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By W. J. Douglas

Before discussing minicomputer software for the mineral industry, it is helpful to explain some of the computer program terminology. Most of the terms are the same as those applied to large computers. A computer system consists of a machine (hardware) with electronic and mechanical components and instructions (software) that define its operational logic and sequence. This logic is described by sets of commands grouped into programs. Each program has specific objectives related to the computer's operation and to production information from computer data that are input and processed. Software, therefore, is a general term applied to any type of computer program. Instructions to the computer are communicated through languages that convert logical and arithmetic statements into machine operations. The languages may consist of statements resembling mathematical or logical phrases understandable by humans, or they may be coded statements with no apparent resemblance to spoken language but readily understandable by the computer. Computers also translate higher level languages such as FORTRAN or COBOL into machine languages using other programs called Compilers. Programs written in these higher level languages are generally called source code. However, programs written in computer assembly language may also be called source code. The compiled version of the program after it has been translated by the compiler software is called object code. Programs used to "instruct computers how to be computers" are generally called systems software. They relate more to computer operation than to producing externally usable results. Programs producing information for many users-engineers, accountants, managers-are termed applications software. For the most part, applications software is the principal concern of the mineral industry. Programs are developed to fit user requirements as interpreted by programmers. Programs vary in quality, precision, efficiency, accuracy, and complexity, depending on programmer skills and abilities and programming decisions forcing design tradeoffs. A well written program should have speed, efficient use of available hardware resources, accuracy, and an inherently logical structure that aids documentation and subsequent modifications. Programs developed to fit specific requirements are termed customized software. A program organized and prepared for general commercial use is called a package, or a software package, and includes documentation for program use. A form of customized software that takes an existing program or package as its starting point and modifies it is called a customized package. A minicomputer program can be stored on computer cards, standard magnetic tape, magnetic cassette tape, floppy disk, or hard disk. The software purchaser or lessee may select one or more of these media when specifying a program in a software contract. Supporting documentation may include a listing of the program instructions linkages, hardware and storage resource requiremnents, flow charts, and programmer and user manuals. The purchaser must carefully make and clearly understand specifications for media and format of program delivery. This assures that delivered software is compatible with the intended hardware. Mineral Industry Attitudes Toward Computer Software The mining industry has traditionally been conservative concerning computer applications. Furthermore, large computer costs have made these systems accessible only to large companies, for the most part. But in the past few years, mining software systems developed at schools such as Pennsylvania State University and Virginia Polytechnic Institute have gained wider acceptance in the mineral industry. More mining engineers now have academic training in computer application, and computer use is now more acceptable to the mining industry. Mining managers in decisionmaking positions are faced with a new generation of computer technology resulting from the rapid evolution of minicomputers. Not too long ago, manufacturers such as Digital Equipment Corp., Data General, and Hewlett-Packard were considered newcomers. They are now established companies. In addition, Apple, Radio Shack, Commodore, and others have emerged in the growing microcomputer industry. So the mine manager or mining executive now has more options. Mining Software is Limited Along with the rapid evolution in hardware development, much general purpose software is now being developed for minicomputers. The 1981 Apple Software Directory can be obtained for about $14; Radio Shack published the Application Software Source Book in three volumes for $1.95 each. Brochures describing software can be obtained for other minicomputer manufacturers by contacting local sales representatives. Hewlett-Packard software can be obtained and exchanged through HP user's groups. Manufacturers' programming staffs are generally concerned with developing applications software. In some instances, manufacturers will recommend software developed by their hardware users. Until now, however, software development for mining applications has been minimal. This should not be surprising, since software development traditionally lags hardware development by several years. A review of A Directory of Computer Software Applications/Mini-Computers and Micro-Computers, August 1977-1980, published by the US Department of Congress, National Technical Information Service, contains many entries and subject areas. General applications include some references to tunneling machines, but there are virtually no entries specifically relating to

Jan 11, 1981

By Murray Jacobson

Facts obtained by the Bureau of Mines on the dust-explosion hazard in air of materials used in the plastics industry are presented for 313 samples studied in the laboratory. Information is given on ignition temperature of dust clouds and layers, minimum explosive concentration, minimum energy required for ignition, explosion pressure and rates of pressure rise, amount of inert dust required to prevent ignition and flame propagation, and, in some instances, on the limiting oxygen concentration in an atmosphere to prevent ignition by spark and by heated surface. The effects of particle shape, additives, and resin structure on explosibility are discussed. Relative explosibility of the materials is related to the ignition sensitivity and explosion severity and is denoted by an empirical index. Recognition of the degree of hazard will facilitate adoption of adequate measures for preventing ignition and explosion during manufacturing or processing.

Jan 1, 1962

By Richard A. Conkling

A shale layer, buried beneath two or three thousand feet of strata, in some instances, will upon folding become thicker in the synelines and thinner on top of the anticlines. This can be accounted for, in part, by the stretching on the crests of the fold and the compressing in the troughs; but this will by no means account for all of it, as is shown in the example herein set forth. It is my firm belief that the rest of the thickness is due to flow. What causes the movement, however, does not concern us here, SO long as there is movement, for this article purposes to show its effect upon the producing area of different sands. It is the author's hope, in this way, to drop a hint or two that may be valuable to the oil geologist, in making estimates of future productions and values of oil properties. An example will be given from property in the famous Gushing Pool in northeastern Oklahoma, where the author has had occasion to make a detailed study before recommending some property to his company, and has then been able to watch the results of this work. The author never mapped the surface structure in this pool, as this had been done by Frank Buttram when he was with the Oklahoma Geological Survey. We are using, therefore, a section of his map in this article for our surface contours. The main east dip comes farther east than this section shows. From the 10-ft. contours in Fig. 1, it will be seen that the surface folding is very slight, but in the contour map of the Bartlesville sand (Fig. 2), which was the greatest producing sand, we see much more complex folding. It seems that the folding becomes greater with the depth. Folding may have started in Middle Pennsylvanian times and continued through the Upper Pennsylvanian which is found at the surface. This may, or may not, have been the cause of the increase of folding with depth. However, the fact that mostly concerns us is the interval of shale between the Bartlesville sand and the Tucker sand. The Tucker is the next productive sand below the Bartlesville. Not enough wells have been drilled to the Tucker sand to make a contour map of it, but

Jan 1, 1917

By Daxian Z, Youdi Z, Shucai Y

The Huolinhe surface mine is a very large-scale surface coal mine, located in the north-east area of China with a production rate of 1.2 Mtpa. Its coal haulage system has a large capacity, long transportation line and high degree of automation. The system comprises two crushing plants, many belt conveyors, four surge bunkers, one loading bunker, one coal storage and five end product bunkers. In this paper, the network patterns of semi-continuous systems in surface mines are studied, the reliability calculation methods and a simulation model are established and the software for computing the reliability of a semi-continuous system is worked out. By considering the whole coal haulage system in the Huolinhe surface mine, the authors developed the system reliability-numerical simulation method. The steps and the computing results of this method are described in detail. Through the calculation, we can master the present situation of system reliability and the main factors impairing system reliability, expose the system weak links, put forward the ways of enhancing system reliability and furnish the basis for improving the system and equipment. The way of increasing capacity and methods of enhancing system reliability are further raised.

Jan 1, 1995

By V. K. Srivastava, T. Gupta, T. Ghosh

"In recent years, the demand for rare earth elements (REEs) has grown due to increasing demand and global supply shortage. The supply deficit of these critical elements has encouraged the search for new sources, with coal and coal byproducts as possibilities. Coals from certain parts of the world can be rich in REEs and can approach a total concentration of 1,000 ppm. Two Alaskan coal samples, from Healy and Wishbone Hill, were investigated for the effects of density and particle size on REE concentrations for three selected size fractions, and flotation tests were conducted on finer fractions. Additionally, bottom ash and fly ash samples from a power plant were examined for their REE concentrations. The results show that the upgrade potential for REEs on an ash basis from a whole-coal basis ranges from 2:1 for the Wishbone Hill samples to 4:1 for the Healy coal samples. Flotations of the finer fractions of the two coal samples, conducted under similar conditions, revealed higher concentrations of REEs in the tailings. Both coal samples had comparatively higher contents of light-group rare earth elements (LREEs) than heavy-group rare earth elements (HREEs). REE content trends for the power-plant products on an ash basis indicate that fly ash has slightly higher concentrations of both LREEs and HREEs than bottom ash. IntroductionRare earth elements (REEs), also known as rare earth metals, and their compounds are vital components in industrial, automotive, petrochemical, defense and medical applications. Dysprosium in combination with other elements is used in laser materials and nuclear control applications. Neodymium is present in magnets that are used in the manufacture of wind turbines and hybrid cars. Europium, terbium and yttrium are used in devices that have visual displays such as computer screens and laptops (Haxel, Hedrick and Greta, 2002; Bunzli, 2013). REEs pose fewer environmental problems of disposal and recycling than their conventional heavy metal counterparts (Haxel, Hedrick and Greta, 2002). They are key materials for radar systems, avionics, modern national defense and satellites (Cammarata and Sieradzki, 1994; Hedrick, 2010; Martin, 2010; Szumigala and Werdon, 2011; Cordier, 2011; Bunzli, 2013). REEs are often classified into light-group rare earth elements (LREEs) and heavy-group rare earth elements (HREEs). This classification is primarily based on the electronic configuration in the outermost shell. LREEs, ranging from lanthanum to gadolinium, have a single or no spinning electron in the outermost 4f shell while HREEs, ranging from terbium to lutetium, have paired electrons in the 4f shell. This difference in electronic configuration is responsible for the differences in physical and chemical properties of REEs."

Jan 1, 2017

By A G. Guinea

If you were reading this article in a newspaper or similar in the 1800s, you would know that the world was firmly in the grip of the Industrial Revolution. You might have been one of the families that decided that an agriculturally based existence was no longer for you, and that the promise of a factory job was more appealing and more secure. And it was. Financially at least. Not so much from a workplace safety perspective.

May 5, 2022

By R Coleman

The flotation mechanism plays a key role in the flotation process. It is used to provide the contact between solid particles and bubbles and also the energy for these particles and bubbles to attach. The mechanism must therefore provide sufficient mixing to keep the solids in suspension so that they can be transported into the froth and recovered to the concentrate. The design of the mechanism is critical and over the past decade Outotec has developed and optimised a new mechanism design to improve metallurgical and energy performance. The FloatForce® mechanism consists of a rotor and stator arrangement and has been specifically designed to provide sustained mixing at higher air flows and lower power inputs.Over 500 FloatForce® mechanisms have been installed in existing and new operations. This paper outlines the technological aspects of the FloatForce® mechanism and provides metallurgical, operational and energy performance results from a number of flotation circuits in which these have been installed.

Aug 8, 2011

By Daniel Tempelis, Tom Freeman, Eric Fordham, John Shamma, Steven Duke

The Arrowhead Tunnels in southern California are being completed by MWD under stringent groundwater in?ow limits established by the U.S. Forest Service. Pre-excavation grouting, new TBMs and a bolted, gasketed, pre-cast concrete segment initial lining are employed to control water in?ows. The effectiveness of prescribed water control measures was analyzed using conservative assumptions with the analytical techniques described by Goodman (1964), Heuer (1995), and numerical modeling. Analyses results suggest groundwater in?ows to the tunnels can be maintained well below the limits with aggressive pre-excavation grouting balanced against a reasonable rate of advance and quality erection of the initial lining system.

Jan 1, 2003

By S. Goto, S. Yamashita, K. Hata

"The average consumption of zinc dust for purification of zinc leaching solution is more than 25 kg per tonne of electrolytic zinc. Authors proposed to remove impurities in zinc leaching solution by electrolysis instead of cementation by zinc dust. The effects of copper and arsenic on electrodeposition of cobalt in zinc sulfate solution were examined fundamentally using a potentiostat. It is observed that cobalt is easily deposited on a cathode at potentials under -480mV with arsenic. Mesh cathodes of stainless steel and lead anodes were used in a small electrolytic cell and the electrolyte was circulated through 'the electrodes during the electrolysis. The effect of electrolyte circulating rate , pH, cell temperature, current density, and concentration of copper and arsenious ions on removal of cobalt were studied. Removal of Cd and Ni are also examined.IntroductionCobalt is difficult to remove from a zinc leaching solution by a simple cementation reaction using zinc dust. However, it is easily precipitated by zinc dust with co-addition of arsenious or stibinous oxide and copper ion in practical operations(I), (2), (3). The consumption of zinc dust for purification is 16-152 kg per tonne of electrolytic zinc and 65% of this zinc dust consumption is used for cobalt purification. The average retention time for purification of cobalt is 4.5 hours (1). A more economical process for purification is desired instead of zinc dust. The mechanism of this acceleration effect of copper and arsenious oxide on removal of cobalt are explained by the authorsas follows; a galvanic cell is formed between zinc dust and copper which is precipitated firstly, and cobalt is reduced on copper as Co-As alloy by this galvanic current(2). This assumption was confirmed in experiments using a galvanic cell with a membrane( 4). The following galvanic reactions occur between zinc dust and copper precipitate; on copper cathode,2H+ + 2e -= Hz(g)2Coz+ + 2HAs02 + 6H ++ 10e -= 2CoAs + 4HzOand on zinc anode,Zn = Zn = 2+ 2e –This galvanic current becomes almost zero in a zinc sulfate solution which includes only cobalt and no arsenious oxide, and cobalt is weakly deposited on a copper cathode. Cobalt deposition requiers a high degree of cathodic polarization. However, the galvanic current flows almost constantly in an electrolyte, which includes arsenious oxide, and the cathode potential is kept at about -500mV. Cobalt is precipitated as Co-As on the cathode.The authors assumed that cobalt may be removed by electrolysis at a very low current density instead of zinc dust and the following experiments were carried out. In the first part of this paper, the fundamental experiments using a potentiostat on the behaviour of cobalt in zinc sulfate solution are described. In the second part, the results of the electrolysis are reported. Cobalt is removed by a new type of an electrolytic cell, which was desigoed to <Iccelerate the rate of deposition of cobalt. The removal of cadmium and nickel in a solution which includes cobalt and arsenic are also examined."

Jan 1, 1997

By Janusz Majta

The aim of this work is to investigate the control of microstructure evolution through variation of particular deformation parameters in the two-phase (intercritical) region. Niobium-microalloyed and low-carbon steels were investigated. A detailed examination of the factors affecting the ferrite microstructures of tested steels indicated that there were distinct advantages of finishing at temperatures in the austenite-ferrite region. The various results of deformation in the two-phase region are presented. Consequently, the influence of the most important process parameters on the microstructure evolution and mechanical response of the material is determined. The prime objective of the realized research work is the determination of relationship between the history of deformation and final product quality i.e. texture and mechanical properties. To reach the objective, the constitutive equations are proposed for modeling the effects of the hot-deformation process occurring in the austenite and austenite-ferrite region of low carbon and microalloyed steels on the mechanical properties of the resulting product. These models link advanced, finite element approaches simulating metal flow and heat transfer during hot-plastic deformation with constitutive equations describing microstructural processes and mechanical properties.

Jan 1, 2003

By A. J. Forney

A high-Btu gas was made at the Bruceton, Pa., laboratories of the Bureau of Mines to demonstrate the feasibility of using the gas as a nonpolluting fuel for automobiles. The pilot plants at Bruceton were revised to combine the processes of coal gasification, gas purification, and catalytic methanation in one overall system. Tests in the Bureau&apos;s test automobiles at Bartlesville, Okla., showed the Synthane gas was less polluting than natural gas.

Jan 1, 1972

By Victor E. Kral

"SUMMARYA preliminary examination of the Buena Vista iron deposit was made in June 1942 by Paul E. Pesonen, mining engineer of the Bureau of Mines. Subsequent examinations were made by D. W. Butner, of the Bureau, in March 1943, and by the author in July 1944, who recommended exploration by diamond drilling, trenching, and sampling. Work on the project was done during the period March 28 to May 26, 1945.Property holdings, comprising 16 claims known as the Buena Vista group, are situated in sec. 4, T. 24 N., R. 34 E., Mount Diablo base and meridian, north Churchill County, about 37 miles east of Lovelock, Nev.Three diamond-drill holes totaling 575 feet were drilled; 45 small pits and ten trenches, totaling 435 linear feet, were excavated, and 84 channel samples totaling 862 feet were obtained under supervision of the Bureau.Purpose of the project was to determine the possible downward extension of the mineralized sections exposed in the outcrops and to determine grade of the ore.Bureau work was confined to one claim only - the Iron Mountain."

Jun 1, 1947

By Mark K. Larson

Calibration of LaModel for deep coal mines begins with adjustment of overburden stiffness for load transfer distance. This calibration determines whether mining induced stresses are concentrated in the immediate abutment of the gob, or spread over a wider area. In the absence of site information, an empirically-based estimate is often used. Where data is available, a recommended calibration procedure can be followed, as is done in this case study at a deep western longwall mine, with minor modifications and extensions. In this case, data sources included borehole pressure cells, flatjacks installed in series with support Cans, and observed changes in ground conditions. Calibration was based on the first detection of mining-induced stress from the advancing longwall. Detection was found to depend on the type and sensitivity of measurement. Borehole pressure cell data with a 20-psi-increase detection threshold were chosen as the standard, in accord with data used in deriving empirical relationships. Application of this standard produced a load transfer distance estimate roughly four times the empirical relationship developed by Peng and Chiang (1984). This is a significant deviation with important implications for panel design at this site. Data from flatjacks, ground condition observations, and borehole pressure cells with higher threshold values, were tightly clustered and show load transfer distances from two to four times empirical guidance. Ratios between various measurements can be used to adjust measurements to the standard (although they may depend on mine geology). Once established, ratios can be used to adjust estimates, say from support flatjacks or ground observations, to the standard, where borehole pressure cell data is not available.`

Jan 1, 2012

By G. Diáz

The PLACID process applied to the recycling of spent lead-acid batteries is being developed by an European Consortium within the Brite-Euram II programme. The status of the project entitled "Lead Recovery from Lead Oxide Secondaries" is described in this paper. The main laboratory and batch experimental results and the preliminary feasibility study are summarised. The description of the demonstration pilot plant and continuous campaigns programme for 1995 are also included. An interesting global approach is proposed, integrating the Placid process in the existing spent battery recycling pyrometallurgical facilities. This yields important improvements in the overall process. Grids would be easily treated by the conventional pyrometallurgical route, obtaining lead alloys,, while battery pastes, slags and fumes would be fed to the Placid process, obtaining pure electrolytic lead (>99.99 %), ideal for battery paste manufacturing. The implementation of the Placid process into the existing battery recycling pyrometallurgical facilities is analyzed from technical, environmental and economical viewpoints. Greater overall lead recovery, lower operating costs, reduced waste production, environmentally safer residues and much better lead product quality are the key advantages. The authors draw the following final conclusion : Integration of the Placid process with conventional pyrometallurgical treatment is a feasible and very attractive alternative route for spent lead-acid battery recycling.

Jan 1, 1995

By M, C Silveira, C Ellice, D Christensen

Peak Gold Mines (PGM), a member of the Rio Tinto Group, is an underground and open cut gold mining operation located near Cobar, NSW. A multi-phase study was initiated in 2001 in support of developing a dry æmoisture store and releaseÆ cover system design for the PGM tailings dam, which contains potentially acid-forming tailings material. The first phase consisted of characterising the tailings and potential cover material (waste rock from an open cut operation) as well as soil-atmosphere cover design modelling. The second phase involved construction of two cover system field trials on the tailings dam and installation of a variety of field instruments to monitor the hydraulic performance of the test covers during all seasons of the year. Field performance monitoring commenced in April 2002 and will continue for a minimum of two wet-dry climate cycles (third phase), prior to using the field data for calibration and subsequent validation of numerical models developed for the cover system trials (fourth phase). This paper describes the work completed for the first two project phases and also discusses the initial performance of the cover system trials.

Jan 1, 2003

By J. D. Forrester

In striving to develop this discussion about "Manpower for Industrial Mineral Industries" two fundamental classes of manpower are encountered. These are: 1) The Labor Force, comprised of unskilled and semi-skilled, nonprofessional personnel who participate in conducting economic, mineral deposit operations and; 2) The Professional People involved in the science, engineering, and management of such industrial enterprises. The commentary given here will be directed primarily to a review of the characteristics of the second or latter class. To pursue successfully a career as a scientist or engineer in today&apos;s industrial and social complex, it is necessary that technical knowledge must have been acquired by training and study in an institution of higher learning. Also, to act effectively, the individual must have achieved some degree of specialzation, although this element often is developed to most notable degree by post-graduate exposure and experience. In addition, and especially in the case of "management," it is desirable, indeed it is even necessary, that an individual recognize and appreciate the fundamental humanistic-sociological controls, and their nuances, as these elements exist to shape his total environment.

Jan 1, 1969

By S. Parkash, A. J. Szladow

Vigorous agitation of suspensions of coking coals in water (or light mineral oils) will often result in catast rophic loss of caking properties. It is shown that this deterioration is not a consequence of oxidation of the coals (by dissolved oxygen), but that it can be qualitatively connected with internal "solid-state" reactions which appear to derive their activation energies from cavitation of the liquid.

Jan 1, 1971

By S. J. Neethling

"Flotation is a complex process with many factors that influence the performance of a cell. This paper examines the impact of several key variables on the performance of flotation cells. The study makes use of a simulator for the froth phase of the flotation vessel, as the main purpose of this study is to separate the impact of different variables from one another.In experiments it is very difficult to separate the effect of variables from one another as a change in a singe input parameter, such as air rate, invariably also affects many of the other key variables, such as bubble size and bubble bursting rates. This interaction between variables makes it very hard to experimentally separate the impact of, for instance, the air rate from that of bubble size or bursting rate. In the simulator, though, it easy to make independent changes to these variables.In order to achieve this a base case simulation that is typical of many of the rougher cells found in sulphide flotation circuits was carried out. Four key variables, air rate, incoming bubble size, surface bubble size and the fraction of the bubbles flowing out of the cell unburst, were varied in order to obtain the system’s response.The most significant results were obtained when the bubble size was varied. An increase in the incoming bubble size has the effect of reducing the pulp zone recovery, but increases the froth zone recovery. If it were possible to vary the incoming bubble size without influencing the overflowing bubble size, the impact of the change would be unclear because of these two competing effects. The effect of a change in the overflowing bubble size has an opposite effect on the froth recovery, with larger bubbles resulting in lower froth recoveries."

Jan 1, 2003

By T. Takayama Filho

Votorantim Metais Zinco is a smelting facility which produces SHG zinc, zinc alloys, sulfuric acid, liquid SO2, copper sulfate, cadmium metal and silver concentrate. It is located at Juiz de Fora, Minas Gerais State, Brazil. This facility has been operating since 1980 and its current capacity is 95,000 tonnes of zinc per year, using mostly imported sulfide concentrates.The plant uses the conventional roast-leach electrowinning (RLE) process, in which iron is removed from the circuit as jarosite. The residues generated by the RLE process, which amount to about 200 t/day (dry weight), were until 10 years ago, deposited in tailing ponds having no impervious lining. More recently, jarosite and other wastes have been deposited in a properly built reservoir, but this is reaching its maximum capacity. In order to decommission these disposal operations and to reclaim the sites in an environmentally acceptable manner, Votorantim Metais concluded in 2004 a rehabilitation project for the old tailings pond and prepared detailed plans for managing the current and future disposal of jarosite-bearing residues. This paper describes the procedure for removing iron from the hydrometallurgical circuit and discusses the past and current status of the residue disposal sites, as well as the future challenges related to the environmentally acceptable handling of iron residues.

Jan 1, 2006

By Glenn C. Waterman

THE diamond drill is a very important tool in exploration and development testing and its use is increasing. In almost all cases results of diamond drilling are analyzed on the basis of grade and tons. A proper evaluation of core and sludge assays is important if drilling results are to be acceptable as a basis for geologic and engineering appraisal. The relatively wide variation in assay averages as calculated by various well-known combining methods indicates that the engineering choice of a method may affect the outcome of the drilling in terms of ore and waste. The problem of combining assay results from core and sludge samples has been discussed many times in conference and in the literature.&apos;-&apos; Most writers agree that the field of disagreement in methods is large and that the engineer on the job must consider features unique to his drilling, pick one of several combining methods, and depart from the rules when abnormal results come in. All the discussion to date can be summed up by the admission that as yet there is no fairly simple, generally acceptable combining method that is practicable over a wide range of drilling conditions, ground conditions, and ore occurrence. The combining problem is important in evaluating drilling results at Chuquicamata. Recently a reappraisal has been made of recovery variables and their effect on assays, with the result that a new combining method is offered which fits average drilling conditions and is mathematically reasonable. It is simple in application, fundamentally correct, and an improvement over most combining methods. At Chuquicamata diamond drillholes are used to outline the grade and position of blocks of normal and marginal grade oxide, mixed, and sulphide ore. Most holes penetrate all classes of material (and waste), and it is important for mining programs as well as ore reserves to know almost precisely the soluble and insoluble copper content of mineralized ground. At present three classes of ore are mined and treated differently. For an orderly sequence of mining operations which can provide regular daily tonnages of all three ore types and keep grade at certain levels with minimum variation, ore type and its grade must be predicted. Diamond drilling plus geologic mapping and bench sampling are tools for prediction. And drilling data are largely used to calculate grade of material more than a few meters away from bench faces. The orebody at Chuquicamata" is criss-crossed by millions of barren or mineralized weak to fairly strong slips and fault fissures. Mineralization is diverse and encompasses many quartz and oxide or sulphide-bearing copper veins, as well as seams and disseminated grains. Copper occurs in oxide or sulphide minerals or mixtures of these two mineral types. Rock conditions vary from intensely seri-citized (soft and porous) through clay-altered ground to almost fresh granodiorite. The result is an orebody which offers many obstacles to good and consistent core recovery in diamond drilling. Recovery varies considerably in the several alteration zones, the various types of oxide and sulphide ores, and the position and inclination of the drillhole within the complex fracture pattern. As core recovery drops sludge samples must be used with core samples to calculate grade. Many years of drilling at Chuquicamata indicate that in good grade oxide zones and in the sulphide areas core recovery is good and the ground uniformly mineralized. Moderate loss of core, therefore, does not markedly affect grade calculations based on core assays. An early core-sludge combining method used core assays at face value as indicating grade down to 50 pct core recovery, but below this recovery percentage sludge samples were used and weighted according to the standard Longyear chart. This method apparently did not introduce serious errors, but it abruptly used sludge assays with high weighting factors representing 100 pct return irrespective of actual percentage of sludge recovered. Recent drilling activities have been directed toward outlining the marginal ore areas. The non-uniform mineralization and generally poorer core recovery in such ground indicated that a more exact core-sludge combining method was required to equate wide differences between core and sludge assays and recovery. In fringe ore areas at Chuquicamata core recovery averages about 50 pct, from a minimum of 10 to 15 pct to a maximum of 100 pct. Sludge recovery is likewise variable and averages perhaps 80 pct even though holes are cemented as water return falls off. In a homogeneously mineralized area cut by many slips and faults, with hard and soft ribs, loss of core is loss of ground which has a grade similar to that of core recovered, and core assays approximate true grade. In this case sludge samples need not be used. However, it would be unusual to know beforehand that an area is uniformly mineralized, and in fact this condition is probably uncommon. Generally the distribution of valuable minerals in the ground does not exactly compare with their recoverability in core. Thus, in the usual case, loss of core decreases the

Jan 1, 1956