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By D. J. Dodds, W. L. Schroeder

INTRODUCTION The plate loading test is a simple, useful tool in rock mechanics. The test consists of applying load to a rock surface and noting the resulting deflections. Plate loading tests are typically used to obtain modulus of deformation and related material properties, but can also provide information on blast damage and in situ stresses (1). Properties obtained are of course dependent on test procedure and test environment . In order to eliminate extraneous results it is essential that the interrelationship between the physical test environment and various rock properties obtained be thoroughly understood. Test interpretation is based upon elasticity methods, and the general assumptions made during analysis which include the following: 1. The rock is homogeneous, isotropic, elastic and continuous. 2. The stress is induced in a semi-infinite solid. 3. The plate is perfectly rigid or completely flexible. 4. Rock properties are independent of in situ stresses. 5. The plate and rock surface are smooth and parallel.

Jan 1, 1974

By R. M. Goktan

Rock brittleness plays an important role in the cutting action of picks on rock surfaces. It controls the ease with which cracks can propagate through the rocks. Although rock brittleness is known as a property that contributes to the cuttability of rocks, despite considerable research effort, there is still much uncertainty about the relation between rock brittleness and rock cutting efficiency. This fact can be attributed to the lack of a universally accepted brittleness concept and a brittleness measurement method. The existing publications of some researchers have, in a way, tended to confuse the understanding of brittleness in the general field of rock excavation where it is expected that the energy consumption of cutting should decrease with increasing brittleness of rock, other conditions being equal. However, this sometimes conflicts with the brittleness concept commonly used in rock mechanics, where the more brittle the rock the higher its mechanical strength. The ratio of rock compressive strength to tensile strength is considered by many authors to give a valuable brittleness index for drag pick operations. Hence, in this contribution the ratio of uniaxial compressive strength to tensile strength BI is considered as an index of rock brittleness, and a new methodology is proposed for its use in rock cutting efficiency analyses of drag tool operations. Validation of the suggested approach is supported by available experimental data in the literature. Contrary to the conclusions reached previously by other authors, it is shown that an increase in rock brittleness is accompanied by an increase in the cutting efficiency, other conditions being equal. Keywords: brittleness index, rock brittleness, cutting efficiency, specific energy, rock excavation.

Jan 1, 2005

Solvent extraction has recently been introduced into Australian hydrometallurgical practice for the production of a high grade uranium concentrate from El Sherana ore by a sulphuric acid leach and solvent extraction process. The solvent is a 5 per cent solution of tri(iso-octyl)amine in kerosene modified with 4 per cent of a long chain alcohol. The stripping reagent is a molar solution of sodium chloride.Preliminary testing for the development of the process showed that the leach liquor was quite amenable to the solvent extraction process and that the equilibrium and rate considerations of both the extraction and stripping steps were very favourable.The industrial plant contains four stages of extraction, three stages of chloride stripping and one stage of secondary carbonate stripping. An internal type of mixer-settler is used for the stagewise contact, the design being based on tests with model equipment.The performance and control of the industrial plant is satisfactory; 99·7 per cent of the uranium is recovered for a loss of 0·3 gallons of kerosene and 0· 4 pounds of amine per 1,000 gallons of liquor treated.INTRODUCTIONThe processing of El Sherana uranium ore from the South Alligator River valley commenced in April, 1959, and thereby introduced into Australian hydrometallurgical practice the unit operation of solvent extraction on an industrial scale. Although there are now some twelve mineral processing plants in the United States and Canada using solvent extraction, its application to the field of primary hydrometallurgy is quite new. Prior to 1956 none of these twelve plants was operating and hydrometallurgical application waslimited to the refining of comparatively high grade uranium compounds and fission products from nitrate and nitric acid solutions.

Jan 1, 1961

By Michael J. Beus

This Bureau of Mines report describes a tunnel stress relaxation gage (TSR) developed to measure initial radial displacement around full-sized underground openings. The TSR technique was shown to be a valid concept in previous field verification tests. Sensitivity has been improved by employing a titanium alloy cantilever in the transducer head, which also permits a deeper sensor location. Use of improved fabrication methods such as stainless steel bellows and sputtering techniques and use of an environmental chamber for testing greatly increased overall reliability. A miniature data acquisition system (DAS) was interfaced directly to the transducer for increased versatility and containment entirely within a borehole. The present TSR system is suitable for use around full-size underground excavations, particularly machine-bored openings. Field evaluation of the improved instrumentation verified the design goals.

Jan 1, 1978

By Murad Y. Abu-Farsakh

This paper presents the analyses of load-transfer (t-z) behavior of twelve prestressed concrete (PSC) instrumented test piles that were driven in different locations of Louisiana. The load transfer method is an efficient and practical tool for the analysis of single driven pile to predict the ultimate load. The test piles were instrumented with vibrating wire strain gauges in order to calculate the shear transfer for different soil layers during the static load test. The static load test was performed on all the test piles after 10 to 14 days of end of driving. Empirical load-transfer models were proposed previously by different researchers (Fleming 1992, Hirayama 1990, Krasinski 2012, Bohn et al. 2017) after analyzing the instrumented test pile results. For this study, load transfer of each soil layer was measured and compared with the previously developed existing model. The stiffness parameter (M) for the hyperbolic equation was calibrated in order to best match the measurements. The good agreement of the proposed curves was then confirmed by applying them to assess the overall load-settlement curve of other pile load test results available in the literature. INTRODUCTION The load transfer mechanism (stress-strain relationship) for an axially loaded pile usually comprises of three loading mechanisms: axial deformation in the pile (z), soil skin friction along the shaft (qs), and soil end-bearing (qb). The development of soil skin friction with axial deformation is referred as the t-z curve, and the development of soil end-bearing with axial deformation is referred as the q-z curve. Figure 1 presents the load transfer mechanisms in an axially loaded pile and the corresponding spring mass models for t-z and q-z curves (API, 2002). In order to construct the load transfer curve in clay under vertical load, the axial load transfer (t-z) curve and end-bearing load transfer (q-z) for that particular soil should be assessed separately. The axial load transfer (t-z) method is probably the most widely used technique to study the problem of single axially loaded piles. Therefore, the load transfer through the shaft of the pile and are getting more and more important compared to the only the pile capacity analyses. The load transferred from shaft to the surrounding clay soil is a function of the width of the pile and the surface roughness of the pile and clay properties. The development of a representative procedure allows the assessment of the t-z curve in soil (sand and/or clay) that leads to the prediction of a nonlinear vertical load-settlement response at the pile head.

Jan 1, 2018

By P. Golledge, A. D. S. Gillies

An investigation has been carried on samples of three Queensland coal dusts to determine the potential explosibility of dust-gas mixtures. The explosion potential of the samples was classified by the lean and rich limits of explosibility and the limiting oxygen concentrations for each sample. Plotting of these points showed 2-dimensional flammability limit surfaces for coal dust/oxygen, methane/oxygen and coal dust/methane mixtures. From these plots the 3-dimensional flammability envelopes defining the explosibility of the mixtures were defined. The explosion limits of the coal dust/methane/oxygen system were seen to be influenced most by the explosibility characteristics of coal dust. Methane exerted a stronger influence over the explosion limits when the coal had a low volatile content

Jun 19, 1905

Geological hazards such as faulting, basement ridges, and zones of "thin" (< 6 m) coal have a major impact on mining economics of underground operations in Huntly Coalfield. Experience has shown that drillhole-based investigations do not yield sufficiently detailed models of the coal seam to allow management of the planning risks associated with these hazards. Consequently, operational performance is affected by unplanned costs associated with lower productivity, loss of coal reserves, and expensive strata control remedies in problem ground conditions. Huntly Coalfield is a challenging environment for acquisition of good quality seismic reflection data due to the very thick (10-85m) weathering layer. Since 1994, successful acquisition of 2D and 3D data has been achieved through a combination of careful testing of technical parameters and experimental trials prior to committing to production recording. High resolution seismic reflection (HRSR) is proving to be an investigations technique which generates accurate and reliable models of the coal seam and associated structures, such as normal faults and topography of the surface on which the coal seam rests. The HRSR technique has been applied and developed in the Okowhao Sector where Huntly East Mine is developing and extracting coal reserves. Results of a recent 3D survey demonstrate that this technique is capable of revolutionising risk management in mine planning for underground mines in structurally complicated coal deposits.

Jan 1, 1997

The expansion of hydrometallurgical operations, declining ore grades and upwardly spiralling production increases the demand for fresh and recycled water with low levels of contaminants. The minerals industry is also increasingly being forced both by regulatory and cost pressures to reduce the amount of liquid waste they produce. This requires a strong focus on waste reduction by recycling, regeneration and reuse. However, these measures are often not enough in arid countries for a forward progress and expansion of their mining activities.   It is often the case that in the arid and semi-arid countries the only available water is either sea water or underground (brackish to hypersaline) saline waters. Brackish waters can be desalted at a reasonable cost but the desalination of highly saline waters is challenging and expensive.   There are emerging reports that sea water and in some cases hypersaline underground waters are now used by various mining industries as process water. This study explores the possibility of the use of sea water in various mineral processing and hydrometallurgical processes and briefly discusses the benefits and problems related to the use of saline waters at the mine and mill site. Several cases studies and preliminary laboratory test results are presented.

Jun 1, 2010

By T. Gammatikopoulos, C. Gibson, M. Aghamirian

Lithium is an alkali metal found in brine deposits in the United States, Chile and Argentina, as well as in hard rock deposits in Australia and North America. In hard rock deposits, spodumene (LiAl(Si2O6)) is the major economic lithium bearing mineral. Spodumene is typically upgraded through a combination of dense media separation, flotation and magnetic separation. One of the major spodumene concentrate quality specifications is the iron oxide content because it will help determine if the concentrate is considered ceramic grade for use in ceramics and glass or chemical grade for use in lithium ion batteries. The rejection of iron bearing silicate minerals from artificial ore composites (high amphibole and low amphibole, high quartz/feldspar) from a hard-rock spodumene deposit was investigated using magnetic separation and flotation. The efficacy of Wet High Intensity Magnetic Separation (WHIMS) in iron rejection was found to be dependent on the mineralogy of the iron-bearing silicate minerals including modal distribution, liberation and association. When magnetic separation was conducted prior to flotation, the Fe2O3 grade in the final flotation spodumene concentrate was reduced from ~3% to ~1% Fe2O3 , and improved lithium recovery in flotation was observed. It was determined that it was most effective to conduct WHIMS on the flotation feed after scrubbing and de-sliming because this reduced the required magnetic field to recover iron-bearing minerals, likely because slime coating was greatly reduced. Flotation collector screening of four different collectors with varying rosin acid content demonstrated a potential increase in selective flotation of spodumene over some iron silicate minerals with decreasing rosin acid content in the fatty acid collector. However, due to marginal difference in flotation results with the various collectors tested, further testing is required to confirm the observations made and establish a hypothesis regarding the effect of rosin acid content.

Jan 1, 2017

By Bruce Richardson

A contractor-manufactured 4.75m (15'-7") diameter EPB shield excavated a 115m (375 ft) long tunnel under the San Antonio River as part of the Salado Creek to Dos Rios Pipeline Interconnect Project in San Antonio, Texas. Lignite, limestone concretions, and sandstone in the face of the tunnel required the use of disc cutters. Less than 7.6m (25 ft) of sand and gravel hydraulically connected the top of the tunnel to the channel of the river. Fully lagged steel ribs with filter fabric were used for initial ground support and water control. This and other contractor manufactured TBMs in the 1.2 to 4.75m (4 to 16 ft) range are presented with descriptions of the jobsites, equipment, performances, and problems.

Jan 1, 2008

By S. P. Ball, A. J. Monhemius

In a laboratory study under acidic oxidising conditions, the thiocyanate system gave results at least as good as cyanide and considerably better than thiourea, with modest consumption of SCN (less than 1 kg/t ore). For both cyanide and thiocyanate lixiviants a residence time of about 24 h was required for maximum gold extraction, which was generally in the range of 92-96%. The adsorption of gold from thiocyanate leach liquors was found to be rapid, but activated carbon catalyses the autoreduction of ferric iron to ferrous iron in thiocyanate solutions, suggesting that ion exchange may be a better recovery route

Dec 1, 1995

By C. Tan, C. Detournay

Wellbore stability is a major concern for drilling in naturally fractured formations. The infiltration of drilling mud into the fractures is a factor, which may compromise wellbore integrity due to the loss of strength experienced by the fractures. The reduction in the fracture frictional and cohesive properties is attributed to weakening of the infill materials and lubrication of fracture asperities by the mud filtrate. One way to investigate the influence of mud infiltration on wellbore stability in fractured formations is to use a numerical modeling approach. A requirement for the numerical model is the ability to predict the region of mud infiltration. This paper describes a numerical technique to model the extent of mud infiltration for application in coupled fluid-mechanical simulations in densely fractured rock masses using the computer code, UDEC. Several factors are considered including fracture pattern, in-situ stresses, reduction in joint frictional angle and cohesion, viscosity of the mud filtrate and fracture plugging. Results of numerical simulations are presented to illustrate the technique and show the influence of these factors on the extent of mud infiltration. Un des problèmes importants posés par le forage en milieu fissuré saturé, est celui du maintient de la stabilité du puit. L’infiltration de boue de forage dans le massif peut avoir pour effet de réduire les propriétés frictionnelles et cohésives des fractures et de compromettre ainsi la stabilité du puit de forage. Le radoucissement des propriétés des fractures est attribué à la dégradation du materiau de remplissage et au pouvoir lubrifiant des boues. L’analyse numérique offre un moyen d’investiguer l’influence jouée par l’infiltration de boue sur la stabilité du puit. Un des critères de sélection du modèle numérique sera son pouvoir de prédiction du domaine d’infiltration de boue. Cet article décrit une technique numérique permettant de modéliser l’infiltration de boue de forage dans le cadre de simulations hydro-mécaniques, en milieu à haute densité de fractures, effectuées avec le logiciel de calcul UDEC. Parmis les facteurs tenus en compte, on trouvera la nature du réseau de fractures, les contraintes in-situ, le radoucissement en friction et cohésion des joints, la viscosité de la boue et le bourrage des fractures. Des résultats de simulations sont présentés pour illustrer la technique et montrer l’influence de ces facteurs sur la taille du domaine d’infiltration de boue. Bohrlochstabilität ist ein wichtiger Aspekt für das Bohren in geklüfteten Gebirgsformationen. Das Eindringen der Bohrlochstützflüssigkeit in die Klüfte kann die Bohrlochintegrität wegen des Verlustes der Festigkeit des Kluftsystems gefährden. Die Reduktion der Reibung und kohäsiven Eigenschaften ist der Schwächung der Kluftfüllung und der Schmierwirkung der eingerungenen Stützflüssigkeit in Bezug auf die Kluft-Asperities geschuldet. Numerische Berechnungen sind ein Weg zur Untersuchung des Einflusses der Infiltration der Bohrlochstützflüssigkeit auf die Bohrlochstabilität in geklüfteten Gebirgsformationen. Eine Voraussetzung für numerische Modelle ist die Fähigkeit den Bereich der Infiltration der Stützflüssigkeit zu prognostizieren. Diese Publikation beschreibt ein numerisches Verfahren, um die Reichweite der Infiltration von Stützflüssigkeiten mittels fluid-mechanisch gekoppelter Simulationen im engständig geklüfteten Gebirge mit dem Programm UDEC zu modellieren. Verschiedene Faktoren, wie Kluftmuster, Gebirgsspannungszustand, Reduktion von Kluftreibungswinkel- und kohäsion, Viskosität der Stützflüssigkeit und Rissabdichtung wurden untersucht. Ergebnisse numerischer Simulationen werden präsentiert, um die Vorgehensweise zu illu

Jan 1, 2003

[This is the sixth in a series of reports on properties of commercial motor fuels, made in accordance with a cooperative Agreement between the Cooperative Fuel Research (C.F.R.) Committee and the Bureau of tines of the Department of the Interior. The first report gave data on motor gasolines sold during the winter of 1935.-36.3/ The present report cover brands of gasoline represented by 1,490 samples plus thus: from the Pacific Coat, which ;sere averaged by the Pacific Coast Technical Group before being submitted and are published exactly as they were submitted. In some areas reports were received from 8 to 10 companies on the same brands of gasoline, Whereas in other areas only one Company reported on a brand. Thus, it can be seen that soma of the data are more representative than others. The inclusion of data from several cities within some of the districts has improved the report by reducing the number of brands reported by only one company. Severe changes have been made in the districts. A new district, Memphis, Tenn., has been formed to include Arkansas any western Tennessee. The Rocky Mountain area, have been divided into three sections. Salt Lake City and Denver form the Middle Rocky Mountain district; Laramie, Wyo., Idaho, Montana, and. Spokane, Wash., are included in the North Rocky Mountain district, and Arizona, New Mexico , and El Paso, Tex., have been combined to represent the South Rock Mountain district. The Cleveland district has been expanded to include Ohio ant. Indiana. Eastern Pennsylvania, Maryland, and northern Virginia are included in the Washington (D. C.) district. The Atlanta district includes Georgia, South Carolina; Mississippee, and northern Florida.]

Jan 1, 1938

By I. L. Nichols

The inplace cyanidation leaching of gold from placer deposits is a potential method for treating gravels too deeply buried and too low in gold content to be processed economically by conventional dredging methods. Laboratory experiments were made to evaluate those placer cyanidation factors adaptable to small-scale studies. The variables investigated included gold particle size and location in sand beds, cyanide solution flow rate, and cyanide solution strength as factors affecting gold solubility rates. The solution flow rate, in turn, was influenced by variables such as bed slope, solution head pressure, and sand size, and the effects of these factors were studied. Free gold, minus 150-mesh and finer in size, is rapidly dissolved by dilute cyanide solutions from mixtures of gold and silica sand prepared to simulate placer deposits. About 94 percent of minus 325-mesh free gold was extracted in 5 hours from silica sand mixtures, and 94 percent extraction of minus 150-mesh gold was obtained in 21 hours with 0.1 percent NaCN solutions. Moving solutions were almost twice as effective in leaching free gold from silica sand mixtures than stagnant solutions.

Jan 1, 1971

By B. C. Lewis

Have technological advancements in underground coal mining driven people's skills to new highs or have the expanded skills of mining people driven the industry's technological advancements. Who knows? What we do know is that both our technology and our people have made meaningful and significant advancements. Overall, longwall systems continue to increase productivity and retreat faster. Globally, gate road development is the primary bottleneck in a longwall mine. The primary bottleneck in gate road development is roofbolting. Generally, roofbolting is the bottleneck in room and pillar operations as well. This paper will present an integrated manufacturer's (Joy Mining Machinery) vision of the future in comparison to current equipment performance. Particular emphasis will be placed on roofbolter technologies.

Jan 1, 1999

By Nicholas Chlumecky

One of the oldest mine supports in use today is timber cribbing. In many mining operations material, installation and maintenance costs for timber cribbings are substantial. Their performance characteristics also add to mining costs. During the 1970'6, the U.S. Bureau of Mines recognized many of the deficiencies of timber cribbing and very successfully initiated the development of steel-fiber- reinforced (SFR) concrete blocks. Since the early 1980's this SFR concrete cribbing has been manufactured as a high quality product which has found increasing acceptance by mine operators. The rapid acceptance of the SFR concrete block cribbing has proven that its use is eliminating many of the deficiencies of timber cribbing while providing superior load carrying capability. The use of SPR concrete blocks to build the cribbing is based on the same principle as wood. That is, stacking longitudinal, rectangular blocks in layers in a crisscross manner. The blocks are positioned at right angles to the blocks of the layer below. With this situation, the possibility of misalignment exists when the concrete blocks at the base are not placed exactly parallel or when the blocks of the base are subject to unequal settlement. Such misalignments creates localized, high stress areas which reduces the load capacity of the cribbing made from SFR concrete blocks. Recognizing the problem of misalignment, the Underground Supports Division of Commercial Shearing, Inc., conceived a circular, one-piece, steel-fiber-reinforced concrete cribbing which is being marketed under the name - Donut Cribbing. This concept eliminates the possibility of misalignment and provides 100% bearing between layers of stacked cribbing as well as other advantages. The purpose of this paper is to discuss the performance characteristics, installation speed and economical factors of each of the three cribbing types -- timber cribbing, SFR concrete block cribbing and SFR concrete Donut Cribbing.

Jan 1, 1986

By C. W. Siyasiya, K. A. Annan, W. E. Stumpf

"SynopsisThe relationship between niobium content and austenite grain growth has been investigated through hot rolling simulation on a Bähr dilatometer. The effect of delay time between passes during rough rolling in Nbmicroalloyed steels with nitrogen contents typical for electric arc furnace (EAF) melting was studied. The results indicate that the grain growth constants n, Q, and A increase with an increase in Nb content. The activation energy for austenite grain growth Q was found to be in the range of 239 to 572 kJ/mol, the exponential constant n ranged from 2.8 to 6.2, and the material and processing condition constant A from 4.24 × 1012 to 4.96 × 1028, for steels with niobium contents ranging from 0.002% Nb to 0.1% Nb. A general constitutive equation for the prediction of austenite grain growth in these Nb-microalloyed steels under rough rolling conditions has been developed. Good agreement between the experimental and the predicted values was achieved with this constitutive equation.IntroductionGrain refinement has been found to increase both the strength and toughness of steels (Gao and Baker, 1998; Sharma, Lakshmanan, and Kirkaldy, 1984; Seok et al., 2014; Maalekian et al., 2012). It is also known that the austenite grain size directly influences the microstructure, and thus the mechanical properties, of the steel (Maalekian et al., 2012; Yue et al., 2010). Effective grain growth control is reported to be achieved through addition of precipitate-forming elements, such as Nb that, slow down the grain boundary migration through pinning and solute drag mechanisms (Yu et al., 2010; Olasolo et al., 2011; Alogab et al., 2007). Much work has been carried out on austenite grain lsize control by the addition of precipitate-forming elements that have a strong affinity for interstitial elements, such as carbon and nitrogen, which form the dispersed pinning particles to inhibit the austenite grain growth (Alogab et al. 2007; Hodgson and Gibbs, 1992; Nanba et al., 2003; Flores and Martinez, 1997; Rollett, Srolovitz and Anderson, 1989). Austenite grain growth can be described using a conventional or a modelling approach. With conventional approaches (e.g. metallography), in-situ monitoring of austenite grain growth at high temperatures is impossible. Modelling the grain growth behaviour based on available data is the ideal option. To quantitatively describe austenite grain growth therefore requires development of a sound mathematical austenite grain growth equation that accounts for the effects of the varying microalloying elements in inhibiting austenite grain growth. Numerous attempts have been made to develop an empirical model based on the general equation developed by Sellars and Whiteman (1979). Many of these models do not account for the direct effects of the microalloying elements such as Nb in austenite grain growth control [Fu et al., 2011; Wang and Wang, 2008; Wang et al., 2006; Shanmugama et al., 2005; Banerjee et al., 2010; Pous-Romeroa et al., 2013). The current work has considered this limitation, taking into account the direct effect of niobium in grain growth control during thermal processing. This is done by incorporating the initial austenite grain size Do and the microalloying element niobium in the development of a constitutive equation for grain growth prediction in Nb-containing microalloyed steels."

Jan 1, 2015

By Michael Schmitz, Eugene Ahrenholtz, William A. Heitbrink, Jeanne A. Zimmer, Andrew B. Cecala, Ernest S. Moyer, Earle H. Andrews, Chris C. Coppock, John A. Organiscak

Many different types of surface mining equipment use enclosed cabs to protect equipment operators from health and safety hazards. The overburden removal and mining process can be extremely dusty and can cause excessive dust exposure. To study this issue, a cooperative research effort was established between the National Institute for Occupational Safety and Health, U.S. Silica Co., Clean Air Filter Co., and Red Dot Corp. in an effort to lower respirable dust levels in an enclosed cab on an older surface drill at a silica sand operation. Throughout this research effort, a number of modifications were incorporated into the drill's filtration and pressurization system, as well as in other areas, to improve its design and performance. An average cab efficiency of 93.4% was determined with gravimetric sampling instruments when comparing the outside with the inside cab dust levels on the final design. Although this study considered just one operation, the goal was to identify cost-effective improvements that could be implemented on all types of enclosed cabs to lower respirable dust concentrations. Two critical components for an effective enclosed cab system are having a properly designed, installed, and maintained filtration and pressurization system, along with a method for maintaining structural cab integrity, which allows the cab to be positively pressurized. Another important component is maintaining cab cleanliness. Although this research was originally directed toward the mining industry, it is also applicable to agricultural or construction equipment.

By Henry P. Chandler

[Diamond, because of its extreme hardness and abrasion resistance, has an important function in precision engineering and automation. With the increasing; requirements of modern production for fine tolerances, interchange-ability, and speed, it has become even more important. In spite of the supply of other abrasive and hard materials and of ultrasonic, electrospark rued other substitute grinding, methods, world industry seams likely to absorb large quantities of diamond for industrial purposes. An increasing part of the world's needs will be supplied by manufactured diamond, which was introduced commercially by General Electric Co. in 1957. Use of diamond for glass cutting roes bark several centuries, mid diamond drilling of rock became important to the mining industry M the 1870's. Today, diamond drilling is the most extensively used method of exploring the world's ore reserves; diamond drills two also used to determined the nature of bedrock below the foundations of buildings, dams, and bridges. Diamond drill bits are now used extensively in the petroleum industry, and replacement or steel rock bits with diamond drill bits in hard rock formations has affected substantial savings.]

Jan 1, 1964

By Henry P. Chandler

[Diamond, because of its extreme hardness and abrasion resistance, has an important function in precision engineering and automation. With the increasing; requirements of modern production for fine tolerances, interchangeability, and speed, it has become even hors, important in spite of the supply of other abrasive and hard materials and of ultrasonic, electrospspark rued other substitute grinding methods world industry seems likely to absorb large quantities of diamond for industrial purposes. An increasing part of the world's needs will be supplied by manufactured diamond, which was introduced commercially by General Electric Co. in 1957. Use of diamond for glass cutting goes bark several centuries, mid diamond drilling of rock became important to the mining industry M the 1870's. Today, diamond drilling is the most extensively used method of exploring the world's ore reserves; diamond drills two also used to determine the nature of bedrock below the foundations of buildings, dams, and bridges. Diamond drill bits are now used extensively in the petroleum industry, and replacement or steel rock bits with diamond drill bits in hard rock formations has effected substantial savings.]

Jan 1, 1964