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By Leonard H. Goldman, Harold E. Marr

The PGT uranium assay probe is a borehole tool developed by Princeton Gamma-Tech over the last several years. It has the ability to do an in-situ assay of uranium in the presence of any amount of disequilibrium. It has some advantages over coring including cost, speed of analysis, and accuracy. In this paper we would like to give a brief description of the measurement and then show some sample logs from South Texas. Uranium exploration and development is carried out primarily by gamma logging since uranium daughters are prolific emitters of gamma rays. The conventional gross gamma tool for uranium logging is limited in value because of the inability of this tool to distinguish uranium from its daughters and other naturally occurring radioisotopes, such as potassium and thorium. This problem becomes severe in cases of disequilibrium. Disequilibrium, in a geological context, is defined as the condition when the gamma radiations from the daughter products are being emitted in a location different from that of the parent uranium. In the decay chain of uranium almost all the gamma radiation emitted in the entire chain comes from the daughter product, bismuth-214. Bismuth-214 is separated from uranium by several long-lived isotopes that are chemically active and have different physical properties, often resulting in shifts in the location of bismuth- 214 relative to the parent uranium. In the United States orebodies exhibiting disequilibrium are a common occurrence and the use of a gross gamma log to delineate uranium orebodies can lead to errors. At present the solution to the disequilibrium problem is extensive coring followed by chemical analyses of the cores. There are several drawbacks in using this technique. First is the high cost of coring, the second is the fact that no results are available for days, or typically, weeks after the drilling is done. Thus for development work, coring and drilling must be done on a grid basis and many additional holes are cored to ensure that the entire orebody is mapped. Another disadvantage to cores is the fact that a small volume is sampled, the volume of the core itself. This leads to problems in the mapping out of the orebody when the ore de- posit is not very homogeneous. The PGT probe described in this paper is a new solution to the disequilibrium problem. Basically, the probe measures radiations that come almost directly from uranium itself. The first daughter of uranium, which is protactinium-234 (Pa-234), is only separated from uranium by a 24-day half-life and no disequilibrium problems build up in such a short time. The PGT probe measures the intensity of a one MeV gamma line emitted by Pa-234 and, using this information, calculates the concentration of uranium. The PGT probe is 24" in diameter and 12 feet long. The probe contains a microprocessor which passes the information to a larger minicomputer in the truck. All data is analyzed on site, and the results from a high speed printer are presented to the geologist. Data is also available on 9- track IBM compatible tape for further processing. The PGT probe output is linear with uranium concentration. The only correction factor is for borehole size, and that only becomes important in boreholes bigger than seven inches in diameter. Dead time is compensated in the probe itself and no problems have been encountered in ore zones up to several percent UjO8. In addition to the uranium assay, a conventional gross gamma log is plotted alongside. Grade thicknesses for zones above cutoff are calculated as well as disequilibrium factors. COMPARISONS During its commercial operation PGT logged a series of 18 holes that had been cored and assayed. All of the holes in this series were logged in normal operation by regular field operators. The time to log each hole was generally under an hour, and in typical operation a PGT logging truck will do between 7 and 8 holes a day. The results of the comparison of the PGT and the core assays are presented in a series of figures showing plots of the PGT assay, core analysis and gross gamma measurements. The first three figures show individual holes with the gross gamma plotted along with the core and the PGT assays. All three logs were from holes on the reduced side of a rollfront deposit in South Texas. In Figure 1 we see the two wings of the roll- front at 143 ft and 150 ft separated by a barren zone. The wings are well defined both by the PGT assay and the core. There is approximately a one foot shift which can be attributed to drilling errors. The gross gamma is showing a rather severe discrepancy, being considerably lower and not showing the barren zone. The grade thickness calcula-

Jan 1, 1980

By C. Pin, J. Bruce Wagner

In order to demonstrate the role of defect chemistry in the solid state to a process-metallurgy reaction, laboratory experiments were carried aut to remove copper from liquid lead using lead sulfide which had been doped to provide definite concentrations of cation vacancies. The removal of copper decreases in the order: bismuth- or antimony-doped PbS, undoped PbS or tin-doped PbS, and silver-doped PbS. The data are explained using the simple mass -action law and in terms of the exceedingly rapid interstitial diffusion of coppw in PbS to vacant cation sites. Results are in agree-ment with thermodynamic predictions and certain industrial practices that copper may be removed from lead below the limit of its coexistence with pure Cu,S and pure PbS. The role of defects in solids has been exploited in semiconductors and many device applications, in explaining tarnish formation, dissolution rates, and mechanical properties. The application of these principles to many process-metallurgical problems has not received as much attention. It was the purpose of this study to illustrate the role of defect structures of solids in a process-metallurgical application. When lead is refined, the ore, galena (PbS), is reduced by a series of operations to liquid lead (lead bullion) containing impurities such as copper, bismuth, antimony, arsenic, and silver depending on the original composition, the fluxes added, and the particular type of operation, see Fig. 1. In order to produce a pure lead, a series of refining operations are carried out. A typical lead-bullion analysis before drossing is shown in Table I. Copper is removed first as its presence increases the zinc consumption during the desilverizing process. For preliminary copper removal the lead bullion is brought to a temperature of 440°C in a kettle of 60 metric tons capacity. Some tar (or sawdust or resins) is usually added and the kettle is cooled slowly to 400°C while the liquid is stirred. A solid phase, called a dross, floats on top of the liquid and the particles of the solid phase adhere to the tar. This "hot dross" is collected. It contains mostly lead and copper which are partly oxidized and/or sulfurized if the lead bullion contains some sulfur.*

Jan 1, 1963

By R. T. Hukki, A. M. Gaudin

Previous work on the principles of comminution has shown: (I) that the surface produced is proportional to work input (Rittinger law,1a-3); (2) that there is regularity to the weight distribution of the fragments according to size.4-10 In this paper it is brought out that the surface on the fragments is distributed in definite and simple relation to size. The experimental work has involved: I. Construction of an apparatus capable of measuring the surface of mineral fragments independently of the chemical composition of the fragments and independently of the site of the surface; 2. Refining the methods available for measurement of particle size; 3. Designing and building a crusher capable of operating on very small quantities of mineral, if necessary on single crystals, and in such fashion as to minimize handling losses of material. Complete experiments have been carried out with massive quartz and individual quartz crystals. partial experiments, lacking surface measurements, have been made with glass spheres, galena, sphalerite, fluo-rite, salt and coal. Introduction The existence of regularity in weight distribution with size was noted many years ago, especially by A. 0. Gates;' the subject was also studied in detail by one of us.6 In the latter paper it was shown that rocks can be divided into two classes: homogeneous rocks, which show no preferential breaking, and heterogeneous rocks, which show preferential breaking at the grain size of the rock. It was shown, furthermore, that the fragments obtained by rupturing a homogeneous rock occur (in the fine range) in such abundance as to permit the writing of a relatively simple equation to relate the weight retained on a screen to the screen opening. With screens of which the openings are in constant ratio, the weight retained, w, is related to the screen size x by the equation w = Cxm [I] In this equation C and m are experimental constants. A plot of weight retained against particle size is a straight line of slope m if the scales for x and w are both logarithmic. In the fine range, the slopes of the size-distribution graphs plotted according to the method described above vary within a limited range. An inspection of a number of size-distribution data by various experimenters indicates that the slope very seldom exceeds 1.0, but is usually greater than 0.7. More recently, schuhmann8 proposed a method of charting that has so many advantages of its own that it has been used primarily in this work. For fine particles Schuhmann has found that the data are represented by the equation (x)m k [2]

Jan 1, 1947

By A. M. Gaudin, R. T. Hukki

Previous work on the principles of comminution has shown: (I) that the surface produced is proportional to work input (Rittinger law,1a-3); (2) that there is regularity to the weight distribution of the fragments according to size.4-10 In this paper it is brought out that the surface on the fragments is distributed in definite and simple relation to size. The experimental work has involved: I. Construction of an apparatus capable of measuring the surface of mineral fragments independently of the chemical composition of the fragments and independently of the site of the surface; 2. Refining the methods available for measurement of particle size; 3. Designing and building a crusher capable of operating on very small quantities of mineral, if necessary on single crystals, and in such fashion as to minimize handling losses of material. Complete experiments have been carried out with massive quartz and individual quartz crystals. partial experiments, lacking surface measurements, have been made with glass spheres, galena, sphalerite, fluo-rite, salt and coal. Introduction The existence of regularity in weight distribution with size was noted many years ago, especially by A. 0. Gates;' the subject was also studied in detail by one of us.6 In the latter paper it was shown that rocks can be divided into two classes: homogeneous rocks, which show no preferential breaking, and heterogeneous rocks, which show preferential breaking at the grain size of the rock. It was shown, furthermore, that the fragments obtained by rupturing a homogeneous rock occur (in the fine range) in such abundance as to permit the writing of a relatively simple equation to relate the weight retained on a screen to the screen opening. With screens of which the openings are in constant ratio, the weight retained, w, is related to the screen size x by the equation w = Cxm [I] In this equation C and m are experimental constants. A plot of weight retained against particle size is a straight line of slope m if the scales for x and w are both logarithmic. In the fine range, the slopes of the size-distribution graphs plotted according to the method described above vary within a limited range. An inspection of a number of size-distribution data by various experimenters indicates that the slope very seldom exceeds 1.0, but is usually greater than 0.7. More recently, schuhmann8 proposed a method of charting that has so many advantages of its own that it has been used primarily in this work. For fine particles Schuhmann has found that the data are represented by the equation (x)m k [2]

Jan 1, 1947

By L. S. Darken

It has been known for sometime that in an ionic lattice, such as that of Ag,S or FeO, the migration velocity of the anion may differ markedly from that of the cation, the cation being usually the more mobile. It has been shown, for example, that during the formation of silver sulphide tarnish on silver, the tarnish layer grows principally by the motion of silver cations through an essentially stationary silver sulphide lattice. Similarly, the growth of wüstite scale on iron proceeds principally by motion of iron ions, this being accomplished with the aid of vacant iron lattice sites into which the iron may readily move. Likewise investigations of solid solutions of various salts show that there is usually considerable difference in the mobility of the different cations. Measurements of the mobility of various metals in liquid mercury indicate that the various metals move at different rates relative to the mercury. In view of the foregoing it seems reasonable to suppose that when any single phase solution is acted upon by a field, the atoms of different elements respond in different ways; in particular, that the force arising from a particular concentration gradient in a binary alloy would cause the atoms of one component to move with a drift velocity which is in general different from that of the atoms of the other component. The recent experiments of Smigelskas and Kirkendall' support this viewpoint, since they found, in essence, that during diffusion in alpha brass zinc moves appreciably faster than copper. This was evidenced by the relative motion of inert molybdenum wires. Such a phenomenon is incompatible with the place interchange theory of diffdsion proposed by several authors, most recently by Bir-chenall and Mehl.2 This theory has, however, also been questioned3v4 for other reasons, principally because of the high energy required for direct atomic interchange. The rather large difference between self-diffusivity, as determined by tracer technique, and mutual diffusivity, as determined with the aid of another element at low concentration, might also be interpreted as favoring the above idea; however. Birchenall and Mehl have pointed out that there is another possible interpretation of this difference; this is discussed later. A rather interesting and pertinent observation was made by Schwartz, who noticed that tungsten lamp filaments, heated by direct current, commonly fail by necking down in the region at the temperature gradient near the positive end, with a concomitant swelling at the corresponding position near the negative end. He introduces considerable auxiliary evidence to show that this phenomenon is occasioned by the motion of tungsten cations which migrate in the high temperature region from the positive end toward the negative end. The mechanism of this migration is not clearly understood. If, however, this experimental evidence be accepted, we are forced to conclude that alloying elements in the tungsten may migrate by the same or a Similar mechanism, whatever it may be, at a greater Or lesser rate, thus giving rise

Jan 1, 1949

By L. S. Darken

It has been known for sometime that in an ionic lattice, such as that of Ag,S or FeO, the migration velocity of the anion may differ markedly from that of the cation, the cation being usually the more mobile. It has been shown, for example, that during the formation of silver sulphide tarnish on silver, the tarnish layer grows principally by the motion of silver cations through an essentially stationary silver sulphide lattice. Similarly, the growth of wüstite scale on iron proceeds principally by motion of iron ions, this being accomplished with the aid of vacant iron lattice sites into which the iron may readily move. Likewise investigations of solid solutions of various salts show that there is usually considerable difference in the mobility of the different cations. Measurements of the mobility of various metals in liquid mercury indicate that the various metals move at different rates relative to the mercury. In view of the foregoing it seems reasonable to suppose that when any single phase solution is acted upon by a field, the atoms of different elements respond in different ways; in particular, that the force arising from a particular concentration gradient in a binary alloy would cause the atoms of one component to move with a drift velocity which is in general different from that of the atoms of the other component. The recent experiments of Smigelskas and Kirkendall' support this viewpoint, since they found, in essence, that during diffusion in alpha brass zinc moves appreciably faster than copper. This was evidenced by the relative motion of inert molybdenum wires. Such a phenomenon is incompatible with the place interchange theory of diffdsion proposed by several authors, most recently by Bir-chenall and Mehl.2 This theory has, however, also been questioned3v4 for other reasons, principally because of the high energy required for direct atomic interchange. The rather large difference between self-diffusivity, as determined by tracer technique, and mutual diffusivity, as determined with the aid of another element at low concentration, might also be interpreted as favoring the above idea; however. Birchenall and Mehl have pointed out that there is another possible interpretation of this difference; this is discussed later. A rather interesting and pertinent observation was made by Schwartz, who noticed that tungsten lamp filaments, heated by direct current, commonly fail by necking down in the region at the temperature gradient near the positive end, with a concomitant swelling at the corresponding position near the negative end. He introduces considerable auxiliary evidence to show that this phenomenon is occasioned by the motion of tungsten cations which migrate in the high temperature region from the positive end toward the negative end. The mechanism of this migration is not clearly understood. If, however, this experimental evidence be accepted, we are forced to conclude that alloying elements in the tungsten may migrate by the same or a Similar mechanism, whatever it may be, at a greater Or lesser rate, thus giving rise

Jan 1, 1949

By C. P. Besse, N. F. LeBlanc

Described in this paper are oceanographic data which should be considered by an offshore design engineer and methods for developing a design wave height from the oceanographic data. The selection of a design wave is predicated on contemplated waves which might affect the site throughout the life of the structure. Selection of a design wave height may be based on (1) arbitrarily established recurrence Frequencies of hurricanes affecting the structure (predicted wave heights are associated with the expected variations of forces resulting from these waves) and (2) a risk-type evaluation wherein all possible storms affecting the area are considered (anticipated wave heights are associated with both investment plus risk costs and expected variations of forces). It is shown how the following oceanographic predictions are integrated into design considerations: (1) a classification of storm intensity which considers all recorded storms which affected the design area, (2) the recurrence interval of storms of a given- intensity (this interval is dependent on the extent of the geographical area considered in the design problem) and (3) a forecast of all wave heights which might affect the area (geometry of a structure often necessitates consideration of waves from a multiplicity of directions). The authors believe that the described techniques can result in selecting an adequate and reasonable design wave. INTRODUCTION Since the inception of offshore operations in the Gulf of Mexico, engineers engaged in designing suuctural facilities have been plagued with the problem of selecting an adequate and reasonable design wave. In the development of any offshore structure it is mandatory that the engineer evaluate the ability of the structure to withstand the ocean waves to which it will be subjected. Selecting such design waves quite naturally necessitates a coalition of the oceanographer and the design engineer. The oceanographer must provide a detailed knowledge of scientific principles which govern the behavior of waters in the Gulf of Mexico. He should also have an adequate knowledge of the manner in which design waves are utilized by the engineer. Although the design engineer's primary responsibility is applying the oceanographer's specialized knowledge in the creation of real structures, it is important that he possess some knowledge of related oceanographic principles to reasonably evaluate and apply the recommendations of the oceanographer. In the Gulf of Mexico it is the hurricane wind waves which generally govern the design of an offshore facility. The oceanographer must therefore develop techniques for predicting the heights, periods and frequency of all hurricane waves which might affect a particular structure. From this mass of oceanographic data, the design engineer must select the design waves which will apply to his particular design. PAST STUDIES ON FREQUENCY AND AMPLITUDE OF HURRICANE WIND WAVES Past oceanographic studies on the frequency of hurricane wave heights in the Gulf of Mexico have been devoted largely to predicting the recurrence interval of hurricanes which will generate maximum significant waves of given heights. The maximum significant wave height is the average height of the highest one third of the waves in that portion of the storm producing maximum wave heights. Since these waves occur over a relatively small portion of the storm (Fig. 1) and since the paths of hurricanes vary considerably (Fig. 2), the recurrence frequency of such heights is largely a function of the extent of the geographical area considered. In establishing the frequency of maximum significant waves for the entire American Gulf coast, the major fully developed hurricanes which affected the coastline from BrOwnsville, Tex., to Key West, Fla., were considered (Fig. 2). These Storms were selected and described by C. L-

By J. M. W. Mackenzie

A microelectrophoresis technique has been used to measure the zeta potential of quartz over a range of pH and ferric iron concentration. The results have been discussed in terms of the adsorption of ferric cations and ferric hydroxide to the quartz surface. Possible relationships between the experimental results and the flotation of quartz have been examined. The adsorption of multivalent cations at the surface of quartz has been studied by many investigators who have used a variety of experimental techniques ranging from streaming potential 1 to radiometric2 measurements. Two possible mechanisms of cation activation of quartz have emerged from the results of these investigations viz: the adsorption of the cation to the negatively charged quartz surface, followed by adsorption of the collector anion to the adsorbed cation site, or: formation of a cation-collector complex which is then adsorbed to the quartz surface. In many natural and industrial systems one of the most prevalent activating species for quartz is ferric iron, this is especially so in the acid-circuit, anionic flotation of iron ore. The adsorption of ferric iron to the quartz surface is complicated by the ability of ferric iron to form complexes with anions, a phenomena which is of minor importance in one of the most widely studied quartz activation processes, ca ++ activation.* *The pK value for [ca(oH)+]/ [ca2+] [oh-] is 1.46 indicating that the influence of Ca (OH)+ ions will be minor in all but strongly alkaline solutions. In order to obtain a better understanding of quartz activation by ferric iron the zeta potential of quartz in the presence of ferric iron has been measured over a range of pH and ferric iron concentration. EXPERIMENTAL METHODS Materials: Selected samples of "rock clystal" quartz from New England, N.S.W., were ground in a pebble mill, washed for three hours in boiling concentrated hydrochloric acid, washed in hot chromic acid and then washed repeatedly with distilled water until the washing water gave no trace of chloride ion.

Jan 1, 1967

By D. Weinstein

Yieldilzg in annealed arc-cast molybdenunz in torsion was studied as a function of strain rate and tem-perature. The temperature dependence of the yield point for different strain rates was used to calculate a heat of activation for the yield point. The heat of activation was not a constant but was approximately a linear function of the stress at yield. It is proposed that the rate effect in yielding is determined in part by a site place-change of C (or other interstitial atom) in the metal. THE low-temperature embrittlement phenomenon in metals and alloys has been known to exist for a long time. Although a transition from ductile to brit-tle behavior has been observed in some close-packed hexagonal metals1 and a face-centered cubic alloy, the most common class of metals exhibiting this be-havior has a body-centered cubic lattice structure. For example, a ductile to brittle transition has been observed in iron,3 molybdenum,4 chromium,5 colum-bium,6 and tungsten.7 In the present investigation, molybdenum specimens were tested in torsion over a wide range of temperatures at three widely separated strain rates, and the temperature for onset of embrittlement was determined. Characteristic of body-centered cubic metals and closely associated with plastic deformation is the appearance of a sharp upper and lower yield point. Theoretical explanation of the yield point in iron and low-carbon steel is due to Cottrell,8 who attributes the phenomenon to the pinning of dislocations by the formation of impurity atmospheres around the dislocations. These atmospheres tend to lock the dislocations and make them more difficult to move. The stress required to move a dislocation and thereby cause plastic deformation is greatly increased, and thus an upper yield point is observed. In addition, theoretical analysis,9 as well as experimental observations, show that the upper yield point is strongly a function of temperature. The upper yield point is observed to decrease with an increase in testing temperature, and above a certain temperature (-700° K in iron) it no longer appears. This is consistent with the concept that thermal vibrations will help free a dislocation from its atmosphere, so that the external stress required to free a dislocation from its pinning atmosphere decreases with increasing temperature. Furthermore, with increasing temperature the equilibrium concentration of impurity atoms around a dislocation decreases exponentially with the result that the dislocation is less firmly pinned. In Cottrell's theory of yield point a static model is visualized in which the pinning atmospheres, particularly interstitial atoms, are immobile, and the dislocations are anchored to stationary positions in the lattice. However, experiments1,7 show the upper yield point to be time-dependent or a function of the rate of straining, a high strain rate causing a high upper yield point. Present theory does not adequately account for the rate dependence of the yield point, and the exact function of the interstitial atom is not under stood. Nevertheless, observation of the temperature dependence and rate dependence strongly suggests that the upper yield point phenomenon is due to the interaction between dislocations and pinning atoms, and that a diffusion mechanism is important in determining the yield point.

Jan 1, 1962

By Albert L. Toenges

Alaska requires an adequate fuel supply for its development, and has large potential coal reserves ranging from lignite to subbituminous and anthracite. Coal production in the Territory now is less than the requirements. In L947, production was 361,000 tons, divided about equally between bituminous coal from the Matanuska field and subbituminous coal from the Nenana field. There is need for development of modern mechanized mines, which should produce the required output with a minimum of workers. These mines should not be thought of in the light of large potential capacity, as in the States. However, these new mines should be developed by modern methods, which should result in lower costs than at Present. Because of the diverse physical conditions in the coal fields, intensive investigation by diamond drilling is necessary to properly plan the development and equipment of mine sites at minimum cost. The Bureau of Mines is doing this now in the Wishbone Hill area of the Matanuska field. All coal land in Alaska is government-owned and subject to the Coal Leasing Act. Coal mining in Alaska has been handicapped by an inadequate supply of dependable workers. Wage scales have been very high in recent years, and "floaters" have been attracted to the coal mines. This type of labor is not conducive to efficient operation. Modernization of mines will require skilled and dependable workers and to induce such men to become interested in coal mining in Alaska, modern facilities, such as modern houses, schools, churches, and recreation halls, must be provided near the mines. Alaska is still a frontier and improvements in living standards must accompany development of mines in order that a stable community may be established. Coal is known to have been mined in Alaska at Port Graham, on Cook Inlet, by the Russians in 1854. During the Klondike gold rush in 1898, coal was mined in scattered areas for use on steamers plying the Yukon River and its navigable tributaries. After the Alaska Railroad was built, two important fields were developed—the Nenana and the Matanuska (Fig 1). The Bering River field was explored by the Guggenheim interests at one time, and a railroad to the area was constructed. However, the field was abandoned because of litigation and reported unsatisfactory physical condition of the beds. There are areas that today are unimportant but which may be developed in the future. Possibly the most important of these is the deposits of subbituminous coal adjacent to Cook Inlet, near Homer, on the Kenai Peninsula (see Fig 1). It is expected that the demand for coal in the Kenai Peninsula will increase because the population in that area has increased as a result of agricultural development. Numerous outcrops of coal are exposed on the peninsula and development of a mine there would obviate dependence on supplies of coal from the Matanuska field. Coal from this field must be shipped approximately 160 miles by rail to Seward and transported thence by boat about 180 miles to Homer. There has been no regular boat service from Anchorage to Homer. There are deposits of coal in the Arctic region but a description of them will not be given in this paper, which will describe the more important deposits in the Alaska Railroad belt. The results of a reconnaissance in the Arctic have been described.' Description of Fields MATANUSKA FIELD The Matanuska field lies in the valleys of the Matanuska River and its tributaries and their separating ridges. This field has been interpreted by geologists as a sunken fault block that separated the Talkeetna Range of mountains from the Chugach Range. The Matanuska River flows west along the south side of the field and the Glenn highway, which extends from Anchorage via Palmer to the Richardson highway near Glen Allan, follows the Matanuska Valley. This road to the coal field can be traveled the year around. Although the snow-

Jan 1, 1950

By Louis P. Gignac

INTRODUCTION The selection of trackless equipment for underground mining can be a complex engineering problem due to the wide range of equipment sizes and operating modes. Computer simulation is particularly useful in estimating the performance of different systems for specific rock- handling problems. A hybrid simulator, incorporating some of the features of deterministic and stochastic simulation, was developed in order to handle not only queuing delays at loading and dumping points, but a1 so traffic interferences. Any number of vehicles can operate in any one of four basic modes (LHD, LAF, FEL, HFC) in parallel or in series. If the units use common roadways, loading and dumping points, certain operating delays will occur and be registered by the simulator and thus give a better evaluation of the marginal productivity of each additional unit. Based on a typical layout of drawpoints and ore passes for the sub-level stoping method, productivity and operating costs of different rock-handling systems will be examined. 1 . COMPUTER SIMULATION Numerous applications of computer simulations are reported in the 1iterature for various mining problems. Depending on the complexity of the system to be studied, simulation models were conceived with different degrees of sophistication. Three different types of simulators are generally recognized: stochastic, deterministic, and hybrid. Stochastic or Monte Carl o simulation randomly generates items, transactions, or events from some population defined by a frequency distribution and produces some expected future situations. Because this type of simulation is governed by the input of probability distributions, it requires a detailed knowledge of the system to be simulated; it implies expensive and time-consuming studies and reports to gene- rate this input information. A major short- coming of stochastic techniques is in new equipment evaluation, where the lack of data is unavoidable, and in new system design where the conditions are outside the range of the known historical behavior of the equipment. However, probabilistic simulation is almost essential for the study of cyclic queues and traffic problems. Deterministic simulation studies a system by generating performances on the basis of the mechanical capabilities of the vehicles and the physical limitations of the mining scheme. It is based on the engineering principle that the engine converts its energy into a rimpull at the wheels, which is in turn opposed by the rolling resistance and the grade of the ground; the machine is accelerated or decelerated until the tractive and resistive forces are in equilibrium, at which point it moves at constant speed. The information required by this technique, such as rimpull charts and equipment weight, is readily available from equipment suppliers. However, equipment performance at the mining site is also dictated by human and environmental conditions and changes with time and usage. For this reason, deterministic simulation generally overestimates the system capabilities; these must then be adjusted by efficiency factors based on observation and experience. Recently, hybrid simulation models, using both stochastic and deterministic techniques, have been built with some of the events generated stochasticly and others being deterministic. This compromising approach originated at the Pennsylvania State University. O'Nei1 (1966) designed a simulator for truck-and- shovel operations that allows for transportation from multiple faces to mu1tiple destinations. Each truck performs according to its mechanical capabilities while its loading and dumping time and its load fluctuate according to specific probability distributions. A major advance in the simulation of mining systems is due to Sanford's model (1969) of underground coal mining operations. The originality of the model is in the use of an Executive System Control which sets up the initial system, de- fines the operation conditions , and instructs continuously four sub-assemblies representing shuttle cars, trains, continuous miners , and conveyors, which in turn generate a feed-back of their movement to the Executive Control System for further instructions. The model has enough flexibility to simulate simultaneous and sequential jobs that characterize any dynamic system. Sanford's early work evolved slowly to what is known today as the Under- ground Materials Handling Simulator for coal mining (Manula, 1974).

Jan 1, 1981

Although the 71 Minerals operation is now closed down and the operating data presented is almost five years old, it is well worth describing since it was the first heap leaching operation conducted on a primarily silver ore. Tombstone was discovered in 1877 by Ed Schieffelen; and it became one of the most famous mining towns in the West through the stories connected with Wyatt Earp, Doc Holliday, and the Clanton brothers. Like many silver deposits .in the western United States, the Tombstone ores were relatively shallow. Several million ounces of silver were recovered in the relatively few years the camp was active; but mining virtually ceased by the early 1900s and was only continued in a small way until the 19409, a history similar to that of Tuscarora. The 71 Minerals operation was started in May 1975 and continued until late 1978 within the city limits of Tombstone on waste dumps; one was the' Lucky Cuss, Schieffelen's discovery, which had accumulated from the old underground operations. This waste material was mostly less than 50 mm (2 in.) in size, although there was some larger lumps. The grade was about 34 g Ag and 0.5 g Au per mt (1.0 oz Ag and 0.015 oz Au per st). The Tombstone dumps contained approximately 1,000,000 tons. The dumps and patented claims were held by a single owner, Tombstone Development Company, thus sufficient leaching material could be acquired from one source rather than dealing with a number of individuals, as is usual in putting together leaching ventures in old mining camps. 71 Minerals Ltd. was formed and a lease of the properties obtained. A site was selected close to the major mine dumps not far from down- town Tombstone. Pads approximately 90 m (300 ft) wide and 180 m (600 ft) long with an 8-degree slope were prepared using compacted old mill tailings as a base sealant on the pads. Mining was done at a rate of about 2,000 tons per day with a dozer, two scrapers, a front-end loader, and 30 ton trucks. The ore was dumped by the scrapers as it came from the dumps with no screening or crushing in 460 mm (18 in. ) layers and trimmed with the loader. Based on bulk sampling and laboratory testing, the majority of thegold and silver values were recovered within 30 days of leaching.

Jan 1, 1981

By H. Cecil Spicer

The results described in this article are based On field work conducted during the periods April-May, I939, and May-July, 1940. The United States Potash Co. is mining potash on Government land under a permit from the Department Of the Interior and the geophysical investigation was completed under a cooperative arrangemerit made between that company and the Conservation Branch Of the Geological Survey. The writer, a member Of the SeCtion of Chemistry and Physics of the Geologic Branch, was assigned to this investigation. Four definite objectives were in mind for the geophysical work in the studies over the salt deposits. The first was to determine the measure Of success that could be attained in this type of work with the resistivity methods that were to be employed. These methods had been introduced into the work of the Conservation Branch by Benjamin E. Jones for the investigation of dam sites, and have been used under his direction by the author for such work. If the method proved to be be an effort was to be made to contour the top of the salt beds and also the other formation boundaries known to be present in this area. Salt-water aquifers were to be studied in an effort to determine their boundaries, and an attempt was to be made to delineate the potash-bearing beds. Earlier Studies Others have made, and reported, restivity studies over saliferous deposits in different areas. Friedell and Messrs. Schlumberger2 reported geophysical work performed in the discovery of the salt domes of Alsace; Carrette and Kelly? described the geology of the same area. Leonardon and Kelly' published a resistivity curve obtained over the Hettenschlag dome, and a further discussion of this same area was given by the Messrs. Schlumberger6 in a communication. Messrs. Alty6 described studies on salt deposits in which the single-probe method was used. sinerez7 mentions that electrical methods were tried over salt deposits in Spain. Geoffrey and Charrin8 show a resistivity curve obtained over marl, gypsiferous marl and salt which is similar to that obtained over the New Mexico salt deposits. Kelly9 reported resistivity work performed with the ground Comparaor of Zuschlag over the salt deposits near Syracuse, N. Y., where the Salina formation is at a depth of 700 to 800 ft. Some structural studies on the potash basin of Alsace are described by Poldini.10 Another single-probe resistivity study, made over salt deposits in New Mexico, is briefly described by Heiland,11 through the courtesy of Harry Aurand, of the Midwest Refining co, Geological Features OF Area Covered The area discussed in this paper is in Eddy County, southeastern New Mexico, a

Jan 1, 1946

By A. M. Gaudin

IT is only in recent years that substantial progress has been made in developing a physico-chemical picture of the solid state. The molecular concept, so useful in dealing with gases, was naturally carried over to the field of crystalline solids; it has resulted in the firm implanting of erroneous concepts that only now are being eradicated successfully. Two simply written and effective books on the subject are Crystal Chemistry by Stillwell1 and An Introduction to Crystal Chemistry by Evans.' A more complete treatment of the subject is available in a book by Wells.' The monograph by Hückel4 also touches on a subject most easily perceived by reference to the brief introduction by Bragg,5 that master of the field. These texts make it clear that while some solids are built of molecules, many are built of ions, others of atoms connected in the form of giant molecules, and still others of cations and electrons. The various lattices in which these entities are systematically arranged, the joint use of several of these entities, and the transitional character of some of the bonds make for the great variety of crystalline solids. The purpose of this paper is to point out a most important corollary of present views on the structure of solids. In this connection the classification of solids in Table I is helpful. Atomic crystals are those formed by the noble gases, e.g., helium and argon. They are soft, sublime at very low temperature, of very low specific gravities, and not encountered in ores. Molecular crystals are uncommon among inorganic materials, common among organic materials. Typical examples from both inorganic and organic fields are sulphur, iodine, naphthalene, benzene, and carbon tetrachloride. These crystals are soft and have low specific gravities; where the molecules are small, the sublimation temperature is low. Filament and sheet crystals are rare. They are typified by elemental selenium and elemental arsenic, respectively. Graphite and molybdenite come near being sheet crystals. These crystals are soft in some directions, tough in others, sublime at various temperatures. Diamantine crystals, typified by diamond, are very few in number, stable at high temperatures, and extremely hard. Ionic crystals are common. Most salts, acids, and alkalies belong in the two classes of ionic crystals; examples are rock salt, fluorite, calcite, and angle-site. The salts, acids, and alkalies that do not belong in these classes are more properly regarded as transitional between ionic crystals, framework crystals, and diamantine crystals, e.g., ice and quartz. Fiber crystals are relatively uncommon mineral-ogically speaking, but common in the fields of living processes. Examples are asbestos, silk, cellulose, and wool. Many fiber crystals are so little known even now that their crystallinity may be doubted. Layer crystals, among the more interesting and useful of solids, include a wide variety of substances

Jan 1, 1956

By H. Cecil Spicer

The results described in this article are based On field work conducted during the periods April-May, I939, and May-July, 1940. The United States Potash Co. is mining potash on Government land under a permit from the Department Of the Interior and the geophysical investigation was completed under a cooperative arrangemerit made between that company and the Conservation Branch Of the Geological Survey. The writer, a member Of the SeCtion of Chemistry and Physics of the Geologic Branch, was assigned to this investigation. Four definite objectives were in mind for the geophysical work in the studies over the salt deposits. The first was to determine the measure Of success that could be attained in this type of work with the resistivity methods that were to be employed. These methods had been introduced into the work of the Conservation Branch by Benjamin E. Jones for the investigation of dam sites, and have been used under his direction by the author for such work. If the method proved to be be an effort was to be made to contour the top of the salt beds and also the other formation boundaries known to be present in this area. Salt-water aquifers were to be studied in an effort to determine their boundaries, and an attempt was to be made to delineate the potash-bearing beds. Earlier Studies Others have made, and reported, restivity studies over saliferous deposits in different areas. Friedell and Messrs. Schlumberger2 reported geophysical work performed in the discovery of the salt domes of Alsace; Carrette and Kelly? described the geology of the same area. Leonardon and Kelly' published a resistivity curve obtained over the Hettenschlag dome, and a further discussion of this same area was given by the Messrs. Schlumberger6 in a communication. Messrs. Alty6 described studies on salt deposits in which the single-probe method was used. sinerez7 mentions that electrical methods were tried over salt deposits in Spain. Geoffrey and Charrin8 show a resistivity curve obtained over marl, gypsiferous marl and salt which is similar to that obtained over the New Mexico salt deposits. Kelly9 reported resistivity work performed with the ground Comparaor of Zuschlag over the salt deposits near Syracuse, N. Y., where the Salina formation is at a depth of 700 to 800 ft. Some structural studies on the potash basin of Alsace are described by Poldini.10 Another single-probe resistivity study, made over salt deposits in New Mexico, is briefly described by Heiland,11 through the courtesy of Harry Aurand, of the Midwest Refining co, Geological Features OF Area Covered The area discussed in this paper is in Eddy County, southeastern New Mexico, a

Jan 1, 1946

By W. M. McKewan

Magnetite pellets were reduced in flowing hydrogen at pressures up to 40 atm over a temperature range of 350° to 500°C. The rate of weight loss of oxygen per unit area of the reaction surface was found to be constant with time at each temperature and pressure. The reaction rate was found to be directly proportional to hydrogen pressure up to 1 atm and to approach a maximum rate at high pressures. The results can be explained by considering the reaction surface to be sparsely occupied by adsorbed hydrogen at low pressures and saturated at high pressures. PREVIOUS investigation1,2 have shown that the reduction of iron oxides in hydrogen is controlled at the reaction interface. Under fixed conditions of temperature, hydrogen pressure, and gas composition, the reduction rate is constant with time, per unit surface area of residual oxide, and is directly proportional to the hydrogen pressure up to one atmosphere. The reduction rate of a sphere of iron oxide can be described3 by the following equation which takes into account the changing reaction surface area: where ro and do are the initial radius and density of the sphere; t is time; R is the fractional reduction; and R, is the reduction rate constant with units mass per area per time. The quantityis actually the fractional thickness of the reduced layer in terms of fractional reduction R. It was found in a previous investigation2 of the reduction of magnetite pellets in H2-H,O-N, mixtures, that the reaction rate was directly proportional to the hydrogen partial pressure up to 1 atm at a constant ratio of water vapor to hydrogen. Water vapor poisoned the oxide surface by an oxidizing reaction and markedly slowed the reduction. The enthalpy of activation was found to be + 13,600 cal per mole. It was also found that the magnetite reduced to meta-stable wüstite before proceeding to iron metal. The following equation was derived from absolute reaction-rate theory4,8 to expfain the experimental data: where Ro is the reduction rate in mg cm-2 min-'; KO contains the conversion units; Ph2 and PH2O are the hydrogen and water vapor partial pressures in atmospheres; Ke is the equilibrium constant for the Fe,O,/FeO equilibrium; Kp is the equilibrium constant for the poisoning reaction of water vapor; L is the total number of active sites; k and h are Boltzmann's and Planck's constants; and AF is the free energy of activation. Tenenbaum zind Joseph5 studied the reduction of iron ore by hydrogen at pressures over 1 atm. They showed that increasing the hydrogen pressure materially increased the rate of reduction. This is in accordance with the work of Diepschlag,6 who found that the rate of reduction of iron ores by either carbon monoxide or hydrogen was much greater at higher pressures. He used pressures as high as 7 atm. In order to further understand the mechanism of the reduction of iron oxide by hydrogen it was decided to study the effect of increasing the hydrogen pressure on rebduction rates of magnetite pellets. EXPERIMENTAL PROCEDURE The dense magnetite pellets used in these experiments were made in the following manner. Reagent-grade ferric oxide was moistened with water and hand-rolled into spherical pellets. The pellets were heated slowly to 550°C in an atmosphere of 10 pct H2-90 pct CO, and held for 1 hr. They were then heated slowly to 1370°C in an atmosphere of 2 pct H2-98 pct CO, then cooled slowly in the same atmosphere. The sintered pellets were crystalline magnetite with an apparent density of about 4.9 gm per cm3. They were about 0.9 cm in diam. The porosity of the pellets, which was discontinuous in nature, was akrout 6 pct. The pellets were suspended from a quartz spring balance in a vertical tube furnace. The equipment is shown in Fig. 1. Essentially the furnace consists of a 12-in. OD stainless steel outer shell and a 3-in. ID inconel inner shell. The kanthal wound 22 in. long, 1 1/2, in. ID alumina reaction tube is inside the inconel inner shell. Prepurified hydrogen sweeps the reaction tube to remove the water vapor formed during the reaction. The hydrogen is static in the rest of the furnace. The sample is placed at the bottom of the furnace in a nickel wire mesh basket suspended by nickel wire from the quartz spring. The furnace is then sealed, evacuated, and refilled with argon several times to remove all traces of oxygen. It is then evacuated, filled with

Jan 1, 1962

By D. E. Spiller

Introduction Precious metals recovery from ore can generally be accomplished using gravity concentration, flotation, and/or hydrometallurgical (leaching) techniques. The objective of this paper is to show why gravity concentration can be an important part of recovery systems that employ leaching as the primary unit operation. A brief discussion of modem gravity concentration equipment is also presented. Discussion Gravity concentration of ores has generated increasing interest in recent years. Reasons for this interest include: • Gravity concentration is environmentally attractive. There is little or no use of reagents. Hence, it is relatively nonpolluting. • The cost of cyanide has continued to increase. Therefore, cost savings may be realized whenever leaching feed tonnage can be reduced by preconcentration. • Compared to flotation and leaching, gravity equipment costs are low per processed ton. Field installation costs for gravity circuits usually are less because many' units are supplied as self-contained modules. Also, the cost required to supply services, particularly power, to a gravity plant site are also less. In situations where preconcentration at coarse particle size is applicable, significant grinding equipment savings may be possible. • Gravity circuit operating costs are also relatively low compared to typical flotation and leaching circuits. Reagents, power, maintenance, and manpower savings in a well-engineered gravity plant may be realized. Again, if grinding is reduced, significant power and steel (media and liners) savings are possible. •In recent years, more efficient gravity concentrating devices have been developed. Benefits to Precious Metal Leaching Gravity beneficiation can complement precious metal leaching in two ways. First, the recovery of coarse liberated values before leaching may reduce leach time requirements and may reduce reagent consumption. Second, gravity preconcentration can reduce the size of a leach plant by decreasing the quantity of material to be leached. Coarse gold and silver have been shown to leach rather slowly. Kameda (1949) and Habashi (1967) have investigated the kinetics of cyanide leaching systems. They concur that in a heterogeneous reaction, the rate of gold and silver dissolution is directly proportional to the surface area. Thus, the instantaneous rate of dissolution for spherical 0.37 mm (400 mesh) gold is theoretically -25 times faster than for the same amount of gold at .841 mm (20 mesh), based on data from Fuerstenau, Chander, and Abouzeid (1979). Conversely, coarse liberated, +.841 mm (20 mesh), gold is more readily recovered by gravity concentration than is fine, -.037 mm (400 mesh) gold. Therefore, it is apparent that the two recovery systems complement one another. Figure 1 data demonstrates the potential synergism. A sample of - 3.327 mm (6 mesh) Nevada gold-bearing ore was cyanide leached using conventional bottle-roll test procedures. Gold extraction was determined as a function of leaching time. A second sample split from the same leach feed material was hand jigged to remove a coarse heavy mineral fraction, including virtually all of the +.210 mm (65 mesh) liberated free gold. This second sample, with the coarse gold and heavy minerals removed, was subjected to an identical cyanide leach procedure. Figure 1 presents the resulting comparative extraction data. Note that the percent gold extraction for the sample containing no +.210 mm (65 mesh) free gold includes the coarse gold recovered by gravity. The data show that the sample containing coarse gold required about 72 hours of leaching time to achieve 80% extraction. This compared to about 22 hours of leaching time for 80% gold recovery from the sample that contained only -.210 mm (65 mesh) free gold. Thus, there was a 69% reduction in leaching time. The improved extraction data is not wholly attributable to coarse gold removal, but rather it was the combination of gold removal and rejection of other heavy mineral cyanide consumers or leach retardants. Further investigation was not warranted at this time. Preconcentration is the second manner in which leaching systems can benefit from gravity concentration. The premise is that preconcentration can reduce the quantity of leach feed, which, in turn, may reduce leaching costs. Figure 2 presents preliminary data developed by CSMRI for US Minerals Exploration (USMX). Centennial Exploration Inc., in agreement with USMX, is proceeding with evaluations to determine the suitability of various processing schemes for recovery of gold values from the Montana Tunnels property. The data shows how the ore can be preconcentrated by gravity techniques to result in a reduced feed tonnage to secondary extraction techniques, presumably flotation or cyanide leaching. Testing has shown that Reichert cones, followed by treating the cone concentrate on spirals, can deliver about 88% gold recovery in about 13% weight, that is, 87% weight rejection. Consequently, fine grinding and reagent costs are attributable to only 13% of the plant feed rate. Cost data is not yet available, but the potential exists for significant cost savings.

Jan 1, 1985

By E. T. Turkdogan, W. L. Worrell

The rate of reaction of hydrogen sulfide with ferrous sulfide was studied by measuring the initial rates of sulfidation of iron strips in hydrogen sulfide-hydrogen-argon mixtures at 670°, 800°, and 900" C. The time-dependent surface sulfur activity is derived from the instantaneous rate of sulfidation with the assumption that diffusion in the sulfide layer is in a pseudo-steady state with the gas-sulfide chemical reaction. The rate of sulfur transfer from hydrogen sulfide to the surface of iron sulfide is proportional to the partial pressure of hydrogen sulfide and inversely proportional to the activity of sulfur at the surface of the sulfide layer. The derived rate equation is based on the assumption that most of the surface sites on the chemisorbed layer of iron sulfide are occupied by sulfur atoms and that the slow rate-controlling reaction is the dissociation of hydrogen sulfide on the chemisorbed layer. The experimental results are in reasonable accord with this reaction model. 1 HE slow approach to parabolic growth rate in the sulfidation of iron in hydrogen sulfide-hydrogen mixtures is a manifestation of slow approach to surface equilibrium between the gas and the surface of the sulfide layer. For example, at 800°C and Fig. 7 in Part I, the parabolic growth rate begins after approximately 1 day of sulfidation time. With decreasing temperature and decreasing partial pressure of hydrogen sulfide, the time necessary to reach gas-sulfide surface equilibrium is much longer. These observations are similar to those reported previously by Turkdogan et al.' on the oxidation of iron to wustite in hydrogen-water vapor mixtures. The slow approach to gas-sulfide equilibrium is well-demonstrated by the results in Fig. 1 where the square of the weight gain per unit area, ( g S per sq cmI2, is plotted against time for gas mixtures having PH g//>H = 1.0 with 0, 25, 50, and 67 pct Ar at 800°C. The value of 1.5 X lo-' (g S per sq cm)' corresponds to almost complete sulfidation of the iron strip (- 0.05 cm thick) to iron sulfide. The points fall on S-shaped curves. If the inflection parts of the curves are considered to be linear, thus indicating parabolic growth rate and the establishment of gas-sulfide equilibrium, their slopes would have to be the same for a fixed ratio in the gas mixture. Such is not the case, and the slopes for the "linear" parts of the S-shaped curves are lower than the value when gas-sulfide surface equilibrium is established. The subject matter of this paper is the kinetics of the surface reaction of hydrogen sulfide with iron sulfide during the early stages of sulfidation of an iron strip. EXPERIMENTAL RESULTS The apparatus and materials used were the same as those discussed in Part I. In the present experiments of relatively short duration, a purified iron strip, 5 by 2 by 0.05 cm, which was suspended in the uniform hot zone of a vertical zircon tube, reacted with a flowing gas mixture of hydrogen sulfide-hydrogen-argon. The sample was suspended from a gold chain attached to a calibrated silica spring. The amount of sulfur picked up by the iron, which formed a layer of iron sulfide, was determined by measuring the displacement of a reference point on the silica spring, using a cathetom-eter. In all cases, the degreased sample was first annealed in a stream of oxygen-free dry hydrogen for several hours to remove any impurities such as oxygen, nitrogen, or carbon which might have been present on the surface of the sample.' The rate measurements were carried out at 670°, 800°, and 900° C in hydrogen sulfide-hydrogen-argon mixtures with pH2 s/Ph2 ratios from 4 to 0.1. In a few experiments of short duration no sulfur deposition was observed in gas mixtures with (comments concerning sulfur deposition at high pH s/ph ratios were made in Part I.) Typical examples of the results obtained are shown in Fig. 2 for two temperatures and two gas compositions. With the present experimental technique, reproducible rate data could be obtained only after a uniform

Jan 1, 1969

By Gerald G. Griswold, James O. Greenslade, Cherie Tilley, Richard Reseigh

INTRODUCTION The Harrison Western Corporation, a leading Denver based mine contracting and engineering concern, is presently engaged in sinking two 1,006 m (3,300 ft) shafts for the Phillips Uranium Corporation at their Nose Rock Project, approximately 13 miles northeast of the small community of Crownpoint in McKinley County, New Mexico. The Nose Rock Project is the first attempt by the Phillips Uranium Corporation to tap the deep uranium reserves in what has become known as the Grants Mineral Belt. (See Figure 1) Project Description Phillips Uranium Corporation's plan for the large 2700 metric ton per day (2950 tons/day) mining facility calls for a series of deep access and ventilation shafts ranging from 4.27 m (14 ft) to 5.49 m (18 ft) in diameter to approximate depths of 1,006 m (3,300 ft). The initial pair of shafts consists of one production shaft and one ventilation shaft separated by a distance of 91 m (300 ft). The interbedded layers of sedimentary sandstones and shales to be penetrated by the shafts contain several major water producing aquifers, the deepest being the mineralized zone called the Westwater Canyon Member of the Morrison Formation. A series of temporary and permanent water pumping stations is planned. Generally, the temporary stations are located above major aquifers to facilitate water removal while sinking through the aquifer and the permanent stations constitute what, in the final mode, will be the mine dewatering system. In addition, Phillips Uranium Corporation has In- stalled and is maintaining a system of depressurization wells that temporarily pump the major aquifers and considerably reduce the water inflows during shaft construction. The major aquifers are also chemically grouted prior to sinking. Site work for the project was initiated in the fall of 1976. Full scale shaft sinking commenced in November of 1977 on the 4.88 m (16 ft) diameter ventilation shaft and on the 5.49 m (18 ft) production shaft by another contractor. Harrison Western Corporation began work on the project on November 4, 1979 wlth the production shaft at a depth of 633 m (2,076 ft) and the ventilation shaft at a depth of 474 m (1,554 ft). This paper will address only the portion of shaft sinking completed by Harrison Western. Geology and Hydrology The Nose Rock Project is located on the Chaco Slope in the southern extreme of the San Juan Basin in northwest New Mexico. The southern San Juan Basin is generally bound by the Defiance Uplift to the west, the Zuni Uplift to the south and the Nacimiento Uplift to the east. The Grants Mineral Belt occupies most of the southern portion of the San Juan Basin and this project is located on the northern extreme of the Grants Mineral Belt. The San Juan Basin is comprised of sedimentary rock of continental, marginal-marine and marine origin, that dip northward from the Zuni Uplift and Chaco Slope into the interior of the San Juan Basin. (See Figure 2) Major Formations The major geologic formations to be penetrated range from mudstone and shales to siltstones and sandstones. The sandstones are highly productive aquifers which, under static conditions, would flow artesian. Water temperatures in the aquifers are high and therefore are a force to be dealt with. Temperatures range from 18ºC (65OF) in the upper aquifers to 48ºC (118º'F) in the lower. The mudstones are generally bentonitlc. (See Figure 2) GALLUP SANDSTONE: The Gallup Sandstone is the first major regressive wedge in the San Juan Basin of the Cretaceous era and at this project is about 35 m (115 ft) thick. It is medium grained and prior to depressurization carried a hydrostatic water pressure of over 72.5 kg per cm2 (1,031 psi) which 1s artesian. Compressive strength ranges from 334.7 kg per cm2 (4,760 psi) to 421.8 kg per cm2 (6,000 psi). Water temperature is approximately 30°C (86°F).

Jan 1, 1982

By C. G. Dunn, E. F. Koch, K. T. Aust

Strain-induced grain boundary migration was studied in a series of silicon-iron (3% pct Si) bicrystals of controlled orientations. Each bicrystal was given a 7 pct cold-rolling strain rind annealed at 1100°C. The direction of boundary migration was found to depend on orientation; results for several orientations related by a common [110] axis are given. Analysis of the micrographic and X-ray data is made in terms of the residual strain-energy densities within the crystals (energy per unit volurne) and a driving force on the boundary due to an energy density difference across the boundary. Relative strain energies were obtained for the various orientations investigated. A CHROME-acetic acid electroetching method for revealing dislocation sites in silicon iron was previously applied to clarify the structural features and the energetics involved in strain-induced grain boundary migration.',' The present paper is a continuation of this study, but is primarily concerned with the influence of crystal orientation. Sperry, as reported by Beck,3 attempted to determine the factors that influence the preferred growth of one grain over another in aluminum due to strain-induced boundary migration. He found that the particular grain of a pair which work hardened more was invaded, although exceptions to this correlation were noted. The index of work hardening was determined from microhardness measurements of each grain before and after cold-rolling. In the present study, orientation itself was taken as a useful variable for studying the behavior of individual grains in a bicrystal and the direction of boundary migration, since the extent of work hardening is orientation dePendent." The effect of strain on boundary migration is evident from a consideration of driving forces. Thus, in the absence of inclusions, the driving force (per unit area of boundary) for growth of grain A into grain B when a bicrystal is strained and annealed may be expressed as follows:2

Jan 1, 1960