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By Paul T. Allsman

Recently the U.S. Bureau of Mines completed organizational changes that, for the first time since the beginning of World War 11,. re-emphasize mining research as an important part of its responsibilities. A progress report follows on the Bureau's improved program for mining research. During World War II the Bureau's mining research lapsed in favor of short-range, more urgent activities. Since the end of the war mining has grad- ually returned to an economy where reduced costs and increased efficiency are essential to a vigorous industry, and demand for improvement through expanded research is again pre-eminent. In recognizing this situation, the Bureau is again emphasizing mining technology and has reinstituted some of its earlier mining research activities. Recent research, however, follows a more scientific approach in solving mining problems because new technology, particularly new instrumentation, has developed rapidly during the past decade.

Jan 7, 1960

By J. Quigley

As the outcrop mines in the West developed into underground operations, systems of ground support were gradually evolved. In the early coal mines there was little need for support except near the dirt line in portals, where stone masonry was common. Where the top was shaley or broken, native pine props with light cross bars and legs furnished enough support even in Utah's 25-ft coal seams. As depth of workings increased. roofs and backs of the same general nature as those near the surface became more and more unstable and required more and more support. Some coal airways show this tendency very clearly. From the surface down the same type of roof shows deterioration which an experienced eye can translate into a measure of depth under surface rather than change in rock characteristics. Rock bolts, developed by various companies and by the U. S. Bureau of Mines, have become an effective substitute for timber in sections of some metal and nonmetal mines formerly requiring escessive timber support, and further use of war surplus landing mats, chain link fencing, and a new punched channel developed by one of the steel companies has enabled other mines to operate deposits where costs of timber and lack of clearance for timber support would have prohibited mining. The block caving mines have made extensive use of reinforced concrete underground to achieve similar ends under difficult conditions. Steel sets are standard in many Bureau of Reclamation projects, although these are usually covered in with concrete to make the permanent structures the Bureau's reclamation projects require. But the use of steel in mining operations is limited and has been confined principally to the iron ore mines of Michigan, Wisconsin, and Minnesota. Some mines have installed used rail as posts, caps, and crossbars, but a rail section is not suited for load carrying, and used rails are generally brittle. having a tendency to fail without warning when overloaded. European mines were the first to reach the size of worked out areas and depths of cover resulting in major roof problems. The Europeans resorted to pack walls and masonry walls, in conjunction with timber arched sets. rail arches, and combination timber and rail and steel arches. The give in these pack walls and wooden blocking was supplemented by a hinge in the center of the arch. This design is called an articulated arch Through various refinements of this principle of the support giving graduallv with the load. Toussaint-Heintzmann developed the yielding or sliding arches, in which yield is accomplished by friction in the overlapping joints of the arch. This type has gained widespread acceptance in the Ruhr and Lorraine Basin and is being manufactured by Bethlehem Steel for sale in this country. In North America the anthracite mines in Pennsylvania, followed by certain iron ore mines in upper Michigan and Canada, were the first to employ these arches to any extent. The practice was later adopted by Kennecott at Ruth, Nev., and by others. Despite high initial cost, the use of these arches is growing in many parts of the country because of their suitability in heavy ground. In its present form of manufacture the yield-able arch consists of open U-shaped rolled section with heavy beads on the edge. The open edge of the U is placed toward the wall. The section nests in another section of the same dimensions, and an arch can be built up from rolled radii and tangents of various weights and lengths. Sections are fastened together by U bolts and saddles. The lap on the joint varies from 12 to 24 in., and ordinarily the bolts are tightened with a 1-in. drive air wrench. The arches are spaced with channel struts held by J bolts and saddles. Sections can also be obtained that are composed of various combinations of radii and tangents and true circles. The joints can be placed to bear against anticipated loads and asymmetrical loads imposed by dipping strata. In the arches now being manufactured clearance widths up to 19 ft are obtainable in weights of sections from 9 to 30 lb per ft. The circular cross sections are available in the same weights ranging from 8 to 16 ft diam. At present most of the arches sold are supplied only in carload lots. It is hoped that demand will grow so that distributors can stock various weights and sections to give small operators a chance to try this new type of rock support under their own particular conditions. Several excellent papers have discussed the properties of various sections now manufactured, the dimensions of the sets obtainable, and their application under widely differing conditions. The present article will describe the methods and results of a special use of the arches at Kaiser Steel mine No. 3. Sunnyside, Utah. Problem at Mine No. 3 : In 1953 Kaiser Steel Corp. laid out Sunnyside mine No. 3 to recover coking coal left by the previous operator, Utah Fuel Co.. below workings that had been abandoned in 1928. Two seams had been worked, the upper and lower, separated by 30 to 42 ft of rock. Approximately 10 million tons of coal had been extracted from this area some 3000 ft down the itch from the outcrop to a 1500-ft depth of cover. The mine had been opened by slopes in both upper and lower seams. Sometime in the late 1920's the lower slope

Jan 1, 1960

By Robert W. Hunt

I have frequently stated that while the chemical composition of steel is important, yet even greater importance is connected with the mechanical and heat treatment of the metal. During the past year I encountered such a positive example of that fact that I deem it worth putting upon record. A prominent railway system divided an order for open-hearth steel rails between two steel works, both of which are under the control of the same corporation; giving to one about 18,000 tons, and to the other 7,500 tons of the same section and to be made under the same specifications. The rolling results obtained in the two mills varied so widely that a study of the figures is intensely interesting and serves to illustrate the advantages obtained by carefu1 ingot casting, and, quite as pertinently, the possible benefits of careful subsequent heating and rolling with moderate reductions in the rolling process. The smaller order was rolled complete in four installments during the same months that the larger order was being made in six separate installments; but, to permit of exact comparisons, the totals of the four installments (completing the order with the mill which I will call A) are given with the totals of the first four installments of the larger order, made by the mill designated as B. These rolling results are: Mill A. Mill B. Number of rollings,............................................ 4 4 Total number of rails rolled................................ 18,278 27,832 Percentage of rails cut to short lengths because of flaws near ends, etc......................................... 0.7 7.6 Percentage of rails made second quality for flaws, etc. 0.9 6.3 Percentage of rails scrapped for flaws, etc............... 0.6 4.5 Percentage of rails scrapped for failure at drop test... none 3.4 It should be stated that the figures given above cover all the reasons for putting the rails in the classes stated, Thus a part of the percentage of rails cut to short lengths may have been

Jan 1, 1914

By Robert E. Ennis

This somewhat misnomered "continuous" face section is, in most mines today, still far from perfect continuity. Achieving uninterrupted flow of coal from the mining machine to the outside has been a long sought for goal. Clearly, the largest problem to be solved in continuous mining today is one of increasing the cutting time of the miner. Full machine utilization can never be achieved with the new high capacity miners as long as their performance is tied to that of the shuttle car. A recent development has proven, however, that truly continuous mining and haulage is possible. The Bell & Zoller Coal Co. working with the Research and Development Department of Hewitt-Robins Inc. developed and perfected a new mining system which offers advantages in terms of increased productivity at reduced mining costs and enhances the safety of personnel at the face. This new system involves the use of two pieces of equipment that form an unbroken link between the mining machine and the mine belt haulage system. These pieces are a Mobile Bridge Conveyor and an Extensible Panel Conveyor.

Jan 4, 1965

By Gail Moulton

THE oilfields in Illinois are located principally along the LaSalle anticline in the southeastern part of the state. The oil produced comes most largely from beds of Pennsylvanian and Mississippian age, but there is an increasing important production from deeper horizons, as will be noted under new development. The oil is largely of paraffin base, and has an average specific gravity of about 35° Baume. The rank of Illinois as an oil producer has dropped from third since 1913, when its production was exceeded only by that of California and Oklahoma, to eighth in 1923. This has been the result of failure to find new pools of considerable size to offset the declining production of the old wells and of the greatly increased production of some of the other states. The noteworthy features of petroleum production in Illinois during 1924 are: the low rate of decline for the state as a whole; the smaller percentage of dry holes; and the larger average initial yield of the new wells.

Jan 3, 1925

By Gill Montgomery

The strong upward curve of fluorspar consumption continued through 1968, with domestic producers unable to furnish more than 30% of U.S. requirements. Stocks of all grades were quite short at all points during most of 1968. This resulted in price increases as both domestic and foreign producers sought to cover spiralling labor costs. Further increases are probable for 1969. All Illinois mines were closed by strikes in January and February. The strong trend in metallurgical imports reflects the increased use of fluorspar in steelmaking, as new oxygen process steel plants come into production. The growth of use of all fluorocarbon chemicals continues to require additional acid grade fluorspar, with military uses a major factor. Several new aluminum smelting facilities coming into production are adding to the aluminum fluoride needs, bringing further pressure upon the world supply of acid grade fluorspar. The world-wide consumption pressure on all grades of fluorspar is pushing prices up, and no end to the tight supply is in sight, even assuming that all the new projects cited here are finished on schedule.

Jan 3, 1969

PRESIDENT SAMUEL A TAYLOR, District 3 PITTSBURGH, PA PAST PRESIDENTS WILLIAM KELLY, District 5 IRON MOUNTAIN, MICH J V W. REYNDERS, District 0 NEW YORK, N Y FIRST VICE-PRESIDENT E DEGOLYER, NEW YORK, N Y TREASURER CHARLES F RAND. . . NEW YORK, N Y

Jan 1, 1923

By Gail Moulton

THE oilfields in Illinois are located principally along the LaSalle anti-cline in the southeastern part of the state. The oil produced comes most largely from beds of Pennsylvanian and Mississippian age, but there is an increasing important production from deeper horizons, as will be noted under new development. The oil is largely of paraffine base, and has an average specific gravity of about 35° Baume. The rank of Illinois as an oil producer has dropped from third since 1913, when its production was exceeded only by that of California and Oklahoma, to eighth in 1923. This has been the result of failure to find new pools of considerable size to offset the declining production of the old wells and of the greatly increased production of some of the other states. The noteworthy features of petroleum production in Illinois during 1924 are: the low rate of decline for the state as a whole; the smaller percentage of dry holes; and the larger average initial yield of the new wells.

Jan 3, 1925

By W. N. Poundstone, P. C. Thakur

Introduction Horizontal drilling in coal mines is a relatively new technology. The earliest recorded drilling in the United States was done in 1958 at the Humphrey mine of Consolidation Coal Co. for degasification of coal seams. Spindler and Poundstone experimented with vertical and horizontal holes for several years. They concluded in 1960 that horizontal drilling in advance of underground mining appeared to offer the most promising prospect (for degasification) but effective and extensive application would be dependent upon the ability to drill long holes, possibly 300 to 600 m, with reasonably precise directional control and within practical cost limits (Spindler and Poundstone, 1960). Mining Research Division of Conoco Inc., the parent company of Consolidation Coal Co., began a research program in the early 1970s to achieve the above objective. The technology needed to drill nearly 300 m in advance of working faces was developed by 1975 and experiments on advance degasification with such deep holes began in 1976. Preliminary results of this research have already been published (Thakur and Davis, 1977). To date nearly 4.5 km of horizontal holes have been drilled for advance degasification and earlier results were reconfirmed. In summary, these are: • The greatest impact of these boreholes was felt in the face area where methane concentrations were reduced to nearly 0.3% in course of two to three months from original values of nearly 0.95%. • The methane concentration in the section return reduced to 50% of its original value immediately after the boreholes were completed, indicating a capture ratio of 50%. • The total methane emission in the section (rib and face emission plus the borehole production) did not increase but rather gradually declined with time. • Initial production from 300 m deep boreholes in the Pittsburgh seam varied from 3 m3/min to 6 m3/min but then slowly declined as workings advanced inby of the drill site (well head) exposing a larger surface area parallel to the borehole. Encouraged by these results, it was decided to design a horizontal drilling system that would be mobile and compatible with other face equipment. A mobile horizontal drill can be divided into three subsystems: the drill rig, the drill bit guidance system, and borehole surveying instruments. The drill rig provides the thrust and torque necessary to drill 75- to 100-mm diam holes up to 600 m deep and contains the mud circulation and gas cuttings separation systems. The drill bit guidance system guides the bit up, down, left, or right as desired. Borehole surveying instruments measure the pitch, roll, and azimuth of the borehole assembly. Additionally, it also indicates the thickness of coal between the borehole and the roof or floor of the coal seam. Thus, it becomes a powerful tool for locating the presence of faults, clay veins, sand channels, and the thickness of coal seam in advance of mining. In recent years, many other potential uses of horizontal boreholes have come to light, such as in situ gasification, longwall blasting, improved auger mining, and oil and gas production from shallow deposits. The purpose of this paper is to describe the hardware and procedure for drilling deep horizontal holes. The Drilling Rig [Figures 1 and 2] show the two components of the mobile drilling rig: the drill unit and the auxiliary unit. The equipment (except for the chassis) was designed by Conoco Inc. and fabricated by J. H. Fletcher and Co. of Huntington, WV. The drill unit. It is mounted on a four-wheel drive chassis driven by two Staffa hydraulic motors with chains. The tires are 369 X 457 mm in size and provide a ground clearance of 305 mm. The prime mover is a 30-kw explosion-proof electric motor which is used only for tramming. Once the unit is Crammed to the drill site, electric power is disconnected and hydraulic power from the auxiliary unit is turned on. Four floor jacks are used to level the machine and raise the drill head to the desired level. Two 5-t telescopic hydraulic props, one on each side, anchor the drill unit to the roof. The drill unit houses the feed carriage, the drilling console, 300 m of 3-m-long NQ, drill rods, and the electric cable reel for instruments. The feed carriage is mounted more or less centrally, has a feed of 3.3 m, and can swing laterally by ± 17°. It can also sump forward by 1.2 m. The drill head has a "through" chuck such that drill pipes can be fed from the side or back end. General specifications of the feed carriage are: [ ] The auxiliary unit. The chassis for the auxiliary unit is identical to the drill unit but the prime movers are two 30-kW explosion proof electric motors. It is equipped with a methane detector- activated switch so that power will be cut off at a preset methane concentration in the air. No anchoring props are needed for this unit. The auxiliary unit houses the hydraulic power pack, the water (mud) circulating pump, control boxes for electric motors, a trailing cable spool, and a steel tank which serves for water storage and closed-loop separation of drill cuttings and gas.

Jan 1, 1981

By C. S. Herzig

Some time ago, in Mexico, our signal-bells in a 700-foot shaft caused us considerable annoyance by continually getting out of order, each time so delaying our hoisting operations that we naturally desired to remedy this evil. There were two mays open: either to patch up the old bell, which was of the ordinary pattern, every time it failed to work, or else to devise some new arrangement.. On consultation with our foreman we designed a signal-device which, during the number of months I watched its operation, worked satisfactorily, without once getting out of order. We sought to produce a simple device, in which no greater pull on the lever would be necessary from one level than from another; to counterbalance independently the weight of the pendant bell-rope, so that there would be no direct weight on the working-parts of the bell itself, and likewise to arrange it so as to necessitate only a light pull on the lever in signaling; and, finally, to make some sort of trip-arrangement, so that whenever the signaling-lever underground passed through a certain arc the signal would be given in the engine-room. By this means we wished to obviate the ill effects of sudden heavy pulls and rough usage in general, such as all signaling

Jan 1, 1901

By Roshan B. Bhappu

Selenium is found most frequently as an accessory mineral in the ores of lead, copper, and nickel, and is recoverable as a byproduct in the treatment of many of the ores of these metals. The geographic distribution of the selenium industry closely follows that of electrolytic copper, with the United States and Canada producing approximately 75% of the total output of the non-communist world. This situation is problem number one for selenium-its dependence upon the electrolytic refining of copper- for this byproduct source is not sufficiently flexible to permit a normal supply-demand balance. Furthermore, selenium has become a strategic material in short supply. Thus, new sources are being sought by both government and private interests. Although considerable attention has been given to this effort during the last few years, hardly any research has been published concerning the recovery of small amounts of selenium present in low-grade deposits. In such ores the metal occurs as native selenium or as selenides of iron, copper, silver, lead, and bismuth. In recent years, some native selenium (in both the gray and red form) and selenides, especially iron selenide (ferroselite), reportedly have been found in the sandstones of the Morrison formation near Grants. New Mexico. Similar occurrences have been reported in the Hagan coal basin, in Sandoval County, New Mexico. Samples from New Mexico ores have contained from a trace amount to as high as 0.425% Se. Some of the samples from uranium mines in the Grants area represent mixed ore and mill feed fur uranium reduction plants. In such cases, the selenium usually is reported as an impurity and is lost in the tailings. At present, no attempt is made to recover this waste metal.

Jan 8, 1962

OFFICERS OF THE WOMAN'S AUXILIARY AIME President-Mrs Robert D Coombs, 375 Paramus Road, Paramus, N J First Vice-President-Mrs W McG Peirce, Troy Court 73 F, New England Avenue, Sum¬mit, N J Second Vice-President-Mrs Andrew E Beer, Richardson Avenue, Sea Cliff, Long Island, N Y Third Vice-President-Mrs Ira T Hook, 494 Norton Parkway, New Haven, Conn Fourth Vice-President-Mrs John R Kenney, 427 W Wrightwood Avenue, Chicago 14, Ill Fifth Vice-President-Mrs Alfonso Ballon, Montero Rosas 115, Barranco, Lima, Peru Recording Secretary-Mrs Arnold H Miller, 601 West 115th St, New York 25, N Y Assistant Recording Secretary-Mrs R J Mechin, 66 East 79th Street, New York 21, N Y Corresponding Secretary-Mrs Theodore Nagel, 76 Remsen St, Brooklyn 1, N Y Treasurer-Mrs Robert W Rowen, 116 East 68th St, New York 21, N Y Assistant Treasurer-Mrs Samuel H Dolbear, 11 Broadway, New York 4, N Y Assistant Treasurer-Mrs H A Kursell, 12 Murray Hill Road, Scarsdale, N Y

Jan 1, 1956

By Charles A. Kelliher

In November of 1957, the Aliquippa Works started operation of the third basic oxygen furnace shop in North America. This high speed basic steelmaking method provided a very economical increase in capacity at the Works. The success of these two (2) 81-ton furnaces led to the construction of a second B.O.F. shop, producing heats of 230 tons at J&L's Cleveland Works in 1962. The experience gained operating both shops provided the background for the design of the new steelmaking complex at the Aliquippa Works. This new complex consists of a three (3) furnace shop with two (2) furnaces blowing alternately producing heats ranging from 120 to 207 tons. This variation in heat size is predicated on the requirement that approximately 20% of the shop production will be used to supply steel to a six (6) strand casting machine, producing 4' through 7" billets. The new B.O.F. shop has replaced all other steelmaking units including the #1 Shop, where operations were discontinued in September of 1968. With the advent of the strand casting facilities in September of 1969, many of the standard shop practices had to be changed to compensate for higher tap temperatures, longer handling times, and reduced ladle availability. The subsequent changes in these areas led to the evolution of the strand cast ladle practice which is described in this paper.

Jan 1, 1972

By Lester Uren

WITH the depletion of our older, and relatively shallow, oilfields and the necessity for securing new production from deeper horizons, much attention is being given to the improvement of oil-well pumps in order that they may function satisfactorily under the more difficult conditions imposed by increased depth. Until recently, practically all of the world's petroleum was secured from wells less than 3000 ft. deep, whereas horizons are now being explored to depths of from 5000 to 7000 ft. in some of the more prolific fields, and it seems probable that the greater part of the future supply must come from depths in excess of 3000 ft. While much of the early production in a new field is obtained by natural-flow methods, when the stimulus of high gas pressure fails, recourse must be had to some method of pumping. The perfection of a pump capable of economically and efficiently lifting oil from depths ranging from 3000 to 7000 ft. is therefore a matter of prime importance to the oil-producing industry. This paper is offered as an estimate of the present state of development of the oil-well plunger pump and as a review of the general principles involved in its operation in deep-well pumping. A design for a new type of oil-well pump embodying several novel features, is also described.

Jan 9, 1925

By Joseph Hyde Pratt, Douglas B. Sterrett

Monazite is one of the minerals which, for a long time, was considered somewhat rare in its occurrence, but, upon a commercial demand arising for it, prospectors and engineers soon located large deposits of it in the Carolinas arid Brazil, and the supply has always been able to meet the demand. During 1908 further sources of supply of monazite have been discovered and developed in Idaho. North and South Carolina, however, are the only States that have thus far put any monazite on the market. Monazite is essentially an anhydrous phosphate of the rare-earth metals,ceriunl, lanthanum, and didymium,(Ce,La,Di)PO,. There is nearly always present a varying but small percentage of thoria, Tho2, and silicic acid, SiO2,, which are very probably united in the form of a thorium silicate, ThSiO4. Some mona-zites contain but a fraction of a per cent. of thoria, while others have been recorded that showed the presence of from 18 to 32 per cent.; but the majority contain from 3 to 9 per cent. of this oxide. It is the presence of the thorium oxide that gives the monazite its commercial value. The analysis occasionally shows also the presence of other constituents, as the yttrium and erbium oxides, zirconia, alumina, magnesia, lime, iron oxides, manganese oxide, and titanium oxide. Monazite is light-yellow, honey-yellow, reddish-, brownish-, or greenish-yellop. in color, with a resinous to vitreous luster, and is translucent to subtransparent. It is brittle, with a con-choidal to uneven fracture, and is from 5 to 5.5 in hardness, and from 4.64 to 5.3 in specific gravity. It crystallizes in the monoclinic system, and some crystals have been observed that werc 6 in. in length. The more perfect crystals are,-however,

Jan 1, 1910

By Nicholas J. Grant, Irmgard Rump, Bill C. Giessen

The system W-Hf was determined by use of metal -lographic and X-ray methods. The only interrnetal-lie phase W2Hf melts peritectically at 2650° ± 50°C. A eutectic between W2Hf and ß-Hf solid solution exists at 78 at. pct Hf arul 1930º ± 10°C. The addition of tungsten loulers the hafnium transfornzation; there is a eutectoid at 93 at. pct Hf and 1560°C. The solubility limits of the terminal solid solutions were determined. At the beginning of this investigation, the system had not been elaborated; only crystallographic work had been done to determine the structure of the occurring intermetallic compound W2Hf, and a certain analogy to the system W-Zr was to be expected. Special emphasis was placed in this program on the Hf-rich part of the diagram. Following the completion of our experiments, a phase diagram was suggested by Braun and RUdY.1 EXPERIMENTAL METHODS The investigation utilized tungsten powder supplied by the General Electric Co. with a purity of about 99.9 pct and hafnium crystal bar of about 97.7 pct purity, 2.3 pct Zr, supplied by Foote Mineral Co. Typical analyses are given in Table I. The procedures followed were identical with the ones described for the Re-Nb diagram.' Tungsten powder was compacted at 16,000 psi and the necessary amount of hafnium was added in the form of small pieces cut from the crystal bar, with a reasonable excess of tungsten powder to make up for powder losses on melting. High hafnium or tungsten melts were prepared from premelted tungsten and hafnium or by employing master alloys. The melting was done in a Heraeus arc-furnace under argon. Melting and remelting up to 8 times resulted in fairly homogeneous alloys. No weight

Jan 1, 1962

By T. H. Janes

NATURAL abrasives of some type are found in all countries of the world. In order of their hardness the principal natural abrasives are diamond, corundum, emery, and garnet, which are termed high grade, and the various forms of silica, including pumice, pumicite, ground feldspar, china clay and, most important, sandstone. The properties qualifying materials for use as abrasives are hardness, toughness, grain shape and size, character of fracture, and purity or uniformity. For manufacture of bonded grain abrasives such as grinding wheels, the stability of the abrasive and its bonding characteristics are also important. No single property is paramount for all uses. Extreme hardness and toughness are needed for some applications, as in diamonds for drill bits, while for other purposes the capacity of the abrasive to break down slowly under use and to develop fresh cutting edges is of greatest importance, as with garnet for sandpaper. In dentifrices, soaps, and metal polishes, of course, hardness and toughness are objectionable. First among the natural abrasives, industrial diamonds are essentially of three types: l—bort, which includes off-color, flawed, or broken fragments unsuitable for gems; 2—carbonado, or black diamond, a very hard and extremely tough aggregate of very small diamond crystals; and 3—ballas, a very hard, tough globular mass of diamond crystals radiating from a common center. Bort comes from all diamond-producing centers, carbonados only from Brazil, and ballas chiefly from Brazil, although a few of this last group come from South Africa. By far the largest producer of industrial diamonds is the Belgian Congo; the Gold Coast, Angola, the Union of South Africa, and Sierra Leone supply most of the remainder. There is no production in Canada, which imports $6 to $9 million worth of industrial diamonds annually. Industrial diamonds find innumerable uses in modern industry. They are used for diamond drill bits for the mining industry; in diamond dies for wire drawing; in diamond-tipped tools for truing abrasive wheels and for turning and boring hard rubber, fibers, and plastics; and in diamond-toothed saws for sawing stone, glass, and metals. High-speed tool steels, cemented carbides, and other hard, dense alloys can be cut, sharpened, or shaped efficiently only with diamond-tipped tools and diamond grinding wheels. .. Second only to the diamond in hardness is corundum, an impure form of the ruby and sapphire gems consisting of alumina and oxygen (Al²O³) with impurities such as silica and ferric oxide. Corundum generally crystallizes from magmas rich in alumina and deficient in silica, as in the nepheline syenites of eastern Ontario. Grain corundum is used in the manufacture of grinding wheels; very coarse grain is used in snagging wheels. Both types of wheels are employed in the metal trades, where the hardness of corundum, coupled with its characteristic fracturing into sharp cutting edges, makes it an ideal cutting tool. The finest corundum (flour grades) is used for fine grinding of glass and high-precision lenses. From 1900 to 1921 Canada was the world's leading producer of corundum. Following this period the deposits located in northern Transvaal of the Union of South Africa supplied more and more of the world's requirements, and since 1940 South Africa has provided almost the entire output, which has ranged between 2500 to 7000 tons a year during the last decade. Minor amounts have also been produced in Mozambique, India, and Nyassaland. Opportunities for Mining Corundum Corundum deposits in southeastern Ontario are of three types, which may be described as follows: 1—Scattered, irregularly-shaped deposits of coarse-grained corundum which could be mined by means of small pits. About 10 groups of such deposits are known. Although the tonnage of individual deposits of this type is not great, it has been estimated that several years' ore supply is available for a small tonnage operation. Deposits average about 9 pct corundum. 2—Large irregular deposits of coarse-grained corundum which would require mining by adit with possibly a scavenger operation on the remains of former surface deposits. The Craigmont deposit of this type produced about 20,000 tons of corundum concentrate during operations between 1900 and 1913. Most of the readily available surface ore was removed by operators during that time. Reserves of ore above road level have been estimated to average 7 pct corundum, but none of the so-called reserves have been blocked out, or even indicated, by diamond drilling. From 1944 to 1946, 2025 tons of

Jan 1, 1955

By Howard A. Smith

Of late considerable experimental and theoretical interest has been shown in the rates of transformation from a single phase, usually a supercooled solid solution, into one or more phases. Such reactions may involve both diffusion and transformation of the major constituent, as in iron alloys, or it may simply involve diffusion, as in superstructure formation and in age-hardening systems. Most of the work has been confined to ferrous alloy1-9† although two investigations have been made on copper alloys10*". That such work may be of considerable practical importance has been demonstrated by Bain12, by the workers at the Kaiser Wilhelm Institut fur Eisen-for~chung'13, 14, and by the everyday use of precipitation and age-hardening principles15. Experiments in this country have generally followed Davenport and Bain's technique of rapid supercooling followed by isothermal treatment. In Germany16, 17 the work has been extended to the study of the influence of accurately controlled and measured rates of cooling. The work on steel indicates that there are two subcritical temperature ranges where reaction starts sooner after quenching and proceeds at a more rapid rate than at other temperatures. At suberitical temperatures above Ar" (temperature of martensite formation) where reaction is dependent upon atomic migration there is a period of time of which the length depends upon the alloy content and the temperature, before which no reaction has been detected. Davenport and Bain' find that different sorts of atoms in solid solution in gamma iron affect the length of this " prereaction" period differently, manganese probably being the most effective in lengthening it. It is very difficult to believe that nothing occurs within these "prereaction" regions, for if this were so there is no reason why any reaction at all should be observed. In the light of experimental facts and theoretical considerations it is certainly

Jan 1, 1935

By Howard A. Smith

Of late considerable experimental and theoretical interest has been shown in the rates of transformation from a single phase, usually a supercooled solid solution, into one or more phases. Such reactions may involve both diffusion and transformation of the major constituent, as in iron alloys, or it may simply involve diffusion, as in superstructure formation and in age-hardening systems. Most of the work has been confined to ferrous alloy1-9† although two investigations have been made on copper alloys10*". That such work may be of considerable practical importance has been demonstrated by Bain12, by the workers at the Kaiser Wilhelm Institut fur Eisen-for~chung'13, 14, and by the everyday use of precipitation and age-hardening principles15. Experiments in this country have generally followed Davenport and Bain's technique of rapid supercooling followed by isothermal treatment. In Germany16, 17 the work has been extended to the study of the influence of accurately controlled and measured rates of cooling. The work on steel indicates that there are two subcritical temperature ranges where reaction starts sooner after quenching and proceeds at a more rapid rate than at other temperatures. At suberitical temperatures above Ar" (temperature of martensite formation) where reaction is dependent upon atomic migration there is a period of time of which the length depends upon the alloy content and the temperature, before which no reaction has been detected. Davenport and Bain' find that different sorts of atoms in solid solution in gamma iron affect the length of this " prereaction" period differently, manganese probably being the most effective in lengthening it. It is very difficult to believe that nothing occurs within these "prereaction" regions, for if this were so there is no reason why any reaction at all should be observed. In the light of experimental facts and theoretical considerations it is certainly

Jan 1, 1935

By John L. Schroder

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

Jan 1, 1981