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By Rudolph G. Wuerker

Charles T. Holland (Head, Dept. of Mining Engineeri*, Virginia Polytechnical Inst., Blacksburg, Va.) Mr. Wuerker has presented a very interesting discussion of the use of triaxial test methods for investigating the strength properties of rocks. Such methods, no doubt, eventually will develop considerable information of interest to those concerned with the design of mine layouts, particularly in the field of pillar design. From his discussion of my recent article, "Cause and Occurrence of Coal Mine Bumps" (Holland Mining Engineering 1958, p. 933-1002), it is evident that in one place at least I did not make my meaning clear to him and perhaps others. To clear the matter up I think it best to quote from the article, somewhat more fully than did Mr. Wuerker, as follows: "4) In actual operations — because rocksare not perfectly elastic, homogeneous, nor isotropic and because local yield does occur — the maximum stress as demonstrated by Phillips (Ref. 22, pp. 64, 65) and indicated by much experience in mining, does not occur at the walls of the opening but at a short distance inside the pillar. Furthermore, the maximum stress does not reach as great a value as theoretical considerations and laboratory experimental methods indicate.* Actual distance inside the pillar, measured from the wall, at which the maximum stress exists, has not been determined. Observations in many mines, however, indicate that this distance could have a mini-value of one to six or eight times the bed thickness and that it is probably affected by width and height of the opening, depth of cover, and relative values of the elasticity and plasticity of materials comprising the roof, floor, and coal seam. The actual value of the stress produced probably lies between the theoretical maximum and the average stress concentration that would be produced if the weight of the strata above the unsupported opening were evenly distributed over the pillars for a distance equal to the opening width." The footnote reference in the above quotation referred to the following: "*For example, the Pocahontas No. 4 coal bed in southern West Virginia is mined under cover up to 1800 ft thick. Development openings are driven 18 to 20 ft wide, and the bed is about 6 ft thick. According to the work of Panek, the tangential wall stress at mid-bed height under these conditions would reach values between 4000 and 5000 psi. Actual tests of 3-in. cubes of this coal show its compressive strength would be much less than this, perhaps as low as 400 psi. Yet the pillars usually show no evidence of failure in these headings. In this same bed at a depth of 800 ft, the author has seen an opening 225 ft between supports lying between two old groves approximately 1100 ft apart. According to the theoretical considerations, the stress in the pillar walls would have been about 18,000 psi, yet the pillar showed little or no evidence of weight. In view of these observations, it is clear that the wall stress does not attain the maximum values indicated by theory." (Underlining added to original wording.) By referring to Fig. 2A of my paper it will be noted that theoretically the maximum pillar stress would occur at the pillar wall, i.e., at the passageway surface of the pillar. Obviously this cannot be correct in the cases of stress ranging from 4000 to 18000 psi since the coal at the surface of the pillar is under no constraint and cannot have a strength much greater than 400 or 500 psi. Hence, my conclusion that the maximum stress does not occur at the wall but back in the pillar some distance from the wall. Since these stresses are pushed back in the pillar from the wall, it is also obvious that the loads transferred to the pillar from the opening will be spread over a greater area and hence Pillar stresses will not rise to the values postulated by theory and photoelastic experiment. Further since to visual inspection the coal along the pillar wall did not appear to be failed the conclusion was reached that the stress shift was caused by local elastic or plastic yield and by difference in the elastic modulus of the rocks composing the mine floor, mine roof, and coal bed. Later on under the heading "Strength of Mine Pillars" (pages 1000-1002) the effects of constraint is briefly described. Also a formula taking into account constraint is developed relating pillar strength to the uniaxial strength of coal and the L/T ratio of the pillar. Since my paper was written, reports of experiments conducted in South Africa (Denkhaus, et. al., 1959), in Sweden (Hast 19581, and in Canada (McInnes, et.al., 1959) reveal that the conclusion expressed relative to the existence of a low stress area existing around the edges of pillars and solid faces as described above is generally correct. But it seems possible that where the wall stress developed is less than the unconfined strength of the rock composing the pillar and where the roof, floor, and pillar

Jan 1, 1961

By A. F. Taggart

THE following notes represent significant excerpts from a mass of records of experimental work done in the ore-dressing laboratory at the Columbia School of Mines during the years 1926 to 1928-inclusive. CLASSIFICATION OF EXPERIMENTAL WORK The experiments performed may be grouped for purposes of description under the following general -headings: I. Collecting agents. a. A method for quantifying collecting effect. b. Coating with undissolved collecting agents (oils) c. Action of dissolved collecting agents. II. Frothing agents. a. A method for quantifying frothing effect. b. Relation between frothing effect and chemical composition. III. Inorganic reagents. a. Methods of studying the effects of these reagents. b. Effect on slime dispersion. c. Effect on sulfides. SUMMARY OF THE ORIGINS OF PRESENT-DAY FLOTATION PRACTICE The first practicable, foolproof method of froth flotation was described in U. S. patent 835120, issued in 1906 to Sulman, Picard and Ballot, and in the equivalent patents in other countries. A number of less simple methods of producing the same result had been described previously in patent publications and otherwise.1 The reagents specified in all of these early patents were "oils" and, in addition, some inorganic substance, usually an acid. The quantities of reagents recommended and added were enormous when' compared with those used today.

Jan 1, 1929

By C. C. Whittier

PLANS are well matured for the joint meeting of the Coal Division and the Ohio Section of the Institute at Columbus, Ohio, Oct. 27 and 28, at which a large attendance is expected. The proceedings for a day and a half will be devoted largely to the uses of coal, the program providing for two technical sessions in the auditorium of Battelle Memorial Institute (505 King Ave.) on Friday, and various plant inspec¬tions on Saturday morning. By way of diversion on Saturday afternoon arrangements have been made for attendance en bloc at the football game between Ohio State and Northwestern, 100 seats having been reserved for the game at $2.40 each-as long as they last. An inventory of the high lights of the meeting would be incomplete without reference to the informal banquet at the Deshler-Wallick hotel on Friday evening, for which Eli T. Conner, Chairman of the Coal Division, is down for a talk, and Howard N. Eavenson, Vice-president of the Institute, will be the principal speaker. The program in detail is as follows:

Jan 1, 1933

By Henry Wurtz

OBSERVING in the Engineering and Mining Journal, of January 16th, 1875, page 35, a report of a brief discussion upon the nature and origin of this unique and interesting coal, I take the liberty-on thus finding it a subject of interest to members of the Institute, and especially as my name came into this discussion-to communicate some results which may serve at least to overthrow certain erroneous ideas that have prevailed. While I would not claim to have made much approach to an understanding of this mineral-the whole of what I call Apozoic Mineralogy being as yet dark and almost unknown ground-yet I believe I have shown that few minerals of such importance and abundance, and so long before the world, have been so singularly misunderstood. On first examination of a sample of the substance to which the name of carbonite has been given, my surprise was not small, at failing to recognize in it one individual characteristic of true coke; neither the hardness, lustre, color, streak, porosity, sonorosity, structure, fracture, nor any of the so-called "pyrognostic" characters. Indeed, comparison with any coke, or variety or modification thereof, seemed altogether fantastic. Therefore the controversy regarding supposed trap dykes, whose existence at the locality is denied by some, seems useless, as we have no question of a natural coking, there having been no coking at all.

Jan 1, 1875

By Richard A. Mullins, James J. Merle

Systematic sampling and analysis in coal-washing plants results in product control and economical operation. A well-organized laboratory system reduces operating costs and increases sales if the operating and sales companies make full use of information it supplies. The operating cost of a control laboratory is less than 1 pct per ton of coal produced. THE system of laboratory control as practiced by the Ayrshire group of mines was begun with the construction and organization of the first laboratory in conjunction with the completion of its first wash-ery in 1941. The primary purpose of this laboratory was to maintain a check on the quality of the coal produced from the washing plant. The laboratory was equipped to determine proximate analyses, float-and-sink tests, and screen analyses, and was staffed by a chemist. an assistant. and a technician. Members AIME, are Assistant Preparation Manager and Chief Chemist, respectively, Ayrshire Collieries Corp. and Subsidiaries, Danville, Ill. Joint AIME-ASME Fuels Conference. French Lick. October 1949. TP 2855 F. Discussion (2 copies) may be sent to Transactions AIME before June 30, 1950. Manuscript received Aug. 22, 1949. Soon it became apparent (1) that product control could be accomplished, (2) that a substantial reduction in operating costs could be effected by close control of coal losses in the rejects, and (3) that information furnished by the laboratory was of continuous value to the operating and sales companies. Consequently the laboratory function was expanded to supply them with additional data as required. As the parent company expanded and new mines were added, control laboratories were established at each mine equipped with washeries, and a central laboratory was maintained at one of the mines that was located equally convenient to all of them. A well-planned control laboratory assures production of a uniform, high-quality product. Whenever coal of substandard grade is loaded inadvertently, the sales company can be informed and the proper channel of distribution made. Conversely only constant and strict laboratory supervision can insure proper production of the various grades. Knowing the product, the producer can keep out of many customers' arguments that may be both awkward and expensive. Double checking between customers and mine laboratories have solved many disputes' Some nager insist On buying coal On the analysis basis only, with penalties for substandard coal and premiums for coal above normal quality. A substantial percentage of the coal sold by the Ayrshire group is of this nature. The usual procedure is for the customer to sample and analyze the coal as it is unloaded at the plant, and the mine laboratory samples it as it is loaded at the mine for subsequent analysis by the central laboratory. Only the unloaded moisture is considered, rather than the average of mine and plant moisture, and the buyer sends duplicate samples to the central mine laboratory for this determination. The average of the two analyses determines the price of coal at the mine. In this particular case, the laboratory plays an important part in increasing realization for two reasons: (1) every attempt is made to maintain plant efficiency and product quality as high as possible, (2) check on analyses and sampling by the buyer or seller.

Jan 1, 1951

By Richard A. Mullins, James J. Merle

Systematic sampling and analysis in coal-washing plants results in product control and economical operation. A well-organized laboratory system reduces operating costs and increases sales if the operating and sales companies make full use of information it supplies. The operating cost of a control laboratory is less than 1 pct per ton of coal produced. THE system of laboratory control as practiced by the Ayrshire group of mines was begun with the construction and organization of the first laboratory in conjunction with the completion of its first wash-ery in 1941. The primary purpose of this laboratory was to maintain a check on the quality of the coal produced from the washing plant. The laboratory was equipped to determine proximate analyses, float-and-sink tests, and screen analyses, and was staffed by a chemist. an assistant. and a technician. Members AIME, are Assistant Preparation Manager and Chief Chemist, respectively, Ayrshire Collieries Corp. and Subsidiaries, Danville, Ill. Joint AIME-ASME Fuels Conference. French Lick. October 1949. TP 2855 F. Discussion (2 copies) may be sent to Transactions AIME before June 30, 1950. Manuscript received Aug. 22, 1949. Soon it became apparent (1) that product control could be accomplished, (2) that a substantial reduction in operating costs could be effected by close control of coal losses in the rejects, and (3) that information furnished by the laboratory was of continuous value to the operating and sales companies. Consequently the laboratory function was expanded to supply them with additional data as required. As the parent company expanded and new mines were added, control laboratories were established at each mine equipped with washeries, and a central laboratory was maintained at one of the mines that was located equally convenient to all of them. A well-planned control laboratory assures production of a uniform, high-quality product. Whenever coal of substandard grade is loaded inadvertently, the sales company can be informed and the proper channel of distribution made. Conversely only constant and strict laboratory supervision can insure proper production of the various grades. Knowing the product, the producer can keep out of many customers' arguments that may be both awkward and expensive. Double checking between customers and mine laboratories have solved many disputes' Some nager insist On buying coal On the analysis basis only, with penalties for substandard coal and premiums for coal above normal quality. A substantial percentage of the coal sold by the Ayrshire group is of this nature. The usual procedure is for the customer to sample and analyze the coal as it is unloaded at the plant, and the mine laboratory samples it as it is loaded at the mine for subsequent analysis by the central laboratory. Only the unloaded moisture is considered, rather than the average of mine and plant moisture, and the buyer sends duplicate samples to the central mine laboratory for this determination. The average of the two analyses determines the price of coal at the mine. In this particular case, the laboratory plays an important part in increasing realization for two reasons: (1) every attempt is made to maintain plant efficiency and product quality as high as possible, (2) check on analyses and sampling by the buyer or seller.

Jan 1, 1951

By T. F. Witherbee

On .the 22d of November, 1879, white, iron unexpectedly ap peared while working the Cedar Point Furnace, Port Henry, N Y., on the following burden, calculated to turn out mill and foundry iron: Anthracite coal,. ., .. .. 8000 pounds. Connellsville coke,. ..1500 " Total,..4500 " Old Bed ore,........ 3750 " New Bed fine ore,. ..2000. " New Bed chunk ore,. .. 1000 " Kearnev hematite ore,.750 " Total,..... 7500 " Magnesian limestone,. 1665 " Common limestone,. ...835 " Total,........ 2500 " The production per week since making mill iron-—from September 1st, 1879, to date, seven weeks—was 412 gross tons. Ore was not immediately taken off, as nothing serious was looked for. The iron for the next week graded from No. 4 to white, and in six days the make was 2741/2 tons. At 10 p.m., Friday, the 28th, a slip of -14 feet occurred, and on Saturday, at 5 A.M., another of 3 feet on the south side and 7 feet on the north side took place. At this time it was found that the south side had been hanging for over a week—a fact which had not been reported. Throwing off the wind, to produce slips and reduce pressure, had been tried with no effect. The stock, as seen through the tuyeres, seemed to consist almost entirely of coal, with just enough infusible cinder to cement it into a mass through which the blast could not be forced. At 3.50 A.M., Sunday, the 30th, the first cinder seen in seventeen hours came into tuyeres Nos. 1, 2, 3, and 6. At 9.30 A.M. No. 3 was taken out to see if the stock

Jan 1, 1881

By W. Spencer Hutchinson

THE relative importance of mineral production in British South Africa is about as follows: Gold, $200,000,000; diamonds, $40,000,000; coal, $18,-000,000; asbestos; $3,000,000; chrome ore, $2,000,000. In 1926 the gold mines paid $42,000,000 in dividends, the diamond mines $13,000,000, coal nearly $3,000,000, others less than $500,000. The recorded history of South Africa starts with the visits of the Dutch and the English in the sixteenth century, followed by the settlement of Cape Colony by the Dutch East India Company in 1651: The English acquired Capetown in 1806 and conflicts between English and Boers were a part of the history, from that, time on. Transvaal was settled in 1835, following the Great Boer Trek. The mining of diamonds became im-portant in 1870; the production of gold from the Rand in 1890;' the export of chrome ore in 1910; and the dis-covery of platinum in 1925. South Africa has a race problem, resulting not alone from the disparity of numbers between whites and natives, more than seven blacks to each white, twenty to one in Southern Rhodesia, and three. hundred to one in Northern Rhodesia; but because of the division of the white race between English and Cape Dutch or Afrikaans. The natives are also of many tribes.

Jan 6, 1927

By W. J. Schuster

Safety in coal mines depends largely upon adequate training of the foreman. Although management must provide modern and safe equipment and at all times keep mines in first class condition from a safety viewpoint, final results will be determined by the quality of supervision. HANNA COAL CO., Division of Pittsburgh Consolidation Coal Co., operates three large underground mines in eastern Ohio. The section of Pittsburgh No. 8 coal seam in which these mines are located varies in thickness from 52 to 64 in. It is immediately overlain by a stratum of shaly material 12 to 15 in. thick locally known as draw slate, which is structurally very weak and which disintegrates rapidly upon exposure to atmosphere. Immediately above the draw slate as it is normally found is a band of extremely high ash material 6 to 12 in. thick known as roof coal or rooster coal, and above this is a stratum of conglomerate material varying from 4 to 10 ft in depth. Overlying the conglomerate is a relatively thick stratum of limestone, the first stable material above the Pittsburgh coal seam in eastern Ohio. With the method of full-seam mining that has been adopted, draw slate is shot down, loaded with the coal, and removed in the preparation plants. The roof coal then becomes the permanent roof. The major problem in mining the No. 8 seam in eastern Ohio is control of the roof. Since the strata above the draw slate contains no material with a structure firm enough to provide self-support, the roof begins to sag in a relatively short time after the coal and draw slate have been removed. The problem thus becomes one of getting temporary safety posts under this roof as quickly as possible to prevent a break or separation from occurring either in the roof coal or in the conglomerate above it. Haulage System The Pittsburgh No. 8 seam in eastern Ohio is relatively level, with only minor local dips. Throughout the Hanna Coal Co. mines, entries are generally 12 ft wide. Rooms are driven on a 60" angle on 30-ft centers and are 22 ft wide. No attempt is made to extract the 8-ft pillars between. The entire length of main line haulage is gunited in one mine, and a major portion in another. Two of the mines have single-track main haulage roads with passways. The third, a new mine, is double-tracked, and the roof is supported by steel crossbars, 60 lb or heavier, spaced on 4-ft centers and lagged. In recent years timbering on main line and secondary haulage roads has been accomplished by one of two methods: 1—crossbars are supported on a small section of post set in a hitch hole in the rib, or 2—or a hole is drilled in the rib about 12 in. below the roof, of sufficient depth to fasten securely a short length of 40-lb rail, the bottom of the rail facing the roof, on which a short post is set directly under the crossbar. At present the hitch-hole timbering method is favored. At two of the mines the main line haulage locomotives are 26-ton, 8-wheel units. These locomotives are of the axleless type, each wheel being individually mounted on the frame. The motorman's compartment is encircled by 3-in. armor plate for the protection of the occupants. At the third underground mine conventional 15-ton locomotives are being used. However, these locomotives have been completely rebuilt in the company's shops. Equipment has been streamlined and quarters have been provided for two people, who are protected by heavy steel plate in much the same way described above. This modernization program has been completed on all secondary haulage locomotives at the three mines, and the company is well on the way to similar equipment of the 6-ton section locomotives. The following additional features have been included in their modernization: 1—additional support for the motors to prevent their falling to the middle of the track and derailing the locomotives should a break occur in the suspension bar support; 2—installation of additional bracing to prevent brake rigging from becoming displaced and causing derailments; 3—enclosure of all electric wiring in conduit or raceway; 4—provision of an enclosed compartment for the storage of re-railers, jacks, and other equipment, so that they need not be carried on the outside of the motor; and 5—redesign of the end of the locomotive opposite the operator's compartment to prevent anyone's mounting from that direction. It is interesting to note that some

Jan 1, 1955

By D. L. Rainey, E. R. Goter, W. R. Hudspeth

THE area in which spodumene-bearing pegmatites occur extends from Gaffney, S. C., in a northerly direction to Lincolnton, N. C., a distance of about 16 miles. The zone averages 2 miles in width. Interest in this area was first aroused by the discovery of small amounts of cassiterite in the pegmatites and in greissen which occurs on the walls of some of the pegmatites. Attempts were made from 1880 into the 1920's to mine and concentrate cassiterite, but there were no successful operations. In 1935 L. M. Williams became interested in the area and began prospecting by trenching and sinking several small shafts. He gradually gained control of a considerable acreage south of the city of Kings Mountain, N. C. Mr. Williams states that he produced some ore from a shaft which he shipped to the Maywood Chemical Co. in the late 1930's. In 1937 G. H. Chambers of the Foote Mineral Co. visited the area and examined several properties, but the lithium market was too small to support the necessary concentrating plant.

Jan 9, 1953

EDWARD HART*, Easton, Pa. (written discussion?) .-In 1895 I visited the chemical plant of the Messrs. Chance at Oldbury, England, under the guidance of Mr. France, the manager. In the stock house I saw a pile of coal brasses with adhering coal and said to Mr. France, "I should think you would get dark acid." "Yes," he replied, "our acid has always been rather black. and our customers have grown used to it. Some time ago we ran out of brasses and could get only Spanish pyrite. Our product became white and the customers began to complain, so I put a little sugar in each carboy." E. A. HOLBROOK,* Pittsburgh, Pa. (written discussion?).-Mr. Davis says, "A very large tonnage of pyrite is annually being thrown in the waste in the coal mines of this country." This quantity is much larger than is generally realized by people not intimately associated with coal mining. At the beginning of the war this country seemed threatened with a short-age of pyrite. The U. S. Bureau of Mines conducted a general investiga-tion of the pyrite resources of the country in order to ascertain what material was commercially available. The general pyrite investigation was in charge of H. A. Buehler, with the subsection on coal pyrite in charge of E. A. Holbrook.

Jan 10, 1919

By H. M. Hobart

This paper deals principally with investigations undertaken by the Welding Research Sub-committee of the Welding Committee of the Emergency Fleet Corporation. The general object of the investigations has been to extend the use of welding in the construction of merchant ships and, specifically, to provide a definite basis for obtaining the greatest economy and efficiency in employing welding in place of riveting in the construction of the hulls of such ships. Composition of_ Ship-plate Steel The chemical composition of the steel employed in such hull construction varies with the thickness of the plates. Through the courtesy of Mr. H. Jasper Cox, of Lloyd's Register of Shipping, the following information may be given concerning the kind of steel plate employed in American shipyards in 1918 for the hull construction of merchant ships. Lloyd's requirements do not relate to the chemical composition. They require a tensile strength of 58,000 lb. per sq. in. (40.75 kg. per sq. mm.) for their lower limit and 72,000 lb. per sq. in. (50.59 kg. per sq. mm.) for their upper limit. For the information of the Committee, Lloyd's obtained from their surveyors at various works data of the carbon content, which is as follows: Works Carbon Content for Plates 1/4 In. Thick 1 In. Thick A..................... 0.14 0.23 B..................... 0.14 0.25 C2.................. 0.19 0.25 D................. 0.20 0.30 E Upper limit..... 0.35 Lower limit..... 0 24 0.29 Upper limit,.... 0.25 0.30 Lower limit..... 0.21 0.27 Upper limit..... 0.25 0.35 Lower limit..... 0.22 0.28

Jan 1, 1920

By C. C. Whittier

CIVILIZATION'S PROGRESS, which has multiplied man's comforts, conveniences, a n d happiness, is based upon the extensive employment of natural minerals and sources of energy. Mineral resources are basic factors in modern economic development, machine industry, international trade and world power. A survey of mineral consumption shows that the United States leads the world in the production and consumption of energy materials, of metals, and of the large and diverse array of earth materials that fall in the nonmetallic mineral group. The use of nonrnetallic minerals exceeded both the metals and the fuels in the long period before the industrial age, but it is only in the last two decades that consumption of non- metals has kept pace with and approximated in value the output of metals. Although the data of production in the first half of the last century are meager and fragmentary, the record of the past fifty years-the period of most rapid growth-is available, and reveals an astounding growth.

Jan 1, 1933

By J. A. Holmes

SHUTTING-IN the Rangely gas well was an interesting problem because of the high rock pressure and the volume of gas developed, as well as the difficulties encountered. After nearly a week's open flow, the rock pressure was 1275 lb., which corresponds with a 2950 ft. hydrostatic head. The volume of gas was between 45,000,000 and 50,000,000 cu. ft. per day. The Rangeley oil field, which now has a daily production of 100 bbl. of shale oil from shallow depth, lies approximately 100 miles north and 30 miles west of Grand Junction, Colo.; not far from the Utah line. The, well we are considering was drilled on the apex of a large clearly defined. Structure1 in the SE.1/4 sec. 30, T. 2 S., R. 102 W., and entered the gas sand at 2954 ft. on March 2, 1925. The condition of the well at the time the gas was encountered was as follows: 20 ft. of 20-in. conductor cemented with ten sacks at 40 ft. The 15 1/2-in. casing was pulled when the 12 1/2-in. was cemented. 1166 ft. of 12 1/2-in. casing, cemented with fifteen sacks. 2531 ft. of 10-in, casing, cemented with ten sacks; neither the 12 1/2-in. nor the 10-in, casing shut off water but they were cemented for protection. 2938 ft. of 8 1/4-in. 36-lb. casing, hanging on a spider in the collar with a forged-steel, high-pressure bradenhead between it and the 10-in. casing. An 8 1/4-in. drilling, or master, gate and a control head were in place on the 8 1/4-in. casing, and all was in readiness for the bringing in of the well.

Jan 1, 1926

By Alden Greninger

METALLURGISTS have long believed that martensite in steel forms as plates along the octahedral {111} planes of austenite. Much has been written about mechanisms whereby units of the austenite lattice are pictured as transforming to martensite by shearing movements initiated along the octahedral planes of austenite, supposedly resulting in plates of martensite lying parallel to these planes of shear. A critical inspection of two or three photomicrographs of quenched hypereutectoid steel led us to the conclusion that the orientation habit of martensite, at least in hypereutectoid austenite, could not possibly be octahedral. Inasmuch as recent studies30,31 of the martensite-type reaction in nonferrous alloy systems have established the irrational orientation habit as characteristic of this type of lattice transformation, the need for a thorough restudy of the crystallography of martensite formation in steel was evident. The present paper reports the results of such a study, extended to include both cementite and some of the products of constant-temperature decomposition of austenite. Also reported are a few of the results obtained from a microscopic and X-ray study of the austempering process in very high-carbon steel.

Jan 1, 1940

By J. T. Pardee

INTRODUCTION PLACER is a Spanish word, the definitions of which include "an extensive bank of sand or gravel" and "a place where currents of water deposit particles of gold."l The term, probably first used in the western hemisphere by Spanish or Mexican gold miners, is now generally applied to all detrital deposits that yield valuable minerals by washing. In the Western States placer products other than gold, including the silver alloyed with it, are chiefly sapphires, produced in Montana, and platinum alloys recovered in California and Oregon. During the war tungsten ore (scheelite) was obtained from placers in the Atolia district, California, and a number of diamonds have been found in the Sierra Nevada gold belt. Small amounts of stream tin have been produced in the Black Hills of South Dakota and a little monazite sand in the Boise Basin. Idaho. Magnetite, chromite, ilmenite, zircon, and other useful minerals are more or less abundant in the beach placers of the Pacific coast and in the heavy residues of placer mining elsewhere, but the problems of profitably separating and marketing them remain to be solved. Minerals of lead, quicksilver and other metals occur in many of the placers and although not plentiful enough as a rule to be worth recover-ng, their presence has, in several instances, led to the discovery of valuable lodes, notably at Leadville, Colorado. Historical summary.-In New Mesico, Arizona, and Southern California, placer gold was mined by Mexicans and Spanish priests in the first half of the 19th century or earlier. With these exceptions history of placer mining in the Western States begins with Marshall's discovery of gold in northern California in 1848. During the next twenty years placers were found in all of the principal mining districts that are known today. The richer deposits were soon mined out but a relatively large production was maintained from the leaner deposits chiefly by hydraulic

Jan 1, 1933

By Francis P. Sinn

IN the zinc smelting industry the year 1947 seems to have been one of putting one's house in order rather than one of any material technical development or radical change in operating conditions. Labor generally has been in better supply but several plants report a scarcity of skilled workmen. Some plants continue to operate on the basis of a six-day week and will probably continue to do so until labor is more plentiful. Only one plant is known to have operated on a curtailed basis because of labor shortage, but here the difficulty was lack of proper housing facilities. Necessary materials and equipment for much-needed maintenance and modernization have been in short supply so these programs have often been delayed. Laborsaving devices of the "Payloader" type have been more generally used for handling materials. Slab zinc production was discontinued during the last months of the year at Danville, 111. and at Langeloth, Pa. Both of these plants used the Hegeler type of furnaces fired with producer gas. It is understood that the rolling mill and possibly the acid plant at Danville will continue to operate. At Langeloth acid will be produced from

Jan 1, 1948

By George W. Maynard

IN the course of an examination of some of the California hydraulie mines in November last, I visited the property of the Gold Run Ditch and Mining Company, near Dutch Flat, Placer County. This is one of the most important and extensively worked mines in the district. The gold occurs in the characteristic blue gravel, which averages 175 feet in thickness, the lower 40-60 feet being made tip of cement gravel, which resists the action of water, and can only be loosened by blasting. The specimen which I have the pleasure of laying before the members was presented to me by Mr. I. L. Gould, the intelligent superintendent of the mines, who informs me that he found it in the old river channel, about twelve feet above the bedrock. The flattened water-worn nugget of gold, about the size of a kidney-bean, is imbedded in blue cement gravel, around which quartz has crystallized. When found the projecting portion of the nugget was enveloped in quartz, the core of gravel and gold having only been discovered after breaking the lump of quartz. On the quartz there is a shell of cement. The specimen is a remarkable confirmation of the theory of the deposition of quartz from solution. DISCUSSION. DR. T. STERRY HUNT, in commenting upon this occurrence, remarked that it is in accordance with what we already know of the recency of some of the quartz of this region, and cited the microscopic

Jan 1, 1880

By E. J. Schmitz

This section was obtained last year during an examination of the iron-ore resources of the Rich Patch Mountain region and along Craig's creek valley. The geological members below the Oriskany and Lower Helderberg are exposed along the gap in a beautiful arch, while the higher formations appear in a more or less disturbed state on both sides of this arch, and are partly covered by dèbris. I have thought it of interest to the Institute to reproduce the drawing of this section at the gap which I made in my note-book at the time of my examination; those parts of the section, which lie at both sides of the arch, are only approximated. I give also a number of notes and measurements, referring to the Clinton formation and especially to the characteristics of the fossiliferous ore-seam opened in the various tunnels along the arch (see section). I. In Tunnel C: For the first 110 to 120 feet to second shute, we find the ore only here and there in small deposits, and interchanging with, or changing into, either a very siliceous limestone or a sandstone. About 10 feet beyond shute we have : Sandstone roof. Clay-slate, 211/2 inches Brown lean ore, 1 inch. Sandy clay, 3 to 31/4 inches. 1. Dark .brown ore, 3 inches. 2. Fossil-ore, changing into sandstone or very siliceous limestone, 2 inches. 3. Brown lean ore, 6 inches. Clay and slate below, 1 foot. 194 feet from entrance : Sandstone roof. Clay-slate, 4 inches. Clay 15 inches. Fossil-ore, 63 to 7 inches. Clay and ore, If inches. Lean brown ore, 2 inchea. Clay to bottom, 2 feet.

Jan 1, 1896

By Frederick Görannsen

McDuffie county, once a part of Columbia county, lies in the eastern part of central Georgia, about 20 miles west of the Savannah river, and bounded on the northtwest by Little river. Wrightsboro, now almost forgotten, was one of the principal towns of Georgia before the Revolutionary war, and much of the land hereafter described as belonging to one of the principal gold-bearing sections of the South had been taken up by the early agricultural settlers, and was already under cultivation. Indeed, some of the present mining companies can trace their chain of title back to the original grant of King George III., made in 1771. The first discovery of gold in Georgia, however, was not made until 1823, when two English miners, who had emigrated to this country and were traveling as peddlers through this section, discovered quartz, rich in gold, on what is now known as " the 40-acre lot," and owned by the Columbia Mining Go. These men had no money to buy the lands, and not being able to stake off a claim and begin work, as is the custom in other places, they were forced to seek the aid of the native farmers. In this we are told that they were for a long time unsuccessful; the farmers and land-owners not knowing or caring anything about gold mining. In 1826, Jeremiah Griffin, a wealthy farmer, became interested with them, and they did some prospecting and located several rich veins. Mr. Griffin soon became enthusiastic, and bought about three thousand acres of supposed gold-lands, lying along Little river.. This purchase was unfortunate for the mining industry, as it effectually shut out all other prospectors, and confined entirely to Mr. Griffin and his associates the mining development of the whole region. As a consequence, the ground was never covered, arid there are virgin lands in this section now, which offer to the prospector as

Jan 1, 1903