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CHARLES F. WILLIS,* Bisbee, Ariz.-(written discussion?).-The consensus of the discussion of the paper of Dr. Lanza indicates that the physical examination, while it is probably a good thing, is fought by the workingman, and that, because of this fact, it has been proved unsuccessful. The physical examination standing alone is worth but little, and could easily be made a subject both of ridicule and dissension unless the company having such examination shows its own good faith in promoting a thoroughly better health program. It is easily seen why a workman would resent his employer expecting him to be physically fit, if at the same time the employer provides un-healthful, unsanitary, working conditions, or if the town in which the employees are expected to live is dirty and unkempt. One mocks the other. The employer cannot say, "You must remain healthy so that I can get by with unhealthy conditions." But if working- conditions are as good as can be obtained to keep men well, the employer can ask his men to be in a healthy condition. A State examination and standard would have many difficulties, owing to the fact that a man would pass or would not pass the standard set, thus eliminating the discretion on the part of the employer in placing men whose physical condition might well permit working in one place and not another. Any physical examination that is run for the purpose of eliminating the physically unfit is unjust, both to the worker and to the nation as a whole; a State examination would make a distinct dividing line, whereas examination by the employer is conducted with a vision of the positions available. The workman's opposition to the physical examination comes from the fact that he has been taught to believe that it is an interference in his personal affairs, that he can be clean or dirty as he chooses, that he can he healthy or unhealthy, and that it is nobody's business but his own. The war has taught us, however, that the individual is no longer the unit and that all such propositions must be based on the greatest good for the greatest number.

Jan 6, 1919

Edward Halse, Puerto Berrio, Colombia, S. A. (communication to the Secretary): I have read with much pleasure the interesting and valuable paper by Mr. Kunz, and hope that the following brief notes, gathered a few years ago, while a resident in Mexico City, may help to elucidate the subjcct: Turquoise.—This was known to the Aztecs as Xihuitl. Santiago Ramirez states that they found it in the Cerro Xicohtzonc, close to Atzcapatzalco, a suburb of the City of Mexico (compare page 59). Opal.—This was known to the ancient Mexicans, for they named it mezcuitlatt (compare page 63). Jade.—Under this was iucluded a third mineral, prehnite, not mentioned by Mr. Kunz. According to James D. Dana, part of the "jade " of China is prehnite; and Humboldt informs us, in his work on New Spain, that the same species of jade is known in some parts of Mexico as mahagua (majagua ?). The same writer says, in his Views of the Cordilleras, that the Aztec name Tecpatl included flint, hornstone, and green jade; and finally, in his Travels in South America," he discusses the nature of the ancient amazon-stones, and declares them to have been made out of a jade resembling " compact feldspar," one of the constituents of the gabbro verde di Corsica. IIence those stones were probably composed of nephrite. According to Humboldt, the form given to them most frequently is that of the Babylomian cylinder, longitudinally perforated, and loaded with inscriptions and figures. They were also cut by the natives into very thin plates, perforated at the center, suspended by a thread, and worn as amulets. According to the historian Clavijero, the specific name given by the Aztecs to the nephritic stone (jadeite) was Quitzalitztli,

Jan 1, 1902

By Winthrop P. Haynes

The symposium on production for the year 1944 includes more foreign papers than any one of the past three years, because of a partial relaxation of the censorship in many Western Hemisphere countries. The committee was not successful, however, in securing papers from Europe and the Near and Far East at this time, with the exception of Saudi Arabia and Bahrein. Where possible, these papers include summaries upon production for the missing war years, so that we shall have no permanent gap in the records. At the close of the war, we hope again to publish the usual more complete form of report for all important oil-producing countries. EXCERPTS FROM CIRCULAR TO AUTHORS In order to facilitate interpretation of the data in this chapter, we print the following excerpts from the Circular to Authors. The field is the unit in this tabulation. In cases of fields extending across State boundaries, such as Rodessa, it is suggested that each State author treat the section of the field in his State as a unit, and by a footnote indicate that the field extends into an adjacent State. Each place in the table may represent one of three possibilities; either the proper entry is determinable and can be supplied by the author, or an approximate figure can be supplied which is the author's best guess and should be entered followed by an x, or it does not apply to the particular field and the space is left blank. Contributions of great value may be made by the author in many cases where entries are not subject to precise determination. In such cases the author should use his good judgment and make the best entry possible under the circumstances. The entry of a zero is a positive declaration, and it is an important declaration where it is in order. It is thought that the nearest whole numbers are sufficiently accurate for our purposes except as to percentage of sulphur in oil. If an author desires to report any other figures to tenths, he may do so. The quantity of gas produced should include, where possible, gas sold or otherwise marketed, and gas blown into the air, burned as flares or otherwise wasted. Segregation of these figures would be interesting if the authors can make such segregation. In any event, the figures should represent as nearly as possible the total quantity of gas removed from the reservoir. . Under the columns on "Depth," the average depth to the top of the productive zones and to the bottom of the productive wells, when subtracted, should give the approximate thickness of the productive zone. For fields where this is not true because of unusually high dip or for some other reasons, it is suggested that the authors indicate in their text the approximate average thickness of the productive zone. The net thickness of the producing formation should be the thickness of the producing zone, less the estimated amount to cover the portions of the zone that do not yield oil, such as dense shales, etc. It is recognized that for some fields the authors can only make rough guesses; in such cases, they should enter their best estimate followed by an x. Average production per acre-foot need not be reported as it can

Jan 1, 1945

By Paul Pietrokowsky

THE formation of intermediate phases in the solid state reaction of titanium with silicon, germanium. and tin (of subgroup 4B in the periodic table) was the subject of a recent paper.' Further investigation of the system Ti-Sn revealed the presence of a new compound on the titanium-rich side of this phase diagram. Metallographic evidence indicated that this new phase was situated very close to 75 atomic pct Ti. The present work is concerned with the crystal structure of the intermediate phase Ti3Sn. Iodide-process titanium metal, furnished by the New Jersey Zinc Co., was used in this investigation. The metallic tin was received in powder form from Charles Hardy Inc., New York; its purity was 99.80 pct. The titanium rod was machined into small cups 1 cm in diam and about 1.5 cm in height. The tin powder was compacted, melted, and then placed in the titanium cups and alloyed by electric arc melting in a helium atmosphere. The alloys, weighing approximately 8 g, were sealed in evacuated quartz tubes and homogenized at 1030°C for 5 days. This isothermal heat treatment was terminated by a water quench from the soaking temperature. Filings of the alloyed pellets were sealed in evacuated quartz bulbs and quenched from 1030°C into liquid argon. A 14.32 cm Debye Scherrer X-ray camera was used for the powder diffraction study. The copper radiation was filtered. X-ray diffraction data for the compound Ti3Sn are given in Table I. The data were indexed on the basis of a hexagonal lattice. Good agreement between observed and calculated values of the square of the reciprocal interplanar spacings was obtained with the following expression: (1/d)2 = 0.03810 (h2 + hk + k2) + 0.04410 (l2) Unit cell parameters were calculated by the method of least squares from the reflections (20.3), (22.2), (40.1), and (42.1); ao = 5.916 & 0.004A, co = 4.764 ± 0.004A, and co/ao = 0.805. The relatively small size of the unit cell allowed the unambiguous indexing of most of the reflections from planes of large spacing. An inspection of the assigned indices (Table I) reveals the absence of (hk.l) reflections when 1 2n. A systematic absence of this type leads to the space group C 6/mmc or one of its subgroups. Assuming, for a first approximation, a linear increase in the density of titanium with the addition of tin, it follows that there are two stoichiometric molecules of Ti3Sn per unit cell. The density calculated from X-ray measurements is 5.194 g cm-'. At this point it became clear that Ti3Sn might be isomorphous with Mg3Cd. The 6 Ti and 2 Sn atoms were placed in the following positions of space group D4 6h, C 6/mmc: 6Tiin (h): X 2X 1/4; 22;; 1/4;Xx 1/4;x2x3/4; 2x x 3/4; x x 4; with x = 516 2 Sn in (c): 1/3 2/3 1/4; 2/3 1/3 3/4.

Jan 1, 1953

By Ralph K. Foster

During five underground mine fires which occurred in Arizona during 1980 and 1981, sealing the fire area became necessary. To minimize leakage into the fire area, ventilation control measures were instituted to balance pressure across the bulkheads. Problems en- countered in sealing the fire areas and measures taken to improve these conditions are discussed. The routing of the ventilation and ventilation control to en- sure the workers' safety were also important considerations in reopening the mines. The use of continuous CO monitors is discussed. One important consideration was the condition of the fire, and chromatographic analysis was used to establish this. Graphs comparing the Trickett ratio, carbon monoxide, carbon dioxide, and oxygen concentrations are given. The Trickett ratio was useful but needed to be augmented by the comparison of CO, C02, and 02. Problems with getting good samples from sealed areas and recommended procedures that were developed during these fires are discussed.

Jan 1, 1982

By W. W. Mein

IN March 1949 the Calaveras Cement Co. was sued by five landowners whose properties are located in the vicinity of the plant. These landowners—all of them cattle ranchers—sued for dust damages of $120,338 and for an injunction preventing the company from casting dust upon their properties in injurious quantities. The issue was split, the jury deciding the amount of damages and the court handling the injunction features. The action came to trial before a jury in April of that year and resulted in damages being awarded in the amount of $7,508. A month later the court issued its injunction requiring recovery of stack dust to an 87 pct minimum. The Calaveras plant, shown in Fig. 1, is located three miles from San Andreas in the heart of the Mother Lode country, about 45 miles east of Stockton, Calif. Since it is in a small town, the company's responsibilities to its employees and to the community are different from those of plants located in large centers of population. Construction of the plant was begun in 1925, and production was started the following year. Standard gray Portland cement as well as several specialty cements are produced. Production facilities have been continually enlarged so that the present capacity is more than double what it was 25 years, ago. The most important item in the company's expansion program was the purchase in 1945 of an 11 ft 3 in. x 360 ft Allis-Chalmers kiln which had been declared surplus by the Defense Plant Corp. The company is now able to produce about 2,500,000 bbl of cement a year, and employment at the plant is approximately 300. The production of cement has always involved a dust problem, solution of which has been attempted in a number of different ways. By far the most efficient method of catching dust discharge is electric precipitation. Soon after the company went into production in the 1920's, the landowners near the plant began complaining about dust discharge. The company settled the matter by paying them a total of $27,000 for dust damages incurred during the period from 1929 to 1938. In the latter year the two-unit Cot-trell Electric Precipitator shown in Fig. 2 was installed and collected over 85 pct of the dust resulting from operation of the two 11 ft 3 in. x 10 ft x 240 in. kilns. From 1938 until 1946 the landowners registered no objection and were apparently satisfied with that dust recovery. In 1946, however, the substantially higher production resulting from operation of the new kiln immediately overtaxed the facilities of the existing two-unit precipitator. In a short time claims for dust damages were again received from the landowners. The company informed them that because of postwar shortages it would take several years to install a new precipitator. The company stated that it intended to purchase an additional precipitator and offered in the meanwhile to pay the landowners a fair amount to cover their damages. This offer was rejected and the landowners filed suit in the Superior Court of Calaveras County asking for total damages of $120,-338 and for the injunction outlined above. Case for the Ranchers The attorneys for the plaintiffs produced three different types of witnesses: first, the landowners themselves and members of their families; second, other cattle raisers who were sympathetic to the plaintiffs; and third, several types of technical experts: veterinarians, soil chemists, and an aerial photographer. The testimony of these witnesses was designed to establish that the flue dust from the plant had not only damaged the land and the forage, but had also caused fluorine poisoning to their animals. By a combination of these causes, the plaintiffs attempted to prove substantial loss of profits.

Jan 1, 1952

By Paul D. Conatore

INTRODUCTION There are important reasons for a discussion of tungsten resources, reserves, and production in the Circum-Pacific area. First, the world's chief tungsten deposits, as well as most of the world's tungsten reserves and production, occur in this region. It is well known that the world's largest tungsten reserves are located in southeastern China and that for many years, the largest individual mine in the world was there. Although China still has the world's greatest tungsten production, the very high-grade scheelite mine of Canada Tungsten Mining Corporation in the Northwest Territories is the largest producer of tungsten today. There is certainly a great quantity of tungsten in Asia, but the strategic importance of this fact is now offset by the wide distribution of mines and production facilities throughout the world, especially in other parts of the Circum-Pacific area such as Australia, Canada, and the United States. In addition, much of the Circum-Pacific area is comprised of Mesozoic-Cenozoic orogenic belts. These global tectonic units are regarded as very favorable for additional tungsten deposits, particularly scheelite-bearing tactites, and consequently, prospecting and exploration will most likely be concentrated in the Circum-Pacific area. Second, tungsten must be regarded as one of the, most important metals of modern industry because of its very special properties. It has the highest melting point, the highest tensile strength at elevated temperatures, and the smallest compressibility of any metal. The metal also possesses a very high density, excellent corrosion resistance, good thermal and electrical conductivity, and a low coefficient of expansion. As a result, tungsten has found increasing importance in a wide range of industries. From the filament in an electric lamp, to cutting tools and drilling bits, to the exotic radiation shields that protect supersonic aircraft and spacecraft, tungsten plays an indispensable role in our daily lives. The primary objective of this paper is to present an overview of important facets of known and suspected tungsten in the Circum-Pacific area. Resources, reserves, current production, planned capacity expansions, and new operations, as well as an assessment of the probability for development of deposits in the Circum-Pacific area, are discussed. RESOURCES The average crustal abundance of tungsten has been estimated at 0.0015 kilograms per tonne. A comparison of the abundance of various metals in crustal rocks to that of tungsten is presented in Table 1, which shows that tungsten abundance is similar to that of its commonly associated metals, tin and molybdenum. Table 1. AVERAGE CRUSTAL ABUNDANCE OF VARIOUS METALS (Grams per Tonne) [ ] With careful thought, it can be realized that tungsten ore deposits result from the concentration of the metal, through normal geologic processes, to levels substantially greater than its average crustal abundance. The minimum technologically and economically workable tungsten concentration, or cutoff grade, is a function of (1) deposit tonnage, (2) mining and milling methods, (3) production tonnage, (4) capital and operating costs, (5) tungsten market conditions, and (6) value of associated recoverable metals. The tungsten cutoff grade that is currently exploitable at a profit varies from 0.09% W03 to 1.55% W03, reflecting concentration factors from 470 to 8200, as shown in Table 2. Table 2. CURRENT TUNGSTEN CUTOFF GRADES [ ]

Jan 1, 1982

By John L. JR. Schroder

INTRODUCTION-SYSTEM DESIGN The design of an underground mining operation requires the integration of transportation, ventilation, ground control, and mining methods to form a system which provides the highest possible degree of safety for mine personnel; the lowest cost per ton of product; the most suitable quality of final product, considering its intended use; the maximum percent recovery of the reserve, consistent with cost and subsidence rights ; and the minimum disturbance to the environment. The selection of mining method is generally the controlling factor in overall mine design. Some important considerations in the choice of mining method are : 1) Depth of cover over the coal seam. 2) Strength and thickness of rock strata in the overburden. 3) Characteristics of the coal seam, including thickness, nature and location of impurities or irregularities, dip (or pitch), nature and direction of cleavage, hardness, and structural strength of the coal. 4) Nature and strength of the immediate roof (top) over the coal seam. 5) Nature and strength of the floor (bottom) under the coal seam. 6) Presence and amount of explosive gas (methane). 7) Quantity of water likely to be encountered in the mining operation. 8) Any previous or concurrent mining in seams above or below the coal seam to be worked. 9) Any restrictions on recovery required for subsidence control. Topographical and geological reports and maps of the area are usually available from state and federal geological surveys, and contain excellent general information to guide more detailed investigations. Exploratory drilling, and the plotting and analysis of the information thus obtained, are essential steps in any development program, and aid in the correlation and evaluation of information gained by other means. Other good sources of information are operating coal mines that may be in the same

Jan 1, 1981

By M. S. NORTH

IT may be a far cry from the days of the old horse whim, and it is relatively a long way back to hand production in factories. Modern machinery has made possible deep shaft-sinking, newer methods have increased the recovery of mineral. Technically, excavating and ore dressing have advanced as has mass production and its many ramifications in the manufacture of commercial product. To those of the mining industry who would have us believe that mining and manufacturing are totally different enterprises, it can be said that certain differences do exist. These differences rather than being fundamental are the result of adhering to past practices which were possibly sound years ago but do not measure up today. Differences in managerial control, sales, and distribution, cost finding, etc., are often so pronounced that efforts to compare or contrast are almost futile.

Jan 1, 1930

By Benjamin F. Tillson

THE past seven years, and 1937 in particular, have witnessed the return of New Jersey iron mining to a place of importance. Following the World War period, little mining was done for several reasons. The properties were operated by small merchant furnaces whose demand was not sufficiently large to warrant large-scale methods with their attendant low operating costs. Under those conditions, the ore produced could not compete with that from the Great Lakes. However, when on Nov. 1, 1.929, the Alan Wood Steel Co., of Conshohocken, Pa., leased the Scrub Oak and Washington properties at Mine Hill and Oxford respectively, they made radical changes in the mining and milling processes which greatly reduced the cost of production and pointed the way to a renewed interest in mining in New Jersey. The following factors have been advanced as influencing the reopening of New Jersey mines:

Jan 1, 1938

By AIME AIME

ED DIX, after studying both mechanical and electrical engineering at Cornell, started out to be an electrical engineer, then taught material testing at Cornell, and decided to become a metallurgist. He was successively employed by the Morse Chain Co. as metallographist, by the Baltimore Copper Smelting and Rolling Co., as chief of the testing department of the Bureau of Aircraft Production, as assistant engineer of tests of the Aluminum Castings Co., and as chief of the metals branch, engineering division, U. S. Air Service. Since 1923 he has been with the Aluminum Co. of America, now as chief metallurgist.

Jan 1, 1936

By P. K. Strangway, H. U. Ross

Briquets consisting of pure artificial magnetite, pure artificial hematite, and mixtures of the two were reduced by hydrogen in a loss-in-weight furnace at temperatures in the range 500° to 1000° . The rate of reduction of the pure hematite briquets increased continuously with increased temperature. In contrast, the pure nmgnetite briquets exhibited a pronounced rate ninimutn at about 700°C. Metallographic studies of partially reduced briquets rerlealed that, at this temperature, the he.matite samples reduced in a topo-chemical manner while the magnetite ones reduced uniformly throughout, and after partial reduction their cross sections contained a mixture of iron and unreacted wustite grains. No iron shells could be detected on the surfices of any of these uwstite grains. X-ray diffraction investigations indicated that these grains had a rzinimum lattice parameter when they had been formed at the rate rninimum temperature. Also, it was found that an activation energy of 41,000 cal per mole zoas required for reduction when only these wustite grains were present. Thus, it is suggested that the overall reduction rate of the rnagnetile su?nples at temperatures in the range influenced by the rate nzinirnum phenomenon was limited by the rate qf iron ion diffusion in the unreacted wustite grains. THE rate minimum phenomenon, which has often been observed when reducing iron oxides at a temperature of about 700°C, is one of the most interesting, yet unresolved, problems in the field of reduction kinetics. Basic principles of chemical kinetics and 'In some instance, a second rate minimum has been observed at about 900°C. Since most investigators are in agreement that this minimum is directly related to the transformation from a to y iron (which takes place at 911°C) and since it was not encountered during the present reduction tests, it will not be referred to in this vaver. fundamental laws of diffusion all agree that, as the temperature is increased, the rate of reduction should also increase. However, with certain ores, it has been found that their reduction rate actually decreases with an increase in temperature up to some value X where a minimum reduction rate is reached. With further temperature increases beyond X the rate becomes more rapid again. Temperature X is usually referred to as the "rate minimum temperature", while the overall type of behavior constitutes the "rate minimum phenomenon". This phenomenon has been reported by numerous investigators. They have found rate minima during the reduction of both artifiial' and natural374 magnetites and artificia15j6 and natural5" hematites. Rate minima have been observed when reducing high-purity material2 or low-grade ores,3'4 when studying particles in the micronsize range5 or relatively large agglomerates,g10 and during reduction with either hydrogen7 or carbon monoxide.11"2 Previously, this phenomenon has been attributed to many factors; these include sintering and recrystallization of the iron formed during reduction374 changes in microporosity of the ore upon redction,"" formation of dense iron shells around retained wustite grains,11716 and chem-isorption,17 to name only a few. However, most investigators who have reported a rate minimum merely speculated as to what seemed to influence it and they did not examine the fundamental causes. Consequently, the present experimental study was initiated in order to evaluate the basic factors which could be associated with this phenomenon. MATERIALS AND METHODS The experimental techniques, followed during this investigation, are similar to those which have been described previously.18 The chemically pure magnetic powder was prepared by partially reducing Fisher reagent-grade hematite with a gaseous mixture of carbon monoxide and carbon dioxide in a rotating-drum furnace. Three-quarter-inch diam cylindrical briquets which weighed about 12 g were formed from this magnetite powder and pure hematite powder. All of the briquets were sintered while they were slowly raised through the 1200°C hot zone of a vertical tube furnace. An argon stream was continually flushed through this furnace in order to prevent oxidation of the magnetite briquets, while in the case of the pure hematite briquets sintering was carried out in air. The sintered hematite briquets had a density of 5.06 g per cu cm while the density of the sintered magnetite briquets was 4.27 g per cu cm. The sintered briquets were reduced by purified hydrogen in a loss-in-weight furnace at temperatures in the range 500" to 1000°C. In all instances, the critical reducing gas velocity was exceeded and, in order to ensure that the results were reproducible, duplicate briquets of each type were reduced under each set of experimental conditions. A continuous record of the weight loss during reduction was obtained with the aid of a Statham transducer. The present experimental setup was capable of detecting a change in weight as small as 10 mg. Since a weight loss of over 2 g usually occurred during each reduction test, an accuracy of better than 0.5 pct of the total weight loss could be achieved. RESULTS AND DISCUSSION Reducibility Tests. In the first set of experiments, pure hematite and pure magnetite briquets were used.

Jan 1, 1969

By AIME AIME

THIS year's Chairman of the Mineral industry Education Division is, like his predecessors, no novice in that field, having been in 1928 Chairman of the Engineering Education Committee which labored so well that it was enlarged into a Division of the Institute's activities . For almost a quarter of a century lie has been a dean in mining and engineering schools, with considerable experience before that as a teacher. A native-born New Englander (June 23, 1881), he naturally went to Massachusetts Institute of Technology where he received the Bachelor's degree in mining in 1904. Just why a Fitchburg. Massachusetts boy yearned to he a mining engineer he has never explained, but why should any boy ever have to explain why lie wants t? be a mining engineer? Like the old rhyme about the reasons why a man should drink, "any other reason why" is adequate..

Jan 1, 1945

THE illustration below shows the design of the face of the clock to be erected as a memorial to the American engineers who gave their lives overseas in the World War. It will be placed in the tower of the library at Louvain, which has been rebuilt through contributions from America. Large clocks seldom have figures on their faces, and each hour on this one will be marked by a gold star, the four faces containing 48 stars, one for each State of the Union. Contributions toward the memorial have been received from every one of the States, and from Alaska and Hawaii as well, but additional subscriptions are invited by the Com-mittee which is arranging for the memorial.

Jan 3, 1928

IN the footnote on the first page of Prof. Stoek's paper, as printed in vol. xxviii. of the Transactions, I alluded to him, under an erroneous impression, for which he was in no way responsible, as " the present Director of the Scranton Schools." This incorrect statement placed him in a false position, as possibly having authorized the use of a title to which he had no claim. In fact, Prof. Stoek has never had any official connec-

Jan 1, 1900

By T. B. Armstrong

Electrical energy conservation sees that service facilities are operated only when needed and that production equipment is operated under an optimum condition. Specific energy consumption (kw-hr per tonne) is not regularly recorded for comminution circuits because of variations in ore characteristics and the low grinding efficiency (0.1 to 2.0%) of the equipment. Improved data acquisition can produce meaningful results. Particle size monitor systems and density gauges permit comparison of energy (kw-hr) and production (tonne) for a "fixed" condition. Finding the operating condition producing the lowest unit energy consumption provides a target for an effective energy management program.

Jan 1, 1982

By Phillip Crowson

INTRODUCTION This discusses some of the economic risks and uncertainties which face any company investing in new mineral ventures. These differ mainly in degree rather than kind from other large capital intensive projects, except that economic risks are compounded with technical risks. Mines face a wide variety of physical risks, and in addition the ore reserves may not prove as ample, nor as amenable to treatment as the feasibility studies indicate. On the economic front, mineral projects are subject to risks of fluctuating prices and sales volumes, no matter where they are located, or how they are financed. Typically, they are heavy users of capital compared with their owners' internally generated funds. Long term debt of various types is still the favoured form of finance. A project's currencies and cost often differ from each other and from those of the parent company. Facing up to the various risks associated with fluctuating and uncertain revenues, interest rates and exchange rates are amongst the hardest tasks for natural resource companies. ATTITUDES TO THE MINING INDUSTRY Some have questioned whether the game itself is now worth playing. They have argued that the mining industry's mediocre rewards in the past decade have been insufficient, compared with the risks involved. They can see no prospect of dramatic improvement in the next decade. Demand is highly cyclical and tends to grow less rapidly than economic activity, as a whole. Barriers to entry are low in most mineral markets, but impediments to exit can be substantial. Exit is especially problematic in those minerals where there are large state shareholdings and/or where less developed countries are major producers. The consequence is claimed to be an endemic tendency to excess capacity, and prices barely adequate to cover marginal cash costs. Many of the petroleum companies that moved into mining with such high expectations in the late 1970s have retreated, often bearing the scars of heavy losses. Individual shareholders, taken collectively, place low valuations on their investments in mining companies. The price/earnings ratios of the major mineral producing companies are low compared with their historical averages and with those of other industries. PRICE: EARNINGS RATIOS (October 1988) [UK Industrials 12.0 RTZ 8.4 Cons Gold 12.2 US Industrials 13 - 13.4 Alcan Alcoa Amax Asarco Cyprus Minerals Freeport Copper Inco Inspiration Magma Copper Newmont Mining Nord Resources Phelps Dodge Reynolds Metal Canada TSE 300 10.6 Cominco 8.7 Falconbridge 5.3 Noranda 7.0 Rio Algom 7.2 Teck Corporation 17.] NOTE: Mining companies' p/e based on prospective 1988 earnings, from Kleinwort Benson Securities' weekly Mining World, October 1988. Until 1987, it was argued that share prices correctly reflected the companies' poor earnings potential. Subsequently, the argument has been that earnings have been unnaturally boosted by cyclically high metal prices. The stock market valuations, therefore, correctly reflect future earnings, or at least expected earnings. This seems to be a case of Heads, I win; Tails, you lose. The underlying analysis of metal markets appears

Jan 1, 1990

By Richard C. Timberlake

The disposal of phosphatic clays has presented a problem to the phosphate industry since the mining of phosphate rock first began in Polk County. As the flotation process was introduced in the late 1920's the problem of clay disposal was increased significantly since clay is present in proportionally greater quantities in reserves yielding flotation concentrates. Because of their physical character and the tremendous surface area per unit volume, these clays have the characteristic of retaining large volumes of water as they are slurried during processing. The disposal of clay and the recovery of a portion of the water require settling areas with a capacity ranging up to 2 cu ft for each cubic foot of phosphate matrix mined. According to a recent study by the Bureau of Mines, the average cost for disposal of these wastes is 24.5[c] per ton of product. This is a major cost of phosphate rock production.

Jan 12, 1969

By BLAllEY STEVENS

(Canal Zone Meeting, November, 1910.) I. INTRODUCTION. TEH object of this paper is to show how igneous intrusion is governed by definite mechanical laws. A distinction is made between dikes and fissures, and the various characteristics of intrusions are explained on an exact scientific basis. The modification of rock-stresses by intrusion is then considered and extensive isostress regions are recognized. Finally, a complete classification of intrusions is constructed covering all pos-sible cases. The generalizations of observed data, taken from Geikie's Textbook of Geology, conform to the laws of intrusion herein stated, and the deductions based upon these laws. No authority, however, is quoted for the type which I have named a corrugated intrusion. Its existence is a necessary deduction from the laws of intrusion, and even the entire absence of examples in technical publications cannot disprove its reality. In all probability, corrugated fissures would have remained undiscovered, but for the working of mineral veins. As intrusions of tabular form are seldom worked for commercial purposes, it has been left for theory to anticipate the discovery of corrugated dikes. In the light of these laws of intrusion and the corresponding laws of fissures,1 there seems to be a remarkable uniformity of stress-distribution in rocks at moderate depths. This renders .possible the mathematical calculation which should help us to approximate exact science in this and kindred branches of applied geology.

Jan 1, 1911

By G. A. Swanquist, E. M. Morales

INTRODUCTION The idea of water management and control at the Church Rock Mill operations began to take shape in February 1979. At that time, we were already investigating the feasibility of decreasing the fresh water requirements so that the solids would become the limiting factor in tailings impoundment utilization. The area for solution evaporation could be kept at a fraction of the normal requirements under the standard process of full water usage. The Church Rock Mill is an acid leach circuit followed by solids/liquid separation with thickeners in counter current decantation, and solvent extraction. Following the normal design of acid leach circuits, reuse of tailings solution was not incorporated in the original mill process design. INITIAL WATER CONTROL INVESTIGATIONS The investigations to decrease the fresh water requirements centered around modifying the grinding circuit from the present semi-autogenous grinding (SAG) mill in closed circuit with hydrocyclones, to open circuit grinding with a rod mill. The open circuit grinding with the SAG mill and rod mill in series had the potential of decreasing the water requirements for grinding and leach dilution by approximately 50% or 1.4 m3/min (300 gpm). The grinding pulp density would be maintained at 70 to 72% solids, and the leach dilution to 50% solids would be accomplished with acid tailings liquor recycle. In such a grinding circuit arrangement, the SAG mill would provide the primary or coarse grind, and the rod mill would be used for the fine grind. By the SAG mill and rod mill series grinding method of water control and other secondary water controls in various places downstream from the grinding circuit, the required necessary evaporation area was estimated at 120 acres of liquid surface. A second method of water control at grinding was investigated. A two-stage cyclone classification circuit appeared to have a good potential of achieving the same water reduction at a much lower capital and operating cost. However, in retrospect, this would not have been a viable method since a high slime recycle load would have been established hindering classification. The use of reagents to neutralize the acid tailings solution was not considered seriously at that time, since it would have materially increased operating costs, although it would have also allowed more tailings solution recycle and consequently, less fresh water usage. However, with the tailings solution deposition area available at that time, it was not then necessary to incur the high cost of neutralization. The control expected by the series grinding of semiautogenous and rod mills would have been sufficient to maintain a water consumption/evaporation equilibrium well in line with the available land area. IMPLEMENTATION OF NEUTRALIZATION OPERATIONS During the summer of 1979, the UNC Church Rock Mill experienced a tailings dam breach which resulted in a prolonged mill shutdown. Upon resumption of operations at the end of October 1979, tailings deposition was restricted to a small portion of the tailings impoundment area. Figure 1 shows the general tailings area and the limits of the present deposition area in the central part including the borrow pits. These borrow pits had been excavated to provide materials for tailings dam construction. Immediately after resumption of operations, it became evident that it would be necessary to control the quantity of liquid to be evaporated because of the small confined area available for tailings solution deposition and to maximize the deposition time in the tailings area. The water control required had to be exercised on a large scale, and to be in operation as quickly as possible. An obvious solution was to reuse the tailings liquor in mill process. Immediate steps were taken to install the necessary equipment for tailings neutralization on an interim basis. Anhydrous ammonia was selected as the primary neutralization reagent since it was the quickest system that could be placed in operation. Previous laboratory tests indicated fair results with ammonia neutralization. Such a system required a minimum of installed equipment and handling. INITIAL NEUTRALIZATION OPERATIONS Actual neutralization operations began on November 26, 1979. The raffinate solution which normally would have been discarded was pumped to a 3.7 m (12ft) diam by 4.3 m (14ft) tank for reagent contact, see Figure 2. At this tank, anhydrous ammonia was added directly from the tanker trailers and controlled at pH 7.0 nominally. Agitation was provided by air sparging. The neutralized product formed a highly viscous slurry in the grinding circuit which resulted in pumping and cyclone classification problems.

Jan 1, 1982