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By William H. McCracken, William G. Holroyd

"The People's Republic of China could very well be considered the largest untapped mineral and metal resource in the world. The proven reserves of antimony, barite, bauxite, fluorspar, graphite, lithium, magnesite, mercury, molybdenum, phosphate, pyrite, rare earths, talc, tin, titanium, tungsten, vanadium and zinc are among the largest in the world.Any company involved in the purchase or supply of industrial raw materials has undoubtedly followed the phenomenal growth of some of the Chinese mineral commodities, where growths in production of more than 200010 have occurred during the past ten years, for commodities like barite, cement, gold, gympsum silver and talc. Others, like bauxite and phosphate, experienced production increases in one year alone of over 45%, from 1986 through 1987!A popular rationale in the United States during the past two years has been the acknowledgment by Professor David Calleo, of Johns Hopkins School of Advanced Studies, that ""America is not sinking-the rest of the world is rising"". While we recognized this rise to be that of economic power for Japan, Korea, Brazil, Taiwan and, more recently, the newly-combined Germanies, China has also successfully completed her own modern five year development binge. But with each boom there is also a bust, and the start of the 1990sfor China shows signs of economic distress. China posted a budget deficit equivalent of US$1.9 billion in 1989 coupled with official inflation at 18010. Projections for 1990 are for US$1.8 billion deficit and inflation as high as 24%. However, government spending in the first seven months of the year climbed 16.4%, outpacing an 11.6% rise in revenue. Spending increases have been related to the government policy to keep prices on domestic goods artificially low, through subsidies, and to bailout inefficient state companies."

Jan 1, 1991

By R. V. Kumar, F. Tailoka

In order to use ZnO laden dust as a possible desulphurization reagent, it is important to evaluate thermodynamics of the Zn-O-S system. At temperatures greater than 1450 K, there is an uncertainty in the thermodynamic data for the reaction of zinc with sulfur to form Zinc sulfide. In this work, the standard free energy has been determined using an electrochemical cell: Pt, Mo, MoO2/YSZ/ZnO, ZnS, S02, Pt., between 1198 and 1602 K. AG° varies from -145,880 to -88,100 J (± 2500) , with a phase change to ZnS (g) by sublimation occurring between 1450 and 1460 K. This is supported by thermogravimetric analysis which shows about 80% weight loss in ZnS from 1273 to 1473 K. Feasibility reactions were also performed and confirmed that ZnS (g) is formed when ZnO reacts with FeS (1473 to 1653 K) or with Fe-Csat-S(1473-1673 K). There is therefore potential for the utilization of ZnO laden waste as an additional or alternative reagent for desulfurisation.

Jan 1, 2004

By M. Jiang, X. Fan, W. X. Chen, Z. K. Guo, H. H. Zou

"Some improvements are carried out for elasto-plastic model by taking the shear dilation effects and relaxation effects of deep rocks into accounted. The high pressure equations of states with Mie-Grüneisen form are also introduced to describe the relation of pressure-volumetric strain. Numerical simulations of free field responses for deep underground explosions are conducted by using the user subroutines which compiled by means of the secondary development functions of LS-DYNA9703D codes. It is indicated that the dynamic responses of free field are well simulated based on this improved elasto-plastic model, and the analytical results are in good agreement with the data of U.S. Hardhat nuclear test.INTRODUCTIONDynamic behaviors of deep rocks for underground explosions are obviously different from that of shallow underground explosions and have aroused great attentions of international experts who work for rock engineering. The dynamic models of deep rocks could be roughly divided into classic elasto-plastic model and fracture damage model according to different theoretical foundation. M. E.Kipp and D. E.Grady et al. are the outstanding representatives who engaged in the researches of fracture damage mechanics. Researches of dynamic problems for geomaterials were carried out by C.C.Grigorian and the conclusion that incompressible elasto-plastic medium model could not be used to solve the problems of closed underground explosion was derived, and therefore C.C.Grigorian model was proposed. In this model, C.C.Grigorian assumed that the average hydrostatic pressures and the densities of medium had one to one relationship, and the path of loading or unloading is different from each other. For shear deformations, analytical solutions of the problems were derived according to the model which was slightly different from Prandtl-Reuss model, the constitutive equations were closed by Mises-Schleiher constitutive model. However, the analysis showed that there were two inadequacies in C.C.Grigorian model. Firstly, the shear dilation effects of fractured medium after wave front could not be considered. Secondly, the relaxation characteristics of the rocks in fractured region were not taken into account."

Jan 1, 2015

By E. Haccuria

Due to the growing share of electrical cars, the use of lithium ion batteries significantly increased. Recycling of these batteries is essential to safely dispose hazardous materials as well as to recover valuables (Cu, Ni, Co, etc.). In order to optimise the recycling process, accurate information is required on the slag phase equilibria for battery smelting. The slag is a multi-component system containing alumina from the battery cases, silica and lime from fluxes, and manganese and lithium from the electrode materials. The present study accurately determined the phase equilibria in the "MnO"-Al2O3-SiO2 sub-ternary system at metal alloy saturation. Particular attention was given to the accuracy and reliability of the final results by highlighting the different reaction pathways, mass transfer- and reaction mechanisms taking place in the system during experiments. This attention enabled improved experimental methodology and measurements. Based on the present study, further measurements will be undertaken in the quaternary "MnO"-Al2O3-CaO-SiO2 system at low "MnO" concentrations, which closely represents the future recycling industrial slags.

Jan 1, 2014

By P. M. Huck, R. John

"The National Uranium Tailings Program was established in 1982 to develop, in part, a mathematical predictive model which would allow the assessment of the impact of uranium mill tailings on the environment and particularly on humans. . To achieve this , various studies were undertaken to establish the role played by key constituents of the tailings. This paper summarizes the findings of a study carried out under that program, to examine the leachability of barium-radium sulphate sludges produced in the treatment of uranium mill tailings decants. The investigators performed detailed chemical an alysis of the sludge, applied geochemical computer models to investigate sludge leaching behaviour, and conducted experiments to assess the impact of bacteria on leaching. The modelling showed that the redox state o f the sludge-leachant system was the most important factor. Substantial bacterially-mediated dissolutio n of the sludge and release of radium was demonstrated experimentally under suitable reducing conditions . INTRODUCTIONIn September 1981, Phillip A. Lapp presented the final report of the National Technical Planning Group on uranium tailings research to the federal government (Lapp, 1981). Lapp' s group had performed an in-depth survey of the status of uranium tailings research in Canada and, as a result, recommended that a national program be funded in the amount of $18 .6 million. Half of this fund ing was to come from the federal government, with the two producing provinces , Ontario and Saskatchewan, providing the balance. However , the provinces declined to support the program and the federal government decided to inaugurate a reduced program with $8.5 million o f funds .In late 1982, the formation of the National Uranium Tailings Program (NUTP) was announced by the minister of state for mines. A primary objective of this program was to develop a mathematical predictive model that would permit the assessment of the impact of uranium mill tailings on the environment, a nd particularly on humans. The program was to use existing information to the greatest possible extent, and then fund research to fill in gaps or substantiate data where necessary .The NUTP was established to administer this program of contract research over a five-year sunset life. By the end of the 1986-87 fiscal year the NUTP had completed about 100 contracts. One of those projects was to study the effect of placing barium-radium sludge ba ck within the tailings matrix. Th is paper gives the results of that study."

Jan 1, 1989

By Suzanne Paradis

Geographic distribution ? Deposit economics ? Temporal distribution ? Tectonic settings ? Basin architecture ? Morphology ? Ore-fluid chemistries Key exploration criteria

May 1, 2006

By J. Palarski

In the Polish coal mining industry, the use of mine waste in underground backfill has been the most common means of providing ground support to minimize surface subsidence, increasing extraction ratios, and reducing the quantity of waste for surface disposal. Over the last decade attention has been focused on the use of different waste as filling material of underground workings and grouting of roof fall rocks in caving area. In the paper, a brief history of the development of fill technology in Polish coal mining industry is presented. Next, the paper discusses various criteria that should be taken under consideration in the preparation process of a fill slurry and grout, fill distribution systems, mining geometry and placement methods. Moreover, in the paper evaluation of the potential of utilizing coarse and fine waste as a resource material in the production of a backfill slurry and grout for filling and injection in abandoned mines is presented.

May 1, 2007

By Eirik Sundvor, Hany Doss, Peter Vogt, Kathleen Crane

"Abstract - In 1989-1990, the SeaMARC II side-looking sonar (11 to 12 kHz) and swath bathymetric system imaged more than 80 000 km2 of the seafloor in the Norwegian-Greenland Sea and southern Arctic Ocean. One of our main goals was to investigate the highly oblique (115°) junction between the Mohns and Knipovich ridges, and to determine, using new morphotectonic data, whether or not this junction is stable or in a state of readjustment. These findings are presented in this paper.Along the northern Mohns Ridge, we observed a highly segmented rift valley undisturbed by transform faults. In contrast to the elevated Reykjanes Ridge, the Mohns Ridge is dominated by deep en echelon fault-bounded troughs, which are bordered by high rift valley volcanoes. These segment boundaries are interpreted to be sites of recent to present volcanic activity, based on their high acoustic reflectivity. The northwestern flank of the Mohns Ridge is marked by shallow quasi-linear ridges parallel to the present orientation of the Mohns Ridge. The orientation and geographic position of these ridges suggest that they were formed at the Mohns Ridge. Only in the northernmost cases are some of these off-axial ridges non-linear. The degree of the non-linearities increases slightly with proximity to the Mohns-Knipovich bend. In addition, because no transform fault was detected between the Mohns and Knipovich ridges, we conclude that the Knipovich Ridge must be obliquely spreading to the NW-SE."

Jan 1, 1999

By Doris Stüben, Geoffrey P. Glasby, Akira Usui, Jörg-Detlef Eckhardt, Bruce W. Mountain, Zsolt Berner

"Abstract - Twenty-seven marine Mn and Fe deposits chosen for their diverse origins have been analyzed for five platinum-group elements (PGE). The PGE display their highest concentrations in hydrogenous Mn crusts and nodules, lesser concentrations in diagenetic nodules and two to three orders of magnitude lower concentrations in hydrothermal Mn and Fe crusts. This difference of behavior reflects the well-known fractionation of Mn and Fe from the other transition elements, rare earth elements (REE) and PGE in hydrothermal Mn and Fe crusts. Pt, Ru, Rh, and Ir show a close geochemical coherence in these deposits and are differentiated from Pd which shows a negative anomaly with respect to the other PGE in hydrogenous and diagenetic Mn deposits. Pd is less depleted than the other PGE and the Pd anomaly much less pronounced in the hydrothermal Mn and Fe crusts relative to the hydrogenous and diagenetic Mn deposits.Stability field diagrams show no evidence for the oxidation of Pt to the tetravalent state in seawater as suggested by some authors. Rather, Pt appears to be present in seawater as Pt(OH)2 0. Adsorption of Pt(OH)2 0 onto the surface of Mn and Fe oxyhydroxide minerals may explain the enrichment of Pt in marine Mn deposits. However, Pt metal is the thermodynamically stable solid phase of Pt under seawater conditions and reduction of Pt(OH)2 0 to Pt metal, particularly in the vicinity of the oxygen minimum zone, is possible, although the high Ce/La ratios of the Co-rich Mn crusts do not support this hypothesis. Pt, Ru, Rh, and Ir display their maximum concentrations in the Corich Mn crusts. This may reflect, among other things, the low growth rates of these deposits. The stability field diagram of Pd shows that Pd is undersaturated in seawater and occurs in seawater dominantly as PdCl4 2- and anionic mixed-hydroxide-chloride complexes. This would explain the anomalous position of Pd among the PGE with respect to its uptake into marine Mn deposits. A study of inter-element associations indicates that the incorporation of the PGE from meteoritic dust plays only a minor role in the uptake of these elements into marine Mn deposits. The PGE remain the most poorly studied group of elements in marine Mn deposits. The data presented here emphasize the need for the establishment of a more comprehensive database of the PGE in marine Mn deposits in order to understand more fully their uptake into marine Mn deposits and their pathways through the oceans."

Jan 1, 1999

"Sedimented hydrothermal precipitates of silica, now fine-grained quartz, are described from a Pb-Zn-bearing vein system. Their discrimination from the wall-accreted fine-grained quartz that is common in the shallow parts of epithermal systems is discussed. Local fine-grained (<0.3 mm) quartz accumulations occur in a suite of veins with otherwise normal drusiform and crustified infills. This sediment may fill the vein above chokes in steep segments (axial plugs), or form continuous layers within the footwall material where the vein is inclined at low to moderate angles. Pads of fine-grained sediment are deposited on the upwards-facing surfaces of wall-rock clasts and of drusiform crystals growing from the vein walls. The asymmetry of these deposits differentiates them from the more common symmetrical, crustified walllining deposits of fine-grained quartz and opaline silica, and requires a gravity-controlled, sedimentary depositional mechanism.Thin section examination shows that much of the fine-grained quartz is present as elongate prisms. The prism habit was present soon after deposition, but it is not possible to identify unequivocally the original sedimented grains. Sedimentation of vein- and wall-rock-derived detritus is also recognized. Deposition of the fine-grained sediment accompanies normal in situ drusiform growth of quartz and other vein minerals. The mammilated and spherulitic textures associated with accretion of amorphous quartz are entirely absent from the Tyndrum veins with sedimented materials. The literature on modern hydrothermal waters and physical chemistry of silica precipitation shows that precipitates of silica suspended in hydrothermal fluids are amorphous and derived from colloidal silica. It is argued that much of the suspended silica was present as quartz at the time of deposition or was converted from amorphous silica almost immediately after deposition.Hydrothermal sediments and their distribution potentially provide information on flow directions and velocity in veins. Plugs of sediment obstruct vertical flow and lead to local flows with large horizontal components. It is shown that sedimentation features occur in other deposits and can involve other minerals. If the features seen here can be scaled up to the size of major veins, they may result in up and downdip variations in mineral assemblages and abundances, which may affect grade."

Jan 1, 2007

By A. Farzanegan, D. A. Lowther, A. R. Laplante

"Off-line optimization studies are often necessary to improve the efficiency of grinding circuits. These studies are primarily based on the mathematical modelling of processing units (e.g., ball mills and hydrocyclones) and computer simulations. To complete an optimization task, process engineers must possess skills and knowledge of different subtasks involved in such efforts, e.g., plant audit, laboratory tests, and data analysis. Such know-how can be in part provided by Knowledge-Based Systems (KBSs). One such system, being developed in C Language Integrated Production System (CLIPS), is presented here, with focus on the estimation of ball mill selection functions for the purpose of both diagnostic and simulation, and its use for the optimization of ball size. Some of the interpretation and diagnostic rules will be presented, as well as grinding kinetics and classification data likely to fire them.IntroductionSince the late eighties there has been a growing trend in applying Knowledge-Based Systems (KBSs) to mineral processing [Meech 1990, Bearman and Milne 1992). Table l lists some KBS (often referred to as expert systems) applications that have been used mainly as tools for improving on-line monitoring and control of grinding circuits. However, there has been fewer attempts to add the symbolic processing powers of KBSs to conventional off-line grinding simulators. Figure 1 shows a relatively standard procedure to perform an off-line optimization study [Napier-Munn and Lynch 1992]. In brief, a typical program includes taking representative samples from a number of streams, running laboratory tests on collected samples, estimating model parameters which describe physical processing units (e.g. ball mills and hydrocyclones) validating model predictions and using models for simulation trials. One inevitably needs to be familiar with concepts of process modelling and simulation as well as various computer programs to be able to complete all steps of the study. Much of this ""expertise"" can be captured by KBSs, given their inherent capabilities for symbolic knowledge representation and manipulation."

Jan 1, 1997

By Robert B. Parsons

"The Whitehorse Mining Initiative (WMI) brought together all of the key stakeholders in Canada&apos;s mining industry to develop a framework whereby the industry can meet the challenges that it faces into the 21st century. The WMI Accord7 which was signed at the annual Mines Ministers Conference in Victoria, British Columbia, on September 137 1994, touches all of the important issues that confront the industry, including taxation. IntroductionSeptember 13, 1994, was a historical day for Canada&apos;s mining industry. On that day, on the occasion of the annual Mines Ministers Conference in Victoria, British Columbia, the Whitehorse Mining Initiative (WMI) Accord was signed by the leaders of the five principal stakeholders in the industry: industry; government; labour; environmentalists; and aboriginals. The Accord is the culmination of two years of hard work and intense collaboration by these stakeholders. But, the Accord is not the end result. The Accord can better be described as a springboard to a prosperous future for mining in Canada.The WMI had its beginnings at the Mines Ministers Conference in Whitehorse, Yukon, in September 1992 (hence, the name of the initiative). At that time, the mining industry was well aware of the serious challenges facing the industry, including significantly increased competition for mineral investment from other mining countries, coupled with an atmosphere of uncertainty surrounding land access, environmental regulations, and taxation. The diversion of investment abroad was hurting, and would continue to hurt, all Canadians. Something had to be done. At the 1992"

Jan 1, 1994

By Peter N. Calder

Long range mine planning involves developing a mining sequence that schedules the extraction of the ore and waste materials within a final pit limit. The objective is to define a sequence that best meets the defined strategic objectives. The main steps in the creation of an open pit mine plan are the final pit limit design, the design and sequencing of the mining phases, equipment selection and operating cost estimation. Flexibility is the key strategic element in developing a mine plan. Planning the extraction sequences and rates for the various mining areas is a challenging and demanding activity. It is often necessary to consider numerous alternative strategies and what if scenarios. The number of alternatives that can be studied with limited manpower and time resources is restricted. In order to investigate strategic aspects of mine planning, a system to generate workable mine plans rapidly is required. The concept of Visual Mine Planning is that the engineer can visualize the current plan, easily change a component of the plan, such as the annual cut-off grade schedule or the production rate within a particular Phase, and immediately see the effect on the mineralogical and cash flows. If the desired result is not achieved, a change is made and the effect is again immediately seen. This paper presents results of research in this area conducted at the Pontificia Universidad Católica de Chile. The work includes the examination of cut-off grade strategy, sequencing, blending, stockpiling and shovel-truck fleet requirements using simulation.

May 1, 2003

By P. M. May, V. Gella

The deportment and speciation of trace elements during mining and minerals processing is becoming an area of increasing concern with regards to potential health and environment risks. The use of chemical modelling can enhance our basic understanding of the deportment and speciation of trace metals under conditions present in gold processing solutions, and assist in laboratory and field investigations. In this paper, we report the results of chemical speciation modelling using the JESS software package for the trace toxic elements Pb, Cd, Hg, Se and Te in cyanidation solutions of varying salinity and relate the models to experimental data. The speciation of mercury is examined in detail.

Jan 1, 2011

By Richard Dawson

Presentation Outline? Northeast BC Coal Fields Overview and History ?New mines and projects in development ?Design Issues for steeply dipping footwall slopes ?Design issues for angle-of-repose waste rock dumps

May 1, 2006

By Robert B. Parsons

"There is a widespread concern that certain of Finance Minister Michael Wilson&apos;s Tax Reform proposals will likely lead to a significant decline in flow through funding after 1988. This does not bode well for the junior exploration sector, which relies heavily on flow-through to finance exploration programs. The exploration industry is actively pursuing various solutions to the problems posed by Tax Reform, in order to ensure that flow-through has a future.IntroductionWhile the proposals contained in Finance Minister Michael Wilson&apos;s Tax Reform White Paper may not be as far-reaching as some people had expected, nevertheless the combination of the existing tax rules and proposed new rules offers sufficient complexity to keep pencils sharpened for many months. After having had an opportunity to study Tax Reform since June 18, 1987, the sharpened pencils are suggesting that the White Paper is not without its shortcomings and pitfalls. Insofar as the mineral exploration industry is affected, there is widespread concern that adoption of certain Tax Reform proposals could spell near disaster for mineral exploration in Canada. More specifically, there seems to be a consensus among the industry, as well as some federal and provincial government officials, that the announced phase-out of the ""mining exploration depletion allowance"" (MEDA) would reduce the appeal of flow-through shares to the point where only a fraction of exploration funding would be financed in the future by flow-through."

Jan 1, 1987

By Don Peel, Jeremy Richards

Abstract - Aggregates (sand, gravel, and crushed stone) are low unit-cost products extracted in very large volumes for the construction of buildings, roads, and other infrastructure essential to modern society. Because of their low unit value, transportation costs are a key factor in resource economics, and deposits are commonly developed close to market (i.e., close to towns and cities, or along low-cost transportation corridors). This proximity results in potential conflict with residents over land use, disturbance, and pollution. Management of aggregate resources in Alberta is examined in the light of resource geology and distribution, and governance. A case history of development of the Calahoo-Villeneuve deposit is described, and the conflicts between residents and developers that led to establishment of an Area Structure Plan (ASP) are explored. The plan sets limits to, but at the same time safeguards, resource extraction, and defines terms for compensation to residents through a voluntary levy on production (Community Enhancement Fund). This fund is used to support community activities and to pay for a groundwater monitoring program. The ASP is examined within the context of the "Seven Questions to Sustainability" as set out by Mining,Minerals and Sustainable Development-North America (2002). It is concluded that the ASP, for the most part, provides a good model for conflict resolution and sustainable resource development, which could usefully be applied in other jurisdictions. The ASP was developed at a municipal level, and adoption at a provincial level would aid sustainable development of aggregate resources across the province.

Jan 1, 2003

By A. Anderko, V. G. Papangelakis, G. Moldoveanu, G. Azimi, M. Carlos

"OLI Analyzer is a software package that uses the powerful Mixed Solvent Electrolyte (MSE) model to simulate the behavior of multicomponent electrolyte solutions from infinite dilution to the limit of fused salt, and from temperatures below the freezing point up to near critical temperature of the mixture. The software also allows the creation of thermodynamic parameters for new chemical systems unavailable yet in public-domain or commercial software databanks. This communication reviews the basics of the model and provides some examples of modeling hydrometallurgical applications with emphasis on high temperature applications, including calcium sulfate scale formation in autoclaves, high temperature pH inference and iron control. INTRODUCTIONModeling of electrolyte systems has been of particular interest to various industrial processes, such as separation processes (e.g., solution crystallization, extractive distillation, seawater desalination or bio-separations), environmental applications (e.g., gas treatment, wastewater treatment or chemical waste disposal) and hydrometallurgy (e.g., pH control and neutralization, iron control, scaling and fouling of equipment). Using a chemical model, time-effective predictions of various properties of electrolytes can be obtained, which is beneficial not only during process monitoring, but also during process optimization and process scale up. As a result, pilot scale studies can sometimes be eliminated where budgetary constraints exist. Development of such a powerful model requires the use of a speciation-based model, in which solution chemistry is explicitly addressed (as compared with some models that treat electrolytes either as undissociated or fully dissociated systems), despite being computationally challenging. In addition, as a feature of electrolyte systems, speciation equilibria inherently influence the phase equilibria due to complex formation, ion pairing, and acid-base reactions. Therefore, how the electrolyte solutions behave at various conditions may differ significantly due to the non-ideality, which must be carefully addressed to obtain a model that is applicable to a wide range of conditions such as concentration, temperature, pressure and solvent system."

Jan 1, 2012

"The Dome Mine, located in South Porcupine Ont. has been in operation since 1910 and is owned and operated by Placer Dome Inc. The current milling facilities were constructed in two phases with the first being commissioned in 1982. It consists of a grinding, gravity separation, thickening, and leaching circuits. The second phase was commissioned in 1988 with the addition of the CIP, stripping, electrowinning, and carbon regeneration circuits.It is now common practice in the gold processing community to add liquid oxygen to leach circuits to increase both recovery and kinetics. Along with these benefits the metallurgical group at the Dome realized the potential to replace compressed air with liquid oxygen as a source of oxygen for the dissolution of gold. A plant trial of liquid oxygen was undertaken during the fall of 1991. The results of this first test were favourable enough to warrant further investigation, and a second plant trial was conducted in December 1991.The data generated as a result of each trial revealed that oxygen could be economically substituted for compressed air as a source of dissolved 02. The energy savings in required horsepower enabled a rapid payback period. Thus the project was approved in the spring of 1992 and l should be operational during the final quarter of 1992. INTRODUCTIONIn a continuing effort to reduce operating costs and improve recovery at the Dome mill it was decided to investigate the feasibility of adding liquid oxygen (02) to the leach circuit. It is now common practice in the gold processing community to add 02 to the leaching process to increase both kinetics and recovery. It was anticipated that an increase in kinetics would allow us to eliminate one or more leach tanks while maintaining acceptable recoveries. The metallurgical group felt that along with these benefits, the potential was also there to reduce power consumption through the reduction in the processing of compressed air which is quite costly (12 cents/1000 cubic feet per minute in 1991)."

Jan 1, 1993

By Alfred C. Lane

WE recently received from Professor A. C. Lane, Emeritus Professor of Geology and Mineralogy, Tufts College, Mass., and a Corresponding Member of this Institute, a very interesting account of some recent developments in radioactive methods of determining the age of minerals and, therefore, of the rocks in which they occur. It deals in particular with studies of the minerals of certain pegmatite dykes on the Huron claims and Bear claims in southeastern Manitoba, which, the results indicate, are among the oldest rocks of the earth&apos;s crust. The following article presents a non-mathematical summary of Professor Lane&apos;s paper . . It will be noted that he is anxious to obtain suitable samples of certain minerals and rocks for further age studies. We hope some o our members may be able to supply him with the material he needs. It may be well to explain briefly how the age determinations are made. Uranium is continually breaking down, or disintegrating in successive steps through radium, etc., to a final product which is lead (uranium-lead), and the rate at which this change takes place is known. Minerals containing uranium will therefore contain lead also, and the lead-uranium ratio mul-tiplied by a certain factor (approximately 7 ,600) will give the age of the mineral in millions of years. Thorium also disintegrates at a known rate to give lead (thorium-lead) as a final product, and the age of a mineral containing thorium can thus be calculated from the lead-thorium ratio. Thorium breaks down more slowly than uranium. In unit time, one gram of thorium produces about as much lead as 0.36 grams of uranium.-ED.

Jan 1, 1938