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By E. J. Hammer

Crushing and grinding of gypsum demands con- trolled processing to a fineness suitable for further treatment of the mineral into end products, and into various sizes of material which are themselves saleable products. The majority of gypsum tonnage ultimately ends up in stucco for wallboard. Therefore, mineral reduction is normally designed toward this end, but it is done in a manner that permits drawing off intermediate products to meet various customer requirements. This forces companies into compromises at times in equipment installations. Normally, 5 to 6 different sizes intermediate to the end product are marketed and these are generally the fineness of material to be used as stucco for wallboard. These sizes are produced by controlled crushing, grinding and sizing. How Ore Characteristics Guide Processing First, gypsum as a mineral (CaS0;2H,O) is number two on the Mohs scale two of hardness; only talc is softer, Despite being soft, gypsum is tough, a factor which is of critical importance when developing equipment specifications. In addition, of the increasing volumes of rock handled, the associated and included impurities such as anhydrite, silica or lime- stones are found to be relatively abrasive.

Jan 1, 1970

By V. Niemitz

Approximately 30 miles east of Chicago on the southern shores of Lake Michigan stands Bethlehem Steels newest fully integrated steelmaking facility-the billion dollar Burns Harbor plant. The first phase of what will ultimately be the most completely integrated and flexible materials handling system for a steel mill in the western hemisphere is now complete.

Jan 1, 1970

By R. R. French

Investigations were conducted by the lndiana Geological Survey for some dry methods of bene-ficiating low-grade gypsum ore. Seventy-two batch and continuous flow tests were performed with a roller mill, rod mill, pebble mill, electronic color sorter, electrostatic separator, and an air separator. Approximately 650 size analyses and 550 chemical analyses were performed during the investigation. Batch samples were tested by the Survey, and most of the continuous flow tests were handled by com-mercial laboratories. INTRODUCTION Although many companies producing gypsum have been interested in dry beneficiation, very little information has been published in the past. One of the most comprehensive investigations was reported by the Canadian Department of Mines.5 Other reports of interest have been published by the Canadian Department of Mines,' the South Australian Department of Mines,2 and the U.S. Bureau of Mines.3 Some beneficiating practices, such as hand picking, selective mining, crushing and screening, milling, and air classifying, were already in use in the Canadian industry prior to MacPherson's investigations.5 MacPherson examined the effect of tabling, air separation, screening, flotation, electrostatic separation, calcining, washing, and various types of milling, in his efforts to eliminate dolomite, limestone, and small amounts of silica and clay from the gypsum ore. RAW MATERIAL Gypsum and anhydrite occur within the lower part of the St. Louis Limestone (Mississippian) in southwestern Indiana. Gypsum in single beds 10 or more ft thick occur at Shoals, Martin County; near Freedom, Owen County; near Bloomfield, Greene County; and in the Devonian strata of LaPorte County. Only the Shoals deposit has been exploited commercially. The western edge of the Shoals deposit is contaminated by a continuous bed of shale, about 1 1/2 to 2 ft thick, near the top of the evaporite and by thin continuous strata or irregular masses of carbonate rock. The low-grade material used in these investigations was obtained from the waste pile of the National Gypsum Co.'s plant at Shoals. The waste ore averaged about 67.4% gypsum and was contaminated by various amounts of shale, dolomite, and limestone. All the material had been previously crushed and screened to minus 1 1/4 to plus 3/8 in. X-ray analyses of powdered, sedimentated, gly-colated, and heat-treated samples of the shale showed that it was composed of slightly structurally disordered illite, Fe-rich chlorite, and very finegrained disseminated silt. The clays and silt were partly cemented with carbonate material. Light-gray argillaceous limestone and gray or brown porous dolomite made up most of the carbonate rock contamination. Crushing Characteristics: The rate unweathered gypsum, carbonate rock, and shale reduce in size was determined by crushing handpicked samples in a rod mill and screening at minus 100 mesh (.0059 in.). Fig. 1 graphically represents the data. These data indicate that carbonate rock should be relatively easy to separate from gypsum, but that shale should be difficult to separate from gypsum by differential crushing. Controlled Samples: Eight rod mill tests of hand-picked samples of mixed gypsum and shale and mixed gypsum and carbonate rock were made. Sample weight and crushing weight were standardized, but the scalping screen size was varied from 3 to 10 mesh (.265 to .0787 in.) in order to obtain the optimum purity and recovery. The data obtained from the tests (see Table I) illustrate that the relatively hard carbonate rock allows appreciable beneficiation (13.6 to 18%), but the low strength gypsum and shale allows only minimal separation (3.1 to 7.5%).* Semi control led Samples: During the investigation considerable slaking of the shale was noted when the ore was subjected to alternate wetting and drying. As demonstrated in laboratory tests, as much as 76% shale can be removed by two cycles of wetting and drying in a 48-hour period with subsequent screening at .265 in. Five ore samples, stockpiled and weathered, were screened, rod-mill crushed and rescreened at .157 or .187 in. with excellent results (Table 11).

Jan 1, 1967

Jan 1, 1897

By ANTON GRAY

In considering the possibilities and costs of discovering minerals by exploration. mineral occurrences may be classified roughly according to the size of the target they offer to the various methods that have been used to search them out. This classification is advantageous because the methods of search which might be expected to give results in one case may be totally inapplicable in others. Mineral deposits for the most part have been found in groups, or districts, in which the individual deposits occur under the same general geological conditions and usually contain more or less the same metals. There are, also, what are apparently isolated de- posits, although if the truth were fully known many of these probably would not be isolated. These districts, such as the Belgian Congo copper fields, the California Mother Lode, and the Linares lead district of Spain, form the first division of my classification. The second division is formed of the individual deposits of these districts, for example, Kambove mine in the Congo, the Kennedy-Argonaut vein in California, and the Cruz vein at Linares. The third division consists of the separate ore bodies that make up the deposits

Jan 1, 1949

By Tell Ertl

An annual invitational address by an outstanding man in mining, geology, or geophysics who has contributed significantly to the progress of technology in these fields. IN 1954, the first year the award was conferred, Fred Searles, Jr., remarked, "The earlier years are the easiest." In this, the second year, it was easy to choose the outstanding mining engineer. Our conferee this year has been destined to mine. He comes from pioneer stock, and though a son of the American Revolution he is most proud that all four of his grandparents came to the Jordan River Valley of Utah the "first summer," which all Utahns will recognize as 1847. At the time of discovery of high-grade ore in Bingham, his grandfather, Archibald Gardner, had a crew of men getting out saw timber in the area. The first claim staked in Bingham Canyon was named the Jordan, and Bishop Gardner was the colocator of the claim as well as the man to record it. E. D. Gardner was born in West Jordan, Utah, in view of Little Cottonwood Canyon, the site of the Emma Mine. Park City in the Wasatch Mountains a few dozen miles to the east, and Tintic, not much further to the south, were developing their vast ore-bodies throughout his youth. As a boy he was near the present Midvale metallurgical area and could see the Lark and Bingham Canyon mine dumps and imagine the mining activities at Tooele, Ophir, and Mercur just over the nearby Oquirrh Range. He was 11 years old when the first car of copper ore was shipped from Bingham Canyon. It was not surprising that he attended the University of Utah and graduated with an engineer of mines degree. Five years with the Utah Apex in Bingham Canyon as chief engineer and assistant superintendent completed his training for the 44 years of unselfish and lightly rewarded service he was to give the mining industry as a Government engineer. All of us in mining are familiar with the great work he carried on and directed during the genera- tion he supervised the Southwest Experimental Station at Tucson. He has written scores of papers and books. His observations and experiments on drilling and blasting have led to the important improvements in this field during the past quarter century. Whereas those of us who consider ourselves widely informed about underground metal mining methods make hasty trips through a half dozen or dozen mines a year, our conferee has visited them all—not only the metal mines, but also coal and hundreds of nonmetallic mines, in the United States, Canada, Latin America, and overseas. His keen observations and analytical mind have resulted in an encyclopedic knowledge of mining and mines. His improvements in mining technology have been steady and predictable. His elucidation of mining problems to the many young engineers that have come under his guidance have made them grow strong and useful to his industry. When he chooses to stop, his influence will continue to expand and prosper because of the inspiration and dedication he instilled in so many of us. The profits from his ideas have been distributed throughout the mining industry. He has remained a technical man who felt that he could serve the mining industry best as a Government engineer. But he is the staunchest advocate of the belief that the public should gain from his work through private industry. This is not the first recognition E. D. Gardner has received. The Department of the Interior awarded him the coveted Medal for Distinguished Service in October 1949, and he received the Engineering & Mining Journal's Salute in March 1951. His friends who are presenting him the Daniel C. Jackling Award today know this great mining engineer simply as "Ed" Gardner.

Jan 1, 1956

EXECUTIVE COMMITTEES OF LOCAL SECTIONS New York L. W. FRANCIS, Chairman, WILLARD S. MORSE, Vice-Chairman. THOMAS -T. READ, Secretary, Woolworth Bldg., New York: N. Y. P. A. MOSMAN, Treasurer. LOUIS D: HUNTOON. Boston HENRY L. SMYTH, Chairman. ALFRED C. LANE, Vice-Chairman. AUGUSTUS H. EUSTIS, Secretary-Treasurer, 131 State St., Boston, Mass. TIMOTHY W. SPRAGUE, HENRY A. WENTWORTH. Columbia F. A. THOMSON, Chairman. GEORGE W. RODDEWIG, Vice-Chairman. LYNDON K. ARMSTRONG, Secretary-Treasurer, P. O. Drawer 2154, Spokane, Wash. R. S. McCAFFERY, S. H. RICHARDSON.

Jan 10, 1914

By Robert T. Gdagher, Allison Butts

EDUCATIONAL trends as reflected in curricular changes are of interest and importance in engineering educa¬tion both as matters of record and as considerations for the future. The data on which the evidence of this report is based were obtained by sending questionnaires to all schools in the United States granting the undergraduate degree in mining engineering, metallurgy, or metallurgical engineering. The questionnaire had two parts, one inquiring as to the general nature of revisions made or planned, and the other asking for information on specific courses added to or dropped from the curriculum, or given more or less time than formerly. The frequency with which curricular changes are made, even in normal times, is notable. Although it was expected that the period since 1939-40 would show numerous revisions, it was somewhat surprising to find that of 62 mining or metallurgical curricula in existence in 1939-40 and reported in the present survey, 58 had been revised or are shortly to be revised, 52 having already been changed during this period. Moreover, approximately half of the mining schools that have already revised their curricula, and probably a similar proportion of the metallurgical schools, are about to make further important changes.

Jan 1, 1948

By John L. Miles

John L. Miles (Arthur D. Little, 1nc.)—Pollack and orris" have reported measurements on electron tunneling through A1-A12O3-A1 sandwiches in which the oxide was formed by gaseous oxidation in a glow discharge. From these measurements they deduced the asymmetry of the barrier and, since this is small, conclude that the mechanism suggested by Mott19 for the growth of oxide in thin A12O3 films is inapplicable. In earlier papers20 Pollack and Morris report similar work for oxide films grown thermally. In this case they find a greater asymmetry and conclude that the Mott mechanism is valid. I would like to point out that both these conclusions are quite unjustified. Mott suggests that the growth of the oxide film on aluminum results from the passage of ions through the already present film of oxide under the action of an electric field. This field results from a constant voltage which is in effect a contact potential between metal on one side of the barrier and adsorbed oxygen ions on the other side of the barrier. The theory does not require that the oxide grown is nonuniform either in stoichiometry or structure. It does however specifically assume that the partial layer of ionized oxygen on the surface remains adsorbed on the surface of the growing oxide. In other words, the so-called "built-in field" remains in the oxide only as long as the ionized oxygen is present. When a counter electrode of aluminum is deposited on the oxide, it will react with the adsorbed oxygen on the surface of the oxide, thus forming a small additional amount of oxide. It is clear, then, that there is no requirement in the Mott theory of oxide growth which would necessitate tunneling currents through an Al-A1203-A1 sample to be different when the polarity is reversed. Neither does the theory eliminate the possibility that some additional mechanism could cause the tunneling barrier to be asymmetric and hence tunneling currents to be a function of polarity in such a sandwich. Thus these tunneling-currents measurements are not germane to the question of whether the Mott mechanism is the true method of growth of aluminum oxide films. In fact, it is not surprising that there should be a difference between the oxide properties at the two interfaces (with resulting asymmetry in the tunneling barrier) since the growth conditions and growth rates must have been quite different at these two positions. S. R. Pollack and C. E. Morris (authors' reply)— The point raised by Miles above is one has caused some confusion in the past. The following is an attempt to clarify this point. The built-in field which is responsible for the growth of the thermal oxide at low temperatures arises, according to Mott, because of the passage of electrons from the Fermi surface of the oxidizing metal to surface states introduced by the adsorbed oxygen. It is assumed that the energy of these surface states lies below the Fermi energy of the metal. Electrons therefore continue to flow from the metal to the surface until the built-in electric field raises the potential energy of the surface states to the value of the Fermi energy in the metal, at which time equilibrium is obtained between the surface states and the metal. That is in equilibrium as many excess electrons pass from the metal to the surface per unit time as vice versa. The surface of the oxide prior to deposition of a metallic counterelectrode can then be pictured as follows. The Fermi energy lies in the energy gap of the oxide and is essentially pinned at the energy of the oxygen surface states. The vacuum work function of the oxide is then given by the sum of the electron affinity of the oxide (i.e., the difference in energy between the vacuum and the conduction-band minimum) plus the energy difference between the conduction-band minimum and the Fermi energy. The deposition of a metal onto the surface of the oxide can result in a transfer of electrons across the extremely thin oxide only if there is a contact potential difference between the deposited metal and the parent metal or oxide. That is if the vacuum work function of the deposited metal differs from that of the parent metal, then charge can be redistributed across the oxide in order to equilibriate the Fermi energy across the structure. (It should be

Jan 1, 1965

(Members are urged to send in for this column any notes of interest concerning themselves or their fellow-members.) Members and guests who registered at Institute headquarters during .the period Jan. 10 to Feb. 10, 1915: N. H. Emmons, 2d, Dover, Mass. R. 0. Hocking, Redruth, England. Paul W. Gaebelein, Cornucopia, Ore. G. H. Carnahan, New York, N. Y. H. D. Kinney, Easton, Pa. W. A. Wilson, Salt Lake City, Utah. W. D. McDougall, New York, N. Y. H. V. Winchell, Minneapolis, Minn. Kirby Thomas, New York, N. Y. Mrs. H. V. Winchell, Minneapolis, Minn. V. T. Lawshe, Newark, N. J. Keijiro Nishio, Tokyo, Japan. Henry S. Stebbins, who has been connected with the firm of Oglebay, Norton & Co., Cleveland, since 1892, has resigned to accept a position with M. A. Hanna & Co. of the same city. E. L. Newhouse has been chosen First Vice-President of the American Smelting & Refining Co. in place of the late Barton Sewell.

Jan 3, 1915

By Frank Firmstone

In April, 1873, No. 2 furnace at the Glendon Iron Works being out of blast, it was decided to alter it from an open to a closed top. The three side flues, through which a part of the gas was formerly taken off, were 15 feet below the top, and as, for various reasons, it was not convenient to cut new flues through the brickwork at the top, as is commonly done with closed-top furnaces, a modification of Coingt's charger was employed. This apparatus, as figured by De Vathaire,* consists of a cup or hopper, like that used with the cup and cone, and a central pipe for taking off the gas, which descends some distance into the furnace, and has a projection around it forming a seat for a ring of a triangular cross-section, which closes the opening between the cup and the central gas-pipe. The charge is put into the cup, and by lowering the ring, is thrown into the furnace, a part going outside of the ring toward the walls, and a part through the inside toward the gas-pipe. In this form the apparatus was not applicable, for: 1st. With a gas-pipe three feet in diameter, in a top eight feet in diameter, the openings left by lowering the ring would not be large enough to let lump coal pass through. 2d. For the charger to shut tight, the ring must bear equally against the projection made for it on the gas-pipe, and against the edge of the cup. This would not be difficult to effect when the apparatus is first put up, but a comparatively small change in the relative position of the parts, such as is almost certain to occur from expansion, would cause the ring to touch the pipe or the cup, whichever happened to be the lower, first, and leave a leak between it (the ring) and the other. In the plan adopted (Figs. 5 and 6, Plate I), the central opening in the ring is closed by the bottom of the gas-pipe, whereby more room is left for the passage of the stock when the charger is open, than if the pipe descended into the furnace; and the pipe, instead of being rigidly supported, rests on the ring, when the charger is closed, and follows it for two or three inches as it opens, until stopped by the counter-balance lever C. When the ring is raised to close the furnace top, it comes in contact first with the bottom edge of the gas-pipe, then both are raised together, until stopped by the ring touching the edge of the cup. In this way a good joint is made at both places.

By D. S. Flett, A. W. Fletcher

Equilibrium studies on the extraction of nickel and cobalt with kerosine solutions of naphthenic acid have shown that an exchange extraction reaction occurs at pH 5.5. The nickel/cobalt separation factor is constant at 1.8 for constant total metal molarity and varying nickel/cobalt ratios. The separation factor decreases with increasing total metal molarity in the organic phase beyond 0.2 M and also decreases with increasing temperature. From the equilibrium data, it has been possible to derive a mathematical model for the separation of nickel from cobalt by exchange extraction in multistage systems. Experimental data from a continuously operated multistage mixer/settler apparatus has shown a reasonable correspondence with computer-calculated data. The effective separation of nickel and cobalt in sulfate solution remains a problem in hydrometallurgy and the hope that this would be solved by solvent extraction has not yet been fulfilled. With chloride solutions, advantage may be taken of the ability of cobalt to form anionic complexes with the chloride ion. It can then be readily separated from nickel, which does not form stable chloro complexes, by extraction with a suitable long chain amine. However, in hydro metallurgical operations, sulfate solutions are generally obtained in which no extractable anionic species are present. Thus, the possibility of using cationic extractants must be considered, and in this paper attention is directed to the use of carboxylic acids. The method of separation studied has been termed exchange extraction, which involves replacement of a metal in the organic phase with a more acidic metal in the aqueous phase. Thus, (BR2).+ (Az+)aqt=(AR,).+ (B2+)aq (I) where metal A is more acidic than metal B, R represents the acidic radical derived from the acid RH, and the subscripts e and aq refer to the organic and aqueous phases, respectively. Ashbrook and Ritcey' have used this method for the separation of cobalt from nickel using the sodium salt of di-2 ethyl hexyl phosphoric acid, which preferentially extracts cobalt. Some nickel is coextracted, and this is removed by exchange with cobalt ions in the feed solution by suitable countercurrent operation in a pulsed column. Much work has been carried out by a number of workers in Russia on the general use of exchange extraction for the separation of metal ions using car-boxylic acids. Gindin et aL a have demonstrated that this technique could be applied to the separation of nickel from cobalt using a C--C. carboxylic acid and have applied the technique to the production of high purity cobalt solutions for electrolysis. Further worka was concerned with the development of a process for the separation of nickel from cobalt in a pulsed column. This system permitted the separation of iron and copper from nickel and cobalt in one system. The procedure involved center feeding with acid backwashing at the top and alkali addition lower down the column. Thus the system operated under a pH gradient and the metals were distributed in the column in the order of their basicities. A similar application was studied by Gel'perin et al,4,5 for the removal of copper and iron impurities from a nickel anolyte by means of a C10-C,12 fatty acid fraction. Ginden et al,' and Fletcher and Wilson' have studied the effect of pH on the extraction of a number of metals with carboxylic acids. These studies showed that metals such as iron, copper, lead, zinc, nickel cobalt, and manganese are extracted at pH values close to the pH of hydroxide precipitation. Nickel is extracted at a slightly lower pH than cobalt and thus the nickel/cobalt separation factor has a value not much greater than 1. More basic work on complex identification has been reported by Fletcher and Flett: by Tanaka; and Jay-cock and Jones." These studies have suggested that at low loadings in the organic phase, the nickel and cobalt carboxylates appear to be dimeric and solvated by free carboxylic acid molecules. As the concentration of metal in the organic phase increases, the complex changes and larger polymeric species are formed. In order to permit assessment of the potential of carboxylic acids as extraction reagents for separation of

Jan 1, 1971

By G. W. Nabor, A. S. Odeh

The effect of production history of a well on the results of two-rate flow tests, and conventional build-up analyses was investigated. The effect was examined by means of digital computers and an R-C network model, respectively, for wells with infinite and finite radii of drainage. For systems which behave as infinite, it was found that production history and the duration of production at constant rate prior to the initiation of the test have important effects on the results. During build-up time equal to about one-fourth of the stabilized time, correct permeability-thickness product calculations can be made. For wells with finite radii of drainage, the time was determined during which the straight line can be satisfactorily used for permeability-thickness product calculations in case of drawdowns and build-ups. On build-ups, the dimensionless time (based on the external radius) during which the straight line gives reliable results was detertriined to be about 1/12. This is one-fourth as long as that of the drawdown. The investigation was done theoretically, and subsequently was verified by R-C network model runs. General interpretive rules were formulated which, if not followed, could lead to serious errors. Moreover, a recommended testing procedure is reported. INTRODUCTION The method used by most reservoir engineers for estimating formation characteristics in a producing well is the analysis of pressure build-up data. The method originally devised by Horner' makes use of the point source solution to the diffusion equation. This solution is approximated by a logarithmic function and the superposition principle is employed to arrive at the well known pressure build-up equation:where q, the flow rate, is in reservoir B/D; ft is in cp; kh is in md-ft; At is the shut-in time; and t is the producing time. At and t are in any consistent time units. Ey. 1 is applicable to a well of unlimited drainage radius which produces at a constant rate q from zero to time t and is then shut in. Such a constant production rate seldom obtains in practice. Therefore. a correction term must be applied to Eq. I to account for the varying rate. Two theoretically accurate methods are available for treating the variable rate case. The first, originally derived by Horner,' is based on the application of the superposition theorem. It requires knowlege of production history of the well as a function of time and results in lengthy and laborious calculations. The second t*q* niethod is suited for short production tests and requires that the shut-in time be at least one and one-half times the production time. A third method which is not based on any theoretical justification and which was suggested by Horner as a "good working approximation" is the one used by the majority of reservoir analysts. especially when the well has been producing for a long time and the t*q* method is not practicable. The key to this method is in choosing or determining the t that appears in Eq. 1. Horner suggested using a corrected time t, in place of t. t, is calculated by dividing the total cumulative production by the last established rate. Therefore, a normal procedure of pressure build-up testing is to stabilize the well at a constant rate for at least 24 hours before shut in and to use the stabilized rate to calculate t,. The analysis is then made by plotting either or P. and examining the resulting plot for the expected straight line to calculate kh and the original reservoir pressure. Recently, Russell" proposed a method for determining formation characteristics from two-rate flow tests. His method reduces to pressure build-up if the second flow rate is zero. Russell uses the Horner simplified procedure for calculating a corrected t,. His method also requires the stabilization of the well at a constant rate q which is used to calculate t,. Theoretically, the above procedure is valid for a well with an unlimited radius of drainage or with a limited radius as long as the boundary effect has not been felt by the well. Several authors'' derived formulas which allow the estimation of time during which limited reservoirs behave as infinite ones and, thus, can be treated by unsteady-state mechanics. One equation derived by Swift and Kiel' terminates the application of unsteady-state theory when the drainage radius reaches one-half the reservoir radius. Thereafter, steady-state behavior obtains. Another equation derived by Jones'" initiates steady-state

Jan 1, 1967

By M. G. Jones

AT the Edwards mine a 4 by 81/2-ft two-compartment shaft is used for men and supplies in the older workings down to the 900-ft level. All ore is hoisted through a 5 by 15-ft three-compartment vertical shaft which extends to the 1500-ft level. Ore pockets are on the 1300- and 1500-ft levels. The two-compartment countershaft used below the latter level is 6 by 12 ft inclined at 42°. Ore from the countershaft is hoisted to the 1350-ft level where it flows by gravity to the 1500-ft level ore pocket. One-ton skips are used in balance in the countershaft and two-ton skips, also in balance, from the 1500-It level to the surface. These skips are slung under the man cages. Each level has an ore pocket of 200 tons' capacity. Development at Edwards is similar to that at Balmat except that haulage drifts are only 7 by 7 ft. They are mucked with Eimco-Finlay No. 12 loaders. A drill carriage similar to that used at Balmat is being tried out on the new 2300-ft level, the present bottom of the mine. Drifts are driven below grade and later raised 6 in. and ballasted with waste leaving a ditch 6 by 12 in. at one side for drainage. All development is done on an incentive bonus system, the miner paying for his explosives.

Jan 1, 1947

By A. A. Venghiattis

A rational approach to the selection of the appropriate perforator to use in each specific zone of an oil well is presented. The criteria presently in use for this choice bear little resemblance with actual down-hole condilions. These environmental conditions affect the elastic properties of rocks. One of these elastic properties, acoustic velocity, is suggested as the leading parameter to adopt for the choice of a perforator because, being currently measured in the natural location of the formation, it takes into account all of the effects of compaction, saturation, temperature, etc., which are overlooked in the laboratory. Equations and curves in relation with this suggestion are given to allow the prediction of the depth of perforation of bullets and shaped charges when an acoustic log has been run in the zone to be perforated. INTRODUCTION When an oil company has to decide on the perforator to choose for a completion job, I wonder if it is really understood that, to date, there is no rational way of selecting the right perforator on the basis of what it will do down-hole. This situation stems from the fact that the many varieties of existing perforators, bullets or shaped charges, are promoted on the basis of their performance in the laboratory, but very little is said on how this performance will be affected by subsurface conditions such as the combination of high overburden pressure and high temperature, for example. The purpose of this paper is to show the limitations of the existing ways of evaluating the performance of perforators, to show that performances obtained in laboratories cannot be extended to down-hole conditions because the elastic properties of rocks are affected by these conditions and, finally, to suggest and justify the use of the acoustic velocity of rocks, as the parameter to utilize for the anticipation of the performance of a perforator in true down-hole environment. EVALUATING THE PERFORMANCE OF A PERFORATOR It is natural, of course, to judge the performance of a perforator from the size of the hole it makes in a predetermined target. Considering that the ultimate target for an oilwell perforator is the oil-bearing formation preceded in most cases by a layer of cement and by the wall of a steel casing, the difficulties begin with the choice of an adequate experimental target material. For obvious reasons of convenience, the first choice that came to the mind of perforator designers was mild steel. This is a reasonable choice for the comparison of two perforators in first approximation. Mild steel is commercially available in a rather consistent state and quality, and is comparatively inexpensive. The trouble with mild steel is that it represents a yardstick very much contracted; minute variations in depth of penetration or hole diameter and shape may be significant though difficult to measure. The penetration of projectiles in steel being a function of the Brinell hardness of the steel (Gabeaud, O'Neill, Grun-wood, Poboril, et al), it is often difficult to decide whether to attribute a small difference in penetration to a variation on the target hardness or to an actual variation on the efficiency of the projectile. Another target material which has been widely used for testing the efficiency of bullets or shaped charges in an effort to represent a formation—a mineral target as opposed to an all-steel target—is cement cast in steel containers. This type of target, although offering a larger scale for measuring penetrations, proved so unreliable because of its poor repeatability that it had to be abandoned by most designers. The drawbacks of these target materials, and particularly their complete lack of similarity with an oil-bearing formation, became so evident that a more realistic target arrangement was sought until a tacit agreement was reached between customers and designers of oilwell perforators on a testing target of the type shown on Fig. 1. This became almost a necessity about seven years ago because of the introduction of a new parameter in the evaluation of the efficiency of a perforator, the well flow index (WFI). The WFI is the ratio (under predetermined and constant conditions of ambiance, pressure and temperature) of the permeability to a ceitain grade of kerosene of the target core (usually Berea sandstone) after verforation. to its vermeabilitv before perforation. The value of this index ;or the present state if the perforation technique varies from 0 to 2.5, the good perforators presently available rating somewhere around 2.0 and the poor ones around 0.8, There is no doubt that, to date, the WFI type of test is by far the most significant one for comparing perforators. It is obvious that a demonstration of a perforator

By Alexander Anderson

TABLES showing the drift and inclination of wells surveyed in the years 1924 to 28' and in the year 1929' have already been published. Each of these tables included a little over 1,000,000 ft. of rotary hole. In the year 1930 the table -shown-in . Fig. 1, comprising, the results of surveys .of 1,030,344 ft. of hole and representing 11,642 individual survey readings, was compiled. For that purpose we selected 'I only wells that had been drilled in California during that year. The footage of Fig. 1 differs from the two earlier tables in that the wells were all drilled in the year 1930. In the earlier tables, the footage shown was surveyed in the years designated, but some of the wells were drilled in earlier years.

Jan 1, 1931

By W. A. Turcotte, A. D. Paananen

Introduction The large reserve of fine grained oxidized iron-formation at the Tilden mine has been the object of research and development efforts to concentrate the iron oxides as far back as 1949. Due to the nonmagnetic nature of the ore and the fine grinding required to liberate the iron oxide minerals, this crude ore was not amenable to concentration by conventional methods. The iron oxides of the Tilden, ore body have a grain size of less than 25 microns and recovery of the finer, well-liberated iron oxides is essential. Conventional methods of desliming employing cyclones or thickeners were not feasible because of the excessive loss of iron oxides in the finer fractions. Development of selective flocculation-desliming was a key to commercialization of the process. Operations started in late 1974 with Algoma Steel Corp. Ltd., J & L Steel Corp., The Steel Company of Canada Ltd., Wheeling-Pittsburgh Steel Corp., Sharon Steel Corp., and The Cleveland-Cliffs Iron Co. as participants. Cleveland-Cliffs operates and manages the operation. Development of the Tilden Flowsheet The geology and ore reserves of the Tilden mine have been detailed in a paper by Villar and Dawe (1975). A joint program was undertaken in 1961 with the US Bureau of Mines in Minneapolis using the flowsheet developed by the Bureau employing the selective flocculation-desliming and calcium activated anionic silica flotation method (Frommer, et al, 1966; Frommer, 1964; Frommer, Wasson, and Veith, 1973). During this time, parallel testing at Cleveland-Cliffs Research Laboratory and Pilot Plant centered on the same type of desliming but was followed by the cationic flotation of silica with amine collectors (Columbo and Jacobs. 1976). The cationic silica flotation system was eventually chosen for its overall efficiency and simplicity. Regardless of the flotation method chosen, the technique of selective flocculation-desliming prior to flotation is the key to the success of the process. The flowsheet is described in detail by Villar and Dawe (1975). [Figure 1] shows a simplified one-line flowsheet of the Tilden concentrator. A total tailings thickener has been added to the original flowsheet and was placed in operation in 1978. The total-tailings thickener overflow reports to the reuse water pond and the underflow is pumped approximately 8 km (5 miles) to a storage basin. A flowsheet of the reuse water system is shown in [Fig. 2]. Selective Flocculation-Desliming Data have been published on the mechanisms and factors affecting selective flocculation in iron oxide-silica systems. The intent of this paper is not to discuss the theoretical aspects of selective flocculation, but rather to present experience gained from the commercial Tilden operation and from bench and pilot plant testing of fine-grained oxidized iron ores. From the bench and pilot plant testing prior to plant startup, certain reagent combinations and rates for the commercial Tilden plant were established. In the experience gained from three years of plant operation at Tilden, some of these reagent dosage rates have required significant adjustments due to changes in reuse water quality and to meet the requirements of varying ore types. Reuse Water The process water quality is a major concern at the Tilden mine and is constantly being monitored for selected chemical and physical characteristics. This monitoring has continued on a regular basis in order to gain a more thorough understanding of the interactions taking place in a dynamic water system and particularly as water quality is influenced by seasonal variations. Control of the reuse water chemistry is essential to the Tilden process both in the selective flocculation-desliming and flotation stages of concentration. With roughly 75% of the reuse water used in grinding-desliming operations, it is readily apparent that the biggest "reagent" in the selective flocculation-desliming process is water. Not enough can be said about the close control that must be exercised on the overall reuse water system. Control of the chemical treatment of the feed to the total tailings thickener is of utmost importance in order to produce a reuse water for the concentrator that is compatible with all stages of the concentrating process. There are many analyses made which aid in judging the quality of the water. Some of these are shown in [Table 1]. Five are particularly important and are monitored daily so that reagent adjustments can be made as required: suspended solids, calcium hardness, pH, dissolved silica concentration and temperature.

Jan 1, 1981

By Emil Gathmann

Steel as it is poured, or teemed, into the mold for forming the ingot may be broadly separated into two divisions; i.e., effervescing or gassy steel, also termed evolution steel, and non-effervescing or killed steel, also termed solution steel. Between these primary divisions there are various types having the characteristics of both divisions but really nut belonging to either; such steels are termed semi-piping, rising, or wild, as the type may be. True effervescing steel should contain large volumes of gases, which are evolved while the metal is being teemed from the ladle nozzle into the mold, and continue to escape while the temperature of the steel is falling prior to its solidification the top of the ingot remaining liquid, due to the evolution of gases, until an ingot skin of considerable thickness has been formed. These gases consist principally of hydrogen, carbon monoxide, nitrogen, and ammonia. It is generally understood that nitrogen gases are the first evolved and these form the skin blowliolcs, troublesome at times, in the solidifying ingot. Ingots made of effervescing steel will always contain a large number of blowholes. Such blowholes are not deemed objectionable in certain products if they occur well inside the ingot where they will not be subjcct to oxidation upon cooling, reheating, and rolling or forging of the ingot. Very little top or bottom discard is taken from this type of ingot, as pipes, or large shrinkage cavities, at the upper portion of the ingot do not usually occur, the difference in volume between the liquid and the solid steel (6 to 10 per cent.) being compensated by the innumerable blowholes distributed throughout the body of the ingot. Of the 40,000,000 tons of steel made in the United States during the year 1919, at least 35,000,000 tons of ingots were made of gassy or semi-gassy steel. Killed, or solution, steel is termed true piping steel from the characteristic pipe or shrinkage cavity that usually occurs in the uppermost central portion of the ingot.

Jan 1, 1922

By Emil Gathmann

Steel as it is poured, or teemed, into the mold for forming the ingot may be broadly separated into two divisions; i.e., effervescing or gassy steel, also termed evolution steel, and non-effervescing or killed steel, also termed solution steel. Between these primary divisions there are various types having the characteristics of both divisions but really nut belonging to either; such steels are termed semi-piping, rising, or wild, as the type may be. True effervescing steel should contain large volumes of gases, which are evolved while the metal is being teemed from the ladle nozzle into the mold, and continue to escape while the temperature of the steel is falling prior to its solidification the top of the ingot remaining liquid, due to the evolution of gases, until an ingot skin of considerable thickness has been formed. These gases consist principally of hydrogen, carbon monoxide, nitrogen, and ammonia. It is generally understood that nitrogen gases are the first evolved and these form the skin blowliolcs, troublesome at times, in the solidifying ingot. Ingots made of effervescing steel will always contain a large number of blowholes. Such blowholes are not deemed objectionable in certain products if they occur well inside the ingot where they will not be subjcct to oxidation upon cooling, reheating, and rolling or forging of the ingot. Very little top or bottom discard is taken from this type of ingot, as pipes, or large shrinkage cavities, at the upper portion of the ingot do not usually occur, the difference in volume between the liquid and the solid steel (6 to 10 per cent.) being compensated by the innumerable blowholes distributed throughout the body of the ingot. Of the 40,000,000 tons of steel made in the United States during the year 1919, at least 35,000,000 tons of ingots were made of gassy or semi-gassy steel. Killed, or solution, steel is termed true piping steel from the characteristic pipe or shrinkage cavity that usually occurs in the uppermost central portion of the ingot.

Jan 1, 1922

By Charles H. Behre

This paper discusses education and training for economic geologists other than petroleum geologists. Candidates enter economic geology through liberal arts colleges, engineering schools and university graduate study. Whatever their backgrounds, rigorous courses are desirable—now conceded in theory, but not adequately recognized in practice. Besides basic sciences (each studied long enough to give a fair comprehension of its basic tenets), a functional command of English and two modern foreign languages is needed, as well as a broad understanding of mining, milling and metallurgy. A year of economics and finance is recommended. Surveying and drafting are essential skills. Yet geology should be represented in each term; otherwise the initial enthusiasm for the science, once contact is broken, may never be regained. A five-year curriculum is thus designed to take care of all major requirements and culminate in the M. S. degree. This curriculum reduces "cultural" courses below the average liberal arts requirements, but this is regarded as necessary. The pursuit of "culture" is assigned, as in most engineering and medical curricula, to extra college years or extracurricular time. To avoid the danger of over-crowding the schooling, the Doctorate in geology is preferred wherever possible. Its two added years should permit wider professional education; more browsing in "cultural" pastures; due attention to broader social implications; and some training in the research now increasingly required of the mineral industry. "In-course" training through cooperation between school and industry is especially advo- cated. The Institute should take the initiative in stimulating this practice. Introduction Training a student in geology for a career in the mineral industry is still a moot question, one that is likely to be looked at from many different angles, each of which will reflect the background of the individual considering it. From what follows, the training of petroleum geologists is omitted since, although theirs is an equally important phase of economic geology, it is based upon different essentials. The general subject was recently effectively discussed, but from a somewhat different viewpoint, by Professor McKinstry.' The practical problems that confront the young mining geologist are highly varied and in the eyes of his employer apparently almost any demands seem justified. The mining executive wants from the mining geologist results related mainly to overall operations, reports or forecasts that are largely recordable on paper and chiefly in terms of "discovery thinking." The local mining engineer may have many specific questions of his own, chiefly relating to details of geology that apply to mining practice, which he will address to the mining geologist; these usually deal with production quantities; frequently also they necessitate the immediate handling of pressing but apparently minor matters: shall the drill be moved; how soon will we encounter the watercourse which made so much trouble for us above? The client employing a consultant often wants advice or good judg-

Jan 1, 1949