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By T C. Souza Pinto, M Safari, F S. Hoseinian, D Deglon, L Leal Filhoc

In this study, the effect of hydrodynamic parameters on the iron ore reverse was investigated in a mechanical flotation cell. The work carries out using the case study of Iron ore from Vale in Brazil. The influence of hydrodynamic factors such as froth height, impeller speed, superficial gas velocity and solids percentage were evaluated on the quartz flotation. The results showed that the hydrodynamic conditions have a great effect on the flotation performance, especially on the fine and coarse quartz. The size-by-size analysis of the froth products showed that froth height, impeller speed, superficial gas velocity and solids percentage have a significant effect on true flotation quartz particles. The increase in the froth height decreased the recovery of quartz particles. The increase in the impeller speed increases the recovery of quartz particles to an optimum. The increase in the superficial gas velocity improved the flotation of coarse quartz particles. The increase in the solids percentage increases the recovery of quartz particles.

Sep 18, 2023

By Lynn C. Jacobsen

Among the unforeseen consequences of the 1973 Arab oil embargo has been a considerable array of new or increased taxes on the so-called energy minerals. These taxes will be the subject of this report. Both Federal and State taxes have been enacted, but I will be concerned mostly with state severance taxes and particularly those on uranium. Severance taxes are considered to include all taxes having the distinctive feature of being applied on a natural resource at the stage of extraction. The tax may be based on units of production or on value, and if on values it may be on gross value or on gross value less either arbitrary or cost-related deductions. The tax has a number of aliases - resource excise tax, conservation tax, privilege tax, mining excise tax, ad valorem production tax, and more - and this makes comparison of tax burdens among states difficult. The windfall profit tax on oil is an example of a severance tax at the Federal level. Severance taxes are an established feature of state tax systems, but they continue to be a controversial issue, and proposals to raise or modify existing severance taxes are regularly submitted to the legislatures of the Western energy producing states. No concensus exists as to what is a reason- able and proper level of severance taxation or to the form it should take. The taxes which have been adopted by the various states reflect the interaction of a variety of interests and the specific circum- stances in each state. What follows is a summary of theoretical, practical, and emotional viewpoints and arguments that surface in any statehouse in which a severance tax bill has been introduced. The New Mexico experience will be heavily relied upon. THE ECONOMISTS Marginal effects. A severance tax which is based on a gross percentage of revenue or on units of production is a constant addition to variable costs, and to the mine operator has the same effect as any other increase in operating costs. The direction of these effects is straightforward: the tax will cause the property to have a lowered present value, to be mined at a lower rate than without the tax, raise the minimum grade that will be mined, lead to lower total recovery, make marginal properties sub-marginal and discriminate in favor of richer, more profitable operations (Lockner, 1965; Steele, 1967). In the short run, production facilities are fixed and imposition of a severance tax will have little effect on production levels. In the longer term, capital is mobile and investment and exploration expenditures will shift from minerals and jurisdictions with high taxes to those with low taxes. Over a considerable range of taxation the effect will be to change the relative position of the taxing state, but an overly optimistic evaluation of the capacity of mineral producers to absorb a tax can bring an industry to a halt. It is generally acknowledged that imposition of high severance taxes on taconite in Minnesota stopped development completely, and that only the adoption of a constitutional amendment limiting the amount of taxes that could be imposed in the future brought the firms back and encouraged them to make the huge investments required (Weaton, 1969). A tax which is a percentage of the net operating income (gross revenue less cash operating costs) does not influence the cut-off grade for recovery nor change the time preference for extraction, and hence, is free of the negative features of the tax applied to gross revenues or units of production. In theory it is a more efficient tax but relative administrative complexity and inherent difficulty in predicting revenue have discouraged its use. The Wyoming severance tax on uranium, which uses grade of ore as well as price in establishing taxable value, is the most cost related, and hence, the most neutral and efficient of the various state severance taxes on uranium. Economic rent. Despite the discrimination and the anti-conservation aspect inherent in most severance taxes, economists generally endorse their use because they are seen as a vehicle to appropriate rents - that is, returns greater than the long-run competitive supply price. Conspicuous examples of supposed economic rents are the returns to oil producers because of the OPEC cartel, the returns of the uranium producers under AEC buying contracts in the 19501s, and the high prices obtained by the uranium producers for contracts entered into in the 1976-1979 period. Mining of coal in the Western states is believed by some to generate huge economic rents because of the OPEC caused increase in price of a competitive fuel (McLure, 1978, p. 261), and possibly because of clean air regulations favoring the burning of low-sulfur coal. In theory, such surplus returns could be taxed completely away without affecting supply. In practice, the situation is more complex (Steele, 1967, pp. 234-236); economic rent of mineral production is an elusive quantity involving as it does replacement costs, and technical and market risk, and it, like beauty or pornography, probably exists mostly in the eye of the beholder. Rent may also be perceived to be present in the upper portion of a cyclic market which also has a downside. Where rent exists, it is almost certain to be short-lived - cartels self- destruct, government subsidies end, competitive adjustments occur - but the taxes imposed to capture it tend to be immortal. There is little doubt that the perception of un- usual and undeserved (obscene) profits in the mid- and late 1970's was a major factor in the adoption of energy mineral taxes strikingly higher than had been previously considered. At the New Mexico legislature of 1977 supporters of a moderate tax were repeatedly confronted with some variant of the statement, "You can't expect me to believe that a

Jan 1, 1982

By Stephen C. Tadolini

Effective barrier pillar design is an essential component for safe and productive underground coal mining. Barrier pillar design methodologies that incorporate sound engineering judgment have been used for practical everyday usage. The next logical step is to utilize numerical modeling techniques that help combine practical experience and empirical observations into barrier pillar design analysis. A case study is presented that describes the barrier pillar design process, but also highlights the importance of considering the global mine response by evaluating: adjacent pillar stabilities, impact of intersection and entry widths, capacity of primary and secondary bolting systems and rib stabilization used for the safe and efficient removal of the longwall face equipment.

Jan 1, 2013

By David Regalado

En los últimos años se presentaron pérdidas en el proceso de ejecución de chimeneas principales (por derrumbes y rehabilitaciones) en Unidad Minera Orcopampa. Este artículo muestra cómo se viene superando el problema con un proyecto basado en el conocimiento de la geología del terreno y la aplicación de conceptos y herramientas de geomecánica, de forma tal que la ejecución de una chimenea principal —bien sea para ventilación con Raise Bore o Raise Climber (Alimak)— cumpla su función y perdure a través del tiempo.

Feb 28, 2019

By Spencer Ness, Yazen Khasawneh

Onshore wind turbines are complex and dynamic systems, undergoing variable environmental and mechanical loads. These dynamic loads are transferred through the turbine components and tower to the foundation system and, subsequently, the adjacent soil. As the size of onshore wind turbines continues to grow, intermediate-type foundations are being developed and implemented to better leverage the strength of the adjacent soils while avoiding some of the drawbacks of deep foundations. However, these foundations can be relatively sensitive to ground conditions. When considering a wind energy site that may consist of dozens of wind turbines across thousands of acres, it can be difficult to determine a design stratigraphy that is reflective of the entire site and takes conservative approaches to all potential failure modes and design checks. As intermediate foundations are inherently a soil-structure interaction problem, computer-aided numerical methods are often necessary. To highlight this condition a typical intermediate foundation with tower and turbine is assessed under eighteen different soil profiles within a finite element software and performance is compared.

Oct 7, 2024

By Duberney Hincapié-Ladino

O presente trabalho estuda os parâmetros de permeabilidade de hidrogênio de um tubo API 5L X80, e uma chapa de aço grau X80, onde a principal diferença está na composição química, o primeiro contém 0,07%C e 0,04%Nb e o segundo 0,04%C e 0,102%Nb. As amostras foram cortadas com espessura de aproximadamente 1 mm, lixadas e recobertas com um filme de níquel, em uma das faces. Nos ensaios de permeabilidade foi utilizada uma célula modificada tipo Devanathan-Stachurski, com a solução A da norma NACE TM0284, com injeção de H2S no lado de geração e 0,2M NaOH no lado de detecção. As curvas de corrente em função do tempo obtidas passaram por tratamentos matemáticos (método tlag), permitindo a obtenção dos parâmetros de difusividade aparente, concentração máxima de hidrogênio e número de traps (sítios de ancoramento). Tais parâmetros mostraram-se iguais para os dois materiais. As curvas foram normalizadas e modificadas de maneira a eliminar o efeito da espessura das amostras. Estas novas curvas foram comparadas com o modelo teórico da segunda lei de Fick. A comparação evidenciou que o procedimento inicial para a obtenção dos parâmetros de permeabilidade mostra-se eficiente e vantajoso por apresentar maior praticidade. Pôde-se concluir que a semelhança no comportamento dos parâmetros de permeabilidade foi devida às similaridades nas suas microestruturas. Os resultados obtidos no presente trabalho evidenciam que o tipo e quantidade de traps nestes materiais são determinados pela microestrutura.

Aug 17, 2017

By J. W. Cooksley

Seismic methods provide an efficient and comprehensive approach to overburden studies pertinent to mining exploration and development, and to other mining and civil engineering problems such as rock mechanics, slope stability, and foundation engineering. For the purpose of defining geologic units and structural features, these methods are generally regarded as the most accurate, but most expensive, of the commonly-used geophysical exploration methods. Although the accuracy and cost of seismic work are generally affected adversely by rugged topography and complicated geologic conditions, it is in rough terrain and complex geology that seismic methods offer important advantages in overburden investigations. For example, to find the surface of rock underlying unconsolidated overburden at depths of approximately 200 feet, a 50-foot spacing of drill holes along the profile line would be required to yield a degree of resolution and accuracy similar to that obtained from a 50-foot spacing between seismic detectors along the same line. See Figure 1. In cases similar to that shown in Figure 1, a twelve-channel recording seismic system would be used. The main components of such a system would be: 1. detectors (commonly referred to as geophones) which convert the ground movement resulting from seismic waves into an electrical signal. 2. a multi-conductor cable which connects the seismic detectors to the amplifiers. 3. ampliiiers, amplify and filter the electrical signals . 4. oscillograph, records the amplified signal. 5. the blaster and firing line. A typical layout of the seismic spread and the components of the system Is shown in Figure 2.

Jan 1, 1968

By Michael L. Free

Bacterial oxidation of an arsenopyritic gold-ore .concentrate was carried out with continuous-flow .operation in 14-liter, mechanically agitated reactors. Samples from the slurry reactors were separated into solid and liquid fractions and analyzed separately to determine the electrochemical rates of sulfide conversion by the bacteria and the rates of direct bacterial oxidation of sulfide. The rates of the individual mechanisms are compared to the overall rates of biooxidation in the continuous-flow slurry reactors. The results show that the commonly hypothesize4 direct and indirect mechanisms of biooxidation both play a significant role in the bacterial oxidation of sulfide ores.

Jan 1, 1991

By G. W. McDonald

"The mineralogical studies done on Hope Brook ore samples indicated that a heap leach gold recovery process may be possible. In the metallurgicalprogram that followed, column tests confirmed this interpretation. A 9300 tonne demonstration heap leach test, in the late fall of 1985, reaffirmed laboratory results while identifying operating conditions that will have to be addressed in a production heap leach plan. Operating plans, gold recoveries and cost areas will be presented.Another important factor in a successful operation is the environment approach.LocationThe Hope Brook gold deposit is located 5 km inland from Cinq Cerf Bay on the south coast of Newfoundland. Port au x Basques is 80 km west and Burgeo 40 km to the east of Hope Brook. As there are no roads in the area, access to the site is by sea or air (Fig. I). The Hope Brook orebody is near the saddle of three watersheds flowing to Cinq Cerf Brook, Boat Hole Brook and Betty's Pond. Acceptable solutions to several environmental concerns can be obtained by using the relative sensitivities of these watersheds.The terrain at the site is generally rolling to hummocky with numerous small ponds separated with rock outcrops and patches of peat covering. Tree vegetation is sparse except in the sheltered areas around Couteau Bay and Cinq Cerf Brook. GeologyThe Chetwynd deposit is hosted by the Lower to Middle Ordovician Georges Brook Formation of the La Poile Group, a thick sequence of volcanic and sedimentary rocks.The Hope Brook Zone contains the largest concentration of gold found to date at Chetwynd. The zone occurs as an intensely silicified lens 100 m to 550 m long (average 400 m) by up to 60 m in width and forms the eastern portion of a more extensive, 4 km long , alteration zone trending at 053 degrees Az and dipping 70 degrees southeast.The Hope Brook Zone contains massive finely granular quartz, scattered blue quartz eyes, 3070 to 8% pyrite, minor calcopyrite and trace molybdenite. Barren silicification envelopes the gold mineralization. The zone is flanked to the southeast by a 200 metre thick aluminosilicate alteration zone and to the northwest by a 10 metre barren pyritic siliceous fragmental rock . The original lithology may be either a thick felsic pyroclastic sequence or a quartz porphyry sill that has been altered by hydrothermal processes. Silica flooding of the permeable host was accompanied by gold deposition."

Jan 1, 1989

By R. A. Seitz

This paper presents a framework for analyzing the theory and industrial practice of coal flotation and gives some examples of its use for understanding flotation phenomena and optimizing/controlling flotation circuit performance. It is based on extensive laboratory and in plant test work conducted over the past several years by researchers at MTU as well as an analysis of the literature. Previous researchers have usually considered either the surface chemistry or the kinetics of coal flotation behavior, only rarely have these factors been considered together. However, these factors must be considered together in order to gain a clear understanding of the theory underlying coal flotation such that its practical application can be optimized. Fortunately, this complex objective can be achieved by considering the recovery and rate of recovery of the different types of particles present in the feed to coal flotation circuits and the fundamental mechanisms responsible for these recovery phenomena. The influence of three major groups of variables must be considered: control variables (reagent additions, aeration rate, etc.); disturbance variables (feed pH, percent solids, etc.); and circuit design variables (number of cells, circuit arrangement, etc.). Each of these groups of variables affects process kinetics in a clearly understandable manner, which, once determined, is extremely useful in circuit design and optimization. This paper includes a discussion of the use of the proposed framework to explain the effects of some coal characteristics on flotation performance. In addition, an example of using this analysis to optimize the performance of a coal flotation circuit using frother and collector addition levels is included.

Jan 1, 1985

By Zhitao Ma

The Cast-in-place Concrete thin-wall Pipe pile, referred to as PCC pile, is a new kind of pile for soft ground improvement. In this paper, firstly, the general introductions of the new pile technique, mainly including the technique principle, the structure of pile-driving machine, and the technological process were given, then based on the results of in-situ static lateral loading test, the pile lateral capacity, the relationship of load-deflection of pile at the ground surface, the lateral deflections versus depth and the soil reaction along the pile shaft were analyzed.

Jan 1, 2006

By J. Lindenau

One of the significant benefits of electronic detonators is their safety, especially their relative insensitivity to extraneous electrical energy. The various brands of electronic detonators on the market have different resistance to electrical stimuli, but all have safety structures designed to afford a significant level of protection. A common source of extraneous electrical energy is lightning. This paper discusses the nature of the energy that occurs with a lightning strike and the resistance offered by electronic detonators. Four actual cases of exposure of electronic detonators to lightning strikes are considered. Electronic detonators, like other initiation systems, are vulnerable to very close or direct lightning strikes. The incidents are a reminder that all blast patterns need to be vacated on the approach and during the progress of a lightning storm. 1. Orica

Jan 1, 2008

By R. M. Balderrama

Bench-scale laboratory flotation and gravity separation tests were conducted on tailings samples to remove the sulfidic material, mainly pyrite, the source of acid generation. A combination of xanthate collectors, promoters, and frothers were used during flotation. Pyrite recoveries were in the range of 42 to 97%, depending on the tailings being treated. Sulfide sulfur contents of 12.8 to 0.37% in the feeds were reduced to 8.68 to 0.01% in the treated tails. Flotation tests were conducted to evaluate the ARD potential as a function of percent pyrite remaining in the tails. Standard ARD predictive tests were used to evaluate the success of the treatment. In some cases, removal of only 50 to 55% of the pyritic fraction was required, thereby demonstrating the conversion of the waste material from acidic to non-acidic. A laboratory vanning table was used to evaluate the amenability of sulfide-bearing tailings samples to gravity separation. The pyrite recoveries varied from 38 to 86%. The sulfide sulfur content of 12.8 to 0.37% in the feeds was reduced to 6.0 to 0.14% in the treated tails. Predictive ARD tests performed on tailings before and after the gravity removal of pyrite showed that most samples changed from "probably" acid producing to the "uncertain" range. Data reported and analyzed in this paper demonstrate source control for ARD prevention through the removal of metal sulfides from sulfide-bearing wastes using conventional flotation and gravity separation techniques.

Jan 1, 1995

By H. D. Merchant

NUMEROUS publications have examined hot hardness of metals and alloys. Some have studied creep in long-time hardness tests, few of which, however, were tested under a spherical indentor. 1-3 The results of Mulhearn and Tabor' indicate a parabolic-type creep for indium and lead, whereas Moore and Tabor2 how a logarithmic-type creep for indium. Similar semilog relationships between hardness and time have been found by Goffard and wheeler3 for magnesium, aluminum, and their alloys. In this note, the elevated-temperature hardness of some complex alloys, shown in Table I, was examined to discover whether any basic information about the deformation behavior of the alloys could be obtained. One of the alloys, H-13 alloy steel, was tested for short-time creep tests to examine the hardness-time relationship at various temperatures. A standard Brinell Hardness Tester, mounted with an appropriate furnace and 99 pct A12O3 poly-crystalline indentor, was employed for the purpose. The alloys were tested at temperatures from room to 1400°F for 30 sec under 1500-kg load. The creep studies were conducted for about 8500 sec at 7l°, 500°, 1000°, and 1200°F. For constants A and B, a relationship of the type H = Aexp(-BT) [ll was obtained for all alloys between hardness, H, and temperature, T. In the semilogarithmic plot, the data points for each alloy were arranged into two groups, each group on a straight line with a specific set of A and B values. These results are in agreement with many such observations on hot hardness, notably those of Westbrook for pure metals,4 The thermal softening coefficient, B, and transition temperature, Tt, for various alloys are shown in Table I. The change in slope around the transition temperature suggests an apparent change in the mechanism of deformation, probably from the shear (below Tt) to the diffusion type of mechanism. At the temperatures above Tt, for constants A' and B, a relationship of the type was obtained between H and T, Fig. 1. The nature of the equation, where R is gas constant, suggests the possibility of a thermally activated mechanism of deformation above Tt. The constant B' may hence be defined as the apparent activation energy of indentation. The B' values of various alloys are shown in Table I. A plot of B vs B' gives a curvilinear relation shown in Fig. 2. The indentation-creep data for H-13 alloy steel is shown in Fig. 3. At 71" and 500°F, the creep initially follows the logarithmic time law. However, the indentation size stabilizes after 7 sec at 71°F, and after 10 sec at 500°F. Further increase in loading time has no effect on indentation size. The creep of 1000° and 1200°F follows the logarithmic time law for the first 1000 sec, after which the

Jan 1, 1964

By Cyril S. Taylor, Junius D. Edwards

Magnesium is the lightest metal used for structural purposes, for which reason perhaps more than usual interest is attached to measurements of its density. Although the density of solid magnesium has been det,ermined frequently, no measurements of the density of the liquid metal are available. Because of unusual experimental difficulties in measuring the density of the liquid, only a limited number of measurements of good precision were secured. The results, especially the value for the crystallization shrinkage, are of great interest in connection with the casting of the metal. A number of samples for these measurements were made available through the courtesy of the American Magnesium Corp. They were in the form of extruded bars 3/8 in- in diameter and several were of exceptional purity, as indicated by careful analyses. Table 1 gives the density values (at 20" C.) for magnesium of varying degrees of purity. The density was measured at room temperature by comparison of the weight in air, and when immersed in distilled water. The necessary buoyancy corrections were applied, so that the density could be expressed in absolute measure—grams per milliliter. The effect of the buoyancy of the immersed suspension and the surface-tension pull of the water upon the suspension were eliminated from the results by a preliminary weighing of the suspension immersed to the working depth. Great care was necessary to prevent the introduction of a significant error by the formation of gas bubbles upon the clean magnesium surfaces; these are sometimes very minute and easily escape observation. They may be detached by raising the specimen from the water and again immersing; this should be done just prior to completing the weighing. Their formation may be almost entirely prevented during a measurement by previously immersing the specimen in a solution of paraffin in petroleum ether. The thin film of paraffin remaining after the evaporation of the solvent prevents wetting of the magnesium surface by the water. In one such determination, the paraffin coating on a 22-gm. Specimen

Jan 1, 1923

By Junius D. Edwards, Cyril S. Taylor

Magnesium is the lightest metal used for structural purposes, for which reason perhaps more than usual interest is attached to measurements of its density. Although the density of solid magnesium has been det,ermined frequently, no measurements of the density of the liquid metal are available. Because of unusual experimental difficulties in measuring the density of the liquid, only a limited number of measurements of good precision were secured. The results, especially the value for the crystallization shrinkage, are of great interest in connection with the casting of the metal. A number of samples for these measurements were made available through the courtesy of the American Magnesium Corp. They were in the form of extruded bars 3/8 in- in diameter and several were of exceptional purity, as indicated by careful analyses. Table 1 gives the density values (at 20" C.) for magnesium of varying degrees of purity. The density was measured at room temperature by comparison of the weight in air, and when immersed in distilled water. The necessary buoyancy corrections were applied, so that the density could be expressed in absolute measure—grams per milliliter. The effect of the buoyancy of the immersed suspension and the surface-tension pull of the water upon the suspension were eliminated from the results by a preliminary weighing of the suspension immersed to the working depth. Great care was necessary to prevent the introduction of a significant error by the formation of gas bubbles upon the clean magnesium surfaces; these are sometimes very minute and easily escape observation. They may be detached by raising the specimen from the water and again immersing; this should be done just prior to completing the weighing. Their formation may be almost entirely prevented during a measurement by previously immersing the specimen in a solution of paraffin in petroleum ether. The thin film of paraffin remaining after the evaporation of the solvent prevents wetting of the magnesium surface by the water. In one such determination, the paraffin coating on a 22-gm. Specimen

Jan 1, 1923

By D. Harrington

"Coal—mine explosions are accidents that can and should be prevented. In former years hundreds of lives were lost each year in the United States as a result of such explosions, but after 1932 the numerous precautionary measures adopted had reduced their frequency and severity 75 percent or more until in 1940 several very disastrous explosions marred the good record. Unfortunately, both the number and severity of explosions seem to be tending to increase compared with the relatively good achievement from 1933 to 1940. The requisites for an explosion are ever present in all soft-coal and many hard-coal mines. A certain combination of circumstances, such as a flame or an arc in a cloud of dust or in a body of gas or both may start an explosion at any time. The fact that the frequency and severity of explosions were lowered for 6 or 7 years is no guarantee that such freedom from explosions will continue, as the bad record of 1940 has shown, and underground workers should feel honor bound to exercise the utmost care so that they will not help to bring about the circumstances that will cause an explosion.Although mine operators bear the main responsibility for preventing explosions, miners can do many things to help. As about 9 out of 10 explosions begin at a working face, it is largely within the power of workers to prevent them. All miners should do their part willingly and should not defend a fellow workman from punishment, even from discharge, for disobeying necessary rules, whose disregard may cause the death not only of the safety-rule breaker but also of many of his coworkers.When a miner is careless and is injured some other way than by an explosion he may be the only one to suffer, but if his carelessness causes an explosion he not only endangers his own life but also that of every other man in the mine and possibly the lives of persons outside the mine.Experiments have shown that ignition of as small a quantity as 150 cubic feet of an explosive mixture of methane and air under certain circumstances can start an explosion that will traverse an entire mine. Thus, ignition of an explosive mixture of gas 1 foot down from the roof and 13 feet back from the face of a 12-foot entry might cause a widespread explosion if the right quantity and kind of dust were present. Many persons have ignited much larger quantities of gas without being killed, but they survived only because dust, confinement, and other conditions were not exactly ""right."""

Nov 1, 1940

By AIME AIME

OUR own Institute of Metals and Iron and Steel divisions cooperated with the Iron and Steel Division of the American Society of Mechanical Engineers, the American Welding Society, and the American Society for Steel Treating in a busy week at Cleveland. The morning sessions were held at the Hotel Cleveland and the afternoon ones at the Auditorium, where the metallurgical exhibition under the auspices of the American Society for Steel Treating not only occupied the arena of the Auditorium but completely filled the huge adjacent Annex. In the intervals of sessions the members thronged the exhibits but in the evenings the local attendance was so great that if the crowds had been any larger it would have been difficult to see the exhibits. With so many firms, both producers of metals and of equipment accessory to their production and use, it would be impossible to mention them -all and unfair to single out a few, since no two individuals' judgment would coincide as to relative interest and importance. In any case an exhibit is a thing to be seen rather than described, and these were well worth seeing.

Jan 1, 1929

By C. S. Lord

"The Regal Silver mine is 5 miles north-northwest of Albert canyon; a station on the main line of the Canadian Pacific railway; 21 miles east of Revelstoke; British Columbia.Development, commenced in 1918, comprises more than 8,000 feet of workings from six adits, one of which extends into the Regal Silver property from the adjacent Snowflake ground. Production has been limited to a little tungsten concentrate recovered recently from a few r..undred tons of ore treated in a small underground mill. The property has received some attention as a possible source of tin. The deposits are large quartz veins containing irregular sulphide bodies. Ore minerals normally make up less than 1 per cent of the veins and include pyrite, galena, sphalerite, scheelite, and stannite. The veins are approximately parallel with the bedding of the enclosing graphitic, siliceous to calcareous, slates and argillites. These strata are of Precambrian age, strike about northwest, and dip northeast. No other rocks are known in the vicinity of the workings . Granitic rocks, intrusive into t'he sediments, outcrop 4 miles to the southwest and 7 miles to the northeast and may underlie the property at no great depth."

Jan 1, 1954

By R. J. Matetic, J. S. Peterson, P. G. Kovalchik

The National Institute for Occupational Safety and Health (NIOSH) has initiated a study of a roof bolter to reduce noise exposure to mine roof-bolter operators. An important segment of this research entails determining the affect of various drilling configurations on the performance (penetration rate) and sound power emissions when drilling into granite. Test conditions included using various combinations of rotational speeds and thrusts, using 2.54- and 3.49-mm- (1- and 1 3/8-in.-) diameter hexagonal and round drill steels, using vacuum and wet conditions and using drill media of differing compressive strengths. This paper details the affects of each of these variables on the performance and sound power level emission. When drilling into granite, it was found that wet drilling generated lower sound power levels and performed better than vacuum drilling.