized in solid-liquid separations (i.e., dewatering or clarification) for coal products, and for tailings slurries prior to their disposal in impoundments. Coagulants function via double-layer compression1 to bring colloidal particles together, while flocculants promote bridging between the grouped colloids – and the combined result is enhanced sedimentation (Wills, 2006). Defoaming or anti-foaming agents may also be required to avoid fouling of dewatering operations."

Jan 1, 2012

By C. J. Sullivan

"The outlook for supplying the world's metal needs in the next twenty-five years is good, although in several cases basic costs are likely to increase with rising demand. Metal prices calculated at a constant dollar from 1900 to the present show that for nickel, copper, silver, lead, zinc and tin, prices -and presumably production costs -fell from 1900 to the early 1930s. Since then, they have generally risen, apparently reflecting some depletion in relation to demand. This tendency has been accentuated since the post-World War II adoption of managed, full-employment, growth economics, which have resulted in a sharp escalation in world demand for metals. (Abandonment of such policies, apparently now under consideration in North America, would, of course, affect the pre-dictions of this paper.) Nevertheless, metal prices generally are still below those prevailing in 1900. Exploration potential exists for disseminated ores of many metals still thought of as characteristic of lode and vein deposits. These include uranium, silver, gold, tin and nickel and, to a lesser extent, lead and zinc. Considering the discovery potential for some principal metals in relation to expected demand and prices, I would tend to rate them as follows: molybdenum, zinc, lead, uranium, silver, gold, tin, nickel and copper."

Jan 1, 1970