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By P. Somasundaran, R. D. Kulkarni

Reagentizing at elevated temperature, reported in the past as beneficial for the flotation of hematite using oleate, is studied here as a function of collector concentration, solution pH and ionic strength at various levels of conditioning temperature. The study revealed strong interactions between variables; particularly, the effect of conditioning temperature was found to strongly depend on the ionic strength of the solution. Thus, while an increase of conditioning temperature at lower ionic strengths or that of ionic strength at lower temperatures resulted in an increase of both flotation and grade, an increase of the former at higher ionic strength or that of the latter at higher temperatures caused a significant decrease in both responses. These observations have been explained in terms of the increased chemisorption of oleate at elevated temperatures and the temperature effect of ionic-strength on the salting out of the oleate from the bulk solution. The above effects which were first observed during Hallimond cell flotation tests were subsequently tested with Denver cell using low-grade iron ore. The results obtained using the two test procedures were in agreement with each other. The implications of these effects and interactions for process control of optimum flotation performance must be noted since variation in the levels of the above parameters are likely under plant conditions.

Jan 1, 1978

By John J. Collins

[CONTENTS PAGE Purpose and scopeI Core samplingI Sludge sampling.....7 Combining core and sludge assays13 Deviation and surveying of drill holes17 Conclusions24 Acknowledgments25 Bibliography25] PURPOSE AND SCOPE The purpose of this paper is to review a few of the problems involved in the interpretation of diamond-drill core and sludge samples, with the hope that it will stimulate discussion and bring forth some of the information on the subject that has been accumulated by various organizations. The release of these data would benefit the mining industry as a whole. Particularly valuable would be the details of drilling programs that have been tested by actual mining operations, as most of the available published material is unsupported by production records. The scope of this paper is limited to a few of the commonest problems of interpreting diamond-drill core and sludge samples and the deviation of holes. It does not include the description of routine operations performed by the drillers, nor the estimation of ore reserves. The methods of calculating reserves have been described 25,26,31,32.50,65 but more information is needed on the results shown by actual mining operations. CORE SAMPLING The accuracy of diamond-drill-hole sampling depends in large measure on the percentage of core recovery. As a general rule, the longer the run, the poorer is the recovery. Although the longer runs allow cheaper drilling costs, the determining factor should be the percentage of recovery desired. The problem is one of balancing accuracy against costs. Holes of larger diameter may show improved recovery, except as Joralemon* points out that there are some conditions in which small holes give better core recovery than large holes. This is particularly true, he says, in rocks like shattered quartzite, where larger core tends to break in angular fragments and grind up, while the diameter of smaller core is less than the distance between joint planes and grinding is not so serious. In a large measure the length of the sample run should depend on the type of deposit. Favorable drilling may allow uniform sample runs of 5 ft., 10 ft., or perhaps 20 ft. In veins or beds of relatively narrow widths and changing characteristics, however, the ore zone may be overrun and ground in a core barrel full of waste rock. Generally it is desirable to break the sample at a change in the rock or ore. Such a change, often indicated by a color change in the sludge water, should be a signal for the driller to make a "dry" block and to pull out that run regardless of the length. Such a procedure permits the segregation of waste from ore samples so

Jan 1, 1946

The information in Tables 1 and 2, on the operations in the Dutch East Indies and North Borneo, has been kindly furnished to the Institute through the courtesy of Mr. J. August Kessler by Mr. B. H. van der Linden. It affords a very good picture of the situation in that region for the year 1933.

Jan 1, 1934

By Frank Firmstone

(Ottawa Meeting, October, 1889. Substituted for the briefer note on the same subject. pre sented at the meeting and subsequently distributed in preliminary pamphlet edition.) Prof. H. Hoefer's theory of blasting was published in the Oesterr. Zeitschrift, xxviii., 1880, and xxix., 1881; and Part 111. in Nos. 15, 16 and 17, xxx., 1882, and subsequent numbers of that

Jan 1, 1890

By Kichizo Niwa, Toshio Yokokawa, Mitsuo Shimoji, Yoshihiko Watanabe, Satoshi Kado

A LTHOUGH a systematic research on diffusion in liquid metals has not been carried out, partial studies have been developed by various workers in several systems. A few recent papers among them have shown that this line of approach is quite useful for understanding the structure of the liquid state. Furthermore, it has been found in kinetic

Jan 1, 1958

By W. C. Hagel, H. J. Beattie

Seven austenitic alloys of varions base compositions and minor-alloy additions were solution-treated, aged systematically between 1200oand 1800oF, and examined by X-ray and electron metallography. Intragranular preczpitations of µ, Laves, s, ?', Ni3Ti, and x phases were observed as a function of composition and aging time and temperatwre. Phase solubility limits were detevtnitzed within 100Fo intervals. These inter metallic compounds fall into two distinct general classes, and whichever class predomznates depends on base composition. It has become increasingly evident that multicom-ponent austenitic alloys are well characterized by their precipitation processes. Since certain groups of elements act as one, the relationships among these processes are reasonably simple; complete identification of such processes is usually attainable by a systematic aging study with a combination of techniques centered on microscopy and diffraction. Several nickel- and cobalt-base alloys illustrating cellular precipitation and its interaction with general precipitation were reported previously.1 The group of alloys covered in the present paper demonstrates precipitation-hardening reactions involving two distinct classes of intermetallic compounds where the predominating class appears to depend on base composition. This dependency ties in with a crystal-chemistry regularity first observed some twenty years ago by Laves and Wallbaum but never amplified to our knowledge. Results of electron-microscope and X-ray diffraction studies on systematically aged hot-rolled alloys known commercially as S-816, S-590, Rene-41, Incoloy-901, M-308, and M-647 are reported here. Some of these alloys have previously undergone minor-phase analyses by other investiators. Alloy S-816 was investigated by Rosenbaum, Lane and Grant,3 and Weeton and Signorelli.4 Rosenbaum found only CbC in hot-rolled bars. Lane and Grant found CbC and a small amount of M6C in the cast structure and stated that both carbides form during aging, most of the precipitation being CbC. Weeton and Signorelli found CbC, M23C6 and a weak indication of a phase after a slow step-down cooling cycle from 2250°F. Rosenbaum also investigated hot-rolled samples of S-590 and identified CbC and M6C. Preliminary information on Rene-41, gained partly from the present work, was reported by Morris.5 Long-time precipitation phenomena in Incoloy-901 at 1350°Fwere investigated by Clark and Iwanski.B heir raw data re- semble those of our present heat with 0.1 pct B, while their interpretation of these data resembles our interpretation of data from another heat with only 0.001 pct B; they made no statement as to boron content. No previous minor-phase studies of alloys M-308 or M-647 have been reported. EXPERIMENTAL METHODS Table I gives alloy compositions in both weight and atomic percent. Specimens were solution-treated from 1700º to 2200ºF, aged at logarithmic-time intervals up to 1000 hours between 1200 and 1800 F, and examined in accordance with procedures previously described in detail. ' ' Phase extractions were carried out in electrolytic cells containing 800 ml of either 7 pct HC1 in denatured ethanol or 20 pct H3PO4 in water. After electrolysis for 48 hr at 0.1 to 0.2 amp per sq inch, residues were separated by filtration or centrifuging. X-ray powder patterns of residues were recorded on a diffractometer for accuracy and on film for sensitivity. Lattice parameters were calculated by least-squares analyses of indexed sin 8 values, and relative abundances were estimated from intensities of strongest lines of each phase. These phase abundances denote relative amounts with respect to each other rather than to the alloy. Mechanically polished specimens were etched in a freshly mixed solution of 92 pct HC1, 5 pct H2SO4, and 3 pct HNO3. Parlodion replicas for the electron microscope were chromium-shadowed in high vacuum at a glancing angle of 20deg. All electron micrographs are reproduced here with the shadowing source above. The correspondence betweenelectronmicrostructures and phases identified by X-rays was established by a high redundancy of correlation between relative amounts at different stages of aging and examination above and below critical transformation or solubility temperatures. EXPERIMENTAL RESULTS S-816 and S-590—The phases found in S-816 and S-590 after various aging and solutioning treatments are listed in Table 11. These data and the observed

Jan 1, 1962

By L. Guttman

THE equilibrium diagram of the indium-thallium system was of interest to us in connection with a study of the superconducting properties of metallic solid solutions in progress at this Institute. For this purpose, a series of alloys was prepared covering the range from pure indium to 75 atomic pet TI, and X-ray diffraction patterns were obtained. Roughly speaking, the results indicated a region of continuous decrease in the axial ratio of the face-centered tetragonal structure from the value ca. 1.08 in pure indium to unity at about 23 atomic pct TI. From this concentration to the solubility limit, the structure was face-centered cubic, a form not reported by Hansen.1 At this point we became aware of the work of Valentiner,2 who had found the same structures at room temperature but had not investigated further the relationship between them. To study the transformation f.c.c.??f.c.t., and to clarify the phase diagram, we undertook the work reported in this paper and that which follows." Preparation of Alloys Pure indium and thallium* (both about 99.9 pct, as estimated from spectroscopic analyses) were weighed out in quantities sufficient to prepare 10 to 25 g of alloy of the desired concentration. (Occasionally indium was mixed with a previously pre- pared solution.) The metals were melted over a flame, in an open graphite crucible, stirred with a graphite rod, and poured into a graphite trough. The rough slug was hammered and swaged into a rod of 2 to 3 mm diam, and annealed in a drying oven at about 125°C for 1 to 2 days. Samples were taken from the rod for analysis, as well as for diffraction and other measurements. The thallium was determined by electrometric titration, using a modification of the method of Beale and co-workers.' The precision of analysis was generally about 2 0.2 pct of the thallium content. The rods were sometimes found to vary in thallium content as much as 1.5 pct from end to end, but since analyses were also made close to the segments used in the various studies, the composition was usually known as accurately as the analyses could be made. Where one less significant figure is given, the error is estimated to be ±0.4 pct of the thallium content. X-Ray Diffraction Measurements Three different cameras were used: (1) A 7 cm Debye camera, with oscillating specimen (manufactured by the Picker X-ray Corp., Cleveland, Ohio); (2) a 9 cm diam Debye camera of the type designed by Bradley;" (3) a 10 cm diam symmetrical focusing back-reflection camera (manufactured by Geo. C. Wyland, Ramsay, N. J.). Samples were prepared from the homogenized rods, either by filing under liquid nitrogen, or more often, in the form of wires or foils made by working at room temperature or liquid nitrogen temperature. Sharp patterns were obtained from specimens annealed at room temperature, although higher annealing temperatures were also used (cf. below). Generally, copper radiation was used; a few patterns were obtained with

Jan 1, 1951

By John Blatchford, H. O. Hofman

The leading antimony mineral is stibnite. In smelting stibnite ore two processes are available, precipitation and roasting-reduction. The former is suited only for high-grade ores. As low-grade ores are more common than high-grade, roasting-reduction is of greater importance than precipitation. In the roasting process the aim may be to leave the oxidized antimony in the ore, or it may be to volatilize as much of the antimony as possible, collect the volatilized oxide as a rich intermediary product and smelt it for antimony, leaving the gangue poor enough to be considered a waste product. Whichever way the roast is conducted certain difficulties inherent in stibnite are encountered. These are: 1. The low melting point of stibnite which, according to Pélabon,' is 550°C., according to Wagemann2 540°C., and according to Borgstroma 546°C. 2. The ignition temperature: According to Friedrich,4 stibnite, if heated in air, begins to oxidize at 290°C. if the size of a grain is 0.1 mm. in diameter; at 343", if 0.1 to 0.2 mm.; and 430" if 0.2 mm. 3. The fusibility of a mixture of Sb2S33 and Sb203 which in the form of kermesite (Sb2S3)z.Sbz03 melts at 517°C.6 4. The volatility of Sb2Ss and SbzOs, for which no numerical data appear to exist, although practical experience has shown that they are volatile at low temperatures. As regards the oxidation of metallic antimony, we have the experimental evidence of C. F. Plattner6 that when fused and brought to a red heat, it burns with a bluish-white flame to Sb2Oa which passes off as a

Jan 1, 1916

By Richard Akerman

At the International Sessions of the Iron and Steel Institute of Great Britain, the American Institute of Mining Engineers and the Verein Deutscher EisenhUttenleute, held in Allegheny City, Pa., in October, 1890, Sir James Kitson, then President of the Iron and Steel Institute, presented an account by Sir Henry Bessemer of the origin of the process which bears his name.? The paper graplhically told how, after the first successes immediately following the first reports given at Cheltenham of the new process, there rapidly succceded such obstacles and difficulties in its practical application, that the whole matter was nearly abandoned in 1858. Suddenly, however, the situation changed, so that at length it became possible

Jan 1, 1894

By F. F. Colcord

THE electrolytic separation of silver and gold has been practiced by the refineries in the United States for a good many years; and probably because of frequent visiting between officials of plants and the consequent exchange of views, operations in the various silver and gold refineries are very similar. We find, for instance, they practically all use electrolytes of approximately the same composition, which, no doubt, is more the result of experience than of studies of electrolytes. At the new electrolytic parting plant of the U. S. S. Lead Refinery, Inc., East Chicago, Ind., considerable attention has been given to the, composition of electrolytes, especially to their conductivity and their effect on the character of the silver deposit. We are not aware that anything has been recently published on this subject and are, therefore, presenting such data as we have with the idea that, although it will not be wholly new, it may stimulate interest in the subject. EFFECT OF COPPER CONTENT ON CONDUCTIVITY The first work, was to determine the specific conductivity of silver nitrate and copper nitrate solution. Concentrated solutions of silver nitrate and copper nitrate were prepared by dissolving analyzed chemically-pure salts in distilled water, and determining the silver and copper in each. Definite amounts of the concentrated solutions were taken, mixed and diluted to a definite volume. The silver and the copper were determined in each of these solutions and the conductivity was, then determined. The plotted results are shown in Fig. 1 and 2. The effect of increasing quantities of silver and, copper is readily seen. A comparison of the two sets of curves shows conclusively the benefit of holding the copper content of the electrolyte above 50 g. per liter, as its

Jan 2, 1926

By J. E. Pogue

It is the purpose of this paper to attempt to establish three theses which may be stated in advance as follows: 1. The crude oil potential is the accumulation of surplus initial production. 2. The crude oil potential is a semi-inventory and therefore is a causal factor in the price of crude petroleum. 3. The price of crude petroleum no longer correlates with above-ground inventories but does correlate with corrected inventories (i. e., above-ground storage plus the inventory equivalent of the crude oil potential). The factors and principles set forth in this study are thought to yield an approximate answer to a number of questions of active interest in the petroleum industry today, to wit: (a) How long would be required to eliminate the potential if all drilling ceased? (b) What would be the indicated crude oil production of the United States in 1931 if proration were abandoned? (c) What economic change would be necessary to warrant a higher price for crude oil? Definitions For the purposes of this study the following definitions may be stated: The crude oil potential in the United States is the quantity of oil that all the oil wells would make the first 24 hr. if permitted to flow unrestricted. The surplus potential is the above-mentioned quantity minus the volume currently produced. Initial production is the first day's unrestricted flow of an oil well. Aggregate initial production is the sum of the initials of all wells completed during a year. Surplus initial is the initial not needed to bring production into balance with demand. The surplus initial is equal to the crude oil potential minus the current rate of production. The annual production-equivalent of the crude oil potential is the volume of oil that would be produced in one year if all wells were permitted

Jan 1, 1931

By John M. Cummings, Warren. Harry V.

THE Geology Department of the University of British Columbia has undertaken the task of examining the ores from as many as possible of the gold mines of British Columbia. The object of this work is two- fold. First, it is known that detailed mineralographic studies are useful in attacking ore-dressing problems, and these studies are intended to be helpful to mill operators. Second, it is hoped that mineralogical and mineralographical studies will prove useful adjuncts to those of lithology and structure in throwing more light on problems related to the origin of the deposits. The paper shows that gold, for all practical purposes, is not present in an ore mineral in solid solution nor as a eutectic with any mineral; if the latter were true the gold particles would be distributed equally throughout that mineral. The gold occurs either as native gold or as a gold-silver telluride and is not distributed regularly through any mineral or minerals. The relationship between the gold or gold-bearing telluride and the associated minerals affords a means of classification that is not only simple but also appears to be directly related to the geological nature of the deposit, which may be summarized as follows: 1. Disseminated Gold Type.-Precious minerals in extremely small grains, which are distributed without regard to grain size, fractures or grain boundaries: (1) Hedley variety-gold in native form; (2) Surf Point variety-gold predominantly as telluride. 2. Veining Gold Type.-Precious minerals in grains of various sizes, which occur mainly along fractures and grain boundaries: (1) Cariboo gold quartz-goldin native form. (2) Waneta variety-gold as telluride. Application Te Ore Dressing These mineralographic studies have proved to be of value to mill operators, and future studies of a similar nature should prove increasingly useful because every year provides a further opportunity to correlate

Jan 1, 1937

By Rodney P. Smith

The rate of motion of the boundary between a single-phase a-iron region and a two phase a-iron plus ?-iron, or a-iron plus cementite region has been measured on decarburization at several temperatures between 500" and 865°C. These data, together with data for the carbon content of a-iron at the boundary, yield the diffusivity of carbon in a-iron. The activation energy for carbon diffusion is 19.8 kcal per mole for the temperature range —50° to 150°C and increases to an average value of 23.0 kcaL per mole for the temperature range 727" to 865°C. AS part of an investigation of the diffusivity of carbon in iron using a steady-state method,' the diffusivity of carbon in a-iron was determined at the temperatures 802" and 851°C. The diffusion constant thus obtained was larger, by nearly a factor of two, than that predicted from the combined results of stanley2 and of Wert.3 It seemed desirable, therefore, to continue the investigation. Since the temperature range in which the steady-state method can be conveniently used is limited, we have chosen a decarburization method, based on the laws of diffusion in metal accompanied by a phase change.4,5 If the initial carbon content of the Fe-C alloy is such that two phases coexist at the decar-burizing temperature* and decarburization is car- ried out such that the surface is maintained at substantially zero wt pct. C, the carbon distribution after a time, t, will be as shown in Fig. 1. The boundary between the single-phase and two-phase regions moves from y = 0 to y = x in the time, t, where x is proportional4 to tl". If the initial carbon (content of the sample is Ci, and CB is

Jan 1, 1962

By S. R. Goodman, Hsun Hu

A study has hem made of the formation of annealing textures in an 18-8 austenitic stainless steel (Type 304L) from various deformation textures obtained by rolling at different temperatures. When the deformation texture is a mixture of the ferritic type and the brass type owing to the pres -ence of both martensitic ferrite and retained aus-tenite in the specimen, recrystallization takes place by the growth of the existing austenite phase. In a previous report,' it was shown that the rolling texture of austenitic stainless steel (Type 304L) changed gradually from the brass type to the copper type with increasing temperature of deformation above 200°C. These changes are similar to those in high-purity silver2,3 and electrolytic copper;4 a brass-type texture is favored at low rolling temperatures, whereas a copper-type texture is favored During the course of rolling -texture transition from the brass type to the copper type, the subsequent recrystallization textures change accordingly. The orientation relationship between the annealing textures and the various rolling textures, being consistent with previous observations on various fcc metals, can be described as [Ill] rotations of approximately 25 to 40 deg. Carhide precipitation may influence the annealing textures. at high rolling temperatures. Furthermore, the annealing textures in high-purity silver5 and electrolytic copper4 were found to depend entirely on the prior deformation texture. From a copper-type rolling texture a strong cube texture will form upon recrystallization, whereas from a brass-type rolling texture the annealing texture will be quite different from the cube orientation. In an earlier comm~nication,6 the formation of a strong cube texture in 18-8 austenite stainless steels (Types 304 and 304L) was reported briefly by the authors. The present paper constitutes the results of a complete study of the annealing textures obtained from a

Jan 1, 1965

By H. W. Miller, V. H. Wilhem

Although the year 1933 was a period of uncertainty, considerable new development was initiated, with a high percentage of favorable results, for owing to financial conditions only projects of merit were proposed and developed. Unfavorable marketing conditions caused severe financial losses to refinery and sales departments of nearly all companies during the first half of the year. In anticipation of stabilized Government control, earnings were generally favorable during the third quarter but failure of the Government to take legal action against violators of the proration orders, and lack of agreement on a definite plan of curtailment, resulted in considerable overproduction and demoralization of the market structure during most of the final quarter. However, toward the close of the year Government action against violators of the Oil Code had a tendency to decrease overproduction materially and give the market a firmer tone. As a whole, the price structure of crude oil was maintained at a high level during the year; in fact, at a much higher level than the price of refinery products warranted. At no time during the year was production within 10,000 bbl. daily of the state allotment, overproduction of crude reaching a peak of 70,000 bbl. on Sept. 7, average daily average for the year being about 27,000 barrels. Numerous plans for equitable curtailment were prepared and tested during the year, none of which fully solved the many and intricate problems faced by operators who were in most cases willing to curtail if they could feel that cooperation was being practiced by their neighbors. Outstanding events in California oildom during the period under discussion may be classified under the following headings: 1. New discoveries. (a) New development in proven areas. (b) Deeper zones in settled pools. 2. Unproductive wildcat operations. 3. Whipstocking practice and procedure. 4. Progress of unit and orderly plans of development.

Jan 1, 1934

By Sherwin F. Kelly, Bela Low, William B. Creagmile

Electrical methods and instruments for geophysical exploration have been almost exclusively applied, during these years of development of the art, by a few companies specializing in this field. The control of patents, the cost of the instruments and the general lack of published information on details of field procedure and office interpretation have given these owners a monopoly in carrying out electrical surveys. The development of the Megger Ground Tester1 seems likely to change this situation, and to enable mining engineers and geologists, without special training in geophysics, to carry out simple reconnaissance electrical surveys. Nevertheless, the need for such special training and experience in planning surveys and interpreting their results remains, and probably i always will remain, indispensable for a successful outcome. The unique thing about, the Megger Ground Tester, which gives rise to this hope for its general use, is its simplicity of operation. The four binding posts of the instrument are connected by insulated wires to four stakes driven into the ground at appropriate points. The crank of the Megger is then turned, and the resistance of the ground between the two inside stakes is read directly, in ohms, by the deflection of a pointer over a scale. The apparatus is shown in Fig. 1. Fundamentally, the principle of operation is that of determining the resistance of a four-terminal conductor, as applied by Frank Wenner to the measurement of earth resistivity. "A four-terminal conductor is a conductor provided with two terminals to which current leads may be connected and two terminals to which potential leads may be connected. The resistance of such a conductor is the difference in potential between the potential terminals divided by the current entering and leaving

Jan 1, 1932

By J. J. B. Rutherford

IT is now well known that troublesome intercrystalline corrosion may occur in austenitic stainless steels following exposure of the metal to a temperature within the range 1000° to 1500° F. (540° to 815° C.). The present paper describes a satisfactory method of estimating the extent of such corrosion, based on the measurement of the electrical resistance of a specimen before and after attack. This new method enabled us to study quantitatively the effect of several factors upon intergranular corrosion in the 18 Cr, 8 Ni type of alloy. The results show that susceptibility to this attack increases with increasing carbon content and grain size and appears to pass through a maximum for certain combinations of temperature of sensitization and period during which the alloy was maintained at that temperature; and are in complete accord with our interpretation of the mechanism of this phenomenon. The method is probably applicable to other metals or alloys subject to intercrystalline attack, such as the aluminum alloys of the duralumin type. The methods hitherto in use for estimating the degree of intergranular attack fall into three types: (1) microscopic examination,1 (2) macroscopic examination of fractures, and (3) determination of the time required for complete failure or disintegration .2 None of these lends itself very well to a measurement of the extent of corrosion. The first two are qualitative in nature and the third provides an arbitrary value largely dependent on individual judgment, since failure is a progressive phenomenon and not a sudden event. Our experience is that weight-loss determinations, although valuable in some types of corrosion investigations, bear no simple relation to intercrystalline corrosion in this type of alloy, as is to be expected since the phenomenon probably involves only the thinnest films between adjacent metallic grains.

Jan 1, 1932

By Richard H. Sibson

Changes in seismic style along the San Andreas fault system appear to correlate with strike-parallel variations in regional heat flow. Large earthquake ruptures are associated with colder segments of the fault zone, while comparatively high levels of microearthquake activity and small to moderate shocks occur along the hotter segments, often in association with aseismic creep. Such behavior is consistent with geotherm and strain rate dependent profiles of shear resistance versus depth, constructed for quartz-bearing rocks. These profiles suggest that the transition from frictional to quasi-plastic behavior with depth should increase by a few kilometers passing from the hotter to the colder portions of the fault zone, giving rise to long-wavelength concentrations of distortional strain energy near the base of the seismogenic zone in the cold segments. Some support for this hypothesis comes from the observed deepening of microseismic activity passing northwest and southeast from the central Californian active region to the currently locked, ~400 Ian segments of the San Andreas fault that ruptured in 1906 and 1857.

Jan 1, 1982

By D. D. Porter, C. Fairhurst

Crack propagation in the region of a statically pressurized borehole is investigated to determine a role of the sustained borehole pressure following detonation in a blast. The case of a single-hole bench blast is reduced to a plate model, which is considered both theoretically and experimentally. Based on the principle of least work, it is hypothesized that the path of any crack in the plate will coincide with one of a family of maximum principal stress trajectories. These trajectories were computed, and critical experiments in glass, designed to test the effects of controlled crack origin and of changed trajectories from different loading configurations, confirm this hypothesis. It is concluded that under ideal conditions the crack path can be predicted and that cracks can be produced in the absence of either high-amplitude stresses or stress waves. Energy considerations for crack extension are discussed, and, based on the strain energy distribution, a relationship between hole burdens and spacings is revealed, a critical burden is demonstrated, and a maximum crater width is shown to exist.

Jan 1, 1971

By Joseph T. Singwald

INTRODUCTION THE purpose of this chapter is to present the diagnostic features (geologic, mineralogic, chemical, and physical) of the principal types of hypogene ore deposits recognized in current genetic classifications, and to classify the ore deposits of the western United States into those types. The genetic divisions used and the criteria determining them are essentially those followed by Lindgren in his Mineral Deposits. Deviations from Lindgren represent either changed conceptions since 1928 (the date of the third edition of Mineral Deposits) due to advance in knowledge or the inevitable differences of opinion between experts in active fields of investigation. Though nineteen economic geologists have been given free hand in presenting their particular topics, there are no fundamental departures in the chapter from the principles set forth by Lindgren. It would be entirely beyond the capacity of a single chapter to give a comprehensive geologic description of all the ore deposits of the western United States. Descriptions of individual deposits have been restricted to those features that are of most diagnostic genetic value. All of the more important deposits receive that much attention. Deposits of lesser economic importance and those inadequately known geologically are treated more briefly or merely cited under what seems to be their proper genetic assignment. The geographic limits of the descriptive matter are the Black Hills and the United States between the Rocky Mountains and the pacific Coast. Capacity of the chapter has made it necessary to impose these geographic limits.

Jan 1, 1933