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By Charles L. Karr

Grinding is a necessary component in the processing of a number of minerals, and improvements in this area could provide substantial cost savings for the minerals industry. Optimizing the process of grinding, however, is a difficult task because there are multiple objectives; i.e., several aspects of the process are important including the fineness of the ground product, the energy consumed in the process, and the viscosity characteristics of the final slurry. Genetic algorithms (GAs) are search algorithms based on the mechanics of natural genetics and have been proven capable of solving multiple objective optimization problems. These robust search techniques are able to rapidly locate near-optimum solutions across a broad spectrum of very difficult optimization problems. In this paper, two varieties of GA are used to optimize a grinding process as it is described by a computer model: (1) a simple genetic algorithm (SGA) and (2) a micro genetic algorithm (MGA). The performance of these techniques is compared to the performance of a more conventional search technique, a simplex algorithm. Results indicate that the GAs are efficient, versatile, quite capable of improving the grinding process, and easily incorporated into the toolbox of today's process engineer.

Jan 1, 1993

By Pedro E. Rengifo

Splicing methods have undergone considerable developments over the last 2Oyears. Continuous conveyor belt service is dependent entirely on the strength and life of the splice to hold the two ends together. Ultimately, belting performance is dependent on the quality, efficiency, and technique of the splicer. As customers demand better belting performance and running tensions increase, the need for splices that perform as efficiently as the belting has increased also. Higher dynamic belt constructions have also dictated the need for "new"sp1icing techniques. Regardless of the belt type used or spliced, one item that is most necessary with all belt types is the quality of the workmanship and standardized splicing methods that employ all of the necessary elements required to ensure reliable field service. This paper will explore the use of Goodyear-issued internal standards for field splicing following the constraints of quality and efficiency for fabric and steel cord reinforced belting. Also included are the 10 most common mistakes made by splicers, Goodyear-issued Field Quality Assurance Standards, and check lists for end users to adhere to the manufacturers' requirements for splicing including materials and specifications for conveyor belt splicing and repairs.

Jan 1, 2004

By D. R. Dixon

Since the critical role of oxygen in xanthate flotation of sulphides was established (1) subsequent studies have been concerned mainly with the galena-xanthate system. It is therefore surprising to find at the conclusion of a comprehensive review of the topic by Granville, Finkelstein and Allison (2) that it was not possible for them to draw unequivocable conclusions on the mechanism of xanthate adsorption. It was apparent that some new advances were likely if systems other than galena-xanthate (Pbs/x-) were examined. (2) Specifically a less reactive sulphide such as ZnS may interact with flotation reagents at a slower rate than PbS and more information per unit time gathered. Again ZnS is far less reactive electrochemically than PbS or stated equivalently, it is a poorer semiconductor than PbS. More importantly, the ability of ZnS to act as a semi-conductor can be controlled photochemically rather than by direct doping reactions for which it is difficult to assess the uniformity of doping. Thus the conductivity of ZnS can be made the same as that of PbS by irradiating the ZnS with ultraviolet light at circa 360 n.m. (3)

Jan 1, 1974

Computer applications in mine 'production' planning and control are concerned with the here and now. In production planning and control we are dealing with tactics as opposed to strategy. Our objective is to make the best of the situation in the short term, i.e., in a relatively fixed environment with relatively fixed plant, equipment, and labor. Environmental factors include not only the geology of the deposit but also market factors (such as price) and governmental constraints and regulations. Mine production planning systems are applied at the interface between concept and execution. Mine production control systems are applied at the interface between execution and revised operating practices or a revised concept. Fig. 1 shows the information flow that takes place regardless of whether the planning and control systems are manual or automatic. The feedback that results depends on the feedback mechanism that has been established, and this feedback can be enhanced by careful systems analysis and design. Chronologically, production planning and control activities support the last in the series of line functions that are ordinarily performed by mining companies. The first of these is exploration, the second is evaluation and development, and the third and final function is production.

Jan 1, 1979

By E. A. Rychkun

It is essential for a. mining company to determine an optimal mining strategy which will maximize the return on investment. In the case of Placer Development Ltd., the Lerch-Grossman three-dimensional optimization technique has been implemented on a digital computer to assist in the determination of such a strategy. It is the purpose of this chapter to explain and illustrate the methodology of the Placer Development Ltd. computer system with emphasis on the feasibility phase of a mine's development. In the Placer Development Ltd. strategy determination process, it is essential that certain objectives be considered: 1) There must be some means of constructing a realistic computer model of an ore body which gives a significant weight to geological constraints. 2) Data must be accurate and quantifiable. 3) Computer solutions must be unique, i.e., approximation or iteration methods of determining optimal solutions are undesirable. A method must be used which, when given fixed parameters and data, yields a mathematically sound unique solution. The following material is a presentation of how these objectives have been implemented. The flow of this outline will be from the general to the specific, with an example application.

Jan 1, 1979

One of the largest mining shows in the world is set take place April 15-18 in Santiago, Chile. Expomin 2008 is expected to attract more than 60,000 professionals from around the world who are involved in all aspects of the mining industry. Expomin has become an important place for mining leaders to meet, organizers said, ?with great expectations for the development of new business in international markets.? This is the 10th Expomin. The event, held every two years, is expected to at-tract exhibitors from more than 25 countries, representing nearly 1,000 companies and more than 3,000 brands related to the mining industry, organizers said. Most all of the world?s largest equipment manufacturers and suppliers ? surface and underground ? will be represented. The importance of the event to the Chilean and international mining industry can be seen by the increase in size of the exhibition ? 13 percent more surface space in 2008, compared with the 2006 Expomin. The exhibit will be broken down into four pavilions, covering 34,054 m2 (355,570 sq ft). An outdoor area for the large mining equipment will cover 16,120 m2 (173,520 sq ft).

Jan 1, 2008

By D. A. Rice, R. G. Swanton, A. May, O. C. Carter

As part of a cooperative effort between the US Bureau of Mines and the Florida Institute of Phosphate Research (FIPR), with input from the phosphate industry, the conversion of phosphogypsum to sulfur is being investigated. The proposed process incorporates a thermal reduction of phosphogypsum to calcium sulfide (CaS) and a hydrometallurgical treatment to convert calcium sulfide to ammonium bisulfide (NH4SH), which is then oxidized using a catalyst to produce elemental sulfur. The paper summarizes the results of continuing laboratory studies using an activated carbon catalyst which was loaded with sulfur through oxidation of ammonium bisulfide solution. The extraction of the sulfur that forms in situ on the catalyst is a key area in the development of the sulfur recovery process. Two approaches for removing the sulfur are being investigated: (1) thermal treatment to volatilize sulfur. and (2) leaching the sulfur using liquid anhydrous ammonia. The research has shown that it is technically feasible to recover over 90% of the sulfur from the carbon by either volatilization or ammonia leaching. Locked cycle testing has demonstrated that the carbon has the potential to be recycled after ammonia leaching.

Jan 1, 1987

By Marcel Haffen, Jean Janin

The purpose of grouting is to modify the permeability and strength characteristics of the subsoil in such a way that the planned structure can be efficiently constructed at a given location. This technique, which originally underwent considerable development in the field of dams construction is constantly evolving and it becomes more and more important in urban zones of intensive underground development for projects such as transport tunnels, stations, car parks, ect. Grouting becomes more and more indispensable whatever the natural characteristics of that subsoil ; such is the case particularly when the planned work runs through cohesionless granular soils, usually water-bearing such as alluvium, sands, disturbed ground, fill material, etc. The selection of the grouting method and the extent of treatment required at depends on two fundamental factors. 1º) nature and behaviour of subsoil to be treated. There is no need to stress the necessary of a good knowledge of geotechnical, hydrological and chemical characteristics of the ground to be treated. At the present time the specialists in these fields have available numerous methods of analysis, either laboratory or field tests, which enable to evolve a suitable treatment.

Jan 1, 1997

By Robert S. Saunders

Cast iron tubbing for two centuries was the only practical watertight shaft lining for deep waterbearing formations. However, since World War II composite welded steel and concrete lining has gained favor and today is often preferred. While tubbing may not be applicable in all cases, a good argument can still be made for this time-honored method. Watertight linings are complex structures designed to withstand both hydrostatic fluid pressure, non-uniform loading created by ground forces, and vertical bending caused by subsidence. Resulting stresses in the lining can be high. To date linings have been designed that withstand hydrostatic pressures as high as 1,500 psi. Watertight linings must be robust, constructed of the highest quality materials, and manufactured and installed with precision. Therefore, such linings are expensive. Today's ductile cast iron tubbing is greatly superior to gray iron formerly used for tubbing, and is stronger, and more resistant to corrosion than welded steel lining. Tubbing, unlike steel linings, can be installed in wet conditions and used to control water inflow and stabilize unconsolidated ground as the shaft is deepened. Steel lining requires absolutely dry conditions for welding, which often necessitates expensive ground freezing and a primary lining.

Jan 1, 1985

By R. Y. Wan, J. R. Parga, J. D. Miller

The direct recovery of precious metals from a1kaline cyanide solution is frequently accomplished by the well-established Merrill-Crowe process involving zinc-dust cementation. This is particularly true for silver. Plant data from two operations are presented and analyzed in terms of intrinsic reaction features. In such Merrill-Crowe plants a plate-and-frame filter press acts as a semicontinuous fixed-bed reactor with a distribution of particle retention times. For the plants studied, 99Yo of the silver is recovered with a solution retention time of less than 2 min. Differences in plant operating conditions and product characteristics can be related to the nature of the surface deposit of silver which forms on the zinc particles. From laboratory experiments and plant samples it has been found that the presence of lead in the system activates a change in the silver deposit morphology to the dendritic state which affects the rate of silver deposition as well as the filter cake porosity. Finally the plate-and-frame press is considered from an engineering perspective as a semi- continuous fixed - bed reactor to describe the behavior of the system.

Jan 1, 1987

By Sean E. Armstrong, Deepak Malhotra

Gold extraction from refractory ores as a percentage of total gold production is increasing. The processing technology options for treating difficult-to-process refractory ores are also increasing. The best processing option is dependent on many factors including feed grade and the cause for ore refractoriness. The causes for ore refractoriness are many foldCpreg-rob­bing, encapsulation in pyrite, arsenopyrite or silica, presence of cyanocides, presence of cyanide-insoluble gold compounds, etc.1. The first step in the process development of a refractory gold deposit is to determine the cause for ore refractoriness. The traditional approach of undertaking detailed mineralogical examination of ore types, major and minor mineral constituents and their association does not necessarily provide the metallur­gist all the information needed for characterization of gold-bear­ing ores. For process development programs it is desirable to complement traditional mineralogical methods with diagnostic leach testing, which attempts to quantify the deportation of gold in various mineral matrices. This paper briefly reviews the diagnostic leaching proce­dures and its applications for a wide range of gold-bearing refractory ores, both primary and by-product.

Jan 1, 1996

By Darryl J. Butcher

The Akjoujt Project is operated by MORAK SA, a company incorporated in the Islamic Republic of Mauritania. MORAK is jointly owned by General Gold International SA (A wholly owned subsidiary of General Gold Resources NL.), SAMIN, and the International Finance Corporation. The project was devel­oped to treat approximately 2.1 million tonnes of TORCO (Treatment of Refractory Copper Ores) tailings containing an average 3.2gAu/t, and 0.75%Cu/t. The process involves the use of ammoniacal cyanidation for gold extraction, and conventional carbon adsorption, and eventual desorption, of gold values. This is believed to be only the second commercial application of this leach chemistry in the world. The other being a small vat leach operation on the Paris Mine Dumps. (This operation was described by Mr M Ruane in a paper to a previous Randol Forum.) Initial work on the process, and the Akjoujt process design assumed that the reaction involved was anaerobic. This paper describes the operating experience, plant trial, and eventual installation which has lead MORAK to the conclusion that the process is not anaerobic, but requires oxygen, or an oxidant to proceed.

Jan 1, 1995

By N. J. Peberdy, C. N. Moreton, K. C. Garner

Introduction During the past decade a major objective of the process industry has been to use digital computer technology to improve plant operating efficiencies. This objective implied some form of optimization, a concept that has various interpretations depending on the view of the prospective user. For the purpose of this paper, optimization of a process plant is defined as the establishment and setting of plant operating conditions that maximize some mathematical yield function, i.e. maximum profit, minimum residue, etc. Analysis of these objectives and the available design and implementation techniques led to the conclusion that digital computer and optimization techniques are not the stumbling blocks, but rather the development and derivation of the mathematical models of the unit operations and process plants to be optimized. Such models should not only describe the optimized (steady-state) objective, but also how one steers to this state (control algorithm). Due to the multidisciplinary nature of the skills associated with the design and operation of process plants, the development of suitable models by a single discipline, such as the process control engineer, was found to be not only difficult but often impossible, due to budget and human resource limitations. To over-come these limitations, a computer aided design (CAD) tool has been developed. It aims to provide a productivity tool to the various disciplines, at the same time coordinating the technical input from each. The system described is but the starting point in an evolutionary development of a tool that, with use, is becoming more efficient and cost effective to use. Development has become an application engineering activity rather than the preserve of the computer specialist. Project phasing The development of a mathematical description of a process plant requires coordination of information from conceptual design to operation management. The activities required to build and operate a process plant are divided into four basic chronological activities or phases. These activities are often undertaken by different organizations and disciplines. As a result, continuity is often lost with the resultant loss of critical design data. The major activities are considered to be: conceptual and flowsheeting; detailing around the P & ID; building and commissioning; and plant operation. The CAD system described provides a design tool to be used for each of these activities, as well as providing continuity between the activities and the disciplines involved. The heart of the system is the dynamic simulation of the flowsheet. Each of the activities will be discussed, leading to two simple examples that demonstrate the use of the simulator. Figure 1 shows a schematic format of the various activities and the path followed by the dynamic flowsheet simulator in the life of a project. Flowsheet development The prime requirements in the design and develop¬ment of a process flowsheet are • selection of the correct unit operations to achieve the most economic (capital and operating) beneficiation of the specified reserve ; • the sizing of the unit operations to achieve the desired results, as a function of the projected feed rates etc., to handle the time related (dynamics) of the process; and • the production of a set of engineering documents showing the drawn and labeled flowsheet with an equipment list and process specification for each of the unit operations. The question may well be asked at this stage why dynamic flowsheet simulation should be considered when steady state modeling has been found to be adequate to date. With the increases encountered in the cost of capital, one often cannot afford the luxury of designing around the compounding worst case technique. Further, a more accurate design of the control surges can be achieved. No information is lost in that the steady state solution is in fact a subset of the dynamic model. In generalized state space modeling, the differential equations describing the process dynamics are illustrated in the following matrix notation: XDOT=A.X+B.U(1) Y =C.X+D.U(2) where XDOT describes the set of first order derivatives of the system state Vector, and X- is the system state Vector; A - is the system matrix operator which in the general nonlinear case is both a function of X and time ; U- is the process input vector; B - is the input mapping matrix; Y - is the set of observations; C - is the output mapping matrix which maps X - onto Y; and D- maps the input onto the observations. Thus, by time integration of the system dynamic equations, described in (1), the dynamic trajectory away from any set of initial conditions can be deter¬mined. Further, by finding the conditions at which XDOT = 0, the steady state solution can be determined.

Jan 1, 1987

By Gordon M. Pugh, David G. Rasmussen

INTRODUCTION Square-set timbering of stopes developed from stull support methods because veins too wide for stulling were being mined. In general, the void caused by the stoping of the ore is filled with a system of interlocking timbers. Timber framework supports the wall rock, the mining operations, and provides access. A timbered stoping method can be used in all widths of veins at any dip. The timbering can be normal and parallel to the planes of the walls or at angles to these planes. Irregularly shaped ore bodies can be worked by timbered methods. Pinching or swelling of the vein will not adversely affect the method. Timbered stoping is especially advanta¬geous where weak ground is encountered in the vein or the wall rock. The ground is unsupported only until timber sets are stood. These stopes can be filled with sand or waste when desirable. The customary method of developing a square-set timbered stope with haulage drifts above and below and timbered raises on each endline is shown in Fig. 1. The drifts are timbered the full stoping length. The raises have two compartments with the manway and timber slide in one compartment and the chute in the other. The drifts and the raises cannot be widely spaced as handling timbers is an important consideration. Stoping can begin immediately above the drift timber and continue in both directions and upward from the raise. Breasting down each blast round for only one timber set laterally is the common practice. The blasted ore falls to a lower floor where it is slushed or trammed to the chute. Drilling can proceed on the upper floor while broken ore is being removed from the stope. As shown in Fig. 2, square-set timbering may be used in cut-and-fill stopes to support the back and walls until fill is added. There are various ways of developing an ore block for timbered stoping. Fig. 3 depicts the situation for the main haulage in the vein with an intermediate drift separated from it by a sill pillar. The ore is slushed into the chute connecting the two drifts. The situation in Fig. 4 is identical to that in Fig. 3 except that no sill pillar is used. In Fig. 5, the haulage drift development is done in the footwall with crosscuts driven to intersect the ore body. The intermediate drift development is above the crosscuts with a minimal sill pillar. The main bottleneck in timbered stoping is in the timbering process. Drilling in the stope is generally held up while timbering is done. Two or three men are re¬quired to do the timbering and an additional one or two men are needed to transport and raise or lower the tim¬ber. Good organization is essential to timbering. Skill must be exercised in standing the timber to support the ground and still maintain good production. COSTS AND PRODUCTIVITIES Development and stoping costs are presented in Tables 1 through 7 for the situations in Figs. 3 and 5,

Jan 1, 1982

By J. G. Smith, L. P. Sheets

Introduction Potential applications that exploit the electrical properties of coal measure rocks include: (1) radar sensing of coal face, floor, and roof for automated mining operations; (2) underground wireless communications; and (3) sensing extent of subsidence, blasting operations, coal gasification bums, and moisture migrations. Impediments to exploitation of electrical properties include: (1) a lack of reliable electrical properties data for in situ conditions and (2) a lack of correlation data between electrical properties and other relevant physical properties. In this paper data are presented for electrical conductivity and permittivity for Appalachian and Illinois shales for a frequency range 2 x 10 to 2 x 10 Hz. These data are useful in establishing in situ electrical property variability, lower limits, and anisotropy. Electrical proper¬ties measurement and values for other coal measure rocks are discussed as well. Laboratory measurement For the frequency range investigated, a capacitance bridge and Q-meter were employed. These instruments are designed to yield bulk values of permittivity and conductivity. Disk samples of thickness 0.396 cm (0.156 in.) and diameter 2.54 cm (1 in.) were machined from cores obtained from the two coal basins. While both the capacitance bridge and the Q-meter must be balanced manually, the bridge has an analog-to-digital interface and an attached computer specifically designed to expedite data collection and interpretation. Sample holders are critical components in the measurement process. A Hartshom-Ward holder was employed with the bridge and a Marconi micrometer jig was used with the Q-meter. Neither commercial sample holder was designed to regulate ambient humidity conditions. Because water adsorbed on sample faces may cause errors approaching 100%, special enclosures were designed for both holders. Each enclosure contains a flush-mounted externally-manipulable carousel, an externally-manipulable rigid arm that can accomodate translational motion and three-dimensional rotation, a compartment for humidity regulating solids or liquids, and a humidity sensor. Each enclosure will accomodate several samples that can be manipulated within the enclosure without opening it. Experience gained during this research demonstrated that humidity regulation was necessary to obtain repeatable results. Grinding and polishing shale to a very thin thickness (about 0.4 mm) was shown to cause changes in electrical properties as well. These latter changes were attributed to alterations in the water content. Theoretical considerations A very comprehensive discussion of the electrical properties of sedimentary rocks is available in literature (Sen and Chew, 1983). These authors reviewed the work of others and proposed modifications to better explain the frequency dependent behavior of the permittivity and conductivity of rocks. A large portion of their article was devoted to explanations of large relative permittivities at low frequencies such as observed in this research. They noted that the electrical properties of formations containing shales and clays are the most difficult to explain. Sen and Chew noted the need for additional experimental data and further refinements in theory. Results Shales, limestones, and sandstones were examined for a single 150-m (492-ft) core from Pennsylvania and for a dark shale from a southern Illinois coal mine. Figures 1 and 2 illustrate the conductivities and relative permitivities for the southern Illinois dark shale at a single location. The differences in electrical properties clearly

Jan 1, 1987

By Owen Kingman

This paper discusses grade control of ore mined at Tennessee Copper Company. Mineral zoning and the influence of mineral zoning on production grade are discussed and illustrated. In order to make this most understandable we will first briefly examine the flow sheet at Tennessee Copper to indicate the path followed by the raw material toward its various products. Then we will discuss some of the characteristics of the ore, specifically the distribution or zoning of the minerals in the ore which cause some of the grade control problems. Finally we Will discuss same of the steps that are taken to combat these problems. The flow sheet is illustrated as plate 1. The mined ore is allied to obtain 3 usable products: Copper concentrate, iron concentrate and zinc concentrate. Copper is found in the mineral chalcopyrite, CuFeS2. The Copper concentrate from the mill contains about 20% copper. These concentrates are smelter in reverberatory furnace and Pierce-Smith converter to blister copper containing 99.2% copper. Some metal is cast into 360 lb. pigs and shipped to the refinery. Some is made into shot copper and used locally to make copper sulfate. Copper sulfate is marketed from Copperhill principally in fungicides.

Jan 1, 1960

By Ernst Langer

INTRODUCTION Morro do Niquel is located near the small town of Pratdáolis in the southwest part of the State of Minas Gerais, Brazil, about 300 km in a straight line north of São Paulo and 300 krn west of Belo Horizonte. The deposit is known since 1935. Systematic exploration started, however, only in 1957 and production with one furnace in 1962. Since 1969, after the installation of a second furnace, the mine produces about 2 500 tons of nickel, contained in ferronickel, per year. This production is now consumed totally by the Brazilian steel industry. The "Morro do Niquel" is a serpentinite stock of 900 by 400 m which rises 200 m high above the surrounding metamorphic rocks of Algokian age (see Figure 1). On top of the hill there is a leached barren zone of about 200 by 400 m, generally 20-30 m deep, which consists practically only of a boxwork of quartz colored brown by limonite. Surrounding this zone on the sides of the hill is weathered, decomposed serpentinite which contains about 213 of the economic nickel mineralization. Roughly 113 of the ore reserves lie below the leached overburden representing ore of a different type. The geological map and cross-section, Figure 2, give a clear picture of the occurrence.

Jan 1, 1979

By Dennis Arthur Fenton

The hydrodynamic bearing was first described by, Reynolds in 1886, and has since been widely applied in motors, engines, compressors, hydroelectric turbines, and other machinery. For various reasons, the hydrostatic bearing currently predominates in the large, horizontal rotating machinery field (e.g. grinding mills). However, the current industry trend towards increasing size and energy efficiency has resulted in renewed interest in the advantages of hydrodynamic bearings. These advantages include structural improvements, reduced bearing friction, improved bearing life, improved transient characteristics, and reduced lubricant pump size and power requirements. In particular, the higher energy efficiency results in substantial savings on large machines. This paper describes some aspects of the design of large hydrodynamic bearings based on thirty years, of experience in the design of such bearings on grinding mills ranging in journal size from 2.1 m to 6.4 m, see Table 1.

Jan 1, 1985

By D. C. Sisti

A paper was presented during the 1970 SME Fall Meeting on the Stinson Preparation Facilities by representatives of Beaver Creek Consolidated Cool Company and Heyl & Patterson, Inc. This paper summarized a combined approach to development of a flow diagram and selection of cleaning equipment required to produce a uniform metallurgical coal at maximum recovery with special emphasis on sulphur reduction. These facilities were located in the Elkhorn. Coal Fields of eastern Kentucky and, in particular, the area of Wayland, Knott County, Kentucky, where approximately forty-five- million tons of Elkhorn No. 3 coal could he recovered. The facilities incorporated a Bradford Breaker for reduction of the ROM coal to minus 1-1/2 x 0, 6000 ton-raw coal storage, preparation plant, water clarification and thermal drying facilities, clean coal storage and a 4000 TPH unit train loading facility.

Jan 1, 1973

By W. S. Fyfe

Gold is mobilized or made soluble under all crustal conditions given appropriate fluid chemistry with molecules which complex gold. In the surface environment chloride, thiosulphate and a host of organics may mobilize gold. In the epithermal range bisulphide appears effective as shown by the classic studies in the Taupo volcanic zone of New Zealand. In the high grade metamorphic to igneous ranges little is know but it appears that gas molecules in the system CO2 -CO-H20-S-C1 can do the job. Precipitation may occur by changes in P-T-EL-pH or boiling where such changes influence the liquid concentration. Of the known regimes information is good for epithermal systems, poor for surface lateritic environments, inadequate for high-T systems. Gold is often concentrated in bio-systems both living and dead. The influence of biosystems is little appreciated. There is a great potential for the discovery of new types of gold deposits and in particular, gold in weathering environments, gold in very high-T environments, gold in strike-slip faults and thrust regimes, and gold as a by-product in materials like coal and other organic debris. By the year 2500 we may find our noble metal resources in the asteroids.

Jan 1, 1987