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By G. G. Oberfell

THOUGH the largest volume use of natural gas has been, is. and in all probability will continue to be as a fuel for domestic and industrial heating, it has various market outlets, both as a fuel and as a raw material for the chemical industry. Natural gas is a preferred type of fuel where ease of control, fuel uniformity, and freedom from ash are of primary importance. Other industrially important uses are as a source of carbon black and as a fuel in various low-cost heating operations. Many other uses are of varying importance and new potential uses are continually being uncovered, some being of economic importance to the gas indus¬try as a whole, but most of them involve such small volumes of gas that they are only of passing interest. Since various products extracted from natural gas and recovered as by-products from petroleum refining, such as liquefied petroleum gas and fuel oil, are being utilized in many industrial and domestic heating applications, some consideration will have to be given such materials in order to present a reasonably complete story of the importance of natural gas. Some of these materials may prove to be transient competitors and will not be available when more profitable uses are found for them. Meanwhile, however, the potential volumes of such materials available, the current volumes being marketed, and the nature of the utilization are considered as constituting an essential part of the over-all fuel picture.

Jan 1, 1946

By Scott Tzcrner

WITHIN recent years people have begun to realize the importance and significance of the mining and allied industries. The leading part the engineer plays in civilization is becoming recognized. However accurate quantitative knowledge of the industrial importance of mining is still seldom possessed except by those close to this business. It is true that there are a few who go to the extreme and represent the whole progress of civilization as a reflection of man's gradual mastery of mineral utilization, but on the whole, the magnitude of the-industry is underestimated. In this paper I shall call attention briefly to the importance of mining in the United States, in Canada, and in the world. Ordinarily, the annual primary mineral production of the United States is about $5,500,000,000. The average for the last 5 years has been a little over that, but last year, sadly enough, it was less than 31/4 billion. Just now, we are on the decline, and have been for the last two years. In Canada, the 5-year average was about $268,000,000, and last year it was 227 million. Due in part to gold mines (in 1930, for the first time, Canada's gold production exceeded that of the United States), the Canadian average is holding up better than ours. Average world mineral production over the last -5 years has been estimated at about $12,000,000;000 whereas in 1931 it was less than than 8 billion.

Jan 1, 1932

By John D. Sullivan

MAJOR technical advances seldom occur in a single year, and this is especially true with aluminum and magnesium where marked improvements in metallurgical processes and products took place during the war years. Nevertheless, the light metals and alloys, particularly aluminum, are advancing in commercial importance and are finding their niche in industry. New applications during the year have resulted from a better over-all knowledge of properties, handling, etc., rather than from revolutionary new developments.

Jan 1, 1948

John M. Cairns, in an interesting letter dated June. 19, 1918, tells us of his experiences in Italy. He says, "It may interest you to know I came out to Italy after being on the Afghan frontier of Indian Baluchistan, in August last year, and for some time was posted at Turin as Railway Transport officer. At that time Turin was in the toils of the riots which were the forerunners and preliminaries which led up to the great Italian retreat (Capretto). Since then I have been all over Italy from (deleted by the censor) in Transportation intelligence, and now have just been transferred to the Directorate of Requisitions and Hirings, which now permits great opportunities of going nearly all over Italy (deleted by the censor). My address is L. of C. Branch, D. R. & H., A. P. 0. L/1, I. E. F.

Jan 9, 1918

By R. J. Wysor

Since the outbreak of the European war, few problems of raw-material supply have commanded more nation-wide attention than potash. It is well known that before the war the domestic production of potash was an insignificant percentage of the imports. The average annual importation of raw potash salts for several years prior to 1914 was slightly over 300,000 net tons, and of other potash manure salts about 700,000 tons. The sudden and almost total cessation of these imports created a unique and stringent situation. Methods of recovering potash from feldspar and other native mineral sources, and reclamation from hitherto waste products, have received a marked impetus. Soaring prices have been a keen incentive to research and industrial development. Although several brief articles concerning the possibilities of potash recovery have appeared in recent trade journals, it still may be a matter of some surprise to the average technical mind that potash might be reclaimed as a profitable byproduct in the manufacture of pig iron. At the present time it may be of special interest to present some data, largely of a technical nature, on this subject. A fairly thorough search of the literature reveals a number of articles concerning salts of the alkali metals in the blast furnace. Many of them deal with the theoretical rôle of alkali cyanides in the furnace. Several discuss the probable effect of the alkalies on the furnace brickwork. Two or three ambitious patents have been granted for reclaiming potash or other products from blast-furnace gas. However, we have heard nothing further as to the practical application of these patents. Little literature of importance has appeared during the last 10 years concerning alkalies in blast-furnace practice, and I have discovered no record whatsoever as to the actual sale or commercial disposal of flue dust for its potash content until this was inaugurated in our plant at Bethlehem. A bibliography of the most important articles discovered is appended. About 4 years ago, in the course of investigating blast-furnace stove efficiencies, I analyzed the fine, yellowish fume of which a considerable

Jan 1, 1917

The American Society of Mechanical Engineers extends an invitation to members of the Institute to participate in an exceedingly interesting excursion on Saturday, November 11. Permission has been secured for a visit to the plant of the Electric Boat Co. at New London, Conn. There will be run a special-test on a high-power 8-cylinder, 4-cycle Diesel engine. A large number of submarine and other engines in various stages of construction will be seen, also the boring of torpedo tubes, cylinders and other equipment for submarines. The drafting rooms and foundry mill also be open for inspection. The party will have an opportunity to see at close range the submerging of several submarines, and an attack on a vessel on the surface, an exhibit which is being arranged by courtesy of Rear Admiral A. W. Grant, who is in command of the submarine forces of the United States. The Boston members will leave South Station on train No. 7 at 8.30 A. M. Those from Providence will board this train at 9.36 A. M. The Worcester members will leave on train No. 745 at 8.36 A. M. The New York contingent will leave the Grand Central Terminal at 8.31 A. M. on train No. 8. This train will leave New Haven at 10.30 A. M. Upon arrival at New London, each group will go directly to the Mohican Hotel, where a "get-acquainted" luncheon will be served

Jan 10, 1916

By David Sinclair

THE dimensions and shapes of mine structures may at present be determined by (1) field experience, (2) structural calculations, and (3) barodynamic tests.§ None of these, however, provide information as to the stresses, their direction and distribution in a mine structure. For the design of pillars, the placing of openings relative to working places such as gangways, haulage levels, etc., this information is desirable. Photoelastic methods provide this and, while relatively new, their appli-cation in all engineering fields is assuming increasing importance. This paper, therefore, will present the method with a few applications to mining, and with sufficient reference for further study by the reader. PART I THE PHOTOELASTIC METHOD The photoelastic method of stress measurement determines the stress distribution in a two-dimensional model by optical means. It makes use of the fact that when a piece of isotropic transparent material, such as glass, celluloid, or Bakelite, is stressed and viewed in polarized** light a picture is seen which indicates by its color bands of light, or fringes, the magnitude of the stresses, their direction and their distribution.

Jan 1, 1940

By A. W. Gauger

DESPITE many handicaps and in the face of many discouragements anthracite and bituminous coal producers continue to supply the needs of the nation now vastly multiplied by the demands of the greatest war of all time, total output being about 620,000,000 tons of bituminous and 64,445,000 of anthracite. The progress made by this industry during the national emergency reflects more credit on all connected therewith than will ever be given. Not only has the industry been called upon to produce more coal than ever before but it has also sent representatives to England to study and advise on methods for increasing production there, and has co-operated with other Allied Nations by welcoming engineers sent to this country to study American practice. One noteworthy development has been the growth of strip mining in the

Jan 1, 1945

By Harry C. Wiess

RECENT announcement of further restrictions on gasoline consumption in the Mid-West and Southwest has focused public attention on current discussions of an oil scarcity. Conflicting arguments are advanced on the one hand that we have plenty of oil and will not need to restrict consumption as soon as transportation facilities are adequate, and on the other hand that a great impending shortage will require most drastic reductions in civilian consumption in order to provide adequate supplies for military purposes. Data can be presented to support both views, the result being that the public is confused and uncertain of where the truth lies. For a nation with about half of the known crude-oil reserves of the world and two thirds of the total production it seems almost incredible to the layman that any shortage can exist. Those familiar with estimates of future demand. however. show increasing concern regarding our ability to meet military demands without further restrictions in civilian use or wasteful production from our remaining reserves. Only by considering such facts as are available and can be made public can a true appraisal be made of whether or not we are faced with a shortage that will amount to a crisis in crude oil.

Jan 1, 1943

By I. C. Edwards, W. J. Dengler, D. F. Lillie

By 1959 the milling plant of Bicr oft Uranium Mines Ltd. had been in operation for two years. During this time many changes, both physical and chemical, had been made in an effort to improve plant efficiency. Investigational work had been facilitated greatly by the fact that the Bicroft mill consists to a large extent of two parallel circuits; however, the number of interrelated variables is great, and it is difficult to measure, let alone control, all of them simultaneously. The Bicroft mill staff feels that much progress has been made, but there is much yet to be done and many questions still to be answered. The Addendum outlines noteworthy developments to the fall of 1960. The property of Bicroft Uranium Mines is located in Cardiff Township in the Highlands of Haliburton County, southeastern Ontario, some 140 miles northeast of the city of Toronto and 70 miles due north of Lake Ontario. The ore-bearing dikes are classed as mafic. nonsegregated, syenite and granite pegmatite. Microline, microline perthite, quartz, sodic plagioclase, and pyroxene or biotite are the main constituents with uraninite, uranothorite, fluorite, titanite, cryolite, calcite, pyrite, pyrrhotite, and molybdenite as important accessories. The mill was designed for a nominal capacity of 1000 tpd with all sections except grinding, leaching, and clarification capable of 1500 tons. Feed was entered to one mill unit on Oct. 29, 1956, and to the second parallel line on November 13. The total feed rate was at 1000 tpd on November 15. The first precipitate was produced on November 12. By August 1958 the average entry had been increased to 1410 tpd without the installation of any additional major equipment. The overall recovery has been greater than 93.0 pct on several months, but a recovery of 92.5 pct appears to be most economical. Operating time for eight months in 1958 has been 97.1 pct although all grinding mills were relined during this period. A generalized flowsheet is shown in Fig. 1 and the plant layout in Fig. 2. The ore is crushed in three stages to -3/8-in. and then is wet ground in two stages to approximately 50 pct -200 mesh. The pulp is thickened to 68 pct solids and agitated by air for 33 hr at a pH of 1.9 as maintained by the addition of 93 pct sulfuric acid. Separation of the uranium-bearing pregnant liquor from the residue is accomplished by five-stage countercurrent decantation (CCD), following which the liquor is clarified for removal of fine slimes. The clarified liquor is treated in the ion exchange equipment in which both the upgrading of the solution and the removal of some impurities is accomplished. Addition of magnesia to the high-grade eluate from ion exchange precipitates the uranium as sodium-magnesium diuranate. After being filtered and dried this precipitate is packaged in drums for shipment. The residue from CCD and the barren solution from ion exchange are neutralized by the addition of lime and pumped to the tailings disposal area. CRUSHING All crushing is done on surface in a conventional three-stage unit consisting of a 36x48-in. Birdsboro Buchanan jaw crusher, a 4 1/4-ft standard Symons cone crusher, and a 4-ft Symons shorthead. Both the two primary and the two secondary screens are 4X 8-ft Symons rod decks. Moisture content of the feed ranges from 3 to 4 pct. In the initial installation the primary screens were equipped with 5/16-in. rods at 1 1/4-in. spacing and the secondaries with 5/16-in. rods at 1/2-in. spacing. With this arrangement the average crushing rate was better than 180 tph. To reduce the work required of the grinding circuit as tonnage was increased, several changes were made in the crushing circuit. By September 1957, both secondary screens had been reduced to 3/8-in. spacing, and rod size had been reduced to 3/16-in. to provide increased open area. Average throughput was reduced to 160 tph. Later, 50 pct of one primary screen was decreased to 1/2-in. opening to better balance the load between the two cone crushers. In May 1958,

Jan 1, 1961

By Nathaniel Arbiter

There is a history in all men's lives, Figuring the nature of the times deceas'd, The which observ'd, a man may prophesy, With a near aim, of the main chance of things. W. Shakespeare, Henry IV; Part 2 Introduction This nation's first century embraced two stages of the Industrial Revolution. During one, what had been a colonial agricultural economy began to industrialize; water power, then steam after 1794, were the energy sources; coal and iron were the essential ingredients. The second stage started after 1850; aided by rich and diverse mineral resources, the country began its transition from the Iron Age to the Age of Metals. Early civilizations had been built on stone, and fairly high levels were sustained on iron. But the spectacular advances in the past century in communication, in construction, in transportation by sea, rail, land and air, and in much that characterizes modern civilization have depended increasingly on the use of the complete metallic and nonmetallic resources of the earth's crust. Thus it was appropriate to define the Industrial Revolution as “the period during which man's relationship to natural resources became utterly changed”, 1 with minerals playing a major and indispensable role. But we are now becoming aware that the relationship of man to natural resources must change again. On every hand the dangers inherent in the contamination of land, sea and air by the wastes of civilization are becoming apparent. And from the growing realization that mineral wealth is finite must eventually come other far reaching changes in mineral use and distribution. For on the scale of centuries we cannot continue to exploit mineral resources even at present rates, let alone at expanded rates, without eventual depletion of the more abundant resources, and early exhaustion of the less abundant. In the past our problems were relatively easily met by the development of new and improved machinery and processes. But the future will

Jan 1, 1971

By Lester Guttman

The connection between short-range order and thermodynamic activities in binary solid solutions has been pointed out by Birchenall1 who calculated approximate values of the energy of interaction of Zn and Cu and of the degree of short-range order in alpha-brass at one composition and two temperatures. The purpose of this note is to call attention to a somewhat more accurate theory than that used by Birchenall and to extend the calculations to a wider range of temperatures and compositions as a means of testing its applicability. This is an example of the well-known general method of comparing measured thermodynamic functions of a system with those calculated from a microscopic model by means of statistical mechanics. In this case, mathematical approximations must be used which make difficult any decision about the validity of the model. Birchenall's statistical method resembles closely that calletl by Fowler and Guggenheim2 the "quasi-chemical" method which has been shown to lead in certain cases to results identical with those obtained by the method of Bethe.3 The quasi-chemical method has been extended by Takagi4 to give general formulas for the free energy of binary solid solutions based on several lattices at all compositions and temperatures. Specifically, he treats the four systems typified by: I. ß—brass; 2. a— brass; 3. AuCus; 4. AuCu. When the temperature is so high that no long-range order exists, these formulas reduce to the same form for all lattice types, namely: F - FO = (E - EO) - T(S - S°) = ½N(c — x)(2vAB — vAa - Vbb) + M1/2KTzN[x log x + 2(c - x) log (c - X) + (I - 26 + X) log (1 - 2c + x)] -kT(z - I)N[c log c+(I-c) log (I -c)] Eq 1 Here the symbols have the following meanings: F—Helmholtz free energy E—nergy 5—ntropy k—the gas constant per molecule z—coordination number, (e.g. I2 in a-brass). N—total number of atoms c—atomic fraction of A Vaa, vbb, vab—nergy per bond of the corresponding bonds log means log, throughout The superscript ° denotes the thermodynamic fuliction in the standard state, which has been chosen to be pure A or B with the same crystal structure as the solid solution. The quantity x is the ratio of the number of A-A bonds to the total number and for minimum F satisfies the equilibrium condition Vaa + Vbb — 2Vab _ (c — x)2 kT l0g x(i - 2C + x The free energy may also be written in terms of /La and B, the chemical potentials or partial free energies per alom:

Jan 1, 1949

By Lester Guttman

The connection between short-range order and thermodynamic activities in binary solid solutions has been pointed out by Birchenall1 who calculated approximate values of the energy of interaction of Zn and Cu and of the degree of short-range order in alpha-brass at one composition and two temperatures. The purpose of this note is to call attention to a somewhat more accurate theory than that used by Birchenall and to extend the calculations to a wider range of temperatures and compositions as a means of testing its applicability. This is an example of the well-known general method of comparing measured thermodynamic functions of a system with those calculated from a microscopic model by means of statistical mechanics. In this case, mathematical approximations must be used which make difficult any decision about the validity of the model. Birchenall's statistical method resembles closely that calletl by Fowler and Guggenheim2 the "quasi-chemical" method which has been shown to lead in certain cases to results identical with those obtained by the method of Bethe.3 The quasi-chemical method has been extended by Takagi4 to give general formulas for the free energy of binary solid solutions based on several lattices at all compositions and temperatures. Specifically, he treats the four systems typified by: I. ß—brass; 2. a— brass; 3. AuCus; 4. AuCu. When the temperature is so high that no long-range order exists, these formulas reduce to the same form for all lattice types, namely: F - FO = (E - EO) - T(S - S°) = ½N(c — x)(2vAB — vAa - Vbb) + M1/2KTzN[x log x + 2(c - x) log (c - X) + (I - 26 + X) log (1 - 2c + x)] -kT(z - I)N[c log c+(I-c) log (I -c)] Eq 1 Here the symbols have the following meanings: F—Helmholtz free energy E—nergy 5—ntropy k—the gas constant per molecule z—coordination number, (e.g. I2 in a-brass). N—total number of atoms c—atomic fraction of A Vaa, vbb, vab—nergy per bond of the corresponding bonds log means log, throughout The superscript ° denotes the thermodynamic fuliction in the standard state, which has been chosen to be pure A or B with the same crystal structure as the solid solution. The quantity x is the ratio of the number of A-A bonds to the total number and for minimum F satisfies the equilibrium condition Vaa + Vbb — 2Vab _ (c — x)2 kT l0g x(i - 2C + x The free energy may also be written in terms of /La and B, the chemical potentials or partial free energies per alom:

Jan 1, 1949

By Roger L. Beals, George A. Tweedy

I. INTRODUCTION. THE results of the cyanide-operations, given in detail in the following paper, show the progress that is being made at the Minas del Tajo. The old pan-amalgamation process, in operation up to and including 1905, while paying a profit on high-grade ores, was no longer able to treat profitably the ores in sight at that time, hence an alteration in the process was imperative. The success of this alteration is eloquently expressed by the following data Pan- Amalgamation. Cyanidation. 1905. 1907. 1903. Tons treated, . . 51,387 53,983 69,300 Value per ton (U. S. currency),. $10.75 $8.39 $8.28 Extraction, per cent., 65.00 88.50 S7.45 Extraction, per ton. .- $7.00 $7.4.; $7.24 Total cost, per ton treated, 6.50 4.311 4.01 Profit, per ton treated, . . 0.50 3.07 3.23.;

Feb 1, 1910

By Robert T. MacMillan

Of all the mineral substances utilized by man, salt or sodium chloride has one of the longest and most varied histories. Because all animal life is descended from marine organisms, sodium and chlorine became necessary to life, and as sodium chloride meets requirements most readily, common salt has been essential to human and animal diets from earliest times. As civilization progressed, man learned to evaporate sea water and brines of saline lakes and springs to obtain salt, and gradually ceased to depend on the flesh of animals and the occasional salt outcrops or "salt licks" they frequented. He also learned that salt had a multitude of uses, particularly as a preservative of meat and other foods. The importance of salt in the minds of early men may be readily seen from many allusions in the Bible and other ancient writings. Expressions such as "not worth his salt," and "the salt of the earth" are deeply embedded in the English language. Salt has symbolized friendship, fidelity, purity, and hospitality. It has been used as currency; had religious significance; caused wars; and has been a favorite commodity for taxation. The English word "salary" stems from the Latin word for salt, in which Roman soldiers received part of their pay. Although salt today retains its dietary importance, it has thousands of other uses. Of each 100 pounds produced in the United States less than three pounds is for table use. The other 97 pounds goes for agricultural, industrial, and chemical uses. Fortunately, reserves of salt are enormous and reasonably well distributed on the face of the earth. The sea is an inexhaustible source of salt which may be had at prices which vary with climate and other factors. In addition, large underground salt deposits and many salt lakes, springs and playas are scattered throughout the world. Most countries have access to a salt supply, although some are more favored than others. Properties Crystallized sodium chloride or common salt is known as halite. Its molecular weight is 58.454 and it contains, by weight, 39.34 pct sodium and 60.66 pct chlorine. Alternate positions in the cubic lattice are occupied, respectively, by negative chloride and positive sodium ions; the crystal form is isometric. Crystallization from water produces concentric shells, and when broken, a crystal shows conchoidal fracture. Salt has a hardness of 2.5; its specific gravity ranges from 2.1 to 2.6 for rock salt and is 2.165 for the pure crystal. The refractive index is 1.554; it melts at 800.8 ± 0.5°C and boils at 1413°C. Its heat of fusion is 123.59 cal/ gram. Salt is transparent or translucent and highly diathermous. It is colorless when pure and has a vitreous luster. Salt containing traces of iron oxides has varying shades of yellow, orange, brown, pink, or red. The peculiar shade of red sometimes found in that produced by solar evaporation of sea water has been attributed to tiny organisms. Blue mottlings sometimes seen in halite crystals have been attributed to colloidal sodium. Salt is soluble in water to the extent of 35.7 parts per 100 parts of water at 0°C and 39.8 parts per 100 of water at 100°C. The small difference in solubility with increasing temperature is important in the economics of producing salt by evaporating brine. Salt has a negative heat of solution which is 1.281 kg-cal/ mole at 18°C in 200 moles of water.

Jan 1, 1960

By O. P. Arora, M. Metzger

Single-phase aluminum containing 1 to 600ppm copper was studied in 7 to 26 pct HCl. The corrosion rate in the autocatalytic stage was resolved into a constant intrinsic component and an acdelerating autocatalytic component, and attention was focused on the part of this stage where the corrosion rate could be described by a simple empirical relation. Autocatalytic corrosion in this period was localized and its rate increased rapidly with copper content and with the strength and chlaride content of the acid. The effects of adding cupric ion to 16 pct HCI were functionally and quantitatively inconsistent with the autocatalytic rates observed. A theory of these rates was given based on the deposition in nzetallic contact with the aluminum of part of the copper introduced by corrosion. It has long been known in a general way that aluminum containing sufficient copper suffers in hydrochloric acid an autocatalytic acceleration of corrosion resulting from the introduction into the acid of copper ions and their reduction on the specimen as elemental copper, which provides cathodes of low hydrogen overvoltage.'-3 In a previous paper, this phenomenon was identified in single-phase high-purity material at copper levels as low as 20 ppm and an empirical equation describing autocatalytic corrosion rates in 16 and 20 pct HC1 was presented. In the present work the range of acid strength and chemistry studied was extended, a more accurate empirical equation for the autocatalytic rate was determined, and a theory of this rate was formulated. A major source of interest in this system is the intergranular corrosion, which is also strongly influenced by copper content,= and an objective of the present work on general corrosion was to provide a basis for studying the role of copper content in intergranular corrosion, which is experimentally much less accessible.

Jan 1, 1963

By L. D. HUNTOON

MY first article on Canadian Gold, published in the Canadian Mining Magazine in 1911 expressed the view that the Hollinger mine would repay all the money invested and that other mines would be developed in this area. Many published forecasts have since been made. Quoting from the Northern Miner of Oct. 29, 1931: "It will be noted in studying the chart prepared by this engineer that his forecast for 1931 at $50,000,000 was too modest, as the output for this country this year will be closer to $54,000,000."

Jan 1, 1932

By Frank Rieber

THE discovery that strongly magnetic bodies localized near the surface of the earth could be detected by the distortion which they produced in the resultant magnetic field marked the beginning of magnetic surveying methods. From an original ability to detect bodies of magnetic iron ore and the like when located very close to the, surface, these methods have been extended until today they promise to give much information with regard to the structure of such slightly magnetic material as sedimentary rock containing only a very small proportion of iron.1 The recent extensions have been made possible through the development of more delicate instruments, and of methods for their use. From the original compass and dip needle, the design of apparatus has progressed until equipment Is typified by magnetic balances capable of measuring the components of the earth's field to an extremely high degree of accuracy. It seems unlikely that the limit of such instrumental development has been reached. Just as the change from compass and dip needle has enabled the location of relatively minor changes in magnetic materials, so additional developments in the direction of increased sensitivity, as well as in greater dependability and constancy of operation, should reveal positively many slight changes which either escape notice in the present surveys or are so small that they cannot with certainty be separated from uncontrollable errors due to inconstant operation of the equipment. The ability to read smaller and smaller variations does not mean, of course, that deductions as to the causes of these variations will be made as accurately and definitely as -is possible with the more pronounced anomalies.

Jan 1, 1928

By Robert M. Weidenhammer

For years before the war, Coal had the reputation of being a sick industry. Currently it is operating at peak production and succeeding pretty well in keeping out of the red. But, says Mr. Weidenhammer, it will have a relapse as soon as the war ends unless (1) working capital can be built up; (2) it gets the support of the people and Congress; and (3) a truly long-range national fuel policy is formulated.

Jan 1, 1943

By John B. Hastings

THE reconnaissance of the Goldfield mining-district, described in this paper, was made in May and June, 1905, and, though this time was too short for a complete report, the work accomplished may serve as a basis for more thorough future research. Dr. Berkey has examined the rocks collected by myself, and I am using his classifications. As a result of further field-work, and Dr. Berkey's examination of the rocks, this paper is an elaboration and correction of my views expressed in the Gold-field Sun, May 12, 1905. The sketch-map, Fig. 1, illustrates the geology of the Goldfield mining-district. Goldfield is an eruptive complex, consisting of alaskite (binary granite), hornblende-andesite, hornblende-dacite, rhyolite, pyroxene-andesite, pyroxene-dacite (sometimes containing, a small quantity of olivine), quartz-felsite, olivine-pyroxene-ande¬site, and basalt. Considering this list to be arranged in the order of eruption, the age-sequence of the rocks conforms to Richthofen's law, formulated in 1868. From his observations in Europe and America, propylite, andesite, trachyte, rhyolite and basalt, occurring together, succeed one another. In a general way, the medium and more acidic rocks precede the most asic-a result supposed by some to have arisen from their relative position beneath the surface, and due to a rude stratification by gravity in the original cooling magma during the older history of the earth, or to the same differentiation occurring during a quiescent (molten ?) period preceding eruption, being aided by the ease with which acidic rocks, mixed with water vapors, become fusible. In effect, the more basic and less re-

Mar 1, 1906