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By Carlo Massa

The Societâ Anonima di Miniere e di Alti Fòrni, familiarly known as the " Elba Company," works the rich ore-deposits of the Island of Elba under a long-term contract with the Italian Government. The ore-deposits are scattered over the eastern and southeastern coast; but as these parts of the island are not well provided with ports, the blast-furnaces were built at Porto-ferraio, the principal town of the island, situated on the northern shore, and possessing a magnificent natural harbor where vessels even as large as the battleships of the Italian navy can comfortably anchor. In the selection of Portoferraio the cost of transporting the iron-ore from the different mines to the blast-furnaces has been reduced to a minimum, and shelter has been provided for the company's flotilla of tugs and barges, as well as for the steamers carrjing coal and pig-iron. The whole plant, of which a general view is given in Fig. 1, comprises: 1. A discharging-pier with unloading-cranes. The ore and coal are transported from this pier by means of an aerial cable-railway to the coal- and ore-storage yards. This cable-railway is supported by an iron bridge extending from the pier to the shore and by a wooden trestle extending from the shore to the yards. 2. Blast-furnaces, two in number, with all the accessory apparatus, such as blowing-engines, dry purifiers, Cowper hot-blast stoves, hoists, etc. 3. Coke-ovens, two batteries, with coal-bin, crushers and boilers. 4. Engine-house containing the blast-engines and the electric generating-station. 5. Pumping-plant. 6. Narrow-gauge railways.

Jan 1, 1905

By H. F. Yancey, M. R. Greer

At the annual meeting of this Institute held two years ago a new method1 of estimating the grindability of coal was described, based on experimental work carried on by the Bureau of Mines at its Northwest Experiment Station. Since that time, several organizations concerned with the testing or utilization of coal as pulverized fuel have adopted and used the method in determining the grindability of several hundred samples of coal. In addition, a series of comparative tests of this method and three others has been carried out in five laboratories under the auspices of Committee D-5 of the American Society for Testing Materials. As a result the Committee has recommended that the Bureau of Mines method, designated as the "ball-mill method," and the Hardgrove method2, previously advanced, be accepted as tentative standards3. Since the ball-mill method was originally developed and published, an opportunity has been presented to apply it to a larger number of coals and to study intensively some of the principles upon which the method is based. This paper presents a résumé of these further studies and includes a comparison with the Hardgrove-machine method. Trial runs were also made with another procedure recently proposed—the C.I.T. roll-test method4. Principles of Methods In the ball-mill method, the relative amounts of energy necessary to grind coals to the same fineness are determined by the number of revolutions of the mill required to reduce 80 per cent of the feed (500 grams of 10 to 200-mesh coal) fine enough to pass a 200-mesh screen. This is a

Jan 1, 1936

By J. W. Spretnak, G. Sachs

The: iron-rich iron-nickel alloys have attracted considerable academic interest in recent years. The carbon-free alloys are of minor practical importance, but they are the base of many alloys with various outstanding properties. The iron-nickel alloys, therefore, have been investigated extensively regarding both their structures and their properties. The researches on these alloys up to 1938 have been collected and critically reviewed by J. S. Marsh,l and will be discussed in some detail in the sections of this paper dealing with specific subjects. These numerous investigations have not succeeded in establishing the equilibrium conditions in this system. Alloys containing more than a certain amount of nickel (8 to 10 per cent Ni) undergo the allotropic transformation extremely sluggishly, both on heating and cooling, showing a large hysteresis," which is not dependent upon the rate of cooling and persists even with very slow rates of cooling.3 Honda4 and Merica4 have therefore resigned themselves to proposing a diagram (Fig. I) for practical use, illustrating the structural relations under commercial conditions instead of attempting to establish the true equilibrium diagram. Marsh is less pessimistic and suggests an equilibrium diagram (Fig. 2) which conforms approximately to the facts known about this system. Recent X-ray investigations by Owen-Sully5 and Bradley-Gold-schmidt6 on powdered alloys indicate that the previous work on the iron-nickel system yielded very incomplete results. These investigators agree (Figs. 3 and ,+) that alloys in the powdered form containing more than 8 per cent and up to about 35 per cent Ni decompose into a stable heterogeneous mix-

Jan 1, 1941

By H. F. Yancey, M. R. Greer

At the annual meeting of this Institute held two years ago a new method1 of estimating the grindability of coal was described, based on experimental work carried on by the Bureau of Mines at its Northwest Experiment Station. Since that time, several organizations concerned with the testing or utilization of coal as pulverized fuel have adopted and used the method in determining the grindability of several hundred samples of coal. In addition, a series of comparative tests of this method and three others has been carried out in five laboratories under the auspices of Committee D-5 of the American Society for Testing Materials. As a result the Committee has recommended that the Bureau of Mines method, designated as the "ball-mill method," and the Hardgrove method2, previously advanced, be accepted as tentative standards3. Since the ball-mill method was originally developed and published, an opportunity has been presented to apply it to a larger number of coals and to study intensively some of the principles upon which the method is based. This paper presents a résumé of these further studies and includes a comparison with the Hardgrove-machine method. Trial runs were also made with another procedure recently proposed—the C.I.T. roll-test method4. Principles of Methods In the ball-mill method, the relative amounts of energy necessary to grind coals to the same fineness are determined by the number of revolutions of the mill required to reduce 80 per cent of the feed (500 grams of 10 to 200-mesh coal) fine enough to pass a 200-mesh screen. This is a

Jan 1, 1936

By G. Sachs, J. W. Spretnak

The: iron-rich iron-nickel alloys have attracted considerable academic interest in recent years. The carbon-free alloys are of minor practical importance, but they are the base of many alloys with various outstanding properties. The iron-nickel alloys, therefore, have been investigated extensively regarding both their structures and their properties. The researches on these alloys up to 1938 have been collected and critically reviewed by J. S. Marsh,l and will be discussed in some detail in the sections of this paper dealing with specific subjects. These numerous investigations have not succeeded in establishing the equilibrium conditions in this system. Alloys containing more than a certain amount of nickel (8 to 10 per cent Ni) undergo the allotropic transformation extremely sluggishly, both on heating and cooling, showing a large hysteresis," which is not dependent upon the rate of cooling and persists even with very slow rates of cooling.3 Honda4 and Merica4 have therefore resigned themselves to proposing a diagram (Fig. I) for practical use, illustrating the structural relations under commercial conditions instead of attempting to establish the true equilibrium diagram. Marsh is less pessimistic and suggests an equilibrium diagram (Fig. 2) which conforms approximately to the facts known about this system. Recent X-ray investigations by Owen-Sully5 and Bradley-Gold-schmidt6 on powdered alloys indicate that the previous work on the iron-nickel system yielded very incomplete results. These investigators agree (Figs. 3 and ,+) that alloys in the powdered form containing more than 8 per cent and up to about 35 per cent Ni decompose into a stable heterogeneous mix-

Jan 1, 1941

ANY discussion of State-supported schools of mining and metallurgy needs to be prefaced by a definition, since the first school to offer a mining curriculum, the Pennsylvania. Polytechnic College, was established by a grant from the State. But, so far as can be determined, it received no further State support. It would be tiresome to go into precise details, and it will be enough to stipulate that by State schools are meant those which derive their main financial support from regular appropriations made by a State legislature. The University of Michigan was the first of these to. offer a mineral industry curriculum; its story, as well as those of Wisconsin and Illinois, has been related in the preceding chapter.* Arranging the others in chronological order involves making a decision as to what weight to attach to plans for giving instruction, as contrasted with its effective initiation. This may appropriately be illustrated by the history of mineral industry education in California. CALIFORNIA Among those who came to California in 1849 and the following years were many New Englanders who had a keen interest in education. Some of them, mostly Congregationalists and Presbyterians, sought to establish a school of higher education around San Francisco Bay and eventually succeeded in opening the "Scientific and Classical School at Contra Costa" in Oakland, at Broadway and 5th St., on June 90, 1853. This prospered so well that it was chartered by the State as the College of California" on April, 13, 1855. Developing so rapidly that its quarters became. cramped, in 1864 it not only bought a tract of

Jan 1, 1941

By R. A. David, D. J. Vink, D. L. Katz

A phase diagram showing boundary curve and quantity of liquid in the two-phase region was determined for a mixture of natural gas and natural gasoline in the region of its critical conditions. The temperatures and pressures of phase measurements were in the range of 85 to 212 F. and 1300 to 2600 Ib. per sq. in., respectively, with the critical conditions at 169.5 F. and 2615 Ib. per sq. in. abs. Color phenomena were observed in the region of the boundary curve from 102' to 192 F. Approximate densities of the single-phase and two-phase regions and analysis of the system are included. Boundary curves between the single-phase and the two-phase regions have been determined for several binary mixtures containing hydrocarbons. 2,3,4.6,7,10,11,12,14 These investigators did not report the relative amounts of liquid and vapor within the two-phase region. The equilibrium values obtained from the dew-point and bubble-point data can be used to compute the lines showing percentage of liquid on the pressure-temperature phase diagram8 but the positions of the lines near the critical temperature and pressure are uncertain. Relative amounts of vapor and liquid were obtained for a gasoline and a naphtha1 within the two-phase area but not in the region of the critical temperature and pressure. The bubble-point and dew-point lines, as well as the percentage liquid lines within the two-phase region, were determined by visual observations in glass apparatus. Apparatus An arrangement of the apparatus is given in Fig. 1, showing the Jerguson gauge A with glass windows B. Pressure was supplied by the

Jan 1, 1940

By F. W. Osterwald, C. R. Dunrud

A continuously recording seismic network was constructed in 1962 by the U.S. Geological Survey to locate epicenters and record incidence of bumps (bounces, rock bursts) that occur in the bituminous coal mines of the Book Cliffs coal field near Sunny-side, Utah. The coal is mined because of its value as coking coal, although these bumps may be a hazard to life and property. Daily records of tremors caused by bumps for 1 3/4 years indicate that a seasonal pattern, as well as a daily pattern, exists for the number of bumps that occur in a given period. Maxima occur in May and June and November and December. Marked increases at 5-day to 9-day intervals are superimposed on these seasonal maxima. The largest bumps commonly occur during seasonal maxima when the rate of occurrence suddenly decreases and the amplitude of the individual bumps increases. Knowledge of this pattern may lead to prediction of general locations and periods of increased hazard from bumps. Experience to date has shown that prediction of precise times and locations of hazardous bumps is not possible, and may never be; primarily because even a small bump can be a hazard to life and property. Some bumps or bump sequences are actually composites, consisting or two or more discrete bumps a few tenths of a second to a few seconds apart. Violent and spontaneous releases of coal and rock from faces, ribs and roofs of mines (termed bumps or bounces by miners) are a common hazard to life and property in the coal mines located in the Book Cliffs near Sunnyside, Utah (Fig. 1). These bumps

Jan 1, 1965

By R. A. David, D. L. Katz, D. J. Vink

A phase diagram showing boundary curve and quantity of liquid in the two-phase region was determined for a mixture of natural gas and natural gasoline in the region of its critical conditions. The temperatures and pressures of phase measurements were in the range of 85 to 212 F. and 1300 to 2600 Ib. per sq. in., respectively, with the critical conditions at 169.5 F. and 2615 Ib. per sq. in. abs. Color phenomena were observed in the region of the boundary curve from 102' to 192 F. Approximate densities of the single-phase and two-phase regions and analysis of the system are included. Boundary curves between the single-phase and the two-phase regions have been determined for several binary mixtures containing hydrocarbons. 2,3,4.6,7,10,11,12,14 These investigators did not report the relative amounts of liquid and vapor within the two-phase region. The equilibrium values obtained from the dew-point and bubble-point data can be used to compute the lines showing percentage of liquid on the pressure-temperature phase diagram8 but the positions of the lines near the critical temperature and pressure are uncertain. Relative amounts of vapor and liquid were obtained for a gasoline and a naphtha1 within the two-phase area but not in the region of the critical temperature and pressure. The bubble-point and dew-point lines, as well as the percentage liquid lines within the two-phase region, were determined by visual observations in glass apparatus. Apparatus An arrangement of the apparatus is given in Fig. 1, showing the Jerguson gauge A with glass windows B. Pressure was supplied by the

Jan 1, 1940

By R. C. Hirschfeld, H. H. Einstein, R. W. Bruhn, R. A. Nelson

The objective of the model studies described in this paper is to determine the effect of planar discontinuities on the strength and deformability of a rock mass. A model material was used because it satisfied concurrently three requirements that available natural-rock samples did not: (1) low strength, which was desirable for minimizing the loads that had to be applied in the laboratory; (2) ease of producing test specimens with geometrically regular joint patterns; and (3) uniformity of the test specimens. The model tests were performed on specimens made from a single modeling material and tested under triaxial stress conditions with [u,=u,]. Results are presented in this paper for tests on specimens that had (1) a single joint set inclined at several angles to the major principal direction, including 0º and 90°, and (2) two joint sets that were mutually perpendicular, one set perpendicular to and one set parallel to the major principal direction. Several different joint spacings were used in each series. Future tests will include a series with two sets of joints that make oblique angles with each other and with the major principal direction. The results of model tests and tests on cores of jointed rock by several investigators (e.g., Müller and Pacher,l Moore,2 Krsmanovic and Milic,3 Hayashi,4 Rosenblad,5 Jaeger,6 and Lane and Heck 7, have contributed significantly to the design of these experiments, which are believed to be the first in which a comprehensive study has been made of the combined effects under triaxial loading of joint spacing and joint orientation (Fig. 1).

Jan 1, 1970

By J. H. Bechtold, R. Kossowsky

1 HE superplastic behavior of the eutectoid A1-78 wt pct Zn alloy has been thoroughly investigated by Back-ofen et al.' The superplastic elongations and the marked resistance to necking were rationalized in terms of high strain rate sensitivity. In a subsequent paper2 superplastic behavior was formulated to show Nabarro-Herring diffusional creep as rate controlling at low strain rates, giving way to a dislocation climb process at higher strain rates. In a paper devoted to an interpretation of superplasticity in two-phase alloys, Packer and sherby3 have included the results of an examination of the structure of an Al-Zn eutectoid specimen before and after superplastic deformation. No significant change in grain size or directionality was observed in the deformed microstructures. This one observation led the authors3 to suggest that con- tinuous recrystallization or grain boundary migration was responsible for superplasticity. The purpose of this note is to report our observations on the superplastic behavior of the Al-Zn eutectoid alloy which differ in certain respects from works previously reported. Following Hayden et al., the results are discussed in terms of dislocation climb as the important factor during superplastic deformation. A heat of nominally high (99.995) purity 22 wt pct A1-78 wt pct Zn was induction-melted and cast into a 0.5 by 6 by 12 in. slab. The slab was heated to 350°C and rolled to 1/8-in.-thick plate. The plate was then cold-rolled to 0.040-in. thickness, annealed at 35OaC, and rolled to the final thickness of 0.020 in.* Speci-

Jan 1, 1969

By W. O. Crosby

Washington Camp, in Santa Cruz county, Arizona, is a small and little-known mining-district situated on the lower, eastern slope of the Patagonia mountains, about 20 miles east of Nogales and a like distance south of Patagonia Station on the Sonora railroad, which connects at Benson, 83 miles from Nogales, with the main line of the Southern Pacific. This district is also about 4 miles north of the international boundary, 35 miles west of Bisbee and 40 miles north of Cananea, in Sonora. The topography of the district, which lies at a general elevation of 5,500 ft. above the sea, is only very moderately rugged, and presents no obstacles to mining-operations. Although some of the claims of the camp, including the Pride of the West,, Belmont and Holland, were extensively worked for silver 25 years ago, they passed, at moderate depths, as in so many other districts, out of the argentiferous lead carbonate and sulphide, into zinc, copper and iron sulphides ; and for two decades the camp was abandoned and almost forgotten. In recent years, however, its apparent possibilities as a copper-producer have led to a revival of mining-activity; but not, as yet, with conspicuous success. Although economically relatively unimportant, the deposits of Washington Camp are, mineralogically and structurally, nevertheless, typical examples of ore-bodies developed in connection with the garnet ledge now recognized as a normal feature of granite-limestone contacts; and, in the opinion of the writer, this is an instance where a minor example is yet essentially normal and capable of throwing important light upon the origin and genetic relations of the type.

Jan 1, 1906

By Jay A. Carpenter

IN six years the construction of Hoover Dam and the power plants probably will have reached the operating stage and this vast new source of power will then be continuously available for industry. The height of the darn will be 580 ft. and the average annual flow of the Colorado River is calculated at approximately 24,000 cu.ft. per sec. If this full head and average flow can be maintained the year round, about one million horsepower will be generated. The U. S. Reclamation engineers, taking into consideration the probable range in flow and head, have set the figure for power contracts at 660,000 firm horsepower, which can be assured at all times of the year. During the months of heavy run-off of water from the Colorado River Basin the power plants should be able to generate the full 1,000,000 hp. capacity of the power plants, so there will be 340,000 excess or secondary horsepower. The cost of firm power at the switchboard will be close to 2.15 mills per kw.-hr., equal to $14.05 per hp.-yr., and the cost of the secondary or off-peak power will be close to 0.8 mills per kw.-hr., or $5.22 per hp.-yr. In no place in the country can such cheap power be obtained today. The electrochemical industry is in a state of flux because the power costs from its old sources have increased so much (to $30 per hp.-yr. at Niagara) that the industries have had to seek new sources, so they have gone to Canada and Norway and built new plants.

Jan 1, 1932

By R. J. Armstrong, J. J. McKay

The Montana Phosphate Products Co. is currently operating three underground phosphate mines in Powell County, MOnt. † In this area the Phosphoria formation is from 35 to 50 ft thick and contains a bed of phosphate rock varying in thickness from 2 1/2 to 5 ft, overlain by 12 to 30 ft of cherty quartzite, and underlain by about the same thickness of quartzite and shaly to cherty beds. In general, the phosphate bed has a reasonably hard quartzite footwall, as well as a hard cherty hanging wall, both of which greatly facilitate the mining operation. Folding has deformed the phosphate bed to a considerable degree in the area. It is carried to surface by several of the anticlines and lowered to considerable depths in some of the syn-clines. The main structural features affecting the mining operations of the company are the Garrison anticline and the adjoining syncline and succeeding limb of a second anticline on the east (Fig I). The axis of the folding strikes roughly northwest-southeast. The three mines, namely, the Anderson, Graveley, and Luke are on different limbs of the above folds. Accordingly, the dip of the bed, and consequently the mining method, in each mine differs to a considerable degree from that of the others. For this reason, each operation will be dealt with separately. Anderson Mine LOCATION AND DEVELOPMENT Topographically this mine is in a narrow valley, the bottom of which has an altitude of 5200 ft. The phosphate bed outcrops near the ridge on the east and dips towards the valley floor at an angle of from 25 to 30°,

Jan 1, 1950

E. A. HOLBROOK,*Urbana, Ill.-To those who have followed the development of powdered coal two questions often occur. First, as to the moisture in the coal. In Illinois we recognize that the bituminous coals contain about 12 to 15 per cent. of what we call "contained moisture," that is, the moisture is present in the coal although this may appear absolutely dry and dusty. In addition, the surface moisture may be present in any amount. I would like to ask what is the relative effect of these two forms of moisture upon the work of pulverizing. Does Mr. Collins refer to the contained moisture or to the surface moisture in estimating the degree to which the coal must be dried? H. R. COLLINS.-In the lignite coals, of which this country possesses a great deal and is beginning to develop them to considerable extent, the "contained" or "combined" moisture does not .trouble us; we have no difficulty in reducing lignites to a high degree of fineness. But when dealing with bituminous, sub-bituminous, or semi-bituminous, we, prefer to reduce the combined moisture as well as the hydroscopic moisture as far as possible. We have recently put into operation, at a plant, furnaces and boilers consuming the lignite from northern New Mexico, which contains between 4 and 5 per cent. moisture as we pulverize and burn it. The evaporating efficiencies under the boilers have been so remarkable that we wish to check the results half a dozen times before quoting them. We have also just started two boilers at the Garfield smelter, and have obtained the same high efficiencies.

Jan 11, 1918

By H. K. Shearer

Oil production in north Louisianat in 1939 was 25,249,640 bbl., a decrease of 11.2 per cent from 1938. The only important increases in production were in the Cotton Valley and Shreveport fields, but Caddo, Homer, Sligo and Zwolle also made slight gains. Greatest decreases were in the Lisbon and Rodessa fields. Xatural gas production of 313,333 million cu. ft. was an increase of 5.6 per cent over 1938. The increase was accounted for in the Monroe field, while all other fields showed only minor variations from the production of the previous year. Well completions in 1939, as compared with 1938, were as follows: The decline in number of completions was due entirely to lack of proved areas for drilling, and would have been greater except for a revival of interest in the old Caddo shallow field. A majority of the wells completed during the year were in various old, shallow fields, so the average depth of drilling was much less than in several preceding years, notwithstanding a few very deep tests. No new fields were discovered, the only wildcat well reported as a producer being a very small oil well in northwestern De Soto Parish, which is of no apparent commercial importance. Deep gas-distillate production in the Cotton Valley formation was opened at Lake Bistineau and Lisbon, and oil at Shongaloo, but all these wells were too small to encourage additional drilling. Extensions and Developments Caddo Field.—More active drilling was donc in the 36-year old Caddo field in 1939 than in any of the newer fields, with completion of 133 oil

Jan 1, 1940

By E. W. Schilling

THE-separation of hematite by hysteretic repulsion was first brought to the attention of the public in 1922, by W. M. Mordey1. Three-years later another paper2 was published and after another four years a third paper3 appeared in the South African publications. Certain data were lacking in these papers. In order to continue the work intelligently a knowledge of the shapes of the hysteresis curves for certain minerals was very necessary. This information was not available until the present year4. It was known that reduction of certain ores rendered them amenable to this process of separation but definite data in. the form of curves showing exactly the effect of such treatment were lacking. Prob-ably our best source of information on the separation of minerals by the use of alternating-current magnetic fields today is the reports from the U. S. Bureau of Mines 5-7. It is not the purpose of this paper to tell the reader in detail how to make a commercial separator. Experimental models have recently been made7 and the results obtained have been so good that it is the opinion of the authors that the public will soon take an active interest in the subject and its development. The writers have constructed a separator that is considerably different in construction and operation from the two types described by Mr. Davis. This will be described; but the real purpose of this paper is to outline certain experiments and give curves showing data that have a fundamental bearing upon the practical construction of a separator of this type.

Jan 1, 1936

By H. K. Shearer

Oil production in north Louisianat in 1939 was 25,249,640 bbl., a decrease of 11.2 per cent from 1938. The only important increases in production were in the Cotton Valley and Shreveport fields, but Caddo, Homer, Sligo and Zwolle also made slight gains. Greatest decreases were in the Lisbon and Rodessa fields. Xatural gas production of 313,333 million cu. ft. was an increase of 5.6 per cent over 1938. The increase was accounted for in the Monroe field, while all other fields showed only minor variations from the production of the previous year. Well completions in 1939, as compared with 1938, were as follows: The decline in number of completions was due entirely to lack of proved areas for drilling, and would have been greater except for a revival of interest in the old Caddo shallow field. A majority of the wells completed during the year were in various old, shallow fields, so the average depth of drilling was much less than in several preceding years, notwithstanding a few very deep tests. No new fields were discovered, the only wildcat well reported as a producer being a very small oil well in northwestern De Soto Parish, which is of no apparent commercial importance. Deep gas-distillate production in the Cotton Valley formation was opened at Lake Bistineau and Lisbon, and oil at Shongaloo, but all these wells were too small to encourage additional drilling. Extensions and Developments Caddo Field.—More active drilling was donc in the 36-year old Caddo field in 1939 than in any of the newer fields, with completion of 133 oil

Jan 1, 1940

By H. A. Doerner

PROPOSALS to use hydrocarbon or natural gases for the reduction of zinc from oxide materials may be traced back through Patent Office files to the early years of the present century. Natural gas at rates cheap enough to compete with solid fuels has been available at or near one major zinc district for more than a decade. That the seemingly meritorious and economically interesting applications of these proposals have not devel-oped into workable processes for direct production of zinc by natural gas cannot be completely ascribed to the proverbial conservatism of the zinc industry. It is possible to produce spelter commercially in normal times from zinc oxide and carbonaceous reducing agents without having a very precise understanding of the chemistry of the process. The reduc-tion by hydrocarbons is not, however, in this class, and the technical complexity of this reduction metallurgy and chemistry prohibits solution of the inherent difficulties by the "hit and miss" methods that are some-times thought to be practical. In a thermodynamic study of the chemistry of zinc smelting, Maier1 made a preliminary study of the chemistry of the use of methane for reducing zinc oxide by thermodynamic means, pointing out that the following reactions, the limits of which could be theoretically predicted, were important: ZnO + CH4 = Zn(gas) + CO + 2H2 [1] CH4 = C -I- 2H2 [2] ZnO + CO = Zn(gas) + CO2 [3] ZnO + H2 = Zn(gas) + H2O [4] Other possible reactions, not discussed in the reference quoted, are: CO2 + CH4 = 2CO + 2H2 [5] H2O + CH4 = CO + 3H2 [6]

Jan 1, 1933

By Alfred Wandke

The problem of vein formation has been of particular interest to the writer for years. As his work for a long time was confined largely to districts showing large deposits of copper ore, it was natural that the efficiency of replacement, as one if not the chief control of the emplacement of the ore, seemed a particularly attractive hypothesis. Of late years, in almost daily underground work in the Guanajuato district, he has collected evidence which makes it certain that in a number of cases the ore solutions were under sufficient pressure to force the rock walls apart and to hold them apart, thus offering an open space for the deposition of vein and ore-bearing material. This paper will concern itself with conditions frequently met with in hypogene ore deposits of the vein type, and will deal in particular with ore occurrence in precious-metal veins of the type classified by Lindgrenl as epithermal deposits, or metalliferous deposits formed near the surface by ascending thermal waters2 and in genetic connection with igneous rocks. To account for the emplacement of this type of ore deposit various writers have suggested the following agencies: 1. Shattering of the wall rocks. 2. Pressure of growing crystals. 3. Magmation, as treated at length by Spurr3. 4. Replacement. 5. Openings produced by folding. 6. Shearing due to gravity. 7. Shrinkage produced by the passage of pre-ore solutions. 8. Contraction joints produced by lateral secretion. To this list there may be added another agency, a discussion of which forms the basis of this paper: 9. Pressure of the ore-bearing solutions.

Jan 1, 1931