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By Lawrence Wright

THE occurrence of gold, gold-silver, silver-lead-zinc ores in the post-Cambrian sediments in the Black Hills of South Dakota, and their genetic relationship to the Tertiary intrusives, is well known and accepted, but the occurrence of gold in the pre-Cambrian rocks at the Homestake mine, which underlie this Tertiary gold mineralization, has given rise to differ-ences of opinion as to the period of major gold introduction into the older rocks. Fig. 1 illustrates. the distribution of mineralization along the axis of the Tertiary uplift in both pre-Cambrian and post-Cambrian rocks. The following possibilities have been presented: 1. The Homestake gold deposit was formed in pre-Cambrian time and the deposits in the overlying Cambrian sediments formed during Ter-tiary time. 2. The Homestake lode existed at the beginning of Cambrian time, but was enriched by the passage of Tertiary auriferous solutions. 3. The Homestake lode was represented by pre-Cambrian quartz-chlorite sulfide mineralization, very low in gold content and the gold superimposed on the older nearly barren mineralization during the Ter-tiary metallogenic epoch. 4. The sulfides and sulfarsenides as well as gold were deposited in both pre-Cambrian and post-Cambrian rocks during the Tertiary period. Those favoring the first proposition feel that the question is pretty well settled, while the proponents of the second theory are more flexible in their view, feeling that the amount of gold introduced in either period is still an open question. The third and fourth theories, with some modifi-cations, are supported by the proponents of the Tertiary theory, who feel that the evidence strongly favors that period. The following pages are intended to present the evidence and to give the reaction of various observers with my own comments and conclu-sions; also, the accumulated facts of observation gathered over a period of close association with the area under discussion, beginning in 1919.

Jan 1, 1936

In the- past, at Great Boulder Gold Mines Ltd,, ,' s.. number of attempts ' ha'tre been made to remove water ' `solublo copper and' iron sa'lt's from calcined pyritic concentrates, but various problems have arisen and the methodsi ve been abandoned. A method of rapid washing has now been developed,, and although some problems still. exist,, a workable `process has boreh established .which. has; resulted in 'substantial savings of 'reagents used for. the. cyanidation of calcine

Jan 1, 1964

By R. A. Snodgrass

Heap leaching is a topic that is gradually generating more interest in South Africa as more non-Witwatersrand gold deposits are being investigated. This was evident from the number of delegates (85) who supported the SAIMM School on Heap Leaching, which was held at Mintek from 29th February to 3rd March, 1988.

Jan 1, 1988

By Richard W. Hanford

The geotechnical construction industry generally considers soil mixing to be defined as an in situ ground improvement or treatment method by which a dry or wet reagent is introduced into the ground and is blended with the soil by mechanical or rotary mixing tools. This results in relatively homogenous mixtures whose engineering properties are improved and are greater than the soil properties before mixing. Reagents usually include cement, but may also include processed clay such as bentonite, when a reduction in hydraulic conductivity is desired, or other proprietary chemicals when chemical stabilization is the objective. Mixing may be either shallow or deep. Shallow Mixing is the term arbitrarily used for treatment of soils within the upper 30 feet; Deep Mixing denotes treatment below 30 feet to the depth limits of the equipment. Mixing equipment may consist of single or multiple-shaft tools having cutting and mixing blades of many different configurations. To avoid using proprietary nomenclature, reference to Shallow Mixing Methods (SMM) and Deep Mixing Methods (DMM) are the preferred terms. Although originally developed and patented in the United States in 1956, in situ construction using various soil mixing methods is more prevalent in Japan and the Scandinavian countries. Reintroduced into the United States from Japan in 1986 for ground improvement and liquefaction mitigation at Jackson Lake Dam, Wyoming, acceptance of soil mixing methods has been gradual but slow. Applications typically include:

Jan 1, 2001

By Harold M. Smith

Important discoveries of new oil fields were made in 1937 in the State of Illinois. Oil production, which was virtually constant during 1934, 1935, and 1936 at about 4,400,000 barrels a year, a increased to 7,499,000, barrels during 1937, and in 1938 this production was trebled. In 1939, 94,302,0003/ barrels were produced (almost four times the 1938 quantity), making Illinois one of the cost important oil-producing areas in the United States. The Bureau of Mines has analyzed 35 samples of petroleum from these new Illinois fields and presents the analyses herein. Included with them in this report are analyses of seven samples from fields developed before 1936.

Jan 1, 1940

By L. Salinas

Lance injection of gas and particles into a molten bath is currently practised in metallurgical processes (Mitsubishi lances for example). Several experimental and theorical studies have been conducted in the past on this topic. However, neither detailed calculations nor experimental studies of local flow patterns have been published. In the present work, a numerical simulation of the interaction of a gaseous vertical descending jet and a liquid surface was done, using the turbulence k-e model. There is a fair agreement between the calculated and the experimental values. The results of this study demonstrate that it is crucial that the gas jet velocity profile and turbulent characteristic are correctly formulated in order to correctly simulate the system.

Jan 1, 1999

By B. R. Neufeld, M. G. Heximer, S. J. Roach, W. G. Van Luven, D. G. Reynolds

"Teck Metals Ltd. operates an integrated zinc-lead complex at Trail, British Columbia, Canada. In the zinc plant, zinc concentrates are roasted to produce calcine, which is then processed in the leaching circuit for zinc recovery. Calcine is first dissolved at pH <2.0. This is followed by a precipitation stage using additional calcine that removes iron as a ferric hydroxide precipitate which is recycled to the lead operations. It is during this pH adjustment that impurities, notably arsenic, antimony and germanium, are co-precipitated with ferric hydroxide which is the primary removal phase for these elements. Recent processing conditions have resulted in lower iron inputs to the leaching circuit and this has resulted in insufficient co-precipitation of key impurities. This paper summarizes the influence of iron concentrations on impurity removal using laboratory and plant scale surveys, and emphasizes key specification limits for the primary iron removal circuit.INTRODUCTIONThe Sulphide Leach Plant (SLP) at Teck Metals Ltd., Trail Operations produces a zinc sulphate electrolyte from three different zinc bearing streams:1. Calcine, primarily containing zinc oxide, from the roasters2. Zinc electrolyte from the Oxide Leach Plant (OLP) is produced by leaching zinc oxide fume from the pyrometallurgical lead smelting operations3. Zinc slurry from the Zinc Pressure Leach (ZPL) autoclaveThe feed sources are blended and introduced to the iron removal process to precipitate iron in the form of a hydrolyzed iron precipitate which is recycled to the lead smelting operation. Along with iron, impurities, namely arsenic, antimony, germanium and silica, also co-precipitate; this process acts as the primary removal step for these elements. Following iron removal, the electrolyte is further processed in the zinc dust purification circuits. Cadmium and copper are removed in the cold stage circuit via zinc dust cementation, followed by cobalt cementation in the hot stage circuit."

Jan 1, 2016

By B. C. Allen

Grain boundary grooving has been studied in chromium, molybdenum, and tungsten under a variety of conditions using high vacuum techniques and tantalum -gettered argon. The average surface free energy of solid chromium, and the chromium-liquid silver interface free energy were respectively found to be 2200 ± 250 and 500 i 130 ergs per sq cm from groove formation kinetics and estimates of pertinent volume difffusion coefficients. The results for chromium were unffected by variations in interstitial content ranging from 0.003 to 0.09 pct C, or 0.003 to 0.03 pct O. Surface diffusion is the primary mechanism of groove formation in chromium under 1 atm argon at 1200" to 140O°C, and is essentially unaffected by 0.003 to 0.09 pct C, 0.003 to 0.03 pct O , metastable nitrogen contents up to -0.01 pct, and up to 2 torr Ag vapor. At higher temperatures, the major mechanism is volume diffusion in argon or evaporation-condensation in stutic vacuum. Surface diffusion occurs in molybdenum at 0.5 to 0.96 and in tungsten at 0.5 to 0.9 of the absolute melting tempera -ture by a single mechanism, possibly by the migration of single adatoms or vacancies. Results were slightly affected by up to 23 tory Sn vapor, and in molybdenum were essentially unaffected by 0.5 Ti or carbon in the range 0.002 to 0.02 pct. Volume difffusion through the liquid is the mechanism of groove formation in chromium-liquid silver at 1200" to 1400°C and in molybdenum-, Mo-0.5Ti-, and tungsten-liquid tin at 1200" to 2000°C. The solid-liquid interface free energies involved were estimated from grooving kanetics. WHEN a grain boundary intersects a solid surface, a groove tends to form along the line of intersection at temperatures above about half the absolute melting point (0.5 TM). The groove progressively grows by preferential atomic migration either by diffusion or evaporation. Establishment of a groove angle occurs in accordance with the grain boundary and surface free energies involved. The motivation for groove formation is a reduction in the total surface free energy of the system. This study is a continuation of previous work on thermal grooving of chromium, molybdenum, and tungsten.&apos; The temperature ranges were extended, and the effect of metallic and interstitial impurities was evaluated. The results were such that certain interface free energies and surface self-diffusion coefficients were deduced from the grooving kinetics. EXPERIMENTAL WORK Materials and Preparation. As indicated in Table I, the 0.05-0.08-cm-thick chromium, molybdenum, and tungsten sheet used was nominally 99.99 pct after recrystallization. Two lots of molybdenum with about the same analysis, Mo-0.5Ti,* and tungsten were ob- *Alloy compsitions are expressed in weight percent . tained commercially. Extruded chromium rod,&apos; prepared from iodide process crystals, was warm rolled to sheet at 700°C. Sheet of three Cr-0 impurity alloys containing up to 0.03 pct 0 was prepared by warm rolling arc melted, extruded, and swaged rod. Two Cr-C impurity alloys containing up to 0.09 pct C were made by equilibrating unalloyed chromium with a known amount of CH4 for 24 hr at 1150°C in previously evacuated quartz capsules. Chromium containing nominally 0.015 and 0.06 pct N was similarly prepared by equilibration with NH3. The sheet was recrystallized to give a stable grain size about equal to the sheet thickness. Molybdenum and Mo-O.5Ti were recrystallized in a tantalum resistance furnace 1 hr at 1 x lo-5 torr at 2300" and 220O°C, respectively. Tungsten was similarly annealed for 1 hr at 2500°C. Chromium and its impurity alloys were outgassed at 1100°C and recrystallized 1 hr at 1700°C under 1 atm Ar. Except for nitrogen, the impurity content stayed roughly constant. Nitrogen in both alloys was reduced to <0.001 pct. In fact, over 80 pct of the added nitrogen was lost after outgassing at llOO°C and annealing sheet 1 hr at 1300°C in argon in the presence of tantalum. Such a rapid loss can be rationalized since -2 torr N are required for equilibrium with 0.04 pct N in solution,3 while the equilibrium pressure is ~10-5 torr over tantalum at 1300°C.4 The recrystallized sheet was cut into small coupons which were metallographically ground and polished on one side with a minimum of grain boundary relief. The surface roughness was on the order of 0.01 µ. The tin and silver used were nominally 99.999 spec-trographically pure. After being outgassed at 1100°C and equilibrated in a molybdenum crucible for 0.5 hr at 1800°C in argon, the tin contained 3 ppm 0, <0.3 ppm N, and 0.1 ppm H. Following outgassing at 900°C and equilibration in a chromium crucible 1 hr at 1400°C in argon, the gas content of the silver was 1 ppm O, <0.5 ppm N, and 0.3 ppm H. Grooving Under Argon or Vacuum. All specimens were placed in unsealed containers made from rod or sheet of the same alloy, thereby enabling the polished surface to achieve gas-solid equilibrium. The annealing fixtures are shown in Fig. 1. The specimen was placed in a resistance furnace with a tantalum or Ta-10W heating element plus tantalum fixtures or radiation shields. Chromium was outgassed at 1100°C, and molybdenum and tungsten were outgassed at 1900°C to 1 x l0-5 torr or at the grooving temperature, whichever was lower. In vacuum anneals, the specimen was then heated directly to the intended grooving temperature. In argon anneals, 99.996 Ar was admitted

Jan 1, 1970

By H. J. McQueen

The modeling of the extrusion of 6061 alloy and its composites with 10 to 20 vol% Al203 or SiC by two techniques. The uniaxial finite element method FEM (DEFORM" ) provided force-stroke curves and temperature rise over the range 450-500 °C, 2.6-5mm/s and extrusion ratios of 31 and 64. The traditional technique considers ideal work and redundant work as well as friction and uses average temperatures and strain rates. The two techniques are used to clarify each other and to extend the analysis to 400 and 350 °C. The calculated efficiencies are compared to measured values in extrusion trials and to values derived for 7075 extrusion analyses. The analyses are based on constitutive equations determined by torsion testing tests.

Jan 1, 2004

By J. R. Woolsey

In late 1988, the Committee for Coordination of Joint Prospecting for Mineral Resources in South Pacific Offshore Areas (CCOP/SOPAC), Suva, Fiji, consulted the Continental Shelf Division of the Marine Minerals Technology Center regarding low-tech, low-cost, reconnaissance sampling systems for a variety of nearshore needs. Materials of interest to several member island nations included silica and calcareous aggregate for cement manufacture, sand for beach replenishment, heavy minerals, and precious metals. A principal criteria of the system was that it be of low-tech design, and as far as possible, suitable for construction on the islands from available materials. It should also be operable with SOPAC personnel on island vessels of opportunity. The system selected to satisfy these requirements was a convertible drill of basic airlift design, capable of operating with easy modification as either a vibralift or airlift, depending on the desired application. The basic system included a drill pipe constructed of heavy duty 76 mm (3") black iron pipe, divided into three 3 meter sections (for ease of transport), fitted with an air intake manifold and bit at the lower end. A 25 mm (1") galvanized pipe assembled in three similar sections and clamped to the drill pipe served as a water jet to assist in cutting. Air was supplied to the manifold by means of a 12 mm (1/2") pipe also clamped along the length of the drill pipe. Suitable hoses supplied water and air to the upper ends of the respective pipes by means

Jan 1, 1989

By G. E. Johnson

A bench-scale study was made of removing hydrogen sulfide from synthesis gas at elevated pressure by iron oxide impregnated on wood chips. The gas contained 0.02 to 0.06 percent oxygen. The removal of hydrogen sulfide by iron oxide impregnated on wood chips is more efficient at elevated pressure. At constant space velocity, longer periods of operation at 400 p.s.i.g. are possible before the exit gas reaches a given maximum concentration of hydrogen sulfide, compared with 200 p.s.i.g. or atmospheric pressure. In tests at room temperature, 60° C., and 100° C., the most effective removal of hydrogen sulfide was obtained at room temperature and the least effective at 100° C. Dry impregnated wood chips removed only about half as much hydrogen sulfide as chips wetted to a water content of 50 percent.

Jan 1, 1962

By Anil Kumar

In underground mine production units that employ discrete-vehicle face haulage, feeders are used in the belt network so that vehicles can unload rapidly without transmitting to the conveyor network the high material flow rates that result from rapid unloading. They prevent production bottlenecks at the face, while reducing capacity requirements for downstream materials handling equipment. Similarly, surge bins may be installed at intermediate locations in the network to smooth flows from a number of upstream sources, thereby reducing downstream belt capacity requirements. This paper introduces new stochastic process models to temporally describe loading patterns from unit operations and techniques for computing the probability of various fill levels for the feeder or surge bin. These results may be used to analyze the effect of alternative bin or feeder capacities and discharge rates on the performance and costs of the materials handling system.

Jan 1, 1994

By Y. L. Su

This paper describes a case study where solutions were sought to the truck queuing that occurred at a central processing plant. Ore from three production shafts at Falconbridge Limited&apos;s Sudbury Opera¬tions is hauled by three trucking contractors to Strathcona Mill. On return trips, the classified mill tailing is carried back to the mines for backfilling. The ore feeder at the mill handles three times the tonnage designed for and the situation is not expected to improve. Excessive truck queuing and consequent mine production interruptions are therefore of great concern. During the study, stochastic models were formulated and programmed for the IBM/AT personal computer. Basic information sought from the models were truck waiting time and ore production interruptions. The existing system was tested, not only to verify the validity of the models, but also to understand the causes of the problem. Several alternatives were simulated and a simple solution selected for implementation.

Jan 1, 1986

By Lauri Gregg

How Can Man Meet the Carbon-Free Energy Challenge ? ? Increases in Energy Efficiency can displace 1/2 to 2/3 of the Carbon-Free Energy required to stabilize at 550 ppmv ? Renewable Energies require too much land and thus can displace 5 to 10 % of the energy requirement ? Large new sources of carbon free energy are needed ? Conservation is desirable but provides only a small and variable contribution ? People will have to adjust to higher levels of CO2 in the atmosphere as energy demand continues to grow

Nov 1, 2002

By Shuji Owada

Scrap electrical and electronic appliances, so called "E-waste", are not a present target to be collected and recycled under Japanese regulations. This material, however, contains considerable amounts of base, precious, and rare metals and it is necessary to recover these elements for maintaining stable supply and establishing "the society of environmentally-sound material-cycle". This paper describes recent trends of rare metals recycling in Japan and technological approaches to achieve the above objective. Also a research work to concentrate rare metals from the printed wiring boards by combining brand new comminution and physical separation methods is discussed.

Jan 1, 2011

By G. H. Damon

Since 1963, Bureau of Mines Information Circular 8179 has served the mining industry as a fundamental safety guide in the field of blasting agents. In the intervening 14 years, many changes have occurred, and this report presents revised and new recommendations which recognize these changes. For example, AN-FO is now supplied mostly premixed, whereas in 1963 much of it was mixed by the blaster; aluminum metal (A1) and other fuels are now often added to AN-FO to increase strength, and flake aluminum powder is used as a sensitizer in water gels; and water gels or slurries that are now extensively used were just coming into practical use in 1963. To provide the widest possible margin of safety, some of the Bureau&apos;s recommendations are more stringent than existing regulations,

Jan 1, 1977

By William R. Nash

The scope of work for the fast track construction of the Weeks Island Replacement Facility, Weeks Island, Louisiana included the design and construction of two salt mines. Mine #1 - An interim underground mining level consisting of a 975 m (3200 ft) incline and 3520 m of 5.5 m x 7.3 m (11560 ft of 18 ft x 24 ft) drill and blast excavation; raise boring; core drilling; roadheader excavation; complete bulk material handling facilities utilizing an existing production shaft. Mine #2 - Simultaneous with the interim mine construction a new one million ton per year underground salt mine was constructed consisting of: two 5.5 m diameter x 381 m (18 ft diameter x 1250 ft) deep shafts; 76450 cu m (100,000 cu yd) of drill and blast bottom excavation; surface and undergound bulk material handling systems (conveyors, skip loaders, shaft equipment, hoisting); ground freezing for water control for both the production and service shafts; the design of the first underground doublewall slipform installation of a dynamic bitumen shaft lining system; the emergency grouting of both the existing production shaft and the interim mining level in the salt dome; 227 mt x 64 m (250 ton x 210 ft) high structural steel production headframe; 2.2 MW (3000 hp) double drum mine hoist; service shaft headframe; and service buildings.

Jan 1, 1987

By H. R. Peterson

The control of autogenous grinding circuits is very similar to the control of conventional grinding circuits. In both circuits the classifier must be operated to achieve the required degree of mineral liberation. Crude ore grade and grinding mill density are important in both circuits. The biggest difference between the control of the two circuits is the pronounced effect that crude ore changes have on autogenous circuits. The importance of crude grade, weight recovery, size and hardness is greatly magnified because the crude ore in the autogenous circuit is also supplying the grinding media. Crude ore sizing is a particularly critical factor in achieving efficient primary autogenous milling. Because of the above, computer control is advantageous for autogenous circuits. Changes in crude ore may necessitate rapid changes in the entire circuit control strategy, and only a computer can facilitate these changes. Also, the techniques of control are very different for conventional and for autogenous grinding. Set-point control is usually satisfactory in conventional circuits, but the multiplicity of varying conditions in an autogenous circuit usually require some type of computer optimizing search routine. Autogenous mills can be separated into two general types. In primary autogenous mills the media is obtained from the mill feed, and in pebble mills the sized pebble media is added separately from the material being ground. PRIMARY AUTOGENOUS MILL CIRCUIT CONTROL - FIGURE 1 Power Draw Primary autogenous mills are usually run at full motor loading so production will be at maximum. Therefore, power draw must be closely controlled; this is done by adjusting feed rate. The versatility of computer control is extremely valuable for power control, especially during starting and stopping. To bring the mill power up as fast as possible at

Jan 1, 1982

By Steve Scott

Outline of Talk Seafloor Massive Sulfides (SMS) and Seafloor Sedimentary Sulfides (SSS) Ocean mining of SMS (Nautilus Minerals) Environmental issues Summary

May 1, 2013

Results are presented on the elution of gold cyanide and base-metal cyanide complexes from strongand weakbase resins. It is shown that thiocyanate anions, zinc cyanide anions, and thiourea in acid solution are effective eluants of strong-base resins, but that it is generally necessary for electrowinning to be incorporated in the elution cycle if fast rates of elution are to be achieved. Weakbase resins are eluted with sodium hydroxide solution, which is shown to be far simpler and far more effective than the elution of strong-base resins. The effects of parameters such as concentration of the eluant, temperature, and electrowinning efficiency on the rate of elution of the resins are examined.

Jan 1, 1984