Search Documents

The administration came on as a strong supporter of the mining industry in April of 1982 when President Reagan delivered his long-awaited minerals policy statement. He promised to reduce America's minerals vulnerability, and called for spending billions on meeting stockpile goals for strategic minerals, opening up federal lands for mineral exploration, elimination of barriers to deep sea mining, and regulatory relief. He defended the favorable tax incentives in the Economic Recovery Act as a stimulus to private research and development that would ensure the availability of materials essential to the nation's economy and national defense. But the administration just didn't seem to get anywhere. Congress, environmentalists, and even foreign governments fought White House-proposed legislation on all fronts, delivering the ultimate coup in forcing Environmental Protection Agency Administrator Anne Burford's resignation and the subsequent EPA staff house cleaning in early 1983. Anti-Reaganites scored victory after victory against Reagan's efforts to stimulate the minerals industry. Congress was stalemated on so many mining-related issues that not much was done either for or against the industry. And the US was not to get its way on the issue of sea mining either. Most of Reagan's mineral policy objectives failed to be met. Three months after the National Materials and Minerals Program Plan was presented and the Cabinet Council on Natural Resources and the Environment was made its coordinator, the head of the Cabinet Council James Watt blamed lack of progress in reviving the mining industry and creating a better strategic stockpile on the weak economy and the House of Representatives, which repeatedly thwarted efforts to open wilderness lands to mining. Congress The 97th Congress spent much of its time saying no in 1982-to the Reagan administration's deep cuts in energy and environment programs, to major changes in clean air and water laws, to oil and gas leasing in wilderness, and to killing the Department of Energy. Most of 1982 (and 1981) was spent in heated budget disputes. Some things that did not happen: • The administration and industry failed to get changes in controls of hazardous air pollutants and sulfur dioxide emissions that are implicated in the phenomenon known as acid rain. Industry had wanted to relax requirements for new industries building in clean air regions where the air act demands prevention of significant deterioration (PSD) of air quality, and to relax requirements tightening up the regulation of emissions of hazardous air pollutants. The air battle is expected to continue on five major fronts-acid rain, hazardous air pollutants, PSD, automobile pollution, and nonattainment. • Regulatory reform legislation to overhaul the way government carries out the law died a slow death last year. Business groups and the administration said federal agencies should be required to consider cost-effective measures of reaching regulatory objectives of protecting public health, safety, and the environment. Opponents, including environmentalists, feared such action would delay, weaken, or scuttle important regulations. • Congress turned thumbs down several times on proposals for oil and gas leasing in wilderness but could not agree on any new wilderness recommendations (see The Wilderness Battle). • Congress refused to open the door to the Reagan administration's plan to raise up to $4 billion a year from sales of federal lands. The administration identified surplus and excess federal lands, mostly obsolete buildings or isolated tracts of land, that could be sold by the General Services Administration (GSA) to help out the federal budget deficit. Congress took no action. Some things that did happen: • Congress extended the Defense Production Act (DPA) for six months through March 1983 without changing the 32-year-old law. That came after it failed to resolve sharp differences over proposals for critical minerals programs. Differences concerned both the amount of funds and the scope of programs that would be authorized under the DPA's Title III. Some proponents pressed for $5 billion in funding for loan guarantees or purchase commitments to spur domestic production of minerals such as cobalt. Other members of Congress wanted smaller amounts of funding, and the Reagan administration, until about November, had opposed any use of federal funds for strategic mineral programs. These measures were certain to come up again before the DPA extension expired in March. • House supporters of the Critical Materials Act of 1982 were unable to come up with the twothirds majority needed to pass the bill, so it died on the House floor in December. The bill proposed that a council be established with responsibility for coordinating federal materials research and development. The administration opposed the council creation contending that the Cabinet Council

Jan 5, 1983

By F. W. Lee

Historical-From the beginning of time, all ingenuity of mankind has been concentrated upon the methods of finding gold and unusual deposits in the earth. An illustration (Fig. 1) from the old treatise by Agricola, "De Re Metallica," published in 1580, will serve to show the im-plicit faith of that generation in divining methods. However, it was not until 1920 that real progress was made in prospecting by using the latest advances of the physical sciences. The public interest was stimulated by the successes of these methods on the part of commercial oper-ators, and governmental agencies received many requests for information concerning their relia-bility. There were also, in the late 1920's.high- pressure mine-promotion schemes which used geophysical methods in a very questionable manner, symbolized in Figure 2 as of 1928 by an elec-trified forked stick. Authoritative information concerning such practices for public protection was needed to curb such notorious undertakings. Dr. Scott Turner, then Director of the United States Bureau of Mines, thoroughly understood the situation and was first in the governmental de-partments to recognize the possible value of a study of modern prospecting methods. The Bureau of Mines began this investigation by employing Drs. A. S. Eve and D. A. Keys of McGill University for short periods in the summer in 1927. Their first publication [see 1 of "References" at end of paper] served to illustrate the fundamental scientific principles which underlie geophysical prospecting. This was followed by a second publication [21 giving the results of field-tests. In the light of the rapid improvements during the intervening ten years, these two papers take a historical position. Later a full-time position under Civil Service was planned by the Bureau of Mines for con-tinuous investigations and research concerning geophysics and its applications to prospecting. It was Turner's idea that. since the oil-industry had been making very rapid progress with good results, if mineral mining could also benefit to the same degree, it would be of great help to that industry.

Jan 1, 1940

By Angus D. Campbell

Introduction Gowganda forms part of the general Cobalt area. Its rocks and ores are very similar to those of the other parts of the area. While its total production of silver is only 4 per cent of that of the famous Cobalt silver camp, its 1928 shipments contained 42 1/2 per cent as much silver as those of Cobalt for that year. During twenty years of production, 15,000,000 ounces of silver have been shipped from Gowganda. Of this, over 8,000,000 ounces have been shipped in the past five years. The area has thus made for several years a substantial contribution to the wealth of Ontario. Its future depends to a great extent on the priee of silver, which is now, unfortunately, at a record low price. This paper is a discussion of how the Gowganda ore-shoots occur, together with some notes on the milling of the ores at the Castle-Trethewey Mines. The first part is written in the hope of stimulating further study of the silver occurrences, which may lead to further discoveries. The second part, besides being a matter of record, may be of some use to operators of small mills. The drawings in the several Figures illustrating the text are by W. D. Stroud, mine superintendent of the Castle-Trethewey Mines, the benefit of whose opinions I have had in compiling these notes.

Jan 1, 1930

By Ken A. Pfaff, Ray Daigh

This paper will discuss state-of-the-art applications of GPS automation in mobile conveying systems. Robotic mobile conveying systems increase profitability, optimize stacking and reclaiming operations, and control complex interfaces more accurately than other systems. We will also discuss the application process in machine-to-machine coordination, selection of the appropriate GPS system, and Ethernet considerations. As the leading supplier of GPS-controlled mobile conveying systems, we'll draw on our experience at Morenci, Radomiro Tomic, Zaldivar, El Abra (Figure 1), and El Tesoro mines in the US and South America to demonstrate system reliability and the lessons we've learned through analysis of these projects.

Jan 1, 2002

By Adam T. Young

This paper will describe the process of using low density bulk emulsion as a means to maximize the production of an oversize or “rip rap” aggregate size range (8 inch to 72 inch) that the quarry customer has a market demand for. It will also discuss the pre-blast and post-blast metrics used during the product trials and evaluation.

Jan 1, 2017

(Quality can be defined as that which is acceptable to the market and can be supplied with a predictable degree of uniformity and dependability at a low cost. The market for any mining product is downstream processing, whether it be an alumina refinery, a gold processing plant or a flotation plant. The cost of that downstream process is partly dependent on uniformity of its feed material both in physical and chemical terms. With more operations adopting procedures which require quality assurances in line with International Standards, from their raw material suppliers, miners must look to their grade control processes to provide uniformity and predicability.This is not a new concept. The mining industry has constantly been working with ahighly variable raw material supplied by Mother Nature, from whom we cannot demand quality assurances. Through the processes of exploration, resource and reserve definition, long and short term mine planning and day to day grade control an end product has been supplied which consistently meets our customers requirements, in an economic fashion. When any of these processes fail, then penalties are incurred which can range from increased mineral processing costs to loss of markets and in the ultimate case, failure of a mining operation.

Jan 1, 1992

By R J. Goldie

The Monty Copper Gold Deposit is an ultra-high grade mine in Sandfire Resource’s Doolgunna region which was completely drilled out and developed within two years of commencing mine development. During this period, a total of 986 grade control diamond drill holes were completed, assayed, and validated, 15 levels developed, and 3136 faces mapped. The aggressive schedule meant a high flow of geological data was produced, validated, and incorporated into regular geological model updates. To process this data at a rate which allowed for timely use, more robust data processing methodologies needed to be generated. A new validation system was implemented which required two levels of validation being applied to any diamond drilling update. Step one was the validation of initial physical data including survey pick-ups and logging. This was done prior to new drill data being added to the geological model. Step two was the validation of assay data which was required prior to resource estimation. The implementation of Seequent’s Leapfrog Geo modelling software also allowed for a more seamless and efficient modelling workflow. The use of the Leapfrog Geo vein systems allowed for more rapid generation of geological models which then afforded more time for stringent assessment of the mineralisation system. An example of this was the introduction of cross-shift peer reviews in which opposing rosters of geologists would rigorously evaluate the previous rosters work prior to reporting. This additional level of validation resulted in more robust geological models and the identification of new ore trends. This presentation will detail the evolution of the Monty Geological model from a simple tabular indicated resource into a complex highly refined measured resource. Themes will include how the model was produced using workflows developed and optimised to meet key deliverables.

Mar 22, 2022

By D. E. Cameron

"INTRODUCTION Grade control requirements for base and precious metal projects are an important input to both conceptual and feasibility mine plans. It’s the author’s experience that grade control input is insufficient at these critical stages. The few exceptions are a stimulus for this paper. A significant portion of CRC’s practice has involved assisting operations to solve grade control issues which were finally recognized as contributing to negative production variances. Even in operations perceived to be successful, deficiencies in grade control are often masked by measures taken by an operation to compensate a deficiency in one area with outperformance in another. The advantages in having a realistic and adequate grade control plan developed at an early project stage by a geologist(s) with considerable operations experience are manifold. It’s important for the geologist to prepare clear inputs into the mine plan backed by detailed supporting information in usable, flexible formats. When the decision is made to advance a project, the exploration team passes its model to a mine planner. The team doesn’t usually provide a detailed grade control plan with the block model, thus the planner tends to treat grade control as an activity to be rolled into a broader operating category. The consequences of highly compartmentalized mine planning can be severe in the long run. Once a plan is tabled, and especially once production begins, it is very difficult to improve grade control outside the fixed parameters of the operation. Major fixes tend to be costly in terms of time and dollars. Implementing needed changes to the grade control practices and culture in an established mine can present almost insurmountable difficulties. Hypothetical examples of grade control planning are presented to illustrate the author’s points. The diagrams are conceptual and schematic; any resemblance to actual deposits is coincidental. BEYOND 50¢/TON In more than a few cases, grade control cost is buried in a subcategory of mining cost with little more consideration than a plugged number. It is possible to do a word search in 43-101 Technical Reports on advanced projects and without finding reference to “ore control” or “grade control”. The idea is to reach the orebody by the shortest and least expensive means, achieving production and investor payback at the earliest possible occasion. This entails a low stripping ratio pit or a decline ramp with sills on ore to prepare the first stopes. The processes to achieve the target production, one of which is grade control, will fit into this framework. After all, there is a block model and the planner can see the grade and tons in each block. The exploration geologist whose responsibility was to bring a large percentage of the deposit into mineral resource owns the model and has released it to planning. Now comes the planning stage. Mine geologists haven’t been hired yet and they will be phased in with production. What could go wrong? Larger companies may have the geologists with operating depth who will be inserted into the mine planning discussions, but it’s not a given. Junior companies must often delegate the conceptual and detailed planning tasks to consultant groups. Is a senior-level grade control review part of the scope of work for the mine planning? If a good grade control plan is in place before the mine geology team is staffed, a key element of success is assured."

Jan 1, 2018

By B. M. Davis

The Colosseum Mine is within the Clark Mountain mining district located approximately 72 km (42 miles) southwest of Las Vegas. Nevada in San Bernardino County, California. Gold mineralization at the Colosseum Mine is hosted in two 150 m by 210 m (500 ft X 700 ft) interconnected. rhyolitic intrusive breccia pipes that intruded Precambrian crystalline basement rocks and over-lying Paleozoic marine sedimentary rocks. Sub-sequent erosion (de-roofing) of all of the Paleozoic section and a portion of the Precambrian section has exposed the pipes to the present level (probably a significant depth in the original breccia pipe system).

Jan 1, 1989

By L. G. Martin

Early mining at Manhattan demonstrated that blasthole assays alone were insufficient to control the disposition of material. A program was began using controlled blasting, intense sampling and panning of crushed samples, fire assay checks, and geologic inspections to sort material in the pits. Statistical data confirms that the method provides effective control at minimal cost. This cost is easily offset by additional tonnage found in areas considered to be waste.

Jan 1, 1980

By R. H. Duthie

As at any other mine in Canada, grade control procedures are used at Steep Rock Iron Mines (1) in order to ensure that concentrator and pellet-plant operator s have a uniform feed so that they can manufacture a pellet to suit buyers' specifications and (2) to maximize ore recovery so that as little as possible finds its way to the waste dump or is downgraded by contamination. At Steep Rock, material grading 40% to 66 % Fe is considered ore. The ore may contain up to 10% sulphur. These ranges create six different stock pile types, with the possibility of more if large concentrations of arsenic are encountered. Although grading and mining techniques used to accomplish these ends are fairly standard, there is an appreciation and willingness by hourly and staff pit personnel to make grade control effective. This produces vertical and horizontal communication, which is necessary for success in this field. At Steep Rock, the waste-to-ore ratio is greater than at any other iron ore mine in Canada. Also, a high percentage of the ore mined is direct pellet feed. For these reasons, .grade control is very important.

Jan 1, 1977

By Amos QG

The Paddington I and proposed Paddington II Pits are both located in what is, by Eastern Goldfields standards, a large tonnage-low grade orebody. The Pits have been designed to supply ore to a substantial Treatment Plant at the designed rate of 875,000 tpa. (This throughput is currently being increased to 1,200,000 tpa).Generally the orebody lends itself to large tonnage mining techniques, relying on only a relatively small amount of sampling. The surface enrichment zone and depleted zone are reasonably complex and require more intensive grade control and sampling techniques as typically utilised in many surface mines in the Eastern Goldfields, although as experience and understanding of the nature of the orebody was gained, less sampling became necessary.

Jan 1, 1986

By N Clarke, J Hunt, A Barros, L Keeney

The Gramalote orebody is a large low-grade gold deposit situated in the San Roque municipality, 124 km north-east of Medellin in Antioquia, Colombia. It is jointly owned by AngloGold Ashanti (AGA) and B2Gold and is currently in Feasibility Study phase. In 2013 AGA requested CRCORE to undertake a preliminary study of the potential application at Gramalote of pre-concentration by screening, part of the Grade Engineering suite. 160 samples of coarse assay rejects (-3 mm) were tested and showed one of the strongest responses seen worldwide to that time, suggesting that about 70% of the gold could be recovered into 40% of the mass. This was seen as potentially markedly improving the Gramalote economics. A large-scale testing program was implemented on site to follow up these results. A total of 18 samples of 17 t each were mined along a pre-existing exploration adit. A complex test flowsheet allowed size fractions to be generated from the as-received material as well as after crushing to 53, 23 and 3 mm, all from the same head sample. The procedures were designed after carrying out a heterogeneity study to measure sampling errors. The coarser size fractions were designed to study the effect of crushing on upgrade response and predict the response on open-pit run-of-mine ore. The finer size fractions were designed to investigate means of predicting the upgrade response across the orebody. The large-scale testing closely confirmed the average upgrade response as predicted from drill core assay rejects but found that only the -53 mm crushed material accurately predicted the upgrade response of individual samples. Ore geochemistry was able to usefully distinguish samples with good and poor response. A small study on drill core suggested that, for Gramalote, fine crushed material distinguishes vein associated and disseminated values but not other factors that control actual outcomes.

Nov 10, 2020

By G. S. Adisoma

To address the problem of grade estimation in a general three-dimensional shape and the uncertainty associated with the estimate, the technique of jackknifing/block kriging short-cut is proposed. A new estimator called jackknife kriging is introduced first. Through the jackknife variance, a confidence limit for the reserve grade estimate can be calculated. Unlike the kriging variance, which is more a measure of data configuration and is independent of data values, the jackknife variance reflects the true variability of the data. This approach provides a simple way to set a confidence level for global estimation of resources.

Jan 1, 1995

By P F. Hodkiewicz, J de Lacey, M Stewart, R Lane

"Implicit modelling is an approach to spatial modelling in which the distribution of a target variable is described by a unique mathematical function that is derived directly from the underlying data and high-level parametric controls specified by the user. This modelling approach may be applied to discrete variables such as lithology (after converting the discrete codes to numeric values) or to continuous variables such as geochemical grades. This paper discusses the estimation of continuous (grade) variables using implicit modelling.One of the underlying engines of implicit modelling for producing this mathematical function description is the radial basis function (RBF). In essence, the RBF is a weighted sum of functions positioned on each data point. A system of linear equations is solved to derive weights and the coefficients of any underlying drift model coefficients. Once derived, the RBF may be solved for any unsampled point or averaged over any volume to provide an estimate of grade. It is possible, for example, to query the RBF on a regular grid to derive an estimate of block grades. Given the ease of creation of an RBF, and its ability to predict grade, the question arises as to how the grades derived from the solution of an RBF compare with grade estimates derived from conventional geostatistical interpolation methods (eg ordinary kriging (OK)).The purpose of this paper is to describe in lay terms: the basic structure of an RBF the role of parametric choice in the solution of RBFs and how this influences the character of the solution the fundamental similarities and differences between RBFs and conventional geostatistical estimators.Using a high-resolution conditional simulation, we show that in many situations RBF and OK estimates are very similar.CITATION:Stewart, M, de Lacey, J, Hodkiewicz, P F and Lane, R, 2014. Grade estimation from radial basis functions – how does it compare with conventional geostatistical estimation?, in Proceedings Ninth International Mining Geology Conference 2014 , pp 129–140 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Aug 18, 2014

By A. W. Jolliffe

DESPITE the widespread occurrence of scheelite in Canada, domestic production of this strategic mineral is still quite insufficient to meet wartime needs. Two difficulties have invariably arisen in prospecting for or developing scheelite deposits: scheelite is a difficult mineral to identify, and secondly, its distribution is commonly so erratic that the value of a deposit cannot be determined without arduous and expensive methods of sampling and wet assay. Scheelite's property of fluorescing under certain ultra-violet lamps overcomes the first difficulty and is the basis for a quantitative method developed to overcome the second. It is found that, by use of an ultra-violet lamp, the value of many scheelite deposits may be accurately and speedily determined. The method requires neither elaborate apparatus nor exceptional skill on the part of the operator, and is most applicable to those deposits where the bulk of the scheelite occurs in fairly pure aggregates that are at least one-tenth of an inch across. It has been used in grading some two hundred scheelite-bearing veins in the Yellow-knife-Beaulieu region, Northwest Territories, and various occurrences in the Porcupine district, Ontario. The method requires the measurement of the total area of scheelite exposed in any reasonably large measured cross-section of a deposit. From the areal percent of scheelite so obtained, the tungstic oxide (WO,) content of that part of the deposit may be calculated by means of equations of simple derivation.

Jan 1, 1942

Graduate education is an integral part of the Center's research program. The scope of. work and the duration of each research project is calculated, in part, by taking into consideration the needs of the graduate research program and graduate training. Full development of student involvement, as demonstrated by the research practicum which is offered to qualified senior undergraduates at Penn State University and is designed to acquaint them with research methods and techniques and inform them of the opportunities available in this field. and the fulfillment of graduate program requirements are of the utmost concern. The Pennsylvania State University and West Virginia University have accredited mining engineering curricula and rank among the schools with the largest enrollment in this area in the nation. The number of undergraduate students enrolled in mining engineering at Penn State and West Virginia University account for nearly 20%, of the total undergraduate enrollment in this discipline in schools across the United States. The Pennsylvania State University. West Virginia University, Massachusetts Institute of Technology, University of Minnesota, and Michigan Technological University, have granted a total of thirty-five (35) doctorate and masters degrees which can be directly attributed to research conducted in the Center.' Of these graduates, fifteen(15) have found employment in the mineral sector of the economy, i.e., in private industry, with government agencies, and at various universities, worldwide. In addition, a number of those graduating with masters degrees are currently pursuing a doctorate degree.

Aug 31, 1989

By K. Horikawa, S. Kitahata, H. Kobayashi

"It has been clarified that the Al-5%Mg alloys containing 200 mass ppm of sodium showed grain boundary (GB) fracture, even when tested at room temperature, as well as at high temperatures (~500°C). SEM/EDX study revealed that the GB fracture was associated with the segregation of sodium on grain boundaries of the Al-Mg base alloys. Differential scanning calorimetry (DSC) revealed that the GB fracture at room temperature of Al-Mg alloys was caused by sodium segregation in the solid state. It was also shown that the tendency of the GB fracture strongly depended on the heat treatment; the alloys after the solution heat treatment showed severe GB fracture compared with the alloys after the homogenizing treatment. Moreover, it was shown that the GB fracture at room temperature by sodium segregation was suppressed by the addition of bismuth or indium. The suppression of the GB fracture by the additional elements was believed to be the scavenging effects by forming the sodium bearing compounds in grains.INTRODUCTIONIt is widely known that Al-Mg base alloys containing high amount of magnesium(~5 mass%)show better workability at room temperature, while that the alloys show grain boundary (GB) embrittlement at higher temperatures ranging from 200 to 500°C, depending on grain size(Otsuka, 1984), sodium impurity level(Ransley, 1959, Okada, 1997, Horikawa, 2001)and testing strain rate(Yamada, 2012). In the case of coarse-grained Al-5%Mg alloys (~300 ?m), 2 mass ppm of sodium causes severe GB fracture around 300°C, however, the Al-5%Mg-2ppm alloy does not show GB fracture at room temperature. It has also been shown that the GB embrittlement caused by 2ppm of sodium was suppressed by the additional elements, such as bismuth (Talbot, 1995), antimony (Ueda, 1997) and indium (Horikawa, 2012). Basedon these facts, we have concluded that the GB embrittlement at higher temperatures of Al-Mg alloys is attributed to the synergy effects of GB segregation of atomic sodium and GB sliding. For the GB embrittlement mechanism of Al-Mg alloys, involvement of low melting point metallic phases has been pointed out (Lynch, 2002),since the GB embrittlement appeared only at high temperatures. Up to date, the effects of high amount of sodium addition more than 2 ppm on GB fracture were not fully investigated in Al-Mg alloys. In the present study, the effect of 100 ppm ordered sodium impurity on GB fracture of Al-5%Mg alloys was examined, together with the effect of another additional elements."

Jan 1, 2017

By Davenport, Edmund S.

THE specific aim of this work has been to study certain forms of internal deterioration which occur in tungsten filaments when subjected to high temperatures under various conditions, and to determine the cause of such deterioration. This would naturally lead to a consideration of methods of control or means of prevention of the phenomena. The deterioration was first noticed as a peculiar condition in the grain boundaries of certain tungsten filaments which had been burned t for long periods in lamps. In these cases it was noted that the grain bound aries contained a number of minute black dots which were at first thought to be non-metallic inclusions. It was demonstrated later that these dots or pits, as they were designated, could be readily produced by burning filaments in an atmosphere of flowing hydrogen. This method was convenient and adequate for the purpose, and was adopted for most of the work discussed in this paper. The evidence accumulated to date indicates that these pits arc actually small voids between the grains. The purpose of this paper is to, present the information on this interesting subject gathered during a period of about 3 years. As applied to tungsten, the subject appears to be of considerable importance, experience having shown that this pitting is frequently associated with poor performance of filaments in lamps.

Jan 1, 1927

By R. S. French

THE purpose of this paper is to present data that have been obtained during the past two years concerning the effects of prior cold-work and temperature and time of anneal upon the recrystallization and grain growth of 70-30 cartridge brass. It was desirable to study certain of these phases so that an accurate picture of the principles of the subject could be shown. The work is not intended to provide explicit annealing data, but to provide material examples that may help to clarify analogous problems concerning this alloy. Specifications often set limitations upon the grain size of annealed materials because of the importance of grain size upon subsequent manufacturing operations. It was, therefore, worth while to study the variables that affect the recrystallized grain size of this material. C. H. Mathewson and A. Phillips,1 W. R. Webster,2 and others have presented annealing characteristic curves of this alloy. A recent typical curve presented by R. S. Pratt3 is shown in Fig. I. The tensile properties and grain sizes are shown as functions of the annealing temperature. Such curves serve as a useful guide in determining the physical properties of annealed material, but as they are made generally under carefully controlled laboratory conditions they do not indicate the performance of metal annealed in a mill muffle, where conditions are different and the amounts of metal require necessarily longer heating times and temperatures. Study of the effect of time and temperature upon grain growth and subsequent recrystallization was made with a coil of metal having the following analysis: 70.04 per cent copper; 0.007 lead; 0.007 iron; 0.00 tin; 0.00 silicon; 0.001 nickel; 0.000 phosphorus; balance zinc. The sample coil was obtained from metal that had been rerolled from hot-rolled mill stock, and was received at 0.228-in. gauge, soft, with a grain size of 0.125 mm. This material was then rolled 43.5 per cent to 0.125-in. gauge and annealed to a 0.053-mm. grain size. In this condition, samples were cut and used in all of the experimental work reported in this paper. TIME The first study was of crystal growth at a constant temperature over a moderate length of time. Material was cut from the stock coil at 0.129-in. size and rolled 75 per cent hard to 0.032-in. gauge. From this piece small samples were cut ½ by 2 in., suitable for grain-size determinations. Twelve samples were placed in an electric furnace uniformly across the width, approximately an inch from the floor, A thermocouple was wired to the center sample, so that the approximate metal temperature could be followed. At various

Jan 1, 1944