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By R. Macleod, G. G. Bursey, T. R. C. Aston, J. E. Gale

In 1991 the problems of water inflow at the mine were addressed by a three-phase study. A three-dimensional finite-element computer code, CFEST (Coupled Fluid, Energy and Solute Transport), was used to model the system of groundwater flow around the mine, allowing assessment of the nature of the hydrological regime and of the various recharge mechanisms and sources of inflow. A regional (111 km2) model was used to simulate conditions of low to average mine inflow and provide boundary conditions for the subsequent local (16.8 km2) model. The regional model produced inflows of 0.26 m3/s and the local model 0.25 m3/s. With the use of constant head conditions to simulate a saturated flood plain along the Gays River and on doubling the rate of surface recharge, the local model produced a maximum mine inflow of 0.255 m3/s, in contrast to a measured peak mine inflow of 0.37 m3/s. The discrepancy suggests that during periods of high river level surface water gains access to features with high permeability, such as sinkholes, that may be connected directly or indirectly to the mine workings. Improved simulation of high inflow conditions can probably be achieved by determining the hydraulic conductivity of the river-bed and flood-plain sediments and modelling known sinkholes as discrete units. Possibilities for controlling the amount of inflow to the mine include sealing the flood plain with dykes, checking regularly for new sinkholes, which should be filled and capped, maintaining adequate mine drainage, and monitoring well levels and pressures on a continuous basis.

Jan 12, 1993

By R. V. Ramani, W. Miola

"A relationship exists between the quartz contents in the underground coal nine airborne dust samples and those in the coal and host rocks that are mined [17, 18, 19] The prescribed method for quartz analysis in respirable airborne coal dust samples is the MSHA P-7 method. Accurate quartz analysis procedures are needed for bulk samples in order to predict the potential quartz content in airborne nine dust, which in turn will aid the design of quartz dust control procedures during mining. thereby reducing the airborne quartz dust in underground atmospheres. The requirements of this method are that the amount of quartz is the sample be less than 250ug, and the total sample weight less than 2,500 ug. Unlike with airborne dust samples, there are no limitations to the available mass of bulk samples. However, these are no standard procedures for the preparation of bulk samples for scanning or prescribed methods for quartz analysis. The NIOSH and MSHA methods are certified for roped* dust and the acceptance of these methods for bulk samples assumes that the bulk samples will be reduced to the conditions specified for respirable dust samples. An alternative method is X-ray diffraction, which provides higher average quartz values than those obtained from P-7 method for the same samples.An investigation was carried out to determine the optimal procedure for preparing the bulk samples for the IR and XRD analyses. In this paper, the investigations on the effects of calibration, particle sizes, matrix composition, interferrous, and behavior of the filter substances on IR, XRD and FTIR results are presented. The error introduced by the presence of kaolinite and a new sample asking procedure to reduce it are discussed. The problems experienced with conventional sample holders for scanning were eliminated with the design and development of a new hollow sample holder. Quantitative comparison of quartz determinations by IR, XRD and MR methods on coal, roof and floor rocks, and airborne dust samples are presented. The important factors affecting the results of quartz analysis methods are: 1) bulk sample preparation for obtaining representative and homogeneous analysis samples: 2) particle size distributions of the analysis samples and calibration standards; 3) qualitative matrix composition of the analysis sample; 4) matching calibration standards to analysis sample; 5) substrates for sample deposition during analysis sample preparation; 6) procedures for analysis sample mounting; 7) selection of proper portions of she response profile for insanity measurement; and 8) interferences of spurious phases with the critical analyses. The recommendations of this study are important to enable comparisons and interpretations of analysis and research results."

Nov 1, 1995

By Paul F. Gnirk, Ralph A. Wagner, Joe L. Ratigan

This thermomechanical analysis used the finite element method to investigate the behavior of crushed salt backfill in a waste disposal room situated in a salt dome repository. The first of two objectives was to determine the transient temperature rise and degree of thermomechanical consolidation that occur in the backfill as a function of drillhole depths. The second objective involved the evaluation of closure due to salt creep of unlined emplacement drillholes and the determination of pressure on steel sleeve liners in the drillholes should liners become necessary for canister retrieval. The retrievability period was considered to extend for 25 years after waste emplacement. The canisters were assumed to contain ten-year old high level waste with a thermal output of 4.3 kW at the time of emplacement.

Jan 1, 1981

By Bhaskar B. Thapa

The proposed Caldecott fourth bore will consist of a two lane highway tunnel along California State Route 24 near the City of Oakland. The proposed design and construction sequence for the 15-m-diameter tunnel are based on the New Austrian Tunneling Method (NATM). The initial support system incorporates combinations of shotcrete, rock dowels, lattice girders, spiles, and grouted steel pipe canopies. The final lining is cast-in-place reinforced concrete. A waterproofing membrane and drainage system are placed between the initial and final linings. State Route 24 is a lifeline route, required to be open to emergency vehicles within 72 hours after a major earthquake, defined as having a return period of 1,500 years and a peak ground acceleration of 1.2 g. Although the seismic design criteria are stringent, the design of the tunnel lining system is ultimately controlled by static ground loads in the weak rock along the alignment.

Jan 1, 2008

By L. W. Luo

Zeolite in some regions or countries of the world have been the subjects of materials for environmental remediation involving the use of removal to heavy metal ions and some organic pollutant as a sorbent because of its capacious ions exchange and huge surface area. This article addresses the equilibrium and kinetics for manganese adsorption using zeolite modified by hexadecyl trimethyl ammonium bromide (HTMAB) as a sorbent material over a range of pH between 3.4~7.2 with eight different Mn(?) solution concentrations. PHzpc (pH of zero point charge) of the sorbent was examined according to the method proposed by Tripathy and Kanungo, and a value of 6.91 was obtained. The experimental data fit langmuir?s model for the majority of pH and Mn(?) solution concentrations tested (0.92<R2<0.97). The maximal adsorption capacity, qm ascending with pH between 3.4~7.2, rise from 15.01mg?g-1 at 3.4 to 19.46 mg?g-1 at 7.2. Besides, the constant of Freundlich Kf have the same trend with qm, increases with pH ascending. And the sorption intensity, represented by parameter 1/n in Freundlich?s model, is favorable in entire range of metal ions concentration studied. Finally, kinetics data accurately fit to pseudo-second order which indicate that there must be sorption of Mn(?) behavior occurring on inner-sphere of the sorbent.

Jan 1, 2014

By Pat Wilmoth, Joseph P. Gildner, Dan Nowak, Shane Yanagisawa, Don Z. Painter, Gordon F. Revey

Frontier/Traylor is presently completing construction of twin tunnels for the Tri-County Metropolitan Transit District of Oregon’s (Tri-Met) westside lightrail system. The tunnels are each 4,550 m (14,935 ft) in length and 6.48 m (21.29 ft) in diameter. The 1/3 of each tunnel was driven from the west portal using drill and blast methods and the remaining 2/3 was driven from the east portal using a TBM. The paper describes: The difficulties encountered by the TBM mining the weathered Columbia River Basalts. The execution of drill and blast work despite challenging ground conditions, stringent noise and vibrations specifications, and public relations problems. The excavation and lining of the Washington Park Station 79 m (260 ft) below the park zoo.

Jan 1, 1997

NATURE OF ORETHE Edna May ore consists mainly of clean quartz of a moderately hard and tough nature. The gold content is &quot;free&quot; and fairly coarse, so that a large percentage is recovered by amalgamation. The ore is practically free from metallic minerals.GENERAL OUTLINE OF PLANT AND TREATMENTThe ore, received from underground in trucks, is broken by a jaw breaker, then stamp-milled, follow~d by partial filie-grinding in pans. Mercury is used both in the mill boxes and pans. The pulp, on leaving the pans, passes over amalgamating tables and is then elevated by tailings pulp to cone classifiers and separated into a sand and slime product, each product receiving a separate cyanide treatment-sand by leaching in vats and slime by agitation and decantation in a &quot;Trent&quot; plant. Gold solutions from both sand and slime are precipitated together by zinc shavings in the usual type of precipitation boxes. Accumulated slime is trucked from the dam to a vortex mixer and from this point receives with the cement slime the same treatment.ORE BREAKING AND TRANSPORTThe ore is trucked from the brace of the shaft along an overhead line to the breaker station. Hence it is, by means of a &quot;kick-up&quot; dumped upon a grizzly, set with 2-in. spaces, the oversize being broken by a 15 x &apos;9 Fraser and Chalmer jaw...

Jan 1, 1919

By Linli Wu

During the measurement of contact angle, a misty band was observed near the substrate. Hsien-Nan Ho and Shinn-Tyan Wu thought this was because the oxygen atoms on the interface migrate to the droplet surface to form an oxide band near the substrate. But from our experiments misty band appeared before the drop reach to the substrate. Theoretically speaking, the oxygen partial was the same everywhere in the vacuum furnace. So there was no condition to provide enough oxygen forming oxide. This appearance would be explained more reasonably with the optics principle. Most reflected light would be absorbed by the substrate and the light cannot reach the observation area, so the misty band formed.

Jan 1, 2006

By R. Stenne

This paper deals with a complementary soil investigation which being part of the contract helped understand the behavior of a softened clay and adjusted the design of a retaining structure accordingly. The investigated softened clay proved to have lost its original strength but had maintained some characteristics of its stress history and in particular high horizontal stress. Pressuremeter tests and flat dilatometer tests were of interest to estimate the at rest earth pressure. A design consisting of a T-shaped slurry wall in conjunction with transverse walls was the most effective solution to cope with high active pressures and low passive pressures.

Jan 1, 2000

D. M. Riordan has been appointed a member of the Institute Com¬mittee of the Engineers&apos; Reserve Corps movement. Our Committee, therefore, now consists of Henry S. Drinker, Chairman, Messrs. Arthur S. Dwight, Warren A. Wilbur and D. M. Riordan.

Jan 1, 1916

By S. J. Dai

The cadmium and cyanide are main poisonous components in cyanide electroplating cadmium waste water of an electroplating plant in Shenyang. The content of cadmium is about 26 mg/L and the content of cyanide is about 11.782 mg/L in this waste water. The main form of cadmium and cyanide are ions which are Cd2+and CN?. Because the cadmium and cyanide exceeded the standard seriously, the waste water must be disposed before it discharges. The microbiological method of treating heavy metals in wastewater has many advantages. For example, it has a fast adsorption velocity, high processing efficiency, wide range of pH and temperature, few invest, low running cost, no the second pollution and so on. At the same time, the CN? could be degradated by some microbiology. The physical nature, the chemical nature of Bacillus mucilaginosus, the adsorbing condition and adsorbing regular of Bacillus mucilaginosus to cadmium in the wastewater are studied by using Bacillus mucilaginosus as adsorbent removing cadmium from electroplating wastewater. The experimental results show that the adsorbing rate of cadmium is over 92%, under the room temperature(about 25?), stiring revolution in adsorption being 800 r/min for 30 min, pH being 5 , the bacteria being cultured after 5d with the biomass of Bacillus mucilaginosus 40g/L (wet weight). The mechanism in biosorption process of Bacillus mucilaginosus to cadmium is analyzed and discussed by TEM , Zeta potential,and infrared spectroscopy analysis. The results showed, the chemical involving is main adsorbing form, while electrostatic attraction, ions exchange, hydrogen bonding and Van Der Waals force are concerned cooperatively. ?NH2 ?, ?C=O?, ?C=O?NH?CH2, ?CH3, ?OH are main adsorbing groups. At the same time, the floatablity of removing cyanide by Bacillus mucilaginosus is explored.

Jan 1, 2014

By Creelman C. A

The removal of a horizontal piIlar between Nos. 9 and 11 levels (1,116 feet from the collar of main shaft) was successfully carried out by blast hole drilling, and, to the best of the authors&apos; knowledge, this mass blast of 40,000 tons of ore (requiring the use of 7,150 Ibs. of explosive and 5,385 feet of primacord) was the first occasion on which a task of this magnitude has been carried out underground in an Australian mine.Blast hole drilling was introduced by this company approximately fifteen months ago at New Cobar Mine in sub-level stoping.This experimental drilling and blasting gave very valuable information as to the correct technique to be adopted when the final plans were being prepared for the removal of the horizontal pillar at New Occidental Mine.The dimensions of this pillar were approximately 15 feet long, and from 40 to 60 feet wide, and 65 feet in depth.The block of ore extended to 35 feet above the level and 30 feet below, the upper section being partially excavated to form the bell-hole floor and grizzly chambers used for drawing off the broken ore in the shrink stope above the No. 10 level.Description of Ore-bodyThe main ore-body is situated almost vertically in a well-defined shear zone at the junction of sandstone and slate, the sandstone forming the eastern and the slate the western wall.The ore-body consists of highly silicified slate (chert) sparsely impregnated with sulphides, containing a small percentage of copper and bismuth.The total length of the ore-body is approximately 450 feet, with a maximum width of 60 feet in the main section, which is about 200 feet long.This is the section shown in longitudinal and cross-section (Fig. 1).The ore-body is divided by a horse of mullock in the northern end into two legs, the eastern and western, which are approximately 250 feet long and averaging 25 feet in width.This ore-body is strong, hard and abrasive with extremely strong walls, an ideal proposition for open stoping and mass blasting.MiningIn all levels above No. 9 the cut and fill method of ore extraction was adopted. On Nos. 10 and 11 levels the shrinkage method was introduced with economical results, and no difficulty had ever been experienced with shabby or bad walls.Shrink stoping had been carried upwards from No. 11 level to within 10 feet of No. 10 level, when mining hazards developed, and instead of...

Jan 1, 1944

By H. J. McQueen

The irregular history of Mg wrought products is briefly described. The temperature and strain rate dependence of microstructural evolution, flow stress and ductility of Mg alloys in hot working, are described. The flow curves rose rapidly to a peak stress which was lower as temperature T rose and strain rate e declined and above 300°C the curves extended into plateaus until failure. Clearly grains not oriented for slip undergo mechanical twinning in the initial stages (a 0.15) at all temperatures. Basal slip proceeds in suitable grains and in the twins. The stress concentrations at grain and twin boundaries lead to slip on non-basal systems and to the formation of subgrains with greater dynamic recovery (DRV) at higher T or lower e. With increasing strain, misorientation builds up resulting in dynamic recrystallization (DRX) first at twin intersections and later at grain boundaries which have become quite serrated. Even after extensive straining at high temperatures, the new grains are found mainly along the boundaries of the original grains, leaving their centers with only basal slip except when nucleation at twins leads to completion of DRX throughout a grain. Despite similar shear modulus and melting point to Al, hot mechanical forming behavior of Mg alloys differ due to differences in crystal slip systems, twinning, and second phases. Moreover, the influences on forming of alloy additions (solutes, segregation in casting, dispersoids, precipitation) and impurities are not as well catalogued as for Al. Despite the benefits from dynamic recrystallization, varied grain orientation effects, heterogeneous substructures and the resulting stress concentrations result in considerably lower ductility for Mg alloys at the same stress level as for Al materials. Application of these theories to extrusion, rolling and forging and the effects on product properties are surveyed.

Jan 1, 2006

By W. G. Bearden, G. C. Howard, J. W. Spurlock

An investigation of the factors af-fec.ting the inter-zonal flow of fluids in the casing-wellbore annrc1rt.s of an oil or gas ivell is presented Laborntory tests revealed that failure of the caring-cement bond allows communi-cation of fluid at pressure differentials near 1.000 psi. Perforating with a 11011011: carrier gun does not shatter or crack the cement sufficiently to allow communication through these cracks and does not seriously affect the casing-cement bond failure pressure. The pressure to cause communication at the casing-cement bond can he increared to 3,000 psi by. limiting pipe deformation during cementing and subsequent operations. Communication can be prevented, however. up to pressures sufficient to cause the cement to fail or the casing to col-lapse, by attaching to the casing a seal ring of deformable ruhber molded between two steel flanges. When installed, one flange is attached rigidlv to the casing to serve as back-up for the gasket While tile other flange is movable. To date, these gasket seal rings have been field-tested in 27 Wells. Althotrgh communication has been noted in two wells, inter-zonal flow has been prevented in other wells in the same area by installing more seal rings between the communicaring zones. INTRODUCTION The inter-zonal flow of fluids behind casing cemented in oil wells during normal production or stimulation operations is a major operating problem. If it cccurs during production operations. it can seriously limit the pressure to which a reservoir may be depleted without harmful invasion of unwanted fluids. If it occurs during stimulation operations, it may preclude the possibility of stimulating the desired zone. This communication can be caused by failure of the bond between the casing and cement, failure of the bond between the cement and formation, or failure of the cement itself. This paper presents the results of an investigation of factors affecting com-munication at the casing-cement bond and methods which aid in preventing it. LABORATORY INVESTIGATIONS The laboratory tests performed in this study were divided into three phases. The first phase consisted of tests to determine if perforating would shatter and crack the cement sheath so severely that communication would occur through the cement itself. The second phase consisted of tests to determine more precisely the cause for the casing-cement bond failure. The third phase consisted of tests to evaluate the effectiveness of various de-formable seals attached to the casing in preventing communication. EFFECT OF PERFORATING, The effect of perforating was invest~gated in tests performed with apparatus shown on Fig. 1. Cement was poured into the annulur space hetween 5%-in. casing and 8%-in. casing and allowed to cure for 72 hours. The apparatus was then perforated with a hollow carrier gun containing eight duPont 26-A shaped charges. Bull plugs were placed over the perforations in the 8 5/8-in. casing and hydraulic pressure was applied inside the 5 1/2i-in. casing. The pressure to cause fluid communication past the cement sheath was observed and termed the "bond failure pressure". Several different cement compositions were included in these tests, the results of which are shown in Table 1. In Tests 1 through 4 of Table 1, bond failure occurred at- the inter- .

Jan 1, 1966

By Iman G. Ghanad

El presente texto describe un nuevo método para el tratamiento de concentrados de cobre con alto contenido de arsénico utilizando el carbón activado como catalizador. Para ello, se realizaron pruebas de lixiviación con concentrados de enargita de tres minas de Chile, Perú y Estados Unidos, donde los resultados señalaron que la disolución de la enargita fue más rápido con la influencia del carbón en la solución lixiviante, incluso después de haber reciclado el carbón.

Sep 12, 2011

H. H. Kellogg (Columbia University)—The accurate measurements of the equilibrium gas ratios for the reaction: Pb(1) + H2S = PbS(c) + H2 [I] reported in this paper are a distinct contribution to the literature, and the authors are to be congratulated. I wish to comment, however, on the correlation of the data which is presented. The authors show a straight line correlation of log H2S/H2 vs 1/T, Fig. 1, and are satisfied with this for calculation of ?Fo even when extrapolated to low temperature (427 °C). Heat capacity data for the constituents of this reaction are available (at least to 900°K), however, and ACP for reaction [I] is finite and positive in the temperature range studied. Simplification of the heat capacity equations yields: ?CP= 2.71 + 1.65 x 10-3T (298°-900°K) This positive value of ?CP should result in a small but noticeable curvature of a plot of log K vs 1/T. That the experimental data fail to show such a curvature may be traced to another oversimplification of the author&apos;s treatment of their data. They assume that the activity of liquid lead is unity for all temperatures, so that

Jan 1, 1961

By J Samosir, L Snyman

Northparkes was the first mine in Australia to use block cave mining method which relies on gravity and natural rock stresses to fragment and recover the ore. It was also the first hard rock mine to use hydraulic fracturing, in conjunction with CSIRO, to promote caving of E26 Lift 1. The technique was later used on E26 Lift 2 wedge and E48 prior to undercutting.Northparkes production is currently sourced from the E48 Lift 1 block cave mine and E26SLC. The E48 block cave contains economic ore to the north and south of the current cave footprint. To recover this ore the footprint has been extended on the north and south with two extraction drives and one extraction drive, respectively. Modelling of cavability above the additional drives indicated that the cave would not readily propagate to a sufficient height of draw to mobilise the ore and tended to arch over into the existing cave. To address the modelling results and to reduce the risk of the project, rock mass preconditioning was adopted.This fracturing campaign was performed from surface drill holes adjacent the subsidence zone angled to intersect the higher grade and higher elevation ore zones.Optical televiewer surveys, run prior to fracturing, picked intervals and fault zones to be avoided. Holes were resurveyed post-fracturing to detect newly created fractures and as a measure of success of the program.During fracturing operations water and gel fractures were run at varying depths and pumping pressure was logged for each fracture. The mine seismic system monitored significant events and dye in the fluids utilised for tracking water inflow locations during underground inspections.Towards the end of the project, guar fibres from gel were detected within the mill circuit and required treatment to resume optimum processing.CITATION:Webster, S, Snyman, L and Samosir, J, 2016. Preconditioning E48 cave extension adjacent to an active cave, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 471–478 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By J. B. Carman

This paper, describing the mining practices and methods at the mine of the Molyb¬denum Corporation of America, is one of a series of similar papers on mining methods in the various mines of the United States being prepared by the Bureau of Mines. The mine of the Molybdenum Corporation of America is in the Red River mining dis¬trict, Taos County, northern New Mexico (fig. 1), The mill and camp are in the valley of Red River, about 7 miles east of the town of Questa; the mine is 1 ¼ miles away, in Sulphur Gulch, a tributary of Red River. The mine is about 600 feet higher than the mill, at an altitude of about 8,700 feet. The climate is cold in winter, but does not interfere serious¬ly with continuous operation. The mine normally produces about 40 tons of sulphide molybde¬num ore per day, which is concentrated at the local mill and chipped to the plant of the Molybdenum Corporation at Washington, Pa.; there it is made into either ferromelybdenum or "molyte" (calcium molybdate), for use in alloys. The ore is mined from narrow, irregular veins by the cut-and-fill method. About 65 men are normally employed underground and on the surface at the mine.

Jan 1, 1931

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

DURING an earlier examination of high-temperature alloy, A-286, the presence of an unknown intermetallic compound was verified by X-ray diffraction. Owing to its prominent appearance at grain boundaries, the arbitrary name of G phase was assigned.&apos; Low-silicon, vacuum-melted heats were found to contain no G phase, and this investigation was initiated to determine the influence of silicon on G-phase formation; additional work was undertaken to extend existing data on other intermetallic compounds and the aging reactions in this group of alloys. Taylor and Floyd2-4 observed that the Ni3Al phase (y&apos;) and the Ni8Ti phase (7)) are the only equilibrium intermetailic compounds in nickel ternary alloys containing up to 25 pct Cr and 10 pct Ti or Al. They found that y&apos; can dissolve considerable nickel, chromium, and titanium, although the stoichio-metric composition of 7 remains fixed. Nordheim and Grant5 confirmed that age hardening of 80 pct Ni-20 pct Cr alloys of the Nimonic-80 type is due to precipitation of y&apos;, where aluminum is partially replaced by titanium. They suggest that optimum hardness and ductility result from increasing the titanium to aluminum ratio toward the end of the y&apos; solubility range and from increasing total titanium and aluminum content to the maximum limit permitted by processing. Such information is necessary for those seeking to improve the service-temperature range and long-time structural stability of high-temperature components. Experimental Methods Compositions of materiais studied. are listed in Table I. Alloys D, E, and F possess representative A-286 analyses; silicon increases from less than 0.02 to 1.75 pct in alloys A to H; in alloys I to K, titanium decreases from 2.24 to 0.39 pct, and aluminum increases from 0.1 6 to 240 pct. Alloys A and D were solution heat treated for 4 hr at 1700°F, oil quenched and aged for 0.5, 2, 6, 12, 30, 70, 200, and 1000 hr at 1200°, 1300°, 1400°, and 1500°F. Therefore, a total of 33 specimens was required for each

Jan 1, 1958

By John K. Gustafson

The title of my talk is "The Gold Miner and the Future of Gold." This title might just as accurately have been stated as "Gold and the Future of the Gold Miner." Since prehistoric times gold has been sought by mankind for its beauty and its unusual physical and chemical properties. Early in the dawn of civilization it became the ultimate unit of value and lubricated trade between peoples. For at least 6000 years, gold has been used to barter for other commodities. It has been prospected for, treasured, made into works of art and personal adornment, and from time to time has been the object of conquest. Because of its predominant role in recent centuries as a basis for money, economists began to think of it solely in these terms. Annoyed by the disciplinary pressure of gold on the money manager&apos;s desire to manipulate money, the famous economist, John Maynard Keynes, characterized it as a "barbaric relic of the past", a characterization repeated by William McChesney Martin, Jr., when he was head of the Federal Reserve Bank. Gold, however, has physical and chemical properties that make it one of the most useful metals in the modern world.&apos; It is the most ductile metal known. An ounce of gold, for example, can be drawn into a continuous wire over 35 miles long. It also is so malleable that an ounce of gold can be beaten into films ten one-millionths of an inch thick sufficient to cover 68 sq ft of surface. It has a density of 19.3 and is so heavy that 1 cu ft of gold weighs more than half a ton. Gold is nonmagnetic and has a high electric conductivity, only slightly less than silver and copper. Gold is so inert to all the chemicals found in nature that gold coins and jewelry buried beneath the soil or at the bottom of the sea for thousands of years appear to be as bright and perfect as when they were first immersed. Finally, gold has an extremely high reflectivity both to light and infrared rays. Because of these qualities, in addition to its rare beauty, industrial and artistic uses of gold have been growing rapidly. On a world basis, a recent study estimated that in 1960 about 750 tons of gold were used for fabrication, and that the amount had grown to about 1296 tons in 1968. My objective in this talk is to discuss with you the present and future supply of and demand for gold on a worldwide basis and the effect these forces are likely to have on the price the miner can expect to receive for the gold he produces. This is a highly controversial and risky subject to discuss before any audience. Nevertheless, it is a subject that I live with constantly as Chairman of the

Jan 1, 1972