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By Robert H. Richards, E. E. Bugbee

Friends often ask how accurate the work of our little stamp mill is, or express the opinion that a little mill cannot do good work. As a reply we would like to place on record the results of a few tests. There are two periods of work in our laboratory; the fall term, when the class collectively goes through all our chief laboratory-processes, and the spring term, when the students work up their theses, each electing some one process or investigation and devoting himself wholly, or almost wholly, to that. Some of the tests, the results of which are recorded in this paper, were made in the fall term; the preparation of the apparatus, the sampling and the assaying being done largely by assistants, with the aid of the students. Others were made in the spring term as thesis-work, and the results are due wholly to. the students. The complete " tree " of our process is patterned after the-

Jan 1, 1904

The Mining Act (1992) and the Petroleum Act (1980) provide for the Government of Papua New Guinea (PNG) to take up equity holdings in mining and petroleum projects. The price the Government pays for its share is based on the historical cost of exploration and development on the project to the date of government equity acquisition. The equity level to be acquired is not fixed and ranges up to 30o for mining and up to 22.5s for petroleum at the discretion of the Government of the time.The objective of this paper is to examine the pros and cons of State equity holdings in PNG from the point of view of both the State and the developer. Using an economic model of the PNG mining taxation system an assessment is made of the effective return on investment received by the State from such equity holdings. The results are compared with government revenues from other taxation measures.

Jan 1, 1994

By R. Gong, R. Bhaskar

A coal mine study was conducted to evaluate the effectiveness of a compressed-air, foam spray system installed under a continuous miner boom and directed to cover the pan and the gathering arm. The study's objectives were to evaluate the foam, underboom sprays' effect on: • the respirable dust concentration in the ambient air, and • the quartz concentration in the airborne, respirable dust. The foam generation and delivery system's engineering design is described in the paper, followed by descriptions of the mine and the dust sampling strategy. The data were analyzed to study the foam's effects on respirable dust and quartz concentrations at the continuous miner cab, the face return and the intake. The data indicate reductions in the dust's quartz content, ranging from 19.7% to 64.6%, in eight of 11 comparisons of the foam vs. no foam cuts. In addition, airborne intake dust reductions were observed in eight of 11 comparisons.

Jan 1, 1993

By George L. Porter

Mr. President and Gentlemen of the Institute of Mining Engineers: . Unofficially representing the people of the vicinage, it is my pleasant duty to welcome you to the city of Bridgeport, to the valley of the Naugatuck, to the State of Connecticut. The importance and wide-reaching influences of the investigations for which your Institute is organized, the beneficial results which have directly and indirectly blessed mankind from your and kindred studies, the distinguished position which has been achieved in the scientific world by the Institute as a society, and the personal reputation which is the proper recognition of the ability and knowledge of its individual members, assure all that in attempting to honor you we are ourselves honored. In the republic of knowledge no fictitious rewards dignify the incompetent and the ignorant—the attested success of inventions and discoveries in the workshop of nature differentiates her real citizenship. Your present place of meeting is wisely selected ; for this senti-

Jan 1, 1895

By S. L. Hoyt

ABOUT three years ago eight standard steels were prepared for the cooperative investigation of methods for oxygen analysis, sponsored by the Iron and Steel Division of the American Institute of Mining and Metallurgical Engineers and by the National Bureau of Standards. A preliminary report of the results was made at the annual meeting of the A.I.M.E. in February, 1936. ? This report showed the reliability of vacuum-fusion methods and further brought out certain advantages of the fractional vacuum-fusion method. The results obtained by the authors with the latter method will be discussed here, with some com-ments on the procedure for those who are interested in determinations of gases in steel. Some additional comments are offered on the use of the polarizing microscope for identifying the inclusions in the steel to check and amplify the findings of the fractional vacuum-fusion analysis. For details of the fractional method, see the paper by L. Reeve1.

Jan 1, 1937

By P. Massacci

This study deals with the development and utilization of computer models for evaluating the extent to which variability of raw material grades can be reduced from the deposit to the processing plant. The specific case of a cement works is examined. The deposit and the elementary quarring operations were modeled for the medium and long-term planning of production with the objective of predicting grade variability of the flow stream in time. The feeds inferred from previous modellings were used for simulating storage operations. In particular, the storage process (linear stockpile, as an alternative, blending from various heaps) was modelled in order to select the main parameters of the process to minimize grade variations of the feed to mill. The ways followed for modelling the prehomogenization process are described. The homogenization performance and efficiency in the silo stage has also been studied and an estimate made of the distribution of residence time on the basis of input and output sampling.

Jan 1, 1986

By Ruilin Yang

This paper presents a fragmentation model for large production blasts. The model uses peak particle velocity (PPV) induced from the blast as a controlling parameter to predict the fragmentation size distribution. The PPV can be related to shock pressure or strain under a given rock condition. The fragmentation size is calculated at three-dimensional grid points within the blast volume. The grid size defines the calculation resolution of the model. The fragment size distribution is assumed to be in the same form as the crack distribution within a cube (of the size equals to the grid size) surrounding a grid point. The crack distribution in rock from impact is based on the finding from previous researchers (Seaman et al., 1976). The fines and oversized blocks are calculated explicitly. The summation of the size distribution at all calculation grid points over a specified volume of the blast yields an overall size distribution for the volume.

Jan 1, 2015

Reduce potential for steering errors during tramming of articulated vehicles, particularly when the operator is seated to the rear of the machine pivot point and is tramming in reverse. Approach Position-sensing and feedback cylinders were applied to the steering cylinders of two S&S cleanup tractors to cause the steering-control lever to match the orientation of the vehicle sections. The vehicles were tested in two working mines. How It Works A position-sensing cylinder (see Figure 1, Item A) is attached to one of the steering cylinders in the cleanup tractor steering system. As the steering cylinder piston rod is actuated by movement of the control lever, hydraulic oil flows from the position sensing cylinder to the feedbck-cylinder (B), causing the feedback-cylinder piston and rod to move. The outside end of the rod repositions the the steering-control lever until its angular position corresponds to the orientation of the vehicle sections.

Jan 1, 1978

By A. S. M’Creath, E. V. d’Invilliers

The rapid development of the southern coal and iron-ore fields during the past few years, and especially in the latter half of the year 1886, and the avidity with which everything relating to the industrial situation there is read and absorbed by the professional and non-professional public, has led to the preparation of a brief paper for the Institute upon a comparison of the raw materials available on or about January 1st, 1887, at three prominent centers of consumption. While disclaiming any originality or priority in the treatment of the resources of these districts, where so much valuable and interesting work has been performed in the past by several members of the Institute, we hope that the presentation of some analyses of samples personally secured by us in the several districts selected, and prepared for a comparative study of the character of the materials actually used and to be used by the furnaces of the "New

Jan 1, 1887

By Y. Nakada, U. F. Kocks, B. Chalmers

The stress-strain behavior of the gold single crystals in easy glide was found to be affected by the specimen dimension which is parallel to the projection of the Burgers vector of the primary-slip system. The larger this dimension is, the larger is the slope of easy glide. Previously severa1 investigators attributed the size effects to either the existence of surface films or the grip constraints. However, in this experiment both of these possible causes were not present. It is proposed that the length of slip path (defined as the crystal dimension parallel to the Burgers vector of the primary system) is the controlling factor in the size effect observed in gold. THERE are many possible effects of the specimen dimension on the work-hardening behavior of single crystals: grip effects which prevent end regions of the crystal from deformation or rotation; effects of a surface film, for example a coherent oxide; effects of a subsurface layer of accidental or intentional

Jan 1, 1964

Control dust generated during overburden drilling at surface coal mines using either wet suppression or dry collection systems. Approach For the wet suppression systems, a range of water flow rates was tested over a number of holes. Each hole was drilled at a specific and constant flow rate. A recording flow meter was mounted in the water line near the control system pump. For the dry collection systems, each drill was tested with the front of the shroud set at different heights above the ground. Because of the irregularity of the ground surface, all height measurements were taken at the front of the shroud. Background Wet drilling systems consist of a water tank mounted on the drill from which water is pumped into the downhole air line. The water droplets in the bail air conglomerate dust particles as they travel up the the annular space of the drilled hole, thus controlling dust as the air bails the cuttings from the hole.

Jan 1, 1987

By S. P. Singh

Destress blasting is commonly used in the mines to minimize the occurrence of rockbursts. The fracturing created by destressing in the vicinity of the face reduces the stress concentration by pushing the zone of high stress deeper into the rock mass. But the destressing practice by blasting may be devastating near the faults or other sensitive high stress zones. To avoid severe rockbursts in such situations, the application of chemical destressing has been proposed in this paper. A laboratory investigation was conducted on the rocks in the Sudbury basin to examine the change in the material properties with an aim of assessing the feasibility of destressing by chemical means. The favourable change observed in the rock properties led to the suggestion that the injection of surfactants in boreholes would enhance fracture propagation similar to what is currently done by blasting but in a safer, inexpensive and non-violent manner. The current destressing practices in Ontario mines have also been reviewed in this paper.

Jan 1, 1987

By Li N, Grimsey E. J

A technique has been developed for the fast measurement of the liquidus temperature of molten salt systems. The method employs a type K thermocouple embedded within the centre of a copper cylinder. The cylinder is immersed into the molten salt bath and the resultant heating curve is recorded using a PC-based data logging system. Upon immersion of the cylinder into the bath, a layer of salt freezes from the melt onto the surface. When this layer remelts during heating, the shape of the heating curve exhibits a change. The onset of this change can be detected by numerical differentiation of the heating curve, and the temperature at the onset represents an estimate of the liquidus of the melt. This work describes the technique and its application to the measurement of liquidus temperatures of MgC12 - NaCl and BaC12 - NaCl salt mixtures, in addition to a number of solidus temperatures.

Jan 1, 1996

By R. Schempp

DURING the past few years, general interest in the steel-producing and steel-consuming industries has been centered on the so-called "inherent characteristics" of steels. While often vaguely described, these char-acteristics are known to influence the response to heat-treatment and the hardening characteristics of the material. Although most of the recent papers and discussions have associated the "inherent characteristics" with the austenitic grain size and empha-sized the importance of it, comparatively little is known of the variables that may affect the size of the austenite grain. The work to be described in this paper was carried out during the course of a study on the inherent characteristics of tool steel containing one per cent cart on. The discrepancies encountered in the determination and classification of the austenitic grain size led to in investigation of some of the variants influencing the austenitic grain size as determined by standard methods.

Jan 1, 1937

By Marsh S. Watson, Robert A. Howard

An electrolytic model study has been made of the relative productivity of perforated casing. The results show that the relative productivity is roughly one-half to two-thirds of that predicted from point-sink calculations. This discrepancy can he satisfactorily explained on the basis of casing interference. The relative productivity was found to he insensitive to spatial arrangement of the perforations. INTRODUCTION The relative productivity of wells with perforated casing has been treated mathematically by Muskat.' In his treatment the perforations are represented by small spheres, thus enabling him to approximate the flow by that to point sinks. By neglecting interference between the flow into the various spheres representing the perforations, one may deduce the approximate formula Qu 1/rp - 1/rw • (1) I + b/2n _________ 2n In re/rw Where Q is the flow rate into spherical sinks located in the median plane of the sand laver Qo is the open hole flow rate (uncased hole of radius rw) b is the thickness of sand layer under consideration (always one foot in this paper) n is the number of spherical sinks in the sand layer rp is the radius of a spherical sink rw is the well radius re is the drainage radius of the well. Fig. 1 is a comparison of values calculated from equation (1) with Mus-kat's values. It will be observed that the approximate values are in error by less than 21/2 per cent. The disturbing effect of the casing on the flow line; is not explicitly taken into account by Muskat, but he reasons that interference between the flow pat- terns from the various point sinks will result in a negligible flow in the region within the well radius, and that no appreciable error will result from not explicitly excluding flow from this region. This line of reasoning is open to question, however, as the flow impedance, in the immediate vicinity of the well, of a hemispherical cavity in contact with an opening in the casing is twice that of a spherical sink in a continuous sand layer. There will be a difference, moveover, between the flow into a hemispherical cavity and that into a circular hole in the casing. .This latter difference can best be appreciated by comparing the flow from a semi-infinite medium into a hemispherical cavity at the edge of the medium with the flow out of a circular opening of the same radius as the hemisphere and which is also on the edge of the medium. In this case2 ------= —2, showing that the difference in flow rates into differently shaped cavities is quite appreciable. It was the purpose of the investigation reported here to determine to what extent flow into circular perforations in casing departs from the values calculated by Muskat. For this purpose an electrolytic model was used.

Jan 1, 1950

By John C. McDonald

This report is a continuation of an earlier one with a similar titlell to which the reader is referred for such details of procedure as do not appear here. A brief summary will be given of the objects and methods of the research at this time. It was pointed out in the previous paper that properties of magnesium alloys, as reported by different workers, often differ. This was thought to be due to differences in the preparation of the specimens tested. The ideal way to compare alloys would be to prepare each of them in so many ways that reasonable assurance would exist that the best properties of each alloy had been developed. The alloys would then be compared on the basis of these properties. The treatment actually given the alloys of these studies is necessarily a compromise with completeness. Nevertheless, enough treatments have been given so that a considerable degree of assurance exists that the properties obtained are representative of the alloy as such, and not merely of the manner in which it was worked and heat-treated. Procedure The alloys were cast in the form of cylindrical ingots, which were extruded into bar before being rolled. Some of the ingots were made in 2-in. diameter molds whereas all of the alloys of the previous paper were cast in 4.in. molds. For the larger ingots, the extruded bar was 2 by 0.140 in.; lor the 2-in. ingots, it was I by 0.100 in. Preliminary work indicated that strip rolled from both sizes of the bars would have substantially the same properties. The bar was rolled at some temperature in the range 400' to 800°F., for a total reduction of 50 per cent. The temperature and reduction per pass were so selected that no cold cracking occurred, but were such as to leave the metal in a semihard condition. The hot-rolled metal was annealed at several temperatures in the range 400' to 800°F.; it was also cold-rolled, and given solution and aging treatments. Two standard test bars corresponding to each treatment were pulled in tension, and the average was obtained. Twelve treatments, in all, were given each alloy. The properties of the annealed specimen having the highest percentage of elongation were selected to represent the alloy in the annealed condition. The properties of the cold-rolled specimen having the highest yield strength were selected to represent the alloy in the cold-rolled condition. These properties were then plotted against percentage composition by analysis. Smooth curves were drawn among the points, thus graphically averaging the results over the entire range studied. The percentage of elongation in the cold-rolled state was not plotted, since it was always low, and varied in an irregular manner with composition. Alloys Studied Magnesium-calcium Alloys.—Fig. I presents the results on the alloys of the rnag-

Jan 1, 1941

By Harry H. Angst

THE history and efficiency of 40-ton capacity dump trucks for surface waste removal at the New Cornelia opencut copper mine, at Ajo, Ariz., are summed up in this paper. Tabulations of truck performance, together with detailed cost figures, prove the value of truck transportation for certain special operations at a large mine. Emphasis is given to the fact that truck transportation not only reduces the haulage costs but also reduces the breaking ground and shovel-loading costs per ton. The New Cornelia opencut copper mine is in the desert. The climate is ideal for seven months of the year, but the five summer months are uncomfortably hot. The elevation is 1820 ft. above sea level and the annual rainfall is approximately 6 inches. The ore body is a monzonite-porphyry deposit. The waste-rock capping consists of hard rhyolite, conglomerate and porphyry. All the material is hard and cannot be excavated without blasting. The rhyolite and conglomerate waste is very blocky. The weight of the rock in place is 2.16 tons per cubic yard. The average mine production per day is 22,000 tons of ore and 18,000 tons of waste rock, the latter consisting of surface rock and material within the ore body too low in grade to send to the concentrator. The rock is loaded by electric shovels with 4 ½ -cu. yd. dippers. The primary transportation of ore to the concentrator and waste to the dumps is by 30-yd. dump cars and oil-burning steam locomotives; therefore truck haulage of waste is a minor factor of the New Cornelia operation. However, as New Cornelia was one of the first mines to use large-capacity dump trucks for haulage, the results obtained are of interest. EQUIPMENT On the south side of the New Cornelia is a hill rising about 500 ft. above the normal surface elevation, roughly 1000 ft. in diameter at its base, called locally Arkansas Mountain peak. Exploratory drilling in this area developed additional ore that could be made accessible for open pit operation only by moving the mountain face a maximum distance of 400 ft. to the south. The slope of the mountain adjacent to the pit averaged 35°, and the small area involved precluded the use of train haulage for the removal of the 4,000,000 tons of waste estimated above the normal pit elevation. A study of dump-truck haulage at Boulder Dam and San Gabriel Dam led to the decision to use large-capacity end-dump trucks rather than smaller trucks, for the following reasons: 1. The truck would have to withstand the impact of hard, heavy chunks, some of them weighing as much as 10 tons, which would be dumped from the 4 ½ -cu. yd. dipper. 2. The coarse, rocky, abrasive material would soon damage a light truck body. 3. The body of a small truck could not be efficiently loaded with coarse rock.

Jan 1, 1941

By John C. McDonald

This report is a continuation of an earlier one with a similar titlell to which the reader is referred for such details of procedure as do not appear here. A brief summary will be given of the objects and methods of the research at this time. It was pointed out in the previous paper that properties of magnesium alloys, as reported by different workers, often differ. This was thought to be due to differences in the preparation of the specimens tested. The ideal way to compare alloys would be to prepare each of them in so many ways that reasonable assurance would exist that the best properties of each alloy had been developed. The alloys would then be compared on the basis of these properties. The treatment actually given the alloys of these studies is necessarily a compromise with completeness. Nevertheless, enough treatments have been given so that a considerable degree of assurance exists that the properties obtained are representative of the alloy as such, and not merely of the manner in which it was worked and heat-treated. Procedure The alloys were cast in the form of cylindrical ingots, which were extruded into bar before being rolled. Some of the ingots were made in 2-in. diameter molds whereas all of the alloys of the previous paper were cast in 4.in. molds. For the larger ingots, the extruded bar was 2 by 0.140 in.; lor the 2-in. ingots, it was I by 0.100 in. Preliminary work indicated that strip rolled from both sizes of the bars would have substantially the same properties. The bar was rolled at some temperature in the range 400' to 800°F., for a total reduction of 50 per cent. The temperature and reduction per pass were so selected that no cold cracking occurred, but were such as to leave the metal in a semihard condition. The hot-rolled metal was annealed at several temperatures in the range 400' to 800°F.; it was also cold-rolled, and given solution and aging treatments. Two standard test bars corresponding to each treatment were pulled in tension, and the average was obtained. Twelve treatments, in all, were given each alloy. The properties of the annealed specimen having the highest percentage of elongation were selected to represent the alloy in the annealed condition. The properties of the cold-rolled specimen having the highest yield strength were selected to represent the alloy in the cold-rolled condition. These properties were then plotted against percentage composition by analysis. Smooth curves were drawn among the points, thus graphically averaging the results over the entire range studied. The percentage of elongation in the cold-rolled state was not plotted, since it was always low, and varied in an irregular manner with composition. Alloys Studied Magnesium-calcium Alloys.—Fig. I presents the results on the alloys of the rnag-

Jan 1, 1941

The statistical methods described in the previous chapter permit the estimation of the average value p of a deposit, and the calculation of confidence limits for this value. They are based on the assumption of independence of sample values. As soon as a reasonable number of samples has been obtained from a deposit, local valuation, or estimation of blocks of ore within the mineral deposit, becomes necessary. The assumption of independence of values must then be rejected. Local valuation is possible only if there is a relationship between the value of a sample and the value of the surrounding ore, provided this relationship is a function of the position of the sample with respect to the blocks of ore to be valued. Whichever method is used for the valuation of a block of ore, the following assumptions are always made: ? The values of samples located near or inside the block are related to the value of the block. ? The values of the samples located closest to the block are most closely related to the value of the block. These assumptions will hold true only if the following assumption can also be made: ? There exists a relationship between sample values which is a function of the distance between samples. We are saying that the value x (z) of a sample centred at a point z has properties which are functions of this point. A certain spatial structure exists in the sample distribution. We are therefore dealing with a regionalized phenomenon, and we must treat x (z) as a regionalized variable. This can be done statistically by means of a model chosen to represent the spatial structure of the phenomenon. We shall see that the relationship between block values and sample values can be deduced from the relationship between sample values, and all local valuation problems can be solved using the statistical model obtained from the analysis of the sample values. It is important to realize that this statistical model is obtained by analysing the properties of known sample values, and will be used for the estimation of unknown block values. Such a statistical inference is valid only if the model developed represents the properties of both the sampled section of the ore body and the section to be valued: some stationarity conditions must be satisfied, and the model with the least restrictive conditions is preferred. In the following chapters, the most important models used in spatial geostatistics are presented. The models which can be used when there is no significant drift (trends) in values are described in Chapters 3-1 1. These models can also be used to solve some specific valuation problems when a linear drift is present. A general study of the more difficult problem of analysis of an ore body whose values present a drift is described in Chapter 12. Note that the area considered for local valuation of a block of ore is often small enough for any drift which might be present to be ignored.

Jan 1, 1978

By Laajalehto K

The basic condition necessary for flotation is hydrophobicity of the surface of the mineral to be floated. For sulphides, this condition usually requires treatment with a collector solution. The conditions for this treatment have until recently usually been chosen by the trial and error principle which has indeed been working relatively well under favourable conditions; ie for simple homogeneous ores. However, the present tendency to increasing use of complex and often relatively lean ores sets increasing requirements for the control of the flotation process. This development is the reason for the present rapid development of process control methods in flotation. In addition to the already well-established practices of pH and reagent feed controls, the importance of measuring and controlling the electrochemical potential of the ore particles to be floated is recognised in the case of sufficiently conductive minerals. In fact, the electrochemical potential seems to be the basic quantity determining the flotation behaviour of such relatively well-conducting minerals as sulphides. Since the hydrophobicity of the mineral and, hence, its flotation properties are ultimately determined by the composition and structure of its surface, information on these under different process conditions is important for design and operation of efficient flotation processes. The basic requirement set for the methods used for obtaining this information is high surface sensitivity of the method. The recent rapid development of surface characterisation has produced several methods which fulfil this requirement. Their application to the problem of characterising surfaces of mineral samples in contact with collector solution is, however, often complicated. The main reason for this is the vacuum environment necessary for the measurement. In the case of flotation experiments this means that in most of these methods the measurement cannot be made in situ, but the sample must be extracted from the liquid and subsequently evacuated in the vacuum chamber of the instrument. It is essential to carry out these steps so as to avoid to the extent possible changes in the sample surface. For the purpose of establishing whether this has been accomplished it is important to compare the results of methods operating in vacuum with some available in situ method. An optimal choice of methods seems therefore to be a combination of the available powerful vacuum methods with in situ measurements. The most usual combination seems to be X-ray photoelectron spectroscopy (XPS or ESCA), Fourier transform infrared spectroscopy (FTIR) and electrochemical measurements. This choice combines the unique possibilities for direct elemental and chemical characterisation offered by XPS (Cecile, 1985) with the in situ capability of FTIR and electrochemistry. In the XPS measurements, it is essential to apply a special sample handling technique to avoid loss or damage of some sensitive species of the collector-based layer on the mineral surface. In the following will be given some examples of the application of the XPS technique in combination with electrochemical methods of sample treatment to studies of the layer formed on sulphide substrates in ethyl xanthate (EX)

Jan 1, 1993