Search Documents

Discussion of the paper of CHESTER W. WASHBURNE, presented at the New York meeting, February, 1915, and printed in Bulletin No. 9S, February, 1915, pp. 469 to 471. ROSWELL H. JOHNSON, Pittsburgh, Pa.-I hope that this contribution of Mr. Washburne's is only the first of a series dealing more in detail with the very important problems involved. Pores are of two kinds: Those which are entirely inclosed, so that they do not belong to a system of communicating pores tapped by the bore hole or shot hole; second, those which do so communicate. Porosity, of course, includes both. But since pores of the first class are valueless to us, we should confine our attention to the latter, for which I propose the term "effective porosity." This should be measured by the Wisconsin method, based on the quantity of fluid that can be introduced by the aid of vacuum. Another factor which requires attention in this connection is the dependence of the extractability upon the rate of loss of pressure, as affected by the number of holes, and the rapidity of their completion, the existence of uncontrolled wells, the use by other operators of vacuum pumps upon the casing head, the exhaustion of a gas field in the same reservoir prior to the discovery of the oil, etc. The extractability depends upon the pressure available for the exclusion of the oil from the reservoir into the hole. The action of gravity in bringing oil into the hole is relatively small where the pores are very small, as is so frequently the case.

Jan 5, 1915

By F. D. Rosi

IN the production of single crystals by the Bridg-man method of solidification from the melt in vacuum at a crucible lowering rate of 0.25 in. per hr, a cellular structure was frequently observed in copper and copper-base alloys at the terminal surface of the as-cast crystals (i.e., the surface representing the last portion of the crystal to solidify). The geometrical form of this structure varied from crystal to crystal, but, in general, could be classified as either hexagonal or quadrilateral. Fig. 1 shows examples of this cellular structure, which is similar to that reported by Buergerl and, more recently, by Pond and Kessler&apos; and Rutter and Chalmers. In the micrographs of Figs. lb and c, the cubic structure in the alloy crystals is obscured somewhat by excessive surface evaporation in the final stages of solidification. X-ray orientation studies indicate that the traces outlining the various geometrical forms correspond to octahedral planes, which are the planes of greatest reticular density in the face-centered cubic lattice. It would appear from this that the view first propounded by Bravais,4 that the surface energies and normal growth velocities of the different crystal planes are inversely proportional to their reticular densities, applies to this cellular structure, since those surviving are the planes of greatest atomic density. Thus, the observed variation in the geometrical form of this structure in crystals of different orientation is readily understandable from the distribution of the (111) planes in the standard {111}, (1101, and (1001 stereographic projections. Depending upon whether the crystal axis (i.e., the direction of crystallization) coincides with a <111>, <111>, or <100> direction, the cellular structure viewed from a surface perpendicular to the crystal axis will consist of a network of regular hexagons, skewed hexagons (with interfacial angles of 110" and 125"), or cubes, respectively. It follows, moreover, that off-orientations from these principal directions will yield modifications of these three basic geometric configurations. In this connection, it is interesting to note that the bounding planes of the hexagonal structure observed in tin by Rutter and Chalmers3 showed no preferred orientation.

Jan 1, 1954

By F.S. Norcross

Manganese has long been considered one of the United States&apos; most important strategic raw materials. Its indispensabil-ity in steel manufacture makes it vital to the nation&apos;s industrial life. Coupled with this indispensability is the fact that domestic producers have not been able as yet to supply more than a small part of the nation&apos;s manganese needs; consequently the United States has had to depend upon such distant foreign sources as the U.S.S.R., British India, the African Gold Coast and Brazil for the major portion of its ore. The great bulk of the mineral is consumed in the form of ferromanganese, an alloy that averages 80 per cent manganese and 20 per cent mainly iron and carbon. Manganese is used as a deoxidizer and desulphurizer in steel manufacture. By combination with the residual oxygen and sulphur of the bath, it helps to produce a clean, sound metal. Approximately 14 lb. of manganese, it is estimated, is used in making one ton of steel. For standard-grade ferromanganese, the ore should have a minimum of about 48 per cent Mn and preferably more. Beneficiation methods have not yet been developed for making the immense low-grade deposits in the United States salable at prevailing prices. Dependence upon foreign sources thrust the United States into serious difficulties during the World War. At the start of hostilities in 1914, the nation was obtaining about four-fifths of its ore from the Eastern Hemisphere. Domestic production had been negligible, amounting to only 3000 to 7000 tons a year. As the war continued, shipments from the East, endangered by sea attack and blockade, dwindled rapidly. Imports from Brazil mounted. In this grave emergency, the United States, starting almost from scratch and under the stimulus of high prices, succeeded by 1918 in producing a peak of 3II,000 tons, about 35 per cent of its consumption that year. Since the war, the United States has depended upon foreign sources for more than nine-tenths of its high-grade ore. During 1936, 1937 and 1938, imports for consumption averaged 736,000 tons a year. During the same period, domestic shipments averaged 21,000 tons a year. Of the imports, the U.S.S.R. accounted for an annual average of 280,000 tons, the Gold Coast 208,000 tons, India 74,000 tons, and Brazil 72,500 tons. But India and Brazil, which in 1936 ranked third and fourth in the list of importers, were displaced in 1937 and 1938 by a new and much nearer source—Cuba. From less than I per cent of United States imports in 1931, the island republic increased its shipments to more than 27 per cent in 1938. Cuba&apos;s average for this three-year period was 97,000 tons, and its total for 1938 was 131,000 tons. History The story of the economic development of manganese in Cuba dates back to the Spanish-American War days. John Green-way, then one of Theodore Roosevelt&apos;s

Jan 1, 1943

By F. S. Norcross

Manganese has long been considered one of the United States&apos; most important strategic raw materials. Its indispensabil-ity in steel manufacture makes it vital to the nation&apos;s industrial life. Coupled with this indispensability is the fact that domestic producers have not been able as yet to supply more than a small part of the nation&apos;s manganese needs; consequently the United States has had to depend upon such distant foreign sources as the U.S.S.R., British India, the African Gold Coast and Brazil for the major portion of its ore. The great bulk of the mineral is consumed in the form of ferromanganese, an alloy that averages 80 per cent manganese and 20 per cent mainly iron and carbon. Manganese is used as a deoxidizer and desulphurizer in steel manufacture. By combination with the residual oxygen and sulphur of the bath, it helps to produce a clean, sound metal. Approximately 14 lb. of manganese, it is estimated, is used in making one ton of steel. For standard-grade ferromanganese, the ore should have a minimum of about 48 per cent Mn and preferably more. Beneficiation methods have not yet been developed for making the immense low-grade deposits in the United States salable at prevailing prices. Dependence upon foreign sources thrust the United States into serious difficulties during the World War. At the start of hostilities in 1914, the nation was obtaining about four-fifths of its ore from the Eastern Hemisphere. Domestic production had been negligible, amounting to only 3000 to 7000 tons a year. As the war continued, shipments from the East, endangered by sea attack and blockade, dwindled rapidly. Imports from Brazil mounted. In this grave emergency, the United States, starting almost from scratch and under the stimulus of high prices, succeeded by 1918 in producing a peak of 3II,000 tons, about 35 per cent of its consumption that year. Since the war, the United States has depended upon foreign sources for more than nine-tenths of its high-grade ore. During 1936, 1937 and 1938, imports for consumption averaged 736,000 tons a year. During the same period, domestic shipments averaged 21,000 tons a year. Of the imports, the U.S.S.R. accounted for an annual average of 280,000 tons, the Gold Coast 208,000 tons, India 74,000 tons, and Brazil 72,500 tons. But India and Brazil, which in 1936 ranked third and fourth in the list of importers, were displaced in 1937 and 1938 by a new and much nearer source—Cuba. From less than I per cent of United States imports in 1931, the island republic increased its shipments to more than 27 per cent in 1938. Cuba&apos;s average for this three-year period was 97,000 tons, and its total for 1938 was 131,000 tons. History The story of the economic development of manganese in Cuba dates back to the Spanish-American War days. John Green-way, then one of Theodore Roosevelt&apos;s

Jan 1, 1943

By E. D. Fields, R. W. Sayers, M. C. Tippett

The Duval Corp. porphyry copper deposits at Copper Canyon and Copper Basin, though widely separated, form an econornic unit requiring integrated exploitation. Contrasts in mineralization, host rocks, and mode of occurrence present unique mining and milling problems. Mixed oxide-sulfide ore is treated in extensive dump leaching facilities in both areas. Complex Cu-Au-Ag ore is treated in a 4000-tpd mill at Copper Canyon. In both areas, hypogene metallization occurs within large aureoles of metamoiphism and hydrothennal alteration related to quartz monzonite intrusions of mid-Tertiary age. Supergene processes fitrther altered the rocks and enriched the hypogene protore. At Copper Canyon, hypogene copper and iron sulfides with gold and silver occur in fractures, as partial replacement of favorable beds, and as disseminations in Paleozoic sedimentary rocks. The lower part of the Pennsylvanian Battle formation was a particularly favorable host. Metallization occurs to a lesser extent in quartz monzonite. Metal zoning is well-developed. The deposits at Copper Basin consist principally of supergene copper minerals in arenites of the Cambrian Harmony formation. Oxidation of hypogene copper and iron sulfides in tactite zones has formed at least two commercial deposits; intersections of fractures with favorable beds exerted important ore controls. Recently, the Copper Canyon and Copper Basin properties of Duval Corp. have been added to the list of porphyry copper mines in Nevada, marking the first new copper open pit in this state in 15 years. The properties are situated in the Battle Mountain

Jan 1, 1970

By Konrad Stern

The terms asphalt and bitumen have been applied interchangeably, although incorrectly on occasion, for centuries to various bituminous materials that were found in nature. Native bituminous materials of only the solid types, deposits of which are found on or near the surface of the ground, together with the principal asphaltic type petroleum bitumens will be considered in this chapter. The international dictionary compiled by the "Permanent International Association of Road Congresses" still gives the full name as "Asphaltic Bitumen" but of recent years the word "Bitumen" has been recognized as most appropriate and is defined by the American Society for Testing Materials as follows: "Mixtures of hydrocarbons of natural or pyrogenous origin, or combinations of both, frequently accompanied by their nonmetallic derivatives, which may be gaseous, liquid, semisolid or solid and which are completely soluble in carbon disulfide." Asphaltic pyrobitumens, as defined by Abraham,2 is a species of pyrobitumen, including dark-colored, comparatively hard and nonvolatile solids; composed of hydrocarbons, substantially free from oxygenated bodies; sometimes associated with mineral matter, the nonmineral constituents being infusible and largely insoluble in carbon disulfide. Deposits of native bituminous materials are found scattered over the entire world, but many are relatively unimportant as far as commerce is concerned. No attempt has been made to cover all of the known deposits. The principal bituminous materials of commercial interest are: 1. Native asphalts, solid or semisolid, associated with mineral matter such as Trinidad Lake asphalt, Rock asphalt and Selenitza, Boeton and Iraq asphalts. 2. Native Asphaltites, such as gilsonite, grahamite and glance pitch, conspicuous by their hardness, brittleness and comparatively high softening point. 3. Asphaltic bitumens obtained from nonasphaltic, semi-asphaltic and asphaltic crude petroleum by distillation, blowing with air and the cracking of residual oils. 4. Asphaltic pyrobitumens of which wurtzilite and elaterite are of chief interest industrially as they depolymerize upon heating, becoming fusible and soluble in contrast to their original properties in these respects.2 5. Mineral waxes, such as ozokerite, characterized by their high crystallizable paraffine content. Native Lake Asphalt At Brighton situated in the southwestern part of the Island of Trinidad is one of the largest deposits of native asphalt in the world.3 The lake is oval in shape, covering an area of 114 acres and having a depth of 285 ft at its center. The material forming this deposit is an emulsion of water and bitumen with a suspension of mineral matter consisting of impalpably fine clay dispersed by nature in the asphalt, and small quantities of silica and vegetable matter. The entire mass of asphalt is in slow but constant motion as evidenced by the migration of islands of vegetation from one place to an-

Jan 1, 1960

By Louis Katona

The practical execution of the design for rolling-mills presented by the writer at the Paris meeting* of thc Iron and Steel Institute in 1900 involves the determination of some questions not yet discussed, among which is the determinatioir of the amount of power required to perform the rolling of pieces of iron and steel of given dimensions. It is necessary to know this factor if we would put motors of proper capacity to the respective pairs of rolls, or, rcciprocally, if, having standard motors at our disposal, we would design grooves to suit them. Moreover, this factor is involved in giving right dimensions to every part of the rolls and housings. Expert designers of engines for driving rolling-mills of the present type receive very indefinite directions, such as: that the motor is to drive a light, medium or heavy train; that it must work with fly-wheel or reversing gear; that the number of revolutions per minute should not exceed 40 or 60, and that at a given speed the power developed should be from 100 to 200 H. P., or from 1,000 to 2,500 13. P. It frequently happens, however, that an cngine of 200 H. P. is forced under the circumstances to press or develop as much as 300 H. P., while, on the other hand, the ,1,500-11. P. engine may be rolling-stock which could be worked with a maximum expenditure of 60 to 80 H. P. Of course such variatior~s as these do not permit the best adjustment of parts or the best economy of power and fuel. The design of roll-trains is even more vaguely limited. Every part of a train, from the point where it connects with the engine to the last groove in the rolls, bears evidence that there are no rules for calculating even approximately the dimensions of the main-shafts, couplings, pinions, gears, rolls, trunnions,

Jan 1, 1904

By Neil Styler

This paper presents an analysis of measurements of inter-burden deformations above six longwall faces. An attempt is made to demonstrate some correlation between the movements at the various sites, and to examine their importance with respect to predicting caving height, disruption of overlying seams, and disruption of aquifers. This analysis demonstrates some significant differences between predicted surface subsidence, and inter-burden deformation. In addition it is shown that the caving height above a longwall face is equal to 8 to 12 times the extraction height, with a zone of fractured rock extending to approximately 50 times the extraction height above the seam.

Jan 1, 1984

By Walter Harvey Weed

AMONG the many causes of that perplexing feature of mine-exploitation, the unequal distribution of the ore, the influence of the country-rock upon the vein-contents has long been accepted as an important factor in certain districts, but the general application of the theory has not been proved. It is now possible to obtain trustworthy data with which to test the theory, and either to confirm or to overthrow this time-honored tradition. By the searching methods of modern petrography and chemistry, rock-determinations are now scientifically made, while the examination of thin sections of ores supplements field- and laboratory-study, and affords conclusive evidence of the paragenesis of the ore-minerals. In the great mass of data regarding mineral deposits accumulated during the past century, there are some facts which stand the test as to reliability; but the greater part are not available for use in this discussion. Within the last 20 years, however, many able workers have contributed careful and accurate accounts of various ore-deposits; and it is by the facts given in such papers, and by personal experience, that. I have become convinced that there is in some districts a true relation between the country-rock and the mineral contents of the veins. My own interest in the subject arose from the observation of a number of striking instances of the variation of vein-contents with the nature of the inclosing rock. Having already recorded certain observations of this kind, I venture to present in this paper further notes, together with a few facts from the literature of the subject, which seem to prove the correctness of my view. It is apparent that if the relation holds true, though in limited districts only, it will be of great practical in-

Jan 1, 1913

The fourth National Exposition of Chemical Industries will be held in the Grand Central Palace, New York, during the week of Sept. 23, 1918. Dr. Bacon, of the advisory committee, is now head of the Chemical Warfare Section of the National Army, and a member of General Pershing&apos;s staff. The coming Exposition will be the largest ever held, and it will be necessary to use four floors of the Grand Central Palace. The exposition is a war-time necessity, and regarding it as such, each exhibitor is planning his exhibit so that it will be of. the greatest benefit to the country.

Jan 8, 1918

By John D. Erickson

The concepts of long-range, open pit planning presented here are not new. The new idea is how the factors that control the location of the final pit limits can be considered altogether as one large, simultaneous equation. The X, or unknown quantity that is being solved for, is a long-range pit design that fulfills the desired objectives. The objectives of a final pit plan are determination of the extent and location of ore reserves, the allowable stripping necessary to uncover the ore, the final pit surface intercept, final pit topography and the contained metal values in both ore and waste.

Jan 4, 1968

By J. Th. G. Overbeek, R. Schumann, P. L. De Bruyn

THE technique of concentrating valuable minerals from lean ores by flotation depends upon the creation of a finite contact angle at the three-phase contact, mineral-water-air. If the mineral is completely wetted by the water phase, contact angle zero, there is no tendency for air bubbles to attach themselves to the mineral. However, when the contact angle is finite, the surface free energy of the system, water-air bubble-mineral particle, can be diminished by contact between the bubble and the particle, and if not too heavy the mineral will be levitated in the froth. With a few exceptions, all clean minerals are completely wetted by pure water. Thus the art of flotation consists in adding substances to the water to make a finite contact angle with the mineral to be floated, but to leave the other minerals with a zero contact angle. The contact angle concept and experimental measurements of contact angles have played important roles in flotation research for several decades.1-3 Nevertheless, there remain unanswered some basic questions as to the scientific significance of the contact angle and the nature of the processes by which flotation reagents affect contact angles.

Jan 5, 1954

By J. J. Casey, R. S. Busk, D. L. Leman

The mechanical properties and the phase-temperature relationships of magnesium-lithium-aluminum, magnesium-lithium-zinc, and magnesium-lithium-aluminum-zinc alloys are presented. It is shown that the strengths of some of these alloys can be tripled by heat treating and aging but that the high strength is accompanied by brittleness and lack of stability. MAGNESIUM-LITHIUM alloys are interesting because the hexagonal structure of magnesium can be changed into the more ductile and workable body-centered cubic structure by the addition of only 10 pct lithium.1 After Loonam2 determined that the ductility of the magnesium-lithium alloys is destroyed by even trace quantities of sodium, it was possible to prepare ductile alioys and study their mechanical properties. Jackson3 and coworkers have ably described their results with both the binary and polynary magnesium-lithium alloys. The present paper is a report of the mechanical properties of wrought magnesium-lithium-aluminurn, magnesium-lithium-zinc, and magnesium-lithium-aluminum-zinc alloys. Experimental Procedure The alloys were made by melting 7 lb of magnesium in a steel crucible under a molten flux of 75 pct LiCl + 25 pct LiF3 previously dried at 1600°F. The metal was heated to 1300°F for alloying aluminum and zinc and then cooled to 1250°F for adding lithium (sodium content: 0.01 to 0.04 pct). After the lithium had been alloyed, dry LiF powder was sprinkled on the melt to thicken the excess flux. After a 15 min holding period, the flux was skimmed off. Paraffin vapors were used to protect the metal as it was poured into 3 in. diam by 11 in. long magnesium molds. Billets were extruded into 3/8-in. diam rod and 1/16 x 3/4-in. strip; sheet was prepared from 1/8x 7/8-in. extruded strip, first by hot rolling and then by cold rolling 2 pct per pass. Hot rollability, or the temperature range through which the alloys could be rolled, was determined by rolling the strip two passes at 30 pct reduction per pass. Cold rollability, or the percentage of cold reduction to cause detrimental cracking, was determined on 0.064-in. hot-rolled sheet. Standard ASTM procedures were followed to obtain the mechanical properties, using 0.2 pct offset for the yield strengths. The level of properties produced with commercial magnesium alloys using the procedure described is given in a previous publication." Results Magnesium - Lithium - Aluminum System: The good workability of magnesium-lithium alloys is illustrated by the data in table I, which shows approximately how the extrusion pressure decreases as the amount of cubic phase increases. Binary magnesium-lithium alloys are soft and weak, but aluminum raises their strengths con-

Jan 1, 1951

By T. D. Tiemann

The extraction of iron oxide from several types of siliceous iron ore by digestion in sulfuric acid solutions was investigated in the temperature range from 80 to 258°F at concentrations from 10-60% H2SO4. Degree and rate of extraction were found to be critical with respect to both temperature and acid concentration, requiring temperatures in excess of 250° F and acid concentrations of 50% to effect 80-90% extraction of iron oxide in 60 min. Rate of extraction is directly related to surface area and apparently controlled by the rate of chemical reaction. The activation energy was found to be approximately 25,000 cal per g mol. Extraction characteristics of the several ores were found to be similar. The Department of Minerals and Metals Engineering at the University of Wisconsin conducts a continuing research program to develop processes for the utilization of low-grade iron ore deposits such as the nonmagnetic taconites of the Wisconsin Gogebic range. Methods under study include high-intensity magnetic and high-tension electrical concentration, flotation, direct reduction and chemical extraction. Concentration of a number of low-grade siliceous iron ores by the extraction of silica in sodium hydroxide solutions has been reported by the writer and others in the literature.1,2,3,4 Residual concentrates containing as much as 65% iron have been obtained from taconites containing less than 30%. Currently an alternative approach is under study, namely the dissolution of iron oxides from siliceous gangue by extraction in acid, with subsequent recovery of the iron from solution. Such a process for extracting iron oxide from the low-grade oclitic deposits of Alberta with hydrochloric acid was investigated and described by Gravenor, Govett and Rigg.5 The current investigation, which is entirely devoted to extraction with sulfuric acid, is the subject of this paper. In part, the objective of this research was to determine the possibility of leaching iron ores in situ with sulfuric acid. The investigation of a recovery method is left to later research. The ores investigated contained hematite (Fe2O3) as the principal iron-bearing mineral and minor amounts of goethite (Fe2O3 .H2O), magnetite (Fe3O4), and iron-bearing silicates. The gangue was essentially quartz occurring as single crystals and microcrystalline aggregates. Detailed description of the ores may be found in the literature.1,2,4,6 A comparison of the specific ores used in this investigation is shown in the partial analyses of Table I. EXPERIMENTAL METHODS All extractions were made at atmospheric pressure using beakers with a mechanical stirrer for those tests run below the boiling point, and Erlenmeyer flasks for those at the boiling point. A thermostatically controlled hot plate was used for heating, and this maintained the mean temperature within the solution to within ±3°F during extraction. The sample of ore for extraction was weighed to + 0.02 g. For tests below the boiling point, the sample was added to the beaker containing the sulfuric acid solution at the desired temperature. For the boiling-point tests, the sample was added to the Erlenmeyer flask followed by distilled water and the

Jan 1, 1968

By Frank R. Van Horn

In the summer of 1908, R. B. Cochran, Superintendent of the Compania Metalurgica Mexicana at Sierra Mojada, Mexico, presented to the Department of Geology and Mineralogy at Case School of Applied Science an interesting series of silver-, copper-, and lead-ores from the Veta Rica mine. These ores contained several interesting minerals which were associated in a somewhat peculiar manner, so that I was impelled to make a closer study of their occurrence. The investigation has brought out several new facts concerning the geology of the district and the geological occurrence of the ores, and therefore has seemed worthy of record. Two papers have been published previously about the region, one by Chisml in 1887, and the other by Malcolmson² in 1902. These articles, however, treat of the district more from the stand-point of the metallurgist and mining engineer, and not much attention is devoted to its mineralogy and economic geology. 11. Geographical Location of the District. The Sierra Mojada is situated in the extreme western part of the State of Coahuila, near the Chihuahua boundary. It is reached best via the Mexican Central railroad from El Paso, Tex., to Escalon, Chihuahua, a distance of 494 miles. From this point, a branch line, the Mexican Northern railroad, runs 78 miles in a NE. direction to the mines, which are its northern terminus. The railroad was built about 1890, practically on account of the Sierra Mojada mining-district.

Jan 1, 1913

By Robert E. Wilson, J. K. Roberts

IN order to make clear the reasons for the basic importance of petroleum and natural gas in the world today, and the problems faced by our scientists and technologists in using efficiently these great natural resources and finding possible replacements for them, it will be necessary to present a brief discussion of hydrocarbon chemistry The most important use of petroleum products is as fuel, particularly for the various forms of the internal-combustion engine There are, of course, hundreds of thousands of chemical compounds that give off heat when they burn, that is, when they combine with the oxygen of the air If a capable chemist were assigned the problem of finding the ideal volatile liquid fuel for use in an engine, he would probably begin by referring to the tables that give the heats of combustion of the chemical elements Of all the ninety-odd elements, hydrogen shows up with by far the highest heat of combustion-about 52,000 British thermal units per pound Unfortunately, however, hydrogen is a very light gas, which can be liquefied only at very low temperatures To burn it as fuel in an automobile would require a balloon about as big as the car to hold the equivalent of a gallon of gasoline, or, the hydrogen could be compressed in heavy steel cylinders, but -this would require about 125 pounds of steel per pound of hydrogen. Obviously, then, hydrogen itself cannot be considered

Jan 1, 1947

By Henry Faul

MEASUREMENT of radioactivity of rocks and ores has developed into a complete method of geophysical exploration. The problem falls into three natural categories: (I) surface radiation measurement in the field and underground; (2) radioactivity logging of drillholes; and (3) laboratory analysis of samples. Portable counters are used in the field for tracing radioactive formations and for quantitative estimates of radioactive content of surface rock. Wartime advances in battery design make it possible to construct small precision counters that can be carried easily. Even the smallest conventional diamond drillholes can be logged, and actual content of the radioactive element can be measured. The exact grade of very thin active layers or veins can be estimated only approximately. Samples may be analyzed for their alpha, beta or gamma activity, and beta assaying is the best suited to rapid routine operation. Simple calibration with standard samples is sufficient for rough work, but a density correction is necessary when greater precision is required. Samples with high emanating power should be fixed and stored for three weeks to reestablish the radium-radon equilibrium prior to precision assaying. Carnotite can be fixed by sintering or molding with plastics. Among the important new developments, a low-voltage Geiger tube has been designed recently, and crystal scintillation counters hold great promise for high-efficiency gamma-ray measurement.

Jan 1, 1947

By Alvin F. Kroll

BUNKER Hill & Sullivan Mining & Concentrating Co. has three major sources of ore at present: high grade square-set ore, low grade caving ore, and low grade reclaimed washed jig tailing. These three ores constitute the feed to the 3000-tpd concentrator that produces lead-silver, zinc, and pyrite concentrates. Each ore has different characteristics of grindability, mineral particle size, composition, and content, but all are amenable to the same mill circuit and reagents. The gangue is primarily quartzite. The Bunker Hill concentrator is now using a coarse primary grind followed by a regrind of sand fractions of lead rougher tailing, lead middling, and lead cleaner tailing, and further regrind of sand fractions of zinc middling and zinc cleaner tailing. This is done in order to recover all valuable minerals at the largest size possible. The tendency to overgrind the ore particles, which are more easily ground than the gangue particles, is thereby reduced-lessening their loss in the flotation tailings. The coarse primary grind and regrind method has the advantages of: providing more selective grinding, minimizing sliming, giving a cleaner lead-zinc separation, and reducing mill requirements for reagents and water. Improved lead-zinc separation raises overall recovery and also increases lead and zinc recovery in the respective concentrates by keeping middling particles out of concentrate and tailing.

Jan 6, 1954

By Emile Hiertz

THE first press was installed in June, 1910, and the second in March,1911. They produce 1,000 briquettes per hour, weighing 5 kg. (11.05 1b.) each, under a pressure of about 400 kg. per square centimeter (5,689.2 lb. per square inch). The chloride of magnesium is received from the potash mines at Hanover in tank cars in approximately a 35 per cent. solution. The quantity of solution added to the flue dust varies between 2 and 3 per cent., so that the briquettes contain about 1 per cent of MgCl2. To fresh dust as much as 10 per cent. of coke breeze may be added and bri¬quettes made that still have a crushing strength of from 25 to 30 kg. (377 to 426.6 lb. per square inch) after 36 hr., and 45 kg. (639.9 lb. per square inch) after six days. After having treated 140,000 tons of the material, the reports of the blast furnaces show that the briquettes improved the action of a furnace and produced less dust than did Minette ore. As much as 35 per cent. of briquettes is added to the furnace charge without bad effects on operations. The presence of chlorine did not produce any corrosion in the furnace, downtakes or other piping. The presence of a certain amount of chlorine in the dust reduces the amount of chloride of magnesium which it is necessary to add for briquetting.

Jan 12, 1913

By G. F. Loughlin

The subject of this lecture might well have been assigned to an economist or banker rather than to a geologist, but, as it was deliberately assigned to me, it is to be treated from a geologist&apos;s viewpoint. The term precious metals ordinarily includes the platinum group as well as gold and silver. Platinum, like silver, has had a great decline in price during the last few years, but has not been a medium of exchange and therefore has aroused comparatively little comment. Its relation to price level is like that of commodities in general, and will be dismissed without further comment. Of the two precious metals used as mediums of exchange gold, because of its adoption as the basis of most monetary systems and because of its threatened shortage in the near future; has been a subject of general concern to governments, financiers, and economists; silver, on the other hand, which has flooded the market of late has brought forth cries for help, direct or indirect, from producers and to a less extent from the largest users, especially China, whose purchasing power has been greatly curtailed, but it fails to arouse the interest that gold does. Many predictions have been made by economists, bankers, and others regarding future supply of gold and its effect on prices but the differences among these predictions are about as many as the number of prophets. Since gold is the standard by which the value of commodities as a whole is to be measured, it would seem that the greater the ratio of gold supply to commodities the higher the price level and vice

Jan 1, 1932